Influence of Atmospheric Transport on Estimates of Variability in the Global Methane Burden
Pandey, Sudhanshu ; Houweling, Sander ; Krol, Maarten ; Aben, Ilse ; Nechita-Banda, Narcisa ; Thoning, Kirk ; Röckmann, Thomas ; Yin, Yi ; Segers, Arjo ; Dlugokencky, Edward J. - \ 2019
Geophysical Research Letters 46 (2019)4. - ISSN 0094-8276 - p. 2302 - 2311.
atmospheric burden - atmospheric transport - CH emissions - interhemispheric difference - methane - TM5
We quantify the impact of atmospheric transport and limited marine boundary layer sampling on changes in global and regional methane burdens estimate using tracer transport model simulations with annually repeating methane emissions and sinks but varying atmospheric transport patterns. We find the 1σ error due to this transport and sampling effect on annual global methane increases to be 1.11 ppb/year and on zonal growth rates to be 3.8 ppb/year, indicating that it becomes more critical at smaller spatiotemporal scales. We also find that the trends in inter-hemispheric and inter-polar difference of methane are significantly influenced by the effect. Contrary to a negligible trend in the inter-hemispheric difference of measurements, we find, after adjusting for the transport and sampling, a trend of 0.37 ± 0.06 ppb/year. This is consistent with the emission trend from a 3-D inversion of the measurements, suggesting a faster increase in emissions in the Northern Hemisphere than in the Southern Hemisphere.
Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange
Alden, C.B. ; Miller, J.B. ; Gatti, L.V. ; Gloor, M.M. ; Laan-Luijkx, I.T. van der; Krol, M.C. ; Guan, K. ; Michalak, A.M. ; Touma, T. ; Andrew, A. ; Basso, L.S. ; Correia, C.S.C. ; Domingues, L.G. ; Joiner, J. ; Lyapustin, A. ; Peters, W. ; Shiga, Y.P. ; Thoning, K. ; Velde, I.R. van der; Leeuwen van, T.T. ; Yadav, V. ; Diffenbaugh, N.S. - \ 2016
Global Change Biology 22 (2016)10. - ISSN 1354-1013
Understanding tropical rainforest carbon exchange and its response to heat and drought is critical for quantifying the effects of climate change on tropical ecosystems, including global climate–carbon feedbacks. Of particular importance
for the global carbon budget is net biome exchange of CO2 with the atmosphere (NBE), which represents nonfire carbon fluxes into and out of biomass and soils. Subannual and sub-Basin Amazon NBE estimates have relied heavily on
process-based biosphere models, despite lack of model agreement with plot-scale observations. We present a new analysis of airborne measurements that reveals monthly, regional-scale (~1–8 9 106 km2) NBE variations. We
develop a regional atmospheric CO2 inversion that provides the first analysis of geographic and temporal variability in Amazon biosphere–atmosphere carbon exchange and that is minimally influenced by biosphere model-based first
guesses of seasonal and annual mean fluxes. We find little evidence for a clear seasonal cycle in Amazon NBE but do find NBE sensitivity to aberrations from long-term mean climate. In particular, we observe increased NBE (more carbon
emitted to the atmosphere) associated with heat and drought in 2010, and correlations between wet season NBE and precipitation (negative correlation) and temperature (positive correlation). In the eastern Amazon, pulses of
increased NBE persisted through 2011, suggesting legacy effects of 2010 heat and drought. We also identify regional differences in postdrought NBE that appear related to long-term water availability. We examine satellite proxies and
find evidence for higher gross primary productivity (GPP) during a pulse of increased carbon uptake in 2011, and lower GPP during a period of increased NBE in the 2010 dry season drought, but links between GPP and NBE
changes are not conclusive. These results provide novel evidence of NBE sensitivity to short-term temperature and moisture extremes in the Amazon, where monthly and sub-Basin estimates have not been previously available.