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N. Arnold - One of the best experts on this subject based on the ideXlab platform.
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Modeled subglacial water flow routing supports localized intrusive heating as a possible cause of Basal Melting of Mars' south polar ice cap
Journal of Geophysical Research. Planets, 2019Co-Authors: N. Arnold, S. Conway, F. Butcher, M. BalmeAbstract:The discovery of an ~20‐km‐wide area of bright subsurface radar reflections, interpreted as liquid water, beneath the Martian south polar layered deposits (SPLD) in data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument, and the discovery of two geologically recent potential eskers (landforms produced by subglacial melt) associated with viscous flow features in Martian midlatitudes, has suggested recent Basal Melting of Martian ice deposits may be feasible, possibly due to locally elevated geothermal heating. Locations of terrestrial subglacial lakes and major drainage axes have been successfully predicted from subglacial hydraulic potential surfaces calculated from surface topography and ice thickness. Here, we use surface topography from the Mars Orbiter Laser Altimeter and SPLD bed elevations derived from MARSIS data to calculate the subglacial hydraulic potential surface beneath the SPLD and determine whether the observed high reflectance area coincides with predicted subglacial lake locations. Given the sensitivity of terrestrial predictions of lake locations to Basal topography, we derive over 1,000 perturbed topographies (using noise statistics from the MARSIS data) to infer the most likely locations of possible subglacial water bodies and drainage axes. Our results show that the high reflectance area does not coincide with any substantial predicted lake locations; three nearby lake locations are robustly predicted however. We interpret this result as suggesting that the high reflectance area (assuming the interpretation as liquid is correct) is most likely a hydraulically isolated patch of liquid confined by the surrounding cold‐based ice, rather than a topographically‐constrained subglacial lake.
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Code and Data Readme for “Modeled subglacial water flow routing supports localized intrusive heating as a possible cause of Basal Melting of Mars’ south polar ice cap"
2019Co-Authors: N. Arnold, Frances E.g. Butcher, Susan J. Conway, M. BalmeAbstract:Computer code and derived data developed during the research reported in "Modeled subglacial water flow routing supports localized intrusive heating as a possible cause of Basal Melting of Mars’ south polar ice cap" published in Journal of Geophysical Research-Planets. See the file 'Code and Data Readme.rtf' for detailed information about the contents of this dataset.
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Recent Basal Melting of a mid-latitude glacier on Mars
Journal of Geophysical Research: Planets, 2017Co-Authors: Frances E.g. Butcher, M. Balme, C. Gallagher, N. Arnold, A. Hagermann, Susan J. Conway, Stephen R. LewisAbstract:Evidence for past Basal Melting of young (late Amazonian), debris-covered glaciers in Mars’ mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial Melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential Basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.
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Recent Basal Melting of a Mid-Latitude Glacier on Mars
Journal of Geophysical Research. Planets, 2017Co-Authors: Frances Butcher, M. Balme, C. Gallagher, N. Arnold, S. Conway, A. Hagermann, S. LewisAbstract:Evidence for past Basal Melting of young (late Amazonian-aged), debris-covered glaciers in Mars' mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial Melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential Basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.
David M. Holland - One of the best experts on this subject based on the ideXlab platform.
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novel monitoring of antarctic ice shelf Basal Melting using a fiber optic distributed temperature sensing mooring
Geophysical Research Letters, 2014Co-Authors: Scott Kobs, David M. Holland, V. Zagorodnov, A. A. Stern, Scott W. TylerAbstract:Measuring Basal Melting of ice shelves is challenging and represents a critical component toward understanding ocean-ice interactions and climate change. In November 2011, moorings containing fiber-optic cables for distributed temperature sensing (DTS) were installed through the McMurdo Ice Shelf, Antarctica, (~200 m) and extending ~600 m into the ice shelf cavity. The high spatial resolution of DTS allows for transient monitoring of the thermal gradient within the ice shelf. The gradient near the ice-ocean interface is extrapolated to the in situ freezing temperature in order to continuously track the ice-ocean interface. Seasonal melt rates are calculated to be ~1.0 mm d−1 and 8.6 mm d−1, and maximum Melting corresponds to the arrival of seasonal warm surface water in the ice shelf cavity between January and April. The development of continuous, surface-based techniques for measuring Basal Melting represents a significant advance in monitoring ice shelf stability and ice-ocean interactions.
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Novel monitoring of Antarctic ice shelf Basal Melting using a fiber‐optic distributed temperature sensing mooring
Geophysical Research Letters, 2014Co-Authors: Scott Kobs, David M. Holland, V. Zagorodnov, A. A. Stern, Scott W. TylerAbstract:Measuring Basal Melting of ice shelves is challenging and represents a critical component toward understanding ocean-ice interactions and climate change. In November 2011, moorings containing fiber-optic cables for distributed temperature sensing (DTS) were installed through the McMurdo Ice Shelf, Antarctica, (~200 m) and extending ~600 m into the ice shelf cavity. The high spatial resolution of DTS allows for transient monitoring of the thermal gradient within the ice shelf. The gradient near the ice-ocean interface is extrapolated to the in situ freezing temperature in order to continuously track the ice-ocean interface. Seasonal melt rates are calculated to be ~1.0 mm d−1 and 8.6 mm d−1, and maximum Melting corresponds to the arrival of seasonal warm surface water in the ice shelf cavity between January and April. The development of continuous, surface-based techniques for measuring Basal Melting represents a significant advance in monitoring ice shelf stability and ice-ocean interactions.
