The South Atlantic subtropical underwater (STUW) is a high-salinity water mass formed by subduction within the subtropical gyre. It is a major component of the subtropical cell and affects stratification in the downstream direction due to its high salinity characteristics. Understanding the interannual variability in STUW subduction is essential for quantifying the impact of subtropical variability on the tropical Atlantic. Using the output from the ocean state estimate of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO), this study investigates the interannual variability in STUW subduction from 1992 to 2016. We find that heat fluxes, wind stress, and wind stress curl cause interannual variability in the subduction rate. Heat fluxes over the subduction area modulate the sea surface buoyancy and regulate the mixed layer depth (MLD) during its deepening and shoaling phases. Additionally, the wind stress curl and zonal wind stress can modulate the size of the subduction area by regulating the probability of particles entrained into the mixed layer within 1 year of tracing. This analysis evaluates the influence of subtropical wind patterns on the South Atlantic subsurface high-salinity water mass, highlighting the impact of heat and wind on the interannual changes in the oceanic component of the hydrological cycle.

南大西洋亚热带水下（STUW）是在亚热带回旋中通过俯冲作用形成的高盐度水团。它是亚热带细胞的主要组成部分，并由于其高盐度特性而在下游方向影响分层。了解STUW俯冲的年际变化对于量化亚热带变化对热带大西洋的影响至关重要。利用估算海洋环流和气候的财团的海洋状态估算结果（ECCO），本研究调查了1992年至2016年STUW俯冲的年际变化。我们发现热通量，风应力和风应力卷曲导致俯冲率的年际变化。俯冲区域上的热通量调节海面浮力，并在加深和浅滩阶段调节混合层深度（MLD）。另外，风应力卷曲和纬向风应力可以通过调节在追踪的1年内夹带到混合层中的颗粒的概率来调节俯冲面积的大小。该分析评估了亚热带风型对南大西洋地下高盐度水质的影响，强调了热风​​对水文循环海洋成分年际变化的影响。