Glacier Change in the Cariboo Mountains, British Columbia, Canada

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Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . 1 − C) sea- ◦ 0.12 % a 0.87 ± + (1952–1985) to 0.41 1 − − . From 1952 to 1985, nine 1 − 0.04 m w.e. a and Hock, 2011). The largest GIC ± ć C) and accumulation ( 0.05 % a ◦ 0.14 ) contribute a significant amount to total ± 2 − 0.38 + 0.19 1 km 3368 3367 − < , 2012). ć for the period 1985–2005. Temperatures increased from the 1 − 3.2 %). Our comparison of surface area change with glacier morphometry − 0.07 m w.e. a ± erent epochs. ff 32 mm, Recent studies of glacier change use a variety of remotely-sensed products that in- 0.50 This discussion paper is/has beenPlease under refer review to for the the corresponding journal final The paper Cryosphere in (TC). TC if available. − clude aerial photography (Koblet et al., 2010; Tennant et al., 2012), satellite imagery 2009; Hood et al., 2009;with Moore et downstream al., impacts, 2009; are Marshallvolume. et altered As al., glaciers when 2011). and These glaciers ice inputs,land undergo caps along ice (GIC; changes sheets) all in lose glaciers volume, outside extentcontributions sea of and to level the rises Antarctic sea (Radi andAlaska level Green- regions rise (Gardner include etstrates the al., that, collectively, Canadian 2011; small glaciers Berthier Arctic ( GIC et Archipelago volume al., (Bahr and and 2010), Gulf Radi but of recent work demon- 1 Introduction Glaciers are important components ofter the along hydrologic with system. They organic contribute and meltwa- inorganic materials to freshwater systems (Bogdal et al., Thinning rates likewise− accelerated, from earlier to the latter periodsons, for the and ablation average ( precipitation( decreased, particularlycorroborates in previous the studies that accumulation showsurface season primary area. We relations also between find, extent however,for that change the di and strength and sign of these relations varied We calculated dimensional change forColumbia 33 for the glaciers latter in half theriod of Cariboo 1952–2005; the Mountains twentieth area of century. retreat All British glaciers glaciers averaged receded advanced. during Following the 1985, pe- retreat rates accelerated to Abstract The Cryosphere Discuss., 8, 3367–3411,www.the-cryosphere-discuss.net/8/3367/2014/ 2014 doi:10.5194/tcd-8-3367-2014 © Author(s) 2014. CC Attribution 3.0 License. Glacier change in the CaribooBritish Mountains, Columbia, Canada (1952–2005) M. J. Beedle, B. Menounos, and R.Geography Wheate Program, University of Northern British Columbia, PrinceReceived: George, 20 BC, May Canada 2014 – Accepted: 2Correspondence June to: 2014 M. – J. Published: Beedle 25 ([email protected]) June 2014 Published by Copernicus Publications on behalf of the European Geosciences Union. 5 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | during the 1 − . Cariboo Mountains 2 ord the ability to document ff 0.58 m water equivalent (w.e.) a 3370 3369 − erent years, we thus report a mean area-weighted C respectively (Environment Canada, 2012). ff ◦ of ice at a rate of 3 Annual length change of Castle Creek Glacier in the Cariboo Mountains is more The objectives of this study are to: (1) document the extent and volume change of year: 1952 for photos1971; taken and in 1985 1946, for 1952, those of or 1984 1955; or 1970 1985. for All those annual rates of of 1967, extent 1970, or or volume change itives or negatives using aavailable photogrammetric as scanner digital whereas imagery aerialrior from triangulation orientation; 2005 BC (AT) was scans Ministryfrom of (digital 0.2 Environment, photos to 1998). 1.1 with m Ground depending sampling availabletaken on in scanning distance exte- late resolution ranges summer, and but image dates scale.ages range Most to from photos estimate mid-July were glacier to length late-September. We and1984, used area all 1985, change, im- whereas and only 2005 thosefor from each were 1946, subregion used 1952, were taken to in determine di surface-elevation change. As photos 2.1 Imagery and supplemental data We measured glacier extent and surfacetained elevation from change from the aerial British photographs(Table Columbia 1). ob- Imagery Government prior and to Canada 2005 National was Air scanned at Photo a Library resolution of 12–14 µm from diapos- creased temperatures and increased winter precipitation.the Bolch first et satellite al. inventory (2010) completed ofCariboo glaciers in Mountains western Canada, (2005) identifyingglaciers with 536 lost glaciers a 7.06 in km total the period surface 1985–1999 area (Schiefer et of al., 731 2007). km 2 Methods mier Range (a Cariboo MountainsMaurer subrange) et contribute al. to (2012) the found ColumbiaHolocene that River maximum (Fig. glaciers extents 1). of around the 2.73–2.49 kadid Cariboo and Mountains not that nearly begin major reached retreat untilglaciers their of the of the glaciers the early Premier 20th Range century. advanced Luckman in et the al. 1960s (1987) and showed 1970s that in some response to de- boo Mountains contributes to the Fraser River; however, some glaciers in the Pre- closely related to changes ofMountains glaciers (Beedle in et the Coast al., Mountains 2009). than Meltwater those from of the the Rocky majority of glaciers in the Cari- 1.1 Study area and previous work The Cariboo Mountains are theCanada northernmost (Fig. range 1). of The the ColumbiaRocky climate Mountains Mountains of of the to BC, Cariboo thecipitation Mountains east, (1971–2000 is and climate transitional, drier normals) wetter(Barkerville, than than averages BC) the 1014 the and and Coast lee 679 Mountains.temperature mm (McBride, averages Total on 1.9 annual BC) the and pre- sides 4.4 windward of the Cariboo Mountains, and annual a subset of glaciers inthe the Cariboo climatological Mountains conditions of that Britisharea. Columbia could (BC); explain and observed (2) assess glacier change in the study sis is therefore limitedglacier change to for the up to laststudy three 30 decades we years. prior use Air to aerial the photosa beginning photogrammetry a subset of to the of investigate satellite glaciers the1985–2005. era. in In extent The this western and use Canada volume oftend for change aerial the the of photography glacier periods thus inventory 1952–1970, studies providesuse of 1970–1985, of a Schiefer aerial and method et photography to also al. providesusing (2007) temporally an lower-resolution and ex- independent satellite Bolch check imagery. et against al. glacier mapping (2010). The et al., 2002). Typicallysess changes these in studies glaciers for employ2009; a a particular Bolch combination region et (Schiefer of et(e.g., al., al., geomatic Bolch 2010). 2007; et data Abermann al., Comprehensive et to 2010),(e.g., inventories al., and as- Schiefer of measurement et of glacier al., glacier extent volume 2007) change and primarily of change rely large regions on satellite borne instruments. Such analy- (Paul et al., 2004; Berthier et al., 2010), and laser altimetry (Sapiano et al., 1998; Arendt 5 5 20 25 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ). We used 2 62), and Premier = 10.0 km n > 3000 m), an elevation just ∼ http://www.genetics.forestry.ubc. 47), Quanstrom region ( 3372 3371 ) interpolates and extracts climate data for spe- = n 212) to estimate Cariboo Mountains glacier climatology, and for = n 103) to estimate sub-regional climatology. We compare monthly tempera- = n Within the three Cariboo Mountains subregions, we selected 33 glaciers represent- Eleven check patches, located on stable surfaces around each glacier region (Fig. 2), We use ClimateWNA (Wang et al., 2012) to assess the variability in temperature To investigate dominant synoptic patterns over the Cariboo Mountains, we use the ing five size classessurface (0.1–0.5, area 0.5–1.0, as 1.0–5.0, our 5.0–10.0, primary and criterion to select glaciers as many studies find it to be both in terms ofand (3) temporal representativeness resolution based and ontain spatial average glaciers glacier scale; presented morphometry (2) inaerial of snow photography Bolch Cariboo reduce cover et Moun- potential and glaciers al. forto contrast; (2010). study glacier (Table Snowcover 1). aspect Sun and angle andof poor with contrast, respect slope contrast particularly of leads for older to someissues south-facing in local glaciers. our areas We selection omitted of of glaciers a high with subset. reflectivity these and an absence With the exception ofsively 2005, photographed glaciers in of any thesubregions of given Cariboo the year, Mountains Cariboo and Mountains were withtle we not suitable Creek photographic thus comprehen- Glacier coverage: (1) concentrate area; the(Figs. (2) our Cas- 1 the study and Quanstrom 2). on Mountain We selected three area; our and subset (3) of glaciers the based Premier on: Range (1) availability of imagery, were used to quantifypatch the is relative comprised accuracy of of 25tematic the individual stereo bias checkpoints models in of (Fig. a stereosurfaces five-meter 3). were grid; models Each created we check from from estimated these the sys- 11glacier mean mean surface-elevation residuals measurements. residuals and used of to the apply a check correction