Oceanography The Official Magazine of
The Oceanography Society
Volume 29 Issue 02

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Volume 29, No. 2
Pages 92 - 101

Modeling Salinity Exchanges Between the Equatorial Indian Ocean and the Bay of Bengal

Tommy G. Jensen Hemantha W. Wijesekera Ebenezer S. NyadjroPrasad G. Thoppil Jay F. Shriver K.K. SandeepVimlesh Pant
Article Abstract

With a focus on the Bay of Bengal, models ranging from a 1/12.5° global ocean model to a ¼° regional Indian Ocean model to a 2 km local high-resolution coupled model are used to simulate salinity exchanges in the Indian Ocean. Global Hybrid Coordinate Ocean Model simulations show a surprisingly large persistent flow of high-salinity water from the equatorial Indian Ocean into the Bay of Bengal during the northeast monsoon, although it is weaker than during the southwest monsoon. On average, salt is transported into the Bay of Bengal between 83°E and 95°E, and low-salinity water flows southward near the east coast of Sri Lanka and east of 95°E. The Regional Ocean Modeling System shows that knowledge of river input of freshwater is essential for modeling surface salinities correctly in the Bay of Bengal. High-resolution coupled model simulations are in agreement with recent observations and show that a strong subsurface current with a speed of about 1 m s–1 intrudes into the Bay of Bengal beneath southward-flowing low-salinity water during the northeast monsoon. The subsurface high-salinity water, which originates in the northern Arabian Sea, spreads northward into the Bay of Bengal and downward along constant density surfaces. North of 10°N, the model simulation implies that mixing takes place on density surfaces at depths of 100–150 m after advection of cold, low-salinity water from the north, and subsequent stirring of the two water masses. Vertical diffusion plays an insignificant role in this mixing.

Citation

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.

References

Antonov, J., D. Seidov, T. Boyer, R. Locarnini, A. Mishonov, H. Garcia, O. Baranova, M. Zweng, and D. Johnson. 2010. World Ocean Atlas 2009: Volume 2, Salinity. S. Levitus, ed., US Government Printing Office, Washington, DC, 184 pp, ftp://ftp.nodc.noaa.gov/pub/WOA09/DOC/woa09_vol2_text.pdf.

Bleck, R. 2002. An oceanic general circulation model framed in hybrid isopycnic-Cartesian coordinates. Ocean Modelling 4:55–88, https://doi.org/10.1016/S1463-5003(01)00012-9.

Bleck, R., and S.G. Benjamin. 1993. Regional weather prediction with a model combining terrain-following and isentropic coordinates: Part 1. Model description. Monthly Weather Review 121(6):1,770–1,785, https://doi.org/10.1175/1520-0493(1993)121​<1770:RWPWAM>2.0.CO;2.

Bleck, R., and D.B. Boudra. 1981. Initial testing of a numerical ocean circulation model using a hybrid (quasi–isopycnic) vertical coordinate. Journal of Physical Oceanography 11(6):755–770, https://doi.org/10.1175/1520-0485(1981)011​<0755:ITOANO>2.0.CO;2.

Bonjean, F., and G.S. Lagerloef. 2002. Diagnostic model and analysis of the surface currents in the tropical Pacific Ocean. Journal of Physical Oceanography 32(10):2,938–2,954, https://doi.org/10.1175/1520-0485(2002)032​<2938:DMAAOT>2.0.CO;2.

Booij, N., R.C. Ris, and L.H. Holthuijsen. 1999. A third-generation wave model for coastal regions: Part I. Model description and validation. Journal of Geophysical Research 104:7,649–7,666, https://doi.org/10.1029/98JC02622.

Chatterjee, A., D. Shankar, S.S.C. Shenoi, G.V. Reddy, G.S. Michael, M. Ravichandran, V.V. Gopalkrishna, E.R. Rao, T.U. Bhaskar, and V.N. Sanjeevan. 2012. A new atlas of temperature and salinity for the North Indian Ocean. Journal of Earth System Science 121(3):559–593, https://doi.org/10.1007/s12040-012-0191-9.

Chen, S., M. Flatau, T.G. Jensen, T. Shinoda, J. Schmidt, P. May, J. Cummings, M. Liu, P.E. Ciesielski, C.W. Fairall, and others. 2015. A study of CINDY/DYNAMO MJO suppressed phase. Journal of Atmospheric Science 72:3,755–3,779, https://doi.org/10.1175/JAS-D-13-0348.1.

