A Regional Index of Northeast Pacific Variability Based on Satellite Altimeter Data

An index of climate variability to monitor the state of the upper ocean is proposed for the northeast (NE) Pacific Ocean based on sea surface height (SSH) data from satellite altimetry. While sea surface temperature (SST) is often used characterize ocean variability, SSH reflects the integrated influence of temperature and salinity anomalies through the water column. A canonical correlation analysis shows that SSH and SST anomalies vary coherently at large spatial scales and low frequencies over the region. SSH anomalies are less subject to short period variability and the temporal components for SSH resemble smoothed, low-pass-filtered versions of the SST components. Also examined is the relationship between the SST-based Pacific Decadal Oscillation (PDO) index and the large-scale, upper ocean variability reflected in the leading principal component of SSH anomalies. The comparison demonstrates that the SSH principal component provides a robust index of regional climate variability that is less noisy than the PDO. The results are used to examine the 1998–2002 climate event over the NE Pacific.