EGU2020-18765
https://doi.org/10.5194/egusphere-egu2020-18765
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Blowing snow in Antarctica and its contribution to the surface mass balance

Franziska Gerber1,2, Varun Sharma1,2, and Michael Lehning1,2
Franziska Gerber et al.
  • 1CRYOS, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
  • 2WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland (gerberf@slf.ch)

On the windiest, coldest and driest continent of the world, blowing snow is frequently active, especially during the winter months. Coastal regions with strong katabatic winds are especially prone to blowing snow and its sublimation. However, the contribution of blowing snow to the surface mass balance from snow blown off the continent and blowing snow sublimation is not well constraint by direct measurements. Furthermore, model and satellite assessments disagree on the magnitude of the effect.

Current studies of the Antarctic surface mass balance are mainly based on regional climate models. However, most models rely on rather simple representations of the snow cover as well as blowing snow. With the aim of improving the surface mass balance representation and specifically snow transport and sublimation due to blowing snow, we coupled the well-established snow model SNOWPACK to the Weather Research and Forecasting Model (WRF). The new coupled model, called ‘CRYOWRF’, is aimed at an improved representation of snow and snow-atmosphere interaction in all cryospheric environments.

CRYOWRF simulations show good agreement with measurements at meteorological stations on the Antarctic continent. Moreover, the timing of modeled blowing snow events agrees well with few local blowing snow measurements. Monthly frequencies of simulated and satellite-derived spatial blowing snow distributions result in similar patterns. We will present estimates of the amount and importance of blowing snow on the surface mass balance in Antarctica based on 8 years of simulations (2010-2018), with a special focus on blowing snow sublimation. The introduced model will be useful for future predictions of surface mass balance estimates, which are important to assess the contribution of the Antarctic ice sheet to sea level rise in a warming world.

How to cite: Gerber, F., Sharma, V., and Lehning, M.: Blowing snow in Antarctica and its contribution to the surface mass balance, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18765, https://doi.org/10.5194/egusphere-egu2020-18765, 2020

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  • CC1: Comment on EGU2020-18765, Josué Gehring, 04 May 2020

    Very nice study, thank you! The Amery region appears to have strong sublimation and relatively low precipitation leading to a negative SMB in summer. Do you know of any studies that confirm that? 

    • AC1: Reply to CC1, Franziska Gerber, 11 May 2020

      Dear Josué, Thank you for this question. Indeed the sublimation exceeds precipitation in the Amery region in our model, even in the annual mean. We do not know of any study reporting about this for the summer month in particular. However, there is indication for strong sublimation in this region in other publications (e.g. Agosta, 2019). A recent study by Smith et al., 2020 based on ICESat and ICESat-2 measurements also shows a negative mass balance trend in the Amery region. However, they attribute it mainly to ice loss by melting. Concerning precipitation there is a study by Turner et al., 2018 showing that the Amery ice shelf gets 50 % of its annual precipitation in less than 10 days of heaviest precipitation. We did not analyze the precipitation event yet but it would definitely be interesting to analyze whether such heavy precipitation events are well represented. Moreover, it might be related to the precipitation distribution in the forcing data (i.e. ERA5) as for several other reanalysis datasets patterns with low annual mean precipitation have been reported previously (Broomwich et al., 2011).

      Agosta, C., Amory, C., Kittel, C., Orsi, A., Favier, V., Gallée, H., van den Broeke, M. R., Lenaerts, J. T. M., van           Wessem, J. M., van de Berg, W. J., Fettweis, X., 2019: Estimation of the Antarctic surface mass      balance using the regional climate model MAR (1979-2015) and identification of dominant processes,               The Cryosphere, 13, 281 – 296, doi:10.5194/tc-13-281-2019

      Broomwich, D. H., J .P. Nicolas, and A. J. Monaghan, 2011: An Assessment of Precipitation Changes over Antarctica and the Southern Ocean since 1989 in Contemporary Global Reanalysis, Journal of Climate, 24, 4189-4209, doi:10.1175/2011JCLI4074.1.

      Smith B., H. A. Fricker, A. S. Gardner, B. Medley, J. Nilsson, F. S. Paolo, N. Holschuh, S. Adusumilli, K. Brunt, B. Csatho, K. Harbeck, T. Markus, T. Neumann, M. R. Siegfried, H. J. Zwally, 2020: Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes, Science, doi:10.1126/science.aaz5845.

