Observed and modeled MOC related flow into the Caribbean Sea and the North Atlantic Ocean

Abstract

The transport of South Atlantic Water (SAW) into the northern hemisphere is investigated in this work. This flow represents the upper branch of the Meridional Overturning Circulation (MOC) and thus has a direct influence on the global heat budget. A variety of data is used: direct hydrographic and velocity observations from ship surveys, profiles from Argo floats and data from an ocean model (FLAME). The model and the observations show high consistency in the strength of the mean total inflow into the Caribbean, its range of variability, and the distribution of water from the South Atlantic. During the ship cruises large rings were observed at 16 degrees N. The ring propagation is investigated in FLAME and the complex interaction of the rings with the Lesser Antilles discussed. The spreading of SAW into the North Atlantic is analyzed. The mean SAW transport into the Caribbean derived from observations is estimated to be 9.3 Sv. The analysis with FLAME yields a similar transport. When the rings observed at 16 degrees N are taken into account the total SAW transport is 15.3 Sv. Since the upper layer MOC transport is in the order of 16-18 Sv, the remaining SAW transport by the STCs is less than 3 Sv.