BG Biogeosciences BG Biogeosciences 1726-4189 Copernicus Publications Göttingen, Germany 10.5194/bg-9-5095-2012 Controlling factors of the oxygen balance in the Arabian Sea's OMZ Resplandy L. 1 Lévy M. 2 Bopp L. 1 Echevin V. 2 Pous S. 3 Sarma V. V. S. S. 4 Kumar D. 4 LSCE – Laboratoire des Sciences du Climat et de l'Environnement (CEA, CNRS, UVSQ), UMR8212, IPSL, France LOCEAN – Laboratoire d'Océanographie et du Climat: Experimentation et Approches Numériques (CNRS, IRD, UPMC, MNHN), IPSL, France Museum National d'Histoire Naturelle, Paris, France National Institute of Oceanography, Goa, India 13 12 2012 9 12 5095 5109 Copyright: © 2012 L. Resplandy et al. 2012 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://bg.copernicus.org/articles/9/5095/2012/bg-9-5095-2012.html The full text article is available as a PDF file from https://bg.copernicus.org/articles/9/5095/2012/bg-9-5095-2012.pdf

The expansion of OMZs (oxygen minimum zones) due to climate change and their possible evolution and impacts on the ecosystems and the atmosphere are still debated, mostly because of the unability of global climate models to adequatly reproduce the processes governing OMZs. In this study, we examine the factors controlling the oxygen budget, i.e. the equilibrium between oxygen sources and sinks in the northern Arabian Sea OMZ using an eddy-resolving biophysical model. <br><br> Our model confirms that the biological consumption of oxygen is most intense below the region of highest productivity in the western Arabian Sea. The oxygen drawdown in this region is counterbalanced by the large supply of oxygenated waters originated from the south and advected horizontally by the western boundary current. Although the biological sink and the dynamical sources of oxygen compensate on annual average, we find that the seasonality of the dynamical transport of oxygen is 3 to 5 times larger than the seasonality of the biological sink. In agreement with previous findings, the resulting seasonality of oxygen concentration in the OMZ is relatively weak, with a variability of the order of 15% of the annual mean oxygen concentration in the oxycline and 5% elsewhere. This seasonality primarily arises from the vertical displacement of the OMZ forced by the monsoonal reversal of Ekman pumping across the basin. In coastal areas, the oxygen concentration is also modulated seasonally by lateral advection. Along the western coast of the Arabian Sea, the Somali Current transports oxygen-rich waters originated from the south during summer and oxygen-poor waters from the northeast during winter. Along the eastern coast of the Arabian Sea, we find that the main contributor to lateral advection in the OMZ is the Indian coastal undercurrent that advects southern oxygenated waters during summer and northern low-oxygen waters during winter. In this region, our model indicates that oxygen concentrations are modulated seasonally by coastal Kelvin waves and westward-propagating Rossby waves. <br><br> Whereas on seasonal time scales the sources and sinks of oxygen are dominated by the mean vertical and lateral advection (Ekman pumping and monsoonal currents), on annual time scales we find that the biological sink is counterbalanced by the supply of oxygen sustained by mesoscale structures (eddies and filaments). Eddy-driven advection hence promotes the vertical supply of oxygen along the western coast of the Arabian Sea and the lateral transport of ventilated waters offshore the coast of Oman and southwest India.

