Brief communication: Recent changes in summer Greenland blocking captured by none of the CMIP5 models
Brief communication: Recent changes in summer Greenland blocking captured by none of the CMIP5 models
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DOI：
10.5194/tc-12-3287-2018
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发表时间：
2018-10-16
期刊：
影响因子：
5.2
通讯作者：
Hall, Richard J.
中科院分区：
文献类型：
--
作者：
Hanna, Edward;Fettweis, Xavier;Hall, Richard J.
最近的研究指出，自20世纪90年代以来，格陵兰地区的高压阻塞（格陵兰阻塞指数，GBI）在夏季显着增加。北大西洋涛动（NAO）指数的负趋势表明，这种环流变化通常被强调为格陵兰冰盖（GrIS）最近观测到的表面融化记录的主要驱动力。在这里，我们比较再分析为基础的GBI记录与耦合模式相互比较项目5（CMIP 5）的全球气候模式套件在1950-2100年。我们发现，最近的夏季GBI的增长远远超出了过去重建和未来GBI预测（RCP4.5和RCP8.5）的范围。这些模型一致预测未来GBI的减少（与NAO的增加有关），这突出了如果最近观察到的环流变化继续存在，当前气候模型可能存在的关键缺陷。鉴于格陵兰地区的大气压力与下游（如欧洲西北部）的极端气温和降水之间存在着良好的联系，这就对模拟的北大西洋急流变化的准确性和由此产生的北方欧洲人口稠密地区的气候异常以及使用全球和区域气候模式对GrIS质量平衡的未来预测提出了质疑。
Recent studies note a significant increase in highpressure blocking over the Greenland region (Greenland Blocking Index, GBI) in summer since the 1990s. Such a general circulation change, indicated by a negative trend in the North Atlantic Oscillation (NAO) index, is generally highlighted as a major driver of recent surface melt records observed on the Greenland Ice Sheet (GrIS). Here we compare reanalysis-based GBI records with those from the Coupled Model Intercomparison Project 5 (CMIP5) suite of global climate models over 1950-2100. We find that the recent summer GBI increase lies well outside the range of modelled past reconstructions and future GBI projections (RCP4.5 and RCP8.5). The models consistently project a future decrease in GBI (linked to an increase in NAO), which highlights a likely key deficiency of current climate models if the recently observed circulation changes continue to persist. Given well-established connections between atmospheric pressure over the Greenland region and air temperature and precipitation extremes downstream, e.g. over northwest Europe, this brings into question the accuracy of simulated North Atlantic jet stream changes and resulting climatological anomalies over densely populated regions of northern Europe as well as of future projections of GrIS mass balance produced using global and regional climate models.