Measuring Marine Hydrodynamics from Space Using Planet Satellite Imagery

The inference of coastal ocean dynamics from consecutive remote sensing images plays a central role in a diverse range of domains such as marine conservation, spatial planning, as well as flood risk. We present a methodology for systematically identifying spatially overlapping image pairs in coastal regions from the PlanetScope archive, with minute-scale time lags and the potential for velocity field inference using classical algorithms. This ability is demonstrated through the novel estimation of submesoscale eddies from PlanetScope image pairs across a range of contexts. These include sea ice floes in the Siberian Sea of Okhotsk, a cyanobacterial bloom in the Baltic Sea, and suspended sediment in the Port of Al-Fao located in the Arabian Gulf. Additionally, comparison of the latter with coinciding velocity fields from a Delft3D model shows good quantitative agreement in regions with high suspended sediment concentration. We successfully develop a workflow pipeline for identifying and processing image pairs from these opportunistic overlaps, unlocking a new large-scale data source of coastal ocean surface velocities to be used alongside modelling frameworks.