patches. for 2.3 Trend Glacier subset selection tically distributed throughout the2009). Within photos each (Schiefer subregion we anderrors used Gilbert, common (Kääb GCPs 2007; and to reduce BarrandGCPs Vollmer, systematic consisted 2000; et positional of al., Schiefer stable andlated bedrock stereo Gilbert, features models (BC or 2007; Ministry boulders Schiefer of obtained Environment, et 1998). from al., aerial 2007). triangu- rived from tie points and common ground control points (GCP) horizontally and ver- glaciers within three intervals (1952–1970,elevation change 1970–1985, for and two 1985–2005) epochs and (1952–1985 surface- and 1985–2005). and precipitation during the periodselevation for change. which The we ClimateWNA measure v4.72 glacier program extent and ( surface- are calculated using the actual duration between images. We report extent change of 2.2 Photogrammetry We used the Vrcreate Mapping stereo photogrammetry models software from suite aerial (Cardinal photos. Systems Exterior LLC) orientation to for the models was de- eral atmospheric conditionsabove in the the uppermost middle extentclimatic troposphere conditions of ( for most balance years glaciersmulation (October–September), seasons, in and defined for the as ablation and June–September Cariboo and accu- Mountains. October–May, respectively. We assess ca/cfcg/ClimateWNA/ClimateWNA.html glaciers of the Castleregion Creek ( region ( ture precipitation data from(Déry ClimateWNA et with al., measurements at 2010)conditions Castle for at Creek 2009–2011 high Glacier to elevations in estimate the the Cariboo ability Mountains. ofNational ClimateWNA to Centers represent forsearch Environmental (NCEP/NCAR) Protection/National reanalysis Center dataheight for anomalies. (Kalnay Atmospheric The et 700 Re- hPa al., geopotential 1996) surface provides of a 700 good hPa indicator geopotential of gen- cific locations for western2002) North and America, historical relying data onof (Mitchell downscaled temperature and PRISM and Jones, (Daly precipitation. 2005)eraged et Refer to ClimateWNA al., to generate output Wang monthly for etfor time points all al. series 33 along (2012) glaciers the for ( details. center-line We every use 100 m av- in elevation 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) and 2 1 km > in the accumulation 3 − erent periods. We used two methods to esti- ). Poor contrast in the earliest photographs in- 3374 3373 ff 2 1 km < in the ablation area and 750 kg m 3 erent glacier subsets by epoch based on aerial photo cover- − ff To estimate regional (Cariboo Mountains) glacier extent change, we extrapolated To calculate glacier-wide volume change from point measurements, we multiplied av- Poor contrast and snowcover limit our analysis of glacier surface elevation change Mountains glaciers. from measurements of ourative subset extent of change studied bymate size glaciers Cariboo class using Mountains for surface-elevation the change: di averagechange first, rates the of average of our surface-elevation subset rel- elevation of change seven glaciers; with and elevation,each second, defined the 50 m average as gradient bin, the of1985. average and We surface- compare of integrated extrapolated all values it withume measurements results with change from within (Schiefer the recent et work Cariboo al., that included 2007) Mountains vol- and glacier extent hypsometry change (Bolch of et al., 2010) of Cariboo erage of the twoet extents al., that 2010). define All aing values given presented period a in (e.g., density water Arendt of equivalentarea et (w.e.) 900 (e.g., al., kg are Beedle m 2002; calculated et Barrand byglacier’s al., assum- median 2014); elevation ablation (Table 2). and accumulation areas are defined by each surface. Elevation bins andhypsometries glacier created surface from were theto derived an same from absence point epoch-specific of measurements.measurements measurements glacier Where in for the poor that accumulation contrast elevationyear. area, bin led This we from used approach the surface-elevation assumeschange, stereo that an model surface assumption of elevation and that azones, extent would prior but underwent be or one negligible inappropriate subsequent thatwas in is applied. the more We calculated rapidly likely glacier in changing wide the ablation average accumulation thickness zones change where based this on the assumption av- vations to the bins with missingthat values. This rely assumption was on necessary the only27 earliest for % periods year of of total glacier photography surface (1952); area. missing data totalerage a elevation change maximum for of each 50 m elevation bin and summed over the entire glacier have measurements, assigning the average surface-elevation change of these obser- hibited data collection over portionsglaciers. of In glacier these accumulation areas, zones we for extrapolate four from of the the three seven highest elevation bins where we age and snowcover. Collectively, our analysisglaciers allows us for to the compare epochs areaand change 1952–1985, for for 1985–2005, 33 26 and glaciers 1952–2005subset). in (33-glacier the subset), additional epochs 1952–1970, andto 1970–1985 seven (26-glacier glaciers forglaciers, the we periods measured surface 1952–1985, elevation on 1985–2005, aon 100 and a m 50 grid 1952–2005. m for For grid large glaciers for these ( small glaciers ( (e.g., Koblet et al., 2010). Delineationlematic of as planimetric seasonal glacier snow area above coverestimates the masks of TSL the glacier is glacier surface prob- area. margin, Mapping andsurface of can features ice such erroneously divides as relied inflate crevasses on and surface runnels;der elevation these to and divides compare were dimensional held changes constantanalysis in for or- was a made given ice for body di through time. Extent-change Kiwa Glacier (glacier 32 in Fig. 2 and Table2.4 3) are land-terminating glaciers. Data collection and analysis We manually collected glacierdirectly extents from and the pointand stereo measurements glacier of models. extents surface Complete wereline elevation glacier (TSL), updated thus for outlines eliminating previous were errantly years mapping mapped seasonal only snow for below cover 2005, as the glacierized transient area snow- et al., 1999; Hoelzle et al.,2010; 2003; Paul Paul et and al., Andreassen, 2004;size Andreassen 2009). et class Our al., as 2008; analysis these Bolch oversampled glaciers etmeltwater glaciers al., likely contributions play in to a the dominant their largest Beer role respective and in watersheds Sharp, regional 2007; (e.g., volume Paul change Arendt and and et Haeberli, al., 2008). All 2006; ice De- masses with the exception of the key morphometric determinant of glacier extent change (e.g., Serandbrei-Barbero 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | σ of (1) (2) (3) σ 5 m for ± ): 2 E er approach 5.5 to 1.3 m, ff ∼ for the accumu- ). To account for 3 Z − ∆ E 4.7 %) as an estimate of error ± is the error in our density assump- 10 m (e.g., Tennant and Menounos, ρ ± E 5 pixels) yields widths of ± 5 or 10 m for reduced contrast ( ) after Barrand et al. (2010) as: er ( ± is the surface area of each 50 m bin. 3376 3375 ff VOL bin E A ) and ) as: w.e. w.e. 2 Z Z Z ∆ ∆ ∆ E E 2 ective degrees of freedom that range from 1 to 5. ρ 2 ) ff E bin + A 2 ) and the added error of ρ 2 2 1 bin Z E E E 2 ∆ ( + E is the error ( 1 ). We estimate error in our measurements of surface-elevation change in 2 1 bin 3 X q is density expressed as a water-equivalent conversion factor (0.9 in the abla- E ) assuming a correlation scale of 1000 m (Barrand et al., 2010). We calculated − bin = n v u u t ρ E q = = w.e. Z Z Previous work indicated a spatial correlation of 1000 m in photogrammetric DEMs We used cross-validation to test the accuracy of our extrapolation of Cariboo Moun- We estimate volume change error ( We used the standard deviation of 275 check points in 11 check patches to esti- VOL ∆ ∆ E Converting to water equivalent units througherror density term. assumptions imparts To an estimate additional errorlation in zone the we density used assumption900 a kg of m range 750 kg of m possiblewater equivalent values units for ( accumulation-zone density (600– E 2013). Error in measurementsof of check surface-elevation points, change whereas incheck for points the the ( ablation accumulation area zone is it 1 is theE quadrature sum of 1 Average errors for the2.3–3.6 % 33-glacier for subset extent range change.Table from 1) These and 0.8–2.4 % glacier errors dimensions. for vary extents, depending and on from imagemate resolution error (see ingreater our uncertainty measurements over surfaces of with reducedmeasurements surface-elevation contrast, above change we the added TSL. ( an Incontrast, error cases of we where increased measurements this are added absent due error to term poor to We estimated error in(Granshaw glacier and Fountain, extent 2006). and Ourdepending extent bu on change image based resolution. on Errorsquared in error a extent (RMSE) bu change of is the calculated error as estimates the for root the mean years that define a given period. 