Despite all the subzero temperatures the Polar Vortex threw at it, Lake Superior never quite froze over entirely this winter and already appears to be losing some ice cover.

Satellite photos from the most recent clear day - Tuesday - show vast areas of what appears to be open water just off Minnesota and Ontario's North Shore and many other areas of the lake.

And some areas that have ice cover appear to show fissures and cracks as the lake ice diminishes due to warm temperatures, rain and windy conditions.

With no cold snaps anywhere in the forecast it's unlikely the lake ice will grow much again this season.

Estimates - based on satellite temperature data taken of the lake's surface - topped out at 95 percent ice cover for the big lake earlier in March. But that number quickly dropped and now sits at about 80 percent, based on the estimates by the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory.

The most recent satellite photo appears to show even less than 80 percent ice cover.

The western tip of Lake Superior near Duluth and Superior, and around the Apostle Island, appears well-locked in solid ice. Losing those vast sheets of ice still on Superior won't be easy or quick. Despite the recent warm and windy streak it could still take many weeks - even months - for the most solid Lake Superior ice to melt. As Duluthians well know, there has been remnant ice on the lake and beaches well into May some years, and in some cases into June.

Across the Great Lakes about 50 percent of the lakes are still ice-covered, according to the NOAA estimates.