Observed variability of the West India Coastal Current on the continental slope from 2009–2018

Abstract

We describe the variability of the West India Coastal Current (WICC) during October 2008 to October 2018 using data from ADCP (acoustic Doppler current profiler) moorings deployed on the continental slope off the west coast of India. The four moorings are deployed off Mumbai (\(\sim 20^\circ \hbox {N}\)), Goa (\(\sim 15^\circ \hbox {N}\)), Kollam (\(\sim 9^\circ \hbox {N}\)), and Kanyakumari (\(\sim 7^\circ \hbox {N}\)). This 10-year data set allows us to attach a statistical significance to the conclusions drawn by Amol et al. (2014) on the basis of four years (October 2008–October 2012) of ADCP data. The longer data set confirms the earlier finding that intraseasonal variability in the 30–90-day band dominates the variability of the WICC at all locations and that this intraseasonal variability peaks during the winter monsoon. The annual cycle (300–400 days) is strong and statistically significant at all locations. The phase propagates upward for the annual cycle and this phase difference is seen in the relative phases of both, the ADCP currents at 25 and 48 m as well as the 48 m ADCP and satellite-derived currents. The intra-annual (100–250 days) and intraseasonal currents show instances of both upward and downward phase propagation. The alongshore wavelet coherence is high on seasonal time scales between adjacent mooring locations and several instances of high coherence are seen even on intraseasonal time scales. Data gaps off Goa and Kanyakumari restrict the significant wavelet power to the ADCP records off Kollam and Mumbai, and the coherence analysis shows that the WICC off Kollam leads Mumbai on seasonal scales. The direction of the alongshore WICC is, however, largely determined by the direction of the significantly larger intraseasonal component. Though the climatological seasonal cycle over the whole record does show the canonical equatorward flow during the summer monsoon (June–September) and poleward flow during the winter monsoon (November–February), the scatter around the daily mean is very high. The data show that the WICC may flow in either direction on a given day of the year, with this unpredictability of direction being stronger off Kollam, where the 1-σ band of the daily mean alongshore WICC shows that it can flow in either direction in most months. The seasonality is stronger off Mumbai, where the width of the 1-σ band is less. The decade-long continuous record off Kollam and Mumbai shows that the sub-annual alongshore WICC at both locations is significant and is comparable to or stronger than the annual component. The cross-shore sub-annual current is also strong off Kollam and is seen to be associated with eddy-like circulations.

This is a preview of subscription content, access via your institution.

Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Figure 16

References

  1. Amol P, Shankar D, Aparna S G, Shenoi S S C, Fernando V, Shetye S R, Mukherjee A, Agarvadekar Y, Khalap S T and Satelkar N P 2012 Observational evidence from direct current measurements for propagation of remotely forced waves on the shelf of the west coast of India; J. Geophys. Res. 117, https://doi.org/10.1029/2011JC007606.

  2. Amol P, Shankar D, Fernando V, Mukherjee A, Aparna S G, Fernandes R, Michael G S, Khalap S T, Satelkar N P, Agarvadekar Y, Gaonkar M G, Tari A P, Kankonkar A and Vernekar S P 2014 Observed intraseasonal and seasonal variability of the West India Coastal Current on the continental slope; J. Earth Syst. Sci. 123 1045–1074, https://doi.org/10.1007/s12040-014-0449-5.

    Article  Google Scholar 

  3. AVISO 1996 AVISO User Handbook: Merged TOPEX/Poseidon Products. Tech. rep., Collecte Localisation Satellites, France.

  4. Bell C, Vassie J M and Woodworth P L 1998 POL/PSMSL Tidal Analysis Software Kit 2000 TASK-2000. Tech. rep., Permanent Service for Mean Sea Level, UK.

  5. Bonjean F and Lagerloef G S E 2002 Diagnostic model and analysis of the surface currents in the tropical Pacific Ocean; J. Phys. Oceanogr. 32 2938–2954, https://doi.org/10.1175/1520-0485(2002)032<2938:DMAAOT>2.0.CO;2.

    Article  Google Scholar 

  6. Chassignet E P, Hurlburt H E, Smedstad O M, Halliwell G R, Hogan P J, Wallcraft A J, Baraille R and Bleck R 2007 The hycom (hybrid coordinate ocean model) data assimilative system; J. Marine Syst. 65(1–4) 60–83.

    Article  Google Scholar 

  7. Chatterjee A, Shankar D, Shenoi S S C, Reddy G V, Michael G S, Ravichandran M, Gopalkrishna V V, Rao E P R, Bhaskar T V S U and Sanjeevan V N 2012 A new atlas of temperature and salinity for the north Indian Ocean; J. Earth Syst. Sci. 121 559–593, https://doi.org/10.1007/s12040-012-0191-9.

