UC Berkeley

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 (T_min), 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 T_min, ice cover, and continental-scale atmospheric circulation patterns (r ≥ 0.65, P < 0.001).