Abstract
Ice-wedge networks underlie polygonal terrain and comprise the most widespread form of massive ground ice in continuous permafrost. Here, we show that climate-driven thaw of hilltop ice-wedge networks is rapidly transforming uplands across Banks Island in the Canadian Arctic Archipelago. Change detection using high-resolution WorldView images and historical air photos, coupled with 32-year Landsat reflectance trends, indicate broad-scale increases in ponding from ice-wedge thaw on hilltops, which has significantly affected at least 1500 km2 of Banks Island and over 3.5% of the total upland area. Trajectories of change associated with this upland ice-wedge thermokarst include increased micro-relief, development of high-centred polygons, and, in areas of poor drainage, ponding and potential initiation of thaw lakes. Millennia of cooling climate have favoured ice-wedge growth, and an absence of ecosystem disturbance combined with surface denudation by solifluction has produced high Arctic uplands and slopes underlain by ice-wedge networks truncated at the permafrost table. The thin veneer of thermally-conductive mineral soils strongly links Arctic upland active-layer responses to summer warming. For these reasons, widespread and intense ice-wedge thermokarst on Arctic hilltops and slopes contrast more muted responses to warming reported in low and subarctic environments. Increasing field evidence of thermokarst highlights the inherent climate sensitivity of the Arctic permafrost terrain and the need for integrated approaches to monitor change and investigate the cascade of environmental consequences.
Highlights
Ice wedges form due to thermal contraction, cracking of the ground and infilling typically by snowmelt that refreezes to form a vein of ice [1,2]
Millennia of cooling climate have favoured ice-wedge growth, and an absence of ecosystem disturbance combined with surface denudation by solifluction has produced high Arctic uplands and slopes underlain by ice-wedge networks truncated at the permafrost table
The strong linear relationship between the ice-wedge melt pond area and Landsat shortwave infrared (SWIR) reflectance in upland terrain (Figure A4) suggests that SWIR trends can provide a sensitive indicator of long-term, thermokarst-driven changes in the melt pond area
Summary
Ice wedges form due to thermal contraction, cracking of the ground and infilling typically by snowmelt that refreezes to form a vein of ice [1,2]. Over millennia, repeated cracking can cause large ice wedges to develop [3]. The surface expression of ice-wedge networks, is ubiquitous in unconsolidated deposits throughout the circumpolar Arctic [4]. Because wedge ice is typically encountered near the top of permafrost, climate-driven thaw may cause ponding in troughs and in extreme cases thaw lake development [5,6,7], the formation of high-centred polygons [8], and the reconfiguration of hydrological pathways [9,10]. The broad distribution and thaw sensitivity of ice-wedge networks suggests that evolution of polygonal terrain will have a major influence on landscRaepmeotefSoernms. Iniceth-weeCdgaenandetiwanorkAsrcsutigcg, ehstisllttohpatseavnodlutsiolonpoefspdoilsysgeocntaeldtebryrailnarwgiellehpaivgeenaemtiacjoarnidnflaunetnic-seyonngenetic ice weldangdessc[a3p]eaforermpraonvdiencgoleoxgticraelmanedlybsioegnesoicthiveemticoacl lpirmocaetsesews aacrrmosisnag.wMarmillienngnciiracuomf cpooolalrinAgrcdtiuc.ring the Holocene [I1n1t]hheaCvaenfaadviaonuArerdctitch, ehigllrtopwstahnodfslaorpgees diciessweceteddgbeys l[a1r2g]e. eOpnigeBnaentikcsaInsdlaanndti-asynndgienneottichiecresimilar high Awrcetdigcelsan[3d] sacraepperso,vtihneg aebxtsreenmceelyofsesnusriftiavceetdoiscltiumrabtaenwceasrm, siungc.hMasillfienreni[a13o]f aconodlinthgedgurraindguathlesurface denudHatoilooncenoef [h11il]lhtoavpesfaavnodurseldotpheesgrboywsthooliffllaurcgteioicne w[1e4d]g,ehsa[1s2]p. rOondBuacnekds Iuslpanladnadndteinrroathinerusinmdilearrlain by anti-syhniggheAnerctiticc ilcaen-dwsceadpgese, tnheetawbsoernkcse tohf asut rgfarcoewdidstouwrbnanwceasr,dsuocnh arsecfieredi[n13g] asnlodptehse gwrahdeurael tshuerfraeceis a net removdsayelnnogufednsaeuttiiorcfnaicocefe-hwmielldtaogtpeesrniaeantlwd(osFlriokgpsuetsrhebaty1gs)roo[l3wif,l1ud5co]twi.onnTwh[1ae4rs]d,ehocanosrnpecdreoiddtiiuoncgnesdslouinppcelasrnewadhsteeerretrhathienelruienkideselairhnlaoeitnordbeymtahonvatati-lwedge ice andof rseulrifcatcePmleaitsetroiacle(nFeigumreas1s)i[v3,e15i]c.eThaerseeecnoncdoiutinontesriendcreaatseorthcelloikseelithoootdhethbatawseedogfetihceeacnodnrteelimctporary activePllaeyisetorce(Fneigmuraessi1v;e TicaeblaereSe2n)co[1u6n–te1r8e]d. atSporarcsloeslye tvoetghetabtaesed obfatrhreencosnitenmtphoerahryigahctiAvercltaiycerlack an organi(cFilgauyrer1,;wTahbilcehS2w) [o1u6–ld18]o.tShpearrwseliyseveagcettatotedbubaffrererntshine tehfefehcigtsh oAfrcstuicmlamckearnworagramniicnlagyoern, wachticivhe layer develowpomulednot t[h1e9r]woisredarcitvteo fbeuefdfebratchkesetfhfeacttstyofpsicuamllmyesrtawbairlmisiengthoenrmacotikvaerlsatyienr dsuevbealorcptmiceannt [d19l]owor-Arctic envirodnrmiveenfetesd[b6a,c7k,2s 0th].atTtyhpeiscaellfyascttaobrislisceotmhebrminoekatorsthineisguhbtaernctitchaendselonwsi-tAivrcittiyc eonfvciroolndmAenrtcsti[c6,7p,2e0r]m. afrost terrainTdrhtoievseaenbfrathucatpowrts,ccclooinmmtrabaitsnetei-ndtgoriwhveietihnghttthheenamwtho,ercesoesnnustbridtaiuvsiettidynoogrfwlcooicltadhliAstehrdcetricmesppoeorrenmssaeufsrboosdfteutceeordsryaosintretmlooacpbarroluitsepectdtecdlrim,elsoapwteo--nses of ecosysAtermcticpproertmecatferdos,tleonwv-irAonrcmtiecnptse[r7m,16a,f1r7o,2s1t,e22n]v. ironments [7,16,17,21,22]
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