The Glacial Geomorphology of Upper Godthåbsfjord (Nuup Kangerlua) in Southwest Greenland
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Journal of Maps ISSN: (Print) 1744-5647 (Online) Journal homepage: http://www.tandfonline.com/loi/tjom20 The glacial geomorphology of upper Godthåbsfjord (Nuup Kangerlua) in southwest Greenland Danni M. Pearce, Douglas W. F. Mair, Brice R. Rea, James M. Lea, J. Edward Schofield, Nicholas Kamenos & Kathryn Schoenrock To cite this article: Danni M. Pearce, Douglas W. F. Mair, Brice R. Rea, James M. Lea, J. Edward Schofield, Nicholas Kamenos & Kathryn Schoenrock (2018) The glacial geomorphology of upper Godthåbsfjord (Nuup Kangerlua) in southwest Greenland, Journal of Maps, 14:2, 45-55, DOI: 10.1080/17445647.2017.1422447 To link to this article: https://doi.org/10.1080/17445647.2017.1422447 © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps View supplementary material Published online: 08 Feb 2018. Submit your article to this journal Article views: 16 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tjom20 JOURNAL OF MAPS, 2018 VOL. 14, NO. 2, 45–55 https://doi.org/10.1080/17445647.2017.1422447 Science The glacial geomorphology of upper Godthåbsfjord (Nuup Kangerlua) in southwest Greenland Danni M. Pearcea, Douglas W. F. Mairb, Brice R. Reaa, James M. Leab, J. Edward Schofielda, Nicholas Kamenosc and Kathryn Schoenrockd aDepartment of Geography, University of Aberdeen, Aberdeen, UK; bSchool of Environmental Sciences, University of Liverpool, Liverpool, UK; cSchool of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK; dSchool of Natural Sciences, National University of Ireland, Galway, UK ABSTRACT ARTICLE HISTORY The Greenland Ice Sheet (GrIS) is known to have experienced widespread retreat over the last Received 10 July 2017 century. Information on outlet glacier dynamics, prior to this, are limited due to both a lack of Revised 22 December 2017 observations and a paucity of mapped or mappable deglacial evidence which restricts our Accepted 26 December 2017 understanding of centennial to millennial timescale dynamics of the GrIS. Here we present 2 KEYWORDS glacial geomorphological mapping, for upper Godthåbsfjord, covering 5800 km at a scale of Geomorphology; tidewater 1:92,000, using a combination of ASTER GDEM V2, a medium-resolution DEM (error <10 m glacier; Godthåbsfjord; horizontal and <6 m vertical accuracy), panchromatic orthophotographs and ground truthing. Greenland Ice Sheet; Little Ice This work provides a detailed geomorphological assessment for the area, compiled as a Age; moraine single map, comprising of moraines, meltwater channels, streamlined bedrock, sediment lineations, ice-dammed lakes, trimlines, terraces, gullied sediment and marine limits. Whilst some of the landforms have been previously identified, the new information presented here improves our understanding of ice margin behaviour and can be used for future numerical modelling and landform dating programmes. Data also form the basis for palaeoglaciological reconstructions and contribute towards understanding of the centennial to millennial timescale record of this sector of the GrIS. 1. Introduction Lea, Mair, Nick, Rea, Weidick, et al., 2014). The record has been extended to the century timescale by employ- In the early 2000s, the Greenland Ice Sheet (GrIS) ing historical maps, written accounts, aerial photos experienced the largest ice-mass loss recorded in the from the 1930s onwards and the identification of Little instrumental record, largely attributed to increased Ice Age (LIA;c. AD 1300–1850) extent from remotely surface melting (Hanna et al., 2013) and enhanced sensed imagery (e.g. Kjeldsen et al., 2015). Reconstruc- ice discharge from accelerating marine/fjord terminat- tions over these timescales are extremely important ing outlets (Amundson et al., 2010; Howat, Box, Ahn, when contextualising the present dynamic changes, Herrington, & McFadden, 2010). Compared to the because the length of the observational record makes east coast of Greenland, the west has exhibited strong it difficult to capture glacial behaviour that acts on cen- warming associated with changes in summer general tennial to millennial scales. Thus, current high-resol- circulation (Van As et al., 2014). Despite this warming ution observational data may be biased towards trend, the land-terminating glacier outlets are currently short-term fluctuations (Vieli & Nick, 2011), rather experiencing a regional slowdown in recession (Ted- than longer term response to climate forcing. This, in stone et al., 2015), whereas tidewater glaciers have gen- addition to their nonlinear response to climate forcing erally increased in velocity and undergone significant could lead to inaccurate mass loss projections and retreat (Joughin et al., 2008; Kjeldsen et al., 2015; concomitant contributions to future sea-level rise