Recent estimate of sea-level rise in the Gulf of Thailand

The annual local mean sea level (MSL) at 13 tide gauge stations bordering the Gulf of Thailand in Thai waters was used to investigate the apparent sea-level rise over the last 25 years (1985-2009). The annual local MSL was computed by averaging the hourly tidal data at each station for the whole year. The data at 11 stations showed a higher average annual local MSL than the mean Thailand MSL, which was set up over a century ago. The data from most stations showed rising trends of sea level, although at different rates depending on the station location. Averaging the annual local MSL by region into a single time series revealed a linear trend for the sea-level rise of about 5 mm/yr in the last 25-year time span. Land subsidence at the river mouths where the tide- gauge stations are usually located seems to play a major role in the observed higher annual local MSL. The findings are a warning that Thailand may face severe coastal recession in the near future if no measures are taken to halt the land subsidence near the coast.