Natural and unnatural oil slicks in the G ulf of M exico

When wind speeds are 2–10 m s −1 , reflective contrasts in the ocean surface make oil slicks visible to synthetic aperture radar (SAR) under all sky conditions. Neural network analysis of satellite SAR images quantified the magnitude and distribution of surface oil in the Gulf of Mexico from persistent, natural seeps and from the Deepwater Horizon (DWH) discharge. This analysis identified 914 natural oil seep zones across the entire Gulf of Mexico in pre‐2010 data. Their ∼0.1 µm slicks covered an aggregated average of 775 km 2 . Assuming an average volume of 77.5 m 3 over an 8–24 h lifespan per oil slick, the floating oil indicates a surface flux of 2.5–9.4 × 10 4 m 3 yr −1 . Oil from natural slicks was regionally concentrated: 68%, 25%, 7%, and