Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models.
Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface-atmosphere CO2 fluxes from an intercomparison of atmospheric CO2 inversion models (the TransCom 3 project), which includes 16 transport models and model variants. We find an uptake of CO2 in the southern extratropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO2. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO2 observation network within the tropics.
Gurney
Kevin Robert
KR
Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80523, USA.
Law
Rachel M
RM
Denning
A Scott
AS
Rayner
Peter J
PJ
Baker
David
D
Bousquet
Philippe
P
Bruhwiler
Lori
L
Chen
Yu-Han
YH
Ciais
Philippe
P
Fan
Songmiao
S
Fung
Inez Y
IY
Gloor
Manuel
M
Heimann
Martin
M
Higuchi
Kaz
K
John
Jasmin
J
Maki
Takashi
T
Maksyutov
Shamil
S
Masarie
Ken
K
Peylin
Philippe
P
Prather
Michael
M
Pak
Bernard C
BC
Randerson
James
J
Sarmiento
Jorge
J
Taguchi
Shoichi
S
Takahashi
Taro
T
Yuen
Chiu-Wai
CW