Meteorological conditions in a thinner Arctic sea ice regime from winter to summer during the Norwegian Young Sea Ice expedition (N-ICE2015)

Science.gov (United States)

Cohen, Lana; Hudson, Stephen R.; Walden, Von P.; Graham, Robert M.; Granskog, Mats A.

2017-07-01

Atmospheric measurements were made over Arctic sea ice north of Svalbard from winter to early summer (January-June) 2015 during the Norwegian Young Sea Ice (N-ICE2015) expedition. These measurements, which are available publicly, represent a comprehensive meteorological data set covering the seasonal transition in the Arctic Basin over the new, thinner sea ice regime. Winter was characterized by a succession of storms that produced short-lived (less than 48 h) temperature increases of 20 to 30 K at the surface. These storms were driven by the hemispheric scale circulation pattern with a large meridional component of the polar jet stream steering North Atlantic storms into the high Arctic. Nonstorm periods during winter were characterized by strong surface temperature inversions due to strong radiative cooling ("radiatively clear state"). The strength and depth of these inversions were similar to those during the Surface Heat Budget of the Arctic Ocean (SHEBA) campaign. In contrast, atmospheric profiles during the "opaquely cloudy state" were different to those from SHEBA due to differences in the synoptic conditions and location within the ice pack. Storm events observed during spring/summer were the result of synoptic systems located in the Barents Sea and the Arctic Basin rather than passing directly over N-ICE2015. These synoptic systems were driven by a large-scale circulation pattern typical of recent years, with an Arctic Dipole pattern developing during June. Surface temperatures became near-constant 0°C on 1 June marking the beginning of summer. Atmospheric profiles during the spring and early summer show persistent lifted temperature and moisture inversions that are indicative of clouds and cloud processes.

Direct observations of atmosphere - sea ice - ocean interactions during Arctic winter and spring storms

Science.gov (United States)

Graham, R. M.; Itkin, P.; Granskog, M. A.; Assmy, P.; Cohen, L.; Duarte, P.; Doble, M. J.; Fransson, A.; Fer, I.; Fernandez Mendez, M.; Frey, M. M.; Gerland, S.; Haapala, J. J.; Hudson, S. R.; Liston, G. E.; Merkouriadi, I.; Meyer, A.; Muilwijk, M.; Peterson, A.; Provost, C.; Randelhoff, A.; Rösel, A.; Spreen, G.; Steen, H.; Smedsrud, L. H.; Sundfjord, A.

2017-12-01

To study the thinner and younger sea ice that now dominates the Arctic the Norwegian Young Sea ICE expedition (N-ICE2015) was launched in the ice-covered region north of Svalbard, from January to June 2015. During this time, eight local and remote storms affected the region and rare direct observations of the atmosphere, snow, ice and ocean were conducted. Six of these winter storms passed directly over the expedition and resulted in air temperatures rising from below -30oC to near 0oC, followed by abrupt cooling. Substantial snowfall prior to the campaign had already formed a snow pack of approximately 50 cm, to which the February storms contributed an additional 6 cm. The deep snow layer effectively isolated the ice cover and prevented bottom ice growth resulting in low brine fluxes. Peak wind speeds during winter storms exceeded 20 m/s, causing strong snow re-distribution, release of sea salt aerosol and sea ice deformation. The heavy snow load caused widespread negative freeboard; during sea ice deformation events, level ice floes were flooded by sea water, and at least 6-10 cm snow-ice layer was formed. Elevated deformation rates during the most powerful winter storms damaged the ice cover permanently such that the response to wind forcing increased by 60 %. As a result of a remote storm in April deformation processes opened about 4 % of the total area into leads with open water, while a similar amount of ice was deformed into pressure ridges. The strong winds also enhanced ocean mixing and increased ocean heat fluxes three-fold in the pycnocline from 4 to 12 W/m2. Ocean heat fluxes were extremely large (over 300 W/m2) during storms in regions where the warm Atlantic inflow is located close to surface over shallow topography. This resulted in very large (5-25 cm/day) bottom ice melt and in cases flooding due to heavy snow load. Storm events increased the carbon dioxide exchange between the atmosphere and ocean but also affected the pCO2 in surface waters

Sea Ice Edge Location and Extent in the Russian Arctic, 1933-2006

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Sea Ice Edge Location and Extent in the Russian Arctic, 1933-2006 data are derived from sea ice charts from the Arctic and Antarctic Research Institute (AARI),...

Improving Arctic Sea Ice Edge Forecasts by Assimilating High Horizontal Resolution Sea Ice Concentration Data into the US Navy’s Ice Forecast Systems

Science.gov (United States)

2016-06-13

1735-2015 © Author(s) 2015. CC Attribution 3.0 License. Improving Arctic sea ice edge forecasts by assimilating high horizontal resolution sea ice...concentration data into the US Navy’s ice forecast systems P. G. Posey1, E. J. Metzger1, A. J. Wallcraft1, D. A. Hebert1, R. A. Allard1, O. M. Smedstad2...error within the US Navy’s operational sea ice forecast systems gained by assimilating high horizontal resolution satellite-derived ice concentration

Dynamics of sea-ice biogeochemistry in the coastal Antarctica during transition from summer to winter

Directory of Open Access Journals (Sweden)

Suhas Shetye

2017-05-01

Full Text Available The seasonality of carbon dioxide partial pressure (pCO2, air-sea CO2 fluxes and associated environmental parameters were investigated in the Antarctic coastal waters. The in-situ survey was carried out from the austral summer till the onset of winter (January 2012, February 2010 and March 2009 in the Enderby Basin. Rapid decrease in pCO2 was evident under the sea-ice cover in January, when both water column and sea-ice algal activity resulted in the removal of nutrients and dissolved inorganic carbon (DIC and increase in pH. The major highlight of this study is the shift in the dominant biogeochemical factors from summer to early winter. Nutrient limitation (low Si/N, sea-ice cover, low photosynthetically active radiation (PAR, deep mixed layer and high upwelling velocity contributed towards higher pCO2 during March (early winter. CO2 fluxes suggest that the Enderby Basin acts as a strong CO2 sink during January (−81 mmol m−2 d−1, however it acts as a weak sink of CO2 with −2.4 and −1.7 mmol m−2 d−1 during February and March, respectively. The present work, concludes that sea ice plays a dual role towards climate change, by decreasing sea surface pCO2 in summer and enhancing in early winter. Our observations emphasize the need to address seasonal sea-ice driven CO2 flux dynamics in assessing Antarctic contributions to the global oceanic CO2 budget.

Winter snow conditions on Arctic sea ice north of Svalbard during the Norwegian young sea ICE (N-ICE2015) expedition

Science.gov (United States)

Merkouriadi, Ioanna; Gallet, Jean-Charles; Graham, Robert M.; Liston, Glen E.; Polashenski, Chris; Rösel, Anja; Gerland, Sebastian

2017-10-01

Snow is a crucial component of the Arctic sea ice system. Its thickness and thermal properties control heat conduction and radiative fluxes across the ocean, ice, and atmosphere interfaces. Hence, observations of the evolution of snow depth, density, thermal conductivity, and stratigraphy are crucial for the development of detailed snow numerical models predicting energy transfer through the snow pack. Snow depth is also a major uncertainty in predicting ice thickness using remote sensing algorithms. Here we examine the winter spatial and temporal evolution of snow physical properties on first-year (FYI) and second-year ice (SYI) in the Atlantic sector of the Arctic Ocean, during the Norwegian young sea ICE (N-ICE2015) expedition (January to March 2015). During N-ICE2015, the snow pack consisted of faceted grains (47%), depth hoar (28%), and wind slab (13%), indicating very different snow stratigraphy compared to what was observed in the Pacific sector of the Arctic Ocean during the SHEBA campaign (1997-1998). Average snow bulk density was 345 kg m-3 and it varied with ice type. Snow depth was 41 ± 19 cm in January and 56 ± 17 cm in February, which is significantly greater than earlier suggestions for this region. The snow water equivalent was 14.5 ± 5.3 cm over first-year ice and 19 ± 5.4 cm over second-year ice.

Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation

Directory of Open Access Journals (Sweden)

D. Handorf

2012-01-01

Full Text Available The response of the Arctic atmosphere to low and high sea ice concentration phases based on European Center for Medium-Range Weather Forecast (ECMWF Re-Analysis Interim (ERA-Interim atmospheric data and Hadley Centre's sea ice dataset (HadISST1 from 1989 until 2010 has been studied. Time slices of winter atmospheric circulation with high (1990–2000 and low (2001–2010 sea ice concentration in the preceding August/September have been analysed with respect to tropospheric interactions between planetary and baroclinic waves. It is shown that a changed sea ice concentration over the Arctic Ocean impacts differently the development of synoptic and planetary atmospheric circulation systems. During the low ice phase, stronger heat release to the atmosphere over the Arctic Ocean reduces the atmospheric vertical static stability. This leads to an earlier onset of baroclinic instability that further modulates the non-linear interactions between baroclinic wave energy fluxes on time scales of 2.5–6 d and planetary scales of 10–90 d. Our analysis suggests that Arctic sea ice concentration changes exert a remote impact on the large-scale atmospheric circulation during winter, exhibiting a barotropic structure with similar patterns of pressure anomalies at the surface and in the mid-troposphere. These are connected to pronounced planetary wave train changes notably over the North Pacific.

Monitoring Forsmark. Snow depth, snow water content and ice cover during the winter 2010/2011

Energy Technology Data Exchange (ETDEWEB)

Wass, Eva (Geosigma AB (Sweden))

2011-07-15

Snow depth and ice cover have been measured and observed during the winter 2010/2011. This type of measurements started in the winter 2002/2003 and has been ongoing since then. In addition to these parameters, the water content of the snow was calculated at each measurement occasion from the weight of a snow sample. Measurements and observations were conducted on a regular basis from the beginning of November 2010 until the middle of April 2011. A persistent snow cover was established in the end of November 2010 and remained until the beginning of April 2011 at the station with longest snow cover duration. The period of ice cover was 160 days in Lake Eckarfjaerden, whereas the sea bay at SFR was ice covered for 135 days

Monitoring Forsmark. Snow depth, snow water content and ice cover during the winter 2010/2011

International Nuclear Information System (INIS)

Wass, Eva

2011-07-01

Snow depth and ice cover have been measured and observed during the winter 2010/2011. This type of measurements started in the winter 2002/2003 and has been ongoing since then. In addition to these parameters, the water content of the snow was calculated at each measurement occasion from the weight of a snow sample. Measurements and observations were conducted on a regular basis from the beginning of November 2010 until the middle of April 2011. A persistent snow cover was established in the end of November 2010 and remained until the beginning of April 2011 at the station with longest snow cover duration. The period of ice cover was 160 days in Lake Eckarfjaerden, whereas the sea bay at SFR was ice covered for 135 days

Under the sea ice: Exploring the relationship between sea ice and the foraging behaviour of southern elephant seals in East Antarctica

Science.gov (United States)

Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D.; Massom, Robert A.; Reid, Phillip; Sumner, Michael; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Bailleul, Frédéric; Hindell, Mark A.; Charrassin, Jean-Benoit

2017-08-01

Investigating ecological relationships between predators and their environment is essential to understand the response of marine ecosystems to climate variability and change. This is particularly true in polar regions, where sea ice (a sensitive climate variable) plays a crucial yet highly dynamic and variable role in how it influences the whole marine ecosystem, from phytoplankton to top predators. For mesopredators such as seals, sea ice both supports a rich (under-ice) food resource, access to which depends on local to regional coverage and conditions. Here, we investigate sex-specific relationships between the foraging strategies of southern elephant seals (Mirounga leonina) in winter and spatio-temporal variability in sea ice concentration (SIC) and coverage in East Antarctica. We satellite-tracked 46 individuals undertaking post-moult trips in winter from Kerguelen Islands to the peri-Antarctic shelf between 2004 and 2014. These data indicate distinct general patterns of sea ice usage: while females tended to follow the sea ice edge as it extended northward, the males remained on the continental shelf despite increasing sea ice. Seal hunting time, a proxy of foraging activity inferred from the diving behaviour, was longer for females in late autumn in the outer part of the pack ice, ∼150-370 km south of the ice edge. Within persistent regions of compact sea ice, females had a longer foraging activity (i) in the highest sea ice concentration at their position, but (ii) their foraging activity was longer when there were more patches of low concentration sea ice around their position (either in time or in space; 30 days & 50 km). The high spatio-temporal variability of sea ice around female positions is probably a key factor allowing them to exploit these concentrated patches. Despite lack of information on prey availability, females may exploit mesopelagic finfishes and squids that concentrate near the ice-water interface or within the water column (from

A Possible Link Between Winter Arctic Sea Ice Decline and a Collapse of the Beaufort High?

Science.gov (United States)

Petty, Alek A.

2018-03-01

A new study by Moore et al. (2018, https://doi.org/10.1002/2017GL076446) highlights a collapse of the anticyclonic "Beaufort High" atmospheric circulation over the western Arctic Ocean in the winter of 2017 and an associated reversal of the sea ice drift through the southern Beaufort Sea (eastward instead of the predominantly westward circulation). The authors linked this to the loss of sea ice in the Barents Sea, anomalous warming over the region, and the intrusion of low-pressure cyclones along the eastern Arctic. In this commentary we discuss the significance of this observation, the challenges associated with understanding these possible linkages, and some of the alternative hypotheses surrounding the impacts of winter Arctic sea ice loss.

Sensitivity of the sea ice concentration over the Kara-Barents Sea in autumn to the winter temperature variability over East Asia

Science.gov (United States)

Cho, K. H.; Chang, E. C.

2017-12-01

In this study, we performed sensitivity experiments by utilizing the Global/Regional Integrated Model system with different conditions of the sea ice concentration over the Kara-Barents (KB) Sea in autumn, which can affect winter temperature variability over East Asia. Prescribed sea ice conditions are 1) climatological autumn sea ice concentration obtained from 1982 to 2016, 2) reduced autumn sea ice concentration by 50% of the climatology, and 3) increased autumn sea ice concentration by 50% of climatology. Differently prescribed sea ice concentration changes surface albedo, which affects surface heat fluxes and near-surface air temperature. The reduced (increased) sea ice concentration over the KB sea increases (decreases) near-surface air temperature that leads the lower (higher) sea level pressure in autumn. These patterns are maintained from autumn to winter season. Furthermore, it is shown that the different sea ice concentration over the KB sea has remote effects on the sea level pressure patterns over the East Asian region. The lower (higher) sea level pressure over the KB sea by the locally decreased (increased) ice concentration is related to the higher (lower) pressure pattern over the Siberian region, which induces strengthened (weakened) cold advection over the East Asian region. From these sensitivity experiments it is clarified that the decreased (increased) sea ice concentration over the KB sea in autumn can lead the colder (warmer) surface air temperature over East Asia in winter.

Arctic sea ice, Eurasia snow, and extreme winter haze in China.

Science.gov (United States)

Zou, Yufei; Wang, Yuhang; Zhang, Yuzhong; Koo, Ja-Ho

2017-03-01

The East China Plains (ECP) region experienced the worst haze pollution on record for January in 2013. We show that the unprecedented haze event is due to the extremely poor ventilation conditions, which had not been seen in the preceding three decades. Statistical analysis suggests that the extremely poor ventilation conditions are linked to Arctic sea ice loss in the preceding autumn and extensive boreal snowfall in the earlier winter. We identify the regional circulation mode that leads to extremely poor ventilation over the ECP region. Climate model simulations indicate that boreal cryospheric forcing enhances the regional circulation mode of poor ventilation in the ECP region and provides conducive conditions for extreme haze such as that of 2013. Consequently, extreme haze events in winter will likely occur at a higher frequency in China as a result of the changing boreal cryosphere, posing difficult challenges for winter haze mitigation but providing a strong incentive for greenhouse gas emission reduction.

Influence of the Gulf Stream on the Barents Sea ice retreat and Eurasian coldness during early winter

International Nuclear Information System (INIS)

Sato, Kazutoshi; Inoue, Jun; Watanabe, Masahiro

2014-01-01

Abnormal sea-ice retreat over the Barents Sea during early winter has been considered a leading driver of recent midlatitude severe winters over Eurasia. However, causal relationships between such retreat and the atmospheric circulation anomalies remains uncertain. Using a reanalysis dataset, we found that poleward shift of a sea surface temperature front over the Gulf Stream likely induces warm southerly advection and consequent sea-ice decline over the Barents Sea sector, and a cold anomaly over Eurasia via planetary waves triggered over the Gulf Stream region. The above mechanism is supported by the steady atmospheric response to the diabatic heating anomalies over the Gulf Stream region obtained with a linear baroclinic model. The remote atmospheric response from the Gulf Stream would be amplified over the Barents Sea region via interacting with sea-ice anomaly, promoting the warm Arctic and cold Eurasian pattern. (letter)

Effects of lead structure in Bering Sea pack ice on the flight costs of wintering spectacled eiders

Science.gov (United States)

Bump, Joseph K.; Lovvorn, James R.

2004-10-01

In polar regions, sea ice is critical habitat for many marine birds and mammals. The quality of pack ice habitat depends on the duration and spacing of leads (openings in the ice), which determine access to water and air for diving endotherms, and how often and how far they must move as leads open and close. Recent warming trends have caused major changes in the extent and nature of sea ice at large scales used in climate models. However, no studies have analyzed lead structure in terms of habitat for ice-dependent endotherms, or effects of climate on ice habitat at scales relevant to their daily movements. Based on observations from an icebreaker and synthetic aperture radar (SAR) images, we developed methods to describe the dynamics and thermodynamics of lead structure relative to use by spectacled eiders ( Somateria fischeri) wintering in pack ice of the Bering Sea. By correlating lead structure with weather variables, we then used these methods to estimate changes in lead dynamics from 1945 to 2002, and effects of such changes on flight costs of the eiders. For 1991-1992, when images were available about every 3 days throughout winter, SAR images were divided among five weather regimes defined by wind speed, wind direction, and air temperature. Based on 12.5-m pixels, lead shape, compass orientation, and fetch across leads did not differ among the weather regimes. However, the five regimes differed in total area of open water, leads per unit area, and distance between leads. Lead duration was modeled based on air temperature, wind, and fetch. Estimates of mean daily flight time for eiders, based on lead duration and distance between neighboring leads, differed among regimes by 0 to 15 min. Resulting flight costs varied from 0 to 158 kJ day -1, or from 0% to 11% of estimated field metabolic rate. Over 57 winters (1945-2002), variation among years in mean daily flight time was most influenced by the north-south wind component, which determined pack divergence

Hibernation in an antarctic fish: on ice for winter.

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Hamish A Campbell

Full Text Available Active metabolic suppression in anticipation of winter conditions has been demonstrated in species of mammals, birds, reptiles and amphibians, but not fish. This is because the reduction in metabolic rate in fish is directly proportional to the decrease in water temperature and they appear to be incapable of further suppressing their metabolic rate independently of temperature. However, the Antarctic fish (Notothenia coriiceps is unusual because it undergoes winter metabolic suppression irrespective of water temperature. We assessed the seasonal ecological strategy by monitoring swimming activity, growth, feeding and heart rate (f(H in N. coriiceps as they free-ranged within sub-zero waters. The metabolic rate of wild fish was extrapolated from f(H recordings, from oxygen consumption calibrations established in the laboratory prior to fish release. Throughout the summer months N. coriiceps spent a considerable proportion of its time foraging, resulting in a growth rate (G(w of 0.18 +/- 0.2% day(-1. In contrast, during winter much of the time was spent sedentary within a refuge and fish showed a net loss in G(w (-0.05 +/- 0.05% day(-1. Whilst inactive during winter, N. coriiceps displayed a very low f(H, reduced sensory and motor capabilities, and standard metabolic rate was one third lower than in summer. In a similar manner to other hibernating species, dormancy was interrupted with periodic arousals. These arousals, which lasted a few hours, occurred every 4-12 days. During arousal activity, f(H and metabolism increased to summer levels. This endogenous suppression and activation of metabolic processes, independent of body temperature, demonstrates that N. coriiceps were effectively 'putting themselves on ice' during winter months until food resources improved. This study demonstrates that at least some fish species can enter a dormant state similar to hibernation that is not temperature driven and presumably provides seasonal energetic

Circulation and water properties in the landfast ice zone of the Alaskan Beaufort Sea

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Weingartner, Thomas J.; Danielson, Seth L.; Potter, Rachel A.; Trefry, John H.; Mahoney, Andy; Savoie, Mark; Irvine, Cayman; Sousa, Leandra

2017-09-01

Moorings, hydrography, satellite-tracked drifters, and high-frequency radar data describe the annual cycle in circulation and water properties in the landfast ice zone (LIZ) of the Alaskan Beaufort Sea. Three seasons, whose duration and characteristics are controlled by landfast ice formation and ablation, define the LIZ: ;winter;, ;break-up;, and ;open-water;. Winter begins in October with ice formation and ends in June when rivers commence discharging. Winter LIZ ice velocities are zero, under-ice currents are weak ( 5 cm s-1), and poorly correlated with winds and local sea level. The along-shore momentum balance is between along-shore pressure gradients and bottom and ice-ocean friction. Currents at the landfast ice-edge are swift ( 35 cm s-1), wind-driven, with large horizontal shears, and potentially unstable. Weak cross-shore velocities ( 1 cm s-1) imply limited exchanges between the LIZ and the outer shelf in winter. The month-long break-up season (June) begins with the spring freshet and concludes when landfast ice detaches from the bottom. Cross-shore currents increase, and the LIZ hosts shallow ( 2 m), strongly-stratified, buoyant and sediment-laden, under-ice river plumes that overlie a sharp, 1 m thick, pycnocline across which salinity increases by 30. The plume salt balance is between entrainment and cross-shore advection. Break-up is followed by the 3-month long open-water season when currents are swift (≥20 cm s-1) and predominantly wind-driven. Winter water properties are initialized by fall advection and evolve slowly due to salt rejection from ice. Fall waters and ice within the LIZ derive from local rivers, the Mackenzie and/or Chukchi shelves, and the Arctic basin.

Greater sage-grouse winter habitat use on the eastern edge of their range

Science.gov (United States)

Christopher C. Swanson; Mark A. Rumble; Nicholas W. Kaczor; Robert W. Klaver; Katie M. Herman-Brunson; Jonathan A. Jenks; Kent C. Jensen

2013-01-01

Greater sage-grouse (Centrocercus urophasianus) at the western edge of the Dakotas occur in the transition zone between sagebrush and grassland communities. These mixed sagebrush (Artemisia sp.) and grasslands differ from those habitats that comprise the central portions of the sage-grouse range; yet, no information is available on winter habitat selection within this...

Effects of sea-ice and biogeochemical processes and storms on under-ice water fCO2 during the winter-spring transition in the high Arctic Ocean: Implications for sea-air CO2 fluxes

Science.gov (United States)

Fransson, Agneta; Chierici, Melissa; Skjelvan, Ingunn; Olsen, Are; Assmy, Philipp; Peterson, Algot K.; Spreen, Gunnar; Ward, Brian

2017-07-01

We performed measurements of carbon dioxide fugacity (fCO2) in the surface water under Arctic sea ice from January to June 2015 during the Norwegian young sea ICE (N-ICE2015) expedition. Over this period, the ship drifted with four different ice floes and covered the deep Nansen Basin, the slopes north of Svalbard, and the Yermak Plateau. This unique winter-to-spring data set includes the first winter-time under-ice water fCO2 observations in this region. The observed under-ice fCO2 ranged between 315 µatm in winter and 153 µatm in spring, hence was undersaturated relative to the atmospheric fCO2. Although the sea ice partly prevented direct CO2 exchange between ocean and atmosphere, frequently occurring leads and breakup of the ice sheet promoted sea-air CO2 fluxes. The CO2 sink varied between 0.3 and 86 mmol C m-2 d-1, depending strongly on the open-water fractions (OW) and storm events. The maximum sea-air CO2 fluxes occurred during storm events in February and June. In winter, the main drivers of the change in under-ice water fCO2 were dissolution of CaCO3 (ikaite) and vertical mixing. In June, in addition to these processes, primary production and sea-air CO2 fluxes were important. The cumulative loss due to CaCO3 dissolution of 0.7 mol C m-2 in the upper 10 m played a major role in sustaining the undersaturation of fCO2 during the entire study. The relative effects of the total fCO2 change due to CaCO3 dissolution was 38%, primary production 26%, vertical mixing 16%, sea-air CO2 fluxes 16%, and temperature and salinity insignificant.

Bio-optical properties of Arctic drift ice and surface waters north of Svalbard from winter to spring

Science.gov (United States)

Kowalczuk, Piotr; Meler, Justyna; Kauko, Hanna M.; Pavlov, Alexey K.; Zabłocka, Monika; Peeken, Ilka; Dybwad, Christine; Castellani, Giulia; Granskog, Mats A.

2017-06-01

We have quantified absorption by CDOM, aCDOM(λ), particulate matter, ap(λ), algal pigments, aph(λ), and detrital material, aNAP(λ), coincident with chlorophyll a in sea ice and surface waters in winter and spring 2015 in the Arctic Ocean north of Svalbard. The aCDOM(λ) was low in contrast to other regions of the Arctic Ocean, while ap(λ) has the largest contribution to absorption variability in sea ice and surface waters. ap(443) was 1.4-2.8 times and 1.3-1.8 times higher than aCDOM(443) in surface water and sea ice, respectively. aph(λ) contributed 90% and 81% to ap(λ), in open leads and under-ice waters column, and much less (53%-74%) in sea ice, respectively. Both aCDOM(λ) and ap(λ) followed closely the vertical distribution of chlorophyll a in sea ice and the water column. We observed a tenfold increase of the chlorophyll a concentration and nearly twofold increase in absorption at 443 nm in sea ice from winter to spring. The aCDOM(λ) dominated the absorption budget in the UV both in sea ice and surface waters. In the visible range, absorption was dominated by aph(λ), which contributed more than 50% and aCDOM(λ), which contributed 43% to total absorption in water column. Detrital absorption contributed significantly (33%) only in surface ice layer. Algae dynamics explained more than 90% variability in ap(λ) and aph(λ) in water column, but less than 70% in the sea ice. This study presents detailed absorption budget that is relevant for modeling of radiative transfer and primary production.

Arctic Sea Ice, Eurasia Snow, and Extreme Winter Haze in China

Science.gov (United States)

Zou, Y.; Wang, Y.; Xie, Z.; Zhang, Y.; Koo, J. H.

2017-12-01

Eastern China is experiencing more severe haze pollution in winter during recent years. Though the environmental deterioration in this region is usually attributed to the high intensity of anthropogenic emissions and large contributions from secondary aerosol formation, the impact of climate variability is also indispensable given its significant influence on regional weather systems and pollution ventilation. Here we analyzed the air quality related winter meteorological conditions over Eastern China in the last four decades and showed a worsening trend in poor regional air pollutant ventilation. Such variations increased the probability of extreme air pollution events, which is in good agreement with aerosol observations of recent years. We further identified the key circulation pattern that is conducive to the weakening ventilation and investigated the relationship between synoptic circulation changes and multiple climate forcing variables. Both statistical analysis and numerical sensitivity experiments suggested that the poor ventilation condition is linked to boreal cryosphere changes including Arctic sea ice in preceding autumn and Eurasia snowfall in earlier winter. We conducted comprehensive dynamic diagnosis and proposed a physical mechanism to explain the observed and simulated circulation changes. At last, we examined future projections of winter extreme stagnation events based on the CMIP5 projection data.

Late winter biogeochemical conditions under sea ice in the Canadian High Arctic

Directory of Open Access Journals (Sweden)

Helen S. Findlay

2015-12-01

Full Text Available With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO2 uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO2 measurements during spring, summer or autumn, but there are few data for the winter or winter–spring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (78° 43.11′ N, 104° 47.44′ W in the Canadian High Arctic. Results show relatively low surface water (1–10 m nitrate (<1.3 µM and total inorganic carbon concentrations (mean±SD=2015±5.83 µmol kg−1, total alkalinity (mean±SD=2134±11.09 µmol kg−1 and under-ice pCO2sw (mean±SD=286±17 µatm. These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season.

SERSO: Summer sun against winter ice; SERSO: Mit Sommer-Sonne gegen Winter-Glatteis

Energy Technology Data Exchange (ETDEWEB)

Eugster, W J [Polydynamics Engineering, Zuerich (Switzerland); Hess, K [Polydynamics Engineering, Bremgarten-Bern (Switzerland); Hopkirk, R J [Polydynamics Engineering, Maennedorf (Switzerland)

1997-12-01

Road surfaces absorb energy from the incoming solar radiation in the summer months. The SERSO project was conceived to collect this energy, store it and reuse it during the following winter period to eliminate ice formation on those same road surfaces. The acronym SERSO (Sonnenenergierueckgewinnung aus Strassenoberflaechen) means `solar energy recuperation from road surfaces`. This pilot unit having been conceived, researched an applied to a bridge on the Swiss national expressway A8 near Daerligen on the south side of the lake of Thun was officially opened on 22nd August 1994. Heat exchanger tubes carrying a water/glycol heat transfer fluid were built into the roadbed on the bridge, covering a total area of some 1`300 m{sup 2}. In summer these collect heat from the exposed carriageways, which is then transported in a closed hydraulic circuit to the neighbouring cylindrical underground rock heat storage volume. Within a diameter of 31.5 m and a depth of 65 m heat is exchanged between the heat transfer fluid and the rock via an array of 91 borehole heat exchangers. The operation of the pilot plant has been accompanied by detailed measurement campaign, whereby a total of 132 sensors are interrogated by remote datalogger. The data consist of temperature measurements at several depths and positions both in the roadbed and in the rock storage volume, of energy fluxes in the hydraulic system and of relevant meteorological data. The experiences gianed during the first two years of operation have shown that sufficient heat can indeed be collected in summer to maintain the bridge free of ice during the following winter. Moreover the energy balances derived from the measurements in the low temperature rock heat store have confirmed the predicted storage efficiency. (orig./AKF) [Deutsch] cVerkehrsflaechen heizen sich im Sommer durch Sonneneinstrahlung stark auf. Diese Sommerwaerme zu sammeln, zwischenzuspeichern und im Winter zur Verhinderung von Glatteisbildung wieder zu

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: Mean seasonal cycle

Science.gov (United States)

Li, Linghan; McClean, Julie L.; Miller, Arthur J.; Eisenman, Ian; Hendershott, Myrl C.; Papadopoulos, Caroline A.

2014-12-01

The seasonal cycle of sea ice variability in the Bering Sea, together with the thermodynamic and dynamic processes that control it, are examined in a fine resolution (1/10°) global coupled ocean/sea-ice model configured in the Community Earth System Model (CESM) framework. The ocean/sea-ice model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea Ice Model (CICE). The model was forced with time-varying reanalysis atmospheric forcing for the time period 1970-1989. This study focuses on the time period 1980-1989. The simulated seasonal-mean fields of sea ice concentration strongly resemble satellite-derived observations, as quantified by root-mean-square errors and pattern correlation coefficients. The sea ice energy budget reveals that the seasonal thermodynamic ice volume changes are dominated by the surface energy flux between the atmosphere and the ice in the northern region and by heat flux from the ocean to the ice along the southern ice edge, especially on the western side. The sea ice force balance analysis shows that sea ice motion is largely associated with wind stress. The force due to divergence of the internal ice stress tensor is large near the land boundaries in the north, and it is small in the central and southern ice-covered region. During winter, which dominates the annual mean, it is found that the simulated sea ice was mainly formed in the northern Bering Sea, with the maximum ice growth rate occurring along the coast due to cold air from northerly winds and ice motion away from the coast. South of St Lawrence Island, winds drive the model sea ice southwestward from the north to the southwestern part of the ice-covered region. Along the ice edge in the western Bering Sea, model sea ice is melted by warm ocean water, which is carried by the simulated Bering Slope Current flowing to the northwest, resulting in the S-shaped asymmetric ice edge. In spring and fall, similar thermodynamic and dynamic

Generation of Fullspan Leading-Edge 3D Ice Shapes for Swept-Wing Aerodynamic Testing

Science.gov (United States)

Camello, Stephanie C.; Lee, Sam; Lum, Christopher; Bragg, Michael B.

2016-01-01

The deleterious effect of ice accretion on aircraft is often assessed through dry-air flight and wind tunnel testing with artificial ice shapes. This paper describes a method to create fullspan swept-wing artificial ice shapes from partial span ice segments acquired in the NASA Glenn Icing Reserch Tunnel for aerodynamic wind-tunnel testing. Full-scale ice accretion segments were laser scanned from the Inboard, Midspan, and Outboard wing station models of the 65% scale Common Research Model (CRM65) aircraft configuration. These were interpolated and extrapolated using a weighted averaging method to generate fullspan ice shapes from the root to the tip of the CRM65 wing. The results showed that this interpolation method was able to preserve many of the highly three dimensional features typically found on swept-wing ice accretions. The interpolated fullspan ice shapes were then scaled to fit the leading edge of a 8.9% scale version of the CRM65 wing for aerodynamic wind-tunnel testing. Reduced fidelity versions of the fullspan ice shapes were also created where most of the local three-dimensional features were removed. The fullspan artificial ice shapes and the reduced fidelity versions were manufactured using stereolithography.

Arctic continental shelf morphology related to sea-ice zonation, Beaufort Sea, Alaska

Science.gov (United States)

Reimnitz, E.; Toimil, L.; Barnes, P.

1978-01-01

Landsat-1 and NOAA satellite imagery for the winter 1972-1973, and a variety of ice and sea-floor data were used to study sea-ice zonation and dynamics and their relation to bottom morphology and geology on the Beaufort Sea continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast ice and westward-drifting pack ice of the Pacific Gyre is controlled by major coastal promontories. Pronounced linear pressure- and shear-ridges, as well as hummock fields, form along this boundary and are stabilized by grounding, generally between the 10- and 20-m isobaths. Slippage along this boundary occurs intermittently at or seaward of the grounded ridges, forming new grounded ridges in a widening zone, the stamukhi zone, which by late winter extends out to the 40-m isobath. Between intermittent events along the stamukhi zone, pack-ice drift and slippage is continuous along the shelf edge, at average rates of 3-10 km/day. Whether slippage occurs along the stamukhi zone or along the shelf edge, it is restricted to a zone several hundred meters wide, and ice seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major ice-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of ice up to 400 m in the last 25 years. The sea floor seaward of these shoals within the stamukhi zone shows high ice-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large ice ridges and our sea floor data in the stamukhi zone indicate that much of the available marine energy is expended here, while the inner shelf and coast, where the relatively undeformed fast ice grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to sea-ice zonation, ice dynamics, and bottom

Remarkable link between projected uncertainties of Arctic sea-ice decline and winter Eurasian climate

Science.gov (United States)

Cheung, Hoffman H. N.; Keenlyside, Noel; Omrani, Nour-Eddine; Zhou, Wen

2018-01-01

We identify that the projected uncertainty of the pan-Arctic sea-ice concentration (SIC) is strongly coupled with the Eurasian circulation in the boreal winter (December-March; DJFM), based on a singular value decomposition (SVD) analysis of the forced response of 11 CMIP5 models. In the models showing a stronger sea-ice decline, the Polar cell becomes weaker and there is an anomalous increase in the sea level pressure (SLP) along 60°N, including the Urals-Siberia region and the Iceland low region. There is an accompanying weakening of both the midlatitude westerly winds and the Ferrell cell, where the SVD signals are also related to anomalous sea surface temperature warming in the midlatitude North Atlantic. In the Mediterranean region, the anomalous circulation response shows a decreasing SLP and increasing precipitation. The anomalous SLP responses over the Euro-Atlantic region project on to the negative North Atlantic Oscillation-like pattern. Altogether, pan-Arctic SIC decline could strongly impact the winter Eurasian climate, but we should be cautious about the causality of their linkage.

Parallel algorithm for determining motion vectors in ice floe images by matching edge features

Science.gov (United States)

Manohar, M.; Ramapriyan, H. K.; Strong, J. P.

1988-01-01

A parallel algorithm is described to determine motion vectors of ice floes using time sequences of images of the Arctic ocean obtained from the Synthetic Aperture Radar (SAR) instrument flown on-board the SEASAT spacecraft. Researchers describe a parallel algorithm which is implemented on the MPP for locating corresponding objects based on their translationally and rotationally invariant features. The algorithm first approximates the edges in the images by polygons or sets of connected straight-line segments. Each such edge structure is then reduced to a seed point. Associated with each seed point are the descriptions (lengths, orientations and sequence numbers) of the lines constituting the corresponding edge structure. A parallel matching algorithm is used to match packed arrays of such descriptions to identify corresponding seed points in the two images. The matching algorithm is designed such that fragmentation and merging of ice floes are taken into account by accepting partial matches. The technique has been demonstrated to work on synthetic test patterns and real image pairs from SEASAT in times ranging from .5 to 0.7 seconds for 128 x 128 images.

Improvement in simulation of Eurasian winter climate variability with a realistic Arctic sea ice condition in an atmospheric GCM

International Nuclear Information System (INIS)

Lim, Young-Kwon; Ham, Yoo-Geun; Jeong, Jee-Hoon; Kug, Jong-Seong

2012-01-01

The present study investigates how much a realistic Arctic sea ice condition can contribute to improve simulation of the winter climate variation over the Eurasia region. Model experiments are set up using different sea ice boundary conditions over the past 24 years (i.e., 1988–2011). One is an atmospheric model inter-comparison (AMIP) type of run forced with observed sea-surface temperature (SST), sea ice, and greenhouse gases (referred to as Exp RSI), and the other is the same as Exp RSI except for the sea ice forcing, which is a repeating climatological annual cycle (referred to as Exp CSI). Results show that Exp RSI produces the observed dominant pattern of Eurasian winter temperatures and their interannual variation better than Exp CSI (correlation difference up to ∼0.3). Exp RSI captures the observed strong relationship between the sea ice concentration near the Barents and Kara seas and the temperature anomaly across Eurasia, including northeastern Asia, which is not well captured in Exp CSI. Lagged atmospheric responses to sea ice retreat are examined using observations to understand atmospheric processes for the Eurasian cooling response including the Arctic temperature increase, sea-level pressure increase, upper-level jet weakening and cold air outbreak toward the mid-latitude. The reproducibility of these lagged responses by Exp RSI is also evaluated. (letter)

Improvement in Simulation of Eurasian Winter Climate Variability with a Realistic Arctic Sea Ice Condition in an Atmospheric GCM

Science.gov (United States)

Lim, Young-Kwon; Ham, Yoo-Geun; Jeong, Jee-Hoon; Kug, Jong-Seong

2012-01-01

The present study investigates how much a realistic Arctic sea ice condition can contribute to improve simulation of the winter climate variation over the Eurasia region. Model experiments are set up using different sea ice boundary conditions over the past 24 years (i.e., 1988-2011). One is an atmospheric model inter-comparison (AMIP) type of run forced with observed sea-surface temperature (SST), sea ice, and greenhouse gases (referred to as Exp RSI), and the other is the same as Exp RSI except for the sea ice forcing, which is a repeating climatological annual cycle (referred to as Exp CSI). Results show that Exp RSI produces the observed dominant pattern of Eurasian winter temperatures and their interannual variation better than Exp CSI (correlation difference up to approx. 0.3). Exp RSI captures the observed strong relationship between the sea ice concentration near the Barents and Kara seas and the temperature anomaly across Eurasia, including northeastern Asia, which is not well captured in Exp CSI. Lagged atmospheric responses to sea ice retreat are examined using observations to understand atmospheric processes for the Eurasian cooling response including the Arctic temperature increase, sea-level pressure increase, upper-level jet weakening and cold air outbreak toward the mid-latitude. The reproducibility of these lagged responses by Exp RSI is also evaluated.

Ikaite crystal distribution in winter sea ice and implications for CO2 system dynamics

Science.gov (United States)

Rysgaard, S.; Søgaard, D. H.; Cooper, M.; Pućko, M.; Lennert, K.; Papakyriakou, T. N.; Wang, F.; Geilfus, N. X.; Glud, R. N.; Ehn, J.; McGinnis, D. F.; Attard, K.; Sievers, J.; Deming, J. W.; Barber, D.

2013-04-01

The precipitation of ikaite (CaCO3 ⋅ 6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1 m thick land-fast ice site and a 0.3 m thick polynya site, both in the Young Sound area (74° N, 20° W) of NE Greenland. Ikaite crystals, ranging in size from a few μm to 700 μm, were observed to concentrate in the interstices between the ice platelets in both granular and columnar sea ice. In vertical sea ice profiles from both locations, ikaite concentration determined from image analysis, decreased with depth from surface-ice values of 700-900 μmol kg-1 ice (~25 × 106 crystals kg-1) to values of 100-200 μmol kg-1 ice (1-7 × 106 crystals kg-1) near the sea ice-water interface, all of which are much higher (4-10 times) than those reported in the few previous studies. Direct measurements of total alkalinity (TA) in surface layers fell within the same range as ikaite concentration, whereas TA concentrations in the lower half of the sea ice were twice as high. This depth-related discrepancy suggests interior ice processes where ikaite crystals form in surface sea ice layers and partly dissolve in layers below. Melting of sea ice and dissolution of observed concentrations of ikaite would result in meltwater with a pCO2 of <15 μatm. This value is far below atmospheric values of 390 μatm and surface water concentrations of 315 μatm. Hence, the meltwater increases the potential for seawater uptake of CO2.

Ikaite crystal distribution in Arctic winter sea ice and implications for CO2 system dynamics

Science.gov (United States)

Rysgaard, S.; Søgaard, D. H.; Cooper, M.; Pućko, M.; Lennert, K.; Papakyriakou, T. N.; Wang, F.; Geilfus, N. X.; Glud, R. N.; Ehn, J.; McGinnnis, D. F.; Attard, K.; Sievers, J.; Deming, J. W.; Barber, D.

2012-12-01

The precipitation of ikaite (CaCO3·6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1 m thick land-fast ice site and a 0.3 m thick polynya site, both in the Young Sound area (74° N, 20° W) of NE Greenland. Ikaite crystals, ranging in size from a few µm to 700 µm were observed to concentrate in the interstices between the ice platelets in both granular and columnar sea ice. In vertical sea-ice profiles from both locations, ikaite concentration determined from image analysis, decreased with depth from surfaceice values of 700-900 µmol kg-1 ice (~ 25 × 106 crystals kg-1) to bottom-layer values of 100-200 µmol kg-1 ice (1-7 × 106 kg-1), all of which are much higher (4-10 times) than those reported in the few previous studies. Direct measurements of total alkalinity (TA) in surface layers fell within the same range as ikaite concentration whereas TA concentrations in bottom layers were twice as high. This depth-related discrepancy suggests interior ice processes where ikaite crystals form in surface sea ice layers and partly dissolved in bottom layers. From these findings and model calculations we relate sea ice formation and melt to observed pCO2 conditions in polar surface waters, and hence, the air-sea CO2 flux.

Abnormal Winter Melting of the Arctic Sea Ice Cap Observed by the Spaceborne Passive Microwave Sensors

Directory of Open Access Journals (Sweden)

Seongsuk Lee

2016-12-01

Full Text Available The spatial size and variation of Arctic sea ice play an important role in Earth’s climate system. These are affected by conditions in the polar atmosphere and Arctic sea temperatures. The Arctic sea ice concentration is calculated from brightness temperature data derived from the Defense Meteorological Satellite program (DMSP F13 Special Sensor Microwave/Imagers (SSMI and the DMSP F17 Special Sensor Microwave Imager/Sounder (SSMIS sensors. Many previous studies point to significant reductions in sea ice and their causes. We investigated the variability of Arctic sea ice using the daily and monthly sea ice concentration data from passive microwave observations to identify the sea ice melting regions near the Arctic polar ice cap. We discovered the abnormal melting of the Arctic sea ice near the North Pole even during the summer and the winter. This phenomenon is hard to explain only surface air temperature or solar heating as suggested by recent studies. We propose a hypothesis explaining this phenomenon. The heat from the deep sea in Arctic Ocean ridges and/or the hydrothermal vents might be contributing to the melting of Arctic sea ice. This hypothesis could be verified by the observation of warm water column structure below the melting or thinning arctic sea ice through the project such as Coriolis dataset for reanalysis (CORA.

Safe Loads on Ice Sheets (Ice Engineering. Number 13)

National Research Council Canada - National Science Library

Haynes, F. D; Carey, Kevin L; Cattabriga, Gioia

1996-01-01

Every winter, ice sheets that grow on lakes and rivers in northern states are used for ice roads, ice bridges, construction platforms, airstrips, and recreational activities, It becomes very important...

Arctic multiyear ice classification and summer ice cover using passive microwave satellite data

Science.gov (United States)

Comiso, J. C.

1990-08-01

The ability to classify and monitor Arctic multiyear sea ice cover using multispectral passive microwave data is studied. Sea ice concentration maps during several summer minima have been analyzed to obtain estimates of ice surviving the summer. The results are compared with multiyear ice concentrations derived from data the following winter, using an algorithm that assumes a certain emissivity for multiyear ice. The multiyear ice cover inferred from the winter data is approximately 25 to 40% less than the summer ice cover minimum, suggesting that even during winter when the emissivity of sea ice is most stable, passive microwave data may account for only a fraction of the total multiyear ice cover. The difference of about 2×106 km2 is considerably more than estimates of advection through Fram Strait during the intervening period. It appears that as in the Antarctic, some multiyear ice floes in the Arctic, especially those near the summer marginal ice zone, have first-year ice or intermediate signatures in the subsequent winter. A likely mechanism for this is the intrusion of seawater into the snow-ice interface, which often occurs near the marginal ice zone or in areas where snow load is heavy. Spatial variations in melt and melt ponding effects also contribute to the complexity of the microwave emissivity of multiyear ice. Hence the multiyear ice data should be studied in conjunction with the previous summer ice data to obtain a more complete characterization of the state of the Arctic ice cover. The total extent and actual areas of the summertime Arctic pack ice were estimated to be 8.4×106 km2 and 6.2×106 km2, respectively, and exhibit small interannual variability during the years 1979 through 1985, suggesting a relatively stable ice cover.

Field investigations of apparent optical properties of ice cover in Finnish and Estonian lakes in winter 2009

Directory of Open Access Journals (Sweden)

Ruibo Lei

2011-03-01

Full Text Available A field programme on light conditions in ice-covered lakes and optical properties of lake ice was performed in seven lakes of Finland and Estonia in February–April 2009. On the basis of irradiance measurements above and below ice, spectral reflectance and transmittance were determined for the ice sheet; time evolution of photosynthetically active radiation (PAR transmittance was examined from irradiance recordings at several levels inside the ice sheet. Snow cover was the dominant factor for transmission of PAR into the lake water body. Reflectance was 0.74–0.92 in winter, going down to 0.18–0.22 in the melting season. The bulk attenuation coefficient of dry snow was 14–25 m–1; the level decreased as the spring was coming. The reflectance and bulk attenuation coefficient of snow-free ice were 0.1–0.4 and 1–5 m–1. Both were considerably smaller than those of snow cover. Seasonal evolution of light transmission was mainly due to snow melting. Snow and ice cover not only depress the PAR level in a lake but also influence the spectral and directional distribution of light.

Seasonal regional forecast of the minimum sea ice extent in the LapteV Sea

Science.gov (United States)

Tremblay, B.; Brunette, C.; Newton, R.

2017-12-01

Late winter anomaly of sea ice export from the peripheral seas of the Atctic Ocean was found to be a useful predictor for the minimum sea ice extent (SIE) in the Arctic Ocean (Williams et al., 2017). In the following, we present a proof of concept for a regional seasonal forecast of the min SIE for the Laptev Sea based on late winter coastal divergence quantified using a Lagrangian Ice Tracking System (LITS) forced with satellite derived sea-ice drifts from the Polar Pathfinder. Following Nikolaeva and Sesterikov (1970), we track an imaginary line just offshore of coastal polynyas in the Laptev Sea from December of the previous year to May 1 of the following year using LITS. Results show that coastal divergence in the Laptev Sea between February 1st and May 1st is best correlated (r = -0.61) with the following September minimum SIE in accord with previous results from Krumpen et al. (2013, for the Laptev Sea) and Williams et a. (2017, for the pan-Arctic). This gives a maximum seasonal predictability of Laptev Sea min SIE anomalies from observations of approximately 40%. Coastal ice divergence leads to formation of thinner ice that melts earlier in early summer, hence creating areas of open water that have a lower albedo and trigger an ice-albedo feedback. In the Laptev Sea, we find that anomalies of coastal divergence in late winter are amplified threefold to result in the September SIE. We also find a correlation coefficient r = 0.49 between February-March-April (FMA) anomalies of coastal divergence with the FMA averaged AO index. Interestingly, the correlation is stronger, r = 0.61, when comparing the FMA coastal divergence anomalies to the DJFMA averaged AO index. It is hypothesized that the AO index at the beginning of the winter (and the associated anomalous sea ice export) also contains information that impact the magnitude of coastal divergence opening later in the winter. Our approach differs from previous approaches (e.g. Krumpen et al and Williams et al

Determining the ice seasons severity during 1982-2015 using the ice extents sum as a new characteristic

Science.gov (United States)

Rjazin, Jevgeni; Pärn, Ove

2016-04-01

Sea ice is a key climate factor and it restricts considerably the winter navigation in sever seasons on the Baltic Sea. So determining ice conditions severity and describing ice cover behaviour at severe seasons interests scientists, engineers and navigation managers. The present study is carried out to determine the ice seasons severity degree basing on the ice seasons 1982 to 2015. A new integrative characteristic is introduced to describe the ice season severity. It is the sum of ice extents of the ice season id est the daily ice extents of the season are summed. The commonly used procedure to determine the ice season severity degree by the maximal ice extent is in this research compared to the new characteristic values. The remote sensing data on the ice concentrations on the Baltic Sea published in the European Copernicus Programme are used to obtain the severity characteristic values. The ice extents are calculated on these ice concentration data. Both the maximal ice extent of the season and a newly introduced characteristic - the ice extents sum are used to classify the winters with respect of severity. The most severe winter of the reviewed period is 1986/87. Also the ice seasons 1981/82, 1984/85, 1985/86, 1995/96 and 2002/03 are classified as severe. Only three seasons of this list are severe by both the criteria. They are 1984/85, 1985/86 and 1986/87. We interpret this coincidence as the evidence of enough-during extensive ice cover in these three seasons. In several winters, for example 2010/11 ice cover extended enough for some time, but did not endure. At few other ice seasons as 2002/03 the Baltic Sea was ice-covered in moderate extent, but the ice cover stayed long time. At 11 winters the ice extents sum differed considerably (> 10%) from the maximal ice extent. These winters yield one third of the studied ice seasons. The maximal ice extent of the season is simple to use and enables to reconstruct the ice cover history and to predict maximal ice

NASA/FAA/NCAR Supercooled Large Droplet Icing Flight Research: Summary of Winter 1996-1997 Flight Operations

Science.gov (United States)

Miller, Dean; Ratvasky, Thomas; Bernstein, Ben; McDonough, Frank; Strapp, J. Walter

1998-01-01

During the winter of 1996-1997, a flight research program was conducted at the NASA-Lewis Research Center to study the characteristics of Supercooled Large Droplets (SLD) within the Great Lakes region. This flight program was a joint effort between the National Aeronautics and Space Administration (NASA), the National Center for Atmospheric Research (NCAR), and the Federal Aviation Administration (FAA). Based on weather forecasts and real-time in-flight guidance provided by NCAR, the NASA-Lewis Icing Research Aircraft was flown to locations where conditions were believed to be conducive to the formation of Supercooled Large Droplets aloft. Onboard instrumentation was then used to record meteorological, ice accretion, and aero-performance characteristics encountered during the flight. A total of 29 icing research flights were conducted, during which "conventional" small droplet icing, SLD, and mixed phase conditions were encountered aloft. This paper will describe how flight operations were conducted, provide an operational summary of the flights, present selected experimental results from one typical research flight, and conclude with practical "lessons learned" from this first year of operation.

