Glaciation, climate history, changing marine levels and the evolution of the Northeast Water polynya

The morphology of the bank- and trough system in the Northeast Water (NEW) polynya area is to a large extent a result of glacial erosion and deposition by an extended Inland Ice which reached the continental shelf. The last deglaciation of the fjords and forelands adjacent to the polynya took place shortly before 9000 radiocarbon yr B.P. At that time the marine level stood 80 m higher than today, which meant a water depth over much of the Ob Bank and parts of the Belgica Bank twice as deep as presently. This probably gave the East Greenland Current a more unimpeded southward flow, with less eddy effects. In combination with the generally warmer climate of the early Holocene (with less ice coming out of the Polar Basin, a larger influx of Atlantic Water leading to more ice melting in the NEW area, and probably no ice drift hindering fast-ice barrier in the south), this probably meant that no polynya existed at that time. Instead there was a more general open water summer situation. After 5000 yr B.P. climate deteriorated and glaciers expanded. As the isostatic rise of land and near coast bottoms continued, resulting in shallowing banks, both the bathymetric and climatic situation responsible for the existence of todayʹs polynya gradually came into existence. The shallowing Ob Bank began to obstruct ice drift from the north and an ice-drift hindering fast-ice barrier was created in the south. But even after 500 yr B.P. it is likely that shorter spells of more generally open water existed, during which marine based paleoeskimos (Independence II) and neoeskimos (Thule) immigrated along the at other times totally ice-bound coasts of North Greenland.