The Atmospheric Processes on the Variation of Thermal Fronts and Chlorophyll-a Concentration Over the Indonesian Fisheries Management Area 711 During the Indian Ocean Dipole Events

The Indonesian Fisheries Management Area (IFMA) 711, covering the North Natuna Sea, Karimata Strait, and Natuna Sea, has abundant pelagic fisheries resources and significant economic potential. Predicting fishing ground areas based on oceanographic parameters like thermal fronts and chlorophyll-a concentrations is essential for optimizing fisheries management. This study aims to investigate atmospheric processes on thermal front dynamics and chlorophyll-a concentration variation over the IFMA 711, as well as the influence of the Indian Ocean Dipole (IOD) as a major climate driver. The analysis of thermal front variation involved calculating the sea surface temperature gradients and analyzing atmospheric processes through wind stress and wind stress curl from January 2018 to December 2022. The results show that the atmospheric conditions, such as wind and rainfall patterns, influence seasonal variations in thermal fronts and chlorophyll-a concentrations over the IFMA 711. The correlation study reveals a significant correlation between wind stress and SST gradient, while chlorophyll-a concentration is more significantly correlated to the total precipitation. The IOD modulates variations in wind and rainfall patterns on an interannual timescale. Wind stress curl is increasing, and total precipitation is decreasing during the 2019 positive IOD event. In contrast, the anomalously warm SST during the negative IOD event in 2022 led to a drop in wind stress curl and increased rainfall. Due to increasing wind stress in 2019, the thermal front was more prevalent, while heavier rainfall in 2022 resulted in an increase in chlorophyll-a concentration.