Understanding climate
for the benefit of society

Arctic sea ice alters circulation and climate in the Norwegian Sea

Andreas Born presents his dissertation on 24.9.2010 for PhD at the University of Bergen: Ocean circulation and climate at the Eemian and last glacial inception.

Body

While future projections of climate continuously improve, an independent estimate can be achieved by looking into the geological past. The Eemian interglacial 126,000 years ago, thus predating the last ice age, has often been used as an example for the warmer climate expected for the end of this century.

Output from a spectrum of climate models show that as Arctic climate cooled towards the end of the Eemian interglacial, more sea ice was exported along the east coast of Greenland and into the North Atlantic. Since salt is rejected during the freezing process, this event also enhanced the southward transport of freshwater and resulted in a drastic weakening of the surface ocean current system called the subpolar gyre. Among the consequences of a weaker gyre is the northward displacement of the North Atlantic Current bringing warm subtropical waters to the European shores and increased heat transport into the Nordic Seas, counteracting the general high latitude cooling. At the end of the Eemian, the anomalously warm Nordic Seas delayed the growth of ice sheets over Scandinavia by several millenia.

Implications of a warmer Arctic

With a warming Arctic in the next decades a similar - albeit reverse - change can be expected. Less freshwater transport by a shrinking sea ice cover might result in a stronger subpolar gyre circulation, eventually decreasing the amount of Atlantic water entering the Nordic Seas. Exploiting the usefulness of paleo climate analogues, this study highlights that the loss of Arctic sea ice not only affects local communities and ecosystems, but also has dynamical implications that go beyond the Arctic realm. It introduces a new mechanism to explain climate changes found in geological archives, emphasizing the surface circulation changes as opposed to the deep overturning circulation.
 

Date and Place of defense

24.9.2010, 10.15 Geophysical Institute, Allegaten 70
 

Contact person

Andreas Born:andreas.born@bjerknes.uib.no Phone: 55582461