The Fate of Surface Freshwater Entering the Indonesian Seas

The fate of freshwater entering the Indonesian Seas is investigated using a Lagrangian particle tracking model. The Indonesian Seas are located underneath the atmospheric deep convection and receive one of the largest amounts of rainfall around the globe. This freshwater disperses to the Indian Ocean through the Indonesian Throughflow (ITF), making the Indonesian Seas a source of freshwater for the Indian Ocean. We find that the dispersion from the near‐surface water of the Indonesian Seas occurs in about six months, primarily by advection through the Lombok/Sunda Straits and the Timor Strait. The Java Sea is the source of freshwater for the Lombok/Sunda Strait outflows and Flores-Banda Seas is the source of freshwater for the Timor Strait outflow. Despite that the salinity of the Lombok/Ombai Straits outflows are lower, we find the Timor Strait outflow to play an equal role in the dispersion of precipitated freshwater. The amount of freshwater escaping to the Indian Ocean is about the same, suggesting that precipitation over the Java Sea and the Flores-Banda Seas can affect the Indian Ocean with roughly the same magnitude. Mixing with the thermocline water occurs along the shelf breaks and steep coastlines when the monsoonal winds strengthen and induce upwelling events. Vertical mixing provides a pathway for the surface freshwater to enter the ITF thermocline and enter the Indian Ocean. For the main pathway of the ITF, our model suggests that it is the Java Sea precipitated freshwater during winter that is entering the ITF thermocline.