Six Olympic swimming pools per second
The Greenland and Antarctic ice caps have lost more than 500 billion tons per year, or six Olympic swimming pools per second, since 2000. But climate models had previously underestimated their contribution to future sea level rise by only considering the effects of rising air temperatures on the ice – and neglecting interaction complexes between the atmosphere, oceans, ice caps and certain glaciers.
Researchers from South Korea and the United States have determined how high the sea level rise will be by 2050 according to the various scenarios of the UN climate experts IPCC. If current climate policies continue — which includes countries’ commitments under the 2015 Paris climate agreement that we already know we cannot meet — melting in Antarctica and Greenland would increase by about half meters lead water level.
A value that would rise to 1.4 meters in the worst case if there were a significant increase in greenhouse gas emissions.
Melting and uncontrollable decay
The scientists’ study, published this week in the journal Nature Communication, also highlights when runaway melting and break-up of these ice sheets could occur.
“Our model has thresholds between 1.5°C and 2°C warming – 1.8°C is our best estimate – for accelerating ice loss and sea level rise,” explains Fabian Schloesser of the University of Hawaii, co-author of the study . Since pre-industrial times, global temperatures have already risen by almost 1.2°C.
Long-term ocean rise of 13 meters
Scientists have long known that the West Antarctic and Greenland ice sheets, which could raise sea levels by 13 meters in the long term, have “tipping points” beyond which their disintegration would be inevitable. However, the temperatures associated with this phenomenon had never been accurately identified.
Other studies published in Nature this week also show that West Antarctica’s Thwaites Glacier is breaking in unexpected ways. This Britain-sized glacier has already retreated 14km since the 1990s, but the phenomenon has not been well understood due to a lack of data.
Signs of accelerated erosion
An expedition of British and American scientists drilled a hole two Eiffel Towers (600 meters) deep through the thick tongue of ice pushed into the Admundsen Sea by Thwaites. They found evidence of accelerated erosion — with inverted staircase formations — and cracks opened by seawater.
“The warm water seeps into the cracks and wears down the glacier at its weakest point,” says Britney Schmidt, author of one of the studies and a professor at Cornell University in New York.
Less time than expected?
For its part, another study published in Earth’s Future suggests that rising oceans will destroy cropland and sources of drinking water, and force millions of people into exile sooner than expected. “The time we have to prepare for a major flood load may be much shorter than previously thought,” the authors conclude.