Tracing iron cycling from the ice sheets to the polar oceans

The polar oceans play a significant role in climate through uptake of anthropogenic carbon and heat via biological and physical mechanisms. However, the factors driving patterns of primary production in coastal regions are still uncertain; the impact of glacial meltwater in particular is poorly understood. Our changing climate is driving an increase in delivery of glacial meltwater to the ocean in both the northern and southern hemispheres. In addition to influencing physical structure of the water column, this meltwater can also impact marine productivity by supplying nutrients, including essential trace metals such as iron (Fe) that have the potential to stimulate phytoplankton growth. However, little is known about the fate of this glacially-derived Fe, although a recent study suggests that in Greenland fjords most Fe is lost to sinking particles close to the site of input. Critically, our ability to constrain current Fe supply from meltwater requires a better understanding of the cycling of Fe between dissolved and particulate phases, and the time scales governing these processes. This project will address this gap by using naturally-occurring isotopes of radium (Ra) and other tracers to assess time scales of loss and dispersion of dissolved and particulate Fe in glacial marine environments.