Detecting low frequency oscillations of the Pacific Ocean by the ocean upper layer temperature data

Researchers have paid much attention to the long term (surface) horizontal (mostly zonal) heat distribution in the upper ocean layers and found some important low frequency oscillations, but there is not a good index yet for these oscillations. In this study, we applied a simple method to the historical upper ocean layer (surface down to 400 m, from the year 1955 to 2001) temperature dataset to detect all these possible low frequency oscillations in the Pacific Ocean. Results showed that the Pacific Ocean has many kinds of low frequency oscillations including from bi-annual events, El Nin˜o/La Nin˜a events to some not well-explained oscillations that may have a period of around 27 years. Results also showed a strong oscillation of the vertical heat distribution and a strange meridional oscillation. Analysis suggested that the unusual vertical oscillation might be related to the solar radiance anomaly. The meridional oscillation of about 14 year period may be caused by the deep ocean circulation anomaly and its relationship to the Earth´s nutation and polar motion should be further studied. This study may help reveal some unknown dynamical process in the Pacific Ocean while providing a reasonable and physical index to depict the low frequency oscillations. It may also interest those researchers in the fields of ocean science, geophysical science and astronomical science.