Macro-Nutrient Stoichiometry of Glacier Algae From the Southwestern Margin of the Greenland Ice Sheet

Glacier algae residing within the surface ice of glaciers and ice sheets play globally significant roles in biogeochemical cycling, albedo feedbacks, and melt of the world’s cryosphere. Here, we present an assessment of the macro-nutrient stoichiometry of glacier algal assemblages from the southwestern Greenland Ice Sheet (GrIS) margin, where widespread glacier algal blooms proliferate during summer melt seasons. Samples taken during the mid-2019 ablation season revealed overall lower cellular carbon (C), nitrogen (N), and phosphorus (P) content than predicted by standard microalgal cellular content:biovolume relationships, and elevated C:N and C:P ratios in all cases, with an overall estimated C:N:P of 1,997:73:1. We interpret lower cellular macro-nutrient content and elevated C:N and C:P ratios to reflect adaptation of glacier algal assemblages to their characteristic oligotrophic surface ice environment. Such lower macro-nutrient requirements would aid the proliferation of blooms across the nutrient poor cryosphere in a warming world. Up-scaling of our observations indicated the potential for glacier algal assemblages to accumulate ∼ 29 kg C km2 and ∼ 1.2 kg N km2 within our marginal surface ice location by the mid-ablation period (early August), confirming previous modeling estimates. While the long-term fate of glacier algal autochthonous production within surface ice remains unconstrained, data presented here provide insight into the possible quality of dissolved organic matter that may be released by assemblages into the surface ice environment.

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Algal growth and weathering crust state drive variability in western Greenland Ice Sheet ice albedo

The Cryosphere ◽

10.5194/tc-14-521-2020 ◽

2020 ◽

Vol 14 (2) ◽

pp. 521-538 ◽

Cited By ~ 5

Author(s):

Andrew J. Tedstone ◽

Joseph M. Cook ◽

Christopher J. Williamson ◽

Stefan Hofer ◽

Jenine McCutcheon ◽

...

Keyword(s):

Algal Blooms ◽

Algal Bloom ◽

Ice Sheet ◽

Algal Growth ◽

Greenland Ice Sheet ◽

Weathering Crust ◽

Near Surface ◽

Ice Surfaces ◽

Surface Ice ◽

The Impact

Abstract. One of the primary controls upon the melting of the Greenland Ice Sheet (GrIS) is albedo, a measure of how much solar radiation that hits a surface is reflected without being absorbed. Lower-albedo snow and ice surfaces therefore warm more quickly. There is a major difference in the albedo of snow-covered versus bare-ice surfaces, but observations also show that there is substantial spatio-temporal variability of up to ∼0.4 in bare-ice albedo. Variability in bare-ice albedo has been attributed to a number of processes including the accumulation of light-absorbing impurities (LAIs) and the changing physical properties of the near-surface ice. However, the combined impact of these processes upon albedo remains poorly constrained. Here we use field observations to show that pigmented glacier algae are ubiquitous and cause surface darkening both within and outside the south-west GrIS “dark zone” but that other factors including modification of the ice surface by algal bloom presence, surface topography and weathering crust state are also important in determining patterns of daily albedo variability. We further use observations from an unmanned aerial system (UAS) to examine the scale gap in albedo between ground versus remotely sensed measurements made by Sentinel-2 (S-2) and MODIS. S-2 observations provide a highly conservative estimate of algal bloom presence because algal blooms occur in patches much smaller than the ground resolution of S-2 data. Nevertheless, the bare-ice albedo distribution at the scale of 20 m×20 m S-2 pixels is generally unimodal and unskewed. Conversely, bare-ice surfaces have a left-skewed albedo distribution at MODIS MOD10A1 scales. Thus, when MOD10A1 observations are used as input to energy balance modelling, meltwater production can be underestimated by ∼2 %. Our study highlights that (1) the impact of the weathering crust state is of similar importance to the direct darkening role of light-absorbing impurities upon ice albedo and (2) there is a spatial-scale dependency in albedo measurement which reduces detection of real changes at coarser resolutions.

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Algal growth and weathering crust structure drive variability in Greenland Ice Sheet ice albedo

10.5194/tc-2019-131 ◽

2019 ◽

Cited By ~ 3

Author(s):

Andrew J. Tedstone ◽

Joseph M. Cook ◽

Christopher J. Williamson ◽

Stefan Hofer ◽

Jenine McCutcheon ◽

...

