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One drifter about to leave the Gulf

June 21st, 2010 1 comment

Figure 1:  Little change in the oil slick forecast.  Check out the Horizon Marine drifter that came off the west Florida outer shelf and is now in the Loop Current. It is already east of Key West.

Figure 2:  Lets add the currents, from the HyCOM model (white vectors) and from the HF Radar networks (red/orange/green vectors).  We’ll use this to zoom into the two slicks.

Figure 3: Zoom into the northern slick near the drill site. The most significant development in the datasets available is that the HF Radar network has picked up a shift in the 25 hour average currents shown here. Most currents in the HF radar field now have a westward flow component.

Figure 4: Here we overlay the HYCOM current vectors in white, and most of these vectors are still running to the east in northern part of the slick.  Looks like HyCOM has not yet picked up the current shift observed in the HF Radar on the middle to inner shelf.

Figure 5:  Now we move over to the Florida shelf and zoom into that Horizon Marine drifter that left the outer shelf and drifted into the Loop Current. It is moving rapidly eastward, and is now well past Key West.  Note that there is a low concentration slick exactly at the point where this drifter made the turn into the Loop Current.

Figure 6:  Flipping the HyCOM sea surface height (colors) and surface current vectors (white arrows), we see how well HyCOM is doing in the region on the outer shelf. The Horizon Marine drifter made it across the narrow shear zone between the southwest flowing Loop Current Eddy, and the northeast flowing Loop Current, and is now on its way out of the Gulf.  The oil slick in the NOAA forecast is still in the part of the flow that is recirculating in the Loop Current Eddy.

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Glider data on June 21st

June 21st, 2010 No comments

Glider operations continue today with several gliders potentially being recovered by the end of the day by Mote teams deployed this morning.

For the four gliders in the Northern gulf where in and near the spill site, the gliders continue to conduct a range of surveys.  The iRobot/APL glider continues its high resolution survey.  The 2 NAVO gliders are flying in formation towards the spill zone.  The Scripps/WHOI glider is maintaining its offshore survey. The NAVO and Scripps/WHOI glider reveal a stratified system.  The features observed in the NAVO gliders is no longer evident however there are some indications of the bottom nepheloid layers.

In the spill zone, the Seaglider continues it high resolution survey.  The unique features observed in the spill area is not found in any of the other zones.  The mid-water CDOM plume has now been an consistent and bright feature observed over the last two weeks and as this structure has not been observed by any of the other gliders predictions and discussion between the team believes this is an oil plume.

The gliders along the West Florida shelf show a remarkably consistent picture.  All particle, plankton, and CDOM variability is associated with bottom layers below the pycnocline.  The along shore transect by WALDO, which is surfing the southerly flowing current, also shows little along shelf variability.

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Mini subs from Rutgers helping to predict spread of oil in the Gulf

June 21st, 2010 No comments

Monday, June 21, 2010

BY JAMES M. O’NEILL
The Record
STAFF WRITER

Rutgers oceanographer Scott Glenn observing data sent back by two gliders in the Gulf of Mexico.

A Rutgers University ocean lab has two remote-controlled gliders, or small robotic submarines, in the Gulf of Mexico helping federal agencies predict the path of the oil plume from the BP spill.

Shortly after the spill occurred in April, the National Oceanic and Atmospheric Administration turned to ocean experts at Rutgers’ Coastal Ocean Observation Lab. The lab sent down two research gliders with sensors to collect ocean data in the Gulf. They remain deployed off Tampa, Fla.

The Rutgers team has also taken the lead role in consolidating all the data coming in from a small fleet of other research equipment scattered through the Gulf. Having all the information sent to the lab in New Brunswick has enabled scientists from NOAA and other government agencies to get a more complete picture of the oil spill — and its possible path.

“This is what we do, and so when we heard about the disaster, we knew this was how we could contribute,” said Josh Kohut, a Rutgers oceanographer associated with the lab.

So far, the gliders have sent updates about the flow of ocean currents as well as water temperature and salinity readings, which researchers are using to create models that predict where the oil spill might go.

The gliders are also reading the colors of fluorescent light in the water, which can be produced by aquatic life and other organic material, including oil. Several gliders stationed along the Louisiana and Mississippi coast near the spill have detected certain fluorescent bands that are distinctly different and that researchers think may be produced by the oil. They are awaiting confirmation from signals from shipboard sensors.

The Rutgers gliders off Tampa have not yet detected this kind of fluorescence. Instead, they have so far recorded the fluorescent bands that scientists say are consistent with the region.

The lab has used gliders for a decade to measure the speed, salinity and water temperature of the ocean currents off New Jersey. Last year, the Rutgers team became the first to successfully send one of the remote-controlled gliders clear across the Atlantic, from New Jersey to Spain.

Array of applications

Rutgers’ use of the gliders has helped change oceanography and provides a wealth of new information on the ocean with a wide array of applications that can help at-sea rescues, the fishing industry and, now, federal officials monitoring the BP oil spill.

