Description: The origin of two acoustic sediment units has been studied based on lithological facies, chronology and benthic stable isotope values as well as on foraminifera and clay mineral assemblages in six marine sediment cores from Kveithola, a small trough west of Spitsbergenbanken on the western Barents Sea margin. We have identified four time slices with characteristic sedimentary environments. Before c. 14.2 cal. ka, rhythmically laminated muds indicate extensive sea ice cover in the area. From c. 13.9 to 14.2 cal. ka, muds rich in ice-rafted debris were deposited during the disintegration of grounded ice on Spitsbergenbanken. From c. 10.3 to 13.1 cal. ka, sediments with heterogeneous lithologies suggest a shifting influence of suspension settling and iceberg rafting, probably derived from a decaying Barents Sea Ice Sheet in the inner-fjord and land areas to the north of Kveithola. Holocene deposition was episodic and characterized by the deposition of calcareous sands and shell debris, indicative of strong bottom currents. We speculate that a marked erosional boundary at c. 8.2 cal. ka may have been caused by the Storegga tsunami. Whilst deposition was sparse during the Holocene, Kveithola acted as a sediment trap during the preceding deglaciation. Investigation of the deglacial sediments provides unprecedented details on the dynamics and timing of glacial retreat from Spitsbergenbanken.

Description: The southwestern Barents Sea has experienced profound erosion during the last ∼2.7 m.y. that has resulted in the development of a characteristic glacial morphology of the continental shelf and deposition of a several-kilometer-thick sediment fan along the western margin prograding into the deep sea. In the period from ca. 2.7 to 1.5 Ma, proglacial processes, including fluvial and glaciofluvial erosion, dominated. For this period, the total average erosion of the shelf was 170–230 m, the average erosion rate was 0.15–0.2 mm/yr, and the average sedimentation rates on the fan were 16–22 cm/k.y. Subglacial erosion affected an area of ∼575,000 km2 during the period from ca. 1.5 to 0.7 Ma. Total average erosion is estimated at 330–420 m for this interval, and the average erosion rate was 0.4–0.5 mm/yr. Average sedimentation rates were 50–64 cm/k.y. During the last ∼0.7 m.y., glacial erosion mainly has occurred beneath fast-flowing paleo–ice streams topographically confined to troughs (∼200,000 km2). The total average erosion is estimated at 440–530 m, average erosion rate is 0.6–0.8 mm/yr, and average sedimentation rate on the continental slope is 18–22 cm/k.y. The amount of erosion was mainly determined by the duration of the glaciations and the location, velocity, and basal properties of the ice streams. In total, glacial erosion of the troughs has been relatively high throughout the last ∼2.7 m.y. at ∼1000–1100 m. For the banks, erosion is inferred to have increased from ca. 2.7 Ma to a peak between 1.5 and 0.7 Ma. Subsequently, little erosion occurred in these areas, which implies a total of 500–650 m of erosion. Compared with other high-latitude areas, our rates are among the highest so far reported. This comparison also demonstrates that there have been large variations in the rate of sediment delivery to the glaciated continental margins.

Description: Ice streams dominate the discharge of continental ice sheets. Recent observations and reconstructions have revealed that large-scale reorganizations in their flow trajectory (flow switching) can occur over relatively short time scales. However, the underlying causes of such behavior, and the extent to which they are predictable, are poorly known. This paper documents a major episode of ice-stream flow switching during the late Weichselian deglaciation of the southwestern Barents Sea and explores various hypotheses for its causation. Regional bathymetric data show that two ice streams that had similar, adjoining, topographically constrained source areas had very different trajectories and dynamics on the outer shelf. At the late Weichselian maximum, the Håkjerringdjupet ice stream flowed westward along the cross-shelf trough of Håkjerringdjupet, while the Sørøya Trough ice stream flowed northward into Ingøydjupet, forming a tributary of the Bjørnøyrenna ice stream. Initial retreat of the Håkjerringdjupet ice stream was rapid but with episodic periods of grounding. As it retreated onto the higher, rougher topography of the inner shelf, we infer a reduction in ice velocity and a dramatic decrease in the pace of retreat, as recorded by nested sequences of recessional moraines. Following (and probably in response to) this, we suggest that there was a short-lived surge/readvance of an adjacent lobe onto Fugløybanken. In contrast, the adjacent Sørøya Trough ice stream remained active throughout deglaciation, before retreating rapidly, with no stillstands or readvances. We argue that the different retreat histories of the ice streams were determined by variations in bed topography/bathymetry, which modulated the grounding line response to sea-level variation. Such a mechanism is likely to be an important control on the long-term behavior of marine-based ice streams and outlet glaciers in Antarctica and Greenland and suggests that gathering data on their subglacial topography should be a priority.