Geomorphology 246 (2015) 433–444

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Geomorphology

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Holocene cirque glacier activity in Rondane, southern Norway

Bjørn Christian Kvisvik a,b,d,⁎, Øyvind Paasche c, Svein Olaf Dahl b,d

a Uni Climate, Uni Research AS, Allégaten 55, NO-5007 Bergen, Norwayb Bjerknes Centre for Climate Research, Bergen, Norwayc Bergen Marine Research Cluster, Prof. Keysersgate 8, NO-5020, University of Bergen, Norwayd Department of Geography, University of Bergen, Fosswinckelsgate 6, NO-5020 Bergen, Norway

⁎ Corresponding author at: Department of GeogrFosswinckelsgate 6, NO-5020 Bergen, Norway.

E-mail address: bckv@cowi.no (B.C. Kvisvik).

http://dx.doi.org/10.1016/j.geomorph.2015.06.0460169-555X/© 2015 Elsevier B.V. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 18 February 2015Received in revised form 27 June 2015Accepted 29 June 2015Available online 3 July 2015

Keywords:Cirque glacierRondaneLake sedimentsCatchment samples

Skriufonnen is a small cirque glacier (0.03 km2) in the continentalmountains of Rondane in southern Norway. Atpresent, it is the only glacier in Rondane, and very little is known about Holocene glacier fluctuations in thisregion. Direct observations of the glacier began in 2002, since which time Skriufonnen has been in a state ofstrong decline. In order to provide a temporal context, past glacier fluctuations were reconstructed based on aseries of short HTH gravity cores (n = 8) and long piston cores (n = 6) retrieved from three downstream lakesof Skriufonnen. The cores were analysed for selectedmagnetic properties (χbulk, ARM, SIRM, 77 K/293 K), organiccontent (LOI), and geochemical trace elements. Soil catchment samples (n = 6) were collected along a transectrunning from the three lakes up to the present glacier terminus. Bulk susceptibility (χbulk) measurements showthat the finest fractions systematically return the highest values and that ferromagnetic minerals are depletedwith distance to the glacier front. Thismeans that periods dominated by paramagneticminerals indicate very littleor no glacier activity, whereas intervals with more ferromagnetic minerals suggest increased glacier activity. Thequantitative core analyses indicate that Skriufonnen existed prior to 10,200 b2k (years before A.D. 2000) anddisappeared ~10,000 b2k. No glacier activity is recorded from c. 10,000 b2k until the glacier reoccurred at theonset of the local Neoglacial period, c. 4000 b2k. The glacier attained its maximum extent between 3200 and2400 b2k and during the end of the ‘Little Ice Age’ (LIA) c. A.D. 1800. Neoglacial fluctuations of Skriufonnen arein line with shifts in local summer temperatures and show a delayed Neoglacial inception compared to westernNorway.

© 2015 Elsevier B.V. All rights reserved.

1. Introduction

Glaciers are unevenly distributed in southern Norway, with large icecaps dominating west of the major water divide and smaller cirque gla-ciers in the eastern and central regions. High-altitude cirque glaciersfound up to c. 2300 m asl in the eastern region are mainly polythermal(partly frozen to the substratum), whereas ice caps along the westerncoast with low-altitude outlet glaciers down to 300 m asl are generallytemperate (all basal ice is at the melting point) (Andreassen andWindsvold, 2012).

Southern Norway has a strong climatic gradient from the maritimewestern coast with increasing continentality eastward. This is reflectedin an increase in the equilibrium-line altitude (ELA) of modern glaciersfrom c. 1300 m asl on the western coast to c. 2200 m asl in easternJotunheimen (Liestøl, 1967; Lie et al., 2004). Ålfotbreen (61°44′N, 5°39′E) in the west receives c. 4000 mm water equivalent (w.e.) at the ELAcompared to Gråsubreen (61°39′N, 8°37′E) in eastern Jotunheimen,

aphy, University of Bergen,

which receives only c. 750 mmw.e. at the ELA (Liestøl, 1967). Becausethis climatic gradient results from the topographic barrier of the centralmountain ridge and the Westerlies, we can plausibly assume that it hasbeen relatively stable throughout the Holocene with respect to its effecton the glaciers, although few systematic investigations have taken place.

Skriufonnen is the easternmost glacier in southern Norway and islocated in the Rondane mountains (61°53′N, 9°49′E) 100 km east ofJotunheimen (Fig. 1E). Rondane is one of the most continental parts ofNorway with local precipitation of only 200–400 mm w.e./y, most ofwhich is falling during summer (www.met.no). Presently, Skriufonnenis the only glacier in Rondane with an ELA of 1450 m asl, and no previ-ous studies of glacier variability exist for the region.

During recent decades, a number of continuous high-resolutionHolocene glacier reconstructions have been published based on glacierswest of the major water divide (e.g., Karlén and Matthews, 1992; Dahland Nesje, 1996; Bakke et al., 2005; Nesje et al., 2008; Vasskog et al.,2012). This detailed coverage is in stark contrast to the few existingcontinuous reconstructions east of the watershed in southern Norway(e.g., Sandvold et al., 2001; Lie et al., 2004; Matthews and Dresser,2008; Støren et al., 2008), of which all are from the eastern part ofJotunheimen (Fig. 1E). The lack of glacier reconstructions fromRondane

A

B

C

D

E

Fig. 1.Pictures of Skriufonnen glacier during three selectedyears: (A) 2005, (B) 2006, and (C) 2011. (D) Image of the frontal part of the glacier in 2002. Sincemonitoring started in2002, theglacier has retreated. (E) Thenewglacier record fromRondane is compared to glacier reconstructions from Jotunheimen andwesternNorway (see Fig. 10). Dotted line represents themainwater divide in southernNorway, while numbers represent siteswith data presented in Fig. 10 (1=Velle et al., 2010; 2= Støren et al., 2012; 3=Vasskog et al., 2012; 4=Matthews andDresser, 2008); and 5 = the location of Folgefonna (Bakke et al., 2005).

