Tree-ring reconstructed temperature index for coastal northern Japan: Implications for western North Pacific variability

While paleoclimatic studies have extended our understanding of North Pacific climate variability, these have been almost exclusively based on proxies from western North America. We present a tree-ring reconstruction of June to September coastal air temperatures for Nemuro, northeastern Japan for the past four centuries. It explains 36% of the variance in instrumental temperatures and correlates significantly with indices of the atmosphere-ocean circulation. Spectral analyses reveal robust bidecadal peaks that appear associated with regional modes of western North Pacific variability. At decadal time scales, Nemuro temperatures appear to be influenced by the confluence of the Kuroshio and Oyashio currents, a primary centre of action driving Pacific Decadal Variability. Regime shifts (e.g. 1976) are weakly expressed relative to western North America. These aspects of western North Pacific climate are regionally distinct relative to those elsewhere in the basin, with greater complexity than can be attributed to the Pacific Decadal Oscillation (PDO) alone.