Glaciological and chemical studies on ice cores from Hans Tausen ice cap, Greenland

DEFF Research Database (Denmark)

Clausen, H.B.; Stampe, Mia; Hammer, C.U.

2001-01-01

The paper presents studies of various chemical and isotopical parameters from ice cores drilled in the northernmost located ice cap, Hans Tausen Iskappe, Pearyland, Greenland (HT). The 346 m main core (MC95) was drilled to bedrock in 1995 as well as a 35 m shallow core (SC95). A 60 m shallow core...... (SC75) and a 51 m shallow core (SC76) was drilled at two different positions in 1975 and 1976, respectively. A 6 m shallow core (SC94) was drilled in 1994. Continuous stable isotope records exist for all of these cores, total b-activity only from SC75 and SC76. Continuous ECM inferred acidity records...... exist along the 1995 cores (MC95 and SC95) and finally detailed records of dust and water soluble ion concentrations exist on selected parts of MC95. To determine a time scale for the ice core is an important prerequisite for the interpretation of other records. The age scale is based on acid layers...

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.A.N.

2014-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Ice core records provide an annual-scale, 'instrumental-quality' baseline of atmospheric temperature and circulation changes back many thousands of years. (author)

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.A.N.

2015-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Ice core records provide an annual-scale, 'instrumental-quality' baseline of atmospheric temperature and circulation changes back many thousands of years. (author).

Devon island ice cap: core stratigraphy and paleoclimate.

Science.gov (United States)

Koerner, R M

1977-04-01

Valuable paleoclimatic information can be gained by studying the distribution of melt layers in deep ice cores. A profile representing the percentage of ice in melt layers in a core drilled from the Devon Island ice cap plotted against both time and depth shows that the ice cap has experienced a period of very warm summers since 1925, following a period of colder summers between about 1600 and 1925. The earlier period was coldest between 1680 and 1730. There is a high correlation between the melt-layer ice percentage and the mass balance of the ice cap. The relation between them suggests that the ice cap mass balance was zero (accumulation equaled ablation) during the colder period but is negative in the present warmer one. There is no firm evidence of a present cooling trend in the summer conditions on the ice cap. A comparison with the melt-layer ice percentage in cores from the other major Canadian Arctic ice caps shows that the variation of summer conditions found for the Devon Island ice cap is representative for all the large ice caps for about 90 percent of the time. There is also a good correlation between melt-layer percentage and summer sea-ice conditions in the archipelago. This suggests that the search for the northwest passage was influenced by changing climate, with the 19th-century peak of the often tragic exploration coinciding with a period of very cold summers.

Deep ice coring at Dome Fuji Station, Antarctica

Directory of Open Access Journals (Sweden)

Yoshiyuki Fujii

1999-03-01

Full Text Available Deep ice coring was carried out at Dome Fuji Station, Antarctica in 1995 and 1996 following a pilot borehole drilled and cased with FRP pipes in 1993,and reached 2503.52m in December 1996. Total numbers of ice coring runs below the pilot borehole and chip collection were 1369 and 837 respectively. The mean coring depths per run and per day were 1.75m and 8.21m respectively. We report the outline of the coring operation, the system, coring method, and troubles encountered during the coring work.

Pre-cometary ice composition from hot core chemistry.

Science.gov (United States)

Tornow, Carmen; Kührt, Ekkehard; Motschmann, Uwe

2005-10-01

Pre-cometary ice located around star-forming regions contains molecules that are pre-biotic compounds or pre-biotic precursors. Molecular line surveys of hot cores provide information on the composition of the ice since it sublimates near these sites. We have combined a hydrostatic hot core model with a complex network of chemical reactions to calculate the time-dependent abundances of molecules, ions, and radicals. The model considers the interaction between the ice and gas phase. It is applied to the Orion hot core where high-mass star formation occurs, and to the solar-mass binary protostar system IRAS 16293-2422. Our calculations show that at the end of the hot core phase both star-forming sites produce the same prebiotic CN-bearing molecules. However, in the Orion hot core these molecules are formed in larger abundances. A comparison of the calculated values with the abundances derived from the observed line data requires a chemically unprocessed molecular cloud as the initial state of hot core evolution. Thus, it appears that these objects are formed at a much younger cloud stage than previously thought. This implies that the ice phase of the young clouds does not contain CN-bearing molecules in large abundances before the hot core has been formed. The pre-biotic molecules synthesized in hot cores cause a chemical enrichment in the gas phase and in the pre-cometary ice. This enrichment is thought to be an important extraterrestrial aspect of the formation of life on Earth and elsewhere.

Peeking Below the Snow Surface to Explore Amundsen Sea Climate Variability and Locate Optimal Ice-Core Sites

Science.gov (United States)

Neff, P. D.; Fudge, T. J.; Medley, B.

2016-12-01

Observations over recent decades reveal rapid changes in ice shelves and fast-flowing grounded ice along the Amundsen Sea coast of the West Antarctic Ice Sheet (WAIS). Long-term perspectives on this ongoing ice loss are needed to address a central question of Antarctic research: how much and how fast will Antarctic ice-loss raise sea level? Ice cores can provide insight into past variability of the atmospheric (wind) forcing of regional ocean dynamics affecting ice loss. Interannual variability of snow accumulation on coastal ice domes grounded near or within ice shelves reflects local to regional atmospheric circulation near the ice-ocean interface. Records of snow accumulation inferred from shallow ice cores strongly correlate with reanalysis precipitation and pressure fields, but ice cores have not yet been retrieved along the Amundsen Sea coast. High-frequency airborne radar data (NASA Operation IceBridge), however, have been collected over this region and we demonstrate that these data accurately reflect annual stratigraphy in shallow snow and firn (1 to 2 decades of accumulation). This further validates the agreement between radar snow accumulation records and climate reanalysis products. We then explore regional climate controls on local snow accumulation through comparison with gridded reanalysis products, providing a preview of what information longer coastal ice core records may provide with respect to past atmospheric forcing of ocean circulation and WAIS ice loss.

The isotopic composition of methane in polar ice cores

Science.gov (United States)

Craig, H.; Chou, C. C.; Welhan, J. A.; Stevens, C. M.; Engelkemeir, A.

1988-01-01

Air bubbles in polar ice cores indicate that about 300 years ago the atmospheric mixing ratio of methane began to increase rapidly. Today the mixing ratio is about 1.7 parts per million by volume, and, having doubled once in the past several hundred years, it will double again in the next 60 years if current rates continue. Carbon isotope ratios in methane up to 350 years in age have been measured with as little as 25 kilograms of polar ice recovered in 4-meter-long ice-core segments. The data show that: (1) in situ microbiology or chemistry has not altered the ice-core methane concentrations, and (2) that the carbon-13 to carbon-12 ratio of atmospheric CH4 in ice from 100 years and 300 years ago was about 2 per mil lower than at present. Atmospheric methane has a rich spectrum of isotopic sources: the ice-core data indicate that anthropogenic burning of the earth's biomass is the principal cause of the recent C-13H4 enrichment, although other factors may also contribute.

Tree ring and ice core time scales around the Santorini eruption

Science.gov (United States)

Löfroth, Elin; Muscheler, Raimund; Aldahan, Ala; Possnert, Göran; Berggren, Ann-Marie

2010-05-01

When studying cosmogenic radionuclides in ice core and tree ring archives around the Santorini eruption a ~20 year discrepancy was found between the records (Muscheler 2009). In this study a new 10Be dataset from the NGRIP ice core is presented. It has a resolution of 7 years and spans the period 3752-3244 BP (1803-1295 BC). The NGRIP 10Be record and the previously published 10Be GRIP record were compared to the IntCal datasets to further investigate the discrepancy between the ice core and tree ring chronologies. By modelling the 14C production rate based on atmospheric 14C records a comparison could be made to the 10Be flux which is assumed to represent the 10Be production rate. This showed a time shift of ~23 years between the records. The sensitivity of the results to changes in important model parameters was evaluated. Uncertainties in the carbon cycle model cannot explain a substantial part of the timing differences. Potential influences of climate and atmospheric processes on the 10Be deposition were studied using δ18O from the respective cores and GISP2 ice core ion data. The comparison to δ18O revealed a small but significant correlation between 10Be flux and δ18O when the 14C-derived production signal was removed from the 10Be curves. The ion data, as proxies for atmospheric circulation changes, did not show any correlations to the 10Be record or the 10Be/14C difference. When including possible data uncertainties there is still a minimum discrepancy of ~10 years between the 10Be ice core and the 14C tree ring record. Due to lack of alternative explanations it is concluded that the ice core and/or the tree ring chronologies contains unaccounted errors in this range. This also reconciles the radiocarbon 1627-1600 BC (Friedrich et al., 2006) and ice core 1642±5 BC (Vinther et al., 2006) datings of the Santorini eruption. Friedrich, W.L., Kromer, B., Friedrich, M., Heinemeier, J., Pfeiffer, T., & Talamo, S., 2006: Santorini eruption radiocarbon dated to

Low-latitude ice cores and freshwater availability

Science.gov (United States)

Kehrwald, Natalie Marie

2009-12-01

Recent retreat of Tibetan Plateau glaciers affects at least half a billion people. Himalayan glaciers seasonally release meltwater into tributaries of the Indus, Ganges, and Brahmaputra Rivers and supply freshwater necessary to support agricultural and economic practices. Tibetan Plateau glaciers are retreating more rapidly than mountain glaciers elsewhere in the world, and this retreat is accelerating. The Naimona'nyi (30°27'N; 81°91'E, 6050 m a.s.l), Guliya (35°17'N; 81°29'E, 6710 m a.s.l.) and Dasuopu (28°23'N; 85°43'E, 7200 m a.s.l.) ice cores place this recent retreat into a longer time perspective through quantifying climate parameters such as past temperature, aridity, and atmospheric chemistry. Naimona'nyi has not accumulated mass since at least 1950, as evidenced by the virtual lack of radiogenic isotopes (36Cl, 3 H, and beta radioactivity) present in the ice core. These isotopes were produced by U.S. and Soviet atmospheric thermonuclear bomb tests conducted in the 1950s and 1960s and provide independent dating horizons for the ice cores. Lead-210 dates imply that the uppermost preserved glacial ice on Naimona'nyi formed during the 1940s. While this is the highest documented glacial thinning in the world other glaciers at elevations similar to that of Naimona'nyi, such as Kilimanjaro (3°4'S; 37°21'E, 5893 m a.s.l.), are also losing mass at their summits. The global scope of high-elevation glacial thinning suggests that ablation on the Earth's highest ice fields may be more prevalent as global mean temperatures continue to increase. Glacial thinning has not been taken into account in future projections of regional freshwater availability, and the net mass loss indicates that Himalayan glaciers currently store less freshwater than assumed in models. The acceleration of Tibetan Plateau glacial retreat has been hypothesized to be due in part to deposition of black carbon (BC) from biomass burning on to ice fields, thereby lowering the reflectivity of

Reassessment of the Upper Fremont Glacier ice-core chronologies by synchronizing of ice-core-water isotopes to a nearby tree-ring chronology

Science.gov (United States)

Chellman, Nathan J.; McConnell, Joseph R.; Arienzo, Monica; Pederson, Gregory T.; Aarons, Sarah; Csank, Adam

2017-01-01

The Upper Fremont Glacier (UFG), Wyoming, is one of the few continental glaciers in the contiguous United States known to preserve environmental and climate records spanning recent centuries. A pair of ice cores taken from UFG have been studied extensively to document changes in climate and industrial pollution (most notably, mid-19th century increases in mercury pollution). Fundamental to these studies is the chronology used to map ice-core depth to age. Here, we present a revised chronology for the UFG ice cores based on new measurements and using a novel dating approach of synchronizing continuous water isotope measurements to a nearby tree-ring chronology. While consistent with the few unambiguous age controls underpinning the previous UFG chronologies, the new interpretation suggests a very different time scale for the UFG cores with changes of up to 80 years. Mercury increases previously associated with the mid-19th century Gold Rush now coincide with early-20th century industrial emissions, aligning the UFG record with other North American mercury records from ice and lake sediment cores. Additionally, new UFG records of industrial pollutants parallel changes documented in ice cores from southern Greenland, further validating the new UFG chronologies while documenting the extent of late 19th and early 20th century pollution in remote North America.

Ice core melt features in relation to Antarctic coastal climate

NARCIS (Netherlands)

Kaczmarska, M.; Isaksson, E.; Karlöf, L.; Brandt, O.; Winther, J.G.; van de Wal, R.S.W.; van den Broeke, M.R.; Johnsen, S.J.

2006-01-01

Measurement of light intensity transmission was carried out on an ice core S100 from coastal Dronning Maud Land (DML). Ice lenses were observed in digital pictures of the core and recorded as peaks in the light transmittance record. The frequency of ice layer occurrence was compared with climate

Continuous methane measurements from a late Holocene Greenland ice core

DEFF Research Database (Denmark)

Rhodes, R.H.; Mitchell, L.E.; Brook, E.J.

2013-01-01

Ancient air trapped inside bubbles in ice cores can now be analysed for methane concentration utilising a laser spectrometer coupled to a continuous melter system. We present a new ultra-high resolution record of atmospheric methane variability over the last 1800yr obtained from continuous analysis...... of a shallow ice core from the North Greenland Eemian project (NEEM-2011-S1) during a 4-week laboratory-based measurement campaign. Our record faithfully replicates the form and amplitudes of multi-decadal oscillations previously observed in other ice cores and demonstrates the detailed depth resolution (5.3cm......), rapid acquisition time (30mday) and good long-term reproducibility (2.6%, 2s) of the continuous measurement technique.In addition, we report the detection of high frequency ice core methane signals of non-atmospheric origin. Firstly, measurements of air from the firn-ice transition region...

Microstructural Location and Composition of Impurities in Polar Ice Cores, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — This data set contains measurements of impurities and ions in three polar ice cores: the Vostok 5G ice core and the Byrd ice core from Antarctica, and the Greenland...

Frozen Nature - A high-alpine ice core record reveals fire and vegetation dynamics in Western Europe over the past millennium

Science.gov (United States)

Brügger, S.; Gobet, E.; Sigl, M.; Osmont, D.; Schwikowski, M.; Tinner, W.

2017-12-01

Wild fires are an ecological disturbance agent across ecosystems, driving vegetation dynamics and resulting in disruption of habitats (Moritz et al. 2014).We analyze pollen and spores as proxies for vegetation composition, structure and agricultural activity, microscopic charcoal as a proxy for fire activity, and spheroidal carbonaceous particles (SCPs or soots) as a proxy for fossil fuel combustion which preserve in ice cores over millennia (Eichler et al. 2011).Our high-alpine ice core (4452 m a.s.l.) from Colle Gnifetti, Swiss Alps is located in the center of Western Europe, thus allowing to assess vegetation and societal responses to climatic change and wildfire disturbance on a subcontinental scale. The record covers the last millennium with an excellent chronological control (Jenk et al. 2009, Sigl et al. 2009), particularly over the most recent 200 years - the period that experienced important climatic changes and an increasing globalization of economy.The Colle Gnifetti record reflects large scale impacts such as extreme weather, societal innovations, agricultural crises and pollution of the industrial period in Western Europe. Pollution tracers occur in the record as early as 1750 AD and coincide with the shift to large-scale maize production in Northern Italy and with increased fire activity. Our multiproxy record may allow desentagling the role of climate and humans for vegetation composition and biomass burning. The attribution of causes may significantly advance our understanding of future vegetation and fire dynamics under global change conditions. To our knowledge we present the first long-term high-resolution palynological record of a high elevation ice core in Europe.REFERENCESEichler et al. (2011): An ice-core based history of Siberian forest fires since AD 1250. Quaternary Science Reviews, 30(9), 1027-1034.Jenk et al. (2009): A novel radiocarbon dating technique applied to an ice core from the Alps indicating late Pleistocene ages. Journal of

Beryllium-10 in the Taylor Dome ice core: Applications to Antarctic glaciology and paleoclimatology

Energy Technology Data Exchange (ETDEWEB)

Steig, E.J.

1996-12-31

An ice core was drilled at Taylor dome, East Antarctica, reaching to bedrock at 554 meters. Oxygen-isotope measurements reveal climatic fluctuations through the last interglacial period. To facilitate comparison of the Taylor Dome paleoclimate record with geologic data and results from other deep ice cores, several glaciological issues need to be addressed. In particular, accumulation data are necessary as input for numerical ice-flow-models, for determining the flux of chemical constituents from measured concentrations, and for calculation of the offset in age between ice and trapped air in the core. The analysis of cosmogenic beryllium-10 provides a geochemical method for constraining the accumulation-rate history at Taylor Dome. High-resolution measurements were made in shallow firn cores and snow pits to determine the relationship among beryllium-10 concentrations, wet and dry deposition mechanisms, and snow-accumulation rates. Comparison between theoretical and measured variations in deposition over the last 75 years constrains the relationship between beryllium-10 deposition and global average production rates. The results indicate that variations in geomagnetically-modulated production-rate do not strongly influence beryllium-10 deposition at Taylor Dome. Although solar modulation of production rate is important for time scales of years to centuries, snow-accumulation rate is the dominant control on ice-core beryllium-10 concentrations for longer periods. Results show that the Taylor Dome core can be used to provide new constraints on regional climate over the last 130,000 years, complementing the terrestrial and marine geological record from the Dry Valley, Transantarctic Mountains and western Ross Sea.

Precipitation variations recorded in Guliya ice core in the past 400 years

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

Based on the Guliya ice core records, the precipitation in the past 400 years was retrieved. Its rela tions with other regions were also analyzed. The results demonstrated that there were two high-precipitation periods and two low-precipitation periods in Guliya ice core since 1571 AD. The average precipitation in the two high-precipitation periods was 42 mm (21%) higher than that in the two low-precipitation periods. The precipitation recorded in the Guliya ice core was consistent with that in Dunde ice core. The variation trends of precipitation in the Guliya ice core and the northern hemisphere are similar. During the extremely wet years in the northern hemisphere, the precipitation recorded in the Guliya ice core was two times the long-term average. However, the annual precipitation was 38% less than that of the long-term average in extremely dry years.

Dating of 30m ice cores drilled by Japanese Antarctic Research Expedition and environmental change study

Science.gov (United States)

Motoyama, H.; Suzuki, T.; Fukui, K.; Ohno, H.; Hoshina, Y.; Hirabayashi, M.; Fujita, S.

2017-12-01

1. Introduction It is possible to reveal the past climate and environmental change from the ice core drilled in polar ice sheet and glaciers. The 54th Japanese Antarctic Research Expedition conducted several shallow core drillings up to 30 m depth in the inland and coastal areas of the East Antarctic ice sheet. Ice core sample was cut out at a thickness of about 5 cm in the cold room of the National Institute of Polar Research, and analyzed ion, water isotope, dust and so one. We also conducted dielectric profile measurement (DEP measurement). The age as a key layer of large-scale volcanic explosion was based on Sigl et al. (Nature Climate Change, 2014). 2. Inland ice core Ice cores were collected at the NDF site (77°47'14"S, 39°03'34"E, 3754 m.a.s.l.) and S80 site (80°00'00"S, 40°30'04"E, 3622 m.a.s.l.). Dating of ice core was done as follows. Calculate water equivalent from core density. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. We determined the key layer with nssSO42 - peak corresponding to several large volcanic explosions. The accumulation rate was kept constant between the key layers. As a result, NDF was estimated to be around 1360 AD and S80 was estimated to be around 1400 AD in the deepest ice core. 3. Coastal ice core An ice core was collected at coastal H15 sites (69°04'10"S, 40°44'51"E, 1030 m.a.s.l.). Dating of ice core was done as follows. Calculate water equivalent from ice core density. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. Basically we decided to summer (December) and winter (June) due to the seasonal change of the water isotope (δD or δ18O). In addition to the seasonal change of isotope, confirm the following. Maximum of SO42- / Na +, which is earlier in time than the maximum of water isotope. Maximum of MSA at about the same time as the maximum of the

First investigations of an ice core from Eisriesenwelt cave (Austria

Directory of Open Access Journals (Sweden)

B. May

2011-02-01

Full Text Available Investigations into the genesis and dynamical properties of cave ice are essential for assessing the climate significance of these underground glaciers. We drilled an ice core through a 7.1 m-thick ice body filling a large cavern of the dynamic ice cave Eisenriesenwelt (Austria. In addition to visual core inspections, quasi-continuous measurements at 2 cm resolution comprised particulate matter, stable water isotope (δ¹⁸O, δD and electrolytic conductivity profiles supplemented by specifically selected samples analyzed for tritium and radiocarbon. We found that recent ablation led to an almost complete loss of bomb-derived tritium removing any ice accumulated since, at least, the early fifties leaving the actual ice surface even below the natural tritium level. The small particulate organic masses rendered radiocarbon dating inconclusive, though a crude estimate gave a basal ice age in the order of several thousand years. The visual stratigraphy and all investigated parameters showed a clear dichotomy between the upper 2 m and the bottom 3 m of the core, which points to a substantial change in the ice formation process. Main features of the core comprise the changing appearance and composition of distinct cryocalcite layers, extremely low total ion content and a surprisingly high variability of the isotope signature. Co-isotope evaluation (δD versus δ¹⁸O of the core in comparison with data from precipitation and karst spring water clearly indicate that ice formation is governed by (slow freezing of dripping water.

Toward an integrated ice core chronology using relative and orbital tie-points

Science.gov (United States)

Bazin, L.; Landais, A.; Lemieux-Dudon, B.; Toyé Mahamadou Kele, H.; Blunier, T.; Capron, E.; Chappellaz, J.; Fischer, H.; Leuenberger, M.; Lipenkov, V.; Loutre, M.-F.; Martinerie, P.; Parrenin, F.; Prié, F.; Raynaud, D.; Veres, D.; Wolff, E.

2012-04-01

Precise ice cores chronologies are essential to better understand the mechanisms linking climate change to orbital and greenhouse gases concentration forcing. A tool for ice core dating (DATICE [developed by Lemieux-Dudon et al., 2010] permits to generate a common time-scale integrating relative and absolute dating constraints on different ice cores, using an inverse method. Nevertheless, this method has only been applied for a 4-ice cores scenario and for the 0-50 kyr time period. Here, we present the bases for an extension of this work back to 800 ka using (1) a compilation of published and new relative and orbital tie-points obtained from measurements of air trapped in ice cores and (2) an adaptation of the DATICE inputs to 5 ice cores for the last 800 ka. We first present new measurements of δ18Oatm and δO2/N2 on the Talos Dome and EPICA Dome C (EDC) ice cores with a particular focus on Marine Isotopic Stages (MIS) 5, and 11. Then, we show two tie-points compilations. The first one is based on new and published CH4 and δ18Oatm measurements on 5 ice cores (NorthGRIP, EPICA Dronning Maud Land, EDC, Talos Dome and Vostok) in order to produce a table of relative gas tie-points over the last 400 ka. The second one is based on new and published records of δO2/N2, δ18Oatm and air content to provide a table of orbital tie-points over the last 800 ka. Finally, we integrate the different dating constraints presented above in the DATICE tool adapted to 5 ice cores to cover the last 800 ka and show how these constraints compare with the established gas chronologies of each ice core.

Microshear in the deep EDML ice core analyzed using cryogenic EBSD

Science.gov (United States)

Kuiper, Ernst-Jan; Pennock, Gill; Drury, Martyn; Kipfstuhl, Sepp; Faria, Sérgio; Weikusat, Ilka

2017-04-01

Ice sheets play an important role in sea level evolution by storing large amounts of fresh water on land. The ice in an ice sheet flows from the interior of the ice sheet to the edges where it either melts or calves into the ocean. This flow of ice results from internal deformation of the ice aggregate. Dislocation creep is assumed to be the dominant deformation mechanism for polar ice and is grain size insensitive. Recently, a different deformation mechanism was identified in the deeper part of the EDML ice core (Antarctica) where, at a depth of 2385 meters, the grain size strongly decreases, the grain aspect ratio increase and, the inclination of the grain elongation changes (Faria et al., 2006; Weikusat et al., 2017). At this depth the borehole displacement increases strongly (Weikusat et al., 2017), which indicates a relatively high strain rate. Part of this EDML ice core section was studied using cryogenic electron backscattered diffraction (cryo-EBSD) (Weikusat et al, 2011). EBSD produces high resolution, full crystallographic (a-axis and c-axis) maps of the ice core samples. EBSD samples were taken from an ice core section at 2392.2 meter depth. This section was chosen for its very small grain size and the strongly aligned grain boundaries. The EBSD maps show a very low orientation gradient of <0.3° per millimetre inside the grains, which is 5-10 times lower than the orientation gradients found in other parts of the ice core. Furthermore, close to some grain boundaries, a relatively strong orientation gradient of 1°-2° per millimetre was found. The subgrain boundaries developed such that they elongate the sliding boundaries in order to accommodate the incompatibilities and maintain the strongly aligned grain boundary network. We identify the dominant deformation mechanism in this part of the ice core as grain boundary sliding accommodated by localized dislocation creep, which is a process similar to microshear (Drury and Humpreys, 1988). The existence of

Initial Continuous Chemistry Results From The Roosevelt Island Ice Core (RICE)

Science.gov (United States)

Kjær, H. A.; Vallelonga, P. T.; Simonsen, M. F.; Neff, P. D.; Bertler, N. A. N.; Svensson, A.; Dahl-Jensen, D.

2014-12-01

The Roosevelt Island ice core (79.36° S, -161.71° W) was drilled in 2011-13 at the top of the Roosevelt Island ice dome, a location surrounded by the Ross ice shelf. The RICE ice core provides a unique opportunity to look into the past evolution of the West Antarctic Ice sheet. Further the site has high accumulation; 0.26 m of ice equivalent is deposited annually allowing annual layer determination for many chemical parameters. The RICE core was drilled to bedrock and has a total length of 763 metres. Preliminary results derived from water isotopes suggest that the oldest ice reaches back to the Eemian, with the last glacial being compressed in the bottom 60 metres. We present preliminary results from the RICE ice core including continuous measurements of acidity using an optical dye method, insoluble dust particles, conductivity and calcium. The core was analyzed at the New Zealand National Ice Core Research Facility at GNS Science in Wellington. The analytical set up used to determine climate proxies in the ice core was a modified version of the Copenhagen CFA system (Bigler et al., 2011). Key volcanic layers have been matched to those from the WAIS record (Sigl et al., 2013). A significant anti-correlation between acidity and calcium was seen in the Holocene part of the record. Due to the proximity to the ocean a large fraction of the calcium originates from sea salt and is in phase with total conductivity and sodium. In combination with the insoluble dust record, calcium has been apportioned into ocean-related and dust-related sources. Variability over the Holocene is presented and attributed to changing inputs of marine and dust aerosols.

Variability of sea salts in ice and firn cores from Fimbul Ice Shelf, Dronning Maud Land, Antarctica

Science.gov (United States)

Paulina Vega, Carmen; Isaksson, Elisabeth; Schlosser, Elisabeth; Divine, Dmitry; Martma, Tõnu; Mulvaney, Robert; Eichler, Anja; Schwikowski-Gigar, Margit

2018-05-01

Major ions were analysed in firn and ice cores located at Fimbul Ice Shelf (FIS), Dronning Maud Land - DML, Antarctica. FIS is the largest ice shelf in the Haakon VII Sea, with an extent of approximately 36 500 km2. Three shallow firn cores (about 20 m deep) were retrieved in different ice rises, Kupol Ciolkovskogo (KC), Kupol Moskovskij (KM), and Blåskimen Island (BI), while a 100 m long core (S100) was drilled near the FIS edge. These sites are distributed over the entire FIS area so that they provide a variety of elevation (50-400 m a.s.l.) and distance (3-42 km) to the sea. Sea-salt species (mainly Na+ and Cl-) generally dominate the precipitation chemistry in the study region. We associate a significant sixfold increase in median sea-salt concentrations, observed in the S100 core after the 1950s, to an enhanced exposure of the S100 site to primary sea-salt aerosol due to a shorter distance from the S100 site to the ice front, and to enhanced sea-salt aerosol production from blowing salty snow over sea ice, most likely related to the calving of Trolltunga occurred during the 1960s. This increase in sea-salt concentrations is synchronous with a shift in non-sea-salt sulfate (nssSO42-) toward negative values, suggesting a possible contribution of fractionated aerosol to the sea-salt load in the S100 core most likely originating from salty snow found on sea ice. In contrast, there is no evidence of a significant contribution of fractionated sea salt to the ice-rises sites, where the signal would be most likely masked by the large inputs of biogenic sulfate estimated for these sites. In summary, these results suggest that the S100 core contains a sea-salt record dominated by the proximity of the site to the ocean, and processes of sea ice formation in the neighbouring waters. In contrast, the ice-rises firn cores register a larger-scale signal of atmospheric flow conditions and a less efficient transport of sea-salt aerosols to these sites. These findings are a

Sub-annual North Pacific hydroclimate variability since 1450AD from updated St. Elias ice core isotope and accumulation rate records

Science.gov (United States)

Kreutz, K. J.; Campbell, S. W.; Winski, D.; Osterberg, E. C.; Kochtitzky, W. H.; Copland, L.; Dixon, D.; Introne, D.; Medrzycka, D.; Main, B.; Bernsen, S.; Wake, C. P.

2017-12-01

A growing array of high-resolution paleoclimate records from the terrestrial region bordering the Gulf of Alaska (GoA) continues to reveal details about ocean-atmosphere variability in the region during the Common Era. Ice core records from high-elevation ranges in proximity to the GoA provide key information on extratropical hydroclimate, and potential teleconnections to low latitude regions. In particular, stable water isotope and snow accumulation reconstructions from ice cores collected in high precipitation locations are uniquely tied to regional water cycle changes. Here we present new data collected in 2016 and 2017 from the St. Elias Mountains (Eclipse Icefield, Yukon Territories, Canada), including a range of ice core and geophysical measurements. Low- and high-frequency ice penetrating radar data enable detailed mapping of icefield bedrock topography and internal reflector stratigraphy. The 1911 Katmai eruption layer can be clearly traced across the icefield, and tied definitively to the coeval ash layer found in the 345 meter ice core drilled at Eclipse Icefield in 2002. High-resolution radar data are used to map spatial variability in 2015/16 and 2016/17 snow accumulation. Ice velocity data from repeat GPS stake measurements and remote sensing feature tracking reveal a clear divide flow regime on the icefield. Shallow firn/ice cores (20 meters in 2017 and 65 meters in 2016) are used to update the 345 meter ice core drilled at Eclipse Icefield in 2002. We use new algorithm-based layer counting software to improve and provide error estimates on the new ice core chronology, which extends from 2017 to 1450AD. 3D finite element modeling, incorporating all available geophysical data, is used to refine the reconstructed accumulation rate record and account for vertical and horizontal ice flow. Together with high-resolution stable water isotope data, the updated Eclipse record provides detailed, sub-annual resolution data on several aspects of the regional

Electrical conductivity measurements from the GISP2 and GRIP Greenland ice cores

DEFF Research Database (Denmark)

Dahl-Jensen, Dorthe; Clausen, Henrik Brink; Taylor, K. C.

1993-01-01

. Here we present electrical conductivity records for the Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice-core Project (GRIP) ice cores, drilled 28 km apart to enable direct comparison of the results. The upper parts of both records are consistent with previous evidence from other Greenland cores...

On the use of δ18Oatm for ice core dating

Science.gov (United States)

Extier, Thomas; Landais, Amaelle; Bréant, Camille; Prié, Frédéric; Bazin, Lucie; Dreyfus, Gabrielle; Roche, Didier M.; Leuenberger, Markus

2018-04-01

Deep ice core chronologies have been improved over the past years through the addition of new age constraints. However, dating methods are still associated with large uncertainties for ice cores from the East Antarctic plateau where layer counting is not possible. Indeed, an uncertainty up to 6 ka is associated with AICC2012 chronology of EPICA Dome C (EDC) ice core, which mostly arises from uncertainty on the delay between changes recorded in δ18Oatm and in June 21st insolation variations at 65°N used for ice core orbital dating. Consequently, we need to enhance the knowledge of this delay to improve ice core chronologies. We present new high-resolution EDC δ18Oatm record (153-374 ka) and δO2/N2 measurements (163-332 ka) performed on well-stored ice to provide continuous records of δ18Oatm and δO2/N2 between 100 and 800 ka. The comparison of δ18Oatm with the δ18Ocalcite from East Asian speleothems shows that both signals present similar orbital and millennial variabilities, which may represent shifts in the InterTropical Convergence Zone position, themselves associated with Heinrich events. We thus propose to use the δ18Ocalcite as target for δ18Oatm orbital dating. Such a tuning method improves the ice core chronology of the last glacial inception compared to AICC2012 by reconciling NGRIP and mid-latitude climatic records. It is especially marked during Dansgaard-Oeschger 25 where the proposed chronology is 2.2 ka older than AICC2012. This δ18Oatm - δ18Ocalcite alignment method applied between 100 and 640 ka improves the EDC ice core chronology, especially over MIS 11, and leads to lower ice age uncertainties compared to AICC2012.

A relationship between ion balance and the chemical compounds of salt inclusions found in the Greenland Ice Core Project and Dome Fuji ice cores

DEFF Research Database (Denmark)

Johnsen, Sigfus Johann; Dahl-Jensen, Dorthe; Steffensen, Jørgen Peder

2008-01-01

We have proposed a method of deducing the chemical compounds found in deep polar ice cores by analyzing the balance between six major ions (Cl-, NO3 -, SO4 2-, Na+, Mg2+, and Ca2+). The method is demonstrated for the Holocene and last glacial maximum regions of the Dome Fuji and GRIP ice cores...... on individual salt inclusions. The abundances in the ice cores are shown to reflect differences in climatic periods (the acidic environment of the Holocene versus the reductive environment of the last glacial maximum) and regional conditions (the marine environment of Antarctica versus the continental...

Cosmogenic 10Be Depth Profile in top 560 m of West Antarctic Ice Sheet Divide Ice Core

Science.gov (United States)

Welten, K. C.; Woodruff, T. E.; Caffee, M. W.; Edwards, R.; McConnell, J. R.; Bisiaux, M. M.; Nishiizumi, K.

2009-12-01

Concentrations of cosmogenic 10Be in polar ice samples are a function of variations in solar activity, geomagnetic field strength, atmospheric mixing and annual snow accumulation rates. The 10Be depth profile in ice cores also provides independent chronological markers to tie Antarctic to Greenland ice cores and to tie Holocene ice cores to the 14C dendrochronology record. We measured 10Be concentrations in 187 samples from depths of 0-560 m of the main WAIS Divide core, WDC06A. The ice samples are typically 1-2 kg and represent 2-4 m of ice, equivalent to an average temporal resolution of ~12 years, based on the preliminary age-depth scale proposed for the WDC core, (McConnell et al., in prep). Be, Al and Cl were separated using ion exchange chromatography techniques and the 10Be concentrations were measured by accelerator mass spectrometry (AMS) at PRIME lab. The 10Be concentrations range from 8.1 to 19.1 x 10^3 at/g, yielding an average of (13.1±2.1) x 10^3 at/g. Adopting an average snow accumulation rate of 20.9 cm weq/yr, as derived from the age-depth scale, this value corresponds to an average 10Be flux of (2.7±0.5) x 10^5 atoms/yr/cm2. This flux is similar to that of the Holocene part of the Siple Dome (Nishiizumi and Finkel, 2007) and Dome Fuji (Horiuchi et al. 2008) ice cores, but ~30% lower than the value of 4.0 x 10^5 atoms/yr/cm2 for GISP2 (Finkel and Nishiizumi, 1997). The periods of low solar activity, known as Oort, Wolf, Spörer, Maunder and Dalton minima, show ~20% higher 10Be concentrations/fluxes than the periods of average solar activity in the last millennium. The maximum 10Be fluxes during some of these periods of low solar activity are up to ~50% higher than average 10Be fluxes, as seen in other polar ice cores, which makes these peaks suitable as chronologic markers. We will compare the 10Be record in the WAIS Divide ice core with that in other Antarctic as well as Greenland ice cores and with the 14C treering record. Acknowledgment. This

Annual layering in the NGRIP ice core during the Eemian

Directory of Open Access Journals (Sweden)

A. Svensson

2011-12-01

Full Text Available The Greenland NGRIP ice core continuously covers the period from present day back to 123 ka before present, which includes several thousand years of ice from the previous interglacial period, MIS 5e or the Eemian. In the glacial part of the core, annual layers can be identified from impurity records and visual stratigraphy, and stratigraphic layer counting has been performed back to 60 ka. In the deepest part of the core, however, the ice is close to the pressure melting point, the visual stratigraphy is dominated by crystal boundaries, and annual layering is not visible to the naked eye. In this study, we apply a newly developed setup for high-resolution ice core impurity analysis to produce continuous records of dust, sodium and ammonium concentrations as well as conductivity of melt water. We analyzed three 2.2 m sections of ice from the Eemian and the glacial inception. In all of the analyzed ice, annual layers can clearly be recognized, most prominently in the dust and conductivity profiles. Part of the samples is, however, contaminated in dust, most likely from drill liquid. It is interesting that the annual layering is preserved despite a very active crystal growth and grain boundary migration in the deep and warm NGRIP ice. Based on annual layer counting of the new records, we determine a mean annual layer thickness close to 11 mm for all three sections, which, to first order, confirms the modeled NGRIP time scale (ss09sea. The counting does, however, suggest a longer duration of the climatically warmest part of the NGRIP record (MIS5e of up to 1 ka as compared to the model estimate. Our results suggest that stratigraphic layer counting is possible basically throughout the entire NGRIP ice core, provided sufficiently highly-resolved profiles become available.

Climatic Changes on Tibetan Plateau Based on Ice Core Records

Science.gov (United States)

Yao, T.

2008-12-01

Climatic changes have been reconstructed for the Tibetan Plateau based on ice core records. The Guliya ice core on the Tibetan Plateau presents climatic changes in the past 100,000 years, thus is comparative with that from Vostok ice core in Antarctica and GISP2 record in Arctic. These three records share an important common feature, i.e., our climate is not stable. It is also evident that the major patterns of climatic changes are similar on the earth. Why does climatic change over the earth follow a same pattern? It might be attributed to solar radiation. We found that the cold periods correspond to low insolation periods, and warm periods to high insolation periods. We found abrupt climatic change in the ice core climatic records, which presented dramatic temperature variation of as much as 10 °C in 50 or 60 years. Our major challenge in the study of both climate and environment is that greenhouse gases such as CO2, CH4 are possibly amplifying global warming, though at what degree remains unclear. One of the ways to understand the role of greenhouse gases is to reconstruct the past greenhouse gases recorded in ice. In 1997, we drilled an ice core from 7100 m a.s.l. in the Himalayas to reconstruct methane record. Based on the record, we found seasonal cycles in methane variation. In particular, the methane concentration is high in summer, suggestiing active methane emission from wet land in summer. Based on the seasonal cycle, we can reconstruct the methane fluctuation history in the past 500 years. The most prominent feature of the methane record in the Himalayan ice core is the abrupt increase since 1850 A.D.. This is closely related to the industrial revolution worldwide. We can also observe sudden decrease in methane concentration during the World War I and World War II. It implies that the industrial revolution has dominated the atmospheric greenhouse gas emission for about 100 years. Besides, the average methane concentration in the Himalayan ice core is

An automated approach for annual layer counting in ice cores

Science.gov (United States)

Winstrup, M.; Svensson, A.; Rasmussen, S. O.; Winther, O.; Steig, E.; Axelrod, A.

2012-04-01

The temporal resolution of some ice cores is sufficient to preserve seasonal information in the ice core record. In such cases, annual layer counting represents one of the most accurate methods to produce a chronology for the core. Yet, manual layer counting is a tedious and sometimes ambiguous job. As reliable layer recognition becomes more difficult, a manual approach increasingly relies on human interpretation of the available data. Thus, much may be gained by an automated and therefore objective approach for annual layer identification in ice cores. We have developed a novel method for automated annual layer counting in ice cores, which relies on Bayesian statistics. It uses algorithms from the statistical framework of Hidden Markov Models (HMM), originally developed for use in machine speech recognition. The strength of this layer detection algorithm lies in the way it is able to imitate the manual procedures for annual layer counting, while being based on purely objective criteria for annual layer identification. With this methodology, it is possible to determine the most likely position of multiple layer boundaries in an entire section of ice core data at once. It provides a probabilistic uncertainty estimate of the resulting layer count, hence ensuring a proper treatment of ambiguous layer boundaries in the data. Furthermore multiple data series can be incorporated to be used at once, hence allowing for a full multi-parameter annual layer counting method similar to a manual approach. In this study, the automated layer counting algorithm has been applied to data from the NGRIP ice core, Greenland. The NGRIP ice core has very high temporal resolution with depth, and hence the potential to be dated by annual layer counting far back in time. In previous studies [Andersen et al., 2006; Svensson et al., 2008], manual layer counting has been carried out back to 60 kyr BP. A comparison between the counted annual layers based on the two approaches will be presented

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.

2004-01-01

Ice cores are the most direct, continuous, and high resolution archive for Late Quaternary paleoclimate reconstruction. Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate migration strategies for New Zealand. (author). 23 refs., 15 figs., 1 tab

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

How Will Sea Ice Loss Affect the Greenland Ice Sheet? On the Puzzling Features of Greenland Ice-Core Isotopic Composition

Science.gov (United States)

Pausata, Francesco S. R.; Legrande, Allegra N.; Roberts, William H. G.

2016-01-01

The modern cryosphere, Earth's frozen water regime, is in fast transition. Greenland ice cores show how fast theses changes can be, presenting evidence of up to 15 C warming events over timescales of less than a decade. These events, called Dansgaard/Oeschger (D/O) events, are believed to be associated with rapid changes in Arctic sea ice, although the underlying mechanisms are still unclear. The modern demise of Arctic sea ice may, in turn, instigate abrupt changes on the Greenland Ice Sheet. The Arctic Sea Ice and Greenland Ice Sheet Sensitivity (Ice2Ice Chttps://ice2ice.b.uib.noD) initiative, sponsored by the European Research Council, seeks to quantify these past rapid changes to improve our understanding of what the future may hold for the Arctic. Twenty scientists gathered in Copenhagen as part of this initiative to discuss the most recent observational, technological, and model developments toward quantifying the mechanisms behind past climate changes in Greenland. Much of the discussion focused on the causes behind the changes in stable water isotopes recorded in ice cores. The participants discussed sources of variability for stable water isotopes and framed ways that new studies could improve understanding of modern climate. The participants also discussed how climate models could provide insights into the relative roles of local and nonlocal processes in affecting stable water isotopes within the Greenland Ice Sheet. Presentations of modeling results showed how a change in the source or seasonality of precipitation could occur not only between glacial and modern climates but also between abrupt events. Recent fieldwork campaigns illustrate an important role of stable isotopes in atmospheric vapor and diffusion in the final stable isotope signal in ice. Further, indications from recent fieldwork campaigns illustrate an important role of stable isotopes in atmospheric vapor and diffusion in the final stable isotope signal in ice. This feature complicates

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.

2009-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate mitigation strategies for New Zealand. Ice core records provide an annual-scale, 'instrumental-quality' baseline of atmospheric temperature and circulation changes back many thousands of years. (author). 45 refs., 16 figs., 2 tabs.

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.

2009-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate mitigation strategies for New Zealand. Ice core records provide an annual-scale, 'instrumental-quality' baseline of atmospheric temperature and circulation changes back many thousands of years. (author). 27 refs., 18 figs., 2 tabs

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.A.N.

2012-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate mitigation strategies for New Zealand. Ice core records provide an annual-scale, 'instrumental-quality' baseline of atmospheric temperature and circulation changes back many thousands of years. (author). 28 refs., 20 figs., 1 tab.

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.

2008-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate mitigation strategies for New Zealand. Ice core records provide an annual-scale, 'instrumental-quality' baseline of atmospheric temperature and circulation changes back many thousands of years. (author). 27 refs., 18 figs., 2 tabs

PIXE analysis as a tool for dating of ice cores from the Greenland ice sheet

International Nuclear Information System (INIS)

Hansson, H.C.; Swietlicki, E.; Larsson, N.P.O.; Johnsen, S.J.

1993-01-01

Sections from the 2037 m long Dye 3 ice core drilled in 1979-1981 in the ice sheet of Southern Greenland were analysed with PIXE. The seven selected sections were from depths between 1778 and 1813 m, which corresponds to a time interval between about 8 500 and 10 000 years B.C. at the end of the last Ice Age. During this time period, fast climatic changes of several degrees centrigrade per century are known to have taken place. The exact time scales of these changes need yet to be verified by renewed measurements using nonconventional stratigraphic dating techniques such as PIXE. The problem is highly relevant for the prediction of climatic changes in our present age. A new sample preparation technique was developed which enables the determination of annual thicknesses of the parts of the ice core representing 10 000-40 000 years before present, where the thickness of the annual ice layers are believed to be less than 2.5 cm. More commonly used techniques of dating, such as measurements of oxygen and hydrogen isotopes δ 18 O and δD, nitrate, acidity or conductivity all have difficulties in resolving annual cycles in thicknesses of less than about 2 cm. The new technique involves sublimation of 18 cm long ice sections, after which the material contained in the ice is deposited on the thin backing. In this way, the material to be analysed is preconcentrated through the removal of the H 2 O, while still retaining the spatial distribution pattern of the various water soluble and insoluble components along the ice core. The resulting spatial resolution of the sublimation technique is estimated to be ±1 mm. A PIXE analysis was performed in contiguous millimeter steps across the sublimated ice sections. Estimations of annual ice layer thicknesses were based on the patterns of seasonal variation along the ice sections for several major and minor elements quantified with PIXE. (orig./TW)

Visual-stratigraphic dating of the GISP2 ice core: Basis, reproducibility, and application

Science.gov (United States)

Alley, R. B.; Shuman, C. A.; Meese, D. A.; Gow, A. J.; Taylor, K. C.; Cuffey, K. M.; Fitzpatrick, J. J.; Grootes, P. M.; Zielinski, G. A.; Ram, M.; Spinelli, G.; Elder, B.

1997-11-01

Annual layers are visible in the Greenland Ice Sheet Project 2 ice core from central Greenland, allowing rapid dating of the core. Changes in bubble and grain structure caused by near-surface, primarily summertime formation of hoar complexes provide the main visible annual marker in the Holocene, and changes in "cloudiness" of the ice correlated with dustiness mark Wisconsinan annual cycles; both markers are evident and have been intercalibrated in early Holocene ice. Layer counts are reproducible between different workers and for one worker at different times, with 1% error over century-length times in the Holocene. Reproducibility is typically 5% in Wisconsinan ice-age ice and decreases with increasing age and depth. Cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50,000 years. Visible observations are not greatly degraded by "brittle ice" or many other core-quality problems, allowing construction of long, consistently sampled time series. High accuracy requires careful study of the core by dedicated observers.

Evidence for propagation of cold-adapted yeast in an ice core from a Siberian Altai glacier

Science.gov (United States)

Uetake, Jun; Kohshima, Shiro; Nakazawa, Fumio; Takeuchi, Nozomu; Fujita, Koji; Miyake, Takayuki; Narita, Hideki; Aizen, Vladimir; Nakawo, Masayoshi

2011-03-01

Cold environments, including glacier ice and snow, are known habitats for cold-adapted microorganisms. We investigated the potential for cold-adapted yeast to have propagated in the snow of the high-altitude Belukha glacier. We detected the presence of highly concentrated yeast (over 104 cells mL-1) in samples of both an ice core and firn snow. Increasing yeast cell concentrations in the same snow layer from July 2002 to July 2003 suggests that the yeast cells propagated in the glacier snow. A cold-adapted Rhodotorula sp. was isolated from the snow layer and found to be related to psychrophilic yeast previously found in other glacial environments (based on the D1/D2 26S rRNA domains). 26S rRNA clonal analysis directly amplified from meltwater within the ice core also revealed the presence of genus Rhodotorula. Analyses of the ice core showed that all peaks in yeast concentration corresponded to the peaks in indices of surface melting. These results support the hypothesis that occasional surface melting in an accumulation area is one of the major factors influencing cold-adapted yeast propagation.

δ13C-CH4 in ice core samples

DEFF Research Database (Denmark)

Sperlich, Peter

Ice core records of δ13C-CH4 reflect the variability of CH4 biogeochemistry in response to climate change and show this system is far more complex than expected. The first part of this work is concerned with the development of analytical techniques that allow 1) precise referencing and 2) measure......Ice core records of δ13C-CH4 reflect the variability of CH4 biogeochemistry in response to climate change and show this system is far more complex than expected. The first part of this work is concerned with the development of analytical techniques that allow 1) precise referencing and 2......) measurements of δ13C-CH4 in ice core samples as is required when δ13C-CH4 records that are measured in several laboratories are merged for analysis. Both the referencing and measurement techniques have been compared to further laboratories which proofed the accuracy of the analytical systems. The second part...

A High-Resolution Continuous Flow Analysis System for Polar Ice Cores

DEFF Research Database (Denmark)

Dallmayr, Remi; Goto-Azuma, Kumiko; Kjær, Helle Astrid

2016-01-01

of Polar Research (NIPR) in Tokyo. The system allows the continuous analysis of stable water isotopes and electrical conductivity, as well as the collection of discrete samples from both inner and outer parts of the core. This CFA system was designed to have sufficiently high temporal resolution to detect...... signals of abrupt climate change in deep polar ice cores. To test its performance, we used the system to analyze different climate intervals in ice drilled at the NEEM (North Greenland Eemian Ice Drilling) site, Greenland. The quality of our continuous measurement of stable water isotopes has been......In recent decades, the development of continuous flow analysis (CFA) technology for ice core analysis has enabled greater sample throughput and greater depth resolution compared with the classic discrete sampling technique. We developed the first Japanese CFA system at the National Institute...

Geostatistical analysis and isoscape of ice core derived water stable isotope records in an Antarctic macro region

Science.gov (United States)

Hatvani, István Gábor; Leuenberger, Markus; Kohán, Balázs; Kern, Zoltán

2017-09-01

Water stable isotopes preserved in ice cores provide essential information about polar precipitation. In the present study, multivariate regression and variogram analyses were conducted on 22 δ2H and 53 δ18O records from 60 ice cores covering the second half of the 20th century. Taking the multicollinearity of the explanatory variables into account, as also the model's adjusted R2 and its mean absolute error, longitude, elevation and distance from the coast were found to be the main independent geographical driving factors governing the spatial δ18O variability of firn/ice in the chosen Antarctic macro region. After diminishing the effects of these factors, using variography, the weights for interpolation with kriging were obtained and the spatial autocorrelation structure of the dataset was revealed. This indicates an average area of influence with a radius of 350 km. This allows the determination of the areas which are as yet not covered by the spatial variability of the existing network of ice cores. Finally, the regional isoscape was obtained for the study area, and this may be considered the first step towards a geostatistically improved isoscape for Antarctica.

Towards a new common Greenland Ice Core Chronology for the last 5000 years

Science.gov (United States)

Winstrup, Mai; Olander Rasmussen, Sune; Møllesøe Vinther, Bo; Cook, Eliza; Svensson, Anders; McConnell, Joe; Steffensen, Jørgen Peder

2017-04-01

Since the development of the Greenland Ice Core Chronology 2005 (GICC05), it has been widely used as a reference chronology in paleoclimate research. However, recent research (Sigl et al, 2015) demonstrated that this timescale has small, but significant, issues over historical time. These discrepancies was found by counting annual layers in high-resolution chemistry records from the NEEM S1 shallow core, and confirmed by linking via 10Be marker horizons to the layer-counted WAIS Divide ice core, Antarctica, and accurately-dated tree-ring series. This work showed that a revision of GICC05 is required prior to 1250AD. We here refine and extend this work. Layer-counting in a single core will always involve some uncertainty, and we hence use data from multiple Greenland ice cores, for which high-resolution impurity records recently have been measured. These ice cores have been synchronized using volcanic marker horizons, and the layer-counting is performed automatically using the StratiCounter algorithm (Winstrup et al, 2012), while ensuring that the number of layers between volcanic horizons are the same in all cores. Based on this extended multiple-core data set, we are further able to extend the new Greenland timescale another few thousand years back in time. This will, among others, provide a new ice-core date for the catastrophic volcanic eruption ( 1600 BC) that destroyed the Greek Minoan culture, an important time marker in Greek history.

Location of a new ice core site at Talos Dome (East Antarctica

Directory of Open Access Journals (Sweden)

I. Tabacco

2006-06-01

Full Text Available In the frame of glaciology and palaeoclimate research, Talos Dome (72°48lS; 159°06lE, an ice dome on the East Antarctic plateau, represents the new selected site for a new deep ice core drilling. The increasing interest in this region is due to the fact that the ice accumulation is higher here than in other domes in East Antarctica. A new deep drilling in this site could give important information about the climate changes near the coast. Previous papers showed that the dome summit is situated above a sloped bedrock. A new position on a relatively flat bedrock 5-6 km far from here in the SE direction was defined as a possible new ice core site for an European (Italy, France, Swiss and United Kingdom drilling project named as TALDICE (TALos Dome Ice Core Project. This point, named as ID1 (159°11l00mE; 72°49l40mS, became the centre of the Radio Echo Sounding (RES flight plan during the 2003 Italian Antarctic expedition, with the aim of confirming the new drilling site choice. In this paper 2001 and 2003 RES data sets have been used to draw a better resolution of ice thickness, bottom morphology and internal layering of a restricted area around the dome. Based on the final results, point ID1 has been confirmed as the new coring site. Finally, the preliminary operations about the installation of the summer ice core camp (TALDICE at ID1 site carried out during the XX Italian Antarctic expedition (November 2004-December 2005 are briefly described.

Eemian interglacial reconstructed from a Greenland folded ice core

DEFF Research Database (Denmark)

Dahl-Jensen, Dorthe; Albert, M. R.; Aldahan, A.

2013-01-01

Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new No...

Paleoclimate from ice cores : abrupt climate change and the prolonged Holocene

International Nuclear Information System (INIS)

White, J.W.C.

2001-01-01

Ice cores provide valuable information about the Earth's past climates and past environments. They can also help in predicting future climates and the nature of climate change. Recent findings in ice cores have shown large and abrupt climate changes in the past. This paper addressed abrupt climate changes and the peculiar nature of the Holocene. An abrupt climate change is a shift of 5 degrees C in mean annual temperature in less than 50 years. This is considered to be the most threatening aspect of potential future climate change since it leaves very little time for adaptation by humans or any other part of the Earth's ecosystem. This paper also discussed the arrival of the next glacial period. In the past 50 years, scientists have recognized the importance of the Earth's orbit around the sun in pacing the occurrence of large ice sheets. The timing of orbital forcing suggests that the Earth is overdue for the next major glaciation. The reason for this anomaly was discussed. Abrupt climate shifts seem to be caused by mode changes in sensitive points in the climate system, such as the North Atlantic Deep Water Formation and its impact on sea ice cover in the North Atlantic. These changes have been observed in ice cores in Greenland but they are not restricted to Greenland. Evidence from Antarctic ice cores suggest that abrupt climate change may also occur in the Southern Hemisphere. The Vostok ice core in Antarctica indicates that the 11,000 year long interglacial period that we are in right now is longer than the previous four interglacial periods. The Holocene epoch is unique because both methane and carbon dioxide rise in the last 6,000 years, an atypical response from these greenhouse gases during an interglacial period. It was suggested that the rise in methane can be attributed to human activities. 13 refs., 2 figs

Deriving micro- to macro-scale seismic velocities from ice-core c axis orientations

Science.gov (United States)

Kerch, Johanna; Diez, Anja; Weikusat, Ilka; Eisen, Olaf

2018-05-01

One of the great challenges in glaciology is the ability to estimate the bulk ice anisotropy in ice sheets and glaciers, which is needed to improve our understanding of ice-sheet dynamics. We investigate the effect of crystal anisotropy on seismic velocities in glacier ice and revisit the framework which is based on fabric eigenvalues to derive approximate seismic velocities by exploiting the assumed symmetry. In contrast to previous studies, we calculate the seismic velocities using the exact c axis angles describing the orientations of the crystal ensemble in an ice-core sample. We apply this approach to fabric data sets from an alpine and a polar ice core. Our results provide a quantitative evaluation of the earlier approximative eigenvalue framework. For near-vertical incidence our results differ by up to 135 m s-1 for P-wave and 200 m s-1 for S-wave velocity compared to the earlier framework (estimated 1 % difference in average P-wave velocity at the bedrock for the short alpine ice core). We quantify the influence of shear-wave splitting at the bedrock as 45 m s-1 for the alpine ice core and 59 m s-1 for the polar ice core. At non-vertical incidence we obtain differences of up to 185 m s-1 for P-wave and 280 m s-1 for S-wave velocities. Additionally, our findings highlight the variation in seismic velocity at non-vertical incidence as a function of the horizontal azimuth of the seismic plane, which can be significant for non-symmetric orientation distributions and results in a strong azimuth-dependent shear-wave splitting of max. 281 m s-1 at some depths. For a given incidence angle and depth we estimated changes in phase velocity of almost 200 m s-1 for P wave and more than 200 m s-1 for S wave and shear-wave splitting under a rotating seismic plane. We assess for the first time the change in seismic anisotropy that can be expected on a short spatial (vertical) scale in a glacier due to strong variability in crystal-orientation fabric (±50 m s-1 per 10 cm

Deconvolution-based resolution enhancement of chemical ice core records obtained by continuous flow analysis

DEFF Research Database (Denmark)

Rasmussen, Sune Olander; Andersen, Katrine K.; Johnsen, Sigfus Johann

2005-01-01

Continuous flow analysis (CFA) has become a popular measuring technique for obtaining high-resolution chemical ice core records due to an attractive combination of measuring speed and resolution. However, when analyzing the deeper sections of ice cores or cores from low-accumulation areas...... of the data for high-resolution studies such as annual layer counting. The presented method uses deconvolution techniques and is robust to the presence of noise in the measurements. If integrated into the data processing, it requires no additional data collection. The method is applied to selected ice core...

