WHAT’S THAT, DEEP IN THE GULF OF MEXICO?

Scientists don’t know as much as they should about the furthest fathoms of a valuable body of water – but that’s about to change.

THE SURFACE

Three hundred and seventy kilometres southwest of New Orleans, a vessel called the Turritella floats on the surface of the Gulf of Mexico. It’s an FPSO, which stands for floating production, storage and offloading facility; basically a cross between an oil platform and a tanker. This particular FPSO belongs to Shell Oil Company, and it is connected by very long pipes to the deepest oil and gas well in the world, in an area called Stones Field. There’s just one huge problem: in a strong storm, an FPSO like the Turritella can cut loose from the well and run.

Three kilometres away, a yellow sensor buoy called a metocean station monitors meteorological and oceanic conditions. This helps Shell protect the Turritella from unexpected storms, which could dislodge the pipes from the oil well, which would be a disaster. Every well in the gulf has a metocean station, but the Turritella’s is special: it is tied to the bottom of the gulf by a plasma rope, a shark-resistant tether that cuts through a rare watery territory that scientists know very little about.

Water deep beneath the surface has its own weather: cold and warm masses of water interacting and forming currents, just as air does in the atmosphere. Storms can brew underwater, affecting the health of the gulf’s R12-billion fishery, and the operation of its wells, which in 2015 produced 553 million barrels of crude oil and 36 billion cubic metres of natural gas (16 per cent and 4 per cent of total US production, respectively). Oil companies monitor for bad weather, but there is a lot more to study, and many oceanographers would love to expand their research deeper. But the equipment required to do so is expensive. That’s why two oceanographers with whom Shell scientists had previously collaborated – Stephan Howden, from the University of Southern Mississippi, and Steve Dimarco, from Texas A&M – were thrilled when Shell contacted them in August 2016 and invited them to attach sensors to the Turritella’s metocean station’s 2 900-

metre tether. The idea is that Howden and Dimarco journey with Shell to deploy new instruments, which will hang from the line like charms on a bracelet, filling in, metre by metre, the picture of the deep.

“With the surface, I can pretty much assure you currents are going clockwise, looking down at the basin,” says Dimarco. Water in the gulf comes in from the Yucatan, shadows the American Gulf Coast and leaves. “But once I get away from deeper than 200 or 300 metres from the surface, I can’t tell you which way they’re going. That’s crazy.” Dimarco pauses. “And I’m the one who would know.”

Nineteen years ago, with improving technologies allowing oil and gas companies to shift focus from relatively shallow wells on the continental shelf to deepwater projects, Dimarco was on a team that won a US Government contract to gather all the data that had been collected on the deep gulf. There wasn’t much. But the authors noted that the oil and gas companies were gathering a lot of useful information to protect their people and equipment and suggested they share it. That suggestion eventually became law and led to the Stones Field collaboration.

Today Dimarco studies hypoxia, a lack of oxygen in water that every summer produces a dead zone for sea life on the continental shelf of Louisiana. It’s caused largely by water that has become hypoxic due to an abundance of nutrients pouring in from the Mississippi River. Ocean currents can pull that water into the deeper gulf, where it’s less of an issue, but Dimarco can’t be sure the problem disappears entirely. At Stones Field, he plans to install fluorometers to measure biological activity and dissolved-oxygen meters to watch for hypoxia throughout the water column, to ensure that the dead zone doesn’t expand.

A depth of 1 000 metres marks the edge of Shell’s legally required observations. But they have an interest in what’s going on further down. “They’re having to put pipes down from that rig all the way to the ocean floor,” Dimarco says, “and if a current comes by and strums that pipe like a guitar string, it Used to determine carbon levels in the water, which helps assess nutrients entering the gulf.

could vibrate, and that vibration could cause fatigue, and the fatigue could cause it to fail.”

Dimarco and Howden will add current sensors throughout the water column. But at 1 000 metres, pressure is 100 times that at the surface. Instruments that can function in those conditions are expensive. Hiring a boat just to place instruments might cost R150 000 a day at the cheapest, says Howden. Dimarco says a good boat is probably more like R300 000 a day, and adds that just paying out 2 900 metres of rope is a full day’s work. By giving the universities both the line and the boat, Shell isn’t just making the work convenient – it’s making it possible.

THE ULTRADEEP

Fifty metres from the seafloor, Howden wants a turbidity sensor to measure the amount of sediment in the water. Deep eddies disturb material on the floor, introducing nutrients that feed organisms at the bottom of the food chain, which has ripple effects for the animals up top. With a system the size of the ocean, ripple effects and long-term patterns are of great significance. For scientists like Dimarco and Howden, beholden for funding to US organisations such as the National Science Foundation and the National Oceanic and Atmospheric Administration that fund work for, at most, a few years at a time, it’s practically impossible to study some aspects of the gulf, which may unfold over a decade or more.

But in April and every six months thereafter, until Turritella goes home for good – decades from now – Shell will send a boat out to the metocean station for routine maintenance. It will carry emissaries of the two universities. The crew will trigger a remote-control release that floats ten metres off the seafloor and then pull up the rope. Data will be collected and new instruments will be added as part of the longest, deepest study of the Gulf of Mexico ever known, and knowledge will grow in an unprecedented way. Then the rope will be reattached to its anchor; two stacks of four railroad wheels. They’re fixed to the ocean floor, 5 200 metres above a monumental cache of oil and 2 900 metres below the surface of the gulf, sentinel to two resources of incalculable value.