As long as there are people in California now, the granite summits of Sierra Nevada hold blocks of ice. This is according to new research showing that glaciers may have existed since the last ice age, more than 11,000 years ago.
Already dramatically reduced since the late 1800s, the remains of these glaciers are retreating year by year and are predicted to completely melt this century as global temperatures continue to rise.
In a study published this week, scientists looked into the distant past of some of the largest glaciers in Sierra Nevada by shaving rock fragments near the edge of the ice and analyzing the rocks.
They discovered that one of Yosemite National Park and two large glaciers adjacent to the park, presumably covered in ice rocks since the end of the last ice age. They also discovered that another small, almost melting glacier has been around for at least 7,000 years, probably longer than previously known.
“When these glaciers die, it means that we will be the first people to see ice-free peaks in Yosemite,” said Andrew Jones, a researcher at the University of Wisconsin in Madison.
The journal Science Advances shows that the Sierra glacier is older than previously suggested in previous studies.
The authors of the study, including scientists from other universities and National Park Service, write that California glaciers are believed to have reached their maximum range around 30,000 years ago, and that the study shows that “future glaciers-free Sierra Nevada is unprecedented in human history.”
Glaciers are shrinking rapidly around the world as temperatures rise due to fossil fuel use and rising greenhouse gas levels.
Jones said many of the glaciers he and his colleagues are studying in California have lost an estimated 70% to 90% of ice since the late 1800s.
The photo and the written account show how far the Sierra glacier has retreated.
On one expedition in 1872, John Muir used wooden stakes from the McClure Glacier. Muir wrote that when he looked into another “huge snow bank” “4-500 yards long and 0.5 miles wide,” he saw a mass of rocks and dirt pushed by moving ice, “I cried.”A living glacier!”
In 1883, Israel Russell in Yosemite was a single block of ice for a US geological survey. Now it is divided into eastern and western parts, and the ice is halting.
The East Liele Glacier, seen by backpackers along the John Muir Trail, has lost an estimated 95% of its volume since the late 1800s, researchers said.
In Sierra Nevada, snow covers the sturdy landscape, melts and erupts in streams and rivers in winter, feeding alpine ecosystems and filling reservoirs.
When snow disappears by the end of summer, glaciers often remain in the shadows of the peaks release meltwater that keeps flowing when it is dry all year round.
This water from the glacier serves as a “stabilizing force” that allows the mountain range to be maintained through drought, Jones said. However, he added that the water will eventually disappear as the glacier continues to retreat, and that some streams that feed the Tuolum River in Yosemite run dry at times.
“It tells us that in the end we’ve left behind the so-called boundaries of normalcy,” he said. “We are basically crossing the lines in the sand from what the glacier did for all of the recorded history of humans.”
Sierra Nevada snowpacks also look at the effects of rising temperatures. That’s the average snow line.
In the latest research, scientists note that summer temperatures in California warmed around 3.6 degrees Fahrenheit in the last century, describing mountain glaciers as “sensitive climate indicators.”
They visited the glacier and collected rock samples on their research trips in 2018, 2021 and 2023.
“Glaciers are a touchstone between the past and present, and it’s very visceral to be able to see how it once looked and what it was today,” Jones said.
Although California’s glaciers are decreasing, larger mountain glaciers elsewhere in the world still have more intact ice, allowing efforts to stop the use of fossil fuels.
“If we can continue to warm up to a gentle level rather than a very high level, we will preserve the numerous glaciers that are actually lost,” he said. “We need to take government action and take steps to reduce artificial greenhouse gas emissions.”
