Narrow Surface Fractures Destabilize Ice Sheets

Nature Geoscience, 19 June 2023

Meltwater flows into millions of hairline cracks across the surface of the Greenland and Antarctic ice sheets, transferring heat deep into the ice and rendering them more vulnerable to climate warming than previously estimated. These centimeter-wide fractures are too small to be detected by satellites, but they allow streams of meltwater to seep down hundreds of meters before freezing closed. Collectively, water pouring through these cracks weakens the inside of the ice sheet, damaging its structural integrity such that it flows and melts much faster. Before this study, researchers mainly focused on large-scale fracturing driven by meltwater lakes, which force open massive “moulins” or chasms that can reach over one kilometer in depth. This study reveals a slower mode of fracturing that occurs through a very similar mechanism, but takes place across hundreds of thousands of tiny cracks in the ice, even in areas far from meltwater lakes or moulins. The cracks don’t necessarily reach the base of the ice sheet, but send liquid water deep into its center, producing considerable damage. Increasing surface melt and fracturing across Greenland, West Antarctica and portions of East Antarctica pose a serious threat to future ice sheet stability. This newly-recognized process could produce much faster ice sheet loss and resulting sea level rise than previously modeled, again making clear the importance of keeping global temperatures within 1.5°C Paris limits.

https://www.nature.com/articles/s41561-023-01208-0