EGU2020-18595
https://doi.org/10.5194/egusphere-egu2020-18595
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

A new method for characterising the Antarctic Circumpolar Currents using Argo float temperature and salinity profiles

Luke Roberts1, Rhiannon Jones1,2, Matthew Donnelly3, and Katharine Hendry1
Luke Roberts et al.
  • 1University of Bristol, Earth Sciences, United Kingdom of Great Britain and Northern Ireland (lr16476@bristol.ac.uk)
  • 2University of Southampton, National Oceanography Centre Southampton, European Way, Southampton, SO14 3ZH, UK
  • 3British Oceanographic Data Centre, National Oceanography Centre, Joseph Proudman Building, Brownlow Street, Liverpool, L3 5DA, UK

Argo is an array of automated profiling floats, which have allowed the rapid development of high-resolution and high-quality oceanographic data acquisition. The international program has been in operation since the 1990s providing continuous hydrographic data globally. There are now over a million individual float profiles, contributing to our understanding of global ocean physical properties, such as circulation processes at both a local and regional scale. With these innovations come the challenges of data processing, and compilation of user-friendly data products. For example, the Southern Ocean is a critical region that modulates our climate, via heat exchange, carbon storage, biogeochemistry, and primary productivity. An improved quantified understanding of Southern Ocean currents, informed by Argo, must be implemented in policy-relevant high-resolution climate models to advance our understanding of future change.

 

In May 2019, a new collaboration was formed between the Southern Ocean Argo Resource Centre (British Oceanographic Data Centre) and the University of Bristol. The aims were two-fold: to produce a method for characterising Southern Ocean frontal zones using Argo floats, and to train early career researchers in the University sector in data processing and management. We have created a publicly available code that characterises physical features of the Antarctic Circumpolar Current using Argo float profiles, using minimal software, and without the need to access high-performance computers. The code categorises each profile based on the temperature and salinity ‘fingerprints’ of zones between each Southern Ocean front. This allows the user to produce output surface plots from user-specified time-slices and geographic areas, and so compare frontal movement in time and space.

How to cite: Roberts, L., Jones, R., Donnelly, M., and Hendry, K.: A new method for characterising the Antarctic Circumpolar Currents using Argo float temperature and salinity profiles, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18595, https://doi.org/10.5194/egusphere-egu2020-18595, 2020

Comments on the presentation

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Presentation version 2 – uploaded on 07 May 2020
Updated 07/05/2020 - Higher resolution version
  • CC1: Comment on EGU2020-18595, Krissy Reeve, 07 May 2020

    Hi Luke, I really like your poster and enjoyed your presentation in the live chat earlier! I was just wondering what sort of length scales do you apply here, and whether you are able to identify/say anything about the influence of mesoscale eddies on the fronts? 

    • AC1: Reply to CC1, Luke Roberts, 07 May 2020

      Hi Krissy, 

      Thanks for your comment and interest. I ran the 'soarc code' (as we call it) for 2011 to 2017, using all Argo data south of 35 degrees. This time scale was chosen so we could compare my results to previously published data which uses higher powered models. The AD test for normal distribution of latitudes within a longitudinal bins was taken for 2011 to 2017, and we saw that there was fair normal distribtion in most zones.

      Regarding mesoscale eddies, there is definiatley some evidence in the Scotia Sea Southern Zone for eddies. The bimodal distirubtion of the SZ profiles in nearly all years is indicative of a meandering zone path. But that was the main idenitfication of mesoscale strucutres. 

      Ah I have just realised by 'length scale' you may mean length, not time... The longitudinal bins (sections) we use are 10 degrees wide, and this seems to provide adequate accuracy to average yearly and monthly locations to assess trends.

      Please do follow up with any more thoughts or questions if anything is unclear.

      Thanks again, Luke

      • CC5: Reply to AC1, Krissy Reeve, 12 May 2020

        Thanks a lot for your response Luke (sorry for my own delayed response...)! It's some really nice work you've done here! Do you have plans to publish this work (in addition to already providing the source code)? I think I might have an idea for an experiment in the Weddell Gyre region which would involve using your code, and so I hope to contact you at some point in the near (or possibly not so near as I'm already buried under) future (I'm also friends with Matt, so I can contact him too).

        I hope you had a successful EGU week! :-)

        • AC4: Reply to CC5, Luke Roberts, 18 May 2020

          Hi Krissy,

          Thanks for your response. 

          Currently there is no plan to publish the work as it was my masters thesis. Having said that, I would be interested in doing so, so any more thoughts and ideas you have would be great! I would be very intriuiged to hear what you had in mind in the weddell gyre, as the floats there seem to capture the gyre very nicely in the code. 

          Do email Matt or me (lr16476@bristol.ac.uk) in the future. 

          Best

          Luke

  • CC2: Comment on EGU2020-18595, naomi krauzig, 07 May 2020

    Thank you for the interesting display. You mention that the code is made available. Could you share maybe the link of it ? 

    All the best,  

    Naomi 

    • AC3: Reply to CC2, Luke Roberts, 07 May 2020

      Hi there,

      Here is the link. There is a report within the link which give detail of how to run the code. But please contact me with any quieries.

      https://github.com/argosoarc/soarc_floatchar

      Best,

      Luke 

  • AC2: Comment on EGU2020-18595, Luke Roberts, 07 May 2020

    Hi there,

    Here is the link. There is a report within the link which give detail of how to run the code. But please contact me with any quieries.

    https://github.com/argosoarc/soarc_floatchar

    Best,

    Luke 

     

    • CC3: Reply to AC2, naomi krauzig, 07 May 2020

      Thank you very much! 

    • CC4: Reply to AC2, naomi krauzig, 07 May 2020

      Thank you very much! 

  • CC6: Interannual variability of fronts, Alexander Haumann, 15 May 2020

    Thanks for the very interesting display, Luke! Great work! The very large interannual variability in the frontal positions seems really exciting (Figure 4).

    Would it be correct to say that there seems to be larger interannual variability of the frontal position for the more southern fronts compared to the SAZ?

    If so, would you expect this to be a circumpolar feature?

    Do you know why there might be a difference in how the fronts change over time?

    The background for these questions is that there is a lot of discussion on whether or not fronts can shift in a changing climate or if they are stable due to topographic steering.

Presentation version 1 – uploaded on 04 May 2020 , no comments