The Evolution of the Patagonian Ice Sheet from 35 Ka to the Present Day (PATICE) T
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Earth-Science Reviews 204 (2020) 103152 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Invited Review The evolution of the Patagonian Ice Sheet from 35 ka to the present day (PATICE) T Bethan J. Daviesa,⁎, Christopher M. Darvillb, Harold Lovellc, Jacob M. Bendlea, Julian A. Dowdeswelld, Derek Fabele, Juan-Luis Garcíaf, Alessa Geigerf,q, Neil F. Glasserg, Delia M. Gheorghiue, Stephan Harrisonh, Andrew S. Heini, Michael R. Kaplanj, Julian R.V. Martina, Monika Mendelovai, Adrian Palmera, Mauri Peltok, Ángel Rodése, Esteban A. Sagredof,l,m,n, Rachel K. Smedleyo, John L. Smelliep, Varyl R. Thorndycrafta a Centre for Quaternary Research, Department of Geography, Royal Holloway University of London, Egham Hill, Egham, Surrey TW20 0EX, UK b Department of Geography, The University of Manchester, Oxford Road, Manchester M13 9PL, UK c School of the Environment, Geography and Geosciences, University of Portsmouth, Buckingham Building, Lion Terrace, Portsmouth PO1 3HE, UK d Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK e Scottish Universities Environmental Research Centre (SUERC), Rankine Avenue, East Kilbride G75 0QF, UK f Instituto de Geografía, Facultad de Historia, Geografía y Ciencia Política, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Macul, Santiago 782- 0436, Chile g Department of Geography and Earth Sciences, Aberystwyth University, Wales, SY23 3DB, UK h College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK i School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK j Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA k Nichols College, 121 Centre Road, PO Box 5000, Dudley, MA 01571, USA l Millenium Nuclei Palaeoclimate, ANID Millennium Science Initiative, Santiago, Chile m Estación Patagonia de Investigaciones Interdisciplinarias UC, Pontificia Universidad Católica de Chile, Chile. n OHM-I, LabEx DRIIHM. Programme "investissements d'avenir": ANR-11-LABX-0010), INEE-CNRS, Paris, France o Department of Geography and Planning, University of Liverpool, Liverpool L69 7ZT, UK p School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester LE1 7RH, UK q School of Geographical & Earth Sciences, University of Glasgow, G12 8QQ, Glasgow, UK ARTICLE INFO ABSTRACT Keywords: We present PATICE, a GIS database of Patagonian glacial geomorphology and recalibrated chronological data. Patagonia PATICE includes 58,823 landforms and 1,669 geochronological ages, and extends from 38°S to 55°S in southern Ice Sheet South America. We use these data to generate new empirical reconstructions of the Patagonian Ice Sheet (PIS) Geochronology and subsequent ice masses and ice-dammed palaeolakes at 35 ka, 30 ka, 25 ka, 20 ka, 15 ka, 13 ka (synchronous Quaternary with the Antarctic Cold Reversal), 10 ka, 5 ka, 0.2 ka and 2011 AD. At 35 ka, the PIS covered of 492.6 x103 km2, Glaciation had a sea level equivalent of ~1,496 mm, was 350 km wide and 2090 km long, and was grounded on the Pacific Geomorphology continental shelf edge. Outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams. The PIS reached its maximum extent by 33 – 28 ka from 38°S to 48°S, and earlier, around 47 ka from 48°S southwards. Net retreat from maximum positions began by 25 ka, with ice-marginal stabilisation then at 21 – 18 ka, which was then followed by rapid, irreversible deglaciation. By 15 ka, the PIS had separated into disparate ice masses, draining into large ice- Abbreviations: GIS, Geographical Information System; LGM, Last Glacial Maximum; LLGM, Local Last Glacial Maximum; PIS, Patagonian Ice Sheet; ACR, Antarctic Cold Reversal; Lago GCBA, Lago General Carrera/Buenos Aires; Lago CP, Lago Cochrane/Pueyrredón; UE/BV, Última Esperanza /Bella Vista—Río Gallegos Lobe; SWW, Southern Westerly Winds; m asl, metres above sea level; ka, thousands of years ago; cal. ka BP, calibrated thousands of years ago; Gt, Gigatonnes; DEM, Digital Elevation Model; MIS, Marine Isotope Stage; SLE, Sea Level Equivalent; ACC, Antarctic Circumpolar Current; SAM, Southern Annular Mode; MSL, Monte San Lorenzo; OSL, Optically stimulated luminescence; SD, Standard deviation; μ, Mean ⁎ Corresponding author. E-mail address: [email protected] (B.J. Davies). https://doi.org/10.1016/j.earscirev.2020.103152 Received 17 September 2019; Received in revised form 10 March 2020; Accepted 10 March 2020 Available online 18 March 2020 0012-8252/ © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). B.J. Davies, et al. Earth-Science Reviews 204 (2020) 103152 dammed lakes along the eastern margin, which strongly influenced rates of recession. Glacial readvances or stabilisations occurred at least at 14 – 13 ka, 11 ka, 6 – 5 ka, 2 – 1 ka, and 0.5 – 0.2 ka. We suggest that 20th century glacial recession (% a-1) is occurring faster than at any time documented during the Holocene. 