Ice Layer Findings Boost Sea Level Rise Accuracy

A newly discovered process for how ice sheet meltwater moves and freezes could enhance predictions of global sea level rise. Researchers from The University of Texas at Austin, NASA's Jet Propulsion Laboratory (JPL), and the Geological Survey of Denmark and Greenland (GEUS) have identified how impermeable ice layers form beneath the surface, a key factor in determining the impact of ice sheet meltwater on sea levels.

Mohammad Afzal Shadab, a graduate student at UT's Oden Institute for Computational Engineering and Sciences, led the study published in Geophysical Research Letters. Under the guidance of Marc Hesse and Cyril Grima from UT's Jackson School of Geosciences, Shadab's research found that while firn (porous, old snow) usually absorbs and refreezes meltwater, impermeable ice layers can form, directing meltwater to the sea.

The study introduces a new mechanism where ice layers form based on a balance between warmer meltwater flowing through firn and the surrounding cold ice freezing it. This new understanding helps better predict how much meltwater firn can retain.

By comparing their models with data from a 2016 Greenland study, the researchers confirmed that their new mechanism accurately reflects observed conditions. The research also revealed that the position of ice layers could indicate past thermal conditions.

Currently, Greenland's meltwater contribution exceeds Antarctica’s, with Greenland adding about 270 billion tons of water annually compared to Antarctica's 140 billion tons. The study highlights the importance of understanding ice layers for accurate sea level rise predictions, which currently vary from 5 to 55 centimeters by 2100.