Little Ice Age and neoglacial landforms at the Inland Ice margin, Isunguata Sermia, Kangerlussuaq, west Greenland

Little Ice Age and neoglacial landforms at the Inland Ice margin,Isunguata Sermia, Kangerlussuaq, west Greenland

STEVEN L. FORMAN, LILIANA MARIN, CORNELIS VAN DER VEEN, CATHERINE TREMPER AND BEA CSATHO

BOREAS Forman, S. L., Marın, L., van der Veen, C., Tremper, C. & Csatho, B. 2007 (October): Little Ice Age andneoglacial landforms at the Inland Ice margin, Isunguata Sermia, Kangerlussuaq, west Greenland. Boreas, Vol.36, pp. 341�351. Oslo. ISSN 0300-9483.

Neoglacial and Little Ice Age (LIA) limits occur within 2 km of the Inland Ice margin in the Kangerlussuaq areaon west Greenland. The LIA limit is clearly demarcated by ice-cored and non-ice-cored moraines, out-washsurfaces and trimlines. Rhizocarpon sp. thalli of 5/16 mm on these landforms indicate a 1�2 km retreat of theInland Ice in the past c. 100 years, coincident with peripheral thinning of the ice. An older neoglacial moraine hostof Rhizocarpon sp. thalli �/40 mm indicates a minimum limiting age of �/400 BP, whereas Optically StimulatedLuminescence (OSL) ages on aeolian silt capping the moraine yield close limiting ages of c. 2000 BP. Aeolian siltdeposition beyond neoglacial limits yields OSL ages of c. 3000 BP, potentially coeval with advance of the InlandIce. Aeolian sedimentation and the inferred age of the moraine are coincident with pronounced cooling inferredfrom palaeolimnological records from west and south Greenland. This neoglacial event at c. 2000 BP is probablyof similar extent to the LIA maximum, because of the paucity of preserved moraine remnants.

Steven L. Forman (e-mail: [email protected]) and Liliana Marın, Department of Earth and Environmental Sciences,University of Illinois at Chicago, 845 W. Taylor Street, Chicago, IL 60607�7059, USA; Cornelis van der Veen,Catherine Tremper and Bea Csatho, Byrd Polar Research Center, The Ohio State University, 1090 E. Carmack Rd,Columbus, OH 43210�1002, USA; received 21st September 2006, accepted 24th November 2006.

The Greenland Ice Sheet in the Kangerlussuaq (SøndreStrøm) area of west Greenland is a relatively stablepassive ice margin with small outlet glaciers. Morainesequences in this area are common in inner and outerfjord settings and reflect early deglaciation c. 16.8�11.1 cal. kyr BP (Long et al. 1999; Bennike & Bjorck2002; Long & Roberts 2003) from a maximum positionat the continental shelf edge (Kelly 1985; Funder &Hansen 1996). Up to six prominent moraine belts havebeen identified on the central-west coast dated between12.3 and 6.8 cal. kyr BP (van Tatenhove et al. 1996).Radiocarbon ages of basal lake sediments from withinthe inner most moraine sequence adjacent to theInland Ice indicate deglaciation by c. 6 kyr BP (Bennike& Bjorck 2002). Many studies have concluded that icemargins were at or c. 5�20 km behind present limits byc. 7000�5000 cal. yr ago (e.g. Ten Brink & Weidick1974; Weidick 1984; Kelly 1985; Funder 1989; Weidicket al. 1990; van Tatenhove et al. 1996; Anderson et al.1999; Bennike & Bjorck 2002; Long & Roberts 2002),in response to higher summer temperatures, driven byinsolation, and decreased precipitation (Anderson &Leng 2004). Ice cores from central Greenland recordmaximum summer warmth, with a c. 2.58C increasecompared with the 20th century, between c. 8000 and5000 cal. yr BP (Dahl-Jensen et al. 1998). Geophysicalmodelling of the effect of this warmth on the Green-land Ice Sheet places the margin tens to hundreds ofkilometres inland in the early Holocene compared withthe present position (Tarasov & Peltier 2002). Thesubsequent ice sheet re-advance at c. 4.4 cal. kyr BP is

