Investigating southern African Holocene climate - bridging from the early Holocene to today

调查南部非洲全新世气候 - 从全新世早期到今天的桥梁

• 批准号: 416063878
• 负责人: Dr. Joel Arnault, Ph.D.
• 金额: --
• 依托单位: Lehrstuhl für Regionales Klima und Hydrologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/416063878?language=en
• 关键词: Investigating; southern; African; Holocene; climate

Due to its position between the subtropical and the temperate zone, southern African climate is highly sensitive to climatic variabilities, as is evident also in the present 3-year drought. Climate variability is characterized by changes in strength and position of the temperate Westerlies, Inter-Tropical Convergence Zone (ITCZ), and Congo Air Boundary (CAB), as well as by Sea Surface Temperature (SST) variabilities. The complexity of the climate system is also evident in the isotope signal of Holocene proxy records, which shows, even over small distances, high regional climate variability. The extent to which Holocene rainfall variability of southern Africa is linked to the coupling between northern and southern hemispheric climate, local insolation or SST, is not fully understood yet. A crucial question for improved understanding of Southern African climate variability of past and present days is the interplay between Benguela and Agulhas current dynamics, related ocean SSTs), the strength and position of ITCZ and CAB, and the extent of summer and winter rainfall dominated areas. Summer and winter rainfall regimes are most likely not independent of each other. A connection between summer and winter rains might exist through land – atmosphere feedback mechanisms. With this project we aim at improving the understanding of the processes that governed past and present climate variability of southern Africa and at explaining the isotopic signal of proxy records, which are altered by surface evaporation and terrestrial water flows. For this purpose we will perform, on the one hand, highly resolved global coupled model simulations for different time slices to investigate the influence of ocean – -atmosphere interactions. This part of the study will be complemented by atmosphere-only sensitivity experiments to isolate the effects of single factors contributing to Holocene climate evolution. As a methodological innovation we will, on the other hand, implement the so-called tagging of stable water isotopes in the atmospheric and terrestrial compartments of a regional climate model. The combination of stable water isotope modelling with atmospheric and terrestrial water tagging from the major moisture source regions, i.e. Indian and Atlantic Ocean, offers the unique opportunity not only to investigate differences in proxy records, but also to analyze changes in atmospheric dynamics and land – atmosphere feedback mechanisms that influence southern African climate dynamics on a regional scale. With this approach, for the first time, a technique only recently developed in present-day atmospheric modelling will be implemented and extended to answer open questions in climate research. For the interpretation of model results and proxy records and for an analysis of the added value of high-resolution climate modelling for past climates, we will use the most recent southern African Holocene proxy records.

由于地处亚热带和温带之间，南部非洲的气候对气候变化非常敏感，这在目前持续三年的干旱中也很明显。气候变率的特征是温带西风带、热带辐合带（ITCZ）和刚果空气边界（CAB）的强度和位置变化，以及海温（SST）的变率。气候系统的复杂性也体现在全新世代用记录的同位素信号中，表明即使在小距离上，区域气候变化也很大。南非全新世降雨变率在多大程度上与南北半球气候、当地日照或海温之间的耦合有关，目前尚未完全了解。提高对过去和现在南部非洲气候变率的理解的一个关键问题是本格拉和阿古拉斯洋流动力学、相关海洋海温、ITCZ和CAB的强度和位置以及夏季和冬季降雨主导地区的程度之间的相互作用。夏季和冬季的降雨情况很可能不是相互独立的。夏季和冬季降雨之间的联系可能通过陆地大气反馈机制存在。通过这个项目，我们的目标是提高对控制南部非洲过去和现在气候变化的过程的理解，并解释代用记录的同位素信号，这些同位素信号被地表蒸发和陆地水流改变。为此，我们一方面将进行不同时间段的高分辨率全球耦合模式模拟，以研究海洋-大气相互作用的影响。这部分研究将由仅对大气进行敏感性实验来补充，以分离对全新世气候演化有贡献的单一因素的影响。另一方面，作为一种方法上的创新，我们将在区域气候模型的大气和陆地隔间中实施所谓的稳定水同位素标记。稳定水同位素模拟与来自主要水汽源区（即印度洋和大西洋）的大气和陆地水标记相结合，不仅提供了独特的机会来研究代用记录的差异，而且还分析了在区域尺度上影响南部非洲气候动力学的大气动力学和陆-气反馈机制的变化。有了这种方法，一种最近才在当今大气模拟中发展起来的技术将第一次得到实施和扩展，以回答气候研究中的开放性问题。为了解释模式结果和替代记录，以及分析过去气候的高分辨率气候模型的附加价值，我们将使用最新的南部非洲全新世替代记录。

项目成果

A Joint Soil‐Vegetation‐Atmospheric Modeling Procedure of Water Isotopologues: Implementation and Application to Different Climate Zones With WRF‐Hydro‐Iso

• DOI: 10.1029/2021ms002562
• 发表时间: 2021-09
• 期刊: Journal of Advances in Modeling Earth Systems
• 影响因子: 6.8
• 作者: J. Arnault;G. Jung;B. Haese;B. Fersch;Thomas Rummler;Jianhui Wei;Zhenyu Zhang;H. Kunstmann