Scientists have discovered that a new “tipping point” may be about to be reached, with Antarctica heading towards “uncontrolled melting” of its ice sheets, according to a study published Tuesday.
The melting is caused by now warmer ocean water seeping between the ice and the land it sits on.
A climate tipping point is a critical threshold beyond which a system reorganizes, often abruptly and/or irreversibly, resulting in a series of cascading consequences.
Antarctica’s ice sheets sit on bedrock and extend beyond the coast to float on the sea. Previous studies have shown that seawater, whose temperature rises as a result of global warming caused by human activities, could infiltrate into the meeting zone between the land and the sea and thus progress under the terrestrial ice, ever further inland.
The study published Tuesday in the journal Nature Geoscience confirms this hypothesis and quantifies it through modeling: as sea water warms, intrusion accelerates over short distances of 100 meters up to tens of kilometers, melting the ice by heating it from below, explains the lead author of the study and researcher at the British Antarctic Survey, Alexander Bradley.
This “may lead to the passing of a tipping point, beyond which ocean water enters in an unlimited manner under the ice sheet, via a process of uncontrolled melting,” warns the study.
With the risk of sea level rise, when accelerated melting outpaces the formation of new ice on the continent, threatening coastal populations around the world.
However, the models used by the United Nations Intergovernmental Panel on Climate Change to project the impact of global warming on Antarctica did not take this phenomenon into account. They also systematically underestimated the ice loss observed so far, according to the study, which says these models need to be updated.
But above all, “this only highlights the need for urgent climate action to prevent these tipping points from being exceeded,” underlines Mr. Bradley.
In May, the temperature of the planet’s oceans rose again, for the 14e month in a row, a new monthly record, reaching an average of 20.93°C, according to the European Copernicus network.
“Every tenth of a degree [de réchauffement] brings us closer to this type of process, these tipping points are getting closer and closer,” warns Alexandre Bradley.