Ocean margin densities and paleoestimates of the Atlantic meridional overturning circulation: A model study



An eddy-permitting numerical ocean model is used to test to what extent the Atlantic meridional overturning circulation (MOC) can be reconstructed from sea water densities at the ocean margins. By gradually reducing the number of locations where the densities are known and by adding systematic and random errors comparable to those expected in paleoreconstructions of sea water densities, we test if a reliable picture of the MOC can still be obtained. Our results show that even with only 0.07% of the boundary densities the mean state of the MOC as well as its variability can be reconstructed. The addition of a systematic error results in an overestimation or underestimation of the meridional transport. With a random error similar to the one expected for paleoestimates of the density the mean state of the MOC can still be reproduced, especially north of 40°N. However, the random noise largely masks the relatively modest MOC variability observed in the model run. For both systematic and random noise in the density field there is a larger sensitivity for MOC reconstructions the closer a location is from the equator. For a measuring campaign that aims to infer past states of the Atlantic MOC on the basis of boundary densities, the present study suggests that the best strategy is to collect data that allow estimation of the basin-wide vertical density structure between 40°N and 50°N. Information from only a few latitudes is sufficient for a reasonable representation of the mean MOC state.