 References Aumont, O. and Bopp, L.: Globalizing results from ocean in situ iron fertilization studies, Global Biogeochem. Cy., 20, GB2017, <a href="http://dx.doi.org/10.1029/2005GB002591">https://doi.org/10.1029/2005GB002591</a>, 2006. Aumont, O., Maier-Reimer, E., Blain, S., and Monfray, P.: An ecosystem model of the global ocean including Fe, Si, P colimitations, Global Biogeochem. Cy., 17, 1060, <a href="http://dx.doi.org/10.1029/2001GB001745">https://doi.org/10.1029/2001GB001745</a>, 2003. Banse, K.: Hydrography of the Arabian Sea Shelf of India and Pakistan and effects on demersal fishes, Deep-Sea Research and Oceanographic Abstracts, 15, 45–48, IN7–IN10, 49–79, <a href="http://dx.doi.org/10.1016/0011-7471(68)90028-4">https://doi.org/10.1016/0011-7471(68)90028-4</a>, 1968. Banse, K.: Seasonality of phytoplankton chlorophyll in the central and northern Arabian Sea, Deep-Sea Res. Pt. I, 34, 713–723, <a href="http://dx.doi.org/10.1016/0198-0149(87)90032-X">https://doi.org/10.1016/0198-0149(87)90032-X</a>, 1987. Banse, K.: On the coupling of hydrography, phytoplankton, zooplankton, and settling organic particles offshore in the Arabian Sea, P. Indian AS-Earth, 103, 125–161, 1994. Barnier, B., Madec, G., Penduff, T., Molines, J., Treguier, A., Sommer, J.&nbsp;L., Beckmann, A., Biastoch, A., Boning, C., Dengg, J., Derval, C., Durand, E., Gulev, S., Remy, E., Talandier, C., Theetten, S., Maltrud, M., McClean, J., and Cuevas, B.&nbsp;D.: Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy permitting resolution, Ocean Dynam., 56, 543–567, <a href="http://dx.doi.org/10.1007/s10236-006-0082-1">https://doi.org/10.1007/s10236-006-0082-1</a>, 2006. Bauer, S., Hitchcock, G.&nbsp;L., and Olson, D.&nbsp;B.: Influence of monsoonally-forced Ekman dynamics upon the surface-layer depth and plankton biomass distribution in the Arabian Sea, Deep-Sea Res., 38, 531–553, 1991. Bianchi, D., Dunne, J.&nbsp;P., Sarmiento, J.&nbsp;L., and Galbraith, E.&nbsp;D.: Data-based estimates of suboxia, denitrification, and N<sub>2</sub>O production in the ocean and their sensitivities to dissolved O<sub>2</sub>, Global Biogeochem. Cy., 26, GB2009, <a href="http://dx.doi.org/10.1029/2011GB004209">https://doi.org/10.1029/2011GB004209</a>, 2012. Blanke, B. and Delecluse, P.: Variability of the tropical atlantic ocean simulated by a general circulation model with two different mixed-layer physics, J. Phys. Oceanogr., 23, 1363–1388, 1993. Brink, K., Arnone, R., Coble, P., Flagg, C., Jones, B., Kindle, J., Lee, C., and Phinney, D.: Monsoons boost biological productivity in Arabian Sea, Eos Trans. AGU, 79, 165–169, <a href="http://dx.doi.org/10.1029/98EO00120">https://doi.org/10.1029/98EO00120</a>, 1998. Brock, J.&nbsp;C. and McClain, C.&nbsp;R.: Interannual Variability in Phytoplankton Blooms Observed in the Northwestern Arabian Sea During the Southwest Monsoon, J. Geophys. Res., 97, 733–750, 1992. Brock, J.&nbsp;C., McClain, C.&nbsp;R., Luther, M.&nbsp;E., and Hay, W.&nbsp;W.: The phytoplankton bloom in the northwestern Arabian Sea during the Southwest Monsoon of 1979, J. Geophys. Res., 96, 20623–20642, 1991. Brodeau, L., Barnier, B., Penduff, T., Tréguier, A.