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Karen J. Heywood - One of the best experts on this subject based on the ideXlab platform.
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Winter seal-based observations reveal glacial Meltwater surfacing in the southeastern Amundsen Sea
Communications Earth & Environment, 2021Co-Authors: Yixi Zheng, Karen J. Heywood, Benjamin G. M. Webber, David P. Stevens, Louise C. Biddle, Lars Boehme, Brice LooseAbstract:Determining the injection of glacial Meltwater into polar oceans is crucial for quantifying the climate system response to ice sheet mass loss. However, Meltwater is poorly observed and its pathways poorly known, especially in winter. Here we present winter Meltwater distribution near Pine Island Glacier using data collected by tagged seals, revealing a highly variable Meltwater distribution with two Meltwater-rich layers in the upper 250 m and at around 450 m, connected by scattered Meltwater-rich columns. We show that the hydrographic signature of Meltwater is clearest in winter, when its presence can be unambiguously mapped. We argue that the buoyant Meltwater provides near-surface heat that helps to maintain polynyas close to ice shelves. The Meltwater feedback onto polynyas and air-sea heat fluxes demonstrates that although the processes determining the distribution of Meltwater are small-scale, they are important to represent in Earth system models. A highly variable Meltwater distribution with interlinked layers and columns is found in the Amundsen Sea in winter, and it may sustain polynyas in the region, according to hydrographic data obtained by seals.
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Upper Ocean Distribution of Glacial Meltwater in the Amundsen Sea, Antarctica
Journal of Geophysical Research: Oceans, 2019Co-Authors: Louise C. Biddle, Brice Loose, Karen J. HeywoodAbstract:Pine Island Ice Shelf, in the Amundsen Sea, is losing mass due to increased heat transport by warm ocean water penetrating beneath the ice shelf and causing basal melt. Tracing this warm deep water and the resulting glacial Meltwater can identify changes in melt rate and the regions most affected by the increased input of this freshwater. Here, optimum multi‐parameter analysis is used to deduce glacial Meltwater fractions from independent water mass characteristics (standard hydrographic observations, noble gases and oxygen isotopes), collected during a ship‐based campaign in the eastern Amundsen Sea in February‐March 2014. Noble gases (neon, argon, krypton and xenon) and oxygen isotopes are used to trace the glacial melt and meteoric water found in seawater and we demonstrate how their signatures can be used to rectify the hydrographic trace of glacial Meltwater, which provides a much higher resolution picture. The presence of glacial Meltwater is shown to mask the Winter Water properties, resulting in differences between the water mass analyses of up to 4 g kg−1 glacial Meltwater content. This discrepancy can be accounted for by redefining the ”pure” Winter Water endpoint in the hydrographic glacial Meltwater calculation. The corrected glacial Meltwater content values show a persistent signature between 150 ‐ 400 m of the water column across all of the sample locations (up to 535 km from Pine Island Ice Shelf), with increased concentration towards the west along the coastline. It also shows, for the first time, the signature of glacial Meltwater flowing off‐shelf in the eastern channel.
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Vigorous lateral export of the Meltwater outflow from beneath an Antarctic ice shelf
Nature, 2017Co-Authors: Alberto C. Naveira Garabato, Karen J. Heywood, Louise C. Biddle, Adrian Jenkins, Alexander Forryan, Pierre Dutrieux, Liam Brannigan, Yvonne L. Firing, Satoshi KimuraAbstract:The mechanism producing Antarctic Meltwater at depth is elucidated and modelled. As ice shelves melt, they deliver fresh water to the ocean. The resulting mixing process affects not only the salinity of the ocean, but also the upwelling of warmer deep waters. Climate models use an extremely simplified approximation with ice-shelf Meltwater being delivered near the surface, but observations show lateral export at depth instead. This shortcoming in the models is understandable, however, as the underlying physical mechanisms have remained unclear. Alberto Naveira Garabato et al . now present a series of detailed observations from Pine Island Bay, Antarctica. They show that the Meltwater plume coming from the base of the ice shelf is diverted by lateral shear forces in a process called centrifugal instability. Idealized modelling suggests that the process is likely to be important for Antarctic ice shelves. The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change^ 1 , 2 . The increased freshwater output from Antarctica is important in determining sea level rise^ 1 , the fate of Antarctic sea ice and its effect on the Earth’s albedo^ 4 , 5 , ongoing changes in global deep-ocean ventilation^ 6 , and the evolution of Southern Ocean ecosystems and carbon cycling^ 7 , 8 . A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported Meltwater. This is usually represented by climate-scale models^ 3 , 4 , 5 , 6 , 7 , 8 , 9 as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the Meltwater to be concentrated at deeper levels^ 10 , 11 , 12 , 13 , 14 . Here we use observations of the turbulent properties of the Meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the Meltwater. We show that the initial ascent of the Meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of Meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing Meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.
