Quantifying carbon burial on the Northwest Australian shelf: Connections with Late Pleistocene climatic patterns

The Pleistocene is characterized by substantial variations in ice volume and pronounced climatic oscillations. Over the last 1 million years, glacial-interglacial climate cycles are marked by increasing amplitude and by a pronounced decrease in pCO₂ levels during glacial intervals. The mechanisms driving this carbon cycle reorganization, and a full quantification of oceanic and sedimentary carbon sinks during glacials, remain unresolved. To address this question, we measure organic and inorganic δ¹³C, as well as the total organic carbon (TOC) to quantify export productivity and organic carbon burial changes on the NW Shelf of Australia.

Bulk carbonate sediments from IODP Expedition 356 Site U1460 (27°22′S, 112°55′E), collected at a water depth of 214.5 mbsf, are the focus of this study. This site, located on the outer North West Shelf of Australia, is influenced by the competition between the southward flowing oligotrophic Leeuwin Current and the colder norward flowing West Australian Current. During glacial intervals, the West Australian Current is dominant, facilitating enhanced productivity through wind driven upwelling. These dynamics suggest that the region could have acted as a significant organic carbon sink during Late Pleistocene glacials, with high rates of organic carbon accumulation on the western Australian shelf and continental slopes. Here, we present preliminary results from δ¹³C and TOC analyses spanning the last ~600,000 years. These data provide insights into the variability of organic carbon burial and its contribution to the global carbon cycle in the Mid- to Late Pleistocene, advancing our understanding of carbon storage mechanisms in response to climatic shifts.