Transforming our understanding of climate shifts in the North African dust belt and upskilling Earth System Models to simulate them

改变我们对北非沙尘带气候变化的理解，并提高地球系统模型的模拟能力

• 批准号: NE/X000869/1
• 负责人: Paul Wilson
• 金额: $ 73.52万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX000869%2F1
• 关键词: Transforming; our; understanding; climate; shifts

As Earth heats up in the coming decades, global rainfall patterns will shift with uncertain regional outcomes. Nowhere is this problem more acute than in North Africa. The world's largest hot desert and biggest source of atmospheric dust, the Sahara, grew by >10% in the 20th century. In the semi-arid Sahel and Mediterranean borderlands, where annual rainfall amounts are low and inter-annual rainfall variability is high, tens of millions of people live in extreme water stress with sometimes devastating consequences as during the late 20th century Sahel drought. These are major incentives to understand the mechanisms driving past variability in the climate of North Africa. However, the instrumental record is short (~150 yrs) and geological and archaeological data reveal a capacity for far more extreme shifts in North African climate. Paced by Earth's gradually changing orbit around the Sun and millennial-scale variability in the climate system, North Africa's past climate has shifted repeatedly between drier and dustier conditions than today and humid green Sahara periods (GSPs) when the desert was transformed into a well vegetated landscape crosscut by rivers and lakes, populated by hippopotamuses and our early ancestors (most recently during the African Humid Period, AHP, ~14.5 to 5 thousand years ago, ka).What caused these past shifts? What do they imply for the future? We lack convincing answers to these questions because the extreme shifts indicated by the palaeo-data are not reproduced by the computer models used to predict future change. A main weakness of the existing palaeo-data is their limited diagnosis of mechanistic control. North Africa has two latitudinal and seasonally distinct rainfall regimes, the summer monsoon and winter westerly storm track, but we know too little of their temporal and spatial contributions to the profound changes in humidity-aridity and vegetation recorded in the data. A main weakness in the models is that we do not know whether their lack of skill reflects missing processes and feedbacks that dampen the response to climate forcing or whether they adequately represent the key processes but are inadvertently hard-wired for stability because uncertain parameter values are determined solely by evaluation against contemporary observational targets. We propose to transform our understanding of climate shifts in the North African dust belt and to upskill models to successfully simulate them by capitalizing on recent breakthroughs that we have made (see Track Record). We will develop proxy climate records for a bellwether Saharan region to tease apart past variability in summer monsoon and winter storm-track rainfall (see Objectives). And we will configure an IPCC-class Earth System model (ESM) that shows novel power to green the Sahara and is sufficiently computationally inexpensive to permit adequate sampling of parameter space to confront our new proxy records (see Objectives). This will allow us to develop a mechanistic understanding of extreme change and to translate our findings to those scientists who are developing the next generation of ESMs that will be used to predict future change over the coming decades (see Academic Beneficiaries).

随着接下来几十年的地球升温，全球降雨模式将随着区域结果的不确定而变化。这个问题比北非更为严重。世界上最大的炎热沙漠和最大的大气灰尘来源，撒哈拉沙漠在20世纪增长了10％。在半干旱的萨赫勒和地中海边境地区，年度降雨量很低，青年降雨差异很高，数以千计的人生活在极端的水压力下，有时造成毁灭性的后果，如20世纪后期的萨赫勒干旱。这些是了解推动北非气候中过去变化的机制的主要激励措施。但是，工具记录是短的（〜150年），地质和考古数据揭示了北非气候的极端变化能力。 Paced by Earth's gradually changing orbit around the Sun and millennial-scale variability in the climate system, North Africa's past climate has shifted repeatedly between drier and dustier conditions than today and humid green Sahara periods (GSPs) when the desert was transformed into a well vegetated landscape crosscut by rivers and lakes, populated by hippopotamuses and our early ancestors (most recently during the African Humid Period, AHP, 〜14.5至5000年前，ka）。是什么原因导致了这些过去的转变？他们对未来意味着什么？我们缺乏对这些问题的令人信服的答案，因为古数据所指示的极端变化不是由用于预测未来变化的计算机模型复制的。现有的古数据的主要弱点是它们对机械控制的诊断有限。北非有两个纬度和季节性独特的降雨制度，夏季季风和冬季西风轨道，但我们对数据中记录的湿度和植被的深刻变化的时间和空间贡献很少。模型中的一个主要弱点是，我们不知道他们缺乏技能反映了缺少的过程和反馈，这些过程会抑制对气候强迫的反应，还是充分代表关键过程，而是无意中的稳定性方面是坚硬的，因为不确定的参数值仅通过针对现代观察目标评估来确定不确定的参数值。我们建议改变我们对北非尘埃腰带气候变化的理解，并转向提高技能模型，以成功地模拟它们，以利用我们最近取得的突破（请参阅往绩记录）。我们将为撒哈拉州的领头羊地区开发代理气候记录，以嘲笑夏季季风和冬季风暴轨道降雨的过去变异性（请参阅目标）。我们将配置一个IPCC级地球系统模型（ESM），该模型显示了绿色的新功能，并且在计算上足够便宜，以允许对参数空间进行足够的采样以面对我们的新代理记录（请参阅目标）。这将使我们能够对极端变化的机械理解发展，并将我们的发现转化为那些正在发展下一代ESM的科学家，这些ESM将用于预测未来几十年的未来变化（请参阅学术受益人）。

项目成果

Monsoon-driven changes in aeolian and fluvial sediment input to the central Red Sea recorded throughout the last 200,000 years

过去 20 万年记录的红海中部风沙和河流沉积物输入的季风驱动变化

• DOI: 10.5194/cp-2023-33
• 发表时间: 2023
• 作者: Ehrmann W