Quantifying glacier retreat in Patagonia: A 27-year remote sensing study of the Upsala and Perito Moreno Glaciers

The Patagonian Icefields in the Andes Mountains represent South America’s largest solid freshwater reserves and are highly sensitive indicators of regional climate variability. This study analyzes the contrasting behaviors of two emblematic Glaciers of the Southern Patagonia Icefield: Upsala Glacier, characterized by sustained retreat and Perito Moreno Glacier, historically considered relatively stable. Using Landsat 5, 7, and 8 imageries from 1997–2023, we provide a quantitative assessment of frontal displacement, area change, and retreat dynamics, offering additional insights beyond prior studies. For Upsala Glacier, we confirm and refine earlier reports of significant retreat, measuring ∼6989 ± 0.56 m of frontal loss, an average retreat rate of −304.55 ± 0.78 m/year (p < 0.05), and a statistically significant acceleration of −1.9 ± 1.11 m/year 2 . Surface area declined by ∼ 73.5 ± 0.22 km 2 (∼9% of its 1997 extent), at an average rate of −3 ± 0.17 km 2 /year, with continued retreat after 2023 (100 ± 15 m in 2024 and 291.5 ± 15 m in 2025). In contrast, Perito Moreno Glacier exhibited near-equilibrium conditions with no sustained frontal retreat for most of the study period, but since 2016 has undergone a marked transition toward sustained frontal retreat, with retreat rates reaching −55 ± 0.78 m/year and accounting for nearly two-thirds of its total area loss since 1997 (∼3 ± 0.15 km 2 ), with spatially asymmetric retreat–advance dynamics. Recent observations further confirm this shift, with a pronounced retreat event in 2025 reaching ∼−385 ± 15 m representing the largest frontal recession recorded over the study period. These contrasting Glacier responses highlight the strong influence of Glacier geometry and local dynamics on frontal behavior, emphasizing the importance of sustained satellite monitoring and the integration of complementary datasets for understanding the future evolution of Patagonian Glaciers.