Climate Variability and the Pacific Ocean
Differences Between Long-term Changes and Short-term Variances
In recent years, global warming and climate change have been big topics in the news. While there is major concern with the effects of a rapidly changing planet, the climate experience variability on a natural level.
For the Pacific Ocean, there are two patterns of variability that occur naturally and have been doing so for thousands of years. They are the Pacific Decadal Oscillation and the El-Nino Southern Oscillation.
Pacific Decadal Oscillation: Long-term Regimes of the Pacific Ocean
The Pacific Decadal Oscillation, commonly known as PDO, is a long-term climate cycle affecting primarily the Pacific Ocean. Marked by two different "regimes" warm and cold, PDO cycles on the order of decades, most often twenty to thirty years.
PDO is most evident in the Northeast Pacific, the area of ocean near the west coast of America. A warm regime will typically result in enhanced coastal productivity in Alaska. This increase in productivity can be seen throughout the marine food web. Warm phases can lead to increase in fisheries catches.
During the cool regime of PDO, the opposite of the warm phase effects are seen. These include a decrease in overall productivity.
The effects seen in Alaska during the regimes are confined mostly to that region. Down the west coast of the continental United States, the opposite effects are seen. For this area, warm regimes result in decreased productivity and cool regimes mean increased productivity.
El-Nino Southern Oscillation: Short-term Variation Phases Within the PDO
In contrast to the long-term phases of PDO, there is a cycle of shorter term changes called El-Nino Southern Oscillation, or ENSO. While PDO cycles in terms of decades, ENSO cycles can last from six to eighteen months.
The effects of ENSO are seen primarily in the tropics, especially along the equator moving masses of warm and cold water west towards Tahiti and Australia. Like PDO, ENSO cycles in warm, El Nino, and cool, La Nina, phases.
A warm phase, most commonly referred to as an El Nino event, is marked by weak winds that drive upwelling along the west coast of South America. When these winds stop, it also stops the movement of water in the currents running along the equator. This results in a drought year for countries in the Western Pacific like Australia. Productivity also decreases because of the shutdown of upwelling.
During a cool, or La Nina, phase the winds are stronger and the effects are increased productivity along South America because of stronger upwelling, however the stronger winds move large masses of water across the ocean and that water mass can have effects like floods and bad storms.
Global Warming and Climate Patterns: The Threat of the Unknown
While global warming is an overall concern for the planet, it is still unclear how global climate change will effect natural climate variations like PDO and ENSO patterns. Some speculate that the intensity of the patterns effects will be exaggerated and intensified, or that the length of the cycles will change.
But the truth is that little is known about the long term consequences and affects as the planet's climate continues to change. It serves to be an area where research is not only necessary, but is essential to our ability to adapt to our changing world.
References:
The Pacific Decadal Oscillation by Nathan Mantua, PhD
Introduction to ENSO from the University of Florida
Pacific Ocean
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