10Be evidence for the Matuyama-Brunhes geomagnetic reversal in the EPICA Dome C ice core.

Science.gov (United States)

Raisbeck, G M; Yiou, F; Cattani, O; Jouzel, J

2006-11-02

An ice core drilled at Dome C, Antarctica, is the oldest ice core so far retrieved. On the basis of ice flow modelling and a comparison between the deuterium signal in the ice with climate records from marine sediment cores, the ice at a depth of 3,190 m in the Dome C core is believed to have been deposited around 800,000 years ago, offering a rare opportunity to study climatic and environmental conditions over this time period. However, an independent determination of this age is important because the deuterium profile below a depth of 3,190 m depth does not show the expected correlation with the marine record. Here we present evidence for enhanced 10Be deposition in the ice at 3,160-3,170 m, which we interpret as a result of the low dipole field strength during the Matuyama-Brunhes geomagnetic reversal, which occurred about 780,000 years ago. If correct, this provides a crucial tie point between ice cores, marine cores and a radiometric timescale.

The Second Deep Ice Coring Project at Dome Fuji, Antarctica

Directory of Open Access Journals (Sweden)

Hideaki Motoyama

2007-09-01

Full Text Available Throughout the history of the polar icecaps, dust and aerosols have been transported through the atmosphere to the poles, to be preserved within the annually freezing ice of the growing ice shields. Therefore, the Antarctic ice sheet is a “time capsule" for environmental data, containing information of ancient periods of Earth’s history. To unravel this history and decode cycles in glaciations and global change is among the major goals of the Dome Fuji Ice Coring Project.

Experimental results on improved JARE deep ice core drill-Experiments in Rikubetsu, Hokkaido in 2002 -

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Takao Kameda

2002-07-01

Full Text Available Deep ice coring to bedrock (3028m in depth at Dome Fuji Station is planned during three successive summer seasons starting from 2003/2004. An improved JARE deep ice core drill (12.2m in length and 3.8m in maximum core length was developed in December 2001 for the ice coring at Dome Fuji. In January/February of 2002,we performed experiments on drill performance using artificial ice blocks in Rikubetsu, Hokkaido. In this paper, we outline the experiment and report the results. It was found through the experiment that an ice core of 3.8m length was smoothly obtained by the improved drill with three screws in the chip chamber and cutting pitch of 5mm/cycle. About 45000 small holes 1.2mm in diameter were made on the surface of the chip chamber. These small holes enabled liquid to circulate between cutters and outside of the drill through the chip chamber in the drill. The dry density of the chips was 440 to 500kg/m^3 and the chip recovery rate during ice coring was 65 to 91%. A check valve installed at the bottom of the chip chamber to prevent outflow of chips from the drill was not tested enough, but more durability is needed for the valve. The newly developed motor system and core catchers of the drill worked perfectly. The average coring speed was 24.5cm/min with cutting pitch of 5mm/cycle. The average power consumption during ice coring was 171W.

Ice core records of climate variability on the Third Pole with emphasis on the Guliya ice cap, western Kunlun Mountains

Science.gov (United States)

Thompson, Lonnie G.; Yao, Tandong; Davis, Mary E.; Mosley-Thompson, Ellen; Wu, Guangjian; Porter, Stacy E.; Xu, Baiqing; Lin, Ping-Nan; Wang, Ninglian; Beaudon, Emilie; Duan, Keqin; Sierra-Hernández, M. Roxana; Kenny, Donald V.

2018-05-01

Records of recent climate from ice cores drilled in 2015 on the Guliya ice cap in the western Kunlun Mountains of the Tibetan Plateau, which with the Himalaya comprises the Third Pole (TP), demonstrate that this region has become warmer and moister since at least the middle of the 19th century. Decadal-scale linkages are suggested between ice core temperature and snowfall proxies, North Atlantic oceanic and atmospheric processes, Arctic temperatures, and Indian summer monsoon intensity. Correlations between annual-scale oxygen isotopic ratios (δ18O) and tropical western Pacific and Indian Ocean sea surface temperatures are also demonstrated. Comparisons of climate records during the last millennium from ice cores acquired throughout the TP illustrate centennial-scale differences between monsoon and westerlies dominated regions. Among these records, Guliya shows the highest rate of warming since the end of the Little Ice Age, but δ18O data over the last millennium from TP ice cores support findings that elevation-dependent warming is most pronounced in the Himalaya. This, along with the decreasing precipitation rates in the Himalaya region, is having detrimental effects on the cryosphere. Although satellite monitoring of glaciers on the TP indicates changes in surface area, only a few have been directly monitored for mass balance and ablation from the surface. This type of ground-based study is essential to obtain a better understanding of the rate of ice shrinkage on the TP.

Deuterium excess record in a southern Tibetan ice core and its potential climatic implications

Energy Technology Data Exchange (ETDEWEB)

Zhao, Huabiao; Xu, Baiqing; Yao, Tandong; Wu, Guangjian; Lin, Shubiao; Gao, Jing; Wang, Mo [Chinese Academy of Sciences, Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Beijing (China)

2012-05-15

A 55-m long ice core, drilled close to bedrock from Mt. Noijin Kangsang on the southern Tibetan Plateau in summer 2007, was annually dated covering the period of 1864-2006 AD. The stable isotope ratios ({delta} {sup 18}O and {delta}D) of the ice core were measured and thereby the deuterium excess (d) was calculated by d = {delta}D - 8*{delta} {sup 18}O for the individual ice samples. Results show that the d values of the ice samples were predominantly controlled by the moisture sources. The significant increasing trend of annual mean d values along the ice core is mainly related to the rapid warming of the tropical Indian Ocean, although the tendency is subjected to the modulation by the western-derived moisture. The decreasing Indian monsoon precipitation on the southern Tibetan Plateau, physically linked with the increasing tropical Indian Ocean SST, reduced the share of monsoon precipitation in the annual total accumulation, making an additional contribution to the significant increase of annual mean d in the Noijin Kangsang ice core with high values during the past 143 years. (orig.)

Identifying deformation mechanisms in the NEEM ice core using EBSD measurements

Science.gov (United States)

Kuiper, Ernst-Jan; Weikusat, Ilka; Drury, Martyn R.; Pennock, Gill M.; de Winter, Matthijs D. A.

2015-04-01

Deformation of ice in continental sized ice sheets determines the flow behavior of ice towards the sea. Basal dislocation glide is assumed to be the dominant deformation mechanism in the creep deformation of natural ice, but non-basal glide is active as well. Knowledge of what types of deformation mechanisms are active in polar ice is critical in predicting the response of ice sheets in future warmer climates and its contribution to sea level rise, because the activity of deformation mechanisms depends critically on deformation conditions (such as temperature) as well as on the material properties (such as grain size). One of the methods to study the deformation mechanisms in natural materials is Electron Backscattered Diffraction (EBSD). We obtained ca. 50 EBSD maps of five different depths from a Greenlandic ice core (NEEM). The step size varied between 8 and 25 micron depending on the size of the deformation features. The size of the maps varied from 2000 to 10000 grid point. Indexing rates were up to 95%, partially by saving and reanalyzing the EBSP patterns. With this method we can characterize subgrain boundaries and determine the lattice rotation configurations of each individual subgrain. Combining these observations with arrangement/geometry of subgrain boundaries the dislocation types can be determined, which form these boundaries. Three main types of subgrain boundaries have been recognized in Antarctic (EDML) ice core¹². Here, we present the first results obtained from EBSD measurements performed on the NEEM ice core samples from the last glacial period, focusing on the relevance of dislocation activity of the possible slip systems. Preliminary results show that all three subgrain types, recognized in the EDML core, occur in the NEEM samples. In addition to the classical boundaries made up of basal dislocations, subgrain boundaries made of non-basal dislocations are also common. ¹Weikusat, I.; de Winter, D. A. M.; Pennock, G. M.; Hayles, M

Extraction of trapped gases in ice cores for isotope analysis

International Nuclear Information System (INIS)

Leuenberger, M.; Bourg, C.; Francey, R.; Wahlen, M.

2002-01-01

The use of ice cores for paleoclimatic investigations is discussed in terms of their application for dating, temperature indication, spatial time marker synchronization, trace gas fluxes, solar variability indication and changes in the Dole effect. The different existing techniques for the extraction of gases from ice cores are discussed. These techniques, all to be carried out under vacuum, are melt-extraction, dry-extraction methods and the sublimation technique. Advantages and disadvantages of the individual methods are listed. An extensive list of references is provided for further detailed information. (author)

TALDICE-1 age scale of the Talos Dome deep ice core, East Antarctica

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D. Buiron

2011-01-01

Full Text Available A new deep ice core drilling program, TALDICE, has been successfully handled by a European team at Talos Dome, in the Ross Sea sector of East Antarctica, down to 1620 m depth. Using stratigraphic markers and a new inverse method, we produce the first official chronology of the ice core, called TALDICE-1. We show that it notably improves an a priori chronology resulting from a one-dimensional ice flow model. It is in agreement with a posteriori controls of the resulting accumulation rate and thinning function along the core. An absolute uncertainty of only 300 yr is obtained over the course of the last deglaciation. This uncertainty remains lower than 600 yr over Marine Isotope Stage 3, back to 50 kyr BP. The phasing of the TALDICE ice core climate record with respect to the central East Antarctic plateau and Greenland records can thus be determined with a precision allowing for a discussion of the mechanisms at work at sub-millennial time scales.

Glacial–interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-δ15N measurements

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E. Capron

2013-05-01

Full Text Available Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: outputs of a firn densification model, and measurements of δ15N of N2 in air trapped in ice core, assuming that δ15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML Antarctic regions. Combined with available ice core air-δ15N measurements from the EPICA Dome C (EDC site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our δ15N profiles reveal a heterogeneous response of the firn structure to glacial–interglacial climatic changes. While firn densification simulations correctly predict TALDICE δ15N variations, they systematically fail to capture the large millennial-scale δ15N variations measured at BI and the δ15N glacial levels measured at JRI and EDML – a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas–ice depth offset during the Laschamp event (~41 ka and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model–δ15N data mismatch for this site. While we could not conduct an in-depth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the δ15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification

First identification and characterization of Borrobol-type tephra in the Greenland ice cores

DEFF Research Database (Denmark)

Cook, Eliza; Davies, Siwan M.; Guðmundsdóttir, Esther R.

2018-01-01

in the ice-cores or that it relates to just one of the ice-core events. A firm correlation cannot be established at present due to their strong geochemical similarities. The older tephra horizon, found within all three ice-cores and dated to 17326 ± 319 a b2k, can be correlated to a known layer within marine....... The older deposit is consistent with BT age estimates derived from Scottish sites, while the younger deposit overlaps with both BT and PT age estimates. We suggest that either the BT in Northern European terrestrial sequences represents an amalgamation of tephra from both of the GI-1e events identified...

Chronology of Pu isotopes and 236U in an Arctic ice core.

Science.gov (United States)

Wendel, C C; Oughton, D H; Lind, O C; Skipperud, L; Fifield, L K; Isaksson, E; Tims, S G; Salbu, B

2013-09-01

In the present work, state of the art isotopic fingerprinting techniques are applied to an Arctic ice core in order to quantify deposition of U and Pu, and to identify possible tropospheric transport of debris from former Soviet Union test sites Semipalatinsk (Central Asia) and Novaya Zemlya (Arctic Ocean). An ice core chronology of (236)U, (239)Pu, and (240)Pu concentrations, and atom ratios, measured by accelerator mass spectrometry in a 28.6m deep ice core from the Austfonna glacier at Nordaustlandet, Svalbard is presented. The ice core chronology corresponds to the period 1949 to 1999. The main sources of Pu and (236)U contamination in the Arctic were the atmospheric nuclear detonations in the period 1945 to 1980, as global fallout, and tropospheric fallout from the former Soviet Union test sites Novaya Zemlya and Semipalatinsk. Activity concentrations of (239+240)Pu ranged from 0.008 to 0.254 mBq cm(-2) and (236)U from 0.0039 to 0.053 μBq cm(-2). Concentrations varied in concordance with (137)Cs concentrations in the same ice core. In contrast to previous published results, the concentrations of Pu and (236)U were found to be higher at depths corresponding to the pre-moratorium period (1949 to 1959) than to the post-moratorium period (1961 and 1962). The (240)Pu/(239)Pu ratio ranged from 0.15 to 0.19, and (236)U/(239)Pu ranged from 0.18 to 1.4. The Pu atom ratios ranged within the limits of global fallout in the most intensive period of nuclear atmospheric testing (1952 to 1962). To the best knowledge of the authors the present work is the first publication on biogeochemical cycles with respect to (236)U concentrations and (236)U/(239)Pu atom ratios in the Arctic and in ice cores. Copyright © 2013 Elsevier B.V. All rights reserved.

Direct north-south synchronization of abrupt climate change record in ice cores using Beryllium 10

Directory of Open Access Journals (Sweden)

G. M. Raisbeck

2007-09-01

Full Text Available A new, decadally resolved record of the ¹⁰Be peak at 41 kyr from the EPICA Dome C ice core (Antarctica is used to match it with the same peak in the GRIP ice core (Greenland. This permits a direct synchronisation of the climatic variations around this time period, independent of uncertainties related to the ice age-gas age difference in ice cores. Dansgaard-Oeschger event 10 is in the period of best synchronisation and is found to be coeval with an Antarctic temperature maximum. Simulations using a thermal bipolar seesaw model agree reasonably well with the observed relative climate chronology in these two cores. They also reproduce three Antarctic warming events observed between A1 and A2.

Solid and gaseous inclusions in the EDML deep ice core: origins and implications for the physical properties of polar ice

Science.gov (United States)

Faria, S. H.; Kipfstuhl, S.; Garbe, C. S.; Bendel, V.; Weikusat, C.; Weikusat, I.

2010-12-01

The great value of polar deep ice cores stems mainly from two essential features of polar ice: its crystalline structure and its impurities. They determine the physical properties of the ice matrix and provide proxies for the investigation of past climates. Experience shows that these two essential features of polar ice manifest themselves in a multiscale diversity of dynamic structures, including dislocations, grain boundaries, solid particles, air bubbles, clathrate hydrates and cloudy bands, among others. The fact that these structures are dynamic implies that they evolve with time through intricate interactions between the crystalline structure, impurities, and the ice flow. Records of these interactions have been carefully investigated in samples of the EPICA deep ice core drilled in Dronning Maud Land, Antarctica (75°S, 0°E, 2882 m elevation, 2774.15 m core length). Here we show how the distributions of sizes and shapes of air bubbles correlate with impurities and the crystalline structure, how the interaction between moving grain boundaries and micro-inclusions changes with ice depth and temperature, as well as the possible causes for the abrupt change in ice rheology observed in the MIS6-MIS5e transition. We also discuss how these observations may affect the flow of the ice sheet and the interpretation of paleoclimate records. Micrograph of an EDML sample from 555m depth. One can identify air bubbles (dark, round objects), microinclusions (tiny defocused spots), and a grain boundary pinned by a bubble. The width of the image is 700 micrometers.

Using high resolution tritium profiles to quantify the effects of melt on two Spitsbergen ice cores

NARCIS (Netherlands)

van der Wel, L.G.; Streurman, H.J.; Isaksson, E.; Helsen, M.M.; van de Wal, R.S.W.; Martma, T.; Pohjola, V.A.; Moore, J.C.; Meijer, H.A.J.

2011-01-01

Ice cores from small ice caps provide valuable climatic information, additional to that of Greenland and Antarctica. However, their integrity is usually compromised by summer meltwater percolation. To determine to what extent this can affect such ice cores, we performed high-resolution tritium

Using high-resolution tritium profiles to quantify the effects of melt on two Spitsbergen ice cores

NARCIS (Netherlands)

Wel, L.G. van der; Streurman, H.J.; Isaksson, E.; Helsen, M.M.; Wal, R.S.W. van de; Martma, T.; Pohjola, V.A.; Moore, J.C.; Meijer, H.A.J.

2011-01-01

Ice cores from small ice caps provide valuable climatic information, additional to that of Greenland and Antarctica. However, their integrity is usually compromised by summer meltwater percolation. To determine to what extent this can affect such ice cores, we performed high-resolution tritium

Proxies and measurement techinques for mineral dust in antarctic ice cores

DEFF Research Database (Denmark)

Ruth..[], Urs; Bigler, Matthias

2008-01-01

analysis), elemental analysis (inductively coupled plasma mass spectroscopy at pH 1 and after full acid digestion), and water-insoluble elemental analysis (proton induced X-ray emission). Antarctic ice core samples covering the last deglaciation from the EPICA Dome C (EDC) and the EPICA Dronning Maud Land......-MS measurements depends on the digestion method and is different for different elements and during different climatic periods. EDC and EDML samples have similar dust composition, which suggests a common dust source or a common mixture of sources for the two sites. The analyzed samples further reveal a change...

Detailed history of atmospheric trace elements from the Quelccaya ice core (Southern Peru) during the last 1200 years

Science.gov (United States)

Uglietti, C.; Gabrielli, P.; Thompson, L. G.

2013-12-01

The recent increase in trace element concentrations, for example Cr, Cu, Zn, Ag, Pb, Bi, and U, in polar snow and ice has provided compelling evidence of a hemispheric change in atmospheric composition since the nineteenth century. This change has been concomitant with the expansion of the Industrial Revolution and points towards an anthropogenic source of trace elements in the atmosphere. There are very few low latitude trace element ice core records and these are believed to be sensitive to perturbations of regional significance. To date, these records have not been used to document a preindustrial anthropogenic impact on atmospheric composition at low latitudes. Ice cores retrieved from the tropical Andes are particularly interesting because they have the potential to reveal detailed information about the evolution and environmental consequences of mineral exploitation related to the Pre Inca Civilizations, the Inca Empire (1438-1533 AD) and the subsequent Spanish invasion and dominance (1532-1833 AD). The chemical record preserved in the ice of the Quelccaya ice cap (southern Peruvian Andes) offers the exceptional opportunity to geochemically constrain the composition of the tropical atmosphere at high resolution over the last ~1200 years. Quantification of twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V, and Zn) was performed by ICP-SFMS over 105 m of the Quelccaya North Dome core (5600 m asl, 128.57 m) by analyzing 2450 samples. This provides the first atmospheric trace element record in South America spanning continuously and at high resolution for the time period between 1990 and 790 AD. Ag, As, Bi, Cd, Cr, Co, Cu, Mn, Mo, Sb, Sn, Pb and Zn show increases in concentration and crustal enrichment factor starting at different times between 1450 and 1550 AD, in concomitance with the expansions of the Inca Empire and, subsequently, the Spanish Empire well before the inception of the Industrial Revolution. This

Trace elements in a dated ice core from Antarctica

International Nuclear Information System (INIS)

Keshin, S.S.; Xudong Huang; Olmez, I.; Langway, C.C. Jr.

1992-01-01

Aerosol particles from both natural and anthropogenic sources are emitted into the atmosphere and transported by wind systems by various mechanisms. Once airborne, the particles, which contain various trace elements, accumulate on the earth's surface as either condensation nuclei or by dry fallout processes. In the polar regions, these particles are incorporated and deposited in snow layers in sequential time-unit increments. The trace analysis of elements contained in dated annual snow layers provides a measure of the elemental chemistry content of the atmosphere for the same time interval. A 164-m-deep, 10-cm-diam ice core was obtained at Byrd Station, Antarctica, in November 1989. Other physical and chemistry studies on this ice core have identified its detailed chronology in annual increments for the past 1360 yr. This study presents the results of the instrumental neutron activation analysis (INAA) measurements made on 26 individually dated samples of this core, selected between the 6.43- and 118.15-m depths

Solving the riddle of interglacial temperatures over the last 1.5 million years with a future IPICS "Oldest Ice" ice core

Science.gov (United States)

Fischer, Hubertus

2014-05-01

The sequence of the last 8 glacial cycles is characterized by irregular 100,000 year cycles in temperature and sea level. In contrast, the time period between 1.5-1.2 million years ago is characterized by more regular cycles with an obliquity periodicity of 41,000 years. Based on a deconvolution of deep ocean temperature and ice volume contributions to benthic δ18O (Elderfield et al., Science, 2012), it is suggested that glacial sea level became progressively lower over the last 1.5 Myr, while glacial deep ocean temperatures were very similar. At the same time many interglacials prior to the Mid Brunhes event showed significantly cooler deep ocean temperatures than the Holocene, while at the same time interglacial ice volume remained essentially the same. In contrast, interglacial sea surface temperatures in the tropics changed little (Herbert et al., Science,2010) and proxy reconstructions of atmospheric CO2 using δ11B in planktic foraminifera (Hönisch et al., Science, 2009) suggest that prior to 900,000 yr before present interglacial CO2 levels did not differ substantially from those over the last 450,000 years. Accordingly, the conundrum arises how interglacials can differ in deep ocean temperature without any obvious change in ice volume or greenhouse gas forcing and what caused the change in cyclicity of glacial interglacial cycles over the Mid Pleistocene Transition. Probably the most important contribution to solve this riddle is the recovery of a 1.5 Myr old ice core from Antarctica, which among others would provide an unambiguous, high-resolution record of the greenhouse gas history over this time period. Accordingly, the international ice core community, as represented by the International Partnership for Ice Core Science (IPICS), has identified such an 'Oldest Ice' ice core as one of the most important scientific targets for the future (http://www.pages.unibe.ch/ipics/white-papers). However, finding stratigraphically undisturbed ice, which covers this

The significance of volcanic ash in Greenland ice cores during the Common Era

Science.gov (United States)

Plunkett, G.; Pilcher, J. R.; McConnell, J. R.; Sigl, M.; Chellman, N.

2017-12-01

Volcanic forcing is now widely regarded as a leading natural factor in short-term climate variability. Polar ice cores provide an unrivalled and continuous record of past volcanism through their chemical and particulate content. With an almost annual precision for the Common Era, the ice core volcanic record can be combined with historical data to investigate the climate and social impacts of the eruptions. The sulfate signature in ice cores is critical for determining the possible climate effectiveness of an eruption, but the presence and characterization of volcanic ash (tephra) in the ice is requisite for establishing the source eruption so that location and eruptive style can be better factored in to climate models. Here, we review the Greenland tephra record for the Common Era, and present the results of targeted sampling for tephra of volcanic events that are of interest either because of their suspected climate and societal impacts or because of their potential as isochrons in paleoenvironmental (including ice core) archives. The majority of identifiable tephras derive from Northern Hemisphere mid- to high latitude eruptions, demonstrating the significance of northern extra-tropical volcanic regions as a source of sulfates in Greenland. A number of targets are represented by sparse or no tephra, or shards that cannot be firmly correlated with a source. We consider the challenges faced in isolating and characterizing tephra from low latitude eruptions, and the implications for accurately modelling climate response to large, tropical events. Finally, we compare the ice core tephra record with terrestrial tephrostratigraphies in the circum-North Atlantic area to evaluate the potential for intercontinental tephra linkages and the refinement of volcanic histories.

Correlating Ice Cores from Quelccaya Ice Cap with Chronology from Little Ice Age Glacial Extents

Science.gov (United States)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.

2010-12-01

Proxy records indicate Southern Hemisphere climatic changes during the Little Ice Age (LIA; ~1300-1850 AD). In particular, records of change in and around the tropical latitudes require attention because these areas are sensitive to climatic change and record the dynamic interplay between hemispheres (Oerlemans, 2005). Despite this significance, relatively few records exist for the southern tropics. Here we present a reconstruction of glacial fluctuations of Quelccaya Ice Cap (QIC), Peruvian Andes, from pre-LIA up to the present day. In the Qori Kalis valley, extensive sets of moraines exist beginning with the 1963 AD ice margin (Thompson et al., 2006) and getting progressively older down valley. Several of these older moraines can be traced and are continuous with moraines in the Challpa Cocha valley. These moraines have been dated at chronology of past ice cap extents are correlated with ice core records from QIC which show an accumulation increase during ~1500-1700 AD and an accumulation decrease during ~1720-1860 AD (Thompson et al., 1985; 1986; 2006). In addition, other proxy records from Peru and the tropics are correlated with the records at QIC as a means to understand climate conditions during the LIA. This work forms the basis for future modeling of the glacial system during the LIA at QIC and for modeling of past temperature and precipitation regimes at high altitude in the tropics.

1500 Years of Annual Climate and Environmental Variability as Recorded in Bona-Churchill (Alaska) Ice Cores

Science.gov (United States)

Thompson, L. G.; Mosley-Thompson, E. S.; Zagorodnov, V.; Davis, M. E.; Mashiotta, T. A.; Lin, P.

2004-12-01

In 2003, six ice cores measuring 10.5, 11.5, 11.8, 12.4, 114 and 460 meters were recovered from the col between Mount Bona and Mount Churchill (61° 24'N; 141° 42'W; 4420 m asl). These cores have been analyzed for stable isotopic ratios, insoluble dust content and concentrations of major chemical species. Total Beta radioactivity was measured in the upper sections. The 460-meter core, extending to bedrock, captured the entire depositional record at this site where ice temperatures ranged from -24° C at 10 meters to -19.8° C at the ice/bedrock contact. The shallow cores allow assessment of surface processes under modern meteorological conditions while the deep core offers a ˜1500-year climate and environmental perspective. The average annual net balance is ˜~1000 mm of water equivalent and distinct annual signals in dust and calcium concentrations along with δ 18O allow annual resolution over most of the core. The excess sulfate record reflects many known large volcanic eruptions such as Katmai, Krakatau, Tambora, and Laki which allow validation of the time scale in the upper part of the core. The lower part of the core yields a history of earlier volcanic events. The 460-m Bona-Churchill ice core provides a detailed history of the `Little Ice Age' and medieval warm periods for southeastern Alaska. The source of the White River Ash will be discussed in light of the evidence from this core. The 460-m core also provides a long-term history of the dust fall that originates in north-central China. The annual ice core-derived climate records from southeastern Alaska will facilitate an investigation of the likelihood that the high resolution 1500-year record from the tropical Quelccaya Ice Cap (Peru) preserves a history of the variability of both the PDO and the Aleutian Low.

Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium

Science.gov (United States)

Bohleber, Pascal; Erhardt, Tobias; Spaulding, Nicole; Hoffmann, Helene; Fischer, Hubertus; Mayewski, Paul

2018-01-01

Among ice core drilling sites in the European Alps, Colle Gnifetti (CG) is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a Little Ice Age cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100-1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.

Greenland ice core evidence for spatial and temporal variability of the Atlantic Multidecadal Oscillation

NARCIS (Netherlands)

Chylek, P.; Folland, C.K.; Frankcombe, L.M.; Dijkstra, H.A.; Lesins, G.; Dubey, M.

2012-01-01

[1] The Greenland δ18O ice core record is used as a proxy for Greenland surface air temperatures and to interpret Atlantic Multidecadal Oscillation (AMO) variability. An analysis of annual δ18O data from six Arctic ice cores (five from Greenland and one from Canada's Ellesmere Island) suggests a

The Mount Logan (Yukon) Ice Cores: Preliminary Results

Science.gov (United States)

Fisher, D. A.

2004-05-01

Three ice cores were taken at different elevations on or near My Logan in the years 2001 and 2002. The summit core (PRCol) comes from the summit plateau ( 5340 masl, length 187 m to bedrock, mean temperature -29 C ) and was done by the Geological Survey of Canada. The NIPR group cored 210m on the flanks of the mountain at King Col (4200 masl mean temperature -16C) and the UNH group cored 20 km from the mountain at Eclipse "Dome" (3015 masl,length 345 m mean temperature -5C) . The three cores were done cooperatively by GSC, NIPR and UNH and cover nominally 30 ka, 1 ka and 2ka respectively . Located very close to the Gulf of Alaska these core records are thought to reflect the climate history of the Pacific Ocean and having three widely spaced elevations, the sites "see" different distances to different sources. The lowest site (Eclipse) has excellent seasonals but a very muted δ 18O history with no obvious little ice age, whereas the most recent 1ka of the PRCol summit sites contains two very large and sudden δ 18O and d (deuterium excess) shifts at 1850 AD and ~ 800 AD. The δ 18O shifts which happen from one year to the next are about 4 o/oo . The summit site (PRCol) δ 18O response is "backwards", ie the Little Ice Age δ 18O values are 4 o/oo more positive than recent ones. The PRCol δ 18O and d suggest that the source water can either be ëlocalí (Gulf of Alaska) or very distant (tropics) . The Eclipse site seems only to get the local water . A massive dust storm originating in central Asia (Gobi) in April 2001 dumped a visible layer all over the St Elias Mountains and this layer was sampled, to provide a calibration "Asian dust event". The satellite and isotoic signatures both agreed that Gobi was the source. The PRCol record covers the Holocene and well back into the ice age. The transition is defined by a sudden ECM shift on the flanks of a more gradual O18 shift. Acknowledgements. Logan consortium consists of : Geological Survey of Canada : Jocelyne

High-resolution 129I bomb peak profile in an ice core from SE-Dome site, Greenland.

Science.gov (United States)

Bautista, Angel T; Miyake, Yasuto; Matsuzaki, Hiroyuki; Iizuka, Yoshinori; Horiuchi, Kazuho

2018-04-01

129 I in natural archives, such as ice cores, can be used as a proxy for human nuclear activities, age marker, and environmental tracer. Currently, there is only one published record of 129 I in ice core (i.e., from Fiescherhorn Glacier, Swiss Alps) and its limited time resolution (1-2 years) prevents the full use of 129 I for the mentioned applications. Here we show 129 I concentrations in an ice core from SE-Dome, Greenland, covering years 1956-1976 at a time resolution of ∼6 months, the most detailed record to date. Results revealed 129 I bomb peaks in years 1959, 1962, and 1963, associated to tests performed by the former Soviet Union, one year prior, in its Novaya Zemlya test site. All 129 I bomb peaks were observed in winter (1958.9, 1962.1, and 1963.0), while tritium bomb peaks, another prominent radionuclide associated with nuclear bomb testing, were observed in spring or summer (1959.3, and 1963.6; Iizuka et al., 2017). These results indicate that 129 I bomb peaks can be used as annual and seasonal age markers for these years. Furthermore, we found that 129 I recorded nuclear fuel reprocessing signals and that these can be potentially used to correct timing of estimated 129 I releases during years 1964-1976. Comparisons with other published records of 129 I in natural archives showed that 129 I can be used as common age marker and tracer for different types of records. Most notably, the 1963 129 I bomb peak can be used as common age marker for ice and coral cores, providing the means to reconcile age models and associated trends from the polar and tropical regions, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chronology of Pu isotopes and {sup 236}U in an Arctic ice core

Energy Technology Data Exchange (ETDEWEB)

Wendel, C.C., E-mail: cato.wendel@umb.no [Isotope Laboratory, Department of Plant and Environmental Sciences, Agricultural University of Norway, P.O. Box 5003, N-1432 Aas (Norway); Oughton, D.H., E-mail: deborah.oughton@umb.no [Isotope Laboratory, Department of Plant and Environmental Sciences, Agricultural University of Norway, P.O. Box 5003, N-1432 Aas (Norway); Lind, O.C., E-mail: ole-christian.lind@umb.no [Isotope Laboratory, Department of Plant and Environmental Sciences, Agricultural University of Norway, P.O. Box 5003, N-1432 Aas (Norway); Skipperud, L., E-mail: lindis.skipperud@umb.no [Isotope Laboratory, Department of Plant and Environmental Sciences, Agricultural University of Norway, P.O. Box 5003, N-1432 Aas (Norway); Fifield, L.K., E-mail: keith.fifield@anu.edu.au [Department of Nuclear Physics, Australian National University, Canberra ACT 0200 (Australia); Isaksson, E., E-mail: elisabeth.isaksson@npolar.no [Norwegian Polar Institute, Fram Centre, Hjalmar Johansens Gate 14, N9296 Tromsø (Norway); Tims, S.G., E-mail: steve.tims@anu.edu.au [Department of Nuclear Physics, Australian National University, Canberra ACT 0200 (Australia); Salbu, B., E-mail: brit.salbu@umb.no [Isotope Laboratory, Department of Plant and Environmental Sciences, Agricultural University of Norway, P.O. Box 5003, N-1432 Aas (Norway)

2013-09-01

In the present work, state of the art isotopic fingerprinting techniques are applied to an Arctic ice core in order to quantify deposition of U and Pu, and to identify possible tropospheric transport of debris from former Soviet Union test sites Semipalatinsk (Central Asia) and Novaya Zemlya (Arctic Ocean). An ice core chronology of {sup 236}U, {sup 239}Pu, and {sup 240}Pu concentrations, and atom ratios, measured by accelerator mass spectrometry in a 28.6 m deep ice core from the Austfonna glacier at Nordaustlandet, Svalbard is presented. The ice core chronology corresponds to the period 1949 to 1999. The main sources of Pu and {sup 236}U contamination in the Arctic were the atmospheric nuclear detonations in the period 1945 to 1980, as global fallout, and tropospheric fallout from the former Soviet Union test sites Novaya Zemlya and Semipalatinsk. Activity concentrations of {sup 239+240}Pu ranged from 0.008 to 0.254 mBq cm{sup −2} and {sup 236}U from 0.0039 to 0.053 μBq cm{sup −2}. Concentrations varied in concordance with {sup 137}Cs concentrations in the same ice core. In contrast to previous published results, the concentrations of Pu and {sup 236}U were found to be higher at depths corresponding to the pre-moratorium period (1949 to 1959) than to the post-moratorium period (1961 and 1962). The {sup 240}Pu/{sup 239}Pu ratio ranged from 0.15 to 0.19, and {sup 236}U/{sup 239}Pu ranged from 0.18 to 1.4. The Pu atom ratios ranged within the limits of global fallout in the most intensive period of nuclear atmospheric testing (1952 to 1962). To the best knowledge of the authors the present work is the first publication on biogeochemical cycles with respect to {sup 236}U concentrations and {sup 236}U/{sup 239}Pu atom ratios in the Arctic and in ice cores. - Highlights: • Concentrations and atom ratios of Pu and {sup 236}U determined in an Arctic ice core. • Concentrations of U and Pu found to be higher pre- than post-moratorium. • U and Pu concentrations

Measurement of the fracture toughness of polycrystalline bubbly ice from an Antarctic ice core

Directory of Open Access Journals (Sweden)

J. Christmann

2015-05-01

Full Text Available The critical fracture toughness is a material parameter describing the resistance of a cracked body to further crack extension. It is an important parameter for simulating and predicting the breakup behavior of ice shelves from the calving of single icebergs to the disintegration of entire ice shelves over a wide range of length scales. The fracture toughness values are calculated with equations that are derived from an elastic stress analysis. Additionally, an X-ray computer tomography (CT scanner was used to identify the density as a function of depth. The critical fracture toughness of 91 Antarctic bubbly ice samples with densities between 840 and 870 kg m−3 has been determined by applying a four-point bending technique on single-edge v-notched beam samples. The examined ice core was drilled 70 m north of Kohnen Station, Dronnning Maud Land (75°00' S, 00°04' E; 2882 m. Supplementary data are available at doi:10.1594/PANGAEA.835321.

Retrieving a common accumulation record from Greenland ice cores for the past 1800 years

DEFF Research Database (Denmark)

Andersen, Katrine K.; Ditlevsen, Peter D.; Rasmussen, Sune Olander

2006-01-01

In the accumulation zone of the Greenland ice sheet the annual accumulation rate may be determined through identification of the annual cycle in the isotopic climate signal and other parameters that exhibit seasonal variations. On an annual basis the accumulation rate in different Greenland ice...... cores is highly variable, and the degree of correlation between accumulation series from different ice cores is low. However, when using multiyear averages of the different accumulation records, the correlation increases significantly. A statistical model has been developed to estimate the common...

RICE ice core: Black Carbon reflects climate variability at Roosevelt Island, West Antarctica

Science.gov (United States)

Ellis, Aja; Edwards, Ross; Bertler, Nancy; Winton, Holly; Goodwin, Ian; Neff, Peter; Tuohy, Andrea; Proemse, Bernadette; Hogan, Chad; Feiteng, Wang

2015-04-01

The Roosevelt Island Climate Evolution (RICE) project successfully drilled a deep ice core from Roosevelt Island during the 2011/2012 and 2012/2013 seasons. Located in the Ross Ice Shelf in West Antarctica, the site is an ideal location for investigating climate variability and the past stability of the Ross Ice Shelf. Black carbon (BC) aerosols are emitted by both biomass burning and fossil fuels, and BC particles emitted in the southern hemisphere are transported in the atmosphere and preserved in Antarctic ice. The past record of BC is expected to be sensitive to climate variability, as it is modulated by both emissions and transport. To investigate BC variability over the past 200 years, we developed a BC record from two overlapping ice cores (~1850-2012) and a high-resolution snow pit spanning 2010-2012 (cal. yr). Consistent results are found between the snow pit profiles and ice core records. Distinct decadal trends are found with respect to BC particle size, and the record indicates a steady rise in BC particle size over the last 100 years. Differences in emission sources and conditions may be a possible explanation for changes in BC size. These records also show a significant increase in BC concentration over the past decade with concentrations rising over 1.5 ppb (1.5*10^-9 ng/g), suggesting a fundamental shift in BC deposition to the site.

Denali Ice Core MSA: A Record of North Pacific Primary Productivity

Science.gov (United States)

Polashenski, D.; Osterberg, E. C.; Winski, D.; Kreutz, K. J.; Wake, C. P.; Ferris, D. G.; Introne, D.; Campbell, S. W.

2017-12-01

The high nutrient, low chlorophyll region of the North Pacific is one of the most biologically productive marine ecosystems in the world and forms the basis of commercial, sport, and subsistence fisheries worth more than a billion dollars annually. Marine phytoplankton prove to be important both as the primary producers in these ecosystems and as a major source of biogenic sulfur emissions which have long been hypothesized to serve as a biological control on Earth's climate system. Despite their importance, the record of marine phytoplankton abundance and the flux of biogenic sulfur from these regions is not well constrained. In situ measurements of marine phytoplankton from oceanographic cruises over the past several decades are limited in both spatial and temporal resolution. Meanwhile, marine sediment records may provide insight on million year timescales, but lack decadal resolution due to slow sediment deposition rates and bioturbation. In this study, we aim to investigate changes in marine phytoplankton productivity of the northeastern subarctic Pacific Ocean (NSPO) over the twentieth century using the methanesulfonic acid (MSA) record from the Mt. Hunter ice cores drilled in Denali National Park, Alaska. These parallel, 208 meter long ice cores were drilled during the 2013 field season on the Mt. Hunter plateau (63° N, 151° W, 4,000 m above sea level). Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) modeling is used to identify likely source areas in the NSPO for MSA being transported to the core site. SeaWiFS satellite imagery allows for a direct comparison of chlorophyll a concentrations in these source areas with MSA concentrations in the core record through time. Our findings suggest that the Denali ice core MSA record reflects changes in the biological productivity of marine phytoplankton and shows a significant decline in MSA beginning in 1961. We investigate several hypotheses for potential mechanisms driving this MSA decline

Synchronising EDML and NorthGRIP ice cores using d18O of atmospheric oxygen (d18 Oatm) and CH4 measurements over MIS5 (80-123 kyr)

DEFF Research Database (Denmark)

Capron, E; Landais, A; Lemieux-Dudon, B

2010-01-01

Water isotope records from the EPICA Dronning Maud Land (EDML) and the NorthGRIP ice cores have revealed a one to one coupling between Antarctic Isotope Maxima (AIM) and Greenland Dansgaard-Oeschger (DO) events back to 50 kyr. In order to explore if this north-south coupling is persistent over...... Marine Isotopic Stage 5 (MIS 5). a common timescale must first be constructed. Here, we present new records of delta O-18 of O-2 (delta O-18(atm)) and methane (CH4) measured in the air trapped in ice from the EDML (68-147 kyr) and NorthGRIP (70-123 kyr) ice cores. We demonstrate that, through the period...... of interest, CH4 records alone are not sufficient to construct a common gas timescale between the two cores. Millennial-scale variations of delta O-18(atm) are evidenced over MIS 5 both on the Antarctic and Greenland ice cores and are coupled to CH4 profiles to synchronise the NorthGRIP and EDML records...

Annual layering in the NGRIP ice core during the Eemian

DEFF Research Database (Denmark)

Svensson, Anders; Bigler, Matthias; Kettner, Ernesto

2011-01-01

ice, annual layers can clearly be recognized, most prominently in the dust and conductivity profiles. Part of the samples is, however, contaminated in dust, most likely from drill liquid. It is interesting that the annual layering is preserved despite a very active crystal growth and grain boundary....... In this study, we apply a newly developed setup for high-resolution ice core impurity analysis to produce continuous records of dust, sodium and ammonium concentrations as well as conductivity of melt water. We analyzed three 2.2m sections of ice from the Eemian and the glacial inception. In all of the analyzed...

Climatic changes on orbital and sub-orbital time scale recorded by the Guliya ice core in Tibetan Plateau

Institute of Scientific and Technical Information of China (English)

姚檀栋; 徐柏青; 蒲健辰

2001-01-01

Based on ice core records in the Tibetan Plateau and Greenland, the features and possible causes of climatic changes on orbital and sub-orbital time scale were discussed. Orbital time scale climatic change recorded in ice core from the Tibetan Plateau is typically ahead of that from polar regions, which indicates that climatic change in the Tibetan Plateau might be earlier than polar regions. The solar radiation change is a major factor that dominates the climatic change on orbital time scale. However, climatic events on sub-orbital time scale occurred later in the Tibetan Plateau than in the Arctic Region, indicating a different mechanism. For example, the Younger Dryas and Heinrich events took place earlier in Greenland ice core record than in Guliya ice core record. It is reasonable to propose the hypothesis that these climatic events were affected possibly by the Laurentide Ice Sheet. Therefore, ice sheet is critically important to climatic change on sub-orbital time scale in some ice ages.

Optimization of High-Resolution Continuous Flow Analysis for Transient Climate Signals in Ice Cores

DEFF Research Database (Denmark)

Bigler, Matthias; Svensson, Anders; Kettner, Ernesto

2011-01-01

Over the past two decades, continuous flow analysis (CFA) systems have been refined and widely used to measure aerosol constituents in polar and alpine ice cores in very high-depth resolution. Here we present a newly designed system consisting of sodium, ammonium, dust particles, and electrolytic...... meltwater conductivity detection modules. The system is optimized for high- resolution determination of transient signals in thin layers of deep polar ice cores. Based on standard measurements and by comparing sections of early Holocene and glacial ice from Greenland, we find that the new system features...

A study of the decontamination procedures used for chemical analysis of polar deep ice cores

Directory of Open Access Journals (Sweden)

Takayuki Miyake

2009-11-01

Full Text Available We investigated the decontamination procedures used on polar deep ice cores before chemical analyses such as measurements of the concentrations of iron species and dust (microparticles. We optimized cutting and melting protocols for decontamination using chemically ultraclean polyethylene bags and simulated ice samples made from ultrapure water. For dust and ion species including acetate, which represented a high level of contamination, we were able to decrease contamination to below several μg l^ for ion concentrations and below 10000 particles ml^ for the dust concentration. These concentration levels of ion species and dust are assumed to be present in the Dome Fuji ice core during interglacial periods. Decontamination of the ice core was achieved by cutting away approximately 3 mm of the outside of a sample and by melting away approximately 30% of a sample's weight. Furthermore, we also report the preparation protocols for chemical analyses of the 2nd Dome Fuji ice core, including measurements of ion and dust concentrations, pH, electric conductivity (EC, and stable isotope ratios of water (δD and δO, based on the results of the investigation of the decontamination procedures.

Tracking the El Nino events from Antarctic ice core records

International Nuclear Information System (INIS)

Keskin, S.S.; Oelmez, I.

2004-01-01

Sodium and chlorine measurements were made by instrumental neutron activation analysis (INAA) on stratigraphically dated ice core samples from Byrd Station, Antarctica, for the last three centuries. The time period between 1969 and 1989 showed an enhanced impact on the Antarctic ice sheets from oceans in the form of marine aerosols. A disturbed ocean-atmosphere interface due to El Ni Southern Oscillation (ENSO) events seems to be a candidate for this observation in Antarctica. (author)

A 21 000-year record of fluorescent organic matter markers in the WAIS Divide ice core

Science.gov (United States)

D'Andrilli, Juliana; Foreman, Christine M.; Sigl, Michael; Priscu, John C.; McConnell, Joseph R.

2017-05-01

Englacial ice contains a significant reservoir of organic material (OM), preserving a chronological record of materials from Earth's past. Here, we investigate if OM composition surveys in ice core research can provide paleoecological information on the dynamic nature of our Earth through time. Temporal trends in OM composition from the early Holocene extending back to the Last Glacial Maximum (LGM) of the West Antarctic Ice Sheet Divide (WD) ice core were measured by fluorescence spectroscopy. Multivariate parallel factor (PARAFAC) analysis is widely used to isolate the chemical components that best describe the observed variation across three-dimensional fluorescence spectroscopy (excitation-emission matrices; EEMs) assays. Fluorescent OM markers identified by PARAFAC modeling of the EEMs from the LGM (27.0-18.0 kyr BP; before present 1950) through the last deglaciation (LD; 18.0-11.5 kyr BP), to the mid-Holocene (11.5-6.0 kyr BP) provided evidence of different types of fluorescent OM composition and origin in the WD ice core over 21.0 kyr. Low excitation-emission wavelength fluorescent PARAFAC component one (C1), associated with chemical species similar to simple lignin phenols was the greatest contributor throughout the ice core, suggesting a strong signature of terrestrial OM in all climate periods. The component two (C2) OM marker, encompassed distinct variability in the ice core describing chemical species similar to tannin- and phenylalanine-like material. Component three (C3), associated with humic-like terrestrial material further resistant to biodegradation, was only characteristic of the Holocene, suggesting that more complex organic polymers such as lignins or tannins may be an ecological marker of warmer climates. We suggest that fluorescent OM markers observed during the LGM were the result of greater continental dust loading of lignin precursor (monolignol) material in a drier climate, with lower marine influences when sea ice extent was higher and

Changes in Black Carbon Deposition to Antarctica from Two Ice Core Records, A.D. 1850-2000

Science.gov (United States)

Bisiaux, Marion M.; Edward, Ross; McConnell, Joseph R.; Curran, Mark A. J.; VanOmmen, Tas D.; Smith, Andrew M.; Neumann, Thomas A.; Pasteris, Daniel R.; Penner, Joyce E.; Taylor, Kendrick

2012-01-01

Continuous flow analysis was based on a steady sample flow and in-line detection of BC and other chemical substances as described in McConnell et al. (2007). In the cold room, previously cut one meter ice core sticks of 3x3cm, are melted continuously on a heated melter head specifically designed to eliminate contamination from the atmosphere or by the external parts of the ice. The melted ice from the most inner part of the ice stick is continuously pumped by a peristaltic pump and carried to a clean lab by Teflon lines. The recorded signal is continuous, integrating a sample volume of about 0.05 mL, for which the temporal resolution depends on the speed of melting, ice density and snow accumulation rate at the ice core drilling site. For annual accumulation derived from the WAIS and Law Dome ice cores, we assumed 3.1 cm water equivalent uncertainty in each year's accumulation from short scale spatial variability (glaciological noise) which was determined from several measurements of annual accumulation in multiple parallel ice cores notably from the WAIS Divide ice core site (Banta et al., 2008) and from South Pole site (McConnell et al., 1997; McConnell et al., 2000). Refractory black carbon (rBC) concentrations were determined using the same method as in (Bisiaux et al., 2011) and adapted to continuous flow measurements as described by (McConnell et al., 2007). The technique uses a single particle intracavity laser induced incandescence photometer (SP2, Droplet Measurement Technologies, Boulder, Colorado) coupled to an ultrasonic nebulizer/desolvation (CETAC UT5000) Flow Injection Analysis (FIA). All analyses, sample preparation etc, were performed in a class 100 cleanroom using anti contamination "clean techniques". The samples were not acidified.

Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS

DEFF Research Database (Denmark)

Müller, Wolfgang; Shelley, J. Michael G.; Rasmussen, Sune Olander

2011-01-01

Cryo-cell UV-LA-ICPMS is a new technique for direct chemical analysis of frozen ice cores at high spatial resolution (dust records and annual layer signatures at unprecedented spatial/time resolution. Uniquely......, the location of cation impurities relative to grain boundaries in recrystallized ice can be assessed....

Revised estimates of Greenland ice sheet thinning histories based on ice-core records

DEFF Research Database (Denmark)

Lecavalier, B.S.; Milne, G.A.; Fisher, D.A.

2013-01-01

-based reconstructions and, to some extent, the estimated elevation histories. A key component of the ice core analysis involved removing the influence of vertical surface motion on the dO signal measured from the Agassiz and Renland ice caps. We re-visit the original analysis with the intent to determine if the use...... of more accurate land uplift curves can account for some of the above noted discrepancy. To improve on the original analysis, we apply a geophysical model of glacial isostatic adjustment calibrated to sea-level records from the Queen Elizabeth Islands and Greenland to calculate the influence of land...... in this selection is further complicated by the possible influence of Innuitian ice during the early Holocene (12-8 ka BP). Our results indicate that a more accurate treatment of the uplift correction leads to elevation histories that are, in general, shifted down relative to the original curves at GRIP, NGRIP, DYE...

Direct observation of salts as micro-inclusions in the Greenland GRIP ice core

DEFF Research Database (Denmark)

Dahl-Jensen, Dorthe; Sakurai, Toshimitsu; Iizuka, Yoshinori

2009-01-01

We provide the first direct evidence that a number of water-soluble compounds, in particular calcium sulfate (CaSO4·2H2O) and calcium carbonate (CaCO3), are present as solid, micron-sized inclusions within the Greenland GRIP ice core. The compounds are detected by two independent methods: micro...... distributions of the micro-inclusions. These results suggest that water-soluble aerosols in the GRIP ice core are dependable proxies for past atmospheric conditions. Udgivelsesdato: December...

Archival processes of the water stable isotope signal in East Antarctic ice cores

Science.gov (United States)

Casado, Mathieu; Landais, Amaelle; Picard, Ghislain; Münch, Thomas; Laepple, Thomas; Stenni, Barbara; Dreossi, Giuliano; Ekaykin, Alexey; Arnaud, Laurent; Genthon, Christophe; Touzeau, Alexandra; Masson-Delmotte, Valerie; Jouzel, Jean

2018-05-01

The oldest ice core records are obtained from the East Antarctic Plateau. Water isotopes are key proxies to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in trajectory-based Rayleigh distillation and isotope-enabled climate models. However, a quantitative understanding of processes potentially altering snow isotopic composition after deposition is still missing. In low-accumulation sites, such as those found in East Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretability of an ice core's isotopic composition. By combining observations of isotopic composition in vapour, precipitation, surface snow and buried snow from Dome C, a deep ice core site on the East Antarctic Plateau, we found indications of a seasonal impact of metamorphism on the surface snow isotopic signal when compared to the initial precipitation. Particularly in summer, exchanges of water molecules between vapour and snow are driven by the diurnal sublimation-condensation cycles. Overall, we observe in between precipitation events modification of the surface snow isotopic composition. Using high-resolution water isotopic composition profiles from snow pits at five Antarctic sites with different accumulation rates, we identified common patterns which cannot be attributed to the seasonal variability of precipitation. These differences in the precipitation, surface snow and buried snow isotopic composition provide evidence of post-deposition processes affecting ice core records in low-accumulation areas.

Comparison of northern and central Greenland ice cores records of methanesulfonate covering the last glacial period

DEFF Research Database (Denmark)

Jonsell, U.; Hansson, M. E.; Siggaard-Andersen, M-L-

2007-01-01

Methanesulfonate (MS-) is measured in ice cores with the objective to obtain a proxy record of marine phytoplankton production of dimethylsulfide (DMS). We present a continuous MS- record covering the last glacial period from the North Greenland Ice Core Project (NGRIP) ice core and compare...... this record with the corresponding records previously presented from Greenland and, in particular, with the GISP2 ice core located 320 km south of NGRIP. Despite that the records have similar mean concentrations, their responses to climatic changes during the last glacial period are slightly different. NGRIP...... MS- concentrations were higher during the cold marine isotopic stages (MIS) 2 and 4 and lower during the warm MIS 5. This long-term trend in MS-, which is similar to the inverse of the corresponding trend in d 18O, is not detected in the GISP2 MS- record. A systematic response in MS- concentrations...

Particle shape accounts for instrumental discrepancy in ice core dust size distributions

Science.gov (United States)

Folden Simonsen, Marius; Cremonesi, Llorenç; Baccolo, Giovanni; Bosch, Samuel; Delmonte, Barbara; Erhardt, Tobias; Kjær, Helle Astrid; Potenza, Marco; Svensson, Anders; Vallelonga, Paul

2018-05-01

The Klotz Abakus laser sensor and the Coulter counter are both used for measuring the size distribution of insoluble mineral dust particles in ice cores. While the Coulter counter measures particle volume accurately, the equivalent Abakus instrument measurement deviates substantially from the Coulter counter. We show that the difference between the Abakus and the Coulter counter measurements is mainly caused by the irregular shape of dust particles in ice core samples. The irregular shape means that a new calibration routine based on standard spheres is necessary for obtaining fully comparable data. This new calibration routine gives an increased accuracy to Abakus measurements, which may improve future ice core record intercomparisons. We derived an analytical model for extracting the aspect ratio of dust particles from the difference between Abakus and Coulter counter data. For verification, we measured the aspect ratio of the same samples directly using a single-particle extinction and scattering instrument. The results demonstrate that the model is accurate enough to discern between samples of aspect ratio 0.3 and 0.4 using only the comparison of Abakus and Coulter counter data.

Impact of climate fluctuations on deposition of DDT and hexachlorocyclohexane in mountain glaciers: Evidence from ice core records

International Nuclear Information System (INIS)

Wang Xiaoping; Gong Ping; Zhang, Qianggong; Yao Tandong

2010-01-01

How do climate fluctuations affect DDT and hexachlorocyclohexane (HCH) distribution in the global scale? In this study, the interactions between climate variations and depositions of DDT and HCH in ice cores from Mt. Everest (the Tibetan Plateau), Mt. Muztagata (the eastern Pamirs) and the Rocky Mountains were investigated. All data regarding DDT/HCH deposition were obtained from the published results. Concentrations of DDT and HCH in an ice core from Mt. Everest were associated with the El Nino-Southern Oscillation. Concentrations of DDT in an ice core from Mt. Muztagata were significantly correlated with the Siberia High pattern. Concentrations of HCH in an ice core from Snow Dome of the Rocky Mountains responded to the North Atlantic Oscillation. These associations suggested that there are some linkages between climate variations and the global distribution of persistent organic pollutants. - Our study approves the potential contribution of ice core records of POPs to transport mechanisms of POPs.

Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium

Directory of Open Access Journals (Sweden)

P. Bohleber

2018-01-01

Full Text Available Among ice core drilling sites in the European Alps, Colle Gnifetti (CG is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a Little Ice Age cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100–1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.

A comparison of the present and last interglacial periods in six Antarctic ice cores

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V. Masson-Delmotte

2011-04-01

Full Text Available We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC, EPICA Dronning Maud Land (EDML, Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during the glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories, which are compared to ice sheet model results. Our results suggest that elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models.

Past temperature reconstructions from deep ice cores: relevance for future climate change

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V. Masson-Delmotte

2006-01-01

Full Text Available Ice cores provide unique archives of past climate and environmental changes based only on physical processes. Quantitative temperature reconstructions are essential for the comparison between ice core records and climate models. We give an overview of the methods that have been developed to reconstruct past local temperatures from deep ice cores and highlight several points that are relevant for future climate change. We first analyse the long term fluctuations of temperature as depicted in the long Antarctic record from EPICA Dome C. The long term imprint of obliquity changes in the EPICA Dome C record is highlighted and compared to simulations conducted with the ECBILT-CLIO intermediate complexity climate model. We discuss the comparison between the current interglacial period and the long interglacial corresponding to marine isotopic stage 11, ~400 kyr BP. Previous studies had focused on the role of precession and the thresholds required to induce glacial inceptions. We suggest that, due to the low eccentricity configuration of MIS 11 and the Holocene, the effect of precession on the incoming solar radiation is damped and that changes in obliquity must be taken into account. The EPICA Dome C alignment of terminations I and VI published in 2004 corresponds to a phasing of the obliquity signals. A conjunction of low obliquity and minimum northern hemisphere summer insolation is not found in the next tens of thousand years, supporting the idea of an unusually long interglacial ahead. As a second point relevant for future climate change, we discuss the magnitude and rate of change of past temperatures reconstructed from Greenland (NorthGRIP and Antarctic (Dome C ice cores. Past episodes of temperatures above the present-day values by up to 5°C are recorded at both locations during the penultimate interglacial period. The rate of polar warming simulated by coupled climate models forced by a CO2 increase of 1% per year is compared to ice-core

Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records

DEFF Research Database (Denmark)

Buizert, C.; Sowers, T.; Blunier, T.

2013-01-01

During rapid variations of the atmospheric mixing ratio of a trace gas, diffusive transport in the porous firn layer atop ice sheets and glaciers alters the isotopic composition of that gas relative to the overlying atmosphere. Records of past atmospheric trace gas isotopic composition from ice...... cores and firn need to be corrected for this diffusive fractionation artifact. We present a novel, semi-empirical method to accurately estimate the magnitude of the diffusive fractionation in the ice core record. Our method (1) consists of a relatively simple analytical calculation; (2) requires only...... commonly available ice core data; (3) is not subject to the uncertainties inherent to estimating the accumulation rate, temperature, close-off depth and depth-diffusivity relationship back in time; (4) does not require knowledge of the true atmospheric variations, but uses the smoothed records obtained...

Search for sterile neutrinos with IceCube DeepCore

Energy Technology Data Exchange (ETDEWEB)

Terliuk, Andrii [DESY, Platanenallee 6, 15738 Zeuthen (Germany); Collaboration: IceCube-Collaboration

2016-07-01

The DeepCore detector is a sub-array of the IceCube Neutrino Observatory that lowers the energy threshold for neutrino detection down to approximately 10 GeV. DeepCore is used for a variety of studies including atmospheric neutrino oscillations. The standard three-neutrino oscillation paradigm is tested using the DeepCore detector by searching for an additional light, sterile neutrino with a mass on the order of 1 eV. Sterile neutrinos do not interact with the ordinary matter, however they can be mixed with the three active neutrino states. Such mixture changes the picture of standard neutrino oscillations for atmospheric neutrinos with energies below 100 GeV. The capabilities of DeepCore detector to measure such sterile neutrino mixing will be presented in this talk.

Drilling, processing and first results for Mount Johns ice core in West Antarctica Ice Sheet

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Franciele Schwanck

Full Text Available ABSTRACT: An ice core, 92.26 m in length, was collected near the ice divide of the West Antarctica ice sheet during the 2008/2009 austral summer. This paper described the fieldwork at the Mount Johns site (79º55'S; 94º23'W and presented the first results of the upper 45.00 m record covering approximately 125 years (1883 - 2008, dated by annual layer counting and volcanic reference horizons. Trace element concentrations in 2,137 samples were determined using inductively coupled plasma mass spectrometry. The concentrations obtained for Al, Ba, Ca, Fe, K, Mg, Mn, Na, Sr and Ti are controlled by climate variations, the transport distance, and the natural sources of these aerosols. Natural dust contributions, mainly derived from the arid areas of Patagonia and Australia, are important sources for aluminum, barium, iron, manganese and titanium. Marine aerosols from sea ice and transported by air masses are important sources of sodium and magnesium. Calcium, potassium and strontium showed considerable inputs of both continental dust and marine aerosols.

McCall Glacier record of Arctic climate change: Interpreting a northern Alaska ice core with regional water isotopes

Science.gov (United States)

Klein, E. S.; Nolan, M.; McConnell, J.; Sigl, M.; Cherry, J.; Young, J.; Welker, J. M.

2016-01-01

We explored modern precipitation and ice core isotope ratios to better understand both modern and paleo climate in the Arctic. Paleoclimate reconstructions require an understanding of how modern synoptic climate influences proxies used in those reconstructions, such as water isotopes. Therefore we measured periodic precipitation samples at Toolik Lake Field Station (Toolik) in the northern foothills of the Brooks Range in the Alaskan Arctic to determine δ18O and δ2H. We applied this multi-decadal local precipitation δ18O/temperature regression to ∼65 years of McCall Glacier (also in the Brooks Range) ice core isotope measurements and found an increase in reconstructed temperatures over the late-20th and early-21st centuries. We also show that the McCall Glacier δ18O isotope record is negatively correlated with the winter bidecadal North Pacific Index (NPI) climate oscillation. McCall Glacier deuterium excess (d-excess, δ2H - 8*δ18O) values display a bidecadal periodicity coherent with the NPI and suggest shifts from more southwestern Bering Sea moisture sources with less sea ice (lower d-excess values) to more northern Arctic Ocean moisture sources with more sea ice (higher d-excess values). Northern ice covered Arctic Ocean McCall Glacier moisture sources are associated with weak Aleutian Low (AL) circulation patterns and the southern moisture sources with strong AL patterns. Ice core d-excess values significantly decrease over the record, coincident with warmer temperatures and a significant reduction in Alaska sea ice concentration, which suggests that ice free northern ocean waters are increasingly serving as terrestrial precipitation moisture sources; a concept recently proposed by modeling studies and also present in Greenland ice core d-excess values during previous transitions to warm periods. This study also shows the efficacy and importance of using ice cores from Arctic valley glaciers in paleoclimate reconstructions.

Measurements of acetylene in air extracted from polar ice cores

Science.gov (United States)

Nicewonger, M. R.; Aydin, M.; Montzka, S. A.; Saltzman, E. S.

2016-12-01

Acetylene (ethyne) is a non-methane hydrocarbon emitted during combustion of fossil fuels, biofuels, and biomass. The major atmospheric loss pathway of acetylene is oxidation by hydroxyl radical with a lifetime estimated at roughly two weeks. The mean annual acetylene levels over Greenland and Antarctica are 250 ppt and 20 ppt, respectively. Firn air measurements suggest atmospheric acetylene is preserved unaltered in polar snow and firn. Atmospheric reconstructions based on firn air measurements indicate acetylene levels rose significantly during the twentieth century, peaked near 1980, then declined to modern day levels. This historical trend is similar to that of other fossil fuel-derived non-methane hydrocarbons. In the preindustrial atmosphere, acetylene levels should primarily reflect emissions from biomass burning. In this study, we present the first measurements of acetylene in preindustrial air extracted from polar ice cores. Air from fluid and dry-drilled ice cores from Summit, Greenland and WAIS-Divide Antarctica is extracted using a wet-extraction technique. The ice core air is analyzed using gas chromatography and high-resolution mass spectrometry. Between 1400 to 1800 C.E., acetylene levels over Greenland and Antarctica varied between roughly 70-120 ppt and 10-30 ppt, respectively. The preindustrial Greenland acetylene levels are significantly lower than modern levels, reflecting the importance of northern hemisphere fossil fuel sources today. The preindustrial Antarctic acetylene levels are comparable to modern day levels, indicating similar emissions in the preindustrial atmosphere, likely from biomass burning. The implications of the preindustrial atmospheric acetylene records from both hemispheres will be discussed.

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

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Florian Steinbach

2017-09-01

Full Text Available The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modeling and analyzed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD have been used together with c-axis orientations using an optical technique (Fabric Analyser. Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighboring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modeling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be

The relevance of grain dissection for grain size reduction in polar ice: insights from numerical models and ice core microstructure analysis

Science.gov (United States)

Steinbach, Florian; Kuiper, Ernst-Jan N.; Eichler, Jan; Bons, Paul D.; Drury, Martyn R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

2017-09-01

The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to

Ancient biomolecules from deep ice cores reveal a forested southern Greenland

DEFF Research Database (Denmark)

Willerslev, Eske; Cappellini, Enrico; Boomsma, Wouter Krogh

2007-01-01

It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the...

Digital Imaging for Siple Dome Ice Core Analysis, Antarctica, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — This data set contains high-resolution digital images of thin and thick sections cut from the 1003 meter Siple Dome A main ice core. The images are useful for...

Roosevelt Island Climate Evolution Project (RICE): A 65 Kyr ice core record of black carbon aerosol deposition to the Ross Ice Shelf, West Antarctica.

Science.gov (United States)

Edwards, Ross; Bertler, Nancy; Tuohy, Andrea; Neff, Peter; Proemse, Bernedette; Feiteng, Wang; Goodwin, Ian; Hogan, Chad

2015-04-01

Emitted by fires, black carbon aerosols (rBC) perturb the atmosphere's physical and chemical properties and are climatically active. Sedimentary charcoal and other paleo-fire records suggest that rBC emissions have varied significantly in the past due to human activity and climate variability. However, few paleo rBC records exist to constrain reconstructions of the past rBC atmospheric distribution and its climate interaction. As part of the international Roosevelt Island Climate Evolution (RICE) project, we have developed an Antarctic rBC ice core record spanning the past ~65 Kyr. The RICE deep ice core was drilled from the Roosevelt Island ice dome in West Antarctica from 2011 to 2013. The high depth resolution (~ 1 cm) record was developed using a single particle intracavity laser-induced incandescence soot photometer (SP2) coupled to an ice core melter system. The rBC record displays sub-annual variability consistent with both austral dry-season and summer biomass burning. The record exhibits significant decadal to millennial-scale variability consistent with known changes in climate. Glacial rBC concentrations were much lower than Holocene concentrations with the exception of several periods of abrupt increases in rBC. The transition from glacial to interglacial rBC concentrations occurred over a much longer time relative to other ice core climate proxies such as water isotopes and suggests . The protracted increase in rBC during the transition may reflected Southern hemisphere ecosystem / fire regime changes in response to hydroclimate and human activity.

Dronning Maud Land, Antarctica, Ice Core, 1991 and 1992, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — Major ion concentration values (Na, Mg, Ca, Cl, NO3, SO4, MSA) were analyzed from a 20-meter ice core drilled in Dronning Maud Land, Antarctica (location - 65 01'...

Construction on a new deep ice coring site at Dome Fuji Station -Operations carried out by the JARE-44 Dome Fuji overwintering team-

Directory of Open Access Journals (Sweden)

Takao Kameda

2005-07-01

Full Text Available Eight members of the 44th Japanese Antarctic Research Expedition (JARE-44 stayed at Dome Fuji Station (77°19′01″S, 39°42′11″E; 3810 m a.s.l.; ice thickness 3028±15 m; mean air temperature -54.4°C; lowest air temperature -79.7°C from January 19, 2003 to January 25, 2004 for glaciological, meteorological, and upper atmospheric observations, and for construction at a new ice coring site for deep ice coring. The construction was a continuation of the activities of JARE-43; JARE-44 primarily carried out interior work at the ice coring site. The following works were carried out during the overwintering period and are described in this paper: retrieval of casing pipes from the borehole, enlargement of the borehole, insertion of casing pipes into the borehole, movement of the winch system from the old to the new ice coring sites (44.5 m apart, floor construction, construction and preparation of a 10 m depth pit for the rotating mast, construction of stairs between the old and the new ice coring sites, construction of working tables, assembling the mast and the small goliath crane, setting up a lifter, testing the winch system, setting the winch for the chip collector, cable replacement for deep ice coring, assembling of a deep ice core drill, adjustment of a rotating mast, enlargement of caves for ice core storage, and general electrical work in the new ice coring site. The total working time for the above operations was 593.5 person-days. Since the average working time was 6 h/day, the total working time was 3561 person-hours. Preparations for borehole temperature measurements in a 2503 m borehole and the ice coring operation that was mainly conducted by the JARE-45 team are briefly described.

Antarctic-wide array of high-resolution ice core records reveals pervasive lead pollution began in 1889 and persists today

DEFF Research Database (Denmark)

McConnell, J.R.; Maselli, OJ; Sigl, Michael

2014-01-01

Interior Antarctica is among the most remote places on Earth and was thought to be beyond the reach of human impacts when Amundsen and Scott raced to the South Pole in 1911. Here we show detailed measurements from an extensive array of 16 ice cores quantifying substantial toxic heavy metal lead...... of changes in lead deposition across Antarctica, as well as the characteristic isotopic signature of Broken Hill lead found throughout the continent, suggest that this single emission source in southern Australia was responsible for the introduction of lead pollution into Antarctica at the end of the 19th...

The EDC3 chronology for the EPICA Dome C ice core

Directory of Open Access Journals (Sweden)

F. Parrenin

2007-08-01

Full Text Available The EPICA (European Project for Ice Coring in Antarctica Dome C drilling in East Antarctica has now been completed to a depth of 3260 m, at only a few meters above bedrock. Here we present the new EDC3 chronology, which is based on the use of 1 a snow accumulation and mechanical flow model, and 2 a set of independent age markers along the core. These are obtained by pattern matching of recorded parameters to either absolutely dated paleoclimatic records, or to insolation variations. We show that this new time scale is in excellent agreement with the Dome Fuji and Vostok ice core time scales back to 100 kyr within 1 kyr. Discrepancies larger than 3 kyr arise during MIS 5.4, 5.5 and 6, which points to anomalies in either snow accumulation or mechanical flow during these time periods. We estimate that EDC3 gives accurate event durations within 20% (2σ back to MIS11 and accurate absolute ages with a maximum uncertainty of 6 kyr back to 800 kyr.

Combined ice core and climate-model evidence for the collapse of the West Antarctic Ice Sheet during Marine Isotope Stage 5e.

Science.gov (United States)

Steig, Eric J.; Huybers, Kathleen; Singh, Hansi A.; Steiger, Nathan J.; Frierson, Dargan M. W.; Popp, Trevor; White, James W. C.

2015-04-01

It has been speculated that collapse of the West Antarctic Ice Sheet explains the very high eustatic sea level rise during the last interglacial period, marine isotope stage (MIS) 5e, but the evidence remains equivocal. Changes in atmospheric circulation resulting from a collapse of the West Antarctic Ice Sheet (WAIS) would have significant regional impacts that should be detectable in ice core records. We conducted simulations using general circulation models (GCMs) at varying levels of complexity: a gray-radiation aquaplanet moist GCM (GRaM), the slab ocean version of GFDL-AM2 (also as an aquaplanet), and the fully-coupled version of NCAR's CESM with realistic topography. In all the experiments, decreased elevation from the removal of the WAIS leads to greater cyclonic circulation over the West Antarctic region. This creates increased advection of relatively warm marine air from the Amundsen-Bellingshausen Seas towards the South Pole, and increased cold-air advection from the East Antarctic plateau towards the Ross Sea and coastal Marie Byrd Land. The result is anomalous warming in some areas of the East Antarctic interior, and significant cooling in Marie Byrd Land. Comparison of ice core records shows good agreement with the model predictions. In particular, isotope-paleotemperature records from ice cores in East Antarctica warmed more between the previous glacial period (MIS 6) and MIS 5e than coastal Marie Byrd Land. These results add substantial support to other evidence for WAIS collapse during the last interglacial period.

Lithology and chronology of ice-sheet fluctuations (magnetic susceptibility of cores from the western Ross Sea)

Science.gov (United States)

Jennings, Anne E.

1993-01-01

The goals of the marine geology part of WAIS include reconstructing the chronology and areal extent of ice-sheet fluctuations and understanding the climatic and oceanographic influences on ice-sheet history. As an initial step toward attaining these goals, down-core volume magnetic susceptibility (MS) logs of piston cores from three N-S transects in the western Ross Sea are compared. The core transects are within separate petrographic provinces based on analyses of till composition. The provinces are thought to reflect the previous locations of ice streams on the shelf during the last glaciation. Magnetic susceptibility is a function of magnetic mineral composition, sediment texture, and sediment density. It is applied in the western Ross Sea for two purposes: (1) to determine whether MS data differentiates the three transects (i.e., flow lines), and thus can be used to make paleodrainage reconstructions of the late Wisconsinan ice sheet; and (2) to determine whether the MS data can aid in distinguishing basal till diamictons from diamictons of glacial-marine origin and thus, aid paleoenvironmental interpretations. A comparison of the combined data of cores in each transect is presented.

Estimating Past Temperature Change in Antarctica Based on Ice Core Stable Water Isotope Diffusion

Science.gov (United States)

Kahle, E. C.; Markle, B. R.; Holme, C.; Jones, T. R.; Steig, E. J.

2017-12-01

The magnitude of the last glacial-interglacial transition is a key target for constraining climate sensitivity on long timescales. Ice core proxy records and general circulation models (GCMs) both provide insight on the magnitude of climate change through the last glacial-interglacial transition, but appear to provide different answers. In particular, the magnitude of the glacial-interglacial temperature change reconstructed from East Antarctic ice-core water-isotope records is greater ( 9 degrees C) than that from most GCM simulations ( 6 degrees C). A possible source of this difference is error in the linear-scaling of water isotopes to temperature. We employ a novel, nonlinear temperature-reconstruction technique using the physics of water-isotope diffusion to infer past temperature. Based on new, ice-core data from the South Pole, this diffusion technique suggests East Antarctic temperature change was smaller than previously thought. We are able to confirm this result using a simple, water-isotope fractionation model to nonlinearly reconstruct temperature change at ice core locations across Antarctica based on combined oxygen and hydrogen isotope ratios. Both methods produce a temperature change of 6 degrees C for South Pole, agreeing with GCM results for East Antarctica. Furthermore, both produce much larger changes in West Antarctica, also in agreement with GCM results and independent borehole thermometry. These results support the fidelity of GCMs in simulating last glacial maximum climate, and contradict the idea, based on previous work, that the climate sensitivity of current GCMs is too low.

An ultra-clean technique for accurately analysing Pb isotopes and heavy metals at high spatial resolution in ice cores with sub-pg g{sup -1} Pb concentrations

Energy Technology Data Exchange (ETDEWEB)

Burn, Laurie J. [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth 6845, Western Australia (Australia); Rosman, Kevin J.R. [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth 6845, Western Australia (Australia)], E-mail: K.Rosman@curtin.edu.au; Candelone, Jean-Pierre [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth 6845, Western Australia (Australia); Vallelonga, Paul [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth 6845, Western Australia (Australia); Istituto per la Dinamica dei Processi Ambientali (IDPA-CNR), Dorsoduro 2137, 30123 Venice (Italy); Burton, Graeme R. [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth 6845, Western Australia (Australia); Smith, Andrew M. [Australian Nuclear Science and Technology Organisation (ANSTO), PMB 1, Menai, NSW 2234 (Australia); Morgan, Vin I. [Australian Antarctic Division and Antarctic Climate and Ecosystems CRC, Private Bag 80, Hobart, Tasmania 7001 (Australia); Barbante, Carlo [Istituto per la Dinamica dei Processi Ambientali (IDPA-CNR), Dorsoduro 2137, 30123 Venice (Italy); Hong, Sungmin [Korea Polar Research Institute, Songdo Techno Park, 7-50, Songdo-dong, Yeonsu-gu, Incheon 406-840 (Korea, Republic of); Boutron, Claude F. [Laboratoire de Glaciologie et Geophysique de l' Environnement du CNRS, 54, rue Moliere, B.P. 96, 3840.2 St Martin d' Heres Cedex (France)

2009-02-23

Measurements of Pb isotope ratios in ice containing sub-pg g{sup -1} concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g{sup -1} and fg g{sup -1} concentrations in Polar ice, were also measured. The final blank amounted to 0.2 {+-} 0.2 pg of Pb with {sup 206}Pb/{sup 207}Pb and {sup 208}Pb/{sup 207}Pb ratios of 1.16 {+-} 0.12 and 2.35 {+-} 0.16, respectively, 1.5 {+-} 0.4 pg of Ba and 0.6 {+-} 2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only {approx}5%, {approx}14% and {approx}0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g{sup -1}, 0.3 pg g{sup -1} and 2.3 fg g{sup -1}. Uncertainties in the Pb isotopic ratio measurements were degraded by only {approx}0.2%.

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.

2006-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate mitigation strategies for New Zealand. (author). 27 refs., 18 figs., 2 tabs

Climate change from air in ice cores

International Nuclear Information System (INIS)

Riedel, K.

2013-01-01

How sensitive is our climate to greenhouse gas concentrations? What feedbacks will trigger further emissions in a warming world and at which thresholds? Over the last 200 years human activity has increased greenhouse gases to well beyond the natural range for the last 800,000 years. In order to mitigate changes - or adapt to them - we need a better understanding of greenhouse gas sources and sinks in the recent past. Ice cores with occluded ancient air hold the key to understanding the linkages between climate change and greenhouse gas variations. (author). 22 refs., 1 tab.

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.

2005-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate mitigation strategies for New Zealand. (author). 27 refs., 18 figs., 3 tabs

Stable isotope analysis in ice core paleoclimatology

International Nuclear Information System (INIS)

Bertler, N.

2007-01-01

Ice cores from New Zealand and the Antarctic margin provide an excellent means of addressing the lack of longer-term climate observations in the Southern Hemisphere with near instrumental quality. Their study helps us to improve our understanding of regional patterns of climate behaviour in Antarctica and its influence on New Zealand, leading to more realistic regional climate models. Such models are needed to sensibly interpret current Antarctic and New Zealand climate variability and for the development of appropriate mitigation strategies for New Zealand. (author). 27 refs., 18 figs., 2 tabs

The Spatial and Temporal Variability of the North Atlantic Oscillation Recorded in Ice Core Major Ion Time Series

Science.gov (United States)

Wawrzeniak, T. L.; Wake, C. P.; Fischer, H.; Fisher, D. A.; Schwikowski, M.

2006-05-01

The North Atlantic Oscillation represents a significant mode of atmospheric variability for the Arctic and sub- Artic climate system. Developing a longer-term record of the spatial and temporal variability of the NAO could improve our understanding of natural climate variability in the region. Previous work has shown a significant relationship between Greenland ice core records and the NAO. Here, we have compared sea-salt and dust records from nine ice cores around the Arctic region to sea level pressure and NAO indices to evaluate the extent to which these ice cores can be used to reconstruct the NAO.

High-resolution Greenland Ice Core data show abrupt climate change happens in few years

DEFF Research Database (Denmark)

Steffensen, Jørgen Peder; Andersen, Katrine Krogh; Bigler, Matthias

2008-01-01

The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture...... source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition...

Trials and Tribulations of Fluorescent Dissolved Organic Matter Chemical Interpretations: A case study of polar ice cores

Science.gov (United States)

D'Andrilli, J.

2017-12-01

Excitation emission matrix fluorescence spectroscopy is widely applied for rapid dissolved organic matter (DOM) characterization in aquatic systems. Fluorescent DOM surveys are booming, not only as a central focus in aquatic environments, but also as an important addition to interdisciplinary research (e.g., DOM analysis in concert with ice core paleoclimate reconstructions, stream metabolism, hydrologic regimes, agricultural developments, and biological activity), opening new doors, not just for novelty, but also for more challenges with chemical interpretations. Recently, the commonly used protein- versus humic-like classifications of DOM have been ineffective at describing DOM chemistry in various systems (e.g., ice cores, wastewaters, incubations/engineered). Moreover, the oversimplification of such classifications used to describe fluorescing components, without further scrutiny, has become commonplace, ultimately producing vague reporting. For example, West Antarctic ice core DOM was shown to contain fluorescence in the low excitation/emission wavelength region, however resolved fluorophores depicting tyrosine- and tryptophan-like DOM were not observed. At first, as literature suggested, we reported this result as protein-like, and concluded that microbial contributions were dominant in deep ice. That initial interpretation would disintegrate the conservation paradigm of atmospheric composition during deposition, the crux of ice core research, and contradict other lines of evidence. This begged the question, "How can we describe DOM chemistry without distinct fluorophores?" Antarctic ice core DOM was dominated by neither tyrosine- nor tryptophan-like fluorescence, causing "unusual" looking fluorescent components. After further examination, deep ice DOM was reported to contain fluorescent species most similar to monolignols and tannin-like phenols, describing the precursors of lignin from low carbon producing environments, consistent with marine sediment

Effect of periodic melting on geochemical and isotopic signals in an ice core from Lomonosovfonna, Svalbard

NARCIS (Netherlands)

Pohjola, V.A.; Moore, J.C.; Isaksson, E.; Jauhiainen, T.; Wal, R.S.W. van de; Martma, T.; Meijer, H.A.J.; Vaikmäe, R.

2002-01-01

[1] We examine the quality of atmospherically deposited ion and isotope signals in an ice core taken from a periodically melting ice field, Lomonosovfonna in central Spitsbergen, Svalbard. The aim is to determine the degree to which the signals are altered by periodic melting of the ice. We use

Annually resolved southern hemisphere volcanic history from two Antarctic ice cores

Science.gov (United States)

Cole-Dai, Jihong; Mosley-Thompson, Ellen; Thompson, Lonnie G.

1997-07-01

The continuous sulfate analysis of two Antarctic ice cores, one from the Antarctic Peninsula region and one from West Antarctica, provides an annually resolved proxy history of southern semisphere volcanism since early in the 15th century. The dating is accurate within ±3 years due to the high rate of snow accumulation at both core sites and the small sample sizes used for analysis. The two sulfate records are consistent with each other. A systematic and objective method of separating outstanding sulfate events from the background sulfate flux is proposed and used to identify all volcanic signals. The resulting volcanic chronology covering 1417-1989 A.D. resolves temporal ambiguities about several recently discovered events. A number of previously unknown, moderate eruptions during late 1600s are uncovered in this chronology. The eruption of Tambora (1815) and the recently discovered eruption of Kuwae (1453) in the tropical South Pacific injected the greatest amount of sulfur dioxide into the southern hemisphere stratosphere during the last half millennium. A technique for comparing the magnitude of volcanic events preserved within different ice cores is developed using normalized sulfate flux. For the same eruptions the variability of the volcanic sulfate flux between the cores is within ±20% of the sulfate flux from the Tambora eruption.

Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

DEFF Research Database (Denmark)

Capron, E.; Landais, A.; Chappellaz, J.

2010-01-01

Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized...... that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict, questioning the Greenland ice core temperature records as a proxy for AMOC changes throughout the glacial period....

Annually resolved ice core records of tropical climate variability over the past ~1800 years.

Science.gov (United States)

Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

2013-05-24

Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

Atmosphere aerosol/dust composition over central Asia and western Siberia derived from snow/ice core records and calibrated with NASA remote sensing data

Science.gov (United States)

Aizen, V. B.; Aizen, E. M.; Joswiak, D. R.; Surazakov, A. B.; Takeuchi, N.

2007-12-01

storm land surface records and remote sensing aerosol data at the monthly/seasonal/annual to event/daily scale. For instance, in southwestern Asia, severe drought developed from 1998 to 2002 has intensified the frequency, duration, and spatial coverage of large dust storms originated in Iran, Afghanistan, Tajikistan, Taklimakan and Goby Deserts. The Pamir and Tien Shan ice-core records revealed, that concentration of major and REE elements during summer is about two times greater in period of 1998-2002 than at the following years. Our qualitative analysis based on ice-core records, the MODIS and SeaWiFS images and determined the origin of dust, transport pathways and aerosol spatial distribution over central Asia and western Siberia in summer 2000, 2001 and 2002. The transport pathways were reconstructed on the basis of visibility observations and NCAR MM5-predicted winds with further validation against of satellite data and isotope- geochemical ice-core data analysis.

Multilayer Formation and Evaporation of Deuterated Ices in Prestellar and Protostellar Cores

Science.gov (United States)

Taquet, Vianney; Charnley, Steven B.; Sipilä, Olli

2014-08-01

Extremely large deuteration of several molecules has been observed toward prestellar cores and low-mass protostars for a decade. New observations performed toward low-mass protostars suggest that water presents a lower deuteration in the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimensional model of a collapsing core to properly follow the formation and the deuteration of interstellar ices as well as their subsequent evaporation in the low-mass protostellar envelopes with the aim of interpreting the spatial and temporal evolutions of their deuteration. The astrochemical model follows the formation and the evaporation of ices with a multilayer approach and also includes a state-of-the-art deuterated chemical network by taking the spin states of H2 and light ions into account. Because of their slow formation, interstellar ices are chemically heterogeneous and show an increase of their deuterium fractionation toward the surface. The differentiation of the deuteration in ices induces an evolution of the deuteration within protostellar envelopes. The warm inner region is poorly deuterated because it includes the whole molecular content of ices, while the deuteration predicted in the cold external envelope scales with the highly deuterated surface of ices. We are able to reproduce the observed evolution of water deuteration within protostellar envelopes, but we are still unable to predict the super-high deuteration observed for formaldehyde and methanol. Finally, the extension of this study to the deuteration of complex organics, important for the prebiotic chemistry, shows good agreement with the observations, suggesting that we can use the deuteration to retrace their mechanisms and their moments of formation.

Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores

International Nuclear Information System (INIS)

Taquet, Vianney; Charnley, Steven B.; Sipilä, Olli

2014-01-01

Extremely large deuteration of several molecules has been observed toward prestellar cores and low-mass protostars for a decade. New observations performed toward low-mass protostars suggest that water presents a lower deuteration in the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimensional model of a collapsing core to properly follow the formation and the deuteration of interstellar ices as well as their subsequent evaporation in the low-mass protostellar envelopes with the aim of interpreting the spatial and temporal evolutions of their deuteration. The astrochemical model follows the formation and the evaporation of ices with a multilayer approach and also includes a state-of-the-art deuterated chemical network by taking the spin states of H 2 and light ions into account. Because of their slow formation, interstellar ices are chemically heterogeneous and show an increase of their deuterium fractionation toward the surface. The differentiation of the deuteration in ices induces an evolution of the deuteration within protostellar envelopes. The warm inner region is poorly deuterated because it includes the whole molecular content of ices, while the deuteration predicted in the cold external envelope scales with the highly deuterated surface of ices. We are able to reproduce the observed evolution of water deuteration within protostellar envelopes, but we are still unable to predict the super-high deuteration observed for formaldehyde and methanol. Finally, the extension of this study to the deuteration of complex organics, important for the prebiotic chemistry, shows good agreement with the observations, suggesting that we can use the deuteration to retrace their mechanisms and their moments of formation.

Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores

Energy Technology Data Exchange (ETDEWEB)

Taquet, Vianney; Charnley, Steven B. [Astrochemistry Laboratory and The Goddard Center for Astrobiology, Mailstop 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770 (United States); Sipilä, Olli [Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki (Finland)

2014-08-10

Extremely large deuteration of several molecules has been observed toward prestellar cores and low-mass protostars for a decade. New observations performed toward low-mass protostars suggest that water presents a lower deuteration in the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimensional model of a collapsing core to properly follow the formation and the deuteration of interstellar ices as well as their subsequent evaporation in the low-mass protostellar envelopes with the aim of interpreting the spatial and temporal evolutions of their deuteration. The astrochemical model follows the formation and the evaporation of ices with a multilayer approach and also includes a state-of-the-art deuterated chemical network by taking the spin states of H{sub 2} and light ions into account. Because of their slow formation, interstellar ices are chemically heterogeneous and show an increase of their deuterium fractionation toward the surface. The differentiation of the deuteration in ices induces an evolution of the deuteration within protostellar envelopes. The warm inner region is poorly deuterated because it includes the whole molecular content of ices, while the deuteration predicted in the cold external envelope scales with the highly deuterated surface of ices. We are able to reproduce the observed evolution of water deuteration within protostellar envelopes, but we are still unable to predict the super-high deuteration observed for formaldehyde and methanol. Finally, the extension of this study to the deuteration of complex organics, important for the prebiotic chemistry, shows good agreement with the observations, suggesting that we can use the deuteration to retrace their mechanisms and their moments of formation.

Denali Ice Core Record of North Pacific Sea Surface Temperatures and Marine Primary Productivity

Science.gov (United States)

Polashenski, D.; Osterberg, E. C.; Kreutz, K. J.; Winski, D.; Wake, C. P.; Ferris, D. G.; Introne, D.; Campbell, S. W.

2016-12-01

Chemical analyses of precipitation preserved in glacial ice cores provide a unique opportunity to study changes in atmospheric circulation patterns and ocean surface conditions through time. In this study, we aim to investigate changes in both the physical and biological parameters of the north-central Pacific Ocean and Bering Sea over the twentieth century using the deuterium excess (d-excess) and methanesulfonic acid (MSA) records from the Mt. Hunter ice cores drilled in Denali National Park, Alaska. These parallel, 208 m-long ice cores were drilled to bedrock during the 2013 field season on the Mt. Hunter plateau (63° N, 151° W, 3,900 m above sea level) by a collaborative research team consisting of members from Dartmouth College and the Universities of Maine and New Hampshire. The cores were sampled on a continuous melter system at Dartmouth College and analyzed for the concentrations major ions (Dionex IC) and trace metals (Element2 ICPMS), and for stable water isotope ratios (Picarro). The depth-age scale has been accurately dated to 400 AD using annual layer counting of several chemical species and further validated using known historical volcanic eruptions and the Cesium-137 spike associated with nuclear weapons testing in 1963. We use HYSPLIT back trajectory modeling to identify likely source areas of moisture and aerosol MSA being transported to the core site. Satellite imagery allows for a direct comparison between chlorophyll a concentrations in these source areas and MSA concentrations in the core record. Preliminary analysis of chlorophyll a and MSA concentrations, both derived almost exclusively from marine biota, suggest that the Mt. Hunter ice cores reflect changes in North Pacific and Bering Sea marine primary productivity. Analysis of the water isotope and MSA data in conjunction with climate reanalysis products shows significant correlations (psea surface temperatures in the Bering Sea and North Central Pacific. These findings, coupled with

Large-scale drivers of Caucasus climate variability in meteorological records and Mt El'brus ice cores

Science.gov (United States)

Kozachek, Anna; Mikhalenko, Vladimir; Masson-Delmotte, Valérie; Ekaykin, Alexey; Ginot, Patrick; Kutuzov, Stanislav; Legrand, Michel; Lipenkov, Vladimir; Preunkert, Susanne

2017-05-01

A 181.8 m ice core was recovered from a borehole drilled into bedrock on the western plateau of Mt El'brus (43°20'53.9'' N, 42°25'36.0'' E; 5115 m a.s.l.) in the Caucasus, Russia, in 2009 (Mikhalenko et al., 2015). Here, we report on the results of the water stable isotope composition from this ice core with additional data from the shallow cores. The distinct seasonal cycle of the isotopic composition allows dating by annual layer counting. Dating has been performed for the upper 126 m of the deep core combined with 20 m from the shallow cores. The whole record covers 100 years, from 2013 back to 1914. Due to the high accumulation rate (1380 mm w.e. year-1) and limited melting, we obtained isotopic composition and accumulation rate records with seasonal resolution. These values were compared with available meteorological data from 13 weather stations in the region and also with atmosphere circulation indices, back-trajectory calculations, and Global Network of Isotopes in Precipitation (GNIP) data in order to decipher the drivers of accumulation and ice core isotopic composition in the Caucasus region. In the warm season (May-October) the isotopic composition depends on local temperatures, but the correlation is not persistent over time, while in the cold season (November-April), atmospheric circulation is the predominant driver of the ice core's isotopic composition. The snow accumulation rate correlates well with the precipitation rate in the region all year round, which made it possible to reconstruct and expand the precipitation record at the Caucasus highlands from 1914 until 1966, when reliable meteorological observations of precipitation at high elevation began.

Newall Glacier Snow Pit and Ice Core, 1987 to 1989, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — Snow pit and ice core data from the Newall Glacier (location - 162 30' East, 77 35' South) were collected during 1987 and 1988. These include information on...

Volcanic eruptions recorded in the Illimani ice core (Bolivia: 1918–1998 and Tambora periods

Directory of Open Access Journals (Sweden)

M. De Angelis

2003-01-01

Full Text Available Acid layers of volcanic origin detected in polar snow and ice layers are commonly used to document past volcanic activity on a global scale or, conversely, to date polar ice cores. Although most cataclysmic eruptions of the last two centuries (Pinatubo, El Chichon, Agung, Krakatoa, Cosiguina, Tambora, etc. occurred in the tropics, cold tropical glaciers have not been used for the reconstruction of past volcanism. The glaciochemical study of a 137 m ice core drilled in 1999 close to the summit of Nevado Illimani (Eastern Bolivian Andes, 16°37' S, 67°46' W, 6350 m asl demonstrates, for the first time, that such eruptions are recorded by both their tropospheric and stratospheric deposits. An 80-year ice sequence (1918-1998 and the Tambora years have been analyzed in detail. In several cases, ash, chloride and fluoride were also detected. The ice records of the Pinatubo (1991, Agung (1963 and Tambora (1815 eruptions are discussed in detail. The potential impact of less important regional eruptions is discussed.

A gas extraction system for the measurement of carbon dioxide and carbon isotopes in polar ice cores

International Nuclear Information System (INIS)

Steig, E.

1992-06-01

Knowledge of the distribution of Carbon 13 in the glacial ocean, atmosphere, and biosphere is important to understanding the causes of glacial/interglacial changes in atmospheric CO 2 levels. Although deep-ocean Carbon 13 values are well-constrained by ocean sediment studies, model-based estimates of changes in the carbon budget for the biosphere and atmosphere vary considerably. Measurement of atmospheric Carbon 13 in CO 2 in ice cores will provide additional constraints on this budget and will also improve estimates of changes in the ocean surface layer Carbon 13. Direct measurement of ancient atmospheric Carbon 13 can be accomplished through polar ice core studies. A gas-extraction line for ice cores has been designed and constructed with particular attention to the specific difficulties of measuring Carbon 13 in CO 2 . The ice is shaved, rather than crushed, to minimize fractionation effects resulting from gas travel through long air-paths in the ice. To minimize the risk of isotopic contamination and fractionation within the vacuum line, CO 2 is separated immediately from the air; the CO 2 concentration is then measured by a simple pressure/volume comparison rather than by gas chromatography or spectroscopy. Measurements from Greenland ice core samples give an average value of 280±2 ppM CO 2 for preindustrial samples, demonstrating that the extraction system gives accurate, precise determinations Of CO 2 concentrations. Measurement of δ 13 C from polar ice samples has not been achieved at this time. However, results on standard air samples demonstrate a precision for δ 13 C of less than 0.2 per-thousand at the 95% confidence level

Cool Science Explains a Warming World: Using Ice Core Science to Bridge the Gap Between Researchers and the K-12 Classroom

Science.gov (United States)

Huffman, L. T.

2017-12-01

Changing ice has urgent implications for people around the world. The Ice Drilling Program Office (IDPO) provides scientific leadership and oversight of ice coring and drilling activities funded by the US National Science Foundation and also has goals to enhance education and communication of current research information. In a time when misinformation is rampant and climate change science is suspect, it is essential that students receive accurate scientific information and engage in learning activities that model complex ideas through engaging and age appropriate ways, while also learning to validate and recognize reliable sources. The IDPO Education and Outreach (EO) office works to create resources, activities and professional development that bridge the gap between ice core science research and educators and their students. Ice core science is on the cutting edge of new discoveries about climate change and understanding better the past to predict the future. Hands-on inquiry activities based on ice core data allow teachers to lead their students to new discoveries about climate secrets hidden deep in the ice. Capitalizing on the inherent interest in the extremes of the Polar Regions, IDPO materials engage students in activities aligned with NGSS standards. Ice drilling technologies make an ideal platform for intertwining engineering concepts and practices with science research to meet the SEP (Science and Engineering Practices) in the NGSS. This session will highlight how the IDPO EO office has built a community of ice core scientists willing to take part in education and outreach projects and events and share some of the resources available to K-12 educators. We will highlight some of the successes and lessons learned as we continually evolve our work toward more effective science education and communication highlighting ice core and climate change science.

Expression and partial characterization of an ice binding protein from a bacterium isolated at a depth of 3,519 meters in the Vostok ice core, Antarctica

Directory of Open Access Journals (Sweden)

Amanda Marie Achberger

2011-12-01

Full Text Available Cryopreservation of microorganisms in ancient glacial ice is possible if lethal levels of macromolecular damage are not incurred and cellular integrity is not compromised via intracellular ice formation or recrystallization. Previously, a bacterium (isolate 3519-10 recovered from a depth of 3,519 meters below the surface in the Vostok ice core was shown to secrete an IBP that inhibits the recrystallization of ice. To explore the advantage that IBPs confer to ice-entrapped cells, experiments were designed to examine the expression of 3519-10’s IBP gene and protein at different temperatures, assess the effect of the IBP on bacterial viability in ice, and determine how the IBP influences the physical structure of the ice. Total RNA isolated from cultures grown between 4 to 25⁰C and analyzed by reverse transcription-PCR indicated constitutive expression of the IBP gene. SDS-PAGE analysis of 3519-10’s extracellular proteins also revealed a polypeptide of the predicted size of the 54 kDa IBP at all temperatures tested. In the presence of 100 µg mL-1 of extracellular protein from 3519-10, the survival of Escherichia coli was increased by greater than 34-fold after freeze-thaw cycling. Microscopic analysis of ice formed in the presence of the IBP indicated that per mm2 field of view, there were ~5 times as many crystals as in ice formed in the presence of washed 3519-10 cells and non-IBP producing bacteria, and ~10 times as many crystals as in filtered deionized water. Presumably, the effect that the IBP has on bacterial viability and ice crystal structure is due to its activity as an inhibitor of ice recrystallization. A myriad of molecular adaptations are likely to play a role in bacterial persistence under frozen conditions, but the ability of 3519-10’s IBP to control ice crystal structure, and thus the liquid vein network within the ice, may provide one explanation for its successful survival deep within the Antarctic ice sheet for

Interlaboratory comparison of {sup 10}Be concentrations in two ice cores from Central West Antarctica

Energy Technology Data Exchange (ETDEWEB)

Woodruff, Thomas E., E-mail: woodruft@purdue.edu [PRIME Laboratory, Purdue University, West Lafayette, IN 47907 (United States); Welten, Kees C. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Caffee, Marc W. [PRIME Laboratory, Purdue University, West Lafayette, IN 47907 (United States); Nishiizumi, Kunihiko [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2013-01-15

To improve sample processing efficiency for cosmogenic radionuclide measurements in samples from the West Antarctic Ice Sheet Divide core, two chemical lines, one at Purdue University and one at University of California, Berkeley, are being used. Sections from two shallow ice cores from West Antarctica were processed at each lab, while all {sup 10}Be accelerator mass spectrometry measurements were performed at PRIME Lab, Purdue University. Duplicate samples gave {sup 10}Be results that are identical to within the AMS measurement uncertainties of 2-3%.

Reconstruction of Antarctic climate change using ice core proxy records from the coastal Dronning Maud Land, East Antarctica

Digital Repository Service at National Institute of Oceanography (India)

Thamban, M.; Laluraj, C.M.; Naik, S.S.; Chaturvedi, A.

the austral summer of 2003. The retrieved ice core samples were labelled, packed in good quality LDPE containers and subsequently shipped in -20ºC deep freezer facilities. These cores were archived in frozen conditions in custom-made expanded polypropylene...: Glaciochemistry, Stable isotope, Ice core, Solar activity, Dronning Maud Land, Antarctica. regions offer continuous and highly resolved long-term records of reliable information on major atmospheric parameters like temperature, composition and trace gases. Among...

Long memory effect of past climate change in Vostok ice core records

International Nuclear Information System (INIS)

Yamamoto, Yuuki; Kitahara, Naoki; Kano, Makoto

2012-01-01

Time series analysis of Vostok ice core data has been done for understanding of palaeoclimate change from a stochastic perspective. The Vostok ice core is one of the proxy data for palaeoclimate in which local temperature and precipitation rate, moisture source conditions, wind strength and aerosol fluxes of marine, volcanic, terrestrial, cosmogenic and anthropogenic origin are indirectly stored. Palaeoclimate data has a periodic feature and a stochastic feature. For the proxy data, spectrum analysis and detrended fluctuation analysis (DFA) were conducted to characterize periodicity and scaling property (long memory effect) in the climate change. The result of spectrum analysis indicates there exist periodicities corresponding to the Milankovitch cycle in past climate change occurred. DFA clarified time variability of scaling exponents (Hurst exponent) is associated with abrupt warming in past climate.

An automated approach for annual layer counting in ice cores

Directory of Open Access Journals (Sweden)

M. Winstrup

2012-11-01

Full Text Available A novel method for automated annual layer counting in seasonally-resolved paleoclimate records has been developed. It relies on algorithms from the statistical framework of hidden Markov models (HMMs, which originally was developed for use in machine speech recognition. The strength of the layer detection algorithm lies in the way it is able to imitate the manual procedures for annual layer counting, while being based on statistical criteria for annual layer identification. The most likely positions of multiple layer boundaries in a section of ice core data are determined simultaneously, and a probabilistic uncertainty estimate of the resulting layer count is provided, ensuring an objective treatment of ambiguous layers in the data. Furthermore, multiple data series can be incorporated and used simultaneously. In this study, the automated layer counting algorithm has been applied to two ice core records from Greenland: one displaying a distinct annual signal and one which is more challenging. The algorithm shows high skill in reproducing the results from manual layer counts, and the resulting timescale compares well to absolute-dated volcanic marker horizons where these exist.

Assessment of the Relationship between Andean Ice Core Precipitation Indicators and Amazon River Discharge

Science.gov (United States)

Johnson, N.; Alsdorf, D.; Thompson, L.; Mosley-Thompson, E.; Melack, J.

2006-12-01

Prior to the last 100 years, there is a significant lack of hydrologic knowledge for the Amazon Basin. A 100- year record of discharge from the city of Manaus, located at the confluence of the Solimoes and Negro rivers, is the most complete record for the basin. Inundated wetlands play a key role in carbon out-gassing to the atmosphere whereas discharge from the Amazon River contributes about 20% of the total freshwater flux delivered to the world's oceans. As discharge (Q) and inundation are directly related to precipitation, we are developing a method to extend our understanding of Q and inundation into the 19^{th} century. Using proxy data preserved in Andean glaciers and ice caps and recovered from ice cores, annually resolved histories of δ^{18)O and mass accumulation are available. The latter is a proxy for local precipitation amount whereas δ18O is influenced by continental scale processes (i.e., evaporation, convection) as well as by temperature and hence, by varying climate regimes. We have correlated the accumulation and δ18O records from Core 1 drilled on the Quelccaya ice-cap in the southern Andes of Peru with the Manaus discharge data. As ice core annual layers correspond to the thermal year (in Peru, July to June of the following year) and the discharge records are kept daily (January to December), we averaged 365 days of Q data seeking the optimal correlation for each start and end date. The best statistical relationship between δ18O and Q (r = -0.41, p = < 0.001) is attained when Q is averaged from March 16 to March 15 of the following year. We also correlated 23 years of ENSO events, which are linked to both Amazon River discharge and ice core δ18O (r = -0.60, p = < 0.001). These linear relationships are used to create Amazon discharge for the 20^{th} century and to extrapolate Q into the 19^{th} century. Previously developed relationships between Q and mainstem inundated area are then used to estimate inundated area along the main Amazon

Supporting evidence from the EPICA Dronning Maud Land ice core for atmospheric CO2 changes during the past millennium

International Nuclear Information System (INIS)

Siegenthaler, Urs; Monnin, Eric; Kawamura, Kenji; Spahni, Renato; Schwander, Jakob; Stauffer, Bernhard; Stocker, Thomas F.; Fischer, Hubertus

2005-01-01

The most direct method of investigating past variations of the atmospheric CO 2 concentration before 1958, when continuous direct atmospheric CO 2 measurements started, is the analysis of air extracted from suitable ice cores. Here we present a new detailed CO 2 record from the Dronning Maud Land (DML) ice core, drilled in the framework of the European Project for Ice Coring in Antarctica (EPICA) and some new measurements on a previously drilled ice core from the South Pole. The DML CO 2 record shows an increase from about 278 to 282 parts per million by volume (ppmv) between ad 1000 and ad 1200 and a fairly continuous decrease to a mean value of about 277 ppmv around ad 1700. While the new South Pole measurements agree well with DML at the minimum at ad 1700 they are on average about 2 ppmv lower during the period ad 1000-1500. Published measurements from the coastal high-accumulation site Law Dome are considered as very reliable because of the reproducibility of the measurements, high temporal resolution and an accurate time scale. Other Antarctic ice cores could not, or only partly, reproduce the pre-industrial measurements from Law Dome. A comparison of the trends of DML and Law Dome shows a general agreement. However we should be able to rule out co-variations caused by the same artefact. Two possible effects are discussed, first production of CO 2 by chemical reactions and second diffusion of dissolved air through the ice matrix into the bubbles. While the first effect cannot be totally excluded, comparison of the Law Dome and DML record shows that dissolved air diffusing to bubbles cannot be responsible for the pre-industrial variation. Therefore, the new record is not a proof of the Law Dome results but the first very strong support from an ice core of the Antarctic plateau

ICE AND DUST IN THE QUIESCENT MEDIUM OF ISOLATED DENSE CORES

International Nuclear Information System (INIS)

Boogert, A. C. A.; Huard, T. L.; Knez, C.; Cook, A. M.; Chiar, J. E.; Decin, L.; Blake, G. A.; Tielens, A. G. G. M.; Van Dishoeck, E. F.

2011-01-01

The relation between ices in the envelopes and disks surrounding young stellar objects (YSOs) and those in the quiescent interstellar medium (ISM) is investigated. For a sample of 31 stars behind isolated dense cores, ground-based and Spitzer spectra and photometry in the 1-25 μm wavelength range are combined. The baseline for the broad and overlapping ice features is modeled, using calculated spectra of giants, H 2 O ice and silicates. The adopted extinction curve is derived empirically. Its high resolution allows for the separation of continuum and feature extinction. The extinction between 13 and 25 μm is ∼50% relative to that at 2.2 μm. The strengths of the 6.0 and 6.85 μm absorption bands are in line with those of YSOs. Thus, their carriers, which, besides H 2 O and CH 3 OH, may include NH + 4 , HCOOH, H 2 CO, and NH 3 , are readily formed in the dense core phase, before stars form. The 3.53 μm C-H stretching mode of solid CH 3 OH was discovered. The CH 3 OH/H 2 O abundance ratios of 5%-12% are larger than upper limits in the Taurus molecular cloud. The initial ice composition, before star formation occurs, therefore depends on the environment. Signs of thermal and energetic processing that were found toward some YSOs are absent in the ices toward background stars. Finally, the peak optical depth of the 9.7 μm band of silicates relative to the continuum extinction at 2.2 μm is significantly shallower than in the diffuse ISM. This extends the results of Chiar et al. to a larger sample and higher extinctions.

Snow Accumulation Variability Over the West Antarctic Ice Sheet Since 1900: A Comparison of Ice Core Records With ERA-20C Reanalysis

Science.gov (United States)

Wang, Yetang; Thomas, Elizabeth R.; Hou, Shugui; Huai, Baojuan; Wu, Shuangye; Sun, Weijun; Qi, Shanzhong; Ding, Minghu; Zhang, Yulun

2017-11-01

This study uses a set of 37 firn core records over the West Antarctic Ice Sheet (WAIS) to test the performance of the twentieth century from the European Centre for Medium-Range Weather Forecasts (ERA-20C) reanalysis for snow accumulation and quantify temporal variability in snow accumulation since 1900. The firn cores are allocated to four geographical areas demarcated by drainage divides (i.e., Antarctic Peninsula (AP), western WAIS, central WAIS, and eastern WAIS) to calculate stacked records of regional snow accumulation. Our results show that the interannual variability in ERA-20C precipitation minus evaporation (P - E) agrees well with the corresponding ice core snow accumulation composites in each of the four geographical regions, suggesting its skill for simulating snow accumulation changes before the modern satellite era (pre-1979). Snow accumulation experiences significantly positive trends for the AP and eastern WAIS, a negative trend for the western WAIS, and no significant trend for the central WAIS from 1900 to 2010. The contrasting trends are associated with changes in the large-scale moisture transport driven by a deepening of the low-pressure systems and anomalies of sea ice in the Amundsen Sea Low region.

Measuring the triple O2 isotopic composition of air trapped in ice cores and quantifying thecauses of δ18Oatm Millennial Scale Variations

DEFF Research Database (Denmark)

Reutenauer, Corentin

of O2 isotopologues as global tracers of past changes in the climate system. The evolution of the past atmosphere can be retrieved from the air bubbles occluded n polar ice cores back to 800 kyr. However, elemental and isotopic fractionation processes alter O2 isotope ratios during the transport......, or the reproducibility of ice core δ18Oatm measurements is estimated with 21 Late Holocene Neem (Greenland) icecore samples from the same depth. A melt-extraction method is applied on these large samples (⋍ 30 g) and δ18Oatm , δO2/N2 and δ15N are measured in an O2 /N2/Ar mixture by isotope ratio mass spectrometry...... of the analytical system to reproduce δ18Oatm and δO2/N2 is estimated as 0.028‰ (1 σ) and 0.021‰ (1 σ), respectively. Fifth, thanks to improving isotope measurement techniques, millennial scale variations of δ18Oatm and 17Δatm preserved in polar ice cores have been revealed. In particular, a systematic δ18Oatm...

Measurement of neutrino oscillations in atmospheric neutrinos with the IceCube DeepCore detector

Energy Technology Data Exchange (ETDEWEB)

Yanez Garza, Juan Pablo

2014-06-02

The study of neutrino oscillations is an active field of research. During the last couple of decades many experiments have measured the effects of oscillations, pushing the field from the discovery stage towards an era of precision and deeper understanding of the phenomenon. The IceCube Neutrino Observatory, with its low energy subarray, DeepCore, has the possibility of contributing to this field. IceCube is a 1 km{sup 3} ice Cherenkov neutrino telescope buried deep in the Antarctic glacier. DeepCore, a region of denser instrumentation in the lower center of IceCube, permits the detection of neutrinos with energies as low as 10 GeV. Every year, thousands of atmospheric neutrinos around these energies leave a strong signature in DeepCore. Due to their energy and the distance they travel before being detected, these neutrinos can be used to measure the phenomenon of oscillations. This work starts with a study of the potential of IceCube DeepCore to measure neutrino oscillations in different channels, from which the disappearance of ν{sub μ} is chosen to move forward. It continues by describing a novel method for identifying Cherenkov photons that traveled without being scattered until detected direct photons. These photons are used to reconstruct the incoming zenith angle of muon neutrinos. The total energy of the interacting neutrino is also estimated. In data taken in 343 days during 2011-2012, 1487 neutrino candidates with an energy between 7 GeV and 100 GeV are found inside the DeepCore volume. Compared to the expectation from the atmospheric neutrino flux without oscillations, this corresponds to a deficit of about 500 muon neutrino events. The oscillation parameters that describe the data best are sin{sup 2}(2θ{sub 23})=1(>0.94 at 68 % C.L.) and vertical stroke Δm{sup 2}{sub 32} vertical stroke =2.4{sub -0.4}{sup +0.6}.10{sup -3} eV{sup 2}, which are in agreement with the results reported by other experiments. The simulation follows the data closely

Reconciling radiocarbon and ice core timescales over the Holocene - Cosmogenic radionuclides as synchronization tools

Science.gov (United States)

Muscheler, R.; Adolphi, F.; Mekhaldi, F.

