Gulf spill is the largest marine oil accident

An independent, peer-reviewed research has revealed that the Gulf spill is the largest marine oil accident ever which spewed around 4.1 million barrels of oil into the Gulf of Mexico.

"We wanted to do an independent estimate because people had the sense that the numbers were not necessarily accurate," said Timothy Crone from Columbia University.

The new study divides the flow rate into two periods: April 22 to June 3, when oil spurted from a jagged break in the riser; and after June 3, when the riser was cut, and oil temporarily spewed into the ocean unimpeded.

Crone and colleague Maya Tolstoy used optical plume velocimetry, a visual analysis technique, to determine the final number.

The technique uses high-resolution video from underwater cameras to track the motion of turbulent billows and flows in the water, breaking down the movement pixel by pixel.

"Video from the earlier period indicated a flow of about 56,000 barrels a day. After the pipe was cut, the rate went to about 68,000", they said.

Accounting for time elapsed, the authors subtracted 804,877 barrels collected by BP at the site, to come up with a total of 4.4 million barrels that escaped.

Moreover, a 20 % margin of error rate left them with 4.1 million barrels.

The researchers pointed out that the flows could have variedon each day, and the analysis did not include video of several other leaks from smaller holes further up the pipe, which are thought to have grown with time.

"We clearly acknowledge the limits of our technique; we're unlikely to ever know the exact figure," Crone said.

Tolstoy added, "This is not the last word. It is the first peer-reviewed word. But we think it's a really good ballpark."

The paper appeared in this week's early online edition of the leading journal Science.