By David L. Brown
The Great Lakes are artifacts of the last Ice Age, gouged from the earth by massive glaciers that once covered much of Canada and the upper part of the present United States. They form the largest freshwater system in the world. They are also a harbinger of climate change, because they are growing hotter, thus acting as “canaries in the coal mine” for global warming.
I’m particularly aware of this change because for six years in the 1960s I lived in a high-rise apartment on Chicago’s northside. The building was called Shoreline Towers for the fact that Lake Michigan was right outside my window. Waves sometimes washed over the retaining wall to soak my car in the parking lot. In those days, come winter the lake began to freeze over. Not all the way, but out several miles. When there was a strong east wind the ice would sometimes break up into slabs six or eight inches thick and pile up along the shore.
My friends who live in Chicago tell me that that’s no longer the case today. Lake Michigan does not freeze, and that’s about as clear as any evidence I can think of that the lake is warmer than it was 40 years ago.
Lake Superior, the "canary in the mine"
According to an article posted on the Scientific American website (here), this trend has not only been measured, but shows signs of accelerating. All the Great Lakes have been affected, but climate scientists have been keeping a particular eye on Lake Superior, the largest, deepest, and most northerly of the lakes. The canary of canaries.
The article, “Lake Superior, a Natural Global Warming Gauge, is Running a Fever,” quoted Cameron Davis, the senior adviser to the U.S. Environmental Protection Agency on the Great Lakes: “Total ice cover on the lake has shrunk by about 20 percent over the past 37 years, he said. Though the change has made for longer, warmer summers, it’s a problem because ice is crucial for keeping water from evaporating and it regulates the natural cycles of the Great Lakes.”
This year the trend is even more apparent, with Lake Superior on track to reach or exceed its 1998 record-high temperatures of 68 degrees Fahrenheit. Ominously, data from several buoys that measure temperatures in the lake “reveal that the waters are some 15 degrees warmer than they would normally be at this time of year,” the SciAm article quotes Jay Austin, a professor of physics at the University of Minnesota-Duluth. Dr. Austin is associated with the university’s Large Lakes Observatory (link here).
The warming lake waters are not only evidence of global warming, they may be changing the ecology of these freshwater seas by allowing harmful species to gain a foothold there. For example, the charmingly named blood-sucking sea lamprey is spreading through the lakes. Like the vampires of folk myth, these creatures latch onto the sides of trout and hang on, sucking the fish’s blood until it dies.
There are serious concerns about the effect on native American tribespeople who live around the lake and depend upon its waters. Besides threatening their fisheries, increasing warmth threatens their ability to harvest wild rice, a major source of revenue.
When we hear that the waters of a huge lake are 15 degrees warmer than usual, that’s more than just a canary cheeping in a coal mine. Unless, of course, it’s the mythical 500-pound canary from a very old schoolyard joke.*
As I’ve noted in some recent posts, it’s vexing that as evidence of global warming continues to pile up, there seems to be less acceptance of the danger by the general public, not more as one might suspect. Perhaps this is due in part to the short memory horizon of most younger people. Someone who wasn’t around Chicago 40 years ago won’t remember when the ice piled up on the shore each winter. They won’t remember the time in the 1970s when a bitter west wind created a wind chill in the range of minus 80 degrees, threatening to freeze the pipes in my house even though the furnace was running constantly.
Sadly, those who view events in the world from a short timeline cannot have an accurate indication of any trend. It’s too easy to assume that not much is going on, and that those stories Grandpa told about the frigid winters of the past are just that, stories. This problem of what might be called timeline myopia is particularly true in the case of climate change, which may seem to occur slowly but which in fact is speeding at an unprecedented rate.
We’ve already seen that 2010 is the hottest on record so far, and most months have set records worldwide. We also see that Arctic sea ice has been running at record low levels this year, that the Greenland ice sheet is melting faster than ever, and a multitude of other warnings. Other canaries, entire flocks of the little yellow harbingers. Will no one hear them?
* “What does the 500 pound canary say? CHEEEP!” Sorry.