Gebhardt, Catalina, Adhikari, Dilip, Matthiessen, Jens J., Gross, Felix, Elger, Judith , Krastel, Sebastian and Geissler, Wolfram H. (2018) Slope instability and glacial overprint at the northern Svalbard margin . [Poster] In: AGU Fall Meeting 2018. , 10.-14.12.2018, Washington, D.C., USA .

Abstract

Hydroacoustic and high-resolution seismic data reveal that glacial processes and slope instability extensively shaped shelf north of Svalbard and Nordaustlandet as well as the southern Yermak Plateau (YP). Glacial features of different shape and age are linked to the Middle to Upper Pleistocene glaciation history in the Arctic Ocean: (1) Mega-scale glacial lineations (MSGL) were formed either by an ice-shelf advance from Svalbard, or by a coherent mass of large-scale icebergs e exiting the Arctic Ocean across the YP; (2) quasi-linear, huge ploughmarks crosscutting the MSGL were formed by keels of a mega-iceberg or by several icebergs trapped in multi-year sea ice; (3) freshly-looking large iceberg ploughmarks; and (4) irregularly shaped smaller-scale ploughmarks incised by the keels of small single icebergs. In close proximity to NW Spitsbergen, a grounding-zone wedge was encountered that potentially represents the maximum extent of the youngest advance of the Svalbard-Barents ice sheet.

The shelf and slope of Nordaustlandet were subject to the giant Hinlopen/Yermak Megaslide (HYM) some 30 ka ago. Seismic data acquired during an expedition in 2013 reveal complex internal deformation of the slope sediments, and partly incomplete secondary sliding processes of different generations can be identified. Gas seeping with enhanced methane concentrations identified in the water column, and paleo pockmarks and a former gas-pipe structure revealed by the seismic data are likely linked to the mass failure. Gas seeping is still active and together with the internal deformation of the sediments suggests that large parts of the current Nordaustlandet shelf and slope are preconditioned to fail completely in future.

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