ERS-1/2 SAR detection of natural film on the ocean surface

Ocean mesoscale phenomena such as eddies and current convergence zones can often be seen in SAR images due to characteristic patterns caused by natural film induced damping of the waves. Such films have also been found to exert a significant effect on air-sea gas exchange, which may be important for the global scale climate system. Satellite synthetic aperture radar (SAR) may prove very useful to quantify the extent of natural film. To investigate the composition of these films and their effect on radar return, samples of the sea surface were taken simultaneously with ERS-1/2 SAR coverage of a fjord (the Korsfjord experiment), and later in coastal ocean areas (COASTWATCH'95). During COASTWATCH'95, simultaneous observations were made with a shipmounted C-band dual-polarized Doppler radar, and surface drifters were deployed to investigate the surface current variations in vicinity of the slicks. The dependence of the existence of slicks on wind speed is also investigated, and an estimate of natural film distribution during the experiment period given.