Fairall, C.W., E.F. Bradley, J.S. Godfrey, G.A. Wick, J.B. Edson, and G.S. Young. 1996a. Cool-skin and warm-layer effects on sea surface temperature. Journal of Geophysical Research 101(C1):1,295–1,308, https://doi.org/​10.1029/95JC03190.

Fairall, C.W., E.F. Bradley, D.P. Rogers, J.B. Edson, and G.S. Young. 1996b. Bulk parameterization of air-sea fluxes for Tropical Ocean-Global Atmosphere Coupled-Ocean Atmosphere Response Experiment. Journal of Geophysical Research 101(C2):3,747–3,764, https://doi.org/​10.1029/95JC03205.

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.

Haidvogel, D.B., H. Arango, W.P. Budgell, B.D. Cornuelle, E. Curchitser, E. Di Lorenzo, K. Fennel, W.R. Geyer, A.J. Hermann, L. Lanerolle, and others. 2008. Ocean forecasting in terrain-following coordinates: Formulation and skill assessment of the Regional Ocean Modeling System. Journal of Computational Physics 227(7):3,595–3,624, https://doi.org/​10.1016/j.jcp.2007.06.016.

Haidvogel, D.B., H.G. Arango, K. Hedstrom, A. Beckmann, P. Malanotte-Rizzoli, and A.F. Shchepetkin. 2000. Model evaluation experiments in the North Atlantic Basin: Simulations in nonlinear terrain-following coordinates. Dynamics of Atmospheres and Oceans 32(3):239–281, https://doi.org/10.1016/S0377-0265(00)00049-X.

Han, W. 2005. Origins and dynamics of the 90-day and 30–60 day variations in the equatorial Indian Ocean. Journal of Physical Oceanography 35:708–728, https://doi.org/10.1175/JPO2725.1.

Han, W., and J.P. McCreary Jr. 2001. Modeling salinity distributions in the Indian Ocean. Journal of Geophysical Research 106:859–877, https://doi.org/10.1029/2000JC000316.

Jensen, T.G. 1993. Equatorial variability and resonance in a wind-driven Indian Ocean model. Journal of Geophysical Research 98:22,533–22,552, https://doi.org/10.1029/93JC02565.

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. 2003. Cross-equatorial pathways of salt and tracers from the northern Indian Ocean: Modelling results. Deep Sea Research Part II 50:2,111–2,128, https://doi.org/10.1016/S0967-0645(03)00048-1.

Jensen, T.G., T. Shinoda, S. Chen, and M. Flatau. 2015. Ocean response to CINDY/DYNAMO MJOs in air-sea coupled COAMPS. Journal of the Meteorological Society of Japan 93A:157–178, https://doi.org/10.2151/jmsj.2015-049.

Kantha, L.H., and C.A. Clayson. 2004. On the effect of surface gravity waves on mixing in the oceanic mixed layer. Ocean Modelling 6:101–124, https://doi.org/10.1016/S1463-5003(02)00062-8.

Large, W.G., J.C. McWilliams, and S.C. Doney. 1994. Oceanic vertical mixing: A review and a model with a nonlocal boundary layer parameterization. Reviews of Geophysics 32(4):363–403, https://doi.org/10.1029/94RG01872

Locarnini, R.A., A.V. Mishonov, J.I. Antonov, T.P. Boyer, H.E. Garcia, O.K. Baranova, M.M. Zweng, and D.R. Johnson. 2010. World Ocean Atlas 2009: Volume 1, Temperature. S. Levitus, ed., NOAA Atlas NESDIS, 68, 184 pp, ftp://ftp.nodc.noaa.gov/pub/WOA09/DOC/woa09_vol1_text.pdf.

Love, B.S., A.J. Matthews, and G.S. Lister, 2011. The diurnal cycle of precipitation over the Maritime Continent in a high-resolution atmospheric model. Quarterly Journal of the Royal Meteorology Society 137:934–947, https://doi.org/10.1002/qj.809.

Matsuno, T. 1966. Quasi-geostrophic motions in the equatorial area. Journal of the Meteorological Society of Japan 44:25–43.

McCreary, J.P., W. Han, D. Shankar, and S.R. Shetye, 1996. Dynamics of the East India Coastal Current: Part 2. Numerical solutions. Journal of Geophysical Research 101:13,993–14,010, https://doi.org/​10.1029/96JC00560.

Mellor, G.L., and T. Yamada. 1982. Development of a turbulence closure model for geophysical fluid problems. Reviews of Geophysics and Space Physics 20:851–875, https://doi.org/10.1029/RG020i004p00851.

