The image at right is a composite of the most recent MODIS satellite image of the spill area in the Gulf of Mexico and a National Weather Service model of the Loop Current. It was created by Brad Johnson of Think Progress’ The Wonk Room.

The composite image shows that the oil spill area has almost certainly reached the Loop Current, which is one of the major currents in the Gulf of Mexico. The loop current runs right past the Florida Keys and then meets up with the Gulf Stream, and if the tar balls that have been washing up on Key West beaches over the last day or two are from the spill (they may be from older spills years ago), then we should assume that the MODIS satellite imagery is the minimum extent of the spill area. Given that scientists aboard a NOAA survey ship have observed a plume at least 45 km long and 10 km wide that’s thousands of feet below the surface (and thus not visually detectable from the surface), it’s reasonable to say that the observed surface slick does not represent the full extent of the spill to date. And NOAA has now closed 19% of federally-controlled Gulf waters to all fishing (map).