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Benjamin M Jones - One of the best experts on this subject based on the ideXlab platform.
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shifting balance of thermokarst lake Ice regimes across the arctic coastal plain of northern alaska
Geophysical Research Letters, 2012Co-Authors: Christopher D Arp, Benjamin M Jones, Matthew S WhitmanAbstract:[1] 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.
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hydrogeomorphic processes of thermokarst lakes with grounded Ice and Floating Ice regimes on the arctic coastal plain alaska
Hydrological Processes, 2011Co-Authors: Christopher D Arp, Benjamin M Jones, Frank E Urban, Guido GrosseAbstract:Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded Ice) and deeper lakes maintaining perennial liquid water (Floating Ice). Thus, lake depth relative to maximum Ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum Ice thickness by analysing remotely sensed, water quality, and climatic data over a 35-year period. Shoreline erosion rates due to permafrost degradation ranged from < 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P − EL) with periods of full and nearly dry basins. Shorter-term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long-term record for only shallow lakes. Our analysis suggests that grounded-Ice lakes are Ice-free on average 37 days longer than Floating-Ice lakes resulting in a longer period of evaporative loss and more frequent negative P − EL. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum Ice thickness in ACP lakes. Copyright © 2011 John Wiley & Sons, Ltd.
Christopher D Arp - One of the best experts on this subject based on the ideXlab platform.
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shifting balance of thermokarst lake Ice regimes across the arctic coastal plain of northern alaska
Geophysical Research Letters, 2012Co-Authors: Christopher D Arp, Benjamin M Jones, Matthew S WhitmanAbstract:[1] 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.
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hydrogeomorphic processes of thermokarst lakes with grounded Ice and Floating Ice regimes on the arctic coastal plain alaska
Hydrological Processes, 2011Co-Authors: Christopher D Arp, Benjamin M Jones, Frank E Urban, Guido GrosseAbstract:Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded Ice) and deeper lakes maintaining perennial liquid water (Floating Ice). Thus, lake depth relative to maximum Ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum Ice thickness by analysing remotely sensed, water quality, and climatic data over a 35-year period. Shoreline erosion rates due to permafrost degradation ranged from < 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P − EL) with periods of full and nearly dry basins. Shorter-term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long-term record for only shallow lakes. Our analysis suggests that grounded-Ice lakes are Ice-free on average 37 days longer than Floating-Ice lakes resulting in a longer period of evaporative loss and more frequent negative P − EL. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum Ice thickness in ACP lakes. Copyright © 2011 John Wiley & Sons, Ltd.
Andrey Koshurnikov - One of the best experts on this subject based on the ideXlab platform.
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evidence for an Ice shelf covering the central arctic ocean during the penultimate glaciation
Nature Communications, 2016Co-Authors: Martin Jakobsson, Johan Nilsson, Leif G Anderson, Jan Backman, Goran Bjork, Thomas M Cronin, Nina Kirchner, Andrey KoshurnikovAbstract:The hypothesis of a km-thick Ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating Ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of Ice shelves should, however, exist where Ice grounded along their flow paths. Here we present new evidence of Ice-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an Ice shelf extending over the entire central Arctic Ocean during at least one previous Ice age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions >1-km thick, central Arctic Ocean Ice shelf dated to marine isotope stage 6 (∼ 140 ka). Bathymetric highs were likely critical in the Ice-shelf development by acting as pinning points where stabilizing Ice rises formed, thereby providing sufficient back stress to allow Ice shelf thickening.
H A Fricker - One of the best experts on this subject based on the ideXlab platform.
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pervasive Ice sheet mass loss reflects competing ocean and atmosphere processes
Science, 2020Co-Authors: Ben Smith, H A Fricker, Johan Nilsson, Fernando S Paolo, Alex S Gardner, Brooke Medley, Nicholas Holschuh, Susheel Adusumilli, Kelly M BruntAbstract:Quantifying changes in Earth's Ice sheets and identifying the climate drivers are central to improving sea level projections. We provide unified estimates of grounded and Floating Ice mass change from 2003 to 2019 using NASA's Ice, Cloud and land Elevation Satellite (IceSat) and IceSat-2 satellite laser altimetry. Our data reveal patterns likely linked to competing climate processes: Ice loss from coastal Greenland (increased surface melt), Antarctic Ice shelves (increased ocean melting), and Greenland and Antarctic outlet glaciers (dynamic response to ocean melting) was partially compensated by mass gains over Ice sheet interiors (increased snow accumulation). Losses outpaced gains, with grounded-Ice loss from Greenland (200 billion tonnes per year) and Antarctica (118 billion tonnes per year) contributing 14 millimeters to sea level. Mass lost from West Antarctica's Ice shelves accounted for more than 30% of that region's total.
