New research published in the journal Nature Communications shows that the deepest parts of the Great Lakes are warming up. While it has been known that global warming causes increased ice melting and rising ocean temperatures, little has been said about the impact of climate change on deep lake waters.
The study found that the deepest parts of the Great Lakes have been seeing a steady increase in temperature over the past three decades. Researchers analyzed 30 years of data, including hourly temperature recordings in deep waters. The temperature readings at 500 feet below the water surface reveal a consistent increase. The researchers have established an average of 0.11°F temperature rise per decade in Lake Michigan’s deep waters. Further, winters in the region have become shorter over the period in question.
According to Eric Anderson, lead author of the study and a researcher with the National Oceanic and Atmospheric Administration (NOAA) at the Great Lakes Environmental Research Laboratory, the changes in deep water temperatures are affecting biodiversity. Species like whitefish and yellow perch are already facing detrimental impacts from the warming waters.
“We can already see declines in reproductive success in certain species that time up with the increases we see in water temperature,” Anderson explained.
In lakes, there are seasonal flows where warm water comes to the surface and cold water is pushed down. It is through this process that oxygen and nutrients are released to deep lake fish and other creatures. According to Anderson, rising temperatures affect this water cycling and, as a result, disrupt the food web.
The warming could have far-reaching consequences to the ecology and economy of the regions around the Great Lakes. Currently, the tourism and fishing industries here provide over 1.3 million jobs and are worth $82 billion in wages, much of which could be lost. Meanwhile, millions of people rely on the Great Lakes for drinking water, but warming can also cause an increase in toxic algal blooms. Unfortunately, the impacts on lake biodiversity and the economy of the region could be permanent.
As Anderson explained, “Once we get past that point, we’ve affected things on an ecological level that aren’t necessarily reversible.”
Image via David Mark