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

古新世-始新世最高温度(PETM)是大约5600万年前的全球变暖事件。PETM是由向大气和海洋释放温室气体(包括二氧化碳和/或甲烷)引起的。地球系统模型已经被用来限制PETM碳排放的规模、时间和影响。然而，碳循环反馈对整个PETM环境变化的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应对PETM全球变化。该项目将在中等复杂的地球系统模型中增加陆地碳循环的表示。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施加新的限制。此外，该项目还将支持加州大学河滨分校为河滨社区学院的本科生提供的研究体验。这些实习是加州大学河滨分校地球科学发展计划的基石。该计划的目标是社区大学和四年制计划之间的关键节点，目标是培养多样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的一个关键不确定性来源。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至关重要的洞察。通过将陆地碳循环的表示添加到为古新世晚期配置的中等复杂性地球系统模型中，拟议的研究将能够评估潜在的碳循环反馈对大气二氧化碳升高和全球气温升高的依赖时间的响应。此外，拟议的研究将更新目前海洋和大气甲烷循环的图示，使用陆地甲烷生产和氧化的模型图示。这一更新的模型cGENIE-Ents将用于评估多个拟议的PETM碳排放情景，包括将模型输出与现有的代理数据集进行比较。CGENIE-Ents模型的计算效率将允许在整个~200KYR PETM持续时间内进行实验，从而不仅评估事件开始期间陆地碳循环反馈的潜力，而且评估它们在确定地球系统恢复时间尺度方面的潜在作用。所有模型组件将在模型集成期间耦合，产生随时间推移的陆地和海洋碳循环响应的一致输出。新的PETM模拟将提供对PETM碳排放的修订估计，并对陆地生物圈的反馈行为(积极和消极)提供限制。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.