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| Abstract Submission No. | ABS-2022-07-0135 |
| Title of Abstract | Elevated levels of isoprene in the MBL of Arabian Sea during spring inter-monsoon season |
| Authors | L. K. Sahu*, Nidhi Tripathi, Arvind Singh, Ravi Yadav, Meenu |
| Organisation | Physical Research Laboratory |
| Address | Physical Research Laboratory (PRL), Ahmedabad, Gujarat, India Pincode: 380009 Mobile: 7600700256 E-mail: lokesh@prl.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | Isoprene was measured in marine air samples collected on-board R/V Sagar Sampada over the Arabian Sea during spring inter-monsoon 2017. Arabian Sea is a thick oxygen minimum zone (OMZ) where production of phytoplankton in the surface water is very high. Incidentally, the year 2017 was the warmest on record for the global ocean with positive SST anomalies (>0.5oC) over the Arabian Sea during the study period. The variations of isoprene tend to follow the distribution of Chl-a in seawater with lower (0.38±0.14 ppbv) and higher (0.75±0.17 ppbv) values over the central and northern regions, respectively. Major enhancements exceeding 0.6 ppbv were associated with the blooms of Trichodesmium and Thalassiosira in oligotrophic, high SST (>28oC), and calm conditions. The high abundances of diatoms and cyanobacteria, intense solar flux and high SST favored production of isoprene from both microbial and abiotic sources and sea-to-air flux. This is the first measurement of isoprene in the MBL of northern Indian Ocean and the levels fall in the higher range of those reported for some highly productive oceanic regions of the world. This study highlights the implications of ⿿Arabian Sea Paradox on regional atmospheric chemistry. The combination of elevated emissions of BVOC from seawater and NOx from shipping activities could play major role in atmospheric chemistry over Arabian Sea. |