Collaborative Research: Carbon Isotope and geotracer-enabled simulation of the Transient Climate Evolution of the Deglacial Ocean (C-iTRACE-O)

全球气候在最后一次冰消期（21，000至11，000年前）经历了巨大的变化，全球变暖约3.5°C，海平面上升约80米，大型大陆冰盖消失。大幅度的信号和广泛的古气候数据的可用性使这一时期成为研究气候变化机制和验证最先进的地球系统模型（ESM）的绝佳目标。然而，到目前为止，模型模拟不能直接与古气候记录进行比较，因为模型没有模拟重建所基于的地球化学示踪剂（“代理”）。为了解决这一问题，并深入了解有关冰消期海洋翻转环流演变的几个长期存在的科学问题，该项目将利用社区地球系统模型（CESM 1）海洋模型中新开发的同位素模块，对冰消期进行首次瞬态海洋模拟，以便对多个海洋古代理进行直接的模型数据比较。该项目将通过支持两名研究生在气候建模和模型数据比较方面的培训，并为一名早期职业女性科学家提供项目领导经验，从而为STEM劳动力发展做出贡献。该项目的成果将用于博尔德的科罗拉多大学和威斯康星大学麦迪逊分校的本科生和研究生课程，并将通过项目网站和普通受众谈话纳入公共宣传。模拟的输出（称为C-iTRACE-O）将通过地球系统网格网关免费提供，允许整个古气候社区将其用于研究。模拟结果还将提供给古气候模型相互比较项目瞬时冰消期工作组，以便与其他ESM的冰消期模拟结果进行比较，对CESM C-iTRACE进行评估。（d13 C和D14 C），Neoadenosine（eNd），和钚/钍（231 Pa/230 Th）通过敏感性实验，研究引起冰川中同位素和地质示踪剂分布变化的物理机制。通过瞬态模拟，将有可能解决一些长期存在的科学问题，通过直接比较观察和评估模型本身的示踪剂循环关系，如：-什么是神秘间隔期间释放的低放射性碳CO2的来源和路线？- 最后一次冰消期大西洋d13 C演变对深海环流的影响是什么？d13 C变化有多少是由营养物和空气-海洋气体交换效应与环流变化引起的？- 为什么南极中层水的冰消期演化在代理人之间存在争议，特别是在钕和碳同位素方面？- 231 Pa/230 Th如何代表北大西洋深环流和南大洋上升流的冰消期演化？

Global climate has undergone large changes during the last deglaciation (21,000 to 11,000 years ago), with a warming of ~3.5°C globally, a sea level rise of ~80 m, and the disappearance of the large continental ice sheets. The large magnitude of the signals and the availability of extensive paleoclimate data make this period an excellent target for investigating the mechanisms underlying climate change and for the validation of state-of-the-art Earth System Models (ESMs). However, up until now model simulations could not be directly compared with the paleoclimate records, as the models did not simulate the geochemical tracers ("proxies") on which the reconstructions are based. To address this issue and provide insights into several long-standing scientific questions about the evolution of the ocean's overturning circulation during the deglaciation, this project will perform the first transient ocean simulation of the deglaciation with the newly developed isotope modules in the ocean model of the Community Earth System Model (CESM1), allowing for direct model-data comparison of multiple marine paleo proxies. This project will contribute to STEM workforce development by supporting the training of two graduate students in climate modeling and model-data comparisons and by providing project leadership experience for an early career female scientist, who will work in close collaboration with U.S. and international colleagues. Results from this project will be used in undergraduate and graduate classes at the University of Colorado at Boulder and the University of Wisconsin-Madison and will be incorporated into public outreach through a project website and through general-audience talks. The output of the simulation (called C-iTRACE-O) will be made freely available though the Earth System Grid gateway, allowing the entire paleoclimate community to use it for their research. The simulation will also be contributed to the Paleoclimate Model Intercomparison Project transient deglacial working group, allowing for an evaluation of the CESM C-iTRACE compared to the deglacial simulations from other ESMs.By directly simulating oceanic carbon-isotopes (d13C and D14C), Neodymium (eNd), and Protactinium/Thorium (231Pa/230Th) for the deglaciation and by carrying out sensitivity experiments to investigate the physical mechanisms causing the changing isotopic and geotracer distributions in the transient simulation, it will be possible to address some long-standing scientific questions through direct comparisons to observations and by evaluating tracer-circulation relationships in the model itself, such as:- What was the source and routing of the low-radiocarbon CO2 released during the Mystery Interval? - What is the implication of the d13C evolution in the Atlantic for the deep ocean circulation during the last deglaciation and how much of the d13C change was caused by nutrient- and air-sea gas exchange effects versus circulation changes? - Why is the deglacial evolution of Antarctic Intermediate Water controversial among proxies, notably in eNd and carbon isotopes? - How does 231Pa/ 230Th represent the deglacial evolution of North Atlantic deep circulation and Southern Ocean upwelling?