WorldWideScience

Sample records for glacier terminus contrast

  1. A GIS tool for two-dimensional glacier-terminus change tracking

    Science.gov (United States)

    Urbanski, Jacek Andrzej

    2018-02-01

    This paper presents a Glacier Termini Tracking (GTT) toolbox for the two-dimensional analysis of glacier-terminus position changes. The input consists of a vector layer with several termini lines relating to the same glacier at different times. The output layers allow analyses to be conducted of glacier-terminus retreats, changes in retreats over time and along the ice face, and glacier-terminus fluctuations over time. The application of three tools from the toolbox is demonstrated via the analysis of eight glacier-terminus retreats and fluctuations at the Hornsund fjord in south Svalbard. It is proposed that this toolbox may also be useful in the study of other line features that change over time, like coastlines and rivers. The toolbox has been coded in Python and runs via ArcGIS.

  2. Controls on the inland propagation of terminus-driven speedups at Helheim Glacier, SE Greenland

    Science.gov (United States)

    Kehrl, L. M.; Joughin, I. R.; Smith, B.

    2017-12-01

    Tidewater glaciers are very sensitive to changes in the stress balance near their termini. When submarine melt or iceberg calving reduce lateral or basal resistance near the terminus, the glacier typically must speed up to produce the additional longitudinal and lateral stress gradients necessary to restore stress balance. Once speedup near the terminus is initiated, it can propagate inland through longitudinal stress coupling, thinning-induced changes in the effective pressure, and/or a steepening of surface slopes. The controls on these processes and the timing and spatial extent of the inland response, however, remain poorly understood. In this study, we use a three-dimensional, Full Stokes model (Elmer/Ice) to investigate the effects of different ice rheology and basal sliding parameterizations on the inland propagation of speedups at Helheim Glacier, SE Greenland. Using satellite observations of terminus position, we force the model with the observed 3-km, 2013/14 retreat history and allow the model to evolve in response to this retreat. We run a set of simulations that vary the ice rheology (constant or spatially variable ice temperature) and basal sliding law (linear, nonlinear, and effective-pressure-dependent). Our results show that the choice of parameterizations affect the timing and spatial extent of the inland response, but that the range of acceptable parameters can be constrained by comparing the model results to satellite observations of surface velocity and elevation.

  3. Numerical Modeling of Climatic Change from the Terminus Record of Lewis Glacier, Mount Kenya.

    Science.gov (United States)

    Kruss, Phillip Donald

    Over the last 100 years, the glaciers and lakes of East Africa have undergone dramatic change in response to climatic forcing. However, the available conventional meterological series have not proven sufficient to explain these environmental events. The secular climatic change at Lewis Glacier, Mount Kenya (0(DEGREES)9'S, 37(DEGREES)19'E), is reconstructed from its terminus record documented since 1893. The short-time-step numerical model developed for this study consists of climate and ice dynamics segments. The climate segment directly computes the effect on the net balance of change in the four forcings: precipitation, albedo, cloudiness, and temperature. The flow segment calculates the dynamic glacier response to net balance variation. Climatic change occurs over a wide range of time scales. Each glacier responds in a unique fashion to this spectrum of climatic forcings. The response of the Lewis terminus extent to repeated sinusoidal fluctuation in the net balance is calculated. The net balance versus elevation profile is separately translated along the orthogonal balance and elevation axes. Net balance amplitudes of 0.1 to 0.5 m a('-1) of ice and 10 to 50 m elevation, respectively, and periods ranging from 20 to 1000 years are covered. Consideration of the Lewis response is perspective with similar results for Hintereisferner, Storglaciaren, and Berendon and South Cascade Glaciers identifies general characteristics of the time lag and amplitude of the terminus response. The magnitude and timing of the change in only one of the climatic forcings precipitation, albedo, cloudiness, or temperature necessary to produce the retreat of the Lewis terminus from its late 19th century maximum are computed. Equivalent changes for two scenarios of simultaneous variation, namely precipitation/albedo/cloudiness and temperature/albedo, are also estimated. These numerical results are interpreted in the light of long-term lake level, river flow, and instrumental information. A

  4. Mass balance, meteorology, area altitude distribution, glacier-surface altitude, ice motion, terminus position, and runoff at Gulkana Glacier, Alaska, 1996 balance year

    Science.gov (United States)

    March, Rod S.

    2003-01-01

    The 1996 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier Basin were evaluated on the basis of meteorological, hydrological, and glaciological data. Averaged over the glacier, the measured winter snow balance was 0.87 meter on April 18, 1996, 1.1 standard deviation below the long-term average; the maximum winter snow balance, 1.06 meters, was reached on May 28, 1996; and the net balance (from August 30, 1995, to August 24, 1996) was -0.53 meter, 0.53 standard deviation below the long-term average. The annual balance (October 1, 1995, to September 30, 1996) was -0.37 meter. Area-averaged balances were reported using both the 1967 and 1993 area altitude distributions (the numbers previously given in this abstract use the 1993 area altitude distribution). Net balance was about 25 percent less negative using the 1993 area altitude distribution than the 1967 distribution. Annual average air temperature was 0.9 degree Celsius warmer than that recorded with the analog sensor used since 1966. Total precipitation catch for the year was 0.78 meter, 0.8 standard deviations below normal. The annual average wind speed was 3.5 meters per second in the first year of measuring wind speed. Annual runoff averaged 1.50 meters over the basin, 1.0 standard deviation below the long-term average. Glacier-surface altitude and ice-motion changes measured at three index sites document seasonal ice-speed and glacier-thickness changes. Both showed a continuation of a slowing and thinning trend present in the 1990s. The glacier terminus and lower ablation area were defined for 1996 with a handheld Global Positioning System survey of 126 locations spread out over about 4 kilometers on the lower glacier margin. From 1949 to 1996, the terminus retreated about 1,650 meters for an average retreat rate of 35 meters per year.

  5. Contrasting medial moraine development at adjacent temperate, maritime glaciers: Fox and Franz Josef Glaciers, South Westland, New Zealand

    Science.gov (United States)

    Brook, Martin; Hagg, Wilfried; Winkler, Stefan

    2017-08-01

    Medial moraines form important pathways for sediment transportation in valley glaciers. Despite the existence of well-defined medial moraines on several glaciers in the New Zealand Southern Alps, medial moraines there have hitherto escaped attention. The evolving morphology and debris content of medial moraines on Franz Josef Glacier and Fox Glacier on the western flank of the Southern Alps is the focus of this study. These temperate maritime glaciers exhibit accumulation zones of multiple basins that feed narrow tongues flowing down steep valleys and terminate 400 m above sea level. The medial moraines at both glaciers become very prominent in the lower ablation zones, where the medial moraines widen, and develop steeper flanks coeval with an increase in relative relief. Medial moraine growth appears somewhat self-limiting in that relief and slope angle increase eventually lead to transport of debris away from the medial moraine by mass-movement-related processes. Despite similarities in overall morphologies, a key contrast in medial moraine formation exists between the two glaciers. At Fox Glacier, the medial moraine consists of angular rockfall-derived debris, folded to varying degrees along flow-parallel axes throughout the tongue. The debris originates above the ELA, coalesces at flow-unit boundaries, and takes a medium/high level transport pathway before subsequently emerging at point-sources aligned with gently dipping fold hinges near the snout. In contrast at Franz Josef Glacier, the medial moraine emerges farther down-glacier immediately below a prominent rock knob. Clasts show a mix of angular to rounded shapes representing high level transport and subglacially transported materials, the latter facies possibly also elevated by supraglacial routing of subglacial meltwater. Our observations confirm that a variety of different debris sources, transport pathways, and structural glaciological processes can interact to form medial moraines within New Zealand

  6. Glaciers

    Science.gov (United States)

    Hambrey, Michael; Alean, Jürg

    2004-12-01

    Glaciers are among the most beautiful natural wonders on Earth, as well as the least known and understood, for most of us. Michael Hambrey describes how glaciers grow and decay, move and influence human civilization. Currently covering a tenth of the Earth's surface, glacier ice has shaped the landscape over millions of years by scouring away rocks and transporting and depositing debris far from its source. Glacier meltwater drives turbines and irrigates deserts, and yields mineral-rich soils as well as a wealth of valuable sand and gravel. However, glaciers also threaten human property and life. Our future is indirectly connected with the fate of glaciers and their influence on global climate and sea level. Including over 200 stunning photographs, the book takes the reader from the High-Arctic through North America, Europe, Asia, Africa, New Zealand and South America to the Antarctic. Michael Hambrey is Director of the Centre for Glaciology at the University of Wales, Aberystwyth. A past recipient of the Polar Medal, he was also given the Earth Science Editors' Outstanding Publication Award for the first edition of Glaciers (Cambridge, 1995). Hambrey is also the author of Glacial Environments (British Columbia, 1994). JÜrg Alean is Professor of Geography at the Kantonsschule ZÜrcher Unterland in BÜlach, Switzerland.

  7. Contrasting evolution patterns between glacier-fed and non-glacier-fed lakes in the central Tibetan Plateau and driving force analysis

    Science.gov (United States)

    Song, C.; Sheng, Y.

    2015-12-01

    High-altitude lakes in the Tibetan Plateau (TP) showed strong spatio-temporal variability during past decades. The lake dynamics can be associated with several key factors including lake type, supply of glacial meltwater, local climate variations. It is important to differentiate these factors when analyzing the driving force of lakes dynamics. With a focus on lakes over the Tanggula Mountains of the central TP, this study investigates the temporal evolution patterns of lake area and water level of different types: glacier-fed closed lake, non-glacier-fed closed lake and upstream lake (draining into closed lakes). We collected all available Landsat archive data and quantified the inter-annual variability of lake extents. Results show accelerated expansions of both glacier-fed and non-glacier-fed lakes during 1970s-2013, and different temporal patterns of the two types of lakes: the non-glacier-fed lakes displayed a batch-wise growth pattern, with obvious growth in 2002, 2005 and 2011 and slight changes in other years, while glacier-fed lakes showed steady expanding tendency. The contrasting patterns are confirmed by the distinction of lake level change between the two groups derived from satellite altimetry during 2003-2009. The upstream lakes remained largely stable due to natural drainage regulation. The intermittent expansions for non-glacier-fed lakes were found to be related to excessive precipitation events and positive "precipitation-evaporation". In contrast, glacier-fed lake changes showed weak correlations with precipitation variations, which imply a joint contribution from glacial meltwater to water budgets. A simple estimation reveals that the increased water storage for all of examined lakes contributed from precipitation/evaporation (0.31±0.09 Gt/yr) slightly overweighed the glacial meltwater supply (0.26±0.08 Gt/yr).

  8. Stable oxygen isotope variability in two contrasting glacier river catchments in Greenland

    DEFF Research Database (Denmark)

    Yde, Jacob C.; Knudsen, Niels T.; Steffensen, Jørgen P.

    2016-01-01

    the Greenland Ice Sheet (GrIS). At the Mittivakkat Gletscher river, a small river draining a local temperate glacier in southeast Greenland, diurnal oscillations in δ18O occurred with a 3 h time lag to the diurnal oscillations in run-off. The mean annual δ18O was -14.68±0.18‰ during the peak flow period...... event. Overall, a comparison of the δ18O compositions from glacial river water in Greenland shows distinct differences between water draining local glaciers and ice caps (between -23.0 and -13.7 ‰) and the GrIS (between -29.9 and -23.2 ‰). This study demonstrates that water isotope analyses can be used......Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of δ18O variations in Greenlandic rivers, we examined two contrasting glacierised catchments disconnected from...

  9. Spatiotemporal variability of oxygen isotope compositions in three contrasting glacier river catchments in Greenland

    DEFF Research Database (Denmark)

    Knudsen, N. Tvis; Yde, J.C.; Steffensen, J.P.

    2015-01-01

    composition is controlled by the proportion between snowmelt and ice melt with episodic inputs of rainwater and occasional storage and release of a specific water component due to changes in the subglacial drainage system. At Kuannersuit Glacier River on the island Qeqertarsuaq, the δ18O characteristics were......Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of spatio-temporal δ18O variations in glacier rivers, we have examined three glacierized catchments in Greenland...... of diurnal oscillations, and in 2003 there were large diurnal fluctuations in δ18O. At Watson River, a large catchment at the western margin of the Greenland Ice Sheet, the spatial distribution of δ18O in the river system was applied to fingerprint the relative runoff contributions from sub-catchments. Spot...

  10. Dynamic interactions between glacier and glacial lake in the Bhutan Himalaya

    Science.gov (United States)

    Tsutaki, S.; Fujita, K.; Yamaguchi, S.; Sakai, A.; Nuimura, T.; Komori, J.; Takenaka, S.; Tshering, P.

    2012-04-01

    .9-18.8 m yr-1 at the Thorthormi Glacier while -12.0-2.7 m yr-1 at the Lugge Glacier. This result suggests that decreasing in flow velocity towards the terminus in the Thorthormi Glacier causes compressive flow. It suggests that the compressive flow of the Thorthormi Glacier counterbalanced surface melting, resulting in inhibition of the surface lowering. In contrast, the extensional flow of the Lugge Glacier accelerated the surface lowering. Speed up of glacier terminus induced extensional flow regime causes the thinning of ice and increase in basal motion, which will lead to further flow acceleration. Such positive feedbacks have been found over the ice streams in the polar ice sheets. In this study we showed the observational evidences, in which the similar feedbacks make contrast the terminus behaviors of glaciers in the Bhutan Himalaya. If the supraglacial lake on Thorthormi Glacier expanded, the surface lowering may be accelerated in the future.

  11. Tropical Glaciers

    Science.gov (United States)

    Fountain, Andrew

    The term "tropical glacier" calls to mind balmy nights and palm trees on one hand and cold, blue ice on the other. Certainly author Gabriel Garcia Marqez exploited this contrast in One Hundred Years of Solitude. We know that tropical fish live in warm, Sun-kissed waters and tropical plants provide lush, dense foliage populated by colorful tropical birds. So how do tropical glaciers fit into this scene? Like glaciers everywhere, tropical glaciers form where mass accumulation—usually winter snow—exceeds mass loss, which is generally summer melt. Thus, tropical glaciers exist at high elevations where precipitation can occur as snowfall exceeds melt and sublimation losses, such as the Rwenzori Mountains in east Africa and the Maoke Range of Irian Jaya.

  12. Glaciers of Europe

    Science.gov (United States)

    Williams, Richard S.; Ferrigno, Jane G.

    1993-01-01

    ALPS: AUSTRIAN: An overview is provided on the occurrence of the glaciers in the Eastern Alps of Austria and on the climatic conditions in this area, Historical documents on the glaciers have been available since the Middle Ages. Special glaciological observations and topographic surveys of individual glaciers were initiated as early as 1846. Recent data in an inventory based on aerial photographs taken in 1969 show 925 glaciers in the Austrian Alps with a total area of 542 square kilometers. Present research topics include studies of mass and energy balance, relations of glaciers and climate, physical glaciology, a complete inventory of the glaciers, and testing of remote sensing methods. The location of the glacier areas is shown on Landsat multispectral scanner images; the improved capabilities of the Landsat thematic mapper are illustrated with an example from the Oztaler Alpen group. ALPS: SWISS: According to a glacier inventory published in 1976, which is based on aerial photography of 1973, there are 1,828 glacier units in the Swiss Alps that cover a total area of 1fl42 square kilometers. The Rhonegletscher, currently the ninth largest in the country, was one of the first to be studied in detail. Its surface has been surveyed repeatedly; velocity profiles were measured, and the fluctuations of its terminus were mapped and recorded from 1874 to 1914. Recent research on the glacier has included climatological, hydrological, and massbalance studies. Glaciological research has been conducted on various other glaciers in Switzerland concerning glacier hydrology, glacier hazards, fluctuations of glacier termini, ice mechanics, ice cores, and mass balance. Good maps are available showing the extent of glaciers from the latter decades of the 19th century. More recently, the entire country has been mapped at scales of 1:25,000, 1:50,000, 1:100,000, 1:200,000, and 1:500,000. The 1:25,000-scale series very accurately represents the glaciers as well as locates

  13. Glaciers of North America - Glaciers of Alaska

    Science.gov (United States)

    Molnia, Bruce F.

    2008-01-01

    literature for each of the 11 mountain ranges, the large island, the island chain, and the archipelago was conducted to determine both the individual and the regional status of Alaskan glaciers and to characterize changes in thickness and terminus position of representative glaciers in each mountain range or island group. In many areas, observations used for determining changes date from the late 18th or early 19th century. Temperature records at all Alaskan meteorological recording stations document a 20th century warming trend. Therefore, characterizing the response of Alaska's glaciers to changing climate helps to quantify potential sea-level rise from past, present, and future melting of glacier ice (deglaciation of the 14 glacierized regions of Alaska), understand present and future hydrological changes, and define impacts on ecosystems that are responding to deglacierization. Many different types of data were scrutinized to determine baselines and to assess the magnitude of glacier change. These data include the following: published descriptions of glaciers (1794-2000), especially the comprehensive research by Field (1975a) and his colleagues in the Alaska part of Mountain Glaciers of the Northern Hemisphere, aerial photography (since 1926), ground photography (since 1884), airborne radar (1981-91), satellite radar (1978-98), space photography (1984-94), multispectral satellite imagery (since 1972), aerial reconnaissance and field observations made by many scientists during the past several decades, and various types of proxy data. The published and unpublished data available for each glacierized region and individual glacier varied significantly. Geospatial analysis of digitized U.S. Geological Survey (USGS) topographic maps is used to statistically define selected glaciological parameters in the eastern part of the Alaska Range. The analysis determined that every mountain range and island group investigated can be characterized by significant glac

  14. Detecting frontal ablation processes from direct observations of submarine terminus morphology

    Science.gov (United States)

    Fried, M.; Carroll, D.; Catania, G. A.; Sutherland, D. A.; Stearns, L. A.; Bartholomaus, T. C.; Shroyer, E.; Nash, J. D.

    2017-12-01

    Tidewater glacier termini couple glacier and ocean systems. Subglacial discharge emerging from the terminus produces buoyant plumes that modulate submarine melting, calving, fjord circulation and, in turn, changes in ice dynamics from back-stress perturbations. However, the absence of critical observational data at the ice-ocean interface limits plume and, by extension, melt models from incorporating realistic submarine terminus face morphologies and assessing their impact on terminus behavior at tidewater glaciers. Here we present a comprehensive inventory and characterization of submarine terminus face shapes from a side-looking, multibeam echo sounding campaign across Kangerdlugssuaq Sermerssua glacier, central-west Greenland. We combine these observations with in-situ measurements of ocean stratification and remotely sensed subglacial discharge, terminus positions, ice velocity, and ice surface datasets to infer the spectrum of processes sculpting the submarine terminus face. Subglacial discharge outlet locations are confirmed through observations of sediment plumes, localized melt-driven undercutting of the terminus face, and bathymetry of the adjacent seafloor. From our analysis, we differentiate terminus morphologies resulting from submarine melt and calving and assess the contribution of each process to the net frontal ablation budget. Finally, we constrain a plume model using direct observations of the submarine terminus face and conduit geometry. Plume model simulations demonstrate that the majority of discharge outlets are fed by small discharge fluxes, suggestive of a distributed subglacial hydrologic system. Outlets with the largest, concentrated discharge fluxes are morphologically unique and strongly control seasonal terminus position. At these locations, we show that the spatiotemporal pattern of terminus retreat is well correlated with time periods when local melt rate exceeds ice velocity.

  15. Glaciation of alpine valleys: The glacier - debris-covered glacier - rock glacier continuum

    Science.gov (United States)

    Anderson, Robert S.; Anderson, Leif S.; Armstrong, William H.; Rossi, Matthew W.; Crump, Sarah E.

    2018-06-01

    Alpine ice varies from pure ice glaciers to partially debris-covered glaciers to rock glaciers, as defined by the degree of debris cover. In many low- to mid-latitude mountain ranges, the few bare ice glaciers that do exist in the present climate are small and are found where snow is focused by avalanches and where direct exposure to radiation is minimized. Instead, valley heads are more likely to be populated by rock glaciers, which can number in the hundreds. These rock-cloaked glaciers represent some of the most identifiable components of the cryosphere today in low- to mid-latitude settings, and the over-steepened snouts pose an often overlooked hazard to travel in alpine terrain. Geomorphically, rock glaciers serve as conveyor belts atop which rock is pulled away from the base of cliffs. In this work, we show how rock glaciers can be treated as an end-member case that is captured in numerical models of glaciers that include ice dynamics, debris dynamics, and the feedbacks between them. Specifically, we focus on the transition from debris-covered glaciers, where the modern equilibrium line altitude (ELA) intersects the topography, to rock glaciers, where the modern ELA lies above the topography. On debris-covered glaciers (i.e., glaciers with a partial rock mantle), rock delivered to the glacier from its headwall, or from sidewall debris swept into the glacier at tributary junctions, travels englacially to emerge below the ELA. There it accumulates on the surface and damps the rate of melt of underlying ice. This allows the termini of debris-covered glaciers to extend beyond debris-free counterparts, thereby decreasing the ratio of accumulation area to total area of the glacier (AAR). In contrast, rock glaciers (i.e., glaciers with a full rock mantle) occur where and when the environmental ELA rises above the topography. They require avalanches and rockfall from steep headwalls. The occurrence of rock glaciers reflects this dependence on avalanche sources

  16. Glaciers bring more precipitation over south slope of the Himalayas and less moisture to the Tibetan Plateau

    Science.gov (United States)

    Yang, K.; Lin, C.; Chen, D.

    2017-12-01

    Due to the warming climate, significant retreat of glaciers in the Himalayan region is observed. Thus, it is crucial to understand whether and how the glaciers impact (feedback to) regional climate. Due to lack of observational data, most processes with glaciers are however not well documented. For instance, convergence takes place when summertime upslope flows of warm and moist air masses meet cool and dry katabatic winds over a glacier slope, which may induce local convections and precipitations. This work intends to test this hypothesis according to an experiment conducted with the Weather Research and Forecasting (WRF) Model focusing on the Himalayan region. Three cases are designed for the experiment: a) a normal run as the control case; b) a sensitive run with land use ice/snow replaced by bare ground tundra and the maximum snow albedo set to 0.25; and c) a sensitive run with land use ice/snow replaced by bare ground tundra and no new snowing. According to differences between the control case and both the two sensitive cases, here we found that glaciers overall leads to less precipitation over glacier-covered areas and north of the Himalayas, which can be attributed to the suppressing of cooling glacier surfaces to upslope moist flows. By contrast, a zone of extra more precipitation (that can be up to 200 mm for JJA) is clearly found over the south slope of the Himalayas at elevation of 4-5 km where it meets the glacier terminus, accompanied with the convergence of upslope air masses and katabatic winds. Case b) reflects a smaller such effect when compared to case c), possibly because it takes a portion of energy for ice/snow melting. When it comes to impacts on water vapor transport, glaciers will result approximately 2% less moisture flowing into the Tibetan Plateau.

  17. Sediment transport drives tidewater glacier periodicity.

    Science.gov (United States)

    Brinkerhoff, Douglas; Truffer, Martin; Aschwanden, Andy

    2017-07-21

    Most of Earth's glaciers are retreating, but some tidewater glaciers are advancing despite increasing temperatures and contrary to their neighbors. This can be explained by the coupling of ice and sediment dynamics: a shoal forms at the glacier terminus, reducing ice discharge and causing advance towards an unstable configuration followed by abrupt retreat, in a process known as the tidewater glacier cycle. Here we use a numerical model calibrated with observations to show that interactions between ice flow, glacial erosion, and sediment transport drive these cycles, which occur independent of climate variations. Water availability controls cycle period and amplitude, and enhanced melt from future warming could trigger advance even in glaciers that are steady or retreating, complicating interpretations of glacier response to climate change. The resulting shifts in sediment and meltwater delivery from changes in glacier configuration may impact interpretations of marine sediments, fjord geochemistry, and marine ecosystems.The reason some of the Earth's tidewater glaciers are advancing despite increasing temperatures is not entirely clear. Here, using a numerical model that simulates both ice and sediment dynamics, the authors show that internal dynamics drive glacier variability independent of climate.

  18. Response of small glaciers to climate change: runoff from glaciers of the Wind River range, Wyoming

    Science.gov (United States)

    Bliss, A. K.; Stamper, B.

    2017-12-01

    Runoff from glaciers affects downstream ecosystems by influencing the quantity, seasonality, and chemistry of the water. We describe the present state of glaciers in the Wind River range, Wyoming and consider how these glaciers will change in the future. Wind River glaciers have been losing mass in recent decades, as seen with geodetic techniques and by examining glacier morphology. Interestingly, the 2016/7 winter featured one of the largest snowfalls on record. Our primary focus is the Dinwoody Glacier ( 3 km^2, 3300-4000 m above sea level). We present data collected in mid-August 2017 including glacier ablation rates, snow line elevations, and streamflow. We compare measured glacier mass loss to streamflow at the glacier terminus and at a USGS stream gauge farther downstream. Using a hydrological model, we explore the fate of glacial runoff as it moves into downstream ecosystems and through ranchlands important to local people. The techniques used here can be applied to similar small-glacier systems in other parts of the world.

  19. Mapping tide-water glacier dynamics in east Greenland using landsat data

    Science.gov (United States)

    Dwyer, John L.

    1995-01-01

    Landsat multispectral scanner and thematic mapper images were co-registered For the Kangerdlugssuaq Fjord region in East Greenland and were used to map glacier drainage-basin areas, changes in the positions of tide-water glacier termini and to estimate surface velocities of the larger tide-water glaciers. Statistics were compiled to document distance and area changes to glacier termini. The methodologies developed in this study are broadly applicable to the investigation of tide-water glaciers in other areas. The number of images available for consecutive years and the accuracy with which images are co-registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data.Three domains of glacier state were interpreted: net increase in terminus area in the southern part of the study area, net loss of terminus area for glaciers in upper Kangerdlugssuaq Fjord and a slight loss of glacier terminus area northward from Ryberg Fjord. Local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions Ice-surface velocity estimates were derived for several glaciers using automated image cross-correlation techniques The velocity determined for Kangerdlugssuaq Gletscher is approximately 5.0 km a−1 and that for Kong Christian IV Gletscher is 0.9 km a−1. The continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice-front calving.

  20. Biotic diversity of benthic macroinvertebrates at contrasting glacier-fed systems in Patagonia Mountains: The role of environmental heterogeneity facing global warming.

    Science.gov (United States)

    Miserendino, María Laura; Brand, Cecilia; Epele, Luis B; Di Prinzio, Cecilia Y; Omad, Guillermo H; Archangelsky, Miguel; Martínez, Oscar; Kutschker, Adriana M

    2018-05-01

    Patagonia is by far the largest glacierized area in South America. However, little is known about ecology, functioning and biodiversity of glacier-fed streams facing global warming. We investigated changes in environmental features and macroinvertebrate communities along a longitudinal gradient of glacier influence of two Patagonian systems that differ in glacier cover magnitude and the spatial sequence of lotic and lentic phases. Both glaciers, Torrecillas (~5.5km 2 , Torrecillas system) and Cónico (~0.44km 2 , Baggilt system), are retreating. Longitudinal distribution of benthic invertebrates partially fitted to predictions for glacierized temperate systems, with Diamesinae spp. dominating at closest sites to the Cónico, and Orthocladiinae increasing downstream, but patterns were unclear at Torrecillas. Generalized Linear Model identified chlorophyll a and conductivity as having significant effect on richness and density respectively at Torrecillas; detritus biomass and gravel influenced species richness, and boulder percentage and water temperature affected density, at Baggilt. Canonical Correspondence Analyses integrating benthic biota and environmental variables revealed that a higher environmental heterogeneity at Baggilt, related with spatial dimension (unshaded/shaded reaches, wetland reaches), local resources (detritus, bryophytes) and temperature, probably explained the unexpected high richness in benthic assemblages (67 taxa). Environmental conditions imposed by the lake outlet (proglacial) at Torrecillas resulted in a less diverse community (31 taxa). Finally our results suggest that these isolated, small glacier-fed streams typical of the Patagonian landscape appear highly vulnerable to global warming. Endemic elements could disappear at upper segments being replaced by other species common at rhithral environments, which might increase local diversity (alfa diversity) but decrease regional diversity (gamma diversity). From an ecosystem perspective

  1. From Glaciers to Icebergs

    Science.gov (United States)

    Zhang, Wendy

    I will describe works from a collaboration between physics and glaciology that grew out of interactions at the Computations in Science seminar Leo Kadanoff organized at the University of Chicago. The first project considers the interaction between ocean waves and Antarctic ice shelves, large floating portions of ice formed by glacial outflows. Back-of-envelop calculation and seismic sensor data suggest that crevasses may be distributed within an ice shelf to shield it from wave energy. We also examine numerical scenarios in which changes in environmental forcing causes the ice shelf to fail catastrophically. The second project investigates the aftermath of iceberg calving off glacier terminus in Greenland using data recorded via time-lapse camera and terrestrial radar. Our observations indicate that the mélange of icebergs within the fjord experiences widespread jamming during a calving event and therefore is always close to being in a jammed state during periods of terminus quiescence. Joint work with Jason Amundson, Ivo R. Peters, Julian Freed Brown, Nicholas Guttenberg, Justin C Burton, L. Mac Cathles, Ryan Cassotto, Mark Fahnestock, Kristopher Darnell, Martin Truffer, Dorian S. Abbot and Douglas MacAyeal. Kadanoff Session DCMP.

  2. Combination of UAV and terrestrial photogrammetry to assess rapid glacier evolution and map glacier hazards

    Science.gov (United States)

    Fugazza, Davide; Scaioni, Marco; Corti, Manuel; D'Agata, Carlo; Azzoni, Roberto Sergio; Cernuschi, Massimo; Smiraglia, Claudio; Diolaiuti, Guglielmina Adele

    2018-04-01

    Tourists and hikers visiting glaciers all year round face hazards such as sudden terminus collapses, typical of such a dynamically evolving environment. In this study, we analyzed the potential of different survey techniques to analyze hazards of the Forni Glacier, an important geosite located in Stelvio Park (Italian Alps). We carried out surveys in the 2016 ablation season and compared point clouds generated from an unmanned aerial vehicle (UAV) survey, close-range photogrammetry and terrestrial laser scanning (TLS). To investigate the evolution of glacier hazards and evaluate the glacier thinning rate, we also used UAV data collected in 2014 and a digital elevation model (DEM) created from an aerial photogrammetric survey of 2007. We found that the integration between terrestrial and UAV photogrammetry is ideal for mapping hazards related to the glacier collapse, while TLS is affected by occlusions and is logistically complex in glacial terrain. Photogrammetric techniques can therefore replace TLS for glacier studies and UAV-based DEMs hold potential for becoming a standard tool in the investigation of glacier thickness changes. Based on our data sets, an increase in the size of collapses was found over the study period, and the glacier thinning rates went from 4.55 ± 0.24 m a-1 between 2007 and 2014 to 5.20 ± 1.11 m a-1 between 2014 and 2016.

  3. Debris thickness patterns on debris-covered glaciers

    Science.gov (United States)

    Anderson, Leif S.; Anderson, Robert S.

    2018-06-01

    Many debris-covered glaciers have broadly similar debris thickness patterns: surface debris thickens and tends to transition from convex- to concave-up-down glacier. We explain this pattern using theory (analytical and numerical models) paired with empirical observations. Down glacier debris thickening results from the conveyor-belt-like nature of the glacier surface in the ablation zone (debris can typically only be added but not removed) and from the inevitable decline in ice surface velocity toward the terminus. Down-glacier thickening of debris leads to the reduction of sub-debris melt and debris emergence toward the terminus. Convex-up debris thickness patterns occur near the up-glacier end of debris covers where debris emergence dominates (ablation controlled). Concave-up debris thickness patterns occur toward glacier termini where declining surface velocities dominate (velocity controlled). A convex-concave debris thickness profile inevitably results from the transition between ablation-control and velocity-control down-glacier. Debris thickness patterns deviating from this longitudinal shape are most likely caused by changes in hillslope debris supply through time. By establishing this expected debris thickness pattern, the effects of climate change on debris cover can be better identified.

  4. Sudden increase in tidal response linked to calving and acceleration at a large Greenland outlet glacier

    DEFF Research Database (Denmark)

    de Juan, Julia; Elósegui, Pedro; Nettles, Meredith

    2010-01-01

    strongly with the step-like increases in glacier speed and longitudinal strain rate associated with glacial earthquakes. The enhanced response to the ocean tides may be explained by a temporary disruption of the subglacial drainage system and a concomitant reduction of the friction at the ice......Large calving events at Greenland's largest outlet glaciers are associated with glacial earthquakes and near-instantaneous increases in glacier flow speed. At some glaciers and ice streams, flow is also modulated in a regular way by ocean tidal forcing at the terminus. At Helheim Glacier, analysis...

  5. Spatial and temporal melt variability at Helheim Glacier, East Greenland, and its effect on ice dynamics

    DEFF Research Database (Denmark)

    Andersen, M. L.; Larsen, T. B.; Nettles, M.

    2010-01-01

    Understanding the behavior of large outlet glaciers draining the Greenland Ice Sheet is critical for assessing the impact of climate change on sea level rise. The flow of marine-terminating outlet glaciers is partly governed by calving-related processes taking place at the terminus but is also in...

  6. Glaciers along proposed routes extending the Copper River Highway, Alaska

    Science.gov (United States)

    Glass, R.L.

    1996-01-01

    Three inland highway routes are being considered by the Alaska Department of Transportation and Public Facilities to connect the community of Cordova in southcentral Alaska to a statewide road system. The routes use part of a Copper River and Northwest Railway alignment along the Copper River through mountainous terrain having numerous glaciers. An advance of any of several glaciers could block and destroy the roadway, whereas retreating glaciers expose large quantities of unconsolidated, unvegetated, and commonly ice-rich sediments. The purpose of this study was to map historical locations of glacier termini near these routes and to describe hazards associated with glaciers and seasonal snow. Historical and recent locations of glacier termini along the proposed Copper River Highway routes were determined by reviewing reports and maps and by interpreting aerial photographs. The termini of Childs, Grinnell, Tasnuna, and Woodworth Glaciers were 1 mile or less from a proposed route in the most recently available aerial photography (1978-91); the termini of Allen, Heney, and Schwan Glaciers were 1.5 miles or less from a proposed route. In general, since 1911, most glaciers have slowly retreated, but many glaciers have had occasional advances. Deserted Glacier and one of its tributary glaciers have surge-type medial moraines, indicating potential rapid advances. The terminus of Deserted Glacier was about 2.1 miles from a proposed route in 1978, but showed no evidence of surging. Snow and rock avalanches and snowdrifts are common along the proposed routes and will periodically obstruct the roadway. Floods from ice-dammed lakes also pose a threat. For example, Van Cleve Lake, adjacent to Miles Glacier, is as large as 4.4 square miles and empties about every 6 years. Floods from drainages of Van Cleve Lake have caused the Copper River to rise on the order of 20 feet at Million Dollar Bridge.

  7. Subglacial discharge at tidewater glaciers revealed by seismic tremor

    Science.gov (United States)

    Bartholomaus, Timothy C.; Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.

    2015-01-01

    Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, affects fjord circulation, and is a central component of proglacial marine ecosystems. However, our present inability to track subglacial discharge and its variability significantly hinders our understanding of these processes. Here we report observations of hourly to seasonal variations in 1.5–10 Hz seismic tremor that strongly correlate with subglacial discharge but not with basal motion, weather, or discrete icequakes. Our data demonstrate that vigorous discharge occurs from tidewater glaciers during summer, in spite of fast basal motion that could limit the formation of subglacial conduits, and then abates during winter. Furthermore, tremor observations and a melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.

  8. Little Ice Age climate reconstruction from ensemble reanalysis of Alpine glacier fluctuations

    Directory of Open Access Journals (Sweden)

    M. P. Lüthi

    2014-04-01

    Full Text Available Mountain glaciers sample a combination of climate fields – temperature, precipitation and radiation – by accumulation and melting of ice. Flow dynamics acts as a transfer function that maps volume changes to a length response of the glacier terminus. Long histories of terminus positions have been assembled for several glaciers in the Alps. Here I analyze terminus position histories from an ensemble of seven glaciers in the Alps with a macroscopic model of glacier dynamics to derive a history of glacier equilibrium line altitude (ELA for the time span 400–2010 C.E. The resulting climatic reconstruction depends only on records of glacier variations. The reconstructed ELA history is similar to recent reconstructions of Alpine summer temperature and Atlantic Multidecadal Oscillation (AMO index, but bears little resemblance to reconstructed precipitation variations. Most reconstructed low-ELA periods coincide with large explosive volcano eruptions, hinting at a direct effect of volcanic radiative cooling on mass balance. The glacier advances during the LIA, and the retreat after 1860, can thus be mainly attributed to temperature and volcanic radiative cooling.

  9. Investigating plume dynamics at the ocean-glacier interface with turbulence profiling and autonomous vessels

    Science.gov (United States)

    Jackson, R. H.; Nash, J. D.; Sutherland, D. A.; Amundson, J. M.; Kienholz, C.; Skyllingstad, E. D.; Motyka, R. J.

    2017-12-01

    The exchanges of heat and freshwater at tidewater glacier termini are modulated by small-scale turbulent processes. However, few observations have been obtained near the ocean-glacier interface, limiting our ability to quantify turbulent fluxes or test melt parameterizations in ocean-glacier models. Here, we explore the turbulent plume dynamics at LeConte Glacier, Alaska with three extensive field campaigns in May, August and September (2016-17). Two autonomous vessels collected repeat transects of velocity and water properties near the glacier, often within 20 m of the terminus. Concurrent shipboard surveying measured turbulence with a vertical microstructure profiler, along with water properties and velocity. These high-resolution surveys provide a 3D view of the circulation and allow us to quantify turbulent fluxes in the near-glacier region. We observe two regimes at the terminus: an energetic upwelling plume driven by subglacial discharge at a persistent location, and submarine melt-driven convection along other parts of the terminus. We trace the evolution of the subglacial discharge plume as it flows away from the glacier, from an initial stage of vigorous mixing to a more quiescent outflow downstream. Resolving these spatial patterns of upwelling and mixing near glaciers is a key step towards understanding submarine melt rates and glacial fjord circulation.

  10. Ice thickness profile surveying with ground penetrating radar at Artesonraju Glacier, Peru

    Science.gov (United States)

    Chisolm, Rachel; Rabatel, Antoine; McKinney, Daene; Condom, Thomas; Cochacin, Alejo; Davila Roller, Luzmilla

    2014-05-01

    Tropical glaciers are an essential component of the water resource systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean glaciers in recent decades. The shrinkage of Andean glaciers influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some glaciers. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical glaciers in Peru and how climate change is likely to impact glacial melt and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to glaciers in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect glaciers in terms of thickness changes. In the upper Paron Valley (Cordillera Blanca, Peru), an emerging lake has begun to form at the terminus of the Artesonraju Glacier, and this lake has key features, including overhanging ice and loose rock likely to create slides, that could trigger a catastrophic GLOF if the lake continues to grow. Because the glacier mass balance and lake mass balance are closely linked, ice thickness measurements and measurements of the bed slope of the Artesonraju Glacier and underlying bedrock can give us an idea of how the lake is likely to evolve in the coming decades. This study presents GPR data taken in July 2013 at the Artesonraju Glacier as part of a collaboration between the Unidad de Glaciologia y Recursos Hidricos (UGRH) of Peru, the Institut de Recherche pour le Développement (IRD) of France and the University of Texas at Austin (UT) of the United States of America. Two different GPR units belonging to UGRH and UT were used for subsurface imaging to create ice thickness profiles and to characterize the total volume of ice in the glacier. A common midpoint

  11. Exploring the links between transient water inputs and glacier velocity in a small temperate glacier in southeastern Alaska

    Science.gov (United States)

    Heavner, M.; Habermann, M.; Hood, E. W.; Fatland, D. R.

    2009-12-01

    Glaciers along the Gulf of Alaska are thinning and retreating rapidly. An important control on the rate at which ice is being lost is basal motion because higher glacier velocities increase the rate at which ice is delivered to ablation zones. Recent research has focused on understanding the effects of sub-glacial water storage on glacier basal motion. In this study, we examined two seasons of the effect of hydrologic controls (from large rainfall events as well as a glacier lake outburst floods) on the velocity of the Lemon Creek Glacier in southeastern Alaska. Lemon Creek Glacier is a moderately sized (~16~km2) temperate glacier at the margin of the Juneau Icefield. An ice-marginal lake forms at the head of the glacier and catastrophically drains once or twice every melt season. We have instrumented the glacier with two meteorological stations: one at the head of the glacier near the ice-marginal lake and another several kilometers below the terminus. These stations measure temperature, relative humidity, precipitation, incoming solar radiation and wind speed and direction. Lake stage in the ice-marginal lake was monitored with a pressure transducer. In addition, Lemon Creek was instrumented with a water quality sonde at the location of a US Geological Survey gaging station approximately 3 km downstream from the glacier terminus. The sonde provides continuous measurements of water temperature, dissolved oxygen, turbidity and conductivity. Finally, multiple Trimble NetRS dual frequency, differential GPS units were deployed on the glacier along the centerline of the glacier. All of the instruments were run continuously from May-September 2008 and May-September 2009 and captured threee outburst floods associated with the ice-marginal lake drainage as well as several large (>3~cm) rainfall events associated with frontal storms off of the Gulf of Alaska in late summer. Taken together, these data allow us to test the hypothesis that water inputs which overwhelm

  12. Glacier Photograph Collection

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Glacier Photograph Collection is a database of photographs of glaciers from around the world, some dating back to the mid-1850's, that provide an historical...

  13. World Glacier Inventory

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The World Glacier Inventory (WGI) contains information for over 130,000 glaciers. Inventory parameters include geographic location, area, length, orientation,...

  14. Glaciers between two drivers

    DEFF Research Database (Denmark)

    Machguth, Horst

    2014-01-01

    It is assumed that the monsoon is the dominant influence on Himalayan glaciers. However, a study now investigates the importance of the mid-latitude Westerlies and shows that glacier changes can be triggered from afar.......It is assumed that the monsoon is the dominant influence on Himalayan glaciers. However, a study now investigates the importance of the mid-latitude Westerlies and shows that glacier changes can be triggered from afar....

  15. Accessing the inaccessible: making (successful) field observations at tidewater glacier termini

    Science.gov (United States)

    Kienholz, C.; Amundson, J. M.; Jackson, R. H.; Motyka, R. J.; Nash, J. D.; Sutherland, D.

    2017-12-01

    Glaciers terminating in ocean water (tidewater glaciers) show complex dynamic behavior driven predominantly by processes at the ice-ocean interface (sedimentation, erosion, iceberg calving, submarine melting). A quantitative understanding of these processes is required, for example, to better assess tidewater glaciers' fate in our rapidly warming environment. Lacking observations close to glacier termini, due to unpredictable risks from calving, hamper this understanding. In an effort to remedy this lack of knowledge, we initiated a large field-based effort at LeConte Glacier, southeast Alaska, in 2016. LeConte Glacier is a regional analog for many tidewater glaciers, but better accessible and observable and thus an ideal target for our multi-disciplinary effort. Our ongoing campaigns comprise measurements from novel autonomous vessels (temperature, salinity and current) in the immediate proximity of the glacier terminus and additional surveys (including multibeam bathymetry) from boats and moorings in the proglacial fjord. These measurements are complemented by iceberg and glacier velocity measurements from time lapse cameras and a portable radar interferometer situated above LeConte Bay. GPS-based velocity observations and melt measurements are conducted on the glacier. These measurements provide necessary input for process-based understanding and numerical modeling of the glacier and fjord systems. In the presentation, we discuss promising initial results and lessons learned from the campaign.

  16. Dry calving processes at the ice cliff of an antarctic local glacier: the study case of Strandline Glacier (Northern Victoria Land, Antarctica)

    Science.gov (United States)

    Smiraglia, C.; Motta, M.; Vassena, G.; Diolaiuti, G.

    2003-04-01

    In Antartic coastal area, where the ice sheet and the large outlet glaciers do not reach the sea and where some rugged mountain chains are often present, many small glaciers can be found. They are the so called local or alpine type glaciers, which have their terminus ground-based such as the real alpine glaciers and rarely reach the main valley floors. They are practically isolated and independent from the supply flowing down from the plateau and their mass balance is mainly controlled by sublimation and aeolic erosion and accumulation. The glaciers closer to the coast are submitted to the melting as well, and when the terminus is cliff-shaped they are also affected by dry calving. The most known and studied Antarctic local glaciers are placed in the Dry Valleys region (Chinn, 1985), but this kind of glaciers is also diffused all along the Northern Victoria Land coastal region (Chinn and others, 1989). Since the first Italian Antarctic expedition (1985), many studies have been carried out on this type of glaciers, which can be usefull for detailed mass balance evaluations and for obtaining information about the effects of the present climatic dynamics on the Antarctic coastal environment (Baroni and Orombelli, 1987; Baroni and others, 1995; Meneghel, 1999; Vassena and others., 2001). The Strandline Glacier (74 41 S; 164 07 E), in particular is a small alpine glacier (0,79 kmq) on the coast of Terra Nova Bay, Northern Victoria Land; it is a cold glacier where accumulation and ablation basins are mainly controlled by wind processes. Its terminus forms in the central part a grounded ice cliff about 30 m high, about 130 m far from the sea. On that glacier mass balance, surface velocity and calving rate were measured. During the southern summer season 2000-2001 many topographycal profiles of the ice cliff were surveyed by using both classical topographical and glaciological methods (total station and stakes) and GPS technique. It was so possible to detect the short term

  17. Dynamic behavior of the Bering Glacier-Bagley icefield system during a surge, and other measurements of Alaskan glaciers with ERS SAR imagery

    Science.gov (United States)

    Lingle, Craig S.; Fatland, Dennis R.; Voronina, Vera A.; Ahlnaes, Kristina; Troshina, Elena N.

    1997-01-01

    ERS-1 synthetic aperture radar (SAR) imagery was employed for the measurement of the dynamics of the Bagley icefield during a major surge in 1993-1994, the measurement of ice velocities on the Malaspina piedmont glacier during a quiescent phase between surges, and for mapping the snow lines and the position of the terminus of Nabesna glacier on Mount Wrangell (a 4317 m andesitic shield volcano) in the heavily glacierized Saint Elias and Wrangell Mountains of Alaska. An overview and summary of results is given. The methods used include interferometry, cross-correlation of sequential images, and digitization of boundaries using terrain-corrected SAR imagery.

  18. Water, ice, and meteorological measurements at South Cascade glacier, Washington, balance year 2003

    Science.gov (United States)

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2005-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass-balance quantities for balance year 2003. The 2003 glacier-average maximum winter snow balance was 2.66 meters water equivalent, which was about equal to the average of such balances for the glacier since balance year 1959. The 2003 glacier summer balance (-4.76 meters water equivalent) was the most negative reported for the glacier, and the 2003 net balance (-2.10 meters water equivalent), was the second-most negative reported. The glacier 2003 annual (water year) balance was -1.89 meters water equivalent. The area of the glacier near the end of the balance year was 1.89 square kilometers, a decrease of 0.03 square kilometer from the previous year. The equilibrium-line altitude was higher than any part of the glacier; however, because snow remained along part of one side of the upper glacier, the accumulation-area ratio was 0.07. During September 13, 2002-September 13, 2003, the glacier terminus retreated at a rate of about 15 meters per year. Average speed of surface ice, computed using a series of vertical aerial photographs dating back to 2001, ranged from 2.2 to 21.8 meters per year. Runoff from the subbasin containing the glacier and from an adjacent non-glacierized basin was gaged during part of water year 2003. Air temperature, precipitation, atmospheric water-vapor pressure, wind speed, and incoming solar radiation were measured at selected locations on and near the glacier. Summer 2003 at the glacier was among the warmest for which data are available.

  19. Increased Mass Loss and Asynchronous Behavior of Marine-Terminating Outlet Glaciers at Upernavik Isstrøm, NW Greenland

    DEFF Research Database (Denmark)

    Larsen, Signe Hillerup; Khan, Shfaqat Abbas; Ahlstrøm, Andreas Peter

    2016-01-01

    In order to model and predict future behavior of marine terminating glaciers, it is essential to understand the different factors that control a glaciers response to climate change. Here we present a detailed study of the asynchronous changes in dynamic behavior of four adjacent marine...... between 1992 and 2013. These observations point out the fact that the UI glaciers are reacting to climate change on different timescales. The asynchronous behavior of the four neighboring glaciers is explained in terms of the individual glaciersâĂŹ geometry and terminus position. The northernmost glacier...... is believed to have had a floating tongue between 1985 and 2007 which disintegrated in 2007-2008. This release of back stress destabilized the glacier causing it to accelerate and thin rapidly. We suggest that the ice tongue broke up due to ocean-warming induced thinning in the late 1990s. Recent response...

  20. Storm-induced water dynamics and thermohaline structure at the tidewater Flade Isblink Glacier outlet to theWandel Sea (NE Greenland)

    DEFF Research Database (Denmark)

    Kirillov, Sergei; Dmitrenko, Igor; Rysgaard, Soren

    2017-01-01

    In April 2015, an ice-tethered conductivity-temperature-depth (CTD) profiler and a down-looking acoustic Doppler current profiler (ADCP) were deployed from the landfast ice near the tidewater glacier terminus of the Flade Isblink Glacier in the Wandel Sea, NE Greenland. The 3-week time series...

  1. Neoglacial fluctuations of Deming Glacier, Mt. Baker, Washington USA.

    Science.gov (United States)

    Osborn, G.; Menounos, B.; Scott, K.; Clague, J. J.; Tucker, D.; Riedel, J.; Davis, P.

    2007-12-01

    Deming Glacier flows from the upper west slopes of Mt. Baker, a stratovolcano in the Cascade Range of Washington, USA. The north and south lateral moraines of Deming Glacier are composed of at least four tills separated by layers of detrital wood and sheared stumps in growth position. The stratigraphy records fluctuations of the glacier during the Holocene. The outer ten rings of an in situ stump from the middle wood layer, which is about 40 m below the north lateral moraine crest and 1.2 km downvalley from the present glacier terminus, yielded an age of 1750 ± 50~~ 14C yr BP [1810-1550 cal yr BP]. The stump revealed at least 300 rings and thus records a period of landscape stability and relatively restricted glaciation for several hundred years prior to ca. 1750 14C yr BP . Samples from the lowest wood layer also have been submitted for radiocarbon dating. Outer rings of detrital wood samples collected from two wood mats exposed in the south lateral moraine, 2.3 km downvalley of the glacier terminus, returned radiocarbon ages of 1600 ± 30~~ 14C yr BP [1550- 1410 cal yr BP] and 430 ± 30~~ 14C yr BP [AD 1420-1620]. These data indicate that Deming Glacier advanced over a vegetated moraine sometime after 1810 cal yr BP to a position less extensive that it achieved at the peak of the Little Ice Age. The glacier then receded before it began its final and most extensive Holocene advance after AD 1420. The older advance is correlative with the 'First Millennium AD' advance, recently recognized throughout western North America. The younger advance coincides with an advance of Mt. Baker's Easton Glacier [AD 1430-1630], and advances of many alpine glaciers elsewhere in western North America. Our data suggest that glaciers on Mt. Baker fluctuated in a similar manner to alpine glaciers in the Coast Mountains of British Columbia and in other mountain ranges of northwest North America during Neoglaciation.

  2. Can we use ice calving on glacier fronts as a proxy for rock slope failures?

    Science.gov (United States)

    Abellan, Antonio; Penna, Ivanna; Daicz, Sergio; Carrea, Dario; Derron, Marc-Henri; Jaboyedoff, Michel; Riquelme, Adrian; Tomas, Roberto

    2015-04-01

    Ice failures on glacier terminus show very similar fingerprints to rock-slope failure (RSF) processes, nevertheless, the investigation of gravity-driven instabilities that shape rock cliffs and glacier's fronts are currently dissociated research topics. Since both materials (ice and rocks) have very different rheological properties, the development of a progressive failure on mountain cliffs occurs at a much slower rate than that observed on glacier fronts, which leads the latter a good proxy for investigating RSF. We utilized a terrestrial Laser Scanner (Ilris-LR system from Optech) for acquiring successive 3D point clouds of one of the most impressive calving glacier fronts, the Perito Moreno glacier located in the Southern Patagonian Ice Fields (Argentina). We scanned the glacier terminus during five days (from 10th to 14th of March 2014) with very high accuracy (0.7cm standard deviation of the error at 100m) and a high density of information (200 points per square meter). Each data series was acquired at a mean interval of 20 minutes. The maximum attainable range for the utilized wavelength of the Ilris-LR system (1064 nm) was around 500 meters over massive ice (showing no-significant loss of information), being this distance considerably reduced on crystalline or wet ice short after the occurrence of calving events. As for the data treatment, we have adapted our innovative algorithms originally developed for the investigation of both precursory deformation and rockfalls to study calving events. By comparing successive three-dimensional datasets, we have investigated not only the magnitude and frequency of several ice failures at the glacier's terminus (ranging from one to thousands of cubic meters), but also the characteristic geometrical features of each failure. In addition, we were able to quantify a growing strain rate on several areas of the glacier's terminus shortly after their final collapse. For instance, we investigated the spatial extent of the

  3. Methods for Automating Analysis of Glacier Morphology for Regional Modelling: Centerlines, Extensions, and Elevation Bands

    Science.gov (United States)

    Viger, R. J.; Van Beusekom, A. E.

    2016-12-01

    The treatment of glaciers in modeling requires information about their shape and extent. This presentation discusses new methods and their application in a new glacier-capable variant of the USGS PRMS model, a physically-based, spatially distributed daily time-step model designed to simulate the runoff and evolution of glaciers through time. In addition to developing parameters describing PRMS land surfaces (hydrologic response units, HRUs), several of the analyses and products are likely of interest to cryospheric science community in general. The first method is a (fully automated) variation of logic previously presented in the literature for definition of the glacier centerline. Given that the surface of a glacier might be convex, using traditional topographic analyses based on a DEM to trace a path down the glacier is not reliable. Instead a path is derived based on a cost function. Although only a single path is presented in our results, the method can be easily modified to delineate a branched network of centerlines for each glacier. The second method extends the glacier terminus downslope by an arbitrary distance, according to local surface topography. This product is can be used to explore possible, if unlikely, scenarios under which glacier area grows. More usefully, this method can be used to approximate glacier extents from previous years without needing historical imagery. The final method presents an approach for segmenting the glacier into altitude-based HRUs. Successful integration of this information with traditional approaches for discretizing the non-glacierized portions of a basin requires several additional steps. These include synthesizing the glacier centerline network with one developed with a traditional DEM analysis, ensuring that flow can be routed under and beyond glaciers to a basin outlet. Results are presented based on analysis of the Copper River Basin, Alaska.

  4. Measuring past glacier fluctuations from historic photographs geolocated using Structure from Motion

    Science.gov (United States)

    Vargo, L.; Anderson, B.; Horgan, H. J.; Mackintosh, A.; Lorrey, A.; Thornton, M.

    2017-12-01

    Quantifying glacier fluctuations is important for understanding how the cryosphere responds to climate variability and change. Photographs of past ice extents have become iconic images of climate change, but until now incorporating these images into quantitative estimates of glacier change has been problematic. We present a new method to quantitatively measure past glacier fluctuations from historic images. The method uses a large set of modern geolocated photographs and Structure from Motion (SfM) to calculate the camera parameters for the historic images, including the location from which they were taken. We initially apply this method to a small maritime New Zealand glacier (Brewster Glacier, 44°S, 2 km2), and quantify annual equilibrium line altitudes (ELAs) and length changes from historic oblique aerial photographs (1981 - 2017). Results show that Brewster has retreated 364 ± 12 m since 1981 and, using independent field measurements of terminus positions (2005 - 2014), we show that this SfM-derived length record accurately captures glacier change. We calculate the uncertainties associated with this method using known coordinates of bedrock features surrounding the glacier. Mean uncertainties in the ELA and length records are 7 m and 11 m, respectively. In addition to Brewster, 49 other New Zealand glaciers have been monitored by aerial photographs since 1978. However, the length records for these glaciers only include years of relative advance or retreat, and no length changes have been quantified. We will ultimately apply this method to all 50 glaciers, expanding the database of New Zealand glacier fluctuations that until now included only a few glaciers. This method can be further applied to any glacier with historic images, and can be used to measure past changes in glacier width, area, and surface elevation in addition to ELA and length.

  5. Glaciers of Asia

    Science.gov (United States)

    Williams, Richard S.; Ferrigno, Jane G.

    2010-01-01

    This chapter is the ninth to be released in U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, a series of 11 chapters. In each of the geographic area chapters, remotely sensed images, primarily from the Landsat 1, 2, and 3 series of spacecraft, are used to analyze the specific glacierized region of our planet under consideration and to monitor glacier changes. Landsat images, acquired primarily during the middle to late 1970s and early 1980s, were used by an international team of glaciologists and other scientists to study various geographic regions and (or) to discuss related glaciological topics. In each glacierized geographic region, the present areal distribution of glaciers is compared, wherever possible, with historical information about their past extent. The atlas provides an accurate regional inventory of the areal extent of glacier ice on our planet during the 1970s as part of a growing international scientific effort to measure global environmental change on the Earth?s surface. The chapter is divided into seven geographic parts and one topical part: Glaciers of the Former Soviet Union (F-1), Glaciers of China (F-2), Glaciers of Afghanistan (F?3), Glaciers of Pakistan (F-4), Glaciers of India (F-5), Glaciers of Nepal (F?6), Glaciers of Bhutan (F-7), and the Paleoenvironmental Record Preserved in Middle-Latitude, High-Mountain Glaciers (F-8). Each geographic section describes the glacier extent during the 1970s and 1980s, the benchmark time period (1972-1981) of this volume, but has been updated to include more recent information. Glaciers of the Former Soviet Union are located in the Russian Arctic and various mountain ranges of Russia and the Republics of Georgia, Kyrgyzstan, Tajikistan, and Kazakstun. The Glacier Inventory of the USSR and the World Atlas of Ice and Snow Resources recorded a total of 28,881 glaciers covering an area of 78,938 square kilometers (km2). China includes many of the mountain-glacier

  6. Geomorphic observations from southwestern terminus of Palghat ...

    Indian Academy of Sciences (India)

    4National Centre for Earth Science Studies, Thiruvananthapuram, Kerala 695 031, India. ∗ .... Geomorphic observations from SW terminus of Palghat Gap, south India. 823. Figure. 2. ... tical point of view to determine an average state.

  7. Seismic observations of subglacial water discharge from glacier-dammed lake drainage at Lemon Creek Glacier, Alaska

    Science.gov (United States)

    Labedz, C. R.; Bartholomaus, T. C.; Gimbert, F.; Amundson, J. M.; Vore, M. E.; Karplus, M. S.; Tsai, V. C.

    2017-12-01

    Subglacial water flow affects the dynamics of glaciers, influencing basal sliding, sediment transport, fracturing, and terminus dynamics. However, the difficulty of directly observing glacial hydrologic systems creates significant challenges in understanding such glacier behavior. Recently-developed descriptions of ground motion generated by subglacial water flow provide a promising basis for new and unique characterization of glacial hydrologic systems. Particularly, high-frequency ( 1.5-20 Hz) seismic tremor observed near glaciers has been shown to correlate with subglacial runoff. In addition, specific properties of subglacial water flow like water pressure, conduit size, sediment flux, and grain size can be inferred by examining hysteretic behavior over time between different parts of these signals. In this study, we observe the seismic signals generated by subglacial water flow using a high-density array of more than 100 nodes deployed for 10-25 days, and six broadband seismometers deployed for 80 days at Lemon Creek Glacier, Alaska. Specifically, we examine the 36-hour drainage of a glacier-dammed lake into subglacial conduits, comparing hydrologic metrics such as lake level, precipitation, and outlet stream flow rate to the power of seismic signals. Our node array captures this annually-significant hydraulic transient with sensors spaced approximately every 250 m over the majority of the 5.7 km long glacier. This and other lake drainage events provide natural experiments for exploring glaciohydraulic tremor, because the increased water flux through the glacier increases the power of the tremor and hosts the hysteretic behaviors described previously. Analysis of the tremor from events such as this can be extended to further understand subglacial runoff at Lemon Creek glacier and for glacier hydrology in general.

  8. Changes of glacier lakes using multi-temporal remote sensing data: A case study from India

    Directory of Open Access Journals (Sweden)

    Kumar Rai Praveen

    2017-01-01

    Full Text Available The present study used the potential of Landsat multispectral data and ASTER-DEM data to identify the changes of glacier lakes in part of Chandra basin and surrounding of Himachal Pradesh of India from 1989 to 2013. The Barashigri, Chotashigri, Hamtahand Parvati glacier are the major glaciers within the area. The Landsat data of TM (1989 and 2009, ETM+ (2001 and OLI-TIRS (2013 sensors having different band combinations were analysed to monitor variation in the glacier lakes and area of glaciers and terminus whereas ASTER-DEM data was used for relief information. Glaciers terminus and glacial lakes were identified and mapped using false-colour composites (FCC with band combinations of red, near-infrared (NIR and shortwave infrared (SWIR, and a true-colour composite of red, green and NIR, of Landsat TM/ETM+ images and normalized difference water index (NDWI methods. It is observed that the number of lakes in the study area increased by 18.69% during the past 34 years while it was increased from 68 in 1989 to 89 in 2013. During the analysis, it is also found that the snow and glacier covered area within this period is also reduced from 1,317.39 to 1,125.59 km2.

  9. Water, Ice, and Meteorological Measurements at South Cascade Glacier, Washington, Balance Years 2004 and 2005

    Science.gov (United States)

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2007-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass-balance quantities for balance years 2004 and 2005. The North Cascade Range in the vicinity of South Cascade Glacier accumulated smaller than normal winter snowpacks during water years 2004 and 2005. Correspondingly, the balance years 2004 and 2005 maximum winter snow balances of South Cascade Glacier, 2.08 and 1.97 meters water equivalent, respectively, were smaller than the average of such balances since 1959. The 2004 glacier summer balance (-3.73 meters water equivalent) was the eleventh most negative during 1959 to 2005 and the 2005 glacier summer balance (-4.42 meters water equivalent) was the third most negative. The relatively small winter snow balances and unusually negative summer balances of 2004 and 2005 led to an overall loss of glacier mass. The 2004 and 2005 glacier net balances, -1.65 and -2.45 meters water equivalent, respectively, were the seventh and second most negative during 1953 to 2005. For both balance years, the accumulation area ratio was less than 0.05 and the equilibrium line altitude was higher than the glacier. The unusually negative 2004 and 2005 glacier net balances, combined with a negative balance previously reported for 2003, resulted in a cumulative 3-year net balance of -6.20 meters water equivalent. No equal or greater 3-year mass loss has occurred previously during the more than 4 decades of U.S. Geological Survey mass-balance measurements at South Cascade Glacier. Accompanying the glacier mass losses were retreat of the terminus and reduction of total glacier area. The terminus retreated at a rate of about 17 meters per year during balance year 2004 and 15 meters per year during balance year 2005. Glacier area near the end of balance years 2004 and 2005 was 1.82 and 1.75 square kilometers, respectively. Runoff from the basin containing the glacier and from an adjacent nonglacierized basin was

  10. Acceleration of Humboldt glacier, north Greenland

    Science.gov (United States)

    Jeong, S.; Howat, I.; Noh, M. J.; King, M. D.

    2017-12-01

    Here we report on recent abrupt acceleration on the flow speed of Humboldt Glacier (HG) in northern Greenland. The mean annual discharge of this glacier in 2000 was estimated as 8.4Gt/a, placing it among the largest outlet glacier draining the northern coast (Enderlin et al., 2014). Using a combination of remote sensing datasets, we find that following a slight slowing before 2010, HG suddenly sped up by a factor of three between 2012 and 2013, maintaining that increased speed through 2016. Speedup was accompanied by up to 10 m of thinning near the terminus and followed slower, longer-term thinning and retreat. Here we assess possible causes for the speedup, potential for continued acceleration and implication to ice sheet mass balance. ReferenceEnderlin, E. M., I. M. Howat, S. Jeong, M.-J. Noh, J. H. van Angelen, and M. R. van den Broeke (2014), An improved mass budget for the Greenland ice sheet, Geophys. Res. Lett., 41, 866-872, doi:10.1002/2013GL059010.

  11. Optical Remote Sensing of Glacier Characteristics: A Review with Focus on the Himalaya

    Science.gov (United States)

    Racoviteanu, Adina E.; Williams, Mark W.; Barry, Roger G.

    2008-01-01

    The increased availability of remote sensing platforms with appropriate spatial and temporal resolution, global coverage and low financial costs allows for fast, semi-automated, and cost-effective estimates of changes in glacier parameters over large areas. Remote sensing approaches allow for regular monitoring of the properties of alpine glaciers such as ice extent, terminus position, volume and surface elevation, from which glacier mass balance can be inferred. Such methods are particularly useful in remote areas with limited field-based glaciological measurements. This paper reviews advances in the use of visible and infrared remote sensing combined with field methods for estimating glacier parameters, with emphasis on volume/area changes and glacier mass balance. The focus is on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor and its applicability for monitoring Himalayan glaciers. The methods reviewed are: volumetric changes inferred from digital elevation models (DEMs), glacier delineation algorithms from multi-spectral analysis, changes in glacier area at decadal time scales, and AAR/ELA methods used to calculate yearly mass balances. The current limitations and on-going challenges in using remote sensing for mapping characteristics of mountain glaciers also discussed, specifically in the context of the Himalaya. PMID:27879883

  12. Role of the synaptobrevin C terminus in fusion pore formation

    DEFF Research Database (Denmark)

    Ngatchou, Annita N; Kisler, Kassandra; Fang, Qinghua

    2010-01-01

    Neurotransmitter release is mediated by the SNARE proteins synaptobrevin II (sybII, also known as VAMP2), syntaxin, and SNAP-25, generating a force transfer to the membranes and inducing fusion pore formation. However, the molecular mechanism by which this force leads to opening of a fusion pore...... stimulation, the SNARE complex pulls the C terminus of sybII deeper into the vesicle membrane. We propose that this movement disrupts the vesicular membrane continuity leading to fusion pore formation. In contrast to current models, the experiments suggest that fusion pore formation begins with molecular...

  13. Modeled and measured glacier change and related glaciological, hydrological, and meteorological conditions at South Cascade Glacier, Washington, balance and water years 2006 and 2007

    Science.gov (United States)

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2010-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass balance quantities for balance years 2006 and 2007. Mass balances were computed with assistance from a new model that was based on the works of other glacier researchers. The model, which was developed for mass balance practitioners, coupled selected meteorological and glaciological data to systematically estimate daily mass balance at selected glacier sites. The North Cascade Range in the vicinity of South Cascade Glacier accumulated approximately average to above average winter snow packs during 2006 and 2007. Correspondingly, the balance years 2006 and 2007 maximum winter snow mass balances of South Cascade Glacier, 2.61 and 3.41 meters water equivalent, respectively, were approximately equal to or more positive (larger) than the average of such balances since 1959. The 2006 glacier summer balance, -4.20 meters water equivalent, was among the four most negative since 1959. The 2007 glacier summer balance, -3.63 meters water equivalent, was among the 14 most negative since 1959. The glacier continued to lose mass during 2006 and 2007, as it commonly has since 1953, but the loss was much smaller during 2007 than during 2006. The 2006 glacier net balance, -1.59 meters water equivalent, was 1.02 meters water equivalent more negative (smaller) than the average during 1953-2005. The 2007 glacier net balance, -0.22 meters water equivalent, was 0.37 meters water equivalent less negative (larger) than the average during 1953-2006. The 2006 accumulation area ratio was less than 0.10, owing to isolated patches of accumulated snow that endured the 2006 summer season. The 2006 equilibrium line altitude was higher than the glacier. The 2007 accumulation area ratio and equilibrium line altitude were 0.60 and 1,880 meters, respectively. Accompanying the glacier mass losses were retreat of the terminus and reduction of total glacier area. The

  14. Emerging Glacial Lakes in the Cordillera Blanca, Peru: A Case Study at Arteson Glacier

    Science.gov (United States)

    Chisolm, R. E.; Mckinney, D. C.; Gomez, J.; Voss, K.

    2012-12-01

    Tropical glaciers are an essential component of the water resources systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean glaciers in recent decades. The shrinkage of Andean glaciers influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some glaciers. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical glaciers in Peru and how climate change is likely to impact glacial melt and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to glaciers in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect glacier mass balance. This study presents GPR data taken in July 2012 at the Arteson glacier in the Cordillera Blanca, Peru. A new lake has begun to form at the terminus of the Arteson glacier, and this lake has key features, including overhanging ice and loose rock likely to create landslides, that could trigger a catastrophic GLOF if the lake continues to grow. This new lake is part of a series of three lakes that have formed below the Arteson glacier. The two lower lakes, Artesonraju and Paron, are much larger so that if there were an avalanche or landslide into the new lake below Arteson glacier, the impact could potentially be more catastrophic than a GLOF from one single lake. Estimates of how the lake mass balance is likely to evolve due to the retreating glacier are key to assessing the flood risk from this dynamic three-lake system. Because the glacier mass balance and lake mass balance are closely linked, the ice thickness measurements and measurements of the bed slope of the Arteson glacier and underlying bedrock give us a clue to how the lake is likely to evolve. GPR measurements of

  15. Neoglacial fluctuations of terrestrial, tidewater, and calving lacustrine glaciers, Blackstone-Spencer Ice Complex, Kenai Mountains, Alaska

    Science.gov (United States)

    Crossen, Kristine June

    1997-12-01

    The glaciers surrounding the Blackstone-Spencer Ice Complex display a variety of termini types: Tebenkov, Spencer, Bartlett, Skookum, Trail, Burns, Shakespeare, Marquette, Lawrence, and Ripon glaciers end in terrestrial margins; Blackstone and Beloit glaciers have tidewater termini; and Portage Glacier has a calving lacustrine margin. In addition, steep temperature and precipitation gradients exist across the ice complex from the maritime environment of Prince William Sound to the colder, drier interior. The Neoglacial history of Tebenkov Glacier, as based on overrun trees near the terminus, shows advances ca. 250- 430 AD (calibrated date), ca. 1215-1275 AD (calibrated date), and ca. 1320-1430 AD (tree ring evidence), all intervals of glacier advance around the Gulf of Alaska. However, two tidewater glaciers in Blackstone Bay retreated from their outermost moraines by 1350 AD, apparently asynchronously with respect to the regional climate signal. The most extensive Kenai Mountain glacier expansions during Neoglaciation occurred in the late Little Ice Age. The outermost moraines are adjacent to mature forest stands and bog peats that yield dates as old as 5,600 BP. Prince William Sound glaciers advanced during two Little Ice Age cold periods, 1380-1680 and 1830-1900 AD. The terrestrial glaciers around the Blackstone-Spencer Ice Complex all built moraines during the 19th century and began retreating between 1875 and 1900 AD. Portage and Burns glaciers began retreating between 1790 and 1810 AD, but their margins remained close to the outermost moraines during the 19th century. Regional glacier fluctuations are broadly synchronous in the Gulf of Alaska region. With the exception of the two tidewater glaciers in Blackstone Bay, all glaciers in the Kenai Mountains, no matter their sizes, altitudes, orientations, or types of margins, retreated at the end of the Little Ice Age. The climate signal, especially temperature, appears to be the strongest control on glacier

  16. Glaciers and society

    DEFF Research Database (Denmark)

    Gagné, Karine; Rasmussen, Mattias Borg; Orlove, Ben

    2014-01-01

    As icons of a world set in motion by human action, glaciers are often highlighted as quintessential evidences of global climate change. Although there is a general agreement among scientists that glaciers around the world are receding, much of the discussions on the subject tend to be oriented...... true when esthetic and economic values are assigned to glaciers. Real and perceived changes in the form, reach and out-flow of water impact the local populations, and shape the kinds of action undertaken by communities, local actors, state authorities, and international organizations. The paper...

  17. OPTICAL FLOW FOR GLACIER MOTION ESTIMATION

    Directory of Open Access Journals (Sweden)

    C. Vogel

    2012-07-01

    Full Text Available Quantitative measurements of glacier flow over time are an important ingredient for glaciological research, for example to determine the mass balances and the evolution of glaciers. Measuring glacier flow in multi-temporal images involves the estimation of a dense set of corresponding points, which in turn define the flow vectors. Furthermore glaciers exhibit rather difficult radiometry, since their surface usually contains homogeneous areas as well as weak texture and contrast. To date glacier flow is usually observed by manually measuring a sparse set of correspondences, which is labor-intensive and often yields rather irregular point distributions, with the associated problems of interpolating over large areas. In the present work we propose to densely compute motion vectors at every pixel, by using recent robust methods for optic flow computation. Determining the optic flow, i.e. the dense deformation field between two images of a dynamic scene, has been a classic, long-standing research problem in computer vision and image processing. Sophisticated methods exist to optimally balance data fidelity with smoothness of the motion field. Depending on the strength of the local image gradients these methods yield a smooth trade-off between matching and interpolation, thereby avoiding the somewhat arbitrary decision which discrete anchor points to measure, while at the same time mitigating the problem of gross matching errors. We evaluate our method by comparing with manually measured point wise ground truth.

  18. Application of a minimal glacier model to Hansbreen, Svalbard

    Directory of Open Access Journals (Sweden)

    J. Oerlemans

    2011-01-01

    Full Text Available Hansbreen is a well studied tidewater glacier in the southwestern part of Svalbard, currently about 16 km long. Since the end of the 19th century it has been retreating over a distance of 2.7 km. In this paper the global dynamics of Hansbreen are studied with a minimal glacier model, in which the ice mechanics are strongly parameterised and a simple law for iceberg calving is used. The model is calibrated by reconstructing a climate history in such a way that observed and simulated glacier length match. In addition, the calving law is tuned to reproduce the observed mean calving flux for the period 2000–2008.