    Article  Google Scholar 

  8. Duchon C E 1979 Lanczos filtering in one and two dimensions; J. Appl. Meteorol. 18 1016–1022.

    Article  Google Scholar 

  9. Johannessen O M, Subbaraju G and Blindheim J 1987 Seasonal variations of the oceanographic conditions of the southwest coast of India during 1971–1975; FiskDir. Skr. Ser. HavUnders 18 247–261.

    Google Scholar 

  10. Kutsuwada K and McPhaden M 2002 Intraseasonal variations in the upper equatorial Pacific Ocean prior to and during the 1997–98 El Niño; J. Phys. Oceanogr. 32(4) 1133–1149, https://doi.org/10.1175/1520-0485(2002)032<1133:IVITUE>2.0.CO;2.

    Article  Google Scholar 

  11. Maraun D and Kurths J 2004 Cross wavelet analysis: significance testing and pitfalls; Nonlinear Process. Geophys. 11 505–514.

    Article  Google Scholar 

  12. Maraun D, Kurths J and Holschneider M 2007 Nonstationary gaussian processes in wavelet domain: Synthesis, estimation and significance testing; Phys. Rev. E 75 016707.

    Article  Google Scholar 

  13. McCreary J P, Kundu P K and Molinari R L 1993 A numerical investigation of dynamics, thermodynamics and mixed-layer processes in the Indian Ocean; Prog. Oceanogr. 31 181–244, https://doi.org/10.1016/0079-6611(93)90002-U.

    Article  Google Scholar 

  14. Menemenlis D, Campin J-M, Heimbach P, Hill C, Lee T, Nguyen A, Schodlok M and Zhang H 2008 Ecco2: High resolution global ocean and sea ice data synthesis; Mercator. Ocean Quarterly Newsletter 31 13–21.

    Google Scholar 

  15. Mukherjee A and Kalita B 2019 Signature of La Niña in interannual variations of the East India Coastal Current during spring; Clim. Dyn. 52 1–18, https://doi.org/10.1007/s00382-018-4601-9.

    Article  Google Scholar 

  16. Mukherjee A, Shankar D, Chatterjee A and Vinayachandran P N 2018 Numerical simulation of the observed near-surface East India Coastal Current on the continental slope; Clim. Dyn. 50 3949–3980, https://doi.org/10.1007/s00382-017-3856-x.

    Article  Google Scholar 

  17. Mukherjee A, Shankar D, Fernando V, Amol P, Aparna S G, Fernandes R, Michael G S, Khalap S T, Satelkar N P, Agarvadekar Y, Gaonkar M G, Tari A P, Kankonkar A and Vernekar S P 2014 Observed seasonal and intraseasonal variability of the East India Coastal Current on the continental slope; J. Earth Syst. Sci. 123 1197–1232, https://doi.org/10.1007/s12040-014-0471-7.

    Article  Google Scholar 

  18. Mukhopadhyay S, Shankar D, Aparna S G and Mukherjee A 2017 Observations of the sub-inertial, near-surface east india coastal current; Cont. Shelf Res. 148 159–177, https://doi.org/10.1016/j.csr.2017.08.020.

    Article  Google Scholar 

  19. Schott F A and McCreary J P 2001 The monsoon circulation of the Indian Ocean; Prog. Oceanogr. 51 1–123, https://doi.org/10.1016/S0079-6611(01)00083-0.

    Article  Google Scholar 

  20. Shankar D 2000 Seasonal cycle of sea level and currents along the coast of India; Curr. Sci. 78 279–288.

    Google Scholar 

  21. Shankar D and Shetye S R 1997 On the dynamics of the Lakshadweep high and low in southeastern Arabian Sea; J. Geophys. Res. 102 12,551–12,562.

    Article  Google Scholar 

  22. Shankar D, Vinayachandran P N and Unnikrishnan A S 2002 The monsoon currents in the north Indian Ocean; Prog. Oceanogr. 52 63–120, https://doi.org/10.1016/S0079-6611(02)00024-1.

    Article  Google Scholar 

  23. Shetye S, Shenoi S, Gouveia A, Michael G, Sundar D and Nampoothiri G 1991a Wind-driven coastal upwelling along the western boundary of the Bay of Bengal during the southwest monsoon; Cont. Shelf Res. 11 1397–1408, https://doi.org/10.1016/0278-4343(91)90042-5.

    Article  Google Scholar 

  24. Shetye S R, Gouveia A D, Shenoi S S C, Michael G S, Sundar D, Almeida A M and Santanam K 1991b The coastal current of western India during the northeast monsoon; Deep Sea Res. 38 1517–1529.

