Paleoceanography of the Northern Indian Ocean: Linkages to Monsoon and Global Thermohaline Paleocirculation

Abstract

The foraminiferal assemblages and other marine and terrestrial indicators suggest the onset of the Indian monsoon in the middle or even early Miocene. A number of marine and terrestrial paleoarchives monitor the general pattern of the intensified SW (summer) Indian monsoon during warm stages and NE (winter) monsoon during cold stages at glacial–interglacial and millennial timescales. The numerous short-lasting events were superimposed on this pattern during the Pleistocene–Holocene. The primary forcing mechanisms of the monsoon variability are contrast in land–ocean sensible heating and tropospheric latent heating which in turn largely depend on the orbital parameters of the Earth. Remarkable monsoon-induced variations are ascertained in surface circulation, coastal and open-ocean upwellings, primary production, and intensity of the oxygen minimum zone. Besides, the hydrological parameters and microfossil assemblages in the northern Indian Ocean have been significantly affected by variations in the intensity of the return branch of the global thermohaline circulation as well as the rate of the NADW and Southern Ocean waters propagation into the tropical Indian Ocean during the high (interglacial) and low (glacial) sea level stands. The most pronounced environmental changes are associated with the reorganization of the THC over the terminations.