Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 6 , 10 , ` eres, 11 , 1 2 Discussions ´ egoz The Cryosphere , Y. Lejeune , J. L. Ceballos ´ 9 en 5 , V. Jomelli 1 , M. M ´ e de Savoie/Grenoble-INP, ´ aceres 13 ` eres, France , and P. Wagnon 7 , M. Scheel ´ etude des Transferts en Hydrologie 9 , V. Favier ´ eophysique de l’Environnement , B. C ¨ 2 urich, Switzerland 4 ´ eographie Physique (LGP) UMR 8591, , J. Mendoza 5 , M. Villacis , C. Huggel 2478 2477 15 2 , J. Gomez , G. Consoli 3 2 ´ a D.C., Colombia , W. Suarez , L. Maisincho , J.-E. Sicart 14 , A. Soruco 8 2 ´ ´ eo France/UJF-Grenoble 1/Universit , T. Condom u 1,12 ´ et 2,7 ´ on de Guevara E11-253, Quito, Ecuador , M. Vuille , P. Ginot , P. Ribstein 7 2,7 , B. Francou 13 , M. Collet 1 2 ˜ naquito N36-14 y Corea, Quito, Ecuador UPS-Paris 1/CNRS/UVM-Paris 12, Laboratoire de G IRD/CNRS/IFSTTAR/M CEN, CNRM-GAME, Meteo-France/CNRS, Saint Martin d’H UMSA, IHH, Calle 30, CotaUMPC/CNRS/EPHE, Cota, Sisyphe La UMR Paz, 7619, Bolivia Paris,SENAMHI, 75252, av. France Las Palmas s/n, Lima, Peru This discussion paper is/has been under review for the journal The Cryosphere (TC). Please refer to the corresponding final paper in TC if available. Department of Atmospheric and Environmental Sciences, University at Albany, Albany,Department NY, of Geography, University of Zurich, 8057 Z IDEAM, Carrera 10 N20-30, Bogot EPN, DICA, Ladr INAMHI, I UMSA, IGEMA, Calle 27, CotaANA, Cota, UGRH, La Huaraz, Paz, Per Bolivia IRD/UJF-Grenoble 1/CNRS/Grenoble-INP, Laboratoire d’ UJF-Grenoble 1/CNRS, Laboratoire de Glaciologie et G 11 Meudon, 92195, France 12 Observatoire des Sciences de l’Univers Grenoble (OSUG) UMS 222, St Martin d’H 8 USA 9 10 38400, France 13 14 15 Received: 13 June 2012 – Accepted: 21Correspondence June to: 2012 A. – Rabatel Published: ([email protected]) 16 July 2012 Published by Copernicus Publications on behalf of the European Geosciences Union. The Cryosphere Discuss., 6, 2477–2536,www.the-cryosphere-discuss.net/6/2477/2012/ 2012 doi:10.5194/tcd-6-2477-2012 © Author(s) 2012. CC Attribution 3.0 License. 6 5 Review article of the currentglaciers state in of the tropical Andes: a multi-century perspective on glacier evolution and climate change A. Rabatel et Environnement (LTHE) UMR3 5564, Grenoble, 38041, France 4 R. Basantes Y. Arnaud R. Galarraga E. Ramirez (LGGE) UMR 5183,2 Grenoble, 38041, France 1 7 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − ˜ no C at ◦ 4 + Cdecade ◦ 0.76 m w.e. in the period − 2480 2479 in the last 70 yr. The higher frequency of El Ni 1 − Cdecade ◦ erent cordilleras, Francou and Vincent (2007) estimated the to- ff 0.2 m w.e. in the period 1964–1975 to − . 2 The Intergovernmental Panel on Climate Change (IPCC) pointed to the role of moun- proportion of the population lives in arid regions to the West of the Andes (especially in evidenced a warming trend atgood high agreement with elevations air-temperature during measurements the andVuille 20th reanalysis et data century. al. presented This (2003) by result andacross is Bradley the in et tropical al. Andes (2009), for theelevations showing above period an 4000 1939–1998. m increase An a.s.l. of is increase 0.10 (Bradley projected of for more et the than al., 21st century 2006; usinga Urrutia IPCC temperature scenario and change A2 Vuille, could 2009). leadthe With to complete no a disappearance major of change small reduction into glaciers, in the precipitation, whose glacial current such upper equilibrium-line coverage reaches and altitude are (ELA). even located This to is close a serious concern because a large ablation occurs all yeartime round response of on the the positionconsequently lowest of to part the changes glacier of terminus in theet to climate glaciers al., changes (e.g. in resulting 1999). mass Francou in Recently,borehole balance, et a using drilled and al., near short- englacial the 1995, temperature summit 2003, of measurements 2004; Illimani in (6340 Wagnon m a a.s.l., 138 Bolivia), m Gilbert deep et al. (2010) Peru. Based on theseple inventories and of current glaciers rates intal of di retreat glacier documented surface-area for1920 a in km sam- the intertropical Andes in thetain glaciers early as 2000s keyglaciers indicators to are of known be recent to climate be around Kaser especially change and sensitive (Lemke Osmaston, to et 2002). climate Due change al., to (e.g. 2007). the Hastenrath, Tropical specific 1994; climate conditions in the tropical zone, The tropical Andesbetween is Peru host (71 %), toGlacier Bolivia more inventories (20 than %), have been Ecuador 99 %dan, conducted (4 %) of 1991; in and Poveda almost all and Colombia-Venezuela all tropical Pineda, (4 tropical %). glaciers 2009; mountain UGRH, (Kaser, ranges 2010) 1999) (Jor- from 1975 in Bolivia to 2006 in 1 Introduction mass balance variability at thedisplay interannual a to significant decadal trend timecannot in scale. the explain Precipitation tropical the did Andes not a glacier in significant the recession. rate 20th of On century, 0.10 events and the and consequently other changes hand, ingether temperature its with a increased spatial warming at andthe troposphere temporal recent over dramatic the occurrence shrinkage tropical since of Andes glaciers the may in late thus this explain part 1970s much of to- of the world. ical Andes, it shouldon be small noted glaciers that atand as which low could a altitudes disappear percentage, that insurements this the do performed coming is not in years/decades. much Bolivia, Monthly havesurface mass more Ecuador a temperature balance and pronounced permanent of mea- Colombia the accumulation showed Pacific zone, Ocean that is variability the of main the factor governing variability of the the last three decades is17th–early unprecedented 18th since the century). maximum In extensionbeen terms of some the of sporadic LIA gains changes (mid onnegative in several over mass glaciers, the balance, we past show 50 althoughical that yr, there Andes with the have a trend that mean has ispoint mass been slightly in balance quite the more deficit trend for negative appeared glaciersdecreasing than in in the from the the late computed trop- 1970s global with1976–2010. mean average. In annual addition, A mass even break if balance glaciers per are year currently retreating everywhere in the trop- The aim of thisthe paper studies is of to glaciers providethe the in current status community the of with tropical thein a Andes glaciers surface comprehensive in conducted area overview the in and of context length, recent of we climate decades show change. leading In that terms to the of glacier changes retreat in the tropical Andes over Abstract 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ers against ff ort has been ff ort has been made to re- ff 2482 2481 man et al., 2003; Ramirez et al., 2003; Ginot ff C higher temperatures during the austral wet summer in October to March, ◦ erent characteristics. Troll (1941) distinguished the inner tropical climate with ff C to 2 ◦ The objective of this review is to provide the scientific community with a comprehen- In addition to this permanent monitoring, considerable e To better understand glaciological processes, to link climate parameters and their seasonality (maximum cloud cover duringstable austral humidity summer). In conditions the cause humid accumulation inner tropics, and ablation to occur simultaneously mate which when subtropicalMay to conditions September prevail, and is whenMarch. characterized tropical The by conditions tropical prevail a climate by drythroughout is a characterized wet season the by season in year homogeneous in temperature with(1 October conditions to a slightthan seasonality during of the air australlar temperature dry radiation winter in is in the May alsothe outer to more extra-terrestrial September). tropics or irradiance At less in low constant latitudes, the throughout incident outer so- the tropics year, is as attenuated the by seasonality pronounced of cloud 2.1 Climate settings From a climatological point of view,with the intertropical di zone can bemore divided into or two less zones continuous precipitation throughout the year and the outer tropical cli- dressed also include whetheris the unprecedent glacial since retreat the ofis LIA, tropical related and glaciers to whether in the the recentissues glacial observed decades to recession increase estimate in in the the future atmosphericfunctioning behavior tropical temperature. of of Andes high-altitude These glaciers glacierized are and watersheds their important in impacts coming on decades. the hydrological 2 General settings and methodologies (e.g. Thompson et al.,et 1985, al., 2006; 2010; Ho Gilbert et al., 2010). sive overview of studies performed onwhich allow glaciers the in current the status tropical of Andes the in glaciers recent to decades, be determined. Research questions ad- time-scale over the last millenium and about climate warming during the 20th century livia which revealed important information about climate variations at a multidecadal consists of measuring themethods, glacier and mass of balance measuringsensing using studies the glaciological have glacier and been surfaceto hydrological performed energy reconstruct using balance. changes aerial In inglaciers photographs the in parallel, and the volume, remote- area satellite surface since images area the middle and of length the ofconstruct 20th glacier century. a fluctuations large from moraine number evidenceimum since across of the the tropical Little Andes Ice (e.g. AgeFinally, Rabatel (LIA) ice et max- cores al., have 2005a, 2008a; been Jomelli retrieved et from al., several 2009). summits in Ecuador, Peru and Bo- made by IRD (the FrenchAndean Institute partners of in Research Bolivia, andteams Ecuador Development), such and in as: Peru, association the as with “Tropical Glaciology wellthe Group” as Department at other the of international University Geography of scientific of Innsbruck at Geography (Austria), at the the Ohio University State of Zurich University (Switzerland). (USA) The or observation system the mainly Department a consequence, mountain glaciershighly in seasonal the precipitation tropical at Andes times2008a). act when as rainfall critical is bu low or even absent (Vuillevariability et to al., glacier massnent balance, glacier and monitoring to networks document haveand been current Bolivia. set glacier The up changes, in oldest perma- eachglaciers data country began series in between are Colombia the available early in 1970s. Peru Since where the early partial 1990s, surveillance an of important e the supply of water fromtural high and altitude domestic glacierized mountain consumption chains asis is well all crucial as for the for agricul- hydropower moreconditions (Vergara as et true a al., since part 2007). these of This and the regions a seasonal dry also cycle, with season exhibit limited lasting a seasonal from temperature combination May/June variability to of