- Dona Paula, Goa, India.
- +91-0832- 2450327
- iiosc2020[at]nio[dot]org
Abstract Submission No. | ABS-2022-10-0181 |
Title of Abstract | Ventilation changes in intermediate waters of the Arabian Sea from the Last Glacial Maximum to the Holocene |
Authors | Kumari Nisha*, Sushant S. Naik, Pankaj Kumar, Smita Naik |
Organisation | CSIR-National Institute of Oceanography, Dona-Paula, Goa |
Address | SAS-28, NIO colony, Dona Paula, Goa- 403004 Panaji, Goa, India Pincode: 403004 Mobile: 9757315413 E-mail: nisha.121kumari@gmail.com |
Country | India |
Presentation | Oral |
Abstract | During the northern hemispheric stadials: Henrich Stadial 1(HS1; 17.5-14.5 kyr BP) and Younger Drays (YD; ~12.8-11.2 kyr BP) there was an increase in the atmospheric CO2 while the atmospheric radiocarbon declined. The mechanism for such atmospheric changes still remains uncertain. Studies from the Atlantic and Pacific Ocean have inferred that one of the possible source for this drop in atmospheric 14C could be due to enhanced upwelling of radiocarbon depleted deep-water from the Southern Ocean during the last deglaciation. However evidence to support this role of the Southern Ocean is still lacking. In this study we have reconstructed the ventilation age of the intermediate water of the Arabian Sea for over the past 25 kyr using paired mixed-species benthic and mono-species planktic foraminiferal radiocarbon measurements from Core AAS 9/21 (1800 mbsl). Results show pulse of an old water mass (~1500 14C years) during the Last Glacial Maximum (LGM) which improved during the Holocene (~400 14C years). Radiocarbon record of the core along with stable carbon isotope of benthic foraminifera Cibicidoides wuellerstorfi suggest poorly ventilated and nutrient rich water mass existed during the LGM. In Henrich Stadial 1, the ventilation age and δ13C data indicates incursion of Antarctic Intermediate Water (AAIW) into the southeastern Arabian Sea due to the decreased export of North Atlantic Deep Water (NADW) into the northern Indian Ocean, which was compensated by northward expansion of southern sourced AAIW. This increase in AAIW penetration was consistent with a CO2 peak observed in an earlier study (Naik et al., 2015) from the same area, suggesting that the southern sourced water was nutrient rich, CO2 rich and poorly ventilated, which expelled the CO2 into the atmosphere from the intermediate water. Decrease in ventilation age during the Bølling-Allerød (B-A; ~14.5-12.8 kyr BP) indicate resumption of NADW. During Holocene (~10 kyr BP) there was a shift towards better ventilated and δ13C rich water, suggesting increased flow of NADW to the core site. This study supports existence of poorly ventilated deep water mass in the Southern Ocean during the LGM which upwelled into the intermediate water during deglaciation and resulted in enhanced northward flow of 14C depleted AAIW. |