Preprints
https://doi.org/10.5194/tc-2021-91
https://doi.org/10.5194/tc-2021-91

  24 Mar 2021

24 Mar 2021

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

Impact of the melt-albedo feedback on the future evolution of the Greenland Ice Sheet with PISM-dEBM-simple

Maria Zeitz1,2, Ronja Reese1, Johanna Beckmann1, Uta Krebs-Kanzow3, and Ricarda Winkelmann1,2 Maria Zeitz et al.
  • 1Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, P.O. Box 60 12 03, 14412 Potsdam, Germany
  • 2University of Potsdam, Institute of Physics and Astronomy, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
  • 3Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany

Abstract. Surface melting of the Greenland Ice Sheet contributes a large amount to current and future sea-level rise. Increased surface melt, algae growth, debris, and dust deposition lower the reflectivity of the ice surface and thereby increase melt rates: the so-called melt-albedo feedback describes this potentially self-sustaining increase in surface melting. Here we present a simplified version of the diurnal Energy Balance Model (dEBM-simple) which is implemented as a surface melt module in the Parallel Ice Sheet Model (PISM). dEBM-simple is a modification of diurnal Energy Balance Model (dEBM), a surface melt scheme of intermediate complexity useful for simulations over centennial to multi-millennial timescales. dEBM-simple is computationally efficient, suitable for standalone ice-sheet modeling and includes a simple representation of the melt-albedo feedback. Using dEBM-simple and PISM, we find that this feedback increases ice loss until 2300 through surface warming by 60 % for the high-emission scenario RCP8.5. With an increase of 90 %, the effect is more pronounced for lower surface warming under RCP2.6. Furthermore, assuming an immediate darkening of the ice surface over all summer months, we estimate an upper bound for this effect to be +70 % in the RCP8.5 scenario and a more than fourfold increase under RCP2.6. With dEBM-simple implemented in PISM, we find that the melt-albedo feedback is an essential contributor to mass loss in dynamic simulations of the Greenland Ice Sheet under future warming.

Maria Zeitz et al.

Status: open (until 19 May 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • AC1: 'Comment on tc-2021-91', Maria Zeitz, 01 Apr 2021 reply

Maria Zeitz et al.

Maria Zeitz et al.

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Short summary
With the increasing melt of the Greenland Ice Sheet, which contributes to sea-level rise, the surface of the ice darkens. The dark surfaces absorb more radiation and thus experience increased melt, resulting in the melt-albedo feedback. Using a simple surface melt model we estimate that this positive feedback contributes to additional 60 % ice loss in a high warming scenario and additional 90 % ice loss for moderate warming. Albedo changes are important for Greenland’s future ice loss.