Isoscapes of δ 18 O and δ 2 H reveal climatic forcings on Alaska and Yukon precipitation

Spatially extensive Arctic stable isotope data are sparse, inhibiting the climatic understanding required to interpret paleoclimate proxy records. To fill this need, we constrained the climatic and physiographic controls on δ 18 O and δD values of stream waters across Alaska and the Yukon to derive interpolated isoscape maps. δ 18 O is strongly correlated to winter temperature parameters and similarity of the surface water line (δ 2 H = 8.0 × δ 18 O + 6.4) to the Global Meteoric Water Line suggests stream waters are a proxy for meteoric precipitation. We observe extreme orographic δ 18 O decreases and a trans‐Alaskan continental gradient of −8.3‰ 1000 km −1 . Continental gradients are high in coastal zones and low in the interior. Localized δ 18 O increases indicate inland air mass penetration via topographic lows. Using observed δ 18 O/temperature gradients, we show that δ 18 O decreases in a ∼24 ka permafrost ice wedge relative to the late Holocene indicate mean annual and coldest quarter temperature reductions of 8.9 ± 1.7°C and 17.2 ± 3.2°C, respectively. Oxygen and hydrogen isotope spatial variability controlled by altitude, latitude, and continentality δ 18 O and δ 2 H isoscapes reveal physiographic variability in surface water isotope values Strong control of mean annual and winter temperature on δ 18 O values assists paleoclimatic interpretation of isotopic proxy records