Hostname: page-component-848d4c4894-m9kch Total loading time: 0 Render date: 2024-06-02T14:50:26.029Z Has data issue: false hasContentIssue false
  • English
  • Français

Decadal Variations in Oceanic Properties of the Arabian Sea Water Column since Geosecs

Published online by Cambridge University Press:  26 July 2016

Ravi Bhushan ,
Koushik Dutta ,
Rajesh Agnihotri ,
R Rengarajan  and
Satinder Pal Singh
Ravi Bhushan*
Affiliation:
Geosciences Division, Physical Research Laboratory, Ahmedabad 38009, India
Koushik Dutta
Affiliation:
Geosciences Division, Physical Research Laboratory, Ahmedabad 38009, India Department of Earth and Planetary Sciences, Northwestern University, Evanston, Illinois 60208, USA
Rajesh Agnihotri
Affiliation:
Geosciences Division, Physical Research Laboratory, Ahmedabad 38009, India Radio and Atmospheric Science Division, National Physical Laboratory, New Delhi 110012, India
R Rengarajan
Affiliation:
Geosciences Division, Physical Research Laboratory, Ahmedabad 38009, India
Satinder Pal Singh
Affiliation:
Geosciences Division, Physical Research Laboratory, Ahmedabad 38009, India
*
2.Corresponding author. Email: bhushan@prl.res.in.
Get access Rights & Permissions [Opens in a new window]

Abstract

This article reports temporal changes in the measured oceanic geochemical properties of the Arabian Sea and the equatorial Indian Ocean by reoccupying six stations investigated during the GEOSECS expedition in 1977 and 1978. Observed differences are interpreted in terms of plausible changes in the environment and climate that have occurred in response to natural or anthropogenic processes. The depth profiles of major parameters such as dissolved oxygen, ΣCO2, major nutrients (silicates, nitrates, and phosphates), and radiocarbon in dissolved inorganic carbon were measured during the cruises between 1994 and 1998 along with temperature and salinity. Most stations in the Arabian Sea show an increase in salinity by ∼0.2 to 0.3 salinity units in the top 400 m, whereas one station in the equatorial Indian Ocean showed a decrease in salinity by ∼0.1 units, indicating a likely change in the evaporation-precipitation (E-P) balance. The ΣCO2 increased by an average of 8 μM within the top 1200 m of the Arabian Sea. The depth profiles of nitrates and dissolved oxygen for the central Arabian Sea stations show significant variations, while only marginal changes are seen for silicates and phosphates relative to the GEOSECS data. The decrease in Δ14C of surface waters is due to the steady decrease in atmospheric 14C concentration since GEOSECS, and the Δ14C increase in subsurface waters is attributed to the downward vertical diffusion of bomb 14C interpreted in terms of atmosphere to ocean transfer and lateral advection of water masses.

