Preprints
https://doi.org/10.5194/egusphere-2022-37
https://doi.org/10.5194/egusphere-2022-37
 
04 Apr 2022
04 Apr 2022
Status: this preprint is open for discussion.

Assessing Bare Ice Albedo Simulated by MAR over the Greenland Ice Sheet (2000–2021) and Implications for Meltwater Production Estimates

Raf Antwerpen1, Marco Tedesco1,2, Xavier Fettweis3, Patrick Alexander1,2, and Willem Jan van de Berg4 Raf Antwerpen et al.
  • 1Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
  • 2NASA Goddard Institute for Space Studies, New York, NY, USA
  • 3Department of Geography, University of Liège, Liège, Belgium
  • 4Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands

Abstract. Surface mass loss from the Greenland ice sheet (GrIS) has accelerated over the past decades, mainly due to enhanced surface melting and liquid water runoff in response to atmospheric warming. A large portion of runoff from the GrIS originates from exposure of the darker bare ice in the ablation zone when the overlying snow melts, where surface albedo plays a critical role in modulating the energy available for melting. In this regard, it is imperative to understand the processes governing albedo variability to accurately project future mass loss from the GrIS. Bare ice albedo is spatially and temporally variable and contingent on non-linear feedbacks and the presence of light-absorbing constituents. An assessment of models aiming at simulating albedo variability and associated impacts on meltwater production is crucial for improving our understanding of the processes governing these feedbacks and, in turn, surface mass loss from Greenland. Here, we report the results of a comparison of the bare ice extent and albedo simulated by the regional climate model Modèle Atmosphérique Régional (MAR) with satellite imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the GrIS below 70° N. Our findings suggest that MAR overestimates bare ice albedo by 22.8 % on average in this area during the 2000–2021 period with respect to the estimates obtained from MODIS. Using an energy balance model to parameterize meltwater production, we find this bare ice albedo bias can lead to an underestimation of total meltwater production from the bare ice zone below 70° N of 42.8 % during the summers of 2000–2021.

Raf Antwerpen et al.

Status: open (until 31 May 2022)

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Raf Antwerpen et al.

Raf Antwerpen et al.

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Short summary
The ice on Greenland has been melting more rapidly over the last years. Most of this melt comes from the exposure of ice when the overlying snow melts. This ice is darker than snow and takes up more sunlight, which leads to more melt. However, the actual color of the ice remains hard to simulate in models. In this paper we show that one model, MAR, simulates the color of the ice too bright. We also show that this means that the model may underestimate how fast the ice on Greenland is melting.