Amplified inception of European Little Ice Age by sea ice-ocean-atmosphere feedbacks

Lehner, Flavio; Born, Andreas; Raible, Christoph; Stocker, Thomas (2013). Amplified inception of European Little Ice Age by sea ice-ocean-atmosphere feedbacks. Journal of Climate, 26(19), pp. 7586-7602. American Meteorological Society 10.1175/JCLI-D-12-00690.1

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The inception of the Little Ice Age (~1400–1700 AD) is believed to have been driven by an interplay of external forcing and climate system internal variability. While the hemispheric signal seems to have been dominated by solar irradiance and volcanic eruptions, the understanding of mechanisms shaping the climate on a continental scale is less robust. In an ensemble of transient model simulations and a new type of sensitivity experiments with artificial sea ice growth, the authors identify a sea ice–ocean–atmosphere feedback mechanism that amplifies the Little Ice Age cooling in the North Atlantic–European region and produces the temperature pattern suggested by paleoclimatic reconstructions. Initiated by increasing negative forcing, the Arctic sea ice substantially expands at the beginning of the Little Ice Age. The excess of sea ice is exported to the subpolar North Atlantic, where it melts, thereby weakening convection of the ocean. Consequently, northward ocean heat transport is reduced, reinforcing the expansion of the sea ice and the cooling of the Northern Hemisphere. In the Nordic Seas, sea surface height anomalies cause the oceanic recirculation to strengthen at the expense of the warm Barents Sea inflow, thereby further reinforcing sea ice growth. The absent ocean–atmosphere heat flux in the Barents Sea results in an amplified cooling over Northern Europe. The positive nature of this feedback mechanism enables sea ice to remain in an expanded state for decades up to a century, favoring sustained cold periods over Europe such as the Little Ice Age. Support for the feedback mechanism comes from recent proxy reconstructions around the Nordic Seas.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Physics Institute > Climate and Environmental Physics
08 Faculty of Science > Physics Institute
08 Faculty of Science > Other Institutions > Teaching Staff, Faculty of Science

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Lehner, Flavio; Born, Andreas; Raible, Christoph and Stocker, Thomas

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

0894-8755

Publisher:

American Meteorological Society

Language:

English

Submitter:

Doris Rätz

Date Deposited:

12 Sep 2014 16:57

Last Modified:

26 Jun 2016 01:50

Publisher DOI:

10.1175/JCLI-D-12-00690.1

BORIS DOI:

10.7892/boris.47714

URI:

https://boris.unibe.ch/id/eprint/47714

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