Bad Arctic plotting on global maps

[adele-morrison]

A few of the recipes with global maps have the Arctic plotted incorrectly with Canada extending all the way to the north pole. This includes:

• ~Bathymetry.ipynb~
• Compare_SSH_model_obs.ipynb
• Extract_Variables_at_Ocean_Bottom.ipynb

It would be nice to fix these, as explained how in Making_Maps_with_Cartopy.ipynb