Dating of two nearby ice cores from the Illimani, Bolivia

Abstract

In order to establish a chronology of two nearby ice cores from a glacier at Illimani (6438 m), Bolivia, a broad dating approach is presented here, which in particular makes use of the fast, simple, and nearly nondestructive electrical conductivity method (ECM) that provides a highly resolved record. Thus, ECM is suited for counting annual layers in the ice, especially for ice cores extracted from high‐mountain glaciers with a fast layer thinning. Furthermore, ECM can be used for detecting volcanic signals. Annual signals in the ECM record of the Illimani ice core were identified using the 1964 A.D. tritium reference horizon and were counted along 125 m or 90% of the core, representing the time period from 1200 ± 240 A.D. (estimated accumulated error) to 1999 A.D. The resulting age–depth relationship was supported by counting annual peaks in the microparticle record as well as by nuclear dating using the decay of 210Pb. The identification of volcanic signals originating from eruptions such as Pinatubo (1991 A.D.), El Chichón (1982 A.D.), Agung (1963 A.D.), Krakatoa (1883 A.D.), Tambora (1815 A.D.), and the Unknown 1258 A.D. significantly reduced the uncertainty of annual layer counting (ALC) to ±2 years in the vicinity of these events.

Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

“…This finding is consistent with data from other alpine glaciers, where the thinning is minor above 50 m (see e.g. Schwerzmann et al, 2006;Knüsel et al, 2003). The average net accumulation rate at Pío XI is comparable to precipitation amounts at the Chilean coast, but not as high as the 10 m weq expected for the Icefield (Carrasco et al, 2002).…”

“…Since the end of the Little Ice Age (LIA, late 19th Century) most of the Patagonian glaciers have been retreating and thinning, contributing significantly to sea-level rise (Glasser et al, 2011), with only a few in a state of equilibrium or advance Masiokas et al, 2009a, b). Glacier retreat is interpreted primarily as a response to regional atmospheric warming and to a lesser extent to precipitation decrease .…”

Towards radiocarbon dating of ice cores

“…The first study site is Nevado Illimani (16.628 S, 67.778 W), a permanently covered ice cap in the Bolivian Andes, where two parallel ice cores (to depths of 136.7 and 138.7 m) were drilled in 1999 in a joint expedition of the Paul Scherrer Institut (PSI, Switzerland) and the Institut de Recherche pour le Développement (IRD, France). Description of site characteristics, first dating models and climatic interpretations exist for both cores (De Angelis and others, 2003;Knü sel and others, 2003;Ramirez and others, 2003;Knü sel and others, 2005). The Amazon basin upwind of the ice-core site is considered to be a main source of carbonaceous aerosols (Graham and others, 2003;Guyon and others, 2004).…”

Glacier mass balance reconstruction by sublimation induced enrichment of chemical species on Cerro Tapado (Chilean Andes)

“…Thompson et al, 1985), Huascarán (Peru) (e.g. Thompson et al, 1995), Sajama (Bolivia) (Thompson et al, 1998) and Illimani (Bolivia) (Knüsel et al, 2002;De Angelis et al, 2003;Correia et al, 2003).…”