Glacial geomorphology of the northwest Laurentide Ice Sheet on the northern Interior Plains and western Canadian Shield, Canada

ABSTRACT The majority of the Northwest Territories of mainland Canada was covered by the Laurentide Ice Sheet during the Last Glacial Maximum. The increasing coverage of high resolution remotely sensed data provides new opportunities to map the glacial geomorphology and study the glacial history of this remote location. Here we present a comprehensive map of glacial landforms within the northern Interior Plains and adjacent areas of the Canadian Shield, comprising around 6% of the Laurentide Ice Sheet bed. Twelve landform types were mapped from the high resolution ArcticDEM: ice flow parallel lineations, subglacial ribs, crevasse-squeeze ridges, major and minor moraine crests, hummocky terrain complexes and ridges, shear margin moraines, major, minor and lateral and submarginal meltwater channels, esker ridges and complexes, glaciofluvial complexes, perched deltas, raised shorelines and aeolian dunes. Together, these landforms provide a record of the highly dynamic behaviour of the northwest sector of the Laurentide Ice Sheet.


Introduction
The Laurentide Ice Sheet (LIS) was the largest ephemeral Pleistocene ice sheet to grow and almost completely disappear during the last glacial cycle.At the Last Glacial Maximum (LGM) the LIS coalesced with the Cordilleran Ice Sheet (CIS) east of the Rocky Mountains, while the northwest sector of the LIS reached its all-time maximum extent along the eastern range fronts of the Mackenzie and Richardson mountains during the local LGM, around 22.1 cal ka BP (Figure 1; Kennedy et al., 2010).While the ice dynamics of this sector of the ice sheet and formation of glacial lakes along the retreating ice sheet margin have been interpreted on a broad scale (Lemmen et al., 1994;Dyke, 2004;Kleman & Glasser, 2007;Brown, 2012), a detailed understanding of the ice sheet configuration and the ice-drainage network, and how it changed through the ice advance and deglacial stages, remains incomplete (Margold et al., 2018).
The glacial geomorphology of the northwest sector of the LIS has been mapped by a number of researchers at a variety of scales.At a local to regional scale, much of the Northwest Territories is covered by detailed National Topographic System (NTS) surficial geological maps (see Figure 2 and references therein).At a broader scale, Brown et al. (2011) produced a glacial geomorphological map of the northwest sector of the LIS and Duk-Rodkin (2022) recently published a compilation map of the Mackenzie Mountains and foothills.Prest et al. (1968) produced the Glacial Map of Canada, which was the first ice-sheet-wide map of glacial landforms.More recently, Shaw et al. (2010) and Kleman et al. (2010) both produced generalized ice flow maps of the entire North American Ice Sheet Complex, comprising the Cordilleran, Laurentide and Innuitian ice sheets at the LGM.However, large gaps remain in the spatial coverage of the surficial maps, while the broad scale map of Brown et al. (2011) lacks detail due to limited data resolution at the time of mapping.Thus, our knowledge of the glacial geomorphology of the northwest LIS can be augmented using newer high resolution digital elevation models (DEMs) now available for the region (Chandler et al., 2018;Stokes et al., 2015).
Recent work has focused on determining the timing of the deglaciation of the northwest sector of the LIS and subsequent opening of the ice-free corridor, which allowed for the exchange of flora and fauna between North America and unglaciated Beringia (Stoker et al., 2022;Clark et al., 2022;Reyes et al., 2022).However, our understanding of the glacial dynamics in this region remains poor, particularly with regards to the behaviour of the major ice streams (Margold et al., 2018) and the configuration of the ice divides over time (Bednarski, 2008).Here, we use the high resolution ArcticDEM v3 mosaic (2 m resolution; Porter et al., 2018) to produce a detailed glacial landform map of the northwest sector of the LIS.The resulting glacial geomorphological map will underpin future investigations into the advance and retreat dynamics of this sector of the LIS.

