18th December

Irish lake features in global analyses on climate change

Lough Feeagh, Co Mayo, is one of 235 lakes worldwide that was monitored in a 25 study. More than 60 global scientists participated in the research which is now published in the journal, Geophysical Research Letters.L.Feeagh Ireland

Lough Feenagh, Co Mayo, one of 235 lakes worldwide in a 25 year monitoring study. Photo Mary Dillane, Marine Institute

The study found that lakes are warming on average 0.34˚C every decade, and at a greater rate than either the oceans or the atmosphere, with profound effects that threaten freshwater supplies and ecosystems. While representing a fraction of the world’s lakes, they contain more than half of the globe’s freshwater supply.

 

Ecological monitoring

The Marine Institute measures the surface water temperature of Lough Feeagh as part of long-term ecological monitoring of the Burrishoole catchment. The research station is an internationally important index site for diadromous fish monitoring, and water temperature is a crucial variable controlling growth, migration and survival of salmon, trout and eel in the catchment.

The surface water of Lough Feeagh warmed at a rate of 0.35° C per decade between 1985 and 2009 although at a lower rate than some other northern hemisphere lakes.

“We want to be careful that we don’t dismiss some of these lower rates of change,” remarked co-author Stephanie Hampton, director of Washington State University’s Center for Environmental Research, Education and Outreach.

“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.”

Increased methane

The study warns that at the current rate, algal blooms, which can ultimately rob water of oxygen, are projected to increase 20 percent in lakes over the next century. And algal blooms that are toxic to fish and animals will increase by five percent. These rates imply that emissions of methane ― a greenhouse gas 25 times more powerful than carbon dioxide ― will increase four percent over the next decade.

“Lakes are important because society depends on surface water for the vast majority of human uses,” she added.

“Not just for drinking water, but manufacturing, energy production and crop irrigation. Protein from freshwater fish is especially important in the developing world.”

Temperature is one of the most fundamental and critical physical properties of water. It controls a host of other properties that include intricate living processes that have evolved within strict boundaries. When the temperature swings quickly and widely from the norm, life forms in a lake can change dramatically and even disappear.

"These results suggest that large changes in our lakes are not only unavoidable but are probably already happening,” added lead author Catherine O'Reilly, Associate Professor of Geology at Illinois State University.

Funded in part by NASA and the National Science Foundation, the study is the largest of its kind and the first to use a combination of long-term hand measurements and temperature measurements made from satellites, offsetting the shortcomings of each method.

Satellite measurements

Study co-author Simon Hook, science division manager at the NASA Jet Propulsion Laboratory, said satellite measurements provide a broad view of lake temperatures over the entire globe. But they only measure surface temperature, while hand measurements can detect changes in temperature throughout a lake. Also, satellite measurements go back only 30 years while some lake measurements can go back more than a century.

“The inclusion of data from Lough Feeagh in this study highlights the value of collecting local environmental long-term data to inform global analyses,” said Dr Elvira de Eyto, a biologist at the Marine Institute facility in Burrishoole and one of the studies co-authors.

“Sharing of such data with global scientific networks makes an important contribution to worldwide climate change analyses, and our understanding of how the warming climate will affect our valuable aquatic resources,” remarked the institutes CEO, Dr Peter Heffernan.

The researchers noted that various climate factors are associated with the warming trend. In northern climates, lakes are losing their ice cover earlier and many areas of the world have less cloud cover, exposing their waters more to the sun’s warming rays.

Many lake temperatures are rising faster than the average air temperatures. Some of the greatest warming is seen at northern latitudes where rates can average 0.72˚C per decade.

Warm-water, tropical lakes may be seeing less dramatic temperature increases; however increased any warming can still have large negative impacts on fish. This can be particularly important in the African Great Lakes ― home to one-fourth of the planet’s freshwater supply and an important source of fish for food.

In general, the researchers found that “pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes”.

Geophysical Research Letters http://onlinelibrary.wiley.com/doi/10.1002/2015GL066235/full

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