1. Introduction GLIMMER (Rutt et al., 2009) now make it possible to simulate PIS evolution from the Last Glacial Maximum (LGM) to present. However, Glacier recession is accelerating in Patagonia (Aniya, 1999; Davies such models clearly require a robust geological framework (including and Glasser, 2012; Meier et al., 2018; Braun et al., 2019), causing sea accurate inferences of the direction of ice flow, timing of ice-free con- level rise (Gardner et al., 2013; Malz et al., 2018), enlarging glacial ditions, ice-marginal locations, extent and thickness, with an evaluation lakes and increasing flood riskLoriaux ( and Casassa, 2013; Wilson of uncertainty, at different times), against which they can be calibrated et al., 2018), and affecting water availability and hydropower oppor- (cf. Ely et al., 2019; Hughes et al., 2016). tunities (Huss and Hock, 2018; Milner et al., 2017). The Southern Andes There is a large volume of ages and geomorphology constraining region had a mass loss of 1,208 Gt from 1961 to 2016, and is the largest past ice sheet extent and dynamics across Patagonia. The first quanti- contributor to global sea level rise outside of Greenland and Alaska fied reconstructions of the evolution of the PIS with chronological (Zemp et al., 2019). This mass loss from global glaciers provides a constraints relied on radiocarbon dating (Mercer, 1968; Mercer, 1970; global contribution of 0.92 ± 0.39 mm a-1 to global sea-level rise (to- Porter, 1981; Clapperton, 1995). Chronologies of pre-LGM ice extent talling 27 ± 22 mm from 1961 – 2016), accounting for 25 – 30% of used 40Ar/39Ar (and K-Ar) dating of interbedded moraines and volcanic total observed sea level rise; this is equivalent to mass loss from the sequences (e.g. Singer et al., 2004a, 2004b; Clague et al., 2020). Glacier Greenland Ice Sheet and exceeds loss from Antarctica (Zemp et al., recession over the last few centuries has been mapped using licheno- 2019). In order to understand how future climate change will influence metry (Winchester and Harrison, 2000; Garibotti and Villalba, 2017), the world’s glaciers, and how this will affect societies, it is imperative to dendrochronology (e.g. Winchester et al., 2014), and historical docu- model future climate, glacier response and hydrology. Detailed analyses ments dating from the exploration era (e.g. Casassa et al., 1997). More of past glacier-climate interactions can be used to constrain and test recently, the application of innovative forms of cosmogenic nuclide numerical models and to untangle externally driven changes versus exposure-age dating (Ackert et al., 2008; Douglass et al., 2006; García internally forced changes (e.g. climate compared with calving, ice di- et al., 2012; Hein et al., 2011; Kaplan et al., 2005, 2011; Cogez et al., vide change and topography). 2018), cosmogenic nuclide depth profiles (Darvill et al., 2015b; Hein During past glacial periods, the Patagonian Ice Sheet (PIS) was et al., 2009), optically stimulated luminescence dating (Blomdin et al., centred on the central chain of the Andes, stretched from ~38°S to 55°S, 2012; Smedley et al., 2016; García et al., 2019), tephrochronology consisted of terrestrial lobes that retreated into large palaeolakes on the (Kilian et al., 2003; Stern, 2008; Stern et al., 2016; Weller et al., 2015) east, and is inferred to have reached the continental shelf on the west and varve-age dating (Bendle et al., 2017a, 2019) has resulted in new coast. The past behaviour of the PIS during different climate states and insights into the timing and dynamics of both ice-sheet behaviour and during rapid climatic transitions could shed insights into the ways in palaeolake development. which the region is sensitive to changes and could respond to future However, age calculation techniques differ between studies, at climate change. Reconstruction of the evolution of the former PIS times using different erosion corrections (often untested), outlier-re- provides a unique insight into past terrestrial cryospheric and climatic moval strategies, marine reservoir effects for radiocarbon dating, and change in the southern mid-latitudes, a particularly data-sparse area of different calibration curves. Further, the calibration of radiocarbon the globe, and forms an important proxy for changes in circum-hemi- dating (Hogg et al., 2013;