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One of the main italian glaciers, the Miage glacier is located on the southeast side of the Mont Blanc massif. Its front reaches an elevation of 1750 m in the Val Veny. Characteristics of the Miage are : debris cover glacier, which smoothes over the fluctuations ; huge lateral moraines (150 m high) ; morainic amphitheatre around the juxtaglacial Miage lake. With Present fluctuations (since 1860) of small amplitude, the Miage glacier is atypical. Various data (moraine geometry, pedology, iconography, radiocarbon dating, lichenometry, dendrochronology) are used to reconstitue several Miage advances during the Little Ice Age (LIA). This study - contrary to some authors - considers that the LIA plays a small part in the Miage morainic complex setting up. Several elements about the amphitheatre and the lateral morames suggests that their genesis is very former to Göschenen 2 for this one, to the Central Middle Ages for that ones., Situé sur le versant sud-est du massif du Mont Blanc, le glacier du Miage est l'un des principaux glaciers italiens. Son front atteint 1750 m d'altitude dans le Val Veny. Le Miage se caractérise par sa qualité de glacier noir (filtrage des variations), ses moraines latérales de grande dimension (150 m de commandement) et son amphithéâtre morainique autour du lac du Miage. Les variations actuelles (depuis 1860) sont de faible amplitude, ce qui fait du Miage un glacier au comportement atypique. Divers arguments (géométrie des moraines, pédologie, documents anthropiques, radiodatations, lichénométrie, dendrochronologie) permettent de reconstituer plusieurs des avancées du Miage lors du Petit Âge Glaciaire (PAG). Cette étude montre que bien que certains auteurs attribuent la mise en place de la plus grande partie du complexe morainique du Miage au PAG, celui-ci n'y entre en fait que pour une faible part. Plusieurs éléments concernant l'amphithéâtre et les moraines latérales montrent que leur genèse est très antérieure au Göschenen 2 pour le premier, au Moyen Âge central pour les secondes., Deline Philip. Les variations holocènes récentes du glacier du Miage (Val Veny, Val d'Aoste) [Late holocène fluctuations of the Miage glacier (Val Veny, Valley of Aosta)]. In: Quaternaire, vol. 10, n°1, 1999. pp. 5-13.

Some researchers propose that summer insolation controls long-term changes in glacier extent during the Holocene. If this hypothesis is correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Although the chronology of Holocene glacier fluctuations in the Northern Hemisphere is well established, much uncertainty remains in the ages of Holocene glacier fluctuations in the Southern Hemisphere, especially South America. Here we report on latest Pleistocene and Holocene glacier fluctuations at the southern end of the Andes north and west of Ushuaia, Argentina. Surface exposure ages (10Be) from glaciated bedrock beyond cirque moraines indicate that alpine areas were free of ice by ca 16.9 ka. One, and in some cases two, closely spaced moraines extend up to 2 km beyond Little Ice Age moraines within many of the cirques in the region. The mean age of five 10Be ages from two pre-Little Ice Age moraines is 14.27–12.67 ka, whereas a minimum limiting radiocarbon age for a smaller, recessional moraine in one cirque is 12.38–12.01 ka. Our ages imply that, following glacier retreat beginning about 18.52–17.17 ka, cirque glaciers first advanced during the Antarctic Cold Reversal (14.5–12.9 ka) and may have later advanced or stabilized in the Younger Dryas Chronozone (12.9–11.7 ka). Based on the distribution of thick, geochemically distinct, and well-dated Hudson tephra, no Holocene moraines appear to be older than 7.96–7.34 ka. At some sites, there is evidence for one or more advances of glaciers sometime between 7.96–7.34 ka and 5.29–5.05 ka to limits only tens of meters beyond Little Ice Age maximum positions. Taken together, the data: 1) do not support the summer insolation hypothesis to explain Holocene glacier fluctuations in southernmost Patagonia; 2) confirm paleobotanical evidence for a warm, dry early Holocene; and 3) suggest that some glaciers in the region reached extents comparable to those of the Little Ice Age shortly before 5.29–5.05 ka. Fil: Menounos, Brian. University of Northern British Columbia; Canadá Fil: Clague, John J.. University Fraser Simon; Canadá Fil: Osborn, Gerald. University of Calgary; Canadá Fil: Thompson Davis, P.. Bentley University; Estados Unidos Fil: Ponce, Juan Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Goehring, Brent. Purdue University; Estados Unidos Fil: Maurer, Malyssa. University of Northern British Columbia; Canadá Fil: Rabassa, Jorge Oscar. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Austral de Investigaciones Cientificas; Argentina Fil: Coronato, Andrea Maria Josefa. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Austral de Investigaciones Cientificas; Argentina Fil: Marr, Rob. University Fraser Simon; Canadá