2015-12-01

The atmospheric production rates of cosmogenic radionuclides, such as 14C and 10Be, vary globally due to external processes, namely the solar and geomagnetic modulation of the galactic cosmic ray flux as well as solar proton events. This signature is recorded in various archives such as ice cores (10Be) and tree-rings (14C). Hence, cosmogenic radionuclides offer a means to continuously assess timescale differences between two of the most widely used timescales in paleoclimatology - the radiocarbon and the ice core timescales. Short lived solar proton events additionally provide distinct marker horizons that allow synchronization of discrete horizons at annual precision. We will present a cosmogenic radionuclide based synchronization of the Greenland ice core timescale (GICC05, Svensson et al., 2008) and the radiocarbon timescale (IntCal13, Reimer et al., 2013) over the Holocene. This synchronization allows radiocarbon dated and ice core paleoclimate records to be compared on a common timescale at down to sub-decadal precision. We will compare these results to independent discrete isochrones obtained from tephrochronology and solar proton events. In addition, we will discuss implications for the accuracy and uncertainty estimates of GICC05 over the Holocene. Reimer, P. J., Bard, E., Bayliss, A., Beck, J. W., Blackwell, P. G., Bronk Ramsey, C., Buck, C. E., Cheng, H., Edwards, R. L., Friedrich, M., Grootes, P. M., Guilderson, T. P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T. J., Hoffmann, D. L., Hogg, A. G., Hughen, K. A., Kaiser, K. F., Kromer, B., Manning, S. W., Niu, M., Reimer, R. W., Richards, D. A., Scott, E. M., Southon, J. R., Staff, R. A., Turney, C. S. M., and van der Plicht, J.: IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000 Years cal BP, Radiocarbon, 55, 1869-1887, 10.2458/azu_js_rc.55.16947, 2013. Svensson, A., Andersen, K. K., Bigler, M., Clausen, H. B., Dahl-Jensen, D., Davies, S. M., Johnsen, S. J., Muscheler, R., Parrenin

Inverse stochastic–dynamic models for high-resolution Greenland ice core records

Directory of Open Access Journals (Sweden)

N. Boers

2017-12-01

Full Text Available Proxy records from Greenland ice cores have been studied for several decades, yet many open questions remain regarding the climate variability encoded therein. Here, we use a Bayesian framework for inferring inverse, stochastic–dynamic models from δ18O and dust records of unprecedented, subdecadal temporal resolution. The records stem from the North Greenland Ice Core Project (NGRIP, and we focus on the time interval 59–22 ka b2k. Our model reproduces the dynamical characteristics of both the δ18O and dust proxy records, including the millennial-scale Dansgaard–Oeschger variability, as well as statistical properties such as probability density functions, waiting times and power spectra, with no need for any external forcing. The crucial ingredients for capturing these properties are (i high-resolution training data, (ii cubic drift terms, (iii nonlinear coupling terms between the δ18O and dust time series, and (iv non-Markovian contributions that represent short-term memory effects.

Inverse stochastic-dynamic models for high-resolution Greenland ice core records

Science.gov (United States)

Boers, Niklas; Chekroun, Mickael D.; Liu, Honghu; Kondrashov, Dmitri; Rousseau, Denis-Didier; Svensson, Anders; Bigler, Matthias; Ghil, Michael

2017-12-01

Proxy records from Greenland ice cores have been studied for several decades, yet many open questions remain regarding the climate variability encoded therein. Here, we use a Bayesian framework for inferring inverse, stochastic-dynamic models from δ18O and dust records of unprecedented, subdecadal temporal resolution. The records stem from the North Greenland Ice Core Project (NGRIP), and we focus on the time interval 59-22 ka b2k. Our model reproduces the dynamical characteristics of both the δ18O and dust proxy records, including the millennial-scale Dansgaard-Oeschger variability, as well as statistical properties such as probability density functions, waiting times and power spectra, with no need for any external forcing. The crucial ingredients for capturing these properties are (i) high-resolution training data, (ii) cubic drift terms, (iii) nonlinear coupling terms between the δ18O and dust time series, and (iv) non-Markovian contributions that represent short-term memory effects.

Climate Changes Documented in Ice Core Records from Third Pole Glaciers, with Emphasis on the Guliya Ice Cap in the Western Kunlun Mountains over the Last 100 Years

Science.gov (United States)

Thompson, L. G.; Yao, T.; Beaudon, E.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.

2016-12-01

The Third Pole (TP) is a rapidly warming region containing 100,000 km2 of ice cover that collectively holds one of Earth's largest stores of freshwater that feeds Asia's largest rivers and helps sustain 1.5 billion people. Information on the accelerating warming in the region, its impact on the glaciers and subsequently on future water resources is urgently needed to guide mitigation and adaptation policies. Ice core histories collected over the last three decades across the TP demonstrate its climatic complexity and diversity. Here we present preliminary results from the flagship project of the Third Pole Environment Program, the 2015 Sino-American cooperative ice core drilling of the Guliya ice cap in the Kunlun Mountains in the western TP near the northern limit of the region influenced by the southwest monsoon. Three ice cores, each 51 meters in length, were recovered from the summit ( 6700 masl) while two deeper cores, one to bedrock ( 310 meters), were recovered from the plateau ( 6200 masl). Across the ice cap the net balance (accumulation) has increased annually by 2.3 cm of water equivalent from 1963-1992 to 1992-2015, and average oxygen isotopic ratios (δ18O) have enriched by 2‰. This contrasts with the recent ablation on the Naimona'nyi glacier located 540 km south of Guliya in the western Himalaya. Borehole temperatures in 2015 on the Guliya plateau have warmed substantially in the upper 30 meters of the ice compared to temperatures in 1992, when the first deep-drilling of the Guliya plateau was conducted. Compared with glaciers in the northern and western TP, the Himalayan ice fields are more sensitive to both fluctuations in the South Asian Monsoon and rising temperatures in the region. We examine the climatic changes of the last century preserved in ice core records from sites throughout the TP and compare them with those reconstructed for earlier warm epochs, such as the Medieval Climate Anomaly ( 950-1250 AD), the early Holocene "Hypsithermal

Precipitation regime influence on oxygen triple-isotope distributions in Antarctic precipitation and ice cores

Science.gov (United States)

Miller, Martin F.

2018-01-01

The relative abundance of 17O in meteoric precipitation is usually reported in terms of the 17O-excess parameter. Variations of 17O-excess in Antarctic precipitation and ice cores have hitherto been attributed to normalised relative humidity changes at the moisture source region, or to the influence of a temperature-dependent supersaturation-controlled kinetic isotope effect during in-cloud ice formation below -20 °C. Neither mechanism, however, satisfactorily explains the large range of 17O-excess values reported from measurements. A different approach, based on the regression characteristics of 103 ln (1 +δ17 O) versus 103 ln (1 +δ18 O), is applied here to previously published isotopic data sets. The analysis indicates that clear-sky precipitation ('diamond dust'), which occurs widely in inland Antarctica, is characterised by an unusual relative abundance of 17O, distinct from that associated with cloud-derived, synoptic snowfall. Furthermore, this distinction appears to be largely preserved in the ice core record. The respective mass contributions to snowfall accumulation - on both temporal and spatial scales - provides the basis of a simple, first-order explanation for the observed oxygen triple-isotope ratio variations in Antarctic precipitation, surface snow and ice cores. Using this approach, it is shown that precipitation during the last major deglaciation, both in western Antarctica at the West Antarctic Ice Sheet (WAIS) Divide and at Vostok on the eastern Antarctic plateau, consisted essentially of diamond dust only, despite a large temperature differential (and thus different water vapour supersaturation conditions) at the two locations. In contrast, synoptic snowfall events dominate the accumulation record throughout the Holocene at both sites.

Detection prospects for GeV neutrinos from collisionally heated gamma-ray bursts with IceCube/DeepCore.

Science.gov (United States)

Bartos, I; Beloborodov, A M; Hurley, K; Márka, S

2013-06-14

Jet reheating via nuclear collisions has recently been proposed as the main mechanism for gamma-ray burst (GRB) emission. In addition to producing the observed gamma rays, collisional heating must generate 10-100 GeV neutrinos, implying a close relation between the neutrino and gamma-ray luminosities. We exploit this theoretical relation to make predictions for possible GRB detections by IceCube + DeepCore. To estimate the expected neutrino signal, we use the largest sample of bursts observed by the Burst and Transient Source Experiment in 1991-2000. GRB neutrinos could have been detected if IceCube + DeepCore operated at that time. Detection of 10-100 GeV neutrinos would have significant implications, shedding light on the composition of GRB jets and their Lorentz factors. This could be an important target in designing future upgrades of the IceCube + DeepCore observatory.

New Crustal Boundary Revealed Beneath the Ross Ice Shelf, Antarctica, through ROSETTA-Ice Integrated Aerogeophysics, Geology, and Ocean Research

Science.gov (United States)

Tinto, K. J.; Siddoway, C. S.; Bell, R. E.; Lockett, A.; Wilner, J.

2017-12-01

Now submerged within marine plateaus and rises bordering Antarctica, Australia and Zealandia, the East Gondwana accretionary margin was a belt of terranes and stitched by magmatic arcs, later stretched into continental ribbons separated by narrow elongate rifts. This crustal architecture is known from marine geophysical exploration and ocean drilling of the mid-latitude coastal plateaus and rises. A concealed sector of the former East Gondwana margin that underlies the Ross Ice Shelf (RIS), Antarctica, is the focus of ROSETTA-ICE, a new airborne data acquisition campaign that explores the crustal makeup, tectonic boundaries and seafloor bathymetry beneath RIS. Gravimeters and a magnetometer are deployed by LC130 aircraft surveying along E-W lines spaced at 10 km, and N-S tie lines at 55 km, connect 1970s points (RIGGS) for controls on ocean depth and gravity. The ROSETTA-ICE survey, 2/3 completed thus far, provides magnetic anomalies, Werner depth-to-basement solutions, a new gravity-based bathymetric model at 20-km resolution, and a new crustal density map tied to the 1970s data. Surprisingly, the data reveal that the major lithospheric boundary separating East and West Antarctica lies 300 km east of the Transantarctic Mountains, beneath the floating RIS. The East and West regions have contrasting geophysical characteristics and bathymetry, with relatively dense lithosphere, low amplitude magnetic anomalies, and deep bathymetry on the East Antarctica side, and high amplitude magnetic anomalies, lower overall density and shallower water depths on the West Antarctic side. The Central High, a basement structure cored at DSDP Site 270 and seismically imaged in the Ross Sea, continues beneath RIS as a faulted but coherent crustal ribbon coincident with the tectonic boundary. The continuity of Gondwana margin crustal architecture discovered beneath the West Antarctic Ice Sheet requires a revision of the existing tectonic framework. The sub-RIS narrow rift basins and

All-flavour Search for Neutrinos from Dark Matter Annihilations in the Milky Way with IceCube/DeepCore

CERN Document Server

INSPIRE-00266703

2016-01-01

We present the first IceCube search for a signal of dark matter annihilations in the Milky Way using all-flavour neutrino-induced particle cascades. The analysis focuses on the DeepCore sub-detector of IceCube, and uses the surrounding IceCube strings as a veto region in order to select starting events in the DeepCore volume. We use 329 live-days of data from IceCube operating in its 86-string configuration during 2011-2012. No neutrino excess is found, the final result being compatible with the background-only hypothesis. From this null result, we derive upper limits on the velocity-averaged self-annihilation cross-section, , for dark matter candidate masses ranging from 30 GeV up to 10 TeV, assuming both a cuspy and a flat-cored dark matter halo profile. For dark matter masses between 200 GeV and 10 TeV, the results improve on all previous IceCube results on , reaching a level of 10^{-23} cm^3 s^-1, depending on the annihilation channel assumed, for a cusped NFW profile. The analysis demonstrates that all-f...

10Be and δ2H in polar ice cores as a probe of the solar variability's influence on climate

International Nuclear Information System (INIS)

Raisbeck, G.M.; Yiou, F.; Jouzel, J.; Domaine Univ., 38 - St-Martin-d'Heres; Petit, J.R.

1990-01-01

By using the technique of accelerator mass spectrometry, it is now possible to measure detailed profiles of cosmogenic (cosmic ray produced) 10 Be in polar ice cores. Recent work has demonstrated that these profiles contain information on solar activity, via its influence on the intensity of galactic cosmic rays arriving in the Earth's atmosphere. It has been known for some time that, as a result of temperature-dependent fractionation effects, the stable isotope profiles δ 2 O and δ 2 H in polar ice cores contain palaeoclimate information. Thus by comparing the 10 Be and stable isotope profiles in the same ice core, one can test the influence of solar variability on climate, and this independent of possible uncertainties in the absolute chronology of the records. We present here the results of such a comparison for two Antarctic ice cores; one from the South Pole, covering the past ca. 1000 years, and one from Dome C, covering the past ca. 3000 years. (author)

Detection of Organic Compounds in Ice Cores for Application to Palaeoclimate Reconstruction - Methodological Development

Science.gov (United States)

Giorio, C.; King, A. C. F.; Wolff, E. W.; Kalberer, M.; Thomas, E. R.; Mulvaney, R.

2016-12-01

Records of inorganic gases and particles trapped in ice core layers have provided some of the most important insights to our understanding of climate of the last 800,000 years. Organic compounds within the ice, however, are an un-tapped reservoir of information. In particular, two groups of compounds emitted from the terrestrial biosphere, fatty acids and terpene secondary oxidation aerosols (SOAs), display characteristics required for ice core paleoclimate reconstruction; emission rates depend on atmospheric states (e.g. temperature), compounds survive long-distance transport in the atmosphere to high altitudes and latitudes (Grannas et al., 2004; Fu et al., 2013 among others), and are shown to survive in ice layers up to 450 yrs old for fatty acids in Greenland (Kawamura et al., 1996) and 350 yrs for SOAs in Alaska (Pokhrel et al., 2015). Here, we aim to develop a single method for quantification of all compounds of interest over longer timescales and further locations using liquid chromatography (LC) ultrahigh resolution mass spectrometry (LTQ Orbitrap). Initial quantification of compound contamination from sources such as drilling fluids and storage bags, diffusing through outer ice core surfaces, suggests compound contamination is limited to the outer few mm's of ice over periods of a few months. Detection limits were in the order of 1-5 ppb for the compounds of interest, leading to the trial of pre-concentration methods using stir bar sorbtive extraction (SBSE) to facilitate detection of ppt concentration levels, as expected for these types of compounds based on previous analysis of snow samples (Pokhrel et al., 2015). Detection of these compounds seems highly viable, with promise for long-term records being achieved in the near future. Fu et al.(2013) Biogeosciences, 10(2), 653-667; Grannas et al.(2004) Global Biogeochem. Cycles, 18, GB1006; Kawamura et al.(1996) Geophys. Res. Lett., 23(19), 2665-2668; Pokhrel et al.(2015) Atmos. Environ., 130, 105-112.

Volcanic synchronisation of the EPICA-DC and TALDICE ice cores for the last 42 kyr BP

Science.gov (United States)

Severi, M.; Udisti, R.; Becagli, S.; Stenni, B.; Traversi, R.

2012-04-01

An age scale synchronisation between the Talos Dome and the EPICA Dome C ice cores was carried on through the identification of several common volcanic signatures for the last 42 kyr. Using this tight stratigraphic link we transferred the EDC age scale to the Talos Dome ice core producing a new age scale for the last 12 kyr. We estimated the discrepancies between the modeled TALDICE-1 age scale and the new one during the studied period, by evaluating the ratio R of the apparent duration of temporal intervals between pairs of isochrones. Except for a very few cases, R ranges between 0.8 and 1.2 corresponding to an uncertainty of up to 20% in the estimate of the time duration in at least one of the two ice cores. At this stage our approach does not allow us unequivocally to find out which of the models is affected by errors, but, taking into account only the historically known volcanic events, we found that discrepancies up to 200 years appears in the last two millennia in the TALDICE-1 model, while our new age scale shows a much better agreement with the volcanic absolute horizons. Thus, we propose for the Talos Dome ice core a new age scale (covering the whole Holocene) obtained by a direct transfer, via our stratigraphic link, from the EDC modelled age scale by Lemieux-Dudon et al. (2010).

Ultra-trace Measurements in the WAIS Divide 06A Ice Core, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — These data contain the results of gas chromatography mass spectrometry (GC-MS) analysis of 207 samples from the WAIS Divide 06A ice core. The trace gases found in...

Little Ice Age Fluctuations of Quelccaya Ice Cap, Peru

Science.gov (United States)

Stroup, J. S.; Kelly, M. A.; Lowell, T.

2009-12-01

A record of the past extents of Quelccaya Ice Cap (QIC) provides valuable information about tropical climate change from late glacial to recent time. Here, we examine the timing and regional significance of fluctuations of QIC during the Little Ice Age (LIA; ~1300-1850 AD). One prominent set of moraines, known as the Huancane I moraines, is located ~1 km from the present-day western ice cap margin and provides a near-continuous outline of the most recent advance of QIC. This moraine set was radiocarbon dated (~298 ± 134 and 831 ± 87 yr BP) by Mercer and Palacios (1977) and presented as some of the first evidence for cooling in the tropics during the Little Ice Age. Recent field investigations in the QIC region focused on refining the chronology of the Huancane I moraines. In 2008, new stratigraphic sections exposed by local lake-flooding events revealed multiple layers of peat within the Huancane I moraines. In both 2008 and 2009, samples were obtained for 10Be dating of boulders on Huancane I moraines. A combination of radiocarbon and 10Be ages indicate that the Huancane I moraines were deposited by ice cap expansion after ~3800 yr BP and likely by multiple advances at approximately 1000, 600, 400, and 200 yr BP. Radiocarbon and 10Be chronologies of the Huancane I moraines are compared with the Quelccaya ice core records (Thompson et al., 1985; 1986; 2006). Accumulation data from the ice core records are interpreted to indicate a significant wet period at ~1500-1700 AD followed by a significant drought at ~1720-1860 AD. We examine ice marginal fluctuations during these times to determine influence of such events on the ice cap extent.

Extracting the annual signal from Greenland ice-core chemistry and isotopic records

DEFF Research Database (Denmark)

Rasmussen, Sune Olander; Andersen, Katrine K.; Andersen, Marie Louise Siggaard

2002-01-01

Stratigraphic dating of ice cores by identification and counting of annual cycles in, for example, chemical measurements requires skill and experience. The work presented here investigates a method of data enhancement which is a first step towards an automated and more objective method of annual...

All-flavour search for neutrinos from dark matter annihilations in the Milky Way with IceCube/DeepCore

Energy Technology Data Exchange (ETDEWEB)

Aartsen, M.G.; Hill, G.C.; Robertson, S.; Wallace, A.; Whelan, B.J. [University of Adelaide, Department of Physics, Adelaide (Australia); Abraham, K.; Bernhard, A.; Coenders, S.; Holzapfel, K.; Huber, M.; Jurkovic, M.; Krings, K.; Resconi, E.; Turcati, A.; Veenkamp, J. [Technische Universitaet Muenchen, Physik-department, Garching (Germany); Ackermann, M.; Bernardini, E.; Blot, S.; Bretz, H.P.; Cruz Silva, A.H.; Franckowiak, A.; Gluesenkamp, T.; Gora, D.; Jacobi, E.; Karg, T.; Kintscher, T.; Kunwar, S.; Middell, E.; Mohrmann, L.; Nahnhauer, R.; Satalecka, K.; Schoenwald, A.; Spiering, C.; Stasik, A.; Stoessl, A.; Strotjohann, N.L.; Terliuk, A.; Usner, M.; Santen, J. van; Yanez, J.P. [DESY, Zeuthen (Germany); Adams, J. [University of Canterbury, Department of Physics and Astronomy, Private Bag 4800, Christchurch (New Zealand); Aguilar, J.A.; Ansseau, I.; Heereman, D.; Meagher, K.; Meures, T.; O' Murchadha, A.; Pinat, E.; Raab, C. [Universite Libre de Bruxelles, Science Faculty CP230, Brussels (Belgium); Ahlers, M.; Braun, J.; Chirkin, D.; Day, M.; Desiati, P.; Diaz-Velez, J.C.; Fahey, S.; Feintzeig, J.; Ghorbani, K.; Gladstone, L.; Griffith, Z.; Halzen, F.; Hanson, K.; Hoshina, K.; Jero, K.; Karle, A.; Kelley, J.L.; Kheirandish, A.; Krueger, C.; Mancina, S.; McNally, F.; Merino, G.; Sabbatini, L.; Tobin, M.N.; Tosi, D.; Vandenbroucke, J.; Van Rossem, M.; Wandkowsky, N.; Wendt, C.; Westerhoff, S.; Wille, L.; Xu, D.L. [University of Wisconsin, Department of Physics, Wisconsin IceCube Particle Astrophysics Center, Madison, WI (United States); Ahrens, M.; Bohm, C.; Dumm, J.P.; Finley, C.; Flis, S.; Hultqvist, K.; Walck, C.; Wolf, M.; Zoll, M. [Stockholm University, Department of Physics, Oskar Klein Centre, Stockholm (Sweden); Altmann, D.; Anton, G.; Katz, U.; Kittler, T.; Tselengidou, M. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen Centre for Astroparticle Physics, Erlangen (Germany); Andeen, K. [Marquette University, Department of Physics, Milwaukee, WI (United States); Anderson, T.; Arlen, T.C.; Dunkman, M.; Huang, F.; Keivani, A.; Lanfranchi, J.L.; Pankova, D.V.; Quinnan, M.; Tesic, G. [Pennsylvania State University, Department of Physics, University Park, PA (United States); Archinger, M.; Baum, V.; Boeser, S.; Del Pino Rosendo, E.; Di Lorenzo, V.; Eberhardt, B.; Ehrhardt, T.; Foesig, C.C.; Koepke, L.; Krueckl, G.; Sandroos, J.; Steuer, A.; Wiebe, K. [University of Mainz, Institute of Physics, Mainz (Germany); Arguelles, C.; Axani, S.; Collin, G.H.; Conrad, J.M.; Jones, B.J.P.; Moulai, M. [Massachusetts Institute of Technology, Department of Physics, Cambridge, MA (United States); Auffenberg, J.; Bissok, M.; Glagla, M.; Haack, C.; Hansmann, B.; Hansmann, T.; Kemp, J.; Konietz, R.; Leuermann, M.; Leuner, J.; Penek, Oe.; Raedel, L.; Reimann, R.; Rongen, M.; Schimp, M.; Schoenen, S.; Schumacher, L.; Stahlberg, M.; Vehring, M.; Wallraff, M.; Wickmann, S.; Wiebusch, C.H. [RWTH Aachen University, III. Physikalisches Institut, Aachen (Germany); Bai, X. [South Dakota School of Mines and Technology, Physics Department, Rapid City, SD (United States); Barwick, S.W.; Yodh, G. [University of California, Department of Physics and Astronomy, Irvine, CA (United States); Bay, R.; Filimonov, K.; Price, P.B.; Woschnagg, K. [University of California, Department of Physics, Berkeley, CA (United States); Beatty, J.J. [Ohio State University, Department of Physics, Center for Cosmology and Astro-Particle Physics, Columbus, OH (United States); Ohio State University, Department of Astronomy, Columbus, OH (United States); Becker Tjus, J.; Bos, F.; Eichmann, B.; Kroll, M.; Mandelartz, M.; Schoeneberg, S.; Tenholt, F. [Ruhr-Universitaet Bochum, Fakultaet fuer Physik and Astronomie, Bochum (Germany); Becker, K.H.; Bindig, D.; Helbing, K.; Hickford, S.; Hoffmann, R.; Kopper, S.; Naumann, U.; Obertacke Pollmann, A.; Omairat, A.; Posselt, J.; Soldin, D. [University of Wuppertal, Department of Physics, Wuppertal (Germany); BenZvi, S. [University of Rochester, Department of Physics and Astronomy, Rochester, NY (United States); Berghaus, P. [National Research Nuclear University, Moscow Engineering Physics Institute (MEPhI), Moscow (Russian Federation); Berley, D.; Blaufuss, E.; Cheung, E.; Felde, J.; Hellauer, R.; Hoffman, K.D.; Huelsnitz, W.; Maunu, R.; Olivas, A.; Schmidt, T.; Song, M.; Sullivan, G.W.; Wissing, H. [University of Maryland, Department of Physics, College Park, MD (United States); Besson, D.Z. [University of Kansas, Department of Physics and Astronomy, Lawrence, KS (United States); Binder, G.; Gerhardt, L.; Klein, S.R.; Miarecki, S.; Tatar, J. [University of California, Department of Physics, Berkeley, CA (United States); Lawrence Berkeley National Laboratory, Berkeley, CA (United States); and others

2016-10-15

We present the first IceCube search for a signal of dark matter annihilations in the Milky Way using all-flavour neutrino-induced particle cascades. The analysis focuses on the DeepCore sub-detector of IceCube, and uses the surrounding IceCube strings as a veto region in order to select starting events in the DeepCore volume. We use 329 live-days of data from IceCube operating in its 86-string configuration during 2011-2012. No neutrino excess is found, the final result being compatible with the background-only hypothesis. From this null result, we derive upper limits on the velocity-averaged self-annihilation cross-section, left angle σ{sub A}v right angle, for dark matter candidate masses ranging from 30 GeV up to 10 TeV, assuming both a cuspy and a flat-cored dark matter halo profile. For dark matter masses between 200 GeV and 10 TeV, the results improve on all previous IceCube results on left angle σ{sub A}v right angle, reaching a level of 10{sup -23} cm{sup 3} s {sup -1}, depending on the annihilation channel assumed, for a cusped NFW profile. The analysis demonstrates that all-flavour searches are competitive with muon channel searches despite the intrinsically worse angular resolution of cascades compared to muon tracks in IceCube. (orig.)

Ice age aerosol content from east Antarctic ice core samples and past wind strength

International Nuclear Information System (INIS)

Petit, J.R.; Briat, M.; Royer, A.

1981-01-01

The possible link between the aerosol content from the 905 deep Dome C ice core (East Antartica) which spans some 32,000 yr (Lorius et al. Nature; 280:644 (1979)) and climate, is considered. No evidence of major global or local volcanic activity was found though large marine and continental inputs (respectively 5 and 20 times higher than present) were observed at the end of the last Glacial stage. It is considered that they reflect glacial age climate with stronger atmospheric circulation, enhanced aridity and faster aerosol transport towards the Antarctic continent. (U.K.)

Dead-ice environments

DEFF Research Database (Denmark)

Krüger, Johannes; Kjær, Kurt H.; Schomacker, Anders

2010-01-01

glacier environment. The scientific challenges are to answer the key questions. What are the conditions for dead-ice formation? From which sources does the sediment cover originate? Which melting and reworking processes act in the ice-cored moraines? What is the rate of de-icing in the ice-cored moraines...

Volcanic synchronisation of the EPICA-DC and TALDICE ice cores for the last 42 kyr BP

Directory of Open Access Journals (Sweden)

M. Severi

2012-03-01

Full Text Available The age scale synchronisation between the Talos Dome and the EPICA Dome C ice cores was carried on through the identification of several common volcanic signatures. This paper describes the rigorous method, using the signature of volcanic sulphate, which was employed for the last 42 kyr of the record. Using this tight stratigraphic link, we transferred the EDC age scale to the Talos Dome ice core, producing a new age scale for the last 12 kyr. We estimated the discrepancies between the modelled TALDICE-1 age scale and the new scale during the studied period, by evaluating the ratio R of the apparent duration of temporal intervals between pairs of isochrones. Except for a very few cases, R ranges between 0.8 and 1.2, corresponding to an uncertainty of up to 20% in the estimate of the time duration in at least one of the two ice cores. At this stage our approach does not allow us to unequivocally identify which of the models is affected by errors, but, taking into account only the historically known volcanic events, we found that discrepancies up to 200 yr appear in the last two millennia in the TALDICE-1 model, while our new age scale shows a much better agreement with the volcanic absolute horizons. Thus, we propose for the Talos Dome ice core a new age scale (covering the whole Holocene obtained by a direct transfer, via our stratigraphic link, from the EDC modelled age scale by Lemieux-Dudon et al. (2010.

Constraints on N2O budget changes since pre-industrial time from new firn air and ice core isotope measurements

NARCIS (Netherlands)

Bernard, S.; Röckmann, T.; Kaiser, J.; Barnola, j.m.; Fischer, H; Blunier, T.; Chappellaz, J.

2006-01-01

A historical record of changes in the N2O isotope composition is important for a better understanding of the global N2O atmospheric budget. Here we have combined measurements of trapped gases in the firn and in ice cores of one Arctic site (North GReenland Ice core Project – NGRIP) and one Antarctic

Layer disturbances and the radio-echo free zone in ice sheets

Directory of Open Access Journals (Sweden)

R. Drews

2009-08-01

Full Text Available Radio-echo sounding of the Antarctic and Greenlandic ice sheets often reveals a layer in the lowest hundreds of meters above bedrock more or less free of radio echoes, known as the echo-free zone (EFZ. The cause of this feature is unclear, so far lacking direct evidence for its origin. We compare echoes around the EPICA drill site in Dronning Maud Land, Antarctica, with the dielectric properties, crystal orientation fabrics and optical stratigraphy of the EPICA-DML ice core. We find that echoes disappear in the depth range where the dielectric contrast is blurred, and where the coherency of the layers in the ice core is lost due to disturbances caused by the ice flow. At the drill site, the EFZ onset at ~2100 m marks a boundary, below which the ice core may have experienced flow induced disturbances on various scales. The onset may indicate changing rheology which needs to be accounted for in the modeling of ice sheet dynamics.

Paleo-Climate and Glaciological Reconstruction in Central Asia through the Collection and Analysis of Ice Cores and Instrumental Data from the Tien Shan

International Nuclear Information System (INIS)

Vladimir Aizen; Donald Bren; Karl Kreutz; Cameron Wake

2001-01-01

While the majority of ice core investigations have been undertaken in the polar regions, a few ice cores recovered from carefully selected high altitude/mid-to-low latitude glaciers have also provided valuable records of climate variability in these regions. A regional array of high resolution, multi-parameter ice core records developed from temperate and tropical regions of the globe can be used to document regional climate and environmental change in the latitudes which are home to the vase majority of the Earth's human population. In addition, these records can be directly compared with ice core records available from the polar regions and can therefore expand our understanding of inter-hemispheric dynamics of past climate changes. The main objectives of our paleoclimate research in the Tien Shan mountains of middle Asia combine the development of detailed paleoenvironmental records via the physical and chemical analysis of ice cores with the analysis of modern meteorological and hydrological data. The first step in this research was the collection of ice cores from the accumulation zone of the Inylchek Glacier and the collection of meteorological data from a variety of stations throughout the Tien Shan. The research effort described in this report was part of a collaborative effort with the United State Geological Survey's (USGS) Global Environmental Research Program which began studying radionuclide deposition in mid-latitude glaciers in 1995

Paleo-Climate and Glaciological Reconstruction in Central Asia through the Collection and Analysis of Ice Cores and Instrumental Data from the Tien Shan

Energy Technology Data Exchange (ETDEWEB)

Vladimir Aizen; Donald Bren; Karl Kreutz; Cameron Wake

2001-05-30

While the majority of ice core investigations have been undertaken in the polar regions, a few ice cores recovered from carefully selected high altitude/mid-to-low latitude glaciers have also provided valuable records of climate variability in these regions. A regional array of high resolution, multi-parameter ice core records developed from temperate and tropical regions of the globe can be used to document regional climate and environmental change in the latitudes which are home to the vase majority of the Earth's human population. In addition, these records can be directly compared with ice core records available from the polar regions and can therefore expand our understanding of inter-hemispheric dynamics of past climate changes. The main objectives of our paleoclimate research in the Tien Shan mountains of middle Asia combine the development of detailed paleoenvironmental records via the physical and chemical analysis of ice cores with the analysis of modern meteorological and hydrological data. The first step in this research was the collection of ice cores from the accumulation zone of the Inylchek Glacier and the collection of meteorological data from a variety of stations throughout the Tien Shan. The research effort described in this report was part of a collaborative effort with the United State Geological Survey's (USGS) Global Environmental Research Program which began studying radionuclide deposition in mid-latitude glaciers in 1995.

Constraining recent lead pollution sources in the North Pacific using ice core stable lead isotopes

Science.gov (United States)

Gross, B. H.; Kreutz, K. J.; Osterberg, E. C.; McConnell, J. R.; Handley, M.; Wake, C. P.; Yalcin, K.

2012-08-01

Trends and sources of lead (Pb) aerosol pollution in the North Pacific rim of North America from 1850 to 2001 are investigated using a high-resolution (subannual to annual) ice core record recovered from Eclipse Icefield (3017 masl; St. Elias Mountains, Canada). Beginning in the early 1940s, increasing Pb concentration at Eclipse Icefield occurs coevally with anthropogenic Pb deposition in central Greenland, suggesting that North American Pb pollution may have been in part or wholly responsible in both regions. Isotopic ratios (208Pb/207Pb and 206Pb/207Pb) from 1970 to 2001 confirm that a portion of the Pb deposited at Eclipse Icefield is anthropogenic, and that it represents a variable mixture of East Asian (Chinese and Japanese) emissions transported eastward across the Pacific Ocean and a North American component resulting from transient meridional atmospheric flow. Based on comparison with source material Pb isotope ratios, Chinese and North American coal combustion have likely been the primary sources of Eclipse Icefield Pb over the 1970-2001 time period. The Eclipse Icefield Pb isotope composition also implies that the North Pacific mid-troposphere is not directly impacted by transpolar atmospheric flow from Europe. Annually averaged Pb concentrations in the Eclipse Icefield ice core record show no long-term trend during 1970-2001; however, increasing208Pb/207Pb and decreasing 206Pb/207Pb ratios reflect the progressive East Asian industrialization and increase in Asian pollutant outflow. The post-1970 decrease in North American Pb emissions is likely necessary to explain the Eclipse Icefield Pb concentration time series. When compared with low (lichen) and high (Mt. Logan ice core) elevation Pb data, the Eclipse ice core record suggests a gradual increase in pollutant deposition and stronger trans-Pacific Asian contribution with rising elevation in the mountains of the North Pacific rim.

Calibrated cryo-cell UV-LA-ICPMS elemental concentrations from the NGRIP ice core reveal abrupt, sub-annual variability in dust across the GI-21.2 interstadial period

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D. Della Lunga

2017-05-01

Full Text Available Several abrupt shifts from periods of extreme cold (Greenland stadials, GS to relatively warmer conditions (Greenland interstadials, GI called Dansgaard–Oeschger events are recorded in the Greenland ice cores. Using cryo-cell UV-laser-ablation inductively coupled-plasma mass spectrometry (UV-LA-ICPMS, we analysed a 2.85 m NGRIP ice core section (2691.50–2688.65 m depth, age interval 84.86–85.09 ka b2k, thus covering  ∼  230 years across the transitions of GI-21.2, a short-lived interstadial prior to interstadial GI-21.1. GI-21.2 is a  ∼  100-year long period with δ18O values 3–4 ‰ higher than the following  ∼  200 years of stadial conditions (GS-21.2, which precede the major GI-21.1 warming. We report concentrations of major elements indicative of dust and/or sea salt (Na, Fe, Al, Ca, Mg at a spatial resolution of  ∼  200 µm, while maintaining detection limits in the low-ppb range, thereby achieving sub-annual time resolution even in deep NGRIP ice. We present an improved external calibration and quantification procedure using a set of five ice standards made from aqueous (international standard solutions. Our results show that element concentrations decrease drastically (more than 10-fold at the warming onset of GI-21.2 at the scale of a single year, followed by relatively low concentrations characterizing the interstadial part before gradually reaching again typical stadial values.

Ice flow Modelling of the Greenland Ice Sheet

DEFF Research Database (Denmark)

Nielsen, Lisbeth Tangaa

Models of ice flow have a range of application in glaciology, including investigating the large-scale response of ice sheets to changes in climate, assimilating data to estimate unknown conditions beneath the ice sheet, and in interpreting proxy records obtained from ice cores, among others. In t...... a steady state with respect to the reference climate at the end of the simulation and that the mass balance of the ice sheet at this time was more sensitive to recent climate fluctuations than the temperature forcing in the early or mid-Holocene.......Models of ice flow have a range of application in glaciology, including investigating the large-scale response of ice sheets to changes in climate, assimilating data to estimate unknown conditions beneath the ice sheet, and in interpreting proxy records obtained from ice cores, among others....... In this PhD project, the use of ice flow models for the interpretation of the age-structure of the Greenland ice sheet, i.e. the depth within the ice, at which ice deposited at given times are found at present day. Two different observational data sets of this archive were investigated. Further, paleo...

The WAIS Melt Monitor: An automated ice core melting system for meltwater sample handling and the collection of high resolution microparticle size distribution data

Science.gov (United States)

Breton, D. J.; Koffman, B. G.; Kreutz, K. J.; Hamilton, G. S.

2010-12-01

Paleoclimate data are often extracted from ice cores by careful geochemical analysis of meltwater samples. The analysis of the microparticles found in ice cores can also yield unique clues about atmospheric dust loading and transport, dust provenance and past environmental conditions. Determination of microparticle concentration, size distribution and chemical makeup as a function of depth is especially difficult because the particle size measurement either consumes or contaminates the meltwater, preventing further geochemical analysis. Here we describe a microcontroller-based ice core melting system which allows the collection of separate microparticle and chemistry samples from the same depth intervals in the ice core, while logging and accurately depth-tagging real-time electrical conductivity and particle size distribution data. This system was designed specifically to support microparticle analysis of the WAIS Divide WDC06A deep ice core, but many of the subsystems are applicable to more general ice core melting operations. Major system components include: a rotary encoder to measure ice core melt displacement with 0.1 millimeter accuracy, a meltwater tracking system to assign core depths to conductivity, particle and sample vial data, an optical debubbler level control system to protect the Abakus laser particle counter from damage due to air bubbles, a Rabbit 3700 microcontroller which communicates with a host PC, collects encoder and optical sensor data and autonomously operates Gilson peristaltic pumps and fraction collectors to provide automatic sample handling, melt monitor control software operating on a standard PC allowing the user to control and view the status of the system, data logging software operating on the same PC to collect data from the melting, electrical conductivity and microparticle measurement systems. Because microparticle samples can easily be contaminated, we use optical air bubble sensors and high resolution ice core density

Snow precipitation at four ice core sites in East Antarctica: provenance, seasonality and blocking factors

Energy Technology Data Exchange (ETDEWEB)

Scarchilli, Claudio [ENEA, Rome (Italy); Universita degli studi di Trieste, Trieste (Italy); Frezzotti, Massimo; Ruti, Paolo Michele [ENEA, Rome (Italy)

2011-11-15

Snow precipitation is the primary mass input to the Antarctic ice sheet and is one of the most direct climatic indicators, with important implications for paleoclimatic reconstruction from ice cores. Provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites (Dome C, Law Dome, Talos Dome, and Taylor Dome) in East Antarctica were analysed with air mass back trajectories calculated using the Lagrangian model and the mean composite data for precipitation, geopotential height and wind speed field data from the European Centre for Medium Range Weather Forecast from 1980 to 2001. On an annual basis, back trajectories showed that the Atlantic-Indian and Ross-Pacific Oceans were the main provenances of precipitation in Wilkes Land (80%) and Victoria Land (40%), respectively, whereas the greatest influence of the ice sheet was on the interior near the Vostok site (80%) and in the Southwest Ross Sea (50%), an effect that decreased towards the coast and along the Antarctic slope. Victoria Land received snowfall atypically with respect to other Antarctica areas in terms of pathway (eastern instead of western), seasonality (summer instead of winter) and velocity (old air age). Geopotential height patterns at 500 hPa at low (>10 days) and high (2-6 days) frequencies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the Tasman Sea-Eastern Indian Ocean at higher latitudes (60-70 S) than normal. This could be considered part of an atmospheric blocking event, with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low-frequency positive anomalies. (orig.)

Estimation of precipitation rates by measurements of {sup 36}Cl in the GRIP ice core with the PSI/ETH tandem accelerator

Energy Technology Data Exchange (ETDEWEB)

Wagner, G.; Baumgartner, S.; Beer, J. [EAWAG, Duebendorf (Switzerland); Synal, H.A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

1997-09-01

Within the European Greenland ice core project (GRIP) {sup 36}Cl AMS measurements have been performed on ice core samples from Summit (Greenland, 73{sup o}N, 37{sup o}W). Most data analysed so far are from the lower part of the ice core. The {sup 36}Cl concentration is well correlated with {delta}{sup 18}O, which is considered as a proxy for paleotemperatures. Assuming that the deposition rate of radionuclides is independent of {delta}{sup 18}O, {sup 36}Cl is used to estimate the relationship between accumulation and {delta}{sup 18}O. The results confirm that the rapid changes of {delta}{sup 18}O, the so-called Dansgaard-Oeschger events, are also reflected in the precipitation rate. (author) 1 fig., 3 refs.

Phylogenetic and physiological diversity of microorganisms isolated from a deep greenland glacier ice core

Science.gov (United States)

Miteva, V. I.; Sheridan, P. P.; Brenchley, J. E.

2004-01-01

We studied a sample from the GISP 2 (Greenland Ice Sheet Project) ice core to determine the diversity and survival of microorganisms trapped in the ice at least 120,000 years ago. Previously, we examined the phylogenetic relationships among 16S ribosomal DNA (rDNA) sequences in a clone library obtained by PCR amplification from genomic DNA extracted from anaerobic enrichments. Here we report the isolation of nearly 800 aerobic organisms that were grouped by morphology and amplified rDNA restriction analysis patterns to select isolates for further study. The phylogenetic analyses of 56 representative rDNA sequences showed that the isolates belonged to four major phylogenetic groups: the high-G+C gram-positives, low-G+C gram-positives, Proteobacteria, and the Cytophaga-Flavobacterium-Bacteroides group. The most abundant and diverse isolates were within the high-G+C gram-positive cluster that had not been represented in the clone library. The Jukes-Cantor evolutionary distance matrix results suggested that at least 7 isolates represent new species within characterized genera and that 49 are different strains of known species. The isolates were further categorized based on the isolation conditions, temperature range for growth, enzyme activity, antibiotic resistance, presence of plasmids, and strain-specific genomic variations. A significant observation with implications for the development of novel and more effective cultivation methods was that preliminary incubation in anaerobic and aerobic liquid prior to plating on agar media greatly increased the recovery of CFU from the ice core sample.

Novel automated inversion algorithm for temperature reconstruction using gas isotopes from ice cores

Directory of Open Access Journals (Sweden)

M. Döring

2018-06-01

Full Text Available Greenland past temperature history can be reconstructed by forcing the output of a firn-densification and heat-diffusion model to fit multiple gas-isotope data (δ15N or δ40Ar or δ15Nexcess extracted from ancient air in Greenland ice cores using published accumulation-rate (Acc datasets. We present here a novel methodology to solve this inverse problem, by designing a fully automated algorithm. To demonstrate the performance of this novel approach, we begin by intentionally constructing synthetic temperature histories and associated δ15N datasets, mimicking real Holocene data that we use as true values (targets to be compared to the output of the algorithm. This allows us to quantify uncertainties originating from the algorithm itself. The presented approach is completely automated and therefore minimizes the subjective impact of manual parameter tuning, leading to reproducible temperature estimates. In contrast to many other ice-core-based temperature reconstruction methods, the presented approach is completely independent from ice-core stable-water isotopes, providing the opportunity to validate water-isotope-based reconstructions or reconstructions where water isotopes are used together with δ15N or δ40Ar. We solve the inverse problem T(δ15N, Acc by using a combination of a Monte Carlo based iterative approach and the analysis of remaining mismatches between modelled and target data, based on cubic-spline filtering of random numbers and the laboratory-determined temperature sensitivity for nitrogen isotopes. Additionally, the presented reconstruction approach was tested by fitting measured δ40Ar and δ15Nexcess data, which led as well to a robust agreement between modelled and measured data. The obtained final mismatches follow a symmetric standard-distribution function. For the study on synthetic data, 95 % of the mismatches compared to the synthetic target data are in an envelope between 3.0 to 6.3 permeg for δ15N and 0.23 to 0

Ice Core Perspective on Mercury Pollution during the Past 600 Years.

Science.gov (United States)

Beal, Samuel A; Osterberg, Erich C; Zdanowicz, Christian M; Fisher, David A

2015-07-07

Past emissions of the toxic metal mercury (Hg) persist in the global environment, yet these emissions remain poorly constrained by existing data. Ice cores are high-resolution archives of atmospheric deposition that may provide crucial insight into past atmospheric Hg levels during recent and historical time. Here we present a record of total Hg (HgT) in an ice core from the pristine summit plateau (5340 m asl) of Mount Logan, Yukon, Canada, representing atmospheric deposition from AD 1410 to 1998. The Colonial Period (∼1603-1850) and North American "Gold Rush" (1850-1900) represent minor fractions (8% and 14%, respectively) of total anthropogenic Hg deposition in the record, with the majority (78%) occurring during the 20th Century. A period of maximum HgT fluxes from 1940 to 1975 coincides with estimates of enhanced anthropogenic Hg emissions from commercial sources, as well as with industrial emissions of other toxic metals. Rapid declines in HgT fluxes following peaks during the Gold Rush and the mid-20th Century indicate that atmospheric Hg deposition responds quickly to reductions in emissions. Increasing HgT fluxes from 1993 until the youngest samples in 1998 may reflect the resurgence of Hg emissions from unregulated coal burning and small-scale gold mining.

Millennial-scale instability of the Antarctic Ice Sheet during the last glaciation.

NARCIS (Netherlands)

Kanfoush, S.L.; Hodell, D.A.; Charles, C.D.; Guilderson, T.P.; Mortyn, P.G.

2000-01-01

Records of ice-rafted detritus (IRD) concentration in deep-sea cores from the southeast Atlantic Ocean reveal millennial-scale pulses of IRD delivery between 20,000 and 74,000 years ago. Prominent IRD layers correlate across the Polar Frontal Zone, suggesting episodes of Antarctic Ice Sheet

TRACEing Last Glacial Period (25-80 ka b2k) tephra horizons within North Atlantic marine cores and exploring links to the Greenland ice-cores

Science.gov (United States)

Abbott, P. M.; Davies, S. M.; Griggs, A. J.; Bourne, A. J.; Cook, E.; Pearce, N. J. G.; Austin, W. E. N.; Chapman, M.; Hall, I. R.; Purcell, C. S.; Scourse, J. D.; Rasmussen, T. L.

2015-12-01

Tephrochronology is a powerful technique for the correlation and synchronisation of disparate palaeoclimatic records from different depositional environments and has considerable potential for testing climatic phasing. For example, the relative timing of atmospheric and marine changes caused by the abrupt climatic events that punctuated the last glacial period within the North Atlantic region. Here we report on efforts to establish a framework of tephra horizons within North Atlantic marine sequences that can correlate these records and if traced in the Greenland ice-cores can act as isochronous tie-lines. Investigations have been conducted on a network of marine cores from a number of sites across the North Atlantic. Tephra horizons have been identified using cryptotephra extraction techniques more commonly applied to the study of terrestrial sequences. There are two main challenges with assessing cryptotephras in the glacial North Atlantic; i) determining the transportation processes and ii) assessing the influence of secondary reworking processes and the stratigraphic integrity of the isochrons. These processes and their influence are investigated for each cryptotephra using shard size variations, major element heterogeneity and co-variance of IRD input for some cores. Numerous Icelandic cryptophras have been successfully identified in the marine records and we will discuss the integration of a number of these with an isochronous nature into a marine tephra framework and how potential correlations to the Greenland ice-core tephra framework are determined. Spatial patterns in the nature of tephra records that are emerging from the core network will be highlighted to outline some of the key areas that could be explored in the future. In addition, the synchronisation of multiple North Atlantic records to the Greenland ice-cores using the North Atlantic Ash Zone II to test the synchroneity of an abrupt cooling in the North Atlantic will be discussed.

The Antarctic ice core chronology (AICC2012): an optimized multi-parameter and multi-site dating approach for the last 120 thousand years

Science.gov (United States)

Veres, D.; Bazin, L.; Landais, A.; Toyé Mahamadou Kele, H.; Lemieux-Dudon, B.; Parrenin, F.; Martinerie, P.; Blayo, E.; Blunier, T.; Capron, E.; Chappellaz, J.; Rasmussen, S. O.; Severi, M.; Svensson, A.; Vinther, B.; Wolff, E. W.

2013-08-01

The deep polar ice cores provide reference records commonly employed in global correlation of past climate events. However, temporal divergences reaching up to several thousand years (ka) exist between ice cores over the last climatic cycle. In this context, we are hereby introducing the Antarctic Ice Core Chronology 2012 (AICC2012), a new and coherent timescale developed for four Antarctic ice cores, namely Vostok, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML) and Talos Dome (TALDICE), alongside the Greenlandic NGRIP record. The AICC2012 timescale has been constructed using the Bayesian tool Datice (Lemieux-Dudon et al., 2010) that combines glaciological inputs and data constraints, including a wide range of relative and absolute gas and ice stratigraphic markers. We focus here on the last 120 ka, whereas the companion paper by Bazin et al. (2013) focuses on the interval 120-800 ka. Compared to previous timescales, AICC2012 presents an improved timing for the last glacial inception, respecting the glaciological constraints of all analyzed records. Moreover, with the addition of numerous new stratigraphic markers and improved calculation of the lock-in depth (LID) based on δ15N data employed as the Datice background scenario, the AICC2012 presents a slightly improved timing for the bipolar sequence of events over Marine Isotope Stage 3 associated with the seesaw mechanism, with maximum differences of about 600 yr with respect to the previous Datice-derived chronology of Lemieux-Dudon et al. (2010), hereafter denoted LD2010. Our improved scenario confirms the regional differences for the millennial scale variability over the last glacial period: while the EDC isotopic record (events of triangular shape) displays peaks roughly at the same time as the NGRIP abrupt isotopic increases, the EDML isotopic record (events characterized by broader peaks or even extended periods of high isotope values) reached the isotopic maximum several centuries before. It is

The Antarctic ice core chronology (AICC2012: an optimized multi-parameter and multi-site dating approach for the last 120 thousand years

Directory of Open Access Journals (Sweden)

D. Veres

2013-08-01

Full Text Available The deep polar ice cores provide reference records commonly employed in global correlation of past climate events. However, temporal divergences reaching up to several thousand years (ka exist between ice cores over the last climatic cycle. In this context, we are hereby introducing the Antarctic Ice Core Chronology 2012 (AICC2012, a new and coherent timescale developed for four Antarctic ice cores, namely Vostok, EPICA Dome C (EDC, EPICA Dronning Maud Land (EDML and Talos Dome (TALDICE, alongside the Greenlandic NGRIP record. The AICC2012 timescale has been constructed using the Bayesian tool Datice (Lemieux-Dudon et al., 2010 that combines glaciological inputs and data constraints, including a wide range of relative and absolute gas and ice stratigraphic markers. We focus here on the last 120 ka, whereas the companion paper by Bazin et al. (2013 focuses on the interval 120–800 ka. Compared to previous timescales, AICC2012 presents an improved timing for the last glacial inception, respecting the glaciological constraints of all analyzed records. Moreover, with the addition of numerous new stratigraphic markers and improved calculation of the lock-in depth (LID based on δ15N data employed as the Datice background scenario, the AICC2012 presents a slightly improved timing for the bipolar sequence of events over Marine Isotope Stage 3 associated with the seesaw mechanism, with maximum differences of about 600 yr with respect to the previous Datice-derived chronology of Lemieux-Dudon et al. (2010, hereafter denoted LD2010. Our improved scenario confirms the regional differences for the millennial scale variability over the last glacial period: while the EDC isotopic record (events of triangular shape displays peaks roughly at the same time as the NGRIP abrupt isotopic increases, the EDML isotopic record (events characterized by broader peaks or even extended periods of high isotope values reached the isotopic maximum several centuries before

The ice-core record - Climate sensitivity and future greenhouse warming

Science.gov (United States)

Lorius, C.; Raynaud, D.; Jouzel, J.; Hansen, J.; Le Treut, H.

1990-01-01

The prediction of future greenhouse-gas-warming depends critically on the sensitivity of earth's climate to increasing atmospheric concentrations of these gases. Data from cores drilled in polar ice sheets show a remarkable correlation between past glacial-interglacial temperature changes and the inferred atmospheric concentration of gases such as carbon dioxide and methane. These and other palaeoclimate data are used to assess the role of greenhouse gases in explaining past global climate change, and the validity of models predicting the effect of increasing concentrations of such gases in the atmosphere.

210Po/210Pb Activity Ratios as a Possible `Dating Tool' of Ice Cores and Ice-rafted Sediments from the Western Arctic Ocean - Preliminary Results

Science.gov (United States)

Krupp, K.; Baskaran, M. M.

2016-02-01

We have collected and analyzed a suite of surface snow samples, ice cores, ice-rafted sediments (IRS) and aerosol samples from the Western Arctic for Po-210 and Pb-210 to examine the extent of disequilibrium between this pair to possibly use 210Po/210Pb activity ratio to date different layers of ice cores and time of incorporation of ice-rafted sediments into the sea ice. We have earlier reported that the activity concentrations of 210Pb in IRS vary over an order of magnitude and it is 1-2 orders of magnitude higher than that of the benthic sediments (1-2 dpm/g in benthic sediments compared to 25 to 300 dpm/g in IRS). In this study, we have measured 210Po/210Pb activity ratios in aerosols from the Arctic Ocean to constrain the initial 210Po/210Pb ratio at the time of deposition during precipitation. The 210Po activity concentration in recent snow is compared to surface ice samples. The `age' of IRS incorporation can be calculated as follows: [210Po]measured = [210Po]initial + [210Pb] (1 - exp(-λt)) (1) where λ is the decay constant of 210Po, 138.4 days, and `t' is the in-growth time period. From this equation, `t' can be calculated as follows: t = (-1/λ) [ln (1- ((210Po/210Pb)measured - (210Po/210Pb)initial)] (2) The assumption involved in this approach are: i) there is no preferential uptake of 210Po (highly biogenic - S group); and iii) both 210Po and 210Pb remain as closed system. The calculated age using equation (2) will be discussed and presented.

Rapid Access Ice Drill: A New Tool for Exploration of the Deep Antarctic Ice Sheets and Subglacial Geology

Science.gov (United States)

Goodge, J. W.; Severinghaus, J. P.

2014-12-01

The Rapid Access Ice Drill (RAID) will penetrate the Antarctic ice sheets in order to core through deep ice, the glacial bed, and into bedrock below. This new technology will provide a critical first look at the interface between major ice caps and their subglacial geology. Currently in construction, RAID is a mobile drilling system capable of making several long boreholes in a single field season in Antarctica. RAID is interdisciplinary and will allow access to polar paleoclimate records in ice >1 Ma, direct observation at the base of the ice sheets, and recovery of rock cores from the ice-covered East Antarctic craton. RAID uses a diamond rock-coring system as in mineral exploration. Threaded drill-pipe with hardened metal bits will cut through ice using reverse circulation of Estisol for pressure-compensation, maintenance of temperature, and removal of ice cuttings. Near the bottom of the ice sheet, a wireline bottom-hole assembly will enable diamond coring of ice, the glacial bed, and bedrock below. Once complete, boreholes will be kept open with fluid, capped, and made available for future down-hole measurement of thermal gradient, heat flow, ice chronology, and ice deformation. RAID will also sample for extremophile microorganisms. RAID is designed to penetrate up to 3,300 meters of ice and take sample cores in less than 200 hours. This rapid performance will allow completion of a borehole in about 10 days before moving to the next drilling site. RAID is unique because it can provide fast borehole access through thick ice; take short ice cores for paleoclimate study; sample the glacial bed to determine ice-flow conditions; take cores of subglacial bedrock for age dating and crustal history; and create boreholes for use as an observatory in the ice sheets. Together, the rapid drilling capability and mobility of the drilling system, along with ice-penetrating imaging methods, will provide a unique 3D picture of the interior Antarctic ice sheets.

