Modelling the carbon cycle in the soils and rivers of Switzerland with radiocarbon
File(s)
Author(s)
Brunmayr, Alexander
Type
Thesis
Abstract
Each year, humans emit over 10 billion tonnes of carbon into the atmosphere as CO2 through fossil fuel combustion and land use changes. Around one third of this anthropogenic CO2 is then taken up by the terrestrial ecosystem, reducing the rate of CO2 accumulation in the atmosphere and thus slowing down climate change. However, the future of this terrestrial carbon sink is uncertain, as major Earth System Models (ESMs) produce contradictory future projections. Two of the most important sources of uncertainty are the persistence of soil organic carbon (SOC), and the role of the lateral carbon transport (LCT) through inland waters. In this work, I constrain the SOC and LCT dynamics and their environmental sensitivities with measurements of radiocarbon (14C), the radioactive carbon isotope, which is a powerful tracer of the carbon cycle. Current ESMs are already known to systematically overestimate the 14C content of SOC and to thus likely overestimate the future terrestrial carbon sink. However, in a model evaluation with a global soil dataset, I reveal that the new generation of soil models, which aims to replace the old generation employed by ESMs, also produces incorrect 14C predictions for SOC. To improve upon the new-generation models, I develop a novel SOC model, constrained with highly informative 14C measurements for forest soils of Switzerland. I then create an isotopic model for riverine dissolved inorganic carbon, which represents 90% of LCT through rivers, to assess the role of LCT in the terrestrial carbon balance and national CO2 budget of Switzerland. Although Switzerland is my main focus as an ideal study site, with its abundance of data and contrasting landscapes undergoing rapid change, the novel modeling methods and scientific insights in this thesis can be upscaled to advance our understanding of carbon cycle dynamics on a global scale.
Version
Open Access
Date Issued
2024-10-03
Date Awarded
2024-12-01
Copyright Statement
Attribution 4.0 International Licence (CC BY)
License URL
Advisor
Graven, Heather
Sponsor
Swiss National Science Foundation
Grant Number
193770
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)