Structure and Variability of Water Properties between Antarctic Intermediate Water (AAIW) and North Atlantic Deep Water (NADW) in the South Atlantic Ocean.

The distributions of mid-depth water properties (temperature, salinity, oxygen, nutrients, and other tracers) in the South Atlantic Ocean are set by salty well-ventilated, and relatively nutrient-poor North Atlantic Deep Water (NADW) spreading southward towards the Southern Ocean (SO) underneath fresher, and also well-ventilated and relatively nutrient-poor Antarctic Intermediate Water (AAIW, spreading northward from the SO). Water in between the NADW and AAIW in the South Atlantic Ocean is characterized by small gradients in temperature, low oxygen levels, and high nutrient levels, with salinity stratification dominating the vertical density gradient. We describe the mean and time varying properties of this transition region using Argo data, a WOCE climatology, and hydrographic sections. We focus on how this water contributes to changes in heat and freshwater storage in the South Atlantic, studying connections to the observed warming of the SO over the last few decades.