Sunday, January 24, 2021

Great Lakes Ice Cover Nears Record Low



Jan 23, 2021 satellite image of 4 of the 5 Great Lakes (excluding Superior) on a rare day when there are clear skies across the region in winter. Notice Lake Michigan is essentially ice-free except for some ice visible in Green Bay. Saginaw Bay on Lake Huron also had ice cover but the shallow western end of Lake Erie, was devoid of ice at a time of the year when it is normally covered. 

What do you notice, or should I say, NOT notice on the Great Lakes in the above satellite image? Well, it is smack dab in the heart of the winter season and yet there is precious little ice cover on the lakes. The image above shows a cloud-free Lake Michigan along with Saginaw Bay on Lake Huron and a few cloud free zones on western Lake Erie and the northern half of Lake Ontario (Lake Superior is not visible in this image). Notice, the only areas with any ice cover are Green Bay and Saginaw Bay. Even the very shallow western end of Lake Erie is ice-free.


Map of the Great Lakes showing the ice cover and thickness on January 21, 2021.  Only the shallower bays have developed any ice cover so far this season. 



This image of the Niagara River Ice Boom at the east end of Lake Erie at Buffalo, NY shows something that does not happen very often. There is no ice to be seen and its the third week in January. The boom is installed every winter to keep ice from going down the Niagara River and causing jams that could disrupt power production at the Niagara Power Project. 

All of the lakes are way below where they should for ice cover this season.  Overall, the Great Lakes normally have about 17% ice cover by this point in the season and right now it is at less than 3%. Below is a look at each lake, showing the long-term averages for ice cover through the season. I highlighted January 21st to compare the average ice coverage for the date vs. January 21st, 2021. The numbers are mind-boggling. On Lake Erie, the shallowest of all of the Great Lakes, the ice cover should be at 45% at this point in the season, but its only 3% ice-covered!  Click on each lake image to see a larger view.   






 




So, just why has there been so little ice cover on the Great Lakes?  Well, they answer is pretty straightforward, it is directly connected to the average air temperature across the region so far this winter.  An analysis of the temperatures for select U.S. stations across the Great Lakes (adjacent Canadian stations are similar) show just how warm it’s been, with locations anywhere from 4 to 8 degrees above normal. In fact, stations across the Upper Great Lakes Region are seeing their Top 5 warmest winters on record and at St. Ste. Marie on the eastern shore of Lake Superior, it has been a record warm winter so far.



Season-To-Date average temperature departures for selected locations through January 21,2021.  Notice that the Great Lakes Region is currently running from 4 to 8 degrees above normal. 


Great Lakes Ice Season

Each of The Great Lakes typically develop a range of ice cover every winter season.  It takes a while into the winter to actually get cold enough to develop ice. That’s because there is such a huge volume of water in the lakes and it takes a lot of time for that water to cool to the freezing point. Fun Fact: If you emptied all of the water in the Great Lakes, it would cover the entire United States to a depth of about 9 feet!

The animation below highlights the weekly median ice cover at 2-week intervals from January 1st through May 1st  over the period 1973-2002.  Typically ice begins to develop in bays and shallow areas by early January, and by mid to late February Lake Erie often freezes over completely.  Others, like Lake Michigan and Ontario rarely develop more than 20% ice cover.



Weekly median ice coverage across the Great Lakes every 2 weeks from January 1st through May1st for 1973-2000. 

One thing that stands out when you view the growth of ice cover through the season above is how quickly Lake Erie ices up compared to the other Great Lakes.  It all has to do with the volume of water contained in each lake, and the ratio of the surface area of the lake to the volume.  If you look at the Great Lakes statistics, you can see how much shallower Lake Erie is compared to the other lakes.   Let’s compare two adjacent lakes that are about the same size when you look at them from above, Erie and Ontario.  Lake Erie has a surface area of 9,910 mi2 , while Lake Ontario has a bit smaller surface area of 7,340 mi2.  However, Lake Ontario has a volume that is over 3 times that of Lake Erie (393 mi3 vs. 117 mi3).  Lake Ontario is 802 ft. at its deepest point, while Lake Erie is only 210 ft. at its deepest point and its average depth is only 62 ft.  It takes a lot longer to cool down the much greater volume of Lake Ontario that is over 3 times that of Lake Erie.  There is also a much greater ratio of Lake Erie's volume of water exposed to the cold air above.  It’s like putting a shallow, circular pan of water into a freezer next to a deep pail with the same circular size (surface area).  That shallow pan ices up much more quickly. 