Map area
The glacial landform map covers an area of approximately 900,000 km 2 and is bounded by the 60°N parallel to the south, the 110°W meridian to the east, the coastline of the Northwest Territories and Nunavut to the north (comprising the Beaufort Sea, Amundsen Gulf, Dolphin and Union Strait, and Coronation Gulf), and the edge of the Canadian Cordillera to the west (encompassing the Richardson and Mackenzie mountains; see the red outline in Figure 1).The map area is made up of two physiographic regions: (1) the Interior Plains on the western side, which contains the contemporary Mackenzie River Valley and Mackenzie Delta; and (2) the Canadian Shield on the eastern side, which is composed of Precambrian igneous and metamorphic rocks (Bostock, 2014;Slaymaker & Kovanen, 2017).The Precambrian shield boundary divides these two physiographic regions (Figure 1) and the eastern map boundary, along the 110°W meridian, was chosen so that the map covers the transition onto the shield area and subsequent change in subglacial bed composition.The map area covers approx.6% of the LIS bed.

Landform mapping
The study area was divided in half along the 65°N parallel and the two halves were mapped independently by the first two authors.To ensure consistency, a trial area was initially chosen for both researchers to map simultaneously.Their resulting maps were then compared by all team members and the glacial landform categories were defined using both polygon and polyline shapefiles.Following best-practice (Chandler et al., 2018), both researchers then used a repeat-pass method to identify each landform in their respective study areas using a variety of scales between 1:50,000 and 1:100,000.To ensure further consistency, once mapping was completed, the two researchers switched map areas and checked each other's mapped landforms.The resulting landform shapefiles were then combined into a single map.Each landform has been identified from the imagery based on its morphology, spatial arrangement and association with other landforms as outlined below.The map does not include glacial landforms produced by local montane ice masses in the Mackenzie Mountains.

Ice flow parallel lineations
Ice flow parallel lineations include drumlins, flutes, mega-scale glacial lineations, streamlined bedrock and crag-and-tails (see Figure 3 for examples).These landforms represent a variety of depositional and erosional ridges formed subglacially that are elongate parallel to palaeo-ice flow (Boulton & Clark, 1990a, 1990b;Clark, 1993Clark, , 1999;;King et al., 2009).Additionally, this category includes lineations that were identified by a distinct colour change in the Image Mosaic of Canada v1, and which may be related to a subtle topographic expression (Figure 4).Each landform crest was drawn as a single line and the ice flow direction was drawn with an arrow where the stoss and lee side of the lineation could be identified.Ice flow parallel lineations usually occur in fields or swarms made up of hundreds of lineations with similar morphology, spacing and orientation.

Subglacial ribs
Subglacial ribs, also termed ribbed moraine, traction ribs or Rogen moraine, consist of large ridges of sediment that are formed subglacially and usually occur in swarms (Aylsworth & Shilts, 1989;Lundqvist, 1989;Hättestrand & Kleman, 1999;Dunlop & Clark, 2006).Individual ribs may be curved and may have an asymmetric cross-profile (Figure 3(e, f)).Subglacial ribs often occur in fields made up of multiple ribs, and although the morphology and size of subglacial ribs is highly variable (Dunlop & Clark, 2006;Stokes et al., 2016), ribs belonging to the same field often have a regular shape.

Moraines
Terminal moraines occur as broadly linear, straight or arcuate-shaped ridges that form by the deposition or deformation of glaciogenic sediment at the margins of active glaciers (Figure 5(c, d)) (Benn & Evans, 2010).Moraines can exhibit both sharp and broad ridge crests.Where the moraine is >200 m wide it was mapped as a polygon (moraine crest major) and where it is <200 m wide it was mapped as a polyline (moraine crest minor).Where the identification of the moraine is more speculative, it was mapped as an uncertain moraine.

Hummocky terrain
Hummocky terrain is an irregular undulating surface consisting of mounds of sediment alternating with depressions (Figure 6) (Brown et al., 2011;Stroeven et al., 2013;Lindholm & Heyman, 2016).Hummocky terrain displays a diverse range of morphologies, which can appear chaotic and irregular.Where distinct linear and curvilinear ridges occur within hummocky terrain they were marked with a polyline.

