Changes in drylands in Argentina during the phases of the Pacific Decadal Oscillation (1961–2022)

Abstract

This study examines dryland changes in Argentina during the Pacific Decadal Oscillation (PDO) phases between 1961 and 2022. Using monthly temperature and precipitation data from the Climate Research Unit (CRU), the Aridity Index (AI) was calculated to delineate drylands according to the United Nations Convention to Combat Desertification (UNCCD) criteria. The PDO index was used to identify the positive and negative phases of the teleconnection, and to explore how drylands change during these phases. These drylands display oscillations at various frequencies (quasi?decadal, multiannual, and interannual), with quasi?decadal cycles (9 years) being the most prominent. An inverse correlation was observed between the PDO index and total dryland extent (r = − 0.15). On average, during negative (positive) PDO phases, drylands expand (contract) by 0.89% (0.83%), with the most notable changes occurring in central Argentina, where they advance (retreat) eastward (westward). The expansion (reduction) of drylands during negative (positive) phases is driven by decreased (increased) precipitation and increased (reduced) evaporative demand, whereas southern Patagonia exhibits the opposite pattern. These conditions during negative (positive) phases are associated with South Pacific cooling (warming), which strengthens (weakens) the Subtropical High and Subpolar Lows at lower and mid?levels of the atmosphere, while at upper levels, changes in the meridional temperature gradient weaken (intensify) the Subtropical Jet and intensify (weaken) the Polar Jet, promoting a more zonal (meridional) circulation. These results are key for monitoring drylands in vulnerable regions such as central Argentina and Patagonia, where small variations in water availability can lead to environmental and socioeconomic problems.