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New ocean technology primed to reveal Gulf of Maine's dimensions

Data could provide insights into climate change and other environmental concerns
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By Lori Valigra

WHAT MARINE biologist wouldn't want to jump aboard Jules Verne's fictitious Nautilus submarine and study the ocean in a living lab “Twenty Thousand Leagues Under the Sea?” While that type of fantastic technology may never become a reality, today's scientists are improving instruments that will tell them more about the Gulf of Maine and western Atlantic Ocean from the sea floor to its surface. The instruments are designed to send back data as they are collecting it, rather than researchers having to wait up to a year for an instrument to be brought in for downloading data.

The diversity of the Gulf of Maine has attracted a multitude of scientists from universities, government and private industry, along with their gizmos. The University of Maine, for example, is in the process of testing a new, 8-foot-diameter satellite dish that will be able to collect detailed ocean temperature and color data from newer, higher resolution satellites to study trends on the ocean's surface.

Also on the surface and reaching down to about 10 meters from the ocean floor along the Gulf of Maine coast are ten high-tech buoys managed by the Gulf of Maine Ocean Observing System (GoMOOS). The buoys measure currents, temperature, salinity, density, oxygen and phytoplankton with the aim of revealing more about the fine details of the water column structure.

At the ocean floor, the Gulf of Maine Mapping Initiative (GOMMI) is using so-called multibeam acoustic and other technologies to discover more about the sea bottom's features and inhabitants.

Newer technologies may yield even more information about the Gulf of Maine. For example, the University of Maine plans to buy gliders this fall that could move up and down the water column and be deployed for up to six months to provide detailed information on the water and its inhabitants at specific levels.

The new technologies have the potential to tell scientists and marine managers what types of sediment and animals make up the sea floor, the chemical and biological composition of the water column, plankton distribution and other information. A fuller understanding of the typical habitats and conditions of the gulf could help identify abnormal situations that might change the health and balance of the area. Eventually, instruments might even serve as predictors that could warn weeks ahead of time that conditions are ripe for a possible red tide or other phenomenon.

“The Gulf of Maine is an incredibly diverse piece of coastal ocean, more so than any other piece of coastal ocean in the United States,” said Andrew Thomas, professor of oceanography at the University of Maine, Orono, who is leading the satellite dish program. “The diversity is what makes it such a great laboratory for doing research.”

Satellites - the ultimate bird's eye view

Installing the satellite dish seemed an odd event by anyone's reckoning. In mid-May, a crane lifted a large dome atop a building in the heart of the forested campus of the University of Maine, Orono. Though far from the sea, the dome contained the large satellite dish that would collect highly detailed views of the ocean. It is one of a handful of such high-tech dishes in the United States that can collect ocean temperature and color data closer to shore and in much more detail from the newer National Aeronautics and Space Administration (NASA) and Indian Space Research Organisation (IRSO) satellites.

Thomas hopes the data will provide new insight into the general health and functioning of the gulf and help link these to broad scale events like shifts in the North Atlantic Oscillation (NAO). The NAO has a major impact on western North Atlantic water masses and also on winter weather along the Eastern Seaboard. “If our understanding is good enough to know that an NAO event is occurring, and if we understand the dynamics well enough, in the future we will be able to make some sort of assessment on what effect this will have on the Gulf of Maine a couple years down the road,” Thomas said. “Will the event bring colder or warmer water into the Gulf of Maine, and is that water nutrient rich or poor?”

The new dish still is being tested before it goes online fully in a scientific setting. It is collecting temperature data from two NASA satellites and the ISROs Ocean Colour Monitor (OCM) satellite, both of which deliver their data streams in a high-density X-Band transmission. The NASA satellites, which have been in orbit for two or so years, have a sensitive instrument on them called the moderate resolution imaging spectroradiometer (MODIS). But Thomas still plans to keep using data from the University of Maine's older L-band satellite reception system that gets ocean surface temperature from National Oceanographic and Atmospheric Administration (NOAA) weather satellites.

