Antarctica’s ice shelves have an “Achilles’ heel,” and it’s the melting that’s taking place beneath the surface, not on the surface, according to an international climate study newly published in the journal Nature Climate Change. The study urges scientists to pay more attention to sub-shelf melting, which in some glaciers accounts for 90% of the continent’s ongoing annual ice loss.
Jonathan Bamber, a professor with the University of Bristol’s School of Geographical Sciences, coauthored the study with colleagues at Utrecht University and the University of California. The researchers relied on a combination of satellite data and computer-model simulations to track the present and future melting that the Antarctic glaciers’ surfaces and undersides are undergoing. The simulations repeatedly showed that what’s going on beneath the surface is as important as—if not more important than—any ice loss that scientists have been witnessing taking place aboveground.
This underwater ice loss affects some ice shelves more than others. Bramber and his colleagues can already pinpoint some of the more affected ice shelves by looking at the current extent of their ice loss. Further research may quantify the underwater melt levels of many more.
That Antarctica is losing ice is certainly not news to climate scientists. Topographic data collected over the last few decades has made clear that surface-level iceberg production and melting has been causing extended trends of continental ice shrinkage in much of the continent.
That shrinkage amounted to about 70 gigatons of the continent’s land ice a year from 1992 through 2011. The continent’s sea ice made some shrinkages in many areas, as well, coupled with a few smaller increases in a few others as a direct result of the melting. This led to some slight increases in a few areas of the continent’s sea ice—increases that, while too small to compensate for the larger losses, still fueled some false claims by a few climate-change skeptics that “Antarctica’s ice is expanding.”
Overall ice loss is not only happening, but there is even more of it taking place sub-surface than researchers may have thought, Bramber and his colleagues conclude. This challenges conventional thinking in that researchers over the last few decades have primarily focused on the surface-level processes of icebergs forming and breaking away from the main ice shelves. This, they believed, was the main driver of long-term ice loss.
Bramber and his colleagues encourage scientists to reconsider. Recognizing the role of subsurface melting, which in many cases may be far larger than that of iceberg breakage, may be critical to a more precise understanding of how ice sheets may interact with oceans and the changing climate in the decades to come.
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