A Coast Guard spokesman says winter enthusiasts are putting themselves at danger taking advantage of early ice buildup at a time that ships are still moving on the Great Lakes.
Coast Guard cutters like the Duluth-based Alder are routinely cutting paths through the ice for ships -- creating open water not always obvious to people on the ice.
Lake shipping continues on Lake Superior until at least mid-January, said Coast Guard Lt. Luke Sanders.
"The [Duluth] Aerial Lift Bridge closes on the 15th, but ships can still move in the harbor after that if they come into the Superior entry," he said.
Sanders said few people are venturing onto the Duluth-Superior harbor ice, although some have been setting up fishing shelters on ice near Superior, what the Coast Guard calls the front channel.
Sanders said ice will be broken in the Duluth-Superior harbor until well into January.
"Even a few days after [the 15th] there may be some large ships laying up in the Duluth-Superior area," he said.
The Coast Guard has noticed people in close proximity to tracks cut into the ice for ships.
Coast Guard responders also worry about warmer temperatures and rain forecast for later this week, conditions that can quickly deteriorate what ice is in place.