434 B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

has consequently prevented comparative analysis of changing glacierand climatic gradients across the watershed during the Holocene.

The main objective of this study is therefore to reconstruct glaciervariations at Skriufonnen in Rondane for the last 10,000 years.Skriufonnen sends sediment-laden meltwater flowing into andthrough three downstream lakes. Sediment cores from all threelakes, in combination with surface soil catchment samples, form thebasis for this glacier reconstruction.

We compare and discuss potential similarities and differences inglacier variability in Rondane with Holocene climate and glacier fluctu-ations in western Norway and eastern Jotunheimen at multidecadal tocentennial time scales.

2. Study area

2.1. Topography

Wide open valleys, fluvial gorges, and arêtes characterize thelandscape of Rondane, with 10 peaks exceeding 2000 m. With a few

exceptions, the glacial troughs are poorly developed, whereas maturecirques left by local glaciers are cut deep into the mountains. The mainreason for this is suggested to be the action of cold-based ice sheetsduring major glaciations and polythermal and/or temperate cirqueglaciers during interstadials or cold spells during interglacial periods(Dahl et al., 1997; Kleman, 2008). Lateral drainage channels — largeglaciofluvial and glaciolacustrine landforms that were deposited andformed by meltwater from past decaying ice sheets — are common inthe area (Mannerfelt, 1940, 1945; Strøm, 1945; Gjessing, 1960). Remnantsof moraines exist but are scarce. Landforms such as rock glaciers (relict orinactive) are present in all but a few cirques (Barsch and Treter, 1976;Kvisvik, 2003) located above 1450 m altitude, which is probably close tothe local permafrost limit (Isaksen et al., 2007).

2.2. Study area

Skriufonnen is a small glacier in a north-facing cirque along anuppertributary valley leading toDørålen, themain valley in northernRondane(Fig. 2). Skriufonnen has retreated rapidly since monitoring began in

Fig. 2.Aerial photo showing the study site in Rondane, east-central Norway, including the Skriufonnen glacier and the downstream lakes that were cored (orange crosses). Catchment soilsampling sites are shown by red triangles. Sediment-laden meltwater drains from the glacier and through two lakes (Upper Dørålvatn and Middle Dørålvatn) before entering LowerDørålvatn. A western tributary branch also enters the lower lake. Cores from Lower Dørålvatn (square outlined in a white dotted line) are shown in the inset. (For interpretation of thereferences to colour in this figure legend, the reader is referred to the web version of this article.)

435B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

2002 (total glacier areawas c. 0.06 km2 in 2004 and c. 0.03 km2 in 2011),and at present Skriufonnen is best defined as an ice apron with little orno internal deformation (Fig. 1A–D). However, a frontal moraine andstriations on exposed bedrock in the glacier foreland suggest thatformer extentswere larger (Fig. 3). A lobe of grey, partly eroded bedrockin front of Skriufonnen with only small lichens of the speciesRhizocarpon geographicum defines the 0.12-km2 large area of the lastglacier advance (Figs. 1, 2, and 3).

Downstream of Skriufonnen are three small and shallow lakes:Upper Dørålvatn (alt. 1300 m), Middle Dørålvatn (alt. 1273 m), andLower Dørålvatn (alt. 1266 m) (Fig. 2). Scattered superficial depositsand exposed bedrock dominate the area between Upper Dørålvatnand Skriufonnen (Fig. 3). Seasonal meltwater originating fromSkriufonnen drains through this foreland, whereas bushes and grass-land cover the shores around the two lower lakes. Mt. Vassberget(alt. 1855 m) is located just east of Skriufonnen, whereas a large andundulating plateau at altitudes of 1700–1800 m covers the area justsouth of Skriufonnen.

2.3. Bedrock

The bedrock in Rondane is dominated by arkosic sparagmite,an Eocambrian sandstone that partly consists of metamorphosedsandstone and conglomerates with a relatively high content of quartzand feldspar (Siedlecka, 1984; Sigmond et al., 1986). The amount ofquartz varies between 80% and 87% (Strøm, 1945; Holmsen, 1963),while feldsparmakes upmost of the remainingminerals. The sparagmiteis relatively resistant to chemical weathering, making the soil rich inquartz and dry and sandy.

2.4. Climate

The climate in Rondane is continental, with a mean annual air tem-perature of −1.5 °C at 1000 m and a mean summer (May–September)air temperature of 6.8 °C. The estimated mean winter (October–April)precipitation at 1000 m is 176 mm w.e./y based on the records of threenearby climate stations, Fokstua (alt. 974 m), Folldal (alt. 709 m), andHøvringen (alt. 935 m). Southwesterly winds predominate in Rondanethroughout the year (Bjørbæk, 1993) and have a seemingly large impacton the spatial distribution of leeward snow accumulation. However,occasional snow-bearing winds from the S-SE in wintertime are ofgreat local importance. Local snow depths can be several metres,although annual variations are considerable.

3. Methods

The reconstruction of Holocene glacier fluctuations presented belowis based on a combination of geomorphological mapping (Fig. 3), whichwas carried out during the field seasons of 2002, 2004, 2007, and 2009,and soft sediment analysis. The HTH (Hans Tore Hansson) and pistonsediment cores retrieved from the lakes were subject to a suite of anal-yseswith emphasis onmagnetic and geochemical properties, aswas thecase for the surface soil sediment samples that were collected along atransect running from the glacier snout and down to the lowermostlake (Figs. 2, 3, and 4). Plenty of aquatic mosses in Lower Dørålvatnmade analyses of organic content and grain size in the cores challeng-ing; consequently, the organic content and grain size of most coresfrom this lake were not measured. Age–depth relationships in Upperand Lower Dørålvatn were determined by combining 210Pb dating and20 accelerator mass spectrometry (AMS) radiocarbon dates.

