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Project details
| Title: | Quantifying Dust Fluxes in the Southern Ocean Time Series using Thorium Isotopes in Seawater |
| Id: | 2650 |
| Investigator(s): | George Rowland
|
| Description: | This project aims to quantify the flux of mineral dust and associated nutrients supplied to the Southern Ocean using measurements of thorium in seawater. One isotope (232Th) traces dust, while another (230Th) is a time-keeper. The data will be used to assess agreement between different methods of dust flux estimation, including sediment traps and dust deposition models (which are associated with large uncertainties). Extending a time series of thorium samples collected at the SOTS site will provide us with samples from five of eight years (2018–2025), allowing us to create a modern baseline dust flux estimate for the site and to test assumptions about thorium’s geochemistry. Few data exist to investigate annual-multiannual changes in thorium concentrations: using this time series we can test whether estimates of thorium residence time, and therefore dust flux, are accurate. Comparing these recent annual-multiannual samples to legacy samples (from 1997) will also allow decadal scale differences in dust and thorium to be assessed. These research questions can be summarised as follows: 1. What is the magnitude of dust (and trace metal) flux to the SOTS site and ACC-SWOT sites and how does this vary over annual and decadal timescales? 2. How well do different measures of dust flux agree at the SOTS site? 3. Are changes in thorium concentrations consistent with residence time estimates? Using low-contamination methods we will analyse 5–10 L of seawater per sample collected from the CTD rosette, quantifying dust fluxes through the whole water column, with a particular focus on resolving details in the upper ocean. |
| Years: | 2025 |
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 | Investigator | Description |
|---|---|---|
| IN2025_V02 [details] |
Elizabeth Shadwick | The primary objective is to first deploy a new set of SOTS moorings (SOFS-14 and SAZ-27) and then recover the existing SOTS moorings (SOFS-13, and SAZ-26). Each of the SOTS moorings deliver 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, and underway measurements. 1. Deploy SOFS-14 meteorology/biogeochemistry mooring 2. Deploy SAZ-27 sediment trap mooring 3. Recover SOFS-13 meteorology/biogeochemistry mooring 4. Recover SAZ-26 sediment trap mooring 5. CTD sampling (3 cast to 4550m, 2 to 600m) at the SOTS site, including collecting samples for nutrients, oxygen, dissolved inorganic carbon, alkalinity, and eDNA analyses 6. Ship meteorological observations at SOFS buoys for comparisons 7. Deployment of BGC-Argo Float (with additional UVP sensor recently refurbished after the SOLACE float was recovered). 8. Recovery of ACC-SWOT mooring at 55S site (deployed on the FOCUS IN2023_V07 voyage). 9. Deployment of BoM drifters at site of ACC-SWOT mooring recovery; CTD cast for post-calibration of recovered sensors. 10. Carry out underway air and water sampling and sensor measurements, including bio-optics and bio-acoustics |