Crater Lake is famous for its stunning blue and crystal-clear water, but that feature could be a thing of the past someday.
Warming air temperature could threaten the water in Oregon's most-popular National Park, according to a new report by the U.S. Geological Survey, the result of sustained climate change in the Pacific Northwest.
The clear water comes as the result of cold and warm water mixing deep within the lake. As the surface water becomes colder in the winter it sinks to the bottom, forcing deeper water upward, resulting an upswelling of nutrients to the top. Those upward-moving nutrients encourage important algae growth, while the sinking water replenishes dissolved oxygen in the depths of the lake.
But if air temperature continues to warm in coming winters, officials warn, that mixing process will slow, if not stop completely.
The U.S. Geological Survey came to the results using a computer model that ran six different climate scenarios through the year 2100. Under the least severe warming, the deep water mixing occurred on average once every three years. Under the most severe warming, the process stopped entirely.
Right now that mixing occurs about every other year, said Tamara Wood, a hydrologist for the U.S. Geological Survey. If mixing becomes less frequent, the biological growth in the lake could swing from being less than normal to much higher than normal when the water eventually does mix.
"One of the things we expect is the clarity of the lake will become more variable," Wood explained. "Our model doesn't actually predict what the ecological effects will be, but we can hypothesize ... what some of the effects might be."
The climate change models were based on wind, solar radiation and atmospheric temperature data, estimating different levels of warming over time. Pinning down the exact effects on the lake's ecosystem will require further analysis using more complex models, according to the report, a process that will take years to complete.
But that process is of great importance to the scientists charged with studying and caring for the massive lake.
"Changes in climate that may affect water clarity are of particular interest to the Park from a lake-health perspective," Scott Girdner, a lake biologist at Crater Lake, said in a press release.
And, of course, changes in water quality are of particular interest to the hundreds of thousands of people who flock to the park each year to see it. But while the changes are of great ecological concern, they could be too subtle for tourists - or even Mother Nature for that matter - to notice.
"It's not obvious what the effects of a warming climate might be on the bottom of a lake 600 meters below the surface," Wood said. "The lake has evolved over millennia, really, and so I think it's a little hard to say what the effects of altering climates might be on a system that's kind of intricate and complex, and has evolved over a long period of time."
If their models are correct, however, some kind of change is definitely in store for Crater Lake, whether we notice it or not.
--Jamie Hale | jhale@oregonian.com | @HaleJamesB