Algal photophysiology drives darkening and melt of the Greenland Ice Sheet
Blooms of Zygnematophycean “glacier algae” lower the bare ice albedo of the Greenland Ice Sheet (GrIS), amplifying summer energy absorption at the ice surface and enhancing meltwater runoff from the largest cryospheric contributor to contemporary sea-level rise. Here, we provide a step change in cur...
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Online Access: | http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084142/ http://www.ncbi.nlm.nih.gov/pubmed/32094168 https://doi.org/10.1073/pnas.1918412117 |
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ftpubmed:oai:pubmedcentral.nih.gov:7084142 2023-05-15T16:21:01+02:00 Algal photophysiology drives darkening and melt of the Greenland Ice Sheet Williamson, Christopher J. Cook, Joseph Tedstone, Andrew Yallop, Marian McCutcheon, Jenine Poniecka, Ewa Campbell, Douglas Irvine-Fynn, Tristram McQuaid, James Tranter, Martyn Perkins, Rupert Anesio, Alexandre 2020-03-17 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084142/ http://www.ncbi.nlm.nih.gov/pubmed/32094168 https://doi.org/10.1073/pnas.1918412117 en eng National Academy of Sciences http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084142/ http://www.ncbi.nlm.nih.gov/pubmed/32094168 http://dx.doi.org/10.1073/pnas.1918412117 Copyright © 2020 the Author(s). Published by PNAS. http://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY) (http://creativecommons.org/licenses/by/4.0/) . CC-BY Physical Sciences Text 2020 ftpubmed https://doi.org/10.1073/pnas.1918412117 2020-03-29T01:37:27Z Blooms of Zygnematophycean “glacier algae” lower the bare ice albedo of the Greenland Ice Sheet (GrIS), amplifying summer energy absorption at the ice surface and enhancing meltwater runoff from the largest cryospheric contributor to contemporary sea-level rise. Here, we provide a step change in current understanding of algal-driven ice sheet darkening through quantification of the photophysiological mechanisms that allow glacier algae to thrive on and darken the bare ice surface. Significant secondary phenolic pigmentation (11 times the cellular content of chlorophyll a) enables glacier algae to tolerate extreme irradiance (up to ∼4,000 µmol photons⋅m(−2)⋅s(−1)) while simultaneously repurposing captured ultraviolet and short-wave radiation for melt generation. Total cellular energy absorption is increased 50-fold by phenolic pigmentation, while glacier algal chloroplasts positioned beneath shading pigments remain low-light–adapted (E(k) ∼46 µmol photons⋅m(−2)⋅s(−1)) and dependent upon typical nonphotochemical quenching mechanisms for photoregulation. On the GrIS, glacier algae direct only ∼1 to 2.4% of incident energy to photochemistry versus 48 to 65% to ice surface melting, contributing an additional ∼1.86 cm water equivalent surface melt per day in patches of high algal abundance (∼10(4) cells⋅mL(−1)). At the regional scale, surface darkening is driven by the direct and indirect impacts of glacier algae on ice albedo, with a significant negative relationship between broadband albedo (Moderate Resolution Imaging Spectroradiometer [MODIS]) and glacier algal biomass (R(2) = 0.75, n = 149), indicating that up to 75% of the variability in albedo across the southwestern GrIS may be attributable to the presence of glacier algae. Text glacier Greenland Ice Sheet PubMed Central (PMC) Greenland Proceedings of the National Academy of Sciences 117 11 5694 5705 |
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Open Polar |
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PubMed Central (PMC) |
op_collection_id |
ftpubmed |
language |
English |
topic |
Physical Sciences |
spellingShingle |
Physical Sciences Williamson, Christopher J. Cook, Joseph Tedstone, Andrew Yallop, Marian McCutcheon, Jenine Poniecka, Ewa Campbell, Douglas Irvine-Fynn, Tristram McQuaid, James Tranter, Martyn Perkins, Rupert Anesio, Alexandre Algal photophysiology drives darkening and melt of the Greenland Ice Sheet |
