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The hidden impacts of disappearing glaciers
by Sarah Boon
No climate change news story or documentary is complete without a close-up shot of the front of a calving glacier, huge chunks of ice falling dramatically into the heaving ocean. Ominous music plays in the background as the narrator declares doom for glaciers.
It’s true – climate change is turning our glaciers into thinner and shorter shadows of their Little Ice Age selves. This fun video explains exactly how we measure how much glaciers have changed – and how they’ll change in the future.
In 2009, researchers at the USGS predicted that Glacier National Park in Montana would be ice-free by 2020 — only seven years from now. Just two weeks ago, new research showed that Arctic glacier melt is ‘accelerating’, and is now ‘irreversible.’
Here in Alberta we can see glacier change in action at the Athabasca Glacier, the main outlet glacier of the Columbia Icefield. Parks Canada has installed signposts marking the location of the glacier terminus in various years during the past century – a retreat of two kilometres over the past two centuries.
While disappearing glaciers have an obvious effect on the tourism industry (think Brewster coaches driving up the Athabasca Glacier), there are other – less obvious – reasons we worry about these dramatic alterations to the alpine landscape.
Glaciologists around the globe often sell the importance of their research by saying that people rely on glaciers for their water supply. However, a 2010 study calculated that the number of people who depend on glacier water supply varies globally with both population density and watershed size. In non-arid regions outside the mid-latitudes in particular, glaciers provide only part – rather than all – of river flow.
What about in Canada? Again, that depends on where you live. In Banff, for example, in dry years up to 47% of river flow comes from glaciers in the Bow River watershed. Farther downstream in Calgary, however, on average only 2.5% of Bow River water is from glacier melt.
Rather than consider only the total amount of water from glaciers, we need to think about when that water reaches the river. Glacier melt peaks during the late summer/early fall –this is when snowmelt is long finished, and usually corresponds with the greatest human demand for water. So glaciers can augment river flow late in the summer, especially during dry years.
With climate change, increased glacier melt should increase late summer flow in glacier-fed rivers. As glacier retreat continues, however, there’s less ice left to melt, and eventually that late summer flow augmentation will stop. In much of BC, most glaciated watersheds have already reached this point, and are now seeing declining streamflow as glaciers continue to shrink. In the Yukon and far northern BC, however, summer streamflow is still rising as glacier melt increases.
Hydropower is one of the main energy sources in BC, and several of BC Hydro’s generating plants are located in regions affected by glacier melt, such as the Coast Mountains and Columbia Basin. BC Hydro is well aware that glacier decline will affect their ability to generate power in these regions – the key is to determine how much water comes from the glaciers, and then model how that water supply will change as the glaciers shrink.
New hydro projects, however, are using river energy – rather than reservoirs – to generate electricity. In northern BC, the Forrest Kerr run-of-the-river hydro project is expected to provide 195 MW of power from the Iskut River. Trouble is, this river receives a high proportion of flow from glacier melt – and as glaciers continue to retreat, that power generating potential will decline.
Ecology and biodiversity
Imagine you’re a water bug (invertebrate) living in a glacier-fed stream, enjoying a fairly constant range of water temperature and quality over a period of centuries. As the glacier retreats and feeds less meltwater into the stream, however, the water temperature and alkalinity go up while the amount of sediment decreases. Turns out this new habitat isn’t overly hospitable for you anymore, and you can’t compete with new invertebrates that thrive on these conditions and are moving in in droves.
Given that invertebrates form the base of a larger food web that includes salmonids and other species, the far-reaching effects of glacier change are obvious. When you consider that changes in water quality also affect those larger species (e.g., cold-water salmonids such as bull trout and cutthroat trout), the problem becomes even more complex.
While glaciers themselves move very slowly, glacier lake outburst floods (GLOFs) are fast and potentially deadly. As temperatures warm and glacier melt increases, meltwater often collects in lakes at the toe of the glacier. These lakes can be dammed by either glacier ice or morainal debris that keeps the lake contained. Once the lake reaches a certain level, however, the dam can be breached, allowing the stored meltwater to flow downstream in a catastrophic flood. Here in Canada we’ve seen this happen at the Llewellyn Glacier in northern BC.
So next time you’re watching the news and an awe-inspiring glacier shot comes up to illustrate climate change, consider the cascading effects of glacier thinning and retreat. Chances are you’ll never look at those pictures the same way again.
Tagged with: Andes • Arctic • Athabasca Glacier • BC Hydro • Bhutan • Bow River • British Columbiam run-of-river • canada • climate change • Coast Mountains • Columbia Basin • Columbia Icefield • Forrest Kerr • Glacier National Park • glaciers • Jasper National Park • Llewellyn Glacier • Nepal • Peru • Pyrenees • Rockies • Sarah Boon • water • watersheds