Ice free Arctic Ocean, an Early Holocene analogue.

Extensive systems of wave generated beach ridges along the North Greenland coasts show that these areas once saw seasonally open water. In addition to beach ridges, large amounts of striated boulders in and on the marine sediments from the same period also indicate that the ocean was open enough for ice bergs to drift along the shore and drop their loads. Presently the North Greenland coastline is permanently beleaguered by pack ice, and ice bergs are very rare and locked up in the sea ice. Predictions of the rapidly decreasing sea ice in the Arctic Ocean generally point to this area as the last to become ice free in summer. We therefore suggest that the occurrence of wave generated shores and abundant ice berg dropped boulders indicate that the Arctic Ocean was nearly free of sea ice in the summer at the time when they were formed. The beach ridges occur as isostatically raised "staircases", and C14-dated curves for relative sea level change show that they were formed in the Early Holocene. A large set of samples of molluscs from beach ridges and marine sediments were collected in the summer of 2007, and are presently being dated to give a precise dating of the ice free interval. Preliminary results indicate that it fell within the interval from c. 8.5 to c. 6 ka - being progressively shorter from south to north. We therefore conclude that for a priod in the Early Holocene, probably for a millenium or more, the Arctic Ocean was free of sea ice at least for shorter periods in the summer. This may serve as an analogue to the predicted "greenhouse situation" expected to appear within our century.