Why lakes are hot and cold at the same time

By Author  |  Published: 10th Sep 2019  8:06 pm

While studying the effects of global warming on lakes, researchers found out why lakes may remain cool in deeper levels and warm on the surface. The temperature of a lake represents an important constraint on the amount of carbon dioxide and methane it emits into the atmosphere.

According to the study published in the journal, Limnology and Oceanography Letters, an international research team has now examined these interactions more closely and discovered unexpected effects.The main focus of the investigations was the water temperature and greenhouse gas production in the deeper parts of the lakes.

“The surface-water warming and the loss of transparency have the effect that more heat is trapped in the upper layers of the lakes, leaving the deeper waters thermally isolated,” said lead author Dr. Maciej Bartosiewicz from the Department of Environmental Sciences at the University of Basel.”Under some circumstances, this can even lead to the cooling of water masses near the bottom of the lake,” continued Bartosiewicz.

The subtle cooling slows down respiratory decay processes and carbon dioxide production in the lakes, increasing carbon burial within the sediments. “All in all, global warming increases the greenhouse gas potential of lakes, as expected. However, this has less to do with the warming directly, and more to do with increased oxygen depletion at the bottom of these lakes,” concluded Bartosiewicz.