An analysis of air temperature records for Macquarie Island: decadal warming, ENSO cooling and southern hemisphere circulation patterns

Abstract

Macquarie Island lies close to, but on the eastern side of the boundary between the eastern (pacific) and western (India-Australia) limbs of the Southern Oscillation. Its temperature record matches that of the area east and southeast of New Zealand, rather than Tasmania. Temperature is influenced by atmospheric pressures in the Southern Ocean to the east and west, which can result in a warm northeasterly or cold southerly airflow over the island. It is a sensitive indicator of climatic trends because of its location at high latitude in a longitudinal region of frequent ridge formation and blocking in the Southern Hemisphere circulation. Temperature records for Macquarie Island (1949-86) show a trend (twice the global average), accelerating in the last 20 years with eight of the ten warmest years occuring in the last decade. The greatest average rate of warming has occurred in late summer and early autumn and the lowest in spring. In severe ENSO years the isiand cools. The warming is marked, in relation to the annual mean (4.8°C), and the biological effects should be considered.