Collaborative Research: P2C2--isotope-enabled TRAnsient Climate Evolution of the last 21,000 years (iTRACE21)----Understanding Deglacial Climate/Isotope Changes Using iCESM

这项研究利用最先进的同位素地球系统模型 (ESM) 调查了上次冰消期（21,000 至 11,000 年前）气候变化的机制。本项目要解决的主要科学问题是：（1）水的同​​位素组成与全球气候变化之间的关系是什么？ （2）气候系统如何应对末次冰消期不断变化的气候强迫，以及每种强迫的贡献是什么：日照、大气温室气体、大陆冰盖和融水？这些模拟将允许研究气候从年际到轨道时间尺度的连续演化和突变。瞬态模拟的类型标志着模型数据比较的革命性突破，允许直接数据和模型时间序列比较，并将对未来使用模型和观测进行的古气候研究产生重大影响。拟议的模拟将对古气候界的研究产生突破性影响，为许多其他社区项目提供模型数据。它将为未来几代 ESM 与冰冻圈和生物地球化学耦合模型的系统测试奠定基础。具体来说，新版本的 NCAR 社区 ESM (CESM) 启用了水同位素示踪剂，将以全耦合模式运行 21,000 至 11,000 年前的时期。主要模拟将受到日照、大气温室气体浓度、大陆冰盖、海平面和融水的规定变化的强迫，而敏感性模拟将分别研究不同强迫的影响。与使用 CCSM3 运行的上一代瞬态模型（3 度）相比，该模拟将以更高的分辨率（大气中 2 度，海洋 1 度）运行。此外，稳定水同位素示踪剂已包含在大气、陆地表面、海洋和海冰模型中，并将首先针对末次盛冰期（LGM，21,000 年前）和当前气候时间切片进行测试，然后在瞬态模式下运行末次冰消期。所提出的瞬态模拟的一个中心任务是与数据社区密切合作，探索模型数据比较的新范式，重点是同位素的直接时间序列比较。同位素时间序列的模拟将显着改善古气候模型与数据的比较，因为它将减少同位素推断和代理记录的绝对年代学所产生的不确定性。该项目将为威斯康星大学和俄勒冈州立大学的学生提供研究生研究的基础。

This research investigates the mechanisms of climate changes during the last deglaciation (21,000 to 11,000 years ago) using a state-of-the-art isotope-enabled Earth System Model (ESM). The major scientific questions to be addressed in this project are: (1) What are the relationships between the isotopic composition of water and climate changes over the globe? (2) How does the climate system respond to changing climate forcings of the last deglaciation, and what is the contribution from each forcing: insolation, atmospheric greenhouse gases, continental ice sheets, and meltwater? The simulations will allow the study of the continuous evolution and abrupt changes of climate from interannual to orbital time scales. The type of transient simulation marks a transformative breakthrough in model-data comparison, allowing for direct data and model time series comparisons, and will have a significant impact on future paleoclimate studies using both models and observations. The proposed simulations will have a ground breaking impact on research in the paleoclimate community, providing model data for a number of other community projects. It will lay a foundation for a systematic test of future generations of ESMs with coupled cryosphere and biogeochemical models. Specifically, the new version of NCAR's community ESM (CESM), enabled with water isotope tracers, will be run in fully-coupled mode for the period 21,000 to 11,000 years ago. The main simulation will be forced by prescribed changes in insolation, atmospheric greenhouse gas concentrations, continental ice sheets, sea level, and meltwater, while sensitivity simulations will investigate the effect of the different forcings separately. This simulation will be run at a higher resolution (2 degrees in the atmosphere and 1 degree in the ocean) than the previous generation transient model run with CCSM3 (3 degrees). Furthermore, stable water isotope tracers have been included in the atmosphere, land-surface, ocean, and sea-ice models and will be tested first for the Last Glacial Maximum (LGM, 21,000 years ago) and present climate time slices before being run in transient mode for the last deglaciation. One central task of the proposed transient simulations is to explore a new paradigm of model-data comparison in close collaboration with the data community, focusing on direct time series comparisons of isotopes. The simulation of isotope time series will improve paleoclimate model-data comparison significantly, because it will reduce the uncertainties arising from both the inference of isotopes and the absolute chronology of the proxy records. The project will provide the basis for graduate research for students from the University of Wisconsin and Oregon State University.