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Oceanic seesaw links northern and southern hemisphere during abrupt climate change

25 February 2009

Very large and abrupt changes in temperature recorded over Greenland and across the North Atlantic during the last Ice Age were actually global in extent, according to an international team of researchers led by Cardiff University.

New research, published in the journal Nature today, supports the idea that changes in ocean circulation within the Atlantic played a central role in abrupt climate change on a global scale.

Using a sediment core taken from the seafloor in the South Atlantic, the team were able to create a detailed reconstruction of ocean conditions in the South Atlantic during the final phases of the last ice age.

Dr Stephen Barker, Cardiff University’s School of Earth and Ocean Sciences and lead author on the paper, said: "During this period very large and abrupt changes in temperature were observed across the North Atlantic region. However, evidence for the direct transmission of these shifts between the northern and southern hemispheres has so far been lacking".

The new study suggests that abrupt changes in the north were accompanied by equally abrupt but opposite changes in the south. It provides the first concrete evidence of an immediate seesaw connection between the North and South Atlantic. The data shows, for example, that an abrupt cooling in the north would be accompanied by a rapid southerly shift of ocean fronts in the Southern Ocean, followed by more gradual warming across the south.

Dr Barker explains: "The most intuitive way to explain these changes is by varying the strength of ocean circulation in the Atlantic. By weakening the circulation, the heat transported northwards would be retained in the south."

Climate physicist, Dr Gregor Knorr, co-author of the study and now based at the Alfred Wegener Institute in Germany, said: "Our new results agree with climate models that predict a rapid transmission of climate signals between the two hemispheres as a consequence of abrupt changes in ocean circulation."

The study has wide implications for our understanding of abrupt climate change. Dr Ian Hall, School of Earth and Ocean Sciences, said: "While it is unlikely that an abrupt change in climate, related to changes in ocean circulation, will occur in the near future, our results suggest that if such an extreme scenario did occur, its effects could be felt globally within years to decades."

-ENDS-

Notes to editors:

1. ‘Interhemispheric Atlantic seesaw response during the last deglaciation’ is published in Nature on 26 February 2009. The authors are: Stephen Barker, School of Earth and Ocean Sciences, Cardiff University (lead author).

Jennifer Pike and Ian R. Hall, School of Earth and Ocean Sciences, Cardiff University. Paula Diz, Laboratoire des Bio-Indicateurs Actuels et Fossiles, Angers University, France. Maryline J. Vautravers, British Antarctic Survey, Cambridge. Gregor Knorr, Alfred Wegener Institute, Germany. Wallace S. Broecker, Lamont-Doherty Earth Observatory of Columbia University.

2. Cardiff University

Cardiff University is recognised in independent government assessments as one of Britain’s leading teaching and research universities and is a member of the Russell Group of the UK’s most research intensive universities. Among its academic staff are two Nobel Laureates, including the winner of the 2007 Nobel Prize for Medicine, Professor Sir Martin Evans. Founded by Royal Charter in 1883, today the University combines impressive modern facilities and a dynamic approach to teaching and research. The University’s breadth of expertise in research and research-led teaching encompasses: the humanities; the natural, physical, health, life and social sciences; engineering

and technology; preparation for a wide range of professions; and a longstanding commitment to lifelong learning. Visit the University website at: www.cardiff.ac.uk

3. Cardiff School of Earth and Ocean Sciences

Cardiff University’s School of Earth and Ocean Sciences is one of the top geoscience units in the UK. It is a large, international research school with more than 30 leading international research scientists. These researchers are addressing some of the most significant research themes in world science at the moment, including global change, the origin and evolution of life, environmental science, natural resource exploration, and the evolution of Earth and planets.

For further information, please contact:

Dr Stephen Barker
School of Earth and Ocean Sciences
Cardiff University

Email: BarkerS3@cardiff.ac.uk
Telephone: +44(0)29 208 74328

Ms Jill Wilmott-Doran

Email: Wilmott-DoranJ@cardiff.ac.uk

Telephone: +44(0)29 2087 0298

Extension: 70298