Biogeochemical Controls on Paleoceanographic Proxies: The Antarctic Sea Ice Environment

The Southern Ocean features prominently in many hypotheses developed to explain the drop in atmospheric CO2 during Quaternary glaciations. Critical to the testing of these hypotheses is our ability to reconstruct past conditions of Southern Ocean primary productivity, nutrient availability and utilisation based on isotopic and trace element proxies. One aspect of these proxy records not fully investigated is the extent to which they are influenced by materials formed within sea ice, an environment vastly different from that of the open water column. Most proxies are calibrated for open ocean settings, so material produced within sea ice could potentially confound proxy-based reconstructions of water column conditions. Detailed studies on sea ice material are lacking for most isotopic and trace element proxies used in the Southern Ocean.

I am investigating various influences of the near shore sea ice environment that control surface water productivity and nutrient cycling in Ryder Bay and Marguerite Bay, Antarctica. This was then compared to the composition of organic matter flux to the seafloor with several sediment trap moorings and box cores taken in the area. Using stable isotope and elemental tracers gives an insight into how organic matter is formed and exported in this environment. Understanding how geochemical signatures relate to the levels of nutrient cycling and carbon export in this non-open Ocean environment around Antarctica will provide more accurate interpretations of sediment core records in these Southern Ocean environments.

The stable isotopic and trace element composition of nutrients and organic matter show marked differences in sea ice compared to surface waters. The next question will be answered by the sediment traps currently being analysed; Does sea ice influence the geochemical signatures used in paleoproductivity reconstructions?

The overall goal of this research is to "calibrate" paleoproductivity proxies for continental shelf environments of the Southern Ocean, using the high resolution time series data being gathered.