How big is the pond? How deep? How many gallons? What are the current inhabitants?
If they are native turtles, and your pond is deep enough (or you keep it agitated enough) not to freeze completely, then possibly it could survive the winter. A better option would be for you to keep a tank, tub, or temporary pond inside the house where you could overwinter the turtles, just to be sure that they could survive the winter.
Depending on the species of turtles, they will likely need different conditions to be able to overwinter/hibernate in NJ.