This overview, or retrospective, has two objectives. The first is to demonstrate how the principles of ‘mountain geoecology’ were applied in an attempt to counteract the political and socio-economic impacts of a major and misguided environmental orthodoxy-the Theory of Himalayan Environmental Degradation (henceforth to be referred to as the ‘Theory’). The second is to explore the difficulties of transferring the results of on-going scholarly mountain research into the public and political decision-making process. In this sense the paper should be regarded as a case study of the potentially serious effects of exaggerated and emotionally based responses to orthodoxies founded on assumptions and latter-day myths. A third objective, reserved for the companion paper in this issue, outlines the origins of mountain geoecology and explores how academic research influenced the inclusion of high level concern for mountain problems within AGENDA 21, one of the principal results of the 1992 UN Conference on Environment and Development (popularly known as the Rio Earth Summit) and declaration of 2002 as the International Year of Mountains. The original environmental orthodoxy (the Theory) has been eclipsed since the turn of the Millennium by a new populist alarm proposing that the current climate warming will cause all the Himalayan glaciers to disappear in the near future. From this it would follow that, as the glacier melt progresses, numerous large glacial lakes, forming as a consequence, would burst and the ensuing floods would annihilate many millions of people. Eventually, as the glaciers disappeared vital rivers, such as the Ganges and Brahmaputra, would wither to seasonal streams heralding further massive loss of life due to desertification and starvation. This current environmental alarm could be regarded as a present day parallel to the original Theory and will be examined in the final section of the paper. Between 1970 and about 1985 it was almost universal wisdom amongst scholars and development specialists, as well as conservationists, that the Himalaya were on the brink of environmental, and hence socio-economic and political collapse. This theme of gloom and doom was taken up avidly by journalists, politicians, and diplomats; it influenced the expenditure of large sums of aid and development money, and augmented periodic international confrontations. In concise terms, in the early 1970s an assumed approaching environmental disaster was perceived to be driven by relentless growth in the population of subsistence hill communities and their dependence on mountain forests for fuel, fodder, building materials, and conversion to agricultural land. The assumption of rapid and catastrophic deforestation of steep hillslopes under a monsoon climate (the World Bank predicted that there would be no accessible forest remaining in Nepal by the year 2000) led inexorably to a series of dependent assumptions: increasing soil erosion and worsening landslide incidence; accelerated flooding and siltation on the plains of Gangetic India and Bangladesh; social and political unrest, if not serious armed conflict – the notion of a world super-crisis, considering that the region in question contained about ten percent of the world’s entire human population and about thirty percent of its poorest. As will be emphasized later, none of this all-embracing construct was based on reliable evidence, but it was accepted world-wide as a given. It represents a prime example of the dangers associated with convenient adoption of environmental myths, or environmental orthodoxies, especially where the myth is a Western ‘scientific’ construct. I characterized it as The Theory of Himalayan Environmental Degradation (Ives, 1985)., Esta perspectiva global, o retrospectiva, tiene dos objetivos. El primero es demostrar cómo se aplicaron los principios de la “geoecología de montaña” en un intento por contrarrestar los impactos políticos y socioeconómicos de una errónea ortodoxia ambiental, la Teoría de la Degradación Ambiental del Himalaya (en adelante referida como la “Teoría”). El segundo es explorar las dificultades para transferir los resultados de la investigación científica en montaña a los procesos públicos de decisión. En este sentido, el artículo debería ser contemplado como un estudio de caso de los efectos potencialmente serios de las exageradas respuestas a las ortodoxias basadas en suposiciones y mitos de última hora. Un tercer objetivo, reservado a otro trabajo publicado en este volumen, subraya los orígenes de la geoecología de montaña y explora cómo la investigación académica influyó en la incorporación de la preocupación por los problemas de la montaña en la AGENDA 21, uno de los principales resultados de la Conferencia de Naciones Unidas de 1992 sobre Medio Ambiente y Desarrollo (popularmente conocida como la Cumbre de Río), y la declaración de 2002 como el Año Internacional de las Montañas. La ortodoxia ambiental original (la Teoría) ha sido eclipsada desde el cambio de milenio por una nueva alarma populista que propone que el actual calentamiento climático hará que todos los glaciares del Himalaya desaparezcan en un futuro próximo. De ahí puede deducirse que, a medida que la fusión glaciar progrese, numerosos lagos glaciares reventarían y las consiguientes avenidas aniquilarían a millones de personas. Eventualmente, tras la desaparición de los glaciares, algunos ríos fundamentales, como el Ganges y el Brahmaputra podrían convertirse en ríos estacionales ocasionando la pérdida masiva de vidas humanas debido a la desertificación y el hambre. Esta alarma ambiental podría ser vista como paralela a la Teoría original, y será examinada en la parte final de este artículo. Entre 1970 y 1985 se mantuvo la opinión entre los científicos y especialistas en desarrollo, así como entre los conservacionistas, de que el Himalaya estaba al borde del colapso ambiental, socioeconómico y político. Este pesimismo y predestinación fue adoptado ávidamente por periodistas, políticos y diplomáticos, e influyó en la dedicación de grandes sumas de dinero y ayudas. En pocas palabras, a comienzos de los años setenta se asumió la ocurrencia de un desastre ambiental determinado por el crecimiento demográfico de comunidades que dependían de los bosques de montaña para la obtención de energía, forraje, materiales de construcción y expansión de los terrenos agrícolas. La asunción de una rápida y catastrófica deforestación de laderas pendientes bajo clima monzónico (el Banco Mundial predijo que no habría bosques accesibles en Nepal hacia el año 2000) condujo inexorablemente a aceptar otras suposiciones: aumento de la erosión del suelo y acentuación de la incidencia de los deslizamientos; incremento de la magnitud y frecuencia de las avenidas y del transporte de sedimento en las llanuras del Ganges en India y Bangladesh; conflictividad social y política, cuando no serios conflictos armados, es decir, la noción de una supercrisis mundial, teniendo en cuenta que la región en cuestión contiene alrededor del 10 por ciento de la población mundial y alrededor de la tercera parte de los más pobres. Como se pone de relieve a continuación, ninguna de esas ideas se basaba en evidencias fiables, pero fueron aceptadas mundialmente como un hecho. Representan un ejemplo claro de los peligros asociados a la adopción de mitos u ortodoxias ambientales, especialmente donde el mito es una construcción “científica” del mundo occidental. Yo la definí como la Teoría de la Degradación Ambiental del Himalaya (Ives, 1985).

