Linking terrestrial and marine carbon cycling across the Paleocene-Eocene Thermal Maximum via intermediate complexity Earth system modeling

古新世-始新世最热期（英语：Paleocene-Eocene Thermal Maximum，PETM）是大约5600万年前的全球变暖事件。PETM是由温室气体（包括二氧化碳和/或甲烷）释放到大气和海洋中引起的。地球系统模型已被用来限制PETM碳排放的规模，时间和影响。然而，碳循环反馈对整个PETM环境变化严重程度的贡献仍不清楚。一个关键的差距是陆地碳循环如何响应PETM全球变化。该项目将在一个中等复杂程度的地球系统模型中增加陆地碳循环的代表性。该模型将模拟二氧化碳和甲烷在植被、土壤、大气和海洋之间的循环。这项研究将对地球碳循环对碳排放和全球变暖的敏感性提出新的限制。此外，该项目还将为来自滨江社区学院的本科生提供在加州大学滨江分校的研究经验。这些实习是加州大学滨江地球科学发展计划的基石。该计划的目标是社区学院和4年制课程之间的关键时刻，目标是建立一个多元化的地球科学本科生群体。碳循环反馈是未来气候变化预测中不确定性的一个关键来源。对过去全球变暖事件的研究，如PETM，有可能为这些反馈在温暖的地球上的运作提供关键的见解。通过将陆地碳循环的代表性添加到为古新世晚期配置的中等复杂性地球系统模型中，拟议的研究将允许评估潜在碳循环反馈对较高大气CO2和较高全球温度的随时间变化的响应。此外，拟议的研究将更新海洋和大气甲烷循环的当前表示与陆地生产和甲烷氧化的模拟表示。更新后的模型cGENIE-ENTS将用于评估多个拟议的PETM碳排放情景，包括将模型输出与可用的代理数据集进行比较。计算效率的cGENIE-ENTS模型将允许实验运行的整个约200 kyr PETM的持续时间，从而评估不仅在事件的发生过程中陆地碳循环反馈的潜力，而且其潜在的作用，在确定地球系统恢复的时间尺度。在模型整合过程中，所有模型组成部分都将被耦合，从而产生陆地和海洋碳循环随时间变化的一致输出。新的PETM模拟将提供PETM碳排放量的修订估计，并提供对陆地生物圈反馈行为（积极和消极）的限制。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The Paleocene-Eocene Thermal Maximum (PETM) was a global warming event approximately 56 million years ago. The PETM was caused by the release of greenhouse gases (including carbon dioxide and/or methane) to the atmosphere and oceans. Earth system models have been employed to constrain the magnitude, timing, and impacts of PETM carbon emissions. However, the contribution of carbon cycle feedbacks to the severity of environmental changes across the PETM remains unclear. One key gap is how the terrestrial carbon cycle responded to PETM global change. This project will add a representation of the terrestrial carbon cycle to an intermediate complexity Earth system model. That model will simulate the cycling of carbon dioxide and methane between vegetation, soils, the atmosphere, and the oceans. This study will place new constraints on the sensitivity of Earth’s carbon cycle to carbon release and global warming. In addition, this project will support research experiences at UC Riverside for undergraduate students from Riverside Community College. These internships are a cornerstone of UC Riverside’s Geoscience Development program. That program targets the critical juncture between community college and 4-year programs with the goal of building a diverse population of undergraduates in the geosciences. Carbon cycle feedbacks are a key source of uncertainty in future climate change projections. Study of past global warming episodes, like the PETM, has the potential to provide crucial insight into the operation of these feedbacks on a warm Earth. By adding a representation of the terrestrial carbon cycle to an intermediate complexity Earth system model configured for the late Paleocene, the proposed research will allow evaluation of the time-dependent response of potential carbon cycle feedbacks in response to higher atmospheric CO2 and higher global temperature. In addition, the proposed research will update a current representation of ocean and atmosphere methane cycling with a modeled representation of the terrestrial production and oxidation of methane. This updated model, cGENIE-ENTS, will be used to evaluate multiple proposed PETM carbon emissions scenarios, including comparison of model output against available proxy datasets. The computational efficiency of the cGENIE-ENTS model will allow experiments to be run for the entire ~200 kyr PETM duration and thus evaluate not only the potential for terrestrial carbon cycle feedbacks during the onset of the event, but also their potential role in determining the timescale of Earth system recovery. All model components will be coupled during model integration, producing consistent output for the response of both the terrestrial and marine carbon cycle through time. New PETM simulations will provide revised estimates for PETM carbon emissions and provide constraints on the feedback behavior (both positive and negative) of the terrestrial biosphere.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.