Atmospheric iron fluxes over the last deglaciation: Climatic implications

A decrease in the micronutrient iron supply to the Southern Ocean is widely believed to be involved in the atmospheric CO2 increase during the last deglaciation. Here we report the first record of atmospheric iron fluxes as determined in 166 samples of the Dome C ice core and covering the last glacial-interglacial transition (22-9 kyr B. P.). It reveals a decrease in fallout flux from 24x10(-2) mg Fe m(-2) yr(-1) during the Last Glacial Maximum to 0.7x10(-2) mg Fe m(-2) yr(-1) at the onset of the Holocene. The acid leachable fraction of iron determined in our samples was the 60% of the total iron mass in glacial samples, about twice the value found for Holocene samples. This emerging difference in iron solubility over different climatic stages provides a new insight for evaluating the iron hypothesis over glacial/interglacial periods.