Sediment flux from a fjord during glacial periods, Isfjorden, Spitsbergen

Sediment has accumulated in Isfjorden, a deep fjord in Spitsbergen, at a rate of similar to 1.7 km(3)/k.y. during the past 13 k.y. Between 200 ka and 13 ka the fjord was free of ice for similar to 120 ky. Assuming a similar sediment delivery rate during this ice-free time, similar to 200 km(3) of sediment would have accumulated in the fjord. An alternative calculation based on erosion rates suggests that 400 km(3) could have been delivered to Isfjorden during this 120 k.y. Seismic studies have identified a similar to 330 km(3) package of sediment on the continental shelf and slope west of Isfjorden. This sediment is believed to have accumulated between 200 ka and 13 ka. Herein we argue that this is sediment that was originally deposited in the fjord, and that it was transferred to the shelf by glaciers in the similar to 70 ka during which the fjord was occupied by ice. Calculations using a steady-state numerical model suggest that the sediment could have been moved in a deforming layer of subglacial till and in subglacial melt streams at rates of 7.6 x 10(6) m(3) a(-1) and 0.3 x 10(6) m(3) a(-1) respectively, resulting in a total flux of similar to 7.9 x 10(6) m(3) a(-1). It is unlikely that much sediment was moved in a basal layer of dirty ice, as intense basal melting would have inhibited sediment entrainment. Of the time that glaciers occupied the fjord, similar to 60% would have been required to evacuate the accumulated sediment. During the remaining time, the ice could have been deepening the fjord.