Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production
The Arctic spring phytoplankton bloom has been reported to commence under a melting sea ice cover as transmission of photosynthetically active radiation (PAR; 400–700 nm) suddenly increases with the formation of surface melt ponds. Spatial variability in ice surface characteristics, i.e., snow thick...
Published in: | Elementa: Science of the Anthropocene |
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Online Access: | https://doi.org/10.1525/elementa.363 https://doaj.org/article/6e4de553abb2409e840bc17b3e23d005 |
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fttriple:oai:gotriple.eu:oai:doaj.org/article:6e4de553abb2409e840bc17b3e23d005 2023-05-15T15:03:39+02:00 Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production L. C. Matthes J. K. Ehn S. L.-Girard N. M. Pogorzelec M. Babin C. J. Mundy 2019-06-01 https://doi.org/10.1525/elementa.363 https://doaj.org/article/6e4de553abb2409e840bc17b3e23d005 en eng BioOne 2325-1026 doi:10.1525/elementa.363 https://doaj.org/article/6e4de553abb2409e840bc17b3e23d005 undefined Elementa: Science of the Anthropocene, Vol 7, Iss 1 (2019) Under-ice downwelling average cosine Under-ice spectral light field Under-ice PAR propagation Sea ice melt progression Spring phytoplankton bloom Arctic primary production geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2019 fttriple https://doi.org/10.1525/elementa.363 2023-01-22T19:23:15Z The Arctic spring phytoplankton bloom has been reported to commence under a melting sea ice cover as transmission of photosynthetically active radiation (PAR; 400–700 nm) suddenly increases with the formation of surface melt ponds. Spatial variability in ice surface characteristics, i.e., snow thickness or melt pond distributions, and subsequent impact on transmitted PAR makes estimating light-limited primary production difficult during this time of year. Added to this difficulty is the interpretation of data from various sensor types, including hyperspectral, multispectral, and PAR-band irradiance sensors, with either cosine-corrected (planar) or spherical (scalar) sensor heads. To quantify the impact of the heterogeneous radiation field under sea ice, spectral irradiance profiles were collected beneath landfast sea ice during the Green Edge ice-camp campaigns in May–June 2015 and June–July 2016. Differences between PAR measurements are described using the downwelling average cosine, 'μd', a measure of the degree of anisotropy of the downwelling underwater radiation field which, in practice, can be used to convert between downwelling scalar, 'E0d', and planar, 'Ed', irradiance. A significantly smaller 'μd'(PAR) was measured prior to snow melt compared to after (0.6 vs. 0.7) when melt ponds covered the ice surface. The impact of the average cosine on primary production estimates, shown in the calculation of depth-integrated daily production, was 16% larger under light-limiting conditions when 'E0d' was used instead of 'Ed'. Under light-saturating conditions, daily production was only 3% larger. Conversion of underwater irradiance data also plays a role in the ratio of total quanta to total energy (EQ/EW, found to be 4.25), which reflects the spectral shape of the under-ice light field. We use these observations to provide factors for converting irradiance measurements between irradiance detector types and units as a function of surface type and depth under sea ice, towards improving primary production estimates. Article in Journal/Newspaper Arctic Phytoplankton Sea ice Unknown Arctic Elementa: Science of the Anthropocene 7 |
institution |
Open Polar |
collection |
Unknown |
op_collection_id |
fttriple |
language |
English |
topic |
Under-ice downwelling average cosine Under-ice spectral light field Under-ice PAR propagation Sea ice melt progression Spring phytoplankton bloom Arctic primary production geo envir |
spellingShingle |
Under-ice downwelling average cosine Under-ice spectral light field Under-ice PAR propagation Sea ice melt progression Spring phytoplankton bloom Arctic primary production geo envir L. C. Matthes J. K. Ehn S. L.-Girard N. M. Pogorzelec M. Babin C. J. Mundy Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production |
topic_facet |
Under-ice downwelling average cosine Under-ice spectral light field Under-ice PAR propagation Sea ice melt progression Spring phytoplankton bloom Arctic primary production geo envir |
description |
The Arctic spring phytoplankton bloom has been reported to commence under a melting sea ice cover as transmission of photosynthetically active radiation (PAR; 400–700 nm) suddenly increases with the formation of surface melt ponds. Spatial variability in ice surface characteristics, i.e., snow thickness or melt pond distributions, and subsequent impact on transmitted PAR makes estimating light-limited primary production difficult during this time of year. Added to this difficulty is the interpretation of data from various sensor types, including hyperspectral, multispectral, and PAR-band irradiance sensors, with either cosine-corrected (planar) or spherical (scalar) sensor heads. To quantify the impact of the heterogeneous radiation field under sea ice, spectral irradiance profiles were collected beneath landfast sea ice during the Green Edge ice-camp campaigns in May–June 2015 and June–July 2016. Differences between PAR measurements are described using the downwelling average cosine, 'μd', a measure of the degree of anisotropy of the downwelling underwater radiation field which, in practice, can be used to convert between downwelling scalar, 'E0d', and planar, 'Ed', irradiance. A significantly smaller 'μd'(PAR) was measured prior to snow melt compared to after (0.6 vs. 0.7) when melt ponds covered the ice surface. The impact of the average cosine on primary production estimates, shown in the calculation of depth-integrated daily production, was 16% larger under light-limiting conditions when 'E0d' was used instead of 'Ed'. Under light-saturating conditions, daily production was only 3% larger. Conversion of underwater irradiance data also plays a role in the ratio of total quanta to total energy (EQ/EW, found to be 4.25), which reflects the spectral shape of the under-ice light field. We use these observations to provide factors for converting irradiance measurements between irradiance detector types and units as a function of surface type and depth under sea ice, towards improving primary production estimates. |
format |
Article in Journal/Newspaper |
author |
L. C. Matthes J. K. Ehn S. L.-Girard N. M. Pogorzelec M. Babin C. J. Mundy |
author_facet |
L. C. Matthes J. K. Ehn S. L.-Girard N. M. Pogorzelec M. Babin C. J. Mundy |
author_sort |
L. C. Matthes |
title |
Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production |
title_short |
Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production |
title_full |
Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production |
title_fullStr |
Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production |
title_full_unstemmed |
Average cosine coefficient and spectral distribution of the light field under sea ice: Implications for primary production |
title_sort |
average cosine coefficient and spectral distribution of the light field under sea ice: implications for primary production |
publisher |
BioOne |
publishDate |
2019 |
url |
https://doi.org/10.1525/elementa.363 https://doaj.org/article/6e4de553abb2409e840bc17b3e23d005 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Phytoplankton Sea ice |
genre_facet |
Arctic Phytoplankton Sea ice |
op_source |
Elementa: Science of the Anthropocene, Vol 7, Iss 1 (2019) |
op_relation |
2325-1026 doi:10.1525/elementa.363 https://doaj.org/article/6e4de553abb2409e840bc17b3e23d005 |
op_rights |
undefined |
op_doi |
https://doi.org/10.1525/elementa.363 |
container_title |
Elementa: Science of the Anthropocene |
container_volume |
7 |
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1766335509218459648 |