Abstract
Agricultural production and the availability of fresh water in Indian subcontinent critically depend on the monsoon rains. Therefore it is vital to understand the causal mechanisms underlying the observed changes in the Indian monsoon in the past. Paleomonsoon reconstructions show that the water discharge from the Ganges-Brahmaputra River system to the Bay of Bengal was maximum in the early to mid-Holocene; data from the Western Arabian Sea and Omanian speleothems indicate declining monsoon winds during the Holocene, whereas records from the South West Monsoon (SWM) precipitation dominated eastern Arabian Sea show higher runoff from the Western Ghats indicating gradually increasing monsoon precipitation during the Holocene. Thus there exists considerable spatial variability in the monsoon in addition to the temporal variability that needs to be assessed systematically. Here we discuss the available high resolution marine and terrestrial paleomonsoon records such as speleothems and pollen records of the SWM from important climatic regimes such as Western Arabian Sea, Eastern Arabian Sea, Bay of Bengal to assess what we have learnt from the past and what can be said about the future of water resources of the subcontinent in the context of the observed changes.
Highlights
The Indian economy is based on agriculture, which mostly depends on the monsoon rain and to some extent on river flow and ground water resources
We present below a comparative analysis of multiproxy studies from diverse terrestrial and marine realms divided into different time periods, which would help us to understand the spatiotemporal variability and complexity of the south Asian monsoon
The above discussion shows that there exists a large spatial variability in monsoon records, which becomes more pronounced on shorter timescales
Summary
The Indian economy is based on agriculture, which mostly depends on the monsoon rain and to some extent on river flow and ground water resources. The inherent seasonality of monsoon circulation leads to cool, dry winters and warm, wet summers over the Asian landmass. These seasonal changes in atmospheric circulation and precipitation affect the ocean, leading to a strong seasonality in the strength and direction of ocean currents, sea-surface. Journal of Geological Research temperature (SST), and salinity patterns, as is observed in the Indian Ocean and the South China Sea (SCS) In specific regions, such as the Northwestern Arabian Sea, these dynamics lead to well-defined seasonal upwelling regimes in the open-ocean and near-shore environments [9]. Monsoons are components of the global climate that play an important role in water resources of the Indian subcontinent. To understand full variability of monsoon, which assumes added importance in view of the presently experienced global warming, we require records of monsoon during differing climatic conditions extending back to thousands of years
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