How to manually set colorbar ticks in figure

I am trying to manually change the ticks of the color bar of the figure, not able to give clim to the colormap for some reason. Is there a workaround this ?

can you please post the code that generates this figure?

    import numpy as np
    import matplotlib.pyplot as plt
    from matplotlib import cm
    from matplotlib import rc, rcParams
    from mpl_toolkits.mplot3d import Axes3D
    from scipy.interpolate import griddata
    import matplotlib.gridspec as gridspec

    # 2D-arrays from DataFrame
    x1 = np.linspace(df['x'].min(), df['x'].max(), len(df['x'].unique()))
    y1 = np.linspace(df['y'].min(), df['y'].max(), len(df['y'].unique()))

    x, y via meshgrid for vectorized evaluation of 2 scalar/vector fields over 2-D grids, given
    one-dimensional coordinate arrays x1, x2,..., xn.

    x2, y2 = np.meshgrid(x1, y1)

    # Interpolate unstructured D-dimensional data.
    z2 = griddata((df['x'], df['y']), df['z'], (x2, y2), method='cubic')

    # Ready to plot

    fig = plt.figure(211,figsize=(15,20))
    ax = fig.add_subplot(211, projection='3d')
    spec = gridspec.GridSpec(ncols=1, nrows=2,
                             height_ratios=[4, 1])

    surf = ax.plot_surface(x2, y2, z2, rstride=1, cstride=1, cmap=cm.terrain,
                           linewidth=1, antialiased=False)

    cset = ax.contourf(x2, y2, z2, zdir='z2', offset=-80, cmap=cm.terrain, antialiased=True)
    fig.colorbar(surf, shrink=0.5, aspect=5, extend='both')

    rcParams['legend.fontsize'] = 20

    rc('text', usetex=True)
    rc('axes', linewidth=2)
    rc('font', weight='bold')

    rcParams['text.latex.preamble'] = [r'\usepackage{sfmath} \boldmath']

    ax.set_zticks([-70, -50, -30, -10, 10, 30, 50, 70, 90, 110])
    plt.title(r'\textbf{Bedford Basin Bathymatry}', fontsize=20)
    plt.xlabel(r'\textbf{Latitude}', fontsize=20, labelpad= 23)
    plt.ylabel(r'\textbf{Longitude}', fontsize=20, labelpad= 20)
    ax.set_zlabel(r'\textbf{Elevation}', fontsize=20, labelpad= 10)

    fig.savefig('Bedford_BASIN_BATHY_view5.png', dpi=600)