International audience; A 14-m long piston core was retrieved from Lake Le Bourget, NWAlps (France), in order to provide a continuous record of flooding events of the Rhone River during the Holocene. The selection of the coring site was based on high resolution seismic profiling, in an area with limited mass wasting deposits and accumulated proximal Rhone River inter-and underflow deposits. The age-depth model of this core is based on (i) 14 AMS radiocarbon dates, (ii)radionuclide dating(137Cs) and (iii) the identification of historical data (flood events, eutrophication of the lake).The sedimentary record dates back to 9400 cal BP, and includes a thin mass wasting event deposited around 4500 cal BP. A multi-proxy approach was used to track the evolution and origin of clastic sedimentation during the Holocene, in order to identify periods of higher hydrologic al activity in the catchment area. Spectrophotometry was used to detect fluctuations in clastic supply and the study of clay minerals (especially the Illite crystallinity index) allowed locating the main source area of fine grained clastic particles settling at the lake after flood events. This dataset highlights up to 12 periods of more intense flooding events over the last 9400 years in Lake Le Bourget and shows that the main source area of clastic particles during this period is the upper part of the Arve River drainage basin. This part of the catchment area drains several large glaciers from the Mont-Blanc Massif, and fluctuations in Rhone River flood supply in Lake Le Bourget is interpreted as resulting essentially from Mont-Blanc Glacier activity during the Holocene.The comparison of clastic sedimentationin Lake Le Bourget with periods of increasing land use and periods of Alpine glacier and mid-European lake level fluctuations, suggest that the core LDB04 clastic record in Lake Le Bourget is a continuous proxy of the Holocene hydrologic al history of the NW Alps.

The aim of this paper is to document the evolution of glaciers in the tropical Andes (between 10 degrees N and 16 degrees S) for the last millennium, based on moraines dated by lichenometry and radiocarbon, lake sediment records and historical documents. Viewed collectively, several glacial advances occurred synchronously. The first advance is dated around AD 1200-1350. The maximum glacial extent (MGE), defined as the furthest down-valley extent recorded synchronously by the majority of glaciers, occurred around 1630-1680 in Bolivia and Peru (the outer tropics) and around AD 1730 in Ecuador, Colombia and Venezuela (the inner tropics). Subsequently. during the 18th and 19th centuries, glaciers retreated continuously with only minor synchronous readvances. In the outer tropics, minor glacial advances occurred around 1730,1760,1800,1850, and 1870. In the inner tropics, synchronous minor advances occurred around 1760,1820 and 1880. Between the MGE and the early 20th century, glaciers lost about 30% of their total length. The retreat was slow between the 17th and 18th centuries but then became more marked. Use of the accumulation area ratio (AAR) method or historical observations in the different cordilleras revealed an increase in the equilibrium line altitude (ELA) of about 300 m from the MGE onward. Palaeoclimatic hypotheses, based on glaciological models run in different countries, suggest a cool and humid period in the 16-18th centuries followed by a colder and drier period in the 19th century. The reduction of glaciers observed from the middle of the 19th century is due to increasingly warmer conditions than before. Here, quantitative estimates are proposed to explain the evolution of the glaciers. In Venezuela, results indicate for the period 1250-1820 that mean air temperatures were 3.2 +/- 1.4 degrees C cooler and precipitation was about 22% higher than at present. In Ecuador, temperatures of between 0.8 degrees and 1.1 degrees C lower than today, and between 25% and 35% higher accumulation than today, appear to have occurred in the 18th century, followed by a short drier but colder period at the beginning of the 19th century. In Bolivia, the MGE could be a consequence of a decrease in temperature of 1.1 to 1.2 degrees C, and a 20 to 30% increase in accumulation or an increase in cloudiness of about 1-2/10. We discuss not only external climatic forcing but also the coincidence between glacier expansion and a decrease in solar irradiance. Dating uncertainties, however, have made the role of volcanism in glacier fluctuations impossible to determine. Finally, we discuss the relationships between ENSO and glacier fluctuations in recent centuries, which do not match directly with current knowledge of modern teleconnections between tropical Pacific SSTs and variations in glacier mass balance.

Dating moraines by lichenometry enabled us to reconstruct glacier recession in the Bolivian Andes since the Little Ice Age maximum. On the 15 proglacial margins studied, we identified a system of ten principal moraines that marks the successive positions of glaciers over the last four centuries. Moraines were dated by performing statistical analysis of lichen measurements based on the extreme values theory. Like glaciers in many mid-latitude mountain areas, Bolivian glaciers reached their maximal extent during the second half of the 17th century. This glacier maximum coincides with the Maunder minimum of solar irradiance. By reconstructing the equilibrium-line altitude and changes in mass-balance, we think the glacier maximum may be due to a 20 to 30% increase in precipitation and a 1.1 to 1.2 °C decrease in temperature compared with present conditions. In the early 18th century, glaciers started to retreat at varying rates until the late 19th to early 20th century; this trend was generally associated with decreasing accumulation rates. By contrast, glacier recession in the 20th century was mainly the consequence of an increase in temperature and humidity. These results are consistent with observations made in the study region based on other proxies.

