Also return axes

We need axes to add eddy contours.

Inst_eddies/Analysis/plot_velocity.py

@@ -89,7 +89,7 @@ def plot_velocity(input_file, window, undefined, scale):
 
     ax.gridlines(draw_labels=True)
     ax.coastlines()
-    return fig
+    return fig, ax
 
 
 if __name__ == "__main__":
@@ -124,7 +124,7 @@ if __name__ == "__main__":
     )
     parser.add_argument("input_file", help="NetCDF file containing velocity")
     args = parser.parse_args()
-    fig = plot_velocity(
+    fig, ax = plot_velocity(
         args.input_file, args.window, args.undefined, args.scale
     )