In July, the scientists flew to collect samples to what they thought was Oodaaq Island, that has been known since 1978.
But when they checked their position with the Danish official in charge of registering Arctic islands, they were 800m (2,625ft) further north.
The 60X30m island is the closest point of land to the North Pole, they say.
Greenland is a vast autonomous Arctic territory that belongs to Denmark.
“The island was discovered during a Danish-Swiss research expedition, which I was co-ordinating,” scientific leader Morten Rasch of the Arctic Station in Greenland, University of Copenhagen, told the BBC.
“We wanted among many other things to visit Oodaaq Island, which was previously known as the northernmost island.”
Mr Rasch said his team “wanted to sample the island to look for new species being adapted to a life in this very extreme environment”.
“We were six people in a small helicopter, and when we reached the position of Oodaaq Island, we could not find it,” he said, adding that maps were not very accurate in that part of the world.