Fig. 3. Geomorphologic map of the study area. The height interval of transect A1–A2 is shown in Fig. 4A. Many of the landforms and surficial deposits are remnants of the last, or evenprevious, deglaciations.

436 B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

3.1. Coring

Two HTH cores (DVH104 and DVH204) were retrieved from LowerDørålvatn in August 2004, and the upper 3 cm of core DVH204 wasdated by 210Pb, while six AMS radiocarbon dates were obtained fromthe lower levels of the cores (Table 1). Prior to the first coring campaign,the lake was surveyed using an echo sounder (Garmin Fishfinder 160).In August 2008, an additional six HTH cores were retrieved (Fig. 2). Ofthese, three (DVH108, DVH208, and DVH608) were from the smallbasin in Lower Dørålvatn, one was from the inlet of Lower Dørålvatn

A

Fig. 4. (A) Surface soil samples were collected along a transect running from the glacier snoutsurface soil samples. The overall pattern is reproduced in all samples and is very consistent. Fgrain-size fractions. The black circle indicates the mean χbulk LIA values for piston core sam(DVP509). Note the drop in χbulk from catchment sample S411 to S311 caused by sedimentat

(DVH308), one was from Middle Dørålvatn (DVH408), and one wasfrom Upper Dørålvatn (DVH508).

Investigating sediment depths in the three lakes with a metal rodrevealed up to 3 m of sediment in Lower and Upper Dørålvatn. Duringawinter field campaign inMarch 2009,five piston coreswere retrieved:one from Upper Dørålvatn (DVP609) and four from Lower Dørålvatn(DVP109, DVP209, DVP409, and DVP509) (Fig. 2). A piston corer with110-mm-diameter PVC tubes (Nesje, 1992) operated from a 2-m-highrig was used to obtain in excess of 3 m of sediment. The sedimentcores were split into 1.5-m sections andwere kept inside a cabin during

B

down to Lower Dørålvatn (transect shown in Fig. 3). (B) χbulk values and grain size foriner fractions are strongest and signal strength decreases nonlinearly toward the largestples in Upper Dørålvatn (DVP609), while the open circle represents Lower Dørålvatnion of material in Upper Dørålvatn.

Table 114C and 210Pb dates from Lower Dørålvatn (DVH104, DVH204, and DVP509) and Upper Dørålvatn (DVP609).

Core Date Depth (cm) 14C-age (BP)210Pb error age

Calibrated age BP (2σ) Weighted mean(BP)

Weighted mean(b2k)

DVH104 Poz-13704 7 100 ± 30 270–20 140 190Poz-15933 13 385 ± 30 430–320 370 420Poz-10730 15 2455 ± 30 2710–2360 2530 2580Poz-13705 17 2615 ± 35 2840–2710 2770 2820

DVH204 Lead05 0.5 4 ± 9 0Lead10 1 11 ± 10 7Lead15 1.5 20 ± 13 16Lead20 2 37 ± 20 33Lead25 2.5 68 ± 51 64Lead30 3 131 ± 336 127Poz-10731 12 790 ± 30 760–670 720 770Poz-13706 16 680 ± 30 680–560 620 670

DVP509 Poz-31619 9.5 300 ± 30 460–300 380 430Poz-32070 9.5 545 ± 30 640–520 580 630ETH-45929 25.5 1360 ± 50 1340–1190 1260 1310Poz-31618 40.5 2520 ± 50 2750–2430 2590 2640ETH-45930 78.5 4190 ± 30 4840–4620 4730 4780Poz-31620 141.5 4980 ± 50 5890–5600 5750 5800Poz-31622 237 6420 ± 50 7430–7270 7350 7400ETH-45931 268.5 7810 ± 30 8640–8540 8590 8640ETH-45932 293.5 8550 ± 30 9550–9490 9520 9570Poz-31623 307.5 8890 ± 60 10,200–9770 9980 10,030

DVP609 ETH-45933 21.5 85 ± 25 260–30 140 190ETH-45934 123.5 745 ± 25 730–660 690 740Poz-31616 203.5 3350 ± 40 3690–3480 3580 3630Poz-31617 293.5 5050 ± 40 5910–5660 5790 5840

0

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Fig. 5. Rock magnetic properties for HTH core DVH104 indicate that ‘harder’ magneticminerals dominate the local input, as evident from the S-ratio. The exception is an anomalyrecorded at a depth of 15–17 cm, where input of more ferromagnetic minerals seems todominate. This peak is not reproduced in any other core except perhaps in DVH608, buthere values are much weaker. The general trend of ARM and σIRM is comparable, althoughvariations are observed, which apart from the shifting composition of magnetic mineralsmight be explained by changes in magnetic grain size.

437B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

fieldwork to prevent freezing. The sediment cores were later stored in acold room (+4 °C) prior to opening, splitting, and laboratory analyses.

3.2. Catchment soil samples

Surface soil samples were collected along the river in the drainagearea of Skriufonnen. Five samples were collected along the presentriver channel, which originates at the glacier terminus (Figs. 1D and 2)and runs through Upper, Middle, and Lower Dørålvatn. Samples S811and S411 were collected between the glacier and Upper Dørålvatn;the former was taken closest to the glacier front (Figs. 2, 3, and 4).Samples S111, S211, and S311 were all collected between Upper andMiddle Dørålvatn. No suitable sampling sites were located fartherdownstream. One additional nonglacial sample (S709) was collectedfrom the only western tributary stream, representing potential inputfrom the western part of the catchment.

