Dynamical Reconstruction of Upper-Ocean Conditions in the Last Glacial Maximum Atlantic

Abstract

Proxies indicate that the Last Glacial Maximum (LGM) Atlantic Ocean was marked by increased meridional and zonal near sea surface temperature gradients relative to today. Using a least squares fit of a full general circulation and sea ice model to upper-ocean proxy data with specified error estimates, a seasonally varying reconstruction is sought of the Atlantic Ocean state that is consistent with both the known dynamics and the data. With reasonable uncertainty assumptions for the observations and the adjustable (control) variables, a consistent LGM ocean state is found, one not radically different from the modern one. Inferred changes include a strengthening of the easterly and westerly winds, leading to strengthened subtropical and subpolar gyres, and increased upwelling favorable winds off the coast of Africa, leading to particularly cold SSTs in those regions.