| Abstract Submission No. | ABS-1.2-0141 |
| Title of Abstract | Observed High Frequency Variability of Coastal Currents Around the Indian Subcontinent. |
| Authors | Krishnapriya M S*, Dr. Rohith B, Dr. Francis P. A |
| Organisation | Indian National Centre for Ocean Information Services |
| Address | INCOIS residential quarters, Pragathi nagar Hyderabad, Telangana, India Pincode: 500090 E-mail: mangalathillam.kps-rf@incois.gov.in |
| Country | India |
| Presentation | Oral |
| Abstract | Coastal currents play a vital role in regulating regional climate and driving biogeochemical processes in the coastal ocean. Variability in the coastal currents impact a wide range of sectors such as fisheries, offshore industries, shipping sector etc. While seasonal and intraseasonal variability in coastal currents have been studied extensively (Shetye & Shenoi, 1988; Shankar, 2002; Amol et al., 2014, Mukherjee et al., 2014), high-frequency variability (HF, <25 days) remains largely unexplored in the Indian waters. This study investigates the HF variability in coastal currents around the Indian subcontinent using long-term observations from Acoustic Doppler Current Profilers (ADCPs) deployed at both shelf and slope locations. Hourly, quality-controlled, de-tided currents were rotated into alongshore and cross-shore components. Spectral analysis reveals pronounced HF current variability across the Indian subcontinent, with stronger energy on the continental shelf compared to the slope. Within the HF band, quasi-biweekly oscillations (16¿24 day, 8¿16 day), quasi-weekly oscillations (2¿8 day), and internal waves (2 h¿2 day) are identified. Quasi-biweekly oscillations are consistently strong and exhibit clear seasonal modulation in northern locations (Goa, Mumbai, Gopalpur, Visakhapatnam), whereas southern regions (Kollam, Kanyakumari, Cuddalore, Kakinada) display weaker seasonality. In contrast, the quasi-weekly band shows little seasonal variation. Among shelf sites, Kakinada exhibits the strongest HF variability, while Cuddalore is the weakest. Strong coherency across locations reveals the presence of coastally trapped waves (1¿4.4 m/s) during the summer monsoon. On the shelf, faster propagation suggests shelf waves, while in-phase oscillations indicate the influence of large-scale wind forcing. Subsurface signals are also significant, sometimes surpassing surface variability. Occasional vertical phase propagation are also observed. In summary, significant HF coastal current variabilities exist along the Indian subcontinent, spanning multiple frequency bands. They exhibit propagatory patterns, vertical propagation, and strong subsurface variability, likely driven by combination of local and remote forcing mechanisms. |
| Keywords | ADCP, Coastal currents, Indian subcontinent, High frequency variability, Shelf and Slope currents, Wave propagation, Subsurface current variability. |