Samples were collected from the East Antarctic margin, aboard the Australian Marine National Facility R/V Investigator from January 14th to March 5th 2017 (IN2017_V01; Armand et al., 2018). This marine geoscience expedition, named the “Sabrina Sea Floor Survey”, focused notably on studying the interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles. Ten litres seawater samples were collected using a CTD rosette equipped with Niskin® bottle and filtered through a 0.45µm Millipore GWSC04510: Ground Water sampling capsule, directly into acid-cleaned 10 L polyethylene jerrycans. Samples were then acidified to pH 2 with 2 mL/L of distilled 6M HCl in a laminar flow hood. These samples were analysed for thorium isotopes (230Th and 232Th), a tracer of particle dynamics. The sample preparation was carried out in the clean lab of the Institute for Marine and Antarctic Studies (UTAS, Hobart). Seawater samples were acidified with HF (final concentration 0.6 mM, Middag et al., 2015), spiked with 10 pg of 229Th (NIST 4328C, National Institute of Standards and Technology, USA) and left to equilibrate for at least 48h. Samples were preconcentrated using Nobias® PA1L (Hitachi Technologies, Japan) cartridges, following the procedure of Pérez-Tribouillier et al., (2019). The separation and purification of thorium isotopes were performed by anion-exchange chemistry (Anderson et al., 2012). Purified Th fractions were analysed using an Element II Sector Field Inductively Coupled Plasma Mass Spectrometer (SF-ICP-MS, Thermo Fischer Scientific, Bremen, Germany) at the Central Science Laboratory (CSL) of the University of Tasmania. Sample introduction was achieved using an Aridius® II desolvating nebulizer (DSN, CETAC Technologies, USA). The capacitive guard electrode was activated to maximise signal sensitivity. Raw intensities of 230Th and 232Th were blank and mass bias corrected. Concentrations were calculated using the isotope dilution equation reported in Sargent et al., (2002). References - Anderson, R. F., Fleisher, M. Q., Robinson, L. F., Edwards, R. L., Hoff, J. A., Moran, S. B., … Francois, R. (2012). GEOTRACES intercalibration of 230Th, 232Th, 231Pa, and prospects for 10Be. Limnology and Oceanography: Methods, 10(4), 179–213. - Armand, L. K., O’Brien, P. E., Armbrecht, L., Baker, H., Caburlotto, A., Connell, T., … Young, A. (2018). Interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles (IN2017-V01): Post-survey report. ANU Research Publications - Middag, R., Séférian, R., Conway, T. M., John, S. G., Bruland, K. W., and de Baar, H. J. W. (2015). Intercomparison of dissolved trace elements at the Bermuda Atlantic Time Series station. Marine Chemistry, 177, 476–489. - Pérez-Tribouillier, H., Noble, T. L., Townsend, A. T., Bowie, A. R., and Chase, Z. (2019). Pre-concentration of thorium and neodymium isotopes using Nobias chelating resin: Method development and application to chromatographic separation. Talanta, 1–10. - Sargent, M., Harrington, C., and Harte, R. (2002). Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS). Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS). Royal Society of Chemistry.

Oceanographic measurements were conducted along CLIVAR Southern Ocean meridional repeat transect SR3 between Tasmania and Antarctica from October to December 2001. A total of 135 CTD vertical profile stations were taken, more than half to within 20 m of the bottom. Over 2200 Niskin bottle water samples were collected for the measurement of salinity, dissolved oxygen, nutrients, CFC's, CCl4, dissolved inorganic carbon, alkalinity, 13C, DMS/DMSP/DMSO, halocarbons, barium, barite, ammonia, del30Si, dissolved and particulate organic carbon, particulate silica, 15N-nitrate, 18O, 234Th, 230Th, 231Pa, primary productivity and biological parameters, using a 24 bottle rosette sampler. Near surface current data were collected using a ship mounted ADCP. Two sediment trap moorings were serviced, and a third mooring was deployed at a new location. A summary of all CTD data and data quality is presented in the data report. This work was completed as part of ASAC project 1335.