associated with 0.58C cooling, inferred from ice cores(Dahl-Jensen et al. 1998). Studies of climate proxiesfrom lake sediment records in southern (Kaplan et al.2002) and west Greenland (Funder & Fredskild 1989;Anderson et al. 1999) and Baffin Island (Moore et al.2001) reveal a decrease in summer temperatures of]/28C at c. 3000�2000, 1000 and 300 years ago. Thiswidespread cooling may have heralded the re-advanceof the Greenland ice margin, which has yet to beadequately defined in the moraine record (Weidicket al. 1990; Anderson et al. 1999).

Concomitant with changes in extent of Inland Ice inthe Kangerlussuaq area over the past 5000 years hasbeen the development of extensive aeolian sand se-quences proximal to sandurs and regional loess deposi-tion on adjacent upland surfaces (Willemse et al. 2003).Radiocarbon ages for the aeolian sand record showpeak particle influx rates at c. 4850�3700, 3250�2800and 2200�1800 cal. yr BP and a noticeable increasebetween 1500 and 400 cal. yr BP, associated withrejuvenation of the proglacial sandur system. Loessdeposition on adjacent upland surfaces has been nearlycontinuous for the past 5000 years and shows similarpeak influx rates as the aeolian sand record (Willemseet al. 2003). Lake sediment records from west Green-land also show elevated sediment influx rates at c.4000 cal. yr BP, which may herald the start of neogla-ciation on west Greenland (Anderson et al. 1999).

The expansion of glaciers in the Little Ice Age (LIA),c. AD 1300�1900, is well recognized across the north-ern hemisphere (Grove 1988, 2001). In many Arctic

DOI 10.1080/00173130601173301 # 2007 Taylor & Francis

areas, particularly those influenced by warm waters ofNorth Atlantic origin, the LIA is often the mostextensive advance since the Last Glacial Maximum(LGM) (e.g. Svendsen & Mangerud 1997; Lubinskiet al. 1999; Nesje et al. 2001). Historic records indicatethat the glacier position during the late LIA at c.AD 1880 in the Kangerlussuaq area was equal to orgreater than the prior maximum position in theHolocene because of the apparent absence of olderneoglacial moraines (Weidick 1984). The timing of LIAevents on Greenland has been clarified through ice-core studies, which show decreased accumulationassociated with cooling (c. 0.58C) at the GISP2 coresite centred at AD 1200, 1500 and 1800 (Meese et al.1994; Dahl-Jensen et al. 1998). Other ice-core recordsfrom northern Greenland show 1�28C cooling betweenc. AD 1640 and 1720, and 1800 and 1860 (Fischer et al.1998).

Photogrammetric analyses and field studies of icemarginal areas south of Kangerlussuaq have documen-ted 150�500 m of retreat between AD 1942 and 1978(Gordon 1981). Recent moraines exposed and stabi-lized in the 20th century have yielded maximumRhizocarpon geographicum thalli of 9 mm, whereasouter moraines have supported thalli of 15��/50 mmin diameter. These thalli diameters, assuming anunrealistic linear growth rate (Werner 1990), yieldmoraine ages of c. AD 1745, 1850, 1855, 1930 and1944, similar to young lichen-based ages for analogouslandforms inland of Kangerlussuaq (Ten Brink &Weidick 1974; Ten Brink 1975). However, radiocarbonages of basal lake sediments and peats from within theinner-most moraine sequence, adjacent to the InlandIce, indicate deglaciation by c. 6 kyr BP (van Tatenhoveet al. 1996; Bennike & Bjorck 2002). The lichen-basedages are gross underestimates because growth curvesare asymptotic by c. 400 years ago (Werner 1990).Thus, uncertainty remains on what landforms reflect

the final retreat from the LIA maximum and whetherthere is a geomorphic record of earlier neoglacialevents.

