Giant dust particles at Nevado Illimani: a proxy of summertime deep convection over the Bolivian Altiplano

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.

Prefacing unexplored archives from Central Andean surface-to-bedrock ice cores through a multifaceted investigation of regional firn and ice core glaciochemistry

“…2.Raw and smoothed (1 σ Gaussian) glaciochemistry ( δ 18 O, Fe, Na, Na + , Mg, Mg 2+ ) measurements from QU-18 (a, blue) and IL-17 short core (b, red) by depth in meters. The vertical highlights indicate where the years are located by depth from annual layer counting (QU-18) and from Lindau and others (2021, IL-17).…”

“…in 2017 by a team from the Ice Memory project and supported by French and Bolivian institutions. The field campaign and drilling procedure for this ice core are detailed in Lindau and others (2021). Surface-to-bedrock ice cores at Nevado Illimani reach a depth of 137–139 m (Hoffmann and others, 2003; Knüsel and others, 2003; Ramirez and others, 2003).…”

“…Illimani Glacier (6438 m), located on the eastern margin of the Bolivian Altiplano, ~450 km SE from Quelccaya, also exhibits well-preserved environmental signals within ice strata for the mid to late Holocene period (e.g. Correia and others, 2003; Hoffmann and others, 2003; Knüsel and others, 2003, 2005; Kellerhals and others, 2010; Eichler and others, 2015, 2017; Osmont and others, 2019; Lindau and others, 2021).…”

Gentle Topography Increases Vertical Transport of Coarse Dust by Orders of Magnitude

“…In this sense, hill topography is not expected to entirely explain the transport of coarse dust into the free atmosphere, where long‐range transoceanic transport occurs (Engelstaedter et al., 2006; Perry et al., 1997). Rather, we expect topography to play a key dynamical role in the near‐surface region, where the transport mechanisms discussed here connect entrained dust above the surface with large‐scale thermal motions higher in the convective boundary layer, which thereafter lift dust to the free atmosphere (Freire et al., 2016; Klose & Shao, 2013; Lindau et al., 2021).…”

“…The present study extends upon these passive scalar transport studies to evaluate the effect of topography on coarse dust particles. The impetus for the study is to identify the intermediate mechanisms bridging the initial entrainment of dust particles near the ground to their eventual transport into the upper atmosphere by large‐scale motions such as convective plumes (Freire et al., 2016; Lindau et al., 2021; Klose & Shao, 2013). The ultimate goal is to improve global dust models by providing insight into the near‐surface wind dynamics which both enhance the uplift of coarse dust and are missing from current dust models.…”