Over 7,500 lakes in western Greenland have undergone a significant ecological transformation due to extreme climatic conditions. Atmospheric rivers (ARs) have turned these lakes from carbon sinks into carbon sources, a new study published in the Proceedings of the National Academy of Sciences (PNAS) has revealed.
In September 2022, record heat and heavy rains driven by ARs altered the physical, biological, and biogeochemical characteristics of these lakes. ARs, often referred to as “rivers in the sky,” are narrow regions in the atmosphere that transport water vapor outside tropical areas, as defined by the National Oceanic and Atmospheric Administration (NOAA).
The influx of rainfall instead of snow, alongside remnants of Hurricane Fiona, caused unprecedented melting of the Greenland Ice Sheet. The study observed a 22% increase in dissolved organic carbon concentrations compared to averages from 2013-2022, leading to substantial ecological shifts.
The lakes’ iconic blue waters turned dark brown within a year, a phenomenon akin to millennia-long changes in boreal lakes. The browning reduced light penetration by 50%, severely impacting biodiversity, particularly plankton populations. This alteration disrupted the region’s carbon cycle, shifting lakes from carbon sinks to sources with over a 350% increase in carbon dioxide flux. Methane concentrations also rose by 72% in August 2023 compared to 2014.
The transformations continued through the summer of 2024, affecting local communities who depend on these lakes for drinking water. Residents reported issues with taste, odor, and potential health risks. The study highlighted that similar ecosystem transformations in history, such as the 1861-62 winter megaflood in California, caused long-term ecological and economic damage.
Researchers warn that such transformations in Greenland’s lake ecosystems underscore the urgent need for adaptive strategies. These findings reveal the potential for compound climate extremes to induce irreversible ecological tipping points, calling for their integration into future climate scenarios and response plans.