August/September warm (Kaser et and al., dry 2010). As Peru and Bolivia, where the percentage of glaciers is the highest). As a consequence, 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ˜ no are not uniform sp. were made on each ˜ na/El Ni ¨ uller (1985) applied this technique 2484 2483 Rhizocarpon Geographicum C dating (Gouze et al., 1986; Seltzer, 1992). In Bolivia, 14 ˜ no years (warm phase of ENSO) tend to be warm and dry, ˜ no-Southern Oscillation (ENSO) phenomenon (e.g. Francou and ˜ na years (ENSO cold phase) are associated with cold wet conditions on ˜ no event may vary considerably, for instance between the northern coast of studies Glacier length, surface area and ELA for the LIA maximum and the following moraine New insight into glacier fluctuations during the LIA concerning the entire intertropical years of mass balance measurementsFrancou, for 1995; three Hastenrath of and them Ames, (Kaser 1995a,b; et Ames al., and 1990; Hastenrath, Ames 1996). and 2.3 20th century observations: from field measurements to remote-sensing 2.3.1 Pioneering studies Unlike mid-latitude glaciers where continuous massfor balance series five have been to available sixbefore 1990. decades, Data information on on glacier terminusin glacier fluctuations the in have Peruvian been Cordillera the available Blanca for tropical since four the glaciers Andes late was 1940s, very and since scarce the late 1970s, a few stages were reconstructed usingmoraines digital (Rabatel et elevation al., modelsCharquini 2006, (DEM) Massif 2008a; in on Bolivia, Jomelli Rabatel the et etthe al. al., basis most (2006) 2009). of computed important For changes the moraine in five stages volume glaciers between by in reconstructing Cerro glacier hypsometry. Andes has been gained intry. the Systematic past measurements decade of thanks tomoraine moraine in dating several using proglacial lichenome- (Solomina margins et in al., 2007; Bolivia Jomelli (Rabatelstatistical et approach et al., was al., 2008), developed and 2005a, toory, Ecuador 2008a), process as (Jomelli data Peru the et based al., largest onet 2009). the lichens al., A extreme 2006; measured new values Naveau for the- et moraine al., 2007). dating are extreme values (Cooley where the main moraine stagesfor are relative represented). M dating inperiod Bolivia, 750–1900 and AD, but Rodbell without providing (1992)during a the dated detailed period. chronology Peruvian of LIA glacier moraines fluctuations to the on glacier forelands (see the maps of the Bolivian eastern cordillera by Jordan, 1991, Quelccaya ice cap, Thompson etto al. (1986) AD assumed 1900. that Lichenometry the LIA has lasted also from been AD used 1500 to date very well preserved moraines of their maximum extentconjectural. and Historical the sources stages andriod of mining (Broggi, settlements their 1945) established subsequent indicate in retreatcenturies, that the then glaciers remained began colonial advanced highly to considerably pe- retreat duringEcuador after the (Hastenrath, AD 16th–19th 1981). 1860 Some inusing authors Peru tried glacier (Ames and to evidence Francou, date with 1995)Gouze the and et LIA in al. the (1986)ice tropical suggested extension. Andes 670–280 In calyrBP Peru, on as the the basis interval of displaying evidence maximum found in the ice core retrieved on the Peru and the Southern Peruvian Altiplano region. 2.2 Reconstruction of LIA glacier changes In the early 1980s,glaciers Hastenrath in (1981) the and tropical Clapperton Andes were (1983) much already larger mentioned during that the LIA than today, but the date many studies and there is generalis agreement related that to a significant the fraction ElPizarro, of 1985; Ni this Aceituno, variability 1988; Vuille et al.,studies 2000; concluded Garreaud that and El Aceituno, 2001). Ni while These La Ni the Altiplano. However, the climateacross the characteristics intertropical of Andes La region. Evenof Ni at an the El scale of Ni a country, the consequences sonality of specific humidity, cloudoccurs cover only and during precipitation. the Thus, wet notable seasonis accumulation and reduced ablation, for which is the strongeasterly rest during flow of the of wet the moisture months, year fromannual (Kaser, the timescales, the 2001). Amazon strong basin Precipitation variability (e.g. mainly of Garreaud summer results et precipitation from al., has an 2003). been described At in inter- throughout the year, whereas the outer tropics are characterized by pronounced sea- 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 | usivity ff ), and a joint international 2486 2485 ort is now part of a permanent monitoring network called GLACIO- ff http://www-lgge.ujf-grenoble.fr/ServiceObs/index.htm cients. Measurements of energy fluxes on tropical glaciers began in the 1960s ffi The interpretation of point-scale energy flux measurements can lead to erroneous Glacier mass balance was computed using the glaciological method (Paterson, seasonality of sky emission. Sicart et al. (2011) appliedHolmgren the (2005) spatially to distributed the energy Boliviandrological balance Zongo year. model Glacier The of at Hock model an and cell calculates hourly from time the measurements step surface collected for energyis at an based fluxes entire a on hy- for weather equations each station ofcally located glacier have mass a in grid and physical the energy interpretation ablation conservation (Beven,physical 1989), area. quantities. and so The It the they model parameters can had theoreti- bethe to linked be calculation to adjusted of measurable to albedo, tropicalduring due high mountains to the mainly the wet for frequent season, alternation and of of melt long-wave and incoming snowfall radiation, periods due to the pronounced solar radiation to melttributed energy energy depends balance on modelspheric the is forcing location thus and of required the the toglacier total weather investigate melt glacier station. the to mass A link water balancesonal dis- between climate resources and atmo- forcing downstream. to on the With quantify mass the the balance and contribution objective meltwater of of discharge of investigating tropical sea- glaciers, coe but are still relatively1995, rare automated (e.g. weather Platt, stations 1966;in began to the Hastenrath, be ablation 1978; used area Hardy(Wagnon to of et et monitor Zongo al., al., surface Glacier, 1999; 1998). energy in Favier fluxes In et Bolivia, al., and 2004b). Antizana 15generalizations Glacier, of in melt characteristics Ecuador whenFor they are example, extrapolated albedo to is the whole highly glacier. variable near the snowline, so that the contribution of wave and long-wave radiation fluxes and theRadiation turbulent fluxes fluxes of sensible on and latent glaciersturbulent heat. can fluxes are be generally accuratelytwo derived measured levels from of with wind, aerodynamic radiometersvery temperature profile whereas and accurate methods humidity and with measurements. require one These parameters or methods such are as not roughness lengths or eddy di energy balance equation whose main terms on temperate tropical glaciers are short- Climate controls glacier masssnow balance surface. through The energy energy and available for mass melt fluxes can at be the calculated ice as or the residual of the at any time duringheight the and density) year. was In measured thecations. at To upper compute the the part end annual of of masscalculated the balance the using hydrological of DEM year glacier, the has at net glaciers, been two glacier(Bolivia accumulation defined to hypsography p. was (snow and four 8, lo- Ecuador) l. 15 orColombia). computed using by aerial maps photogrammetry from the National Geographical2.3.3 Institute (Peru, Surface energy balance: measurements and modeling 1994). In theand lower Colombia) part of stake of emergencepending were the made of using glacier, the a monthly glacier). networkas of Snow measurements stake 10 height emergence (in to and measurements 25 Bolivia, stakes because density (de- snowfall Ecuador measurements can are occur required at the as glacier well surface 2000), in Peru incollaborative 2003, e and inCLIM Colombia ( starting inproject 2006 called GREAT (Table ICE, 1 involving academiclivia, and and Ecuador Fig. research institutions and 1). in Peru. This ing France, Bo- network, In Zongo addition, in two Boliviaglaciers of and in Antisana the the 15 glaciers in2011). tropics that Ecuador, referenced are belong by among to the the this benchmark World monitor- Glacier Monitoring Service (WGMS, In 1991, a projectof by two the glaciers Frenchbalance, for IRD and and a Bolivian surface full1995). partners energy permanent The enabled balance monitoring same instrumentation (Francou of monitoring and system their Ribstein, was mass 1995; set balance, up Francou hydrological in et Ecuador al., in 1995 (Francou et al., 2.3.2 Monitoring mass balance in the field 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | cient. Brecher ffi 2488 2487 resolution. Hence actual temperature measurements on or near the glaciers, ◦ Finally, Rabatel et al. (2012) showed that the method to reconstruct annual mass Variations in glacier volume at a decadal time scale since the mid-1950s were re- Recent studies focused on glacierto variations Bolivia in during the the intertropical LIA Andes (e.g. from Rabatel Venezuela et al., 2005a, 2006, 2008a; Polissar et al., 2006; that are somewhat higher thanand reanalized surface data. However, temperatures reanalized are temperaturesimilar data significantly at correlated, the as surface changes and in in the temperature adjacent are free air (Bradley et3 al., 2006). Results 3.1 Glacier changes since the LIA maximum studies showed thatAndes this with data reasonable set accuracykept (e.g. simulates Bradley in near-surface et mind temperature al.,a that trends 2009). Nonetheless 2.5 in here it the we shouldfor are be example considering on Zongo free-tropospheric or temperature Antisana glaciers, based may on show absolute temperature readings atmospheric circulation at a regionalon to global variables scale, many that recent studiesprecipitation, are have humidity focused relevant and convective for cloud cover the2003, (Wagnon et glacier 2004; al., Favier energy 1999; Francou etet balance, et al., al., al., such 2004a; 2012). as Sicart Athe temperature, et common tropical al., theme Pacific 2005; inmodulating Sea glacier Vuille all mass surface balance et these at temperature al., interannual studiesstudies time (SST) 2008b; scales. was is A and Salzmann summary presented the review the by of significant these relying Vuille ENSO on role et temperature phenomenon al. data played from (2008a). in by NCEP/NCAR Here, reanalysis (Kalnay we et build al., 1996). on Recent this earlier work by Consoli, 2011). 