Temperature variability and its governing mechanisms within the Jailolo Strait, Indonesia

Abstract

Long-term reanalysis data from the Bluelink ReANalysis 2020 (BRAN2020) are used to investigate temperature variability from 2010 to 2020 in the Jailolo Strait–Halmahera Sea, which is part of the Indonesian Throughflow (ITF) eastern route. The analysis shows that net surface heat flux (NSHF) mainly affects semiannual mixed layer temperature (MLT) variability. Vertical turbulent mixing cools the mixed layer from below, while the vertical and horizontal advection have less impact on the MLT heat budget. In the upper thermocline (40–100 m), two temperature minima occur: one in April due to outflow to the Pacific Ocean, and another in August due to uplifted water. Different cooling processes mark the dominant annual variation in the mid thermocline (100–150 m depth) and the lower thermocline (150–200 m). The cooling process is mainly associated with the transport from the Pacific Ocean into the Indonesian Seas (inflow) in the mid-thermocline, while it is generally related to the outflow transport in the lower thermocline. Interannual temperature variation is marked by the relatively colder (warmer) sea surface temperature and shallowing (deepening) thermocline during the El Niño (La Niña) period, which is associated with the upwelling (downwelling) Rossby wave propagation. It is also found that the colder (warmer) temperature in the upper 200 m during the El Niño (La Niña) period correlates with the weaker (stronger) inflow from the Pacific Ocean into the Indonesian Seas.