Ice Penetrating Radar Reveals Spatially Variable Features in Basal Channel under the Nansen Ice Shelf, Terra Nova Bay, Antarctica

Science.gov (United States)

Wray, P. L.; Dow, C. F.; Mueller, D.; Lee, W. S.; Lindzey, L.; Greenbaum, J. S.; Blankenship, D. D.

2017-12-01

The stability of Antarctic ice shelves is of great concern as their current thinning and future collapse will contribute to sea-level rise via the acceleration of grounded tributary glaciers into the ocean. The study of the sub-ice-shelf environment is essential for understanding ice-ocean interaction, where warming ocean temperatures have already begun to threaten the long-term viability of Antarctic ice shelves. Obtaining direct measurements of the sub-ice-shelf cavity remains challenging. Here, we demonstrate that ground-based geophysical methods can deliver high resolution monitoring and mapping of the spatial and temporal changes in features, melt rates, and ice mass transport of this environment. In November 2016, 84 km of ground-based, low frequency, Ice Penetrating Radar (IPR) surveys were completed on three sites over the Nansen Ice Shelf in Terra Nova Bay, Antarctica. The surveys examined an ocean-sourced basal channel incised into the bottom of the shelf, originally detected from a large surface depression. Results reveal high resolution features of a several kilometre-wide, 100 m high channel, with 40 m high sub-channels, zones of significant marine ice accumulation, and basal crevasses penetrating large fractions of the ice shelf thickness. Data from multiple airborne geophysical surveys were compared to the November 2016 IPR data to calculate mass change both spatially and temporally. Many of the smaller scale features we detected are not represented through hydrostatic equilibrium as calculated from ice thicknesses, due to bridging stresses, and as such can not be detected with satellite based remote sensing methods. Our in-field geophysical methods produced high-resolution information of these features, which underscores the need for similar surveys over vulnerable ice shelves to better understand ice-ocean processes.

Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

Directory of Open Access Journals (Sweden)

E. Capron

2010-06-01

Full Text Available Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka and characterized by short Dansgaard-Oeschger (DO events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka, a time period corresponding to relatively high sea level. The results display a succession of abrupt events associated with long Greenland InterStadial phases (GIS enabling us to highlight a sub-millennial scale climatic variability depicted by (i short-lived and abrupt warming events preceding some GIS (precursor-type events and (ii abrupt warming events at the end of some GIS (rebound-type events. The occurrence of these sub-millennial scale events is suggested to be driven by the insolation at high northern latitudes together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This shows that for extraordinary long stadial durations the accompanying Antarctic warming amplitude cannot be described by a simple linear relationship between the two as expected from the bipolar seesaw concept. We also show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict, questioning the Greenland ice core temperature records as a proxy for AMOC changes throughout the glacial period.

Life Cores: A Sci-Art Collaboration Between a Snow/Ice Researcher, an Artist/Educator, Students, and Street Road Artists Space

Science.gov (United States)

Dooley, J.; Courville, Z.; Artinian, E.

2016-12-01

BackgroundStreet Road Artists Space Summer 2015 show was Sailing Stones. Works presented scenarios on tension between transience and permanence, highlighting cultural constructs imposed onto landscape and place. Dooley's installation, CryoZen Garden, operated as visual metaphor, modeling cryospheric processes and explored effects of melting polar ice caps on a warming world. A grant from Pennsylvania Partners in the Arts, with a focus on sharing contemporary works which were participatory, conceptual, and polar science research-based, allowed for a new project to engage community members, particularly students.MethodsIn this project students were introduced to the work of Dooley, artist/educator and Courville, snow/ice researcher. Students created `Life Cores', a take on ice and sediment coring scientists use as evidence of Earth's atmospheric and geologic changes. Students were given plastic tubes 2' long and 2" in diameter and were asked to add a daily layer of materials taken from everyday life, for a one month period. Students chose materials important to them personally, and kept journals, reflecting on items' significance, and/or relationship to life and world events. After creation of the Life Cores, Courville and Dooley visited students, shared their work on polar research, what it's like to live and work on ice, and ways science and art can intertwine to create better understanding of climate change issues. Students used core logging sheets to make observations of each others' life cores, noting layer colors, textures and deposition rates as some of the characteristics researchers use in ice and sediment core interpretation. Students' work was exhibited at Street Road and will remain on Street Road's website. Courville and Dooley presented to the general public during the opening. ConclusionsParticipants were better able to answer the question, How do we know what we know from coring? by relating the science to something that is known and personal, such as

A new method based on low background instrumental neutron activation analysis for major, trace and ultra-trace element determination in atmospheric mineral dust from polar ice cores

Energy Technology Data Exchange (ETDEWEB)

Baccolo, Giovanni, E-mail: giovanni.baccolo@mib.infn.it [Graduate School in Polar Sciences, University of Siena, Via Laterina 8, 53100, Siena (Italy); Department of Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126, Milano (Italy); INFN, Section of Milano-Bicocca, P.zza della Scienza 3, 20126, Milano (Italy); Clemenza, Massimiliano [INFN, Section of Milano-Bicocca, P.zza della Scienza 3, 20126, Milano (Italy); Department of Physics, University of Milano-Bicocca, P.zza della Scienza 3, 20126, Milano (Italy); Delmonte, Barbara [Department of Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126, Milano (Italy); Maffezzoli, Niccolò [Centre for Ice and Climate, Niels Bohr Institute, Juliane Maries Vej, 30, 2100, Copenhagen (Denmark); Nastasi, Massimiliano; Previtali, Ezio [INFN, Section of Milano-Bicocca, P.zza della Scienza 3, 20126, Milano (Italy); Department of Physics, University of Milano-Bicocca, P.zza della Scienza 3, 20126, Milano (Italy); Prata, Michele; Salvini, Andrea [LENA, University of Pavia, Pavia (Italy); Maggi, Valter [Department of Environmental Sciences, University of Milano-Bicocca, P.zza della Scienza 1, 20126, Milano (Italy); INFN, Section of Milano-Bicocca, P.zza della Scienza 3, 20126, Milano (Italy)

2016-05-30

Dust found in polar ice core samples present extremely low concentrations, in addition the availability of such samples is usually strictly limited. For these reasons the chemical and physical analysis of polar ice cores is an analytical challenge. In this work a new method based on low background instrumental neutron activation analysis (LB-INAA) for the multi-elemental characterization of the insoluble fraction of dust from polar ice cores is presented. Thanks to an accurate selection of the most proper materials and procedures it was possible to reach unprecedented analytical performances, suitable for ice core analyses. The method was applied to Antarctic ice core samples. Five samples of atmospheric dust (μg size) from ice sections of the Antarctic Talos Dome ice core were prepared and analyzed. A set of 37 elements was quantified, spanning from all the major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe) to trace ones, including 10 (La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu) of the 14 natural occurring lanthanides. The detection limits are in the range of 10{sup −13}–10{sup −6} g, improving previous results of 1–3 orders of magnitude depending on the element; uncertainties lies between 4% and 60%. - Highlights: • A new method based on neutron activation for the multi-elemental characterization of atmospheric dust entrapped in polar ice cores is proposed. • 37 elements were quantified in μg size dust samples with detection limits ranging from 10{sup −13} to 10{sup −6} g. • A low background approach and a clean analytical protocol improved INAA performances to unprecedented levels for multi-elemental analyses.

[The relevance of core muscles in ice hockey players: a feasibility study].

Science.gov (United States)

Rogan, S; Blasimann, A; Nyffenegger, D; Zimmerli, N; Radlinger, L

2013-12-01

Good core strength is seen as a condition for high performance in sports. In general, especially maximum voluntary contraction (MVC) and strength endurance (SE) measurements of the core muscles are used. In addition, a few studies can be found that examine the core muscles in terms of MVC, rate of force development (RFD) and SE. Primary aims of this feasibility study were to investigate the feasibility regarding recruiting process, compliance and safety of the testing conditions and raise the force capabilities MVC, RFD and SE of the core muscles in amateur ice hockey players. Secondarily, tendencies of correlations between muscle activity and either shot speed and sprint time shall be examined. In this feasibility study the recruitment process has been approved by 29 ice hockey players, their adherence to the study measurements of trunk muscles, and safety of the measurements was evaluated. To determine the MVC, RFD and SE for the ventral, lateral and dorsal core muscles a dynamic force measurement was performed. To determine the correlation between core muscles and shot speed and 40-m sprint, respectively, the rank correlation coefficient (rho) from Spearman was used. The recruited number of eight field players and one goal-keeper was not very high. The compliance with 100 % was excellent. The players reported no adverse symptoms or injuries after the measurements. The results show median values for the ventral core muscles for MVC with 46.5 kg for RFD with 2.23 m/s2 and 96 s for the SE. For lateral core muscle median values of the lateral core muscles for MVC with 71.10 kg, RFD with 2.59 m/s2 and for SE over 66 s were determined. The dorsal core muscles shows values for MVC 69.7 kg, for RFD 3.39 m/s2 and for SE of 75 s. High correlations between MVC of the ventral core muscles (rho = -0.721, p = 0.021), and between the SE of the ventral core muscles (rho = 0.787, p = 0.012), and the shot velocity rate were determined. Another

Formation of Glycerol through Hydrogenation of CO Ice under Prestellar Core Conditions

Science.gov (United States)

Fedoseev, G.; Chuang, K.-J.; Ioppolo, S.; Qasim, D.; van Dishoeck, E. F.; Linnartz, H.

2017-06-01

Observational studies reveal that complex organic molecules (COMs) can be found in various objects associated with different star formation stages. The identification of COMs in prestellar cores, I.e., cold environments in which thermally induced chemistry can be excluded and radiolysis is limited by cosmic rays and cosmic-ray-induced UV photons, is particularly important as this stage sets up the initial chemical composition from which ultimately stars and planets evolve. Recent laboratory results demonstrate that molecules as complex as glycolaldehyde and ethylene glycol are efficiently formed on icy dust grains via nonenergetic atom addition reactions between accreting H atoms and CO molecules, a process that dominates surface chemistry during the “CO freeze-out stage” in dense cores. In the present study we demonstrate that a similar mechanism results in the formation of the biologically relevant molecule glycerol—HOCH2CH(OH)CH2OH—a three-carbon-bearing sugar alcohol necessary for the formation of membranes of modern living cells and organelles. Our experimental results are fully consistent with a suggested reaction scheme in which glycerol is formed along a chain of radical-radical and radical-molecule interactions between various reactive intermediates produced upon hydrogenation of CO ice or its hydrogenation products. The tentative identification of the chemically related simple sugar glyceraldehyde—HOCH2CH(OH)CHO—is discussed as well. These new laboratory findings indicate that the proposed reaction mechanism holds much potential to form even more complex sugar alcohols and simple sugars.

Search for nonstandard neutrino interactions with IceCube DeepCore

Science.gov (United States)

Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Al Samarai, I.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bagherpour, H.; Bai, X.; Barron, J. P.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Bourbeau, E.; Bourbeau, J.; Bradascio, F.; Braun, J.; Brayeur, L.; Brenzke, M.; Bretz, H.-P.; Bron, S.; Brostean-Kaiser, J.; Burgman, A.; Carver, T.; Casey, J.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; DeLaunay, J. J.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Dvorak, E.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Glauch, T.; Glüsenkamp, T.; Goldschmidt, A.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Hallgren, A.; Halzen, F.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; Hünnefeld, M.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Kalaczynski, P.; Kang, W.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kim, J.; Kim, M.; Kintscher, T.; Kirby, C.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Köpke, L.; Kopper, C.; Kopper, S.; Koschinsky, J. P.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Kyriacou, A.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Liu, Q. R.; Lu, L.; Lünemann, J.; Luszczak, W.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Micallef, J.; Momenté, G.; Montaruli, T.; Moore, R. W.; Moulai, M.; Nahnhauer, R.; Nakarmi, P.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Plum, M.; Price, P. B.; Przybylski, G. T.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Rea, I. C.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sälzer, T.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Santander, M.; Sarkar, S.; Sarkar, S.; Satalecka, K.; Schlunder, P.; Schmidt, T.; Schneider, A.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soedingrekso, J.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stachurska, J.; Stamatikos, M.; Stanev, T.; Stasik, A.; Stettner, J.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strotjohann, N. L.; Stuttard, T.; Sullivan, G. W.; Sutherland, M.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Tung, C. F.; Turcati, A.; Turley, C. F.; Ty, B.; Unger, E.; Usner, M.; Vandenbroucke, J.; Van Driessche, W.; van Eijndhoven, N.; Vanheule, S.; van Santen, J.; Vehring, M.; Vogel, E.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandler, F. D.; Wandkowsky, N.; Waza, A.; Weaver, C.; Weiss, M. J.; Wendt, C.; Werthebach, J.; Westerhoff, S.; Whelan, B. J.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, J.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Yuan, T.; Zoll, M.; IceCube Collaboration

2018-04-01

As atmospheric neutrinos propagate through the Earth, vacuumlike oscillations are modified by Standard Model neutral- and charged-current interactions with electrons. Theories beyond the Standard Model introduce heavy, TeV-scale bosons that can produce nonstandard neutrino interactions. These additional interactions may modify the Standard Model matter effect producing a measurable deviation from the prediction for atmospheric neutrino oscillations. The result described in this paper constrains nonstandard interaction parameters, building upon a previous analysis of atmospheric muon-neutrino disappearance with three years of IceCube DeepCore data. The best fit for the muon to tau flavor changing term is ɛμ τ=-0.0005 , with a 90% C.L. allowed range of -0.0067 <ɛμ τ<0.0081 . This result is more restrictive than recent limits from other experiments for ɛμ τ. Furthermore, our result is complementary to a recent constraint on ɛμ τ using another publicly available IceCube high-energy event selection. Together, they constitute the world's best limits on nonstandard interactions in the μ -τ sector.

A plot-scale study of firn stratigraphy at Lomonosovfonna, Svalbard, using ice cores, borehole video and GPR surveys in 2012-14

DEFF Research Database (Denmark)

Marchenko, Sergey; Pohjola, Veijo A.; Pettersson, Rickard

2017-01-01

Spatial heterogeneity of snow and firn properties on glaciers introduces uncertainty in interpretation of point and profile observations and complicates modelling of meltwater percolation and runoff. Here we present a study of the temporal and spatial dynamics of firn density and stratigraphy...... at the plot-scale (≈10 m × 10 m × 10 m) repeated annually during 2012-14 at the Lomonosovfonna icefield, Svalbard. Results from cores, video inspections in boreholes and radar grid surveys are compared. Ice layers 0.1-50 cm thick comprised ≈8% of the borehole length. Most of them are 1-3 cm thick and could...... in individual boreholes. However, the match between the high amplitude peaks in the grid-averaged radar signal and horizons of preferential ice layer formation revealed by averaging the video surveys over multiple boreholes is higher. These horizons are interpreted as buried firn layers previously exposed...

Inverse stochastic-dynamic models for high-resolution Greenland ice core records

DEFF Research Database (Denmark)

Boers, Niklas; Chekroun, Mickael D.; Liu, Honghu

2017-01-01

as statistical properties such as probability density functions, waiting times and power spectra, with no need for any external forcing. The crucial ingredients for capturing these properties are (i) high-resolution training data, (ii) cubic drift terms, (iii) nonlinear coupling terms between the 18O and dust......Proxy records from Greenland ice cores have been studied for several decades, yet many open questions remain regarding the climate variability encoded therein. Here, we use a Bayesian framework for inferring inverse, stochastic-dynamic models from 18O and dust records of unprecedented, subdecadal...

A new CF-IRMS system for quantifying stable isotopes of carbon monoxide from ice cores and small air samples

Directory of Open Access Journals (Sweden)

Z. Wang

2010-10-01

Full Text Available We present a new analysis technique for stable isotope ratios (δ¹³C and δ¹⁸O of atmospheric carbon monoxide (CO from ice core samples. The technique is an online cryogenic vacuum extraction followed by continuous-flow isotope ratio mass spectrometry (CF-IRMS; it can also be used with small air samples. The CO extraction system includes two multi-loop cryogenic cleanup traps, a chemical oxidant for oxidation to CO₂, a cryogenic collection trap, a cryofocusing unit, gas chromatography purification, and subsequent injection into a Finnigan Delta Plus IRMS. Analytical precision of 0.2‰ (±1δ for δ¹³C and 0.6‰ (±1δ for δ¹⁸O can be obtained for 100 mL (STP air samples with CO mixing ratios ranging from 60 ppbv to 140 ppbv (~268–625 pmol CO. Six South Pole ice core samples from depths ranging from 133 m to 177 m were processed for CO isotope analysis after wet extraction. To our knowledge, this is the first measurement of stable isotopes of CO in ice core air.

High-Frequency Observations of Temperature and Dissolved Oxygen Reveal Under-Ice Convection in a Large Lake

Science.gov (United States)

Yang, Bernard; Young, Joelle; Brown, Laura; Wells, Mathew

2017-12-01

Detailed observations of thermal structure over an entire winter in a large lake reveal the presence of large (10-20 m) overturns under the ice, driven by diurnal solar heating. Convection can occur in the early winter, but the most vigorous convection occurred near the end of winter. Both periods are when our lake ice model suggest thinner ice that would have been transparent. This under-ice convection led to a deepening of the mixed layer over time, consistent with previous short-term studies. During periods of vigorous convection under the ice at the end of winter, the dissolved oxygen had become supersaturated from the surface to 23 m below the surface, suggesting abundant algal growth. Analysis of our high-frequency observations over the entire winter of 2015 using the Thorpe-scale method quantified the scale of mixing. Furthermore, it revealed that changes in oxygen concentrations are closely related to the intensity of mixing.

Early Holocene climate oscillations recorded in three Greenland ice cores

DEFF Research Database (Denmark)

Rasmussen, Sune Olander; Vinther, Bo Møllesøe; Clausen, Henrik Brink

2007-01-01

around 9.3 ka before present, and the Preboreal Oscillation during the first centuries of the Holocene. For each of these sections, we present a d18O anomaly curve and a common accumulation signal that represents regional changes in the accumulation rate over the Greenland ice cap....... and accumulation anomalies that are common to the three cores in the Early Holocene (7.9–11.7 ka before present). Three time periods with significant and synchronous anomalies in the d18O and accumulation signals stand out: the well-known 8.2 ka event, an event of shorter duration but of almost similar amplitude...

High resolution climate reconstructions of recent warming using instrumental and ice core records from coastal Antarctica

Digital Repository Service at National Institute of Oceanography (India)

Thamban, M.; Naik, S.S.; Laluraj, C.M.; Ravindra, R.

for the past 4 years (Thamban et al., 2006). Chronological control for the IND-25/B5 ice core was based on multiple and complimentary methods: (i) atomic bomb (Tritium) markers; (ii) annual layer counting using stable isotope records; and (iii) volcanic...

Core-level photoemission revealing the Mott transition

International Nuclear Information System (INIS)

Kim, Hyeong-Do; Noh, Han-Jin; Kim, K.H.; Oh, S.-J.

2005-01-01

Ru 3d core-level X-ray photoemission spectra of various ruthenates are examined. They show in general two-peak structures, which can be assigned as the screened and unscreened peaks. The screened peak is absent in a Mott insulator, but develops into a main peak as the correlation strength becomes weak. This spectral behavior is well explained by the dynamical mean-field theory calculation for the single-band Hubbard model with the on-site core-hole potential using the exact diagonalization method. The new mechanism of the core-level photoemission satellite can be utilized to reveal the Mott transition phenomenon in various strongly correlated electron systems

A 600-year annual ¹⁰Be record from the NGRIP ice core, Greenland

DEFF Research Database (Denmark)

Berggren, A.M.; Johnsen, Sigfus Johann; Vinther, Bo Møllesøe

2009-01-01

in an ice core from the NGRIP site in Greenland. NGRIP and Dye-3 10Be exhibits similar long-term variability, although occasional short term differences between the two sites indicate that at least two high resolution 10Be records are needed to assess local variations and to confidently reconstruct past...

Formation of Glycerol through Hydrogenation of CO Ice under Prestellar Core Conditions

Energy Technology Data Exchange (ETDEWEB)

Fedoseev, G.; Chuang, K.-J.; Qasim, D.; Linnartz, H. [Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Ioppolo, S. [School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Dishoeck, E. F. van, E-mail: gfedo@oact.inaf.it [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)

2017-06-10

Observational studies reveal that complex organic molecules (COMs) can be found in various objects associated with different star formation stages. The identification of COMs in prestellar cores, i.e., cold environments in which thermally induced chemistry can be excluded and radiolysis is limited by cosmic rays and cosmic-ray-induced UV photons, is particularly important as this stage sets up the initial chemical composition from which ultimately stars and planets evolve. Recent laboratory results demonstrate that molecules as complex as glycolaldehyde and ethylene glycol are efficiently formed on icy dust grains via nonenergetic atom addition reactions between accreting H atoms and CO molecules, a process that dominates surface chemistry during the “CO freeze-out stage” in dense cores. In the present study we demonstrate that a similar mechanism results in the formation of the biologically relevant molecule glycerol—HOCH{sub 2}CH(OH)CH{sub 2}OH—a three-carbon-bearing sugar alcohol necessary for the formation of membranes of modern living cells and organelles. Our experimental results are fully consistent with a suggested reaction scheme in which glycerol is formed along a chain of radical–radical and radical–molecule interactions between various reactive intermediates produced upon hydrogenation of CO ice or its hydrogenation products. The tentative identification of the chemically related simple sugar glyceraldehyde—HOCH{sub 2}CH(OH)CHO—is discussed as well. These new laboratory findings indicate that the proposed reaction mechanism holds much potential to form even more complex sugar alcohols and simple sugars.

Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

Science.gov (United States)

Hudait, Arpa; Molinero, Valeria

2014-06-04

Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by

Continuous Chemistry in Ice Cores

DEFF Research Database (Denmark)

Kjær, Helle Astrid

on parameters involved in the study of photolysis as a source of in situ CO2. The concentration of organic substances in Greenland ice is poorly known due to their low levels and the fact that only a few studies evaluate the concentrations of specific organic compounds. Light does not penetrate deep...... depth was found as a function of wavelength. Further, by computational chemistry hybrid density functional methods (DFT), the four most common conformers of pyruvic acid were investigated in both gas, water and ice using the DFT model CAM-B3LYP with dielectric medium methods. A de rease of the energy...

Major Ion Concentrations in WDC05Q and WDC06A Ice Cores (WAIS Divide), Version 1

Data.gov (United States)

National Aeronautics and Space Administration — This data set contains major ion concentrations from the chemical analysis of two WAIS Divide ice cores (WDC05Q, 0-114 m; WDC06A, 0-129 m). The analytical technique...

Five millennia of frozen vegetation and fire dynamics from an ice core in the Mongolian Altai

Science.gov (United States)

Brügger, S. O.; Gobet, E.; Sigl, M.; Osmont, D.; Papina, T.; Rudaya, N.; Schwikowski, M.; Tinner, W.

2017-12-01

). An ice-core based history of Siberian forest fires since AD 1250. Quat Sci Rev 30(9) Herren et al. (2013). The onset of Neoglaciation 6000 years ago in western Mongolia revealed by an ice core from the Tsambagarav mountain range. Quat Sci Rev 69 IPCC; Climate Change (2013): The Physical Science Basis. IPCC Working Group I Contribution to AR5

Ice core based Pb pollution from gasoline in South America in the context of a 2000 year metallurgical history

Science.gov (United States)

Eichler, Anja; Gramlich, Gabriela; Kellerhals, Thomas; Tobler, Leonhard; Schwikowski, Margit

2015-04-01

Lead (Pb) is highly neurotoxic and, in contrast to many other heavy metals including cobalt, copper, and zinc, it has no beneficial effects to humans even at low concentrations. The introduction of leaded gasoline in the 1920s initiated a period of unabated growth in the global emissions of Pb. Prior to the onset of leaded gasoline phase-out in the 1970s, atmospheric Pb levels increased dramatically. Long-term histories of Pb pollution in Eastern and Western Europe, Asia, and North America suggest that emissions from leaded gasoline within the Northern Hemisphere are dominant compared to that from metallurgy and coal combustion during the second half of the 20th century. However, there is no equivalent data for Southern America. Although exploitation of the extensive polymetallic deposits of the Andean Altiplano in South America since pre-colonial times has caused substantial emissions of neurotoxic Pb into the atmosphere, its historical significance compared to recent Pb pollution from leaded gasoline is not yet resolved. Here we present the first comprehensive, high-resolution two millennia Pb emission history for South America, based on ice core records of Pb concentrations, Pb enrichment factors (EFs), and Pb isotope ratios from Illimani glacier in Bolivia. Complementary to local air pollution recorded in lake sediments, ice cores from mid latitude glaciers provide information about more extended source areas. Illimani is the highest mountain of the eastern Bolivian Andes and is located at the northeastern margin of the Bolivian Altiplano. The ice core Pb deposition history revealed enhanced Pb EFs due to metallurgical processing for silver production during periods of the Tiwanaku/Wari culture (AD 450-950), the Inca empires (AD 1450-1532), colonial times (AD 1532-1900), and tin production at the beginning of the 20th century. After the 1960s 208Pb/207Pb ratios decreased significantly, whereas Pb EFs increased by a factor of three compared to the emission level

Archive of Geosample Data and Information from the University of Wisconsin Ice Island T3 Core Collection

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — From 1963 to 1972, 349 piston cores were collected from the Arctic Ocean using Ice Island T3 as a sampling platform and sent to the University of Wisconsin-Madison...

Arctic sea-ice ridges—Safe heavens for sea-ice fauna during periods of extreme ice melt?

Science.gov (United States)

Gradinger, Rolf; Bluhm, Bodil; Iken, Katrin

2010-01-01

The abundances and distribution of metazoan within-ice meiofauna (13 stations) and under-ice fauna (12 stations) were investigated in level sea ice and sea-ice ridges in the Chukchi/Beaufort Seas and Canada Basin in June/July 2005 using a combination of ice coring and SCUBA diving. Ice meiofauna abundance was estimated based on live counts in the bottom 30 cm of level sea ice based on triplicate ice core sampling at each location, and in individual ice chunks from ridges at four locations. Under-ice amphipods were counted in situ in replicate ( N=24-65 per station) 0.25 m 2 quadrats using SCUBA to a maximum water depth of 12 m. In level sea ice, the most abundant ice meiofauna groups were Turbellaria (46%), Nematoda (35%), and Harpacticoida (19%), with overall low abundances per station that ranged from 0.0 to 10.9 ind l -1 (median 0.8 ind l -1). In level ice, low ice algal pigment concentrations (Turbellaria, Nematoda and Harpacticoida also were observed in pressure ridges (0-200 ind l -1, median 40 ind l -1), although values were highly variable and only medians of Turbellaria were significantly higher in ridge ice than in level ice. Median abundances of under-ice amphipods at all ice types (level ice, various ice ridge structures) ranged from 8 to 114 ind m -2 per station and mainly consisted of Apherusa glacialis (87%), Onisimus spp. (7%) and Gammarus wilkitzkii (6%). Highest amphipod abundances were observed in pressure ridges at depths >3 m where abundances were up to 42-fold higher compared with level ice. We propose that the summer ice melt impacted meiofauna and under-ice amphipod abundance and distribution through (a) flushing, and (b) enhanced salinity stress at thinner level sea ice (less than 3 m thickness). We further suggest that pressure ridges, which extend into deeper, high-salinity water, become accumulation regions for ice meiofauna and under-ice amphipods in summer. Pressure ridges thus might be crucial for faunal survival during periods of

Capillary ion chromatography with on-column focusing for ultra-trace analysis of methanesulfonate and inorganic anions in limited volume Antarctic ice core samples.

Science.gov (United States)

Rodriguez, Estrella Sanz; Poynter, Sam; Curran, Mark; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Paull, Brett

2015-08-28

Preservation of ionic species within Antarctic ice yields a unique proxy record of the Earth's climate history. Studies have been focused until now on two proxies: the ionic components of sea salt aerosol and methanesulfonic acid. Measurement of the all of the major ionic species in ice core samples is typically carried out by ion chromatography. Former methods, whilst providing suitable detection limits, have been based upon off-column preconcentration techniques, requiring larger sample volumes, with potential for sample contamination and/or carryover. Here, a new capillary ion chromatography based analytical method has been developed for quantitative analysis of limited volume Antarctic ice core samples. The developed analytical protocol applies capillary ion chromatography (with suppressed conductivity detection) and direct on-column sample injection and focusing, thus eliminating the requirement for off-column sample preconcentration. This limits the total sample volume needed to 300μL per analysis, allowing for triplicate sample analysis with Application to composite ice-core samples is demonstrated, with coupling of the capillary ion chromatograph to high resolution mass spectrometry used to confirm the presence and purity of the observed methanesulfonate peak. Copyright © 2015 Elsevier B.V. All rights reserved.

Identification and synchronization of the common cosmic-ray signal in the IntCal13 14C calibration and the Greenland ice-core 10Be records

Science.gov (United States)

Muscheler, Raimund; Adolphi, Florian; Bronk Ramsey, Christopher; Rasmussen, Sune; Hughen, Konrad; Cooper, Alan; Turney, Chris

2017-04-01

The production rates of cosmogenic radionuclides (such as 10Be and 14C) are modulated by the solar and geomagnetic shielding of galactic cosmic rays. In addition, 14C and 10Be are influenced by the carbon cycle and the atmospheric transport and deposition, respectively. Isolating and identifying the common production signal allows us to synchronize ice core 10Be and tree ring 14C records during the Holocene (Adolphi and Muscheler, 2016), thereby connecting ice core climate records with 14C-dated records. Extending this comparison further back in time is challenging due to deteriorating quality of the 14C calibration record, IntCal13, (Reimer et al., 2013) and possible unidentified climate influences on the ice-core 10Be records. Nevertheless, by focusing on the most prominent production-rate features this comparison can be extended far back into the last glacial where, for example, the linkage of tree-ring based Kauri 14C data and the Greenland ice-core time scale (GICC05) suggested unresolved data and/or time scale differences around the period of the Laschamp geomagnetic field minimum at about 42000 yrs BP (Muscheler et al., 2014). Here we show that the data underlying the IntCal13 14C record and the ice-core 10Be records exhibit common variability that allows us to tentatively link the ice core GICC05 time scale to the radiocarbon time scale for almost the complete radiocarbon dating range. The observed time scale differences could be related to uncertainties in both the U/Th-based dating of the IntCal13 calibration data set and the GICC05 time scale, and we show that the two can be reconciled within the uncertainties of the ice-core layer counting. This direct comparison between IntCal13 and 10Be also suggests that the 14C differences shown in (Muscheler et al., 2014) around the Laschamp geomagnetic field minimum can be reduced by moderate adjustments to the GICC05 time scale. References: Adolphi, F., and Muscheler, R., 2016, Synchronizing the Greenland ice

A sublimation technique for high-precision measurements of δ13CO2 and mixing ratios of CO2 and N2O from air trapped in ice cores

Directory of Open Access Journals (Sweden)

H. Fischer

2011-07-01

Full Text Available In order to provide high precision stable carbon isotope ratios (δ13CO2 or δ13C of CO2 from small bubbly, partially and fully clathrated ice core samples we developed a new method based on sublimation coupled to gas chromatography-isotope ratio mass spectrometry (GC-IRMS. In a first step the trapped air is quantitatively released from ~30 g of ice and CO2 together with N2O are separated from the bulk air components and stored in a miniature glass tube. In an off-line step, the extracted sample is introduced into a helium carrier flow using a minimised tube cracker device. Prior to measurement, N2O and organic sample contaminants are gas chromatographically separated from CO2. Pulses of a CO2/N2O mixture are admitted to the tube cracker and follow the path of the sample through the system. This allows an identical treatment and comparison of sample and standard peaks. The ability of the method to reproduce δ13C from bubble and clathrate ice is verified on different ice cores. We achieve reproducibilities for bubble ice between 0.05 ‰ and 0.07 ‰ and for clathrate ice between 0.05 ‰ and 0.09 ‰ (dependent on the ice core used. A comparison of our data with measurements on bubble ice from the same ice core but using a mechanical extraction device shows no significant systematic offset. In addition to δ13C, the CO2 and N2O mixing ratios can be volumetrically derived with a precision of 2 ppmv and 8 ppbv, respectively.

Air content and O2/N2 tuned chronologies on local insolation signatures in the Vostok ice core are similar

Science.gov (United States)

Lipenkov, V.; Raynaud, D.; Loutre, M.-F.; Duval, P.; Lemieux-Dudon, B.

2009-04-01

An accurate chronology of ice cores is needed for interpreting the paleoclimatic record and understanding the relation between insolation and climate. A new domain of research in this area has been initially stimulated by the work of M. Bender (2002) linking the record of O2/N2 ratio in the air trapped in the Vostok ice with the local insolation. More recently, it has been proposed that the long-term changes in air content, V, recorded in ice from the high Antarctic plateau is also dominantly imprinted by the local summer insolation (Raynaud et al., 2007). The present paper presents a new V record from Vostok, which is compared with the published Vostok O2/N2 record for the same period of time (150-400 ka BP) by using the same spectral analysis methods. The spectral differences between the two properties and the possible mechanisms linking them with insolation through the surface snow structure and the close-off processes are discussed. The main result of our study is that the two experimentally independent local insolation proxies lead to absolute (orbital) time scales, which agree together within a standard deviation of 0.6 ka. This result strongly adds credibility to the air content of ice and the O2 to N2 ratio of the air trapped in ice as equally reliable and complementary tools for accurate dating of existing and future deep ice cores. References: M. Bender, Orbital tuning chronology for the Vostok climate record supported by trapped gas composition, Earth and Planetary Science Letters 204(2002) 275-289. D. Raynaud, V. Lipenkov, B. Lemieux-Dudon, P. Duval, M.F. Loutre, N. Lhomme, The local insolation signature of air content in Antarctic ice: a new step toward an absolute dating of ice records, Earth and Planetary Science Letters 261(2007) 337-349.

Unravelling source regions of ice rafted debris within three NE Atlantic marine sediment cores during the deglacial interval: a multi-proxy approach

Science.gov (United States)

Small, David; Hibbert, Fiona; Austin, Bill

2010-05-01

Ice-rafted debris (IRD) within marine sediments of the North Atlantic provide an important archive of glacial activity on adjacent landmasses and attest to the activity of multiple calving ice margins during the last glacial cycle. IRD records therefore provide a means to reconstruct ice sheet dynamics and their interaction with the climate system, providing evidence of both the source of the ice and the location of melting (e.g. Ruddiman, 1977; Bond and Lotti, 1995). The complex interaction of the circum-Atlantic ice sheets and limitations of individual techniques often hinders firm source designations (i.e. IRD may be derived from multiple sources which cannot be differentiated by, for example, visual characterisation). Initial work identified diagnostic grain types that could be attributed to source areas of palaeo ice-sheets (eg: Bond & Lotti 1995) however, for the BIS, "diagnostic" basalt may be derived from sources to the east and west of the cores (Hibbert et al 2009, Scourse et al 2009). We therefore, utilise a multi-proxy approach to investigate the deglacial dynamics of the last British Ice Sheet (BIS) using inter alia lithic characterisation, fluxes of IRD to the core sites, magnetic susceptibility and a magnetic un-mixing model. A novel application of major element geochemistry of garnets contained within ice-rafted debris of the three high resolution marine sediment cores is presented. Garnets can be used to infer provenance (e.g. Oliver 2001) as major element composition may be assigned to specific metamorphic terranes. The IRD present within these cores is believed to be predominantly sourced from the BIS (cf: Knutz et al 2001, Hibbert et al 2009). This assertion is tested through multiple analytical techniques used and replication of records across the Hebridean shelf into the deep ocean. References • Bond, G.C. & Lotti, R., 1995. Iceberg discharges into the North Atlantic on millennial timescales during the last glaciation. Science 267. pp. 1005

Sulfur mass loading of the atmosphere from volcanic eruptions: Calibration of the ice core record on basis of sulfate aerosol deposition in polar regions from the 1982 El Chichon eruption

Science.gov (United States)

Sigurdsson, Haraldur; Laj, Paolo

1990-01-01

Major volcanic eruptions disperse large quantities of sulfur compound throughout the Earth's atmosphere. The sulfuric acid aerosols resulting from such eruptions are scavenged by snow within the polar regions and appear in polar ice cores as elevated acidity layers. Glacio-chemical studies of ice cores can, thus, provide a record of past volcanism, as well as the means for understanding the fate of volcanic sulfur in the atmosphere. The primary objectives of this project are to study the chemistry and physical properties of volcanic fallout in a Greenland Ice Core in order to evaluate the impact of the volcanic gases on the atmospheric chemistry and the total atmospheric mass of volcanic aerosols emitted by major volcanic eruptions. We propose to compare the ice core record to other atmospheric records performed during the last 10 years to investigate transport and deposition of volcanic materials.

Ground ice conditions in Salluit, Northern Quebec

Science.gov (United States)

Allard, M.; Fortier, R.; Calmels, F.; Gagnon, O.; L'Hérault, E.

2011-12-01

Salluit in Northern Québec (ca. 1300 inhabitants) faces difficult ground ice conditions for its development. The village is located in a U-shaped valley, along a fjord that was deglaciated around 8000 cal BP. The post-glacial marine limit is at the current elevation of 150 m ASL. Among the mapped surficial geology units, three contain particularly ice-rich permafrost: marine clays, till and silty colluviums. A diamond drill was used to extract 10 permafrost cores down to 23 m deep. In addition, 18 shallow cores (to 5 m deep) were extracted with a portable drill. All the frozen cores were shipped to Québec city where ground ice contents were measured and cryostructures were imaged by CT-Scanning. Water contents, grain-size and pore water salinity were measured. Refraction seismic profiles were run to measure the depth to bedrock. GPR and electrical resistivity surveys helped to map ice-rich areas. Three cone penetration tests (CPT) were run in the frozen clays to depths ranging from 8 to 21 m. Maximum clay thickness is ca. 50 m deep near the shoreline. The cone penetration tests and all the cores in clays revealed large amounts of both segregated and aggradational ice (volumetric contents up to 93% over thicknesses of one meter) to depths varying between 2.5 and 4 m, below which the ice content decreases and the salinity increases (values measured up to 42 gr/L between 4.5 and 6 m deep). Chunks of organic matter buried below the actual active layer base indicate past cryoturbations under a somewhat warmer climate, most probably associated with intense frost boil action, as widely observed today. The stony till has developed large quantities of segregation ice which can be seen in larger concentrations and as thicker lenses under boulders and in matrix rich (≥ 50% sand and silt) parts of the glacial sediment. As digging for a sewage pond was undertaken in winter 2008 by blasting, the clast-influenced cryostructure of the till could be observed in cuts and in

Anomalously-dense firn in an ice-shelf channel revealed by wide-angle radar

Science.gov (United States)

Drews, R.; Brown, J.; Matsuoka, K.; Witrant, E.; Philippe, M.; Hubbard, B.; Pattyn, F.

2015-10-01

The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium for which knowledge of the depth-averaged density is essential. The densification from snow to ice depends on a number of local factors (e.g. temperature and surface mass balance) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar datasets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. Using a novel algorithm including traveltime inversion and raytracing with a prescribed shape of the depth-density relationship, we show that the depth to internal reflectors, the local ice thickness and depth-averaged densities can reliably be reconstructed. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggests that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals 10 % denser firn inside compared to outside the channel. The denser firn in the ice-shelf channel should be accounted for when using the hydrostatic ice thickness for determining basal melt rates. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.

Antarctic-Wide Array of High-Resolution Ice Core Records Reveals Pervasive Lead Pollution Began in 1889 and Persists Today

Science.gov (United States)

McConnell, J. R.; Maselli, O. J.; Sigl, M.; Vallelonga, P.; Neumann, Thomas Allen; Anschutz, H.; Bales, R. C.; Curran, M. A. J.; Das, S. B.; Edwards, R.;

Neutrino oscillations with the full IceCube DeepCore detector

Energy Technology Data Exchange (ETDEWEB)

Yanez Garza, Juan Pablo [DESY, Zeuthen (Germany); Collaboration: IceCube-Collaboration

2013-07-01

The IceCube detector and its low energy extension, DeepCore, have recorded over 300,000 atmospheric neutrino events since completion almost two years ago. With an energy threshold of about 10 GeV and the possibility of observing different baselines between source and detector location, these events can be used to probe neutrino oscillations with unprecedented statistics. However, the measurement uncertainties, due to unknown properties of the detector and the medium where it stands, limit the sensitivity of such a study. The particular analysis under discussion is a special attempt to diminish the impact of systematic uncertainties while keeping a large high quality neutrino sample. The tools developed for it, as well as the current status of the analysis are presented.

Assimilating the ICE-6G_C Reconstruction of the Latest Quaternary Ice Age Cycle Into Numerical Simulations of the Laurentide and Fennoscandian Ice Sheets

Science.gov (United States)

Stuhne, G. R.; Peltier, W. R.

2017-12-01

We analyze the effects of nudging 100 kyr numerical simulations of the Laurentide and Fennoscandian ice sheets toward the glacial isostatic adjustment-based (GIA-based) ICE-6G_C reconstruction of the most recent ice age cycle. Starting with the ice physics approximations of the PISM ice sheet model and the SeaRISE simulation protocols, we incorporate nudging at characteristic time scales, τf, through anomalous mass balance terms in the ice mass conservation equation. As should be expected, these mass balances exhibit physically unrealistic details arising from pure GIA-based reconstruction geometry when nudging is very strong (τf=20 years for North America), while weakly nudged (τf=1,000 years) solutions deviate from ICE-6G_C sufficiently to degrade its observational fit quality. For reasonable intermediate time scales (τf=100 years and 200 years), we perturbatively analyze nudged ice dynamics as a superposition of "leading-order smoothing" that diffuses ICE-6G_C in a physically and observationally consistent manner and "higher-order" deviations arising, for instance, from biases in the time dependence of surface climate boundary conditions. Based upon the relative deviations between respective nudged simulations in which these biases follow surface temperature from ice cores and eustatic sea level from marine sediment cores, we compute "ice core climate adjustments" that suggest how local paleoclimate observations may be applied to the systematic refinement of ICE-6G_C. Our results are consistent with a growing body of evidence suggesting that the geographical origins of Meltwater Pulse 1B (MWP1b) may lie primarily in North America as opposed to Antarctica (as reconstructed in ICE-6G_C).

Synchronisation of the EDML and EDC ice cores for the last 52 kyr by volcanic signature matching

DEFF Research Database (Denmark)

Severi, M.; Becagli, S.; Castellano, E.

2007-01-01

stratigraphic link between EDML and EDC, which was dated by a simpler 1D ice-flow model. The synchronisation between the two EPICA ice cores was done through the identification of several common volcanic signatures. This paper describes the rigorous method, using the signature of volcanic sulfate, which...... to find out which of the models is affected by errors, but assuming that the thinning function at both sites and accumulation history at Dome C (which was drilled on a dome) are correct, this anomaly can be ascribed to a complex spatial accumulation variability (which may be different in the past compared...

Measuring stable isotopes of hydrogen and oxygen in ice by means of laser spectrometry : The Bolling transition in the Dye-3 (south Greenland) ice core

NARCIS (Netherlands)

Trigt, R. van; Meijer, H.A.J.; Sveinbjornsdottir, A.E.; Johnsen, S.J.; Kerstel, E.R.Th.

2002-01-01

We report on the first application of a new technique in ice-core research, based on direct absorption infrared laser spectrometry (LS), for measuring H-2 O-17 and O-18 isotope ratios. The data are used to calculate the deuterium excess d (defined as delta(2)H - 8delta(18)O) for a section of the

A refined TALDICE-1a age scale from 55 to 112 ka before present for the Talos Dome ice core based on high-resolution methane measurements

Directory of Open Access Journals (Sweden)

S. Schüpbach

2011-09-01

Full Text Available A precise synchronization of different climate records is indispensable for a correct dynamical interpretation of paleoclimatic data. A chronology for the TALDICE ice core from the Ross Sea sector of East Antarctica has recently been presented based on methane synchronization with Greenland and the EDC ice cores and δ¹⁸O_ice synchronization with EDC in the bottom part (TALDICE-1. Using new high-resolution methane data obtained with a continuous flow analysis technique, we present a refined age scale for the age interval from 55–112 thousand years (ka before present, where TALDICE is synchronized with EDC. New and more precise tie points reduce the uncertainties of the age scale from up to 1900 yr in TALDICE-1 to below 1100 yr over most of the refined interval and shift the Talos Dome dating to significantly younger ages during the onset of Marine Isotope Stage 3. Thus, discussions of climate dynamics at sub-millennial time scales are now possible back to 110 ka, in particular during the inception of the last ice age. Calcium data of EDC and TALDICE are compared to show the impact of the refinement to the synchronization of the two ice cores not only for the gas but also for the ice age scale.

Search for indications of the neutrino mass hierarchy using IceCube/DeepCore

Energy Technology Data Exchange (ETDEWEB)

Leuermann, Martin; Vehring, Markus; Wallraff, Marius; Wiebusch, Christopher [III. Physikalisches Institut B, RWTH Aachen (Germany); Collaboration: IceCube-Collaboration

2016-07-01

In 2015, the Nobel prize in physics was awarded for ''the discovery of neutrino oscillations, which shows that neutrinos have mass'', showing the high relevance of neutrino masses for modern particle physics. However, the ordering of the three neutrino masses is still unknown and is often referred to as neutrino mass hierarchy. Its measurement is a major goal for future experiments. One strategy is to measure matter effects in the oscillation pattern of atmospheric neutrinos e.g. as proposed for the PINGU extension of the IceCube neutrino observatory. Already now, the IceCube/DeepCore detector at the Geographic South Pole can be used to search for this signature. In this talk, we present an analysis based on data taken between 2011 and 2015. Due to recent improvements in the detector's reconstruction performance and the quality of the data selection, a measurement on the significance level of 1 sigma is expected.

Two Millennia of Pb Pollution Related to Altiplano Metallurgical Activities and Leaded Gasoline in South America from Illimani Ice Core

Science.gov (United States)

Eichler, A.; Gramlich, G.; Kellerhals, T.; Tobler, L.; Schwikowski, M.

2014-12-01

The exploitation of the extended polymetallic deposits of the Altiplano in South America led to significant emissions of the neurotoxic Pb into the atmosphere already since pre-Colonial times. Long-term histories of Pb pollution in Eastern and Western Europe, Asia, and North America suggest that within the Northern Hemisphere emissions from metallurgy and coal combustion are minor compared to that from leaded gasoline during the second half of the 20th century. However, there is no equivalent data for Southern America. Here we present the first comprehensive, high-resolution two millennia Pb emission history for South America, based on an ice core record from Illimani glacier in Bolivia. Illimani is the highest mountain of the eastern Bolivian Andes and is located at the northeastern margin of the Bolivian Altiplano. The 2000 year ice-core based decadal Pb deposition history revealed highest Pb Enrichment Factors (EFs) during the period 1965-85. Metallurgical processing for silver production during periods of the Tiwanaku culture (400-900 AD), the Inca empire (1450-1532 AD), colonial times (1532-1900 AD), and the tin production at the beginning of the 20th century were identified as major sources for enhanced Pb EFs before the 1960s. Gasoline related Pb emissions in 1965-85, however, led to a threefold increase of the Pb EFs compared to the emission level from metal production, considerably preceding those of the past 2000 years. This finding is complementary to the local air pollution signal preserved in lake sediments and in good agreement with various studies from the Northern Hemisphere.

Calcareous nannofossil evidence for Marine Isotope Stage 31 (1 Ma) in the AND-1B Core, ANDRILL McMurdo Ice Shelf Project (Antarctica).

Science.gov (United States)

Villa, G.; Persico, D.; Wise, S. W.; Gadaleta, A.

2009-04-01

During the austral summer 2006 the ANDRILL Program recovered a 1285 m-long succession of cyclic glacimarine sediments from the McMurdo Ice Shelf (MIS). The aim of the MIS Project was to obtain continuous Neogene (c. 0-10 Ma) glacial, glacimarine, volcanic, and biogenic sediments that have accumulated in the region of the McMurdo Ice Shelf (Ross Sea) nourished by ice flowing from East Antarctic Ice Sheet (EAIS) outlet glaciers in the Transantarctic Mountains (TAM). The MIS AND-1B drill core represents the longest and most complete (98% recovery) geological record from the Antarctic continental margin to date, and will provide a key reference record of climate and ice-sheet variability through the Late Neogene; detailed investigations of this record will contribute for improving our knowledge of Antarctica's influence on global climate. Preliminary on-ice analysis of the smear slides of the Andrill core revealed calcareous microfossils (dinoflagellates, calciosponge spicula and small foraminifera) occurring with variable concentrations. The presence of thoracosphaerid fragments in the smear slides of the first 600 mbsf (Quaternary), probably belong to the species Thoracosphaera saxea (Stradner 1961), and Thoracosphaera heimi (Kamptner, 1941) and other, potentially undescribed species (Villa & Wise 1998), suggests either a peculiar adaptation to this environment, due to their ability to develop cysts or warmer conditions at the time of their deposition, or a combination of both. However, they represent an additional element to use with the other proxies for inferring palaeoenvironmental conditions of the core. Subsequent shore-based analyses of 100 samples from 86-96 mbsf revealed for the first time the presence of Pleistocene coccolithophorids at these high southern latitudes (77° S), including: Coccolithus pelagicus, small Gephyrocapsa, Reticulofenestra asanoi, Pseudoemiliania lacunosa, Dictyoccocites productus, Reticulofenestra sp., Reticulofenestra minutula

Stable isotopes and their relationship to temperature and precipitation as recorded in low latitude ice cores

International Nuclear Information System (INIS)

Thompson, L.G.; Davis, M.E.; Pin-Nan, Lin

2002-01-01

The potential of stable isotopic ratios ( 18 O/ 16 O and 2 H/ 1 H) in mid to low latitude glaciers as modern tools for paleoclimate reconstruction is reviewed. The isotopic composition of precipitation should be viewed not only as a powerful proxy indicator of climate, but also as an additional parameter for understanding climate-induced changes in the water cycle, on both regional and global scales. To interpret quantitatively the ice core isotopic records, the response of the isotopic composition of precipitation to long-term fluctuations of key climatic parameters (temperature, precipitation amount, relative humidity) over a given area should be known. Furthermore, it is important to establish the transfer functions that relate the climate-induced changes of the isotopic composition of precipitation to the isotope record preserved in the glacier. The factors that govern the values of stable isotopes in snowfall are enigmatic and as yet no satisfactory model has been developed to link them directly with any one meteorological or oceanographic factor. This is particularly problematic in the high altitude glaciers in the tropics, where complications are present due not only to continental effects, but also to altitude effects and convective air mass instability, particularly in the monsoon climates of the tropics. This paper presents long and short-term perspectives of isotopic composition variations in ice cores spanning the last 25,000 years from the mid- to low-latitude glaciers. The isotopic records will also be examined as a function of the altitude of the individual coring sites which ranges from 5325 meters to 7200 meters. On the short, term isotopic records from ice cores from the Andes of South America, the Tibetan Plateau and Kilimanjaro in Africa through the year 2000 will be presented. All the tropical glaciers for which data exist are disappearing, and these sites show isotopic enrichment in the 20th century that suggests that large scale low latitude

Geophysical Investigations of Habitability in Ice-Covered Ocean Worlds

Science.gov (United States)

Vance, Steven D.; Panning, Mark P.; Stähler, Simon; Cammarano, Fabio; Bills, Bruce G.; Tobie, Gabriel; Kamata, Shunichi; Kedar, Sharon; Sotin, Christophe; Pike, William T.; Lorenz, Ralph; Huang, Hsin-Hua; Jackson, Jennifer M.; Banerdt, Bruce

2018-01-01

Geophysical measurements can reveal the structures and thermal states of icy ocean worlds. The interior density, temperature, sound speed, and electrical conductivity thus characterize their habitability. We explore the variability and correlation of these parameters using 1-D internal structure models. We invoke thermodynamic consistency using available thermodynamics of aqueous MgSO4, NaCl (as seawater), and NH3; pure water ice phases I, II, III, V, and VI; silicates; and any metallic core that may be present. Model results suggest, for Europa, that combinations of geophysical parameters might be used to distinguish an oxidized ocean dominated by MgSO4 from a more reduced ocean dominated by NaCl. In contrast with Jupiter's icy ocean moons, Titan and Enceladus have low-density rocky interiors, with minimal or no metallic core. The low-density rocky core of Enceladus may comprise hydrated minerals or anhydrous minerals with high porosity. Cassini gravity data for Titan indicate a high tidal potential Love number (k2>0.6), which requires a dense internal ocean (ρocean>1,200 kg m-3) and icy lithosphere thinner than 100 km. In that case, Titan may have little or no high-pressure ice, or a surprisingly deep water-rock interface more than 500 km below the surface, covered only by ice VI. Ganymede's water-rock interface is the deepest among known ocean worlds, at around 800 km. Its ocean may contain multiple phases of high-pressure ice, which will become buoyant if the ocean is sufficiently salty. Callisto's interior structure may be intermediate to those of Titan and Europa, with a water-rock interface 250 km below the surface covered by ice V but not ice VI.

Broad-scale predictability of carbohydrates and exopolymers in Antarctic and Arctic sea ice

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Underwood, Graham J. C.; Aslam, Shazia N.; Michel, Christine; Niemi, Andrea; Norman, Louiza; Meiners, Klaus M.; Laybourn-Parry, Johanna; Paterson, Harriet; Thomas, David N.

2013-01-01

Sea ice can contain high concentrations of dissolved organic carbon (DOC), much of which is carbohydrate-rich extracellular polymeric substances (EPS) produced by microalgae and bacteria inhabiting the ice. Here we report the concentrations of dissolved carbohydrates (dCHO) and dissolved EPS (dEPS) in relation to algal standing stock [estimated by chlorophyll (Chl) a concentrations] in sea ice from six locations in the Southern and Arctic Oceans. Concentrations varied substantially within and between sampling sites, reflecting local ice conditions and biological content. However, combining all data revealed robust statistical relationships between dCHO concentrations and the concentrations of different dEPS fractions, Chl a, and DOC. These relationships were true for whole ice cores, bottom ice (biomass rich) sections, and colder surface ice. The distribution of dEPS was strongly correlated to algal biomass, with the highest concentrations of both dEPS and non-EPS carbohydrates in the bottom horizons of the ice. Complex EPS was more prevalent in colder surface sea ice horizons. Predictive models (validated against independent data) were derived to enable the estimation of dCHO concentrations from data on ice thickness, salinity, and vertical position in core. When Chl a data were included a higher level of prediction was obtained. The consistent patterns reflected in these relationships provide a strong basis for including estimates of regional and seasonal carbohydrate and dEPS carbon budgets in coupled physical-biogeochemical models, across different types of sea ice from both polar regions. PMID:24019487

Broad-scale predictability of carbohydrates and exopolymers in Antarctic and Arctic sea ice.

Science.gov (United States)

Underwood, Graham J C; Aslam, Shazia N; Michel, Christine; Niemi, Andrea; Norman, Louiza; Meiners, Klaus M; Laybourn-Parry, Johanna; Paterson, Harriet; Thomas, David N

2013-09-24

Sea ice can contain high concentrations of dissolved organic carbon (DOC), much of which is carbohydrate-rich extracellular polymeric substances (EPS) produced by microalgae and bacteria inhabiting the ice. Here we report the concentrations of dissolved carbohydrates (dCHO) and dissolved EPS (dEPS) in relation to algal standing stock [estimated by chlorophyll (Chl) a concentrations] in sea ice from six locations in the Southern and Arctic Oceans. Concentrations varied substantially within and between sampling sites, reflecting local ice conditions and biological content. However, combining all data revealed robust statistical relationships between dCHO concentrations and the concentrations of different dEPS fractions, Chl a, and DOC. These relationships were true for whole ice cores, bottom ice (biomass rich) sections, and colder surface ice. The distribution of dEPS was strongly correlated to algal biomass, with the highest concentrations of both dEPS and non-EPS carbohydrates in the bottom horizons of the ice. Complex EPS was more prevalent in colder surface sea ice horizons. Predictive models (validated against independent data) were derived to enable the estimation of dCHO concentrations from data on ice thickness, salinity, and vertical position in core. When Chl a data were included a higher level of prediction was obtained. The consistent patterns reflected in these relationships provide a strong basis for including estimates of regional and seasonal carbohydrate and dEPS carbon budgets in coupled physical-biogeochemical models, across different types of sea ice from both polar regions.

