Green bay, wisconsin, is located at an imaginary line running north-south on the globe. what does the line represent?

The imaginary line passing over Green Bay, Wisconsin, running 'north-south on the globe' represents the degrees of longitude.

Explanation:

A longitude is an 'imaginary line' that runs vertically from the 'north pole' to the 'south pole' intersecting all the latitudes in its path making coordinate points. The degrees on the longitude are denoted by the south direction in the 'southern hemisphere' and by the north direction in the 'northern hemisphere'. As the longitudes move towards the poles from the 'equator', the distance between them goes on decreasing.

No it is an oblate spheroid apparently