Summer Greenland Blocking Diversity and Its Impact on the Surface Mass Balance of the Greenland Ice Sheet
Summer Greenland Blocking Diversity and Its Impact on the Surface Mass Balance of the Greenland Ice Sheet
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DOI：
10.1029/2021jd035489
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发表时间：
2022-02
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影响因子：
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通讯作者：
J. Preece;L. Wachowicz;T. Mote;M. Tedesco;X. Fettweis
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作者：
J. Preece;L. Wachowicz;T. Mote;M. Tedesco;X. Fettweis
自世纪以来，格陵兰冰盖（GrIS）地表径流的增加与格陵兰岛阻塞频率的增加有关。然而，一系列的天气模式可以被认为是阻塞流和不加区别地总结所有阻塞类型的努力可能无法捕捉GrIS响应的相应差异。为了解释这些差异，我们使用ERA 5再分析来识别夏季阻塞，使用两个独立的阻塞指标：格陵兰阻塞指数（GBI）和Pelly和霍斯金斯的阻塞指数（2003，https：//doi.org/10.1175/1520-0469（2003）0602.0.CO;2）。然后，我们进行了自组织地图分析，客观地分类天气条件在格陵兰岛阻塞事件，并确定了三个主要的阻塞类型：（a）高振幅欧米茄块，（B）低振幅，静止的夏季脊，（c）气旋波破碎模式。使用Modèle Atmosphere érique Régional输出，我们记录了每种阻塞类型的表面能量和质量平衡的时空进展。相对于所有的阻塞事件，夏季脊模式产生更多的融化在南部冰盖，欧米茄块产生更多的融化在北方冰盖，和气旋波破碎模式产生更多的融化在格陵兰岛东北部。我们的研究结果表明，夏季格陵兰岛阻塞的最近趋势在很大程度上是由欧米茄模式的增加，并建议欧米茄块发挥了核心作用，在最近的加速GrIS质量损失。此外，GBI表现出对Omega模式的相对偏差，这可能有助于解释为什么它测量到夏季格陵兰岛阻塞的趋势比其他阻塞指标更强。
The increase in Greenland Ice Sheet (GrIS) surface runoff since the turn of the century has been linked to a rise in Greenland blocking frequency. However, a range of synoptic patterns can be considered blocked flow and efforts that summarize all blocking types indiscriminately likely fail to capture consequential differences in GrIS response. To account for these differences, we employ ERA5 reanalysis to identify summer blocking using two independent blocking metrics: the Greenland Blocking Index (GBI) and the blocking index of Pelly and Hoskins (2003, https://doi.org/10.1175/1520-0469(2003)0602.0.CO;2). We then conduct a self‐organizing map analysis to objectively classify synoptic conditions during Greenland blocking episodes and identify three primary blocking types: (a) a high‐amplitude Omega block, (b) a lower‐amplitude, stationary summer ridge, and (c) a cyclonic wave breaking pattern. Using Modèle Atmosphérique Régional output, we document the spatiotemporal progression of the surface energy and mass balance for each blocking type. Relative to all blocking episodes, summer ridge patterns produce more melt over the southern ice sheet, Omega blocks produce more melt across the northern ice sheet, and cyclonic wave breaking patterns produce more melt in northeast Greenland. Our results indicate that the recent trend in summer Greenland blocking was largely driven by an increase in Omega patterns and suggest that Omega blocks have played a central role in the recent acceleration of GrIS mass loss. Furthermore, the GBI exhibited a relative bias toward Omega patterns, which may help explain why it has measured stronger trends in summer Greenland blocking than other blocking metrics.