Motyka et al., 2017; Murray et al., 2010; Van den (Nick, Vieli, Howat, & Joughin, 2009). Predicting the Broeke et al., 2009). responses of both land and tidewater glaciers is crucial Satellite imagery recorded since the 1970s has facili- given the current unprecedented warming trend tated the reconstruction of glacier fluctuations in west (Andresen et al., 2012; Khan et al., 2015). We present Greenland, but prior to this, estimating the spatial a glacial geomorphological map, associated with land- and temporal changes is rather more challenging due terminating and tidewater glaciers, located in upper to the sparse proxy records and lack of direct obser- Godthåbsfjord, SW Greenland, which can be used to vations (Lea, Mair, Nick, Rea, van As, et al., 2014; contexulise the present-day changes. CONTACT Danni M. Pearce [email protected] Supplemental data for this article can be accessed at https://doi.org/10.1080/17445647.2017.1422447 © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 46 D. M. PEARCE ET AL. 2. Study area Qamanaarsuup Sermia (QS) and Kangaasarsuup Sermia (KSS). A further three ice sheet outlets Godthåbsfjord (Nuup Kangerlua) in southwest Green- terminate in marine conditions: Narsap Sermia (NS), land (c. 64–65°N, 49–51°W) is one of the largest fjord systems in the world. It is c. 190 km in length, up to Akullersuup Sermia (AS) and Kangiata Nunaata ∼ 7 km wide and covers a total area of c. 2013 km2 Sermia (KNS). Surrounding bedrock covers 80% of (Figure 1). The uppermost branch of Godthåbsfjord, the mapped area, and is predominantly composed of – Kangersuneq, is located approximately 80 km inland Archaean Gneiss (c. 3900 3600 Ma yr) with the tec- from the coast and connects the marine environment tonic fabric approximately SW to NE (Henriksen, to the margin of the GrIS. Six outlets drain this sector Higgins, Kalsbeek, & Pulvertaft, 2000). The fjord land- of the ice sheet and reach sea level, or close to sea level. scape has an arborescent configuration with numerous Of these, three ice sheet outlets terminate on land, with branches and outlets. Mountain summits are typically extensive sandur plains in front of their termini. These between 500 and 1480 m above sea level (a.s.l.), with are (from north to south): Kangilinnguata Sermia (KS), steep valley sides mostly in excess of c. 30°. Typically, Figure 1. (Main panel) Aerial map of upper Godthåbsfjord showing outlets from the GrIS. The red line indicates the approximate extent of the outlets during the LIA (redrawn from Weidick, Bennike, Citterio, & Nørgaard-Pedersen, 2012). The white line indicates the locations of the Kapisillit moraines (redrawn from Weidick et al., 2012 and Larsen et al., 2014). (Inset, top left) Landsat image (2013) of the wider fjord system into which Godthåbsfjord is connected with. The capital of Greenland, Nuuk, is labelled. The black box denotes the mapped area featured in this study. (Inset, top right) Location of the study area in Greenland. JOURNAL OF MAPS 47 interconnected lakes are present in the valley floors, which took place during a total of six weeks of field- whilst numerous smaller bedrock controlled lakes can work in 2015 and 2016. Google Earth was used for be found at higher altitudes. 3D landform visualisation and reconnaissance of val- leys/landforms prior to field work. Advanced Spaceborne Thermal Emission and 3. Brief glacial history Reflection Radiometer (ASTER) global (GDEM V2) During the Last Glacial Maximum the ice sheet in West data (https://asterweb.jpl.nasa.gov/gdem.asp), gridded Greenland extended onto the continental shelf and to 30 m2 resolution, was used as a first pass. At this res- began to disintegrate ∼17 cal ka BP (Knutz, Sicre, olution only the largest glacial features, such as troughs, Ebbesen, Christiansen, & Kuijpers, 2011). Around were visible on the DEM (Figure 2(A)) and so a med- coastal areas, the early Holocene glacial history is rela- ium-resolution DEM was used to complement the tively well known. Larsen et al. (2014) proposed a rapid GDEM (Korsgaard, Nuth, Khan, Kjeldsen, Anders, and early deglaciation from the coast, between 11.4 and et al., 2016; Korsgaard, Nuth, Khan, Kjeldsen, Bjørk, 10.4 cal ka BP. Inland of this and within the study area, et al., 2016)(Figure 2(B)). Based on a 1985 aerial survey approximately 10–30 km from the present-day ice conducted by the Agency for Data Supply and Effi- margin, prominent moraines (also referred to as the ciency (previously the Danish Geodata Agency), this Kapisillit [old orthography: Kapisigdlit] moraines, DEM had an associated ground control (GR96) and Figure 1), are thought to mark a major standstill, or error <10 m horizontal and <6 m vertical accuracy readvance of the ice sheet somewhere between 10.4 (https://data.nodc.noaa.gov/cgi-bin/iso?id=gov.noaa. and 8.2 ka cal BP (Beschel, 1961; Larsen et al., 2014; nodc:0145405).