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Vigorous lateral export of the Meltwater outflow from beneath an Antarctic ice shelf
Nature, 2017Co-Authors: Alberto C. Naveira Garabato, Karen J. Heywood, Louise C. Biddle, Adrian Jenkins, Alexander Forryan, Pierre Dutrieux, Liam Brannigan, Yvonne L. Firing, Satoshi KimuraAbstract:The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change1, 2. The increased freshwater output from Antarctica is important in determining sea level rise1, the fate of Antarctic sea ice and its effect on the Earth’s albedo4, 5, ongoing changes in global deep-ocean ventilation6, and the evolution of Southern Ocean ecosystems and carbon cycling7, 8. A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported Meltwater. This is usually represented by climate-scale models3–5, 9 as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the Meltwater to be concentrated at deeper levels10, 11, 12, 13, 14. Here we use observations of the turbulent properties of the Meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the Meltwater. We show that the initial ascent of the Meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of Meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing Meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.
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Glacial Meltwater Identification in the Amundsen Sea
Journal of Physical Oceanography, 2017Co-Authors: Louise C. Biddle, Karen J. Heywood, Jan Kaiser, Adrian JenkinsAbstract:AbstractPine Island Ice Shelf, in the Amundsen Sea, is losing mass because of warm ocean waters melting the ice from below. Tracing Meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type. Here, optimum multiparameter analysis is used to deduce glacial Meltwater fractions from water mass characteristics (temperature, salinity, and dissolved oxygen concentrations), collected during a ship-based campaign in the eastern Amundsen Sea in February–March 2014. Using a one-dimensional ocean model, processes such as variability in the characteristics of the source water masses on shelf and biological productivity/respiration are shown to affect the calculated apparent Meltwater fractions. These processes can result in a false Meltwater signature, creating misleading apparent glacial Meltwater pathways. An alternative glacial Meltwater calculation is suggested, using a pseudo–Circumpolar Deep Water endpoint and using an artificial increase...
Louise C. Biddle - One of the best experts on this subject based on the ideXlab platform.
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Winter seal-based observations reveal glacial Meltwater surfacing in the southeastern Amundsen Sea
Communications Earth & Environment, 2021Co-Authors: Yixi Zheng, Karen J. Heywood, Benjamin G. M. Webber, David P. Stevens, Louise C. Biddle, Lars Boehme, Brice LooseAbstract:Determining the injection of glacial Meltwater into polar oceans is crucial for quantifying the climate system response to ice sheet mass loss. However, Meltwater is poorly observed and its pathways poorly known, especially in winter. Here we present winter Meltwater distribution near Pine Island Glacier using data collected by tagged seals, revealing a highly variable Meltwater distribution with two Meltwater-rich layers in the upper 250 m and at around 450 m, connected by scattered Meltwater-rich columns. We show that the hydrographic signature of Meltwater is clearest in winter, when its presence can be unambiguously mapped. We argue that the buoyant Meltwater provides near-surface heat that helps to maintain polynyas close to ice shelves. The Meltwater feedback onto polynyas and air-sea heat fluxes demonstrates that although the processes determining the distribution of Meltwater are small-scale, they are important to represent in Earth system models. A highly variable Meltwater distribution with interlinked layers and columns is found in the Amundsen Sea in winter, and it may sustain polynyas in the region, according to hydrographic data obtained by seals.
