Lake Tahoe from above Emerald Bay. Photo: Craig Miller
Some lakes in Northern California and Nevada are warming twice as fast as the surrounding air temperature, raising concerns that climate change may be affecting aquatic ecosystems more rapidly than terrestrial ones, according to a recently published study.
Researchers from the Tahoe Environmental Research Center, UC Davis and NASA’s Jet Propulsion Laboratory in Pasadena, studied Lake Tahoe, Lake Almanor, Clear Lake, and Mono Lake in California, and Nevada’s Pyramid and Walker Lakes, by analyzing 18 years of temperature data from satellite sensors.
Long-established instrument buoys provided a flow of temperature data for Tahoe, dating back to 1968, which allowed the team to calibrate satellite readings, raising confidence in data gathered from the other lakes. Previous studies have documented the warming of Lake Tahoe but John Reuter, associate director of the Tahoe Environmental Research Center (TERC), says the new study takes that information one step further.
“This study really shows that this phenomenon is happening on a much larger scale than just Lake Tahoe,” said Reuter.
All of the lakes studied showed a strong warming trend among summer nighttime temperatures between 1992 and 2008. The two lakes that warmed the most during that time, Almanor and Mono, warmed 4.3 degrees (F). During that time Lake Tahoe’s surface waters warmed 3.7 degrees, averaging .23 degrees annually. In contrast, Tahoe City’s air temperature increased just .1 degree each year.
TERC director Geoffrey Schladow, who co-authored the study, said there is no doubt in his mind that rising lake temperatures are related to climate change, and he expects that it’s happening across the world, not just in Northern California and Nevada.
“The significance of this study is that across the western United States these very different lakes are displaying signs of warming. It’s not just a Tahoe issue, it’s a regional issue. And in all likelihood, it’s a global issue,”said Schladow.
Over the next six months, researchers will be using the remote sensors to extend the study to 50 lakes across the world to evaluate whether or not large lakes everywhere are warming at similar rates.
Warmer temperatures can affect water circulation, which influences the amount of oxygen and nutrients available throughout the lake. A 2008 study from TERC predicts that warming due to climate change could dramatically affect the amount of mixing in Lake Tahoe, which would deplete the bottom water of oxygen and drastically disrupt the food web.
“Temperature is one of the conditions that dictates who lives in the lakes,” said Schladow. “Warmer temperatures may make the lakes more hospitable to invasive species and put native species under stress. I’m not saying this is happening yet, but it could.”
In his article about the study, Matt Weiser of the Sacramento Bee has some examples of how warmer temperatures can affect lake ecosystems. And KQED news editor Dan Brekke has assembled an interactive map (below), showing the locations and some temperature data for lakes in the study.
View California’s Warming Lakes in a larger map