This study investigates the impact of monthly Ganges–Brahmaputra river discharge variations on Bay of Bengal salinity and temperature during the period 1992–1999. The Ganges–Brahmaputra river discharge is characterized by a well-defined seasonal cycle with strong interannual variations. The highest/lowest yearly peak discharge occurs in summer 1998/summer 1992, with 1998 value amounting to twice that of 1992. This river discharge is then used to force an ocean general circulation model. Our main result is that the impact of these rivers on the variability of Bay of Bengal sea surface salinity is strong in the northern part, with excess run-off forcing fresh anomalies, and vice versa. Most of the years, the influence of the interannual variability of river discharge on the Bay salinity does not extend south of ~10°N. This stands in contrast with the available observations and is probably linked to the relatively coarse resolution of our model. However, the extreme discharge anomaly of 1998 is exported through the southern boundary of the Bay and penetrates the south-eastern Arabian Sea a few months after the discharge peak. In response to the discharge anomalies, the model simulates significant mixed-layer temperature anomalies in the northern Bay of Bengal. This has the potential to influence the climate of the area. From our conclusions, it appears necessary to use a numerical model with higher resolution (both on the horizontal and vertical) to quantitatively investigate the upper Bay of Bengal salinity structure.
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Bentamy A, Quilfen Y, Gohin F, Grima N, Lenaour M and Servain J 1996 Determination and validation of average wind fields from ERS-1 scatterometer measurements; Global Atmos. Ocean Syst. 4 1–29.
Blanke B and Delecluse P 1993 Variability of the tropical Atlantic Ocean simulated by a general circulation model with two different mixed layer physics; J. Phys. Oceanogr. 23 1363–1388.
Chowdhury M R and Ward N 2004 Hydro-meteorological variability in the Greater Ganges–Brahmaputra–Meghna Basins; Int. J. Climatol. 24 1495–1508, doi: 10.1002/joc.1076.
Dai A and Trenberth K E 2002 Estimates of freshwater discharge from continents: Latitudinal and seasonal variations; J. Hydrometeorol. 3 660–687.
Dai A, Qian T and Trenberth K E 2009 Changes in continental freshwater discharge from 1948 to 2004, J. Climate 22(10) 2773–2792, doi: 10.1175/2008JCLI2592.1.
de Boyer Montégut C, Madec G, Fischer A S, Lazar A and Iudicone D 2004 Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology; J. Geophys. Res. 109 C12003, doi: 10.1029/2004JC002378.
de Boyer Montégut C 2005 Couche mélangée océanique et bilan thermohalin de surface dans l’Océan Indien Nord; PhD thesis, University of Paris VI, 181 pp. Available on tel.archives-ouvertes.fr/docs/00/05/58/75/PDF/these_clem_pdf_edition_20051025.pdf.
de Boyer Montégut C, Vialard J, Shenoi S S C, Shankar D, Durand F, Ethé C and Madec G 2007 Simulated seasonal and interannual variability of mixed layer heat budget in the northern Indian Ocean; J. Climate 20 3249–3268.
Delcroix T, Dessier A, Gouriou Y and McPhaden M 2005 Time and space scales for sea surface salinity in the tropical oceans; Deep-Sea Res. 52 787–813.
Durand F, Shankar D, de Boyer Montégut C, Shenoi S S C, Blanke B and Madec G 2007 Modeling the barrier-layer formation in the south-eastern Arabian Sea; J. Climate 20 2109–2120, doi: 10.1175/JCLI4112.1.
Durand F, Shankar D, Birol F and Shenoi S S C 2009 Spatio-temporal structure of the East India Coastal Current from satellite altimetry; J. Geophys. Res. 114 C02013, doi: 10.1029/2008JC004807.
Fekete B M, Vorosmarty C J and Grabs W 2000 Global, composite runoff fields based on observed river discharge and simulated water balances; Documentation for UNH-GRDC Composite Runoff Fields, v.1.0, Global Runoff Data Center, Koblenz, Germany.
Gadgil S, Joseph P V and Joshi N V 1984 Ocean–atmopshere coupling over monsoon regions; Nature 312 141–143.
Gopalakrishna V V, Johnson Z, Salgaonkar G, Nisha K, Rajan C K and Rao R R 2005 Observed variability of sea surface salinity and thermal inversions in the Lakshadweep Sea during contrast monsoons; Geophys. Res. Lett. 32 L18605, doi: 10.1029/2005GL023280.
Han W and McCreary J P 2001 Modeling salinity distributions in the Indian Ocean; J. Geophys. Res. 106 859–877.