Wave–ice interactions in the neXtSIM sea-ice model

Directory of Open Access Journals (Sweden)

T. D. Williams

2017-09-01

Full Text Available In this paper we describe a waves-in-ice model (WIM, which calculates ice breakage and the wave radiation stress (WRS. This WIM is then coupled to the new sea-ice model neXtSIM, which is based on the elasto-brittle (EB rheology. We highlight some numerical issues involved in the coupling and investigate the impact of the WRS, and of modifying the EB rheology to lower the stiffness of the ice in the area where the ice has broken up (the marginal ice zone or MIZ. In experiments in the absence of wind, we find that wind waves can produce noticeable movement of the ice edge in loose ice (concentration around 70 % – up to 36 km, depending on the material parameters of the ice that are used and the dynamical model used for the broken ice. The ice edge position is unaffected by the WRS if the initial concentration is higher (≳ 0.9. Swell waves (monochromatic waves with low frequency do not affect the ice edge location (even for loose ice, as they are attenuated much less than the higher-frequency components of a wind wave spectrum, and so consequently produce a much lower WRS (by about an order of magnitude at least.In the presence of wind, we find that the wind stress dominates the WRS, which, while large near the ice edge, decays exponentially away from it. This is in contrast to the wind stress, which is applied over a much larger ice area. In this case (when wind is present the dynamical model for the MIZ has more impact than the WRS, although that effect too is relatively modest. When the stiffness in the MIZ is lowered due to ice breakage, we find that on-ice winds produce more compression in the MIZ than in the pack, while off-ice winds can cause the MIZ to be separated from the pack ice.

White Sea's Severe Winter Hydrological Hazard and Its Effect On Decrease of Population of Greenland Seals (1998/99 Winter Ecological Catastrophe)

Science.gov (United States)

Melentyev, Konstantin V.; Chernook, Vladimir I.

Types of hydrological hazards are various but its agencies are especially diversified . At this study hazard effects will be assessed for White Sea population of Greenland seals - a representatives of high level of marine fodder chains and the prime part of the Arctic nature. Number of population and type of their migration are strongly depended from different meteorological and hydrological parameters and processes, climate change and anthropogenical press, including pollution and fur-seal fishery, create additional problems. Especially hard situation happens now with the ice- associated sea mammals (p olar bear, seal, walrus, etc.). Mass destruction of seals in the White Sea (ecological catastrophe) which happens periodically is close connected with different kind of meteorological and hydrological hazard. Greenland seals selected these water areas for whelping where a rookeries are organized on pack ice. But severe winter conditions (long-run severe frosts and NE winds) can modify ice regime of the White Sea which lead to effect "blocking" of pack ice (and whelping rookeries) inside the "Basin". These features stimulated strong reduction number ofseals (especially pups). Marine biology use modelling of the system "sea mammal-media", study "behavior factors" and mammals biodiversity at the different natural conditions. But the main critical goal is the development of special observational network for the White Sea and contiguous regions. A contemporary technologies assume integration of remote sensing and in situ hydro-chemical measurements. Airborne IR and visible observation of the marginal Arctic seas became now an indispensable part of marine ecological investigations. Application of satellite data for monitoring of sea mammals has been attractive also but practical use is restrained by its small spatial resolution, daytime illumination and cloud influence in the Arctic. Launching ERS synthetic aperture radar (SAR) in 1991, which provides global all- weather

36 CFR 1002.19 - Winter activities.

Science.gov (United States)

2010-07-01

... RECREATION § 1002.19 Winter activities. (a) Skiing, snowshoeing, ice skating, sledding, innertubing, tobogganing and similar winter sports are prohibited on Presidio Trust roads and in parking areas open to...

[Comparison of red edge parameters of winter wheat canopy under late frost stress].

Science.gov (United States)

Wu, Yong-feng; Hu, Xin; Lü, Guo-hua; Ren, De-chao; Jiang, Wei-guo; Song, Ji-qing

2014-08-01

In the present study, late frost experiments were implemented under a range of subfreezing temperatures (-1 - -9 degrees C) by using a field movable climate chamber (FMCC) and a cold climate chamber, respectively. Based on the spectra of winter wheat canopy measured at noon on the first day after the frost experiments, red edge parameters REP, Dr, SDr, Dr(min), Dr/Dr(min) and Dr/SDr were extracted using maximum first derivative spectrum method (FD), linear four-point interpolation method (FPI), polynomial fitting method (POLY), inverted Gaussian fitting method (IG) and linear extrapolation technique (LE), respectively. The capacity of the red edge parameters to detect late frost stress was explicated from the aspects of the early, sensitivity and stability through correlation analysis, linear regression modeling and fluctuation analysis. The result indicates that except for REP calculated from FPI and IG method in Experiment 1, REP from the other methods was correlated with frost temperatures (P frost temperatures (P frost temperatures which indicated that LE method is the best for REP extraction. In Experiment 1 and 2, only Dr(min) and Dr/Dr(min), calculated by FD method simultaneously achieved the requirements for the early (their correlations with frost temperatures showed a significant level P frost temperatures al- ways keep a consistent direction). Dr/SDr calculated from FD and IG methods always had a low sensitivity in Experiment 2. In Experiment 1, the sensitivity of Dr/SDr from FD was moderate and IG was high. REP calculated from LE method had a lowest sensitivity in the two experiments. Totally, Dr(min) and Dr/Dr(min) calculated by FD method have the strongest detection capacity for frost temperature, which will be helpful to conducting the research on early diagnosis of late frost injury to winter wheat.

Measurements of IN and BIO-IN with the fast ice nucleus chamber FINCH at Mt. Zugspitze, Mt. Puy de Dôme and Jungfraujoch during fall and winter

Science.gov (United States)

Nillius, B.; Frank, F.; Bingemer, H.; Curtius, J.; Bundke, U.

2013-05-01

In this work we present IN measurements at Mt. Zugspitze, Germany, 2650 m.a.s.l., Mt. Puy de Dôme, France, 1464 m.a.s.l. and Jungfraujoch, Switzerland, 3580 m a.s.l during fall and winter 2012 with the instrument FINCH HALO (Fast Ice Nucleus Chamber for the High Altitude and LOng range research aircraft HALO). In this device the temperature and super saturation for activation of Ice Nuclei (IN) and the growth to ice crystals is obtained by mixing three gas flows of different temperatures and moisture. After the growth of IN and Cloud Condensation Nuclei (CCN) to macroscopic ice crystals and super-cooled water droplets in the development chamber, they are counted using an optical detector. The discrimination between ice and water is made by measuring the circular depolarization ratio of the backscattered laser light of each individual particle. IN are classified as biological particles by measuring their individual intrinsic-fluorescence during the winter campaigns in average 30-40 % of the IN show an intrinsic fluorescence and are supposed to be of biological origin.

Contrasts in Sea Ice Formation and Production in the Arctic Seasonal and Perennial Ice Zones

Science.gov (United States)

Kwok, R.

2006-01-01

Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. 3-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the mid-winter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m) - this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by: local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and, the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice.

State of Arctic Sea Ice North of Svalbard during N-ICE2015

Science.gov (United States)

Rösel, Anja; King, Jennifer; Gerland, Sebastian

2016-04-01

The N-ICE2015 cruise, led by the Norwegian Polar Institute, was a drift experiment with the research vessel R/V Lance from January to June 2015, where the ship started the drift North of Svalbard at 83°14.45' N, 21°31.41' E. The drift was repeated as soon as the vessel drifted free. Altogether, 4 ice stations where installed and the complex ocean-sea ice-atmosphere system was studied with an interdisciplinary Approach. During the N-ICE2015 cruise, extensive ice thickness and snow depth measurements were performed during both, winter and summer conditions. Total ice and snow thickness was measured with ground-based and airborne electromagnetic instruments; snow depth was measured with a GPS snow depth probe. Additionally, ice mass balance and snow buoys were deployed. Snow and ice thickness measurements were performed on repeated transects to quantify the ice growth or loss as well as the snow accumulation and melt rate. Additionally, we collected independent values on surveys to determine the general ice thickness distribution. Average snow depths of 32 cm on first year ice, and 52 cm on multi-year ice were measured in January, the mean snow depth on all ice types even increased until end of March to 49 cm. The average total ice and snow thickness in winter conditions was 1.92 m. During winter we found a small growth rate on multi-year ice of about 15 cm in 2 months, due to above-average snow depths and some extraordinary storm events that came along with mild temperatures. In contrast thereto, we also were able to study new ice formation and thin ice on newly formed leads. In summer conditions an enormous melt rate, mainly driven by a warm Atlantic water inflow in the marginal ice zone, was observed during two ice stations with melt rates of up to 20 cm per 24 hours. To reinforce the local measurements around the ship and to confirm their significance on a larger scale, we compare them to airborne thickness measurements and classified SAR-satellite scenes. The

Atmospheric components of the surface energy budget over young sea ice: Results from the N-ICE2015 campaign

Science.gov (United States)

Walden, Von P.; Hudson, Stephen R.; Cohen, Lana; Murphy, Sarah Y.; Granskog, Mats A.

2017-08-01

The Norwegian young sea ice campaign obtained the first measurements of the surface energy budget over young, thin Arctic sea ice through the seasonal transition from winter to summer. This campaign was the first of its kind in the North Atlantic sector of the Arctic. This study describes the atmospheric and surface conditions and the radiative and turbulent heat fluxes over young, thin sea ice. The shortwave albedo of the snow surface ranged from about 0.85 in winter to 0.72-0.80 in early summer. The near-surface atmosphere was typically stable in winter, unstable in spring, and near neutral in summer once the surface skin temperature reached 0°C. The daily average radiative and turbulent heat fluxes typically sum to negative values (-40 to 0 W m-2) in winter but then transition toward positive values of up to nearly +60 W m-2 as solar radiation contributes significantly to the surface energy budget. The sensible heat flux typically ranges from +20-30 W m-2 in winter (into the surface) to negative values between 0 and -20 W m-2 in spring and summer. A winter case study highlights the significant effect of synoptic storms and demonstrates the complex interplay of wind, clouds, and heat and moisture advection on the surface energy components over sea ice in winter. A spring case study contrasts a rare period of 24 h of clear-sky conditions with typical overcast conditions and highlights the impact of clouds on the surface radiation and energy budgets over young, thin sea ice.

Polynya dynamics and associated atmospheric forcing at the Ronne Ice Shelf

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Ebner, Lars; Heinemann, Günther

2014-05-01

The Ronne Ice Shelf is known as one of the most active regions of polynya developments around the Antarctic continent. Low temperatures are prevailing throughout the whole year, particularly in winter. It is generally recognized that polynya formations are primarily forced by offshore winds and secondarily by ocean currents. Many authors have addressed this issue previously at the Ross Ice Shelf and Adélie Coast and connected polynya dynamics to strong katabatic surge events. Such investigations of atmospheric dynamics and simultaneous polynya occurrence are still severely underrepresented for the southwestern part of the Weddell Sea and especially for the Ronne Ice Shelf. Due to the very flat terrain gradients of the ice shelf katabatic winds are of minor importance in that area. Other atmospheric processes must therefore play a crucial role for polynya developments at the Ronne Ice Shelf. High-resolution simulations have been carried out for the Weddell Sea region using the non-hydrostatic NWP model COSMO from the German Meteorological Service (DWD). For the austral autumn and winter (March to August) 2008 daily forecast simulations were conducted with the consideration of daily sea-ice coverage deduced from the passive microwave system AMSR-E. These simulations are used to analyze the synoptic and mesoscale atmospheric dynamics of the Weddell Sea region and find linkages to polynya occurrence at the Ronne Ice Shelf. For that reason, the relation between the surface wind speed, the synoptic pressure gradient in the free atmosphere and polynya area is investigated. Seven significant polynya events are identified for the simulation period, three in the autumn and four in the winter season. It can be shown that in almost all cases synoptic cyclones are the primary polynya forcing systems. In most cases the timely interaction of several passing cyclones in the northern and central Weddell Sea leads to maintenance of a strong synoptic pressure gradient above the

Ross Ice Shelf, Antarctic Ice and Clouds

Science.gov (United States)

1991-01-01

In this view of Antarctic ice and clouds, (56.5S, 152.0W), the Ross Ice Shelf of Antarctica is almost totally clear, showing stress cracks in the ice surface caused by wind and tidal drift. Clouds on the eastern edge of the picture are associated with an Antarctic cyclone. Winds stirred up these storms have been known to reach hurricane force.

Sea ice roughness: the key for predicting Arctic summer ice albedo

Science.gov (United States)

Landy, J.; Ehn, J. K.; Tsamados, M.; Stroeve, J.; Barber, D. G.

2017-12-01

Although melt ponds on Arctic sea ice evolve in stages, ice with smoother surface topography typically allows the pond water to spread over a wider area, reducing the ice-albedo and accelerating further melt. Building on this theory, we simulated the distribution of meltwater on a range of statistically-derived topographies to develop a quantitative relationship between premelt sea ice surface roughness and summer ice albedo. Our method, previously applied to ICESat observations of the end-of-winter sea ice roughness, could account for 85% of the variance in AVHRR observations of the summer ice-albedo [Landy et al., 2015]. Consequently, an Arctic-wide reduction in sea ice roughness over the ICESat operational period (from 2003 to 2008) explained a drop in ice-albedo that resulted in a 16% increase in solar heat input to the sea ice cover. Here we will review this work and present new research linking pre-melt sea ice surface roughness observations from Cryosat-2 to summer sea ice albedo over the past six years, examining the potential of winter roughness as a significant new source of sea ice predictability. We will further evaluate the possibility for high-resolution (kilometre-scale) forecasts of summer sea ice albedo from waveform-level Cryosat-2 roughness data in the landfast sea ice zone of the Canadian Arctic. Landy, J. C., J. K. Ehn, and D. G. Barber (2015), Albedo feedback enhanced by smoother Arctic sea ice, Geophys. Res. Lett., 42, 10,714-10,720, doi:10.1002/2015GL066712.

Late winter under ice pelagic microbial communities in the high Arctic Ocean and the impact of short-term exposure to elevated CO2 levels

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Adam eMonier

2014-09-01

Full Text Available Polar Oceans are natural CO2 sinks because of the enhanced solubility of CO2 in cold water. The Arctic Ocean is at additional risk of accelerated ocean acidification (OA because of freshwater inputs from sea ice and rivers, which influence the carbonate system. Winter conditions in the Arctic are of interest because of both cold temperatures and limited CO2 venting to the atmosphere when sea ice is present. Earlier OA experiments on Arctic microbial communities conducted in the absence of ice cover, hinted at shifts in taxa dominance and diversity under lowered pH. The Catlin Arctic Survey provided an opportunity to conduct in situ, under-ice, OA experiments during late Arctic winter. Seawater was collected from under the sea ice off Ellef Ringnes Island, and communities were exposed to three CO2 levels for 6 days. Phylogenetic diversity was greater in the attached fraction compared to the free-living fraction in situ, in the controls and in the treatments. The dominant taxa in all cases were Gammaproteobacteria but acidification had little effect compared to the effects of containment. Phylogenetic net relatedness indices suggested that acidification may have decreased the diversity within some bacterial orders, but overall there was no clear trend. Within the experimental communities, alkalinity best explained the variance among samples and replicates, suggesting subtle changes in the carbonate system need to be considered in such experiments. We conclude that under ice communities have the capacity to respond either by selection or phenotypic plasticity to heightened CO2 levels over the short term.

Enhanced tropospheric BrO over Antarctic sea ice in mid winter observed by MAX-DOAS on board the research vessel Polarstern

Directory of Open Access Journals (Sweden)

T. Wagner

2007-06-01

Full Text Available We present Multi AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS observations of tropospheric BrO carried out on board the German research vessel Polarstern during the Antarctic winter 2006. Polarstern entered the area of first year sea ice around Antarctica on 24 June 2006 and stayed within this area until 15 August 2006. For the period when the ship cruised inside the first year sea ice belt, enhanced BrO concentrations were almost continuously observed. Outside the first year sea ice belt, typically low BrO concentrations were found. Based on back trajectory calculations we find a positive correlation between the observed BrO differential slant column densities (ΔSCDs and the duration for which the air masses had been in contact with the sea ice surface prior to the measurement. While we can not completely rule out that in several cases the highest BrO concentrations might be located close to the ground, our observations indicate that the maximum BrO concentrations might typically exist in a (possibly extended layer around the upper edge of the boundary layer. Besides the effect of a decreasing pH of sea salt aerosol with altitude and therefore an increase of BrO with height, this finding might be also related to vertical mixing of air from the free troposphere with the boundary layer, probably caused by convection over the warm ocean surface at polynyas and cracks in the ice. Strong vertical gradients of BrO and O₃ could also explain why we found enhanced BrO levels almost continuously for the observations within the sea ice. Based on our estimated BrO profiles we derive BrO mixing ratios of several ten ppt, which is slightly higher than many existing observations. Our observations indicate that enhanced BrO concentrations around Antarctica exist about one month earlier than observed by satellite instruments. From detailed radiative transfer simulations we find that MAX-DOAS observations are up to about one order of

Ice cream structure modification by ice-binding proteins.

Science.gov (United States)

Kaleda, Aleksei; Tsanev, Robert; Klesment, Tiina; Vilu, Raivo; Laos, Katrin

2018-04-25

Ice-binding proteins (IBPs), also known as antifreeze proteins, were added to ice cream to investigate their effect on structure and texture. Ice recrystallization inhibition was assessed in the ice cream mixes using a novel accelerated microscope assay and the ice cream microstructure was studied using an ice crystal dispersion method. It was found that adding recombinantly produced fish type III IBPs at a concentration 3 mg·L -1 made ice cream hard and crystalline with improved shape preservation during melting. Ice creams made with IBPs (both from winter rye, and type III IBP) had aggregates of ice crystals that entrapped pockets of the ice cream mixture in a rigid network. Larger individual ice crystals and no entrapment in control ice creams was observed. Based on these results a model of ice crystals aggregates formation in the presence of IBPs was proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Removable cruciform for ice condenser ice basket

International Nuclear Information System (INIS)

Scrabis, C.M.; Mazza, G.E.; Golick, L.R.; Pomaibo, P.

1987-01-01

A removable cruciform for use in an ice basket having a generally cylindrical sidewall defining a central, vertical axis of the ice basket and plural, generally annular retaining rings secured to the interior of the cylindrical sidewall of the ice basket at predetermined, spaced elevations throughout the axial height of the ice basket is described comprising: a pair of brackets, each comprising a central, base portion having parallel longitudinal edges and a pair of integral legs extending at corresponding angles relative to the base portion from the perspective parallel longitudinal edges thereof; a pair of support plate assemblies secured to and extending in parallel, spaced relationship from one of the pair of brackets; a pair of slide support plates secured to the other of the pair of brackets and extending therefrom in spaced, parallel relationship; and spring means received within the housing and engaging the base portions of the brackets and applying a resilient biasing force thereto for maintaining the spaced relationship thereof

Ecology of southern ocean pack ice.

Science.gov (United States)

Brierley, Andrew S; Thomas, David N

2002-01-01

Around Antarctica the annual five-fold growth and decay of sea ice is the most prominent physical process and has a profound impact on marine life there. In winter the pack ice canopy extends to cover almost 20 million square kilometres--some 8% of the southern hemisphere and an area larger than the Antarctic continent itself (13.2 million square kilometres)--and is one of the largest, most dynamic ecosystems on earth. Biological activity is associated with all physical components of the sea-ice system: the sea-ice surface; the internal sea-ice matrix and brine channel system; the underside of sea ice and the waters in the vicinity of sea ice that are modified by the presence of sea ice. Microbial and microalgal communities proliferate on and within sea ice and are grazed by a wide range of proto- and macrozooplankton that inhabit the sea ice in large concentrations. Grazing organisms also exploit biogenic material released from the sea ice at ice break-up or melt. Although rates of primary production in the underlying water column are often low because of shading by sea-ice cover, sea ice itself forms a substratum that provides standing stocks of bacteria, algae and grazers significantly higher than those in ice-free areas. Decay of sea ice in summer releases particulate and dissolved organic matter to the water column, playing a major role in biogeochemical cycling as well as seeding water column phytoplankton blooms. Numerous zooplankton species graze sea-ice algae, benefiting additionally because the overlying sea-ice ceiling provides a refuge from surface predators. Sea ice is an important nursery habitat for Antarctic krill, the pivotal species in the Southern Ocean marine ecosystem. Some deep-water fish migrate to shallow depths beneath sea ice to exploit the elevated concentrations of some zooplankton there. The increased secondary production associated with pack ice and the sea-ice edge is exploited by many higher predators, with seals, seabirds and whales

Winter survival of Scots pine seedlings under different snow conditions.

Science.gov (United States)

Domisch, Timo; Martz, Françoise; Repo, Tapani; Rautio, Pasi

2018-04-01

Future climate scenarios predict increased air temperatures and precipitation, particularly at high latitudes, and especially so during winter. Soil temperatures, however, are more difficult to predict, since they depend strongly on the fate of the insulating snow cover. 'Rain-on-snow' events and warm spells during winter can lead to thaw-freeze cycles, compacted snow and ice encasement, as well as local flooding. These adverse conditions could counteract the otherwise positive effects of climatic changes on forest seedling growth. In order to study the effects of different winter and snow conditions on young Scots pine (Pinus sylvestris L.) seedlings, we conducted a laboratory experiment in which 80 1-year-old Scots pine seedlings were distributed between four winter treatments in dasotrons: ambient snow cover (SNOW), compressed snow and ice encasement (ICE), flooded and frozen soil (FLOOD) and no snow (NO SNOW). During the winter treatment period and a 1.5-month simulated spring/early summer phase, we monitored the needle, stem and root biomass of the seedlings, and determined their starch and soluble sugar concentrations. In addition, we assessed the stress experienced by the seedlings by measuring chlorophyll fluorescence, electric impedance and photosynthesis of the previous-year needles. Compared with the SNOW treatment, carbohydrate concentrations were lower in the FLOOD and NO SNOW treatments where the seedlings had almost died before the end of the experiment, presumably due to frost desiccation of aboveground parts during the winter treatments. The seedlings of the ICE treatment showed dead needles and stems only above the snow and ice cover. The results emphasize the importance of an insulating and protecting snow cover for small forest tree seedlings, and that future winters with changed snow patterns might affect the survival of tree seedlings and thus forest productivity.

Changes in the seasonality of Arctic sea ice and temperature

Science.gov (United States)

Bintanja, R.

2012-04-01

Observations show that the Arctic sea ice cover is currently declining as a result of climate warming. According to climate models, this retreat will continue and possibly accelerate in the near-future. However, the magnitude of this decline is not the same throughout the year. With temperatures near or above the freezing point, summertime Arctic sea ice will quickly diminish. However, at temperatures well below freezing, the sea ice cover during winter will exhibit a much weaker decline. In the future, the sea ice seasonal cycle will be no ice in summer, and thin one-year ice in winter. Hence, the seasonal cycle in sea ice cover will increase with ongoing climate warming. This in itself leads to an increased summer-winter contrast in surface air temperature, because changes in sea ice have a dominant influence on Arctic temperature and its seasonality. Currently, the annual amplitude in air temperature is decreasing, however, because winters warm faster than summer. With ongoing summer sea ice reductions there will come a time when the annual temperature amplitude will increase again because of the large seasonal changes in sea ice. This suggests that changes in the seasonal cycle in Arctic sea ice and temperature are closely, and intricately, connected. Future changes in Arctic seasonality (will) have an profound effect on flora, fauna, humans and economic activities.

Observations of Recent Arctic Sea Ice Volume Loss and Its Impact on Ocean-Atmosphere Energy Exchange and Ice Production

Science.gov (United States)

Kurtz, N. T.; Markus, T.; Farrell, S. L.; Worthen, D. L.; Boisvert, L. N.

2011-01-01

Using recently developed techniques we estimate snow and sea ice thickness distributions for the Arctic basin through the combination of freeboard data from the Ice, Cloud, and land Elevation Satellite (ICESat) and a snow depth model. These data are used with meteorological data and a thermodynamic sea ice model to calculate ocean-atmosphere heat exchange and ice volume production during the 2003-2008 fall and winter seasons. The calculated heat fluxes and ice growth rates are in agreement with previous observations over multiyear ice. In this study, we calculate heat fluxes and ice growth rates for the full distribution of ice thicknesses covering the Arctic basin and determine the impact of ice thickness change on the calculated values. Thinning of the sea ice is observed which greatly increases the 2005-2007 fall period ocean-atmosphere heat fluxes compared to those observed in 2003. Although there was also a decline in sea ice thickness for the winter periods, the winter time heat flux was found to be less impacted by the observed changes in ice thickness. A large increase in the net Arctic ocean-atmosphere heat output is also observed in the fall periods due to changes in the areal coverage of sea ice. The anomalously low sea ice coverage in 2007 led to a net ocean-atmosphere heat output approximately 3 times greater than was observed in previous years and suggests that sea ice losses are now playing a role in increasing surface air temperatures in the Arctic.

First Observation of Rock Motion on Racetrack Playa, Death Valley National Park—Role of a Persistent Pool, Sun, Zephyrs, Windowpane Ice, and Tugboats

Science.gov (United States)

Norris, R. D.; Norris, J. M.

2014-12-01

Trails in the mud-cracked surface of Racetrack Playa have been scored by hundreds of rocks up to 320 kg, but the mechanism of movement is debated. In Winter 2013-2014, we observed rocks in motion associated with a transient pool formed by winter precipitation. The pond was 7 cm deep on the southern edge of the playa, tapering to a mud flat to the north. Freezing during cold winter nights formed floating "windowpane" ice 3-5 mm thick. Rocks repeatedly moved on sunny days under light winds of 3-5 m/second, as the ice broke up near midday and was set into motion by wind stress on melt pools and the ice surface. Ice panels shoved rocks along the mud like a tugboat, sometimes forming moving imbricated ice piles upstream of the rocks and in other cases moving faster than the rocks and forming brash-filled leads downstream. GPS units mounted in experimental rocks recorded a creeping pace of 2-6 m/minute, a speed that made it difficult to observe trail formation visually. The 2013-2014 pond formed on November 20-24 and persisted through early February 2014. During this time rocks were observed moving at least five times, and studies of "stiz marks" formed by rocks at the ends of trail segments show that there were likely 3-5 additional move events. Observed travel times ranged from a few seconds to 16 minutes. In one event, two experimental rocks 153 m apart began moving simultaneously and traveled 64.1 and 65.6 m respectively, ultimately moving 157-162 m in subsequent events. Rock motion depends on the creation of winter pools sufficiently deep to allow the formation of floating ice and exposed to the light winds and sun needed for ice breakup. The combination of these events is extremely rare, leading to highly episodic trail formation. Our observations differ from previous hypotheses in that the rocks were moved by thinner ice, at slower speeds, and by lighter winds than predicted.

Aircraft Surveys of the Beaufort Sea Seasonal Ice Zone

Science.gov (United States)

Morison, J.

2016-02-01

The Seasonal Ice Zone Reconnaissance Surveys (SIZRS) is a program of repeated ocean, ice, and atmospheric measurements across the Beaufort-Chukchi sea seasonal sea ice zone (SIZ) utilizing US Coast Guard Arctic Domain Awareness (ADA) flights of opportunity. The SIZ is the region between maximum winter sea ice extent and minimum summer sea ice extent. As such, it contains the full range of positions of the marginal ice zone (MIZ) where sea ice interacts with open water. The increasing size and changing air-ice-ocean properties of the SIZ are central to recent reductions in Arctic sea ice extent. The changes in the interplay among the atmosphere, ice, and ocean require a systematic SIZ observational effort of coordinated atmosphere, ice, and ocean observations covering up to interannual time-scales, Therefore, every year beginning in late Spring and continuing to early Fall, SIZRS makes monthly flights across the Beaufort Sea SIZ aboard Coast Guard C-130H aircraft from USCG Air Station Kodiak dropping Aircraft eXpendable CTDs (AXCTD) and Aircraft eXpendable Current Profilers (AXCP) for profiles of ocean temperature, salinity and shear, dropsondes for atmospheric temperature, humidity, and velocity profiles, and buoys for atmosphere and upper ocean time series. Enroute measurements include IR imaging, radiometer and lidar measurements of the sea surface and cloud tops. SIZRS also cooperates with the International Arctic Buoy Program for buoy deployments and with the NOAA Earth System Research Laboratory atmospheric chemistry sampling program on board the aircraft. Since 2012, SIZRS has found that even as SIZ extent, ice character, and atmospheric forcing varies year-to-year, the pattern of ocean freshening and radiative warming south of the ice edge is consistent. The experimental approach, observations and extensions to other projects will be discussed.

Greater sage-grouse winter habitat use on the eastern edge of their range

Science.gov (United States)

Swanson, Christopher C.; Rumble, Mark A.; Grovenburg, Troy W.; Kaczor, Nicholas W.; Klaver, Robert W.; Herman-Brunson, Katie M.; Jenks, Jonathan A.; Jensen, Kent C.

2013-01-01

Greater sage-grouse (Centrocercus urophasianus) at the western edge of the Dakotas occur in the transition zone between sagebrush and grassland communities. These mixed sagebrush (Artemisia sp.) and grasslands differ from those habitats that comprise the central portions of the sage-grouse range; yet, no information is available on winter habitat selection within this region of their distribution. We evaluated factors influencing greater sage-grouse winter habitat use in North Dakota during 2005–2006 and 2006–2007 and in South Dakota during 2006–2007 and 2007–2008. We captured and radio-marked 97 breeding-age females and 54 breeding-age males from 2005 to 2007 and quantified habitat selection for 98 of these birds that were alive during winter. We collected habitat measurements at 340 (177 ND, 163 SD) sage-grouse use sites and 680 random (340 each at 250 m and 500 m from locations) dependent sites. Use sites differed from random sites with greater percent sagebrush cover (14.75% use vs. 7.29% random; P 2 use vs. 0.94 plants/m2 random; P ≤ 0.001), but lesser percent grass cover (11.76% use vs. 16.01% random; P ≤ 0.001) and litter cover (4.34% use vs. 5.55% random; P = 0.001) and lower sagebrush height (20.02 cm use vs. 21.35 cm random; P = 0.13) and grass height (21.47 cm use vs. 23.21 cm random; P = 0.15). We used conditional logistic regression to estimate winter habitat selection by sage-grouse on continuous scales. The model sagebrush cover + sagebrush height + sagebrush cover × sagebrush height (wi = 0.60) was the most supported of the 13 models we considered, indicating that percent sagebrush cover strongly influenced selection. Logistic odds ratios indicated that the probability of selection by sage-grouse increased by 1.867 for every 1% increase in sagebrush cover (95% CI = 1.627–2.141) and by 1.041 for every 1 cm increase in sagebrush height (95% CI = 1.002–1.082). The

Ice Algae-Produced Carbon Is Critical for Overwintering of Antarctic Krill Euphausia superba

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Doreen Kohlbach

2017-09-01

Full Text Available Antarctic krill Euphausia superba (“krill” constitute a fundamental food source for Antarctic seabirds and mammals, and a globally important fisheries resource. The future resilience of krill to climate change depends critically on the winter survival of young krill. To survive periods of extremely low production by pelagic algae during winter, krill are assumed to rely partly on carbon produced by ice algae. The true dependency on ice algae-produced carbon, however, is so far unquantified. This confounds predictions on the future resilience of krill stocks to sea ice decline. Fatty acid (FA analysis, bulk stable isotope analysis (BSIA, and compound-specific stable isotope analysis (CSIA of diatom- and dinoflagellate-associated marker FAs were applied to quantify the dependency of overwintering larval, juvenile, and adult krill on ice algae-produced carbon (αIce during winter 2013 in the Weddell-Scotia Confluence Zone. Our results demonstrate that the majority of the carbon uptake of the overwintering larval and juvenile krill originated from ice algae (up to 88% of the carbon budget, and that the dependency on ice algal carbon decreased with ontogeny, reaching <56% of the carbon budget in adults. Spatio-temporal variability in the utilization of ice algal carbon was more pronounced in larvae and juvenile krill than in adults. Differences between αIce estimates derived from short- vs. long-term FA-specific isotopic compositions suggested that ice algae-produced carbon gained importance as the winter progressed, and might become critical at the late winter-spring transition, before the phytoplankton bloom commences. Where the sea ice season shortens, reduced availability of ice algae might possibly not be compensated by surplus phytoplankton production during wintertime. Hence, sea ice decline could seriously endanger the winter survival of recruits, and subsequently overall biomass of krill.

Environmental predictors of ice seal presence in the Bering Sea.

Science.gov (United States)

Miksis-Olds, Jennifer L; Madden, Laura E

2014-01-01

Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover) as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20-30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season.

Environmental predictors of ice seal presence in the Bering Sea.

Directory of Open Access Journals (Sweden)

Jennifer L Miksis-Olds

Full Text Available Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20-30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season.

Production of ethanol from winter barley by the EDGE (enhanced dry grind enzymatic process

Directory of Open Access Journals (Sweden)

Kurantz M

2010-04-01

Full Text Available Abstract Background US legislation requires the use of advanced biofuels to be made from non-food feedstocks. However, commercialization of lignocellulosic ethanol technology is more complex than expected and is therefore running behind schedule. This is creating a demand for non-food, but more easily converted, starch-based feedstocks other than corn that can fill the gap until the second generation technologies are commercially viable. Winter barley is such a feedstock but its mash has very high viscosity due to its high content of β-glucans. This fact, along with a lower starch content than corn, makes ethanol production at the commercial scale a real challenge. Results A new fermentation process for ethanol production from Thoroughbred, a winter barley variety with a high starch content, was developed. The new process was designated the EDGE (enhanced dry grind enzymatic process. In this process, in addition to the normal starch-converting enzymes, two accessory enzymes were used to solve the β-glucan problem. First, β-glucanases were used to hydrolyze the β-glucans to oligomeric fractions, thus significantly reducing the viscosity to allow good mixing for the distribution of the yeast and nutrients. Next, β-glucosidase was used to complete the β-glucan hydrolysis and to generate glucose, which was subsequently fermented in order to produce additional ethanol. While β-glucanases have been previously used to improve barley ethanol production by lowering viscosity, this is the first full report on the benefits of adding β-glucosidases to increase the ethanol yield. Conclusions In the EDGE process, 30% of total dry solids could be used to produce 15% v/v ethanol. Under optimum conditions an ethanol yield of 402 L/MT (dry basis or 2.17 gallons/53 lb bushel of barley with 15% moisture was achieved. The distillers dried grains with solubles (DDGS co-product had extremely low β-glucan (below 0.2% making it suitable for use in both ruminant

The engineering approach to winter sports

CERN Document Server

Cheli, Federico; Maldifassi, Stefano; Melzi, Stefano; Sabbioni, Edoardo

2016-01-01

The Engineering Approach to Winter Sports presents the state-of-the-art research in the field of winter sports in a harmonized and comprehensive way for a diverse audience of engineers, equipment and facilities designers, and materials scientists. The book examines the physics and chemistry of snow and ice with particular focus on the interaction (friction) between sports equipment and snow/ice, how it is influenced by environmental factors, such as temperature and pressure, as well as by contaminants and how it can be modified through the use of ski waxes or the microtextures of blades or ski soles. The authors also cover, in turn, the different disciplines in winter sports:  skiing (both alpine and cross country), skating and jumping, bob sledding and skeleton, hockey and curling, with attention given to both equipment design and on the simulation of gesture and  track optimization.

Shifting balance of thermokarst lake ice regimes across the Arctic Coastal Plain of northern Alaska

Science.gov (United States)

Arp, Christopher D.; Jones, Benjamin M.; Lu, Zong; Whitman, Matthew S.

2012-01-01

The balance of thermokarst lakes with bedfast- and floating-ice regimes across Arctic lowlands regulates heat storage, permafrost thaw, winter-water supply, and over-wintering aquatic habitat. Using a time-series of late-winter synthetic aperture radar (SAR) imagery to distinguish lake ice regimes in two regions of the Arctic Coastal Plain of northern Alaska from 2003–2011, we found that 18% of the lakes had intermittent ice regimes, varying between bedfast-ice and floating-ice conditions. Comparing this dataset with a radar-based lake classification from 1980 showed that 16% of the bedfast-ice lakes had shifted to floating-ice regimes. A simulated lake ice thinning trend of 1.5 cm/yr since 1978 is believed to be the primary factor driving this form of lake change. The most profound impacts of this regime shift in Arctic lakes may be an increase in the landscape-scale thermal offset created by additional lake heat storage and its role in talik development in otherwise continuous permafrost as well as increases in over-winter aquatic habitat and winter-water supply.

Ecology under lake ice

NARCIS (Netherlands)

Hampton, Stephanie E.; Galloway, Aaron W. E.; Powers, Stephen M.; Ozersky, Ted; Woo, Kara H.; Batt, Ryan D.; Labou, Stephanie G.; O'Reilly, Catherine M.; Sharma, Sapna; Lottig, Noah R.; Stanley, Emily H.; North, Rebecca L.; Stockwell, Jason D.; Adrian, Rita; Weyhenmeyer, Gesa A.; Arvola, Lauri; Baulch, Helen M.; Bertani, Isabella; Bowman, Larry L., Jr.; Carey, Cayelan C.; Catalan, Jordi; Colom-Montero, William; Domine, Leah M.; Felip, Marisol; Granados, Ignacio; Gries, Corinna; Grossart, Hans-Peter; Haberman, Juta; Haldna, Marina; Hayden, Brian; Higgins, Scott N.; Jolley, Jeff C.; Kahilainen, Kimmo K.; Kaup, Enn; Kehoe, Michael J.; MacIntyre, Sally; Mackay, Anson W.; Mariash, Heather L.; Mckay, Robert M.; Nixdorf, Brigitte; Noges, Peeter; Noges, Tiina; Palmer, Michelle; Pierson, Don C.; Post, David M.; Pruett, Matthew J.; Rautio, Milla; Read, Jordan S.; Roberts, Sarah L.; Ruecker, Jacqueline; Sadro, Steven; Silow, Eugene A.; Smith, Derek E.; Sterner, Robert W.; Swann, George E. A.; Timofeyev, Maxim A.; Toro, Manuel; Twiss, Michael R.; Vogt, Richard J.; Watson, Susan B.; Whiteford, Erika J.; Xenopoulos, Marguerite A.

Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experi-ence periods of snow and ice cover. Relatively little is known of winter ecology in these systems,due to a historical research focus on summer ‘growing seasons’. We executed the first global

Characteristics of Winter Surface Air Temperature Anomalies in Moscow in 1970-2016 under Conditions of Reduced Sea Ice Area in the Barents Sea

Science.gov (United States)

Shukurov, K. A.; Semenov, V. A.

2018-01-01

On the basis of observational data on daily mean surface air temperature (SAT) and sea ice concentration (SIC) in the Barents Sea (BS), the characteristics of strong positive and negative winter SAT anomalies in Moscow have been studied in comparison with BS SIC data obtained in 1949-2016. An analysis of surface backward trajectories of air-particle motions has revealed the most probable paths of both cold and warm air invasions into Moscow and located regions that mostly affect strong winter SAT anomalies in Moscow. Atmospheric circulation anomalies that cause strong winter SAT anomalies in Moscow have been revealed. Changes in the ways of both cold and warm air invasions have been found, as well as an increase in the frequency of blocking anticyclones in 2005-2016 when compared to 1970-1999. The results suggest that a winter SIC decrease in the BS in 2005-2016 affects strong winter SAT anomalies in Moscow due to an increase in the frequency of occurrence of blocking anticyclones to the south of and over the BS.

Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice

Science.gov (United States)

Lewis, Ceri N.; Brown, Kristina A.; Edwards, Laura A.; Cooper, Glenn; Findlay, Helen S.

2013-01-01

The Arctic Ocean already experiences areas of low pH and high CO2, and it is expected to be most rapidly affected by future ocean acidification (OA). Copepods comprise the dominant Arctic zooplankton; hence, their responses to OA have important implications for Arctic ecosystems, yet there is little data on their current under-ice winter ecology on which to base future monitoring or make predictions about climate-induced change. Here, we report results from Arctic under-ice investigations of copepod natural distributions associated with late-winter carbonate chemistry environmental data and their response to manipulated pCO2 conditions (OA exposures). Our data reveal that species and life stage sensitivities to manipulated OA conditions were correlated with their vertical migration behavior and with their natural exposures to different pCO2 ranges. Vertically migrating adult Calanus spp. crossed a pCO2 range of >140 μatm daily and showed only minor responses to manipulated high CO2. Oithona similis, which remained in the surface waters and experienced a pCO2 range of <75 μatm, showed significantly reduced adult and nauplii survival in high CO2 experiments. These results support the relatively untested hypothesis that the natural range of pCO2 experienced by an organism determines its sensitivity to future OA and highlight that the globally important copepod species, Oithona spp., may be more sensitive to future high pCO2 conditions compared with the more widely studied larger copepods. PMID:24297880

Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska

Science.gov (United States)

Alexeev, Vladimir; Arp, Christopher D.; Jones, Benjamin M.; Cai, Lei

2016-01-01

Field measurements, satellite observations, and models document a thinning trend in seasonal Arctic lake ice growth, causing a shift from bedfast to floating ice conditions. September sea ice concentrations in the Arctic Ocean since 1991 correlate well (r = +0.69,p Research and Forecasting model output produced a 7% decrease in lake ice growth when 2007/08 sea ice was imposed on 1991/92 climatology and a 9% increase in lake ice growth for the opposing experiment. Here, we clearly link early winter 'ocean-effect' snowfall and warming to reduced lake ice growth. Future reductions in sea ice extent will alter hydrological, biogeochemical, and habitat functioning of Arctic lakes and cause sub-lake permafrost thaw.

Comparison of mesoscale model and tower measurements of surface fluxes during Winter Icing and Storms Program/Atmospheric Radiation Measurement 91

International Nuclear Information System (INIS)

Oncley, S.P.; Dudhia, J.

1994-01-01

This study is an evaluation of the ability of the Pennsylvania State University/National Center for Atmospheric Research (NCAR) mesoscale model (MM4) to determine surface fluxes to see if measured fluxes should be assimilated into model runs. Fluxes were compared from a high-resolution (5 km grid spacing) MM4 run during one day of the Winter Icing and Storms Programs/Atmospheric Radiation Measurement (WISP/ARM) experiment (over NE Colorado in winter 1991) with direct flux measurements made from a tower over a representative site by a three-dimensional sonic anemometer and fast response temperature and humidity sensors. This tower was part of the NCAR Atmosphere-Surface Turbulent Exchange Research (ASTER) facility. Also, mean values were compared to check whether any differences were due to the model parameterization or model variables

Arctic sea ice trends, variability and implications for seasonal ice forecasting.

Science.gov (United States)

Serreze, Mark C; Stroeve, Julienne

2015-07-13

September Arctic sea ice extent over the period of satellite observations has a strong downward trend, accompanied by pronounced interannual variability with a detrended 1 year lag autocorrelation of essentially zero. We argue that through a combination of thinning and associated processes related to a warming climate (a stronger albedo feedback, a longer melt season, the lack of especially cold winters) the downward trend itself is steepening. The lack of autocorrelation manifests both the inherent large variability in summer atmospheric circulation patterns and that oceanic heat loss in winter acts as a negative (stabilizing) feedback, albeit insufficient to counter the steepening trend. These findings have implications for seasonal ice forecasting. In particular, while advances in observing sea ice thickness and assimilating thickness into coupled forecast systems have improved forecast skill, there remains an inherent limit to predictability owing to the largely chaotic nature of atmospheric variability. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

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

Early spawning of Antarctic krill in the Scotia Sea is fuelled by “superfluous” feeding on non-ice associated phytoplankton blooms

Science.gov (United States)

Schmidt, Katrin; Atkinson, Angus; Venables, Hugh J.; Pond, David W.

2012-01-01

The spawning success of Antarctic krill ( Euphausia superba) is generally assumed to depend on substantial winter sea ice extent, as ice biota can serve as a food source during winter/spring and the seasonal ice melt conditions the upper water column for extensive phytoplankton blooms. However, direct observations during spring are rare. Here we studied krill body condition and maturity stage in relation to feeding (i.e. stomach fullness, diet, absorption of individual fatty acids and defecation rate) across the Scotia Sea in November 2006. The phytoplankton concentrations were low at the marginal ice zone (MIZ) in the southern Scotia Sea (Stn. 1, 2, and 3), high in open waters of the Southern Antarctic Circumpolar Current Front (SACCF) in the central Scotia Sea (Stn. 5), and moderate further north (Stn. 6 and 7). Krill had low lipid reserves (˜6.5% of dry mass, DM), low mass:length ratios (˜1.7 mg DM mm -1), and small digestive glands (˜7% of total DM) near the ice edge. The stomachs contained lithogenic particles, diatom debris, and bacterial fatty acids, but low proportions of diatom-indicating fatty acids, which suggest that these krill were feeding on detritus rather than on fresh ice algae. In the SACCF, krill had higher lipid reserves (˜10% of DM), high mass:length ratios (˜2.2 mg DM mm -1), and large digestive glands (˜16% of total DM). Stomach content and tissue composition indicate feeding on diatoms. In the north, moderate food concentrations co-occurred with low lipid reserves in krill, and moderate mass:length ratios and digestive gland sizes. Only in the phytoplankton bloom in the SACCF had the mating season already started and some females were about to spawn. Based on the way krill processed their food at the different stations, we indicate two mechanisms that can lead to fast regeneration of body reserves and oocyte maturation in E. superba. One is "superfluous" feeding at high food concentrations, which maximises the overall nutrient gain

Life in Ice: Microbial Growth Dynamics and Greenhouse Gas Production During Winter in a Thermokarst Bog Revealed by Stable Isotope Probing Targeted Metagenomics

Science.gov (United States)

Blazewicz, S.; White, R. A., III; Tas, N.; Euskirchen, E. S.; Mcfarland, J. W.; Jansson, J.; Waldrop, M. P.

2016-12-01

Permafrost contains a reservoir of frozen C estimated to be twice the size of the current atmospheric C pool. In response to changing climate, permafrost is rapidly warming which could result in widespread seasonal thawing. When permafrost thaws, soils that are rich in ice and C often transform into thermokarst wetlands with anaerobic conditions and significant production of atmospheric CH4. While most C flux research in recently thawed permafrost concentrates on the few summer months when seasonal thaw has occurred, there is mounting evidence that sizeable portions of annual CO2 and CH4 efflux occurs over winter or during a rapid burst of emissions associated with seasonal thaw. A potential mechanism for such efflux patterns is microbial activity in frozen soils over winter where gasses produced are partially trapped within ice until spring thaw. In order to better understand microbial transformation of soil C to greenhouse gas over winter, we applied stable isotope probing (SIP) targeted metagenomics combined with process measurements and field flux data to reveal activities of microbial communities in `frozen' soil from an Alaskan thermokarst bog. Field studies revealed build-up of CO2 and CH4 in frozen soils suggesting that microbial activity persisted throughout the winter in soils poised just below the freezing point. Laboratory incubations designed to simulate in-situ winter conditions (-1.5 °C and anaerobic) revealed continuous CH4 and CO2 production. Strikingly, the quantity of CH4 produced in 6 months in frozen soil was equivalent to approximately 80% of CH4 emitted during the 3 month summer `active' season. Heavy water SIP targeted iTag sequencing revealed growing bacteria and archaea in the frozen anaerobic soil. Growth was primarily observed in two bacterial phyla, Firmicutes and Bacteroidetes, suggesting that fermentation was likely the major C mineralization pathway. SIP targeted metagenomics facilitated characterization of the primary metabolic

Acquisition of Ice Thickness and Ice Surface Characteristics in the Seasonal Ice Zone by CULPIS-X during the US Coast Guard’s Arctic Domain Awareness Program

Science.gov (United States)

2014-09-30

OBJECTIVES • What is the volume of sea ice in the Beaufort Sea Seasonal Ice Zone (SIZ) and how does this evolve during summer as the ice edge...retreats? Recent observations suggest that the remaining ice in the Beaufort Sea is younger and thinner in recent years in part because even the oldest...surrounding ice . Recent analyses have indicated that ponds on thinner ice are often darker, accelerating the ice - albedo feedback over thin ice in summer

Long-term monitoring of sea ice conditions in the Kerch Strait by remote sensing data

Science.gov (United States)

Lavrova, Olga Yu.; Mityagina, Marina I.; Bocharova, Tatiana Yu.; Kostianoy, Andrey G.

2017-10-01

The results of multi-year satellite monitoring of ice conditions in the Kerch Strait connecting the Black and Azov Seas are discussed. The issue gained importance in view of the ongoing construction of the Crimean Bridge across the strait. Our monitoring has been based on the whole variety of available satellite data including visible and radar data over the past 17 years. Every year the Azov Sea becomes fully or partially covered by ice during the cold season. In severe winters, ice often is carried to the Kerch Strait and even the Black Sea. An analysis of ice drift hydrometeorological conditions is presented. The ice conditions of 2017 are under special consideration. Everyday satellite monitoring of the Kerch Strait, including the construction area of the Crimean Bridge, revealed ice formation and drift features on the way from the Azov Sea through the Kerch Strait as well as ice interaction with the piers of the main and technological bridges under construction. It was found that, even under strong northeast winds, ice can pass neither through the piers, nor via the widest shipway. At present, it is hard to discern the impacts of the two bridges on floating ice, nevertheless when the construction is over and the technological bridge is gone, by all appearances the main bridge will strongly affect ice conditions in the Kerch Strait. This perspective calls for continuous satellite monitoring of the area that is enabled by cutting-edge systems and technologies.

Linescan camera evaluation of SSM/I 85.5 GHz sea ice retrieval

DEFF Research Database (Denmark)

Garrity, Caren; Lubin, Dan; Kern, Stefan

2002-01-01

misclassify clouds over open water as sea ice, and is therefore unreliable for locating the sea ice edge. The best algorithm for locating the sea ice edge is found to be the SEA LION algorithm, which explicitly uses meteorological reanalysis data to correct for atmospheric contamination. For total sea ice...

Methane isotopic signature of gas bubbles in permafrost winter lake ice: a tool for quantifying variable oxidation levels

Science.gov (United States)

Sapart, C. J.; Boereboom, T.; Roeckmann, T.; Tison, J.-L.

2012-04-01

Methane (CH4) is a strong greenhouse gas and its atmospheric mixing ratio has strongly increased since pre-industrial times. This increase was primarily due to emissions from anthropogenic sources, but there is growing concern about possible feedbacks of natural sources in a changing climate. Thawing of permafrost areas in the Arctic is considered as an important feedback, since the Arctic region undergoes the fastest climate change and hosts large carbon stocks. Subarctic lakes are considered as "hotspots" for CH4 emissions, but the role of the ice cover during the winter period is not well understood to date. Here, we present measurements of CH4 mixing ratio and δ13C-CH4 in 4 types of bubbles identified in subarctic lake ice covers located in a sporadic or discontinuous permafrost area. Our analysis reveals that different bubble types contain CH4 with different, specific isotopic signatures. The evolution of mixing ratio and δ13C-CH4 suggest that oxidation of dissolved CH4 is the most important process determining the isotopic composition of CH4 in bubbles. This results from gas exsolution occurring during the ice growth process. A first estimate of the CH4 oxidation budget (mean = 0.12 mg CH4 m-2 d-1) enables to quantify the impact of the ice cover on CH4 emissions from subartic lakes. The increased exchange time between gases coming from the sediments and the water column, due to the capping effect of the lake ice cover, reduces the amount of CH4 released "as is" and favours its oxidation into carbon dioxide; the latter being further added to the HCO3- pool through the carbonate equilibration reactions.

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.

Tracing Atlantic Water Signature in the Arctic Sea Ice Cover East of Svalbard

Directory of Open Access Journals (Sweden)

Vladimir V. Ivanov

2012-01-01

Full Text Available We focus on the Arctic Ocean between Svalbard and Franz Joseph Land in order to elucidate the possible role of Atlantic water (AW inflow in shaping ice conditions. Ice conditions substantially affect the temperature regime of the Spitsbergen archipelago, particularly in winter. We test the hypothesis that intensive vertical mixing at the upper AW boundary releases substantial heat upwards that eventually reaches the under-ice water layer, thinning the ice cover. We examine spatial and temporal variation of ice concentration against time series of wind, air temperature, and AW temperature. Analysis of 1979–2011 ice properties revealed a general tendency of decreasing ice concentration that commenced after the mid-1990s. AW temperature time series in Fram Strait feature a monotonic increase after the mid-1990s, consistent with shrinking ice cover. Ice thins due to increased sensible heat flux from AW; ice erosion from below allows wind and local currents to more effectively break ice. The winter spatial pattern of sea ice concentration is collocated with patterns of surface heat flux anomalies. Winter minimum sea ice thickness occurs in the ice pack interior above the AW path, clearly indicating AW influence on ice thickness. Our study indicates that in the AW inflow region heat flux from the ocean reduces the ice thickness.

