Terrestrial carbon sink observed from space: variation of growth rates and seasonal cycle amplitudes in response to interannual surface temperature variability Institute of Environmental Physics (IUP), University of Bremen FB1, Bremen, Germany
03 Jan 2014
Received: 01 Aug 2013 – Published in Atmos. Chem. Phys. Discuss.: 30 Aug 2013Abstract. The terrestrial biosphere is currently acting as a net carbon sink on the
global scale, exhibiting significant interannual variability in strength. To
reliably predict the future strength of the land sink and its role in
atmospheric CO2 growth, the underlying biogeochemical processes and
their response to a changing climate need to be well understood. In
particular, better knowledge of the impact of key climate variables such as
temperature or precipitation on the biospheric carbon reservoir is essential.
Revised: 03 Dec 2013 – Accepted: 04 Dec 2013 – Published: 03 Jan 2014
It is demonstrated using nearly a decade of SCIAMACHY (SCanning Imaging
Absorption spectroMeter for Atmospheric CHartographY) nadir measurements that
years with higher temperatures during the growing season can be robustly
associated with larger growth rates in atmospheric CO2 and smaller
seasonal cycle amplitudes for northern mid-latitudes. We find linear
relationships between warming and CO2 growth as well as seasonal
cycle amplitude at the 98% significance level. This suggests that the
terrestrial carbon sink is less efficient at higher temperatures during the
analysed time period. Unless the biosphere has the ability to adapt its
carbon storage under warming conditions in the longer term, such a
temperature response entails the risk of potential future sink saturation via
a positive carbon-climate feedback.
Quantitatively, the covariation between the annual CO2 growth rates
derived from SCIAMACHY data and warm season surface temperature anomaly
amounts to 1.25 ± 0.32 ppm yr−1 K−1 for the Northern
Hemisphere, where the bulk of the terrestrial carbon sink is located. In
comparison, this relationship is less pronounced in the Southern Hemisphere.
The covariation of the seasonal cycle amplitudes retrieved from satellite
measurements and temperature anomaly is −1.30 ± 0.31 ppm K−1
for the north temperate zone. These estimates are consistent with those from
the CarbonTracker data assimilated CO2 data product, indicating that
the temperature dependence of the model surface fluxes is realistic.
Citation: Schneising, O., Reuter, M., Buchwitz, M., Heymann, J., Bovensmann, H., and Burrows, J. P.: Terrestrial carbon sink observed from space: variation of growth rates and seasonal cycle amplitudes in response to interannual surface temperature variability, Atmos. Chem. Phys., 14, 133-141, doi:10.5194/acp-14-133-2014, 2014.