Glaciers in South America

G. CASASSA CENTROAUSTRAL ANTARCTICA 8.1 INTRODUCTION UNIVERSIDADDE MAGALLANES The presently glacierized area in South America is PUNTAARENAS, CHILE estimated at some 26,000 kmz (LAHS(ICS1)I UNEP/UNESCO, 1989), with the bulk of this ice L. E. ESPIZUA mass being found in the Patagonian Ice Fields and INSTITUTOARGENTINO DE Tierra del Fuego. A great number of mountain gla- NIVOLOGÍAY GLACIOLOGÍA, IAN- ciers exist in the Andes of Argentina, Bolivia, Chile, IGLA-CONICET Colombia, Ecuador, Peru and Venezuela. The follow- MENDOZA,ARGENTINA ing text illustrates mainly the situation in Argentina, Bolivia, Chile and Peru. B. FRANCOU AND P. RIBSTEIN ORSTOM LA PAZ,BOLIVIA 8.2 DISTRIBUTION AND CHARACTERISTICS A. AMES Glaciers in South America occur along the high HUARAZ,PERU Andes. More than half of the Andean range is located in Chile and Argentina (Fig. 8.1). In northern Chile J. ALEAN and Argentina (17"-27"S),the highest summits rise EGLISAU,SWITZERLAND above 6,000 m a.s.l., with a high plateau (Altiplano) extending several tens of kilometres to the east. To the south, the Ancles are concentrated along a narrower belt only a few tens of kilometres wide. Aconcagua, located in Argentina at 33"S, is the highest summit not only of South America but of the entire western hemi- sphere. South of 34", the elevation of the highest sum- mits decreases rapidly (Table 8.1). In their northern part, the Chilean Andes start at 17"s latitude and straddle Bolivia to 23"s. The cli- mate here is dominated by the subtropical high pres- sure of the Pacific with associated arid conditions. The main precipitation source comes from the Atlantic and occurs during the summer months,

Fonds Documentaire ORSTOM 125 Ex cote : : Into the second century of worldwide glacier monitoring

I 1 750 w

16's

- 38"s

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220s

- 42's

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26'5

- 46"s

30'5 -

50's Córdoba a - -

340s .-

-5405 -

Figure 8.1 Map of Chile and Argentina. (left) - northem part; (right) - southem parc Numbers'represent the high mountains of the Andes as shown in Table 8.1. amounting to only a few tens of mml year in the occur on high volcanoes in this area (e.g., Parinacota mountain areas. The orographic effect on precipita- and Pomerape). tion results here in an east-west gradient of the equi- Of all the tropical regions (i.e., areas between the librium line altitude (ELA, Fig. S.2), the precipitation tropic of Capricorn and the tropic of Cancer), the being higher in the east. The precipitation decreases mountains of Peru have the largest number of gla- southward as the distance from the humidity source ciers. At the same time, the Andes of Peru are in the Atlantic increases. Only very few mountain densely populated. On the one hand, the local popu- glaciers with areas generally smaller than 15 km' lation benefits from continuous and reliable melhva-

7000 -

6000 - 5000 hE - 4000- C .-O 3000- > al 6 2000- Figure 8.2 North-south variation 1000 - of the regional snow-line on the 04 westem margin of the Andes 1 I I I (continuous line) and on the east- em side (dotted line), and high- 15 25 35 45 55 S est elevation of peaks (line join- Lat itude (degrees) ing triangles). The snow-lines are adapted from Nogami (1972). 126 Glaciers Soiith America 'P Ir! in

ter runoff but, on the other hand, is frequently TABLE 8.1 Highest Andean summits along a north- affected by glacier catastrophes of various kinds. south transect from the Bolivian-Chilian border to the Catastrophic events caused by ice avalanches and very south of the American continent. proglacial lake outflows happen from time to time in Moiiiitaiii Lntitirde Elevation all Cordilleras (high mountain ranges) of the S Peruvian Andes. They have caused serious damage in (O) u hi) the lower valleys, destroying towns, villages, roads, 1 Volcán Tacora 17 43 5,988 bridges, paths, etc. In many cases, people were 2 Volcán Parinacota 18 10 6,330 killed. Since the catastrophes usually occurred unex- 3 Cerro Sillajhuay 19 45 5,995 pectedly and suddenly, there was little chance for 4 Cerro Copa 20 37 5,320 people to escape. For example, during a particularly 5 Volcán San Pedro 21 54 6,154 tragic event in 1941, at least 4,000 people drowned in 6 Sairecábur 22 42 5,970 the town of Huaraz as a result of the outflow from 7 Pular 23 11 6,225 two small proglacial lakes in the Cordillera Blanca. 8 Llullaillaco 24 42 6,723 This event led to the realization that it was necessary 9 Volcán Lastarria 25 11 5,700 to (a) make an inventory of dangerous proglacial 10 Cerros Colorados 26 11 6,049 lakes and (b) lower or to strengthen the outlet of the 11 Ojos del Salado 27 Oï 6,880 most dangerous lakes if settlements were endan- 12 Cerro del Potro 28 23 5,830 gered and if this was technically at all possible. For 13 Cerro del Toro 29 Oï 6,380 this purpose, the Comisión de Control de Lagunas de 14 Cerro de la Tórtolas 29 57 6,332 la Cordillera Blanca was set up. The development of 15 Cerro Alto 30 34 5,430 hydroelectric power further increased interest in 16 Cerro Maruez 30 42 4,750 glaciers, particularly in the Cordillera Blanca. At first, 17 Chanchones 31 56 5,370 four glaciers were chosen for a pilot study on mass 18 Cerro Ojotas 31 57 5, O 70 balance measurements. Two more glaciers were 19 Mercedario 31 28 6,770 added to this network later on. Understanding gla- 20 Cerro Volcán 32 32 6,130 cier fluctuations in the Peruvian Andes is also of 21 Cerro Aconcagua 32 39 6,959 great importance in connection Frith the formation of 22 Nevado Juncal 33 04 6,110 new lakes as a result of rapid tongue retreat. In par- 23 Volcán Tupungato 33 22 6,550 allel with this work, cooperation with the Temporary 24 Maipo 34 11 5,290 Technical Secretariat for the World Glacier Inventory 25 Alto los Arrieros 34 37 4,986 was initiated. The inventory was made possible by 26 Sosneado 34 4s 5,159 the availability of various sets of aerial photographs, 27 Volcán Peteroa 35 15 4,090 some of which were taken in the aftermath of the 28 Campanario 35 56 4,002 biggest glacier catastrophe to occur in Peru in recent 29 Volcán Domuyo 36 37 4,709 centuries, the gigantic rock and ice avalanche from 30 Chillán 36 50 3,122 Nevado Huascarán in 1970. 31 Volcán Tromen 37 os 3,9 79 From 23"s to 51"S, the Andes are shared by 32 Volcán Antuco 37 25 2,985 Argentina and Chile. Climatic conditions from 23" to 33 Volcán Callaqui 37 55 3,080 30"s range from arid to semi-arid, with precipitation 34 Volcán Llaima 38 42 3,124 increasing slightly south of 23"s as the region 35 Volcán Villarrica 39 25 2,840 affected by the westerlies is approached. The precip- 36 Volcán Puyehue 40 3s 2,240 itation increase results in an ELA decrease to :the 37 Monte Tronador 41 10 3,460 west from 6,600 m at 24"s to 4,700 m at 30"s 38 Nevado Minchinmávida 42 52 2,470 (Fig. 8.2). The transition from an eastern precipita- 39 Volcán Corcovado 43 12 2,300 tion source to a western source appears in Fig. 8.2 as 40 Cerro Melimoyu 44 o5 2,400 the intersection of the ELA on the western side of the 41 Cerro Catedral 44 56 3,060 Andes and the ELA on the eastern side at 27"s. 42 CerroMacá 45 06 2,960 Glacierization is limited in this area to very few small 43 San Valentin 46 37 3,910 mountain glaciers (in general less than 1kml) occur- 44 Cerro San Lorenzo 47 37 3,700 ring on the highest summits (e.g., Cerros Colorados, 45 Cerro Mellizo Sur 48 33 3,050 Tres Cruces, Los Tronquitos). At 30"S, a clear influ- 46 Cerro Fitz Roy 49 17 3,441 ence of the westerly circulation occurs, with pro- 47 Murallón 49 4s 3,600 nounced seasonality in precipitation during the win- 48 Cerro Bertrand 49 57 3,270 ter months associated with low pressure systems 49 Cerro Paine Grande 51 O2 3,100 from the Pacific. By contrast, summer conditions are 50 Monte Burney 52 20 1,750 dry owing to the presence of the subtropical high- 51 Monte Córdova 53 19 1,219 pressure system. A marked precipitation increase 52 Monte Darwin 54 44 2,438 explains the existence of important mountain and 53 Monte Hardy 55 24 1,036 valley glaciers from 32's to 35"S, where many sum- mits exceed 5,000 m a.s.1. and a few even 6,000 m 127 Y Into the second century of worldwide glacier monitoring 11

