Roy Mendelssohn | Searcharxiv

arXiv2012

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

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..

stat.AP↗

arXiv2012

An Analysis of North Pacific Subsurface Temperatures Using State-Space Techniques

North Pacific subsurface temperature data from the Simple Ocean Data Assimilation model at 10m, 50m, 75m, 100m and 150m depths, are analyzed using a combination of state-space decomposition and subspace identification techniques to examine the spatial structure of thermal variability within the upper water column. We identify four common trends from our analysis that display the major broad-scale patterns in the North Pacific over a 47 year period (1958-2004): (1) a basin-wide near-surface warming trend that identifies the mid 1980's as a change point from a cooling to a warming trend; (2) a contrasting cooling in the central basin and warming along the coast of North America that began in the early 1970's; (3) a cooling along the transition zone and the west coast of North America that becomes dominant around 1998; (4) and contrasting differences in the subarctic and subtropical gyres displaying differences in processes at each depth. We also provide a detailed analysis of the temperature variability at four chosen locations: 52.5N 142.5W (Gulf of Alaska), 37.5N 172.5W (central basin), 37.5N 137.5W (off coast of California), and 27.5N 137.5W (off coast of Baja California) for both 10m and 150m depths. These results identify subsurface structure, regional heterogeneity, and they also display important differences and similarities in the patterns of subsurface temperature variability when compared to previously published temperature patterns.

stat.AP↗