Shear margin moraines
Shear margin moraines consist of long (10-30 km), broad ridges of sediment located at the edge of a field of highly attenuated streamlined landforms (Figure 6) (Dyke & Morris, 1988;Stokes & Clark, 2002).Shear margin moraines were mapped as a polyline along the crest or center of the ridge.The national topographic tiles that intersect the mapped area are labelled.The coverage of 1:250,000 (blue shading), 1:125,000 (green shading), 1:100,000 (purple shading) and 1:50,000 (orange shading) surficial geology maps from the Geological Survey of Canada are shown.The 1:100,000 scale maps are from Duk-Rodkin (2009a,2009b, 2010a,2010b,2011a,2011b,2011c,2011d)    meltwater channels are formed by water draining away from the ice sheet terminus (Mannerfelt, 1949;Greenwood et al., 2007Greenwood et al., , 2016;;Margold et al., 2011).Here, we map subglacial and proglacial meltwater channels as one meltwater channel category as they can be difficult to distinguish based on geomorphology alone and, in many cases, the channels may transport different sources of meltwater at different stages of the ice sheet evolution.Thus, these meltwater channels have a wide range of sizes, morphologies and sinuosities, and contain bifurcating and anastomosing channels.Where the meltwater channel is <1 km wide we draw a polyline in the center of the incised topography and where it is >1 km wide we draw a polygon encompassing the entire channel.
Lateral and submarginal meltwater channels are distinguished in our map as a regular series of parallel or subparallel channels that dip in the same direction and have low to medium sinuosity (Figure 6) (Greenwood et al., 2007(Greenwood et al., , 2016)).Lateral and submarginal meltwater channels often occur as a sequence of channels perched on the valley sides and sub-parallel to local contours.Channel networks are uncommonly observed and they may terminate in downslope chutes.Lateral and submarginal meltwater channels are drawn as a polyline in the center of the incised topography.

Eskers
Eskers are sinuous depositional ridges of glaciofluvial sand and gravel (Shreve, 1985;Hebrand & Åmark, 1989;Storrar et al., 2014).Individual esker ridges often align to form networks up to 200 km long, but the morphology along the network may vary from continuous esker ridges to large esker complexes or deltas (Figure 7) (Margold et al., 2011;Storrar et al., 2020).Individual esker ridges were mapped as a polyline along the ridge crest and eskers with a complex morphology were mapped as a polygon around the esker complex.

Glaciofluvial complex
Glaciofluvial complexes are deposits of glaciofluvial sand and gravel that can have a wide variety of morphologies, including flat topped, channelized, pitted or ridged deposits (see Figure 7).Glaciofluvial complexes also form in a wide variety of environments, including within or at the terminus of meltwater channels, proximal to or associated with eskers, or perched on valley walls (known as kame terraces).

Perched deltas
Deltas form when sediment that is transported by a river or stream is discharged into a body of water (e.g. a lake).Deltas can be identified by flat top surfaces and steeply dipping frontal beds (Figure 7).Perched deltas are deposited into transient ice-dammed lakes that form when the natural water drainage path is blocked by a retreating ice margin  (Mannerfelt, 1949;Stroeven et al., 2016;Dulfer & Margold, 2021).These deltas remain perched on the valley slopes once the glacial lake drains.

Raised shorelines
Raised shorelines are small (<200 m wide) continuous linear ridges or benches that form parallel to topography but may be tilted over time due to differential glacial isostatic uplift (Figure 8).Raised shorelines usually occur as a series and may stretch for tens of kilometers.Raised shorelines form by the erosion or deposition of sediment along a former shoreline, forming a wave-cut cliff or beach ridge.

