Present-Day Climate Variability in the Tropical Atlantic

Abstract

Paleoproxy records of the Holocene and last glacial period suggest that the meridional position of the Atlantic Intertropical Convergence Zone {(ITCZ)} and hence the thermally direct circulation in that region changed significantly in the past, a behavior similar to that of a leading mode of interannual-decadal climate variability in the present- day tropical Atlantic. This chapter explores how knowledge of this mode of variability may be usefully employed to advance hypotheses for understanding tropical Atlantic paleoclimate change. A review of past coupled general circulation model {(CGCM)} studies reveals that change to the Atlantic {ITCZ} meridional position is pervasive in two situations of paleoclimate interest; namely, modification of the Atlantic thermohaline circulation, and adjustment to last glacial maximum {(LGM)} boundary conditions. Comparison of atmosphere- ocean general circulation model {LGM} simulations from the Paleoclimate Modeling Intercomparison Project {(PMIP)} shows, however, that the magnitude of the latter adjustment is model dependent. Accurate paleoproxy records of tropical Atlantic climate may therefore be able to provide crucial constraints on acceptable coupled model behavior.