2.3.5 Climate data With the aim of linking changes in glacier mass balance with climate variability and successfully tested, validated, and applied on 11 Bolivian glaciers (Bermejo, 2010; first developed for mid-latitude glaciers (Rabatel et al., 2005b, 2008b), and was then applied a combined remote sensingin data volume and in modeling approach the togeodetic Cordillera estimate method Vilcanota, changes Southern to Peru computeuseful for volume to a variation similar validate over period. andand the This adjust hydrological whole type methods. glacier mass of Such surface balanceBolivia is by an data Soruco very adjustment calculated et was al. using (2009b). performed both for glaciological Zongobalance Glacier based in on snowlinea altitude proxy (SLA) of measured the ELA on can satellite be images used and for glaciers used in as the outer tropical zone. This method was constructed for 26and glaciers two in glaciers Bolivia inprocessed (Rabatel Ecuador (Caceres, et using 2010) al., photogrammetric onCordillera 2006; Blanca, the restitution Peru, Soruco Mark basis techniques. and of et Seltzer (2005)1962 For aerial al., assessed and changes 1999 photograph three 2009a,b) in using pairs volume similar between glaciers photogrammetric techniques, while in Salzmann et the al. (2012) Kalis Glacier (Quelccaya ice cap, Peru).and Aerial satellite photographs images (available since (available the since 1950s) inventories the (Jordan, late 1970s) 1991; have Georges, been2005; widely 2004; Morris used Silverio for et glacier andPineda, al., Jaquet, 2006; 2009; 2005; Raup UGRH, Jordan eta et 2010) decadal al., al., to 2007; and interannual RacoviteanuBasantes, to timescale 2010; et Caceres, quantify since al., 2010; the Collet, variations 2007; 2010). mid-20th Poveda in century and glacier (Rabatel et surface al., area 2006; at To complete glaciological datavolume before time the series beginning of ina field terms measurements, regional and scale, of to remote-sensing calculate changes techniquesand these in have Thompson changes proved at surface (1993) to used area be terrestrial very and photogrammetry e to quantify the retreat of Qori 2.3.4 Contribution of remote sensing 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ered ff 14 AD). For ± er in size (ranging from ff 2490 2489 erences from the evolution of glaciers in temperate ff 26 AD in Bolivia (Rabatel et al., 2005a, 2008a). These 11 AD). This moraine stage can also be found along ± ± 5400 m a.s.l.), that have no accumulation zone have almost < 27 AD in Peru (Solomina et al., 2007; Jomelli et al., 2008), and be- ), aspect (all are represented) and maximum altitude (ranging from 2 ± 24 AD and 1686 ± A general withdrawal19th with century two and periods onenounced. of The in changes the accelerated in lastcenturies retreat: surface three are one area homogenous decades, in that even the0.5 though occurred the to latter the 3.3 during being late km glaciers the the5300 di m 18th most to and pro- 6000 m 19th a.s.l.). Since the middle of the 20thfrom century, that the of rate Zongo other Glacier glaciers. retreated Within has di the sample of glaciers plotted in Fig. 3, Zongo completely disappeared. Glacier is the only6000 one m with a.s.l.) an and accumulationlower hence area altitudes above still (i.e. 5500 has m a.s.l. a (reaching large accumulation zone. Small glaciers at – – Figure 3 shows changes in surface area of Bolivian glaciers since the LIA maximum. The withdrawal from the post-LIA maximum extension and the absence of a major Following the period of maximum extension, the evolution of glaciers in the inner and The LIA maximum extension period in the outer tropics is dated to the 17th century glaciers retreated by about 1000 m in length from theOnly mid-17th to the the best late documented 19th glaciersthe century. for recent both decades the are LIA plotted.pared period to This (Rabatel the figure et retreat shows al., that the 2008a) occurred current and four glacier centuries withdrawal ago. com- Two main features are: 1870 to the early 20th century) in both innerreadvance and outer in tropics the (Jomelli 19th etentire al., century tropical 2009). belt (equivalent are to thelatitudes the main of magnitude di the of Northern LIA Hemisphere. maximum) In in Bolivia, the Rabatel et al. (2006) observed that withdrawal was more pronounced and accelerated in the late 19th century (from about rian glaciers on summit higher than 5700 m a.s.l.) and about 1800 AD. After 1840 AD, advance was also documented2004). from Finally, this reliable early historical 19thphase sources century documented in advance from Ecuador was lake sediments also (Francou, in concomitant Venezuela with (Polissar an et advance al.,outer 2006). tropics was remarkablyoccurred homogeneous during (Jomelli the et al., lateamong the 2009). 18th moraine A and stages slow first observedconsequence withdrawal along of half the an of proglacial advancing margins, the glacier(Rabatel two because 19th et are they al., century. clearly partly 2008a); In the removed they the previous are deposits outer dated tropics, to about 1730 AD (LIA maximum for Ecuado- titude above 5700 m a.s.l.,those it whose was maximum dated altitude tothe is the lower, early early the 19th 18th maximum century centuryproglacial extension (1730 (1830 period margins was of dated glaciersa to located smaller on glacial summits advance above than 5700 m the a.s.l., one but that testifies occured to during the maximum extent. The glacial advances extended further than those that occurred inwith the dates 14th varying century. slightly from oneare mountain range around to 1630 another. The lichenometrictween dates 1657 dates are concomitant with anotherin glacial Venezuela advance (Polissar documented et fromoccurred al., lake in 2006). sediments two In distinct the periods inner (Jomelli tropics, et al., the 2009). LIA For maximum glaciers extension with a maximum al- information on glacier advancesstages in and the lake sediments. intertropical An Andes earlynium glacial documented was advance documented from at in moraine the Venezuela beginning fromsome of lake glaciers the sediments in last (Polissar Peru millen- et and al.,this Bolivia 2006) 14th from and century moraine glacial for stages stage (Jomelli is absent et in al., most 2009). valley glaciers, However, suggesting that younger Solomina et al., 2007; Jomelli et al., 2008, 2009). Figure 2 (upper panel) summarizes 5 5 15 10 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in 2 . Al- 2 ˜ no years (e.g. in 1962 to 60.8 km 2 ered slightly because of the meth- ff 2492 2491 . Intermediate estimations show that the mean 2 to 527 km 2 ˜ na conditions at the turn of the 21st century resulted in a slight slowdown in Figure 5 shows changes in the length of five glaciers in the Peruvian Cordillera glaciers, i.e. an almostend balanced of situation the during 1970s, changed the to 1950s a and retreat 1960s, that which, varied according at to the the size and maximum changes in the Cordillera(Ramirez Real et (part al., of 2001; the Rabatelchanges et Codillera in al., oriental) surface 2006; have area Soruco been ofChacaltaya et documented Glacier the al., (Francou three 2009a,b). et best Figure al., documented 5(Rabatel 2000; illustrates glaciers et Ramirez of al., et the 2006) al., Cordilleraof and 2001), Real: Charquini Zongo direct Sur Glacier measurements Glacier (Soruco infrom et the aerial al., early photographs 2009b). 1990s, after Before estimates 1940 theglaciers of at beginning surface showed a areas a decadal were time similar retrieved scale. pattern Zongo and as Charquini the Sur one previously described for the Peruvian 3.2.2 The Bolivian Andes In Bolivia, Jordan (1991) published(oriental a complete and inventory occidental), of on glacierscampaigns in the from both basis 1984. Cordilleras Total of glacierizedthough aerial area there photographs was has taken estimated been in to no be 1975 more about and recent 560 field km glacier inventory of these cordilleras, glacier are available for thethis 1970s, date, a changes break inin point glacier the in length early the were 1970s. Since very trendand the the limited; appeared end glaciers Broggi in of have Glacier the 1976–77. retreated1982–83, 1970s, even Before between 1997–98, glacial advanced 500 2004–05) withdrawal resulted and has in been 600tent m a significant La in more Ni length. pronounced El retreat;the Ni whereas retreating persis- trend. Ampato, Southern Peru) shrank2000. by about 26 %, from 82.6 km Blanca. Direct annual measurements began betweenformation 1968 for and 1949 1980, was but added additional based in- on aerial photographs. For glaciers for which data Racoviteanu et al. (2007) reported that the glaciated area on Coropuna (Cordillera and Thompson et al.2005 (2006) than noted between a 10 1963 times and greater 1978, loss with in an area accelerated between retreat 1991 in and the 1990s. Finally, fields were included. Buttreat the main in conclusion the was lastand the two the same, decades. 2000s, i.e. UGRH from a 723 (2010) km annual marked reported loss glacier in a re- surface 27 area %largest has loss increased glacierized between since mountain the the range late 1960s inSalzmann 1990s et Peru, (Fig. al. the 4). (2012) For Cordillera reported the Vilcanotaan a second in 32 almost % Southern loss unvarying Peru, in glacierglacier area of between area Quelccaya 1962 ice between and cap 2006, 1962 in including the and Cordillera 1985. Vilcanota, Brecher For and Qori Thompson (1993) Kalis, an outlet retreat between 1962 andglaciers 2003 in the (depending Huandoy-Artesonraju onAt the Massif the scale (northern source of part considereddigitized the whole maps for of Cordillera 1962) and the Blanca, satellite for CordilleraRacoviteanu several et inventories images Blanca). al., were (e.g. 2008; performed Georges, UGRH, using ods 2010). 2004; used Results Silverio di to and delineate Jaquet, glacier 2005; contours, for example whether or not perennial snow tury before slowingmarked down readvance during in the thetreat first in 1920s. half the This of 1930s–1940s eventIn (Broggi, the the was 1945; period 20th followed from Kaser 1950 century, by1995a). and to with This another Georges, 1970, retreat a glaciers significant 1997; was retreated followed Georges, re- small byKaser very 2004). a and slowly but general (Hastenrath Georges, acceleration and 1997). (Ames Ames, Markdecreased and and Francou, by 1995; Seltzer (2005) about showedBlanca) 35 that % glacier between in surface 1962 area the and Queshque 1999. Massif Raup (southern et part al. of (2007) the documented Cordillera a 20 % to 30 % 3.2.1 The Peruvian Andes The Peruvian Andes are probablyBlanca, Kinzl the (1969) best reported documented that glacial glacier area. retreat In accelerated the during Cordillera the late 19th cen- 3.2 Changes in glacier surface area in recent decades 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . Fig- on av- 1 − 1 − in the late 1990s 2 from the late 1970s to the early 1 − in the 1950s to 79 km 2 2494 2493 in 2003 representing a total loss of 87 %. 2 ). 