Determination of long term sea level rise in the northern Indian Ocean

Abstract

Ocean based disasters and sea level rise threatens the sustainability of coastal habitats and community. Prediction of hazards and assessment of vulnerability are critical to adapt appropriate coastal plans, management strategies to facilitate preparedness and mitigation of impacts. A study is carried out to determine the long term sea level variability in the Indian Ocean. Sea level records from islands of Indian Ocean namely; Diego-Garcia, Maldives, Mauritius, Sri Lanka, and Zanzibar and each of one station from the northern Bay of Bengal (Bangladesh) and Arabian Sea (Pakistan) were selected to assess the temporal and spatial sea level rise in the northern Indian Ocean (NIO). Sea level rise is independently estimated using the data of high frequency permanent sea level stations during the period of 1993-2012 and monthly average means of AVISO Satellite data during the last 19 years Seasonal and inter-annual sea level variability in the NIO reveals that the seasonal cycle has large variation of mean amplitude variability, approximately 40–60 cm along the northern most part of Bay of Bengal with maximum values in October to November and minimum values in July-August. The analysis of the development of the seasonal cycle in the NIO indicates no long-term changes in the amplitude and phase but a large inter-annual variability. On the seasonal timescale, mass variation dominates the sea level variation in the coastal regions of NIO. Gravity Recovery and Climate Experiment observes an obvious water mass variation in the deep basin, which is consistent with the result from steric - corrected altimetry. On the inter annual timescales, the mean sea level variation in the NIO shows large oscillations, which are mainly caused by the steric effect. The trend of mean sea level variation inferred from altimetry in the NIO is 5 ± 0.4 mm/year for the period of 1993–2012, which is significantly higher than the global sea level rise rate of 3.6 ± 0.4 mm/yr in the same period. There is significant difference in sea level trend in Bay of Bengal and Arabian Sea; trend is twice higher in Bay of Bengal than Arabian Sea.