A GCM‐based analysis of circulation controls on δ18O in the southwest Yukon, Canada: Implications for climate reconstructions in the region

To improve our understanding of paleoclimatic records in the southwest Yukon, we examined controls on precipitation δ18O using an isotopically‐equipped atmospheric general circulation model (GCM). Our results show that, particularly during the cool‐season, elevated δ18O is associated with a deeper Aleutian Low and stronger southerly moisture flow, while lower δ18O is associated with the opposite meteorological conditions. These results suggest that the large mid‐19th century shift towards lower δ18O values seen in paleoclimate records from the region was associated with a shift towards a weaker Aleutian Low. While in disagreement with a previous interpretation of this shift, it is consistent with records of glacial advance and tree‐ring growth during the same period, and observational studies of Aleutian Low controls on temperature and precipitation in the region.