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remote sensing Article Fluctuation of Glacial Retreat Rates in the Eastern Part of Warszawa Icefield, King George Island, Antarctica, 1979–2018 Rafał Pudełko 1,2,*, Piotr Jan Angiel 1, Mariusz Potocki 1,3,4, Anna J˛edrejek 2 ID and Małgorzata Kozak 2 ID 1 Department of Antarctic Biology, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawi´nskiego5a, 02-106 Warsaw, Poland; [email protected] (P.J.A.); [email protected] (M.P.) 2 Department of Bioeconomy and Systems Analysis, Institute of Soil Science and Plant Cultivation—State Research Institute, Czartoryskich 8, 24-100 Puławy, Poland; [email protected] (A.J.); [email protected] (M.K.) 3 Climate Change Institute, University of Maine, Orono, ME 04469, USA 4 School of Earth and Climate Sciences, University of Maine, Orono, ME 04469, USA * Correspondence: [email protected]; Tel.: +48-81-4786-765 Received: 28 March 2018; Accepted: 30 May 2018; Published: 7 June 2018 Abstract: Antarctica is a region of the world where climate change is visible in the rapid melting of glaciers. This is particularly evident in marginal zones, where the pace of glacial retreat has systematically accelerated. The effective mapping of these changes is possible with the use of remote sensing methods. This study assesses changes in glacier margin positions between 1979 and 2018 in the Antarctic Specially Protected Area 128 (ASPA-128) on King George Island, South Shetland Islands, Antarctica. In 1979, 19.8 km2 of the study area was glaciated. Over the following 39 years, an area of 6.1 km2 became ice-free, impacting local ecosystems both on land and in Admiralty Bay. The reduction in glacier extent was different in time and depended on the glacier type. Land-terminating glaciers had the fastest retreat rates below 200 m a.s.l. and were influenced mostly by surface melting. The reduction of tidewater glaciers occurred primarily in areas below 100 m a.s.l., with the most pronounced ice extent decreases occurring below 50 m a.s.l. The observed rates of front retreat suggest that glacier retreat rates were fastest between 1989–2001 and 2007–2011, with reduced retreat rates between 2001 and 2007. During the last 7 years, the lowest rate of regression was recorded in the entire analysed period (1979–2018). Changes in the areal extent of glaciers were compared with the climate record available for King George Island. The observed fluctuations in glacier retreat rates could be correlated to oscillations in annual Positive Degree-Days. The spatial analyses were based on aerial photographs (1956, 1979), theodolite measurements (1989), GPS survey (2001, 2007), and satellite images (2011, 2018). Keywords: glacier recession; surface melting; climate change; temperature change; Positive Degree-Day 1. Introduction 1.1. Characterization of the Research Area The Antarctic Peninsula region and islands of the southern Atlantic Ocean have been identified as a region of notable dynamic change in glacial and climatic systems [1–5]. Over the last 50 years, large areas along the southern shoreline of King George Island have become ice-free. Several new nunataks have emerged, illustrating a significant reduction of glacier thickness. The late-Holocene maximum extent of glaciers on King George Island is marked by large ice-cored moraines, which Remote Sens. 2018, 10, 892; doi:10.3390/rs10060892 www.mdpi.com/journal/remotesensing Remote Sens. 2018, 10, 892 2 of 25 Remote Sens. 2018, 10, x FOR PEER REVIEW 2 of 26 were formed at the termination of the Little Ice Age (LIA) at the beginning of the 20th century [6]. Lichenometricwere formed studiesat the termination of moraine of agesthe Little in ASPA-128 Ice Age (LIA) and ASPA-151at the beginning (Antarctic of the Specially 20th century Protected [6]. Areas)Lichenometric indicate that studies the post-LIAof moraine glacier ages retreatin ASPA- was128 relatively and ASPA-151 slow until (Antarctic the 1940s Specially [6]. The Protected first field studiesAreas) of indicate glaciers that in Admiralty the post-LIA Bay glacier were retreat conducted was relatively in the 1950s slow and until reported the 1940s a general [6]. The reduction first field in icestudies extent of [7 ].glaciers Since in the Admiralty 1950s, an Bay increased were conducted glacier retreat in the 1950s has been and reportedreported a on general King Georgereduction Island in byice numerous extent [7]. studies Since the [6, 81950s,–12]. Anan increased increase inglacier surface retreat temperature has been reported was also on observed King George over Island the past severalby numerous years. According studies [6,8–12]. to a simple An increase ice dynamic in surf modelace temperature described by was Knap also et observed al. [13], suchover conditionsthe past several years. According to a simple ice dynamic model described by Knap et al. [13], such conditions are likely to affect the glacial state of the King George Island ice caps. Moreover, there is evidence are likely to affect the glacial state of the