Dating moraines by lichenometry enabled us to reconstruct glacier recession in the Bolivian Andes since the Little Ice Age maximum. On the 15 proglacial margins studied, we identified a system of tell principal moraines that marks the successive positions of glaciers over the last four Centuries. Moraines were dated by perl'onning statistical analysis of lichen rneaSUrenients based on the extrerne values theory. Like glaciers ill many mid-latitude mountain areas, Bolivian glaciers reached their maximal extent during the second half of the 17th century. This glacier maximum coincides with the Maunder minimum of solar irradiance. By reconstructing the equilibrium-line altitude and changes in mass-balance, we think the glacier maximum may be due to a 20 to 30% increase in precipitation and a 1.1 to 1.2 degrees C decrease in temperature compared with present conditions. In the early 18th century, glaciers started to retreat at varying rates until the late 19th to early 20th century; this trend was generally associated with decreasing accumulation rates. By contrast, glacier recession in the 20th century was mainly the consequence of an increase in temperature and humidity. These results are consistent with observations made ill the study region based on other proxies.

Radiocarbon dating at the base of sediment cores retrieved from high altitude proglacial lakes Bramant and Blanc Huez (Grandes Rousses Massif 2500 m altitude) based on high resolution seismic reflection profiling, suggest that these lakes were ice free since the end of the Lateglacial period, and that their catchment areas were largely free of glaciers during the first part of the Holocene. The development of a neoglacial period implying increasing clastic sedimentation in these proglacial lakes is then characterized by several rapid glacier fluctuations. During the Early and Late Bronze Age periods, for example, enhanced organic sedimentation in Lake Bramant suggest that glaciers in this part of the massif were probably smaller than today. The maximum extension of Holocene glaciers in this massif was then reached during the Little Ice Age. A synthesis of archaeological investigations and the identification of several metallic contaminations in lacustrine sediments, allow documenting the evolution at high altitude of mining activities. High content of Copper between 3770-3870 cal BP in Lake Bramant sediments can for example be related to Early Bronze Age mining artefacts recently identified between 2200 and 2600 m within chalcopyrite ore deposits next to the catchment area of Lake Bramant in the Northern part of the massif. In the southern part of the massif, two peaks highlighting high content of Silver in Lake Blanc Huez recent sediments can similarly be related to a well documented Lead Silver mining industry at the lake shore between AD 1236 and 1330. The origins of an older peak in Silver in Lake Blanc Huez and of a clear peak in Copper and Lead during the Roman period between AD 1 15-330 in Lake Bramant, are however not clearly understood., Des datations à la base de carottages localisés à partir de profils «sismique réflexion » à plus de 2500 m d'altitude dans les remplissages des lacs proglaciaires de Bramant et de Blanc Huez (Massif des Grandes Rousses) indiquent que ces deux lacs ont été déglacés depuis la fin du Tardiglaciaire et que leurs bassins versants ont été très faiblement englacés durant la première partie de l'Holocène. Le développement d'un néoglaciaire impliquant le retour d'une sédimentation détritique dans ces lacs proglaciaires est ensuite marqué par des fluctuations rapides de l 'activité glaciaire. Durant les périodes du Bronze ancien et récent en particulier, la prédominance d'une sédimentation organique dans le Lac de Bramant implique que les glaciers étaient probablement plus réduits qu'aujourd'hui dans le nord du massif. Dans l'ensemble du massif, l'extension maximale des glaciers holocènes semble avoir été atteinte au cours du dernier millénaire durant le Petit Age Glaciaire. La synthèse de fouilles archéologiques d 'altitude dans ce massif et l 'identification dans les sédiments lacustres de pics de métaux permet de préciser l 'évolution de la paléo-métallurgie en altitude. Un pic de Cuivre entre 3770 et 3870 cal BP dans le Lac de Bramant peut ainsi être lié à la découverte de sites d 'exploitation d 'un filon de chalcopyrite entre 2200 et 2600 m d 'altitude à proximité du bassin versant. Au sud du massif, deux pics d'Argent reconnus dans les sédiments récents du Lac Blanc Huez peuvent également être reliés au développement d'une mine de Plomb argentifère en bordure du lac entre AD 1236 et 1330. Par contre, l 'origine d 'un pic d 'Argent plus ancien dans le Lac Blanc Huez et celle d'un pic de Plomb et de Cuivre durant l'apogée de la période romaine entre AD 115-330 dans le lac de Bramant restent encore à expliquer., Chapron Emmanuel, Bailly-Maître Marie-Christine, Anselmetti Flavio, Guyard Hervé, Saint Onge Guillaume, Desmet Marc, Chauvel Catherine, Winiarski Thierry, Magand Olivier, Arnaud Fabien, Charlet Laurent, Deline Philip, Magny Michel, Mélières Marie-Antoinette. Impact des fluctuations glaciaires et des anciennes activités minières d'altitude sur la sédimentation lacustre proglaciaire au cours du Tardiglaciaire et de l'Holocène dans le massif des Grandes Rousses, Alpes Occidentales, France. In: Collection EDYTEM. Cahiers de géographie, numéro 6, 2008. Du climat à l’homme, dynamique holocène de l’environnement dans le Jura et les Alpes. pp. 39-50.

