New modeling work has shown that if the current climate change continues through 2100, the Antarctic ice cap could contribute up to five meters to sea level rise in subsequent centuries. These results, which do not take into account the increase linked to the melting of the Greenlandic ice sheet and mountain glaciers, were published in the Journal of Glaciology.
Much like an ice cube out of the freezer, glaciers and ice caps take a while to readjust when their surroundings heat up rapidly. If the return to equilibrium takes a few minutes for the ice cube, it is evaluated in decades for the glaciers and in centuries, even in millennia for the ice sheets of Greenland and Antarctica.
Understanding how these huge masses of ice will readjust to the current warming is a major stake for the hundreds of millions of people living near the coasts and whose number continues to grow. Indeed, the sea level rise expected at the end of the century is far from representing the total rise that we would incur if global greenhouse gas emissions were not rapidly reduced.
Towards a sea level rise of several meters
Against this background, a team of researchers recently set out to assess the response of the ice sheet to theAntarctic (the largest) to a more or less warmed climate and maintained at this level for several centuries. In other words, the climatic conditions reached in 2100 are considered constant until the next millennium in order to allow the ice sheet to reach its new equilibrium.
An extension of the simulations carried out within the framework of the sixth polar ice cap model intercomparison project (ISMIP6), the study shows that with uncontrolled warming, the contribution of the Antarctic ice cap to sea level rise is staggered from 1.5 to more than 5 meters by the year 3000, the average being around 3.5 meters. Conversely, if a strong and coordinated action is quickly put in place, this contribution would amount to only a few tens of centimeters.
Furthermore, the West Antarctic ice sheet systematically collapses in uncontrolled warming scenarios. This high sensitivity is due to the fact that the western cap rests on a bedrock essentially located below sea level unlike the eastern cap. Thus, it is subject to dynamic instabilities which, once a certain heating threshold has been crossed, lead to dislocation in several deeply irreversible stages.
Multisecular consequences that depend on our current actions
The results obtained are based on the SICOPOLIS model (acronym for SImulation COde for POLythermal Ice Sheets). In total, fourteen simulations were carried out in the uncontrolled warming scenario and three in the context of controlled warming. In fact, the warmer the climate, the greater the uncertainty, which requires a greater number of simulations to frame the range of possibilities. Finally, it should be noted that this work does not take into account the elevation associated with the melting of mountain glaciers nor that associated with the retreat of the Greenlandic ice sheet.
« This study clearly demonstrates that the impact of 21st century climate change on the Antarctic ice sheet extends far beyond the 21st century itself and the most serious consequences will probably not be visible until later », Summarizes Christopher Chambers, main author of the paper. ” Future work will include more realistic scenario-based simulations, as well as the use of other ice cap models to model the consequences. ».