How do I plot contours on a 3D plane created by patch?

As you can see in the attached image, the plane has different latitudes, longitudes, and depth for each grid point. However, contour requires a vector each for x and y, the length of which must match the dimensions of the value matrix (which is slip). But that is impossible as the grid points have different x values even in the same column and y values in the same row. Is it possible to plot a contour onto the plane?