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Brief communication: CMIP6 does not suggest any atmospheric blocking increase in summer over Greenland by 2100
International Journal of Climatology ( IF 3.9 ) Pub Date : 2020-12-21 , DOI: 10.1002/joc.6977
Alison Delhasse 1 , Edward Hanna 2 , Christoph Kittel 1 , Xavier Fettweis 1
Affiliation  

The Greenland blocking index (GBI), an indicator of the synoptic‐scale circulation over Greenland, has been anomalously positive during most summers since the late 1990s. Such changes in atmospheric circulation, favouring anticyclonic conditions, have led to an increase in Greenland summer temperatures, a decrease in cloud cover and larger surface melt. The GBI is therefore a key indicator of melting and surface mass balance variability over the Greenland ice sheet. However, the models of fifth phase of the Coupled Model Intercomparison Project (CMIP5) do not represent the increase in GBI that is suggested by recent observations, and do not project any significant increase in GBI until 2100. In this study, the new generation of CMIP6 Earth‐system models is evaluated in order to analyse the evolution of the future GBI. All CMIP5 and CMIP6 projections reveal the same trend towards a decrease of the GBI until 2100 and no model reproduces the strong increase in the persistence of summer blocking events observed over the last few decades. Significant melting events related to a highly positive GBI, as observed in summer 2019, are still not considered by CMIP6 models and therefore the projected surface melt increase of the ice sheet could be underestimated if such summer circulation changes persist in the next decades.

中文翻译:

简要交流:CMIP6并未表明到2100年夏季格陵兰的大气阻塞增加

自1990年代后期以来,在大多数夏季,格陵兰阻塞指数(GBI)一直是格陵兰上空天气尺度环流的指标。大气环流的这种变化有利于反气旋条件,导致格陵兰夏季温度升高,云量减少和更大的表面融化。因此,GBI是格陵兰冰原上融化和表面质量平衡变化的关键指标。但是,耦合模型比较项目(CMIP5)的第五阶段模型不能代表最近观察到的GBI的增加,并且在2100年之前都不会预测GBI的任何显着增加。评估了CMIP6地球系统模型,以分析未来GBI的演变。直到2100年,所有CMIP5和CMIP6的预测都显示出GBI下降的相同趋势,并且没有任何模型能够再现过去几十年来观察到的夏季阻滞事件持续性的强劲增长。CMIP6模型仍未考虑与2019年夏季观察到的与高度正相关的GBI相关的重大融化事件,因此,如果未来几十年这种夏季环流变化继续存在,冰盖的预计表面融化增加可能会被低估。
更新日期:2020-12-21
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