I think I know that boat, and if so, she isn't originally from the Great Lakes. In any case, I'm going with "ice cutter". I'm guessing that jagged edge would only work on really thin ice.
FYI - I believe the icebreaker here on the Great Lakes (USCG's Mackinaw) use mass rather than a sharp, jagged edge to "cut" the ice in most instances. Sorry for the off-topic diversion, but I found her ice breaking characteristics interesting:
3 knots ahead in 32" solid level ice
10 knots ahead in 14" solid level ice
2 knots astern in 30" solid level ice
3 knots ahead and 2 knots astern in 8' brash ice
Average .5 knots ahead, backing and ramming in 42"solid level ice Average 0.5 knots ahead, backing and ramming in 5' refrozen brash ice Average 0.5 knots ahead, backing and ramming a 12' pressure ridge Fully penetrate a 10' pressure ridge in 4 rams or less within 30 minutes