Ocean warming has been uncovered as the primary cause of melting glaciers on the western Antarctic Peninsula.
The new study, carried out by scientists from Swansea University and the British Antarctic Survey, will enable researchers to better predict ice loss from this region – which is currently one of the largest contributors to sea-level rise.
Published today in the journal Science, the findings show that glaciers flowing to the coast on the western side of the Peninsula reveal a distinct spatial correlation with ocean temperature patterns. While those in the south retreat rapidly, those in the north show little change.
About 90% of the 674 glaciers in the Peninsula region have retreated since records began – in as recently as the 1940s.
Swansea University team leader Dr Alison Cook said: “Scientists know that ocean warming is affecting large glaciers elsewhere on the continent, but thought that atmospheric temperatures were the primary cause of all glacier changes on the Peninsula.
“We now know that’s not the case.”
Cook continues: “The numerous glaciers on the Antarctic Peninsula give a key insight as to how environmental factors control ice behaviour on a wide scale. Almost all glaciers on the western side end in the sea, and we’ve been able to monitor changes in their ice fronts using images as far back as the 1940s.
“Glaciers here are extremely diverse and yet the changes in their frontal positions showed a strong regional pattern.”
One of the aims of the study was to understand what was causing these differences, and in particular why glaciers in the north-west of the region showed less retreat than those located further south. Looking at the ocean temperature records has revealed this crucial link.
The scientists looked at ocean temperature measurements around the Peninsula dating back several decades, together with photography and satellite data for all 674 glaciers.
A strong pattern was determined between ocean temperatures and the north-south gradient of increasing glacier retreat: water is cold in the north-west and becomes increasingly warmer at depths below 100m further south.
Importantly, the research found that the warm water at mid-depths in the southerly region has been warming since the 1990s, at the same time as the acceleration in glacier retreat.
“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,” co-author Professor Mike Meredith from the British Antarctic Survey adds.
“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 the shallower depths in recent decades, causing glacier retreat to accelerate.”
A third author, Swansea’s Professor Tavi Murray, concludes: “The glaciers on the Antarctic Peninsula are rapidly changing – almost all of the Peninsula’s glaciers have retreated since the 1940s. We have known the region is a climate warming hotspot for a while, but we couldn’t explain what was causing the pattern of glacier change.
“This new study shows that a warmer ocean is the key to understanding the behaviour of glaciers on the Antarctic Peninsula. Currently the Peninsula makes one of the largest contributions to sea-level rise, which means understanding this link will improve predications of sea-level rise.”