Steep reverse bed slope at the grounding line of the Weddell Sea sector in West Antarctica

Ross, Neil; Bingham, Robert G.; Corr, Hugh; Ferraccioli, Fausto; Jordan, Tom A.; Brocq, A. M. Le; Rippin, David M.; Young, D. A.; Blankenship, D. D.; Siegert, Martín J.

doi:10.1038/ngeo1468

Cited by 116 publications

(145 citation statements)

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“…Hellmer et al (2012) show that future changes in circulation may allow for more inflow of warm deep water into the ice shelf cavity, displacing the high-salinity shelf water beneath FRIS by the end of the 21st century and increasing basal melt rates an order of magnitude higher than at present. In this warm state, the associated rapid thinning of the ice shelf would reduce the buttressing of the large marine-based grounded ice sheet surrounding FRIS (Ross et al, 2012), significantly accelerating future sea level rise (Mengel et al, 2016). Furthermore, simulations by Hellmer et al (2017) show that the increased meltwater production will sustain the warm inflow even if atmospheric conditions were reversed to a colder state, suggesting the existence of an irreversible tipping point once melting increases past a certain threshold.…”

Section: Introductionmentioning

confidence: 99%

Tidal influences on a future evolution of the Filchner–Ronne Ice Shelf cavity in the Weddell Sea, Antarctica

et al. 2018

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Abstract. Recent modeling studies of ocean circulation in the southern Weddell Sea, Antarctica, project an increase over this century of ocean heat into the cavity beneath Filchner-Ronne Ice Shelf (FRIS). This increase in ocean heat would lead to more basal melting and a modification of the FRIS ice draft. The corresponding change in cavity shape will affect advective pathways and the spatial distribution of tidal currents, which play important roles in basal melting under FRIS. These feedbacks between heat flux, basal melting, and tides will affect the evolution of FRIS under the influence of a changing climate. We explore these feedbacks with a three-dimensional ocean model of the southern Weddell Sea that is forced by thermodynamic exchange beneath the ice shelf and tides along the open boundaries. Our results show regionally dependent feedbacks that, in some areas, substantially modify the melt rates near the grounding lines of buttressed ice streams that flow into FRIS. These feedbacks are introduced by variations in meltwater production as well as the circulation of this meltwater within the FRIS cavity; they are influenced locally by sensitivity of tidal currents to water column thickness (wct) and non-locally by changes in circulation pathways that transport an integrated history of mixing and meltwater entrainment along flow paths. Our results highlight the importance of including explicit tidal forcing in models of future mass loss from FRIS and from the adjacent grounded ice sheet as individual ice-stream grounding zones experience different responses to warming of the ocean inflow.

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Section: Introductionmentioning

confidence: 99%

Tidal influences on a future evolution of the Filchner–Ronne Ice Shelf cavity in the Weddell Sea, Antarctica

et al. 2018

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“…The ice sheet, and topographical and geological settings of the region are known well through an extensive airborne geophysical survey of the IIS, undertaken in 2010-11. The grounding line of the IIS is located on the edge of a steep reverse-sloping bed, meaning it is at a physical threshold of potential marine ice-sheet instability (Ross et al 2012).…”

Section: Potential Groundwater Locationmentioning

confidence: 99%

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

Siegert

Kulessa

Bougamont

et al. 2017

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Is groundwater abundant in Antarctica and does it modulate ice flow? Answering this question matters because ice streams flow by gliding over a wet substrate of till. Water fed to icestream beds thus influences ice-sheet dynamics and, potentially, sea-level rise. It is recognized that both till and the sedimentary basins from which it originates are porous and could host a reservoir of mobile groundwater that interacts with the subglacial interfacial system. According to recent numerical modelling, up to half of all water available for basal lubrication, and time lags between hydrological forcing and ice-sheet response as long as millennia, may have been overlooked in models of ice flow. Here, we review evidence in support of Antarctic groundwater and propose how it can be measured to ascertain the extent to which it modulates ice flow. We present new seismoelectric soundings of subglacial till, and magnetotelluric and transient electromagnetic forward models of subglacial groundwater reservoirs. We demonstrate that multifaceted and integrated geophysical datasets can detect, delineate and quantify the groundwater contents of subglacial sedimentary basins and, potentially, monitor groundwater exchange rates between subglacial till layers. The paper thus describes a new area of glaciological investigation and how it should progress in future.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. Water beneath the ice sheetAntarctic ice-sheet flow is fundamentally affected by water at the bed, as it reduces basal friction to encourage sliding and weakens till to enable bed deformation. Subglacial hydrology -the flow of water beneath the ice -is therefore a key element of the ice-sheet system. Studies to date on subglacial hydrology, and its impact on ice flow, have concentrated on water at or very near to the bed of the ice sheet.Basal water modulation of ice flow can be achieved in a number of ways. Over an impermeable bed, water can flow through channels cut either downwards into the substrate or upwards into the ice. Enhanced basal water pressures may occur where the channels and their linkages are distributed, increasing overriding ice flow through a reduction in the substrate's effective pressure. Conversely, where a well-organized channel system is formed, water pressures are lower and the hydrological effect on ice flow is reduced. If the ice stream rests on permeable subglacial till, its strength can affect ice flow as controlled by porewater pressures. High pressures lead to a reduction in material strength by pushing till grains apart, reducing bed friction and thus

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“…From the smooth quality of the bed, Ross and colleagues 5 infer that soft sediments are underlying these two ice streams. If so, the smooth bed indicates that the area has probably been free of ice cover in the past.…”

Section: News and Viewsmentioning

confidence: 99%

“…So far, indication for accelerating ice loss 4 has mainly been found in the Amundsen embayment at the root of the Antarctic Peninsula. Two papers, published in Nature Geoscience 5 and Nature 6 , indicate that the Weddell Sea sector to the east of the peninsula may soon become susceptible to fast change, too.…”

mentioning

confidence: 99%

“…Now, Ross et al 5 and Hellmer et al 6 focus their attention on the Filchner-Ronne Ice Shelf in the Weddell Sea sector, which has so far seemed stable. Worryingly, Hellmer and colleagues conclude that, over the course of the twenty-first century, warm pulses of ocean currents are likely to reach this ice shelf and induce basal melt, whereas Ross and colleagues find that beneath the grounded ice streams that feed the Filchner-Ronne Ice Shelf, the bed has steep retrograde slopes.…”

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confidence: 99%

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Vulnerable ice in the Weddell Sea

Humbert

2012

Nature Geosci

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Steep reverse bed slope at the grounding line of the Weddell Sea sector in West Antarctica

Cited by 116 publications

References 30 publications

Tidal influences on a future evolution of the Filchner–Ronne Ice Shelf cavity in the Weddell Sea, Antarctica

Tidal influences on a future evolution of the Filchner–Ronne Ice Shelf cavity in the Weddell Sea, Antarctica

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

Vulnerable ice in the Weddell Sea

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