International audience; he evolution of high-altitude glaciers and human activities in the Grandes Rousses massif is documented by high-resolution seismic reflection profiling and multiproxy analysis of short sediment cores in proglacial Lake Blanc Huez. These lacustrine data are compared with historical chronicles, geomorphological features and glaciological studies in this region of the western Alps and they allow the documentation of recent environmental changes. The specific geometry of high-amplitude reflections in the uppermost seismic unit, the lithology of short cores and the available limnological data in the lake suggest that clastic particles eroded by the glaciers and transported in suspension by glacial melt waters in early summer essentially develop homopycnal flood events in the lake. A conceptual model linking fluctuations of glacier equilibrium line altitudes in the catchment area with sedimentary facies retrieved in the lake basin is proposed. This approach allows reconstructing continuous glacier fluctuations since AD1820–1850 and suggests several phases of glacier fluctuations during the Little Ice Age (LIA). These reconstructions are based on changes in lacustrine sediment laminations, density, magnetic susceptibility, reflectance spectra, organic matter and Arsenic content. The age-depth model of short sediment cores is provided by 210Pb, 137Cs and 241Am radionuclide dating. This chronology is further supported by identifying in lacustrine sediments the impact of (i) the nearby M 5.3 Corrençon earthquake in AD 1962, (ii) the development of the ski resort at high-altitude close to the lake and (iii) the last advance of glaciers during the LIA in AD1820–1850 and the following phase of glacier retreat observed in the alpine region at the end of the LIA in AD 1880. Frequent sandy layers enriched in organic matter and associated with fluctuations in the Arsenic concentrations may result from hydraulic remobilisation of Middle Age mine tailings at the lake shore by snow melt or heavy rain fall events during the LIA.

In this article we present the reconstruction of fluctuations of Alibek valley glacier situated in the Teberda valley, Western Caucasus. The former positions of glacier of the past 120 years were reconstructed basing on the old photographs of 1904, 1921, remote sensing data of 1955, 1987, 2007, 2008 and 2012, plans created in 20th century. Since the middle of 20th century Alibek Glacier decreased by 650 m in length and by 0,67 km2 in area and its tongue has risen by 110 m.

International audience; Holocene glacier variations pre-dating the Little Ice Age are poorly known in the western Alps. Studied for two centuries, the Miage morainic amphitheatre (MMA) is composed of three subconcentric sets of c. 25 moraines. Because of its location and of a dominant mode of morainic accretion, the MMA is a well-preserved marker of the glacier dynamics during the Neoglacial. Radiocarbon dates were obtained by digging and coring in inter-morainic depressions of the MMA and through a deep core drilling in a dammed-lake infill (Combal); complementary data for the inner MMA were obtained by lichenometry and dendrochronology. Radiocarbon chronology shows that (i) the MMA not only pre-dates the Little Ice Age (LIA), but was built at least since 5029–4648 cal. yr BP (beginning of the Neoglacial); (ii) outer sets of moraines pre-date 2748–2362 cal. yr BP; (iii) the MMA dammed the Lake Combal from 4.8 to 1.5 cal. kyr BP, while lakes/ponds formed inside the moraines (e.g. from 2147–1928 to 1506–1295 cal. yr BP). The ‘Neoglacial model' proposed here considers that the MMA formed during the whole Neoglacial by a succession of glacier advances at 4.8–4.6 cal. ky BP (early Neoglacial), around 2.5 cal. ky BP (end of Göschener I), at AD 600–900 (end of Göschener II) and during the LIA, separated by raising phases of the right-lateral moraine by active dumping because of the Miage debris cover.

The evolution of about fifteen glaciers of the Bolivian Eastern Cordillera (16-17°S; 68°W), since their Little Ice Age (LIA) maximum till the late 20th century, has been reconstructed on the basis on ten main moraines observed on the glacier forelands and six aerial photographs. A correspondence between the moraines from a glacier margin to another has been established using geomorphological criteria. These moraines have been dated by lichenometry (Rhizocarpon geographicum s.l.) using a new statistical method based on the extreme values theory. Glacier maximal extent has been dated from the second half of the 17th century. Glaciers kept, until the first half of the 18th century, a quite similar position. From the 1730s – 40s, they began to retreat nearly continuously. The most important moraines attest to periods of standstill or small advances which were never strong enough to remove former moraines. Glacier retreat accelerated during the late 19th and early 20th centuries. Over the 20th century retreat remains fast. Over the whole studied period, glaciers lost about 60% of their maximal extent and the ELA rose by about 135 m. Moraines' dating as well as Bolivian glaciers' evolution since the late 19th century are in good agreement with data available in other places of the tropical Andes such as in Peru and Equator. A synchronism in glacier evolution at a regional scale due to a common climatic forcing can be stressed. We suppose that the Bolivian glaciers' maximal extent was forced by enhanced precipitation (20 to 30% higher than current mean) and reduced temperature (0.4 to 0.6°C lower than current mean). In addition, we can note the concomitance between periods of low solar activity and periods of glacier advances. Retreat from the first half of the 18th century could be mainly due to a decrease in precipitation. These hypothesis agree with the results obtained from the scarce climate proxies available in this part of the Andes such as the ice core retrieved in the southern Peru Quelccaya ice cap. During the late 19 – early 20th century, numerous and intense El Niño events, pointed out by several indicators, could be responsible of the accelerated glacier recession which precipitated the LIA ending in the tropical Andes. Unlike the former periods during which glacier evolution appears to have been mainly controlled by precipitation, their retreat during the 20th century seems to have been the result from a combined increase in temperature and humidity., L'évolution d'une quinzaine de glaciers de la Cordillère Orientale de Bolivie (16-17°S ; 68°W), depuis leur phase d'extension maximale du Petit Age Glaciaire (PAG) jusqu'à la fin du 20ème siècle, a pu être reconstruite sur la base des dix principales moraines observées sur les marges proglaciaires et de six couples de photographies aériennes. L'ensemble des moraines, dont la correspondance géomorphologique a pu être établie d'un glacier à l'autre, a été daté par lichenométrie (Rhizocarpon geographicum s.l.) en utilisant une nouvelle méthode de traitement statistique des données basée sur la théorie des valeurs extrêmes. Le maximum d'extension des glaciers est daté de la deuxième moitié du 17ème siècle. Les glaciers ont gardé, jusque durant la première moitié du 18ème siècle, une position quasiment équivalente à ce maximum. A partir des années 1730-40 s'amorce une phase de retrait continue des glaciers. Les moraines les plus importantes attestent de périodes de stagnation des fronts ou de réavancées n'ayant cependant jamais été d'ampleur suffisante pour remanier les dépôts morainiques précédemment mis en place. La fin du 19ème et le début du 20ème siècle sont marqués par une accélération du recul des glaciers. Durant le 20ème siècle, la décrue reste rapide. Sur l'ensemble de la période d'étude, les glaciers enregistrent une perte moyenne de près de 60% de leur surface maximale, ce qui correspond à une remontée d'environ 135 m de l'altitude de leur ligne d'équilibre. Les datations du maximum du PAG et des stades morainiques ultérieurs, aussi bien que l'évolution des glaciers boliviens depuis la fin du 19ème siècle sont concordants avec les données disponibles dans d'autres massifs des Andes intertropicales, notamment au Pérou et en Equateur. On émet l'hypothèse d'un synchronisme de l'évolution des glaciers à l'échelle régionale en réponse à un forçage climatique commun. L'interprétation paléoclimatique des données obtenues permet de supposer que l'extension maximale des glaciers boliviens correspond à une période pendant laquelle les précipitations étaient supérieures de 20 à 30% à leur niveau actuel et les températures inférieures de 0,4 à 0,6°C. En outre, on note la concomitance entre les périodes de moindre activité solaire et celles d'avancée des glaciers. Le retrait, à partir de la première moitié du 18ème siècle, serait en grande partie dû à une baisse des précipitations. Ces hypothèses sont en accord avec les indications issues d'autres « proxies » du climat, encore peu nombreux dans cette région des Andes, que sont par exemple les carottes de glace extraites de la calotte glaciaire de Quelccaya au sud du Pérou. L'occurrence de nombreux et intenses phénomènes El Niño à la fin du 19ème et au début du 20ème siècle, mise en évidence par plusieurs indicateurs, pourrait être responsable de l'accélération du retrait des glaciers à cette période et aurait sans doute précipité la fin du PAG à l'échelle des tropiques andins. Contrairement aux périodes précédentes pendant lesquelles l'évolution des glaciers semble avoir été principalement contrôlée par les précipitations, leur retrait durant le 20ème siècle apparaît comme résultant d'une hausse combinée des températures et de l'humidité.

