Hydro‐Atmospheric Variability and Dust Dynamics in Southern South America During the Last ∼62 ka

Abstract

Loess is a key continental archive for reconstructing past atmospheric circulation and evaluating paleoclimate models. In southern South America (SSA), the Pampean loess constitutes the thickest and most extensive paleo-dust deposit south of the Equator, providing a valuable basis for reconstructing the dust cycle in the Southern Hemisphere. This study integrates grain size, compositional, and magnetic analyses with a new chronological framework from three Pampean loess sections spanning the last ~62 ka. Results reveal close correspondence between moisture availability—mainly controlled by precipitation—and aeolian settling mechanisms in the Pampean dust sink region, distinguishing intervals dominated by wet and dry deposition. Comparisons of dust mass accumulation rate (DMAR) for different grain size fractions and paleo-proxy data in potential dust source areas over the last 25 ka highlight major paleoclimatic shifts. Reduced fine-grained DMAR during the Last Glacial Maximum (LGM) resulted from (1) reduced dust deposition due to more arid conditions which weakened wet scavenging of far-travelled dust, and from (2) humid conditions in distal sources that limited dust emission. In contrast, enhanced coarse-grained DMAR in Pampean loess during the LGM likely reflects an enhanced low-elevation sub-polar westerly jet, which triggered proximal source activation. Postglacial drying of distal dust source regions enhanced dust emissions, while a more humid Pampas enhanced local wet scavenging of distal dust, concomitant with enhanced soil development. These findings underscore variable climatic controls on dust accumulation in the Pampean region during the last glacial-interglacial cycle.