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Long time series (1984-2020) of albedo variations on the Greenland ice sheet from harmonized Landsat and Sentinel 2 imagery

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Albedo is a key factor in modulating the absorption of solar radiation on ice surfaces. Satellite measurements have shown a general reduction in albedo across the Greenland ice sheet over the past few decades, particularly along the western margin of the ice sheet, a region known as the Dark Zone (albedo < 0.45). Here we chose a combination of Landsat 4-8 and Sentinel 2 imagery to enable us to derive the longest record of albedo variations in the Dark Zone, running from 1984 to 2020. We developed a simple, pragmatic and efficient sensor transformation to provide a long time series of consistent, harmonized satellite imagery. Narrow to broadband conversion algorithms were developed from regression models of harmonized satellite data and in situ albedo from the Program for Monitoring of the Greenland Ice Sheet (PROMICE) automatic weather stations. The albedo derived from the harmonized Landsat and Sentinel 2 data shows that the maximum extent of the Dark Zone expanded rapidly between 2005 and 2007, increasing to ∼280% of the average annual maximum extent of 2900 km2 to ∼8000 km2 since. The Dark Zone is continuing to darken slowly, with the average annual minimum albedo decreasing at a rate of ∼-0.0006+0.0004 a-1 (p = 0.16, 2001-2020).

OriginalsprogEngelsk
TidsskriftJournal of Glaciology
ISSN0022-1430
DOI
StatusE-pub ahead of print - mar. 2023

Bibliografisk note

Funding Information:
This publication is part of the Deep Purple Project. The project receives funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program under grant agreement No 856416. DEMs provided by the Polar Geospatial Center under NSF-OPP awards 1043681, 1559691, and 1542736. The authors thank the editor Dr Carleen Reijmer, Dr Nicolas Cullen and the two anonymous referees for their constructive comments. We thank all the contributors to the Google Earth Engine community. We also express our gratitude to Ate H. Jaarsma who helped proofread the manuscript draft and Dr Athanasios Zervas who helped with the server.

Funding Information:
This publication is part of the Deep Purple Project. The project receives funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program under grant agreement No 856416. DEMs provided by the Polar Geospatial Center under NSF-OPP awards 1043681, 1559691, and 1542736.

Publisher Copyright:
© The Author(s), 2023. Published by Cambridge University Press on behalf of The International Glaciological Society.

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