Data illustrating the link between winds and ocean around western Antarctica. The migration of the southern hemisphere westerly winds (SHWW) coincide with upwelling of Cirumpolar Deep Water (CDW) in the Amundsen Sea. Graphic: Sev Kender / British Antarctic Survey

By Sev Kender
19 October 2017

(The Conversation) – The vast expanse of the Antarctic is a region of the world particularly vulnerable to climate change, where ice loss has the potential to significantly increase sea levels.

Now, for possibly the first time in 7,000 years, a phenomenon known as “upwelling” (the upward flow of warmer ocean water to the surface), is thought to have caused recent ice shelf collapse around the continent – and the glacial thinning associated with it.

Ice shelves floating on water are the oceanic extension of land glaciers and ice sheets, and the primary region for ice loss. As these shelves break apart, the flow of continental ice held up behind them accelerates.

The ocean surrounding Antarctica is extremely cold, but water over 300m deep, Circumpolar Deep Water (CDW), is about 3⁰C above the melting point of ice. Normally, the very cold water above keeps this away from ice shelves. But in some areas, CDW is spilling onto the shallow Antarctic continental shelf, causing the ice to thin.

Ice shelf thinning has accelerated in recent decades, but the picture is not the same everywhere. While the east of the Antarctic has shown modest gains in ice thickness, the west has outstripped this with significant ice loss – up to 18% in vulnerable areas like the Amundsen and Bellingshausen Seas.

The pattern of ice loss and other observations indicate that warmer water upwelling beneath these ice shelves is driving it. But what has caused this upwelling? Is it related to human activity? And how concerned should we be?

Two teams led by scientists from the British Antarctic Survey, both of which I have been working with, set out to tackle these precise questions by focusing on two vulnerable areas. One site is in Pine Island Bay, in the Amundsen Sea, and the other is in Marguerite Bay, in the Bellingshausen Sea.

The aims of the studies are similar – to monitor the extent of upwelling warm water onto the continental shelf over the past 10,000 years, in order to understand when this last occurred and what the impact was. [more]

Warm waters melting Antarctic ice shelves may have appeared for the first time in over 7,000 years

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