Sea Level Variability and Trends in the North Indian Ocean

Sea level rise (over the globe as well as over the Indian Ocean) is one of the most serious issues considering its potential threat to the low-lying coastal areas and coastal population. TOPEX/Poseidon altimeter observations suggest a sea level rise over the Arabian Sea and Bay of Bengal. The rate of sea level rise over the Arabian Sea is about 0.5–3 mm/year, whereas over the Bay of Bengal, it is 0.75–6 mm/year. Major contributors to these changes in the Indian Ocean are steric effect and short-term climate variability such as El Nino–Southern Oscillation (ENSO) and the Indian Ocean Dipole. This affirms that sea level trends over north Indian Ocean get modulated by inter-annual and decadal scale natural climate variability. The inter-annual variability is stronger than decadal variability, which in turn is stronger than the long-term sea level trend. Sea level change in the Indian Ocean is about 1.5 mm/year in the past sixty years or so, whereas the global sea level trends are a bit higher. This picture completely changed in the recent years with very significant sea level rise in the Indian Ocean and is comparable to the global trends. A future projection for the sea level rise over the Indian Ocean based on the highest emission scenario is 40–67 cm for the averaged span of 2071–2100 with the base period of 1921–1990.