Tiny but Mighty: a diatom and geochemical investigation of dynamic environmental changes along the Wilkes Land margin, East Antarctica between 2-3 Ma
Otago Geology's Grace Duke will present her PhD research on using diatom and geochemical proxies to investigate the Plio-Pleistocene climate of East Antarctica.
What happens when atmospheric temperature changes by 2–3⁰C? A few degrees cooler or warmer than pre-industrial temperatures dictate the presence of large ice sheets, the strength and position of global circulation patterns, and the survival of ecosystems. Diatom and geochemical proxies from IODP site U1361 located on the Wilkes Land continental rise, East Antarctica demonstrate dynamic shifts in Southern Ocean sea surface conditions after the intensification of Northern Hemisphere Glaciation (~2.7-2.8 Ma) and into the early Pleistocene.
Diatoms are phytoplankton that construct their frustule out of silica and their fossil remains are well preserved in Southern Ocean sediments. The inferred environmental preferences of extant and extinct diatom species are the basis for sea surface condition reconstructions and diatom-bound nitrogen isotopes is used to interpret changes in nutrient consumption as supply and demand varies depending on surface conditions.
The demand for nutrients is inferred by weight percent and mass accumulation rate of biogenic silica in bulk sediment which is used as a proxy for primary productivity. Bulk sediment carbon isotopes are used to study mixing in the upper water column above Site U1361 and bulk sediment nitrogen isotopes demonstrates changes in the global nitrogen cycle.
The amalgamation of all these records reveal that the ecosystem of the Wilkes Land margin is sensitive to shifts in position of Southern Ocean fronts and the extent East Antarctic Ice Sheet caused by interhemispheric feedbacks in the aftermath of NHG.