1 (Caceres, 2010), which represents a loss of 57 % or 1.6 %yr − in the mid-2000s. This represents a total shrinkage of about 51 %, four 2 2 in 1952 to 0.3 km 0.5 %yr 2 ∼− Between the early 1940sidence and in the early Peru 1960s, (Broggi, information Uruashraju, was scarce, Yanamarey), but Bolivia ev- (Charquini, Chacal- remained almost the same. A clear change intreat glacier accelerated evolution can but belate stepwise: seen 1970s, the in the second first the in late acceleration the 1970s, mid-1990s, in when and the the the re- retreat third in occurred the in early 2000s. These taya) and Colombia( (Sierra Nevada del Cocuy)From indicates the a early 1960s moderate to retreat the second half of the 1970s, glacier snout positions – – – In Venezuela, Morris et al. (2006) reported that glacier surface area decreased from 3.2.5 Summary at the scale ofIn the terms intertropical of Andes changes in5), surface the area evolution and of length glaciers since in the the mid-20th century intertropical (Figs. Andes 4 can and be summarized as follows: times greater during the secondare period. frequently located Glaciers on in active the volcanoes,by and Cordillera several the Central strong volcanic of glacier Colombia eruptions lossNevado was in del accelerated Ruiz recent in years 1985,resulted (Huggel and in on et a Nevado 30 al., del % loss Huila 2007), of where most glacier eruptions notably surface in area on 20072.03 in km and two 2008 years. and 1970s; (2) there2000s; was and a (3) a retreat major of increaseColombian in mountain about glacier ranges, 2 retreat Morris %yr occurred et duringthat al. the (2006) glacier 2000s. and For area Poveda all and the decreased Pinedaand (2009) to from found 43.8 km 89.3 km 2006; Herrera and Ruiz, 2009), shows that: (1) glaciers hardly changed in the 1960s In Colombia, a compilationglacierized of mountain glacier range, surface-area Sierra mapping Nevada at del the Cocuy scale (Florez, of 1991; the Ceballos most et al., face area computed fromAntisana satellite 12 images and at 15 an1990s also (Fig. document almost 5). the annual However, increased resolution smallThese loss advances on advances of by glaciers match both surface glaciers area positiveof occurred mass since Ecuadorian in the balance glaciers 2000 early years to and and changes 2008. indicate in mass the balance. rapid3.2.4 response The Andes of Colombia and Venezuela tury (Basantes, 2010; Caceres,the 2010; 1962–1997 period, Collet, the 2010). surface These area27.7 of to studies the 11.8 showed km glaciers on thaterage Chimborazo over (Fig. decreased 4). from For Cotopaxi andand Antisana 33 volcanoes, %, the loss respectively inthat for surface the area the retreat was increased 37 period % during 1979–2007. the second Intermediate part information of the indicates period (Fig. 4). Changes in sur- Cotopaxi Volcano (5897 m a.s.l.) showednant that between Cotopaxi glaciers 1956 remained and almostbetween 1976 stag- 1976 and and then 1997. The lostlet calculated approximately glaciers lost 30 of % on total ofure Cotopaxi mass their 6 (thickness) between shows surface of 1976 recent area selected updatesALOS) and out- mostly which 1997 based enabled on was reconstruction satelliteVolcano, 78 images m, of and (LANDSAT, ASTER changes or and additionally, in 3–4 documented mw.e.yr glaciera.s.l.) glacier surface and area shrinkage Chimborazo on (6268 on m Cotopaxi both a.s.l., Antisana not (5753 shown m in Fig. 6) since the mid-20th cen- but the retreat started to accelerate in the late3.2.3 1970s. The Ecuadoran Andes In Ecuador, results obtained by Jordan et al. (2005) using photogrammetry on the altitude of the glacier concerned. Chacaltaya Glacier retreated throughout the period, 5 5 15 10 25 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | over the 1 rmed that − erent meth- ffi ff . On the other 1 − ; and (2) glaciers 1 5400 m a.s.l.) such − > 0.76 mw.e.yr − in latitude between Zongo 2 mw.e.yr ◦ − 1.2 mw.e.yr − 2496 2495 , they will probably completely disappear in one 1 − over the 1964–1975 period to 1 5400 m a.s.l.) such as Yanamarey, Chacaltaya, Charquini − < 1.2 mw.e.yr − 0.2 mw.e.yr . Taking into account: (1) glacier size and maximum altitude depen- 1 − − Although some glaciers sporadicallysignal over had the a past positive 50 yr mass has balance, beenThe the permanently late negative. average 1970s breakface area point, is already equally apparent discussed from mean with annual respect mass balance to per changes year, decreas- in sur- decades. Glaciers in the tropical Andesthan appear glaciers to monitored have worldwide. hadat In more an negative addition, accelerated mass rate tropical after balances glacierswent 1976, an while began accelerated those to retreat located shrink about at mid/high 15 latitudes yr under- later, in the 1990s. ing from 1976–2010 period. A slight increase in the rate of glacier mass loss occurred during the past two phases of accelerated retreat wereeven interrupted short by 2 readvances like to in 3 yr Ecuador with in reduced 1999–2000 retreat and or in 2008–2009. – – – – Figure 8 is a summary of mean annual mass-balance per period combining all avail- These long-term trends were superimposed on strong interannual variability. High 0.6 mw.e.yr bining all survey methods). Four important points in this graph are worth emphasizing: with a deficit of around or two decades (notewhich disappeared that in this 2010). is already the caseable for measurements made Chacaltaya in Glacier Colombia, Ecuador,ods in Peru and (geodetic, Bolivia, Bolivia hydrological, using glaciological di andations mass in balance snowline altitude). reconstructions The fromabout quantity vari- of twenty available glaciers data has in increased the with time 1960s–1970s from to about thirty glaciers in the 2000s (com- altitude glaciers experienced major fluctuationspositive between mass a balance balanced or andhand, even deficits a small slightly reaching glaciers morea such than permanently Chacaltaya, negative Charquini masssmall Sur, balance glaciers in and with no recent Yanamarey permanent years. experienced accumulation Thus, zones it are can very be unbalanced a and that, Francou et al., 2007). Sur and La Conejeras,which showed an still average have trend aas of large Zongo, Artesonraju, accumulation zone Antisana− at 15 and high Los elevationsdency; (2) ( Crespos, the showed distance between anand the La average glaciers Conerejas; monitored: trend and 21 of (3)balance were distinct homogenous hydrological over year the timing; wholegests regional period. common This changes large-scale coherent in forcing glacier mass influencing response climatic sug- variability at regional scale (e.g. 1971) and Zongo Glacier (Cordilleradrological Real – data). Bolivia, since It 1973, shouldinterrupted reconstructed from be several hy- noted times thatsumed. and measurements Over to the on last complete Yanamarey 40glaciers Glacier the yr, two at were missing distinct low patterns data, of altitudes a loss ( can linear be trend distinguished: (1) was small as- retreat (in terms ofaltitudes percentage) that is do not notably have morein a the pronounced permanent coming accumulation on years/decades. zone, small and glaciers which could at disappear low 3.3 Interannual variability of glacier massFigure balance 7 showsColombia the and cumulative Bolivia annual forThe mass which longest balance series field available of are measurements for the Yanamarey have Glacier (Cordillera been eight Blanca conducted – glaciers Peru, (Table since between 1). Glacier shrinkage in themaximum extension three of the last LIA (mid-17th–early decadesretreat 18th appears century). is In to observed addition, even everywhere be if in glacier unprecedented the since intertropical the Andes, it should be noted that this 5 5 10 15 25 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- ff is closely linked S ers. ff ), which is partly compensated by the S ). Due to the low latitude, L 2498 2497 in the ablation area (e.g. Kaser et al., 1996; Soruco 1 − ect on the melt rate, appears to be a primary variable controlling the amount ff Albedo appears to be a major determinant in melting. At a daily time step, a close Precipitation and temperature, first during the main precipitation period (between February and May), and second duringare the therefore secondary crucial maximum for (September/October), the annual mass balance. Significant snowfall in February–May cou et al., 2004).changes. Glaciers in the inner tropics are thusrelation, very was shown sensitive between to albedoin temperature and albedo net go radiation hand (Favierquently, et in al., the hand 2004b). frequency with Changes and changesa in intensity major role the of in short-wave snowfall, attenuating radiation the which balance. melting can Conse- processes. occur all year long, play 4.1.1 Specificities of the inner tropics Concerning Antisana 15 Glacier,scales, Favier mean et ablation al. ratesinter-annual (2004a,b) remained variability found almost of that constantyear-to-year at the variations throughout seasonal mass in the time air balance year, temperature of and which determine the the the glacier snowline altitude was (Fran- mainly controlled by et al., 2009b), implyingKuhn a (1984) noted significant the contribution influence of ofthe the energy the fluxes length lowest at of the the areas scale ablationsnow to of period. cover the total Areal Zongo throughout simulation ablation. Glacier the of showed ablation thatvertical the season mass frequent were changes balance the in gradients mainseasonality of explanation of tropical precipitation for is glaciers the not (Sicart marked thethe same et seasonality in al., of the 2011). inner melting and However, at outer the the tropics. Consequently, glacier surface also di changes in sky long-waveseasonal radiation changes and in solidglaciers energy precipitation, (Wagnon fluxes et cloud al., and coveret 2001; mass controls al., Francou et 2011). the balance al., Tropical glaciers on 2003,ents are 2004; low-latitude of characterized Favier about high-altitude by et large 2 al., mw.e.