Admittedly seconded; while it's not a huge problem, it's always felt a bit wrong to me. (The base is clearly buried in the ground, not ice or cold water.)
If I were to suggest how to do so, I'd include an additional parameter to be defined on a zone which would prevent both the player and the aliens from setting up bases within it:
regions:
- type: STR_ARCTIC_NO_BASE
areas:
- [W, X, -Y, -Z]
noBases: true
The problem is, the game would need to always observe this rule regardless of which zone is active, since STR_ARCTIC_NO_BASE is not supposed to be used for actual missions. So I don't know.