ScienceDaily (May 2, 2008) — Scientists confirm computer model predictions that oxygen-depleted zones in tropical oceans are expanding, possibly because of climate change. An international team of physical oceanographers including a researcher from Scripps Institution of Oceanography at UC San Diego has discovered that oxygen-poor regions of tropical oceans are expanding as the oceans warm, limiting the areas in which predatory fishes and other marine organisms can live or enter in search of food.
The new study is led by Lothar Stramma from the Leibniz Institute of Marine Sciences (IFM-GEOMAR) in Kiel, Germany, and is co-authored by Janet Sprintall, a physical oceanographer at Scripps Oceanography and others. The researchers found through analysis of a database of ocean oxygen measurements that levels in tropical oceans at a depth of 300 to 700 meters (985 to 2,300 feet) have declined during the past 50 years. The ecological impacts of this increase could have substantial biological and economical consequences.
"We found the largest reduction in a depth of 300 to 700 meters (985 to 2,300 feet) in the tropical northeast Atlantic, whereas the changes in the eastern Indian Ocean were much less pronounced," said Stramma. "Whether or not these observed changes in oxygen can be attributed to global warming alone is still unresolved. The reduction in oxygen may also be caused by natural processes on shorter time scales."
Sprintall said the oxygen-poor areas have the potential to move into coastal areas via currents that flow from the mid-depth tropical oceans, where the oxygen changes were observed, and along the west coast of continents.
"The width of the low-oxygen zone is expanding deeper but also shoaling toward the ocean surface," said Sprintall, a specialist in observing changes of fluxes in ocean properties such as heat distribution.
Sprintall contributed data to the study gathered during recent cruises undertaken as part of the Climate Variability and Predictability (CLIVAR) program, a long-running study operated by the World Climate Research Programme that seeks to understand climate through ocean-atmosphere interactions.
The study, "Expanding Oxygen-Minimum Zones in the Tropical Oceans," appears in the May 2 edition of the journal Science. The research team includes Stramma, Sprintall, NOAA scientist Gregory Johnson, and Volker Mohrholz from the Institute for Baltic Sea Research in Warnemünde, Germany.
The team selected ocean regions for which they could obtain the greatest amount of data to document the decline in oxygen. Some of the more recent data came from oxygen sensors which have been added to about 150 of the profiling floats used in Argo, a worldwide network of sensors that track basic ocean conditions such as temperature and salinity. There are more than 3,000 Argo floats operating in the world's oceans, and Sprintall said the quality of the data gathered by the Argo floats suggests that more units in the network should be outfitted with oxygen sensors.
Lisa Levin, a biological oceanographer at Scripps Oceanography who studies oxygen-minimum zones that intercept the seafloor, said an expansion of oxygen-minimum zones in the oceans could lead to diminished biodiversity and to the expanded distributions of organisms that have adapted to live in hypoxic, or oxygen-poor waters.
"I think it's uncharted territory," said Levin, who was not affiliated with the study. "Thicker oxygen minimum zones could affect nutrient cycling, predator-prey relationships and plankton migrations. Where the expanding oxygen-minimum zones impinge on continental margins, we could see huge ecosystem changes."
The results of the study are an important milestone for the ongoing work of the new Collaborative Research Centre (SFB 754) "Climate -- Biogeochemistry Interactions in the Tropical Ocean" funded by the German Research Foundation, which started its first phase in January 2008 in close cooperation with the University of Kiel. The SFB aims to better define the interactions between climate and biogeochemistry on a quantitative basis.WEATHER NOTE
Current Disaster Events
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Events in this list are picked up from multiple sources and automatically analyzed by a computer program to determine the likelihood of humanitarian intervention. News, damage maps and humanitarian situation reports are collected automatically from over 1000 on-line sources.Car built to intercept a tornado
ARVADA - Images of tornadoes captured by storm chasers often show a funnel of destruction as it rolls towards or through communities.
"We want to get the shot no one has gotten before and that's a tornado coming directly at us and impacting us," said Casey.
