A 50-70 year climatic oscillation over the North Pacific and North America

The chronology of interdecadal climatic regime shifts is examined, using instrumental data over the North Pacific, North America and the tropical oceans, and reconstructed climate records for North America, In the North Pacific and North America, climatic regime shifts around 1890 and in the 1920s with alternating polarities are detected, whose spatial structure is similar to that of the previously-known climatic shifts observed in the 1940s and 1970s. Sea-surface temperatures in the tropical Indian Ocean-maritime continent region exhibit changes corresponding to these four shifts. Spectra obtained by the Multi-Taper-Method suggest that these regime shifts are associated with 50-70 year climate variability over the North Pacific and North America. The leading mode of the empirical orthogonal functions of the air-temperature reconstructed from tree-rings in North America exhibits a spatial distribution that is reminiscent of instrumentally observed air-temperature differences associated with the regime shifts. The temporal evolution of this mode is characterized by a 50-70 year oscillation in the eighteenth and nineteenth centuries. This result, combined with the results of the analyses of the instrumental data, indicates that the 50-70 year oscillation is prevalent from the eighteenth century to the present in North America.