Radical Spatial Shift of Atmospheric Circulation Pattern: The Driving Force for Recent Rapid Changes in Arctic Climate System

Superimposed on the global-warming-forced long-term changing trends, a conspicuous rapid change episode occurred in the Arctic climate system in the most recent decade. This rapid change episode is coincidently characterized by an acceleration of sea ice cover decline and Eurasian river discharge rise and a shift of maximum surface air temperature trend from Eurasian continent to the Arctic Ocean from mid-1990s until 2006 and concluded by the extreme events of the sea ice cover loss and the Eurasian river discharge increase in 2007.

To understand these rapid changes, we analyzed multidisciplinary data sets, and detected drastic, systematic spatial changes in large-scale atmospheric circulations, showing a sudden jump from the conventional tri-polar Arctic/North Atlantic Oscillation (AO/NAO) to an unprecedented dipolar leading pattern, following accelerated northeastward shifts of the AO/NAO centers of action. This radically shifted spatial pattern 'Arctic Rapid change Pattern (ARP)' represents the rapid climate change signature in the North Hemisphere atmospheric circulation, enhancing Arctic and lower latitude climate interactions, providing an accelerating impetus for the observed rapid changes in Arctic climate system and playing a decisive role in forming the extreme climate events in 2007. In particular, the record low of sea ice coverage in summer 2007 is not a single-year random event. It is a cumulative consequence of multiyear polarization of ARP toward its negative phase from 2000 through 2006 and a swift phase swinging in 2006-07. In addition, the identified pattern shift has also been found to provide skillful predicative information for rapid change events in future.