Kevin Speer

Research

Global Inverse Model

Abstract

The first fully global inverse estimate of a decade mean ocean circulation is made using data mainly from the World Ocean Circulation experiment (WOCE). Hydrographic sections and direct current measurements are used to determine transports and to constrain boundary currents and dense overflows. The 18 boxes defined by these sections are divided into 45 isopycnal (neutral density) layers. Diapycnal transfers within the boxes are allowed, representing advective fluxes and mixing processes. Air-sea fluxes at the surface produce transfers between outcropping layers. The model derives a global overturning circulation consistent with the various observations, revealing two global-scale meridional circulation cells: an Upper Cell, with sinking in the Arctic and subarctic regions and upwelling in the Southern Ocean, and a Lower Cell, with sinking around the Antarctic continent and abyssal upwelling mainly below the mid-ocean ridge crest.