DULUTH, Minn. (AP) — Rapidly rising water levels in the Great Lakes are damaging shorelines and leading to uncertainty for lakeshore residents.
Duluth has dealt with three major storms on Lake Superior in less than two years; the latest hit last October. The construction-project supervisor for the city, Mike LeBeau, said the high water levels are making the storms even more destructive, Minnesota Public Radio News reported. Duluth officials estimate the cost of the total damage from the three storms at nearly $30 million.
“It’s been hard for the city to catch its breath, frankly,” LeBeau said.
Around the Great Lakes, beaches have disappeared, docks have been submerged and shorelines are eroding. Lake levels began rising rapidly in 2014. This summer, lakes Erie and Ontario reached their highest levels ever recorded, thanks to months of abnormally wet weather keeping stream flows into the Great Lakes well above average. Lake Superior, meanwhile, has set new monthly records.
The higher lake levels are a boon for the shipping industry, which was complaining about record low water levels only six years ago. Deeper water allows ships to carry more cargo.
As an example, Jayson Hron, Duluth Seaway Port Authority spokesman, cites the lake freighter Edwin H. Gott. This ship can carry an additional 267 tons of iron ore for every extra inch of its “draft,” which refers to the distance between the waterline and the deepest point of the ship’s hull.
“That’s something like $26,000 worth of extra ore per inch, so if you multiply that by 2 or 3 inches of water level, and then multiply it by more than 30 trips over the course of a shipping season, it adds up to some significant benefits,” Hron said.
Great Lakes water levels began quickly dropping in the late 1990s and continued to do so for the next 15 years. Warm lake temperatures led to high evaporation rates, causing the decreased levels, said Drew Gronewold, a University of Michigan environmental science professor and former hydrologist at the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory.
“There really isn’t a period of below-average water levels in the record for quite that long a time period,” Gronewold said. Data on the Great Lakes go back a century.
Gronewold said the quick transition was “one of the most rapid water level increases in history.”
Lauren Fry, a hydrologist at the U.S. Army Corps of Engineers’ Detroit district, said the current spike in water levels has been driven by an increase in rain and snowfall over the Great Lakes and surrounding places.
“Over the past six years, we’ve had above-average water supply more often than not,” Fry said, “so, it’s been an ongoing building of high water levels, culminating this season.”
Increased precipitation, including more extreme rainstorms, is one of the signs of climate change in the Upper Midwest. The warmer the air, Gronewold said, the more moisture it can hold.
But the rise in water levels has also coincided with extremely cold winters, including the “polar vortex” cold snap in 2014, which produced record-breaking ice cover on the Great Lakes. Because that ice took a long time to melt, the cold snap actually slowed evaporation rates.
Gronewold said it’s now a tug of war between increased precipitation and the likelihood of evaporation increasing again.
“The oscillation between those two extremes is what could be leading to more future rapid oscillations between extreme water levels, as well,” he said.