Abstract. Basin-scaled freshening of Antarctic Intermediate Water (AAIW) is reported to have dominated South Atlantic Ocean during period from 2005 to 2014, as shown by the gridded monthly means Argo (Array for Real-time Geostrophic Oceanography) data. The relevant investigation was also revealed by two transatlantic occupations of repeated section along 30° S, from World Ocean Circulation Experiment Hydrographic Program. Freshening of the AAIW was compensated by the opposing salinity increase of thermocline water, indicating the contemporaneous hydrological cycle intensification. This was illustrated by the precipitation less evaporation change in the Southern Hemisphere from 2000 to 2014, with freshwater input from atmosphere to ocean surface increasing in the subpolar high-precipitation region and vice versa in the subtropical high-evaporation region. Against the background of hydrological cycle augment, the decreased transport of Agulhas Leakage (AL) was proposed to be one of the contributors for the associated freshening of AAIW. This indirectly estimated variability of AL, reflected by the weakening of wind stress over the South Indian Ocean since the beginning of 2000s, facilitates the freshwater input from source region and partly contributes to the observed freshened AAIW. Both of our mechanical analysis is qualitative, but this work would be helpful to validate and test predictably coupled sea-air model simulations.
Freshening of Antarctic Intermediate Water in the South Atlantic Ocean in 2005–2014
