The recent cold snap is good news for Lake Superior.
Ice coverage on Lake Superior skyrocketed over the past week, with 33% of the lake covered in ice as of Monday, according to the National Oceanic and Atmospheric Administration's (NOAA) Great Lakes Environmental Research Laboratory (GLERL).
On Feb. 6, ice coverage on the lake was less than 6%.
Here's a look from the International Space Station above Duluth and Lake Superior on Feb. 15:
Prior to this past week of arctic weather, the Great Lakes were nearing historic lows in terms of ice coverage, MPR News reported. In late January, only about 4% of Lake Superior was covered in ice, when the average that time of year is 20%.
The long-term average annual maximum ice cover on Lake Superior is 61.5%, NOAA says, with ice coverage fluctuating from year to year.
Here's a look at maximum ice coverage the lake has seen in recent decades (here's a list of maximum percent coverage and the date it was achieved):
But in recent years, ice coverage on Lake Superior has seen extreme highs and lows. Last year, ice coverage on the lake maxed out at 22.6%, while in 2019 it reached 94.9%.
The problem with these extremes is that if Lake Superior sees multiple years of lower than average ice coverage it can have negative impacts on the lake's ecosystem.
"At this time I'm not that worried, but if next year is another low ice year, the whole lake will warm up," Jia Wang, a NOAA Great Lakes Environmental Research Laboratory research scientist and ice climatologist told the Star Tribune in January. "What concerns me is if these kinds of lows continue for several years — that will have a bigger impact."
When there is less ice on the lake, the water absorbs more of the sun's rays, causing it to continue to warm – and Lake Superior's waters are already among the faster warming in the world. Warmer waters could make Superior more hospitable to invasive species, harm the lake's current ecosystem, and could create the right environment for harmful algae blooms, researchers have said. The lack of ice can also contribute to faster shore erosion.
So, although this past week of subzero, record-breaking cold did cause problems for Minnesotans, it was good for the lake.
But even with the bitterly cold weather adding a significant amount of ice to Superior and other lakes, the National Weather Service in Duluth is reminding people that ice is never 100% safe.
In a tweet on Feb. 15, satellite images show ice breaking away from the Twin Ports as the wind shifted.