A previously unknown sub-glacial basin that is almost the size of New Jersey residing beneath the West Antarctic Ice Sheet near the Weddell Sea has prompted scientists to reevaluate the ice sheet location most at risk of collapse.
“If we were to invent a set of conditions conducive to retreat of the West Antarctic Ice Sheet, this would be it,” said Don Blankenship, senior research scientist at The University of Texas at Austin’s Institute for Geophysics and co-author on the new paper. “With its smooth bed that slopes steeply toward the interior, we could find no other region in West Antarctica more poised for change than this newly discovered basin at the head of the Filchner-Ronne Ice Shelf. The only saving grace is that losing the ice over this new basin would only raise sea level by a small percentage of the several meters that would result if the entire West Antarctic Ice Sheet destabilized.”
The researchers from The University of Texas at Austin compared data about the newly discovered sub-glacial basin with data they had previously collected from other locations across the West Antarctic Ice Sheet that also appeared to be vulnerable, including Pine Island Glacier and Thwaites Glacier.
Despite the fact that the amount of ice stored within the newly discovered basin is less than that stored in other locations, it may still be closer to a tipping point.
“This is a significant discovery in a region of Antarctica that at present we know little about,” said Professor Martin Siegert of the University of Edinburgh, who led the project. “The area is on the brink of change, but it is impossible to predict what the impact of this change might be without further work enabling better understanding of how the West Antarctic Ice Sheet behaves.”
The seaward edge of the newly discovered basin lies just inland of the ice sheet’s grounding line, where streams of ice flowing toward the sea begin to float.
Two features of the basin, which is entirely below sea level, are particularly worrisome to scientists: First, like a cereal bowl, its edges slope down steeply. If the grounding line begins to retreat upstream, seawater will replace it and more ice will begin to float. The study’s authors predict that this positive feedback mechanism would sustain retreat of the ice sheet until eventually all of the ice filling the basin goes afloat. Second, the bed of the basin on which the ice rests is smooth. There are few big bumps, or “pinning points,” to hold back sliding ice.