7 September 2011

The ocean network

By
In the inky depths of the Pacific, an 800 km network of sensors is pioneering a new way of studying the oceans.
ocean network

Credit: iStockPhoto, NEPTUNE Canada

It’s the last frontier, a vast, unexplored world where crucial processes occur – climate change, seafood production and earthquakes.

But if the subject is huge, so is the laboratory that will help us understand it. Like a Doctor Who variation on the mythical kraken, the underwater observatory called NEPTUNE has electronic tentacles that are encircling the globe.

A titanium-framed robotic explorer commanded by geosciences professor Laurenz Thomsen at Jacobs University in Bremen, Germany, captures a photographic panorama of beds of Calyptogena magnifica, unusual giant clams that thrive on sulphur from hydrothermal vents more than 800 m deep.

Meanwhile, multiple hydrophones allow bioacoustics researcher Michel André, from the Technical University of Catalonia in Barcelona, Spain, to eavesdrop on the sound melange of marine mammals and shipping along a busy sea route.

While at the University of Alberta in Canada, evolutionary biologist Sally Leys and computing scientist Herb Yang aim eight lenses to track in 3D the growth and movement of sponges and barnacles on a wave-battered rocky pinnacle.

These scientists, and hundreds more in 70 other countries, are utilising a salt-water laboratory that plunges from a pinnacle 25 m below the surface of the Pacific Ocean to a ridge nearly 2,700 m deep, stretching roughly 300 km out to sea from the west coast of Canada.

Known as NEPTUNE (North-East Pacific Time-Series Underwater Networked Experiments), this unique lab is a pathfinder for studying what happens in the ocean in real time, a feat previously impossible with traditional shipboard expeditions or submersibles. NEPTUNE’s projected 25-year lifespan means ocean scientists will no longer be limited to snapshots, but will be able to watch deep sea processes as they unfold.

There is a lot to study: a recent report from the U.S. National Academy of Sciences estimated that 95% of the world’s ocean and 99% of the ocean floor remains unexplored. Some of the most crucial challenges – from climate change to earthquakes – facing the global community can’t be effectively tackled without a much better handle on intertwined biological, chemical and geological ocean processes.

“It’s time to bring all the data together in a multidisciplinary way to try to understand the ocean as a whole system,” says Mairi Best, a geophysicist from the University of Victoria in British Columbia and NEPTUNE’s associate director for science.

Boutique seafloor observatories appeared more than a decade ago, followed by coastal installations such as VENUS, a pilot project for NEPTUNE. But NEPTUNE is the first observatory to provide a systemic overview, with 800 km of fibre optic cable carrying high-voltage electricity and high-volume data to and from roughly 100 instruments and other devices to computers around the globe. Its far-reaching tentacles enclose approximately 70,000 km2 of the Pacific seafloor – roughly the size of Tasmania.

The region under this close observation is the Juan de Fuca tectonic plate. Named after a 16th century Greek navigator who explored for the King of Spain, the 200,000 km2 plate stretches alongside the U.S. states of Oregon and Washington and the Canadian province of British Columbia.

Although the smallest of the 13 principal tectonic plates that make up the Earth’s crust, Juan de Fuca offers a rich ocean science smorgasbord, proffering hydrothermal vents, gas hydrates, oxygen-dead zones, plentiful whales and other marine mammals, underwater landslides, mass salmon migrations, as well as different plate tectonic movements associated with swarms of minor earthquakes and tsunamis.

The triangle-shaped northern portion of the plate hosting NEPTUNE also encompasses five dominant types of bathymetric environment – the coastal embayment between land and sea, the transition from continental shelf to slope, the mid-slope region, the abyssal plain of the deep ocean and a mid-ocean ridge where new crust emerges.

DOZENS OF EXPERIMENTS have been operating in these archetypal locations since December 2009, when NEPTUNE’s looped power and data cable was connected to the western shore of Vancouver Island and thus to the Internet. That meant that not only could the global science community access its devices and instruments from anywhere in the world, but also that anyone could register online for free and follow the results in real time.

