Chemistry Department Seminar: Laramie Jensen '15,
"Iron and other trace metals in global ocean: from the Arctic to the Antarctic"
Trace metals like iron (Fe), copper (Cu), nickel (Ni), zinc (Zn), cadmium (Cd), and manganese (Mn) are essential micronutrients for phytoplankton (algae) in the ocean, despite being present in very low concentration (10-9M). Metals can enter the ocean via rivers, coastal sediments, hydrothermal vents, and aerosol deposition. Subsequently, they become integrated with the biological pump, which represents carbon uptake, export, and storage. As a result, the distribution of trace metals in the ocean is typically governed by biological cycling through surface uptake and the regeneration of sinking cells in the deep ocean. This is especially true for Fe, which can limit the growth of algae across large swathes of the global ocean. The Southern Ocean, surrounding the Antarctic continent, is an important site of carbon storage and is also very Fe-limited. Adding Fe to this area of the ocean can stimulate growth of algae and promote carbon dioxide uptake.
In the Arctic Ocean, continental shelves and rivers play an outsize role in trace metal supply, while biological cycling is relatively inactive in the oligotrophic, ice-covered basin. Productivity is increasing across the Arctic, potentially due to an increase in nutrient supply, although this has not been directly measured. Pacific water flowing through the Bering Strait supplies trace metals and nutrients to the Arctic, accounting for up to half of the productivity. However, the inflow through the Bering Strait is not well-constrained, geochemically, and is increasing in volume transport, temperature, and freshness. New data show that trace metal concentrations (Fe, Mn, Cu, Ni, in particular) are closely tied to variations in temperature and salinity in the Bering Strait, making them potential tracers of water mass circulation in the rapidly changing Arctic.
*This seminar counts towards the chemistry major seminar attendance requirement.