Browsing by Autor "Vincent Jomelli"

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A major advance of tropical Andean glaciers during the Antarctic cold reversal
(Nature Portfolio, 2014) Vincent Jomelli; Vincent Favier; Mathias Vuille; Régis Braucher; Léo Martin; Pierre‐Henri Blard; Christopher M. Colose; Daniel Brunstein; Feng He; Myriam Khodri
Analyse de la structure d'un glacier rocheux du domaine tropical (Caquella, sud-Lipez, Bolivie)
(Société hydrotechnique de France, 2001) Denis Fabre; Bernard Francou; Vincent Jomelli; Brigitte Kaiser; Yves Arnaud; Bernard Pouyaud; Claudio Smiraglia; François Valla
Click to increase image sizeClick to decrease image sizeThe Caquella rock glacier (5960-5400 m asl), by the size (one kilometre long) is probably the most important active rock glacier in the Inner Tropics. In this arid high mountain environment glaciers are lacking and rock glaciers represent, with the salt lakes, the best indicators of the climatic variability. Moreover, they behave as water reservoirs in the present hydrological cycle marked by very scarce precipitation. Direct observations and geoelectrical soundings make it possible to identify interstitial ice in the permafrost. Nevertheless, the resistivity curve profile, the ice distribution in the debris mass as well as observations from the surface topography, bring clear evidences that this rock glacier is in recession. The Caquella rock glacier results from a long evolution, which has probably its origin in the early Holocene. Presence of a very recent moraine in the upper part suggests presence of ELA on the rock glacier during the Little Ice Age.
Evidence of moist niches in the Bolivian Andes during the mid-Holocene arid period
(SAGE Publishing, 2013) Marie‐Pierre Ledru; Vincent Jomelli; Laurent Brémond; Teresa Ortuño; Pablo Cruz; Ilham Bentaleb; Florence Sylvestre; Adèle Kuentz; Stephan Beck; Céline Martin
To examine the climate of the mid-Holocene and early human settings in the Andes when the Altiplano was recording the most arid phase of the Holocene, we analyzed plant-related proxies (pollen, phytoliths, diatoms, stable isotopes) from a sediment core sampled at high elevation in the Eastern Cordillera of Bolivia. Our study was carried out in the wetland of Tiquimani (16°12′06.8″S; 68°3′51.5″W; 3760 m), on a well-known pathway between Amazonia and Altiplano. The 7000-year old record shows a two-step mid-Holocene with a dry climate between 6800 and 5800, followed by a wetter period that lasted until 3200 cal. yr BP. In the Central Andes of Bolivia, a widespread aridity was observed on the Altiplano during the mid-Holocene. However, here, we show that moisture was maintained locally by convective activity from the Amazon lowlands. During the arid interval between 5000 and 4000 yr BP, these niches of moisture produced specific grasslands that may have enabled the survival of an archaic culture of hunter–gatherers on the Puna. This development occurred 2000 years before expansion of quinoa cultivation on the Puna.
Glacier recession on Cerro Charquini (16° S), Bolivia, since the maximum of the Little Ice Age (17th century)
(Cambridge University Press, 2006) Antoine Rabatel; Abraham Machaca; Bernard Francou; Vincent Jomelli
Abstract Cerro Charquini, Bolivia (Cordillera Real, 5392 ma.s.l.) was selected as a site to reconstruct glacier recession since the maximum of the Little Ice Age (LIA) in the central Andes. Five glaciers, located on differently exposed slopes, present comprehensive and well-preserved morainic systems attributed to former centuries. The moraines were dated by lichenometry and show a consistent organization on the different slopes. The past geometry of the glaciers was reconstructed using ground topography and aerophotogrammetry. Lichenometric dating shows that the LIA maximum occurred in the second half of the 17th century, after which the glaciers have receded nearly continuously. Over the last decades of the 20th century (1983–97), recession rates increased by a factor of four. On the northern and western slopes, glaciers receded more than on the southern and eastern slopes (by 78% and 65% of their LIA maximum area, respectively). The mean equilibrium-line altitude (ELA) rose by about 160 m between the LIA maximum and 1997. Recession rates were analysed in terms of climatic signal, suggesting that glacier recession since the LIA maximum was mainly due to a change in precipitation and that the 19th century may have been drier. For the 20th century, a temperature rise of about 0.6°C appears to be the main cause of glacier recession. Recent climatic conditions from 1983 to 1997 correspond to a mass deficit of about 1.36m w.e.a –1 . If such conditions persist, the small glaciers below 5300ma.s.l. in the Cordillera Real should disappear completely in the near future.