Are interdecadal sea level changes along the Indian coast influenced by variability of monsoon rainfall?

The Mumbai (Bombay) tide gauge data, the only century-long record in the In dian Ocean, show that interdecadal changes in sea level mimic those in rain fall over the Indian subcontinent. We propose that the link between rainfal l and sea level arises from changes in salinity in coastal waters. Rivers f ed by southwest monsoon (June-September) rainfall bring a large fraction of the runoff to the Bay of Bengal, from where it is transported to the west coast of India by an equatorward East India Coastal Current, which is trigg ered partly by the withdrawal of the southwest monsoon. The West India Coas tal Current carries the low-salinity water from the bay as well as the runo ff from local rivers northward. The advection of the riverine inflow to Mum bai occurs within a season. but the slow mixing in the ocean forces changes in the cross-shore density gradient on longer timescales. This density gra dient forces a two-layer geostrophic circulation, with a surface current, w hich flows with the lighter water on its right, and an undercurrent. Lower (higher) salinity at the coast implies higher (lower) coastal sea level and a rise (fall) of the pycnocline at the coast. Thus the interdecadal variab ility of sea level along the Indian coast can be Linked directly to the var iability of the monsoon, the major aspect of the climate of the region, but by a mechanism that is different from those generally proposed to link sea level to climate change; these hypotheses usually invoke a change in volum e because of global warming.