Investigating the role of moisture source seasonality in the meridional gradient in precipitation δ18O and d-excess seasonality along coastal western Greenland
Abstract
An increase in precipitation in the Arctic has been identified as a robust feature of warming across model simulations of the coming century. Processes driving precipitation changes are predicted to be seasonally varying in response to a combination of local evaporation and remote moisture transport. Modern observational data suggest variable regional sensitivity to moisture transport processes. For example, along coastal western Greenland, there exists a strong meridional gradient in the seasonal cycle of precipitation amount, δ18O, and deuterium-excess (dxs). Thule, in northwestern Greenland, exhibits low mean annual precipitation and strong seasonal variation in precipitation δ18O and dxs, with modest increases in monthly total precipitation in July and August corresponding to 18O-enriched and low dxs precipitation. In contrast, Kangilinnguit, in southwestern Greenland, receives significantly more annual precipitation than Thule, but demonstrates negligible seasonal variation in precipitation δ18O and only moderate seasonal variation in dxs. We hypothesize that the seasonal cycle of moisture sources is the primary cause of the observed gradient of seasonality of precipitation δ18O and dxs along the western Greenland coast. We test this hypothesis through the analysis of instrumental records from several Danish Meteorological Institute stations and ECMWF reanalysis data spanning the late 20th and early 21st centuries. We investigate (1) the sensitivity of precipitation amount, δ18O and d-excess to sea surface temperatures and sea ice extents in Baffin Bay and the Labrador Sea, (2) correlations between precipitation amount, δ18O and d-excess and large-scale modes of atmospheric variability, and (3) the primary moisture sources for these two sites and their seasonality with HYSPLIT back trajectory modeling. Evaluation of historical variability in precipitation amount and source regions in relation to ocean, atmosphere, and sea ice variability in an area with distinct gradients in precipitation δ18O will improve constraints on the regional importance of mechanisms projected to drive future changes, and aid in the interpretation of these signals from paleo-records of precipitation isotopes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP21F1477C
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSESDE: 1041 Stable isotope geochemistry;
- GEOCHEMISTRYDE: 1655 Water cycles;
- GLOBAL CHANGEDE: 1833 Hydroclimatology;
- HYDROLOGY