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Cold snaps preceded iceberg pulses during the last Ice Age

Nature publishes results from ocean sediment core records

Cold snaps preceded iceberg pulses during the last Ice Age

Armadas of icebergs have probably not been the cause of abrupt climate shifts in the North Atlantic over the past 440,000 years, according to a study published in Nature on 17th April 2015.

Some studies had proposed that pulses of icebergs may have caused cycles of abrupt climate change by introducing fresh water to the surface, causing changes in ocean circulation. However, new findings by a team led by Dr Stephen Barker (Cardiff University), and including Dr David Thornalley (UCL Geography), suggest that icebergs generally arrived too late to trigger cold events in the North Atlantic.

Abrupt climate change (a transition between warm and cold conditions) was a  common feature of the Late Pleistocene, the world’s most recent period of repeated glaciations. The occurrence of cold events in the North Atlantic seems to have corresponded with the dispersal of icebergs that had broken away from ice sheets bordering the North Atlantic. There has been no consensus, however, on whether this “iceberg calving” was a cause or a consequence of climate change.

Ocean sediment core records of ice-rafted debris and temperature-sensitive plankton over the last four glacial cycles indicate that there was a delay between pronounced surface cooling and the arrival of icebergs. Thus the team suggest that melting icebergs were not the trigger for cooling events, although they may have enhanced or prolonged these cold conditions.



Image: Lukas Jonkers, Cardiff

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