Weirdness in regridding some siconc data

[kyleredilla]

Some of these variables have weird grids that we don't yet seem to have the right recipe for handling. E.g. siconc data for NorESM2-MM:

As you can see the results are unsavory. There is no siconca data available for NorESM2-MM, so we do need to figure out a way of handling this. Potentially an issue with getting the lat/lon bounds? this is done with cf_xarray inside the the xESMF regridding function.

USing bilinear for these cases might be the simplest solution, it causes gaps in the high latitudes but data doesn't look borked.

This particular source grid looks like this:

Coordinates:
             CF Axes: * X: ['i']
                      * Y: ['j']
                      * T: ['time']
                        Z: n/a

      CF Coordinates:   longitude: ['longitude']
                        latitude: ['latitude']
                      * time: ['time']
                        vertical: n/a

       Cell Measures:   area, volume: n/a

      Standard Names:   area_type: ['type']
                        latitude: ['latitude']
                        longitude: ['longitude']
                      * time: ['time']

              Bounds:   n/a

       Grid Mappings:   n/a

Data Variables:
       Cell Measures:   area, volume: n/a

      Standard Names:   sea_ice_area_fraction: ['siconc']

              Bounds:   T: ['time_bnds']
                        latitude: ['vertices_latitude']
                        longitude: ['vertices_longitude']
                        time: ['time_bnds']

       Grid Mappings:   n/a