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Where's the ice? Historic low Superior and Great Lakes ice cover

Ice cover less than 2 percent on Lake Superior this month

Duluth ship canal
Duluth ship canal shows blue water and no ice cover on February 22, 2024.
Lake Superior Maritime Museum

The Great Lakes have never looked like this in February.

Ice cover is at record low levels this month on Lake Superior and other Great Lakes. Lake Superior continues to hover around the record low 1.7 percent ice cover observed in the middle of this month.

Lake Superior ice cover
Lake Superior ice cover. The black line represents 2023-24, which is at historical lows.
Great Lakes Environmental Research Lab

The average ice cover for Lake Superior this time of year is around 40 percent. Great Lakes total ice coverage was measured at 2.7 percent on Feb. 11.

Great Lakes ice cover
Great Lakes ice cover. The black line is 2023-24.
Great Lakes Environmental Research Lab.

Bryan Mroczka, a physical scientist with the Great Lakes Environmental Research Lab, cites this winter as the new low benchmark for Great Lakes ice cover.

“We’ve crossed a threshold in which we are at a historic low for ice cover for the Great Lakes as a whole … We have never seen ice levels this low in Mid-February on the lakes since our records began in 1973.”

Here are the readings for ice cover as of Feb. 11. Some of these are trending even lower as of Thursday:

  • Lake Superior, 1.7 percent

  • Lake Michigan, 2.6 percent

  • Lake Huron, 5.9 percent

  • Lake Erie, 0.05 percent

  • Lake Ontario, 1.7 percent

Warmer than 2012

The first months of 2012 are the benchmark for warmth in the Upper Midwest and Great Lakes regions, but the start of 2024 is even warmer.

The chart below shows air temperature readings from buoys in Duluth Harbor. You can see this winter is running even warmer than the previous record year of 2021.

Duluth harbor temperatures
Duluth Harbor air temperatures
Jay Austin, University of Minnesota Duluth

I reached out to Great Lakes researcher Jay Austin from the University of Minnesota Duluth to get some additional perspective on why this winter is unique.

Hi Paul-

I suspect you know about as much as I do at this stage- we're all looking at the same NIC data. One analysis I did a few days ago (see attached) shows that winter air temps to this point of the season are even warmer than 2012, which I think of as the gold standard for a warm, low ice winter. This implies a very early onset to the "summer" stratified season; open lake will probably stratify mid- to late MAy, as opposed to a more typical early July. Downstream: warmer summer water temperatures. Good for a comfortable swim come this July/August, but also tends to foreshadow algal blooms.

I currently have two over-winter platforms deployed in Superior; it will be interesting to see what went on below the surface over the winter. Those are slated to be recovered this spring.

Also attached: average ice cover on Superior pre- and post 1998. Striking.

One last bit- we had a bit of ice growth earlier this week when we had a day or two of cold air, but at this stage there's really little hope for more ice- we are getting over 2x as much sunlight per day than at the winter solstice, which is all being absorbed by the lake. Oddly, at this time of year we would not yet have reached peak coverage, which typically occurs in early March.

jay-

Here’s this striking graph of ice cover trends on Lake Superior. Note how climate change and Minnesota’s warmer winters have significantly impacted ice cover since 1997:

Great Lakes ice cover before and after 1997
Lake Superior ice cover trends before and after 1997.
Jay Austin, University of Minnesota Duluth

Record warm winter

The combination of climate change and our super El Niño are combining to drive the warmest winter on record. Winter temperatures since Dec. 1 rank as the first or second warmest across the Great Lakes basin.

Winter temperature ranking
2023-24 Winter temperature ranking.
National Oceanic and Atmospheric Administration, via Iowa Emergency Management

Climate change has warmed Minnesota winters by more than 5 degrees overall on average since 1970.

Winter warming since 1970
Winter warming since 1970.
NOAA, via Climate Central

The strong El Niño this winter is adding additional warming to our winter season by shifting jet stream patterns further northward and delivering a persistent feed of mild Pacific air into the Great Lakes region.

El Niño impacts
Typical El Niño winter impacts
NOAA

Lake Superior typically sees peak ice cover in early March. With the forecast looking much warmer than average for the next few weeks, it’s unlikely that we’ll see a significant increase in ice cover this season.

NOAA 8 to 14-day temperature outlook
8 to 14-day temperature outlook
NOAA