“We can’t look at the whole ocean but we can identify a critical area where we’ll get the most bang-for-our-buck scientifically. And it turned out to be right in our own scientific playground,” says NEPTUNE project director and University of Victoria palaeontologist Chris Barnes.

NEPTUNE was originally conceived in 2000 as a co-ordinated Canada-U.S. project covering the shared Juan de Fuca plate. But the American proposal ran into funding problems in the U.S. Congress and is only now building momentum. It’s not expected to be operating until 2014 at the earliest and under the less-than-sexy name, the Ocean Observatories Initiative (OOI) Regional Scale Nodes (RSN).

Funding has also been a continuing concern for Canada’s NEPTUNE. While the national and provincial governments readily provided the bulk of the $100 million capital cost, they’ve been less eager to guarantee the $15 million combined annual operating costs of NEPTUNE and VENUS. The current Federal proposal is a grants competition that would cover only 40% of the operating bills for five years.

Despite such ‘big science’ costs and technological challenges, plans for other undersea observatories are popping up around the world. The Marine Cable Hosted Observatory (MACHO) in Taiwan, the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) in Japan and an installation in Turkey’s Sea of Marmara will all focus on tsunamis and earthquakes.

Wider science goals are being considered for installations off the Canary Islands, Svalbard (part of a slowly unfolding European Union plan), the South China Sea and India. Offshore oil and gas operators are also showing interest in similar cabled systems to monitor the aquatic environment in real time before they start up and during operations.

This gives them environmental credibility, demonstrating environmental stewardship, says Glen Viau, chief operating officer of Vancouver-based OceanWorks International, which designed and built crucial electrical junction boxes for both VENUS and NEPTUNE.

For the next four or five years, however, NEPTUNE will reign as the world’s largest and most technologically advanced seafloor observatory; already it is generating data at a prodigious rate of about 10 million scalar measurements daily.

That data, and how it is massaged and distributed, is a key element in the paradigm shift being wrought by seafloor observatories. For many ocean scientists, being introduced to NEPTUNE’s flood of data is akin to stepping through a wormhole to emerge in some parallel universe. Until recently their research was largely based on measurements that came in dribs and drabs – creatures hauled from the frigid depths and flopping on a ship’s deck, a few frenetic hours in a cramped, stinking submersible, or short-term readings from seafloor instruments with limited battery life.

Not surprisingly, most ocean scientists were data hoarders, keeping their findings under tight wraps until they could publish research papers. Meanwhile technological revolutions in other disciplines such as genetics and astronomy saw those researchers posting data publicly almost as soon as it was acquired.

But a shared facility such as NEPTUNE is eroding that tradition, with universal and immediate access to the observations sparking manifold collaborations, giving birth to a new speciality of ocean informatics and encouraging a Wikipedia-like approach to knowledge building. “Right now, how quickly the data becomes public is a shifting comfort zone for everybody,” says Best.

Having experimental observations available in real time on the Internet doesn’t trigger any discomfort for University of Victoria biology graduate student Katleen Robert.

Robert tackled the seemingly arcane topic of bioturbation, the burrowing and general churning of sediment caused by animals living in or on the ocean floor. This churning speeds the decomposition of phytoplankton and zooplankton which have fallen as ‘marine snow’.

Marine ecologist Kim Juniper from the University of Victoria, compares bioturbation to “raking your garden to speed up what goes on in the soil.”

In the ocean, this decomposition releases carbon dioxide back into the water column where it is taken up by plankton in the continuous recycling of carbon. The rate of bioturbation, Juniper says, is probably a key limiting factor in how well the world’s oceans serve as sinks for carbon dioxide.

Yet scientists had only the vaguest idea what that rate was, since they were dependent on observations from autonomous landers that captured video or stills at predetermined intervals and only so long as battery power lasted.

By contrast, Robert had the luxury of 24/7 access to a video camera located on an instrument platform 400 m down the seafloor slope in Barkley Canyon. To minimise light pollution for the marine life, the video lamps were turned on only 60 minutes a day.