Aeolian dunes
Longitudinal and parabolic aeolian dunes are distinctive ridges of aeolian sediment that range in size from a few hundred meters to tens of kilometers (Figure 8).Aeolian dunes often have sharp crests and they can occur as a field of dunes or as single longitudinal landforms.Fields of aeolian dunes have been previously identified across the once glaciated regions of Canada (Koster, 1988;Wolfe et al., 2004;Bateman & Murton, 2006;Norris et al., 2017).We choose to include aeolian dunes as the only non-glacial landform in our map because, in northern Canada, they are relict features that likely formed by the windblown re-deposition of glaciofluvial and glaciolacustrine sediment within cold environments directly following deglaciation.The dune crest is digitised as a polyline.

Accuracy and completeness
Our large study area (∼900,000 km 2 ) is covered by high resolution remotely sensed data (2 m resolution) and, therefore, it is not possible to capture every glacial landform (for example, every ice flow parallel lineation within a swarm of lineations).However, we believe our repeat pass mapping method using a variety of scales has allowed us to map the representative distribution of landforms across the entire study area.We acknowledge that some of the mapped glacial landforms may be misinterpreted.For example, in some cases eskers can be difficult to distinguish from moraines, dykes and dunes, but, they are usually differentiated based on their high sinuosity and association with other meltwater landforms.Similarly, small recessional moraines and crevasse-squeeze ridges can be difficult to differentiate.We acknowledge that our record of the smaller glacial landforms, such as crevasse-squeeze ridges, may be incomplete as their size is often at or below the resolution of our mapping data.However, our map can be used in combination with existing surficial geological maps that may capture these smaller glacial landforms, as they were often mapped with stereo pairs of aerial photographs.

Ice flow parallel lineations
In total, 76,630 ice flow parallel lineations were mapped throughout the study area.In general, our ice flow parallel lineations match, but add considerable detail to, the generalized flow maps of both Kleman et al. (2010) and Shaw et al. (2010) and the glacial geomorphological map of Brown et al. (2011).The mapped ice flow parallel lineations usually occur in discrete swarms of lineations with similar size, spacing and orientation, which can collectively form convergent and divergent patterns.Cross-cutting lineations occur in a number of locations and ice flow parallel lineations can be superimposed on subglacial ribs (Figure 3(e, f)), indicating that ice flow direction varied over time.
The mapped lineations range in size from tens of meters to 30 km in length, with the longest of these lineations having the dimensions of mega-scale glacial lineations (MSGLs), which typically have elongation ratios >10:1 (Stokes & Clark, 1999) and range in length from a few thousand metres to tens of kilometres (Spagnolo et al., 2014) (Figure 3(c, d)).A wide variety of ice flow parallel lineations occur across the map area that may represent varying subglacial depositional and erosional environments, including drumlins, flutes, crag-andtails (Figure 3(a, b)), and MSGLs (Figure 3(g, h)).

Subglacial ribs
In total, 2396 subglacial ribs were mapped across the study area.The subglacial ribs vary in length (transverse to flow) from 0.1 km to 15 km and they have a variety of shapes.However, ribs belonging to the same swarm usually have a regular size and morphology.Subglacial ribs are located at a variety of elevations, occurring on the valley floors as well as on the high elevation plateaus.Ice flow parallel lineations are often superimposed on subglacial ribs and the varying orientation of the ribs and lineations can indicate the ice flow direction has varied over time (Figure 3(e, f)) (Ely et al., 2016).

Crevasse-squeeze ridges
In total, 2110 crevasse-squeeze ridges have been mapped.They generally occur in fields as short (<3 km), narrow, straight or wavy ridges of sediment with irregular spacing.They are sometimes superimposed on other subglacial bedforms, such as drumlins, and they are often orientated perpendicular to the surrounding ice flow parallel lineations.

Moraines
A total of 44 major moraine crests (polygon) and 768 minor moraine crests (polyline) have been mapped across the study area.Additionally, 210 uncertain moraine crests have been mapped (polyline).Multiple moraine crests can be linked together to form a moraine complex that is up to 70 km long and 2 km wide.The geometry of moraine crests is influenced by the topography and they are often aligned with other ice marginal glacial landforms (Figure 5(c, d)).Moraine crests consist of both terminal and lateral moraines and they sometimes occur as a series of recessional moraines.

