Projecting Wintertime Newly Formed Arctic Sea Ice through Weighting CMIP6 Model Performance and Independence  

作　　者：Jiazhen ZHAO Shengping HE Ke FAN Huijun WANG Fei LI 

机构地区：[1]Key Laboratory of Meteorological Disaster,Ministry of Education/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science&Technology,Nanjing 210044,China [2]Geophysical Institute,University of Bergen and Bjerknes Centre for Climate Research,Bergen 5007,Norway [3]School of Atmospheric Science,Sun Yat-sen University,and Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,China [4]Nansen Environmental and Remote Sensing Center and Bjerknes Centre for Climate Research,Bergen 5007,Norway [5]Nansen-Zhu International Research Center,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China [6]Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,China

出　　处：《Advances in Atmospheric Sciences》2024年第8期1465-1482,共18页大气科学进展（英文版）

基　　金：supported by the Chinese–Norwegian Collaboration Projects within Climate Systems jointly funded by the National Key Research and Development Program of China (Grant No.2022YFE0106800);the Research Council of Norway funded project,MAPARC (Grant No.328943);the support from the Research Council of Norway funded project,COMBINED (Grant No.328935);the National Natural Science Foundation of China (Grant No.42075030);the Postgraduate Research and Practice Innovation Program of Jiangsu Province (KYCX23_1314)。

摘　　要：Precipitous Arctic sea-ice decline and the corresponding increase in Arctic open-water areas in summer months give more space for sea-ice growth in the subsequent cold seasons. Compared to the decline of the entire Arctic multiyear sea ice,changes in newly formed sea ice indicate more thermodynamic and dynamic information on Arctic atmosphere–ocean–ice interaction and northern mid–high latitude atmospheric teleconnections. Here, we use a large multimodel ensemble from phase 6 of the Coupled Model Intercomparison Project(CMIP6) to investigate future changes in wintertime newly formed Arctic sea ice. The commonly used model-democracy approach that gives equal weight to each model essentially assumes that all models are independent and equally plausible, which contradicts with the fact that there are large interdependencies in the ensemble and discrepancies in models' performances in reproducing observations. Therefore, instead of using the arithmetic mean of well-performing models or all available models for projections like in previous studies, we employ a newly developed model weighting scheme that weights all models in the ensemble with consideration of their performance and independence to provide more reliable projections. Model democracy leads to evident bias and large intermodel spread in CMIP6 projections of newly formed Arctic sea ice. However, we show that both the bias and the intermodel spread can be effectively reduced by the weighting scheme. Projections from the weighted models indicate that wintertime newly formed Arctic sea ice is likely to increase dramatically until the middle of this century regardless of the emissions scenario.Thereafter, it may decrease(or remain stable) if the Arctic warming crosses a threshold(or is extensively constrained).

关 键 词：wintertime newly formed Arctic sea ice model democracy model weighting scheme model performance model independence 

分 类 号：P467[天文地球—大气科学及气象学] P731.15