All catchment samples were sieved into five different size classes(250, 125, 63, 38, and 20 μm) and dried prior to measurements of bulksusceptibility (χbulk). The χbulk measurements were carried out atroom temperature (293 K) and with the samples submerged in liquidnitrogen at 77K. A high ratio (max3.8) suggests that paramagneticmin-erals dominate the sample, whereas a lower ratio indicates an increas-ing amount of ferromagnetic particles (Lanci and Lowrie, 1997) and isdirectly related to the presence of freshly eroded bedrock. This can betransferred to the results of the lacustrine sediments where similarmeasurements are carried out as described in the following paragraph.

3.3. Laboratory analyses

3.3.1. Magnetic propertiesSediment samples subjected to magnetic analyses were measured

on split cores, in plastic bags and in plastic boxes (n = 680). Surfacesusceptibility on split cores was measured with a Bartington MS2Epoint sensor (2.8mmwide) at 0.2-cm intervals. Initialmagnetic suscep-tibility (χ) was determined using a KLY-2 induction bridge (sensitivity:4°–10−8 SI) and a Multi-Function Kappa Bridge (MFK1-FA) (2 × 10−8).As with catchment samples, susceptibility was measured at 293 and at77 K.

Additional magnetic properties were measured for DVH104 andDVH204 in order to get better control on variations in magnetic grainsize and mineralogy. A solenoid was used to 175 mT, followed by apulse magnetizer (Redcliffe, maximum field 4.2 T). Anhystereticremanent magnetization (ARM) was imposed with a 0.1 mT DC fieldand a 100 mT AC field in a 2G AF-demagnetizer. Isothermal remanentmagnetization (IRM) was measured on a Digico spinner (noise level:5°–10−7 Am−1). The ratio between IRM2T (occasionally referred to as‘saturation isothermal magnetisation’, SIRM) and the backfield of−100 mT is termed the S-ratio. It is indicative of changes in magneticmineralogywhere values close to 1.0 indicate the dominance ofmagne-tite (Fe3O4), whereas lower values suggest an increasing presence of‘harder’ minerals such as haematite (Fe2O3). Notably ARM follows thegeneral pattern of IRM (Fig. 5). The correlation is significant betweenARM and IRM3T (r2 = 0.62), which tends to indicate a relatively

438 B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

uniformmagnetic grain-size distribution. Average ARM/SIRMvalues are0.03 ± 0.01.

3.3.2. Geochemistry and organic matter contentThe split piston cores were also analysed on an Itrax XRF core

scanner (Croudace et al., 2006). Cores DVP209, DVP409, DVP509,and DVP609 were analysed on a chromium X-ray source tube at10-mm resolution and a 10-s counting period.

Cores DVH104, DVH204, DVH608, and DVP509 were analysed fororganic matter content by loss-on-ignition (LOI) (Dean, 1974; Heiriet al., 2001). Samples were mostly retrieved at 0.5-cm intervals with asyringe (1 cm3), but at 1-cm intervals with a cube-sampler (1 cm3)where aquatic mosses were in abundance, weighed (wet bulk density)and dried for 12 h at 105 °C before being weighed again (dry bulkdensity, DBD). Samples were then put in a furnace at room temperatureand heated to 550 °C for 1 h. Samples were then cooled in a vacuumdesiccator until room temperature was reached (c. 30 min) andweighed.

3.4. Dating, chronology, and age–depth modelling

Based on stratigraphic variations in MS and organic matter, samplesfor radiocarbon dating were chosen and then washed in distilled waterbefore being dried at 50 °C for 24 h. Samples were analysed at PoznanRadiocarbon Laboratory and at ETH in Zürich. Samples for 210Pb datingwere collected from HTH core DVH104 and analysed for the activity of210Pb, 226Ra, and 137Cs using gamma spectrometry at theGammaDatingCentre, Institute of Geography at the University of Copenhagen.The measurements were carried out on a Canberra low-backgroundGe-detector.

Consequently, the age–depth relationships are based on one 210Pbdated sequence from DVH104, six AMS radiocarbon dates in totalfrom DVH104 and DVH204, four AMS radiocarbon dates from DVP609and 10 AMS radiocarbon dates from DVP509. CLAM 2.2 was used toconstruct the age–depth relationships using a smooth spline with 0.15spar and run with 10,000 iterations (Blaauw, 2010).

3.5. Glacier reconstructions based on lake sediments combinedwith surfacesoils

The main purpose of coring downstream glacier-fed lakes is toprovide a continuous reconstruction of past glacier activity, which intheory allows for well-dated time series covering thousands of years(Karlén, 1981). The approach has been widely adopted since Karlén(1976) first developed it. The number of methods used to analyseglaciolacustrine sediments is growing (Bakke and Paasche, 2014), andas a result detailed information can be collected at ultra-high resolution.By coring a chain of downstream lakes and comparing the cores tocatchment sediment signatures (see Section 4.2 below), the possibilityfor testing internal reproducibility and accuracy from individual lakescan potentially result in increased robustness (e.g., Bakke et al., 2010).This approach is adopted and developed here.

A reoccurring challenge for many previously published glacier stud-ies based on lake sediments is, nevertheless, the basic assumption thatall minerogenic sediments deposited are glacigenic and that the impactof paraglacial and extra-glacial sediments is negligible. Documentingthe glacial ‘fingerprint’ in the lake sedimentary record requires thedetailed analysis of different grain sizes from sediments in theproximityof the glacier (moraines included) and of samples from the extra-glacialpart of the catchment samples (e.g., Rosenbaum et al., 2012). Forinstance, Vasskog et al. (2012) used magnetic susceptibility propertiesto show how soil signatures from LIA moraines compare well withmaximum glacier activity as inferred from lake sediment cores, butthat extra-glacial signatures dominated during the Holocene ThermalMaximum (HTM), a time when multiple studies indicate that glaciersin western Norway were absent.