    Equilibrium states are studied for a wide range of values of the equilibrium line altitude. The dynamics of the glacier are strongly nonlinear. The height-mass balance feedback and the water depth-calving flux feedback give rise to cusp catastrophes in the system.

    For the present climatic conditions Hansbreen cannot survive. Depending on the imposed climate change scenario, in AD 2100 Hansbreen is predicted to have a length between 10 and 12 km. The corresponding decrease in ice volume (relative to the volume in AD 2000 is 45 to 65%.

    Finally the late-Holocene history of Hansbreen is considered. We quote evidence from dated peat samples that Hansbreen did not exist during the Holocene Climatic Optimum. We speculate that at the end of the mid-Holocene Climatic Optimum Hansbreen could advance because the glacier bed was at least 50 m higher than today, and because the tributary glaciers on the western side may have supplied a significant amount of mass to the main stream. The excavation of the overdeepening and the formation of the shoal at the glacier terminus probably took place during the Little Ice Age.

  19. Modelled and observed mass balance of Rikha Samba Glacier, Nepal, Central Himalaya

    Science.gov (United States)

    Gurung, T. R.; Kayastha, R. B.; Fujita, K.; Sinisalo, A. K.; Stumm, D.; Joshi, S.; Litt, M.

    2016-12-01

    Glacier mass balance variability has an implication for the regional water resources and it helps to understand the response of glacier to climate change in the Himalayan region. Several mass balance studies have been started in the Himalayan region since 1970s, but they are characterized by frequent temporal gaps and a poor spatial representatively. This study aims at bridging the temporal gaps in a long term mass balance series of the Rikha Samba glacier (5383 - 6475 m a.s.l.), a benchmark glacier located in the Hidden Valley, Mustang, Nepal. The ERA Interim reanalysis data for the period 2011-2015 is calibrated with the observed meteorological variables from an AWS installed near the glacier terminus. We apply an energy mass balance model, validated with the available in-situ measurements for the years 1998 and 2011-2015. The results show that the glacier is shrinking at a moderate negative mass balance rate for the period 1995 to 2015 and the high altitude location of Rikha Samba also prevents a bigger mass loss compared to other small Himalayan glaciers. Precipitation from July to January and the mean air temperature from June to October are the most influential climatic parameters of the annual mass balance variability of Rikha Samba glacier.

  20. Water, ice, and meteorological measurements at South Cascade Glacier, Washington, balance year 2002

    Science.gov (United States)

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2004-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass balance quantities for balance year 2002. The 2002 glacier-average maximum winter snow balance was 4.02 meters, the second largest since 1959. The 2002 glacier summer, net, and annual (water year) balances were -3.47, 0.55, and 0.54 meters, respectively. The area of the glacier near the end of the balance year was 1.92 square kilometers, and the equilibrium-line altitude and the accumulation area ratio were 1,820 meters and 0.84, respectively. During September 20, 2001 to September 13, 2002, the terminus retreated 4 meters, and computed average ice speeds in the ablation area ranged from 7.8 to 20.7 meters per year. Runoff from the subbasin containing the glacier and from an adjacent non-glacierized basin were measured during part of the 2002 water year. Air temperature, precipitation, atmospheric water-vapor pressure, wind speed and incoming solar radiation were measured at selected locations near the glacier.

  1. Hillslope failure and paraglacial reworking of sediments in response to glacier retreat, Fox Valley, New Zealand.

    Science.gov (United States)

    McColl, Samuel T.; Fuller, Ian C.; Anderson, Brian; Tate, Rosie

    2017-04-01

    Climate and glacier fluctuations influence sediment supply to glacier forelands, which in turn influences down-valley hazards to infrastructure and tourism within glacier forelands. At Fox Glacier, one of New Zealand's most iconic and popular glaciers, rapid retreat has initiated a range of hillslope and valley floor responses, that present a cascade of hazards and changes that need to be carefully managed. Fox Glacier has retreated many kilometres historically, with 2.6 km of retreat since the mid-20th century, and a phase of rapid retreat of 50-340 m per year since 2009. To study the system response to past and ongoing glacial retreat at the Fox valley, morphological changes are being observed using time-lapse photography and the annual collection of high-resolution digital elevation models (DEMs) and orthophoto mosaics. The DEMs are being produced using Structure from Motion photogrammetry from UAV/RPAS and helicopter platforms, and are being used, along with manual ground surveying, to produce ground surface change models (DoDs; DEMs of Difference) and sediment budgets for the valley. Results from time-lapse photography and DoDs show that glacial retreat has initiated destabilisation and (mostly chronic) mass movement of surficial glacial sediments on the valley slopes near the glacier terminus. Alluvial fans farther down valley are actively growing, reworking glacial and landslide sediments from tributary catchments. These paraglacial sediments being delivered to the proglacial river from the glacier terminus and alluvial fans are driving aggradation of the valley floor of decimetres to metres per year and maintaining a highly dynamic braid plain. Valley floor changes also include the melting of buried dead ice, which are causing localised subsidence at the carpark and one of the alluvial fans. The unstable slopes and active debris fans, aggrading and highly active river channel, ground subsidence, add to the spectacle but also the hazards of the Fox valley

  2. Directly measuring melt at a vertical face tidewater glacier: is it possible?

    Science.gov (United States)

    Sutherland, D.; Amundson, J. M.; Duncan, D.; Jackson, R. H.; Kienholz, C.; Motyka, R. J.; Nash, J. D.

    2017-12-01

    Direct observations of melt on the underwater portion of tidewater glaciers have proved elusive, mostly due to the inherent dangers of making measurements next to a calving ice front. Additionally, the melting process itself is often masked by large ice speeds, variable calving across the glacier front, and enhanced melting due to rising subglacial discharge plumes. Here, we use repeat multibeam sonar images of LeConte Glacier to assess the possibility of measuring terminus melt in situ. LeConte Glacier is a fast-moving tidewater system in southeast Alaska with ice speeds of 25 m d-1 and previously estimated submarine melting that accounts for 50% of ice loss at the front. In August 2016, May 2017, and September 2017, we conducted intensive fieldwork at the 1.5 km long, 250 m deep glacier front, collecting dozens of repeat multibeam images of the underwater terminus. Combined with coincident time-lapse photography and surface radar measurements, we attempt to disentangle the ambient melt at the glacier face from ice motion and calving. We use a suite of oceanographic observations of the emerging subglacial discharge plume to separate portions of the glacier front that show evidence of enhanced melting versus portions outside of the affected plume areas. We find a complex, time-varying geometry, with regions of undercutting, overcutting, and large discharge channels. Measurements like these are critical to i) improving numerical model parameterizations of coupled glacier-ocean interactions and ii) developing a process-based understanding of how the literal ice-ocean boundary evolves in time and space.

  3. Spatio Temporal Change of Selected Glaciers Along Karakoram Highway from 1994-2017 Using Remote Sensing and GIS Techniques

    Science.gov (United States)

    Anwar, Yasmeen; Iqbal, Javed

    2018-04-01

    With the acceleration of global warming glaciers are receding rapidly. Monitoring of glaciers are important because they caused outburst of floods the past. This research delivers a systematic approach for the assessment of glaciers i.e. Batura, Passu, Ghulkin and Gulmit cover along the Karakoram Highway. Main reason to select these glaciers was their closeness to Karakoram Highway which plays an important role in China-Pakistan economic corridor (CPEC). This study incorporates the techniques of Geographical Information System and Remote Sensing (GIS & RS). For this study, Landsat 4,5,7,8 images were taken for the years of 1994, 2002, 2009, 2013 and 2017. Using the said images supervised classification was done in ArcMap 10.3 version to identify the changes in glaciers. The area was categorized into six major classes' i.e. Fresh snow, Glaciers, Debris, Vegetation, Water bodies and Open land. Classified results showed a decrease in the area of Glaciers, almost 3.5% from 1994 to 2017. GLIMS data about boundary of glaciers of 1999 and 2007 was compared with the classified results which show decrease in terminus of glaciers. Batura glacier has been receded almost 0.6 km from 1999 to 2017, whereas Passu glaciers receded 0.3 km, whereas Gulmit and Ghulkin glaciers are more stable than Passu and Batura with the difference of -0.05 and +0.57 km respectively. At the end results from classified maps were compared with the climatic data. Wherein temperature is rapidly increasing resulting in melting of glaciers and can cause shrinkage of fresh water as well as destruction to Karakoram highway in case of outburst floods.

  4. The GLIMS Glacier Database

    Science.gov (United States)

    Raup, B. H.; Khalsa, S. S.; Armstrong, R.

    2007-12-01

    The Global Land Ice Measurements from Space (GLIMS) project has built a geospatial and temporal database of glacier data, composed of glacier outlines and various scalar attributes. These data are being derived primarily from satellite imagery, such as from ASTER and Landsat. Each "snapshot" of a glacier is from a specific time, and the database is designed to store multiple snapshots representative of different times. We have implemented two web-based interfaces to the database; one enables exploration of the data via interactive maps (web map server), while the other allows searches based on text-field constraints. The web map server is an Open Geospatial Consortium (OGC) compliant Web Map Server (WMS) and Web Feature Server (WFS). This means that other web sites can display glacier layers from our site over the Internet, or retrieve glacier features in vector format. All components of the system are implemented using Open Source software: Linux, PostgreSQL, PostGIS (geospatial extensions to the database), MapServer (WMS and WFS), and several supporting components such as Proj.4 (a geographic projection library) and PHP. These tools are robust and provide a flexible and powerful framework for web mapping applications. As a service to the GLIMS community, the database contains metadata on all ASTER imagery acquired over glacierized terrain. Reduced-resolution of the images (browse imagery) can be viewed either as a layer in the MapServer application, or overlaid on the virtual globe within Google Earth. The interactive map application allows the user to constrain by time what data appear on the map. For example, ASTER or glacier outlines from 2002 only, or from Autumn in any year, can be displayed. The system allows users to download their selected glacier data in a choice of formats. The results of a query based on spatial selection (using a mouse) or text-field constraints can be downloaded in any of these formats: ESRI shapefiles, KML (Google Earth), Map

  5. The imbalance of glaciers after disintegration of Larsen-B ice shelf, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    H. Rott

    2011-03-01

    Full Text Available The outlet glaciers to the embayment of the Larsen-B Ice Shelf started to accelerate soon after the ice shelf disintegrated in March 2002. We analyse high resolution radar images of the TerraSAR-X satellite, launched in June 2007, to map the motion of outlet glaciers in detail. The frontal velocities are used to estimate the calving fluxes for 2008/2009. As reference for pre-collapse conditions, when the glaciers were in balanced state, the ice fluxes through the same gates are computed using ice motion maps derived from interferometric data of the ERS-1/ERS-2 satellites in 1995 and 1999. Profiles of satellite laser altimetry from ICESat, crossing the terminus of several glaciers, indicate considerable glacier thinning between 2003 and 2007/2008. This is taken into account for defining the calving cross sections. The difference between the pre- and post-collapse fluxes provides an estimate on the mass imbalance. For the Larsen-B embayment the 2008 mass deficit is estimated at 4.34 ± 1.64 Gt a−1, significantly lower than previously published values. The ice flow acceleration follows a similar pattern on the various glaciers, gradually decreasing in magnitude with distance upstream from the calving front. This suggests stress perturbation at the glacier front being the main factor for acceleration. So far there are no signs of slow-down indicating that dynamic thinning and frontal retreat will go on.

  6. Regional cooling caused recent New Zealand glacier advances in a period of global warming.

    Science.gov (United States)

    Mackintosh, Andrew N; Anderson, Brian M; Lorrey, Andrew M; Renwick, James A; Frei, Prisco; Dean, Sam M

    2017-02-14

    Glaciers experienced worldwide retreat during the twentieth and early twenty first centuries, and the negative trend in global glacier mass balance since the early 1990s is predominantly a response to anthropogenic climate warming. The exceptional terminus advance of some glaciers during recent global warming is thought to relate to locally specific climate conditions, such as increased precipitation. In New Zealand, at least 58 glaciers advanced between 1983 and 2008, and Franz Josef and Fox glaciers advanced nearly continuously during this time. Here we show that the glacier advance phase resulted predominantly from discrete periods of reduced air temperature, rather than increased precipitation. The lower temperatures were associated with anomalous southerly winds and low sea surface temperature in the Tasman Sea region. These conditions result from variability in the structure of the extratropical atmospheric circulation over the South Pacific. While this sequence of climate variability and its effect on New Zealand glaciers is unusual on a global scale, it remains consistent with a climate system that is being modified by humans.

  7. Climate, glacier mass balance and runoff (1993-2005) for the Mittivakkat Glacier catchment, Ammassalik Island, SE Greenland, and in a long term perspective (1898-1993)

    DEFF Research Database (Denmark)

    Mernild, Sebastian H.; Kane, D.L.; Hansen, Birger

    2008-01-01

    temperatures (MAAT) occur in the coastal area, indicating an approximately 20-d shorter thawing period. The higher lying glacier area, in contrast, experiences an increasing MAAT, an approximately 40-d longer thawing period and a 60-d longer snow-free period. The Mittivakkat Glacier net mass balance has been...... almost continuously negative, corresponding to an average loss of glacier volume of 0.4% yr-1. The total catchment runoff is averaging 1973±281 mm w.eq. yr-1, and around 30% of the runoff is explained by glacier net loss. Over the 106 years (1898-2004) MAAT has, on average, increased significantly...

  8. The effect of temperature change on the microbial diversity and community structure along the chronosequence of the sub-arctic glacier forefield of Styggedalsbreen (Norway).

    Science.gov (United States)

    Mateos-Rivera, Alejandro; Yde, Jacob C; Wilson, Bryan; Finster, Kai W; Reigstad, Laila J; Øvreås, Lise

    2016-04-01

    Microbial communities in the glacier forefield of Styggedalsbreen, Norway, were investigated along a chronosequence from newly exposed soil to vegetated soils using next-generation sequencing of the 16S rRNA gene. In order to monitor the short-term effect of temperature on community successions along the soil gradient, the soil samples were incubated at three different temperatures (5°C, 10°C and 22°C). The microbial community composition along the chronosequence differed according to distance from the glacial terminus and incubation temperature. Samples close to the glacier terminus were dominated by Proteobacteria at 5°C and 10°C, while at 22°C members of Chloroflexi, Acidobacteria and Verrucomicrobia in addition to Proteobacteria accounted for most of the diversity, indicating that sites close to the glacier terminus are more closely related to former subglacial environments. Within the Archaea domain, members of the phylum Euryarchaeota dominated in samples closer to the glacier terminus with a shift to members of the phyla Thaumarchaeota-Crenarchaeota with increased soil age. Our data indicate that composition and diversity of the microbial communities along the glacier forefield depend not only on exposure time but are also to a large degree influenced by soil surface temperature and soil maturation. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  9. Modeling the Rock Glacier Cycle

    Science.gov (United States)

    Anderson, R. S.; Anderson, L. S.

    2016-12-01

    Rock glaciers are common in many mountain ranges in which the ELA lies above the peaks. They represent some of the most identifiable components of today's cryosphere in these settings. Their oversteepened snouts pose often-overlooked hazards to travel in alpine terrain. Rock glaciers are supported by avalanches and by rockfall from steep headwalls. The winter's avalanche cone must be sufficiently thick not to melt entirely in the summer. The spatial distribution of rock glaciers reflects this dependence on avalanche sources; they are most common on lee sides of ridges where wind-blown snow augments the avalanche source. In the absence of rockfall, this would support a short, cirque glacier. Depending on the relationship between rockfall and avalanche patterns, "talus-derived" and "glacier-derived" rock glaciers are possible. Talus-derived: If the spatial distribution of rock delivery is similar to the avalanche pattern, the rock-ice mixture will travel an englacial path that is downward through the short accumulation zone before turning upward in the ablation zone. Advected debris is then delivered to the base of a growing surface debris layer that reduces the ice melt rate. The physics is identical to the debris-covered glacier case. Glacier-derived: If on the other hand rockfall from the headwall rolls beyond the avalanche cone, it is added directly to the ablation zone of the glacier. The avalanche accumulation zone then supports a pure ice core to the rock glacier. We have developed numerical models designed to capture the full range of glacier to debris-covered glacier to rock glacier behavior. The hundreds of meter lengths, tens of meters thicknesses, and meter per year speeds of rock glaciers are well described by the models. The model can capture both "talus-derived" and "glacier-derived" rock glaciers. We explore the dependence of glacier behavior on climate histories. As climate warms, a pure ice debris-covered glacier can transform to a much shorter rock

  10. Simulating ice thickness and velocity evolution of Upernavik Isstrøm 1849-2012 by forcing prescribed terminus positions in ISSM

    Science.gov (United States)

    Haubner, Konstanze; Box, Jason E.; Schlegel, Nicole J.; Larour, Eric Y.; Morlighem, Mathieu; Solgaard, Anne M.; Kjeldsen, Kristian K.; Larsen, Signe H.; Rignot, Eric; Dupont, Todd K.; Kjær, Kurt H.

    2018-04-01

    Tidewater glacier velocity and mass balance are known to be highly responsive to terminus position change. Yet it remains challenging for ice flow models to reproduce observed ice margin changes. Here, using the Ice Sheet System Model (ISSM; Larour et al. 2012), we simulate the ice velocity and thickness changes of Upernavik Isstrøm (north-western Greenland) by prescribing a collection of 27 observed terminus positions spanning 164 years (1849-2012). The simulation shows increased ice velocity during the 1930s, the late 1970s and between 1995 and 2012 when terminus retreat was observed along with negative surface mass balance anomalies. Three distinct mass balance states are evident in the reconstruction: (1849-1932) with near zero mass balance, (1932-1992) with ice mass loss dominated by ice dynamical flow, and (1998-2012), when increased retreat and negative surface mass balance anomalies led to mass loss that was twice that of any earlier period. Over the multi-decadal simulation, mass loss was dominated by thinning and acceleration responsible for 70 % of the total mass loss induced by prescribed change in terminus position. The remaining 30 % of the total ice mass loss resulted directly from prescribed terminus retreat and decreasing surface mass balance. Although the method can not explain the cause of glacier retreat, it enables the reconstruction of ice flow and geometry during 1849-2012. Given annual or seasonal observed terminus front positions, this method could be a useful tool for evaluating simulations investigating the effect of calving laws.

  11. Mechanisms of basal ice formation in polar glaciers: An evaluation of the apron entrainment model

    Science.gov (United States)

    Fitzsimons, Sean; Webb, Nicola; Mager, Sarah; MacDonell, Shelley; Lorrain, Regi; Samyn, Denis

    2008-06-01

    Previous studies of polar glaciers have argued that basal ice can form when these glaciers override and entrain ice marginal aprons that accumulate adjacent to steep ice cliffs. To test this idea, we have studied the morphology, structure, composition, and deformation of the apron and basal ice at the terminus of Victoria Upper Glacier in the McMurdo dry valleys, which are located on the western coast of the Ross Sea at 77°S in southern Victoria Land, Antarctica. Our results show that the apron has two structural elements: an inner element that consists of strongly foliated ice that has a steep up-glacier dip, and an outer element that lacks a consistent foliation and has a down-glacier, slope-parallel dip. Although strain measurements show that the entire apron is deforming, the inner element is characterized by high strain rates, whereas relatively low rates of strain characterize the outer part of the apron. Co-isotopic analyses of the ice, together with analysis of solute chemistry and sedimentary characteristics, show that the apron is compositionally different from the basal ice. Our observations show that aprons may become deformed and partially entrained by advancing glaciers. However, such an ice marginal process does not provide a satisfactory explanation for the origin of basal ice observed at the ice margin. Our interpretation of the origin of basal ice is that it is formed by subglacial processes, which are likely to include deformation and entrainment of subglacial permafrost.

  12. GLACIERS OF THE KORYAK VOLCANO

    Directory of Open Access Journals (Sweden)

    T. M. Manevich

    2012-01-01

    Full Text Available The paper presents main glaciological characteristics of present-day glaciers located on the Koryaksky volcano. The results of fieldwork (2008–2009 and high-resolution satellite image analysis let us to specify and complete information on modern glacial complex of Koryaksky volcano. Now there are seven glaciers with total area 8.36 km2. Three of them advance, two are in stationary state and one degrades. Moreover, the paper describes the new crater glacier.

  13. Impact of External Forcing on Glacier Dynamics at Jakobshavn Isbræ during 1840-2012

    DEFF Research Database (Denmark)

    Muresan, Ioana Stefania; Khan, Shfaqat Abbas; Aschwanden, Andy

    warm period occurred. To control the acceleration and retreat based on observed front positions during 1840-2012, we use an ocean model modifier that implements forcing at the ocean boundary using melange back pressure offsets. The mean temperature anomaly in west Greenland, the North Atlantic......Greenland's main outlet glaciers have more than doubled their contribution to global sea-level rise over the past decade through acceleration of ice discharge. One of the triggering mechanisms is a reduction in resistance (buttressing) at the marine based glacier front (i.e. through reduced...... thickness or retreat of the floating tongue of a glacier) caused by enhanced calving or a longer-term thinning due to a mass deficit of the ice sheet. Recent findings indicate the reduced buttressing at the marine terminus is responsible for the recent dynamic changes observed in Greenland...

  14. The Open Global Glacier Model

    Science.gov (United States)

    Marzeion, B.; Maussion, F.

    2017-12-01

    Mountain glaciers are one of the few remaining sub-systems of the global climate system for which no globally applicable, open source, community-driven model exists. Notable examples from the ice sheet community include the Parallel Ice Sheet Model or Elmer/Ice. While the atmospheric modeling community has a long tradition of sharing models (e.g. the Weather Research and Forecasting model) or comparing them (e.g. the Coupled Model Intercomparison Project or CMIP), recent initiatives originating from the glaciological community show a new willingness to better coordinate global research efforts following the CMIP example (e.g. the Glacier Model Intercomparison Project or the Glacier Ice Thickness Estimation Working Group). In the recent past, great advances have been made in the global availability of data and methods relevant for glacier modeling, spanning glacier outlines, automatized glacier centerline identification, bed rock inversion methods, and global topographic data sets. Taken together, these advances now allow the ice dynamics of glaciers to be modeled on a global scale, provided that adequate modeling platforms are available. Here, we present the Open Global Glacier Model (OGGM), developed to provide a global scale, modular, and open source numerical model framework for consistently simulating past and future global scale glacier change. Global not only in the sense of leading to meaningful results for all glaciers combined, but also for any small ensemble of glaciers, e.g. at the headwater catchment scale. Modular to allow combinations of different approaches to the representation of ice flow and surface mass balance, enabling a new kind of model intercomparison. Open source so that the code can be read and used by anyone and so that new modules can be added and discussed by the community, following the principles of open governance. Consistent in order to provide uncertainty measures at all realizable scales.

  15. Listening to Glaciers: Passive hydroacoustics near marine-terminating glaciers

    Science.gov (United States)

    Pettit, E.C.; Nystuen, J.A.; O'Neel, Shad

    2012-01-01

    The catastrophic breakup of the Larsen B Ice Shelf in the Weddell Sea in 2002 paints a vivid portrait of the effects of glacier-climate interactions. This event, along with other unexpected episodes of rapid mass loss from marine-terminating glaciers (i.e., tidewater glaciers, outlet glaciers, ice streams, ice shelves) sparked intensified study of the boundaries where marine-terminating glaciers interact with the ocean. These dynamic and dangerous boundaries require creative methods of observation and measurement. Toward this effort, we take advantage of the exceptional sound-propagating properties of seawater to record and interpret sounds generated at these glacial ice-ocean boundaries from distances safe for instrument deployment and operation.

  16. Estimating stream discharge from a Himalayan Glacier using coupled satellite sensor data

    Science.gov (United States)

    Child, S. F.; Stearns, L. A.; van der Veen, C. J.; Haritashya, U. K.; Tarpanelli, A.

    2015-12-01

    The 4th IPCC report highlighted our limited understanding of Himalayan glacier behavior and contribution to the region's hydrology. Seasonal snow and glacier melt in the Himalayas are important sources of water, but estimates greatly differ about the actual contribution of melted glacier ice to stream discharge. A more comprehensive understanding of the contribution of glaciers to stream discharge is needed because streams being fed by glaciers affect the livelihoods of a large part of the world's population. Most of the streams in the Himalayas are unmonitored because in situ measurements are logistically difficult and costly. This necessitates the use of remote sensing platforms to obtain estimates of river discharge for validating hydrological models. In this study, we estimate stream discharge using cost-effective methods via repeat satellite imagery from Landsat-8 and SENTINEL-1A sensors. The methodology is based on previous studies, which show that ratio values from optical satellite bands correlate well with measured stream discharge. While similar, our methodology relies on significantly higher resolution imagery (30 m) and utilizes bands that are in the blue and near-infrared spectrum as opposed to previous studies using 250 m resolution imagery and spectral bands only in the near-infrared. Higher resolution imagery is necessary for streams where the source is a glacier's terminus because the width of the stream is often only 10s of meters. We validate our methodology using two rivers in the state of Kansas, where stream gauges are plentiful. We then apply our method to the Bhagirathi River, in the North-Central Himalayas, which is fed by the Gangotri Glacier and has a well monitored stream gauge. The analysis will later be used to couple river discharge and glacier flow and mass balance through an integrated hydrologic model in the Bhagirathi Basin.

  17. Bacteria at glacier surfaces: microbial community structures in debris covered glaciers and cryoconites in the Italian Alps

    Science.gov (United States)

    Azzoni, Roberto; Franzetti, Andrea; Ambrosini, Roberto; D'Agata, Carlo; Senese, Antonella; Minora, Umberto; Tagliaferri, Ilario; Diolaiuti, Guglielmina

    2014-05-01

    Supraglacial debris has an important role in the glacier energy budget and has strong influence on the glacial ecosystem. Sediment derives generally from rock inputs from nesting rockwalls and are abundant and continuous at the surface of debris-covered glaciers (i.e. DCGs; glaciers where the ablation area is mainly covered by rock debris) and sparse and fine on debris-free glaciers (DFGs). Recently, evidence for significant tongue darkening on retreating debris-free glaciers has been drawing increasing attention. Fine particles, the cryoconite, are locally abundant and may form cryoconite holes that are water-filled depressions on the surface of DFGs that form when a thin layer of cryoconite is heated by the sun and melts the underlying ice. There is increasing evidence that cryoconite holes also host highly diverse microbial communities and can significantly contribute to global carbon cycle. However, there is almost no study on microbial communities of the debris cover of DCGs and there is a lack of data from the temporal evolution of the microbial communities in the cryoconites. To fill these gaps in our knowledge we characterized the supraglacial debris of two Italian DCGs and we investigated the temporal evolution of microbial communities on cryoconite holes in DFG. We used the Illumina technology to analyse the V5 and V6 hypervariable regions of the bacterial 16S rRNA gene amplified from samples collected distances from the terminus of two DCGs (Miage and Belvedere Glaciers - Western Italian Alps). Heterotrophic taxa dominated bacterial communities, whose structure changed during downwards debris transport. Organic carbon of these recently exposed substrates therefore is probably provided more by allochthonous deposition of organic matter than by primary production by autotrophic organisms. We used ARISA fingerprinting and quantitative PCR to describe the structure and the evolution of the microbial communities and to estimate the number of the total

  18. Estimation of basal shear stresses from now ice-free LIA glacier forefields in the Swiss Alps

    Science.gov (United States)

    Fischer, Mauro; Haeberli, Wilfried; Huss, Matthias; Paul, Frank; Linsbauer, Andreas; Hoelzle, Martin

    2013-04-01

    accuracy of the ice thickness determination and thus on the accuracy of the LIA DEMs used. Good results are expected for LIA valley or mountain glaciers with ice thicknesses larger than 100 m at the position of their terminus in 1973. Calculated shear stresses are representative in terms of average values over 20 to 40% of the total glacier length in 1850. Shear stresses strongly vary with glacier size, topographic conditions and climate. This study confirmed that reasonable values for mean basal shear stress of mountain glaciers can be estimated from an empirical and non-linear relation using the vertical extent as a proxy for mass turnover. The now available database could be used to independently test the plausibility of approaches applying simple flow models.

  19. Tidal Modulation of Ice Flow on Kangerdlugssuaq and Helheim Glaciers, East Greenland, from High-Rate GPS Measurements

    DEFF Research Database (Denmark)

    Hamilton, G. S.; Stearns, L. A.; Elosegui, P.

    knowledge of ice thickness and fjord bathymetry. Here, we use high-rate GPS measurements collected at sites within a few km of the calving fronts of Kangerdlugssuaq and Helheim glaciers to examine the effect of ocean tide on ice flow. Data were collected at 5-15 s sampling rate during several campaign...... appears to have a short floating tongue, based on an analysis of GPS data collected in June-August 2006 at several stations located at increasing distances from the calving front. Glacier uplift was in phase with measured and modeled tidal height, but attenuated rapidly beyond ~~1 km from the terminus. We...

  20. Storm-induced water dynamics and thermohaline structure at the tidewater Flade Isblink Glacier outlet to theWandel Sea (NE Greenland)

    DEFF Research Database (Denmark)

    Kirillov, Sergei; Dmitrenko, Igor; Rysgaard, Soren

    2017-01-01

    In April 2015, an ice-tethered conductivity-temperature-depth (CTD) profiler and a down-looking acoustic Doppler current profiler (ADCP) were deployed from the landfast ice near the tidewater glacier terminus of the Flade Isblink Glacier in the Wandel Sea, NE Greenland. The 3-week time series...... are likely attributable to subglacial water from the Flade Isblink Ice Cap. It was also found that the semidiurnal periodicities in the temperature and salinity time series were associated with the lunar semidiurnal tidal flow. The vertical structure of tidal currents corresponded to the first baroclinic...... mode of the internal tide with a velocity minimum at similar to 40 m. The tidal ellipses rotate in opposite directions above and below this depth and cause a divergence of tidal flow, which was observed to induce semidiurnal internal waves of about 3 m height at the front of the glacier terminus...

  1. Comparison of tropical and subtropical glacier surface energy balance in Africa and South America

    Science.gov (United States)

    Nicholson, L.; Prinz, R.; Kinnard, C.; Mölg, T.; Winkler, M.; Kaser, G.

    2010-05-01

    Tropical glaciers exist only at high altitude, and meteorological and surface energy balance studies of these glaciers can tell us much about the conditions and changes occurring in the mid troposphere. Understanding the surface energy balance and resultant mass balance regime of tropical glaciers is prerequisite to predicting glacier evolution, and future meltwater contributions to local hydrological resources, in response to future climate scenarios. Tropical glacier mass balance variability is strongly linked to precipitation and, via this, to multi-annual climate oscillations such as ENSO and IOZM, so it is useful to understand what role these differing regional influences play in comparison to the similarities imposed by the overarching tropical climate conditions and seasonality. New surface energy balance and mass balance data is available from Lewis glacier (Kenya, 0°09' S; 37°18' E), and here we use an energy and mass balance model to determine the surface energy flux characteristics at this site through a wet and dry season. Results are compared with those from Kersten glacier (Tanzania, 3°04' S; 37°21' E) to understand how conditions at these two glaciers compare and thus what coherent and contrasting climatic information glaciological records from these two sites can be expected to deliver. Meteorological data available from glacier stations on Antizana (Ecuador, 0°25' S; 78°09' W), Artesonraju (Peru, 8°28' S; 77°38' W) Zongo (Bolivia, 16°39' S; 67°47' W) and Guanaco (Chile, 29°20' S; 70°00' W) glaciers in South America offer the opportunity to examine how the surface fluxes and seasonal variability of the energy balance compares to those of the African glaciers. We include the extra-tropical Chilean example for comparison with the similarly high altitude, cold ice of Kersten glacier.

  2. Modelling historical and recent mass loss of McCall Glacier, Alaska, USA

    Directory of Open Access Journals (Sweden)

    C. Delcourt

    2008-03-01

    Full Text Available Volume loss of valley glaciers is now considered to be a significant contribution to sea level rise. Understanding and identifying the processes involved in accelerated mass loss are necessary to determine their impact on the global system. Here we present results from a series of model experiments with a higher-order thermomechanically coupled flowline model (Pattyn, 2002. Boundary conditions to the model are parameterizations of surface mass balance, geothermal heating, observed surface and 10 m ice depth temperatures. The time-dependent experiments aim at simulating the glacier retreat from its LIA expansion to present according to different scenarios and model parameters. Model output was validated against measurements of ice velocity, ice surface elevation and terminus position at different stages. Results demonstrate that a key factor in determining the glacier retreat history is the importance of internal accumulation (>50% in the total mass balance. The persistence of a basal temperate zone characteristic for this polythermal glacier depends largely on its contribution. Accelerated glacier retreat since the early nineties seems directly related to the increase in ELA and the sudden reduction in AAR due to the fact that a large lower elevation cirque – previously an important accumulation area – became part of the ablation zone.

  3. Recent glacier retreat and climate trends in Cordillera Huaytapallana, Peru

    Science.gov (United States)

    López-Moreno, J. I.; Fontaneda, S.; Bazo, J.; Revuelto, J.; Azorin-Molina, C.; Valero-Garcés, B.; Morán-Tejeda, E.; Vicente-Serrano, S. M.; Zubieta, R.; Alejo-Cochachín, J.

    2014-01-01

    We analyzed 19 annual Landsat Thematic Mapper images from 1984 to 2011 to determine changes of the glaciated surface and snow line elevation in six mountain areas of the Cordillera Huaytapallana range in Peru. In contrast to other Peruvian mountains, glacier retreat in these mountains has been poorly documented, even though this is a heavily glaciated area. These glaciers are the main source of water for the surrounding lowlands, and melting of these glaciers has triggered several outburst floods. During the 28-year study period, there was a 55% decrease in the surface covered by glaciers and the snowline moved upward in different regions by 93 to 157 m. Moreover, several new lakes formed in the recently deglaciated areas. There was an increase in precipitation during the wet season (October-April) over the 28-year study period. The significant increase in maximum temperatures may be related to the significant glacier retreat in the study area. There were significant differences in the wet season temperatures during El Niño (warmer) and La Niña (colder) years. Although La Niña years were generally more humid than El Niño years, these differences were not statistically significant. Thus, glaciers tended to retreat at a high rate during El Niño years, but tended to be stable or increase during La Niña years, although there were some notable deviations from this general pattern. Climate simulations for 2021 to 2050, based on the most optimistic assumptions of greenhouse gas concentrations, forecast a continuation of climate warming at the same rate as documented here. Such changes in temperature might lead to a critical situation for the glaciers of the Cordillera Huaytapallana, and may significantly impact the water resources, ecology, and natural hazards of the surrounding areas.

  4. Variable glacier response to atmospheric warming, northern Antarctic Peninsula, 1988–2009

    Directory of Open Access Journals (Sweden)

    B. J. Davies

    2012-09-01

    flat profiles. In contrast, the higher and steeper tidewater glaciers on the eastern Antarctic Peninsula will attain more stable frontal positions after low-lying ablation areas are removed, reaching equilibrium more quickly.

  5. Purification of recombinant C-terminus polyhistidine tagged human ...

    African Journals Online (AJOL)

    Dell

    2012-05-03

    May 3, 2012 ... this research, C-terminus polyhistidine tagged human recombinant calcitonin which was ... range protein molecular weight marker was from SIGMA. PCR- ... supernatant was stored at -80°C until needed for further assays.

  6. The 24 July 2008 outburst flood at the western Zyndan glacier lake and recent regional changes in glacier lakes of the Teskey Ala-Too range, Tien Shan, Kyrgyzstan

    Directory of Open Access Journals (Sweden)

    C. Narama

    2010-04-01

    Full Text Available On 24 July 2008, a glacier lake outburst flood (GLOF occurred at the western (w- Zyndan glacier lake in the Tong District of Ysyk-Köl Oblast, Kyrgyzstan. The flood killed three people and numerous livestock, destroyed infrastructure, and devastated potato and barley crops as well as pastures. Tuurasuu village and a downstream reservoir on the Zyndan river escaped heavy damage because the main flood was diverted toward the Tong river. RTK-GPS and satellite data (Landsat 7 ETM+, ALOS/PRISM, and ALOS/AVNIR-2 reveal that the flood reduced the lake area from 0.0422 km2 to 0.0083 km2, discharging 437 000 m3 of water. This glacier lake was not present in a Landsat 7 ETM+ image taken on 26 April 2008. It formed rapidly over just two and half months from early May to the late July, when large amounts of snow and glacier melt water became trapped in a basin in the glacier terminus area, blocked by temporary closure of the drainage channel through the terminal moraine that included much dead-ice. In the same mountain region, most other glacier-lake expansions were not particularly large during the period from 1999–2008. Although events like the w-Zyndan glacier lake outburst occur infrequently in the high Central Asian mountains, such fast developing, short-lived lakes are particularly dangerous and not easy to monitor using satellite data. Appropriate measures to protect against such lake outburst hazards in this region include educating residents on glacier hazards and monitoring techniques, providing frequently updated maps of glacier lakes, and planning and monitoring land-use, including house locations.

  7. Recent dynamic changes on Fleming Glacier after the disintegration of Wordie Ice Shelf, Antarctic Peninsula

    Science.gov (United States)

    Friedl, Peter; Seehaus, Thorsten C.; Wendt, Anja; Braun, Matthias H.; Höppner, Kathrin

    2018-04-01

    The Antarctic Peninsula is one of the world's regions most affected by climate change. Several ice shelves have retreated, thinned or completely disintegrated during recent decades, leading to acceleration and increased calving of their tributary glaciers. Wordie Ice Shelf, located in Marguerite Bay at the south-western side of the Antarctic Peninsula, completely disintegrated in a series of events between the 1960s and the late 1990s. We investigate the long-term dynamics (1994-2016) of Fleming Glacier after the disintegration of Wordie Ice Shelf by analysing various multi-sensor remote sensing data sets. We present a dense time series of synthetic aperture radar (SAR) surface velocities that reveals a rapid acceleration of Fleming Glacier in 2008 and a phase of further gradual acceleration and upstream propagation of high velocities in 2010-2011.The timing in acceleration correlates with strong upwelling events of warm circumpolar deep water (CDW) into Wordie Bay, most likely leading to increased submarine melt. This, together with continuous dynamic thinning and a deep subglacial trough with a retrograde bed slope close to the terminus probably, has induced unpinning of the glacier tongue in 2008 and gradual grounding line retreat between 2010 and 2011. Our data suggest that the glacier's grounding line had retreated by ˜ 6-9 km between 1996 and 2011, which caused ˜ 56 km2 of the glacier tongue to go afloat. The resulting reduction in buttressing explains a median speedup of ˜ 1.3 m d-1 ( ˜ 27 %) between 2008 and 2011, which we observed along a centre line extending between the grounding line in 1996 and ˜ 16 km upstream. Current median ice thinning rates (2011-2014) along profiles in areas below 1000 m altitude range between ˜ 2.6 to 3.2 m a-1 and are ˜ 70 % higher than between 2004 and 2008. Our study shows that Fleming Glacier is far away from approaching a new equilibrium and that the glacier dynamics are not primarily controlled by the loss of the

  8. Rapid thinning and collapse of lake calving Yakutat Glacier, Southeast Alaska

    Science.gov (United States)

    Trussel, Barbara Lea

    Glaciers around the globe are experiencing a notable retreat and thinning, triggered by atmospheric warming. Tidewater glaciers in particular have received much attention, because they have been recognized to contribute substantially to global sea level rise. However, lake calving glaciers in Alaska show increasingly high thinning and retreat rates and are therefore contributors to sea level rise. The number of such lake calving systems is increasing worldwide as land-terminating glaciers retreat into overdeepened basins and form proglacial lakes. Yakutat Glacier in Southeast Alaska is a low elevation lake calving glacier with an accumulation to total area ratio of 0.03. It experienced rapid thinning of 4.43 +/- 0.06 m w.e. yr-1 between 2000-2010 and terminus retreat of over 15 km since the beginning of the 20th century. Simultaneously, adjacent Yakutat Icefield land-terminating glaciers thinned at lower but still substantial rates (3.54 +/- 0.06 m w.e. yr -1 for the same time period), indicating lake calving dynamics help drive increased mass loss. Yakutat Glacier sustained a ˜3 km long floating tongue for over a decade, which started to disintegrate into large tabular icebergs in 2010. Such floating tongues are rarely seen on temperate tidewater glaciers. The floating ice was weakened by surface ablation, which then allowed rifts to form and intersect. Ice velocity from GPS measurements showed that the ice on the floating tongue was moving substantially faster than grounded ice, which was attributed to rift opening between the floating and grounded ice. Temporal variations of rift opening were determined from time-lapse imagery, and correlated well with variations in ice speeds. Larger rift opening rates occurred during and after precipitation or increased melt episodes. Both of these events increased subglacial discharge and could potentially increase the subaqueous currents towards the open lake and thus increase drag on the ice underside. Simultaneously

  9. Glacier seismology: eavesdropping on the ice-bed interface

    Science.gov (United States)

    Walter, F.; Röösli, C.

    2015-12-01

    Glacier sliding plays a central role in ice dynamics. A number of remote sensing and deep drilling initiatives have therefore focused on the ice-bed interface. Although these techniques have provided valuable insights into bed properties, they do not supply theorists with data of sufficient temporal and spatial resolution to rigorously test mathematical sliding laws. As an alternative, passive seismic techniques have gained popularity in glacier monitoring. Analysis of glacier-related seismic sources ('icequakes') has become a useful technique to study inaccessible regions of the cryosphere, including the ice-bed interface. Seismic monitoring networks on the polar ice sheets have shown that ice sliding is not only a smooth process involving viscous deformation and regelation of basal ice layers. Instead, ice streams exhibit sudden slip episodes over their beds and intermittent phases of partial or complete stagnation. Here we discuss new and recently published discoveries of basal seismic sources beneath various glacial bodies. We revisit basal seismicity of hard-bedded Alpine glaciers, which is not the result of pure stick-slip motion. Sudden changes in seismicity suggest that the local configuration of the subglacial drainage system undergoes changes on sub daily time scales. Accordingly, such observations place constraints on basal resistance and sliding of hard-bedded glaciers. In contrast, certain clusters of stick-slip dislocations associated with micro seismicity beneath the Greenland ice sheet undergo diurnal variations in magnitudes and inter event times. This is best explained with a soft till bed, which hosts the shear dislocations and whose strength varies in response to changes in subglacial water pressure. These results suggest that analysis of basal icequakes is well suited for characterizing glacier and ice sheet beds. Future studies should address the relative importance between "smooth" and seismogenic sliding in different glacial environments.

  10. Arctic polynya and glacier interactions

    Science.gov (United States)

    Edwards, Laura

    2013-04-01

    Major uncertainties surround future estimates of sea level rise attributable to mass loss from the polar ice sheets and ice caps. Understanding changes across the Arctic is vital as major potential contributors to sea level, the Greenland Ice Sheet and the ice caps and glaciers of the Canadian Arctic archipelago, have experienced dramatic changes in recent times. Most ice mass loss is currently focused at a relatively small number of glacier catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater glaciers accelerate and iceberg calving rates increase when warming ocean currents increase melt on the underside of floating glacier ice and when adjacent sea ice is removed causing a reduction in 'buttressing' back stress. Thus localised changes in ocean temperatures and in sea ice (extent and thickness) adjacent to major glacial catchments can impact hugely on the dynamics of, and hence mass lost from, terrestrial ice sheets and ice caps. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~50,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas play a vital role in the heat balance of the polar oceans and strongly impact regional oceanography. Where polynyas develop adjacent to tidewater glaciers their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. Areas of open water also play a significant role in controlling the potential of the atmosphere to carry moisture, as well as allowing heat exchange between the atmosphere and ocean, and so can influence accumulation on (and hence thickness of) glaciers and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring

  11. Airborne Surface Profiling of Alaskan Glaciers

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set consists of glacier outline, laser altimetry profile, and surface elevation change data for 46 glaciers in Alaska and British Columbia, Canada,...

  12. Rock glaciers, Central Andes, Argentina, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — Primary rock glaciers are fed by avalanche chutes. At the El Salto rock glacier, surveys have been undertaken in order to determine the creep rate. Between 1981 and...

  13. Visualizing Glaciers and Sea Ice via Google Earth

    Science.gov (United States)

    Ballagh, L. M.; Fetterer, F.; Haran, T. M.; Pharris, K.

    2006-12-01

    The NOAA team at NSIDC manages over 60 distinct cryospheric and related data products. With an emphasis on data rescue and in situ data, these products hold value for both the scientific and non-scientific user communities. The overarching goal of this presentation is to promote products from two components of the cryosphere (glaciers and sea ice). Our Online Glacier Photograph Database contains approximately 3,000 photographs taken over many decades, exemplifying change in the glacier terminus over time. The sea ice product shows sea ice extent and concentration along with anomalies and trends. This Sea Ice Index product, which starts in 1979 and is updated monthly, provides visuals of the current state of sea ice in both hemispheres with trends and anomalies. The long time period covered by the data set means that many of the trends in ice extent and concentration shown in this product are statistically significant despite the large natural variability in sea ice. The minimum arctic sea ice extent has been a record low in September 2002 and 2005, contributing to an accelerated trend in sea ice reduction. With increasing world-wide interest in indicators of global climate change, and the upcoming International Polar Year, these data products are of interest to a broad audience. To further extend the impact of these data, we have made them viewable through Google Earth via the Keyhole Markup Language (KML). This presents an opportunity to branch out to a more diverse audience by using a new and innovative tool that allows spatial representation of data of significant scientific and educational interest.

  14. A particle based simulation model for glacier dynamics

    Directory of Open Access Journals (Sweden)

    J. A. Åström

    2013-10-01

    Full Text Available A particle-based computer simulation model was developed for investigating the dynamics of glaciers. In the model, large ice bodies are made of discrete elastic particles which are bound together by massless elastic beams. These beams can break, which induces brittle behaviour. At loads below fracture, beams may also break and reform with small probabilities to incorporate slowly deforming viscous behaviour in the model. This model has the advantage that it can simulate important physical processes such as ice calving and fracturing in a more realistic way than traditional continuum models. For benchmarking purposes the deformation of an ice block on a slip-free surface was compared to that of a similar block simulated with a Finite Element full-Stokes continuum model. Two simulations were performed: (1 calving of an ice block partially supported in water, similar to a grounded marine glacier terminus, and (2 fracturing of an ice block on an inclined plane of varying basal friction, which could represent transition to fast flow or surging. Despite several approximations, including restriction to two-dimensions and simplified water-ice interaction, the model was able to reproduce the size distributions of the debris observed in calving, which may be approximated by universal scaling laws. On a moderate slope, a large ice block was stable and quiescent as long as there was enough of friction against the substrate. For a critical length of frictional contact, global sliding began, and the model block disintegrated in a manner suggestive of a surging glacier. In this case the fragment size distribution produced was typical of a grinding process.

  15. Seasonal and inter-annual variability in velocity and frontal position of Siachen Glacier (Eastern Karakorum) using multi-satellite data

    Science.gov (United States)

    Usman, M.; Furuya, M.; Sakakibara, D.; Abe, T.

    2017-12-01

    The anomalous behavior of Karakorum glaciers is a hot topic of discussion in the scientific community. Siachen Glacier is one of the longest glaciers ( 75km) in Karakorum Range. This glacier is supposed to be a surge type but so far no studies have confirmed this claim. Detailed velocity mapping of this glacier can possibly provide some clues about intra/inter-annual changes in velocity and observed terminus. Using L-band SAR data of ALOS-1/2, we applied the feature tracking technique (search patch of 128x128 pixels (range x azimuth) , sampling interval of 12x36 pixels) to derive velocity changes; we used GAMMA software. The velocity was calculated by following the parallel flow assumption. To calculate the local topographic gradient unit vector, we used ASTER-GDEM. We also used optical images acquired by Landsat 5 Thematic Mapper (TM), the Landsat 7 Enhanced Thematic Mapper Plus (ETM+) to derive surface velocity. The algorithm we used is Cross-Correlation in Frequency domain on Orientation images (CCF-O). The velocity was finally calculated by setting a flow line and averaging over the area of 200x200m2. The results indicate seasonal speed up signals that modulate inter-annually from 1999 to 2011, with slight or no change in the observed frontal position. However, in ALOS-2 data, the `observed terminus' seems to have been advancing.

  16. Rapid Holocene glacier fluctuations in arctic Norway in concert with the strength and spatial pattern of the westerlies

    Science.gov (United States)

    Bakke, J.; Dahl, S.

    2011-12-01

    latitudes during the Holocene. Superimposed on the gradual increase in glacier-covered areas, the four largest glacier advances are bracketed between 7400-7000, 1400-1200, 900-700 and 300-150 years before AD 2000. In contrast to most reconstructed glaciers in Scandinavia, we found that the largest glacier advance at Okstindan was not associated with the "Little Ice Age", but rather to an earlier period centered about AD 700. Periods with glacier advances are all associated with periods of increased winter precipitation along the coast of Norway and hence a stronger effect of the westerlies, where differences in the distribution of precipitation are assumed to reflect changes in the position of the westerlies.

  17. Microbial communities of the Lemon Creek Glacier show subtle structural variation yet stable phylogenetic composition over space and time

    Directory of Open Access Journals (Sweden)

    Cody Springer Sheik

    2015-05-01

    Full Text Available Glaciers are geologically important yet transient ecosystems that support diverse, biogeochemically significant microbial communities. During the melt season glaciers undergo dramatic physical, geochemical and biological changes that exert great influence on downstream biogeochemical cycles. Thus, we sought to understand the temporal melt-season dynamics of microbial communities and associated geochemistry at the terminus of Lemon Creek Glacier (LCG in coastal southern Alaska. Due to late season snowfall, sampling of LCG occurred in three interconnected areas: proglacial Lake Thomas, the lower glacial outflow stream and the glacier’s terminus. LCG associated microbial communities were phylogenetically diverse and varied by sampling location. However, Betaproteobacteria, Alphaproteobacteria and Bacteroidetes dominated communities at all sampling locations. Strict anaerobic groups such as methanogens, SR1, and OP11 were also recovered from glacier outflows, indicating anoxic conditions in at least some portions of the LCG subglacial environment. Microbial community structure was significantly correlated with sampling location and sodium concentrations. Microbial communities sampled from terminus outflow waters exhibited day-to-day fluctuation in taxonomy and phylogenetic similarity. However, these communities were not significantly different from randomly constructed communities from all three sites. These results indicate that glacial outflows share a large proportion of phylogenetic overlap with downstream environments and that the observed significant shifts in community structure are driven by changes in relative abundance of different taxa, and not complete restructuring of communities. We conclude that LCG glacial discharge hosts a diverse and relatively stable microbiome that shifts at fine taxonomic scales in response to geochemistry and likely water residence time.

  18. Hpa1 harpin needs nitroxyl terminus to promote vegetative growth ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Home; Journals; Journal of Biosciences; Volume 39; Issue 1. Hpa1 harpin needs nitroxyl terminus to ... Hansong Dong1 Chunling Zhang1. State Ministry of Education Key Laboratory of Integrated Management of Crop Pathogens and Insect Pests, Nanjing Agricultural University, Jiangsu, 210095, China ...

  19. Quantification and Analysis of Icebergs in a Tidewater Glacier Fjord Using an Object-Based Approach.

    Directory of Open Access Journals (Sweden)

    Robert W McNabb

    Full Text Available Tidewater glaciers are glaciers that terminate in, and calve icebergs into, the ocean. In addition to the influence that tidewater glaciers have on physical and chemical oceanography, floating icebergs serve as habitat for marine animals such as harbor seals (Phoca vitulina richardii. The availability and spatial distribution of glacier ice in the fjords is likely a key environmental variable that influences the abundance and distribution of selected marine mammals; however, the amount of ice and the fine-scale characteristics of ice in fjords have not been systematically quantified. Given the predicted changes in glacier habitat, there is a need for the development of methods that could be broadly applied to quantify changes in available ice habitat in tidewater glacier fjords. We present a case study to describe a novel method that uses object-based image analysis (OBIA to classify floating glacier ice in a tidewater glacier fjord from high-resolution aerial digital imagery. Our objectives were to (i develop workflows and rule sets to classify high spatial resolution airborne imagery of floating glacier ice; (ii quantify the amount and fine-scale characteristics of floating glacier ice; (iii and develop processes for automating the object-based analysis of floating glacier ice for large number of images from a representative survey day during June 2007 in Johns Hopkins Inlet (JHI, a tidewater glacier fjord in Glacier Bay National Park, southeastern Alaska. On 18 June 2007, JHI was comprised of brash ice ([Formula: see text] = 45.2%, SD = 41.5%, water ([Formula: see text] = 52.7%, SD = 42.3%, and icebergs ([Formula: see text] = 2.1%, SD = 1.4%. Average iceberg size per scene was 5.7 m2 (SD = 2.6 m2. We estimate the total area (± uncertainty of iceberg habitat in the fjord to be 455,400 ± 123,000 m2. The method works well for classifying icebergs across scenes (classification accuracy of 75.6%; the largest classification errors occur in areas

  20. Morphological characteristics of overdeepenings in high-mountain glacier beds

    Science.gov (United States)

    Haeberli, Wilfried; Cochachin, Alejo; Fischer, Urs; Giráldez, Claudia; Linsbauer, Andreas; Salazar, Cesar

    2014-05-01

    the parameters surface area, length, width, depth, volume, forward/adverse slope and their statistical interrelations are determined with their corresponding uncertainty ranges. For sample (b) basal shear stress (as used in the model), thermal ice types, glacier size/type, relation to flow characteristics (position along flow, confined-unconfined, confluence-diffluence-channel-forefield) are also included. As a principal problem thereby remains the unsolved question of when exactly the overdeepenings had formed (present-day conditions, Holocene maximum stages, ice ages?). Some results nevertheless remain safe. The most striking phenomenon is the high variability of geometries observed with modelled as well as measured forms: small features can, for instance, be deep and large features shallow. Overdeepenings can form under conditions of low to high basal shear stresses at cirque, confluence, channel and terminus positions. Rather than the exact size, locations and general parameter values of overdeepenings from different model runs appear to be robust and comparable. Only weak correlations seem to exist between the investigated geometrical parameters; rather uncertain indications are found of an optimal elongation for maximum depths. Inclinations of adverse slopes do not differ significantly from those of forward slopes and are in most cases far higher than limiting values for floatation within the overdeepenings. Lakes, which fill exposed overdeepenings, can be dammed by huge (lateral/terminal) moraines or may form in polished rock beds but have comparable spreads of geometrical characteristics in both cases.

  1. C-terminus glycans with critical functional role in the maturation of secretory glycoproteins.

    Directory of Open Access Journals (Sweden)

    Daniela Cioaca

    Full Text Available The N-glycans of membrane glycoproteins are mainly exposed to the extracellular space. Human tyrosinase is a transmembrane glycoprotein with six or seven bulky N-glycans exposed towards the lumen of subcellular organelles. The central active site region of human tyrosinase is modeled here within less than 2.5 Å accuracy starting from Streptomyces castaneoglobisporus tyrosinase. The model accounts for the last five C-terminus glycosylation sites of which four are occupied and indicates that these cluster in two pairs--one in close vicinity to the active site and the other on the opposite side. We have analyzed and compared the roles of all tyrosinase N-glycans during tyrosinase processing with a special focus on the proximal to the active site N-glycans, s6:N337 and s7:N371, versus s3:N161 and s4:N230 which decorate the opposite side of the domain. To this end, we have constructed mutants of human tyrosinase in which its seven N-glycosylation sites were deleted. Ablation of the s6:N337 and s7:N371 sites arrests the post-translational productive folding process resulting in terminally misfolded mutants subjected to degradation through the mannosidase driven ERAD pathway. In contrast, single mutants of the other five N-glycans located either opposite to the active site or into the N-terminus Cys1 extension of tyrosinase are temperature-sensitive mutants and recover enzymatic activity at the permissive temperature of 31°C. Sites s3 and s4 display selective calreticulin binding properties. The C-terminus sites s7 and s6 are critical for the endoplasmic reticulum retention and intracellular disposal. Results herein suggest that individual N-glycan location is critical for the stability, regional folding control and secretion of human tyrosinase and explains some tyrosinase gene missense mutations associated with oculocutaneous albinism type I.

  2. Glacier area changes in Northern Eurasia

    International Nuclear Information System (INIS)

    Khromova, Tatiana; Nosenko, Gennady; Kutuzov, Stanislav; Muraviev, Anton; Chernova, Ludmila

    2014-01-01

    Glaciers are widely recognized as key indicators of climate change. Recent evidence suggests an acceleration of glacier mass loss in several key mountain regions. Glacier recession implies landscape changes in the glacial zone, the origin of new lakes and activation of natural disaster processes, catastrophic mudflows, ice avalanches, outburst floods, etc. The absence or inadequacy of such information results in financial and human losses. A more comprehensive evaluation of glacier changes is imperative to assess ice contributions to global sea level rise and the future of water resources from glacial basins. One of the urgent steps is a full inventory of all ice bodies and their changes. The first estimation of glacier state and glacier distribution on the territory of the former Soviet Union has been done in the USSR Glacier Inventory (UGI) published in 1965–1982. The UGI is based on topographic maps and air photos and reflects the status of the glaciers in the 1940s–1970s. There is information about 28 884 glaciers with an area of 7830.75 km 2 in the inventory. It covers 25 glacier systems in Northern Eurasia. In the 1980s the UGI has been transformed into digital form as a part of the World Glacier Inventory (WGI). Recent satellite data provide a unique opportunity to look again at these glaciers and to evaluate changes in glacier extent for the second part of the 20th century. About 15 000 glacier outlines for the Caucasus, Polar Urals, Pamir Alay, Tien Shan, Altai, Kamchatka and Russian Arctic have been derived from ASTER and Landsat imagery and can be used for glacier change evaluation. Results of the analysis indicate the steady trend in glacier shrinkage in all mountain regions for the second part of the 20th century. Glacier area loss for the studied regions varies from 13% (Tien Shan) to 22.3% (Polar Urals). The common driver, most likely, is an increase in summer air temperature. There is also a very large variability in the degree of

  3. Three Decades of Volume Change of a Small Greenlandic Glacier Using Ground Penetrating Radar, Structure from Motion, and Aerial Photogrammetry

    DEFF Research Database (Denmark)

    Marcer, M.; Stentoft, Peter Alexander; Bjerre, Elisa

    2017-01-01

    Glaciers in the Arctic are losing mass at an increasing rate. Here we use surface topography derived from Structure from Motion (SfM) and ice volume from ground penetrating radar (GPR) to describe the 2014 state of Aqqutikitsoq glacier (2.85 km) on Greenland's west coast. A photogrammetrically...... derived 1985 digital elevation model (DEM) was subtracted from a 2014 DEM obtained using land-based SfM to calculate geodetic glacier mass balance. Furthermore, a detailed 2014 ground penetrating radar survey was performed to assess ice volume. From 1985 to 2014, the glacier has lost 49.8 ± 9.4 10 m...... aerial photography. To address this issue, surface elevation in low contrast areas was measured manually at point locations and interpolated using a universal kriging approach. We conclude that ground-based SfM is well suited to establish high-quality DEMs of smaller glaciers. Provided favorable...

  4. Determining the apical terminus of root-end resected teeth using three modern apex locators: a comparative ex vivo study.

    Science.gov (United States)

    ElAyouti, A; Kimionis, I; Chu, A-L; Löst, C

    2005-11-01

    To assess ex vivo the accuracy of various electronic apex locators in locating the apical terminus of root-end resected teeth. Ninety extracted human posterior teeth (182 root canals) were prepared to a minimum size of 40 and filled with gutta-percha and sealer. After resection of the apical 3 mm of the root, the root canal filling was removed using HERO rotary instruments. The size of the root canal at the apical terminus after removal of the filling ranged from size 50 to 90. The root canal length to the apical terminus was determined using 3 apex locators (Root ZX, Raypex4 and Apex Pointer). A new mounting model that utilized a micrometer was used to perform the measurements and to visually determine the actual position of the apical terminus. The frequency of locating the apical terminus and the corresponding 95% confidence interval (CI) were calculated. Additionally, the coefficient of repeatability of each apex locator and the limits of inter-operator agreement were determined. All apex locators showed an acceptable repeatability (0.02-0.03 mm coefficient of repeatability) and narrow limits of inter-operator agreement (+0.07 and -0.07 mm). The accuracy of determining the apical terminus within 1 mm in the root canal was as follows: Root ZX 90% (164/182 root-canals) [95%CI: 86-94%], Raypex4 74% (135/182 root-canals) [95%CI: 68-80%], and Apex Pointer 71% (129/182 root canals) [95%CI: 65-77%]. No over-instrumentation resulted when the Root ZX device was used. In contrast, using the Raypex4 or the Apex Pointer device resulted in over-instrumentation in 8 of 182 root canals (4%). Under the conditions of this study all three apex locators were able to detect the apical terminus of root-end resected teeth with an acceptable range. The Root ZX device was the most accurate without over-instrumentation of the root canals.

  5. Inspection of Alpine glaciers with cosmic-ray muon radiography

    Science.gov (United States)

    Nishiyama, Ryuichi; Ariga, Akitaka; Ariga, Tomoko; Ereditato, Antonio; Lechmann, Alessandro; Mair, David; Scampoli, Paola; Schlunegger, Fritz; Vladymyrov, Mykhailo

    2016-04-01

    Radiography using cosmic-ray muons represents a challenging method for probing the bedrock topography beneath Alpine glaciers. We present the current status of our feasibility study at Eiger glacier, situated on the western flank of the Eiger in the Jungfrau region, Central Swiss Alps. The muon radiography is a technique that has been recently developed to investigate the internal density profiles of geoscientific targets. It is based on the measurement of the absorption of the cosmic-ray muons inside a material. Because the energy spectrum of cosmic-ray muons and the energy dependence of muon range have been studied well during the past years, the attenuation of the muon flux can be used to derive the column density, i.e. the density integrated along the muon trajectories, of geoscientific targets. This technique has recently been applied for non-invasive inspection of volcanoes, nuclear reactors, seismic faults, caves and etc. The greatest advantage of the method in the field of glacier studies is that it yields a unique solution of the density underneath a glacier without any assumption of physical properties inside the target. Large density contrasts, as expected between glacier ice (˜ 1.0g/cm3) and bedrock (˜ 2.5g/cm3), would allow us to elucidate the shape of the bedrock in high resolution. Accordingly, this technology will provide for the first time information on the bedrock surface beneath a steep and non-accessible Alpine glacier, in a complementary way with respect to other exploration methods (drilling, ground penetrating radar, seismic survey, gravity explorations and etc.). Our first aim is to demonstrate the feasibility of the method through a case study at the Eiger glacier, situated in the Central Swiss Alps. The Eiger glacier straddles the western flank of the Eiger between 3700 and 2300 m above sea level (a.s.l.). The glacier has shortened by about 150 m during the past 30 years in response to the ongoing global warming, causing a concern for

  6. Classification of debris-covered glaciers and rock glaciers in the Andes of central Chile

    Science.gov (United States)

    Janke, Jason R.; Bellisario, Antonio C.; Ferrando, Francisco A.

    2015-07-01

    In the Dry Andes of Chile (17 to 35° S), debris-covered glaciers and rock glaciers are differentiated from true glaciers based on the percentage of surface debris cover, thickness of surface debris, and ice content. Internal ice is preserved by an insulating cover of thick debris, which acts as a storage reservoir to release water during the summer and early fall. These landforms are more numerous than glaciers in the central Andes; however, the existing legislation only recognizes uncovered or semicovered glaciers as a water resource. Glaciers, debris-covered glaciers, and rock glaciers are being altered or removed by mining operations to extract valuable minerals from the mountains. In addition, agricultural expansion and population growth in this region have placed additional demands on water resources. In a warmer climate, as glaciers recede and seasonal water availability becomes condensed over the course of a snowmelt season, rock glaciers and debris-covered glaciers contribute a larger component of base flow to rivers and streams. As a result, identifying and locating these features to implement sustainable regional planning for water resources is important. The objective of this study is to develop a classification system to identify debris-covered glaciers and rock glaciers based on the interpretation of satellite imagery and aerial photographs. The classification system is linked to field observations and measurements of ice content. Debris-covered glaciers have three subclasses: surface coverage of semi (class 1) and fully covered (class 2) glaciers differentiates the first two forms, whereas debris thickness is critical for class 3 when glaciers become buried with more than 3 m of surface debris. Based on field observations, the amount of ice decreases from more than 85%, to 65-85%, to 45-65% for semi, fully, and buried debris-covered glaciers, respectively. Rock glaciers are characterized by three stages. Class 4 rock glaciers have pronounced

  7. The Ku80 carboxy terminus stimulates joining and artemis-mediated processing of DNA ends

    DEFF Research Database (Denmark)

    Weterings, Eric; Verkaik, Nicole S; Keijzers, Guido

    2008-01-01

    Repair of DNA double-strand breaks (DSBs) is predominantly mediated by nonhomologous end joining (NHEJ) in mammalian cells. NHEJ requires binding of the Ku70-Ku80 heterodimer (Ku70/80) to the DNA ends and subsequent recruitment of the DNA-dependent protein kinase catalytic subunit (DNA-PK(CS)) an......Repair of DNA double-strand breaks (DSBs) is predominantly mediated by nonhomologous end joining (NHEJ) in mammalian cells. NHEJ requires binding of the Ku70-Ku80 heterodimer (Ku70/80) to the DNA ends and subsequent recruitment of the DNA-dependent protein kinase catalytic subunit (DNA......-PK(CS)) and the XRCC4/ligase IV complex. Activation of the DNA-PK(CS) serine/threonine kinase requires an interaction with Ku70/80 and is essential for NHEJ-mediated DSB repair. In contrast to previous models, we found that the carboxy terminus of Ku80 is not absolutely required for the recruitment and activation...... was phosphorylated to normal levels. This resulted in severely reduced levels of Artemis nuclease activity in vivo and in vitro. We therefore conclude that the Ku80 carboxy terminus is important to support DNA-PK(CS) autophosphorylation at specific sites, which facilitates DNA end processing by the Artemis...

  8. The Ku80 carboxy terminus stimulates joining and artemis-mediated processing of DNA ends.

    Science.gov (United States)

    Weterings, Eric; Verkaik, Nicole S; Keijzers, Guido; Florea, Bogdan I; Wang, Shih-Ya; Ortega, Laura G; Uematsu, Naoya; Chen, David J; van Gent, Dik C

    2009-03-01

    Repair of DNA double-strand breaks (DSBs) is predominantly mediated by nonhomologous end joining (NHEJ) in mammalian cells. NHEJ requires binding of the Ku70-Ku80 heterodimer (Ku70/80) to the DNA ends and subsequent recruitment of the DNA-dependent protein kinase catalytic subunit (DNA-PK(CS)) and the XRCC4/ligase IV complex. Activation of the DNA-PK(CS) serine/threonine kinase requires an interaction with Ku70/80 and is essential for NHEJ-mediated DSB repair. In contrast to previous models, we found that the carboxy terminus of Ku80 is not absolutely required for the recruitment and activation of DNA-PK(CS) at DSBs, although cells that harbored a carboxy-terminal deletion in the Ku80 gene were sensitive to ionizing radiation and showed reduced end-joining capacity. More detailed analysis of this repair defect showed that DNA-PK(CS) autophosphorylation at Thr2647 was diminished, while Ser2056 was phosphorylated to normal levels. This resulted in severely reduced levels of Artemis nuclease activity in vivo and in vitro. We therefore conclude that the Ku80 carboxy terminus is important to support DNA-PK(CS) autophosphorylation at specific sites, which facilitates DNA end processing by the Artemis endonuclease and the subsequent joining reaction.

  9. The Ku80 Carboxy Terminus Stimulates Joining and Artemis-Mediated Processing of DNA Ends▿

    Science.gov (United States)

    Weterings, Eric; Verkaik, Nicole S.; Keijzers, Guido; Florea, Bogdan I.; Wang, Shih-Ya; Ortega, Laura G.; Uematsu, Naoya; Chen, David J.; van Gent, Dik C.

    2009-01-01

    Repair of DNA double-strand breaks (DSBs) is predominantly mediated by nonhomologous end joining (NHEJ) in mammalian cells. NHEJ requires binding of the Ku70-Ku80 heterodimer (Ku70/80) to the DNA ends and subsequent recruitment of the DNA-dependent protein kinase catalytic subunit (DNA-PKCS) and the XRCC4/ligase IV complex. Activation of the DNA-PKCS serine/threonine kinase requires an interaction with Ku70/80 and is essential for NHEJ-mediated DSB repair. In contrast to previous models, we found that the carboxy terminus of Ku80 is not absolutely required for the recruitment and activation of DNA-PKCS at DSBs, although cells that harbored a carboxy-terminal deletion in the Ku80 gene were sensitive to ionizing radiation and showed reduced end-joining capacity. More detailed analysis of this repair defect showed that DNA-PKCS autophosphorylation at Thr2647 was diminished, while Ser2056 was phosphorylated to normal levels. This resulted in severely reduced levels of Artemis nuclease activity in vivo and in vitro. We therefore conclude that the Ku80 carboxy terminus is important to support DNA-PKCS autophosphorylation at specific sites, which facilitates DNA end processing by the Artemis endonuclease and the subsequent joining reaction. PMID:19103741

  10. A database of worldwide glacier thickness observations

    DEFF Research Database (Denmark)

    Gärtner-Roer, I.; Naegeli, K.; Huss, M.

    2014-01-01

    One of the grand challenges in glacier research is to assess the total ice volume and its global distribution. Over the past few decades the compilation of a world glacier inventory has been well-advanced both in institutional set-up and in spatial coverage. The inventory is restricted to glacier...... the different estimation approaches. This initial database of glacier and ice caps thickness will hopefully be further enlarged and intensively used for a better understanding of the global glacier ice volume and its distribution....... surface observations. However, although thickness has been observed on many glaciers and ice caps around the globe, it has not yet been published in the shape of a readily available database. Here, we present a standardized database of glacier thickness observations compiled by an extensive literature...... review and from airborne data extracted from NASA's Operation IceBridge. This database contains ice thickness observations from roughly 1100 glaciers and ice caps including 550 glacier-wide estimates and 750,000 point observations. A comparison of these observational ice thicknesses with results from...

  11. Internationally coordinated glacier monitoring: strategy and datasets

    Science.gov (United States)

    Hoelzle, Martin; Armstrong, Richard; Fetterer, Florence; Gärtner-Roer, Isabelle; Haeberli, Wilfried; Kääb, Andreas; Kargel, Jeff; Nussbaumer, Samuel; Paul, Frank; Raup, Bruce; Zemp, Michael

    2014-05-01

    Internationally coordinated monitoring of long-term glacier changes provide key indicator data about global climate change and began in the year 1894 as an internationally coordinated effort to establish standardized observations. Today, world-wide monitoring of glaciers and ice caps is embedded within the Global Climate Observing System (GCOS) in support of the United Nations Framework Convention on Climate Change (UNFCCC) as an important Essential Climate Variable (ECV). The Global Terrestrial Network for Glaciers (GTN-G) was established in 1999 with the task of coordinating measurements and to ensure the continuous development and adaptation of the international strategies to the long-term needs of users in science and policy. The basic monitoring principles must be relevant, feasible, comprehensive and understandable to a wider scientific community as well as to policy makers and the general public. Data access has to be free and unrestricted, the quality of the standardized and calibrated data must be high and a combination of detailed process studies at selected field sites with global coverage by satellite remote sensing is envisaged. Recently a GTN-G Steering Committee was established to guide and advise the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. Several online databases containing a wealth of diverse data types having different levels of detail and global coverage provide fast access to continuously updated information on glacier fluctuation and inventory data. For world-wide inventories, data are now available through (a) the World Glacier Inventory containing tabular information of about 130,000 glaciers covering an area of around 240,000 km2, (b) the GLIMS-database containing digital outlines of around 118,000 glaciers with different time stamps and

  12. Simple tool for the rapid, automated quantification of glacier advance/retreat observations using multiple methods

    Science.gov (United States)

    Lea, J.

    2017-12-01

    The quantification of glacier change is a key variable within glacier monitoring, with the method used potentially being crucial to ensuring that data can be appropriately compared with environmental data. The topic and timescales of study (e.g. land/marine terminating environments; sub-annual/decadal/centennial/millennial timescales) often mean that different methods are more suitable for different problems. However, depending on the GIS/coding expertise of the user, some methods can potentially be time consuming to undertake, making large-scale studies problematic. In addition, examples exist where different users have nominally applied the same methods in different studies, though with minor methodological inconsistencies in their approach. In turn, this will have implications for data homogeneity where regional/global datasets may be constructed. Here, I present a simple toolbox scripted in a Matlab® environment that requires only glacier margin and glacier centreline data to quantify glacier length, glacier change between observations, rate of change, in addition to other metrics. The toolbox includes the option to apply the established centreline or curvilinear box methods, or a new method: the variable box method - designed for tidewater margins where box width is defined as the total width of the individual terminus observation. The toolbox is extremely flexible, and has the option to be applied as either Matlab® functions within user scripts, or via a graphical user interface (GUI) for those unfamiliar with a coding environment. In both instances, there is potential to apply the methods quickly to large datasets (100s-1000s of glaciers, with potentially similar numbers of observations each), thus ensuring large scale methodological consistency (and therefore data homogeneity) and allowing regional/global scale analyses to be achievable for those with limited GIS/coding experience. The toolbox has been evaluated against idealised scenarios demonstrating

  13. Brief communication: Getting Greenland's glaciers right - a new data set of all official Greenlandic glacier names

    Science.gov (United States)

    Bjørk, A. A.; Kruse, L. M.; Michaelsen, P. B.