(100m) vertical 2004a; mass Sicart balance gradi- of melt energy at the surface of tropical glaciers. Thus, by causing strong seasonal with cloud cover andback surface e albedo, which, due to its strong variability and its feed- 4.1 Factors controlling seasonal changes inLong-term mass balance surface energy balance1999, (SEB) 2001; field Sicart campaigns et2004a,b) in al., revealed 2005), Bolivia that Peru (Wagnon inmostly (Juen et controlled the et al., by al., tropics, net 2007) the short-wavenegative net and radiation variability long-wave ( Ecuador radiation of budget (Favier ( SEB et al., in the ablation areas is characterized by an almost balancedeven situation a in short both period thea of marked outer loss and mass in inner gain 2009. tropics on with La Conejeras Glacier (2007–2008) followed4 by Discussion (4800 to 5000 m a.s.l.)a.s.l.). and At the a upper ablation monthlythe zone scale, energy of the balance Zongo mass (melt Glacier energy) balance (5000first and in to decade, snow the i.e. 5200 accumulation m 1991–2001, ablation at the zone thein patterns glacier reflects 1995 remained surface. changes and In almost in 1997–1998 the the1994, same: on 1996 ablation the peaked and three 1999–2000 glaciersence were appeared monitored between more at the balanced. this innerof time, and In Antisana outer whereas the 15 tropics: 1993– Glacier 2001–2006 the did continuous period, not high a appear ablation in rates di Bolivia until 2004. The 2006–2011 period was Figure 9 shows theemergence cumulative was monthly measured mass monthly, balanceevation taking of ranges into five include account glaciers the the onLa snow/ice which whole Conejeras density. stake glacier glaciers The (mostly surfaces el- ablation of zones), Chacaltaya, the Charquini lower Sur zone of and Antizana 15 Glacier 3.4 Synchronicity of the ablation rates throughout the intertropical Andes 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect. Long periods without ff C isotherm consistently oscillates ◦ ˜ no year were mainly due to reduced 2500 2499 C can move the snow-rain limit about 150 m up ◦ Few studies have investigated the physical causes of the high correlation between Finally, Wagnon et al. (2001) showed that the high melt rates measured at the Zongo The high sensitivity of Ecuadorian and Colombian glaciers to climate is closely linked of the atmosphere. Furthermore,phase: rain atmospheric or snow, temperature and the controls surface the albedo can precipitation be linked to the air temperature during ing energy flux butmakes is sense poorly correlated because with temperature,energy air as fluxes temperature. well However, (Kuhn, as this 1993; melt correlation pends Sicart on rate, the includes et temperature most al.,depends gradient atmospheric on 2008). between air ice The humidity, which and is turbulent limitedtion air. sensible by of The saturation heat temperature turbulent humidity, which, only. latent flux The in static turn, heatwith de- stability is increasing flux a of air func- the temperature, air reducingradiance above turbulent a depends convection. glacier Clear-sky mainly surface long-wave increases ir- on the humidity and temperature of the near-surface layer ture (e.g. La Casiniere, 1974; Zuzeland and Cox, outer 1975; tropics, Braithwaite, 1981). a In significantair both correlation the temperature has inner at been 500 found hPa(Francou between level et mass derived al., balance from 2003, and 2004). reanalysis data at a monthlyair time temperature scale and ice melt. Paradoxically, net radiation is generally the main incom- incoming radiation becausecreases cloud long-wave emission clear during skyshowed emission the that from wet during the the season thinin dry considerably atmosphere. a season, cloudless These in- turbulent sky. authors fluxes also are increased by4.1.3 katabatic winds Relation between air temperature andMany ablation authors on found tropical a glaciers high correlation between glacier or snow melt and air tempera- accumulation and very large ablation. Glacier weather station during the 1997–1998solid El precipitation Ni and associatedthat low glaciers albedo. in In the addition, outer Sicart tropics are et characterized al. by (2005) marked showed seasonality of long-wave onset of the wet season causes a very negative mass balance due to reduced snow which interrupts the period of high melt caused by solar radiation. Any delay in the long-wave radiation due to thehigh low altitudes, emissivity and not of primarily theKaser due thin et to cloudless sublimation al., atmosphere as 1996; postulated at Wagnonto in et very earlier December, al., the studies 1999). (e.g. meltwater During discharge thenual progressively transition values increases season to due from reach September to itsalbedo. high highest From solar an- January irradiance, with tomelt the April, rate, sun which the close is frequent toconvective nevertheless clouds. zenith, snowfall maintained The and in annual by low mass the high glacier balance long-wave wet depends radiation on season emitted the reduces onset from of the the wet season, In the outer tropics,is where closely liquid related precipitation(Wagnon to is et the al., rare 2001; total onThree Francou glaciers, amount seasons et the can and al., be mass 2003; thethe distinguished balance Favier for dry seasonal et outer season distribution al., tropical from glaciers 2004a; of May (Sicart Sicart precipitation to et et August, al., al., 2011). melt 2005). In is low, mainly due to the surface deficit in through the ablation zone ofinfluence the the glaciers, melt and processes azone by minor determining (a variation the in temperature phase air increasethe of temperature glacier). of precipitation can This in 1 explains the whyand ablation the the relation freezing level between line thevariations is altitude (Kuhn, a 1989; of decisive Kaser, the parameter 2001). equilibrium in line the glaciers’ sensitivity4.1.2 to climatic Specificities of the outer tropics snowfall lead to athe significant equinox increase (March/April in and September) melt whenis rate, potential maximum. particularly incoming shortwave in radiation the periods close to to the absence of temperature seasonality. The 0 clearly reduces the ensuing melting due to the albedo e 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ˜ no ects on ff ˜ no events result ˜ no), precipitation C higher during El Ni ◦ C–1.3 ◦ ˜ no 3.4 region. The bottom graph ˜ na periods, opposite conditions pre- ˜ na in above average signals. However, 2502 2501 erences in the response of glaciers in this region to ff ˜ no events than in an average month. On the other hand, the ˜ na (Vuille et al., 2000), enhancing sensible heat flux to the glacier 2 region. ˜ na event resulted in a positive mass balance on La Conejeras Glacier. + ˜ no 1 ect of the Pinatubo eruption in June 1991 (Francou et al., 2003), the situation Ocean ff Concerning the Cordillera Blanca in Peru, the mechanisms linking ENSO and glacier During periods when ENSO is near neutral conditions, other atmospheric forcing, In Bolivia, variations in the interannual glacier mass balance are also to a large ex- In Colombia, the impacts of ENSO on glaciers are similar to those in Ecuador. It In Ecuador, as shown by Francou et al. (2004) and Vuille et al. (2008a), the two such as variations in South American monsoon intensity and duration, the so-called glaciers has also beenelevation highlighted is by related Arnaud primarily to et precipitation al. and (2001) to showing a that lessermass balance the degree are to snowline similar temperature. to thosescale in Bolivia, control with on the SSTa interannual exertingin the mass negative prevailing large- balance mass balance variations. anomalies, Typically,these El and teleconnections La Ni are Ni spatially unstable andglacier ENSO mass events balance with have reversed been e observed (Vuille et al., 2008b). that occurred between 2001 andacteristics 2005 observed is still in beingENSO) ENSO analyzed. could Nevertheless, variability explain new (Central the char- slight Pacific/Easternthe di ENSO Pacific phenomenon, or particularly “Modoki” of for a the forthcoming outer paper tropics, by Francou this et point al. will Finally, be ENSO the influence on focus Sajama Volcano average, the near-surface summer temperaturethan is during 0.7 La Ni surface. During the relativelyvail, wet which and can cold lead Lathe to Ni lower near graph equilibrium insystematic, mass Fig. for balance. 10, However, example the as overpositive response can mass the of be balance 1992–1995 mass anomaly seen in balance anding on the to 2001–2005 e 1992–95 the period periods. has SSTa Although forcing been attributed the is to not the cool- tent controlled by SSTaet in al., 2003; the Vuille tropical etdecreases al., Pacific 2008a). by (Francou During 10–30 and % the ENSO Ribstein, and(Vuille warm dry 1995; et phase periods (El Francou al., occur Ni 2000). moreaccumulation This frequently and situation decreases during albedo austral increases on summer incoming the solar glacier radiation, surface (Wagnon reduces et snow al., 2001). On negative during El2007/08 Ni La Ni slight deficit in precipitationalbedo and and cloudiness, the explains the highphase unvarying brings melt low cooler rates values temperatures, (Favierfor of higher et long the snowfall al., periods, and 2004a,b). preventsnow increased albedo (0.8) In cloudiness, and from contrast, decreases which, dropping available theduring energy below cold austral for the winter melt. ENSO boost To typical a sublimation lesser values and extent, reduce of stronger melting. the winds fresh has been observed that monthly mass balance was up to three and a half times more opposite phases of15 ENSO explain Glacier. the Since(November–February) highly the and contrasted the SSTa situations atmosphericAndes peak on is response delayed in the to by three ENSO Antizana theimal months, over from year-to-year Central variability February the of to Ecuadorian Pacific the May. Duringprecipitation mass warm during balance at ENSO is phases, the the max- increasing melting temperatures boreal favor point winter up to 5100–5200 m a.s.l., which, together with the Figure 10 shows time seriesface of temperature monthly anomalies mass (SSTa). balanceshows The anomalies the top and average graph Pacific monthly sea focuses massjeras sur- on balance (2006–2011) of the glaciers Antisana inner with 15focuses tropics on (1995–2011) the and the and SSTa outer La of tropics, Cone- 2011), with the Chacaltaya the (1991–2005) Ni average and monthly Charquini Sur massof glaciers balance the (2002–2011) of Ni and Zongo the (1991– SSTa energy balance through changes in the net short-wave radiation budget4.2 via the albedo. Regional forcing of the mass balance interannual variability: the Pacific precipitation events. Thus a change in the freezing level can have an impact on the 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1800 ∼ C below today’s values, ◦ C to 1.1 ◦ 1730 AD can be considered to be ∼ 2504 2503 1620 AD and ∼ set increasing ablation at low altitude. From sensitivity studies, ff C cooler, and precipitation about 22 % higher than at present. ◦ C, and a 20 % to 30 % increase in accumulation. C lower than at the turn of the 21st century (Baumann, 2006). ◦ ◦ O of the snow/ice between the late 16th and early 19th century. The 1.4 18 erence between tropical and mid-latitude glaciers is that the tropical ± δ O content between ff 18 δ 1860 AD) which could be related to relatively wetter conditions. C to 1.2 C to 1.5 ◦ ◦ ∼ In Bolivia, the PME of1.1 the LIA could be the result of a decrease in temperature of In Ecuador, air temperature mayand have been a 0.8 25 %18th to century. 