A possible paleoclimatic ENSO indicator in the spatial variation of annual tree‐ring ¹⁴C

Preliminary investigations show regional differences in atmospheric ¹⁴C activity archived in tree‐ring cellulose may reflect oceanic and atmospheric shifts associated with ENSO (El Niño‐Southern Oscillation) events. Much of the shared variation between sites in Washington and Arizona can be attributed to global forcings such as anthropogenic ¹⁴C‐depleted CO₂ emissions and modulation of ¹⁴C production. The contrasted residual variation between the Washington and Arizona data sets correlates with the annual Southern Oscillation Index (SOI) of the previous year. The spatial differences between Δ¹⁴C data sets may provide a proxy indicator of ENSO phenomenon.