By August, the sun has melted away winter snow, revealing a mountaintop wrapped in thick bodies of ice. A shiny ice cap stands out against the blue sky. Towering 10,778 feet above sea level, Mount Baker holds the second largest glacial system in the contiguous United States. But like others around the world, Baker’s glaciers are receding.
Past weather records show a trend of warmer, wetter winters and less snow accumulation. The resulting glacial recession on Mount Baker will alter the ecosystems connected to these massive bodies of ice because glacial melt provides a late summer water supply that humans and salmon rely on.
According to a masters thesis written by Joel Harper, a former Western Washington University geology graduate student, Mount Baker glaciers retreated in the 1940s, advanced from the 1950s to the early 1980s, and retreated again in the mid 1980s.
For the past five years, Doug Clark, an associate professor of geology at Western, has measured the end of the Easton Glacier, located on the south slope of Mount Baker, and found the glacier has receded approximately 150 feet within that time.
"The glaciers on Mount Baker are retreating, but slowly," Clark said. "They may advance some in the future, but not enough to counteract the retreat of the past 100 years."
Glaciers accumulate mass when snow falls on the glacier in the winter, said Joe Wood, a geography graduate student at Western. The snow left over at the end of the summer compresses and recrystallizes, eventually adding to the glacier’s size.
Glacial recession depends on how much snow accumulates in the winter and how much snow and ice the glaciers lose in the summer, said Jon Riedel, a geologist for the North Cascades National Park.
The Pacific Northwest recently experienced warmer summers and winters, Riedel said. In these winters the glaciers on Mount Baker received less snow and more rain, resulting in less snow accumulation, he said.
However, glaciers do not respond to just one year of weather, Clark said. "If we have one good snow year and another bad, the glaciers aren’t going to immediately show that," he said. "It typically takes 10 to 15 years for a glacier to respond to a changing climate."
Clark said the glaciers respond in part to Pacific Decadal Oscillation, a normal Pacific Northwest climate cycle. PDO consists of several decade-long periods of warm, dry climate conditions and switches to cooler, wetter climate conditions, said Andy Bach, an associate professor of environmental geography at Western’s Huxley College of the Environment. PDO has a large impact on the Pacific Northwest climate, he said.
Bach questioned if global warming will counteract the PDO, or if the PDO will mask global warming.
"I don’t know for sure which is going to dominate," Bach said. "Most say global warming will overwhelm PDO."
If global warming plays out as predicted, snowpacks will decrease and glacial mass will diminish, Bach said.
North Cascade glaciers at lower elevations are shrinking and may even disappear. However, the high elevation of Mount Baker will allow the glaciers to remain longer, Clark said.
"It would take drastic weather changes for the Mount Baker glaciers to disappear," Clark said.
The average end-of-summer snowline altitude, an indicator of how much snow remains on the glacier at the end of the melt season, has risen on Mount Baker glaciers, said Robert Burrows, formerly a geologist for the North Cascades National Park. This indicates less snow supply to the glacier and will result in recession, he said.
Altering Connecting Ecosystems
As glaciers recede, ecosystems move upslope. Alpine plants migrate and plant succession occurs, said David Hooper, an associate professor of biology at Western. Succession is the replacement of bare soil with fast growing plants, which are then replaced by progressively slower growing phases of species.
Receding glaciers expose sand, gravel and rocks, Hooper said. The soil is incapable of supporting vegetation initially, but nitrogen fixers such as lichen and herbaceous plants colonize the bare ground, making nutrients more available, Hooper said. As more nutrients are available, red alder, another nitrogen-fixing plant, moves in, followed by other tree species, he said.
"You can see this succession happening below the Coleman Glacier," Hooper said, referring to the glacier located on the west slope of Mount Baker.
The treeline on the mountain is also progressing upslope. The treeline is the point on alpine terrain where trees stop growing.
Global warming can create conditions suitable for the establishment of trees at higher elevations, said David Wallin, a professor at Huxley studying forest ecosystems.
In order to survive, seedlings need to be well established before the snow falls in the winter, Wallin said. Seedlings need long, warm summers to survive, which rarely happens above the treeline.
Wallin said more seedlings survive in a climate of long summers and warm winters. With a warmer climate the trees will fill in and raise the treeline, he said.
In response to forests moving upslope, animal habitats, like those of marmots, are shrinking, Bach said. Trees are invading the grassy areas where marmots live, forcing them upslope, he said.
"The marmots can only move up as high as the mountain," Bach said.
Salmon & Streams
The amount of snow and ice melt flowing into nearby streams will change as Mount Baker glaciers recede.
From June until October, glaciers begin supplying streams with water, according to a report written by Mauri Pelto, director for the North Cascades Glacier Climate Project. The NCGCP is a group from Nichols College in Dudley, Mass. that annually measures glaciers in the North Cascades.
The glaciers on Mount Baker flow into the Baker River and the North and Middle Forks of the Nooksack River. Many fish species use the Nooksack River, including the endangered chinook salmon. In the fall, if a decrease in glacial melt occurs, input of cool water flows may decrease causing the water temperature to increase, Bach said. Adult salmon, fry and eggs have certain temperature requirements for survival, he said.
Salmon prefer water temperatures around 50 degrees Fahrenheit. The chance of survival for fish decreases as the water temperature rises to 70 degrees, said Steve Seymour, a watershed steward biologist for the Washington Department of Fish and Wildlife.
Flooding, another result of glacial recession, also impacts salmon, Seymour said.
Glacial recession will increase the frequency of flooding. A glacier acts as an aquifer by absorbing snowmelt in the spring. But if glaciers reduce in size they will store less meltwater and flood streams and rivers, Pelto said.
Flooding affects salmon by washing away redds, gravel nests salmon dig to lay their eggs. They dig these nests six inches under the gravel, but a flood can wash out one to two feet of gravel. Salmon are spawning in unstable conditions because flooding in the location of redds is already an issue.
"Not having stable spawning habitat likely is one of the major limiting factors slowing down the recovery of our Nooksack salmon," Seymour said.
Water Supply
Aside from wildlife ecosystems, glacial recession also affects the people of Whatcom County. The Nooksack River supplies drinking water, hydroelectric power, recreation, fisheries habitat, irrigation and several industries with water. Bach said glacial melt has provided humans with water for decades, and humans expect rivers are always going to serve as a water supply.
"We are living on borrowed time with the summer water that the glaciers are providing us," he said.
The scientific community needs to take into account that worldwide weather patterns can affect Mount Baker, Clark said.
Global warming is a grand experiment, he said.
"There’s a lot of things we don’t know are going to happen, things we don’t fundamentally understand about how the climate works," Clark said. "It’s grand because the whole globe is involved, not because it’s great."