Early work by Oldfield et al. (1979) and Stober and Thompson (1979)examined catchment magnetic signatures for various reasons, but itwas Snowball (1993) who first used catchment soil samples in orderto test the coherency of glacier reconstructions based on lake sedi-ment records by means of a detailed examination of correspondingrock magnetic properties. The study shows, for instance, that theconcentration of magnetite increased during glacier expansion,whereas previously deposited magnetite in the catchment soil wasconverted to haematite and thus had little impact on the ‘glaciersignal’ as inferred from core data.

Later studies based on rock magnetic properties of lake sedimentshave been used to reconstruct past glacier variability in differentgeographical regions, including Abisko in northern Sweden (Snowballand Sandgren, 1996), the Cascade Range in the USA (Reynolds et al.,2004), and Andøya in northern Norway (Paasche et al., 2007) andwestern Norway (Vasskog et al., 2012).

Combining catchment sediment signatures, as characterized bymagnetic properties, with lake sediment records has shown great po-tential when it comes to validating glacier variability as inferred fromglaciolacustrine cores (Rosenbaum et al., 2012; Vasskog et al., 2012).By collecting catchment samples that are sieved into different fractionsprior to analysis, the possibility for amore detailed understanding of theinteraction between the production and transport of glacial sedimentand downstream lake sediment archives have opened up.

4. Results and discussions

4.1. Geomorphological mapping

Undulating plateaus consisting of heavily weathered bedrock fromwhich fluvial channels drain and pronounced escarpments delineatethe higher areas. Recurring features on these surrounding plateausinclude sorted ground patterns, active and relict. Erratics, which areindicators of the former presence of large ice sheets, are observed inDørålen and at other sites in Rondane but are not abundant in themain valleys (Kvisvik, 2003). Meltwater channels are common featuresin Rondane and are observed up to 1750-m altitude in the vicinity ofDørålen. Striations are rare in Rondane, with just a few examplesidentified (Shakesby et al., 1987; Håvik, 2003; Kvisvik, 2003), and theytend to align with the general topography.

Dørålvatn valley holds thick glaciofluvial deposits subject to fluvialreworking, in addition to a few eskers (see Fig. 3). The valley sides arecovered by scree, and debris flow trajectories can be traced downslopefrom the talus apex. At several places the scree slopes advance onto al-luvial fans. A poorly developed moraine is also deposited in the glacierforeland. Moreover, meltwater channels originating from Skriufonnencut through thick deposits with a coarse matrix. The bedrock in frontof Skriufonnen stands out from the surroundings because of its greycolour, while a bouldary marginal moraine defines the outer limit ofthe grey area. The difference in colour is caused by the lack of lichenson the bedrock and diamicton, and measurements of the lichenR. geographicum within this area show a mean size of 15 mm whilelichens beyond this area cover most rocks and bedrock (120 mm andlarger).

4.2. Catchment data

The MS measurements and the MS ratio reveal strikingly consistentpatterns (Fig. 6). The relationship between the strength of theMS signaland the MS ratio suggests that higher MS values are associated withlower MS ratios and more ferromagnetic material and vice versa. Thisrelationship is statistically significant (r2 = 0.6, p b 0.001) and is alsovery different from the samples collected from the tributary river chan-nel (Figs. 2 and 6). When samples are broken down into individualgrain-size fractions, going from 250 to 20 μm, a statistically significantinverse exponential weakening of the MS signal is present. Another

y = -2.212ln(x) - 19.085

r 2 = 0.60

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r 2 = 0.48

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Fig. 6.χbulk versusMS ratio values for catchment samples, including one (S709) from thetributary river from the western part of the valley (see Figs. 2 and 3). The two parametersexhibit a strong, inverse relationship (r2 = 0.6, p N 0.01), suggesting that lower MS ratiovalues correspond to strongMS values. The samples from thewestern branch have higherMS values, butmagnetic strength and physical grain size are inverse and differ significant-ly from the overall trend downstream of Skriufonnen.

DVP609

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th

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Fig. 8. Age–depth models for the two investigated piston cores from Upper Dørålvatn(DVP609) and Lower Dørålvatn (DVP509). A 210Pb date confirms that the top sedimentsare present in the cores fromLowerDørålvatn. Themodels indicate that the sedimentationrate in DVP609 was nearly linear between 6000 and 1000 b2k before the sedimentationincreased significantly. In DVP509, an increase in the sedimentation rate is evidentbetween 7000 and 5000 b2k, but it is otherwise linear. The prime reason for this increasedsedimentation is likely the growth and production of organic matter.

439B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

key observation in this data set is that the MS signal weakensnonlinearly as one moves away from the glacier (Fig. 4).

The strongest magnetic susceptibility signal is carried by the smallestgrain sizes in all samples, except those from the tributary riverwhere thepattern is reversed (not shown here). A nonproportional weakeningtakes place between samples from between the glacier and UpperDørålvatn and those situated downstream (Fig. 4). A likely explanationfor this ‘jump’ is that suspended sediment is deposited in the open-ended lake, thus trapping a certain fraction of the total downstreamsediment load.

