California's weather hasn't been kind to Mt. Shasta's glaciers. Can they survive?

For the past two years, Mt. Shasta has emerged from winter covered in thick blankets of white snow that conceal what decades of drought have done to the Northern California mountain's ancient glaciers.

The seasonal snows come and go on the 14,179-foot peak. For hundreds of years, the glaciers have clung to the mountain's steep slopes, slowly changing and moving over time.

But for the past few decades, droughts and periods of abnormally warm weather have caused the glaciers to shrink.

Scientists have studied the glaciers and documented their demise as climate change — with its warmer temperatures and dearth of snow — has slowly caused Mt. Shasta's glacial masses to dwindle, especially during the 2020-22 drought.

For the past two winters, average to above-average snow has fallen on Mt. Shasta. Will two seasons of robust snowfall help the glaciers recover from the damage done during droughts over the past decade?

That's not likely, scientist still say.

Will recent above-average snowfalls help the glaciers?

Hassan Basagic, a geographer who documented changes in the glaciers over the past 12 years, said the recent two years of above-average snowfall helps preserve the glaciers. But the mountain needs above-average snowfall to happen for at least another decade for the glaciers to substantially recover, he said.

Maps of the mountain note seven glaciers: Whitney, Bolam, Hotlum, Wintun, Konwakiton, Watkins and Mud Creek.

Several consecutive years of at least average snowfall and cooler summers are needed to help the glaciers recover, agreed Mauri Pelto, a scientist at Nichols College in Dudley, Massachussetts.

"They've been shrinking really fast. A couple of them have disappeared," said Pelto, who has studied the Mt. Shasta glaciers, and others in the West, for more than 40 years.

"Last year was an OK year, but didn't help them. It didn't hurt them either. This year probably will be similar," Pelto predicts. "You'd have a decent snowpack out there, maybe 150% of normal. But given how our summers have been, that's not even been enough to sustain the glaciers."

Whitney Glacier, on the mountain's north side, is the longest in California. At about 2.5 miles long, it is getting smaller and breaking into two parts, Pelto said. Whitney Glacier lost an estimated 25% to 30% of its total area from 2020 to 2022, with similar effects recorded on the mountain's other glaciers, he said.

In 2021, melted ice from the Konwakiton glacier on the south side of Mt. Shasta cascaded the side of the mountain, flooding Mud Creek, washing out roads and threatening the water supply for the town of McCloud, a former logging town just south of Mt. Shasta.

The long-term outlook for Mt. Shasta's glaciers is not good, considering the trend toward a warmer climate and less precipitation, Pelto said.

"If you asked me, 'are they going to return in anybody's lifetime or our grandkids' lifetimes?,' the answer would be 'no,'" he said.

National Weather Service records bear out the increase in temperature.

The weather service has recorded the temperatures in the city of Mount Shasta for decades. The city sits on the lower shoulders of the mountain at about 3,500 feet in elevation.

From 1970 through 2023, the average annual temperature recorded in Mount Shasta has risen 3 degrees, from 48.2 degrees in the early 1970s to 51.2 degrees in the early 2020s, according to Ryan Sandler, a meteorologist with the weather service office in Medford, Oregon.

A day-to-day difference of 3 degrees is not a lot, but spread out over a 50-year timeline, the rise in temperature is significant, Sandler said.

"That's just a lot. I mean, that changes the climate a few degrees. It's quite a shift," Sandler said. "That's a big number."

U.S. Forest Service rangers have for many years climbed the mountain to take photos of the glaciers to document the changes in them, said Nick Meyers, the Mt. Shasta Wilderness Program Manager.

The photos are taken from the same location from late August to early October in order to capture images of the glaciers without seasonal snow. The pictures are part of the Glacier Rephoto Project, which documents glaciers on Mt. Shasta and throughout the West, Meyers said.

The trend in warmer temperatures is not limited to the Northern California region, he said.

"That's similar to what we're seeing globally. I think that's pretty close to the global average trend from the 70s. I think it's close to about 3 degrees Fahrenheit," he said.

Mt. Shasta is the second-most southern volcano in the Cascade Range. Lassen Peak, also in Northern California, is the southern-most volcano in the Cascades.

Glaciers also are suffering in other nearby areas.

Basagic took part in a study of glaciers in the nearby Trinity Alps, which are west of Mt. Shasta in the Klamath Mountains. That study looked at the glaciers from the 1880s until 2013 and found "catastrophic" decline in their size.

Many of the glaciers shrank more than 80% during that time and some of them even disappeared, according to the study.

Basagic, who has studied glaciers in the West for some 20 years, said the shrinking ice is evidence of what is going on with the region's climate in general.

Not only have the temperatures shown an upward trend over the past 50 years, but in the past five years, high temperatures in Mount Shasta have spiked, Sandler said.

The highest temperature ever recorded was 106 degrees on July 29, 2022. The previous record was 105, which was recorded on July 28, 2022, Sandler said.

There were seven days in 2022 when the temperature reached 100 degrees or higher, he said. There were six days with 100 degrees or higher in 2021; and 2023, 2017 and 1981 had four 100-plus degree days, he said.

Even the years with the most 90-degree days in Mount Shasta are grouped within the past 10 years, Sandler said, ticking off 65 90-degree days in 2021; 57 90-degree days in 2022 and 54 90-degree days in 2017, he said.

'Water so pure, you can drink directly from the mountain'

Starting in 2012, Basagic began working on a project to capture photos of the glaciers each year to record changes in them. The project entails taking photos of the glaciers at similar locations at the end of the summer season, before snow begins falling again.

"They indicate there's a change going on because that's what they're responding to ― temperature and precipitation. And so, as those glaciers move, you could kind of track the climate and all glaciers kind of tell the story a little bit differently," Basagic said. "It's like the Trinity Alps will tell the story a little bit differently than, say, the Sierra and Mt. Shasta glaciers. But when you take them as a whole, they're telling you what's going on with the climate."

"They're telling us that things are definitely getting warmer and the precipitation patterns are changing," he said.

Chris Carr, who owns Shasta Mountain Guides, takes hikers on treks up the mountain and over the glaciers to the summit of Mt. Shasta. During those trips, Carr sees the glaciers from a different perspective.

From a distance, the glaciers look like static patches of white on the mountain. But up close, hikers get a more detailed view, he said.

In some places, the glaciers are more than 100 feet deep, he said. "There's large crevasses and places where you can explore and icefalls that you can walk around. So it's quite interesting," said Carr. "It's quite a dynamic landscape that changes from season to season."

"People don't realize there's a couple of high tarns, which are high lakes, at the base of the glaciers, with water so pure you can drink directly from the mountain and there are cascading streams from the runoff from the glaciers. So it's quite active. And like I said, it's very beautiful, with wildflowers late in the summer," Carr said.

Reporter Damon Arthur welcomes story tips at 530-338-8834, by email at damon.arthur@redding.com and on X, formerly known as Twitter, at @damonarthur_RS. Help local journalism thrive by subscribing today!