Ocean circulation and climate at the Eemian and last glacial inception
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Combining a hierarchy of climate models of varying complexity with marine proxy data, we show that the North Atlantic surface circulation played an important role for the climate of the Eemian and the last glacial inception. As insolation decreases, increasing Arctic sea ice export causes a freshwater transport into the subpolar North Atlantic. Amplified by a nonlinear response of the subpolar gyre this leads to a reorganization of the surface currents and a stronger heat transport into the Nordic Seas. The resulting warming of this region delayed Scandinavian inception. This work introduces a relatively new concept into the field of paleoceanography: the subpolar gyre as an active component of the climate system. This is based on recent advances in physical oceanography and allows for a new and physically consistent interpretation of proxy data. Moreover, the sensitivity of the subpolar gyre to different boundary conditions is discussed, improving the understanding of the underlying mechanism.
Paper I: Climate Dynamics 35(7-8), Born, A.; K. H. Nisancioglu and P. Braconnot, Sea ice induced changes in ocean circulation during the Eemian, pp.1361–1371. Published version. Copyright 2010 Springer. Full text not available in BORA due to publisher restrictions. The published version is available at: http://dx.doi.org/10.1007/s00382-009-0709-2Paper II: Born, A.; K. H. Nisancioglu, B. Risebrobakken and A. Levermann (2010), Late Eemian warming in the Nordic Seas as seen in proxy data and climate models. Accepted version. In revision for publishing in Paleoceanography. Full text not available in BORA.Paper III: Climate of the Past Discussions 6, Born, A.; M. Kageyama and K. H. Nisancioglu, Warm Nordic Seas delayed glacial inception in Scandinavia, pp.1503–1523. Published version available at: http://dx.doi.org/10.5194/cp-6-817-2010 Submitted version. Copyright 2010 Born et. al. Submitted to Climate of the Past 6, pp. 817-826. Published by Copernicus Publications. This work is distributed under the Creative Commons Attribution 3.0 License.Paper IV: Geochemistry Geophysics Geosystems 11, Q06011, Born, A. and A. Levermann, The 8.2 ka event: abrupt transition of the subpolar gyre toward a modern North Atlantic circulation, 8 pp. Published version. Copyright 2010 American Geophysical Union. All rights reserved. Reproduced with permission. http://dx.doi.org/10.1029/2009GC003024Paper V: Climate Dynamics, Montoya, M.; A. Born and A. Levermann, Reversed North Atlantic gyre dynamics in present and glacial climate. Accepted version. Copyright 2010 Springer. Reproduced with permission. The published version is available at: http://dx.doi.org/10.1007/s00382-009-0729-yPaper VI: Born, A. and J. Mignot (2010), The Atlantic subpolar gyre as a stochastically forced oscillator. Draft version. Full text not available in BORA.