15 Mar 2023
 | 15 Mar 2023
Status: this preprint is currently under review for the journal TC.

Surface mass balance modelling of the Juneau Icefield highlights the potential for rapid ice loss by the mid-21st century

Ryan N. Ing, Jeremy C. Ely, Julie M. Jones, and Bethan J. Davies

Abstract. Plateau icefields are large stores of freshwater, preconditioned to enhanced mass loss due to their gently sloping accumulation areas. Accurately modelling the mass-balance of these icefields is therefore vital for obtaining projections of their future contribution to sea-level rise. Here, we use the COupled Snowpack and Ice surface energy and mass-balance model in PYthon (COSIPY) to simulate the historical and potential future mass balance of the Juneau Icefield, Alaska – a high elevation (>1200 m) plateau icefield. We force the model with dynamically downscaled climate simulations, pertaining to both the past and potential future (RCP 8.5) conditions. The rich dataset of surface mass balance observations of the Juneau Icefield allows us to tune COSIPY, providing confidence in our future predictions and highlighting changes to the icefield between the years 1980 and 2019. Icefield-wide negative mass balances were simulated from the start of the 21st century, as many glaciers transitioned from positive to negative mass-balances. Under RCP8.5, the model simulates increasing negative mass balance across Juneau Icefield, with the entire icefield potentially displaying a negative mass balance by the mid-21st century. This simulated loss of accumulation is driven by increased temperatures and reduced amounts of snowfall, exposing more of the icefield to thinning. Ice thinning is likely to be exacerbated by the exposure of ice to melting across the plateau surface, and prolonged melt may lead to an increase in disconnections, splitting glaciers between their accumulation and ablation areas at icefalls. The similar hypsometry of other high latitude plateau icefields and ice caps may mean that similar processes will act to determine their potential fate in our changing climate.

Ryan N. Ing et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on tc-2023-33', Andrew Bliss, 17 Mar 2023
  • RC1: 'Comment on tc-2023-33', Anonymous Referee #1, 26 Apr 2023
  • RC2: 'Comment on tc-2023-33', Tobias Sauter, 08 May 2023

Ryan N. Ing et al.

Ryan N. Ing et al.


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Short summary
Many of the glaciers in Alaska are losing ice, contributing to sea-level rise. Here, we study the inputs and outputs for the Juneau Icefield. We first model the historical changes to snowfall and melt, constraining our model with observations. We then project future changes to the icefield, which show that icefield-wide loss of ice is likely. Losses are driven by rising temperatures, and less snowfall. The exposure of ice, and the break-up of glaciers due to thinning may accelerate ice loss.