-M., and Gulev, S.: An ERA40 based atmospheric forcing for global ocean circulation models, Ocean Model., 31, 88–104, <a href="http://dx.doi.org/10.1016/j.ocemod.2009.10.005">https://doi.org/10.1016/j.ocemod.2009.10.005</a>, 2009. Chaigneaun, A., Eldin, G., and Dewitt, B.: Eddy activity in the four major upwelling systems from altimetry (1992–2007), Progr. Oceanogr., 83, 117–123, 2009. Codispoti, L.&nbsp;A., Brandes, J.&nbsp;A., Christensen, J.&nbsp;P., Devol, A.&nbsp;H., Naqvi, S. W.&nbsp;A., Paerl, H.&nbsp;W., and Yoshinari, T.: The oceanic fixed nitrogen and nitrous oxide budgets: moving targets as we enter the anthropocene?, Sci. Mar., 65, 85–105, 2001. de&nbsp;Sousa, S.&nbsp;N., Kumar, M.&nbsp;D., Sardessai, S., Sarma, V. V. S.&nbsp;S., and Shirodkar, P.&nbsp;V.: Seasonal variability in oxygen and nutrients in the central and eastern Arabian Sea, Curr. Sci., 71, 847–851, 1996. Diaz, R.&nbsp;J. and Rosenberg, R.: Spreading dead zones and consequences for marine ecosystems., Science, 321, 26–29, 2008. Dutkiewicz, S., Follows, M.&nbsp;J., and Parekh, P.: Interactions of the iron and phosphorus cycles: A three-dimensional model study, Global Biogeochem. Cy., 19, GB1021, <a href="http://dx.doi.org/10.1029/2004GB002342">https://doi.org/10.1029/2004GB002342</a>, 2005. Falkowski, P.: Evolution of the nitrogen cycle and its influence on the biological sequestration of CO<sub>2</sub> in the ocean, Nature, 327, 242–244, 1997. Findlater, J.: A major low-level air current near the Indian Ocean during the northern summer, Q. J. R. Meteorol. Soc., 95, 362–380, 1969. Fischer, A.&nbsp;S., Weller, R.&nbsp;A., Rudnick, D.&nbsp;L., Eriksen, C.&nbsp;C., Lee, C.&nbsp;M., Brink, K.&nbsp;H., Fox, C.&nbsp;A., and Leben, R.&nbsp;R.: Mesoscale eddies, coastal upwelling, and the upper-ocean heat budget in the Arabian Sea, Deep-Sea Res. Pt. II, 49, 2231–2264, <a href="http://dx.doi.org/10.1016/S0967-0645(02)00036-X">https://doi.org/10.1016/S0967-0645(02)00036-X</a>, the 1994–1996 Arabian Sea Expedition: Oceanic Response to Monsoonal Forcing, Part 5, 2002. Flagg, C. and Kim, H.-S.: Upper ocean currents in the northern Arabian Sea from shipboard ADCP measurements during the 1994–1996 U.S. JGOFS and ONR programs, Deep-Sea Res. Pt. II, 45, 1917–1960, 1998. Froelicher, T.&nbsp;L., Joos, F., Plattner, G.-K., Steinacher, M., and Doney, S.&nbsp;C.: Natural variability and anthropogenic trends in oceanic oxygen in a coupled carbon cycle–climate model ensemble, Global Biogeochem. Cy., 23, GB1003, <a href="http://dx.doi.org/10.1029/2008GB003316">https://doi.org/10.1029/2008GB003316</a>, 2009. Garrison, D.&nbsp;L., Gowing, M.&nbsp;M., and Hughes, M.&nbsp;P.: Nano- and microplankton in the northern Arabian Sea during the Southwest Monsoon, August–September 1995 A US-JGOFS study, Deep-Sea Res. Pt. II, 45, 2269–2299, <a href="http://dx.doi.org/10.1016/S0967-0645(98)00071-X">https://doi.org/10.1016/S0967-0645(98)00071-X</a>, 1998. Gnanadesikan, A., Dunne, J. P., and John, J.: Understanding why the volume of suboxic waters does not increase over centuries of global warming in an Earth System Model, Biogeosciences, 9, 1159–1172, <a href="http://dx.doi.org/10.5194/bg-9-1159-2012">https://doi.org/10.5194/bg-9-1159-2012</a>, 2012. Han, W., McCreary, J.