Tuesday, 17 January 2017

Layering of ocean around Antarctica signals major melt

Ocean layering around Antarctica could signal major meltdown
Study warns of 10-foot sea level rise

Sunlit icebergs gleam on the horizon in the Antarctic Sound.


15 January, 2017


Staff Report
As scientists learn more about the dynamics of the ocean around Antarctica, they’ve discovered a climate warming signal. Distinct layers of water, marked by temperature boundaries, are forming right now, leading to conditions similar to about 14,000 years ago, when Antarctic ice sheets melted rapidly, raising global sea level by more than 10 feet.
The reason for the layering is that global warming in parts of Antarctica is causing land-based ice to melt, adding massive amounts of cool freshwater to the ocean surface,” said lead author Dr Chris Fogwill, from the University of New South Wales’ Climate Change Research Centre.
At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers in the Amundsen Sea Embayment. It appears global warming is replicating conditions that, in the past, triggered significant shifts in the stability of the Antarctic ice sheet.”
The study was published last week in the Nature journal Scientific Reports.
By looking at what happened in the past we can gain insights into where our planet may be heading,” said co-author UNSW Professor Chris Turney.
The accelerating melting of land ice into the sea makes the surface of the ocean around Antarctica colder, less salty and more easily frozen, leading to extensive sea ice in some areas; one of the likely causes of increasing sea ice around Antarctica.
The researchers tracked changes in ice sheet elevation and regional climate by studying the chemical makeup of ancient blue ice from a ‘horizontal ice core’ in the Weddell Sea Embayment, a region that today drains more than 22 percent of the entire Antarctic Ice Sheet. When combined with ice sheet and climate modelling, the new data clearly showed that when the waters around the Antarctic became more stratified, the ice sheets melted much more quickly.

The big question is whether the ice sheet will react to these changing ocean conditions as rapidly as it did 14,000 years ago,” said author Dr, Nick Golledge, a senior research fellow at the University of Victoria’s Antarctic Research Centre.

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