Soil Moisture Variability Intensifies and Prolongs Eastern Amazon Temperature and Carbon Cycle Response to El Nino-Southern Oscillation
Soil Moisture Variability Intensifies and Prolongs Eastern Amazon Temperature and Carbon Cycle Response to El Nino-Southern Oscillation
复制标题
DOI：
10.1175/jcli-d-18-0150.1
复制
发表时间：
2019-02-01
影响因子：
4.9
通讯作者：
Hoffman, Forrest M.
中科院分区：
文献类型：
--
作者：
Levine, Paul A.;Randerson, James T.;Hoffman, Forrest M.
厄尔尼诺-南方涛动（ENSO）是亚马逊地区气候和碳循环变化的重要驱动因素。赤道太平洋海面温度（SST）异常直接通过大气环流的变化驱动与温度的遥相关。这些环流变化也会影响降水，从而影响土壤湿度，从而通过陆地-大气耦合对温度产生额外的间接影响。为了将 ENSO 海温异常的直接影响与土壤湿度的间接影响区分开来，进行了一项机制否认实验，以将其在百亿亿次级地球系统模型 (E3SM) 中的变异性与 1982 年至 2016 年观测到的海表温度强制解耦。发现土壤湿度变异性会放大和扩大海温强迫对 E3SM 中亚马逊东部温度和碳通量的影响。在雨季，ENSO 海温异常的直接环流驱动效应主导了整个亚马逊地区的温度和碳循环变化。在接下来的旱季，ENSO海温异常消散后，土壤湿度变化成为东部地区的主要驱动因素，解释了厄尔尼诺和拉尼娜年份之间67%-82%的温差以及85%-91%的碳通量差异。这些结果强调，在将这些因素对陆地碳循环年际变化的相对贡献归因时，需要考虑温度和水文之间的相互依赖性。具体来说，当离线模型被迫进行观测或重新分析时，当温度自身的变异性通过陆地-大气耦合受到水文调节时，温度的贡献可能会被高估。
El Nino-Southern Oscillation (ENSO) is an important driver of climate and carbon cycle variability in the Amazon. Sea surface temperature (SST) anomalies in the equatorial Pacific drive teleconnections with temperature directly through changes in atmospheric circulation. These circulation changes also impact precipitation and, consequently, soil moisture, enabling additional indirect effects on temperature through land-atmosphere coupling. To separate the direct influence of ENSO SST anomalies from the indirect effects of soil moisture, a mechanism-denial experiment was performed to decouple their variability in the Energy Exascale Earth System Model (E3SM) forced with observed SSTs from 1982 to 2016. Soil moisture variability was found to amplify and extend the effects of SST forcing on eastern Amazon temperature and carbon fluxes in E3SM. During the wet season, the direct, circulation-driven effect of ENSO SST anomalies dominated temperature and carbon cycle variability throughout the Amazon. During the following dry season, after ENSO SST anomalies had dissipated, soil moisture variability became the dominant driver in the east, explaining 67%-82% of the temperature difference between El Nino and La Nina years, and 85%-91% of the difference in carbon fluxes. These results highlight the need to consider the interdependence between temperature and hydrology when attributing the relative contributions of these factors to interannual variability in the terrestrial carbon cycle. Specifically, when offline models are forced with observations or reanalysis, the contribution of temperature may be overestimated when its own variability is modulated by hydrology via land-atmosphere coupling.