Novel insights into the Northeast Winter Monsoon

世界上一些产量最高的农业地区在南亚和东亚。这种高有机生产力是由热带地区夏季和冬季季风的季节性逆转所维持的。由于季风风带来了每年的大部分降雨量，它们对数十亿人的生存至关重要。例如，世界85%以上的大米种植在亚洲季风地区，该地区也拥有世界50%以上的人口。季风环流也是热量在全球范围内传输的主要方式之一，因此影响到气候系统的所有部分。许多研究都集中在亚洲夏季风上，但我们对亚洲冬季风的了解存在重大差距，我们的目标是在这里解决这一问题。研究季风需要记录降雨和温度等参数如何在空间和时间上变化的数据。然而，仪器数据只有在过去100年左右的大多数情况下才能获得。这不足以记录所有可能的模式和变化。要超越仪器记录，我们需要找到气候变化的自然记录器。通过大量的观测、古气候学和模型研究，已经很好地描述了亚洲夏季风的过去和现在的变化。然而，我们对亚洲冬季风的了解要少得多，因为它在IPCC使用的气候模型中没有得到很好的代表，而且它过去的变异性只受到古气候指标的粗略限制。因此，在我们对冬季季风的理解上存在着重大的知识鸿沟，这限制了我们评估越南、斯里兰卡、印度或菲律宾等高度依赖冬季季风雨的地区未来降雨变化轨迹的能力。基于石笋的热带过去降雨量变化的重建改变了我们对夏季风动态及其与全球气候联系的理解。我们建议利用洞穴石笋的强度作为越南中部的气候档案，那里约75%的年降水量由亚洲冬季风控制。我们的初步工作已经在这个地区发现了洞穴，这些洞穴生长在过去的4万年里。这将使我们能够在与现代相似的条件下以及在与今天截然不同的背景气候状态下确定冬季风变化的驱动因素和幅度。我们将使用两种独立的方法来重建降雨和温度的变化。碳同位素和镁/钙比，我们证明了它们与从地表渗入洞穴的水量直接相关。本德尔和他的合作者开创了一种新的生物标志物代理，可以用来从单个石笋中分离出温度和水文。使用这些方法，我们将：1.提供所需的缺失数据，以填补我们在这里确定的知识缺口，并改变我们在IPCC用来预测未来气候变化的模型中测试冬季季风表示的能力。这是提高对人类诱导的气候强迫的冬季季风响应模式预报的信心的最有力的方法之一。2.为决策者和政策制定者提供附加值，他们负责引导该区域农业生产和地质灾害的未来变化。我们在越南的经验丰富的当地合作伙伴将把我们的调查结果与越南的中央和地方当局联系起来，使我们的下一份提案能够与他们共同制作，并密切符合他们的需求。3.到2050年，英国将跻身全球前20大经济体之列，扩大英国的研究足迹。我们与当地科学家和当局的接触为长期合作研究奠定了基础，这将使英国和越南都受益。

Some of the most productive agricultural regions in the world are in Southern and Eastern Asia. This high organic productivity is sustained by the seasonal reversal of the winds in the tropics: the summer and winter monsoons. Because monsoon winds bring much of the yearly rainfall, they are critical to the survival of billions of people. For example, more than 85% of the world's rice is grown in the Asian Monsoon region, which also hosts more than 50% of the world's population. Monsoonal circulation is also one of the main ways heat is transported across the globe, and therefore affects all parts of the climate system. Numerous studies have focused on the Asian Summer Monsoon, but our knowledge of the Asian Winter Monsoon has significant gaps which we aim to address here. Studying the monsoon requires data that document how parameters such as rainfall and temperature change in space and time. However, instrumental data are only available in most cases for the last 100 years or so. This is not sufficient to record the full range of possible patterns and changes. To go beyond the instrumental record, we need to find natural recorders of climate change. The past and present variability of the Asian Summer Monsoon has been well characterized using numerous observational, palaeoclimatological and modelling studies. However, we know much less about the Asian Winter Monsoon which is poorly represented in the climate models used by the IPCC, and its past variability is only loosely constrained by palaeoclimate proxies. Therefore, there is a significant knowledge gap in our understanding of the winter monsoon which limits our ability to evaluate future trajectories of rainfall variability in places which are highly dependent on the winter monsoon rain, such as Vietnam, Sri Lanka, India or the Philippines. Stalagmite-based reconstructions of past rainfall variability in the tropics have transformed our understanding of summer monsoon dynamics and its links to global climate. We propose to use the strengths of cave stalagmites as climate archives in Central Vietnam where ~75% of annual precipitation is controlled by the Asian Winter Monsoon. Our preliminary work has identified speleothems in this region which grew over the last 40,000 years. This will allow us to determine the drivers and magnitude of changes winter monsoon under conditions similar to modern and under a background climate state very different to today's. We will use 2 independent methods to reconstruct changes in rainfall and temperature.1. Carbon isotopes and Mg/Ca ratios which we demonstrated that they are directly related to the amount of water infiltrating into the cave from the surface.2. A new biomarker proxy pioneered by co-I Bendle and his collaborators which can be used to deconvolve temperature and hydrology from individual stalagmites.Using these methods, we will:1. Provide the missing data needed to close the knowledge gap identified we identified here, and transforms our ability to test the winter monsoon representation in models used by IPCC to forecast future climate changes. This is one of the most robust ways to improve confidence in model forecasts of winter monsoon response to human-induced climate forcing. 2. Provide added value to decision and policy makers, who are responsible for navigating future changes in agricultural production and geohazards in the region. Our experienced local partners in Vietnam will make the link between our findings and central and regional authorities in Vietnam, permitting our next proposal to be co-produced with them and closely suited to their needs. 3. Enhancing the UK research footprint in a country that will to be one of the top 20 global economies by 2050. Our engagement with local scientists and authorities sets the foundations for long-term collaborative research which will benefit both the UK and Vietnam.