RICK DURNFORD lassoes icebergs for a living. The ship he captains, the Maersk Detector, unspools thick polypropylene rope, circles around a floating island of ice to form a loop, tows the berg away and releases it onto a new course. It is a tricky process. In the patch of the North Atlantic where Captain Durnford operates, not far from where the Titanic sank, waves can reach 30 metres (100 feet) in height and fog blinds him 40% of the time in the clearest months. Icebergs can break apart or roll without warning. But the biggest risk is that the rope will get entangled in the ship’s propellers in high seas. “There is a little bit of skill involved,” he says.

The Detector mainly diverts icebergs not to protect shipping but to shield five offshore oil platforms on the Grand Banks, 300km (200 miles) east of the Canadian province of Newfoundland and Labrador. The threat can come from icebergs that rise above the water to the height of office blocks, one of which ran aground off Ferryland in April, or from growlers, the size of cars above the water’s surface. These can be blasted with a water cannon.

When the Hibernia oilfield was discovered in 1979 on the Grand Banks, a plateau in shallow waters, many doubted that petroleum could be pumped safely. The area lies in the path of the Labrador Current, a conveyor belt for icebergs calved off Greenland’s glaciers. Anything bigger than a medium-sized berg (with a submerged portion that extends down 80 metres) can run aground if it is not carried east or west by the current. This year more than 900 icebergs, double the average number, have drifted below 48°N, the latitude south of which they pose a danger to shipping. Most went nowhere near the oilfields. But it takes just one to mangle pipes bringing oil to the surface. Even growlers are a threat to floating platforms and ships on the open ocean. Since Hibernia’s crude oil started flowing in 1997 no platform has been seriously damaged, though floating platforms have had to suspend production to move out of the path of an iceberg that abruptly changed course. Iceberg avoidance may soon get harder. On June 14th the 750,000-tonne Hebron platform was set down on the seabed of the Grand Banks, providing icebergs with another target. Oil firms are eyeing opportunities in the deeper waters of the Orphan Basin and in the Flemish Pass, popularly called Iceberg Alley. There, bergs that would ground on the Grand Banks sail through on stronger currents. Captain Durnford’s berg-towing operation is the low-tech end of an increasingly high-tech enterprise. Satellites are the first scouts, spotting objects that might pose a threat. A scattering of white pixels could be a ship, a pod of whales or even a range of high waves, says Desmond Power, head of remote sensing at C-CORE, which developed software to interpret satellite scans. Based on facial-recognition technology, it can distinguish bergs from belugas. To get a closer look, Beechcraft King Air prop planes operated by PAL Aerospace survey as far north as the Davis Strait during iceberg season, from April to the end of June. Craig Trickett, a sensor operator fresh from a flight that spotted 100 icebergs of interest, thinks he has the “the coolest job on the planet”.

The closer they come to the platforms, the more their operators want to know. Software from Rutter, a Canadian firm, uses ordinary radar data from supply ships like the Maersk Detector to help judge whether an iceberg is on a collision course with an oil platform. The SeaDragon, a prototype vessel, uses lasers above the water and sonar below to provide three-dimensional pictures, which can help predict an iceberg’s path.

The firms behind the iceberg-deflecting technology are finding other uses for it. C-CORE is using satellite imagery to watch how buildings respond to tunnelling for Ottawa’s public-transport system. Rutter helps spot drug-smugglers in the Caribbean. Brad de Young, who developed the SeaDragon, says its successor, the SeaDuck, could survey submerged structures like the bases of offshore wind turbines.

The technology does not replace the work of Captain Durnford, who is temporarily in command of the Maersk Detector until he rejoins his usual ship. Despite its dangers, “I’ve never missed a night’s sleep,” he says. As oil platforms move farther into Iceberg Alley, he and other ice-wranglers will cheerfully follow.