Evidence for the existence of Persian Gulf Water and Red Sea Water in the Bay of Bengal


The high-salinity water masses that originate in the North Indian Ocean are Arabian Sea High-Salinity Water (ASHSW), Persian Gulf Water (PGW), and Red Sea Water (RSW). Among them, only ASHSW has been shown to exist in the Bay of Bengal. We use CTD data from recent cruises to show that PGW and RSW also exist in the bay. The presence of RSW is marked by a deviation of the salinity vertical profile from a fitted curve at depths ranging from 500 to 1000 m; this deviation, though small (of the order of ~0.005 psu and therefore comparable to the CTD accuracy of 0.003 psu), is an order of magnitude larger than the ~0.0003 psu fluctuations associated with the background turbulence or instrument noise in this depth regime, allowing us to infer the existence of RSW throughout the bay. PGW is marked by the presence of a salinity maximum at 200–450 m; in the southwestern bay, PGW can be distinguished from the salinity maximum due to ASHSW because of the intervening Arabian Sea Salinity Minimum. This salinity minimum and the maximum associated with ASHSW disappear east and north of the south-central bay (85°E, 8°N) owing to mixing between the fresher surface waters that are native to the bay (Bay of Bengal Water or BBW) with the high-salinity ASHSW. Hence, ASHSW is not seen as a distinct water mass in the northern and eastern bay and the maximum salinity over most of the bay is associated with PGW. The surface water over most of the bay is therefore a mixture of ASHSW and the low-salinity BBW. As a corollary, we can also infer that the weak oxygen peak seen within the oxygen-minimum zone in the bay at a depth of 250–400 m is associated with PGW. The hydrographic data also show that these three high-salinity water masses are advected into the bay by the Summer Monsoon Current, which is seen to be a deep current extending to 1000 m. These deep currents extend into the northern bay as well, providing a mechanism for spreading ASHSW, PGW, and RSW throughout the bay.

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We thank Satheesh Shenoi and Virupaxa Banakar for useful discussions on water masses and T. V. S. Udaya Bhaskar for clarifications on Argo protocols. This paper has benefitted considerably from the critical comments from Julian McCreary and three anonymous reviewers. We thank the masters, officers, and crew of all the cruises for their assistance, and the personnel from Elcome Marine (for SK-175), Norinco (for SN-065 and SK-296), and the CSIR-NIO ship cell (Mahesh Korgaonkar and Buddhadas Patole for SSK-047, Shashikant Velip and M. Kalliathan for SSK-062, and Santosh Gawas and Amey Kambli for SSK-070) for their assistance in collecting the CTD data. DS acknowledges the contribution of his colleagues on cruise SK-175 (M. Dileep Kumar, P. S. Rao, Y. K. Somayajulu, U Chit Kyaw, U Ye Lwin, and Comdr. S. K. Mishra) in collecting the CTD data. The Argo data were collected and made freely available by the International Argo Program and the national programmes that contribute to it (, The Argo Programme is part of the Global Ocean Observing System. Ferret was used extensively for analysis and GMT (Generic Mapping Tools) for graphics. Funding for this work came from the Ministry of Earth Sciences (Government of India) through their CTCZ (Continental Tropical Convergence Zone) programme; additional support was provided by CSIR (Council of Scientific and Industrial Research, New Delhi) through the programme OCEAN FINDER. VJ acknowledges funding support from CSIR and Charls Antony’s help with GMT. This is CSIR-NIO contribution 5916 and ESSO-INCOIS contribution 262. We dedicate this paper to Bhuvaneshwari Sridhar, our young colleague on SN-065, who passed away in a tragic accident in March 2014.

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Jain, V., Shankar, D., Vinayachandran, P.N. et al. Evidence for the existence of Persian Gulf Water and Red Sea Water in the Bay of Bengal. Clim Dyn 48, 3207–3226 (2017).

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  • Water masses
  • Indian Ocean
  • Arabian Sea High-Salinity Water
  • Persian Gulf Water
  • Red Sea Water
  • Oxygen minimum zone
  • Summer Monsoon Current
  • CTD