University of Tasmania

The global overturning circulation influences our global climate through heat and carbon uptake, ocean ventilation, biogeochemical cycling, and sea level rise. The formation and export of Antarctic Bottom Water (AABW) in the Southern Ocean is key component of the overturning circulation. Thus, changes in the overturning circulation have global-scale consequences. Observations and modelling show that changes are underway and mainly driven by changes in the freshwater budget on the shelf in a few key locations (Rintoul et al. 2026). This project will investigate variability and change in the deep global overturning circulation by combining historical observations with novel ocean observing technology to observe Antarctic Bottom Water with unprecedented spatial and temporal resolution.

The harsh environment of the Southern Ocean makes collecting in-situ observations especially difficult and the resulting data are severely seasonally biased. Full-depth observations required to observe AABW are outside the range of typical core Argo profiling floats, and thus even more sparse in space and time. The advent of Deep Argo – autonomous profiling floats capable of measuring the full-depth of the ocean and under sea ice – are changing the way we understand variability in the deep ocean (e.g. Foppert et al. 2021; Thomas et al. 2020; Zilberman et al. 2020). This project will use 9+ years of data from an array of Deep Argo floats in the Australian Antarctic Basin, first deployed in 2018 and continually reseeded with additional floats to maintain the array. New data from the Multidisciplinary Investigations of the Southern Ocean (MISO) voyage in 2024 and upcoming MISO-2 voyage in 2027 also provide in-situ data of AABW properties, adding to a multi-decadal timeseries of observed AABW variability and change along key pathways of the deep overturning circulation. The MISO-2 voyage will also deploy four Deep Argo floats equipped with dissolved oxygen sensors to allow basin-scale mapping of ventilation by the deep overturning circulation for the first time. Together, these datasets make-up a unique and novel perspective of AABW variability and change, and ventilation of the deep ocean.

https://www.utas.edu.au/research/degrees/available-projects?id=12367

Contact: Annie Foppert (Annie.foppert@utas.edu.au)