    2015-12-01

    Place names in Greenland can be difficult to get right, as they are a mix of Greenlandic, Danish, and other foreign languages. In addition, orthographies have changed over time. With this new data set, we give the researcher working with Greenlandic glaciers the proper tool to find the correct name for glaciers and ice caps in Greenland and to locate glaciers described in the historic literature with the old Greenlandic orthography. The data set contains information on the names of 733 glaciers, 285 originating from the Greenland Ice Sheet (GrIS) and 448 from local glaciers and ice caps (LGICs).

  14. How do glacier inventory data aid global glacier assessments and projections?

    Science.gov (United States)

    Hock, R.

    2017-12-01

    Large-scale glacier modeling relies heavily on datasets that are collected by many individuals across the globe, but managed and maintained in a coordinated fashion by international data centers. The Global Terrestrial Network for Glaciers (GTN-G) provides the framework for coordinating and making available a suite of data sets such as the Randolph Glacier Inventory (RGI), the Glacier Thickness Dataset or the World Glacier Inventory (WGI). These datasets have greatly increased our ability to assess global-scale glacier mass changes. These data have also been vital for projecting the glacier mass changes of all mountain glaciers in the world outside the Greenland and Antarctic ice sheet, a total >200,000 glaciers covering an area of more than 700,000 km2. Using forcing from 8 to 15 GCMs and 4 different emission scenarios, global-scale glacier evolution models project multi-model mean net mass losses of all glaciers between 7 cm and 24 cm sea-level equivalent by the end of the 21st century. Projected mass losses vary greatly depending on the choice of the forcing climate and emission scenario. Insufficiently constrained model parameters likely are an important reason for large differences found among these studies even when forced by the same emission scenario, especially on regional scales.

  15. Deglaciation and its impact on permafrost and rock glacier evolution: New insight from two adjacent cirques in Austria.

    Science.gov (United States)

    Kellerer-Pirklbauer, Andreas; Kaufmann, Viktor

    2018-04-15

    Glaciers and permafrost are strongly linked to each other in mid-latitude mountain regions particularly with polythermal glaciers. This linkage is not only climatically defined but also in terms of geomorphic and glaciological processes. We studied two adjacent cirques located in the Central Austria. We focussed on the deglaciation since the Little Ice Age (LIA) maximum (c.1850CE) and its relevance for permafrost and rock glacier evolution since then. One cirque is occupied by a glacier remnant whereas the second one is occupied by an active rock glacier which was partly overridden by a glacier during the LIA. We applied a multidisciplinary approach using field-based techniques including geoelectrics, geodetic measurements, and automatic monitoring as well as historic maps and photographs, remote sensing, and digital terrain analysis. Results indicate almost complete deglaciation by the end of the last millennium. Small-scale tongue-shaped landforms of complex origin formed during the last decades at finer-grained slope deposits below the cirque headwalls. Field evidences and geophysics results proved the existence of widespread sedimentary ice beneath a thin veneer of debris at these slopes. The variable thickness of the debris layer has a major impact on differential ablation and landform evolution in both cirques. The comparison of digital elevation models revealed clear mass losses at both cirques with low rates between 1954 and 2002 and significantly higher rates since then. The central and lower part of the rock glacier moves fast transporting sediments and ice downvalley. In contrast, the upper part of the rock glacier is characterised by low debris and ice input rates. Both effects cause a significant decoupling of the main rock glacier body from its nourishment area leading eventually to rock glacier starvation. This study demonstrates the importance of a decadal-scale and multidisciplinary research approach in determining the development of alpine

  16. Surge dynamics on Bering Glacier, Alaska, in 2008–2011

    Directory of Open Access Journals (Sweden)

    M. Braun

    2012-11-01

    Full Text Available A surge cycle of the Bering Glacier system, Alaska, is examined using observations of surface velocity obtained using synthetic aperture radar (SAR offset tracking, and elevation data obtained from the University of Alaska Fairbanks LiDAR altimetry program. After 13 yr of quiescence, the Bering Glacier system began to surge in May 2008 and had two stages of accelerated flow. During the first stage, flow accelerated progressively for at least 10 months and reached peak observed velocities of ~ 7 m d−1. The second stage likely began in 2010. By 2011 velocities exceeded 9 m d−1 or ~ 18 times quiescent velocities. Fast flow continued into July 2011. Surface morphology indicated slowing by fall 2011; however, it is not entirely clear if the surge is yet over. The quiescent phase was characterized by small-scale acceleration events that increased driving stresses up to 70%. When the surge initiated, synchronous acceleration occurred throughout much of the glacier length. Results suggest that downstream propagation of the surge is closely linked to the evolution of the driving stress during the surge, because driving stress appears to be tied to the amount of resistive stress provided by the bed. In contrast, upstream acceleration and upstream surge propagation is not dependent on driving stress evolution.

  17. Glacier Snowline Determination from Terrestrial Laser Scanning Intensity Data

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    Hannah Prantl

    2017-07-01

    Full Text Available Accurately identifying the extent of surface snow cover on glaciers is important for extrapolating end of year mass balance measurements, constraining the glacier surface radiative energy balance and evaluating model simulations of snow cover. Here, we use auxiliary information from Riegl VZ-6000 Terrestrial Laser Scanner (TLS return signals to accurately map the snow cover over a glacier throughout an ablation season. Three classification systems were compared, and we find that supervised classification based on TLS signal intensity alone is outperformed by a rule-based classification employing intensity, surface roughness and an associated optical image, which achieves classification accuracy of 68–100%. The TLS intensity signal shows no meaningful relationship with surface or bulk snow density. Finally, we have also compared our Snow Line Altitude (SLA derived from TLS with SLA derived from the model output, as well as one Landsat image. The results of the model output track the SLA from TLS well, however with a positive bias. In contrast, automatic Landsat-derived SLA slightly underestimates the SLA from TLS. To conclude, we demonstrate that the snow cover extent can be mapped successfully using TLS, although the snow mass remains elusive.

  18. OPTICAL FLOW APPLIED TO TIME-LAPSE IMAGE SERIES TO ESTIMATE GLACIER MOTION IN THE SOUTHERN PATAGONIA ICE FIELD

    Directory of Open Access Journals (Sweden)

    E. Lannutti

    2016-06-01

    Full Text Available In this work, we assessed the feasibility of using optical flow to obtain the motion estimation of a glacier. In general, former investigations used to detect glacier changes involve solutions that require repeated observations which are many times based on extensive field work. Taking into account glaciers are usually located in geographically complex and hard to access areas, deploying time-lapse imaging sensors, optical flow may provide an efficient solution at good spatial and temporal resolution to describe mass motion. Several studies in computer vision and image processing community have used this method to detect large displacements. Therefore, we carried out a test of the proposed Large Displacement Optical Flow method at the Viedma Glacier, located at South Patagonia Icefield, Argentina. We collected monoscopic terrestrial time-lapse imagery, acquired by a calibrated camera at every 24 hour from April 2014 until April 2015. A filter based on temporal correlation and RGB color discretization between the images was applied to minimize errors related to changes in lighting, shadows, clouds and snow. This selection allowed discarding images that do not follow a sequence of similarity. Our results show a flow field in the direction of the glacier movement with acceleration in the terminus. We analyzed the errors between image pairs, and the matching generally appears to be adequate, although some areas show random gross errors related to the presence of changes in lighting. The proposed technique allowed the determination of glacier motion during one year, providing accurate and reliable motion data for subsequent analysis.

  19. Using Metaphorical Models for Describing Glaciers

    Science.gov (United States)

    Felzmann, Dirk

    2014-01-01

    To date, there has only been little conceptual change research regarding conceptions about glaciers. This study used the theoretical background of embodied cognition to reconstruct different metaphorical concepts with respect to the structure of a glacier. Applying the Model of Educational Reconstruction, the conceptions of students and scientists…

  20. The atmospheric boundary layer over melting glaciers

    NARCIS (Netherlands)

    Oerlemans, J.

    1998-01-01

    Results from a number of glacio-meteorological experiments carried out over melting glaciers are summarized. It is shown that in summer the microclimate of a glacier tongue is dominated by katabatic flow, initiated by the downward sensible heat flux. Characteristic obstacle height is an

  1. The response of glaciers to climate change

    NARCIS (Netherlands)

    Klok, Elisabeth Jantina

    2003-01-01

    The research described in this thesis addresses two aspects of the response of glaciers to climate change. The first aspect deals with the physical processes that govern the interaction between glaciers and climate change and was treated by (1) studying the spatial and temporal variation of the

  2. Glaciers in 21st Century Himalayan Geopolitics

    Science.gov (United States)

    Kargel, J. S.; Wessels, R.; Kieffer, H. H.

    2002-05-01

    Glaciers are ablating rapidly the world over. Nowhere are the rates of retreat and downwasting greater than in the Hindu Kush-Himalaya (HKH) region. It is estimated that over the next century, 40,000 square kilometers of present glacier area in the HKH region will become ice free. Most of this area is in major valleys and the lowest glaciated mountain passes. The existence and characteristics of glaciers have security impacts, and rapidly changing HKH glaciers have broad strategic implications: (1) Glaciers supply much of the fresh water and hydroelectric power in South and Central Asia, and so glaciers are valuable resources. (2) Shared economic interests in water, hydroelectricity, flood hazards, and habitat preservation are a force for common cause and reasoned international relations. (3) Glaciers and their high mountains generally pose a natural barrier tending to isolate people. Historically, they have hindered trade and intercultural exchanges and have protected against aggression. This has further promoted an independent spirit of the region's many ethnic groups. (4) Although glaciers are generally incompatible with human development and habitation, many of the HKH region's glaciers and their mountains have become sanctuaries and transit routes for militants. Siachen Glacier in Kashmir has for 17 years been "the world's highest battlefield," with tens of thousands of troops deployed on both sides of the India/Pakistan line of control. In 1999, that conflict threatened to trigger all-out warfare, and perhaps nuclear warfare. Other recent terrorist and military action has taken place on glaciers in Kyrgyzstan and Tajikistan. As terrorists are forced from easily controlled territories, many may tend to migrate toward the highest ground, where definitive encounters may take place in severe alpine glacial environments. This should be a major concern in Nepali security planning, where an Army offensive is attempting to reign in an increasingly robust and brutal

  3. Boundary layer models for calving marine outlet glaciers

    Directory of Open Access Journals (Sweden)

    C. Schoof

    2017-10-01

    Full Text Available We consider the flow of marine-terminating outlet glaciers that are laterally confined in a channel of prescribed width. In that case, the drag exerted by the channel side walls on a floating ice shelf can reduce extensional stress at the grounding line. If ice flux through the grounding line increases with both ice thickness and extensional stress, then a longer shelf can reduce ice flux by decreasing extensional stress. Consequently, calving has an effect on flux through the grounding line by regulating the length of the shelf. In the absence of a shelf, it plays a similar role by controlling the above-flotation height of the calving cliff. Using two calving laws, one due to Nick et al. (2010 based on a model for crevasse propagation due to hydrofracture and the other simply asserting that calving occurs where the glacier ice becomes afloat, we pose and analyse a flowline model for a marine-terminating glacier by two methods: direct numerical solution and matched asymptotic expansions. The latter leads to a boundary layer formulation that predicts flux through the grounding line as a function of depth to bedrock, channel width, basal drag coefficient, and a calving parameter. By contrast with unbuttressed marine ice sheets, we find that flux can decrease with increasing depth to bedrock at the grounding line, reversing the usual stability criterion for steady grounding line location. Stable steady states can then have grounding lines located on retrograde slopes. We show how this anomalous behaviour relates to the strength of lateral versus basal drag on the grounded portion of the glacier and to the specifics of the calving law used.

  4. An inventory and estimate of water stored in firn fields, glaciers, debris-covered glaciers, and rock glaciers in the Aconcagua River Basin, Chile

    Science.gov (United States)

    Janke, Jason R.; Ng, Sam; Bellisario, Antonio

    2017-11-01

    An inventory of firn fields, glaciers, debris-covered glaciers, and rock glaciers was conducted in the Aconcagua River Basin of the semiarid Andes of central Chile. A total of 916 landforms were identified, of which rock glaciers were the most abundant (669) and occupied the most total area. Glaciers and debris-covered glaciers were less numerous, but were about five times larger in comparison. The total area occupied by glaciers and debris-covered glaciers was roughly equivalent to the total area of rock glaciers. Debris-covered glaciers and rock glaciers were subcategorized into six ice-content classes based on interpretation of surface morphology with high-resolution satellite imagery. Over 50% of rock glaciers fell within a transitional stage; 85% of debris-covered glaciers were either fully covered or buried. Most landforms occupied elevations between 3500 and 4500 m. Glaciers and firn occurred at higher elevations compared to rock glaciers and debris-covered glaciers. Rock glaciers had a greater frequency in the northern part of the study area where arid climate conditions exist. Firn and glaciers were oriented south, debris-covered glaciers west, and rock glaciers southwest. An analysis of water contribution of each landform in the upper Andes of the Aconcagua River Basin was conducted using formulas that associate the size of the landforms to estimates of water stored. Minimum and maximum water storage was calculated based on a range of debris to ice content ratios for debris-covered glaciers and rock glaciers. In the Aconcagua River Basin, rock glaciers accounted for 48 to 64% of the water stored within the landforms analyzed; glaciers accounted for 15 to 25%; debris-covered glaciers were estimated at 15 to 19%; firn fields contained only about 5 to 8% of the water stored. Expansion of agriculture, prolonged drought, and removal of ice-rich landforms for mining have put additional pressure on already scarce water resources. To develop long

  5. Bovine adenovirus type 3 containing heterologous protein in the C-terminus of minor capsid protein IX

    International Nuclear Information System (INIS)

    Zakhartchouk, Alexander; Connors, Wayne; Van Kessel, Andrew; Tikoo, Suresh Kumar

    2004-01-01

    Earlier, we detected pIX of BAdV-3 as a 14-kDa protein in purified virions. Analysis of BAdV-3 pIX using different region antibodies revealed that the N-terminus and central domain of the pIX contain immunogenic sites and are not exposed on the surface of BAdV-3 virion. This suggested that the C-terminus of BAdV-3 pIX (125 amino acid) may be exposed on the virion and may be used as a site for incorporation of heterologous peptides or proteins. We constructed recombinant BAV950 containing a small peptide (21 amino acid), including the RGD motif or recombinant BAV951 containing enhanced yellow-green fluorescent protein (EYFP) fused to the C-terminus of pIX. Western blot analysis demonstrated that the chimeric pIX-RGD was incorporated into virion capsids. Incorporation of the RGD motif into the pIX resulted in significant augmentation of BAdV-3 fiber knob-independent infection of the integrin-positive cells, suggesting that RGD motifs are displayed on the surface of virion capsids and are accessible for binding to integrins. Analysis of BAV951 revealed that the chimeric pIX is incorporated into virion capsids and EYFP containing the C-terminus of pIX is exposed on the surface of the virion. Moreover, insertion of chimeric pIXs was maintained without change through successive rounds of viral replication. These results suggested that in contrast to major capsid proteins (hexon, penton, fiber), the minor capsid protein IX can be use for the incorporation of targeting ligands based on either small peptides or longer polypeptides

  6. Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources

    International Nuclear Information System (INIS)

    Spencer, Robert G M; Vermilyea, Andrew; Fellman, Jason; Hood, Eran; Raymond, Peter; Stubbins, Aron; Scott, Durelle

    2014-01-01

    Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier outflow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous feature of glacier outflow. We observed no systematic depletion in Δ 14 C-DOC with increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ 13 C-DOC, Δ 14 C-DOC and fluorescence signatures appear to have been influenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ 14 C-DOC of stream samples at the outflow (−181.7 to −355.3‰) was comparable to the Δ 14 C-DOC for snow samples from the accumulation zone (−207.2 to −390.9‰), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century. (papers)

  7. Ocean impact on Nioghalvfjerdsfjorden Glacier, Northeast Greenland

    Science.gov (United States)

    Schaffer, Janin; Kanzow, Torsten; von Appen, Wilken-Jon; Mayer, Christoph

    2017-04-01

    The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers around Greenland. The largest of three outlet glaciers draining the Northeast Greenland Ice Stream is Nioghalvfjerdsfjorden Glacier (also referred to as 79 North Glacier). Historic observations showed that warm waters of Atlantic origin are present in the subglacial cavity below the 80 km long floating ice tongue of the Nioghalvfjerdsfjorden Glacier and cause strong basal melt at the grounding line, but to date it has been unknown how those warm water enter the cavity. In order to understand how Atlantic origin waters carry heat into the subglacial cavity beneath Nioghalvfjerdsfjorden Glacier, we performed bathymetric, hydrographic, and velocity observations in the vicinity of the main glacier calving front aboard RV Polarstern in summer 2016. The bathymetric multibeam data shows a 500 m deep and 2 km narrow passage downstream of a 310 m deep sill. This turned out to be the only location deep enough for an exchange of Atlantic waters between the glacier cavity and the continental shelf. Hydrographic and velocity measurements revealed a density driven plume in the vicinity of the glacier calving front causing a rapid flow of waters of Atlantic origin warmer 1°C into the subglacial cavity through the 500 m deep passage. In addition, glacially modified waters flow out of the glacier cavity below the 80 m deep ice base. In the vicinity of the glacier, the glacially modified waters form a distinct mixed layer situated above the Atlantic waters and below the ambient Polar water. At greater distances from the glacier this layer is eroded by lateral mixing with ambient water. Based on our observations we will present an estimate of the ocean heat transport into the subglacial cavity. In comparison with historic observations we find an increase in Atlantic water temperatures throughout the last 20 years. The resulting

  8. Construction and expression of eukaryotic expression vectors of full-length, amino-terminus and carboxyl-terminus Raf gene

    Directory of Open Access Journals (Sweden)

    Zhuomin WANG

    2008-06-01

    Full Text Available Background and objective Raf is a key molecule in the Ras-Raf-MEK-ERK signal transduction pathway and is highly activated in different human carcinomas. However, its biological functions and regulation mechanisms are still unclear. The aims of this study were to construct eukaryotic expression vectors with Raf full encoding region, truncated amino-terminus and carboxyl-terminus, respectively. Methods Eukaryotic expression vectors of pCMV-Tag2b-Raf-1, pCMV-Tag2b-N-Raf and pCMV-Tag2b-C-Raf were constructed by gene recombination technique and confirmed by restriction enzyme analysis and DNA sequencing. Furthermore, the expression of these fusion proteins was detected by western blot in transient transfected 293T cells. Results The sequences and open reading frames of these three vectors were completely consistent with experimental design. All target proteins can be detected in 293T cells. Conclusion Eukaryotic expression vectors of pCMV-Tag2b-Raf-1, pCMV-Tag2b-N-Raf and pCMV-Tag2b-C-Raf were successfully constructed and can be expressed in 293T cells.

  9. Glaciers in Patagonia: Controversy and prospects

    Science.gov (United States)

    Kargel, J. S.; Alho, P.; Buytaert, W.; Célleri, R.; Cogley, J. G.; Dussaillant, A.; Guido, Z.; Haeberli, W.; Harrison, S.; Leonard, G.; Maxwell, A.; Meier, C.; Poveda, G.; Reid, B.; Reynolds, J.; Rodríguez, C. A. Portocarrero; Romero, H.; Schneider, J.

    2012-05-01

    Lately, glaciers have been subjects of unceasing controversy. Current debate about planned hydroelectric facilities—a US7- to 10-billion megaproject—in a pristine glacierized area of Patagonia, Chile [Romero Toledo et al., 2009; Vince, 2010], has raised anew the matter of how glaciologists and global change experts can contribute their knowledge to civic debates on important issues. There has been greater respect for science in this controversy than in some previous debates over projects that pertain to glaciers, although valid economic motivations again could trump science and drive a solution to the energy supply problem before the associated safety and environmental problems are understood. The connection between glaciers and climate change—both anthropogenic and natural—is fundamental to glaciology and to glaciers' practical importance for water and hydropower resources, agriculture, tourism, mining, natural hazards, ecosystem conservation, and sea level [Buytaert et al., 2010; Glasser et al., 2011]. The conflict between conservation and development can be sharper in glacierized regions than almost anywhere else. Glaciers occur in spectacular natural landscapes, but they also supply prodigious exploitable meltwater.

  10. Quantifying seasonal velocity at Khumbu Glacier, Nepal

    Science.gov (United States)

    Miles, E.; Quincey, D. J.; Miles, K.; Hubbard, B. P.; Rowan, A. V.

    2017-12-01

    While the low-gradient debris-covered tongues of many Himalayan glaciers exhibit low surface velocities, quantifying ice flow and its variation through time remains a key challenge for studies aimed at determining the long-term evolution of these glaciers. Recent work has suggested that glaciers in the Everest region of Nepal may show seasonal variability in surface velocity, with ice flow peaking during the summer as monsoon precipitation provides hydrological inputs and thus drives changes in subglacial drainage efficiency. However, satellite and aerial observations of glacier velocity during the monsoon are greatly limited due to cloud cover. Those that do exist do not span the period over which the most dynamic changes occur, and consequently short-term (i.e. daily) changes in flow, as well as the evolution of ice dynamics through the monsoon period, remain poorly understood. In this study, we combine field and remote (satellite image) observations to create a multi-temporal, 3D synthesis of ice deformation rates at Khumbu Glacier, Nepal, focused on the 2017 monsoon period. We first determine net annual and seasonal surface displacements for the whole glacier based on Landsat-8 (OLI) panchromatic data (15m) processed with ImGRAFT. We integrate inclinometer observations from three boreholes drilled by the EverDrill project to determine cumulative deformation at depth, providing a 3D perspective and enabling us to assess the role of basal sliding at each site. We additionally analyze high-frequency on-glacier L1 GNSS data from three sites to characterize variability within surface deformation at sub-seasonal timescales. Finally, each dataset is validated against repeat-dGPS observations at gridded points in the vicinity of the boreholes and GNSS dataloggers. These datasets complement one another to infer thermal regime across the debris-covered ablation area of the glacier, and emphasize the seasonal and spatial variability of ice deformation for glaciers in High

  11. Dissolved organic carbon fractionation accelerates glacier-melting: A case study in the northern Tibetan Plateau.

    Science.gov (United States)

    Hu, Zhaofu; Kang, Shichang; Yan, Fangping; Zhang, Yulan; Li, Yang; Chen, Pengfei; Qin, Xiang; Wang, Kun; Gao, Shaopeng; Li, Chaoliu

    2018-06-15

    In glacierized regions, melting process has a significant effect on concentrations and light absorption characteristics of dissolved organic carbon (DOC), potentially resulting in variations of its radiative forcing, which is not yet relevant research at glacier region of the Tibetan Plateau (TP). In this study, DOC fractionation and its radiative forcing change during the melting process were investigated at Laohugou glacier No. 12 (LHG glacier) in western Qilian Mts., northern TP. DOC concentrations in fresh snow, snowpit and surface ice samples were 0.38 ± 0.06, 0.22 ± 0.11 and 0.60 ± 0.21 mg L -1 , respectively. Their mass absorption cross-section at 365 nm (MAC 365 ) were 0.65 ± 0.16, 4.71 ± 3.68 and 1.44 ± 0.52 m 2  g -1 , respectively. The MAC 365 values of snowpit samples showed a significant negative correlation with DOC concentrations, indicating DOC with high MAC 365 values were likely to be kept in snow during the melting process. Topsoil samples of LHG glacierized region likely contributed a lot to snowpit DOC with high MAC 365 values due to their similar absorption spectra. Spatially, the DOC concentration of surface ice samples increased from terminus to the upper part of the glacier. Correspondingly, the MAC 365 value showed decreased trend. In the freezing experiment on surface ice and topsoil samples, small part of DOC with high MAC 365 value was also likely to enter first frozen solid phase. In addition, the radiative forcing caused by snowpit and surface ice DOC increased around 7.64 ± 2.93 and 4.95 ± 1.19 times relative to fresh snow DOC, indicating the snow/ice melting caused by increased light-absorbing DOC needs to be considered in the future research. Copyright © 2018 Elsevier B.V. All rights reserved.

  12. Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

    Science.gov (United States)

    Sauber, Jeanne M.; Molnia, Bruce F.

    2004-07-01

    Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes ( ML≥2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes ( Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake ( Ms=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass

  13. C-terminus-mediated voltage gating of Arabidopsis guard cell anion channel QUAC1.

    Science.gov (United States)

    Mumm, Patrick; Imes, Dennis; Martinoia, Enrico; Al-Rasheid, Khaled A S; Geiger, Dietmar; Marten, Irene; Hedrich, Rainer

    2013-09-01

    Anion transporters in plants play a fundamental role in volume regulation and signaling. Currently, two plasma membrane-located anion channel families—SLAC/SLAH and ALMT—are known. Among the ALMT family, the root-expressed ALuminium-activated Malate Transporter 1 was identified by comparison of aluminum-tolerant and Al(3+)-sensitive wheat cultivars and was subsequently shown to mediate voltage-independent malate currents. In contrast, ALMT12/QUAC1 (QUickly activating Anion Channel1) is expressed in guard cells transporting malate in an Al(3+)-insensitive and highly voltage-dependent manner. So far, no information is available about the structure and mechanism of voltage-dependent gating with the QUAC1 channel protein. Here, we analyzed gating of QUAC1-type currents in the plasma membrane of guard cells and QUAC1-expressing oocytes revealing similar voltage dependencies and activation–deactivation kinetics. In the heterologous expression system, QUAC1 was electrophysiologically characterized at increasing extra- and intracellular malate concentrations. Thereby, malate additively stimulated the voltage-dependent QUAC1 activity. In search of structural determinants of the gating process, we could not identify transmembrane domains common for voltage-sensitive channels. However, site-directed mutations and deletions at the C-terminus of QUAC1 resulted in altered voltage-dependent channel activity. Interestingly, the replacement of a single glutamate residue, which is conserved in ALMT channels from different clades, by an alanine disrupted QUAC1 activity. Together with C- and N-terminal tagging, these results indicate that the cytosolic C-terminus is involved in the voltage-dependent gating mechanism of QUAC1.

  14. Modeling the Long-Term Evolution of Supraglacial Ice Cliffs on Himalayan Debris-Covered Glaciers

    Science.gov (United States)

    Buri, P.; Miles, E. S.; Steiner, J. F.; Ragettli, S.; Pellicciotti, F.

    2016-12-01

    Supraglacial ice cliffs are present on debris-covered glaciers worldwide and provide the only direct atmosphere-ice interface over the lower sections of these glaciers. Low albedo and high longwave emissions from surrounding debris cause very high melt rates, accounting for a significant portion of total glacier mass loss. As a result, ice cliffs affect glacier downwasting and mass balance. Additionally, and in contrast to the debris-covered ice, high melt at cliffs turns them into dynamic features, directly affecting glacier surface evolution. While conceptual ideas about the formation, evolution and collapse of ice cliffs exist, their life cycles have never been thoroughly documented. Based on observations obtained from high-resolution aerial and terrestrial images analyzed with Structure-from-Motion and with data from automatic weather stations on two glaciers in the Nepalese Himalaya, we simulate the evolution of selected ice cliffs over several seasons using a new physically-based model of cliff backwasting. The 3D model calculates the energy-balance at the cliff scale and includes the cliff interaction with supraglacial ponds and reburial by debris. We consider cliffs of different shape, orientation and slope, and we show that backwasting leads to a variety of evolution typologies, with cliffs that maintain a constant, self-similar geometry, cliffs that grow laterally and cliffs that disappear through slope shallowing and debris melt-out. Most cliffs persist over several seasons. The presence of a pond appears to be the key control for cliffs to survive, while east and west facing cliffs grow because of higher radiation receipts. We use the model to test the hypothesis that south-facing cliffs do not survive. We show that most south-facing cliffs demise after one melt season on both glaciers, because of high input of solar radiation exceeding the longwave radiation receipt. For north facing features, the longwave radiation receipts at lower cliff sections

  15. Changing pattern of ice flow and mass balance for glaciers discharging into the Larsen A and B embayments, Antarctic Peninsula, 2011 to 2016

    Science.gov (United States)

    Rott, Helmut; Abdel Jaber, Wael; Wuite, Jan; Scheiblauer, Stefan; Floricioiu, Dana; Melchior van Wessem, Jan; Nagler, Thomas; Miranda, Nuno; van den Broeke, Michiel R.

    2018-04-01

    We analysed volume change and mass balance of outlet glaciers on the northern Antarctic Peninsula over the periods 2011 to 2013 and 2013 to 2016, using high-resolution topographic data from the bistatic interferometric radar satellite mission TanDEM-X. Complementary to the geodetic method that applies DEM differencing, we computed the net mass balance of the main outlet glaciers using the mass budget method, accounting for the difference between the surface mass balance (SMB) and the discharge of ice into an ocean or ice shelf. The SMB values are based on output of the regional climate model RACMO version 2.3p2. To study glacier flow and retrieve ice discharge we generated time series of ice velocity from data from different satellite radar sensors, with radar images of the satellites TerraSAR-X and TanDEM-X as the main source. The study area comprises tributaries to the Larsen A, Larsen Inlet and Prince Gustav Channel embayments (region A), the glaciers calving into the Larsen B embayment (region B) and the glaciers draining into the remnant part of the Larsen B ice shelf in Scar Inlet (region C). The glaciers of region A, where the buttressing ice shelf disintegrated in 1995, and of region B (ice shelf break-up in 2002) show continuing losses in ice mass, with significant reduction of losses after 2013. The mass balance numbers for the grounded glacier area of region A are -3.98 ± 0.33 Gt a-1 from 2011 to 2013 and -2.38 ± 0.18 Gt a-1 from 2013 to 2016. The corresponding numbers for region B are -5.75 ± 0.45 and -2.32 ± 0.25 Gt a-1. The mass balance in region C during the two periods was slightly negative, at -0.54 ± 0.38 Gt a-1 and -0.58 ± 0.25 Gt a-1. The main share in the overall mass losses of the region was contributed by two glaciers: Drygalski Glacier contributing 61 % to the mass deficit of region A, and Hektoria and Green glaciers accounting for 67 % to the mass deficit of region B. Hektoria and Green glaciers accelerated significantly in 2010

  16. Role of glacier runoff in the Heihe Basin

    OpenAIRE

    坂井, 亜規子; 藤田, 耕史; 中尾, 正義; YAO, Tandong

    2005-01-01

    We estimated the fluctuation of precipitation and air temperature from Dunde ice core data since 1606 comparing to meteorological data taken near the July 1st glacier since 1930s. Then, we calculated the discharges from glaciers and glacier-free areaFurthermore, we analyzed the sensitivity of those discharges to meteorological factor. The result revealed that calculated discharge from glacier-free area increased with precipitation. Meanwhile, calculated discharge from glaciers decreased with ...

  17. Glacier Instability, Rapid Glacier Lake Growth and Related Hazards at Belvedere Glacier, Macugnaga, Italy

    Science.gov (United States)

    Huggel, C.; Kaeaeb, A.; Haeberli, W.; Mortara, G.; Chiarle, M.; Epifani, F.

    2002-12-01

    Starting in summer 2000, Belvedere Glacier, near Macugnaga, Italian Alps, developed an extraordinary change in flow, geometry and surface appearance. A surge-type flow acceleration started in the lower parts of the Monte-Rosa east face, leading to strong crevassing and deformation of Belvedere Glacier, accompanied by bulging of its orographic right margin. In September 2001, a small supraglacial lake developed on the glacier. High water pressure and accelerated movement lasted into winter 2001/2002. The ice, in places, started to override moraines from the Little Ice Age. In late spring and early summer 2002, the supraglacial lake grew at extraordinary rates reaching a maximum area of more than 150'000 m2 by end of June. The evolution of such a large supraglacial lake, a rather unique feature in the Alps, was probably enabled by changes in the subglacial drainage system in the course of the surge-like developments with high water pressure in the glacier. At the end of June, an enhanced growth of the lake level with a rise of about 1 m per day was observed such that the supraglacial lake became a urgent hazard problem for the community of Macugnaga. Emergency measures had to be taken by the Italian Civil Protection. The authors thereby acted as the official expert advisers. Temporal evacuations were ordered and a permanent monitoring and alarm system was installed. Pumps with a maximum output of 1 m3/s were brought to the lake. Bathymetric studies yielded a maximum lake depth of 55 m and a volume of 3.3 millions of cubic meters of water. Aerial photography of 1995, 1999, September 2001 and October 2001 was used to calculate ice flow velocities and changes in surface altitude. Compared to the period of 1995 to 1999, the flow accelerated by about five times in 2001 (max. speeds up to 200 m/yr). Surface uplift measured was about 10-15 m/yr. The results of the photogrammetric studies were used to evaluate different possible lake-outburst scenarios, in particular

  18. An in-vitro comparison of the radiographic and actual gutta-percha terminus.

    Science.gov (United States)

    Namazikhah, M S; Ghiai, M; Parkin, M J; Puccinelli, L

    2000-06-01

    The purpose of this study was to investigate the difference between the radiographic gutta-percha terminus and the actual gutta-percha terminus of human molars by comparing radiographic obturation results with actual obturation results. Forty maxillary palatal roots and 50 mandibular distal roots were randomly selected from a population of 540. They were then mounted in stone and radiographed. Conventional endodontic therapy was completed using stainless-steel K files and lateral condensation. Each radiographic gutta-percha terminus was evaluated under 4.5x magnification by three examiners following the completion of root canal therapy. These results were recorded. Each tooth was then removed from its mounting, and the actual gutta-percha terminus was evaluated under 4.5x magnification. These results were recorded and compared to the radiographic gutta-percha terminus results. In all 90 teeth examined, the actual gutta-percha terminus was equal to or longer than the radiographic gutta-percha terminus. In the 50 mandibular distal roots, the actual gutta-percha terminus averaged 0.645 mm longer than the radiographic gutta-percha terminus. In the 40 maxillary palatal roots, this difference measured 0.6375 mm.

  19. Glacier development and topographic context

    DEFF Research Database (Denmark)

    López-Moreno, J. I.; Nogués-Bravo, David; Chueca-Cía, J.

    2006-01-01

    This paper analyses the topographic context of the remaining glaciated areas in the Maladeta Massif (Central Spanish Pyrenees). These ice-covered surfaces have been incorporated into a geographic information system (GIS) in an attempt at correlating the presence of ice with a range of topographic...... and recent evolution of each glacial body. Thus, the joint effect of altitude, exposure to incoming solar radiation, slope and mean curvature is able to explain more than 70 per cent of the observed variance. Copyright © 2006 John Wiley & Sons, Ltd....... variables obtained from a digital elevation model. The use of generalized additive models and binary regression tree models enabled us (i) to quantify the spatial variability in the distribution of glaciers attributable to characteristics of the local terrain, (ii) to investigate the interaction between...

  20. ROCK GLACIERS IN THE KOLYMA HIGHLAND

    Directory of Open Access Journals (Sweden)

    A. A. Galanin

    2012-01-01

    Full Text Available Based on remote mapping and field studies inGrand Rapids, Tumansky,Hasynsky,Del-Urechen Ridges as well as Dukchinsky and Kilgansky Mountain Massifs there were identified about 1160 landforms which morphologically are similar to the rock glaciers or they develop in close association with them. Besides tongue-shaped cirque rock glaciers originated due to ablation, a large number of lobate-shaped slope-associated rock glaciers were recognized. Significant quantity of such forms are developing within the active neotectonic areas, in zones of seismic-tectonic badland and in association with active earthquakes-controlling faults. Multiplication of regional data on volcanic-ash-chronology, lichenometry, Schmidt Hammer Test, pollen spectra and single radiocarbon data, most of the active rock glaciers were preliminary attributed to the Late Holocene.

  1. Rock glaciers, Prealps, Vaud, Switzerland, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — The investigated area forms part of the western lobe of the Prealps (Swiss Prealps). The 25 identified fossil rock glaciers are found mainly in the Prealpes medianes...

  2. Glacier monitoring and glacier-climate interactions in the tropical Andes: A review

    Science.gov (United States)

    Veettil, Bijeesh Kozhikkodan; Wang, Shanshan; Florêncio de Souza, Sergio; Bremer, Ulisses Franz; Simões, Jefferson Cardia

    2017-08-01

    In this review, we summarized the evolution of glacier monitoring in the tropical Andes during the last few decades, particularly after the development of remote sensing and photogrammetry. Advantages and limitations of glacier mapping, applied so far, in Venezuela, Colombia, Ecuador, Peru and Bolivia are discussed in detail. Glacier parameters such as the equilibrium line altitude, snowline and mass balance were given special attention in understanding the complex cryosphere-climate interactions, particularly using remote sensing techniques. Glaciers in the inner and the outer tropics were considered separately based on the precipitation and temperature conditions within a new framework. The applicability of various methods to use glacier records to understand and reconstruct the tropical Andean climate between the Last Glacial Maximum (11,700 years ago) and the present is also explored in this paper. Results from various studies published recently were analyzed and we tried to understand the differences in the magnitudes of glacier responses towards the climatic perturbations in the inner tropics and the outer tropics. Inner tropical glaciers, particularly those in Venezuela and Colombia near the January Intertropical Convergence Zone (ITCZ), are more vulnerable to increase in temperature. Surface energy balance experiments show that outer tropical glaciers respond to precipitation variability very rapidly in comparison with the temperature variability, particularly when moving towards the subtropics. We also analyzed the gradients in glacier response to climate change from the Pacific coast towards the Amazon Basin as well as with the elevation. Based on the current trends synthesised from recent studies, it is hypothesized that the glaciers in the inner tropics and the southern wet outer tropics will disappear first as a response to global warming whereas glaciers in the northern wet outer tropics and dry outer tropics show resistance to warming trends due to

  3. Fuzzy Cognitive Maps for Glacier Hazards Assessment: Application to Predicting the Potential for Glacier Lake Outbursts

    Science.gov (United States)

    Furfaro, R.; Kargel, J. S.; Fink, W.; Bishop, M. P.

    2010-12-01

    Glaciers and ice sheets are among the largest unstable parts of the solid Earth. Generally, glaciers are devoid of resources (other than water), are dangerous, are unstable and no infrastructure is normally built directly on their surfaces. Areas down valley from large alpine glaciers are also commonly unstable due to landslide potential of moraines, debris flows, snow avalanches, outburst floods from glacier lakes, and other dynamical alpine processes; yet there exists much development and human occupation of some disaster-prone areas. Satellite remote sensing can be extremely effective in providing cost-effective and time- critical information. Space-based imagery can be used to monitor glacier outlines and their lakes, including processes such as iceberg calving and debris accumulation, as well as changing thicknesses and flow speeds. Such images can also be used to make preliminary identifications of specific hazardous spots and allows preliminary assessment of possible modes of future disaster occurrence. Autonomous assessment of glacier conditions and their potential for hazards would present a major advance and permit systematized analysis of more data than humans can assess. This technical leap will require the design and implementation of Artificial Intelligence (AI) algorithms specifically designed to mimic glacier experts’ reasoning. Here, we introduce the theory of Fuzzy Cognitive Maps (FCM) as an AI tool for predicting and assessing natural hazards in alpine glacier environments. FCM techniques are employed to represent expert knowledge of glaciers physical processes. A cognitive model embedded in a fuzzy logic framework is constructed via the synergistic interaction between glaciologists and AI experts. To verify the effectiveness of the proposed AI methodology as applied to predicting hazards in glacier environments, we designed and implemented a FCM that addresses the challenging problem of autonomously assessing the Glacier Lake Outburst Flow

  4. The length of the glaciers in the world

    DEFF Research Database (Denmark)

    Machguth, Horst; Huss, M.; Huss, M.

    2014-01-01

    a fully automated method based on glacier surface slope, distance to the glacier margins and a set of trade-off functions. The method is developed for East Greenland, evaluated for the same area as well as for Alaska, and eventually applied to all ∼ 200000 glaciers around the globe. The evaluation...... highlights accurately calculated glacier length where DEM quality is good (East 10 Greenland) and limited precision on low quality DEMs (parts of Alaska). Measured length of very small glaciers is subject to a certain level of ambiguity. The global calculation shows that only about 1.5% of all glaciers...... are longer than 10km with Bering Glacier (Alaska/Canada) being the longest glacier in the world at a length of 196 km. Based on model output we derive global and regional area-length scaling laws. Differences among regional scaling parameters appear to be related to characteristics of topography and glacier...

  5. Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland

    DEFF Research Database (Denmark)

    Nettles, M.; Larsen, T. B.; Elósegui, P.

    2008-01-01

    Geodetic observations show several large, sudden increases in flow speed at Helheim Glacier, one of Greenland's largest outlet glaciers, during summer, 2007. These step-like accelerations, detected along the length of the glacier, coincide with teleseismically detected glacial earthquakes and major...... iceberg calving events. No coseismic offset in the position of the glacier surface is observed; instead, modest tsunamis associated with the glacial earthquakes implicate glacier calving in the seismogenic process. Our results link changes in glacier velocity directly to calving-front behavior...... at Greenland's largest outlet glaciers, on timescales as short as minutes to hours, and clarify the mechanism by which glacial earthquakes occur. Citation: Nettles, M., et al. (2008), Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland....

  6. ICESat laser altimetry over small mountain glaciers

    Directory of Open Access Journals (Sweden)

    D. Treichler

    2016-09-01

    Full Text Available Using sparsely glaciated southern Norway as a case study, we assess the potential and limitations of ICESat laser altimetry for analysing regional glacier elevation change in rough mountain terrain. Differences between ICESat GLAS elevations and reference elevation data are plotted over time to derive a glacier surface elevation trend for the ICESat acquisition period 2003–2008. We find spatially varying biases between ICESat and three tested digital elevation models (DEMs: the Norwegian national DEM, SRTM DEM, and a high-resolution lidar DEM. For regional glacier elevation change, the spatial inconsistency of reference DEMs – a result of spatio-temporal merging – has the potential to significantly affect or dilute trends. Elevation uncertainties of all three tested DEMs exceed ICESat elevation uncertainty by an order of magnitude, and are thus limiting the accuracy of the method, rather than ICESat uncertainty. ICESat matches glacier size distribution of the study area well and measures small ice patches not commonly monitored in situ. The sample is large enough for spatial and thematic subsetting. Vertical offsets to ICESat elevations vary for different glaciers in southern Norway due to spatially inconsistent reference DEM age. We introduce a per-glacier correction that removes these spatially varying offsets, and considerably increases trend significance. Only after application of this correction do individual campaigns fit observed in situ glacier mass balance. Our correction also has the potential to improve glacier trend significance for other causes of spatially varying vertical offsets, for instance due to radar penetration into ice and snow for the SRTM DEM or as a consequence of mosaicking and merging that is common for national or global DEMs. After correction of reference elevation bias, we find that ICESat provides a robust and realistic estimate of a moderately negative glacier mass balance of around −0.36 ± 0.07

  7. What Influences Climate and Glacier Change in the Southwestern China?

    Science.gov (United States)

    Yasunari, Teppei J.

    2012-01-01

    The subject of climate change in the areas of the Tibetan Plateau (TP) and the Himalayas has taken on increasing importance because of available water resources from their mountain glaciers. Many of these glaciers over the region have been retreating, while some are advancing and stable. Other studies report that some glaciers in the Himalayas show acceleration on their shrinkage. However, the causes of the glacier meltings are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. However, it is vital that we pursue further study to enable the future prediction on glacier changes.

  8. Confirmation of a blocked amino terminus of sulfhydryl oxidase

    International Nuclear Information System (INIS)

    Janolino, V.G.; Morrison-Rowe, S.J.; Swaisgood, H.E.

    1990-01-01

    The isolation of sulfhydryl oxidase from bovine milk in a suitably pure form for sequencing was carried out by transient covalent affinity chromatography of diafiltered whey using cysteinylsuccinamidopropyl-glass as matrix. The glutathione-eluted proteins were separated by SDS-PAGE. By radiolabeling the affinity chromatography-purified enzyme with [ 14 C]iodoacetate before subjecting to SDS-PAGE, the sulfhydryl oxidase band was identified, because sulfhydryl oxidase is known to be inactivated by alkylation of one sulfhydryl group per mole. The results confirmed that sulfhydryl oxidase corresponds to the 85 (± 5)-kDa band observed on SDS-PAGE. The protein band corresponding to radiolabeled sulfhydryl oxidase was recovered from SDS-PAGE gels by electrophoretic elution and by electroblotting on polyvinylidene difluoride membrane and subjected to gas phase sequencing. Precautions were taken during electrophoretic elution to prevent reactions that result in N-terminal blocking. Both methods of protein recovery yielded negative results when subjected to sequence analysis indicating that the N-terminus of sulfhydryl oxidase is blocked

  9. Monitoring Unstable Glaciers with Seismic Noise Interferometry

    Science.gov (United States)

    Preiswerk, L. E.; Walter, F.

    2016-12-01

    Gravity-driven glacier instabilities are a threat to human infrastructure in alpine terrain, and this hazard is likely to increase with future changes in climate. Seismometers have been used previously on hazardous glaciers to monitor the natural englacial seismicity. In some situations, an increase in "icequake" activity may indicate fracture growth and thus an imminent major break-off. However, without independent constraints on unstable volumes, such mere event counting is of little use. A promising new approach to monitor unstable masses in Alpine terrain is coda wave interferometry of ambient noise. While already established in the solid earth, application to glaciers is not straightforward, because the lack of inhomogeneities typically suppresses seismic coda waves in glacier ice. Only glaciers with pervasive crevasses provide enough scattering to generate long codas. This is requirement is likely met for highly dynamic unstable glaciers. Here, we report preliminary results from a temporary 5-station on-ice array of seismometers (corner frequencies: 1 Hz, array aperture: 500m) on Bisgletscher (Switzerland). The seismometers were deployed in shallow boreholes, directly above the unstable tongue of the glacier. In the frequency band 4-12 Hz, we find stable noise cross-correlations, which in principle allows monitoring on a subdaily scale. The origin and the source processes of the ambient noise in these frequencies are however uncertain. As a first step, we evaluate the stability of the sources in order to separate effects of changing source parameters from changes of englacial properties. Since icequakes occurring every few seconds may dominate the noise field, we compare their temporal and spatial occurrences with the cross-correlation functions (stability over time, the asymmetry between causal and acausal parts of the cross-correlation functions) as well as with results from beamforming to assess the influence of these transient events on the noise field.

  10. Glacier change in the Gangdise Mountains, southern Tibet, since the Little Ice Age

    Science.gov (United States)

    Zhang, Qian; Yi, Chaolu; Fu, Ping; Wu, Yubin; Liu, Jinhua; Wang, Ninglian

    2018-04-01

    Delineating glacier change during the Little Ice Age (LIA) is of great importance when attempting to understand regional climatic changes and can also help to improve the understanding of any predictions of future glacial changes. However, such knowledge is still lacking for some critical regions of the Tibetan Plateau (TP). In this study, we mapped 4188 contemporary glaciers and reconstructed 1216 LIA areas of glacial coverage in the Gangdise Mountains to the north of the Himalaya using Google Earth satellite imagery. We estimated their paleoglacial areas and equilibrium line altitudes (ELAs) based on the toe-to-headwall altitude ratio (THAR) method. Results show that most glaciers are small (ELA ranges from 5516 to 6337 m asl; the LIA ELA ranged from 5476 to 6329 m asl. Contemporary and LIA ELA values rise from southeast to northwest. As a general rule, the rise in the ELA value decreases from the eastern to the central Gangdise Mountains and then increases westward, with a mean ELA rise of 45 m. Multiple regression models suggest that 46.8% of the glacier area loss can be explained by glacier elevation, area, and slope. However, only 15.5% of the rise in ELA values can be explained by glacial geometric, topographic, or locational parameters. The spatial pattern of modern ELA values in this region appears inversely related to precipitation, which decreases from southeast to northwest, implying that precipitation is one of the key controls of ELAs. This is also consistent with results from elsewhere in High Asia. In contrast to the Gangdise Mountains' eastern and western sectors, glaciers in the central sector have undergone less change, i.e., in terms of reductions in length, area loss, and rises in ELA. Topography can of course also influence glacial change by creating shielding and/or rainshadow effects and by affecting local temperatures.

  11. Assembly patterns of soil-dwelling lichens after glacier retreat in the European Alps.

    Science.gov (United States)

    Nascimbene, Juri; Mayrhofer, Helmut; Dainese, Matteo; Bilovitz, Peter Othmar

    2017-06-01

    To assess the spatial-temporal dynamics of primary succession following deglaciation in soil-dwelling lichen communities. European Alps (Austria, Switzerland and Italy). Five glacier forelands subjected to relevant glacier retreat during the last century were investigated. In each glacier foreland, three successional stages were selected at increasing distance from the glacier, corresponding to a gradient of time since deglaciation between 25 and 160 years. In each successional stage, soil-dwelling lichens were surveyed within five 1 × 1 m plots. In addition to a classical ecological framework, based on species richness and composition, we applied a functional approach to better elucidate community assembly mechanisms. A positive relationship was found between species richness and time since deglaciation indicating that richer lichen communities can be found at increasing terrain ageing. This pattern was associated with compositional shifts, suggesting that different community assemblages can be found along the successional stages. The analysis of β-diversity revealed a significant nested pattern of species assemblages along the gradient (i.e. earlier successional stages hosted a subset of the species already established in older successional stages), while the turnover component was less relevant. Considering functional groups, we found contrasting patterns in relation to time since deglaciation: the incidence of species with a cyanobacterial photobiont and those reproducing by spores decreased, while that of species reproducing by vegetative propagules increased. This study reveals that community assembly patterns of soil-dwelling lichens in alpine glacier forelands are ruled by mechanisms of directional species accumulation and trait selection that involve a trade-off between different functional strategies. Functional traits that reflect the dispersal and adaptation capability of the species underpin the colonization success of soil-dwelling lichens in

  12. GlacierRocks - Glacier-Headwall Interaction and its Influence on Rockfall Activity

    Science.gov (United States)

    Hartmeyer, Ingo; Keuschnig, Markus; Krautblatter, Michael; Helfricht, Kay; Leith, Kerry; Otto, Jan-Christoph

    2017-04-01

    Climate models predict continued climate warming and a decrease of Austrian glaciers to less than 20% of their present area by the end of this century. Rockfall from freshly exposed headwalls has been documented as an increasing risk factor with considerable significance for man and high-alpine infrastructure. Recent findings of a five-year terrestrial laserscanning campaign (2011-2016) monitoring glacial headwalls at the Kitzsteinhorn (3.203 m a.s.l.), Hohe Tauern Range, Austria, show the dramatic impact of glacier thinning on adjacent headwalls: 80 % of the detected rockfall volumes were triggered from areas located less than 20 m above the current glacier surface. Despite these implications, little is known about the thermal, mechanical and hydrological processes that operate at the glacier-headwall interface (randkluft). Systemic in-situ monitoring of stability-relevant parameters are lacking, leaving fundamental gaps in the understanding of rockfall preconditioning in glacial headwalls and the geomorphological evolution of glaciated catchments. In this contribution we introduce the recently approved research project 'GlacierRocks', which starts in 2017 and will run for at least three years. 'GlacierRocks' will establish the worldwide first research site for long-term monitoring of stability-relevant processes inside a randkluft system. Based on the acquired monitoring data 'GlacierRocks' is pursuing three overall aims at (1) gaining a better understanding of rockfall preconditioning in randklufts and related geomorphological shaping of headwalls, (2) analyzing poorly understood glacial thinning dynamics near headwalls, and (3) estimating present and future rockfall hazard potential in headwalls on a regional scale. The three system components (headwall, glacier, randkluft) will be investigated by combining geomorphological, glaciological and meteorological methods. 'GlacierRocks' will continuously monitor rock temperature, rock moisture, frost cracking

  13. Updating the New Zealand Glacier Inventory

    Science.gov (United States)

    Baumann, S. C.; Anderson, B.; Mackintosh, A.; Lorrey, A.; Chinn, T.; Collier, C.; Rack, W.; Purdie, H.

    2017-12-01

    The last complete glacier inventory of New Zealand dates from the year 1978 (North Island 1988) and was manually constructed from oblique aerial photographs and geodetic maps (Chinn 2001). The inventory has been partly updated by Gjermundsen et al. (2011) for the year 2002 (40% of total area) and by Sirguey & More (2010) for the year 2009 (32% of total area), both using ASTER satellite imagery. We used Landsat 8 OLI/TIRS satellite data from February/March 2016 to map the total glaciated area. Clean and debris-covered ice were mapped semi-automatically. The band ratio approach was used for clean ice (ratio: red/SWIR). We mapped debris-covered ice using a supervised classification (maximum likelihood). Manual post processing was necessary due to misclassifications (e.g. lakes, clouds) or mapping in shadowed areas. It was also necessary to manually combine the clean and debris-covered parts into single glaciers. Additional input data for the post processing were Sentinel 2 images from the same time period, orthophotos from Land Information New Zealand (resolution: 0.75 m, date: Nov 2014), and the 1978/88 outlines from the GLIMS database (http://www.glims.org/). As the Sentinel 2 data were more heavily cloud covered compared to the Landsat 8 images, they were only used for post processing and not for the classification itself. Initial results show that New Zealand glaciers covered an area of about 1050 km² in 2016, a reduction of 16% since 1978. Approximately 17% of glacier area was covered in surface debris. The glaciers in the central Southern Alps around Mt Cook reduced in area by 24%. Glaciers in the North Island of New Zealand reduced by 71% since 1988, and only 2 km² of ice cover remained in 2016. Chinn, TJH (2001). "Distribution of the glacial water resources of New Zealand." Journal of Hydrology (NZ) 40(2): 139-187 Gjermundsen, EF, Mathieu, R, Kääb, A, Chinn, TJH, Fitzharris, B & Hagen, JO (2011). "Assessment of multispectral glacier mapping methods and

  14. Storm-induced water dynamics and thermohaline structure at the tidewater Flade Isblink Glacier outlet to the Wandel Sea (NE Greenland)

    Science.gov (United States)

    Kirillov, Sergei; Dmitrenko, Igor; Rysgaard, Søren; Babb, David; Toudal Pedersen, Leif; Ehn, Jens; Bendtsen, Jørgen; Barber, David

    2017-11-01

    In April 2015, an ice-tethered conductivity-temperature-depth (CTD) profiler and a down-looking acoustic Doppler current profiler (ADCP) were deployed from the landfast ice near the tidewater glacier terminus of the Flade Isblink Glacier in the Wandel Sea, NE Greenland. The 3-week time series showed that water dynamics and the thermohaline structure were modified considerably during a storm event on 22-24 April, when northerly winds exceeded 15 m s-1. The storm initiated downwelling-like water dynamics characterized by on-shore water transport in the surface (0-40 m) layer and compensating offshore flow at intermediate depths. After the storm, currents reversed in both layers, and the relaxation phase of downwelling lasted ˜ 4 days. Although current velocities did not exceed 5 cm s-1, the enhanced circulation during the storm caused cold turbid intrusions at 75-95 m depth, which are likely attributable to subglacial water from the Flade Isblink Ice Cap. It was also found that the semidiurnal periodicities in the temperature and salinity time series were associated with the lunar semidiurnal tidal flow. The vertical structure of tidal currents corresponded to the first baroclinic mode of the internal tide with a velocity minimum at ˜ 40 m. The tidal ellipses rotate in opposite directions above and below this depth and cause a divergence of tidal flow, which was observed to induce semidiurnal internal waves of about 3 m height at the front of the glacier terminus. Our findings provide evidence that shelf-basin interaction and tidal forcing can potentially modify coastal Wandel Sea waters even though they are isolated from the atmosphere by landfast sea ice almost year-round. The northerly storms over the continental slope cause an enhanced circulation facilitating a release of cold and turbid subglacial water to the shelf. The tidal flow may contribute to the removal of such water from the glacial terminus.

  15. Rock glaciers on South Shetland Islands, Antarctic Peninsula, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — In the South Shetland Islands the investigators found eight active rock glaciers, no relict or fossil examples, and seven protalus ramparts. The rock glaciers are...

  16. Climatic control on extreme sediment transfer from Dokriani Glacier ...

    Indian Academy of Sciences (India)

    glaciers have received more attention for the water resources management and hydropower develop- ment in the Himalayas ..... Glacier melt runoff represents the integrated basin response to various ..... for policy implementation; Him. Geol.

  17. Rock glaciers in the Pyrenees, Spain and France, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This study and inventory of active rock glaciers was carried out by means of the usual techniques used in the study of alpine permafrost. First, the rock glaciers...

  18. Can shrubs help to reconstruct historical glacier retreats?

    International Nuclear Information System (INIS)

    Buras, Allan; Hallinger, Martin; Wilmking, Martin

    2012-01-01

    In the 21st century, most of the world’s glaciers are expected to retreat due to further global warming. The range of this predicted retreat varies widely as a result of uncertainties in climate and glacier models. To calibrate and validate glacier models, past records of glacier mass balance are necessary, which often only span several decades. Long-term reconstructions of glacier mass balance could increase the precision of glacier models by providing the required calibration data. Here we show the possibility of applying shrub growth increments as an on-site proxy for glacier summer mass balance, exemplified by Salix shrubs in Finse, Norway. We further discuss the challenges which this method needs to meet and address the high potential of shrub growth increments for reconstructing glacier summer mass balance in remote areas. (letter)

  19. Monitoring of Gangotri glacier using remote sensing and ground ...

    Indian Academy of Sciences (India)

    for activating fast melting and affecting the glacier health significantly. Apart from climatic ... glacier health were also validated using high resolution satellite imageries and field visit. A deglaciation ...... Contribution of Work- ing Group I to the ...

  20. Modeled climate-induced glacier change in Glacier National Park, 1850-2100

    Science.gov (United States)

    Hall, M.H.P.; Fagre, D.B.

    2003-01-01

    The glaciers in the Blackfoot-Jackson Glacier Basin of Glacier National Park, Montana, decreased in area from 21.6 square kilometers (km2) in 1850 to 7.4 km2 in 1979. Over this same period global temperatures increased by 0.45??C (?? 0. 15??C). We analyzed the climatic causes and ecological consequences of glacier retreat by creating spatially explicit models of the creation and ablation of glaciers and of the response of vegetation to climate change. We determined the melt rate and spatial distribution of glaciers under two possible future climate scenarios, one based on carbon dioxide-induced global warming and the other on a linear temperature extrapolation. Under the former scenario, all glaciers in the basin will disappear by the year 2030, despite predicted increases in precipitation; under the latter, melting is slower. Using a second model, we analyzed vegetation responses to variations in soil moisture and increasing temperature in a complex alpine landscape and predicted where plant communities are likely to be located as conditions change.

  1. Contrast Materials

    Science.gov (United States)

    ... is mixed with water before administration liquid paste tablet When iodine-based and barium-sulfate contrast materials ... for patients with kidney failure or allergies to MRI and/or computed tomography (CT) contrast material. Microbubble ...

  2. Amyloid fibril formation of peptides derived from the C-terminus of CETP modulated by lipids

    Energy Technology Data Exchange (ETDEWEB)

    García-González, Victor [Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 México, DF (Mexico); Mas-Oliva, Jaime, E-mail: jmas@ifc.unam.mx [Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 México, DF (Mexico); División de Investigación, Facultad de Medicina, Universidad Nacional Autónoma de México, 04510 México, DF (Mexico)

    2013-04-26

    Highlights: •The secondary structure of a C-terminal peptide derived from CETP was studied. •Lipids modulate secondary structure changes of a C-terminal peptide derived from CETP. •Lysophosphatidic acid maintains a functional α-helix and prevents fibril formation. •Transfer of lipids by CETP is related to the presence of an α-helix at its C-end. -- Abstract: Cholesteryl-ester transfer protein (CETP) is a plasmatic protein involved in neutral lipid transfer between lipoproteins. Focusing on the last 12 C-terminus residues we have previously shown that mutation D{sub 470}N promotes a conformational change towards a β-secondary structure. In turn, this modification leads to the formation of oligomers and fibrillar structures, which cause cytotoxic effects similar to the ones provoked by amyloid peptides. In this study, we evaluated the role of specific lipid arrangements on the structure of peptide helix-Z (D{sub 470}N) through the use of thioflavin T fluorescence, peptide bond absorbance, circular dichroism and electron microscopy. The results indicate that the use of micelles formed with lysophosphatidylcholine and lysophosphatidic acid (LPA) under neutral pH induce a conformational transition of peptide helix-Z containing a β-sheet conformation to a native α-helix structure, therefore avoiding the formation of amyloid fibrils. In contrast, incubation with phosphatidic acid does not change the profile for the β-sheet conformation. When the electrostatic charge at the surface of micelles or vesicles is regulated through the use of lipids such as phospholipid and LPA, minimal changes and the presence of β-structures were recorded. Mixtures with a positive net charge diminished the percentage of β-structure and the amount of amyloid fibrils. Our results suggest that the degree of solvation determined by the presence of a free hydroxyl group on lipids such as LPA is a key condition that can modulate the secondary structure and the consequent formation of

  3. Amyloid fibril formation of peptides derived from the C-terminus of CETP modulated by lipids

    International Nuclear Information System (INIS)

    García-González, Victor; Mas-Oliva, Jaime

    2013-01-01

    Highlights: •The secondary structure of a C-terminal peptide derived from CETP was studied. •Lipids modulate secondary structure changes of a C-terminal peptide derived from CETP. •Lysophosphatidic acid maintains a functional α-helix and prevents fibril formation. •Transfer of lipids by CETP is related to the presence of an α-helix at its C-end. -- Abstract: Cholesteryl-ester transfer protein (CETP) is a plasmatic protein involved in neutral lipid transfer between lipoproteins. Focusing on the last 12 C-terminus residues we have previously shown that mutation D 470 N promotes a conformational change towards a β-secondary structure. In turn, this modification leads to the formation of oligomers and fibrillar structures, which cause cytotoxic effects similar to the ones provoked by amyloid peptides. In this study, we evaluated the role of specific lipid arrangements on the structure of peptide helix-Z (D 470 N) through the use of thioflavin T fluorescence, peptide bond absorbance, circular dichroism and electron microscopy. The results indicate that the use of micelles formed with lysophosphatidylcholine and lysophosphatidic acid (LPA) under neutral pH induce a conformational transition of peptide helix-Z containing a β-sheet conformation to a native α-helix structure, therefore avoiding the formation of amyloid fibrils. In contrast, incubation with phosphatidic acid does not change the profile for the β-sheet conformation. When the electrostatic charge at the surface of micelles or vesicles is regulated through the use of lipids such as phospholipid and LPA, minimal changes and the presence of β-structures were recorded. Mixtures with a positive net charge diminished the percentage of β-structure and the amount of amyloid fibrils. Our results suggest that the degree of solvation determined by the presence of a free hydroxyl group on lipids such as LPA is a key condition that can modulate the secondary structure and the consequent formation of amyloid

  4. Using marine sediment archives to reconstruct past outlet glacier variability

    DEFF Research Database (Denmark)

    Andresen, Camilla Snowman; Straneo, Fiamma; Ribergaard, Mads

    2013-01-01

    Ice-rafted debris in fjord sediment cores provides information about outlet glacier activity beyond the instrumental time period. It tells us that the Helheim Glacier, Greenland’s third most productive glacier, responds rapidly to short-term (3 to 10 years) climate changes....

  5. Determining glacier velocity with single frequency GPS receivers

    NARCIS (Netherlands)

    Reijmer, C.H.; van de Wal, R.S.W.; Boot, W.

    2011-01-01

    A well-known phenomenon in glacier dynamics is the existence of a relation between the glacier velocity and available amount of melt water (Zwally et al., 2002; Van de Wal et al., 2008). This relation is of particular importance when estimating the reaction of glaciers and ice sheets to climate

  6. Tidal Movement of Nioghalvfjerdsfjorden Glacier, Northeast Greenland: Observations and Modelling

    DEFF Research Database (Denmark)

    Reeh, Niels; Mayer, C.; Olesen, O. B.

    2000-01-01

    Nioghalvfjerdsfjorden glacier is a > 60 km long and 20 km wide floating outlet glacier located at 79 degrees 30' N, 22 degrees W, draining a large area of the northeast Greenland ice sheet. Climate, mass-balance and dynamics studies were carried out on the glacier in three field seasons in 1996...

  7. Climate reconstructions derived from global glacier length records

    NARCIS (Netherlands)

    Klok, E.J.; Oerlemans, J.

    2004-01-01

    As glacier length fluctuations provide useful information about past climate, we derived historic fluctuations in the equilibrium-line altitude (ELA) on the basis of 19 glacier length records from different parts of the world. We used a model that takes into account the geometry of the glacier,

  8. Francis Bacon's Valerius Terminus and the Voyage to the "Great Instauration".

    Science.gov (United States)

    Serjeantson, Richard

    2017-01-01

    Francis Bacon's earliest surviving natural philosophical treatise (composed circa 1603) bears the title Valerius Terminus of the Interpretation of Nature. This study, resting on fresh attention to the surviving authorial manuscript, has three goals. It begins by identifying a lost precursor work apparently entitled "Of Active Knowledge." It then examines the significance of the pseudonyms Bacon chose to introduce his ideas, considering especially his invocation of Erasmus's emblem, the Roman deity Terminus. Finally, it shows how the Valerius Terminus's global vision of contemporary knowledge ultimately helped shape the iconography of Bacon's published Instauratio magna.

  9. The spatial variable glacier mass loss over the southeast Tibet Plateau and the climate cause analyses

    Science.gov (United States)

    Ke, L.; Ding, X.; Song, C.; Sheng, Y.

    2016-12-01

    Temperate glaciers can be highly sensitive to global climate change due to relatively humid and warm local climate. Numerous temperate glaciers are distributed in the southeastern Tibet Plateau (SETP) and their changes are still poorly represented. Based on a latest glacier inventory and ICESat altimetry measurements, we examine the spatial heterogeneity of glacier change in the SETP (including the central and eastern Nyainqêntanglha ranges) and further analyze its relation with climate change by using station-based and gridded meteorological data. Our results show that SETP glaciers experienced drastic surface lowering at about -0.84±0.26 m a-1 on average over 2003-2008. Debris-covered ice thinned at an average rate of -1.13±0.32 m a-1, in comparison with -0.92±0.17 m a-1 over the debris-free ice areas. The thinning rate is the strongest in the southeastern sub-region (up to -1.24 m a-1 ) and moderate ( -0.45 m a-1 ) in the central and northwestern parts, which is in general agreement with the pattern of surface mass changes based on the GRACE gravimetry observation. Long-term climate data at weather stations show that, in comparison with the period of 1992-2002, mean temperature increased by 0.46 °C - 0.59 °C in the recent decade (2003-2013); while the change of summer precipitation exhibited remarkably spatial variability, following a southeast-northwest contrasting pattern (decreasing by over 10% in the southeast, to stable level in the central region, and increment up to 10% in the northwest). This spatially variable precipitation change is consistent with results from CN05 grid data and ERA re-analysis data, and agrees well with the spatial pattern of glacier surface elevation changes. The results suggest that overall negative glacier mass balances in SETP are governed by temperature rising, while the different precipitation change could contribute to inconsistent glacier thinning rates. The spatial pattern of precipitation decrease and mass loss might

  10. Mutations in the catalytic core or the C-terminus of murine leukemia virus (MLV) integrase disrupt virion infectivity and exert diverse effects on reverse transcription

    International Nuclear Information System (INIS)

    Steinrigl, Adolf; Nosek, Dagmara; Ertl, Reinhard; Guenzburg, Walter H.; Salmons, Brian; Klein, Dieter

    2007-01-01

    Understanding of the structures and functions of the retroviral integrase (IN), a key enzyme in the viral replication cycle, is essential for developing antiretroviral treatments and facilitating the development of safer gene therapy vehicles. Thus, four MLV IN-mutants were constructed in the context of a retroviral vector system, harbouring either a substitution in the catalytic centre, deletions in the C-terminus, or combinations of both modifications. IN-mutants were tested for their performance in different stages of the viral replication cycle: RNA-packaging; RT-activity; transient and stable infection efficiency; dynamics of reverse transcription and nuclear entry. All mutant vectors packaged viral RNA with wild-type efficiencies and displayed only slight reductions in RT-activity. Deletion of either the IN C-terminus alone, or in addition to part of the catalytic domain exerted contrasting effects on intracellular viral DNA levels, implying that IN influences reverse transcription in more than one direction

  11. Seismological observations of glaciers dynamic on the Spitsbergen archipelago

    Directory of Open Access Journals (Sweden)

    Fedorov A. V.

    2016-03-01

    Full Text Available The paper provides a brief description of results of Spitsbergen glacier observations by the seismic method. The study has been carried out both by permanent and temporary stations data. Characteristic features of glacier-related seismic events have been shown. Main areas of glacier seismic activity on the Archipelago have been revealed. A detailed study of Horsund-fjord glacier activity has been carried out using local seismic station HSPB data. Temporal and spatial distributions of glacier-related events have been obtained for the area. Season variations in temporal distribution of the events have been found

  12. Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge

    Directory of Open Access Journals (Sweden)

    M. Jay-Allemand

    2011-08-01

    Full Text Available Variegated Glacier (Alaska is known to surge periodically after a sufficient amount of cumulative mass balance is reached, but this observation is difficult to link with changes in the basal conditions. Here, using a 10-yr dataset, consisting of surface topography and surface velocity observations along a flow line for 25 dates, we have reconstructed the evolution of the basal conditions prior to and during the 1982–1983 surge. The model solves the full-Stokes problem along the central flow line using the finite element method. For the 25 dates of the dataset, the basal friction parameter distribution is inferred using the inverse method proposed by Arthern and Gudmundsson (2010. This method is here slightly modified by incorporating a regularisation term in the cost function to avoid short wavelength changes in the friction parameter. Our results indicate that dramatic changes in the basal conditions occurred between 1973 to 1983. Prior to the surge, periodic changes can be observed between winter and summer, with a regular increase of the sliding from 1973 to 1982. During the surge, the basal friction decreased dramatically and an area of very low friction moved from the upper part of the glacier to its terminus. Using a more complex friction law, these changes in basal sliding are then interpreted in terms of basal water pressure. Our results support that dramatic changes took place in the subglacial drainage system of Variegated Glacier, moving from a relatively efficient drainage system prior to the surge to an inefficient one during the surge. By reconstructing the water pressure evolution at the base of the glacier it is possible to propose a scenario for the hydrological history leading to the occurrence of a surge.

  13. A complex relationship between calving glaciers and climate

    Science.gov (United States)

    Post, A.; O'Neel, S.; Motyka, R.J.; Streveler, G.

    2011-01-01

    Many terrestrial glaciers are sensitive indicators of past and present climate change as atmospheric temperature and snowfall modulate glacier volume. However, climate interpretations based on glacier behavior require careful selection of representative glaciers, as was recently pointed out for surging and debris-covered glaciers, whose behavior often defies regional glacier response to climate [Yde and Paasche, 2010]. Tidewater calving glaciers (TWGs)mountain glaciers whose termini reach the sea and are generally grounded on the seaflooralso fall into the category of non-representative glaciers because the regional-scale asynchronous behavior of these glaciers clouds their complex relationship with climate. TWGs span the globe; they can be found both fringing ice sheets and in high-latitude regions of each hemisphere. TWGs are known to exhibit cyclic behavior, characterized by slow advance and rapid, unstable retreat, largely independent of short-term climate forcing. This so-called TWG cycle, first described by Post [1975], provides a solid foundation upon which modern investigations of TWG stability are built. Scientific understanding has developed rapidly as a result of the initial recognition of their asynchronous cyclicity, rendering greater insight into the hierarchy of processes controlling regional behavior. This has improved the descriptions of the strong dynamic feedbacks present during retreat, the role of the ocean in TWG dynamics, and the similarities and differences between TWG and ice sheet outlet glaciers that can often support floating tongues.

  14. A Facies Model for Temperate Continental Glaciers.

    Science.gov (United States)

    Ashley, Gail Mowry

    1987-01-01

    Discusses the presence and dynamics of continental glaciers in the domination of the physical processes of erosion and deposition in the mid-latitudes during the Pleistocene period. Describes the use of a sedimentary facies model as a guide to recognizing ancient temperate continental glacial deposits. (TW)

  15. Pattern of Glacier Recession in Indian Himalaya

    Science.gov (United States)

    Singh, Ajay; Patwardhan, Anand

    All currently available climate models predict a near-surface warming trend under the influence of rising levels of greenhouse gases in the atmosphere. In addition to the direct effects on climate — for example, on the frequency of heat waves — this increase in surface temperatures has important consequences for the cryosphere subsequently hydrological cycle, particularly in regions where water supply is currently dominated by melting snow or ice. The Indian Himalayan region occupies a special place in the mountain ecosystems of the world. These geodynamically young mountains are not only important from the standpoint of climate and as a provider of life, giving water to a large part of the Indian subcontinent, but they also harbor a rich variety of flora, fauna, human communities and cultural diversity. Glaciers in this region are changing in area as well as in volume like those in other parts of the world. Studies have been carried out for recession in some of these glaciers using remote sensing as well as field observation techniques. Spatiotemporal pattern in the recession rate of the studied glaciers has been presented in this paper. Plausible causes for the recession have been also discussed. Finally, future scopes for observation and analysis in glaciers recession have been suggested.

  16. The Greater Caucasus Glacier Inventory (Russia, Georgia and Azerbaijan)

    Science.gov (United States)

    Tielidze, Levan G.; Wheate, Roger D.