9NEWS caught up with Casey last month in Arvada. He was overseeing construction and fine-tuning of the TIV2. The second version of the Tornado Intercept Vehicle weighs 16,500 pounds (by comparison the average SUV or truck weighs around 4,000 pounds), boasts bulletproof windows and a specially designed chassis that will help protect the vehicle and the four passengers it can carry when it tries to penetrate a tornado.
"There are special panels that are driven down to the ground when it's time to intercept. They'll help shield us and probably more importantly prevent the wind from getting underneath the TIV and picking us up," said Casey.
All the protection and preparation for the TIV, which Casey estimates cost hundreds of thousands of dollars to construct, is for an IMAX documentary on severe weather. Casey has been chasing storms for the past six years, trying to capture the shot of a tornado passing over his vehicle. He's been in seven previous tornados, but "the shot" has eluded him.
"Event though we've been in seven tornados with this vehicle (referring to TIV1), those were too weak or they happened at night, there was always something wrong," said Casey.
In pursuit of the "right" tornado, Casey says he needed a more agile vehicle. TIV1 was a two-wheel drive vehicle. TIV2, with a retrofitted super diesel engine from Arvada-based ATS Diesel Performance, is a 10-wheel drive vehicle. Casey says it will help the storm chasing team overcome rough terrain.
"The old vehicle was two-wheel drive, so whenever we went down a dirt road trying to get to a tornado, that thing would get stuck in the mud and we'd be done for the day," Casey said.
For Casey, the images of inside a tornado are the ones he needs to get the necessary funding for the documentary.
"Everyone has seen what a tornado looks like, but not inside. We're trying to take people point blank to where they've never been. Without that shot, it won't sell," said Casey.
So he and his crew have, for the past five years, spent two months on the road eating junk food, driving tens of thousands of miles and trying to get intercept the right twister. Casey's motivation is movie-making.
Joshua Wurman, although just as enthusiastic, is motivated by the scientific aspects to be extracted from Casey's endeavors.
"The goal is to understand the differences between thunderstorms that make strong tornadoes and the ones that don't," said Wurman.
Wurman is a scientist at the Center for Severe Weather Research in Boulder. He will follow Casey in a separate truck with a mobile Doppler radar system. He will help the TIV2 navigate towards a tornado, and perhaps more importantly, Wurman says, communicate with Casey and crew on when not to head towards one.
Wurman is hoping the TIV2 and its capabilities will help gather data on a tornado's most destructive and least understood zone: the lower 30 feet.
"In order to fill that gap, those really important pieces of the puzzle about what's going on at the lowest level of the tornado, we're using a combination of unmanned pods and the TIV," said Wurman.
He's hoping the TIV and the pods will collect data on wind speeds and details of the destruction the lower zone produces. While many may see the endeavor as a thrill seeking ride, Wurman argues otherwise. He says the risks the team is taking will hopefully one day minimize the ones everyday people may face when a tornado strikes.
"By understanding the strong winds inside the tornado we can learn better how tornadoes do damage, just how strong the winds are in the strongest tornados, how do they relate to the types of damage that occur. We can build better structures in the future so they can better resist tornado damage so that people don't die inside when a tornado hits," said Wurman.
So far this year, nearly 100 people have died in the aftermath of tornadoes. It's the largest number of deaths associated with tornado activity since 1998 when 130 people died, according to the National Weather Service.
The storm chasers began their pursuits in April and plan to be on the road through June. More information on their chasing efforts can be found at http://dsc.discovery.com/tv/storm-chasers/storm-chasers.html.
One dies, one rescued from boat
Rough seas damage wind farm research vessel
By JEFF MONTGOMERY
The News Journal
One crewman died Monday after gale force winds and giant waves damaged a specialized research ship launched in March to study Delaware's offshore wind power resources.
Coast Guard Petty Officer Nick Cangemi said one of two crew members rescued by helicopter from the the RV Russell W. Peterson did not have any vital signs when pulled from the ship, reportedly after one of its tripod supporting legs had broken while the ship was propped out of the water.
"We took both people to the hospital in Maryland, where the hospital declared one of the gentlemen deceased," Cangemi said.
They were taken to Peninsula Regional Medical Center in Salisbury.
The ship, dispatched by a New Jersey company working for wind power developer Bluewater Wind LLC, was left adrift and ran aground off Bethany Beach. It ran into trouble on a day when the Coast Guard reported five rescues and a series of distress calls as winds in excess of 50 mph battered the coast.
