Greenland or High Greenland is the country up on the fells above the tarn. It’s as wild as wild says Peggy when Nancy semaphores Make Wildcat Spitzbergen. Try Alaska. Cross Greenland. Peggy knows ... before she is interrupted by Molly (WH10). It is on the eastern hills, above Dixon's Farm and Holly Howe.
So the next day they decide to cross Greenland. They climbed through the woods .... and travelled far and fast on the top of the fells. They had had their dinner up in High Greenland ... Then they find the cragfast sheep (WH11) and decide to go to Dixon’s farm a better (or quicker) way, down the road through that wood where you saw the charcoal-burners that first summer (WH12).
Later they send a despatch to Nancy via Fanny at Holly Howe and the doctor: North Polar Expedition. Crossed Greenland. Reached Spitzbergen by ice. Captain Flint’s houseboat is frozen in (WH13). Mention of the houseboat results in Nancy sending them the key of the houseboat so they can use it as a base (WH14).