Glaciers in the Sierra Nevada could disappear for the first time in millennia.
A scientific study warns of the accelerated retreat of these ice bodies.
The glaciers of the Sierra Nevada are considered one of the most sensitive indicators of climate change. Their retreat, which has accelerated in recent decades, poses an unprecedented scenario in the planet's recent history.
A study published in the journal Science Advances, led by Andrew G. Jones of the University of Wisconsin-Madison, analyzed the behavior of the Conness, Maclure, and East Lyell glaciers, located near Yosemite National Park in California. The research concludes that these ice bodies maintained continuous coverage during the Holocene, a period that began about 11,700 years ago.
The keyword "Sierra Nevada glaciers" appears in the first records of the study, which used advanced techniques to date rocks' exposure to carbon-14 and beryllium-10. The results show extremely low concentrations of these elements, indicating that the ice blocked cosmic radiation for thousands of years.
In addition, 17 bedrock samples and 55 moraine blocks were collected, allowing reconstruction of the maximum extent of the glaciers at different times during the Holocene. The East Lyell Glacier, the smallest in the area, is believed to have grown about 7,000 years ago, earlier than previously thought.
What the study reveals about the Sierra Nevada glaciers have retreated and are showing signs of disappearing.
Researchers confirm continuous ice cover throughout the Holocene.
According to the scientific team, the projected disappearance of these ancient ice sheets in the Sierra Nevada by the end of the 21st century represents an unprecedented phenomenon since before the Holocene. "When these glaciers die, we will be the first humans to see ice-free peaks in Yosemite," Jones said.
The study also warns that global warming caused by human activities is raising the glacial equilibrium line in California above all historical records. This trend could lead to a scenario unparalleled in the western United States during the current interglacial period.
The Sierra Nevada glaciers have lost between 70% and 90% of their mass since the late 19th century. Historical photographs and accounts from expeditions, such as John Muir's in 1872, document the steady retreat of ice in the region.
In addition to the physical retreat of the Sierra Nevada glaciers, the study highlights the ecological and social implications their disappearance could have. These bodies of ice not only regulate the flow of water into California's valleys and basins, but also sustain fragile ecosystems that depend on seasonal melting.
Ecological impact of the loss of glaciers in the Sierra Nevada in California
The disappearance would affect the region's water supply and biodiversity.
The total loss of glaciers would affect the availability of water for human consumption, agricultural irrigation, and hydroelectric power generation. In areas like the Central Valley, where much of the food supplying the United States , the impact could be significant. "This change represents a challenge for water management in the coming decades," the authors warn.
On the other hand, glacial retreat also alters the landscape and biodiversity. Species adapted to extreme cold, such as lichens, mosses, and certain insects, could disappear along with the ice. Furthermore, rising temperatures in high mountain areas favor the spread of invasive species and disrupt the natural balance.
The study notes that even during the warmest episodes of the Holocene, the Sierra Nevada glaciers managed to persist. This reinforces the idea that the current warming is anthropogenic, that is, linked to human activity. The burning of fossil fuels, deforestation, and the intensive use of natural resources are factors contributing to the global rise in temperatures.
In scientific terms, researchers highlight the usefulness of cosmogenic isotopes for reconstructing glacial history. These techniques allow us to estimate how long a rock was exposed to the sky and, therefore, whether it was covered by ice. In this case, the extremely low concentrations of carbon-14 and beryllium-10 indicate that ice was present throughout almost the entire Holocene.
The research also raises questions about how sedimentary records are interpreted in paleoclimate studies. According to the authors , some previous models underestimated the duration of ice in the Sierra Nevada, which could have led to erroneous conclusions about the region's climate history.
On a cultural level, the disappearance of the glaciers would have a symbolic impact. Yosemite and its snow-capped peaks are part of the American collective imagination, and their transformation could alter the experience of millions of visitors. “Seeing those peaks without ice will profoundly change the relationship between people and the landscape,” the document states.
Finally, the study calls for strengthening climate change mitigation policies . While the disappearance of the Sierra Nevada glaciers seems inevitable in the short term, the researchers insist that reducing greenhouse gas emissions can prevent even more extreme scenarios in other regions of the planet.