Cangemi said the Coast Guard's Philadelphia office would investigate. He added that he could not say Monday if the Peterson was attempting to move to shore at the time of the accident, or if its unusual design and shallow hull were suited for heavy seas.
The Peterson is a type of boat that can raise itself out of the water on supporting legs, or "spuds."
"It was reported that the spuds were down and one had broken," Cangemi said. "Whether or not they were actively engaged [in moving] I have no idea."
The Coast Guard will investigate whether the Peterson should have operated at sea under the conditions that developed Monday morning.
"They'll take into account the type of vessel, what types of waves and sea state it's rated for, and also take into account the pilot of that boat, the previous record and experience in the area, all those things are taken into account," Cangemi said.
Officials with New Jersey-based Aqua Survey Inc., the boat's operator, and Bluewater declined immediate comment on the incident, as did Collin Clement, who skippered the boat to Delaware in March but was not aboard Monday.
Ken Hayes, Aqua Survey's president, released a brief statement Monday saying that the Peterson had two captains aboard at the time of the accident.
"I can't say anything about it," Clement said during a brief telephone interview.
Jim Lanard, a spokesman for Bluewater Wind, said late Monday the crewman who died was from another state. He declined to say where the surviving captain was from.
"While we're committed to building the Delaware offshore wind park, now is not the time to be addressing any other issues than sharing the family's grief and mourning," Lanard said.
The Peterson, a former Gulf Coast oil industry service boat, was working 14 miles off Rehoboth Beach on Monday when a fast-growing coastal storm whipped up 19-foot and higher waves -- triple their earlier height -- in a few hours not far from the accident scene.
Those waves grew to a height of nearly 21 feet after the accident, heights never recorded in May since a federal data buoy began recording conditions in 1986. Only a few dozen larger waves have been recorded at the buoy, 28 miles southeast of Cape May, N.J., and then only in January or February.
The Peterson, a 25-year-old research vessel that had seen service in the Gulf of Mexico, was renamed March 29 and sent to sea to support Bluewater Wind LLC's efforts to build a 150-turbine offshore wind farm in Atlantic waters east of Delaware.
Features of the boat include three 70-foot legs that can be lowered to the ocean floor, creating a tripod that can lift the boat out of the water for stability during research measurements. Those legs appeared damaged when the boat came to rest Monday at Bethany Beach.
The boat sent out a distress call at 8:46 a.m. while trying to negotiate swells of 12 to 14 feet, in winds that were were blowing at 30 to 40 knots. Coast Guard officials did not say if the boat's tripod legs were deployed at the time.
"Aqua Survey is not releasing names at this point," Hayes, Aqua Survey's president, said. "Our hearts and prayers are with the family and friends of the lost mariner."
"Haitian police and peacekeepers from the UN mission in Haiti have recovered the bodies of some 20 victims. The search continues," police inspector-general Fritz Jean said.
"Five children aged two to five perished in the shipwreck," said Evil Lavilette, mayor of south-western Pestel, from where the ferry set out for Port-au-Prince.
"Among the victims, 11 bodies have been deposited at the capital's university hospital morgue," the mayor said, adding that other victims' remains were taken to a hospital in nearby Gressier.
"There are some survivors, but we lack precise information on the number of people travelling aboard the ferry at the time of the accident. There is no authority controlling maritime transport," Mr Lavilette said in Port-au-Prince.
More than 100 people were aboard the vessel, according to police.
Member of parliament Accluche Louis-Jeune said there were as many as 200 passengers aboard the ferry when it sank about 11pm yesterday, a few kilometres from Port-au-Prince.
"At the moment, no survivors have been rescued," the MP said.
Mayor Lavilette said: "The ship's captain waited in vain for the Haitian coast guard to come to the rescue" of his passengers, many of whom were shop owners and their families.
He said the ferry was named Praise the Lord.
The accident comes a little over a year after the May 4, 2007 capsizing of a sailboat ferrying immigrants from Haiti to the US.
Fifty-nine people drowned and 78 survived in that accident in shark-infested waters near the Turks and Caicos archipelago.
Enjoy the weekend!