Dynamics of the East India Coastal Current: 2. Numerical solutions

McCreary, Julian P.; Han, Weiqing; Shankar, D.; Shetye, S.R.

doi:10.1029/96jc00560

Cited by 237 publications

(216 citation statements)

References 18 publications

(3 reference statements)

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“…Anomalous easterlies in the equatorial band force upwelling equatorial Kelvin waves that shoal the OCD and TCD in the EEIO. These signals further propagate around the rim of the bay as upwelling coastal Kelvin waves, thereby shoaling the TCD and OCD there (e.g., McCreary et al, 1993McCreary et al, , 1996Aparna et al, 2012). Similar to what happens on the seasonal scale , easterly zonal wind stress anomalies in the vicinity of Sri Lanka and the STI force a downwelling coastal Kelvin wave that propagates poleward along the western Indian coastline, resulting in a deepening of the TCD and OCD there.…”

Section: Physical Control Of the Interannual Oxygen Variability Off Tmentioning

confidence: 97%

Positive Indian Ocean Dipole events prevent anoxia off the west coast of India

et al. 2017

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Abstract. The seasonal upwelling along the west coast of India (WCI) brings nutrient-rich, oxygen-poor subsurface waters to the continental shelf, favoring very low oxygen concentrations in the surface waters during late boreal summer and fall. This yearly-recurring coastal hypoxia is more severe during some years, leading to coastal anoxia that has strong impacts on the living resources. In the present study, we analyze a 1/4 • resolution coupled physical-biogeochemical regional oceanic simulation over the 1960-2012 period to investigate the physical processes influencing the oxycline interannual variability off the WCI, that being a proxy for the variability on the shelf in our model. Our analysis indicates a tight relationship between the oxycline and thermocline variations in this region on both seasonal and interannual timescales, thereby revealing a strong physical control of the oxycline variability. As in observations, our model exhibits a shallow oxycline and thermocline during fall that combines with interannual variations to create a window of opportunity for coastal anoxic events. We further demonstrate that the boreal fall oxycline fluctuations off the WCI are strongly related to the Indian Ocean Dipole (IOD), with an asymmetric influence of its positive and negative phases. Positive IODs are associated with easterly wind anomalies near the southern tip of India. These winds force downwelling coastal Kelvin waves that propagate along the WCI and deepen the thermocline and oxycline there, thus preventing the occurrence of coastal anoxia. On the other hand, negative IODs are associated with WCI thermocline and oxycline anomalies of opposite sign but of smaller amplitude, so that the negative or neutral IOD phases are necessary but not the sufficient condition for coastal anoxia. As the IODs generally start developing in summer, these findings suggest some predictability to the occurrence of coastal anoxia off the WCI a couple of months ahead.

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Section: Physical Control Of the Interannual Oxygen Variability Off Tmentioning

confidence: 97%

Positive Indian Ocean Dipole events prevent anoxia off the west coast of India

et al. 2017

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“…The EICC starts flowing southward in September (Fig. SB2), as a coastally trapped current McCreary et al 1996). Around that time, the BoB shows a rather zonally uniform salinity distribution with very fresh (SSS ~26) water in the northern BoB and saltier water (SSS ~33) in the central and southern BoB.…”

Section: Velipalaiyam a Fishing Village Near Nagapattinammentioning

confidence: 99%

“…The EICC reverses twice a year under the influence of alternating monsoons (e.g., Shankar et al 1996;McCreary et al 1996;Durand et al 2009): it flows northward from February to September and southward from October to January (see Fig. SB2).…”

Section: The East Indian Coastal Currentmentioning

confidence: 99%

Salinity Measurements Collected by Fishermen Reveal a “River in the Sea” Flowing Along the Eastern Coast of India

Chaitanya

Lengaigne

Vialard

et al. 2014

Bulletin of the American Meteorological Society

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“…The weakening of the southwest monsoon winds after July, coupled with remote forcing from the eastern Bay of Bengal and the equatorial Indian Ocean, forces an equatorward East India Coastal Current (EICC) in the northern bay; the EICC is poleward along the rest of the Indian east coast [Sherye et al, 1991a;McCreary et al, 1993McCreary et al, , 1996. Together, these currents trap the runoff in the northern bay.…”

Section: Hypothesismentioning

confidence: 99%

Are interdecadal sea level changes along the Indian coast influenced by variability of monsoon rainfall?

Shankar¹,

Shetye²

1999

J. Geophys. Res.

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Abstract. The Mumbai (Bombay) tide gauge data, the only century-long record in the Indian Ocean, show that interdecadal changes in sea level mimic those in rainfall over the Indian subcontinent. We propose that the link between rainfall and sea level arises from changes in salinity in coastal waters. Rivers fed by southwest monsoon (June-September) rainfall bring a large fraction of the runoff to the Bay of Bengal, from where it is transported to the west coast of India by an equatorward East India Coastal Current, which is triggered partly by the withdrawal of the southwest monsoon. The West India Coastal Current carries the low-salinity water from the bay as well as the runoff from local rivers northward. The advection of the fivefine inflow to Mumbai occurs within a season, but the slow mixing in the ocean forces changes in the cross-shore density gradient on longer timescales. This density gradient forces a two-layer geostrophic circulation, with a surface current, which flows with the lighter water on its fight, and an undercurrent. Lower (higher) salinity at the coast implies higher (lower) coastal sea level and a rise (fall) of the pycnocline at the coast. Thus the interdecadal variability of sea level along the Indian coast can be linked directly to the variability of the monsoon, the major aspect of the climate of the region, but by a mechanism that is different from those generally proposed to link sea level to climate change; these hypotheses usually invoke a change in volume because of global warming.

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Dynamics of the East India Coastal Current: 2. Numerical solutions

Cited by 237 publications

References 18 publications

Positive Indian Ocean Dipole events prevent anoxia off the west coast of India

Positive Indian Ocean Dipole events prevent anoxia off the west coast of India

Salinity Measurements Collected by Fishermen Reveal a “River in the Sea” Flowing Along the Eastern Coast of India

Are interdecadal sea level changes along the Indian coast influenced by variability of monsoon rainfall?

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