If you’ve ever built a sandcastle on the beach, you’ve seen how seawater in the sand can quickly damage the castle. A new study from the British Antarctic Survey concludes that warm seawater may work in a similar way on the lower parts of land-based ice sheets, melting them faster than previously thought.
This means that computer models used to predict the melting activity of Antarctic ice sheets may underestimate how much the long-term warming of water under the ice contributes to the melting, concludes the study published Tuesday in the journal Nature Geoscience.
Faster melting of ice sheets could bring more flooding sooner than expected for coastal communities along the US East Coast, where they are already seeing more high flood days along the coast and coastal rivers.
The study is at least the second in five weeks to report that warmer ocean water could help melt ice on glaciers and ice sheets faster than previously modeled. Scientists are working to improve these essential models that are being used to help plan for sea level rise.
Relatively warmer ocean water can penetrate long distances across the boundary known as the “grounding zone,” where land-based ice meets the sea and floating ice shelves, seeping between the land below and the ice sheet, reports new study. And this could have “dramatic consequences” by contributing to sea level rise.
“We have identified the possibility of a new tipping point in Antarctic ice melt,” said lead author Alex Bradley, an ice dynamics researcher on the survey. “This means that our predictions of sea level rise may be significant underestimates.”
“Ice sheets are very sensitive to melting in their grounding zone,” Bradley said. “We find that land zone melting exhibits ‘tipping point’ behavior, where a very small change in ocean temperature can cause a very large increase in land zone melting, which would lead to a very great change in the flow of the ice upon it.”
The study follows an unrelated study published in May that found “robust melting” on Antarctica’s Thwaites Glacier, commonly known as the “Doomsday Glacier”. This study, published in the Proceedings of the National Academy of Sciences, reported clear evidence that warm seawater is pumping beneath the glacier.
Land-based ice sheets in Antarctica and Greenland gradually slide toward the ocean, forming a boundary at the edge of the sea where melting can occur. Scientists report that melting along these zones is a major factor in rising sea levels around the globe.
Water seeping under an ice sheet opens up new cavities, and those cavities let in more water, which in turn melts even larger chunks of ice, the British Antarctic Survey concluded. Small increases in water temperature can speed up that process, but computer models used by the Intergovernmental Panel on Climate Change and others don’t take that into account, the authors found.
“This lacks physics, which is not in our ice sheet models. They don’t have the ability to simulate melting under the ground ice, which is what we think is happening,” Bradley said. “We’re working to put that into our models right now.”
The lead author of the earlier study, published in May, Eric Rignot, a glaciologist at the University of California, Irvine, told USA TODAY that much more seawater flows into the glacier than previously thought, making the glacier “more vulnerable to ocean warming, and is more likely to break up as the ocean warms.”
On Tuesday, Rignot said the survey research provides “additional incentives to study this part of the glacier system in more detail,” including the importance of tides, which make the problem more significant.
“These and other studies showing a greater sensitivity of the glacier to warm water mean that sea level rise this coming century will be much greater than predicted and perhaps as much as twice as much. big,” Rignot said.
Contributed by: Doyle Rice, USA TODAY