E-Mail IMAGE: Moraines constructed during repeated advance-retreat cycles of one of the glaciers that extended out from the Southern Alps in New Zealand during the last ice age. Around 18,000 years ago,... view more Credit: Photo courtesy of Aaron Putnam Orono, Maine -- The origins of ice age climate changes may lie in the Southern Hemisphere, where interactions among the westerly wind system, the Southern Ocean and the tropical Pacific can trigger rapid, global changes in atmospheric temperature, according to an international research team led by the University of Maine. The mechanism, dubbed the Zealandia Switch, relates to the general position of the Southern Hemisphere westerly wind belt -- the strongest wind system on Earth -- and the continental platforms of the southwest Pacific Ocean, and their control on ocean currents. Shifts in the latitude of the westerly winds affects the strength of the subtropical oceanic gyres and, in turn, influences the release of energy from the tropical ocean waters, the planet's "heat engine." Tropical heat spreads rapidly through the atmosphere and ocean to the polar regions of both hemispheres, acting as the planet's thermostat.