HYdroclimate Reconstruction in Arid eXtremes (HYRAX): understanding the mechanisms of global desertification

极端干旱地区的水文气候重建（HYRAX）：了解全球荒漠化的机制

• 批准号: NE/X017575/1
• 金额: $ 86.11万
• 依托单位: Northumbria University
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX017575%2F1
• 关键词: HYdroclimate; Reconstruction; Arid; eXtremes; HYRAX

Earth is experiencing clear warming toward climate states humans have not seen since the stone age. Adaptation to these changes will be challenging. Drylands (water-limited regions) cover almost half of Earth's land surfaces, supporting almost 40% of the world's population. The International Panel on Climate Change predicts further dryland aridification by the end of this century, plunging populations already experiencing water shortages into crisis. However, global climate models disagree in both the direction and scale of future hydroclimate change and only suggest medium confidence for predicted outcomes. Further, previously warm and high-CO2 periods in Earth's geological history, such as the late Pliocene (~3 Ma), almost uniformly suggest more humidity in dryland regions during globally warmer conditions. This "Dryland Hydroclimate Paradox" must be urgently addressed to improve our forecast on the climate impacts of future climate change in global dryland regions.The geological past may be the best, indeed only, tool to understand how Earth's processes operate under previously warmer and colder climate states, allowing us to identify the key drivers controlling aridity in global subtropical zones. The proposed research will exploit the emerging potential of dryland cave deposits (e.g. stalagmites) to be used as 'ancient-rain gauges', switching on when there is enough rainfall and recording the exact timing of past wet periods. Dating stalagmites allows us to identify exactly when subtropical zones were more humid in the past and under what conditions this occurred (globally warmer or cooler climate states). Project HYRAX will deliver an unprecedented dataset of changes in positive hydro-balance in subtropical drylands over the last ~6 million years by using a unique combination of radiometric dating and statistical evaluation techniques. As speleothems form they also trap other useful information that can be used as a proxy for the environmental conditions at the time of formation. Using a combination of these clues trapped and preserved in speleothems for millions of years such as: fossil pollen, fossil water and fossil micro-organisms, the environment at the time the stalagmite grew will be reconstructed. This will deliver unique quantitative information about the local vegetation, rainfall composition and amount and surface temperature during past wet periods. Combining unique records, cutting edge techniques, state of the art analytical approaches and proxy system modelling techniques, this project will translate this information into real world climate data, allowing us to test how skilful models are in predicting these ancient environments. This will be a significant leap forward in our understanding of how drylands respond to changes in global temperature and atmospheric CO2 concentrations. My central aim is to provide much needed benchmarks for terrestrial hydroclimate simulations and data-model comparison to better understand the physics underlying change in dryland climate in the future. Without this, it will remain challenging for stakeholders to develop mitigation targets and government policies.

地球正在经历明显的气候变暖，气候状态是人类自石器时代以来从未见过的。适应这些变化将具有挑战性。旱地（水资源有限的地区）几乎覆盖了地球陆地表面的一半，养活了世界上近 40% 的人口。国际气候变化专门委员会预测，到本世纪末，旱地将进一步干旱，使已经经历缺水的人们陷入危机。然而，全球气候模型对未来水文气候变化的方向和规模都存在分歧，并且仅对预测结果给出了中等可信度。此外，地球地质历史上以前的温暖和高二氧化碳时期，例如上新世晚期（约3 Ma），几乎一致表明在全球变暖的条件下，旱地地区的湿度更高。必须紧急解决这一“旱地水文气候悖论”，以改善我们对未来气候变化对全球旱地地区气候影响的预测。过去的地质可能是了解地球过程在以前较暖和较冷的气候状态下如何运作的最佳工具，实际上是唯一的工具，使我们能够确定控制全球亚热带地区干旱的关键驱动因素。拟议的研究将利用旱地洞穴沉积物（例如石笋）作为“古代雨量计”的新兴潜力，在降雨充足时开启并记录过去潮湿期的准确时间。石笋年代测定使我们能够准确地确定亚热带地区过去何时更加潮湿以及在什么条件下发生这种情况（全球变暖或凉爽的气候状态）。 HYRAX 项目将通过使用放射性测年和统计评估技术的独特组合，提供过去约 600 万年亚热带旱地正水平衡变化的前所未有的数据集。当洞穴形成时，它们还会捕获其他有用的信息，这些信息可以用作形成时环境条件的代理。结合这些被困在洞穴中并保存了数百万年的线索，例如花粉化石、水化石和微生物化石，将重建石笋生长时的环境。这将提供有关过去潮湿时期当地植被、降雨成分和降雨量以及地表温度的独特定量信息。该项目结合独特的记录、尖端技术、最先进的分析方法和代理系统建模技术，将这些信息转化为现实世界的气候数据，使我们能够测试模型在预测这些古老环境方面的熟练程度。这将是我们对旱地如何应对全球温度和大气二氧化碳浓度变化的理解的重大飞跃。我的中心目标是为陆地水文气候模拟和数据模型比较提供急需的基准，以更好地了解未来旱地气候变化的物理原理。如果没有这一点，利益相关者制定缓解目标和政府政策仍将面临挑战。