Data Trawler - Project details

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Project details

Title: Quantification of dust deposition to the ocean using thorium isotopes in seawater and aerosol sampling.
Id: 2589
Investigator(s): Zanna Chase
University of Tasmania - Institute of Marine and Antarctic Studies [details]

Description: Quantification of dust deposition to the ocean using thorium isotopes in seawater and aerosol sampling. This piggyback project is part of an ARC Discovery Project (CIs Zanna Chase, Andrew Bowie and Peter Strutton, UTAS) entitled ‘Dust to the ocean: does it really increase productivity?” The purpose of the larger project and of this piggyback is to quantify dust deposition to the ocean and its chemical and ecological impact by using new geochemical techniques. The SOTS site is unique in the Southern Hemisphere because we can compare a number of different methods to estimate dust deposition and can also look at interannual variability in dust deposition. In terms of national benefit, mineral dust is an important, yet difficult to quantify source of nutrients to the ocean. This project will deliver more accurate estimates of dust deposition to the ocean around Australia, a region where dust models perform poorly. The expected benefit of the project includes better dust models used to predict future changes in dust deposition to the ocean. Accurate dust predictions are critical for predicting future ocean fish production and carbon uptake. Priority 1 is to collect filtered seawater samples (10L) from a depth profile at the SOTS site. Ideally the full water column depth, but if time is limited the upper 1,500m. These samples will be analysed for 230Th and 232Th concentrations at UTAS. We would also retain sample aliquots for possible future analysis of rare earth elements and Nd isotope composition, pending further funding. For this we would need the CTD-rosette (36 bottle ideally), a laminar flow bench and milli-Q water, all MNF-supplied. We would supply jerry-cans for sampling, storage boxes for the jerry-cans, cartridge filters, and HCl for acidification. Priority 2 is to collect rainwater and aerosol samples using the ship’s aerosol sampling apparatus. These samples would be analysed for labile and total bioactive trace metals, as well as 232Th, at UTAS. For this we would need the MNF aerosol sampling lab. We would supply filters and storage containers for filters. Priority 3 is to collect seawater particulates using in-situ pumps. These samples would be analysed for 230Th and 232Th concentrations at UTAS as well as particulate organic carbon, inorganic carbon and opal. For this we would need the MNF and UTAS ISPs. We would supply filters, batteries and storage containers for filters. The three sample types provide three independent measures of dust flux.
Years: 2021

List of surveys that this project was on.

Use [details] link to view survey details (map, reports, metadata etc) including links to download data.

Survey InvestigatorDescription

Dr Shadwick (ACE CRC) The Southern Ocean has a predominant role in the movement of heat and carbon dioxide into the ocean interior moderating Earth’s average surface climate. The IMOS SOTS sub-facility uses a set of two automated moorings to measure these processes under extreme conditions, where they are most intense and have been least studied. The atmosphere-ocean exchanges occur on many timescales, from daily insolation cycles to ocean basin decadal oscillations and thus high frequency observations sustained over many years are required. The current context of anthropogenic forcing of rapid climate change adds urgency to the work. The primary objective is to first deploy a new set of SOTS moorings (SOFS-9 and SAZ-22) and then recover the existing SOTS moorings (SOFS-8 and SAZ-21). Each of the SOTS moorings delivers to specific aspects of the atmosphere-ocean exchanges: • the SAZ sediment trap mooring collects samples to quantify the transfer of carbon and other nutrients to the ocean interior by sinking particles and investigate their ecological controls. • the Southern Ocean Flux Station (SOFS) mooring measures meteorological and ocean properties important to air-sea exchanges, ocean stratification, waves, currents and biological productivity and ecosystem structure. Water samples are collected for more detailed nutrient and plankton investigations after recovery. Ancillary work will obtain supporting information on atmospheric and oceanographic conditions using CTD casts, underway measurements, Triaxus towed body, Continuous Plankton Recorder and autonomous profiling Biogeochemical-Argo floats, and potentially casts of a bio-optical sensor package.
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