what causes the pacific decadal oscillation

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Where does Pacific decadal oscillation occur?

the Pacific OceanThe Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N.

What is Pacific decadal oscillation in simple terms?

The Pacific Decadal Oscillation (PDO) is a long-term ocean fluctuation of the Pacific Ocean. The PDO waxes and wanes approximately every 20 to 30 years. From ocean surface topography data, together with other ocean and atmospheric data, scientists can determine whether we are in a 'cool' phase or a 'warm' phase.

What is Pacific decadal variability?

The natural internal variability at decadal-to-multidecadal timescales in the Pacific Ocean is termed as the Pacific decadal variability, which is generally referred as the PDO (Mantua et al., 1997) for the North Pacific pattern, or the IPO (Power et al., 1998, 1999; Folland et al., 1999; Allan, 2000) for the basin- ...

What is the Pacific decadal oscillation quizlet?

Pacific Decadal Oscillation; Pattern in climate that reverses on a 20-30 year timescale and is dominant in the North Pacific; a positive phase associated with cooler water in the Northwest Pacific, Strongly Correlated with salmon returns due to impact on Upwelling. IPCC. Intergovernmental panel on Climate Change.

What phase is the Pacific decadal oscillation?

negative phaseAs of July, 2022 the Pacific decadal oscillation is in a negative phase with the index reaching approximately -1.1. The negative phase started in late 2019 and reached its nadir in late 2021 with an index value of approximately -2.9. So the PDO has been in a negative phase for about 2.5 years.

Is the PDO real?

PDO stands for polydioxanone, a dissolvable material that's commonly used in surgical sutures. You may also see face threading procedures marketed as a “sugar lift,” since PDO threads are made from long chains of polysaccharide (aka sugar). Some threads also have tiny barbs or cones that help them attach to the tissue.

How is the Pacific decadal oscillation calculated?

The PDO Index is calculated by spatially averaging the monthly sea surface temperature (SST) of the Pacific Ocean north of 20°N. The global average anomaly is then subtracted to account for global warming (Mantua, 2000).

What is the difference between ENSO and PDO?

While the ENSO is related to the interconnections between ocean and atmosphere in the tropical eastern Pacific, the PDO is a combination of different physical processes operating on different time scales, including remote tropical forcing (ENSO), oceanic thermal inertia, and atmospheric forcing in response to the ...

How is PDO calculated?

PDO is the sum of a team's 5v5 shooting percentage (the number of goals they score divided by the number of shots on goal they generate) and their 5v5 save percentage (the number of shots their goalies stop divided by the number of shots on goal they allow).

What ocean oscillations have an influence on weather and climate?

El Niño is a warming of surface waters in the eastern tropical Pacific Ocean. Together with, La Niña, these make up two of the three states of the constantly changing El Niño/Southern Oscillation (ENSO) that can affect weather patterns around the globe.

What happens to the Aleutian low during a PDO warm phase quizlet?

During a PDO warm phase, the Aleutian low is well developed and its strong counterclockwise winds steer mild and relatively dry air masses into the Pacific Northwest.

How does the Pacific decadal oscillation affect climate?

It is thought that negative phases could be linked to times of slower warming. This is because cold phases of the PDO tend to increase mixing of colder, deep ocean waters with warmer surface waters. This temporarily reduces the rate of global warming caused by increasing greenhouse gas emissions.

How do you calculate Pacific decadal oscillation?

The PDO Index is calculated by spatially averaging the monthly sea surface temperature (SST) of the Pacific Ocean north of 20°N. The global average anomaly is then subtracted to account for global warming (Mantua, 2000).

What is ENSO and PDO?

The El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) account for a large part of modern climate variability.

What does a negative PDO mean?

The Pacific Decadal Oscillation Alternatively, when the climate anomaly patterns are reversed, the PDO has a negative value and is thus in its cool phase. During a typical PDO cold mode, cool sea surface temperatures extend from the equator northward along the coast of North America into the Gulf of Alaska.

How often does the Pacific decadal oscillation occur?

