Climate Change Causing Lakes to Warm

Climate change is more than warming air temperatures. New research using satellites has shown that large lakes are also warming quite rapidly, sometimes faster than the air around them. This is the first time satellites have been used to put together such an in-depth analysis.

Researchers from NASA’s Jet Propulsion laboratory, Tahoe Environmental Research Center, and University of Leicester joined forces to analyze satellite data from the last 30 years. The new study, published in Geophysical Research Letters, analyzed the surface temperatures of 174 of the world’s 364 largest lakes.

Globally, the researchers found that these lakes’ surface temperatures increased almost a degree Fahrenheit per decade. In the Northern Hemisphere, the warming was even more dramatic, with temperatures increasing nearly two degrees Fahrenheit per decade.

Even more interesting is that lake temperatures are generally rising faster than the surrounding air temperatures. For example, in the Lake Tahoe region, researchers found surface waters of the lake are warming nearly twice as fast as the air temperatures.

Lake Tahoe played an important role in the research. Because it has been studied so rigorously and for so long, researchers were able to use on-the-ground measurements to verify the precision of the satellites. They found satellites were accurate to within 0.2 degrees Fahrenheit of recorded temperatures.

Better for swimming but…

Warming surface waters might be good for human swimmers, but they can have dire consequences for ecosystems. As water warms on the surface, mixing with deeper water slows down. This is in part because the warm water acts as a cap, preventing cold bottom water from reaching the surface.

Without regular mixing, oxygen gets depleted in the depths of the lake. And without oxygen, life can’t thrive and so dead zones start to occur and the entire ecology of the lake shifts.

Lake Tahoe has dealt with a number of environmental problems over the years from a loss of clarity to increases in nitrogen. All these problems have local solutions, though. The current increase in temperature can be attributed to climate change, the causes which cannot be fully addressed by regional solutions.

The problems with a warming lake extend beyond its boundaries as well. For example, Lake Tahoe has a major outlet in the Truckee River. As the water quality in Tahoe goes, so it goes in the Truckee River and Pyramid Lake in northern Nevada, which it empties into. Water quality issues will also affect irrigation projects downstream.

The results of the study also raise some interesting questions about the interactions between lakes and regional climate. Why are lake surfaces warming faster than the surrounding air? Could there be any feedbacks involved, making the warming trends even more pronounced?

Answering these questions will give people a better understanding of some of the lesser thought of effects of climate change. They also put climate change in a regional context and give it a face, which is more likely to spur action.

Photo Credit: Flickr