2.5 Error analysis tions in three epochs: 1952–1985, 1985–2005,of and these 1952–2005. six We test used cases the tousing variability estimate two error methods: in (1) our mean extrapolation annual of rate surface-elevation of change surface elevation change of the glacier sub- We used the standard deviation ofin these our 15 extrapolation test of cases the ( our extent of extrapolation all of Cariboo surface-elevation change, Mountainsinto we glaciers. two To partitioned estimate scenarios our error where seven in weset glacier withheld and subset three retain and the four remainder individual as glaciers a as training a set. validation Each scenario was applied to observa- to 2,000 m, yielding e tains glacier extent and surface-elevationlation, change. we In our partitioned test the of50, 26-glacier and glacier subset 25 extent % into extrapo- of four thea individual scenarios training glaciers where as set. a we Set validation withheld selection setretained was 75, and glaciers randomized retained of the within varying remainder each as size.tions size in Each class, five ensuring of epochs: 1952–1970, each the 1970–1985, set three 1985–2005, 1952–1985, scenarios and was 1952–2005. applied to observa- (Rolstad et al., 2009), andments ( others have calculated adegrees number of of independent freedom measure- change for in each epochs with glacier completecorrelation spatial from tool coverage. in point Using ArcGIS the measurements 10.1 Incremental we Spatial of calculated Auto- correlation surface-elevation distances that range from 350 where where tion zone, 0.75 intions, the assumed accumulation to zone), be and 0 in the ablation area and 0.15 in the accumulation zone. 5 5 20 25 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2.7 %, ± ) using rel- 2 from 1952– 11.2 − 1 − whereas our sub- ◦ for 1970–1985, and compared to 21 % for 2 2.9 %) of their surface 1 − ± 0.10 % a ). ± 1 − ). Individual glacier area loss 10.6 2 − ( 0.05 0.13 % a − 2 2.3 % (Table 3). ± ± erences, however, are not statistically 6.2 ff 0.08 − − 1.89 km 0.089 m w.e. a ± size class compared to 20 % in our sample. ± , or 3378 3377 2 2 1.1 % (5.0–10 km ± ; these di ◦ 1.4 %. Recession for 22 of the 33 glaciers exceeded from 1985–2005. Rates of area change aver- 1.51 km ± 13.9 − ± 1 − 3.9 % for the Castle, Quanstrom, and Premier regions re- 31.7 for 1952–1970, ) to − 8.39 ± 2 1 − − ); and (2) mean surface-elevation change within each collective 4.2 1 − − from 1985–2005. During the period 1985–2005, 30 glaciers re- 0.12 % a 1.6 to ± 1 ± − 0.18 % a 0.5 0.41 ± − − 0.10 % a 2.0 %, and 0.03 3.3 % (0.5–1.0 km + 0.077 m w.e. a ± ± ± ± After 1985, all glaciers throughout the region shrank (Fig. 7).Extrapolating The from the av- Bolch et al. (2010) inventory of 2005 (731 km Glaciers that advanced were generally shorter, smaller, steeper, and had higher me- While glaciers on average shrank during the period 1952–2005, their change during Glaciers in our study also more commonly face north, northeast, and southwest Our glacier subset also oversamples higher elevations (Fig. 5). Area-altitude distribu- 0.40 6.2 16.4 erage rate1985, of to aged area change− increasedceded, and from the areaperiod of 1985–2005 two was glaciers did not change. Total surfaceative area change area of change the we of our estimated 26-glacier that subset in and 1952, based the on Cariboo area Mountains loss contained per a size glacierized class, area of gibly changed tended to beGlaciers steep, that but changed were little were longerthan also than advancing higher those ones. and glaciers Receding flowed that glaciers overadvanced all advanced. a or had greater did northerly elevation not range aspects, change whereas had those no that dominant aspect. intervening epochs was more1970, for complex example, (Table five 3 oficantly 26 and change. glaciers Fig. Between advanced, the 7). seven years receded,shrank, Over 1970 and and and the 14 the 1985, did period area two not1985 1952– of of signif- nine 26 16 glaciers glaciers glaciers advanced, advanced, 12 did eight receded, not and change. 11 For had the nodian discernable and cumulative extent minimum period change. elevations 1952– than glaciers that receded (Table 4). Glaciers that negli- − varied from the uncertainties inlargest the glaciers data. (glaciers 28, Absolute 31,tent extent change and for change 33), the which is period. comprise dominated 50 % by of three the total of subset the ex- spectively. Absolute area change by size class over the same period varied from area (Table 3). Relative area change− varied by subregion, with losses of (Fig. 6). Cariboo Mountains glaciersset have has an average an slope averagesignificant. of 21.1 slope of 18.7 3.2 Extent change Between 1952–2005, glaciers lost 15.11 tion of glaciers in the Premierof range, glacier for in example, the are Cariboo higherthe than Mountains the whereas Castle average the and elevation hypsometry Quanstrom ofCariboo our areas Mountains. glacier are subset more from similar to the total glacierized area of the 3.1 Regional representativeness As expected, our glacierin subset all undersamples size ice classes massesMountains except of (40 the %) the largest fall Cariboo size inIn Mountains class contrast, the our (Fig. 1.0–5.0 subset km 4). containsthe 61 Most % Cariboo glaciers glaciers Mountains. exceeding in Eliminating 5.0 the km foursubset of Cariboo (glaciers the 30–33; five Table largest 3)identical glaciers would to from result glaciers our in in 33-glacier the a Cariboo size-class Mountains. distribution that is nearly set ( 50 m elevation bin for the glacier subset ( 3 Results 5 5 25 20 10 15 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 2 0.10) . Two 1 37 km − ± p < w.e. during 3 13.5 %) of Bolch − ( 2 0.02 m w.e. a 0.048 km ± ± (Table 6 and Fig. 9). Net , and continued to shrink 2 1 0.10) and 0.316 ( − 0.23 114 km − − erence of 7.7 %. The Cariboo 0.345 p < ff − 38 km , still 2.5 % less than the 845 km 2 ± 39 km 0.07 m w.e. a ± 0.210 for length and area respectively, and ± − 0.05) and relative area change for the pe- er from our measurements from 2005 aerial 3380 3379 ff 0.50 p < − and 0.235 and 1 0.05) indicating that glaciers with more surface area at 0.358, − − = r p < 0.05) negatively with glacier length and area, indicating that the reported by Bolch et al. (2010), a di 0.487, -values of w.e. Volume lossw.e., and during this loss the accelerated first to period (1952–1985) totaled r p < 2 = 3 3 r 0.043 m w.e. a by 1985. ± 2 . By 1970 glacier cover declined to 805 2 for this 28-glacier subset, and thus the Bolch et al. (2010) inventory, based 6.8 %) for the period 1985–2005 compared to 1 − 0.14 0.051 km 0.059 km − ( 37 km − ± ± 2 ± 39 km ± The relation between area change and glacier morphometry temporally varies (Ta- Based on the extrapolation procedure described above, we estimate a net change of We directly compare glacier extent and extent change (1985–2005) for 28 glaciers 0.3 % a 0.480 0.195 53 km glaciers, both of which advanced over the same period, markedly thickened between 3.3 Volume change Over the− − periodthe 1952–1985, later period (1985–2005).rates These the of volume losses correspondthinning to seven respective rates thinning over the glaciers period 1952 of to 2005 averaged our study lost lost less absolute and relativewas surface no area, except correlation. during Median thefor glacier latter the period elevation period when is there 1952–1985 correlatedriod 1952–2005 with ( ( absolute areahigher change elevations experienced less area change in these two periods. larger glaciers in absolute termstween lost relative more area surface change area1952–1985 and in we both all find periods. length The and relationthese area be- correlations varies for with length time. andfor For area the change the period to period 1985–2005. 0.328 Large ( riod, glaciers whereas thus small lost glaciers more lostsurface more relative relative slope area area in is in the the correlated earliercept latter with pe- period. for absolute Average glacier relative and area relative change area change from in 1985–2005, all indicating periods, steeper ex- glaciers generally was higher than during previousperiod epochs, may but have that been the overestimated in absolute previous surface studies. area lost inble this 5). For threechange periods correlates ( – 1952–1985, 1985–2005, and 1952–2005 – absolute area 2010). Our results thus demonstrate that glacier loss during the period 1985–2005 Mountains glacierized area for 1952 wasof 824 the 1985 TRIM extents used in previous work (Schiefer et al., 2007; Bolch et al., included some late-lying snowin as the glacier, TRIM resulting dataset. Errant inarea mapping loss overestimation of reported of late-lying in 1985 snowof the thus extents this led Bolch comparison. to et 52 al. % (2010) more inventory surface- than we− find for the 28et glaciers al. (2010). We estimate Caribooin Mountains 1985, glacier vs. extent 845 to km have been 785 of the method used bymanually Bolch by et the al. (2010). provinceuse The here, of 1985 average British 5 TRIM % extents, Columbia largerand however, than digitized from 1985 our photographs, extents. the but Late-lying same snow referencesnowline is to aerial helped prevalent additional in photographs us photographs the we distinguish in 1984 snowfields years with from a glacierized higher area. The TRIM mapping Resource Inventory Management (TRIM) programLandsat