A method for combined Sr-Nd-Hf isotopic analysis of <10 mg dust samples: implication for ice core science

Science.gov (United States)

Ujvari, Gabor; Wegner, Wencke; Klötzli, Urs

2017-04-01

Aeolian mineral dust particles below the size of 10-20 μm often experience longer distance transport in the atmosphere, and thus Aeolian dust is considered an important tracer of large-scale atmospheric circulation. Since ice core dust is purely Aeolian in origin, discrimination of its potential source region(s) can contribute to a better understanding of past dust activity and climatic/environmental causes. Furthermore, ice core dust source information provides critical experimental constraints for model simulations of past atmospheric circulation patterns [1,2]. However, to identify dust sources in past dust archives such as ice cores, the mineralogy and geochemistry of the wind-blown dust material must be characterized. While the amount of dust in marine cores or common terrestrial archives is sufficient for different types of analyses and even for multiple repeat measurements, dust content in ice cores is usually extremely low even for the peak dusty periods such as the Last Glacial Maximum (LGM) (5-8 mg dust/kg ice; [3]). Since the most powerful dust fingerprinting methods, such as REE composition and Sr-Nd-Pb isotopic analyses are destructive there is a clear need to establish sequential separation techniques of Sr, Nd, Pb and other REEs to get the most information out of small (5-10 mg) dust samples recovered from ice cores. Although Hf isotopes have recently been added as a robust tool of aerosol/dust source discrimination (e.g. [4,5,6,7]), precise Hf isotopic measurements of small (reliable 176Hf/177Hf (and also 87Sr/86Sr, 143Nd/144Nd) ratios. Along with the standards 50, 10 and 5 mg aliquots of the fine (affected by acid treatment and these signatures are extremely stable both within run (0.000008 variability for the three aliquots, i.e. 0.15 ɛNd unit) and between runs of different laboratories (0.00006, ca 1 ɛNd unit). Hf isotopic compositions varied within 1 (NUS) and 5 ɛHf units (BEI) between the three aliquots, but the BEI sample always gave more

Atmospheric CO2 variations over the last three glacial-interglacial climatic cycles deduced from the Dome Fuji deep ice core, Antarctica using a wet extraction technique

International Nuclear Information System (INIS)

Kawamura, Kenji; Nakazawa, Takakiyo; Aoki, Shuji

2003-01-01

A deep ice core drilled at Dome Fuji, East Antarctica was analyzed for the CO 2 concentration using a wet extraction method in order to reconstruct its atmospheric variations over the past 320 kyr, which includes three full glacial-interglacial climatic cycles, with a mean time resolution of about 1.1 kyr. The CO 2 concentration values derived for the past 65 kyr are very close to those obtained from other Antarctic ice cores using dry extraction methods, although the wet extraction method is generally thought to be inappropriate for the determination of the CO 2 concentration. The comparison between the CO 2 and Ca 2+ concentrations deduced from the Dome Fuji core suggests that calcium carbonate emitted from lands was mostly neutralized in the atmosphere before reaching the central part of Antarctica, or that only a small part of calcium carbonate was involved in CO 2 production during the wet extraction process. The CO 2 concentration for the past 320 kyr deduced from the Dome Fuji core varies between 190 and 300 ppmv, showing clear glacial-interglacial variations similar to the result of the Vostok ice core. However, for some periods, the concentration values of the Dome Fuji core are higher by up to 20 ppmv than those of the Vostok core. There is no clear indication that such differences are related to variations of chemical components of Ca 2+ , microparticle and acidity of the Dome Fuji core

The Influence of Ice Properties on Borehole Deformation at the West Antarctic Ice Sheet Divide

Science.gov (United States)

Sinkler, E.; Pettit, E. C.; Obbard, R. W.

2017-12-01

It is widely known that ice flow is affected by many properties, including crystal fabric and impurities, though these relationships are not fully understood. This study uses data from the West Antarctic Ice Sheet (WAIS) Divide borehole to better determine the influence of such properties on ice flow. The WAIS Divide borehole, the byproduct of the 2006-2012 coring project, offers a unique opportunity to study deep Antarctic Ice. Thanks to the work of many researchers, extensive data on ice properties are available from both coring and borehole logging at this site. The borehole, kept open with a density-approximating fluid, closes and tilts due to ice flow. We have tracked this deformation over two years using a set of repeat measurements with an Acoustic Televiewer. This tool acts as an acoustic caliper allowing us to view cross-sections of the borehole shape and size with up to 1.25 degree azimuthal resolution and a depth resolution as high as 1.4 mm. In addition, the tool collects tilt and azimuth data. These measurements are compared to a 1D Glen's Flow Law model for borehole closure that uses density differences between the ice and borehole fluid as its driving force and incorporates temperature effects. This is then compared to ice properties like crystal fabric and impurities in order to determine the influence of these properties on ice deformation at this site. Crystal fabric has appeared as an important factor in this study.This work builds on that of others who have studied in-situ deep ice through borehole deformation (e.g. Paterson, 1977 and Dahl-Jensen and Gundestrup, 1987). Our results have implications for ice flow modeling and therefore interpretation of depth-age relationships in deep ice cores.

Observations of brine plumes below melting Arctic sea ice

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A. K. Peterson

2018-02-01

Full Text Available In sea ice, interconnected pockets and channels of brine are surrounded by fresh ice. Over time, brine is lost by gravity drainage and flushing. The timing of salt release and its interaction with the underlying water can impact subsequent sea ice melt. Turbulence measurements 1 m below melting sea ice north of Svalbard reveal anticorrelated heat and salt fluxes. From the observations, 131 salty plumes descending from the warm sea ice are identified, confirming previous observations from a Svalbard fjord. The plumes are likely triggered by oceanic heat through bottom melt. Calculated over a composite plume, oceanic heat and salt fluxes during the plumes account for 6 and 9 % of the total fluxes, respectively, while only lasting in total 0.5 % of the time. The observed salt flux accumulates to 7.6 kg m−2, indicating nearly full desalination of the ice. Bulk salinity reduction between two nearby ice cores agrees with accumulated salt fluxes to within a factor of 2. The increasing fraction of younger, more saline ice in the Arctic suggests an increase in desalination processes with the transition to the new Arctic.

Observations of brine plumes below melting Arctic sea ice

Science.gov (United States)

Peterson, Algot K.

2018-02-01

In sea ice, interconnected pockets and channels of brine are surrounded by fresh ice. Over time, brine is lost by gravity drainage and flushing. The timing of salt release and its interaction with the underlying water can impact subsequent sea ice melt. Turbulence measurements 1 m below melting sea ice north of Svalbard reveal anticorrelated heat and salt fluxes. From the observations, 131 salty plumes descending from the warm sea ice are identified, confirming previous observations from a Svalbard fjord. The plumes are likely triggered by oceanic heat through bottom melt. Calculated over a composite plume, oceanic heat and salt fluxes during the plumes account for 6 and 9 % of the total fluxes, respectively, while only lasting in total 0.5 % of the time. The observed salt flux accumulates to 7.6 kg m-2, indicating nearly full desalination of the ice. Bulk salinity reduction between two nearby ice cores agrees with accumulated salt fluxes to within a factor of 2. The increasing fraction of younger, more saline ice in the Arctic suggests an increase in desalination processes with the transition to the new Arctic.

A fast semi-quantitative method for Plutonium determination in an alpine firn/ice core

Science.gov (United States)

Gabrieli, J.; Cozzi, G.; Vallelonga, P.; Schwikowski, M.; Sigl, M.; Boutron, C.; Barbante, C.

2009-04-01

Plutonium is present in the environment as a consequence of atmospheric nuclear tests carried out in the 1960s, nuclear weapons production and releases by the nuclear industry over the past 50 years. Plutonium, unlike uranium, is essentially anthropogenic and it was first produced and isolated in 1940 by deuteron bombardment of uranium in the cyclotron of Berkeley University. It exists in five main isotopes, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, derived from civilian and military sources (weapons production and detonation, nuclear reactors, nuclear accidents). In the environment, 239Pu is the most abundant isotope. Approximately 6 tons of 239Pu have been released into the environment as a result of 541 atmospheric weapon tests Nuclear Pu fallout has been studied in various environmental archives, such as sediments, soil and herbarium grass. Mid-latitude ice cores have been studied as well, on Mont Blanc, the Western Alps and on Belukha Glacier, Siberian Altai. We present a Pu record obtained by analyzing 52 discrete samples of an alpine firn/ice core from Colle Gnifetti (M. Rosa, 4450 m a.s.l.), dating from 1945 to 1991. The239Pu signal was recorded directly, without preliminary cleaning or preconcentration steps, using an ICP-SFMS (Thermo Element2) equipped with a desolvation system (APEX). 238UH+ interferences were negligible for U concentrations lower than 50 ppt as verified both in spiked fresh snow and pre-1940 ice samples. The shape of 239Pu profile reflects the three main periods of atmospheric nuclear weapons testing: the earliest peak starts in 1954/55 to 1958 and includes the first testing period which reached a maximum in 1958. Despite a temporary halt in testing in 1959/60, the Pu concentration decreased only by half with respect to the 1958 peak. In 1961/62 Pu concentrations rapidly increased reaching a maximum in 1963, which was about 40% more intense than the 1958 peak. After the sign of the "Limited Test Ban Treaty" between USA and URSS in 1964, Pu

High-frequency paleoclimatic variability: a spectral analysis of the Vostok ice-core isotopic record

Energy Technology Data Exchange (ETDEWEB)

Yiou, P.; Genthon, C.; Jouzel, J.; Le Treut, H.; Lorius, C.; Ghil, M.; Korotkevich, Y.S.

1988-01-01

This paper uses a recently analysed isotopic record from an ice core drilled at the Soviet Antartic Station VOSTOK, representing a total time span of about 160,000 years. Results obtained show the existence of a significative climatic variability at the time scale of 10,000 years and below. The many spectral peaks appear to be approximate linear combination of a little number among them, a clear indication of the non linear nature of climate fluctuations at these ''short'' time scales.

Thallium as a tracer for preindustrial volcanic eruptions in an ice core record from Illimani, Bolivia.

Science.gov (United States)

Kellerhals, Thomas; Tobler, Leonhard; Brütsch, Sabina; Sigl, Michael; Wacker, Lukas; Gäggeler, Heinz W; Schwikowski, Margit

2010-02-01

Trace element records from glacier and ice sheet archives provide insights into biogeochemical cycles, atmospheric circulation changes, and anthropogenic pollution history. We present the first continuous high-resolution thallium (Tl) record, derived from an accurately dated ice core from tropical South America, and discuss Tl as a tracer for volcanic eruptions. We identify four prominent Tl peaks and propose that they represent signals from the massive explosive eruptions of the "unknown 1258" A.D. volcano, of Kuwae ( approximately 1450 A.D.), Tambora (1815 A.D.), and Krakatoa (1883 A.D.). The highly resolved record was obtained with an improved setup for the continuous analysis of trace elements in ice with inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The new setup allowed for a stronger initial acidification of the meltwater and shorter tubing length, thereby reducing the risk of memory effects and losses of analytes to the capillary walls. With a comparison of the continuous method to the established conventional decontamination and analysis procedure for discrete samples, we demonstrate the accuracy of the continuous method for Tl analyses.

EBSD in Antarctic and Greenland Ice

Science.gov (United States)

Weikusat, Ilka; Kuiper, Ernst-Jan; Pennock, Gill; Sepp, Kipfstuhl; Drury, Martyn

2017-04-01

Ice, particularly the extensive amounts found in the polar ice sheets, impacts directly on the global climate by changing the albedo and indirectly by supplying an enormous water reservoir that affects sea level change. The discharge of material into the oceans is partly controlled by the melt excess over snow accumulation, partly by the dynamic flow of ice. In addition to sliding over bedrock, an ice body deforms gravitationally under its own weight. In order to improve our description of this flow, ice microstructure studies are needed that elucidate the dominant deformation and recrystallization mechanisms involved. Deformation of hexagonal ice is highly anisotropic: ice is easily sheared in the basal plane and is about two orders of magnitude harder parallel to the c-axis. As dislocation creep is the dominant deformation mechanism in polar ice this strong anisotropy needs to be understood in terms of dislocation activity. The high anisotropy of the ice crystal is usually ascribed to a particular behaviour of dislocations in ice, namely the extension of dislocations into partials on the basal plane. Analysis of EBSD data can help our understanding of dislocation activity by characterizing subgrain boundary types thus providing a tool for comprehensive dislocation characterization in polar ice. Cryo-EBSD microstructure in combination with light microscopy measurements from ice core material from Antarctica (EPICA-DML deep ice core) and Greenland (NEEM deep ice core) are presented and interpreted regarding substructure identification and characterization. We examined one depth for each ice core (EDML: 656 m, NEEM: 719 m) to obtain the first comparison of slip system activity from the two ice sheets. The subgrain boundary to grain boundary threshold misorientation was taken to be 3-5° (Weikusat et al. 2011). EBSD analyses suggest that a large portion of edge dislocations with slip systems basal gliding on the basal plane were indeed involved in forming subgrain

Evaluation of aerosol composition changes in the last 60 years around southeastern Greenland by analyzing micro-inclusions in the SE-Dome ice core using Raman spectroscopy.

Science.gov (United States)

Ando, T.; Iizuka, Y.; Ohno, H.; Sugiyama, S.

2017-12-01

Emission regulation of anthropogenic NOX and SOX since late 90's rather caused excess atmospheric ammonium (NH3) in agricultural regions (Warner et al., 2017, Geophys. Res. Lett.). The Arctic is one of the most sensitive areas for future warming. Aerosols in the Arctic are transported from the Northern Hemisphere and mostly experience wet deposition (Breider et al., 2014, Jour. of Geophys. Res.: Atmos.). Ice cores preserve past water-soluble aerosols. From these viewpoints, ice cores from the Arctic is suitable to evaluate recent variation in aerosol composition due to human activity in the Northern Hemisphere and aerosol transportation. We analyzed ion concentrations in the ice core samples from a southeastern dome in Greenland (SE-Dome). The concentrations increased for NH4+ and decreased for SO42- after late 90's. The NH4+ increasing trend is due to excess NH3 emission in North America. Cloud nuclei formation depends on chemical form of aerosols. Thus, differences in chemical forms of these ammonium aerosols in SE-Dome samples are important to evaluate the effect on climate change in Greenland. In this study, we identified the chemical form of aerosols (water-soluble inclusions) in the SE-Dome ice core by using micro-Raman spectroscopy. SE-Dome ice core samples were collected in 2015 and enabled us to reconstruct seasonal variation owing to extremely higher accumulation rate ( 1m/yr.). The ice samples were sublimated and accumulated inclusions on the Ni sheets in a clean booth under -22 degrees Celsius. We identified CaSO4, Na2SO4, (NH4)2SO4, NaNO3, NH4NO3 by Raman spectra. This is the first report to identify ammonium salts ((NH4)2SO4 and NH4NO3) from ice core sample. In the summer samples, the relative abundances of CaSO4 and NaNO3 are lower but (NH4)2SO4 are higher than those in the spring samples. NH4+ rapidly react with SO24- under higher temperature. Higher concentration of NH3 in the warmest season possibly enhanced the formation of (NH4)2SO4 in North

Levoglucosan Levels in Alaskan Ice Cores as a Record of Past Wildfires

Science.gov (United States)

Dunham, M. E.; Osterberg, E. C.; Kehrwald, N. M.; Kennedy, J.; Ferris, D. G.

2017-12-01

Glaciers in southeast Alaska are significant contributors to global sea-level rise, and therefore understanding the mechanisms driving their recent mass loss is crucial for predicting future sea-level change. Fire activity in Alaska has increased dramatically during the last decade, adding a potential new source of light-absorbing organic material (soot) to the Juneau Icefield that can reduce albedo and enhance surface melt rates. The goal of this project is to create an accurate record of Alaskan wildfires to understand how Alaskan glacial mass balance is affected by the deposition of organic aerosols from wildfires. Previously, oxalate, ammonia, and potassium ion levels have been used as proxies for past wildfire activity, but these ions all have broader emission sources in addition to wildfires. Here we develop a record of past Alaskan fire events and climate from: (1) levels of a biomass burning indicator, levoglucosan, which only forms when cellulose is burned over 300 °C, (2) major ions including oxalate, ammonia, and potassium; (3) the number and size distribution of particles to quantify trace amounts of soot from wildfires; and (4) stable water isotope ratios as a proxy for past temperature in ice cores. We utilize a total of four shallow ice cores, ranging from 7 to 9 m in length, that were collected by a biogeochemistry team during the Juneau Icefield Research Program (JIRP) in 2016. Complications include our limited understanding of the conservation and degradation of levoglucosan over time or during the firnification process. We hypothesize that particle counts will be correlated with levoglucosan peaks, co-varying with wildfire frequency and temperatures over time. Based on previous work, we also expect to find correlations between levoglucosan and oxalate ion concentrations, even though oxalate ions have sources in addition to wildfire activity.

Why Drill More than One Ice Core? Paleoclimate Reconstruction along a Vertical Transect in the Saint Elias Mountains

Science.gov (United States)

Wake, C. P.; Yalcin, K.; Kreutz, K. J.; Mayewski, P. A.; Fisher, D.; Holdsworth, G.

2004-05-01

The Arctic represents one of the key regions on Earth in our efforts to document and understand global change. The St. Elias mountain range in the southwestern Yukon Territory has recently been the focus of an international ice core research.. The broad elevational extent of snow accumulation zones in this region (ranging from 2500 to 5300 m asl) allows for the detailed investigation of environmental change extending from the planetary boundary layer through to the free troposphere via the collection and analysis of ice cores from different elevations. Multi-parameter, high resolution glaciochemical records are currently available from the Northwest Col on Mt. Logan (5340 m asl, 103 m deep; 270 year record;) and from three cores recovered from the Eclipse Icefield (3107 m asl) in 1996 (160 m deep; 100 year record) and in 2002 (345 m and 140 m deep). Snow accumulation rates at Eclipse are about 5 times larger than the summit average of 0.30 m water equivalent. Despite their close proximity, the climate signals recorded on the summit of Mt. Logan also differ from those at Eclipse. For example, while the Mt. Logan record shows no increase in sulfate or nitrate deposition over the past 100 years, all three Eclipse cores shows a clear increase in nitrate and sulfate deposition beginning in the late 1940s due to an increase in anthropogenic emissions in Eurasia during this time period. Over the last century, the sulfate time-series from Eclipse records from 32 discrete volcanic events, primarily from Alaskan, Aleutian, or Kamchatkan eruptions, while the summit site only records 8 volcanic events. The Eclipse summer d18O record displays a significant positive relationship with summer temperatures at both coastal and interior Alaskan sites, while the Mt. Logan d18O time-series does not correlate well with instrumental temperature records or most circum-Arctic paleoclimate records. Conversely, the summit ice core accumulation time-series strongly correlates with

Spatial Variability of accumulation across the Western Greenland Ice Sheet Percolation Zone from ground-penetrating-radar and shallow firn cores

Science.gov (United States)

Lewis, G.; Osterberg, E. C.; Hawley, R. L.; Marshall, H. P.; Birkel, S. D.; Meehan, T. G.; Graeter, K.; Overly, T. B.; McCarthy, F.

2017-12-01

The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. Increased melting in the GrIS percolation zone over the past several decades has led to increased mass loss at lower elevations due to recent warming. Uncertainties in mass balance are especially large in regions with sparse and/or outdated in situ measurements. This study is the first to calculate in situ accumulation over a large region of western Greenland since the Program for Arctic Regional Climate Assessment campaign during the 1990s. Here we analyze 5000 km of 400 MHz ground penetrating radar data and sixteen 25-33 m-long firn cores in the western GrIS percolation zone to determine snow accumulation over the past 50 years. The cores and radar data were collected as part of the 2016-2017 Greenland Traverse for Accumulation and Climate Studies (GreenTrACS). With the cores and radar profiles we capture spatial accumulation gradients between 1850-2500 m a.s.l and up to Summit Station. We calculate accumulation rates and use them to validate five widely used regional climate models and to compare with IceBridge snow and accumulation radars. Our results indicate that while the models capture most regional spatial climate patterns, they lack the small-scale spatial variability captured by in situ measurements. Additionally, we evaluate temporal trends in accumulation at ice core locations and throughout the traverse. Finally, we use empirical orthogonal function and correlation analyses to investigate the principal drivers of radar-derived accumulation rates across the western GrIS percolation zone, including major North Atlantic climate modes such as the North Atlantic Oscillation, Atlantic Multidecadal Oscillation, and Greenland Blocking Index.

High-resolution continuous flow analysis setup for water isotopic measurement from ice cores using laser spectroscopy

Science.gov (United States)

Emanuelsson, B. D.; Baisden, W. T.; Bertler, N. A. N.; Keller, E. D.; Gkinis, V.

2014-12-01

Here we present an experimental setup for water stable isotopes (δ18O and δD) continuous flow measurements. It is the first continuous flow laser spectroscopy system that is using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS; analyzer manufactured by Los Gatos Research - LGR) in combination with an evaporation unit to continuously analyze sample from an ice core. A Water Vapor Isotopic Standard Source (WVISS) calibration unit, manufactured by LGR, was modified to: (1) increase the temporal resolution by reducing the response time (2) enable measurements on several water standards, and (3) to reduce the influence from memory effects. While this setup was designed for the Continuous Flow Analysis (CFA) of ice cores, it can also continuously analyze other liquid or vapor sources. The modified setup provides a shorter response time (~54 and 18 s for 2013 and 2014 setup, respectively) compared to the original WVISS unit (~62 s), which is an improvement in measurement resolution. Another improvement compared to the original WVISS is that the modified setup has a reduced memory effect. Stability tests comparing the modified WVISS and WVISS setups were performed and Allan deviations (σAllan) were calculated to determine precision at different averaging times. For the 2013 modified setup the precision after integration times of 103 s are 0.060 and 0.070‰ for δ18O and δD, respectively. For the WVISS setup the corresponding σAllan values are 0.030, 0.060 and 0.043‰ for δ18O, δD and δ17O, respectively. For the WVISS setup the precision is 0.035, 0.070 and 0.042‰ after 103 s for δ18O, δD and δ17O, respectively. Both the modified setups and WVISS setup are influenced by instrumental drift with δ18O being more drift sensitive than δD. The σAllan values for δ18O of 0.30 and 0.18‰ for the modified (2013) and WVISS setup, respectively after averaging times of 104 s (2.78 h). The Isotopic Water Analyzer (IWA)-modified WVISS setup used during the

A 400-year ice core melt layer record of summertime warming in the Alaska Range

Science.gov (United States)

Winski, D.; Osterberg, E. C.; Kreutz, K. J.; Wake, C. P.; Ferris, D. G.; Campbell, S. W.; Baum, M.; Raudzens Bailey, A.; Birkel, S. D.; Introne, D.; Handley, M.

2017-12-01

Warming in high-elevation regions has socially relevant impacts on glacier mass balance, water resources, and sensitive alpine ecosystems, yet very few high-elevation temperature records exist from the middle or high latitudes. While many terrestrial paleoclimate records provide critical temperature records from low elevations over recent centuries, melt layers preserved in alpine glaciers present an opportunity to develop calibrated, annually-resolved temperature records from high elevations. We present a 400-year temperature record based on the melt-layer stratigraphy in two ice cores collected from Mt. Hunter in the Central Alaska Range. The ice core record shows a 60-fold increase in melt frequency and water equivalent melt thickness between the pre-industrial period (before 1850) and present day. We calibrate the melt record to summer temperatures based on local and regional weather station analyses, and find that the increase in melt production represents a summer warming of at least 2° C, exceeding rates of temperature increase at most low elevation sites in Alaska. The Mt. Hunter melt layer record is significantly (p<0.05) correlated with surface temperatures in the central tropical Pacific through a Rossby-wave like pattern that induces high temperatures over Alaska. Our results show that rapid alpine warming has taken place in the Alaska Range for at least a century, and that conditions in the tropical oceans contribute to this warming.

100,000-year-long terrestrial record of millennial-scale linkage between eastern North American mid-latitude paleovegetation shifts and Greenland ice-core oxygen isotope trends

Science.gov (United States)

Litwin, Ronald J.; Smoot, Joseph P.; Pavich, Milan J.; Markewich, Helaine Walsh; Brook, George; Durika, Nancy J.

2013-01-01

We document frequent, rapid, strong, millennial-scale paleovegetation shifts throughout the late Pleistocene, within a 100,000+ yr interval (~ 115–15 ka) of terrestrial sediments from the mid-Atlantic Region (MAR) of North America. High-resolution analyses of fossil pollen from one core locality revealed a continuously shifting sequence of thermally dependent forest assemblages, ranging between two endmembers: subtropical oak-tupelo-bald cypress-gum forest and high boreal spruce-pine forest. Sedimentary textural evidence indicates fluvial, paludal, and loess deposition, and paleosol formation, representing sequential freshwater to subaerial environments in which this record was deposited. Its total age"depth model, based on radiocarbon and optically stimulated luminescence ages, ranges from terrestrial oxygen isotope stages (OIS) 6 to 1. The particular core sub-interval presented here is correlative in trend and timing to that portion of the oxygen isotope sequence common among several Greenland ice cores: interstades GI2 to GI24 (≈ OIS2–5 d). This site thus provides the first evidence for an essentially complete series of "Dansgaard"Oeschger" climate events in the MAR. These data reveal that the ~ 100,000 yr preceding the Late Glacial and Holocene in the MAR of North America were characterized by frequently and dynamically changing climate states, and by vegetation shifts that closely tracked the Greenland paleoclimate sequence.

Major 20th century changes of water-soluble humic-like substances (HULISWS) aerosol over Europe inferred from Alpine ice cores

Science.gov (United States)

Guilhermet, J.; Preunkert, S.; Voisin, D.; Baduel, C.; Legrand, M.

2013-05-01

Using a newly developed method dedicated to measurements of water-soluble humic-like substances (HULISWS) in atmospheric aerosol samples, the carbon mass quantification of HULISWS in an Alpine ice core is achieved for the first time. The method is based on the extraction of HULISWS with a weak anion-exchanger resin and the subsequent quantification of the extracted carbon fraction with a total organic carbon (TOC) analyzer. Measurements were performed along a Col du Dôme (4250 m above sea level, French Alps) ice core covering the 1920-2004 time period. The HULISWS concentrations exhibit a well-marked seasonal cycle with winter minima close to 7 ppbC and summer maxima ranging between 10 and 50 ppbC. Whereas the winter HULISWS concentrations remained unchanged over the twentieth century, the summer concentrations increased from 20 ppbC prior to the Second World War to 35 ppbC in the 1970-1990s. These different trends reflect the different types of HULISWS sources in winter and summer. HULISWS are mainly primarily emitted by domestic wood burning in winter and secondary in summer being produced from biogenic precursors. For unknown reason, the HULISWS signal is found to be unusual in ice samples corresponding to World War II.

Geochemical analysis of ice cores from Antarctic crossing-preliminary results

International Nuclear Information System (INIS)

Hammes, Daiane; Simoes, Jefferson; Ceron, Masiel; Santos, Maria; Vieria, Rosemary

2009-01-01

Two ice cores, IC-5 (82 Celsius degrade 30.5'S, 79 Celsius degrade 28'W, 950 m a.s.l.; 42.5 m) and one IC-6 (81 Celsius degrade 03'S, 79 Celsius degrade 51'W, 750 m a.s.l; 36 m) were collected as part of the 2004/2005 Chilean (with Brazilian collaboration) ITASE traverse from Patriot Hills to the South Pole. Mean accumulation rates in water equivalent calculated for the upper 10 m at the IC5 site is 0.37 m a-1 and 0.33 m a-1 at the site IC6. Coregistered samples (1595 for IC5 and 1368 for IC6) were obtained using a discrete continuous melter system with a pure nickel melt head at the Climate Change Institute under class 100 clean room conditions. All samples were analysed by ion chromatography (IC), inductively coupled plasma field mass spectrometry (ICP-MS), and stable isotope ratio mass spectrometry (IRMS).

Spatiotemporal Variability of Meltwater Refreezing in Southwest Greenland Ice Sheet Firn

Science.gov (United States)

Rennermalm, A. K.; Hock, R.; Tedesco, M.; Corti, G.; Covi, F.; Miège, C.; Kingslake, J.; Leidman, S. Z.; Munsell, S.

2017-12-01

A substantial fraction of the summer meltwater formed on the surface of the Greenland ice sheet is retained in firn, while the remaining portion runs to the ocean through surface and subsurface channels. Refreezing of meltwater in firn can create impenetrable ice lenses, hence being a crucial process in the redistribution of surface runoff. To quantify the impact of refreezing on runoff and current and future Greenland surface mass balance, a three year National Science Foundation funded project titled "Refreezing in the firn of the Greenland ice sheet: Spatiotemporal variability and implications for ice sheet mass balance" started this past year. Here we present an overview of the project and some initial results from the first field season in May 2017 conducted in proximity of the DYE-2 site in the percolation zone of the Southwest Greenland ice sheet at elevations between 1963 and 2355 m a.s.l.. During this fieldwork two automatic weather stations were deployed, outfitted with surface energy balance sensors and 16 m long thermistor strings, over 300 km of ground penetrating radar data were collected, and five 20-26 m deep firn cores were extracted and analyzed for density and stratigraphy. Winter snow accumulation was measured along the radar tracks. Preliminary work on the firn-core data reveals increasing frequency and thickness of ice lenses at lower ice-sheet elevations, in agreement with other recent work in the area. Data collected within this project will facilitate advances in our understanding of the spatiotemporal variability of firn refreezing and its role in the hydrology and surface mass balance of the Greenland Ice Sheet.

Resolving climate change in the period 15-23 ka in Greenland ice cores: A new application of spectral trend analysis

NARCIS (Netherlands)

de Jong, M.G.G.; Nio, D.S.; Böhm, A.R.; Seijmonsbergen, H.C.; de Graaff, L.W.S.

2009-01-01

Northern Hemisphere climate history through and following the Last Glacial Maximum is recorded in detail in ice cores from Greenland. However, the period between Greenland Interstadials 1 and 2 (15-23 ka), i.e. the period of deglaciation following the last major glaciation, has been difficult to

Measurement of Atmospheric Neutrino Oscillations at 6-56 GeV with IceCube DeepCore

Science.gov (United States)

Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Al Samarai, I.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bagherpour, H.; Bai, X.; Barron, J. P.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Bourbeau, J.; Bradascio, F.; Braun, J.; Brayeur, L.; Brenzke, M.; Bretz, H.-P.; Bron, S.; Brostean-Kaiser, J.; Burgman, A.; Carver, T.; Casey, J.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; DeLaunay, J. J.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Glauch, T.; Glüsenkamp, T.; Goldschmidt, A.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Hallgren, A.; Halzen, F.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; Hünnefeld, M.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Kalaczynski, P.; Kang, W.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kim, J.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Köpke, L.; Kopper, C.; Kopper, S.; Koschinsky, J. P.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Kyriacou, A.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Liu, Q. R.; Lu, L.; Lünemann, J.; Luszczak, W.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Micallef, J.; Momenté, G.; Montaruli, T.; Moore, R. W.; Moulai, M.; Nahnhauer, R.; Nakarmi, P.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Plum, M.; Price, P. B.; Przybylski, G. T.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Rea, I. C.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sälzer, T.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Sarkar, S.; Satalecka, K.; Schlunder, P.; Schmidt, T.; Schneider, A.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soedingrekso, J.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stachurska, J.; Stamatikos, M.; Stanev, T.; Stasik, A.; Stettner, J.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Tung, C. F.; Turcati, A.; Turley, C. F.; Ty, B.; Unger, E.; Usner, M.; Vandenbroucke, J.; Van Driessche, W.; van Eijndhoven, N.; Vanheule, S.; van Santen, J.; Vehring, M.; Vogel, E.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandler, F. D.; Wandkowsky, N.; Waza, A.; Weaver, C.; Weiss, M. J.; Wendt, C.; Werthebach, J.; Westerhoff, S.; Whelan, B. J.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, J.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Yuan, T.; Zoll, M.; IceCube Collaboration

2018-02-01

We present a measurement of the atmospheric neutrino oscillation parameters using three years of data from the IceCube Neutrino Observatory. The DeepCore infill array in the center of IceCube enables the detection and reconstruction of neutrinos produced by the interaction of cosmic rays in Earth's atmosphere at energies as low as ˜5 GeV . That energy threshold permits measurements of muon neutrino disappearance, over a range of baselines up to the diameter of the Earth, probing the same range of L /Eν as long-baseline experiments but with substantially higher-energy neutrinos. This analysis uses neutrinos from the full sky with reconstructed energies from 5.6 to 56 GeV. We measure Δ m322=2.31-0.13+0.11×10-3 eV2 and sin2θ23=0.5 1-0.09+0.07, assuming normal neutrino mass ordering. These results are consistent with, and of similar precision to, those from accelerator- and reactor-based experiments.

Snow nitrate photolysis in polar regions and the mid-latitudes: Impact on boundary layer chemistry and implications for ice core records

Science.gov (United States)

Zatko, Maria C.

The formation and recycling of nitrogen oxides (NOx=NO+NO 2) associated with snow nitrate photolysis has important implications for air quality and the preservation of nitrate in ice core records. This dissertation examines snow nitrate photolysis in polar and mid-latitude regions using field and laboratory based observations combined with snow chemistry column models and a global chemical transport model to explore the impacts of snow nitrate photolysis on boundary layer chemistry and the preservation of nitrate in polar ice cores. Chapter 1 describes how a global chemical transport model is used to calculate the photolysis-driven flux and redistribution of nitrogen across Antarctica, and Chapter 2 presents similar work for Greenland. Snow-sourced NOx is most dependent on the quantum yield for nitrate photolysis as well as the concentration of photolabile nitrate and light-absorbing impurities (e.g., black carbon, dust, organics) in snow. Model-calculated fluxes of snow-sourced NOx are similar in magnitude in Antarctica (0.5--7.8x108 molec cm-2 s -1) and Greenland (0.1--6.4x108 molec cm-2 s-1) because both nitrate and light-absorbing impurity concentrations in snow are higher (by factors of 2 and 10, respectively) in Greenland. Snow nitrate photolysis influences boundary layer chemistry and ice-core nitrate preservation less in Greenland compared to Antarctica largely due to Greenland's proximity to NOx-source regions. Chapter 3 describes how a snow chemistry column model combined with chemistry and optical measurements from the Uintah Basin Winter Ozone Study (UBWOS) 2014 is used to calculate snow-sourced NOx in eastern Utah. Daily-averaged fluxes of snow-sourced NOx (2.9x10 7--1.3x108 molec cm-2 s-1) are similar in magnitude to polar snow-sourced NO x fluxes, but are only minor components of the Uintah Basin boundary layer NOx budget and can be neglected when developing ozone reduction strategies for the region. Chapter 4 presents chemical and optical

Aromatic acids in a Eurasian Arctic ice core: a 2600-year proxy record of biomass burning

Science.gov (United States)

Grieman, Mackenzie M.; Aydin, Murat; Fritzsche, Diedrich; McConnell, Joseph R.; Opel, Thomas; Sigl, Michael; Saltzman, Eric S.

2017-04-01

Wildfires and their emissions have significant impacts on ecosystems, climate, atmospheric chemistry, and carbon cycling. Well-dated proxy records are needed to study the long-term climatic controls on biomass burning and the associated climate feedbacks. There is a particular lack of information about long-term biomass burning variations in Siberia, the largest forested area in the Northern Hemisphere. In this study we report analyses of aromatic acids (vanillic and para-hydroxybenzoic acids) over the past 2600 years in the Eurasian Arctic Akademii Nauk ice core. These compounds are aerosol-borne, semi-volatile organic compounds derived from lignin combustion. The analyses were made using ion chromatography with electrospray mass spectrometric detection. The levels of these aromatic acids ranged from below the detection limit (0.01 to 0.05 ppb; 1 ppb = 1000 ng L-1) to about 1 ppb, with roughly 30 % of the samples above the detection limit. In the preindustrial late Holocene, highly elevated aromatic acid levels are observed during three distinct periods (650-300 BCE, 340-660 CE, and 1460-1660 CE). The timing of the two most recent periods coincides with the episodic pulsing of ice-rafted debris in the North Atlantic known as Bond events and a weakened Asian monsoon, suggesting a link between fires and large-scale climate variability on millennial timescales. Aromatic acid levels also are elevated during the onset of the industrial period from 1780 to 1860 CE, but with a different ratio of vanillic and para-hydroxybenzoic acid than is observed during the preindustrial period. This study provides the first millennial-scale record of aromatic acids. This study clearly demonstrates that coherent aromatic acid signals are recorded in polar ice cores that can be used as proxies for past trends in biomass burning.

Surface studies of water isotopes in Antarctica for quantitative interpretation of deep ice core data

Science.gov (United States)

Landais, Amaelle; Casado, Mathieu; Prié, Frédéric; Magand, Olivier; Arnaud, Laurent; Ekaykin, Alexey; Petit, Jean-Robert; Picard, Ghislain; Fily, Michel; Minster, Bénédicte; Touzeau, Alexandra; Goursaud, Sentia; Masson-Delmotte, Valérie; Jouzel, Jean; Orsi, Anaïs

2017-07-01

Polar ice cores are unique climate archives. Indeed, most of them have a continuous stratigraphy and present high temporal resolution of many climate variables in a single archive. While water isotopic records (δD or δ18O) in ice cores are often taken as references for past atmospheric temperature variations, their relationship to temperature is associated with a large uncertainty. Several reasons are invoked to explain the limitation of such an approach; in particular, post-deposition effects are important in East Antarctica because of the low accumulation rates. The strong influence of post-deposition processes highlights the need for surface polar research programs in addition to deep drilling programs. We present here new results on water isotopes from several recent surface programs, mostly over East Antarctica. Together with previously published data, the new data presented in this study have several implications for the climatic reconstructions based on ice core isotopic data: (1) The spatial relationship between surface mean temperature and mean snow isotopic composition over the first meters in depth can be explained quite straightforwardly using simple isotopic models tuned to d-excess vs. δ18O evolution in transects on the East Antarctic sector. The observed spatial slopes are significantly higher (∼ 0.7-0.8‰·°C-1 for δ18O vs. temperature) than seasonal slopes inferred from precipitation data at Vostok and Dome C (0.35 to 0.46‰·°C-1). We explain these differences by changes in condensation versus surface temperature between summer and winter in the central East Antarctic plateau, where the inversion layer vanishes in summer. (2) Post-deposition effects linked to exchanges between the snow surface and the atmospheric water vapor lead to an evolution of δ18O in the surface snow, even in the absence of any precipitation event. This evolution preserves the positive correlation between the δ18O of snow and surface temperature, but is

Investigating the Microscopic Location of Trace Elements in High-Alpine Glacier Ice

Science.gov (United States)

Avak, Sven Erik; Birrer, Mario; Laurent, Oscar; Guillong, Marcel; Wälle, Markus; Jenk, Theo Manuel; Bartels-Rausch, Thorsten; Schwikowski, Margit; Eichler, Anja

2017-04-01

proxies in glaciers partially affected by melting. References Della Lunga, D., Müller, W., Rasmussen, S. O. & Svensson, A. 2014: Location of cation impurities in NGRIP deep ice revealed by cryo-cell UV-laser-ablation ICPMS, Journal of Glaciology, 60, 970-988. Eichler, A., Schwikowski, M., Gäggeler, H. W. 2001: Meltwater-induced relocation of chemical species in Alpine firn, Tellus B, 53, 192-203. Reinhardt, H., Kriews, M., Miller, H., Schrems, O., Lüdke, C., Hoffmann, E. & Skole, J. 2001: Laser ablation inductively coupled plasma mass spectrometry: a new tool for trace element analysis in ice cores, Fresenius' Journal of Analytical Chemistry, 370, 629-636. Schwikowski, M., Barbante, C., Doering, T., Gäggeler, H. W., Boutron, C., Schotterer, U., Tobler, L., van de Velde, K., Ferrari, C., Cozzi, G., Rosman, K., Cescon, P. 2004: Post-17th-Century Changes of European Lead Emissions Recorded in High-Altitude Alpine Snow and Ice, Environmental Science & Technology, 38, 957-964. Sneed, S. B., Mayewski, P. A., Sayre, W. G., Handley, M. J., Kurbatov, A. V., Taylor, K. C., Bohleber, P., Wagenbach, D., Erhardt, T. & Spaulding, N. E. 2015: New LA-ICP-MS cryocell and calibration technique for sub-millimeter analysis of ice cores, Journal of Glaciology, 61, 233-242.

Microgram level radiocarbon (14C) determination on carbonaceous particles in ice

DEFF Research Database (Denmark)

Jenk, Theo Manuel; Szidat, S.; Schwikowski, M.

2007-01-01

Accelerator mass spectrometry; Organic carbon; Elemental carbon; Radiocarbon dating; Ice cores; Paleo-record Udgivelsesdato: June......Accelerator mass spectrometry; Organic carbon; Elemental carbon; Radiocarbon dating; Ice cores; Paleo-record Udgivelsesdato: June...

Lichenometry in the Cordillera Blanca, Peru: “Little Ice Age” moraine chronology

Science.gov (United States)

Solomina, Olga; Jomelli, Vincent; Kaser, Georg; Ames, Alcides; Berger, Bernhard; Pouyaud, Bernard

2007-10-01

This paper is a comparison and compilation of lichenometric and geomorphic studies performed by two independent teams in the Cordillera Blanca, Peru, in 1996 and 2002 on 66 "Little Ice Age" moraines of 14 glaciers. Using eleven new control points, we recalibrated the initial rapid growth phase of the previously established Rhizocarpon subgenus Rhizocarpon growth curve. This curve was then used to estimate the age of "Little Ice Age" moraines. The time of deposition of the most prominent and numerous terminal and lateral moraines on the Pacific-facing side of the Cordillera Blanca (between AD 1590 and AD 1720) corresponds to the coldest and wettest phase in the tropical Andes as revealed by ice-core data. Less prominent advances occurred between AD 1780 and 1880.

Two Extreme Climate Events of the Last 1000 Years Recorded in Himalayan and Andean Ice Cores: Impacts on Humans

Science.gov (United States)

Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.; Kenny, D. V.; Lin, P.

2013-12-01

In the last few decades numerous studies have linked pandemic influenza, cholera, malaria, and viral pneumonia, as well as droughts, famines and global crises, to the El Niño-Southern Oscillation (ENSO). Two annually resolved ice core records, one from Dasuopu Glacier in the Himalaya and one from the Quelccaya Ice Cap in the tropical Peruvian Andes provide an opportunity to investigate these relationships on opposite sides of the Pacific Basin for the last 1000 years. The Dasuopu record provides an annual history from 1440 to 1997 CE and a decadally resolved record from 1000 to 1440 CE while the Quelccaya ice core provides annual resolution over the last 1000 years. Major ENSO events are often recorded in the oxygen isotope, insoluble dust, and chemical records from these cores. Here we investigate outbreaks of diseases, famines and global crises during two of the largest events recorded in the chemistry of these cores, particularly large peaks in the concentrations of chloride (Cl-) and fluoride (Fl-). One event is centered on 1789 to 1800 CE and the second begins abruptly in 1345 and tapers off after 1360 CE. These Cl- and F- peaks represent major droughts and reflect the abundance of continental atmospheric dust, derived in part from dried lake beds in drought stricken regions upwind of the core sites. For Dasuopu the likely sources are in India while for Quelccaya the sources would be the Andean Altiplano. Both regions are subject to drought conditions during the El Niño phase of the ENSO cycle. These two events persist longer (10 to 15 years) than today's typical ENSO events in the Pacific Ocean Basin. The 1789 to 1800 CE event was associated with a very strong El Niño event and was coincidental with the Boji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive droughts are documented in Central and South America. Likewise, the 1345 to 1360 CE event, although poorly documented

Central Tibetan Plateau atmospheric trace metals contamination: a 500-year record from the Puruogangri ice core

Science.gov (United States)

Beaudon, E.; Gabrielli, P.; Sierra Hernandez, R.; Wegner, A.; Thompson, L. G.

2017-12-01

Since the 1980s, Asia has experienced enormous industrial development from rapid population growth, industrialization and consequent large-scale environmental changes. The inherent generated atmospheric pollution currently contributes to half of all Earth's anthropogenic trace metals emissions. Asian trace metal aerosols, when deposited on glaciers of the surrounding mountains of the Tibetan Plateau (TP), leave a characteristic chemical fingerprint. Interpreting trace element (TE) records from glaciers implies a thorough comprehension of their provenance and temporal variability. It is then essential to discriminate the TEs' natural background components from their anthropogenic components. Here we present 500-year TE records from the Puruogangri ice core (Tibet, China) that provide a highly resolved account of the impact of past atmospheric influences, environmental processes and human activities on the central TP. A decreasing aeolian dust input to the ice cap allowed the detection of an atmospheric pollution signal. The anthropogenic pollution contribution emerges in the record since the early 1900s and increases substantially after 1935. The metallurgy (Zn, Pb and steel smelting) emission products from the former Soviet Union and especially from central Asia likely enhanced the anthropogenic deposition to the Puruogangri ice cap between 1935 and 1980, suggesting that the westerlies served as a conveyor of atmospheric pollution to central Tibet. The impact of this industrial pollution cumulated with that of the hemispheric coal and gasoline combustion which are respectively traced by Sb and Pb enrichment in the ice. The Chinese steel production accompanying the Great Leap Forward (1958-1961) and the Chinese Cultural Revolution (1966-1976) is proposed as a secondary but proximal source of Pb pollution affecting the ice cap between 1958 and 1976. The most recent decade (1980-1992) of the enrichment time series suggests that Puruogangri ice cap recorded the early

Sulphate and chloride aerosols during Holocene and last glacial periods preserved in the Talos Dome Ice Core, a peripheral region of Antarctica

Directory of Open Access Journals (Sweden)

Yoshinori Iizuka

2013-04-01

Full Text Available Antarctic ice cores preserve the record of past aerosols, an important proxy of past atmospheric chemistry. Here we present the aerosol compositions of sulphate and chloride particles in the Talos Dome (TD ice core from the Holocene and Last Glacial Period. We find that the main salt types of both periods are NaCl, Na2SO4 and CaSO4, indicating that TD ice contains relatively abundant sea salt (NaCl from marine primary particles. By evaluating the molar ratio of NaCl to Na2SO4, we show that about half of the sea salt does not undergo sulphatisation during late Holocene. Compared to in inland Antarctica, the lower sulphatisation rate at TD is probably due to relatively little contact between sea salt and sulphuric acid. This low contact rate can be related to a reduced time of reaction for marine-sourced aerosol before reaching TD and/or to a reduced post-depositional effect from the higher accumulation rate at TD. Many sulphate and chloride salts are adhered to silicate minerals. The ratio of sulphate-adhered mineral to particle mass and the corresponding ratio of chloride-adhered mineral both increase with increasing dust concentration. Also, the TD ice appears to contain Ca(NO32 or CaCO3 particles, thus differing from aerosol compositions in inland Antarctica, and indicating the proximity of peripheral regions to marine aerosols.

Modelling the regional climate and isotopic composition of Svalbard precipitation using REMOiso: a comparison with available GNIP and ice core data

NARCIS (Netherlands)

Divine, D.V.; Sjolte, J.; Isaksson, E.; Meijer, H.A.J.; van de Wal, R.S.W.; Martma, T.; Pohjola, V.; Sturm, C.; Godtliebsen, F.

2011-01-01

Simulations of a regional (approx. 50 km resolution) circulation model REMOiso with embedded stable water isotope module covering the period 1958-2001 are compared with the two instrumental climate and four isotope series (δ18O) from western Svalbard. We examine the data from ice cores drilled on

Modelling the regional climate and isotopic composition of Svalbard precipitation using REMOiso : a comparison with available GNIP and ice core data

NARCIS (Netherlands)

Divine, D. V.; Sjolte, J.; Isaksson, E.; Meijer, H. A. J.; van de Wal, R. S. W.; Martma, T.; Pohjola, V.; Sturm, C.; Godtliebsen, F.

2011-01-01

Simulations of a regional (approx. 50 km resolution) circulation model REMOiso with embedded stable water isotope module covering the period 1958-2001 are compared with the two instrumental climate and four isotope series (d18O) from western Svalbard. We examine the data from ice cores drilled on

High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution.

Science.gov (United States)

Lecavalier, Benoit S; Fisher, David A; Milne, Glenn A; Vinther, Bo M; Tarasov, Lev; Huybrechts, Philippe; Lacelle, Denis; Main, Brittany; Zheng, James; Bourgeois, Jocelyne; Dyke, Arthur S

2017-06-06

We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4-5 °C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800-7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland.

Correlation of Greenland ice-core isotope profiles and the terrestrial record of the Alpine Rhine glacier for the period 32-15 ka

NARCIS (Netherlands)

de Jong, M.G.G.; de Graaff, L.W.S.; Seijmonsbergen, A.C.; Böhm, A.R.

2011-01-01

We present a newly extended stratigraphic subdivision of the Greenland NGRIP, GRIP and GISP2 ice cores for the period 32-15 ka. Our classification emphasizes the multiscale nature of the climatic oscillations. Spectral trend analysis of isotopic data supports this interpretation. We compare this

Century-long Record of Black Carbon in an Ice Core from the Eastern Pamirs: Estimated Contributions from Biomass Burning

Energy Technology Data Exchange (ETDEWEB)

Wang, Mo; Xu, B.; Kaspari, Susan D.; Gleixner, Gerd; Schwab, Valerie; Zhao, Huabiao; Wang, Hailong; Yao, Ping

2015-08-01

We analyzed refractory black carbon (rBC) in an ice core spanning 1875-2000 AD from Mt. Muztagh Ata, the Eastern Pamirs, using a Single Particle Soot Photometer (SP2). Additionally a pre-existing levoglucosan record from the same ice core was used to differentiate rBC that originated from open fires, energy-related combustion of biomass, and fossil fuel combustion. Mean rBC concentrations increased four-fold since the mid-1970s and reached maximum values at the end of 1980s. The observed decrease of the rBC concentrations during the 1990s was likely driven by the economic recession of former USSR countries in Central Asia. Levoglucosan concentrations showed a similar temporal trend to rBC concentrations, exhibiting a large increase around 1980 AD followed by a decrease in the 1990s that was likely due to a decrease in energy-related biomass combustion. The time evolution of levoglucosan/rBC ratios indicated stronger emissions from open fires during the 1940s-1950s, while the increase in rBC during the 1980s-1990s was caused from an increase in energy-related combustion of biomass and fossil fuels.

The glacial inception as recorded in the NorthGRIP Greenland ice core: timing, structure and associated abrupt temperature changes

Energy Technology Data Exchange (ETDEWEB)

Landais, Amaelle [UMR CEA-CNRS, CEA Saclay, IPSL/Laboratoire des Sciences du Climat et de l' Environnement, Gif-sur -Yvette (France); Hebrew University, Institute of Earth Sciences, Givat Ram, Jerusalem (Israel); Masson-Delmotte, Valerie; Jouzel, Jean; Minster, Benedicte [UMR CEA-CNRS, CEA Saclay, IPSL/Laboratoire des Sciences du Climat et de l' Environnement, Gif-sur -Yvette (France); Raynaud, Dominique [LGGE, UMR CNRS-UJF, St Martin d' Heres (France); Johnsen, Sigfus [University of Copenhagen, Department of Geophysics, Copenhagen (Denmark); Huber, Christof; Leuenberger, Markus; Schwander, Jakob [University of Bern, Physics Institute, Bern (Switzerland)

2006-02-01

The mechanisms involved in the glacial inception are still poorly constrained due to a lack of high resolution and cross-dated climate records at various locations. Using air isotopic measurements in the recently drilled NorthGRIP ice core, we show that no evidence exists for stratigraphic disturbance of the climate record of the last glacial inception ({proportional_to}123-100 kyears BP) encompassing Dansgaard-Oeschger events (DO) 25, 24 and 23, even if we lack sufficient resolution to completely rule out disturbance over DO 25. We quantify the rapid surface temperature variability over DO 23 and 24 with associated warmings of 10{+-}2.5 and 16{+-}2.5 C, amplitudes which mimic those observed in full glacial conditions. We use records of {delta}{sup 18}O of O{sub 2} to propose a common timescale for the NorthGRIP and the Antarctic Vostok ice cores, with a maximum uncertainty of 2,500 years, and to examine the interhemispheric sequence of events over this period. After a synchronous North-South temperature decrease, the onset of rapid events is triggered in the North through DO 25. As for later events, DO 24 and 23 have a clear Antarctic counterpart which does not seem to be the case for the very first abrupt warming (DO 25). This information, when added to intermediate levels of CO{sub 2} and to the absence of clear ice rafting associated with DO 25, highlights the uniqueness of this first event, while DO 24 and 23 appear similar to typical full glacial DO events. (orig.)

Characterization of atmospheric trace elements in the Puruogangri ice core: a preliminary account of Tibetan Plateau environmental and contamination histories

Science.gov (United States)

Beaudon, E.; Gabrielli, P.; Sierra Hernandez, R.; Wegner, A.; Thompson, L. G.

2014-12-01

Asia is facing enormous challenges including large-scale environmental changes, rapid population growth and industrialization. The inherent generated pollution contributes to half of all Earth's anthropogenic trace metals emissions that, when deposited to glaciers of the surrounding mountains of the Third Pole region, leave a characteristic chemical fingerprint. Records of past atmospheric deposition preserved in snow and ice from Third Pole glaciers provide unique insights into changes of the chemical composition of the atmosphere and into the nature and intensity of the regional atmospheric circulation systems. The determination of the elemental composition of aeolian dust stored in Himalayan and Tibetan Plateau glaciers can help to qualify the potential contamination of glacial meltwater as a part of the greater fresh Asian water source. The 215 m long Puruogangri ice core retrieved in 2000 at 6500 m a.s.l. in central Tibetan Plateau (Western Tanggula Shan, China) provides one of the first multi-millennium-long environmental archives (spanning the last 7000 years and annually resolved for the last 400 years) obtained from the Tibetan Plateau region. The Puruogangri's area is climatologically of particular interest because of its location at the boundary between the monsoon (wet) and the westerly (dry) dominated atmospheric circulation. The major objective of this study is to determine the concentration of trace and ultra-trace elements in the Puruogangri ice core between 1600 and 2000 AD in order to characterize the atmospheric aerosols entrapped in the ice. Particular attention is given to assess the amount of trace elements originating from anthropogenic sources during both the pre-industrial and industrial periods. The distinction between the anthropogenic contribution and the crustal background may rely on the precise decoupling of the dry and wet seasons signals, the former being largely influenced by dust contribution.

1500-year Record of trans-Pacific Dust Flux collected from the Denali Ice Core, Mt. Hunter, Alaska

Science.gov (United States)

Saylor, P. L.; Osterberg, E. C.; Koffman, B. G.; Winski, D.; Ferris, D. G.; Kreutz, K. J.; Wake, C. P.; Handley, M.; Campbell, S. W.

