Pacific Decade Oscillation

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La Niña anomaly and PDO anomaly of sea surface temperatures in the period April 14-21, 2008
Course of the PDO between 1900 and today
Reconstructed PDO events since 1660 using tree ring chronologies from Southern California

The Pacific Decade Oscillation (abbreviation PDO; English pacific decadal oscillation ) describes an abrupt change in the surface temperature in the northern Pacific Ocean .

The phenomenon of the Pacific Decade Oscillation was recognized and named in 1996 by Steven Hare of the University of Washington . The arrangement of warm and cold water areas in the northern Pacific determined by the PDO determines the main flow direction of the jet stream and thus has long-term and significant effects on the weather.

Changes in the state of the PDO correlated with greater changes in the ecosystem of the northeastern Pacific: Warm phases resulted in higher biological productivity in the coastal regions of Alaska , but reduced productivity off the west coast of the USA . Cold phases showed an inverted north-south pattern with regard to the productivity of these marine ecosystems.

effect

The following climate anomalies in North America are associated with extreme phases of PDO:

Climate anomaly PDO warm phase PDO cold phase
Surface temperatures of the northeast and tropical Pacific ↗ Above average ↘ Below average
Air temperatures in Northwest America (October-March) ↗ Above average ↘ Below average
Air temperatures in the southeastern United States (October – March) ↘ Below average ↗ Above average
Rainfall in the south of the USA / north of Mexico (October-March) ↗ Above average ↘ Below average
Rainfall in Northwest North America and the Great Lakes (October – March) ↘ Below average ↗ Above average
Amount of snow in northwest North America in spring ↘ Below average ↗ Above average
Flooding risk on the northwestern Pacific coast in winter and spring ↘ Below average ↗ Above average

Independent studies suggest that there were only two complete PDO cycles in the past century: a cold PDO regime that lasted from 1890 to 1924 and from 1947 to 1976, whereas warm PDO regimes lasted from 1925 to 1946 and from 1977 to the mid-1990s. PDO fluctuations in the 20th century took place in two cycles: one had a duration of 15-25 years, the other a duration of 50-70 years. The greatest changes in the state of the PDO over a decade from 1706 to 1977 took place in 1750, 1905 and 1947. The pronounced bi-decadal oscillation of the PDO index was only visible in a weakened form from the late 18th to the middle of the 19th century.

The PDO differs significantly from the El Niño-Southern Oscillation (ENSO): PDO events lasted in the 20th century for a duration of 20 to 30 years, whereas ENSO events only lasted 6 to 18 months. On the other hand, PDO events are noticeable in the North Pacific region of America, with lesser effects in tropical regions. With the ENSO, however, it is exactly the opposite.

El Niño events can be weakened by a cold phase of the PDO, while La Niña events can be intensified. In 2008, a change in the PDO to a cold regime was noted, amplifying the effects of the existing La Niña.

It is not known which mechanisms are behind the PDO. Therefore, there is little predictability of this climate factor. Some climate models show PDO-like oscillations, but mostly for different reasons. The quality of decade-specific climate projections is determined by understanding the mechanism behind the PDO. But even without an exact theory, detailed knowledge of the PDO annual climate forecasts for the North America region improves, because a state usually lasts for many years. Alexander et al. (2008) were able to use a statistical model to predict the state of PDO over a period of up to 4 years with good results; the PDO forecasts issued by NOAA are created using this model.

The ability of the PDO to remain in one state for decades shows that “normal” climatic conditions can differ over a period of time that roughly corresponds to the length of a human life.

See also

Web links

Individual evidence

  1. ^ A b Franco Biondi, Alexander Gershunov, Daniel R. Cayan: North Pacific Decadal Climate Variability since 1661 . In: Journal of Climate . Volume 14, No. 1 , 2001, p. 5–10 , doi : 10.1175 / 1520-0442 (2001) 014 <0005: npdcvs> 2.0.co; 2 ( PDF file; 183 kB [accessed on May 24, 2013]).
  2. ^ Nathan J. Mantua et al .: A Pacific interdecadal climate oscillation with impacts on salmon production . In: Bulletin of the American Meteorological Society . Volume 78, No. 6 , 1997, pp. 1069-1079 , doi : 10.1175 / 1520-0477 (1997) 078 <1069: APICOW> 2.0.CO; 2 ( PDF file; 974 kB [accessed on May 24, 2013]). PDF file; 974 kB ( Memento of the original from January 12, 2012 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.atmos.washington.edu
  3. ↑ Mike Bettwy: Moody Pacific Unleashes Another Climate Mystery. NASA - Goddard Space Flight Center , April 15, 2004, archived from the original on March 15, 2013 ; accessed on May 24, 2013 .
  4. ^ Nathan J. Mantua, Steven R. Hare: The Pacific Decadal Oscillation . In: Journal of Oceanography . Volume 58, No. 1 , 2002, p. 35–44 , doi : 10.1023 / A: 1015820616384 ( PDF file; 440 kB [accessed on May 24, 2013]).
  5. ^ Nathan J. Mantua: The Pacific Decadal Oscillation and Climate Forecasting for North America. Joint Institute for the Study of the Atmosphere and Oceans, 1999, archived from the original on March 10, 2013 ; accessed on May 24, 2013 .
  6. ↑ a b c d Joint Institute for the Study of the Atmosphere and Ocean: The Pacific Decadal Oscillation (PDO). University of Washington , 2000, archived from the original on February 8, 2006 ; accessed on May 24, 2013 .
  7. ^ Alan Buis: Larger Pacific Climate Event Helps Current La Nina Linger. NASA / Caltech - Jet Propulsion Laboratory , April 21, 2008, archived from the original on October 17, 2012 ; accessed on May 24, 2013 .
  8. ↑ Michael A. Alexander et al .: Forecasting Pacific SSTs: Linear Inverse Model Predictions of the PDO . In: Journal of Climate . Volume 21, No. 2 , 2008, p. 385–402 , doi : 10.1175 / 2007JCLI1849.1 ( PDF file; 2.28 MB [accessed May 24, 2013]).
  9. ↑ Climate Diagnostics Center and Physical Science Division: Linear Inverse Modeling Tropical SST Anomalies Forecast. CIRES / ESRL / NOAA , archived from the original on February 19, 2013 ; accessed on May 24, 2013 .