Regional sea level variability, total relative sea level rise and its impacts on islands and coastal zones of Indian Ocean over the last sixty years

Abstract

Indian Ocean is the home to many tropical low lying islands and highly populated coastal zones. Since a few recent decades, many of these zones have been gaining a lot of international attention due to fears of sea level rise and possible submersions of islands. In this study we estimate sea level rise and regional sea level variability in Indian Ocean (20°E–140°E, 30°N–35°S) over a period of 60years from 1950 until 2009. We determine the climatic factors that influence the sea level change and variability in this region. We find that the changes in the Indian Ocean sea level are of steric origin and are also driven by short-term Indian Ocean Dipole events. The trend in this region over 60years amounts to 1.5mm/yr, a value lesser (although not statistically different) than the global mean sea level rise over the same period. There is also an east–west increase in sea level trend pattern below 15°S latitude which is more amplified since the two recent decades. Climate-related sea level changes are also studied at different sites in the Indian ocean corresponding to the existence of tide gauge records and has been found that over the long term period (60years), the sea level trend at most of the individual locations are well within the global mean sea level rise. Total relative sea level change which is the sum of climate-related sea level change and vertical land motion is also estimated at 5 locations with the help of GPS and DORIS measures.