35 % increase in accumulation appears to have occurred in the In Colombia, the air temperature1.2 during the PME of the LIA was estimated to be In Venezuela, for thebeen period 3.2 AD 1250–1820, average air temperature may have O records from Andean speleothems and lake records also confirm that, in this re- – – – – The last decades of the 19th century were characterized by a substantial glacier A major di Quantitatively, the application of simple climate/glacier models (Polissar et al., 2006; 18 the first half of the 19thJomelli century et al., in 2009) Bolivia with and two PeruAD small as and glacier well advances (Rabatel (moraine et stages al., dated 2006, from 2008a; retreat at aclimate regional proxies scale and which theWebster, could first 1999). be instrumental measurements due (Kraus, to 1955; dry Torrence and conditions as documented in is also apparent in pollencumulation analyses from of the Quelccaya Sajama ice ice corewas core probably (Thompson (Liu not et et continuous al., al., since 2005) 1985). distinctand and moraines However, the net the were ac- late deposited recession between 19th–early thethose 20th PME never reached centuries, a indicative magnitude of as great small as glacial those advances, in although the PME. It was the case during glaciers began to retreat justhave after 1740–1750 been AD, associated a long withthe trend drier of analysis conditions. recession of which Indeed, paleo-lake may drieret levels al., on conditions 2003). the The are shift Peruviano-Bolivian indicated to Altiplano drier by (Chepstow-Lusty conditions between the late 18th and early 19th centuries gion, the LIA periodSajama must ice have core been (Liu wet etarea (Bird al., of et 2005), the along al., Bolivian with 2011). Altiplano dendroclimatologicalconditions Pollen studies (Morales during analyses in et the from the al., PME the same of 2012), the are LIA. also in agreementRabatel with et wetter al., 2008a; Jomelli et al., 2009) highlights several points: one based on ice coreThompson evidence (Fig. et 2 al. lower (2006) panel). andcrease For Vimeux example, in et in the al. several ice (2009) cores, minimum noted a marked centennial-scale de- related to increasing convectiveδ activity during the PME (Vimeux et al., 2009). New The formation of moraines at asnout distance of during about the 800 to period 1000mass m of from balance maximum the present was extent glacier (PME) veryfrom of positive, the the generating glacier LIA a to meansRabatel significant o that et transfer al. the of (2006) specific icethus suggested increasing that downstream accumulation conditions rates, may and, haveing in been to conjunction a wetter with decrease during lower in the temperatures, the LIA, lead- freezing level. This hypothesis is consistent with other proxies, mid-latitude disturbances tracking abnormally north ofand their usual the path South-Atlantic (Ronchail, 1995) convergencebalance zone, variability. also have an impact on4.3 interannual mass Causes of glacier retreat since the LIA maximum “surazos”, which cause precipitation during the dry period due to Southern Hemisphere 5 5 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) in 1 − C since ◦ Cdecade ◦ erence between ff S, i.e. in Ecuador ◦ ects. However, stud- ff S), except during strong ◦ 16 ∼ S, Vuille et al. (2008a) showed ◦ N and 23 ◦ S) and Bolivia ( ◦ 2506 2505 9 ∼ cult to document because of the lack of high-quality ffi (in Bolivia) to more than 2.5 %/decade (in Ecuador). Simi- 1 − C over the 20th century. It should be noted that this increase in tem- ◦ 0.2 ± high altitudes. These authors quantifiedof a 1.1 mean rise inperature atmospheric is temperature the onlyas evidence most recorded weather in stations the are located Andes below at 4000 the m a.s.l. elevation of glaciers, the last 70 yr, which1939. represents These an findings overall temperatureand confirm increase Seltzer, results of 2005), 0.68 obtained Bolivia(Quintana-Gomez, and by 2000; Northern other Villacis, Chile 2008) authors and (VuilleEcuador in along et to the al., Northern Peru entire 2000) Chile (Mark tropical (Vuillenificant and Andes and warming Ecuador from trend Bradley, 2000), and a all reduced ofdaily daily whom minimum temperature and range reported (di maximum a temperatures). sig- Consistentperature, with Gilbert this et increase al. in (2010) tem- in showed a from 138 m englacial deep temperature boreholethat measurements drilled a near the warming summit trend of can Illimani (6340 also m be a.s.l., Bolivia) identified along the temperature profile at very Temperature is by farweather the stations best located documented betweenthat near-surface 1 climate air parameter. temperature increased Based significantly on (by 0.10 279 at an annualand scale Northern/Central and Peru. Inversely, during in Southernmost the Peru weather and wet the stations Bolivian season) indicated Altiplano, et north a al., decreasing of 2006). trend 11 (Vuille et al.,Changes 2003; in Haylock humiditycontinuous are records very exist. hard However,found to a based quantify significant on increase as, in CRU05from in relative data, humidity 0.5 the %decade for Vuille the Andes, et 1950–1995larly, no period based al. ranging on long-term (2003) NCEP reanalysisincreasing data, trend Salzmann in et specific al.past humidity (2012) 50 found in yr. a the significant Southern Peruvian AltiplanoDuring over the the 1974–2005 period,the outgoing inner long-wave radiation tropics, (OLR) suggestingwhereas decreased an in in the increase outer tropics, in the convectiveThis opposite trend pattern activity is is and documented consistent (Vuille cloud et with al., cover, precipitation 2003). trends in the same period. Precipitation changes are di long-term precipitation records. Moreover, the variabilityis at higher the than decadal the time multidecadal scale ies trend, showed partly an due to increasing ENSO trend e in precipitation after the mid-20th century (both ˜ no events, the ablation zone tended to be located above the annual mean freezing – – – – Figure 11 shows changes in freezing level height in the Andean Cordillera docu- freezing level. in Peru, and Cordilleraat Real each in site Bolivia) as using aIn the backdrop. the elevation For inner range each tropics of site,zone the (Antisana the extended grid in ablation down cell zone Ecuador), to including during thetion the rates. freezing the site In level, 1955–2011 was the thus selected. period, outer explaining tropicsEl the the of Ni ablation Peru year-round ( strong abla- line during the first halflevels of led the to study a period. situationeven But in the of which recent the the marked ablation Cordillera increase zones in Real of freezing are the Cordillera mostly Blanca located and within today the range of the annual mean mented based on NCEP-NCARusing reanalysis monthly data. temperatures and Freezing geopotential level heightmean and height for plotted was as the a computed 1955–2011 12-month period running at three sites (Antisana in Ecuador, Cordillera Blanca 4.4.1 Climate changes in recent decades Recently, Vuille et al. (2008a) presented aalong review the of climate tropical changes Andes. in These the authors 20th century reported that: 4.4 Causes of the accelerated retreat in the last 30 yr 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ˜ no led to marked warming ected the glacier mass balance ff erent, because in the outer tropics the coast of South American ob- ff ff 2508 2507 erent general circulation models used in the 4th assess- levels from scenario A2, Bradley et al. (2006) showed that ff 2 C. The maximum temperature increase is predicted to occur ◦ ˜ no period (1990–1995), and causing the only slightly positive ˜ na led to cooling (Antisana) or at least stabilization of the cumu- 5 + ect of the volcanic sulfate aerosols in the stratosphere hence in- ff C to ˜ no since the late 1970s, together with a warming troposphere over the ◦ 4 + modeling C at the glacier snout up to the late 1970s, when temperatures started to rise and cu- Finally it is interesting to note that the beginning of the accelerated retreat of tropi- Quantitatively, the freezing level height has increased by about 60 m and 160 m over Figure 12 shows cumulative temperature (monthly mean values of NCEP-NCAR re- ◦ ysis of glacier masssnow balance model and to equilibrium-line the altitude Zongo by Glacier applying in the two CROCUS contrasted wet seasons (2004–2005 and ment of the IPCC, andprojected CO changes in mean annual(2090 free-air to temperatures 2099) between along (1990increase the to by tropical 1999) Andes and atin an the elevation high higher mountains thanVuille of (2009), 4000 Ecuador, m Peru using a.s.l. and a will Boliviasions high-resolution (Bradley regional with et climate respect al., model, 2006). toglaciers came Urrutia to changes to and changes in similar in conclu- near-surface air temperature. temperature, To test Lejeune (2009) the performed response a of sensitivity anal- mechanisms of variability at a decadal scale (e.g. Francou4.5 and Vincent, 2007). Possible future changes in tropical glaciers in the Andes: resultsUsing of results from eight di cal glaciers occurred atcurve the after same 1976 time (Trenberth as etPacific a and al., other major 2007) tropical increase that regions. Glaciers in incorporatesderwent all the accelerated the around retreat global warming the since Pacific temperature of 1976 anduntil the Indian (with oceans tropical the the un- exception early of 2000s,In glaciers the in which Northern New are Zealand Hemisphere, also fromthe Alaska influenced main to by Northern forcing ENSO, Russia, isthe but and the beginning throughout in North Europe, of the Atlantic accelerated opposite Oscillation, retreat way). resulting period in: (late (1) 1980s/early a 1990s); slight and time (2) lag distinct in we can assume thatcurence the of higher El Ni frequency andtropical Andes, the explain change much of inthe the the recent world. spatio-temporal dramatic shrinkage oc- of glaciers in this part of mass balance in the entire decade on Chacaltaya Glacier (Francou et al., 2003). Thus, through a cooling e terrupting the long El Ni started to rise in the past two years. 