Possible abrupt shift in the land uptake of carbon

Claudie Beaulieu, Princeton University, beaulieu@princeton.edu (Presenter)
Jorge L. Sarmiento, Princeton University, jls@princeton.edu
Sara Mikaloff-Fletcher, National Institute of Water and Atmospheric Research, s.mikalofffletcher@niwa.co.nz
Jie Chen, University of Missouri-Kansas City, chenj@umkc.edu
David Medvigy, Princeton University, dmedvigy@princeton.edu

A recent study of the net land carbon sink suggests that the net land carbon uptake abruptly increased after 1988/1989. Determining the nature and exact time of this increase is difficult due to the large variability in the land uptake of carbon. Here we use a change point detection technique, which is designed to detect the timing and magnitude of level shifts in time series and to discriminate between several types of changes (e.g. constant mean, abrupt shift in the mean, linear trend or linear trend with a level shift). We apply this technique to the net land carbon sink estimated using the Mauna Loa and South Pole atmospheric CO2 records, fossil fuel estimates, and a suite of ocean models. We confirm that it is likely that an abrupt shift in the mean of the net land uptake of carbon occurred in 1988. After taking into account the variability in the net land uptake of carbon due to the influence of volcanic aerosols and the El Niño Southern Oscillation, we find that there is a step increase of about 1 Pg C/yr in 1988 (significant at the 99% and 96% confidence level for Mauna Loa and South Pole, respectively). By also applying our change point detection technique to the atmospheric growth rate of CO2, we find that it is likely that the atmospheric growth rate of CO2 exhibits a level shift in 1988 of approximately -1 Pg C/year, which is most likely due to the shift in the net land uptake of carbon.

Presentation Type:  Poster

Session:  Coupled Processes at Land-Atmosphere-Ocean Interfaces   (Mon 4:00 PM)

Associated Project(s): 

• Buermann, Wolfgang: Detection and Attribution of Rapid Large-scale Shifts in the Terrestrial Carbon Cycle ...details

Poster Location ID: 10