A new study shows the Great Lakes have been changing color since the late 1980s, but researchers don’t know the reason for sure.
The NASA-funded study of lake color changes over the last 36 years has given scientists the widest-ever view of America’s freshwater resources.
The open access dataset shows in part that Lake Michigan has been getting bluer.
According to Simon Topp, the lead author of the study and a doctoral researcher at the University of North Carolina at Chapel Hill, there could be many reasons for the gradual change.
“That could definitely be due to a reduction of nutrient inputs because of policies like the Clean Water Act; It could be due to invasive zebra mussels,” Topp said. “There’s a variety of drivers that might be causing that, but overall we can kind of take that as a first step.”
Lake color usually changes from season to season, but the changes that Lake Michigan and other lakes have seen over time are more long-lasting.
“On average in Michigan, in the spring — so in like May and June — we’re generally seeing bluer observations over time,” Topp said. “Thirty years ago, the lakes were typically kind of greener in the May/June period where we’d typically see spring algal blooms.”
Topp said the study, which was authored by a group of scientists from universities across the country, can be used by anyone as a jumping-off point for their own analysis.
“The study went hand-in-hand with a public database that now anybody can use to say, look at their local lake without having to go in and pull and analyze all of the remote sensing data themselves,” Topp said.
The dataset includes detailed remote sensing analysis of more than 26,000 lakes.
Those who wish to view the data for themselves can find it at the American Geophysical Union’s website.