We analyzed the role of Indian Ocean warming and positive Indian Ocean Dipole (IOD) events on the chlorophyll concentrations in the Eastern Arabian Sea (EAS). Positive IOD years were found to be less favorable for inducing coastal upwelling in the region. Significant negative correlation between positive IODs and chlorophyll concentrations show that in the event of occurrence of frequent positive IOD events under a warming regime, the chlorophyll concentration is likely to decrease during fall.

Surface wind-waves properties during Indian summer monsoon is investigated based on measured data at 9-15 m water depth at 4 sites in nearshore waters of the eastern Arabian Sea. Significant wave height varied from 0.7 to 5.5 m with average ratio of crest height of wave to height of the same wave as 0.58 to 0.67. Extreme crest height is 1.23 to 1.35 times significant wave height. Measured waves were predominantly swell. Numerical wave model could estimate the wave height well during wave growth.

Assessment of design waves is performed using generalized extreme value (GEV) and generalized Pareto distribution (GPD) based on buoy data for 8 years and ERA-Interim reanalysis data for 38 years. The initial distribution method underestimates return levels compared to GPD. Intercomparison of return levels by block maxima and r-largest method for GEV theory shows that return level for 100 years is 7.24 m by r-largest series. A single storm can cause a large difference in the 100-year H_s value.

Waves measured at 12 m in the near-shore waters of the Gulf of Mannar for a 1-year period are used to examine the predominance of wind seas and swells through spectral characterization. The waves of the study region are under the control of sea breeze, with the maximum in the late evening and the minimum in the early morning. A total of 53 % of the surface height variance in the study area results from swells from the southeast and south; the remainder are wind seas from the east and southeast.

The information on wave spectral shapes that is required for designing marine structures is presented based on wave data collected from January 2011 to December 2015 in the coastal waters of the eastern Arabian Sea. The variations in the high-frequency tail of the wave spectrum in different months are presented. The slope of the high-frequency tail of the monthly average wave spectra is high during the Indian summer monsoon period (June–September) compared to other months.