from imagery 1980s from aerial 2003–2007. photography The and a 2005 semi-automated extents process, average of 2 this % larger inventory,aerial created than photographs through our with extents much manually higher digitized resolution.tory from However, the uses Bolch an et area-weighted al. dateboo (2010) (2005); Mountains inven- is the from actual 2006. date∼ Relative of area imagery change covering for the theon period Cari- 2006 1985–2005 averaged imagery, willphotos. not This significantly provides di evidence of the quality of the 2005 inventory and the precision 824 to 785 common to the Bolch etventory al. relies (2010) on inventory and glacier this extents study mapped (Fig. by 8). the The British Bolch et Columbia al. Government in- Terrain 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 use area of ff w.e. for the pe- 3 1.167 km ± 7.580 − w.e) using elevation-averaged sur- 3 3.0 %) respectively. − ) were even more important for previous 2 C for the ablation and accumulation season ◦ 3382 3381 1.315 km 2.044 and 44 mm ( ± ± 5 km − 0.87 > + 6.242 4.027 − − the coast of northern BC and southeastern Alaska (accumu- 3.2 %) and 0.38 and − + ff 2.170 and ± 32 mm ( − 2.312 − cult, especially when glacier change is assessed over multiple epochs. ffi Most studies of glacier change note increased scatter of percent area change for These synoptic conditions broadly accord with the Pacific Decadal Oscillation (PDO; Geopotential height (700 hPa) anomalies, based on 1952–2005 mean fields, reveal Accumulation season and annual precipitation decreased during the period of study, Extrapolation of these thinning rates to unmeasured glaciers in the Cariboo Moun- imagery, or from themay fast also response impact times of the small inferred glaciers. relative Late-lying area seasonal change snow of small glaciers, and could play and 75 % from 1985–2005. Selectionis of di a representative subset of glaciers for a region smaller glaciers (Serandbrei-Barbero etet al., al., 1999; 2004; Kääb DeBeer et and Sharp,and al., 2007; Andreassen, 2001; Andreassen 2009). Paul, et This al., 2002; scatter 2008;factors Paul Bolch may (DeBeer et arise al., from and 2010; the Paul Sharp,concluded influence of 2007; that local Paul this topographic and scatter Andreassen, could 2009). also Kääb be et the al. result (2001) of using low-resolution satellite will contribute most to volumesize change for class a dominated given volume region.2005, While change glaciers losses in of the the from 1–5epochs. Cariboo km large The Mountains glaciers for two the largest ( ple, period accounted glaciers for 1985– for 94 % which of the we total calculated volume change volume for change, seven glaciers for from exam- 1952–1985, from 1977 to at least the mid-1990s. 4 Discussion 4.1 Regional representativeness Our glacier subset represents a compromisethe between availability regional of representativeness and suitable aerial photography. We oversampled large glaciers as they Mantua et al., 1997),decades and a plays pattern a prominent ofNorth role Pacific America in (e.g., climate determining Bitz variability glacier1971–1985) and mass that were Battisti, balance largely persists 1999). in coincident The for northwest withIn earlier multiple a two contrast, cool periods the phase (1950–1970 of latest and the period PDO (1985–2005) from coincided 1947 to with 1976. a warm phase of the PDO lation season). ablation seasons forpressure the anomalies periods were 1952–19701952–1970. centered and These areas over 1971–1985 of the low (Fig.a pressure Yukon 12). weakened prominent Territory during These trough the and along period low- anomalously northern 1971–1985 the low with pressure Coast BC over Mountains much from of (ablationA central season) marked North and America change di (accumulation inpressure season). present circulation during occurred the for(ablation period season) the 1986–2005, and with later o ridges period over with south anomalously central Alaska high but little change occurred during1985) the to ablation season the (Fig. latter 11). perioddecreased From (1986–2005), by the accumulation-season earlier and (1952– annual precipitation an area of persistent low pressure in western Canada during the accumulation and face elevation change measurements from these seven glaciers. 3.4 Relation to climate Surface temperature increased(Fig. 10). during From the the earlierperatures (1952–1985) period increased to by of the latter study,respectively. epoch (1986–2005), particularly average tem- after 1985 net change from 1952–2005. Five glaciers continuously thinned and receded. tains yields volume lossesriods of 1952–1985 and 1985–2005change respectively. ( We obtain lower estimates of volume 1952–1985 (Table 6). Both of these glaciers thinned after 1985, but experienced little 5 5 20 25 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2.9 %), ± erence is ff 10.6 w.e. (Table 6). − 3 and glaciers lost 0.61 and average or 1 − 2 − 0.05 km in the early-to-mid 1980s erent methods of extrap- ± ff 0.01 to 1.89 km 1 − + ± 0.48 0.16 m w.e. a − ± 10 m a 15.11 − − ; Tennant and Menounos, 2013) and 0.14 1 − − ). This discrepancy could arise from time- 3 ; Berthier et al., 2010). However, our average 3384 3383 ) for the Cariboo Mountains. 1 3 − w.e. Using our two di 2.17 km 3 ), whereas in our study it is 5.8 %. This di ± 0.3 m w.e. a 2 ± 1.17 km erent volume change estimates for the period 1952– ± ff 2.31 0.6 7.06 km − 1.0 km − − 0.10 m w.e. a < 7.58 ± vs. , resulting in a net loss of − 0.05); it supports our hypothesis that late-lying seasonal snow 3 1 ected by late-lying seasonal snow cover. The standard deviation − ff in the early-1990s (Beedle et al., 2009). Tennant and Menounos 0.48 p < and 1 − w.e. The two smallest glaciers of our study thickened and advanced and lost − (Sapiano et al., 1998). 3 3 1 1 2.04 km − − test, ± F 40 m a − 1.32 km 0.06 km 0.12 m w.e. a 4.03 ± ± ± − 6.24 The post-1985 accelerated thinning of Cariboo Mountain glaciers agrees with other Unlike the period 1985–2005, our methods of extrapolation to Cariboo Mountains From 1952–1985 thinning rates averaged Our finding of glacier advance in the period 1952–1985 accords with the advance During the period 1985–2005, glaciers shrank eight times faster than the period 0.20 0.58 m w.e. a 0.23 0.21 m w.e. a − forming poorly duringglaciers epochs advanced. with We recommend higher further surface study mass of extrapolation balance of and regional where volume some over the period 1985–1999,− glaciers of theolation Cariboo described Mountains in Sect. thinned( 3.3, by our a estimates rate yield of comparable estimatesglaciers of yield ice significantly loss 1985 di ( varying magnitude of ice dynamics leading to extrapolation from a small subset per- − over the same period.River Brewis Basin (2012) (Fig. also 1) found thickened and that advanced four during of the six periodstudies glaciers 1955–1970. of in glacier the change Canoe 2004; in northwest Brewis, 2012; North Tennant America and (e.g., Menounos, Rasmussen 2013). and Schiefer Conway, et al. (2007) found that − This rate ofof thinning the is Columbia considerablyAlaskan Icefield less glaciers ( ( then long-termthinning rate thinning is rates similar to forfrom those the glaciers reported mid-1950s for to nine− the North mid-1990s, America which glaciers range for from the period and Alberta, which increased after 1979 and again4.3 after 2000. Thickness change Observed thinning rates during the period 1952–2005 averaged (2013) also found increased recession rates for glaciers of the Columbia Icefield of BC to about in the Premier Rangeelsewhere described in by BC Luckman during et this2012; al. period Tennant (1987) and (Koch and Menounos, et with 2013). al.,a glacier 2009; Studies multi-decadal expansion Menounos period that et (e.g., only DeBeer al., determinenot and 2009; capture net Sharp, Brewis, minor recession 2007, advances over 2009; like Jiskoot those et of al., the 2009) present may study. 1952–1985, and five times fasterCreek than Glacier 1970–1985 (glacier (Fig. 7). 