This study examines the effects of coastal upwelling on the longitudinal water density gradient within the estuary of Baía de Todos os Santos (BTS), its effect on the gravitational circulation at the estuary entrance, and the reverse effect of gravitational circulation on the coastal upwelling. This investigation was based on a 1-year dataset of observed water temperature, mean velocities, and river discharge, as well as 2 years of numerical simulation of the estuarine flow. The results show that the upwelling regulates the thermohaline field in front of the BTS, decreasing water temperature (up to 3 °C), and increasing density (up to 0.3 kg/m³), and have sufficient intensity to more than double the speed, or even establish, the gravitational circulation. It was frequently observed that the water temperature falls after an increase in the subtidal flow shear, suggesting that the estuarine gravitational circulation acts as a facilitator to the upwelling process. Numerical simulations indicate that the coastal upwelling events are also capable of reestablishing the gravitational circulation at times with weak longitudinal density gradient, a scenario that tends to become more frequent and intense in the near future due to the ongoing climate changes.

本研究探讨了沿海上升流对托多斯桑托斯湾 (BTS) 河口内纵向水密度梯度的影响、其对入海口重力环流的影响以及重力环流对沿海上升流的反向影响。这项调查基于 1 年的水温、平均流速和河流流量观测数据集，以及 2 年的河口流量数值模拟。结果表明，上升流调节了BTS前面的温盐场，降低了水温（高达3°C），增加了密度（高达0.3 kg/m ³），并且具有足够的强度，使速度增加一倍以上，甚至建立重力循环。人们经常观察到，潮下流切变增加后水温下降，这表明河口重力环流对上升流过程起到了促进作用。数值模拟表明，沿海上升流事件有时也能够在纵向密度梯度较弱的情况下重建重力环流，由于持续的气候变化，这种情况在不久的将来往往会变得更加频繁和强烈。