Configuration, history and impact of the Norwegian Channel Ice Stream HANS PETTER SEJRUP, EILIV LARSEN, HAFLIDI HAFLIDASON, IDA M. BERSTAD, BERIT O. HJELSTUEN, HAFDIS E. JONSDOTTIR, EDWARD L. KING, JON LANDVIK, ODDVAR LONGVA, ATLE NYGA ˚ RD, DAG OTTESEN, STA ˚ LE RAUNHOLM, LEIF RISE AND KNUT STALSBERG Sejrup, H. P., Larsen, E., Haflidason, H., Berstad, I. M., Hjelstuen, B. O., Jonsdottir, H., King, E. L., Landvik, J., Longva, O., Nyga ˚rd, A., Ottesen, D., Raunholm, S., Rise, L. & Stalsberg, K. Configuration, history and im- pact of the Norwegian Channel Ice Stream. Boreas, Vol. 32, pp. 18–36. Oslo. ISSN 0300–9483. The Norwegian Channel between Skagerrak, in the southeast, and the continental margin of the northern North Sea, in the northwest, is the result of processes related to repeated ice stream activity through the last 1.1 m yr. In such periods the Skagerrak Trough (700 m deep) has acted as a confluence area for glacial ice from southeastern Norway, southern Sweden and parts of the Baltic. Possibly related to the threshold in the Norwegian Channel off Jæren (250 m deep), the ice stream, on a number of occasions over the last 400 ka, inundated the coastal lowlands and left an imprint of NW-oriented ice directional features (drumlins, stone orientations in tills and striations). Marine interstadial sediments found up to 200 m a.s.l. on Jæren have been suggested to reflect glacial isostasy related to the Norwegian Channel Ice Stream (NCIS). In the channel itself, the ice stream activity is evidenced by mega-scale glacial lineations on till surfaces. As a result of subsidence, the most complete sedimentary records of early phases of the NCIS are preserved close to the continental margin in the North Sea Fan region. The strongest evidence for ice stream erosion during the last glacial phase is found in the Skagerrak. On the continental slope the ice stream activity is evidenced by the large North Sea Fan, which is mainly a result of deposition of glacial-fed debris flows. Northwards of the North Sea Fan, rapid deposition of meltwater plume deposits, possibly related to the NCIS, is detected as far north as the Vøring Plateau. The NCIS system offers a unique possibility to study ice stream related processes and the impact the ice stream development had on open ocean sedimentation and circulation. Hans Petter Sejrup (sejrup@geo.uib.no), Haflidi Haflidason, Ida M. Berstad, Berit Hjelstuen, Atle Nyga ˚rd and Sta ˚ le Raunholm, Department of Earth Science, University of Bergen, Alle ´gt. 41, NO-5007 Bergen, Norway; Eiliv Larsen, Oddvar Longva, Dag Ottesen, Leif Rise and Knut Stalsberg, Geological Survey of Norway, NO-7491 Trondheim, Norway; Edward L. King, Bedford Institute of Oceanography, Dartmouth, N.S. Nova Scotia B2Y 4A2, Canada; Jon Landvik, Agricultural University of Norway, NO-2432 A ˚ s, Norway; Hafdis E. Jonsdottir, Public Roads Administration, Midhusvegi 1, Akureyri, IS-600, Iceland; received 18th March 2002, accepted 3rd September 2002. Ice streams, both present and Pleistocene, have received increased attention from the scientific community during the past decade (Bentley 1987; Alley et al. 1989; Alley & MacAyeal 1994; Marshall & Clarke 1996; Sejrup et al. 1998; Stokes & Clark 2001). The impact of former marine-based ice streams has become evident, especially with increased use of new acoustic survey techniques. The role ice streams played in the Pleistocene should not be understated, despite a still fragmentary picture. There is increased understanding of how this component of ice sheets acted as major transport agents for sediments derived from the con- tinents to the deep sea, and of the influence they had on sculpting the continental margins. However, beyond this the ability of ice streams to rapidly deliver large quantities of fresh water to the ocean, and thereby the potential to force climate change, has received much attention recently. Furthering our understanding of these features requires close interaction between scien- tists covering a broad spectrum of special fields including glaciology, sedimentary geology, Quaternary stratigraphy, hydrology, palaeoceanography and model- ling. Important new information on the role the Pleisto- cene ice streams have played comes from research groups investigating the North Atlantic continental margins (Sejrup et al. 1996; Vorren & Laberg 1997; King et al. 1998; MacLean 2001). The location and structure of the large trough mouth fans have been central in this research (Fig. 1). Instabilities of marine- based ice streams have also been invoked to explain high frequency climate variability evidenced in deep- sea cores and Greenland ice cores. The North Atlantic Heinrich layers have been explained by rapid disinte- gration of ice streams on the eastern side of the Laurentide Ice Sheet (Alley & MacAyeal 1994; Andrews et al. 1994; Bond & Lotti 1995; Vidal et al. 1999). There is also evidence showing that complexity of the IRD signal during the last glaciation increases northwards in the Atlantic and into the Nordic Sea region (Elliot et al. 1998; Dowdeswell et al. 1999). This is most likely related to the large number of marine terminating palaeo-ice streams in this area and possibly to a complex ice stream response to climate and sea level changes. The Norwegian Channel Ice Stream (NCIS) system, DOI 10.1080/03009480310001029. # 2003 Taylor & Francis