Regional geophysical data analysis near Cape Darnley, East Antarctica.

Antarctic Coast Bathymetry in the region of Cape Darnley

Background.

Cold, dense Antarctic bottom water (AABW) is a major contributor to the global ocean circulation. AABW production was recently discovered off Cape Darnley. This is one of only four regions producing this globally significant water mass around the Antarctic margin (Ohshima et al., 2013). Knowledge of AABW export pathways in this region is poorly understood due to a lack of detailed bathymetry, although a new high-resolution (100 m) bathymetric compilation of the Cape Darnley region in East Antarctica has been released (Smith et al., 2020), which brings all bathymetric data together.

The production of AABW is susceptible to increased freshwater input due to enhanced ice shelf melt (Aoki et al., 2020). Holocene sediments from the region link past AABW production to changes in the Cape Darnley polynya (Borchers et al., 2016). However, longer records, including periods warmer than present, are required to resolve the driving mechanisms between ice shelf melt, sea-ice formation and bottom water production under a warming climate. The aims of the overlying research program that this Master's project sits within (i.e. Antarctic Bottom Water production in the past: Records from marine sediments, Cape Darnley, East Antarctica) are:

i) to understand past changes in AABW production using long sediment cores from the continental slope over multiple warm periods during the Pleistocene;

ii) develop an improved bathymetry model to support oceanographic modelling of AABW pathways.

This Master project has the objective of undertaking a data review on previously collected seafloor geophysical data held by Geoscience Australia and/or other Antarctic nations, to facilitate identifying target locations for future Pleistocene coring sites on the RV Investigator mission (IN2022_V01) to the Cape Darnley region (15 Jan. -11 Mar. 2022; Chief Scientist Dr Alix Post). The sediment cores will be crucial to providing records of previous warmer interglacials and will provide an analogue for understanding the impact of any future changes in bottom water production associated with a warming climate.

Subject to Marine National Facility and ANU travel and pandemic policies, and success with the Master project, the student may be invited to participate on the 2022 voyage. The project has the potential to be expanded to a PhD project at ANU as a result of voyage data becoming available for additional research opportunities.

Resources:

Australian Antarctic Data Center Gazetter: Cape Darnley.  https://data.aad.gov.au/aadc/gaz/display_name.cfm?gaz_id=247

Aoki, S., Katsumata,K., Hamaguchi, M., Noda, A., Shimada, K., Hirano, D., Simizu, D., Aoyama, Y., Doi, K. and Nogi, Y.F,. 2020. Freshening of Antarctic Bottom Water off Cape Darnley, East Antarctica. Journal of Geophysical Research: Oceans, 125(8):https://doi.org/10.1029/2020JC016374

Borchers, A., Dietze, E., Kuhn, G., Esper, O., Voigt, I., Hartmann, K., Diekmann, B., 2016. Holocene ice dynamics and bottom-water formation associated with Cape Darnley polynya activity recorded in Burton Basin, East Antarctica. Marine Geophysical Research 37, 49-70.

Ohshima, K.I., Fukamachi, Y., Williams, G.D., Nihashi, S., Roquet, F., Kitade, Y., Tamura, T., Hirano, D., Herraiz-Borreguero, L., Field, I., Hindell, M., Aoki, S., Wakatsuchi, M., 2013. Antarctic Bottom Water production by intense sea-ice formation in the Cape Darnley polynya. Nature Geoscience 6, 235.

Smith, J., Nogi, Y., Spinoccia, M., Dorschel, B., Leventer, A. 2020. Cape Darnley Bathymetry Grid v.1. Geoscience Australia, Canberra. https://doi.org/10.26186/135334

Partnerships

This project is offered under Geoscience Australia's supported Master projects program at the Research School of Earth Sciences at ANU.