14 December 2010

Deepwater Horizon oil spill: Scientists respond with research

Posted by mohi

Often research is driven by a desire to understand the fine details of a specific process; any application is often years in the future. But when the Deepwater Horizon drilling rig atop the Macondo oil well exploded on April 20, scientists used their tools to analyze an immediate problem.

oil spill

The Deepwater Horizon oil spill, observed from the Internation Space Station. Image courtesy of NASA

Lectures during OS21G “Lessons Learned From the Deepwater Horizon Oil Spill: Biological and Chemical Oceanography I” highlighted some of these efforts.

A team led by Arne Diercks at the University of Southern Mississippi had loaded their research vessel for a planned trip to map an area of seafloor in the Gulf of Mexico. But after the explosion sent oil gushing into the ocean, the plans changed.

Diercks and his team renamed their mission the “Deepwater Horizon Oil Spill Response Cruise” and quickly changed the equipment on their research vessel. Two weeks after the spill, they traveled around the broken wellhead, collecting water and sediment samples to establish baselines before oil significantly contaminated the ocean.

But on May 12,  sensors detected compounds in oil consistently at depths of 700 and 1100 meters below sea level. The team abandoned their original sampling plan and spent the last four days of their trip redesigning their experiment so they could map these two subsurface oil layers. They found the strongest layer extended to the south-southwest of the leaking Macondo well.

Ocean circulation models predicted that oil would also travel northeast of the wellhead. One month after the explosion, a team led by David Hollander at the University of South Florida sampled water at various depths about 20 miles from the well. The team detected oil in their samples, but now they had to prove that it came from the Macondo well–a perfect challenge for Hollander. As a chemical oceanographer, he specializes in identifying molecules in the ocean.

Hollander says his team became “CSI: Oil Spill.” They determined the unique chemical fingerprint of the Macondo oil and found that it matched the one from the oil at their sampling site.

Videos of oil gushing from the broken pipe intrigued Timothy Crone at Columbia University because they resembled the hydrothermal vents he studies.

Several years ago, Crone developed a method to measure the fluid flow from these vents based on videos of the streaming water. He applied this method to video of the flowing oil to estimate the volume of oil dumped into the ocean. His estimates closely match those now determined by the government. Crone says his technique could help resolve scientists’ questions about how the flow rate changed over time.

But questions still persist. Two days ago, Hollander returned from sampling sediment in the Gulf of Mexico. He says he was most puzzled by a thick black mud he found in shallow water less than a kilometer from shore. How did this mud form and why was it found so close to shore?

Though the Macondo well is sealed, the scientific mysteries continue. “It’s not over,” Hollander says.

–Melissae Fellet is a science communication graduate student at UC Santa Cruz.