Ship passages may have stopped, but the recency of ice-cutting before they stopped combined with the reasonably swift flow of the water beneath would dissaude me from marching across. I'd certainly walk out on a shallow portion and test it out though.

Remarkable how the larger lakes are almost frozen across. Its a positively rare event, and rarer still in the high-carbon era. http://www.glerl.noaa.gov/res/glcfs/...&type=N&lake=l

Considering what de Troit means, I am not sure we can call this body of water the straits of Detroit. Unlike, say, Gibraltar or my namesake, the city was named after the physical description of the waterway.

Water [[or "river"): de Troit / Detroit. Translated: The Strait.
City: de Troit / Detroit. Tranlated: [the City on/of] The Strait