Ice Control with Brine Spread with Nozzles on Highways

DEFF Research Database (Denmark)

Bolet, Lars; Fonnesbech, Jens Kristian

2010-01-01

on the major roads (150 km) in the municipality of North Funen from the winter 2007/8. The result has been a dramatically reduction in the number of traffic accidents on slippery roads during the winter season. From 7 and 5 accidents in the previous 2 winters to 1 accident in the winter 2007/8. Neighbouring...... municipalities had an increasing number of traffic accidents on slippery roads in the same period.......During the years 1996-2006, the former county of Funen, Denmark, gradually replaced pre-wetted salt with brine spread with nozzles as anti-icing agent in all her ice control activities. The replacement related to 1000 kilometres of highways. Jeopardizing neither road safety nor traffic flow...

Polar-Tropical Coupling in the Winter Stratosphere

Science.gov (United States)

Scott, R.

2017-12-01

A distinct pattern of enhanced equatorial potential vorticitygradients during QBO westerly anomalies, enhanced subtropicalgradients during QBO easterlies, is used to motivate a new formulationof dynamical coupling between the tropics and winter polar vortexbased on remote transfer of finite amplitude wave activity defined interms of lateral potential vorticity displacements. While the weakpotential vorticity gradients in the surf zone imply laterallyevanescent Rossby waves, transfer of wave activity from the polarvortex edge to the subtropical barrier or to the QBO westerly phaseequatorial gradients arises from nonlocality of potential vorticityinversion and the large horizontal displacements of the vortex edge.Our approach goes beyond the traditional description of the effect ofQBO wind anomalies on linear wave propagation through the stratospherevia wave reflection at the zero wind line; linear wave theory isappealing but neglects the long horizontal and vertical wavelengthsinvolved and the inhomogeneous background potential vorticity. Aparticular issue of outstanding interest is whether and how therelatively shallow QBO anomalies can influence the deep verticallypropagating waves on the edge of the winter stratospheric polarvortex. Process studies with a mechanistic model with prescribed QBOand carefully controlled high-latitude wave forcing are analyzed,guided by a reexamination of meteorological reanalysis, to address howsuch a dynamical linkage may influence in particular the resonantexcitation of the winter vortex, and the occurrence ofvortex-splitting sudden warming events. We quantify the associatedtransfer of wave activity from vortex edge to the tropics, considerunder what conditions this becomes a significant source of easterlymomentum in the driving of the QBO itself, and how the structure ofthe Brewer-Dobson circulation varies in response to the location ofthe QBO westerly winds in any given winter.

Time-lapse imagery of Adélie penguins reveals differential winter strategies and breeding site occupation.

Science.gov (United States)

Black, Caitlin; Southwell, Colin; Emmerson, Louise; Lunn, Daniel; Hart, Tom

2018-01-01

Polar seabirds adopt different over-wintering strategies to survive and build condition during the critical winter period. Penguin species either reside at the colony during the winter months or migrate long distances. Tracking studies and survey methods have revealed differences in winter migration routes among penguin species and colonies, dependent on both biotic and abiotic factors present. However, scan sampling methods are rarely used to reveal non-breeding behaviors during winter and little is known about presence at the colony site over this period. Here we show that Adélie penguins on the Yalour Islands in the Western Antarctic Peninsula (WAP) are present year-round at the colony and undergo a mid-winter peak in abundance during winter. We found a negative relationship between daylight hours and penguin abundance when either open water or compact ice conditions were present, suggesting that penguins return to the breeding colony when visibility is lowest for at-sea foraging and when either extreme low or high levels of sea ice exist offshore. In contrast, Adélie penguins breeding in East Antarctica were not observed at the colonies during winter, suggesting that Adélie penguins undergo differential winter strategies in the marginal ice zone on the WAP compared to those in East Antarctica. These results demonstrate that cameras can successfully monitor wildlife year-round in areas that are largely inaccessible during winter.

Large sea ice outflow into the Nares Strait in 2007

DEFF Research Database (Denmark)

Kwok, R.; Pedersen, L.T.; Gudmandsen, Preben

2010-01-01

Sea ice flux through the Nares Strait is most active during the fall and early winter, ceases in mid- to late winter after the formation of ice arches along the strait, and re-commences after breakup in summer. In 2007, ice arches failed to form. This resulted in the highest outflow of Arctic sea...... at Fram Strait. Clearly, the ice arches control Arctic sea ice outflow. The duration of unobstructed flow explains more than 84% of the variance in the annual area flux. In our record, seasonal stoppages are always associated with the formation of an arch near the same location in the southern Kane Basin...... ice in the 13-year record between 1997 and 2009. The 2007 area and volume outflows of 87 x 10(3) km(2) and 254 km(3) are more than twice their 13-year means. This contributes to the recent loss of the thick, multiyear Arctic sea ice and represents similar to 10% of our estimates of the mean ice export...

Relating C-band Microwave and Optical Satellite Observations as A Function of Snow Thickness on First-Year Sea Ice during the Winter to Summer Transition

Science.gov (United States)

Zheng, J.; Yackel, J.

2015-12-01

The Arctic sea ice and its snow cover have a direct impact on both the Arctic and global climate system through their ability to moderate heat exchange across the ocean-sea ice-atmosphere (OSA) interface. Snow cover plays a key role in the OSA interface radiation and energy exchange, as it controls the growth and decay of first-year sea ice (FYI). However, meteoric accumulation and redistribution of snow on FYI is highly stochastic over space and time, which makes it poorly understood. Previous studies have estimated local-scale snow thickness distributions using in-situ technique and modelling but it is spatially limited and challenging due to logistic difficulties. Moreover, snow albedo is also critical for determining the surface energy balance of the OSA during the critical summer ablation season. Even then, due to persistent and widespread cloud cover in the Arctic at various spatio-temporal scales, it is difficult and unreliable to remotely measure albedo of snow cover on FYI in the optical spectrum. Previous studies demonstrate that only large-scale sea ice albedo was successfully estimated using optical-satellite sensors. However, space-borne microwave sensors, with their capability of all-weather and 24-hour imaging, can provide enhanced information about snow cover on FYI. Daily spaceborne C-band scatterometer data (ASCAT) and MODIS data are used to investigate the the seasonal co-evolution of the microwave backscatter coefficient and optical albedo as a function of snow thickness on smooth FYI. The research focuses on snow-covered FYI near Cambridge Bay, Nunavut (Fig.1) during the winter to advanced-melt period (April-June, 2014). The ACSAT time series (Fig.2) show distinct increase in scattering at melt onset indicating the first occurrence of melt water in the snow cover. The corresponding albedo exhibits no decrease at this stage. We show how the standard deviation of ASCAT backscatter on FYI during winter can be used as a proxy for surface roughness

Icing losses on wind turbines

Energy Technology Data Exchange (ETDEWEB)

Duncan, T.; Fotsing, I.; Pearson, S. [Garrad Hassan Canada Inc., Ottawa, ON (Canada)

2010-07-01

This PowerPoint presentation discussed some of the energy losses that can occur as a result of icing on wind turbines. Airfoil deterioration can occur in the presence of rime and glaze ice. Anemometers are also impacted by ice, and shut-downs can occur as a result of icing events. Availability deficits that occur during the winter months can lead to annual energy losses of 0.5 percent. The impact of icing events on total wind power energy production in Quebec is estimated at between 1.3 percent to 2.7 percent. Ice loss estimates are considered during the pre-construction phases of wind power projects. However, ice loss prediction methods are often inaccurate. Studies have demonstrated that preconstruction masts show a reasonable correlation with wind turbine icing, and that icing losses are site-specific. tabs., figs.

Guidelines to Facilitate the Evaluation of Brines for Winter Roadway Maintenance Operations.

Science.gov (United States)

2017-09-19

This document presents guidelines to facilitate the evaluation of brines for winter weather roadway maintenance applications in Texas. Brines are used in anti-icing applications which typically consist of placing liquid snow and ice control chemicals...

Monitoring water phase dynamics in winter clouds

Science.gov (United States)

Campos, Edwin F.; Ware, Randolph; Joe, Paul; Hudak, David

2014-10-01

This work presents observations of water phase dynamics that demonstrate the theoretical Wegener-Bergeron-Findeisen concepts in mixed-phase winter storms. The work analyzes vertical profiles of air vapor pressure, and equilibrium vapor pressure over liquid water and ice. Based only on the magnitude ranking of these vapor pressures, we identified conditions where liquid droplets and ice particles grow or deplete simultaneously, as well as the conditions where droplets evaporate and ice particles grow by vapor diffusion. The method is applied to ground-based remote-sensing observations during two snowstorms, using two distinct microwave profiling radiometers operating in different climatic regions (North American Central High Plains and Great Lakes). The results are compared with independent microwave radiometer retrievals of vertically integrated liquid water, cloud-base estimates from a co-located ceilometer, reflectivity factor and Doppler velocity observations by nearby vertically pointing radars, and radiometer estimates of liquid water layers aloft. This work thus makes a positive contribution toward monitoring and nowcasting the evolution of supercooled droplets in winter clouds.

Monitoring the Variation in Ice-Cover Characteristics of the Slave River, Canada Using RADARSAT-2 Data—A Case Study

Directory of Open Access Journals (Sweden)

Thuan Chu

2015-10-01

Full Text Available The winter regime of river-ice covers in high northern latitude regions is often a determining factor in the management of water resources, conservation of aquatic ecosystems and preservation of traditional and cultural lifestyles of local peoples. As ground-based monitoring of river-ice regimes in high northern latitudes is expensive and restricted to a few locations due to limited accessibility to most places along rivers from shorelines, remote sensing techniques are a suitable approach for monitoring. This study developed a RADARSAT-2 based method to monitor the spatio-temporal variation of ice covers, as well as ice types during the freeze-up period, along the main channel of the Slave River Delta in the Northwest Territories of Canada. The spatio-temporal variation of ice covers along the river was analyzed using the backscatter-based coefficient of variation (CV in the 2013–2014 and 2014–2015 winters. As a consequence of weather and flow conditions, the ice cover in the 2013–2014 winter had the higher variation than the 2014–2015 winter, particularly in the potential areas of flooded/cracked ice covers. The river sections near active channels (e.g., Middle Channel and Nagle Channel, Big Eddy, and Great Slave Lake also yielded higher intra-annual variation of ice cover characteristics during the winters. With the inclusion of backscatter and texture analysis from RADARSAT-2 data, four water and ice cover classes consisting of open water, thermal ice, juxtaposed ice, and consolidated ice, were discriminated in the images acquired between November and March in both the studied winters. In addition to river geomorphology and climatic conditions such as river width, sinuosity or air temperature, the fluctuation of water flows during the winter has a significant impact on the variation of ice cover as well as the formation of different ice types in the Slave River. The RADARSAT-2 based monitoring algorithm can also be applied to other

Road salt application planning tool for winter de-icing operations

Science.gov (United States)

Trenouth, William R.; Gharabaghi, Bahram; Perera, Nandana

2015-05-01

Road authorities, who are charged with the task of maintaining safe, driveable road conditions during severe winter storm events are coming under increasing pressure to protect salt vulnerable areas (SVAs). For the purpose of modelling urban winter hydrology, the temperature index method was modified to incorporate ploughing and salting considerations and was calibrated using winter field data from two sites in Southern Ontario and validated using data collected from a section of Highway 401 - Canada's busiest highway. The modified temperature index model (MTIM) accurately predicted salt-induced melt (R2 = 0.98 and 0.99, RMSE = 19.9 and 282.4 m3, CRM = -0.003 and 0.006 for calibration and validation sites respectively), and showed a demonstrable ability to calculate the Bare Pavement Regain Time (BPRT). The BPRT is a key factor on road safety and the basis for many winter maintenance performance standards for different classes of highways. Optimizing salt application rate scenarios can be achieved using the MTIM with only two meteorological forecast inputs for the storm event - readily available on-line through the Road Weather Information System (RWIS) - and can serve as a simple yet effective tool for winter road maintenance practitioners seeking to optimize salt application rates for a given storm event in salt vulnerable areas.

Three Years of High Resolution Year-Round Monitoring of Ice-Wedge Thermal Contraction Cracking in Svalbard

Science.gov (United States)

Christiansen, H. H.

2006-12-01

Most likely ice-wedges are the most widespread periglacial landform in lowlands with continuous permafrost. With a changing climate it is important to understand better the geomorphological processes controlling ice- wedge growth and decay, as they might cause large changes to the surface of the landscape, particularly if the active layer thickness increases causing melting of the most ice-rich permafrost top layer. As most settlements on permafrost are located in lowland areas, ice-wedge formation can also influence the infrastructure. Understanding the processes of ice-wedge growth and their thaw transformation into ice-wedge casts are essential when using contemporary ice wedges as analogues of Pleistocene thermal contraction cracking in palaeoenvironmental reconstructions. As ice-wedges are largely controlled by winter conditions, improved understanding of the factors controlling their growth will enable better palaeoclimatic reconstructions both directly from ice-wedges, but also from ice-wedge casts, than just mean winter temperatures. Detailed studies of ice-wedge dynamics, including quantification of movement, have only been done in very few places in the Arctic. In high arctic Svalbard at 78°N climate at sea level locates these islands close to the southern limit of the continuous permafrost zone, with MAAT of as much as -4 to -6°C. However, thermal contraction cracking is demonstrated to be widespread in the Adventdalen study area in Svalbard. The year-round field access from the University Centre in Svalbard, UNIS, has enabled the collection of different continuous or high frequency ice-wedge process monitoring data since 2002 to improve the understanding of the geomorphological activity of this landform. In all the winters the air temperature was below -30°C for shorter or longer periods. During all the winters, the temperature in the top permafrost was below -15°C both in the ice-wedge top for shorter or longer periods. The snow cover was

Time-lapse imagery of Adélie penguins reveals differential winter strategies and breeding site occupation

Science.gov (United States)

Southwell, Colin; Emmerson, Louise; Lunn, Daniel

2018-01-01

Polar seabirds adopt different over-wintering strategies to survive and build condition during the critical winter period. Penguin species either reside at the colony during the winter months or migrate long distances. Tracking studies and survey methods have revealed differences in winter migration routes among penguin species and colonies, dependent on both biotic and abiotic factors present. However, scan sampling methods are rarely used to reveal non-breeding behaviors during winter and little is known about presence at the colony site over this period. Here we show that Adélie penguins on the Yalour Islands in the Western Antarctic Peninsula (WAP) are present year-round at the colony and undergo a mid-winter peak in abundance during winter. We found a negative relationship between daylight hours and penguin abundance when either open water or compact ice conditions were present, suggesting that penguins return to the breeding colony when visibility is lowest for at-sea foraging and when either extreme low or high levels of sea ice exist offshore. In contrast, Adélie penguins breeding in East Antarctica were not observed at the colonies during winter, suggesting that Adélie penguins undergo differential winter strategies in the marginal ice zone on the WAP compared to those in East Antarctica. These results demonstrate that cameras can successfully monitor wildlife year-round in areas that are largely inaccessible during winter. PMID:29561876

Using ice melting and ice rolling technologies to remove ice from sub-transmission and transmission lines at Manitoba Hydro

International Nuclear Information System (INIS)

Farias, A. R.

1999-01-01

Development of an of an Ice Storm Management program by Manitoba Hydro to reduce ice storm damage to its 8 kV feeders to 115 kV transmission lines, is discussed. The program consists of the de-icing of overhead lines, either by ice melting, or ice rolling. Ice melting involves the placement of a three-phase short at a calculated point. The term ice rolling denotes a process of mechanically stripping the ice from conductors. The most recent major ice storm experienced by Manitoba Hydro was in the winter of 1997/1998. During the period from February 6 to February 17, 1998, a total of 83 'ice melt' procedures were performed to melt the ice from 2,628 km of overhead line (7,883 km of conductor), in addition to 'ice rolling'. This paper describes Manitoba Hydro's 25-years' experience with ice melting and it also describes the advantages and disadvantages of both ice melting and ice rolling. Although not a panacea to combat the effects of ice storms, ice melting was found to be the most effective way of removing ice from overhead transmission and sub-transmission lines. Ice rolling was also found to be effective. Other tools that have been found to be useful by various utilities in combating ice storm damage include improved structure and line design, system design that provide more redundancies and emergency sources, and standby generators at critical load points

Importance of ice for the «White Olympics»

Directory of Open Access Journals (Sweden)

A. F. Renkel

2016-01-01

Full Text Available Organization of any winter Olympic game, often called as «White Olympics», requires interfacing between sports, technology and glaciology. History of the Olympic winter games and the Norwegian figure skater Sonia Henie, first and the only three-time Olympic champion (1928, 1932, 1936 in ladies figure skating, is presented in the article. Leaving the amateurish sport, Henie became a Hollywood star of the ballet on ice. She was introduced to the inventor Frank Zamboni, who created the ice re-surfacer (the ice-cleaning combine to restore the ice on skating rinks. Using the combine by Henie during her tours in the United States served to advertise this machine, and the name Zamboni had become a trademark for machines «Zamboni».

Semi-automated Digital Imaging and Processing System for Measuring Lake Ice Thickness

Science.gov (United States)

Singh, Preetpal

Canada is home to thousands of freshwater lakes and rivers. Apart from being sources of infinite natural beauty, rivers and lakes are an important source of water, food and transportation. The northern hemisphere of Canada experiences extreme cold temperatures in the winter resulting in a freeze up of regional lakes and rivers. Frozen lakes and rivers tend to offer unique opportunities in terms of wildlife harvesting and winter transportation. Ice roads built on frozen rivers and lakes are vital supply lines for industrial operations in the remote north. Monitoring the ice freeze-up and break-up dates annually can help predict regional climatic changes. Lake ice impacts a variety of physical, ecological and economic processes. The construction and maintenance of a winter road can cost millions of dollars annually. A good understanding of ice mechanics is required to build and deem an ice road safe. A crucial factor in calculating load bearing capacity of ice sheets is the thickness of ice. Construction costs are mainly attributed to producing and maintaining a specific thickness and density of ice that can support different loads. Climate change is leading to warmer temperatures causing the ice to thin faster. At a certain point, a winter road may not be thick enough to support travel and transportation. There is considerable interest in monitoring winter road conditions given the high construction and maintenance costs involved. Remote sensing technologies such as Synthetic Aperture Radar have been successfully utilized to study the extent of ice covers and record freeze-up and break-up dates of ice on lakes and rivers across the north. Ice road builders often used Ultrasound equipment to measure ice thickness. However, an automated monitoring system, based on machine vision and image processing technology, which can measure ice thickness on lakes has not been thought of. Machine vision and image processing techniques have successfully been used in manufacturing

Impacts of extratropical storm tracks on Arctic sea ice export through Fram Strait

Science.gov (United States)

Wei, Jianfen; Zhang, Xiangdong; Wang, Zhaomin

2018-05-01

Studies have indicated regime shifts in atmospheric circulation, and associated changes in extratropical storm tracks and Arctic storm activity, in particular on the North Atlantic side of the Arctic Ocean. To improve understanding of changes in Arctic sea ice mass balance, we examined the impacts of the changed storm tracks and cyclone activity on Arctic sea ice export through Fram Strait by using a high resolution global ocean-sea ice model, MITgcm-ECCO2. The model was forced by the Japanese 25-year Reanalysis (JRA-25) dataset. The results show that storm-induced strong northerly wind stress can cause simultaneous response of daily sea ice export and, in turn, exert cumulative effects on interannual variability and long-term changes of sea ice export. Further analysis indicates that storm impact on sea ice export is spatially dependent. The storms occurring southeast of Fram Strait exhibit the largest impacts. The weakened intensity of winter (in this study winter is defined as October-March and summer as April-September) storms in this region after 1994/95 could be responsible for the decrease of total winter sea ice export during the same time period.

Multisensor Analyzed Sea Ice Extent - Northern Hemisphere (MASIE-NH)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Multisensor Analyzed Sea Ice Extent Northern Hemisphere (MASIE-NH) products provide measurements of daily sea ice extent and sea ice edge boundary for the...

The Impact of Stratospheric Circulation Extremes on Minimum Arctic Sea Ice Extent

Science.gov (United States)

Smith, K. L.; Polvani, L. M.; Tremblay, B.

2017-12-01

The interannual variability of summertime Arctic sea ice extent (SIE) is anti-correlated with the leading mode of extratropical atmospheric variability in preceding winter, the Arctic Oscillation (AO). Given this relationship and the need for better seasonal predictions of Arctic SIE, we here examine the role of stratospheric circulation extremes and stratosphere-troposphere coupling in linking the AO and Arctic SIE variability. We show that extremes in the stratospheric circulation during the winter season, namely stratospheric sudden warming (SSW) and strong polar vortex (SPV) events, are associated with significant anomalies in sea ice concentration in the Bering Straight and the Sea of Okhotsk in winter, the Barents Sea in spring and along the Eurasian coastline in summer in both observations and a fully-coupled, stratosphere-resolving general circulation model. The accompanying figure shows the composite mean sea ice concentration anomalies from the Whole Atmosphere Community Climate Model (WACCM) for SSWs (N = 126, top row) and SPVs (N = 99, bottom row) for winter (a,d), spring (b,e) and summer (c,f). Consistent with previous work on the AO, we find that SSWs, which are followed by the negative phase of the AO at the surface, result in sea ice growth, whereas SPVs, which are followed by the positive phase of the AO at the surface, result in sea ice loss, although the dynamic and thermodynamic processes driving these sea ice anomalies in the three Arctic regions, noted above, are different. Our analysis suggests that the presence or absence of stratospheric circulation extremes in winter may play a non-trivial role in determining total September Arctic SIE when combined with other factors.

Winter in the Ouachitas--a severe winter storm signature in Pinus echinata in the Ouachita Mountains of Oklahoma and Arkansas, USA

Science.gov (United States)

Douglas J. Stevenson; Thomas B. Lynch; Pradip Saud; Robert Heineman; Randal Holeman; Dennis Wilson; Keith Anderson; Chris Cerny; James M. Guldin

2016-01-01

Each year severe winter storms (≈ice storms) damage trees throughout the southern USA. Arkansas and Oklahoma have a history of severe winter storms. To extend that history back beyond the reach of written records, a distinctive tree ring pattern or signature is needed. Storm-caused breakage, branch loss and bending stress provide that signature. We found a severe storm...

Ocean Profile Measurements During the Seasonal Ice Zone Reconnaissance Surveys

Science.gov (United States)

2014-09-30

ice cover in 2014. The consequent reduced melting early in the summer delays the onset of sea - ice - albedo feed back in accelerating melt throughout the...Chukchi sea seasonal sea ice zone (SIZ) utilizing US Coast Guard Arctic Domain Awareness (ADA) flights of opportunity. This report covers our grant...region between maximum winter sea ice extent and minimum summer sea ice extent. As such, it contains the full range of positions of the marginal ice

Dazzled by ice and snow: improving medium ocean color images in Arctic waters

Science.gov (United States)

Babin, M.; Goyens, C.; Belanger, S.

2016-02-01

The importance of phytoplankton blooms for the Arctic marine ecosystem is well recognized but studies disagree as the consequences of sea ice melt on the phytoplankton distribution and growth. This limited understanding in actual and future Arctic phytoplankton dynamics mostly results from a lack of accurate data at the receding ice-edges where phytoplankton blooms are known to occur. Ocean color sensors on-board satellites represent therefore a crucial tool providing a synoptic view of the ocean systems over broad spatio-temporal scales. However, today the use of ocean color data in Arctic environments remains strongly compromised due to, among others, sea ice contamination. Indeed, medium ocean color data along the receding ice edge are "dazzled" by nearby and/or sub-pixel highly reflective ice floes. Standard ocean color data methods ignore ice-contamination during data processing which deteriorates the quality of the radiometric data and subsequent satellite derived bio-geochemical products. Moreover, since Arctic phytoplankton spring blooms typically develop along the receding ice-edges, ignoring ice-contaminated pixels may lead to wrong interpretation of satellite data. The present study shows how adjacent and sub-pixel sea-ice floes affect the retrieved ocean color data. A correction approach is also suggested to improve the "dazzled" ocean color pixels along the receding ice edge in the aim to provide additional support to better understand current and future trends in phytoplankton dynamics.

Microtopographic control on the ground thermal regime in ice wedge polygons

Science.gov (United States)

Abolt, Charles J.; Young, Michael H.; Atchley, Adam L.; Harp, Dylan R.

2018-06-01

The goal of this research is to constrain the influence of ice wedge polygon microtopography on near-surface ground temperatures. Ice wedge polygon microtopography is prone to rapid deformation in a changing climate, and cracking in the ice wedge depends on thermal conditions at the top of the permafrost; therefore, feedbacks between microtopography and ground temperature can shed light on the potential for future ice wedge cracking in the Arctic. We first report on a year of sub-daily ground temperature observations at 5 depths and 9 locations throughout a cluster of low-centered polygons near Prudhoe Bay, Alaska, and demonstrate that the rims become the coldest zone of the polygon during winter, due to thinner snowpack. We then calibrate a polygon-scale numerical model of coupled thermal and hydrologic processes against this dataset, achieving an RMSE of less than 1.1 °C between observed and simulated ground temperature. Finally, we conduct a sensitivity analysis of the model by systematically manipulating the height of the rims and the depth of the troughs and tracking the effects on ice wedge temperature. The results indicate that winter temperatures in the ice wedge are sensitive to both rim height and trough depth, but more sensitive to rim height. Rims act as preferential outlets of subsurface heat; increasing rim size decreases winter temperatures in the ice wedge. Deeper troughs lead to increased snow entrapment, promoting insulation of the ice wedge. The potential for ice wedge cracking is therefore reduced if rims are destroyed or if troughs subside, due to warmer conditions in the ice wedge. These findings can help explain the origins of secondary ice wedges in modern and ancient polygons. The findings also imply that the potential for re-establishing rims in modern thermokarst-affected terrain will be limited by reduced cracking activity in the ice wedges, even if regional air temperatures stabilize.

Turbulent heat transfer as a control of platelet ice growth in supercooled under-ice ocean boundary layers

Science.gov (United States)

McPhee, Miles G.; Stevens, Craig L.; Smith, Inga J.; Robinson, Natalie J.

2016-04-01

Late winter measurements of turbulent quantities in tidally modulated flow under land-fast sea ice near the Erebus Glacier Tongue, McMurdo Sound, Antarctica, identified processes that influence growth at the interface of an ice surface in contact with supercooled seawater. The data show that turbulent heat exchange at the ocean-ice boundary is characterized by the product of friction velocity and (negative) water temperature departure from freezing, analogous to similar results for moderate melting rates in seawater above freezing. Platelet ice growth appears to increase the hydraulic roughness (drag) of fast ice compared with undeformed fast ice without platelets. Platelet growth in supercooled water under thick ice appears to be rate-limited by turbulent heat transfer and that this is a significant factor to be considered in mass transfer at the underside of ice shelves and sea ice in the vicinity of ice shelves.

Ice processes affect habitat use and movements of adult cutthroat trout and brook trout in a Wyoming foothills stream

Science.gov (United States)

Lindstrom, J.W.; Hubert, W.A.

2004-01-01

Habitat use and movements of 25 adult cutthroat trout Oncorhynchus clarkii and 25 adult brook trout Salvelinus fontinalis from fall through winter 2002-2003 were assessed by means of radiotelemetry in a 7-km reach of a Rocky Mountains foothills stream. Temporal dynamics of winter habitat conditions were evaluated by regularly measuring the features of 30 pools and 5 beaver Castor canadensis ponds in the study reach. Groundwater inputs at three locations raised mean daily water temperatures in the stream channel during winter to 0.2-0.6??C and kept at least 250 m of the downstream channel free of ice, but the lack of surface ice further downstream led to the occurrence of frazil ice and anchor ice in pools and unstable habitat conditions for trout. Pools in segments that were not affected by groundwater inputs and beaver ponds tended to be stable and snow accumulated on the surface ice. Pools throughout the study reach tended to become more stable as snow accumulated. Both cutthroat trout and brook trout selected beaver ponds as winter progressed but tended to use lateral scour pools in proportion to their availability. Tagged fish not in beaver ponds selected lateral scour pools that were deeper than average and stable during winter. Movement frequencies by tagged fish decreased from fall through winter, but some individuals of both species moved during winter. Ice processes affected both the habitat use and movement patterns of cutthroat trout and brook trout in this foothills stream.

Photophysiology and cellular composition of sea ice algae

International Nuclear Information System (INIS)

Lizotte, M.P.

1989-01-01

The productivity of sea ice algae depends on their physiological capabilities and the environmental conditions within various microhabitats. Pack ice is the dominant form of sea ice, but the photosynthetic activity of associated algae has rarely been studied. Biomass and photosynthetic rates of ice algae of the Weddell-Scotia Sea were investigated during autumn and winter, the period when ice cover grows from its minimum to maximum. Biomass-specific photosynthetic rates typically ranged from 0.3 to 3.0 μg C · μg chl -1 · h -1 higher than land-fast ice algae but similar to Antarctic phytoplankton. Primary production in the pack ice during winter may be minor compared to annual phytoplankton production, but could represent a vital seasonal contribution to the Antarctic ecosystem. Nutrient supply may limit the productivity of ice algae. In McMurdo Sound, congelation ice algae appeared to be more nutrient deficient than underlying platelet ice algae based on: lower nitrogen:carbon, chlorophyll:carbon, and protein:carbohydrate; and 14 C-photosynthate distribution to proteins and phospholipids was lower, while distribution to polysaccharides and neutral lipids was higher. Depletion of nitrate led to decreased nitrogen:carbon, chlorophyll:carbon, protein:carbohydrate, and 14 C-photosynthate to proteins. Studied were conducted during the spring bloom; therefore, nutrient limitation may only apply to dense ice algal communities. Growth limiting conditions may be alleviated when algae are released into seawater during the seasonal recession of the ice cover. To continue growth, algae must adapt to the variable light field encountered in a mixed water column. Photoadaptation was studied in surface ice communities and in bottom ice communities

Numerical simulation of formation and preservation of Ningwu ice cave, Shanxi, China

Science.gov (United States)

Yang, S.; Shi, Y.

2015-10-01

Ice caves exist in locations where annual average air temperature is higher than 0 °C. An example is Ningwu ice cave, Shanxi Province, the largest ice cave in China. In order to quantitatively investigate the mechanism of formation and preservation of the ice cave, we use the finite-element method to simulate the heat transfer process at this ice cave. There are two major control factors. First, there is the seasonal asymmetric heat transfer. Heat is transferred into the ice cave from outside very inefficiently by conduction in spring, summer and fall. In winter, thermal convection occurs that transfers heat very efficiently out of the ice cave, thus cooling it down. Secondly, ice-water phase change provides a heat barrier for heat transfer into the cave in summer. The calculation also helps to evaluate effects of global warming, tourists, colored lights, climatic conditions, etc. for sustainable development of the ice cave as a tourism resource. In some other ice caves in China, managers have installed airtight doors at these ice caves' entrances with the intention of "protecting" these caves, but this in fact prevents cooling in winter and these cave ices will entirely melt within tens of years.

Application of remotely piloted aircraft systems in observing the atmospheric boundary layer over Antarctic sea ice in winter

Directory of Open Access Journals (Sweden)

Marius O. Jonassen

2015-10-01

Full Text Available The main aim of this paper is to explore the potential of combining measurements from fixed- and rotary-wing remotely piloted aircraft systems (RPAS to complement data sets from radio soundings as well as ship and sea-ice-based instrumentation for atmospheric boundary layer (ABL profiling. This study represents a proof-of-concept of RPAS observations in the Antarctic sea-ice zone. We present first results from the RV Polarstern Antarctic winter expedition in the Weddell Sea in June–August 2013, during which three RPAS were operated to measure temperature, humidity and wind; a fixed-wing small unmanned meteorological observer (SUMO, a fixed-wing meteorological mini-aerial vehicle, and an advanced mission and operation research quadcopter. A total of 86 RPAS flights showed a strongly varying ABL structure ranging from slightly unstable temperature stratification near the surface to conditions with strong surface-based temperature inversions. The RPAS observations supplement the regular upper air soundings and standard meteorological measurements made during the campaign. The SUMO and quadcopter temperature profiles agree very well and, excluding cases with strong temperature inversions, 70% of the variance in the difference between the SUMO and quadcopter temperature profiles can be explained by natural, temporal, temperature fluctuations. Strong temperature inversions cause the largest differences, which are induced by SUMO's high climb rates and slow sensor response. Under such conditions, the quadcopter, with its slower climb rate and faster sensor, is very useful in obtaining accurate temperature profiles in the lowest 100 m above the sea ice.

Tropospheric characteristics over sea ice during N-ICE2015

Science.gov (United States)

Kayser, Markus; Maturilli, Marion; Graham, Robert; Hudson, Stephen; Cohen, Lana; Rinke, Annette; Kim, Joo-Hong; Park, Sang-Jong; Moon, Woosok; Granskog, Mats

2017-04-01

Over recent years, the Arctic Ocean region has shifted towards a younger and thinner sea-ice regime. The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in this new ice regime north of Svalbard. Here we analyze upper-air measurements made by radiosondes launched twice daily together with surface meteorology observations during N-ICE2015 from January to June 2015. We study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, sudden increases in moisture content and temperature, temperature inversions and boundary layer dynamics. The influence of synoptic cyclones is strongest under polar night conditions, when radiative cooling is most effective and the moisture content is low. We find that transitions between the radiatively clear and opaque state are the largest drivers of changes to temperature inversion and stability characteristics in the boundary layer during winter. In spring radiative fluxes warm the surface leading to lifted temperature inversions and a statically unstable boundary layer. The unique N-ICE2015 dataset is used for case studies investigating changes in the vertical structure of the atmosphere under varying synoptic conditions. The goal is to deepen our understanding of synoptic interactions within the Arctic climate system, to improve model performance, as well as to identify gaps in instrumentation, which precludes further investigations.

"Crystals within Crystals: The Story of Sea Ice". A Classroom-Based Outreach Project Communicating Cutting-Edge Ocean Science to School Pupils

Science.gov (United States)

Butler, B.

2016-02-01

'Crystals within Crystals: The story of sea ice' is a UK based outreach project based that uses a range practical tools to engage school students with cutting edge scientific research that relates to the use of some of the world's most powerful X-rays in sea ice research. The project is delivered in the form of a classroom workshop that first introduces school pupils (aged 11-14) to seawater and the salts that give it a salinity. The pupils are then shown how the presence of salts within seawater results in very important physical changes when the liquid freezes, which includes different structural and optical properties of the ice. The properties of the ice are then linked to the presence of countless microscopic salt crystals that are trapped within the microstructure of the frozen seawater, which is explained with use of a novel crystal growth demonstration. Given that there is currently no way of successfully removing these salt crystals from the ice, the workshop culminates in explaining how some of the worlds most powerful X-rays can be used to investigate processes that otherwise remain elusive. The workshop introduces students to the fundamental principles of scientific enquiry, the sea ice environment, and the power of X-rays in investigating the properties of crystals. Here we present information that outlines a host of practical and project management tools that are applicacble to outreach projects in the the field of ocean sciences, with the aim of seeding ideas and interest for other graduate student to enage with the public during their studies.

STS-48 ESC Earth observation of ice pack, Antarctic Ice Shelf

Science.gov (United States)

1991-01-01

STS-48 Earth observation taken aboard Discovery, Orbiter Vehicle (OV) 103, is of the breakup of pack ice along the periphery of the Antarctic Ice Shelf. Strong offshore winds, probably associated with katabatic downdrafts from the interior of the continent, are seen peeling off the edges of the ice shelf into long filaments of sea ice, icebergs, bergy bits, and growlers to flow northward into the South Atlantic Ocean. These photos are used to study ocean wind, tide and current patterns. Similar views photographed during previous missions, when analyzed with these recent views may yield information about regional ice drift and breakup of ice packs. The image was captured using an electronic still camera (ESC), was stored on a removable hard disk or small optical disk, and was converted to a format suitable for downlink transmission. The ESC documentation was part of Development Test Objective (DTO) 648, Electronic Still Photography.

Enhanced wintertime greenhouse effect reinforcing Arctic amplification and initial sea-ice melting.

Science.gov (United States)

Cao, Yunfeng; Liang, Shunlin; Chen, Xiaona; He, Tao; Wang, Dongdong; Cheng, Xiao

2017-08-16

The speeds of both Arctic surface warming and sea-ice shrinking have accelerated over recent decades. However, the causes of this unprecedented phenomenon remain unclear and are subjects of considerable debate. In this study, we report strong observational evidence, for the first time from long-term (1984-2014) spatially complete satellite records, that increased cloudiness and atmospheric water vapor in winter and spring have caused an extraordinary downward longwave radiative flux to the ice surface, which may then amplify the Arctic wintertime ice-surface warming. In addition, we also provide observed evidence that it is quite likely the enhancement of the wintertime greenhouse effect caused by water vapor and cloudiness has advanced the time of onset of ice melting in mid-May through inhibiting sea-ice refreezing in the winter and accelerating the pre-melting process in the spring, and in turn triggered the positive sea-ice albedo feedback process and accelerated the sea ice melting in the summer.

Proceedings of the 14. workshop of the Committee on River Ice Processes and the Environment : hydraulics of ice covered rivers

International Nuclear Information System (INIS)

Morse, B.; Bergeron, N.; Gauthier, Y.

2007-01-01

Ice processes play a significant role in the hydrologic regime of Canadian rivers. The Committee on River Ice Processes and the Environment (CRIPE) identifies high-priority topics for research and development and promotes research programs at Canadian colleges and universities. This workshop reviewed the hydraulic aspects of river ice phenomena in an effort to clarify the effects of ice cover on river flow characteristics. Other issues of concern were also discussed, notably ice formation, ice jams, winter operation of hydroelectric power plants, environmental aspects of river ice, and climate change. The workshop featured 12 poster sessions and 40 presentations, of which 5 have been catalogued separately for inclusion in this database. refs., tabs., figs

Export of Ice-Cavity Water from Pine Island Ice Shelf, West Antarctica

Science.gov (United States)

Thurnherr, Andreas; Jacobs, Stanley; Dutrieux, Pierre

2013-04-01

Stability of the West Antarctic Ice Sheet is sensitive to changes in melting at the bottom of floating ice shelves that form the seaward extensions of Antarctic glaciers flowing into the ocean. Not least because observations in the cavities beneath ice shelves are difficult, heat fluxes and melt rates have been inferred from oceanographic measurements obtained near the ice edge (calving fronts). Here, we report on a set of hydrographic and velocity data collected in early 2009 near the calving front of the Amundsen Sea's fast-moving and (until recently) accelerating Pine Island Glacier and its associated ice shelf. CTD profiles collected along the southern half of the meridionally-trending ice front show clear evidence for export of ice-cavity water. That water was carried in the upper ocean along the ice front by a southward current that is possibly related to a striking clockwise gyre that dominated the (summertime) upper-ocean circulation in Pine Island Bay. Signatures of ice-cavity water appear unrelated to current direction along most of the ice front, suggesting that cross-frontal exchange is dominated by temporal variability. However, repeated hydrographic and velocity measurements in a small "ice cove" at the southern end of the calving front show a persistent strong (mean velocity peaking near 0.5 ms-1) outflow of ice-cavity water in the upper 500 m. While surface features (boils) suggested upwelling from deep below the ice shelf, vertical velocity measurements reveal 1) that the mean upwelling within the confines of the cove was too weak to feed the observed outflow, and 2) that large high-frequency internal waves dominated the vertical motion of water inside the cove. These observations indicate that water exchange between the Pine Island Ice Shelf cavity and the Amundsen sea is strongly asymmetric with weak broad inflow at depth and concentrated surface-intensified outflow of melt-laden deep water at the southern edge of the calving front. The lack of

Decontamination and winter conditions

International Nuclear Information System (INIS)

Quenild, C.; Tveten, U.

1984-12-01

The report deals with two decontamonation experiments under winter conditions. A snow-covered parking lot was contaminated, and the snow was subsequently removed using standard snow-moving equipment. The snow left behind was collected and the content of contaminant was determined. A non-radioactive contaminant was used. A decontamination factor exceeding 100 was obtained. Although the eksperimental conditions were close to ideal, it is reason to believe that extremely efficient removal of deposited materials on a snow surface is achivable. In another investigation, run-off from agricultural surface, contaminated while covered with snow, was measured A lycimeter was used in this experiment. A stable layer of ice and snow was allowed to form before contamination. The run-off water was collected at each thaw period until all snow and ice was gone. Cs-134 was used as contaminant. Roughly 30% of the Cs-134 with which the area was contaminated ran off with the melt water. Following a reactor accident situation, this would have given a corresponding reduction in the long term doses. Both of these experiments show that consequence calculation assumptions, as they are currently applied to large accident assessment, tend to overestimate the consequences resulting from accidents taking place under winter conditions

The Dehn Collection of Arctic Sea Ice Charts, 1953-1986

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The National Snow and Ice Data Center holds a collection of charts depicting ice conditions in the seas off Alaska and western Canada coasts. Ice edge position and...

The History of Winter: teachers as scientists

Science.gov (United States)

Koenig, L.; Courville, Z.; Wasilewski, P. J.; Gow, T.; Bender, K. J.

2013-12-01

The History of Winter (HOW) is a NASA Goddard Space Flight Center-funded teacher enrichment program that was started by Dr. Peter Wasilewski (NASA), Dr. Robert Gabrys (NASA) and Dr. Tony Gow (Cold Regions Research and Engineering Laboratory, or CRREL) in 2001 and continues with support and involvement of scientists from both the NASA Cryospheric Sciences Laboratory and CREEL. The program brings educators mostly from middle and high schools but also from state parks, community colleges and other institutions from across the US to the Northwood School (a small, private boarding school) in Lake Placid, NY for one week to learn about several facets of winter, polar, and snow research, including the science and history of polar ice core research, lake ice formation and structure, snow pack science, winter ecology, and remote sensing including current and future NASA cryospheric missions. The program receives support from the Northwood School staff to facilitate the program. The goal of the program is to create 'teachers as scientists' which is achieved through several hands-on field experiences in which the teachers have the opportunity to work with polar researchers from NASA, CRREL and partner Universities to dig and sample snow pits, make ice thin sections from lake ice, make snow shelters, and observe under-ice lake ecology. The hands-on work allows the teachers to use the same tools and techniques used in polar research while simultaneously introducing science concepts and activities to support their classroom work. The ultimate goal of the program is to provide the classroom teachers with the opportunity to learn about current and timely cryospheric research as well as to engage in real fieldwork experiences. The enthusiasm generated during the week-long program is translated into classroom activities with guidance from scientists, teachers and educational professionals. The opportunity to engage with polar researchers, both young investigators and renowned

[Winter sport injuries in childhood (author's transl)].

Science.gov (United States)

Hausbrandt, D; Höllwarth, M; Ritter, G

1979-01-01

3374 accidents occurring on the field of sport during the years 1975--1977 accounted for 19% of all accidents dealt with at the Institute of Kinderchirurgie in Graz. 51% of the accidents were caused by the typical winter sports: skiing, tobogganing, ice-skating and ski-jumping with skiing accounting for 75% of the accidents. The fracture localization typical of the different kinds of winter sport is dealt with in detail. The correct size and safety of the equipment were found to be particularly important in the prevention of such accidents in childhood.

Seasonal reversal at Miryang Eoreumgol (Ice Valley), Korea: observation and monitoring

Science.gov (United States)

Byun, Hi-Ryong; Tanaka, Hiroshi L.; Choi, Pom-Yong; Kim, Do-Woo

2011-12-01

We investigate an anomalous phenomenon evident in the Miryang Eoreumgol (Ice Valley), Korea: The wind and water are cold during summer and warm during winter, and ice formation does not occur in winter but in summer. We have initiated observations and investigations into the origin of heat sources particularly with regard to the mechanism of ice formation in summer. Previous theories, e.g., concerning underground gravity currents, water evaporation, diurnal and seasonal respirations of the talus, effects of ground heat, radiation and topography, etc., are considered. After a calculation of heat sources, we propose two new concepts—a repetitious heat separation mechanism and a positive feedback mechanism of cold air generation—to demonstrate that the heat mechanism of the seasonal reversal of the ice valley may be controlled by the use of the phase change between ice and water vapor with only a small amount of additional unknown energy.

Effects of dirty snow in nuclear winter simulations

International Nuclear Information System (INIS)

Vogelmann, A.M.; Robock, A.; Ellingson, R.G.

1988-01-01

A large-scale nuclear war would inject smoke into the atmosphere from burning forests, cities, and industries in targeted areas. This smoke could fall out onto snow and ice and would lower cryospheric albedos by as much as 50%. A global energy balance climate model is used to investigate the maximum effect these ''dirty snow'' albedos have on the surface temperature in nuclear winter simulations which span several years. These effects are investigated for different nuclear winter scenarios, snow precipitation rates, latitudinal distributions of smoke, and seasonal timings. We find that dirty snow, in general, would have a small temperature effect at mid- and low latitudes but could have a large temperature effect at polar latitudes, particularly if the soot is able to reappear significantly in later summers. Factors which limit the climatic importance of the dirty snow are (1) the dirty snow albedo is lowest when the atmosphere still contains a large amount of light-absorbing smoke; (2) even with dirty snow, sea ice areas can still increase, which helps maintain colder temperatures through the sea ice thermal inertial feedback; (3) the snow and ice areas affected by the dirty snow albedos are largest when there is little seasonal solar insolation; and (4) the area affected by the dirty snow is relatively small under all circumstances. copyright American Geophysical Union 1988

The role of ice dynamics in shaping vegetation in flowing waters.

Science.gov (United States)

Lind, Lovisa; Nilsson, Christer; Polvi, Lina E; Weber, Christine

2014-11-01

Ice dynamics is an important factor affecting vegetation in high-altitude and high-latitude streams and rivers. During the last few decades, knowledge about ice in streams and rivers has increased significantly and a respectable body of literature is now available. Here we review the literature on how ice dynamics influence riparian and aquatic vegetation. Traditionally, plant ecologists have focused their studies on the summer period, largely ignoring the fact that processes during winter also impact vegetation dynamics. For example, the freeze-up period in early winter may result in extensive formation of underwater ice that can restructure the channel, obstruct flow, and cause flooding and thus formation of more ice. In midwinter, slow-flowing reaches develop a surface-ice cover that accumulates snow, protecting habitats under the ice from formation of underwater ice but also reducing underwater light, thus suppressing photosynthesis. Towards the end of winter, ice breaks up and moves downstream. During this transport, ice floes can jam up and cause floods and major erosion. The magnitudes of the floods and their erosive power mainly depend on the size of the watercourse, also resulting in different degrees of disturbance to the vegetation. Vegetation responds both physically and physiologically to ice dynamics. Physical action involves the erosive force of moving ice and damage caused by ground frost, whereas physiological effects - mostly cell damage - happen as a result of plants freezing into the ice. On a community level, large magnitudes of ice dynamics seem to favour species richness, but can be detrimental for individual plants. Human impacts, such as flow regulation, channelisation, agriculturalisation and water pollution have modified ice dynamics; further changes are expected as a result of current and predicted future climate change. Human impacts and climate change can both favour and disfavour riverine vegetation dynamics. Restoration of streams

Environmental problems related to winter traffic safety conditions

OpenAIRE

Hääl, Maire-Liis; Sürje, Peep

2006-01-01

The changeable Nordic climate has added problems to road maintenance and the environment to ensure traffic safety under winter conditions. The widespread use of salt (NaCl) for snow and ice removal from roads has resulted in environmental impacts in many areas. Some of the problems associated with the use of NaCl are the corrosion of bridges, road surfaces and vehicles and damage to roadside vegetation and aquatic system that are affected by water from de-iced roads. Accumulation of hard meta...

Monitoring Bedfast Ice and Ice Phenology in Lakes of the Lena River Delta Using TerraSAR-X Backscatter and Coherence Time Series

Directory of Open Access Journals (Sweden)

Sofia Antonova

2016-11-01

Full Text Available Thermokarst lakes and ponds are major elements of permafrost landscapes, occupying up to 40% of the land area in some Arctic regions. Shallow lakes freeze to the bed, thus preventing permafrost thaw underneath them and limiting the length of the period with greenhouse gas production in the unfrozen lake sediments. Radar remote sensing permits to distinguish lakes with bedfast ice due to the difference in backscatter intensities from bedfast and floating ice. This study investigates the potential of a unique time series of three-year repeat-pass TerraSAR-X (TSX imagery with high temporal (11 days and spatial (10 m resolution for monitoring bedfast ice as well as ice phenology of lakes in the zone of continuous permafrost in the Lena River Delta, Siberia. TSX backscatter intensity is shown to be an excellent tool for monitoring floating versus bedfast lake ice as well as ice phenology. TSX-derived timing of ice grounding and the ice growth model CLIMo are used to retrieve the ice thicknesses of the bedfast ice at points where in situ ice thickness measurements were available. Comparison shows good agreement in the year of field measurements. Additionally, for the first time, an 11-day sequential interferometric coherence time series is analyzed as a supplementary approach for the bedfast ice monitoring. The coherence time series detects most of the ice grounding as well as spring snow/ice melt onset. Overall, the results show the great value of TSX time series for monitoring Arctic lake ice and provide a basis for various applications: for instance, derivation of shallow lakes bathymetry, evaluation of winter water resources and locating fish winter habitat as well as estimation of taliks extent in permafrost.

Dispersal of solitary bees and bumblebees in a winter oilseed rape field

DEFF Research Database (Denmark)

Calabuig, Isabel

2000-01-01

Dispersal distributions of solitary bees and bumblebees were studied in a winter oilseed rape field. Window-traps were placed in the rape field along a line transect perpendicular to the field edge. 19 species of solitary bees were recorded and all but four species are polylectic, including...... Brassicaceae as host-plant family. Through non-linear regression, the decline in solitary bee individuals versus distance from field edge significantly fitted a steep two-parameter exponential decay function. Activity of solitary bees was clearly highest within 30 metres from the field edge. Apparently......, solitary bees do not play any noteworthy role in the pollination of winter oilseed rape in Denmark. The traps yielded ten species of bumblebees, and a significant linear correlation was found between numbers of individuals and distance from the field edge. This result is attributed to bumblebee foraging...

A robust empirical seasonal prediction of winter NAO and surface climate.

Science.gov (United States)

Wang, L; Ting, M; Kushner, P J

2017-03-21

A key determinant of winter weather and climate in Europe and North America is the North Atlantic Oscillation (NAO), the dominant mode of atmospheric variability in the Atlantic domain. Skilful seasonal forecasting of the surface climate in both Europe and North America is reflected largely in how accurately models can predict the NAO. Most dynamical models, however, have limited skill in seasonal forecasts of the winter NAO. A new empirical model is proposed for the seasonal forecast of the winter NAO that exhibits higher skill than current dynamical models. The empirical model provides robust and skilful prediction of the December-January-February (DJF) mean NAO index using a multiple linear regression (MLR) technique with autumn conditions of sea-ice concentration, stratospheric circulation, and sea-surface temperature. The predictability is, for the most part, derived from the relatively long persistence of sea ice in the autumn. The lower stratospheric circulation and sea-surface temperature appear to play more indirect roles through a series of feedbacks among systems driving NAO evolution. This MLR model also provides skilful seasonal outlooks of winter surface temperature and precipitation over many regions of Eurasia and eastern North America.

The Effect of Seasonal Variability of Atlantic Water on the Arctic Sea Ice Cover

Science.gov (United States)

Ivanov, V. V.; Repina, I. A.