    2018-01-01

    There have been numerous studies of glaciers in the Greater Caucasus, but none that have generated a modern glacier database across the whole mountain range. Here, we present an updated and expanded glacier inventory at three time periods (1960, 1986, 2014) covering the entire Greater Caucasus. Large-scale topographic maps and satellite imagery (Corona, Landsat 5, Landsat 8 and ASTER) were used to conduct a remote-sensing survey of glacier change, and the 30 m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM; 17 November 2011) was used to determine the aspect, slope and height distribution of glaciers. Glacier margins were mapped manually and reveal that in 1960 the mountains contained 2349 glaciers with a total glacier surface area of 1674.9 ± 70.4 km2. By 1986, glacier surface area had decreased to 1482.1 ± 64.4 km2 (2209 glaciers), and by 2014 to 1193.2 ± 54.0 km2 (2020 glaciers). This represents a 28.8 ± 4.4 % (481 ± 21.2 km2) or 0.53 % yr-1 reduction in total glacier surface area between 1960 and 2014 and an increase in the rate of area loss since 1986 (0.69 % yr-1) compared to 1960-1986 (0.44 % yr-1). Glacier mean size decreased from 0.70 km2 in 1960 to 0.66 km2 in 1986 and to 0.57 km2 in 2014. This new glacier inventory has been submitted to the Global Land Ice Measurements from Space (GLIMS) database and can be used as a basis data set for future studies.

  17. Changes in the Surface Area of Glaciers in Northern Eurasia

    Science.gov (United States)

    Khromova, T.; Nosenko, G.

    2012-12-01

    Glaciers are widely recognized as key indicators of climate change. Recent evidence suggests an acceleration of glacier mass loss in several key mountain regions. Glacier recession implies the landscape changes in the glacial zone, origin of new lakes and activation of natural disaster processes, catastrophic mudflows, ice avalanches, outburst floods, and etc. The presence of glaciers in itself threats to human life, economic activity and growing infrastructure. Economical and recreational human activity in mountain regions requires relevant information on snow and ice objects. Absence or inadequacy of such information results in financial and human losses. A more comprehensive evaluation of glacier changes is imperative to assess ice contributions to global sea level rise and the future of water resources from glacial basins. One of the urgent steps is a full inventory of all ice bodies, their volume and changes The first estimation of glaciers state and glaciers distribution in the big part of Northern Eurasia has been done in the USSR Glacier Inventory published in 1966 -1980 as a part of IHD activity. The Inventory is based on topographic maps and air photos and reflects the status of the glaciers in 1957-1970y. There is information about 23796 glaciers with area of 78222.3 km2 in the Inventory. It covers 23 glacier systems on Northern Eurasia. In the 80th the USSR Glacier Inventory has been transformed in the digital form as a part of the World Glacier Inventory. Recent satellite data provide a unique opportunity to look again at these glaciers and to evaluate changes in glacier extent for the second part of XX century. In the paper we report about 15 000 glaciers outlines for Caucasus, Pamir, Tien-Shan, Altai, Syntar-Khayata, Cherskogo Range, Kamchatka and Russian Arctic which have been derived from ASTER and Landsat imagery and could be used for glacier changes evaluation. The results show that glaciers are retreating in all these regions. There is, however

  18. Grounding line processes on the Totten Glacier

    Science.gov (United States)

    Cook, S.; Watson, C. S.; Galton-Fenzi, B.; Peters, L. E.; Coleman, R.

    2017-12-01

    The Totten Glacier has been an area of recent interest due to its large drainage basin, much of which is grounded below sea level and has a history of large scale grounding line movement. Reports that warm water reaches the sub-ice shelf cavity have led to speculation that it could be vulnerable to future grounding line retreat. Over the Antarctic summer 2016/17 an array of 6 GPS and autonomous phase-sensitive radar (ApRES) units were deployed in the grounding zone of the Totten Glacier. These instruments measure changes in ice velocity and thickness which can be used to investigate both ice dynamics across the grounding line, and the interaction between ice and ocean in the subglacial cavity. Basal melt rates calculated from the ApRES units on floating ice range from 1 to 17 m/a. These values are significantly lower than previous estimates of basal melt rate produced by ocean modelling of the subglacial cavity. Meanwhile, GPS-derived velocity and elevation on the surface of the ice show a strong tidal signal, as does the vertical strain rate within the ice derived from internal layering from the ApRES instruments. These results demonstrate the significance of the complex grounding pattern of the Totten Glacier. The presence of re-grounding points has significant implications for the dynamics of the glacier and the ocean circulation within the subglacial cavity. We discuss what can be learned from our in situ measurements, and how they can be used to improve models of the glacier's future behaviour.

  19. 2017 Rapid Retreat Of Thwaites Glacier

    Science.gov (United States)

    Milillo, P.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.

    2017-12-01

    We employ data from the second generation of SAR systems e.g. the Italian COSMO- SkyMed (CSK) constellation and the German TanDEM-X (TDX) formation to monitor grounding line retreat using short repeat-time interferometry and accurate InSAR DEM on Thwaites glacier in the Amundsen Sea Embayment (ASE), West Antarctica. The ASE is a marine-based ice sheet with a retrograde bed containing enough ice to raise global sea level by 120 cm. Several studies have inferred the mechanical properties of portions of ASE using observationally constrained numerical models, but these studies offer only temporal snapshots of basal mechanics owing to a dearth of observational time series. Prior attempts of grounding lines mapping have been limited because few space-borne SAR missions offer the short-term repeat pass capability required to map the differential vertical displacement of floating ice at tidal frequencies with sufficient detail to resolve grounding line boundaries in areas of fast ice deformation. Using 1-day CSK repeat pass data and TDX DEMs, we collected frequent, high-resolution grounding line measurements of Thwaites glaciers spanning 2015-2017. We compare the results with ERS data spanning 1996-2011, and Sentinel-1a 2014-2015 data. Between 2011 and 2017 we observe a maximum retreat of 5-7 km across the main Thwaites glacier tongue and Thwaites Eastern ice shelf (TEIS) corresponding to an increased retreat rate of 0.5 km/yr. Grounding line retreat has been fueled by the enhanced intrusion of warm, salty, subsurface ocean water of circumpolar deep water origin onto the continental shelf, beneath the floating ice shelf, to reach the glacier grounding zone and melt it from below at rates varying from 50 to 150 m/yr. The retreat rate varies depending on the magnitude of ice melt by the ocean, the rate of ice thinning and the shape of the glacier surface and bed topography.

  20. Surge of a Complex Glacier System - The Current Surge of the Bering-Bagley Glacier System, Alaska

    Science.gov (United States)

    Herzfeld, U. C.; McDonald, B.; Trantow, T.; Hale, G.; Stachura, M.; Weltman, A.; Sears, T.

    2013-12-01

    Understanding fast glacier flow and glacial accelerations is important for understanding changes in the cryosphere and ultimately in sea level. Surge-type glaciers are one of four types of fast-flowing glaciers --- the other three being continuously fast-flowing glaciers, fjord glaciers and ice streams --- and the one that has seen the least amount of research. The Bering-Bagley Glacier System, Alaska, the largest glacier system in North America, surged in 2011 and 2012. Velocities decreased towards the end of 2011, while the surge kinematics continued to expand. A new surge phase started in summer and fall 2012. In this paper, we report results from airborne observations collected in September 2011, June/July and September/October 2012 and in 2013. Airborne observations include simultaneously collected laser altimeter data, videographic data, GPS data and photographic data and are complemented by satellite data analysis. Methods range from classic interpretation of imagery to analysis and classification of laser altimeter data and connectionist (neural-net) geostatistical classification of concurrent airborne imagery. Results focus on the characteristics of surge progression in a large and complex glacier system (as opposed to a small glacier with relatively simple geometry). We evaluate changes in surface elevations including mass transfer and sudden drawdowns, crevasse types, accelerations and changes in the supra-glacial and englacial hydrologic system. Supraglacial water in Bering Glacier during Surge, July 2012 Airborne laser altimeter profile across major rift in central Bering Glacier, Sept 2011

  1. Measuring Surface Deformation in Glacier Retreated Areas Based on Ps-Insar - Geladandong Glacier as a Case Study

    Science.gov (United States)

    Mohamadi, B.; Balz, T.

    2018-04-01

    Glaciers are retreating in many parts of the world as a result of global warming. Many researchers consider Qinghai-Tibetan Plateau as a reference for climate change by measuring glaciers retreat on the plateau. This retreat resulted in some topographic changes in retreated areas, and in some cases can lead to geohazards as landslides, and rock avalanches, which is known in glacier retreated areas as paraglacial slope failure (PSF). In this study, Geladandong biggest and main glacier mass was selected to estimate surface deformation on its glacier retreated areas and define potential future PSF based on PS-InSAR technique. 56 ascending and 49 descending images were used to fulfill this aim. Geladandong glacier retreated areas were defined based on the maximum extent of the glacier in the little ice age. Results revealed a general uplift in the glacier retreated areas with velocity less than 5mm/year. Obvious surface motion was revealed in seven parts surround glacier retreated areas with high relative velocity reached ±60mm/year in some parts. Four parts were considered as PSF potential motion, and two of them showed potential damage for the main road in the study area in case of rock avalanche into recent glacier lakes that could result in glacier lake outburst flooding heading directly to the road. Finally, further analysis and field investigations are needed to define the main reasons for different types of deformation and estimate future risks of these types of surface motion in the Qinghai-Tibetan Plateau.

  2. Modelling glacier-bed overdeepenings and possible future lakes for the glaciers in the Himalaya-Karakoram region

    DEFF Research Database (Denmark)

    Linsbauer, A.; Frey, H.; Haeberli, W.

    2016-01-01

    Surface digital elevation models (DEMs) and slope-related estimates of glacier thickness enable modelling of glacier-bed topographies over large ice-covered areas. Due to the erosive power of glaciers, such bed topographies can contain numerous overdeepenings, which when exposed following glacier...... retreat may fill with water and form new lakes. In this study, the bed overdeepenings for ∼28000 glaciers (40 775km2) of the Himalaya-Karakoram region are modelled using GlabTop2 (Glacier Bed Topography model version 2), in which ice thickness is inferred from surface slope by parameterizing basal shear...... stress as a function of elevation range for each glacier. The modelled ice thicknesses are uncertain (±30%), but spatial patterns of ice thickness and bed elevation primarily depend on surface slopes as derived from the DEM and, hence, are more robust. About 16 000 overdeepenings larger than 104m2 were...

  3. Three Decades of Volume Change of a Small Greenlandic Glacier Using Ground Penetrating Radar, Structure from Motion, and Aerial Photogrammetry

    DEFF Research Database (Denmark)

    Marcer, M.; Stentoft, Peter Alexander; Bjerre, Elisa

    2017-01-01

    of ice, corresponding to roughly a quarter of its 1985 volume (148.6 ± 47.6 10 m) and a thinning rate of 0.60 ± 0.11 m a. The computations are challenged by a relatively large fraction of the 1985 DEM (∼50% of the glacier surface) being deemed unreliable owing to low contrast (snow cover) in the 1985......Glaciers in the Arctic are losing mass at an increasing rate. Here we use surface topography derived from Structure from Motion (SfM) and ice volume from ground penetrating radar (GPR) to describe the 2014 state of Aqqutikitsoq glacier (2.85 km) on Greenland's west coast. A photogrammetrically...... derived 1985 digital elevation model (DEM) was subtracted from a 2014 DEM obtained using land-based SfM to calculate geodetic glacier mass balance. Furthermore, a detailed 2014 ground penetrating radar survey was performed to assess ice volume. From 1985 to 2014, the glacier has lost 49.8 ± 9.4 10 m...

  4. Internationally coordinated glacier monitoring - a timeline since 1894

    Science.gov (United States)

    Nussbaumer, Samuel U.; Armstrong, Richard; Fetterer, Florence; Gärtner-Roer, Isabelle; Hoelzle, Martin; Machguth, Horst; Mölg, Nico; Paul, Frank; Raup, Bruce H.; Zemp, Michael

    2016-04-01

    Changes in glaciers and ice caps provide some of the clearest evidence of climate change, with impacts on sea-level variations, regional hydrological cycles, and natural hazard situations. Therefore, glaciers have been recognized as an Essential Climate Variable (ECV). Internationally coordinated collection and distribution of standardized information about the state and change of glaciers and ice caps was initiated in 1894 and is today organized within the Global Terrestrial Network for Glaciers (GTN-G). GTN-G ensures the continuous development and adaptation of the international strategies to the long-term needs of users in science and policy. A GTN-G Steering Committee coordinates, supports and advices the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. In this presentation, we trace the development of the internationally coordinated glacier monitoring since its beginning in the 19th century. Today, several online databases containing a wealth of diverse data types with different levels of detail and global coverage provide fast access to continuously updated information on glacier fluctuation and inventory data. All glacier datasets are made freely available through the respective operational bodies within GTN-G, and can be accessed through the GTN-G Global Glacier Browser (http://www.gtn-g.org/data_browser.html). Glacier inventory data (e.g., digital outlines) are available for about 180,000 glaciers (GLIMS database, RGI - Randolph Glacier Inventory, WGI - World Glacier Inventory). Glacier front variations with about 45,000 entries since the 17th century and about 6,200 glaciological and geodetic mass (volume) change observations dating back to the 19th century are available in the Fluctuations of Glaciers (FoG) database. These datasets reveal clear evidence that

  5. Studying the Effects of Amazonian Land Cover Change on Glacier Mass Balance in the Tropical Andes

    Science.gov (United States)

    Mark, B. G.; Fernandez, A.; Gabrielli, P.; Montenegro, A.; Postigo, J.; Hellstrom, R. A.

    2017-12-01

    Recent research has highlighted several ongoing environmental changes occurring across Tropical South America, including Andean glacier retreat, drought, as well as changes in land-use and land-cover. As the regional climate of the area is mostly characterized by land-ocean interactions, the atmospheric convection in the Amazon, and the effect of the Andes on circulation patterns, it follows that changes in one of those regions may affect the other. Most scholars who have studied the causes of tropical glaciers' fluctuations have not analyzed the linkages with changes in the Amazon with the same attention paid to the influence of Pacific sea surface temperature. Here we study the response of glacier surface mass balance in the Cordillera Blanca, Peru (10°S), to a scenario where the Amazonian rainforest is replaced by savannas. We ran climatic simulations at 2-km spatial resolution utilizing the Weather Research and Forecasting (WRF) model considering two scenarios: (a) control (CRTL), with today's rainforest extent; and (b) land cover change (LCC), where all the rainforest was replaced by savanna. WRF output was in turn ingested into a glacier energy and mass balance (GEMB) model that we validate by reconstructing both the accumulated mass balance from available observations, and the altitudinal distribution of mass balance in the region. Seasonal comparison between CRTL and LCC scenarios indicates that forest replacement by savanna results in more positive glacier mass balance. This shift to more positive mass balance contrasts with a (WRF) modeled rise in the elevation of the freezing line (0°C) between 30 to 120 m for the LCC scenario. Our results are surprising because most previous studies have shown that reducing Amazon forest cover diminishes rainfall and increases temperature, suggesting that glaciers should lose mass. We hypothesize and discuss implications of possible land-atmospheric processes that might drive this tropical glacier response to

  6. Thresholds of glacier hydrologic change and emergent vulnerabilities in a tropical Andean waterscape

    Science.gov (United States)

    Mark, B. G.; Bury, J.; Carey, M.; McKenzie, J. M.; Huh, K. I.; Baraer, M.; Eddy, A.

    2011-12-01

    Over the past 50+ years, dramatic glacier mass loss in the Cordillera Blanca, Peru, has been causing downstream hydrologic transformations, with implications for domestic, agricultural and industrial water resources. Coincidental expansion of social and economic development throughout the Santa River watershed, which drains into the Pacific Ocean, raises concerns about sustaining future water supplies. Hydrologic models predict water shortages decades in the future, but conflicts have already arisen in the watershed due to either real or perceived shortages. Moreover, increased water usage since 1950 suggests resilience to presumed thresholds given a concomitant decrease in supply. Therefore modeled thresholds do not align well with historical realities. Our collaborative research couples multiscalar observations of changes in glacier volume, hydrology, and land usage with social and economic data about perceptions of and responses to environmental change. We also examine various water withdrawal mechanisms and institutions transecting the entire watershed: agriculture, land use, irrigation, hydroelectricity generation, and mining. We quantify glacier volume loss using multi-temporal surface elevation maps of selected valley glaciers based on state-of-the-art laser altimetry (LIDAR), ASTER satellite imagery and aerial photogrammetry spanning 1962 to 2008. Results show glacier surface area loss is between 30% and 86%, while measured volume loss is 2 to 12 times greater than empirically derived scaling relationships predict. Based on historical runoff and glacier data, the upper Santa River watershed is found to be on the descending limb of a conceptual multi-decadal hydrograph. The actual distribution of dry season water supply is illustrated based on a 2011 synoptic survey of Santa River discharge from the coastal effluent to headwaters. Our results suggest that critical changes in glacier volume and water supply are not perceived or acknowledged consistently

  7. Small Glacier Area Studies: A New Approach for Turkey

    Science.gov (United States)

    Yavasli, Dogukan D.; Tucker, Compton J.

    2012-01-01

    Many regions of Earth have glaciers that have been neglected for study because they are small. We report on a new approach to overcome the problem of studying small glaciers, using Turkey as an example. Prior to our study, no reliable estimates of Turkish glaciers existed because of a lack of systematic mapping, difficulty in using Landsat data collected before 1982, snowpack vs. glacier ice differentiation using existing satellite data and aerial photography, the previous high cost of Landsat images, and a lack of high-resolution imagery of small Turkish glaciers. Since 2008, a large number of area of nine smaller glaciers in Turkey. We also used five Landsat-3 Return Beam Videcon (RBV) 30 m pixel resolution images, all from 1980, for six glaciers. The total area of Turkish glaciers decreased from 23 km2 in the 1970s to 10.1 km2 in 2007-2011. By 2007-2011, six Turkish glaciers disappeared, four were < 0.3 km2, and only three were 1.0 km2 or larger. No trends in precipitation from 1970 to 2006 and cloud cover from 1980 to 2010 were found, while surface temperatures increased, with summer minimum temperatures showing the greatest increase. We conclude that increased surface temperatures during the summer were responsible for the 56% recession of Turkish glaciers from the 1970s to 2006-2011.

  8. Fate of Glaciers in the Tibetan Plateau by 2100

    Science.gov (United States)

    Duan, K.

    2017-12-01

    As the third polar on the Earth, the Tibetan plateau holds more than 40,000 glaciers which have experienced a rapid retreat in recent decades. The variability of equilibrium line altitude (ELA) indicates expansion and wastage of glacier directly. Here we simulated the ELA variability in the Tibetan Plateau based on a full surface energy and mass balance model. The simulation results are agreement with the observations. The ELAs have risen at a rate of 2-8m/a since 1970 throughout the Plateau, especially in the eastern Plateau where the ELAs have risen to or over the top altitude of glacier, indicating the glaciers are accelerating to melting over there. Two glaciers, XD glacier in the center of the Plateau and Qiyi glacier in the Qilian Mountain, are chosen to simulate its future ELA variability in the scenarios of RCP2.6, RCP4.5 and RCP 8.5 given by IPCC. The results show the ELAs will arrive to its maximum in around 2040 in RCP2.6, while the ELAs will be over the top altitude of glaciers in 2035-2045 in RCP4.5 and RCP8.5, suggesting the glaciers in the eastern Plateau will be melting until the disappear of the glaciers by the end of 2100.

  9. Southwest Greenland's Alpine Glacier History: Recent Glacier Change in the Context of the Holocene Geologic Record

    Science.gov (United States)

    Larocca, L. J.; Axford, Y.; Lasher, G. E.; Lee, C. W.

    2017-12-01

    Due to anthropogenic climate change, the Arctic region is currently undergoing major transformation, and is expected to continue warming much faster than the global average. To put recent and future changes into context, a longer-term understanding of this region's past response to natural climate variability is needed. Given their sensitivity to modest climate change, small alpine glaciers and ice caps on Greenland's coastal margin (beyond the Greenland Ice Sheet) represent ideal features to record climate variability through the Holocene. Here we investigate the Holocene history of a small ( 160 square km) ice cap and adjacent alpine glaciers, located in southwest Greenland approximately 50 km south of Nuuk. We employ measurements on sediment cores from a glacier-fed lake in combination with geospatial analysis of satellite images spanning the past several decades. Sedimentary indicators of sediment source and thus glacial activity, including organic matter abundance, inferred chlorophyll-a content, sediment major element abundances, grain size, and magnetic susceptibility are presented from cores collected from a distal glacier-fed lake (informally referred to here as Per's Lake) in the summer of 2015. These parameters reflect changes in the amount and character of inorganic detrital input into the lake, which may be linked to the size of the upstream glaciers and ice cap and allow us to reconstruct their status through the Holocene. Additionally, we present a complementary record of recent changes in Equilibrium Line Altitude (ELA) for the upstream alpine glaciers. Modern ELAs are inferred using the accumulation area ratio (AAR) method in ArcGIS via Landsat and Worldview-2 satellite imagery, along with elevation data obtained from digital elevation models (DEMs). Paleo-ELAs are inferred from the positions of moraines and trim lines marking the glaciers' most recent expanded state, which we attribute to the Little Ice Age (LIA). This approach will allow us to

  10. Comparison of Glaciological and Gravimetric Glacier Mass Balance Measurements of Taku and Lemon Creek Glaciers, Southeast Alaska

    Science.gov (United States)

    Vogler, K.; McNeil, C.; Bond, M.; Getraer, B.; Huxley-Reicher, B.; McNamara, G.; Reinhardt-Ertman, T.; Silverwood, J.; Kienholz, C.; Beedle, M. J.

    2017-12-01

    Glacier-wide annual mass balances (Ba) have been calculated for Taku (726 km2) and Lemon Creek glaciers (10.2 km2) since 1946 and 1953 respectively. These are the longest mass balance records in North America, and the only Ba time-series available for Southeast Alaska, making them particularly valuable for the global glacier mass balance monitoring network. We compared Ba time-series from Taku and Lemon Creek glaciers to Gravity Recovery and Climate Experiment (GRACE) mascon solutions (1352 and 1353) during the 2004-2015 period to assess how well these gravimetric solutions reflect individual glaciological records. Lemon Creek Glacier is a challenging candidate for this comparison because it is small compared to the 12,100 km2 GRACE mascon solutions. Taku Glacier is equally challenging because its mass balance is stable compared to the negative balances dominating its neighboring glaciers. Challenges notwithstanding, a high correlation between the glaciological and gravimetrically-derived Ba for Taku and Lemon Creek glaciers encourage future use of GRACE to measure glacier mass balance. Additionally, we employed high frequency ground penetrating radar (GPR) to measure the variability of accumulation around glaciological sites to assess uncertainty in our glaciological measurements, and the resulting impact to Ba. Finally, we synthesize this comparison of glaciological and gravimetric mass balance solutions with a discussion of potential sources of error in both methods and their combined utility for measuring regional glacier change during the 21st century.

  11. Expression and purification of antimicrobial peptide adenoregulin with C-amidated terminus in Escherichia coli.

    Science.gov (United States)

    Cao, Wei; Zhou, Yuxun; Ma, Yushu; Luo, Qingping; Wei, Dongzhi

    2005-04-01

    Adenoregulin is a 33 amino acid antimicrobial peptide isolated from the skin of the arboreal frog Phyllomedusa bicolor. Natural adenoregulin is synthesized with an amidated valine residue at C-terminus and shows lethal effects against filamentous fungi, as well as a broad spectrum of pathogenic microorganisms. A synthetic gene for adenoregulin (ADR) with an additional amino acid glutamine at C-terminus was cloned into pET32a vector to allow expression of ADR as a Trx fusion protein in Escherichia coli BL21(DE3). The resulting expression level of the fusion protein could reach up to 20% of the total cell proteins. The fusion protein could be purified effectively by Ni2+-chelating chromatography. Released from the fusion protein by enterokinase cleavage and purified to homogeneity, the recombinant ADR displayed antimicrobial activity similar to that of the synthetic ADR reported earlier. Comparing the antimicrobial activities of the recombinant adenoregulin with C-amidated terminus to that without an amidated C-terminus, we found that the amide of glutamine at C-terminus of ADR improved its potency on certain microorganisms such as Tritirachium album and Saccharomyces cerevisiae.

  12. Glaciers and ice caps outside Greenland

    Science.gov (United States)

    Sharp, Marin; Wolken, G.; Burgess, D.; Cogley, J.G.; Copland, L.; Thomson, L.; Arendt, A.; Wouters, B.; Kohler, J.; Andreassen, L.M.; O'Neel, Shad; Pelto, M.

    2015-01-01

    Mountain glaciers and ice caps cover an area of over 400 000 km2 in the Arctic, and are a major influence on global sea level (Gardner et al. 2011, 2013; Jacob et al. 2012). They gain mass by snow accumulation and lose mass by meltwater runoff. Where they terminate in water (ocean or lake), they also lose mass by iceberg calving. The climatic mass balance (Bclim, the difference between annual snow accumulation and annual meltwater runoff) is a widely used index of how glaciers respond to climate variability and change. The total mass balance (ΔM) is defined as the difference between annual snow accumulation and annual mass losses (by iceberg calving plus runoff).

  13. On tritium content in the Abramov glacier layers

    International Nuclear Information System (INIS)

    Voronskaya, G.N.; Nikolishin, I.Ya.; Romanov, V.V.

    1976-01-01

    Using the common pattern of the analysis of tritium in natural waters its concentration was determined in sampeles of annual layers of the Abramov glacier (Pamir-Altai) at the height of 4500 m above the sea level for 1927-1972. The tritium activity was measured with the help of the liquid scintillation spectrometer with the 10 per cent accuracy. The nature of the obtained curve of the distribution of tritium in the Abramov glacier annual layers was close to its, distribution in glaciers of Greenland, in the Fedchenko glacier and in the precipitation of Teheran. The absolute values of tritium concentrations in the Pamir glaciers are significantly lower than in glaciers of Greenlad. The maximum of tritium concentrations is observed in samples which correspond to 1963, its value approximating to 800 tritium units

  14. An Analysis of Mass Balance of Chilean Glaciers

    Science.gov (United States)

    Ambinakudige, S.; Tetteh, L.

    2013-12-01

    Glaciers in Chile range from very small glacierets found on the isolated volcanoes of northern Chile to the 13,000 sq.km Southern Patagonian Ice Field. Regular monitoring of these glaciers is very important as they are considered as sensitive indicators of climate change. Millions of people's lives are dependent on these glaciers for fresh water and irrigation purpose. In this study, mass balances of several Chilean glaciers were estimated using Aster satellite images between 2007 and 2012. Highly accurate DEMs were created with supplementary information from IceSat data. The result indicated a negative mass balance for many glaciers indicating the need for further monitoring of glaciers in the Andes.

  15. Seasonal dynamic thinning at Helheim Glacier

    DEFF Research Database (Denmark)

    Bevan, Suzanne L.; Luckman, Adrian; Khan, Shfaqat Abbas

    2015-01-01

    of 671±70kgm-3 and calculate that total water equivalent volume loss from the active part of the glacier (surface flow speeds >1 m day-1) ranges from 0.5 km3 in 2011 to 1.6 km3 in 2013. A rough ice-flux divergence analysis shows that at lower elevations (... the time series, that melt-induced acceleration is most likely the main driver of the seasonal dynamic thinning, as opposed to changes triggered by retreat....

  16. The retreat of mountain glaciers: what can satellites tell us?

    International Nuclear Information System (INIS)

    Berthier, E.

    2008-01-01

    Mountain glaciers are one of the best indicators of climate change and their rapid wastage make them a strong contributor to sea level rise. The estimated 160,000 mountain glaciers are spread all around the globe and remain difficult to access. Consequently, only a limited number (about 50 glaciers) are regularly monitored in the field. Today, high resolution satellite optical images are combined to some advanced methodologies to survey their fast and alarming evolution. (author)

  17. Global-scale hydrological response to future glacier mass loss

    Science.gov (United States)

    Huss, Matthias; Hock, Regine

    2018-01-01

    Worldwide glacier retreat and associated future runoff changes raise major concerns over the sustainability of global water resources1-4, but global-scale assessments of glacier decline and the resulting hydrological consequences are scarce5,6. Here we compute global glacier runoff changes for 56 large-scale glacierized drainage basins to 2100 and analyse the glacial impact on streamflow. In roughly half of the investigated basins, the modelled annual glacier runoff continues to rise until a maximum (`peak water') is reached, beyond which runoff steadily declines. In the remaining basins, this tipping point has already been passed. Peak water occurs later in basins with larger glaciers and higher ice-cover fractions. Typically, future glacier runoff increases in early summer but decreases in late summer. Although most of the 56 basins have less than 2% ice coverage, by 2100 one-third of them might experience runoff decreases greater than 10% due to glacier mass loss in at least one month of the melt season, with the largest reductions in central Asia and the Andes. We conclude that, even in large-scale basins with minimal ice-cover fraction, the downstream hydrological effects of continued glacier wastage can be substantial, but the magnitudes vary greatly among basins and throughout the melt season.

  18. Towards Quantification of Glacier Dynamic Ice Loss through Passive Seismic Monitoring

    Science.gov (United States)

    Köhler, A.; Nuth, C.; Weidle, C.; Schweitzer, J.; Kohler, J.; Buscaino, G.

    2015-12-01

    Global glaciers and ice caps loose mass through calving, while existing models are currently not equipped to realistically predict dynamic ice loss. This is mainly because long-term continuous calving records, that would help to better understand fine scale processes and key climatic-dynamic feedbacks between calving, climate, terminus evolution and marine conditions, do not exist. Combined passive seismic/acoustic strategies are the only technique able to capture rapid calving events continuously, independent of daylight or meteorological conditions. We have produced such a continuous calving record for Kronebreen, a tidewater glacier in Svalbard, using data from permanent seismic stations between 2001 and 2014. However, currently no method has been established in cryo-seismology to quantify the calving ice loss directly from seismic data. Independent calibration data is required to derive 1) a realistic estimation of the dynamic ice loss unobserved due to seismic noise and 2) a robust scaling of seismic calving signals to ice volumes. Here, we analyze the seismic calving record at Kronebreen and independent calving data in a first attempt to quantify ice loss directly from seismic records. We make use of a) calving flux data with weekly to monthly resolution obtained from satellite remote sensing and GPS data between 2007 and 2013, and b) direct, visual calving observations in two weeks in 2009 and 2010. Furthermore, the magnitude-scaling property of seismic calving events is analyzed. We derive and discuss an empirical relation between seismic calving events and calving flux which for the first time allows to estimate a time series of calving volumes more than one decade back in time. Improving our model requires to incorporate more precise, high-resolution calibration data. A new field campaign will combine innovative, multi-disciplinary monitoring techniques to measure calving ice volumes and dynamic ice-ocean interactions simultaneously with terrestrial laser

  19. Improving estimation of glacier volume change: a GLIMS case study of Bering Glacier System, Alaska

    Directory of Open Access Journals (Sweden)

    M. J. Beedle

    2008-04-01

    Full Text Available The Global Land Ice Measurements from Space (GLIMS project has developed tools and methods that can be employed by analysts to create accurate glacier outlines. To illustrate the importance of accurate glacier outlines and the effectiveness of GLIMS standards we conducted a case study on Bering Glacier System (BGS, Alaska. BGS is a complex glacier system aggregated from multiple drainage basins, numerous tributaries, and many accumulation areas. Published measurements of BGS surface area vary from 1740 to 6200 km2, depending on how the boundaries of this system have been defined. Utilizing GLIMS tools and standards we have completed a new outline (3630 km2 and analysis of the area-altitude distribution (hypsometry of BGS using Landsat images from 2000 and 2001 and a US Geological Survey 15-min digital elevation model. We compared this new hypsometry with three different hypsometries to illustrate the errors that result from the widely varying estimates of BGS extent. The use of different BGS hypsometries results in highly variable measures of volume change and net balance (bn. Applying a simple hypsometry-dependent mass-balance model to different hypsometries results in a bn rate range of −1.0 to −3.1 m a−1 water equivalent (W.E., a volume change range of −3.8 to −6.7 km3 a−1 W.E., and a near doubling in contributions to sea level equivalent, 0.011 mm a−1 to 0.019 mm a−1. Current inaccuracies in glacier outlines hinder our ability to correctly quantify glacier change. Understanding of glacier extents can become comprehensive and accurate. Such accuracy is possible with the increasing volume of satellite imagery of glacierized regions, recent advances in tools and standards, and dedication to this important task.

  20. The p21 ras C-terminus is required for transformation and membrane association

    DEFF Research Database (Denmark)

    Willumsen, B M; Christensen, A; Hubbert, N L

    1984-01-01

    The Harvey murine sarcoma virus (Ha-MuSV) transforming gene, v-rasH, encodes a 21,000 molecular weight protein (p21) that is closely related to the p21 proteins encoded by the cellular transforming genes of the ras gene family. The primary translation product (prop21), which is found in the cytosol...... of these biochemical features of the protein, we have now studied a series of deletion mutants located at or near the C-terminus of the viral p21 protein. Our tissue culture studies indicate that amino acids located at or near the C-terminus are required for cellular transformation, membrane association and lipid...

  1. Bacillus subtilis SepF binds to the C-terminus of FtsZ.

    Science.gov (United States)

    Król, Ewa; van Kessel, Sebastiaan P; van Bezouwen, Laura S; Kumar, Neeraj; Boekema, Egbert J; Scheffers, Dirk-Jan

    2012-01-01

    Bacterial cell division is mediated by a multi-protein machine known as the "divisome", which assembles at the site of cell division. Formation of the divisome starts with the polymerization of the tubulin-like protein FtsZ into a ring, the Z-ring. Z-ring formation is under tight control to ensure bacteria divide at the right time and place. Several proteins bind to the Z-ring to mediate its membrane association and persistence throughout the division process. A conserved stretch of amino acids at the C-terminus of FtsZ appears to be involved in many interactions with other proteins. Here, we describe a novel pull-down assay to look for binding partners of the FtsZ C-terminus, using a HaloTag affinity tag fused to the C-terminal 69 amino acids of B. subtilis FtsZ. Using lysates of Escherichia coli overexpressing several B. subtilis cell division proteins as prey we show that the FtsZ C-terminus specifically pulls down SepF, but not EzrA or MinC, and that the interaction depends on a conserved 16 amino acid stretch at the extreme C-terminus. In a reverse pull-down SepF binds to full-length FtsZ but not to a FtsZΔC16 truncate or FtsZ with a mutation of a conserved proline in the C-terminus. We show that the FtsZ C-terminus is required for the formation of tubules from FtsZ polymers by SepF rings. An alanine-scan of the conserved 16 amino acid stretch shows that many mutations affect SepF binding. Combined with the observation that SepF also interacts with the C-terminus of E. coli FtsZ, which is not an in vivo binding partner, we propose that the secondary and tertiary structure of the FtsZ C-terminus, rather than specific amino acids, are recognized by SepF.

  2. Bacillus subtilis SepF binds to the C-terminus of FtsZ.

    Directory of Open Access Journals (Sweden)

    Ewa Król

    Full Text Available Bacterial cell division is mediated by a multi-protein machine known as the "divisome", which assembles at the site of cell division. Formation of the divisome starts with the polymerization of the tubulin-like protein FtsZ into a ring, the Z-ring. Z-ring formation is under tight control to ensure bacteria divide at the right time and place. Several proteins bind to the Z-ring to mediate its membrane association and persistence throughout the division process. A conserved stretch of amino acids at the C-terminus of FtsZ appears to be involved in many interactions with other proteins. Here, we describe a novel pull-down assay to look for binding partners of the FtsZ C-terminus, using a HaloTag affinity tag fused to the C-terminal 69 amino acids of B. subtilis FtsZ. Using lysates of Escherichia coli overexpressing several B. subtilis cell division proteins as prey we show that the FtsZ C-terminus specifically pulls down SepF, but not EzrA or MinC, and that the interaction depends on a conserved 16 amino acid stretch at the extreme C-terminus. In a reverse pull-down SepF binds to full-length FtsZ but not to a FtsZΔC16 truncate or FtsZ with a mutation of a conserved proline in the C-terminus. We show that the FtsZ C-terminus is required for the formation of tubules from FtsZ polymers by SepF rings. An alanine-scan of the conserved 16 amino acid stretch shows that many mutations affect SepF binding. Combined with the observation that SepF also interacts with the C-terminus of E. coli FtsZ, which is not an in vivo binding partner, we propose that the secondary and tertiary structure of the FtsZ C-terminus, rather than specific amino acids, are recognized by SepF.

  3. Contrast media

    International Nuclear Information System (INIS)

    Decazes, Ph.

    2004-01-01

    The Guerbet firm, which holds 69% of the capital on the contrast media for medical imagery, could sale about 20% of this capital in order to accelerate its development in the United States, one of its next market with the Japan. (O.M.)

  4. Structure and changing dynamics of a polythermal valley glacier on a centennial timescale - Midre Lovenbreen, Svalbard

    DEFF Research Database (Denmark)

    Hambrey, M. J.; Murray, T.; Glasser, N. F.

    2005-01-01

    structural glaciology, polythermal glacier, Svalbard, ground-penetrating radar, numerical modeling......structural glaciology, polythermal glacier, Svalbard, ground-penetrating radar, numerical modeling...

  5. Present dynamics and future prognosis of a slowly surging glacier

    Directory of Open Access Journals (Sweden)

    G. E. Flowers

    2011-03-01

    Full Text Available Glacier surges are a well-known example of an internal dynamic oscillation whose occurrence is not a direct response to the external climate forcing, but whose character (i.e. period, amplitude, mechanism may depend on the glacier's environmental or climate setting. We examine the dynamics of a small (∼5 km2 valley glacier in Yukon, Canada, where two previous surges have been photographically documented and an unusually slow surge is currently underway. To characterize the dynamics of the present surge, and to speculate on the future of this glacier, we employ a higher-order flowband model of ice dynamics with a regularized Coulomb-friction sliding law in both diagnostic and prognostic simulations. Diagnostic (force balance calculations capture the measured ice-surface velocity profile only when non-zero basal water pressures are prescribed over the central region of the glacier, coincident with where evidence of the surge has been identified. This leads to sliding accounting for 50–100% of the total surface motion in this region. Prognostic simulations, where the glacier geometry evolves in response to a prescribed surface mass balance, reveal a significant role played by a bedrock ridge beneath the current equilibrium line of the glacier. Ice thickening occurs above the ridge in our simulations, until the net mass balance reaches sufficiently negative values. We suggest that the bedrock ridge may contribute to the propensity for surges in this glacier by promoting the development of the reservoir area during quiescence, and may permit surges to occur under more negative balance conditions than would otherwise be possible. Collectively, these results corroborate our interpretation of the current glacier flow regime as indicative of a slow surge that has been ongoing for some time, and support a relationship between surge incidence or character and the net mass balance. Our results also highlight the importance of glacier bed

  6. Climate Change and Glacier Retreat: Scientific Fact and Artistic Opportunity

    Science.gov (United States)

    Fagre, D. B.

    2008-12-01

    Mountain glaciers continue to retreat rapidly over most of the globe. In North America, at Glacier National Park, Montana, recent research results from Sperry Glacier (2005-2007) indicate negative mass balances are now 3-4 times greater than in the 1950s. A geospatial model of glacier retreat in the Blackfoot-Jackson basin suggested all glaciers would be gone by 2030 but has proved too conservative. Accelerated glacier shrinkage since the model was developed has mirrored an increase in actual annual temperature that is almost twice the rate used in the model. The glaciers in Glacier National Park are likely to be gone well before 2030. A variety of media, curricula, and educational strategies have been employed to communicate the disappearance of the glaciers as a consequence of global warming. These have included everything from print media and television coverage to podcasts and wayside exhibits along roads in the park. However, a new thrust is to partner with artists to communicate climate change issues to new audiences and through different channels. A scientist-artist retreat was convened to explore the tension between keeping artistic products grounded in factually-based reality while providing for freedom to express artistic creativity. Individual artists and scientists have worked to create aesthetic and emotional images, using painting, poetry, music and photography, to convey core messages from research on mountain ecosystems. Finally, a traveling art exhibit was developed to highlight the photography that systematically documents glacier change through time. The aim was to select photographs that provide the most compelling visual experience for an art-oriented viewer and also accurately reflect the research on glacier retreat. The exhibit opens on January 11, 2009

  7. Simulation of historic glacier variations with a simple climate-glacier model

    NARCIS (Netherlands)

    Oerlemans, J.

    1988-01-01

    Glacier variations during the last few centuries have shown a marked coherence over the globe. Characteristic features are the maximum stand somewhere in the middle of the nineteenth century, and the steady retreat afterwards (with some minor interrruptions depending on the particular region).

  8. Tracer-based identification of rock glacier thawing in a glacierized Alpine catchment

    Science.gov (United States)

    Engel, Michael; Penna, Daniele; Tirler, Werner; Comiti, Francesco

    2017-04-01

    Current warming in high mountains leads to increased melting of snow, glacier ice and permafrost. In particular rock glaciers, as a creeping form of mountain permafrost, may release contaminants such as heavy metals into the stream during intense melting periods in summer. This may have strong impacts on both water quantity and quality of fresh water resources but might also harm the aquatic fauna in mountain regions. In this context, the present study used stable isotopes of water and electrical conductivity (EC) combined with trace, major and minor elements to identify the influence of permafrost thawing on the water quality in the glacierized Solda catchment (130 km2) in South Tyrol (Italy). We carried out a monthly sampling of two springs fed by an active rock glacier at about 2600 m a.s.l. from July to October 2015. Furthermore, we took monthly water samples from different stream sections of the Solda River (1110 to m a.s.l.) from March to November 2015. Meteorological data were measured by an Automatic Weather Station at 2825 m a.s.l. of the Hydrographic Office (Autonomous Province of Bozen-Bolzano). First results show that water from the rock glacier springs and stream water fell along the global meteoric water line. Spring water was slightly more variable in isotopic ratio (δ2H: -91 to - 105 ) and less variable in dissolved solutes (EC: 380 to 611 μS/cm) than stream water (δ2H: -96 to - 107 ‰ and EC: 212 to 927 μS/cm). Both spring water and stream water showed a pronounced drop in EC during July and August, very likely induced by increased melt water dilution. In both water types, element concentrations of Ca and Mg were highest (up to 160 and 20 mg/l, respectively). In September, spring water showed higher concentrations in Cu, As, and Pb than stream water, indicating that these elements partly exceeded the concentration limit for drinking water. These observations highlight the important control, which rock glacier thawing may have on water quality

  9. Modifications of the C terminus affect functionality and stability of yeast triacylglycerol lipase Tgl3p.

    Science.gov (United States)

    Koch, Barbara; Schmidt, Claudia; Ploier, Birgit; Daum, Günther

    2014-07-11

    Lipid droplets are specific organelles for the storage of triacylglycerols and steryl esters. They are surrounded by a phospholipid monolayer with a small but specific set of proteins embedded. Assembly and insertion of proteins into this surface membrane is an intriguing question of lipid droplet biology. To address this question we studied the topology of Tgl3p, the major triacylglycerol lipase of the yeast Saccharomyces cerevisiae, on lipid droplets. Employing the method of limited proteolysis of lipid droplet surface proteins, we found that the C terminus of Tgl3p faces the inside of the organelle, whereas the N terminus is exposed at the cytosolic side of lipid droplets. Detailed analysis of the C terminus revealed a stretch of seven amino acids that are critical for protein stability and functionality. The negative charge of two aspartate residues within this stretch is crucial for lipase activity of Tgl3p. A portion of Tgl3p, which is located to the endoplasmic reticulum, exhibits a different topology. In the phospholipid bilayer of the endoplasmic reticulum the C terminus faces the cytosol, which results in instability of the protein. Thus, the topology of Tgl3p is important for its function and strongly dependent on the membrane environment. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  10. The N-terminus of TDP-43 promotes its oligomerization and enhances DNA binding affinity

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chung-ke [Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan (China); Wu, Tzong-Huah [Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan (China); Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Institute of Biochemistry, Academia Sinica, Taipei 115, Taiwan (China); Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu 300, Taiwan (China); Wu, Chu-Ya [Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan (China); Graduate Institute of Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Chiang, Ming-hui; Toh, Elsie Khai-Woon [Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan (China); Hsu, Yin-Chih; Lin, Ku-Feng [Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan (China); Liao, Yu-heng [Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan (China); Huang, Tai-huang, E-mail: bmthh@gate.sinica.edu.tw [Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan (China); Department of Physics, National Taiwan Normal University, Taipei 106, Taiwan (China); Huang, Joseph Jen-Tse, E-mail: jthuang@chem.sinica.edu.tw [Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan (China)

    2012-08-24

    Highlights: Black-Right-Pointing-Pointer The N-terminus of TDP-43 contains an independently folded structural domain (NTD). Black-Right-Pointing-Pointer The structural domains of TDP-43 are arranged in a beads-on-a-string fashion. Black-Right-Pointing-Pointer The NTD promotes TDP-43 oligomerization in a concentration-dependent manner. Black-Right-Pointing-Pointer The NTD may assist nucleic acid-binding activity of TDP-43. -- Abstract: TDP-43 is a DNA/RNA-binding protein associated with different neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-U). Here, the structural and physical properties of the N-terminus on TDP-43 have been carefully characterized through a combination of nuclear magnetic resonance (NMR), circular dichroism (CD) and fluorescence anisotropy studies. We demonstrate for the first time the importance of the N-terminus in promoting TDP-43 oligomerization and enhancing its DNA-binding affinity. An unidentified structural domain in the N-terminus is also disclosed. Our findings provide insights into the N-terminal domain function of TDP-43.

  11. MEASURING SURFACE DEFORMATION IN GLACIER RETREATED AREAS BASED ON PS-INSAR – GELADANDONG GLACIER AS A CASE STUDY

    Directory of Open Access Journals (Sweden)

    B. Mohamadi

    2018-04-01

    Full Text Available Glaciers are retreating in many parts of the world as a result of global warming. Many researchers consider Qinghai-Tibetan Plateau as a reference for climate change by measuring glaciers retreat on the plateau. This retreat resulted in some topographic changes in retreated areas, and in some cases can lead to geohazards as landslides, and rock avalanches, which is known in glacier retreated areas as paraglacial slope failure (PSF. In this study, Geladandong biggest and main glacier mass was selected to estimate surface deformation on its glacier retreated areas and define potential future PSF based on PS-InSAR technique. 56 ascending and 49 descending images were used to fulfill this aim. Geladandong glacier retreated areas were defined based on the maximum extent of the glacier in the little ice age. Results revealed a general uplift in the glacier retreated areas with velocity less than 5mm/year. Obvious surface motion was revealed in seven parts surround glacier retreated areas with high relative velocity reached ±60mm/year in some parts. Four parts were considered as PSF potential motion, and two of them showed potential damage for the main road in the study area in case of rock avalanche into recent glacier lakes that could result in glacier lake outburst flooding heading directly to the road. Finally, further analysis and field investigations are needed to define the main reasons for different types of deformation and estimate future risks of these types of surface motion in the Qinghai-Tibetan Plateau.

  12. Tidal bending of glaciers: a linear viscoelastic approach

    DEFF Research Database (Denmark)

    Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph

    2003-01-01

    In theoretical treatments of tidal bending of floating glaciers, the glacier is usually modelled as an elastic beam with uniform thickness, resting on an elastic foundation. With a few exceptions, values of the elastic (Young's) modulus E of ice derived from tidal deflection records of floating...

  13. The retreat of the world's mountain glaciers during recent decades

    International Nuclear Information System (INIS)

    Francou, B.; Vincent, Ch.

    2009-01-01

    Glaciers have become essential tools for measuring changes in the global environment. Here, we analyze glacier evolution during the last few decades and we wonder whether the observed retreat remains in the range of glacier fluctuations since the mid-Holocene. The main fluctuations experienced by glaciers during the last millenniums, and particularly during the Little Ice Age (-1300 A.D. to ∼1860 A.D.), are presented succinctly. The recent 1960-2005 period, well documented both by ground and remote sensing observations, shows important disparities between different massifs concerning the timing and the magnitude of glacier fluctuations, which depend on regional climatic conditions. The links between glacier mass balance evolution and climate is clear when approached from an energy balance but the variables commonly considered are only temperature and precipitation. The strong correlation existing between these variables and the mass balance evolution makes it possible to simulate glaciers in the future in function of distinct climatic scenarios. Modeling glacier retreat for the 21. century is an important goal because it will allow the impacts on water resource and sea level to be assessed. (authors)

  14. A glacier runoff extension to the Precipitation Runoff Modeling System

    Science.gov (United States)

    A. E. Van Beusekom; R. J. Viger

    2016-01-01

    A module to simulate glacier runoff, PRMSglacier, was added to PRMS (Precipitation Runoff Modeling System), a distributed-parameter, physical-process hydrological simulation code. The extension does not require extensive on-glacier measurements or computational expense but still relies on physical principles over empirical relations as much as is feasible while...

  15. Irreversible mass loss of Canadian Arctic Archipelago glaciers

    NARCIS (Netherlands)

    Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; van Angelen, J.H.|info:eu-repo/dai/nl/325922470; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Gardner, A.S.; Wouters, Bert|info:eu-repo/dai/nl/304120146; van Meijgaard, E.

    2013-01-01

    The Canadian Arctic Archipelago (CAA) contains the largest volume of glacier ice on Earth outside of Antarctica and Greenland. In the absence of significant calving, CAA glacier mass balance is governed by the difference between surface snow accumulation and meltwater runoff—surface mass balance.

  16. Velocities of antarctic outlet glaciers determined from sequential Landsat images

    Science.gov (United States)

    MacDonald, Thomas R.; Ferrigno, Jane G.; Williams, Richard S.; Lucchitta, Baerbel K.

    1989-01-01

    Approximately 91.0 percent of the volume of present-day glacier ice on Earth is in Antarctica; Greenland contains about another 8.3 percent of the volume. Thus, together, these two great ice sheets account for an estimated 99.3 percent of the total. Long-term changes in the volume of glacier ice on our planet are the result of global climate change. Because of the relationship of global ice volume to sea level (± 330 cubic kilometers of glacier ice equals ± 1 millimeter sea level), changes in the mass balance of the antarctic ice sheet are of particular importance.Whether the mass balance of the east and west antarctic ice sheets is positive or negative is not known. Estimates of mass input by total annual precipitation for the continent have been made from scattered meteorological observations (Swithinbank 1985). The magnitude of annual ablation of the ice sheet from calving of outlet glaciers and ice shelves is also not well known. Although the velocities of outlet glaciers can be determined from field measurements during the austral summer,the technique is costly, does not cover a complete annual cycle,and has been applied to just a few glaciers. To increase the number of outlet glaciers in Antarctica for which velocities have been determined and to provide additional data for under-standing the dynamics of the antarctic ice sheets and their response to global climate change, sequential Landsat image of several outlet glaciers were measured.

  17. CALICE: Calibrating Plant Biodiversity in Glacier Ice

    Science.gov (United States)

    Festi, Daniela; Cristofori, Antonella; Vernesi, Cristiano; Zerbe, Stefan; Wellstein, Camilla; Maggi, Valter; Oeggl, Klaus

    2017-04-01

    The objective of the project is to reconstruct plant biodiversity and its trend archived in Alpine glacier ice by pollen and eDNA (environmental DNA) during the last five decades by analyzing a 40 m ice core. For our study we chose the Adamello glacier (Trentino - Südtirol, Lombardia) because of i) the good preservation conditions for pollen and eDNA in ice, ii) the thickness of the ice cap (270m) and iii) the expected high time resolution. The biodiversity estimates gained by pollen analysis and eDNA will be validated by historical biodiversity assessments mainly based on vegetation maps, aerial photos and vegetation surveys in the catchment area of the Adamello glacier for the last five decades. This historical reconstruction of biodiversity trends will be performed on a micro-, meso- and macro-scale (5, 20-50 and 50-100 Km radius, respectively). The results will serve as a calibration data set on biodiversity for future studies, such as the second step of the coring by the POLLiCE research consortium (pollice.fmach.it). In fact, arrangements are currently been made to drill the complete ice cap and retrieve a 270 m thick core which has the potential to cover a time span of minimum 400 years up to several millennia. This second stage will extend the time scale and enable the evaluation of dissimilarity/similarity of modern biodiversity in relation to Late Holocene trends. Finally, we believe this case study has the potential to be applied in other glaciated areas to evaluate biodiversity for large regions (e.g. central Asian mountain ranges, Tibet and Tian Shan or the Andes).

  18. Tibetan Plateau glacier and hydrological change under stratospheric aerosol injection

    Science.gov (United States)

    Ji, D.

    2017-12-01

    As an important inland freshwater resource, mountain glaciers are highly related to human life, they provide water for many large rivers and play a very important role in regional water cycles. The response of mountain glaciers to future climate change is a topic of concern especially to the many people who rely on glacier-fed rivers for purposes such as irrigation. Geoengineering by stratospheric aerosol injection is a method of offsetting the global temperature rise from greenhouse gases. How the geoengineering by stratospheric aerosol injection affects the mass balance of mountain glaciers and adjacent river discharge is little understood. In this study, we use regional climate model WRF and catchment-based river model CaMa-Flood to study the impacts of stratospheric aerosol injection to Tibetan Plateau glacier mass balance and adjacent river discharge. To facilitate mountain glacier mass balance study, we improve the description of mountain glacier in the land surface scheme of WRF. The improvements include: (1) a fine mesh nested in WRF horizontal grid to match the highly non-uniform spatial distribution of the mountain glaciers, (2) revising the radiation flux at the glacier surface considering the surrounding terrain. We use the projections of five Earth system models for CMIP5 rcp45 and GeoMIP G4 scenarios to drive the WRF and CaMa-Flood models. The G4 scenario, which uses stratospheric aerosols to reduce the incoming shortwave while applying the rcp4.5 greenhouse gas forcing, starts stratospheric sulfate aerosol injection at a rate of 5 Tg per year over the period 2020-2069. The ensemble projections suggest relatively slower glacier mass loss rates and reduced river discharge at Tibetan Plateau and adjacent regions under geoengineering scenario by stratospheric aerosol injection.

  19. A revised Canadian perspective: progress in glacier hydrology

    Science.gov (United States)

    Munro, D. Scott

    2005-01-01

    Current research into glacier hydrology is occurring at a time when glaciers around the world, particularly those whose hydrological regimes affect populated areas, are shrinking as they go through a state of perpetual negative annual mass balance. Small glaciers alone are likely to contribute 0·5 to 1 mm year-1 to global sea-level rise, with associated reductions in local freshwater resources, impacts upon freshwater ecosystems and increased risk of hazard due to outburst floods. Changes to the accumulation regimes of glaciers and ice sheets may be partly responsible, so the measurement and distribution of snowfall in glacierized basins, a topic long represented in non-glacierized basin research, is now beginning to receive more attention than it did before, aided by the advent of reliable automatic weather stations that provide data throughout the year. Satellite data continue to be an important information source for summer meltwater estimation, as distributed models, and their need for albedo maps, continue to develop. This further entails the need for simplifications to energy balance components, sacrificing point detail so that spatial calculation may proceed more quickly. The understanding of surface meltwater routing through the glacier to produce stream outflow continues to be a stimulating area of research, as demonstrated by activity at the Trapridge Glacier, Canada, and Canadian involvement in the Haut Glacier d'Arolla, Switzerland. As Canadian glacier monitoring continues to evolve, effort must be directed toward developing situations where mass balance, meltwater generation and flow routing studies can be done together at selected sites. Copyright

  20. Characterization of meltwater 'ingredients' at the Haig Glacier, Canadian Rockies: the importance of glaciers to regional water resources

    Science.gov (United States)

    Miller, K.; Marshall, S.

    2017-12-01

    With rising temperatures, Alberta's glaciers are under stresses which change and alter the timing, amount, and composition of meltwater contributions to rivers that flow from the Rocky Mountains. Meltwater can be stored within a glacier or it can drain through the groundwater system, reducing and delaying meltwater delivery to glacier-fed streams. This study tests whether the glacier meltwater is chemically distinct from rain or snow melt, and thus whether meltwater contributions to higher-order streams that flow from the mountains can be determined through stream chemistry. Rivers like the Bow, North Saskatchewan, and Athabasca are vital waterways for much of Alberta's population. Assessing the extent of glacier meltwater is vital to future water resource planning. Glacier snow/ice and meltwater stream samples were collected during the 2017 summer melt season (May- September) and analyzed for isotope and ion chemistry. The results are being used to model water chemistry evolution in the melt stream through the summer season. A chemical mixing model will be constructed to determine the fractional contributions to the Haig meltwater stream from precipitation, surface melt, and subglacial meltwaters. Distinct chemical water signatures have not been used to partition water sources and understand glacier contributions to rivers in the Rockies. The goal of this work is to use chemical signatures of glacial meltwater to help assess the extent of glacier meltwater in Alberta rivers and how this varies through the summer season.

  1. The energy balance on the surface of a tropical glacier tongue. Investigations on glacier Artesonraju, Cordillera Blanca, Perú.

    Science.gov (United States)

    Juen, I.; Mölg, T.; Wagnon, P.; Cullen, N. J.; Kaser, G.

    2006-12-01

    The Cordillera Blanca in Perú is situated in the Outer Tropics spanning from 8 to 10 ° South. Solar incidence and air temperature show only minor seasonal variations whereas precipitation occurs mainly from October to April. An energy balance station was installed on the tongue of glacier Artesonraju (4850 m a.s.l.) in March 2004. In this study each component of the energy balance on the glacier surface is analysed separately over a full year, covering one dry and one wet season. During the dry season glacier melt at the glacier tongue is app. 0.5 m we per month. In the wet season glacier melt is twice as much with 1 m we per month. This is due to higher energy fluxes and decreased sublimation during the wet season. With an energy balance model that has already been proved under tropical climate conditions (Mölg and Hardy, 2004) each energy flux is changed individually to evaluate the change in the amount of glacier melt. First results indicate that a change in humidity related variables affects glacier melt very differently in the dry and wet season, whereas a change in air temperature changes glacier melt more constantly throughout the year.

  2. Geographic Names of Iceland's Glaciers: Historic and Modern

    Science.gov (United States)

    Sigurðsson, Oddur; Williams, Richard S.

    2008-01-01

    Climatic changes and resulting glacier fluctuations alter landscapes. In the past, such changes were noted by local residents who often documented them in historic annals; eventually, glacier variations were recorded on maps and scientific reports. In Iceland, 10 glacier place-names are to be found in Icelandic sagas, and one of Iceland's ice caps, Snaefellsjokull, appeared on maps of Iceland published in the 16th century. In the late 17th century, the first description of eight of Iceland's glaciers was written. Therefore, Iceland distinguishes itself in having a more than 300-year history of observations by Icelanders on its glaciers. A long-term collaboration between Oddur Sigurdsson and Richard S. Williams, Jr., led to the authorship of three books on the glaciers of Iceland. Much effort has been devoted to documenting historical glacier research and related nomenclature and to physical descriptions of Icelandic glaciers by Icelanders and other scientists from as far back as the Saga Age to recent (2008) times. The first book, Icelandic Ice Mountains, was published by the Icelandic Literary Society in 2004 in cooperation with the Icelandic Glaciological Society and the International Glaciological Society. Icelandic Ice Mountains was a glacier treatise written by Sveinn Palsson in 1795 and is the first English translation of this important scientific document. Icelandic Ice Mountains includes a Preface, including a summary of the history and facsimiles of page(s) from the original manuscript, a handwritten copy, and an 1815 manuscript (without maps and drawings) by Sveinn Palsson on the same subject which he wrote for Rev. Ebenezer Henderson; an Editor's Introduction; 82 figures, including facsimiles of Sveinn Palsson's original maps and perspective drawings, maps, and photographs to illustrate the text; a comprehensive Index of Geographic Place-Names and Other Names in the treatise; References, and 415 Endnotes. Professional Paper 1746 (this book) is the second

  3. Rock Glacier Response to Climate Change in the Argentinian Andes

    Science.gov (United States)

    Drewes, J.; Korup, O.; Moreiras, S.

    2017-12-01

    Rock glaciers are bodies of frozen debris and ice that move under the influence of gravity in permafrost areas. Rock glaciers may store a large amount of sediments and play an important role as prime movers of debris in the Andean sediment cascade. However, little is known about how much sediment and water rock glaciers may store at the mountain-belt scale, and the few existing estimates vary considerably. We address this question for the Argentinian Andes, for which a new glacial inventory containing more than 6500 rock glaciers gives us the opportunity to analyse their relevance within the sediment cascade. We examine the inventory for catchments in five sub-regions, i.e. the Desert Andes (22°-31°S); the Central Andes (31°-36°S); the Northern Andes of Patagonia (36°-45°S); the Southern Andes of Patagonia (45°-52°S); and Tierra del Fuego (52°-55°S), together with climate variables of the WorldClim datasets, and digital topographic data, to estimate how rock-glacier extents may change under different past and future climate scenarios. We observe for the northern Desert Andes that rock glacier toes are at 4000 to 5000 m a.s.l. and a mean annual temperature range of 3° and 8°C, though most rock glaciers are in areas with mean annual temperatures between -5 and 5°C, marking a distinct thermal niche. Rock glaciers are traditionally viewed as diagnostic of sporadic alpine permafrost and their toes are often near the annual mean 0°C isotherm. However, we find that only rock glaciers in the southern Desert Andes and Central Andes are located where annual mean temperature is -2°C. Future scenarios project an increase of > four degrees in these areas, which may further degrade ground ice and potentially change the rates at which rock glaciers advance. Where active rock glaciers become inactive their coarse material, which was formerly bound by ice, may be released into the sediment cascade, whereas accelerating or rapidly downwasting rock glaciers may either

  4. Mercury Hazard Assessment for Piscivorous Wildlife in Glacier National Park

    KAUST Repository

    Stafford, Craig P.

    2016-12-14

    We examined the mercury hazard posed to selected piscivorous wildlife in Glacier National Park (GNP), Montana. Logging Lake was our focal site where we estimated the dietary mercury concentrations of wildlife (common loon [Gavia immer], American mink [Neovison vison], river otter [Lontra canadensis], and belted kingfisher [Megaceryle alcyon]) by assuming that fishes were consumed in proportion to their relative abundances. To evaluate if Logging Lake provided a suitable baseline for our study, we made geographic comparisons of fish mercury levels and investigated the distribution and abundance of high mercury fishes within GNP. We complimented our assessment by examining selenium:mercury molar ratios in fishes from Logging Lake and Saint Mary Lake. Our results suggest fish consumption does not imperil wildlife from Logging Lake based on published thresholds for adverse mercury effects, but some hazard may exist particularly if there is strong feeding selectivity for the most contaminated species, northern pikeminnow (Ptychocheilus oregonensis). The geographic comparisons of fish mercury levels, together with the distribution and abundance of high mercury fishes within GNP, suggest that Logging Lake provided a relatively protective baseline among our study lakes. Risk may be further reduced by the molar excess of selenium relative to mercury, particularly in the smaller fishes typically consumed by GNP wildlife. Our findings contrast with studies from northeastern US and southeastern Canada where greater mercury hazard to wildlife exists. An emergent finding from our research is that waterborne concentrations of methylmercury may provide limited insight into regional differences in fish mercury levels.

  5. Mercury Hazard Assessment for Piscivorous Wildlife in Glacier National Park

    KAUST Repository

    Stafford, Craig P.; Downs, Christopher C.; Langner, Heiko W.

    2016-01-01

    We examined the mercury hazard posed to selected piscivorous wildlife in Glacier National Park (GNP), Montana. Logging Lake was our focal site where we estimated the dietary mercury concentrations of wildlife (common loon [Gavia immer], American mink [Neovison vison], river otter [Lontra canadensis], and belted kingfisher [Megaceryle alcyon]) by assuming that fishes were consumed in proportion to their relative abundances. To evaluate if Logging Lake provided a suitable baseline for our study, we made geographic comparisons of fish mercury levels and investigated the distribution and abundance of high mercury fishes within GNP. We complimented our assessment by examining selenium:mercury molar ratios in fishes from Logging Lake and Saint Mary Lake. Our results suggest fish consumption does not imperil wildlife from Logging Lake based on published thresholds for adverse mercury effects, but some hazard may exist particularly if there is strong feeding selectivity for the most contaminated species, northern pikeminnow (Ptychocheilus oregonensis). The geographic comparisons of fish mercury levels, together with the distribution and abundance of high mercury fishes within GNP, suggest that Logging Lake provided a relatively protective baseline among our study lakes. Risk may be further reduced by the molar excess of selenium relative to mercury, particularly in the smaller fishes typically consumed by GNP wildlife. Our findings contrast with studies from northeastern US and southeastern Canada where greater mercury hazard to wildlife exists. An emergent finding from our research is that waterborne concentrations of methylmercury may provide limited insight into regional differences in fish mercury levels.

  6. Storm-induced water dynamics and thermohaline structure at the tidewater Flade Isblink Glacier outlet to the Wandel Sea (NE Greenland

    Directory of Open Access Journals (Sweden)

    S. Kirillov

    2017-11-01

    Full Text Available In April 2015, an ice-tethered conductivity–temperature–depth (CTD profiler and a down-looking acoustic Doppler current profiler (ADCP were deployed from the landfast ice near the tidewater glacier terminus of the Flade Isblink Glacier in the Wandel Sea, NE Greenland. The 3-week time series showed that water dynamics and the thermohaline structure were modified considerably during a storm event on 22–24 April, when northerly winds exceeded 15 m s−1. The storm initiated downwelling-like water dynamics characterized by on-shore water transport in the surface (0–40 m layer and compensating offshore flow at intermediate depths. After the storm, currents reversed in both layers, and the relaxation phase of downwelling lasted ∼ 4 days. Although current velocities did not exceed 5 cm s−1, the enhanced circulation during the storm caused cold turbid intrusions at 75–95 m depth, which are likely attributable to subglacial water from the Flade Isblink Ice Cap. It was also found that the semidiurnal periodicities in the temperature and salinity time series were associated with the lunar semidiurnal tidal flow. The vertical structure of tidal currents corresponded to the first baroclinic mode of the internal tide with a velocity minimum at ∼ 40 m. The tidal ellipses rotate in opposite directions above and below this depth and cause a divergence of tidal flow, which was observed to induce semidiurnal internal waves of about 3 m height at the front of the glacier terminus. Our findings provide evidence that shelf–basin interaction and tidal forcing can potentially modify coastal Wandel Sea waters even though they are isolated from the atmosphere by landfast sea ice almost year-round. The northerly storms over the continental slope cause an enhanced circulation facilitating a release of cold and turbid subglacial water to the shelf. The tidal flow may contribute to the removal of such water from the glacial terminus.

  7. The length of the world's glaciers - a new approach for the global calculation of center lines

    DEFF Research Database (Denmark)

    Machguth, Horst; Huss, M.

    2014-01-01

    length using an automated method that relies on glacier surface slope, distance to the glacier margins and a set of trade-off functions. The method is developed for East Greenland, evaluated for East Greenland as well as for Alaska and eventually applied to all similar to 200 000 glaciers around...... appear to be related to characteristics of topography and glacier mass balance. The present study adds glacier length as a key parameter to global glacier inventories. Global and regional scaling laws might prove beneficial in conceptual glacier models....

  8. Glaciers of Avacha group of volcanoes in Neoholocene

    Directory of Open Access Journals (Sweden)

    T. M. Manevich

    2016-01-01

    Full Text Available The study of moraines at the Avacha volcano group revealed that glaciers changes at all volcanoes within the group happened almost synchronously. Glacial deposits could be grouped into three generations, corresponding to three periods of glacier fluctuations in Neoholocene. The largest glaciation within the group occurred ~2000 years ago. Fragments of moraine, corresponding to that period were found only in the moraine complex of the Ditmar Glacier which was 15% larger then today at that time. The most of moraines at the Avacha volcano group were formed during the Little Ice Age, which in the studied region continued up to the first decades of XX centuries. The maximal advance of glaciers probably happened in XVII century. The moraine corresponding to that period was found at the Kozelsky Glacier valley. At present time the total area of glaciers which moraines were described and dated approaches 21.46  km2. The area of reconstructed moraines corresponding to the Little Ice Age is estimated to be 2.79 km2, therefore at that period the total glaciation area reaches 24,25 км2 exceeding the present area by 13%. It could be claimed that in general during the time past the Little Ice Age the glaciation nature and glacier types did not change sufficiently. The rate of glacier degradation at various parts of the group is different and depends mainly on exposition. At the valleys of four glaciers we found moraines formed in the middle of XX century. They may appear in 1941–1952 when the unfavorable weather conditions leaded to stable negative anomalies in accumulation have happened.

  9. Conserved region at the COOH terminus of human immunodeficiency virus gp120 envelope protein contains an immunodominant epitope

    International Nuclear Information System (INIS)

    Palker, T.J.; Matthews, T.J.; Clark, M.E.

    1987-01-01

    A highly immunogenic epitope from a conserved COOH-terminal region of the human immunodeficiency virus (HIV) gp120 envelope protein has been identified with antisera from HIV-seropositive subjects and a synthetic peptide (SP-22) containing 15 amino acids from this region (Ala-Pro-Thr-Lys-Ala-Lys-Arg-Arg-Val-Val-Gln-Arg-Glu-Lys-Arg). Peptide SP-22 absorbed up to 100% of anti-gp120 antibody reactivity from select HIV + patient sera in immunoblot assays and up to 79% of serum anti-gp120 antibody reactivity in competition RIA. In RIA, 45% of HIV-seropositive subjects had antibodies that bound to peptide SP-22. Human anti-SP-22 antibodies that bound to and were eluted from an SP-22 affinity column reacted with gp120 in RIA and immunoblot assays but did not neutralize HIV or inhibit HIV-induced syncytium formation in vitro, even though these antibodies comprised 70% of all anti-gp120 antibodies in the test serum. In contrast, the remaining 30% of SP-22 nonreactive anti-gp120 antibodies did not react with gp120 in immunoblot assays but did react in RIA and neutralized HIV in vitro. Thus, ≅ 50% of HIV-seropositive patients make high titers of nonneutralizing antibodies to an immunodominant antigen on gp120 defined by SP-22. Moreover, the COOH terminus of gp120 contains the major antigen or antigens identified by human anti-gp120 antibodies in immunoblot assays

  10. Structure of the human MLH1 N-terminus: implications for predisposition to Lynch syndrome

    International Nuclear Information System (INIS)

    Wu, Hong; Zeng, Hong; Lam, Robert; Tempel, Wolfram; Kerr, Iain D.; Min, Jinrong

    2015-01-01

    The crystal structure of the human MLH1 N-terminus is reported at 2.30 Å resolution. The overall structure is described along with an analysis of two clinically important mutations. Mismatch repair prevents the accumulation of erroneous insertions/deletions and non-Watson–Crick base pairs in the genome. Pathogenic mutations in the MLH1 gene are associated with a predisposition to Lynch and Turcot’s syndromes. Although genetic testing for these mutations is available, robust classification of variants requires strong clinical and functional support. Here, the first structure of the N-terminus of human MLH1, determined by X-ray crystallography, is described. The structure shares a high degree of similarity with previously determined prokaryotic MLH1 homologs; however, this structure affords a more accurate platform for the classification of MLH1 variants

  11. Structure of the human MLH1 N-terminus: implications for predisposition to Lynch syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hong; Zeng, Hong; Lam, Robert; Tempel, Wolfram [University of Toronto, 101 College Street, Toronto, ON M5G 1L7 (Canada); Kerr, Iain D., E-mail: ikerr@myriad.com [Myriad Genetic Laboratories Inc., 320 Wakara Way, Salt Lake City, UT 84108 (United States); Min, Jinrong, E-mail: ikerr@myriad.com [University of Toronto, 101 College Street, Toronto, ON M5G 1L7 (Canada); University of Toronto, Toronto, ON M5G 1L7 (Canada)

    2015-07-28

    The crystal structure of the human MLH1 N-terminus is reported at 2.30 Å resolution. The overall structure is described along with an analysis of two clinically important mutations. Mismatch repair prevents the accumulation of erroneous insertions/deletions and non-Watson–Crick base pairs in the genome. Pathogenic mutations in the MLH1 gene are associated with a predisposition to Lynch and Turcot’s syndromes. Although genetic testing for these mutations is available, robust classification of variants requires strong clinical and functional support. Here, the first structure of the N-terminus of human MLH1, determined by X-ray crystallography, is described. The structure shares a high degree of similarity with previously determined prokaryotic MLH1 homologs; however, this structure affords a more accurate platform for the classification of MLH1 variants.

  12. Distribution and transportation of mercury from glacier to lake in the Qiangyong Glacier Basin, southern Tibetan Plateau, China.

    Science.gov (United States)

    Sun, Shiwei; Kang, Shichang; Huang, Jie; Li, Chengding; Guo, Junming; Zhang, Qianggong; Sun, Xuejun; Tripathee, Lekhendra

    2016-06-01

    The Tibetan Plateau is home to the largest aggregate of glaciers outside the Polar Regions and is a source of fresh water to 1.4 billion people. Yet little is known about the transportation and cycling of Hg in high-elevation glacier basins on Tibetan Plateau. In this study, surface snow, glacier melting stream water and lake water samples were collected from the Qiangyong Glacier Basin. The spatiotemporal distribution and transportation of Hg from glacier to lake were investigated. Significant diurnal variations of dissolved Hg (DHg) concentrations were observed in the river water, with low concentrations in the morning (8:00am-14:00pm) and high concentrations in the afternoon (16:00pm-20:00pm). The DHg concentrations were exponentially correlated with runoff, which indicated that runoff was the dominant factor affecting DHg concentrations in the river water. Moreover, significant decreases of Hg were observed during transportation from glacier to lake. DHg adsorption onto particulates followed by the sedimentation of particulate-bound Hg (PHg) could be possible as an important Hg removal mechanism during the transportation process. Significant decreases in Hg concentrations were observed downstream of Xiao Qiangyong Lake, which indicated that the high-elevation lake system could significantly affect the distribution and transportation of Hg in the Qiangyong Glacier Basin. Copyright © 2016. Published by Elsevier B.V.

