Antarctic sea water shows ‘no sign’ of warming

Watts Up With That?
Tuesday , January 12th, 2010

From the Australian: SEA water under an East Antarctic ice shelf showed no sign of higher temperatures despite fears of a thaw linked to global warming that could bring higher world ocean levels, first tests showed yesterday.

The drilling rig that was used – ironically it uses hot water to drill! Keith Makinson and Keith Nicholls from British Antarctic Survey hot water drilling the Filchner Ronne Ice-Shelf in a previous expedition.

Sensors lowered through three holes drilled in the Fimbul Ice Shelf showed the sea water is still around freezing and not at higher temperatures widely blamed for the break-up of 10 shelves on the Antarctic Peninsula, the most northerly part of the frozen continent in West Antarctica.

Antarctic sea water shows ‘no sign’ of warming Antarktisk Fimbulisen

“The water under the ice shelf is very close to the freezing point,” Ole Anders Noest of the Norwegian Polar Institute wrote after drilling through the Fimbul, which is between 250m and 400m thick.

“This situation seems to be stable, suggesting that the melting under the ice shelf does not increase,” he wrote of the first drilling cores.

The findings, a rare bit of good news after worrying signs in recent years of polar warming, adds a small bit to a puzzle about how Antarctica is responding to climate change, blamed largely on human use of fossil fuels.

Antarctica holds enough water to raise world sea levels by 57m if it ever all melted, so even tiny changes are a risk for low-lying coasts or cities from Beijing to New York.

Instruments attached to the cabel
Ole Anders Nøst attaches temperature sensors to the cable as it is lowered into the borehole. Image: Lars Henrik Smedsrud

The Institute said the water under the Fimbul was about -2.05C. Salty water freezes at a slightly lower temperature than fresh water.

TuneUp Utilities 2010

And it was slightly icier than estimates in a regional model for Antarctica, head of the Norwegian Polar Institute’s Center for Ice, Climate and Ecosystems, Nalan Koc, said.

“The important thing is that we are now in a position to monitor the water beneath the ice shelf.

“If there is a warming in future we can tell.”

She said data collected could go into a new report by the UN’s Intergovernmental Panel on Climate Change, due in 2013-14.

The last IPCC report, in 2007, did not include computer models for sea temperature around the Fimbul Ice Shelf.


From the expedition web site:

We observed a roughly 50 meter deep layer of water with temperatures very close to the freezing point, about -2.05 degrees, just beneath the ice shelf. The highest observed temperature was about -1.83 degrees close to the bottom. The temperatures are very similar to temperature data collected by elephant seals in 2008 and by British Antarctic Survey using an autosub below the ice shelf in 2005.

We collected three profiles from the underside of the ice to the seabed at 653 meters below sealevel. No trace of the relatively warm deep water that upwells over the continental slope was found. It will be exciting to see if this is the situation all year round, says Ole Anders Nøst.

For more on how the drilling was done, see this PDF of the method and equipment here

More on the project here

View the original article at Watts Up With That?


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