Etude des variations du cycle du carbone au cours de l'Holocène à partir de l'analyse couplée CO2-CH4 piégés dans les glaces polaires
Extracted air from polar ices of Greenland and Antarctica constitute a real archive of the past atmospheres of our planet. The aim of this study was to understand the carbon fluxes under natural atmosphere in order to examine the future carbon cycle under anthropogenic atmosphere from the analyses of CO2 and CH4 atmospheric concentrations during the Holocene (the last 10,000 yBP). These results were analysed in the light of a three-box atmospheric model of methane. We estimated the\ nterpolar gradient then the relative contribution of methane sources in low and middle-high northem latitudes during the Holocene. Thanks to comparisons between temporal evolution of these sources, and paleoclimatic reconstructions based on continental and marine records, as weil as climatic models coupling atmosphere ocean vegetation systems, methane variations were attribuled to latitudinal variations in sources distribution. These CH4 changes allowed us to constrain the possible effects of each carbon reservoir on CO2 variations during the same period. The major conclusion of this work is that the ocean have played a key role and have initiated CO2 changes while continental biosphere could have played a regulator role