2018-01-01

Under the influence of global warming, the sea ice in the Arctic Ocean (AO) is expected to reduce with a transition toward a seasonal ice cover by the end of this century. A comparison of climate-model predictions with measurements shows that the actual rate of ice cover decay in the AO is higher than the predicted one. This paper argues that the rapid shrinking of the Arctic summer ice cover is due to its increased seasonality, while seasonal oscillations of the Atlantic origin water temperature create favorable conditions for the formation of negative anomalies in the ice-cover area in winter. The basis for this hypothesis is the fundamental possibility of the activation of positive feedback provided by a specific feature of the seasonal cycle of the inflowing Atlantic origin water and the peaking of temperature in the Nansen Basin in midwinter. The recently accelerated reduction in the summer ice cover in the AO leads to an increased accumulation of heat in the upper ocean layer during the summer season. The extra heat content of the upper ocean layer favors prerequisite conditions for winter thermohaline convection and the transfer of heat from the Atlantic water (AW) layer to the ice cover. This, in turn, contributes to further ice thinning and a decrease in ice concentration, accelerated melting in summer, and a greater accumulation of heat in the ocean by the end of the following summer. An important role is played by the seasonal variability of the temperature of AW, which forms on the border between the North European and Arctic basins. The phase of seasonal oscillation changes while the AW is moving through the Nansen Basin. As a result, the timing of temperature peak shifts from summer to winter, additionally contributing to enhanced ice melting in winter. The formulated theoretical concept is substantiated by a simplified mathematical model and comparison with observations.

A sea ice model for the marginal ice zone with an application to the Greenland Sea

DEFF Research Database (Denmark)

Pedersen, Leif Toudal; Coon, Max D.

2004-01-01

A model is presented that describes the formation, transport, and desalinization of frazil and pancake ice as it is formed in marginal seas. This model uses as input the total ice concentration evaluated from Special Sensor Microwave Imager and wind speed and direction. The model calculates...... the areal concentration, thickness, volume concentration, and salinity of frazil ice as well as the areal concentration, thickness, and salinity of pancakes. A simple parameterization for the Odden region of the Greenland Sea is presented. The model is run for the winter of 1996-1997. There are direct...... observations of the thickness and salinity of pancakes and the volume concentration of frazil ice to compare with the model. The model results compare very well with the measured data. This new ice model can be tuned to work in marginal seas elsewhere to calculate ice thickness, motion, and brine rejection...

Sea Ice, Climate and Fram Strait

Science.gov (United States)

Hunkins, K.

1984-01-01

When sea ice is formed the albedo of the ocean surface increases from its open water value of about 0.1 to a value as high as 0.8. This albedo change effects the radiation balance and thus has the potential to alter climate. Sea ice also partially seals off the ocean from the atmosphere, reducing the exchange of gases such as carbon dioxide. This is another possible mechanism by which climate might be affected. The Marginal Ice Zone Experiment (MIZEX 83 to 84) is an international, multidisciplinary study of processes controlling the edge of the ice pack in that area including the interactions between sea, air and ice.

Methane excess in Arctic surface water-triggered by sea ice formation and melting.

Science.gov (United States)

Damm, E; Rudels, B; Schauer, U; Mau, S; Dieckmann, G

2015-11-10

Arctic amplification of global warming has led to increased summer sea ice retreat, which influences gas exchange between the Arctic Ocean and the atmosphere where sea ice previously acted as a physical barrier. Indeed, recently observed enhanced atmospheric methane concentrations in Arctic regions with fractional sea-ice cover point to unexpected feedbacks in cycling of methane. We report on methane excess in sea ice-influenced water masses in the interior Arctic Ocean and provide evidence that sea ice is a potential source. We show that methane release from sea ice into the ocean occurs via brine drainage during freezing and melting i.e. in winter and spring. In summer under a fractional sea ice cover, reduced turbulence restricts gas transfer, then seawater acts as buffer in which methane remains entrained. However, in autumn and winter surface convection initiates pronounced efflux of methane from the ice covered ocean to the atmosphere. Our results demonstrate that sea ice-sourced methane cycles seasonally between sea ice, sea-ice-influenced seawater and the atmosphere, while the deeper ocean remains decoupled. Freshening due to summer sea ice retreat will enhance this decoupling, which restricts the capacity of the deeper Arctic Ocean to act as a sink for this greenhouse gas.

Trends in Arctic Sea Ice Volume 2010-2013 from CryoSat-2

Science.gov (United States)

Tilling, R.; Ridout, A.; Wingham, D.; Shepherd, A.; Haas, C.; Farrell, S. L.; Schweiger, A. J.; Zhang, J.; Giles, K.; Laxon, S.

2013-12-01

Satellite records show a decline in Arctic sea ice extent over the past three decades with a record minimum in September 2012, and results from the Pan-Arctic Ice-Ocean Modelling and Assimilation System (PIOMAS) suggest that this has been accompanied by a reduction in volume. We use three years of measurements recorded by the European Space Agency CryoSat-2 (CS-2) mission, validated with in situ data, to generate estimates of seasonal variations and inter-annual trends in Arctic sea ice volume between 2010 and 2013. The CS-2 estimates of sea ice thickness agree with in situ estimates derived from upward looking sonar measurements of ice draught and airborne measurements of ice thickness and freeboard to within 0.1 metres. Prior to the record minimum in summer 2012, autumn and winter Arctic sea ice volume had fallen by ~1300 km3 relative to the previous year. Using the full 3-year period of CS-2 observations, we estimate that winter Arctic sea ice volume has decreased by ~700 km3/yr since 2010, approximately twice the average rate since 1980 as predicted by the PIOMAS.

Weather Support for the 2002 Winter Olympic and Paralympic Games.

Science.gov (United States)

Horel, J.; Potter, T.; Dunn, L.; Steenburgh, W. J.; Eubank, M.; Splitt, M.; Onton, D. J.

2002-02-01

The 2002 Winter Olympic and Paralympic Games will be hosted by Salt Lake City, Utah, during February-March 2002. Adverse weather during this period may delay sporting events, while snow and ice-covered streets and highways may impede access by the athletes and spectators to the venues. While winter snowstorms and other large-scale weather systems typically have widespread impacts throughout northern Utah, hazardous winter weather is often related to local terrain features (the Wasatch Mountains and Great Salt Lake are the most prominent ones). Examples of such hazardous weather include lake-effect snowstorms, ice fog, gap winds, downslope windstorms, and low visibility over mountain passes.A weather support system has been developed to provide weather information to the athletes, games officials, spectators, and the interested public around the world. This system is managed by the Salt Lake Olympic Committee and relies upon meteorologists from the public, private, and academic sectors of the atmospheric science community. Weather forecasting duties will be led by National Weather Service forecasters and a team of private, weather forecasters organized by KSL, the Salt Lake City NBC television affiliate. Other government agencies, commercial firms, and the University of Utah are providing specialized forecasts and support services for the Olympics. The weather support system developed for the 2002 Winter Olympics is expected to provide long-term benefits to the public through improved understanding,monitoring, and prediction of winter weather in the Intermountain West.

Elevator deflections on the icing process

Science.gov (United States)

Britton, Randall K.

1990-01-01

The effect of elevator deflection of the horizontal stabilizer for certain icing parameters is investigated. Elevator deflection can severely change the lower and upper leading-edge impingement limits, and ice can accrete on the elevator itself. Also, elevator deflection had practically no effect on the maximum local collection efficiency. It is shown that for severe icing conditions (large water droplets), elevator deflections that increase the projected height of the airfoil can significantly increase the total collection efficiency of the airfoil.

Evaluation of the Viking-Cives towplow for winter maintenance.

Science.gov (United States)

2014-01-01

To maximize efficiency while minimizing costs within ODOTs winter maintenance budget, ODOT is : evaluating new methods of snow and ice removal. One method is the use of the Viking-Cives TowPlow. The : TowPlow is pulled behind a tandem axle truck a...

Ice fishing by wintering Bald Eagles in Arizona

Science.gov (United States)

Teryl G. Grubb; Roy G. Lopez

1997-01-01

Northern Arizona winters vary within and between years with occasional heavy snows (up to 0.6 m) and extreme cold (overnight lows -18 to -29°C) interspersed with dry periods, mild temperatures (daytime highs reaching 10°C), and general loss of snow cover at all but highest elevations. Lakes in the area may freeze and thaw partially or totally several times during a...

Prediction of thermal behavior of pervious concrete pavements in winter.

Science.gov (United States)

2017-05-15

Because application of pervious concrete pavement (PCPs) has extended to cold-climate regions of the United States, the safety and : mobility of PCP installations during the winter season need to be maintained. Timely application of salt, anti-icing,...

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.

Use of the X-Band Radar to Support the Detection of In-Flight Icing Hazards by the NASA Icing Remote Sensing System

Science.gov (United States)

Serke, David J.; Politovich, Marcia K.; Reehorst, Andrew L.; Gaydos, Andrew

2009-01-01

The Alliance Icing Research Study-II (AIRS-II) field program was conducted near Montreal, Canada during the winter of 2003. The NASA Icing Remote Detection System (NIRSS) was deployed to detect in-flight icing hazards and consisted of a vertically pointing multichannel radiometer, a ceilometer and an x-band cloud radar. The radiometer was used to derive atmospheric temperature soundings and integrated liquid water, while the ceilometer and radar were used only to define cloud boundaries. The purpose of this study is to show that the radar reflectivity profiles from AIRS-II case studies could be used to provide a qualitative icing hazard.

Copepods in ice-covered seas—Distribution, adaptations to seasonally limited food, metabolism, growth patterns and life cycle strategies in polar seas

Science.gov (United States)

Conover, R. J.; Huntley, M.

1991-07-01

While a seasonal ice cover limits light penetration into both polar seas for up to ten months a year, its presence is not entirely negative. The mixed layer under sea ice will generally be shallower than in open water at the same latitude and season. Ice forms a substrate on which primary production can be concentrated, a condition which contrasts with the generally dilute nutritional conditions which prevail in the remaining ocean. The combination of a shallow, generally stable mixed layer with a close proximity to abundant food make the under-ice zone a suitable nursery for both pelagic and benthic species, an upside-down benthos for opportunistic substrate browsers, and a rich feeding environment for species often considered to be neritic in temperate environments. Where the ice cover is not continuous there may be a retreating ice edge that facilitates the seasonal production of phytoplankton primarily through increased stability from the melt water. Ice edge blooms similarly encourage secondary production by pelagic animals. Pseudocalanus acuspes, which may be the most abundant and productive copepod in north polar latitudes, initiates growth at the start of the "spring bloom" of epontic algae, reaching sexual maturity at breakup or slightly before. In the Southern Hemisphere, the small neritic copepod Paralabidocera antarctica and adult krill have been observed to utilize ice algae. Calanus hyperboreus breeds in the dark season at depth and its buoyant eggs, slowly developing on the ascent, reach the under-ice layer in April as nauplii ready to benefit from the primary production there. On the other hand, C. glacialis may initiate ontogenetic migrations and reproduction in response to increased erosion of ice algae due to solar warming and melting at the ice-water interface. While the same species in a phytoplankton bloom near the ice edge reproduces actively, those under still-consolidated ice nearby can have immature gonads. Diel migration and diel feeding

Ross sea ice motion, area flux, and deformation

Science.gov (United States)

kwok, Ron

2005-01-01

The sea ice motion, area export, and deformation of the Ross Sea ice cover are examined with satellite passive microwave and RADARSAT observations. The record of high-resolution synthetic aperture radar (SAR) data, from 1998 and 2000, allows the estimation of the variability of ice deformation at the small scale (10 km) and to assess the quality of the longer record of passive microwave ice motion. Daily and subdaily deformation fields and RADARSAT imagery highlight the variability of motion and deformation in the Ross Sea. With the passive microwave ice motion, the area export at a flux gate positioned between Cape Adare and Land Bay is estimated. Between 1992 and 2003, a positive trend can be seen in the winter (March-November) ice area flux that has a mean of 990 x 103 km2 and ranges from a low of 600 x 103 km2 in 1992 to a peak of 1600 x 103 km2 in 2001. In the mean, the southern Ross Sea produces almost twice its own area of sea ice during the winter. Cross-gate sea level pressure (SLP) gradients explain 60% of the variance in the ice area flux. A positive trend in this gradient, from reanalysis products, suggests a 'spinup' of the Ross Sea Gyre over the past 12 yr. In both the NCEP-NCAR and ERA-40 surface pressure fields, longer-term trends in this gradient and mean SLP between 1979 and 2002 are explored along with positive anomalies in the monthly cross-gate SLP gradient associated with the positive phase of the Southern Hemisphere annular mode and the extrapolar Southern Oscillation.

Sea Ice Retreat and its Impact on the Intensity of Open-Ocean Convection in the Greenland and Iceland Seas

Science.gov (United States)

Moore, K.; Våge, K.; Pickart, R. S.; Renfrew, I.

2016-12-01

The air-sea transfer of heat and freshwater plays a critical role in the global climate system. This is particularly true for the Greenland and Iceland Seas, where these fluxes drive ocean convection that contributes to Denmark Strait Overflow Water, the densest component of the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). This buoyancy transfer is most pronounced during the winter downstream of the ice edge, where the cold and dry Arctic air first comes in contact with the relatively warm ocean surface. Here we show that the wintertime retreat of sea ice in the region, combined with different rates of warming for the atmosphere and sea surface of the Greenland and Iceland Seas, has resulted in statistically significant reductions of approximately 20% in the magnitude of the winter air-sea heat fluxes since 1979. Furthermore, it is demonstrated that modes of climate variability other than the North Atlantic Oscillation (NAO) are required to fully characterize the regional air-sea interaction in this region. Mixed-layer model simulations imply that a continued decrease in atmospheric forcing will exceed a threshold for the Greenland Sea whereby convection will become depth limited, reducing the ventilation of mid-depth waters in the Nordic Seas. In the Iceland Sea, further reductions have the potential to decrease the supply of the densest overflow waters to the AMOC.

Kleptoparasitism by bald eagles wintering in south-central Nebraska

Science.gov (United States)

Jorde, Dennis G.; Lingle, G.R.

1988-01-01

Kleptoparasitism on other raptors was one means by which Bald Eagles (Haliaeetus leucocephalus) secured food along the North Platte and Platte rivers during the winters of 1978-1980. Species kelptoparasitized were Ferruginous Hawk (Buteo regalis), Red-tailed Hawk (B. jamaicensis), Rough-legged Hawk (B. lagopus), Golden Eagle (Aquila chrysaetos), and Bald Eagle. Stealing of prey occurred more often during the severe winter of 1978-1979 when ice cover restricted eagles from feeding on fish than during the milder winter of 1979-1980. Kleptoparasitism occurred principally in agricultural habitats where large numbers of Mallards (Anas platyrhynchos) were foraging. Subadults watched adults steal food and participated in food-stealing with adults, which indicated interspecific kleptoparasitism may be a learned behavior. We suggest factors that may favor interspecific kleptoparasitism as a foraging strategy of Bald Eagles in obtaining waterfowl during severe winters.

Impacts of Changed Extratropical Storm Tracks on Arctic Sea Ice Export through Fram Strait

Science.gov (United States)

Wei, J.; Zhang, X.; Wang, Z.

2017-12-01

Studies have indicated a poleward shift of extratropical storm tracks and intensification of Arctic storm activities, in particular on the North Atlantic side of the Arctic Ocean. To improve understanding of dynamic effect on changes in Arctic sea ice mass balance, we examined the impacts of the changed storm tracks and activities on Arctic sea ice export through Fram Strait through ocean-sea ice model simulations. The model employed is the high-resolution Massachusetts Institute of Technology general circulation model (MITgcm), which was forced by the Japanese 25-year Reanalysis (JRA-25) dataset. The results show that storm-induced strong northerly wind stress can cause simultaneous response of daily sea ice export and, in turn, exert cumulative effects on interannual variability and long-term changes of sea ice export. Further analysis indicates that storm impact on sea ice export is spatially dependent. The storms occurring southeast of Fram Strait exhibit the largest impacts. The weakened intensity of winter storms in this region after 1994/95 could be responsible for the decrease of total winter sea ice export during the same time period.

A State-Space Model for River Ice Forecasting

National Research Council Canada - National Science Library

Daly, Steven

2003-01-01

Each winter ice forms on rivers streams, and navigable waterways, causing many problems through its effects on the operation of hydraulic control structures, locks and dams, hydropower plants, and water intakes...

Do pelagic grazers benefit from sea ice? Insights from the Antarctic sea ice proxy IPSO25

Directory of Open Access Journals (Sweden)

K. Schmidt

2018-04-01

Full Text Available Sea ice affects primary production in polar regions in multiple ways. It can dampen water column productivity by reducing light or nutrient supply, provide a habitat for ice algae and condition the marginal ice zone (MIZ for phytoplankton blooms on its seasonal retreat. The relative importance of three different carbon sources (sea ice derived, sea ice conditioned, non-sea-ice associated for the polar food web is not well understood, partly due to the lack of methods that enable their unambiguous distinction. Here we analysed two highly branched isoprenoid (HBI biomarkers to trace sea-ice-derived and sea-ice-conditioned carbon in Antarctic krill (Euphausia superba and relate their concentrations to the grazers' body reserves, growth and recruitment. During our sampling in January–February 2003, the proxy for sea ice diatoms (a di-unsaturated HBI termed IPSO25, δ13C  =  −12.5 ± 3.3 ‰ occurred in open waters of the western Scotia Sea, where seasonal ice retreat was slow. In suspended matter from surface waters, IPSO25 was present at a few stations close to the ice edge, but in krill the marker was widespread. Even at stations that had been ice-free for several weeks, IPSO25 was found in krill stomachs, suggesting that they gathered the ice-derived algae from below the upper mixed layer. Peak abundances of the proxy for MIZ diatoms (a tri-unsaturated HBI termed HBI III, δ13C  =  −42.2 ± 2.4 ‰ occurred in regions of fast sea ice retreat and persistent salinity-driven stratification in the eastern Scotia Sea. Krill sampled in the area defined by the ice edge bloom likewise contained high amounts of HBI III. As indicators for the grazer's performance we used the mass–length ratio, size of digestive gland and growth rate for krill, and recruitment for the biomass-dominant calanoid copepods Calanoides acutus and Calanus propinquus. These indices consistently point to blooms in the MIZ as an important feeding

Do pelagic grazers benefit from sea ice? Insights from the Antarctic sea ice proxy IPSO25

Science.gov (United States)

Schmidt, Katrin; Brown, Thomas A.; Belt, Simon T.; Ireland, Louise C.; Taylor, Kyle W. R.; Thorpe, Sally E.; Ward, Peter; Atkinson, Angus

2018-04-01

Sea ice affects primary production in polar regions in multiple ways. It can dampen water column productivity by reducing light or nutrient supply, provide a habitat for ice algae and condition the marginal ice zone (MIZ) for phytoplankton blooms on its seasonal retreat. The relative importance of three different carbon sources (sea ice derived, sea ice conditioned, non-sea-ice associated) for the polar food web is not well understood, partly due to the lack of methods that enable their unambiguous distinction. Here we analysed two highly branched isoprenoid (HBI) biomarkers to trace sea-ice-derived and sea-ice-conditioned carbon in Antarctic krill (Euphausia superba) and relate their concentrations to the grazers' body reserves, growth and recruitment. During our sampling in January-February 2003, the proxy for sea ice diatoms (a di-unsaturated HBI termed IPSO25, δ13C = -12.5 ± 3.3 ‰) occurred in open waters of the western Scotia Sea, where seasonal ice retreat was slow. In suspended matter from surface waters, IPSO25 was present at a few stations close to the ice edge, but in krill the marker was widespread. Even at stations that had been ice-free for several weeks, IPSO25 was found in krill stomachs, suggesting that they gathered the ice-derived algae from below the upper mixed layer. Peak abundances of the proxy for MIZ diatoms (a tri-unsaturated HBI termed HBI III, δ13C = -42.2 ± 2.4 ‰) occurred in regions of fast sea ice retreat and persistent salinity-driven stratification in the eastern Scotia Sea. Krill sampled in the area defined by the ice edge bloom likewise contained high amounts of HBI III. As indicators for the grazer's performance we used the mass-length ratio, size of digestive gland and growth rate for krill, and recruitment for the biomass-dominant calanoid copepods Calanoides acutus and Calanus propinquus. These indices consistently point to blooms in the MIZ as an important feeding ground for pelagic grazers. Even though ice

Polar bears experience skeletal muscle atrophy in response to food deprivation and reduced activity in winter and summer.

Science.gov (United States)

Whiteman, John P; Harlow, Henry J; Durner, George M; Regehr, Eric V; Rourke, Bryan C; Robles, Manuel; Amstrup, Steven C; Ben-David, Merav

2017-01-01

When reducing activity and using stored energy during seasonal food shortages, animals risk degradation of skeletal muscles, although some species avoid or minimize the resulting atrophy while experiencing these conditions during hibernation. Polar bears may be food deprived and relatively inactive during winter (when pregnant females hibernate and hunting success declines for other demographic groups) as well as summer (when sea ice retreats from key foraging habitats). We investigated muscle atrophy in samples of biceps femoris collected from free-ranging polar bears in the Southern Beaufort Sea (SBS) throughout their annual cycle. Atrophy was most pronounced in April-May as a result of food deprivation during the previous winter, with muscles exhibiting reduced protein concentration, increased water content, and lower creatine kinase mRNA. These animals increased feeding and activity in spring (when seal prey becomes more available), initiating a period of muscle recovery. During the following ice melt of late summer, ~30% of SBS bears abandon retreating sea ice for land; in August, these 'shore' bears exhibited no muscle atrophy, indicating that they had fully recovered from winter food deprivation. These individuals subsequently scavenged whale carcasses deposited by humans and by October, had retained good muscle condition. In contrast, ~70% of SBS bears follow the ice north in late summer, into deep water with less prey. These 'ice' bears fast; by October, they exhibited muscle protein loss and rapid changes in myosin heavy-chain isoforms in response to reduced activity. These findings indicate that, unlike other bears during winter hibernation, polar bears without food in summer cannot mitigate atrophy. Consequently, prolonged summer fasting resulting from climate change-induced ice loss creates a risk of greater muscle atrophy and reduced abilities to travel and hunt.

Frequent sea-ice breakup in Lutzow-Holmbukta, Antarctica, based on analysis of ice condition from 1980 to 2003

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Shuki Ushio

2003-11-01

Full Text Available The history of sea-ice breakup in Lutzow-Holmbukta, Antarctica, has been investigated for the period 1980-2003. Though spatial and temporal scales for breakups are different among each event, breakup phenomena have occurred at least 19 times. The geographical sites of breakups are almost the same in the bay and commencement is usually in autumn. In particular, the 1997/1998 event covered a wide area and was of long duration. Since then, autumn to early winter breakup has continued until winter 2003. It is suggested that a southerly wind field, small snow depth and mild winter prior to the breakup are factors which favor breakup events.

Recruiting first generation college students into the Geosciences: Alaska's EDGE project

Science.gov (United States)

Prakash, A.; Connor, C.

2008-12-01

Funded in 2005-2008, by the National Science Foundation's Geoscience Education Division, the Experiential Discoveries in Geoscience Education (EDGE) project was designed to use glacier and watershed field experiences as venues for geospatial data collected by Alaska's grade 6-12 middle and high school teachers and their students. EDGE participants were trained in GIS and learned to analyze geospatial data to answer questions about the warming Alaska environment and to determine rates of ongoing glacier recession. Important emphasis of the program was the recruitment of Alaska Native students of Inupiat, Yup'ik, Athabascan, and Tlingit populations, living in both rural and urban areas around the state. Twelve of Alaska's 55 school districts have participated in the EDGE program. To engage EDGE students in the practice of scientific inquiry, each was required to carry out a semester scale research project using georeferenced data, guided by their EDGE teacher and mentor. Across Alaska students investigated several Earth systems processes including freezing conditions of lake ice; the changes in water quality in storm drains after rainfall events; movements of moose, bears, and bison across Alaskan landscapes; changes in permafrost depth in western Alaska; and the response of migrating waterfowl to these permafrost changes. Students correlated the substrate beneath their schools with known earthquake intensities; measured cutbank and coastal erosion on northern rivers and southeastern shorelines; tracked salmon infiltration of flooded logging roads; noted the changing behavior of eagles during late winter salmon runs; located good areas for the use of tidal power for energy production; tracked the extent and range of invasive plant species with warming; and the change of forests following deglaciation. Each cohort of EDGE students and teachers finished the program by attended a 3-day EDGE symposium at which students presented their research projects first in a

The mass and energy balance of ice within the Eisriesenwelt cave, Austria

Directory of Open Access Journals (Sweden)

F. Obleitner

2011-03-01

Full Text Available Meteorological measurements were performed in a prominent ice cave (Eisriesenwelt, Austria during a full annual cycle. The data show the basic features of a dynamically ventilated cave system with a well distinguished winter and summer regime.

The calculated energy balance of the cave ice is largely determined by the input of long-wave radiation originating at the host rock surface. On average the turbulent fluxes withdraw energy from the surface. This is more pronounced during winter due to enhanced circulation and lower humidity. During summer the driving gradients reverse sign and the associated fluxes provide energy for melt.

About 4 cm of ice were lost at the measurement site during a reference year. This was due to some sublimation during winter, while the major loss resulted from melt during summer. Small amounts of accumulation occurred during spring due to refreezing of seepage water.

These results are largely based on employing a numerical mass and energy balance model. Sensitivity studies prove reliability of the calculated energy balance regarding diverse measurement uncertainties and show that the annual mass balance of the ice strongly depends on cave air temperature during summer and the availability of seepage water in spring.

Ice condensation on sulfuric acid tetrahydrate: Implications for polar stratospheric ice clouds

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T. J. Fortin

2003-01-01

Full Text Available The mechanism of ice nucleation to form Type 2 PSCs is important for controlling the ice particle size and hence the possible dehydration in the polar winter stratosphere. This paper probes heterogeneous ice nucleation on sulfuric acid tetrahydrate (SAT. Laboratory experiments were performed using a thin-film, high-vacuum apparatus in which the condensed phase is monitored via Fourier transform infrared spectroscopy and water pressure is monitored with the combination of an MKS baratron and an ionization gauge. Results show that SAT is an efficient ice nucleus with a critical ice saturation ratio of S*ice = 1.3 to 1.02 over the temperature range 169.8-194.5 K. This corresponds to a necessary supercooling of 0.1-1.3 K below the ice frost point. The laboratory data is used as input for a microphysical/photochemical model to probe the effect that this heterogeneous nucleation mechanism could have on Type 2 PSC formation and stratospheric dehydration. In the model simulations, even a very small number of SAT particles (e.g., 10-3 cm-3 result in ice nucleation on SAT as the dominant mechanism for Type 2 PSC formation. As a result, Type 2 PSC formation is more widespread, leading to larger-scale dehydration. The characteristics of the clouds are controlled by the assumed number of SAT particles present, demonstrating that a proper treatment of SAT is critical for correctly modeling Type 2 PSC formation and stratospheric dehydration.

The Unusual Southern Hemisphere Stratosphere Winter of 2002

Science.gov (United States)

Newman, Paul A.; Nash, Eric R.

2003-01-01

The southern hemisphere stratospheric winter of 2002 was the most unusual winter yet observed in the southern hemisphere climate record. Temperatures near the edge of the Antarctic polar vortex were considerably warmer than normal over the entire course of the winter. The polar night jet was considerably weaker than normal, and was displaced more poleward than has been observed in previous winters. These record high temperatures and weak jet resulted from a series of wave events that took place over the course of the winter. The first large event occurred on 15 May, and the final warming occurred on 25 October. The propagation of these wave events from the troposphere is diagnosed from time series of Eliassen-Palm flux vectors. The wave events tended to occur irregularly over the course of the winter, and pre-conditioned the polar night jet for the extremely large wave event of 22 September. This large wave event resulted in the first ever observed major stratospheric warming in the southern hemisphere. This wave event split the Antarctic ozone hole. The combined effect of the wave events of the 2002 winter resulted in the smallest ozone hole observed since 1988.

Ice and AIS: ship speed data and sea ice forecasts in the Baltic Sea

Directory of Open Access Journals (Sweden)

U. Löptien

2014-12-01

Full Text Available The Baltic Sea is a seasonally ice-covered marginal sea located in a densely populated area in northern Europe. Severe sea ice conditions have the potential to hinder the intense ship traffic considerably. Thus, sea ice fore- and nowcasts are regularly provided by the national weather services. Typically, the forecast comprises several ice properties that are distributed as prognostic variables, but their actual usefulness is difficult to measure, and the ship captains must determine their relative importance and relevance for optimal ship speed and safety ad hoc. The present study provides a more objective approach by comparing the ship speeds, obtained by the automatic identification system (AIS, with the respective forecasted ice conditions. We find that, despite an unavoidable random component, this information is useful to constrain and rate fore- and nowcasts. More precisely, 62–67% of ship speed variations can be explained by the forecasted ice properties when fitting a mixed-effect model. This statistical fit is based on a test region in the Bothnian Sea during the severe winter 2011 and employs 15 to 25 min averages of ship speed.

Mapping Arctic Bottomfast Sea Ice Using SAR Interferometry

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Dyre O. Dammann

2018-05-01

Full Text Available Bottomfast sea ice is an integral part of many near-coastal Arctic ecosystems with implications for subsea permafrost, coastal stability and morphology. Bottomfast sea ice is also of great relevance to over-ice travel by coastal communities, industrial ice roads, and marine habitats. There are currently large uncertainties around where and how much bottomfast ice is present in the Arctic due to the lack of effective approaches for detecting bottomfast sea ice on large spatial scales. Here, we suggest a robust method capable of detecting bottomfast sea ice using spaceborne synthetic aperture radar interferometry. This approach is used to discriminate between slowly deforming floating ice and completely stationary bottomfast ice based on the interferometric phase. We validate the approach over freshwater ice in the Mackenzie Delta, Canada, and over sea ice in the Colville Delta and Elson Lagoon, Alaska. For these areas, bottomfast ice, as interpreted from the interferometric phase, shows high correlation with local bathymetry and in-situ ice auger and ground penetrating radar measurements. The technique is further used to track the seasonal evolution of bottomfast ice in the Kasegaluk Lagoon, Alaska, by identifying freeze-up progression and areas of liquid water throughout winter.

The effect of changing sea ice on the vulnerability of Arctic coasts

OpenAIRE

K. R. Barnhart; I. Overeem; R. S. Anderson

2014-01-01

Shorefast sea ice prevents the interaction of the land and the ocean in the Arctic winter and influences this interaction in the summer by governing the fetch. In many parts of the Arctic the sea-ice-free season is increasing in duration, and the summertime sea ice extents are decreasing. Sea ice provides a first order control on the vulnerability of Arctic coasts to erosion, inundation, and damage to settlements and infrastructure. We ask how the changing sea ic...

Ice damage in loblolly pine: understanding the factors that influence susceptibility

Science.gov (United States)

Doug P. Aubrey; Mark D. Coleman; David R. Coyle

2007-01-01

Winter ice storms frequently occur in the southeastern United States and can severely damage softwood plantations. In January 2004, a severe storm deposited approximately 2 cm of ice on an intensively managed 4-year-old loblolly pine (Pinus taeda L.) plantation in South Carolina. Existing irrigation and fertilization treatments presented an...

Understanding the Importance of Oceanic Forcing on Sea Ice Variability

Science.gov (United States)

2010-12-01

problem, which includes ice thickness. Thorndike et al. (1975) recognized that many of the physical properties of sea ice depend upon its thickness...IMB2005B are presented below. In agreement with previous studies (e.g., Thorndike and Colony 1982), they show that during the winter months (December...During the Past 100 Years, 33, 2, 143– 154. 148 Thorndike , A.S., and R. Colony, 1982: Sea ice motion in response to geostrophic winds. Journal of

Coastal sea-ice processes in Alaska and their relevance for sediment dynamics and coastal retreat (Invited)

Science.gov (United States)

Eicken, H.; Kapsch, M.; Johnson, M. A.; Weyapuk, W. U., Jr.

2009-12-01

Sea ice plays an important, complicated role in Arctic coastal sediment dynamics. It helps protect the shoreline from wave action and constrains coastal permafrost thaw; at the same time, sea ice is a highly effective sediment erosion and transport agent. For the coastline of (sub-)Arctic Alaska we have examined key processes that govern the role of sea ice as a geologic agent. Based on passive microwave satellite data for the time period 1979 to 2008 and augmented by field measurements and observations conducted by local sea-ice experts in coastal communities from 2006 onwards, we determined the onset of coastal ice spring break-up and fall freeze-up. These two events define the start and end of the open-water season during which the coast is rendered most vulnerable to thermal and dynamic processes promoting erosion. Satellite data show significant trends toward later fall freeze-up in many locations and moreover provide a picture of the statistical significance and variability of such trends in great spatio-temporal detail. Coastal ice observations suggest that important sea-ice processes (such as formation of ice berms) that precede freeze-up as detected by passive microwave data need to be taken into consideration in evaluating the vulnerability of the coastline and the specific threat of individual storms. Field observations, satellite data and local knowledge also highlight the substantial change in winter sea-ice regimes over the past two decades, with a much more mobile ice cover enhancing winter sediment transport. Ultimately, the shorter sea-ice season and the greater mobility and the lack of stability of winter coastal sea ice work in concert to increase the vulnerability of the coastline to erosion and flooding. At the same time, these changes provide a mechanism for effective redistribution and cross-shelf transport of sediments that prepares the stage for further erosive action in subsequent seasons.

Evaluation of alternative snow plow cutting edges.

Science.gov (United States)

2009-05-01

With approximately 450 snow plow trucks, the Maine Department of Transportation (MaineDOT) uses in : excess of 10,000 linear feet of plow cutting edges each winter season. Using the 2008-2009 cost per linear : foot of $48.32, the Departments total co...

Spirit Scans Winter Haven

Science.gov (United States)

2006-01-01

At least three different kinds of rocks await scientific analysis at the place where NASA's Mars Exploration Rover Spirit will likely spend several months of Martian winter. They are visible in this picture, which the panoramic camera on Spirit acquired during the rover's 809th sol, or Martian day, of exploring Mars (April 12, 2006). Paper-thin layers of light-toned, jagged-edged rocks protrude horizontally from beneath small sand drifts; a light gray rock with smooth, rounded edges sits atop the sand drifts; and several dark gray to black, angular rocks with vesicles (small holes) typical of hardened lava lie scattered across the sand. This view is an approximately true-color rendering that combines images taken through the panoramic camera's 753-nanometer, 535-nanometer, and 432-nanometer filters.

Fundamental Ice Crystal Accretion Physics Studies

Science.gov (United States)

Struk, Peter M.; Broeren, Andy P.; Tsao, Jen-Ching; Vargas, Mario; Wright, William B.; Currie, Tom; Knezevici, Danny; Fuleki, Dan

2012-01-01

Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 g/m3, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 mm in 3 min. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component

Observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

Science.gov (United States)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-01-01

Based on airborne spectral imaging observations three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and ice floes have been identified and quantified. A method is presented to discriminate sea ice and open water in case of clouds from imaging radiance measurements. This separation simultaneously reveals that in case of clouds the transition of radiance between open water and sea ice is not instantaneously but horizontally smoothed. In general, clouds reduce the nadir radiance above bright surfaces in the vicinity of sea ice - open water boundaries, while the nadir radiance above dark surfaces is enhanced compared to situations with clouds located above horizontal homogeneous surfaces. With help of the observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge. This affected distance Δ L was found to depend on both, cloud and sea ice properties. For a ground overlaying cloud in 0-200 m altitude, increasing the cloud optical thickness from τ = 1 to τ = 10 decreases Δ L from 600 to 250 m, while increasing cloud base altitude or cloud geometrical thickness can increase Δ L; Δ L(τ = 1/10) = 2200 m/1250 m for 500-1000 m cloud altitude. To quantify the effect for different shapes and sizes of the ice floes, various albedo fields (infinite straight ice edge, circles, squares, realistic ice floe field) were modelled. Simulations show that Δ L increases by the radius of the ice floe and for sizes larger than 6 km (500-1000 m cloud altitude) asymptotically reaches maximum values, which corresponds to an infinite straight ice edge. Furthermore, the impact of these 3-D-radiative effects on retrieval of cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30% in retrievals of cloud optical thickness and effective radius reff, respectively. With help of Δ L quantified here, an

Role of the Tropical Pacific in recent Antarctic Sea-Ice Trends

Science.gov (United States)

Codron, F.; Bardet, D.; Allouache, C.; Gastineau, G.; Friedman, A. R.; Douville, H.; Voldoire, A.

2017-12-01

The recent (up to 2016) trends in Antarctic sea-ice cover - a global increase masking a dipole between the Ross and Bellingshausen-Weddel seas - are still not well understood, and not reproduced by CMIP5 coupled climate models. We here explore the potential role of atmospheric circulation changes around the Amundsen Sea, themselves possibly forced by tropical SSTs, an explanation that has been recently advanced. As a first check on this hypothesis, we compare the atmospheric circulation trends simulated by atmospheric GCMs coupled with an ocean or with imposed SSTs (AMIP experiment from CMIP5); the latter being in theory able to reproduce changes caused by natural SST variability. While coupled models simulate in aggregate trends that project on the SAM structure, strongest in summer, the AMIP simulations add in the winter season a pronounced Amundsen Sea Low signature (and a PNA signature in the northern hemisphere) both consistent with a Niña-like trend in the tropical Pacific. We then use a specific coupled GCM setup, in which surface wind anomalies over the tropical Pacific are strongly nudged towards the observed ones, including their interannual variability, but the model is free to evolve elsewhere. The two GCMs used then simulate a deepening trend in the Amundsen-Sea Low in winter, and are able to reproduce a dipole in sea-ice cover. Further analysis shows that the sea-ice dipole is partially forced by surface heat flux anomalies in early winter - the extent varying with the region and GCM used. The turbulent heat fluxes then act to damp the anomalies in late winter, which may however be maintained by ice-albedo feedbacks.

Influence of landfast ice on the hydrography and circulation of the Baltic Sea coastal zone

Directory of Open Access Journals (Sweden)

Ioanna Merkouriadi

2013-02-01

Full Text Available The influence of landfast ice on hydrography and circulation is examined inSantala Bay, adjacent to the Hanko Peninsula, Gulf of Finland. Three-dimensionalelectromagnetic current meters and conductivity-temperature-depth (CTD sensorswere deployed in winters 1999-2000 and 2000-2001 during the Finnish-Japanese"Hanko 9012" experiment. In each winter, data collection started one month beforethe initial ice formation and lasted until one month after the ice had meltedcompletely. Temperature and salinity are compared with long-term data from theTvärminne Zoological Station, also located on the Hanko Peninsula. Thewater temperature was 2°C less than the long-term average. Iceformation and melting show up in the salinity evolution of the water body,which makes salinity a good indicator of ice formation and breakup in SantalaBay. The circulation under the ice became weaker by almost 1 cm s-1.

Satellite Remote Sensing of Snow Depth on Antarctic Sea Ice: An Inter-Comparison of Two Empirical Approaches

Directory of Open Access Journals (Sweden)

Stefan Kern

2016-05-01

Full Text Available Snow on Antarctic sea ice plays a key role for sea ice physical processes and complicates retrieval of sea ice thickness using altimetry. Current methods of snow depth retrieval are based on satellite microwave radiometry, which perform best for dry, homogeneous snow packs on level sea ice. We introduce an alternative approach based on in-situ measurements of total (sea ice plus snow freeboard and snow depth, which we use to compute snow depth on sea ice from Ice, Cloud, and land Elevation Satellite (ICESat total freeboard observations. We compare ICESat snow depth for early winter and spring of the years 2004 through 2006 with the Advanced Scanning Microwave Radiometer aboard EOS (AMSR-E snow depth product. We find ICESat snow depths agree more closely with ship-based visual and air-borne snow radar observations than AMSR-E snow depths. We obtain average modal and mean ICESat snow depths, which exceed AMSR-E snow depths by 5–10 cm in winter and 10–15 cm in spring. We observe an increase in ICESat snow depth from winter to spring for most Antarctic regions in accordance with ground-based observations, in contrast to AMSR-E snow depths, which we find to stay constant or to decrease. We suggest satellite laser altimetry as an alternative method to derive snow depth on Antarctic sea ice, which is independent of snow physical properties.

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

Risk management model of winter navigation operations

International Nuclear Information System (INIS)

Valdez Banda, Osiris A.; Goerlandt, Floris; Kuzmin, Vladimir; Kujala, Pentti; Montewka, Jakub

2016-01-01

The wintertime maritime traffic operations in the Gulf of Finland are managed through the Finnish–Swedish Winter Navigation System. This establishes the requirements and limitations for the vessels navigating when ice covers this area. During winter navigation in the Gulf of Finland, the largest risk stems from accidental ship collisions which may also trigger oil spills. In this article, a model for managing the risk of winter navigation operations is presented. The model analyses the probability of oil spills derived from collisions involving oil tanker vessels and other vessel types. The model structure is based on the steps provided in the Formal Safety Assessment (FSA) by the International Maritime Organization (IMO) and adapted into a Bayesian Network model. The results indicate that ship independent navigation and convoys are the operations with higher probability of oil spills. Minor spills are most probable, while major oil spills found very unlikely but possible. - Highlights: •A model to assess and manage the risk of winter navigation operations is proposed. •The risks of oil spills in winter navigation in the Gulf of Finland are analysed. •The model assesses and prioritizes actions to control the risk of the operations. •The model suggests navigational training as the most efficient risk control option.

Multiscale Observation System for Sea Ice Drift and Deformation

Science.gov (United States)

Lensu, M.; Haapala, J. J.; Heiler, I.; Karvonen, J.; Suominen, M.

2011-12-01

The drift and deformation of sea ice cover is most commonly followed from successive SAR images. The time interval between the images is seldom less than one day which provides rather crude approximation of the motion fields as ice can move tens of kilometers per day. This is particulary so from the viewpoint of operative services, seeking to provide real time information for ice navigating ships and other end users, as leads are closed and opened or ridge fields created in time scales of one hour or less. The ice forecast models are in a need of better temporal resolution for ice motion data as well. We present experiences from a multiscale monitoring system set up to the Bay of Bothnia, the northernmost basin of the Baltic Sea. The basin generates difficult ice conditions every winter while the ports are kept open with the help of an icebreaker fleet. The key addition to SAR imagery is the use of coastal radars for the monitoring of coastal ice fields. An independent server is used to tap the radar signal and process it to suit ice monitoring purposes. This is done without interfering the basic use of the radars, the ship traffic monitoring. About 20 images per minute are captured and sent to the headquarters for motion field extraction, website animation and distribution. This provides very detailed real time picture of the ice movement and deformation within 20 km range. The real time movements are followed in addition with ice drifter arrays, and using AIS ship identification data, from which the translation of ship cannels due to ice drift can be found out. To the operative setup is associated an extensive research effort that uses the data for ice drift model enhancement. The Baltic ice models seek to forecast conditions relevant to ship traffic, especilly hazardous ones like severe ice compression. The main missing link here is downscaling, or the relation of local scale ice dynamics and kinematics to the ice model scale behaviour. The data flow when

Dissolved and particulate trace metal micronutrients under the McMurdo Sound seasonal sea ice: basal sea ice communities as a capacitor for iron

Science.gov (United States)

Noble, Abigail E.; Moran, Dawn M.; Allen, Andrew E.; Saito, Mak A.

2013-01-01

Dissolved and particulate metal concentrations are reported from three sites beneath and at the base of the McMurdo Sound seasonal sea ice in the Ross Sea of Antarctica. This dataset provided insight into Co and Mn biogeochemistry, supporting a previous hypothesis for water column mixing occurring faster than scavenging. Three observations support this: first, Mn-containing particles with Mn/Al ratios in excess of the sediment were present in the water column, implying the presence of bacterial Mn-oxidation processes. Second, dissolved and labile Co were uniform with depth beneath the sea ice after the winter season. Third, dissolved Co:PO3−4 ratios were consistent with previously observed Ross Sea stoichiometry, implying that over-winter scavenging was slow relative to mixing. Abundant dissolved Fe and Mn were consistent with a winter reserve concept, and particulate Al, Fe, Mn, and Co covaried, implying that these metals behaved similarly. Elevated particulate metals were observed in proximity to the nearby Islands, with particulate Fe/Al ratios similar to that of nearby sediment, consistent with a sediment resuspension source. Dissolved and particulate metals were elevated at the shallowest depths (particularly Fe) with elevated particulate P/Al and Fe/Al ratios in excess of sediments, demonstrating a sea ice biomass source. The sea ice biomass was extremely dense (chl a >9500 μg/L) and contained high abundances of particulate metals with elevated metal/Al ratios. A hypothesis for seasonal accumulation of bioactive metals at the base of the McMurdo Sound sea ice by the basal algal community is presented, analogous to a capacitor that accumulates iron during the spring and early summer. The release and transport of particulate metals accumulated at the base of the sea ice by sloughing is discussed as a potentially important mechanism in providing iron nutrition during polynya phytoplankton bloom formation and could be examined in future oceanographic

Snow Climatology of Arctic Sea Ice: Comparison of Reanalysis and Climate Model Data with In Situ Measurements

Science.gov (United States)

Chevooruvalappil Chandran, B.; Pittana, M.; Haas, C.

2015-12-01

Snow on sea ice is a critical and complex factor influencing sea ice processes. Deep snow with a high albedo and low thermal conductivity inhibits ice growth in winter and minimizes ice loss in summer. Very shallow or absent snow promotes ice growth in winter and ice loss in summer. The timing of snow ablation critically impacts summer sea ice mass balance. Here we assess the accuracy of various snow on sea ice data products from reanalysis and modeling comparing them with in situ measurements. The latter are based on the Warren et al. (1999) monthly climatology derived from snow ruler measurements between 1954-1991, and on daily snow depth retrievals from few drifting ice mass balance buoys (IMB) with sufficiently long observations spanning the summer season. These were compared with snow depth data from the National Center for Environmental Prediction Department of Energy Reanalysis 2 (NCEP), the Community Climate System Model 4 (CCSM4), and the Canadian Earth System Model 2 (CanESM2). Results are quite variable in different years and regions. However, there is often good agreement between CanESM2 and IMB snow depth during the winter accumulation and spring melt periods. Regional analyses show that over the western Arctic covered primarily with multiyear ice NCEP snow depths are in good agreement with the Warren climatology while CCSM4 overestimates snow depth. However, in the Eastern Arctic which is dominated by first-year ice the opposite behavior is observed. Compared to the Warren climatology CanESM2 underestimates snow depth in all regions. Differences between different snow depth products are as large as 10 to 20 cm, with large consequences for the sea ice mass balance. However, it is also very difficult to evaluate the accuracy of reanalysis and model snow depths due to a lack of extensive, continuous in situ measurements.

Mapping of Ice in the Odden by Satellite and Airborne Remote Sensing

DEFF Research Database (Denmark)

Pedersen, Leif Toudal; Hansen, K.Q.; Valeur, H.

1999-01-01

A detailed analysis of the ice conditions in the Odden area of the Greenland Sea was carried out using data from active and passive microwave sensors, supplemented by airborne data. The study focuses on the 1992-1993 winter season, the only winter during the period 1993-1995 in which an Odden...

Classification of freshwater ice conditions on the Alaskan Arctic Coastal Plain using ground penetrating radar and TerraSAR-X satellite data

Science.gov (United States)

Jones, Benjamin M.; Gusmeroli, Alessio; Arp, Christopher D.; Strozzi, Tazio; Grosse, Guido; Gaglioti, Benjamin V.; Whitman, Matthew S.

2013-01-01

Arctic freshwater ecosystems have responded rapidly to climatic changes over the last half century. Lakes and rivers are experiencing a thinning of the seasonal ice cover, which may increase potential over-wintering freshwater habitat, winter water supply for industrial withdrawal, and permafrost degradation. Here, we combined the use of ground penetrating radar (GPR) and high-resolution (HR) spotlight TerraSAR-X (TSX) satellite data (1.25 m resolution) to identify and characterize floating ice and grounded ice conditions in lakes, ponds, beaded stream pools, and an alluvial river channel. Classified ice conditions from the GPR and the TSX data showed excellent agreement: 90.6% for a predominantly floating ice lake, 99.7% for a grounded ice lake, 79.0% for a beaded stream course, and 92.1% for the alluvial river channel. A GIS-based analysis of 890 surface water features larger than 0.01 ha showed that 42% of the total surface water area potentially provided over-wintering habitat during the 2012/2013 winter. Lakes accounted for 89% of this area, whereas the alluvial river channel accounted for 10% and ponds and beaded stream pools each accounted for landscape features such as beaded stream pools may be important because of their distribution and role in connecting other water bodies on the landscape. These findings advance techniques for detecting and knowledge associated with potential winter habitat distribution for fish and invertebrates at the local scale in a region of the Arctic with increasing stressors related to climate and land use change.

Activities of the wintering party of the 36th Japanese Antarctic Research Expedition, 1995-1996

Directory of Open Access Journals (Sweden)

Shigemi Meshida

1997-11-01

Full Text Available The wintering party of the 36th Japanese Antarctic Research Expedition (JARE-36 executed its planned activities at Syowa and Dome Fuji Stations from 1995 to 1996. The wintering party at Syowa Station, consisting of 31 personnel, carried out its observations and logistic work from February 1,1995 to January 31,1996. Routine and some specific observations for studies of upper atmosphere physics, meteorology, solid earth geophysics, biology and medical science were performed without any serious problems for a full year. Continuous observation of the magnetosphere had started using an HF radar system constructed during the austral summer of 1994/95. A seed plant was discovered near Nurume Lake, Langhovde. It was the first report of a seed plant growing in continental Antarctica. An architect took part in the wintering party for the first time and maintained decrepit buildings. Support work for the wintering party at Dome Fuji Station was one of the principal tasks at Syowa Station. A trip to the Dome Fuji Station was carried out to transport supplies and fuel in the austral spring of 1995. The first wintering activities at Dome Fuji Station started from January 29,1995. The wintering party, consisting of 9 personnel, carried out meteorological and glaciological observations together with deep ice core drilling and some construction work. Consequently, ice cores of 600m depth were obtained successfully.

Hydrogen-Bonding Surfaces for Ice Mitigation

Science.gov (United States)

Smith, Joseph G., Jr.; Wohl, Christopher J.; Kreeger, Richard E.; Hadley, Kevin R.; McDougall, Nicholas

2014-01-01

Ice formation on aircraft, either on the ground or in-flight, is a major safety issue. While ground icing events occur predominantly during the winter months, in-flight icing can happen anytime during the year. The latter is more problematic since it could result in increased drag and loss of lift. Under a Phase I ARMD NARI Seedling Activity, coated aluminum surfaces possessing hydrogen-bonding groups were under investigation for mitigating ice formation. Hydroxyl and methyl terminated dimethylethoxysilanes were prepared via known chemistries and characterized by spectroscopic methods. These materials were subsequently used to coat aluminum surfaces. Surface compositions were based on pure hydroxyl and methyl terminated species as well as mixtures of the two. Coated surfaces were characterized by contact angle goniometry. Receding water contact angle data suggested several potential surfaces that may exhibit reduced ice adhesion. Qualitative icing experiments performed under representative environmental temperatures using supercooled distilled water delivered via spray coating were inconclusive. Molecular modeling studies suggested that chain mobility affected the interface between ice and the surface more than terminal group chemical composition. Chain mobility resulted from the creation of "pockets" of increased free volume for longer chains to occupy.

Increased Surface Wind Speeds Follow Diminishing Arctic Sea Ice

Science.gov (United States)

Mioduszewski, J.; Vavrus, S. J.; Wang, M.; Holland, M. M.; Landrum, L.

