Geomorphology and development of a high-latitude channel system: the INBIS channel case (NW Barents Sea, Arctic)

The INBIS (Interfan Bear Island and Storfjorden) channel system is a rare example of a deep-sea channel on a glaciated margin.The system is located between two trough mouth fans (TMFs) on the continental slope of the NW Barents Sea: the BearIsland and the Storfjorden–Kveithola TMFs. New bathymetric data in the upper part of this channel system show a series ofgullies that incise the shelf break and minor tributary channels on the upper part of the continental slope. These gullies andchannels appear far more developed than those on the rest of the NW Barents Sea margin, increasing in size downslope andeventually merging into the INBIS channel. Morphological evidence suggests that the Northern part of the INBIS channelsystem preserved its original morphology over the last glacial maximum (LGM), whereas the Southern part experiencedthe emplacement of mass transport glacigenic debris that obliterated the original morphology. Radiometric analyses wereapplied on two sediment cores to estimate the recent (~ 110 years) sedimentation rates. Furthermore, analysis of grain sizecharacteristics and sediment composition of two cores shows evidence of turbidity currents. We associate these turbiditycurrents with density-driven plumes, linked to the release of meltwater at the ice-sheet grounding line, cascading down theslope. This type of density current would contribute to the erosion and/ or preservation of the gullies’ morphologies duringthe present interglacial. We infer that Bear Island and the shallow morphology around it prevented the flow of ice streamsto the shelf edge in this area, working as a pin (fastener) for the surrounding ice and allowing for the development of theINBIS channel system on the inter-ice stream part of the slope. The INBIS channel system was protected from the burial byhigh rates of ice-stream derived sedimentation and only partially affected by the local emplacement of glacial debris, whichinstead dominated on the neighbouring TMF systems.