01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0037 |
| Title of Abstract | Variability of thermocline currents on the continental slope in the eastern Arabian Sea |
| Authors | Ankit Sinha*, Dr. Shankar Doraiswamy , Dr. Amol Prakash, Dr. Aparna Saieesh Gandhi, Kankonkar Ashok, Fernando Vijayan, Narayan Pandurang Satelkar, Khalap Sadashiv Tarachand, Tari A Prakash, Gaonkar Mithun Gurudas |
| Organisation | CSIR-NIO |
| Address | NIO Colony, Dona Paula, Panjim, Goa Panjim, Goa, India Pincode: 403004 E-mail: ankitsinha.nio@csir.res.in |
| Country | India |
| Presentation | Poster |
| Abstract | We present an analysis of the variability of sub-surface, essentially thermocline, currents on the continental slope in the eastern Arabian Sea, i.e., off the Indian west coast. This analysis is based on data from ADCP (acoustic Doppler current profiler) measurements; the near-surface (roughly top 200 m) currents have been described earlier (Amol et al. 2014, Chaudhuri et al. 2021), but the thermocline currents have not been analysed yet. We show that the thermocline currents from these ADCPs present a challenge owing to periodic data gaps that were not seen in the near-surface currents. Inspection of the data shows that these gaps occur during the night, i.e., from dusk to dawn, and they follow a diurnal cycle, suggesting a link to the diel vertical migration (DVM) of zooplankton. These gaps are more prominent at ADCP moorings located within the oxygen minimum zone (OMZ) in the eastern Arabian Sea (EAS). For moorings outside the OMZ, such as Kanyakumari or Okha, these periodic gaps are absent, pointing to the OMZ⿿s role in reducing the zooplankton population in the thermocline and thus limiting the backscatter signal necessary for viable ADCP measurements. Our analysis focuses on sub-inertial currents. To ensure reliable interpretation of thermocline variability at these timescales, gap-filling methods were carefully optimised. The objective was to preserve the spectral characteristics at longer periods while avoiding artificial high-frequency noise caused by the Gibbs phenomenon. We applied a robust approach (Mukhopadhyay et al. 2020) that combines cubic spline interpolation with grafting techniques. Comparison of wavelet spectra before and after gap-filling reveals minor discrepancies at shorter periods, but overall consistency in power trends and intensities at longer periods. The gap-filled records provide a remarkable data set of currents. A brief description of the variability of the sub-inertial thermocline currents will be presented. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | ADCP, Diel Vertical Migration, Oxygen Minimum Zone, Wavelet, Thermocline currents |
| For Awards | yes |
| Date Of Birth | 08-03-1994 |
| ECSN Registration Number | IIOE2-ECSN-0154 |