Changes in groundwater drought associated with anthropogenic warming
Changes in groundwater drought associated with anthropogenic warming
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DOI：
10.5194/hess-23-1393-2019
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发表时间：
2019-03-11
影响因子：
6.3
通讯作者：
McKenzie, Andrew A.
中科院分区：
文献类型：
--
作者：
Bloomfield, John P.;Marchant, Benjamin P.;McKenzie, Andrew A.
本文首次提出了在没有降水长期变化的情况下，与人为变暖相关的地下水干旱变化的经验证据。利用1891年至2015年英国白垩含水层的两个独特的地下水位数据集，分析了每月地下水位、降水和温度的标准化指数，结果表明降水不足是地下水干旱形成和传播的主要控制因素。然而，在研究期间，地下水干旱的长期变化显示与人为变暖有关。这包括个别地下水干旱月份的频率和强度增加，地下水干旱事件的频率、幅度和强度增加，以及较长时间的地下水干旱事件和持续时间少于1年的干旱事件增加的趋势。我们还发现了一个转变，从19世纪末地下水干旱与降水干旱的巧合，到21世纪初降水干旱和炎热时期的巧合越来越多。在缺乏降水亏缺长期变化的情况下，我们推断地下水干旱性质的变化是由于与人为变暖相关的蒸散发（ET）的变化。我们注意到，尽管两个研究地点的地下水位相对较深，但白垩中至少30米的厚毛细条纹意味着ET不应受到任何地点降水的限制。ET可能通过主要的地下水干旱事件得到地下水的支持，因此，与人为变暖相关的ET的长期变化可能驱动白垩含水层地下水干旱现象的长期变化。考虑到全球浅层地下水的范围，人为变暖可能广泛影响温带环境地下水干旱特征的变化。
Here we present the first empirical evidence for changes in groundwater drought associated with anthropogenic warming in the absence of long-term changes in precipitation. Analysing standardised indices of monthly groundwater levels, precipitation and temperature, using two unique groundwater level data sets from the Chalk aquifer, UK, for the period 1891 to 2015, we show that precipitation deficits are the main control on groundwater drought formation and propagation. However, long-term changes in groundwater drought are shown to be associated with anthropogenic warming over the study period. These include increases in the frequency and intensity of individual groundwater drought months, and increases in the frequency, magnitude and intensity of episodes of groundwater drought, as well as an increasing tendency for both longer episodes of groundwater drought and for an increase in droughts of less than 1 year in duration. We also identify a transition from a coincidence of episodes of groundwater drought with precipitation droughts at the end of the 19th century, to an increasing coincidence with both precipitation droughts and with hot periods in the early 21st century. In the absence of long-term changes in precipitation deficits, we infer that the changing nature of groundwater droughts is due to changes in evapotranspiration (ET) associated with anthropogenic warming. We note that although the water tables are relatively deep at the two study sites, a thick capillary fringe of at least 30 m in the Chalk means that ET should not be limited by precipitation at either site. ET may be supported by groundwater through major episodes of groundwater drought and, hence, long-term changes in ET associated with anthropogenic warming may drive long-term changes in groundwater drought phenomena in the Chalk aquifer. Given the ex-tent of shallow groundwater globally, anthropogenic warming may widely effect changes to groundwater drought characteristics in temperate environments.