    Article  Google Scholar 

  25. Shetye S R 1998 West India Coastal Current and Lakshadweep high/low; Sadhana 23 637–651.

    Article  Google Scholar 

  26. Shetye S R and Gouveia A D 1998 Coastal circulation in the north Indian Ocean: Coastal segment (14, SW); In: The Sea (ed.) Robinson A R, John Wiley and Sons, New York, USA, pp. 523–556.

    Google Scholar 

  27. Shetye S R, Gouveia A D, Shankar D, Shenoi S S C, Vinayachandran P N, Sundar D, Michael G S and Nampoothiri G 1996 Hydrography and circulation in the western Bay of Bengal during the northeast monsoon; J. Geophys. Res. 101 14,011–14,025, https://doi.org/10.1029/95JC03307.

    Article  Google Scholar 

  28. Shetye S R, Gouveia A D, Shenoi S S C, Sundar D, Michael G S, Almeida A M and Santanam K 1990 Hydrography and circulation of the west coast of India during the southwest monsoon 1987; J. Mar. Res. 48 359–378.

    Article  Google Scholar 

  29. Shetye S R, Gouveia A D, Shenoi S S C, Sundar D, Michael G S and Nampoothiri G 1993 The western boundary current of the seasonal subtropical gyre in the Bay of Bengal; J. Geophys. Res. 98 945–954, https://doi.org/10.1029/92JC02070.

    Article  Google Scholar 

  30. Shetye S R and Shenoi S S C 1988 Seasonal cycle of surface circulation in the coastal North Indian Ocean; Proc. Indian Acad. Sci. (Earth Planet Sci.) 97(1) 53–62.

    Google Scholar 

  31. Sikhakolli R, Sharma R, Basu S, Gohil B S, Sarkar A and Prasad K V S R 2013 Evaluation of OSCAR ocean surface current product in the tropical Indian Ocean using in-situ data; J. Earth Syst. Sci. 122 187–199.

    Article  Google Scholar 

  32. Torrence C and Compo G P 1998 A practical guide to wavelet analysis; Bull. Am. Meteorol. Soc. 79(1) 61–78, https://doi.org/10.1175/1520-0477(1998)079<0061:APGTWA>2.0.CO;2.

    Article  Google Scholar 

  33. Vialard J, Shenoi S S C, McCreary J P, Shankar D, Durand F, Fernando V and Shetye S R 2009 Intraseasonal response of the northern Indian Ocean coastal waveguide to the Madden–Julian oscillation; Geophys. Res. Lett. 36, https://doi.org/10.1029/2009GL038450.

Download references

Acknowledgements

The ADCP mooring project has been supported by grants from the Council of Scientific and Industrial Research (CSIR) (under the Supra-Institutional Program of CSIR–NIO during 2007–2012, under OCEAN FINDER during 2012–2017, and TRIMFish thereafter) and the Ministry of Earth Sciences (MoES, via INCOIS) through its programme on Ocean Observing Networks. The support from INCOIS, the CSIR–NIO ship cell, and the officers and crew on board the research vessels are acknowledged with gratitude. A Chaudhuri was supported by the Science and Engineering Research Board (SERB) vide project PDF/2017/000302. Ferret has been used for analysis and Ferret and GMT (Generic Mapping Tools) have been used for graphics; the FORTRAN code for wavelet analysis and the R package for wavelet coherence spectra were downloaded from http://paos.colorado.edu/research/wavelets and http://tocsy.agnld.uni-potsdam.de/wavelets, respectively. The OSCAR data were obtained from the Physical Oceanography DAAC of the JetPropulsion Laboratory (downloaded from http://www.oscar.noaa.gov/). The SSHA altimeter product was produced and distributed by the Copernicus Marine and Environment Monitoring Service (CMEMS) (http://www.marine.copernicus.eu) The ECCO2 Ocean State estimate was downloaded from ftp://ecco.jpl.nasa.gov/ECCO2/cube92_latlon_quart_90S90N/ and the HyCOM Reanalysis product from https://hycom.org/dataserver/gofs-3pt1/reanalysis. The validation of these two model-based data products is due to the comments received from an anonymous reviewer. This is CSIR–NIO contribution 6465.

Author information

Affiliations

Authors

Corresponding author

Correspondence to D Shankar.

Additional information

Communicated by C Gnanaseelan

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Chaudhuri, A., Shankar, D., Aparna, S.G. et al. Observed variability of the West India Coastal Current on the continental slope from 2009–2018. J Earth Syst Sci 129, 57 (2020). https://doi.org/10.1007/s12040-019-1322-3

Download citation

Keywords

  • Eastern boundary currents
  • ADCP
  • seasonal variability
  • intraseasonal variability
  • interannual variability
  • WICC
  • Arabian Sea
  • Indian Ocean