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Project details

Title: International nutrient inter-comparison study in the Southern Ocean: quantifying and identifying the causes of differences in dissolved inorganic nutrient datasets between global seagoing laboratories - Phase 2
Id: 2579
Investigator(s): Andreas Marouchos
CSIRO Oceans & Atmosphere - Hobart [details]

Years: 2023


Conference abstract

Journal Article


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List of surveys that this project was on.

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Survey InvestigatorDescription

Andreas Marouchos (CSIRO NCMI)

INIV 2023 is a phase 2 of the international inter-comparison voyage previously conducted by CSIRO in 2017 in which several possible analytical errors were speculated and will be extensively explored in this voyage. The exercise will be carried out on a 15-day voyage along the hydrographic repeat GO-SHIP SR03 transect line in Southern Ocean. GO-SHIP SR03 transect line is selected due to its availability of long-measured historical nutrient data and its proximity to the home port, Hobart Tasmania. As the focus of this voyage is to preserve the nutrient analysis routine from each laboratory; therefore, various participating team will also utilise several laboratory spaces available on RV Investigator to organise and install their instrumentations. Containerised hydrochemistry lab will also be set up on this voyage which can be utilised for any additional secondary experiments.

INIV 2023 will mainly exploit the full-depth CTD. Each participant will collect CTD/Niskin water samples and analyse the sample on board daily. Approximately one CTD cast is planned for every 24 hours targeting a similar daily shift schedule. The CTD will cover the full spatial water profile– which can be up to the maximum of 30 depths – where single sample will be collected for each depth. Specific depths will be identified by the science party during the downcast to ensure specific water masses are targeted. Dissolved oxygen and salinity will also be sampled by MNF hydrochemistry team to calibrate CTD sensor. Approximately 11 stations along the SR03 transect line up to 55°S, 141°E and at the Southern Ocean Time Series (SOTS) will be sampled throughout the duration of this voyage. One of the stations will be dedicated as a precision CTD cast where all Niskin bottles are fired at three depths, the upper circumpolar deep water (UCDW), lower circumpolar deep water (LCDW) and the deep chlorophyll max (DCM) which is carried out for reproducibility purpose.

Nutrient measurement results from this voyage will also be compared with available historical data from both SR03 transect line and SOTS. Unified method of calculation for expanded measurement uncertainty will also be proposed abroad with all participants to determine statistical significance of the datasets.

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