Volcanoes 101 . Site map . A growing body of evidence indicates that a swirling mass of Arctic air has wide-ranging climate effects in the Northern Hemisphere and may be affected by human activities, researchers said earlier this month. The stronger polar vortex of the Arctic oscillation s positive phase brings cool winds across eastern Canada, while North Atlantic storms bring rain and mild temperatures to northern Europe and drought conditions prevail in the Mediterranean. The evidence indicates the acceleration of a counterclockwise spinning ring of air around the polar region could be responsible for warmer winters in Scandinavia and Siberia, thinning of the stratospheric ozone layer, and significant changes in surface winds that might have contributed to Arctic ice thinning.
Researchers call the phenomenon the Arctic Oscillation.
Wallace, doctoral student David Thompson and Mark Baldwin, a research scientist with Northwest Research Associates Inc., discussed the findings at the American Geophysical Union's fall meeting in San Francisco. The weaker polar vortex of the negative phase allows cold air to plunge into the midwestern United States and western Europe, and storms bring rain to the Mediterranean. The Arctic Oscillation is a seesaw pattern in which atmospheric pressure at polar and middle latitudes fluctuates between positive and negative phases. The positive phase brings the opposite conditions, steering ocean storms farther north and bringing wetter weather to Alaska, Scotland and Scandinavia and drier conditions to areas such as California, Spain and the Middle East. In recent years the Arctic Oscillation has been mostly in its positive phase, research has shown.