Evidence of the El Niño/La Niña Climatic Events in New Zealand Over the Last Century

Abstract

We investigate interrelations between the mean sea level, sea surface temperature, atmospheric temperature and pressure at four tide gauges in New Zealand (Auckland, Wellington, Lyttelton, and Dunedin) with records available for over a century. The least-squares linear regression analysis is applied to estimate linear (secular) trends in the seasonally-adjusted time series. The detrended annual data are then used to analyze the influence of (quasi)periodical climatic cycles on the variability of these recorded data. In particular, we assess the presence of climatic signals attributed to: (i) the inter-annual El Niño Southern Oscillation (ENSO) cycle of El Niño/La Niña events (described by the Southern Oscillation Index - SOI) and (ii) the Inter-decadal Pacific Oscillation (IPO) of the long-term climate cycle occurring over whole Pacific Ocean with a typical period of about 15-30 years. The correlation analysis reveals the presence of significant signal of the SOI and IPO in the mean sea level data in Auckland. The signature of the SOI and IPO attenuates towards higher geographical latitudes. The SOI and IPO also significantly modulate sea surface temperature and atmospheric temperature variations, while the signatures of these climatic cycles are much less pronounced in atmospheric pressure fluctuations.