4.4.2 Linking current climate change and glacierThe evolution in higher the tropical SST Andes served of after the the tropicalretreat 1976 Pacific throughout Pacific Ocean the climate o tropicalfrequency, shift, large-scale Andes. most This atmospheric likely strong events.type, helped occurred signal The in is to Pinatubo June superimposed 1991 accelerate eruption, and on glacier an for higher several event months a of this glaciers are located inrelative an to area with the a freezingZongo dryer line. Glacier climate Hence snout and from were therefore mainlyconsequently 1955 at below negative. higher to freezing However, elevations since the and the mid thefreezing early cumulative 1990s, point 2000s, temperature and temperatures the was as at temperature a the has result the reached cumulative temperature curve flattened out and even Fig. 11. At Antisana0 and in themulative Cordillera temperature Blanca, became the positive. temperature Temperaturessince, have was meaning continued that, very to except increase close for short ever they to intervals have remained associated positive. with For the example, cold inand phase 1997/1998 in of El 1999/2000 ENSO, Ni La Ni lative temperature (Cordillera Blanca),the but Cordillera this Real event (Bolivia) was appears to short be lived. a The little di situation in the last five and a halfcan decades in be the partially inner traced and back outer toBradley tropics, the respectively. et This increase al., increase in the 2009). tropical Pacific SST (Diaz et al., 2003; analysis data) at the elevation of the glacier snout for the same three locations as in 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 1 − ect on ff 1.2 mw.e.yr − 5150 m a.s.l. (Rabatel C increase in air tem- C) simulated at the el- ◦ ◦ ∼ 5 + C to ◦ 4 + 30m. With such a result and assuming ± currently located at 2510 2509 0 ect of atmospheric temperature via the sensible ff ect has not yet been quantified. in the last 70 yr), we assume that atmospheric warming is ff 1 − over the last three and a half decades. Whereas smaller glaciers ˜ na periods, when due to a change in frequency and/or in precipi- 1 − Cdecade ◦ ˜ no and La Ni 0.6 mw.e.yr hand, specific humidity (whichmight also has play also a role beento in melting, increasing glacier but in shrinkage this by e the transfering tropical energy from Andes) sublimation Interannual variability of mass balance is high, with negative mass balance oc- interannual to decadal time scale. In the verymore high-altitude specifically mountains the net of short-waveat the radiation the budget, tropical glacier control Andes, surface the during energyalbedo, radiation the solid balance fluxes, melt precipitation season. and controls Consequently, seasonalin through changes its the in e energy mass fluxes balancea and of significant hence and these spatially glaciers. coherentthe trend Because 20th in precipitation the century tropical has (unlike Andesof not temperature, since which 0.10 displayed the has middle of increasedthe at main the factor significant explaining the rate tion current of glacier recession. atmospheric However, a warminga large is change propor- transmitted in to phase.Ni a This glacier finding through was precipitation confirmedtation via amounts, by a observations change made ofments phase during revealed determines El that albedo. Energy the balance directheat measure- e flux plays a minor role in ice melt in a tropical environment. On the other − whith no accumulation zonei.e. have at shrunk twice the at rate anunprecedent of since average the the former. rate LIA In of maximum, either i.e.and case, since the the the current second early half retreat 18th of appears century. the to 17th be century curring much more frequently thanbalances, periods which with near-equilibrium occurred or in positivecific mass only SST a is few the years. main The factor variability controlling of the the variability tropical of the Pa- mass balance at the The magnitude of glacier retreatglaciers is that directly still related have an to accumulation the zone size above 5400 of m the a.s.l. glacier. have typically Large lost Consistent with most mountain glaciershave been worldwide, retreating glaciers at in an increasing thepositive rate mass tropical since balances Andes the have late been 1970s. observedbalance Although on sporadic has some glaciers, been thebalance average permanently mass deficits negative of over the tropicalthe the Andes world. past rank among 50 the yr. most The negative observed mean in mass – – – – the following conclusions: 5 Summary and concluding remarks This review of glacier changes overservations the of last some 50 representative yr glaciers and in two the decades tropical of Andes constant enabled field us ob- to highlight et al., 2012), suchat an increase the would end locate ofa the ELA subsequent the between drastic 21st 5630 reduction century,the and in 6050 i.e. Cordillera its m Real, in a.s.l. surface such area. themost an If upper glaciers extrapolated increase in reaches to this in ofbe other massif. the supplemented the glaciers However, ELA and these in Zongo expanded would results by Glacier, are causeELA the with preliminary, analysis the to and of disappearance other they the of sensitivity need meteorologicaltime of to scales. parameters mass balance (precipitation, and humidity, radiation) at longer perature, the increase in ELAthat would changes be in 150 ELAmentioned projected are changes linearly in proportionalevation air of to temperature the changes ( glaciers in foron the temperature, the end the order of of above the 480 21st to century 900 would m. result With in ELA an ELA increase 2005–2006). The results of this analysis showed that for a 1 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ce for the Environment, ffi http://www-lgge.ujf-grenoble. ´ ´ u, Helvetas Swiss Intercooperation, eveloppement) through the Andean a del Per ı ´ 2512 2511 ) and through the JEAI-IMAGE, and by the Grant a e Hidrolog ı ´ We are grateful to all those who took part in field campaigns for mass The ongoing recession offor Andean regions depending glaciers on will water resources become supplied increasingly by glacierized problematic mountain catch- Given the current climatic context, andature the projected future by changes in both atmospheric globaltropical temper- and Andes regional could disappear climate during models,5400 m many the a.s.l. glaciers 21th are in century, the and the most those vulnerable. located below ments, particularly in Peru.is This beyond issue the was scope notrecent of studies specifically the (e.g. discussed present Bradley here, review, et but as al., it 2006; it has Villacis, been 2008; Kaser highlighted et in al., several 2010). – – Aside from continuing and expanding the field monitoring programs, it is therefore of The publication of this article is financed by CNRS-INSU. the TRMM mission scientistsused. and associated NASA personnel for the production of the data SENESCYT-EPN-PIC-08-506. We also acknowledge fundingComunidad from, Andina and de collaboration Naciones with,Swiss (CAN) the Agency and for Development the and World Cooperation,the the Bank, Servicio Swiss the Nacional Federal de O Inter-American-Institute, Meteorolog the US-NSF, the US State Department andfree CARE. Special access thanks to to the Landsat USGS-EDCISIS images. for allowing SPOT program, us images contract were #503.online provided data Visualizations through system, the used developed CNES/SPOT-Image and in maintained Fig. by the 1 NASA were GES DISC. produced We with also acknowledge the Giovanni fr/ServiceObs/SiteWebAndes/index.htm part of the French glaciers observatory service: GLACIOCLIM ( balance measurements. IRD researchersA. B. Coudrain are Pouyaud, acknowledged R. foring Gallaire, their participation program E. in Cadier, in the P.mann, development the Garreta of Mario and intertropical the glacier Rohrer, Andes. monitor- funded Walter We by the Silverio, also French Cesar appreciate IRD (Institut Portocarrero collaboration de with and Recherche pour Nadine Bryan le Salz- D Mark. This study was Acknowledgements. critical importance, to focusprovide on policy- glacio-hydrological and modeling decision-makersmanage and with water analysis adequate resources in in and regions order useful with to information rapidly on shrinking glaciated how areas. to 5 5 20 15 10 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , erent ff ` ere Royale ´ Etud. 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M.: Economic impacts264, of 2007. rapid glacier retreat in the Andes, Eos, 88, 261– Per D., Rahimzadeh, F., Renwick,surface J.A., and Rusticucci, atmospheric M., climateBasis, Soden, change, edited B., in: by: and Climate Solomon, Zhai,Tignor, Change S., M. P.: 2007: Observations: Qin, and The D., Miller, PhysicalNew Manning, H. York, Science M., NY, L., USA, Chen, Cambridge 235–336, 2007. Z., University Press, Marquis, Cambridge, M., United Averyt,gen, Kingdom K. Bonn, and B., Germany, 1941. 2009b. tation in ice cores from the Quelccaya ice cap, Peru, Science, 229, 971–973, 1985. Mashiotta, T., and Mountain, K.: AbruptAcad. tropical Sci., climate 103 change: past , and 10536–10543. present, doi: Proc. Natl. mate, 12, 2679–2690, 1999. doi: naud, Y., Favier, V., and Lejeune,and Y.: Mass 2006, balance using of Glaciar glaciological, Zongo, hydrological Bolivia, and between 1956 geodetic methods, Ann. 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T.: Lichenometric and radiocarbon dating of Holocene glaciation, Cordillera Blanca, 5 5 30 25 20 15 10 30 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | a W d N 0 0 22 48 ◦ ◦ 2006 c S 4 W 75 0 0 9 ◦ 29 ◦ 2005 c S 0 W 78 0 0 9 ◦ 29 0.63 1.71 0.22 ◦ 1995 W 78 c S 0 b 0 0 ˜ no year, J. Glaciol., 47 , 21–28, 16 39 ◦ ◦ 0.60 1971 W 77 c S 9 b 0 0 27 57 ◦ ◦ 2003 S 8 W 77 c 2523 2524 0 0 17 09 ◦ Sur 15 Crespos Conejeras ◦ 2002 , 2008a. c S 16 W 68 0 0 21 07 ◦ ◦ 1991–2009 ¨ artner-Roer, I., Hoelzle, M., Paul, F., and Haeberli, W., S 16 W 68 c 0 0 15 10 ◦ ◦ Zongo Chacaltaya Charquini Artesonraju Yanamarey Antisana Los La 68 ) 1.94 – 0.32 5.39 2 Characteristics of the glaciers monitored and date of the beginning of the observations. 10.1016/j.earscirev.2008.04.002 Resour. Res., 11, 174–176, 1975. budget of Glaciar Zongo,2001. Bolivia, during the 1997/98, El Ni Nussbaumer, S.ICSU(WDS)/IUGG(IACS)/UNEP/UNESCO/WMO, World Glacier U., Monitoring Service,Switzerland, Zurich, G 102 pp., 2011. Zongo Glacier, Cordillera Real, Bolivia, J. Geophys. Res., 104, 3907–3923, 1999. change and tropical Andeandoi: glaciers: past, present and future, Earth-Sci. Rev., 89,Peru and 79–96, its relationship with62, 14–28, climate 2008b. and the large-scale circulation, Glob. Planet. Change, Andes: observations and model results, Climatic Change, 59, 75–99, 2003. and its relation to tropical2000. Pacific and Atlantic forcing, J. Geophys. Res., 105, 12447–12460, Location 16 mass-balance survey Surface area (km Max. elevation (m a.s.l.)Min. elevation (m a.s.l.)Aspect 6000First year of 4900 5396 – 5300 1991 SE 4985 5979 4685 S 5200 4725 5760 S 5760 4780 WSW 4680 4960 4720 SW NW SW NW La Conerejas Glacier is locatedSurface on area Nevado Santa in Isabel 2006. (Fig. 1). IDEAM. LMI Great Ice. a b c d Zuzel, J. F. and Cox, L. M.: Relative importance of meteorological variables in snowmelt, Water Table 1. WGMS: Glacier Mass Balance Bulletin #11 (2008–2009), edited by: Zemp, M., Wagnon, P., Ribstein, P., Francou, B., and Sicart, J. E.: Anomalous heat and mass balance Wagnon, P., Ribstein, P., Francou, B., and Pouyaud, B.: Annual cycle of energy balance of Vuille, M., Kaser, G., and Juen, I.: Glacier mass balance variability in the Cordillera Blanca, Vuille, M., Francou, B., Wagnon, P., Juen, I., Kaser, G., Mark, B. G., and Bradley, R. S.: Climate Vuille, M., Bradley, R. S., Werner, M., and Keimig, F.: 20th century climate change in the tropical Vuille, M., Bradley, R. S., and Keimig, F.: Interannual climate variability in the Central Andes 5 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and July (c) tree

