Bathymetry and geological structures beneath the Ross Ice Shelf at the mouth of Whillans Ice Stream, West Antarctica, modeled from ground‐based gravity measurements

Muto, Atsuhiro; Christianson, Knut; Horgan, Huw; Anandakrishnan, S.; Alley, Richard B.

doi:10.1002/jgrb.50315

Cited by 17 publications

(18 citation statements)

References 84 publications

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“…The magnitude of GHF anomalies where basement outcrops at the surface can be several W m −2 , relative to background values of ~100 mW m −2 (e.g., Davis et al, ; Fisher et al, ; Villinger et al, ). The gravity data collected at WGZ suggests that basement topography may exist (Muto et al, ), but there is no such evidence at SLW. The gravity data are consistent with a crustal fault, which could enhance permeability by several orders of magnitude relative to unfaulted bedrock (Seront et al, ), focusing vertical fluid advection and elevating GHF.…”

Section: Resultsmentioning

confidence: 99%

Spatially Variable Geothermal Heat Flux in West Antarctica: Evidence and Implications

Begeman

Tulaczyk

Fisher

2017

Geophysical Research Letters

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Geothermal heat flux (GHF) is an important part of the basal heat budget of continental ice sheets. The difficulty of measuring GHF below ice sheets has directly hindered progress in the understanding of ice sheet dynamics. We present a new GHF measurement from below the West Antarctic Ice Sheet, made in subglacial sediment near the grounding zone of the Whillans Ice Stream. The measured GHF is 88 ± 7 mW m−2, a relatively high value compared to other continental settings and to other GHF measurements along the eastern Ross Sea of 55 mW m−2 and 69 ± 21 mW m−2 but within the range of regional values indicated by geophysical estimates. The new GHF measurement was made ~100 km from the only other direct GHF measurement below the ice sheet, which was considerably higher at 285 ± 80 mW m−2, suggesting spatial variability that could be explained by shallow magmatic intrusions or the advection of heat by crustal fluids. Analytical calculations suggest that spatial variability in GHF exceeds spatial variability in the conductive heat flux through ice along the Siple Coast. Accurate GHF measurements and high‐resolution GHF models may be necessary to reliably predict ice sheet evolution, including responses to ongoing and future climate change.

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Section: Resultsmentioning

confidence: 99%

Spatially Variable Geothermal Heat Flux in West Antarctica: Evidence and Implications

Begeman

Tulaczyk

Fisher

2017

Geophysical Research Letters

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“…For example, the present bathymetry grid under Ross Ice Shelf, an area of roughly 490,000 km 2 , was developed from an array of about 150 active seismic measurements obtained with a typical spacing of ~55 km during the RIGGS program in the 1970s (Greischar et al, ; Greischar & Bentley, ). Recent programs have used inversion of ground gravimetry (e.g., Cochran & Bell, ; Muto, Christianson, et al, ; Muto, Anandakrishnan, & Alley, ) or airborne gravimetry (e.g., Tinto & Bell, ; Tinto et al, ) to improve resolution of sub‐ice shelf bathymetry maps to ~10 km; however, these estimates are only accurate to O (100) m in depth and rely on labor‐intensive field campaigns or dedicated airborne campaigns at sufficiently dense track spacing.…”

Section: Models Of Barotropic Tide Height and Currentsmentioning

confidence: 99%

Ocean Tide Influences on the Antarctic and Greenland Ice Sheets

Padman

Siegfried

Fricker

2018

Reviews of Geophysics

161

160

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Ocean tides are the main source of high‐frequency variability in the vertical and horizontal motion of ice sheets near their marine margins. Floating ice shelves, which occupy about three quarters of the perimeter of Antarctica and the termini of four outlet glaciers in northern Greenland, rise and fall in synchrony with the ocean tide. Lateral motion of floating and grounded portions of ice sheets near their marine margins can also include a tidal component. These tide‐induced signals provide insight into the processes by which the oceans can affect ice sheet mass balance and dynamics. In this review, we summarize in situ and satellite‐based measurements of the tidal response of ice shelves and grounded ice, and spatial variability of ocean tide heights and currents around the ice sheets. We review sensitivity of tide heights and currents as ocean geometry responds to variations in sea level, ice shelf thickness, and ice sheet mass and extent. We then describe coupled ice‐ocean models and analytical glacier models that quantify the effect of ocean tides on lower‐frequency ice sheet mass loss and motion. We suggest new observations and model developments to improve the representation of tides in coupled models that are used to predict future ice sheet mass loss and the associated contribution to sea level change. The most critical need is for new data to improve maps of bathymetry, ice shelf draft, spatial variability of the drag coefficient at the ice‐ocean interface, and higher‐resolution models with improved representation of tidal energy sinks.

