Browsing by Autor "Abraham Machaca"

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46 years of environmental records from the Nevado Illimani glacier group, Bolivia, using digital photogrammetry
(Cambridge University Press, 2013) Rafael da Rocha Ribeiro; Edson Ramírez; Jefferson Cárdia Simões; Abraham Machaca
Abstract This study determines variations in ice extent of Nevado Illimani, Bolivia (16°38' S, 67°44' W), from 1963 to 2009. The results are compared with net accumulation rate variations obtained from a local ice core. We then propose an interpretation of the recent environmental history (last 46 years) of the region based on a study of remotely sensed and ice-core data. From 1963 to 2009, Nevado Illimani lost a total ice area of 9.49 ±1.09 km 2 , a 35% reduction. Area variations generally followed variations in net accumulation rates during this period. Despite the current glacier area reduction trend, the Nevado Illimani glaciers will not completely disappear in the next few decades.
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.