Estimating the Loss of Himalayan Glaciers under Global Warming Using the δ¹⁸O–Salinity Relation in the Bay of Bengal

Abstract

Quantifying the water loss of Himalayan glaciers due to global warming from direct measurement is difficult, as some glaciers are advancing or stable in spite of an overall retreat. We use a novel approach to provide an alternative estimate of the amount of Himalayan ice melt. Because a major part of this melted ice debouches into the Bay of Bengal through the Ganga–Brahmaputra basin, it causes significant variations in the oxygen isotopic composition (δ18O) and salinity (S) of the sea surface water and their mutual linear relationship. We document the temporal change in the δ18O–S relation for the bay at three different times during the period from 1994 to 2006, and using a model, we infer that 2.4 × 1011 m3 water was lost by melting from the Ganga–Brahmaputra basin during this period.