Abstract
Abstract. For the first time, this article presents a large dataset of precipitation isotopic measurements (δ18Op and δ2Hp) sampled every day or 2 d from seven sites on a west-to-east transect across northern Spain for 2010–2017. The main aim of this study is to (1) characterize the rainfall isotopic variability in northern Spain at daily and monthly timescales and (2) assess the principal factors influencing rainfall isotopic variability. The relative role of air temperature and rainfall in determining the stable isotope composition of precipitation changes along the west-to-east transect, with air temperature being highly correlated with δ18Op at daily and monthly timescales, while a few sites along the transect show a significant negative correlation with precipitation. The highest air temperature–δ18Op dependency is found for a station located in the Pyrenees. Frontal systems associated with North Atlantic cyclones are the dominant mechanism inducing precipitation in this region, particularly in winter. This study allows an exploration of the role of air mass source and trajectory in determining the isotopic composition of rainfall in northern Iberia by characterizing the moisture uptake for three of the seven stations. The importance of continental versus marine moisture sources is evident, with clear seasonal and spatial variations. In addition, the type of precipitation (convective versus frontal rainfall) plays a key role, with convective rainfall associated with higher δ18Op values. This comprehensive spatiotemporal approach to analyzing the rainfall isotopic composition represents another step forward towards developing a more detailed, mechanistic framework for interpreting stable isotopes in rainfall as a paleoclimate and hydrological tracer.
Highlights
The oxygen isotopic composition of rainfall (δ18Op) is often considered the dominant influence on the isotopic composition of terrestrial archives used to reconstruct past climate (e.g., Leng, 2006)
The Mallorca and Barcelona samples and the remaining samples from Ortigosa de Cameros (50 samples) were analyzed at the Scientific and Technological Centre at the University of Barcelona, δ2H via a thermal conversion elemental analyzer (TCEA) for pyrolysis coupled to a Thermo Delta Plus XP mass spectrometer, and δ18O with a MAT 253 Thermo Fisher spectrometer coupled with a gas bench
Our results suggest that this similarity between the two stations located at the western and eastern ends of the northern Iberian Peninsula (IP) is due, firstly, to the initial condensate of water vapor generated over the North Atlantic and, secondly, to the influence of air masses originating in the Mediterranean Sea, together with the much warmer temperatures there than at the other three sites
Summary
The oxygen isotopic composition of rainfall (δ18Op) is often considered the dominant influence on the isotopic composition of terrestrial archives (ice cores, speleothems or authigenic lacustrine carbonates) used to reconstruct past climate (e.g., Leng, 2006). Few paleoclimate reconstructions are supported by an in-depth understanding of the regional climatic controls on δ18Op (e.g., Treble et al, 2005). It has long been established that δ18Op is an integrated product of air mass history modulated by specific prevailing meteorological conditions, in particular air temperature and amount of precipitation (Craig, 1961; Dansgaard, 1964). This implies that several dominant factors may control δ18Op variability depending on the site location, i.e., latitude, continentality, elevation, seasonal distribution, local air temperature, and the amount and source of precipitation (Rozanski et al, 1993). A detailed study of current δ18Op values and their variability in a given region is essential to reconstructing past climate changes using δ18O in regional climate archives (Lachniet, 2009)
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