Knowledge of recent marginal changes of the Green-land Ice Sheet is particularly relevant to satellite-basedaltimetry surveys indicating thinning of the ice sheetperiphery below 1500 m in the past c. 10 years (Krabillet al. 2000; Johannessen et al. 2005). A landmark studyby Weidick (1968) documented historic fluctuations ofc. 500 inland and local glacier margins in west Green-land. Details were provided for 135 inland lobesbetween 608 and 748 north, of which 94% showedretreat since the mid-19th century, interrupted byminor halts and re-advances around AD 1880 and1920. Retreat accelerated post-1930s and particularlyin the last decade in the 20th century (Greve 2000;Krabill et al. 2000; Abdalati & Steffen 2001; Johan-nessen et al. 2005). The net retreat of inland ice lobes ofthe Greenland Ice Sheet since the historic maximum inthe 18th and 19th centuries has been 1�2 km, withcalving margins diminished by ]/5 km (Weidick 1968;Abdalati & Steffen 2001).

This study focused on the ice marginal area forIsunguata Sermia, approximately 26 km northeast ofKangerlussuaq, which is similar to many glacier lobesalong the west Greenland Ice Sheet margin, observedfrom Landsat images (Figs 1, 2A). We defined, throughcareful mapping, intensive measurement of lichens onice-scoured bedrock surfaces, stranded erratics andboulders on moraines, multiple LIA limits. We identi-fied a potential neoglacial limit c. 2000 cal. yr BP basedon stratigraphic and geomorphic superposition ofmoraines and optically stimulated dating of aeoliansilt that caps moraines of the Isunguata Sermia margin.This assessment of neoglaciation variation provides acontext within which to evaluate changes in theGreenland margin in the late 20th century.

Fig. 1. A. Greenland Ice Sheet. B. The Kangerlussuaq area showing the Inland Ice margin and Isunguata Sermia lobe, which were the focus ofthis study. The inner Ørkendalen moraine system is also shown, deposited c. 6 kyr BP (van Tatenhove et al. 1996).

342 Steven L. Forman et al. BOREAS 36 (2007)

Geochronology

Lichenometry

Chronological control was provided by lichenometry(Locke et al. 1979) on recently exposed bedrock anddeposited moraines and out-wash immediately adja-cent to the Inland Ice. We usually measured�/50 lichen

diameters (measurement precision of 0.5 mm) perlandform with the maximum diameter of an inscribedcircle method (Locke et al. 1979), with a bias towardsthe largest lichens present. The ubiquitous yellow-green crustose lichen Rhizocarpon sp. was measuredand has been used previously in west Greenlandto constrain the age of moraine sequences (Beschel& Weidick 1973; Ten Brink 1973; Gordon 1981).

Fig. 2. A. Landsat thematic image2�/ of the Isunguata Sermia InlandIce margin. The dark reflector atthe ice edge is an ice marginaldebris-laden zone. The noticeablebright reflector beyond the icemargin is recently depositedmoraines, many ice-cored. Noticethe location of the stratigraphicstudy site Ørkendalen drift 1(OK1). B. Enhanced subsection ofaerial photograph 886 L 846(Danish Polar Center), taken on9th July 1985. The Little Ice Agelimit is shown, which is a light tonearea composed of mostly ice-coredmoraines and bedrock trimline.Notice the location of thestratigraphic study siteØrkendalen drift 2 (OK2).