This pattern suggests that as the glacier advances, thus reducing thedistance between the snout and Upper Dørålvatn, the strength of theMS signal is likely to increase because more fines will be producedand transported downstream. As the glacier retreats, this pattern shouldbe reversed. At the onset of the Neoglacial when the glacier rejuvenated(Figs. 7 and 8), the sedimentation rate increases in the basin closest to

1.0x10-8

2.0x10-8

3.0x10-8

4.0x10-8

5.0x10-8

0 10 20 30 40 50

χbul

k (m

3 kg

-1)

Depth (cm)

DVH108

DVH208

DVH308

DVH408

DVH508

DVH608

DVH104

DVH204

DVP509

Fig. 7. Variations in magnetic susceptibility (MS) for eight HTH cores and one piston core(DVP509). Amajor peak is observed in all cores but varies in terms of depth likely becauseof different sedimentation rates. Magnetic strength before and after this peak are compa-rable. The fact that the pattern is reproduced in all cores suggests a shared sedimentationhistory within and between lakes through the time interval in question.

the glacier (Upper Dørålen), whereas very little change is recorded inthe lower basin. The reason for this is probably that the upper lake isvery efficient in trapping most of the sediments, especially the coarserones, and that the overall production of organic matter is higher in thelower lake, which would compensate for the variable input of glaciallyproduced fines. This suggests that the changes in grain sizes areprobably somewhat larger in the upper lake compared to the onesdownstream, which could explain the minor differences observed inthe MS records from the two lakes (Fig. 9).

4.3. Core data

The Lower Dørålvatn is shallow, and the transparent water columnstimulates the production of aquatic mosses in places on the lake bot-tom, but a low influx of sediment is also a prerequisite. As a result, thecores have alternating layers of aquatic mosses but heavily dominatethe middle sections of cores (c. 80–240 cm depth) (Fig. 9). This isreflected by themagnetic susceptibility that indicates a bimodal system;high values in the lowest part of the core, a quiescent phase in themiddle and a return to higher values in the upper 0.8 m of the cores.The aquatic mosses influence the LOI significantly, thus giving highlyvariable results in the middle sections of the cores (Fig. 9).

TheMS (χbulk) in the short cores shows striking internal similaritiesbetween cores and somewhat different sedimentation rates, especiallywhen compared to the piston core DVP509 (Fig. 7). All short coresexcept DVH508 from Upper Dørålvatn show lower χbulk toward thetop and bottom of the cores. The magnetic properties of DVH104show that ‘harder’ minerals indicated by the S-ratio identify a peak ata depth of 15–17 cm (Fig. 5). The source of this peak might thereforebe locally deposited sediments, potentially a debris flow from thenorthern valley side that fits nicely with the catchment sample analysis(sample S709).

The geochemical data suggests the same bimodal signature asobserved for magnetic susceptibility and titanium (Ti) (Fig. 9). TheItrax core scanner results show high counting rates that most likely re-flect the variations in the influx ofminerogenic elementary compositionof the local bedrock (Section 2). The influx of minerogenic material isthus reflected by the Itrax-XRF core scanner results. This is also reflectedby the high correlation between Ti and MS in DVP509 (r2 = 0.8). Themajor mineral in the bedrock, quartz, is by nature diamagnetic,explaining, in part, the weak magnetic signal in catchment samplesand in the lake sediments downstream from Skriufonnen. The signalin DVP509 is, in general, reproduced in core DVP409 (Fig. 9).

Fig. 9.Magnetic susceptibility (MS) and titanium (Ti) data from piston cores DVP609 (Upper Dørålvatn), DVP409 (Lower Dørålvatn proximal site), and DVP509 (Lower Dørålvatn distalsite). Lower panel shows organic content (LOI) anddry bulk density (DBD) inDVP509. Less aquatic-moss at the site ofDVP409 results in a lower sedimentation rate in themiddle section ofthe core. DVP409 was only measured for surface magnetic susceptibility. The large amplitudes in DVP609 illustrate the proximity to Skriufonnen, as the signal of Ti and MS is most likelyinfluenced by frequent changes in grain size.

440 B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

The Ti andMS variability are poorly correlated for cores DVP609 andDVP509 (Fig. 2) when compared by depth, even though both are ~3 mlong (Fig. 9). Comparing the results by age, however, gives a muchbetter comparison (Fig. 10), although the glacial signature in the uppercore (DVP609) is distorted by larger changes in grain size, probably as

a result of periods of increased runoff (Fig. 8). Melting snow or ice oralternatively precipitation might remobilize sediments readily availablein the glacier foreland. The main characteristics of both cores are astrengthening of the MS and XRF signal from 4000 b2k until recently,when the signal in Lower Dørålvatn was back at ‘zero’ again (Fig. 7).

441B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

4.4. Glacier variability in a regional context

Holocene fluctuations of Skriufonnen are based on age models(Fig. 8) for Upper (DVP609) and Lower Dørålvatn (DVP509), alongwith theMS and Ti results fromDVP609 andDVP509, and are comparedto other local and regional climate and glacier fluctuations (Fig. 10).Magnetic properties and Ti correlate well internally and are consideredto represent an influx of particles produced by Skriufonnen throughouttheHolocene (Section 4.2)making it a good indicator of glacier variability.

Fig. 10. (A) Rondane glacier variability as inferred from variations in MS (this study). (B) Locreconstructions from Jotunheimen and Rondane (Støren et al., 2012). (D) Glacier reconstruct(E) A regional glacier reconstruction from Jotunheimen (61°23′N, 8°21′E) (Matthews and Dreto variations in summer temperatures, especially in the Neoglacial phase. Between 2400 and 5same time, temperature reconstructions show only modest changes in summer temperatureversus Rondane, which is likely indicative of the larger influence of the Westerlies (Støren andpresented above are shown in Fig. 1.

In the following, we divide, based on variability in the glacier record fromRondane aswell as other environmental archives, theHolocene into threetemporal periods.

