The
interannual variability of atmospheric CO2 growth rate shows
remarkable correlation with the El Niño Southern Oscillation (ENSO).
Here we present results from mechanistically based terrestrial carbon cycle
model VEgetation-Global-Atmosphere-Soil (VEGAS) and the Hamburg Ocean Carbon
Cycle Model (HAMOCC), both forced by observed climate fields such as
precipitation and temperature. Land is found to contribute to most of the
interannual variability with a magnitude of about 5 Pg y-1 and the
simulated land-atmosphere flux shows a correlation of 0.59 with the CO2
growth rate observed at Mauna Loa from 1965 to
2000. Ocean-atmosphere flux varies by about 1 Pg y y-1, and is
largely out of phase with land flux. On land, much of the change comes from the
tropical regions such as the Amazon and Indonesia where ENSO related climate anomalies are in the same
direction across much of the tropics. The sub-continental variations over North
America and Eurasia are comparable to the
tropics but the total interannual variability is about 1 Pg y-1 due
to the cancellation from the sub-regions. This has implication for flux
measurement network distribution.
Author: N. Zeng
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