The East Greenland continental margin (65°N) since the last deglaciation: Changes in seafloor properties and ocean circulation

Abstract

Nine gravity cores collected on the East Greenland continental margin off Kangerdlugssuaq Fjord reveal a drastic decrease in average sedimentation rates from the cross-shelf through the continental slope (from 43.2 cm/kyrs to 2.2 cm/kyrs, respectively). Since the last deglaciation, beginning at <15, 000 yrs B.P., both carbonate and non-carabonate accumulation rates have been controlled by the decrease in glaciers and sea ice and the increase in surface-water circulation. CaCo 3 and non-CaCO 3 accumulation rates at about 14,000 yrs B.P. were high on the outer shelf, followed by high values at the inner shelf about 9000 yrs B.P., suggestive or rapid glacier retreat. About 9000 yrs B.P., the northerly flowing Irminger Current and the southerly flowing East Greenland Current may have increased intensity leading to distinct increases in CaCO 3 accumulation (>2g/cm 2kyrs). At 4000 yrs B.P., both CaCO 3 and non-CaCO 3 accumulation rates became high (<g/cm 2kyrs); since 3000 yrs B.P. these rates distinctly decreased. Melting of glaciers and current activity, which drastically changed in space and time controlled the terrigenous sediment input, and thus the grain-size distribution and the physical properties of sediments, across the shelf. These observations suggest that current winnowing on sediments is one of the dominant processes at present. This is seen in the acoustic reflectivity and in the acoustically hard seafloor, particularly at the upper continental slope. In addition, icebergs transported southward along the continental margin, have scoured the sediment surface in water depths <350m.