Live Science reports:

Thousands of Greenland’s crystal-clear blue lakes have turned a murky brown thanks to global warming — and the worst part is that they’ve started emitting carbon dioxide.

Record heat and rain in 2022 pushed the lakes of West Greenland past a tipping point, so rather than absorbing carbon dioxide (CO₂), they began to emit it into the atmosphere, according to a new study.

The changes began in fall, which is normally a snowy time for Greenland. However, heat waves turned snow into rain and thawed the island’s permafrost — frozen ground that stores carbon, iron and other elements. The rains then washed these elements into lakes, turning them brown.

Less sunlight was able to penetrate the lakes as they darkened, which had a ripple effect on the microscopic plankton living in the water. The number of plankton absorbing CO₂ through photosynthesis — the process of turning sunlight into energy — declined, while the amount of plankton breaking down and releasing carbon increased, according to a statement released by the University of Maine.

The lakes normally absorb CO₂ in the summer, but by the following year they had flipped to become carbon dioxide producers. These types of widespread changes would normally take centuries. Researchers have observed the browning of lakes across the Northern Hemisphere, including the U.S., but it typically takes multiple decades — much longer than the transformation of Greenland’s lakes.

“The magnitude of this and the rate of change were unprecedented,” study lead author Jasmine Saros, a professor of paleolimnology and lake ecology at the University of Maine, said in the statement.

The researchers published their findings Tuesday (Jan. 21) in the journal PNAS. [Continue reading…]