Abstract
Tree-ring carbon isotope discrimination (Δ13C) and oxygen isotopes (δ18O) collected from white pine (Pinus strobus) trees adjacent to Lake Superior show potential to produce the first winter-specific paleoclimate reconstruction with inter-annual resolution for this region. Isotopic signatures from 1976 to 2015 were strongly linked to antecedent winter minimum temperatures (Tmin), Lake Superior peak ice cover, and regional to continental-scale atmospheric winter pressure variability including the North American Dipole. The immense thermal inertia of Lake Superior underlies the unique connection between winter conditions and tree-ring Δ13C and δ18O signals from the following growing season in trees located near the lake. By combining these signals, we demonstrate feasibility to reconstruct variability in Tmin, ice cover, and continental-scale atmospheric circulation patterns (r ≥ 0.65, P < 0.001).
Highlights
Trees growing in cold environments do not directly record winter conditions in their tree-rings because they are dormant during this period
White pine tree-ring δ18O and Δ13C chronologies were characterized by series inter-correlation of 0.76 and 0.54, respectively, while expressed population signals[42] were 0.94, and 0.85, respectively
Our results provide evidence that tree-ring Δ13C and δ18O of white pines growing adjacent to Lake Superior show potential to provide novel proxy records of winter temperature anomalies with inter-annual resolution
Summary
Trees growing in cold environments do not directly record winter conditions in their tree-rings because they are dormant during this period. Due to the strong variability in Lake Superior water temperatures, we hypothesized that by sampling stable isotope signals fixed in cellulose during the spring and early summer, trees will have recorded winter season conditions rather than growing season conditions as have been demonstrated in other coastal locations. We test this hypothesis using tree-ring carbon and oxygen isotopes collected from white pines (Pinus strobus L.) growing 2.3 km distance from the Lake Superior shoreline, at a location where strong summer lake-effect air temperature gradients have been documented using a high-density network of temperature sensors[26]
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