Years ago it used to get really cold here in Kansas and paddle wheels were used to churn small stock ponds so the cattle could get water. When used in this manner, the paddle would be completely submerged and there might be a thin layer of ice on the pond, but the cattle could easily break this themselves. Most of these paddles were powered by electric motors, but in windy conditions, a windmill would work. If the paddle where positioned so that it broke the surface of the water, it would aerate the pond. Of course this might not be necessary as catfish live well in small ponds here in Kansas without any aeration. There are algae that fix oxygen into the water naturally and as you said, after the pole shift the rainfall will take care of oxygenation.
Offered by Roger.