The benefit of the new X-band satellite dish system is that both temperature and color data can be picked up simultaneously as the satellites pass overhead. “This is an advantage when you're trying to understand the relationship between physical processes in the ocean and the biological response,” Thomas said. The tracking dish can follow the satellite when it is in range, and an image of the data is ready within five minutes.

The newer satellites offer crisper images nearer to the shore. The earlier satellites show a resolution of about one kilometer, meaning that every pixel on the computer is one kilometer big. That makes it difficult to see details, especially near the coast line. “The OCM data has 300-meter resolution, and MODIS has channels with 250-meter and 500-meter resolution” Thomas said. “These higher resolutions will allow us to address marine issues much closer to the coast and in finer detail than we were able to before.”

Buoys get more sensitive

Satellites and their receivers aren't the only instruments getting more sensitive. Neal Pettigrew, chief scientist of GoMOOS and associate professor of physical oceanography at the University of Maine, Orono, said his group's network of buoys soon will be fitted with more powerful microprocessors and software that can collect and transmit more detailed information. The buoys have been designed to accommodate more sensors and repair faulty ones with relative ease, all within the hostile weather systems of the gulf and western Atlantic.

GoMOOS, funded primarily by NOAA, essentially expanded upon the Penobscot Bay project throughout the Gulf of Maine. Ten buoys were first deployed in 2001 to measure a wide range of environmental conditions including wind, waves, temperature, dissolved oxygen and color. Optical sensors on the buoys can measure properties like chlorophyll fluorescence, which gives some measure of how much phytoplankton is in the water. GoMOOS has a total of 20 buoys: ten are on the water from Gloucester, Massachusetts, to Nova Scotia and the other ten are on land being repaired or upgraded at any given time. The buoys are placed up to 15 miles off shore, or where the water is about 100 meters deep. Fishermen, scientists, surfers, the Coast Guard, the National Weather Service and educators all access the GoMOOS Web site to get information on water conditions.

“GoMOOS was the only way to make significant progress on some of the problems we've been studying around the Gulf of Maine for 50 years,” Pettigrew said. The buoys yielded some initial surprises, including reversals of the coastal water system flow that scientists hadn't even suspected. “Most water doesn't make it from eastern Maine to western Maine. It just turns offshore around the Penobscot Bay area and recirculates or goes off into deeper water,” he said.

Since the buoys have been deployed, Pettigrew and his colleagues have worked at making them more hardy and able to gather more information. One example was a new inductive modem system, which is a method for sending the data from submerged sensors up to a buoy. Rather than having a tangle of electrical wires from each of the underwater sensors to the buoy, the inductive modem technique uses the voltage fluctuation that the sensor generates to send the data. The data are then moved or induced into the strong steel cable that holds the buoy in place and move up the cable to the buoy.

“GoMOOS is collecting a lot of background information now so we can start to see patterns and start to interpret and understand what the important factors are that made the 1990s a terrific decade for lobsters, for example, compared to the 1960s,” he said. “We don't know those answers yet. But we feel optimistic that we're going to learn those answers as we gather more data and see more examples of the biological variation being correlated with physical changes.”

No silver bullet

Pettigrew, Thomas and other scientists know their technologies won't be able to provide all the information they'd like to see about the Gulf of Maine, so they are sharing data. For example, the GoMOOS Web site includes satellite and other data such as information from the Coastal Ocean Dynamics Application Radar (CODAR) land-based stations that use radio waves to produce maps of ocean currents throughout the gulf. There also are regional partnerships such as the Gulf of Maine Ocean Data Partnership that is coordinated by GoMOOS and is collecting physical, biological, chemical and geologic data from various governmental, research, nonprofit and academic entities including the Maine Department of Marine Resources and the National Marine Fisheries Service.

The scientists also are watching new technologies that might fill in some information gaps. One technology they are excited about is autonomous underwater vehicles (AUVs) or gliders, which NOAA and a handful of universities already are testing in waters. The University of Maine plans to buy gliders and put them into the water either later this year or next year.

“The nice thing about the gliders is it's like a submarine slicing through the water, and it can make excursions up and down in the water column as it's sailing along,” enthused Thomas. “So it gives you this vertical picture of the phytoplankton and the temperature structure.” The satellite provides a look at only the ocean surface, to give it a two-dimensional view. The glider provides data in other directions, so it fills in the picture of what the ocean is doing.