a.s.1. (e.g., Mercedario, Aconcagua, Juncal could be due, at least in part, to a particular condition Tupungato, Marniolejo). South of 35'5, the highest affecting the mass balance which is that, on these gla- summits rarely exceed 4,000 m, which restricts the ciers, the accumulation period stretches throughoil t development of glaciers to mainly volcanic cones the summer and is therefore synchronous to the period (e.g., Peteroa, Domuyo, Antuco, Callaqui, Llaima, in which ablation is at its maximum. Thus, a deficit in Lanín, Osorno) to 42"s. Precipitation increases from precipitation during this season translates directly into about 200 "/year at 30"s to 2,000 mm at 40"s. strong ablation tied to the increase in direct radiation. There is a strong orographic effect on circulation, It could also be suggested that, with the summer rain- with an important reduction in precipitation on the fall, an increase in the temperature would shift the eastern side of the Andes. South of 42"S, in the snow-rain boundary to higher altitudes, causing a sig- region known as Patagonia, the climate is wet tem- nificant contribution in sensible heat over the majority perate, being completely dominated by the westerly of the glacier (Lliboutry et d., 1977rz). circulation, with high precipitation and reduced sea- sonality. This results in a larger glacierized area. Three small ice caps from 40 to 100 km2 exist on the

Chilean side from 42"s to 44"s: Minchinmávida, 8.3 EXISTING INVENTORIES ~~ Yanteles and Melimoyu. The Patagonian Andes have Early glacier inventories of Chile and Argentina haTe been carved extensively by Pleistocene glaciers, been summarized by Mercer (1967). The distribution resulting in a complex pattern of fjords both in the of glaciers in Chile has been described by Llibout? Pacific and in large pedemontane lakes to the east. (1956), who was the first to conduct detailed glacio- The orographic effect on circulation in Patagonia is logical work in Chile. In the late 1970s, the Dirección highly pronounced, with precipitation amounts in General de Aguas of the Ministry of Public Works excess of 5,000 "/year in certain areas to the west started a detailed glacier inventory programme. As and as little as 200 "/!-ear or less on the Pampa to part of this programme, glaciers have been inven- the east. South of 46"S, the two largest ice bodies of toried in the Río Maipo basin (33" to 34"s; Maragunic, the southern hemisphere outside Antarctica are to be 1979), in the Río Cachapoal basin (34"s; Caviedes, found: the Northern Patagonia Ice Field, with an area 1979), in the Río Aconcagua catchment (32"s; of about 4,200 km2 (Aniya, 198S), and the larger Valdivia, 19S4), in the Río Mataquito basin (35"s; Southern Patagonia Ice Field covering about Noveroy, 19ST), in the north of Chile (18" to 32'; 13,000 kmz (Aniya et d., 1992). Glacier Upsala, a Garín, 1986) and in the Lake District (37" to 41" 30's; 60 km-long outlet on the eastern margin of the Rivera, 1989). In addition, a preliminary glacier inven- Southern Patagonia Icefield, is the largest glacier in tory based on 1:250,000 maps has been compiled for South America. the Northern Patagonia Ice Field by Valdivia (1979r7, From 51"s to 55"S, the Andes lie completely in 197927). A more precise and complete glacier invento?. Chile, changing from a north-south to an east-west for the Northern Patagonia Ice Field based on 1:50,00@ orientation. In this area, the third-largest glacier cartography has been compiled by Aniya (198s). body in South America is found: Cordillera Darwin in Table 8.2 summarizes the glacier inventoT in Chile. Tierra del Fuego, with an estimated area of The total area covered by detailed glacier inventories 2,000 kmz. Smaller ice caps exist in Peninsula Muñoz is 5,515 km',, representing approximately only one- Gamero, Isla Santa Inés and Isla Hoste. At 55"s) near fourth of the total glacier area in Chile (cf. Table 8.3). Ushuaia in Tierra del Fuego, a subdued portion of the In Argentina, Helbling and Reichter explored the Andes with reduced glacierization is again shared high Cordillera between Mt. Aconcagua and with Argentina. Mt. Tupungato from 1907 to 1912 (Reichter, 1929; Glaciers in Bolivia, Colombia, Ecuador, Peru and 1967). Helbling (1919; 1935; 1940) published an accu- Venezuela are mostly mountain glaciers existing under rate map of the Río del Plomo valley (33"s) on a scale tropical climatic conditions. Recent studies carried out of 1:25,000, describing the glaciers and fluctuations of in the Central Andes (Thompson, 1992; cf. also the glaciers' termini since 1909-1934; Groeber (19470; Hastenrath and Kruss, 1992, for Kenya) suggest that 194727; 1951; 1955) studied the geology and described the effects of global warming could be more pro- the glaciers in the Central Andes; Lliboutry (1956) nounced in the short term for tropical glaciers like published maps and measured the englaciated area these than for glaciers of high and medium latitudes. between 32"jO'S and 35"s and the glaciers in Other studies also indicate that tropical glaciers are Patagonia. Feruglio (1957) described the glaciers in excellent indicators of short-term climatic variations, the Cordillera Argentina between 21"s and 51"s. An as seen in the Andes by their response to anomalies of inventory of Patagonian glaciers was first undertaken short duration and of variable intensity resulting from by Lliboutty (1956) and Bertone (1960). In the the El Niño phenomena (ENSO) (Thompson et al., provinces of Mendoza (33"s) and San Juan (31"S), the al., 1984; Francou et al., 1995; Ribstein et 1995). The Instituto Argentino de Nivología y Glaciología (IAN- sensitivity of tropical glaciers to climatic variability is IGLA-CONICET) has compiled glacier inventories still inadequately explained, mostly due to the lack of (IAHS(ICSI)/UNEP/UNESCO,1989) in the following data available on net mass balances and on the climatic basins: Río Mendoza: Corte and Espizua (1978; 1981) variables that control these glaciers. This sensitivity identified 1,035 ice bodies bigger than 0.02 km' that 128 ,I , (1 *ta' ' Glaciers in South America Y

