Quantifying bioalbedo: a new physically based model and discussion of empirical methods for characterising biological influence on ice and snow albedo.

Journal article


Cook, J. M., Hodson, Andrew J., Flanner, Mark, Gardner, Alex, Tedstone, Andrew, Williamson, Christopher, Irvine-Fynn, Tristram D. L., Nilsson, Johan, Bryant, Robert and Tranter, Martyn 2017. Quantifying bioalbedo: a new physically based model and discussion of empirical methods for characterising biological influence on ice and snow albedo. The Cryosphere. https://doi.org/10.5194/tc-11-2611-2017
AuthorsCook, J. M., Hodson, Andrew J., Flanner, Mark, Gardner, Alex, Tedstone, Andrew, Williamson, Christopher, Irvine-Fynn, Tristram D. L., Nilsson, Johan, Bryant, Robert and Tranter, Martyn
Abstract

The darkening effects of biological impurities on ice and snow have been recognised as a control on the surface energy balance of terrestrial snow, sea ice, glaciers and ice sheets. With a heightened interest in understanding the impacts of a changing climate on snow and ice processes, quantifying the impact of biological impurities on ice and snow albedo (bioalbedo) and its evolution through time is a rapidly growing field of research. However, rigorous quantification of bioalbedo has remained elusive because of difficulties in isolating the biological contribution to ice albedo from that of inorganic impurities and the variable optical properties of the ice itself. For this reason, isolation of the biological signature in reflectance data obtained from aerial/orbital platforms has not been achieved, even when ground-based biological measurements have been available. This paper provides the cell-specific optical properties that are required to model the spectral signatures and broadband darkening of ice. Applying radiative transfer theory, these properties provide the physical basis needed to link biological and glaciological ground measurements with remotely sensed reflectance data. Using these new capabilities we confirm that biological impurities can influence ice albedo, then we identify 10 challenges to the measurement of bioalbedo in the field with the aim of improving future experimental designs to better quantify bioalbedo feedbacks. These challenges are (1) ambiguity in terminology, (2) characterising snow or ice optical properties, (3) characterising solar irradiance, (4) determining optical properties of cells, (5) measuring biomass, (6) characterising vertical distribution of cells, (7) characterising abiotic impurities, (8) surface anisotropy, (9) measuring indirect albedo feedbacks, and (10) measurement and instrument configurations. This paper aims to provide a broad audience of glaciologists and biologists with an overview of radiative transfer and albedo that could support future experimental design.

The darkening effects of biological impurities on ice and snow have been recognised as a control on the surface energy balance of terrestrial snow, sea ice, glaciers and ice sheets. With a heightened interest in understanding the impacts of a changing climate on snow and ice processes, quantifying the impact of biological impurities on ice and snow albedo (<q>bioalbedo</q>) and its evolution through time is a rapidly growing field of research. However, rigorous quantification of bioalbedo has remained elusive because of difficulties in isolating the biological contribution to ice albedo from that of inorganic impurities and the variable optical properties of the ice itself. For this reason, isolation of the biological signature in reflectance data obtained from aerial/orbital platforms has not been achieved, even when ground-based biological measurements have been available. This paper provides the cell-specific optical properties that are required to model the spectral signatures and broadband darkening of ice. Applying radiative transfer theory, these properties provide the physical basis needed to link biological and glaciological ground measurements with remotely sensed reflectance data. Using these new capabilities we confirm that biological impurities can influence ice albedo, then we identify 10 challenges to the measurement of bioalbedo in the field with the aim of improving future experimental designs to better quantify bioalbedo feedbacks. These challenges are (1) ambiguity in terminology, (2) characterising snow or ice optical properties, (3) characterising solar irradiance, (4) determining optical properties of cells, (5) measuring biomass, (6) characterising vertical distribution of cells, (7) characterising abiotic impurities, (8) surface anisotropy, (9) measuring indirect albedo feedbacks, and (10) measurement and instrument configurations. This paper aims to provide a broad audience of glaciologists and biologists with an overview of radiative transfer and albedo that could support future experimental design.

KeywordsAlbedo; Glaciology; Glacier change
Year2017
JournalThe Cryosphere
PublisherCopernicus Publications
ISSN19940424
Digital Object Identifier (DOI)https://doi.org/10.5194/tc-11-2611-2017
Web address (URL)http://hdl.handle.net/10545/622325
hdl:10545/622325
Publication dates17 Nov 2017
Publication process dates
Deposited15 Mar 2018, 15:46
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Archived with thanks to The Cryosphere

ContributorsUniversity of Sheffield, University of Derby, University Centre in Svalbard, California Institute of Technology, University of Michigan, University of Bristol and Aberystwyth University
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https://repository.derby.ac.uk/item/932y3/quantifying-bioalbedo-a-new-physically-based-model-and-discussion-of-empirical-methods-for-characterising-biological-influence-on-ice-and-snow-albedo

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