The research described in this thesis addresses two aspects of the response of glaciers to climate change. The first aspect deals with the physical processes that govern the interaction between glaciers and climate change and was treated by (1) studying the spatial and temporal variation of the glacier albedo from satellite images, (2) investigating the spatial distribution of the surface energy and mass balance of a glacier, and (3) investigating the sensitivity of the mass balance to climate change. All of these studies are focused on Morteratschgletscher in Switzerland. The second aspect is the climatic interpretation of glacier length fluctuations. This was studied by developing a model that calculates historical mass balance records from global glacier length fluctuations. To increase our understanding of the variations in glacier albedo, we derived surface albedos from 12 Landsat images. This constituted a stringent test for the retrieval methodology applied because Morteratschgletscher is very steep and rugged, which strongly influences the satellite signal. We aimed to retrieve surface albedos while taking into account all important processes that influence the relationship between the satellite signal and the surface albedo, e.g. the topographic effects on incoming solar radiation, and the anisotropic nature of the reflection pattern of ice and snow surfaces. We then analysed the spatial and temporal pattern of the surface albedo. We developed a two-dimensional mass balance model based on the surface energy balance to study the spatial distribution of the energy and mass balance fluxes of Morteratschgletscher. Meteorological data from weather stations in the vicinity of Morteratschgletscher serve as input for the model. We corrected incoming solar radiation for shading, aspect, slope, reflection from surrounding slopes, and obstruction of the sky. Ignoring these effects results in an increase in solar radiation of 37%, causing a decrease in the mass balance of 0.34 m w.e. We modelled the mass balance for 1999 and 2000 and analysed the spatial distribution. We then ran the model for a period of 23 years and calculated the mass balance sensitivity to climate change by perturbing air temperature and precipitation. The mass balance sensitivity to temperature and precipitation are –0.59 m w.e. a-1 K-1 and 0.17 m w.e. a-1 per 10 percent respectively. We also used three other albedo parameterisations to calculate the mass balance sensitivity since albedo parameterisations are often regarded as a main source of error in mass balance models. We concluded that an accurate estimate of the mass balance sensitivity requires a parameterisation that captures the process of a decreasing snow albedo when a snow pack gets older or thinner. To extract a climate signal from worldwide glacier length fluctuations, we developed a simple model. The climate signal is represented as a reconstruction of the mass balance and the equilibrium line altitude (ELA). The model was tested on seventeen European glacier length records and then applied to nineteen glacier length records from different parts of the world. Between 1910 and 1959, the average increase in the reconstructed ELAs is 33 m. This implies that during the first half of the twentieth century, the climate was warmer or drier than before. The reconstructed ELAs decrease to lower elevations after 1960 and up till 1980, when most of the reconstructions end. The results can be translated into a global temperature increase of about 0.8 K for the period 1910-1959

