Global ice-cliff survey tests disputed theory behind projections of accelerated sea level rise

A new study led by the Woods Hole Oceanographic Institution (WHOI) has analyzed the tallest ice cliffs surrounding Earth's ice sheets, offering valuable insights into a controversial process that could impact future sea level rise projections. Marine ice-cliff instability (MICI) suggests that extremely tall ice cliffs (above 100 meters) may become unstable and trigger a cycle of rapid, self-sustaining ice loss.

However, this mechanism has never been directly observed, leading to debates about its inclusion in sea level rise projections. To test the theory against real-world data, researchers examined 15,330 individual satellite observations collected around the margins of Earth's ice sheets using satellite laser altimetry. This technique measures surface elevation by timing the travel time of laser pulses from a satellite to Earth's surface and back.

The findings show that ice-sheet models might underestimate the rapid breakup of tall ice cliffs, but also demonstrate that glaciers often retreat into regions with less favorable conditions for continued retreat. While these observations confirm some aspects of marine ice-cliff instability, they also indicate that other factors can limit rapid ice loss.

The study helps improve models of ice sheet contribution to future sea level rise, which is crucial for coastal communities facing rising seas.