Mechanism on how the spring Arctic sea ice impacts the East Asian summer monsoon
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Observational analysis and purposely designed coupled atmosphere–ocean (AOGCM) and atmosphere-only (AGCM) model simulations are used together to investigate a new mechanism describing how spring Arctic sea ice impacts the East Asian summer monsoon (EASM). Consistent with previous studies, analysis of observational data from 1979 to 2009 show that spring Arctic sea ice is significantly linked to the EASM on inter-annual timescales. Results of a multivariate Empirical Orthogonal Function analysis reveal that sea surface temperature (SST) changes in the North Pacific play a mediating role for the inter-seasonal connection between spring Arctic sea ice and the EASM. Large-scale atmospheric circulation and precipitation changes are consistent with the SST changes. The mechanism found in the observational data is confirmed by the numerical experiments and can be described as follows: spring Arctic sea ice anomalies cause atmospheric circulation anomalies, which, in turn, cause SST anomalies in the North Pacific. The SST anomalies can persist into summer and then impact the summer monsoon circulation and precipitation over East Asia. The mediating role of SST changes is highlighted by the result that only the AOGCM, but not the AGCM, reproduces the observed sea ice-EASM linkage.
KeywordsEast Asian Summer Monsoon Western North Pacific Subtropical High East Asian Summer Monsoon Index Atmosphere General Circulation Model East Asian Summer Monsoon Precipitation
This work was supported by Chinese National Basic Research Program (2009CB421406) and Chinese Academy of Sciences Innovation Program (XDA05110203) and by the Norwegian Research Council through the Impact of “Blue Arctic” on Climate at High Latitudes (BlueArc 207650/E10) and Exploring Decadal to Century Scale Variability and Changes in the East Asia (DecCen 193690) and the Arctic and sub-Arctic climate system and ecological response to the early twentieth century warming (ARCWARM 178239/E10) projects. Dr. Gong D.Y. was supported by the National Natural Science Foundation of China.
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