28) Annual increased recession from of about Castle sistent with other studies2012; of Tennant et glacier al., change 2012; Tennant inour and 33-glacier Menounos, BC subset 2013). (DeBeer over While this and net periodrecession glacier Sharp, is change negative for 2007; of ( 11 Brewis, ofvanced during these the glaciers period was 1952–1985. not significant. Nine of these 11 glaciers ad- significant ( plays a role in observationsmapping of increased of scatter 1985 for glacier smaller extents glaciers,area. and errantly that mapped the seasonal TRIM snow cover as glacierized 4.2 Area change Our results indicate net recession of Cariboo Mountains glaciers from 1952–2005, con- we compared the standard deviation inmeasured relative for area 28 change glaciers of inour the smallest both analysis glaciers is Bolch as less et a al.of (2010) relative and area in change ourfor from the study, 1985–2005 which smallest for based glaciers the ( on Bolch et al. (2010) inventory is 8.1 % a role in the observation of increased scatter for smaller glaciers. To assess this factor 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4.1 % − 5.4, and − 7.5, 9.0, and − − 9.3, 4.6, − − 3.4, 11.2, + − 2.5, − ering climatic regimes. ff 3386 3385 value (not significant) is negative. It appears r 0.1) indicating generally more relative area change for smaller glaciers (Table 5). Precipitation consistently decreased over the three periods of analysis for the ac- There was little temperature change, or decreased temperatures from 1952–1970 Studies have typically found no significant correlation among other morphometric We also find that median, minimum, and maximum glacier elevations (along with el- 5.4 % for our five size classes, arranged from smallest to largest (Table 3). Surface p < response. cumulation season and annually (Fig.an 11). accumulation Decreased season annual precipitationtion phenomenon, is negligibly changed. whereas primarily Cool average accumulation seasonhave ablation temperatures counteracted from season decreased 1971–1985 precipitation, may precipita- leadingto to that snow accumulation of comparable thebetween period 1952–1985, 1952–1970. a Some, but resultretained not accumulation, of all, and both glaciers length individual thickened and glacier and slope hypsometry advanced angle leading that led to to more a more rapid terminus Columbia Icefield of the Canadian Rocky Mountains. to 1971–1986, but following(Fig. 1985, 10). temperatures After 1985, increased increased inand annual ablation the temperature seasons, occurred Cariboo but in change Mountains both duringablation the the season. accumulation accumulation season is double that of the Mean annual and seasonal temperatures1985, increased from whereas 1952–2005, wintertime particularly precipitation after that slightly observed decreased glacier (Figs. loss 9 resultedtation), and from a 10). increased finding (decreased) It in temperatures is agreementtains (precipi- with likely (Luckman previous et studies al., fortemperatures as 1987; glaciers the in Brewis, recent the cause 2012). for Caribooin Previous accelerated Moun- mass maritime studies loss environments of implicate North (Rasmussen rising Americannant and glaciers surface and Conway, Menounos 2004; (2013) Arendt also et observed al., 2009). the Ten- role of decreased precipitation for the tain ranges, and how time-variableextent glacier change and dynamics glacier might geometry. obscure relations between 4.5 Relations to climate whether the temporal changes we observed in this study are present for other moun- evation range) correlate with areaconstant change, through but the time (Table strength 5). of A these study associations with is a not larger sample size is required to assess 2009). Other parameters include slope,elevation. We, aspect, however, find and correlation median, between minimum, slopeSlope and and correlates absolute maximum area with in relative all1952–2005, area periods. but change not from for 1952–1985, thethat and the latter on steeper period glaciers a 1985–2005 lost nethowever, (Table as less 5). basis slope absolute This is from and highly relation, relative correlated indicating with surfaceet glacier area, al., surface may area 2003). be and length spurious, (e.g., Hoelzle for the samethat size the classes, magnitude and ofof the a glacier given change glacier; they is apparently not vary with simply di relatedparameters and to area dimensional change (Paul, attributes et 2002; Granshaw al., and 2008; Fountain, Bolch 2006; et Andreassen al., 2010; DeBeer and Sharp, 2009; and Paul and Andreassen, with extent change (Serandbrei-Barbero2004; et Andreassen al., et 1999; al., Hoelzle 2008;1985–2005, et Bolch we al., et 2003; al., find Paul 2010;− average et Paul relative and al., Andreassen, area 2009).area change From and of relative( area change duringHowever, the from 1952–1985, period a 1985–2005 perioddoes are not with apply; reduced weakly average rates relative correlated area of change recession was or advance, this strain regional variability of surface-elevation change. 4.4 Relations of extent change toGlacier glacier surface morphometry area is the single morphometric parameter that commonly correlates change from a subset of glaciers, but with a more robust sample size to better con- 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C above ◦ from 1985–2005. C to 2.7 ◦ 1 − 0.070 m w.e. a ± ). Thinning rates also accelerated from 1 − 0.500 − 3388 3387 0.12 % a ± (1952–1985) to ), and some glaciers advanced. After 1985, glacier reces- 1 1 − − . Slow glacier recession rates characterized the epoch 1952– 1 − , such warming would result in a rise in the ELA of 300 to 450 m. Given 0.10 % a 1 − ± 0.05 % a 0.043 m w.e. a C m ◦ 0.05 ± ± − erent climatic regimes. The inventory of Bolch et al. (2010) possibly overestimated the recession of Cariboo Our results indicate that relations between glacier change and dimensional attributes Previous studies suggest that glaciologists need to further examine intra- and inter- Glaciers of the Cariboo Mountains will continue to strongly recede for the remain- ClimateWNA records indicate that wetter and cooler periods align with anomalous ff 0.143 mass balance. Mountains glaciers from 1985–2005. For 28smaller common than glaciers, our the extents average 2005et 2 % al. extents (2010) generated and withmapping 5 % of the smaller late-lying semi-automated than seasonal the snow method as 1985 of glacierized extents area Bolch of in theof the TRIM TRIM the dataset, dataset. glaciers likely due ofrelated to this to study ice are dynamics not and stable the through complex way time; glaciers this respond non-stationarity to may changes be in surface − Temperatures increased from 1952–2005, primarilyseason after precipitation 1985, decreased whereas over accumulation thein period temperature of study, and indicating decreases thatchange. in both increases precipitation explain the observed pattern of glacier di 5 Conclusions During the periodof 1952–2005, glaciers 0.19 of1985 the ( Cariboo Mountainssion receded rates at increased eightfold a (0.41 rate will be variable with respect toever. glacier Selection morphometry, climate of and glacier benchmark response,testing how- glaciers of and the representative regional glaciertain representativeness subsets, et of as existing al., well benchmark 2009)glacier as glaciers should extent (e.g., and be Foun- thickness based change, on and regional with glacier respect morphometry, to recent varying decadal glacier response in a priori selection of a representative subset of glaciers. Regional representativeness sessments of decadal area and thickness change can be used to make an informed glaciers will lose 80–90 % of their volume by 2100regional (Marshall mass et balance al., 2011). variabilitymeans (Braithwaite, of 2002), making an and a conclude(Fountain priori that selection et of there a al., are regionally-representativechange no benchmark 2009). measurements glacier limits The assessments of paucity regionaluse representativeness. Widespread of of remotely-sensed traditional imagery mass-balanceever, to provides derive and a glacier means glacier extents todecadal and document length timescales. changes surface of elevation, We glacier how- demonstrate extent that and comprehensive volume glacier change on inventories and as- (AAR) of 60 % indicatesapproximately a 2375 present m. steady-state A ELA risefrom for in Cariboo 60 the % Mountains ELA to glaciers of of betweenout from 12 of 300 and balance to and 5 %, 450sistent greatly m leaving diminished with would glaciers by reduce the of the the the mid-21st finding AAR century. Cariboo for Such Mountains the a grossly decline eastern is slopes con- of the Rocky Mountains that predicts earlier work and expandinfluenced the glacier spatial change domain during of the these mid-20th climate to early-21st anomalies centuries. andder how of they the 21stthe century. Projections 1971–2000 suggest mean annual warmingcludes by of a the 1.8 portion 2050s ofof for the 0.006 the Premier Range Columbia (Murdock Basincurrent et glacier of al., hypsometry 2013). BC, (Fig. Assuming an 5), a an area lapse assumed that rate steady-state accumulation-area in- ratio low-pressure (1952–1970 and 1971–1985),anomalous and high-pressure drier (1985–2005) (Fig. and 12).anomalies warmer Previous over periods studies northwest note align North high-pressure recession with America and after thinning the (e.g.,and late-1970s Bitz Conway, 2004). with and Our coincident Battisti, findings 1999; glacier for Hodge glaciers of et the al., Cariboo 1998; Mountains Rasmussen agree with this 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 2009. , 2012. 10.1029/2009GL039533 3390 3389 , 2006. , 2008. , 2009. , 2010. 10.5194/tc-6-763-2012 , 2010. , V.: Significant contribution to total mass from very small glaciers, The We acknowledge research funding provided through the Western Cana- ć 10.1029/2005JF000436 10.5194/tc-2-131-2008 10.5194/tc-3-205-2009 10.1657/1938-4246-42.2.188 10.1038/NGEO737 glaciers in the Monashee Mountains, British Columbia, Canada, J. 