Keyword(s):

Algal Blooms ◽

Algal Bloom ◽

Ice Sheet ◽

Algal Growth ◽

Greenland Ice Sheet ◽

Weathering Crust ◽

Near Surface ◽

Ice Surfaces ◽

Surface Ice ◽

The Impact

Abstract. One of the primary controls upon the melting of the Greenland Ice Sheet (GrIS) is albedo. There is a major difference in the albedo of snow-covered versus bare-ice surfaces, but observations also show that there is substantial spatio-temporal variability of up to ~ 0.4 in bare-ice albedo. Variability in bare ice albedo has been attributed to a number of processes including the accumulation of Light Absorbing Impurities (LAIs) and the changing physical properties of the near-surface ice. However, the combined impact of these processes upon albedo remains poorly constrained. Here we use field observations to show that among LAIs, pigmented glacier algae are ubiquitous and cause surface darkening both within and outside the south-west GrIS dark zone, but that other factors including modification of underlying ice properties by algal bloom presence, surface topography and weathering crust development are also important in determining patterns of daily albedo variability. We further use unmanned aerial system observations to examine the scale gap in albedo between ground versus remotely-sensed measurements made by Sentinel-2 (S-2) and MODIS. S-2 observations provide a highly conservative estimate of algal bloom presence because algal blooms occur in patches much smaller than the ground resolution of S-2 data. Nevertheless, the bare-ice albedo distribution at the scale of 20 × 20 m S-2 pixels is generally unimodal and unskewed. Conversely, bare ice surfaces have a left-skewed albedo distribution at MODIS MOD10A1 scales. Thus, when MOD10A1 observations are used as input to energy balance modelling then meltwater production can be under-estimated by ~ 2 %. Our study highlights that (1) the impact of physical ice surface processes is of similar importance to the direct darkening role of light-absorbing impurities upon ice albedo and (2) there is a spatial scale dependency in albedo measurement which reduces detection of real changes at coarser resolutions.

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Increase of ice discharge from Greenland's peripheral tidewater glaciers over recent decades

10.5194/egusphere-egu21-10539 ◽

2021 ◽

Author(s):

Marco Möller ◽

Beatriz Recinos ◽

Ben Marzeion

Keyword(s):

Mass Loss ◽

Cross Sections ◽

Ice Sheet ◽

Regression Tree ◽

Greenland Ice Sheet ◽

Tidewater Glaciers ◽

Glacier Ice ◽

Extrapolation Scheme ◽

Flux Gate ◽

Surface Ice

The Greenland Ice Sheet is losing mass at increasing rates. Substantial amounts of this mass loss occur by ice discharge. The ice sheet is surrounded by thousands of peripheral glaciers, which are dynamically decoupled from the ice sheet, and which account for ~10 % of the global glacier ice volume outside the two main ice sheets. Rather low-lying along the coasts, these peripheral glaciers are also losing mass at increasing, but disputed, rates. The total absence of knowledge about the role and share of solid ice discharge in this mass loss adds to the controversy. Since the quantification of ice discharge is still pending, a full understanding of ice mass loss processes in this globally important glacier region is substantially hampered.Here, we present the first estimation of ice discharge from Greenland's peripheral tidewater glaciers. For each of these 760 glaciers, we combine an idealized rectangular flux gate cross sections derived from modelling with the Open Global Glacier Model with surface ice flow velocities derived from the ITS_LIVE and MEaSUREs remote sensing datasets to calculate glacier specific ice discharge on both annual and multi-annual time scales over the period 1985 to 2018. For the few glaciers not covered by either of the employed original datasets or modelling methods we use a regression tree-based extrapolation scheme to estimate the necessary input data for our calculation.Our findings indicate a significant overall increase of ice discharge over the study period although several individual glaciers show contrasting developments. This increase became especially apparent across the southern parts of Greenland. Our results also show that the total of the ice discharge from Greenland's peripheral tidewater glaciers is dominated by few major contributors and that this dominance is completely time-independent.