4.4.1. 10,200 to 9000 b2kThe oldest part of the lake record from Lower Dørålvatn carries

minerogenic sediment with a signature nearly identical to that ofthe later LIA maximum (Fig. 9; DVP409 and DVP509), which suggeststhat a glacier was present at 10,200 b2k. The sharp drop in MS at c.

al summer temperatures from Råtåsjøen (62°16′N, 9°50′E) (Velle et al., 2010). (C) Floodion from a large catchment in western Norway (61°56′N, 6°52′E) (Vasskog et al., 2012).sser, 2008). Glacier variations in Rondane during the Holocene seem to be closely linked50 b2k, the glacier held an intermediate position, probably similar to present day. At thecompared to modern conditions. During these periods, floods increased in JotunheimenPaasche, 2014). The geographical locations of the different proxy-based reconstructions

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10,000 b2k suggests that the glacier(s) disappeared rapidly aroundthis time (Fig. 10). The glacier retreat occurred slightly earlier thanfor glaciers in Jotunheimen that prevailed until roughly 9700 b2k(Matthews et al., 2000, 2005; Matthews and Dresser, 2008), which isprobably because the regional ELA is lower in Rondane compared toJotunheimen.

Lie et al. (2004) suggested the advance of a polythermal glacier at10,100 b2k in eastern Jotunheimen, after which the glacier rapidlyretreated and disappeared. Ice caps and outlet glaciers farther west,such as Hardangerjøkulen and Folgefonna, also retreated around10,200 b2k, but the latter readvanced at 9700 and 9100 b2k (Bakkeet al., 2005) (Fig. 1E). The readvance at 9100 b2k was the largestHolocene glacier advance for Hardangerjøkulen (Dahl and Nesje,1996). The sudden retreat of glaciers seems to be a shared feature inJotunheimen and Rondane, although summer temperature reconstruc-tions do not indicate any significant warming during the time intervalin question (Bjune et al., 2005; Velle et al., 2005, 2010). Having notedthat, summer insolation was close to a maximum at 10,000 b2k andthe tree line was comparable to present day or even higher. In a recentstudy, the temporal lag between temperature reconstructions based onchironomides and macrofossils versus pollen posits that the HoloceneOptimum should be pushed back which would result in a maximumaround 11,500 to 9000 years ago, and are consequently more inline with the evidence from Rondane (Valiranta et al., 2015). Reliableestimates of changes in winter precipitation from Rondane arenonexistent.

4.4.2. From 9000 to 4000 b2kIn Jotunheimen, glaciers were absent until c. 8000 b2k, but at least

one glacier rejuvenated around 7500 b2k and existed until it againdisappeared about 6800 b2k (Matthews et al., 2005). From 6000 b2konward, the glacier was present, and by 3800 b2k it had reached asize comparable to present day (Lie et al., 2004). The glacier fingerprintof Skriufonnen in the lake sediment records is completely absentuntil c. 4000 b2k, which sets it apart compared to the records fromJotunheimen. Several of the glaciers along the western coast are sug-gested to have reformed around 5000 b2k, which might be explainedby their somewhat higher sensitivity to changes in winter precipitation(Bakke et al., 2005) or simply by differential topography. Also note thathigh-resolution flood reconstructions adjacent to Rondane indicatelittle or no flood activity in the period ranging from 9000 b2k to4000 b2k (Fig. 10C),which is likely indicative of limited snow reservoirsin the mountains during this interval (Bøe et al., 2006; Støren andPaasche, 2014).

Summer temperatures are generally high (+1 °C) compared topreindustrial conditions for what is sometimes called ‘the HoloceneThermal Optimum’ (HTO) (Velle et al., 2010). The combined insightfrom temperature records and detailed flood reconstructions suggestthat perhaps this period was, on average, not only warmer but perhapsalso drier than at present (Fig. 10). An effect of such conditions wouldbe that the local ELA would ascend well above 1500 m altitude atSkriufonnen. Given the fact that glaciers in Jotunheimen most likelyreceived more precipitation than Skriufonnen (Bjune et al., 2005),this might explain why some of them reformed during the interval7500–6800 b2k and existed permanently from 6000 to 5000 b2k.

De Jong et al. (2009) argued that one can find dry and warm condi-tions in continental parts of southern Scandinavia between 8000 and4000 b2k, especially between 7000 and 5000 b2k. During these inter-vals, δ18O values were low in Lake Spaime (alt. 887m), which is locatedsome 100 km northeast of Rondane, and are interpreted to reflectsustained North Atlantic Oscillation (NAO) negative conditions onlypunctuated by a centennial excursion centred at 6500 b2k (Gieseckeet al., 2008). However, as recently discussed by Paasche and Støren(2014), invoking the NAO exclusively in order to explain reorganiza-tions in atmospheric circulation patterns carries clear limitations.

4.4.3. The last 4000 yearsIn Rondane, the lake sediment evidence (Fig. 10) would appear to

suggest that the glacier rejuvenated around 4000 b2k after being absentfor nearly 6000 years. The MS records from both lakes suggests that agradual butmodest glacier growth culminated in two advances, peakingfirst at 3200 b2k and then with a major advance around 2800 b2k, afterwhich the glacier became smaller again. It remained small (or absent)until the onset of the LIA, which in Rondane commenced around A.D.1450 and lasted until A.D. 1800. Since then, the glacier has been in astate of retreat.

Temporal variations of Neoglacial advances in southern Norway arerelatively large, although many cirques and outlet glaciers on averagehave had two or three major advances during the last 4000 years,with the LIA often assumed to be the largest based on morainesand lake records. The intercomparison of advances during this periodquickly becomes a question of resolution, noise, age–depth controland response time. Even so, the onset (around 4000 b2k) and thethree periods of enhanced glacier activity (3200, 2800 b2k, andA.D. 1450) align with several other glacier records but also pairs wellwith many paleoclimatic studies.

Several different but complementary proxy records show distinctclimate change toward cooler summers and wetter winters around4000 b2k. This is reflected in a considerable lowering of the tree linelocally (Velle et al., 2005) and at other nearby sites (Dahl and Nesje,1996); a shift in δ18O values of bulk organic matter (De Jong et al.,2009); chironomid assemblage changes in favour of species indicative ofcooler temperatures (Velle et al., 2010); and increased growth of bogs(Barnekow et al., 2008) and also macrofossil distributions (Eide, 2003).

