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Seasonal Variations in Moisture Origin Explain Spatial Contrast in Precipitation Isotope Seasonality on Coastal Western Greenland
Author(s) -
Cluett A. A.,
Thomas E. K.,
Evans S. M.,
Keys P. W.
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033543
Subject(s) - seasonality , climatology , moisture , precipitation , arctic , environmental science , groenlandia , atmospheric sciences , water content , oceanography , geology , ice sheet , geography , ecology , meteorology , biology , geotechnical engineering
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 (δ 2 H Precip ) expressions. Historical observations of δ 2 H Precip reveal a contrast in seasonality between southwestern and northwestern coastal Greenland: δ 2 H Precip in northwestern Greenland varies in phase with local temperature, whereas δ 2 H Precip in southwestern Greenland is decoupled from local temperature and exhibits little seasonal variation. We test the hypothesis that reduced δ 2 H Precip seasonality 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 δ 2 H Precip and 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 δ 2 H Precip in a simple Rayleigh model, which confirm the importance of source temperature and starting isotopic compositions in determining δ 2 H Precip for these regions. δ 2 H Precip sensitivity to moisture source variability suggests these coastal Arctic settings may yield paleoclimate records sensitive to the moisture transport processes predicted to amplify future precipitation.