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The Response of Ice Shelf Basal Melting to Variations in Ocean Temperature
Journal of Climate, 2008Co-Authors: Paul R. Holland, Adrian Jenkins, David M. HollandAbstract:Abstract A three-dimensional ocean general circulation model is used to study the response of idealized ice shelves to a series of ocean-warming scenarios. The model predicts that the total ice shelf Basal melt increases quadratically as the ocean offshore of the ice front warms. This occurs because the melt rate is proportional to the product of ocean flow speed and temperature in the mixed layer directly beneath the ice shelf, both of which are found to increase linearly with ocean warming. The behavior of this complex primitive equation model can be described surprisingly well with recourse to an idealized reduced system of equations, and it is shown that this system supports a melt rate response to warming that is generally quadratic in nature. This study confirms and unifies several previous examinations of the relation between melt rate and ocean temperature but disagrees with other results, particularly the claim that a single melt rate sensitivity to warming is universally valid. The hypothesized ...
J W Head - One of the best experts on this subject based on the ideXlab platform.
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early mars climate near the noachian hesperian boundary independent evidence for cold conditions from Basal Melting of the south polar ice sheet dorsa argentea formation and implications for valley network formation
Icarus, 2012Co-Authors: James L Fastook, J W Head, D R Marchant, Francois Forget, Jeanbaptiste MadeleineAbstract:Currently, and throughout much of the Amazonian, the mean annual surface temperatures of Mars are so cold that Basal Melting does not occur in ice sheets and glaciers and they are cold-based. The documented evidence for extensive and well-developed eskers (sediment-filled former sub-glacial meltwater channels) in the south circumpolar Dorsa Argentea Formation is an indication that Basal Melting and wet-based glaciation occurred at the South Pole near the Noachian-Hesperian boundary. We employ glacial accumulation and ice-flow models to distinguish between Basal Melting from bottom-up heat sources (elevated geothermal fluxes) and top-down induced Basal Melting (elevated atmospheric temperatures warming the ice). We show that under mean annual south polar atmospheric temperatures (-100°C) simulated in typical Amazonian climate experiments and typical Noachian-Hesperian geothermal heat fluxes (45-65mW/m 2), south polar ice accumulations remain cold-based. In order to produce significant Basal Melting with these typical geothermal heat fluxes, the mean annual south polar atmospheric temperatures must be raised from today's temperature at the surface (-100°C) to the range of -50 to -75°C. This mean annual polar surface atmospheric temperature range implies lower latitude mean annual temperatures that are likely to be below the Melting point of water, and thus does not favor a " warm and wet" early Mars. Seasonal temperatures at lower latitudes, however, could range above the Melting point of water, perhaps explaining the concurrent development of valley networks and open basin lakes in these areas. This treatment provides an independent estimate of the polar (and non-polar) surface temperatures near the Noachian-Hesperian boundary of Mars history and implies a cold and relatively dry Mars climate, similar to the Antarctic Dry Valleys, where seasonal Melting forms transient streams and permanent ice-covered lakes in an otherwise hyperarid, hypothermal climate. © 2012 Elsevier Inc.
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valleys on hecates tholus mars origin by Basal Melting of summit snowpack
Planetary and Space Science, 2006Co-Authors: Caleb I Fassett, J W HeadAbstract:Abstract Valley networks observed on the martian surface are found mostly on Noachian-aged highlands units, but a few occur on younger volcanic edifices. Enigmatically, they do not occur on all younger volcanoes of similar age or location. Using new data, we reanalyze the radially arrayed valleys on the flanks of Hecates Tholus, a Hesperian-aged shield volcano, and test the hypothesis that these valleys might have formed via Basal Melting of summit snowpack. We find that magmatic intrusions with reasonable geometries provide sufficient heat flux to cause Basal Melting of snowpack, with the resulting meltwater interpreted to be responsible for incision of the observed valleys. Valley morphology is similar to valleys observed adjacent to seasonally Melting Antarctic Dry Valley glaciers formed on comparable slopes, supporting the hypothesis of a snowmelt origin. These relatively young valley networks are thus plausibly interpreted to form under circumstances in which summit snow accumulation was melted during one or more episodes of high localized heat flux.
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Basal Melting of snow on early mars a possible origin of some valley networks
Geophysical Research Letters, 2003Co-Authors: Michael H Carr, J W HeadAbstract:[1] Valley networks appear to be cut by liquid water, yet simulations suggest that early Mars could not have been warmed enough by a CO2-H2O greenhouse to permit rainfall. The vulnerability of an early atmosphere to impact erosion, the likely rapid scavenging of CO2 from the atmosphere by weathering, and the lack of detection of weathering products all support a cold early Mars. We explore the hypothesis that valley networks could have formed as a result of Basal Melting of thick snow and ice deposits. Depending on the heat flow, an early snowpack a few hundred meters to a few kilometers thick could undergo Basal Melting, providing water to cut valley networks.
