Lakes’ temperature is rising faster than that of the oceans, a phenomenon registered globally and with significant implications for climate change. The large scale study addressing the issue of lakes warming rapidly at the global level sampled hundreds of lakes worldwide and involved over 60 scientists on all continents.
The findings were presented at the American Geophysical Union meeting taking place on December 16th in San Francisco, California. Oceans and sea level rise have been under the spotlight for a while now. Global warming has been proved to negatively affect oceans and impact the level of the sea in numerous scientific studies. Yet, not as many took a closer look at what’s happening with the world’s lakes, also a source of fresh drinking water and thriving ecosystems.
The recent study addressed this issue and found that lakes’ temperature is rising faster than that of the oceans. This rapid spike could soon translate into the loss of ecosystems or the loss of clean and fresh drinking water. Moreover, millions of tons of carbon could be released and converted into methane. Both methane and carbon dioxide stocked in sediments in the world’s lakes are high contributors to the greenhouse gas effect and thus global warming.
Over the past 25 years, the global increase in temperature during summertime was registered to be approximately one third of a degree per decade. It might seem insignificant. Yet, consider that the global agreement on climate change tries to limit global warming at a maximum of 2 degrees Celsius above pre-industrial levels, unless we want to head directly into a disaster.
For the 235 lakes under scrutiny, even this global increase in temperature already shows significant impacts.The scientists compiled measurements from the bottom of the lakes, satellite data, and others. Overall, the lakes warmed on average by 0.34 degrees Celsius per decade. Oceans have warmed by 0.12 degrees Celsius per decade in the period between 1985 and 2009.
Surely, the mass of water in the oceans is far bigger than that of lakes. However, the world’s lakes are at risk as they also warm faster than surface air. Surface air temperature warmed by 0.25 degrees Celsius per decade in the period between 1979 and 2012.
One explanation might be that with warmer winters, the ice season and thus the cooling effect is simmering down. With ice no longer acting as an insulator, lake water is almost constantly exposed to warm surface air.
According to the study, another possible explanation is that less clouds due to climate change mean less filtering. Thus, lake water is more exposed to sunlight throughout the year. With lakes absorbing more and more heat, lake water becomes stratified. Dense cold water remains at the bottom, with dense warm water floating closer to the surface. For several species dwelling in these lakes and depending on lower temperatures for survival and a healthy habitat, the fact that lakes’ temperature is rising faster than that of the oceans at the global level spells trouble.
Forced to reduce the habitat area, the species’ movement will affect biodiversity and ecosystems. In addition, higher temperatures of lake water brood the conditions for the emergence of bacteria as well as toxic organisms.
Photo Credits: Wikimedia
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