Interannual to Decadal Changes in the Western Boundary Circulation in the Atlantic at 11°S

The western boundary current system off Brazil is a key region for variations of the Atlantic meridional overturning circulation (AMOC) and the southern subtropical cell. In July 2013 a mooring array was installed off the Brazilian coast at 11°S similar to an array installed between 2000 and 2004 at the same location. Two recent research cruises (2013 and 2014) and the first 10.5 months of moored observations are analyzed in comparison to the observations a decade ago. Average transports of the North Brazil Undercurrent and the Deep Western Boundary Current (DWBC) have not changed between the two observational periods. DWBC eddies that are predicted to disappear with a weakening AMOC, are still present with similar characteristics. Interannual transport variability as assessed between 2000-2004 from observations is consistently found in the output of a forced ocean model. Upper layer changes in salinity and oxygen within the last decade are consistent with an increased Agulhas leakage, while at depths water mass changes are likely related to changes in the North Atlantic as well as tropical circulation changes. An additional research cruise as well as the recovery of the next period of moored observations (May 2014 – September 2015) is currently been carried out and will give further insight in long term variability of transports and waster masses at this location.