  13. Paired dating of pith and outer edge (terminus) samples from prehispanic Caribbean wooden sculptures

    Science.gov (United States)

    Fiona Brock; Joanna Ostapkowicz; Christopher Bronk Ramsey; Alex Wiedenhoeft; Caroline. Cartwright

    2012-01-01

    Radiocarbon dating of historical and archaeological wood can be complicated, sometimes involving issues of “inbuilt” age in slow-growing woods, and/or the possibility of reuse or long delays between felling and use of the wood. Terminus dates can be provided by dating the sapwood, or the outermost edge of heartwood, while a date from the pith can give an indication of...

  14. Ice thickness measurements and volume estimates for glaciers in Norway

    Science.gov (United States)

    Andreassen, Liss M.; Huss, Matthias; Melvold, Kjetil; Elvehøy, Hallgeir; Winsvold, Solveig H.

    2014-05-01

    Whereas glacier areas in many mountain regions around the world now are well surveyed using optical satellite sensors and available in digital inventories, measurements of ice thickness are sparse in comparison and a global dataset does not exist. Since the 1980s ice thickness measurements have been carried out by ground penetrating radar on many glaciers in Norway, often as part of contract work for hydropower companies with the aim to calculate hydrological divides of ice caps. Measurements have been conducted on numerous glaciers, covering the largest ice caps as well as a few smaller mountain glaciers. However, so far no ice volume estimate for Norway has been derived from these measurements. Here, we give an overview of ice thickness measurements in Norway, and use a distributed model to interpolate and extrapolate the data to provide an ice volume estimate of all glaciers in Norway. We also compare the results to various volume-area/thickness-scaling approaches using values from the literature as well as scaling constants we obtained from ice thickness measurements in Norway. Glacier outlines from a Landsat-derived inventory from 1999-2006 together with a national digital elevation model were used as input data for the ice volume calculations. The inventory covers all glaciers in mainland Norway and consists of 2534 glaciers (3143 glacier units) covering an area of 2692 km2 ± 81 km2. To calculate the ice thickness distribution of glaciers in Norway we used a distributed model which estimates surface mass balance distribution, calculates the volumetric balance flux and converts it into thickness using the flow law for ice. We calibrated this model with ice thickness data for Norway, mainly by adjusting the mass balance gradient. Model results generally agree well with the measured values, however, larger deviations were found for some glaciers. The total ice volume of Norway was estimated to be 275 km3 ± 30 km3. From the ice thickness data set we selected

  15. Rapid melting dynamics of an alpine glacier with repeated UAV photogrammetry

    Science.gov (United States)

    Rossini, Micol; Di Mauro, Biagio; Garzonio, Roberto; Baccolo, Giovanni; Cavallini, Giuseppe; Mattavelli, Matteo; De Amicis, Mattia; Colombo, Roberto

    2018-03-01

    Glacial retreat is a major problem in the Alps, especially over the past 40 years. Unmanned aerial vehicles (UAVs) can provide an unparalleled opportunity to track the spatiotemporal variations in rapidly changing glacial morphological features related to glacial dynamics. The objective of this study is to evaluate the potential of commercial UAV platforms to detect the evolution of the surface topography and morphology of an alpine glacier over a short time scale through the repeated acquisition of high-resolution photogrammetric data. Two high-resolution UAV surveys were performed on the ablation region of the Morteratsch Glacier (Swiss Alps) in July and September 2016. First, structure-from-motion (SfM) techniques were applied to create orthophotos and digital surface models (DSMs) of the glacial surface from multi-view UAV acquisitions. The geometric accuracy of DSMs and orthophotos was checked using differential global navigation satellite system (dGNSS) ground measurements, and an accuracy of approximately 17 cm was achieved for both models. High-resolution orthophotos and DSMs made it possible to provide a detailed characterization of rapidly changing glacial environments. Comparing the data from the first and the second campaigns, the evolution of the lower part of the glacier in response to summer ablation was evaluated. Two distinct processes were revealed and accurately quantified: an average lowering of the surface, with a mean ice thinning of 4 m, and an average horizontal displacement of 3 m due to flowing ice. These data were validated through a comparison of different algorithms and approaches, which clearly showed the consistency of the results. The melt rate spatial patterns were then compared to the glacial brightness and roughness maps derived from the September UAV acquisition. The results showed that the DSM differences describing the glacial melt rates were inversely related to the glacial brightness. In contrast, a positive but weaker

  16. A potyvirus vector efficiently targets recombinant proteins to chloroplasts, mitochondria and nuclei in plant cells when expressed at the amino terminus of the polyprotein.

    Science.gov (United States)

    Majer, Eszter; Navarro, José-Antonio; Daròs, José-Antonio

    2015-09-01

    Plant virus-based expression systems allow quick and efficient production of recombinant proteins in plant biofactories. Among them, a system derived from tobacco etch virus (TEV; genus potyvirus) permits coexpression of equimolar amounts of several recombinant proteins. This work analyzed how to target recombinant proteins to different subcellular localizations in the plant cell using this system. We constructed TEV clones in which green fluorescent protein (GFP), with a chloroplast transit peptide (cTP), a nuclear localization signal (NLS) or a mitochondrial targeting peptide (mTP) was expressed either as the most amino-terminal product or embedded in the viral polyprotein. Results showed that cTP and mTP mediated efficient translocation of GFP to the corresponding organelle only when present at the amino terminus of the viral polyprotein. In contrast, the NLS worked efficiently at both positions. Viruses expressing GFP in the amino terminus of the viral polyprotein produced milder symptoms. Untagged GFPs and cTP and NLS tagged amino-terminal GFPs accumulated to higher amounts in infected tissues. Finally, viral progeny from clones with internal GFPs maintained the extra gene better. These observations will help in the design of potyvirus-based vectors able to coexpress several proteins while targeting different subcellular localizations, as required in plant metabolic engineering. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Hydro-chemical Characterization of Glacier Melt Water of Ponkar Glacier, Manang, Nepal.

    Science.gov (United States)

    Shrestha, R.; Sandeep, S.

    2017-12-01

    The study was carried out in Ponkar Glacier, representing Himalayan glacier of Nepal. The study aims in determining the physical-chemical properties of the glacier melt water. The sampling sites included moraine dammed, Ponkar Lake at 4100 m a.s.l to the downstream glaciated stream at 3580 m a.s.l. The water samples were collected from the seven different sites. Temperature was recorded by digital multi-thermometer on site. The samples were brought to the laboratory and the parameters were analyzed according to the APHA, AWWA and WEF standards. The glacier meltwater was slightly basic with pH 7.44 (±0.307). The meltwater was found to be in the range 30-60 which implies the water is moderately soft resulting value of concentration 36.429±8.664 mg CaCO3 L-1 and the electrical conductivity was found to be 47.14 (±11.18) µS/cm. The concentration of anion was in the order of HCO3 - > Cl- > SO42- > NO3- > TP-PO43- with the concentration 194.286±40.677, 55.707±30.265, 11.533±1.132 mgL-1, 1.00±0.7 mgL-1 and 0.514±0.32 mgL-1 respectively. Calcium carbonate weathering was found out to be the major source of dissolved ions in the region. The heavy metals were found in the order Al>Fe>Mn>Zn with concentration 1.34±0.648, 1.103±0.917, 0.08±0.028 and 0.023±0.004 mgL-1 respectively. The concentration of iron, manganese and zinc in some sites were below the detection limit. These results represent baseline data for the physical-chemical properties of the glacier meltwater

  18. Mendenhall Glacier Visitor Center vehicular and pedestrian traffic congestion study

    Science.gov (United States)

    2007-05-01

    The Mendenhall Glacier Visitor Center of Tongass National Forest in Juneau, Alaska is experiencing vehicular and pedestrian congestion. This study was initiated by the United States Forest Service, Alaska Region, in cooperation with Western Federal L...

  19. Glacier shrinkage and water resources in the Andes

    Science.gov (United States)

    Francou, Bernard; Coudrain, Anne

    For more than a century glaciers around the world have been melting as air temperatures rise due to a combination of natural processes and human activity. The disappearance of these glaciers can have wide-ranging effects, such as the creation of new natural hazards or changes in stream flow that could threaten water suppliesSome of the most dramatic melting has occurred in the Andes mountain range in South America. To highlight the climatic and glacial change in the Andes and to encourage the scientific community to strengthen the glacier observation network that stretches from Colombia to the Patagonian ice fields, the Instituto Nacional de Recursos Naturales (INRENA), Perú, and the Institute of Research and Development (IRD), France, recently organized the second Symposium on Mass Balance of Andean Glaciers in Huaráz,Perú.

  20. Glacier-influenced sedimentation on high-latitude continental margins

    National Research Council Canada - National Science Library

    Dowdeswell, J. A; Cofaigh, C. Ó

    2002-01-01

    This book examines the process and patterns of glacier-influenced sedimentation on high-latitude continental margins and the geophysical and geological signatures of the resulting sediments and landform...

  1. Discovering Chile's hidden water treasures – rock glaciers | IDRC ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2011-05-30

    May 30, 2011 ... This means the research methods for investigating rock glaciers are ... group advising Chile's national environmental protection agency on ... Communities' perception of climate change risks in South America's Atlantic coasts.

  2. Rock glaciers, Fletschhorn Area, Valais, Switzerland, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains a total amount of 74 rock glaciers which were investigated in the Fletschhorn Area in the southern Swiss Alps during the summer of 1995. The...

  3. Investigating cold based summit glaciers through direct access to the glacier base: a case study constraining the maximum age of Chli Titlis glacier, Switzerland

    Science.gov (United States)

    Bohleber, Pascal; Hoffmann, Helene; Kerch, Johanna; Sold, Leo; Fischer, Andrea

    2018-01-01

    Cold glaciers at the highest locations of the European Alps have been investigated by drilling ice cores to retrieve their stratigraphic climate records. Findings like the Oetztal ice man have demonstrated that small ice bodies at summit locations of comparatively lower altitudes may also contain old ice if locally frozen to the underlying bedrock. In this case, constraining the maximum age of their lowermost ice part may help to identify past periods with minimum ice extent in the Alps. However, with recent warming and consequent glacier mass loss, these sites may not preserve their unique climate information for much longer. Here we utilized an existing ice cave at Chli Titlis (3030 m), central Switzerland, to perform a case study for investigating the maximum age of cold-based summit glaciers in the Alps. The cave offers direct access to the glacier stratigraphy without the logistical effort required in ice core drilling. In addition, a pioneering exploration had already demonstrated stagnant cold ice conditions at Chli Titlis, albeit more than 25 years ago. Our englacial temperature measurements and the analysis of the isotopic and physical properties of ice blocks sampled at three locations within the ice cave show that cold ice still exists fairly unchanged today. State-of-the-art micro-radiocarbon analysis constrains the maximum age of the ice at Chli Titlis to about 5000 years before present. By this means, the approach presented here will contribute to a future systematic investigation of cold-based summit glaciers, also in the Eastern Alps.

  4. Contrasting Climate Change Impact on River Flow from Glacierised Catchments in the Himalayan and Andes Mountains

    Science.gov (United States)

    Pellicciotti, F.; Ragettli, S.; Immerzeel, W. W. W.

    2016-12-01

    Glaciers and glacierised catchments in mountainous regions react to a changing climate in different manners depending on climate and glacier characteristics. Despite the key role of mountain ranges as natural water towers, their hydrological balance and future changes in glacier runoff associated with climate warming remain poorly understood because of high meteorological variability, physical inaccessibility and the complex interplay between climate, cryosphere and hydrological processes. We use a state-of-the art glacio-hydrological model informed by data from high altitude observations and the latest CMIP5 climate change scenarios to quantify the climate change impact on glaciers and runoff for two contrasting catchments vulnerable to changes in the cryosphere. The two catchments are located in the Central Andes of Chile and in the Nepalese Himalaya in close vicinity of densely populated areas. Although both sites are projected to experience a strong decrease in glacier area, they show remarkably different hydrological responses. Icemelt is on a rising limb in Langtang at least until 2041-2050 and starts to decrease afterwards, while in Juncal icemelt was already beyond its tipping point at the beginning of the 21st century. This contrasting response can be explained by differences in the elevation distribution of the glaciers in the two regions. In Juncal, many glaciers are melting up to the highest elevations already during the reference period (2000-2010) and increasing melt rates due to higher air temperatures cannot compensate the loss of glacier area. In Langtang, large sections of the glaciers at high elevations are currently not exposed to melt, but will be in the future, thus compensating for the loss of glacier area at lower elevations. As a result of these changes and projected changes in precipitation, in Juncal runoff will sharply decrease in the future and the runoff seasonality is sensitive to projected climatic changes. In Langtang, future water

  5. Rock glaciers in the Suntar‑Khayata Range

    Directory of Open Access Journals (Sweden)

    V. M. Lytkin

    2016-01-01

    Full Text Available The remote map‑making technique and results of field investigations made possible for the first time to reveal a great number of rock glaciers within the area of the Suntar‑Khayata Range (North‑East Asia. A total of 540 formations were identified. Among them, 47 rock glaciers were classified as corrie (cirque tongue‑shaped formations and 493 ones – as niche lobe‑shaped (single‑ and multi‑lobe rock glaciers. Occurrence of such formations is 8.4/100 km2, that is the largest in the North‑East Asia. The rock glaciers in this region are found within a range of true altitudes from 1297 up to 2402 m asl. The majority of active features, however, are confined to the interval between 1500 and 1900 m asl. Rock glaciers occur in the altitudinal range of 1297 to 2402 m asl. The majority of active features, however, are confined to the interval between 1500 and 1900 m asl, and the main part of active formations is located within the range of 1500‑2500 m. The frequency analysis of true altitudes of the rock‑glacier occurrence indicates that their formation can be caused by the hypsometry of the region relation to morphoclimatic zonality.

  6. Updated Estimates of Glacier Mass Change for Western North America

    Science.gov (United States)

    Menounos, B.; Gardner, A. S.; Howat, I.; Berthier, E.; Dehecq, A.; Noh, M. J.; Pelto, B. M.

    2017-12-01

    Alpine glaciers are critical components in Western North America's hydrologic cycle. We use varied remotely-sensed datasets to provide updated mass change estimates for Region 2 of the Randolf Glacier Inventory (RGI-02 - all North American glaciers outside of Alaska). Our datasets include: i) aerial laser altimetry surveys completed over many thousands of square kilometers; and ii) multiple Terabytes of high resolution optical stereo imagery (World View 1-3 and Pleiades). Our data from the period 2014-2017 includes the majority of glaciers in RGI-02, specifically those ice masses in the Rocky Mountains (US and Canada), Interior Ranges in British Columbia and the Cascade Mountains (Washington). We co-registered and bias corrected the recent surface models to the Shuttle Radar Topographic Mapping (SRTM) data acquired in February, 2000. In British Columbia, our estimates of mass change are within the uncertainty estimates obtained for the period 1985-2000, but estimates from some regions indicate accelerated mass loss. Work is also underway to update glacier mass change estimates for glaciers in Washington and Montana. Finally, we use re-analysis data (ERA interim and ERA5) to evaluate the meteorological drivers that explain the temporal and spatial variability of mass change evident in our analysis.

  7. Tropical New World Glacier Recession from the mid-1980s to the mid-2000s

    Science.gov (United States)

    Slayback, D. A.; Tucker, C. J.

    2010-12-01

    We report on the systematic retreat of all glaciers in the tropics of the New World from the mid-1980s to the mid-2000s. These glaciers comprise 99% of the world’s tropical glaciers and occur in Bolivia, Peru, Ecuador, Colombia, Venezuela, and Mexico. It was necessary to use a large quantity of Landsat satellite data (124 images), selecting multiple images for every glacier for both epochs, to minimize confusion of glacier area with snow. Change in glacier extent was combined with a digital elevation model (DEM) to provide information on the elevation and aspect of areas of glacier recession. Overall, we found glacier recession of approximately 30% over twenty years, declining from ~2500 km2 from the mid-1980s to ~1800 km2 in the mid-2000s. In addition, there was a strong association of glacier recession with elevation and aspect. We discuss these trends in relation to hypothesized climatic influences.

  8. Glaciers and hydrological changes in the Tien Shan: simulation and prediction

    International Nuclear Information System (INIS)

    Aizen, V B; Aizen, E M; Kuzmichonok, V A

    2007-01-01

    In this study, we estimated the current glacier state and forecast the potential impact of global and regional climate change on the glaciers and glacier runoff in the Tien Shan. General (G) and detailed (D) simulations were developed based on assessment of the Tien Shan glacier recession between 1943 and 2003 using an iterative stepwise increase in the equilibrium line altitude of 20 m. The G simulation was developed for 2777 grids each of which covered over 1000 km 2 of glacier surface and D for the 15 953 Tien Shan glaciers. Both simulations employed glacier morphometric characteristics derived from Digital Elevation Model based on remote sensing data, high resolution maps and in situ GPS validation. Simulated changes in glacier area demonstrated that a possible increase in air temperature of 1 deg. C at E-barLA must be compensated by a 100 mm increase in precipitation at the same altitude if Tien Shan glaciers are to be maintained in their current state. An increase in mean air temperature of 4 deg. C and precipitation of 1.1 times the current level could increase E-barLA by 570 m during the 21st century. Under these conditions, the number of glaciers, glacier covered area, glacier volume, and glacier runoff are predicted to be 94%, 69%, 75%, and 75% of current values. The maximum glacier runoff may reach as much as 1.25 times current levels while the minimum will likely equal zero

  9. Seasonal and altitudinal variations in snow algal communities on an Alaskan glacier (Gulkana glacier in the Alaska range)

    International Nuclear Information System (INIS)

    Takeuchi, Nozomu

    2013-01-01

    Snow and ice algae are cold tolerant algae growing on the surface of snow and ice, and they play an important role in the carbon cycles for glaciers and snowfields in the world. Seasonal and altitudinal variations in seven major taxa of algae (green algae and cyanobacteria) were investigated on the Gulkana glacier in Alaska at six different elevations from May to September in 2001. The snow algal communities and their biomasses changed over time and elevation. Snow algae were rarely observed on the glacier in May although air temperature had been above 0 ° C since the middle of the month and surface snow had melted. In June, algae appeared in the lower areas of the glacier, where the ablation ice surface was exposed. In August, the distribution of algae was extended to the upper parts of the glacier as the snow line was elevated. In September, the glacier surface was finally covered with new winter snow, which terminated algal growth in the season. Mean algal biomass of the study sites continuously increased and reached 6.3 × 10 μl m −2 in cell volume or 13 mg carbon m −2 in September. The algal community was dominated by Chlamydomonas nivalis on the snow surface, and by Ancylonema nordenskiöldii and Mesotaenium berggrenii on the ice surface throughout the melting season. Other algae were less abundant and appeared in only a limited area of the glacier. Results in this study suggest that algae on both snow and ice surfaces significantly contribute to the net production of organic carbon on the glacier and substantially affect surface albedo of the snow and ice during the melting season. (letter)

  10. Recent glacier mass balance and area changes in the Kangri Karpo Mountains from DEMs and glacier inventories

    Directory of Open Access Journals (Sweden)

    K. Wu

    2018-01-01

    Full Text Available Due to the influence of the Indian monsoon, the Kangri Karpo Mountains in the south-east of the Tibetan Plateau is in the most humid and one of the most important and concentrated regions containing maritime (temperate glaciers. Glacier mass loss in the Kangri Karpo is an important contributor to global mean sea level rise, and changes run-off distribution, increasing the risk of glacial-lake outburst floods (GLOFs. Because of its inaccessibility and high labour costs, information about the Kangri Karpo glaciers is still limited. Using geodetic methods based on digital elevation models (DEMs derived from 1980 topographic maps from the Shuttle Radar Topography Mission (SRTM (2000 and from TerraSAR-X/TanDEM-X (2014, this study has determined glacier elevation changes. Glacier area and length changes between 1980 and 2015 were derived from topographical maps and Landsat TM/ETM+/OLI images. Results show that the Kangri Karpo contained 1166 glaciers with an area of 2048.50 ± 48.65 km2 in 2015. Ice cover diminished by 679.51 ± 59.49 km2 (24.9 ± 2.2 % or 0.71 ± 0.06 % a−1 from 1980 to 2015, although nine glaciers advanced. A glacierized area of 788.28 km2, derived from DEM differencing, experienced a mean mass loss of 0.46 ± 0.08 m w.e. a−1 from 1980 to 2014. Shrinkage and mass loss accelerated significantly from 2000 to 2015 compared to 1980–2000, consistent with a warming climate.

  11. Recent glacier mass balance and area changes in the Kangri Karpo Mountains from DEMs and glacier inventories

    Science.gov (United States)

    Wu, Kunpeng; Liu, Shiyin; Jiang, Zongli; Xu, Junli; Wei, Junfeng; Guo, Wanqin

    2018-01-01

    Due to the influence of the Indian monsoon, the Kangri Karpo Mountains in the south-east of the Tibetan Plateau is in the most humid and one of the most important and concentrated regions containing maritime (temperate) glaciers. Glacier mass loss in the Kangri Karpo is an important contributor to global mean sea level rise, and changes run-off distribution, increasing the risk of glacial-lake outburst floods (GLOFs). Because of its inaccessibility and high labour costs, information about the Kangri Karpo glaciers is still limited. Using geodetic methods based on digital elevation models (DEMs) derived from 1980 topographic maps from the Shuttle Radar Topography Mission (SRTM) (2000) and from TerraSAR-X/TanDEM-X (2014), this study has determined glacier elevation changes. Glacier area and length changes between 1980 and 2015 were derived from topographical maps and Landsat TM/ETM+/OLI images. Results show that the Kangri Karpo contained 1166 glaciers with an area of 2048.50 ± 48.65 km2 in 2015. Ice cover diminished by 679.51 ± 59.49 km2 (24.9 ± 2.2 %) or 0.71 ± 0.06 % a-1 from 1980 to 2015, although nine glaciers advanced. A glacierized area of 788.28 km2, derived from DEM differencing, experienced a mean mass loss of 0.46 ± 0.08 m w.e. a-1 from 1980 to 2014. Shrinkage and mass loss accelerated significantly from 2000 to 2015 compared to 1980-2000, consistent with a warming climate.

  12. Very small glaciers under climate change: from the local to the global scale

    Science.gov (United States)

    Huss, M.; Fischer, M.

    2015-12-01

    Very small glaciers (climate archive. Very small glaciers have generally shorter response times than valley glaciers and their mass balance is strongly dependent on snow redistribution processes. Worldwide glacier monitoring has focused on medium-sized to large glaciers leaving us with a relatively limited understanding of the behavior of very small glaciers. With warming climate there is an increasing concern that very small glaciers might be the first to disappear. Already in the next decades this might result in the complete deglaciation of mountain ranges with glacier equilibrium lines close to the highest peaks, such as in the Rocky Mountains, the European Alps, the Andes or parts of High Mountain Asia. In this contribution, we present a comprehensive modelling framework to assess past and future changes in very small glaciers at the mountain-range scale. Among other processes our model accounts for snow redistribution, changes in glacier geometry and dynamic changes in debris-coverage, and computes e.g. distributed mass balance, englacial temperature and proglacial runoff. Detailed glacier projections until 2060 are shown for the Swiss Alps based on new data sets, and the 21st century contribution of all very small glaciers worldwide to sea-level rise is quantified using a global model. Grid-based modelling of surface mass balance and retreat for 1133 very small glaciers in Switzerland indicates that 70% of them will completely vanish within the next 25 years. However, a few avalanche-fed glaciers at low elevation might be able to survive even substantial atmospheric warming. We find relatively high static and dynamic sensitivities for gently-sloping glaciers. At the global scale, glaciers presently smaller than 1 km2 make up for only 0.7% of total ice volume but account for 6.7% of sea-level rise contribution during the period 2015-2025. This indicates that very small glaciers are a non-negligible component of global glacier change, at least in the near

  13. Glacier dynamics over the last quarter of a century at Helheim, Kangerdlugssuaq and 14 other major Greenland outlet glaciers

    Directory of Open Access Journals (Sweden)

    S. L. Bevan

    2012-09-01

    Full Text Available The Greenland ice sheet is experiencing increasing rates of mass loss, the majority of which results from changes in discharge from tidewater glaciers. Both atmospheric and ocean drivers have been implicated in these dynamic changes, but understanding the nature of the response has been hampered by the lack of measurements of glacier flow rates predating the recent period of warming. Here, using Landsat-5 data from 1985 onwards, we extend back in time the record of surface velocities and ice-front position for 16 of Greenland's fastest-flowing tidewater glaciers, and compare these to more recent data from Landsat-7 and satellite-borne synthetic-aperture radar. Climate re-analysis data and sea surface temperatures from 1982 show that since 1995 most of Greenland and its surrounding oceans have experienced significant overall warming, and a switch to a warming trend. During the period from 1985 to 1995 when Greenland and the surrounding oceans were not warming, major tidewater outlet glaciers around Greenland, including Kangerdlugssuaq and Helheim, were dynamically stable. Since the mid-1990s, glacier discharge has consistently been both greater and more variable. Together, these observations support the hypothesis that recent dynamic change is a rapid response to climate forcing. Both air and ocean temperatures in this region are predicted to continue to warm, and will therefore likely drive further change in outlet glacier discharge.

  14. Glacier surge mechanism based on linked cavity configuration of the basal water conduit system

    Science.gov (United States)

    Kamb, Barclay

    1987-08-01

    viscous heat dissipation in the flow of water through the orifices is treated in detail under the assumption of local heat transfer, which guarantees that the heating effects are not underestimated. This treatment brings to light a melting-stability parameter Ξ that provides a measure of the influence of viscous heating on orifice cavitation, similar but distinct for step and wave orifices. Orifice shapes and the amounts of roof meltback are determined by Ξ. When Ξ ≳ 1, so that the system is "viscous-heating-dominated," the orifices are unstable against rapid growth in response to a modest increase in water pressure or in orifice size over their steady state values. This growth instability is somewhat similar to the jökulhlaup-type instability of tunnels, which are likewise heating-dominated. When Ξ ≲ 1, the orifices are stable against perturbations of modest to even large size. Stabilization is promoted by high sliding velocity ν, expressed in terms of a ν-½ and ν-1 dependence of Ξ for step and wave cavities. The relationships between basal water pressure and water flux transmitted by linked cavity models of step and wave orifice type are calculated for an empirical relation between water pressure and sliding velocity and for a particular, reasonable choice of system parameters. In all cases the flux is an increasing function of the water pressure, in contrast to the inverse flux-versus-pressure relation for tunnels. In consequence, a linked cavity system can exist stably as a system of many interconnected conduits distributed across the glacier bed, in contrast to a tunnel system, which must condense to one or at most a few main tunnels. The linked cavity model gives basal water pressures much higher than the tunnel model at water fluxes ≳1 m3/s if the bed roughness features that generate the orifices have step heights or wave amplitudes less than about 0.1 m. The calculated basal water pressure of the particular linked cavity models evaluated is about 2

  15. Bathymetry of Torssukatak fjord and one century of glacier stability

    Science.gov (United States)

    An, L.; Rignot, E. J.; Morlighem, M.

    2017-12-01

    Marine-terminating glaciers dominate the evolution of the Greenland Ice Sheet(GrIS) mass balance as they control 90% of the ice discharge into the ocean. Warm air temperatures thin the glaciers from the top to unground ice fronts from the bed. Warm oceans erode the submerged grounded ice, causing the grounding line to retreat. To interpret the recent and future evolution of two outlet glaciers, Sermeq Avangnardleq (AVA) and Sermeq Kujatdleq (KUJ) in central West Greenland, flowing into the ice-choked Torssukatak fjord (TOR), we need to know their ice thickness and bed topography and the fjord bathymetry. Here, we present a novel mapping of the glacier bed topography, ice thickness and sea floor bathymetry near the grounding line using high resolution airborne gravity data from AIRGrav collected in August 2012 with a helicopter platform, at 500 m spacing grid, 50 knots ground speed, 80 m ground clearance, with submilligal accuracy, i.e. higher than NASA Operation IceBridge (OIB)'s 5.2 km resolution, 290 knots, and 450 m clearance. We also employ MultiBeam Echo Sounding data (MBES) collected in the fjord since 2009. We had to wait until the summer of 2016, during Ocean Melting Greenland (OMG), to map the fjord bathymetry near the ice fronts for the first time. We constrain the 3D inversion of the gravity data with MBES in the fjord and a reconstruction of the glacier bed topography using mass conservation (MC) on land ice. The seamless topography obtained across the grounding line reveal the presence of a 300-m sill for AVA, which explains why this glacier has been stable for a century, despite changes in surface melt and ocean-induced melt and the presence of a deep fjord (800 m) in front of the glacier. For KUJ, we also reveal the presence of a wide sill (300 m depth) near the current ice front which explains its stability and the stranding of iceberg debris in front of the glacier. The results shed new light on the evolution of these glaciers and explain their

  16. Exploring the mobility of cryoconite on High-Arctic glaciers

    Science.gov (United States)

    Irvine-Fynn, T. D.; Hodson, A. J.; Bridge, J. W.; Langford, H.; Anesio, A.; Ohlanders, N.; Newton, S.

    2010-12-01

    There has been a growing awareness of the significance of biologically active dust (cryoconite) on the energy balance of, and nutrient cycling at glacier surfaces. Moreover, researchers have estimated the mass of biological material released from glacier ice to downstream environments and ecosystems, including the melt-out of cells from emergent ice in the ablation area. However, the processes, rates and mechanisms of cryoconite mobility and transport have not been fully explored. For many smaller valley glaciers in the High-Arctic, the climate dictates only a thin (~ 1m) layer of ice at the glacier surface is at the melting point during the summer months. This surface ice is commonly characterized by an increased porosity in response to incident energy and hydraulic conditions, and has been termed the “weathering crust”. The presence of cryoconite, with its higher radiation absorption, exacerbates the weathering crust development. Thus, crucially, the transport of cryoconite is not confined to simply a ‘smooth’ ice surface, but rather also includes mobility in the near-surface ice matrix. Here, we present initial results from investigations of cryoconite transport at Midtre Lovénbreen and Longyearbreen, two north-facing valley glaciers in Svalbard (Norway). Using time-lapse imagery, we explore the transport rates of cryoconite on a glacier surface and consider the associations between mobility and meteorological conditions. Results suggest some disparity between micro-, local- and plot-scale observations of cryoconite transport: the differences imply controlling influences of cryoconite volume, ice surface topography and ice structure. While to examine the relative volumes of cryoconite exported from the glacier surface by supraglacial streams we employ flow cytometry, using SYBR-Green-II staining to identify the biological component of the suspended load. Preliminary comparisons between shallow (1m) ice cores and in-stream concentrations suggest

  17. Mass balance model parameter transferability on a tropical glacier

    Science.gov (United States)

    Gurgiser, Wolfgang; Mölg, Thomas; Nicholson, Lindsey; Kaser, Georg

    2013-04-01

    The mass balance and melt water production of glaciers is of particular interest in the Peruvian Andes where glacier melt water has markedly increased water supply during the pronounced dry seasons in recent decades. However, the melt water contribution from glaciers is projected to decrease with appreciable negative impacts on the local society within the coming decades. Understanding mass balance processes on tropical glaciers is a prerequisite for modeling present and future glacier runoff. As a first step towards this aim we applied a process-based surface mass balance model in order to calculate observed ablation at two stakes in the ablation zone of Shallap Glacier (4800 m a.s.l., 9°S) in the Cordillera Blanca, Peru. Under the tropical climate, the snow line migrates very frequently across most of the ablation zone all year round causing large temporal and spatial variations of glacier surface conditions and related ablation. Consequently, pronounced differences between the two chosen stakes and the two years were observed. Hourly records of temperature, humidity, wind speed, short wave incoming radiation, and precipitation are available from an automatic weather station (AWS) on the moraine near the glacier for the hydrological years 2006/07 and 2007/08 while stake readings are available at intervals of between 14 to 64 days. To optimize model parameters, we used 1000 model simulations in which the most sensitive model parameters were varied randomly within their physically meaningful ranges. The modeled surface height change was evaluated against the two stake locations in the lower ablation zone (SH11, 4760m) and in the upper ablation zone (SH22, 4816m), respectively. The optimal parameter set for each point achieved good model skill but if we transfer the best parameter combination from one stake site to the other stake site model errors increases significantly. The same happens if we optimize the model parameters for each year individually and transfer

  18. Distributed ice thickness and glacier volume in southern South America

    Science.gov (United States)

    Carrivick, Jonathan L.; Davies, Bethan J.; James, William H. M.; Quincey, Duncan J.; Glasser, Neil F.

    2016-11-01

    South American glaciers, including those in Patagonia, presently contribute the largest amount of meltwater to sea level rise per unit glacier area in the world. Yet understanding of the mechanisms behind the associated glacier mass balance changes remains unquantified partly because models are hindered by a lack of knowledge of subglacial topography. This study applied a perfect-plasticity model along glacier centre-lines to derive a first-order estimate of ice thickness and then interpolated these thickness estimates across glacier areas. This produced the first complete coverage of distributed ice thickness, bed topography and volume for 617 glaciers between 41°S and 55°S and in 24 major glacier regions. Maximum modelled ice thicknesses reach 1631 m ± 179 m in the South Patagonian Icefield (SPI), 1315 m ± 145 m in the North Patagonian Icefield (NPI) and 936 m ± 103 m in Cordillera Darwin. The total modelled volume of ice is 1234.6 km3 ± 246.8 km3 for the NPI, 4326.6 km3 ± 865.2 km3 for the SPI and 151.9 km3 ± 30.38 km3 for Cordillera Darwin. The total volume was modelled to be 5955 km3 ± 1191 km3, which equates to 5458.3 Gt ± 1091.6 Gt ice and to 15.08 mm ± 3.01 mm sea level equivalent (SLE). However, a total area of 655 km2 contains ice below sea level and there are 282 individual overdeepenings with a mean depth of 38 m and a total volume if filled with water to the brim of 102 km3. Adjusting the potential SLE for the ice volume below sea level and for the maximum potential storage of meltwater in these overdeepenings produces a maximum potential sea level rise (SLR) of 14.71 mm ± 2.94 mm. We provide a calculation of the present ice volume per major river catchment and we discuss likely changes to southern South America glaciers in the future. The ice thickness and subglacial topography modelled by this study will facilitate future studies of ice dynamics and glacier isostatic adjustment, and will be important for projecting water resources and

  19. Simulating calving-front changes of Greenland’s marine-terminating glaciers

    DEFF Research Database (Denmark)

    Haubner, Konstanze

    glacier retreat to a certain degree and foremost define the variation of retreat rates. The thesis implies the importance of incorporating glacier-front dynamics into ice sheet models in order to match observations and verifies atmospheric and oceanic forcing as important triggers for glacier retreat...... UI outlet glaciers. The change in mass flux resulting from the prescribed glacier retreat contributes to 70% of UI’s mass change over the simulation periods. The residual mass change is due to surface mass balance. A second simulation on the fastest UI glacier (UI-1) reveals that frontal melt rates...

  20. 20th-century glacial-marine sedimentation in Vitus Lake, Bering Glacier, Alaska, U.S.A.

    Science.gov (United States)

    Molnia, B.F.; Post, A.; Carlson, P.R.

    1996-01-01

    Vitus Lake, the ice-marginal basin at the southeastern edge of Bering Glacier, Alaska, U.S.A., is a site of modern, rapid, glacial-marine sedimentation. Rather than being a fresh-water lake, Vitus Lake is a tidally influenced, marine to brackish embayment connected to the Pacific Ocean by an inlet, the Seal River. Vitus Lake consists of five deep bedrock basins, separated by interbasinal highs. Glacial erosion has cut these basins as much as 250 m below sea level. High-resolution seismic reflection surveys conducted in 1991 and 1993 of four of Vitus Lake's basins reveal a complex, variable three-component acoustic stratigraphy. Although not fully sampled, the stratigraphy is inferred to be primarily glacial-marine units of (1) basal contorted and deformed glacial-marine and glacial sediments deposited by basal ice-contact processes and submarine mass-wasting; (2) acoustically well-stratified glacial-marine sediment, which unconformably overlies the basal unit and which grades upward into (3) acoustically transparent or nearly transparent glacial-marine sediment. Maximum thicknesses of conformable glacial-marine sediment exceed 100 m. All of the acoustically transparent and stratified deposits in Vitus Lake are modern in age, having accumulated between 1967 and 1993. The basins where these three-part sequences of "present-day" glacial-marine sediment are accumulating are themselves cut into older sequences of stratified glacial and glacial-marine deposits. These older units outcrop on the islands in Vitus Lake. In 1967, as the result of a major surge, glacier ice completely filled all five basins. Subsequent terminus retreat, which continued through August 1993, exposed these basins, providing new locations for glacial-marine sediment accumulation. A correlation of sediment thicknesses measured from seismic profiles at specific locations within the basins, with the year that each location became ice-free, shows that the sediment accumulation at some locations

  1. The role of the Cx43 C-terminus in GJ plaque formation and internalization

    International Nuclear Information System (INIS)

    Wayakanon, Praween; Bhattacharjee, Rajib; Nakahama, Ken-ichi; Morita, Ikuo

    2012-01-01

    Highlights: ► Cx43-GFP or -DsRed fusion proteins were expressed in HeLa cells. ► Roles of C-terminus were examined using various mutants. ► Gap junction plaque size was dependent on the length of C-terminus. ► C-terminus dependent gap junction plaque internalization was observed. -- Abstract: Connexin 43 (Cx43) is a major gap junction (GJ) protein found in many mammalian cell types. The C-terminal (CT) domain of Cx43 has unique characteristics in terms of amino acid (aa) sequence and its length differs from other connexins. This CT domain can be associated with protein partners to regulate GJ assembly and degradation, which results in the direct control of gap junction intercellular communication (GJIC). However, the essential roles of the CT regions involved in these mechanisms have not been fully elucidated. In this study, we aimed to investigate the specific regions of Cx43CT involved in GJ formation and internalization. Wild type Cx43 (382aa) and 10 CT truncated mutants were stably expressed in HeLa cells as GFP or DsRed tagged proteins. First, we found that the deletion of 235–382aa from Cx43 resulted in failure to make GJ and establish GJIC. Second, the Cx43 with 242–382aa CT deletion could form functional GJs and be internalized as annular gap junctions (AGJs). However, the plaques consisting of Cx43 with CT deletions (Δ242–382aa to Δ271–382aa) were longer than the plaques consisting of Cx43 with CT deletions (Δ302–382aa). Third, co-culture experiments of cells expressing wild type Cx43 (382) with cells expressing Cx43CT mutants revealed that the directions of GJ internalization were dependent on the length of the respective CT. Moreover, a specific region, 325–342aa residues of Cx43, played an important role in the direction of GJ internalization. These results showed the important roles of the Cx43 C-terminus in GJ expression and its turnover.

  2. The N terminus of monoamine transporters is a lever required for the action of amphetamines

    DEFF Research Database (Denmark)

    Sucic, Sonja; Dallinger, Stefan; Zdrazil, Barbara

    2010-01-01

    The serotonin transporter (SERT) terminates neurotransmission by removing serotonin from the synaptic cleft. In addition, it is the site of action of antidepressants (which block the transporter) and of amphetamines (which induce substrate efflux). We explored the functional importance of the N......(+) entry and accumulation of SERT(T81A) in the inward facing conformation ought to favor amphetamine-induced efflux. Thus, we surmised that the N terminus must play a direct role in driving the transporter into a state that supports amphetamine-induced efflux. This hypothesis was verified by truncating...

  3. Sensitivity of very small glaciers in the Swiss Alps to future climate change

    Directory of Open Access Journals (Sweden)

    Matthias eHuss

    2016-04-01

    Full Text Available Very small glaciers (<0.5 km2 account for more than 80% of the total number of glaciers in mid- to low-latitude mountain ranges. Although their total area and volume is small compared to larger glaciers, they are a relevant component of the cryosphere, contributing to landscape formation, local hydrology and sea-level rise. Worldwide glacier monitoring mostly focuses on medium-sized to large glaciers leaving us with a limited understanding of the response of dwarf glaciers to climate change. In this study, we present a comprehensive modeling framework to assess past and future changes of very small glaciers at the mountain-range scale. Among other processes our model accounts for snow redistribution, changes in glacier geometry and the time-varying effect of supraglacial debris. It computes the mass balance distribution, the englacial temperature regime and proglacial runoff. The evolution of 1,133 individual glaciers in the Swiss Alps is modeled in detail until 2060 based on new distributed data sets. Our results indicate that 52% of all very small glaciers in Switzerland will completely disappear within the next 25 years. However, a few avalanche-fed glaciers at low elevation might be able to survive even substantial atmospheric warming. We find highly variable sensitivities of very small glaciers to air temperature change, with gently-sloping, low-elevation, and debris-covered glaciers being most sensitive.

  4. Surface and thickness variations of Brenva Glacier tongue (Mont Blanc, Italian Alps) in the second half of the 20th century by historical maps and aerial photogrammetry comparisons

    Science.gov (United States)

    D Agata, C.; Zanutta, A.; Muzzu Martis, D.; Mancini, F.; Smiraglia, C.

    2003-04-01

    Aim of this contribution is the evaluation of volumetric and surface variations of Brenva Glacier (Mont Blanc, Italian Alps) during the second half of the 20th century, by GIS-based processing of maps and aerial photogrammetry technique. Brenva Glacier is a typical debris covered glacier, located in a valley on the S-E side of the Mont Blanc. The glacier covers a surface of 7 kmq and shows a length of 7,6 km at maximum. The glacier snout reaches 1415 m a.s.l., which is the lowest glacier terminus of the Italian Alps. To evaluate glacier variations different historical maps were used: 1) The 1959 Map, at the scale 1:5.000, by EIRA (Ente Italiano Rilievi Aerofotogrammetrici, Firenze), from terrestrial photogrammetric survey, published in the Bollettino del Comitato Glaciologico Italiano, 2, n. 19, 1971. 2) The 1971 Map, at the scale 1:5.000, from aerial photogrammetry (Alifoto, Torino) published in the Bollettino del Comitato Glaciologico Italiano, 2, n. 20, 1972. 3) The 1988 Map, at the scale 1:10.000, (Region Aosta Valley, Regional Technical Map) from 1983 aerial photogrammetric survey. 4) The 1999 Map, at the scale 1:10.000, (Region Aosta Valley, Regional Technical Map) from 1991 aerial photogrammetry survey. For the same purpose the following aereal photographs were used: 1) The 1975 image, CGR (Italian General Company aerial Surveys) flight RAVDA (Administrative Autonomous Region Aosta Valley), at the scale 1:17.000. 2) The 1991 image, CGR (Italian General Company aerial Surveys) flight RAVDA (Administrative Autonomous Region Aosta Valley), at the scale 1:17.000. Aerial imageries have been acquired over a long period from 1975 to 1991. The black and white images were scanned at suitable resolution if compared with the imagery scale and several models, representing the glacier tongue area, oriented using the inner and outer orientation parameters delivered with the images, were produced. The digital photogrammetric system, after orientation and matching, produces

  5. Estimating the snow water equivalent on a glacierized high elevation site (Forni Glacier, Italy)

    Science.gov (United States)

    Senese, Antonella; Maugeri, Maurizio; Meraldi, Eraldo; Verza, Gian Pietro; Azzoni, Roberto Sergio; Compostella, Chiara; Diolaiuti, Guglielmina

    2018-04-01

    We present and compare 11 years of snow data (snow depth and snow water equivalent, SWE) measured by an automatic weather station (AWS) and corroborated by data from field campaigns on the Forni Glacier in Italy. The aim of the analysis is to estimate the SWE of new snowfall and the annual SWE peak based on the average density of the new snow at the site (corresponding to the snowfall during the standard observation period of 24 h) and automated snow depth measurements. The results indicate that the daily SR50 sonic ranger measurements and the available snow pit data can be used to estimate the mean new snow density value at the site, with an error of ±6 kg m-3. Once the new snow density is known, the sonic ranger makes it possible to derive SWE values with an RMSE of 45 mm water equivalent (if compared with snow pillow measurements), which turns out to be about 8 % of the total SWE yearly average. Therefore, the methodology we present is interesting for remote locations such as glaciers or high alpine regions, as it makes it possible to estimate the total SWE using a relatively inexpensive, low-power, low-maintenance, and reliable instrument such as the sonic ranger.

  6. Latest Pleistocene and Holocene Glacier Fluctuations in southernmost Patagonia

    Science.gov (United States)

    Menounos, B.; Maurer, M.; Clague, J. J.; osborn, G.; Ponce, F.; Davis, P. T.; Rabassa, J.; Coronato, A.; Marr, R.

    2011-12-01

    Summer insolation has been proposed to explain long-term glacier fluctuations during the Holocene. If correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Testing this insolation hypothesis has been hampered by dating uncertainties of many Holocene glacier chronologies from Patagonia. We report on our ongoing research aimed at developing a regional glacier chronology at the southern end of the Andes north and west of Ushuaia, Argentina. We have found evidence for an advance of cirque glaciers at the end of the Pleistocene; one or locally two closely spaced moraines extend up to 2 km beyond Little Ice Age moraines. Radiocarbon dating of terrestrial macrofossils recovered from basal sediments behind two of these moraines yielded ages of 10,320 ± 25 and 10,330 ± 30 14C yr BP. These moraines may record glacier advances coeval with the Antarctic Cold Reversal; surface exposure dating of these moraines is currently in progress to test this hypothesis. We find no evidence of Holocene moraines older than 6800 14C yr BP, based on the distribution of Hudson tephra of that age. At some sites, there is evidence for an early Neoglacial advance of glaciers slightly beyond (Peru. We have documented multiple wood mats with stumps in growth position separated by till units in a 100 m section of the northeast lateral moraine at Stoppani Glacier (54.78 S, 68.98 W), 50 km west of Ushuaia. Ten radiocarbon ages on these wood mats range in age from 3510 ± 15 to 135 ± 15 14C yr BP. The mats decrease in age up-section; many overlap with published age ranges for Neoglacial advances in western Canada. Taken together, these data: a) do not support the summer insolation hypothesis for Holocene glacier fluctuations in southernmost Patagonia; b) confirm paleobotanical evidence for a warm, dry early Holocene; and c) suggest that many Neoglacial advances in southernmost Patagonia and western North America

  7. Changing Hydrology in Glacier-fed High Altitude Andean Peatbogs

    Science.gov (United States)

    Slayback, D. A.; Yager, K.; Baraer, M.; Mohr, K. I.; Argollo, J.; Wigmore, O.; Meneses, R. I.; Mark, B. G.

    2012-12-01

    Montane peatbogs in the glacierized Andean highlands of Peru and Bolivia provide critical forage for camelids (llama and alpaca) in regionally extensive pastoral agriculture systems. During the long dry season, these wetlands often provide the only available green forage. A key question for the future of these peatbog systems, and the livelihoods they support, is the impact of climate change and glacier recession on their hydrology, and thus forage production. We have already documented substantial regional glacier recession, of, on average, approximately 30% of surface area over the past two decades. As glaciers begin to retreat under climate change, there is initially a period of increased meltwater outflow, culminating in a period of "peak water", and followed by a continual decline in outflows. Based on previous work, we know that some glaciers in the region have already passed peak water conditions, and are now declining. To better understand the impacts of these processes on peatbog hydrology and productivity, we have begun collecting a variety of surface data at several study sites in both Bolivia and Peru. These include precipitation, stream flow, water levels, water chemistry and isotope analyses, and peatbog biodiversity and biomass. These measurements will be used in conjunction with a regional model driven by satellite data to predict likely future impacts. We will present the results from these initial surface measurements, and an overview of satellite datasets to be used in the regional model.

  8. MESOMARK kit detects C-ERC/mesothelin, but not SMRP with C-terminus.

    Science.gov (United States)

    Segawa, Tatsuya; Hagiwara, Yoshiaki; Ishikawa, Kiyoshi; Aoki, Naoko; Maeda, Masahiro; Shiomi, Kazu; Hino, Okio

    2008-05-09

    ERC/mesothelin is expressed on the normal mesothelium and some cancers such as mesothelioma or ovarian carcinoma. A splicing isoform of ERC/mesothelin (known as SMRP), which has an 82-bp insertion and codes for a C-terminus with a hydrophilic, presumably soluble, tail instead of a GPI-anchoring signal, has been reported as a useful marker for the diagnosis of mesothelioma. However, the existence of SMRP has not yet been demonstrated in the serum of mesothelioma patients. To elucidate the existence of SMRP, we have established a new enzyme-linked immunosorbent assay (ELISA) system for SMRP. The ELISA study revealed that N- and C-ERC/mesothelin were detected in sera from mesothelioma patients, but not SMRP, even in these samples. This result showed that the SMRP detected with MESOMARK kit should be lack of soluble C-terminus and indistinguishable from C-ERC/mesothelin. Further study might be necessary to demonstrate the relationship between SMRP and mesothelin.

  9. Capping of the N-terminus of PSD-95 by calmodulin triggers its postsynaptic release

    Science.gov (United States)

    Zhang, Yonghong; Matt, Lucas; Patriarchi, Tommaso; Malik, Zulfiqar A; Chowdhury, Dhrubajyoti; Park, Deborah K; Renieri, Alessandra; Ames, James B; Hell, Johannes W

    2014-01-01

    Postsynaptic density protein-95 (PSD-95) is a central element of the postsynaptic architecture of glutamatergic synapses. PSD-95 mediates postsynaptic localization of AMPA receptors and NMDA receptors and plays an important role in synaptic plasticity. PSD-95 is released from postsynaptic membranes in response to Ca2+ influx via NMDA receptors. Here, we show that Ca2+/calmodulin (CaM) binds at the N-terminus of PSD-95. Our NMR structure reveals that both lobes of CaM collapse onto a helical structure of PSD-95 formed at its N-terminus (residues 1–16). This N-terminal capping of PSD-95 by CaM blocks palmitoylation of C3 and C5, which is required for postsynaptic PSD-95 targeting and the binding of CDKL5, a kinase important for synapse stability. CaM forms extensive hydrophobic contacts with Y12 of PSD-95. The PSD-95 mutant Y12E strongly impairs binding to CaM and Ca2+-induced release of PSD-95 from the postsynaptic membrane in dendritic spines. Our data indicate that CaM binding to PSD-95 serves to block palmitoylation of PSD-95, which in turn promotes Ca2+-induced dissociation of PSD-95 from the postsynaptic membrane. PMID:24705785

  10. The N-terminus of survivin is a mitochondrial-targeting sequence and Src regulator

    Science.gov (United States)

    Dunajová, Lucia; Cash, Emily; Markus, Robert; Rochette, Sophie; Townley, Amelia R.

    2016-01-01

    ABSTRACT Survivin (also known as BIRC5) is a cancer-associated protein that exists in several locations in the cell. Its cytoplasmic residence in interphase cells is governed by CRM1 (also known as XPO1)-mediated nuclear exportation, and its localisation during mitosis to the centromeres and midzone microtubules is that of a canonical chromosomal passenger protein. In addition to these well-established locations, survivin is also a mitochondrial protein, but how it gets there and its function therein is presently unclear. Here, we show that the first ten amino acids at the N-terminus of survivin are sufficient to target GFP to the mitochondria in vivo, and ectopic expression of this decapeptide decreases cell adhesion and accelerates proliferation. The data support a signalling mechanism in which this decapeptide regulates the tyrosine kinase Src, leading to reduced focal adhesion plaques and disruption of F-actin organisation. This strongly suggests that the N-terminus of survivin is a mitochondrial-targeting sequence that regulates Src, and that survivin acts in concert with Src to promote tumorigenesis. PMID:27246243

  11. Identification of a tetramerization domain in the C terminus of the vanilloid receptor.

    Science.gov (United States)

    García-Sanz, Nuria; Fernández-Carvajal, Asia; Morenilla-Palao, Cruz; Planells-Cases, Rosa; Fajardo-Sánchez, Emmanuel; Fernández-Ballester, Gregorio; Ferrer-Montiel, Antonio

    2004-06-09

    TRPV1 (transient receptor potential vanilloid receptor subtype 1) is a member of the TRP channel family gated by vanilloids, protons, and heat. Structurally, TRPV1 appears to be a tetramer formed by the assembly of four identical subunits around a central aqueous pore. The molecular determinants that govern its subunit oligomerization remain elusive. Here, we report the identification of a segment comprising 684Glu-721Arg (referred to as the TRP-like domain) in the C terminus of TRPV1 as an association domain (AD) of the protein. Purified recombinant C terminus of TRPV1 (TRPV1-C) formed discrete and stable multimers in vitro. Yeast two-hybrid and pull-down assays showed that self-association of the TRPV1-C is blocked when segment 684Glu-721Arg is deleted. Biochemical and immunological analysis indicate that removal of the AD from full-length TRPV1 monomers blocks the formation of stable heteromeric assemblies with wild-type TRPV1 subunits. Deletion of the AD in a poreless TRPV1 subunit suppressed its robust dominant-negative phenotype. Together, these findings are consistent with the tenet that the TRP-like domain in TRPV1 is a molecular determinant of the tetramerization of receptor subunits into functional channels. Our observations suggest that the homologous TRP domain in the TRP protein family may function as a general, evolutionary conserved AD involved in subunit multimerization.

  12. Chemo-spectroscopic sensor for carboxyl terminus overexpressed in carcinoma cell membrane.

    Science.gov (United States)

    Stanca, Sarmiza E; Matthäus, Christian; Neugebauer, Ute; Nietzsche, Sandor; Fritzsche, Wolfgang; Dellith, Jan; Heintzmann, Rainer; Weber, Karina; Deckert, Volker; Krafft, Christoph; Popp, Jürgen

    2015-10-01

    Certain carboxyl groups of the plasma membrane are involved in tumorgenesis processes. A gold core-hydroxyapatite shell (AuHA) nanocomposite is introduced as chemo-spectroscopic sensor to monitor these carboxyl groups of the cell membrane. Hydroxyapatite (HA) plays the role both of a chemical detector and of a biocompatible Raman marker. The principle of detection is based on chemical interaction between the hydroxyl groups of the HA and the carboxyl terminus of the proteins. The AuHA exhibits a surface enhanced Raman scattering (SERS) signal at 954 cm(-1) which can be used for its localization. The bio-sensing capacity of AuHA towards human skin epidermoid carcinoma (A431) and Chinese hamster ovary (CHO) cell lines is investigated using Raman microspectroscopic imaging. The localization of AuHA on cells is correlated with scanning electron microscopy, transmission electron microscopy and structured illumination fluorescence microscopy. This qualitative approach is a step towards a quantitative study of the proteins terminus. This method would enable further studies on the molecular profiling of the plasma membrane, in an attempt to provide accurate cell identification. Using a gold core-hydroxyapatite shell (AuHA) nanocomposite, the authors in this paper showed the feasibility of detecting and differentiating cell surface molecules by surface enhanced Raman scattering. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Technical note: Representing glacier geometry changes in a semi-distributed hydrological model

    Directory of Open Access Journals (Sweden)

    J. Seibert

    2018-04-01

    Full Text Available Glaciers play an important role in high-mountain hydrology. While changing glacier areas are considered of highest importance for the understanding of future changes in runoff, glaciers are often only poorly represented in hydrological models. Most importantly, the direct coupling between the simulated glacier mass balances and changing glacier areas needs feasible solutions. The use of a complex glacier model is often not possible due to data and computational limitations. The Δh parameterization is a simple approach to consider the spatial variation of glacier thickness and area changes. Here, we describe a conceptual implementation of the Δh parameterization in the semi-distributed hydrological model HBV-light, which also allows for the representation of glacier advance phases and for comparison between the different versions of the implementation. The coupled glacio-hydrological simulation approach, which could also be implemented in many other semi-distributed hydrological models, is illustrated based on an example application.

  14. "Focus on glaciers": an exposition of geo-photos to attract interest on a vanishing beauty

    Science.gov (United States)

    Rossi, Giuliana; Bohm, Gualtiero; Saraò, Angela

    2016-04-01

    Public awareness of the effects of industrial activity on the environment and climate is growing, but the information needs to be disseminated to a larger number of people, of all ages, to be effective. Images can certainly be an optimal tool to communicate the important message of global warming effects and, thanks to the digital techniques, photography is gaining a new popularity. Anybody, owning just a phone or a tablet, has a camera to catch images that can be immediately spread worldwide via web sites, on-line newspapers, social media or blogs to convey messages and emotions. Fine art photography can surely help in attracting interest and in educating people. For this reason, we organize an exposition of artistic pictures; the beauty of the images attracts the eyes of the public, discovering an unknown reality and gives the opportunity to illustrate the dramatic retreat of the Alpine glaciers, and the majesty of the Antarctic landscape, put in danger by the climate changes. The glaciers are the main characters, with the infinite grey-blue shadows due to change in ice density, the spectacular staircases created by the seracs, and the contrast with the embedding rocks. A sub-set of the images will be presented in this context.

  15. Rockfalls and glacier contraction: Cirque de Troumouse

    Directory of Open Access Journals (Sweden)

    Gellatly, Anne F.

    1994-12-01

    Full Text Available The incidence of rockfalls within the Cirque de Troumouse appears to have been triggered by ice wastage and the resultant geomorphological pattern of rockfall deposits affords an insight into the migration of headwall weathering zones. Observations of the rockfall deposits indicate clear geological controls which maybe directly related to the exposure of the headwall zone during phases of glacier wastage

    [es] Las caldas de piedras en el Circo de Troumouse parecen haber sido desencadenadas por la acción del hielo, y el modelo geomorfológico de depósitos de bloques resultante proporciona una idea sobre la migración de las zonas de meteorización en las paredes. Las observaciones de tales depósitos indican la existencia de claros controles geológicos que pueden relacionarse directamente con la exposición de la pared durante las fases de fusión glaciar.
    [fr] Les chutes des pierres dans le cirque de Troumouse paraissent avoir été déclenchées par l'action de la glace, et le modèle géomorphologique des dépôts de blocs résultant donne une idée de la migration des zones de météorisation dans les parois. Les observations de ces dépôts indiquent l'existence de contrôles géologiques très clairs qui peuvent être directement liés à l'exposition de la paroi durant les phases de fusion glaciaire.

  16. The N-terminus of glycogen phosphorylase b is not required for activation by adenosine 5'-monophosphate.

    Science.gov (United States)

    Bigley, Andrew N; Reinhart, Gregory D

    2010-06-15

    The, so far unsuccessful, search for selective effective inhibitors of glycogen phosphorylase for the treatment of type II diabetes has made phosphorylase an active target of research for the past 20 years. Many crystallographic structures of phosphorylase are currently available to aid in this research. However, those structures have been interpreted, at least in part, on the basis of work conducted with a proteolytically derived form of phosphorylase that lacked the N-terminus (phosphorylase b'). It has been reported that phosphorylase b' shows no allostery, neither homotropic nor heterotropic. The original report on phosphorylase b' examined the allosteric characteristics over very narrow ranges of effector and substrate concentrations and reported the presence of proteolytic cleavages in addition to the removal of the N-terminus. We have applied molecular biological techniques to generate a truncate lacking the N-terminus with known primary structure, and we have established conditions for fully quantifying the allosteric effect of AMP on glycogen phosphorylase b. We report here for the first time the full thermodynamic effect of AMP on phosphorylase b. Our findings with a truncate lacking the N-terminus show that the effect of AMP binding does not depend on the N-terminus.

  17. Impacts of glacier recession and declining meltwater on mountain societies

    DEFF Research Database (Denmark)

    Carey, Mark; Molden, Olivia C.; Rasmussen, Mattias Borg

    2017-01-01

    . It identifies four main areas of existing research: (1) socioeconomic impacts; (2) hydropower; (3) agriculture, irrigation, and food security; and (4) cultural impacts. The article also suggests paths forward for social sciences, humanities, and natural sciences research that could more accurately detect......, including irrigation, agriculture, hydropower, potable water, livelihoods, recreation, spirituality, and demography. Unfortunately, research focusing on the human impacts of glacier runoff variability in mountain regions remains limited, and studies often rely on assumptions rather than concrete evidence...... about the effects of shrinking glaciers on mountain hydrology and societies. This article provides a systematic review of international research on human impacts of glacier meltwater variability in mountain ranges worldwide, including the Andes, Alps, greater Himalayan region, Cascades, and Alaska...

  18. Natural and artificial radioactivity in the Svalbard glaciers

    International Nuclear Information System (INIS)

    Pinglot, J.F.; Pourchet, M.

    1994-01-01

    Natural and artificial radioactivity in the snow of 10 Svalbard glaciers has been measured from 31 ice core samples, drilled between 1981 and 1993. Of these ice cores, seven exhibit the well-known level arising from the fallout of the 1961-62 atmospheric thermonuclear tests. The second level, due to the Chernobyl accident (26 April 1986), has been detected in all the studied glaciers; the maximum 137 Cs fallout reaches 22 Bq kg -1 and shows a high variability. The natural radioactivity, mostly due to 210 Pb, shows an in-depth variation which is not governed by its half-life (22.2 years). These measurements serve many glaciological purposes: absolute dating of the snow layers; air-snow transfer and fallout studies; the determination of mean annual mass balances in the accumulation area of glaciers and their associated spatio-temporal variations. (author)

  19. Supraglacial Ponds Regulate Runoff From Himalayan Debris-Covered Glaciers

    Science.gov (United States)

    Irvine-Fynn, Tristram D. L.; Porter, Philip R.; Rowan, Ann V.; Quincey, Duncan J.; Gibson, Morgan J.; Bridge, Jonathan W.; Watson, C. Scott; Hubbard, Alun; Glasser, Neil F.

    2017-12-01

    Meltwater and runoff from glaciers in High Mountain Asia is a vital freshwater resource for one-fifth of the Earth's population. Between 13% and 36% of the region's glacierized areas exhibit surface debris cover and associated supraglacial ponds whose hydrological buffering roles remain unconstrained. We present a high-resolution meltwater hydrograph from the extensively debris-covered Khumbu Glacier, Nepal, spanning a 7 month period in 2014. Supraglacial ponds and accompanying debris cover modulate proglacial discharge by acting as transient and evolving reservoirs. Diurnally, the supraglacial pond system may store >23% of observed mean daily discharge, with mean recession constants ranging from 31 to 108 h. Given projections of increased debris cover and supraglacial pond extent across High Mountain Asia, we conclude that runoff regimes may become progressively buffered by the presence of supraglacial reservoirs. Incorporation of these processes is critical to improve predictions of the region's freshwater resource availability and cascading environmental effects downstream.

  20. Ecological responses to experimental glacier-runoff reduction in alpine rivers

    DEFF Research Database (Denmark)

    Cauvy-Fraunié, Sophie; Andino, Patricio; Espinosa, Rodrigo

    2016-01-01

    Glacier retreat is a worldwide phenomenon with important consequences for the hydrological cycle and downstream ecosystem structure and functioning. To determine the effects of glacier retreat on aquatic communities, we conducted a 4-year flow manipulation in a tropical glacier-fed stream. Compared...

  1. Midlatitude Forcing Mechanisms for Glacier Mass Balance Investigated Using General Circulation Models

    NARCIS (Netherlands)

    Reichert, B.K.; Bengtsson, L.; Oerlemans, J.

    2001-01-01

    A process-oriented modeling approach is applied in order to simulate glacier mass balance for individual glaciers using statistically downscaled general circulation models (GCMs). Glacier-specific seasonal sensitivity characteristics based on a mass balance model of intermediate complexity are used

  2. Observed thinning of Totten Glacier is linked to coastal polynya variability

    NARCIS (Netherlands)

    Khazendar, A.; Schodlok, M.P.; Fenty, I.; Ligtenberg, S.R.M.; Rignot, Eric; van den Broeke, M.R.

    2013-01-01

    Analysis of ICESat-1 data (2003–2008) shows significant surface lowering of Totten Glacier, the glacier discharging the largest volume of ice in East Antarctica, and less change on nearby Moscow University Glacier. After accounting for firn compaction anomalies, the thinning appears to coincide with

  3. Pond dynamics and supraglacial-englacial connectivity on debris-covered Lirung Glacier

    NARCIS (Netherlands)

    Miles, Evan Stewart; Steiner, Jakob|info:eu-repo/dai/nl/119338653; Willis, Ian C.; Buri, Pascal; Immerzeel, Walter Willem|info:eu-repo/dai/nl/290472113; Chesnokova, Anna; Pellicciotti, Francesca

    The hydrological systems of heavily-downwasted debris-covered glaciers differ from clean-ice glaciers due to the hummocky surface and debris mantle of such glaciers, leading to a relatively limited understanding of drainage pathways. Supraglacial ponds represent sinks within the discontinuous

  4. Rising river flows throughout the twenty-first century in two Himalayan glacierized watersheds

    NARCIS (Netherlands)

    Immerzeel, W.W.|info:eu-repo/dai/nl/290472113; Pelliciotti, F.; Bierkens, M.F.P.|info:eu-repo/dai/nl/125022794

    2013-01-01

    Greater Himalayan glaciers are retreating and losing mass at rates comparable to glaciers in other regions of the world1–5 . Assessments of future changes and their associated hydrological impacts are scarce, oversimplify glacier dynamics or include a limited number of climate models6–9 . Here, we

  5. Holocene glacier variability: three case studies using an intermediate-complexity climate model

    NARCIS (Netherlands)

    Weber, S.L.; Oerlemans, J.

    2003-01-01

    Synthetic glacier length records are generated for the Holocene epoch using a process-based glacier model coupled to the intermediate-complexity climate model ECBilt. The glacier model consists of a massbalance component and an ice-flow component. The climate model is forced by the insolation change

  6. What influences climate and glacier change in southwestern China?

    Science.gov (United States)

    Yasunari, Teppei J.

    2011-12-01

    The subject of climate change in the Tibetan Plateau (TP) and Himalayas has taken on increasing importance because of the availability of water resources from their mountain glaciers (Immerzeel et al 2010). Many of the glaciers over these regions have been retreating, while some are advancing and stable (Yao et al 2004, Scherler et al 2011). Other studies report that some glaciers in the Himalayas show acceleration of their shrinkage (e.g., Fujita and Nuimura 2011). However, the causes of glacier melting are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. Despite this, it is vital that we pursue further study to enable future predictions of glacier changes. The paper entitled 'Climate and glacier change in southwestern China during the past several decades' by Li et al (2011) provided carefully analyzed, quality controlled, long-term data on atmospheric temperature and precipitation during the period 1961-2008. The data were obtained from 111 Chinese stations. The researchers performed systematic analyses of temperature and precipitation over the whole southwestern Chinese domain. They discussed those changes in terms of other meteorological components such as atmospheric circulation patterns, radiation and altitude difference, and then showed how these factors could contribute to climate and glacier changes in the region. Air temperature and precipitation are strongly associated with glacier mass balance because of heat balance and the addition of mass when it snows. Temperature warming trends over many places in southwestern China were unequivocally dominant in all seasons and at higher altitudes. This indicates that the heat contribution to the glaciers has been increasing. On the other hand, precipitation has a wider variability in time and space. It is more difficult to clearly understand the effect of precipitation on the climate and glacier melting characteristics in the whole of southwestern China

  7. Estimating Velocities of Glaciers Using Sentinel-1 SAR Imagery

    Science.gov (United States)

    Gens, R.; Arnoult, K., Jr.; Friedl, P.; Vijay, S.; Braun, M.; Meyer, F. J.; Gracheva, V.; Hogenson, K.

    2017-12-01

    In an international collaborative effort, software has been developed to estimate the velocities of glaciers by using Sentinel-1 Synthetic Aperture Radar (SAR) imagery. The technique, initially designed by the University of Erlangen-Nuremberg (FAU), has been previously used to quantify spatial and temporal variabilities in the velocities of surging glaciers in the Pakistan Karakoram. The software estimates surface velocities by first co-registering image pairs to sub-pixel precision and then by estimating local offsets based on cross-correlation. The Alaska Satellite Facility (ASF) at the University of Alaska Fairbanks (UAF) has modified the software to make it more robust and also capable of migration into the Amazon Cloud. Additionally, ASF has implemented a prototype that offers the glacier tracking processing flow as a subscription service as part of its Hybrid Pluggable Processing Pipeline (HyP3). Since the software is co-located with ASF's cloud-based Sentinel-1 archive, processing of large data volumes is now more efficient and cost effective. Velocity maps are estimated for Single Look Complex (SLC) SAR image pairs and a digital elevation model (DEM) of the local topography. A time series of these velocity maps then allows the long-term monitoring of these glaciers. Due to the all-weather capabilities and the dense coverage of Sentinel-1 data, the results are complementary to optically generated ones. Together with the products from the Global Land Ice Velocity Extraction project (GoLIVE) derived from Landsat 8 data, glacier speeds can be monitored more comprehensively. Examples from Sentinel-1 SAR-derived results are presented along with optical results for the same glaciers.

  8. Modulation of glacier ablation by tephra coverage from Eyjafjallajökull and Grímsvötn volcanoes, Iceland: an automated field experiment

    Science.gov (United States)

    Möller, Rebecca; Möller, Marco; Kukla, Peter A.; Schneider, Christoph

    2018-01-01

    We report results from a field experiment investigating the influence of volcanic tephra coverage on glacier ablation. These influences are known to be significantly different from those of moraine debris on glaciers due to the contrasting grain size distribution and thermal conductivity. Thus far, the influences of tephra deposits on glacier ablation have rarely been studied. For the experiment, artificial plots of two different tephra types from Eyjafjallajökull and Grímsvötn volcanoes were installed on a snow-covered glacier surface of Vatnajökull ice cap, Iceland. Snow-surface lowering and atmospheric conditions were monitored in summer 2015 and compared to a tephra-free reference site. For each of the two volcanic tephra types, three plots of variable thickness ( ˜ 1.5, ˜ 8.5 and ˜ 80 mm) were monitored. After limiting the records to a period of reliable measurements, a 50-day data set of hourly records was obtained, which can be downloaded from the Pangaea data repository (pangaea.de" target="_blank">https://www.pangaea.de; doi:10.1594/PANGAEA.876656). The experiment shows a substantial increase in snow-surface lowering rates under the ˜ 1.5 and ˜ 8.5 mm tephra plots when compared to uncovered conditions. Under the thick tephra cover some insulating effects could be observed. These results are in contrast to other studies which depicted insulating effects for much thinner tephra coverage on bare-ice glacier surfaces. Differences between the influences of the two different petrological types of tephra exist but are negligible compared to the effect of tephra coverage overall.

  9. Snow chemistry of high altitude glaciers in the French Alps

    OpenAIRE

    MAUPETIT, FRANÇOIS; DELMAS, ROBERT J.

    2011-01-01

    Snow samples were collected as snowcores in the accumulation zone of four high altitude glaciers (2980–3540 m.a.s.l.) from each of the 4 highest mountain areas of the French Alps, during 3 consecutive years: 1989, 1990 and 1991. Sampling was performed in spring (∼ May), before the onset of late spring–summer percolation. The accumulated snow therefore reflects winter and spring conditions. A complementary sampling of fresh-snow was performed on an event basis, on one of the studied glaciers, ...

  10. Southern Alaska Glaciers: Spatial and Temporal Variations in Ice Volume

    Science.gov (United States)

    Sauber, J.; Molnia, B. F.; Lutchke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spade, G.

    2004-01-01

    Although temperate mountain glaciers comprise less than 1% of the glacier-covered area on Earth, they are important because they appear to be melting rapidly under present climatic conditions and, therefore, make significant contributions to rising sea level. In this study, we use ICESat observations made in the last 1.5 years of southern Alaska glaciers to estimate ice elevation profiles, ice surface slopes and roughness, and bi-annual and/or annual ice elevation changes. We report initial results from the near coastal region between Yakutat Bay and Cape Suckling that includes the Malaspina and Bering Glaciers. We show and interpret ice elevations changes across the lower reaches of the Bagley Ice Valley for the period between October 2003 and May 2004. In addition, we use off-nadir pointing observations to reference tracks over the Bering and Malaspina Glaciers in order to estimate annual ice elevation change. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topography Mission (SRTM) derived DEMs are used to estimate across track regional slopes between ICESat data acquisitions. Although the distribution and quantity of ICESat elevation profiles with multiple, exact repeat data is currently limited in Alaska, individual ICESat data tracks, provide an accurate reference surface for comparison to other elevation data (e.g. ASTER and SRTM X- and C-band derived DEMs). Specifically we report the elevation change over the Malaspina Glacier's piedmont lobe between a DEM derived from SRTM C-band data acquired in Feb. 2000 and ICESat Laser #2b data from Feb.-March 2004. We also report use of ICESat elevation data to enhance ASTER derived absolute DEMs. Mountain glaciers generally have rougher surfaces and steeper regional slopes than the ice sheets for which the ICESat design was optimized. Therefore, rather than averaging ICESat observations over large regions or relying on crossovers, we are working with well-located ICESat

  11. Revisited Inventory of Glaciers on Axel Heiberg Island, Nunavut

    Science.gov (United States)

    Thomson, L.; Osinski, G.

