STABLE ISOTOPES IN MODERN IRISH SURFACE WATERS: A BASIS FOR PALEOCLIMATE INVESTIGATIONS OF IRELAND

We present the spatial distribution of δ¹⁸O and δD values in fresh surface waters from 144 lakes and rivers in Ireland. Samples were collected during a three-week period in June and July of 2003. Spatial variations in modern meteoric waters give insight into climatic parameters as sources of precipitation, transport, recycling of water, and residence times of water bodies. δ¹⁸O values range from –7.4 to –2.4‰ VSMOW, averaging –5.4‰, while δD values range from –53 to –17‰ and average –37‰. The Local Surface Water Line (LSWL) is characterized as δD=6.24 · δ¹⁸O – 2.93 (R²=0.89). The slope is lower than the Global Meteoric Water Line (GMWL) because these samples are surface waters rather than precipitation samples, thus affected by evaporation that results in values plotting with slopes lower than the GMWL. Samples were also plotted geographically and isotope contour maps were generated of δD, δ¹⁸O, and d-excess showing several pronounced trends due to water recycling and prevailing wind direction. We do not see a strong correlation between altitude of the collection site and isotopic values of surface waters. We sampled 31 lakes and rivers within the Burren region of County Clare due to the abundance of marl lakes and climate research underway in this region. The effects of evapotranspiration are evaluated to describe the nature of water recycling in Ireland. The short duration of sampling in this project provides a snapshot of modern isotope variability to be applied towards long-term lacustrine sediment-based climate change research in Ireland and provide a basis of comparison for other proxy records. Characterization and interpretation of isotope values of modern surface waters are crucial to a better understanding of how climatic parameters relate to paleoclimate records of lake carbonates.