TABLE 8.2 Inventoried glaciers in Chile

Re

TABLE 8.3 Uninventoried glaciers in Chile

La fifiide Region Description Estimated Area (km') 35' to 37" s VI1 & VI11 Río hfaule and Rio Itata basins, glaciers limited to a few high peaks (e.g., Volcán San Pedro, 3,499 m) 50 41' 30' to 45" 30' S X & XI Continental Chiloé and northern Aisén, three main ice caps on Mt. Minchinmávida (2,470 m), Mt. Yanteles (2,042 m), and hlt. Melimoyu (2,400 m) (Lliboutry 1956), plus many smaller mountain glaciers "250 43' 30' to 49" S XI North, East and South-east of Northern Patagonia Icefield, and Xorth-east of Southern Patagonia Icefield. Many mountain glaciers, e.g., Volcán Hudson, Cerro San Lorenzo 400 ' 48" 15' to 52" S XI & XII Southern Patagonia Icefield, total area 13,000 kmz (Aniya et al., 1992), of which 90% is claimed by Chile (Martinic 1982) 11,700 51" 45' to 52" S XII Cordillera Sarmiento, ice caps and mountain glaciers, first explored by Miller 100 52" 40' to 53" S XII Península Muñoz Gamero, icefield on south-western part of peninsula "200 52" 50' to 53" 20' S XII Isla Riesco mountain glaciers 100 53" 45' to 54" s XII Isla Santa Inés, icefield on eastern part of island "250 54" 20' to 54" 50' S XII Cordillera Darwin, 150 km-long icefield, 25 km wide in central part 2,000 55O lo's XII Isla Hoste, ice cap located on Península Cloue, western part of the island, plus smaller glaciers to the East 150 Total 15,200 Note: * indicates areas estimated by Lliboutry (1956). Otherwise, area estimations are made in this study by inspection of 1:500,000 scale maps.

129 Into the second century of worldwide glacier monitoring covered 304 kmz of bare ice and 344 kmz of debris- Detailed glacier inventories (cf. IAHS(ICS1)I covered ice. Río Tunuyán: eastern slopes of Cordón UNEPIUNESCO, 1989) were also compiled in Bolivia del Plata and Cordón del Portillo (the glacierized area (Cordillera Occidental and Cordillera Oriental, is 144 km2, 40% of which corresponds to uncovered Jordan, 1991), Peru (Northern and Southern ice and 60% to covered ice) (Espizua, 1983a; 1983b). In Cordilleras, Ames et al., 1988) and partially in the Río Atuel: Cobos (1979, unpublished IANIGLA Ecuador, Colombia (Sierra Nevada de Santa Marta report) revealed a glacierized area of 186 kmz consist- and various volcanoes) and Venezuela (Sierra Nevada ing of 80% of uncovered ice and 20% of covered ice. de Mérida). In Peru, the Glaciology Division of Río Malargüe: in this basin, the englaciated area cov- ElectroperG in Huaraz completed an inventory which ered 12 km2,2% of bare ice and 9.5% of ice covered by is mainly based on aerial photogrammetric flights debris (Cobos, 1987). The Río San Juan catchment, conducted between 1955 and 1970. The flights in 1970 with Ríos de los Patos, Blanco, Calingasta, Ansilta and were undertaken by NASA and the Servicio Castaño (Aguado, 1983; 1986 (unpublished IANIGLA Aerofotográfico Nacional (SAN) after the catastrophic report); Espizua and Aguado; 1984) has a total glacier- earthquake on May 31. These photographs were ized area of 556 kmz (42% of uncovered ice and 58% of recorded on infrared film and were used for the inven- ice covered by debris). Glacier inventories from the toiy of the Cordillera Blanca. The 1955 material was Patagonian Andes, Argentina, have been published by used for Cordillera Ampato and some zones of the al., al., Rabassa et 1975; Rabassa et 1978a; 1978b; Cordilleras Chila and Huanzo (cf. Fig. 8.3). The rest of 1978c; Rabassa, 1980; 1981; Rabassa et al., 1981; the inventory is based mainly on 1962 pictures. The Rabassa, 1983. At 55"S, Lendaro and Iturraspe studied bulk of the Peruvian ice masses are located in the the Martial Glacier and Roig (1990) studied the geo- Cordilleras Blanca, Vilcanota, Ampato and Central morphology and hydrology of de cirque glaciers in the (Ames et al., 1988; cf. Table 8.4). The total glacier area al. Tierra del Fuego Andes. Rabassa et (1981; 1982) (excluding the insignificant amounts in the Cordilleras compiled a glacier inventory of the James Ross and Barroso and Volcanica) is 2,042 km?. Altogether, 3,044 Vega Islands in the Antarctic Peninsula. glaciers were recorded. Fig. 8.4 shows some interest-

Figure 8.3 Distribution of glaciated Cordilleras (high mountain ranges) in north, 1 central and southem Peru. 300 km The true extent of glaciated areas cannot be on i I shown CHI1 F this scale.

130 I

Glaciers in South America

TABLE 8.4 Number, total area and estimated total ice volume in the Peruvian Cordilleras according to the Peruvian Glacier Inventory of Cordillera Niriirber nlnciers Total nrea (kiirz) Total volme (knr3) 1 Blanca 722 723 22.60 2 Huallanca 56 21 0.43 3 Huayhuash 117 85 2.99 4 Raura. 92 55 1.33 5 LaViuda 129 29 0.43 6 Central 236 117 2.54 7 Huagoruncho so 23 0.40 8 Huaytapallana 152 59 1.15 9 Chonta 95 18 0.26 10 Ampato 93 147 5.12 11 Vilcabamba 98 3s 0.72 12 Urubamba 90 41 0.78 13 Huanzo 115 37 0.60 14 Chila 87 34 0.58 13 LaRaya 48 11 0.16 16 Vilcanota 469 418 12.00 17 Carabaya 236 104 1.96 18 Apolobamba 109 81 2.11 19 Volcanica 20 Barroso Total 3.044 2.042 56.15

ing statistical results from the Cordillera Blanca. Inferior and Glaciar Grande del Kevado del Plomo) Athough this mountain range appears most spectac- and Santiago (Juncal Sur, Museo and Colina). A few ular to any visitor to the Santa Valley, no glacier is glaciers in the Southern Patagonia Ice .Field are larger in surface area than 16.5 km' Oankapampa). presently advancing and Moreno Glacier is largely The longest glacier is Copap (7.0 km). Of particular Stahle. In contrast to the above glaciers, most glaciers interest is the distribution of average glacier altitudes in Chile and Argentina are presently retreating, as (Fig. 8.4b). On the eastern side, average altitudes are indicated by recent moraines and their present sometimes lower than 4,800 m ad. and typically behaviour. The only glacier in Chile presently mon- around 5,000 m. On the western side of the Cordillera, itored for mass balance is Echaurren Norte Glacier at they are significantly higher. Here, average equilib- 33"s. Monitoring has been done by the Dirección rium lines are usually above 5,100 m and sometimes General de Aguas routinely in spring, summer and even above 5,400 m. This can be interpreted as an autumn since 1975. Results have been published for al., effect of precipitation distribution since the main the periods 1975-1983 (Peña et 1984) and advection of moisture is from the Amazon basin in the 1975-1994 (Escobar et al.,, in press) and the pro- east. Nevertheless, quite a large part of the glacier sur- gramme still continues today. With respect to frontal faces are oriented towards the southwest (cf. Fig. 8.4~) variations, the only systematic studies based on aer- because the high valleys on this side of the Cordillera ial photographs and satellite imasery are on glaciers Blanca are somewhat less steep than on the other, of the Northern Patagonia Ice Field (Aniya, 1988; thus providing relatively extensive accumulation areas 1992; Aniya and Enomoto, 1986; Warren, 1993) and al., at high altitudes. Similarly interesting relationships the Southern Patagonia Ice Field (Aniya et 1992; can also be found when comparing the Cordilleras La Warren and Sugden, 1993). Sporadic observations of Viuda, Central, Huaytapallana and Chonta (IAHS glacier variations elsewhere in Chile are described in (ICSI)/UNEP/UNESCO, 1989). It is to be expected Lliboutry (1956), Mercer (1962; 1967) and that a general glacier retreat as a result of continued Marangunic (1964n; 1964b). climatic warming will soon lead to a total loss of gla- In Argentina, some glaciers are presently mon- ciers in the Cordilleras Chonta, Huallanca or La Raya, itored by IANIGLA for mass balance in the EO where only a few small glacierlets can be found. Mendoza basin. Mass-balance measurements in the Cajón del Rubio area began in 1979. Balances were calculated continually up to 1987 but no measure- ments were taken in 1986, 1988 and 1990. Balance 8.4 EXISTING LONG-TERM OBSERVATIONS measurements re-started in 1991. The authors recon- (LENGTH CHANGE, MASS BALANCE, MAPS) structed the accumulation data at Piloto Glacier for In Chile and Argentina, there are several cases of the missing years and analysed the mass balance surging glaciers near Mendoza (Glaciar Horcones behavior of Piloto and Alma Blanca Glaciers (Leiva et

