Indian scientists reveal link between monsoon circulation and Antarctica

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Identifying multiple occurrences of intense and weak monsoon circulation events during the 145 kyr period (approximately one millennium), Indian scientists found that warm / cold conditions in Antarctica show an almost one-to-one coupling with monsoon phases. weak / strong, suggesting a strong mechanical bond between them during the period.

Four scientists from the National Center for Polar and Oceanic Research (NCPOR), Goa, under the Department of Earth Sciences, and the School of Earth, Ocean and Atmospheric Sciences, University of Goa, reconstructed the dynamics of the summer monsoon circulation from an upstream region ideal for exploring its connection to the southern high latitude climate. The available records of past summer monsoon variability are primarily based on reconstruction of downstream hydrology, which is identifiable with the thermodynamics of the system.

“The influence of high northern latitude climate variability on the South Asian summer monsoon has been extensively studied using instrumental and indirect climate data. In comparison, only a few studies have attempted to explore the association of the high southern latitudes of the South Asian summer monsoon. “, according to the study.

The South Asian summer monsoon carries a large amount of heat and humidity across the equator. A low pressure system is developing over the northwest Indian subcontinent and the Tibetan plateau due to significant warming due to the seasonal position of the Sun. Southeasterly winds become southwesterly (summer) monsoon winds after crossing the equator, therefore, a strong correlation between them is expected.

These scientists Manish Tiwari, Sidhesh Nagoji and Rahul Mohan from NCPOR, Goa and Vikash Kumar from the University of Goa, compared the 145 kyr long record of summer monsoon variability inferred from the strength of the southerly winds. is with that of the reconstruction published earlier in 2003 in the western Arabian Sea. reflecting the strength of the southwest monsoon wind.

They presented new data from 145 kyr – the isotopic abundance of oxygen and carbon of two deeply stratified foraminifera species, viz. Globigerinoides ruber and Globorotalia menardii – from a sediment core at submillennial to millennium scale resolution of the southwestern tropical Indian Ocean, a southeasterly windswept region during the boreal summer, which turns into a southwest monsoon wind after crossing the equator.

Study results – published as a “145 kyr record of upstream changes in Indian monsoon circulation and its link to the climate of high southern latitudes” in the journal “Polar Science” in October – said “consistent with our results where hot (cold) Antarctic conditions appear to be causing a synchronous decline (increase) in monsoon circulation, most likely across an equatorial bridge to the Indian Ocean”.

The tropical Indian Ocean, in addition to being directly affected by summer monsoon winds, is also ideal for exploring any inter-hemispheric influence of high southern latitudes on circulation. “Here, we report the isotopic abundance of oxygen and carbon of two species of foraminifera stratified at depth from a sediment core of the tropical southwest Indian Ocean covering a significant part of the last two periods. glacial, “the study said, adding: The isotopic oxygen composition of the depth-stratified foraminiferous species indicates periods of high and low summer monsoon activity from 187.5 kyr to 41.4 kyr BP “.

The isotopic composition of carbon mainly records the signatures of monsoon-induced upwellings during this period. Spectral and wavelet analysis shows dominant power in the precession band throughout the 145 kyr period. “Our record for summer monsoon variability is a multi-proxy record of monsoon wind stress from the western Arabian Sea, an area dominated by a high seasonal summer monsoon wind from the south. Comparison of our record with the Antarctic climate record over the last two ice ages suggest consistent changes in transequatorial summer monsoon flow and temperatures in Antarctica, where warm (cold ) in Antarctica were phase-related to a weak (strong) monsoon circulation.

Millennial-scale variability in the southern high latitude region appears to significantly modulate the sub-orbital variance of transequatorial monsoon flow, most likely influencing sea surface temperatures (SST) in the ocean. Tropical Indian, scientists said.

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