Mapping British Columbia’s Deflating Glaciers
Scientists use technology to find out how much mass glaciers are losing and how fast.
Much of Hakai Institute’s research focuses on a 300-kilometer swath of shore between our two ecological observatories on Quadra Island and Calvert Island. This coastal margin is defined by water, and not just in its fluid form. Bordering the coast are huge sheets of ice and snow that melt and flow into the Pacific Ocean through thousands of rivers and streams. So when we expanded our research umbrella, we started at the top—BC’s coastal glaciers and snowpack. And when it came to methods, we went straight to the obvious tool to study ice and snow—lasers.
Climate change is affecting glaciers at a not-so-glacial pace. In British Columbia, coastal glaciers are especially vulnerable, as they tend to be at lower elevations. It’s not just the edges of glaciers that retreat as global temperatures increase. The glaciers themselves are deflating. Scientists estimate that by 2100, glaciers in western Canada will shrink in volume by 60 to 80 percent relative to 2005. But the total loss of ice can be difficult to measure, especially since glaciers are always shifting around.
“These glaciers aren’t static features on the landscape,” says Brian Menounos, a Hakai Institute collaborator and Canada Research Chair in Glacier Change at the University of Northern British Columbia.
“The hope is that we can better measure how much mass glaciers are losing,” says Menounos. “The old topographic maps suffer because with snow-covered surfaces, the photos were often overexposed and not useable.”
That is where lasers come in. Using a technique called LiDAR, a light pulse is directed from an airplane down to the landscape below. A laser scanner on the plane measures the pulse after it bounces off the land (or ice, in this case) and returns to the plane. By computing the distance that millions of these light pulses travel, LiDAR systems can create a three-dimensional map of the surface.
“The accuracy of LiDAR allows us to measure more subtle ways that glaciers are changing,” says Menounos.
Melting glaciers around the world are one contributor to sea level rise. But coastal glaciers shape BC’s coast in other ways too, and their melting will have tangible consequences here. One big impact will be on rivers.
Melting glaciers also release considerable amounts of rock and sediment that were trapped in the glaciers when they formed. Imagine a kid’s inflatable pool filled with ten buckets of water. Now partially fill that pool with sand and pour in the same ten buckets of water. It overflows.
The same thing happens when melting glaciers release trapped sediment all at once. As these sediments flow down the river, some settles out on the river bottom where it gradually builds up. With their base levels raised, rivers then become more prone to flooding.
The animals that live in the rivers and surrounding ocean will feel these changes. Meltwater from glaciers keeps rivers flowing when all the snow has melted from the land, Menounos says. “This glacial runoff is especially important in times of drought.”
So fluctuations in this glacial melt could have as-yet-unknown impacts on migrating young salmon. Bright silver and the length of a toothbrush, these young salmon enter a whole new seascape as they leave the freshwater rivers where they were born. The salmon smolts swim through the deep fjords, tidal channels, and narrow straits before heading out to the open ocean to grow.
“The upgraded [LiDAR] system that we acquired with Hakai’s support allows us to fly higher and cover a much wider swath of BC,” says Menounos. “This gives us an unprecedented look at BC’s ice fields.”