Effects of Cardamom Mountains on the formation of the winter warm pool in the gulf of Thailand

• A mini warm pool in the Gulf of Thailand was uncovered during the winter for the first time.
• The orographic effect of Cardamom Mountains leads to the formation of the warm pool.
• The interannual variability of the warm pool is well correlated with ENSO.
• The warm pool has a possible implication for the local marine ecosystem.

A small-scale winter warm pool covering an area of about 75,000 km2 in the Gulf of Thailand (GoT) was uncovered using a suite of new high resolution satellite observations and historical in situ data. The core temperature of this warm pool is about 0.5–0.8 °C higher than that of the surroundings. The warm pool exists from the surface to the bottom of the sea. It forms in the first ten days of November, evolves to a mature stage from the mid-November to the early in January, and begins to decay in the mid-January. Our results show the formation of the warm pool is well correlated with the Cardamom Mountains on the Indo-China Peninsula. Due to the orographic effect of Cardamom Mountains, the low surface latent heat flux resulting from the wind wake leads to the formation of the warm pool in the sea. The interannual variability of the warm pool is affected by the El Niño-Southern Oscillation (ENSO) by modulating the strength of northeast monsoon each year. The warm pool has a possible implication for the marine ecosystem in the GoT.