Pulses of warm ocean water that could reach far beneath the Filchner-Ronne Ice Shelf in Antarctica, together with a smooth, steep bed beneath the ice sheet, may affect the ice sheet's stability.
This is the suggestion of two papers published this week in Nature and Nature Geoscience.
Projected changes in warm ocean currents in this region by the end of the 21st century, presented in one of the studies, could erode the buttressing Filchner-Ronne Ice Shelf.
The surface and shape of the sea bed beneath two ice streams that feed the ice shelf - detected in the other study - would be unlikely to delay retreat of the line between grounded and floating ice.
In the Nature article, Hartmut Hellmer and colleagues used models to predict future ocean warming in this region.
Their projections, based on projected loss of sea ice in the Weddell Sea, suggest that winds will drive warm ocean currents far beneath the Filchner-Ronne Ice Shelf.
Towards the end of the 21st century, water temperatures under the ice may be up to two degrees warmer than present temperatures, which the simulations indicate will enhance melting.
Although the results may depend on the specific model used, preliminary results from another model - albeit from shorter simulations - are generally supportive.
In the Nature Geoscience article, Martin Siegert and colleagues surveyed the thickness of the Institute and Moumller ice streams - that feed the Filchner-Ronne Ice Shelf - to determine the underlying landscape.
Their measurements reveal a steep reverse slope and a large subglacial basin (around the size of Wales) upstream of where the West Antarctic Ice Sheet meets the Weddell Sea.
The bed is fairly smooth, with little in the way of 'pinning points' that could delay retreat of the ice sheet.
Angelika Humbert considers the issues associated with both sets of findings in an accompanying News & Views article in Nature Geoscience.
Taken together, she suggests that the smooth, steep surface below the ice sheet and the projected increasing melt rates raise concerns about the Weddell Sea sector of the West Antarctic Ice Sheet.
- © Fairfax NZ News
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