Constraining the exchange of carbon dioxide over the Amazon : New insights from stable isotopes, remote sensing and inverse modeling

• Main Author: Koren, Gerbrand
• Other Authors: Peters, W., Röckmann, T., Luijkx, I.T.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Wageningen University 2020
• Subjects: Cum laude; South Pole; Sodankylä; South pole
• Online Access: https://research.wur.nl/en/publications/constraining-the-exchange-of-carbon-dioxide-over-the-amazon-new-i; https://doi.org/10.18174/524771

In this thesis we study the exchange of CO₂ between the atmosphere and biosphere, with a focus on the Amazon region. The exchange of CO₂ between atmosphere and biosphere occurs through photosynthetic uptake, which we usually refer to as gross primary production (GPP), and through respiratory release, usually referred to as terrestrial ecosystem respiration (TER). The sum of GPP and TER is the net ecosystem exchange (NEE). The focus of the thesis is on quantifying the exchange of CO₂ between biosphere and atmosphere, and the control of environmental variables on this exchange. In particular, the effect of drought on CO₂ exchange, and the post-drought recovery, are major themes of this thesis.Chapter 2 describes the 3-D model that we developed for Δ¹⁷O in atmospheric CO₂ (a potential tracer for GPP). We implemented this tracer in the global atmospheric transport model TM5, which is driven by ERA-Interim meteorological fields. We parameterized the stratospheric source of Δ¹⁷O in CO₂ by exploiting its observed correlation with stratospheric [N₂O]. The exchange between the atmosphere and biosphere is simulated using the terrestrial biosphere model SiBCASA. We also included the contributions of soils, oceans, biomass burning, fossil fuel combustion and the oxidation of atmospheric CO on Δ¹⁷O in CO₂. For CO₂ in the lowest 500 m of the atmosphere, we simulated a Δ¹⁷O signature of 39.6 per meg, which is ~20 per meg lower than estimates from existing box models. Our model results show good agreement with a measured stratospheric Δ¹⁷O in CO₂ profile from Sodankylä (Finland). In addition, we compared model simulations with tropospheric measurements of Δ¹⁷O in CO₂ from Göttingen (Germany) and Taipei (Taiwan), where we found some agreement but also substantial discrepancies. Finally, we showed model results for Zotino (Russia), Mauna Loa (United States), Manaus (Brazil) and South Pole, which we proposed as possible locations for future measurements of Δ¹⁷O in tropospheric CO₂ that can help to further increase our ...