Clim. Past Discuss., 8, 6199-6219, 2012
www.clim-past-discuss.net/8/6199/2012/
doi:10.5194/cpd-8-6199-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
A volcanically triggered regime shift in the subpolar North Atlantic ocean as a possible origin of the Little Ice Age
C. F. Schleussner1,2 and G. Feulner1
1Potsdam Institute for Climate Impact Research, Telegrafenberg A62, 14473 Potsdam, Germany
2Physics Institute, Potsdam University, Potsdam, Germany

Abstract. Among the climatological events of the last millennium, the Northern Hemisphere Medieval Climate Anomaly (MCA), succeeded by the Little Ice Age (LIA) are of exceptional importance. The origin of these regional climate anomalies remains however a subject of debate and besides external influences like solar and volcanic activity, internal dynamics of the climate system might have also played a dominant role. Here, we present transient last millennium simulations of the fully-coupled model Climber 3α forced with stochastically reconstructed wind fields. Our results indicate that short-lived volcanic eruptions might have triggered a cascade of sea-ice – ocean feedbacks in the North Atlantic, ultimately leading to a persistent regime shift in the ocean circulation. We find that an increase in the Nordic Sea sea-ice extent on decadal timescales as a consequence of major volcanic eruptions leads to a spin-up of the subpolar gyre (SPG) and a weakened Atlantic Meridional Overturning Circulation, eventually causing a persistent, basin-wide cooling. These results highlight the importance of regional climate feedbacks such as a regime shift in the subpolar gyre circulation for past and future climate.

Citation: Schleussner, C. F. and Feulner, G.: A volcanically triggered regime shift in the subpolar North Atlantic ocean as a possible origin of the Little Ice Age, Clim. Past Discuss., 8, 6199-6219, doi:10.5194/cpd-8-6199-2012, 2012.
 
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