Hi Sally-J, Johannes and others!
If you are going to Disko Bay, maybe you can manage a trip to Uummannaq to visit Troll's Grotto, and from Uummannaq a boat trip to Mummy cave (Qilakitsoq ruins).
However it is likely that these two (probably non-karstic) caves do not exceed several meters in length, I did not go there. All my information about these 3 caves (with Cave Bings Hule) come from "Lonely Planet: Greenland and the Arctic".
To my knowledge, the only known karstic caves are located far in North Greenland. Have a nice trip ! Greenland is beautiful !
Graham, I would also like to see the possible entrance !
Good caving to all !
Xavier Nogu?s, France