Identification of Submarine Groundwater Discharge using Thermal Infrared Observations in the Arabian Ocean Near Okha Coast, Gujarat, India

In this study we identify a region of submarine groundwater discharge (SGD) near Okha coast, Gujarat, India using thermal infrared remote sensing technique. Observations of brightness temperature (BT) in the thermal infrared spectral region (10.6–11.19 μm) from Landsat-8 satellite in the coastal region showed unique localized cooling in the Arabian Sea during winter. We observed lowering of BT in the range 0.6°– 2.3°C in the coastal region associated with SGD in comparison to sea surface temperature of the ocean during low-tide conditions. Consistent geographical pattern of thermal contrast was observed near the same location (lat. 22°26′54.43″N, long. 69°00′41.67″E) when multi date (11 datasets) thermal data were analysed between 2015 and 2019 in winter. Generally, low-tide conditions show more cooling of ocean surface at the SGD site compared to high-tide conditions, which indicates the process of SGD. Satellite-based assessment was further validated using field- and ship-based measurements.