Scientists Link Sudden Temp Shifts, Tropical Rains To Ocean Salinity - AFP

[hatrack]

Sudden decreases in temperature over Greenland and tropical rainfall patterns during the last Ice Age have been linked for the first time to rapid changes in the salinity of the north Atlantic Ocean, according to research published Oct. 5, 2006, in the journal Nature. The results provide further evidence that ocean circulation and chemistry respond to changes in climate.

Using chemical traces in fossil shells of microscopic planktonic life forms, called formanifera, in deep-sea sediment cores, scientists reconstructed a 45,000- to 60,000-year-old record of ocean temperature and salinity. They compared their results to the record of abrupt climate change recorded in ice cores from Greenland. They found the Atlantic got saltier during cold periods, and fresher during warm intervals.

"The freshening likely reflects shifts in rainfall patterns, mostly in the tropics," Howard Spero of the University of California at Davis said. "Suddenly, we're looking at a record that links moisture balance in the tropics to climate change. And the most striking thing is that a measurable transition is happening over decades."

Spero, who is currently on leave at the National Science Foundation's Marine Geology and Geophysics Program, worked with lead author Matthew Schmidt of the Georgia Institute of Technology and Maryline Vautravers of Cambridge University in the United Kingdom to conduct the research.

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