The upper 200 m of the two northern Indian Ocean embayments, the Bay of Bengal (BoB) and the Arabian Sea (AS), differ sharply in their salinity stratification, as the Asian monsoon injects massive amounts of freshwater into the BoB while removing freshwater via evaporation from the AS. The ocean circulation transfers salt from the AS to the BoB and exports freshwater from the BoB to mitigate the salinity difference and reach a quasi-steady state, albeit with strong seasonality. An energetic field of mesoscale features and an intrathermocline eddy was observed within the BoB during the R/V Revelle November and December 2013 Air-Sea Interactions Regional Initiative cruises, marking the early northeast monsoon phase. Mesoscale features, which display a surprisingly large thermohaline range within their confines, obscure the regional surface water and thermohaline stratification patterns, as observed by satellite and Argo profilers. Ocean processes blend the fresh and salty features along and across density surfaces, influencing sea surface temperature and air-sea flux. Comparing the Revelle observations to the Argo data reveals a general westward migration of mesoscale features across the BoB.
Gordon, A.L., E.L. Shroyer, A. Mahadevan, D. Sengupta, and M. Freilich. 2016. Bay of Bengal: 2013 northeast monsoon upper-ocean circulation. Oceanography 29(2):82–91, https://doi.org/10.5670/oceanog.2016.41.
Akhil, V.P., F. Durand, M. Lengaigne, J. Vialard, M.G. Keerthi, V.V. Gopalakrishna, C. Deltel, F. Papa, and C. de Boyer Montegut. 2014. A modeling study of the processes of surface salinity seasonal cycle in the Bay of Bengal. Journal of Geophysical Research 119:3,926–3,947, https://doi.org/10.1002/2013JC009632.
Bonjean, F., and G.S.E. Lagerloef. 2002. Diagnostic model and analysis of the surface currents in the tropical Pacific Ocean. Journal of Physical Oceanography 32:2,938–2,954, https://doi.org/10.1175/1520-0485(2002)032<2938:DMAAOT>2.0.CO;2.
Dugan, J.P., R. Mied, P. Mignerey, and A. Schuetz. 1982. Compact, intrathermocline eddies in the Sargasso Sea. Journal of Geophysical Research 87:385–393, https://doi.org/10.1029/JC087iC01p00385.
Durack, P.J., and S.E. Wijffels. 2010. Fifty-year trends in global ocean salinities and their relationship to broad-scale warming. Journal of Climate 23:4,342–4,362, https://doi.org/10.1175/2010JCLI3377.1.
Durand, F., D. Shankar, F. Birol, and S.S.C. Shenoi. 2009. Spatiotemporal structure of the East India Coastal Current from satellite altimetry. Journal of Geophysical Research 114, C02013, https://doi.org/10.1029/2008JC004807.
Gadgil, S., P.V. Joseph, and N.V. Joshi. 1984. Ocean-atmosphere coupling over monsoon regions. Nature 312:141–143, https://doi.org/10.1038/312141a0.
Gordon, A.L. 2001. Interocean exchange. Pp. 303–314 in Ocean Circulation and Climate. G. Siedler, J. Church, and J. Gould, eds, Academic Press.
Jensen, T.G. 2001. Arabian Sea and Bay of Bengal exchange of salt and tracers in an ocean model. Geophysical Research Letters 28:3,967–3,970, https://doi.org/10.1029/2001GL013422.
Jensen, T.G., H.W. Wijesekera, E.S. Nyadjro, P.G. Thoppil, J.F. Shriver, K.K. Sandeep, and V. Pant. 2016. Modeling salinity exchanges between the equatorial Indian Ocean and the Bay of Bengal. Oceanography 29(2):92–101, https://doi.org/10.5670/oceanog.2016.42.
Kostianoy, A.G., and I.M. Belkin. 1991. A survey of observations on intrathermocline eddies in the world ocean. Pp. 821–841 in Mesoscale/Synoptic Coherent Structures in Geophysical Turbulence. B.M. Jamart and J.C.J. Nihoul, eds, Elsevier.
Lagerloef, G., F.R. Colomb, D. Le Vine, F. Wentz, S. Yueh, C. Ruf, J. Lilly, J. Gunn, Y. Chao, A. deCharon, G. Feldman, and C. Swift. 2008. The Aquarius/SAC-D Mission: Designed to meet the salinity remote-sensing challenge. Oceanography 21(1):68–81, https://doi.org/10.5670/oceanog.2008.68.
Pant, V., M.S. Girishkumar, T.V.S. Udaya Bhaskar, M. Ravichandran, F. Papa, and V.P. Thangaprakash. 2015. Observed interannual variability of near-surface salinity in the Bay of Bengal. Journal of Geophysical Research 120:3,315–3,329, https://doi.org/10.1002/2014JC010340.
Papa, F., F. Durand, W.B. Rossow, A. Rahman, and S.K. Bala. 2010. Satellite altimeter-derived monthly discharge of the Ganga-Brahmaputra River and its seasonal to interannual variations from 1993 to 2008. Journal of Geophysical Research 115, C12013, https://doi.org/10.1029/2009JC006075.
Rao, R.R., and R. Sivakumar. 2003. Seasonal variability of sea surface salinity and salt budget of the mixed layer of the north Indian Ocean. Journal of Geophysical Research 108(C1), 3009, https://doi.org/10.1029/2001JC000907.
Reynolds, R.W., T.M. Smith, C. Liu, D.B. Chelton, K.S. Casey, and M.G. Schlax. 2007. Daily high-resolution blended analyses for sea surface temperature. Journal of Climate 20:5,473–5,496, https://doi.org/10.1175/2007JCLI1824.1.
