Coherency of multi-scale abrupt changes between the NAO, NPI, and PDO

[1] A scanning t-test and coherency detection algorithm is used to analyze and detect multi-scale abrupt changes in three climate indices; the NAO (North Atlantic Oscillation), PDO (Pacific Decadal Oscillation), and NPI (North Pacific Index). The analysis suggests that decadal fluctuations in atmospheric and ocean circulation are linked between the Atlantic and Pacific Ocean regions. The NPI and PDO are negatively correlated on decadal scales, with change points in about 1915, 1924, 1942, 1961, 1976, and 1988. The longer NAO also displays significant change points around these dates, as well as in 1832, 1865, 1870, and 1881. Decadal changes in the NAO and NPI (PDO) were positively (negatively) correlated prior to the late 1950s, but negatively (positively) correlated during 1962-1988. Although the north Atlantic and north Pacific atmosphere is teleconnected on decadal scales, the change after 1961 suggests it has multiple spatial modes.