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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 9, issue 3
The Cryosphere, 9, 905–923, 2015
https://doi.org/10.5194/tc-9-905-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
The Cryosphere, 9, 905–923, 2015
https://doi.org/10.5194/tc-9-905-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 May 2015

Research article | 07 May 2015

Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet

S. E. Moustafa1, A. K. Rennermalm1, L. C. Smith2, M. A. Miller3, J. R. Mioduszewski1, L. S. Koenig4,*, M. G. Hom5,6, and C. A. Shuman4,7 S. E. Moustafa et al.
  • 1Department of Geography, Rutgers, The State University of New Jersey, 54 Joyce Kilmer Avenue, Piscataway, NJ 08854-8045, USA
  • 2Department of Geography, University of California, Los Angeles, 1255 Bunche Hall, P. O.Box 951524, Los Angeles, CA 90095-1524, USA
  • 3Department of Environmental Sciences, Rutgers, The State University of New Jersey, 14 College Farm Rd, New Brunswick, NJ 08901-8551, USA
  • 4Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA
  • 5Biospheric Sciences Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA
  • 6Science Systems and Applications, Inc., 10210 Greenbelt Rd, Lanham, MD, 20706, USA
  • 7Joint Center for Earth Systems Technology (JCET), University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD, 21250, USA
  • *now at: National Snow and Ice Data Center, University of Colorado, 1540 30th Ave., Boulder CO 80303, USA

Abstract. Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface and, thus, meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates, earlier snowmelt, and amplified melt–albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation area albedo and meltwater production is still relatively unknown. In this study, we analyze albedo and ablation rates using in situ and remotely sensed data. Observations include (1) a new high-quality in situ spectral albedo data set collected with an Analytical Spectral Devices Inc. spectroradiometer measuring at 325–1075 nm along a 1.25 km transect during 3 days in June 2013; (2) broadband albedo at two automatic weather stations; and (3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August 2012 and 2013. We find that seasonal ablation area albedos in 2013 have a bimodal distribution, with snow and ice facies characterizing the two peaks. Our results show that a shift from a distribution dominated by high to low albedos corresponds to an observed melt rate increase of 51.5% (between 10–14 July and 20–24 July 2013). In contrast, melt rate variability caused by albedo changes before and after this shift was much lower and varied between ~10 and 30% in the melting season. Ablation area albedos in 2012 exhibited a more complex multimodal distribution, reflecting a transition from light to dark-dominated surface, as well as sensitivity to the so called "dark-band" region in southwest Greenland. In addition to a darkening surface from ice crystal growth, our findings demonstrate that seasonal changes in GrIS ablation area albedos are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. Thus, seasonal variability in ablation area albedos appears to be regulated primarily as a function of bare ice expansion at the expense of snow, surface meltwater ponding, and melting of outcropped ice layers enriched with mineral materials, enabling dust and impurities to accumulate. As climate change continues in the Arctic region, understanding the seasonal evolution of ice sheet surface types in Greenland's ablation area is critical to improve projections of mass loss contributions to sea level rise.

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