A scientific study details for the first time the underwater cartography of the upper sections of the INBIS channel, a submerged valley that extends along tens of kilometers northwest of the Barents Sea, in the Arctic Ocean. This channel is one of the few underwater valleys in polar latitudes that preserved its particular geological architecture during the last glacial maximum (LGM), according to the new work published in the journal Arktos – The Journal of Arctic Geosciences, in which Professor José Luis Casamor, member of the Consolidated Research Group (GRC) in Marine Geosciences of the Faculty of Earth Sciences of the University of Barcelona (Catalonia, Spain), participates.
Experts from the National Institute of Oceanography and Experimental Geophysics (OGS) in Trieste (Italy) and the University of Tromsø (Norway), among other institutions, have also participated in the new research.
Many of the most unknown landscapes of our planet are submerged under the oceanic waters. Today, the seabed and polar regions are the last two major frontiers of Earth science research. In this context, the application of advanced technologies in scientific campaigns – differential GPS, high-resolution multibeam bathymetry, 2D and 3D seismic reflection, remote-controlled underwater scientific vehicles (ROVs) – has been a real methodological revolution that has increased the accuracy of bathymetric maps of the seabed.
The INBIS channel -interfan Bear island and Storfjorden- is located on the continental margin of the Barents Sea, to the west of Bear Island, in the Norwegian archipelago of the Svalbard Islands. The headwaters are located on the continental shelf – about 500 metres deep – and the farthest part extends to 2,500 metres below the sea surface. INBIS is considered “an exceptional example of a deep submarine channel in polar latitudes, which has formed in an area of the continental margin situated between two important glacial sedimentary fans”, explains José Luis Casamor, co-director of the DEGLABAR oceanographic campaign, which mapped a large part of the INBIS channel on board the oceanographic vessel OGS Explora in 2015.
Near the island of the Bear, in the Svalbard archipelago, the INBIS channel retained its particular underwater relief during the last glacial maximum (image: José Luis Casamor, GRC Marine Geosciences of the UB).
Over thousands of years, the underwater relief of this channel has been sculpted by the action of different geological processes on the polar margins. The gullies are the main topographic structures “that have allowed to reconstruct the geological history of the INBIS channel”, details Leonardo Rui, member of the National Institute of Oceanography and Experimental Geophysics (OGS) of Trieste and first author of the study.
“In particular -continues Rui-, the structure and some characteristics of these formations -for example, the relation between the dimensions and the depth of incision- help to know the possible mechanisms of formation and to distinguish between areas where the gullies predominate or the submarine channels”.
In general, the sediment inputs from ice sheets prevent the formation of gullies and other channel-shaped reliefs in these underwater regions. In the case of the INBIS channel, the proximity to Bear Island has been a decisive factor in halting the advance of the ice sheet and avoiding the covering of the submarine valley with sedimentary materials. “As a result, this submarine valley is one of the few polar channels that has preserved its particular submarine relief during the LGM, which is the time of maximum extension of the ice sheets in the most recent geological history of the planet, more than 20,000 years ago,” says Casamor, a member of the Department of Earth and Ocean Dynamics of the UB.
A similar case would be that of the Albertini Trench, on the northern margin of the Svalbard Archipelago, in the Arctic Ocean. “In this area, the outer shelf receives the sediments carried by the ice currents flowing through the Albertini channel, a process that prevents the formation of sedimentary deposits and facilitates the formation of an underwater channel,” explains Leonardo Rui.
At the top of the INBIS channel, the new bathymetric map describes a system of gullies and minor channels – between the Kveithola and Bear Island sedimentary fans – that cut the continental slope and end up in the main channel. According to the study, the action of the density currents and the turbidity currents generated by the melting water of the ice are factors that have modelled and maintained these erosive structures.
In this geological context, “and especially in the period of maximum expansion of the manto