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Meeting Minutes

All about the Pacific Decadal Oscillation (PDO)

Sept 12th, 2012

Dr. Nate Mantua
University of Washington

Intro Presentation.pptx

On Wednesday, September 12th 2012, approximately 70 Oregon AMS members and guests descended on OMSI in Portland for the opening meeting of the 2012/13 Oregon AMS season. President Steve Pierce welcomed members and guests back for another season of great Oregon AMS meetings. Pierce opened the meeting with a reminder that Oregon AMS dues are now due for the 2012/13 season. Pierce also explained the reasoning behind the executive council approved increase in dues from $7 to $10 per year. See: http://www.ametsoc.org/chapters/oregon/Blogs/2012/2012_9_6_MembershipDueUpdate.html. Pierce also detailed the next two Oregon AMS meetings coming in October and November. For complete details on both of these meetings please see: http://www.ametsoc.org/chapters/oregon/meetings.html. On this evening, special guest speaker Dr. Nate Mantua (University of Washington) gave a detailed presentation on the Pacific Decadal Oscillation (PDO). The synopsis of this lecture comes from Dr. Mantua himself... 

Different aspects of the Pacific Decadal Oscillation were identified by researchers working primarily in climate and fisheries, with a notable multi-authored report of a 1977 climate and ecosystem shift in the Pacific Northwest summarized in a 1991 news article that appeared in the journal Science. Six years later Steven Hare, a phD student in fisheries at the University of Washington at the time, put a name to this phenomenon. The PDO has been associated with extended cool-wet periods in northwest climate from the late 1940s to 1976, and again for the periods 1999-2002 and 2008-present. Warm periods of the PDO were recorded from the mid-20s to mid-40s, from 1977-1998, and from 2003-2007. Variations in the PDO have been associated with major changes in ocean ecosystems from Alaska to California, snowpack and streamflows in northwestern North America, and changes in forest ecosystems along the Pacific coast of North America. The PDO pattern in North Pacific ocean temperatures is primarily driven by variations in the Aleutian Low atmospheric pressure pattern, which itself varies in part due to changes in the El Nino Southern Oscillation. Recent research suggests that the PDO pattern varies across a wide range of time frames with no preferred period of variation, and its predictability is limited to 1 or 2 years into the future. A simple forecast model for the PDO is based on its tendency to persist from one year to the next, and for ENSO variations to "push" the PDO in either one direction or another. For the coming year, this simple model suggests the PDO pattern will remain in its negative state for another year, more negative if we don't have an El Nino in the tropics this winter, and less negative if we do. 

For more information about the PDO and links to data and figures, see http://jisao.washington.edu/pdo.

Click here for Dr. Nate Mantua presentation (pdf)
Click here to watch the meeting on video via youtube, courtsey of Erik Holm

Microsoft Powerpoint (.pps file extension) viewer download (click here)