SAR imaging of ocean surface oil seep trajectories induced by near inertial oscillation

In the Gulf of Mexico, repeated satellite synthetic aperture radar (SAR) observations show circular trajectories of oil slicks with a radius of several km. Some circles overlay onto each other; while in other cases the circles are modified by the ambient current to form a train of spirals. We show that these SAR-observed features originate from oil seeps of the ocean bottom and the circles are induced by near inertial oscillation (NIO). From the SAR images, we have estimated the ambient current velocity from a train of spiral-like circles and verified the NIO by calculating its oscillation period. In this study, we also analyze time series of wind and velocity profiles obtained from a moored buoy and acoustic Doppler current profilers mounted on oil platforms in the area covered by the SAR images. The ocean current analysis confirms that during the SAR imaging times, there were NIOs. Buoy measurements also show that moderate wind of 7 ms− 1 existed 24 h prior to a SAR observation, and it diminished to 2 ms− 1 in 6 h and remained very low for the next 18 h, a condition ideal for producing NIOs.