The Pacific Decadal Oscillation (PDO) is a long-term ocean fluctuation of the Pacific Ocean. The PDO waxes and wanes approximately every 20 to 30 years. From ocean surface topography data, together with other ocean and atmospheric data, scientists can determine whether we are in a ‘cool’ phase or a ‘warm’ phase.

How does the change in location of the cold and warm water masses affect the jet stream?

A. The change in location of the cold and warm water masses alters the path of the jet stream. Put simply, the jet stream in the northern hemisphere delivers storms across the United States. The PDO phase that we appear to have entered will act to steer the jet stream further north over the Western United States.

What satellites measure the shape of the ocean?

Satellites such as Jason-3 and the upcoming Sentinel-6 Michael Frei lich measure the precise shape of the ocean's surface and how this surface changes through time. This helps scientists calculate ocean currents, identify climate trends, and improve weather forecasting models. A recently observed climate trend is the Pacific Decadal Oscillation.

What is the color of the water in the Pacific Ocean?

Image shows a horseshoe of higher than average (warm) water in western Pacific Ocean (red and white), and lower than average (cool) water in the eastern Pacific Ocean (blue and purple).

When was the last phase shift of PDO?

The last PDO phase shift was in 2014, when it turned strongly positive (‘warm’). The PDO is an active topic of research and satellite data, such as that from Jason-3, helps scientists observe and understand the phenomenon. For further information see our January 2000 press release and articles in the press.

When was the last PDO phase?

The phase was then neutral until 2007, when we entered into a ‘cold’ phase that lasted through 2013. The last PDO phase shift was in 2014, when it turned strongly positive (‘warm’).

Who coined the term PDO?

The term PDO was coined in about 1996 by Steven Hare at the University of Washington. He, along with colleagues Nathan Mantua, Yuan Zhang, Robert Francis and Mike Wallace discovered the pattern as part of work on fish population fluctuations. They have given talks that provide excellent information. Q.

What is the Pacific decadal oscillation index?

The Pacific decadal oscillation index is the leading empirical orthogonal function (EOF) of monthly sea surface temperature anomalies ( SST -A) over the North Pacific (poleward of 20°N) after the global average sea surface temperature has been removed. This PDO index is the standardized principal component time series. A PDO 'signal' has been reconstructed as far back as 1661 through tree-ring chronologies in the Baja California area.

When did the polarity of the North Pacific Ocean change?

There is evidence of reversals in the prevailing polarity (meaning changes in cool surface waters versus warm surface waters within the region) of the oscillation occurring around 1925, 1947, and 1977; the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean.

How does Rossby wave propagate the KOE axis?

The propagation of h anomalies in the western pacific changes the KOE axis and strength and impact SST due to the anomalous geostrophic heat transport. Recent studies suggest that Rossby waves excited by the Aleutian low propagate the PDO signal from the North Pacific to the KOE through changes in the KOE axis while Rossby waves associated with the NPO propagate the North Pacific Gyre oscillation signal through changes in the KOE strength.

How does ENSO affect the ocean?

ENSO can influence the global circulation pattern thousands of kilometers away from the equatorial Pacific through the "atmospheric bridge". During El Niño events, deep convection and heat transfer to the troposphere is enhanced over the anomalously warm sea surface temperature, this ENSO-related tropical forcing generates Rossby waves that propagate poleward and eastward and are subsequently refracted back from the pole to the tropics. The planetary waves form at preferred locations both in the North and South Pacific Ocean, and the teleconnection pattern is established within 2–6 weeks. ENSO driven patterns modify surface temperature, humidity, wind, and the distribution of clouds over the North Pacific that alter surface heat, momentum, and freshwater fluxes and thus induce sea surface temperature, salinity, and mixed layer depth (MLD) anomalies.

Why do SST anomalies occur in winter?