But what division of those precious 60 minutes would best capture the sediment-mixing by crawling sea urchins and flatfish such as Dover sole and halibut? The answer, Robert determined by experiment, was five minutes every two hours, allowing two 360° sweeps by the video camera each time.

ANALYSIS OF 300 hours of video captured over 10 months yielded several scientific surprises, which Robert outlined in a presentation to the American Society for Limnology and Oceanography in February 2011. First, the sediments were completely turned over in just three months, accelerating the decomposition of organic material in the marine carbon cycle. Second, most of the bioturbation was accomplished by sea urchins, not the flatfish as previously surmised.

“The sea urchins can travel a lot faster than I thought, usually several centimetres an hour but sometimes more than 20 cm. And they track a much larger surface area because they are six times as abundant as the flatfish,” says Robert.

Third, the flatfish mixed the sediment by nuzzling down into feeding pits in the ocean bottom mud to hide from predators and feed on unsuspecting passers-by. A short-range sonar on the same platform revealed more than 50 such pits in the immediate vicinity that persisted for months. Juniper says the experiment was an important step in refining techniques for the new observatory tools. “We’re at the beginning of a new era and you have to make sure you’ve got the methods right.”

Getting the observing methods right could have life-and-death implications. Canadian government scientists are using NEPTUNE to better understand earthquakes and tsunamis – the consequences of seismic upheavals on the Cascadia fault along the Pacific coast of North America. Canadian Federal government seismologist Garry Rogers says the siting of NEPTUNE’s five seismometers lets researchers get ‘up close and personal’ with the three key mechanisms of plate tectonics – pushing, pulling and sliding.

On the west, the Endeavour mid-ocean ridge is opening where the Pacific and Juan de Fuca plates pull apart, creating new crustal rock from the upwelling molten magma. To the north, the adjoining Juan de Fuca and Explorer plates are sliding past each other in the Nootka fault, similar to the better-known San Andreas fault in California. To the east is a subduction zone where the Juan de Fuca plate dives beneath the continental crust of the North American plate.

“This is one of the most intense offshore seismic areas in the world and will let us get a better handle on these mechanisms. If we understand the seismic behaviour in one such area we can then test whether our conclusions are generic for other, similar zones,” says Rogers.

One such test zone is the Nankai trough off the main Japanese Island of Honshu. That explains why JAMSTEC, the Japan Agency for Marine Earth Science and Technology, deployed 33 short-range seismometers on the seafloor off Vancouver Island for three months last summer to augment NEPTUNE’s own.

That data, retrieved when the battery-operated seismometers came back to the surface, is still being analysed. The U.S. Woods Hole Oceanographic Institution have deployed another 10 broadband seismometers at NEPTUNE, which capture both nearby and distant tremors, but must also be retrieved before the data can be analysed.

International interest is also high in NEPTUNE’s tsunami-meter array, consisting of six recorders that sit as deep as several kilometres down on the sea floor and measure the pressure of the water column above every second. A change of less than half a millimetre in the height of the water column is detected by a frequency shift of the vibrating crystal inside the recorders.

Three of these super-sensitive bottom pressure recorders are aligned in a triangle, with sides of 12.5 km, to form the world’s only tsunami ‘antenna’, at a depth of 2,600 m on the abyssal plain about 200 km offshore.

In a Canadian government research institute on Vancouver Island just off the western coast of Canada, oceanographer Rick Thomson watches for more signals from the pressure recorders, such as the signal in March 2011 that came 45 minutes before the waning Japanese tsunami reached the central and southern shores of the island.

Thomson is Canada’s tsunami expert: “The antenna can extract much more precise information from waves coming through, such as how the speed, amplitude and frequency are changing. That means we can provide a much better estimate of when the waves will arrive at the coast.”

The Japanese tsunami provided a rare chance for a real-life test of the tsunami antenna as it crossed the Pacific. Unfortunately the antenna wasn’t functioning because a device called a media converter, a crucial link for the data-power cable, imploded shortly after installation. A solitary deepwater recorder nearby did detect the tsunami before it hit Vancouver Island, reaching a maximum height of 0.5 m to 1.5 m. In Japan, more than 7,500 km away, waves reached up to 38 m.

