Ocean Temperature & Climate Oscillations
The Pacific Decadal Oscillation, or PDO, is a long-lasting pattern of sea-surface temperature variability in the North Pacific. Unlike El Niño and La Niña, which usually shift over months to a few years, the PDO can influence ocean conditions, weather patterns, fisheries and climate signals for decades.
What Is the Pacific Decadal Oscillation?
The Pacific Decadal Oscillation is a recurring pattern of ocean temperature changes across the North Pacific. It is often described as a basin-scale climate pattern because it affects a very large region rather than one small patch of water.
The PDO is identified by broad sea-surface temperature anomalies north of about 20°N in the Pacific Ocean. These anomalies can remain in one dominant phase for years to decades, influencing marine ecosystems and regional climate.
Quick Definition
The PDO is a long-term North Pacific ocean temperature pattern that alternates between warm and cool phases and can influence fisheries, rainfall, drought, storms and climate variability.
Warm and Cool PDO Phases
The PDO has two broad phases: a warm phase and a cool phase. These phases are based on the pattern of sea-surface temperatures across the North Pacific, not simply whether the whole ocean is warmer or colder.
| PDO phase | North Pacific pattern | Typical influence |
|---|---|---|
| Warm phase | Warmer waters along western North America and cooler waters in parts of the central North Pacific | Can favor different rainfall, temperature and marine ecosystem patterns around the Pacific Rim |
| Cool phase | Cooler waters along western North America and warmer waters in parts of the central North Pacific | Can shift fisheries, storm tracks and regional climate tendencies in different ways |
PDO vs ENSO: What Is the Difference?
The PDO is sometimes compared to ENSO because both involve Pacific Ocean temperature patterns. But they are not the same phenomenon.
- ENSO is centered in the tropical Pacific and includes El Niño, La Niña and neutral phases.
- PDO is centered in the North Pacific and usually changes more slowly.
- ENSO often varies over months to a few years.
- PDO can persist in one phase for many years or decades.
- ENSO and PDO can interact, sometimes reinforcing or weakening climate impacts around the Pacific.
Why the PDO Matters
Fisheries and Marine Ecosystems
The PDO can influence plankton, salmon, sardines, anchovies and other marine populations by changing ocean temperature, nutrient availability and food-web structure in the North Pacific.
Rainfall and Drought Patterns
PDO phases can affect long-term rainfall tendencies around western North America and the broader Pacific Rim, especially when combined with ENSO events.
Storm Tracks
North Pacific temperature patterns can influence atmospheric circulation, jet stream behavior and the paths of storms that affect coastal regions.
Marine Heatwaves
PDO-like background patterns can help set the stage for persistent warm or cool anomalies, including marine heatwaves in parts of the Pacific.
Climate Interpretation
Because the PDO operates over decadal timescales, it can temporarily amplify or mask regional warming trends, making it important for interpreting climate records.
How Is the PDO Monitored?
Scientists monitor the PDO using sea-surface temperature records, ocean observations, atmospheric pressure patterns and statistical indices that track the dominant North Pacific temperature pattern.
- Sea-surface temperature anomalies: reveal warm and cool regions across the North Pacific.
- PDO index: summarizes the dominant temperature pattern into a single value.
- Satellite data: maps ocean temperature patterns over large areas.
- Ocean buoys and ships: provide direct measurements of ocean conditions.
- Climate models: help separate natural variability from long-term warming.
Common Misconceptions About the PDO
The PDO is not the same as El Niño
El Niño is a tropical Pacific event within ENSO. The PDO is a broader North Pacific pattern that changes more slowly.
The PDO does not control global climate by itself
It is one important climate pattern among many. ENSO, ocean heat content, atmospheric circulation and long-term warming all interact.
A PDO phase does not guarantee one weather outcome
The PDO shifts probabilities over large regions and long timescales, but local weather still depends on season, geography and other climate drivers.
Frequently Asked Questions
What does PDO stand for?
PDO stands for Pacific Decadal Oscillation, a long-term pattern of sea-surface temperature variability in the North Pacific.
How is the PDO different from ENSO?
ENSO is centered in the tropical Pacific and changes over months to a few years. The PDO is centered in the North Pacific and can persist for years to decades.
What are the PDO phases?
The PDO has warm and cool phases, based on contrasting sea-surface temperature patterns across the North Pacific.
Does the PDO affect weather?
Yes. PDO phases can influence rainfall, drought, storm tracks and temperature tendencies, especially around the Pacific Rim.
Does the PDO affect fisheries?
Yes. The PDO can influence North Pacific marine ecosystems, including plankton, salmon, sardines, anchovies and other species.