BOREAS 36 (2007) Little Ice Age and neoglacial landforms at the Inland Ice margin, west Greenland 343

Identifying Rhizocarpon sp. to species and subspecieslevels is often difficult (e.g. Innes 1986; Werner 1990)and different subspecies can have different growthrates. Pioneering observations on lichen ecology haveidentified the primary successional species R. super-ficiale, R. norvegicum, R. disporum and R. jemtlandicumon gneissic surfaces of west Greenland (Beschel &Weidick 1973). These species are often referred to asRhizocarpon sp. and are assumed to have similargrowth rates (cf. Ten Brink 1973; Gordon 1981). It isunknown for the measured lichens from west Green-land whether the faster growing Rhizocarpon subspe-cies section Alpicola occurs, which shows a 10�15%faster growth rate compared with corresponding sub-species of Rhizocarpon on Spitsbergen (Werner 1990).Available evidence indicates that this subspecies rarelypredominates on Arctic landscapes (e.g. Innes 1986;Werner 1990). We also measured the black, fibroussubfructicose lichen Pseudephebe minuscula at onelocality (Fig. 3). Pseudephebe minuscula has a growthrate two to five times that of Rhizocarpon sp. (e.g.Miller 1973; Werner 1990).

The species of lichen measured (Rhizocarpon sp.) andthe measurement scheme (diameter of the maximuminscribe circle) were consistent with previous studies inwest Greenland (Beschel & Weidick 1973; Ten Brink1973; Gordon 1981) and provided the data needed

to construct a time-calibrated lichen growth curve(Fig. 4). The colonization time of Rhizocarpon sp. ongneissic erratics in west Greenland has previously beenassumed to be c. 5 years, based on studies of morainesdeposited in the 20th century (Gordon 1981), althoughour studies suggest potentially longer times of upto c. 30 years. LIA gneissic bedrock surfaces showmaximum Rhizocarpon sp. diameters of 16 mm,

Fig. 3. A cross-section from the edge of the Greenland Ice Sheet across a Little Ice Age (LIA) trimline showing the maximum size distributionof the lichen Rhizocarpon sp. and Pseudephebe minuscula on ice-scoured bedrock and overlying erratics.

Fig. 4. Preliminary Rhizocarpon sp. growth curve for west Greenlandcompared with the corresponding lichen growth curves from westSpitsbergen and Baffin Island (modified from Werner 1990).


3�4 mm larger than corresponding lichens on gneissicerratics on bedrock and correlative out-wash deposits(Figs 3, 5). Colonization times are probably shorter(5/10 years) for bedrock because of the inherentstability compared with boulders on ice-cored mor-aines, and many bedrock surfaces are potentially wetterand warmer microenvironments conducive to lichengrowth (Innes 1986). The difference in maximum lichensize between bedrock and overlying erratics of 4 mmindicated that the initial lichen colonization of bedrockmay have preceded erratics by up to 30 years (cf. TenBrink 1973).

The early ‘great growth period’ (cf. Miller 1973) forRhizocarpon sp. thalli on west Greenland is particularlywell documented. Photographic calibration of a 12-year growing period (AD 1958�1970) yielded a 2-mmgrowth of thalli (Ten Brink 1973) and the historicglacier retreat between AD 1932 and 1978 resulted inRhizocarpon sp. 9 mm in diameter (Gordon 1981). Thelater reduction in Rhizocarpon sp. growth rate isconstrained by one data point. A maximum lichendiameter of 22 mm was from a moraine that dammed alake, and basal organic matter (Salix leaves and grassfragments) from this lake yielded a 14C age of 3309/

75 BP (UW-180) (Ten Brink 1973). The correspondingcalendar corrected age range (one sigma) is 520�330 BP(Stuiver et al. 1998) and this age may be an over-estimate by c. 5�30 years, reflecting the stabilizationtime of an ice-cored moraine to host lichen coloniza-tion.

The calibration curve for west Greenland is similar tobetter-constrained lichen growth curves for BaffinIsland (Miller & Andrews 1972) and west Spitsbergen(Werner 1990; Fig. 4), although there are significantdifferences in climate (Table 1). The rate of initial lichengrowth during their first c. 100 years is remarkablyconsistent amongst west Greenland, Baffin Island and

west Spitsbergen, providing a measure of confidence forderived ages for maximum thalli diameter of B/15 mm.This nascent lichen growth curve for west Greenlandprovides an age control for the past c. 300 years, withapproximately 20% precision (Werner 1990), which mayimprove with additional calibration points.

