Submarine landforms and the reconstruction of fast-flowing ice streams within a large Quaternary ice sheet: The 2500-km-long Norwegian-Svalbard margin (57°–80°N)

Abstract

Morphological interpretation of regional and detailed bathymetric data sets on the 2500-km-long Norwegian shelf from the North Sea (57°N) to Svalbard (80°N) has revealed a dynamic ice-fl ow pattern along the western margin of the Scandinavian and Barents/Svalbard ice sheets. About 20 crossshelf troughs with megascale glacial lineations (MSGL; elongate ridges and grooves oriented parallel to trough long axes) are interpreted as former pathways for fastfl owing ice streams. Studies of large-scale margin morphology and seismic profi les have identifi ed large submarine fans at the mouths of several major cross-shelf troughs. Less dynamic ice probably existed on shallower banks. The two largest paleo-ice streams were the Norwegian Channel Ice Stream and Bear Island Trough Ice Stream, each 150-200 km wide at the mouth. The lengths of individual MSGL vary from hundreds of meters to several tens of kilometers, and the distance between ridges varies from 0.1 to 3 km. MSGL amplitudes reach 15 m, but are commonly <10 m. The onset of MSGL and, hence, fast ice fl ow is generally close to the outer coast, at the border zone between crystalline rocks and softer sedimentary rocks. Transverse submarine ridges on various scales, commonly parallel to the shelf edge, refl ect either the maximum ice-sheet position or the recessional pattern of the ice sheet. Lateral ice-stream moraines several tens of kilometers long have also been mapped along the sides of several cross-shelf troughs, identifying the border zone between fast ice fl ow and stagnant or slow-fl owing ice on intervening banks.

Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

“…Similar extensive and elongated MSGLs have been observed on the beds of palaeo-ice streams on the Antarctic shelf, and ones within the former Laurentide and Fennoscandian ice sheets (e.g. Shipp et al, 1999;Stokes and Clark, 2001;Ó Cofaigh et al, 2002Ó Cofaigh et al, , 2005aÓ Cofaigh et al, , b, 2007Dowdeswell et al, 2004;Ottesen et al, 2005;Mosola and Anderson, 2006;Graham et al, 2007).…”

Submarine landform assemblages and sedimentary processes related to glacier surging in Kongsfjorden, Svalbard

“…Based on appearance and dimensions, the grooves and ridges are similar to (mega-scale) glacial lineations (MSGLs; e.g. [1,3,12,29,63,64,76]), which are closely associated with fast ice-flow [47]. Even though lineations in Kongsfjorden are much shorter (max.…”

“…Fast-flowing ice streams drained the Svalbard-Barents Sea Ice-Sheet via the main fjord systems on Svalbard, including Kongsfjorden (e.g. [40,64,65]). A terminal moraine at the shelf break in southern Kongsfjordrenna was inferred to reflect maximum ice extent during the Late Weichselian [65].…”

“…Kongsfjorden and Krossfjorden merge towards the open sea, where a large submarine trough, Kongsfjordrenna, channelled fast-flowing ice streams during the last glacial (e.g. [40,64]). Kongsfjorden is approximately 20 km long and between 4 and 10 km wide.…”

On the reconstruction of palaeo-ice sheets: Recent advances and future challenges

“…In the last decade alone, there are cases where margins have been revised and extended to the edge of the continental shelf for the Laurentide and Innuitian Ice Sheets, the Eurasian Ice Sheet (including the Fennoscandian, Barents Sea and British-Irish Ice Sheets), and the Greenland Ice Sheet (e.g. Ottesen et al, 2005;Shaw et al, 2006;Bradwell et al, 2008;England et al, 2009;Ó Cofaigh et al, 2013). In particular, advances in high-latitude seafloor mapping in the 1990s, especially high resolution multibeam mapping, have helped elucidate the glacial history of the Arctic Ocean (reviewed in Jakobsson et al, 2014).…”