Changes in the occurrence of extreme precipitation events at the Paleocene-Eocene thermal maximum
Changes in the occurrence of extreme precipitation events at the Paleocene-Eocene thermal maximum
复制标题
DOI：
10.1016/j.epsl.2018.08.005
复制
发表时间：
2018-11-01
影响因子：
5.3
通讯作者：
Lunt, Daniel J.
中科院分区：
文献类型：
--
作者：
Carmichael, Matthew J.;Pancost, Richard D.;Lunt, Daniel J.
人们普遍预计，未来全球变暖将增加极端降水事件的发生，但这种水文变化在古气候研究中受到的关注有限。一些关于古新世-始新世最高温度的水文响应的替代研究，类似于56 Ma，最近引用了极端降水事件发生的变化来解释观测，但这些变化在过去的地质中没有用气候模型来研究。在这里，我们使用一个耦合的大气-海洋环流模式HadCM3L，通过比较与可能的PETM和PETM之前的温室气体强迫进行的模拟，来研究PETM开始时极端降水的区域变化。我们的模拟表明，降水的频率-强度关系发生了变化，极端事件在包括赤道非洲和南美洲在内的热带地区的重要性增加。在一些地区，一些极端事件的发生率在整个PETM地区增加了高达70%。虽然最极端的降雨率往往与对流降水的增加有关，但在一些区域，大气环流的动态变化也很重要。尽管大气环流模式在描述每日降水周期和所有极端事件的能力上存在缺陷，因此无法直接比较绝对降雨率，但我们的模拟为解释这一时期的水文指标提供了一个有用的空间框架。我们的结果表明，极端降水行为的变化可能与年平均降水量的变化脱钩，例如在东非，年平均降水量的变化很小，但极端事件的规模和频率大幅增加。这对于解释水文替代记录和我们理解气候和生物地球化学对全球变暖事件的响应具有重要意义。(C)2018年提交人(S)。爱思唯尔出版公司(Elsevier B.V.)
Future global warming is widely anticipated to increase the occurrence of extreme precipitation events, but such hydrological changes have received limited attention within paleoclimate studies. Several proxy studies of the hydrological response to the Paleocene-Eocene Thermal Maximum hyperthermal, similar to 56 Ma, have recently invoked changes in the occurrence of extreme precipitation events to explain observations, but these changes have not been studied for the geologic past using climate models. Here, we use a coupled atmosphere-ocean general circulation model, HadCM3L, to study regional changes in metrics for extreme precipitation across the onset of the PETM by comparing simulations performed with possible PETM and pre-PETM greenhouse gas forcings. Our simulations show a shift in the frequency-intensity relationship of precipitation, with extreme events increasing in importance over tropical regions including equatorial Africa and southern America. The incidence of some extreme events increases by up to 70% across the PETM in some regions. While the most extreme precipitation rates tend to relate to increases in convective precipitation, in some regions dynamic changes in atmospheric circulation are also of importance. Although shortcomings in the ability of general circulation models to represent the daily cycle of precipitation and the full range of extreme events precludes a direct comparison of absolute precipitation rates, our simulations provide a useful spatial framework for interpreting hydrological proxies from this time period. Our results indicate that changes in extreme precipitation behaviour may be decoupled from those in mean annual precipitation, including, for example in east Africa, where the change in mean annual precipitation is small but a large increase in the size and frequency of extreme events occurs. This has important implications for the interpretation of the hydrological proxy record and our understanding of climatic, as well as biogeochemical, responses to global warming events. (C) 2018 The Author(s). Published by Elsevier B.V.