The Glacial Geomorphology of the North-West sector of the Laurentide Ice Sheet

Abstract

This paper presents a new map of the glacial geomorphology of ∼ 800,000 km 2 of north-west Canada. The mapped area includes parts of Northwest Territories and Nunavut which were covered by the Laurentide Ice Sheet during the Late Wisconsinan glaciation. It has been hypothesized that ice streaming occurred here during this time and the area has also been identified as a potential drainage pathway of glacial Lake Agassiz. Mapping was carried out remotely using a range of spaceborne imagery with varying spatial resolutions, including Landsat ETM+, ASTER and SRTM. Aerial photography was also used in areas where cloud obscured the Landsat imagery. The map records 94,780 individual landforms including moraines, eskers, large meltwater channels and lineations. Highly elongate bedforms with convergent flow traces and abrupt lateral margins are abundant throughout the mapped area and most likely represent former zones of streaming flow. Numerous eskers can be traced for tens of kilometres and are found both parallel and sub-parallel to abundant lineations. Moraine ridges are also identified which mark Late Wisconsinan ice margin positions and a series of smaller ridges are also identified within areas of hummocky topography. The map is intended to form the basis of a regional ice sheet reconstruction from the Last Glacial Maximum through to deglaciation, which we suggest is likely to involve marked changes in the spatial and temporal activity of ice streams.

Ice streams in the Laurentide Ice Sheet: Identification, characteristics and comparison to modern ice sheets

“…In contrast, the Amundsen Gulf Ice Stream is thought to have operated throughout deglaciation, and was spatially more stable than both the M'Clure Strait Ice Stream to the north and the Mackenzie Trough Ice Stream to the west Brown, 2012). It is evidenced both by terrestrial landform record on the mainland and on Victoria Island (Sharpe, 1988;Stokes et al, 2006;Kleman and Glasser, 2007;Storrar and Stokes, 2007;Stokes et al, 2009;Brown et al, 2011;Brown, 2012), and by erosion and distinctly streamlined morphology of the seabed in Amundsen Gulf (Supplementary data; Batchelor et al, 2013b).…”

“…The shallow Mackenzie Trough appears to have formed the main ice discharge route, but the landform record indicates that ice drainage was highly dynamic and ice streams operated along different trajectories ( Fig. 9; Brown et al, 2011;Brown, 2012;Margold et al, 2015). Tracks of four major ice streams have been reconstructed in the area: The Mackenzie Trough, Anderson, Bear Lake, and Fort Simpson ice streams (nos.…”

Morphometry and pattern of a large sample (>20,000) of Canadian eskers and implications for subglacial drainage beneath ice sheets

“…Boulton and Clark, 1990;Stokes et al, 2009;Brown et al, 2011). This suggests that eskers have a low potential for preservation beneath dynamic ice sheets, and/or that they form very close to final deglaciation.…”

“…9). It is likely that this reflects the deposition of esker ridges during different phases of rapidly-changing flow trajectories which operated in these areas as ice streams switched on and off (Kleman and Glasser, 2007;Stokes et al, 2009;Brown et al, 2011). The regions supporting these more 'disorganised' eskers exhibit greater variability in topography than the Shield areas (see Fig.…”

Ice streams in the Laurentide Ice Sheet: a new mapping inventory

“…Winsborrow et al (2004) also provided an inventory and supporting evidence for each of the hypothesised ice streams within the LIS. More recently, new remote sensing products and digital elevation models have permitted the glacial landform mapping at a regional and ice sheet scale (Atkinson, Utting, & Pawley, 2014;Brown, Stokes, & O'Cofaigh, 2011;De Angelis, 2007a;Shaw, Sharpe, & Harris, 2010;Storrar & Stokes, 2007;Trommelen & Ross, 2010), augmenting the Glacial Map of Canada (Prest, Grant, & Rampton, 1968).…”