Forward and inverse modeling of Black spruce tree ring series: applications to paleohydrology and paleoclimatology

NSERC DG的长期目标是在温带和寒带等地区进行基于树木年轮的水文气候重建，这些地区严重缺乏过去水文波动的知识。这些重建将提供一个更准确的基线，可以与最近的变化进行比较，并将对这些研究不足的地区长期水文气候变化的起源提出新的见解。为了实现这一目标，我们将提出一种新的代理模型融合方法，专门用于克服树木生长远离环境压力条件地区的树木年代学家遇到的困难。*********在过去的几十年里，树木年代学对理解长期的水文气候变化做出了很大的贡献。然而，在温度和降水共同控制生长速率的地区，它导致了模棱两可的结果。气候重建的基本方法要求在空间分辨率和气候敏感性之间进行权衡，并倾向于将温度敏感（限于纬/高林木线）或降水敏感（限于半干旱地区）的林分作为过去气候的代用物。然而，完善我们对过去不稳定性的理解将迫使年轮科学家从那些对我们对全球变化的理解贡献较小的地区提取强有力的水文气候信号。事实上，这些地区的典型特征是复杂、多元和时变（分歧）的代理气候关系，这是基于树木年轮重建的主要障碍。******这种新颖的重建方法将在北美东北部（NENA）的北方森林中实施，该森林代表了树木年轮与气候关系模糊的地区的典型例子。这种方法将基于两个互补的方面。首先，气候信号提取将依赖于多种代理（树木年轮宽度、碳氧稳定同位素），以加强对温度和降水信号的分析。其次，将利用基于过程的模型来评估代用物与气候之间的关系，该模型基于一个庞大的多代用物测量网络，该网络整合了所有与从树木年轮推断过去气候相关的时间尺度：年际、年际、年代用、千年代用。这个研究项目将产生关于NENA长期水文气候变化和持续性的关键信息，这将有助于提高我们预测（和适应）未来变化的能力。该项目将依托于一个强大而活跃的国家和国际合作网络，并将为学员提供一个极好的机会，参与代表古气候学前沿的研究项目

The long-term objective of this NSERC DG is to produce hydro-climatic, tree-ring-based reconstructions in regions, such as the temperate and the boreal zones, where knowledge on past hydro-fluctuations is critically lacking. These reconstructions will provide a more accurate baseline to which recent changes can be compared and will cast a new light on the origin of long-term hydro-climatic variability in these understudied regions. To achieve this, we will propose a novel proxy-model fusion approach, specifically designed to overcome the difficulties encountered by dendrochronologists in regions where trees grow far from environmentally stressful conditions.*********In the past few decades, dendrochronology has greatly contributed to the understanding of long-term hydro-climatic changes. However, it led to equivocal results in regions where both temperature and precipitation control growth rates. The basic approach to climate reconstruction dictates a trade off between spatial resolution and climate-sensitivity, and favours the inclusion of either temperature-sensitive (restricted to latitudinal / altitudinal tree lines) or precipitation-sensitive (restricted to semi-arid regions) forest stands as proxies for past climates. However, refining our understanding of past instabilities will force tree ring scientists to extract robust hydro-climatic signals from regions that have contributed less to our understanding of global changes. Indeed, such regions are typically characterized by complex, multivariate and time-varying (divergent) proxy-climate relationships that represent major obstacles to the production of tree-ring-based reconstructions.******The novel reconstruction approach will be implemented in North-Eastern North-America (NENA)'s boreal forest which represents an archetypal example of a region where ambiguous tree-ring-to-climate relationships prevail. The approach will be based on two complementary aspects. First, climatic signal extraction will rely on multiple proxies (tree ring widths, carbon and oxygen stable isotopes) in order to strengthen the analysis of both temperature and precipitation signals. Second, relationships between proxies and climate will be assessed using process-based modeling anchored to a vast network of multi-proxy measurements that integrate all temporal scales relevant to infer past climates from tree rings: infra-annual, inter-annual, decadal, millennial. This research program will generate crucial information on long-term hydro-climate variability and persistence in NENA, which will help refine our capacity to predict (and adapt to) future changes. The program will rely on a strong and active network of collaborations at the national and international levels and will represent an excellent opportunity for trainees to be involved in a research initiative that represents the cutting edge of paleoclimatology.**