Articles | Volume 13, issue 6
Ocean Sci., 13, 1035–1044, 2017
https://doi.org/10.5194/os-13-1035-2017
Ocean Sci., 13, 1035–1044, 2017
https://doi.org/10.5194/os-13-1035-2017

Research article 07 Dec 2017

Research article | 07 Dec 2017

An undercurrent off the east coast of Sri Lanka

Arachaporn Anutaliya1, Uwe Send1, Julie L. McClean1, Janet Sprintall1, Luc Rainville2, Craig M. Lee2, S. U. Priyantha Jinadasa3, Alan J. Wallcraft4, and E. Joseph Metzger5 Arachaporn Anutaliya et al.
  • 1Scripps Institution of Oceanography, La Jolla, California, USA
  • 2Applied Physics Laboratory, University of Washington, Seattle, Washington, USA
  • 3National Aquatic Resources Research and Development Agency (NARA) Crow Island, Colombo 15, Sri Lanka
  • 4Center for Ocean–Atmospheric Prediction Studies (COAPS), Florida State University, Tallahassee, Florida, USA
  • 5Naval Research Laboratory, Stennis Space Center, Mississippi, USA

Abstract. The existence of a seasonally varying undercurrent along 8° N off the east coast of Sri Lanka is inferred from shipboard hydrography, Argo floats, glider measurements, and two ocean general circulation model simulations. Together, they reveal an undercurrent below 100–200 m flowing in the opposite direction to the surface current, which is most pronounced during boreal spring and summer and switches direction between these two seasons. The volume transport of the undercurrent (200–1000 m layer) can be more than 10 Sv in either direction, exceeding the transport of 1–6 Sv carried by the surface current (0–200 m layer). The undercurrent transports relatively fresher water southward during spring, while it advects more saline water northward along the east coast of Sri Lanka during summer. Although the undercurrent is potentially a pathway of salt exchange between the Arabian Sea and the Bay of Bengal, the observations and the ocean general circulation models suggest that the salinity contrast between seasons and between the boundary current and interior is less than 0.09 in the subsurface layer, suggesting a small salt transport by the undercurrent of less than 4 % of the salinity deficit in the Bay of Bengal.

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Short summary
Observations and numerical models reveal the existence of the subsurface current in the opposite direction to the surface current off the Sri Lankan east coast. The undercurrent (200–1000 m layer) is most pronounced during the boreal spring and summer and transports more mass than the surface layer (0–200 m). Although the undercurrent is potentially a pathway of salt exchange between the Arabian Sea and the Bay of Bengal, the data and models suggest little salt transport by the undercurrent.