Despite the convergence of evidence pointing at cooler and wetterconditions, the response of Skriufonnen was limited, and not until3200 b2k was the first significant glacier activity documented in thedownstream lake basins (Fig. 10). This might suggest that the regionalELA was well above the present day in Rondane prior to 4000 b2k andthat it was not until 3200 b2k that the climate was favourable for theSkriufonnen glacier. Considering the small size of Skriufonnen, thesensitivity of this small glacier to changes in external forcing is highand suggests that it might have lagged the Neoglacial cooling observedfor mountainous areas farther west. After the first glacier maximum3200–2400 b2k, the glacier retreated and remained small until c.550 b2k. The shift from a larger to a smaller glacier after 2400 b2k is inline with summer temperature reconstructions from Råtåsjøen, whichshows a marked shift toward warmer conditions (Velle et al., 2010).

Apart from a minor cooling at 1300 b2k, the climate was stable andwarm until the onset of the LIA at about A.D. 1450 (Fig. 10). During theLIA, the MS records in combination with the outline afforded by themoraine system suggests that the glacier probably nearly doubled insize relative to the 2007 state and reached a maximum frontal extentlate in the period, about A.D. 1800.

The modern retreat of continental glaciers is mapped in detail by theNorwegian water authorities (NVE); and Storbreen (in Jotunheimen),which holds the world's second longest mass balance record, shows aclimate imbalance for the last 30 years with sustained negative massbalance (Andreassen and Windsvold, 2012). This is very much in linewith observations of Skriufonnen for the last 14 years. If this trend con-tinues at the present speed, the glaciermight be completely absentwithinthe next 15–20 years, which will be the first time in about 4000 years.

5. Conclusions

Here, we have, for the first time, produced a cirque glacier recon-struction from Rondane, southern Norway, covering the last 10,200years. The main findings can be summarized as follows:

• The Skriufonnen glacier has been in a steady retreat since at least theearly 2000s. This has been directly observed for the last 12 years. Aresult of the gradual thinning and retreat is that the size of the glacier

443B.C. Kvisvik et al. / Geomorphology 246 (2015) 433–444

has shrunk from 0.06 to 0.03 km2 during the observation period. Atpresent, there is little or no evidence of ice deformation, suggestingthat Skriufonnen should be labelled as an ice apron rather than aglacier. Noteworthy amounts of sediment-laden meltwater beingreleased from the glacier snout have not been directly observed,althoughmeltwater still appears to remobilize and entrain sedimentsfrom existing deposits to a limited extent.

• Detailed geomorphological mapping reveals that Skriufonnenreached a Holocene maximum position during what is commonlyreferred to as the LIA. During the LIA, the glacier was four times larger(c. 0.12 km2) than the present day size, extending down to 1340 maltitude.

• Analysis of catchment samples taken in a transect downstream fromthe immediate front of Skriufonnen and down to Lower Dørålvatnlake reveals a systematic reduction of rock magnetic signal of surfacesoil samples. This observed pattern is not only valid across differentgrain-size classes (≥20–250 μm), but is also reflected by the propor-tionality between size classes and the strength of MS, as the distanceto the glacier snout increases. Changes in the distribution of paramag-netic versus ferromagnetic minerals, as inferred from MS77/293 Kvalues, follow this depletive pattern, and the MS ratio also indicatesthe presence of two different source areaswithin the same catchment.

• The cross validation of the MS signal within the catchment and thatof the downstream lake cores suggests that glacier activity is recordedin the two lakes subjected to this analysis. The major trends arereproduced by both cores and can be defined as a quiescent phaselasting from c. 10,000 until 4000 b2k when the glacier most likelywas completely melted away, rejuvenation of the glacier startingprior to 3200 b2k and culminating before 2400 b2k, a minimumphase centred between 2400 and 550 b2k, a second Holocene glaciermaximumduring the LIA (A.D. 1450–1800), and amodern retreat anda dynamical shift from being an active deforming glacier to becomingan ice apron.

• The new, high-resolution reconstruction of Skriufonnen, southernNorway's easternmost glacier, is partly in line with other glacier re-constructions from farther west; but it also deviates from the generalpattern. The long absence during the HTO is a recurring feature inglacier reconstructions in Norway and elsewhere. However, theNeoglacial rejuvenation lags records farther west as it does notrejuvenate until around 3200 b2k. The timing of the LIA falls withinrecords farther west. Glacier variability during the last ~4000 yearsindicates considerable changes in winter precipitation and summertemperature, but summer temperature appears to be themore impor-tant of the two.

• The approach adopted here utilizes the glacier as a single sourceof material supply to downstream lakes. Being able to characterizethat sedimentary signal versus secondary supply from extra-glacialsources of the catchment allows for more robust glacier recon-structions than have hitherto been produced and is suggestedhere as an integral part of any new attempt to reconstruct pastglacier variability.

Acknowledgement

Marius Bakkeng, Brent Göring, Henriette Linge, and Torleif Paaschehelped with fieldwork and their assistance is greatly appreciated. Thecoring expedition inMarch 2009would not have been possible withoutDovre Fjellstyre — their help with transport was essential. Magneticmeasurements were carried out at the Paleomagnetic Laboratory atthe Department of Earth Science, University of Bergen, was headed bythe late Professor Reidar Løvlie. This study is a tribute to hismemory. Fi-nally, we are very grateful for the constructive and instructive feedbackfrom three anonymous reviewers, the Editor-in-Chief Richard A. Mar-ston, and also toMathias Trachsel, who all helped to improve the qualityof this paper.

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