While melting Arctic ice makes regular headlines, glaciers in the Pacific Northwest are melting too.
In the Skagit River watershed — home to the most glacial ice in the United States outside of Alaska — an estimated 12.4 square miles of ice has been lost since the 1950s, according to a recent study by staff with North Cascades National Park’s Glacier Monitoring Program.
That’s an area about the size of the city of Mount Vernon.
“The area has already experienced enough glacier loss that a significant amount of water has been lost to the watershed. This is water people use, fish need (and used for) hydropower generation,” U.S. Geological Survey hydrologist Erin Whorton said. “This is an extremely important issue for Washington.”
A certain amount of glacier melt each year is good. During the summer months, it replenishes streams that connect to the Skagit River, thereby supplying water during a time when snowpack is often gone and there is typically little rain.
But over the past several decades glaciers have been melting more during the summer than they have been growing during the winter.
Glaciers in the North Cascades have shrunk an estimated 19 percent since 1959, according to the study. The ice lost is equivalent to about 100 years worth of fresh water supply, based on current consumption rates in Skagit County.
Geologist Jon Riedel, one of the authors of the study and a member of the Skagit Climate Science Consortium, said while he was aware the glaciers were shrinking long before he started the study, he was taken aback by just how much ice has been lost.
“I was surprised by the magnitude of the change in total glacier volume,” said Riedel, who leads the North Cascades National Park’s Glacier Monitoring Program.
The loss of glacial ice is attributed to a combination of less snowpack accumulation, longer melt seasons and higher temperatures in recent decades.
A water issue
During the summer months, glacial melt provides 6 to 12 percent of the water in the Skagit River at Concrete, according to the study.
Riedel said because the glaciers have shrunk, they now provide 24 percent less water than they did in 1959.
“In other words, the block of ice is smaller, so it is logical that it would produce less water,” he said.
The amount of ice lost translates to about 800 billion gallons of water that is no longer available as a reserve for communities in Skagit County.
The study offers the first evidence that the amount of water from glacial melt is decreasing in the Skagit River during the summer months, Riedel said. It’s also the first attempt at quantifying how much ice, and in turn water, has been lost to a warming climate.
State and federal agencies have said for years that the North Cascades glaciers are critical to the state’s water supplies.
An April 2007 fact sheet from the state Department of Ecology concluded that the state is vulnerable to climate change because of its reliance on water from melting snowpack and glaciers during the summer months.
Tom Buroker, of the state Department of Ecology’s water resources program for the Northwest Regional Office, said water supply managers in parts of the state that rely on glacial melt during the summer months should look for ways to store more water during the wet season and to use that water efficiently during the dry season.
Ecology’s role is to protect water resources, either by closing bodies of water to new water rights or by setting limits by such means as instream flow rules, Buroker said. In an effort to protect fish, an instream flow rule on the Skagit River suspends access to water for holders of junior water rights when the river drops below a certain level.
“If glaciers continue to recede, water users subject to instream flows will be required to stop using water earlier in the season,” Buroker said.
A secondary concern
Major water utilities, dam operators and agricultural organizations in the area said less glacial melt is not a top concern for them compared to other climate change impacts and water rights issues.
Farmers’ lack of access to a secure, adequate water supply is a problem regardless of changes to glacial melt because the majority do not have authority to use water from the river to irrigate their crops, said Brandon Roozen, director of the Western Washington Agricultural Association.
Roozen said about 16,000 acres of farmland — about one-quarter of farmland in Skagit County — have junior water rights through the Drainage and Irrigation Improvement District No. 15 and Consolidated Diking Improvement District No. 22. They are affected by the instream flow rule.
Other farmers have no rights to river water, but rely solely on rain and surface water for their irrigation needs.
For those who hold senior water rights, the primary concern regarding climate change is the projected increase in sediment — stones, sand and other materials in the water — as a result of higher flows in the Skagit River during winter, spring and fall.
“We’re going to see a lot more dirt in the river as the glaciers recede,” Anacortes Public Works Director Fred Buckenmeyer said.
He said when the city built its new water treatment plant in 2013, it changed the process it uses to remove sediment so that it can handle three times as much material.
Skagit Public Utility District spokesman Kevin Tate also said sediment is a more pressing concern than changes in glacial melt.
About 55 percent of the PUD’s water comes from the glacier-free Cultus Mountain watershed, and the other 45 percent from the Skagit River, he said. The PUD pumps water from the river as needed, primarily during the summer when the Cultus Mountain streams are low, to keep its 1.5 billion gallon Judy Reservoir full.
More sediment could increase the cost of pumping and filtering water, Tate said.
Seattle City Light, which operates three dams on the upper Skagit River, is concerned about both shrinking glaciers and less snowpack accumulating in the North Cascades. The dams produce hydropower, and are required under a a Federal Energy Regulatory Commission license to maintain river flows favorable for fish.
“We recognize that a percentage of the water coming in to the dams is coming from glaciers, so knowing that glaciers are going to be receding because of climate change, we are concerned about that,” said Crystal Raymond, climate change strategic advisor for Seattle City Light.
The power utility helped fund Riedel’s study on the North Cascades glaciers. It plans to use the data gathered to get an idea of what snow and glacial melt will be like in the future, and how that will influence dam operations on the Skagit River.
Still, Raymond said changes to snowpack are expected to have a bigger impact.
A steady decline
Excluding Alaska, about one-third of the glaciers in the United States are in North Cascades National Park, according to the National Park Service.
Over several decades of monitoring North Cascades glaciers, Riedel has seen dramatic differences between what he’s seen and what’s shown in photographs from the 1950s.
“The change in 56 years is really striking,” he said.
Glaciers grow when snow that doesn’t melt during the warm months is condensed into layers of ice. Each year the glaciers also melt some.
The difference, called mass balance, is monitored closely on some glaciers.
“It’s sort of like a bank account: The snow is the money you’re putting in and the melt is the money you’re taking out, and what is left is your balance,” Whorton of the USGS said.
The National Oceanic and Atmospheric Administration says shrinking glaciers, such as those in the North Cascades, are one of the clearest signs of climate change.
According to the agency’s State of the Climate report, 2015 marked the 36th consecutive year glaciers throughout the world have shrunk.
Riedel said the trend is expected to continue in the North Cascades as temperatures continue to increase and the amount of precipitation that falls as snow decreases.
Of 312 glaciers in the North Cascades National Park, four are included in the park’s monitoring program, which started in 1993.
Those four — Noisy Creek Glacier, Silver Glacier, North Klawatti Glacier and Sandalee Glacier — were included in the recent study, along with South Cascade Glacier just outside the park, which the USGS has monitored since the 1950s.
The USGS published a report in 2010 summarizing that the South Cascade Glacier had shrunk each year since 1953. Whorton said the glacier has continued to shrink in the years since that report.
For the recent study, Riedel and Mike Larrabee, lead technician for the North Cascades monitoring program, collected mass balance measurements and aerial photos of the glaciers.
To determine the mass balance, Riedel and Larrabee visit the glaciers twice a year: In late April to measure how much snow has accumulated and in late September to measure how much snow and ice has melted.
The differences seen between old and new photographs, as well as the steep curve of the graph depicting mass balance over the years, is telling.
All of the glaciers have lost ice, with the declines getting more severe in about 1979, according to the study. Southwest-facing glaciers and those between about 5,250 feet and about 6,890 feet in elevation have melted most rapidly.