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Evaluation of past stratification changes in the Nordic Seas by comparing planktonic foraminiferal δ 18O with a solar-forced model

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons37249

Lorenz,  S. J.
Numerical Model Development and Data Assimilation, The Ocean in the Earth System, MPI for Meteorology, Max Planck Society;

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Citation

Simstich, J., Lorenz, S. J., & Bauch, H. A. (2012). Evaluation of past stratification changes in the Nordic Seas by comparing planktonic foraminiferal δ 18O with a solar-forced model. Marine Micropaleontology, 94-95, 58-71. doi:10.1016/j.marmicro.2012.06.006.


Cite as: http://hdl.handle.net/11858/00-001M-0000-000F-E645-6
Abstract
Density changes in the upper water column of the northern North Atlantic may enhance or reduce vertical convection of surface water with profound effects on meridional overturning and climate in the wider region. This study tests the capability of paired δ 18O values of two planktonic foraminiferal species - Neogloboquadrina pachyderma (s) and Turborotalita quinqueloba - for the reconstruction of near-surface density stratification in high latitudes or the glacial ocean. Foraminiferal data from two sediment cores of crucial areas of the Nordic Seas were compared with insolation-induced thermal stratification changes as obtained by simulations with the general circulation model ECHO-G. The comparison suggests that insolation was the chief mechanism to change thermocline strength during most of the Holocene. Prior to that, stratification depended by and large on the varying amounts of meltwater injected at the sea surface. Similar to the modern central Arctic Ocean, a pronounced and thick halocline prevented surface waters from deep convection in the central Nordic Seas. Parts of the Norwegian Sea, however, were also stratified but more analogous to the modern Greenland Sea, where deep convection can occur in late winter as a result of the density increase upon a combination of cold temperatures and wind stress. Our findings thus support previous results of an active meridional overturning also in a glacial ocean. © 2012 Elsevier B.V.