Scientists monitoring the US oil spill with the European Space Agency (ESA) Envisat radar satellite say that it has entered the Loop Current, a powerful conveyor belt that flows clockwise around the Gulf of Mexico towards Florida.
Dr Bertrand Chapron of Ifremer, the French Research Institute for Exploitation of the Sea, said: ‘With images from space, we have visible proof that at least oil from the surface of the water has reached the current.’
Chapron and Dr Fabrice Collard of France’s CLS have been combining surface roughness and current-flow information with Envisat Advanced Synthetic Aperture Radar (ASAR) data of the area to monitor the proximity of the oil to the current.
A processed ASAR image below, which was acquired on 18 May, clearly shows a long tendril of the oil spill (outlined in white) extending down into the Loop Current.
Collard said: ‘We processed the images to display surface features such as variations in roughness and velocity, which provides insight into the spatial structure of the spill and its transport by surface currents.’
From the ASAR images of 12 and 15 May, the oil spill was observed stretching closer to the Loop Current, raising concerns that it could reach the current and be carried south towards coral reefs in the Florida Keys.
‘Now that oil has entered the Loop Current, it is likely to reach Florida within six days,’ Chapron said.
The scientists warn that since the Loop Current is a very intense, deep ocean current, its turbulent waters will accelerate the mixing of the oil and water in the coming days. ‘This may remove the oil film on the surface and prevent us from tracking it with satellites, but the pollution is likely to affect the coral-reef marine ecosystem,’ Collard added.
Combined efforts using satellite imagery and in-situ measurements of collected water samples will help to fully assess whether oil is in the deep waters of the ocean.
The Loop Current joins the Gulf Stream — the Northern Hemisphere’s most important ocean-current system — sparking fears that oil could enter this system and be carried up to the US’ east coast.
A processed Envisat Advanced Synthetic Aperture Radar (ASAR) image, which was acquired on 18 May 2010, displays ocean surface roughness variations and Doppler-derived ocean surface radial velocities around the oil spill area in the Gulf of Mexico. A long tendril of the oil spill (outlined in white) is visible extending down into the Loop Current (red arrow)