Sea Surface Temperature variability in Northwest Pacific Ocean Analyzed Using Sparse PCA

Abstract:

In the mid-latitude Northwest Pacific Ocean, variations in the Kuroshio Extension and the Subarctic front (the Oyashio Extension) affect the atmosphere (Frankignoul et al. 2011). Frankignoul et al. (2011) applied PCA (EOF) analysis to the position of the SST front to extract the variability. Mitsudera et al. (2018) showed that the variability of the subarctic front is influenced by the topographically controlled flows known as the Isoguchi Jets. Thus, the temperature variations in the mid-latitude Northwest Pacific Ocean reflect the frontal structures. However, PCA analysis of the entire spatio-temporal field of sea surface temperature (SST) in the mid-latitude Northwest Pacific Ocean does not reveal the frontal structures because the PCA analysis picks up many signals from a large spatial dimension. Therefore, sparse PCA analysis, which assumes sparsity, was conducted and compared with the PCA analysis. The NOAA OISST Ver. 2.1 was analyzed. While the spatial patterns in the PCA analysis spread over a wide area and did not reflect the frontal structures, spatial patters in the Sparse PCA analysis were more localized. The relationships with the fronts suggest that the third and fourth principal components in the Sparse PCA correspond to the variability of the Kuroshio Extension and the Oyashio Extension of Frankignoul et al. (2011), respectively.