While the Gulf Oil Spill was bad, as newly released photos vividly show, it could've been a lot worse. New research shows that much of the oil was actually kept offshore by water flowing into the Gulf of Mexico from the Mississippi River.
It turns out that because the spill coincided with the annual spring flood from the Mississippi, which brought greater than usual amounts of fresh water in the Gulf and created "mounds of freshwater which pushed the oil slick offshore." (Science Daily)
University of Pennsylvania's Douglas Jerolmack says that what inspired the research was that, "We noticed that there was a big disconnect between the forecasts of where the oil was going to be the next day and where the oil actually was the next day. That maybe shouldn't be a surprise, because these computer models were not generated to forecast the movement of oil, they were generated to forecast the movement of water."
After examining publicly available data, the researchers determined that, "there was a very persistent mound, a bump or bulge, in the elevation of the sea surface in the vicinity of the Mississippi Delta."
As the flow from the Mississippi declined this bulge disappeared and the oil moved towards shore as expected.
Read the original research, in PLoS One.