Metzger, E.J., H.E. Hurlburt, X. Xu, J.F. Shriver, A.L. Gordon, J. Sprintall, R.D. Susanto, and H.M. van Aken. 2010. Simulated and observed circulation in the Indonesian Seas: 1/12° global HYCOM and the INSTANT observations. Dynamics of Atmospheres and Oceans 50:275–300, https://doi.org/10.1016/j.dynatmoce.2010.04.002.

Metzger, E.J., O.M. Smedstad, P.G. Thoppil, H.E. Hurlburt, J.A. Cummings, A.J. Wallcraft, L. Zamudio, D.S. Franklin, P.G. Posey, M.W. Phelps, and others. 2014. US Navy operational global ocean and Arctic ice prediction systems. Oceanography 27(3):32–43, https://doi.org/​10.5670/oceanog.2014.66.

Murty, V.S.N., Y.V.B. Sarma, D.P. Rao, and C.S. Murty. 1992. Water characteristics, mixing and circulation in the Bay of Bengal during southwest monsoon. Journal of Marine Research 50:207–228, https://doi.org/10.1357/002224092784797700.

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.

Praveen Kumar, B., J. Vialard, M. Lengaigne, V.S. Murty, and M.J. McPhaden. 2012. TropFlux: Air-sea fluxes for the global tropical oceans: Description and evaluation. Climate Dynamics 38:1,521–1,543, https://doi.org/10.1007/s00382-011-1115-0.

Qiu, B., M. Mao, and Y. Kashino. 1999. Intraseasonal variability in the Indo-Pacific throughflow and regions surrounding the Indonesian seas. Journal of Physical Oceanography 29:1,599–1,618, https://doi.org/10.1175/1520-0485(1999)029​<1599:IVITIP>2.0.CO;2.

Saha, S., S. Moorthi, H.-L. Pan, X. Wu, J. Wang, S. Nadiga, P. Tripp, R. Kistler, J. Woollen, D. Behringer, and others. 2010. The NCEP climate forecast system reanalysis. Bulletin of the American Meteorological Society 91:1,015–1,057, https://doi.org/10.1175/2010BAMS3001.1.

Shchepetkin, A.F., and J.C. McWilliams. 2003. A method for computing horizontal pressure-gradient force in an oceanic model with a nonaligned vertical coordinate. Journal of Geophysical Research 108(C3), 3090, https://doi.org/10.1029/2001JC001047.

Shchepetkin, A.F., and J.C. McWilliams. 2005. The Regional Oceanic Modeling System (ROMS): A split-explicit, free-surface, topography-​following-coordinate oceanic model. Ocean Modelling 9(4):347–404, https://doi.org/10.1016/​j.ocemod.2004.08.002.

Shchepetkin, A.F., and J.C. McWilliams. 2009. Computational kernel algorithms for fine-scale, multiprocess, longtime oceanic simulations. Handbook of Numerical Analysis 14:121–183, https://doi.org/10.1016/S1570-8659(08)01202-0.

Sengupta, D., G.N. Bharath Raj, and S.S.C. Shenoi. 2006. Surface freshwater from Bay of Bengal runoff and Indonesian Throughflow to the tropical Indian Ocean. Geophysical Research Letters 33, L22609, https://doi.org/10.1029/2006GL027573.

Shinoda, T., W. Han, E.J. Metzger, and H. Hurlburt. 2012. Seasonal variation of the Indonesian Throughflow in Makassar Strait. Journal of Physical Oceanography 42:1,099–1,123, https://doi.org/​10.1175/JPO-D-11-0120.1.

Smith, W.H.F., and D.T. Sandwell. 1997. Global sea floor topography from satellite altimetry and ship depth soundings. Science 277:1,956–1,962, https://doi.org/10.1126/science.277.5334.1956.

Thoppil, P.G., E.J. Metzger, H.E. Hurlburt, O.M. Smedstad, and H. Ichikawa. 2016. The current system east of the Ryukyu Islands as revealed by a global ocean reanalysis. Progress in Oceanography 141:239–258, https://doi.org/10.1016/j.pocean.2015.12.013.

Vinayachandran, P.N., Y. Masumoto, T. Mikawa, and T. Yamagata. 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., D. Shankar, S. Vernekar, K.K. Sandeep, P. Amol, C.P. Neema, and Abhisek 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. 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.

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 96:20,449–20,454, https://doi.org/10.1029/91JC02424.