Chimie de la carotte EUROCORE (Groenland Central) : variabilité des émissions biologiques au cours du dernier millénaire

Polar ice core provide a unique way to obtain informations allowed a better understanding on change in the biogeochemical cycles during the past. If the study of man-made modification during the last two hundred years are numerous, on the other hand there's a lack of work on the natural climat fluctuations that are the medieval warm periode (1200-1300 A.D.) and the little ice age (1300-1800 A.D.). This study cover this time periode and soluble species trapped in the ice from central Greenland are investigate. The principals results of this study are the chemistry of biomass burning recorded in the ice depends on the atmospheric age of the burning plume. The presence of nitrate in elevate concentration seem to be the chemical signature of young biomass burning plumes, frequency and flux of this input are connected to the climate, with high frequency and low flux during warm periodes and low frequency and high flux during cold periodes, Background chemistry suggests a possible presence of particulate ammonium nitrate during pre-industrial time. The absence of high acid sulfuric loading in the atmosphere in pre industrial time seem to be a possible reason for ammonium nitrate formation. Concentrations of formic acids present in the ice are weIl connected with the story of the canadian vegetation. We confirm a relocation of the MSA from summer to winter layers during buriaI. The lack of knowledge of past marine biogenic emissions can 't allow a comparaison between our marine biogenic tracers and other physic or climatic parameters.