2016-12-01

Mineral dust aerosols are a critical component of the climate system through their influence on atmospheric radiative forcing, ocean productivity, and surface albedo. Dust aerosols derived from Asian deserts are known to reach as far as Europe through efficient transport in the upper tropospheric westerlies. While centennially-to-millennially resolved Asian dust records exist over the late Holocene from North Pacific marine sediment cores and Asian loess deposits, a high-resolution (sub-annual to decadal) record of trans-Pacific dust flux will significantly improve our understanding of North Pacific dust-climate interactions and provide paleoclimatological context for 20th century dust activity. Here we present an annually resolved 1500-year record of trans-Pacific dust transport based on chemical and physical dust measurements in parallel Alaskan ice cores (208 m to bedrock) collected from the summit plateau of Mt. Hunter in Denali National Park. The cores were sampled at high resolution using a continuous melter system with discrete analyses for major ions (Dionex ion chromatograph), trace elements (Element2 inductively coupled plasma mass spectrometer), and stable water isotope ratios (Picarro laser ringdown spectroscopy), and continuous flow analysis for dust concentration and size distribution (Klotz Abakus). We compare the ice core dust record to instrumental aerosol stations, satellite observations, and dust model data from the instrumental period, and evaluate climatic controls on dust emission and trans-Pacific transport using climate reanalysis data, to inform dust-climate relationships over the past 1500 years. Physical particulate and chemical data demonstrate remarkable fidelity at sub-annual resolution, with both displaying a strong springtime peak consistent with periods of high dust activity over Asian desert source regions. Preliminary results suggest volumetric mode typically ranges from 4.5 - 6.5 um, with a mean value of 5.5 um. Preliminary

In search of in-situ radiocarbon in Law Dome ice and firn

CERN Document Server

Smith, A M; Etheridge, D M; Lowe, D C; Hua, Q; Trudinger, C M; Zoppi, U; El-Cheikh, A

2000-01-01

Results of AMS radiocarbon measurements on CO and CO sub 2 separated from firn air directly pumped from the ice sheet, and on CO sub 2 separated from air extracted from ice cores by a dry grating technique, are presented. The firn air samples and ice cores used in this study were collected from the region of Law Dome, Antarctica. No evidence of in-situ sup 1 sup 4 CO sub 2 was found in the firn air samples or the ice core air samples from one site although a slight enhancement of sup 1 sup 4 CO above expected polar atmospheric concentrations was observed for some firn air samples. A clear in-situ sup 1 sup 4 CO sub 2 signal for ice pre-dating the radiocarbon bomb pulse was found, however, in air samples extracted from an ice core from a second site. We compare these results and propose an hypothesis to explain this apparent contradiction. The degree to which in-situ sup 1 sup 4 C is released from the ice crystals during trapping and bubble formation is considered and discussed. The selectivity of the dry grat...

Annual accumulation over the Greenland ice sheet interpolated from historical and newly compiled observation data

Science.gov (United States)

Shen, Dayong; Liu, Yuling; Huang, Shengli

2012-01-01

The estimation of ice/snow accumulation is of great significance in quantifying the mass balance of ice sheets and variation in water resources. Improving the accuracy and reducing uncertainty has been a challenge for the estimation of annual accumulation over the Greenland ice sheet. In this study, we kriged and analyzed the spatial pattern of accumulation based on an observation data series including 315 points used in a recent research, plus 101 ice cores and snow pits and newly compiled 23 coastal weather station data. The estimated annual accumulation over the Greenland ice sheet is 31.2 g cm−2 yr−1, with a standard error of 0.9 g cm−2 yr−1. The main differences between the improved map developed in this study and the recently published accumulation maps are in the coastal areas, especially southeast and southwest regions. The analysis of accumulations versus elevation reveals the distribution patterns of accumulation over the Greenland ice sheet.

Possible Mechanisms for Turbofan Engine Ice Crystal Icing at High Altitude

Science.gov (United States)

Tsao, Jen-Ching; Struk, Peter M.; Oliver, Michael J.

2016-01-01

A thermodynamic model is presented to describe possible mechanisms of ice formation on unheated surfaces inside a turbofan engine compression system from fully glaciated ice crystal clouds often formed at high altitude near deep convective weather systems. It is shown from the analysis that generally there could be two distinct types of ice formation: (1) when the "surface freezing fraction" is in the range of 0 to 1, dominated by the freezing of water melt from fully or partially melted ice crystals, the ice structure is formed from accretion with strong adhesion to the surface, and (2) when the "surface melting fraction" is the range of 0 to 1, dominated by the further melting of ice crystals, the ice structure is formed from accumulation of un-melted ice crystals with relatively weak bonding to the surface. The model captures important qualitative trends of the fundamental ice-crystal icing phenomenon reported earlier (Refs. 1 and 2) from the research collaboration work by NASA and the National Research Council (NRC) of Canada. Further, preliminary analysis of test data from the 2013 full scale turbofan engine ice crystal icing test (Ref. 3) conducted in the NASA Glenn Propulsion Systems Laboratory (PSL) has also suggested that (1) both types of ice formation occurred during the test, and (2) the model has captured some important qualitative trend of turning on (or off) the ice crystal ice formation process in the tested engine low pressure compressor (LPC) targeted area under different icing conditions that ultimately would lead to (or suppress) an engine core roll back (RB) event.

Heterogeneous condensation of ice mantle around silicate core grain in molecular cloud

International Nuclear Information System (INIS)

Hasegawa, H.

1984-01-01

Interstellar water ice grains are observed in the cold and dense regions such as molecular clouds, HII regions and protostellar objects. The water ice is formed from gas phase during the cooling stage of cosmic gas with solid grain surfaces of high temperature silicate minerals. It is a question whether the ice is formed through the homogeneous condensation process (as the ice alone) or the heterogeneous one (as the ice around the pre-existing high temperature mineral grains). (author)

Observations of banding in first-year Arctic sea ice

Science.gov (United States)

Cole, David M.; Eicken, Hajo; Frey, Karoline; Shapiro, Lewis H.

2004-08-01

Horizontal banding features, alternating dark and bright horizontal bands apparent in ice cores and stratigraphic cross sections have long been observed in first-year sea ice and are frequently associated with bands of high and low brine or gas porosity. Observations on the land-fast ice near Barrow, Alaska, in recent years have revealed particularly striking banding patterns and prompted a study of their macroscopic and microscopic characteristics. The banding patterns are quantified from photographs of full-depth sections of the ice, and examples are presented from the Chukchi Sea and Elson Lagoon. Statistics on band spacing are presented, and the growth records for three seasons are employed to estimate their time of formation. These data provide insight into the periodicity of the underlying phenomena. Micrographs are used to examine the microstructural variations associated with various banding features and to quantify the geometry of the constituent brine inclusions associated with high- and low-porosity bands. The micrography revealed that the area fraction of brine inclusions varied by a factor of nearly 3 through the more pronounced high- and low-porosity bands. Vertical micrographs obtained shortly after the materials' removal from the ice sheet showed that significantly larger inclusions form abruptly at the start of the high-porosity bands and frequently terminate abruptly at the end of the band. Crystallographic observations indicated that the high-porosity bands supported the nucleation and growth of crystals having substantially different orientations from the very well aligned columnar structure that characterized the bulk of the sheet.

Evolution of a highly vulnerable ice-cored moraine: Col des Gentianes, Swiss Alps

Science.gov (United States)

Ravanel, L.; Lambiel, C.; Oppikofer, T.; Mazotti, B.; Jaboyedoff, M.

2012-04-01

Rock mass movements are dominant in the morphodynamics of high mountain rock slopes and are at the origin of significant risks for people who attend these areas and for infrastructures that are built on (mountain huts, cable cars, etc.). These risks are becoming greater because of permafrost degradation and glacier retreat, two consequences of the global warming. These two commonly associated factors may affect slope stability by changing mechanical properties of the interstitial ice and modifying the mechanical constraints in these rock slopes. Between 1977 and 1979, significant works were carried out on the Little Ice Age moraine of the Tortin glacier at the Col des Gentianes (2894 m), in the Mont Fort area (Verbier, Switzerland), for the construction of a cable car station and a restaurant. Since the early 1980s, the glacier drastically retreated and the moraine became unstable: its inner slope has retreated for several meters. Various observations and geoelectric measurements indicate that significant volume of massive ice mass is still present within the moraine (ice-cored moraine). Its melting could therefore increase the instability of the moraine. Since 2007, the moraine is surveyed by terrestrial laser scanning (TLS) in order to characterize its evolution: 8 campaigns were conducted between July 2007 and October 2011. The comparison of the high resolution 3D models so obtained allowed the detection and quantification of mass movements that have affected the moraine over this period, essentially by calculating difference maps (shortest oblique distances between two models). Between July 2007 and October 2011, 7 landslides were measured, involving volumes between 87 and 1138 m3. The most important of these occurred during the summers 2009 and 2011. TLS data also allowed identifying: (i) two main areas affected by slower but sometimes substantial movements (displacements of blocks on more than 2 m during a summer period); (ii) significant deposits of

Improving accuracy and precision of ice core δD(CH4 analyses using methane pre-pyrolysis and hydrogen post-pyrolysis trapping and subsequent chromatographic separation

Directory of Open Access Journals (Sweden)

M. Bock

2014-07-01

Full Text Available Firn and polar ice cores offer the only direct palaeoatmospheric archive. Analyses of past greenhouse gas concentrations and their isotopic compositions in air bubbles in the ice can help to constrain changes in global biogeochemical cycles in the past. For the analysis of the hydrogen isotopic composition of methane (δD(CH4 or δ2H(CH4 0.5 to 1.5 kg of ice was hitherto used. Here we present a method to improve precision and reduce the sample amount for δD(CH4 measurements in (ice core air. Pre-concentrated methane is focused in front of a high temperature oven (pre-pyrolysis trapping, and molecular hydrogen formed by pyrolysis is trapped afterwards (post-pyrolysis trapping, both on a carbon-PLOT capillary at −196 °C. Argon, oxygen, nitrogen, carbon monoxide, unpyrolysed methane and krypton are trapped together with H2 and must be separated using a second short, cooled chromatographic column to ensure accurate results. Pre- and post-pyrolysis trapping largely removes the isotopic fractionation induced during chromatographic separation and results in a narrow peak in the mass spectrometer. Air standards can be measured with a precision better than 1‰. For polar ice samples from glacial periods, we estimate a precision of 2.3‰ for 350 g of ice (or roughly 30 mL – at standard temperature and pressure (STP – of air with 350 ppb of methane. This corresponds to recent tropospheric air samples (about 1900 ppb CH4 of about 6 mL (STP or about 500 pmol of pure CH4.

The extreme melt across the Greenland ice sheet in 2012

Science.gov (United States)

Nghiem, S. V.; Hall, D. K.; Mote, T. L.; Tedesco, M.; Albert, M. R.; Keegan, K.; Shuman, C. A.; DiGirolamo, N. E.; Neumann, G.

2012-10-01

The discovery of the 2012 extreme melt event across almost the entire surface of the Greenland ice sheet is presented. Data from three different satellite sensors - including the Oceansat-2 scatterometer, the Moderate-resolution Imaging Spectroradiometer, and the Special Sensor Microwave Imager/Sounder - are combined to obtain composite melt maps, representing the most complete melt conditions detectable across the ice sheet. Satellite observations reveal that melt occurred at or near the surface of the Greenland ice sheet across 98.6% of its entire extent on 12 July 2012, including the usually cold polar areas at high altitudes like Summit in the dry snow facies of the ice sheet. This melt event coincided with an anomalous ridge of warm air that became stagnant over Greenland. As seen in melt occurrences from multiple ice core records at Summit reported in the published literature, such a melt event is rare with the last significant one occurring in 1889 and the next previous one around seven centuries earlier in the Medieval Warm Period. Given its rarity, the 2012 extreme melt across Greenland provides an exceptional opportunity for new studies in broad interdisciplinary geophysical research.

Simulation of the Greenland Ice Sheet over two glacial–interglacial cycles: investigating a sub-ice-shelf melt parameterization and relative sea level forcing in an ice-sheet–ice-shelf model

Directory of Open Access Journals (Sweden)

S. L. Bradley

2018-05-01

Full Text Available Observational evidence, including offshore moraines and sediment cores, confirm that at the Last Glacial Maximum (LGM the Greenland ice sheet (GrIS expanded to a significantly larger spatial extent than seen at present, grounding into Baffin Bay and out onto the continental shelf break. Given this larger spatial extent and its close proximity to the neighbouring Laurentide Ice Sheet (LIS and Innuitian Ice Sheet (IIS, it is likely these ice sheets will have had a strong non-local influence on the spatial and temporal behaviour of the GrIS. Most previous paleo ice-sheet modelling simulations recreated an ice sheet that either did not extend out onto the continental shelf or utilized a simplified marine ice parameterization which did not fully include the effect of ice shelves or neglected the sensitivity of the GrIS to this non-local bedrock signal from the surrounding ice sheets. In this paper, we investigated the evolution of the GrIS over the two most recent glacial–interglacial cycles (240 ka BP to the present day using the ice-sheet–ice-shelf model IMAU-ICE. We investigated the solid earth influence of the LIS and IIS via an offline relative sea level (RSL forcing generated by a glacial isostatic adjustment (GIA model. The RSL forcing governed the spatial and temporal pattern of sub-ice-shelf melting via changes in the water depth below the ice shelves. In the ensemble of simulations, at the glacial maximums, the GrIS coalesced with the IIS to the north and expanded to the continental shelf break to the southwest but remained too restricted to the northeast. In terms of the global mean sea level contribution, at the Last Interglacial (LIG and LGM the ice sheet added 1.46 and −2.59 m, respectively. This LGM contribution by the GrIS is considerably higher (∼  1.26 m than most previous studies whereas the contribution to the LIG highstand is lower (∼  0.7 m. The spatial and temporal behaviour of the northern margin was

δ13Catm and [CO2] measurements in Antarctic ice cores, 160 kyrBP - present

Science.gov (United States)

Eggleston, Sarah; Schmitt, Jochen; Schneider, Robert; Joos, Fortunat; Fischer, Hubertus

2014-05-01

Measurements from Antarctic ice cores allow us to reconstruct atmospheric concentrations of climatically important gases including CO2 over the past 800 kyr. Such measurements show that [CO2] has varied in parallel with Antarctic temperatures on glacial-interglacial timescales. Knowledge of the variations of the stable carbon isotope of CO2, δ13Catm, can help us better understand the processes involved in these fluctuations. Here, we present a first complete δ13Catmrecord extending from 160 kyrBP to the present accompanied by δ15N2 measurements during Marine Isotope Stage 3 (MIS 3, 57 - 29 kyrBP). The present record, measured primarily on ice from the EPICA Dome C and Talos Dome ice cores, has an average resolution of 500 yr, focused mainly on the Last Glacial Maximum and termination (180 yr; Schmitt et al., 2012), MIS 3 (660 yr), and Termination II through MIS 5.4 (590 yr; Schneider et al., 2013). Throughout the record, δ13Catm varies between approximately -6.8 and -6.4‰Following a period of relatively constant δ13Catm at the end of MIS 6 (around -6.8), the boundaries of MIS 5 correspond roughly with the beginning and end of a gradual enrichment in this isotope. In comparison, the more recent record depicts three more abrupt excursions to lighter values around 63 - 59, 46, and 17 kyrBP, in each case followed by a slower return (0.4o over the course of 5 - 15 kyr) to more enriched isotopic values. These coincide with Heinrich events 6, 5, and 1, respectively. No direct correlation is observed between the concentration and carbon isotope of CO2 over the last 160 kyr. The data indicate rather that numerous processes, such as uptake and release of atmospheric CO2 by the ocean and land biosphere, perhaps influenced by regions of growing permafrost during MIS 3 and 4, acting on a variety of timescales must be considered in explaining the evolution of δ13Catm on glacial-interglacial timescales. References: Schmitt, J. et al. Science 336, 711-714 (2012) Schneider

A new set-up for simultaneous high-precision measurements of CO2, δ13C-CO2 and δ18O-CO2 on small ice core samples

Science.gov (United States)

Jenk, Theo Manuel; Rubino, Mauro; Etheridge, David; Ciobanu, Viorela Gabriela; Blunier, Thomas

2016-08-01

Palaeoatmospheric records of carbon dioxide and its stable carbon isotope composition (δ13C) obtained from polar ice cores provide important constraints on the natural variability of the carbon cycle. However, the measurements are both analytically challenging and time-consuming; thus only data exist from a limited number of sampling sites and time periods. Additional analytical resources with high analytical precision and throughput are thus desirable to extend the existing datasets. Moreover, consistent measurements derived by independent laboratories and a variety of analytical systems help to further increase confidence in the global CO2 palaeo-reconstructions. Here, we describe our new set-up for simultaneous measurements of atmospheric CO2 mixing ratios and atmospheric δ13C and δ18O-CO2 in air extracted from ice core samples. The centrepiece of the system is a newly designed needle cracker for the mechanical release of air entrapped in ice core samples of 8-13 g operated at -45 °C. The small sample size allows for high resolution and replicate sampling schemes. In our method, CO2 is cryogenically and chromatographically separated from the bulk air and its isotopic composition subsequently determined by continuous flow isotope ratio mass spectrometry (IRMS). In combination with thermal conductivity measurement of the bulk air, the CO2 mixing ratio is calculated. The analytical precision determined from standard air sample measurements over ice is ±1.9 ppm for CO2 and ±0.09 ‰ for δ13C. In a laboratory intercomparison study with CSIRO (Aspendale, Australia), good agreement between CO2 and δ13C results is found for Law Dome ice core samples. Replicate analysis of these samples resulted in a pooled standard deviation of 2.0 ppm for CO2 and 0.11 ‰ for δ13C. These numbers are good, though they are rather conservative estimates of the overall analytical precision achieved for single ice sample measurements. Facilitated by the small sample requirement

Anomalous flow below 2700 m in the EPICA Dome C ice core detected using δ18O of atmospheric oxygen measurements

Directory of Open Access Journals (Sweden)

M. Leuenberger

2007-06-01

Full Text Available While there are no indications of mixing back to 800 000 years in the EPICA Dome C ice core record, comparison with marine sediment records shows significant differences in the timing and duration of events prior to stage 11 (~430 ka, thousands of years before 1950. A relationship between the isotopic composition of atmospheric oxygen (δ18O of O2, noted δ18Oatm and daily northern hemisphere summer insolation has been observed for the youngest four climate cycles. Here we use this relationship with new δ18O of O2 measurements to show that anomalous flow in the bottom 500 m of the core distorts the duration of events by up to a factor of 2. By tuning δ18Oatm to orbital precession we derive a corrected thinning function and present a revised age scale for the interval corresponding to Marine Isotope Stages 11–20 in the EPICA Dome C ice core. Uncertainty in the phasing of δ18Oatm with respect to insolation variations in the precession band limits the accuracy of this new agescale to ±6 kyr (thousand of years. The previously reported ~30 kyr duration of interglacial stage 11 is unchanged. In contrast, the duration of stage 15.1 is reduced by a factor of 2, from 31 to 16 kyr.

High-resolution continuous-flow analysis setup for water isotopic measurement from ice cores using laser spectroscopy

Science.gov (United States)

Emanuelsson, B. D.; Baisden, W. T.; Bertler, N. A. N.; Keller, E. D.; Gkinis, V.

2015-07-01

Here we present an experimental setup for water stable isotope (δ18O and δD) continuous-flow measurements and provide metrics defining the performance of the setup during a major ice core measurement campaign (Roosevelt Island Climate Evolution; RICE). We also use the metrics to compare alternate systems. Our setup is the first continuous-flow laser spectroscopy system that is using off-axis integrated cavity output spectroscopy (OA-ICOS; analyzer manufactured by Los Gatos Research, LGR) in combination with an evaporation unit to continuously analyze water samples from an ice core. A Water Vapor Isotope Standard Source (WVISS) calibration unit, manufactured by LGR, was modified to (1) enable measurements on several water standards, (2) increase the temporal resolution by reducing the response time and (3) reduce the influence from memory effects. While this setup was designed for the continuous-flow analysis (CFA) of ice cores, it can also continuously analyze other liquid or vapor sources. The custom setups provide a shorter response time (~ 54 and 18 s for 2013 and 2014 setup, respectively) compared to the original WVISS unit (~ 62 s), which is an improvement in measurement resolution. Another improvement compared to the original WVISS is that the custom setups have a reduced memory effect. Stability tests comparing the custom and WVISS setups were performed and Allan deviations (σAllan) were calculated to determine precision at different averaging times. For the custom 2013 setup the precision after integration times of 103 s is 0.060 and 0.070 ‰ for δ18O and δD, respectively. The corresponding σAllan values for the custom 2014 setup are 0.030, 0.060 and 0.043 ‰ for δ18O, δD and δ17O, respectively. For the WVISS setup the precision is 0.035, 0.070 and 0.042 ‰ after 103 s for δ18O, δD and δ17O, respectively. Both the custom setups and WVISS setup are influenced by instrumental drift with δ18O being more drift sensitive than δD. The �

Ice recrystallization inhibition in ice cream by propylene glycol monostearate.

Science.gov (United States)

Aleong, J M; Frochot, S; Goff, H D

2008-11-01

The effectiveness of propylene glycol monostearate (PGMS) to inhibit ice recrystallization was evaluated in ice cream and frozen sucrose solutions. PGMS (0.3%) dramatically reduced ice crystal sizes in ice cream and in sucrose solutions frozen in a scraped-surface freezer before and after heat shock, but had no effect in quiescently frozen solutions. PGMS showed limited emulsifier properties by promoting smaller fat globule size distributions and enhanced partial coalescence in the mix and ice cream, respectively, but at a much lower level compared to conventional ice cream emulsifier. Low temperature scanning electron microscopy revealed highly irregular crystal morphology in both ice cream and sucrose solutions frozen in a scraped-surface freezer. There was strong evidence to suggest that PGMS directly interacts with ice crystals and interferes with normal surface propagation. Shear during freezing may be required for its distribution around the ice and sufficient surface coverage.

Ice formation in subglacial Lake Vostok, Central Antarctica

Science.gov (United States)

Souchez, R.; Petit, J. R.; Tison, J.-L.; Jouzel, J.; Verbeke, V.

2000-09-01

The investigation of chemical and isotopic properties in the lake ice from the Vostok ice core gives clues to the mechanisms involved in ice formation within the lake. A small lake water salinity can be reasonably deduced from the chemical data. Possible implications for the water circulation of Lake Vostok are developed. The characteristics of the isotopic composition of the lake ice indicate that ice formation in Lake Vostok occurred by frazil ice crystal generation due to supercooling as a consequence of rising waters and a possible contrast in water salinity. Subsequent consolidation of the developed loose ice crystals results in the accretion of ice to the ceiling of the lake.

Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy

Science.gov (United States)

Cronin, T. M.; Gemery, L.; Briggs, W.M.; Jakobsson, M.; Polyak, L.; Brouwers, E.M.

2010-01-01

Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25-45 ka), minimal sea ice during the last deglacial (16-11 ka) and early Holocene thermal maximum (11-5 ka) and increasing sea ice during the mid-to-late Holocene (5-0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon. ?? 2010.

Evolution of the eastern part of the Kuusamo Ice Lobe, based on geomorphological interpretation of high-resolution LiDAR data

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P. Sarala

2017-12-01

Full Text Available In this article, we present new glacial geomorphological data from the eastern part of the Kuusamo Ice Lobe (KIL in eastern Finland. The focus is on glacial lineations (about 9000 individual features and interpretation of ice lobe evolution based on streamlined erosional and depositional formations, hummocky and ribbed moraines and glaciofluvial formations. Glacial geomorphological mapping was performed based on interpretation and classification of LiDAR data according to the Geological Survey of Finland’s new Glacier Dynamic database. The results revealed that modern surficial deposits were formed during three different ice flow phases. The oldest remains are seen as occasional NW-SE megalineations and unclassified glacially lineated terrains and erosional valleys representing the Middle Weichselian glaciation. The younger morphologies were formed from the two overlapping drumlin fields of the Tuoppajärvi and Kuusamo ice flow phases, with origins in the Late Weichselian deglaciation. Analysis of different erosional and depositional formation patterns was used to separate ice flow phases and estimate the evolution, subglacial conditions and mass balance of KIL during the last deglaciation. The morphological interpretation revealed that the Tuoppajärvi ice flow stage was large and homogeneous, while the later Kuusamo ice flow stage was more concentrated, narrower and heterogeneous, following a fan-type pattern that is also emphasised by the meltwater channel systems, including both erosional and depositional features. Furthermore, on both margins (northern and southern, part of the ice masses formed stagnant areas. The length of the lineations also indicates both glacier flow velocity and transport distances, which in the case of megalineations and drumlins are longer than in the fluted terrain. Ribbed moraines in the western (core part of KIL indicate a very different depositional environment relating to strong quarrying and short transport

Spatio-Temporal Variability of Recent Snow Accumulation Across the West Antarctic Ice Sheet Divide Using Ultra-High Frequency Radar and Shallow Firn Cores

Science.gov (United States)

Keeler, D. G.; Rupper, S.; Forster, R. R.; Miège, C.; Brewer, S.; Koenig, L.

2017-12-01

The West Antarctic Ice Sheet (WAIS) could be a substantial source of future sea level rise, with 3+ meters of potential increase stored in the ice sheet. Adequate predictions of WAIS contributions, however, depend on well-constrained surface mass balance estimates for the region. Given the sparsity of available data, such estimates are tenuous. Although new data are periodically added, further research (both to collect more data and better utilize existing data) is critical to addressing these issues. Here we present accumulation data from 9 shallow firn cores and 600 km of Ku band radar traces collected as part of the Satellite Era Antarctic Traverse (SEAT) 2011/2012 field season. Using these data, combined with similar data collected during the SEAT 2010/2011 field season, we investigate the spatial variability in accumulation across the WAIS Divide and surrounding regions. We utilize seismic interpretation and 3D visualization tools to investigate the extent and variations of laterally continuous internal horizons in the radar profiles, and compare the results to nearby firn cores. Previous results show that clearly visible, laterally continuous horizons in radar returns in this area do not always represent annual accumulation isochrones, but can instead represent multi-year or sub-annual events. The automated application of Bayesian inference techniques to averaged estimates of multiple adjacent radar traces, however, can estimate annually-resolved independent age-depth scales for these radar data. We use these same automated techniques on firn core isotopic records to infer past snow accumulation rates, allowing a direct comparison with the radar-derived results. Age-depth scales based on manual annual-layer counting of geochemical and isotopic species from these same cores provide validation for the automated approaches. Such techniques could theoretically be applied to additional radar/core data sets in polar regions (e.g. Operation IceBridge), thereby

Organic compounds and suspended matter in the White Sea snow-ice cover

International Nuclear Information System (INIS)

Nemirovskaya, I.; Shevchenko, V.

2008-01-01

The pollution of the White Sea snow-ice cover was estimated by examining the distribution of organic compounds, including oil and pyrogenic hydrocarbons. Ice and snow cores were taken from Chupa Bay and the Kandalaksha Gulf in the Cape Kartesh area in the spring of 2004 and from the mouth of the Severnaya Dvina River in the spring of 2005, 2006, and 2007. This paper presented data on the lipid content, aliphatic hydrocarbons (AHC), polycyclic aromatic hydrocarbons (PAH) and suspended particulate matter in snow, ice and under-ice water. This paper focused on organic compounds and suspended matter (SM) concentrations in the sea snow-ice cover and described the ice forming conditions and interactions of the substances with ice, snow and sub-ice water. The amount of particulate matter and organic compounds in the snow increased sharply near industrial centres. The concentration of compounds decreased further away from these centres, suggesting that most pollutants are deposited locally. The study revealed that organic compounds concentrate in barrier zones, such as snow-ice and water-ice, depending on the source of pollution. There was no obvious evidence of petrogenic sources of PAHs in particulate matter from the White Sea snow-ice cover. The SM and organic compounds accumulated in layers characterized by local depositional processes. The zones remained biogeochemically active even under low temperature conditions, but the accumulation of both SM and organic compounds was at its highest during the initial stage of ice formation. 16 refs., 2 tabs., 4 figs

Ross Ice Drainage System (RIDS) Glaciochemical Analysis, Version 1

Data.gov (United States)

National Aeronautics and Space Administration — The Ross Ice Drainage System (RIDS) project provides a high-resolution record of atmospheric chemical deposition taken from several ice cores and snow pits located...

Comparison of CO/sub 2/ measurements by two laboratories on air from bubbles in polar ice

Energy Technology Data Exchange (ETDEWEB)

Barnola, J.M.; Raynaud, D.; Neftel, A.; Oeschger, H.

1983-06-02

The CO/sub 2/ content of air enclosed in bubbles in polar ice has been reported by two laboratories (in Grenoble and Bern) to be representative of the atmospheric CO/sub 2/ concentration at the time the ice was formed. Such ice core studies indicate lower concentrations in ice formed at the end of the ice age, around 18,000 yr BP, and several explanations have been proposed for such a change. Both laboratories are currently measuring various ice cores in order to determine the pre-AD 1850 CO/sub 2/ level in the atmosphere, which relates to the partitioning of anthropogenic CO/sub 2/ among the atmospheric, biospheric and oceanic reservoirs. The two laboratories use different ice cores and different analytical procedures and, therefore, there is a need to know to what extent the measurements are quantitatively comparable. The results are presented of a comparison between the two laboratories based on measurements from the same ice core sections, which indicate that the measurements can be compared with great confidence. The results suggest that the mean CO/sub 2/ level recorded by Antartic ice for the period 800-2500 yr BP is about 260 p.p.m.v.

Chronicling ice shelf history in the sediments left behind

Science.gov (United States)

Rosenheim, B. E.; Subt, C.; Shevenell, A.; Guitard, M.; Vadman, K. J.; DeCesare, M.; Wellner, J. S.; Bart, P. J.; Lee, J. I.; Domack, E. W.; Yoo, K. C.; Hayes, J. M.

2017-12-01

Collapsing and retreating ice shelves leave unmistakable sediment sequences on the Antarctic margin. These sequences tell unequivocal stories of collapse or retreat through a typical progression of sub-ice shelf diamicton (marking the past positions of grounding lines), sequentially overlain by a granulated facies from beneath the ice shelf, ice rafted debris from the calving line, and finally open marine sediment. The timelines to these stories, however, are troublesome. Difficulties in chronicling these stories recorded in sediment have betrayed their importance to our understanding of a warming world in many cases. The difficulties involve the concerted lack of preservation/production of calcium carbonate tests from the water column above and admixture of relict organic material from older sources of carbon. Here, we summarize our advances in the last decade of overcoming difficulties associated with the paucity of carbonate and creating chronologies of ice shelf retreat into the deglacial history of Antarctica by exploiting the range of thermochemical stability in organic matter (Ramped PyrOx) from these sediment sequences. We describe our success in comparing Ramped PyrOx 14C dates with foraminiferal dates, the relationship between sediment facies and radiocarbon age spectrum, and our ability to push limits of dating sediments deposited underneath ice shelves. With attention to the caveats of recent dating developments, we summarize expectations that geologist should have when coring the Antarctic margins to discern deglacial history. Perhaps most important among these expectations is the ability to design coring expeditions without regard to our ability to date calcium carbonate microfossils within the cores, in essence removing suspense of knowing whether cores taken from crucial paleo ice channels and other bathymetric features will ultimately yield a robust chronology for its sedimentary sequence.

A tentative record of the last 1,000 years of Greenland temperature from occluded air in the GISP2 ice core

Science.gov (United States)

Kobashi, T.; Severinghaus, J. P.; Barnola, J.; Kawamura, K.; Beaudette, R.

2005-12-01

Ice borehole temperature inversion has been used to reconstruct Greenland surface temperature during the last millennium (Dahl-Jensen et al, Science, 1998). However, this technique does not preserve high frequencies because of diffusion of heat in the ice. Here, we present a tentative reconstruction of the past 1,000 years of central Greenland temperature using nitrogen and argon isotopes from occluded air in the GISP2 ice core. This technique preserves decadal-to-centennial-scale temperature variations and complements the borehole technique. Nitrogen and argon isotopes in the porous snow layer (~80m) experience two isotopic fractionations by gravitation and temperature gradients (ΔT) between the top and bottom of the snow layer. The simultaneous analysis of argon and nitrogen isotopes allows us to separate these two effects, and obtain a history of ΔT in the layer. To a first approximation, ΔT change on decadal to centennial time scales is a surface temperature history because the heat conductivity of snow is much smaller than that of ice, and the heat capacity of the ice sheet is quite large. The preliminary ΔT history (20-year interval) shows a Medieval Warm Period in the 11th to 12th centuries and the Little Ice Age in the 15th to 19th centuries. Furthermore, the record shows a clear similarity with the Be-10 record (a proxy for solar activity) with Wolf, Sporer, Maunder, and Dalton minima clearly seen in the cold periods. This finding is consistent with the hypothesis that solar activity influenced Greenland temperature during the past 1000 years.

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice : Insight from Numerical Models and Ice Core Microstructure Analysis

NARCIS (Netherlands)

Steinbach, F.; Kuiper, E.N.; Eichler, J.; Bons, P. D.; Drury, M. R.; Griera, A.; Pennock, G.M.; Weikusat, I.

2017-01-01

The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We

Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis

Directory of Open Access Journals (Sweden)

E. Le Meur

2018-05-01

Full Text Available Results from ground-penetrating radar (GPR measurements and shallow ice cores carried out during a scientific traverse between Dome Concordia (DC and Vostok stations are presented in order to infer both spatial and temporal characteristics of snow accumulation over the East Antarctic Plateau. Spatially continuous accumulation rates along the traverse are computed from the identification of three equally spaced radar reflections spanning about the last 600 years. Accurate dating of these internal reflection horizons (IRHs is obtained from a depth–age relationship derived from volcanic horizons and bomb testing fallouts on a DC ice core and shows a very good consistency when tested against extra ice cores drilled along the radar profile. Accumulation rates are then inferred by accounting for density profiles down to each IRH. For the latter purpose, a careful error analysis showed that using a single and more accurate density profile along a DC core provided more reliable results than trying to include the potential spatial variability in density from extra (but less accurate ice cores distributed along the profile. The most striking feature is an accumulation pattern that remains constant through time with persistent gradients such as a marked decrease from 26 mm w.e. yr−1 at DC to 20 mm w.e. yr−1 at the south-west end of the profile over the last 234 years on average (with a similar decrease from 25 to 19 mm w.e. yr−1 over the last 592 years. As for the time dependency, despite an overall consistency with similar measurements carried out along the main East Antarctic divides, interpreting possible trends remains difficult. Indeed, error bars in our measurements are still too large to unambiguously infer an apparent time increase in accumulation rate. For the proposed absolute values, maximum margins of error are in the range 4 mm w.e. yr−1 (last 234 years to 2 mm w.e. yr−1 (last 592 years, a

Drilling comparison in "warm ice" and drill design comparison

DEFF Research Database (Denmark)

Augustin, L.; Motoyama, H.; Wilhelms, F.

2007-01-01

For the deep ice-core drilling community, the 2005/06 Antarctic season was an exciting and fruitful one. In three different Antarctic locations, Dome Fuji, EPICA DML and Vostok, deep drillings approached bedrock (the ice-water interface in the case of Vostok), emulating what had previously been...... achieved at NorthGRIP, Greenland, (summer 2003 and 2004) and at EPICA Dome C2, Antarctica (season 2004/05). For the first time in ice-core drilling history, three different types of drill (KEMS, JARE and EPICA) simultaneously reached the depth of 'warm ice' under high pressure. After excellent progress...... at each site, the drilling rate dropped and the drilling teams had to deal with refrozen ice on cutters and drill heads. Drills have different limits and perform differently. In this comparative study, we examine depth, pressure, temperature, pump flow and cutting speed. Finally, we compare a few...

Duality of Ross Ice Shelf systems: crustal boundary, ice sheet processes and ocean circulation from ROSETTA-Ice surveys

Science.gov (United States)

Tinto, K. J.; Siddoway, C. S.; Padman, L.; Fricker, H. A.; Das, I.; Porter, D. F.; Springer, S. R.; Siegfried, M. R.; Caratori Tontini, F.; Bell, R. E.

2017-12-01

Bathymetry beneath Antarctic ice shelves controls sub-ice-shelf ocean circulation and has a major influence on the stability and dynamics of the ice sheets. Beneath the Ross Ice Shelf, the sea-floor bathymetry is a product of both tectonics and glacial processes, and is influenced by the processes it controls. New aerogeophysical surveys have revealed a fundamental crustal boundary bisecting the Ross Ice Shelf and imparting a duality to the Ross Ice Shelf systems, encompassing bathymetry, ocean circulation and ice flow history. The ROSETTA-Ice surveys were designed to increase the resolution of Ross Ice Shelf mapping from the 55 km RIGGS survey of the 1970s to a 10 km survey grid, flown over three years from New York Air National Guard LC130s. Radar, LiDAR, gravity and magnetic instruments provide a top to bottom profile of the ice shelf and the underlying seafloor, with 20 km resolution achieved in the first two survey seasons (2015 and 2016). ALAMO ocean-profiling floats deployed in the 2016 season are measuring the temperature and salinity of water entering and exiting the sub-ice water cavity. A significant east-west contrast in the character of the magnetic and gravity fields reveals that the lithospheric boundary between East and West Antarctica exists not at the base of the Transantarctic Mountains (TAM), as previously thought, but 300 km further east. The newly-identified boundary spatially coincides with the southward extension of the Central High, a rib of shallow basement identified in the Ross Sea. The East Antarctic side is characterized by lower amplitude magnetic anomalies and denser TAM-type lithosphere compared to the West Antarctic side. The crustal structure imparts a fundamental duality on the overlying ice and ocean, with deeper bathymetry and thinner ice on the East Antarctic side creating a larger sub-ice cavity for ocean circulation. The West Antarctic side has a shallower seabed, more restricted ocean access and a more complex history of

Road icing forecasting and detecting system

Science.gov (United States)

Xu, Hongke; Zheng, Jinnan; Li, Peiqi; Wang, Qiucai

2017-05-01

Regard for the facts that the low accuracy and low real-time of the artificial observation to determine the road icing condition, and it is difficult to forecast icing situation, according to the main factors influencing the road-icing, and the electrical characteristics reflected by the pavement ice layer, this paper presents an innovative system, that is, ice-forecasting of the highway's dangerous section. The system bases on road surface water salinity measurements and pavement temperature measurement to calculate the freezing point of water and temperature change trend, and then predicts the occurrence time of road icing; using capacitance measurements to verdict the road surface is frozen or not; This paper expounds the method of using single chip microcomputer as the core of the control system and described the business process of the system.

Drumlinised glaciofluvial and glaciolacustrine sediments on the Småland peneplain, South Sweden - new information on the growth and decay history of the Fennoscandian Ice Sheets during MIS 3

Science.gov (United States)

Möller, Per; Murray, Andrew S.

2015-08-01

Dug trenches in sediment-cored drumlins on the Småland peneplain, southern Sweden, occurring intermixed with rock-cored drumlins, revealed sedimentary successions and facies suggesting that the core sediments were primarily deposited proglacially, both in glaciolacustrine settings as delta-front and more distal deeper-water sediments, and as glaciofluvial braidplain sediments. From the relationship between the drumlin sorted-sediment cores and their surficial drape by a till carapace, it is concluded that erosion was the main drumlin-forming process here, reshaping the original sediment morphology into streamlined landforms, after which a more or less thick traction till was deposited over the eroded and/or deformed ice-bed interface. Drumlin formation probably took place during the last deglaciation over the area. The drumlin-core sediments in 14 excavated trenches were dated by Optically Stimulated Luminescence (OSL); most retrieved ages fall into two distinct groups, both within Marine Isotope Stage 3 (c. 60-30 ka). When plotted as mean OSL ages for each site, all but two sites fall either into an older age group, c. 48-56 ka (seven sites), or into a younger age group, c. 28-38 ka (five sites). These age intervals correlate well with the suggested time spans for the Ristinge and Klintholm ice advances in Denmark by ice flowing from the Baltic Basin westwards, terminating in fan-shaped patterns. These interstadial ice advances in the southwestern sector of the Fennoscandian Ice Sheet give rise to enigmatic questions on the physics and mechanics of ice sheet build-up and decay, especially as palaeoenvironmental data for northern Fennoscandia suggest widespread ice-free conditions within roughly the same time fame as the recorded ice advances in the south.

Summer Temperature Trend Over the Past Two Millennia Using Air Content in Himalayan Ice

National Research Council Canada - National Science Library

Hou, S; Chappellaz, J; Jouzel, J; Chu, P. C; Masson-Delmotte, V; Qin, D; Raynaud, D; Mayewski, P. A; Lipenkov, V. Y; Kang, S

2007-01-01

Two Himalayan ice cores display a factor-two decreasing trend of air content over the past two millennia, in contrast to the relatively stable values in Greenland and Antarctica ice cores over the same period...

Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records

Science.gov (United States)

Bock, Michael; Schmitt, Jochen; Beck, Jonas; Seth, Barbara; Chappellaz, Jérôme; Fischer, Hubertus

2017-07-01

Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ13CH4 and δD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial.

Dark ice dynamics of the south-west Greenland Ice Sheet

Science.gov (United States)

Tedstone, Andrew J.; Bamber, Jonathan L.; Cook, Joseph M.; Williamson, Christopher J.; Fettweis, Xavier; Hodson, Andrew J.; Tranter, Martyn

2017-11-01

Runoff from the Greenland Ice Sheet (GrIS) has increased in recent years due largely to changes in atmospheric circulation and atmospheric warming. Albedo reductions resulting from these changes have amplified surface melting. Some of the largest declines in GrIS albedo have occurred in the ablation zone of the south-west sector and are associated with the development of dark ice surfaces. Field observations at local scales reveal that a variety of light-absorbing impurities (LAIs) can be present on the surface, ranging from inorganic particulates to cryoconite materials and ice algae. Meanwhile, satellite observations show that the areal extent of dark ice has varied significantly between recent successive melt seasons. However, the processes that drive such large interannual variability in dark ice extent remain essentially unconstrained. At present we are therefore unable to project how the albedo of bare ice sectors of the GrIS will evolve in the future, causing uncertainty in the projected sea level contribution from the GrIS over the coming decades. Here we use MODIS satellite imagery to examine dark ice dynamics on the south-west GrIS each year from 2000 to 2016. We quantify dark ice in terms of its annual extent, duration, intensity and timing of first appearance. Not only does dark ice extent vary significantly between years but so too does its duration (from 0 to > 80 % of June-July-August, JJA), intensity and the timing of its first appearance. Comparison of dark ice dynamics with potential meteorological drivers from the regional climate model MAR reveals that the JJA sensible heat flux, the number of positive minimum-air-temperature days and the timing of bare ice appearance are significant interannual synoptic controls. We use these findings to identify the surface processes which are most likely to explain recent dark ice dynamics. We suggest that whilst the spatial distribution of dark ice is best explained by outcropping of particulates from

Influence of winter sea-ice motion on summer ice cover in the Arctic

Directory of Open Access Journals (Sweden)

Noriaki Kimura

2013-11-01

Full Text Available Summer sea-ice cover in the Arctic varies largely from year to year owing to several factors. This study examines one such factor, the relationship between interannual difference in winter ice motion and ice area in the following summer. A daily-ice velocity product on a 37.5-km resolution grid is prepared using the satellite passive microwave sensor Advanced Microwave Scanning Radiometer—Earth Observing System data for the nine years of 2003–2011. Derived daily-ice motion reveals the dynamic modification of the winter ice cover. The winter ice divergence/convergence is strongly related to the summer ice cover in some regions; the correlation coefficient between the winter ice convergence and summer ice area ranges between 0.5 and 0.9 in areas with high interannual variability. This relation implies that the winter ice redistribution controls the spring ice thickness and the summer ice cover.

Organic molecules in the polar ice: from chemical analysis to environmental proxies

Science.gov (United States)

Barbante, Carlo; Zennaro, Piero; Giorio, Chiara; Kehrwald, Natalie; Benton, Alisa K.; Wolff, Eric W.; Kalberer, Markus; Kirchgeorg, Torben; Zangrando, Roberta; Barbaro, Elena; Gambaro, Andrea

2015-04-01

The molecular and isotopic compositions of organic matter buried in ice contains information that helps reconstruct past environmental conditions, evaluate histories of climate change, and assess impacts of humans on ecosystems. In recent years novel analytical techniques were developed to quantify molecular compounds in ice cores. As an example, biomass burning markers, including monosaccharide anhydrides, lightweight carboxylic acids, lignin and resin pyrolysis products, black carbon, and charcoal records help in reconstructing past fire activity across seasonal to millennial time scales. Terrestrial biomarkers, such as plant waxes (e.g. long-chain n-alkanes) are also a promising paleo vegetation proxy in ice core studies. Polycyclic aromatic hydrocarbons are ubiquitous pollutants recently detected in ice cores. These hydrocarbons primarily originate from incomplete combustion of organic matter and fossil fuels (e.g. diesel engines, domestic heating, industrial combustion) and therefore can be tracers of past combustion activities. In order to be suitable for paloeclimate purposes, organic molecular markers detected in ice cores should include the following important features. Markers have to be stable under oxidizing atmospheric conditions, and ideally should not react with hydroxyl radicals, during their transport to polar regions. Organic markers must be released in large amounts in order to be detected at remote distances from the sources. Proxies must be specific, in order to differentiate them from other markers with multiple sources. The extraction of glaciochemical information from ice cores is challenging due to the low concentrations of some impurities, thereby demanding rigorous control of external contamination sources and sensitive analytical techniques. Here, we review the analysis and use of organic molecules in ice as proxies of important environmental and climatic processes.

Evidence for middle Eocene Arctic sea ice from diatoms and ice-rafted debris.

Science.gov (United States)

Stickley, Catherine E; St John, Kristen; Koç, Nalân; Jordan, Richard W; Passchier, Sandra; Pearce, Richard B; Kearns, Lance E

2009-07-16

Oceanic sediments from long cores drilled on the Lomonosov ridge, in the central Arctic, contain ice-rafted debris (IRD) back to the middle Eocene epoch, prompting recent suggestions that ice appeared in the Arctic about 46 million years (Myr) ago. However, because IRD can be transported by icebergs (derived from land-based ice) and also by sea ice, IRD records are restricted to providing a history of general ice-rafting only. It is critical to differentiate sea ice from glacial (land-based) ice as climate feedback mechanisms vary and global impacts differ between these systems: sea ice directly affects ocean-atmosphere exchanges, whereas land-based ice affects sea level and consequently ocean acidity. An earlier report assumed that sea ice was prevalent in the middle Eocene Arctic on the basis of IRD, and although somewhat preliminary supportive evidence exists, these data are neither comprehensive nor quantified. Here we show the presence of middle Eocene Arctic sea ice from an extraordinary abundance of a group of sea-ice-dependent fossil diatoms (Synedropsis spp.). Analysis of quartz grain textural characteristics further supports sea ice as the dominant transporter of IRD at this time. Together with new information on cosmopolitan diatoms and existing IRD records, our data strongly suggest a two-phase establishment of sea ice: initial episodic formation in marginal shelf areas approximately 47.5 Myr ago, followed approximately 0.5 Myr later by the onset of seasonally paced sea-ice formation in offshore areas of the central Arctic. Our data establish a 2-Myr record of sea ice, documenting the transition from a warm, ice-free environment to one dominated by winter sea ice at the start of the middle Eocene climatic cooling phase.

Extractive method for obtaining gas inclusions from ice

International Nuclear Information System (INIS)

Strauch, G.; Kowski, P.

1982-01-01

Doubtless important for glaciological investigations of firn and ice is the knowledge about the chemical composition of gases included in ice. A method for quantitative extraction of gases from about 30 kg ice under vacuum is presented in this paper. The procedure was tested with ice cores from a thermoelectrical drill hole near Soviet Antarctic station Novolazarevskaya. The chemical compositions of inclusion gases and the specific gas contents from 6 horizons are pointed out by a table and some graphics. (author)

Use of water stable isotopes in climatology and paleoclimatology illustrated from polar ice cores studies

International Nuclear Information System (INIS)

Jouzel, J.; Lorius, C.

1994-01-01

The isotopic content of ancient waters (deuterium and oxygen 18) gives a key access to past climatic changes. An essentially linear relationship exists between the isotopic content of a precipitation and the temperature of the site (at least for medium and high latitudes). This link between water isotope atmospheric cycle and climate is presented through various isotopic models and illustrated from the deuterium profile obtained along the Vostok ice core in East Antarctica. This 2 km record which covers a full glacial-interglacial cycle (160000 years) confirms the existence of a link between insolation changes and climate (Milankovitch theory). It shows also that the greenhouse effect has played a role in glacial-interglacial changes in amplifying this orbital forcing. (authors). 10 figs., 23 refs

Decoherence in Neutrino Propagation Through Matter, and Bounds from IceCube/DeepCore

Energy Technology Data Exchange (ETDEWEB)

Coloma, Pilar [Fermilab; Lopez-Pavon, Jacobo [CERN; Martinez-Soler, Ivan [Madrid, IFT; Nunokawa, Hiroshi [Rio de Janeiro, Pont. U. Catol.

2018-03-12

We revisit neutrino oscillations in matter considering the open quantum system framework which allows to introduce possible decoherence effects generated by New Physics in a phenomenological manner. We assume that the decoherence parameters $\\gamma_{ij}$ may depend on the neutrino energy, as $\\gamma_{ij}=\\gamma_{ij}^{0}(E/\\text{GeV})^n$ $(n = 0,\\pm1,\\pm2) $. The case of non-uniform matter is studied in detail, both within the adiabatic approximation and in the more general non-adiabatic case. In particular, we develop a consistent formalism to study the non-adiabatic case dividing the matter profile into an arbitrary number of layers of constant densities. This formalism is then applied to explore the sensitivity of IceCube and DeepCore to this type of effects. Our study is the first atmospheric neutrino analysis where a consistent treatment of the matter effects in the three-neutrino case is performed in presence of decoherence. We show that matter effects are indeed extremely relevant in this context. We find that IceCube is able to considerably improve over current bounds in the solar sector ($\\gamma_{21}$) and in the atmospheric sector ($\\gamma_{31}$ and $\\gamma_{32}$) for $n=0,1,2$ and, in particular, by several orders of magnitude (between 3 and 9) for the $n=1,2$ cases. For $n=0$ we find $\\gamma_{32},\\gamma_{31}< 4.0\\cdot10^{-24} (1.3\\cdot10^{-24})$ GeV and $\\gamma_{21}<1.3\\cdot10^{-24} (4.1\\cdot10^{-24})$ GeV, for normal (inverted) mass ordering.

Halogen species record Antarctic sea ice extent over glacial–interglacial periods

Directory of Open Access Journals (Sweden)

A. Spolaor

2013-07-01

Full Text Available Sea ice is an integral part of the earth's climate system because it affects planetary albedo, sea-surface salinity, and the atmosphere–ocean exchange of reactive gases and aerosols. Bromine and iodine chemistry is active at polar sea ice margins with the occurrence of bromine explosions and the biological production of organoiodine from sea ice algae. Satellite measurements demonstrate that concentrations of bromine oxide (BrO and iodine oxide (IO decrease over sea ice toward the Antarctic interior. Here we present speciation measurements of bromine and iodine in the TALDICE (TALos Dome Ice CorE ice core (159°11' E, 72°49' S; 2315 m a.s.l. spanning the last 215 ky. The Talos Dome ice core is located 250 km inland and is sensitive to marine air masses intruding onto the Antarctic Plateau. Talos Dome bromide (Br− is positively correlated with temperature and negatively correlated with sodium (Na. Based on the Br−/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I− and iodate (IO3−, peaks during glacials with lower values during interglacial periods. Although IO3− is considered the most stable iodine species in the atmosphere it was only observed in the TALDICE record during glacial maxima. Sea ice dynamics are arguably the primary driver of halogen fluxes over glacial–interglacial timescales, by altering the distance between the sea ice edge and the Antarctic plateau and by altering the surface area of sea ice available to algal colonization. Based on our results we propose the use of both halogens for examining Antarctic variability of past sea ice extent.

Multiphase Reactive Transport and Platelet Ice Accretion in the Sea Ice of McMurdo Sound, Antarctica

Science.gov (United States)

Buffo, J. J.; Schmidt, B. E.; Huber, C.

2018-01-01

Sea ice seasonally to interannually forms a thermal, chemical, and physical boundary between the atmosphere and hydrosphere over tens of millions of square kilometers of ocean. Its presence affects both local and global climate and ocean dynamics, ice shelf processes, and biological communities. Accurate incorporation of sea ice growth and decay, and its associated thermal and physiochemical processes, is underrepresented in large-scale models due to the complex physics that dictate oceanic ice formation and evolution. Two phenomena complicate sea ice simulation, particularly in the Antarctic: the multiphase physics of reactive transport brought about by the inhomogeneous solidification of seawater, and the buoyancy driven accretion of platelet ice formed by supercooled ice shelf water onto the basal surface of the overlying ice. Here a one-dimensional finite difference model capable of simulating both processes is developed and tested against ice core data. Temperature, salinity, liquid fraction, fluid velocity, total salt content, and ice structure are computed during model runs. The model results agree well with empirical observations and simulations highlight the effect platelet ice accretion has on overall ice thickness and characteristics. Results from sensitivity studies emphasize the need to further constrain sea ice microstructure and the associated physics, particularly permeability-porosity relationships, if a complete model of sea ice evolution is to be obtained. Additionally, implications for terrestrial ice shelves and icy moons in the solar system are discussed.

Ice stratigraphy at the Pakitsoq ice margin, West Greenland, derived from gas records

DEFF Research Database (Denmark)

Schaefer, H.; Petrenko, V. V.; Brook, E. J.

2009-01-01

at Pakitsoq. Sections containing ice from every distinct climatic interval during Termination I, including Last Glacial Maximum, Bolling/Allerod, Younger Dryas and the early Holocene, are identified. In the early Holocene, we find evidence for climatic fluctuations similar to signals found in deep ice cores...... from Greenland. A second glacial-interglacial transition exposed at the extreme margin of the ice is identified as another outcrop of Termination I (rather than the onset of the Eemian interglacial as postulated in earlier work). Consequently, the main structural feature at Pakitsoq is a large......-scale anticline with accordion-type folding in both exposed sequences of the glacial-Holocene transition, leading to multiple layer duplications and age reversals....

What drove the methane cycle in the past - evidence from carbon isotopic data of methane enclosed in polar ice cores

OpenAIRE

Möller, Lars

2013-01-01

During the last glacial cycle, greenhouse gas concentrations fluctuated on decadal and longer timescales. Concentrations of methane, as measured in polar ice cores, show a close connection with Northern Hemisphere temperature variability, but the contribution of the various methane sources and sinks to changes in concentration is still a matter of debate. This thesis assess changes in methane cycling over the past 160,000 years by measurements of the carbon isotopic composition d13C of methan...

Abrupt rise in atmospheric CO2 at the onset of the Bølling/Allerød: in-situ ice core data versus true atmospheric signals

Directory of Open Access Journals (Sweden)

J. Chappellaz

2011-05-01

Full Text Available During the last glacial/interglacial transition the Earth's climate underwent abrupt changes around 14.6 kyr ago. Temperature proxies from ice cores revealed the onset of the Bølling/Allerød (B/A warm period in the north and the start of the Antarctic Cold Reversal in the south. Furthermore, the B/A was accompanied by a rapid sea level rise of about 20 m during meltwater pulse (MWP 1A, whose exact timing is a matter of current debate. In-situ measured CO2 in the EPICA Dome C (EDC ice core also revealed a remarkable jump of 10 ± 1 ppmv in 230 yr at the same time. Allowing for the modelled age distribution of CO2 in firn, we show that atmospheric CO2 could have jumped by 20–35 ppmv in less than 200 yr, which is a factor of 2–3.5 greater than the CO2 signal recorded in-situ in EDC. This rate of change in atmospheric CO2 corresponds to 29–50% of the anthropogenic signal during the last 50 yr and is connected with a radiative forcing of 0.59–0.75 W m−2. Using a model-based airborne fraction of 0.17 of atmospheric CO2, we infer that 125 Pg of carbon need to be released into the atmosphere to produce such a peak. If the abrupt rise in CO2 at the onset of the B/A is unique with respect to other Dansgaard/Oeschger (D/O events of the last 60 kyr (which seems plausible if not unequivocal based on current observations, then the mechanism responsible for it may also have been unique. Available δ13CO2 data are neutral, whether the source of the carbon is of marine or terrestrial origin. We therefore hypothesise that most of the carbon might have been activated as a consequence of continental shelf flooding during MWP-1A. This potential impact of rapid sea level rise on atmospheric CO2 might define the point of no return during the last deglaciation.

Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact approximate to 12,800 Years Ago. 1. Ice Cores and Glaciers

Czech Academy of Sciences Publication Activity Database

Wolbach, W. S.; Ballard, J. P.; Mayewski, P. A.; Adedeji, V.; Bunch, T. E.; Firestone, R. B.; French, T. A.; Howard, G. A.; Israde-Alcántara, I.; Johnson, J. R.; Kimbel, D. R.; Kinzie, Ch. R.; Kurbatov, A.; Kletetschka, Günther; LeCompte, M. A.; Mahaney, W. C.; Mellot, A. L.; Maiorana-Boutilier, A.; Mitra, S.; Moore, Ch. R.; Napier, W. M.; Parlier, J.; Tankersley, K. B.; Thomas, B. C.; Wittke, J. H.; West, A.; Kennett, J. P.

