SEASTAR: A mission to study ocean submesoscale dynamics and small-scale atmosphere-ocean processes in coastal, shelf and polar seas

SEASTAR is a new satellite mission concept that addresses a critical observational gap for synoptic maps of ocean surface currents and wind vectors at 1km spatial resolution that is critical to understand, model and forecast ocean submesoscale dynamics, air-sea interactions and small-scale processes in coastal, shelf and polar seas. High- resolution ocean colour and sea surface temperature images reveal an abundance of fronts, swirls, vortices and filaments at scales between 1-10 km but measurements of ocean surface dynamics at these scales are rare. Complex sea surface temperature patterns and dramatic phytoplankton blooms are fingerprints of dynamic atmosphere-ocean interactions and intense upper ocean vertical processes taking place at small scales. Upper ocean vertical transports and air-sea exchanges represent critical connections within the Earth system, for example as pathways for the uptake by the ocean of heat and anthropogenic atmospheric CO2, and the replenishment with nutrient-rich deep waters of the upper ocean that sustains the marine ecosystem and ocean food chain. Improved spaceborne observations of currents, winds and waves are urgently needed to improve understanding of these processes and validate and improve models that are used for operational predictions and future climate projections.