Stability of the Greenland Ice Sheet: When the Ice Loss Becomes Irreversible

“Our simulations show that the Greenland Ice Sheet can exist in four different steady states in a climate similar to the pre-industrial era,” says Malena Andernach, summarizing a key finding of the study. One of these states corresponds to the situation before industrialization began, with an ice volume of approximately 2.9 million cubic kilometers. “If this ice were to melt completely, it would result in a global sea level rise of about seven meters.” However, significantly smaller ice sheets with 50%, 30%, or 20% of this volume also proved stable.

The Greenland Ice Sheet stabilizes at these values due to several feedback mechanisms. The melt-elevation feedback is particularly significant: As the ice sheet melts, its surface decreases to lower elevations where it is warmer, further intensifying the melting process. In contrast, the isostatic feedback of the solid earth has a stabilizing effect. As the ice sheet’s weight decreases, the bedrock underneath the ice sheet lifts, causing the ice sheet to reach higher elevations. Smaller states are maintained also through the melt-albedo feedback: The loss of snow and ice cover exposes darker, ice-free surfaces that absorb more solar radiation, contributing to an increase in temperature. In addition to these mechanisms, changes in precipitation patterns, atmospheric circulation, and ocean temperature also play a role. Many of these processes have not been considered in simpler models.