AUVs can provide detailed, multi-dimensional views of ocean biology, chemistry and physics for extended periods of time, some as long as six months. The gliders can operate alone or accept new commands from shore during a mission to change their observing strategies. They can travel for several thousand kilometers because the sensors on board are small and require low power. Earlier underwater vehicles called remotely operated vehicles (ROVs) were limited by the tether to a mother ship that controlled them, although they also collected valuable samples.

“The AUVs are the most exciting new technology,” added Thomas Noji, chief of the Ecosystems Processes Division of NOAA Fisheries' Northeast Fisheries Science Center (NEFSC) in Sandy Hook, New Jersey. Noji said the AUVs aren't measuring the ocean in a new way; their advantage is they can get into study areas that would be difficult or too expensive for humans to attempt.

Maps of the deep

Noji is part of the Gulf of Maine Mapping Initiative (GOMMI), a U.S.-Canadian research collaboration to map the sea floor of the Gulf of Maine. About 15 percent of the sea floor was mapped before the survey, and Noji said that will increase significantly when information from a current survey is added.

GOMMI uses a variety of technologies, an important one being the multibeam acoustic instrument being used in a large survey of the Gulf of Maine, part of which took place earlier this year and the remainder of which was scheduled to be completed this fall. The survey included up to 90 ship days across a wide swath of the Gulf of Maine. The Center for Coastal Ocean Mapping at the University of New Hampshire will do most of the basic mapping, and the NEFSC will use those maps to help it decide where to do more groundtruth sampling and get other types of information. “We're mostly looking for habitat characterization and mapping,” Noji said. “These are the two big things we need for fisheries management.”

Susan Snow-Cotter, director of Massachusetts Office of Coastal Zone Management, said GOMMI's strategic goal is to completely map the Gulf of Maine using consistent technology. “We believe sea floor mapping is useful for a range of applications for fisheries management and for environmental management,” she said. NOAA provided the initial $1-million worth of survey time. States like Massachusetts also are working on mapping. She added that the state recently said it would commit $1 million toward additional mapping that will be focused on Cape Cod Bay, because the state already has maps in the works with the U.S. Geological Survey in Woods Hole, Massachusetts, from New Hampshire to Boston Harbor. She said the Canadian participants in GOMMI were asked recently to create a study plan for the Bay of Fundy. “So there's good momentum north of the border as well,” she said.

The GOMMI multibeam technology uses a wide range of frequencies to send signals to the sea floor to see if it is hard or soft, how deep it is and get an idea of its features, such as underwater mountains. The instrumentation includes an on-ship transducer that sends signals to the bottom. The instruments feed information into receivers and computers. Noji said the signals are at frequencies that “to our knowledge” do not interfere with the communications of marine mammals.

Depending on the way a certain frequency reflects back to the ship, the receiver onboard the ship gets information that the computers can turn into very high-resolution bathymetric maps of the sea floor depth several hundred meters down, with accuracy within a few meters. This results in accurate views of the positioning of the sea floor and the altitude or extent to which any feature on the sea floor is raised above the average sea floor height.

“Offshore multibeam technology has revolutionized sea floor mapping. It's akin to what aerial photography did for terrestrial mapping,” he said.

As excited as Noji gets about multibeam and AUV technology, he said no technology could replace a scientist's getting his or her hands on an actual piece of sediment or habitat. Still, he's intrigued by the advance of technology like gliders to get to new ocean frontiers. “The greatest impediment to mapping is not so much the availability of the technology, because there's a lot of good technology out there, but it's being able to get it into the habitats, to get it into those areas to do some measurements,” he said.

For more information:

National Marine Fisheries Service, Northeast Fisheries Science Center
www.nefsc.noaa.gov

University of Maine, Orono's Satellite Oceanography Data Laboratory
www.seasurface.umaine.edu

Gulf of Maine Mapping Initiative
www.gulfofmaine.org/gommi/

Gulf of Maine Ocean Observing System
www.gomoos.org

© 2005 The Gulf of Maine Times