5:15 PM - 7:15 PM
[AOS15-P02] Influence of Monsoons and ENSO on Marine Ecosystem Dynamics in the Gulf of Thailand
Keywords:Gulf of Thailand, Monsoon, ENSO, Phytoplankton
The Gulf of Thailand (GoT) is a Large Marine Ecosystem located in Southeast Asia, influenced by monsoon systems and the El Niño Southern Oscillation (ENSO). Both the monsoons and ENSO play imporntant roles in the variations of phytoplankton in this region. However, there is still lack of information on the mechanisms how monsoons and ENSO change the ecosystem. Previous research has hypothesized these mechanisms based on satellite data, but the controlling mechanisms is still unclear.
This study aims to examine how monsoons and ENSO impact marine ecosystems in the GoT, and the factors that modify phytoplankton under ENSO conditions, using a coupled hydrodynamic-ecosystem model. The model was simulated for both non-ENSO years and ENSO years (El Niño and La Niña events). Results were compared to Sea Surface Temperature (SST) and Sea Surface Chlorophyll-a data from the MODerate-resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. The results show that phytoplankton in the upper GoT, near the Ca Mau Cape, and along the coasts are consistently higher across all seasons and exhibit greater variation compared to offshore areas. Phytoplankton concentrations in coastal regions are influenced by river discharge and wind, which transport nutrients, while offshore phytoplankton dynamics are mainly controlled by water column conditions, which determine nutrient availability through mixing processes.
The results from sensitivity analysis under ENSO conditions indicate that ENSO has a stronger impact during the northeast monsoon and non-monsoon periods compared to the southwest monsoon. ENSO significantly affects phytoplankton, particularly in the northwest GoT, where changes in nutrient transport from the nutrient-rich upper GoT to the main GoT area were observed. Phytoplankton along the coast during El Niño/La Niña events decrease/increase in response to weaker/stronger currents from upper GoT which indicates that less/more nutrients are transported to the region. Additionally, during El Niño/La Niña event, the water column becomes more stratified/mixed due to surface heating and wind strength, which modifies phytoplankton dynamics in the offshore region. This study emphasizes the role of large-scale air-sea interactions in the GoT, revealing regional phytoplankton variations, nutrient transport influences, and the effects of water column stratification and mixing during El Niño/La Niña events.
This study aims to examine how monsoons and ENSO impact marine ecosystems in the GoT, and the factors that modify phytoplankton under ENSO conditions, using a coupled hydrodynamic-ecosystem model. The model was simulated for both non-ENSO years and ENSO years (El Niño and La Niña events). Results were compared to Sea Surface Temperature (SST) and Sea Surface Chlorophyll-a data from the MODerate-resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. The results show that phytoplankton in the upper GoT, near the Ca Mau Cape, and along the coasts are consistently higher across all seasons and exhibit greater variation compared to offshore areas. Phytoplankton concentrations in coastal regions are influenced by river discharge and wind, which transport nutrients, while offshore phytoplankton dynamics are mainly controlled by water column conditions, which determine nutrient availability through mixing processes.
The results from sensitivity analysis under ENSO conditions indicate that ENSO has a stronger impact during the northeast monsoon and non-monsoon periods compared to the southwest monsoon. ENSO significantly affects phytoplankton, particularly in the northwest GoT, where changes in nutrient transport from the nutrient-rich upper GoT to the main GoT area were observed. Phytoplankton along the coast during El Niño/La Niña events decrease/increase in response to weaker/stronger currents from upper GoT which indicates that less/more nutrients are transported to the region. Additionally, during El Niño/La Niña event, the water column becomes more stratified/mixed due to surface heating and wind strength, which modifies phytoplankton dynamics in the offshore region. This study emphasizes the role of large-scale air-sea interactions in the GoT, revealing regional phytoplankton variations, nutrient transport influences, and the effects of water column stratification and mixing during El Niño/La Niña events.