Meridional Overturning Circulation

SAM, Southwest Atlantic MOC Project

SAM, Southwest Atlantic MOC project

Variations in the Atlantic Meridional Overturning Circulation (AMOC) have been linked to critical climate variables such as precipitation and surface air temperature across the northern hemisphere. The Southwest Atlantic Meridional Overturning Circulation Program (SAM), which began in 2009, seeks to capture key components of the AMOC in a hitherto under-sampled region - the South Atlantic Ocean. Numerical climate models have indicated that important water mass transformations are undergone by the AMOC flows in the South Atlantic, however little data has previously been available for the study of these flows. The initial array deployed as part of the SAM project involves a zonal line of three pressure-equipped inverted echo sounders (PIES) and one current-and-pressure-equipped inverted echo sounder (CPIES) deployed near the western boundary at 34.5 S. In 2011 the CPIES was replaced with a PIES. Data from these instruments will be used to monitor the Brazil Current and the Deep Western Boundary Current as they carry components of the AMOC along the western boundary of the basin. Coupled with annual or semiannual hydrographic observations collected on an Argentine or Brazilian research vessel, these data will produce better understanding of the processes involved in AMOC variability in the South Atlantic. The SAM array is funded by the NOAA Climate Observations Division and is a collaboration between AOML-PHOD and scientists in Brazil and Argentina. Additional collaborations with the French, German and South African 'GoodHope' program will allow the SAM observations to provide the first continuous time series observations of basin-wide AMOC flows at this latitude.

Figure: Map indicating the locations of the four PIES/CPIES instruments deployed as part of the SAM project. Also shown (blue arrows) are the near-surface velocities observed by the shipboard-ADCP onboard the Brazilian Navy research vessel Cruzeiro do Sul during the March 2009 deployment cruise.