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Upper Ocean Distribution of Glacial Meltwater in the Amundsen Sea, Antarctica
Journal of Geophysical Research: Oceans, 2019Co-Authors: Louise C. Biddle, Brice Loose, Karen J. HeywoodAbstract:Pine Island Ice Shelf, in the Amundsen Sea, is losing mass due to increased heat transport by warm ocean water penetrating beneath the ice shelf and causing basal melt. Tracing this warm deep water and the resulting glacial Meltwater can identify changes in melt rate and the regions most affected by the increased input of this freshwater. Here, optimum multi‐parameter analysis is used to deduce glacial Meltwater fractions from independent water mass characteristics (standard hydrographic observations, noble gases and oxygen isotopes), collected during a ship‐based campaign in the eastern Amundsen Sea in February‐March 2014. Noble gases (neon, argon, krypton and xenon) and oxygen isotopes are used to trace the glacial melt and meteoric water found in seawater and we demonstrate how their signatures can be used to rectify the hydrographic trace of glacial Meltwater, which provides a much higher resolution picture. The presence of glacial Meltwater is shown to mask the Winter Water properties, resulting in differences between the water mass analyses of up to 4 g kg−1 glacial Meltwater content. This discrepancy can be accounted for by redefining the ”pure” Winter Water endpoint in the hydrographic glacial Meltwater calculation. The corrected glacial Meltwater content values show a persistent signature between 150 ‐ 400 m of the water column across all of the sample locations (up to 535 km from Pine Island Ice Shelf), with increased concentration towards the west along the coastline. It also shows, for the first time, the signature of glacial Meltwater flowing off‐shelf in the eastern channel.
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Vigorous lateral export of the Meltwater outflow from beneath an Antarctic ice shelf
Nature, 2017Co-Authors: Alberto C. Naveira Garabato, Karen J. Heywood, Louise C. Biddle, Adrian Jenkins, Alexander Forryan, Pierre Dutrieux, Liam Brannigan, Yvonne L. Firing, Satoshi KimuraAbstract:The mechanism producing Antarctic Meltwater at depth is elucidated and modelled. As ice shelves melt, they deliver fresh water to the ocean. The resulting mixing process affects not only the salinity of the ocean, but also the upwelling of warmer deep waters. Climate models use an extremely simplified approximation with ice-shelf Meltwater being delivered near the surface, but observations show lateral export at depth instead. This shortcoming in the models is understandable, however, as the underlying physical mechanisms have remained unclear. Alberto Naveira Garabato et al . now present a series of detailed observations from Pine Island Bay, Antarctica. They show that the Meltwater plume coming from the base of the ice shelf is diverted by lateral shear forces in a process called centrifugal instability. Idealized modelling suggests that the process is likely to be important for Antarctic ice shelves. The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change^ 1 , 2 . The increased freshwater output from Antarctica is important in determining sea level rise^ 1 , the fate of Antarctic sea ice and its effect on the Earth’s albedo^ 4 , 5 , ongoing changes in global deep-ocean ventilation^ 6 , and the evolution of Southern Ocean ecosystems and carbon cycling^ 7 , 8 . A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported Meltwater. This is usually represented by climate-scale models^ 3 , 4 , 5 , 6 , 7 , 8 , 9 as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the Meltwater to be concentrated at deeper levels^ 10 , 11 , 12 , 13 , 14 . Here we use observations of the turbulent properties of the Meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the Meltwater. We show that the initial ascent of the Meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of Meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing Meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.
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Vigorous lateral export of the Meltwater outflow from beneath an Antarctic ice shelf
Nature, 2017Co-Authors: Alberto C. Naveira Garabato, Karen J. Heywood, Louise C. Biddle, Adrian Jenkins, Alexander Forryan, Pierre Dutrieux, Liam Brannigan, Yvonne L. Firing, Satoshi KimuraAbstract:The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change1, 2. The increased freshwater output from Antarctica is important in determining sea level rise1, the fate of Antarctic sea ice and its effect on the Earth’s albedo4, 5, ongoing changes in global deep-ocean ventilation6, and the evolution of Southern Ocean ecosystems and carbon cycling7, 8. A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported Meltwater. This is usually represented by climate-scale models3–5, 9 as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the Meltwater to be concentrated at deeper levels10, 11, 12, 13, 14. Here we use observations of the turbulent properties of the Meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the Meltwater. We show that the initial ascent of the Meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of Meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing Meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.
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Glacial Meltwater Identification in the Amundsen Sea
Journal of Physical Oceanography, 2017Co-Authors: Louise C. Biddle, Karen J. Heywood, Jan Kaiser, Adrian JenkinsAbstract:AbstractPine Island Ice Shelf, in the Amundsen Sea, is losing mass because of warm ocean waters melting the ice from below. Tracing Meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type. Here, optimum multiparameter analysis is used to deduce glacial Meltwater fractions from water mass characteristics (temperature, salinity, and dissolved oxygen concentrations), collected during a ship-based campaign in the eastern Amundsen Sea in February–March 2014. Using a one-dimensional ocean model, processes such as variability in the characteristics of the source water masses on shelf and biological productivity/respiration are shown to affect the calculated apparent Meltwater fractions. These processes can result in a false Meltwater signature, creating misleading apparent glacial Meltwater pathways. An alternative glacial Meltwater calculation is suggested, using a pseudo–Circumpolar Deep Water endpoint and using an artificial increase...
