Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone

Detalhes bibliográficos
Autor(a) principal: Freitas, Pedro
Data de Publicação: 2022
Outros Autores: Vieira, Gonçalo, Mora, Carla, Canário, João, Vincent, Warwick F.
Tipo de documento: Artigo
Idioma: eng
Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
Texto Completo: http://hdl.handle.net/10451/55258
Resumo: Thermokarst lakes and ponds are a common landscape feature resulting from permafrost thaw, but their intense greenhouse gas emissions are still poorly constrained as a feedback mechanism for global warming because of their diversity, abundance, and remoteness. Thermokarst waterbodies may be small and optically diverse, posing specifc challenges for optical remote sensing regarding detection, classifcation, and monitoring. This is especially relevant when accounting for external factors that afect water refectance, such as scattering and vegetation shadow casts. In this study, we evaluated the efects of shadowing across optically diverse waterbodies located in the forest–tundra zone of northern Canada. We used ultra-high spatial resolution multispectral data and digital surface models obtained from unmanned aerial systems for modeling and analyzing shadow efects on water refectance at Earth Observation satellite overpass time. Our results show that shadowing causes variations in refectance, reducing the usable area of remotely sensed pixels for waterbody analysis in small lakes and ponds. The efects were greater on brighter and turbid inorganic thermokarst lakes embedded in post-glacial silt–clay marine deposits and littoral sands, where the mean refectance decrease was from -51 to -70%, depending on the wavelength. These efects were also dependent on lake shape and vegetation height and were amplifed in the cold season due to low solar elevations. Remote sensing will increasingly play a key role in assessing thermokarst lake responses and feedbacks to global change, and this study shows the magnitude and sources of optical variations caused by shading that need to be considered in future analyses.
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spelling Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zoneShadowsOptical remote sensingThermokarstUnmanned aerial systemsVegetationLakesThermokarst lakes and ponds are a common landscape feature resulting from permafrost thaw, but their intense greenhouse gas emissions are still poorly constrained as a feedback mechanism for global warming because of their diversity, abundance, and remoteness. Thermokarst waterbodies may be small and optically diverse, posing specifc challenges for optical remote sensing regarding detection, classifcation, and monitoring. This is especially relevant when accounting for external factors that afect water refectance, such as scattering and vegetation shadow casts. In this study, we evaluated the efects of shadowing across optically diverse waterbodies located in the forest–tundra zone of northern Canada. We used ultra-high spatial resolution multispectral data and digital surface models obtained from unmanned aerial systems for modeling and analyzing shadow efects on water refectance at Earth Observation satellite overpass time. Our results show that shadowing causes variations in refectance, reducing the usable area of remotely sensed pixels for waterbody analysis in small lakes and ponds. The efects were greater on brighter and turbid inorganic thermokarst lakes embedded in post-glacial silt–clay marine deposits and littoral sands, where the mean refectance decrease was from -51 to -70%, depending on the wavelength. These efects were also dependent on lake shape and vegetation height and were amplifed in the cold season due to low solar elevations. Remote sensing will increasingly play a key role in assessing thermokarst lake responses and feedbacks to global change, and this study shows the magnitude and sources of optical variations caused by shading that need to be considered in future analyses.SpringerRepositório da Universidade de LisboaFreitas, PedroVieira, GonçaloMora, CarlaCanário, JoãoVincent, Warwick F.2022-11-28T13:02:56Z20222022-01-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/10451/55258engFreitas, P., Vieira, G., Mora, C. & Vincent, W. F. (2022). Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone. Environmental Earth Sciences, 81(22), 522. https://doi.org/10.1007/s12665-022-10640-11866-628010.1007/s12665-022-10640-11866-6299info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2023-11-08T17:02:06Zoai:repositorio.ul.pt:10451/55258Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T22:05:56.959346Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse
dc.title.none.fl_str_mv Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
title Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
spellingShingle Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
Freitas, Pedro
Shadows
Optical remote sensing
Thermokarst
Unmanned aerial systems
Vegetation
Lakes
title_short Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
title_full Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
title_fullStr Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
title_full_unstemmed Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
title_sort Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone
author Freitas, Pedro
author_facet Freitas, Pedro
Vieira, Gonçalo
Mora, Carla
Canário, João
Vincent, Warwick F.
author_role author
author2 Vieira, Gonçalo
Mora, Carla
Canário, João
Vincent, Warwick F.
author2_role author
author
author
author
dc.contributor.none.fl_str_mv Repositório da Universidade de Lisboa
dc.contributor.author.fl_str_mv Freitas, Pedro
Vieira, Gonçalo
Mora, Carla
Canário, João
Vincent, Warwick F.
dc.subject.por.fl_str_mv Shadows
Optical remote sensing
Thermokarst
Unmanned aerial systems
Vegetation
Lakes
topic Shadows
Optical remote sensing
Thermokarst
Unmanned aerial systems
Vegetation
Lakes
description Thermokarst lakes and ponds are a common landscape feature resulting from permafrost thaw, but their intense greenhouse gas emissions are still poorly constrained as a feedback mechanism for global warming because of their diversity, abundance, and remoteness. Thermokarst waterbodies may be small and optically diverse, posing specifc challenges for optical remote sensing regarding detection, classifcation, and monitoring. This is especially relevant when accounting for external factors that afect water refectance, such as scattering and vegetation shadow casts. In this study, we evaluated the efects of shadowing across optically diverse waterbodies located in the forest–tundra zone of northern Canada. We used ultra-high spatial resolution multispectral data and digital surface models obtained from unmanned aerial systems for modeling and analyzing shadow efects on water refectance at Earth Observation satellite overpass time. Our results show that shadowing causes variations in refectance, reducing the usable area of remotely sensed pixels for waterbody analysis in small lakes and ponds. The efects were greater on brighter and turbid inorganic thermokarst lakes embedded in post-glacial silt–clay marine deposits and littoral sands, where the mean refectance decrease was from -51 to -70%, depending on the wavelength. These efects were also dependent on lake shape and vegetation height and were amplifed in the cold season due to low solar elevations. Remote sensing will increasingly play a key role in assessing thermokarst lake responses and feedbacks to global change, and this study shows the magnitude and sources of optical variations caused by shading that need to be considered in future analyses.
publishDate 2022
dc.date.none.fl_str_mv 2022-11-28T13:02:56Z
2022
2022-01-01T00:00:00Z
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/article
format article
status_str publishedVersion
dc.identifier.uri.fl_str_mv http://hdl.handle.net/10451/55258
url http://hdl.handle.net/10451/55258
dc.language.iso.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv Freitas, P., Vieira, G., Mora, C. & Vincent, W. F. (2022). Vegetation shadow casts impact remotely sensed reflectance from permafrost thaw ponds in the subarctic forest-tundra zone. Environmental Earth Sciences, 81(22), 522. https://doi.org/10.1007/s12665-022-10640-1
1866-6280
10.1007/s12665-022-10640-1
1866-6299
dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
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dc.publisher.none.fl_str_mv Springer
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