The disappearance of glaciers greater than expected

How will our glaciers evolve during the 21e century ? In a new study to be published on January 5 in the journal Science, an international team, including scientists from the CNRS and the Paul Sabatier Toulouse III University, reveals a greater loss of glacier mass than previously predicted. According to their work, this loss increases by 14% to 23% compared to previous projections, in particular those that fueled the latest IPCC report. The majority of glaciers on our planet are small glaciers, less than 1 km2, they are the most affected by this loss of mass. Thus, according to the scenario with a limitation of the rise in temperatures to 1.5°C, 49% of the world’s glaciers, including all the small ones, are nevertheless expected to disappear by 2100, then causing a rise of 9 cm sea ​​level. In this hypothesis, the largest glaciers are also impacted, without however disappearing. If the temperature rise reached 4°C, small and large would be affected and 80% of glaciers would then disappear, with a rise in sea level of 15.4 cm. To achieve these results, the scientists relied on the observations of a study which quantified the mass losses of the world’s glaciers, which were widespread and accelerated between 2000 and 2019. This previous information made it possible to calibrate the mathematical model, designed in as part of this new publication, one by one for the 200,000 glaciers present on Earth. In addition, the model now takes into account processes not previously represented, such as mass losses linked to the calving of icebergs and the effect of a debris cover on the surface of the glacier. The mass losses of the largest glaciers, such as those in Alaska, the Canadian Arctic or around Antarctica, keys to future sea level rise, could still be limited with the implementation of measures to contain the increase in temperatures.

Projections of the disappearance of glaciers in 2100 according to two scenarios of increase in the average global temperature. Background, Upsala Glacier, Patagonia
© Etienne Berthier / CNRS / LEGOS

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