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

• Published in: Journal of Glaciology
• Main Authors: Feng, Shunan, Cook, Joseph Mitchell, Anesio, Alexandre Magno, Benning, Liane G., Tranter, Martyn
• Other Authors: Horizon 2020 Framework Programme
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2023
• Subjects: Earth-Surface Processes; Greenland; Ice Sheet; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/jog.2023.11; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143023000114

Abstract 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 km 2 to ~8000 km 2 since. The Dark Zone is continuing to darken slowly, with the average annual minimum albedo decreasing at a rate of $\sim \!-0.0006 \pm 0.0004 \, {\rm a}^{-1}$ ( p = 0.16, 2001–2020).