News•December 4, 2012

Rogue 'Ice Islands' Pose New Threat in the Arctic

Glaciologists were appalled in 2010 when Greenland’s Petermann Glacier discharged a slab of ice four times the size of Manhattan into Baffin Bay. They were appalled again when Petermann dropped a two-Manhattan slab in 2012 — understandably so, since these, along with even more gargantuan ice discharges from Antarctica, are a clear signal that the planet is warming fast.

Derek Mueller is appalled by a more immediate risk, however. After they break off, these enormous slabs of ice — sometimes as much as 300 feet thick — can potentially wander into shipping lanes or slam into drilling rigs before they eventually break up. “People have this misguided view that climate change is reducing ice hazards,” said Mueller, a geographer at Carlton University in Ottawa, said in an interview. “But the danger from these ‘ice islands’ is increasing.”

Credit: Courtesy Anna Crawford (Carleton University)

Determining where ice islands originate, where they wander and how quickly they disintegrate is Mueller’s specialty, so he’s headed to an Arctic conference in Vancouver starting December 10 to brief colleagues on what he’s learned.

“When you look at the last 10 years, you see pieces of glaciers and ice shelves in northwest Greenland and around Ellesmere Island breaking off every so often,” Mueller said.

A normal iceberg is the size of a house or maybe an office building; these so-called ice islands are the size of a small city, and where an iceberg is often jagged, ice islands — born of ice that was already floating in the sea — are wide and flat.

Ice islands come off Antarctica, too, and they’re even bigger: “In the Arctic, we compare them to Manhattan Island,” Mueller said. “In Antarctica, it’s more like Rhode Island.” But Antarctica is essentially uninhabited, and there’s almost no ship traffic.

In the Arctic, however, there’s plenty, and as an ice island thins and breaks up it can, in theory, wander into shallower waters than an iceberg might, endangering nautical traffic and structures that might otherwise be safe.

To try and get a handle on the disintegration process, Mueller and his colleagues tracked down a fragment of the 2010 Petermann discharge known as PIIB, about 1,500 feet long and half as wide, which by the summer of 2011 had drifted down to the coast of Labrador on the northeast coast of Canada.

“We wanted to find the perfect ice island — small enough to survey but big enough to last,” Mueller said. They outfitted the slab with tracking beacons, measured its thickness with radar, and tried, but failed, to get a robotic submarine underneath to see what the bottom looked like.

“The idea was to come back the following year and see what had happened,” he said. “But the whole thing broke up and we never saw it again.”

That in itself is important information, since the rate at which ice islands disintegrate is largely unknown. It also depends on where the ice drifts, so Mueller and his team will be looking for others.

They’re also working to improve the remote tracking of ice islands. The Canadian Ice Service, Mueller said, uses radar satellites to monitor ice conditions. But satellites don’t always see with fine enough detail to pick up smaller ice islands, and when the islands’ surfaces get slushy in summer, the satellites don’t necessarily see them as ice at all, but rather as water. One of Mueller’s students is working on a new processing algorithm that will make radar data easier to distinguish. “It should be ready in about two years,” Mueller said.

The research is clearly a work in progress, in other words. But as the planet continues to warm and more ice floats freely through Arctic waters, there will, unfortunately, be no shortage of new ice islands to study.