Luminescence dating

Aeolian deposits, which are ideal for luminescencedating, occur on upland surfaces and adjacent tosandurs associated with the Inland Ice on west Green-land (Willemse et al. 2003). We identified 0.5-m thickaeolian silt that often caps moraines and drift surfaces(Fig. 6). Luminescence dating of this regional loessshould provide a close minimum-limiting age onemplacement of the subjacent moraine. Previous studieshave indicated that loess deposition on upland surfacesdistant from sandur source areas has been nearlycontinuous for the past 5000 cal. yr BP (Willemseet al. 2003).

A variety of Optically Stimulated Luminescence(OSL) methods was employed to date the loess thatcaps moraines (Table 2). The fine-silt fraction (4�11 mm) was isolated for dating, which has an air fallorigin, maximizing light exposure. Initially, a multiple-aliquot additive-dose method was used (Forman& Pierson 2002) to date the loess. Subsequently,a single-aliquot regeneration protocol was used todate two of the samples (Murray & Wintle 2003; Olleyet al. 2004). The protocols included initial excitationwith infrared light (IR), preferentially accessing thefeldspar signal, and then subsequently with blue light(BL) excitation, reflecting the quartz component. OSLages by these methods overlapped at two sigma andthus were statistically identical (Table 2).

Geomorphic setting

Analysis of remotely sensed images revealed abundantice-cored, steep-sided moraines and a distinct trimlinewithin 1�2 km of the present ice margin for many areasof west Greenland (Csatho et al. in press), potentiallydating from the 19th or 18th centuries (Weidick 1968;Weidick et al. 1990; Humlum 2000). This ‘trimline’zone appears as a distinct bright reflector on Landsatimages and is traceable for hundreds of kilometres(Fig. 2A). Our field research concentrated on a 1-kmstretch of the Isunguata Sermia margin that exhibited adistinct trimline and a correlative moraine sequence(Fig. 2B).

Bedrock trimline

The trimline extends 50�200 m beyond the present icemargin and is well demarcated by bare, striated andmammalated gneissic bedrock with perched erratics

Fig. 5. The size distribution of the lichen Rhizocarpon sp. for LittleIce Age and neoglacial landforms near the Isunguata Sermia InlandIce margin.


(Fig. 7). There is an abundance of erratics ranging fromlarge boulders to small gravel. A number of the largerboulders are classically perched on smaller cobbles.Beyond this margin is an older diamicton with erraticboulders, capped by loess that hosts dense vegetationand exhibits periglacial features, such as ice-wedgepolygons and solifluction lobes.

The trimline zone is subdivided by the presence andtype of lichens (Fig. 3). In a 5�25-m strip immediatelyadjacent to the ice sheet is a bare bedrock zone with aclear absence of lichens. An intermediate zone exhibitsonly P. minuscula, with a maximum diameter of 18 cm,and 5/5-mm diameter Rhizocarpon sp. The outermostlichen zone shows both P. minuscule and Rhizocarponsp. with respective maximum diameters of 33 and16 mm. Erratics in the outer zone host smallerRhizocarpon sp. thalli of 12 mm (Figs 3, 5).

