Air, temperature, precipitation, lake depth and elevation determine the colour, along with factors like algae and silt
Blue lakes all over the world run the risk of turning green-brown if global warming continues, according to a recent study.
Air, temperature, precipitation, lake depth and elevation determine the colour, along with factors like algae and silt, noted the study published September 22, 2022, in Geophysical Research Letters.
Less than a-third of the world’s lakes are blue and often more profound. They are found in high-latitude areas with lots of precipitation and winter ice cover.
Green-brown lakes make up 69 per cent of all lakes. They are more common and can be found in drier areas in the interiors of continents and along coastlines.
The researchers analysed 5.14 million satellite pictures between 2013 and 2020 to identify the most prevalent colours of 85,360 lakes and reservoirs.
They evaluated the most frequent lake colour over seven years to characterise the colour as it might change seasonally due to algal bloom. The authors created an interactive map that allows users to explore the findings.
The study also looked at how varying levels of warming would impact water colour if climate change continues.
“Warmer water, which produces more algal blooms, will tend to shift lakes towards green colours,” said Catherine O’Reilly, an author of the study, in a press release.
The number of blue lakes, abundant in the Rocky Mountains, northeastern Canada, northern Europe and New Zealand, may shrink due to climate change.
The colour of the water is a straightforward yet valuable marker for water quality that can be seen from satellites on a global scale, according to the authors.
Previous researches have employed more complicated and more refined scale metrics to determine overall lake ecosystem health. This methodology offers a tool to investigate how climatic changes affect isolated lakes.
“Changes in water quality that are likely happening when lakes become greener are probably going to mean it’s going to be more expensive to treat that water,” said O’Reilly
In countries like Sweden and Finland, where lakes are widespread culturally, changes to water colour may also have recreational and cultural effects. Lakes in northern Europe will probably lose their winter ice cover as global warming progresses, which could impact winter and cultural activities.
“Nobody wants to go swim in a green lake,” said O’Reilly. Some of the lakes that we might have always thought of as a refuge or spiritual places might be disappearing as the colour changes, he added.
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