Arctic and sub-Arctic lake water ?2H and ?18O along a coastal-inland transect: Implications for interpreting water isotope proxy records

High-latitude lakes are sensitive to climate change and store information about large-scale circulation changes catchment-integrated processes. Lakes mainly recharged by meteoric water, meaning that some lake sediment proxies may indirectly archive the stable isotopic composition of hydrogen (?2H) oxygen (?18O) past precipitation. Yet, despite similar precipitation input, within a region exhibit wide range values due varying influence inflow seasonality evaporation. Moreover, relative sensitivity each these controls vary through time, something is difficult account for. Here, we evaluate impact variable ?2H evaporation on water across northern Fennoscandia (Norway, Finland, Sweden). We measured ?18O 135 spanning from north Norwegian coast along 460 km transect Bothnian Bay, sampled 2018 2020. Our data show both coastal inland distillation during moisture transport, farther Atlantic Ocean additionally impacted estimated for evapo-concentrated (?2HI) using Bayesian method. Resampled had more depleted ?2HI in 2020 than 2019, indicating either was 2H-depleted or winter contributed compared 2019. suggest were response snow-rich winter, associated with extremely positive Arctic Oscillation (AO+) conditions increased supply North Atlantic. find evidence variability this reflects combination seasonal atmospheric changes, Careful consideration processes essential when making inferences based isotope proxies.