Moraine sequence

Three distinct moraines were identified in the easternpart of the field area (Fig. 8). The oldest and mostdistal moraine from the Inland Ice edge is a low (1�3-m high) well-vegetated arcuate ridge, with erraticboulders. Boulders are mostly covered by lichens, withRhizocarpon sp. thalli that exceed 40 mm indicating an

age of c. �/400 years (Fig. 5). Excavations into themoraine ridge (Fig. 8) revealed 25�50-cm thick, verywell sorted, loam to sandy loam (Fig. 6), interpreted asaeolian silt with soil development in the upper 20 cm.This aeolian silt is in sharp contact with underlyingglacial diamicton or out-wash gravels, with no evidencefor pedogenesis or cryogenic activity on the diamictonsurface. OSL dating of this aeolian silt yielded ages of13809/155, 14509/125 and 15209/165 years (Fig. 6),providing a close but minimum limiting age on thesubjacent diamicton. Another exposure (neoglacialmoraine 2; NE2) of this aeolian silt over a diamictoncloser to the Inland Ice edge (Fig. 2B) yielded OSLages of 16509/140, 19509/165 and 21309/200 years(Fig. 6). Farther west,�/2 km from the Inland Ice edge,the basal aeolian silt capping moraines (Ørkendalendrift 1 and 2 sections; OK1 and OK2; Fig. 2A, B)yielded older OSL ages of 29309/260 and 29259/235years (Fig. 6).

There are two major moraines in close proximity tothe Inland Ice edge (Fig. 8). The outermost moraine isnot ice-cored and has an out-wash plain graded to themoraine margin and incised by the present meltwaterstream. This moraine is 2�4 m high, partially vegetatedand hosts Rhizocarpon sp. thalli with a maximumdiameter of 12 mm; the associated out-wash has similar

Table 1. Climate data for Arctic sites relevant for lichen growth studies.

LocationJanuary meantemperature (8C)

July meantemperature (8C)

Mean annualtemperature (8C)

Mean annualprecipitation (cm) Source

Søndre Strømjord (Kangerlussuaq),Greenland (678N, 518W)

�/20.9 10.5 �/6.3 14.5 Weidick et al. (1992)

Godthab, Greenland (648N, 528W) �/5.8 6.6 �/0.8 83.9 Weidick et al. (1992)Baffin Island, Broughton Island

(67833?N, 63847?W)�/23.1 4.4 �/11.3 28.7 Werner (1990)

Ny Alesund, Spitsbergen(78856?N, 11853?W)

�/12.8 5.2 �/5.8 38.5 Werner (1990)

Fig. 6. Stratigraphic sections in neoglacial moraines and Ørkendalen drifts, west Greenland.


lichen diameters (Fig. 5). The innermost moraine isice-cored, steep sided (�/258), 20�30 m high and hostsno lichens. This moraine exhibits three distinct sub-crests and is graded to the current out-wash plain(Fig. 8).

Moraine chronology for the Isunguata SermiaInland Ice margin

A well-vegetated moraine within 1 km of the Isun-guata Sermia Inland Ice margin hosts Rhizocarpon sp.thalli�/40 mm, indicating an age of �/400 years, and iscapped by c. 50 cm of aeolian silt. OSL ages ofbetween c. 1500 and 2000 years of this aeolian siltprovide a close, but minimum, limiting age on theunderlying moraine. Aeolian silt capping glacialdiamicton surfaces beyond this neoglacial limit withinthe Ørkendalen moraine sequence (van Tatenhove

et al. 1996) yielded older ages of c. 3000 years. Weconclude that there is a close chronological associationbetween the basal loess OSL age and subjacentdiamicton because of the sharp contact between thesesediments and a noticeable lack of cryogenesis orweathering on the diamicton surface, indicating lim-ited (c. B/1 kyr BP) exposure time. This difference inage for the aeolian silt capping moraine surfacesindicates that regional loess deposition was initiatedby c. 3 kyr BP, with the moraine surface closest to theInland Ice edge being vacated by at least c. 2000 yearsago. Aeolian silt deposition in the Kangerlussuaq areaon upland surfaces associated with mires supposedlyreflects enhanced sandur sources coupled with winteraridity and less frequent maritime cyclonic activity(Willemse et al. 2003). Accumulation of aeolian siltappears episodic, with two pronounced episodesbetween 4.9 and 3.5 kyr BP and 1.5 and 0.3 kyr BP,and with possible discrete centennial-to-decadal scale

Table 2. Optically Stimulated Luminescence data and ages for aeolian silt, Isunguata Sermia area, west Greenland.