John B. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Paleo ice flow and subglacial Meltwater dynamics in Pine Island Bay, West Antarctica
The Cryosphere, 2013Co-Authors: Frank O Nitsche, Stanley S Jacobs, Robert D Larter, Gerhard Kuhn, Karsten Gohl, John B. Anderson, James A Smith, Claus-dieter Hillenbrand, Martin JakobssonAbstract:Increasing evidence for an elaborate subglacial drainage network underneath modern Antarctic ice sheets suggests that basal Meltwater has an important influence on ice stream flow. Swath bathymetry surveys from previously glaciated continental margins display morphological features indicative of subglacial Meltwater flow in inner shelf areas of some paleo ice stream troughs. Over the last few years several expeditions to the eastern Amundsen Sea embayment (West Antarctica) have investigated the paleo ice streams that extended from the Pine Island and Thwaites glaciers. A compilation of high-resolution swath bathymetry data from inner Pine Island Bay reveals details of a rough seabed topography including several deep channels that connect a series of basins. This complex basin and channel network is indicative of Meltwater flow beneath the paleo-Pine Island and Thwaites ice streams, along with substantial subglacial water inflow from the east. This Meltwater could have enhanced ice flow over the rough bedrock topography. Meltwater features diminish with the onset of linear features north of the basins. Similar features have previously been observed in several other areas, including the Dotson-Getz Trough (western Amundsen Sea embayment) and Marguerite Bay (SW Antarctic Peninsula), suggesting that these features may be widespread around the Antarctic margin and that subglacial Meltwater drainage played a major role in past ice-sheet dynamics.
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swath bathymetry images of subglacial Meltwater features in the amundsen sea embayment west antarctica
EPIC3Fall Meeting of the American Geophysical Union (AGU) San Franscisco Dec 2011 5, 2011Co-Authors: Frankoliver Nitsche, Stanley S Jacobs, Martin Jakobsson, Robert D Larter, Karsten Gohl, John B. AndersonAbstract:There is increasing evidence of an elaborate subglacial Meltwater network underneath Antarctic ice sheets and that this Meltwater has an important impact on the flow dynamics of ice streams. In addition, a growing number swath bathymetry surveys from previous glaciated continental margins shows morphological features indicative of Meltwater features in areas of paleo ice streams. Over the last few years several expeditions into the eastern Amundsen Sea have investigated the paleo ice streams connected to the Pine Island and Thwaites Glaciers. Unusually favorable sea ice conditions in early 2009 and 2010 allowed us to acquire high-resolution swath bathymetry over large, coherent areas of the of the Thwaites and Pine Island paleo ice streams. Together with previous collections, these data reveal details of a rough topography on the inner shelf including several deep channels that connect a series of deeper basins. This complex basin and channel network is indicative of Meltwater flow beneath the paleo-Pine Island and Thwaites ice streams, along with substantial subglacial water inflow from the east. This Meltwater could have enhanced ice flow over the rough bedrock topography. The Meltwater features diminish with the onset of linear features north of the basins. Similar features have been observed at several locations of previously glaciated high-latitude continental margins including the Getz trough system in the central Amundsen Sea and Marguerite Bay in the Antarctic Peninsula. This suggests that these features and the processes that created them are common around the margin. A comparison of the different features allows the identification of the dominant processes and the creation of a conceptual model of subglacial Meltwater flow and its interaction with the ice and underlying substrate.
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evidence for abundant subglacial Meltwater beneath the paleo ice sheet in pine island bay antarctica
Journal of Glaciology, 2003Co-Authors: Ashley L Lowe, John B. AndersonAbstract:Marine-geological and -geophysical data collected from the continental shelf in Pine Island Bay, Antarctica, reveal a complex paleo-subglacial drainage system controlled by bedrock topography and subglacial Meltwater discharge. Significant amounts of freely flowing Meltwater existed beneath former ice sheets in Pine Island Bay. Subglacial drainage is characterized by descriptions of glacial landforms imaged on the sea floor and sedimentary deposits collected in piston cores. Bedrock geology- is characterized using seismic data. Large-scale landforms on the shelf include channels and cavities incised into impermeable crystalline bedrock. There is a transition from randomly oriented channels on the inner shelf to a dendritic pattern of elongate channels on the middle shelf. On the outer shelf, a change in basal conditions occurs where sedimentary deposits bury crystalline bedrock. No evidence for flowing Meltwater exists on sedimentary substrates Instead, Meltwater formed a the ice-sediment contact was incorporated into the sediments, contributing to development of a deforming lied, which was sampled in piston cores. Characterization of subglacial Meltwater processes that occurred in the past may aid in understanding the role Meltwater plays in stability of the West Antarctic ice sheet today.
