Arctic teaches of natural global warming

Hydro International -

Scientists are unravelling the environmental changes that took place around the Arctic during an exceptional episode of ancient global warming. Newly published results from a high-resolution study of sediments collected on Spitsbergen represent a contribution to this endeavour. The study was led by Dr Ian Harding and Prof John Marshall of the University of Southampton's School of Ocean and Earth Science (SOES), based at the National Oceanography Centre, Southampton, UK.

Around 56 million years ago there was a period of global warming called the Paleocene-Eocene Thermal Maximum (PETM), during which global sea surface temperatures increased by approximately 5°C.

The warming of the oceans led to profound ecological changes, including the widespread extinction of many types of foraminifera, tiny single-celled organisms with distinctive shells. Plankton that had previously only prospered in tropical and subtropical waters migrated to higher latitudes. Similar changes occurred on the land, with many animals and plants extending their distributions towards the poles.

Information about the Arctic environment during the PETM has come predominantly from sediment cores drilled from under the pack ice on the Lomonosov Ridge (~ 88°N) by the Integrated Ocean Drilling Program (IODP Site 302-4A). However, these cores do not span the entire PETM and therefore do not provide a complete picture.

To help fill this knowledge gap, Dr Harding's team turned to a site (~78 °N) on Spitsbergen in the high Arctic. Here, 2.5-kilometre-thick sediments span the critical period. During the PETM, the site would have been at around 75 °N, the difference in position being due to the slow movement of tectonic plates over millions of years.

Read more...

Posted via http://batavia08.posterous.com batavia08's posterous