It’s late February. I’m driving from central Wisconsin, where the ice is nearly a foot thick, to Michigan, and surprised to find very little accessible ice remaining in northern Illinois, open water throughout most of northwestern Indiana, and only limited or poor quality ice across the border in southern Michigan.
Traveling into the central portion of the Great Lakes State I note a few individuals out cutting holes—somewhat perilously, I might add—but don’t encounter any appreciable ice until I’m well up I-75. In the process, I begin hearing sobering late ice tales, some ending with unwelcomed cold water immersions. It’s with this in mind I thought a few words covering late ice safety might be appropriate.
The most important thing to understand about late ice might be the meltdown process itself.
In general, ice generally retreats first from the very areas it initially formed—namely, shorelines along shallow bays and flats. These same shallow water regions that cool fastest in early winter warm equally quickly in spring. Even when frozen clear to bottom, this is inherently some of the thinnest and most vulnerable ice, virtually ensuring it will be first to melt away.
The process begins as increasingly intense sunlight melts snow atop thin layers of shore ice and the adjoining shoreline. Run-off accumulates, slowly forming a thin rim of open water directly along shore. As snow continues melting, the now exposed darker colored ground absorbs heat. Since ice in the immediate shallows is frozen solid and in direct contact with the shore and lake bottom, sunlight melts it from the surface, while heat absorbed by the ground is transferred and melts the pack from below, causing rapid deterioration.
At the same time, the loss of white snow on the surface further enhances melting by replacing this highly reflective layer with darker colored ice that absorbs more heat. Once the snow disappears and the immediate shallows open up, sunlight penetrates the water, too, where radiant heat is absorbed and retained, accentuating melting.
As this process continues, open water leads widen along shore. Melt water accumulates on the remaining ice, eventually draining through open cracks, old holes and other openings. This reduced weight on the pack relieves pressure, causing it to lift, or “pop,” enhancing drainage further and causing flowing water to begin eroding remnant ice at an increased rate.
Note select areas will melt more rapidly than others. Shorelines with broad, open southern exposures, for example, receive more light and typically give way first, especially when directly subjected to the afternoon sun. Shallow, dark bottom areas featuring dark colored vegetation or rocks further speed the process, as will exposed boulders, downfallen trees, emergent vegetation or man-made structures such as docks or pilings, as these readily absorb and conduct heat. The presence of springs and currents generated by aerators or natural sources will also create overflows currents undercutting the ice pack–the greater and quicker the flow, the faster melting will occur.
Adjacent deep water basins, which contain thicker ice to begin with and a greater volume of water below, require longer to warm and therefore remain frozen somewhat longer. Adventurous anglers often use this to their advantage, crossing weak shore ice or open water using boards or ladders—some may even float a canoe or boat out toward stable mid-lake packs, thereby extending their season.
Late season snowfall may be enough to accumulate over patches of weak or bad ice, concealing danger.
However, don’t neglect to fully understand the melting process. Remember, shallow waters warm fastest, and such areas aren’t limited to shoreline bays and flats! Ice covering shallow littoral zones around islands, shallow mid-lake rock bars and humps also melts away at a faster rate than ice coating adjacent deep water basins. Beware!
In addition, shorelines may open up surprisingly quickly during a bright, warm spring day, and cracks will widen, so those resorting to board or ladder crossings may find their bridges of adequate length in the morning insufficient by late afternoon. And, on larger waters during windy conditions, large cakes of main lake ice may occasionally break off, separate and float free. At times, groups of late season anglers–along with their gear–find themselves being airlifted to safety, surprised to hear they’ll be rescued, but their equipment will not. During late ice, you must always be aware of your situation and conditions!
As open, shallow expanses widen, run-off increases and temperatures continue warming, winds begin taking a toll, too, accelerating erosion of the pack, while sunlight beating on the surface and along exposed edges causes the overall tensile strength of the ice to lessen. Wave action may now begin causing extensive break-up in select areas.
If you’re still accessing mid-lake areas during this time, you’ll visibly notice remnant ice deteriorating. Gradually deepening surface creases, expanding cracks, and pockets of standing water will form. In between, you’ll find weakened ice soft enough to scratch into with a fingernail, crumbling into long blade-like crystals resembling teeth on a comb.
At this point, be warned: Hard water season is ending. The ice will soon begin displaying a yellowish-gray cast that will grow increasingly dark and mottled—a condition often referred to as “honeycombed,” before softening further and dissipating altogether.
So always be wary, pay attention when traversing late season ice, and remember: “When in doubt, don’t go out!”