title: Mask Ocean or Land from data using Cartopy
body: <p>I would like to mask the Land area from Sea Surface Temperature Data over the globe. I am using Cartopy to plot the data.</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  import cartopy.crs as ccrs
  from netCDF4 import Dataset
  
  f = Dataset('sst.mnmean.nc')
  sst = f.variables['sst'][0,:,:]
  lats = f.variables['lat'][:]
  lons = f.variables['lon'][:]
  
  ax = plt.axes(projection=ccrs.PlateCarree())
  ax.coastlines()
  plot = ax.contourf(lons, lats, sst, 60, transform=ccrs.PlateCarree())
  cb = plt.colorbar(plot)
  plt.show()
  </code></pre>
  
  <p>The above code plots data like this:<br>
  <a href="https://i.stack.imgur.com/fdTR9.png" rel="noreferrer"><img src="https://i.stack.imgur.com/fdTR9.png" alt="enter image description here"></a></p>
  
  <p>I would like to mask out the Land from this.</p>