Preprints
https://doi.org/10.5194/tc-2021-379
https://doi.org/10.5194/tc-2021-379
 
18 Jan 2022
18 Jan 2022
Status: this preprint is currently under review for the journal TC.

How does a change in climate variability impact the Greenland ice-sheet surface mass balance?

Tobias Zolles1,2 and Andreas Born1,2 Tobias Zolles and Andreas Born
  • 1Department for Earth science, University of Bergen, Bergen, Norway
  • 2Bjerknes Centre for Climate Research, Bergen, Norway

Abstract. The future of the Greenland ice-sheet largely depends on the changing climate. When ice-sheet models are run for time periods that extend far beyond the observational record they are often forced by climatology instead of a transient climate. We investigate how this simplification impacts the surface mass balance using the Bergen Snow Simulator. The model was run for up to 500 years using the same atmospheric climatology, but different variability, as forcing. We achieve this by re-arranging the years in the ERA-interim reanalysis while leaving the intra-annual variations unchanged. This changes the surface mass balance by less than 5 % over the entire Greenland ice sheet.

However, using daily averages as forcing introduces large changes in intra-annual variability and thereby overestimates the Greenland-wide surface mass balance by 40 %. The biggest contributor is precipitation followed by temperature. The most important process is that small amounts of snowfall from the daily climatology overestimate the albedo, leading to an increased SMB. We propose a correction that distributes the monthly precipitation over a realistic intra-monthly variability. This approach reduces the SMB overestimation to 15–25 %. We conclude that simulations of the Greenland surface mass and energy balance should be forced with a transient climate. Particular care must be taken if only climatological data is available for simulations with a model that was calibrated with transient data. If daily transient data cannot be used, at least the precipitation should follow a natural daily distribution.

Tobias Zolles and Andreas Born

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of Zolles and Born', Anonymous Referee #1, 04 Mar 2022
  • RC2: 'Comment on tc-2021-379', Anonymous Referee #2, 06 May 2022

Tobias Zolles and Andreas Born

Tobias Zolles and Andreas Born

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Short summary
The Greenland ice-sheet largely depends on the climate state. The uncertainties associated with the year-to-year variability have only a marginal impact on our simulated surface mass budget, this increases our confidence in projections and reconstructions. Basing the simulations based on proxies for, f.ex., temperature, overestimates the surface mass balance, as climatologies lead to small amounts of snowfall every day. This can be reduced by including sub-monthly precipitation variability.