This is a great cross-section illustrating so many of the characteristics of the Great Lakes. A quick glance will point out just how shallow Lake Erie is compared to all of the other Great Lakes.  

   



This table shows the volume of water in each lake as well as its surface area.  The ratio of the surface area of each (A) compared to the volume of water (V) is also shown. Not only does Lake Erie have much less volume of water compared to all of the other Lakes, it also has the greatest ratio of surface area to volume, showing it has a much greater percentage of its volume exposed to the cold air.


Some Implications of Meager Ice Cover

One of the potential dangers with so little ice cover on the Great Lakes this far into the winter season is the fact that ice, especially thick and extensive ice cover that is held fast, helps protect the adjacent shoreline areas from the battering waves and high water that ferocious winter storms can produce.  To add to the potential for serious damage to the shoreline, the water levels of all of the Great Lakes are above the long-term average. Although not quite as high as last winter, some of the lakes are still near record high water levels. The combination of no ice cover and high-water levels is like a ticking time bomb that will keep property owners on guard as the winter wears on. 


Jan 22, 2021 Weekly Great Lakes water levels show how much higher than the long-term  monthly average each lake is right now. The Michigan-Huron complex is running 31 inches above normal, while Lake Ontario is presently only 1 inch above normal.  

From a recreational point of view, less ice cover means less ice-fishing, a sport that is wildly popular in many Great Lakes cities during the winter. For those who do venture out onto the ice, the dangers increase because in many cases the thickness of the ice will not be enough to support vehicles and other gear. 



These great aerial photos compare the ice conditions on Lake Ontario at Sodus Point, along the south shore of the lake about 40 miles east of Rochester, NY. What a difference three years makes.  In January 2018, ice fishing was booming in this region but this year, there is nary an ice cube to be found. (Courtesy John Kucko)

With temperatures as warm as they have been so far this winter, there is not only no lake ice to be found, but the infamous lake-effect snow machine that typically hammers areas downwind of the Great Lakes with heavy snow, has almost completely stalled out. Cities from Buffalo to Marquette have much less snowfall this season because as I have always said, “it takes two to tango to make snow”. You need cold air and moisture, so, ironically, ice-free lakes do not promote lake-effect snow because of the same reason the lakes are ice free, it’s been warm. There hasn’t been much cold air to produce that snowfall.  I also get the question/comment that because there is still so much open water this late into the winter season, that means we could be in store for a major lake-effect snowstorm.  But once again, "it take two to tango" and until we actually do get a cold airmass to cross those open lakes, then we only have half the ingredients to fulfill that prophecy. 




Seasonal snowfall through January 23, 2021 compared to the average for the date. In places like Grand Rapids, Michigan they have picked up only 20% of what they normally get by now. It will take some time this year for Marquette to make it to the 100 inch club and Buffalo is not living up to its snowy reputation either.  


One other implication for the Great Lakes is that less ice cover, or more open water, actually increases the evaporation that occurs off the surface of the lake. Greater evaporation could lower Great Lakes water levels.  Now, in the short-term, based on current high water levels, that could help get us back to normal.  However, climate models suggest that a warmer atmosphere would more permanently increase evaporation in winter, while at the same time increase rainfall and runoff going into the Great Lakes due to the fact that warmer air holds more moisture. Climate change is a very complicated game and I will not be addressing the potential impacts in this article. However, the simple fact that we are living in a world with a background increase in temperatures certainly points toward less ice cover occurring more often in the future. 

As I have said many times, society has been built to live within the confines of the current climate. Any changes in the climate of a region will undoubtedly have some positive impacts but more often will have a negative impact on society because our civilization has been built without much foresight into the future.  

I close with warning anyone who would want to venture out onto the meager ice in bays or along shorelines to be extra careful. It may not be thick enough to support a lot of weight. If you live along the shoreline, stay on guard for warnings about lakeshore flooding and erosion, and if you are waiting for a good lake-effect snowstorm, pray for cold air.  Be safe and enjoy all that winter has to offer!

 

2 comments:

  1. Great article. Skip was amazed at the difference in lake depths and I had no idea Ontario was 300' lower.

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    1. Yes, right off Oswego as a matter of fact. Ontario's deepest point is 802 ft. while Lake Erie's is 210 ft. or 600 ft. deeper !!

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