Evaluating productivity proxies in Antarctic margin sediments

Supervisory Team:

Primary supervisor: Zanna Chase

Co-supervisor: Taryn Noble

Additional supervisors: Layla Creac’h

Brief project description:

Primary productivity on the Antarctic margin forms the base of the marine food chain, is an important part of the global carbon cycle, and is potentially highly sensitive to climate change.

The Antarctic margin experienced dramatic changes associated with the glacial cycles of the Pleistocene, including large changes in ice sheets, sea-ice, ocean temperature and ocean circulation. By studying how primary productivity varied in response to past climate change, paleoceanographers can develop a framework for predicting how productivity might change in response of anthropogenic climate change. However, because we cannot directly measure productivity in the past, we rely on “proxies” of productivity preserved in marine sediment cores. These paleoproductivity proxies include geochemical proxies such as opal, organic carbon, carbon isotopes, and barite, as well as microfossil-based proxies such as diatom abundance and species composition.

The various proxies target different aspects of productivity, and have different biases and uncertainties. A multi-proxy approach, where multiple proxies are combined, can increase confidence in the inferred productivity. However, there have been relatively few studies of productivity proxies in the Antarctic marine environment. This Honours project will compare a large suite of productivity proxies in a series of sediment ‘multicores’ recovered from the east Antarctic slope off Wilkes Land. These cores recover the most recently deposited sediments, allowing a detailed study of proxy behaviour and comparison with modern conditions.

Ultimately, we hope to produce a robust, multi-proxy productivity index that can be applied to paleoceanographic studies.

The project aims are to:

  1. Evaluate the effectiveness of chlorin concentration and loss on ignition as inexpensive alternatives to more costly geochemical techniques for reconstructing productivity
  2. Compare the behaviour of different productivity proxies, between cores and down cores
  3. Compare sediment-based productivity proxies in surface sediments with satellite-based productivity data and oceanographic setting
  4. Determine the feasibility of establishing a productivity index that combines information from multiple proxies (Hebbeln et al. 2002)

Skills students will develop during this research project:

The student will gain skills in laboratory analysis of sediment samples and will gain expertise in sediment geochemistry and Antarctic margin environments. The student will also become familiar with a large suite of geochemical proxy data, including the processing associated with such data. The project will use statistical methods to compare sediment proxies and to derive a multi-proxy index. Finally, the student will learn how to access, plot and interpret satellite-based productivity data.

Authorised by the Executive Director, Institute for Marine and Antarctic Studies
March 24, 2021