&nbsp;P., masumoto, Y., Vialard, J., and Duncan, B.: Basin modes in the equatorial Indian Ocean, J. Phys. Oceanogr., 41, 1252–1270, 2011. Hitchcock, G.&nbsp;L., Key, E.&nbsp;L., and Masters, J.: The fate of upwelled waters in the Great Whirl, August 1995, Deep-Sea Res. Pt. II, 47, 1605–1621, <a href="http://dx.doi.org/10.1016/S0967-0645(99)00156-3">https://doi.org/10.1016/S0967-0645(99)00156-3</a>, 2000. Honjo, S., Dymond, J., Prell, W., and Ittekkot, V.: Monsoon-controlled export fluxes to the interior of the Arabian Sea, Deep-Sea Res. Pt. II, 46, 1859–1902, <a href="http://dx.doi.org/10.1016/S0967-0645(99)00047-8">https://doi.org/10.1016/S0967-0645(99)00047-8</a>, 1999. Kawamiya, M.: Mechanism of offshore nutrient supply in the western Arabian Sea, J. Mar. Res., 59, 675–696, 2001. Keeling, R.&nbsp;F., Koertzinger, A., and Gruber, N.: Ocean Deoxygenation in a warming world, Annu. Rev. Mar. Sci., 2, 199–229, <a href="http://dx.doi.org/10.1146/annurev.marine.010908.163855">https://doi.org/10.1146/annurev.marine.010908.163855</a>, 2010. Keen, T., Kindle, J., and Young, D.: The interaction of Southwest Monsoon upwelling, advection and primary production in the northwest Arabian Sea, J. Mar. Syst., 13, 61–82, 1997. Kim, H.-S., Flagg, C. N., and Howden, S.: Northern {Arabian} Sea variability from TOPEX/Poseidon altimetry data, An extension of the JGOFS/ONR shipboard ADCP study, Deep-Sea Res. Pt. II, 48, 1069–1096, 2001. Klein, P., Hua, B.&nbsp;L., Lapeyre, G., Capet, X., Gentil, S.&nbsp;L., and Sasaki, H.&nbsp;S.: Upper ocean turbulence from high 3-d resolution simulations, J. Phys. Oceanogr., 38, 1748–1763, 2008. Koné, V., Aumont, O., Lévy, M., and Resplandy, L.: Physical and Biogeochemical Controls of the Phytoplankton Seasonal Cycle in the Indian Ocean}: a modeling study, in: {Indian Ocean Biogeochemical Processes and Ecological Variability, edited by: Wiggert, J.&nbsp;D., Hood, R.&nbsp;R., Naqvi, S. W.&nbsp;A., Brink, K.&nbsp;H., and Smith, S.&nbsp;L., 185, 147–166, American Geophysical Union, Washington DC, USA, 2009. Lam, P., Jensen, M. M., Kock, A., Lettmann, K. A., Plancherel, Y., Lavik, G., Bange, H. W., and Kuypers, M. M. M.: Origin and fate of the secondary nitrite maximum in the Arabian Sea, Biogeosciences, 8, 1565–1577, <a href="http://dx.doi.org/10.5194/bg-8-1565-2011">https://doi.org/10.5194/bg-8-1565-2011</a>, 2011. Lee, C.&nbsp;M., Jones, B.&nbsp;H., Brink, K.&nbsp;H., and Fischer, A.&nbsp;S.: The upper-ocean response to monsoonal forcing in the {Arabian Sea}: seasonal and spatial variability, Deep-Sea Res. Pt. II, 47, 1177–1226, 2000. Levin, L. A., Ekau, W., Gooday, A. J., Jorissen, F., Middelburg, J. J., Naqvi, S. W. A., Neira, C., Rabalais, N. N., and Zhang, J.: Effects of natural and human-induced hypoxia on coastal benthos, Biogeosciences, 6, 2063–2098, <a href="http://dx.doi.org/10.5194/bg-6-2063-2009">https://doi.org/10.5194/bg-6-2063-2009</a>, 2009. Levitus, S., Boyer, T., Conkright, M., O'Brian, T., Antonov, J., Stephens, C., Stathopolos, L., Johnson, D., and Gelfeld, R.: World Ocean database 1998, Technical Report NESDID18, NOAA Atlas, 1998. Lévy, M., Estubier, A., and Madec, G.: Choice of an advection scheme for biogeochemical models, Geophys. Res. Lett., 28, 3725–3728, 2001. Lévy, M., Shankar, D., André, J.-M., Shenoi, S. S.