Connection shown between airborne iron and ice ages

Science : According to some theories, airborne particles of iron-rich dust originating in South American deserts and deposited in the oceans boosted the growth of microorganisms, which then absorbed enough carbon dioxide from the air that they helped cause ice ages. A new technique for probing seafloor sediments developed by Alfredo Martínez-García of ETH Zürich in Switzerland and his colleagues may provide the first evidence to support those theories. They examined the levels of nitrates bound to the skeletons of microorganisms called foraminifera , from which they were able to determine the activity levels of microscopic life in the oceans. Martínez-García compared those levels with the concentrations of iron in the same seafloor sediment layers and found a strong correlation between the peaks in iron concentration, biological activity, and ice ages during the past 160 000 years. The data the researchers collected appear to account for only half of the carbon dioxide variation during the ice ages, however. So while the iron deposits may be a significant contributor to the cooling, other factors must have also been involved.