Climate change

Warming Temperatures Threaten Fragile Balance in Canadian Arctic

NY Times,

22 September, 2014

Ellesmere Island, Nunavut — It’s August, and there’s snow on the ground. The six-week summer has already passed; our 24-hour daylight will drop to 16 in just a month’s time. Small, brittle leaves crunch underfoot as I walk across tundra that’s already beginning to freeze for the long winter ahead.

The top of the world is a cold place. I’ve been at a field camp here in the Canadian high Arctic gathering climate change data from one of the most remote and isolated regions of the planet. It is barren, wild and beautiful. Yet this place is not beyond the reach of our carbon emissions.

The land up here is warming faster than most of the planet. The 2013 Intergovernmental Panel on Climate Change report projected that the Arctic would warm much more rapidly than the global average, with warming over the land far greater than over the ocean. And it is a particularly sensitive land, where a diverse array of birds, mammals, and plants eke out an existence through eight months of winter while relying on a delicate balance of summer temperatures.

As a doctoral candidate at McGill University in Montreal, I have spent three years researching how the planet’s changing climate is affecting the polar desert ecology of the high Arctic. It’s precisely this balance of climate and permafrost, ice and ecosystems that I’ve come here to study.

In this wide-open space, with all its dangers and difficulties, lies a land that is deservedly called the Garden Spot of the Arctic. More than 600 miles north of Alaska, it harbors more than 150 species of brightly flowering plants. This is where the North American continent has ended and broken into a disjointed network of islands, some of the largest and least explored on earth.

It’s a difficult place to call home. The polar desert differs from the lower Arctic by its extreme dryness, relative lack of plant life, and brutally cold winters. It would remind me of Middle Eastern deserts — dusty soil, dry riverbeds, spattered flecks of vegetation, beautiful rock formations — if it were not surrounded by towering mountains and ice caps.

Vast stretches of flat, dry desert are cracked by the harsh winters into miles of patterned ground. The winter shatters the land into an array of shapes – polygonal patterns that repeat endlessly over vast distances. They are underlain by massive bodies of buried ice that sit in a fine equilibrium with the surrounding permafrost.

Permafrost occurs in polar and alpine areas where the ground temperature remains below 32 degrees Fahrenheit for many years. But as the planet warms, permafrost can thaw. Together with the melting of ground ice (known as thermokarst), it creates the potential for enormous changes in the Arctic landscape.

The dynamics of thermokarst are of particular interest to Arctic scientists. Wayne Pollard of McGill is a 25-year veteran of high Arctic permafrost research. He has been coming here to study the various thaw processes that give rise to the area’s unique landforms.

“Most importantly under today’s climate,” he says, “are the potential impacts of global warming on permafrost temperature and distribution, which would affect surface erosion and vegetation through runoff and thaw.”

Photo

White Glacier, near the McGill High Arctic Research Station on Axel Heiberg Island, Nunavut. The glacier has been shrinking for the past two decades. Credit Michael Becker

Dr. Pollard has been studying a particular kind of thermokarst landform known as a thaw slump – a vertical exposure of massive buried ice that begins to melt more and more of the ground when exposed to summer air temperatures. These visually impressive features resemble large mudslides eating their way across the surface of the polar desert.

While they are a natural part of the landscape’s evolution, it is the current change in their frequency and distribution that may signify the effects of a warming climate.

The summer of 2012 was one of the hottest on record for the Canadian high Arctic, with an average high in July of 54 degrees Fahrenheit and some days approaching 70. The relatively sweltering heat under the 24-hour sun caused hordes of mosquitoes to erupt, driving the resident wildlife and us nearly insane with their attacks. During that trip north, Dr. Pollard noted not just that there was a 30 percent increase in the number of thaw slumps, but that they were also causing the highest amount of erosion ever observed for this area.

“The broader scientific community supports the idea that extreme summers like 2012 are a sign of increased global warming in polar regions,” he said. “One year on its own can be a simple anomaly; however, several summers within a fixed time period, about 10 years, is more likely part of a longer-term trend.” And whether this trend is part of a natural cycle of warming or linked to human factors, he continued, “is still difficult to resolve.”

Much of the region is still developing, in geologic terms: Areas of lower elevation are relatively young, having risen from the sea as little as 1,000 years ago. Teasing out the effects of climate change, as opposed to natural landscape processes, requires careful analysis.

One way to do this is to examine parallel lines of climate research to see if the trend is detected elsewhere.

On neighboring Axel Heiberg Island, glaciologists Miles Ecclestone of Trent University and Luke Copland of the University of Ottawa are measuring how much mass the glaciers are losing. One hunk of ice in particular, the White Glacier, has one of the longest monitoring program of any glacier in the Canadian Arctic.

“The mass balance and ice core records tell us that recent climate patterns are unusually warm, particularly since the mid-1990s,” Dr. Copeland says. “For the White Glacier, these past two decades of annual mass balance measurement have been overwhelmingly negative; indeed, most glacier mass balances are becoming increasingly negative” — the greatest losses, he added, since records began in the 1950s.

This means that hot summers are becoming more frequent — an ominous sign for polar desert ecosystems that rely on stable ground ice. In addition to the catastrophic collapses of thaw slumps, melting ice causes depressions in the ground that collect snow and water runoff that give rise to meadow and wetland communities in place of desert.

Already there are signs of greening in the high Arctic. And simulated warming sites across the region predict a broad array of changes in plant communities.

The effects of warming don’t stop at the green stuff. Changes in a plant community cascade up the food web to the grazing musk oxen, hares and other herbivores that live in the desert. And while a greener Arctic with more vegetation sounds like a boon to the animals that eat the plants, the end results are not so simple.

Paradoxically, any beneficial effects of a warmer climate on herbivores’ food sources could be offset by rising humidity. That, in turn, means more snowfall, which blankets the plants that the musk ox, the largest Arctic herbivore, needs to survive.

Niels Martin Schmidt is the scientific leader of Zackenberg Research Station in northeastern Greenland, a latitude similar to the Canadian high Arctic. He has been studying the plant-herbivore interactions of musk oxen in Greenland and finding that changing winter conditions regulate their populations.

In particular, after snow-rich winters, the musk oxen have a much harder time getting to their food source and surviving these harsh conditions, and an increase in starved carcasses are found across the area.

If the duration of winter declines, Dr. Schmidt says, the population of musk oxen may gain in the short term. But “in the long run, higher temperatures will lead to fewer musk oxen, because of more unstable winter conditions.”

The high Arctic is changing. The interactions among all the elements of the region are complex, especially given the added influence of human-driven climate change. And that’s the particular threat of climate change: When we disturb one aspect of the system, we affect all the other parts that rely on it, with unforeseen consequences for the Arctic and the entire planet