Icebergs: breaking up is a shattering experience
Scientists fear ‘Doomsday’ Glacier collapse could drag most of West Antarctica’s ice with it
Trouble comes in all shapes and sizes. That is the case with icebergs, the hunks of ice broken off from ice shelves or glaciers. The tiniest fragments — usually about the size of a grand piano — are called growlers. Dodging them caused the oil tanker Exxon Valdez to run aground in 1989. Detecting them by eye or by radar is tricky. That makes them the most hazardous form of ice of all, according to the Canadian Coast Guard.
The iceberg that sank the Titanic was probably 20,000 times heavier than the average growler. The 1912 disaster, which caused the loss of more than 1,500 lives, catalysed the creation of the International Ice Patrol. Its monitoring work, helped by advances such as satellite image analysis, has made the north Atlantic much safer. But icebergs remain a hazard, particularly as shrinking arctic sea ice and a polar cruise boom encourage more traffic.
The real threat is found at the other end of the scale. Tabular icebergs — named after their table-like shape — can be the size of a small country. Their calving from the front edge of a floating ice shelf does not, in itself, contribute to sea-level rise. That is for the same reason that melting ice cubes do not raise the height of a liquid in a glass.
But ice shelves act as a buttress, making land-based glaciers more stable. When these shelves break up, the glacier can flow more rapidly into open water, which does lift sea levels.
Thus the concern about Antarctica’s Thwaites Glacier, which already accounts for about 4 per cent of annual global sea-level rise. Dubbed the “Doomsday Glacier” by Rolling Stone, scientists fear its collapse could drag most of West Antarctica’s ice with it. That might, over centuries, raise sea levels by as much as 10 feet.
Scientists want to drill through the ice shelf to measure the water’s warmth beneath it. But this week it emerged their investigation was being hindered by a huge broken-off chunk of the glacier. Icebergs, it seems, can be problematic in myriad ways.