Type
Articles
Information
Radiocarbon , Volume 56 , Issue 1 , 2014 , pp. 313 - 325
Copyright
Copyright © 2014 by the Arizona Board of Regents on behalf of the University of Arizona 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Agnihotri, R, Kurian, S, Fernandes, M, Reshma, K, D'Souza, W, Naqvi, SWA. 2008. Variability of subsurface denitrification and surface productivity in the coastal eastern Arabian Sea over the past seven centuries. The Holocene 18(5):755–64.CrossRefGoogle Scholar
Anderson, DM, Overpeck, JT, Gupta, AK. 2002. Increase in the Asian Southwest Monsoon during the past four centuries. Science 297(5581):596–9.CrossRefGoogle ScholarPubMed
Bard, E, Arnold, M, Ostlund, GH, Maurice, P, Monfray, P, Duplessy, JC. 1988. Penetration of bomb radiocarbon in the tropical Indian ocean measured by means of accelerator mass spectrometry. Earth and Planetary Science Letters 87(4):379–89.CrossRefGoogle Scholar
Bard, E, Arnold, M, Toggweiler, JR, Maurice, P, Duplessy, J-C. 1989. Bomb 14C in the Indian ocean measured by accelerator mass spectrometry: oceanographic implications. Radiocarbon 31(3):510–22.Google Scholar
Bhushan, R, Chakraborty, S, Krishnaswami, S. 1994. Physical Research Laboratory (Chemistry) radiocarbon date list I. Radiocarbon 36(2):251–6.Google Scholar
Bhushan, R, Krishnaswami, S, Somayajulu, BLK. 1997. 14C in air over the Arabian Sea. Current Science 73(3):273–6.Google Scholar
Bhushan, R, Somayajulu, BLK, Chakraborty, S, Krishnaswami, S. 2000. Radiocarbon in the Arabian Sea water column: temporal variations in bomb 14C inventory since the GEOSECS and the CO2 air-sea exchange studies. Journal of Geophysical Research 105(C6):14,273–82.CrossRefGoogle Scholar
Bhushan, R, Dutta, K, Mulsow, S, Povinec, PP, Somayajulu, BLK. 2003. Distribution of natural and man-made radionuclides during the reoccupation of GEOSECS stations 413 and 416 in the Arabian Sea: temporal changes. Deep Sea Research II 50(17–21):2777–84.CrossRefGoogle Scholar
Bower, AS, Hunt, HD, Price, JF. 2000. Character and dynamics of the Red Sea and Persian Gulf outflows. Journal of Geophysical Research 105(C3):6387–414.Google Scholar
Carpenter, JH. 1965. The Chesapeake Bay Institute technique for the Winkler dissolved oxygen method. Limnology and Oceanography 10(1):141–3.Google Scholar
Chakraborty, S, Dutta, K, Bhattacharyya, A, Nigam, M, Schuur, EAG, Shah, SK. 2008. Atmospheric 14C variability recorded in tree rings from peninsular India: implications for fossil fuel CO2 emission and atmospheric transport. Radiocarbon 50(3):321–30.CrossRefGoogle Scholar
Currie, RI, Fisher, AE, Hargreaves, PM. 1973. Arabian Sea upwelling. In: Zeitzschel, B, Gerlach, SA, editors. The Biology of the Indian Ocean, Volume 3. New York: Springer. p 37–52.CrossRefGoogle Scholar
Dickson, AG, Goyet, C, editors. 1994. Handbook of Methods for the Analysis of the Various Parameters of the Carbon Dioxide System in Seawater, Version 2. CDIAC-74, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.Google Scholar
Duce, RA, LaRoche, J, Altieri, K, Arrigo, KR, Baker, AR, Capone, DG, Cornell, S, Dentener, F, Galloway, J, Ganeshram, RS, Geider, RJ, Jickells, T, Kuypers, MM, Langlois, R, Liss, PS, Liu, SM, Middelburg, JJ, Moore, CM, Nickovic, S, Oschlies, A, Pedersen, T, Prospero, J, Schlitzer, R, Seitzinger, S, Sorensen, LL, Uematsu, M, Ulloa, O, Voss, M, Ward, B, Zamora, L. 2008. Impacts of atmospheric anthropogenic nitrogen on the open ocean. Science 320(5878):893–7.CrossRefGoogle ScholarPubMed
Durack, PJ, Wijffels, SE, Matear, RJ. 2012. Ocean salinities reveal strong global water cycle intensification during 1950 to 2000. Science 336(6080):455–8.CrossRefGoogle ScholarPubMed
