Deep in California’s Sierra Nevada, massive glaciers are disappearing and projected to melt away completely by the beginning of the next century, leaving ice-free peaks for the first time in human history, new research has found.
The mountain range’s glaciers are older than previously known, dating back tens of thousands of years, with some as old as the last ice age, according to an article published last week in Science Advances.
“Our reconstructed glacial history indicates that a future glacier-free Sierra Nevada is unprecedented in human history since known peopling of the Americas ~20,000 years ago,” the article states.
Glaciers around the world are under threat amid the climate crisis. A study published in May of this year found that nearly 40% of glaciers are doomed to melt because of global heating. If such heating increases by 2.7C, which the world is currently on track for, as many as 75% will disappear, causing sea level rise and mass displacement.
Across the American west, glaciers have shrunk significantly since they were first documented in the late 19th century, according to the article.
The new research focuses on four Sierra Nevada glaciers – the Conness, Maclure, Lyell and Palisade glaciers – that are among the largest and likely oldest in the range. Their longevity amid climate warming makes them “bellwethers” for examining glacier disappearance in the west, the article states.
Researchers looked at recently exposed bedrock around the glaciers and took samples to determine how long the area was covered by ice. They found that the glaciers have covered swaths of the range for much longer than previously known – since before humans occupied North America.
California’s glaciers reached their maximum positions as early as 30,000 years ago, the article’s authors wrote, and one of the glaciers researchers looked at is thought to have expanded 7,000 years ago, earlier than previously believed. The disappearance of glaciers, for the first time in human history, shows the dramatic effects of the climate crisis, one author of the study said.
“We’ll be the first to see the ice-free peaks,” said Andrew Jones, the study’s lead author and a doctoral student at the University of Wisconsin-Madison, told the San Francisco Chronicle. “This has ecological implications for plants and animals. And it’s a symbolic loss. Climate change is very abstract, but these glaciers are tangible. They’re iconic features of the American West.”