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CONDITIONS AND PRINCIPAL TIME SCALES FOR Basal Melting OF MARTIAN POLAR CAPS.
2002Co-Authors: M. A. Kreslavsky, J W HeadAbstract:clathrate hydratesand dust in unknown proportions [e.g., 1]. Basal melt-ing of these deposits could occur due to geothermalheating [e.g., 2]. It was suggested [2] that several fea-tures in the PCs, including Chasma Boreale andChasma Australe, were formed by the catastrophic dis-charge of a large subglacial reservoir of Basal meltwa-ter. Recent studies [3-5] added new evidence for melt-water discharge from PCs. In this study we considerenergy and timing constraints related to Basal Meltingof the PCs.
M. Balme - One of the best experts on this subject based on the ideXlab platform.
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Code and Data Readme for “Modeled subglacial water flow routing supports localized intrusive heating as a possible cause of Basal Melting of Mars’ south polar ice cap"
2019Co-Authors: N. Arnold, Frances E.g. Butcher, Susan J. Conway, M. BalmeAbstract:Computer code and derived data developed during the research reported in "Modeled subglacial water flow routing supports localized intrusive heating as a possible cause of Basal Melting of Mars’ south polar ice cap" published in Journal of Geophysical Research-Planets. See the file 'Code and Data Readme.rtf' for detailed information about the contents of this dataset.
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Recent Basal Melting of a mid-latitude glacier on Mars
Journal of Geophysical Research: Planets, 2017Co-Authors: Frances E.g. Butcher, M. Balme, C. Gallagher, N. Arnold, A. Hagermann, Susan J. Conway, Stephen R. LewisAbstract:Evidence for past Basal Melting of young (late Amazonian), debris-covered glaciers in Mars’ mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial Melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential Basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.
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Recent Basal Melting of a Mid-Latitude Glacier on Mars
Journal of Geophysical Research. Planets, 2017Co-Authors: Frances Butcher, M. Balme, C. Gallagher, N. Arnold, S. Conway, A. Hagermann, S. LewisAbstract:Evidence for past Basal Melting of young (late Amazonian-aged), debris-covered glaciers in Mars' mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial Melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential Basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.
Martin J. Siegert - One of the best experts on this subject based on the ideXlab platform.
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Basal Melting over Subglacial Lake Ellsworth and its catchment: insights from englacial layering
Annals of Glaciology, 2020Co-Authors: Neil Ross, Martin J. SiegertAbstract:AbstractDeep-water ‘stable’ subglacial lakes likely contain microbial life adapted in isolation to extreme environmental conditions. How water is supplied into a subglacial lake, and how water outflows, is important for understanding these conditions. Isochronal radio-echo layers have been used to infer where Melting occurs above Lake Vostok and Lake Concordia in East Antarctica but have not been used more widely. We examine englacial layers above and around Lake Ellsworth, West Antarctica, to establish where the ice sheet is ‘drawn down’ towards the bed and, thus, experiences Melting. Layer drawdown is focused over and around the northwest parts of the lake as ice, flowing obliquely to the lake axis becomes afloat. Drawdown can be explained by a combination of Basal Melting and the Weertman effect, at the transition from grounded to floating ice. We evaluate the importance of these processes on englacial layering over Lake Ellsworth and discuss implications for water circulation and sediment deposition. We report evidence of a second subglacial lake near the head of the hydrological catchment and present a new high-resolution bed DEM and hydropotential model of the lake outlet zone. These observations provide insight into the connectivity between Lake Ellsworth and the wider subglacial hydrological system.
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Basal Melting over Subglacial Lake Ellsworth and its catchment: insights from englacial layering
2020Co-Authors: Neil Ross, Martin J. SiegertAbstract:Deep-water ‘stable’ subglacial lakes likely contain microbial life adapted in isolation to extreme environmental conditions. How water is supplied into a subglacial lake, and how water outflows, is important for understanding these conditions. Isochronal radio-echo layers have been used to infer where Melting occurs above Lake Vostok and Lake Concordia in East Antarctica but have not been used more widely. We examine englacial layers above and around Lake Ellsworth, West Antarctica, to establish where the ice sheet is ‘drawn down’ towards the bed and, thus, experiences Melting. Layer drawdown is focused over and around the NW parts of the lake as ice, flowing obliquely to the lake axis, becomes afloat. Drawdown can be explained by a combination of Basal Melting and the Weertman effect, at the transition from grounded to floating ice. We evaluate the importance of these processes on englacial layering over Lake Ellsworth and discuss implications for water circulation and sediment deposition. We report evidence of a second subglacial lake near the head of the hydrological catchment and present a new high-resolution bed DEM and hydropotential model of the lake outlet zone. These observations provide insight into the connectivity between Lake Ellsworth and the wider subglacial hydrological system.
