"In addition, sea ice that is thinner is more mobile and could exit the Arctic faster. In the worst case, these Arctic outflow surges can significantly change the densities of marine surface waters in the extreme North Atlantic. What happens then is hard to predict."
The scenario echoes the premise of a controversial 2004 disaster film, "The Day After Tomorrow," which depicted catastrophic cooling in Europe, dismissed by Dr. de Steur as Hollywood absurdity.
"Ice ages occur on geological time scales of tens of thousands of years," she says. "However, large regional changes could be in store if the ocean circulation changes."
Many scientists are concerned about the future of the ocean circulation system that carries heat north to moderate the European climate.
Essentially, as warm water flows from the tropics to the North Atlantic, it cools and increases in salinity, making it heavier. At the north end of the current, near southern Greenland, these currents are cooled strongly by the atmosphere. This cold, dense oxygenated water sinks and cascades like poured cream south along the sea floor. Further south, it warms and rises, lifting nutrients essential to the marine food chain in the process, then flows north again.
It amounts to a giant "conveyor" known as the Atlantic Thermohaline Circulation, or THC.
The hypothesis is that additional ice melting throughout the Arctic region would dilute northern saltwater and alter its density, causing the conveyor to slow.
According to Detlef Quadfasel of the Hamburg University's climate centre, changes in the THC could be a
|Contact: Terry Collins|
Flanders Marine Institute (VLIZ)