Scientists using satellite imagery found that at least 23 percent of the water released from the mouth of the Mississippi River from July through September 2004 traveled quite a distance - into the Gulf of Mexico, around the Florida Keys, and into the Atlantic Ocean.

This image taken August 14, 2002, by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA’s Terra satellite, shows black water off Sanibel Island, Florida, the hook-shaped island on the western coast at the midway point of the image.

The researchers combined data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra and Aqua satellites with information collected from ships to study the water discharge, appearing as a dark plume that stretched from the Mississippi Delta, around Florida and up to the Georgia coast. MODIS detects the color of the ocean due to changes in the amount of tiny ocean plants floating on the ocean’s surface known as phytoplankton, or algae and other decaying materials.

“This is the first time we have been able to estimate the amount or volume of freshwater discharged and carried over such remote distances. By combining the very detailed data from MODIS with observations from ships, we got a three-dimensional view of the Mississippi plume,” said Chuanmin Hu, of the College of Marine Science, University of South Florida, St. Petersburg, Fla., and lead author of the study. By using MODIS data with information on sea surface currents and sea salt levels (salinity), the scientists estimated that about 20 billion tons of Mississippi River discharge reached the Florida Straits and Gulf Stream off the Georgia coast. This is equivalent to about four times the volume of Lake Okeechobee, the largest lake in Florida.

In early July 2004, the dark water plume traveled south along the eastern edge of the Loop Current off southwest Florida, reaching the Florida Keys by late July 2004. By early August, MODIS images showed that the plume had expanded along the Gulf Steam as far away as the Georgia coast. The plume was typically 30 to 65 feet deep with a width of 6 to 12 miles; although occasionally was as wide as 30-37 miles, before dissipating in October 2004.

While many factors, like ocean eddies - that mix waters of varying characteristics - influence the evolution of such events, climate and weather patterns also play a role. For instance, following the Great Midwest Flood of 1993, Mississippi River water also moved into the Florida Current. In 2004, heavy summertime rainfall may have contributed to the plume’s large size and persistence. But “it’s still too early to know if there is a concrete connection between climate and the occurrence of these events, as much further study is needed,” said Hu.

Complete article (including some more cool images): Satellites Spot Mighty Mississippi – In The Atlantic (NASA)