Over the last 25 years, a NASA and National Science Foundation-funded study has compiled satellite temperature data and ground temperature measurements on more than 235 lakes on six of Earth’s seven continents. The conclusion? Climate change is greatly impacting lakes worldwide, putting freshwater ecosystems in danger.
The lakes, which represent more than half of the world’s freshwater supply, have increased by an average temperature of 0.61 degrees Fahrenheit each decade since the inception of the study. To put that into perspective, scientists involved with the study claim say that the pace in which those lakes are heating is greater than the warming rate of either the world’s oceans or its atmosphere. The increase in temperature will lead to a 20 percent rise in lake-based algal blooms over the century—a significant statistic considering that algal blooms strip oxygen from water.
NASA shared this information in a press release Wednesday after the information was unveiled that same day at the American Geophysical Union meeting in San Francisco. All of the research has been published in Geophysical Research Letters.
A fast or greatly deviated change from the normal water temperature is an issue because it puts a lake’s ecosystem in great danger. The study’s lead author, Catherine O’Reilly, associate professor of geology at Illinois State University, found throughout her research that lakes become active as the temperatures rise.
“These results suggest that large changes in our lakes are not only unavoidable, but are probably already happening,” she said.
Emissions were also touched on in the study. The negative impact of methane, a greenhouse gas that is 25 times more potent than carbon dioxide on 100-year scales, is on pace to increase by 4 percent over the next decade.
“Society depends on surface water for the vast majority of human uses,” said co-author Stephanie Hampton, director of Washington State University’s Center for Environmental Research, Education and Outreach. “Not just for drinking water, but manufacturing, for energy production, for irrigation of our crops. Protein from freshwater fish is especially important in the developing world.”
The satellite measurements that were conducted have given scientists a general understanding of lake temperature’s throughout Earth, according to Simon Hook, the study’s co-author and science division manager at NASA’s Jet Propulsion Laboratory. However, Hook said that the study of lake temperatures via satellite has a shortcoming—only surface temperatures can be measured that way. To examine changes in temperature throughout an entire lake, ground measurements must be conducted. Lake measurements also provide a larger sample size, having been used for more than a century, while satellite examinations of lake temperatures have only been conducted for 30 years.
“Combining the ground and satellite measurements provides the most comprehensive view of how lake temperatures are changing around the world,” he said.
Where a lake is located impacts how it is changing due to warming trends. Lakes in northern regions are being covered by ice for shorter periods of time, losing the layer earlier in the spring. The lakes located in the parts of the world that are experiencing less cloud coverage are now being hit by sunlight more often.
The new research also supports the findings of previous studies—a conclusion that the temperatures of lakes located at high altitudes are rising at an average rate of 1.3 degrees Fahrenheit per decade.
Lakes located in tropical regions aren’t seeing as much of an increase in temperature, though any warming in those lakes can negatively affect fish populations. A drop in fish populations would be an especially damaging blow to the African Great Lakes region, whose population is greatly dependent on fishing for food.
“We want to be careful that we don’t dismiss some of these lower rates of change,” said Hampton. “In warmer lakes, those temperature changes can be really important. They can be just as important as a higher rate of change in a cooler lake.”
To generalize their findings, the research team wrote: “The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.”
Filed Under: Test + measurement • test equipment