Glacier algae accelerate melt rates on the western Greenland Ice Sheet

Cook, Joseph M.; Tedstone, Andrew; Williamson, Christopher; McCutcheon, Jenine; Hodson, Andrew J.; Dayal, Archana; Skiles, M.; Höfer, Stefan; Bryant, Robert G.; McAree, Owen; McGonigle, Andrew J. S.; Ryan, Jonathan C.; Anesio, Alexandre M.; Irvine‐Fynn, Tristram; Hubbard, Alun; Hanna, Edward; Flanner, M.; Mayanna, Sathish; Benning, Liane G.; As, Dirk van; Yallop, Marian L.; McQuaid, James B.; Gribbin, Thomas; Tranter, Martyn

doi:10.5194/tc-2019-58

Cited by 10 publications

(17 citation statements)

References 24 publications

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“…6E), significant deviation from a 1:1 relationship was apparent at higher algal concentrations (F 1,494 = 6.54 × 10 32 , P < 0.001), with MODIS-derived BBA consistently lower as compared to modeled BBA. Additional to the direct impacts of glacier algae on surface ice albedo through pigment-mediated energy capture (this study), indirect perturbations of surface ice physics are also likely important (11,42,43).…”

Section: Secondary Phenolic Pigmentation Dominates Light Absorptionmentioning

confidence: 84%

“…Estimated algal biomass and measured pigment profiles were then used to drive the twostream BioSNICAR-GO radiative transfer model of ref. 11 (Methods) to calculate ice surface BBA over the visible spectrum (λ 350-700nm ), across which glacier algal pigments absorb (Fig. 3).…”

Section: Secondary Phenolic Pigmentation Dominates Light Absorptionmentioning

confidence: 99%

“…Deposition and/or melt-out of mineral dust, soots from incomplete combustion from anthropogenic sources (termed "black carbon") or forest fires ("brown carbon"), and the accumulation of pigmented photoautotrophs (agents of "biological albedo decline") all represent light-absorbing impurities that darken ice surfaces (7). Of these, biologically driven albedo reduction has been proposed by both observational (7)(8)(9)(10), and modeling studies (11) to represent the single largest contributor to albedo decline in the GrIS dark zone in recent decades, matching reports from other regions of the cryosphere (12)(13)(14). Supraglacial photoautotrophic populations of the GrIS include cyanobacteria, typically associated with aggregates of inorganic particles (cryoconite) that melt down into the ice to form water-filled depressions (cryoconite holes) (15)(16)(17)(18), and heavily pigmented Zygnematophycean (Streptophyte) microalgae (hereafter glacier algae) (19) that bloom in the upper few centimeters of surface ice, which is subsequently described as dark or dirty ice (8,9,(19)(20)(21)(22)(23).…”

mentioning

confidence: 99%

“…Supraglacial photoautotrophic populations of the GrIS include cyanobacteria, typically associated with aggregates of inorganic particles (cryoconite) that melt down into the ice to form water-filled depressions (cryoconite holes) (15)(16)(17)(18), and heavily pigmented Zygnematophycean (Streptophyte) microalgae (hereafter glacier algae) (19) that bloom in the upper few centimeters of surface ice, which is subsequently described as dark or dirty ice (8,9,(19)(20)(21)(22)(23). Given the high abundance and large spatial coverage achieved by blooms of glacier algae during summer ablation seasons (8,9,23), glacier algal assemblages represent the most important photoautotrophic component of the GrIS supraglacial environment with regard to biological albedo effects (8,9,11).…”

mentioning

confidence: 99%

“…For glacier algae photosynthesizing in supraglacial environments, the production of a unique purpurogallin phenolic pigment, purpurogallin carboxylic acid-6-O-β-D-glucopyranosidel (26), in addition to the suite of light harvesting and photoprotective pigments typical of green microalgae (23,26,27), has been postulated to provide photoprotection against excessive UV and visible irradiance (23,26,27) and to potentially serve as a mechanism to generate heat and thus liquid water surrounding the cell (28). This pigmentation also likely represents the major agent of biological albedo decline and enhanced surface melt associated with glacier algal blooms (8,9,11,28).…”

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confidence: 99%

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Algal photophysiology drives darkening and melt of the Greenland Ice Sheet

Williamson

Cook²,

Tedstone

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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134

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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.Greenland Ice Sheet | glacier algae | photophysiology | melt | cryosphere

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Section: Secondary Phenolic Pigmentation Dominates Light Absorptionmentioning

confidence: 84%

Section: Secondary Phenolic Pigmentation Dominates Light Absorptionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Algal photophysiology drives darkening and melt of the Greenland Ice Sheet

Williamson

Cook²,

Tedstone

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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134

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Bio-optical Properties of Terrestrial Snow and Ice

Cook

Flanner

Williamson

et al. 2019

Springer Series in Light Scattering

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Seasonal Snowpack Microbial Ecology and Biogeochemistry on a High Arctic Ice Cap Reveals Negligible Autotrophic Activity During Spring and Summer Melt

Dayal,

Hodson,

Šabacká

et al. 2023

JGR Biogeosciences

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Snowpack ecosystem studies are primarily derived from research on snow‐on‐soil ecosystems. Greater research attention needs to be directed to the study of glacial snow covers as most snow cover lies on glaciers and ice sheets. With rising temperatures, snowpacks are getting wetter, which can potentially give rise to biologically productive snowpacks. The present study set out to determine the linkage between the thermal evolution of a snowpack and the seasonal microbial ecology of snow. We present the first comprehensive study of the seasonal microbial activity and biogeochemistry within a melting glacial snowpack on a High Arctic ice cap, Foxfonna, in Svalbard. Nutrients from winter atmospheric bulk deposition were supplemented by dust fertilization and weathering processes. NH4+ and PO43− resources in the snow therefore reached their highest values during late June and early July, at 22 and 13.9 mg m−2, respectively. However, primary production did not respond to this nutrient resource due to an absence of autotrophs in the snowpack. The average autotrophic abundance on the ice cap throughout the melt season was 0.5 ± 2.7 cells mL−1. Instead, the microbial cell abundance was dominated by bacterial cells that increased from an average of (39 ± 19 cells mL−1) in June to (363 ± 595 cells mL−1) in early July. Thus, the total seasonal biological production on Foxfonna was estimated at 153 mg C m−2, and the glacial snowpack microbial ecosystem was identified as net‐heterotrophic. This work presents a seasonal “album” documenting the bacterial ecology of glacial snowpacks.

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Glacier algae accelerate melt rates on the western Greenland Ice Sheet

Cited by 10 publications

References 24 publications

Algal photophysiology drives darkening and melt of the Greenland Ice Sheet

Algal photophysiology drives darkening and melt of the Greenland Ice Sheet

Bio-optical Properties of Terrestrial Snow and Ice

Seasonal Snowpack Microbial Ecology and Biogeochemistry on a High Arctic Ice Cap Reveals Negligible Autotrophic Activity During Spring and Summer Melt

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