Abstract
Subtropical mode water is formed in winter-time deep mixed layer due to
variations in air-sea processes. In the South Atlantic, three formation
cores are identified between 30oS and 40oS: in the west, in the east,
and north of the Subtropical Front. Each one of these three types
presents typical mean thickness and horizontal distribution patterns,
mainly because of local dynamic and thermodynamic characteristics of
each part of the basin. In this study we assess the effects of momentum,
freshwater and radiative fluxes on the variation in volume and
composition of the South Atlantic Subtropical Mode Water (SASTMW).
Sensitivity experiments were designed using the National Center for
Atmospheric Research Community Earth System Model. Multiple one-year
simulations are forced with varying intensity of wind, precipitation and
shortwave radiation. By comparing to a control run, we were able to
determine that the water volume variations in the east (SASTMW type 1)
and south (SASTMW type 3) are significantly affected by precipitation
and shortwave radiation, and thus are more sensitive to thermodynamic
processes. On the other hand, SASTMW type 2 has a greater relationship
with dynamic processes and is influenced by the Indian–Atlantic
interbasin exchanges.