Rapid Change Of The Arctic Sea Ice And Response Of Dominant Modes Of The Atmosphere

Based on the data of Arctic sea ice concentration from National Snow and IceData Center (NSIDC) and Hadley Center (HC), we analyze the characteristic of Arcticsea ice from1979to2012. It turns out that Arctic sea ice is undergoing a rapidprocess of change. The sea ice extent has a trend of decrease and has two decadaltransitions. It can be divided into three stages:①1979~1996，②1997~2006and③2007~2012. The linear trend and oscillation of sea ice was relatively small in firststage. Then the Arctic sea ice decreased quickly and its trend reached to about threetimes than before, but the interannual oscillation was very small.After2007, the trendof decrease was insignificant but the oscillation increased dramatically. The cardinalarea of Arctic sea ice gradually expanded from the edge of the sea to the central areaof the Arctic. At the same time, the characteristic of seasonal has changed obviously:the start time of melting ice came earlier, the start time of freezing ice came later, thesummer time became longer and seasonal oscillation became larger. Besides this, theArctic sea ice extent in central area continues declining in recent years.We analyze the response of atmosphere to the rapid change of Arctic sea icebased on some numerical experiments. We find that, it will cause a significant localwarming and lead to an increase of sea level pressure in the Arctic with the gradualreduction of Arctic sea ice. The variability of Arctic sea ice will directly affect thechange of Arctic Oscillation (AO) and Dipole (DA). Based on the results of modals, ifthe Arctic sea ice continues decreasing, the probability of positive phase of AO willincrease and the extreme AO events will be more than ever. It may lead to moreextreme high weather events in mid-latitude area.We also focus on the variability of Arctic sea ice in the future. Based on thenewly available simulations from the Coupled Model Intercomparison Project Phase5(CMIP5), we have established a new approach to compare the level of which modelsreproduce the observation and select the best of them from31CMIP5models. The approach is based on four factors including the average, trend, span and annual range.It is more objective and can be popularized to other comparison of models. We haveselected six best modals and analyze the variability of Arctic sea ice in the future byusing these results. It turns out that the sea ice will continue declining in each seasonand firstly drop below1million km2(defined as the ice-free state) on September2065under RCP4.5scenario and on September2053under RCP8.5scenario. We alsofocus on the annual cycle of the Arctic sea ice and find out the duration of Arcticmelting season will increase by about200days under RCP8.5scenario relative tocurrent circumstance by the end of the21st century. The change of cardinal area ofArctic sea ice extended from the edge sea to the central part of the Arctic in the futureand the positive phase of theAO will probably be more than ever.