New Evidence That Climate Change Can Have a Rapid Effect on Oceanic Circulation
09.10.2006 - Other
Scientists have been measuring shifts in temperature over Greenland and tropical rainfall patterns at the time of the last ice age, both of which changed the salinity of the north Atlantic Ocean.
Schmidt, Maryline Vautravers of Cambridge University in England, and Howard Spero, professor of geology at UC Davis, reconstructed a 45,000-to-60,000-year-old record of ocean temperature and salinity from the chemical traces in the fossilized shells of tiny planktonic animals recovered from deep sea sediment cores. Dansgaard-Oeschger cycles, which can warm up Greenland by as much as 10 degrees over a decade, lead to a saltier north Atlantic. "The deep ocean circulation is very sensitive to the saltiness of north Atlantic surface waters", said Spero. Warming climate, higher rainfall and fresher conditions can radically alter the Gulf Stream circulation that usually moves warm, salty water to the north, and that keeps Europe relatively temperate. Reduced circulation leads irreversibly to a cooling climate.
"The actual trigger that caused Atlantic circulation to restart during the ice age is still unknown", says Schmidt, but the results show that the salinity of the north Atlantic is central component of oceanic circulation, and that it has the power to alter the climate in just a few decades.
