Study seeks to quantify glacial meltwater in rivers

A recent study to be published in the University of Colorado’s Arctic, Antarctic and Alpine Research journal quantifies for the first time the amount of meltwater from Glacier National Park’s glaciers.

The peer-reviewed scientific study presents a model quantifying the contribution of the Park’s 39 named glaciers to local watersheds. Total glacial coverage in the Park has declined by 35 percent over the last half-century as an increasingly warm atmosphere outpaces the rate at which new precipitation allows glaciers to grow.

The research effort began about five years ago with Whitefish native Adam Clark’s graduate thesis at the University of Montana Geosciences Department, where he studied under another one of the study’s coauthors, Joel Harper. Clark now works for the U.S. Geological Service’s Northern Rocky Mountains Science Center with Dan Fagre, the other co-author of the study.

“There have been a few studies measuring melt at a handful of other glaciers over the years, but as far as calculating a number from all the glaciers in the Park, this is new,” Clark said.

According to the study, impacts to overall flows in the Flathead River will be lower than in rivers and streams east of the Continental Divide, where about two-thirds of the Park’s total glacial melt flows.

Researchers estimate glacial melt contributed about 6.3 percent of total flow in the North Fork of the Flathead River in August 2009 and about 5 percent in August 2010. For the Middle Fork of the Flathead River, the numbers were 7.5 percent and 6.3 percent, and for the St. Mary River, the numbers were 12.7 percent and 8.9 percent.

Meltwater estimates from nonglacial snow and ice was not included in the study. Above 6,500 feet, those sources of runoff can persist until July. The estimate also did not take into account evaporation and loss to groundwater.

Measurements of glaciers and their changing conditions over time are hard to come by owing to their remoteness. Researchers set up temporary weather stations on glaciers in the Park that are chosen for their representative characteristics of the larger glacial area. Clark said it took about a month to set up all the weather stations.

“In 2010, it occupied my entire summer. It was a lot of work,” Clark said. “Each glacier had a weather station installed on it, and I had to hire people to help carry stuff up there.”

Fagre, a research ecologist, co-authored the study with Clark and has spent decades studying the Park’s glaciers and the organisms that depend on them. As global temperatures continue to climb, the effects of a shorter snow season and less snowmelt overall will have more substantial effects to those downstream than just glacial melt, he said.

“The disappearance of the glaciers will clearly have an impact on the biota adapted to high elevations and the central core parts of Glacier National Park,” Fagre said. “They are also harbingers for the kind of effects that disappearing snow will have, that are much broader across the landscape than just the glaciers.”

Extrapolating those numbers to a meaningful prediction of overall water levels for downstream users will require more research.

“I think it’s a good place to start — it’s a good baseline,” Clark said. “I believe it did a good job quantifying glacier melt rates, but my comparison was simply adding up the total water melting off a glacier and comparing it to a stream gauge, which is very limiting since we don’t have many stream gauges.”

He said he hopes future studies by hydrologists will be able to fill in the gaps and help understand how the glacial meltwater actually moves through the system.