An investigation of the controls on Irish precipitation δ18O values on monthly and event timescales

This two-year study investigates the relative influence of meteorological variables (precipitation amount and temperature), atmospheric circulation, air mass history, and moisture source region on Irish precipitation oxygen isotopes (delta O-18(p)) on event and monthly timescales. Single predictor correlations reveal that on the event scale, 20% of delta O-18(p) variability is attributable to the amount effect and 7% to the temperature effect while on the monthly timescale the North Atlantic Oscillation accounts for up to 20% of delta O-18(p) variability and the amount and temperature effects are not significant. In comparison, multivariate linear regression reveals that the interaction of temperature and precipitation amount explains up to 40% of delta O-18(p) variance at event and monthly timescales. Five-day kinematic back trajectories suggest that the amount-weighted mean delta O-18(p) value of southerly- and northerly-derived events are lower by 2aEuro degrees relative to events derived from the west. Because air mass history and atmospheric circulation appear to influence delta O-18(p) in Ireland, Irish paleo-delta O-18(p) proxy records are best interpreted as reflecting a combination of parameters, not just paleotemperature or paleorainfall.