131 Into the second century of worldwide glacier monitoring -* , ~ il :< I 7 , -

a) 7 7'

I 1 I l I I I I I I d O 50 K!l I\

30'

9O

30'

100 , \ 30' 30'

Figure 8.4 (a) Glaciers in the Cordillera Blanca according to surface area; @I) mean glacier elevations in the Cordillera Blanca (notice that the mean elevation is somewhat lower on the eastern side compared \vith the western side of this mountain range);

al., 1986; Leiva and Cabrera, in press). Regarding carried out during the summer of 1993-94 at and glaciers' frontal variations, studies have been made in around the Upsala, Ameghino and Moreno Glaciers the following basins: Río del Plomo basin (33'5) (Skvarca et al., 1995; Naruse et al., 1995; Takeuchi ci (Espizua, 1986; 1987; Espizua and Bengochea, 1990; al., 1995; Aniya and Sato, 1995). Leiva et al., 1989; Llorens and Leiva, in press); Río Until recently, there \vere very few mass balance Tunuyán basin (33'15's) (Llorens and Leiva, 1994); studies available for the Central Andes comparable Rio Atuel basin (34"s) (Cobos and Boninsegna, 1983); to those undertaken for tropical African glaciers, Río Frías basin (41"s) (Villalba et al., 1990). Mercer notably Lewis Glacier (Hastenrath, 1984). This lack (1965; 1968) studied the fluctuations of ice margins in of work is all the more regrettable in that the Central Patagonia. Fluctuations on Castaño Overo Glacier, Andes represent more than 95% of the surface area Mount Tronador, in Northern Patagonia have been of glaciers found in the Tropics. Over the last fifteen studied by Bertani et al., 1985; 1986; Brandani et al., years or so, only the Cordillera Blanca (Peru) has 1986 and on Martial Glacier in Ushuaia (55"s) by provided data on the balances of ablation areas of Lendaro and Iturraspe. A Glacier Research Project in two glaciers, Uruashraju and Yanamarey (Ames, al., Patagonia that included Characteristics of Recent 1985; Kaser et 1990), in addition to data over se\'- Glacier Variations in Patagonia, Sotithem Andes was eral decades concerning the oscillations of the gla-

132 ', ' ' Glaciers iiz Soirth America 4 ~

77"7 Since 1940, a general tendency towards glacier retreat 1 has been documented by aerial photographs taken in $-O $-O KH 1948 and 1962 and by topographic surveys carried out every year since 1968 at the terminus of about half a dozen glaciers of the Cordillera Blanca (Ames, 1985; Kaser et al., 1990). In the early 1970s, an ablation stake network was installed and monitored on the tongues of Uruashraju and Yanamarey. Since 1980-81, the stakes have been measured at the end of 30 both the wet and dry seasons (Kaser and Ames, 1990). Owing to the problems associated with very high altitudes, stakes could only be maintained up to 4,900 m asl. It is noteworthy that accumulation mainly takes place during the rainy season, which usually lasts from October until March or April. There is hardly any seasonal temperature variation. Therefore, ablation takes place at any time of year. The longest record of length fluctuations is detained

9O by the Broggi (located north of Nevado Huascarán, 1.1 km long), Uruashraju (2.5 km) and Yanamarey (1.7 km) Glaciers. The latter two are located in the southern part of Cordillera Blanca. Later on, the Gajap, Huarapasca and Pastoruri Glaciers completed the observational programme. The selection of regu- larly visited glaciers had to be done mainly from the point of view of accessibility. Additional glacier snout positions could be reconstructed using aerial pho- tographs (194s and 1962). The cumulative length 30 changes as recorded by field measurements (Fig. 8.5) indicate a relatively modest retreat from 19-18 until the end of the 1970s. Uruashraju and Yanamarey even recorded a very slight readvance around 1975. Behveen 1948 and 1980, Broggi Glacier retreated, on average, 11 m per year. Nevertheless, the total length loss of 366 m during this period amounted to one- third of the glacier's length in 1970! From 1980 to 1991, the retreat accelerated. Broggi lost an average of 26.2 m per year. In 1991, it retreated by 53.2 m, the 1o1 biggest single-year retreat ever recorded. The glacier was then 654 m shorter than in 1948. The other gla- ciers, including the newly-measured ones, retreated, (c) summarized surface areas and aspects of glaciers according on average, between 17.2-21.1 ni per year. Clearly, to catchment basins. After IAHS(ICSI)UNEP/LJNESCO,19S9. this pronounced ice loss is a general phenomenon in the Cordillera Blanca: maps and terrestrial pho- togrammetric pictures produced by German-Austrian cier's termini. From ice cores taken from the expeditions in the 1930s (Kinzl, 1910b; 1942; Kinzl Quelccaya Ice Cap (Peru), we know that the Little Ice and Schneider, 1950) show various small glaciers Age commenced in the Central Andes around 1480 which have since disappeared. Until now, it has been A.D. and ended around 1880 A. D. (Thompson ef d., difficult to relate the observed glacier retreat to local 1986). According to photographic documentation climatic data, although a simple meteorological sta- analysed by Broggi (1945) in the Peruvian Andes, the tion has been maintained at Querococha, a site 3,980 m retreat at the end of the 19th and beginning of the a.s.1. and 8.5 km belon- Yanamarey. Precipitation 20th centuries is interrupted by a phase of advance measurements commenced in 1954 and temperature between 1909 and 1932. This advance is itself fol- recordings in 1964. During this interval, the record- lowed by a significant retreat in the period ings do not show a clear, systematic increase in tem- 1932-1945. perature. However, at least the small readvance of In Peru, systematic length measurements of gla- Yanamarey and Uruashraju, as well as the decelerated cier tongues and mass balance measurements began retreat of Broggi around 1975, correlates with slightly in 1968 in the Cordillera Blanca. The aim was to esti- lower temperatures and somewhat increased precipi- mate the contribution of meltwater runoff to the tation in the early 1970s. Given that the analysed water available for hydroelectric power production. glaciers were very short, their length varying between

133 Into the second century of worldwide glacier monitoring

O

-100

-200

-300

-400

-500 "\ -600 \=

-700

85 Climatic data I-

8

7.5 1500

7

1000

500

O

Figure 8.5 Cumulative length changes of glaciers in the Cordillera Blanca and climatic record from the station at Querococha. In the 19% upper diagram, dashed lines show length changes inferred from aerial photographs. The snout positions are taken as zero.

