Over the past 40 years, Great Lakes ice cover has decreased by 71 percent, on average. Summer water temperatures have increased more than 2.5 degrees, and water levels have decreased by 29 inches as of January 2013. Water levels were helped tremendously by a wet 2013, but it still leaves the Great Lakes more than a foot below its historic averages. So, how does our arctic cold snap actually help?
The increased ice cover helps reduce evaporative water loss during the current season which helps with overall water levels and reduces the amount of lake effect snow. Lake effect snow typically balances its negative effect by returning to the Great Lakes during the spring thaw, so the benefit may just be for the local residents lumbar regions, but a benefit nonetheless. Even more importantly, the large amounts of ice will help reduce the overall temperature of the lakes, which helps with water loss due to evaporation the following year, helping bring us closer to natural equilibrium. So, as we complain about the temperatures this winter, remember that there is a method to Old Man Winter's madness, that will benefit the region in the future.
I will leave you with this interesting bit of information I found in an article from Lisa Borre of National Geographic's Water Current section. December and January are the worst months for water loss due to evaporation. This may seem counter-intuitive, but high evaporation needs large temperature differences between air and water, low relative humidity, and high wind speeds. During ideal evaporation conditions, it can account for a loss of 0.4 to 0.6 inches of water per day. If that rate of loss occurred over the entire Great Lakes, it would be equivalent to nearly 20 times the flow rate of water at Niagara Falls.
"Nothing is softer or more flexible than water, yet nothing can resist it." Lao Tzu