Ocean warming definitive cause for Antarctic glacier melt

Ocean warming, not a rise in air temperature, is the main reason for the retreat of glaciers on the Western Antarctic Peninsula, propose scientists.

Researchers from Swansea University and the British Antarctic Survey (BAS) investigated the Peninsula as it is one of the largest current contributors to sea-level rise. Around 90% of the 674 glaciers in this region have retreated since 1940, when records began.

Dr Alison Cook, from Swansea University who led the work, said: “The numerous glaciers on the Antarctic Peninsula give a key insight as to how environmental factors control ice behaviour on a wide scale. We were keen to understand what was causing the differences, in particular why the glaciers in the north-west showed less retreat than those that were further south and why there was acceleration in retreat since the 1990s. The ocean temperature records have revealed the crucial link.”

The scientists studied ocean temperature measurements around the Peninsula as well as photography and satellite data of the 674 glaciers. A north-south gradient showing increasing glacier retreat was observed, with colder water in the north-west which becomes warmer further south. Researchers also realised that the warm water at mid-depths in the southern region has been warming since the 1990’s which is when widespread acceleration of glacier retreat began.

Professor Mike Meredith at BAS and co-author, said: “These new findings demonstrate for the first time that the ocean plays a major role in controlling the stability of glaciers on the Western Antarctic Peninsula. Where mid-depth waters from the deep ocean intrude onto the continental shelf and spread towards the coast, they bring heat that causes the glaciers to break up and melt. These waters have become warmer and moved to shallower depths in recent decades, causing glacier retreat to accelerate.”

The study was published in Science.