    2009-05-01

    As documented in the IPCC's Climate Change 2007 report, the high latitude regions of the Northern Hemisphere are experiencing the highest rates of warming. Given that 35% of the global glacial ice exists within the Arctic Archipelago, this region provides an excellent laboratory for monitoring the anticipated degree of glacial recession [1]. Evidence of arctic warming through negative mass balance trends has been detected in several studies already [e.g., 2]. Here, we show the importance and value of historical records in the task of monitoring glacial retreat. A highly detailed inventory developed by S. Ommanney in 1969 [3], has been revisited and transformed into digital format for the purposes of integration with modern inventories. The Ommanney inventory covers the entirety of Axel Heiberg Island , NU, and includes details often lacking in present day inventories, including orientations (accumulation and ablation zones), elevations (highest, lowest, elevation of the snowline, and the mean elevations of both the accumulation and ablation areas), length (of the ablation area, exposed ice, and of the total glacier including debris cover), area (of the ablation area, exposed ice, and of the total glacier), accumulation area ratio (AAR), depth, volume, and a six digit code which gives qualitative details on glacier attributes. This report is one of the most thorough and comprehensive glacier inventory report ever published in Canada. More recent inventories used for comparison include the glacier extents created by the National Topographic System based on photography from 1980-1987, as well as extents developed by Dr. Luke Copland for the Global Land Ice Measurements from Space (GLIMS) database using 1999-2000 satellite imagery. Our preliminary results show that approximately 90% of ice bodies under 0.2km on Axel Heiberg Island have disappeared entirely in the 40 year period of interest. The issue of glacier definition will be discussed as a possible cause of these

  12. Pathways of warm water to the Northeast Greenland outlet glaciers

    Science.gov (United States)

    Schaffer, Janin; Timmermann, Ralph; Kanzow, Torsten; Arndt, Jan Erik; Mayer, Christoph; Schauer, Ursula

    2015-04-01

    The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers surrounding the Greenland coast. The warming and accumulation of Atlantic Water in the subpolar North Atlantic has been suggested to be a potential driver of the glaciers' retreat over the last decades. The shelf regions thus play a critical role for the transport of Atlantic Water towards the glaciers, but also for the transfer of freshwater towards the deep ocean. A key region for the mass balance of the Greenland Ice Sheet is the Northeast Greenland Ice Stream. This large ice stream drains the second-largest basin of the Greenland Ice Sheet and feeds three outlet glaciers. The largest one is Nioghalvfjerdsfjorden (79°N-Glacier) featuring an 80 km long floating ice tongue. Both the ocean circulation on the continental shelf off Northeast Greenland and the circulation in the cavity below the ice tongue are weakly constrained so far. In order to study the relevant processes of glacier-ocean interaction we combine observations and model work. Here we focus on historic and recent hydrographic observations and on the complex bathymetry in the Northeast Greenland shelf region, which is thought to steer the flux of warm Atlantic water onto the continental shelf and into the sub-ice cavity beneath the 79°N-Glacier. We present a new global topography data set, RTopo-2, which includes the most recent surveys on the Northeast Greenland continental shelf and provides a detailed bathymetry for all around Greenland. In addition, RTopo-2 contains ice and bedrock surface topographies for Greenland and Antarctica. Based on the updated ocean bathymetry and a variety of hydrographic observations we show the water mass distribution on the continental shelf off Northeast Greenland. These maps enable us to discuss possible supply pathways of warm modified Atlantic waters on the continental shelf and thus potential ways of heat

  13. Properties of GluR3 receptors tagged with GFP at the amino or carboxyl terminus.

    Science.gov (United States)

    Limon, Agenor; Reyes-Ruiz, Jorge Mauricio; Eusebi, Fabrizio; Miledi, Ricardo

    2007-09-25

    Anatomical visualization of neurotransmitter receptor localization is facilitated by tagging receptors, but this process can alter their functional properties. We have evaluated the distribution and properties of WT glutamate receptor 3 (GluR3) alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (WT GluR3) and two receptors in which GFP was tagged to the amino terminus (GFP-GluR3) or to the carboxyl terminus (GluR3-GFP). Although the fluorescence in Xenopus oocytes was stronger in the vegetal hemisphere because of localization of internal structures (probable sites of production, storage or recycling of receptors), the insertion of receptors into the plasma membrane was polarized to the animal hemisphere. The fluorescence intensity of oocytes injected with GluR3-GFP RNA was approximately double that of oocytes injected with GFP-GluR3 RNA. Accordingly, GluR3-GFP oocytes generated larger kainate-induced currents than GFP-GluR3 oocytes, with similar EC(50) values. Currents elicited by glutamate, or AMPA coapplied with cyclothiazide, were also larger in GluR3-GFP oocytes. The glutamate- to kainate-current amplitude ratios differed, with GluR3-GFP being activated more efficiently by glutamate than the WT or GFP-GluR3 receptors. This pattern correlates with the slower decay of glutamate-induced currents generated by GluR3-GFP receptors. These changes were not observed when GFP was tagged to the amino terminus, and these receptors behaved like the WT. The antagonistic effects of 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione (NBQX) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were not altered in any of the tagged receptors. We conclude that GFP is a useful and convenient tag for visualizing these proteins. However, the effects of different sites of tag insertion on receptor characteristics must be taken into account in assessing the roles played by these receptor proteins.

  14. Ipomoelin, a Jacalin-Related Lectin with a Compact Tetrameric Association and Versatile Carbohydrate Binding Properties Regulated by Its N Terminus

    Science.gov (United States)

    Chang, Wei-Chieh; Liu, Kai-Lun; Hsu, Fang-Ciao; Jeng, Shih-Tong; Cheng, Yi-Sheng

    2012-01-01

    Many proteins are induced in the plant defense response to biotic stress or mechanical wounding. One group is lectins. Ipomoelin (IPO) is one of the wound-inducible proteins of sweet potato (Ipomoea batatas cv. Tainung 57) and is a Jacalin-related lectin (JRL). In this study, we resolved the crystal structures of IPO in its apo form and in complex with carbohydrates such as methyl α-D-mannopyranoside (Me-Man), methyl α-D-glucopyranoside (Me-Glc), and methyl α-D-galactopyranoside (Me-Gal) in different space groups. The packing diagrams indicated that IPO might represent a compact tetrameric association in the JRL family. The protomer of IPO showed a canonical β-prism fold with 12 strands of β-sheets but with 2 additional short β-strands at the N terminus. A truncated IPO (ΔN10IPO) by removing the 2 short β-strands of the N terminus was used to reveal its role in a tetrameric association. Gel filtration chromatography confirmed IPO as a tetrameric form in solution. Isothermal titration calorimetry determined the binding constants (KA) of IPO and ΔN10IPO against various carbohydrates. IPO could bind to Me-Man, Me-Glc, and Me-Gal with similar binding constants. In contrast, ΔN10IPO showed high binding ability to Me-Man and Me-Glc but could not bind to Me-Gal. Our structural and functional analysis of IPO revealed that its compact tetrameric association and carbohydrate binding polyspecificity could be regulated by the 2 additional N-terminal β-strands. The versatile carbohydrate binding properties of IPO might play a role in plant defense. PMID:22808208

  15. Thermal Synthesis of Polypeptides from N-Butyloxycarbonyl Oligopeptides Containing Aspartyl Residue at C-Terminus

    Directory of Open Access Journals (Sweden)

    Toratane Munegumi

    2017-01-01

    Full Text Available The thermal reactions of amino acids have been investigated for pure organic synthesis, materials preparation in industry, and prebiotic chemistry. N-t-Butyloxycarbonyl aspartic acid (Boc-Asp releases 2-butene and carbon dioxide upon heating without solvents. The resulting mixture of the free molten aspartic acid was dehydrated to give peptide bonds. This study describes the thermal reactions of N-t-butyloxycarbonyl peptides (Boc-Gly-L-Asp, Boc-L-Ala-L-Asp, Boc-L-Val-L-Asp, and Boc-Gly-Gly-L-Asp having an aspartic residue at the carboxyl terminus. The peptides were deprotected upon heating at a constant temperature between 110 and 170°C for 1 to 24 h to afford polypeptides in which the average molecular weight reached 7800.

  16. Photogrammetry on glaciers: Old and new knowledge

    Science.gov (United States)

    Pfeffer, W. T.; Welty, E.; O'Neel, S.

    2014-12-01

    In the past few decades terrestrial photogrammetry has become a widely used tool for glaciological research, brought about in part by the proliferation of high-quality, low-cost digital cameras, dramatic increases in image-processing power of computers, and very innovative progress in image processing, much of which has come from computer vision research and from the computer gaming industry. At present, glaciologists have developed their capacity to gather images much further than their ability to process them. Many researchers have accumulated vast inventories of imagery, but have no efficient means to extract the data they desire from them. In many cases these are single-image time series where the processing limitation lies in the paucity of methods to obtain 3-dimension object space information from measurements in the 2-dimensional image space; in other cases camera pairs have been operated but no automated means is in hand for conventional stereometric analysis of many thousands of image pairs. Often the processing task is further complicated by weak camera geometry or ground control distribution, either of which will compromise the quality of 3-dimensional object space solutions. Solutions exist for many of these problems, found sometimes among the latest computer vision results, and sometimes buried in decades-old pre-digital terrestrial photogrammetric literature. Other problems, particularly those arising from poorly constrained or underdetermined camera and ground control geometry, may be unsolvable. Small-scale, ground-based photography and photogrammetry of glaciers has grown over the past few decades in an organic and disorganized fashion, with much duplication of effort and little coordination or sharing of knowledge among researchers. Given the utility of terrestrial photogrammetry, its low cost (if properly developed and implemented), and the substantial value of the information to be had from it, some further effort to share knowledge and methods

  17. An investigation of the thermomechanical features of Laohugou Glacier No. 12 on Qilian Shan, western China, using a two-dimensional first-order flow-band ice flow model

    Science.gov (United States)

    Wang, Yuzhe; Zhang, Tong; Ren, Jiawen; Qin, Xiang; Liu, Yushuo; Sun, Weijun; Chen, Jizu; Ding, Minghu; Du, Wentao; Qin, Dahe

    2018-03-01

    By combining in situ measurements and a two-dimensional thermomechanically coupled ice flow model, we investigate the thermomechanical features of the largest valley glacier (Laohugou Glacier No. 12; LHG12) on Qilian Shan located in the arid region of western China. Our model results suggest that LHG12, previously considered as fully cold, is probably polythermal, with a lower temperate ice layer overlain by an upper layer of cold ice over a large region of the ablation area. Modelled ice surface velocities match well with the in situ observations in the east branch (main branch) but clearly underestimate those near the glacier terminus, possibly because the convergent flow is ignored and the basal sliding beneath the confluence area is underestimated. The modelled ice temperatures are in very good agreement with the in situ measurements from a deep borehole (110 m deep) in the upper ablation area. The model results are sensitive to surface thermal boundary conditions, for example surface air temperature and near-surface ice temperature. In this study, we use a Dirichlet surface thermal condition constrained by 20 m borehole temperatures and annual surface air temperatures. Like many other alpine glaciers, strain heating is important in controlling the englacial thermal structure of LHG12. Our transient simulations indicate that the accumulation zone becomes colder during the last two decades as a response to the elevated equilibrium line altitude and the rising summer air temperatures. We suggest that the extent of accumulation basin (the amount of refreezing latent heat from meltwater) of LHG12 has a considerable impact on the englacial thermal status.

  18. Storage and release of organic carbon from glaciers and ice sheets

    Science.gov (United States)

    Hood, Eran; Battin, Tom J.; Fellman, Jason; O'Neel, Shad; Spencer, Robert G. M.

    2015-02-01

    Polar ice sheets and mountain glaciers, which cover roughly 11% of the Earth's land surface, store organic carbon from local and distant sources and then release it to downstream environments. Climate-driven changes to glacier runoff are expected to be larger than climate impacts on other components of the hydrological cycle, and may represent an important flux of organic carbon. A compilation of published data on dissolved organic carbon from glaciers across five continents reveals that mountain and polar glaciers represent a quantitatively important store of organic carbon. The Antarctic Ice Sheet is the repository of most of the roughly 6 petagrams (Pg) of organic carbon stored in glacier ice, but the annual release of glacier organic carbon is dominated by mountain glaciers in the case of dissolved organic carbon and the Greenland Ice Sheet in the case of particulate organic carbon. Climate change contributes to these fluxes: approximately 13% of the annual flux of glacier dissolved organic carbon is a result of glacier mass loss. These losses are expected to accelerate, leading to a cumulative loss of roughly 15 teragrams (Tg) of glacial dissolved organic carbon by 2050 due to climate change -- equivalent to about half of the annual flux of dissolved organic carbon from the Amazon River. Thus, glaciers constitute a key link between terrestrial and aquatic carbon fluxes, and will be of increasing importance in land-to-ocean fluxes of organic carbon in glacierized regions.

  19. Storage and release of organic carbon from glaciers and ice sheets

    Science.gov (United States)

    Hood, Eran; Battin, Tom J.; Fellman, Jason; O'Neel, Shad; Spencer, Robert G. M.

    2015-01-01

    Polar ice sheets and mountain glaciers, which cover roughly 11% of the Earth's land surface, store organic carbon from local and distant sources and then release it to downstream environments. Climate-driven changes to glacier runoff are expected to be larger than climate impacts on other components of the hydrological cycle, and may represent an important flux of organic carbon. A compilation of published data on dissolved organic carbon from glaciers across five continents reveals that mountain and polar glaciers represent a quantitatively important store of organic carbon. The Antarctic Ice Sheet is the repository of most of the roughly 6 petagrams (Pg) of organic carbon stored in glacier ice, but the annual release of glacier organic carbon is dominated by mountain glaciers in the case of dissolved organic carbon and the Greenland Ice Sheet in the case of particulate organic carbon. Climate change contributes to these fluxes: approximately 13% of the annual flux of glacier dissolved organic carbon is a result of glacier mass loss. These losses are expected to accelerate, leading to a cumulative loss of roughly 15 teragrams (Tg) of glacial dissolved organic carbon by 2050 due to climate change — equivalent to about half of the annual flux of dissolved organic carbon from the Amazon River. Thus, glaciers constitute a key link between terrestrial and aquatic carbon fluxes, and will be of increasing importance in land-to-ocean fluxes of organic carbon in glacierized regions.

  20. Climatic Drivers of Tropical Andean Glacier Recession, c1987 - c2006

    Science.gov (United States)

    Slayback, D. A.; Tucker, C. J.

    2011-12-01

    We report on the climatic trends associated with glacier recession in the tropical Andes from the mid-1980s to the mid-2000s. These glaciers comprise 99% of the world's tropical glaciers and occur in Bolivia, Peru, Ecuador, Colombia, and Venezuela. We previously reported on our comprehensive analysis of Landsat imagery of these glaciers, which indicated an overall recession of approximately 30% in glacierized area between c1987 and c2006, or a drop from ~2500 km2 to ~1800 km2 in total glacier area. In the current work, we have examined trends in temperature, cloud cover, and precipitation and compared these trends with those in glacier recession. For temperature and cloud cover, we use the MERRA reanalysis datasets (Modern Era Retrospective-Analysis for Research and Applications) produced by the NASA Goddard's GMAO (Global Modeling and Assimilation Office), which are based on satellite observations. For precipitation, we use the GPCP (Glocal Precipitation Climatology Project) datasets, which are based on both ground and satellite observations. We find that over the glacierized zones, the only significant trends are those in temperature, which show increases of up to 0.5 degree C per decade over some glacierized areas. Trends in cloud cover and precipitation are not generally significant. We discuss these trends in relation to glacier recession trends for each of the major glacierized areas of the tropical Andes.

  1. Changes of glacier, glacier-fed rivers and lakes in Altai Tavan Bogd National Park, Western Mongolia, based on multispectral satellite data from 1990 to 2017

    Science.gov (United States)

    Batsaikhan, B.; Lkhamjav, O.; Batsaikhan, N.

    2017-12-01

    Impacts on glaciers and water resource management have been altering through climate changes in Mongolia territory characterized by dry and semi-arid climate with low precipitation. Melting glaciers are early indicators of climate change unlike the response of the forests which is slower and takes place over a long period of time. Mountain glaciers are important environmental components of local, regional, and global hydrological cycles. The study calculates an overview of changes for glacier, glacier-fed rivers and lakes in Altai Tavan Bogd mountain, the Western Mongolia, based on the indexes of multispectral data and the methods typically applied in glacier studies. Were utilized an integrated approach of Normalized Difference Snow Index (NDSI) and Normalized Difference Water Index (NDWI) to combine Landsat, MODIS imagery and digital elevation model, to identify glacier cover are and quantify water storage change in lakes, and compared that with and climate parameters including precipitation, land surface temperature, evaporation, moisture. Our results show that melts of glacier at the study area has contributed to significantly increase of water storage of lakes in valley of The Altai Tavan Bogd mountain. There is hydrologic connection that lake basin is directly fed by glacier meltwater.

  2. Glacialmorphological reconstruction of glacier advances and glacial lake outburst floods at the Cachapoal glacier in the Dry Central Andes of Chile (34°S)

    Science.gov (United States)

    Iturrizaga, Lasafam; Charrier, Reynaldo

    2013-04-01

    Throughout the Andes Mountain range of South America a general trend of glacier shrinkage has taken place in the last century. Only a few glaciers have shown a rather non-continuous trend of glacier retreat and temporally advanced or even surged during the mid-19th to 20th century. One of the earliest assumed glacier surges has occurred in the upper Cachapoal catchment area at the homonymous glacier. In climatic respect the Cachapoal glacier is located in the transition zone from the most southern part of the Dry Central Andes of Chile to the more humid zone of the Wet Andes. The region is affected mainly by winter precipitation deriving from the Westerlies. The debris-covered, 12 km-long Cachapoal glacier represents one of the largest valley glaciers in the Central Andes. It is an avalanche-fed glacier with an almost 1500 m-high head wall in its upper catchment area flowing down from Picos del Barroso (5180 m) and terminates at an elevation of 2630 m a.s.l. with a bifurcated glacier tongue. A large moraine complex, almost 2 km in length and 500 m in width, separates the two glacier lobes. During times of advanced glacier tongue positions the Ríos Molina and Cachapoal may be have blocked independently at two distinct localities which are situated about 2300 m apart from each other. A blockage with temporal lake formation has occurred at least in the years 1848, 1955 and 1981 (cf. Plagemann 1887, Peña 1981), from which the rupture of the earliest glacier barrier has been the most devastating. This event is locally reminded as "la gran avenida en seco" in the historical record. Geomorphological evidence of the past historical and modern glacier expansions is given in the proglacial area by a fresh dead-ice hummocky topography and glacial trimlines at the valley flanks. More down valley broad outwash plains and boulder clusters indicate past high energy floods produced by glacier lake outbursts. Regarding the small size of the catchment area of the Río Molina

  3. Glaciers in South Tyrol 1850 - 2006: application of Airborne Laser Scanner data, orthophotos and historical maps for the acquisition of recent and the reconstruction of past glacier extents

    International Nuclear Information System (INIS)

    Knoll, C. C.

    2009-01-01

    In the densely populated high mountain areas of the Alps, glaciers are an important part of the cultural and natural landscape. During the warm summer months they are among the most important freshwater resources for economy sectors such as agriculture or industry, an important component for the tourism industry and of great significance for the production of energy from hydropower. However, they also constitute a potential cause of natural hazards. Due to their direct linkage to temperature and precipitation, glaciers are characterized as one of the best natural climate indicators. For that reason, mountain glaciers have become a key symbol for the ongoing discussion about climate, climate changes and the resulting consequences because their reactions can easily be observed and visualized. The main objective of this doctoral thesis is to contribute to a better understanding of the regional South Tyrolean glacier development through a reconstruction and analysis of the glacier changes that have occurred since the climax of the Little Ice Age at around 1850. Glacier inventories, fieldwork and GIS-assisted reconstructions of historical and calculation of recent glacier topographies are used to depict, analyze and visualize the changes of the South Tyrolean glaciers between the maximum extent of approximately 1850 and the inventories of 1997 and 2006. In a comparison of recent, highly accurate glacier topographies mapped with ALS-methods (Airborne Laser Scanner) with a reconstruction of the Little Ice Age maximum South Tyrolean glaciers were detected to have lost 183.2 km 2 or 66% of their glacier cover in approximately the last 150 years. This comparison also showed a loss in glacier volume of 9 km 3 between 1850 and 2006, which corresponds to a mean ice thickness change of -49 m. These drastic losses in the glacier covered area and volume, which are mainly visible on the glacier tongues of large valley glaciers like Langtauferer- and Suldenferner, clearly show

  4. Characterising Late-Holocene glacier variability in the southern tropical Andes

    Science.gov (United States)

    Bromley, G.; Winckler, G.; Hall, B. L.; Schaefer, J. M.

    2011-12-01

    Accurate resolution of both the timing and magnitude of Late-Holocene climate events, such as the Little Ice Age, is vital in order to test different hypotheses for the causes and propagation of such climate variability. However, in contrast to higher latitudes, well-dated records from the tropics are relatively rare and the overall climatic structure of the last millennium remains unresolved. Much of this uncertainty stems from difficulties associated with radiocarbon dating in these dry, often high-altitude environments, a situation that now is being addressed through the application and refinement of cosmogenic surface-exposure methods. We present detailed Late-Holocene moraine records, resolved with radiocarbon and surface-exposure dating, from sites across the Andes of southern Peru. Specifically, we describe glacial records from both the arid Western Cordillera, where glaciation is limited by moisture availability, and the humid Eastern Cordillera, where ablation is controlled primarily by air temperature. In both locations, the most recent advance is marked by two to three unweathered terminal moraines located several hundred metres beyond the modern ice margins. Our chronology indicates that, while the advance occurred broadly in step with the classic 'Little Ice Age', the maximum glacial extent in southern Peru was achieved relatively early on and that the 18th and 19th centuries were dominated by glacier retreat. In a broader temporal context, our data also confirm that, in contrast to northern temperate latitudes, the event in southern Peru was the most recent significant interruption in a progressive Holocene retreat. The consistency in glacier response between the different climate zones suggests (i) that this pattern of Late-Holocene climate variability was of at least regional extent and (ii) that temperature fluctuations were the primary driving mechanism.

  5. Changing drainage patterns within South Cascade Glacier, Washington, USA, 1964-1992

    Science.gov (United States)

    Fountain, A.G.; Vaughn, B.H.

    1995-01-01

    The theoretical patterns of water drainage are presented for South Cascade Glacier for four different years between 1964 and 1992, during which the glacier was thinning and receding. The theoretical pattern compares well, in a broad sense, with the flow pattern determined from tracer injections in 1986 and 1987. Differences between the patterns may result from the routing of surface meltwater in crevasses prior to entering the body of the glacier. The changing drainage pattern was caused by glacier thinning. The migration of a drainage divide eventually rerouted most of the surface meltwater from the main stream that drained the glacier in 1987 to another, formerly smaller, stream by 1992. On the basis of projected glacier thinning between 1992 and 1999, we predict that the drainage divide will continue to migrate across the glacier.

  6. Glacier protection laws: Potential conflicts in managing glacial hazards and adapting to climate change.

    Science.gov (United States)

    Anacona, Pablo Iribarren; Kinney, Josie; Schaefer, Marius; Harrison, Stephan; Wilson, Ryan; Segovia, Alexis; Mazzorana, Bruno; Guerra, Felipe; Farías, David; Reynolds, John M; Glasser, Neil F

    2018-03-13

    The environmental, socioeconomic and cultural significance of glaciers has motivated several countries to regulate activities on glaciers and glacierized surroundings. However, laws written to specifically protect mountain glaciers have only recently been considered within national political agendas. Glacier Protection Laws (GPLs) originate in countries where mining has damaged glaciers and have been adopted with the aim of protecting the cryosphere from harmful activities. Here, we analyze GPLs in Argentina (approved) and Chile (under discussion) to identify potential environmental conflicts arising from law restrictions and omissions. We conclude that GPLs overlook the dynamics of glaciers and could prevent or delay actions needed to mitigate glacial hazards (e.g. artificial drainage of glacial lakes) thus placing populations at risk. Furthermore, GPL restrictions could hinder strategies (e.g. use of glacial lakes as reservoirs) to mitigate adverse impacts of climate change. Arguably, more flexible GPLs are needed to protect us from the changing cryosphere.

  7. Dendrochronology and late Holocene history of Bering piedmont glacier, Alaska

    Science.gov (United States)

    Wiles, G.C.; Post, A.; Muller, E.H.; Molnia, B.F.

    1999-01-01

    Fluctuations of the piedmont lobe of Bering Glacier and its sublobe Steller Glacier over the past two millennia are reconstructed using 34 radiocarbon dates and tree-ring data from 16 sites across the glaciers' forelands. The general sequence of glacial activity is consistent with well-dated fluctuations of tidewater and land-terminating glaciers elsewhere along the Gulf of Alaska. Extensive forested areas along 25 km of the Bering ice margin were inundated by glacio-lacustrine and glacio-fluvial sediments during a probable ice advance shortly before 500 cal yr A.D. Regrowth of forests followed the retreating ice as early as the 7th century A.D., with frequent interruptions of tree growth due to outwash aggradation. Forests overrun by ice and buried in outwash indicate readvance about 1080 cal yr A.D. Retreat followed, with ice-free conditions maintained along the distal portions of the forefield until the early 17th century after which the ice advanced to within a few kilometers of its outer Neoglacial moraine. Ice reached this position after the mid-17th century and prior to 200 yr ago. Since the early 20th century, glacial retreat has been punctuated by periodic surges. The record from forests overrun by the nonsurging Steller Lobe shows that this western ice margin was advancing by 1250 A.D., reaching near its outer moraine after 1420 cal yr A.D. Since the late 19th century, the lobe has dominantly retreated.

  8. Reconstruction of specific mass balance for glaciers in Western ...

    Indian Academy of Sciences (India)

    Seasonal sensitivity characteristics (SSCs) were developed for Naradu, Shaune Garang, Gor Garang and Gara glaciers, Western Himalaya to quantify the changes in mean specific mass balance using monthly temperature and precipitation perturbations. The temperature sensitivities were observed high during summer ...

  9. Landmark Study Reveals Antarctic Glacier's Long History of Retreat

    OpenAIRE

    Kuska, Dale M.

    2016-01-01

    Faculty Showcase Archive Article Approved for public release; distribution is unlimited. A major study, released in late November in the journal “Nature,” reveals the history of retreat of the massive Pine Island Glacier (PIG) in western Antarctica, widely considered one of the largest contributors to global sea-level rise.

  10. Reconstruction of specific mass balance for glaciers in Western ...

    Indian Academy of Sciences (India)

    Vinay Kumar Gaddam

    2017-06-12

    Jun 12, 2017 ... temperatures and precipitation estimates of ERA 20CM ensemble climate reanalysis datasets to reconstruct the specific mass balance for a period of 110 years, between 1900 and 2010. Mass balance estimates suggest that the Shaune Garang, Gor-Garang and Gara glaciers have experienced both ...

  11. A glacier runoff extension to the Precipitation Runoff Modeling System

    Science.gov (United States)

    Van Beusekom, Ashley E.; Viger, Roland

    2016-01-01

    A module to simulate glacier runoff, PRMSglacier, was added to PRMS (Precipitation Runoff Modeling System), a distributed-parameter, physical-process hydrological simulation code. The extension does not require extensive on-glacier measurements or computational expense but still relies on physical principles over empirical relations as much as is feasible while maintaining model usability. PRMSglacier is validated on two basins in Alaska, Wolverine, and Gulkana Glacier basin, which have been studied since 1966 and have a substantial amount of data with which to test model performance over a long period of time covering a wide range of climatic and hydrologic conditions. When error in field measurements is considered, the Nash-Sutcliffe efficiencies of streamflow are 0.87 and 0.86, the absolute bias fractions of the winter mass balance simulations are 0.10 and 0.08, and the absolute bias fractions of the summer mass balances are 0.01 and 0.03, all computed over 42 years for the Wolverine and Gulkana Glacier basins, respectively. Without taking into account measurement error, the values are still within the range achieved by the more computationally expensive codes tested over shorter time periods.

  12. Melting glaciers signal climate change in Bolivia | IDRC ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2011-05-13

    May 13, 2011 ... Melting glaciers signal climate change in Bolivia ... Global warming is occurring faster at high altitudes, causing the ... and how the local environment was going to change in years to come. ... New economic opportunities and better transportation to markets in La Paz have brought migrants to the area.

  13. Modelling the dynamics and boundary processes of Svalbard glaciers

    NARCIS (Netherlands)

    van Pelt, W.J.J.

    2014-01-01

    The focus of this thesis is on improving our understanding of surface and basal processes in the context of glaciers in Svalbard. At the surface, interactions with the atmosphere and underlying snow determine the surface mass balance. A coupled model is applied to Nordenskiöldbreen, a tidewater

  14. Traileka Glacier X-Stack. Final Scientific/Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Borkar, Shekhar [Intel Federal LLC, Fairfax, VA (United States)

    2015-09-01

    The XStack Traleika Glacier (XSTG) project was a three-year research award for exploring a revolutionary exascale-class machine software framework. The XSTG program, including Intel, UC San Diego, Pacific Northwest National Lab, UIUC, Rice University, Reservoir Labs, ET International, and U. Delaware, had major accomplishments, insights, and products resulting from this three-year effort.

  15. Glaciers et évolution climatique dans les Andes boliviennes. Glacier de Zongo et glacier de Chacaltaya Cordillère Royale, 16°S

    Directory of Open Access Journals (Sweden)

    1995-01-01

    Full Text Available SEDIMENTOLOGY OF THE HUANCANE FORMATION (NEOCOMIAN OF THE CUSCO REGION AND ITS RELATION TO SEA LEVEL VARIATIONS. The Huancane formation (Neocomian of the Cusco region is mainly composed of quartz sandstones which are deposited in fluvial environments. The facies recognized are organized in a vertical sequence: fluvial sheet sandstones, oxidized or eroded surface, the shale facies of alluvial plain and unusual limestone facies of possible marine origin. These vertical facies sequences show that eustatic sea level variations controlled the fluvial sedimentation. The rivers came from the NE and were fed by the erosion of the Brazilian Shield. The sedimentation developed above the boundary of the SW edge of the Eastern basin, and the Cusco-Puno Swell which had locale horst and grabens inherited from pre-neocomian relief. GLACIARES Y EVOLUCIÓN CLIMÁTICA EN LOS ANDES BOLIVIANOS GLACIAR DE ZONGO Y GLACIAR DE CHACALTAYA, CORDILLERA REAL, 16°S. Por su sensibilidad y su plazo de respuesta breve, el glaciar es de un gran interés para analizar la evolución y la variabilidad actuales del clima entre los trópicos. Se presentan los métodos de determinación del balance de masas y del balance hidrológico, con una frecuencia de mediciones mensual. Los resultados recogidos durante tres años (1991-1994 muestran una grande variabilidad. Ésta es controlada sobre todo por la extensión del periodo de precipitaciones en medio de la temporada cálida que dura más o menos 6 meses. Los eventos ENSO (El Niño Southern Oscillation son asociados a balances netamente negativos, lo que es demostrado por la respuesta del glaciar al episodio de 1991-1992 y por la reconstrucción de los balances efectuados en base a los datos hidrológicos durante los dos últimos decenios. El retroceso acelerado de los glaciares tropicales desde los años 1980 es vinculado a la vez a una sucesión de eventos ENSO y al recalentamiento atmosférico. GLACIERS AND CLIMATIC EVOLUTION IN

  16. Assessing Glacier Hazards At Ghiacciaio Del Belvedere, Macugnaga, Italian Alps

    Science.gov (United States)

    Haeberli, W.; Chiarle, M.; Mortara, G.; Mazza, A.

    The uppermost section of the Valle Anzasca behind and above the community of Macugnaga in the Italian Alps is one of the most spectacular high-mountain land- scapes in Europe, with gigantic rock walls and numerous steep hanging glaciers. Its main glacier, Ghiacciaio del Belvedere at the foot of the huge Monte Rosa east face, is a heavily debris-covered glacier flowing on a thick sediment bed. Problems with floods, avalanches and debris flows from this ice body have been known for extended time periods. Most recently, however, the evolution of this highly dynamic environ- ment has become more dramatic. An outburst of Lago delle Locce, an ice-dammed lake at the confluenec of the tributary Ghiacciaio delle Locce with Ghiacciaio del Belvedere, caused heavy damage in 1979 and necessitated site investigation and con- struction work to be done for flood protection. The intermittent glacier growth ten- dency in the 1970es induced strong bulging of the glacier surface and, in places, caused the glacier tongue to override historical morains and to destroy newly-grown forest stands. A surge-type flow acceleration started in the lower parts of the Monte- Rosa east face during summer 2000, leading to strong crevassing and deformation of Ghiacciaio del Belvedere and extreme bulging of its orographic right margin. High water pressure and accelerated movement lasted into winter 2001/2002: the ice now started overriding the LIA moraine near Rifugio Zamboni of the CAI. In addition but rather independently, a most active detachment zone for rock falls and debris flows developed for several years now in the east face of Monte Rosa, somewhat more to the south of the accelerated glacier movement and at an altitude where relatively warm permafrost must be expected. Besides the scientific interest in these phenomena, the growing hazard potential to the local infrastructure must be considered seriously. Es- pecially potentials for the destabilization of large rock and ice masses in the

  17. Development of contrast media

    International Nuclear Information System (INIS)

    Krause, W.

    1993-01-01

    Description of all contrast media (ionic and nonionic monomers, ionic and nonionic dimers) was presented. Chemotoxicity, osmolality and viscosity of some contrast agents were analyzed. The main adverse reactions to ionic and nonionic contrast media were described

  18. Increased Melting of Glaciers during Cotopaxi volcano awakening in 2015

    Science.gov (United States)

    Ramon, Patricio; Vallejo, Silvia; Almeida, Marco; Gomez, Juan Pablo; Caceres, Bolivar

    2016-04-01

    Cotopaxi (5897 m), located about 50 km south of Quito (Ecuador), is one of the most active volcanoes in the Andes and its historical eruptions have caused a great impact on the population by the generation of lahars along its three main drainages (N, S, E). Starting on April 2015 the seismic monitoring networks and the SO2 gas detection network in May 2015 showed a significant increase from their background values, in June a geodetic instrument located in the NE flank started to record inflation; all this indicated the beginning of a new period of unrest. On August 14, five small phreatic explosions occurred, accompanied by large gas and ash emissions, ash falls were reported to the W of the volcano and to the S of Quito capital city. Three new episodes of ash and gas emissions occurred afterwards and towards the end of November 2015, the different monitoring parameters indicated a progressive reduction in the activity of the volcano. Since August 18 almost weekly overflights were made in order to conduct thermal (FLIR camera), visual and SO2 gas monitoring. Towards the end of August thermal measurements showed for the first time the presence of new thermal anomalies (13.5 to 16.3 °C) located in the crevices of the N glaciers, at the same time fumarolic gases were observed coming out from those fractures. On a flight made on September 3, the presence of water coming out from the basal fronts of the northern glaciers was clearly observed and the formation of narrow streams of water running downslope, while it was evident the appearance of countless new crevices in the majority of glacier ends, but also new cracks and rockslides on the upper flanks. All this led to the conclusion that an abnormal process was producing the melting of the glaciers around the volcano. Starting on September it was possible to observe the presence of small secondary lahars descending several streams and we estimated that many of them are due to increased glacier melting. Later

  19. Some notes on the behaviour of tropical glaciers

    Directory of Open Access Journals (Sweden)

    1995-01-01

    Full Text Available QUELQUES OBSERVATIONS SUR LE COMPORTEMENT DES GLACIERS TROPICAUX. Le fait qu’il soit possible sous les Tropiques de tirer des conclusions quasi immédiates sur le climat à partir des fluctuations des glaciers, en raison du caractère relativement homogène des masses d’air, rend les recherches glaciologiques dans ces régions particulièrement importantes. Une des caractéristiques du climat tropical est l’absence de variations thermiques saisonnières significatives. En tenant compte de ce fait, on évoque la relation climat-glacier sous deux de ses aspects : a la sensibilité de la ligne d’équilibre (ELA aux variations climatiques, et b la réponse correspondante des langues glaciaires. On discute de ces aspects par comparaison avec les conditions rencontrées dans les Alpes. La discussion est fondée sur un modèle de gradient vertical du bilan de masse (VGB. Comparée avec les glaciers des latitudes moyennes, la ELA réagit généralement de façon moins sensible, mais cependant plus fortement à un changement de température. Les langues, comme les petits glaciers réagissent de façon sensible à une ablation croissante. Les réponses à des influences dynamiques à long terme sont peu significatives. OBSERVACIONES SOBRE EL COMPORTAMIENTO DE LOS GLACIARES TROPICALES. El hecho de que se pueda llegar en los Trópicos a una conclusión casi inmediata sobre la evolución climática a partir de las fluctuaciones glaciares, debido al carácter relativamente homogéneo de las masas de aire, confiere a los estudios glaciológicos en esas regiones una grande importancia. Una de las características del clima tropical es la ausencia de variación térmica estacional significativa. Bajo este aspecto general, se trata de dos aspectos de la relación clima-glaciar: a la sensibilidad de la altitud de la línea de equilibrio glaciar (ELA a cambios climáticos y b la reacción correspondiente de las lenguas glaciares. Ambos aspectos son discutidos

  20. Earth's Climate History from Glaciers and Ice Cores

    Science.gov (United States)

    Thompson, Lonnie

    2013-03-01

    Glaciers serve both as recorders and early indicators of climate change. Over the past 35 years our research team has recovered climatic and environmental histories from ice cores drilled in both Polar Regions and from low to mid-latitude, high-elevation ice fields. Those ice core -derived proxy records extending back 25,000 years have made it possible to compare glacial stage conditions in the Tropics with those in the Polar Regions. High-resolution records of δ18O (in part a temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although at many sites the early Holocene was warmer than today. Remarkable similarities between changes in the highland and coastal cultures of Peru and regional climate variability, especially precipitation, imply a strong connection between prehistoric human activities and regional climate. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions today are different from those under which these ice fields originated and have been sustained. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth's climate system is underway. Observations of glacier shrinkage during the 20th and 21st century girdle the globe from the South American Andes, the Himalayas, Kilimanjaro (Tanzania, Africa) and glaciers near Puncak Jaya, Indonesia (New Guinea). The history and fate of these ice caps, told through the adventure, beauty and the scientific evidence from some of world's most remote mountain tops, provide a global perspective for contemporary climate. NSF Paleoclimate Program

  1. Spatial and temporal variations in glacier hydrology on Storglaciaeren, Sweden

    International Nuclear Information System (INIS)

    Jansson, Peter; Naeslund, Jens-Ove

    2009-06-01

    The aim of the current research project was to provide a framework of real conditions within which to interpret theory and extrapolate likely conditions beneath a future ice sheet over Fennoscandia. The purpose of this report is to summarize the experimental work on glacier hydrology and basal hydraulic conditions performed on Storglaciaeren, northern Sweden, during the years 1990-2006. Surface fed subglacial hydrological systems are extremely dynamic because the input rates of rain and temperature-controlled surface melt fluctuate, and the geometry of flow paths is constantly changing due to ice deformation which tends to open and close the flow paths. The hydrological system of a glacier is quite unusual because since liquid water flows through conduits made of its solid phase (ice). Understanding the expected dynamic range of a glacier's hydrological system is best studied by in situ measurements. The processes studied on Storglaciaeren can be expected to apply to ice sheet scale, albeit on different spatial scales. Since Storglaciaeren is a polythermal glacier with a large fraction of ice below freezing and at the melting point and with a surface-fed hydrological system of conduits and tunnels, results apply to the lower elevation regions where the surface is composed of ice (ablation zone) rather than composed of snow (accumulation zone) found at higher elevations of the glaciers and ice sheets, Therefore, our results apply to the ablation zone of the past Fennoscandian Ice Sheet. In this report we discuss the measurements made to assess the subglacial conditions that provide a potential analogue for conditions under the Fennoscandian Ice Sheet. For this purpose field work was performed on from 2003 to 2006 yielding subglacial water pressure measurements. We have included a large quantity of unpublished data from Storglaciaeren from different research projects conducted since 1990. Together these data provide a picture of the temporal and spatial water

  2. Spatial and temporal variations in glacier hydrology on Storglaciaeren, Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Peter (Dept. of Physical Geography and Quaternary Geology, Stockholm Univ., Stockholm (Sweden)); Naeslund, Jens-Ove (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

    2009-06-15

    The aim of the current research project was to provide a framework of real conditions within which to interpret theory and extrapolate likely conditions beneath a future ice sheet over Fennoscandia. The purpose of this report is to summarize the experimental work on glacier hydrology and basal hydraulic conditions performed on Storglaciaeren, northern Sweden, during the years 1990-2006. Surface fed subglacial hydrological systems are extremely dynamic because the input rates of rain and temperature-controlled surface melt fluctuate, and the geometry of flow paths is constantly changing due to ice deformation which tends to open and close the flow paths. The hydrological system of a glacier is quite unusual because since liquid water flows through conduits made of its solid phase (ice). Understanding the expected dynamic range of a glacier's hydrological system is best studied by in situ measurements. The processes studied on Storglaciaeren can be expected to apply to ice sheet scale, albeit on different spatial scales. Since Storglaciaeren is a polythermal glacier with a large fraction of ice below freezing and at the melting point and with a surface-fed hydrological system of conduits and tunnels, results apply to the lower elevation regions where the surface is composed of ice (ablation zone) rather than composed of snow (accumulation zone) found at higher elevations of the glaciers and ice sheets, Therefore, our results apply to the ablation zone of the past Fennoscandian Ice Sheet. In this report we discuss the measurements made to assess the subglacial conditions that provide a potential analogue for conditions under the Fennoscandian Ice Sheet. For this purpose field work was performed on from 2003 to 2006 yielding subglacial water pressure measurements. We have included a large quantity of unpublished data from Storglaciaeren from different research projects conducted since 1990. Together these data provide a picture of the temporal and spatial water

  3. The Neoglacial landscape and human history of Glacier Bay, Glacier Bay National Park and Preserve, southeast Alaska, USA

    Science.gov (United States)

    Connor, C.; Streveler, G.; Post, A.; Monteith, D.; Howell, W.

    2009-01-01

    The Neoglacial landscape of the Huna Tlingit homeland in Glacier Bay is recreated through new interpretations of the lower Bay's fjordal geomorphology, late Quaternary geology and its ethnographic landscape. Geological interpretation is enhanced by 38 radiocarbon dates compiled from published and unpublished sources, as well as 15 newly dated samples. Neoglacial changes in ice positions, outwash and lake extents are reconstructed for c. 5500?????"200 cal. yr ago, and portrayed as a set of three landscapes at 1600?????"1000, 500?????"300 and 300?????"200 cal. yr ago. This history reveals episodic ice advance towards the Bay mouth, transforming it from a fjordal seascape into a terrestrial environment dominated by glacier outwash sediments and ice-marginal lake features. This extensive outwash plain was building in lower Glacier Bay by at least 1600 cal. yr ago, and had filled the lower bay by 500 cal. yr ago. The geologic landscape evokes the human-described landscape found in the ethnographic literature. Neoglacial climate and landscape dynamism created difficult but endurable environmental conditions for the Huna Tlingit people living there. Choosing to cope with environmental hardship was perhaps preferable to the more severely deteriorating conditions outside of the Bay as well as conflicts with competing groups. The central portion of the outwash plain persisted until it was overridden by ice moving into Icy Strait between AD 1724?????"1794. This final ice advance was very abrupt after a prolonged still-stand, evicting the Huna Tlingit from their Glacier Bay homeland. ?? 2009 SAGE Publications.

  4. New bradykinin analogues acetylated on their N-terminus: Effect on rat blood pressure and rat uterus

    Czech Academy of Sciences Publication Activity Database

    Labudda-Dawidowska, O.; Sobolewski, D.; Sleszyňska, M.; Derdowska, I.; Slaninová, Jiřina; Wierzba, T.; Prahl, A.

    2006-01-01

    Roč. 12, Supplement (2006), s. 190 ISSN 1075-2617. [European Peptide Symposium /29./. 03.09.2006-08.09.2006, Gdansk] Institutional research plan: CEZ:AV0Z40550506 Keywords : bradykinin * N-terminus * rat uterus Subject RIV: CC - Organic Chemistry

  5. Unprecedented large inverted repeats at the replication terminus of circular bacterial chromosomes suggest a novel mode of chromosome rescue

    Science.gov (United States)

    El Kafsi, Hela; Loux, Valentin; Mariadassou, Mahendra; Blin, Camille; Chiapello, Hélène; Abraham, Anne-Laure; Maguin, Emmanuelle; van de Guchte, Maarten

    2017-01-01

    The first Lactobacillus delbrueckii ssp. bulgaricus genome sequence revealed the presence of a very large inverted repeat (IR), a DNA sequence arrangement which thus far seemed inconceivable in a non-manipulated circular bacterial chromosome, at the replication terminus. This intriguing observation prompted us to investigate if similar IRs could be found in other bacteria. IRs with sizes varying from 38 to 76 kbp were found at the replication terminus of all 5 L. delbrueckii ssp. bulgaricus chromosomes analysed, but in none of 1373 other chromosomes. They represent the first naturally occurring very large IRs detected in circular bacterial genomes. A comparison of the L. bulgaricus replication terminus regions and the corresponding regions without IR in 5 L. delbrueckii ssp. lactis genomes leads us to propose a model for the formation and evolution of the IRs. The DNA sequence data are consistent with a novel model of chromosome rescue after premature replication termination or irreversible chromosome damage near the replication terminus, involving mechanisms analogous to those proposed in the formation of very large IRs in human cancer cells. We postulate that the L. delbrueckii ssp. bulgaricus-specific IRs in different strains derive from a single ancestral IR of at least 93 kbp. PMID:28281695

  6. Radiographic contrast media

    International Nuclear Information System (INIS)

    Golman, K.; Holtz, E.; Almen, T.

    1987-01-01

    Contrast media are used in diagnostic radiology to enhance the X-ray attenuation between a body structure of interest and the surrounding tissue. A detail becomes perceptible on a roentgenogram only when its contrast exceeds a minimum value in relation to the background. Small areas of interest must have higher contrast than the background. The contrast effect depends on concentration of the contrast media with the body. A high contrast media concentration difference thus gives rise to more morphological details in the radiographs. Contrast media can be divided into negative contrast media such as air and gas which attenuate X-rays less than the body tissues, and positive contrast materials which attenuate X-rays more than the body tissues. The positive contrast media all contain either iodine (atomic number 53) or barium (atomic number 56) and can be divided into water-insoluble and water-soluble contrast media

  7. Hydrology, microbiology and carbon cycling at a high Arctic polythermal glacier, (John Evans Glacier, Ellesmere Island, Canada)

    Science.gov (United States)

    Skidmore, Mark Leslie

    Analysis of the hydrology, hydrochemistry and microbiology at polythermal John Evans Glacier and geochemical and isotopic data from Haut Glacier d'Arolla demonstrates that certain subglacial chemical weathering processes are microbially mediated. Subglacial drainage is likely an annual occurrence beneath John Evans Glacier and solute rich subglacial waters indicate over winter storage at the glacier bed. Subglacial microbial populations are also present, and are viable under simulated near in situ conditions at 0.3°C. This suggests that temperate subglacial environments at a polythermal glacier, which are isolated by cold ice above and around them, provide a viable habitat for life where basal water and organic carbon are present throughout the year. Thus, a subglacial microbial ecosystem based upon legacy carbon, (from old soils or surface inputs) rather than primary production may exist, where redox processes are a key component, and seasonal anoxia may occur. The existence of anoxic environments is supported by the presence of strictly anaerobic bacteria (sulphate reducing bacteria and methanogens) in the basal sediments---which are viable in culture at 4°C---and also argues that these bacteria are not washed in with oxygenated surface meltwaters, but are present in the subglacial environment. During the summer meltseason there is a large input of surficial waters to the subglacial system and water residence times are drastically reduced. Hence, kinetic weathering processes dominate, resulting in light delta 13C-DIC (dissolved inorganic carbon) in glacial runoff, as verified by experimental work on CaCO3 and John Evans Glacier sediments. The experiments demonstrate kinetic bedrock fractionation (KBF) during carbonate hydrolysis and that kinetic fractionation of CO2 (KFC) is proportional to the rate of CO2 draw down during the carbonation of carbonates. This results in significantly depleted delta13C-DIC values (≤-16 ‰) relative to the bedrock carbonate

  8. Hydrologic controls on radiogenic Sr in meltwater from an alpine glacier system: Athabasca Glacier, Canada

    International Nuclear Information System (INIS)

    Arendt, C.A.; Stevenson, E.I.; Aciego, S.M.

    2016-01-01

    Filtered subglacial meltwater samples were collected daily during the onset of melt (May) and peak melt (July) over the 2011 melt season at the Athabasca Glacier (Alberta, Canada) and analyzed for strontium-87/strontium-86 ("8"7Sr/"8"6Sr) isotopic composition to infer the evolution of subglacial weathering processes. Both the underlying bedrock composition and subglacial water–rock interaction time are the primary influences on meltwater "8"7Sr/"8"6Sr. The Athabasca Glacier is situated atop Middle Cambrian carbonate bedrock that also contains silicate minerals. The length of time that subglacial meltwater interacts with the underlying bedrock and substrate is a predominant determining factor in solute concentration. Over the course of the melt season, increasing trends in Ca/K and Ca/Mg correspond to overall decreasing trends in "8"7Sr/"8"6Sr, which indicate a shift in weathering processes from the presence of silicate weathering to primarily carbonate weathering. Early in the melt season, rates of carbonate dissolution slow as meltwater approaches saturation with respect to calcite and dolomite, corresponding to an increase in silicate weathering that includes Sr-rich silicate minerals, and an increase in meltwater "8"7Sr/"8"6Sr. However, carbonate minerals are preferentially weathered in unsaturated waters. During the warmest part of a melt season the discharged meltwater is under saturated, causing an increase in carbonate weathering and a decrease in the radiogenic Sr signal. Likewise, larger fraction contributions of meltwater from glacial ice corresponds to lower "8"7Sr/"8"6Sr values, as the meltwater has lower water–rock interaction times in the subglacial system. These results indicate that although weathering of Sr-containing silicate minerals occurs in carbonate dominated glaciated terrains, the continual contribution of new meltwater permits the carbonate weathering signal to dominate. - Highlights: • Glacial meltwater "8"7Sr/"8"6Sr used to

  9. Post-Little Landscape and Glacier Change in Glacier Bay National Park: Documenting More than a Century of Variability with Repeat Photography

    Science.gov (United States)

    Molnia, B. F.; Karpilo, R. D.; Pranger, H. S.

    2004-12-01

    Historical photographs, many dating from the late-19th century are being used to document landscape and glacier change in the Glacier Bay area. More than 350 pre-1980 photographs that show the Glacier Bay landscape and glacier termini positions have been acquired by the authors. Beginning in 2003, approximately 150 of the sites from which historical photographs had been made were revisited. At each site, elevation and latitude and longitude were recorded using WAAS-enabled GPS. Compass bearings to photographic targets were also determined. Finally, using the historical photographs as a composition guide, new photographs were exposed using digital imaging and film cameras. In the laboratory, 21st century images and photographs were compared with corresponding historical photographs to determine, and to better understand rates, timing, and mechanics of Glacier Bay landscape evolution, as well as to clarify the response of specific glaciers to changing climate and environment. The comparisons clearly document rapid vegetative succession throughout the bay; continued retreat of larger glaciers in the East Arm of the bay; a complex pattern of readvance and retreat of the larger glaciers in the West Arm of the bay, coupled with short-term fluctuations of its smaller glaciers; transitions from tidewater termini to stagnant, debris-covered termini; fiord sedimentation and erosion; development of outwash and talus features; and many other dramatic changes. As might be expected, 100-year-plus photo comparisons show significant changes throughout the Glacier Bay landscape, especially at the southern ends of East and West Arms. Surprisingly, recent changes, occurring since the late-1970s were equally dramatic, especially documenting the rapid thinning and retreat of glaciers in upper Muir Inlet.

  10. Do morphometric parameters and geological conditions determine chemistry of glacier surface ice? Spatial distribution of contaminants present in the surface ice of Spitsbergen glaciers (European Arctic).

    Science.gov (United States)

    Lehmann, Sara; Gajek, Grzegorz; Chmiel, Stanisław; Polkowska, Żaneta

    2016-12-01

    The chemism of the glaciers is strongly determined by long-distance transport of chemical substances and their wet and dry deposition on the glacier surface. This paper concerns spatial distribution of metals, ions, and dissolved organic carbon, as well as the differentiation of physicochemical parameters (pH, electrical conductivity) determined in ice surface samples collected from four Arctic glaciers during the summer season in 2012. The studied glaciers represent three different morphological types: ground based (Blomlibreen and Scottbreen), tidewater which evolved to ground based (Renardbreen), and typical tidewater glacier (Recherchebreen). All of the glaciers are functioning as a glacial system and hence are subject to the same physical processes (melting, freezing) and the process of ice flowing resulting from the cross-impact force of gravity and topographic conditions. According to this hypothesis, the article discusses the correlation between morphometric parameters, changes in mass balance, geological characteristics of the glaciers and the spatial distribution of analytes on the surface of ice. A strong correlation (r = 0.63) is recorded between the aspect of glaciers and values of pH and ions, whereas dissolved organic carbon (DOC) depends on the minimum elevation of glaciers (r = 0.55) and most probably also on the development of the accumulation area. The obtained results suggest that although certain morphometric parameters largely determine the spatial distribution of analytes, also the geology of the bed of glaciers strongly affects the chemism of the surface ice of glaciers in the phase of strong recession.

  11. Effect of Topography on Subglacial Discharge and Submarine Melting During Tidewater Glacier Retreat

    Science.gov (United States)

    Amundson, J. M.; Carroll, D.

    2018-01-01

    To first order, subglacial discharge depends on climate, which determines precipitation fluxes and glacier mass balance, and the rate of glacier volume change. For tidewater glaciers, large and rapid changes in glacier volume can occur independent of climate change due to strong glacier dynamic feedbacks. Using an idealized tidewater glacier model, we show that these feedbacks produce secular variations in subglacial discharge that are influenced by subglacial topography. Retreat along retrograde bed slopes (into deep water) results in rapid surface lowering and coincident increases in subglacial discharge. Consequently, submarine melting of glacier termini, which depends on subglacial discharge and ocean thermal forcing, also increases during retreat into deep water. Both subglacial discharge and submarine melting subsequently decrease as glacier termini retreat out of deep water and approach new steady state equilibria. In our simulations, subglacial discharge reached peaks that were 6-17% higher than preretreat values, with the highest values occurring during retreat from narrow sills, and submarine melting increased by 14% for unstratified fjords and 51% for highly stratified fjords. Our results therefore indicate that submarine melting acts in concert with iceberg calving to cause tidewater glacier termini to be unstable on retrograde beds. The full impact of submarine melting on tidewater glacier stability remains uncertain, however, due to poor understanding of the coupling between submarine melting and iceberg calving.

  12. Estimation of Shie Glacier Surface Movement Using Offset Tracking Technique with Cosmo-Skymed Images

    Science.gov (United States)

    Wang, Q.; Zhou, W.; Fan, J.; Yuan, W.; Li, H.; Sousa, J. J.; Guo, Z.

    2017-09-01

    Movement is one of the most important characteristics of glaciers which can cause serious natural disasters. For this reason, monitoring this massive blocks is a crucial task. Synthetic Aperture Radar (SAR) can operate all day in any weather conditions and the images acquired by SAR contain intensity and phase information, which are irreplaceable advantages in monitoring the surface movement of glaciers. Moreover, a variety of techniques like DInSAR and offset tracking, based on the information of SAR images, could be applied to measure the movement. Sangwang lake, a glacial lake in the Himalayas, has great potentially danger of outburst. Shie glacier is situated at the upstream of the Sangwang lake. Hence, it is significant to monitor Shie glacier surface movement to assess the risk of outburst. In this paper, 6 high resolution COSMO-SkyMed images spanning from August to December, 2016 are applied with offset tracking technique to estimate the surface movement of Shie glacier. The maximum velocity of Shie glacier surface movement is 51 cm/d, which was observed at the end of glacier tongue, and the velocity is correlated with the change of elevation. Moreover, the glacier surface movement in summer is faster than in winter and the velocity decreases as the local temperature decreases. Based on the above conclusions, the glacier may break off at the end of tongue in the near future. The movement results extracted in this paper also illustrate the advantages of high resolution SAR images in monitoring the surface movement of small glaciers.

  13. Measurement of glacier velocity at Pik Lenin, Tajikistan, by feature tracking

    Science.gov (United States)

    Kumari, S.; Ghosh, S. K.; Buchroithner, M. F.

    2014-11-01

    Glaciers, especially in mountain area are sensitive indicators of climate fluctuations and also contribute to present rates of sea level rise. In Central Asia, these glaciers are the primary resource for fresh water. Understanding the seasonal behavior of these glaciers would help to make efficient use of the available water reservoir. Different methods have been employed to study glacier displacements in past. The conventional survey techniques are very cost-intensive and highly depend on accessibility to high mountain glaciers also directs us to look for new ways to study these areas. Here remote sensing comes in handy with freely available data and a good coverage with high spatial and temporal resolution. Optical satellite imagery, available free can be effectively used for research purpose. The glacier in this region fed lake Karakul (380 km2), the largest Lake in Tajikistan. The objective is to study the displacement tendency of the Glacier in Pik Lenin area using Landsat 7 dataset. Normalized cross correlation algorithm has been implemented via CIAS to estimate the motion of glacier surface. A number of combination of reference block and search area size were tested for 30 m resolution dataset. As a result the specifications: reference block size of 15 pixels and search area size of 10 pixels was found out as the best set of parameters and considered for further processing. The study derives a reliable set of data depicting the velocities in the glacier which after post processing shows peak velocity of 121 m/y of the glacier.

  14. Glacier Monitoring and Capacity Building: Important Ingredients for Sustainable Mountain Development

    Directory of Open Access Journals (Sweden)

    Samuel U. Nussbaumer

    2017-02-01

    Full Text Available Glacier observation data from major mountain regions of the world are key to improving our understanding of glacier changes: they deliver fundamental baseline information for climatological, hydrological, and hazard assessments. In many mountain ecosystems, as well as in the adjacent lowlands, glaciers play a crucial role in freshwater provision and regulation. This article first presents the state of the art on glacier monitoring and related strategies within the framework of the Global Terrestrial Network for Glaciers (GTN-G. Both in situ measurements of changes in glacier mass, volume, and length as well as remotely sensed data on glacier extents and changes over entire mountain ranges provide clear indications of climate change. Based on experiences from capacity-building activities undertaken in the Tropical Andes and Central Asia over the past years, we also review the state of the art on institutional capacity in these regions and make further recommendations for sustainable mountain development. The examples from Peru, Ecuador, Colombia, and Kyrgyzstan demonstrate that a sound understanding of measurement techniques and of the purpose of measurements is necessary for successful glacier monitoring. In addition, establishing durable institutions, capacity-building programs, and related funding is necessary to ensure that glacier monitoring is sustainable and maintained in the long term. Therefore, strengthening regional cooperation, collaborating with local scientists and institutions, and enhancing knowledge sharing and dialogue are envisaged within the GTN-G. Finally, glacier monitoring enhances the resilience of the populations that depend on water resources from glacierized mountains or that are affected by hazards related to glacier changes. We therefore suggest that glacier monitoring be included in the development of sustainable adaptation strategies in regions with glaciated mountains.

  15. The retreat of the world's mountain glaciers during recent decades; Le retrait des glaciers de montagne dans le monde au cours des dernieres decennies

    Energy Technology Data Exchange (ETDEWEB)

    Francou, B. [Institut de Recherche pour le Developpement (IRD), Mission de Quito, Equateur - LTHE, 38 - Grenoble (France); Vincent, Ch. [Centre National de la Recherche Scientifique (CNRS), UJF, LGGE, 38 - Grenoble (France)

    2009-08-15

    Glaciers have become essential tools for measuring changes in the global environment. Here, we analyze glacier evolution during the last few decades and we wonder whether the observed retreat remains in the range of glacier fluctuations since the mid-Holocene. The main fluctuations experienced by glaciers during the last millenniums, and particularly during the Little Ice Age (-1300 A.D. to {approx}1860 A.D.), are presented succinctly. The recent 1960-2005 period, well documented both by ground and remote sensing observations, shows important disparities between different massifs concerning the timing and the magnitude of glacier fluctuations, which depend on regional climatic conditions. The links between glacier mass balance evolution and climate is clear when approached from an energy balance but the variables commonly considered are only temperature and precipitation. The strong correlation existing between these variables and the mass balance evolution makes it possible to simulate glaciers in the future in function of distinct climatic scenarios. Modeling glacier retreat for the 21. century is an important goal because it will allow the impacts on water resource and sea level to be assessed. (authors)

  16. Bed-Deformation Experiments Beneath a Temperate Glacier

    Science.gov (United States)

    Iverson, N. R.; Hooyer, T. S.; Fischer, U. H.; Cohen, D.; Jackson, M.; Moore, P. L.; Lappegard, G.; Kohler, J.

    2002-12-01

    Fast flow of glaciers and genesis of glacial landforms are commonly attributed to shear deformation of subglacial sediment. Although models of this process abound, data gathered subglacially on the kinematics and mechanics of such deformation are difficult to interpret. Major difficulties stem from the necessity of either measuring deformation near glacier margins, where conditions may be abnormal, or at the bottoms of boreholes, where the scope of instrumentation is limited, drilling disturbs sediment, and local boundary conditions are poorly known. A different approach is possible at the Svartisen Subglacial Laboratory, where tunnels melted in the ice provide temporary human access to the bed of Engabreen, a temperate outlet glacier of the Svartisen Ice Cap in Norway. A trough (2 m x 1.5 m x 0.5 m deep) was blasted in the rock bed, where the glacier is 220 m thick and sliding at 0.1-0.2 m/d. During two spring field seasons, this trough was filled with 2.5 tons of simulated till. Instruments in the till recorded shear (tiltmeters), volume change, total normal stress, and pore-water pressure as ice moved across the till surface. Pore pressure was brought to near the total normal stress by feeding water to the base of the till with a high-pressure pump, operated in a rock tunnel 4 m below the bed surface. Results illustrate some fundamental aspects of bed deformation. Permanent shear deformation requires low effective normal stress and hence high pore-water pressure, owing to the frictional nature of till. Shear strain generally increases upward in the bed toward the glacier sole, consistent with previous measurements beneath thinner ice at glacier margins. At low effective normal stresses, ice sometimes decouples from underlying till. Overall, bed deformation accounts for 10-35 % of basal motion, although this range excludes shear in the uppermost 0.05 m of till where shear was not measured. Pump tests with durations ranging from seconds to hours highlight the need

  17. The 2016 gigantic twin glacier collapses in Tibet: towards an improved understanding of large glacier instabilities and their potential links to climate change

    Science.gov (United States)

    Gilbert, Adrien; Leinss, Silvan; Evans, Steve; Tian, Lide; Kääb, Andreas; Kargel, Jeffrey; Gimbert, Florent; Chao, Wei-An; Gascoin, Simon; Bueler, Yves; Berthier, Etienne; Yao, Tandong; Huggel, Christian; Farinotti, Daniel; Brun, Fanny; Guo, Wanqin; Leonard, Gregory

    2017-04-01

    In northwestern Tibet (34.0°N, 82.2°E) near lake Aru Co, the entire ablation area of an unnamed glacier (Aru-1) suddenly collapsed on 17 July 2016 and transformed into a mass flow that ran out over a distance of over 8 km, killing nine people and hundreds of cattle. Remarkably, a second glacier detachment with similar characteristics (Aru-2) took place 2.6 km south of the July event on 21 September 2016. These two events are unique in several aspects: their massive volumes (66 and 83 Mm3 respectively), the low slope angles ( 200 km h-1) and their close timing within two months. The only similar event currently documented is the 2002 Kolka Glacier mass flow (Caucasus Mountains). The uncommon occurrence of such large glacier failures suggest that such events require very specific conditions that could be linked to glacier thermal regime, bedrock lithology and morphology, geothermal activity or a particular climate setting. Using field and remote sensing observations, retrospective climate analysis, mass balance and thermo-mechanical modeling of the two glaciers in Tibet, we investigate the processes involved in the twin collapses. It appears that both, mostly cold-based glaciers, started to surge about 7-8 years ago, possibly in response to a long period of positive mass balance (1995-2005) followed by a sustained increase of melt water delivery to the glacier bed in the polythermal lower accumulation zone (1995-2016). Inversion of friction conditions at the base of the glacier constrained by surface elevation change rate for both glaciers shows a zone of very low basal friction progressively migrating downward until the final collapse. We interpret this to be the signature of the presence of high-pressure water dammed at the bed by the glacier's frozen periphery and toe. Large areas of low friction at the bed led to high shear stresses along the frozen side walls as evident in surface ice cracking patterns observed on satellite imagery. This process progressively

  18. Cy3 and Cy5 dyes attached to oligonucleotide terminus stabilize DNA duplexes: predictive thermodynamic model.

    Science.gov (United States)

    Moreira, Bernardo G; You, Yong; Owczarzy, Richard

    2015-03-01

    Cyanine dyes are important chemical modifications of oligonucleotides exhibiting intensive and stable fluorescence at visible light wavelengths. When Cy3 or Cy5 dye is attached to 5' end of a DNA duplex, the dye stacks on the terminal base pair and stabilizes the duplex. Using optical melting experiments, we have determined thermodynamic parameters that can predict the effects of the dyes on duplex stability quantitatively (ΔG°, Tm). Both Cy dyes enhance duplex formation by 1.2 kcal/mol on average, however, this Gibbs energy contribution is sequence-dependent. If the Cy5 is attached to a pyrimidine nucleotide of pyrimidine-purine base pair, the stabilization is larger compared to the attachment to a purine nucleotide. This is likely due to increased stacking interactions of the dye to the purine of the complementary strand. Dangling (unpaired) nucleotides at duplex terminus are also known to enhance duplex stability. Stabilization originated from the Cy dyes is significantly larger than the stabilization due to the presence of dangling nucleotides. If both the dangling base and Cy3 are present, their thermodynamic contributions are approximately additive. New thermodynamic parameters improve predictions of duplex folding, which will help design oligonucleotide sequences for biophysical, biological, engineering, and nanotechnology applications. Copyright © 2015. Published by Elsevier B.V.

  19. The N-terminus of Bunyamwera orthobunyavirus NSs protein is essential for interferon antagonism.

    Science.gov (United States)

    van Knippenberg, Ingeborg; Carlton-Smith, Charlie; Elliott, Richard M

    2010-08-01

    Bunyamwera virus NSs protein is involved in the inhibition of cellular transcription and the interferon (IFN) response, and it interacts with the Med8 component of Mediator. A spontaneous mutant of a recombinant NSs-deleted Bunyamwera virus (rBUNdelNSs2) was identified and characterized. This mutant virus, termed mBUNNSs22, expresses a 21 aa N-terminally truncated form of NSs. Like rBUNdelNSs2, mBUNNSs22 is attenuated in IFN-deficient cells, and to a greater extent in IFN-competent cells. Both rBUNdelNSs2 and mBUNNSs22 are potent IFN inducers and their growth can be rescued by depleting cellular IRF3. Strikingly, despite encoding an NSs protein that contains the Med8 interaction domain, mBUNNSs22 fails to block RNA polymerase II activity during infection. Overall, our data suggest that both the interaction of NSs with Med8 and a novel unidentified function of the NSs N-terminus, seem necessary for Bunyamwera virus to counteract host antiviral responses.

  20. Hpa1 harpin needs nitroxyl terminus to promote vegetative growth and leaf photosynthesis in Arabidopsis.

    Science.gov (United States)

    Li, Xiaojie; Han, Liping; Zhao, Yanying; You, Zhenzhen; Dong, Hansong; Zhang, Chunling

    2014-03-01

    Hpa1 is a harpin protein produced by Xanthomonas oryzae, an important bacterial pathogen of rice, and has the growth-promoting activity in plants. To understand the molecular basis for the function of Hpa1, we generated an inactive variant protein, Hpa1 delta NT, by deleting the nitroxyl-terminal region of the Hpa1 sequence and compared Hpa1 delta NT with the full-length protein in terms of the effects on vegetative growth and related physiological responses in Arabidopsis. When Hpa1 was applied to plants, it acted to enhance the vegetative growth but did not affect the floral development. Enhanced plant growth was accompanied by induced expression of growth-promoting genes in plant leaves. The growth-promoting activity of Hpa1 was further correlated with a physiological consequence shown as promoted leaf photosynthesis as a result of facilitated CO2 conduction through leaf stomata and mesophyll cells. On the contrary, plant growth, growth-promoting gene expression, and the physiological consequence changed little in response to the Hpa1 delta NT treatment. These analyses suggest that Hpa1 requires the nitroxyl-terminus to facilitate CO2 transport inside leaf cells and promote leaf photosynthesis and vegetative growth of the plant.

  1. Truncated C-terminus of fibrillin-1 induces Marfanoid-progeroid-lipodystrophy (MPL) syndrome in rabbit.

    Science.gov (United States)

    Chen, Mao; Yao, Bing; Yang, Qiangbing; Deng, Jichao; Song, Yuning; Sui, Tingting; Zhou, Lina; Yao, HaoBing; Xu, Yuanyuan; Ouyang, Hongsheng; Pang, Daxin; Li, Zhanjun; Lai, Liangxue

    2018-04-09

    Various clinical differences have been observed between patients with the FBN1 gene mutation and those with the classical Marfan phenotype. Although FBN1 knockout (KO) or dominant-negative mutant mice are widely used as an animal model for Marfan syndrome (MFS), these mice cannot recapitulate the genotype/phenotype relationship of Marfanoid-progeroid-lipodystrophy (MPL) syndrome, which is caused by a mutation in the C-terminus of fibrillin-1, the penultimate exon of the FBN1 gene. Here, we describe the generation of a rabbit MPL model with C-terminal truncation of fibrillin-1 using a CRISPR/Cas9 system. FBN1 heterozygous ( FBN1 Het) rabbits faithfully recapitulated the phenotypes of MFS, including muscle wasting and impaired connective tissue, ocular syndrome and aortic dilation. Moreover, skin symptoms, lipodystrophy, growth retardation and dysglycemia were also seen in these FBN1 Het rabbits, and have not been reported in other animal models. In conclusion, this novel rabbit model mimics the histopathological changes and functional defects of MPL syndrome, and could become a valuable model for studies of pathogenesis and drug screening for MPL syndrome. © 2018. Published by The Company of Biologists Ltd.

  2. Oxidative stress induces nuclear translocation of C-terminus of α-synuclein in dopaminergic cells

    International Nuclear Information System (INIS)

    Xu Shengli; Zhou Ming; Yu Shun; Cai Yanning; Zhang Alex; Ueda, Kenji; Chan Piu

    2006-01-01

    Growing evidence suggests that oxidative stress is involved in the neuronal degeneration and can promote the aggregation of α-synuclein. However, the role of α-synuclein under physiological and pathological conditions remains poorly understood. In the present study, we examined the possible interaction between the α-synuclein and oxidative stress. In a dopaminergic cell line MES23.5, we have found that the 200 μM H 2 O 2 treatment induced the translocation of α-synuclein from cytoplasm to nuclei at 30 min post-treatment. The immunoactivity of α-synuclein became highly intensive in the nuclei after 2 h treatment. The protein translocated to nucleus was a 10 kDa fragment of C-terminus region of α-synuclein, while full-length α-synuclein remained in cytoplasm. Thioflavine-S staining suggested that the C-terminal fragment in the nuclei has no β-sheet structures. Our present results indicated that 200 μM H 2 O 2 treatment induces the intranuclear accumulation of the C-terminal fragment of α-synuclein in dopaminergic neurons, whose role remains to be investigated

  3. Evolution of Pine Island Glacier subglacial conditions in response to 18 years of ice flow acceleration

    Science.gov (United States)

    Brisbourne, A.; Bougamont, M. H.; Christoffersen, P.; Cornford, S. L.; Nias, I.; Vaughan, D.; Smith, A.

    2017-12-01

    Antarctica's main contribution to sea-level rise originates from the Amundsen Coast, when warm ocean water intrudes onto the continental shelf. As a result, strong melting beneath the ice shelves induces thinning near the grounding line of glaciers, which is ensued by large ice flow speed up diffusing rapidly inland. In particular, ice loss from Pine Island Glacier (PIG) accounts for 20% of the total ice loss in West Antarctica, amounting to 0.12 mm yr-1 of global sea-level rise. Forecasting the future flow of Amundsen Coast glaciers is however hindered by large uncertainties regarding how the thinning initiated at the grounding line is transmitted upstream, and how the grounded flow will ultimately respond. This work aims at elucidating the role of subglacial processes beneath PIG tributaries in modulating the ice flow response to frontal perturbations. We used the Community Ice Sheet Model (CISM 2.0) to perform numerical inversions of PIG surface velocity as observed in 1996 and 2014. Over that time period, ice flow acceleration has been widespread over PIG's basin, and the inversions provide insights into the related evolution of the basal thermal and stress conditions. We assume the latter to be directly related to changes in the properties of a soft sediment (till) layer known to exist beneath PIG. We find that the overall bed strength has weakened by 18% in the region of enhanced flow, and that the annual melt production for PIG catchment increased by 25% between 1996 and 2014. Specifically, regions of high melt production are located in the southern tributaries, where the overall stronger bed allows for more frictional melting. However, we find no significant and widespread change in the basal strength of that region, and we infer that the water produced is transported away in a concentrated hydrological system, without much interaction with the till layer. In contrast, we find that relatively less basal melting occurs elsewhere in the catchment, where the

  4. Air temperature, radiation budget and area changes of Quisoquipina glacier in the Cordillera Vilcanota (Peru)

    Science.gov (United States)

    Suarez, Wilson; Macedo, Nicolás; Montoya, Nilton; Arias, Sandro; Schauwecker, Simone; Huggel, Christian; Rohrer, Mario; Condom, Thomas

    2015-04-01

    The Peruvian Andes host about 71% of all tropical glaciers. Although several studies have focused on glaciers of the largest glaciered mountain range (Cordillera Blanca), other regions have received little attention to date. In 2011, a new program has been initiated with the aim of monitoring glaciers in the centre and south of Peru. The monitoring program is managed by the Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI) and it is a joint project together with the Universidad San Antonio Abad de Cusco (UNSAAC) and the Autoridad Nacional del Agua (ANA). In Southern Peru, the Quisoquipina glacier has been selected due to its representativeness for glaciers in the Cordillera Vilcanota considering area, length and orientation. The Cordillera Vilcanota is the second largest mountain range in Peru with a glaciated area of approximately 279 km2 in 2009. Melt water from glaciers in this region is partly used for hydropower in the dry season and for animal breeding during the entire year. Using Landsat 5 images, we could estimate that the area of Quisoquipina glacier has decreased by approximately 11% from 3.66 km2 in 1990 to 3.26 km2 in 2010. This strong decrease is comparable to observations of other tropical glaciers. In 2011, a meteorological station has been installed on the glacier at 5180 m asl., measuring air temperature, wind speed, relative humidity, net short and longwave radiation and atmospheric pressure. Here, we present a first analysis of air temperature and the radiation budget at the Quisoquipina glacier for the first three years of measurements. Additionally, we compare the results from Quisoquipina glacier to results obtained by the Institut de recherche pour le développement (IRD) for Zongo glacier (Bolivia) and Antizana glacier (Ecuador). For both, Quisoquipina and Zongo glacier, net shortwave radiation may be the most important energy source, thus indicating the important role of albedo in the energy balance of the glacier

  5. Copernicus Big Data and Google Earth Engine for Glacier Surface Velocity Field Monitoring: Feasibility Demonstration on San Rafael and San Quintin Glaciers

    Science.gov (United States)

    Di Tullio, M.; Nocchi, F.; Camplani, A.; Emanuelli, N.; Nascetti, A.; Crespi, M.