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A Detailed Oxygen-18 Profile From The Greenland Ice-Sheet Margin Through The Wisconsinan-Holocene Transition

Annals of Glaciology ◽

10.1017/s0260305500009319 ◽

1990 ◽

Vol 14 ◽

pp. 356 ◽

Cited By ~ 1

Author(s):

Niels Reeh ◽

Anne Letréguilly ◽

Hans Oerter

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Crucial Importance ◽

Potential Yield ◽

Mining Areas ◽

Layer Sequence ◽

North East ◽

Core Profile ◽

Field Season ◽

Surface Ice

About 1500 surface-ice samples for δ18O analysis were collected in the 1988 field season along a 750 m profile perpendicular to the margin of the Greenland ice sheet at Pakitsoq, ca 40 km north-east of Jakobshavn, central West Greenland. The purpose of the study was to evaluate how well the continuity of the layer sequence is preserved in ice-margin records, a question of crucial importance for evaluating the potential yield of using ice margins as “mining areas” for easily accessible old ice for climate and environmental studies. More than half of the 1500 samples were taken continuously as 20 cm samples along a 170 m section through the Wisconsinan-Holocene transition which, previously, had been located at the surface of the ice margin. Along this transition section δ18O values decrease by about 6‰ from −31.5 to 37.5‰ on an average. Detailed studies were made of surface elevations and surface structures (e.g. blue bands) along the “horizontal core” profile which, moreover, was photographed section by section, thus enabling the δ-record to be correlated with surface features. Results of the δ18O analyses are promising. Even though ice from the blue bands has δ-values that are 7–8‰ higher than those of the surrounding white ice, there seems to be no discontinuity in the white-ice δ-record across the blue bands.

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Dissolved organic nutrients dominate melting surface ice of the Dark Zone (Greenland Ice Sheet)

Biogeosciences ◽

10.5194/bg-16-3283-2019 ◽

2019 ◽

Vol 16 (16) ◽

pp. 3283-3296 ◽

Cited By ~ 6

Author(s):

Alexandra T. Holland ◽

Christopher J. Williamson ◽

Fotis Sgouridis ◽

Andrew J. Tedstone ◽

Jenine McCutcheon ◽

...

Keyword(s):

Organic Phase ◽

Stream Water ◽

Inorganic Nitrogen ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Western Coast ◽

Ice Surface ◽

Cryoconite Hole ◽

Melting Surface ◽

Surface Ice

Abstract. Glaciers and ice sheets host abundant and dynamic communities of microorganisms on the ice surface (supraglacial environments). Recently, it has been shown that Streptophyte glacier algae blooming on the surface ice of the south-western coast of the Greenland Ice Sheet are a significant contributor to the 15-year marked decrease in albedo. Currently, little is known about the constraints, such as nutrient availability, on this large-scale algal bloom. In this study, we investigate the relative abundances of dissolved inorganic and dissolved organic macronutrients (N and P) in these darkening surface ice environments. Three distinct ice surfaces, with low, medium and high visible impurity loadings, supraglacial stream water and cryoconite hole water, were sampled. Our results show a clear dominance of the organic phase in all ice surface samples containing low, medium and high visible impurity loadings, with 93 % of the total dissolved nitrogen and 67 % of the total dissolved phosphorus in the organic phase. Mean concentrations in low, medium and high visible impurity surface ice environments are 0.91, 0.62 and 1.0 µM for dissolved inorganic nitrogen (DIN), 5.1, 11 and 14 µM for dissolved organic nitrogen (DON), 0.03, 0.07 and 0.05 µM for dissolved inorganic phosphorus (DIP) and 0.10, 0.15 and 0.12 µM for dissolved organic phosphorus (DOP), respectively. DON concentrations in all three surface ice samples are significantly higher than DON concentrations in supraglacial streams and cryoconite hole water (0 and 0.7 µM, respectively). DOP concentrations are higher in all three surface ice samples compared to supraglacial streams and cryoconite hole water (0.07 µM for both). Dissolved organic carbon (DOC) concentrations increase with the amount of visible impurities present (low: 83 µM, medium: 173 µM and high: 242 µM) and are elevated compared to supraglacial streams and cryoconite hole water (30 and 50 µM, respectively). We speculate that the architecture of the weathering crust, which impacts on water flow paths and storage in the melting surface ice and/or the production of extracellular polymeric substances (EPS), containing both N and P in conjunction with C, is responsible for the temporary retention of DON and DOP in the melting surface ice. The unusual presence of measurable DIP and DIN, principally as NH4+, in the melting surface ice environments suggests that factors other than macronutrient limitation are controlling the extent and magnitude of the glacier algae.

