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 en- ergy 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 c...
Published in: | Proceedings of the National Academy of Sciences |
---|---|
Main Authors: | , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2020
|
Subjects: | |
Online Access: | https://hdl.handle.net/1983/31dba669-7087-4b5c-81e7-0cb3d899b718 https://research-information.bris.ac.uk/en/publications/31dba669-7087-4b5c-81e7-0cb3d899b718 https://doi.org/10.1073/pnas.1918412117 https://research-information.bris.ac.uk/ws/files/223141377/Williamson_et_al._2020_algal_photophysiology_drives_darkening_and_melt_of_the_greenland_ice_sheet.pdf |
id |
ftubristolcris:oai:research-information.bris.ac.uk:publications/31dba669-7087-4b5c-81e7-0cb3d899b718 |
---|---|
record_format |
openpolar |
spelling |
ftubristolcris:oai:research-information.bris.ac.uk:publications/31dba669-7087-4b5c-81e7-0cb3d899b718 2024-05-19T07:40:41+00:00 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 application/pdf https://hdl.handle.net/1983/31dba669-7087-4b5c-81e7-0cb3d899b718 https://research-information.bris.ac.uk/en/publications/31dba669-7087-4b5c-81e7-0cb3d899b718 https://doi.org/10.1073/pnas.1918412117 https://research-information.bris.ac.uk/ws/files/223141377/Williamson_et_al._2020_algal_photophysiology_drives_darkening_and_melt_of_the_greenland_ice_sheet.pdf eng eng https://research-information.bris.ac.uk/en/publications/31dba669-7087-4b5c-81e7-0cb3d899b718 info:eu-repo/semantics/openAccess Williamson , C J , Cook , J , Tedstone , A , Yallop , M , McCutcheon , J , Poniecka , E , Campbell , D , Irvine-Fynn , T , McQuaid , J , Tranter , M , Perkins , R & Anesio , A 2020 , ' Algal photophysiology drives darkening and melt of the Greenland Ice Sheet ' , Proceedings of the National Academy of Sciences of the United States of America , vol. 117 , no. 11 , pp. 5694-5705 . https://doi.org/10.1073/pnas.1918412117 Greenland Ice Sheet glacier algae photophysiology melt cryosphere article 2020 ftubristolcris https://doi.org/10.1073/pnas.1918412117 2024-04-24T00:00:33Z Blooms of Zygnematophycean “glacier algae” lower the bare ice albedo of the Greenland Ice Sheet (GrIS), amplifying summer en- ergy 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 phe- nolic 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 pheno- lic pigmentation, while glacier algal chloroplasts positioned be- neath shading pigments remain low-light–adapted (Ek ∼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 (∼104 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 (R2 = 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. Article in Journal/Newspaper glacier Greenland Ice Sheet University of Bristol: Bristol Research Proceedings of the National Academy of Sciences 117 11 5694 5705 |
institution |
Open Polar |
collection |
University of Bristol: Bristol Research |
op_collection_id |
ftubristolcris |
language |
English |
topic |
Greenland Ice Sheet glacier algae photophysiology melt cryosphere |
spellingShingle |
Greenland Ice Sheet glacier algae photophysiology melt cryosphere 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 |
Greenland Ice Sheet glacier algae photophysiology melt cryosphere |
description |
Blooms of Zygnematophycean “glacier algae” lower the bare ice albedo of the Greenland Ice Sheet (GrIS), amplifying summer en- ergy 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 phe- nolic 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 pheno- lic pigmentation, while glacier algal chloroplasts positioned be- neath shading pigments remain low-light–adapted (Ek ∼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 (∼104 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 (R2 = 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 |
Article in Journal/Newspaper |
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 |
publishDate |
2020 |
url |
https://hdl.handle.net/1983/31dba669-7087-4b5c-81e7-0cb3d899b718 https://research-information.bris.ac.uk/en/publications/31dba669-7087-4b5c-81e7-0cb3d899b718 https://doi.org/10.1073/pnas.1918412117 https://research-information.bris.ac.uk/ws/files/223141377/Williamson_et_al._2020_algal_photophysiology_drives_darkening_and_melt_of_the_greenland_ice_sheet.pdf |
genre |
glacier Greenland Ice Sheet |
genre_facet |
glacier Greenland Ice Sheet |
op_source |
Williamson , C J , Cook , J , Tedstone , A , Yallop , M , McCutcheon , J , Poniecka , E , Campbell , D , Irvine-Fynn , T , McQuaid , J , Tranter , M , Perkins , R & Anesio , A 2020 , ' Algal photophysiology drives darkening and melt of the Greenland Ice Sheet ' , Proceedings of the National Academy of Sciences of the United States of America , vol. 117 , no. 11 , pp. 5694-5705 . https://doi.org/10.1073/pnas.1918412117 |
op_relation |
https://research-information.bris.ac.uk/en/publications/31dba669-7087-4b5c-81e7-0cb3d899b718 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1073/pnas.1918412117 |
container_title |
Proceedings of the National Academy of Sciences |
container_volume |
117 |
container_issue |
11 |
container_start_page |
5694 |
op_container_end_page |
5705 |
_version_ |
1799480264614739968 |