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Abstract Increased precipitation in the Arctic is a robust feature across model simulations of the coming century, driven by intensification of meridional moisture transport and enhanced local evaporation in the absence of sea ice. These mechanisms are associated with distinct, seasonal, spatial, and, likely, precipitation isotope (δ2HPrecip) expressions. Historical observations of δ2HPrecipreveal a contrast in seasonality between southwestern and northwestern coastal Greenland: δ2HPrecipin northwestern Greenland varies in phase with local temperature, whereas δ2HPrecipin southwestern Greenland is decoupled from local temperature and exhibits little seasonal variation. We test the hypothesis that reduced δ2HPrecipseasonality in southwestern Greenland relative to northwestern Greenland results from dynamic moisture source variations, by diagnosing monthly average moisture sources to three sink regions (Kangilinnguit, Ilulissat, and Qaanaaq) using the Water Accounting Model‐2layers model. All domains demonstrate strong intra‐annual moisture source variations. Moisture to the southernmost region is sourced most remotely in summer and most locally in winter, associated with stronger cooling from the source in summer than winter, promoting more negative δ2HPrecipand counteracting local temperature‐driven seasonality. In comparison, moisture transport distance to the northernmost region is relatively constant, as local sea ice restricts northward migration of the winter moisture source. We simulate seasonal patterns in δ2HPrecipin a simple Rayleigh model, which confirm the importance of source temperature and starting isotopic compositions in determining δ2HPrecipfor these regions. δ2HPrecipsensitivity to moisture source variability suggests these coastal Arctic settings may yield paleoclimate records sensitive to the moisture transport processes predicted to amplify future precipitation.
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Northward Shifts in the Polar Front Preceded Bølling and Holocene Warming in Southwestern Scandinavia
Abstract The last deglaciation in northern Europe provides an opportunity to study the hydrologic component of abrupt climate shifts in a region with complex interactions between ice sheets and oceanic and atmospheric circulation. We use leaf wax hydrogen isotopes (δ2H) to reconstruct summer precipitation δ2H and aridity in southwestern Norway from 15.8 to 11.5 ka. We identify transitions to a more proximal moisture source before the ends of Heinrich Stadial 1 and the Younger Dryas, prior to local warming and increased primary productivity in both instances. We infer these changes in moisture delivery to southwestern Norway to be a response to northward shifts in the polar front caused by warm water intrusion into the North Atlantic, which preceded abrupt warming in the circum‐North Atlantic. These results suggest that moisture transport pathways shift northward as warm surface ocean water reaches higher latitudes in the North Atlantic.
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- Award ID(s):
- 1652274
- PAR ID:
- 10386824
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 14
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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