Southern Ocean dynamics, circulation and water mass formation
Prof Matthew England (UNSW)
Staff and students
Dr Annie Foppert (CSIRO staff)
Dr Andrew Lenton (CSIRO staff)
Mr Zhi Li (UNSW PhD student)
Dr Steve Rintoul (CSIRO staff)
Dr Veronica Tamsitt (UNSW staff)
[Music plays and animation waves appear moving up from the bottom of the screen and text appears above: The Centre for Southern Hemisphere Oceans Research]
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Professor Matthew England: The key thing we’re trying to answer in this project is understanding the drivers of the warming in the Southern Ocean.
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The Southern Ocean has warmed at the surface in certain sectors, at depths of the shelves and in the ocean abyss, and that warming could have profound implications for climate and we’re trying to understand exactly what is driving that warming and what we can expect into the future.
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The big reason this research is important is that we need to understand what’s happening with the oceans right at the Antarctic margin.
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This is where the oceans sit right up against the ice shelves and ice sheets and the warming there in certain sectors has been very worrying recently. It’s at a rate that exceeds our expectations.
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With warming there we’re going to see much greater rates of ice melt and that ice melt will drive global sea level rise. So, this is a profound question for humanity.
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The goal with this project in CSHOR is to have a comprehensive understanding of the drivers of warming of the oceans around Antarctica.
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Hundreds of millions of people live near the coast around the globe and are vulnerable to even just one metre of sea level rise. The warming around Antarctica at the moment is enough to melt ice at a rate that will contribute to that sea level rise into the future and that will displace people globally. Understanding this rate of warming at the Antarctic margin will help us understand future sea level rise which will help us plan for this inevitable relocation of communities around the world’s coastlines.
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1. Warming in the surface Southern Ocean
Explore the drivers of the Amundsen-Bellingshausen Sea warming, including warming driven by changes in the pathway / temperatures of the Antarctic Circumpolar Current (ACC), atmospheric teleconnections from the tropics, and coupled ice-ocean feedbacks. A high-resolution ocean model will be used to examine the role of westerly wind anomalies and associated changes in the upwelling and poleward transport of Circumpolar Deep Water. Observations will be used to test and improve the model simulations.
2. Warming in the abyssal ocean
Configure a hierarchy of model experiments to investigate the sensitivity of the lower cell of the Southern Ocean overturning circulation to changes in forcing (wind, heat flux and freshwater fluxes from sea ice melt and melting ice shelves).
3. Warming over the Antarctic continental shelf
Explore what controls the delivery of ocean heat to Antarctic ice shelves. Simulations using global coupled models, high resolution regional models, and idealised process models will be used to assess the sensitivity of ocean – ice shelf interaction to changes in forcing.
4. Carbon uptake in the Southern Ocean
Explore the sensitivity of ocean carbon uptake to changes in the upper cell over the Southern Ocean. A high-resolution biogeochemical model will be used to determine the physical mechanisms responsible for exchange of carbon between the atmosphere and the Southern Ocean (both uptake of anthropogenic carbon and outgassing of natural carbon).
5. Dynamics of the Antarctic Circumpolar Current
Use high resolution models to explore Antarctic Circumpolar Current (ACC) dynamics, with a focus on interaction across scales. The momentum and vorticity budgets of the ACC have long been known to depend on interaction of the current with sea floor bathymetry, but exactly how the large-scale balances are maintained is not understood. Internal waves, sub-mesoscale filaments and mesoscale eddies all likely play a role in determining the response of the current to changes in forcing. High-resolution model studies will be used to explore the impact of local dynamics on the response of the ACC to anomalies in forcing.
CSHOR Science Seminar Project Presentation:
Purich, A., England, M. H., Cai, W., Sullivan, A., & Durack, P. J. (2018). Impacts of Broad-Scale Surface Freshening of the Southern Ocean in a Coupled Climate Model. Journal of Climate, 31(7), 2613-2632. https://doi.org/10.1175/JCLI-D-17-0092.1