Surface circulation in the Gulf of Thailand from remotely sensed observations: seasonal and interannual timescales
- Institute of Marine Science, Burapha University, Chonburi, Thailand
Abstract. The Gulf of Thailand (GoT), a shallow basin located in the western equatorial Pacific, undergoes highly-variable wind influences on both seasonal and interannual timescales. On seasonal timescale, the Asian monsoon prevails, dominating the circulation pattern. The most dominant complex empirical orthogonal function of the Gulf of Thailand (GoT) current explains 28 % of the total variance with the phase relationship following the monsoon seasons. High current variability is observed over the upper GoT (uGoT), along the western boundary which is highly correlated with that at the southeastern entrance, and in the GoT interior. Satellite altimetry suggests that approximately 50 % of the surface current variability is geostrophic set up by wind stress curl, particularly at basin-scale. Also, the study hints at the importance, to sea surface height near the coastline, of coastal trapped Kelvin waves forced by wind stress curl. Wind-driven current accounts for a significant fraction of the ageostrophic flow along the western boundary and the GoT interior; however, its effect is unclear over the uGoT. At interannual timescale, the GoT circulation is directly impacted by both El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). Interestingly, the climate modes affect the circulation over each region of the GoT differently. The IOD highly correlates with interannual variability of current along the GoT western boundary and the southern boundary of the observing domain (8° N), while the ENSO correlates with that in the interior. Over the uGoT, both climate modes explain similar percentage of the interannual current variability.
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