    2018-04-01

    The glaciers are a natural global resource and one of the principal climate change indicator at global and local scale, being influenced by temperature and snow precipitation changes. Among the parameters used for glacier monitoring, the surface velocity is a key element, since it is connected to glaciers changes (mass balance, hydro balance, glaciers stability, landscape erosion). The leading idea of this work is to continuously retrieve glaciers surface velocity using free ESA Sentinel-1 SAR imagery and exploiting the potentialities of the Google Earth Engine (GEE) platform. GEE has been recently released by Google as a platform for petabyte-scale scientific analysis and visualization of geospatial datasets. The algorithm of SAR off-set tracking developed at the Geodesy and Geomatics Division of the University of Rome La Sapienza has been integrated in a cloud based platform that automatically processes large stacks of Sentinel-1 data to retrieve glacier surface velocity field time series. We processed about 600 Sentinel-1 image pairs to obtain a continuous time series of velocity field measurements over 3 years from January 2015 to January 2018 for two wide glaciers located in the Northern Patagonian Ice Field (NPIF), the San Rafael and the San Quintin glaciers. Several results related to these relevant glaciers also validated with respect already available and renown software (i.e. ESA SNAP, CIAS) and with respect optical sensor measurements (i.e. LANDSAT8), highlight the potential of the Big Data analysis to automatically monitor glacier surface velocity fields at global scale, exploiting the synergy between GEE and Sentinel-1 imagery.

  6. Rainfall as primary driver of discharge and solute export from rock glaciers: The Col d'Olen Rock Glacier in the NW Italian Alps.

    Science.gov (United States)

    Colombo, Nicola; Gruber, Stephan; Martin, Maria; Malandrino, Mery; Magnani, Andrea; Godone, Danilo; Freppaz, Michele; Fratianni, Simona; Salerno, Franco

    2018-10-15

    Three hypotheses exist to explain how meteorological variables drive the amount and concentration of solute-enriched water from rock glaciers: (1) Warm periods cause increased subsurface ice melt, which releases solutes; (2) rain periods and the melt of long-lasting snow enhance dilution of rock-glacier outflows; and (3) percolation of rain through rock glaciers facilitates the export of solutes, causing an opposite effect as that described in hypothesis (2). This lack of detailed understanding likely exists because suitable studies of meteorological variables, hydrologic processes and chemical characteristics of water bodies downstream from rock glaciers are unavailable. In this study, a rock-glacier pond in the North-Western Italian Alps was studied on a weekly basis for the ice-free seasons 2014 and 2015 by observing the meteorological variables (air temperature, snowmelt, rainfall) assumed to drive the export of solute-enriched waters from the rock glacier and the hydrochemical response of the pond (water temperature as a proxy of rock-glacier discharge, stable water isotopes, major ions and selected trace elements). An intra-seasonal pattern of increasing solute export associated with higher rock-glacier discharge was found. Specifically, rainfall, after the winter snowpack depletion and prolonged periods of atmospheric temperature above 0 °C, was found to be the primary driver of solute export from the rock glacier during the ice-free season. This occurs likely through the flushing of isotopically- and geochemically-enriched icemelt, causing concomitant increases in the rock-glacier discharge and the solute export (SO 4 2- , Mg 2+ , Ca 2+ , Ni, Mn, Co). Moreover, flushing of microbially-active sediments can cause increases in NO 3 - export. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Inverse vertical migration and feeding in glacier lanternfish (Benthosema glaciale)

    KAUST Repository

    Dypvik, Eivind

    2011-11-08

    A bottom-mounted upward-facing 38-kHz echo sounder was deployed at ~400 m and cabled to shore in Masfjorden (~60 52?N, ~5 24?E), Norway. The scattering layers seen during autumn (September-October) 2008 were identified by trawling. Glacier lanternfish (Benthosema glaciale) were mainly distributed below ~200 m and displayed three different diel behavioral strategies: normal diel vertical migration (NDVM), inverse DVM (IDVM) and no DVM (NoDVM). The IDVM group was the focus of this study. It consisted of 2-year and older individuals migrating to ~200-270 m during the daytime, while descending back to deeper than ~270 m during the night. Stomach content analysis revealed increased feeding during the daytime on overwintering Calanus sp. We conclude that visually searching glacier lanternfish performing IDVM benefit from the faint daytime light in mid-waters when preying on overwintering Calanus sp. 2011 The Author(s).

  8. Investigating the Equatorial Gaps in Snowball Earth Sea Glaciers

    Science.gov (United States)

    Spaulding-Astudillo, F.; Ashkenazy, Y.; Tziperman, E.; Abbot, D. S.

    2017-12-01

    The way photosynthetic life survived the Neoproterozoic Snowball Earth events is still a matter of debate that has deep implications for planetary habitability. One option is that gaps in thick, semi-global ice coverage (sea glaciers) could be maintained at the equator by ocean-ice-atmosphere dynamics. We investigate this idea by modifying a global ocean-thick-marine-ice model developed for modeling Neoproterozoic Snowball Events to account for gaps in thick ice and interactions with atmospheric dynamics. Our hypothesis is that in the parameter regime that allows for sea glacier flow, ice flow will make gaps in the thick ice, and therefore an open ocean solution, less likely. This would suggest that oases in thick ice are a more viable survival mechanism for photosynthetic life during a Snowball Earth event.

  9. New eyes in the sky measure glaciers and ice sheets

    Science.gov (United States)

    Kieffer, Hugh; Kargel, Jeffrey S.; Barry, Roger G.; Bindschadler, Robert; Bishop, Michael P.; MacKinnon, David; Ohmura, Atsumu; Raup, Bruce; Antoninetti, Massimo; Bamber, Jonathan; Braun, Mattias; Brown, Ian; Cohen, Denis; Copland, Luke; DueHagen, Jon; Engeset, Rune V.; Fitzharris, Blair; Fujita, Koji; Haeberli, Wilfried; Hagen, Jon Oue; Hall, Dorothy; Hoelzle, Martin; Johansson, Maria; Kaab, Andi; Koenig, Max; Konovalov, Vladimir; Maisch, Max; Paul, Frank; Rau, Frank; Reeh, Niels; Rignot, Eric; Rivera, Andres; De Ruyter de Wildt, Martiyn; Scambos, Ted; Schaper, Jesko; Scharfen, Greg; Shroder, Jack; Solomina, Olga; Thompson, David; van der Veen, Kees; Wohlleben, Trudy; Young, Neal

    2000-01-01

    The mapping and measurement of glaciers and their changes are useful in predicting sea-level and regional water supply, studying hazards and climate change [Haeberli et al., 1998],and in the hydropower industry Existing inventories cover only about 67,000 of the world's estimated 160,000 glaciers and are based on data collected over 50 years or more [e.g.,Haeberli et al., 1998]. The data available have proven that small ice bodies are disappearing at an accelerating rate and that the Antarctic ice sheet and its fringing ice shelves are undergoing unexpected, rapid change. According to many glaciologists, much larger fluctuations in land ice—with vast implications for society—are possible in the coming decades and centuries due to natural and anthropogenic climate change [Oppenheimer, 1998].

  10. Evidence for the assimilation of ancient glacier organic carbon in a proglacial stream food web

    Science.gov (United States)

    Fellman, Jason; Hood, Eran; Raymond, Peter A.; Hudson, J.H.; Bozeman, Maura; Arimitsu, Mayumi L.

    2015-01-01

    We used natural abundance δ13C, δ15N, and Δ14C to compare trophic linkages between potential carbon sources (leaf litter, epilithic biofilm, and particulate organic matter) and consumers (aquatic macroinvertebrates and fish) in a nonglacial stream and two reaches of the heavily glaciated Herbert River. We tested the hypothesis that proglacial stream food webs are sustained by organic carbon released from glacial ecosystems. Carbon sources and consumers in the nonglacial stream had carbon isotope values that ranged from -30‰ to -25‰ for δ13C and from -14‰ to 53‰ for Δ14C reflecting a food web sustained mainly on contemporary primary production. In contrast, biofilm in the two glacial stream sites was highly Δ14C-depleted (-215‰ to 175‰) relative to the nonglacial stream consistent with the assimilation of ancient glacier organic carbon. IsoSource modeling showed that in upper Herbert River, macroinvertebrates (Δ14C = -171‰ to 22‰) and juvenile salmonids (Δ14C = −102‰ to 17‰) reflected a feeding history of both biofilm (~ 56%) and leaf litter (~ 40%). We estimate that in upper Herbert River on average 36% of the carbon incorporated into consumer biomass is derived from the glacier ecosystem. Thus, 14C-depleted glacial organic carbon was likely transferred to higher trophic levels through a feeding history of bacterial uptake of dissolved organic carbon and subsequent consumption of 14C-depleted biofilm by invertebrates and ultimately fish. Our findings show that the metazoan food web is sustained in part by glacial organic carbon such that future changes in glacial runoff could influence the stability and trophic structure of proglacial aquatic ecosystems.

  11. Updating the results of glacier contribution to the sea level change

    Science.gov (United States)

    Dyurgerov, Mark B.; Abdalati, Waleed Dr. (Technical Monitor)

    2005-01-01

    I have completed an update of global glacier volume change. All data of glacier annual mass balances, surface area over the period 1945/46 till 2004, outside the Greenland and Antarctic ice sheets were included in this update. As the result global glacier volume change have been calculated, also in terms of glacier contribution to sea level change. These results were sent to Working Group 1 and 2 of IPCC-4 as the basis for modeling of sea level towards the end of 2100. In this study I have concentrated on studying glacier systems of different scales, from primary (e.g. Devon ice cap) to regional (e.g. Canadian Arctic), continental scale (e,g., entire Arctic), and global (e.g., change in glacier volume and contribution to sea level rise).

  12. Passive seismic monitoring of the Bering Glacier during its last surge event

    Science.gov (United States)

    Zhan, Z.

    2017-12-01

    The physical causes behind glacier surges are still unclear. Numerous evidences suggest that they probably involve changes in glacier basal conditions, such as switch of basal water system from concentrated large tunnels to a distributed "layer" as "connected cavities". However, most remote sensing approaches can not penetrate to the base to monitor such changes continuously. Here we apply seismic interferometry using ambient noise to monitor glacier seismic structures, especially to detect possible signatures of the hypothesized high-pressure water "layer". As an example, we derive an 11-year long history of seismic structure of the Bering Glacier, Alaska, covering its latest surge event. We observe substantial drops of Rayleigh and Love wavespeeds across the glacier during the surge event, potentially caused by changes in crevasse density, glacier thickness, and basal conditions.

  13. Enhanced ASTER DEMs for Decadal Measurements of Glacier Elevation Changes

    Science.gov (United States)

    Girod, L.; Nuth, C.; Kääb, A.

    2016-12-01

    Elevation change data is critical to the understanding of a number of geophysical processes, including glaciers through the measurement their volume change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system on-board the Terra (EOS AM-1) satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available today, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. We developed MMASTER, an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC) model and the detection and correction of cross-track sensor jitter in order to compute DEMs. Our sensor modeling does not require ground control points and thus potentially allows for automatic processing of large data volumes. When compared to ground truth data, we have assessed a ±5m accuracy in DEM differencing when using our processing method, improved from the ±30m when using the AST14DMO DEM product. We demonstrate and discuss this improved ASTER DEM quality for a number of glaciers in Greenland (See figure attached), Alaska, and Svalbard. The quality of our measurements promises to further unlock the underused potential of ASTER DEMs for glacier volume change time series on a global scale. The data produced by our method will thus help to better understand the response of glaciers to climate change and their influence on runoff and sea level.

  14. Assessing streamflow sensitivity to variations in glacier mass balance

    Science.gov (United States)

    O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis

    2014-01-01

    The mountains ringing the Gulf of Alaska (GOA) receive upwards of 4–8 m yr−1 of precipitation (Simpson et al.2005; Weingartner et al. 2005; O’Neel 2012), much of which runs off into productive coastal waters. The alpine landscape is heavily glacierized, and storage and turnover of water by glaciers substantially influences the regional surface water balance (Neal et al. 2010). In turn, the land-to-ocean flux of freshwater impacts the biogeochemistry, physical oceanography, freshwater and marine ecology of the downstream components of the GOA ecosystem (e.g., Royer et al. 2001; Hood and Scott 2008). In this way, the links between terrestrial and ocean ecosystems along the GOA have widespread impacts on regional socioeconomic issues including water and hydropower resources, fish populations, and sea level change (Dorava and Milner 2000; Royer and Grosch 2006; Cherry et al. 2010; Gardner et al. 2013). Moreover, predicting future changes in physical, chemical and biological processes in near-shore ecosystems along the GOA hinges, in part, on developing a robust understanding of water storage and transfer by glaciers through streams to the ocean.

  15. Climate-induced glacier and snow loss imperils alpine stream insects

    Science.gov (United States)

    Giersch, J. Joseph; Hotaling, Scott; Kovach, Ryan; Jones, Leslie A.; Muhlfeld, Clint C.

    2017-01-01

    Climate warming is causing rapid loss of glaciers and snowpack in mountainous regions worldwide. These changes are predicted to negatively impact the habitats of many range-restricted species, particularly endemic, mountaintop species dependent on the unique thermal and hydrologic conditions found only in glacier-fed and snowmelt-driven alpine streams. Though progress has been made, existing understanding of the status, distribution, and ecology of alpine aquatic species, particularly in North America, is lacking, thereby hindering conservation and management programs. Two aquatic insects – the meltwater stonefly Lednia tumana and the glacier stonefly Zapada glacier – were recently proposed for listing under the U.S. Endangered Species Act due to climate-change-induced habitat loss. Using a large dataset (272 streams, 482 total sites) with high-resolution climate and habitat information, we describe the distribution, status, and key environmental features that limit L. tumana and Z. glacier across the northern Rocky Mountains. Lednia tumana was detected in 113 streams (175 sites) within Glacier National Park (GNP) and surrounding areas. The probability of L. tumana occurrence increased with cold stream temperatures and close proximity to glaciers and permanent snowfields. Similarly, densities of L. tumana declined with increasing distance from stream source. Zapada glacier was only detected in 10 streams (20 sites), six in GNP and four in mountain ranges up to ~600 km southwest. Our results show that both L. tumana and Z. glacier inhabit an extremely narrow distribution, restricted to short sections of cold, alpine streams often below glaciers predicted to disappear over the next two decades. Climate warming-induced glacier and snow loss clearly imperils the persistence of L. tumana and Z. glacier throughout their ranges, highlighting the role of mountaintop aquatic invertebrates as sentinels of climate change in mid-latitude regions.

  16. Retreat of Stephenson Glacier, Heard Island, from Remote Sensing and Field Observations

    Science.gov (United States)

    Mitchell, W.; Schmieder, R.

    2017-12-01

    Heard Island (Australian sub-Antarctic territory, 53 S, 73.5 E) is a volcanic island mantled in glaciers, and a UNESCO World Heritage Site both for its geology and ecology. Lying to the south of the Antarctic Convergence, the changes in response to climate seen on Heard Island are likely to be a bellwether for areas further south. Beginning in 1999, American satellites (Landsat 7, EO-1, and Landsat 8) have produced images of the island on a roughly weekly basis. Although the island is often shrouded in clouds, clear images of at least portions of the island are plentiful enough to create a nearly-annual record of the toe of Stephenson Glacier. During this period, Stephenson Glacier retreated by nearly 5 km, and lost 50% of its area. As a result of this retreat, a portion of the glacier now could be classified as a separate glacier. Additionally, in 2016, terrestrial photographs of Stephenson Glacier were taken during a three-week expedition to Heard Island, which accessed the Stephenson Glacier area by boat via the proglacial Stephenson Lagoon. During that work, sonar indicated some depths in the lagoon exceeding 100 m. Much of the loss in glacier length and area occurred during the mid- and late-2000s, with retreat rates slowing toward 2017. At this time, the glacier has retreated so that the main toe is not far from the base of a tall ice falls, while another toe—perhaps now a separate glacier—is land-based. This type of retreat pattern, fast over water and slower on land, is typical of other tidewater glaciers. Further monitoring of Stephenson Glacier and other glaciers on Heard Island will continue using Landsat 8.

  17. Instruments and Methods: A Low-Cost Glacier-Mapping System

    DEFF Research Database (Denmark)

    Christensen, Erik Lintz; Reeh, Niels; Forsberg, René

    2000-01-01

    the capability of acquiring accurate data on location and ice-surface elevation, and adequate-quality data on ice thickness. The system has been applied successfully in mapping the Nioghalvfjerdsfjorden glacier, northeast Greenland, in spite of the difficult conditions with melting water on the glacier surface....... The measurements from the floating part of the glacier have been evaluated by comparison of radar data with laser-altimeter and in situ measurements....

  18. Review article: Hydrological modeling in glacierized catchments of central Asia – status and challenges

    OpenAIRE

    Y. Chen; W. Li; G. Fang; Z. Li

    2017-01-01

    Meltwater from glacierized catchments is one of the most important water supplies in central Asia. Therefore, the effects of climate change on glaciers and snow cover will have increasingly significant consequences for runoff. Hydrological modeling has become an indispensable research approach to water resources management in large glacierized river basins, but there is a lack of focus in the modeling of glacial discharge. This paper reviews the status of hydrological modeli...

  19. Historical glacier outlines from digitized topographic maps of the Swiss Alps

    Science.gov (United States)

    Freudiger, Daphné; Mennekes, David; Seibert, Jan; Weiler, Markus

    2018-04-01

    Since the end of the Little Ice Age around 1850, the total glacier area of the central European Alps has considerably decreased. In order to understand the changes in glacier coverage at various scales and to model past and future streamflow accurately, long-term and large-scale datasets of glacier outlines are needed. To fill the gap between the morphologically reconstructed glacier outlines from the moraine extent corresponding to the time period around 1850 and the first complete dataset of glacier areas in the Swiss Alps from aerial photographs in 1973, glacier areas from 80 sheets of a historical topographic map (the Siegfried map) were manually digitized for the publication years 1878-1918 (further called first period, with most sheets being published around 1900) and 1917-1944 (further called second period, with most sheets being published around 1935). The accuracy of the digitized glacier areas was then assessed through a two-step validation process: the data were (1) visually and (2) quantitatively compared to glacier area datasets of the years 1850, 1973, 2003, and 2010, which were derived from different sources, at the large scale, basin scale, and locally. The validation showed that at least 70 % of the digitized glaciers were comparable to the outlines from the other datasets and were therefore plausible. Furthermore, the inaccuracy of the manual digitization was found to be less than 5 %. The presented datasets of glacier outlines for the first and second periods are a valuable source of information for long-term glacier mass balance or hydrological modelling in glacierized basins. The uncertainty of the historical topographic maps should be considered during the interpretation of the results. The datasets can be downloaded from the FreiDok plus data repository (https://freidok.uni-freiburg.de/data/15008" target="_blank">https://freidok.uni-freiburg.de/data/15008, https://doi.org/10.6094/UNIFR/15008" target="_blank">https://doi.org/10.6094/UNIFR

  20. Terricolous Lichens in the Glacier Forefield of the Pasterze (Eastern Alps, Carinthia, Austria)

    Science.gov (United States)

    Bilovitz, Peter O.; Wallner, Anja; Tutzer, Veronika; Nascimbene, Juri; Mayrhofer, Helmut

    2016-01-01

    Summary The investigation of lichens on soil, plant debris and terricolous mosses in the glacier forefield of the Pasterze yielded 35 lichen species. Placidiopsis oreades Breuss (Verrucariales) is new to Austria. Three sampling sites were established at increasing distance from the glacier, in order to compare species diversity, abundance and composition within the forefield and with four other glacier forefields of the Eastern Alps. PMID:26877565

  1. IceTrendr: a linear time-series approach to monitoring glacier environments using Landsat

    Science.gov (United States)

    Nelson, P.; Kennedy, R. E.; Nolin, A. W.; Hughes, J. M.; Braaten, J.

    2017-12-01

    Arctic glaciers in Alaska and Canada have experienced some of the greatest ice mass loss of any region in recent decades. A challenge to understanding these changing ecosystems, however, is developing globally-consistent, multi-decadal monitoring of glacier ice. We present a toolset and approach that captures, labels, and maps glacier change for use in climate science, hydrology, and Earth science education using Landsat Time Series (LTS). The core step is "temporal segmentation," wherein a yearly LTS is cleaned using pre-processing steps, converted to a snow/ice index, and then simplified into the salient shape of the change trajectory ("temporal signature") using linear segmentation. Such signatures can be characterized as simple `stable' or `transition of glacier ice to rock' to more complex multi-year changes like `transition of glacier ice to debris-covered glacier ice to open water to bare rock to vegetation'. This pilot study demonstrates the potential for interactively mapping, visualizing, and labeling glacier changes. What is truly innovative is that IceTrendr not only maps the changes but also uses expert knowledge to label the changes and such labels can be applied to other glaciers exhibiting statistically similar temporal signatures. Our key findings are that the IceTrendr concept and software can provide important functionality for glaciologists and educators interested in studying glacier changes during the Landsat TM timeframe (1984-present). Issues of concern with using dense Landsat time-series approaches for glacier monitoring include many missing images during the period 1984-1995 and that automated cloud mask are challenged and require the user to manually identify cloud-free images. IceTrendr is much more than just a simple "then and now" approach to glacier mapping. This process is a means of integrating the power of computing, remote sensing, and expert knowledge to "tell the story" of glacier changes.

  2. Glacier Mass Changes of Lake-Terminating Grey and Tyndall Glaciers at the Southern Patagonia Icefield Derived From Geodetic Observations and Energy and Mass Balance Modeling

    Directory of Open Access Journals (Sweden)

    Stephanie S. Weidemann

    2018-06-01

    Full Text Available In this study we demonstrate how energy and mass fluxes vary in space and time for Grey and Tyndall glaciers at the Southern Patagonia Icefield (SPI. Despite the overall glacier retreat of most Patagonian glaciers, a recent increase in mass loss has been observed, but individual glaciers respond differently in terms of spatial and temporal changes. In this context, the detailed investigation of the effect of mass balance processes on recent glacier response to climate forcing still needs refinement. We therefore quantify surface energy-fluxes and climatic mass balance of the two neighboring glaciers, Grey and Tyndall. The COupled Snow and Ice energy and MAss balance model COSIMA is applied to assess recent surface energy and climatic mass balance variability with a high temporal and spatial resolution for a 16-year period between April 2000 and March 2016. The model is driven by downscaled 6-hourly atmospheric data derived from ERA-Interim reanalysis and MODIS/Terra Snow Cover and validated against ablation measurements made in single years. High resolution precipitation fields are determined by using an analytical orographic precipitation model. Frontal ablation is estimated as residual of climatic mass balance and geodetic mass balance derived from TanDEM-X/SRTM between 2000 and 2014. We simulate a positive glacier-wide mean annual climatic mass balance of +1.02 ± 0.52 m w.e. a−1 for Grey Glacier and of +0.68 ± 0.54 m w.e. a−1 for Tyndall Glacier between 2000 and 2014. Climatic mass balance results show a high year to year variability. Comparing climatic mass balance results with previous studies underlines the high uncertainty in climatic mass balance modeling with respect to accumulation on the SPI. Due to the lack of observations accumulation estimates differ from previous studies based on the methodological approaches. Mean annual ice loss by frontal ablation is estimated to be 2.07 ± 0.70 m w.e. a−1 for Grey Glacier and 3.26 ± 0

  3. Rock glaciers Gruben, Muragl and Murtel, Switzerland: Area-wide flow fields, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — Besides their thermal and mechanical properties, rock glaciers are essentially defined by their kinematics. Knowledge of the permafrost flow field provides important...

  4. Associations between accelerated glacier mass wastage and increased summer temperature in coastal regions

    Science.gov (United States)

    Dyurgerov, M.; McCabe, G.J.

    2006-01-01

    Low-elevation glaciers in coastal regions of Alaska, the Canadian Arctic, individual ice caps around the Greenland ice sheet, and the Patagonia Ice Fields have an aggregate glacier area of about 332 ?? 103 km 2 and account for approximately 42% of all the glacier area outside the Greenland and Antarctic ice sheets. They have shown volume loss, especially since the end of the 1980s, increasing from about 45% in the 1960s to nearly 67% in 2003 of the total wastage from all glaciers on Earth outside those two largest ice sheets. Thus, a disproportionally large contribution of coastal glacier ablation to sea level rise is evident. We examine cumulative standardized departures (1961-2000 reference period) of glacier mass balances and air temperature data in these four coastal regions. Analyses indicate a strong association between increases in glacier volume losses and summer air temperature at regional and global scales. Increases in glacier volume losses in the coastal regions also coincide with an accelerated rate of ice discharge from outlet glaciers draining the Greenland and West Antarctic ice sheets. These processes imply further increases in sea level rise. ?? 2006 Regents of the University of Colorado.

  5. Glacier beds that will be exposed in the future: How will geomorphologic and hydrologic processes develop?

    Science.gov (United States)

    Linsbauer, Andreas; Paul, Frank; Haeberli, Wilfried

    2014-05-01

    The rapid shrinkage of glaciers in the Alps has widespread impacts on relief development and hydrology. Slope failures, collapse of lateral moraines, loose debris in glacier fore-fields, new lakes and changing river beds are among the most visible impacts. They already require increased attention by tourists, monitoring by local authorities and mitigation measures (e.g. www.gletschersee.ch). A view into potential future developments (after glaciers have disappeared) is thus of high interest. With recently developed models that reconstruct glacier bed topography from easily available datasets (e.g. glacier outlines and a DEM) over entire mountain ranges, potential developments of the landscape and hydrology can be quantitatively determined. The modelled glacier beds - though they must be seen as a rough first order approximation only - also allows the investigation of a wide range of glaciological relations and dependencies that have been widely applied but were never investigated for a large sample of glaciers so far. A key reason is that information on glacier thickness distribution and total ice volume is sparse and that the future development of glaciers can only be modelled realistically when a glacier bed is available. Hence, with the glacier beds now available there is a larger number of geomorphological, glaciological and hydrological studies ahead of us. This presentation is providing an overview on the lessons learned about glaciers and their future development from the modelled glacier beds, the expected changes in hydrology (e.g. decreasing glacier volume and formation of new lakes) and potential impacts from the altered geomorphology (e.g. debuttressing of rock walls). In particular the flat tongues of larger valley glaciers are rather thick and leave oversteepened lateral moraines or rock walls behind, towering above overdeepenings in the glacier bed that might be filled with water. It is thus expected that the hazard potential will further increase in

  6. Studies of Bagley Icefield during surge and Black Rapids Glacier, Alaska, using spaceborne SAR interferometry

    Science.gov (United States)

    Fatland, Dennis Robert

    1998-12-01

    This thesis presents studies of two temperate valley glaciers---Bering Glacier in the Chugach-St.Elias Mountains, South Central Alaska, and Black Rapids Glacier in the Alaska Range, Interior Alaska---using differential spaceborne radar interferometry. The first study was centered on the 1993--95 surge of Bering Glacier and the resultant ice dynamics on its accumulation area, the Bagley Icefield. The second study site was chosen for purposes of comparison of the interferometry results with conventional field measurements, particularly camera survey data and airborne laser altimetry. A comprehensive suite of software was written to interferometrically process synthetic aperture radar (SAR) data in order to derive estimates of surface elevation and surface velocity on these subject glaciers. In addition to these results, the data revealed unexpected but fairly common concentric rings called 'phase bull's-eyes', image features typically 0.5 to 4 km in diameter located over the central part of various glaciers. These bull's-eyes led to a hypothetical model in which they were interpreted to indicate transitory instances of high subglacial water pressure that locally lift the glacier from its bed by several centimeters. This model is associated with previous findings about the nature of glacier bed hydrology and glacier surging. In addition to the dynamical analysis presented herein, this work is submitted as a contribution to the ongoing development of spaceborne radar interferometry as a glaciological tool.

  7. The new Inventory of Italian Glaciers: Present knowledge, applied methods and preliminary results

    Science.gov (United States)

    Smiraglia, Claudio; Diolaiuti, Guglielmina; D'Agata, Carlo; Maragno, Davide; Baroni, Carlo; Mortara, Gianni; Perotti, Luigi; Bondesan, Aldino; Salvatore, Cristina; Vagliasindi, Marco; Vuillermoz, Elisa

    2013-04-01

    A new Glacier Inventory is an indispensable requirement in Italy due to the importance of evaluating the present glacier coverage and the recent changes driven by climate. Furthermore Alpine glaciers represent a not negligible water and touristic resource then to manage and promote them is needed to know their distribution, size and features. The first Italian Glacier Inventory dates back to 1959-1962. It was compiled by the Italian Glaciological Committee (CGI) in cooperation with the National Research Council (CNR); this first inventory was mainly based on field data coupled with photographs (acquired on the field) and high resolution maps. The Italian glaciation resulted to be spread into 754 ice bodies which altogether were covering 525 km2. Moreover in the Eighties a new inventory was compiled to insert Italian data into the World Glacier Inventory (WGI); aerial photos taken at the end of the Seventies (and in some cases affected by a high and not negligible snow coverage) were used as the main source of data. No other national inventory were compiled after that period. Nevertheless during the last decade the largest part of the Italian Alpine regions have produced regional and local glacier inventories which in several cases are also available and queried through web sites and web GIS application. The actual need is now to obtain a complete, homogeneous and contemporary picture of the Italian Glaciation which encompasses the already available regional and local data and all the new updated information coming from new sources of data (e.g.: orthophotos, satellite imagines, etc..). The challenge was accepted by the University of Milan, the EvK2CNR Committee and the Italian Glaciological Committee who, with the sponsorship of Levissima Spa, are presently working to compile the new updated Italian Glacier Inventory. The first project step is to produce a unique homogeneous glacier database including glacier boundary and surface area and the main fundamental

  8. Mechanism of the 2016 giant twin glacier collapse in Aru range, Tibet

    Science.gov (United States)

    Gilbert, A.; Leinss, S.; Kääb, A.; Kargel, J. S.; Yao, T.; Gascoin, S.; Leonard, G. J.; Berthier, E.; Karki, A.

    2017-12-01

    In northwestern Tibet (34.0°N, 82.2°E) near lake Aru Co, the entire ablation area of two unnamed glaciers (Aru-1 and Aru-2) suddenly collapsed on 17 July 2016 and 21 September 2016 and transformed into a mass flow that ran out over a distance of over several km, killing nine people. These two events are unique and defined a new kind of glacier behavior almost never observed before. The only similar event currently documented is the 2002 Kolka Glacier mass flow (Caucasus Mountains). Using remote sensing observations and 3D thermo-mechanical modeling of the two glaciers, we reconstructed glacier thermal regime, thickness, basal friction evolution and ice damaging state prior to the collapse. We show that frictional change leading to the collapse occurred in the temperate areas of a polythermal structure that is likely close to equilibrium with the local climate. The collapses were driven by a fast and sustained friction change in the temperate part of the glacier for which the glacier shape was not able to adjust due to the cold-based parts providing strong resisting force to sliding. This led to high stresses on the cold margins of the glacier where ice deformation became partially accommodated by fracturing until the final collapse occurred. Field investigations reveal that those two glaciers are flowing on a soft and fine-grained sedimentary lithology prone to landslide activity in the presence of water. This suggests that fast friction change in the temperate part of the glacier is linked to shear strength weakening in the sediment and till underneath the glacier in response to increasing water pore pressure at the glacier base. The Kolka Glacier mass flow also occurred on pyroclastic rocks well known for their landslide activities. This suggests that the three gigantic glacier collapses documented to date involve specific bedrock lithology where failure is driven by shear strength weakening in the glacier till in a landslide-like process. Contrary to a

  9. Ice thickness estimations based on multi-temporal glacier inventories - potential and challenges

    Science.gov (United States)

    Helfricht, Kay; Huss, Matthias; Otto, Jan-Christoph

    2016-04-01

    The ongoing glacier retreat exposes a large number of surface depressions in the former glacier bed that can be filled with water or act as sediment traps. This has already been observed at various sites in Austria and in other mountain areas worldwide. The formation of glacial lakes can constitute an important environmental and socio-economic impact on high mountain systems including water resource management, sediment delivery, natural hazards, energy production and tourism. In general, information on ice thickness distribution is the basis for simulating future glacier change. We used the approach proposed by Huss and Farinotti (2012) to model the ice thickness distribution and potential locations of subglacial depressions. The study is part of the FUTURELAKE project that seeks to model the formation of new glacier lakes and their possible future evolution in the Austria Alps. The required data on glacier extent, surface elevation and slope were taken from the Austrian Glacier Inventories GI1 from 1969, GI2 from 1998 and GI3 from2006 (Fischer et al., 2015). The different glacier outlines and surface elevations from the inventories enable us to evaluate (i) the robustness of the modelled bedrock depressions with respect to different glacier settings, (ii) the power of the model to simulate recently formed glacial lakes, (iii) the similarities in calculated ice thickness distributions across the inventories and (iv) the feasibility of simulating observed changes in ice thickness and glacier volume. In general, the modelled localization of large potential depressions was relatively stable using the observed glacier settings. A number of examples show that recently formed glacial lakes could be detected by the model based on previous glacier extents. The locations of maximum ice depths within different elevation zones appeared to be sensitive to changes in glacier width. However, observed ice thickness changes and, thus, volume changes between the inventories could

  10. Observations and analysis of self-similar branching topology in glacier networks

    Science.gov (United States)

    Bahr, D.B.; Peckham, S.D.

    1996-01-01

    Glaciers, like rivers, have a branching structure which can be characterized by topological trees or networks. Probability distributions of various topological quantities in the networks are shown to satisfy the criterion for self-similarity, a symmetry structure which might be used to simplify future models of glacier dynamics. Two analytical methods of describing river networks, Shreve's random topology model and deterministic self-similar trees, are applied to the six glaciers of south central Alaska studied in this analysis. Self-similar trees capture the topological behavior observed for all of the glaciers, and most of the networks are also reasonably approximated by Shreve's theory. Copyright 1996 by the American Geophysical Union.

  11. Inventory of glaciers in the Eastern Sayan on the basis of space surveys

    Directory of Open Access Journals (Sweden)

    E. Y. Osipov

    2017-01-01

    Full Text Available Small glaciers (areas smaller 1 km2 are the most numerous in most mountainous and glacial regions of the Earth, but their responses to the present‑day climate change are still to be investigated. The paper presents results of the new inventory of small inter‑continental glaciers located in the Eastern Sayan (South of Eastern Siberia. The previous (1950 glacier inventory was made from data of aerial photography carried out in the middle of the 20th century (USSR Glacier Inventory, КЛ 1950. A more complete inventory of the East Sayan glaciers for the state of 2000 (КЛ 2000 had been performed using the multichannel space images (Landsat Enhanced The‑ matic Mapper (ETM+ of 2000 and 2001, and the Shuttle Radar Topography Mission (SRTM digital elevation model (DEM. In addition, some glaciers from the Inventory KL 1950 were re‑mapped on the basis of the Land‑ sat images (TM, ETM+, 1986‑2011 for years 1950, 1990 and 2010. The glacier outlines, determined on the test site from images of medium (Landsat and high (World View‑1 satellite resolution, were compared that con‑ firmed that errors of mapping of small glaciers did not exceed 15%. The KL 2000 contains data on 172 glaciers with a total area of 16.6±1.9 km2. Glacier sizes are from 0.02 to 1.37 km2. For 1950–2000, the total area of the East Sayan glaciers had decreased by 59% (0.40% per a year. In 1990–2000, the glaciers decreased the most rapidly (by an order of magnitude faster as compared to the period of 1950–1990.. In 2000–2010, the area of glaciation slightly increased (by 4% owing to formation of very small glaciers (area smaller 0.5 km2. On the whole, changes in glacier areas in the years 1950–2010 are in the good agreement with changes in amounts of winter precipita‑ tion and summer temperatures. In addition to regional climatic factors, there are also some local factors related to the topography and microclimate of individual glaciers which do also influence

  12. Enhancement of a parsimonious water balance model to simulate surface hydrology in a glacierized watershed

    Science.gov (United States)

    Valentin, Melissa M.; Viger, Roland J.; Van Beusekom, Ashley E.; Hay, Lauren E.; Hogue, Terri S.; Foks, Nathan Leon

    2018-01-01

    The U.S. Geological Survey monthly water balance model (MWBM) was enhanced with the capability to simulate glaciers in order to make it more suitable for simulating cold region hydrology. The new model, MWBMglacier, is demonstrated in the heavily glacierized and ecologically important Copper River watershed in Southcentral Alaska. Simulated water budget components compared well to satellite‐based observations and ground measurements of streamflow, evapotranspiration, snow extent, and total water storage, with differences ranging from 0.2% to 7% of the precipitation flux. Nash Sutcliffe efficiency for simulated and observed streamflow was greater than 0.8 for six of eight stream gages. Snow extent matched satellite‐based observations with Nash Sutcliffe efficiency values of greater than 0.89 in the four Copper River ecoregions represented. During the simulation period 1949 to 2009, glacier ice melt contributed 25% of total runoff, ranging from 12% to 45% in different tributaries, and glacierized area was reduced by 6%. Statistically significant (p < 0.05) decreasing and increasing trends in annual glacier mass balance occurred during the multidecade cool and warm phases of the Pacific Decadal Oscillation, respectively, reinforcing the link between climate perturbations and glacier mass balance change. The simulations of glaciers and total runoff for a large, remote region of Alaska provide useful data to evaluate hydrologic, cryospheric, ecologic, and climatic trends. MWBM glacier is a valuable tool to understand when, and to what extent, streamflow may increase or decrease as glaciers respond to a changing climate.

  13. Glacier variability in the conterminous United States during the twentieth century

    Science.gov (United States)

    McCabe, Gregory J.; Fountain, Andrew G.

    2013-01-01

    Glaciers of the conterminous United States have been receding for the past century. Since 1900 the recession has varied from a 24 % loss in area (Mt. Rainier, Washington) to a 66 % loss in the Lewis Range of Montana. The rates of retreat are generally similar with a rapid loss in the early decades of the 20th century, slowing in the 1950s–1970s, and a resumption of rapid retreat starting in the 1990s. Decadal estimates of changes in glacier area for a subset of 31 glaciers from 1900 to 2000 are used to test a snow water equivalent model that is subsequently employed to examine the effects of temperature and precipitation variability on annual glacier area changes for these glaciers. Model results indicate that both winter precipitation and winter temperature have been important climatic factors affecting the variability of glacier variability during the 20th Century. Most of the glaciers analyzed appear to be more sensitive to temperature variability than to precipitation variability. However, precipitation variability is important, especially for high elevation glaciers. Additionally, glaciers with areas greater than 1 km2 are highly sensitive to variability in temperature.

  14. Contrast induced nephropathy

    DEFF Research Database (Denmark)

    Stacul, Fulvio; van der Molen, Aart J; Reimer, Peter

    2011-01-01

    PURPOSE: The Contrast Media Safety Committee (CMSC) of the European Society of Urogenital Radiology (ESUR) has updated its 1999 guidelines on contrast medium-induced nephropathy (CIN). AREAS COVERED: Topics reviewed include the definition of CIN, the choice of contrast medium, the prophylactic me...

  15. Generalized phase contrast:

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin

    Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast...

  16. Deciphering the contrasting climatic trends between the central Himalaya and Karakoram with 36 years of WRF simulations

    Science.gov (United States)

    Norris, Jesse; Carvalho, Leila M. V.; Jones, Charles; Cannon, Forest

    2018-02-01

    Glaciers over the central Himalaya have retreated at particularly rapid rates in recent decades, while glacier mass in the Karakoram appears stable. To address the meteorological factors associated with this contrast, 36 years of Climate Forecast System Reanalyses (CFSR) are dynamically downscaled from 1979 to 2015 with the Weather Research and Forecasting (WRF) model over High Mountain Asia at convection permitting grid spacing (6.7 km). In all seasons, CFSR shows an anti-cyclonic warming trend over the majority of High Mountain Asia, but distinctive differences are observed between the central Himalaya and Karakoram in winter and summer. In winter and summer, the central Himalaya has been under the influence of an anti-cyclonic trend, which in summer the downscaling shows has reduced cloud cover, leading to significant warming and reduced snowfall in recent years. Contrastingly, the Karakoram has been near the boundary between large-scale cyclonic and anti-cyclonic trends and has not experienced significant snowfall or temperature changes in winter or summer, despite significant trends in summer of increasing cloud cover and decreasing shortwave radiation. This downscaling does not identify any trends over glaciers in closer neighboring regions to the Karakoram (e.g., Hindu Kush and the western Himalaya) where glaciers have retreated as over the central Himalaya, indicating that there are other factors driving glacier mass balance that this downscaling is unable to capture. While this study does not fully explain the Karakoram anomaly, the identified trends detail important meteorological contributions to the observed differences between central Himalaya and Karakoram glacier evolution in recent decades.

  17. A High-Resolution Sensor Network for Monitoring Glacier Dynamics

    Science.gov (United States)

    Edwards, S.; Murray, T.; O'Farrell, T.; Rutt, I. C.; Loskot, P.; Martin, I.; Selmes, N.; Aspey, R.; James, T.; Bevan, S. L.; Baugé, T.

    2013-12-01

    Changes in Greenland and Antarctic ice sheets due to ice flow/ice-berg calving are a major uncertainty affecting sea-level rise forecasts. Latterly GNSS (Global Navigation Satellite Systems) have been employed extensively to monitor such glacier dynamics. Until recently however, the favoured methodology has been to deploy sensors onto the glacier surface, collect data for a period of time, then retrieve and download the sensors. This approach works well in less dynamic environments where the risk of sensor loss is low. In more extreme environments e.g. approaching the glacial calving front, the risk of sensor loss and hence data loss increases dramatically. In order to provide glaciologists with new insights into flow dynamics and calving processes we have developed a novel sensor network to increase the robustness of data capture. We present details of the technological requirements for an in-situ Zigbee wireless streaming network infrastructure supporting instantaneous data acquisition from high resolution GNSS sensors thereby increasing data capture robustness. The data obtained offers new opportunities to investigate the interdependence of mass flow, uplift, velocity and geometry and the network architecture has been specifically designed for deployment by helicopter close to the calving front to yield unprecedented detailed information. Following successful field trials of a pilot three node network during 2012, a larger 20 node network was deployed on the fast-flowing Helheim glacier, south-east Greenland over the summer months of 2013. The utilisation of dual wireless transceivers in each glacier node, multiple frequencies and four ';collector' stations located on the valley sides creates overlapping networks providing enhanced capacity, diversity and redundancy of data 'back-haul', even close to ';floor' RSSI (Received Signal Strength Indication) levels around -100 dBm. Data loss through radio packet collisions within sub-networks are avoided through the

  18. Lacustrine Records of Holocene Mountain Glacier Fluctuations from Western Greenland

    Science.gov (United States)

    Schweinsberg, A.; Briner, J. P.; Bennike, O.

    2014-12-01

    Recent studies have focused on documenting fluctuations of the Greenland Ice Sheet margin throughout the Holocene but few data exist that constrain past changes of local glaciers independent of the ice sheet. Our research combines proglacial lake sediment analysis with cosmogenic 10Be dating of Holocene moraines and radiocarbon dating of ice-cap-killed vegetation with an overall objective to use this multi-proxy approach to generate a detailed record of the coupled climate-glacier system through the Holocene. Here, we present lacustrine records of mountain glacier variability from continuous pro-glacial lake sediment sequences recovered from two glaciated catchments in northeastern Nuussuaq, western Greenland. We use radiocarbon-dated sediments from Sikuiui and Pauiaivik lakes to reconstruct the timing of advance and retreat of local glaciers. Sediments were characterized with magnetic susceptibility (MS), gamma density, Itrax XRF and visible reflectance spectroscopy at 0.2 cm intervals and sediment organic matter at 0.5 cm intervals. Basal radiocarbon ages provide minimum-age constraints on deglaciation from Sikuiui and Pauiaivik lakes of ~9.6 and 8.7 ka, respectively. Organic-rich gyttja from deglaciation until ~5.0 ka in Pauiaivik Lake suggests minimal glacial extent there while slightly elevated MS values from ~9.0 - 7.0 ka in Sikuiui Lake may reflect early Holocene glacial advances. Minerogenic sediment input gradually increases starting at ~5.0 ka in Pauiaivik Lake, which we interpret as the onset of Neoglaciation in the catchment. Furthermore, a distinct episode of enhanced glacial activity from ~4.0 - 2.2 ka in Sikuiui Lake may be correlative to a period of persistent snowline lowering evidenced by radiocarbon dates of ice-killed vegetation from nearby ice cap margins. Results from these lacustrine records and our ice-killed vegetation dataset suggest a middle Holocene onset of Neoglaciation ~5.0 - 4.0 ka in this region. We are supplementing these records

  19. Der terminus προνοητησ in der Byzantinischen verwaltung

    Directory of Open Access Journals (Sweden)

    Wassiliou-Seibt Alexandra-Kyriaki

    2013-01-01

    Full Text Available The article examines on the basis of the small number of essential literary and sigillographic evidence the scope and duties of the προνοηταí (as a terminus technicus in the Byzantine administration. The earliest evidence comes from the 6th century, the latest from the 12th. Already in the Early Byzantine period the scope of their activities is fixed: administration of domains and municipal and fiscal administration. Acting in the capacity of stewards of private and official real estate these people were responsible for collecting and transmitting taxes to the responsible department, minus an allowance for themselves. Their colleagues in the municipal and provincial administration were revenue officers with special authority. In the provincial administration of the 11th the pronoetai were sometimes also άναγραφείς in their region. Till now we know only one example of a commander of a thema who was at the same time also a προνοητής (Eustathios Charsianites. The προνοηταί τού δημοσίου (scil. fiscus were authorized to exact outstanding taxes. A special case is the προνοητής of the alms-house of Michael Attaleiates in Rhaidestos, because he was the highest administrator of all its estates and dependencies. Normally the προνοηταί were administrators of a lower rank in the domains, subject to the οίκονόμος or the κουράτωρ.

  20. The NH2 terminus regulates voltage-dependent gating of CALHM ion channels.

    Science.gov (United States)

    Tanis, Jessica E; Ma, Zhongming; Foskett, J Kevin

    2017-08-01

    Calcium homeostasis modulator protein-1 (CALHM1) and its Caenorhabditis elegans (ce) homolog, CLHM-1, belong to a new family of physiologically important ion channels that are regulated by voltage and extracellular Ca 2+ (Ca 2+ o ) but lack a canonical voltage-sensing domain. Consequently, the intrinsic voltage-dependent gating mechanisms for CALHM channels are unknown. Here, we performed voltage-clamp experiments on ceCLHM-1 chimeric, deletion, insertion, and point mutants to assess the role of the NH 2 terminus (NT) in CALHM channel gating. Analyses of chimeric channels in which the ceCLHM-1 and human (h)CALHM1 NH 2 termini were interchanged showed that the hCALHM1 NT destabilized channel-closed states, whereas the ceCLHM-1 NT had a stabilizing effect. In the absence of Ca 2+ o , deletion of up to eight amino acids from the ceCLHM-1 NT caused a hyperpolarizing shift in the conductance-voltage relationship with little effect on voltage-dependent slope. However, deletion of nine or more amino acids decreased voltage dependence and induced a residual conductance at hyperpolarized voltages. Insertion of amino acids into the NH 2 -terminal helix also decreased voltage dependence but did not prevent channel closure. Mutation of ceCLHM-1 valine 9 and glutamine 13 altered half-maximal activation and voltage dependence, respectively, in 0 Ca 2+ In 2 mM Ca 2+ o , ceCLHM-1 NH 2 -terminal deletion and point mutant channels closed completely at hyperpolarized voltages with apparent affinity for Ca 2+ o indistinguishable from wild-type ceCLHM-1, although the ceCLHM-1 valine 9 mutant exhibited an altered conductance-voltage relationship and kinetics. We conclude that the NT plays critical roles modulating voltage dependence and stabilizing the closed states of CALHM channels. Copyright © 2017 the American Physiological Society.

  1. USING LANDSAT IMAGES AND GIS TO ASSESS THE CHANGES OF MER DE GLACE AND MARMOLADA GLACIERS, IN THE LAST THREE DECADES

    Directory of Open Access Journals (Sweden)

    M. M. NISTOR

    2014-06-01

    Full Text Available Using Landsat Images and GIS to Assess the Changes of Mer de Glace and Marmolada Glaciers, in the Last Three Decades. We have demonstrated that Mer de Glace Glacier (GL and Marmolada GL are in continuous retreat. The changes in size and status of terminus points were estimated in various time intervals by satellite images (SIs and Geographic Information Systems (GIS techniques, during the last three decades. The aim of the research was to found the value of the ice melting areas of Mer de Glace GL and Marmolada GL and to calculate the decline rate for both GLs. A large number of GLs have lost ice mass all over the world. Often glaciologists monitor the GLs movements under climate changes and they express their opinions about the ocean level rise, ecosystem challenges and the future implications of GLs decline. The analysed information to quantify the Mer de Glace GL and Marmolada GL areas derived from SIs. By manual vectorization we obtained the outlines of GLs in different years. For 1984, 1999, 2013 we defined the limits for Mer de Glace GL and for 1986, 1999, 2013 we defined the limits for Marmolada GL. These vector layers were compared in order to observe the melting area and to establish the withdrawal rate. The first results indicate that Mer de Glace GL area declined by 2.365 km² between 1984 and 2013 and a mean melting rate of 0.082 km²/year was obtained. Marmolada GL decreased by 1.035 km² between 1986 and 2013 and a mean melting rate of 0.038 km²/year was calculated. We believe that these results represent significant quantitative data about GLs movements regarding two different areas in the Alps Range and may provide knowledge for hydrology, geomorphology and environmental sciences.

  2. Can mountain glacier melting explains the GRACE-observed mass loss in the southeast Tibetan Plateau: From a climate perspective?

    Science.gov (United States)

    Song, Chunqiao; Ke, Linghong; Huang, Bo; Richards, Keith S.

    2015-01-01

    The southeast Tibetan Plateau (SETP) includes the majority of monsoonal temperate glaciers in High Mountain Asia (HMA), which is an important source of water for the upper reaches of several large Asian river systems. Climatic change and variability has substantial impacts on cryosphere and hydrological processes in the SETP. The Gravity Recovery and Climate Experiment (GRACE) gravimetry observations between 2003 and 2009 suggest that there was an average mass loss rate of - 5.99 ± 2.78 Gigatonnes (Gt)/yr in this region. Meanwhile, the hydrological data by model calculations from the GLDAS/Noah and CPC are used to estimate terrestrial water storage (TWS) changes with a slight negative trend of about - 0.3 Gt/yr. The recent studies (Kääb et al., 2012; Gardner et al., 2013) reported the thinning rates of mountain glaciers in HMA based on the satellite laser altimetry, and an approximate estimation of the glacier mass budget in the SETP was 4.69 ± 2.03 Gt/yr during 2003-2009. This estimate accounted for a large proportion ( 78.3%) of the difference between the GRACE TWS and model-calculated TWS changes. To better understand the cause of sharp mass loss existing in the SETP, the correlations between key climatic variables (precipitation and temperature) and the GRACE TWS changes are examined at different timescales between 2003 and 2011. The results show that precipitation is the leading factors of abrupt, seasonal and multi-year undulating signals of GRACE TWS anomaly time series, but with weak correlations with the inter-annual trend and annual mass budget of GRACE TWS. In contrast, the annual mean temperature is tightly associated with the annual net mass budget (r = 0.81, p < 0.01), which indirectly suggests that the GRACE-observed mass loss in the SETP may be highly related to glacial processes.

  3. Factors influencing the distribution of native bull trout and westslope cutthroat trout in western Glacier National Park, Montana

    Science.gov (United States)

    D'Angelo, Vincent S.; Muhlfeld, Clint C.

    2013-01-01

    The widespread declines of native bull trout (Salvelinus confluentus) and westslope cutthroat trout (Oncorhynchus clarkii lewisi) populations prompted researchers to investigate factors influencing their distribution and status in western Glacier National Park, Montana. We evaluated the association of a suite of abiotic factors (stream width, elevation, gradient, large woody debris density, pool density, August mean stream temperature, reach surface area) with the occurrence (presence or absence) of bull trout and westslope cutthroat trout in 79 stream reaches in five sub-drainages containing glacial lakes. We modeled the occurrence of each species using logistic regression and evaluated competing models using an information theoretic approach. Westslope cutthroat trout were widely distributed (47 of 79 reaches), and there appeared to be no restrictions on their distribution other than physical barriers. Westslope cutthroat trout were most commonly found in relatively warm reaches downstream of lakes and in headwater reaches with large amounts of large woody debris and abundant pools. By contrast, bull trout were infrequently detected (10 of 79 reaches), with 7 of the 10 (70%) detections in sub-drainages that have not been compromised by non-native lake trout (S. namaycush). Bull trout were most often found in cold, low-gradient reaches upstream of glacial lakes. Our results indicate that complex stream habitats in sub-drainages free of non-native species are important to the persistence of native salmonids in western Glacier National Park. Results from this study may help managers monitor and protect important habitats and populations, inform conservation and recovery programs, and guide non-native species suppression efforts in Glacier National Park and elsewhere.

  4. Perforations during contrast enema

    International Nuclear Information System (INIS)

    Vogel, H.; Steinkamp, U.; Grabbe, E.; Allgemeines Krankenhaus Ochsenzoll, Hamburg

    1983-01-01

    During contrast enema, perforation into the retroperitoneal space can be differentiated from perforation into the peritoneum and perforation into the intestinal wall associated with formation of barium granulomas or submucosal spreading of the contrast medium. Other special forms are perforation with contrast medium embolism of diverticula; of the processus vermiformis; penetration of contrast medium into fistulous systems and from the operated areas. Risk factors are: balloon catheter, intestinal tubes with a hard tip, preternatural anus, excessive enema pressure, contrast medium additions, preceding manipulations, intestinal diseases, advanced age and delegation of manipulations to assistants and unskilled staff. Children are particularly at risk. (orig.) [de

  5. Contrast induced nephropathy

    DEFF Research Database (Denmark)

    Stacul, Fulvio; van der Molen, Aart J; Reimer, Peter

    2011-01-01

    PURPOSE: The Contrast Media Safety Committee (CMSC) of the European Society of Urogenital Radiology (ESUR) has updated its 1999 guidelines on contrast medium-induced nephropathy (CIN). AREAS COVERED: Topics reviewed include the definition of CIN, the choice of contrast medium, the prophylactic me....../min/1.73 m (2) is CIN risk threshold for intravenous contrast medium. • Hydration with either saline or sodium bicarbonate reduces CIN incidence. • Patients with eGFR = 60 ml/min/1.73 m (2) receiving contrast medium can continue metformin normally....

  6. The current state of glaciers within the Koryak Highland and assessment of their development by the middle of this century

    Directory of Open Access Journals (Sweden)

    M. D. Ananicheva

    2012-01-01

    Full Text Available The Koryak Upland, located in Russian Far East, has so far been poorly studied in terms of glaciology. The information contained in the USSR Glacier Inventory (1982 was obtained by analysis of topographic maps and aerial photography. On the publication date, the Inventory of Koryak Upland included 715 glaciers. To study of the current state of Koryak glaciers, we used satellite imageries – Landsat, Terra /Aqua (EOS AM-1 and ASTER. Deciphering the scenes showed that a significant portion of the glaciers melted away since the mid-1970's until now. We have found only 237 glaciers. Some glaciers are appeared to be rock glaciers, filled with detrital material, cemented by ice in a single body. They might be taken for real glaciers while categorization. The analysis of the retreat (reduction in area of Koryak glaciers by groups with the same morphological type and the same aspect was conducted. The total retreat of the glaciers of this region varied from 40 (for those measured in situ to 70% (mean total as compared to aerial photography surveys (1950. This is the most intense reduction among the studied glacier systems of the Russian Subarctic. It can be explained by the changes in atmospheric circulation due to climate change, the Koryak Upland dries out while the increasing of annual air temperatures. Significant reduction of the glacier area was an incentive for us to undertake a work to assess the evolution of the glaciers in the near future. We used a GCM – ECHAM5 (B1 as the climatic scenario. The projection method has got further development: we have estimated the evolution of glacier systems in which the prevailing type is corries (relatively small circus glacier. The results show a diverse picture of glacier reduction by area, but in general the glacierization will not disappear for the period 2049–2060, reducing the extent by only 17% of the contemporary state.

  7. Distinct regions in the C-Terminus required for GLP-1R cell surface expression, activity and internalisation.

    Science.gov (United States)

    Thompson, Aiysha; Kanamarlapudi, Venkateswarlu

    2015-09-15

    The glucagon-like peptide-1 (GLP-1) receptor (GLP-1R), an important drug target in the treatment of type 2 diabetes, is a G-protein coupled receptor (GPCR) that mediates insulin secretion by GLP-1. The N-terminus controls GLP-1R biosynthetic trafficking to the cell surface but the C-terminus involvement in that trafficking is unknown. The aim of this study was to identify distinct regions within the C-terminal domain required for human GLP-1R (hGLP-1R) cell surface expression, activity and internalisation using a number of C-terminal deletions and site-directed mutations. The results of this study revealed that the residues 411-418 within the C-terminal domain of the hGLP-1R are critical in targeting the newly synthesised receptor to the plasma membrane. The residues 419-430 are important for cAMP producing activity of the receptor, most likely by coupling to Gαs. However, the residues 431-450 within the C-terminus are essential for agonist-induced hGLP-1R internalisation. In conclusion, these findings demonstrate the hGLP-1R has distinct regions within the C-terminal domain required for its cell surface expression, activity and agonist-induced internalisation. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  8. Comparing different methods to model scenarios of future glacier change for the entire Swiss Alps

    Science.gov (United States)

    Linsbauer, A.; Paul, F.; Haeberli, W.

    2012-04-01

    There is general agreement that observed climate change already has strong impacts on the cryosphere. The rapid shrinkage of glaciers during the past two decades as observed in many mountain ranges globally and in particular in the Alps, are impressive confirmations of a changed climate. With the expected future temperature increase glacier shrinkage will likely further accelerate and their role as an important water resource more and more diminish. To determine the future contribution of glaciers to run-off with hydrological models, the change in glacier area and/or volume must be considered. As these models operate at regional scales, simplified approaches to model the future development of all glaciers in a mountain range need to be applied. In this study we have compared different simplified approaches to model the area and volume evolution of all glaciers in the Swiss Alps over the 21st century according to given climate change scenarios. One approach is based on an upward shift of the ELA (by 150 m per degree temperature increase) and the assumption that the glacier extent will shrink until the smaller accumulation area covers again 60% of the total glacier area. A second approach is based on observed elevation changes between 1985 and 2000 as derived from DEM differencing for all glaciers in Switzerland. With a related elevation-dependent parameterization of glacier thickness change and a modelled glacier thickness distribution, the 15-year trends in observed thickness loss are extrapolated into the future with glacier area loss taking place when thickness becomes zero. The models show an overall glacier area reduction between 60-80% until 2100 with some ice remaining at the highest elevations. However, compared to the ongoing temperature increase and considering that several reinforcement feedbacks (albedo lowering, lake formation) are not accounted for, the real area loss might even be stronger. Uncertainties in the modelled glacier thickness have only a

  9. The potential for retreating alpine glaciers to alter alpine ecosystems in the Colorado Front Range

    Science.gov (United States)

    Hall, E.; Baron, J.

    2013-12-01

    Glaciers are retreating at an unprecedented rate. In mid-latitude alpine ecosystems the presence of glaciers and rock glaciers govern rates and ecology of alpine and sub-alpine ecosystems. Changes in the thermal environment due to the loss of isothermal habitat and inputs from glacier melt chemistry are altering alpine ecosystems in unpredictable ways. In particular, glacier may be a source of nitrogen that is altering alpine ecosystem dynamics. Loch Vale Watershed (LVWS) located within Rocky Mountain National Park. LVWS contains a surface glacier (Andrew's glacier) and a rock glacier (Taylor's glacier) at the headwater of each of the two drainages within the watershed. We collected precipitation from a National Atmospheric Deposition Site and surface water from multiple alpine lakes and streams during a particularly high and low snow year in the Colorado Front Range. We also sampled stream and lake sediments at each site to analyze the associated microbial community. Concentrations of nitrate and ammonium, relative abundance of amoA (the gene responsible for a key step in the microbial nitrification pathway), and the dual isotope signal to nitrate all point to snow melt as a key deliverer of nitrogen to ecosystems along the Colorado Front Range. However, late summer surface water chemistry is isotopically similar to the chemistry of glacial ice. This suggests that retreating glacier may be an additional source of N to alpine ecosystems and have the potential to alter microbial community composition, biogeochemical rate processes, and ecosystem function. These dynamics are most likely not unique to the Colorado Front Range and should be globally distributed as glaciers continue to retreat in high altitude ecosystems around the world.

  10. Hydrological response in catchments whit debris covered glaciers in the semi-arid Andes, Chile

    Science.gov (United States)

    Caro, A.; McPhee, J.; MacDonell, S.; Pellicciotti, F.; Ayala, A.

    2016-12-01

    Glaciers in the semi-arid Andes Cordillera in Chile have shrank rapidly during the 20th century. Negative mass balance contributes to increase the surface area of debris-covered glaciers. Recent research in Chile suggests that contributions from glaciers to summer season river flow in dry years is very important, however hydrological processes determining the glacier contribution are still poorly understood in the region. This work seeks to determine appropriate parameters for the simulation of melt volume in two watersheds dominated by debris-covered glaciers, in order to understand its variability in time and space, in the area with the largest population in Chile. The hydrological simulation is performed for the Tapado (30°S) and Pirámide (33ºS) glaciers, which can be defined as cold and temperate respectively. To simulate the hydrological behaviour we adopt the physically-based TOPographic Kinematic wave APproximation model (TOPKAPI-ETH). The hydrometeorological records necessary model runs have been collected through fieldwork from 2013 to 2015. Regarding the calibration of the model parameters melting ETI, its observed that the value for TF in Pirámide is a third of the value for Tapado glacier, while SRF is half in Tapado regarding to Pirámide. The runoff in the glaciers, the constant snow and ice storage are higher in Tapado regarding Pirámide. Results show a contribution of glacial outflow to runoff during 2015 of 55% in Tapado and 77% in Pirámide, with maximum contributions between January and March in Tapado and Pirámide between November and March, presenting the relevance of the permanence of snow cover during spring and shelter that provides debris-covered in reducing the melting glacier. The results have allowed to know the relevance of the glacier contribution to mountain streams, allowing to know the calibration parameters most relevant in the hydrology balance of glacier basins in the Andes.

  11. New inventory of glaciers in southeastern part of the Eastern Sayan Mountains

    Directory of Open Access Journals (Sweden)

    E. Yu. Osipov

    2013-01-01

    Full Text Available Satellite images with high (Quick Bird, 2006, WorldView-1, 2008, 0.5–0.6 m and middle (Landsat-7 ETM +, 2001, 15–30 m resolution were used to map contemporary glaciers on two mountain peaks of south-eastern part of East Sayan Ridge – Munky Sardyk (3491 m a.s.l. and Topographov (3089 m a.s.l.. Topographic maps of 1978 and 1981 and Landsat-7 images (summer 2001 were used to assess glacier changes during second half of XX century. Modern terminal and lateral moraines near glacier snouts were used to reconstruct former outlines during the end of the Little Ice Age (middle of XIX century. Also SRTM data and GPS-surveys in Munku-Sardyk area were applied to measure glacier altitudes. GIS technologies allowed forming digital glacier data base with attribute information and new inventory was made. Totally 13 glaciers with area of 5.1 km² were investigated and mapped. Glaciers are located in vertical range from 2800–3490 m a.s.l. (Munku-Sardyk area and 2340–2950 m a.s.l. (Topographov area. Firn line on glaciers vary from 2540 to 3110 m a.s.l., rising to the southeast. On average, over the past 160 years (since the end of the Little Ice Age glaciers have significantly decreased. Ice area has decreased by 49%, length has diminished by 570 m, the glacier snouts has risen by 124 m. Analysis of regional climate data shows that the rate of deglaciation is well correlated with summer temperatures increasing in the second half of XX century, especially in 1980–1990s. A tendency to recover glacier mass balance was revealed during the last decade based on climatic data.

  12. Regional passive seismic monitoring reveals dynamic glacier activity on Spitsbergen, Svalbard

    Directory of Open Access Journals (Sweden)

    Andreas Köhler

    2015-12-01

    Full Text Available Dynamic glacier activity is increasingly observed through passive seismic monitoring. We analysed near-regional-scale seismicity on the Arctic archipelago of Svalbard to identify seismic icequake signals and to study their spatial–temporal distribution within the 14-year period from 2000 until 2013. This is the first study that uses seismic data recorded on permanent broadband stations to detect and locate icequakes in different regions of Spitsbergen, the main island of the archipelago. A temporary local seismic network and direct observations of glacier calving and surging were used to identify icequake sources. We observed a high number of icequakes with clear spectral peaks between 1 and 8 Hz in different parts of Spitsbergen. Spatial clusters of icequakes could be associated with individual grounded tidewater glaciers and exhibited clear seasonal variability each year with more signals observed during the melt season. Locations at the termini of glaciers, and correlation with visual calving observations in situ at Kronebreen, a glacier in the Kongsfjorden region, show that these icequakes were caused dominantly by calving. Indirect evidence for glacier surging through increased calving seismicity was found in 2003 at Tunabreen, a glacier in central Spitsbergen. Another type of icequake was observed in the area of the Nathorstbreen glacier system. Seismic events occurred upstream of the glacier within a short time period between January and May 2009 during the initial phase of a major glacier surge. This study is the first step towards the generation and implementation of an operational seismic monitoring strategy for glacier dynamics in Svalbard.

  13. The sensitivity of flowline models of tidewater glaciers to parameter uncertainty

    Directory of Open Access Journals (Sweden)

    E. M. Enderlin

    2013-10-01

    Full Text Available Depth-integrated (1-D flowline models have been widely used to simulate fast-flowing tidewater glaciers and predict change because the continuous grounding line tracking, high horizontal resolution, and physically based calving criterion that are essential to realistic modeling of tidewater glaciers can easily be incorporated into the models while maintaining high computational efficiency. As with all models, the values for parameters describing ice rheology and basal friction must be assumed and/or tuned based on observations. For prognostic studies, these parameters are typically tuned so that the glacier matches observed thickness and speeds at an initial state, to which a perturbation is applied. While it is well know that ice flow models are sensitive to these parameters, the sensitivity of tidewater glacier models has not been systematically investigated. Here we investigate the sensitivity of such flowline models of outlet glacier dynamics to uncertainty in three key parameters that influence a glacier's resistive stress components. We find that, within typical observational uncertainty, similar initial (i.e., steady-state glacier configurations can be produced with substantially different combinations of parameter values, leading to differing transient responses after a perturbation is applied. In cases where the glacier is initially grounded near flotation across a basal over-deepening, as typically observed for rapidly changing glaciers, these differences can be dramatic owing to the threshold of stability imposed by the flotation criterion. The simulated transient response is particularly sensitive to the parameterization of ice rheology: differences in ice temperature of ~ 2 °C can determine whether the glaciers thin to flotation and retreat unstably or remain grounded on a marine shoal. Due to the highly non-linear dependence of tidewater glaciers on model parameters, we recommend that their predictions are accompanied by

  14. Phase contrast image synthesis

    DEFF Research Database (Denmark)

    Glückstad, J.

    1996-01-01

    A new method is presented for synthesizing arbitrary intensity patterns based on phase contrast imaging. The concept is grounded on an extension of the Zernike phase contrast method into the domain of full range [0; 2 pi] phase modulation. By controlling the average value of the input phase funct...... function and by choosing appropriate phase retardation at the phase contrast filter, a pure phase to intensity imaging is accomplished. The method presented is also directly applicable in dark field image synthesis....

  15. Dialysis and contrast media

    International Nuclear Information System (INIS)

    Morcos, Sameh K.; Thomsen, Henrik S.; Webb, Judith A.W.

    2002-01-01

    In a previous survey we revealed uncertainty among responders about (a) whether or not to perform hemodialysis in patients with severely reduced renal function who had received contrast medium; and (b) when to perform hemodialysis in patients on regular treatment with hemodialysis or continuous ambulatory dialysis who received contrast medium. Therefore, the Contrast Media Safety Committee of The European Society of Urogenital Radiology decided to review the literature and to issue guidelines. The committee performed a Medline search. Based on this, a report and guidelines were prepared. The report was discussed at the Ninth European Symposium on Urogenital Radiology in Genoa, Italy. Hemodialysis and peritoneal dialysis safely remove both iodinated and gadolinium-based contrast media. The effectiveness of hemodialysis depends on many factors including blood and dialysate flow rate, permeability of dialysis membrane, duration of hemodialysis and molecular size, protein binding, hydrophilicity, and electrical charge of the contrast medium. Generally, several hemodialysis sessions are needed to removal all contrast medium, whereas it takes 3 weeks for continuous ambulatory dialysis to remove the agent completely. There is no need to schedule the dialysis in relation to the injection of iodinated or MR contrast media or the injection of contrast agent in relation to the dialysis program. Hemodialysis does not protect poorly functioning kidneys against contrast-medium-induced nephrotoxicity. Simple guidelines are given. (orig.)

  16. Using Muon Radiography to map the Bedrock Geometry underneath an active Glacier: A Case Study in the Central Swiss Alps

    Science.gov (United States)

    Lechmann, Alessandro; Mair, David; Nishiyama, Ryuichi; Ariga, Akitaka; Ariga, Tomoko; Ereditato, Antonio; Scampoli, Paola; Vladymyrov, Mykhailo; Schlunegger, Fritz

    2016-04-01

    In recent years, muon radiography has been successfully applied to tackle geological issues and has enjoyed an increasing interest, mainly because this methodology enriches the geophysical arsenal by another shallow subsurface imaging tool that may give independent constraints on material density. Muons that originate from the collision of cosmic particles with Earth's atmosphere are able to penetrate the material in question and can finally be recorded by a detector. The irradiation intensity can then be inverted to the density of the traversed material. Various successful two-dimensional attempts have already been made to image e.g. magma chambers inside volcanoes (Lesparre et al., 2012; Nishiyama et al., 2014; Tanaka et al., 2005), but this method has yet to be applied for mapping the base of glaciers, where the density contrasts between ice and underlying bedrock are even greater than those between magma and host rock. While a high Alpine setup limits the possibilities to deploy traditional geophysical methods for surveying the base of glaciers (because of inaccessible terrain, poor infrastructure or the presence of water in the ice), muon radiography might prove to be a promising alternative. The muon intensity data from stereo observation can be related to the three-dimensional geometry of the interface between the glacier and its bedrock. Given a suitable input model, this relation can be solved within the framework of geophysical inverse problems. The final model then gives geologists invaluable information on erosional mechanisms underneath active glaciers, as this has not yet been observed. We test this methodology for a site within the Jungfrau region, situated in the central Swiss Alps. Our first goal is to demonstrate the feasibility of the method through a case study at the Eiger glacier, starting from a toy model in a first phase and continuing with real data in a second phase. For this purpose, we installed cosmic-ray detectors at two sites inside

  17. Synchrotron-based P K-edge XANES spectroscopy reveals rapid changes of phosphorus speciation in the topsoil of two glacier foreland chronosequences

    Science.gov (United States)

    Prietzel, Jörg; Dümig, Alexander; Wu, Yanhong; Zhou, Jun; Klysubun, Wantana

    2013-05-01

    Phosphorus (P) is a crucial element for life on Earth, and the bioavailability of P in terrestrial ecosystems, which is dependent on the soil P stock and its speciation, may limit ecosystem productivity and succession. In our study, for the first time a direct speciation of soil P in two glacier foreland chronosequences has been conducted using synchrotron-based X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The chronosequences are located in the forefields of Hailuogou Glacier (Gongga Shan, China) and Damma Glacier (Swiss Alps). The age since deglaciation of the investigated soils ranges from 0 to 120 years at Hailuogou, and from 15 to >700 years at Damma. Differences in climate conditions (cooler at Damma, in contrast to Hailuogou precluding the establishment of forest in advanced ecosystem succession stages) and in the chemical composition of the parent material result in different soil contents of total P and Fe/Al oxyhydroxides, which are much smaller at Damma than at Hailuogou. Nevertheless, both chronosequences show similar trends of their topsoil P status with increasing soil age. Our study reveals a rapid change of topsoil P speciation in glacier retreat areas already during initial stages of pedogenesis: Initially dominating bedrock-derived apatite-P and Al-bound P is depleted; Fe-bound P and particularly organically-bound P is accumulated. Organic P strongly dominates in the topsoil of the mature soils outside the proglacial area of Damma Glacier (age 700-3000 years), and already 50 years after deglacation in the topsoil of the retreat area of Hailuogou Glacier. A key factor for the change in topsoil P speciation is the establishment of vegetation, resulting in soil organic matter (SOM) accumulation as well as accelerated soil acidification and apatite dissolution by organic acids, which are produced by SOM-degrading micro-organisms, mykorrhiza fungi, and plant roots. Particularly the succession of grassland to forest seems to accelerate the

  18. Greenland surface mass-balance observations from the ice-sheet ablation area and local glaciers

    DEFF Research Database (Denmark)

    Machguth, Horst; Thomsen, Henrik H.; Weidick, Anker

    2016-01-01

    Glacier surface mass-balance measurements on Greenland started more than a century ago, but no compilation exists of the observations from the ablation area of the ice sheet and local glaciers. Such data could be used in the evaluation of modelled surface mass balance, or to document changes in g...

