Dynamical Meteorology and Climatology Unit

After a relatively linear decrease since the beginning of satellite observations in 1979, summer Arctic sea-ice extent displayed two extreme lows in 2007 and 2012. Antarctic sea ice, which had been slightly expanding on average from 1979 to 2014, has experienced a series of record lows in all seasons since then, with historical summer minima in 2017, 2022, 2023 and 2024.

The central scientific question of RESIST, is: "Were recent observed summer sea-ice lows driven by the same factors in the Arctic and in the Antarctic, and did their impacts differ significantly"? More specifically, the objective of RESIST is to document, qualitatively and quantitatively, the cause-effect relationships between extreme states of summer sea ice and its potential interacting agents, in both hemispheres. RESIST is a BELSPO project involving UCLouvain and RMIB.

The Liang-Kleeman rate of information transfer (see also Tools) is applied to identify causal dependencies between the different oceanic/atmospheric processes leading to sea-ice lows in both polar regions, but also to test the influence of sea-ice anomalies on autumn and winter atmospheric conditions. The method feeds on existing model simulations (large ensembles, CMIP6, HighResMIP) and runs produced within RESIST.

In a first study, we investigated the drivers of summer Arctic sea-ice changes in 5 CMIP6 large ensembles over 1970-2060 and found that surface air temperature is the most important controlling factor of summer sea-ice extent at interannual time scale, and that winter sea-ice volume and Atlantic Ocean heat transport play a secondary role.

We have also applied the causal method to better understand the causes of changes in summer Antarctic sea-ice extent in the same 5 CMIP6 large ensembles. A paper is in preparation.

Dr. David Docquier, postdoc at RMIB

Dr. Stéphane Vannitsem, supervisor at RMIB