A new study published last week in Nature finds that Antarctica’s massive ice shelves are shrinking due to warm water below. Scientists have long been worried about the implications of shrinking ice sheets for sea-level rise. This study finds that sea levels could indeed rise faster than what previous models have predicted.

What is troubling is that the western part of Antarctica is losing 23 feet of its floating ice sheet each year – a phenomenon that has long puzzled scientists. Many scientists believed warmer air itself was the principal cause of melting ice sheets. The study explains that climate change has had an indirect role here as melting ice sheets are associated with “warm ocean currents thawing the underbelly of the floating extensions of ice sheets and warm air melting them from above”.

The study’s lead, author Hamish Pritchard of the British Antarctic Survey, explains that “we can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt. The oceans can do all the work from below.” Dr. Pritchard further explains that Antarctic winds are changing because of changes in climate, which has, among other things, affected the strength and direction of ocean currents. “These studies and our new results suggest Antarctica’s glaciers are responding rapidly to a changing climate.”

In summary, the ice sheets are highly sensitive to relatively subtle changes in climate through the effects of the wind. Changes in wind currents have pushed warmer water closer to and beneath the floating ice shelves.

This animated video shows the circulation of ocean currents around the Western Antarctic ice shelves.

The study has direct relevance to ACT. As a result of warm summer winds directly melting the snow on the ice shelf surfaces, snow and ice on land glaciers will slide down to the floating shelves and eventually into the sea, causing sea-level rise. The research is timely and provides further evidence to decision-makers about the need to actively prepare for sea-level rise.   

The authors explain that if the Western Antarctic Ice Sheet were to melt – an event that would occur over many years – scientists have estimated it would lift global sea levels by about 16 feet.

The ACT Sea Level Rise session is exploring precedents from other countries and Canadian municipalities in order to develop recommendations for strategic infrastructure planning, generating an overview of what we do and don’t know, and policy options for the path ahead.

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Written by ACT researcher Timothy Shah