Hummocky terrain
Within our map, the majority of hummocky terrain is located in the northwest (Main Map) where large areas of hummocky terrain up to 250 km wide have been mapped.In the south, hummocky terrain is mapped on many of the high elevation plateaus of the Interior Plains, while it has a limited distribution the Canadian Shield to the east, where it is mapped north of Lac de Gras.Within the hummocky terrain polygons, 330 ridges have been mapped along their crestline and these ridges display a wide variety of morphologies from broad ridges of hummocky sediment up to 5 km wide to narrow, sharp-crested ridges (<200 m wide).We note that these ridges are sometimes mapped as moraine crests within the surficial maps from the Geological Survey of Canada (e.g. Duk-Rodkin & Hughes, 1992b,1992f).

Shear margin moraines
Seven shear margin moraines have been mapped in the study area and they range in length from 5.5 km to 13 km.All mapped shear margin moraines occur at the edge of hummocky terrain and mark the transition between attenuated bedforms and hummocky terrain (Figure 6).The mapped shear margin moraines occur at the edge of previously mapped paleo-ice streams (Margold et al., 2015a(Margold et al., , 2015b)).

Meltwater channels
In total, 42 major meltwater channels (>1 km wide), 4266 minor meltwater channels (<1 km wide) and 1338 lateral and submarginal meltwater channels have been mapped across the study area.These channels display a wide range of morphologies, occur across all elevations, and can be several hundred kilometers long.The mapped meltwater channels are evenly distributed across the study area, but the majority of the major meltwater channels are located in the northern section.

Eskers
In total, 290 esker complexes and 9543 esker ridges have been mapped.While the eskers display a full range of orientations, a large majority of mapped eskers have an east-west orientation.Esker ridges have been mapped throughout the study area, however, more than half of these ridges (∼5200) occur on the Canadian Shield on the eastern side.Here, esker ridges often link together to form an esker network several hundred kilometers in length.

Glaciofluvial complex
In total, 218 glaciofluvial accumulations have been mapped within the study area.They range in size from a few hundred meters to 20 km in length and are up to 1 km wide.They occur throughout the study area and are often associated with other deglacial meltwater landforms, such as eskers and perched deltas (Figure 7).

Perched deltas
In total, 57 perched deltas have been mapped across the study area.They range in size from a few hundred meters up to 5 km in length and width and sometimes occur as a series of successive deltas at different elevations.Perched deltas occur throughout the study area.

Raised shorelines
In total, 16,401 raised shorelines have been mapped.They usually occur as a series of parallel ridges or notched flat surfaces that range in size from a few hundred meters to 30 km in length and they can be superimposed on other glacial landforms, such as drumlins and eskers.Raised glaciomarine shorelines have been mapped along the coastline of Nunavut and the Northwest Territories where they record the relative fall in sea level since the LGM.Inland, raised glaciolacustrine shorelines have been extensively mapped through the center of the study area and these mark the former extent of glacial lakes in the region, including glacial lakes McConnell and Mackenzie (Lemmen et al., 1994;Dyke, 2004).

Aeolian dunes
In total, 496 aeolian dunes have been mapped and they range in size from a few hundred meters to 22 km in length.The mapped aeolian dunes have a wide variety of morphologies, but usually occur as a field of dunes that have a regular size and morphology (Figure 8).Within our map area, aeolian dunes are mapped in small fields across the Interior Plains but we could not detect any on the Canadian Shield.

