21 Jan 2021

21 Jan 2021

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

Firn changes at Colle Gnifetti revealed with a high-resolution process-based physical model approach

Enrico Mattea1, Horst Machguth1, Marlene Kronenberg1, Ward van Pelt2, Manuela Bassi3, and Martin Hoelzle1 Enrico Mattea et al.
  • 1Department of Geosciences, University of Fribourg, Fribourg, Switzerland
  • 2Department of Earth Sciences, Uppsala University, Uppsala, Sweden
  • 3Department of Forecasting Systems, Regional Agency for Environmental Protection of Piedmont, Turin, Italy

Abstract. Our changing climate is expected to affect ice core records as cold firn progressively transitions to a temperate state. Thus there is a need to improve understanding and further develop quantitative process modeling, to better predict cold firn evolution under a range of climate scenarios. Here we present the application of a distributed, fully coupled energy balance model, to simulate high-alpine cold firn at Colle Gnifetti over the period 2003–2018. For the first time, we force such a model with high-resolution, long-term and extensively quality-checked meteorological data measured in closest vicinity of the firn site, at the Capanna Margherita (4560 m a.s.l.). The model incorporates the spatial variability of snow accumulation rates, and is calibrated using several, partly unpublished high-altitude measurements from the Monte Rosa area. The simulation reveals a very good overall agreement in the comparison with a large archive of firn temperature profiles. The rate of firn warming at 20 m depth is estimated at 0.44 °C per decade. Our results show that surface melt over the glaciated saddle is increasing by 3–4 mm w.e. yr−2 depending on the location (29–36 % in 16 years), although with large inter-annual variability. Analysis of modeled melt indicates a marked tendency towards small melt events (< 4 mm w.e.), which collectively represent a significant fraction of the melt totals. Atmospheric humidity is found to be a prominent control over melt occurrence, with considerable amounts of sublimation happening in dry conditions. For future developments, we recommend implementing a physical simulation of meltwater infiltration, to be calibrated with more measurements of percolation in cold firn.

Enrico Mattea et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of Mattea et al.', Vincent Verjans, 11 Feb 2021
  • RC2: 'Comment on tc-2020-367', Adrien Gilbert, 17 Feb 2021
  • RC3: 'Comment on tc-2020-367', Anonymous Referee #3, 21 Feb 2021

Enrico Mattea et al.

Model code and software

EBFM Colle Gnifetti Enrico Mattea, Horst Machguth, Marlene Kronenberg, Ward van Pelt, Manuela Bassi, and Martin Hoelzle

Enrico Mattea et al.


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Short summary
In our study we find that climate change is affecting the high-alpine Colle Gnifetti glacier (Swiss/Italian Alps) with an increase in melt amounts and ice temperatures. In the near future this trend could threaten the viability of the oldest ice core record in the Alps. To reach our conclusions, we used for the first time the meteorological data of the highest permanent weather station in Europe (Capanna Margherita, 4560 m), together with an advanced numeric simulation of the glacier.