1985, (black

(wet/dry (wet/dry ratio in the Sajama ean ean hourly 0 based on Liu al., et Liu (

m

General atmospheric PME Soruco Soruco et al., : d numbered. numbered. ´MB

P/A ) in January glacier glacier advances (b) evidenced evidenced in 1 and and are

− c: and and

in 2008 (Incachiriasca), 2009 monitored

s of climate variations rom 1963 to 2006 ( (triangles) f ie

stages and mainly the circulation over South America. The starting starting

igures igures 1c and d. area area are f prox

recipitation recipitation anomaly

in in erent proxies of climate variations (wet/dry moraine or or / ff The The p two pollen species (Poaceae and Asteraceae)

. are are available Product 3B43 V6. 3B43 Product atmospheric atmospheric of different

) 51

52 for glaciers in Ecuador (glacier with a summit above

2526 2525 eneral eneral length length and ote that the g Altiplano

N ropical ropical Andes. Glaciers with countinous mass balance series . b: t

), and data from ice cores come from Thompson et al. ( accumulation. The P/A ratio in the Sajama ice coreaccumulation. Sajama in the P/A ice ratio The

stages stages dated by lichenometry in the pinia).

2012 changes changes in (Venezuela) (Venezuela) with in January (c) and July (d), respectively, from 1998 to 201

) The position of the triangles qualitatively represents the position of the proglacial proglacial margin et et al. ( moraine whose mm/h s ( monitored s glaciers glaciers with mass balance measurements

) and is used as a proxy of moisture on the Altiplano. The precipitation Mean hourly precipitation intensity (mmhr centuries. schematic

lacier a exist. The large red hexagon depicts a sample of 21 glaciers in the Cordillera Real, g

: (d) a ther ther glaciers indicates

Tropical Rainfall Measurement Mission Rainfall Measurement Tropical . from lake sediments O Comparison Comparison of also also ( match match period increased a of

. ). 2 a and represents represents the relative change in abundance all all red hexagons) are labelled. For these glaciers length (yellow cube) and area (blue circle) iated´ iated´ .

comes comes from Morale t ) )

s

2009 ini (Coropuna) and 2010 (Quisoqui dotted frame shows the extent of the precipitation maps precipitation intensity TRMM Figure Figure 1 (sm records Bolivia, for which mass balance reconstructions d is used as a proxy of moisture on the (c) Asteraceae

evidenced evidenced periods) in recent moraines along or below 5700 m a.s.l.), Peru and Bolivia triangles) 2005 an ring 2006 Figure Figure

Glaciers monitored in the tropical Andes. Glaciers with countinous mass balance

and

1180 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 Comparison of moraine stages dated by lichenometry (triangles) and glacier advances 1191 1192 1187 1188 1189 1190 1181 1182 1183 1184 1185 1186 , respectively, from 1998 to 2010 based on TRMM (Tropical Rainfall Measurement Mission) Poaceae ice core (Liu et( al., 2005) representsanomaly the relative evidenced change in in treecome abundance from rings of Thompson comes et two from al. pollen (1985, Morales species 2006). et al. (2012), and data from ice cores periods) in recent centuries. Thethe position moraines of along the a triangles schematic qualitatively proglacialabove represents margin or the for position below glaciers of in 5700 m EcuadorPME (glacier a.s.l.), (black with Peru triangles) a and summit match Bolivia. a Note period that of the increased moraine accumulation. stages The and mainly the evidenced from lake sediments (Venezuela) with di Fig. 2. Fig. 1. (a) series (small red(blue hexagons) circle) are records labelled. alsoCordillera exist. For Real, The these large Bolivia, glaciers red2006 for length hexagon (Soruco which depicts et (yellow mass al., a cube)tored 2009a). balance sample are and Other of numbered. reconstructions glaciers “MB area 21 are initiated” whose indicates glaciersin changes available glaciers in 2008 with in from mass the (Incachiriasca), length balance 1963 and/or 2009 measurements starting to in (Coropuna) area and are 2010 moni- (Quisoquipinia). Product 3B43 V6. circulation over South America. TheFig. dotted 1c frame shows and the d. extent(d) of the precipitation maps in

.

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | period depending on study

nd Bolivia computed before before 1940) and aerial number of values

and and

the decades first of the

varying s s in the Cordillera Real, Bolivia, since the LIA

53 54

2528 2527 . were were available for eight eight glacier

ata ata of d

the year 1963 the year nnual nnual area loss rate between Venezuela a area

fewer for cause of cause of be Compilation of mean annual area loss rate between Venezuela and Bolivia com- Changes in the surface area of eight glaciers in the Cordillera Real, Bolivia, since the . Note that the average is computed from a Changes Changes in the surface . . puted from maps, aerial photographs,Sources satellite images are and direct given topographical invalues measurements. the depending on text. the Notedecades period that of concerned the the study because average period. of is fewer computed data from were a available for varying the number first of Fig. 4. LIA maximum, reconstructed from morainephotographs stages (1940 and (LIA after), maximum for and the before year 1940) 1963. and aerial Fig. 3. Compilation of mean a concerned concerned

. in the text

photographs (1940 and (1940 and after), photographs Figure 3 Figure maximum, reconstructed from moraine stages (LIA maximum

the period the period Figure Figure 4 from maps, aerial photographs, satellite images and direct topographical measurements. Sources are given

1197 1196 1195 1194 1193

1203 1202 1201 1200 1199 1198

h Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Changes

as as cumulative cumulative cumulative lengt shown computed computed from aerial were changes changes in and and are

10 glaciers in Ecuador, Peru and Bolivia. 56 55 in Bolivia and Ecuador 2530 2529 of area 1963. urface urface and and length area area es es for Cotopaxi for volcanoes and 1979, Antisana 1987 and 2007, computed n from field measurements and are plotted as direct direct measurements since the early 1990s compared with compared urface urface Changes Changes in s lacier outli come from from G

. 1980. 1980. 6

Glacier outlines for Cotopaxi and Antisana volcanoes for 1979, 1987 and 2007, com- Changes in surface area and length of 10 glaciers in Ecuador, Peru and Bolivia. Changes surface area surface area

Changes in s

Figure Figure images. satellite from

. 5

Fig. 6. puted from satellite images. in length inlength Peru compared come with from 1980.from field Changes aerial measurements in photographs surface and and areaas from are in cumulative direct changes plotted Bolivia measurements in as and since surface Ecuador area changes the compared were early in with computed 1990s 1963. cumulative and are shown Fig. 5. ength ength in Peru 1213 1214 1211 1212

changes in changes compared compared with photographs and Figure Figure in l

1209 1210 1207 1208 1204 1205 1206

the was

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | s ent

. ) . SLA repres balance balance in the intertropical Each budget is drawn as a 2012 . . The tropical Andes average eight eight glaciers in the tropical Andes.

from Cogley ( from

snowline snowline altitude.

57 58 photogrammetric photogrammetric surveys 2532 2531

1 standard deviation box. The tropical Andes average

± easured easured rates of change in mass measurements are made annually; geodetic measurements 1 standard deviation box variations in - sporadic +/ lobal average comes

g mass mass balance series computed for from from annual and hydrological Cumulative annual mass balance series computed for eight glaciers in the tropical An- Compilation of all available measured rates of change in mass balance in the intertrop- pilation of all available m Cumulative Cumulative chosen common the chosen as reference.

. 7 was Com

Fig. 8. ical Andes. Glaciological andsurements hydrological are pluriannual measurements and are resultthe made from reconstruction annually; sporadic of photogrammetric mass geodetic surveys. balanceas mea- SLA using a represents variations thick in horizontal snowline linewas altitude. contained computed Each in from budget a available is data. drawn The global average comes from Cogley et al. (2012). des. 2006 was chosen as the common reference. Fig. 7. . Glaciological Glaciological 8

2006 Figure Figure

thick thick horizontal line contained in a available The from data. computed Figure Figure Andes. are pluriannual and result reconstruction of mass balance using 1217 1218 1215 1216

1226 1225 1224 1223 1221 1222 1219 1220 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

. Note that for Monthly Monthly mass )

C) between ◦ 2 SSTa. The best +

en both 2005 2005 because the glacier ˜ ropical ropical Andes where the no 3.4 index leading t March March 2006 ˜

Mass balance no 1 the ˜ no 3.4 SSTa (

ember in (°C) between (°C) Junebetween 1995

correlation correlation between mass the averaging averaging filter.

month . The best correlation betwe -

) and Niño3.4 SSTa s Niño3.4 index leading mass balance anomalies 1+2 1+2 SSTa

˜ same same but for the outer tropics (mean of Zongo, no 3.4 index, with the Ni ño 60 the the 59 the 2534 2533 (the (the reference time for the cumulative time series is re re measurements began in

ph: smoothed with a 12

were alance alance for five glaciers Lower Lower gra

Niño3.4 index, with

the

by by 3 months. Vertical bar plot (inset) shows

month lag (see the vertical bar the vertical (see plotmonth inset). lag - Both Both time series

4 Antisana 15 Conejeras and La glacier

a

of at at this time scale Upper graph: time series of monthly mass balance anomalies (m w.e.) for the inner

. was with was between between 0 and 6 months.

Figure Figure 10 tropics (mean and August 2011. anomalies lag SSTa balance anomalies and by Chacaltaya and Charquini Sur glaciers) and Ni series

were were made 1244 1243 1239 1240 1241 1242 1235 1236 1237 1238

Upper graph: time series of monthly mass balance anomalies (m w.e.) for the inner . Cumulative monthly mass balance for five glaciers in the tropical Andes where the Cumulative Cumulative monthly mass b

. small mass balance anomalies by betweentropics 0 (mean and of 6 Zongo, Chacaltaya months. andcorrelation Lower Charquini between graph: Sur both the glaciers) series same and was but Ni for with the a outer 4-month lag (see the vertical bar plot inset). June 1995 and August 2011.Mass Both balance time anomalies series were lag smoothedbetween SSTa by with mass 3 a 12-month months. balance averaging Vertical filter. anomalies bar plot and (inset) the shows the Ni correlation Fig. 10. tropics (mean of Antisana 15 and La Conejeras glaciers) and Ni measurements were made at this timeApril scale 2005, (the except reference for time Conerejas for Glacier thefor where cumulative Zongo time measurements series began and is in Antisana Marchmass 2006). 15 balance Note glaciers, measurements that on only Chacaltaya Glacier thethe were results glacier stopped in of was September too the 2005 small. because ablation zone are plotted. Monthly Fig. 9.

balance balance measurements on Chacaltaya Glacier were stopped in Sept too was April April 2005, except for Conerejas Glacier whe Zongo and Antisana 15 glaciers, only the results of the ablation zone are plotted. Figure Figure 9 measurements

1233 1234 1231 1232 1228 1229 1230 1227 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Peru, Peru, and

and and in NCAR - Peru, Peru, at at glacier snouts

) in NCEP

reanalysis reanalysis data computed from from from the lowest glacier snouts to

s

Ecuador, Ecuador, Cordillera Blanca

Ecuador, Ecuador, Cordillera Blanca

in temperature temperature in

61 62 the Andean Cordillera NCAR 2536 2535

- in t NCEP ( ) for three sites (Antisana 1

201 - a). 55 Bolivia) in parallel with a range of elevation

(19

period at three locations (Antisana hanges in freezing level heigh

Bolivi

C 1

. in 1 n elevation of glaciers at each site (blue shaded area). site (blue at each n elevation of glaciers 1 201 - Cumulative degree months

. Cumulative degree months (NCEP-NCAR temperature reanalysis data) at glacier 2 Changes in freezing level height in the Andean Cordillera computed from NCEP-NCAR

Figure Figure reanalysis data Cordillera Real in the mea 1 llera Real Real llera

r the 1955 1249 1250 1246 1247 1248 1245

Cordi Figure Figure fo Fig. 12. snouts for thein 1955–2011 Peru, period and Cordillera at Real three in Bolivia). locations (Antisana in Ecuador, Cordillera Blanca Fig. 11. reanalysis data (1955–2011) for three sitesCordillera (Antisana in Real Ecuador, in Cordillera Blanca Bolivia) into in Peru, the and parallel mean with elevation of a glaciers range at of each elevations site from (blue the shaded lowest area). glacier snouts

1254 1252 1253 1251