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CARTHE researchers model oil spills to mitigate their impact on coastal life.


Tracking the next oil spill to curb the damage

by Monika Wnuk
Dec 10, 2013


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Monika Wnuk/MEDILL

Marine physicist Dave Ortiz-Suslow deploys a drifter, or buoyant device that moves with and measures ocean currents. The drifter has a GPS device strapped onto to track the drifter’s position at every second. Ortiz-Suslow, of the University of Miami, and other scientists use this data to model ocean currents.

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CARTHE website

Oceanographers and researchers who study fluid dynamics model the hydrocarbon plume, or oil cloud, emitted from a well during an explosion.  Understanding how oil behaves in the deep ocean and predicting how it will move begins at the site of the leak.

The spill pours 5 million barrels of crude oil into the Gulf and it begins a relentless rush to the shore, where scientists follow it as it disrupts ecosystems, wildlife habitats and the beaches that sustain coastal economies.

Luckily this event is only a model and meant to mitigate the devastation caused by large oil spills, should one happen again.

The 2010 Deepwater Horizon oil spill, which leaked an estimated 4.9 million barrels of oil into the Gulf of Mexico in three months, still haunts many places. But scientists are already preparing for the next event with models.

Researchers at 16 different universities are conducting a modeling experiment in Florida’s Panhandle this week to gather data and predict how oil may move onshore during the next event. Knowing that may offer ways to contain or even divert the spill.

They’re part of the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment, a research team funded by the Gulf of Mexico Research Initiative, which independently distributes $500 million donated by British Petroleum to study the impacts of petroleum on public health and the environment.

Administered by the Rosenstiel School of Marine and Atmospheric Science, CARTHE operates under the direction of Tamay Ozgokmen, an oceanographer and expert on geophysical fluid dynamics.

“We’re studying the region most hit by the oil, which includes the coasts surrounding the Gulf,” Ozgokmen said.

Coastal communities in the Gulf collectively support a $20 billion tourism industry, according to the Environmental Protection Agency. An estimated 491 miles of coastline in Louisiana, Mississippi, Alabama, and Florida were contaminated by the spill. Gulf economies lost an estimated $7.6 billion in tourism, according to a study done by Oxford Economies, but the ecological loses were also great. Thousands of animals were found dead and others were “visibly oiled,” in a survey done by The U.S. Fish and Wildlife Service.

In just its second year, CARTHE is at the initial stages of data gathering for oil transport models. In the long-term, researchers will use those models to predict oil transport, inform environmental policy and mitigate the adverse effects of oil well explosions.

Additionally, once models are supplemented by real-time data from experiments, climate scientists can adjust them to predict oil transport in climate change scenarios, such as sea level rise caused by a warmer climate and melting ice caps.

Ozgokmen and his team study how oil travels at the surface and in the deep ocean. Guillaume Novelli, a postdoctoral fellow at RSMAS, studies both dimensions.

“Strangely, what happens in the last 100 meters [of oil transport] to the coast is determined by what happened in the first 100 meters,” and below the surface he said. Understanding 3-D ocean circulation where the well is leaking helps scientists locate area of the ocean where material disperses most rapidly. Mitigating the leak at these high dispersion regions first can mitigate impacts at the coast. 

Novelli and Ozgokmen study fluid dynamics to understand how oil travels from a well within the deep ocean.

Scratching the Surface of the Ocean

Ozgokmen and Novelli are conducting a large ocean experiment this week that will help them understand how oil is transported from outside the surf zone onto a beach. To execute the Surf Zone and Coastal Oil Pathways Experiment, the CARTHE team deployed 250 drifters, or special buoys that move with ocean currents, off of the coast at John Beasley Park on Okaloosa Island, Fla.

The drifters come in different shapes and sizes, but their positions at every second will be tracked either by an attached GPS device or satellite and aggregated into data for that day, location and time.

Alone, drifters only provide some of the data needed to assess the velocity of the surface of the ocean under different weather conditions.

Novelli recalls searching for a tool to measure the velocity at the surface of the ocean when he was first introduced to the experiment. It didn’t take him long to figure out that no such tool existed. Since then, he’s worked to fit the pieces of the surface velocity puzzle together.

“Surface currents are influenced by waves and winds,” at the air-sea interface Novelli explained.

To measure wind speed, he uses a device called an anemometer. He also measures the salinity of the water at the spot he’s testing. Depending on where the boat is anchored, the surrounding water might be fresh water from the bay or salt water from the ocean, a variable that needs to be accounted for to know its relationship to transport at the surface.

To construct data on the behavior of ocean currents, influenced by several factors, the scientists have to collect all the data at one time.

“Our point is to try to combine a lot of different instruments all at once to capture the complete picture of all what could drive the surface currents,” Novelli said.

With the surface covered, the scientists working on SCOPE will release a pink dye into the bay to get a 3-D picture of oil transport.

“The dye goes deeper,” Ozgokmen explained. “It will show us what’s happening in the vertical direction and we’re going to sample it through sensors and aerial platforms,” or small unmanned helicopters, he said.

The importance of that third dimension emerged in the summer of 2012 during CARTHE’s first experiment, the Grand Lagrangian Deployment

For GLAD, scientists deployed 300 drifters at DeSoto Canyon, in the northern Gulf of Mexico. Once back at RSMAS, they were able to track how the drifters moved with the help of satellites.

Data collection was mostly routine, until one riveting day in August when Hurricane Isaac picked a trajectory that tore a path right through a line of drifters and opened up the door to a new and unexpected dimension of data.

Digging for Deeper Data

Shuyi Chen, an oceanographer at RSMAS, watched on the edge of her seat as Hurricane Isaac steered the drifters off their usual course in 2012.

On the CARTHE team, she studies how hurricanes, which frequently form in the Gulf of Mexico, might impact oil transport. When Hurricane Isaac passed through the drifters, she found herself with real-time data for her models.

“Hurricanes are a central piece of the puzzle,” Chen said. The impact of a storm is huge. Then if we add oil to that, we want to know what kind of transport problem we have.”

Hurricanes, characterized by high winds and strong low-pressure systems have the power to stir cold water from the deep ocean and bring it to the surface. This interferes with ocean chemistry and changes temperatures and currents for months, Chen said. Add oil to the equation and this could be messy and costly.

But Hurricane Isaac brought with it one more valuable piece of information for the researchers – it stirred up oil that ocean currents picked up and carried to shore.

“We thought everything else was gone,” Shuyi said. “All of a sudden you see new stuff coming in.”

Scientists had previously speculated that oil-eating bacteria had removed much of the oil from the spill, but here it was washing up on coasts again.

Understanding how oil behaves in the deep ocean and predicting how it will behave during another oil spill “begins at the well head,” says Dr. Andrew Poje, a mathematician at the City University of New York who studies hydrocarbon plume dynamics for CARTHE, in a video explaining that area of research on the CARTHE website.

Poje, along with Ozgokmen, Novelli and others are working to understand and model the hydrocarbon plume, or oil cloud, emitted from a well during an explosion and into an unstable environment of extremely cold sea water “at pressures of 130 atmospheres,” according to Poje.

“The buoyancy flux is equivalent to pumping the heat output of a decent sized nuclear reactor into a half-meter-diameter pipe at the bottom of the Gulf of Mexico,” he said.