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Aerial photography used to derive glacier extent and thickness change data. 10.1029/2004GL020816 10.1029/2008GL034718 , V. and Hock, R.: Regionally di Date10 Sep 194625 Sep Region 1952 C9 Sep Roll 1952 C30 Aug 1955 Q15 Aug 1967 P BC32019 Aug 1970 C A1353815 Jul 1971 P A1353824 Jul # 1977 A14930 of Q31 Jul 1984 BC7019 Scale 15 C16 Aug 1985 BC5394 1:31 C 5 68016 Aug 1985 Q Resolution A21587 1:6011 000 Sep 5 1996 Q, P Contrast A2474325 7 0.38 Aug 15 1:60 2005 C 000 Snowcover BC8407325 1:70 000 Aug 0.84 1:15 2005 BC85071 C 840 BC85075 525 Aug Poor 2005 P 0.84 1:8025 000 Aug 0.98 4 Fair 2005 Q, BCB96106 0.19 P 1:80 8 Q 000 BCC05111 Good 4 Fair 0.96 5 1:70 Poor 000 7 BCC05108 BCC05109 1:60 Good 000 Good 1:60 000 1:60 1.12 000 6 10 Fair BCC05110 Good 0.98 1:40 Fair Fair 000 0.72 1:20 18 000 16 0.72 Poor 0.72 1:20 1:20 000 000 Poor Good 0.48 Fair 0.24 6 Fair Fair Fair 0.24 1:20 0.24 000 Poor Poor Good Fair Fair Fair Good Good 0.24 Fair Good Good Good Good Good ć Regions: C: Castle Creek, Q:Roll Quanstrom, ID: P: BC: Premier provincial Range. aerialContrast: photos, subjective A: determination federal of aerial imageSnowcover: photos. contrast subjective on determination a of scale snowcover from extent. 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A.: Elevation, volume and terminus changes Radi Rolstad, C., Haug, T., and Denby, B.: Spatially integrated geodetic glacier mass balance and Paul, F., Kääb, A., Maisch, M., Kellenberger, T., and Haeberli,Rasmussen, L. W.: A. and Rapid Conway, H.: disintegra- Climate and glacier variability in western North America, Paul, F. and Haeberli, W.: Spatial variability of glacier elevation changes in the Swiss 5 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 9.3 13.9 11.8 6.2 13.4 16.4 4.2 11.2 6.8 1.5 1.3 30.2 6.7 2.8 21.3 27.4 2.1 2.3 4.3 2.7 19.6 28.2 2.0 5.8 1.8 5.8 8.9 0.9 0.5 31.7 23.4 10.1 3.6 17.2 13.3 14.3 4.7 1.3 20.5 5.9 10.3 10.6 − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Area change 1952– 2005 (%) ) 2 7.879 2.694 2.748 0.372 0.244 8.895 2.146 4.057 0.008 0.002 0.002 0.091 0.019 0.008 0.114 0.212 0.014 0.015 0.029 0.023 0.210 0.359 0.020 0.061 0.021 0.083 0.158 0.017 0.011 1.145 0.809 0.344 0.160 0.959 1.082 1.612 0.622 0.178 3.810 1.080 2.189 15.108 − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Area Change 1952– 2005 (km 4.1 9.0 4.6 2.5 7.9 0.2 6.4 0.7 10.6 10.8 19.2 14.2 0.6 25.1 11.4 2.1 7.7 8.6 9.3 0.3 9.7 3.1 5.8 4.7 − − − − − − − − − − − − − − − − − − − − − − − − Area change 1952– 1985 (%) ) 2 3.474 1.746 1.078 0.046 4.287 0.118 2.324 0.001 0.032 0.058 0.149 0.152 0.010 0.907 0.396 0.070 0.428 0.695 1.051 0.043 1.796 0.573 1.245 6.716 − − − 0.205 3.4 − − − − 0.014− 12.0 − 0.0200.007− 7.1 − 2.5 0.0470.0420.103 7.1 0.138 6.3 − 15.1 16.2 0.0090.0180.069 0.9 0.012 1.7 − 5.9 0.021 0.8 0.088− 1.1 − 4.0 − 0.115− − 2.6 − − 0.183− − 1.3 − − Area change 1952– 1985 (km 5.4 5.4 7.5 9.3 11.2 9.2 4.0 5.1 16.8 0.7 3.721.9 12.9 0.0045.2 11.7 2.5 10.1 6.2 8.6 8.1 16.8 16.2 6.3 2.9 7.4 7.3 6.6 8.4 2.0 4.3 8.8 13.5 8.2 6.0 10.3 5.2 5.5 4.4 2.6 12.0 2.9 4.7 − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Area change 1985– 2005 (%) ) 2 4.405 0.948 1.670 0.577 0.198 4.608 2.028 1.733 0.022 0.001 0.006 0.059 0.039 0.015 0.056 0.063 0.061 0.057 0.132 0.161 0.058 0.029 0.079 0.090 0.095 0.148 0.038 0.099 0.238 0.413 0.274 0.275 0.531 0.387 0.561 0.579 0.361 2.014 0.507 0.944 8.392 − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − Area change 1985– 2005 (km 2.0 3.5 0.7 1.1 0.6 3.5 9.7 2.3 2.6 17.2 1.7 1.7 0.7 0.1 1.1 2.5 2.7 0.6 0.1 5.8 0.4 5.0 2.1 2.0 − − − − − − − − − − − − − − − − − − − − − − − − Area change 1970– 1985 (%) ) 2 1.658 0.636 0.160 0.068 0.316 1.212 0.029 0.007 0.019 0.191 0.018 0.019 0.009 0.002 0.020 0.069 0.086 0.027 0.004 0.632 0.050 0.892 0.381 0.408 − − − − − − − − − 0.0390.133− 5.2 No data 15.5 − No data− − No data No− data− No data− No data − 0.006− 0.2 − − − − − − Area change 1970– 1985 (km 3396 3395 ) Z (m) Z (m) Z (m) Z (m) Z (m) 2.1 5.7 3.9 3.1 1.0 2.9 0.5 23.2 8.9 2.2 8.5 3.7 4.9 1.1 3.9 2 − − − − − − − − − − − − − − − Area change 1952– 1970 (%) ) 2 1.816 1.110 0.918 1.112 0.003 0.037 0.008 0.838 0.310 0.076 0.691 0.419 0.904 0.192 0.837 − − − 0.273 4.6 − − 0.027 9.5 0.066 10.0 − 0.078− 6.7 − − − 0.142− 3.2 − − − − Area change 1952– 1970 (km ) 2 Area 2005 (km ) 2 Area 1985 (km ) 2 Area 1970 (km 12345678 C9 P10 P11 P12 P 51313 Q 452 0.10914 Q 641 0.13515 Q 22.7 779 0.15516 P 19.5 922 P 0.21017 731 E 27.5 C 0.26418 W 952 18.0 P 0.276 1366 NE19 21.1 2472 C 0.422 138620 22.2 0.563 N 2587 1552 C 260721 21.3 N 0.648 1173 2471 P 18.3 0.650 SE22 2593 1671 2485 2360 P NW 2619 0.653 25.723 2469 1017 26.6 2523 P 2590 N 0.830 2532 241324 21.2 1419 2480 NW 2682 2386 Q 0.86025 NE 2785 2528 21.6 1327 2379 Q 230 2545 0.913 228326 SE 2420 20.7 2027 2383 2324 213 C 2651 0.983 2256 240627 372 16.2 N 1584 2228 Q 2718 2279 0.995 245228 NE 2692 2415 (Castle 1209 23.8 Creek) Q 272 2621 1.145 2400 209329 NE 2117 (Tête) 2199 24.5 C 2399 Q 394 1.349 2445 2363 199030 NE 2494 436 (David) 1870 26.7 2968 Q 1.609 393 2322 NW 224631 2751 16.7 1796 2407 Q 1.816 2343 266532 401 2733 (Kiwa) 10.8 2965 S 851 2169 Q 2699 2.188 2314 213533 761 5875 E 3002 18.5 P Q 2646 2.464 2662 P 2175 SE 2720 487 15.7 3562 2728 2716 9.645 2.655 2248 2580 12.3 2300 E 2362 477 3.049 2171 2469 3157 585 11.1 P S 18.5 3294 2724 4.280 3093 405 5971 N 17.3 3062 2364 2387 2313 Q 5228 4.625 2478 NE 12.674 909 N 14.9 2421 2172 13.533 3188 7.037 NW 2187 922 11.9 2398 2438 C 2515 16.9 2387 9597 2633 19.3 N 12.8 2449 2482 2044 2352 875 NW 17.154 4010 2436 2052 N 2397 2749 343 SW NE 446 14.782 2490 2463 2198 17.2 2359 2669 2417 1881 7302 2054 2803 2609 1991 705 13.2 2520 2416 2827 2488 19.094 N 2425 3019 617 2789 2061 NE 2616 605 2137 2565 2408 12.8 946 2752 965 1352 2617 2708 1649 798 2056 2319 3339 N 3357 2917 2705 691 571 2334 1987 1708 1491 2273 861 1868 3509 2745 2288 2018 1803 877 2910 1107 Id(Name) Region Length Area Slope (m) Aspect (km Mean Median Min. Max. Range ) Slope and elevation data fromLength TRIM and DEM area and data 2005 from extent. 2005 extent. 2 85.116 83.300 81.642 77.237 19.376 18.266 17.630 16.682 23.303 22.385 22.225 20.555 5.991 6.264 6.196 5.619 1.815 No data 1.769 1.571 No data No data No data No data 54.194 No data 49.907 45.299 No data No data No data No data Extent1952 (km Successive periods Cumulative periods Glacier extent and area change data for glaciers and summed by subregion and size 2 2 2 Morphometric properties of the 33-glacier subset. 2 2 10–50 km 5.0–10 km 1.0–5.0 km 0.5–1.0 km P0.1–0.5 km 51.387 51.585 51.269 49.241 0.198 0.4 Q C 36.125 35.013 33.801 32.068 All 141.960 No data 135.244 126.852 No data No data No data No data 23 P4 P5 P6 P7 Q8 0.137 Q9 0.157 Q10 0.301 P No data11 P 0.283 0.15812 C 0.136 0.284 0.29813 P 0.536 0.310 0.161 C14 0.775 0.135 No data 0.26915 C 0.662 No data 0.303 0.66516 P 0.155 0.291 No No data 0.682 data17 P 0.210 0.478 0.728 0.85318 P 0.264 0.700 0.626 0.001 No 0.276 data 1.07019 Q 0.746 0.422 0.709 1.272 No Q20 0.858 data 0.707 0.563 0.6 No data 1.00321 C 1.109 0.785 No No data data 1.05622 Q 0.648 1.235 No 0.991 data 0.650 No data 1.16623 Q 1.030 No 0.918 data 0.653 0.003 1.432 No24 Q data 1.093 No No data data 0.830 1.767 0.035 No25 Q data 1.244 1.012 No 0.860 data 0.064 1.833 No 1.9 0.913 1.436 Q26 data 1.074 No data 2.199 0.005 1.75927 Q 5.3 1.235 No 0.983 data 0.039 3.609 9.4 28 Q 1.874 1.444 0.995 3.464 2.24829 C 0.6 1.757 1.145 3.393 0.027 3.6 2.77130 P 0.007 1.854 1.349 4.440 0.037 3.154 P31 2.287 1.609 5.584 3.31732 Q 2.7 2.702 1.0 1.816 0.004 8.119 4.58233 P 3.5 3.068 2.188 11.257 No C data 3.323 2.464 0.041 13.296 0.3 7.428 4.555 2.655 10.838 5.156 0.049 13.711 3.049 13.303 18.592 2.2 7.424 10.206 4.280 13.821 18.234 4.625 2.2 0.008 13.253 17.688 21.283 9.645 13.894 7.037 18.042 No 12.674 16.796 data 0.6 20.446 0.039 13.533 17.661 No 0.007 data 14.782 20.038 0.110 17.154 1.7 No data 19.094 0.1 No 0.8 data 0.073 0.5 Id Region Area 1 C 0.117 No data 0.131 0.109 No data No data No data No data Values in bold indicate glacierExtents advance, summed values by in size italics class indicateSummed are recession extents based and (beyond on margin area 2005 change of10–50: extent. may error). none. omit some individual glaciers: All: 18, C: 5 and 18, Q: none, P: 2, 0.1–0.5: none, 0.5–1.0: 8 and 18, 1.0–5.0: none, 5.0–10: none, class. Table 3. Table 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 0.215 0.046 0.393 0.309 − − − − 0.065 0.193 0.131 − − − 0.322 0.513 0.364 0.412 0.431 0.427 0.087 0.310 0.221 − − 0.323 0.1350.260 0.053 0.312 0.518 0.060 0.282 0.440 0.487 − 3398 3397 0.650 0.598 0.358 0.210 0.765 0.523 0.731 0.582 − − − − ) Slope Median Z (m) Min. Z (m) Max. Z (m) Range Z (m) 2 0.556 0.235 0.596 0.597 0.008 0.011 Length Area Slope Median Z Min Z Max Z Range − − − − − 0.05). < p Count Length (m) Area (km cients in bold are significant ( ffi Correlation table (Pearson-product moment) of relations of glacier area change with Median glacier morphometry for glaciers that underwent some advance, receded con- 32 for the periods 1950s–198533 and for 1985–2005. the period 1950s–2005. = = 1952–1985 Absolute Area Change 1952–1985 Relative Area Change 1985–2005 Absolute Area Change 1985–2005 Relative Area Change1952–2005 0.328 Absolute Area Change 0.316 1952–2005 Relative Area Change AdvanceRetreatNo Change 9 11 12 1552 1949 3032 0.653 1.406 3.640 21.6 20.8 15.2 2449 2605 2403 2169 2210 2075 2733 2941 2774 617 794 733 Correlation coe n n Table 5. respect to glacier morphometry for three periods. tinuously, or exhibited no discernable change during the period 1952–1985. Table 4. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 28

