The climate of the Auckland Islands is heavily influenced by two major wind cells. The Polar Easterly Winds to the South and the Westerly Wind belt to the North of the islands. The westerly winds are the prevailing winds in the middle latitudes (between 30° S and 60° S) and blow from high pressure areas in the north down towards the poles. The polar easterlies are the dry, cold, easterly prevailing winds that blow from high pressure areas at the poles towards low pressure areas within the westerlies. These easterly and westerly prevailing winds meet around the latitudes of 60° S.
Depicts the atmospheric circulation cells and the prevailing winds and wind direction for each cell. Source: Indiana University-Purdue University, Indianapolis
The Auckland Islands are located in the Southern Ocean where the Antarctic Convergence in the south meets the Subtropical Convergence in the north. At the zone where they meet, cold water from the Antarctic Circumpolar Current meets, and sinks beneath the relatively warmer Sub-Antarctic water in the north. This warmer water from the north is forced up toward the ocean surface. This convergence zone is approximately 30-50km wide and its position varies between the latitudes of 48° S and 61° S.
Shows the location of the Antarctic Circumpolar Current and the Antarctic Convergence in the Southern Ocean. Source: http://content.answcdn.com
Climate and ocean systems around the Auckland Islands are adjusting to warming atmospheric and ocean temperatures. These changes occur as the temperature at the poles increase by a rate greater than the temperature at the equator, causing the temperature gradient of the Earth to change. This temperature gradient is the main driver of large scale atmospheric circulation. In warmer climates the atmospheric circulation cells that the Earth is split into shift toward each pole causing a change in the climate of the Auckland Islands due to different wind patterns. Climate models predict a southward migration of westerly winds as the climate warms and the greater rate of warming at the poles will result in increased variability in the polar vortex allowing unusual cold excursions across southern New Zealand and warm excursions into the Antarctic. The ocean currents around the Auckland Islands will also be affected. As the temperature at the poles increases, the water will not cool as rapidly and may have a lower salinity, therefore will be less dense. This will result in a change in global ocean currents and affect the Antarctic Convergence zone as well as the ocean currents around the Auckland Islands. Each of these physical processes contributes directly to changing patterns of rainfall, aridity and surface temperature across the New Zealand landmass.
New Zealand’s Sub-Antarctic sits between the Subtropical Front (STF) and the Sub-Antarctic Front (SAF) on the northern boundary of the Antarctic Circumpolar Current (ACC). Source: NIWA