King George Island ice caps. Moreover, there is evidence of of a glacier mass balance deficit and increases in surface energy exchange in this region [11,14,15]. a glacier mass balance deficit and increases in surface energy exchange in this region [11,14,15]. Most Most of the previous studies of glaciers retreat in ASPA-128 simply documented changes in the front of the previous studies of glaciers retreat in ASPA-128 simply documented changes in the front positions of glaciers in different years on maps. These studies were in different scales, mostly focused positions of glaciers in different years on maps. These studies were in different scales, mostly focused on Ecology Glacier, did not include spatial analysis, and did not account for the different behaviours on Ecology Glacier, did not include spatial analysis, and did not account for the different behaviours exhibitedexhibited by by dissimilar dissimilar glacier glaciertypes. types. Therefore,Therefore, it is is difficult difficult to to compare compare these these results results to toeach each other other andand to to calculate calculate glacier glacier retreat retreat rates. rates. ForFor ASPA-128, ASPA-128, there there are are no no reports reports comparing comparing fluctuations fluctuations in in glacier glacier retreat retreat with with the the climate climate data duringdata during the period the period of intensified of intensified reduction reduction in glaciers in glaciers extent extent between between 1979–2018. 1979–2018. Therefore, Therefore, the the aim ofaim this of study this study is to investigateis to investigate the the rate rate of theof th reductione reduction in in glaciated glaciated area for for five five periods—1979–1989, periods—1979–1989, 1989–2001,1989–2001, 2001–2007, 2001–2007, 2007–2011, 2007–2011, and and 2011–2018—for 2011–2018—for different types types of of glaciers. glaciers. GlacierGlacier retreat retreat had had a profound a profound impact impact on local on ecosystemslocal ecosystems including including mammals, mammals, birds, and birds, vegetation. and Thevegetation. diverse avian The anddiverse mammalian avian and species mammalian and vegetation species and are vegetation the reason are why the the reason protected why area the of ASPA-128protected was area created. of ASPA-128 It has beenwas created. shown It that has newly been shown ice-free that areas newly are dynamicallyice-free areas colonisedare dynamically by plant communitiescolonised by [16 plant] and communities nesting bird [16] populations. and nesting Algae, bird lichens,populations. mosses, Algae, fungi, lichens, and plants mosses, have fungi, colonized and theseplants recently have formedcolonized ice-free these areasrecently on theformed glacier ice-free forefields areas and on the nunataks glacier [ 17forefields,18]. These and include nunataks alien species[17,18]. of ThesePoa annua includeL., alien which species were firstof Poa found annua by L., the which author were during first found the mapping by the author of the during forefield the of themapping Ecology Glacierof the inforefield February of 2009the (reportedEcology Glacie by Olechr in and February Chwedorzewska 2009 (reported [19]). Additionally,by Olech and new breedingChwedorzewska areas became [19]). available Additionally, for seals new and breeding birds. Therefore, areas became it is important available to for document seals and changes birds. in Therefore, it is important to document changes in glacier extent and also to identify the cause of these glacier extent and also to identify the cause of these changes. To this point, there has been no integrated changes. To this point, there has been no integrated study of glacier retreat for ASPA-128 comparing study of glacier retreat for ASPA-128 comparing how fast and how much of the area became ice-free how fast and how much of the area became ice-free between 1979 and 2018 as a result of climate between 1979 and 2018 as a result of climate change on King George Island (Figure1). change on King George Island (Figure 1). Figure 1. The study area: (a) the location of King George Island in West Antarctica, (b) the location of Figure 1. The study area: (a) the location of King George Island in West Antarctica, (b) the location the ASPA-128 and ASPA-151 on King George Island; glaciated areas indicated by light grey color, ofice-free the ASPA-128 areas are and in ASPA-151black; 1-Bellingshausen on King George Station, Island; 2-Arctowski glaciated Station, areas indicated 3-Ferraz Station, by light 4-Jubany grey color, ice-freeStation, areas 5-Fildes are in Peninsula, black; 1-Bellingshausen 6-Arctowski Icefield. Station, 2-Arctowski Station, 3-Ferraz Station, 4-Jubany Station, 5-Fildes Peninsula, 6-Arctowski Icefield. Remote Sens. 2018, 10, 892 3 of 25 1.2. Remote Sensing Data for King George Island In the area covered by ASPA-128, it is difficult to conduct scientific research due to numerous obstacles, mainly cliffs and ice crevasses.

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