Sediment deposition in an iceberg-dominated glacimarine environment, East Greenland: basin fill implications

Abstract

Kangerdlugssuaq Fjord, east Greenland (68°N), is an iceberg dominated fjord, receiving in excess of 15 km 3/a in iceberg volume, representing about a thousand fairly-large icebergs each year. In contrast, the estimated combined flux of subglacial and supraglacially derived meltwaters is of the order of 4 km 3/a. Iceberg melt within the fjord accounts for half of the freshwater delivered to the fjord from all sources. Iceberg appear to lose their subglacial debris during their lenghty residence time (2 year) within the sikussaks pinned to the ice margins. Once icebergs escape the confines of the sikussaks, they transit the fjord in about 68 days, melting at rates between 0.05 and 0.1 m/d and releasing englacial sediment to a mid-water, iceberg melt zone. Sedimentation beneath this plume is predicted to range from 2.4 cm/a, near the head of the fjord, to 0.6 cm/a at the most distal (50 km) part of the fjord basin. Much of the sediment that initially accumulates on the steep sidewall margins becomes remobilized and redeposited on the distal basin floor via turbidity currents. Predicted accumulation rates agree with long-term (1400 year) rates obtained from dated cores collected in Kangerdlugssuaq Fjord.