Quantitative assessments of moisture sources and temperature governing rainfall δ18O from 20 years' monitoring records in SW-France: Importance for isotopic-based climate reconstructions

[摘要] In the mid-high latitude region, variations of stable isotopic compositions of atmospheric precipitation (delta O-18(p) and delta D-p) were commonly regarded as reflecting the temperature effect. However, some studies have indicated that changes in moisture sources are important controlling factors for delta(18)Op. To clarify whether there are connections between delta(18)Op and variations of moisture sources in Southwest France (SW-France), whose implications for speleothem delta O-18(p) are of great importance, we have used among the longest isotopic time-series from SW-France (Le Mas and Villars stations) and a 5 days' reconstruction of air mass history during the 1997-2016 A.D period based on the HYSPLIT tracking model. We found the percentage of initial moisture sources (PIMS) as important factors controlling the oxygen isotope composition of precipitation in SW-France, whether monthly or inter-annual timescale was considered. Additionally, we observed that the delta O-18(p) preserved the signal of local temperature, supporting the temperature effect, while no evidence for its amount effect has been observed. These quantified links between PIMS/local-temperature and delta O-18(p) appear useful references to understand the link between stable oxygen isotopes and climate parameters. Our long-term monitoring of delta O-18(p) , d-excess, and moisture sources reveals decadal trends, highlighting a tight coupling in hydrologic systems and relatively fast changes on rainfall sources controlled by atmospheric circulations in SW-France.

[发布日期] 2020-12-01

[关键词] Rainfall;Isotope ratios;HYSPLIT model;Moisture Sources;Temperature;Southwest France