What causes the Pacific decadal oscillation?

[pitot-tube]

What causes the Pacific decadal oscillation in which a large part of the pacific ocean gets hotter than normal - this effect superimposes itself on El Nino.Is the pacific decadal oscillation linked to El Nino - does one cause the other?

 

[reasonmclucus]

What causes the Pacific decadal oscillation in which a large part of the pacific ocean gets hotter than normal - this effect superimposes itself on El Nino.Is the pacific decadal oscillation linked to El Nino - does one cause the other?

At this point the cause is unknown. The terms tends to be used for the North Pacific with the El Nino Southern Oscillation being used for the South Pacific. The PDO is a longer (possibly 20 years) cycle than the ENSO (6 to 18 months) but the ENSO can have periods in which either El Nino (warmer water) or la Nina (cooler water). Both cycles were noticed by fishermen before oceanographers or climatologists took notice.

The warm cycle of the PDO may tend to favor El Nino events with the cool cycle favoring la Nina events. There is a good correlation between these cycles and air temperatures.
http://icecap.us/images/uploads/THE_GREAT_PACIFIC_CLIMATE_SHIFT_II.pdf

the period since the late 70's has been dominated by El Nino events and warmer temperatures. the previous period with la Nina events was cooler. Some climatologists speculate that the current la Nina may indicate the beginning of a period of cooler temperatures.

 

[quicknote]

The Pacific decadal oscillation (PDO) is a long-term climate pattern that affects the temperature of the Pacific Ocean. It is characterized by periods of warmer and cooler sea surface temperatures in the North Pacific, which can last for 20-30 years. The PDO is caused by a combination of factors, including changes in ocean currents, atmospheric circulation patterns, and interactions between the ocean and atmosphere.

One of the main drivers of the PDO is the variation in ocean currents, particularly the strength and direction of the North Pacific Gyre. This gyre is a large circular current that moves water from east to west in the North Pacific. When the gyre is stronger, it brings warmer water from the tropics into the North Pacific, leading to a positive PDO phase (warmer temperatures). Conversely, when the gyre is weaker, it allows colder water from the Arctic to flow southward, resulting in a negative PDO phase (cooler temperatures).

Another factor that influences the PDO is changes in atmospheric circulation patterns. The PDO is closely linked to the Aleutian Low, a semi-permanent low-pressure system that sits in the North Pacific. During a positive PDO phase, the Aleutian Low is stronger, which leads to warmer temperatures in the North Pacific. In a negative PDO phase, the Aleutian Low is weaker, resulting in cooler temperatures.

The PDO can also interact with other climate patterns, such as El Nino. El Nino is a short-term climate pattern that occurs in the tropical Pacific and is characterized by warmer sea surface temperatures. When El Nino occurs at the same time as a positive PDO phase, the two effects can combine, resulting in even warmer temperatures in the North Pacific. However, the PDO and El Nino are not directly linked, and one does not cause the other. They can occur simultaneously, but they are driven by different mechanisms.

In summary, the Pacific decadal oscillation is caused by a combination of factors, including changes in ocean currents, atmospheric circulation patterns, and interactions with other climate patterns such as El Nino. It is a natural climate cycle that can have significant impacts on regional and global weather patterns.