Arctic Ocean awakening as ice melts

Sleepiest ocean is mixing more and supporting more summer
Earth's sleepiest ocean is waking, say researchers.

The Arctic Ocean's ice-capped depths have been quiet for millennia, thanks to winds being largely unable to ruffle the surface and stir things up.

The rapid loss of summer ice cover is changing all that, however, creating internal waves in the Arctic waters that could dramatically change life there — and perhaps even accelerate the sea ice loss.
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"It's a very, very quiet ocean," said Luc Rainville of the University of Washington's Applied Physics Laboratory, in Seattle.

He and his colleague Rebecca A. Woodgate have just published a study in the latest issue of Geophysical Research Letters reporting how Arctic waters along the continental shelves are getting more turbulent as the summer ice disappears and waves start churning the water like in other oceans.

"If you put instruments down in the Pacific or Atlantic oceans you'll see density changes every few hours" indicating the passage of internal waves within the ocean, Rainville explained to Discovery News.

These underwater waves move water up, down, sideways and have been measured at heights of up to 200 meters near Hawaii. The internal waves keep the oceans forever turbulent, fertile and unable to settle into quiet pools with warm waters on top and colder, nutrient-rich waters below.

The ice-topped Arctic Ocean, on the other hand, is just such a stratified, calm place because sea ice muffles all waves "like a big damper," Rainville explained. But that is becoming less the case as summer sea ice melt is opening up ever wider expanses of water around the northern continental shelves of north America and Asia.

All that wave action is expected to bring deep water nutrients closer to the surface, where with sunlight they'll feed summer phytoplankton blooms — forming a vast new foundation for the Arctic marine food web.

Among the more worrisome questions raised by a more turbulent Arctic Ocean is whether or not it could speed up the melting of Arctic sea ice.

"That's a big open question," Rainville said. "It's possible because the Arctic is a very peculiar ocean."

Unlike any other ocean basin, the Arctic has a lot of very fresh, very cold water on top from melted ice, what's called the cold halocline layer. But about 100 meters below is very salty, slightly warmer water. If internal waves become powerful enough to mix these waters, then yes, the warmer surface could accelerate the melting of sea ice.
By Larry O'Hanlon
Source:
http://www.msnbc.msn.com