So… how do they navigate?

I found this pair of photographs on Gab yesterday, showing a lighthouse on Lake Michigan near St. Joseph during and after a winter storm.  Clickit to biggit.

I’ve seen similar photographs before, of course, as I’m sure have most of my readers.  However, I’d never thought about one obvious question.  If the lighthouse is required by ships on the lake for safe navigation, what happens when it’s shrouded in ice and its light can no longer be seen?  Is waterborne traffic suspended until it defrosts?  Is, there, in fact, any waterborne traffic on the Great Lakes during the winter months, or does everything come to a grinding halt until the spring?

I have no idea of the answers, but I’m sure my readers in that part of the world can tell us.  Please let us know in Comments.  Thanks!



  1. Peter,

    It used to be that the Coast Guard ran ice breakers in the Great Lakes (and Lake Saint Clair) up until December 15, and then after March 15. I don't know that that is still the case.

  2. There is typically a 10 week halt to Great Lakes shipping from the end of January to March when the lakes and locks freeze over.

  3. "Is, there, in fact, any waterborne traffic on the Great Lakes during the winter months, or does everything come to a grinding halt until the spring?"

    Mostly the latter.

  4. I'm not an expert, so take it with a grain of salt: Mostly, via GPS or equivalent nowadays. Before that, large ships had systems like LORAN-C, combined with inertial navigation. Large ships also have the equivalent of "Identification Friend or Foe" (IFF) systems called Automatic Identification System. It's tied into an electronic chart display and information system (ECDIS) that shows where the ship is, what the seabed looks like, and what other ships are around.

    The Great Lake lighthouses are automated and exist for small/pleasure craft. These days, even relatively small craft have GPS, and don't usually go out during the winter months.

  5. From my experience up there (CGAS Chicago & Traverse City) when this ices up that much the lake is frozen over.

  6. I grew up right there in Saint Joseph, MI. Indeed, I've jumped off of that catwalk into the water below. There's a second, larger lighthouse just about 100 yds closer to shore from the one pictured, which is at the end of a very long concrete breakwater jutting out into Lake Michigan at the mouth of the Saint Joseph River. We used to jump from the roof of the larger lighthouse into the water as well. When things are cold and stormy enough in the winter for the outer light house to be covered in ice – NOTHING is moving on the Lake. And the larger light is not as exposed to the breaking waves and freezing spray – and usually functions. Most of the marine traffic in that area these days is recreational – although back in the 70's when I lived there, we would occasionally get some big ships in the harbor.

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