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Images: Ocean Conveyor's 'Pump' Switches Back On

In the North Atlantic Ocean, the contrast between frigid, dry winter air and warm water draws heat from the ocean into the atmosphere and leaves ocean water colder and denser. The denser waters sink and feed into the lower limb of a global system of currents often described as the Ocean Conveyor. The process, called deep convection, has far-reaching affects on climate. (Illustration by Jack Cook, Woods Hole Oceanographic Institution)

The Greenland tip jet is a sporadic, low-level atmospheric jet stream characterized by fierce winds on the lee side of Cape Farewell on the southern tip of Greenland. As storms pass through from the southwest, high-level winds descend the glacial slopes on the eastern side of Greenland, accelerating as they drop down over the ocean. In the process, they draw cold air into a relatively small area over the southern Irminger Sea. This phenomenon appears to play a critical role in chilling North Atlantic waters so that they sink to great depths and drive part of the global ocean circulation and climate system. Using NOAA's QuikSCAT satellite, MIT/WHOI Joint Program graduate student Kjetil Våge compiled this image of a tip jet on Dec. 5, 2002. Color indicates wind speeds in meters per second; arrows indicate wind direction. (Courtesy of Kjetil V?ge, Woods Hole Oceanographic Institution)

Kjetil Våge, a graduate student in the MIT/WHOI Joint Program, was lead author of a new report showing the surprising return of convection in northern seas last winter. He was back in the Irminger Sea in the fall of 2008 aboard Woods Hole Oceanographic Institution's research vessel Oceanus.

Bob Pickart, a physical oceanographer at Woods Hole Oceanographic Institution, has long explored frigid, icy seas on both sides of the Arctic Ocean. (Photo by Chris Linder, Woods Hole Oceanographic Institution)