EGU2020-9749
https://doi.org/10.5194/egusphere-egu2020-9749
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Glacier-plume or glacier-fjord circulation models? A model intercomparison for Hansbreen-Hansbukta system, Svalbard

Eva De Andrés, Jaime Otero, and Francisco Navarro
Eva De Andrés et al.
  • Universidad Politécnica de Madrid, ETSI de Telecomunicación, Applied Mathematics, Madrid, Spain (eva.deandres@upm.es)

Up to 30% of the global tidewater mass loss corresponds to frontal ablation through submarine melting and calving. However, the glacier-fjord interactions remain poorly understood and challenging to constrain in the models. We have developed a 2D glacier flowline-plume coupled model that includes subglacial discharge, submarine melting and iceberg calving to simulate Hansbreen-Hansbukta system (SW Svalbard). We run the model for 20 weeks, from April to September of 2010, with weekly information exchange between glacier and plume models. The same set up and constraints of a previous glacier-fjord circulation model are used here, making the results of both simulations comparable. We consider a 200 m-width subglacial discharging channel, which was found to be a good approximation in the previous glacier-fjord model. Submarine melt rates show high sensitivity to the subglacial-discharge and ambient fjord-temperature intraseasonal evolution. Calving rates are highly dependent on both submarine melting and crevasse water depth. Glacier-plume and glacier-fjord coupled models differ in vertically-accumulated submarine melt rates (up to 30 % higher for the glacier-plume model) and show different melt-undercutting front shapes, which have an influence on the net stress fields near the glacier front. The quasi-linear melt-undercutting morphology exhibited by the glacier-plume model promotes higher calving rates than the quasi-parabolic front shape resulting from the glacier-fjord model, although both models predict similar front positions. Given that the glacier-plume model diminishes the computational cost by a factor of >50, we think that it is a good option for projection studies, as long as we apply appropriate constraints to subglacial discharge fluxes and ambient fjord temperatures.

How to cite: De Andrés, E., Otero, J., and Navarro, F.: Glacier-plume or glacier-fjord circulation models? A model intercomparison for Hansbreen-Hansbukta system, Svalbard, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9749, https://doi.org/10.5194/egusphere-egu2020-9749, 2020

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Display material version 2 – uploaded on 06 May 2020
I've added some nice pictures of Hansbreen front
  • CC1: Comment on EGU2020-9749, Stefano Ottolenghi, 08 May 2020

    Hey! Thanks for your presentation. I am particularly interested in the interface between ice and ocean, what is marked as point 4 in your slide Methods. Can you elaborate a bit on how you treat it? Do you have any boundary condition that mimic the behavior there, or do you actually simulate it?

    • AC1: Reply to CC1, Eva De Andrés, 08 May 2020

      Hi Stefano! First of all, both glacier and fjord (or plume) models run asincronously. Time steps are 1 week and 0.5 seconds, respectively. From the fjord side, we impose the glacier front to be a vertical and closed boundary, except at the grounding line, where fluxes are allowed (and the addition of mass is compensated with at the fjord mouth). We estimate submarine melt rates at depth and average them over one week. Then, the glacier front shape is changed and the new glacier domain remeshed. The glacier model runs for one week and we obtain a new front position (depending on calving and ice velocities), so we accordingly modify the fjord domain for the next run. Does this answer your question?

      • CC2: Reply to AC1, Stefano Ottolenghi, 08 May 2020

        Thanks, yes! And how do you treat the open ocean? What kind of boundary conditions do you have for that?

        • AC2: Reply to CC2, Eva De Andrés, 08 May 2020

          At the fjord mouth we impose in and out fluxes and transient temperature and salinity based on observations. For details about the glacier-fjord coupled model, you can go to the paper published coupled years ago: De Andrés et al. (2018),

          • AC4: Reply to AC2, Eva De Andrés, 08 May 2020

            I think I'm not allowed to post a link, let's see this time... De Andrés et al. (2018) in Journal of Glaciology. DOI: 10.1017/jog.2018.61

        • AC3: Reply to CC2, Eva De Andrés, 08 May 2020

          I'll be very happy to discuss about these things at any time ;).

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