The puzzle of grounded Pleistocene ice in the Arctic Ocean and the exhumation of Miocene sediments

• Main Authors: Niessen, Frank, Stein, Rüdiger, Jensen, Laura, Schreck, Michael, Matthiessen, Jens, Fahl, Kirsten, Forwick, Matthias, Gebhardt, Catalina, Kaminski, Michael, Knorr, Gregor, Sauermilch, Isabel, Jokat, Wilfried, Lohmann, Gerrit, Hong, Jong Kuk, Polyak, Leonid, Nam, Seung-Ill
• Format: Conference Object
• Language: unknown
• Published: Geological Survey of Norway 2016
• Subjects: Arctic; Arctic Ocean; Chukchi; East Siberian Sea; Ice Shelf; Iceberg*; Lomonosov Ridge; Sea ice
• Online Access: https://epic.awi.de/id/eprint/42052/; https://hdl.handle.net/10013/epic.48843

Since about 15 years a growing number of evidence is found in water depth up to more than 1000 m of the Arctic Ocean that grounding of ice has occurred in various places including the "Beringian" continental margin north of the present Chukchi and East-Siberian seas and the Lomonosov Ridge. These landforms include moraines, drumlinized features, glacigenic debris flows, till wedges, mega-scale glacial lineations (MSGL), and iceberg plough marks (Polyak et al. 2001, Niessen et al. 2013, Dove et al. 2014, Jakobsson et al. 2014). They suggest that thick ice has occurred not only on nearly all margins of the Arctic Ocean but also covered pelagic areas. In a recent paper, Jakobsson et al. (2016) present more evidence of ice-shelf groundings on bathymetric highs in the central Arctic Ocean, thereby revitalising an old modelling concept of a kilometre-thick ice shelf extending over the entire central Arctic Ocean (Hughes et al. 1977) now dated to Marine Isotope Stage (MIS) 6. Other (including our) studies, however, suggest that the pattern, and, in particular, the timing of these glaciations is more complex. Most recent discoveries on the Lomonosov Ridge have not only gained different information on Pleistocene glaciations but also allowed for the first time to reconstruct upper Miocene Arctic Ocean sea-ice and SST conditions. This became possible since submarine sliding (likely associated with ice grounding) led to removal of younger sediments from steep headwalls and thus exhumation of Miocene to early Quaternary sediments close to the seafloor, allowing the retrieval and analysis of such old sediments by gravity coring (Stein et al. 2016). Submarine glacial landforms from the western and central Arctic Ocean were discovered and investigated during the cruises of RV "Polarstern" in 2008 and 2014, and RV "Araon" in 2012 and 2015. Orientations of some of these landforms suggest that thick ice has flown north into the deep Arctic Ocean from the continental margin of the East Siberian Sea repeatedly (Niessen et al. ...