Bio-optical Properties of Terrestrial Snow and Ice

Cook, Joseph M.; Flanner, M.; Williamson, Christopher; Skiles, S. McKenzie

doi:10.1007/978-3-030-20587-4_3

Cited by 6 publications

(21 citation statements)

References 121 publications

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“…We also occupied the site from 31 May to 1 July, enabling us to observe the retreat dynamics of the winter snowpack for most of the early ablation season. UAS imagery acquired on 21 July 2017 has been presented previously (Cook et al, 2019b), but this study is the first to analyse the full time series of UAS imagery that we acquired at S6. During June there were several episodes of snowpack melting, with most of the snowpack retreating by mid-June and exposing bare ice with heterogeneous albedo.…”

Section: Study Sitesmentioning

confidence: 99%

“…Despite previous studies inferring the potential albedoreducing importance of impurities including cryoconite, emergent dust and liquid meltwater (Greuell, 2000;Bøggild et al, 2010;Wientjes and Oerlemans, 2010), there is an emerging consensus that pigmented glacier algae grow on the ice surface (Uetake et al, 2010;Yallop et al, 2012;Stibal et al, 2017; and are the dominant agent of darkening amongst LAIs (Stibal et al, 2017;Cook et al, 2019b). Glacier algae reduce albedo both directly (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Glacier algae reduce albedo both directly (i.e. the cells absorb shortwave radiation) and indirectly by modifying the underlying ice surface, for instance by maintaining a liquid water film (Cook et al, 2017(Cook et al, , 2019bWilliamson et al, 2019). They are ubiquitous across south-western Greenland (Cook et al, 2019b;Wang et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…the cells absorb shortwave radiation) and indirectly by modifying the underlying ice surface, for instance by maintaining a liquid water film (Cook et al, 2017(Cook et al, , 2019bWilliamson et al, 2019). They are ubiquitous across south-western Greenland (Cook et al, 2019b;Wang et al, 2018). Their growth is principally controlled by (i) the timing of winter snowpack retreat, (ii) meltwater availability and (iii) sufficient photosynthetically active radiation (Williamson et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…For example, on a single day in 2014, LAIs including dust, black carbon and pigmented algae explained 73 % of spatial variability in albedo along a 25 km transect (Ryan et al, 2018). More recently, combined ground sampling, radiative transfer modelling and surface type classification of UASs and satellite imagery showed that algal blooms specifically can cover at least 78 % of ice in the dark zone, generating at least 6 %-9 % additional ice melt in the south-west dark zone during the dark year of 2016 compared to the "average" year of 2017 (Cook et al, 2019b). Higher-resolution imagery is therefore able to bridge the scaling gap and has been crucial in demonstrating that glacier algae are the dominant LAI.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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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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Section: Study Sitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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Light-Absorbing Particles in Snow and Ice: A Brief Journey Across Latitudes

Mauro

Garzonio

Baccolo

et al. 2021

Springer Series in Light Scattering

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Biological albedo reduction on ice sheets, glaciers, and snowfields

Hotaling¹,

Lutz²,

Dial³

et al. 2021

Preprint

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The global cryosphere, Earth's frozen water, is in precipitous decline. The ongoing and predicted impacts of cryosphere loss are diverse, ranging from disappearance of entire biomes to crises of water availability. Covering approximately one-fifth of the Earth, mass loss from the terrestrial cryosphere is driven primarily by a warming atmosphere but reductions in albedo (the proportion of reflected light) also contribute by increasing absorption of solar radiation. In addition to dust and other abiotic impurities, biological communities substantially reduce albedo worldwide. In this review, we provide a global synthesis of biological albedo reduction (BAR) in terrestrial snow and ice ecosystems. We first focus on known drivers-algal blooms and cryoconite (granular sediment on the ice that includes both mineral and biological material)-as they account for much of the biological albedo variability in snow and ice habitats. We then consider an array of potential drivers of BAR whose impacts may be overlooked, such as arthropod deposition, resident organisms (e.g., dark-bodied glacier ice worms), and larger vertebrates, including humans, that visit the cryosphere. We consider both primary (e.g., BAR due to the presence of pigmented algal cells) and indirect (e.g., nutrient addition from arthropod deposition) effects, as well as interactions among biological groups (e.g., birds feeding on ice worms). Collectively, we highlight that in many cases, overlooked drivers and interactions among factors have considerable potential to alter BAR, perhaps rivaling the direct effects of algal blooms and cryoconite. We conclude by highlighting knowledge gaps for the field and detailing a global framework for long-term BAR monitoring. Introduction:The global cryosphere-the compilation of Earth's frozen water-is in rapid, accelerating decline (IPCC, 2019). Covering approximately one-fifth of the Earth's surface at present, mass loss from the terrestrial cryosphere is driven primarily by a warming atmosphere (Fountain et al., 2012;Hock et al., 2019). Over the last 50 years, spring snow cover on land in the Arctic has

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Bio-optical Properties of Terrestrial Snow and Ice

Cited by 6 publications

References 121 publications

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

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

Light-Absorbing Particles in Snow and Ice: A Brief Journey Across Latitudes

Biological albedo reduction on ice sheets, glaciers, and snowfields

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