1 km to 2.5 km, changes in balance were almost of retreat was three times faster between 1983 and immediately followed by changes in terminus posi- 1991 than between 1963 and 1978, while the mass , : tion. An acceleration in the rate of retreat is evident ",-.volumeloss Ivas seven times greater. for all these glaciers starting from 19S2 (Table 8.5): Since 1991, there has been an ongoing pro- the rate of the retreat is three times that of the aver- gramme of glacier monitoring and hydrology in the age retreat in the preceding decades. It is possible to Cordillera Real of Bolivia, the Cordillera Blanca of compare this acceleration to that measured by pho- Peru and some volcanoes in Ecuador, under the aus- togrammetry on the terminus of Quelccaya Ice Cap. pices of the French Scientific Research Institute for According to Brecher and Thompson (1993), the rate Development in Cooperation (ORSTOM) (Francou ci

134 ., I 0 1 Glaciers in South America ‘I A

TABLE 8.5 Length variation of 3 glaciers of Cordillera Blanca (1948-1993) Ler@ Varia tioit Broggi LlrLlaslzrnjLL Ynnarilnrey 1948-1993 -16.0 -11.0 -9.0 (1) 1948-1981 -11.0 -8.0 -6.0 (1) 1982-1993 -30.0 -19.6 -18.6 (1) Total Length in 1982 1.2 2.5 1.6 (1) metres per year (2) kilometres Source: Oficina de Recursos Hidricos; Electroperfi, Huaraz, Peru.

al., 1995). The results obtained in Bolivia from mulation), the effect of seasonal climatic variability, monthly measurements of glacial and hydrological which could influence the net yearly balance, balances of the Zongo and Chacaltaya Glaciers are stretches over at least six months. To analyse the sufficiently definitive to be taken as references for influence of seasonal variability, the present authors other glaciers in the Tropical Andes. These results have measured ablation and accumulation on a present the only measurements of mass balances and monthly basis on the Zongo and Chacaltaya Glaciers, hydrological balances of glacierized basins available two glaciers under study in the Cordillera Real of to date in the Central Andes. Despite the exceptional Bolivia (Fig. 8.6 and 8.7). The results obtained over historical documentation dating from the 18th cen- three years and partially published (Francou et al., tury available on glaciers in Ecuador (Hastenrath, 1995) show that, with respect to net b’alance, a year 1981), it is still impossible to provide a precise expla- can be divided up into three periods (Fig. 8.8). nation for the glacial retreat which started at the end of the Little Ice Age. All we can ascertain from the 1) The early summer months of October, November work of hleyer (1907), confirmed by information col- and December, preceding the rainy period, are lected by Broggi (1945) in Peru, is that glacial retreat months of strong ablation. Ablation is also strong has been occurring since at least 1870. The disap- during the 1 or 2 months at the end of the rainy pearance of numerous glaciers from a number of vol- season, March and April. In November- canoes Lvhich were ice-covered during the 19th cen- December, the firn line is situated at more than tury, such as Pichincha and Sincholagua, suggests 5,500 m, well within the accumulation zone. The that the snotv-line on the Western Cordillera rose, heavy rate of ablation during this period is due to between 1800 and 1975, from 4,650 m to 4,930 m a combination of factors, amongst which: the (Hastenrath 1981). The readvance of Peruvian gla- large quantity of energy at the top of the atmos- ciers around the mid-1920s is equally documented in phere (months around the summer solstice); the Bolivia (Müller, 1985; Jordan, 1991). The anal!-sis of mostly cloud-free skies; the not very high albedo the compelling ground-based photographic archives because the ice is still incompletely covered with assembled by Kinzl (1940a) in 1930 and 19-10 will snow, and the contribution of sensible heat allow, in the near future, precise determination of the owing to the increase in the hygrometry. variations of glaciers’ termini in the Cordillera Blanca 2) The months of accumulation, January-February twenty years before the first aerial photographs. (sometimes March), correspond to the highest On the Chacaltaya Glacier (Francou, unpublished levels of rainfall. It should be noted that the data), according to photographic documentation, a enepgy available for melting, by direct radiation guide mark dating from 1982 and topographic mea- or by sensible heat, remains sufficiently high to surements at the terminus every year since 1991, the induce strong ablation in the lowest part of the ;etreat is estimated at 2.0 mlyear between 1940 and glacier, close to the terminus. Since, at the same 1993. It ranges from an average of 0.95 mlyear for the time, a period of high accumulation dominates period 1940-1982 to 6.05 mlyear (a ratio of 1to 5) for over the greatest part of the surface, the activity the period 1982 to 1993. These results tally with coefficient of the glacier is high for this season, those obtained for the African glaciers in the close to 0.25 m I 100 m in \vater-equivalent. Ruwenzori (Kaser and Noggler, 1991) and on hlount 3) The months of winter, May-August, which are Kenya (Hastenrath and Kruss, 1992). They suggest generally dry and cold, are months in which the that, if the tendency is to persist, numerous minor net balance ought to remain stable. Cloud cover is glaciers may disappear in the next two or three low but the energy at the top of the atmosphere is decades. The balance of glaciers at medium and high 30 % less than in summer and it is just able to latitudes is determined, above all, by the temperature melt or sublime the snowfall accumulation over level of the ablation season (summer), which lasts the period. The energy available for melting is all approximately 3-4 months (Martin, 1977; Lefau- the more insufficient in that the amount of sensi- connier and Hagen, 1990). In the Tropics, because ble heat is also very low. It should be noted, how- the warm season (which favours ablation) is syn- ever, that winter is the season in which the quan- chronous to the rainy season (which favours accu- tities of energy received by the opposite facing

135 =, . * Into the second century of worldwide glacier monitoring b , 'I

A4 R8 O 1000 m - 2 +6

Figure 8.6 Zongo Glacier and the survey system in 1993. 1. Principal peaks -2. Limits of basin -3. Stakes -4. Pits -5. Water-level records - 6. Rain gauges - 7. Thermographs - 8. Pyranometers.

slopes present the greatest contrasts. This explains a difference of approximately 300 m in the ELA of glaciers of most contrasting slopes, which are the NE and SW slopes. However, in August 1994 and in July-August 1995, notable ablation rates were measured on Zongo Glacier T (Francou and Ribstein, unpublished data).

The highest instantaneous discharges from glacier torrent of Zongo Glacier have been measured in the summer, usually in November-December, at the end of dry periods (Fig. 8.9). These events represent the highest values of ablation registered on a daily basis. The frequency and length of these 'dry periods' in the warm season seem to be the important factors in determining the value of the annual net balance. Using ice cores taken from Quelccaya Ice Cap O ablation stakes (Peru), Thompson et al. (1984) demonstrated the O effects of the El Niño phenomena (ENSO events) on snow pits !'i ski run I the accumulation balances of glaciers at high alti- \.i v rainqauqe I tudes; every ENSO event is marked in the Central T thermoqra;h Andes by a' reduction in accumulation rates. This I result tallies with the significant decrease in precipi- tation during the ENSO episodes (Francou and Pizarro, 1985). During the ENSO event of 1991-1992, monthly measurements of balance taken from the Zongo and Chacaltaya Glaciers also show that the ablation rate during these events is significantly high, even at great altitudes (Fig. 8.8 and 8.9). Figure 8.7 Chacaltaya Glaaer and the survey system in 1993. 136 :, u ,I Glaciers iiz South America . L, $1 1

O

-4 r; 3 -8 3 ~ n t1

-16 9111 3 357 11 8 -I2m10 12 2 4 6 8 1012 2 4 6 8 1012 2 4 6 MONTHS (SEP 91-AUG 94) Figure 8.8 Cumulative net balance for the 36 months from September 1991 to * 5200/5100 --E? 4900 August 1994 at Zongo Glacier: 5,200- 7 5,100 m elevation range (black rectan- gles); 4,900 m (white rectangles).

c J Il

Figure 8.9 Monthly precipitation (aver- age from 4 rain gauges) and runoff on 1991 I 1992 I 1993 I 1994 I Zongo Glacier.