Han W and Webster P J 2002 Forcing mechanisms of sea level interannual variability in the Bay of Bengal; J. Phys. Oceanogr. 32 216–239.
Hoyos C D and Webster P J 2007 The role of intraseasonal variability in the nature of Asian monsoon precipitation; J. Climate 20 4402–4424.
Jensen T G 2003 Cross-equatorial pathways of salt and tracers from the northern Indian Ocean: Modelling results; Deep-Sea Res. II 50 2111–2127.
Jian J, Webster P J and Hoyos C D 2009 Large-scale controls on Ganges and Brahmaputra river discharge on intraseasonal and seasonal time-scales; Quart J. Roy. Meteorol. Soc. 135 353–370, doi: 10.1002/qj.384.
Kalnay E and Coauthors 1996 The NCEP/NCAR 40-Year Reanalysis Project; Bull. Amer. Meteor. Soc. 77 437–471.
Levitus S 1998 Climatological Atlas of the World Ocean; NOAA Prof. Paper 13, 173 pp. and 17 microfiche.
Madec G 2008 NEMO reference manual, ocean dynamics component, Note du pôle de modélisation, IPSL, France N°27 ISSN N°1288-1619.
Mariano A J, Ryan E H, Perkins B D and Smithers S 1995 The Mariano Global Surface Velocity Analysis 1.0; Rep. CG-D-34–95, 55 pp., U.S. Coast Guard, Washington, D. C.
Papa F, Durand F, Rahman A, Bala S K and Rossow W B 2010 Satellite altimeter-derived monthly discharge of the Ganga–Brahmaputra River and its seasonal to interannual variations from 1993 to 2008; J. Geophys. Res. 115 C12013, doi: 10.1029/2009JC006075.
Sengupta D, Bharath Raj G N and Shenoi S S C 2006 Surface freshwater from Bay of Bengal runoff and Indonesian throughflow in the tropical Indian Ocean; Geophys. Res. Lett. 33 L22609, doi: 10.1029/2006GL027573.
Shankar D and Shetye S R 1999 Are interdecadal sea level changes along the Indian coast influenced by variability of monsoon rainfall? J. Geophys. Res. 104(C11) 26,031–26,042.
Shankar D, Vinayachandran P N and Unnikrishnan A S 2002 The monsoon currents in the north Indian Ocean; Progr. Oceanogr. 52 63–120.
Shenoi S S C, Shankar D and Shetye S R 2002 Differences in heat budgets of the near-surface Arabian Sea and Bay of Bengal: Implications for the summer monsoon; J. Geophys. Res. 107 3052, doi: 10.1029/2000JC000679.
Shetye S R 1993 The movement and implications of the Ganges–Bramhaputra runoff on entering the Bay of Bengal; Curr. Sci. 64(1) 32–38.
Shetye S R, Shenoi S S C, Gouveia A D, Michael G S, Sundar and Nampoothiri G 1991 Wind-driven coastal upwelling along the western boundary of the Bay of Bengal during the southwest monsoon; Cont. Shelf Res. 11 1397–1408.
Shetye S R, Gouveia A D, Shankar D, Shenoi S S C, Vinayachandran P N, Sundar D, Michael G S and Nampoothiri G 1996 Hydrography and circulation in the western Bay of Bengal during the northeast monsoon; J. Geophys. Res. 101 14,011–14,025, doi: 10.1029/95JC03307.
Vinayachandran P N, Murty V S N and Ramesh Babu V 2002 Observations of barrier layer formation in the Bay of Bengal during summer monsoon; J. Geophys. Res. 107(C12) 8018, doi: 10.1029/2001JC000831.
Vinayachandran P N, Kagimoto T, Masumoto Y, Chauhan P, Nayak S R and Yamagata T 2005 Bifurcation of the East India Coastal Current east of Sri Lanka; Geophys. Res. Lett. 32 L15606, doi: 10.1029/2005GL022864.
Vinayachandran P N and Nanjundiah R S 2009 Indian Ocean sea surface salinity variations in a coupled model; Clim Dyn., doi: 10.1007/s00382–008–0511–6.
Xie P and Arkin P 1997 Analyses of global monthly precipitation using gauge observations, satellite estimates, and numerical model predictions; J. Climate 9 840–858.
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DURAND, F., PAPA, F., RAHMAN, A. et al. Impact of Ganges–Brahmaputra interannual discharge variations on Bay of Bengal salinity and temperature during 1992–1999 period. J Earth Syst Sci 120, 859–872 (2011). https://doi.org/10.1007/s12040-011-0118-x
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DOI: https://doi.org/10.1007/s12040-011-0118-x