Abstract
Abstract. A deeper understanding of past atmospheric circulation variability in the Central Andes is a high-priority topic in paleoclimatology mainly because of the necessity to validate climate models used to predict future precipitation trends and to develop mitigation and/or adaptation strategies for future climate change scenarios in this region. Within this context, we here investigate an 18-year firn core drilled at Nevado Illimani in order to interpret its mineral dust record in relation to seasonal processes, in particular atmospheric circulation and deep convection. The core was dated by annual layer counting based on seasonal oscillations of dust, calcium, and stable isotopes. Geochemical and mineralogical data show that dust is regionally sourced in winter and summer. During austral summer (wet season), an increase in the relative proportion of giant dust particles (∅>20 µm) is observed, in association with oscillations of stable isotope records (δD, δ18O). It seems that at Nevado Illimani both the deposition of dust and the isotopic signature of precipitation are influenced by atmospheric deep convection, which is also related to the total amount of precipitation in the area. This hypothesis is corroborated by regional meteorological data. The interpretation of giant particle and stable isotope records suggests that downdrafts due to convective activity promote turbulent conditions capable of suspending giant particles in the vicinity of Nevado Illimani. Giant particles and stable isotopes, when considered together, can be therefore used as a new proxy for obtaining information about deep convective activity in the past.
Highlights
Climate variability in the Central Andes and the Bolivian Altiplano has a strong link with atmospheric circulation and rainfall anomalies over the rest of tropical South America (e.g., Vuille, 1999)
These were manually decontaminated by mechanical scraping with a clean ceramic knife inside a laminar flow high-efficiency particle air (HEPA) ISO 5 class bench located in an ISO 6 class cold room
We established a chronology for the Nevado Illimani firn core based on annual layer counting (ALC) and considering the pronounced seasonal oscillation of dust concentration, calcium, and stable water isotopes (Fig. 2)
Summary
Climate variability in the Central Andes and the Bolivian Altiplano has a strong link with atmospheric circulation and rainfall anomalies over the rest of tropical South America (e.g., Vuille, 1999). This study shows for the first time that climatic processes control the presence of giant dust particles in Andean firn and ice. We found clear evidence that the convective activity over the Altiplano, reconstructed through the analysis of giant particles, is enhanced during summer periods, which is in agreement with observations concerning atmospheric circulation anomalies in the area (Vuille, 1999). We found clear evidence that the convective activity over the Altiplano, reconstructed through the analysis of giant particles, is enhanced during summer periods, which is in agreement with observations concerning atmospheric circulation anomalies in the area (Vuille, 1999) From this perspective, this study demonstrates the great potential of giant particle records which are strongly influenced by climatic and meteorological processes at high-altitude continental glaciers. This is a first exploratory work; analysis of a longer ice core would be desirable in the future to investigate the relationships between giant dust particle deposition, atmospheric deep convection, and periodic climatic phenomena (La Niña)
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