THE planet arrogantly dubbed “Earth” by its dominant terrestrial species might more accurately be called “Sea”. Seven-tenths of its surface is ocean, yet humanity’s need to breathe air and its inability to resist pressure means this part of the orb is barely understood.

In June a project designed to help correct that will open for business. The seven sites of the United States’ Ocean Observatories Initiative (OOI), scattered around the Atlantic, Pacific and Southern oceans, will measure physical, chemical, geological and biological phenomena from the seabed to the surface. They will join three similar Canadian facilities, VENUS and NEPTUNE in the Pacific, which have been operating since 2006 and 2009 respectively, and the Arctic observatory in Cambridge Bay, an inlet of the Arctic Ocean, which opened in 2012.

The American project was conceived jointly with Canada, which secured funding first. Canada’s near decade-long operational experience should help to provide pointers to make the bigger operation a success. The OOI’s metaphorical flagship is the Cabled Array, which is being deployed off the coasts of Oregon and Washington, to the south of VENUS and NEPTUNE, with which it will collaborate. In particular, these observatories have a remit to study a suboceanic piece of the Earth’s crust called the Juan de Fuca plate, which is being overridden by the North American plate’s progress westward as part of the stately geological dance called plate tectonics.

As its name suggests, the Cabled Array is organised around a submarine cable—a 900km-long power and data connection between its base in Oregon and its seven submarine nodes (see illustration). These nodes are linked, in turn, to 17 junction boxes that distribute power and signals to the system’s instruments, and collect data from them. It is also connected to “profiler moorings” that let instruments travel up and down a wire stretching from the surface to the bottom, allowing a cross-section of the water column to be sampled at regular intervals.

Strange life

One of the Cabled Array’s jobs is to measure the Juan de Fuca plate’s volcanic and seismological activity, including the output of its hydrothermal vents—submarine springs from which superheated mineral-laden water emerges. These support very unusual forms of life which are not found in any other habitat. It will also, though, study more quotidian matters, such as ocean currents and chemistry, and the biological productivity of the area.

The other six observatories are tied to moorings and are powered by battery, sun and wind. They will send their data ashore via satellite. Like the Cabled Array, each has at least one profiler mooring and also a range of instruments at various fixed depths. These moored observatories, though, can reach out beyond the range of their fixed instruments using robots.

Most of these robots are torpedo-shaped ocean gliders (one of which is pictured above) that “fly” long distances through the sea, sampling sunlight penetration, chlorophyll and oxygen concentrations, and the density, pressure, temperature and salinity of the water. The ocean gliders travel by slowly decreasing their buoyancy to sink, and then increasing it again to rise. The hydrodynamic shape of their wings means that both rising and falling drives them forward at a leisurely rate of about 1.5kph.

One observatory, called Pioneer, is also equipped with propeller-driven autonomous underwater vehicles (AUVs), that can swim more strongly against currents. It is one of two moored close to shore—in its case, the shore of New England. The other, Endurance, is off the coast of Oregon. Both will measure processes such as upwelling (important for the recycling of nutrients that have fallen to the seabed), oxygen depletion (which is often caused by pollution), and the dramatic changes in water temperature, salinity and currents that happen where the continental shelf dives into the abyss.

The remaining four observatories are stationed in deeper water. At their sites the seabed is between 2,800 and 5,200 metres below the surface. Irminger Sea is next to Greenland; Argentine Basin lies in the South Atlantic; Southern Ocean is stationed off Chile’s southern tip; Ocean Station Papa is in the Gulf of Alaska. Each of these observatories will sit at one corner of a triangular study area with sides up to 62km long, the other corners of which are occupied by fixed daughter stations. Each study area will also be patrolled by gliders.

In combination, the OOI’s seven observatories will carry 830 instruments, including 32 gliders and three AUVs. The wealth of data this equipment produces will be funnelled back to Rutgers University in New Jersey and then, as is increasingly required of science, made immediately available to all and sundry. This is, after all, a taxpayer-financed project—to the tune of $385m for the construction alone.

Not everyone is happy with such open access. Some old-school oceanographers worry that they will work on a question thrown up by the data, only to be scooped. Many, no doubt, are more used to going to sea to collect samples than having data delivered to their desks. A report earlier this year by America’s National Academy of Sciences was less than enthusiastic about the OOI. It found “a lack of broad community support for this initiative, exacerbated by an apparent absence of scientific oversight during the construction process”.

That absence, though, was probably one reason the project’s co-ordinators, a not-for-profit group called the Consortium for Ocean Leadership, managed to adhere to the OOI’s construction timetable. Having a plan and sticking to it without other people shoving their oars in always makes it easier for contractors to meet their deadlines. Whether such punctuality has been bought at the expense of scientific effectiveness remains to be seen. And failures there will no doubt be. VENUS and NEPTUNE have suffered from corroded instruments, underwater landslides and damage from trawler nets. Canada has learned from these problems. For instance, it now discuss the project with fishermen and points out where equipment is located. Some researchers also think the OOI is short on staff. Canada’s observatories have five researchers overseeing 180 instruments. The OOI’s 830 will be overseen by a mere quartet.

Undersea observatories are ambitious projects, so it will take time to get them right and attract people to use the free data. One way the organisers hope to entice users is by putting instruments on Axial Seamount, an underwater volcano about 480km west of Oregon that could erupt at any time. Being able to monitor an undersea eruption live would be exciting—and not something conventional research methods could manage. There is nothing like a firework display to attract a crowd.