Sack Lunch Seminar (SLS)

Iron and Lead Geochemistry of the Ocean: On the Road to GEOTRACES



Iron (Fe) is a key essential nano-nutrient for marine biota. Most of the lead (Pb) in the ocean is anthropogenic, transported by the atmosphere from civilization into the surface ocean and thenceforward by ocean circulation and particle transport. These elements share a paucity of global ocean data because of the extreme hazards of sample contamination from rusty lead-painted ships. With lack of data comes lack of understanding, so ocean models that require an Fe component to correctly represent the biota suffer from (using Henry Stommel's words) "a peculiar dream-like quality". This year, after 7 years of planning, the global ocean community is embarking on a ten-year effort (GEOTRACES) to map out the distributions of Fe, Pb, and other trace elements and their isotopes, in order to better understand their roles in ocean biogeochemistry and in developing paleoclimate reconstructions. We will be on the first US GEOTRACES transect for 52 days at sea this fall. Using MIT-developed methods that pre-date GEOTRACES, we will demonstrate what we can learn about these elements given even a limited database, and what GEOTRACES promises to deliver at its completion.