Response of the North Atlantic surface and intermediate ocean structure to climate warming of MIS 11

Marcel T. J. van der Meer,Stefan Schouten,Evgenia S. Kandiano,Jaap S. Sinninghe Damsté,Kirsten Fahl,Henning A. Bauch

doi:10.1038/srep46192

Abstract

Investigating past interglacial climates not only help to understand how the climate system operates in general, it also forms a vital basis for climate predictions. We reconstructed vertical stratification changes in temperature and salinity in the North Atlantic for a period some 400 ka ago (MIS11), an interglacial time analogue of a future climate. As inferred from a unique set of biogeochemical, geochemical, and faunal data, the internal upper ocean stratification across MIS 11 shows distinct depth-dependent dynamical changes related to vertical as well as lateral shifts in the upper Atlantic meridional circulation system. Importantly, transient cold events are recognized near the end of the long phase of postglacial warming at surface, subsurface, mid, and deeper water layers. These data demonstrate that MIS 11 coolings over the North Atlantic were initially triggered by freshwater input at the surface and expansion of cold polar waters into the Subpolar Gyre. The cooling signal was then transmitted downwards into mid-water depths. Since the cold events occurred after the main deglacial phase we suggest that their cause might be related to continuous melting of the Greenland ice sheet, a mechanism that might also be relevant for the present and upcoming climate.

Highlights

Investigating past interglacial climates help to understand how the climate system operates in general, it forms a vital basis for climate predictions
Recent global warming is amplified in the North Polar region through enhanced glacier melting[1] and a reduction of the seasonal sea ice cover[2]
It is expected that the northward propagation of oceanic and atmospheric heat and moisture from the adjacent North Atlantic region might experience significant changes due to Greenland Ice Sheet (GIS) melting[3], sea ice loss in the Arctic[4] and the feedback mechanisms related to these processes

Summary

Oceanographical setting

The site where core M23414 was taken (53°32′N, 20°17′W; 2196 m water depth) currently underlies the western edge of the North Atlantic Current (NAC; Fig. 1), one of the most important elements of the AMOC. This location is ideal to detect lateral changes in Subpolar Gyre (SPG) configuration, since the present-day physical property differences between relatively saline and warm waters of the NAC and less saline and cold western waters of the SPG are well established. The strength of the SPG is defined by its feeding currents, the northward-flowing warm water of the NAC and the southward-flowing polar water of the East Greenland Current (EGC)

Results and Discussion

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Function Technique black line represents

Methods

Author Contributions

Additional Information