NOAA RESEARCH NEWS: Climate change is causing significant impacts on the Great Lakes and the surrounding region. As the largest surface freshwater system in the world, the Great Lakes have an enormous impact, seen and unseen, on the more than 34 million people who live within their collective basin. Because of their unique response to environmental conditions, Earth’s large lakes are considered by scientists as key sentinels of climate change.
A long-term study published in Nature Communications today from NOAA reveals a warming trend in deepwater temperatures that foreshadows profound ecological change on the horizon. While less visible than the loss in ice cover and increasing lake surface temperatures, this latest index of climate change adds to the growing evidence of climate change impacts in the region.
Using a 30-year dataset of deep water temperature measurements, NOAA Great Lakes Environmental Research Laboratory scientists investigated how Lake Michigan’s seasonal mixing patterns are being influenced by climate change. As it turns out, what’s happening on the lake’s surface during the summer is actually impacting the lake’s deep waters during the winter.
“We found that this long-term data set not only confirms that Lake Michigan’s deep waters are warming, but also shows that winter is vanishing from them,” said NOAA GLERL’s Eric Anderson, the study’s lead author. As climate change has gradually delayed the onset of cooler autumn weather over the past three decades, the deep waters of Lake Michigan have reflected this change by showing shorter winter seasons.
This key finding may indicate some dramatic changes in the foreseeable future, as an increase in a lake’s overall water temperature can lead to permanent changes in the water’s seasonal mixing patterns. This could eventually alter Lake Michigan’s rate of primary productivity, which would inevitably disrupt the structure of its entire food web — a change that could have negative impacts on fisheries and recreation. “Without high-frequency long-term monitoring of subsurface waters of the world’s deep lakes,” said Anderson, “we will be blind to the impacts of climate change on most of Earth’s fresh surface water.”
Our ability to collect lake surface data with satellites, buoys, and water samples has come a long way over the past few decades in helping scientists understand how large lakes throughout the world respond to climate change. But since many of them — including the Great Lakes — are several hundred feet deep, those surface measurements don’t tell the whole story of what’s going on beyond the sight of satellites. Deep-water measurements at high temporal frequency are much more rare, especially on the time scale of years or decades. Read more:
