Stanford University

*** Ph.D. Thesis/ Oral Defense ***

Leveraging differences across spatial scales and regions to enhance understanding of North American terrestrial carbon exchange

Kelsey Foster

Friday, December 12, 12:00 PM 

Green Earth Science 365 

Department of Earth System Science

Advisor: Dr. Anna Michalak

 Earth's biosphere acts as a carbon sink that helps offset climate change impacts from increased greenhouse gas emissions into the atmosphere. However, the magnitude and strength of the terrestrial carbon sink remain poorly constrained, with competing hypotheses proposed to explain discrepancies between different modeling approaches. This dissertation explores how atmospheric observations can serve as both a constraint on flux estimates and as a tool for understanding regional environmental drivers of carbon fluxes, while analyzing results across spatial scales to identify where and why uncertainties persist. The first chapter examines how bottom-up, terrestrial biosphere models, and top-down, atmospheric inversions, compare across spatial scales ranging from local to continental across North America, and assesses the value of atmospheric observations in yielding more consistent estimates between modeling approaches. The second chapter investigates which specific regions within North America drive disagreements between bottom-up and top-down modeling approaches. The third chapter uses atmospheric observations of both carbon dioxide and methane from aircraft campaigns to examine ecosystem-specific sensitivities to temperature and soil moisture anomalies in North American Arctic-boreal regions. This dissertation demonstrates additional ways to leverage atmospheric constraints to understand terrestrial carbon exchange and highlights the value of looking beyond continental-scale comparisons. These results provide actionable insights for reducing uncertainties in regional carbon budgets and improving model representations of key processes in climate-sensitive regions.

Zoom link https://stanford.zoom.us/j/94126400580?pwd=tLjuiapUPragiq5wHXwPeh2XpFaMQZ.1