Summary of Abstract Submission

Abstract Submission No. IO50-09-0050PresentationPoster

UPPER OCEAN CABON EXPORT IN THE ARABIAN SEA AND THE BAY OF BENGAL USING 234TH/238U AND 210PO/210PB DISEQUILIBRIA

S. Subha Anand*1, R. Rengarajan1, Mangesh Gauns2, Damodar Shenoy3

1 Physical Research Laboratory, Ahmedabad 380 009, India
2 National Institute of Oceanography, Dona Paula, Goa 403004, India
3 National Institute of Oceanography, Dona Paula, Goa 403004, India, India

ABSTRACT :

Vertical seawater profiles of 210Po and 210Pb were obtained simultaneously with 234Th at two time-series stations in the Arabian Sea and the Bay of Bengal, under SIBER (India) programme, to estimate sinking particle fluxes of organic carbon in the euphotic zone. Seawater samples from surface to 800 m depth were collected during October-November 2013 from the Arabian Sea and January-February 2014 from the Bay of Bengal onboard RV Sindu Sankalp (SSK56) and ORV Sagar Kanya (SK308), respectively. They were processed onboard for pre-concentration of 234Th, 210Po, 210Pb and 226Ra. Initial 234Th counting of small-volume (~4 L) samples were carried out at the earliest by a low background anti-coincidence counter (Riso GM25-5) via its β-emitting daughter 234Pa. Total (dissolved + particulate) surface activity of 210Po is low at 100 m at 17 N 68 E due to increased productivity compared to that at 9 N 68 E. The deficiency of total 210Po relative to 210Pb allows to compute the vertical export flux of particulate 210Po. The flux data from the upper ocean show spatial variations with enhanced export fluxes around 17 N 68 E, a region characterized by higher rates of column primary productivity. Using the 210Po export fluxes and the measured C/210Po ratio in the POC at 200 m water depth, carbon export fluxes from the euphotic zone are computed. These values ranged from 3.37 to 7.69 mmol C m-2 d-1. Earlier reported values of carbon export and primary production over these stations will be compared with the present estimates.