Glacier algae accelerate melt rates on the western Greenland Ice Sheet

• Main Authors: Cook, Joseph M., Tedstone, Andrew J., Williamson, Christopher, McCutcheon, Jenine, Hodson, Andrew J., Dayal, Archana, Skiles, McKenzie, Hofer, Stefan, Bryant, Robert, McAree, Owen, McGonigle, Andrew, Ryan, Jonathan, Anesio, Alexandre M., Irvine-Fynn, Tristram D. L., Hubbard, Alun, Hanna, Edward, Flanner, Mark, Mayanna, Sathish, Benning, Liane G., As, Dirk, Yallop, Marian, McQuaid, Jim, Gribbin, Thomas, Tranter, Martyn
• Format: Text
• Language: English
• Published: 2019
• Subjects: Greenland; glacier; Ice Sheet
• Online Access: https://doi.org/10.5194/tc-2019-58; https://www.the-cryosphere-discuss.net/tc-2019-58/

Melting of the Greenland Ice Sheet (GrIS) is the largest single contributor to eustatic sea level and is amplified by the growth of pigmented algae on the ice surface that increase solar radiation absorption. This biological albedo reducing effect and its impact upon sea level rise has not previously been quantified. Here, we combine field spectroscopy with a novel radiative transfer model, supervised classification of UAV and satellite remote sensing data and runoff modelling to calculate biologically-driven ice surface ablation and compare it to the albedo reducing effects of local mineral dust. We demonstrate that algal growth led to an additional 5.5–8.0 Gt of runoff from the western sector of the GrIS in summer 2016, representing 6–9 % of the total. Our analysis confirms the importance of the biological albedo feedback and that its omission from predictive models leads to the systematic underestimation of Greenland’s future sea level contribution, especially because both the bare ice zones available for algal colonization and the length of the active growth season are set to expand in the future.