Reduced Atlantic variability in the mid-Pliocene

Abstract

This study evaluates interannual-to-decadal sea surface temperature (SST) variability in the mid-Pliocene Warm Period within the Pliocene Model Intercomparison Project (PlioMIP). Our results show significantly reduced variability at low latitudes and mid-latitudes in the mid-Pliocene in comparison to the pre-industrial climate. At high latitudes of both hemispheres, the SST variability has increased. Latitudinal changes are likely driven by changes in the meridional SST gradient. Results with respect to the main Atlantic SST modes of variability show that the Atlantic Multidecadal Variability shifts southward and expands eastward due to a southward shift in the North Atlantic Drift position. The Atlantic Meridional Mode amplitude weakens due to increased SST gradient between its two poles. The South Atlantic Subtropical Dipole significantly shifts its southwestern pole towards the South American coast. Moreover, all Atlantic modes of variability have shifted their respective frequencies towards lower values. Our analyses on the PlioMIP simulation results provide a useful constraint in future projections associated with a warmer world when assessing Atlantic SST variability.