Southern Annular Mode

The Southern Annular Mode, also called the Antarctic Oscillation, is the dominant pattern of atmospheric variability in the extratropical Southern Hemisphere: a north-south shift of the belt of westerly winds that circles Antarctica, alternating between a positive phase, in which the belt contracts poleward and strengthens, and a negative phase, in which it expands toward the equator. Its positive phase has trended stronger in recent decades, linked to stratospheric ozone depletion and rising greenhouse gases, with measurable effects on Southern Hemisphere rainfall, ocean circulation and the extent of Antarctic sea ice. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/