Laboratory ID (UIC) 1555 1556 1557 1558

U (ppm)a 0.69/0.1 0.89/0.1 0.69/0.1 0.79/0.1Th (ppm)a 1.49/0.1 4.99/0.1 2.29/0.1 2.29/01K2O (%)a 1.579/0.02 1.809/0.02 1.659/0.02 1.629/0.02a-valueb 0.089/0.01 0.089/0.01 0.099/0.01 0.089/0.01Cosmic dose (mGray/yr)c 0.229/0.02 0.219/0.02 0.229/0.02 0.219/0.02Dose rate (mGray/yr) 1.849/0.07 2.549/0.12 2.199/0.09 1.819/0.07MAAD De (Grays)d 2.809/0.02 7.559/0.03 4.269/0.01 5.289/0.02SAR-IR De (Grays)e 2.669/0.09 3.389/0.11SAR-BL De (Grays)e 2.549/0.21 4.659/0.22MAAD age (years) 15209/165 29309/260 19509/165 29259/235SAR-IR age (years) 14469/124 16509/140SAR-BL age (years) 13809/155 21309/200

aU, Th and K2O values from ICP-MS through Activation Laboratory Ltd, Ontario, Canada.bAlpha efficiency factor as defined by Aitken & Bowman (1975).cFrom Prescott & Hutton (1994).dMultiple-aliquot additive-dose (MAAD) method on the fine-grained polymineral fraction under infrared excitation (after Forman & Pierson2002).eSingle-aliquot regeneration (SAR) method under initial infrared (IR) stimulation and subsequent blue (BL) excitation for 30 discs (Murray &Wintle 2003; Olley et al. 2004).

Fig. 7. A photograph of theGreenland Ice Sheet margin andLittle Ice Age (LIA) trimline (17thJune 2004).


events at c. 3.2, 2.8, 2.2 and 1.9 kyr BP. Lake coresfrom the Kangerlussuaq area show peak accumulationof aeolian sediments from 4.5 to 2.5 kyr BP, witha discrete event at c. 2 kyr BP (Willemse 2002). Theinitiation of aeolian silt deposition on dry moraineand drift surfaces within 2�3 km of the present InlandIce margin may herald additional and proximalglaciofluvial sedimentary systems, with neoglacialexpansion c. 4 kyr BP on west Greenland (Andersonet al. 1999), which may be sources for the aeoliansediment.

Because of the limited moraine record it is difficultto gauge whether this neoglacial event at c. 2000�3000 BP reflects a regional climate-driven response ofthe Inland Ice or local glaciological conditions. Sup-portive evidence for the magnitude and timing of thisneoglacial event are the anomalously high verticalcrustal movements for west Greenland deduced fromcontinuous global positioning system measurements,which is most compatible with an Inland Ice advance

and retreat of approximately 50 km in the past 3�4 kyrBP (Wahr et al. 2001). Pollen records from lakes onwest Greenland show major cooling at c. 2.5 and 2 kyrBP (Funder & Fredskild 1989). In turn, lake sedimentrecords from southern Greenland reveal a markeddecrease in temperature-controlled diatom productivitybetween c. 2 and 1.5 kyr BP, 1 and 0.8 kyr BP and 0.3and 0.1 kyr BP (Kaplan et al. 2002). Two neoglacialadvances of the Isunguata margin are consistent withthis cooling, the oldest, between 2 and 1.5 kyr BP,defined by the probability density function (Singhviet al. 2001) for the OSL ages on associated aeolian silt,and the youngest, c. 100 years old, based on Rhizo-carpon sp. diameters (Fig. 9). The available proxyclimate records indicate pronounced neoglacial coolingin west and south Greenland starting c. 3 kyr BP,coincident with the start of aeolian deposition in thefore of the Isunguata ice margin, and peak deteriora-tion at c. 2 kyr BP, the approximate age of theneoglacial moraine. This advance is probably of similar

