The De Long Trough: a newly discovered glacial trough on the East Siberian continental margin

Abstract

Abstract. Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical mapping and sediment coring data from the East Siberian shelf and slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish -Russian -US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions). The multibeam bathymetry and chirp sub-bottom profiles reveal a set of glacial landforms that include grounding zone formations along the outer continental shelf, seaward of which lies a > 65 m thick sequence of glacio-genic debris flows. The glacial landforms are interpreted to lie at the seaward end of a glacial trough -the first to be reported on the East Siberian margin, here referred to as the De Long Trough because of its location due north of the De Long Islands. Stratigraphy and dating of sediment cores show that a drape of acoustically laminated sediments covering the glacial deposits is older than ∼ 50 cal kyr BP. This provides direct evidence for extensive glacial activity on the Siberian shelf that predates the Last Glacial Maximum and most likely occurred during the Saalian (Marine Isotope Stage (MIS) 6).

Balancing the last glacial maximum (LGM) sea-level budget

“…However, despite attempts to find evidence for a significant LGM ice sheet in this region (Grosswald and Hughes, 2002), none has been found (Brigham-Grette et al, 2003;Gualtieri et al, 2003;Stauch and Lehmkuhl, 2010; Clark, 2011, 2012;Jakobsson et al, 2014). A large ice sheet existed within the region at some point during the Pleistocene, but all evidence for this ice appears to predate the LGM (Niessen et al, 2013;O'Regan et al, 2017). Similarly, parts of the Arctic Ocean appear to have supported grounded ice, in the form of extensive ice shelves (Gasson et al, 2018).…”

Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators

“…Jakobsson and coauthors provide evidence of a kilometer-thick ice shelf covering the entire central Arctic Ocean and extending up to present-day New Siberian Islands during the glacial maximum (Marine Isotope Stage 6, 140 ka BP) [62]. Moreover, another study reported on a glacially excavated trough discovered on the ESAS (De Long Trough), which is also dated to Marine Isotope Stage 6 [64]. However, it seems reasonable to assume the modern exaration processes considering the sedimentation rates (from 0.12 to 1.3 mm year −1 ) estimated for this region in previous studies [11,65].…”

Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

“…This assumption is required because we are not able to distinguish pre-LGM sediments in our data even though we acknowledge that older (pre-LGM) sediment is sometimes preserved in these settings (e.g. Hooke and Elverhøi, 1996;Aarseth, 1997;O'Regan et al, 2017;Jennings et al, 2019). This assumption is justified by theoretical studies of glacial erosion/sediment transport, which are based on observations, that most often suggest that fjords are rapidly and fully excavated during glacial advances (Powell, 1984;Aarseth, 1997;Hjelstuen et al, 2009).…”

“…Where such flow deposits are prolific and occur at the seafloor, they are easily identified as smooth, lobate features in front of known grounding-zone positions marked by terminal moraines (e.g. Ottesen and Dowdeswell, 2006;Flink et al, 2015) or GZWs (e.g. Bjarnardóttir et al, 2013;Esteves et al, 2017).…”