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Microbial Degradation of 2,4-Dichlorophenoxyacetic Acid on the Greenland Ice Sheet

Applied and Environmental Microbiology ◽

10.1128/aem.00400-12 ◽

2012 ◽

Vol 78 (15) ◽

pp. 5070-5076 ◽

Cited By ~ 19

Author(s):

Marek Stibal ◽

Jacob Bælum ◽

William E. Holben ◽

Sebastian R. Sørensen ◽

Anders Jensen ◽

...

Keyword(s):

Microbial Community ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

Dichlorophenoxyacetic Acid ◽

Total Dna ◽

2,4 Dichlorophenoxyacetic Acid ◽

Surface Ice ◽

Pcr Targeting

ABSTRACTThe Greenland ice sheet (GrIS) receives organic carbon (OC) of anthropogenic origin, including pesticides, from the atmosphere and/or local sources, and the fate of these compounds in the ice is currently unknown. The ability of supraglacial heterotrophic microbes to mineralize different types of OC is likely a significant factor determining the fate of anthropogenic OC on the ice sheet. Here we determine the potential of the microbial community from the surface of the GrIS to mineralize the widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Surface ice cores were collected and incubated for up to 529 days in microcosms simulatingin situconditions. Mineralization of side chain- and ring-labeled [14C]2,4-D was measured in the samples, and quantitative PCR targeting thetfdAgenes in total DNA extracted from the ice after the experiment was performed. We show that the supraglacial microbial community on the GrIS contains microbes that are capable of degrading 2,4-D and that they are likely present in very low numbers. They can mineralize 2,4-D at a rate of up to 1 nmol per m2per day, equivalent to ∼26 ng C m−2day−1. Thus, the GrIS should not be considered a mere reservoir of all atmospheric contaminants, as it is likely that some deposited compounds will be removed from the system via biodegradation processes before their potential release due to the accelerated melting of the ice sheet.

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Glacier algae accelerate melt rates on the south-western Greenland Ice Sheet

The Cryosphere ◽

10.5194/tc-14-309-2020 ◽

2020 ◽

Vol 14 (1) ◽

pp. 309-330 ◽

Cited By ~ 10

Author(s):

Joseph M. Cook ◽

Andrew J. Tedstone ◽

Christopher Williamson ◽

Jenine McCutcheon ◽

Andrew J. Hodson ◽

...

Keyword(s):

Sea Level ◽

Algal Blooms ◽

Ice Sheet ◽

Algal Growth ◽

Greenland Ice Sheet ◽

Radiation Absorption ◽

Transfer Model ◽

High Biomass ◽

The South ◽

Ice Surface

Abstract. 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, which increases 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 radiative-transfer model, supervised classification of unmanned aerial vehicle (UAV) and satellite remote-sensing data, and runoff modelling to calculate biologically driven ice surface ablation. We demonstrate that algal growth led to an additional 4.4–6.0 Gt of runoff from bare ice in the south-western sector of the GrIS in summer 2017, representing 10 %–13 % of the total. In localized patches with high biomass accumulation, algae accelerated melting by up to 26.15±3.77 % (standard error, SE). The year 2017 was a high-albedo year, so we also extended our analysis to the particularly low-albedo 2016 melt season. The runoff from the south-western bare-ice zone attributed to algae was much higher in 2016 at 8.8–12.2 Gt, although the proportion of the total runoff contributed by algae was similar at 9 %–13 %. Across a 10 000 km2 area around our field site, algae covered similar proportions of the exposed bare ice zone in both years (57.99 % in 2016 and 58.89 % in 2017), but more of the algal ice was classed as “high biomass” in 2016 (8.35 %) than 2017 (2.54 %). This interannual comparison demonstrates a positive feedback where more widespread, higher-biomass algal blooms are expected to form in high-melt years where the winter snowpack retreats further and earlier, providing a larger area for bloom development and also enhancing the provision of nutrients and liquid water liberated from melting ice. Our analysis confirms the importance of this 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 biological growth season are set to expand in the future.

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Mineral phosphorus drives glacier algal blooms on the Greenland Ice Sheet

Nature Communications ◽

10.1038/s41467-020-20627-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jenine McCutcheon ◽

Stefanie Lutz ◽

Christopher Williamson ◽

Joseph M. Cook ◽

Andrew J. Tedstone ◽

...

