A Reanalysis of North Pacific Sea Surface Temperatures Using State-Space Techniques: The PDO In A New Light

TL;DR

This paper reanalyzes North Pacific sea surface temperatures using advanced state-space methods, revealing new insights into the Pacific Decadal Oscillation and its relation to global warming, tropical dynamics, and Arctic sea ice changes.

Contribution

It introduces state-space decomposition to reanalyze SST data, providing a new perspective on the PDO and identifying multiple underlying trends and cycles.

Findings

Identification of a global warming trend in SST.

Discovery of a sharper warming/cooling trend since the 1970s.

Confirmation that the PDO and Victoria mode are dominated by stationary cycles.

Abstract

North Pacific sea surface temperatures (SST), as used in estimating the PDO, are reanalyzed using state-space decomposition and subspace identification techniques. The reanalysis presents a very different picture of SST in this region. The first common trend reflects a global warming signal. The second common trend modifies this for areas that underwent a sharper warming (cooling) starting in the early 1970's. This trend is also related to dynamics in the tropics and in Arctic sea ice extent. The third common trend is a superposition of changes in pressure centers on the long-term global warming signal. The fourth common trend is the trend that is contained in the original PDO series if analyzed by state-space techniques, and is identical to the trend in the North Pacific High. The first two common stochastic cycles capture the original PDO and so-called "Victoria mode", showing that these series are dominated by stationary behavior..