Climate Extremes Reshape Underwater Light in Lake Tahoe, Study Finds.

Lake Tahoe is undergoing significant changes in underwater light levels as extreme weather events driven by climate change alter the balance of wet and dry conditions in the region. A new study, led by the Tahoe Environmental Research Center at the University of California, Davis, in collaboration with Miami University in Ohio, has uncovered striking variations in ultraviolet (UV) radiation in the lake over nearly two decades.

Published in Limnology and Oceanography Letters, the study examined 18 years of UV irradiance data from Lake Tahoe, a lake long admired for its clarity. Researchers found that UV radiation levels could vary by as much as 100 times between particularly wet and dry years.

These wide-ranging fluctuations were closely linked to climate-induced extremes, which affected the amount of particulate and colored dissolved organic matter in the water. Such materials influence how deeply UV radiation can penetrate the lake.

"During wet years, more organic and particulate matter enters the lake, reducing UV penetration," explained lead author Shohei Watanabe, an associate project scientist at UC Davis. "But in dry years, these materials are scarce, allowing much deeper UV radiation—essentially stripping away the lake’s natural protection and exposing it to more intense sunlight."

In clearer lakes like Tahoe, UV rays can reach depths of several dozen feet, whereas in murkier lakes, the penetration may be limited to just a few inches. This has significant ecological implications, as UV radiation can suppress photosynthesis and impact the behavior of aquatic organisms such as fish and zooplankton. It also plays a role in the lake’s carbon cycle.

The findings emphasize the potential of underwater UV monitoring as an indicator of climate-driven disturbances in aquatic systems. While such monitoring is uncommon, UC Davis has been observing Lake Tahoe since 1968. The addition of UV radiation monitoring began in 2006 as part of a collaborative effort with Miami University, making this one of the few lakes in the world with such a long-term dataset.

"Short-term data wouldn’t have captured these dramatic shifts," Watanabe noted. "It’s the long view that reveals how deeply climate variability is altering natural systems like Lake Tahoe."

Source:https://phys.org/news/2025-05-extreme-weather-underwater-tahoe.html

This is non-financial/medical advice and made using AI so could be wrong.