EGU2020-5647
https://doi.org/10.5194/egusphere-egu2020-5647
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

A circumpolar coupled ocean – Antarctic ice sheet configuration for investigating recent changes in Southern Ocean heat content

Charles Pelletier1, Lars Zipf2, Konstanze Haubner2, Hugues Goosse1, Frank Pattyn2, and Pierre Mathiot3
Charles Pelletier et al.
  • 1UCLouvain, Earth and Life Institute, Centre de Recherches sur la Terre et le Climat Georges Lemaître, Louvain-la-Neuve, Belgium
  • 2Université libre de Bruxelles, Laboratoire de Glaciologie, Bruxelles, Belgium
  • 3Met Office, Exeter, United Kingdom

From 2016 on, observed tendencies of Southern Ocean sea surface temperatures and Antarctic sea ice extent (SIE) have shifted from cooling down (with SIE increase) to warming up (SIE decrease). This change of Southern Ocean surface thermal properties has been sustained since, which indicates that it is not solely due to the interannual variability of the atmosphere, but also to modifications in the ocean itself. Among other physical phenomena, the acceleration of continental ice shelf melt, through its subsequent impact on the Southern Ocean stratification, has been proposed as one of the potential meaningful drivers of the sea ice changes. Reciprocally, recent studies suggest that besides atmosphere forcings, the upper ocean thermal content bears significant impact on ice shelf melt rates and dynamics. Here we present a new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration aiming at investigating the impact of this ocean – continental ice feedback, developed within the framework of the PARAMOUR project. Our setting relies on the ocean and sea ice model NEMO3.6-LIM3 sending ice shelf melt rates to the Antarctic ice sheet model f.ETISh v1.5, who in turn responds to it and provides updated ice shelf cavity geometry. Both technical aspects and first coupled results are presented.

How to cite: Pelletier, C., Zipf, L., Haubner, K., Goosse, H., Pattyn, F., and Mathiot, P.: A circumpolar coupled ocean – Antarctic ice sheet configuration for investigating recent changes in Southern Ocean heat content, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5647, https://doi.org/10.5194/egusphere-egu2020-5647, 2020.

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Display material version 2 – uploaded on 01 May 2020
Including Western Antarctica and longer ocean - ice sheet coupled time series on last slide.
  • CC1: Comment on EGU2020-5647, David Docquier, 06 May 2020

    Hi Charles et al.,

    This is a very interesting and important study. I have 2 questions:

    1) You show that including ice-shelf cavities increases the sea-ice production in front of these ice shelves (mean seasonal cycle). But I was wondering whether you expected a positive trend in the modeled Antarctic sea-ice area, in better agreement with observations, over 1979-2016 with the inclusion of these cavities.

    2) I like your animation of cumulative ice-shelf volume. Do you know how the sea ice behaves over the same time frame?

    3) Are you running the model until present? (which would provide answer to question 1) Do you know how many hours you need for modeling 1 year?

    Thanks and good luck,

    David

    • AC1: Reply to CC1, Charles Pelletier, 06 May 2020

      Hi David,

      Thanks for your comment!

      1) You show that including ice-shelf cavities increases the sea-ice production in front of these ice shelves (mean seasonal cycle). But I was wondering whether you expected a positive trend in the modeled Antarctic sea-ice area, in better agreement with observations, over 1979-2016 with the inclusion of these cavities.

      Including ice shelf cavities leads to a slight increase in sea ice extent. With or without cavities, we typically have too low sea ice minimum (in February), and too high sea ice maximum (August/September), with belated and too slow melt. Technically speaking, including the cavities does yield to decrease the minimum bias, and increase the maximum one, but I would not say it has a significant impact (see top left plot on the 3rd slide). We were more interested in seeing how the model reacts to the freshwater injection.

      2) I like your animation of cumulative ice-shelf volume. Do you know how the sea ice behaves over the same time frame?

      These volume plots are right out of our first ice sheet - NEMO coupled runs, so we have nothing else, but we will definitely investigate the correlation between cavity geometry and adjacent sea ice.

      3) Are you running the model until present? (which would provide answer to question 1) Do you know how many hours you need for modeling 1 year?

      Our setting typically uses ~200 cores, 1 year takes about 6h. That's not counting queueing time. We can right this configuration up to the end of 2018, which matches the time coverage of the ocean reanalysis ORAS5 used as an open ocean boundary condition at 30°S. I think it's supposed to be updated regularly, so we may soon be able to push it to 2019 as well. In the future, we (and more specifically my colleague Deborah Verfaillie) also plan on performing prediction runs for the 2020 - 2050 period, using CMIP6 EC-Earth results as forcings.

Display material version 1 – uploaded on 30 Apr 2020, no comments