Multiple stable isotopes from oak trees in southwestern Scotland and the potential for stable isotope dendroclimatology in maritime climatic regions

Across much of Europe, Eurasia and N. America there exist networks of long tree-ring chronologies which, under favourable circumstances, may be used to provide a record of palaeoclimate information. A proportion of these tree-ring archives, primarily those collected for archaeological dating purposes, represent a significant and largely untapped palaeoenvironmental archive. Such records may be unsuitable for palaeoclimatic reconstruction based solely upon their physical characteristics (ring width and density) owing to weak or poorly expressed climatic forcing. This is especially true of oak chronologies from maritime regions. This study explores the potential for extracting a climate signal from such chronologies by comparing the stable isotope ratios of C, H and O from the rings of common oak (Quercus robur) trees in southwestern Scotland, with local and regional meteorological data. Summer (growing season) climate influences all three isotopes and the relationships identified are consistent with published empirical and mechanistic studies. The climate signal appears strongest in O and weakest in H. The C and O series, in combination, explain 31% of the variance in July–August mean temperature measured locally and 26% when compared with a homogenised gridded dataset for the period AD1957-2002. Over longer timescales the combination of C and O isotopes may also preserve a significant low-frequency signal (July–August r2 = 0.57, 9-year running mean AD1879–1998). These findings demonstrate the potential of stable isotope dendroclimatology for investigating climatic change from oak chronologies in maritime regions.