Waters expected to warm by up to degrees 3 degrees Celsius by mid-century
By Bob Berwyn
Austria’s famed alpine lakes are facing fundamental change as global temperatures continue to warm. The Alpine region as a whole warmed three times as fast as the global average between 1980 and 1999.
Projected increases in water temperatures will likely alter basic structure, function and water quality in famed lakes like the Mondsee, near Salzburg, according to Dr. Martin Dokulil, a retired researcher from the Institute for Limnology at the University of Innsbruck in Austria.
Dokulil analyzed long-term data records for air temperature and surface water temperatures dating back to the mid-1960s from the Austrian Hydrological Yearbooks. He projected temperature trends for nine large lakes, finding that lake surface temperatures are likely to rise by up to 3 degrees Celsius by 2050 as a direct result of climate change.
The research is published online in Springer’s journal Hydrobiologia. The goal of the research was to identify potential changes to help develop adaptation strategies. Austria’s lakes and rivers are crucial to Austria’s tourism industry, generating an essential part of the country’s GDP, the study points out.
“The predicted changes in surface water temperatures will affect the thermal characteristics of the lakes,” Dokulil said. “Warmer water temperatures could lead to enhanced nutrient loads and affect water quality by promoting algal blooms and impairing the biological functions of aquatic organisms,” he said.
“Significant increases in summer temperatures will also affect the carbon cycling in lakes, with potential consequences on atmospheric carbon dioxide levels and the Earth’s climate,” he said.
The study analyzed 1965-2009 temperature data for the nine lakes in Austria’s different climatic regions, showing water temperatures rising parallel to air temperatures, with the biggest increases in the spring and summer.
Warmer water temperatures will lengthen the amount of time the lakes are stratified, and mixing and retention time will also be affected. Changes in the food webs of the lakes are difficult to forecast and will vary according to local environmental conditions, Dokulil explained.
The projected rise in lake surface temperatures by about 3 degrees Celsius in Austrian lakes matches projections for other regions, along with other observed trends, including rapid increases in spring temperatures, earlier onset of thermal stratification, longer duration and higher thermal stability.