Midlatitude SST anomaly patterns tend to recur from one winter to the next but not during the intervening summer, this process occurs because of the strong mixed layer seasonal cycle. The mixed layer depth over the North Pacific is deeper, typically 100-200m, in winter than it is in summer and thus SST anomalies that form during winter and extend to the base of the mixed layer are sequestered beneath the shallow summer mixed layer when it reforms in late spring and are effectively insulated from the air-sea heat flux. When the mixed layer deepens again in the following autumn/early winter the anomalies may again influence the surface. This process has been named "reemergence mechanism" by Alexander and Deser and is observed over much of the North Pacific Ocean although it is more effective in the west where the winter mixed layer is deeper and the seasonal cycle greater.

When was the PDO reconstructed?

MacDonald and Case reconstructed the PDO back to 993 using tree rings from California and Alberta. The index shows a 50–70 year periodicity but is a strong mode of variability only after 1800, a persistent negative phase occurring during medieval times (993–1300) which is consistent with La Niña conditions reconstructed in the tropical Pacific and multi-century droughts in the South-West United States.

Does white noise cause SST anomalies?

Thus an atmospheric white noise generates SST anomalies at much longer timescales but without spectral peaks. Modeling studies suggest that this process contribute to as much as 1/3 of the PDO variability at decadal timescales.

What is the Pacific decadal oscillation?

Closely linked to low frequency modulations of ENSO is the Pacific Decadal Oscillation (PDO: Mantua et al., 1997) or closely related Inter-Decadal Pacific Oscillation (Power et al., 1998). (These phenomena are defined differently but express essentially the same thing.) The associated pattern of surface ocean warming and cooling is similar to ENSO (although the temperature anomaly tends to be broader in a north–south sense). However, changes in the PDO phase occur on multidecadal, rather than inter-annual, timescales. Untangling the influence of this low-frequency variability and anthropogenic long-term change requires care (see discussion of SST in Section 6.2.3 ). The widespread impact of this mode on marine and terrestrial systems has led to transitions between its phases being described as ‘regime shifts’. A number of Pacific marine species are thought to be sensitive to changes in the PDO (see review by Mantua and Hare, 2002). Increases in tropical wind strength and equatorial upwelling associated with the most recent PDO phase change in the late 1990s are consistent with increased CO 2 outgassing from the tropical Pacific in recent years (Feely et al., 2006). The brevity of the data record precludes the identification of any long-term trends in the PDO (Henson et al., 2010). Pacific decadal variability is further explored in Latif and Park (2012, this volume).

How does the Arctic Oscillation affect the North Pacific?

The Arctic Oscillation, evident in sea level pressure over the polar cap, results in a decrease in mid-latitude westerlies when arctic sea level pressures are unusually low ( Thompson et al., 2000 ). The trend since the 1970s has been toward decreasing arctic pressure, which might explain the stronger connections between the Arctic Oscillation and the PDO reported by Overland et al. (1999). While much remains to be done to understand the origins of North Pacific decadal scale climate variability and its connections to the tropics and poles, substantial progress is being made. In particular, considerable progress has been made in explaining the remarkable transition in oceanic conditions associated with the so-called “regime shift” of the mid-1970s. This climate shift was associated with the rapid change in the PDO from the cold to warm phase coincident with the southeastward displacement and intensification of the Aleutian Low ( Trenberth and Hurrell, 1994) as evident in the change in sign of both the PDO and NP indices ( Fig. 3.2 ).

How does PDO affect the climate of West Antarctica?