Keyword(s):

Algal Blooms ◽

Mineral Dust ◽

Ice Sheet ◽

Algal Growth ◽

Greenland Ice Sheet ◽

Surface Melting ◽

Ice Algae ◽

Algae Biomass ◽

Mineral Phosphorus ◽

Glacier Ice

AbstractMelting of the Greenland Ice Sheet is a leading cause of land-ice mass loss and cryosphere-attributed sea level rise. Blooms of pigmented glacier ice algae lower ice albedo and accelerate surface melting in the ice sheet’s southwest sector. Although glacier ice algae cause up to 13% of the surface melting in this region, the controls on bloom development remain poorly understood. Here we show a direct link between mineral phosphorus in surface ice and glacier ice algae biomass through the quantification of solid and fluid phase phosphorus reservoirs in surface habitats across the southwest ablation zone of the ice sheet. We demonstrate that nutrients from mineral dust likely drive glacier ice algal growth, and thereby identify mineral dust as a secondary control on ice sheet melting.

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Morphology of the Ice-sheet Margin Near Thule, Greenland

Journal of Glaciology ◽

10.3189/s0022143000022851 ◽

1970 ◽

Vol 9 (57) ◽

pp. 303-324 ◽

Cited By ~ 3

Author(s):

Roger Leb. Hooke

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Upward Flow ◽

Negative Mass ◽

Glacier Surface ◽

Wind Drift ◽

Katabatic Winds ◽

Basal Ice ◽

Drifting Snow ◽

Surface Ice

Three types of glacier margin are found along the edge of the Greenland ice sheet near Thule: ice cliffs, ramps and ice-cored moraines. Where the glacier margin is perpendicular to prevailing katabatic winds, drifting snow accumulates along it in stagnant wind-drill ice wedges. Upward flow of active ice behind these wedges causes ice originally near the base of the glacier to rise to the surface. Where this basal ice is free of debris, a gently sloping ramp develops. However, where the basal ice contains sufficient debris, a layer of till accumulates on the glacier surface. Ice beneath the till is insulated and a debris-capped ice ridge or ice-cored moraine forms, Ice cliffs occur where the ice-sheet margin is parallel to prevailing winds and is thus swept clear of drifting snow. Although the ice sheet in the Thule area appears to have had a negative mass balance for many years, all three types of glacier margin are believed to be equilibrium forms that can develop and persist on a glacier with a balanced mass budget.Foliation in wind-drift ice wedges generally dips down-glacier but foliation in active ice dips up-glacier. It is inferred that foliation in the wedges was once sedimentary stratification that has been tipped upward and locally overturned.

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Comparison between Greenland ice-margin and ice-core oxygen-18 records

Annals of Glaciology ◽

10.3189/172756402781817365 ◽

2002 ◽

Vol 35 ◽

pp. 136-144 ◽

Cited By ~ 34

Author(s):

Niels Reeh ◽

Hans Oerter ◽

Henrik Højmark Thomsen

Keyword(s):

Ice Core ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

Good Reproducibility ◽

Northern Slope ◽

Central Regions ◽

Surface Ice ◽

Parallel Sampling

AbstractOld ice for palaeoenvironmental studies retrieved by deep core drilling in the central regions of the large ice sheets can also be retrieved from the ice-sheet margins. the δ18O content of the surface ice was studied at 15 different Greenland ice-margin locations. At some locations, two or more records were obtained along closely spaced parallel sampling profiles, showing good reproducibility of the records. We present ice-margin δ18O records reaching back to the Pleistocene. Many of the characteristic δ18O variations known from Greenland deep ice cores can be recognized, allowing an approximate time-scale to be established along the ice-margin records. A flowline model is used to determine the location on the ice sheet where the margin ice was originally deposited as snow. the Pleistocene–Holocene δ18O change at the deposition sites is determined by comparing the δ18O values in the ice-margin record to the present δ18O values of the surface snow at the deposition sites. on the northern slope of the Greenland ice sheet, the Pleistocene–Holocene δ18O change is about 10‰ in contrast to a change of 6–7‰ at locations near the central ice divide. This is in accordance with deep ice-core results. We conclude that δ18O records measured on ice from the Greenland ice-sheet margin provide useful information about past climate and dynamics of the ice sheet, and thus are important (and cheap) supplements to deep ice-core records.

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