Remote Sensing for Subsurface and Deeper Oceans: An overview and a future outlook

The oceans are an important component of Earth’s system and play a crucial role in climate change through the coupled atmosphere–ocean process. Observations are fundamental for studying and understanding the oceans. While in situ measurements are limited, satellites can remotely monitor oceans continuously for extended periods, with broad spatial coverages. These sustained in situ and remotely sensed observations are available for longer time periods; however, the later are limited to the surface ocean. Owing to the unavailability of subsurface observations, the limited studies could focus on understanding subsurface oceanic processes [e.g., subsurface flows and eddies, internal waves (IWs) and tides, undercurrents, and so on] and conducting comprehensive studies of the oceans, such as the recent warming of oceans.