pb11.py

ds_sigma_section = ds_sigma.sel(
  time='2010-01',
  y=slice(-90,10)
).interp(x=230).squeeze()

fig, axarr = plt.subplots(nrows=2, figsize=[10,8], sharex=True)
for ax, var, cmap in zip(
  axarr.flat,
  ['so', 'cfc11'],
  [cmo.haline, cmo.matter]
):
    
    kwargs = dict(yincrease=False, x='lat', y='sigma_0', ax=ax)
    
    ds_sigma_section[var].plot.contourf(
        levels=31, robust=True, cmap=cmap, **kwargs
    )
    ax.axhline(26.4, color='C1')
    ax.set_title('')
# add a bit more space between the panels
fig.subplots_adjust(hspace=0.2)