&nbsp;C., Durand, F., and de&nbsp;Boyer&nbsp;Montégut, C.: Basin-wide seasonal evolution of the Indian Ocean's phytoplankton blooms, J. Geophys. Res., 112, C12014, <a href="http://dx.doi.org/10.1029/2007JC004090">https://doi.org/10.1029/2007JC004090</a>, 2007. Lévy, M., Klein, P., Tréguier, A.-M., Iovino, D., Madec, G., Masson, S., and Takahashi, K.: Modifications of gyre circulation by sub-mesoscale physics, Ocean Model., 34, 1–15, <a href="http://dx.doi.org/10.1016/j.ocemod.2010.04.001">https://doi.org/10.1016/j.ocemod.2010.04.001</a>, 2010. Lierheimer, L.&nbsp;J. and Banse, K.: Seasonal and interannual variability of phytoplankton pigment in the Laccadive (Lakshadweep) Sea as observed by the Coastal Zone Color Scanner, P. Indian AS-Earth, 111, 163–185, 2002. Madec, G.: NEMO, the ocean engine, Note du Pole de modelisation, Institut Pierre-Simon Laplace (IPSL), France, No 27 ISSN No 1288–1619, available at: <a href="www.nemo-ocean.eu/About-NEMO/Reference-manuals">www.nemo-ocean.eu/About-NEMO/Reference-manuals</a>, 2008. Madhupratap, S. P.&nbsp;K., Bhattathiri, P. M.&nbsp;A., Kumar, M.&nbsp;D., Raghukumar, S., Nair, K. K.&nbsp;C., and Ramaiah, N.: Mechanism of the biological response to winter cooling in the northern Arabian Sea, Nature, 384, 549–552, 1996. Manghnani, V., Morrison, J.&nbsp;M., Hopkins, T.&nbsp;S., and Böhm, E.: Advection of upwelled waters in the form of plumes off Oman during the Southwest Monsoon, Deep-Sea Res. Pt. II, 45, 2027–2052, 1998. Marchesiello, P., McWilliams, J.&nbsp;C., and Shchepetkin, A.: Equilibrium structure and dynamics of the California Current System, J. Phys. Oceanogr., 33, 753–783, 2004. Marra, J., Dickey, T.&nbsp;D., Ho, C., Kinkade, C.&nbsp;S., Sigurdson, D.&nbsp;E., Weller, R.&nbsp;A., and Barber, R.&nbsp;T.: Variability in primary production as observed from moored sensors in the central Arabian Sea in 1995, Deep-Sea Res. Pt. II, 45, 2253–2267, <a href="http://dx.doi.org/10.1016/S0967-0645(98)00070-8">https://doi.org/10.1016/S0967-0645(98)00070-8</a>, 1998. McCreary, J.&nbsp;P., Kundu, P.&nbsp;K., and Molinari, R.&nbsp;L.: A numerical investigation of dynamics, thermodynamics and mixed-layer processes in the Indian Ocean, Progr. Oceanogr., 31, 181–244, <a href="http://dx.doi.org/10.1016/0079-6611(93)90002-U">https://doi.org/10.1016/0079-6611(93)90002-U</a>, 1993. McCreary, J.&nbsp;P., Yu, Z., Hood, R., Vinaychandran, P.&nbsp;N., Furue, R., Ishida, A., and Richards, K.: Dynamics of the Indian-Ocean oxygen minimum zones, Progr. Oceanogr., accepted, 2012. Moore, J.&nbsp;K., Doney, S.&nbsp;C., and Lindsay, K.: Upper ocean ecosystem dynamics and iron cycling in a global three-dimensional model, Global Biogeochem. Cy., 18, GB4028, <a href="http://dx.doi.org/10.1029/2004GB002220">https://doi.org/10.1029/2004GB002220</a>, 2004. Morrison, J.&nbsp;M., Codispoti, L.&nbsp;A., Smith, S.&nbsp;L., Wishner, K., Flagg, C., Gardner, W.&nbsp;D., Gaurin, S., Naqvi, S. W.&nbsp;A., Manghnani, V., Prosperie, L., and Gundersen, J.&nbsp;S.: The oxygen minimum zone in the Arabian Sea during 1995 - overall seasonal and geographic patterns, and relationship to oxygen gradients, Deep-Sea Res. Pt. II, 46, 1903–1931, <a href="http://dx.doi.org/10.1016/S0967-0645(99)00048-X">https://doi.org/10.1016/S0967-0645(99)00048-X</a>, 1999. Naqvi, S. W.&nbsp;A., Yoshinari, T.