Spatial patterns in the oxygen isotope composition of daily rainfall in the British Isles
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Understanding the modern day relationship between climate and the oxygen isotopic composition of precipitation (δ18OP) is crucial for obtaining rigorous palaeoclimate reconstructions from a variety of archives. To date, the majority of empirical studies into the meteorological controls over δ18OP rely upon daily, event scale, or monthly time series from individual locations, resulting in uncertainties concerning the representativeness of statistical models and the mechanisms behind those relationships. Here, we take an alternative approach by analysing daily patterns in δ18OP from multiple stations across the British Isles (n = 10–70 stations). We use these data to examine the spatial and seasonal heterogeneity of regression statistics between δ18OP and common predictors (temperature, precipitation amount and the North Atlantic Oscillation index; NAO). Temperature and NAO are poor predictors of daily δ18OP in the British Isles, exhibiting weak and/or inconsistent effects both spatially and between seasons. By contrast δ18OP and rainfall amount consistently correlate at most locations, and for all months analysed, with spatial and temporal variability in the regression coefficients. The maps also allow comparison with daily synoptic weather types, and suggest characteristic δ18OP patterns, particularly associated with Cylonic Lamb Weather Types. Mapping daily δ18OP across the British Isles therefore provides a more coherent picture of the patterns in δ18OP, which will ultimately lead to a better understanding of the climatic controls. These observations are another step forward towards developing a more detailed, mechanistic framework for interpreting stable isotopes in rainfall as a palaeoclimate and hydrological tracer.
KeywordsOxygen isotopes Amount effect NAO British Isles
This research is heavily indebted to the voluntary weather monitors affiliated with the U.K. Met Office and the Climate Observers Link, whose enthusiasm and diligence in collecting daily rainfall samples was central to the conduct of this study—thank you. In particular we thank Sarah Dunn, Ruth Brookshaw, Mike Cinderey, Mike Chalton, John Walker, Jane Corey, David King, Kirsty Murfitt, Richard Griffith, Margaret Airy, Donald Perkins, Malham Tarn FSC Field Centre Staff, Eric Gilbert, Roland Bol, George Darling and Martin Rowley. We thank Joseph Bailey for assistance in producing one of the figures and Bronwyn Dixon for her advice on HYSPLIT modelling. The research was supported by the U.K. Natural Environment Research Council (NERC) through a Fellowship (NE/F014708/1) to JJT. MJ thanks the School of Geography, Planning and Environmental Management at the University of Queensland for a Visiting Fellowship during which some of this manuscript was written. Three anonymous reviewers and the editor Jean Claude Duplessey are thanked for their insightful comments on an earlier draft of this manuscript.
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