Late Holocene climate of coastal Labrador: subseasonal evidence from stable isotope values of tree-rings

English Abstract:

Three centuries of subannual/annual climate data were retrieved from the δ¹⁸O and δ¹³C values of tree-ring cellulose in the temperature-sensitive region of central-coastal Labrador, Canada, situated near the northernmost boundary of the boreal forest. A large cookie of a white spruce (Picea glauca) tree was micromilled using a custom-made computer-controlled micromilling device to retrieve multiple samples per year and/or early and late wood that were subsequently analyzed for δ¹⁸O_cellulose and δ¹³C_cellulose values. The coastal Labrador/Nunatsiavut region is a climatically dynamic region that is significantly influenced by ocean-atmosphere interactions and thus has exceptional potential for studying both, terrestrial and marine climate variability, and their interactions. δ¹⁸O_cellulose values were calibrated to the mean-annual temperature (°C), while δ¹³C_cellulose values were interpreted to represent long-term water budgets. We found a good agreement between reconstructed mean-annual temperatures and major climatic trends and events, including multidecadal warm and cold climate episodes, historical meteorological measurements collected by the Moravian missionaries, modern mean-annual temperatures and salinity anomalies in the NW North Atlantic Ocean, as well as cooling trends induced by major volcanic eruptions such as Lakagígar in 1783-84, Tambora in 1815, and Krakatoa in 1883. Persistent cold intervals are found from 1790 to 1810, 1875 to 1895, and 1950 to 1970, while the warmest intervals are found during the mid-18^th and 19^th centuries. A sharp increase in Suess corrected δ¹³C_cellulose values since the 1960s is possibly related to moisture stress induced by the persistent positive North Atlantic Oscillation (NAO) phase. Moreover, continuous transform wavelet analysis was used to analyze δ¹⁸O_cellulose and δ¹³C_cellulose periodicities and suggest that their interannual and multidecadal periodicities are similar to those of the NAO.