Glaciers will soon disappear

For the first time in human history, Calif.’s glaciers will soon disappear

'We’re entering uncharted territory.'

By Julie Brown Davis

California may be known as the Golden State, with its shimmering beaches and warm Mediterranean climate. But clinging to the rooftop of the High Sierra are the last remnants of glaciers that have existed for thousands of years, since the end of the last Ice Age. 

The Sierra Nevada was carved by glaciers, but scientists previously thought glaciers largely went away as the ice receded. A new study published this week, however, found that glaciers have existed in the Sierra Nevada since the Ice Age and for thousands of years before humans set foot in North America. 

The discovery is all the more profound — and tragic — in light of climate change. Within the past two centuries, California’s glaciers have melted away to fractions of the size they once were, the study’s authors say. Scientists project they will disappear entirely between 2050 and 2100. 

Humans have never before experienced an ice-free Sierra Nevada, the study states. But that day is coming soon. 

“When these glaciers die off, we’ll be the first humans to see ice-free peaks in Yosemite,” said Andrew Jones, the study’s lead author, in a phone interview with SFGATE on Thursday.

Climate change is causing glaciers to melt across the American West, with many small glaciers expected to melt away by 2100. 

In California, scientists have thoroughly documented the shrinkage of glaciers in the Sierra Nevada. John Muir began studying the Lyell Glacier, the largest in Yosemite National Park, some 150 years ago. Muir tracked the glacier’s movement by placing stakes in the ice. Where historic photos from the late 1800s show the Lyell Glacier hugging the entire mountain, today the glacier is severed with just two disparate lobes remaining: the East Lyell and the West Lyell. In 2013, scientists at the National Park Service announced the Lyell Glacier had stopped moving entirely — making some question whether it could even still be called a glacier at all. When a glacier stops flowing, scientists call it dead ice, Jones explained.

“In California, we’re crossing a line in the sand,” Jones said. “We’re entering uncharted territory. Humans here have not seen Yosemite National Park without glaciers before.”

Jones worked with a handful of researchers on the study, including scientists at the National Park Service who have been keeping close watch over the Yosemite glaciers, trekking far into the High Sierra to document the ice as it rescinds and exposes more and more bedrock. 

Researchers studied four of the largest and oldest glaciers in the Sierra Nevada: Conness, Maclure, Lyell and Palisade. The Lyell and Maclure glaciers are in Yosemite National Park. The Conness Glacier abuts the park’s border, to the north. The Palisade Glacier is in the John Muir Wilderness, in the central Sierra Nevada. 

The researchers studied how much the glacial bedrock was exposed to cosmic rays, an indicator of how long the bedrock was buried beneath the ice. Previously, scientists believed that, after the Ice Age, glaciers waxed and waned in the Sierra, perhaps disappearing entirely at points. Now, the data suggests California’s glaciers have existed continually since the end of the Ice Age and throughout the Holocene, 11,700 years ago. 

But within two centuries, the glaciers have been whittled away to fractions of the size they once were, according to the study. Summer temperatures in the Sierra Nevada have increased over the past century by 2 degrees Celsius, or 3.6 degrees Fahrenheit. All four glaciers are projected to melt away entirely by 2100. Shrinking glaciers impact freshwater storage, river runoff and biodiversity, the study states.

Jones says the glaciers in California are a “canary in a coal mine” for the impacts of climate change. Shrinking glaciers impact freshwater storage, river runoff and biodiversity, the study states.

He also said that studying glaciers gives him hope, because evidence shows that curtailing greenhouse gas emissions can have direct effects on slowing down or stopping the ice melt. “People have shown that the pathway that we choose determines how many glaciers survive,” Jones said.