Climate Research Group











































































The Ocean Structure at the Last Glacial Maximum

In this study we assimilate measurements of stable carbon isotope compositions delta 13-C and the ratio of cadmium to calcium (Cd/Ca) concentrations from marine sediments into an ocean general circulation model to reconstruct the flow field of the deep-sea during the last glacial maximum (LGM) 21,000 years ago.

The results of the assimilation confirm that the southward flow of North Atlantic Deep Water was shallower during the LGM and this was accompanied by a strong source of glacial North Atlantic Intermediate Water (see the figure). The optimized glacial flow field in the Southern Ocean is consistent with the Cd/Ca measurements but can not explain delta 13-C changes, suggesting a breakdown of the glacial phosphate-delta 13-C relationship.

References

Winguth, A.M.E., D. Archer, E. Maier-Reimer, and U. Mikolajewicz, Paleonutrient data analysis of the glacial Atlantic using an adjoint ocean general circulation model, in: Inverse Methods in Global Biogeochemical Cycles, AGU Geophysical Mongraph Series, edited by P. Kasibhatla, M. Heimann, D. Harley, N. Mahowald, R. Prinn, and P. Rainer, 171-183, 2000.

Archer, D., A. Winguth, D. Lea, and N. Mahowald, What causes the glacial/interglacial pcoz cycles?, Reviews of Geophysics, 38, 159-189, 2000.

Winguth, A.M.E., D. Archer, E. Maier-Reimer, U. Mikolajewicz, and J.-C. Duplessy, Sensitivity of paleonutrient tracer distribution and deep sea circulation to glacial boundary conditions, Paleoceanography, 14, 304-323, 1999.