Geosci. Model Dev. Discuss., 6, 4417-4445, 2013
© Author(s) 2013. This work is distributed
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This discussion paper has been under review for the journal Geoscientific Model Development (GMD). Please refer to the corresponding final paper in GMD.
Can sparse proxy data constrain the strength of the Atlantic meridional overturning circulation?
T. Kurahashi-Nakamura1, M. Losch2, and A. Paul1
1MARUM – Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Bremen, Germany
2Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

Abstract. In a feasibility study, the potential of proxy data for the temperature and salinity during the Last Glacial Maximum (LGM, about 19 000 to 23 000 yr before present) in constraining the strength of the Atlantic meridional overturning circulation (AMOC) in a general ocean circulation model was explored. The proxy data were simulated by drawing data from four different model simulations at the ocean sediment core locations of the Multiproxy Approach for the Reconstruction of the Glacial Ocean surface (MARGO) project and perturbing these data with realistic noise estimates. The results suggest that our method has the potential of providing estimates of the past strength of the AMOC even from sparse data, but in general paleo-sea surface temperature data without additional prior knowledge about the ocean state during the LGM is not adequate to constrain the model. On the one hand, additional salinity data in the deep ocean and at the sea surface are shown to be highly important in estimating the LGM circulation and as expected, reducing proxy-data errors improves the solutions. Whereas increasing the amount of surface data alone does not appear to be enough for better estimates. Finally, better initial guesses to start the state estimation procedure from greatly improve the performance of the method. Indeed, with a sufficiently good first guess, just the sea-surface temperature data from the MARGO project appear sufficient for reliable estimates of the strength of the AMOC.

Citation: Kurahashi-Nakamura, T., Losch, M., and Paul, A.: Can sparse proxy data constrain the strength of the Atlantic meridional overturning circulation?, Geosci. Model Dev. Discuss., 6, 4417-4445, doi:10.5194/gmdd-6-4417-2013, 2013.
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