For the past 3,000 years, a massive floating platform of ice has fringed the northern coast of Ellesmere Island. Formed by the steady accumulation of sea ice, snow and glacier ice over millennia, the Ellesmere Ice Shelf was approximately 100 metres thick and extended 500 kilometres along the coast. At the turn of the 20th century, this landfast mass of ice added an estimated 8,900 square kilometres of real estate to the northern shore of Ellesmere Island, an area larger than Banff National Park.
During the past hundred years, more than 90 percent of the Ellesmere Ice Shelf has collapsed. By the year 2000, only six segments remained: the Serson, Petersen, Milne, Ayles, Ward Hunt and Markham shelves, totalling less than 900 square kilometres. After the collapse of the Markham Ice Shelf in September, only four remain. They are the last ice shelves in North America.
A diagram showing the formation of the epishelf lake in Disraeli Fiord behind the Ward Hunt Ice Shelf. The ice shelf dams freshwater runoff from surrounding glaciers in the fiord. The freshwater is less dense than the seawater and floats on top. With sufficient runoff the layer of freshwater can build up to a depth equal to the thickness of the ice shelf. A crack that formed in the Ward Hunt Ice Shelf effectively broke the ice shelf dam and resulted in the drainage of the epishelf lake. (Map: Derek Mueller (2003)) Ward Hunt cracks
The Ward Hunt Ice Shelf, at 10 kilometres thick, was the largest of Ellesmere’s shelves. In April 2002, it suffered a crack 50 kilometres long and 10 kilometres wide, running from the southern edge of the shelf to the northern edge. The split compromised the structural integrity of the shelf and allowed its dammed meltwater — the largest epishelf lake in the Arctic — to drain into the Arctic Ocean. Its three billion cubic metres of water was equivalent to the amount that flows over Niagara Falls in one week.
The Ayles Ice Island
In August 2005, the Ayles Ice Shelf made worldwide headlines when it completely calved away from the coast and drifted south with the ocean current, creating the Ayles Ice Island. Approximately 16 kilometres long and five kilometres wide, it was the size of Manhattan and weighed an estimated two billion tonnes. A seismometer at Canadian Forces Station Alert, 260 kilometres to the east, recorded tremors of the calving. But for the magnitude of the break, it all happened surprisingly quickly. A series of satellite images revealed that the loss of the ice shelf lasted no more than two hours.
The Petersen Ice Shelf, south of Ayles, was also crumbling. The shelf edge had receded each summer since 2005 and by 2008 had lost one third of its area. At the same time, hundreds of square kilometers of 50- to 70-year-old landfast sea ice had broken away from the coast, exposing the shelves to further erosion.
Ward Hunt calves
In April 2008 a large network of fresh cracks was discovered riddling the Ward Hunt Ice Shelf, a sign of further weakening. On July 22 and 23 two ice islands, totalling 20 square kilometers, calved from the Ward Hunt Ice Shelf and drifted into the Arctic Ocean. Over the following weeks, the eastern half of the shelf continued to disintegrate, and by the end of August, an estimated total of 42 square kilometres had been lost.
Serson and Markham
In the first week of August 2008, the beautiful rolling hills of the Serson Ice Shelf must have trembled like an earthquake had hit. Two huge sections totalling 122 square kilometres, more than half of the shelf, detached from the coast. A meltwater lake previously dammed by the shelf was likely lost in the breakup, another rare ecosystem washed away.
But the collapse didn’t end there. To the east of the Ward Hunt Ice Shelf, tucked away in a narrow fiord, was the Markham Ice Shelf. A satellite image from July 28 shows the 50-square-kilometre Markham Ice Shelf nestled in the same spot it had likely resided for thousands of years. A satellite image taken two weeks later, on Aug. 12, showed nothing but open water. Sometime in the first two weeks of August the Markham Ice Shelf was lost, having calved completely from the coast and drifted away in the current.
Operation Nunalivut 2008
Because they exist in remote, extreme conditions, relatively little is known about these shelves. The scientists of the Ellesmere Ice Shelves, Ecosystems and Climate Change Project, a research expedition team, have tried to fill in some of the blanks. In April 2008, members of the project, including polar scientist Derek Mueller, glaciologist Luke Copland, and molecular ecologist Andrew Hamilton travelled with the Canadian Rangers on a two-week sovereignty operation to explore the remaining ice shelves on Ellesmere Island. “We could not have been more fortunate,” says Hamilton. “We were actually able to traverse all these ice shelves and collect valuable data at a critical time.”
Hamilton had never travelled to the ice shelves before. “It wasn’t until actually being there and driving across these ice shelves and the incredible rolling hills that I really understood how unique and different ice shelves are from the surrounding sea ice,” he says. “It feels solid and that’s what makes it more incredible — these massive, massive pieces of ancient ice that we drove on a few months ago are gone now, they’re floating in the Arctic Ocean.”