&nbsp;Naik, H., Jayakumar, D.&nbsp;A., Altabet, M.&nbsp;A., Narvekar, P., Devol, A., Brandes, J.&nbsp;A., and Codispoti, L.&nbsp;A.: Budgetary and biogeochemical implications of N<sub>2</sub>O isotope signatures in the Arabian Sea, Nature, 394, 462–464, 1998. Naqvi, S. W. A., Naik, H., Pratihary, A., D'Souza, W., Narvekar, P. V., Jayakumar, D. A., Devol, A. H., Yoshinari, T., and Saino, T.: Coastal versus open-ocean denitrification in the Arabian Sea, Biogeosciences, 3, 621–633, <a href="http://dx.doi.org/10.5194/bg-3-621-2006">https://doi.org/10.5194/bg-3-621-2006</a>, 2006. Nethery, D. and Shankar, D.: Vertical propagation of baroclinic Kelvin waves along the west coast of India, J. Earth Syst. Sc., 116, 331–339, 2007. Olson, D.&nbsp;B., Hitchcock, G.&nbsp;L., Fine, R.&nbsp;A., and Warren, B.&nbsp;A.: Maintenance of the low-oxygen layer in the central Arabian Sea, Deep-Sea Res. Pt. II, 40, 673–685, <a href="http://dx.doi.org/10.1016/0967-0645(93)90051-N">https://doi.org/10.1016/0967-0645(93)90051-N</a>, 1993. Paulmier, A. and Ruiz-Pino, D.: Oxygen minimum zones (OMZs) in the modern ocean, Progr. Oceanogr., 80, 113–128, <a href="http://dx.doi.org/10.1016/j.pocean.2008.08.001">https://doi.org/10.1016/j.pocean.2008.08.001</a>, 2009. Prakash, S., Balakrishnan&nbsp;Nair, T.&nbsp;M., Udaya&nbsp;Bhaskar, T., Prakash, P., and Gilbert, D.: Oxycline variability in the central Arabian Sea: an Argo-oxygen study, J. Sea Res., 71, 1–8, 2012. Rao, R., Molinari, R., and Festa, J.: Evolution of the Climatological Near-Surface Thermal Structure of the Tropical Indian Ocean 1. {D}escription of Mean Monthly Mixed Layer Depth, and Sea Surface Temperature, Surface Current, and Surface Meteorological Fields, J. Geophys. Res., 94, 10801–10815, 1989. Resplandy, L., Lévy, M., Madec, G., Pous, S., Aumont, O., and Kumar, D.: Contribution of mesoscale processes to nutrient budgets in the Arabian Sea, J. Geophys. Res., 116, C11007, <a href="http://dx.doi.org/10.1029/2011JC007006">https://doi.org/10.1029/2011JC007006</a>, 2011. Ryther, J.&nbsp;H. and Menzel, D.&nbsp;W.: On the production, composition, and distribution of organic matter in the Western Arabian Sea, Deep-Sea Res. Pt. I, 12, 199–209, 1965. Sarma, V. V. S.&nbsp;S.: An evaluation of physical and biogeochemical processes regulating perennial suboxic conditions in the water column of the Arabian Sea, Global Biogeochem. Cy., 16, 1082, <a href="http://dx.doi.org/10.1029/2001GB001461">https://doi.org/10.1029/2001GB001461</a>, 2002. Sarmiento, J.&nbsp;L., Hughes, T. M.&nbsp;C., Stouffer, R.&nbsp;J., and Manabe, S.: Simulated response of the ocean carbon cycle to anthropogenic climate warming, Nature, 393, 245–249, 1998. Schott, F.&nbsp;A. and McCreary, J.&nbsp;P.: The monsoon circulation of the Indian Ocean, Progr. Oceanogr., 51, 1–123, 2001. Shchepetkin, A.&nbsp;F. and McWilliams, J.&nbsp;C.: The regional oceanic modeling system {(ROMS)}: a split-explicit, free-surface, topography-following-coordinate oceanic model, Ocean Model., 9, 347–404, <a href="http://dx.doi.org/10.1016/j.ocemod.2004.08.002">https://doi.org/10.1016/j.ocemod.2004.08.002</a>, 2005. Shetye, S.&nbsp;R., Gouveia, A.&nbsp;D., Shenoi, S. S.&nbsp;C., Sundar, D., Michael, G.&nbsp;S., Almeida, A.&nbsp;M., and Santanam, K.: Hydrography and circulation off the West coast of India during the Southwest monsoon 1987, J. Mar. Res., 48, 359–378, 1990. Stramma, L., Johnson, G.