Modern sedimentation in the Northern Barents Sea : input, dipersal and deposition of suspended sediments from glacial meltwater

Abstract

The modern depositional environment of the northern epicontinental Barents Sea varies from proximal to distal glaciomarine. The regional surface sediment distribution is controlled by erosion of shallow banks of the Pleistocene glaciated surface, with the fine material deposited in the deep basins. Near-bottom nepheloid layers are often observed indicating that fine grained sediments are being transported under present conditions. Minor additional sediment is supplied by iceberg rafting englacial material and sea-ice containing aeolian, resuspended, and beach sediments. Glacial flour is supplied by several large stable meltwater outflow locations along the ice front. Because the water is fresh and nearly the same temperature as the ambient coastal water, it is bouyant. Although the traction load deposits as the meltwater plume rises to the sea surface, sand (as well as finer material) may be suspended. This material deposits from suspension at some distance from the discharge location (dependent on both the sediment settling velocity and the velocity of the ambient coastal water, resulting in well-sorted deposits near the outflow location). Most of the sediment in suspension is observed to deposit within a 5km radius of the outflow location, and suspended matter samples obtained 18km offshore were at background levels. However, meltwater plumes can often be observed in the surface water (in satellite photographs) at distances of 30km downstream, indicating transport of glacial sediments along the ice front. Near the Nordaustlandet glacier front surface sediments are disturbed by glaciers advances and retreats which mechanically rework the sediment surface. The southwestern portion of the glacier front, Brasvellbreen, surged 18km between 1936 and 1938. An end moraine was deposited at the maximum extent of the surge. The ice then stagnated and disintegrated through calving. At present on the eastern portion of the Brasvellbreen ice front is active with frequent small (less than 50m) glacier advances and retreats. Evidence for this is shown by the minor ridge and swale moraines in this eastern area.