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This record describes the conductivity-temperature-depth (CTD) data and underway water sample data collected during the CSIRO Investigator transit voyage INVTO1_2024, between 9 March and 20 March 2024. The objective of the voyage was for a safe transit from Fremantle, Western Australia, to Hobart, Tasmania. This record was part of a piggyback project whereby undergraduate students attained at-sea training through the Institute of Marine and Antarctic Studies and the University of Tasmania. The project aim was for students to gain experience with oceanographic data collection, processing and analysis. The CTD data includes 7 CTD profiles that measured conductivity, temperature, pressure, dissolved oxygen, salinity, fluorescence, turbidity and photosynthetically active radiation (PAR). Each of these parameters were collected during each CTD profile. The CTD data also includes calculated measurements of ammonium, nitrate, nitrite, phosphate, silicate, as well as chlorophyll-a, from select rosette bottles. The underway water sample data includes 41 duplicate samples of calculated measurements of chlorophyll-a and associated calculated measurements of ammonium, nitrate, nitrite, phosphate and silicate nutrient concentrations. In both data files, ODV quality flags have been used to indicate data quality.
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Water temperature, averaged across the water column, in Storm Bay followed a distinct seasonal cycle each year, reaching a low of 9 °C and a high of ~ 19 °C. Warmest temperatures were in February, followed by a gradual cooling throughout autumn to a winter minimum in August, then increasing again during spring. Across the sites, the median temperature varied little, with site 3, the most marine of the sites, showing the least spread in values. Median salinity varied little across Storm Bay, being slightly higher at sites 3 and 6, highlighting the marine nature of site 3 and the patterns of seawater circulation in Storm Bay. The lowest salinities were recorded at site 1, where less saline surface waters flow into the bay from the Derwent Estuary. Seasonally, salinity was highest in autumn, with slightly fresher water present in Storm Bay in spring. Some lower salinity values were recorded in July and August, suggesting the presence of less saline subantarctic water flowing into the bay, or freshwater flow from the Derwent. Glider transects show slight lower salinity in summer, then mild stratification in autumn to spring, especially in the shallow regions near the mouth of the Derwent.