Synoptic scale controls on the 18O in precipitation across Beringia

Oxygen isotope records of precipitation (O-18(precip)) from Beringia are thought to reflect synoptic-scale circulation changes associated with the Aleutian Low. To delineate the spatial pattern of O-18(precip) associated with the two dominant modes of Aleutian Low circulation, we combine modern O-18(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 O-18(precip); whereby a strengthened Aleutian Low causes lower (higher) O-18(precip) in western (eastern) Beringia. We compare a new 100 year long O-18 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.