Therefore, both terms of the balance, accumulation The short rainy season, restricted to January- and ablation are influenced by the phenomena. The February, resulted in two periods of strong ablation, ENSO effect can be appreciated on Zongo Glacier by a first one in November-December, stronger than comparing the values obtained for specific net bal- normal, and a second one, more attenuated, in ance, precipitation, specific ablation, specific runoff, March. These two peaks are well reflected in the the Equilibrium Line Altitude and the Accumulation runoff values of the glacier torrent (Fig. 8.9). Area ratio for 1991-92, 1992-93 and 1993-94 (Table Table 8.6 also shows that the ablation (Ag) and 8.6). It is noteworthy that 1992-93 and 1993-94 are runoff (Q) values for the three years are similar, which not ENSO years: the specific net balance was equi- implies that the sublimation rate would be relatively librated during the first period and negative during weak on this type of glacier. It is, however, unquantifi- the second. able, given the imprecision of the measurement. A comparison of the three years reveals that the The balance of Zongo Glacier has been recon- ablation values are significantly different, while the structed using measurements taken at the limnimet- accumulation values, given by the amount of precipi- ric station in 1991-93 and usingreadings taken every tation, are more uniform. More than by a reduced day since 1973 (that is, over 20 years) in a canal that al., amount in total precipitation, the ENSO year recollects the waters of the glacier (Ribstein et 1991-92 has been marked by 1) a rainy season 1995). Fig. 8.10 shows that, for every ENSO event, shorter than normal - at Plataforma de Zongo given by a significant negative value of the South (4,770 m), only 4 months received more than 50 mm Oscillation Index, there is a correspondingly high instead of the usual 7 months during a normal period negative balance value with a possible delay of a few and 2) a reduction in cloud cover during the warm months. This suggests that, in this part of the Andes, season, which resulted in high average radiation val- ENSO events directly control variations in glacier ues linked with above-average maximum tempera- balances. ENSO events explain 4 periods with very tures (values between 1 and 2 standard deviation). negative balances: 1977178, 1982183, 1987188 and

137 'I Into the second century of worldwide glacier monitoring

TABLE 8.6 Zongo Glacier (1991-1993):net balance, ablation, runoff, precipitation, ELA and AAR Q (4) Yen I' Biz (1) P (2) AR (3) ELA (5) AAR (61 1991-92 -1.38 0.92 2.30 2.25 5,300 58 1992-93 0.02 1.06 1.04 1.18 5,100 86 1993-94 -0.73 0.85 1.58 1.56 5,200 67 (1) specific net balance (m of water) (2) precipitation measured near the glacier (4,800-5,200 m) (m of water) (3) specific ablation: Ag = P - Bn (m of water) (4) specific runoff (surface of the glacier: 2.1 km?) (m of water) (5) Equilibrium Line Altitude (in m) (6) Accumulation Area Ratio (in YO)

1991/92 (only the negative balance of 1979-80 does EVENTS not correspond to an ENSO event). 8.5 SPECIAL Subtracting the estimated average amount of Some glaciers in the Central Andes of Argentina rainfall received by the glacier every year (i.e., have experienced rapid advances over several hun- 1.062 m of water) from the average runoff value (i.e., dred metres and are considered surging glaciers. 1.472 m of water) gives an average deficit balance of Examples include the glaciers in the Mendoza basin. 0.41 m apparent during this period of 20 years for Horcones Inferior Glacier on the southern flank o5 Zongo Glacier. Sublimation seems to be low but, if it Mt. Aconcagua surged in 1985 (IAHS(ICSI)/UNEP/ were taken into account, this deficit would be even UNESCO, 1993; Llorens and Leiva, 1994). In the Río more negative. Over these 20 years, only three have del Plomo basin at 33"S, Grande del Juncal Glacier had net positive balances, 1974-73, 1975-76 and surged in 1910 and at some time between 193-1 and 1986-87. For the same three years, the termini of the 1955. Grande del Nevado Glacier surged at the end small glaciers being monitored in the Cordillera of 1933, between 1963 and 1974, and again in 19S4. It Blanca have not retreated, indicating that their bal- dammed up a lake in January 1985 (Helbling, 1919; ances have been positive or in equilibrium (Fig. 8.5). 1935; 1940; Espizua, 1986; 1987; Espizua and This study suggests that the present retreat of Bengochea, 1990; Bruce et nI., 1987; Prieto, 1986; Bolivian glaciers, such as those of Cordillera Blanca IAHS(ICSI)/UNEP/UNESCO, 1988; 1993). The Gla- (Francou et d.,in press), is strongly influenced by ciar Innominate advanced 2,900 m between 1986 and ENSO events. In between these events, periods of 1991 (Llorens and Leiva, in press). In the Río positive or in-equilibrium balances may occur but Tupungato basin, an unnamed glacier to the south of their duration is not such as to reverse the tendency Tupungato Glacier known as Glacier B has advanced for these glaciers to retreat. At the most, they can 1,100 m since 198511986, the position of the front sloiv down the process but only for a short time. remaining unchanged between 1991 and 199-1. From An accelerated glacier retreat has also been the Mesón San Juan ice plateau, a glacier tongue reported from the Andes de Mérida in the north- advanced 750 m from 1985 to 1986 but did not pre- western part of Venezuela (Schubert, 1992; 1993). sent the characteristic chaotic surface (loiv reflectance through analysis of Landsat image) found on other surging glaciers (Llorens and Leiva, 1994).

L, IL

Figure 8.10 Mass balance of Zongo Glacier vs. South Oscillation Index [SOI). Mass balance is reconstructed using hydrological data. SOI is the dif- ference in pressure between Tahiti and Darwin in standardized values. Both wesrepresent 12-month running means.

138 I, Glaciers iiz South America t ,, 18

* TABLE 8.7 Catastrophes produced by glaciers in Peru. All events are from the Cordillera Blanca unless otherwise noted. Where no literature reference is given, the source is personal records by Ames. Abbreviations: IA = ice avalanche; LOF = lake outflow

