Time history of the Pacific Decadal Oscillation (solid line) as defined by the leading principle component SST anomalies north of 20° latitude. The data have had global mean temperature anomalies subtracted to minimize any potential long-term or anthropogenic trend and then passed through a 13-point moving average filter. The Aleutian Low Pressure Index (dotted line) is defined as the winter-time (Jan-Mar) spatial anomaly (in 10E6 km2) of the <1005mb region relative to the 1950-1997 average of 5.63E6 km2. Image courtesy of Exploring Alaska's Seamounts 2002, NOAA/OER.
