Ward Hunt Ice Shelf Breaks Up
A four-square-kilometre chunk of ice has broken off Ward Hunt Ice Shelf - the largest remaining ice shelf in the Arctic - threatening the future of the giant frozen mass.
MODIS Image of Ward Hunt Ice Shelf break up
Scientists say the break, the largest on record since 2005, is the latest indication that climate change is forcing the drastic reshaping of the Arctic coastline, where 9,000 square kilometres of ice have been whittled down to less than 1,000 over the past century.
“Once you unleash this process by cracking the ice shelf in multiple spots, of course we’re going to see this continuing,” said Derek Mueller, a leading expert on the North who discovered the ice shelf’s first major crack in 2002.
Location of Ellesmere Island
Dr. Mueller was part of a team monitoring ice along the northern coast of Ellesmere Island last April that discovered deep new cracks - 18 kilometres long and 40 metres wide - on the edge of Ward Hunt Ice Shelf, a 350-square-kilometre mass of ice that joins tiny Ward Hunt Island to the bigger Ellesmere. The cracks indicated a split was likely to happen.
One of the newly discovered cracks in the Ward Hunt Ice Shelf – Doug Stern
“It may weaken over time; it may melt away slowly, then all of a sudden you pass this threshold,” Dr. Mueller said. “It’s like a bar of soap. If you use the soap over and over again, it gets thinner and thinner. Then all of a sudden, it could break.
While nobody could forecast when the split was going to happen, a sea-ice forecaster with the Canadian Ice Service has said the chunk could float in the Beaufort Gyre, an ice-clogged, clockwise current in the Western Arctic, for some time and is unlikely to be an imminent danger to ships.
Warwick Vincent, director of Laval University’s Centre for Northern Studies, has called the ice break “a significant event” that the shelf has been building toward since it began gradually thinning during the 1950s. Since then, over a 40-year period, the shelf thinned from 70 metres in the early 1950s to about 35 metres in the 1990s.
In 2002, Dr Muller and Dr Vincent were part of a team that discovered that the ice shelf had cracked in two. “Over the last five years or so, there’s been an acceleration of change in this area,” Dr. Vincent said.
“We see this in a variety of indicators, including a gradual increase in air temperatures in this area. Each year it seems we’re crossing a new threshold of environmental change in this area of the world.”
Dr. Vincent said it’s important to note that the Ward Hunt ice break is “small compared to what we’ve seen in the past.”
Indeed, the largest ice break recorded in recent time was significantly larger: In 2005, the Ayles Ice Shelf, one of six in existence in Canada at the time, broke off in its entirety, rendering a 66-square-kilometre ice island that floated out to sea.
Still, the latest break “indicates ongoing change in this very sensitive area,” Dr. Vincent said.
Dr. Mueller, whom Dr. Vincent calls the pre-eminent expert on Ward Hunt Ice Shelf, says he’s concerned that the ice shelves will disappear completely.
“The take-home message for me is that these ice shelves are not regenerating,” he said. “If we’re looking at an indicator of whether climate is to blame, it’s really the lack of regeneration that convinces me. They’re breaking away so rapidly that there’s no hope of regeneration,” he said, adding that is “pretty strong evidence that suggests this is related to global warming.”
The first casualty of the fracturing of the Ward Hunt Ice Shelf occurred between 2000 and 2002, when the largest epishelf lake in the Northern Hemisphere, located in Disraeli fjord, drained into the Arctic Ocean through a giant crack in the ice.
Examining the large north-south crack on the Ward Hunt Ice Shelf that drained the epishelf lake in Disraeli fjord.
Epishelf lakes are a rare ecosystem type that is particularly vulnerable to climate change. They are created when ice shelves completely block the mouth of a fjord. Fresh water that flows into the fjord every summer is plugged behind the ice shelf and floats on top of the saltwater.
A metre-thick layer of ice on the surface of the fjord ensures the two layers of water don’t mix. The distinct layers of water in the Disraeli fjord lake created an ecosystem that supported freshwater and saltwater versions of the same small animals, such as plankton.
Scientists believe the lake was created when the Ward Hunt Ice Shelf formed off the northern flank of Ellesmere Island around 3,000 years ago. According to images taken by Canada’s Radarsat satellite, a massive fracture in the shelf occurred some time between 2000 and 2002, causing the epishelf lake to drain. By the summer of 2003, the lake had drained off the ice into the ocean, leaving no visible signs that it had ever been there.
The sudden draining of the lake also produced a flood into the Arctic Ocean. Researchers at the time estimated the amount of water that drained was the equivalent of a month’s worth of water from Niagara Falls, or around three billion cubic metres of fresh water.
However, the loss of the epishelf lake represents the demise of a very rare ecosystem type as scientists study them as possible analogues for life on a colder Earth and life on other planets. If we are losing them, we are losing the opportunity to study life earlier in Earth history and elsewhere in the Solar System.
A rocky outpost that is dwarfed by the ice shelf named for it, Ward Hunt Island is one of Canada’s northernmost points of land, located about 3,500 kilometres north of Edmonton off the north coast of Ellesmere Island in the Arctic Ocean.
The island, which is only about seven kilometres long and three kilometres wide, is home to Canada’s most northern air landing strip, and has become known in recent decades as a jumping-off point for explorations of the North Pole.
Ward Hunt Island was discovered in 1876 by a British lieutenant on Arctic explorer George Nares’s expedition to find the North Pole, which began in 1875. Lieutenant Pelham Aldrich discovered Ward Hunt Island, named for George Ward Hunt, First Lord of the Admiralty (1874-1988), shortly before George Nares decided his men could not survive another winter in the north, and ended the quest.
The eastern Ward Hunt Ice Shelf showing long (up to 15 km) meltwater lakes that form every summer in troughs on the ice surface – Denis Sarrazin
The island’s ice shelf is a remnant of the compacted snow and ancient sea ice that extended along the northern shores of Ellesmere Island until the early 20th century.
When U.S. explorer Robert Peary trekked across the top of Ellesmere Island in 1906, he travelled mostly across what was then the Ellesmere Island Ice Shelf, which at the time covered about 8,900 square kilometres. That shelf has since split into several separate shelves, of which Ward Hunt is the largest. Together, they add up to less than 900 square kilometres.
On its own, the Ward Hunt Ice Shelf represents only a tiny fraction of the Arctic Ocean's ice. However, its loss is another example of the slowly shrinking ice cover; a loss that scientists suspect will permanently change the Arctic ecosystem and add to global warming, since open water absorbs more solar heat.