2018-01-01

Roč. 126, č. 2 (2018), s. 165-184 ISSN 0022-1376 Institutional support: RVO:67985831 Keywords : biomass burning * comet * deposition * ice core * impact * mass extinction * paleoclimate * paleoenvironment * platinum * trigger mechanism * wildfire * winter * Younger Dryas Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 1.952, year: 2016

Isotope Reanalysis for 20th century: Reproduction of isotopic time series in corals, tree-rings, and tropical ice cores

Science.gov (United States)

Yoshimura, K.

2012-04-01

In the present study, an isotope-incorporated GCM simulation for AD1871 to AD2008 nudged toward the so-called "20th Century Reanalysis (20CR)" atmospheric fields is conducted. Beforehand the long-term integration, a method to downscale ensemble mean fields is proposed, since 20CR is a product of 56-member ensemble Kalman filtering data assimilation. The method applies a correction to one of the ensemble members in such a way that the seasonal mean is equal to that of the ensemble mean, and then the corrected member is inputted into the isotope-incorporated GCM (i.e., IsoGSM) with the global spectral nudging technique. Use of the method clearly improves the skill than the cases of using only a single member and of using the ensemble means; the skill becomes equivalent to when 3-6 members are directly used. By comparing with GNIP precipitation isotope database, it is confirmed that the 20C Isotope Reanalysis's performance for latter half of the 20th century is just comparable to the other latest studies. For more comparisons for older periods, proxy records including corals, tree-rings, and tropical ice cores are used. First for corals: the 20C Isotope Reanalysis successfully reproduced the δ18O in surface sea water recorded in the corals at many sites covering large parts of global tropical oceans. The comparison suggests that coral records represent past hydrologic balance information where interannual variability in precipitation is large. Secondly for tree-rings: δ18O of cellulose extracted from the annual rings of the long-lived Bristlecone Pine from White Mountain in Southern California is well reproduced by 20C Isotope Reanalysis. Similar good performance is obtained for Cambodia, too. However, the mechanisms driving the isotopic variations are different over California and Cambodia; for California, Hadley cell's expansion and consequent meridional shift of the submerging dry zone and changes in water vapor source is the dominant control, but in Cambodia

An Extraction System for Radiocarbon Microanalysis of Dissolved Organic Carbon in Glacier Ice

OpenAIRE

Schindler, Johannes

2017-01-01

Alpine glaciers situated in mid- and low latitudes are valuable archives for paleoclimatology. They offer a continuous record of recent local climatic conditions in regions where the majority of humankind lived and still lives. For meaningful interpretation of an ice core from such an archive, accurate dating is essential. Usually, several complementary approaches are used to establish a depth-age relationship. The oldest part of the ice at the bottom of the ice core suffers annual layer thin...

High-precision dual-inlet IRMS measurements of the stable isotopes of CO2 and the N2O / CO2 ratio from polar ice core samples

Directory of Open Access Journals (Sweden)

T. K. Bauska

2014-11-01

Full Text Available An important constraint on mechanisms of past carbon cycle variability is provided by the stable isotopic composition of carbon in atmospheric carbon dioxide (δ13C-CO2 trapped in polar ice cores, but obtaining very precise measurements has proven to be a significant analytical challenge. Here we describe a new technique to determine the δ13C of CO2 at very high precision, as well as measuring the CO2 and N2O mixing ratios. In this method, ancient air is extracted from relatively large ice samples (~400 g with a dry-extraction "ice grater" device. The liberated air is cryogenically purified to a CO2 and N2O mixture and analyzed with a microvolume-equipped dual-inlet IRMS (Thermo MAT 253. The reproducibility of the method, based on replicate analysis of ice core samples, is 0.02‰ for δ13C-CO2 and 2 ppm and 4 ppb for the CO2 and N2O mixing ratios, respectively (1σ pooled standard deviation. Our experiments show that minimizing water vapor pressure in the extraction vessel by housing the grating apparatus in a ultralow-temperature freezer (−60 °C improves the precision and decreases the experimental blank of the method to −0.07 ± 0.04‰. We describe techniques for accurate calibration of small samples and the application of a mass-spectrometric method based on source fragmentation for reconstructing the N2O history of the atmosphere. The oxygen isotopic composition of CO2 is also investigated, confirming previous observations of oxygen exchange between gaseous CO2 and solid H2O within the ice archive. These data offer a possible constraint on oxygen isotopic fractionation during H2O and CO2 exchange below the H2O bulk melting temperature.

Sea Ice Summer Camp: Bringing Together Arctic Sea Ice Modelers and Observers

Science.gov (United States)

Perovich, D. K.; Holland, M. M.

2016-12-01

The Arctic sea ice has undergone dramatic change and numerical models project this to continue for the foreseeable future. Understanding the mechanisms behind sea ice loss and its consequences for the larger Arctic and global systems is of critical importance if we are to anticipate and plan for the future. One impediment to progress is a disconnect between the observational and modeling communities. A sea ice summer camp was held in Barrow Alaska from 26 May to 1 June 2016 to overcome this impediment and better integrate the sea ice community. The 25 participants were a mix of modelers and observers from 13 different institutions at career stages from graduate student to senior scientist. The summer camp provided an accelerated program on sea ice observations and models and also fostered future collaborative interdisciplinary activities. Each morning was spent in the classroom with a daily lecture on an aspect of modeling or remote sensing followed by practical exercises. Topics included using models to assess sensitivity, to test hypotheses and to explore sources of uncertainty in future Arctic sea ice loss. The afternoons were spent on the ice making observations. There were four observational activities; albedo observations, ice thickness measurements, ice coring and physical properties, and ice morphology surveys. The last field day consisted of a grand challenge where the group formulated a hypothesis, developed an observational and modeling strategy to test the hypothesis, and then integrated the observations and model results. The impacts of changing sea ice are being felt today in Barrow Alaska. We opened a dialog with Barrow community members to further understand these changes. This included an evening discussion with two Barrow sea ice experts and a community presentation of our work in a public lecture at the Inupiat Heritage Center.

Core-collapse supernovae as possible counterparts of IceCube neutrino multiplets

Energy Technology Data Exchange (ETDEWEB)

Strotjohann, Nora Linn; Kowalski, Marek; Franckowiak, Anna [DESY, Zeuthen (Germany); Voge, Markus [Bonn Univ. (Germany). Physikalisches Institut; Collaboration: IceCube-Collaboration

2016-07-01

While an astrophysical neutrino flux has been detected by the IceCube Neutrino Observatory its sources remain so far unidentified. IceCube's Optical Follow-up Program is designed to search for the counterparts of neutrino multiplets using the full energy range of the IceCube detector down to 100 GeV. Two or more muon neutrinos arriving from the same direction within few seconds can trigger follow-up observations with optical and X-ray telescopes. Since 2010 the Palomar Transient Factory has followed up about 40 such neutrino alerts and detected several supernovae. Many of the detections are however likely random coincidences. In this talk I describe our search for supernovae and the prospects of identifying a supernova as a source of high-energy neutrinos.

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).

Late Holocene sea ice conditions in Herald Canyon, Chukchi Sea

Science.gov (United States)

Pearce, C.; O'Regan, M.; Rattray, J. E.; Hutchinson, D. K.; Cronin, T. M.; Gemery, L.; Barrientos, N.; Coxall, H.; Smittenberg, R.; Semiletov, I. P.; Jakobsson, M.

2017-12-01

Sea ice in the Arctic Ocean has been in steady decline in recent decades and, based on satellite data, the retreat is most pronounced in the Chukchi and Beaufort seas. Historical observations suggest that the recent changes were unprecedented during the last 150 years, but for a longer time perspective, we rely on the geological record. For this study, we analyzed sediment samples from two piston cores from Herald Canyon in the Chukchi Sea, collected during the 2014 SWERUS-C3 Arctic Ocean Expedition. The Herald Canyon is a local depression across the Chukchi Shelf, and acts as one of the main pathways for Pacific Water to the Arctic Ocean after entering through the narrow and shallow Bering Strait. The study site lies at the modern-day seasonal sea ice minimum edge, and is thus an ideal location for the reconstruction of past sea ice variability. Both sediment cores contain late Holocene deposits characterized by high sediment accumulation rates (100-300 cm/kyr). Core 2-PC1 from the shallow canyon flank (57 m water depth) is 8 meter long and extends back to 4200 cal yrs BP, while the upper 3 meters of Core 4-PC1 from the central canyon (120 mwd) cover the last 3000 years. The chronologies of the cores are based on radiocarbon dates and the 3.6 ka Aniakchak CFE II tephra, which is used as an absolute age marker to calculate the marine radiocarbon reservoir age. Analysis of biomarkers for sea ice and surface water productivity indicate stable sea ice conditions throughout the entire late Holocene, ending with an abrupt increase of phytoplankton sterols in the very top of both sediment sequences. The shift is accompanied by a sudden increase in coarse sediments (> 125 µm) and a minor change in δ13Corg. We interpret this transition in the top sediments as a community turnover in primary producers from sea ice to open water biota. Most importantly, our results indicate that the ongoing rapid ice retreat in the Chukchi Sea of recent decades was unprecedented during the

Diversity of Holocene life forms in fossil glacier ice

DEFF Research Database (Denmark)

Willerslev, E.; Hansen, Anders J.; Christensen, B.

1999-01-01

Studies of biotic remains of polar ice caps have been limited to morphological identification of plant pollen and spores. By using sensitive molecular techniques, we now demonstrate a much greater range of detectable organisms; from 2000- and 4000-year-old ice-core samples, we obtained...

Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals

Science.gov (United States)

Charrassin, J.-B.; Hindell, M.; Rintoul, S. R.; Roquet, F.; Sokolov, S.; Biuw, M.; Costa, D.; Boehme, L.; Lovell, P.; Coleman, R.; Timmermann, R.; Meijers, A.; Meredith, M.; Park, Y.-H.; Bailleul, F.; Goebel, M.; Tremblay, Y.; Bost, C.-A.; McMahon, C. R.; Field, I. C.; Fedak, M. A.; Guinet, C.

2008-01-01

Polar regions are particularly sensitive to climate change, with the potential for significant feedbacks between ocean circulation, sea ice, and the ocean carbon cycle. However, the difficulty in obtaining in situ data means that our ability to detect and interpret change is very limited, especially in the Southern Ocean, where the ocean beneath the sea ice remains almost entirely unobserved and the rate of sea-ice formation is poorly known. Here, we show that southern elephant seals (Mirounga leonina) equipped with oceanographic sensors can measure ocean structure and water mass changes in regions and seasons rarely observed with traditional oceanographic platforms. In particular, seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone, allowing the major fronts to be mapped south of 60°S and sea-ice formation rates to be inferred from changes in upper ocean salinity. Sea-ice production rates peaked in early winter (April–May) during the rapid northward expansion of the pack ice and declined by a factor of 2 to 3 between May and August, in agreement with a three-dimensional coupled ocean–sea-ice model. By measuring the high-latitude ocean during winter, elephant seals fill a “blind spot” in our sampling coverage, enabling the establishment of a truly global ocean-observing system. PMID:18695241

Where is the 1-million-year-old ice at Dome A?

Science.gov (United States)

Zhao, Liyun; Moore, John C.; Sun, Bo; Tang, Xueyuan; Guo, Xiaoran

2018-05-01

Ice fabric influences the rheology of ice, and hence the age-depth profile at ice core drilling sites. To investigate the age-depth profile to be expected of the ongoing deep ice coring at Kunlun station, Dome A, we use the depth-varying anisotropic fabric suggested by the recent polarimetric measurements around Dome A along with prescribed fabrics ranging from isotropic through girdle to single maximum in a three-dimensional, thermo-mechanically coupled full-Stokes model of a 70 × 70 km2 domain around Kunlun station. This model allows for the simulation of the near basal ice temperature and age, and ice flow around the location of the Chinese deep ice coring site. Ice fabrics and geothermal heat flux strongly affect the vertical advection and basal temperature which consequently control the age profile. Constraining modeled age-depth profiles with dated radar isochrones to 2/3 ice depth, the surface vertical velocity, and also the spatial variability of a radar isochrones dated to 153.3 ka BP, limits the age of the deep ice at Kunlun to between 649 and 831 ka, a much smaller range than previously inferred. The simple interpretation of the polarimetric radar fabric data that we use produces best fits with a geothermal heat flux of 55 mW m-2. A heat flux of 50 mW m-2 is too low to fit the deeper radar layers, and 60 mW m-2 leads to unrealistic surface velocities. The modeled basal temperature at Kunlun reaches the pressure melting point with a basal melting rate of 2.2-2.7 mm a-1. Using the spatial distribution of basal temperatures and the best fit fabric suggests that within 400 m of Kunlun station, 1-million-year-old ice may be found 200 m above the bed, and that there are large regions where even older ice is well above the bedrock within 5-6 km of the Kunlun station.

Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records

DEFF Research Database (Denmark)

Walker, Mike; Johnsen, Sigfus Johann; Rasmussen, Sune Olander

2009-01-01

The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs...... the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene-Holocene boundary have also been recognised....

The carbon dioxide content in ice cores - climatic curves of carbon dioxide. Zu den CO sub 2 -Klimakurven aus Eisbohrkernen

Energy Technology Data Exchange (ETDEWEB)

Heyke, H.E.

1992-05-01

The 'greenhouse effect', which implies a temperature of 15 deg C as against -18 deg C, owes its effect to 80% from water (clouds and gaseous phase) and to 10% from carbon dioxide, besides other components. Whereas water is largely unaccounted for, carbon dioxide has been postulated as the main cause of anticipated climatic catastrophe. The carbon dioxide concentration in the atmosphere has risen presently to such levels that all previous figures seem to have been left far behind. The reference point is the concentration of carbon dioxide in the air bubbles trapped in ice cores of Antartic and Greenland ice dated 160 000 years ago, which show much lower values than at present. A review of the most relevant publications indicates that many basic laws of chemistry seem to have been left largely unconsidered and experimental errors have made the results rather doubtful. Appropriate arguments have been presented. The investigations considered should be repeated under improved and more careful conditions. (orig.).

Contrasting evidence of Holocene ice margin retreat, south-western Greenland

DEFF Research Database (Denmark)

Levy, L. B.; Larsen, N. K.; Davidson, T. A.

2017-01-01

Constraining the Greenland Ice Sheet's (GrIS) response to Holocene climate change provides calibrations for ice sheet models that hindcast past ice margin fluctuations. Ice sheet models predict enhanced ice retreat in south-western Greenland during the middle Holocene; however, few geological...... observations corroborating the extensive retreat are available. We present new data from lake sediment cores from the Isua region, south-western Greenland, which provide constraints on Holocene fluctuations of the GrIS margins. Our data indicate that the main GrIS margin was 30 km west of its present...

Near-Surface Profiles of Water Stable Isotope Components and Indicated Transitional History of Ice-Wedge Polygons Near Barrow

Science.gov (United States)

Iwahana, G.; Wilson, C.; Newman, B. D.; Heikoop, J. M.; Busey, R.

2017-12-01

Wetlands associated with ice-wedge polygons are commonly distributed across the Arctic Coastal Plain of northern Alaska, a region underlain by continuous permafrost. Micro-topography of the ice-wedge polygons controls local hydrology, and the micro-topography could be altered due to factors such like surface vegetation, wetness, freeze-thaw cycles, and permafrost degradation/aggradation under climate change. Understanding status of the wetlands in the near future is important because it determines biogeochemical cycle, which drives release of greenhouse gases from the ground. However, transitional regime of the ice-wedge polygons under the changing climate is not fully understood. In this study, we analyzed geochemistry of water extracted from frozen soil cores sampled down to about 1m depth in 2014 March at NGEE-Arctic sites in the Barrow Environmental Observatory. The cores were sampled from troughs/rims/centers of five different low-centered or flat-centered polygons. The frozen cores are divided into 5-10cm cores for each location, thawed in sealed plastic bags, and then extracted water was stored in vials. Comparison between the profiles of geochemistry indicated connection of soil water in the active layer at different location in a polygon, while it revealed that distinctly different water has been stored in permafrost layer at troughs/rims/centers of some polygons. Profiles of volumetric water content (VWC) showed clear signals of freeze-up desiccation in the middle of saturated active layers as low VWC anomalies at most sampling points. Water in the active layer and near-surface permafrost was classified into four categories: ice wedge / fresh meteoric / transitional / highly fractionated water. The overall results suggested prolonged separation of water in the active layer at the center of low-centered polygons without lateral connection in water path in the past.

EBSD analysis of subgrain boundaries and dislocation slip systems in Antarctic and Greenland ice

Science.gov (United States)

Weikusat, Ilka; Kuiper, Ernst-Jan N.; Pennock, Gill M.; Kipfstuhl, Sepp; Drury, Martyn R.

2017-09-01

Ice has a very high plastic anisotropy with easy dislocation glide on basal planes, while glide on non-basal planes is much harder. Basal glide involves dislocations with the Burgers vector b = 〈a〉, while glide on non-basal planes can involve dislocations with b = 〈a〉, b = [c], and b = 〈c + a〉. During the natural ductile flow of polar ice sheets, most of the deformation is expected to occur by basal slip accommodated by other processes, including non-basal slip and grain boundary processes. However, the importance of different accommodating processes is controversial. The recent application of micro-diffraction analysis methods to ice, such as X-ray Laue diffraction and electron backscattered diffraction (EBSD), has demonstrated that subgrain boundaries indicative of non-basal slip are present in naturally deformed ice, although so far the available data sets are limited. In this study we present an analysis of a large number of subgrain boundaries in ice core samples from one depth level from two deep ice cores from Antarctica (EPICA-DML deep ice core at 656 m of depth) and Greenland (NEEM deep ice core at 719 m of depth). EBSD provides information for the characterization of subgrain boundary types and on the dislocations that are likely to be present along the boundary. EBSD analyses, in combination with light microscopy measurements, are presented and interpreted in terms of the dislocation slip systems. The most common subgrain boundaries are indicative of basal 〈a〉 slip with an almost equal occurrence of subgrain boundaries indicative of prism [c] or 〈c + a〉 slip on prism and/or pyramidal planes. A few subgrain boundaries are indicative of prism 〈a〉 slip or slip of 〈a〉 screw dislocations on the basal plane. In addition to these classical polygonization processes that involve the recovery of dislocations into boundaries, alternative mechanisms are discussed for the formation of subgrain boundaries that are not related to the

Plans and Preliminary Results of Fundamental Studies of Ice Crystal Icing Physics in the NASA Propulsion Systems Laboratory

Science.gov (United States)

Struk, Peter; Tsao, Jen-Ching; Bartkus, Tadas

2017-01-01

This paper describes plans and preliminary results for using the NASA Propulsion Systems Lab (PSL) to experimentally study the fundamental physics of ice-crystal ice accretion. NASA is evaluating whether this facility, in addition to full-engine and motor-driven-rig tests, can be used for more fundamental ice-accretion studies that simulate the different mixed-phase icing conditions along the core flow passage of a turbo-fan engine compressor. The data from such fundamental accretion tests will be used to help develop and validate models of the accretion process. This paper presents data from some preliminary testing performed in May 2015 which examined how a mixed-phase cloud could be generated at PSL using evaporative cooling in a warmer-than-freezing environment.

Inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate.

Science.gov (United States)

Damodaran, Srinivasan

2007-12-26

The inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate produced by papain action was studied. The ice crystal growth was monitored by thermal cycling between -14 and -12 degrees C at a rate of one cycle per 3 min. It is shown that the hydrolysate fraction containing peptides in the molecular weight range of about 2000-5000 Da exhibited the highest inhibitory activity on ice crystal growth in ice cream mix, whereas fractions containing peptides greater than 7000 Da did not inhibit ice crystal growth. The size distribution of gelatin peptides formed in the hydrolysate was influenced by the pH of hydrolysis. The optimum hydrolysis conditions for producing peptides with maximum ice crystal growth inhibitory activity was pH 7 at 37 degrees C for 10 min at a papain to gelatin ratio of 1:100. However, this may depend on the type and source of gelatin. The possible mechanism of ice crystal growth inhibition by peptides from gelatin is discussed. Molecular modeling of model gelatin peptides revealed that they form an oxygen triad plane at the C-terminus with oxygen-oxygen distances similar to those found in ice nuclei. Binding of this oxygen triad plane to the prism face of ice nuclei via hydrogen bonding appears to be the mechanism by which gelatin hydrolysate might be inhibiting ice crystal growth in ice cream mix.

An optimized multi-proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012): 120-800 ka

Science.gov (United States)

Bazin, L.; Landais, A.; Lemieux-Dudon, B.; Toyé Mahamadou Kele, H.; Veres, D.; Parrenin, F.; Martinerie, P.; Ritz, C.; Capron, E.; Lipenkov, V.; Loutre, M.-F.; Raynaud, D.; Vinther, B.; Svensson, A.; Rasmussen, S. O.; Severi, M.; Blunier, T.; Leuenberger, M.; Fischer, H.; Masson-Delmotte, V.; Chappellaz, J.; Wolff, E.

2013-08-01

An accurate and coherent chronological framework is essential for the interpretation of climatic and environmental records obtained from deep polar ice cores. Until now, one common ice core age scale had been developed based on an inverse dating method (Datice), combining glaciological modelling with absolute and stratigraphic markers between 4 ice cores covering the last 50 ka (thousands of years before present) (Lemieux-Dudon et al., 2010). In this paper, together with the companion paper of Veres et al. (2013), we present an extension of this work back to 800 ka for the NGRIP, TALDICE, EDML, Vostok and EDC ice cores using an improved version of the Datice tool. The AICC2012 (Antarctic Ice Core Chronology 2012) chronology includes numerous new gas and ice stratigraphic links as well as improved evaluation of background and associated variance scenarios. This paper concentrates on the long timescales between 120-800 ka. In this framework, new measurements of δ18Oatm over Marine Isotope Stage (MIS) 11-12 on EDC and a complete δ18Oatm record of the TALDICE ice cores permit us to derive additional orbital gas age constraints. The coherency of the different orbitally deduced ages (from δ18Oatm, δO2/N2 and air content) has been verified before implementation in AICC2012. The new chronology is now independent of other archives and shows only small differences, most of the time within the original uncertainty range calculated by Datice, when compared with the previous ice core reference age scale EDC3, the Dome F chronology, or using a comparison between speleothems and methane. For instance, the largest deviation between AICC2012 and EDC3 (5.4 ka) is obtained around MIS 12. Despite significant modifications of the chronological constraints around MIS 5, now independent of speleothem records in AICC2012, the date of Termination II is very close to the EDC3 one.

Evidence for ice-ocean albedo feedback in the Arctic Ocean shifting to a seasonal ice zone.

Science.gov (United States)

Kashiwase, Haruhiko; Ohshima, Kay I; Nihashi, Sohey; Eicken, Hajo

2017-08-15

Ice-albedo feedback due to the albedo contrast between water and ice is a major factor in seasonal sea ice retreat, and has received increasing attention with the Arctic Ocean shifting to a seasonal ice cover. However, quantitative evaluation of such feedbacks is still insufficient. Here we provide quantitative evidence that heat input through the open water fraction is the primary driver of seasonal and interannual variations in Arctic sea ice retreat. Analyses of satellite data (1979-2014) and a simplified ice-upper ocean coupled model reveal that divergent ice motion in the early melt season triggers large-scale feedback which subsequently amplifies summer sea ice anomalies. The magnitude of divergence controlling the feedback has doubled since 2000 due to a more mobile ice cover, which can partly explain the recent drastic ice reduction in the Arctic Ocean.

Wave inhibition by sea ice enables trans-Atlantic ice rafting of debris during Heinrich Events

Science.gov (United States)

Wagner, T. J. W.; Dell, R.; Eisenman, I.; Keeling, R. F.; Padman, L.; Severinghaus, J. P.

2017-12-01

The thickness of the ice-rafted debris (IRD) layers that signal Heinrich Events declines far more gradually with distance from the iceberg sources than would be expected based on present-day iceberg trajectories. Here we model icebergs as passive Lagrangian tracers driven by ocean currents, winds, and sea surface temperatures. The icebergs are released in a comprehensive climate model simulation of the last glacial maximum (LGM), as well as a simulation of the modern climate. The two simulated climates result in qualitatively similar distributions of iceberg meltwater and hence debris, with the colder temperatures of the LGM having only a relatively small effect on meltwater spread. In both scenarios, meltwater flux falls off rapidly with zonal distance from the source, in contrast with the more uniform spread of IRD in sediment cores. In order to address this discrepancy, we propose a physical mechanism that could have prolonged the lifetime of icebergs during Heinrich events. The mechanism involves a surface layer of cold and fresh meltwater formed from, and retained around, densely packed armadas of icebergs. This leads to wintertime sea ice formation even in relatively low latitudes. The sea ice in turn shields the icebergs from wave erosion, which is the main source of iceberg ablation. We find that allowing sea ice to form around all icebergs during four months each winter causes the model to approximately agree with the distribution of IRD in sediment cores.

REGULARITIES OF CONGELATION ICE DEVELOPMENT IN SUBGLACIAL LAKE VOSTOK

Directory of Open Access Journals (Sweden)

V. Ya. Lipenkov

2012-01-01

Full Text Available Petrographic studies performed on the continuous basis along the two ice cores obtained from holes 5G-1 and 5G-2 at Vostok Station has allowed to characterize with great details the evolution of the ice texture and fabric in the 232-m thick stratum of accreted ice formed from theLakeVostokwater. Conventionally the whole thickness of accreted ice is divided into two strata: lake ice 1 and lake ice 2. Lake ice 1 (3537–3618 m, formed in the sallow strait50 kmupstream of Vostok, is characterized by presence of disseminated mineral inclusions of Lake Vostok sediments, as well as of «water pockets» that represent frozen water inclusions trapped during the ice accretion. The latter constitute less than 1% of the total ice volume, their mean size is about0.5 cm. Gases trapped by «water pockets» during ice formation transform into crystalline inclusions of mixed gas hydrates. Accretion of lake ice 2 (3618–3769 m proceeds in the deep part of the lake at a very small rate that does not assume trapping of liquid water inclusions and gases.Both strata of accreted ice are formed by orthotropic crystal growth from pure water. The main tendency in the evolution of accreted ice texture is growth of the mean crystal size with depth as the lake ice becomes younger towards the ice-water interface. The high-amplitude variations of crystal size and orientation observed around this general trend are shown to be linked with temporal and spatial variability of the supercooled melt-water flux from the northern part of the lake towards the ice formation site. The presence of supercooled water at the crystallization front supports persistent preferable growth of ice crystals with sub-horizontally oriented c-axes. The lack of supercooled water in turn support persistent growth of ice crystals with vertical or inclined with respect to the crystallization front c-axis orientation. It means that each of these preferred fabric orientations could serve as an indicator of

Balance of the West Antarctic Ice Sheet

Science.gov (United States)

2002-01-01

For several decades, measurements of the West Antarctic Ice Sheet showed it to be retreating rapidly. But new data derived from satellite-borne radar sensors show the ice sheet to be growing. Changing Antarctic ice sheets remains an area of high scientific interest, particularly in light of recent global warming concerns. These new findings are significant because scientists estimate that sea level would rise 5-6 meters (16-20 feet) if the ice sheet collapsed into the sea. Do these new measurements signal the end of the ice sheet's 10,000-year retreat? Or, are these new satellite data simply much more accurate than the sparse ice core and surface measurements that produced the previous estimates? Another possibility is that the ice accumulation may simply indicate that the ice sheet naturally expands and retreats in regular cycles. Cryologists will grapple with these questions, and many others, as they examine the new data. The image above depicts the region of West Antarctica where scientists measured ice speed. The fast-moving central ice streams are shown in red. Slower tributaries feeding the ice streams are shown in blue. Green areas depict slow-moving, stable areas. Thick black lines depict the areas that collect snowfall to feed their respective ice streams. Reference: Ian Joughin and Slawek Tulaczyk Science Jan 18 2002: 476-480. Image courtesy RADARSAT Antarctic Mapping Project

Late-glacial and Holocene history of changes in Quelccaya Ice Cap, Peru

Science.gov (United States)

Kelly, M. A.; Lowell, T. V.; Schaefer, J. M.; Finkel, R. C.

2008-12-01

Quelccaya Ice Cap in the southeastern Peruvian Andes (~13-14° S latitude) is an icon for climate change. Its rapidly receding outlet, Qori Kalis Glacier, has been monitored since the 1970's. Cores from Quelccaya Ice Cap provide high-resolution information about temperature and precipitation during the past 1,500 years. We extend the understanding of past changes in Quelccaya Ice Cap based on mapping and dating of glacial moraines and associated deposits. Our results include fifty 10Be ages of moraines and bedrock as well as twenty-nine 14C ages of organic material associated with moraines. These results form the basis of a chronology of changes in Quelccaya Ice Cap from ~16,000 yr BP to late Holocene time. Results from 10Be and 14C dating indicate that Quelccaya Ice Cap experienced a significant advance at 12,700-11,400 yr BP. Subsequent to this advance, the ice margin deposited at least three recessional moraine sets. Quelccaya Ice Cap receded to near its present-day margin by ~10,000 yr BP. Neoglacial advances began by ~3,000 yr BP and culminated with a maximum advance during the Little Ice Age. This chronology fits well with prior work which indicates a restricted Quelccaya Ice Cap during middle Holocene time. Moreover, the overlap between moraine and ice core data for the last 1,500 years provides a unique opportunity to assess the influences of temperature and precipitation on past ice cap extents.

Greenland deep boreholes inform on sliding and deformation of the basal ice

Science.gov (United States)

Dahl-Jensen, D.

2017-12-01

Repeated measurements of the deformation of the deep boreholes on the Greenland ice sheet informs on the basal sliding, near basal deformation and in general on the horizontal velocity through the ice. Results of the logging of the boreholes at Dye3, GRIP, NGRIP, NEEM and Camp Century through the last 40 years by the Danish Ice and Climate group will be presented and discussed. The results on the flow will be compared with the information on ice properties, impurity load and bedrock entrained material from the deep ice cores and the radio echo sounding images near the drill sites.The results show that the basal movement often happens in an impurity rich zone above the bedrock while pure basal sliding is limited even in the presence of basal water and significant basal melt.Most of the deep ice core sites are located close to ice divides where the surface velocity is limited so significant basal sliding is not expected. Exceptions are the surface velocities at Camp Century and Dye 3, both being 13 m/yr.Finally, the ongoing deep drilling at EGRIP will shortly be presented where we are drilling in the center of the North East Greenland Ice Stream (NEGIS).

Precipitation and synoptic regime in two extreme years 2009 and 2010 at Dome C, Antarctica – implications for ice core interpretation

Directory of Open Access Journals (Sweden)

E. Schlosser

2016-04-01

Full Text Available At the East Antarctic deep ice core drilling site Dome C, daily precipitation measurements were initiated in 2006 and are being continued until today. The amounts and stable isotope ratios of the precipitation samples as well as crystal types are determined. Within the measuring period, the two years 2009 and 2010 showed striking contrasting temperature and precipitation anomalies, particularly in the winter seasons. The reasons for these anomalies are analysed using data from the mesoscale atmospheric model WRF (Weather Research and Forecasting Model run under the Antarctic Mesoscale Prediction System (AMPS. 2009 was relatively warm and moist due to frequent warm air intrusions connected to amplification of Rossby waves in the circumpolar westerlies, whereas the winter of 2010 was extremely dry and cold. It is shown that while in 2010 a strong zonal atmospheric flow was dominant, in 2009 an enhanced meridional flow prevailed, which increased the meridional transport of heat and moisture onto the East Antarctic plateau and led to a number of high-precipitation/warming events at Dome C. This was also evident in a positive (negative SAM (Southern Annular Mode index and a negative (positive ZW3 (zonal wave number three index during the winter months of 2010 (2009. Changes in the frequency or seasonality of such event-type precipitation can lead to a strong bias in the air temperature derived from stable water isotopes in ice cores.

EBSD analysis of subgrain boundaries and dislocation slip systems in Antarctic and Greenland ice

Directory of Open Access Journals (Sweden)

I. Weikusat

2017-09-01

Full Text Available Ice has a very high plastic anisotropy with easy dislocation glide on basal planes, while glide on non-basal planes is much harder. Basal glide involves dislocations with the Burgers vector b = 〈a〉, while glide on non-basal planes can involve dislocations with b = 〈a〉, b = [c], and b = 〈c + a〉. During the natural ductile flow of polar ice sheets, most of the deformation is expected to occur by basal slip accommodated by other processes, including non-basal slip and grain boundary processes. However, the importance of different accommodating processes is controversial. The recent application of micro-diffraction analysis methods to ice, such as X-ray Laue diffraction and electron backscattered diffraction (EBSD, has demonstrated that subgrain boundaries indicative of non-basal slip are present in naturally deformed ice, although so far the available data sets are limited. In this study we present an analysis of a large number of subgrain boundaries in ice core samples from one depth level from two deep ice cores from Antarctica (EPICA-DML deep ice core at 656 m of depth and Greenland (NEEM deep ice core at 719 m of depth. EBSD provides information for the characterization of subgrain boundary types and on the dislocations that are likely to be present along the boundary. EBSD analyses, in combination with light microscopy measurements, are presented and interpreted in terms of the dislocation slip systems. The most common subgrain boundaries are indicative of basal 〈a〉 slip with an almost equal occurrence of subgrain boundaries indicative of prism [c] or 〈c + a〉 slip on prism and/or pyramidal planes. A few subgrain boundaries are indicative of prism 〈a〉 slip or slip of 〈a〉 screw dislocations on the basal plane. In addition to these classical polygonization processes that involve the recovery of dislocations into boundaries, alternative mechanisms are discussed for the formation of subgrain

An optimized multi-proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012: 120–800 ka

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L. Bazin

2013-08-01

Full Text Available An accurate and coherent chronological framework is essential for the interpretation of climatic and environmental records obtained from deep polar ice cores. Until now, one common ice core age scale had been developed based on an inverse dating method (Datice, combining glaciological modelling with absolute and stratigraphic markers between 4 ice cores covering the last 50 ka (thousands of years before present (Lemieux-Dudon et al., 2010. In this paper, together with the companion paper of Veres et al. (2013, we present an extension of this work back to 800 ka for the NGRIP, TALDICE, EDML, Vostok and EDC ice cores using an improved version of the Datice tool. The AICC2012 (Antarctic Ice Core Chronology 2012 chronology includes numerous new gas and ice stratigraphic links as well as improved evaluation of background and associated variance scenarios. This paper concentrates on the long timescales between 120–800 ka. In this framework, new measurements of δ18Oatm over Marine Isotope Stage (MIS 11–12 on EDC and a complete δ18Oatm record of the TALDICE ice cores permit us to derive additional orbital gas age constraints. The coherency of the different orbitally deduced ages (from δ18Oatm, δO2/N2 and air content has been verified before implementation in AICC2012. The new chronology is now independent of other archives and shows only small differences, most of the time within the original uncertainty range calculated by Datice, when compared with the previous ice core reference age scale EDC3, the Dome F chronology, or using a comparison between speleothems and methane. For instance, the largest deviation between AICC2012 and EDC3 (5.4 ka is obtained around MIS 12. Despite significant modifications of the chronological constraints around MIS 5, now independent of speleothem records in AICC2012, the date of Termination II is very close to the EDC3 one.

Real-time analysis of insoluble particles in glacial ice using single-particle mass spectrometry

Science.gov (United States)

Osman, Matthew; Zawadowicz, Maria A.; Das, Sarah B.; Cziczo, Daniel J.

2017-11-01

Insoluble aerosol particles trapped in glacial ice provide insight into past climates, but analysis requires information on climatically relevant particle properties, such as size, abundance, and internal mixing. We present a new analytical method using a time-of-flight single-particle mass spectrometer (SPMS) to determine the composition and size of insoluble particles in glacial ice over an aerodynamic size range of ˜ 0.2-3.0 µm diameter. Using samples from two Greenland ice cores, we developed a procedure to nebulize insoluble particles suspended in melted ice, evaporate condensed liquid from those particles, and transport them to the SPMS for analysis. We further determined size-dependent extraction and instrument transmission efficiencies to investigate the feasibility of determining particle-class-specific mass concentrations. We find SPMS can be used to provide constraints on the aerodynamic size, composition, and relative abundance of most insoluble particulate classes in ice core samples. We describe the importance of post-aqueous processing to particles, a process which occurs due to nebulization of aerosols from an aqueous suspension of originally soluble and insoluble aerosol components. This study represents an initial attempt to use SPMS as an emerging technique for the study of insoluble particulates in ice cores.

The effects of methanol on the trapping of volatile ice components

OpenAIRE

Burke, Daren J; Brown, Wendy A

2015-01-01

The evaporation of icy mantles, which have been formed on the surface of dust grains, is acknowledged to give rise to the rich chemistry that has been observed in the vicinity of hot cores and corinos. It has long been established that water ice is the dominant species within many astrophysical ices. However, other molecules found within astrophysical ices, particularly methanol, can influence the desorption of volatile species from the ice. Here we present a detailed investigation of the ads...

Uranium isotopes and dissolved organic carbon in loess permafrost: Modeling the age of ancient ice

Science.gov (United States)

Ewing, Stephanie A.; Paces, James B.; O'Donnell, J.A.; Jorgenson, M.T.; Kanevskiy, M.Z.; Aiken, George R.; Shur, Y.; Harden, Jennifer W.; Striegl, Robert G.

2015-01-01

The residence time of ice in permafrost is an indicator of past climate history, and of the resilience and vulnerability of high-latitude ecosystems to global change. Development of geochemical indicators of ground-ice residence times in permafrost will advance understanding of the circumstances and evidence of permafrost formation, preservation, and thaw in response to climate warming and other disturbance. We used uranium isotopes to evaluate the residence time of segregated ground ice from ice-rich loess permafrost cores in central Alaska. Activity ratios of 234U vs. 238U (234U/238U) in water from thawed core sections ranged between 1.163 and 1.904 due to contact of ice and associated liquid water with mineral surfaces over time. Measured (234U/238U) values in ground ice showed an overall increase with depth in a series of five neighboring cores up to 21 m deep. This is consistent with increasing residence time of ice with depth as a result of accumulation of loess over time, as well as characteristic ice morphologies, high segregated ice content, and wedge ice, all of which support an interpretation of syngenetic permafrost formation associated with loess deposition. At the same time, stratigraphic evidence indicates some past sediment redistribution and possibly shallow thaw among cores, with local mixing of aged thaw waters. Using measures of surface area and a leaching experiment to determine U distribution, a geometric model of (234U/238U) evolution suggests mean ages of up to ∼200 ky BP in the deepest core, with estimated uncertainties of up to an order of magnitude. Evidence of secondary coatings on loess grains with elevated (234U/238U) values and U concentrations suggests that refinement of the geometric model to account for weathering processes is needed to reduce uncertainty. We suggest that in this area of deep ice-rich loess permafrost, ice bodies have been preserved from the last glacial period (10–100 ky BP), despite subsequent

Searches for astrophysical neutrinos with IceCube

International Nuclear Information System (INIS)

Williams, D.

2014-01-01

Powerful astrophysical objects such as active galactic nuclei (AGN), core collapse supernovae and gamma ray bursts (GRBs) are potential sources of the highest energy cosmic rays. Many models of cosmic ray proton acceleration predict a corresponding flux of neutrinos in the TeV-PeV energy range. The detection of astrophysical neutrinos requires the largest neutrino detector ever built: IceCube, a cubic-kilometer array located near the geographic South Pole. IceCube has been collecting data throughout its construction, which was complete in December 2010. Data from the partial IceCube detector have already set interesting limits on astrophysical neutrino fluxes, including stringent limits on neutrino production in GRBs. (authors)

Pan-Arctic sea ice-algal chl a biomass and suitable habitat are largely underestimated for multiyear ice.

Science.gov (United States)

Lange, Benjamin A; Flores, Hauke; Michel, Christine; Beckers, Justin F; Bublitz, Anne; Casey, John Alec; Castellani, Giulia; Hatam, Ido; Reppchen, Anke; Rudolph, Svenja A; Haas, Christian

2017-11-01

There is mounting evidence that multiyear ice (MYI) is a unique component of the Arctic Ocean and may play a more important ecological role than previously assumed. This study improves our understanding of the potential of MYI as a suitable habitat for sea ice algae on a pan-Arctic scale. We sampled sea ice cores from MYI and first-year sea ice (FYI) within the Lincoln Sea during four consecutive spring seasons. This included four MYI hummocks with a mean chl a biomass of 2.0 mg/m 2 , a value significantly higher than FYI and MYI refrozen ponds. Our results support the hypothesis that MYI hummocks can host substantial ice-algal biomass and represent a reliable ice-algal habitat due to the (quasi-) permanent low-snow surface of these features. We identified an ice-algal habitat threshold value for calculated light transmittance of 0.014%. Ice classes and coverage of suitable ice-algal habitat were determined from snow and ice surveys. These ice classes and associated coverage of suitable habitat were applied to pan-Arctic CryoSat-2 snow and ice thickness data products. This habitat classification accounted for the variability of the snow and ice properties and showed an areal coverage of suitable ice-algal habitat within the MYI-covered region of 0.54 million km 2 (8.5% of total ice area). This is 27 times greater than the areal coverage of 0.02 million km 2 (0.3% of total ice area) determined using the conventional block-model classification, which assigns single-parameter values to each grid cell and does not account for subgrid cell variability. This emphasizes the importance of accounting for variable snow and ice conditions in all sea ice studies. Furthermore, our results indicate the loss of MYI will also mean the loss of reliable ice-algal habitat during spring when food is sparse and many organisms depend on ice-algae. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Modeling the Sulfate Deposition to the Greenland Ice Sheet From the Laki Eruption

Science.gov (United States)

Oman, L.; Robock, A.; Stenchikov, G.; Thordarson, T.; Gao, C.

2005-12-01

Using the state of the art Goddard Institute for Space Studies (GISS) modelE general circulation model, simulations were conducted of the chemistry and transport of aerosols resulting from the 1783-84 Laki (64°N) flood lava eruption. A set of 3 ensemble simulations from different initial conditions were conducted by injecting our estimate of the SO2 gas into the atmosphere by the 10 episodes of the eruption and allowing the sulfur chemistry model to convert this gas into sulfate aerosol. The SO2 gas and sulfate aerosol is transported by the model and wet and dry deposition is calculated over each grid box during the simulation. We compare the resulting sulfate deposition to the Greenland Ice Sheet in the model to 23 ice core measurements and find very good agreement. The model simulation deposits a range of 169 to over 300 kg/km2 over interior Greenland with much higher values along the coastal areas. This compares to a range of 62 to 324 kg/km2 for the 23 ice core measurements with an average value of 158 kg/km2. This comparison is one important model validation tool. Modeling and observations show fairly large spatial variations in the deposition of sulfate across the Greenland Ice Sheet for the Laki eruption, but the patterns are similar to those we modeled for the 1912 Katmai and 1991 Pinatubo eruptions. Estimates of sulfate loading based on single ice cores can show significant differences, so ideally several ice cores should be combined in reconstructing the sulfate loading of past volcanic eruptions, taking into account the characteristic spatial variations in the deposition pattern.

Optical-televiewer-based identification and characterization of material facies associated with an Antarctic ice-shelf rift

OpenAIRE

Hubbard, B.; Tison, J.-L.; Pattyn, F.; Dierckx, M.; Boereboom, T.; Samyn, D.

2012-01-01

We have drilled 13 boreholes within and around a through-cutting rift on the (unofficially named) Roi Baudouin Ice Shelf, East Antarctica. Logging by optical televiewer (OPTV) combined with core inspection has resulted in the identification and characterization of several material facies. Outside the rift, OPTV-imaged annual layering indicates ~150 years of accumulation over the 66m length of one of the boreholes. Luminosity analysis of this image also reveals the presence of numerous dark me...

Where is the 1-million-year-old ice at Dome A?

Directory of Open Access Journals (Sweden)

L. Zhao

2018-05-01

Full Text Available Ice fabric influences the rheology of ice, and hence the age–depth profile at ice core drilling sites. To investigate the age–depth profile to be expected of the ongoing deep ice coring at Kunlun station, Dome A, we use the depth-varying anisotropic fabric suggested by the recent polarimetric measurements around Dome A along with prescribed fabrics ranging from isotropic through girdle to single maximum in a three-dimensional, thermo-mechanically coupled full-Stokes model of a 70  ×  70 km2 domain around Kunlun station. This model allows for the simulation of the near basal ice temperature and age, and ice flow around the location of the Chinese deep ice coring site. Ice fabrics and geothermal heat flux strongly affect the vertical advection and basal temperature which consequently control the age profile. Constraining modeled age–depth profiles with dated radar isochrones to 2∕3 ice depth, the surface vertical velocity, and also the spatial variability of a radar isochrones dated to 153.3 ka BP, limits the age of the deep ice at Kunlun to between 649 and 831 ka, a much smaller range than previously inferred. The simple interpretation of the polarimetric radar fabric data that we use produces best fits with a geothermal heat flux of 55 mW m−2. A heat flux of 50 mW m−2 is too low to fit the deeper radar layers, and 60 mW m−2 leads to unrealistic surface velocities. The modeled basal temperature at Kunlun reaches the pressure melting point with a basal melting rate of 2.2–2.7 mm a−1. Using the spatial distribution of basal temperatures and the best fit fabric suggests that within 400 m of Kunlun station, 1-million-year-old ice may be found 200 m above the bed, and that there are large regions where even older ice is well above the bedrock within 5–6 km of the Kunlun station.

Ergogenic effects of precooling with cold water immersion and ice ingestion: A meta-analysis.

Science.gov (United States)

Choo, Hui C; Nosaka, Kazunori; Peiffer, Jeremiah J; Ihsan, Mohammed; Abbiss, Chris R

2018-03-01

This review evaluated the effects of precooling via cold water immersion (CWI) and ingestion of ice slurry/slushy or crushed ice (ICE) on endurance performance measures (e.g. time-to-exhaustion and time trials) and psychophysiological parameters (core [T core ] and skin [T skin ] temperatures, whole body sweat [WBS] response, heart rate [HR], thermal sensation [TS], and perceived exertion [RPE]). Twenty-two studies were included in the meta-analysis based on the following criteria: (i) cooling was performed before exercise with ICE or CWI; (ii) exercise longer than 6 min was performed in ambient temperature ≥26°C; and (iii) crossover study design with a non-cooling passive control condition. CWI improved performance measures (weighted average effect size in Hedges' g [95% confidence interval] + 0.53 [0.28; 0.77]) and resulted in greater increase (ΔEX) in T skin (+4.15 [3.1; 5.21]) during exercise, while lower peak T core (-0.93 [-1.18; -0.67]), WBS (-0.74 [-1.18; -0.3]), and TS (-0.5 [-0.8; -0.19]) were observed without concomitant changes in ΔEX-T core (+0.19 [-0.22; 0.6]), peak T skin (-0.67 [-1.52; 0.18]), peak HR (-0.14 [-0.38; 0.11]), and RPE (-0.14 [-0.39; 0.12]). ICE had no clear effect on performance measures (+0.2 [-0.07; 0.46]) but resulted in greater ΔEX-T core (+1.02 [0.59; 1.45]) and ΔEX-T skin (+0.34 [0.02; 0.67]) without concomitant changes in peak T core (-0.1 [-0.48; 0.28]), peak T skin (+0.1 [-0.22; 0.41]), peak HR (+0.08 [-0.19; 0.35]), WBS (-0.12 [-0.42; 0.18]), TS (-0.2 [-0.49; 0.1]), and RPE (-0.01 [-0.33; 0.31]). From both ergogenic and thermoregulatory perspectives, CWI may be more effective than ICE as a precooling treatment prior to exercise in the heat.

Precipitation and ice core isotopes from the Asian Summer Monsoon region reflect coherent ENSO variability

Science.gov (United States)

Cai, Z.; Tian, L.; Bowen, G. J.

2017-12-01

Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.

Radiocarbon analysis in an Alpine ice core: record of anthropogenic and biogenic contributions to carbonaceous aerosols in the past (1650–1940

Directory of Open Access Journals (Sweden)

T. M. Jenk

2006-01-01

Full Text Available Long-term concentration records of carbonaceous particles (CP are of increasing interest in climate research due to their not yet completely understood effects on climate. Nevertheless, only poor data on their concentrations and sources before the 20th century are available. We present a first long-term record of organic carbon (OC and elemental carbon (EC concentrations – the two main fractions of CP – along with the corresponding fraction of modern carbon (fM derived from radiocarbon (14C analysis in ice. This allows a distinction and quantification of natural (biogenic and anthropogenic (fossil sources in the past. CP were extracted from an ice archive, with resulting carbon quantities in the microgram range. Analysis of 14C by accelerator mass spectrometry (AMS was therefore highly demanding. We analysed 33 samples of 0.4 to 1 kg ice from a 150.5 m long ice core retrieved at Fiescherhorn glacier in December 2002 (46°33'3.2" N, 08°04'0.4" E; 3900 m a.s.l.. Samples were taken from bedrock up to the firn/ice transition, covering the time period 1650–1940 and thus the transition from the pre-industrial to the industrial era. Before ~1850, OC was approaching a purely biogenic origin with a mean concentration of 24 μg kg−1 and a standard deviation of 7 μg kg−1. In 1940, OC concentration was about a factor of 3 higher than this biogenic background, almost half of it originating from anthropogenic sources, i.e. from combustion of fossil fuels. The biogenic EC concentration was nearly constant over the examined time period with 6 μg kg−1 and a standard deviation of 1 μg kg−1. In 1940, the additional anthropogenic input of atmospheric EC was about 50 μg kg−1.

Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago

Science.gov (United States)

Eichler, A.; Gramlich, G.; Kellerhals, T.; Tobler, L.; Rehren, Th.; Schwikowski, M.

2017-01-01

The importance of metallurgy for social and economic development is indisputable. Although copper (Cu) was essential for the wealth of pre- and post-colonial societies in the Andes, the onset of extensive Cu metallurgy in South America is still debated. Comprehensive archaeological findings point to first sophisticated Cu metallurgy during the Moche culture ~200-800 AD, whereas peat-bog records from southern South America suggest earliest pollution potentially from Cu smelting as far back as ~2000 BC. Here we present a 6500-years Cu emission history for the Andean Altiplano, based on ice-core records from Illimani glacier in Bolivia, providing the first complete history of large-scale Cu smelting activities in South America. We find earliest anthropogenic Cu pollution during the Early Horizon period ~700-50 BC, and attribute the onset of intensified Cu smelting in South America to the activities of the central Andean Chiripa and Chavin cultures ~2700 years ago. This study provides for the first time substantial evidence for extensive Cu metallurgy already during these early cultures.

Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago.

Science.gov (United States)

Eichler, A; Gramlich, G; Kellerhals, T; Tobler, L; Rehren, Th; Schwikowski, M

2017-01-31

The importance of metallurgy for social and economic development is indisputable. Although copper (Cu) was essential for the wealth of pre- and post-colonial societies in the Andes, the onset of extensive Cu metallurgy in South America is still debated. Comprehensive archaeological findings point to first sophisticated Cu metallurgy during the Moche culture ~200-800 AD, whereas peat-bog records from southern South America suggest earliest pollution potentially from Cu smelting as far back as ~2000 BC. Here we present a 6500-years Cu emission history for the Andean Altiplano, based on ice-core records from Illimani glacier in Bolivia, providing the first complete history of large-scale Cu smelting activities in South America. We find earliest anthropogenic Cu pollution during the Early Horizon period ~700-50 BC, and attribute the onset of intensified Cu smelting in South America to the activities of the central Andean Chiripa and Chavin cultures ~2700 years ago. This study provides for the first time substantial evidence for extensive Cu metallurgy already during these early cultures.

Preliminary biogeochemical assessment of EPICA LGM and Holocene ice samples

Science.gov (United States)

Bulat, S.; Alekhina, I.; Marie, D.; Wagenbach, D.; Raynaud, D.; Petit, J. R.

2009-04-01

We are investigating the biological content (biomass and microbial diversity of Aeolian origin) of EPICA ice core within the frame of EPICA Microbiology consortium*. Two ice core sections were selected from EPICA Dome C and Droning Maud Land, both from LGM and Holocene. Preliminary measurements of DOC (dissolved organic content) and microbial cell concentrations have been performed. Both analyses showed the very low biomass and ultra low DOC content. Trace DNA analyses are in a progress. The ice sections were decontaminated in LGGE cold and clean room facilities benefiting the protocol developed for Vostok ice core studies. The melt water was then shared between two party laboratories for a complementary approach in studying microbial content. Prior to biology the melt water was tested for chemical contaminant ions and organic acids, DOC and dust contents. The biological methods included all the spectra of appropriate molecular techniques (gDNA extraction, PCR, clone libraries and sequencing). As preliminary results, both LGM (well identified by dust fallout) and Holocene ice samples (EDC99 and EDML) proved to be extremely clear (i.e. pristine) in terms of biomass (less then 4 cells per ml) and DOC contents (less then 5 ppbC). There was no obvious difference between LGM and Holocene in cell counts, while LGM showed a bit high organic carbon content. The latter in terms of biology means ultra-oligotrophic conditions (i.e., no possibility for heterotrophic life style). In fact no metabolizing microbial cells or propagating populations are expected at these depths at temperature -38oC and lower (limiting life temperature threshold is -20°C). Nevertheless some life seeds brought in Antarctica with precipitation could be well preserved because the age is rather young (21 kyr and less). Trying to identify these aliens and document their distribution during last climate cycle the meltwater was concentrated about 1000 times down. The genomic DNA was extracted and very

Innovative optical spectrometers for ice core sciences and atmospheric monitoring at polar regions

Science.gov (United States)

Grilli, Roberto; Alemany, Olivier; Chappellaz, Jérôme; Desbois, Thibault; Faïn, Xavier; Kassi, Samir; Kerstel, Erik; Legrand, Michel; Marrocco, Nicola; Méjean, Guillaume; Preunkert, Suzanne; Romanini, Daniele; Triest, Jack; Ventrillard, Irene

2015-04-01

limit of 0.2 ppbv for CH4 and a precision of 0.2o on the δD of H2O within ~1 min of integration time. The spectrometer and the home-made gas sampling has been tested during an oceanographic campaign last summer in the Mediterranean Sea, measuring the vertical distribution of CH4 dissolved in seawater. The project is now moving forward its final goal which consists of employing the probe for a first test season at Concordia station during the Austral summer of 2016/17, and then for the 'oldest ice challenge' drilling season scheduled in the Austral summer of 2017/18. Finally, preliminary results on the isotope ratio measurements of CO18O,13CO2 and 13CO18O will be presented. A novel spectrometer, based on OFCAES technique employing a Quantum Cascade Laser around 4.4 μm wavelength, offers a precision below 0.05 o for the three isotopic anomalies, for 200 ppmv of CO2 samples. The optical device will be employed for laboratory experiments coupling it with a continuous ice-crushing extraction system for analyzing trapped bubbles of gas in Antarctica ice cores. [1] R. Grilli, G. Méjean, S. Kassi, I. Ventrillard, C. Abd-Alrahman, and D. Romanini, 'Frequency Comb Based Spectrometer for in Situ and Real Time Measurements of IO, BrO, NO2, and H2CO at pptv and ppqv Levels.,' Environ. Sci. Technol., vol. 46, no. 19, pp. 10704-10, Oct. 2012. [2] R. Grilli, M. Legrand, A. Kukui, G. Méjean, S. Preunkert, and D. Romanini, 'First investigations of IO, BrO, and NO2 summer atmospheric levels at a coastal East Antarctic site using mode-locked cavity enhanced absorption spectroscopy,' Geophys. Res. Lett., vol. 40, pp. 1-6, Feb. 2013. [3] R. Grilli, N. Marrocco, T. Desbois, C. Guillerm, J. Triest, E. Kerstel, and D. Romanini, 'Invited Article: SUBGLACIOR: An optical analyzer embedded in an Antarctic ice probe for exploring the past climate,' Rev. Sci. Instrum., vol. 85, no. 111301, pp. 1-7, 2014.

Is there 1.5-million-year-old ice near Dome C, Antarctica?