“That was a horrible, devastating event in Japan, but if we had had the antenna operating it would have been absolutely phenomenal data,” says Thomson.

The implosion of the converter wasn’t the only technical glitch in NEPTUNE’s operations since the observatory went online. A spur line carrying data and power at the Endeavour mid-ocean site failed just a month after an especially challenging installation. The platform where Robert was watching sea urchins also got knocked out, probably by a dredging trawler.

Even jellyfish get into the act. Scientists from the Max Planck Institute for Marine Microbiology in Bremen devised sensor needles thinner than a human hair, which the almost 290 kg, 1.3 m long Wally II robotic crawler could drive into the sea floor for a sediment profile. But a large jellyfish became tangled in the apparatus, blocking further use.

Science director Mairi Best takes it all in stride, pointing out that NEPTUNE is running high voltage electricity through salt water under conditions so corrosive that most apparatus has to be titanium coated.
“I’ve had far worse nightmares. Given the number of things that could have gone wrong, we’ve done well,” she says.

THREE CRUISES ARE planned this year to tackle wonky underwater connections, perform routine maintenance and upgrade some existing equipment. More importantly, NEPTUNE will continue to expand its research capabilities – and its physical reach.

A $1.2 million Vertical Profiler (“the most new-fangled piece of equipment we have,” says Best) extends the observatory’s reach by winching a suite of 11 instruments several hundred metres up and down from a base on the ocean floor.

The instruments measure current, carbon dioxide, light, chlorophyll, salinity, temperature, oxygen, nitrate and turbidity to track how carbon moves through the water column. Also on deck is another multi-instrument platform devised by Ifremer, the French government marine research agency, which will spy upon organisms living at hydrothermal vents, where temperatures can reach over 110ºC.

Even more innovative projects are in the works, such as seafloor receivers that interrogate electronic tags embedded in migrating salmon – something already done by the Ocean Tracking Network of Dalhousie University in Halifax, Canada – but add the observatory’s real-time magic by daisy-chaining the data back to shore.

Says Barnes, who retires in June 2011 after shepherding NEPTUNE to reality: “A new technology has come along just when scientifically, politically, economically and environmentally, we need to know a lot more about the processes that are driving change on a global scale. NEPTUNE is the pathfinder. We’ve done it.”

VENUS of Georgia

Before NEPTUNE came VENUS (Victoria Experimental Network Under the Sea), which was the world’s first cabled ocean observatory. While the $100 million NEPTUNE seafloor observatory projects 300 km west from Vancouver Island far into the inky depths of the Pacific Ocean, at a tenth of the price, the modest VENUS observatory pokes just a few dozen kilometres into the shallower coastal waters between the island and mainland Canada.

Yet technological and conceptual groundbreaking by VENUS greatly eased the way for NEPTUNE. And the pioneering observatory, which began operating in February 2006, isn’t mouldering quietly beneath the waves just because big brother NEPTUNE is now hitting top gear.

A $4.4 million government grant announced in January 2011 will double the instrument capacity at three node points along the 44 km of VENUS cables, 40 km in the Strait of Georgia, and four in Saanich Inlet. In addition, VENUS is co-opting three of the province’s coastal passenger ferries as floating research stations, by installing instruments that continually record the water temperature, turbidity and salinity. Those readings will be correlated with weather conditions from a meteorological station and satellite images of phytoplankton blooms.

“We’ll get a synoptic view of what is happening with primary production in the Strait of Georgia,” says VENUS director Verena Tunnicliffe.

VENUS has blazed new trails in other areas of marine research as well, including identifying the slender sole and squat lobster as species which can tolerate oxygen-deprived zones, and which are now becoming widespread in coastal waters around the world. And a forensic scientist infamously placed a dead pig 100 m underwater, using VENUS cameras to gauge the decay of a human body immersed in the ocean – either by accident or from foul play.


Peter Calamai is a science journalist in Ottawa and a contributing editor of Cosmos.
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