Using GIS and streamlined landforms to interpret palaeo‐ice flow in northern Iceland

Abstract

The properties of streamlined glacial landforms and palaeo-flow indicators in the valleys of Viðidalur, Vatnsdalur and Sv ınadalur in northern Iceland were quantified using spatial analyses. Drumlins and mega-scale glacial lineations (MSGL) were visually identified using satellite imagery from Google Earth, the National Land Survey of Iceland (NLSI) Map Viewer and Landsat satellites, and using aerial photographs from the NLSI. A semi-automated technique was developed using ENVI to determine regions in northern Iceland likely to contain streamlined landforms. The outlines of the identified landforms were manually delineated in Google Earth, and all analyses were conducted in ArcGIS using a 20 m digital elevation model (DEM) of Iceland from the NLSI. Smaller features such as flutes, grooves and striations were measured in the field. At least 543 drumlins and 90 MSGL were identified in the three valleys. Average elongation ratios for Viðidalur, Vatnsdalur and Sv ınadalur are 4.3:1, 5.2:1 and 6.7:1, respectively. The average density of streamlined landforms is 2.34 landforms per 1 km 2 . Striations and orientation data of the drumlins and MSGL demonstrate ice flow to the northwest into H unafl oi. Parallel conformity is higher in the valley of Sv ınadalur (9°standard deviation) than in Viðidalur (12°) and Vatnsdalur (16°). Packing values are generally higher in the centre of each valley. The properties of streamlined landforms in the valleys of Viðidalur, Vatnsdalur and Sv ınadalur support the presence of palaeo-ice stream activity on northern Iceland. Palaeo-ice streams flowed from these regions into H unafl oi, supplying ice to the margin of the Iceland Ice Sheet during the Last Glacial Maximum. These palaeo-ice streams provide a mechanism for ice centres from the mainland of Iceland to reach the shelf-slope break.

Glacial geomorphological mapping: A review of approaches and frameworks for best practice

“…Over the last ~15 years there has been increasing use of DEMs in glacial geomorphology, particularly for mapping at the ice-sheet scale (e.g. Hughes et al, 2010;Ó Cofaigh et al, 2010;Evans et al, 2014Evans et al, , 2016dPrincipato et al, 2016;Ojala, 2016;Stokes et al, 2016a;Mäkinen et al, 2017;Norris et al, 2017). DEMs are raster-based models of topography that record absolute elevation, with each pixel or grid cell in a DEM representing the average height for the area it covers (Clark, 1997;Smith et al, 2006).…”

The configuration, sensitivity and rapid retreat of the Late Weichselian Icelandic ice sheet

“…Most Icelandic cross-shelf troughs terminate with a reverse slope in long-profile and a bulging, arcuate terminus in planform ( Figure 2C). Their association with distinct sets of large submarine streamlined ridges, running parallel to trough axes, as well as similar streamlined mega-lineations and striae onshore (Norðdahl, 1991;Bourgeois et al, 2000;Principato et al, 2016), strongly suggest that these areas were regions of streaming ice flow, indicative of widespread temperate subglacial conditions. Often associated with these offshore mega-lineations, are parallel channels up to 75 m in depth, 3 km wide and 20 km long, found incising to depths of 360 m below present-day sea level.…”

“…Glacial lineations are a common landform signature of palaeo-ice sheets, indicative of fast, icestreaming flow (Clark, 1993;Ó Cofaigh et al, 2002;Stokes and Clark, 2002;King et al, 2009), and have been readily identified across the Icelandic shelf to infer the presence of numerous ice streams that drained ice towards the shelf edge and an ice divide across central Iceland from east to west (Bourgeois et al, 2000;Stokes and Clark, 2001;Spagnolo and Clark, 2009;Principato et al, 2016).…”

Sea ice, ice‐rafting, and ocean climate across Denmark Strait during rapid deglaciation (∼16–12 cal ka BP) of the Iceland and East Greenland shelves

“…The H unafl oi/Reykjafjarda all Trough (HT, Fig. 1A) provided a bathymetric outlet for a major ice stream that flowed northward to the Iceland Sea (Bourgeois et al, 2000;Hubbard, 2006;Principato et al, 2016;Patton et al, 2017). Core B997-326PC1 ( Fig.…”