Da te Origin of catastrophe Place of greatest Type of Approx. Reference (iizounfain, lake, etc.) damage (e.g., toion) catastrophe numbcr of victim March 4,1702 ? Huaraz flood ? Alba Herrera, 1969 January 6,1727 Nevado Huandoy Town of Ancash earthquake, 1,500 Alba Herrera, 1969; probably IA, flood Silgado, 1978 January 6,1727 ? Huaraz earthquake, more Alba Herrera, 1969; perhaps flood than 1000 Silgado, 1978 caused by IA February 27, Cerro San Cristobal Monterrey LOF, flood 11 Alba Herrera, 1969 1869 (near Huaraz) June 24,1883 Lake Tambillo (Rajucolta) Macashca LOF caused by IA 'many' Alba Herrera, 1969 Januaiy 22, Nevado Huascaran Villages Shacsha IA ? Aba Herrera, 1969 1917 and Ranrahirca March 14,1932 Lake Solteracocha planting fields in the LOF ? Aba Herrera, 1969; (Cordillera Huayhuash) Quebrada Pacllon Knzl, 1940c January 20, Lake Artesa bridge destroyed LOF none Knzl, 1940c 1938 (Pakliashcocha) near Carhuaz April 20,1941 Lake Suerococha planting fields LOF none Alba Herrera, 1969 (Cordillera Huayhuash) destroyed December 13, Lakes Acoshcocha Huaraz LOF 4,000 Lowther and 1941 and Jircacocha Giesecke, 1942; Track, 1953; Buse, 1957; Femandez, 1957; Oppenheim, 1947; Heim, 194s January 17, Lakes Ayhuiñaraju Chavin de Huantar LOF caused by 300 Indacochea and 1945 and Carhuacocha rock slide from Iberico, 1947; Nev. Huan tsan Spann, 1946 October 20, Lake Jankanirish Hydroelectricpower LOF, possibly 200, Ghíglino, 1950 1950 station of Huallanca caused by IA perhaps 500 June 16,1951 Lake Artesoncocha no damage, water LOF none Fernandez, 1957 absorbed by (first, see below) Laguna Paron October 28, Lake Artesoncocha as above LOF none Femandez, 1957 1951 (second, see above) November 6, Lake Milluacocha minor damage in LOF none 1952 planting fields ? 1953 Lake Tullparaju no damage landslide, waves none downvalley erode artificially modified lake outlet December 8, Lake Tullparaju minor damage in as above none 1959 planting fields January 10, Nevado Huascaran Ranrahirca and IA 4,000 Dollfus and 1962 9 smaller villages Peñaherrera, 1962; Patzelt, 19S5 December 22, Lake Tumarina Quebrada LOF, probably several 1965 Carhuascancha caused by IA .May 31,1970 Nevado Huascaran Yungay, Ranrahirca earthquake causes 20,000 Llíboutry, 1971, Norte (west face) and Matacoto large rock and IA Plafker ef al., 1971; Patzelt 1985; \\'elsch, 1970 May 31,1970 Huascaran Norte Quebrada earthquake causes 14 (north face) Llanganuco rock and IA August 31,1982 Lake Milluacocha bridges and planting lake outburst none fields destroved caused by IA December 16, Nevado Huascaran road blocked IA none 1987 January 20,1989 Nevado Huascaran road and bridge IA none damaged, planting fields destroyed 139 ). Ihto the second century of worldwide glacier monitoring L I, I

Ai 34"S, Laguna Glacier in the Río Atuel basin people were reported dead but other estimates give advanced 1,400 m between 1970 and 1982 (Cobos figures of 500. At the time of the flood, a group of and Boninsegna, 1983). In the Southern Patagonia workers employed by the official institution in charge Ice Field, the position of Moreno Glacier has been of preventing floods was lowering the lake level. The studied in detail owing to the cyclical damming and immediate cause of the disaster was, most probably, periodic catastrophic drainage of the southern arm of a large wave triggered by an ice avalanche from a Lago Argentino. glacier on the western slopes of Nevado Alpamayo, In historic times, most of the catastrophic floods causing progressive erosion o€the overflow channel. and ice avalanches in Peru were recorded in the The outburst volume ivas estimated at some 4 million Cordillera Blanca and Huayhuash. This is only par- m3, increasing downvalley as material from the tially due to the relatively large extent of the ice riverbed and sides got carried along. The material masses. Perhaps equally important is the unusually rushed towards Santa River at a speed of about high population density, in particular in the Santa 30 km/h (Gliiglino, 1950). Valley on the west side of Cordillera Blanca. Perhaps nowhere else in tropical high mountain ranges is there such an intense interaction between glaciers and man. Subsistence agriculture in the mountain 8.6 GAPS AND NEEDS areas of Peru is in part dependent on glacial runoff A basic task to be undertaken is the completion of for irrigation (some people even make a living from the glacier inventoT in Chile and Argentina, as transporting blocks of glacier ice down to local mar- much remains unknown. There is a need to know the kets where it is used to produce ice cream and to cool mass balance of more glaciers along the Andes of drinks). Therefore, a significant part of the popula- Chile and Argentina, not only near Santiago and tion lives within reach of glacial floods and, in some Mendoza as is presently the case, but also in other cases, even within the runout distances of íce parts of the country. avalanches. In other Peruvian Cordilleras, cata- Continuity in the inventorying of glaciers and in strophic events are noted less frequently put do glacier mass balance studies has to be established. In occur. The origins are diverse. Lake outbursts have addition, an interconnected research cooperative various kinds of triggering mechanisms. However, programme is needed to ensure the continuity and most of them have in common that the lakes initially enhancement of present glaciological research. formed as a result of the general retreat of the gla- Training courses are another must. ciers (Oppenheim, 1947; Heim, 19.18; Track, 1953; Fernandez, 1957; Ames et al., 1994). Typically, they are dammed by poorly consolidated morainic mater- ial and perhaps sometimes even by buried stagnant 8.7 SUGGESTED FUTURE DEVELOPMENT OF ice. Extreme rainfall may then weaken the dam until MONITORING ACTIVITY it fails spontaneously. In many cases, landslides and The observed strong glacier retreat in the Peruvian ice avalanches have fallen into the lakes, causing Andes, as well as in other parts of South America waves which erode the lake outlet. Exponential (e.g., Central Andes of Argentina since the beginning increase of discharge then leads to the sudden of the century), is considered an impressive example drainage. The so-called ccaluviona, a turbulent mix- of the importance of glacier fluctuation measure- ture of rock, finer sediment and water then rushes ments, particularly in tropical or subtropical areas. In downvalley causing destruction and often the loss of remote regions or areas ivith few or no systematic cli- many lives. Table 8.7 summarizes all known major matological data records, siich measurements pro- events (including ice avalanches) as far back as the vide a highly sensitive indicator of recent or subre- beginning of the 18th century. Some lakes were cent climatic changes. Continued glacier retreat is made less dangerous by lowering the water level and expected to further affect the local population: new strengthening the outflow. Successful examples of terminal lakes will probably form, thereby creating such work are Laguna Safuna (Lliboutry, 1977; new potential sources of catastrophic flooding. A fur- Lliboutry et al., 1977n; 1977b) or Laguna Llaca above ther loss in ice masses itill, at the same time, tem- Huaraz. A major problem during projects of this kind porarily add to the amount of \vater available for was the steep topography. Usually, the first task was agriculture and hydroelectric power production. In the construction of a road in steep and difficult ter- the long run, however, runoff must decrease: Efforts rain from the Santa valley to the construction site. should be made to continue taking these valuable Not all lake modifications were without problems. measurements, particularly in view of a potentially On October 20, 1950, Lake Jankarurish in the persistent trend of atmospheric warming. However, Quebrada Alpamayo produced an aluvion which the very limited financial means, coupled with the completely destroyed the installations of the small number of personnel trained to carry out this Huallanca hydroelectric power plant under construc- work, poses a serious problem. tion at the time on the lower Santa River. A tunnel The marked sensitivib- of tropical glaciers to cli- was filled with debris and the main bridge and three matic changes means that they are particularly well railway bridges were washed away. Officially, 200 suited as indicators in the current research on global 140 \* I ? Glaciers in South America 1.. . l. warming. The high resolution with which the glacier 2) The possible effects on tropical glaciers of an I transmits this information makes it a unique instru- increase in temperature, as estimated by global ment with few equivalents in the tropical continental circulation models, must be analysed. environment. To follow these processes, it is essen- 3) The impact of ENS0 events according to the lati- tial to establish a long-term network of studied gla- tude (Equator-Tropics) and the areas of climatic ciers in the Central Andes. With this network as a influence in the Cordillera (Amazon and Pacific) starting point, research should be directed towards must be quantified. the following: 4) A rapid and broad glacial retreat for the high Andean catchments must be analysed from the 1) A better understanding of the functioning of viewpoint of potential consequences for the hydro- tropical glaciers must be developed by studying logical regimes and the effects on water resources their balances at shorter time intervals (days, of a possible increase in the risk of glacial hazards months): energy balance, glacial balance, hydro- (avalanches, overflow of glacial lakes). logical balance.