The research described in this thesis addresses two aspects of the response of glaciers to climate change. The first aspect deals with the physical processes that govern the interaction between glaciers and climate change and was treated by (1) studying the spatial and temporal variation of the glacier albedo from satellite images, (2) investigating the spatial distribution of the surface energy and mass balance of a glacier, and (3) investigating the sensitivity of the mass balance to climate change. All of these studies are focused on Morteratschgletscher in Switzerland. The second aspect is the climatic interpretation of glacier length fluctuations. This was studied by developing a model that calculates historical mass balance records from global glacier length fluctuations. To increase our understanding of the variations in glacier albedo, we derived surface albedos from 12 Landsat images. This constituted a stringent test for the retrieval methodology applied because Morteratschgletscher is very steep and rugged, which strongly influences the satellite signal. We aimed to retrieve surface albedos while taking into account all important processes that influence the relationship between the satellite signal and the surface albedo, e.g. the topographic effects on incoming solar radiation, and the anisotropic nature of the reflection pattern of ice and snow surfaces. We then analysed the spatial and temporal pattern of the surface albedo. We developed a two-dimensional mass balance model based on the surface energy balance to study the spatial distribution of the energy and mass balance fluxes of Morteratschgletscher. Meteorological data from weather stations in the vicinity of Morteratschgletscher serve as input for the model. We corrected incoming solar radiation for shading, aspect, slope, reflection from surrounding slopes, and obstruction of the sky. Ignoring these effects results in an increase in solar radiation of 37%, causing a decrease in the mass balance of 0.34 m w.e. We modelled the mass balance for 1999 and 2000 and analysed the spatial distribution. We then ran the model for a period of 23 years and calculated the mass balance sensitivity to climate change by perturbing air temperature and precipitation. The mass balance sensitivity to temperature and precipitation are –0.59 m w.e. a-1 K-1 and 0.17 m w.e. a-1 per 10 percent respectively. We also used three other albedo parameterisations to calculate the mass balance sensitivity since albedo parameterisations are often regarded as a main source of error in mass balance models. We concluded that an accurate estimate of the mass balance sensitivity requires a parameterisation that captures the process of a decreasing snow albedo when a snow pack gets older or thinner. To extract a climate signal from worldwide glacier length fluctuations, we developed a simple model. The climate signal is represented as a reconstruction of the mass balance and the equilibrium line altitude (ELA). The model was tested on seventeen European glacier length records and then applied to nineteen glacier length records from different parts of the world. Between 1910 and 1959, the average increase in the reconstructed ELAs is 33 m. This implies that during the first half of the twentieth century, the climate was warmer or drier than before. The reconstructed ELAs decrease to lower elevations after 1960 and up till 1980, when most of the reconstructions end. The results can be translated into a global temperature increase of about 0.8 K for the period 1910-1959

This research examines moraine and lacustrine records of glacier fluctuations, in combination with palynological records of vegetation change, from the previously unstudied northwestern Ahklun Mountains in southwestern Alaska. Morain mapping reveals that ice-cap outlet glaciers in the study area extended ca. 60 km from the center of the Ahklun Mountians ice dome during the early Wisconsin (sensu lato), and ca. 40 km during the late Wisconsin. Correlations with well-studied moraines in the southern Ahklun Mountains indicate an asymmetry of glaciation over the range, with ice-cap outlet glaciers more extensive to the south. This asymmetry was more striking during the early Wisconsin (s.l.) than during the late Wisconsin. Alpine glaciers have repeatedly advanced from cirques within the study area. Because these alpine glaciers were confluent or sub-confluent with outlet glaciers during the late Wisconsin maximum, the alpine-glacier moraine record is relatively young. Lacustrine sedimentology from Little Swift Lake records significant retreat of alpine glaciers ca 12.8 ka (coeval with the onsent of the North Atlantic Younger Dryas). Moraines upvalley of the lake suggests a minor glacier (or rock glacier) advance occurred ca 5.5 ka. Lacustrine records of vegetation from Little Swift Lake extend back to ca. 13.4 ka. Most vegetation changes resulted from the post-glacial spread of trees and shrubs, including Betula, alnus, and Picea, to their modern ranges. However, pollen assemblages and other paleoclimate proxies suggest some major changes in late-glacial and Holocene climate. Major vegetation change, most notably the dramatic expansion of Poaceae, occurred ca. 100 yr after the 12.8-ka glacier retreat and persisted for more than 2 ka. The inferred reversal to dry (and possibly cool) climate was followed by a period of exceptionally productive mesic conditions during the early Holocene, ca. 11 to 9 ka. The pattern of latest-Quaternary climate changes documented in this study may be evidence that, as previous workers have concluded regarding the Pleistocene glaciations, the late-glacial and early Holocene climate of the Ahklun Mountains region was strongly modulated by changes in the proximity and temperature of the Bering Sea.

We explore the climatic information contained in the record of length fluctuations of Glaciar Frías, in the north Patagonian Andes of Argentina. This record is one of the longest and most detailed glacier records in southern South America, starting in 1639. In order to interpret the length variations of Glaciar Frías since the maximum Little Ice Age extent, we use a combination of a simplified surface energy-balance model to calculate the glacier mass balance, and a flowline model to account for the dynamical response of the glacier to changes in the climatic forcing. The overall retreat of the glacier observed over 1639-2009 is best explained by an annual mean temperature increase of 1.2 °C or a decrease in annual precipitation of 34%, most of which would have occurred during the 20th century. The glacier model is also forced with two independent tree-ring and multi-proxy reconstructions of precipitation and temperature. The uncertainties in these reconstructions are rather large, leading to a wide range in the modelled glacier length that includes most of the observations. However, in both reconstructions, the mid-17th century seems to be too cold and the early 19th century too warm to explain the observed glacier lengths with the glacier model forced with the reconstructions. Forcing with reconstructed precipitation and temperature separately shows that the influence of historical variations in precipitation on the glacier fluctuations of Glaciar Frías is smaller than that of the temperature fluctuations. This suggests that the observed 1639-2009 retreat could be best explained by a warming close to 1.2 °C. Fil: Leclercq, P. W.. Utrecht Univeristy. Faculty Of Sciences; Países Bajos Fil: Pitte, Pedro Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Giessen, R. H.. Utrecht Univeristy. Faculty Of Sciences; Países Bajos Fil: Masiokas, Mariano Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Oerlemans, J.. Utrecht Univeristy. Faculty Of Sciences; Países Bajos

