Linking interannual variability in extreme Greenland blocking episodes to the recent increase in summer melting across the Greenland ice sheet
Linking interannual variability in extreme Greenland blocking episodes to the recent increase in summer melting across the Greenland ice sheet
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DOI：
10.1002/joc.4440
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发表时间：
2016-03-15
期刊：
影响因子：
--
通讯作者：
Mote, Thomas L.
中科院分区：
文献类型：
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作者：
McLeod, Jordan T.;Mote, Thomas L.
大气阻塞通常发生在北方半球的高纬度地区，这是由于持续高压区的发展导致高中心以西的表面温度高于平均温度。虽然格陵兰上空的反气旋环流模式（包括阻塞）的变化和趋势以前已有记录，但缺乏对观测记录中最极端阻塞事件的分析。在这项研究中，极端格陵兰阻塞事件（GBE）从1958年到2013年的历史气候学研究的背景下，异常反气旋环流模式在北大西洋地区在最近几年。基于ERA-40（1958-1978）和ERA-Interim（1979-2013）再分析数据集的组合，格陵兰阻塞指数（GBI）被用来量化500 hPa位势高度异常，以识别极端GBE。自1958年以来，极端阻塞日的年增长率翻了一番，到2013年平均达到每年约20天。从2007年到2013年，极端GBE的频率和持续时间与56年的记录相比前所未有地高，其中大部分增加发生在春季（MAM）和夏季（JJA）。多元线性回归分析表明，极端阻塞的年际变化和大西洋年代际振荡（AMO）是整个格陵兰冰盖（GrIS）表面融水生产的两个主要驱动因素，但北极海冰范围和北大西洋气旋活动也会影响部分GrIS夏季融化的程度。因此，除了较大规模的大气和海洋的变化，较小规模的功能，如热带气旋可以发挥重要作用，在调制GrIS表面融化每年夏天。
Atmospheric blocking commonly occurs over the high latitudes of the Northern Hemisphere, resulting from the development of persistent areas of high pressure that lead to warmer-than-average surface temperatures west of the high centre. While the variability and trends in anticyclonic circulation patterns (including blocking) over Greenland have been previously documented, an analysis of the most extreme blocking events within the observational record is lacking. In this study, a historical climatology of extreme Greenland blocking episodes (GBEs) from 1958 to 2013 is examined within the context of anomalous anticyclonic circulation patterns over the North Atlantic region during recent years. Based on a combination of the ERA-40 (1958-1978) and ERA-Interim (1979-2013) reanalysis data sets, the Greenland Blocking Index (GBI) is used to quantify 500 hPa geopotential height anomalies for the identification of extreme GBEs. The annual rate of extreme blocking days has doubled since 1958, reaching an average of approximately 20 days per year by 2013. The frequency and, to some extent, duration of extreme GBEs were unprecedentedly high from 2007 to 2013 compared to the 56-year period of record, with a majority of the increase occurring during the spring (MAM) and summer (JJA). A multiple linear regression analysis reveals that interannual variability in extreme blocking and the Atlantic Multidecadal Oscillation (AMO) are the two predominant drivers of surface meltwater production across the entire Greenland ice sheet (GrIS), but Arctic sea ice extent and North Atlantic cyclone activity can also influence the extent of summer melting over portions of the GrIS. Thus, in addition to the larger-scale atmospheric and oceanic variability, smaller-scale features such as extratropical cyclones can play a significant role in modulating GrIS surface melting each summer.