Impacts of South Atlantic Ocean thermal variability on changes in drylands in Argentina

This study analyses dryland changes in Argentina between 1961 and 2022, as well as the South Atlantic Ocean Dipole (SAOD) impacts on these changes. Monthly precipitation and mean temperature data, the latter used to calculate potential evapotranspiration (PET), were obtained from the Climatic Research Unit (CRU) database. The Aridity Index (AI) was calculated to define drylands according to the United Nations Convention to Combat Desertification (UNCCD) criteria. Sea surface temperature variability in the South Atlantic was examined using the SAOD index. Drylands in Argentina (50.7%), mainly composed of semiarid climate (29.7%) along with marginal arid (8.9%) and dry subhumid (12.1%) areas, exhibit multiannual and decadal oscillations. A significant positive correlation was found between the SAOD index and Argentine drylands, with an increase in these lands during positive SAOD phases (0.1–4.8%) and a reduction during negative phases (1.7–5.9%). The most pronounced shifts occurred in the central region of the country, where drylands expanded (decreased) eastward (westward) during positive (negative) SAOD phases, which was related to an increase (decrease) in aridity, driven by lower (higher) precipitation and higher (lower) PET. The positive (negative) SAOD phase is characterised by anomalous warming (cooling) in the tropical Atlantic and relative cooling (warming) in the south-western Atlantic, along with a weakened (strengthened) South Atlantic High. These changes in oceanic and atmospheric conditions are closely linked to the occurrence of drier or wetter conditions in Argentina, thereby influencing the extent of drylands across the country. These findings help to understand how teleconnection patterns, particularly the SAOD, influence drylands in Argentina.