Pass Yukon
i.e. the Yukon River--some passes freeze solid enough to cross ice safely but the current is especially strong.
when the water freezes, it freezes from the outside in. So it all starts to freeze slowly, and the ice runs into other ice and builds up on the top; meanwhile, the current stays strong under the surface.
As it stays cold, the ice gets thicker and thicker on top and the current is kept under.