The Great Lakes

“Less than one percent of Earth’s water is fresh, liquid, and accessible, and most of that is found in huge lakes scattered around the globe . . . where most of the water depended upon by human society is found.” Large Lakes Observatory
The Great Lakes of Huron, Ontario, Michigan, Erie, and Superior (“HOMES”) hold almost 20 percent of the world’s freshwater supply, and comprise the largest extent of freshwater on Earth. Put another way, one out of every five drops of liquid freshwater on our planet can be found in the Great Lakes.
The history of the formation of the Great Lakes is fascinating, and begins about .8 billion years ago. Robert Sterner, director of the Large Lakes Observatory, explains this history in the video below.
The Large Lakes Observatory (LLO) is based at the University of Minnesota Duluth. It is a unique institution, with a mission to study the large lakes of the world. Scientists at LLO use some pretty cool technology to investigate the chemistry, biology, and physics of large lakes. This equipment includes autonomous underwater vehicles and meteorological buoys. A lot of the equipment was originally developed for ocean research.
Jay Austin, a physicist at LLO, introduces some of this technology in the featured video at the top of this page. Doug Ricketts, the marine superintendent for LLO, shares more technology in a separate video post about the Blue Heron, a research vessel owned and operated by LLO.
Scientists have identified two primary categories of threats facing the Great Lakes today: biological pollution (such as invasive species) and global climate change. The Great Lakes are among the fastest warming lakes on Earth. Of particular note, summers in the Upper Midwest are getting warmer, but winters are getting even warmer yet, leading to a decline in ice cover on the lakes. Areas of open water absorb more heat, melting more ice and leading to warmer water temperatures not only in the winter, but also in the following summer. The warming lake temperatures are putting stress on the lake’s native inhabitants, some of which have an upper thermal tolerance limit (a temperature above which they cannot thrive and survive).
In order to study climate change trends, scientists need data across extended periods of time. If you’re interested in how scientists capture data from long ago, and why many scientists believe our climate is warming due to human activities, check out: “How Do Scientists Study Ancient Climates?” from NOAA, and “Climate Change: How Do We Know?” from NASA.
Our video story on the cleanup of the St. Louis River, the largest tributary to Lake Superior, includes footage of sediment core sampling by a paleolimnologist. The data collected from these samples allow scientists to study lake and river conditions from hundreds of years ago.

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