A LARGE NORTHERN-HEMISPHERE TERRESTRIAL CO2 SINK INDICATED BY THE C-13 C-12 RATIO OF ATMOSPHERIC CO2/

Measurements of the concentrations and carbon-13/carbon-12 isotope rat ios of atmospheric carbon dioxide can be used to quantify the net remo val of carbon dioxide from the atmosphere by the oceans and terrestria l plants. A study of weekly samples from a global network of 43 sites defined the latitudinal and temporal patterns of the two carbon sinks. A strong terrestrial biospheric sink was found in the temperate latit udes of the Northern Hemisphere in 1992 and 1993, the magnitude of whi ch is roughly half that of the global fossil fuel burning emissions fo r those years. The challenge now is to identify those processes that w ould cause the terrestrial biosphere to absorb carbon dioxide in such large quantities.