Hidden threat lurking in Antarctica's ice shelves

Imagine Antarctica. You’re probably visualizing vast, pristine landscapes of endless snow and frost. But as you read this, an unseen threat might be quietly destabilizing the continent’s icy terrain. 

Globally, scientists have been keeping a close eye on Antarctica, particularly its ice shelves’ condition. And they just highlighted something alarming – there’s double the previously estimated volume of meltwater present. 

This meltwater is largely composed of “slush,” or water-drenched snow, that blankets over half of Antarctica’s ice shelves during summer.

Decoding the ice shelves

Interestingly, this discovery wasn’t the result of a physical expedition but spawned from an innovative union of science and artificial intelligence. 

Though ice shelves’ surfaces accumulate water during the summer months, spotting this slush-filled meltwater has proved challenging. 

“We can use satellite imagery to map meltwater lakes across much of Antarctica, but it’s hard to map slush because it looks like other things, such as shadows from clouds, when viewed from a satellite,” said study lead author Rebecca Dell from the Scott Polar Research Institute (SPRI) at the University of Cambridge.

But artificial intelligence presented effective solutions to this tricky problem. Utilizing the optical data from NASA’s Landsat 8 satellite and training a machine learning model to work with more light wavelengths than the human eye can perceive, the researchers successfully generated monthly records of slush and meltwater lakes across 57 Antarctic ice shelves from 2013 to 2021.

Silent struggle of the ice shelves

Why is this discovery so significant? Well, it lies in the intricate dance of ice, slush, and water. The researchers discovered that in January, at the height of the Antarctic summer, over half (57%) of all meltwater on Antarctica’s ice shelves exists as slush. 

“This slush has never been mapped on a large scale across all of Antarctica’s large ice shelves, so over half of all surface meltwater has been ignored until now,” noted Dell. “This is potentially significant for the hydrofracture process, where the weight of meltwater can create or enlarge fractures in the ice.”

The fractures can destabilize the continent’s surrounding ice shelves. As climate changes lead to increased melting, this meltwater – whether in lakes or slush form – can seep into ice cracks, expanding them. 

This can trigger fractures and the collapse of ice shelves, accelerating inland glacier ice flow into the ocean and contributing to sea level rise.

“Since slush is more solid than meltwater, it won’t cause hydrofracture in the same way that water from a lake does, but it’s definitely something we need to consider when attempting to predict how or whether ice shelves will collapse,” said study co-author Ian Willis, a scientist at SPRI.

Melting models: Are we missing something?

Aside from hydrofracture, slush also severely impacts melt rates. As darker and less reflective surfaces, slush and lakes absorb more heat than snow or ice, causing increased snowmelt. 

Unfortunately, these factors are not currently represented in climate models, which could lead to underestimating ice sheet melting and ice shelf stability.

“I was surprised that this meltwater was so poorly accounted for in climate models,” said Dell. “Our job as scientists is to reduce uncertainty, so we always want to improve our models so they are as accurate as possible.”

“In the future, it’s likely that places in Antarctica that currently don’t have any water or slush will start to change. As the climate continues to warm, more melting will occur, which could have implications for ice stability and sea level rise,” said Willis.

The research is published in the journal Nature Geoscience.

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