Evaluating potential evapotranspiration methods in a rapidly warming Arctic region, SW Spitsbergen (1983–2023)

Hornsund, SW Spitsbergen, Svalbard – area representing atlantic sector of High Arctic Svalbard's warming climate significantly alters its hydrological conditions. Evapotranspiration, a crucial hydrological component, is understudied in this High Arctic environment. In this study, daily potential evapotranspiration (PET) estimates for the period 1983–2023 were calculated using meteorological data from the Polish Polar Station Hornsund (SW Spitsbergen). 11 different PET methods were applied, those include radiation-based, temperature-based, radiation-temperature-based, and combined methods. The results show a large spread in the annual sum of PET ranging from ∼20 mm/y (Kharrufa) through ∼300 mm/y (Penman-Monteith) up to ∼450 mm/y (Abtew). Trends analysis shows different outcomes depending on the length of the averaging period. Using a daily timescale, PET methods tend to show more similar patterns of changes than using monthly timescales. The changes in PET estimates differ between the models, hence classifying PET methods should consider their sensitivity to meteorological changes. PET estimates were compared with pan measurements at a daily time scale in 2022–2023. The Penman method produced the best results in relation to pan measurements. In other cases, despite a relatively high linear correlation, calibration to local conditions is needed to scale the outcomes and limit biases. This study improves understanding of how PET models perform in the rapidly changing High Arctic climate. • Sensitivity study of 11 PET methods to climate change in SW Spitsbergen (1983–2023). • Large spread of annual PET from ∼20 mm/y (Kharrufa) to ∼450 mm/y (Abtew). • Heterogeneous trends were detected for intra-annual PET estimates. • Calibration to local conditions is needed for PET models. • Grouping of PET models must consider their sensitivity to meteorological changes.