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Preprints
https://doi.org/10.5194/tc-2020-148
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2020-148
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  14 Jul 2020

14 Jul 2020

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This preprint is currently under review for the journal TC.

Modelling perennial firn aquifers in the Antarctic Peninsula (1979–2016)

J. Melchior van Wessem1, Christian R. Steger2, Nander Wever3, and Michiel R. van den Broeke1 J. Melchior van Wessem et al.
  • 1Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands
  • 2Institute for Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
  • 3Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA

Abstract. We use two snow models, the IMAU Firn Densification Model (IMAU-FDM) and SNOWPACK, to model firn characteristics in the Antarctic Peninsula (AP). We force these models with mass and energy fluxes from the Regional Atmospheric Climate MOdel (RACMO2.3p2) to construct a 1979–2016 climatology of AP firn density, temperature and liquid water content. A comparison with 75 snow temperature observations at 10 m depth and with density from 11 firn cores, suggests that both snow models perform adequately.

In this study, we focus on the detection of so-called perennial firn aquifers (PFAs), that are formed when surface meltwater percolates into the firnpack in summer, is then buried by snowfall, and does not refreeze during the following winter. In 941 model grid points, covering ~ 28,000 km2, PFAs existed for at least one year in the simulated period, most notably in the western AP. At these locations, surface meltwater production exceeds 150 to 300 mm w.e. yr−1, with accumulation at least an order of magnitude larger.

Most pronounced and widespread are PFAs modelled on and around Wilkins ice shelf. Here, both meltwater production and accumulation rates are sufficiently high to cause PFA formation in most years in the 1979–2016 period, covering a large part of the ice shelf. Other notable PFA locations are Wordie ice shelf, an ice shelf that has almost completely disappeared in recent decades, and the relatively warm northwestern mountain ranges of Palmer Land, where accumulations rates can be extremely large and PFAs are formed frequently.

We find that not only the magnitude of melt and accumulation is important, but also the timing. If large accumulation events occur in the months following an above average summer melt event, this favours PFA formation in that year. Finally, we find that most PFAs are predicted near the grounding lines of the (former) Prince Gustav, Wilkins and Wordie ice shelves. This highlights the need to further investigate how PFAs may impact ice shelf disintegration events, in a similar way as supraglacial lakes do.

J. Melchior van Wessem et al.

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Short summary
This study presents the first modelled estimates of perennial firn aquifers (PFAs) in Antarctica. PFAs are subsurface meltwater bodies that do not refreeze in winter due to the isolating effects of the snow they are buried underneath. They have first been identified in Greenland, but conditions for their existence are also present in the Antarctic Peninsula. These PFAs can have important effects on meltwater retention and ice shelf stability and, consequently, sea-level rise.
This study presents the first modelled estimates of perennial firn aquifers (PFAs) in...
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