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

University Of California-Riverside, Riverside CA

Investigators

Abstract

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.