Pacific Decadal Oscillation

The Pacific Decadal Oscillation (PDO) is a long-term, El Niño-like pattern of climate variability in the Pacific Ocean that persists for 20-30 years at a time. It has both warm and cold phases that have related impacts on Pacific region weather.

Differences from ENSO

While the PDO is similar to the El Niño-Southern Oscillation (ENSO), key differences include:

• The PDO persists for decades while ENSO persists for 1-2 years
• PDO primary climatic fingerprints are in the North Pacific while ENSO’s are in the tropics
• Warm PDO resembles El Niño conditions while cool PDO resembles La Niña

The mechanisms behind the PDO are also currently unknown.

PDO Phases

The PDO has two distinct climate phases:

• Warm phase: More El Niño-like – Favors warmer temperatures in the north Pacific and stronger Aleutian Low pressure system.
• Cool phase: More La Niña-like – Leads to cooler north Pacific Ocean temperatures and weaker Aleutian Low.

Influence on Regional Climate

Shifts in the PDO influence climate variables like temperature and precipitation. Effects include:

• Warmer Alaska temperatures and altered marine ecosystem productivity during warm phase
• Cooler Alaska coastal waters and temperatures during cool phase
• Potential links to decadal precipitation variations across North America

Ongoing research aims to better understand PDO mechanisms and predictability for improved climate forecasting.