West Greenland is renowned for its blue lakes which provide drinking water and help sequester atmospheric carbon.
However, after two months of record heat and heavy precipitation in fall 2022, researchers found that about 7,500 of these lakes turned brown, began emitting carbon, and experienced a decline in water quality. ‘water.
This radical change, reported in a study published in the Proceedings of the National Academy of Sciences (PNAS), highlights how extreme climate events can push Arctic lakes beyond critical tipping points.
Unprecedented changes in a short time
Led by Fulbright Arctic Distinguished Scholar Jasmine Saros of the University of Maine’s Climate Change Institute, an international team studied the rapid transformation of these lakes.
By July 2023, less than a year after the extreme weather conditions of the fall, the physical, chemical and biological properties of the lakes had undergone significant alterations – changes that would normally take place over centuries.
“The scale of this and the pace of change was unprecedented,” said Saros, who is also a professor of paleolimnology and lake ecology at UMaine.
How climate extremes have affected Greenland’s lakes
Greenland usually experiences snowfall in the fall, but record temperatures have turned the precipitation into rain. This change, combined with heat, caused permafrost – frozen soil rich in organic carbon and minerals – to thaw.
When rainwater passed through the thawing ground, it carried an abundance of carbon, iron, magnesium and other elements into the lakes, turning their waters brown.
The influx of dissolved organic carbon and nutrients fueled bacterial growth, affecting the taste, odor and color of the lakes. The increase in metals in water has also raised health concerns.
“Increased dissolved organic matter can interact with drinking water treatment processes to produce chlorination byproducts called trihalomethanes, which can be carcinogenic,” Saros explained.
Such changes not only impact water quality, but also have wider implications for the local communities that rely on these lakes.
Disturbed ecosystems and the carbon cycle
As the lakes browned, water transparency decreased, reducing light penetration and changing plankton dynamics. The reduction in light hampered phytoplankton that normally absorb carbon dioxide through photosynthesis, while organisms that break down organic matter increased.
This change transformed the lakes from carbon sinks to significant sources of carbon dioxide, with emissions increasing by 350%.
“Because the lakes became so brown, it reduced the light entering the system, which tends to favor organisms that use organic carbon pathways instead of photosynthesis,” Saros said.
This change in the behavior of plankton and in the carbon cycle has major consequences on the carbon balance of the Arctic and on local biodiversity.
The role of atmospheric rivers
Researchers identified atmospheric rivers – long, narrow streams of water vapor – as the likely cause of these extreme weather conditions. These phenomena caused record temperatures and precipitation in the region.
The National Oceanic and Atmospheric Administration (NOAA) predicts that atmospheric rivers will become much more common in Greenland and other parts of the world by the end of the century, which could lead to more events like those in Greenland. fall 2022.
Will Greenland’s lakes recover?
This abrupt transformation raises urgent questions about recovery: will the lakes return to their former blue state, or will the changes persist?
“It’s such an overwhelming climatic force that caused all the lakes to react in the same way. Regarding recovery, will it be the same from lake to lake or different? » Saros thought.
Continued monitoring and additional research are crucial. The team’s work relied on long-term observations, including annual water sampling and remote sensors operating year-round, which allowed them to capture the rapid changes caused by this event extreme climate.
“Our study demonstrates the power of long-term observation. I have been working in this field since 2013 and have worked on many projects here. But in the background, my colleagues and I have tried to maintain a consistent data set of observations,” Saros said.
“This is how we were able to capture and quantify the effects of this extreme weather event.”
Future research on Greenland lakes
The study was made possible through extensive collaboration between researchers at UMaine, NOAA, and various international institutions, as well as contributions from numerous doctoral students.
This collective effort has provided valuable insights into how extreme weather events can dramatically alter lake ecosystems and carbon dynamics.
As atmospheric rivers become more common, it is critical to understand their impact on Arctic lakes like those in west Greenland.
Further research into how these lakes recover and how similar events affect other regions will help scientists develop strategies to mitigate and adapt to the impacts of climate change.
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