2017-12-01

Projections of Arctic sea ice through the end of the 21st century indicate the likelihood of a strong reduction in ice area and thickness in all seasons, leading to a substantial thermodynamic influence on the overlying atmosphere. This is likely to have an effect on winds over the Arctic Basin, due to changes in atmospheric stability and/or baroclinicity. Prior research on future Arctic wind changes is limited and has focused mainly on the practical impacts on wave heights in certain seasons. Here we attempt to identify patterns and likely mechanisms responsible for surface wind changes in all seasons across the Arctic, particularly those associated with sea ice loss in the marginal ice zone. Sea level pressure, near-surface (10 m) and upper-air (850 hPa) wind speeds, and lower-level dynamic and thermodynamic variables from the Community Earth System Model Large Ensemble Project (CESM-LE) were analyzed for the periods 1971-2000 and 2071-2100 to facilitate comparison between a present-day and future climate. Mean near-surface wind speeds over the Arctic Ocean are projected to increase by late century in all seasons but especially during autumn and winter, when they strengthen by up to 50% locally. The most extreme wind speeds in the 90th percentile change even more, increasing in frequency by over 100%. The strengthened winds are closely linked to decreasing lower-tropospheric stability resulting from the loss of sea ice cover and consequent surface warming (locally over 20 ºC warmer in autumn and winter). A muted pattern of these future changes is simulated in CESM-LE historical runs from 1920-2005. The enhanced winds near the surface are mostly collocated with weaker winds above the boundary layer during autumn and winter, implying more vigorous vertical mixing and a drawdown of high-momentum air.The implications of stronger future winds include increased coastal hazards and the potential for a positive feedback with sea ice by generating higher winds and

Ikaite crystal distribution in winter sea ice and implications for CO2 system dynamics

DEFF Research Database (Denmark)

Rysgaard, Søren; Søgaard, D.H.; Cooper, M.

2013-01-01

The precipitation of ikaite (CaCO3 ⋅ 6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikai...

Monstrous Ice Cloud System in Titan's Present South Polar Stratosphere

Science.gov (United States)

Anderson, Carrie; Samuelson, Robert; McLain, Jason; Achterberg, Richard; Flasar, F. Michael; Milam, Stefanie

2015-11-01

During southern autumn when sunlight was still available, Cassini's Imaging Science Subsystem discovered a cloud around 300 km near Titan's south pole (West, R. A. et al., AAS/DPS Abstracts, 45, #305.03, 2013); the cloud was later determined by Cassini's Visible and InfraRed Mapping Spectrometer to contain HCN ice (de Kok et al., Nature, 514, pp 65-67, 2014). This cloud has proven to be only the tip of an extensive ice cloud system contained in Titan's south polar stratosphere, as seen through the night-vision goggles of Cassini's Composite InfraRed Spectrometer (CIRS). As the sun sets and the gloom of southern winter approaches, evidence is beginning to accumulate from CIRS far-IR spectra that a massive system of nitrile ice clouds is developing in Titan's south polar stratosphere. Even during the depths of northern winter, nothing like the strength of this southern system was evident in corresponding north polar regions.From the long slant paths that are available from limb-viewing CIRS far-IR spectra, we have the first definitive detection of the ν6 band of cyanoacetylene (HC3N) ice in Titan’s south polar stratosphere. In addition, we also see a strong blend of nitrile ice lattice vibration features around 160 cm-1. From these data we are able to derive ice abundances. The most prominent (and still chemically unidentified) ice emission feature, the Haystack, (at 220 cm-1) is also observed. We establish the vertical distributions of the ice cloud systems associated with both the 160 cm-1 feature and the Haystack. The ultimate aim is to refine the physical and possibly the chemical relationships between the two. Transmittance thin film spectra of nitrile ice mixtures obtained in our Spectroscopy for Planetary ICes Environments (SPICE) laboratory are used to support these analyses.

Isotopic composition on ground ice in Western Yamal (Marre-Sale

Directory of Open Access Journals (Sweden)

I. D. Streletskaya

2013-01-01

Full Text Available The profile of Quaternary sediments near Marre-Salle polar station, Western Yamal Peninsula, has large bodies of tabular ground ice. This profile is considered strata-typical and critical in understanding of paleogeographic conditions of the Arctic in Pleistocene-Holocene. However, interpretation of the profile is under discussion. It consists of two distinct strata: upper layer of 10–15 m thick represented by continental sediments and lower one with a thickness of more than 100 m represented by marine sediments. Lower layer of saline marine clays has lenses of tabular ground ice (more than 20 m thick, the bases of which are below the sea level. Upper continental layer is characterized by syngenetic ice-wedges of different generations. Samples were collected from ice-wedges and tabular ground ice for chemical and isotope analysis. The results of the analysis allow to reconstruct paleogeographic conditions of the sedimentation and freezing of Quaternary sediments. Heavy stable isotope content and relationship between oxygen and hydrogen isotopes show that the ice bodies in the lower layer were formed in-situ within the ground. In the upper layer, heavier isotope content found in younger ice-wedges relative to the old-generation wedges. Formation of massive syngenetic Upper-Pleistocene ice-wedges occurred in conditions of colder winter temperatures than at present. Syngenetic Holocene wedges were formed after Holocene Optimum under winter conditions similar to present. Younger ice wedges formed smaller polygons, were smaller and often were developing in the locations of the degraded old wedges. Results of the isotope analysis of various types of ground ice near Marre-Sale allow reconstructing changes of marine sedimentation to continental one around Kargino time (MIS 3 and changes in climatic conditions in Arctic in Late Pleistocene and Holocene.

Middle-to-late Holocene palaeoenvironmental reconstruction from the A294 ice-cave record (Central Pyrenees, northern Spain)

Science.gov (United States)

Sancho, Carlos; Belmonte, Ánchel; Bartolomé, Miguel; Moreno, Ana; Leunda, María; López-Martínez, Jerónimo

2018-02-01

Perennial ice deposits in caves represent unique, but underexplored, terrestrial sequences that potentially contain outstanding palaeoclimatic records. Here, we present a pioneer palaeoenvironmental study of an ice deposit preserved in a small sag-type cave (A294) in the Central Pyrenees (northern Iberian Peninsula). The 9.25-m-thick sequence, which is dated from 6100 ± 107 to 1888 ± 64 cal BP, represents the oldest known firn ice record worldwide. The stratigraphy (detrital layers, unconformities, and cross stratification), plant macrofossils, and isotopic signature (similarity between the ice linear distribution, δ2H = 7.83δ18O + 8.4, and the Global Meteoric Water Line) of the ice point to the diagenesis of snow introduced to the cave by winter snowstorms. Four phases of rapid ice accumulation (6100-5515, 4945-4250, 3810-3155, and 2450-1890 cal BP) are related to wetter and colder winters. Comparison of the isotopic composition (δ18O and deuterium excess) of the ice with other paleoclimate records show that both source effects and the North Atlantic Oscillation (NAO) mechanism exert a dominant influence on the ice cave record. The NAO signal may be a combination of source effects and rainfall amount. Three intervals with low ice accumulation occurred between the phases of rapid accumulation and were related to drier, and possibly warmer, winters. These centennial-scale episodes appear to be in-phase with regional arid events, as established from high altitude lacustrine records and can be correlated to global Rapid Climate Change events. The current warming trend has dramatically decreased the volume of the ice deposit in cave A294.

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

Polar bears experience skeletal muscle atrophy in response to food deprivation and reduced activity in winter and summer

Science.gov (United States)

Whiteman, John P.; Harlow, Henry J.; Durner, George M.; Regehr, Eric V.; Rourke, Bryan C.; Robles, Manuel; Amstrup, Steven C.; Ben-David, Merav

2017-01-01

When reducing activity and using stored energy during seasonal food shortages, animals risk degradation of skeletal muscles, although some species avoid or minimize the resulting atrophy while experiencing these conditions during hibernation. Polar bears may be food deprived and relatively inactive during winter (when pregnant females hibernate and hunting success declines for other demographic groups) as well as summer (when sea ice retreats from key foraging habitats). We investigated muscle atrophy in samples of biceps femoris collected from free-ranging polar bears in the Southern Beaufort Sea (SBS) throughout their annual cycle. Atrophy was most pronounced in April–May as a result of food deprivation during the previous winter, with muscles exhibiting reduced protein concentration, increased water content, and lower creatine kinase mRNA. These animals increased feeding and activity in spring (when seal prey becomes more available), initiating a period of muscle recovery. During the following ice melt of late summer, ~30% of SBS bears abandon retreating sea ice for land; in August, these ‘shore’ bears exhibited no muscle atrophy, indicating that they had fully recovered from winter food deprivation. These individuals subsequently scavenged whale carcasses deposited by humans and by October, had retained good muscle condition. In contrast, ~70% of SBS bears follow the ice north in late summer, into deep water with less prey. These ‘ice’ bears fast; by October, they exhibited muscle protein loss and rapid changes in myosin heavy-chain isoforms in response to reduced activity. These findings indicate that, unlike other bears during winter hibernation, polar bears without food in summer cannot mitigate atrophy. Consequently, prolonged summer fasting resulting from climate change-induced ice loss creates a risk of greater muscle atrophy and reduced abilities to travel and hunt.

Polar bears experience skeletal muscle atrophy in response to food deprivation and reduced activity in winter and summer

Science.gov (United States)

Harlow, Henry J.; Durner, George M.; Regehr, Eric V.; Rourke, Bryan C.; Robles, Manuel; Amstrup, Steven C.; Ben-David, Merav

2017-01-01

Abstract When reducing activity and using stored energy during seasonal food shortages, animals risk degradation of skeletal muscles, although some species avoid or minimize the resulting atrophy while experiencing these conditions during hibernation. Polar bears may be food deprived and relatively inactive during winter (when pregnant females hibernate and hunting success declines for other demographic groups) as well as summer (when sea ice retreats from key foraging habitats). We investigated muscle atrophy in samples of biceps femoris collected from free-ranging polar bears in the Southern Beaufort Sea (SBS) throughout their annual cycle. Atrophy was most pronounced in April–May as a result of food deprivation during the previous winter, with muscles exhibiting reduced protein concentration, increased water content, and lower creatine kinase mRNA. These animals increased feeding and activity in spring (when seal prey becomes more available), initiating a period of muscle recovery. During the following ice melt of late summer, ~30% of SBS bears abandon retreating sea ice for land; in August, these ‘shore’ bears exhibited no muscle atrophy, indicating that they had fully recovered from winter food deprivation. These individuals subsequently scavenged whale carcasses deposited by humans and by October, had retained good muscle condition. In contrast, ~70% of SBS bears follow the ice north in late summer, into deep water with less prey. These ‘ice’ bears fast; by October, they exhibited muscle protein loss and rapid changes in myosin heavy-chain isoforms in response to reduced activity. These findings indicate that, unlike other bears during winter hibernation, polar bears without food in summer cannot mitigate atrophy. Consequently, prolonged summer fasting resulting from climate change-induced ice loss creates a risk of greater muscle atrophy and reduced abilities to travel and hunt. PMID:28835844

Contribution of Deformation to Sea Ice Mass Balance: A Case Study From an N-ICE2015 Storm

Science.gov (United States)

Itkin, Polona; Spreen, Gunnar; Hvidegaard, Sine Munk; Skourup, Henriette; Wilkinson, Jeremy; Gerland, Sebastian; Granskog, Mats A.

2018-01-01

The fastest and most efficient process of gaining sea ice volume is through the mechanical redistribution of mass as a consequence of deformation events. During the ice growth season divergent motion produces leads where new ice grows thermodynamically, while convergent motion fractures the ice and either piles the resultant ice blocks into ridges or rafts one floe under the other. Here we present an exceptionally detailed airborne data set from a 9 km2 area of first year and second year ice in the Transpolar Drift north of Svalbard that allowed us to estimate the redistribution of mass from an observed deformation event. To achieve this level of detail we analyzed changes in sea ice freeboard acquired from two airborne laser scanner surveys just before and right after a deformation event brought on by a passing low-pressure system. A linear regression model based on divergence during this storm can explain 64% of freeboard variability. Over the survey region we estimated that about 1.3% of level sea ice volume was pressed together into deformed ice and the new ice formed in leads in a week after the deformation event would increase the sea ice volume by 0.5%. As the region is impacted by about 15 storms each winter, a simple linear extrapolation would result in about 7% volume increase and 20% deformed ice fraction at the end of the season.

GLERL Great Lakes Ice Thickness Data Base, 1966-1979

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — During the winters of 1965/66 through 1976/77, NOAA/Great Lakes Environmental Research Laboratory (GLERL) collected weekly ice thickness and stratigraphy data at up...

Barriers to wheelchair use in the winter.

Science.gov (United States)

Ripat, Jacquie D; Brown, Cara L; Ethans, Karen D

2015-06-01

To test the hypothesis that challenges to community participation posed by winter weather are greater for individuals who use scooters, manual and power wheelchairs (wheeled mobility devices [WMDs]) than for the general ambulatory population, and to determine what WMD users identify as the most salient environmental barriers to community participation during the winter. Cross-sectional survey organized around 5 environmental domains: technological, natural, physical, social/attitudinal, and policy. Urban community in Canada. Convenience sample of WMD users or their proxy (N=99). Not applicable. Not applicable. Forty-two percent identified reduced outing frequency in winter months, associated with increased age (χ(3)=6.4, P=.04), lack of access to family/friends for transportation (χ(2)=8.1, P=.04), and primary type of WMD used in the winter (scooter χ(2)=8.8, P=.003). Most reported tires/casters becoming stuck in the snow (95%) or slipping on the ice (91%), difficulty ascending inclines/ramps (92%), and cold hands while using controls or pushing rims (85%); fewer identified frozen wheelchair/scooter batteries, seat cushions/backrests, or electronics. Sidewalks/roads were reported to be problematic by 99%. Eighty percent reported needing additional help in the winter. Limited community access in winter led to a sense of loneliness/isolation, and fear/anxiety related to safety. Respondents identified policies that limited participation during winter. People who use WMDs decrease their community participation in cold weather because of multiple environmental barriers. Clinicians, researchers, and policymakers can take a multidimensional approach to mitigate these barriers in order to enhance community participation by WMD users in winter. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

The Winter 2010 and 2011 FRONT/NIRSS In-Flight Icing Hazard Detection Project

Science.gov (United States)

Serke, David; Hubbert, John; Reehorst, Andrew; Kennedy, Patrick; Politovich, Marcia

2011-01-01

The NASA Icing Remote Sensing System (NIRSS) deploys a vertically-pointing K-band radar, a lidar ceiliometer, and a profiling microwave radiometer to obtain measurements for diagnosing local inflight icing conditions. RAL is working with NASA GRC to develop algorithms and data ingest and display software for the system. NASA has an ongoing activity to develop remote sensing technologies for the detection and measurement of icing conditions aloft. As part of that effort NASA teamed with NCAR to develop software that fuses data from multiple instruments into a single detected icing condition product. The multiple instrument approach, which is the current emphasis of this activity, utilizes a K-band vertical staring radar, a microwave radiometer that detects twelve frequencies between 22 and 59 GHz, and a lidar ceilometer. The radar data determine cloud boundaries, the radiometer determines the sub-freezing temperature heights and total liquid water content, and the ceilometer refines the lower cloud boundary. Data is post-processed in C++ program with a Java-based web display of resultant supercooled LWC profile and aircraft hazard identification. In 2010, a multi-channel scanning radiometer, designed and built by Radiometrics, Inc. under a SBIR grant,,was added to the system to assess its utility in improving icing diagnoses.

Observational Evidence for Enhanced Greenhouse Effect Reinforcing Wintertime Arctic Amplification and Sea Ice Melting Onset

Science.gov (United States)

Cao, Y.; Liang, S.

2017-12-01

Despite an apparent hiatus in global warming, the Arctic climate continues to experience unprecedented changes. Summer sea ice is retreating at an accelerated rate, and surface temperatures in this region are rising at a rate double that of the global average, a phenomenon known as Arctic amplification. Although a lot of efforts have been made, the causes this unprecedented phenomenon remain unclear and are subjects of considerable debate. In this study, we report strong observational evidence, for the first time from long-term (1984-2014) spatially complete satellite records, that increased cloudiness and atmospheric water vapor in winter and spring have caused an extraordinary downward longwave radiative flux to the ice surface, which may then amplify the Arctic wintertime ice-surface warming. In addition, we also provide observed evidence that it is quite likely the enhancement of the wintertime greenhouse effect caused by water vapor and cloudiness has advanced the time of onset of ice melting in mid-May through inhibiting sea-ice refreezing in the winter and accelerating the pre-melting process in the spring, and in turn triggered the positive sea-ice albedo feedback process and accelerated the sea ice melting in the summer.

A Volunteer program guidebook for sport managers organizing large scale ice hockey tournaments

OpenAIRE

Frison, Logan

2010-01-01

The guidebook is a tool to assist the tournament coordinator when recruting, training, and leading the best possible team of ice hockey volunteers to work at International Ice Hockey Federation (IIHF) tournaments and within the Sport Function - Ice Hockey events at Olympic Winter Games. The select volunteers are termed the ‘Ice Hockey Volunteers’ and consist of the six crews that make up the ‘Sport Team’ which work closely with the National Teams (athletes and team staff) and Officials (re...

Calibration of sea ice dynamic parameters in an ocean-sea ice model using an ensemble Kalman filter

Science.gov (United States)

Massonnet, F.; Goosse, H.; Fichefet, T.; Counillon, F.

2014-07-01

The choice of parameter values is crucial in the course of sea ice model development, since parameters largely affect the modeled mean sea ice state. Manual tuning of parameters will soon become impractical, as sea ice models will likely include more parameters to calibrate, leading to an exponential increase of the number of possible combinations to test. Objective and automatic methods for parameter calibration are thus progressively called on to replace the traditional heuristic, "trial-and-error" recipes. Here a method for calibration of parameters based on the ensemble Kalman filter is implemented, tested and validated in the ocean-sea ice model NEMO-LIM3. Three dynamic parameters are calibrated: the ice strength parameter P*, the ocean-sea ice drag parameter Cw, and the atmosphere-sea ice drag parameter Ca. In twin, perfect-model experiments, the default parameter values are retrieved within 1 year of simulation. Using 2007-2012 real sea ice drift data, the calibration of the ice strength parameter P* and the oceanic drag parameter Cw improves clearly the Arctic sea ice drift properties. It is found that the estimation of the atmospheric drag Ca is not necessary if P* and Cw are already estimated. The large reduction in the sea ice speed bias with calibrated parameters comes with a slight overestimation of the winter sea ice areal export through Fram Strait and a slight improvement in the sea ice thickness distribution. Overall, the estimation of parameters with the ensemble Kalman filter represents an encouraging alternative to manual tuning for ocean-sea ice models.

Influence of de-icing salt chemistry on the corrosion behavior of AA6016

DEFF Research Database (Denmark)

Schoukens, Ine; Cavezza, Francesca; Cerezo, Jose

2017-01-01

De-icing salts are commonly used on European roads during winter and are usually based on chlorides of sodium, magnesium, or calcium. The salt selection depends on the local climate and legislation. Therefore, the chemical composition of the de-icing mixture can be very different within Europe. T...

Sea ice inertial oscillations in the Arctic Basin

Directory of Open Access Journals (Sweden)

F. Gimbert

2012-10-01

Full Text Available An original method to quantify the amplitude of inertial motion of oceanic and ice drifters, through the introduction of a non-dimensional parameter M defined from a spectral analysis, is presented. A strong seasonal dependence of the magnitude of sea ice inertial oscillations is revealed, in agreement with the corresponding annual cycles of sea ice extent, concentration, thickness, advection velocity, and deformation rates. The spatial pattern of the magnitude of the sea ice inertial oscillations over the Arctic Basin is also in agreement with the sea ice thickness and concentration patterns. This argues for a strong interaction between the magnitude of inertial motion on one hand, the dissipation of energy through mechanical processes, and the cohesiveness of the cover on the other hand. Finally, a significant multi-annual evolution towards greater magnitudes of inertial oscillations in recent years, in both summer and winter, is reported, thus concomitant with reduced sea ice thickness, concentration and spatial extent.

Impact of partly ice-free Lake Ladoga on temperature and cloudiness in an anticyclonic winter situation – a case study using a limited area model

Directory of Open Access Journals (Sweden)

Kalle Eerola

2014-12-01

Full Text Available At the end of January 2012, a low-level cloud from partly ice-free Lake Ladoga caused very variable 2-m temperatures in Eastern Finland. The sensitivity of the High Resolution Limited Area Model (HIRLAM to the lake surface conditions was tested in this winter anticyclonic situation. The lake appeared to be (incorrectly totally covered by ice when the lake surface was described with its climatology. Both parametrisation of the lake surface state by using a lake model integrated to the NWP system and objective analysis based on satellite observations independently resulted in a correct description of the partly ice-free Lake Ladoga. In these cases, HIRLAM model forecasts were able to predict cloud formation and its movement as well as 2-m temperature variations in a realistic way. Three main conclusions were drawn. First, HIRLAM could predict the effect of Lake Ladoga on local weather, when the lake surface state was known. Second, the current parametrisation methods of air–surface interactions led to a reliable result in conditions where the different physical processes (local surface processes, radiation and turbulence were not strong, but their combined effect was important. Third, these results encourage work for a better description of the lake surface state in NWP models by fully utilising satellite observations, combined with advanced lake parametrisation and data assimilation methods.

Winter warming as an important co-driver for Betula nana growth in western Greenland during the past century.

Science.gov (United States)

Hollesen, Jørgen; Buchwal, Agata; Rachlewicz, Grzegorz; Hansen, Birger U; Hansen, Marc O; Stecher, Ole; Elberling, Bo

2015-06-01

Growing season conditions are widely recognized as the main driver for tundra shrub radial growth, but the effects of winter warming and snow remain an open question. Here, we present a more than 100 years long Betula nana ring-width chronology from Disko Island in western Greenland that demonstrates a highly significant and positive growth response to both summer and winter air temperatures during the past century. The importance of winter temperatures for Betula nana growth is especially pronounced during the periods from 1910-1930 to 1990-2011 that were dominated by significant winter warming. To explain the strong winter importance on growth, we assessed the importance of different environmental factors using site-specific measurements from 1991 to 2011 of soil temperatures, sea ice coverage, precipitation and snow depths. The results show a strong positive growth response to the amount of thawing and growing degree-days as well as to winter and spring soil temperatures. In addition to these direct effects, a strong negative growth response to sea ice extent was identified, indicating a possible link between local sea ice conditions, local climate variations and Betula nana growth rates. Data also reveal a clear shift within the last 20 years from a period with thick snow depths (1991-1996) and a positive effect on Betula nana radial growth, to a period (1997-2011) with generally very shallow snow depths and no significant growth response towards snow. During this period, winter and spring soil temperatures have increased significantly suggesting that the most recent increase in Betula nana radial growth is primarily triggered by warmer winter and spring air temperatures causing earlier snowmelt that allows the soils to drain and warm quicker. The presented results may help to explain the recently observed 'greening of the Arctic' which may further accelerate in future years due to both direct and indirect effects of winter warming. © 2015 John Wiley & Sons

Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

Directory of Open Access Journals (Sweden)

M. Schäfer

2015-07-01

Full Text Available Based on airborne spectral imaging observations, three-dimensional (3-D radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength. The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0–200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500–1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field. The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500–1000 m cloud altitude, which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical

Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

Science.gov (United States)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-07-01

Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength). The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0-200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI) in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500-1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field). The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500-1000 m cloud altitude), which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical properties was investigated

Study on the glaze ice accretion of wind turbine with various chord lengths

Science.gov (United States)

Liang, Jian; Liu, Maolian; Wang, Ruiqi; Wang, Yuhang

2018-02-01

Wind turbine icing often occurs in winter, which changes the aerodynamic characteristics of the blades and reduces the work efficiency of the wind turbine. In this paper, the glaze ice model is established for horizontal-axis wind turbine in 3-D. The model contains the grid generation, two-phase simulation, heat and mass transfer. Results show that smaller wind turbine suffers from more serious icing problem, which reflects on a larger ice thickness. Both the collision efficiency and heat transfer coefficient increase under smaller size condition.

NASA/FAA Tailplane Icing Program: Flight Test Report

Science.gov (United States)

Ratvasky, Thomas P.; VanZante, Judith Foss; Sim, Alex

2000-01-01

This report presents results from research flights that explored the characteristics of an ice-contaminated tailplane using various simulated ice shapes attached to the leading edge of the horizontal tailplane. A clean leading edge provided the baseline case, then three ice shapes were flown in order of increasing severity. Flight tests included both steady state and dynamic maneuvers. The steady state points were 1G wings level and steady heading sideslips. The primary dynamic maneuvers were pushovers to various G-levels; elevator doublets; and thrust transitions. These maneuvers were conducted for a full range of flap positions and aircraft angle of attack where possible. The analysis of this data set has clearly demonstrated the detrimental effects of ice contamination on aircraft stability and controllability. Paths to tailplane stall were revealed through parameter isolation and transition studies. These paths are (1) increasing ice shape severity, (2) increasing flap deflection, (3) high or low speeds, depending on whether the aircraft is in a steady state (high speed) or pushover maneuver (low speed), and (4) increasing thrust. The flight research effort was very comprehensive, but did not examine effects of tailplane design and location, or other aircraft geometry configuration effects. However, this effort provided the role of some of the parameters in promoting tailplane stall. The lessons learned will provide guidance to regulatory agencies, aircraft manufacturers, and operators on ice-contaminated tailplane stall in the effort to increase aviation safety and reduce the fatal accident rate.

Studded and unstudded winter tires in fatal road accidents in Finland.

Science.gov (United States)

Malmivuo, Mikko; Luoma, Juha; Porthin, Markus

2017-07-04

The aim of the study was to compare the safety effects of studded and unstudded winter tires based on fatal road accidents. The data included 958 road accidents involving a passenger car or van that occurred in Finland from November to March between 1997 and 2012. Comparing the proportions of winter tire type in accidents and in general traffic showed that the overall effect of tire type on the number of accidents was not significant, although studded tires reduced fatal accidents by 10-15%. Compared to unstudded tires, studded tires reduced accidents significantly only on bald ice in 2005-2012. Drivers using unstudded tires were more experienced and their profession was more frequently related to driving. In addition, the vehicle age was lower for vehicles with unstudded tires. On the other hand, the state of repair was less pertinent for unstudded than for studded tires. These confounding factors offset their effects to some degree. The risk of fatal road accidents in winter between studded and unstudded tires does not differ significantly. However, the accident risk has recently been substantially higher on bald ice for unstudded than for studded tires. The magnitude of this risk difference is difficult to determine without specific information on exposure by road surface.

Sustained high basal motion of the Greenland ice sheet revealed by borehole deformation

DEFF Research Database (Denmark)

Ryser, Claudia; Luethi, Martin P.; Andrews, Lauren C.

2014-01-01

amount of basal motion contribution to surface velocity of 44-73% in winter, and up to 90% in summer. Measured ice deformation rates show an unexpected variation with depth that can be explained with the help of an ice-flow model as a consequence of stress transfer from slippery to sticky areas...

Circulation and Respiration in Ice-covered Alaskan Arctic Lakes

Science.gov (United States)

MacIntyre, S.; Cortés, A.

2016-12-01

Arctic lakes are ice-covered 9 months of the year. For some of this time, the sediments heat the overlying water, and respiration in the sediments increases specific conductivity, depletes oxygen, and produces greenhouse gases (GHG). Whether anoxia forms and whether the greenhouse gases are sequestered at depth depends on processes inducing circulation and upward fluxes. Similarly, whether the GHG are released at ice off depends on the extent of vertical mixing at that time. Using time series meteorological data and biogeochemical arrays with temperature, specific conductivity, and optical oxygen sensors in 5 lakes ranging from 1 to 150 ha, we illustrate the connections between meteorological forcing and within lake processes including gravity currents resulting from increased density just above the sediment water interface and internal waves including those induced by winds acting on the surface of the ice and at ice off. CO2 production was well predicted by the initial rate of oxygen drawdown near the bottom at ice on and that the upward density flux depended on lake size, with values initially high in all lakes but near molecular in lakes of a few hectares in size by mid-winter. Both CO2 production and within lake vertical fluxes were independent of the rate of cooling in fall and subsequent within lake temperatures under the ice. Anoxia formed near the sediments in all 5 lakes with the concentration of CH4 dependent, in part, on lake size and depth. Twenty to fifty percent of the greenhouse gases produced under the ice remained in the lakes by the time thermal stratification was established in summer despite considerable internal wave induced mixing at the time of ice off. These observations and analysis lay a framework for understanding the links between within lake hydrodynamics, within year variability, and the fraction of greenhouse gases produced over the winter which evade at ice off.

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.

Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave-ice model

Science.gov (United States)

Herman, Agnieszka

2017-11-01

In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

Spatial mapping of multi-year superimposed ice on the glacier Kongsvegen, Svalbard

DEFF Research Database (Denmark)

Brandt, Ola; Kohler, Jack; Lüthje, Mikael

2008-01-01

by GPR. Using the SI spatial depth distribution, we estimate the mean annual accumulation of superimposed ice to be 0.16 +/- 0.06 mw.e.a(-1) (locally up to 0.43 ma(-1) w.e.). This corresponds to similar to 15-33% of the local winter balance and similar to 5-10% of the total winter balance measured since...

Ikaite crystal distribution in Arctic winter sea ice and implications for CO2 system dynamics

DEFF Research Database (Denmark)

Rysgaard, Søren; Søgaard, D. H.; Cooper, M.

2012-01-01

The precipitation of ikaite (CaCO3·6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite...

Analysis of the Warmest Arctic Winter, 2015-2016

Science.gov (United States)

Cullather, Richard I.; Lim, Young-Kwon; Boisvert, Linette N.; Brucker, Ludovic; Lee, Jae N.; Nowicki, Sophie M. J.

2016-01-01

December through February 2015-2016 defines the warmest winter season over the Arctic in the observational record. Positive 2m temperature anomalies were focused over regions of reduced sea ice cover in the Kara and Barents Seas and southwestern Alaska. A third region is found over the ice-covered central Arctic Ocean. The period is marked by a strong synoptic pattern which produced melting temperatures in close proximity to the North Pole in late December and anomalous high pressure near the Taymyr Peninsula. Atmospheric teleconnections from the Atlantic contributed to warming over Eurasian high-latitude land surfaces, and El Niño-related teleconnections explain warming over southwestern Alaska and British Columbia, while warm anomalies over the central Arctic are associated with physical processes including the presence of enhanced atmospheric water vapor and an increased downwelling longwave radiative flux. Preconditioning of sea ice conditions by warm temperatures affected the ensuing spring extent.

Study on accretion of ice on oscillating aerofoils; Shindoyokujo no chakuhyo ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Nishikawa, S; Sugihara, H [Kandenko Co. Ltd., Tokyo (Japan); Kimura, S; Sugiyama, Y [Kanagawa Institute of Technology, Kanagawa (Japan); Tsuboi, K [Ibaraki University, Ibaraki (Japan). Faculty of Engineering

1997-11-25

The effects of pitching and heaving motions of an aerofoil on accretion of ice thereon are investigated for the design of wind turbine blades. The conditions under which an aerofoil shows a heaving motion are 10m/s as wind velocity, -12degC as ambient temperature, 0.5Hz as frequency and 5mm as amplitude. Initial growth of ice is stochastic to a great extent; ice grows rapidly around the seed which is formed by chance somewhere on an laerofoil. The effects of ice appear in the flow field in the vicinity of the aerofoil front edge, as it continues to grow, providing different conditions for water droplets to collide with each other. Average ice shapes can be classified by environment, although at low repeatability. Range of ice accretion varies depending on aerofoil motion, whether it is pitching, heaving or at rest. The most important factor that determines behavior of ice accretion is conditions of the flow field near the aerofoil front edge. In a pitching or heaving motion, its speed is an important factor for growth of ice. 2 refs., 5 figs.

Southern Ocean CO2 sink: the contribution of the sea ice

DEFF Research Database (Denmark)

Delille, B.; Vancoppenolle, Martin; Geilfus, Nicolas-Xavier

2014-01-01

at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea ice cover using the NEMO-LIM3 large-scale sea ice-ocean and provide first esti- mates of spring and summer CO2 uptake from the atmosphere...... by Antarctic sea ice. Over the spring- summer period, the Antarctic sea ice cover is a net sink of atmospheric CO2 of 0.029 Pg C, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO2 of the Southern Ocean....... undersaturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate crystals, and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer...

The injury experience at the 2010 winter paralympic games.

Science.gov (United States)

Webborn, Nick; Willick, Stuart; Emery, Carolyn A

2012-01-01

The objective of this study was to examine incidence proportion and the characteristics of athlete injuries sustained during the 2010 Vancouver Paralympic Games. Descriptive epidemiological study. All medical venues at the 2010 Vancouver Paralympic Games, Canada. A total of 505 athletes from 44 National Paralympic Committees participating in the 2010 Vancouver Winter Paralympic Games. Baseline covariates included sport specificity (ie, ice sledge hockey, alpine skiing, Nordic skiing, wheelchair curling), gender, age, and disability classification. All injuries that occurred during the 2010 Vancouver Paralympic Games. "Injury" was defined as any sport-related musculoskeletal complaint that caused the athlete to seek medical attention during the study period, regardless of the athlete's ability to continue with training or competition. The Injury Surveillance System identified a total of 120 injuries among 505 athletes [incidence proportion = 23.8% (95% confidence interval, 20.11-27.7)] participating in the 2010 Winter Paralympic Games. There was a similar injury incidence proportion among male (22.8%) and female (26.6%) athletes [incidence rate ratio = 1.1 (95% confidence interval, 0.7-1.7)]. Medical encounters for musculoskeletal complaints were generated in 34% of all sledge hockey athletes, 22% of alpine ski racers, 19% of Nordic skiers, and 18% of wheelchair curling athletes. The Injury Surveillance System identified sport injuries in 24% of all athletes participating in the 2010 Winter Paralympic Games. The injury risk was significantly higher than during the 2002 (9.4%) and 2006 (8.4%) Winter Paralympic Games. This may reflect improved data collection systems but also highlights the high risk of acute injury in alpine skiing and ice sledge hockey at Paralympic Games. These data will assist future Organizing Committees with the delivery of medical care to athletes with a disability and guide future injury prevention research.

Temperature Measurements of the Low-Attenuation Radiographic Ice Ball During CT-Guided Renal Cryoablation

International Nuclear Information System (INIS)

Permpongkosol, Sompol; Link, Richard E.; Kavoussi, Louis R.; Solomon, Stephen B.

2008-01-01

During renal cryoablation a low-attenuation area on CT develops around the cryoprobe. Knowledge of the temperature of the growing low-attenuation area can guide therapy and ensure lethal temperatures. Herein, we report thermocouple results and correlating CT images during the development of the low-attenuation 'radiographic ice ball.' Five patients who underwent percutaneous CT-guided renal cryoablation were identified who had thermocouples inserted and serial intraprocedural CT images that included images with thermocouple measurements of 0 o and sub-0 o C. Thermocouples had been percutaneously placed just beyond the edge of the tumors either to ensure adequate cooling or to ensure safety to adjacent critical structures. Renal cryotherapy under CT guidance produced a growing low-attenuation area corresponding to the radiographic ice ball. When the thermocouple measured 0 o C, CT images showed the thermocouple tip at the edge of the low-attenuation ice ball. At lower temperatures the tip was within the low-attenuation ice ball. We conclude that knowledge of the temperature at the ice ball edge during cryoablation can be used to predict the extent of tissue necrosis and thus provide an estimate of cryotherapy effectiveness during the procedure. Further work is necessary to establish a firm relationship between the thermal conditions and the zone of damage

CryoSat: ESA's Ice Explorer Mission: status and achievements

Science.gov (United States)

Parrinello, Tommaso; Mardle, Nicola; Hoyos Ortega, Berta; Bouzinac, Catherine; Badessi, Stefano; Frommknecht, Bjorn; Davidson, Malcolm; Fornari, Marco; Cullen, Robert

2013-04-01

CryoSat-2 was launched on the 8th April 2010 and it is the first European ice mission dedicated to monitoring precise changes in the thickness of polar ice sheets and floating sea ice over a 3-year period. Cryosat-2 carries an innovative radar altimeter called the Synthetic Aperture Interferometric Altimeter (SIRAL) with two antennas and with extended capabilities to meet the measurement requirements for ice-sheets elevation and sea-ice freeboard. Experimental evidence have shown that data is of high quality thanks to an altimeter that is behaving exceptional well within its design specifications. In April 2012, the first winter [2010 -2011] sea-ice variation map of the Arctic was released to the scientific community. Scope of this paper is to describe the current mission status and the main scientific achievements in the last twelve months. Topics will also include programmatic highlights and information on accessing Cryosat products following the new ESA Earth Observation Data Policy.

Arctic landfast sea ice

Science.gov (United States)

Konig, Christof S.

Landfast ice is sea ice which forms and remains fixed along a coast, where it is attached either to the shore, or held between shoals or grounded icebergs. Landfast ice fundamentally modifies the momentum exchange between atmosphere and ocean, as compared to pack ice. It thus affects the heat and freshwater exchange between air and ocean and impacts on the location of ocean upwelling and downwelling zones. Further, the landfast ice edge is essential for numerous Arctic mammals and Inupiat who depend on them for their subsistence. The current generation of sea ice models is not capable of reproducing certain aspects of landfast ice formation, maintenance, and disintegration even when the spatial resolution would be sufficient to resolve such features. In my work I develop a new ice model that permits the existence of landfast sea ice even in the presence of offshore winds, as is observed in mature. Based on viscous-plastic as well as elastic-viscous-plastic ice dynamics I add tensile strength to the ice rheology and re-derive the equations as well as numerical methods to solve them. Through numerical experiments on simplified domains, the effects of those changes are demonstrated. It is found that the modifications enable landfast ice modeling, as desired. The elastic-viscous-plastic rheology leads to initial velocity fluctuations within the landfast ice that weaken the ice sheet and break it up much faster than theoretically predicted. Solving the viscous-plastic rheology using an implicit numerical method avoids those waves and comes much closer to theoretical predictions. Improvements in landfast ice modeling can only verified in comparison to observed data. I have extracted landfast sea ice data of several decades from several sources to create a landfast sea ice climatology that can be used for that purpose. Statistical analysis of the data shows several factors that significantly influence landfast ice distribution: distance from the coastline, ocean depth, as

Human impacts on river ice regime in the Carpathian Basin

Science.gov (United States)

Takács, Katalin; Nagy, Balázs; Kern, Zoltán

2014-05-01

River ice is a very important component of the cryosphere, and is especially sensitive to climatic variability. Historical records of appearance or disappearance and timing of ice phenomena are useful indicators for past climatic variations (Williams, 1970). Long-term observations of river ice freeze-up and break-up dates are available for many rivers in the temperate or cold region to detect and analyze the effects of climate change on river ice regime. The ice regime of natural rivers is influenced by climatic, hydrological and morphological factors. Regular ice phenomena observation mostly dates back to the 19th century. During this long-term observation period, the human interventions affecting the hydrological and morphological factors have become more and more intensive (Beltaos and Prowse, 2009). The anthropogenic effects, such as river regulation, hydropower use or water pollution causes different changes in river ice regime (Ashton, 1986). To decrease the occurrence of floods and control the water discharge, nowadays most of the rivers are regulated. River regulation changes the morphological parameters of the river bed: the aim is to create solid and equable bed size and stream gradient to prevent river ice congestion. For the satisfaction of increasing water demands hydropower is also used. River damming results a condition like a lake upstream to the barrage; the flow velocity and the turbulence are low, so this might be favourable for river ice appearance and freeze-up (Starosolsky, 1990). Water pollution affects ice regime in two ways; certain water contaminants change the physical characteristics of the water, e.g. lessens the freezing point of the water. Moreover the thermal stress effect of industrial cooling water and communal wastewater is also important; in winter these water sources are usually warmer, than the water body of the river. These interventions result different changes in the characteristic features of river ice regime. Selected

Field test and sensitivity analysis of a sensible heat balance method to determine ice contents

Science.gov (United States)

Soil ice content impacts winter vadose zone hydrology. It may be possible to estimate changes in soil ice content with a sensible heat balance (SHB) method, using measurements from heat pulse (HP) sensors. Feasibility of the SHB method is unknown because of difficulties in measuring soil thermal pro...

The Horizontal Ice Nucleation Chamber (HINC): INP measurements at conditions relevant for mixed-phase clouds at the High Altitude Research Station Jungfraujoch

Science.gov (United States)

Lacher, Larissa; Lohmann, Ulrike; Boose, Yvonne; Zipori, Assaf; Herrmann, Erik; Bukowiecki, Nicolas; Steinbacher, Martin; Kanji, Zamin A.

2017-12-01

In this work we describe the Horizontal Ice Nucleation Chamber (HINC) as a new instrument to measure ambient ice-nucleating particle (INP) concentrations for conditions relevant to mixed-phase clouds. Laboratory verification and validation experiments confirm the accuracy of the thermodynamic conditions of temperature (T) and relative humidity (RH) in HINC with uncertainties in T of ±0.4 K and in RH with respect to water (RHw) of ±1.5 %, which translates into an uncertainty in RH with respect to ice (RHi) of ±3.0 % at T > 235 K. For further validation of HINC as a field instrument, two measurement campaigns were conducted in winters 2015 and 2016 at the High Altitude Research Station Jungfraujoch (JFJ; Switzerland, 3580 m a. s. l. ) to sample ambient INPs. During winters 2015 and 2016 the site encountered free-tropospheric conditions 92 and 79 % of the time, respectively. We measured INP concentrations at 242 K at water-subsaturated conditions (RHw = 94 %), relevant for the formation of ice clouds, and in the water-supersaturated regime (RHw = 104 %) to represent ice formation occurring under mixed-phase cloud conditions. In winters 2015 and 2016 the median INP concentrations at RHw = 94 % was below the minimum detectable concentration. At RHw = 104 %, INP concentrations were an order of magnitude higher, with median concentrations in winter 2015 of 2.8 per standard liter (std L-1; normalized to standard T of 273 K and pressure, p, of 1013 hPa) and 4.7 std L-1 in winter 2016. The measurements are in agreement with previous winter measurements obtained with the Portable Ice Nucleation Chamber (PINC) of 2.2 std L-1 at the same location. During winter 2015, two events caused the INP concentrations at RHw = 104 % to significantly increase above the campaign average. First, an increase to 72.1 std L-1 was measured during an event influenced by marine air, arriving at the JFJ from the North Sea and the Norwegian Sea. The contribution from anthropogenic or other

Inter-Relationship Between Subtropical Pacific Sea Surface Temperature, Arctic Sea Ice Concentration, and the North Atlantic Oscillation in Recent Summers and Winters

Science.gov (United States)

Lim, Young-Kwon; Cullather, Richard I.; Nowicki, Sophie M.; Kim, Kyu-Myong

2017-01-01

The inter-relationship between subtropical western-central Pacific sea surface temperatures (STWCPSST), sea ice concentration in the Beaufort Sea (SICBS), and the North Atlantic Oscillation (NAO) are investigated for the last 37 summers and winters (1980-2016). Lag-correlation of the STWCPSST×(-1) in spring with the NAO phase and SICBS in summer increases over the last two decades, reaching r = 0.4-0.5 with significance at 5 percent, while winter has strong correlations in approximately 1985-2005. Observational analysis and the atmospheric general circulation model experiments both suggest that STWCPSST warming acts to increase the Arctic geopotential height and temperature in the following season. This atmospheric response extends to Greenland, providing favorable conditions for developing the negative phase of the NAO. SIC and surface albedo tend to decrease over the Beaufort Sea in summer, linked to the positive surface net shortwave flux. Energy balance considering radiative and turbulent fluxes reveal that available energy that can heat surface is larger over the Arctic and Greenland and smaller over the south of Greenland, in response to the STWCPSST warming in spring. XXXX Arctic & Atlantic: Positive upper-level height/T anomaly over the Arctic and Greenland, and a negative anomaly over the central-eastern Atlantic, resembling the (-) phase of the NAO. Pacific: The negative height/T anomaly over the mid-latitudes, along with the positive anomaly over the STWCP, where 1degC warming above climatology is prescribed. Discussion: It is likely that the Arctic gets warm and the NAO is in the negative phase in response to the STWCP warming. But, there are other factors (e.g., internal variability) that contribute to determination of the NAO phase: not always the negative phase of the NAO in the event of STWCP warming (e.g.: recent winters and near neutral NAO in 2017 summer).

Titan's Stratospheric Condensibles at High Northern Latitudes During Northern Winter

Science.gov (United States)

Anderson, Carrie; Samuelson, R.; Achterberg, R.

2012-01-01

The Infrared Interferometer Spectrometer (IRIS) instrument on board Voyager 1 caught the first glimpse of an unidentified particulate feature in Titan's stratosphere that spectrally peaks at 221 per centimeter. Until recently, this feature that we have termed 'the haystack,' has been seen persistently at high northern latitudes with the Composite Infrared Spectrometer (CIRS) instrument onboard Cassini, The strength of the haystack emission feature diminishes rapidly with season, becoming drastically reduced at high northern latitudes, as Titan transitions from northern winter into spring, In contrast to IRIS whose shortest wavenumber was 200 per centimeter, CIRS extends down to 10 per centimeter, thus revealing an entirely unexplored spectral region in which nitrile ices have numerous broad lattice vibration features, Unlike the haystack, which is only found at high northern latitudes during northern winter/early northern spring, this geometrically thin nitrile cloud pervades Titan's lower stratosphere, spectrally peaking at 160 per centimeter, and is almost global in extent spanning latitudes 85 N to 600 S, The inference of nitrile ices are consistent with the highly restricted altitude ranges over which these features are observed, and appear to be dominated by a mixture of HCN and HC3N, The narrow range in altitude over which the nitrile ices extend is unlike the haystack, whose vertical distribution is significantly broader, spanning roughly 70 kilometers in altitude in Titan's lower stratosphere, The nitrile clouds that CIRS observes are located in a dynamically stable region of Titan's atmosphere, whereas CH4 clouds, which ordinarily form in the troposphere, form in a more dynamically unstable region, where convective cloud systems tend to occur. In the unusual situation where Titan's tropopause cools significantly from the HASI 70.5K temperature minimum, CH4 should condense in Titan's lower stratosphere, just like the aforementioned nitrile clouds, although

Arctic sea ice a major determinant in Mandt's black guillemot movement and distribution during non-breeding season

Science.gov (United States)

Divoky, G.J.; Douglas, David C.; Stenhouse, I. J.

2016-01-01

Mandt's black guillemot (Cepphus grylle mandtii) is one of the few seabirds associated in all seasons with Arctic sea ice, a habitat that is changing rapidly. Recent decreases in summer ice have reduced breeding success and colony size of this species in Arctic Alaska. Little is known about the species' movements and distribution during the nine month non-breeding period (September–May), when changes in sea ice extent and composition are also occurring and predicted to continue. To examine bird movements and the seasonal role of sea ice to non-breeding Mandt's black guillemots, we deployed and recovered (n = 45) geolocators on individuals at a breeding colony in Arctic Alaska during 2011–2015. Black guillemots moved north to the marginal ice zone (MIZ) in the Beaufort and Chukchi seas immediately after breeding, moved south to the Bering Sea during freeze-up in December, and wintered in the Bering Sea January–April. Most birds occupied the MIZ in regions averaging 30–60% sea ice concentration, with little seasonal variation. Birds regularly roosted on ice in all seasons averaging 5 h d−1, primarily at night. By using the MIZ, with its roosting opportunities and associated prey, black guillemots can remain in the Arctic during winter when littoral waters are completely covered by ice.

Breakup ice control structure for the Salmon River in Connecticut

International Nuclear Information System (INIS)

Tuthill, A.M.; White, K.D.

1997-01-01

The Salmon River ice jam problem was investigated and a conceptual design for a breakup ice control structure was developed. Historical ice jam events were reviewed and an ice observation program was conducted during the winter of 1994-95. The factors affecting ice jam frequency and severity were examined. The factors included daily temperature, rainfall quantity and intensity, Salmon River stage and discharge, and Connecticut River tide levels. First, a numerical model was developed to simulate a worst case scenario for ice jams, followed by a conceptual design for a concrete pier ice control structure under two ice breakup scenarios. The first scenario assumed that a semi-intact ice sheet would rest against the piers and retain a floating equilibrium jam upstream, allowing water discharge to pass beneath. The second scenario was based on the assumption that a grounded ice jam in direct contact with the piers would divert water flow around the structure via an armored channel in the overbank area. An ice retention structure consisting of a row of concrete piers, spaced across the main channel, 60 m upstream of an existing dam, was proposed. 11 refs., 6 figs

Warming in the Nordic Seas, North Atlantic storms and thinning Arctic sea ice

Science.gov (United States)

Alexeev, Vladimir A.; Walsh, John E.; Ivanov, Vladimir V.; Semenov, Vladimir A.; Smirnov, Alexander V.

2017-08-01

Arctic sea ice over the last few decades has experienced a significant decline in coverage both in summer and winter. The currently warming Atlantic Water layer has a pronounced impact on sea ice in the Nordic Seas (including the Barents Sea). More open water combined with the prevailing atmospheric pattern of airflow from the southeast, and persistent North Atlantic storms such as the recent extremely strong Storm Frank in December 2015, lead to increased energy transport to the high Arctic. Each of these storms brings sizeable anomalies of heat to the high Arctic, resulting in significant warming and slowing down of sea ice growth or even melting. Our analysis indicates that the recently observed sea ice decline in the Nordic Seas during the cold season around Svalbard, Franz Joseph Land and Novaya Zemlya, and the associated heat release from open water into the atmosphere, contributed significantly to the increase in the downward longwave radiation throughout the entire Arctic. Added to other changes in the surface energy budget, this increase since the 1960s to the present is estimated to be at least 10 W m-2, which can result in thinner (up to at least 15-20 cm) Arctic ice at the end of the winter. This change in the surface budget is an important contributing factor accelerating the thinning of Arctic sea ice.

Sub-daily sea ice motion and deformation from RADARSAT observations

Science.gov (United States)

Kwok, R.; Cunningham, G. F.

2003-01-01

We find a persistent level of oscillatory sea ice motion and deformation, superimposed on the large-scale wind-driven field, in May 2002 (spring) and February 2003 (mid-winter), in the high Arctic over a region centered at approx.(85degreeN, 135degreeW). At this latitude, the RADARSAT wide-swath SAR coverage provides 4??equential observations every day, for ice motion retrieval, with a sampling interval at the orbital period of approx. 101 minutes.

The History of Winter: A Professional Development "Teacher as Scientist" Experiential Learning Field Experience.

Science.gov (United States)

Gabrys, R. E.

2007-12-01

Each year since 2000, the NASA Goddard History of Winter (HOW) program has allowed teachers to develop an understanding of the consequences of one segment of the orbit of the tilted Earth in its path around the sun. Scientists from NASA, CRREL, and Michigan Tech, supported by the Whiteface Observatory, and the science program at Northwood School in Lake Placid, New York, use the weather and the stratigraphy in the ice and snow, consequences of the weather changes, as "teachers" in a team study of the winter record. Snow in the air and on the ground, ice, its crystal structure and axial orientation, and the ecosystem consequences of snow and ice constitute the weeklong content package. Teacher Professional Development Standards A, B, C, and D were the guiding principles in developing HOW with a content structure formulated as protocols to serve as inserts into lesson plans and inquiry guides. The concept of HOW within NASA is to provide understanding of the WHY? and WHAT? of satellite remote sensing. The content is appropriate ground validation in that techniques presented in protocols are identical to those used by professionals who study snow pits, evaluate features in snow metamorphism, and study thin sections of ice cores drilled in ice caps and glaciers. The HOW Teacher as scientist (TAS) model is a flexible model. HOW enables teachers who are required to use inquiry-based facilitation in the classroom to experience inquiry themselves. Teachers with little science content background as well as those with Science degrees have participated in HOW working alongside of the science team. Accommodations are made through differentiation of instruction so that each group leaves with a mastery of the content that is appropriate for the transition to presentation in the classroom. Each year builds on the previous year ensuring a time series record of the history of winter-by itself a learning experience. An offshoot of the NASA Goddard Center History of Winter (HOW

Ice issues relating to the Kashagan phase II development, North Caspian Sea.

Energy Technology Data Exchange (ETDEWEB)

Croasdale, Ken [KRCA, Calgary (Canada); Verlaan, Paul [Shell Development Kashagan, London (United Kingdom)

2011-07-01

The ice conditions in the north Caspian Sea are challenging for the Kashagan field development. The climatic conditions of the area are extreme, with cold winters (-30 degrees C) and hot summers (+40 degrees C). The presence and the quantity of ice are also highly variable from year to year. This paper investigated the major ice-related issues affecting the Kashagan structures and pipelines. An extensive description of the ice environment was provided. Ice design criteria for the offshore rock islands, the pipelines and the layout of the ice protection barriers around the islands were presented. It was found that the ice design methods used in Arctic areas have required some adaptations to meet Caspian conditions. All the islands were designed with an ice encroachment zone to reduce the hazardous effect of the ice rubble encroaching. Rock sloped barriers and steel barriers were implanted around the islands to protect the logistical areas.