141 References

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146

r o

Studies and reports in hydrology 56 Into the second century of worldwide glacier monitoring- rospests and strategies

A contribution to the International Hydrological Programme (IHP) and the Global Enyironment Monitoring System (GEMS)

Prepared by the World Glacier Monitoring Service Edited by W. Haeberli, M. Hoelzle and S. Suter

UNESCO Publishing I r

The designations employed and the presentation of material throughout the publication do not imply the expression of any opinion whatsoever on the part of UNESCO concerning the legal status of any country, territory, city or area or of its authorities, or the delimitation of its frontiers or boundaries.

Published in 1998 by the United Nations Educational, Scientific and Cultural Organization 7, place de Fontenoy, 75700 Paris

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O UNESCO 1998 r

Preface

Although a total amount of water on Earth is generally Although the IHP is basically a scientific and edu- assumed to have remained virtually constant, the cational programme, UNESCO has been aware from rapid growth of population, together with the exten- the beginning of a need to direct its activities towards sion of irrigated agriculture and industrial develop- the practical solutions of the world‘s very real water ment, are putting stress on the quality and quantity resources problems. Accordingly, and in line with the aspects of natural systems. Because of the increasing recommendations of the 1977 United Nations Water problems, society has begun to realize that it can no Conference, the objectives of the Intemational Hydro- longer follow a ’use and discard‘ philosophy - either logical Programme have been gradually expanded in with water resources or any other natural resource. As order to cover not only hydrological processes con- a result, the need for a consistent policy of rational sidered in interrelationship with the environment and management of water resources has become evident. human activities, but also the scientific aspects of Rational water management should be founded multi-purpose utilization and conservation of water upon a thorough understanding of water availability resources to meet the needs of economic and social and movement. Thus, as a contribution to the solution development. Thus, while maintaining IHP’s scien- of the world’s water problems, UNESCO, in 1965, tific concept, the objectives have shifted perceptibly began the first world-wide programme of studies of towards a multi-disciplinary approach to the assess- the hydrological cycle - the Intemational Hydrological ment, planning, and rational management of water Decade (IHD:).The research programme was comple- resources. mented by a major effort in the field of hydrological As part of UNESCO’s contribution to the objectives education and training. The activities undertaken dur- of the IHP, two publication series are issued: ‘Studies ing the Decade proved to be of great interest and value and reports in hydrology’ and ’Technical papers in to Member States. By the end of that period, a majority hydrology‘. In addition to these publications and in of UNESCO’s Member States had formed IHD order to expedite the exchange of information in the National Committees to carry out relevant national areas in which it is most needed, works of a preliminary activities and to participate in regional and inter- nature are issued in the form of technical documents. national cooperation within the IHD programme. The The purpose of the continuing series ’Studies and knowledge of the world’s water resources had sub- reports in hydrology’, to which this volume belongs, stantially improved. Hydrology became widely recog- is to present data collected and the main results of nized as an independent professional option and facili- hydrological studies, as well as to provide informa- ties for training hydrologists had been developed. tion on hydrological research techniques. The pro- 3 I Conscious of the need to expand upon the efforts ceedings of symposia are also sometimes included. It initiated during the Intemational Hydrological is hoped that these volumes will furnish material of Decade and further to the recommendations of both practical and theoretical interest to water Member States, UNESCO launched a new long-term resources scientists and also to those involved in intergovernmental programme in 1975: the Inter- water resources assessment and planning for rational national Hydrological Programme (IHP). water resources management. 5 Contents

Foreword ...... 9

1. Les variations périodiques des glaciers: ...... 11 F.-A. Forel 2. Historical evolution and operational aspects of worldwide glacier monitoring: ...... 35 W. Haeberli 3. Data management and application: ...... 53 M. Hoelzle and M. Triitdler 4. Statistical analysis of glacier mass balance data: ...... 73 L. Reynaud aiid G. Dobrouolski 5. Modelling glacier fluctuations: ...... 85 J. Oerlenians 6. Use of remote-sensing techniques: ...... 97 R. S. Williams, Jr. aiid D. K. Hall 7. Glaciers in North America: ...... 113 C. S. L. Oiiitnaiiney, M. Deiiiufh aiid M. F. Meier 8. Glaciers in South America: ...... 125 G. Casassa, L. E. Espizua, B. Fratzcou,\P. Ribsfein,A. Antes and J. Aleait 9.GlaciersinEurope: ...... 147 J, O. Hagen, G. Zanoiz aizd E. Martínez de PisÓii

10. Glaciers in Africa and New Zealand: . . . . , ...... , ...... , ...... 167 S. Hasfeizrath and T. J. H.Chinii 11.GlaciersinAsia: ...... 177 D. G. Tsvefkov, G. B. Osipoua, Xie Zichii, Wang Zhoizgtai, Y. Agefa nid P. Banst 12. Local glaciers surrounding the continental ice sheets: ...... 197 A. Weidick and E. Morris 13. Monitoring ice sheets, ice caps, and large glaciers: ...... 209 M. F. Meier

Conclusions and recommendations ...... , ...... 215 Appendices ...... 7 Foreword

International coordination of long-term glacier occasion of the centenary of worldwide glacier moni- observations is a century-long tradition. It started toring. Scientific review of the text was accomplished with the establishment of the International Glacier by the consultants and national correspondents of Commission during the 6th International Geological WGMS via correspondence. On 12-13 October 1995, a Congress at Zurich, Switzerland in 1894. The goals two-day workshop with invited experts from various of this worldwide glacier monitoring programme countries and representatives of sponsoring agencies were defined by F.-A. Forel from Geneva, the first was held at the Federal Institute of Technology (ETH), president of the Commission, in a remarkable article Zurich, Switzerland, in order to complete the final entitled Les vnrintiotis périodiques des glnciers. editing of the manuscript and, especially, to formulate Discoiirs prélinziiinire, published on pp. 209-29 of the recommendations for the future. Archives des sciences physiques et naturelles The volume presented here opens with an original (Geneva, Vol. 34). article written by F.-A. Forel and is followed by a Since 1894, the goals of internationally coordi- selection of thematic and regional chapters. As com- nated glacier monitoring have evolved and multi- plete coverage of all glacierized areas of the world plied. Today, the evolution of glaciers and ice caps was beyond practical possibilities, characteristic is recognized as one of the key variables relating to examples are given from all continents, including the early detection strategies in view of possible man- special cases of the continental ice sheets. The conclu- induced climatic change. The general shrinkage of sions and recommendations chapter was discussed, mountain glaciers during the 20th century is a major edited and agreed upon by the participants in the reflection of the fact that rapid secular change in the 1995 expert meeting at ETH Zurich. The Appendices energy balance of the Earth's surface is taking place contain lists of the consultants and national corre- on a global scale. spondents to WGMS as well as a list of the experts As a contribution to the International Hydro- participating in the 1995 meeting and the programme. logical Programme (IHP) of the United Nations Thanks are due to ETH Zurich and UNEP for Educational, Scientific and Cultural Organization funding the expert meeting, to LDJESCO for enabling (UNESCO) and to the Global Environment the present publication and to all authors and review- Monitoring System (GEMS) of the United Nations ers who contributed in one way or another. The Environment Programme (UNEP), the World expression of our special gratitude and admiration i Glacier Monitoring Service (WGMS) of the goes to all those individuals and national/interna- International Commission on Snow and Ice (ICSI/ tional organizations who have initiated, planned, i IAHS), as one of the permanent services of the supported and carried through a unique task for ten Federation of Astronomical and Geophysical Data decades, and hopefully into many more to come. . . . Analysis Services (FAGS/ICSU), collects and pub- lishes standardized glacier data. Wilfried Haeberli, Martin Hoelzle, Stephan Suter The present publication was prepared to mark the Zurich, Novetnber 2995 1i 9 h