Majority of Antarctic ice shelves vulnerable to disintegration

When it comes to sea level rise due to the melting ice sheet in Antarctica, there is a significant difference between the parts of the ice that are land-based and the edges that float in sea, known as ‘ice shelves’. These ice shelves have already added their volume to the sea, and their melting will not contribute to rising sea levels. However, there is an alternative way that these ice shelves can contribute to sea level rise, as several ice shelves hold back land-based ice from flowing into the sea. If these shelves disappear, this ice will be able to flow into the sea unimpeded, causing sea levels to rise. Around 60 percent of Antarctic ice shelves are susceptible to this risk, according to an article published in Nature today.

“For this study, we examined ice shelves that observably delay the flow of ice from the land, but which are also susceptible to breaking up”, explains Utrecht University climate researcher Melchior van Wessem. “That turned out to be the majority of them; around 60 percent.” The ice shelves’ susceptibility is due to fractures in the surface. As the temperature increases in Antarctica, more meltwater accumulates on the surface of the ice. When that happens, the ice shelf is already doomed: the meltwater will flow into the fractures and make them wider, until some or all of the ice shelf breaks up into smaller pieces and floats away.

Relatively small percentage

Van Wessem emphasises that not all of these ice shelves are currently melting. “This study shows which ice shelves are vulnerable and  have a greater chance of disappearing over the long term. Right now we’re still studying which ones are actually melting at this moment. To do that, we look at how much meltwater is already accumulating on the surface of the ice sheets. It seems like that’s the case for only a relatively small percentage of the ice shelves.”

Machine learning

In addition to collaborating with other climate researchers, Van Wessem has also begun working with machine learning scientists, who have trained a ‘neural network’ to identify fractures in ice shelves. “Combining a lot of different data is actually a new method for us, and the results so far are extremely promising”, Van Wessem adds. “The results largely correspond to those obtained with traditional methods. In essence, we’ve opened an entire new line of research in our field of glaciology, one that’s increasingly used in other fields as well. We should be able to use this method for other applications too.”

Publication

Vulnerability of Antarctica’s ice shelves to meltwater-driven fracture
Ching-Yao Lai, Jonathan Kingslake, Martin G. Wearing, Po-Hsuan Cameron Chen, Pierre Gentine, Harold Li, Julian J. Spergel, Jan Melchior van Wessem*
Nature, 26 August  2020, DOI 10.1038/s41586-020-2627-8
* affiliated with Utrecht University