Japan Geoscience Union Meeting 2016

Presentation information

International Session (Oral)

Symbol A (Atmospheric and Hydrospheric Sciences) » A-CG Complex & General

[A-CG09] Development and application of land and ocean biogeochemistry components of Earth system models

Mon. May 23, 2016 3:30 PM - 5:00 PM 102 (1F)

Convener:*Michio Kawamiya(Japan Agency for Marine-Earth Science and Technology), Kaoru Tachiiri(Japan Agency for Marine-Earth Science and Technology), Tomohiro Hajima(Japan Agency for Marine-Earth Science and Technology), Vivek Arora(Canadian Centre for Climate Modelling and Analysis), Chair:Vivek Arora(Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada)

3:45 PM - 4:00 PM

[ACG09-08] Current state of terrestrial CO2 exchange estimations: progresses and remaining issues

*Masayuki Kondo1, Kazuhito Ichii1, Prabir Patra1, Tazu Saeki1 (1.Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology)

Keywords:Terrestrial CO2 exchange, Atmospheric CO2 inversion, Ecosystem model simulation

Terrestrial ecosystems play a critical role in formation of a feedback loop of carbon dioxide (CO2) in atmosphere with atmospheric reservoir and climate, and thus directing a course of the future projection of climate change. The research community has spent significant efforts to understand behaviors of terrestrial ecosystems under a steady rise in atmospheric CO2 concentration and temperature during the recent decades and deepen knowledge about the regional and global patterns of terrestrial CO2 sinks and sources. estimate the terrestrial CO2 exchange, while seeking consistency between simulated and observed CO2 concentrations. The bottom-up approach estimates the terrestrial CO2 exchange using ecosystem models, which simulate the ecosystem-scale carbon cycle by considering the internal biogeochemical mechanisms of carbon flows for each prescribed vegetation type and soil.
However, the current estimates of terrestrial CO2 exchange by the bottom-up and top-down approaches remain inconsistent. As illustrated in the recent IPCC Assessment Report (AR5), the top-down approach tends to indicate stronger CO2 sinks in temperate and boreal regions than the bottom-up approach does. Furthermore, the two approaches exhibited contrasting CO2 sink–source patterns in the tropics; the bottom-up approach indicated CO2 sinks and the top-down approach CO2 sources. As illustrated by these inconsistencies, a consensus on the geographic distribution of the terrestrial CO2 exchange has yet to be established among the research community.
In this study, we elaborate the current status and issues of terrestrial CO2 flux estimations by the top-down and bottom-up approaches. Specifically, we compare the bottom-up estimate from dynamic global vegetation models that are forced by interannual variations of CO2 concentration, climate and land use changes, with the top-down estimate from atmospheric CO2 inversions. We show an improved level of agreement between the two estimates in relation to seasonal variability and, regional and global budgets, since the IPCC AR5. We also discuss the remaining issues causing inconsistency between the two estimates.

This research was supported by Environment Research and Technology Development Funds (2-1401) from the Ministry of the Environment of Japan and Asia-Pacific Network for Global Change Research (APN: grant#ARCP2011-11NMY-Patra/Canadell).