In winter, is pond water warmer with or without a fountain? I have goldfish I know that goldfish can hibernate but I'd like to keep the water warmer for them.  Is moving water colder or warmer than still water?  The water shoots out of "pipes" about 3" above the water's surface.

Thank you for your comments, I have disconnected the water pumps that shoots water into the air.
In nature, fish survive in ponds due to a lack of turnabout of water.

(Fresh) Water has its highest density at 4°C, meaning both warmer and colder water float on top of 4°C water. Wind may push surface water to the bottom, slightly lowering the temperature at the bottom of the pond. Still, once the surface starts to freeze, this proccess is discontinued, creating a temperature-gradient with the relatively warm 4°C water at the bottom - until spring. Thus fish don't freeze to death.

Meaning, leaving your fountain running is a rather bad idea.

As to the issue of possible lack of  oxygen - I can't answer that reliably.