Science

Global warming: a third of Antarctic ice shelves threaten to collapse

In Antarctica, numerous thick glacial structures resembling ice shelves constitute pack ice. With global warming, these structures accumulate meltwater on the surface, the gradual infiltration of which ultimately causes the ice to crack. On a large scale, that means tens of thousands of tonnes of ice could collapse, leading to rising sea levels. Researchers recently estimated that this phenomenon could affect up to a third of Antarctic ice structures.

About a third of the ice shelves holding huge glaciers in Antarctica are at risk of collapsing if humanity does not take enough action on climate change, new projections show. The ice structures surrounding the continent are vulnerable to meltwater on their surface, which causes the ice to crack and disintegrate, a process known as hydrofracturing.

Computer modeling carried out by Ella Gilbert of the University of Reading (UK) and Christoph Kittel of the University of Liège (Belgium), has shown that while the world is warming by 4 ° C above pre-industrial levels, 34 % of the continent’s ice shelves are believed to accumulate meltwater on their surface, a sign that they are in danger of collapsing.

Images showing the gradual collapse of the Larsen B Ice Shelf in Antarctica. © NEO / Rosamund Pearce

The impact of rising temperatures

However, this figure drops to 18% if the temperature rise is controlled to 2 ° C. The world is currently heading for an increase of 2.9 ° C, but, if implemented, climate plans and zero emission targets would reduce that figure to 2.1 ° C. ” The 2 ° C warming means that half of the sea ice is at risk of collapsing. This is the message: the less warming, the better. », Says Gilbert.

She and Kittel used a much higher resolution climate model than previous research, with grid squares 35 kilometers in diameter rather than hundreds of kilometers in diameter. It also more accurately represents the physics of clouds, which is essential, since estimates of the area at risk of collapse depend on the amount of lost ice replaced by snowfall.

melt runoff water platform ice
Graph showing melt (ME), runoff (UK) and surface mass balance (SMB) in gigatonnes per year for the historical period 1980-2009 (Historical) and for the three temperature rise scenarios. © Gilbert & Kittel, 2021

The big difference between the 2 ° C and 4 ° C increase scenarios is that the melting outweighs the impact of snowfall in a world that is 4 ° C warmer. The Larsen C Ice Shelf, east of the Antarctic Peninsula, where a huge iceberg broke off in 2017, has proven to be one of the most at-risk areas.

Sea level rise of up to 10 cm

This study shows that surface melt from ice shelves is spreading southward into parts of the continent where huge reservoirs of inland ice are at risk of losing their protective barrier. If this happens, we can expect a rapid increase in sea level rise along every coastline on our planet. Says Andrew Shepherd of the University of Leeds.

The study does not provide figures on the rise in sea level if the glacial structures collapse and free the glaciers on which they depend. However, according to the researchers, this could potentially contribute to tens of centimeters of elevation. Avoiding a sea level rise of 10 centimeters is expected to put 10 million fewer people in the world at risk of flooding.

Helene Seroussi, from NASA’s Jet Propulsion Lab, says the big breakthrough in the study is to use a higher resolution model. As research identifies ice shelves that could be hydrofractured, Seroussi explains that further analysis of how ice shelves move – the “dynamic stress regime” – is needed to determine which ones. that will actually collapse.

Sources: Geophysical Research Letters

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