Sastry, J., D. Rao, V. Murty, Y. Sarma, A. Suryanarayana, and M. Babu. 1985. Watermass structure in the Bay of Bengal. Mahasagar Bulletin of the National Institute of Oceanography 18(2):153–162,http://www.ijs.nio.org/index.php/msagar/article/view/1811.
Schott, A.F., and J. McCreary. 2001. The monsoon circulation of the Indian Ocean. Progress in Oceanography 51:1–123, https://doi.org/10.1016/S0079-6611(01)00083-0.
Schott, F.A., S.-P. Xie, and J.P. McCreary Jr. 2009. Indian Ocean circulation and climate variability. Reviews of Geophysics 47, RG1002, https://doi.org/10.1029/2007RG000245.
Sengupta, D., G.N. Bharath Raj, and S.S.C. Shenoi. 2006. Surface freshwater from Bay of Bengal runoff and Indonesian Throughflow in the tropical Indian Ocean. Geophysical Research Letters 33, L22609, https://doi.org/10.1029/2006GL027573.
Mahadevan, A., T. Paluszkiewicz, M. Ravichandran, D. Sengupta, and A. Tandon. 2016. Introduction to the special issue on the Bay of Bengal: From monsoons to mixing. Oceanography 29(2):14–17, https://doi.org/10.5670/oceanog.2016.34.
Shankar, D., P.N. Vinayachandran, and A.S. Unnikrishnan. 2002. The monsoon currents in the north Indian Ocean. Progress in Oceanography 52:63–120, https://doi.org/10.1016/S0079-6611(02)00024-1.
Shetye, S.R., A.D. Gouveia, D. Shankar, S.S.C. Shenoi, P.N. Vinayachandran, D. Sundar, G.S. Michael, and G. Nampoothiri. 1996. Hydrography and circulation in the western Bay of Bengal during the northeast monsoon. Journal of Geophysical Research 101(C6):14,011–14,025, https://doi.org/10.1029/95JC03307.
Shetye, S.R., S.S.C. Shenoi, A.D. Govela, G.S. Michael, D. Sundar, and N. Nampoothiri. 1991. Wind-driven coastal upwelling along the western boundary of the Bay of Bengal during the southwest monsoon. Continental Shelf Research 11:1,397–1,408, https://doi.org/10.1016/0278-4343(91)90042-5.
Sprintall, J., G. Siedler, and H. Mercier. 2013. Inter-ocean and interbasin exchanges. Chapter 19 in Ocean Circulation & Climate: A 21st Century Perspective, 2nd ed. G. Siedler, S. Griffies, J. Gould, and J. Church, eds, Academic Press.
Talley, L.D. 2013. Hydrographic Atlas of the World Ocean Circulation Experiment (WOCE): Vol. 4. Indian Ocean. M. Sparrow, P. Chapman, and J. Gould, series eds, International WOCE Project Office, Southampton, UK, 20 pp.
Varkey, M.J., V.S.N. Murty, and A. Suryanarayana. 1996. Physical oceanography of the Bay of Bengal and Andaman Sea. Oceanography and Marine Biology: An Annual Review 34:1–70.
Vinayachandran, P.N., Y. Masurnoto, T. Mikawa, and T. Yarnagata. 1999. Intrusion of the Southwest Monsoon Current into the Bay of Bengal. Journal of Geophysical Research 104:11,077–11,085, https://doi.org/10.1029/1999JC900035.
Vinayachandran, P.N., V.S.N. Murty, and V. Ramesh Babu. 2002. Observations of barrier layer formation in the Bay of Bengal during summer monsoon. Journal of Geophysical Research 107(C12), 8018, https://doi.org/10.1029/2001JC000831.
Vinayachandran, P.N., D. Shankar, S. Vernekar, K.K. Sandeep, P. Amol, C.P. Neema, and A. Chatterjee. 2013. A summer monsoon pump to keep the Bay of Bengal salty. Geophysical Research Letters 40:1,777–1,782, https://doi.org/10.1002/grl.50274.
Wijesekera, H.W., T.G. Jensen, E. Jarosz, W.J. Teague, E.J. Metzger, D.W. Wang, S.U.P. Jinadasa, K. Arulananthan, L.R. Centurioni, and H.J.S. Fernando. 2015. Southern Bay of Bengal currents and salinity intrusions during the northeast monsoon. Journal of Geophysical Research 120:6,897–6,913, https://doi.org/10.1002/2015JC010744.
Wijesekera, H.W., E. Shroyer, A. Tandon, M. Ravichandran, D. Sengupta, S.U.P. Jinadasa, H.J.S. Fernando, N. Agarwal, K. Arualanathan, G.S. Bhat, and others. In press. ASIRI: An ocean-atmosphere initiative for the Bay of Bengal. Bulletin of the American Meteorological Society, https://doi.org/10.1175/BAMS-D-14-00197.1.
Wilson, E.A., and S.C. Riser. 2016. An assessment of the seasonal salinity budget for the upper Bay of Bengal. Journal of Physical Oceanography 46(5):1,361–1,376, https://doi.org/10.1175/JPO-D-15-0147.1.
Wyrtki, K. 1971. Oceanographic Atlas of the International Indian Ocean Expedition. National Science Foundation, OCE/NSF 86-00-001, Washington, DC, 531 pp.
Yu, L., J.J. O’Brien, and J. Yang. 1991. On the remote forcing of the circulation in the Bay of Bengal. Journal of Geophysical Research 96(C11):20,449–20,454, https://doi.org/10.1029/91JC02424.
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