Spatial variability in stable isotope values of surface waters of Eastern Canada and New England

Abstract

• We map distribution of δ 18 O and δD values of surface waters in Eastern Canada/USA. • We assess spatial/temporal variability in δ 18 O and δD of precipitation in E Canada. • Significant agreement between precipitation and surface water δ 18 O/δD values exist. • Winter precipitation dominates recharge, evaporation is important in inland Labrador. • We provide basis/calibration for future paleoenvironmental research in this area. A total of 294 surface water samples were collected in Eastern Canada and the New England states of the USA in 2007, 2009, 2011, and 2013 and analyzed for δ 18 O and δD values to investigate climatic controls on hydrology and to test whether isotope values of surface waters can provide a suitable calibration for evaluation of paleoenvironmental proxy data in this region. Results demonstrate that surface waters in this region exhibit latitudinal gradients, with some overprinting by regional trends. Surface water δ 18 O and δD values range from −2.8‰ to −16.0‰, and from −23.8‰ to −118.5‰, respectively. Regression of all δ 18 O and δD values yields a surface water line (SWL) (δD = 7.53(±0.11)δ 18 O + 3.81(±1.12); r 2 = 0.95; n = 294), similar to slopes of 7.63(±0.06) and 7.96(±0.1) based on monthly and annual precipitation amount-weighted means for GNIP/CNIP stations in this study area. At smaller spatial scales evaporation and greater water residence time generate lake SWL with lower slope (7.50) than river SWL (7.80). At greater spatial scales, δ 18 O and δD values of lakes and rivers show a more uniform distribution, thus reflecting the prevalence of regional over local hydrological effects. Contour maps of surface water δ 18 O and δD values exhibit more detail than existing global precipitation models and suggest (a) a progressive decrease in δ 18 O H2O and δD H2O values towards higher latitudes via Rayleigh distillation and (b) generally higher δ 18 O H2O and δD H2O values in Western Newfoundland likely due to its proximity to the ocean. Contour maps predict the average annual-amount weighted δ 18 O and δD values of precipitation provided by GNIP/CNIP networks fairly well. It was also determined that recycled moisture supplies a significant proportion of precipitation in the southern/western parts of our study area, while evaporation could be a more dominant factor for interior Labrador. In addition, a strong agreement is observed between temperature and precipitation/surface water δ 18 O and δD values, suggesting that δ 18 O and δD values of surface waters can provide a suitable template and aid for ongoing paleoenvironmental research in this region.