RECONSTRUCTION OF PAST TERRESTRIAL CARBON STORAGE IN THE NORTHERN-HEMISPHERE FROM THE OSNABRUCK-BIOSPHERE-MODEL AND PALAEODATA
Résumé
Until now the reconstruction of past carbon storage from data has often been done by using modern carbon databases. The results are Likely a rough approximation of the reality, and can be improved by the use of biosphere models. These models usually need to be parameterized by a large number of environmental inputs, which are often not available from palaeodata. The empirical Osnabruck Biosphere Model (OBM) needs as input only 3 environmental parameters, easily derivable from pollen data. We adapted it to reconstruct the past terrestrial carbon storage from palaeodata. Sensitivity experiments performed by uniformly decreasing the mean annual temperature, average annual precipitation and/or CO2 concentration suggest that temperature and CO2 concentration affect the carbon storage more than does precipitation. The use of the only palaeodata available at a global scale shows that only a weakening of CO2 fertilization must be invoked to reconstruct the Last Glacial Maximum (LGM) carbon storage, which is an intermediate situation between the no-fertilization effect assumed by previous studies and the fertilization effect based on modernist empirical equations. The terrestrial carbon storage in the Northern Hemisphere for this period ranged from 910 to 1270 Pg, which represents an increase of 330 to 710 Pg (a planetary increase of 470 to 1014 Pg from the LGM to the present). This result is similar to our previous reconstruction and agrees broadly with the values estimated on the basis of 0.32 parts per thousand change obtained for global deep ocean delta(13)C.