Dust deposition tracks late-Holocene shifts in monsoon activity and the increasing role of human disturbance in the Puna-Altiplano, northwest Argentina

Abstract

The Puna-Altiplano plateau represents a regionally significant dust source, which is critically located at the nexus between the tropical and sub-polar synoptic systems that dominate the South American climate. Dust emissions in this region would therefore be expected to be sensitive to changes in these systems, in particular the strength and position of the South American Summer Monsoon (SASM). Here, we present a late-Holocene multi-proxy study where changes in dust flux, reconstructed from a high-altitude peat mire, are examined in light of climate variability and human impacts. Results show that for most the 4300 cal. yr BP record, dust flux sensitively tracked changes in SASM activity. Prior to 2600 cal. yr BP relatively high dust flux implies dry conditions prevailed across the Puna-Altiplao in association with reduced SASM activity. The chemistry of dust deposited at this time matched the large endorheic basins on the Puna, which host ephemeral lakes and terminal fans, indicating these were actively supplying dust to the airstream. After 2600 cal. yr BP, SASM activity increased while dust flux decreased and the dust chemistry changed, collectively implying the shutting down of the Puna-Altiplano as a significant dust source. Dust flux increased after 1000 cal. yr BP during the ‘Medieval Warm Period’, associated with a return to drier conditions and reactivation of dust sources across the endorheic basins of the Puna. Natural variability in dust flux was dwarfed, however, by the very significant increase in flux after 400 cal. yr BP following Spanish Colonisation and associated changing landuse practices. This finding attests to the globally significant role of humans on dust emissions.

Did Modern Precipitation Drivers Influence Centennial Trends in the Highlands of the Atacama Desert During the Most Recent Millennium?

“…Instead, the Toconce series agrees with precipitation records from the eastern margins of the southern Altiplano. For instance, reduced monsoonal precipitation prevailed between 1,200 and 750 BP at Cerro Tuzgle (Kock et al., 2020, Figures 1a and 3d) and overall dry conditions are observed between 1,000 and 700 BP at Santa Victoria core (Hooper et al., 2020, Figure 1a). Negative precipitation anomalies are also documented further north in the southern Peruvian Andes (13–14°S), either as lake level reductions between 1,070 and 850 BP (Chepstow‐Lusty et al., 2009) or as a rise in Asteraceae pollen at Cerro Llamoca peat hillock between 1,000 and 550 BP (Schittek et al., 2018, Figures 1a and 3e).…”

“…Tilomonte Spring (Rech et al., 2002), 7. Santa Victoria core (Hooper et al., 2020), 8. Vilama‐Coruto lake system (Morales et al., 2015), 9.…”

“…The most recent millennium provides an ideal time frame for studying the evolution of climate trends and drivers. Recent hydrological reconstructions from the Altiplano‐Puna region, on the eastern Andean flanks, show that this region experienced relatively dry conditions between 1,100 and 700 calibrated years before present (BP; present taken as Common Era 1950), and increased humidity between 400 and 70 BP (Hooper et al., 2020; Kock et al., 2020; Schittek et al., 2016). A coupling between these trends and records of past ENSO variability provides evidence in favour of a long‐term teleconnection with the equatorial Pacific, in agreement with hydrological records from the tropical Andes further north (Bird et al., 2011; Campos et al., 2019; Kanner et al., 2013; Vuille et al., 2012).…”

Surface Morphologies in a Mars-Analog Ca-Sulfate Salar, High Andes, Northern Chile

“…Salar de Pajonales lies in the Arid Diagonal on the divide between regions of dominantly winter rain (generally to the west and south) and dominantly summer (monsoonal) rain (generally to the east and north) (Betancourt et al, 2000;Diederich et al, 2020;Hooper et al, 2020;Palacios et al, 2020, see their Figure 1) and is subject to infrequent freshening events (Bozkurt et al, 2016). Recent rainfall events caused significant flooding and destruction along rivers in the southern reaches of the Atacama Desert (Barrett et al, 2016;Bozkurt et al, 2016;Wilcox et al, 2016;Valdés-Pineda et al, 2017;Cabre et al, 2020) but were insufficient, in large part, to mobilize hillslopes.…”

Holocene dust dynamics: Introduction to the special issue

“…The first part of the special issue is dedicated to the most prominent archives of atmospheric dust that are used nowadays: peatlands, ice and loess. Those first papers show how it is possible to reconstruct dust deposition fluxes and sources and decipher climatic information such as wind regimes, positions and intensities in various climatic conditions from seasonal to monsoonal regimes (Hooper et al, 2020; Martínez Cortizas et al, 2020; Pratte et al, 2020). While peatlands provide detailed and high-resolution chronologies, they are generally limited to the Holocene or the last glacial termination, whereas loess and ice provide a longer prospective.…”