Conclusions and implications
The accompanying Main Map provides a detailed record of the glacial landforms of the northwest sector of the LIS.Supplementary figures S1 to S3 show that our map considerably adds to the landform record described in the existing literature (see Figure 2 and references therein) because it contains a high level of detail, similar to the landform content of many of the surficial geological maps produced by the Geological Survey of Canada, but covers a much greater area (more than 82 NTS map tiles), allowing the mapped surficial glacial geomorphology to be interpreted on an ice-sheet-wide scale.Furthermore, this is the first broad-scale map of this region for many of our landform categories, including crevasse-squeeze ridges, shear margin moraines, lateral and submarginal meltwater channels, glaciofluvial complexes, perched deltas, raised shorelines and aeolian dunes, which adds considerable detail when compared with the broadscale glacial landform map of Brown et al. (2011) (see supplementary figures) and the Glacial Map of Canada (Prest et al., 1968).Thus, this glacial geomorphological map provides additional information that augments our understanding of the complex history of the northwest sector of the LIS during the last deglaciation.Using the glacial inversion method, which is the standard approach employed in empirical palaeo-ice sheet reconstructions (e.g.Kleman & Borgström, 1996;Kleman et al., 1997Kleman et al., , 2006;;Dulfer et al., 2022), the map data can now be used to determine the configuration of the northwest sector of the LIS over time, and in particular, understand the dynamics of this sector of the ice sheet during the last deglaciation.

Software
The hillshade surfaces were produced from the Arctic-DEM data within ESRI ArcMAP 10.6.1.On-screen digitizing of landforms was also undertaken in Arc-MAP 10.6.1 in the ESRI shapefile format.Once mapping was complete, a pdf map was exported from ArcMAP 10.6.1 and the final map was created in Adobe Illustrator 2022.

Figure 1 .
Figure 1.(a) Map showing the extent of the glacial geomorphological map produced in this study (red outline).Elevation data from the 30 Arc-Second DEM of North America (EROS, 2010).Major physiographic features and place names are shown (Natural Resources Canada, 2012).The dashed black line delineates the two major physiographic regions: the Interior Plains to the west and the Canadian Shield to the east.The location of Figures 3-8 are shown by the black boxes.(b) Inset map showing northwestern sector of the North American Ice Sheet Complex at 22.1 cal ka BP drawn from Dalton et al. (2020) with the approximate position of the ice divides and the Keewatin ice dome (K) drawn in dark blue and the coalescence between the LIS and CIS shown by the blue dashed line(Margold et al., 2018).

Figure 2 .
Figure 2. (a) Map showing the extent of the glacial geomorphological map produced in this study (red outline) and previously published maps.The national topographic tiles that intersect the mapped area are labelled.The coverage of 1:250,000 (blue shading), 1:125,000 (green shading), 1:100,000 (purple shading) and 1:50,000 (orange shading) surficial geology maps from the Geological Survey of Canada are shown.The 1:100,000 scale maps are fromDuk-Rodkin (2009a,2009b, 2010a,2010b,2011a,2011b,2011c,2011d), Duk-Rodkin and Huntley (2018),Smith et al. (2021) andHagedorn et al. (2022).The black boxes correspond to broad-scale glacial geomorphological maps.The yellow line shows the eastern extent of the glacial geomorphological map ofBrown et al. (2011).(b) Map showing the coverage of the ArcticDEM.Hillshade imagery derived from the ArcticDEM is shown in grey(Porter et al., 2018) and the pink colour highlights the voids in the current coverage of the DEM.
Figure 2. (a) Map showing the extent of the glacial geomorphological map produced in this study (red outline) and previously published maps.The national topographic tiles that intersect the mapped area are labelled.The coverage of 1:250,000 (blue shading), 1:125,000 (green shading), 1:100,000 (purple shading) and 1:50,000 (orange shading) surficial geology maps from the Geological Survey of Canada are shown.The 1:100,000 scale maps are fromDuk-Rodkin (2009a,2009b, 2010a,2010b,2011a,2011b,2011c,2011d), Duk-Rodkin and Huntley (2018),Smith et al. (2021) andHagedorn et al. (2022).The black boxes correspond to broad-scale glacial geomorphological maps.The yellow line shows the eastern extent of the glacial geomorphological map ofBrown et al. (2011).(b) Map showing the coverage of the ArcticDEM.Hillshade imagery derived from the ArcticDEM is shown in grey(Porter et al., 2018) and the pink colour highlights the voids in the current coverage of the DEM.