&nbsp;C., Sprintall, J., and Mohrholz, V.: Expanding Oxygen-Minimum Zones in the Tropical Oceans, Science, 320, 655–658, <a href="http://dx.doi.org/10.1126/science.1153847">https://doi.org/10.1126/science.1153847</a>, 2008. Stramma, L., Prince, E.&nbsp;D., Schmidtko, S., Luo, J., Hoolihan, J.&nbsp;P., Visbeck, M., Wallace, D. W.&nbsp;R., Brandt, P., and Koertzinger, A.: Expansion of oxygen minimum zones may reduce available habitat for tropical pelagic fishes, Nat. Clim. Change, 2, 33–37, <a href="http://dx.doi.org/10.1038/nclimate1304">https://doi.org/10.1038/nclimate1304</a>, 2011. Stramma, L., Oschlies, A., and Schmidtko, S.: Mismatch between observed and modeled trends in dissolved upper-ocean oxygen over the last 50 yr, Biogeosciences, 9, 4045–4057, <a href="http://dx.doi.org/10.5194/bg-9-4045-2012">https://doi.org/10.5194/bg-9-4045-2012</a>, 2012. Sverdrup, H., U., Johnson, M.&nbsp;W., and Fleming, R.&nbsp;H.: The Ocean: Their Physics, Chemistry and General Biology, Prentice-Hall, p. 696, old Tappan, 1942. Swallow, J., C.: Some aspects of the physical oceanography of the Indian Ocean, Deep-Sea Res., 31, 639–650, 1984. Takahashi, T., Broecker, W.&nbsp;S., and Langer, S.: Redfield ratio based on chemical data from isopycnal surfaces, J. Geophys. Res., 90, 6907–6924, 1985. Treguier, A., Barnier, B., de&nbsp;Miranda, A., Molines, J.&nbsp;M., Grima, N., Imbard, M., Madec, G., Messager, C., Reynaud, T., and Michel, S.: An eddy-permitting model of the {Atlantic circulation}: Evaluating open boundary conditions, J. Geophys. Res., 106, 22115–22129, 2001. Van&nbsp;Leer, B.: Towards the Ultimate Conservative Difference Scheme, V. a Second Order Sequel to Godunov's Method, J. Comput. Phys., 32, 101–136, 1979. Veldhuis, M. J.&nbsp;W., Kraay, G.&nbsp;W., Bleijswijk, J. D. L.&nbsp;V., and Baars, M.&nbsp;A.: Seasonal and spatial variability in phytoplankton biomass, productivity and growth in the northwestern Indian Ocean}: the {Southwest and Northeast Monsoon, 1992-1993, Deep-Sea Res. Pt. I, 44, 425–449, <a href="http://dx.doi.org/10.1016/S0967-0637(96)00116-1">https://doi.org/10.1016/S0967-0637(96)00116-1</a>, 1997. Weller, R.&nbsp;A., Fischer, A.&nbsp;S., Rudnick, D.&nbsp;L., Eriksen, C.&nbsp;C., Dickey, T.&nbsp;D., Marra, J., Fox, C., and Leben, R.: Moored observations of upper-ocean response to the monsoons in the Arabian Sea during 1994–1995, Deep-Sea Res. Pt. II, 49, 2195–2230, <a href="http://dx.doi.org/10.1016/S0967-0645(02)00035-8">https://doi.org/10.1016/S0967-0645(02)00035-8</a>, the 1994–1996 Arabian Sea Expedition: Oceanic Response to Monsoon al Forcing, Part 5, 2002. Wiggert, J.&nbsp;D. and Murtugudde, R.&nbsp;G.: The sensitivity of the southwest monsoon phytoplankton bloom to variations in aeolian iron deposition over the Arabian Sea, J. Geophys. Res., 112, C05005, <a href="http://dx.doi.org/10.1029/2006JC003514">https://doi.org/10.1029/2006JC003514</a>, 2007. Wiggert, J.&nbsp;D., Hood, R., Banse, K., and Kindle, J.: Monsoon-driven biogeochemical processes in the Arabian Sea, Progr. Oceanogr., 65, 176–213, <a href="http://dx.doi.org/10.1016/j.pocean.2005.03.008">https://doi.org/10.1016/j.pocean.2005.03.008</a>, the Arabian Sea of the 1990s: New Biogeochemical Understanding, 2005.