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

这项研究使用最先进的同位素地球系统模型(ESM)研究了最后一次冰川消融(21,000到11,000年前)期间气候变化的机制。这个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)气候系统如何对最后一次冰川消融的气候强迫做出反应，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变和突变。这种类型的瞬变模拟标志着模型数据比较方面的一项革命性突破，允许直接进行数据和模型时间序列比较，并将对未来利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社区的研究产生开创性的影响，为其他一些社区项目提供模型数据。这将为利用冰冻圈和生物地球化学耦合模型对未来几代ESM进行系统测试奠定基础。具体地说，新版NCAR社区ESM(CESM)将在21,000至11,000年前以完全耦合的模式运行。主要模拟将根据日照、大气温室气体浓度、大陆冰盖、海平面和融化水的规定变化而强制进行，而敏感性模拟将分别调查不同强迫的影响。与使用CCSM3运行的上一代瞬变模型(3度)相比，此模拟将以更高的分辨率(大气2度，海洋1度)运行。此外，稳定的水同位素示踪剂已经包括在大气、陆地表面、海洋和海冰模型中，并将首先测试最后一次冰川盛期(LGM，21,000年前)和现在的气候时间片，然后在最后一次冰川消融的瞬变模式下运行。拟议的瞬变模拟的一项中心任务是与数据界密切合作，探索一种新的模型-数据比较范式，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大大改善古气候模式与数据的对比，因为它将减少由同位素推断和替代记录的绝对年代学引起的不确定性。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.