If you’ve ever built a sand castle on the beach, you’ve seen how seawater in the sand can quickly undermine the castle. A new study from the British Antarctic Survey concludes that warmer seawater may act in a similar way on the underside of ground-based ice sheets, causing them to melt faster than previously thought.
That means computer models used to predict the melting activity of Antarctic ice sheets may underestimate how much the long reach of warming water beneath the ice is contributing to the melting, concludes the study published Tuesday in the journal Nature Geoscience.
Faster melting of the ice sheet could mean worse flooding sooner than expected for coastal communities along the U.S. East Coast, where they are already seeing more high tide days along the coast and along coastal rivers.
The study is at least the second in five weeks to report that warmer ocean waters may be helping ice in glaciers and ice sheets melt faster than previously modeled. Scientists are working to improve these crucial models used to help plan for sea level rise.
Relatively warmer ocean water can intrude over large distances beyond the boundary known as the “grounding zone,” where ice on the ground meets the sea and floating ice shelves, which seep between the underlying land and the ice sheet, the new study reports. And that could have ‘dramatic consequences’ when it comes to the contribution to rising sea levels.
“We have identified the possibility of a new tipping point in the melting of the Antarctic ice sheet,” said lead author Alex Bradley, an ice dynamics researcher on the study. “This means that our predictions of sea level rise could be significant underestimates.”
“Ice caps are very sensitive to melting in their grounding zone,” says Bradley. “We find that Earth zone melting exhibits a ‘tipping point-like’ behavior, where a very small change in ocean temperature can cause a very large increase in Earth mass. melting of the zone, which would lead to a very large change in the flow of the ice above it.”
The study follows an unrelated study published in May that showed “vigorous melting” of Antarctica’s Thwaites Glacier, also known as the “Doomsday Glacier.” That study, published in the Proceedings of the National Academy of Sciences, reported visible evidence of warm seawater pumping under the glacier.
The land ice sheets in Antarctica and Greenland are gradually sliding towards the ocean, forming a boundary at the edge of the sea where melting can occur. Scientists report that melting in these zones is a major factor in rising sea levels around the world.
Water penetrating under an ice sheet opens new cavities and those cavities allow more water to pass through, melting even larger chunks of ice, the British Antarctic Survey concluded. Small increases in water temperature can speed up that process, but the computer models used by the Intergovernmental Panel on Climate Change and others don’t take that into account, the authors found.
“This is missing physics, which is not present in our ice sheet models. They don’t have the ability to simulate melting under grounded ice, which is what we believe is happening,” Bradley said.” We are working on incorporating that into our models now.
The lead author of the previous 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 and that it makes the glacier “more sensitive for ocean warming. , and will likely fall apart as the ocean warms.”
On Tuesday, Rignot said the study’s findings provide “additional incentives to study this part of the glacier system in more detail,” including the importance of the tides, which compound the problem.
“These and other studies indicating greater sensitivity of the glacier to warm water mean that sea level rise over the next century will be much greater than expected, and possibly even twice as great,” Rignot said.
Contributing: Doyle Rice, USA TODAY