Decadal Change of Annual Range for the Arctic Sea Ice in Recent 30 Years

摘要

Based on sea ice concentration (SIC) and sea ice extent (SIE) data forrnthe Arctic during the period 1979 – 2008, an annual range index (ARI)rnof the Arctic sea ice was defined by difference of maximum SIErnanomaly in March (winter) and minimum SIE anomaly in Septemberrn(summer). It is found that a significantly decadal change of ARI for thernArctic sea ice, indicating maximum melting SIE for the Arctic in a yearrnround, occurred around mid-1990s. ARI demonstrates a decadal shiftrnfrom negative anomaly in pre-decadal-change stage to positive anomalyrnduring post-decadal-change period, with maximum extreme in 2007rnand minimum extreme in 1996. Seasonality of the decadal shift of ARIrnsignificantly occurs in summer and early autumn, with peak in October.rnSpatial pattern of SIC in four seasons all show an out-of-phasernoscillation in the Arctic Ocean and adjacent marginal seas. This seesawrnpattern indicates that the SIC decreases quickly over the central area ofrnthe Arctic Ocean, especially in Chukchi Sea in summer and earlyrnautumn, while SIC increases in Bering Sea, Barents Sea and Kara Searnduring the fast melting period after mid-1990s, and vice verse beforernmid-1990s. Top three major modes of the annual range of SIC allrnindicate decadal variability, implying the decadal change of the Arcticrnsea ice in around mid-1990s being a robust signal. Further study revealsrnthat the decadal shift of the Arctic sea ice may relate to decadal changernof major modes of atmospheric circulation, namely the ArcticrnOscillation (AO) or dipole anomaly (DA) patterns, and the stormrnactivity in mid-latitude.