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“…The impacts of subglacial flows of continental organic C and nutrients are likely greatest in coastal embayments (Carter & Fricker, 2012), rather than being diluted into the entire volume of the RIS cavity (~125,000 km 3 ; Smethie & Jacobs, 2005). The volume of the GZ embayments is not well constrained, but water column thickness is typically <50 m, and the embayment that receives outflow from SLW is~500 km 2 in area (Carter & Fricker, 2012;Muto et al, 2013). Assuming a water column thickness of 50 m, an embayment volume of 25 km 3 was used for the calculations.…”

Section: Bioelement Export To the Ris Cavitymentioning

confidence: 99%

“…West Antarctica's Gould-Siple Coast (hereafter referred to as "Siple Coast") is the location of one such active subglacial water system (Fricker et al, 2007), which drains fresh water through coastal estuaries into marine waters beneath the southern reaches of the Ross Ice Shelf (RIS) (Carter & Fricker, 2012;Horgan et al, 2013;Muto et al, 2013). The outflows comprise a significant component of the overall freshwater budget of the coastal embayments, with episodic flow rates that can exceed 300 m 3 s −1 during major flooding events and generate variability in the RIS cavity freshwater budget (Carter & Fricker, 2012).…”

Section: Introductionmentioning

confidence: 99%

Biogeochemical Connectivity Between Freshwater Ecosystems beneath the West Antarctic Ice Sheet and the Sub‐Ice Marine Environment

Vick‐Majors

Michaud

Skidmore

et al. 2020

Global Biogeochemical Cycles

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Although subglacial aquatic environments are widespread beneath the Antarctic ice sheet, subglacial biogeochemistry is not well understood, and the contribution of subglacial water to coastal ocean carbon and nutrient cycling remains poorly constrained. The Whillans Subglacial Lake (SLW) ecosystem is upstream from West Antarctica's Gould‐Siple Coast ~800 m beneath the surface of the Whillans Ice Stream. SLW hosts an active microbial ecosystem and is part of an active hydrological system that drains into the marine cavity beneath the adjacent Ross Ice Shelf. Here we examine sources and sinks for organic matter in the lake and estimate the freshwater carbon and nutrient delivery from discharges into the coastal embayment. Fluorescence‐based characterization of dissolved organic matter revealed microbially driven differences between sediment pore waters and lake water, with an increasing contribution from relict humic‐like dissolved organic matter with sediment depth. Mass balance calculations indicated that the pool of dissolved organic carbon in the SLW water column could be produced in 4.8 to 11.9 yr, which is a time frame similar to that of the lakes’ fill‐drain cycle. Based on these estimates, subglacial lake water discharged at the Siple Coast could supply an average of 5,400% more than the heterotrophic carbon demand within Siple Coast embayments (6.5% for the entire Ross Ice Shelf cavity). Our results suggest that subglacial discharge represents a heretofore unappreciated source of microbially processed dissolved organic carbon and other nutrients to the Southern Ocean.

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Bathymetry and geological structures beneath the Ross Ice Shelf at the mouth of Whillans Ice Stream, West Antarctica, modeled from ground‐based gravity measurements

Cited by 17 publications

References 84 publications

Spatially Variable Geothermal Heat Flux in West Antarctica: Evidence and Implications

Spatially Variable Geothermal Heat Flux in West Antarctica: Evidence and Implications

Ocean Tide Influences on the Antarctic and Greenland Ice Sheets

Biogeochemical Connectivity Between Freshwater Ecosystems beneath the West Antarctic Ice Sheet and the Sub‐Ice Marine Environment

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