Li Zongxing - One of the best experts on this subject based on the ideXlab platform.
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quantitative evaluation on the influence from cryosphere Meltwater on runoff in an inland river basin of china
Global and Planetary Change, 2016Co-Authors: Li Zongxing, Yong Song, Li Yongge, Q J Wang, Feng Qi, Li Jianguo, Wang YaminAbstract:Abstract Under climate warming, increasing attention is being directed towards high altitude regions where glaciers are shrinking and frozen soil is in degrading. This study, taken Taolai river in Qilian Mountains as an example, is to quantify the relative contributions of cryosphere Meltwater to outlet river, based on 221 water samples from precipitation, river, groundwater and Meltwater during 2013–2014. The results indicated that cryosphere Meltwater accounted for 49% of the total runoff in the source region, and this contribution rate decreased to 21% at the outlet of basin. In addition, precipitation and Meltwater from cryosphere belt has contributed up to 78% of the outlet river runoff. An inverse altitude effect of stable isotopes for river water and groundwater is likely to occur, which is caused by the relatively larger contribution rate of frozen soil Meltwater in the source region. The results could provide a comprehensive overview on the influence from cryosphere Meltwater to hydrologic process in cold basins.
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contribution from frozen soil Meltwater to runoff in an in land river basin under water scarcity by isotopic tracing in northwestern china
Global and Planetary Change, 2016Co-Authors: Li Zongxing, Yong Song, Q J Wang, Cheng Aifang, Li JianguoAbstract:Abstract Cryosphere Meltwater has been recognized as an important source of local water resources. However, there are few assessments on the contribution from frozen soil Meltwater. In this study, we quantify the fraction from frozen soil Meltwater and glacier snow Meltwater to runoff in Shiyang River, an in-land river basin of northwestern China, where glaciers were disappearing and frozen soil was in degradation. A large number of samples for precipitation, surface water, groundwater, frozen soil Meltwater and glacier snow Meltwater have been collected and analyzed for their isotopic compositions. Results indicated that runoff was mainly generated from the cryosphere belt, and it was found that frozen soil Meltwater was responsible for 20%, on average, of the outlet river water during flood season in the basin. The contribution rates from frozen soil Meltwater to the outlet river runoff changed among the seven sub-basins. The results confirmed that frozen soil Meltwater has played an important role in runoff of in-land river basins, and evaluating its influence on the hydrological process under a climate warming scenario is of great significance.
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study on the contribution of cryosphere to runoff in the cold alpine basin a case study of hulugou river basin in the qilian mountains
Global and Planetary Change, 2014Co-Authors: Li Zongxing, Feng Qi, Li Jianguo, Cheng Aifang, Wang Tingting, Guo Xiaoyan, Pan Yanhui, Jia BingAbstract:Global warming would inevitably lead to the increased glacier-snow Meltwater and mountainous discharge. Taking an example the Hulugou River Basin in the Qilian Mountains, this study confirmed the contribution of cryosphere to runoff by means of the isotope hydrograph separation. The hydro-geochemistry and the isotope geochemistry suggested that both the Meltwater and rainwater infiltrated into the subsurface and fed into the river runoff of the Hulugou River Basin in the form of springs. The isotopic composition of river water and underground water was close to the Local Meteoric Water Line, and the delta O-18 and delta D ranged among precipitation, glacier-snow Meltwater and frozen soil Meltwater. The results indicated that 68% of the recharge of the Hulugou River water was the precipitation, thereinto, glacier-snow Meltwater and frozen soil Meltwater contributing 11% and 21%, respectively. For tributary-1, precipitation accounted for 77% of the total stream runoff, with frozen soil Meltwater accounting for 17%, and glacier-snow Meltwater only supplied 6%. During the sampling period, the contribution of surface runoff from precipitation was 44% to tributary-2, and glacier-snow Meltwater had contributed 42%; only 14% from frozen soil Meltwater. For tributary-3, precipitation accounted for 63% of the total runoff, and other 37% originated from the frozen soil Meltwater. According to the latest observational data, the glacier-snow Meltwater has accounted for 11.36% of the total runoff in the stream outlet, in which the calculation has been verified by hydrograph separation. It is obvious that the contribution of ayosphere has accounted for 1/3 of the outlet runoff in the Hulugou River Basin, which has been an important part of river sources. This study demonstrated that the alpine regions of western China, especially those basins with glaciers, snow and frozen soil, have played a crucial role in regional water resource provision under global warming. (C) 2014 Elsevier B.V. All rights reserved.