      Turner, J., T. Phillips, M. Thamban, W. Rahaman, G. J. Marshall, J. D. Wille, V. Favier, V. H. L. Winton, E. Thomas, Z. Wang, M. van den Broeke, J. S. Hosking, and T. Lachlan-Cope, 2018: The Dominant Role of Extreme Precipitation Events in Antarctic Snowfall Variability, Geophysical Research Letters, 46, 3502-3511, doi:10.1029/2018GL081517.

      • CC4: Reply to AC1, Josué Gehring, 11 May 2020

        Thanks for this detailed answer!

  • CC2: Comment on EGU2020-18765, Christoph Kittel, 05 May 2020

    Dear authors, 
    thanks you for your interesting study. You evaluated the SMB without blowing snow, but what about the SMB in the simulation with blowing snow? 

    • AC2: Reply to CC2, Franziska Gerber, 11 May 2020

      Dear Christoph, Indeed this is a very interesting question. Unfortunately, we do not yet have a long simulation from which we could analyze the surface mass balance with blowing snow. The blowing snow frequency patterns displayed are results from a preliminary simulation in which the occurrence of blowing snow was represented but the interaction of blowing snow with the microphysics scheme was generating too much precipitation. Recent simulations do not suffer from this problem anymore but were only run for a short time period yet.

  • CC3: Comment on EGU2020-18765, Ruth Mottram, 05 May 2020

    This is a really nice study! Very interesting results. I have a few questions, I hope you don't mind answering:

    1) Did you check your SMB (with and without blowing snow) against observations from stakes or radar? Does the coupling improve the results consistently? 

    2) It looks like the frequency has the right pattern but seems to overestimate the frequency generally compared to the Palm reference (thanks for that btw, I was not aware of that study!) so I was wondering if that left you with a lower SMB compared with the observed or if it offsets other errors

    3) what resolution are you running the model at? Is the blowing snow scheme sensitive to resolution?

    4) How does the blowing snow addition affect the total SMB integrated over the whole continent? Is it a few percent or tens of percents? We are looking at implementing something in our regional model to represent blowing snow and I would be interested to hear how significant it is. 

     

    Many thanks for sharing such an interesting presentation. 

    Ruh Mottram, DMI

    • AC3: Reply to CC3, Franziska Gerber, 11 May 2020

      Dear Ruth, thank you for all these interesting questions. For most of them, we unfortunately do not have simulation results yet but model runs and analysis are planned. Below, we try to give you some insight into the current state of the analysis.

      1) Did you check your SMB (with and without blowing snow) against observations from stakes or radar? Does the coupling improve the results consistently?

      As these are preliminary results of our study, we do not have a thorough analysis yet. The SMB displayed only shows the SMB without blowing snow as the simulation with blowing snow was not yet run over a longer period and had some issues with the interaction between blowing snow and precipitation in preliminary simulations, in which the blowing snow frequency was rather well represented (as shown in the presentation). However, we plan to analyze the results against the stake observations and in collaboration with GRACE satellite analysis.

      2) It looks like the frequency has the right pattern but seems to overestimate the frequency generally compared to the Palm reference (thanks for that btw, I was not aware of that study!) so I was wondering if that left you with a lower SMB compared with the observed or if it offsets other errors

      One likely reason for this is that the blowing snow in Palm et al., 2018 is for clear sky conditions only while our blowing snow frequencies are total annual means. Hence, we may have higher frequencies as blowing snow likely occurs during storm events with cloudy sky and precipitation. We cannot yet specify whether this results in too low SMB but the blowing snow frequency may be higher during overcast days compared to clear sky conditions. For further analysis, we plan to calculate blowing snow frequencies for clear sky conditions from our model results.

      3) what resolution are you running the model at? Is the blowing snow scheme sensitive to resolution?

      The horizontal resolution of these simulations is 27 km. The model is very recent and we have not run any sensitivity studies for the resolution. We plan to run sensitivity studies at a local scale down to a resolution of at least 1 km but the model also has the capability for large-eddy-simulations (LES) setups that will allow us to analyze down to 100 m or 50 m.

      4) How does the blowing snow addition affect the total SMB integrated over the whole continent? Is it a few percent or tens of percents? We are looking at implementing something in our regional model to represent blowing snow and I would be interested to hear how significant it is.

      Unfortunately, we cannot answer this question yet. We are about to run first simulations for the validation and to get to a first estimate of the effect in our model. If you are interested, we can keep you updated about our results.

      Franziska Gerber