topic_facet |
Physical Sciences |
description |
Blooms of Zygnematophycean “glacier algae” lower the bare ice albedo of the Greenland Ice Sheet (GrIS), amplifying summer energy absorption at the ice surface and enhancing meltwater runoff from the largest cryospheric contributor to contemporary sea-level rise. Here, we provide a step change in current understanding of algal-driven ice sheet darkening through quantification of the photophysiological mechanisms that allow glacier algae to thrive on and darken the bare ice surface. Significant secondary phenolic pigmentation (11 times the cellular content of chlorophyll a) enables glacier algae to tolerate extreme irradiance (up to ∼4,000 µmol photons⋅m(−2)⋅s(−1)) while simultaneously repurposing captured ultraviolet and short-wave radiation for melt generation. Total cellular energy absorption is increased 50-fold by phenolic pigmentation, while glacier algal chloroplasts positioned beneath shading pigments remain low-light–adapted (E(k) ∼46 µmol photons⋅m(−2)⋅s(−1)) and dependent upon typical nonphotochemical quenching mechanisms for photoregulation. On the GrIS, glacier algae direct only ∼1 to 2.4% of incident energy to photochemistry versus 48 to 65% to ice surface melting, contributing an additional ∼1.86 cm water equivalent surface melt per day in patches of high algal abundance (∼10(4) cells⋅mL(−1)). At the regional scale, surface darkening is driven by the direct and indirect impacts of glacier algae on ice albedo, with a significant negative relationship between broadband albedo (Moderate Resolution Imaging Spectroradiometer [MODIS]) and glacier algal biomass (R(2) = 0.75, n = 149), indicating that up to 75% of the variability in albedo across the southwestern GrIS may be attributable to the presence of glacier algae. |
format |
Text |
author |
Williamson, Christopher J. Cook, Joseph Tedstone, Andrew Yallop, Marian McCutcheon, Jenine Poniecka, Ewa Campbell, Douglas Irvine-Fynn, Tristram McQuaid, James Tranter, Martyn Perkins, Rupert Anesio, Alexandre |
author_facet |
Williamson, Christopher J. Cook, Joseph Tedstone, Andrew Yallop, Marian McCutcheon, Jenine Poniecka, Ewa Campbell, Douglas Irvine-Fynn, Tristram McQuaid, James Tranter, Martyn Perkins, Rupert Anesio, Alexandre |
author_sort |
Williamson, Christopher J. |
title |
Algal photophysiology drives darkening and melt of the Greenland Ice Sheet |
title_short |
Algal photophysiology drives darkening and melt of the Greenland Ice Sheet |
title_full |
Algal photophysiology drives darkening and melt of the Greenland Ice Sheet |
title_fullStr |
Algal photophysiology drives darkening and melt of the Greenland Ice Sheet |
title_full_unstemmed |
Algal photophysiology drives darkening and melt of the Greenland Ice Sheet |
title_sort |
algal photophysiology drives darkening and melt of the greenland ice sheet |
publisher |
National Academy of Sciences |
publishDate |
2020 |
url |
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084142/ http://www.ncbi.nlm.nih.gov/pubmed/32094168 https://doi.org/10.1073/pnas.1918412117 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
glacier Greenland Ice Sheet |
genre_facet |
glacier Greenland Ice Sheet |
op_relation |
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084142/ http://www.ncbi.nlm.nih.gov/pubmed/32094168 http://dx.doi.org/10.1073/pnas.1918412117 |
op_rights |
Copyright © 2020 the Author(s). Published by PNAS. http://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY) (http://creativecommons.org/licenses/by/4.0/) . |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1073/pnas.1918412117 |
container_title |
Proceedings of the National Academy of Sciences |
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117 |
container_issue |
11 |
container_start_page |
5694 |
op_container_end_page |
5705 |
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1766009030114803712 |