The gliders – which look like small yellow torpedoes — are made from plastic and aluminum, are 6 feet long and weigh about 100 pounds. They can operate for more than a month on a bundle of alkaline batteries and use a little more than a watt of power at a time — the equivalent of three or four Christmas tree lights, said David Aragon, a research staffer.

They send data back to the lab by satellite phone in their tail fins.

The gliders move slowly — no more than a half-mile per hour — and because they have no propellers, they can’t move in a straight line. They follow a roller-coaster path. The glider’s nose captures water, which helps push the robot forward and down, and then spits the water out, sending the robot back up toward the surface, said Scott Glenn, a Rutgers oceanographer and a co-founder of the Coastal Ocean Observation Lab.

Researchers can switch out different sensors in a glider’s payload depending on what kind of data they’re seeking.

In addition to Rutgers’ two gliders, the team in New Brunswick is consolidating data from gliders in the Gulf owned by the University of Delaware, the University of Washington and the University of South Florida.

Federal officials are able to obtain information on ocean movement from orbiting satellites that can read deeper water currents, and from shore-based radar that can measure shoreline ocean movement. The gliders are helping them gather information in a zone that neither the satellites nor the radar can read.

Much of the spill cleanup has been focused on the oil on the Gulf’s surface. But some researchers have detected possible plumes of oil weaving through the Gulf far below the water surface.

“Whether an underwater plume of oil really exists is still being debated,” Glenn said.

In the Gulf, the gliders have faced some problems, chiefly groups of remora, also called sucker-fish. They normally hitch free rides on sea turtles, sharks or other larger fish, but apparently have taken a liking to the gliders, Glenn said. As the fish latch on, they prevent the robots from ascending to the surface.

Rutgers currently owns 20 gliders, which cost $70,000 to $100,000 each. Its gliders have been used off the coasts of New Jersey, Puerto Rico, Hawaii and Australia, and in the Mediterranean Sea. Researchers are starting to use the robots in heavy weather to better understand the impact of storms on currents.

“They don’t get seasick,” Glenn said of the gliders.

The lab’s main data collection room looks like a miniature NASA launch control center. Large color monitors cover one wall, and these days show updated color-coded images of the Gulf of Mexico, with warm areas shaded dark orange and cooler areas depicted in greens and blues. Hundreds of thin white arrows on the screens show the direction of Gulf currents.

Antarctica mission

Rutgers' battery-powered gliders are made from plastic and aluminum and weigh about 100 pounds each. They send back data from satellite phones in their tail fins.

In another room, several gliders in various stages of disassemble rest on long tables. On one tables, glider RU24 is being programmed for an upcoming trip to Antarctica.

Rutgers’ Kohut is a member of an task force set up by the state Department of Environmental Protection to monitor the Gulf spill and its potential to reach New Jersey’s beaches.

The oil is in an eddy in the Gulf. For the oil to escape the Gulf, head around Florida and float up the East Coast, that eddy would have to link up with a loop current that feeds into the Gulf Stream.

But the Gulf Stream veers off to the east once it reaches Cape Hatteras, and is more than 200 miles out to sea off the Jersey coast, making it very unlikely for any oil to wash up on New Jersey beaches, Kohut said.

In addition, the prevailing current closer to shore along New Jersey is a flow of colder water that runs south from the Arctic. The oil would have to breach this flow as well for it to move west from the Gulf Stream and hit New Jersey.

A severe hurricane or nor’easter might be able to push the oil in to shore. “It’s not out of the question,” Glenn said, but it is unlikely.

In addition, as the oil moves north it would degrade and change form, Glenn said. Some oil would evaporate off the water’s surface. Bacteria would eat some it, breaking it down. And some would form tar balls and drop to the ocean bottom.

When President Obama announced in March that he wanted to lift a ban on offshore drilling from Florida to Delaware, Governor Christie was quick to attack the idea as a danger to New Jersey’s coastline, tourism and fishing industries.

Glenn said that the closer to New Jersey a spill occurs, the more likely it will affect New Jersey’s shoreline. But because the prevailing current close to shore moves south, a spill off Delaware or Virginia would be less likely to have a major impact on New Jersey than if a spill occurred to the north and east, off Long Island or Massachusetts, Kohut said.

The time of year would also play a role, Kohut said. Summer provides for calmer currents than fall and winter. Wind can have an impact as well. Winds from the southwest, which provide cooling breezes for beachgoers in summer, also tend to drive cold deep water toward the beach.

Heavy rains that might increase the flow of fresh water down the Hudson River and into the Atlantic may also affect the salinity, and thus the buoyancy, of the water off the coast.

‘Our coast is unique’

While ocean temperatures change relatively little around the world from season to season, the most dramatic shifts occur off the East Coast. “Our coast is unique that way. Things are so dynamic in our region,” Kohut said.

“The ocean itself has its own ‘weather’ beneath the surface,” Kohut said. “There are high and low pressure systems, just as in the atmosphere. The high pressure pushes the water clockwise, and the low pressure pushes counterclockwise. And when you get a high and low pressure system next to each other, you get really fast currents in between.

“So many parts of the ocean,” Kohut said, “are still very difficult to predict.

Original Article

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