Plotting error with moll projection for combined Atlantic and Southern Ocean

[pwolfram]

Using the file at https://gist.github.com/43b8c23a27a84da35eadd9304a1b3753, there is a plotting error for the moll projection (which does not show up for moll2):

Script to reproduce error from repository root:

mkdir test_feature_collection
cd test_feature_collection/
ln -s ../ocean/region/North_Atlantic_Ocean/region.geojson NA_region.geojson
ln -s ../ocean/region/South_Atlantic_Ocean/region.geojson SA_region.geojson
ln -s ../ocean/region/Southern_Ocean/region.geojson SO_region.geojson
cd ..
./merge_features.py -d test_feature_collection/ -o AO_SO.geojson
./plot_features.py -f AO_SO.geojson 

Note, found in the process of testing #52. I believe this is a plotting error but it could be an error with preliminary changes in #52.

[pwolfram]

Going further:

./difference_features.py -f AO_SO.geojson -m landice/region/Antarctica_IMBIE1/region.geojson -o AO_SO_masked.geojson
./plot_features.py -f AO_SO_masked.geojson 

moll is even more visibly messed up (geojson file at https://gist.github.com/79c3cc90ef72ad8320e799c4a54eb203)...

[xylar]

@pwolfram, I can reproduce these bugs and will look into them when I have a chance.

[xylar]

@pwolfram, I strongly suspect this is a bug in how shapes including the south (or presumably also the north) pole are handled in cartopy for this projection. It should be pretty easy to set up an example where we plot a box similar to the SouthernOcean in a simplified script to indicate the problem. Note that there are glitches in the Antarctic land coverage in both moll and moll2 projections as well.
Anyway, I don't think this is an issue for this repo. Please close if you agree and open an issue with cartopy instead.

[xylar]

@pwolfram, here is a simpler script demonstrating that the problem is with cartopy, not with our plotting routine:
https://gist.github.com/xylar/b5e1835f031d122d98196ba52cacf027

[pwolfram]

@xylar, I agree. I'll submit an issue with them, will pass on your gist, and reference this issue.

[pwolfram]

The issue is SciTools/cartopy#802, I'm closing this PR for now.