Mid Miocene Indian Monsoon Dynamics

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The livelihoods of more than 2 billion people depend on the Asian monsoon rains, which are still difficult to predict even with the most advanced coupled ocean-atmosphere general circulation models. A detailed understanding how the monsoon behaves under different boundary conditions such as a warmer world with less continental ice cover is vital for these models. We also need to know how and when the monsoon system first intensified, how it subsequently developed and how it has varied in response to various potential influences including global climate changes, mountain building and opening and closing of oceanic gateways. The timing of the intensification of the modern East Asian and Indian monsoon systems is controversial, with some records (e.g. Arabian Sea upwelling) indicating initial intensification occurred ~7–8 million years ago, whereas others (e.g. Loess formation) suggest it was as early as ~22 million years ago, or even earlier. Modeling studies have suggested that the intensification of the monsoon was directly related to the uplift of Tibet, directly linking global climate and tectonics. Here we propose to use new high quality Miocene sediment cores from the Bay of Bengal (Exp. 353) to reconstruct the evolution of the Indian monsoon through the Miocene period (23 to 5.6 million years ago). We will investigate the coupling of continental weathering in the region with global climate on orbital time scales. Using high resolution proxy records of vertical surface ocean mixing by monsoon winds, salinity changes caused by monsoon rains and the weathering flux of trace metals to the ocean, the results of this study will significantly improve our understanding of the development of the Asian monsoon and will contribute to a more accurate modeling of the monsoon system.