Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet
| dc.contributor.author | Moustafa, S. E. | |
| dc.contributor.author | Rennermalm, A. K. | |
| dc.contributor.author | Smith, L. C. | |
| dc.contributor.author | Miller, M. A. | |
| dc.contributor.author | Mioduszewski, J. R. | |
| dc.contributor.author | Koenig, L. S. | |
| dc.contributor.author | Hom, M. G. | |
| dc.contributor.author | Shuman, Christopher | |
| dc.date.accessioned | 2022-02-15T13:26:01Z | |
| dc.date.available | 2022-02-15T13:26:01Z | |
| dc.date.issued | 2015-05-07 | |
| dc.description.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. | en_US |
| dc.description.sponsorship | S. E. Moustafa, A. K. Rennermalm, L. C. Smith and J. R. Mioduszewski were funded by NASA grant NNX11AQ38G and NNX14AH93G. S. E. Moustafa was also funded by NASA Earth and Space Science Fellowship Program NNX12AN98H. Additional funding was provided by Rutgers University faculty research grant. Field logistical support was pro vided by CH2M Hill Polar Field Services and the Kangerlussuaq International Science Station. The authors would like to thank A. Pope M. S. Pelto, and K. Casey as well as two anonymous reviewers for valuable feedback and commentary. | en_US |
| dc.description.uri | https://tc.copernicus.org/articles/9/905/2015/ | en_US |
| dc.format.extent | 19 pages | en_US |
| dc.genre | journal articles | en_US |
| dc.identifier | doi:10.13016/m2u3k7-mfom | |
| dc.identifier.citation | Moustafa, S. E. et al. Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet. The Cryosphere, 9 (2015), p. 905-923. https://doi.org/10.5194/tc-9-905-2015. | en_US |
| dc.identifier.uri | https://doi.org/10.5194/tc-9-905-2015 | |
| dc.identifier.uri | http://hdl.handle.net/11603/24272 | |
| dc.language.iso | en_US | en_US |
| dc.publisher | EGU | en_US |
| dc.relation.isAvailableAt | The University of Maryland, Baltimore County (UMBC) | |
| dc.relation.ispartof | UMBC Joint Center for Earth Systems Technology | |
| dc.relation.ispartof | UMBC Faculty Collection | |
| dc.rights | This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law. | en_US |
| dc.rights | Public Domain Mark 1.0 | * |
| dc.rights.uri | http://creativecommons.org/publicdomain/mark/1.0/ | * |
| dc.title | Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet | en_US |
| dc.type | Text | en_US |
| dcterms.creator | https://orcid.org/0000-0001-9606-767X | en_US |