While the mainstream media has provided extensive coverage of El Nino and La Nina -- the warmer and colder phases of a perpetual oscillation in the surface temperature of the tropical Pacific Ocean -- little attention has been paid to deep-water phases. Several recent publications in leading scientific journals (Science
are adding new dimensions to the link between large-scale ocean circulation patterns and climate. Researchers Dr. Wallace Broecker and researchers at Columbia University's Lamont-Doherty Earth Observatory (see the November 5, 1999 issue of Science
and the November 9, 1999 issue of The New York Times)
found that deep ocean currents, operating as an oceanic "conveyor belt," may hold clues to climate change. The conveyor belt works by transporting warm, increasingly salty, ocean water from the Pacific to the Atlantic Ocean; eventually, the warm water current runs into a cold water current, causing the warm water to cool quickly and sink, due to greater density. In turn, this creates a "sub-surface countercurrent which carries the cool water back to the Indian and Pacific oceans" (2)
. In this week's issue of Nature
(December 2, 1999), German scientist Carsten Ruhlemann and colleagues provide new evidence that the thermohaline circulation has triggered rapid climate change events in the past, including the last deglaciation. In addition, the current issue of Science Times
(December 7, 1999) highlights the connection between thawing Arctic ice sheets and oceanic currents. This week's In The News focuses on ocean circulation patterns and climate change. The seven resources provide background information and specific links to related resources.
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