) 1 − 0.17 0.04 0.21 0.18 0.14 0.04 0.06 ± ± ± ± ± ± ± 0.27 0.22 0.14 0.20 0.39 0.00 0.04 study (Castle, (Castle, study − − − − − − Thickness change 1952–2005 (m w.e. a − ) 1 − 0.23 0.08 0.30 0.22 0.22 0.08 0.15 ± ± ± ± ± ± ± 0.44 0.59 0.41 0.12 0.82 0.57 0.87 − − − − − − Thickness change 1985–2005 (m w.e. a − 3400 3399 ) 1 − 0.20 0.06 0.25 0.22 0.16 0.07 0.15 ± ± ± ± ± ± ± 0.24 0.08 0.02 0.10 0.09 − − − − − change 1952–1985 (m w.e. a Figure 1.Study three red indicate area:the in rectangles this subregions Figure Premier) three in the maps 2. and of location Quanstrom, the and Figure 31 28 26 24 19 11 0.27 Glacier Id Thickness 1 0.56 3 1 2 Study area: the three red rectangles indicate subregions in this study (Castle, Average annual thickness change in meters of water equivalent. Figure 1. Quanstrom, and Premier) and the location of the three maps in Fig. 2. Table 6. 29 from Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

edian, and and edian, n periods. three surement of , including extents for 1952, 1970, 1985, and 2005. Panels show umerical glacier identification, numbered by 2005 surface area 3402 3401 Cariboo Mountains subregions showing subset of 33 glaciers, including extents for Box-and-whisker plots showing the maximum, interquartile range, median, and min-