Is there a see-saw over an ice-free Arctic Ocean?

Science.gov (United States)

Stendel, Martin; Yang, Shuting; Langen, Peter; Rodehacke, Christian; Mottram, Ruth; Hesselbjerg Christensen, Jens

2017-04-01

The "see-saw" in winter temperatures between western Greenland and the Canadian Arctic on one side and northern Europe on the other has been described by Loewe already in 1937, but actually this behaviour was at least known since the Danish colonization of Greenland in the early 18th century. The see-saw is associated with pressure anomalies not only near the region of interest, but as remote as the Mediterranean and the North Pacific. Recent research has pointed out the role of sea ice in maintaining the see-saw in either its warm or its cold phase over extended periods, which strongly affects European winter temperatures. What would happen to the seesaw if Arctic sea ice were to disappear suddenly? In the framework of the FP7-funded project ice2ice, we try to answer this and related questions. We have conducted a very long global simulation with a global climate model interactively coupled to a Greenland ice sheet component, covering the period 1850-3250 at a horizontal resolution of approximately 125 km. Up to 2005, the forcing is from observed greenhouse gas concentrations, and from 2006 onward it follows the extended RCP8.5 scenario, in which greenhouse gas concentrations continue to increase and eventually level out around 2250. With such a strong forcing, all Arctic sea ice has completely disappeared by roughly the same time, and the surface mass balance of the Greenland Ice Sheet becomes strongly negative. We investigate how the see-saw behaves in such an ice-free world and which implications circulation changes have in the Arctic and over Europe. To further elucidate the role of sea ice distribution on the atmospheric flow and the role of surface fluxes in maintaining the Greenland-European see-saw, we intend at a later time to expand our analysis to include a contrasting simulation with both western Greenland and northern Europe covered by ice during the Last Glacier Maximum.

Potential ocean–atmosphere preconditioning of late autumn Barents-Kara sea ice concentration anomaly

Directory of Open Access Journals (Sweden)

Martin P. King

2016-02-01

Full Text Available Many recent studies have revealed the importance of the climatic state in November on the seasonal climate of the subsequent winter. In particular, it has been shown that interannual variability of sea ice concentration (SIC over the Barents-Kara (BK seas in November is linked to winter atmospheric circulation anomaly that projects on the North Atlantic Oscillation. Understanding the lead–lag processes involving the different components of the climate system from autumn to winter is therefore important. This note presents dynamical interpretation for the ice-ocean–atmosphere relationships that can affect the BK SIC anomaly in late autumn. It is found that cyclonic (anticyclonic wind anomaly over the Arctic in October, by Ekman drift, can be responsible for positive (negative SIC in the BK seas in November. The results also suggest that ocean heat transport via the Barents Sea Opening in September and October can contribute to BK SIC anomaly in November.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone

Science.gov (United States)

Lee, C.; Rainville, L.; Gobat, J. I.; Perry, M. J.; Freitag, L. E.; Webster, S.

2016-12-01

The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer and Atlantic waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, how the balance of processes shift as a function of ice fraction and distance from open water, and how these processes impact sea ice evolution, a network of autonomous platforms sampled the atmosphere-ice-ocean system in the Beaufort, beginning in spring, well before the start of melt, and ending with the autumn freeze-up. Four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Gliders penetrated up to 200 km into the ice pack, under complete ice cover for up to 10 consecutive days. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse late in the season as they progress through the MIZ and into open water. Stratification just above the Pacific Summer Water rapidly weakens near the ice edge and temperature variance increases, likely due to mixing or energetic vertical exchange associated with strong

Brief Communication: Mapping river ice using drones and structure from motion

Science.gov (United States)

Alfredsen, Knut; Haas, Christian; Tuhtan, Jeffrey A.; Zinke, Peggy

2018-02-01

In cold climate regions, the formation and break-up of river ice is important for river morphology, winter water supply, and riparian and instream ecology as well as for hydraulic engineering. Data on river ice is therefore significant, both to understand river ice processes directly and to assess ice effects on other systems. Ice measurement is complicated due to difficult site access, the inherent complexity of ice formations, and the potential danger involved in carrying out on-ice measurements. Remote sensing methods are therefore highly useful, and data from satellite-based sensors and, increasingly, aerial and terrestrial imagery are currently applied. Access to low cost drone systems with quality cameras and structure from motion software opens up a new possibility for mapping complex ice formations. Through this method, a georeferenced surface model can be built and data on ice thickness, spatial distribution, and volume can be extracted without accessing the ice, and with considerably fewer measurement efforts compared to traditional surveying methods. A methodology applied to ice mapping is outlined here, and examples are shown of how to successfully derive quantitative data on ice processes.

Estimates of Ice Sheet Mass Balance from Satellite Altimetry: Past and Future

Science.gov (United States)

Zwally, H. Jay; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

A major uncertainty in predicting sea level rise is the sensitivity of ice sheet mass balance to climate change, as well as the uncertainty in present mass balance. Since the annual water exchange is about 8 mm of global sea level equivalent, the 20% uncertainty in current mass balance corresponds to 1.6 mm/yr in sea level change. Furthermore, estimates of the sensitivity of the mass balance to temperature change range from perhaps as much as - 10% to + 10% per K. A principal purpose of obtaining ice sheet elevation changes from satellite altimetry has been estimation of the current ice sheet mass balance. Limited information on ice sheet elevation change and their implications about mass balance have been reported by several investigators from radar altimetry (Seasat, Geosat, ERS-1&2). Analysis of ERS-1&2 data over Greenland for 7 years from 1992 to 1999 shows mixed patterns of ice elevation increases and decreases that are significant in terms of regional-scale mass balances. Observed seasonal and interannual variations in ice surface elevation are larger than previously expected because of seasonal and interannUal variations in precipitation, melting, and firn compaction. In the accumulation zone, the variations in firn compaction are modeled as a function of temperature leaving variations in precipitation and the mass balance trend. Significant interannual variations in elevation in some locations, in particular the difference in trends from 1992 to 1995 compared to 1995 to 1999, can be explained by changes in precipitation over Greenland. Over the 7 years, trends in elevation are mostly positive at higher elevations and negative at lower elevations. In addition, trends for the winter seasons (from a trend analysis through the average winter elevations) are more positive than the corresponding trends for the summer. At lower elevations, the 7-year trends in some locations are strongly negative for summer and near zero or slightly positive for winter. These

Сomputational and experimental researches of ice pieces impact against a plate-imitator of a blade airfoil of an aircraft engine axial compressor

Directory of Open Access Journals (Sweden)

B. F. Shorr

2014-01-01

Full Text Available Ingestion of hailstones and shedding ice in operating aircraft engine can lead to damage of compressor rotating blades, as well as to change of gas-dynamic characteristics, and loss of engine thrust.The paper presents a computational and experimental study results of an ice impact against a thin edge of the steel plate, which simulates a compressor blade.Impacts of the ice bricks against the plate with a velocity corresponding to the circumference rate of blades rotation were realized by the pneumatic gunshots. The trials were carried out under various angles attack between the direction of the ice flight and the plate plane. The experiments has shown that on impact the ice brick is covered by numerous cracks and collapsed just at the very beginning of the interaction with a plate. Thus, a leading edge of the plate has a smoothly bending form without appearing cracks.For modeling the ice an isotropic elastoplastic material was chosen. Its failure was based on shear and rupture criteria. Two models of ice with different size of the yield point were used.The test results and their comparison with the numerical ones have shown the following: 1. Calculations of brick impact against a thin edge of the plate-imitator with accepted ice characteristics yield a correct qualitative picture of the plate damage, but lead to some undersizes of its leading edge bending.2. The ice design model with a larger yield point well reflects a character of the ice brick impact destruction as a formation of numerous cracks in it and splitting the piece into small particles, which was observed in the experiments. The model with smaller yield point shows the ice brick cutting into two parts without cracking.3. The plate damage considerably increases with increasing ice brick attack angle. Under a direct impact against the plate edge, the ice brick is cut into two halves, with no plastic deformations of the plate observed.4. Available results give the grounds to use

Evaluation of the limit ice thickness for the hull of various Finnish-Swedish ice class vessels navigating in the Russian Arctic

Directory of Open Access Journals (Sweden)

Pentti Kujala

2018-05-01

Full Text Available Selection of suitable ice class for ships operation is an important but not simple task. The increased exploitation of the Polar waters, both seasonal periods and geographical areas, as well as the introduction of new international design standards such as Polar Code, reduces the relevancy of using existing experience as basis for the selection, and new methods and knowledge have to be developed. This paper will analyse what can be the limiting ice thickness for ships navigating in the Russian Arctic and designed according to the Finnish-Swedish ice class rules. The permanent deformations of ice-strengthened shell structures for various ice classes is determined using MT Uikku as the typical size of a vessel navigating in ice. The ice load in various conditions is determined using the ARCDEV data from the winter 1998 as the basic database. By comparing the measured load in various ice conditions with the serviceability limit state of the structures, the limiting ice thickness for various ice classes is determined. The database for maximum loads includes 3-weeks ice load measurements during April 1998 on the Kara Sea mainly by icebreaker assistance. Gumbel 1 distribution is fitted on the measured 20 min maximum values and the data is divided into various classes using ship speed, ice thickness and ice concentration as the main parameters. Results encouragingly show that present designs are safer than assumed in the Polar Code suggesting that assisted operation in Arctic conditions is feasible in rougher conditions than indicated in the Polar Code. Keywords: Loads, Serviceability, Limit ice thickness, Polar code

Ice-Ocean Interactions to the North-West of Greenland: Glaciers, Straits, Ice Bridges, and the Rossby Radius (Invited)

Science.gov (United States)

Muenchow, A.; Falkner, K. K.; Melling, H.; Johnson, H. L.; Huntley, H. S.; Ryan, P.; Friends Of Petermann

2010-12-01

Petermann Glacier at 81 N latitude is a major outlet glacier adjacent to Nares Strait. It terminates in a long (70 km), narrow (16 km) and thin (50 m) floating tongue and has a grounding line more than 500 m below sea level. A calving event in 2010 reduced the floating area by 25% and produced a single 240 km2 ice island currently moving south in Nares Strait where it will likely interact with island to potentially create a temporary polynya in Nares Strait. The 2010 calving from Petermann Glacier contributes bridge formed regularly at the southern end of Nares Strait creating the North-Water polynya near 79 N latitude. Since 2006 this ice bridge has largely failed to form, leading, perhaps, to the occasional formation of a secondary ice bridge 300 km to the north where Nares Strait connects to the Arctic Ocean. However, this ice bridge appears to form for shorter periods only. Consequently Arctic sea ice can now exit the Arctic in winter via pathways to the west of Greenland all year. We speculate that this changed ocean and sea ice regime in Nares Strait and the Arctic Ocean may contribute to the recently observed calving events in Petermann Fjord.

The emergence of modern sea ice cover in the Arctic Ocean.

Science.gov (United States)

Knies, Jochen; Cabedo-Sanz, Patricia; Belt, Simon T; Baranwal, Soma; Fietz, Susanne; Rosell-Melé, Antoni

2014-11-28

Arctic sea ice coverage is shrinking in response to global climate change and summer ice-free conditions in the Arctic Ocean are predicted by the end of the century. The validity of this prediction could potentially be tested through the reconstruction of the climate of the Pliocene epoch (5.33-2.58 million years ago), an analogue of a future warmer Earth. Here we show that, in the Eurasian sector of the Arctic Ocean, ice-free conditions prevailed in the early Pliocene until sea ice expanded from the central Arctic Ocean for the first time ca. 4 million years ago. Amplified by a rise in topography in several regions of the Arctic and enhanced freshening of the Arctic Ocean, sea ice expanded progressively in response to positive ice-albedo feedback mechanisms. Sea ice reached its modern winter maximum extension for the first time during the culmination of the Northern Hemisphere glaciation, ca. 2.6 million years ago.

Assessing the performance of winter footwear using a new maximum achievable incline method.

Science.gov (United States)

Hsu, Jennifer; Li, Yue; Dutta, Tilak; Fernie, Geoff

2015-09-01

More informative tests of winter footwear performance are required in order to identify footwear that will prevent injurious slips and falls on icy conditions. In this study, eight participants tested four styles of winter boots on smooth wet ice. The surface was progressively tilted to create increasing longitudinal and cross-slopes until participants could no longer continue standing or walking. Maximum achievable incline angles provided consistent measures of footwear slip resistance and demonstrated better resolution than mechanical tests. One footwear outsole material and tread combination outperformed the others on wet ice allowing participants to successfully walk on steep longitudinal slopes of 17.5° ± 1.9° (mean ± SD). By further exploiting the methodology to include additional surfaces and contaminants, such tests could be used to optimize tread designs and materials that are ideal for reducing the risk of slips and falls. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

The refreezing of melt ponds on Arctic sea ice

Science.gov (United States)

Flocco, Daniela; Feltham, Daniel L.; Bailey, Eleanor; Schroeder, David

2015-02-01

The presence of melt ponds on the surface of Arctic sea ice significantly reduces its albedo, inducing a positive feedback leading to sea ice thinning. While the role of melt ponds in enhancing the summer melt of sea ice is well known, their impact on suppressing winter freezing of sea ice has, hitherto, received less attention. Melt ponds freeze by forming an ice lid at the upper surface, which insulates them from the atmosphere and traps pond water between the underlying sea ice and the ice lid. The pond water is a store of latent heat, which is released during refreezing. Until a pond freezes completely, there can be minimal ice growth at the base of the underlying sea ice. In this work, we present a model of the refreezing of a melt pond that includes the heat and salt balances in the ice lid, trapped pond, and underlying sea ice. The model uses a two-stream radiation model to account for radiative scattering at phase boundaries. Simulations and related sensitivity studies suggest that trapped pond water may survive for over a month. We focus on the role that pond salinity has on delaying the refreezing process and retarding basal sea ice growth. We estimate that for a typical sea ice pond coverage in autumn, excluding the impact of trapped ponds in models overestimates ice growth by up to 265 million km3, an overestimate of 26%.

Inception of the Laurentide Ice Sheet using asynchronous coupling of a regional atmospheric model and an ice model

Science.gov (United States)

Birch, L.; Cronin, T.; Tziperman, E.

2017-12-01

The climate over the past 0.8 million years has been dominated by ice ages. Ice sheets have grown about every 100 kyrs, starting from warm interglacials, until they spanned continents. State-of-the-art global climate models (GCMs) have difficulty simulating glacial inception, or the transition of Earth's climate from an interglacial to a glacial state. It has been suggested that this failure may be related to their poorly resolved local mountain topography, due to their coarse spatial resolution. We examine this idea as well as the possible role of ice flow dynamics missing in GCMs. We investigate the growth of the Laurentide Ice Sheet at 115 kya by focusing on the mountain glaciers of Canada's Baffin Island, where geologic evidence indicates the last inception occurred. We use the Weather Research and Forecasting model (WRF) in a regional, cloud-resolving configuration with resolved mountain terrain to explore how quickly Baffin Island could become glaciated with the favorable yet realizable conditions of 115 kya insolation, cool summers, and wet winters. Using the model-derived mountain glacier mass balance, we force an ice sheet model based on the shallow-ice approximation, capturing the ice flow that may be critical to the spread of ice sheets away from mountain ice caps. The ice sheet model calculates the surface area newly covered by ice and the change in the ice surface elevation, which we then use to run WRF again. Through this type of iterated asynchronous coupling, we investigate how the regional climate responds to both larger areas of ice cover and changes in ice surface elevation. In addition, we use the NOAH-MP Land model to characterize the importance of land processes, like refreezing. We find that initial ice growth on the Penny Ice Cap causes regional cooling that increases the accumulation on the Barnes Ice Cap. We investigate how ice and topography changes on Baffin Island may impact both the regional climate and the large-scale circulation.

Proceedings of the 15. CRIPE workshop on the hydraulics of ice covered rivers

Energy Technology Data Exchange (ETDEWEB)

Hicks, F. [Alberta Univ., Edmonton, AB (Canada). Dept. of Civil and Environmental Engineering] (comp.)

2009-07-01

This workshop focused on the hydraulic aspects of river ice phenomena and the effects of ice cover on flow characteristics. Ice processes play a large role in the hydrologic regime of Canadian rivers and are related to the life cycle of aquatic, terrestrial, and avian species. The most serious impacts of river ice occur during ice-jam flooding, affecting the winter operation of hydroelectric power plants and sometimes resulting in the loss of property and human life. The conference addressed these concerns as well as environmental aspects of river ice, and climatic change. The Committee on River Ice Processes and the Environment (CRIPE) identifies high-priority topics for research and development and promotes research programs at Canadian colleges and universities. In addition to a poster session, the workshop included sessions on ice measurement; freeze-up and frazil; ice processes and the environment; ice hydraulics; ice and river regulation; ice jams and breakup forecasting; ice and infrastructure; and remote sensing. The workshop featured 35 presentations, of which 3 have been catalogued separately for inclusion in this database. refs., tabs., figs.

Proceedings of the 15. CRIPE workshop on the hydraulics of ice covered rivers

International Nuclear Information System (INIS)

Hicks, F.

2009-01-01

This workshop focused on the hydraulic aspects of river ice phenomena and the effects of ice cover on flow characteristics. Ice processes play a large role in the hydrologic regime of Canadian rivers and are related to the life cycle of aquatic, terrestrial, and avian species. The most serious impacts of river ice occur during ice-jam flooding, affecting the winter operation of hydroelectric power plants and sometimes resulting in the loss of property and human life. The conference addressed these concerns as well as environmental aspects of river ice, and climatic change. The Committee on River Ice Processes and the Environment (CRIPE) identifies high-priority topics for research and development and promotes research programs at Canadian colleges and universities. In addition to a poster session, the workshop included sessions on ice measurement; freeze-up and frazil; ice processes and the environment; ice hydraulics; ice and river regulation; ice jams and breakup forecasting; ice and infrastructure; and remote sensing. The workshop featured 35 presentations, of which 3 have been catalogued separately for inclusion in this database. refs., tabs., figs.

Preconditioning of Antarctic maximum sea-ice extent by upper-ocean stratification on a seasonal timescale

OpenAIRE

Su, Zhan

2017-01-01

This study uses an observationally constrained and dynamically consistent ocean and sea ice state estimate. The author presents a remarkable agreement between the location of the edge of Antarctic maximum sea ice extent, reached in September, and the narrow transition band for the upper ocean (0–100 m depths) stratification, as early as April to June. To the south of this edge, the upper ocean has high stratification, which forbids convective fluxes to cross through; consequently, the ocean h...

Surfacing behavior and gas release of the physostome sprat (Sprattus sprattus) in ice-free and ice-covered waters

KAUST Repository

Solberg, Ingrid

2013-10-04

Upward-facing echosounders that provided continuous, long-term measurements were applied to address the surfacing behavior and gas release of the physostome sprat (Sprattus sprattus) throughout an entire winter in a 150-m-deep Norwegian fjord. During ice-free conditions, the sprat surfaced and released gas bubbles at night with an estimated surfacing rate of 3.5 times per fish day-1. The vertical swimming speeds during surfacing were considerably higher (~10 times) than during diel vertical migrations, especially when returning from the surface, and particularly when the fjord was not ice covered. The sprat released gas a few hours after surfacing, suggesting that the sprat gulped atmospheric air during its excursions to the surface. While the surface activity increased after the fjord became ice covered, the records of gas release decreased sharply. The under-ice fish then displayed a behavior interpreted as "searching for the surface" by repeatedly ascending toward the ice, apparently with limited success of filling the swim bladder. This interpretation was supported by lower acoustic target strength in ice-covered waters. The frequent surfacing behavior demonstrated in this study indicates that gulping of atmospheric air is an important element in the life of sprat. While at least part of the population endured overwintering in the ice-covered habitat, ice covering may constrain those physostome fishes that lack a gas-generating gland in ways that remain to be established. 2013 The Author(s).

Distribution and migrations of cetaceans in the Russian Arctic according to observations from aerial ice reconnaissance

Directory of Open Access Journals (Sweden)

Stanislav E Belikov

2002-07-01

Full Text Available This paper is based on 748 observations of belugas (Delphinapterus leucas and 382 observations of baleen whales in the Russian Arctic, the majority of the data provided by aerial reconnaissance of sea ice (ARSI. Although the data are not suitable for the estimation of the number and density of the animals, they represent a multi-year (1958-1995 range of observations to update our knowledge on the seasonal distribution and migrations of the species. Belugas inhabit not only shelf waters but also the zone of the shelf slope and the abyssal zone of the Arctic Ocean, where the animals appear mostly in summer. In winter belugas were observed only in the Barents Sea. In June-August, the frequency of beluga observations was highest in the Laptev Sea, which has previously been believed to have considerably lower numbers of beluga than the Kara and Barents seas. Patterns of seasonal distribution and ice cover suggest the existence of a natural border preventing or reducing population exchange between belugas inhabiting the western and eastern parts of the Russian Arctic. A brief review of available data on distribution of the narwhal (Monodon monoceros in the Russian Arctic is also given. Two species of baleen whales were frequently seen in the Russian Arctic: the bowhead whale (Balaena mysticetus, and the grey whale (Eschrichtius robustus. The majority of such observations were made in the southeastern part of the East-Siberian Sea and the southern part of the Chukchi Sea. In the Bering Sea baleen whales were usually seen near the Chukotka Peninsula, in Anadyr Bay and southeast of it. Whales were usually seen in ice-free water: observations of whales among rarefied ice and near the ice edge were rare. There were considerable annual and seasonal variations in distribution and migrations of baleen whales in the region, probably caused mainly by the dynamics of ice conditions.

Management of Low-Flow Priapism Using the Winter Procedure: A Case Report

Directory of Open Access Journals (Sweden)

Chung-Chin Chen

2003-02-01

Full Text Available Priapism is a prolonged penile erection that is unrelated to sexual stimulation. Low-flow priapism has been associated with sickle cell disease and other hemoglobinopathies, neoplastic syndrome, anticoagulant therapy, psychotropic medication, and idiopathic causes. We report the successful treatment of idiopathic low-flow priapism using the Winter procedure. Initial treatment consisted of aspiration and intracavernous irrigation with iced saline and a vasoconstrictive agent, but in vain. We then performed the Winter procedure, in which fistulas between the corpora cavernosa and the glans penis were created. This resulted in the simultaneous detumescence of the penis, without complication. The erectile function of the penis was normal 1 year after the procedure. This case shows that idiopathic low-flow priapism can be successfully treated using the Winter procedure when conservative treatment fails.

The Horizontal Ice Nucleation Chamber (HINC: INP measurements at conditions relevant for mixed-phase clouds at the High Altitude Research Station Jungfraujoch

Directory of Open Access Journals (Sweden)

L. Lacher

2017-12-01

Full Text Available In this work we describe the Horizontal Ice Nucleation Chamber (HINC as a new instrument to measure ambient ice-nucleating particle (INP concentrations for conditions relevant to mixed-phase clouds. Laboratory verification and validation experiments confirm the accuracy of the thermodynamic conditions of temperature (T and relative humidity (RH in HINC with uncertainties in T of ±0.4 K and in RH with respect to water (RHw of ±1.5 %, which translates into an uncertainty in RH with respect to ice (RHi of ±3.0 % at T > 235 K. For further validation of HINC as a field instrument, two measurement campaigns were conducted in winters 2015 and 2016 at the High Altitude Research Station Jungfraujoch (JFJ; Switzerland, 3580 m a. s. l.  to sample ambient INPs. During winters 2015 and 2016 the site encountered free-tropospheric conditions 92 and 79 % of the time, respectively. We measured INP concentrations at 242 K at water-subsaturated conditions (RHw = 94 %, relevant for the formation of ice clouds, and in the water-supersaturated regime (RHw = 104 % to represent ice formation occurring under mixed-phase cloud conditions. In winters 2015 and 2016 the median INP concentrations at RHw = 94 % was below the minimum detectable concentration. At RHw = 104 %, INP concentrations were an order of magnitude higher, with median concentrations in winter 2015 of 2.8 per standard liter (std L−1; normalized to standard T of 273 K and pressure, p, of 1013 hPa and 4.7 std L−1 in winter 2016. The measurements are in agreement with previous winter measurements obtained with the Portable Ice Nucleation Chamber (PINC of 2.2 std L−1 at the same location. During winter 2015, two events caused the INP concentrations at RHw = 104 % to significantly increase above the campaign average. First, an increase to 72.1 std L−1 was measured during an event influenced by marine air, arriving at the JFJ

Calculation of near-edge x-ray-absorption fine structure at finite temperatures: Spectral signatures of hydrogen bond breaking in liquid water

International Nuclear Information System (INIS)

Hetenyi, Balazs; De Angelis, Filippo; Giannozzi, Paolo; Car, Roberto

2004-01-01

We calculate the near-edge x-ray-absorption fine structure of H 2 O in the gas, hexagonal ice, and liquid phases using heuristic density-functional based methods. We present a detailed comparison of our results with experiment. The differences between the ice and water spectra can be rationalized in terms of the breaking of hydrogen bonds around the absorbing molecule. In particular the increase in the pre-edge absorption feature from ice to water is shown to be due to the breaking of a donor hydrogen bond. We also find that in water approximately 19% of hydrogen bonds are broken

Icing conditions over Northern Eurasia in changing climate

International Nuclear Information System (INIS)

Bulygina, Olga N; Arzhanova, Natalia M; Groisman, Pavel Ya

2015-01-01

Icing conditions, particularly in combination with wind, affect greatly the operation of overhead communication and transmission lines causing serious failures, which result in tremendous economic damage. Icing formation is dangerous to agriculture, forestry, high seas fishery, for land and off coast man-made infrastructure. Quantitative icing characteristics such as weight, thickness, and duration are very important for the economy and human wellbeing when their maximum values exceed certain thresholds. Russian meteorological stations perform both visual and instrumental monitoring of icing deposits. Visual monitoring is ocular estimation of the type and intensity of icing and the date of ice appearance and disappearance. Instrumental monitoring is performed by ice accretion indicator that in addition to the type, intensity and duration of ice deposits reports also their weight and size. We used observations at 958 Russian stations for the period 1977–2013 to analyze changes in the ice formation frequency at individual meteorological stations and on the territory of quasi-homogeneous climatic regions in Russia. It was found that hoar frosts are observed in most parts of Russia, but icing only occurs in European Russia and the Far East. On the Arctic coast of Russia, this phenomenon can even be observed in summer months. Statistically significant decreasing trends in occurrence of icing and hoar frost events are found over most of Russia. An increasing trend in icing weights (IWs) was found in the Atlantic Arctic region in autumn. Statistically significant large negative trends in IWs were found in the Pacific Arctic in winter and spring. (letter)

Sea ice in the Baltic Sea - revisiting BASIS ice, a~historical data set covering the period 1960/1961-1978/1979

Science.gov (United States)

Löptien, U.; Dietze, H.

2014-06-01

The Baltic Sea is a seasonally ice-covered, marginal sea, situated in central northern Europe. It is an essential waterway connecting highly industrialised countries. Because ship traffic is intermittently hindered by sea ice, the local weather services have been monitoring sea ice conditions for decades. In the present study we revisit a historical monitoring data set, covering the winters 1960/1961. This data set, dubbed Data Bank for Baltic Sea Ice and Sea Surface Temperatures (BASIS) ice, is based on hand-drawn maps that were collected and then digitised 1981 in a joint project of the Finnish Institute of Marine Research (today Finish Meteorological Institute (FMI)) and the Swedish Meteorological and Hydrological Institute (SMHI). BASIS ice was designed for storage on punch cards and all ice information is encoded by five digits. This makes the data hard to access. Here we present a post-processed product based on the original five-digit code. Specifically, we convert to standard ice quantities (including information on ice types), which we distribute in the current and free Network Common Data Format (NetCDF). Our post-processed data set will help to assess numerical ice models and provide easy-to-access unique historical reference material for sea ice in the Baltic Sea. In addition we provide statistics showcasing the data quality. The website www.baltic-ocean.org hosts the post-prossed data and the conversion code. The data are also archived at the Data Publisher for Earth & Environmental Science PANGEA (doi:10.1594/PANGEA.832353).

Sea ice in the Baltic Sea - revisiting BASIS ice, a historical data set covering the period 1960/1961-1978/1979

Science.gov (United States)

Löptien, U.; Dietze, H.

2014-12-01

The Baltic Sea is a seasonally ice-covered, marginal sea in central northern Europe. It is an essential waterway connecting highly industrialised countries. Because ship traffic is intermittently hindered by sea ice, the local weather services have been monitoring sea ice conditions for decades. In the present study we revisit a historical monitoring data set, covering the winters 1960/1961 to 1978/1979. This data set, dubbed Data Bank for Baltic Sea Ice and Sea Surface Temperatures (BASIS) ice, is based on hand-drawn maps that were collected and then digitised in 1981 in a joint project of the Finnish Institute of Marine Research (today the Finnish Meteorological Institute (FMI)) and the Swedish Meteorological and Hydrological Institute (SMHI). BASIS ice was designed for storage on punch cards and all ice information is encoded by five digits. This makes the data hard to access. Here we present a post-processed product based on the original five-digit code. Specifically, we convert to standard ice quantities (including information on ice types), which we distribute in the current and free Network Common Data Format (NetCDF). Our post-processed data set will help to assess numerical ice models and provide easy-to-access unique historical reference material for sea ice in the Baltic Sea. In addition we provide statistics showcasing the data quality. The website http://www.baltic-ocean.org hosts the post-processed data and the conversion code. The data are also archived at the Data Publisher for Earth & Environmental Science, PANGAEA (doi:10.1594/PANGAEA.832353).

Radiocarbon and seismic evidence of ice-sheet extent and the last deglaciation on the mid-Norwegian continental shelf

International Nuclear Information System (INIS)

Rokoengen, Kaare; Frengstad, Bjoern

1999-01-01

Reconstruction of the ice extent and glacier chronology on the continental shelf off mid-Norway has been severely hampered by the lack of dates from the glacial deposits. Seismic interpretation and new accelerator mass spectrometer radiocarbon dates show that the ice sheet extended to the edge of the continental shelf at the last glacial maximum. The two youngest till units near the shelf edge were deposited about 15000 and 13500 BP. The results indicate that the ice sheet partly reached the shelf break as late as 11000 BP followed by a deglaciation of most of the continental shelf in less than 1000 years

Planning of traumatological hospital resources for a major winter sporting event as illustrated by the 2005 Winter Universiad.

Science.gov (United States)

Oberladstaetter, J; Kamelger, F S; Rosenberger, R; Dallapozza, Ch; Struve, P; Luger, T; Fink, Ch; Attal, R

2009-03-01

The 22nd Student World Winter Games took place in January 2005 in Innsbruck and Seefeld, Austria. Exactly 1,500 athletes of 50 nationalities competed in 69 events in ten winter sports. A total number of 750 functionaries, 800 volunteers and 85,000 spectators participated in the second largest winter sports event behind the Olympic winter games. The aim of this study was to evaluate the needed resources to ensure traumatological care for an event of that size. At the medical "call-center" all consultations, as well as patient data, diagnosis, and medical treatment were recorded using a preset protocol. Further, all patients treated in the University Hospital Innsbruck were registered with an emphasis on trauma patients. Forty-eight of 65 patients transported to the hospital as a result of the Universiade were trauma patients, 37 of whom were athletes. The gender distribution was 34:14 (m:f). Ice hockey players had the highest rate of injury (25% of all injured athletes), followed by alpine skiers (20.8% of injured athletes). The highest ISS was nine. Forty-three patients got ambulatory treatment, five were admitted to the hospital and surgical treatment was conducted in three cases. Mean patient number was 4.8 per day. No additional personnel, structural, or technical hospital resources were needed to accommodate a large winter sports event like the Universiad. Thus, a level-B trauma center with an emergency room and independent traumatological department with around the clock surgical capability seems to be sufficient to provide traumatological care for an event of this size if the possibility of patient transport to a larger facility exists in the case of catastrophic events.

Phytoplankton-bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge.

Science.gov (United States)

Bertrand, Erin M; McCrow, John P; Moustafa, Ahmed; Zheng, Hong; McQuaid, Jeffrey B; Delmont, Tom O; Post, Anton F; Sipler, Rachel E; Spackeen, Jenna L; Xu, Kai; Bronk, Deborah A; Hutchins, David A; Allen, Andrew E

2015-08-11

Southern Ocean primary productivity plays a key role in global ocean biogeochemistry and climate. At the Southern Ocean sea ice edge in coastal McMurdo Sound, we observed simultaneous cobalamin and iron limitation of surface water phytoplankton communities in late Austral summer. Cobalamin is produced only by bacteria and archaea, suggesting phytoplankton-bacterial interactions must play a role in this limitation. To characterize these interactions and investigate the molecular basis of multiple nutrient limitation, we examined transitions in global gene expression over short time scales, induced by shifts in micronutrient availability. Diatoms, the dominant primary producers, exhibited transcriptional patterns indicative of co-occurring iron and cobalamin deprivation. The major contributor to cobalamin biosynthesis gene expression was a gammaproteobacterial population, Oceanospirillaceae ASP10-02a. This group also contributed significantly to metagenomic cobalamin biosynthesis gene abundance throughout Southern Ocean surface waters. Oceanospirillaceae ASP10-02a displayed elevated expression of organic matter acquisition and cell surface attachment-related genes, consistent with a mutualistic relationship in which they are dependent on phytoplankton growth to fuel cobalamin production. Separate bacterial groups, including Methylophaga, appeared to rely on phytoplankton for carbon and energy sources, but displayed gene expression patterns consistent with iron and cobalamin deprivation. This suggests they also compete with phytoplankton and are important cobalamin consumers. Expression patterns of siderophore- related genes offer evidence for bacterial influences on iron availability as well. The nature and degree of this episodic colimitation appear to be mediated by a series of phytoplankton-bacterial interactions in both positive and negative feedback loops.

Winter-to-winter variations in indoor radon

International Nuclear Information System (INIS)

Mose, D.G.; Mushrush, G.W.; Kline, S.W.

1989-01-01

Indoor radon concentrations in northern Virginia and central Maryland show a strong dependence on weather. Winter tends to be associated with higher than average indoor radon, and summer with lower than average. However, compared to the winter of 1986-1987, the winter of 1987-1988 was warmer and drier. Consequently, winter-to-winter indoor radon decreased by about 25%. This winter-to-winter decrease is unexpectedly large, and simulates winter-to-summer variations that have been reported

Proceedings of the Canadian Institute's winter 2004/2005 conference on energy marketing strategies : proactively defend your energy portfolios from winter price spikes

International Nuclear Information System (INIS)

2004-01-01

This conference addressed the challenges facing energy markets with particular emphasis on the outlook of winter fuels and prices. It was attended by more than 50 energy marketing professionals representing petroleum producers, pipelines, wholesale marketers, storage companies, end users, banks and government. In order to plan portfolios and reduce risks to their bottom lines, buyers and sellers of energy must always be prepared for unexpected ice storms, major pipeline outages or geopolitical events. Merchants in the fuel supply chain depend on basic analysis, correlations and forecasts of supply/demand, transportation and inventory levels. The conference presented strategies and analysis on how commodity prices will move during the winter; North American supply/demand dynamics for natural gas, electricity, heating oils and natural gas liquids; the interplay of fuel storage and price; fuel switching and its impact on the market; portfolio planning; managing the link between weather and fuel prices; seasonal volatility; and, how liquefied natural gas (LNG) is affecting winter supply. The conference featured 16 presentations, of which 6 have been catalogued separately for inclusion in this database. tabs., figs

A novel method for automated grid generation of ice shapes for local-flow analysis

Science.gov (United States)

Ogretim, Egemen; Huebsch, Wade W.

2004-02-01

Modelling a complex geometry, such as ice roughness, plays a key role for the computational flow analysis over rough surfaces. This paper presents two enhancement ideas in modelling roughness geometry for local flow analysis over an aerodynamic surface. The first enhancement is use of the leading-edge region of an airfoil as a perturbation to the parabola surface. The reasons for using a parabola as the base geometry are: it resembles the airfoil leading edge in the vicinity of its apex and it allows the use of a lower apparent Reynolds number. The second enhancement makes use of the Fourier analysis for modelling complex ice roughness on the leading edge of airfoils. This method of modelling provides an analytical expression, which describes the roughness geometry and the corresponding derivatives. The factors affecting the performance of the Fourier analysis were also investigated. It was shown that the number of sine-cosine terms and the number of control points are of importance. Finally, these enhancements are incorporated into an automated grid generation method over the airfoil ice accretion surface. The validations for both enhancements demonstrate that they can improve the current capability of grid generation and computational flow field analysis around airfoils with ice roughness.

Future increases in Arctic precipitation linked to local evaporation and sea-ice retreat.

Science.gov (United States)

Bintanja, R; Selten, F M

2014-05-22

Precipitation changes projected for the end of the twenty-first century show an increase of more than 50 per cent in the Arctic regions. This marked increase, which is among the highest globally, has previously been attributed primarily to enhanced poleward moisture transport from lower latitudes. Here we use state-of-the-art global climate models to show that the projected increases in Arctic precipitation over the twenty-first century, which peak in late autumn and winter, are instead due mainly to strongly intensified local surface evaporation (maximum in winter), and only to a lesser degree due to enhanced moisture inflow from lower latitudes (maximum in late summer and autumn). Moreover, we show that the enhanced surface evaporation results mainly from retreating winter sea ice, signalling an amplified Arctic hydrological cycle. This demonstrates that increases in Arctic precipitation are firmly linked to Arctic warming and sea-ice decline. As a result, the Arctic mean precipitation sensitivity (4.5 per cent increase per degree of temperature warming) is much larger than the global value (1.6 to 1.9 per cent per kelvin). The associated seasonally varying increase in Arctic precipitation is likely to increase river discharge and snowfall over ice sheets (thereby affecting global sea level), and could even affect global climate through freshening of the Arctic Ocean and subsequent modulations of the Atlantic meridional overturning circulation.

Diagnosing sea ice from the north american multi model ensemble and implications on mid-latitude winter climate

Science.gov (United States)

Elders, Akiko; Pegion, Kathy

2017-12-01

Arctic sea ice plays an important role in the climate system, moderating the exchange of energy and moisture between the ocean and the atmosphere. An emerging area of research investigates how changes, particularly declines, in sea ice extent (SIE) impact climate in regions local to and remote from the Arctic. Therefore, both observations and model estimates of sea ice become important. This study investigates the skill of sea ice predictions from models participating in the North American Multi-Model Ensemble (NMME) project. Three of the models in this project provide sea-ice predictions. The ensemble average of these models is used to determine seasonal climate impacts on surface air temperature (SAT) and sea level pressure (SLP) in remote regions such as the mid-latitudes. It is found that declines in fall SIE are associated with cold temperatures in the mid-latitudes and pressure patterns across the Arctic and mid-latitudes similar to the negative phase of the Arctic Oscillation (AO). These findings are consistent with other studies that have investigated the relationship between declines in SIE and mid-latitude weather and climate. In an attempt to include additional NMME models for sea-ice predictions, a proxy for SIE is used to estimate ice extent in the remaining models, using sea surface temperature (SST). It is found that SST is a reasonable proxy for SIE estimation when compared to model SIE forecasts and observations. The proxy sea-ice estimates also show similar relationships to mid-latitude temperature and pressure as the actual sea-ice predictions.

Climate change and the long-term viability of the World's busiest heavy haul ice road

Science.gov (United States)

Mullan, Donal; Swindles, Graeme; Patterson, Tim; Galloway, Jennifer; Macumber, Andrew; Falck, Hendrik; Crossley, Laura; Chen, Jie; Pisaric, Michael

2017-08-01

Climate models project that the northern high latitudes will warm at a rate in excess of the global mean. This will pose severe problems for Arctic and sub-Arctic infrastructure dependent on maintaining low temperatures for structural integrity. This is the case for the economically important Tibbitt to Contwoyto Winter Road (TCWR)—the world's busiest heavy haul ice road, spanning 400 km across mostly frozen lakes within the Northwest Territories of Canada. In this study, future climate scenarios are developed for the region using statistical downscaling methods. In addition, changes in lake ice thickness are projected based on historical relationships between measured ice thickness and air temperatures. These projections are used to infer the theoretical operational dates of the TCWR based on weight limits for trucks on the ice. Results across three climate models driven by four RCPs reveal a considerable warming trend over the coming decades. Projected changes in ice thickness reveal a trend towards thinner lake ice and a reduced time window when lake ice is at sufficient thickness to support trucks on the ice road, driven by increasing future temperatures. Given the uncertainties inherent in climate modelling and the resultant projections, caution should be exercised in interpreting the magnitude of these scenarios. More certain is the direction of change, with a clear trend towards winter warming that will reduce the operation time window of the TCWR. This illustrates the need for planners and policymakers to consider future changes in climate when planning annual haulage along the TCWR.

X-Ray Absorption Spectra of Amorphous Ices from GW Quasiparticle Calculation

Science.gov (United States)

Kong, Lingzhu; Car, Roberto

2013-03-01

We use a GW approach[2] to compute the x-ray absorption spectra of model low- and high-density amorphous ice structures(LDA and HDA)[3]. We include the structural effects of quantum zero point motion using colored-noise Langevin molecular dynamics[4]. The calculated spectra differences in the main and post edge region between LDA and HDA agree well with experimental observations. We attribute these differences to the presence of interstitial molecules within the first coordination shell range in HDA. This assignment is further supported by a calculation of the spectrum of ice VIII, a high-pressure structure that maximizes the number of interstitial molecules and, accordingly, shows a much weaker post-edge feature. We further rationalize the spectral similarity between HDA and liquid water, and between LDA and ice Ih in terms of the respective similarities in the H-bond network topology and bond angle distributions. Supported by grants DOE-DE-SC0005180, DOE DE-SC0008626 and NSF-CHE-0956500.

Sea-ice indicators of polar bear habitat

Science.gov (United States)

Stern, Harry L.; Laidre, Kristin L.

2016-09-01

Nineteen subpopulations of polar bears (Ursus maritimus) are found throughout the circumpolar Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology - the cycle of biological events - is linked to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat) on its way to the summer minimum or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979-2014) mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from -3 to -9 days decade-1 in spring and from +3 to +9 days decade-1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days) and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of -7 to -19 days decade-1, with larger trends in the Barents Sea and central Arctic Basin. The June-October sea-ice concentration is declining in all regions at rates ranging from -1 to -9 percent decade-1. These sea-ice metrics (or indicators of habitat change) were designed to be useful for management agencies and for comparative purposes among subpopulations. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in future reports.

Amplified melt and flow of the Greenland ice sheet driven by late-summer cyclonic rainfall

DEFF Research Database (Denmark)

Doyle, Samuel H.; Hubbard, Alun; van de Wal, Roderik S.W.

2015-01-01

and meteorological variables from the western margin of the Greenland ice sheet during a week of warm, wet cyclonic weather in late August and early September 2011. We find that extreme surface runoff from melt and rainfall led to a widespread acceleration in ice flow that extended 140 km into the ice-sheet interior....... We suggest that the late-season timing was critical in promoting rapid runoff across an extensive bare ice surface that overwhelmed a subglacial hydrological system in transition to a less-efficient winter mode. Reanalysis data reveal that similar cyclonic weather conditions prevailed across southern...

Arctic ice island and sea ice movements and mechanical properties. First quarterly report, October 1-December 31, 1983

Energy Technology Data Exchange (ETDEWEB)

Sackinger, W.M.; Stringer, W.J.

1984-01-01

Research activities for the first quarter are presented for the following tasks: (1) ice island; (2) intrusion of the pack ice edge in the Chukchi Sea; and (3) spray ice adhesion to offshore structure coatings. With respect to the ice island portion of this project the following activities are planned for the year: (1) use aerial photography, satellite imagery, and all available historical records to establish a time history of all of the ice shelves of Ellesmere Island; (2) establish positioning buoys on the existing ice islands to track their trajectories daily and to telemeter daily barometric pressure and temperature, via System Argos; (3) relate geostrophic winds to the observed trajectories; (4) begin to build a pseudo-random model for ice island motion over the long term which would enable a determination of the probability of interaction between ice islands and offshore structures. The overall objective of task 2 is to investigate and analyze the causes and extent of summer time pace ice intrusions into the Chukchi Sea, which would interfere with exploration drilling and emplacement of permanent production structures. For task three a method for evaluating shear and tensile strengths of the interface bond between the sea spray ice layer and the structure or ship surface will be developed. A second more detailed task is to then measure the mechanical properties of this bonded layer for a variety of candidate coatings, as functions of temperature, loading rate, strain rate, salinity, and ice type. 25 references, 92 figures.

Thermal regime of an ice-wedge polygon landscape near Barrow, Alaska

Science.gov (United States)

Daanen, R. P.; Liljedahl, A. K.

2017-12-01

Tundra landscapes are changing all over the circumpolar Arctic due to permafrost degradation. Soil cracking and infilling of meltwater repeated over thousands of years form ice wedges, which produce the characteristic surface pattern of ice-wedge polygon tundra. Rapid top-down thawing of massive ice leads to differential ground subsidence and sets in motion a series of short- and long-term hydrological and ecological changes. Subsequent responses in the soil thermal regime drive further permafrost degradation and/or stabilization. Here we explore the soil thermal regime of an ice-wedge polygon terrain near Utqiagvik (formerly Barrow) with the Water balance Simulation Model (WaSiM). WaSiM is a hydro-thermal model developed to simulate the water balance at the watershed scale and was recently refined to represent the hydrological processes unique to cold climates. WaSiM includes modules that represent surface runoff, evapotranspiration, groundwater, and soil moisture, while active layer freezing and thawing is based on a direct coupling of hydrological and thermal processes. A new snow module expands the vadose zone calculations into the snow pack, allowing the model to simulate the snow as a porous medium similar to soil. Together with a snow redistribution algorithm based on local topography, this latest addition to WaSiM makes simulation of the ground thermal regime much more accurate during winter months. Effective representation of ground temperatures during winter is crucial in the simulation of the permafrost thermal regime and allows for refined predictions of future ice-wedge degradation or stabilization.

Aerodynamic Performance Degradation Induced by Ice Accretion. PIV Technique Assessment in Icing Wind Tunnel

Science.gov (United States)

Gregorio, Fabrizio De

The aim of the present chapter is to consider the use of PIV technique in an industrial icing wind tunnel (IWT) and the potentiality/advantages of applying the PIV technique to this specific field. The purpose of icing wind tunnels is to simulate the aircraft flight condition through cloud formations. In this operational condition ice accretions appear on the aircraft exposed surfaces due to the impact of the water droplets present in the clouds and the subsequent solidification. The investigation of aircraft aerodynamic performances and flight safety in icing condition is a fundamental aspect in the phase of design, development and certification of new aircrafts. The description of this unusual ground testing facility is reported. The assessment of PIV in CIRA-IWT has been investigated. Several technological problems have been afforded and solved by developing the components of the measurement system, such as the laser system and the recording apparatus, both fully remotely controlled, equipped with several traversing mechanism and protected by the adverse environment conditions (temperature and pressure). The adopted solutions are described. Furthermore, a complete test campaign on a full-scale aircraft wing tip, equipped with moving slat and deicing system has been carried out by PIV. Two regions have been investigated. The wing leading-edge (LE) area has been studied with and without ice accretion and for different cloud characteristics. The second activitiy was aimed at the investigation of the wing-wake behavior. The measurements were aimed to characterize the wake for the model in cruise condition without ice formation and during the ice formation.

BRITICE-CHRONO: Constraining rates and style of marine-influenced ice sheet decay to provide a data-rich playground for ice sheet modellers

Science.gov (United States)

Clark, Chris

2014-05-01

Uncertainty exists regarding the fate of the Antarctic and Greenland ice sheets and how they will respond to forcings from sea level and atmospheric and ocean temperatures. If we want to know more about the mechanisms and rate of change of shrinking ice sheets, then why not examine an ice sheet that has fully disappeared and track its retreat through time? If achieved in enough detail such information could become a data-rich playground for improving the next breed of numerical ice sheet models to be used in ice and sea level forecasting. We regard that the last British-Irish Ice Sheet is a good target for this work, on account of its small size, density of information and with its numerous researchers already investigating it. BRITICE-CHRONO is a large (>45 researchers) NERC-funded consortium project comprising Quaternary scientists and glaciologists who will search the seafloor around Britain and Ireland and parts of the landmass in order to find and extract samples of sand, rock and organic matter that can be dated (OSL; Cosmogenic; 14C) to reveal the timing and rate of change of the collapsing British-Irish Ice Sheet. The purpose is to produce a high resolution dataset on the demise on an ice sheet - from the continental shelf edge and across the marine to terrestrial transition. Some 800 new date assessments will be added to those that already exist. This poster reports on the hypotheses that underpin the work. Data on retreat will be collected by focusing on 8 transects running from the continental shelf edge to a short distance (10s km) onshore and acquiring marine and terrestrial samples for geochronometric dating. The project includes funding for 587 radiocarbon, 140 OSL and 158 TCN samples for surface exposure dating; with sampling accomplished by two research cruises and 16 fieldwork campaigns. Results will reveal the timing and rate of change of ice margin recession for each transect, and combined with existing landform and dating databases, will be

Measured Hydrologic Storage Characteristics of Three Major Ice Wedge Polygon Types, Barrow, Alaska

Science.gov (United States)

Chamberlain, A. J.; Liljedahl, A.; Wilson, C. J.; Cable, W.; Romanovsky, V. E.

2014-12-01

Model simulations have suggested that the hydrologic fluxes and stores of Arctic wetlands are constrained by the micro-topographical features of ice wedge polygons, which are abundant in lowland tundra landscapes. Recently observed changes in ice wedge polygon landscapes - in particular, ice wedge degradation and trough formation - emphasize the need to better understand how differing ice wedge polygon morphologies affect the larger hydrologic system. Here we present three seasons of measured end-of-winter snow accumulation, continuous soil moisture and water table elevations, and repeated frost table mapping. Together, these describe the hydrologic characteristics of three main ice wedge polygon types: low centered polygons with limited trough development (representative of a ~500 year old vegetated drained thaw lake basin), and low- and high-centered polygons with well-defined troughs. Dramatic spatiotemporal variability exists both between polygon types and between the features of an individual polygon (e.g. troughs, centers, rims). Landscape-scale end-of-winter snow water equivalent is similar between polygon types, while the sub-polygon scale distribution of the surface water differs, both as snow and as ponded water. Some sub-polygon features appear buffered against large variations in water levels, while others display periods of prolonged recessions and large responses to rain events. Frost table elevations in general mimic the ground surface topography, but with spatiotemporal variability in thaw rate. The studied thaw seasons represented above long-term average rainfall, and in 2014, record high June precipitation. Differing ice wedge polygon types express dramatically different local hydrology, despite nearly identical climate forcing and landscape-scale snow accumulation, making ice wedge polygons an important component when describing the Arctic water, nutrient and energy system.

Assessment of the High Resolution SAR Mode of the RADARSAT Constellation Mission for First Year Ice and Multiyear Ice Characterization

Directory of Open Access Journals (Sweden)

Mohammed Dabboor

2018-04-01

Full Text Available Simulated compact polarimetry from the RADARSAT Constellation Mission (RCM is evaluated for sea ice classification. Compared to previous studies that evaluated the potential of RCM for sea ice classification, this study focuses on the High Resolution (HR Synthetic Aperture Radar (SAR mode of the RCM associated with a higher noise floor (Noise Equivalent Sigma Zero of −19 dB, which can prove challenging for sea ice monitoring. Twenty three Compact Polarimetric (CP parameters were derived and analyzed for the discrimination between first year ice (FYI and multiyear ice (MYI. The results of the RCM HR mode are compared with those previously obtained for other RCM SAR modes for possible CP consistency parameters in sea ice classification under different noise floors, spatial resolutions, and radar incidence angles. Finally, effective CP parameters were identified and used for the classification of FYI and MYI using the Random Forest (RF classification algorithm. This study indicates that, despite the expected high noise floor of the RCM HR mode, CP SAR data from this mode are promising for the classification of FYI and MYI in dry ice winter conditions. The overall classification accuracies of CP SAR data over two test sites (96.13% and 96.84% were found to be comparable to the accuracies obtained using Full Polarimetric (FP SAR data (98.99% and 99.20%.

