Atmospheric dust dynamics in southern South America: A 14-year modern dust record in the loessic Pampean region

Abstract

Mineral aerosols profoundly impact global climate. Modeling of the dust cycle is the main tool used to gauge this effect. However, the scarcity of in situ modern dust flux measurements is the main reason why validation of existing models is hampered. We present the first long-term (14-year) record of dust flux in the Pampas, southern South America, home to the largest loess deposit in the Southern Hemisphere. Measured 14-year mean deposition (40 g m−2 year−1) and horizontal (362 g m−2 year−1) fluxes imply that current models underestimate the power of the central Pampas as a dust sink. Based on cross-spectral analysis, both wet and, to a lesser extent, dry deposition are found to play significant roles in atmospheric dust extraction. Dust is sourced regionally from the South American Arid Diagonal and from the shores of Mar Chiquita lake (~260 km), which we find to be the main contributor of dust particles >30 µm. Cross-spectral and satellite image analyses show that surface wind speed and precipitation at the Puna-Altiplano Plateau are controlling factors for horizontal dust flux in the Pampas. El Niño Southern Oscillation probably plays a role in controlling interannual horizontal dust flux periodicities. Finally, preliminary comparisons between modern vertical dust fluxes and loess accumulation rates point to the Pampas as a more powerful dust sink during the last deglaciation and Antarctic Cold Reversal (18–12.5 ka).

A circumpolar dust conveyor in the glacial Southern Ocean

“…The prominent role of Central South America as a major dust source to the South Pacific SAZ during the LGM has not previously been shown. Modern observations and model simulations show pronounced dust activity in Central South American PSAs near 30°S 27,60,67 . Importantly, Central South American PSAs feature a number of environmental preconditions for the efficient production of fine particles including high relief, (semi)arid conditions with intermittent fluvial activity 26,27,33,67,68 , and increased glacier activity during glacial intervals 69,70 .…”

“…In the present day, the mid-latitude SWW regime intersecting South America spans the lower troposphere westerly winds and the high-altitude jet streams 33 , 72 – 74 . The westerly winds are typically associated with strong dry foehn-like winds promoting dust entrainment on the eastern side of the Andes 28 , 30 , 33 , 39 , 60 , 67 , 75 . The high-altitude westerly jet circulation features a mid-latitude jet stream in the Southern Hemisphere, which is characterized by a weakened subpolar (~60°S) and a strengthened subtropical branch (~30°S) over the South Pacific during austral winter 73 (Fig.…”

Does Satellite Chlorophyll‐a Respond to Southernmost Patagonian Dust? A Multi‐year, Event‐Based Approach

“…Discarding them, the average vertical dust flux is 0.08 g m −2 day −1 . The high and irregular sampling interval (average: 38 days, 15–168 days) makes it difficult to ascertain any annual variability, precluding traditional statistical trend tests, and spectral analysis (e.g., Cosentino, Gaiero, et al, 2020). However, visual inspection indicates no annual periodicity.…”

“…One collector is a pyramidal receptacle (CP), with a 2025‐cm 2 collection surface suited for measuring vertical dust flux (e.g., Cosentino, Gaiero, et al, 2020; Gaiero et al, 2003, 2013; Orange et al, 1990; Skonieczny et al, 2011). The other is a Buffalo Spring Number Eight (BSNE) (Fryrear, 1986), with a 10‐cm 2 collection surface suited for measuring horizontal dust flux (e.g., Cosentino, Gaiero, et al, 2020; Waza et al, 2019). Both collectors were placed 5 m above ground to avoid collecting local saltation material.…”

“…Dust was sampled using two passive collectors installed on the outskirts of Rio Grande city (53.79°S, 67.75°W ) ( Figure 1). One collector is a pyramidal receptacle (CP), with a 2025-cm 2 collection surface suited for measuring vertical dust flux (e.g., Cosentino, Gaiero, et al, 2020;Gaiero et al, 2003Gaiero et al, , 2013Orange et al, 1990;Skonieczny et al, 2011). The other is a Buffalo Spring Number Eight (BSNE) (Fryrear, 1986), with a 10-cm 2 collection surface suited for measuring horizontal dust flux (e.g., Cosentino, Gaiero, et al, 2020;Waza et al, 2019).…”