LONDON: New investigations into Antarctic ice cores show a direct connection between climate changes in the northern and southern hemispheres. A comparison of Antarctic cores with cores from Greenland proves a north-south link and indicates a meridional overturning circulation, or the Atlantic Conveyor, in the process of heat transfer, according to studies carried out by scientists from 10 European countries working on the European Project for Ice Coring in Antarctica (EPICA).
Team leader and paleoclimatologist Hubertus Fischer from the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, writes in the current issue of Nature that it is really astounding how systematic this process worked even for smaller temperature changes in the Antarctic.
While climate changes in the northern hemisphere have been well documented through ice cores from Greenland, there was only sketchy information on such changes in Antarctica.
Fischer and his team has drilled out a core covering a period of 150,000 years from an area in Antarctica and found that even short and small temperature changes in the south were connected to fast changes in the north by the changing Atlantic currents. The meridional overturning circulation carries warm water from the southern hemisphere towards the north to create heat in the northern side. As the warm water meets the Greenland ice sheet, it cools and sinks, returning to the south once again creating the conveyor belt process.
Fischer said the degree of warming in the south is linearly related to the duration of cold periods in the North Atlantic. It is a "bipolar seesaw."
Based on the new synchronized time scale, the scientists could compare high resolution temperature proxy records from the EPICA ice core in Dronning Maud Land in Antarctica and the North Greenland Ice core Project (NGRIP). And it indicated that bipolar seesaw occurred throughout and most probably beyond the last glacial period.
The report warns that localized warming in the far North Atlantic, caused by man-made climate change, could cause the Antarctic ice to melt and contribute to rise in sea levels.
Fischer said, "Today, Antarctica is still a reservoir of cold. We don't see any contribution to global sea-level change because of Antarctica - it's not melting yet. In fact, there has been more precipitation and some models suggest that Antarctica actually will grow a little."
But, this could change as meridional overturning circulation is beginning to falter, he added. The causes for this slowing of the Atlantic conveyor belt could be a runoff of cold water from melting Siberian permafrost or the Greenland ice sheet, triggered by rising atmospheric temperatures.
A disruption can cause a buildup of warmer water off Antarctica, according to the conveyor-belt theory. "If the thermohaline [ocean convection] circulation in the Atlantic slows down just a little, it would cause a warming in the Southern Ocean," Fischer said. "And if you have warming around Antarctica, at a certain point, the fringes of Antarctica will even warm over the melting point. Then we could start to see melting at the borders and runoff and that would contribute to sea-level rise."
According to studies, Antarctica warmed several times between 20,000 and 55,000 years ago while the north was cold and export of warm water from the southern ocean was reduced.
Ten European countries -- Belgium, Denmark, France, Germany, the U.K.., Italy, the Netherlands, Norway, Sweden and Switzerland -- participated in the project.