Figure 3.Box-and-whisker maximum, the plots m range, Figure showing interquartile elevation 275 checkpoints. tominimum of Checkpoints used are residuals surface of models relative of accuracy stereo meadetermine and correctionfor bias in Castle the elevation glaciers i andof change regions surface Quanstrom 1 2 3 4 5 6

Figure Figure 2.Cariboo Mountains subregions showing subset of 33 glaciers from left to righttheCastle, Quanstrom, and Premier subregions. N 2 Tables to 4. corresponds thatsmallest of and to largest, imum of surface elevationrelative residuals accuracy of of 275 stereochange models checkpoints. of glaciers Checkpoints and in bias are the correction used Castle for and to Quanstrom measurement determine regions of in surface three elevation periods. Figure 3. 1952, 1970, 1985, and 2005. Panelssubregions. show Numerical from left glacier to identiﬁcation, rightlargest, numbered the corresponds Castle, by to Quanstrom, 2005 and that surface Premier of area Tables 2 from and smallest 4. to Figure 2. 2 3 4 1 ! 33

average average subset hypsometry

3404 3403 (black).

of total glacierized extent by size class for all Cariboo Mountains this study this

to lighter blue respectively). blue lighter to Fraction Hypsometries Hypsometries for our subset of glaciers (gray),

Fraction of total glacierized extent by size class for all Cariboo Mountains glaciers Hypsometries for our subset of glaciers (gray), average subset hypsometry (black), all ! Figure Figure 5. (black), all Cariboo Mountains glaciers (red), and the Castle, Quanstrom, and Premier subregions (darker ! Figure Figure 4. and (gray) glaciers ! ! ! ! ! ! ! ! 2 3 4 1 1 2 3 4 Figure 5. Cariboo Mountains glaciers (red), andto the lighter Castle, blue Quanstrom, respectively). and Premier subregions (darker Figure 4. (gray) and this study (black). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ! 35

38 e e range, median and (A)32 glaciers for three 32 glaciers for three periods, and (A)

3406 3405

of total surface by aspect for all Cariboo Mountains glaciers (black) (black) glaciers Mountains Cariboo for surface all by aspect of total

Fraction ubset (gray). (gray). ubset

s Box-and-whisker plots displaying maximum, interquartile range, median and mini- Fraction of total surface by aspect for all Cariboo Mountains glaciers (black) and our our

Figure Figure 7. Box-and-whisker plots displaying maximum, interquartil minimum of average annual rates of relative area change for periods, and (B)for 26 individual and for periods, four periods. glaciers ! Figure 6. Figure and for 26 individual glaciers for four periods. 2 3 4 5 1 ! ! ! 1 2 3 (B) Figure 7. mum of average annual rates of relative area change for Figure 6. subset (gray). 39 nge, nge, median, and nge, nge, nge, median,median, andand

quivalent of seven quivalentquivalent of of seven seven

maximum, maximum, interquartile range, median, and maximum, maximum, interquartile range, median, and 3408 3407

whisker plots showing the maximum, interquartile ra whiskerwhisker plotsplots showingshowing thethe maximum,maximum, interquartileinterquartile ra ra

whisker plots display whisker plots display verage verage annual thickness change in meters of water e verage verage verage annual annual thickness thickness change change in in meters meters of of water water e e Box-and-whisker plots display maximum, interquartile range, median, and minimum Box-and-whisker plots showing the maximum, interquartile range, median, and min- minimum percent area change for 28 glaciers from 19 28 for glaciers change area percent minimum Figure 8.Box-and- Bolch et al. (2010).

minimum percent area change for 28 glaciers from from 19 19 28 28 for for glaciers glaciers change change area area percent percent minimum minimum of average annual thicknessperiods. change in meters of water equivalent of seven glaciers for three Figure 9. imum percent area changeet for al. 28 (2010). glaciers from 1985 to 2005 for this study and that of Bolch Figure 8. 3 4 1 2 glaciers for periods.glaciers three Figure 9.Box-and- minimum of a

long-term long-term (1952- age ablation season ues ues indicate averagesfor average ablation season tem- (B) total ablation season precipitation, (B) 3410 3409 average annual temperature. Gray bars and values indicate averages for the Figure Figure 10. ClimateWNA temperature records of deviation from the 2005) mean of (A) average accumulation season temperature, (B)aver temperature, and (C)averageannual the 1952-1970,periods and 1970-1985, averagesfor 1985-2005. temperature. Gray bars and v (C) average accumulation season temperature, total accumulation season precipitation, ClimateWNA temperature records of deviation from the long-term (1952–2005) ClimateWNA precipitation records of deviation from the long-term (1952–2005) the periods 1952-1970, 1970-1985, 1952-1970, 1985-2005.periods and the Figure Figure 11.ClimateWNA precipitation records of deviation from the 2005) mean of (A)total accumulation season precipitation, (B)total precipitation, precipitation, and (C)totalannual precipitation. Gray bars and val 1 2 3 4 5 (A) (A) total annual precipitation. Gray bars and values indicate averages for the periods 1952– 4 5 2 3 1 (C) 1970, 1970–1985, and 1985–2005. Figure 11. mean of and perature, and periods 1952–1970, 1970–1985, and 1985–2005. Figure 10. mean of Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

s 45 lation ive ive < 0.05)< point. mean the a at from grid given 3411 p 0.05) from the mean at a given grid point. p < erent ( ﬀ Geopotential height (700 hPa) anomalies (m) for the accumulation and ablation

Figure 12.Geopotential hPa) accumulation height (700 the anomaliesFigure for ab (m) and of the shows Data 1952-2005 for anomaly. Colorperiod scale define magnitude seasons. Dashed fields. negative and mean solid denote respectively the and posit contours different ( that significantly are anomalies Figure 12. seasons. Color scale shows magnitudemean of fields. anomaly. Data Dashed for and thethat period solid are 1952–2005 contours significantly defines di respectively the denote negative and positive anomalies 3 4 5 1 2