Nov 6, 2017

Algae drive enhanced darkening of bare ice on the Greenland ice sheet

Stibal, Marek, Box, Jason E., Cameron, Karen A., Langen, Peter L., Yallop, Marian L., Mottram, Ruth H., Khan, Alia L., Molotch, Noah P., Chrismas, Nathan A. M., Quaglia, Filippo Calì, Remias et al
Geophysical Research Letters
  • States that surface ablation of the Greenland ice sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells
  • Presents the first quantitative assessment of the microbial contribution to the ice sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the ice sheet
  • Finds that the impact of algae on bare ice darkening in the study area was greater than that of non-algal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling
  • Argues that algal growth is a crucial control of bare ice darkening, and incorporating the algal darkening effect will improve mass balance and sea level projections of the Greenland ice sheet and ice masses elsewhere