The aim of the thesis is the study of the reconstitution of the high altitude lakes story in a changing environment since 10 000 years and the study of the present state of the lakes. The first part explains the story of lakes in high mountains. In the first chapter, the localisation of the lakes is studied at the end of the late-glacial (younger Dryas, about 10200 BP). The second chapter shows the environment changes with the retreat of the glaciers and with the timberline fluctuations during the Holocene period. The two following chapters 3 and 4 describe the interactions between lakes and glaciers (formation-disappearance) during the historic period (little ice age, Contemporary period).Two methods are used to study these environment modifications : geomorphology analysis and dendrochronology applied to subfossil woods well-preserved in peats and lakes, then compared with other palaeoecological approaches (palynology, palaeoentomology, macro-remain, pedoanthracology). The second part is a synthesis about the present state of the high altitude lakes from new measures. First, in chapter 1, the lakes are studied astheir place in mountain society (dangerous lakes, turism, water resources...). Then, in chapter 2, the structure of the database and the methods of measures are developed. Four following chapters describe the lake diversity in the French Alps : location, identification and inventory, morphometry and geomorphology (chapter 3), hydrology and thermic variations, snow cover and ice sheet, its duration (chapters 4 and 5), transparence, mineralisation, oxygenation (chapter 6) abstracted in a typology (multivariate analysis) which is developed in the chapter 7. An atlas gathers together the bathymetric maps and photographs of 43 lakes among the lakes which are studied by the author., L'objectif de cette thèse est de reconstituer l'histoire des lacs d'altitude dans un environnement marqué par des changements profonds depuis 10000 ans et de proposer une vue d'ensemble de l'état actuel des lacs d'altitude dans les Alpes françaises. La première partie est consacrée à l'histoire des lacs au sein des milieux de haute montagne en ayant recours à deux approches, l'analyse géomorphologique et la dendrochronologieappliquée aux bois subfossiles conservés dans les lacs et les tourbières. Les résultats sont confrontés aux données des autres disciplines paléoécologiques dans l'exemple du massif du Taillefer (palynologie, paléoentomologie, pédoanthracologie, étude des macro-restes).Un premier chapitre étudie la position des lacs par rapport à l'extension des glaciers à la fin du Tardiglaciaire (Dryas récent, vers 10200 BP). Le chapitre 2 montre les changements d'environnement des lacs, consécutifs au retrait des glaciers et aux fluctuations de la limite supérieure de la forêt, au cours de l'Holocène. Les deux chapitres suivants 3 et 4 mettent en évidence les interactions lacs-glaciers (création-disparition des lacs en fonction des variations des glaciers) pendant la période historique (petit âge glaciaire, période contemporaine). La deuxième partie étudie les lacs dans leur état actuel. Dans le chapitre 1, les lacs sont replacés dans le contexte de la société (risque de vidange lacustre, ressource en eau, tourisme...). Le deuxième chapitre présente la structure de la base de données relationnelle comprenant 530 lacs naturels situés à plus de 1400 md'altitude et de superficie supérieure ou égale à 0,5 ha et les méthodes d'acquisition des données, en particulier, des données terrain (bathymétrie, mesures physiques et chimiques).Les chapitres 3, 4, 5, 6 et 7 présentent les résultats des mesures, les analyses de toutes les données disponibles pour caractériser et donner une vue d'ensemble de la diversité des lacs d'altitude des Alpes françaises : localisation, identification et inventaire, morphométrie et morphologie des cuvettes lacustres (chapitre 3), étude hydrologique comprenant bassins versants, régimes hydrologiques et variations saisonnières du niveaudes lacs (chapitre 4), régimes thermiques, gel et couverture de glace (chapitre 5), minéralisation, transparence et oxygénation (chapitre 6). Enfin le chapitre 7 propose une classification des lacs d'altitude alpins à partir des informations recueillies et des typologies antérieures, typologies primaires en fonction des paramètres physiques et chimiques et des bassins versants (analyse multivariée). En annexe, un atlas rassemble les cartes bathymétriques de 43 des lacs étudiés par l'auteur, et des photographies de ces lacs.

Glaciers have fluctuated in historic times and the length fluctuations of many glaciers are known. From these glacier length records, a climate reconstruction described in terms of a reconstruction of the equilibrium-line altitude (ELA) or the mass-balance can be extracted. In order to derive a climate signal from numerous glacier length records, a model is needed that takes into account the main characteristics of a glacier, but uses little information about the glacier itself. Therefore, a simple analytical model was developed based on the assumption that the change in glacier length can be described by a linear response equation. Historical length observations, the climate sensitivity and the response time of a glacier were needed to calculate historical equilibrium-line altitudes. Both climate sensitivity and length response time were calculated from a perturbation analysis on the continuity equation. The model was tested on 17 European glacier length records. The results revealed that the ELA of most glaciers increased on average 54 m between AD 1920 and 1950. The results of the analytical model were compared to mass-balance reconstructions calculated with a numerical flowline model and derived from historical temperature and precipitation records. The findings lead us to believe that the analytical model could be very useful to gain information about the historical mass-balance rates and ELAs.