Even if climate records from Greenland and Antarctic ice cores look different, climate of Artic and Antarctic are directly linked. Investigations of an Antarctic ice core indicate a principle connection between both hemispheres by a 'bipolar seesaw'.
Even shorter and weaker temperature changes in the south are connected to fast changes in temperature in the north by change of ocean currents in the Atlantic ocean. Antarctica always warmed in the time period 10,000 to 55,000 years BP whilst the North remained cold. Concurrently, warm water export from the Southern Ocean to the North Atlantic was reduced. In contrast, the Antarctic started to cool every time more warm water started to flow into the North Atlantic during warm events in the north.
This result suggests a general link between long-term climate changes in both hemispheres via this Bipolar Seesaw as a result of Atlantic Meridional Overturning Circulation changes. The Atlantic circulation is an important issue in the global warming debate, as icecap melt water can weaken the Atlantic currents.
In the current issue of Nature, a joint effort of scientists from 10 European nations working together in the European Project for Ice Coring in Antarctica (EPICA) established a precise link between climate records from Greenland and Antarctica using data on global changes in methane concentrations derived from trapped air bubbles in the ice.
The Antarctic ice core analyses were performed on the new EDML (EPICA Dronning Maude Land) ice core, which due to its higher snow accumulation rate allows for reconstruction of higher resolution atmospheric and climate records than previous ice cores from the East Antarctic plateau; a prerequisite for precise synchronisation with the Greenland counterpart. The Greenland ice core analyses were performed on the North Greenland Ice core Project (NGRIP).
Based on the new synchronized time scale the scientists were able to compare high-resolution temperature proxy records from north and south. This showed that the Bipolar Seesaw occurred throughout and most probably beyond the last glacial period.
"It is really astounding how systematically heat is moved between the north and south hemisphere with the Seasaw, causing really dramatic climate changes during the glacial period. It is one of our goals in our new Centre for Interglacial Climate to investigate the importance of this Bipolar Seasaw in our present warm climate," says the Danish researchers from the Ice and Climate group at the Niels Bohr Institute, University of Copenhagen.
The study synchronises the work of EPICA scientists from 10 European countries: Belgium, Denmark, France, Germany, UK, Italy, the Netherlands, Norway, Sweden and Switzerland. "This study is a good example of scientist from different disciplines of ice core research and glaciology collaborating internationally. Modellers, isotope specialists and glaciologists are bringing together their expertise," says Prof. Dr Heinz Miller, head of the EPICA steering committee. As the Danish partner within EPICA, The Ice and Climate group has shipped the NGRIP deep drill to Antarctic every season and has taken part in the analyses on the EDML ice core.
Coordinated by the European Science Foundation (ESF), EPICA is funded by the participating countries and the European Union.
The Ice and Climate group at the Niels Bohr Institute, University of Copenhagen carries out polar research in the Arctic and Antarctic. The research group coordinated the Greenland NGRIP deep ice core project.
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