Climate science: Melting glaciers might contain less ice than previously thought

The total rise in sea levels that would occur if all of the world’s glaciers melted may be 20% less than previously estimated, suggests computational analysis of glacier ice thickness published in Nature Geoscience.

Sea level is on the rise due to melting glaciers, shrinking ice sheets and the thermal expansion of the oceans. Melting glaciers contribute around 25–30% of current sea level rise, but the total amount of water in glaciers remains unclear due to a lack of ice thickness observations.

Romain Millan and colleagues used thousands of satellite images to construct a high-resolution global map of glacier ice motion. Based on this data, the authors were able to compute ice thickness and provide an estimate of the total volume of ice stored in glaciers worldwide. They found that glaciers have a potential to contribute 257mm to sea level rise, which is 20% less than previously estimated. Notable differences to previous assessments were also found regionally, with the results suggesting there is more ice in the Himalayas, but less ice in other regions, such as the tropical Andes of South America, which impact the water availability for local population.

The authors conclude that their results may affect the prediction of glacier evolution worldwide, given the importance of accurate glacier geometry and dynamics for glacier modelling.

Additional, on-site observations of ice thickness that form the foundation of these analyses, are, however, needed. The impact of melting glaciers should also not be mistaken for overall sea level rise projections, which are influenced by other phenomena such as thermal expansion and shrinking ice sheets.