Adrian Jenkins - One of the best experts on this subject based on the ideXlab platform.
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Vigorous lateral export of the Meltwater outflow from beneath an Antarctic ice shelf
Nature, 2017Co-Authors: Alberto C. Naveira Garabato, Karen J. Heywood, Louise C. Biddle, Adrian Jenkins, Alexander Forryan, Pierre Dutrieux, Liam Brannigan, Yvonne L. Firing, Satoshi KimuraAbstract:The mechanism producing Antarctic Meltwater at depth is elucidated and modelled. As ice shelves melt, they deliver fresh water to the ocean. The resulting mixing process affects not only the salinity of the ocean, but also the upwelling of warmer deep waters. Climate models use an extremely simplified approximation with ice-shelf Meltwater being delivered near the surface, but observations show lateral export at depth instead. This shortcoming in the models is understandable, however, as the underlying physical mechanisms have remained unclear. Alberto Naveira Garabato et al . now present a series of detailed observations from Pine Island Bay, Antarctica. They show that the Meltwater plume coming from the base of the ice shelf is diverted by lateral shear forces in a process called centrifugal instability. Idealized modelling suggests that the process is likely to be important for Antarctic ice shelves. The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change^ 1 , 2 . The increased freshwater output from Antarctica is important in determining sea level rise^ 1 , the fate of Antarctic sea ice and its effect on the Earth’s albedo^ 4 , 5 , ongoing changes in global deep-ocean ventilation^ 6 , and the evolution of Southern Ocean ecosystems and carbon cycling^ 7 , 8 . A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported Meltwater. This is usually represented by climate-scale models^ 3 , 4 , 5 , 6 , 7 , 8 , 9 as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the Meltwater to be concentrated at deeper levels^ 10 , 11 , 12 , 13 , 14 . Here we use observations of the turbulent properties of the Meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the Meltwater. We show that the initial ascent of the Meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of Meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing Meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.
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Vigorous lateral export of the Meltwater outflow from beneath an Antarctic ice shelf
Nature, 2017Co-Authors: Alberto C. Naveira Garabato, Karen J. Heywood, Louise C. Biddle, Adrian Jenkins, Alexander Forryan, Pierre Dutrieux, Liam Brannigan, Yvonne L. Firing, Satoshi KimuraAbstract:The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change1, 2. The increased freshwater output from Antarctica is important in determining sea level rise1, the fate of Antarctic sea ice and its effect on the Earth’s albedo4, 5, ongoing changes in global deep-ocean ventilation6, and the evolution of Southern Ocean ecosystems and carbon cycling7, 8. A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported Meltwater. This is usually represented by climate-scale models3–5, 9 as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the Meltwater to be concentrated at deeper levels10, 11, 12, 13, 14. Here we use observations of the turbulent properties of the Meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the Meltwater. We show that the initial ascent of the Meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of Meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing Meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.
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Glacial Meltwater Identification in the Amundsen Sea
Journal of Physical Oceanography, 2017Co-Authors: Louise C. Biddle, Karen J. Heywood, Jan Kaiser, Adrian JenkinsAbstract:AbstractPine Island Ice Shelf, in the Amundsen Sea, is losing mass because of warm ocean waters melting the ice from below. Tracing Meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type. Here, optimum multiparameter analysis is used to deduce glacial Meltwater fractions from water mass characteristics (temperature, salinity, and dissolved oxygen concentrations), collected during a ship-based campaign in the eastern Amundsen Sea in February–March 2014. Using a one-dimensional ocean model, processes such as variability in the characteristics of the source water masses on shelf and biological productivity/respiration are shown to affect the calculated apparent Meltwater fractions. These processes can result in a false Meltwater signature, creating misleading apparent glacial Meltwater pathways. An alternative glacial Meltwater calculation is suggested, using a pseudo–Circumpolar Deep Water endpoint and using an artificial increase...