  19. Exploring uncertainty in glacier mass balance modelling with Monte Carlo simulation

    NARCIS (Netherlands)

    Machguth, H.; Purves, R.S.; Oerlemans, J.; Hoelzle, M.; Paul, F.

    2008-01-01

    By means of Monte Carlo simulations we calculated uncertainty in modelled cumulative mass balance over 400 days at one particular point on the tongue of Morteratsch Glacier, Switzerland, using a glacier energy balance model of intermediate complexity. Before uncertainty assessment, the model was

  20. The timing of the maximum extent of the Rhone Glacier at Wangen a.d. Aare

    Energy Technology Data Exchange (ETDEWEB)

    Ivy-Ochs, S.; Schluechter, C. [Bern Univ. (Switzerland); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Beer, J. [EAWAG, Duebendorf (Switzerland)

    1997-09-01

    Erratic blocks found in the region of Wangen a.d. Aare delineate the maximum position of the Solothurn lobe of the Rhone Glacier. {sup 10}Be and {sup 26}Al exposure ages of three of these blocks show that the glacier withdraw from its maximum position at or slightly before 20,000{+-}1800 years ago. (author) 1 fig., 5 refs.

  1. Early 21st century spatially detailed elevation changes of Jammu and Kashmir glaciers (Karakoram–Himalaya)

    DEFF Research Database (Denmark)

    Vijay, Saurabh; Braun, Matthias

    2018-01-01

    Although a number of studies indicate the regional heterogeneity of the glacier elevation and mass changes in high-mountain Asia in the early 21st century, little is known about these changes with high spatial detail for some of the regions. In this study we present respective glacier elevation a...

  2. Morphometric Controls on Glacier Mass Balance of the Puruogangri Ice Field, Central Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Lin Liu

    2016-11-01

    Full Text Available Evaluating the impacts of climatic changes and morphometric features on glacier mass balance is crucial to providing insight into glacier changes and their effects on regional water resources and ecosystems. Here, we presented an evaluation of morphometric effects on the glacier mass balances of the Puruogangri ice field (PIF on the Tibetan Plateau. A clear spatial variability of glacier mass balances, ranging from −0.035 to +0.019 m·w.e.·year−1, was estimated by comparing the TanDEM-X DEM (2012 with the SRTM-X DEM (2000. In general, the observed glacier mass changes were consistent with our fieldwork investigations. Furthermore, by applying the method of linear regression analysis, we found that the mass changes of individual glaciers on the PIF were mainly dominated by the mean altitude (R = 0.84, p < 0.001, however, they were statistically independent of glacier size, aspect, and surface velocity. At a local scale (grid size of 10 × 10 pixels, apart from the factor of altitude, surface velocity was correlated with glacier mass change.

  3. The hydrological role of snow and glaciers in alpine river basins and their distributed modeling

    NARCIS (Netherlands)

    Verbunt, M.; Gurtz, J.; Jasper, K.; Lang, H.; Warmerdam, P.M.M.; Zappa, M.

    2003-01-01

    A temperature index approach including incoming solar radiation was used as a sub-model in the gridded hydrological catchment model WaSiM-ETH to simulate the melt rate of glacierized areas. Melt water and rainfall are transformed into glacier discharge by using linear reservoir approaches. The

  4. Inferring Ice Thickness from a Glacier Dynamics Model and Multiple Surface Datasets.

    Science.gov (United States)

    Guan, Y.; Haran, M.; Pollard, D.

    2017-12-01

    The future behavior of the West Antarctic Ice Sheet (WAIS) may have a major impact on future climate. For instance, ice sheet melt may contribute significantly to global sea level rise. Understanding the current state of WAIS is therefore of great interest. WAIS is drained by fast-flowing glaciers which are major contributors to ice loss. Hence, understanding the stability and dynamics of glaciers is critical for predicting the future of the ice sheet. Glacier dynamics are driven by the interplay between the topography, temperature and basal conditions beneath the ice. A glacier dynamics model describes the interactions between these processes. We develop a hierarchical Bayesian model that integrates multiple ice sheet surface data sets with a glacier dynamics model. Our approach allows us to (1) infer important parameters describing the glacier dynamics, (2) learn about ice sheet thickness, and (3) account for errors in the observations and the model. Because we have relatively dense and accurate ice thickness data from the Thwaites Glacier in West Antarctica, we use these data to validate the proposed approach. The long-term goal of this work is to have a general model that may be used to study multiple glaciers in the Antarctic.

  5. Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS

    DEFF Research Database (Denmark)

    de Juan, Julia; Elosegui, P.; Nettles, M.

    Observations at high spatial and temporal resolution could be key for improving our understanding of the physical processes that govern outlet-glacier flow variations. We collected simultaneous high-rate GPS observations at several locations distributed along and across Helheim Glacier, East...

  6. Contribution of glacier melt to sea-level rise since AD 1865: a regionally differentiated calculation

    NARCIS (Netherlands)

    Zuo, Z.; Oerlemans, J.

    1997-01-01

    The contribution of glacier melt, including the Greenland ice-sheet, to sea-level change since AD 1865 is estimated on the basis of modelled sensitivity of glacier mass balance to climate change and historical temperature data. Calculations are done in a regionally differentiated manner to overcome

  7. Remote Sensing of Cryosphere: Estimation of Mass Balance Change in Himalayan Glaciers

    Science.gov (United States)

    Ambinakudige, Shrinidhi; Joshi, Kabindra

    2012-07-01

    Glacial changes are an important indicator of climate change. Our understanding mass balance change in Himalayan glaciers is limited. This study estimates mass balance of some major glaciers in the Sagarmatha National Park (SNP) in Nepal using remote sensing applications. Remote sensing technique to measure mass balance of glaciers is an important methodological advance in the highly rugged Himalayan terrain. This study uses ASTER VNIR, 3N (nadir view) and 3B (backward view) bands to generate Digital Elevation Models (DEMs) for the SNP area for the years 2002, 2003, 2004 and 2005. Glacier boundaries were delineated using combination of boundaries available in the Global land ice measurement (GLIMS) database and various band ratios derived from ASTER images. Elevation differences, glacial area, and ice densities were used to estimate the change in mass balance. The results indicated that the rate of glacier mass balance change was not uniform across glaciers. While there was a decrease in mass balance of some glaciers, some showed increase. This paper discusses how each glacier in the SNP area varied in its annual mass balance measurement during the study period.

  8. Recent evolution and degradation of the bent Jatunraju glacier (Cordillera Blanca, Peru)

    Czech Academy of Sciences Publication Activity Database

    Emmer, A.; Loarte, E.C.; Klimeš, Jan; Vilímek, V.

    2015-01-01

    Roč. 228, JAN 1 (2015), s. 345-355 ISSN 0169-555X R&D Projects: GA ČR(CZ) GAP209/11/1000 Institutional support: RVO:67985891 Keywords : debris-covered glacier * rock glacier * surface movements * buried ice degradation * supraglacial lakes Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 2.813, year: 2015

  9. High-resolution monitoring of Himalayan glacier dynamics using unmanned aerial vehicles

    NARCIS (Netherlands)

    Immerzeel, W. W.|info:eu-repo/dai/nl/290472113; Kraaijenbrink, P. D A; Shea, J. M.; Shrestha, A. B.; Pellicciotti, F.; Bierkens, M. F P|info:eu-repo/dai/nl/125022794; De Jong, S. M.|info:eu-repo/dai/nl/120221306

    2014-01-01

    Himalayan glacier tongues are commonly debris covered and they are an important source of melt water. However, they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles. Observations of debris-covered glaciers

  10. Greenland surface mass-balance observations from the ice-sheet ablation area and local glaciers

    NARCIS (Netherlands)

    Machguth, Horst; Thomsen, Henrik H.; Weidick, Anker; Ahlstrøm, Andreas P.; Abermann, Jakob; Andersen, Morten L.; Andersen, Signe B.; Bjørk, Anders A.; Box, Jason E.; Braithwaite, Roger J.; Bøggild, Carl E.; Citterio, Michele; Clement, Poul; Colgan, William; Fausto, Robert S.; Gleie, Karin; Gubler, Stefanie; Hasholt, Bent; Hynek, Bernhard; Knudsen, Niels T.; Larsen, Signe H.; Mernild, Sebastian H.; Oerlemans, Johannes; Oerter, Hans; Olesen, Ole B.; Smeets, C. J P Paul; Steffen, Konrad; Stober, Manfred; Sugiyama, Shin; Van As, Dirk; Van Den Broeke, Michiel R.; Van De Wal, Roderik S W

    2016-01-01

    Glacier surface mass-balance measurements on Greenland started more than a century ago, but no compilation exists of the observations from the ablation area of the ice sheet and local glaciers. Such data could be used in the evaluation of modelled surface mass balance, or to document changes in

  11. Gulkana Glacier, Alaska-Mass balance, meteorology, and water measurements, 1997-2001

    Science.gov (United States)

    March, Rod S.; O'Neel, Shad

    2011-01-01

    The measured winter snow, maximum winter snow, net, and annual balances for 1997-2001 in the Gulkana Glacier basin are determined at specific points and over the entire glacier area using the meteorological, hydrological, and glaciological data. We provide descriptions of glacier geometry to aid in estimation of conventional and reference surface mass balances and descriptions of ice motion to aid in the understanding of the glacier's response to its changing geometry. These data provide annual estimates for area altitude distribution, equilibrium line altitude, and accumulation area ratio during the study interval. New determinations of historical area altitude distributions are given for 1900 and annually from 1966 to 2001. As original weather instrumentation is nearing the end of its deployment lifespan, we provide new estimates of overlap comparisons and precipitation catch efficiency. During 1997-2001, Gulkana Glacier showed a continued and accelerated negative mass balance trend, especially below the equilibrium line altitude where thinning was pronounced. Ice motion also slowed, which combined with the negative mass balance, resulted in glacier retreat under a warming climate. Average annual runoff augmentation by glacier shrinkage for 1997-2001 was 25 percent compared to the previous average of 13 percent, in accordance with the measured glacier volume reductions.

  12. How many stakes are required to measure the mass balance of a glacier?

    Science.gov (United States)

    Fountain, A.G.; Vecchia, A.

    1999-01-01

    Glacier mass balance is estimated for South Cascade Glacier and Maclure Glacier using a one-dimensional regression of mass balance with altitude as an alternative to the traditional approach of contouring mass balance values. One attractive feature of regression is that it can be applied to sparse data sets where contouring is not possible and can provide an objective error of the resulting estimate. Regression methods yielded mass balance values equivalent to contouring methods. The effect of the number of mass balance measurements on the final value for the glacier showed that sample sizes as small as five stakes provided reasonable estimates, although the error estimates were greater than for larger sample sizes. Different spatial patterns of measurement locations showed no appreciable influence on the final value as long as different surface altitudes were intermittently sampled over the altitude range of the glacier. Two different regression equations were examined, a quadratic, and a piecewise linear spline, and comparison of results showed little sensitivity to the type of equation. These results point to the dominant effect of the gradient of mass balance with altitude of alpine glaciers compared to transverse variations. The number of mass balance measurements required to determine the glacier balance appears to be scale invariant for small glaciers and five to ten stakes are sufficient.

  13. Assessing the debris around glaciers using remote sensing and random sets

    NARCIS (Netherlands)

    Bandishoev, Mus; Dilo, Arta; Stein, A.; Fonte, C.C.; Goncalves, L.M.S.; Goncalves, G.

    2011-01-01

    Glacier mapping from satellite multispectral image data is hampered by debris cover on glacier surfaces. Information on the spatial distribution and spatial-temporal dynamics of debris, however, bears various kinds of uncertainties. Debris exhibits the same spectral properties as lateral and

  14. Surge of Hispar Glacier, Pakistan, between 2013 and 2017 detected from remote sensing observations

    Science.gov (United States)

    Rashid, Irfan; Abdullah, Tariq; Glasser, Neil F.; Naz, Heena; Romshoo, Shakil Ahmad

    2018-02-01

    This study analyses the behaviour of an actively surging glacier, Hispar, in Pakistan using remote sensing methods. We used 15 m panchromatic band of Landsat 8 OLI from 2013 to 2017 to assess the changes in glacier velocity, glacier geomorphology and supraglacial water bodies. For the velocity estimation, correlation image analysis (CIAS) was used, which is based on normalized cross-correlation (NCC) of satellite data. On-screen digitization was employed to quantify changes in the glacier geomorphology and dynamics of supraglacial water bodies on the glacier. Our velocity estimates indicate that the upper part of the glacier is presently undergoing an active surge which not only affects the debris distribution but also impacts the development of supraglacial water bodies. Velocities in the actively surging part of the main glacier trunk and its three tributaries reach up to 900 m yr- 1. The surge of Hispar also impacts the distribution of supraglacial debris causing folding of the medial moraines features present on the glacier surface. Changes in the number and size of supraglacial lakes and ponds were also observed during the observation period from 2013 to 2017.

  15. Seismic Investigation of the Glacier de la Plaine Morte, Switzerland

    Science.gov (United States)

    Laske, Gabi; Lindner, Fabian; Walter, Fabian; Krage, Manuel

    2017-04-01

    Glacier de la Plaine Morte is a plateau glacier along the border between Valais and Berne cantons. It covers a narrow elevation range and is extremely vulnerable to climate change. During snow melt, it feeds three marginal lakes that have experienced sudden subglacial drainage in recent years, thereby causing flooding in the Simme Valley below. Of greatest concern is Lac des Faverges at the southeastern end of the glacier that has drained near the end of July in recent years, with flood levels reaching capacity of flood control systems downstream. The lake levels are carefully monitored but precise prediction has not yet been achieved. In the search for precursory ice fracturing to the lake drainage to improve forecast, four seismic arrays comprised of five short-period borehole seismometers provided by Eidgenössische Technische Hochschule (ETH), Zürich as well as fifteen 3-component geophones from the Geophysical Instrument Pool Potsdam (GIPP) collected continuous seismic data for about seven weeks during the summer of 2016. We present initial results on discharge dynamics as well as changing noise levels and seismicity before, during and after the drainage of Lac des Faverges. Compared to previous recent years, the 2016 drainage of Lac des Faverges occurred unusually late on August 28. With an aperture between 100 and 200 m, the small arrays recorded many hundred ice quakes per day. A majority of the events exhibits clearly dispersed, high-frequency Rayleigh waves at about 10 Hz and higher. A wide distribution of events allows us to study azimuthal anisotropy and its relationship with the orientation of glacial crevasses.

  16. A 14-year dataset of in situ glacier surface velocities for a tidewater and a land-terminating glacier in Livingston Island, Antarctica

    Science.gov (United States)

    Machío, Francisco; Rodríguez-Cielos, Ricardo; Navarro, Francisco; Lapazaran, Javier; Otero, Jaime

    2017-10-01

    We present a 14-year record of in situ glacier surface velocities determined by repeated global navigation satellite system (GNSS) measurements in a dense network of 52 stakes distributed across two glaciers, Johnsons (tidewater) and Hurd (land-terminating), located on Livingston Island, South Shetland Islands, Antarctica. The measurements cover the time period 2000-2013 and were collected at the beginning and end of each austral summer season. A second-degree polynomial approximation is fitted to each stake position, which allows estimating the approximate positions and associated velocities at intermediate times. This dataset is useful as input data for numerical models of glacier dynamics or for the calibration and validation of remotely sensed velocities for a region where very scarce in situ glacier surface velocity measurements have been available so far. The link to the data repository is as follows: pangaea.de/10.1594/PANGAEA.846791" target="_blank">http://doi.pangaea.de/10.1594/PANGAEA.846791.

  17. A 14-year dataset of in situ glacier surface velocities for a tidewater and a land-terminating glacier in Livingston Island, Antarctica

    Directory of Open Access Journals (Sweden)

    F. Machío

    2017-10-01

    Full Text Available We present a 14-year record of in situ glacier surface velocities determined by repeated global navigation satellite system (GNSS measurements in a dense network of 52 stakes distributed across two glaciers, Johnsons (tidewater and Hurd (land-terminating, located on Livingston Island, South Shetland Islands, Antarctica. The measurements cover the time period 2000–2013 and were collected at the beginning and end of each austral summer season. A second-degree polynomial approximation is fitted to each stake position, which allows estimating the approximate positions and associated velocities at intermediate times. This dataset is useful as input data for numerical models of glacier dynamics or for the calibration and validation of remotely sensed velocities for a region where very scarce in situ glacier surface velocity measurements have been available so far. The link to the data repository is as follows: http://doi.pangaea.de/10.1594/PANGAEA.846791.

  18. Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

    NARCIS (Netherlands)

    Alderkamp, A.C.; Mills, M.M.; van Dijken, G.L.; Laan, P.; Thuróczy, C.-E.; Gerringa, L.J.A.; de Baar, H.J.W.; Payne, C.D.; Visser, R.J.W.; Buma, A.G.J.; Arrigo, K.R.

    2012-01-01

    The phytoplankton community composition and productivity in waters of the Amundsen Sea and surrounding sea ice zone were characterized with respect to iron (Fe) input from melting glaciers. High Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted

  19. Holocene record of glacier variability from lake sediments reveals tripartite climate history for Svalbard

    Science.gov (United States)

    van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis

    2016-04-01

    The Arctic is responding sensitively to ongoing global climate change, warming and moistening faster than any other region on the planet. Holocene proxy paleoclimate time series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. Glaciers rapidly respond to climate shifts as demonstrated by their current demise around the world. This response has a composite climate signature, marked by shifts in hydroclimate (winter precipitation) as well as (summer) temperature. Attendant changes in glacier size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of glacier activity, based on sediments from Hajeren, a glacier-fed lake on northwest Spitsbergen in the High Arctic Svalbard archipelago. Owing to undisturbed sediments and robust age control, we could resolve variability on a sub-centennial scale. To ensure the accurate detection of glacier activity, we applied a toolbox of physical, magnetic and geochemical proxies in conjunction with multivariate statistics. Our findings indicate a three-stage Holocene climate history for Svalbard, driving by melt water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene glacier maximum around 9.5 ka BP, suggests forcing by the melting LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, glaciers disappeared from the catchment. Glaciers reformed around 4.2 ka BP during the regional onset of the Neoglacial, supporting previous findings. This transition did, however, not mark the onset of persistent glacier activity in the catchment, but a series of centennial-scale cycles of growth and decay, including events around 3.3 and 1.1 ka BP. As orbitally driven insolation declined towards the present, the glaciation threshold

  20. Determining the Current and Future Health of Low-Latitude Andean Glaciers Using an Equilibrium Line Altitude Model and Hypsometric Data from the Randolph Glacier Inventory

    Science.gov (United States)

    Malone, A.; MacAyeal, D. R.

    2015-12-01

    Mountain glaciers have been described as the water towers of world, and for many populations in the low-latitude South American Andes, glacial runoff is vital for agricultural, industrial, and basic water needs. Previous studies of low-latitude Andean glaciers suggest a precarious future due to contemporary warming. These studies have looked at trends in freezing level heights or observations of contemporary retreat. However, regional-scale understanding of low-latitude glacial responses to present and future climate change is limited, in part due to incomplete information about the extent and elevation distribution of low-latitude glaciers. The recently published Randolph Glacier Inventory (RGI) (5.0) provides the necessary information about the size and elevation distribution of low-latitude glaciers to begin such studies. We determine the contemporary equilibrium line altitudes (ELAs) for low-latitude Andean glaciers in the RGI, using a numerical energy balance ablation model driven with reanalysis and gridded data products. Contemporary ELAs tend to fall around the peak of the elevation histogram, with an exception being the southern-most outer tropical glaciers whose modeled ELAs tend to be higher than the elevation histogram for that region (see below figure). Also, we use the linear tends in temperature and precipitation from the contemporary climatology to extrapolate 21stcentury climate forcings. Modeled ELAs by the middle on the century are universally predicted to rise, with outer tropical ELAs rising more than the inner tropical glaciers. These trends continue through the end of the century. Finally, we explore how climate variables and parameters in our numerical model may vary for different warming scenarios from United Nation's IPCC AR5 report. We quantify the impacts of these changes on ELAs for various climate change trajectories. These results support previous work on the precarious future of low latitude Andean glaciers, while providing a richer

  1. Holocene and latest Pleistocene climate and glacier fluctuations in Iceland

    Science.gov (United States)

    Geirsdóttir, Áslaug; Miller, Gifford H.; Axford, Yarrow; Ólafsdóttir, Sædís

    2009-10-01

    Multiproxy climate records from Iceland document complex changes in terrestrial climate and glacier fluctuations through the Holocene, revealing some coherent patterns of change as well as significant spatial variability. Most studies on the Last Glacial Maximum and subsequent deglaciation reveal a dynamic Iceland Ice Sheet (IIS) that responded abruptly to changes in ocean currents and sea level. The IIS broke up catastrophically around 15 ka as the Polar Front migrated northward and sea level rose. Indications of regional advance or halt of the glaciers are seen in late Alleröd/early Younger Dryas time and again in PreBoreal time. Due to the apparent rise of relative sea level in Iceland during this time, most sites contain evidence for fluctuating, tidewater glacier termini occupying paleo fjords and bays. The time between the end of the Younger Dryas and the Preboreal was characterized by repeated jökulhlaups that eroded glacial deposits. By 10.3 ka, the main ice sheet was in rapid retreat across the highlands of Iceland. The Holocene thermal maximum (HTM) was reached after 8 ka with land temperatures estimated to be 3 °C higher than the 1961-1990 reference, and net precipitation similar to modern. Such temperatures imply largely ice-free conditions across Iceland in the early to mid-Holocene. Several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8.5 and 8 ka, but no moraines have been detected from that time. Termination of the HTM and onset of Neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4.5 and 4.0 ka, intensifying between 3.0 and 2.5 ka. Although a distinct warming during the Medieval Warm Period is not dramatically apparent in Icelandic records, the interval from ca AD 0 to 1200 is commonly characterized by relative stability with slow rates of change. The literature most commonly describes Little Ice Age moraines (ca AD 1250-1900) as representing the

  2. Climate warming could increase recruitment success in glacier foreland plants.

    Science.gov (United States)

    Mondoni, Andrea; Pedrini, Simone; Bernareggi, Giulietta; Rossi, Graziano; Abeli, Thomas; Probert, Robin J; Ghitti, Michele; Bonomi, Costantino; Orsenigo, Simone

    2015-11-01

    Glacier foreland plants are highly threatened by global warming. Regeneration from seeds on deglaciated terrain will be crucial for successful migration and survival of these species, and hence a better understanding of the impacts of climate change on seedling recruitment is urgently needed to predict future plant persistence in these environments. This study presents the first field evidence of the impact of climate change on recruitment success of glacier foreland plants. Seeds of eight foreland species were sown on a foreland site at 2500 m a.s.l., and at a site 400 m lower in altitude to simulate a 2·7 °C increase in mean annual temperature. Soil from the site of origin was used to reproduce the natural germination substrate. Recruitment success, temperature and water potential were monitored for 2 years. The response of seed germination to warming was further investigated in the laboratory. At the glacier foreland site, seedling emergence was low (0 to approx. 40 %) and occurred in summer in all species after seeds had experienced autumn and winter seasons. However, at the warmer site there was a shift from summer to autumn emergence in two species and a significant increase of summer emergence (13-35 % higher) in all species except two. Survival and establishment was possible for 60-75 % of autumn-emerged seedlings and was generally greater under warmer conditions. Early snowmelt in spring caused the main ecological factors enhancing the recruitment success. The results suggest that warming will influence the recruitment of glacier foreland species primarily via the extension of the snow-free period in spring, which increases seedling establishment and results in a greater resistance to summer drought and winter extremes. The changes in recruitment success observed here imply that range shifts or changes in abundance are possible in a future warmer climate, but overall success may be dependent on interactions with shifts in other components of the

  3. Helheim 2006: Integrated Geophysical Observations of Glacier Flow

    DEFF Research Database (Denmark)

    Nettles, M.; Ahlstrøm, A.; Elosegui, P.

    , and Tsai, 2006) suggests a link to the hydrological cycle. However, little is understood about the mechanism by which the earthquakes occur. We installed sixteen GPS receivers on Helheim glacier, in a network spanning an upglacier distance of ~25~km from a point ~10~km behind the calving front. We also...... installed three GPS receivers at nearby rock sites to help define a stable reference frame. The stations were deployed in late June, 2006, and retrieved in late August, 2006. The GPS receivers recorded at a rate of at least 5~samples/sec. In addition, we operated several receivers for a few days each just...

  4. The N terminus of cGAS de-oligomerizes the cGAS:DNA complex and lifts the DNA size restriction of core-cGAS activity.

    Science.gov (United States)

    Lee, Arum; Park, Eun-Byeol; Lee, Janghyun; Choi, Byong-Seok; Kang, Suk-Jo

    2017-03-01

    Cyclic GMP-AMP synthase (cGAS) is a DNA-sensing enzyme in the innate immune system. Recent studies using core-cGAS lacking the N terminus investigated the mechanism for binding of double-stranded (ds) DNA and synthesis of 2',3'-cyclic GMP-AMP (cGAMP), a secondary messenger that ultimately induces type I interferons. However, the function of the N terminus of cGAS remains largely unknown. Here, we found that the N terminus enhanced the activity of core-cGAS in vivo. Importantly, the catalytic activity of core-cGAS decreased as the length of double-stranded DNA (dsDNA) increased, but the diminished activity was restored by addition of the N terminus. Furthermore, the N terminus de-oligomerized the 2 : 2 complex of core-cGAS and dsDNA into a 1 : 1 complex, suggesting that the N terminus enhanced the activity of core-cGAS by facilitating formation of a monomeric complex of cGAS and DNA. © 2017 Federation of European Biochemical Societies.

  5. Contrast analysis : A tutorial

    NARCIS (Netherlands)

    Haans, A.

    2018-01-01

    Contrast analysis is a relatively simple but effective statistical method for testing theoretical predictions about differences between group means against the empirical data. Despite its advantages, contrast analysis is hardly used to date, perhaps because it is not implemented in a convenient

  6. Localized Glacier Deformation Associated with Filling and Draining of a Glacier-Dammed Lake and Implications for Outburst Flood Hydraulics

    Science.gov (United States)

    Cunico, M. L.; Walder, J. S.; Fountain, A. G.; Trabant, D. C.

    2001-12-01

    During the summer of 2000, we measured displacements of 22 survey targets on the surface of Kennicott Glacier, Alaska, in the vicinity of Hidden Creek Lake, an ice-dammed lake in a tributary valley that fills and drains annually. Targets were distributed over a domain about equal in width to the lake, from near the glacier/lake margin to a distance of about 1 km from the margin. Targets were surveyed over a 24-day period as the lake filled and then drained. Lake stage was independently monitored. Vertical movement of targets generally fell off with distance d from the lake. As the lake filled, targets with d typically about 0.5 m/d--with a few targets rising slightly faster than the lake. The rate of vertical movement fell off rapidly with distance from the lake: for d = ca. 600 m--roughly twice the local ice thickness--targets moved upward only about 10% as fast as lake stage. Vertical movement of targets with d > ca. 1 km seemed to be uncorrelated with lake stage. The general pattern is consistent with the idea that a wedge of water extended beneath the glacier to a distance of perhaps 300 to 400 m from the visible margin of the lake and exerts buoyant stresses on the ice that were transmitted into the main body of the glacier and caused flexure. This scenario bears some resemblance to tidal deflections of ice shelves or tidewater glaciers. For a given value of lake stage, target elevations were invariably higher as the lake drained than as the lake filled. Moreover, survey targets at a distance of about 400 m or more from the lake continued to rise for some time even after the lake began to drain. The lag time between the beginning of lake drainage and the beginning of target downdrop increased with distance from the lake, with the lag being about 14 hours at a distance of 400 m from the lake. (The lake drained completely in approximately 75 hours.) The likeliest explanations for the departure from reversibility and the existence of the time lag are either (i) a

  7. ESTIMATION OF SHIE GLACIER SURFACE MOVEMENT USING OFFSET TRACKING TECHNIQUE WITH COSMO-SKYMED IMAGES

    Directory of Open Access Journals (Sweden)

    Q. Wang

    2017-09-01

    Full Text Available Movement is one of the most important characteristics of glaciers which can cause serious natural disasters. For this reason, monitoring this massive blocks is a crucial task. Synthetic Aperture Radar (SAR can operate all day in any weather conditions and the images acquired by SAR contain intensity and phase information, which are irreplaceable advantages in monitoring the surface movement of glaciers. Moreover, a variety of techniques like DInSAR and offset tracking, based on the information of SAR images, could be applied to measure the movement. Sangwang lake, a glacial lake in the Himalayas, has great potentially danger of outburst. Shie glacier is situated at the upstream of the Sangwang lake. Hence, it is significant to monitor Shie glacier surface movement to assess the risk of outburst. In this paper, 6 high resolution COSMO-SkyMed images spanning from August to December, 2016 are applied with offset tracking technique to estimate the surface movement of Shie glacier. The maximum velocity of Shie glacier surface movement is 51 cm/d, which was observed at the end of glacier tongue, and the velocity is correlated with the change of elevation. Moreover, the glacier surface movement in summer is faster than in winter and the velocity decreases as the local temperature decreases. Based on the above conclusions, the glacier may break off at the end of tongue in the near future. The movement results extracted in this paper also illustrate the advantages of high resolution SAR images in monitoring the surface movement of small glaciers.

  8. Temporal variations in supraglacial debris distribution on Baltoro Glacier, Karakoram between 2001 and 2012

    Science.gov (United States)

    Gibson, Morgan J.; Glasser, Neil F.; Quincey, Duncan J.; Mayer, Christoph; Rowan, Ann V.; Irvine-Fynn, Tristram D. L.

    2017-10-01

    Distribution of supraglacial debris in a glacier system varies spatially and temporally due to differing rates of debris input, transport and deposition. Supraglacial debris distribution governs the thickness of a supraglacial debris layer, an important control on the amount of ablation that occurs under such a debris layer. Characterising supraglacial debris layer thickness on a glacier is therefore key to calculating ablation across a glacier surface. The spatial pattern of debris thickness on Baltoro Glacier has previously been calculated for one discrete point in time (2004) using satellite thermal data and an empirically based relationship between supraglacial debris layer thickness and debris surface temperature identified in the field. Here, the same empirically based relationship was applied to two further datasets (2001, 2012) to calculate debris layer thickness across Baltoro Glacier for three discrete points over an 11-year period (2001, 2004, 2012). Surface velocity and sediment flux were also calculated, as well as debris thickness change between periods. Using these outputs, alongside geomorphological maps of Baltoro Glacier produced for 2001, 2004 and 2012, spatiotemporal changes in debris distribution for a sub-decadal timescale were investigated. Sediment flux remained constant throughout the 11-year period. The greatest changes in debris thickness occurred along medial moraines, the locations of mass movement deposition and areas of interaction between tributary glaciers and the main glacier tongue. The study confirms the occurrence of spatiotemporal changes in supraglacial debris layer thickness on sub-decadal timescales, independent of variation in surface velocity. Instead, variation in rates of debris distribution are primarily attributed to frequency and magnitude of mass movement events over decadal timescales, with climate, regional uplift and erosion rates expected to control debris inputs over centurial to millennial timescales. Inclusion

  9. A new climate and glacier baseline for the Cordillera Vilcanota, Peru, reduces critical information gaps

    Science.gov (United States)

    Salzmann, Nadine; Huggel, Christian; Rohrer, Mario; Silverio, Walter; Mark, Bryan G.; Cochachin, Alejo; Suarez, Wilson; Giráldez, Claudia

    2013-04-01

    The Cordillera Vilcanota in the Southern Peruvian Andes is the second largest ice-covered Cordillera in Peru (after the Cordillera Blanca) and serves for the Cusco Region as a temporary water storage for fresh-water and hydropower generation and irrigation. Despite the Cordillera Vilcanota's size and socio-economic relevance, there has so far no comprehensive baseline data been available for climate and glacier evolution. In the framework of two jointly launched -Peruvian-Swiss climate change impact and adaptation programs (Climate Change Adaptation Programm - PACC; Glacier Change Adaptation and Desaster Risk Reduction Programm - Glacier 513) significant efforts have been undertaken and are on the way to create a climate, glacier and hazard baseline for the Cordillera Vilcanota. Because of the remoteness of the area and the scarcity of available data, multiple sources such as climate stations, climate reanalysis and satellite data have been collected, processed and analyzed. Based on our data, we found only marginal glacier changes between 1962 and 1985, but a massive ice loss since 1985 (about 30% of area and about 45% of volume). These high numbers corroborate studies from other glacierized cordilleras in Peru. The climate data show overall a moderate increase in air temperature, and mostly weak and not significant trends for precipitation sums, which probably cannot fully explain the observed substantial ice loss. The likely increase of specific humidity in the upper troposphere, where the glaciers are located, probably played a major role in the observed massive of the Cordillera Vilcanota over the past decades. The mass balance measurements initiated in 2010 on two glaciers of the Cordillera Vilcanota, and the climate station installed in 2011 on one of the glaciers, preliminarily indicate that ice loss (in water equivalent) is clearly lower that in the Cordillera Blanca. In the near future the data will provide new and important insights on climate and

  10. RECOGNITION OF DRAINAGE TUNNELS DURING GLACIER LAKE OUTBURST EVENTS FROM TERRESTRIAL IMAGE SEQUENCES

    Directory of Open Access Journals (Sweden)

    E. Schwalbe

    2016-06-01

    Full Text Available In recent years, many glaciers all over the world have been distinctly retreating and thinning. One of the consequences of this is the increase of so called glacier lake outburst flood events (GLOFs. The mechanisms ruling such GLOF events are still not yet fully understood by glaciologists. Thus, there is a demand for data and measurements that can help to understand and model the phenomena. Thereby, a main issue is to obtain information about the location and formation of subglacial channels through which some lakes, dammed by a glacier, start to drain. The paper will show how photogrammetric image sequence analysis can be used to collect such data. For the purpose of detecting a subglacial tunnel, a camera has been installed in a pilot study to observe the area of the Colonia Glacier (Northern Patagonian Ice Field where it dams the Lake Cachet II. To verify the hypothesis, that the course of the subglacial tunnel is indicated by irregular surface motion patterns during its collapse, the camera acquired image sequences of the glacier surface during several GLOF events. Applying tracking techniques to these image sequences, surface feature motion trajectories could be obtained for a dense raster of glacier points. Since only a single camera has been used for image sequence acquisition, depth information is required to scale the trajectories. Thus, for scaling and georeferencing of the measurements a GPS-supported photogrammetric network has been measured. The obtained motion fields of the Colonia Glacier deliver information about the glacier’s behaviour before during and after a GLOF event. If the daily vertical glacier motion of the glacier is integrated over a period of several days and projected into a satellite image, the location and shape of the drainage channel underneath the glacier becomes visible. The high temporal resolution of the motion fields may also allows for an analysis of the tunnels dynamic in comparison to the changing

  11. Challenging the Southern Boundary of Active Rock Glaciers in West Greenland

    Science.gov (United States)

    Langley, K.; Abermann, J.

    2017-12-01

    Rock glaciers are permafrost features abundant in mountainous environments and are characterized as `steadily creeping perennially frozen and ice-rich debris on non-glacierised mountain slopes'. Previous studies investigated both the climatic significance and the dynamics of rock glaciers in Greenland, however, there do not exist studies as far south as the Godthåbsfjord area. We recently found evidence of a active rock glacier near Nuuk, around 250 km further south than the previously suggested southern active limit. It shows no signs of pioneer vegetation, which supports its likely dynamic activity. The rock glacier covers an area of ca. 1 km2and its lowest point is at an elevation of about 250 m a.s.l. Here we present the results of a two year field campaign designed to (I) confirm or reject active rock glacier occurrence in the Godthåbsfjord area with innovative methods, (II) study their dynamic regime and (III) investigate the climatic boundary conditions necessary for active rock glacier occurrence in the Sub-Arctic. We use a number of methods to determine the state of the rock glacier. Movement of the landform is assessed using repeat GPS surveying of marked stones and feature tracking based on ortho-photos and DEMs from repeat UAV deployments. Bottom temperature of snow cover (BTS) measurements give an independent first-order estimate of permafrost occurrence. An air temperature sensor deployed near the snout and recording hourly gives a first order estimate of the temperature gradients between Nuuk and the rock glacier, allowing us to assess the climatic boundary conditions required for rock glacier occurrence. BTS measurements show a clear drop in temperatures over the rock glacier compared to the surrounding areas suggesting an active landform with a well demarcated thermal regime. We will assess this independently with the repeat GPS and UAV surveys and will thus be able to confirm or reject the hypothesis of activity by the end of summer 2017.

  12. Neoglacial and historical glacier changes around Kangersuneq fjord in southern West Greenland

    Directory of Open Access Journals (Sweden)

    Weidick, Anker

    2012-12-01

    Full Text Available The Nuup Kangerlua region in southern West Greenland became eglaciated in the early Holocene and by the mid-Holocene, the margin of the Inland Ice was located east of its present position. Discussion of late Holocene changes in the frontal positions of outlets relies on descriptions, paintings, photographs, maps, data from investigations of Norse ruins, aerial photographs and satellite images.The Kangiata Nunaata Sermia glacier system has receded over 20 km during the last two centuries, indicating a marked response to climatic fluctuations during and since the Little Ice Age (LIA. A large advance between 1700 and 1800 was followed by rapid recession in the first half of the 1800s. Limited data from c. 1850–1920 indicate that although the long-term position of the glacier front remained c. 10–12 km behind the LIA maximum, the late 1800s and the early 1900s may have seen a recession followed by an advance that resulted in a pronounced moraine system. The ice-dammed lake Isvand formed during the LIA maximum when meltwater from the western side of Kangiata Nunaata Sermia drained to the Ameralla fjord in the west. This is in contrast to the drainage pattern before the 1700s, when water probably drained to Kangersuneq in the north. Thinning of Kangiata Nunaata Sermia resulted in total drainage of Isvand between 2000 and 2010 and the discharge of water through Austmannadalen has now returned to the same level as that in medieval times.Other outlets in the region, such as Akullersuup Sermia and Qamanaarsuup Sermia have varied in phase with Kangiata Nunaata Sermia, but with amplitudes of only a few kilometres. In contrast, Narsap Sermia has been nearly stationary and Kangilinnguata Sermia may have advanced until the middle of the 1900s.Lowland marine outlets in south-western Greenland were characterised by large amplitude changes during the Neoglacial. Extreme examples, in addition to Kangiata Nunaata Sermia, are Eqalorutsit Killiit Sermiat at the

  13. Model-data comparisons of crevasses in accelerating glaciers exemplified for the 2011-2013 surge of Bering Glacier, Alaska

    Science.gov (United States)

    Trantow, T.; Herzfeld, U. C.

    2017-12-01

    Glacier acceleration, ubiquitous along the periphery of the major icesheets, presents one of the main uncertainties in modeling future global sea-level rise according to the IPCC 5th Assessment Report (2013). The surge phenomenon is one type of glacial acceleration and is the least understood. During a surge, large-scale elevation change and significant crevassing occurs throughout the entire ice system. Crevasses are the most obvious manifestations of the surge dynamics and provide a source of geophysical information that allows reconstruction of deformation processes. The recent surge of the Bering-Bagley Glacier System (BBGS), Alaska, in 2011-2013 provides an excellent test case to study surging through airborne and satellite observations together with numerical modeling. A 3D full-Stokes finite element model of the BBGS has been created using the Elmer/Ice software for structural and dynamical investigations of the surge. A von Mises condition is applied to modeled surface stresses to predict where crevassing would occur during the surge. The model uses CryoSat-2 derived surface topography (Baseline-C), bedrock topography, Glen's flow law with an isothermal assumption and a uniform linear friction law at the ice/bedrock boundary to represent the surge state in early 2011 when peak velocities were observed. Additionally, geostatistical characterization applied to optical satellite imagery provides an observational data set for model-data comparisons. Observed and modeled crevasse characteristics are compared with respect to their location, magnitude and orientation. Similarity mapping applied to the modeled von Mises stress and observed surface roughness values indicates that the two quantities are correlated. Results indicate that large-scale surface crevasses resulting from a surge are connected to the bedrock topography of the glacier system. The model-data comparisons used in this analysis serve to validate the numerical model and provide insight into the

  14. Reinterpretation of the formation of the "crooked moraine" of the debris-covered Hatunraju Glacier (Cordillera Blanca, Perú)

    Science.gov (United States)

    Iturrizaga, L.

    2012-04-01

    The Hatunraju Glacier (9°00'S/70°40'W) is located in the Parón valley in the northern part of the Cordillera Blanca. The almost 4 km long and steeply inclined glacier flows down from the Huandoy-N-Side (6395 m) into the Parón valley to an elevation of 4250 m a.s.l.. The extremely narrow glacier is in its entire ablation area heavily debris-covered. It is one of the few glaciers, which dam with its debris-mantled glacier tongue a main river in this mountain range. In this case the Hatunraju glacier produces the largest glacier-dammed lake in the Cordillera Blanca, the Laguna Parón. In some other aspects, this glacier proves to be distinct from the majority of the glaciers in the Cordillera Blanca: It is flowing on an almost up to 250 m high moraine pedestal ("moraine-dammed raised bed glacier") and the glacier makes a bend of almost 90° when entering into the main valley. The present paper focuses in particular on the last point: the formation of the so called "crooked moraine". It has been explained by Lliboutry (1977) as a result of a glacier lake outburst and the subsequent destruction of the latero-frontal moraine. The later process supposed to be the trigger of the abrupt change in the flow direction of the lower part of the glacier. Recent investigations suggest an alternative genesis of the crooked moraine considering the distinct phases of the glaciation history of the Parón valley. The here proposed formation pattern is also paradigmatic for other crooked debris-covered glaciers, especially in High Asia. Comparative examples will be provided from the Karakoram and Himalayas. The research work on the Hatunraju Glacier is part of a project on the glacial geomorphology in the Tropical Andes financed by the Alexander von Humboldt-Foundation.

  15. Identification of a Novel EF-Loop in the N-terminus of TRPM2 Channel Involved in Calcium Sensitivity

    Directory of Open Access Journals (Sweden)

    Yuhuan Luo

    2018-06-01

    Full Text Available As an oxidative stress sensor, transient receptor potential melastatin 2 (TRPM2 channel is involved in many physiological and pathological processes including warmth sensing, ischemia injury, inflammatory diseases and diabetes. Intracellular calcium is critical for TRPM2 channel activation and the IQ-like motif in the N-terminus has been shown to be important by mediating calmodulin binding. Sequence analysis predicted two potential EF-loops in the N-terminus of TRPM2. Site-directed mutagenesis combining with functional assay showed that substitution with alanine of several residues, most of which are conserved in the typical EF-loop, including D267, D278, D288, and E298 dramatically reduced TRPM2 channel currents. By further changing the charges or side chain length of these conserved residues, our results indicate that the negative charge of D267 and the side chain length of D278 are critical for calcium-induced TRPM2 channel activation. G272I mutation also dramatically reduced the channel currents, suggesting that this site is critical for calcium-induced TRPM2 channel activation. Furthermore, D267A mutant dramatically reduced the currents induced by calcium alone compared with that by ADPR, indicating that D267 residue in D267–D278 motif is the most important site for calcium sensitivity of TRPM2. In addition, inside-out recordings showed that mutations at D267, G272, D278, and E298 had no effect on single-channel conductance. Taken together, our data indicate that D267–D278 motif in the N-terminus as a novel EF-loop is critical for calcium-induced TRPM2 channel activation.

  16. Seasonal variations in vertical migration of glacier lanternfish, Benthosema glaciale

    KAUST Repository

    Dypvik, Eivind; Rø stad, Anders; Kaartvedt, Stein

    2012-01-01

    The seasonal variations in glacier lanternfish (Benthosema glaciale) vertical distribution and diel vertical migration (DVM) were studied by use of a bottom-mounted upward-facing 38 kHz echo sounder deployed at 392 m depth and cabled to shore in Masfjorden (~6052?N, ~524?E), Norway. Acoustic data from July 2007-October 2008 were analyzed, and scattering layers below ~220 m during daytime were attributed to glacier lanternfish based on net sampling in this, and previous studies, as well as from analysis of the acoustic data. At these depths, three different diel behavioral strategies were apparent: normal diel vertical migration (NDVM), inverse DVM (IDVM), and no DVM (NoDVM). NoDVM was present all year, while IDVM was present in autumn and winter, and NDVM was present during spring and summer. The seasonal differences in DVM behavior seem to correlate with previously established seasonal distribution of prey. We hypothesize that in regions with seasonally migrating zooplankton, such as where calanoid copepods overwinter at depth, similar plasticity in DVM behavior might occur in other populations of lanternfishes. 2012 The Author(s).

  17. Seasonal variations in vertical migration of glacier lanternfish, Benthosema glaciale

    KAUST Repository

    Dypvik, Eivind

    2012-06-05

    The seasonal variations in glacier lanternfish (Benthosema glaciale) vertical distribution and diel vertical migration (DVM) were studied by use of a bottom-mounted upward-facing 38 kHz echo sounder deployed at 392 m depth and cabled to shore in Masfjorden (~6052?N, ~524?E), Norway. Acoustic data from July 2007-October 2008 were analyzed, and scattering layers below ~220 m during daytime were attributed to glacier lanternfish based on net sampling in this, and previous studies, as well as from analysis of the acoustic data. At these depths, three different diel behavioral strategies were apparent: normal diel vertical migration (NDVM), inverse DVM (IDVM), and no DVM (NoDVM). NoDVM was present all year, while IDVM was present in autumn and winter, and NDVM was present during spring and summer. The seasonal differences in DVM behavior seem to correlate with previously established seasonal distribution of prey. We hypothesize that in regions with seasonally migrating zooplankton, such as where calanoid copepods overwinter at depth, similar plasticity in DVM behavior might occur in other populations of lanternfishes. 2012 The Author(s).

  18. Black bear density in Glacier National Park, Montana

    Science.gov (United States)

    Stetz, Jeff B.; Kendall, Katherine C.; Macleod, Amy C.

    2013-01-01

    We report the first abundance and density estimates for American black bears (Ursus americanus) in Glacier National Park (NP),Montana, USA.We used data from 2 independent and concurrent noninvasive genetic sampling methods—hair traps and bear rubs—collected during 2004 to generate individual black bear encounter histories for use in closed population mark–recapture models. We improved the precision of our abundance estimate by using noninvasive genetic detection events to develop individual-level covariates of sampling effort within the full and one-half mean maximum distance moved (MMDM) from each bear’s estimated activity center to explain capture probability heterogeneity and inform our estimate of the effective sampling area.Models including the one-halfMMDMcovariate received overwhelming Akaike’s Information Criterion support suggesting that buffering our study area by this distance would be more appropriate than no buffer or the full MMDM buffer for estimating the effectively sampled area and thereby density. Our modelaveraged super-population abundance estimate was 603 (95% CI¼522–684) black bears for Glacier NP. Our black bear density estimate (11.4 bears/100 km2, 95% CI¼9.9–13.0) was consistent with published estimates for populations that are sympatric with grizzly bears (U. arctos) and without access to spawning salmonids. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

  19. Satellite image atlas of glaciers of the world

    Science.gov (United States)

    Williams, Richard S.; Ferrigno, Jane G.; Williams, Richard S.; Ferrigno, Jane G.

    1988-01-01

    U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, contains 11 chapters designated by the letters A through K. Chapter A provides a comprehensive, yet concise, review of the "State of the Earth's Cryosphere at the Beginning of the 21st Century: Glaciers, Global Snow Cover, Floating Ice, and Permafrost and Periglacial Environments," and a "Map/Poster of the Earth's Dynamic Cryosphere," and a set of eight "Supplemental Cryosphere Notes" about the Earth's Dynamic Cryosphere and the Earth System. The next 10 chapters, B through K, are arranged geographically and present glaciological information from Landsat and other sources of historic and modern data on each of the geographic areas. Chapter B covers Antarctica; Chapter C, Greenland; Chapter D, Iceland; Chapter E, Continental Europe (except for the European part of the former Soviet Union), including the Alps, the Pyrenees, Norway, Sweden, Svalbard (Norway), and Jan Mayen (Norway); Chapter F, Asia, including the European part of the former Soviet Union, China, Afghanistan, Pakistan, India, Nepal, and Bhutan; Chapter G, Turkey, Iran, and Africa; Chapter H, Irian Jaya (Indonesia) and New Zealand; Chapter I, South America; Chapter J, North America (excluding Alaska); and Chapter K, Alaska. Chapters A–D each include map plates.

  20. Extreme radionuclide accumulation on alpine glaciers in cryoconites

    International Nuclear Information System (INIS)

    Lettner, H.; Wilflinger, T.; Hubmer, A.K.; Bossew, P.

    2008-01-01

    Full text: Under environmental conditions when radionuclide fallout will not be diluted by media like soil or water, radionuclides deposited may accumulate to unusual high activities. On glacier surfaces conditions as such exist for aerosols and airborne dust deposited with anthropogenic and natural radionuclides attached on their surfaces. In the course of agglomeration processes initiated by melting and redistribution, these particles may concentrate in small depressions, ice pockets, ablation edges etc. and form substances called cryoconites ('ice dust'). As there is no other matrix than the original aerosol particles, cryoconites are a sink for radionuclides and airborne pollutants and their activity levels are among the highest produced by natural processes observed in environmental media. 137 Cs activities found on glaciers in the Austrian alps are between 255 and 136.000 Bq/kg and predominantly derived from Chernobyl, but also from global fallout. Further anthropogenic radionuclides detected are 134 Cs, 90 Sr, 238,239+240 Pu, 241 Am, 125 Sb, 154 Eu, 60 Co and 207 Bi. In combination with the naturally occurring radionuclides 7 Be and 210 Pb and isotopic ratios such as 134 Cs/ 137 Cs, identification and discrimination of the sources, the nuclear weapon tests and the Chernobyl fallout, can be carried out. (author)

  1. THE INTERNET PRESENTATION OF DATABASES OF GLACIERS OF THE SOUTH OF EASTERN SIBERIA

    Directory of Open Access Journals (Sweden)

    A. D. Kitov

    2017-01-01

    Full Text Available The authors consider the technology for creating databases of glaciers in Southern Siberia and the presentation of these databases on the Internet. The technology consists in the recognition and vectorization of spatial, multi-temporal data using GIS techniques, followed by the formation of databases that reflect the spatial and temporal variation of nival-glacial formations. The results of GIS design are presented on the website IG SB RAS and with the help of Internet service ArcGISonline on the public map. The mapping of databases shows the dynamic of nival-glacial formations for three time phases: the beginning of the 20th century (if you have data, its middle (the catalogs of glaciers and topographic maps and the beginning of the 21st century (according to satellite images and field research. Graphic objects are represented as point, line, and polygonal GIS-themes. Point-themes indicate parameters such as the center, lower and upper boundaries of the glacier. Line-themes determine the length and perimeter of the glacier. Polygonal-themes define the contour of the glacier and its area. The attributive table corresponds to the international standard World Glacier Inventory (WGI. The contours of the glaciers of northern Asia are represented conditionally (ellipses at international portals, and attribute characteristics correspond to the state that was displayed in catalogs of glaciers of the USSR, and they are inaccurate. Considered databases are devoid of these shortcomings. Coordinates of the center of glaciers have been refined. Glaciers contours have boundaries, appropriate to space images or topographic maps, in shp-file format. New glaciers of Baikalskiy and Barguzinskiy ridges are also presented. Existing catalogs and databases still do not include these glaciers. Features of the glaciers are examined in the context of the latitudinal transect of southern Siberia, from the Kodar ridge to the Eastern Sayan. GIS-analysis of the Databases

  2. Modeling glacier beds in the Austrian Alps: How many lakes will form in future?

    Science.gov (United States)

    Koehler, Dominik; Geilhausen, Martin; Linsbauer, Andreas

    2014-05-01

    Glacial retreat exposes landscapes with relief characteristics greatly differing from the former ice covered surfaces. If glacial retreat exposes natural basins capable of forming proglacial lakes, then the downstream hydrologic and geomorphic systems in such catchments will be significantly altered due to discharge modifications, sediment trapping, decoupling effects and long term sediment storage (e.g. Geilhausen et al. 2013). Further implications are related to hydropower management, tourism and natural hazards. Consequently, sound knowledge of present day glacier beds ("proglacial zones of tomorrow") and in particular the total number, locations and characteristics of overdeepenings are of importance. For Austria, however, this important information about significant future changes of high alpine regions is yet missing. An interdisciplinary research project is currently in preparation to close this gap. This paper presents results of a pilot study. We used a novel GIS-based approach (GlabTop, cf. Linsbauer et al. 2012) to compute approximate glacier beds in the Austrian Alps. GlabTop ('Glacier bed Topography') is based on an empirical relation between average basal shear stress and elevation range of individual glaciers and makes use of digital elevation models (DEM), glacier outlines and branch lines (i.e. a set of lines covering all important glacier branches). DEMs and glacier outlines were derived from the Austrian glacier inventory (1998) and branch lines were manually digitized. The inventory includes 911 glaciers of which 876 (96%) were considered and 35 were excluded due to size restrictions ( 0.01 km²) with the potential of forming proglacial lakes when glacier retreat reveals the bed. The total area and volume of all overdeepenings is approx. 10 km² and 236 Mio m³ respectively and 33 lakes will be larger than 1 km³. A total glacier volume of 16 ± 5 km³ with an average ice thickness of 36 ± 11 m was calculated for 1998. Comparisons with

  3. The distribution and hydrological significance of rock glaciers in the Nepalese Himalaya

    Science.gov (United States)

    Jones, D. B.; Harrison, S.; Anderson, K.; Selley, H. L.; Wood, J. L.; Betts, R. A.

    2018-01-01

    In the Nepalese Himalaya, there is little information on the number, spatial distribution and morphometric characteristics of rock glaciers, and this information is required if their hydrological contribution is to be understood. Based on freely available fine spatial resolution satellite data accessible through Google Earth, we produced the first comprehensive Nepalese rock glacier inventory, supported through statistical validation and field survey. The inventory includes the location of over 6000 rock glaciers, with a mean specific density of 3.4%. This corresponds to an areal coverage of 1371 km2. Our approach subsampled approximately 20% of the total identified rock glacier inventory (n = 1137) and digitised their outlines so that quantitative/qualitative landform attributes could be extracted. Intact landforms (containing ice) accounted for 68% of the subsample, and the remaining were classified as relict (not containing ice). The majority (56%) were found to have a northerly aspect (NE, N, and NW), and landforms situated within north- to west-aspects reside at lower elevations than those with south- to- east aspects. In Nepal, we show that rock glaciers are situated between 3225 and 5675 m a.s.l., with the mean minimum elevation at the front estimated to be 4977 ± 280 m a.s.l. for intact landforms and 4541 ± 346 m a.s.l. for relict landforms. The hydrological significance of rock glaciers in Nepal was then established by statistically upscaling the results from the subsample to estimate that these cryospheric reserves store between 16.72 and 25.08 billion m3 of water. This study, for the first time, estimates rock glacier water volume equivalents and evaluates their relative hydrological importance in comparison to ice glaciers. Across the Nepalese Himalaya, rock glacier to ice glacier water volume equivalent is 1:9, and generally increases westwards (e.g., ratio = 1:3, West region). This inventory represents a preliminary step for understanding the

  4. Reconstruction of glacier variability from lake sediments reveals dynamic Holocene climate in Svalbard

    Science.gov (United States)

    van der Bilt, Willem G. M.; Bakke, Jostein; Vasskog, Kristian; D'Andrea, William J.; Bradley, Raymond S.; Ólafsdóttir, Sædis

    2015-10-01

    The Arctic is warming faster than anywhere else on Earth. Holocene proxy time-series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. However, available datasets are scarce, unevenly distributed and often of coarse resolution. Glaciers are sensitive recorders of climate shifts and variations in rock-flour production transfer this signal to the lacustrine sediment archives of downstream lakes. Here, we present the first full Holocene record of continuous glacier variability on Svalbard from glacier-fed Lake Hajeren. This reconstruction is based on an undisturbed lake sediment core that covers the entire Holocene and resolves variability on centennial scales owing to 26 dating points. A toolbox of physical, geochemical (XRF) and magnetic proxies in combination with multivariate statistics has allowed us to fingerprint glacier activity in addition to other processes affecting the sediment record. Evidence from variations in sediment density, validated by changes in Ti concentrations, reveal glaciers remained present in the catchment following deglaciation prior to 11,300 cal BP, culminating in a Holocene maximum between 9.6 and 9.5 ka cal BP. Correspondence with freshwater pulses from Hudson Strait suggests that Early Holocene glacier advances were driven by the melting Laurentide Ice Sheet (LIS). We find that glaciers disappeared from the catchment between 7.4 and 6.7 ka cal BP, following a late Hypsithermal. Glacier reformation around 4250 cal BP marks the onset of the Neoglacial, supporting previous findings. Between 3380 and 3230 cal BP, we find evidence for a previously unreported centennial-scale glacier advance. Both events are concurrent with well-documented episodes of North Atlantic cooling. We argue that this brief forcing created suitable conditions for glaciers to reform in the catchment against a background of gradual orbital cooling. These findings highlight the

  5. Medial moraines of glaciers of the Copper River Basin, Alaska: Discrete landslides dominate over other sources

    Science.gov (United States)

    Kargel, J. S.; Fischer, L.; Furfaro, R.; Huggel, C.; Korup, O.; Leonard, G. J.; Uhlmann, M.; Wessels, R. L.; Wolfe, D. F.

    2009-12-01

    Medial moraines are visually dominant structures of most large valley glaciers in the Copper River Basin (CRB), Alaska. Areally extensive but thin (usually rock falls and talus creep; rocks delivered via snow and ice avalanches; ingestion of lateral moraines along tributary convergences; and basal erosional debris. Evidence indicates that in CRB glaciers, discrete large avalanches predominate as the major contributors of moraine mass. Subglacial erosional debris is predominantly pulverized to small grain sizes and flushed. Many large, young avalanches exist on CRB glaciers. Evidence from colorimetry indicates that many medial moraines actually are landslides that have been sheared and swept downglacier, thus mimicking the form of other types of medial moraines formed where tributaries coalesce and flow down valley. Landcover classification of ASTER imagery, qualitative observations from air photos, and semiquantitative field-based estimations of rock color types indicate that on Allen Glacier, and other CRB glaciers, landslides are the sources of most medial moraines. On Allen and Root Glacier, for example, we see very few boulders with obvious signs of basal abrasion, whereas nearly all boulders exhibit signs of irregular fracture, for example in landslides. Such landslides have large effects on the thermal and mass balance of CRB glaciers, sometimes opposing or in other cases accentuating the effects of global/regional climate change. Considering the link between landslides and seismicity, and that Magnitude 8-9 earthquakes may occur nearby only about once a century, which is also the characteristic response time of large glaciers to climate shifts, seismicity must be considered along with climate change induced glacier responses in the CRB. Ultimately, climate has the final word, and already this is evident in the glacier record. Glacial flour is probably almost entirely from bed erosion. We will present estimates of the contributions of landslides and

  6. Contrast agents for MRI

    International Nuclear Information System (INIS)

    Bonnemain, B.

    1994-01-01

    Contrast agents MRI (Magnetic Resonance Imaging) have been developed to improve the diagnostic information obtained by this technic. They mainly interact on T1 and T2 parameters and increase consequently normal to abnormal tissues contrast. The paramagnetic agents which mainly act on longitudinal relaxation rate (T1) are gadolinium complexes for which stability is the main parameter to avoid any release of free gadolinium. The superparamagnetic agents that decrease signal intensity by an effect on transversal relaxation rate (T2) are developed for liver, digestive and lymph node imaging. Many area of research are now opened for optimal use of present and future contrast agents in MRI. (author). 28 refs., 4 tabs

  7. Compressive Phase Contrast Tomography

    International Nuclear Information System (INIS)

    Maia, Filipe; MacDowell, Alastair; Marchesini, Stefano; Padmore, Howard A.; Parkinson, Dula Y.; Pien, Jack; Schirotzek, Andre; Yang, Chao

    2010-01-01

    When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. Interference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher contrast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).

  8. Downscaling the Local Weather Above Glaciers in Complex Topography

    Science.gov (United States)

    Horak, Johannes; Hofer, Marlis; Gutmann, Ethan; Gohm, Alexander; Rotach, Mathias

    2017-04-01

    Glaciers have experienced a substantial ice-volume loss during the 20th century. To study their response to climate change, process-based glacier mass-balance models (PBGMs) are employed, which require a faithful representation of the state of the atmosphere above the glacier at high spatial and temporal resolution. Glaciers are usually located in complex topography where weather stations are scarce or not existent at all due to the remoteness of such sites and the associated high cost of maintenance. Furthermore. the effective resolution of global circulation models is too large to adequately capture the local topography and represent local weather, which is prerequisite for atmospheric input used by PBGMs. Dynamical downscaling is a physically consistent but computationally expensive approach to bridge the scale gap between GCM output and input needed by PBGMs, while statistical downscaling is faster but requires measurements for training. Both methods have their merits, however, a computationally frugal approach that does not rely on measurements is desirable, especially for long term studies of glacier response to future climate. In this study the intermediate complexity atmospheric research model (ICAR) is employed (Gutmann et al., 2016). It simplifies the wind field physics by relying on analytical solutions derived with linear theory. ICAR then advects atmospheric quantities within this wind field. This allows for computationally fast downscaling and yields a physically consistent set of atmospheric variables. First results obtained from downscaling air temperature, precipitation amount, relative humidity and wind speed to 4 × 4 km2 are presented. Preliminary ICAR is applied for a six month simulation period during five years and evaluated for three domains located in very distinct climates, namely the Southern Alps of New Zealand, the Cordillera Blanca in Peru and the European Alps using ERA Interim reanalysis data (ERAI) as forcing data set. The

  9. Present-day and future contributions of glacier runoff to summertime flows in a Pacific Northwest watershed: implications for water resources

    Science.gov (United States)

    Anne W. Nolin; Jeff Phillippe; Anne Jefferson; Sarah L. Lewis

    2010-01-01

    While the impacts of long-term climate change trends on glacier hydrology have received much attention, little has been done to quantify direct glacier runoff contributions to streamflow. This paper presents an approach for determining glacier runoff contributions to streamflow and estimating the effects of increased temperature and decreased glacier area on future...

  10. A Reduced Risk of Infection with Plasmodium vivax and Clinical Protection against Malaria Are Associated with Antibodies against the N Terminus but Not the C Terminus of Merozoite Surface Protein 1†

    Science.gov (United States)

    Nogueira, Paulo Afonso; Piovesan Alves, Fabiana; Fernandez-Becerra, Carmen; Pein, Oliver; Rodrigues Santos, Neida; Pereira da Silva, Luiz Hildebrando; Plessman Camargo, Erney; del Portillo, Hernando A.

    2006-01-01

    Progress towards the development of a malaria vaccine against Plasmodium vivax, the most widely distributed human malaria parasite, will require a better understanding of the immune responses that confer clinical protection to patients in regions where malaria is endemic. The occurrence of clinical protection in P. vivax malaria in Brazil was first reported among residents of the riverine community of Portuchuelo, in Rondônia, western Amazon. We thus analyzed immune sera from this same human population to determine if naturally acquired humoral immune responses against the merozoite surface protein 1 of P. vivax, PvMSP1, could be associated with reduced risk of infection and/or clinical protection. Our results demonstrated that this association could be established with anti-PvMSP1 antibodies predominantly of the immunoglobulin G3 subclass directed against the N terminus but not against the C terminus, in spite of the latter being more immunogenic and capable of natural boosting. This is the first report of a prospective study of P. vivax malaria demonstrating an association of reduced risk of infection and clinical protection with antibodies against an antigen of this parasite. PMID:16622209

  11. Recent Wetting and Glacier Expansion in the Northwest Himalaya and Karakoram.

    Science.gov (United States)

    Yadav, Ram R; Gupta, Anil K; Kotlia, Bahadur S; Singh, Vikram; Misra, Krishna G; Yadava, Akhilesh K; Singh, Anoop K

    2017-07-21

    Hydroclimatic variability driven by global warming in the climatically vulnerable cold semi-arid to arid northwest (NW) Himalaya is poorly constrained due to paucity of continuous weather records and annually resolved proxies. Applying a network of annually resolved tree-ring-width chronologies from semi-arid region of Kishtwar, Jammu and Kashmir, India, we reconstructed April-May standardized precipitation index extending back to A.D. 1439 (576 years). The reconstructed series is featured by the most conspicuous long-term droughts during the 15 th to early 17 th centuries followed by a general wetting, with 1984-2014 being the wettest interval in the past 576 years. The data, consistent with other independently developed tree-ring-based hydrological records from cold semi-arid to arid NW Himalaya and Karakoram, point to an increased regional wetting in the recent decades. Such an increased wetting might have led to the anomalous behaviour of glaciers in the NW Himalaya and Karakoram in contrast to the general receding trends in the central and eastern Himalaya.

  12. Rock glaciers in crystalline catchments: Hidden permafrost-related threats to alpine headwater lakes.

    Science.gov (United States)

    Ilyashuk, Boris P; Ilyashuk, Elena A; Psenner, Roland; Tessadri, Richard; Koinig, Karin A

    2018-04-01

    A global warming-induced transition from glacial to periglacial processes has been identified in mountainous regions around the world. Degrading permafrost in pristine periglacial environments can produce acid rock drainage (ARD) and cause severe ecological damage in areas underlain by sulfide-bearing bedrock. Limnological and paleolimnological approaches were used to assess and compare ARDs generated by rock glaciers, a typical landform of the mountain permafrost domain, and their effects on alpine headwater lakes with similar morphometric features and underlying bedrock geology, but characterized by different intensities of frost action in their catchments during the year. We argue that ARD and its effects on lakes are more severe in the alpine periglacial belt with mean annual air temperatures (MAAT) between -2°C and +3°C, where groundwater persists in the liquid phase for most of the year, in contrast to ARD in the periglacial belt where frost action dominates (MAAT cycle of aquatic organisms should be considered when reconstructing long-term trends in the ecotoxicological state of lakes. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

  13. Generalized Phase Contrast

    CERN Document Server

    Glückstad, Jesper

    2009-01-01

    Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than the restrictive assumptions of conventional Zernike phase contrast analysis and achieves an expanded range of validity beyond weak phase perturbations. The generalized analysis yields design criteria for tuning experimental parameters to achieve optimal performance in terms of accuracy, fidelity and light efficiency. Optimization can address practical issues, such as finding an optimal spatial filter for the chosen application, ...

  14. Mamografia Espectral de Contraste

    OpenAIRE

    Martins, Inês Santiago; Pereira, Inês; Pacheco, Hugo Pisco; Moutinho, Leonor

    2014-01-01

    A mamografia de contraste é uma aplicação recente possível com a mamografia digital directa, que utiliza contraste iodado endovenoso tendo como princípio a neovascularização induzida no cancro da mama, permitindo obter informação morfológica e funcional. Na mamografia espectral de contraste realiza-se uma aquisição simultânea com alta e baixa energia para cada incidência após administração de contraste iodado endovenoso. É depois feita uma imagem recombinada em que são realçadas as áreas que ...

  15. Aspiration of Barium Contrast

    OpenAIRE

    Fuentes Santos, Cristina; Steen, Bárbara

    2014-01-01

    The aspiration of barium contrast is a rare complication that may occur during studies of the digestive tract. Barium is an inert material that can cause anywhere from an asymptomatic mechanical obstruction to serious symptoms of respiratory distress that can result in patient death. We present the case of a 79-year-old male patient in whom we observed the presence of contrast medium residue in the lung parenchyma as an incidental finding during hospitalization. When the patient’s medical fil...

  16. Changing Climate Drives Lagging and Accelerating Glacier Responses and Accelerating Adjustments of the Hazard Regime

    Science.gov (United States)

    Kargel, Jeffrey

    2013-04-01

    It is virtually universally recognized among climate and cryospheric scientists that climate and greenhouse gas abundances are closely correlated. Disagreements mainly pertain to the fundamental triggers for large fluctuations in climate and greenhouse gases during the pre-industrial era, and exactly how coupling is achieved amongst the dynamic solid Earth, the Sun, orbital and rotational dynamics, greenhouse gas abundances, and climate. Also unsettled is the climate sensitivity defined as the absolute linkage between the magnitude of climate warming/cooling and greenhouse gas increase/decrease. Important questions concern lagging responses (either greenhouse gases lagging climate fluctuations, or vice versa) and the causes of the lags. In terms of glacier and ice sheet responses to climate change, there also exist several processes causing lagging responses to climate change inputs. The simplest parameterization giving a glacier's lagging response time, τ, is that given by Jóhanneson et al. (1989), modified slightly here as τ = b/h, where b is a measure of ablation rate and h is a measure of glacier thickness. The exact definitions of τ, b, and h are subject to some interpretive license, but for a back-of-the-envelope approximation, we may take b as the magnitude of the mean ablation rate over the whole ablation area, and h as the mean glacier thickness in the glacier ablation zone. τ remains a bit ambiguous but may be considered as an exponential time scale for a decreasing response of b to a climatic step change. For some climate changes, b and h can be taken as the values prior to the climate change, but for large climatic shifts, this parameterization must be iterated. The actual response of a glacier at any time is the sum of exponentially decreasing responses from past changes. (Several aspects of glacier dynamics cause various glacier responses to differ from this idealized glacier-response theory.) Some important details relating to the retreat (or

  17. KASHKATASH GLACIER FLUCTUATIONS IN THE XVII–XXI CENTURIES FROM CARTOGRAPHIC, DENDROCHRONOLOGICAL AND LICHENOMETRIC DATA

    Directory of Open Access Journals (Sweden)

    I. S. Bushueva

    2012-01-01

    Full Text Available We focused our study on the retreat of a typical valley glacier Kashkatash, located in the Elbrus Area. We compared the old photographs of the glacier forefields (H. Burmester, 1911; H. Altberg, 1927; E.N. Lukasheva, 1932; unknown author, 1939 with the aerial photograph of 1957, 1965, 1987, maps of scale 1:100 000 (1890 and 1:25 000 (1950s, satellite images (CORONA of 1971, ASTER of 2005, EROS of 2006, oblique photographs taken in 1980s–2000s and plans, created by different researches. Using cartographic material and old photographs we reconstructed 14 positions of glacier tongue over the last 120 years. We estimated the linear glacier retreat and the age of numerous stadial moraines basing on geomorphic, tree-ring and lichenometric data and correlated our results with previous sparse glacier fluctuation reconstructions in this region. We identified at least 13 end moraines within the distance of 900 meters from the up-to-date glacier front position. The minimum age of the outer moraine is 450 years according to the tree-ring data. One tree growing on this moraine was damaged by a boulder falling down from a younger moraine under formation in the period from autumn 1839 to spring 1840. Three moraines were deposited in 1870s–1890s. In 20th century the glacier advanced in 1910-s, 1920-s, and 1970–1980-s.

  18. The Inylchek Glacier in Kyrgyzstan, Central Asia: Insight on Surface Kinematics from Optical Remote Sensing Imagery

    Directory of Open Access Journals (Sweden)

    Mohamad Nobakht

    2014-01-01

    Full Text Available Mountain chains of Central Asia host a large number of glaciated areas that provide critical water supplies to the semi-arid populated foothills and lowlands of this region. Spatio-temporal variations of glacier flows are a key indicator of the impact of climate change on water resources as the glaciers react sensitively to climate. Satellite remote sensing using optical imagery is an efficient method for studying ice-velocity fields on mountain glaciers. In this study, temporal and spatial changes in surface velocity associated with the Inylchek glacier in Kyrgyzstan are investigated. We present a detailed map for the kinematics of the Inylchek glacier obtained by cross-correlation analysis of Landsat images, acquired between 2000 and 2011, and a set of ASTER images covering the time period between 2001 and 2007. Our results indicate a high-velocity region in the elevated part of the glacier, moving up to a rate of about 0.5 m/day. Time series analysis of optical data reveals some annual variations in the mean surface velocity of the Inylchek during 2000–2011. In particular, our findings suggest an opposite trend between periods of the northward glacial flow in Proletarskyi and Zvezdochka glacier, and the rate of westward motion observed for the main stream of the Inylchek.

  19. New results on two well-studied glaciers of the Pamir

    Directory of Open Access Journals (Sweden)

    A. A. Yablokov

    2012-01-01

    Full Text Available In summer 2011, after many years of recession, a group of workers from the Hydrographic expeditionary department of the State Hydrometeorological Survey of the Republic Tajikistan visited the Medvezhiy Glacier (at the source of the Vanch River and the Skogach Glacier (basin of the Obihingo River. Medvezhiy Glacier is a surging one and during this visit it was in its active stage. Its length in comparison with 2005 increased by 800–1000 m, but there was no dam at the Abdukagor River and a dam lake which produces mudflow, as it happened in 1960–70s did not created. At nowadays, the Medvezhiy Glacier advanced a bit further than in time of its previous surge in 2001–2002. The topographic survey of the Skogach