[U-13] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia:

[U13-P11] North Atlantic cooling desiccated western India during Early Holocene: Evidence-based on clumped and stable oxygen isotope analysis of Gastropod

*THAMIZHARASAN SAKTHIVEL^1,2、PROSENJIT GHOSH^1,2、YOGARAJ BANERJEE¹ (1.Centre for Earth Sciences, Indian Institute of Science, Bangalore, India -560012、2.Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, India -560012)

キーワード：Early Holocene , Clumped and Stable isotope of Gastropod, Indian Summer Monsoon, North Atlantic Teleconnection

Last Glacial Period witnessed modulation of Indian Summer Monsoon (ISM) intensity due to its teleconnection with the North Atlantic climatology (Schulz et al.,1998). We investigated here the millennium scale record of Sea Surface Temperature (SST) and δ18O of seawater at coastal location during Early Holocene (12 to 7 kyr BP) based on clumped and stable oxygen isotope composition of well-preserved fossil specimen of Cerithium sp. These shells grow in the tidal environment and has potential to record upwelling process which controls the variation in water and air temperature (Yekta al., 2019). The raised paleo-gulf sedimentary sequence exposed adjoining the region of present-day Arabian Sea i.e., Great Rann of Kutch provided opportunity to study the coastal climate during the time interval when solar variability was minimal. The record of solar variability from the region was earlier studied from the offshore sedimentary archives from the Arabian Sea (Gupta et al., 2003). Our observation revealed variation of coastal apparent Sea Surface Temperature (SST) from 30 to 36°C, which is negatively correlated with upwelling proxy G.bulloides abundance from the adjoining region of Eastern Arabian Sea (Naik et al., 2016). This suggests vertical entrainment of deep water due to wind strength variability drove the upwelling process and regional SST . The estimated equilibrium δ18O of water is consistent with the shift observed in the available record from the Indian Subcontinent (Dixit et al., 2014). We provided here fist evidence of intense monsoonal wind strength assessment at 12.2, 9.47, and 7.9 kyr BP. In contrast, our observation revealed weakening of ISM wind intensity at 9.86, 8.51, and 7.65 kyr BP, which is coherent sea ice variability in the North Atlantic (Bond et al., 2001). Therefore, we showed that North Atlantic climate has strong impact on ISM even during past as seen in the historical data and present day (Borah et al., 2020).