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News Story - Oceanic see-saw links the northern and southern hemisphere during abrupt climate change

Date: 02 Mar 2009

A new study published in the journal ‘Nature’ this week reveals, for the first time, that temperature changes over Greenland and in North Atlantic ocean circulation played a central role in abrupt climate change during the last Ice Age.

An international team of researchers led by Cardiff University and involving British Antarctic Survey (BAS) has created a detailed reconstruction of ocean conditions in the South Atlantic during the final phases of the last age and concluded that the abrupt changes seen in the Northern Hemisphere extended across the entire globe.

By piecing together the evidence left by tiny fossil shells of plankton in the sediment core taken from the seafloor in the South Atlantic the team reconstructed a record of water temperature from 28,000 to 10,000 years ago.

Dr Maryline Vautravers from British Antarctic Survey worked on the micro fossils. She said,

‘The marine sediment core contains many clues to the past environment. It is quite easy to extract the fossilised deep-sea creatures and analyse the chemical composition of the shells. The great thing about these animals is that can estimate exactly when they lived and what the water temperature was at the time.’

Dr Stephen Barker of Cardiff University’s School of Earth and Ocean Sciences and lead author of the paper said, “This time was a rollercoaster for global climate: the large continental ice sheets were melting, sea level was rising and atmospheric carbon dioxide was increasing. Of particular interest to paleoclimatologists were the very large and abrupt changes in temperature observed across the North Atlantic region during this time. We’ve known about abrupt climate shifts in the Northern Hemisphere for many years and while scientists have speculated about the cause of such changes, most agree that variations in the Overturning Circulation within the Atlantic Ocean (which today accounts for significant warming over North West Europe) must have played a role. However, evidence for the direct transmission of these events between the northern and southern hemispheres has so far been lacking.”

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Interhemispheric Atlantic seesaw response during the last deglaciation
Stephen Barker, Paula Diz, Maryline J. Vautravers, Jennifer Pike, Gregor Knorr, Ian R. Hall and Wallace S. Broecker