Dutta, K, Bhushan, R. 2012. Radiocarbon in the Northern Indian Ocean two decades after GEOSECS. Global Biogeochemical Cycles 26: GB2018, doi:10.1029/2010GB004027.CrossRefGoogle Scholar
Dutta, K, Bhushan, R, Somayajulu, BLK, Rastogi, N. 2006. Inter-annual variation in atmospheric Δ14C over the Northern Indian Ocean. Atmospheric Environment 40(24):4501–12.CrossRefGoogle Scholar
Goes, JI, Thoppil, PG, Gomes, H do R, Fasullo, JT. 2005. Warming of the Eurasian landmass is making the Arabian Sea more productive. Science 308(5721):545–7.CrossRefGoogle ScholarPubMed
Hupe, A, Karstensen, J. 2000. Redfield stoichiometry in Arabian Sea subsurface waters. Global Biogeochemical Cycles 14(1):357–72.CrossRefGoogle Scholar
Johnson, KM, King, AE, Seiburth, JM. 1985. Coulometric TCO2 analyses for marine studies; an introduction. Marine Chemistry 16(1):61–82.CrossRefGoogle Scholar
Keller, K, Slater, RD, Bender, M, Key, RM. 2002. Possible biological or physical explanations for decadal scale trends in North Pacific nutrient concentrations and oxygen utilization. Deep-Sea Research II 49(1–3):345–62.Google Scholar
Mitra, AP, Dileep Kumar, M, Kumar, KR, Abrol, YP, Kalra, N, Velayutham, M, Naqvi, SWA. 2002. Global change and biogeochemical cycles: the south Asia region. In: Tyson, P, Fuchs, R, Fu, C, Lebel, L, Mitra, AP, Odada, E, Perry, J, Steffen, W, Virji, H, editors. Global-Regional Linkages in the Earth System. Berlin: Springer. p 75–107.CrossRefGoogle Scholar
Naqvi, SWA. 1994. Denitrification processes in the Arabian Sea. Proceedings of the Indian Academy of Sciences 103(2):279–300.Google Scholar
Naqvi, SWA, Jayakumar, DA, Narvekar, PV, Naik, H, Sarma, VVSS, D'Souza, W, Joseph, S, George, MD. 2000. Increased marine production of N2O due to intensifying anoxia on the Indian continental shelf. Nature 408(6810):346–9.CrossRefGoogle ScholarPubMed
Naqvi, SWA, Naik, H, Pratihary, A, D'Souza, W, Narvekar, PV, Jayakumar, DA, Devol, AH, Yoshinari, T, Saino, T. 2006. Coastal versus open-ocean denitrification in the Arabian Sea. Biogeosciences 3:621–33.Google Scholar
Pahlow, M, Riebesell, U. 2000. Temporal trends in deep ocean Redfield ratios. Science 287(5454):831–3.CrossRefGoogle ScholarPubMed
Prasanna Kumar, S, Muraleedharan, PM, Prasad, TG, Gauns, M, Ramaiah, N, de Souza, SN, Sardesai, S, Madhupratap, M. 2002. Why is the Bay of Bengal less productive during summer monsoon compared to the Arabian Sea? Geophysical Research Letters 29:2235, doi:10.1029/2002GL016013.CrossRefGoogle Scholar
Sabine, CL, Key, RM, Johnson, KM, Millero, FJ, Poisson, A, Sarmiento, JL, Wallace, DWR, Winn, CD. 1999. Anthropogenic CO2 in the Indian Ocean. Global Biogeochemical Cycles 13(1):179–98.CrossRefGoogle Scholar
Shankar, D, Vinayachandran, PN, Unnikrishnan, AS. 2002. The monsoon currents in the north Indian Ocean. Progress in Oceanography 52(1):63–120.CrossRefGoogle Scholar
Shetye, SR, Gouveia, AD, Shenoi, SSC. 1994. Circulation of the water masses of the Arabian Sea. Proceedings of the Indian Academy of Sciences 103(2):107–23.Google Scholar
Somayajulu, BLK, Bhushan, R, Narvekar, PV. 1999. Δ14C, ΣCO2 and salinity of the western Indian Ocean deep waters: spatial and temporal variations. Geophysical Research Letters 26(18):2869–72.CrossRefGoogle Scholar
Stramma, L, Schmidtko, S, Levin, LA, Johnson, GC. 2010. Ocean oxygen minima expansions and their biological impacts. Deep-Sea Research I 57(4):587–95.Google Scholar
Strickland, JDH, Parsons, TR. 1972. A Practical Handbook of Sea-water Analysis. Ottawa: Fisheries Research Board of Canada.Google Scholar
Stuiver, M, Östlund, HG. 1983. GEOSECS Indian Ocean and Mediterranean radiocarbon. Radiocarbon 25(1):1–29.CrossRefGoogle Scholar
Stuiver, M, Polach, HA. 1977. Discussion: reporting of 14C data. Radiocarbon 19(3):355–63.CrossRefGoogle Scholar