The extent of sea ice cover in Arctic was much less than it is today between four and five million years ago. The maximum winter extent did not reaching its current location until around 2.6 million years ago. "We have not seen an ice free period in the Arctic Ocean for 2,6 million years. However, we may see it in our lifetime." says a marine geologist.
Read more: http://snapzu.com/TNY/emergence-of-modern-sea-ice-in-arctic-ocean-26-million-years-ago