Date: Friday, October 19, 2018 - 13:00
Speaker: Professor Fabrice Ardhuin. IFREMER, France
Location: NOC Southampton - Henry Charnock Lecture Theatre (Waterfront Campus).
Abstract: The Sea surface KInematics Multiscale monitoring (SKIM) satellite mission is one of the two candidates under development for ESA Earth Explorer 9. The other candidate is the Far infrared Radiation Understanding and Monitoring (FORUM). Final selection will announced by September 2019, for a launch in 2025.
SKIM uses a Ka-band Doppler radar that includes a sate-of-the-art nadir beam comparable to the altimeter built for Sentinel 6, but in Ka-band, and off-nadir beams that will measure the surface velocity vector and ocean wave spectra across a 300 km swath. This should resolve surface currents and ice drift at spatial scales larger than a 40 km wavelength, and ocean waves with wavelengths larger than 30 m, with a revisit of 99\% of the global oceans, every 4 days on average. Particular science goals of the SKIM mission include the exploration of the unknown equatorial currents, including the patterns of divergence and their impact on the ocean heat budget near the equator, a monitoring of the emerging Arctic up to 82.5°N, and the unprecedented measurement of strong currents and their interaction with ocean waves with expected impacts on air-sea fluxes and extreme waves from boundary currents to the Antarctic circumpolar current. More generally SKIM will measure near-surface drift velocities across all oceans and seas, contributing to a better understanding of the transport of everything that is carried near the surface, from plastics to plankton and heat.
The presence of the nadir altimeter beam will allow a seamless transition from dynamics derived from the existing altimeters, to the exploration of higher resolution details, expanding from geostrophic currents to total surface current vectors. The co-located wave measurements facilitates many applications. Beyond a primary focus of refining sea state biases in surface velocity and sea level estimates, wave data will be used for the investigation of wave-current interactions including extreme sea states and their coastal impact, wave-ice interactions and related feedbacks in the polar Marginal Ice Zones, air-sea fluxes including global carbon capture, and wave contribution to drift.
The ongoing phase A studies, include a refinement of the SKIM performance and mission requirements, as well as validation with airborne instruments, and demonstrations of the use of existing single-component Doppler currents or simulated SKIM data. We present in particular the instrument principle, and an analysis of the SKIM error budget, including wave bias, platform attitude misknowledge and instrument noise. We also discuss the impact on the effective resolution of ocean surface currents in different regimes: equatorial currents, mid-latitude meso-scales, ice edge dynamics.