What we find with Webb will help inform our models and
allow us to understand the mechanisms for
ice formation at very low temperatures,» explained Karin Öberg of the Harvard - Smithsonian Center for Astrophysics, an investigator on the project.
IIRC, the closing off of the isthmus between N and S america explains some changes, and the seperation of SA from the Antarctic some 40 million years ago
allowed the
formation of the antarctic circumpolar current which then
allowed the
formation of the antarctic
ice sheets.