Figure 3 .
Figure 3. Examples of different types of ice flow parallel lineations.(a) ArcticDEM-derived hillshade imagery and (b) geomorphological mapping of crag-and-tails and streamlined bedrock on the Canadian Shield.The stoss and lee side of the crag-and-tail can be inferred, giving the ice flow direction.Additionally, linear depositional ridges and flat-top accumulations of sediments are interpreted as eskers.(c) ArcticDEM-derived hillshade imagery and (d) geomorphological mapping of drumlins and mega-scale glacial lineations.(e)ArcticDEM-derived hillshade imagery and (f) geomorphological mapping of ice flow parallel lineations with a variable direction superimposed on subglacial ribs.Meltwater channels, eskers and glaciofluvial complex are also mapped.(g) Arc-ticDEM-derived hillshade imagery and (h) geomorphological mapping of wavy groove-plough lineations at lower elevations and drumlins at higher elevations.Note that the ridge crest between the groove-plough has been digitized.The location of these figures is shown in Figure1.The incident light azimuth is 315°, the incident light angle is 35°and the vertical exaggeration is 2 across all DEM images.
2.3.7 Meltwater channelsMeltwater channels form in three main locations in relation to an ice mass: lateral and submarginal meltwater channels form by water flowing along ice margins; subglacial meltwater channels are formed by channelized flow at the bed of the ice sheet; and proglacial

Figure 4 .
Figure 4. Example of ice flow parallel lineations identified within the Image Mosaic of Canada v1.(a) ArcticDEM-derived hillshade imagery (incident light azimuth: 315°and angle: 35°; vertical exaggeration is 2) (b) Landsat satellite imagery with Landsat bands 7 (red), 4 (green) and 2 (blue) (Image Mosaic of Canada v1; Government of Canada, 2013) and (c) geomorphological mapping.The location of this figure is shown in Figure 1.

Figure 5 .
Figure 5. (a) ArcticDEM-derived hillshade imagery and (b) geomorphological mapping of crevasse-squeeze ridges.(c) ArcticDEMderived hillshade imagery and (d) geomorphological mapping of major and minor moraine crests.Ice flow parallel lineations, meltwater channels and raised shorelines are also mapped.The location of these figures is shown in Figure 1.The incident light azimuth is 315°, the incident light angle is 35°and the vertical exaggeration is 2 across all DEM images.

Figure 6 .
Figure 6.(a) ArcticDEM-derived hillshade imagery (incident light azimuth: 315°and angle: 35°; vertical exaggeration is 2) and (b) geomorphological mapping.The irregular undulating surfaces at high elevations is mapped as hummocky terrain (purple polygon) and shear margin moraines mark the transition between the corridor of highly attenuated bedforms and the hummocky terrain.The two different categories of meltwater channels and eskers are also mapped.The location of this figure is shown in Figure 1.

Figure 7 .
Figure 7. Example of the glacial meltwater landforms.(a) ArcticDEM-derived hillshade imagery (incident light azimuth: 315°and angle: 35°; vertical exaggeration is 2) and (b) geomorphological mapping of flat topped deltas, esker ridges and complexes and glaciofluvial complexes.Meltwater channels and ice flow parallel lineations were also mapped.The location of this figure is shown in Figure 1.

Figure 8 .
Figure 8. Examples of raised shorelines and aeolian dunes.(a), (c) ArcticDEM-derived hillshade imagery (incident light azimuth: 315°and angle: 35°; vertical exaggeration is 2) and (b), (d) geomorphological mapping.The raised shorelines consist of beach ridges deposited parallel to the topography.The aeolian dune ridges are straight ridges that sometimes form a zig-zag pattern and can cross-cut the glacial landforms.The location of this figure is shown in Figure 1.