Study Reveals Previously Unknown Teleconnection Between Northern Hemisphere Ice Sheets and West Antarctica

The West Antarctic Ice Sheet is considered highly vulnerable to rapid ice loss due to global warming. It is even considered a “tipping element” in the climate system, because it might be irreversibly lost once a self-amplifying feedback sets in. Resting on topography below sea level that further deepens inland, an initial detachment of the ice sheet from its bedrock—for example, due to an incursion of warm water—can lead to runaway retreat of the ice sheet. This feedback mechanism is known as the Marine Ice Sheet Instability.

Previous studies have shown that this instability can be triggered by processes happening on the other side of the globe: For example, melting of the Northern Hemisphere ice sheets increases the global sea level, which can destabilize the marine-based sectors of the West Antarctic Ice Sheet. In addition, melting of the Northern Hemisphere ice sheets can weaken the Atlantic Meridional Overturning Circulation (AMOC), which cools the Northern Hemisphere and leads to an accumulation of heat in the Southern Hemisphere. Based on simulations with a novel coupled climate-ice sheet model, a team of researchers at the Max Planck Institute for Meteorology has found another important teleconnection by which Northern Hemisphere ice sheets can affect the West Antarctic Ice Sheet. The research was part of the Master’s thesis of Pierre Testorf (now at University of Bern) together with Clemens Schannwell, Marie-Luise Kapsch, and Uwe Mikolajewicz.

In an idealized simulation of the past 8,000 years, they removed the ice sheets in Newfoundland, Baffin Island, Alaska, eastern Russia, and Scandinavia, which were still present in a transient simulation of the past 26,000 years but are not in line with ice-sheet reconstructions at this time. The simulation of the 8,000 years from the removal of the ice sheets until present was idealized insofar as the removal was instantaneous and the direct effect of meltwater—on the AMOC, for example— was not accounted for. Therefore, it is not a complete representation of the actual climate evolution, but rather an experiment that allowed the scientists to isolate a previously unknown mechanism in the climate system.