Intradecadal effects on New Zealand temperatures caused by significant El Nino events
The 1982/83 El Nino was a once-in-a-century occurrence with respect to its intensity. Contemporary weather effects resulting from the consequent upset to the global circulation are well publicized. Recent research in the northern hemisphere has documented the creation and propagation of a major oceanic Rossby wave caused by the 1982/83 El Nino. The major wave crest took a decade to cross the Northern Pacific at latitude 40N; its progress at higher latitudes was progressively slower. As the wave crest approached Japan, the geostrophic anticyclonic circulation around it caused a diversion eastwards of the Kuro Shio current. After the wave had passed, the Kuro Shio current was diverted northwards resulting in warmer temperatures in northern Japan. During 1995/96 there have been many reports of rare tropical marine animals in New Zealand waters. It is hypothesised that, as predicted earlier, these events are indicators of a mirror effect in the southern hemisphere of the northern hemisphere Rossby wave. The probable repercussions, past, present and future, of such a wave on the New Zealand climate are explored.