Fig. 8. Photograph of Little IceAge (LIA) and neoglacial morainesand associated out-wash surfacesand interpreted line drawing (20thJune 2004). The numbers (1, 2, 3and 4) are the moraine crests forthe LIA moraine sequence; 1 is theyoungest, 4 the oldest.


extent as the maximum LIA limit because of theapparent paucity of preserved neoglacial moraines (cf.Weidick 1984).

The well-defined trimline and outer non-ice-coredmoraine within 1 km of the Inland Ice edge of theIsunguata Sermia margin that host Rhizocarpon sp.thalli with maximum diameters of 12�16 mm yieldcorresponding ages between 80 and 120 years, coin-cident with the latest LIA advance and retreat in the late19th (1880) and early 20th centuries (Weidick 1968,1984; Gordon 1981). Ice-cored moraines and bedrocksurfaces with sparse lichen cover within a few tens tohundreds of metres of the Isunguata Sermia Inland Iceedge indicate a significant retreat of the margin in thepast c. 50 years. A lichen barren zone 5�25 m wideclosest to the ice margin reflects a retreat in the past c. 10years. However, there is marked variability in the InlandIce margin (Weidick 1991), with the nearby RussellGlacier advancing 7 m/yr between 1968 and 1999,overriding LIA moraine ridges (Knight et al. 2000).

Conclusions

A neoglacial moraine hundreds of metres beyond theLIA limit was identified in the foreground of theIsunguata Sermia Inland Ice margin on west Green-land. Rhizocarpon sp. thalli �/40 mm indicate a mini-

mum limiting age of�/400 years, whereas OSL ages onaeolian silt capping the moraine yield closing limitingages of c. 2000 BP. Aeolian sedimentation appears tohave commenced at or prior to c. 3000 BP and iscoincident with pronounced cooling deduced frompalaeolimnologic records from west and southernGreenland (Funder & Fredskild 1989; Andersonet al. 1999; Kaplan et al. 2002). A neoglacial event atc. 2000 BP is probably of similar magnitude as the LIAmaximum, because of the paucity of preserved moraineremnants.

Well-preserved moraines and trimlines within 1 kmof the Greenland Inland Ice margin reflect advancesand retreats associated with the latest phase of the LIAin the late 19th century and into the 20th century. Thepresence of ice-cored moraines, bedrock surfaces withRhizocarpon sp. thalli with a maximum diameter of5 mm, and lichen-free zones immediately adjacent tothe Inland Ice edge, indicate considerable retreat (upto 1�2 km) of the Isunguata Sermia lobe over the past50 years, coincident with a thinning of peripheral icebelow 1500 m altitude over the past decade (Krabillet al. 2000; Johannessen et al. 2005). Thus, thedocumented thinning and retreat of the Greenlandmargin in the 20th century reflects processes initiatedwith the LIA retreat. These field observations providechronological calibration of the moraines and trimlinesreadily observable by Landsat and ASTER images andenable a better understanding of the dynamics of theGreenland Ice Sheet in the 20th and 21st centuries(Csatho et al. in press).

Acknowledgements. � This research was supported by NASA awardNNG05GD33G. We thank the personnel of Kangerlussuaq Interna-tional Science Support for facilitating the field research and the NewYork Air National Guard for transport to Greenland. J. Gomez andJ. Pierson provided valuable assistance for luminescence dating andstatistical analysis. Reviews by D. H. Roberts, A. Bluszcz and J. A.Piotrowski are much appreciated.

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Documents

Little Ice Age and neoglacial landforms at the Inland Ice margin, Isunguata Sermia, Kangerlussuaq, west Greenland