River ice implications related to water power production in Norway

Energy Technology Data Exchange (ETDEWEB)

Asvall, R.P. [Norwegian Water Resources and Energy Directorate, Oslo (Norway). Hydrology Dept.

2009-07-01

Nearly 99 per cent of the electricity produced in Norway is based on water power. While the period of large power development is over, the current focus lies in developing small hydroelectric power plants. A new market based energy law was implemented in Norway in 1991 to achieve more efficient use of electricity production by means of market forces. Since water regulation influences ice conditions in lakes and rivers, this paper focused on the implications of changes in ice conditions. In Norway, the expected changes in ice conditions are taken into account when issuing permits for water regulations and schemes for water discharge because some waterways are used as winter roads. Follow-up includes both close and long term observations and measurements. The impact of variable price on power was also discussed, with particular reference to ice conditions in cases where water discharge occurs on rivers. This paper summarized selected ice problems and how they have been handled. The paper also included a summary of anticipated climatic changes relevant to ice conditions.

River ice implications related to water power production in Norway

International Nuclear Information System (INIS)

Asvall, R.P.

2009-01-01

Nearly 99 per cent of the electricity produced in Norway is based on water power. While the period of large power development is over, the current focus lies in developing small hydroelectric power plants. A new market based energy law was implemented in Norway in 1991 to achieve more efficient use of electricity production by means of market forces. Since water regulation influences ice conditions in lakes and rivers, this paper focused on the implications of changes in ice conditions. In Norway, the expected changes in ice conditions are taken into account when issuing permits for water regulations and schemes for water discharge because some waterways are used as winter roads. Follow-up includes both close and long term observations and measurements. The impact of variable price on power was also discussed, with particular reference to ice conditions in cases where water discharge occurs on rivers. This paper summarized selected ice problems and how they have been handled. The paper also included a summary of anticipated climatic changes relevant to ice conditions.

Exceptional Arctic warmth of early winter 2016 and attribution to global warming

Science.gov (United States)

van Oldenborgh, Geert Jan; Macias-Fauria, Marc; King, Andrew; Uhe, Peter; Philip, Sjoukje; Kew, Sarah; Karoly, David; Otto, Friederike; Allen, Myles; Cullen, Heidi

2017-04-01

The dark polar winters usually sport the coldest extremes on Earth, however this winter, the North Pole and the surrounding Arctic region have experienced record high temperatures in November and December, with daily means reaching 15 °C (27 °F) above normal and a November monthly mean that was 13 °C (23 °F) above normal on the pole. November also saw a brief retreat of sea-ice that was virtually unprecedented in nearly 40 years of satellite records, followed by a record low in November sea ice area since 1850. Unlike the Antarctic, Arctic lands are inhabited and their socio-economic systems are greatly affected by the impacts of extreme and unprecedented sea ice dynamics and temperatures, such as for example, the timing of marine mammal migrations, and refreezing rain on snow that prevents reindeer from feeding. Here we report on our multi-method rapid attribution analysis of North Pole November-December temperatures. To quantify the rarity of the event, we computed the November-December averaged temperature around the North Pole (80-90 °N) in the (short but North-pole covering) ERA-interim reanalysis. To put the event in context of natural variability, we use a longer and closely related time series based on the northern most meteorological observations on land (70-80 °N). This allows for a reconstruction of Arctic temperatures back to about 1900. We also perform a multi-method analysis of North Pole temperatures with two sets of climate models: the CMIP5 multi-model ensemble, and a large ensemble of model runs in the so-called Weather@Home project. Physical mechanisms that are responsible for temperature and sea ice variability in the North Pole region are also discussed. The observations and the bias-corrected CMIP5 ensemble point to a return period of about 50 to 200 years in the present climate, i.e., the probability of such an extreme is about 0.5% to 2% every year, with a large uncertainty. The observations show that November-December temperatures

Winter and spring diving behavior of bowhead whales relative to prey

KAUST Repository

Heide-Jø rgensen, Mads; Laidre, Kristin L; Nielsen, Nynne H; Hansen, Rikke G; Rø stad, Anders

2013-01-01

There was a marked change in diving behavior from winter through spring and this was likely in response to the changes in sea ice conditions, primary production and potential copepod abundance in the upper part of the water column. Depth and duration of dives changed significantly during this period; however, other dive parameters (for example the proportion of time spent feeding on the bottom of U-dives) remained fairly constant indicating a constant feeding effort. Bowhead whales target copepods at or close to the seabed in winter months in Disko Bay and continue feeding on copepods when they migrate to the surface. However, bowhead whales leave West Greenland before peak abundance of copepods occurs at the surface.

Sea Ice, Hydrocarbon Extraction, Rain-on-Snow and Tundra Reindeer Nomadism in Arctic Russia

Science.gov (United States)

Forbes, B. C.; Kumpula, T.; Meschtyb, N.; Laptander, R.; Macias-Fauria, M.; Zetterberg, P.; Verdonen, M.

2015-12-01

It is assumed that retreating sea ice in the Eurasian Arctic will accelerate hydrocarbon development and associated tanker traffic along Russia's Northern Sea Route. However, oil and gas extraction along the Kara and Barents Sea coasts will likely keep developing rapidly regardless of whether the Northwest Eurasian climate continues to warm. Less certain are the real and potential linkages to regional biota and social-ecological systems. Reindeer nomadism continues to be a vitally important livelihood for indigenous tundra Nenets and their large herds of semi-domestic reindeer. Warming summer air temperatures over the NW Russian Arctic have been linked to increases in tundra productivity, longer growing seasons, and accelerated growth of tall deciduous shrubs. These temperature increases have, in turn, been linked to more frequent and sustained summer high-pressure systems over West Siberia, but not to sea ice retreat. At the same time, winters have been warming and rain-on-snow (ROS) events have become more frequent and intense, leading to record-breaking winter and spring mortality of reindeer. What is driving this increase in ROS frequency and intensity is not clear. Recent modelling and simulation have found statistically significant near-surface atmospheric warming and precipitation increases during autumn and winter over Arctic coastal lands in proximity to regions of sea-ice loss. During the winter of 2013-14 an extensive and lasting ROS event led to the starvation of 61,000 reindeer out of a population of ca. 300,000 animals on Yamal Peninsula, West Siberia. Historically, this is the region's largest recorded mortality episode. More than a year later, participatory fieldwork with nomadic herders during spring-summer 2015 revealed that the ecological and socio-economic impacts from this extreme event will unfold for years to come. There is an urgent need to understand whether and how ongoing Barents and Kara Sea ice retreat may affect the region's ancient

Identification and evaluation of slip and fall risk on ice and snow

OpenAIRE

Gao, Chuansi

2001-01-01

Roads and pavements covered with ice and snow during winter in the Nordic and other cold regions are slippery, which result in the prevalence of slip and fall accidents among not only the public, but also outdoor workers. Literature and injury statistics revealed that the most frequently specified contributory factor for occupational slip, trip and fall accidents in Sweden is snow and ice. Road accident research showed that the largest numbers of traffic casualties occurred during walking, fo...

Estimates of ikaite export from sea ice to the underlying seawater in a sea ice-seawater mesocosm

Science.gov (United States)

Geilfus, Nicolas-Xavier; Galley, Ryan J.; Else, Brent G. T.; Campbell, Karley; Papakyriakou, Tim; Crabeck, Odile; Lemes, Marcos; Delille, Bruno; Rysgaard, Søren

2016-09-01

the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and in winter in ice-covered areas, at the time when Ωaragonite is smallest.

Late Cenozoic Arctic Ocean sea ice and terrestrial paleoclimate.

Science.gov (United States)

Carter, L.D.; Brigham-Grette, J.; Marincovich, L.; Pease, V.L.; Hillhouse, J.W.

1986-01-01

Sea otter remains found in deposits of two marine transgressions (Bigbendian and Fishcreekian) of the Alaskan Arctic Coastal Plain which occurred between 2.4 and 3 Ma suggest that during these two events the southern limit of seasonal sea ice was at least 1600 km farther north than at present in Alaskan waters. Perennial sea ice must have been severely restricted or absent, and winters were warmer than at present during these two sea-level highstands. Paleomagnetic, faunal, and palynological data indicate that the later transgression (Fishcreekian) occurred during the early part of the Matuyama Reversed-Polarity Chron. -from Authors

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.

Spatiotemporal variability in surface energy balance across tundra, snow and ice in Greenland

DEFF Research Database (Denmark)

Lund, Magnus; Stiegler, Christian; Abermann, Jakob

2017-01-01

The surface energy balance (SEB) is essential for understanding the coupled cryosphere–atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and ice. During the snow-free period, the main energy sink for ice sites is surface melt....... For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland Ice Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during...

Polar Sea Ice Monitoring Using HY-2A Scatterometer Measurements

Directory of Open Access Journals (Sweden)

Mingming Li

2016-08-01

Full Text Available A sea ice detection algorithm based on Fisher’s linear discriminant analysis is developed to segment sea ice and open water for the Ku-band scatterometer onboard the China’s Hai Yang 2A Satellite (HY-2A/SCAT. Residual classification errors are reduced through image erosion/dilation techniques and sea ice growth/retreat constraint methods. The arctic sea-ice-type classification is estimated via a time-dependent threshold derived from the annual backscatter trends based on previous HY-2A/SCAT derived sea ice extent. The extent and edge of the sea ice obtained in this study is compared with the Special Sensor Microwave Imager/Sounder (SSMIS sea ice concentration data and the Sentinel-1 SAR imagery for verification, respectively. Meanwhile, the classified sea ice type is compared with a multi-sensor sea ice type product based on data from the Advanced Scatterometer (ASCAT and SSMIS. Results show that HY-2A/SCAT is powerful in providing sea ice extent and type information, while differences in the sensitivities of active/passive products are found. In addition, HY-2A/SCAT derived sea ice products are also proved to be valuable complements for existing polar sea ice data products.

Mass balance of the Amitsulôq ice cap, West Greenland

DEFF Research Database (Denmark)

Ahlstrøm, Andreas P.; Bøggild, Carl Egede; Olesen, Ole B.

2007-01-01

We present detailed mass balance measurements from the Amitsulôq ice cap in West Greenland spanning from 1982 to 1990. The data includes summer and winter balances from 26 stake locations distributed over five transects covering the whole ice cap. The mass balance measurements are combined...... with a recent satellite-derived digital elevation model to calculate the specific balance, which is in turn compared to discharge data from the adjacent Tasersiaq basin. The correlation between specific summer balance and discharge is R2 = 0.93 indicating that the basin discharge is dominated by glacial...... meltwater, linking the hydropower potential of the basin closely to the fate of the adjoining Greenland ice-sheet margin....

Improved ice particle optical property simulations in the ultraviolet to far-infrared regime

International Nuclear Information System (INIS)

Bi, Lei; Yang, Ping

2017-01-01

To derive the bulk radiative properties of ice clouds, aircraft contrails and snow grains, which are fundamental to atmospheric radiative transfer calculations in downstream applications, it is necessary to accurately simulate the scattering of light by individual ice particles. An ice particle optical property database reported in 2013 (hereafter, TAMUice2013) is updated (hereafter, TAMUice2016) to incorporate recent advances in computation of the optical properties of nonspherical particles. Specifically, we employ the invariant imbedding T-matrix (II-TM) method to compute the optical properties of particles with small to moderate size parameters. Both versions use the Improved Geometric Optics Method (IGOM) to compute the optical properties of large ice crystals, but TAMUice2016 improves the treatment of inhomogeneous waves inside the scattering particles in the case where ice is absorptive such as at infrared wavelengths. To bridge the gap between the extinction efficiencies computed from the II-TM and the IGOM, TAMUice2016 includes spectrally dependent higher order terms of the edge effect in addition to the first order counterpart considered in TAMUice2013. Furthermore, the differences between TAMUice2013 and TAMUice2016 are quantified with respect to the computation of the bulk optical properties of ice clouds. - Highlights: • A previous database of the single-scattering properties of ice crystals is improved. • A combination of the invariant imbedding T-matrix and improved geometric optics methods is used. • The treatment of inhomogeneous waves in an absorptive ice crystal is improved. • Higher order terms of the edge effect are considered in the updated database.

PROCESSES PROCEEDING ON CONCRETE COATING SURFACES IN CASE OF THEIR CHEMICAL PROTECTION AGAINST WINTER SLIPPERINESS

Directory of Open Access Journals (Sweden)

M. K. Pshembaev

2016-01-01

Full Text Available Concrete coatings of road traffic highways along with operational loadings caused by flow of traffic are subjected to weather and climate impacts. These are the following impacts: changes in temperature and air humidity, solar radiation,surface wind speed which is participating in formation of active heat-and-mass transfer in a surface layer of the concrete coating. One of the most complicated and important periods in the road traffic highway operation is so called transitional nature period (from Summer to Autumn and from Winter to Spring. These periods are accompanied by intensive rain and snow fall and possible formation of ice loading on the surface of cement and concrete coatings. These impacts significantly deteriorate friction properties of road pavement (friction factor φ is decreased up to 0.4 and less that can be a prerequisite to creation of various accident situations due to sharp increase in braking distance. For example, while having dry pavement the friction factor φ is equal to 0.80–0.85, and during icy condition of the road the factor φ constitutes 0.08–0.15 that consequently entails an increase in braking distance from 7.5 up to 20.0 m and more. It is quite possible that ice layer appears on the surface of concrete coatings when road traffic highways are used in winter season. Various methods are applicable to remove ice from the surface they can include also ice-melting chemicals and sodium chloride NaCl in particular. The chemical decreases freezing temperature of the formed brine and causes ice melting at negative temperature. Processes of NaCl dissolution and ice melting have an endothermic character, in other words these processes are accompanied by heat ingress and due to it temperature is sharply decreasing in the surface layer of the concrete coating which is under the melting ice and in this case phenomenon of thermal shock is observed.

Aerosol impacts on California winter clouds and precipitation during CalWater 2011: local pollution vs. long-range transported dust

OpenAIRE

J. Fan; L. R. Leung; P. J. DeMott; J. M. Comstock; B. Singh; D. Rosenfeld; J. M. Tomlinson; A. White; K. A. Prather; P. Minnis; J. K. Ayers; Q. Min

2013-01-01

Mineral dust aerosols often observed over California in winter/spring, associated with long-range transport from Asia and Sahara, have been linked to enhanced precipitation based on observations. Local anthropogenic pollution, on the other hand, was shown in previous observational and modeling studies to reduce precipitation. Here we incorporate recent developments in ice nucleation parameterizations to link aerosols with ice crystal formation in a spectral-bin cloud microphysical mode...

Aerosol impacts on California winter clouds and precipitation during CalWater 2011: local pollution versus long-range transported dust

OpenAIRE

Fan, J.; Leung, L. R.; DeMott, P. J.; Comstock, J. M.; Singh, B.; Rosenfeld, D.; Tomlinson, J. M.; White, A.; Prather, K. A.; Minnis, P.; Ayers, J. K.; Min, Q.

2014-01-01

Mineral dust aerosols often observed over California in winter and spring, associated with long-range transport from Asia and the Sahara, have been linked to enhanced precipitation based on observations. Local anthropogenic pollution, on the other hand, was shown in previous observational and modeling studies to reduce precipitation. Here we incorporate recent developments in ice nucleation parameterizations to link aerosols with ice crystal formation in a spectral-bin cloud microphysical mod...

Endogenous and exogenous ice-nucleating agents constrain supercooling in the hatchling painted turtle.

Science.gov (United States)

Costanzo, Jon P; Baker, Patrick J; Dinkelacker, Stephen A; Lee, Richard E

2003-02-01

Hatchlings of the painted turtle (Chrysemys picta) commonly hibernate in their shallow, natal nests. Survival at temperatures below the limit of freeze tolerance (approximately -4 degrees C) apparently depends on their ability to remain supercooled, and, whereas previous studies have reported that supercooling capacity improves markedly with cold acclimation, the mechanistic basis for this change is incompletely understood. We report that the crystallization temperature (T(c)) of recently hatched (summer) turtles acclimated to 22 degrees C and reared on a substratum of vermiculite or nesting soil was approximately 5 degrees C higher than the T(c) determined for turtles acclimated to 4 degrees C and tested in winter. This increase in supercooling capacity coincided with elimination of substratum (and, in fewer cases, eggshell) that the hatchlings had ingested; however, this association was not necessarily causal because turtles reared on a paper-covered substratum did not ingest exogenous matter but nevertheless showed a similar increase in supercooling capacity. Our results for turtles reared on paper revealed that seasonal development of supercooling capacity fundamentally requires elimination of ice-nucleating agents (INA) of endogenous origin: summer turtles, but not winter turtles, produced feces (perhaps derived from residual yolk) that expressed ice-nucleating activity. Ingestion of vermiculite or eggshell, which had modest ice-nucleating activity, had no effect on the T(c), whereas ingestion of nesting soil, which contained two classes of potent INA, markedly reduced the supercooling capacity of summer turtles. This effect persisted long after the turtles had purged their guts of soil particles, because the T(c) of winter turtles reared on nesting soil (mean +/- S.E.M.=-11.6+/-1.4 degrees C) was approximately 6 degrees C higher than the T(c) of winter turtles reared on vermiculite or paper. Experiments in which winter turtles were fed INA commonly found in

Detection of icing on wind turbine blades by means of vibration and power curve analysis

DEFF Research Database (Denmark)

Skrimpas, Georgios Alexandros; Kleani, Karolina; Mijatovic, Nenad

2016-01-01

accelerometers and power performance analysis. Features extracted from these two techniques serve as inputs in a decision-making scheme, allowing early activation of de-icing systems or shut down of the wind turbine. An additional parameter is the month of operation, assuring consistent outcomes in both winter......Ice accretion on wind turbines' blades is one of the main challenges of systems installed in cold climate locations, resulting in power performance deterioration and excessive nacelle oscillation. In this work, consistent detection of icing events is achieved utilizing indications from the nacelle...

Sea ice contribution to the air-sea CO(2) exchange in the Arctic and Southern Oceans

DEFF Research Database (Denmark)

Rysgaard...[], Søren; Bendtsen, Jørgen; Delille, B.

2011-01-01

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO(2) and the subsequent effect on air-sea CO(2) exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air......-sea CO(2) exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO(2) uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO(2) uptake in ice-free polar seas. This sea......-sea CO(2) exchange during winter, and (3) release of CO(2)-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO(2) drawdown during primary production in sea ice and surface oceanic waters....

Remotely Estimating Aerial N Uptake in Winter Wheat Using Red-Edge Area Index From Multi-Angular Hyperspectral Data

Directory of Open Access Journals (Sweden)

Bin-Bin Guo

2018-05-01

Full Text Available Remote sensing techniques can be efficient for non-destructive, rapid detection of wheat nitrogen (N nutrient status. In the paper, we examined the relationships of canopy multi-angular data with aerial N uptake of winter wheat (Triticum aestivum L. across different growing seasons, locations, years, wheat varieties, and N application rates. Seventeen vegetation indices (VIs selected from the literature were measured for the stability in estimating aerial N uptake of wheat under 13 view zenith angles (VZAs in the solar principal plane (SPP. In total, the back-scatter angles showed better VI behavior than the forward-scatter angles. The correlation coefficient of VIs with aerial N uptake increased with decreasing VZAs. The best linear relationship was integrated with the optimized common indices DIDA and DDn to examine dynamic changes in aerial N uptake; this led to coefficients of determination (R2 of 0.769 and 0.760 at the −10° viewing angle. Our novel area index, designed the modified right-side peak area index (mRPA, was developed in accordance with exploration of the spectral area calculation and red-edge feature using the equation: mRPA = (R760/R6001/2 × (R760-R718. Investigating the predictive accuracy of mRPA for aerial N uptake across VZAs demonstrated that the best performance was at −10° [R2 = 0.804, p < 0.001, root mean square error (RMSE = 3.615] and that the effect was relatively similar between −20° to +10° (R2 = 0.782, p < 0.001, RMSE = 3.805. This leads us to construct a simple model under wide-angle combinations so as to improve the field operation simplicity and applicability. Fitting independent datasets to the models resulted in relative error (RE, % values of 12.6, 14.1, and 14.9% between estimated and measured aerial N uptake for mRPA, DIDA, and DDn across the range of −20° to +10°, respectively, further confirming the superior test performance of the mRPA index. These results illustrate that the novel index

Short-Term Forecasts Using NU-WRF for the Winter Olympics 2018

Science.gov (United States)

Srikishen, Jayanthi; Case, Jonathan L.; Petersen, Walter A.; Iguchi, Takamichi; Tao, Wei-Kuo; Zavodsky, Bradley T.; Molthan, Andrew

2017-01-01

The NASA Unified-Weather Research and Forecasting model (NU-WRF) will be included for testing and evaluation in the forecast demonstration project (FDP) of the International Collaborative Experiment -PyeongChang 2018 Olympic and Paralympic (ICE-POP) Winter Games. An international array of radar and supporting ground based observations together with various forecast and now-cast models will be operational during ICE-POP. In conjunction with personnel from NASA's Goddard Space Flight Center, the NASA Short-term Prediction Research and Transition (SPoRT) Center is developing benchmark simulations for a real-time NU-WRF configuration to run during the FDP. ICE-POP observational datasets will be used to validate model simulations and investigate improved model physics and performance for prediction of snow events during the research phase (RDP) of the project The NU-WRF model simulations will also support NASA Global Precipitation Measurement (GPM) Mission ground-validation physical and direct validation activities in relation to verifying, testing and improving satellite-based snowfall retrieval algorithms over complex terrain.

Transnational Sea-Ice Transport in a Warmer, More Mobile Arctic

Science.gov (United States)

Newton, R.; Tremblay, B.; Pfirman, S. L.; DeRepentigny, P.

2015-12-01

As the Arctic sea ice thins, summer ice continues to shrink in its area, and multi-year ice becomes rarer, winter ice is not disappearing from the Arctic Basin. Rather, it is ever more dominated by first year ice. And each summer, as the total coverage withdraws, the first year ice is able travel faster and farther, carrying any ice-rafted material with it. Micro-organisms, sediments, pollutants and river runoff all move across the Arctic each summer and are deposited hundreds of kilometers from their origins. Analyzing Arctic sea ice drift patterns in the context of the exclusive economic zones (EEZs) of the Arctic nations raises concerns about the changing fate of "alien" ice which forms within one country's EEZ, then drifts and melts in another country's EEZ. We have developed a new data set from satellite-based ice-drift data that allows us to track groups of ice "pixels" forward from their origin to their destination, or backwards from their melting location to their point of formation. The software has been integrated with model output to extend the tracking of sea ice to include climate projections. Results indicate, for example, that Russian sea ice dominates "imports" to the EEZ of Norway, as expected, but with increasing ice mobility it is also is exported into the EEZs of other countries, including Canada and the United States. Regions of potential conflict are identified, including several national borders with extensive and/or changing transboundary sea ice transport. These data are a starting point for discussion of transborder questions raised by "alien" ice and the material it may import from one nation's EEZ to another's.

Physical and Chemical Implications of Mid-Winter Pumping of Trunda Lakes - North Slope, Alaska

Energy Technology Data Exchange (ETDEWEB)

Hinzman, Larry D. (University of Alaska Fairbanks, Water and Environmental Research Center); Lilly, Michael R. (Geo-Watersheds Scientific); Kane, Douglas L. (University of Alaska Fairbanks, Water and Environmental Research Center); Miller, D. Dan (University of Alaska Fairbanks, Water and Environmental Research Center); Galloway, Braden K. (University of Alaska Fairbanks, Water and Environmental Research Center); Hilton, Kristie M. (Geo-Watersheds Scientific); White, Daniel M. (University of Alaska Fairbanks, Water and Environmental Research Center)

2005-09-30

Tundra lakes on the North Slope, Alaska, are an important resource for energy development and petroleum field operations. A majority of exploration activities, pipeline maintenance, and restoration activities take place on winter ice roads that depend on water availability at key times of the winter operating season. These same lakes provide important fisheries and ecosystem functions. In particular, overwintering habitat for fish is one important management concern. This study focused on the evaluation of winter water use in the current field operating areas to provide a better understanding of the current water use practices. It found that under the current water use practices, there were no measurable negative effects of winter pumping on the lakes studied and current water use management practices were appropriately conservative. The study did find many areas where improvements in the understanding of tundra lake hydrology and water usage would benefit industry, management agencies, and the protection of fisheries and ecosystems.

Adsorption and structure of water on kaolinite surfaces: possible insight into ice nucleation from grand canonical monte carlo calculations.

Science.gov (United States)

Croteau, T; Bertram, A K; Patey, G N

2008-10-30

Grand canonical Monte Carlo calculations are used to determine water adsorption and structure on defect-free kaolinite surfaces as a function of relative humidity at 235 K. This information is then used to gain insight into ice nucleation on kaolinite surfaces. Results for both the SPC/E and TIP5P-E water models are compared and demonstrate that the Al-surface [(001) plane] and both protonated and unprotonated edges [(100) plane] strongly adsorb at atmospherically relevant relative humidities. Adsorption on the Al-surface exhibits properties of a first-order process with evidence of collective behavior, whereas adsorption on the edges is essentially continuous and appears dominated by strong water lattice interactions. For the protonated and unprotonated edges no structure that matches hexagonal ice is observed. For the Al-surface some of the water molecules formed hexagonal rings. However, the a o lattice parameter for these rings is significantly different from the corresponding constant for hexagonal ice ( Ih). A misfit strain of 14.0% is calculated between the hexagonal pattern of water adsorbed on the Al-surface and the basal plane of ice Ih. Hence, the ring structures that form on the Al-surface are not expected to be good building-blocks for ice nucleation due to the large misfit strain.

Sea ice production and transport of pollutants in Laptev Sea, 1979 to 1992

International Nuclear Information System (INIS)

Rigor, I.; Colony, R.

1995-01-01

About 900,000 km 2 of the polar pack ice is transferred annually from the Arctic Basin to the North Atlantic. The largest portion of this exported ice cover is created by the large scale divergence within the ice pack, but a significant portion of the ice cover originates in the marginal seas, either by fall freezing of the seasonally ice free waters or by wintertime advection away from the coast. The main objective of this study was to estimate the annual production of ice in the Laptev Sea and to determine its ultimate fate. The study was motivated by the possibility that ice formed in the Laptev Sea may be an agent for the long range transport of pollutants such as radionuclides. The authors have attempted to characterize the mean and interannual variability of ice production by investigating the winter production and subsequent melt of ice in the Laptev Sea from 1979 through 1992. The general approach was to associate pollution transport with the net exchange of ice area from the Laptev Sea to the perennial ice pack. The primary data sets supporting the study were ice charts, ice motion and geostrophic wind. 3 refs., 4 figs., 1 tab

Atmospheric Profiles, Clouds and the Evolution of Sea Ice Cover in the Beaufort and Chukchi Seas: Atmospheric Observations and Modeling as Part of the Seasonal Ice Zone Reconnaissance Surveys

Science.gov (United States)

2017-06-04

further, changes in lower atmospheric temperature, humidity, winds , and clouds are likely to result from changed sea ice concentrations and ocean...affect changes in cloud properties and cover, • develop novel instrumentation including low cost, expendable, air-deployed micro -aircraft to obtain...from June through October to obtain atmospheric profiles of temperature, humidity, and winds from the time of ice edge retreat in spring to advance

Sea-ice indicators of polar bear habitat

Directory of Open Access Journals (Sweden)

H. L. Stern

2016-09-01

Full Text Available Nineteen subpopulations of polar bears (Ursus maritimus are found throughout the circumpolar Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology – the cycle of biological events – is linked to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat on its way to the summer minimum or rises above the threshold (advance on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979–2014 mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from −3 to −9 days decade−1 in spring and from +3 to +9 days decade−1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of −7 to −19 days decade−1, with larger trends in the Barents Sea and central Arctic Basin. The June–October sea-ice concentration is declining in all regions at rates ranging from −1 to −9 percent decade−1. These sea-ice metrics (or indicators of habitat change were designed to be useful for management agencies and for comparative purposes among subpopulations. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in

The importance of polynyas, ice edges, and leads to marine mammals and birds

Science.gov (United States)

Stirling, Ian

1997-01-01

The correlation between areas of open water in ice-covered seas and increased biological productivity has been noted for some time. To date, most attention has been focused on larger polynyas, such as the Northeast Water and the Northwater. Although spectacular in their own right, these large polynyas represent only part of a vitally important continuum of biological productivity that varies significantly between geographic areas and ice habitats, that includes the multi-year pack of the polar ocean and small localized polynyas in annual ice. Surveys of the distribution and abundance of ringed seals in the Canadian Arctic Archipelago have shown differences in density that are correlated with the presence or absence of polynyas. There is also significant variation in the biological productivity of polynya areas of the Canadian High Arctic Archipelago and northern Greenland, all of which receive inflow from the polar basin. Long-term studies of polar bears and ringed seals in western Hudson Bay and the eastern Beaufort Sea show significant but dissimilar patterns of change in condition and reproductive rates between the two regions and suggest that fundamentally different climatic or oceanographic processes may be involved. Projections of climate models suggest that, if warming occurs, then the extent of ice cover in Hudson Bay may be among the first things affected. Long-term studies of polar bears and ringed seals in the eastern Beaufort Sea and Hudson Bay would suggest these two species to be suitable indicators of significant climatic or oceanographic changes in the marine ecosystem.

The Sentinel-1 Mission: New Opportunities for Ice Sheet Observations

Directory of Open Access Journals (Sweden)

Thomas Nagler

2015-07-01

Full Text Available The Sentinel satellite constellation series, developed by the European Space Agency, represents the dedicated space component of the European Copernicus program, committed to long-term operational services in a wide range of application domains. Here, we address the potential of the Sentinel-1 mission for mapping and monitoring the surface velocity of glaciers and ice sheets. We present an ice velocity map of Greenland, derived from synthetic aperture radar (SAR data acquired in winter 2015 by Sentinel-1A, the first satellite of the Copernicus program in orbit. The map is assembled from about 900 SAR scenes acquired in Interferometric Wide swath (IW mode, applying the offset tracking technique. We discuss special features of IW mode data, describe the procedures for producing ice velocity maps, and assess the uncertainty of the ice motion product. We compare the Sentinel-1 ice motion product with velocity maps derived from high resolution SAR data of the TerraSAR-X mission and from PALSAR data. Beyond supporting operational services, the Sentinel-1 mission offers enhanced capabilities for comprehensive and long-term observation of key climate variables, such as the motion of ice masses.

Two new ways of mapping sea ice thickness using ocean waves

Science.gov (United States)

Wadhams, P.

2010-12-01

TWO NEW METHODS OF MAPPING SEA ICE THICKNESS USING OCEAN WAVES. P. Wadhams (1,2), Martin Doble (1,2) and F. Parmiggiani (3) (1) Dept. of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK. (2) Laboratoire d’Océanographie de Villefranche, Université Pierre et Marie Curie, 06234 Villefranche-sur-Mer, France (2) ISAC-CNR, Bologna, Italy Two new methods of mapping ice thickness have been recently developed and tested, both making use of the dispersion relation of ocean waves in ice of radically different types. In frazil-pancake ice, a young ice type in which cakes less than 5 m across float in a suspension of individual ice crystals, the propagation of waves has been successfully modelled by treating the ice layer as a highly viscous fluid. The model predicts a shortening of wavelengths within the ice. Two-dimensional Fourier analysis of successive SAR subscenes to track the directional spectrum of a wave field as it enters an ice edge shows that waves do indeed shorten within the ice, and the change has been successfully used to predict the thickness of the frazil-pancake layer. Concurrent shipborne sampling in the Antarctic has shown that the method is accurate, and we now propose its use throughout the important frazil-pancake regimes in the world ocean (Antarctic circumpolar ice edge zone, Greenland Sea, Bering Sea and others). A radically different type of dispersion occurs when ocean waves enter the continuous icefields of the central Arctic, when they couple with the elastic ice cover to propagate as a flexural-gravity wave. A two-axis tiltmeter array has been used to measure the resulting change in the dispersion relation for long ocean swell (15-30 s) originating from storms in the Greenland Sea. The dispersion relation is slightly different from swell in the open ocean, so if two such arrays are placed a substantial distance (100s of km) apart and used to observe the changing wave period of arrivals from a given

Ice Water Classification Using Statistical Distribution Based Conditional Random Fields in RADARSAT-2 Dual Polarization Imagery

Science.gov (United States)

Zhang, Y.; Li, F.; Zhang, S.; Hao, W.; Zhu, T.; Yuan, L.; Xiao, F.

2017-09-01

In this paper, Statistical Distribution based Conditional Random Fields (STA-CRF) algorithm is exploited for improving marginal ice-water classification. Pixel level ice concentration is presented as the comparison of methods based on CRF. Furthermore, in order to explore the effective statistical distribution model to be integrated into STA-CRF, five statistical distribution models are investigated. The STA-CRF methods are tested on 2 scenes around Prydz Bay and Adélie Depression, where contain a variety of ice types during melt season. Experimental results indicate that the proposed method can resolve sea ice edge well in Marginal Ice Zone (MIZ) and show a robust distinction of ice and water.

Co-distribution of seabirds and their polar cod prey near the ice edge in southern Baffin Bay

DEFF Research Database (Denmark)

LeBlanc, Mathieu; Gauthier, S; Mosbech, Anders

species, and age-1 polar cod found in bird stomachs were likely individuals associated to ice. At a large scale of hundreds of kilometers, seabirds and age-0 polar cod were more abundant in ice-covered habitats (30 to 100% ice concentration). At medium and small scale of 12.5 and 1 km respectively...

Altitude training considerations for the winter sport athlete.

Science.gov (United States)

Chapman, Robert F; Stickford, Jonathon L; Levine, Benjamin D

2010-03-01

Winter sports events routinely take place at low to moderate altitudes, and nearly all Winter Olympic Games have had at least one venue at an altitude >1000 m. The acute and chronic effects of altitude can have a substantial effect on performance outcomes. Acutely, the decline in oxygen delivery to working muscle decreases maximal oxygen uptake, negatively affecting performance in endurance events, such as cross-country skiing and biathlon. The reduction in air resistance at altitude can dramatically affect sports involving high velocities and technical skill components, such as ski jumping, speed skating, figure skating and ice hockey. Dissociation between velocity and sensations usually associated with work intensity (ventilation, metabolic signals in skeletal muscle and heart rate) may impair pacing strategy and make it difficult to determine optimal race pace. For competitions taking place at altitude, a number of strategies may be useful, depending on the altitude of residence of the athlete and ultimate competition altitude, as follows. First, allow extra time and practice (how much is yet undetermined) for athletes to adjust to the changes in projectile motion; hockey, shooting, figure skating and ski jumping may be particularly affected. These considerations apply equally in the reverse direction; that is, for athletes practising at altitude but competing at sea level. Second, allow time for acclimatization for endurance sports: 3-5 days if possible, especially for low altitude (500-2000 m); 1-2 weeks for moderate altitude (2000-3000 m); and at least 2 weeks if possible for high altitude (>3000 m). Third, increase exercise-recovery ratios as much as possible, with 1:3 ratio probably optimal, and consider more frequent substitutions for sports where this is allowed, such as ice hockey. Fourth, consider the use of supplemental O(2) on the sideline (ice hockey) or in between heats (skating and Alpine skiing) to facilitate recovery. For competitions at sea

Biologically-Oriented Processes in the Coastal Sea Ice Zone of the White Sea

Science.gov (United States)

Melnikov, I. A.

2002-12-01

The annual advance and retreat of sea ice is a major physical determinant of spatial and temporal changes in the structure and function of marine coastal biological communities. Sea ice biological data obtained in the tidal zone of Kandalaksha Gulf (White Sea) during 1996-2001 period will be presented. Previous observations in this area were mainly conducted during the ice-free summer season. However, there is little information on the ice-covered winter season (6-7 months duration), and, especially, on the sea-ice biology in the coastal zone within tidal regimes. During the January-May period time-series observations were conducted on transects along shorelines with coastal and fast ice. Trends in the annual extent of sea ice showed significant impacts on ice-associated biological communities. Three types of sea ice impact on kelps, balanoides, littorinas and amphipods are distinguished: (i) positive, when sea ice protects these populations from grinding (ii) negative, when ice grinds both fauna and flora, and (iii) a combined effect, when fast ice protects, but anchored ice grinds plant and animals. To understand the full spectrum of ecological problems caused by pollution on the coastal zone, as well as the problems of sea ice melting caused by global warming, an integrated, long-term study of the physical, chemical, and biological processes is needed.

Advances in river ice hydrology 1999-2003

Science.gov (United States)

Morse, Brian; Hicks, Faye

2005-01-01

In the period 1999 to 2003, river ice has continued to have important socio-economic impacts in Canada and other Nordic countries. Concurrently, there have been many important advances in all areas of Canadian research into river ice engineering and hydrology. For example: (1) River ice processes were highlighted in two special journal issues (Canadian Journal of Civil Engineering in 2003 and Hydrological Processes in 2002) and at five conferences (Canadian Committee on River Ice Processes and the Environment in 1999, 2001 and 2003, and International Association of Hydraulic Research in 2000 and 2002). (2) A number of workers have clearly advanced our understanding of river ice processes by bringing together disparate information in comprehensive review articles. (3) There have been significant advances in river ice modelling. For example, both one-dimensional (e.g. RIVICE, RIVJAM, ICEJAM, HEC-RAS, etc.) and two-dimensional (2-D; www.river2d.ca) public-domain ice-jam models are now available. Work is ongoing to improve RIVER2D, and a commercial 2-D ice-process model is being developed. (4) The 1999-2003 period is notable for the number of distinctly hydrological and ecological studies. On the quantitative side, many are making efforts to determine streamflow during the winter period. On the ecological side, some new publications have addressed the link to water quality (temperature, dissolved oxygen, nutrients and pollutants), and others have dealt with sediment transport and geomorphology (particularly as it relates to break-up), stream ecology (plants, food cycle, etc.) and fish habitat.There is the growing recognition, that these types of study require collaborative efforts. In our view, the main areas requiring further work are: (1) to interface geomorphological and habitat models with quantitative river ice hydrodynamic models; (2) to develop a manager's toolbox (database management, remote sensing, forecasting, intervention methodologies, etc.) to enable

The African migration and wintering grounds of the Aquatic Warbler Acrocephalus paludicola

DEFF Research Database (Denmark)

Schäffer, Norbert; Walther, Bruno A.; Gutteridge, Kim

2006-01-01

the edges of backwaters, flood basins, lagoons, lakes, ponds, rivers and wadis. Recent research suggests that at least some Aquatic Warblers may actually winter further south than the present data suggest, in countries such as The Gambia, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Ivory Coast, Ghana...

Sea-ice thickness from field measurements in the northwestern Barents Sea

Science.gov (United States)

King, Jennifer; Spreen, Gunnar; Gerland, Sebastian; Haas, Christian; Hendricks, Stefan; Kaleschke, Lars; Wang, Caixin

2017-02-01

The Barents Sea is one of the fastest changing regions of the Arctic, and has experienced the strongest decline in winter-time sea-ice area in the Arctic, at -23±4% decade-1. Sea-ice thickness in the Barents Sea is not well studied. We present two previously unpublished helicopter-borne electromagnetic (HEM) ice thickness measurements from the northwestern Barents Sea acquired in March 2003 and 2014. The HEM data are compared to ice thickness calculated from ice draft measured by ULS deployed between 1994 and 1996. These data show that ice thickness varies greatly from year to year; influenced by the thermodynamic and dynamic processes that govern local formation vs long-range advection. In a year with a large inflow of sea-ice from the Arctic Basin, the Barents Sea ice cover is dominated by thick multiyear ice; as was the case in 2003 and 1995. In a year with an ice cover that was mainly grown in situ, the ice will be thin and mechanically unstable; as was the case in 2014. The HEM data allow us to explore the spatial and temporal variability in ice thickness. In 2003 the dominant ice class was more than 2 years old; and modal sea-ice thickness varied regionally from 0.6 to 1.4 m, with the thinner ice being either first-year ice, or multiyear ice which had come into contact with warm Atlantic water. In 2014 the ice cover was predominantly locally grown ice less than 1 month old (regional modes of 0.5-0.8 m). These two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic; or have a different impact on heat transport from ocean to atmosphere.

East Asian winter monsoon forecasting schemes based on the NCEP's climate forecast system

Science.gov (United States)

Tian, Baoqiang; Fan, Ke; Yang, Hongqing

2017-12-01

The East Asian winter monsoon (EAWM) is the major climate system in the Northern Hemisphere during boreal winter. In this study, we developed two schemes to improve the forecasting skill of the interannual variability of the EAWM index (EAWMI) using the interannual increment prediction method, also known as the DY method. First, we found that version 2 of the NCEP's Climate Forecast System (CFSv2) showed higher skill in predicting the EAWMI in DY form than not. So, based on the advantage of the DY method, Scheme-I was obtained by adding the EAWMI DY predicted by CFSv2 to the observed EAWMI in the previous year. This scheme showed higher forecasting skill than CFSv2. Specifically, during 1983-2016, the temporal correlation coefficient between the Scheme-I-predicted and observed EAWMI was 0.47, exceeding the 99% significance level, with the root-mean-square error (RMSE) decreased by 12%. The autumn Arctic sea ice and North Pacific sea surface temperature (SST) are two important external forcing factors for the interannual variability of the EAWM. Therefore, a second (hybrid) prediction scheme, Scheme-II, was also developed. This scheme not only involved the EAWMI DY of CFSv2, but also the sea-ice concentration (SIC) observed the previous autumn in the Laptev and East Siberian seas and the temporal coefficients of the third mode of the North Pacific SST in DY form. We found that a negative SIC anomaly in the preceding autumn over the Laptev and the East Siberian seas could lead to a significant enhancement of the Aleutian low and East Asian westerly jet in the following winter. However, the intensity of the winter Siberian high was mainly affected by the third mode of the North Pacific autumn SST. Scheme-I and Scheme-II also showed higher predictive ability for the EAWMI in negative anomaly years compared to CFSv2. More importantly, the improvement in the prediction skill of the EAWMI by the new schemes, especially for Scheme-II, could enhance the forecasting skill of

Canadian snow and sea ice: historical trends and projections

Science.gov (United States)

Mudryk, Lawrence R.; Derksen, Chris; Howell, Stephen; Laliberté, Fred; Thackeray, Chad; Sospedra-Alfonso, Reinel; Vionnet, Vincent; Kushner, Paul J.; Brown, Ross

2018-04-01

The Canadian Sea Ice and Snow Evolution (CanSISE) Network is a climate research network focused on developing and applying state of the art observational data to advance dynamical prediction, projections, and understanding of seasonal snow cover and sea ice in Canada and the circumpolar Arctic. Here, we present an assessment from the CanSISE Network on trends in the historical record of snow cover (fraction, water equivalent) and sea ice (area, concentration, type, and thickness) across Canada. We also assess projected changes in snow cover and sea ice likely to occur by mid-century, as simulated by the Coupled Model Intercomparison Project Phase 5 (CMIP5) suite of Earth system models. The historical datasets show that the fraction of Canadian land and marine areas covered by snow and ice is decreasing over time, with seasonal and regional variability in the trends consistent with regional differences in surface temperature trends. In particular, summer sea ice cover has decreased significantly across nearly all Canadian marine regions, and the rate of multi-year ice loss in the Beaufort Sea and Canadian Arctic Archipelago has nearly doubled over the last 8 years. The multi-model consensus over the 2020-2050 period shows reductions in fall and spring snow cover fraction and sea ice concentration of 5-10 % per decade (or 15-30 % in total), with similar reductions in winter sea ice concentration in both Hudson Bay and eastern Canadian waters. Peak pre-melt terrestrial snow water equivalent reductions of up to 10 % per decade (30 % in total) are projected across southern Canada.

Ocean wave generation by collapsing ice shelves

Science.gov (United States)

Macayeal, D. R.; Bassis, J. N.; Okal, E. A.; Aster, R. C.; Cathles, L. M.

2008-12-01

The 28-29 February, 2008, break-up of the Wilkins Ice Shelf, Antarctica, exemplifies the now-familiar, yet largely unexplained pattern of explosive ice-shelf break-up. While environmental warming is a likely ultimate cause of explosive break-up, several key aspects of their short-term behavior need to be explained: (1) The abrupt, near-simultaneous onset of iceberg calving across long spans of the ice front margin; (2) High outward drift velocity (about 0.3 m/s) of a leading phalanx of tabular icebergs that originate from the seaward edge of the intact ice shelf prior to break-up; (3) Rapid coverage of the ocean surface in the wake of this leading phalanx by small, capsized and dismembered tabular icebergs; (4) Extremely large gravitational potential energy release rates, e.g., up to 3 × 1010 W; (5) Lack of proximal iceberg-calving triggers that control the timing of break-up onset and that maintain the high break-up calving rates through to the conclusion of the event. Motivated by seismic records obtained from icebergs and the Ross Ice Shelf that show hundreds of micro- tsunamis emanating from near the ice shelf front, we re-examine the basic dynamic features of ice- shelf/ocean-wave interaction and, in particular, examine the possibility that collapsing ice shelves themselves are a source of waves that stimulate the disintegration process. We propose that ice-shelf generated surface-gravity waves associated with initial calving at an arbitrary seed location produce stress perturbations capable of triggering the onset of calving on the entire ice front. Waves generated by parting detachment rifts, iceberg capsize and break-up act next to stimulate an inverted submarine landslide (ice- slide) process, where gravitational potential energy released by upward movement of buoyant ice is radiated as surface gravity waves in the wake of the advancing phalanx of tabular icebergs. We conclude by describing how field research and remote sensing can be used to test the

Ross Ice Shelf airstream driven by polar vortex cyclone

Science.gov (United States)

Schultz, Colin

2012-07-01

The powerful air and ocean currents that flow in and above the Southern Ocean, circling in the Southern Hemisphere's high latitudes, form a barrier to mixing between Antarctica and the rest of the planet. Particularly during the austral winter, strong westerly winds isolate the Antarctic continent from heat, energy, and mass exchange, bolstering the scale of the annual polar ozone depletion and driving the continent's record-breaking low temperatures. Pushing through this wall of high winds, the Ross Ice Shelf airstream (RAS) is responsible for a sizable amount of mass and energy exchange from the Antarctic inland areas to lower latitudes. Sitting due south of New Zealand, the roughly 470,000-square-kilometer Ross Ice Shelf is the continent's largest ice shelf and a hub of activity for Antarctic research. A highly variable lower atmospheric air current, RAS draws air from the inland Antarctic Plateau over the Ross Ice Shelf and past the Ross Sea. Drawing on modeled wind patterns for 2001-2005, Seefeldt and Cassano identify the primary drivers of RAS.

Comparison of Mars Northern Cap Edge Advance and Recession Rates over the Last 6 Mars Years

Science.gov (United States)

Titus, T. N.; Cushing, G. E.; Langevin, Y.; Brown, A. J.; Themis Science Team; CRISM Science Team

2011-12-01

The most observable parameter that describes the Mars polar seasonal caps is their size, which has been measured since the days of Herschel. The advance and retreat of the polar cap from year to year may exhibit many clues to help elucidate little understood physical processes. For example, summertime heat storage in the regolith could delay the onset of seasonal CO2 cap formation. The evolution of the seasonal cap could also be directly affected by the thermal inertia of the near-surface regolith and place constraints on the depth of the ice table. Parameterizations of the seasonal cap edges provide useful constraints on atmospheric GCMs and mesoscale models. Longitudinally resolving the cap edges as they advance and retreat constrains the times when zonal means are appropriate and when longitudinal asymmetries make zonal means invalid. These same kinds of parameterizations can also be used when modeling other data that have low spatial resolutions, such as Gamma Ray Spectrometer (GRS )and Neutron Spectrometer (NS) data. By knowing where the cap edge should be, coarse spatial data can correct for subpixel mixing caused by large point-spread functions including both frosted and frost-free areas. The northern cap exhibits a near symmetric retreat, which has been well characterized at visible wavelengths by both telescopic and spacecraft observations. However, the advance of the cap has not been well characterized until the 21st century. Kieffer and Titus (2001) have used zonal means to observe surface temperature and visible bolometric albedo variations with season using MGS/TES. The TES thermal observations show an almost perfectly symmetrical advance; i.e., condensation at consistent latitude across all longitudes, with the most northern edge of the seasonal cap occurring between longitudes 245°E to 265°E and the most southern edge of the seasonal cap occurring between 280°E and 30°E. The advance of the northern cap typically leads the advance of the edge of

Effects of marsh pond terracing on coastal wintering waterbirds before and after Hurricane Rita.

Science.gov (United States)

O'Connell, Jessica L; Nyman, John A

2011-11-01

From February to March 2005-2006, we surveyed wintering waterbirds to test effects of terracing on coastal pond use before and after Hurricane Rita. Marsh terracing is intended to slow coastal marsh loss in the Chenier Plain by slowing marsh erosion and encouraging vegetation expansion. Terraces also increase marsh edge in ponds, possibly benefiting waterbirds. We monitored paired terraced and unterraced ponds in three sites within southwestern Louisiana's Chenier Plain. Waterbirds were 75% more numerous in terraced than unterraced ponds. Waterbird richness was similar among ponds when corrected for number of individuals, suggesting terracing increased bird density but did not provide habitat unique from unterraced ponds. Birds were 93% more numerous following Hurricane Rita, mostly due to an influx of migrating waterfowl. Year round residents were similar in number before and after Hurricane Rita. Resident richness did not differ among years after correcting for number of observed individuals. Wading and dabbling foragers were more abundant in terraced ponds and these two guilds represented 74% of birds observed. We detected no difference among ponds for other guilds, i.e., probing, aerial, and diving foragers. Increasing proportion of mash edge increased bird density disproportionately: On average ponds with 10% edge had 6 birds observed and ponds with 30% edge had 16 birds observed. Terraces increased habitat interspersion and were an effective tool for increasing numbers of wintering waterfowl and wading birds. The extent to which terraces were sustainable following hurricane forces is unknown.

Effects of Marsh Pond Terracing on Coastal Wintering Waterbirds Before and After Hurricane Rita

Science.gov (United States)

O'Connell, Jessica L.; Nyman, John A.

2011-11-01

From February to March 2005-2006, we surveyed wintering waterbirds to test effects of terracing on coastal pond use before and after Hurricane Rita. Marsh terracing is intended to slow coastal marsh loss in the Chenier Plain by slowing marsh erosion and encouraging vegetation expansion. Terraces also increase marsh edge in ponds, possibly benefiting waterbirds. We monitored paired terraced and unterraced ponds in three sites within southwestern Louisiana's Chenier Plain. Waterbirds were 75% more numerous in terraced than unterraced ponds. Waterbird richness was similar among ponds when corrected for number of individuals, suggesting terracing increased bird density but did not provide habitat unique from unterraced ponds. Birds were 93% more numerous following Hurricane Rita, mostly due to an influx of migrating waterfowl. Year round residents were similar in number before and after Hurricane Rita. Resident richness did not differ among years after correcting for number of observed individuals. Wading and dabbling foragers were more abundant in terraced ponds and these two guilds represented 74% of birds observed. We detected no difference among ponds for other guilds, i.e., probing, aerial, and diving foragers. Increasing proportion of mash edge increased bird density disproportionately: On average ponds with 10% edge had 6 birds observed and ponds with 30% edge had 16 birds observed. Terraces increased habitat interspersion and were an effective tool for increasing numbers of wintering waterfowl and wading birds. The extent to which terraces were sustainable following hurricane forces is unknown.

