I Agree the page "Extreme cold guide is redundant content with ice sheet guide , but i think a sea ice guide is needed.
I Found this guide.... maybe someone is in progress?
User:Gottoni/User guide/Sea Ice
This page is intended as a catch-all guide for the two very cold biomes, sea ice and ice sheet, as well as any custom planets with lowered temperature. Unless sea ice becomes the only remaining cold biome then this page would remain relevant.
Edit: Also, the guide specifically said that it does not apply for sea ice.
If this page is intended for ice sheet and sea ice but doesnt apply for sea ice then this is an ice sheet guide.
Anyway, this guide isn't obsolete for the time being and will not be deleted.