Does atmospjeric pressure act in a confined liquid?

All the air above a volume pushes down with a certain weight. That is what we call atmospheric pressure. It affects everything. The volume pushes back with an equal weght, and if the weight changes then things are squeezed or expanded until the two opposite forces are again equal. In a canning jar, the pressure inside the jar reduces as the food cools and the lid eventually snaps into a new position. If it does not snap, or if a spoon on the lid does not produce a "ting" sound, then the seal is bad. The lid on a jar with bad seal makes more lie a "tok" sound. So that is one effect of atmospheric pressure on a confinded liquid.