The PDO/IPO and Atlantic Multidecadal Oscillation influence West Antarctic climate in a similar fashion as ENSO (through Rossby wave trains), but they persist for time scales of decades to multidecades, and their spatial impacts differ from ENSO ( Clem and Fogt, 2015; Purich et al., 2016; Meehl et al., 2016 ). For example, Clem and Fogt (2015) demonstrated in austral spring that the negative phase of the PDO is linked to an anomalous cyclone over the Ross Sea that warms West Antarctica and the Ross Ice Shelf, a teleconnection that is distinct from the ENSO teleconnection. The negative phase of the IPO, similar to the PDO, also causes an increase in convective rainfall along the poleward edge of South Pacific Convergence Zone (SPCZ) ( Folland, 2002 ), a prominent band of off-equatorial tropical rainfall that stretches diagonally from the west Pacific warm pool to ~ 30°S, 120°W. Observational and modeling studies have shown that an increase in SPCZ convection tied to the negative phase of the IPO produces a Rossby wave train that results in an anomalous low (high) pressure in the Ross Sea (Amundsen Sea), resulting in warming of West Antarctica and the Ross Ice Shelf and cooling on the Antarctic Peninsula ( Clem and Renwick, 2015; Clem et al., 2019 ). During the summer, IPO-related forcing from the SPCZ produces a low-pressure anomaly over Drake Passage, which enhances cold easterly flow of the sea ice–covered Weddell Sea toward the Antarctic Peninsula resulting in widespread cooling of the Antarctic Peninsula ( Turner et al., 2016 ). The IPO also influences convective rainfall in the central and eastern equatorial Pacific, due to the aforementioned similarities with ENSO events. Analogous to the La Niña teleconnection, the negative phase of the IPO and the corresponding cooling/reduced rainfall over the central equatorial Pacific result in a deep Amundsen Sea low that produces warming and a reduction in sea ice along the western Antarctic Peninsula and cooling/sea ice expansion in the Ross Sea ( Trenberth et al., 2014; Meehl et al., 2016; Purich et al., 2016 ). Therefore the IPO/PDO influence on West Antarctic climate is complex and comprises multiple mechanisms acting simultaneously—opposite sign convective anomalies in the SPCZ and the equatorial Pacific—each of which influences different aspects of regional West Antarctic climate on decadal time scales.

How many stations are influenced by PDO?

The results indicate a total of 205 stations throughout the world (∼54.8%) are influenced by PDO warm ENSO coupled oscillation. A total of 37 stations (∼18.0%) are influenced by PDO warm El Niño phase, whereas, a total of 168 stations are influenced by PDO cool La Niña phase (∼82.0%). The remaining 169 stations throughout the world (∼45.2%) are not influenced by PDO warm ENSO coupled oscillation. In the United States, a total of 80 stations (∼56.3%) are influenced by PDO warm ENSO coupled oscillation. A total of 6 stations (∼7.5%) are influenced by PDO warm El Niño phase and the remaining 74 stations (∼92.5%) are influenced by PDO warm La Niña phase. The rest of the stations in the United States, 62 stations (∼43.7%), are not influenced by this coupled oscillation. The results show that over 50% of stations throughout the world are influenced by this coupled oscillation. PDO warm phase produces higher sea levels when it is coupled with La Niña phase, especially in the United states where more than 90% of stations that are susceptible to PDO warm phase present a higher risk when this phase is coupled with La Niña phase.

Why are instrumental records so challenging?

Decadal time scales are also challenging because on this time scale the natural variability of the climate system becomes difficult to separate from the human influences that have become steadily stronger during the period of instrumental records. Methods are available that may be able to distinguish natural and anthropogenic changes in the observations, but whether they have worked or not is often a judgment call. Methods using climate models with and without human influences can be used to unambiguously separate natural variability from human influences, and these will be discussed in Chapter 13.

What caused the Aleutian low to increase?