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trends and connections across the antarctic cryosphere
Nature, 2018Co-Authors: Andrew Shepherd, H A Fricker, S L FarrellAbstract:Satellite observations have transformed our understanding of the Antarctic cryosphere. The continent holds the vast majority of Earth’s fresh water, and blankets swathes of the Southern Hemisphere in Ice. Reductions in the thickness and extent of Floating Ice shelves have disturbed inland Ice, triggering retreat, acceleration and drawdown of marine-terminating glaciers. The waxing and waning of Antarctic sea Ice is one of Earth’s greatest seasonal habitat changes, and although the maximum extent of the sea Ice has increased modestly since the 1970s, inter-annual variability is high, and there is evidence of longer-term decline in its extent. This paper discusses how Antarctic Ice has changed over recent decades, and how these changes have been recorded in satellite observations.
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volume loss from antarctic Ice shelves is accelerating
Science, 2015Co-Authors: Fernando S Paolo, H A Fricker, Laurie PadmanAbstract:The Floating Ice shelves surrounding the Antarctic Ice Sheet restrain the grounded Ice-sheet flow. Thinning of an Ice shelf reduces this effect, leading to an increase in Ice discharge to the ocean. Using 18 years of continuous satellite radar altimeter observations, we have computed decadal-scale changes in Ice-shelf thickness around the Antarctic continent. Overall, average Ice-shelf volume change accelerated from negligible loss at 25 ± 64 cubic kilometers per year for 1994–2003 to rapid loss of 310 ± 74 cubic kilometers per year for 2003–2012. West Antarctic losses increased by ~70% in the past decade, and earlier volume gain by East Antarctic Ice shelves ceased. In the Amundsen and Bellingshausen regions, some Ice shelves have lost up to 18% of their thickness in less than two decades.
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getting around antarctica new high resolution mappings of the grounded and freely Floating boundaries of the antarctic Ice sheet created for the international polar year
The Cryosphere, 2011Co-Authors: Robert Bindschadler, Kelly M Brunt, H A Fricker, Hyeungu Choi, Amy Wichlacz, R Bingham, Jennifer Bohlander, Hugh F J Corr, Reinhard Drews, Monica HallAbstract:Two Ice-dynamic transitions of the Antarctic Ice sheet - the boundary of grounded Ice features and the freely- Floating boundary - are mapped at 15-m resolution by par- ticipants of the International Polar Year project ASAID us- ing customized software combining Landsat-7 imagery and IceSat/GLAS laser altimetry. The grounded Ice boundary is 53 610 km long; 74 % abuts to Floating Ice shelves or outlet glaciers, 19 % is adjacent to open or sea-Ice covered ocean, and 7 % of the boundary Ice terminates on land. The freely- Floating boundary, called here the hydrostatic line, is the most landward position on Ice shelves that expresses the full am- plitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma) accuracies of the grounded Ice boundary vary an order of magnitude ranging from ±52 m for the land and open-ocean terminating seg- ments to ±502 m for the outlet glaciers. The hydrostatic
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transoceanic wave propagation links Iceberg calving margins of antarctica with storms in tropics and northern hemisphere
Geophysical Research Letters, 2006Co-Authors: Douglas R Macayeal, J N Bassis, Emile A Okal, R C Aster, Kelly M Brunt, Mac L Cathles, Robert Drucker, H A Fricker, Youngjin Kim, Seelye MartinAbstract:[1] We deployed seismometers on the Ross Ice Shelf and on various Icebergs adrift in the Ross Sea (including B15A, a large 100 km by 30 km fragment of B15, which calved from the Ross Ice Shelf in March, 2000). The data reveal that the dominant energy of these Floating Ice masses is in the 0.01 to 0.1 Hz band, and is associated with sea swell generated in the tropical and extra-tropical Pacific Ocean. In one example, a strong storm in the Gulf of Alaska on 21 October 2005, approximately 13,500 km from the Ross Sea, generated swell that arrived at B15A immediately prior to, and during, its break-up off Cape Adare on 27 October 2005. If sea swell influences Iceberg calving and break-up, a teleconnection exists between the Antarctic Ice sheet mass balance and weather systems worldwide.
Guido Grosse - One of the best experts on this subject based on the ideXlab platform.
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hydrogeomorphic processes of thermokarst lakes with grounded Ice and Floating Ice regimes on the arctic coastal plain alaska
Hydrological Processes, 2011Co-Authors: Christopher D Arp, Benjamin M Jones, Frank E Urban, Guido GrosseAbstract:Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded Ice) and deeper lakes maintaining perennial liquid water (Floating Ice). Thus, lake depth relative to maximum Ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum Ice thickness by analysing remotely sensed, water quality, and climatic data over a 35-year period. Shoreline erosion rates due to permafrost degradation ranged from < 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P − EL) with periods of full and nearly dry basins. Shorter-term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long-term record for only shallow lakes. Our analysis suggests that grounded-Ice lakes are Ice-free on average 37 days longer than Floating-Ice lakes resulting in a longer period of evaporative loss and more frequent negative P − EL. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum Ice thickness in ACP lakes. Copyright © 2011 John Wiley & Sons, Ltd.