Preprints
https://doi.org/10.5194/tc-2021-155
https://doi.org/10.5194/tc-2021-155

  15 Jun 2021

15 Jun 2021

Review status: this preprint is currently under review for the journal TC.

Modelling the mass budget and future evolution of Tunabreen, central Spitsbergen

Johannes Oerlemans1, Jack Kohler2, and Adrian Luckman3 Johannes Oerlemans et al.
  • 1Institute for Marine and Atmospheric Research, Utrecht University, Princetonplein 5, Utrecht, 3585CC, The Netherlands
  • 2Norsk Polarinstitutt, Hjalmar Johansengate 14, Trømso, Norway 9296
  • 3Department of Geography, Swansea University, Singleton Park. Swansea, SA2 8PP, United Kingdom

Abstract. Tunabreen is a 26-km long tidewater glacier. It is the most frequently surging glacier in Svalbard, with four documented surges in the past hundred years. We have modelled the evolution of this glacier with a Minimal Glacier Model (MGM), in which ice mechanics, calving and surging are parameterized. The model geometry consists of a flow band to which three tributaries supply mass. The calving rate is set to the mean observed value for the period 2012–2019, and kept constant. For the past 120 years, a smooth Equilibrium Line Altitude (ELA) history is reconstructed by finding the best possible match between observed and simulated glacier length. There is a modest correlation between this ELA history and meteorological observations from Longyearbyen.

The simulated glacier retreat is in good agreement with observations. Runs with and without surging show that the effect of surging on the long term glacier evolution is limited. Due to the low surface slope and associated strong height -mass balance feedback, Tunabreen is very sensitive to changes in ELA. For a constant future ELA equal to the reconstructed value for 2020, the glacier front will retreat by 8 km during the coming hundred years. For an increase of the ELA of 2 m per year, the retreat is projected to be 13 km and Tunabreen becomes a land-based glacier around 2100.

The calving rate is an important parameter: increasing its value by 50 % has about the same effect as a 50 m increase in the ELA, the corresponding equilibrium glacier length being 18 km (as compared to 25.8 km in the reference state).

Response times vary from 150 to 400 years, depending on the forcing and on the state of the glacier (tidewater or land-based).

Johannes Oerlemans et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-155', Francisco Navarro, 12 Aug 2021
    • AC1: 'Reply on RC1', Johannes Oerlemans, 27 Sep 2021
  • RC2: 'Review of "Modelling the mass budget and future evolution of Tunabreen, central Spitsbergen" (tc-2021-155)', Anonymous Referee #2, 23 Aug 2021
    • AC2: 'Reply on RC2', Johannes Oerlemans, 27 Sep 2021
  • AC3: 'Comment on tc-2021-155', Johannes Oerlemans, 27 Sep 2021

Johannes Oerlemans et al.

Johannes Oerlemans et al.

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Short summary
Tunabreen is a 26-km long tidewater glacier. It is the most frequently surging glacier in Svalbard, with four documented surges in the past hundred years. We have modelled this glacier to find out how it react to future climate change. Careful calibration was done against the observed length record for the past 100 years. For a 50 m increase in the equilibrium line altitude (ELA) the length of the glacier will be shortened by 10 km after about 100 years.