The regime shift resulted in an intensification of the Aleutian Low and an increase in the strength of mid-latitude westerlies ( Hanawa et al., 1996; Parrish et al., 2000) over the north central Pacific. This induced cooling in the central North Pacific and warming in the eastern, northern, and southern portions of the basin ( Nitta and Yamada, 1989) due to changes in wintertime atmosphere–ocean heat fluxes, deeper vertical mixing in the central Pacific and changes in wind-driven, surface Ekman transport ( Miller et al., 1994 ). Mid-latitude transport in both the North Pacific Current and the Subtropical Gyre also increased ( Miller et al., 1998; Deser et al., 1999; Parrish et al., 2000 ). There are some suggestions that transport in the western Subarctic Gyre slightly increased ( Miller et al., 1998; Joyce and Dunworth-Baker, 2003) as well, while transport in the Alaskan Gyre appears to have decreased ( Lagerleof, 1995; Parrish et al., 2000 ). The transport changes were accompanied by a southward shift in the position of both the Kuroshio–Oyashio Extension ( Seager et al., 2001) and the Subarctic front ( Joyce and Dunworth-Baker, 2003 ), intensification of the north–south temperature gradient across the Kuroshio–Oyashio Extension ( Miller and Schneider, 2000 ), a deepening of the thermocline in the central Pacific and subsurface cooling in the Subarctic Gyre. The changes in the Kuroshio–Oyashio Extension area were not coincident with local atmospheric forcing ( Xie et al., 2000 ), but instead, lagged the development of central Pacific cooling by about five years ( Nakamura et al., 1997 ). The delayed response of the oceanic gyres to the intensification of the Aleutian Low reflects the longer time required for the deeper portions of the ocean to adjust to changes in the wind stress distribution associated with a sustained intensification of the Aleutian Low.

When did PDO enter a positive regime?

PDO entered a prolonged positive regime since the late 1970s and the frequency of occurrences of El Niño events are increased recently;

How long does the Pacific decadal oscillation last?

The Pacific Decadal Oscillation typically remains in a given phase for many years or even decades (Figure 11), but there can be some variation within a given decadal phase.

What is the PDO phase?

The PDO oscillates between positive and negative phases. The positive phase is characterized by cool SSTs north of Hawaii and warmer than normal sea surface temperatures along the western coast of North America. (Figure 1). The negative phase is a mirror image with warm surface waters in the Central North Pacific and cooler than normal waters along the western coast of North America (Figure 2).

Is the PDO a negative or positive?

At the turn of the century, the PDO entered a long-term negative phase, but there was a positive hiatus between 2014 and 2019. Owing to the long-lasting phases of the PDO and their impact on Northern Hemisphere climates, this climate index is very useful for seasonal prediction.

What Is the Pacific Oscillation?

Imagine a giant blob that lurks in the Pacific Ocean, killing sea birds, damaging the food chain, and causing some species to relocate. So, what is this 'blob'? An oil slick? Toxic waste? Garbage? Nope! Scientists, who actually call it 'the blob,' describe it as a giant chunk of warm ocean water that was first noticed in 2013. Estimates of its size vary, but some say it was 1,000 miles wide by 1,000 miles long by 100 yards deep in 2014, but it continues to grow.

What is the PDO in the ocean?

So far, we know that the PDO is a cyclic change in water temperature in the North Pacific Ocean, and it can affect winter temperatures and precipitation levels. El Niño is the warming of surface ocean waters near the equator in the Pacific Ocean.

Does PDO cause colder temperatures?

For example, during the winter months, the warm PDO causes colder temperatures in the Southeast United States, warmer temperatures in the Northwest parts of North America, and warmer temperatures in the Northeast. Finally, there is less winter precipitation in the Northwestern parts of North America. The cold PDO, on the other hand, causes the ...

Is the PDO warm or cold?

Warm phase is like El Niño, whereas cold phase is like La Niña. One phase only. An interesting tidbit though: when the PDO is in the warm phase, scientists believe it intensifies El Niño, and when it's in the cold phase, it intensifies La Niña. So, back to that blob from the beginning of the lesson.

Does North America have less precipitation in winter?

Finally, there is less winter precipitation in the Northwestern parts of North America. The cold PDO, on the other hand, causes the waters off the Pacific Coastline to cool, and these cold waters form a sideways U around warmer waters further away from the shore.

Abstract

The Pacific Decadal Oscillation (PDO) has been described by some as a long-lived El Niño-like pattern of Pacific climate variability, and by others as a blend of two sometimes independent modes having distinct spatial and temporal characteristics of North Pacific sea surface temperature (SST) variability.

Author information

Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, WA, 98195-4235, U.S.A

Overview

Mechanisms

Impacts

Reconstructions and regime shifts

Predictability

Related patterns

See also

Further reading