Observed intraseasonal and seasonal variability of the West India Coastal Current on the continental slope

Journal of Earth system science

V Fernando1¹  S T Khalap1¹  G S Michael1¹  Y Agarvadekar1¹  D Shankar1¹  P Amol1¹  S G Aparna1¹  A Kankonkar1¹  M G Gaonkar1¹  S P Vernekar1¹  N P Satelkar1¹  R Fernandes1¹  A Mukherjee1¹  A P Tari1¹ 

[1] CSIR–National Institute of Oceanography, Dona Paula, Goa 403 004, India.$$

关键词: Eastern boundary current;    Arabian Sea;    Indian Ocean;    acoustic Doppler current profiler;    seasonal cycle;    intraseasonal variability;    time series.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

We present current data from acoustic Doppler current profilers (ADCPs) moored on the continental slope off the west coast of India. The data were collected at four locations (roughly at Kanyakumari, Kollam, Goa, and Mumbai) extending from ∼7° to ∼20° N during 2008–2012. The observations show that a seasonal cycle, including an annual cycle, is present in the West India Coastal Current (WICC); this seasonal cycle, which strengthens northward, shows considerable interannual variability and is not as strongly correlated along the coast as in climatologies based on ship drifts or the altimeter. The alongshore decorrelation of theWICC is much stronger at intraseasonal periods, which are evident during the winter monsoon all along the coast. This intraseasonal variability is stronger in the south. A striking feature of the WICC is upward phase propagation, which implies an undercurrent whose depth becomes shallower as the season progresses. There are also instances when the phase propagates downward. At the two southern mooring locations off Kollam and Kanyakumari, the cross-shore current, which is usually associated with eddy-like circulations, is comparable to the alongshore current on occasions. A comparison with data from the OSCAR (Ocean Surface Currents Analyses Real-time) data product shows not only similarities, but also significant differences, particularly in the phase. One possible reason for this phase mismatch between the ADCP current at 48 m and the OSCAR current, which represents the current in the 0–30 m depth range, is the vertical phase propagation. Current products based on Ocean General Circulation Models like ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and GODAS (Global Ocean Data Assimilation System) show a weaker correlation with the ADCP current, and ECCO2 does capture some of the observed variability.

【 授权许可】

Unknown