Antioxidant responses in the polar marine sea-ice amphipod Gammarus wilkitzkii to natural and experimentally increased UV levels

International Nuclear Information System (INIS)

Krapp, Rupert H.; Bassinet, Thievery; Berge, Jorgen; Pampanin, Daniela M.; Camus, Lionel

2009-01-01

Polar marine surface waters are characterized by high levels of dissolved oxygen, seasonally intense UV irradiance and high levels of dissolved organic carbon. Therefore, the Arctic sea-ice habitat is regarded as a strongly pro-oxidant environment, even though its significant ice cover protects the ice-associated (=sympagic) fauna from direct irradiation to a large extent. In order to investigate the level of resistance to oxyradical stress, we sampled the sympagic amphipod species Gammarus wilkitzkii during both winter and summer conditions, as well as exposed specimens to simulated levels of near-natural and elevated levels of UV irradiation. Results showed that this amphipod species possessed a much stronger antioxidant capacity during summer than during winter. Also, the experimental UV exposure showed a depletion in antioxidant defences, indicating a negative effect of UV exposure on the total oxyradical scavenging capacity. Another sympagic organism, Onisimus nanseni, was sampled during summer conditions. When compared to G. wilkitzkii, the species showed even higher antioxidant scavenging capacity.

Vancouver winters: Environmental influences on inpatient adult orthopaedic trauma demographics

International Nuclear Information System (INIS)

Noordin, S.; Masri, B. A.

2014-01-01

Objective: To compare the pattern of adult inpatient orthopaedic injuries admitted at three Vancouver hospitals following one of the worst winter snowstorms in the region with the preceding control winter period. Methods: The surveillance study was conducted at the University of British Columbia, Vancouver, Canada, 2007 to 2010. Inpatient adult admissions for orthopaedic injuries at three hospitals were recorded, including age, gender, anatomic location of injury, type of fracture (open or closed), fixation method (internal versus external fixation), and length of acute care hospital stay. Comparisons between admissions during this weather pattern and admission during a previous winter with minimal snow were made. SPSS 19 was used for statistical analysis. Results: Of the 511 patients admitted under Orthopaedic trauma service during the significant winter snowstorms of December 2008 - January 2009, 100 (19.6%) (CI: 16.2%-23.2%) were due to ice and snow, whereas in the preceding mild winter only 18 of 415 (4.3%) (CI: 2.5%-6.8%) cases were related to snow (p<0.05). Ankle and wrist fractures were the most frequent injuries during the index snow storm period (p<0.05). At all the three institutions, 97 (96.5%) fractures were closed during the snowstorm as opposed to 17 (95%) during the control winter period. Internal fixation in 06 (89%) fractures as opposed to external fixation in 12 (11%) patients was the predominant mode of fixation across the board during both time periods. Conclusion: The study demonstrated a significantly higher inpatient orthopaedic trauma volume during the snowstorm more rigorous prospective studies need to be designed to gain further insight to solving these problems from a public health perspective. (author)

A Legacy for IPY: The Global Snowflake Network (GSN) Together With Art and Ice, and Music and Ice; Unique new Features for Science Education.

Science.gov (United States)

Wasilewski, P. J.

2007-12-01

The Global Snowflake Network (GSN) is a program that is simultaneously a science program and an education program. When the validation of the procedures (collection and identification of the type of snowflakes and the associated satellite image archive, as a serial record of a storm), is achieved, then the program becomes a scientific resource. This latter is the ultimate goal. That's why NASA has launched the Global Snowflake Network, a massive project that aims to involve the general public to "collect and classify" falling snowflakes. The data will be compiled into a massive database, along with satellite images, that will help climatologists and others who study climate-related phenomena gain a better understanding of wintry meteorology as they track various snowstorms around the globe. A great deal of information about the atmosphere dynamics and cloud microphysics can be derived from the serial collection and identification of the types of snow crystals and the degree of riming of the snow crystals during the progress of a snow storm. Forecasting winter weather depends in part on cloud physics, which deals with precipitation type, and if it happens to be snow- the crystal type, size, and density of the snowflake population. The History of Winter website will host the evolving snow and ice features for the IPY. Type "Global Snowflake Network" into the search engine (such as GOOGLE) and you will receive a demonstration of the operation of the preliminary GSN by the Indigenous community. The expeditions FINNMARK2007 and the POLAR Husky GoNorth 2007 expedition took the complement of Thermochrons with multimedia instructions for the Global Snowflake Network. This approach demonstrates the continuous Thermochron monitoring of expedition temperature and provides otherwise inaccessible snowflake information to NASA and others interested in the Polar region snow. In addition, reindeer herder and Ph.D. student, Inger Marie G. Eira, will incorporate the HOW, GSN

Observation of hydro-acoustic signal from the Balleny Islands, Ross Sea, Antarctic: Seasonal ice activities and earthquakes from Pacific-Antarctic ridge

Science.gov (United States)

Hong, J. K.; Kang, S. G.; Dziak, R. P.; Park, Y.; Lau, T. K. A.; Haxel, J.; Matsumoto, H.

2017-12-01

From January 2015 to March 2016, five hydrophone moorings were deployed near the Balleny Islands to obtain the long-term hydroacoustic record as a collaborative effort between the NOAA/Pacific Marine Environmental Laboratory and the Korea Polar Research Institute. The goal of this hydro-acoustic project is to understand seasonal sea-ice activities and identify potential underwater volcanic sources within the Balleny seamounts. All five of the hydrophone moorings were recovered in March 2016, however only three of them recorded 14 months of continuous, broadband (1 kHz sample rate) hydro-acoustic data successfully. In spite of coordinating problem by partial recovery, recorded data contain valuable information for seasonal sea-ice activities and earthquakes from Pacific-Antarctic Ridge. We analyzed events from ice-quakes and earthquakes statistically. The number of ice-quakes is maximum in the austral summer while minimum in the austral winter which shows a clear seasonal pattern consistent with freeze-thaw cycles. Comparing with global earthquakes catalogue, number of earthquake events are correlated well with the catalogue. Because the austral winter is more calm by ice-quakes, however, we can detect more earthquakes in this season.

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.

Global warming: Sea ice and snow cover

International Nuclear Information System (INIS)

Walsh, J.E.

1993-01-01

In spite of differences among global climate simulations under scenarios where atmospheric CO 2 is doubled, all models indicate at least some amplification of greenouse warming at the polar regions. Several decades of recent data on air temperature, sea ice, and snow cover of the high latitudes of the Northern Hemisphere are summarized to illustrate the general compatibility of recent variations in those parameters. Despite a data void over the Arctic Ocean, some noteworthy patterns emerge. Warming dominates in winter and spring, as projected by global climate models, with the warming strongest over subpolar land areas of Alaska, northwestern Canada, and northern Eurasia. A time-longitude summary of Arctic sea ice variations indicates that timescales of most anomalies range from several months to several years. Wintertime maxima of total sea ice extent contain no apparent secular trends. The statistical significance of trends in recent sea ice variations was evaluated by a Monte Carlo procedure, showing a statistically significant negative trend in the summer. Snow cover data over the 20-y period of record show a noticeable decrease of Arctic snow cover in the late 1980s. This is of potential climatic significance since the accompanying decrease of surface albedo leads to a rapid increase of solar heating. 21 refs., 3 figs., 1 tab

A combined approach of remote sensing and airborne electromagnetics to determine the volume of polynya sea ice in the Laptev Sea

Directory of Open Access Journals (Sweden)

L. Rabenstein

2013-06-01

Full Text Available A combined interpretation of synthetic aperture radar (SAR satellite images and helicopter electromagnetic (HEM sea-ice thickness data has provided an estimate of sea-ice volume formed in Laptev Sea polynyas during the winter of 2007/08. The evolution of the surveyed sea-ice areas, which were formed between late December 2007 and middle April 2008, was tracked using a series of SAR images with a sampling interval of 2–3 days. Approximately 160 km of HEM data recorded in April 2008 provided sea-ice thicknesses along profiles that transected sea ice varying in age from 1 to 116 days. For the volume estimates, thickness information along the HEM profiles was extrapolated to zones of the same age. The error of areal mean thickness information was estimated to be between 0.2 m for younger ice and up to 1.55 m for older ice, with the primary error source being the spatially limited HEM coverage. Our results have demonstrated that the modal thicknesses and mean thicknesses of level ice correlated with the sea-ice age, but that varying dynamic and thermodynamic sea-ice growth conditions resulted in a rather heterogeneous sea-ice thickness distribution on scales of tens of kilometers. Taking all uncertainties into account, total sea-ice area and volume produced within the entire surveyed area were 52 650 km2 and 93.6 ± 26.6 km3. The surveyed polynya contributed 2.0 ± 0.5% of the sea-ice produced throughout the Arctic during the 2007/08 winter. The SAR-HEM volume estimate compares well with the 112 km3 ice production calculated with a~high-resolution ocean sea-ice model. Measured modal and mean-level ice thicknesses correlate with calculated freezing-degree-day thicknesses with a factor of 0.87–0.89, which was too low to justify the assumption of homogeneous thermodynamic growth conditions in the area, or indicates a strong dynamic thickening of level ice by rafting of even thicker ice.

Northern Alaskan land surface response to reduced Arctic sea ice extent

Energy Technology Data Exchange (ETDEWEB)

Higgins, Matthew E. [University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, CO (United States); Cassano, John J. [University of Colorado, Cooperative Institute for Research in Environmental Sciences, Department of Atmospheric and Oceanic Sciences, Boulder, CO (United States)

2012-05-15

With Arctic sea ice extent at near-record lows, an improved understanding of the relationship between sea ice and the land surface is warranted. We examine the land surface response to changing sea ice by first conducting a simulation using the Community Atmospheric Model version 3.1 with end of the twenty-first century sea ice extent. This future atmospheric response is then used to force the Weather and Research Forecasting Model version 3.1 to examine the terrestrial land surface response at high resolution over the North Slope of Alaska. Similar control simulations with twentieth century sea ice projections are also performed, and in both simulations only sea ice extent is altered. In the future sea ice extent experiment, atmospheric temperature increases significantly due to increases in latent and sensible heat flux, particularly in the winter season. Precipitation and snow pack increase significantly, and the increased snow pack contributes to warmer soil temperatures for most seasons by insulating the land surface. In the summer, however, soil temperatures are reduced due to increased albedo. Despite warmer near-surface atmospheric temperatures, it is found that spring melt is delayed throughout much of the North Slope due to the increased snow pack, and the growing season length is shortened. (orig.)

The role of feedbacks in Antarctic sea ice change

Science.gov (United States)

Feltham, D. L.; Frew, R. C.; Holland, P.

2017-12-01

The changes in Antarctic sea ice over the last thirty years have a strong seasonal dependence, and the way these changes grow in spring and decay in autumn suggests that feedbacks are strongly involved. The changes may ultimately be caused by atmospheric warming, the winds, snowfall changes, etc., but we cannot understand these forcings without first untangling the feedbacks. A highly simplified coupled sea ice -mixed layer model has been developed to investigate the importance of feedbacks on the evolution of sea ice in two contrasting regions in the Southern Ocean; the Amundsen Sea where sea ice extent has been decreasing, and the Weddell Sea where it has been expanding. The change in mixed layer depth in response to changes in the atmosphere to ocean energy flux is implicit in a strong negative feedback on ice cover changes in the Amundsen Sea, with atmospheric cooling leading to a deeper mixed layer resulting in greater entrainment of warm Circumpolar Deep Water, causing increased basal melting of sea ice. This strong negative feedback produces counter intuitive responses to changes in forcings in the Amundsen Sea. This feedback is absent in the Weddell due to the complete destratification and strong water column cooling that occurs each winter in simulations. The impact of other feedbacks, including the albedo feedback, changes in insulation due to ice thickness and changes in the freezing temperature of the mixed layer, were found to be of secondary importance compared to changes in the mixed layer depth.

Improved simulation of Antarctic sea ice due to the radiative effects of falling snow

Science.gov (United States)

Li, J.-L. F.; Richardson, Mark; Hong, Yulan; Lee, Wei-Liang; Wang, Yi-Hui; Yu, Jia-Yuh; Fetzer, Eric; Stephens, Graeme; Liu, Yinghui

2017-08-01

Southern Ocean sea-ice cover exerts critical control on local albedo and Antarctic precipitation, but simulated Antarctic sea-ice concentration commonly disagrees with observations. Here we show that the radiative effects of precipitating ice (falling snow) contribute substantially to this discrepancy. Many models exclude these radiative effects, so they underestimate both shortwave albedo and downward longwave radiation. Using two simulations with the climate model CESM1, we show that including falling-snow radiative effects improves the simulations relative to cloud properties from CloudSat-CALIPSO, radiation from CERES-EBAF and sea-ice concentration from passive microwave sensors. From 50-70°S, the simulated sea-ice-area bias is reduced by 2.12 × 106 km2 (55%) in winter and by 1.17 × 106 km2 (39%) in summer, mainly because increased wintertime longwave heating restricts sea-ice growth and so reduces summer albedo. Improved Antarctic sea-ice simulations will increase confidence in projected Antarctic sea level contributions and changes in global warming driven by long-term changes in Southern Ocean feedbacks.

Polar winter cloud depolarization measurements with the CANDAC Rayleigh-Mie-Raman Lidar

Science.gov (United States)

McCullough, E. M.; Nott, G. J.; Duck, T. J.; Sica, R. J.; Doyle, J. G.; Pike-thackray, C.; Drummond, J. R.

2011-12-01

Clouds introduce a significant positive forcing to the Arctic radiation budget and this is strongest during the polar winter when shortwave radiation is absent (Intrieri et al., 2002). The amount of forcing depends on the occurrence probability and optical depth of the clouds as well as the cloud particle phase (Ebert and Curry 1992). Mixed-phase clouds are particularly complex as they involve interactions between three phases of water (vapour, liquid and ice) coexisting in the same cloud. Although significant progress has been made in characterizing wintertime Arctic clouds (de Boer et al., 2009 and 2011), there is considerable variability in the relative abundance of particles of each phase, in the morphology of solid particles, and in precipitation rates depending on the meteorology at the time. The Canadian Network for the Detection of Atmospheric Change (CANDAC) Rayleigh-Mie-Raman Lidar (CRL) was installed in the Canadian High Arctic at Eureka, Nunavut (80°N, 86°W) in 2008-2009. The remotely-operated system began with measurement capabilities for multi-wavelength aerosol extinction, water vapour mixing ratio, and tropospheric temperature profiles, as well as backscatter cross section coefficient and colour ratio. In 2010, a new depolarization channel was added. The capability to measure the polarization state of the return signal allows the characterization of the cloud in terms of liquid and ice water content, enabling the lidar to probe all three phases of water in these clouds. Lidar depolarization results from 2010 and 2011 winter clouds at Eureka will be presented, with a focus on differences in downwelling radiation between mixed phase clouds and ice clouds. de Boer, G., E.W. Eloranta, and M.D. Shupe (2009), Arctic mixed-phase stratiform cloud properties from multiple years of surface-based measurements at two high-latitude locations, Journal of Atmospheric Sciences, 66 (9), 2874-2887. de Boer, G., H. Morrison, M. D. Shupe, and R. Hildner (2011

Simultaneous monitoring of ice accretion and thermography of an airfoil: an IR imaging methodology

International Nuclear Information System (INIS)

Mohseni, M; Frioult, M; Amirfazli, A

2012-01-01

A novel image analysis methodology based on infrared (IR) imaging was developed for simultaneous monitoring of ice accretion and thermography of airfoils. In this study, an IR camera was calibrated and used to measure the surface temperature of the energized airfoils, and monitor the ice accretion and growth pattern on the airfoils’ surfaces. The methodology comprises the automatic processing of a series of IR video frames with the purpose of detecting ice pattern evolution during the icing test period. A specially developed MATLAB code was used to detect the iced areas in the IR images, and simultaneously monitor surface temperature evolution of the airfoil during an icing test. Knowing the correlation between the icing pattern and surface temperature changes during an icing test is essential for energy efficient design of thermal icing mitigation systems. Processed IR images were also used to determine the ice accumulation rate on the airfoil's surface in a given icing test. The proposed methodology has been demonstrated to work successfully, since the optical images taken at the end of icing tests from the airfoils’ surfaces compared well with the processed IR images detecting the ice grown outward from the airfoils’ leading edge area. (paper)

Reconstruction of historic sea ice conditions in a sub-Arctic lagoon

Science.gov (United States)

Petrich, Chris; Tivy, Adrienne C.; Ward, David H.

2014-01-01

Historical sea ice conditions were reconstructed for Izembek Lagoon, Bering Sea, Alaska. This lagoon is a crucial staging area during migration for numerous species of avian migrants and a major eelgrass (Zostera marina) area important to a variety of marine and terrestrial organisms, especially Pacific Flyway black brant geese (Branta bernicla nigricans). Ice cover is a common feature of the lagoon in winter, but appears to be declining, which has implications for eelgrass distribution and abundance, and its use by wildlife. We evaluated ice conditions from a model based on degree days, calibrated to satellite observations, to estimate distribution and long-term trends in ice conditions in Izembek Lagoon. Model results compared favorably with ground observations and 26 years of satellite data, allowing ice conditions to be reconstructed back to 1943. Specifically, periods of significant (limited access to eelgrass areas) and severe (almost complete ice coverage of the lagoon) ice conditions could be identified. The number of days of severe ice within a single season ranged from 0 (e.g., 2001) to ≥ 67 (e.g., 2000). We detected a slight long-term negative trend in ice conditions, superimposed on high inter-annual variability in seasonal aggregate ice conditions. Based on reconstructed ice conditions, the seasonally cumulative number of significant or severe ice days correlated linearly with mean air temperature from January until March. Further, air temperature at Izembek Lagoon was correlated with wind direction, suggesting that ice conditions in Izembek Lagoon were associated with synoptic-scale weather patterns. Methods employed in this analysis may be transferable to other coastal locations in the Arctic.

About uncertainties in sea ice thickness retrieval from satellite radar altimetry: results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise

Science.gov (United States)

Kern, S.; Khvorostovsky, K.; Skourup, H.; Rinne, E.; Parsakhoo, Z. S.; Djepa, V.; Wadhams, P.; Sandven, S.

2014-03-01

One goal of the European Space Agency Climate Change Initiative sea ice Essential Climate Variable project is to provide a quality controlled 20 year long data set of Arctic Ocean winter-time sea ice thickness distribution. An important step to achieve this goal is to assess the accuracy of sea ice thickness retrieval based on satellite radar altimetry. For this purpose a data base is created comprising sea ice freeboard derived from satellite radar altimetry between 1993 and 2012 and collocated observations of snow and sea ice freeboard from Operation Ice Bridge (OIB) and CryoSat Validation Experiment (CryoVEx) air-borne campaigns, of sea ice draft from moored and submarine Upward Looking Sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer aboard EOS (AMSR-E) and the Warren Climatology (Warren et al., 1999). An inter-comparison of the snow depth data sets stresses the limited usefulness of Warren climatology snow depth for freeboard-to-thickness conversion under current Arctic Ocean conditions reported in other studies. This is confirmed by a comparison of snow freeboard measured during OIB and CryoVEx and snow freeboard computed from radar altimetry. For first-year ice the agreement between OIB and AMSR-E snow depth within 0.02 m suggests AMSR-E snow depth as an appropriate alternative. Different freeboard-to-thickness and freeboard-to-draft conversion approaches are realized. The mean observed ULS sea ice draft agrees with the mean sea ice draft computed from radar altimetry within the uncertainty bounds of the data sets involved. However, none of the realized approaches is able to reproduce the seasonal cycle in sea ice draft observed by moored ULS satisfactorily. A sensitivity analysis of the freeboard-to-thickness conversion suggests: in order to obtain sea ice thickness as accurate as 0.5 m from radar altimetry, besides a freeboard estimate with centimetre accuracy, an ice-type dependent sea ice density is as mandatory

Warmer and wetter winters: characteristics and implications of an extreme weather event in the High Arctic

International Nuclear Information System (INIS)

Hansen, Brage B; Isaksen, Ketil; Benestad, Rasmus E; Kohler, Jack; Pedersen, Åshild Ø; Loe, Leif E; Coulson, Stephen J; Larsen, Jan Otto; Varpe, Øystein

2014-01-01

One predicted consequence of global warming is an increased frequency of extreme weather events, such as heat waves, droughts, or heavy rainfalls. In parts of the Arctic, extreme warm spells and heavy rain-on-snow (ROS) events in winter are already more frequent. How these weather events impact snow-pack and permafrost characteristics is rarely documented empirically, and the implications for wildlife and society are hence far from understood. Here we characterize and document the effects of an extreme warm spell and ROS event that occurred in High Arctic Svalbard in January–February 2012, during the polar night. In this normally cold semi-desert environment, we recorded above-zero temperatures (up to 7 °C) across the entire archipelago and record-breaking precipitation, with up to 98 mm rainfall in one day (return period of >500 years prior to this event) and 272 mm over the two-week long warm spell. These precipitation amounts are equivalent to 25 and 70% respectively of the mean annual total precipitation. The extreme event caused significant increase in permafrost temperatures down to at least 5 m depth, induced slush avalanches with resultant damage to infrastructure, and left a significant ground-ice cover (∼5–20 cm thick basal ice). The ground-ice not only affected inhabitants by closing roads and airports as well as reducing mobility and thereby tourism income, but it also led to high starvation-induced mortality in all monitored populations of the wild reindeer by blocking access to the winter food source. Based on empirical-statistical downscaling of global climate models run under the moderate RCP4.5 emission scenario, we predict strong future warming with average mid-winter temperatures even approaching 0 °C, suggesting increased frequency of ROS. This will have far-reaching implications for Arctic ecosystems and societies through the changes in snow-pack and permafrost properties. (letter)

Warmer and wetter winters: characteristics and implications of an extreme weather event in the High Arctic

Science.gov (United States)

Hansen, Brage B.; Isaksen, Ketil; Benestad, Rasmus E.; Kohler, Jack; Pedersen, Åshild Ø.; Loe, Leif E.; Coulson, Stephen J.; Larsen, Jan Otto; Varpe, Øystein

2014-11-01

One predicted consequence of global warming is an increased frequency of extreme weather events, such as heat waves, droughts, or heavy rainfalls. In parts of the Arctic, extreme warm spells and heavy rain-on-snow (ROS) events in winter are already more frequent. How these weather events impact snow-pack and permafrost characteristics is rarely documented empirically, and the implications for wildlife and society are hence far from understood. Here we characterize and document the effects of an extreme warm spell and ROS event that occurred in High Arctic Svalbard in January-February 2012, during the polar night. In this normally cold semi-desert environment, we recorded above-zero temperatures (up to 7 °C) across the entire archipelago and record-breaking precipitation, with up to 98 mm rainfall in one day (return period of >500 years prior to this event) and 272 mm over the two-week long warm spell. These precipitation amounts are equivalent to 25 and 70% respectively of the mean annual total precipitation. The extreme event caused significant increase in permafrost temperatures down to at least 5 m depth, induced slush avalanches with resultant damage to infrastructure, and left a significant ground-ice cover (˜5-20 cm thick basal ice). The ground-ice not only affected inhabitants by closing roads and airports as well as reducing mobility and thereby tourism income, but it also led to high starvation-induced mortality in all monitored populations of the wild reindeer by blocking access to the winter food source. Based on empirical-statistical downscaling of global climate models run under the moderate RCP4.5 emission scenario, we predict strong future warming with average mid-winter temperatures even approaching 0 °C, suggesting increased frequency of ROS. This will have far-reaching implications for Arctic ecosystems and societies through the changes in snow-pack and permafrost properties.

Modes of supraglacial lake drainage and dynamic ice sheet response

Science.gov (United States)

Das, S. B.; Behn, M. D.; Joughin, I. R.

2011-12-01

We investigate modes of supraglacial lake drainage using geophysical, ground, and remote sensing observations over the western margin of the Greenland ice sheet. Lakes exhibit a characteristic life cycle defined by a pre-drainage, drainage, and post-drainage phase. In the pre-drainage phase winter snow fills pre-existing cracks and stream channels, efficiently blocking past drainage conduits. As temperatures increase in the spring, surface melting commences, initially saturating the snow pack and subsequently forming a surface network of streams that fills the lake basins. Basins continue to fill until lake drainage commences, which for individual lakes occurs at different times depending on the previous winter snow accumulation and summer temperatures. Three styles of drainage behavior have been observed: (1) no drainage, (2) slow drainage over the side into an adjacent pre-existing crack, and (3) rapid drainage through a new crack formed beneath the lake basin. Moreover, from year-to-year individual lakes exhibit different drainage behaviors. Lakes that drain slowly often utilize the same outflow channel for multiple years, creating dramatic canyons in the ice. Ultimately, these surface channels are advected out of the lake basin and a new channel forms. In the post-drainage phase, melt water continues to access the bed typically through a small conduit (e.g. moulin) formed near a local topographic minimum along the main drainage crack, draining the lake catchment throughout the remainder of the melt season. This melt water input to the bed leads to continued basal lubrication and enhanced ice flow compared to background velocities. Lakes that do not completely drain freeze over to form a surface ice layer that persists into the following year. Our results show that supraglacial lakes show a spectrum of drainage behaviors and that these styles of drainage lead to varying rates and timing of surface meltwater delivery to the bed resulting in different dynamic ice

The relation between sea ice thickness and freeboard in the Arctic

Directory of Open Access Journals (Sweden)

V. Alexandrov

2010-09-01

Full Text Available Retrieval of Arctic sea ice thickness from CryoSat-2 radar altimeter freeboard data requires observational data to verify the relation between these two variables. In this study in-situ ice and snow data from 689 observation sites, obtained during the Sever expeditions in the 1980s, have been used to establish an empirical relation between thickness and freeboard of FY ice in late winter. Estimates of mean and variability of snow depth, snow density and ice density were produced on the basis of many field observations. These estimates have been used in the hydrostatic equilibrium equation to retrieve ice thickness as a function of ice freeboard, snow depth and snow/ice density. The accuracy of the ice thickness retrieval has been calculated from the estimated variability in ice and snow parameters and error of ice freeboard measurements. It is found that uncertainties of ice density and freeboard are the major sources of error in ice thickness calculation. For FY ice, retrieval of ≈ 1.0 m (2.0 m thickness has an uncertainty of 46% (37%, and for MY ice, retrieval of 2.4 m (3.0 m thickness has an uncertainty of 20% (18%, assuming that the freeboard error is ± 0.03 m for both ice types. For MY ice the main uncertainty is ice density error, since the freeboard error is relatively smaller than that for FY ice. If the freeboard error can be reduced to 0.01 m by averaging measurements from CryoSat-2, the error in thickness retrieval is reduced to about 32% for a 1.0 m thick FY floe and to about 18% for a 2.4 m thick MY floe. The remaining error is dominated by uncertainty in ice density. Provision of improved ice density data is therefore important for accurate retrieval of ice thickness from CryoSat-2 data.

Results of Low Power Deicer tests on a swept inlet component in the NASA Lewis Icing Research Tunnel

Science.gov (United States)

Bond, Thomas H.; Shin, Jaiwon

1993-01-01

Tests were conducted under a USAF/NASA Low Power Deicer program on two expulsive technologies to examine system performance on hardware representative of a modern aircraft part. The BF Goodrich Electro-Expulsive Deicing System and Pneumatic Impulse Ice Protection system were installed on a swept, compound curve, engine inlet component with varying leading edge radius, and tested through a range of icing and system operating conditions in the NASA Lewis Icing Research Tunnel. A description of the experimental procedure and results, including residual ice thickness, shed ice particle size, and changes in system energy/pressure characteristics are presented.

A Comparison of MODIS/VIIRS Cloud Masks over Ice-Bearing River: On Achieving Consistent Cloud Masking and Improved River Ice Mapping

Directory of Open Access Journals (Sweden)

Simon Kraatz

2017-03-01

Full Text Available The capability of frequently and accurately monitoring ice on rivers is important, since it may be possible to timely identify ice accumulations corresponding to ice jams. Ice jams are dam-like structures formed from arrested ice floes, and may cause rapid flooding. To inform on this potential hazard, the CREST River Ice Observing System (CRIOS produces ice cover maps based on MODIS and VIIRS overpass data at several locations, including the Susquehanna River. CRIOS uses the respective platform’s automatically produced cloud masks to discriminate ice/snow covered grid cells from clouds. However, since cloud masks are produced using each instrument’s data, and owing to differences in detector performance, it is quite possible that identical algorithms applied to even nearly identical instruments may produce substantially different cloud masks. Besides detector performance, cloud identification can be biased due to local (e.g., land cover, viewing geometry, and transient conditions (snow and ice. Snow/cloud confusions and large view angles can result in substantial overestimates of clouds and ice. This impacts algorithms, such as CRIOS, since false cloud cover precludes the determination of whether an otherwise reasonably cloud free grid consists of water or ice. Especially for applications aiming to frequently classify or monitor a location it is important to evaluate cloud masking, including false cloud detections. We present an assessment of three cloud masks via the parameter of effective revisit time. A 100 km stretch of up to 1.6 km wide river was examined with daily data sampled at 500 m resolution, examined over 317 days during winter. Results show that there are substantial differences between each of the cloud mask products, especially while the river bears ice. A contrast-based cloud screening approach was found to provide improved and consistent cloud and ice identification within the reach (95%–99% correlations, and 3%–7% mean

NUMERICAL SIMULATION OF ICE ACCRETION ON AIRFOIL

Directory of Open Access Journals (Sweden)

Nicusor ALEXANDRESCU

2009-09-01

Full Text Available This work consists in the simulation of the ice accretion in the leading edge of aerodynamic profiles and our proposed model encompasses: geometry generation, calculation of the potential flow around the body, boundary layer thickness computation, water droplet trajectory computation, heat and mass balances and the consequent modification of the geometry by the ice growth. The flow calculation is realized with panel methods, using only segments defined over the body contour. The viscous effects are considered using the Karman-Pohlhausen method for the laminar boundary layer. The local heat transfer coefficient is obtained by applying the Smith-Spalding method for the thermal boundary layer. The ice accretion limits and the collection efficiency are determined by computing water droplet trajectories impinging the surface. The heat transfer process is analyzed with an energy and a mass balance in each segment defining the body. Finally, the geometry is modified by the addition of the computed ice thickness to the respective panel. The process by repeating all the steps. The model validation is done using a selection of problems with experimental solution, CIRA (the CESAR project. Hereinafter, results are obtained for different aerodynamic profiles, angles of attack and meteorological parameters

Infrared Spectra and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere

Science.gov (United States)

Anderson, Carrie; Ferrante, Robert F.; Moore, W. James; Hudson, Reggie; Moore, Marla H.

2011-01-01

Spectra and optical constants of nitrile ices known or suspected to be in Titan?s atmosphere have been determined from 2.0 to 333.3 microns (approx.5000 to 30/cm). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan?s winter pole. Ices studied were: HCN, hydrogen cyanide; C2N2, cyanogen; CH3CN, acetonitrile; C2H5CN, propionitrile; and HC3N, cyanoacetylene. Optical constants were calculated, using Kramers-Kronig analysis, for each nitrile ice?s spectrum measured at a variety of temperatures, in both the amorphous- and crystalline phases. Spectra were also measured for many of the nitriles after quenching at the annealing temperature and compared with those of annealed ices. For each of these molecules we also measured the real component, n, of the refractive index for amorphous and crystalline phases at 670 nm. Several examples of the information contained in these new data sets and their usefulness in modeling Titan?s observed features will be presented (e.g., the broad emission feature at 160/cm; Anderson and Samuelson, 2011).

Probing Individual Ice Nucleation Events with Environmental Scanning Electron Microscopy

Science.gov (United States)

Wang, Bingbing; China, Swarup; Knopf, Daniel; Gilles, Mary; Laskin, Alexander

2016-04-01

Heterogeneous ice nucleation is one of the processes of critical relevance to a range of topics in the fundamental and the applied science and technologies. Heterogeneous ice nucleation initiated by particles proceeds where microscopic properties of particle surfaces essentially control nucleation mechanisms. Ice nucleation in the atmosphere on particles governs the formation of ice and mixed phase clouds, which in turn influence the Earth's radiative budget and climate. Heterogeneous ice nucleation is still insufficiently understood and poses significant challenges in predictive understanding of climate change. We present a novel microscopy platform allowing observation of individual ice nucleation events at temperature range of 193-273 K and relative humidity relevant for ice formation in the atmospheric clouds. The approach utilizes a home built novel ice nucleation cell interfaced with Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system is applied for direct observation of individual ice formation events, determining ice nucleation mechanisms, freezing temperatures, and relative humidity onsets. Reported microanalysis of the ice nucleating particles (INP) include elemental composition detected by the energy dispersed analysis of X-rays (EDX), and advanced speciation of the organic content in particles using scanning transmission x-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The performance of the IN-ESEM system is validated through a set of experiments with kaolinite particles with known ice nucleation propensity. We demonstrate an application of the IN-ESEM system to identify and characterize individual INP within a complex mixture of ambient particles.

The cloud-radiative processes and its modulation by sea-ice cover and stability as derived from a merged C3M Data product.

Science.gov (United States)

Nag, B.

2016-12-01

The polar regions of the world constitute an important sector in the global energy balance. Among other effects responsible for the change in the sea-ice cover like ocean circulation and ice-albedo feedback, the cloud-radiation feedback also plays a vital role in modulation of the Arctic environment. However the annual cycle of the clouds is very poorly represented in current global circulation models. This study aims to take advantage of a merged C3M data (CALIPSO, CloudSat, CERES, and MODIS) product from the NASA's A-Train Series to explore the sea-ice and atmospheric conditions in the Arctic on a spatial coverage spanning 70N to 80N. This study is aimed at the interactions or the feedbacks processes among sea-ice, clouds and the atmosphere. Using a composite approach based on a classification due to surface type, it is found that limitation of the water vapour influx from the surface due to change in phase at the surface featuring open oceans or marginal sea-ice cover to complete sea-ice cover is a major determinant in the modulation of the atmospheric moisture and its impacts. The impact of the cloud-radiative effects in the Arctic is found to vary with sea-ice cover and seasonally. The effect of the marginal sea-ice cover becomes more and more pronounced in the winter. The seasonal variation of the dependence of the atmospheric moisture on the surface and the subsequent feedback effects is controlled by the atmospheric stability measured as a difference between the potential temperature at the surface and the 700hPa level. It is found that a stronger stability cover in the winter is responsible for the longwave cloud radiative feedback in winter which is missing during the summer. A regional analysis of the same suggests that most of the depiction of the variations observed is contributed from the North Atlantic region.

Ice sheet hydrology from observations

Energy Technology Data Exchange (ETDEWEB)

Jansson, Peter [Dept. of Physical Geography and Quaternary Geology, Stockholm Univ-, Stockholm (Sweden)

2010-11-15

possible that soft beds through their ability to deform and be eroded can yield quasi-stable patterns of drainage pathways that with either erosion of critical sills or filling of temporary basins may reorganize itself periodically on time scales much shorter than the reorganization of the driving stresses for ice flow. In areas where the surface generated water (melt and rain), the basally generated fluxes dwarf the influx from the surface and hence the drainage system in such areas will be dominated by surface fluxes and variations therein. Since surface fluxes have a strong seasonal variation with no influx during winter, areas experiencing surface influx will also be subject to large seasonal variations in both flux and pressure. In addition, during the melt season, fluxes and also pressures will also vary on diurnal as well as longer time frames in response to variations in air temperature that drives melt and occurrence of precipitation events. The emerging picture of glacier drainage consists of different types of models applicable to different regimes found beneath an ice sheet (with our without surface influx, ice streams, subglacial lakes). It is not, however, clear how these systems are coupled, or even if they are. This makes it inherently difficult to assess what can be expected beneath a given sector of an ice sheet without some detailed understanding of the underlying geology (geothermal fluxes), geomorphology (possible water routing) and ice properties (cold -temperate base and ice thickness)

Ice sheet hydrology from observations

International Nuclear Information System (INIS)

Jansson, Peter

2010-11-01

possible that soft beds through their ability to deform and be eroded can yield quasi-stable patterns of drainage pathways that with either erosion of critical sills or filling of temporary basins may reorganize itself periodically on time scales much shorter than the reorganization of the driving stresses for ice flow. In areas where the surface generated water (melt and rain), the basally generated fluxes dwarf the influx from the surface and hence the drainage system in such areas will be dominated by surface fluxes and variations therein. Since surface fluxes have a strong seasonal variation with no influx during winter, areas experiencing surface influx will also be subject to large seasonal variations in both flux and pressure. In addition, during the melt season, fluxes and also pressures will also vary on diurnal as well as longer time frames in response to variations in air temperature that drives melt and occurrence of precipitation events. The emerging picture of glacier drainage consists of different types of models applicable to different regimes found beneath an ice sheet (with our without surface influx, ice streams, subglacial lakes). It is not, however, clear how these systems are coupled, or even if they are. This makes it inherently difficult to assess what can be expected beneath a given sector of an ice sheet without some detailed understanding of the underlying geology (geothermal fluxes), geomorphology (possible water routing) and ice properties (cold -temperate base and ice thickness)

Seasonal Climate Profiles of an Ice-free Arctic Based on Intra-ring Analyses of δ18O Value in Fossil Wood

Science.gov (United States)

Schubert, B.; Jahren, A. H.

2017-12-01

Arctic sea ice thickness and extent are projected to continue their substantial decline during this century, with an 80% reduction in sea-ice extent by 2050. While there is a clear relationship between mean annual temperature (MAT) and the concentration of atmospheric carbon dioxide (pCO2) across both glacial and interglacial periods, data on seasonal fluctuations is limited. Here we report seasonal temperature estimates for the Arctic during the ice-free conditions of the late early to middle Eocene based upon exquisitely preserved, mummified wood collected from Banks Island, Northwest Territories, Canada ( 74 oN). Annual growth rings identified in the wood specimens were subdivided by hand at sub-millimeter resolution and cellulose was extracted from each sub-sample for determination of stable oxygen isotope (δ18O) value (n = 81). The data reveal a consistent, cyclic pattern of decreasing and increasing δ18O value up to 3‰ across growth rings that was consistent with patterns observed in other modern and fossil wood, including from other high latitude sites. From these data we quantified cold month and warm month seasonal temperatures using a previously published model (Schubert and Jahren, 2015, QSR, 125: 1-14). Our calculations revealed low overall seasonality in the Arctic during the Eocene with above-freezing winters and mild summers, consistent with the presence of high biomass temperate rainforests. These results highlight the importance of warm winters in maintaining ice-free conditions in the Arctic and suggest that increased winter temperatures in today's Arctic in response to rising pCO2 will be of particular importance for Arctic ice-loss.

Observed decreases in the Canadian outdoor skating season due to recent winter warming

International Nuclear Information System (INIS)

Damyanov, Nikolay N; Mysak, Lawrence A; Damon Matthews, H

2012-01-01

Global warming has the potential to negatively affect one of Canada’s primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada. (letter)

Observed decreases in the Canadian outdoor skating season due to recent winter warming

Science.gov (United States)

Damyanov, Nikolay N.; Damon Matthews, H.; Mysak, Lawrence A.

2012-03-01

Global warming has the potential to negatively affect one of Canada’s primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada.

Isotopic measurement in ice, Ledenica Cave, Velebit, Croatia

International Nuclear Information System (INIS)

Horvatincic, N.

1996-01-01

The distribution of radioactive tritium ( 3 H) and stable isotopes of hydrogen ( 2 H/ 1 H) and oxygen ( 18 O/ 16 O) was determined in 45 m long ice deposit found in the Ledenica Cave, Velebit Mt., Croatia. The aim of this work was to determine the influence of the significant radioactive contamination of the atmosphere in sixties to the naturally protected environment. We took ice samples from the ice deposit at each 20 cm from the surface up to 1 m, then at the 3rd, 4th, and 5th m and at the 30th and 40 th m from the surface. The tritium analyses showed the following: The tritium activity at the surface is 1.3 Bq/L, similar as tritium concentration in the recent precipitation in Zagreb area. The maximum tritium activity was measured at the 3th m from the surface, 2.8 Bq/L. It means that the ice layer originated from the time period of 1960-1965 when, because of the thermonuclear weapon tests, the tritium activity of the atmosphere was significantly higher than today. The estimated time period of the ice deposit formation according to the tritium activity distribution and assuming the uniform sedimentation rate of ice, was app. 500 years. This is in good agreement with the 14 C age of ice deposit is 450±100 years. d 18 O and d 2 H values for ice samples range between -6.74 promilles and -10.25 promilles, and -50.3 promilles and -67.9 promilles, respectively. These values indicate the influence mostly of continental climate with dominant part of winter precipitation. A sample of speleothem from the Ledenica Cave was also dated by the 14 C and 230 Th/ 234 U dating methods. The 230 Th/ 234 U age is 301000±55000 years. (author)

The role of the Asian winter monsoon in the rapid propagation of abrupt climate changes during the last deglaciation

Science.gov (United States)

Chu, Guoqiang; Sun, Qing; Zhu, Qingzeng; Shan, Yabing; Shang, Wenyu; Ling, Yuan; Su, Youliang; Xie, Manman; Wang, Xishen; Liu, Jiaqi

2017-12-01

High-resolution temperature records spanning the last deglaciation from low latitudes are scarce; however, they are important for understanding the rapid propagation of abrupt climate events throughout the Northern Hemisphere and the tropics. Here, we present a branched GDGTs-based temperature reconstruction from the sediments of Maar Lake Huguangyan in tropical China. The record reveals that the mean temperature during the Oldest Dryas was 17.8 °C, which was followed by a two-step increase of 2-3 °C to the Bølling-Allerød, a decrease to 19.8 °C during the Younger Dryas, and a rapid warming at the onset of the Holocene. The Oldest Dryas was about 2 °C warmer than the Younger Dryas. The reconstructed temperature was weighted towards the wintertime since the lake is monomictic and the mixing process in winter supplies nutrients from the lake bottom to the entire water column, greatly promoting biological productivity. In addition, the winter-biased temperature changes observed in the study are more distinctive than the summer-biased temperature records from extra-tropical regions of East Asia. This implies that the temperature decreases during abrupt climatic events were mainly a winter phenomenon. Within the limits of the dating uncertainties, the broadly similar pattern of winter-weighted temperature change observed in both tropical Lake Huguangyan and in Greenland ice cores indicates the occurrence of tightly-coupled interactions between high latitude ice sheets and land areas in the tropics. We suggest that the winter monsoon (especially cold surges) could play an important role in the rapid transmission of the temperature signal from the Arctic to the tropics.

On the relationship between atmospheric circulation and the fluctuations in the sea ice extents of the Bering and Okhotsk Seas

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Cavalieri, D. J.; Parkinson, C. L.

1987-01-01

The influence of the hemispheric atmospheric circulation on the sea ice covers of the Bering Sea and the Sea of Okhotsk is examined using data obtained with the Nimbus 5 electrically scanning microwave radiometer for the four winters of the 1973-1976 period. The 3-day averaged sea ice extent data were used to establish periods for which there is an out-of-phase relationship between fluctuations of the two ice covers. A comparison of the sea-level atmospheric pressure field with the seasonal, interannual, and short-term sea ice fluctuations reveal an association between changes in the phase and the amplitude of the long waves in the atmosphere and advance and retreat of Arctic ice covers.

Experimental investigation of ice and snow melting process on pavement utilizing geothermal tail water

International Nuclear Information System (INIS)

Wang Huajun; Zhao Jun; Chen Zhihao

2008-01-01

Road ice and snow melting based on low temperature geothermal tail water is of significance to realize energy cascading utilization. A small scale ice and snow melting system is built in this work. Experiments of dynamic melting processes of crushed ice, solid ice, artificial snow and natural snow are conducted on concrete pavement. The results show that the melting process of ice and snow includes three phases: a starting period, a linear period and an accelerated period. The critical value of the snow free area ratio between the linear period and the accelerated period is about 0.6. The physical properties of ice and snow, linked with ambient conditions, have an obvious effect on the melting process. The difference of melting velocity and melting time between ice and snow is compared. To reduce energy consumption, the formation of ice on roads should be avoided if possible. The idling process is an effective pathway to improve the performance of melting systems. It is feasible to utilize geothermal tail water of about 40 deg. C for melting ice and snow on winter roads, and it is unnecessary to keep too high fluid temperatures during the practical design and applications. Besides, with the exception of solid ice, the density and porosity of snow and ice tend to be decreasing and increasing, respectively, as the ambient temperature decreases

Multiple climate regimes in an idealized lake-ice-atmosphere model

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Sugiyama, Noriyuki; Kravtsov, Sergey; Roebber, Paul

2018-01-01

In recent decades, the Laurentian Great Lakes have undergone rapid surface warming with the summertime trends substantially exceeding the warming rates of surrounding land. Warming of the deepest (Lake Superior) was the strongest, and that of the shallowest (Lake Erie)—the weakest of all lakes. To investigate the dynamics of accelerated lake warming, we considered single-column and multi-column thermodynamic lake-ice models coupled to an idealized two-layer atmosphere. The variable temperature of the upper atmospheric layer—a proxy for the large-scale atmospheric forcing—consisted, in the most general case, of a linear trend mimicking the global warming and atmospheric interannual variability, both on top of the prescribed seasonal cycle of the upper-air temperature. The atmospheric boundary layer of the coupled model exchanged heat with the lake and exhibited lateral diffusive heat transports between the adjacent atmospheric columns. In simpler single-column models, we find that, for a certain range of periodic atmospheric forcing, each lake possesses two stable equilibrium seasonal cycles, which we call "regimes"—with and without lake-ice occurrence in winter and with corresponding cold and warm temperatures in the following summer, respectively, all under an identical seasonally varying external forcing. Deeper lakes exhibit larger differences in their summertime surface water temperature between the warm and cold regimes, due to their larger thermal and dynamical inertia. The regime behavior of multi-column coupled models is similar but more complex, and in some cases, they admit more than two stable equilibrium seasonal cycles, with varying degrees of wintertime ice-cover. The simulated lake response to climate change in the presence of the atmospheric noise rationalizes the observed accelerated warming of the lakes, the correlation between wintertime ice cover and next summer's lake-surface temperature, as well as higher warming trends of the

ALES+: Adapting a homogenous ocean retracker for satellite altimetry to sea ice leads, coastal and inland waters

DEFF Research Database (Denmark)

Passaro, Marcello; Kildegaard Rose, Stine; Andersen, Ole B.

2018-01-01

ice retracker used for fitting specular echoes. Compared to an existing open ocean altimetry dataset, the presented strategy increases the number of sea level retrievals in the sea ice-covered area and the correlation with a local tide gauge. Further tests against in-situ data show that also......Water level from sea ice-covered oceans is particularly challenging to retrieve with satellite radar altimeters due to the different shapes assumed by the returned signal compared with the standard open ocean waveforms. Valid measurements are scarce in large areas of the Arctic and Antarctic Oceans...... the fitting of the signal depending on the sea state and on the slope of its trailing edge. The algorithm modifies the existing Adaptive Leading Edge Subwaveform retracker originally designed for coastal waters, and is applied to Envisat and ERS-2 missions. The validation in a test area of the Arctic Ocean...

Modelling radiative transfer through ponded first-year Arctic sea ice with a plane-parallel model

Directory of Open Access Journals (Sweden)

T. Taskjelle

2017-09-01

Full Text Available Under-ice irradiance measurements were done on ponded first-year pack ice along three transects during the ICE12 expedition north of Svalbard. Bulk transmittances (400–900 nm were found to be on average 0.15–0.20 under bare ice, and 0.39–0.46 under ponded ice. Radiative transfer modelling was done with a plane-parallel model. While simulated transmittances deviate significantly from measured transmittances close to the edge of ponds, spatially averaged bulk transmittances agree well. That is, transect-average bulk transmittances, calculated using typical simulated transmittances for ponded and bare ice weighted by the fractional coverage of the two surface types, are in good agreement with the measured values. Radiative heating rates calculated from model output indicates that about 20 % of the incident solar energy is absorbed in bare ice, and 50 % in ponded ice (35 % in pond itself, 15 % in the underlying ice. This large difference is due to the highly scattering surface scattering layer (SSL increasing the albedo of the bare ice.

Modelling radiative transfer through ponded first-year Arctic sea ice with a plane-parallel model

Science.gov (United States)

Taskjelle, Torbjørn; Hudson, Stephen R.; Granskog, Mats A.; Hamre, Børge

2017-09-01

Under-ice irradiance measurements were done on ponded first-year pack ice along three transects during the ICE12 expedition north of Svalbard. Bulk transmittances (400-900 nm) were found to be on average 0.15-0.20 under bare ice, and 0.39-0.46 under ponded ice. Radiative transfer modelling was done with a plane-parallel model. While simulated transmittances deviate significantly from measured transmittances close to the edge of ponds, spatially averaged bulk transmittances agree well. That is, transect-average bulk transmittances, calculated using typical simulated transmittances for ponded and bare ice weighted by the fractional coverage of the two surface types, are in good agreement with the measured values. Radiative heating rates calculated from model output indicates that about 20 % of the incident solar energy is absorbed in bare ice, and 50 % in ponded ice (35 % in pond itself, 15 % in the underlying ice). This large difference is due to the highly scattering surface scattering layer (SSL) increasing the albedo of the bare ice.

Development flight tests of JetStar LFC leading-edge flight test experiment

Science.gov (United States)

Fisher, David F.; Fischer, Michael C.

1987-01-01

The overall objective of the flight tests on the JetStar aircraft was to demonstrate the effectiveness and reliability of laminar flow control under representative flight conditions. One specific objective was to obtain laminar flow on the JetStar leading-edge test articles for the design and off-design conditions. Another specific objective was to obtain operational experience on a Laminar Flow Control (LFC) leading-edge system in a simulated airline service. This included operational experience with cleaning requirements, the effect of clogging, possible foreign object damage, erosion, and the effects of ice particle and cloud encounters. Results are summarized.

Snow and ice blocking of tunnels

Energy Technology Data Exchange (ETDEWEB)

Lia, Leif

1998-12-31

Hydroelectric power development in cold regions causes much concern about operational reliability and dam safety. This thesis studies the temperature distribution in tunnels by means of air temperature measurements in six tunnel spillways and five diversion tunnels. The measurements lasted for two consecutive winters. The air through flow tunnel is used as it causes cooling of both rock and water. In open spillway tunnels, frost reaches the entire tunnel. In spillway tunnels with walls, the frost zones reach about 100 m from the downstream end. In mildly-inclined diversion tunnels, a frost free zone is located in the middle of the tunnel and snow and ice problems were only observed in the inlet and outlet. Severe aufeis is accumulation is observed in the frost zones. The heat transfer from rock to air, water and ice is calculated and used in a prediction model for the calculation of aufeis build-up together with local field observation data. The water penetration of snow plugs is also calculated, based on the heat balance. It takes 20 to 50 days for water to enter the blocked tunnel. The empirical values are 30 to 60 days, but only 1 day if the temperature of the snow pack is 0{sup o}C. Sensitivity analyses are carried out for temperature variations in rock, snow, water and ice. Systematic field observation shows that it is important for hydropower companies to know about the effects of snow and ice blocking in an area. A risk analysis of dam safety is presented for a real case. Finally, the thesis proposes solutions which can reduce the snow and ice problems. 79 refs., 63 figs., 11 tabs.

Classification of sea ice types with single-band (33.6 GHz) airborne passive microwave imagery

Science.gov (United States)

Eppler, Duane T.; Farmer, L. Dennis; Lohanick, Alan W.; Hoover, Mervyn

1986-09-01

During March 1983 extensive high-quality airborne passive Ka band (33.6 GHz) microwave imagery and coincident high-resolution aerial photography were obtained of ice along a 378-km flight line in the Beaufort Sea. Analysis of these data suggests that four classes of winter surfaces can be distinguished solely on the basis of 33.6-GHz brightness temperature: open water, frazil, old ice, and young/first-year ice. New ice (excluding frazil) and nilas display brightness temperatures that overlap the range of temperatures characteristic of old ice and, to a lesser extent, young/first-year ice. Scenes in which a new ice or nilas are present in appreciable amounts are subject to substantial errors in classification if static measures of Ka band radiometric brightness temperature alone are considered. Textural characteristics of nilas and new ice, however, differ significantly from textural features characteristic of other ice types and probably can be used with brightness temperature data to classify ice type in high-resolution single-band microwave images. In any case, open water is radiometrically the coldest surface observed in any scene. Lack of overlap between brightness temperatures characteristic of other surfaces indicates that estimates of the areal extent of open water based on only 33.6-GHz brightness temperatures are accurate.

The effects of studded tires on fatal crashes with passenger cars and the benefits of electronic stability control (ESC) in Swedish winter driving.

Science.gov (United States)