Synoptic scale controls on the δ¹⁸O in precipitation across Beringia

Oxygen isotope records of precipitation (δ¹⁸O_precip) from Beringia are thought to reflect synoptic-scale circulation changes associated with the Aleutian Low. To delineate the spatial pattern of δ¹⁸O_precip associated with the two dominant modes of Aleutian Low circulation, we combine modern δ¹⁸O_precip and deuterium excess data with climate reanalysis and back trajectory modeling. Aleutian Low strength and position are revealed to systematically affect regional moisture source and δ¹⁸O_precip; whereby a strengthened Aleutian Low causes lower (higher) δ¹⁸O_precip in western (eastern) Beringia. We compare a new 100 year long δ¹⁸O record from the Aleutian Islands with the North Pacific Index, the primary indicator of Aleutian Low strength, and find a significant positive relationship (r = 0.43, P < 0.02, n = 28) that tracks late twentieth century change. This study demonstrates synoptic-scale circulation controls on our isotope record and provides a coherent framework for interpreting existing and emerging paleoisotope data from the region.