Lake Superior Frozen

General Discussions: ASK John: Lake Superior Frozen

By wireburnguy on Friday, March 21, 2008 - 03:22 pm: Edit Post

John,

A week or so ago, I saw the link that was posted here with the pictures of Lake Superior being pretty well frozen on the west end.

That weekend I was at the Porkies and could see some ice, then open water all the way to the horizon. This weekend from the Ontonagon shore, there was maybe 1/4 mile of ice and then waves all the way out. Yesterday I was in Duluth. From the big hill (miller hill), I am sure I could see even further out the horizon and it was all open water.

Just how accurate is the imaging of the lake ice? I have no idea how far a person can see to the hoizon but it has to be several miles. Does the lake freeze out toward the middle beyond where my eyes can see? Or am I just hallucinating?


By frnash on Friday, March 21, 2008 - 08:48 pm: Edit Post

Here's the Great Lakes Ice Chart for Thursday 3-20-2008 (source: National Ice Center):

Ice Chart

It looks like anywhere southwest of a line from the tip of the Keweenaw to the north end of Isle Royale has at least some (< 2 in.) of ice.


By steve_in_il on Saturday, March 22, 2008 - 08:07 am: Edit Post

This satellite view was posted eearlier in the week on George's Eagle Harbor Web.
http://www.eagleharborweb.net/index.htm
The pic is supposed to be from March 16th:
sat

This exact picture is also on the Pasty Cam this morning as well:
http://www.pasty.com/cam/index.html


By wireburnguy on Saturday, March 22, 2008 - 02:02 pm: Edit Post

This (color chart)shows a freeze over from Ontonagon to Duluth. That was my question, I have eyes and can see nothing but open water with waves all the way to the hoizon.

Wikipedia says if your eyes are about 6' off the ground (mine) then you can see about 3 miles to the curve of the horizon. As near as I can tell, Miller Hill is about 700 feet above the lake. Wikipedia says that at 1033 feet (eyes) you can see about 39.4 miles. So, either way, I can see a long ways out.

Either I have a big imagination or I see open water from 3-30ish miles out along the west end of the lake. According to the color graph, I am mistaken and there is 12"+ of ice. Ontonagon clearly has an ice line, maybe 1/4 mile or so out. Clear day in Duluth and it was clearly open water. What am I missing?


By frnash on Saturday, March 22, 2008 - 02:30 pm: Edit Post

wireburnguy:

Ya gotta wonder about the credibility of that National Ice Center chart, eh? (They did say estimated" ice thickness...)
I might even believe that perhaps the satellite can't see "<2 inches" of ice?

I have to agree with you about the visual sighting. "What are we missing?"


By ubee on Saturday, March 22, 2008 - 06:09 pm: Edit Post

Drove from Duluth to Thunder Bay Ont Last wednsday and lake was open as far as you can see. Sat pic showed what i thought was ice. Ice in bays and ports.


By steve_in_il on Monday, March 24, 2008 - 11:02 am: Edit Post

Just to add a follow up, the MODIS imagery from Saturday (March 22) is exceptionally clear. In fact, if you look at the full size views, you can even see what I presume to be the Mackinaw's handiwork in clearing a pathway from the Soo locks out into Whitefish Bay....look for the very straight and narrow path through the ice.

MODIS Site:

http://coastwatch.glerl.noaa.gov/modis/modis.cgi/modis?region=s&page=1

Full size MODIS links for March 22:

http://coastwatch.glerl.noaa.gov/modis/modis.cgi/modis?region=s&page=1&template= sub&image=t1.08082.1644.LakeSuperior.143.250m.jpg

http://coastwatch.glerl.noaa.gov/modis/modis.cgi/modis?region=s&page=1&template= sub&image=a1.08082.1826.LakeSuperior.143.250m.jpg


By wireburnguy on Monday, March 24, 2008 - 07:56 pm: Edit Post

I guess I havent been clear...I agree it is pretty open but the weather has been saying (7-10 days ago) that the west half was nearly froze over and that would limit the LES.

To my eyes, from this area, it was open for miles and miles. Why do they say it was frozen?

John????


By rsvectordude on Tuesday, March 25, 2008 - 10:20 am: Edit Post

It is open where they show ice on those maps....I'll trust my eyes over a website...


By admin on Monday, March 31, 2008 - 08:46 am: Edit Post

I think there are several factors that are at work to cause the descrepencies seen. First is that the map shown above is an "estimate". I do not know how that estimation is made, but it is not done by going out and measuring all the ice on Lake Superior. There are other maps out there that do not deal with thickness, only the % coverage of ice across the lake. I find them to be much more accurate as it is seldome the case where there is 100% ice coverage on the lake. With the exception of fast ice that forms along the shorelines and in bays, most of the ice on the lake is flow ice. A mix of slush and blocks of ice that drift with the winds and lake currents.

That leads to the second factor and that is the ice conditions on the big lake can change very quickly. I observed nearly 100% ice coverage of some type across the western 1/3 of the lake earlier in the month. A few days later, nearly 80% of that ice was gone. So maps that are just a few days old can be in error.

The third is that you may have thought you were seeing pure open water when in fact you might have been seeing a mix of water and slush or ice. Observing the lake at different angles will give a different view of what is out there. I also have some doubt as to how far you can clearly see the lake surface from land. I have been on some pretty high points on some very clear days and watched freighters disappear and suspect that they were not much more than 10 miles away when the did so. So I do not think you are seeing as much of the lake as you think you might be.

However, the biggest factor is how fast the ice can appear and disappear. It can happen in the matter of a day or two.

-John


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