The
Pacific decadal oscillation (PDO) is a pattern of Pacific
climate variabilityClimate variability on earth arises from solar variations, albedo changes, volcanic activity, changes in cloud cover, jet stream patterns, changes in the earth's orbit around the sun, ocean circulation, tectonic changes, and greenhouse gas levels. Over the earth's history in geologic time there...
that shifts phases on at least inter-decadal time scale, usually about 20 to 30 years. The PDO is detected as warm or cool surface waters in the
Pacific OceanThe Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Tepre Pacificum, "peaceful sea", bestowed upon it by the Portuguese explorer Ferdinand Magellan. It extends from the Arctic in the north to Antarctica in the south, bounded by Asia and...
, north of 20° N. During a "warm", or "positive", phase, the west Pacific becomes cool and part of the eastern ocean warms; during a "cool" or "negative" phase, the opposite pattern occurs.
The Pacific (inter-)decadal oscillation was named by Steven R.
The
Pacific decadal oscillation (PDO) is a pattern of Pacific
climate variabilityClimate variability on earth arises from solar variations, albedo changes, volcanic activity, changes in cloud cover, jet stream patterns, changes in the earth's orbit around the sun, ocean circulation, tectonic changes, and greenhouse gas levels. Over the earth's history in geologic time there...
that shifts phases on at least inter-decadal time scale, usually about 20 to 30 years. The PDO is detected as warm or cool surface waters in the
Pacific OceanThe Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Tepre Pacificum, "peaceful sea", bestowed upon it by the Portuguese explorer Ferdinand Magellan. It extends from the Arctic in the north to Antarctica in the south, bounded by Asia and...
, north of 20° N. During a "warm", or "positive", phase, the west Pacific becomes cool and part of the eastern ocean warms; during a "cool" or "negative" phase, the opposite pattern occurs.
The Pacific (inter-)decadal oscillation was named by Steven R. Hare, who noticed it while studying
salmonSalmon is the common name for several species of fish of the family Salmonidae. Several other fish in the family are called trout; the difference is often attributed to the migratory life of the salmon as compared to the residential behaviour of trout, a distinction that holds true for the Salmo...
production patterns. Professor Don J. Easterbrook of Western Washington University, in the face of strong criticism until recent temperature-related events vindicated his science, has been the leading international expert on the "cooling trend" due to the PDO. The two groups described the patterns in 1997.
The mechanism by which the pattern lasts over several years has not been identified; one suggestion is that a thin layer of warm water during summer may shield deeper cold waters. A PDO signal has been reconstructed to 1661 through tree-ring chronologies in the
Baja CaliforniaBaja California is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North Territory of Baja California. It has an area of , or 3.57% of the land mass of Mexico and comprises the northern half of the Baja California peninsula, north...
area.
The
interdecadal Pacific oscillation (IPO or ID) display similar sea-surface temperature (SST) and sea-level pressure (SLP) patterns, with a cycle of 15–30 years, but affects both the north and south Pacific. In the tropical Pacific, maximum SST anomalies are found away from the equator. This is quite different from the quasi-decadal oscillation (QDO) with a period of 8-to-12 years and maximum SST anomalies straddling the equator, thus resembling the
El Niño-Southern OscillationEl Niño-Southern Oscillation is a periodic change in the atmosphere and ocean of the tropical Pacific region. It is defined in the atmosphere by the sign of the pressure difference between Tahiti and Darwin, Australia, and in the ocean by warming or cooling of surface waters of the tropical central...
(ENSO).
Regime shifts
Although there are several patterns of behavior, the most significant one seems to be in
regime shifts between "warm" and "cool" patterns which last 20 to 30 years.
- 1750: PDO displays an unusually strong oscillation.
- 1905: After a strong swing, PDO changed to a "warm" phase.
- 1946: PDO changed to a "cool" phase. [See the blue section of the graph on the right]
- 1977: PDO changed to a "warm" phase.
- 1998: PDO index showed several years of "cool" values, but did not remain in that pattern.
- 2008: The early stages of a cool phase of the basin-wide Pacific Decadal Oscillation.
In all cases in the 1900s, PDO "regime shifts" were related to similar changes in the Tropical ocean.
Related patterns
- ENSO tends to lead PDO/IPO cycling.
- Shifts in the IPO change the location and strength of ENSO activity. The South Pacific Convergence Zone
The South Pacific Convergence Zone , a reverse-oriented monsoon trough, is a band of low-level convergence, cloudiness and precipitation extending from the west Pacific warm pool south-eastwards towards French Polynesia...
moves northeast during El Niño and southwest during La Niña events. The same movement takes place during positive IPO and negative IPO phases respectively. (Folland et al., 2002)
- Interdecadal temperature variations in China
China is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
are closely related to those of the NAOThe North Atlantic oscillation is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea-level between the Icelandic Low and the Azores high. Through east-west oscillation motions of the Icelandic Low and the Azores high, it controls the...
and the NPO.
- The amplitudes of the NAO
The North Atlantic oscillation is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea-level between the Icelandic Low and the Azores high. Through east-west oscillation motions of the Icelandic Low and the Azores high, it controls the...
and NPO increased in the 1960s and interannual variation patterns changed from 3–4 years to 8–15 years.
- Sea level rise is affected when large areas of water warm and expand, or cool and contract.
Further reading
}}
- Steven R. Hare and Nathan J. Mantua, 2001. An historical narrative on the Pacific Decadal Oscillation, interdecadal climate variability and ecosystem impacts, Report of a talk presented at the 20th NE Pacific Pink and Chum workshop, Seattle, WA, 22 March 2001. http://www.iphc.washington.edu/Staff/hare/html/papers/pcworkshop/pcworkshop.pdf
- Nathan J. Mantua and Steven R. Hare, 2002. The Pacific Decadal Oscillation, Journal of Oceanography, Vol. 58, p. 35–44. http://jisao.washington.edu/PNWimpacts/Publications/Pub166.pdf
- Kevin Ho, 2005. Salmon-omics: Effect of Pacific Decadal Oscillation on Alaskan Chinook Harvests and Market Price. Columbia University. http://www.columbia.edu/~kjh2103/Salmon-omics-PDO.pdf