Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments

Climate change is affecting the rate of carbon cycling, particularly in the Arctic. Permafrost degradation through deeper thaw and physical disturbances results in the release of carbon dioxide and methane to the atmosphere and to an increase in lateral dissolved organic matter (DOM) fluxes. Whereas...

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Published in:Biogeosciences
Main Authors: Coch, Caroline, Juhls, Bennet, Lamoureux, Scott F., Lafrenière, Melissa J., Fritz, Michael, Heim, Birgit, Lantuit, Hugues
Format: Text
Language:English
Published: 2019
Subjects:
Online Access:https://doi.org/10.5194/bg-16-4535-2019
https://www.biogeosciences.net/16/4535/2019/
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spelling ftcopernicus:oai:publications.copernicus.org:bg73957 2023-05-15T14:29:39+02:00 Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments Coch, Caroline Juhls, Bennet Lamoureux, Scott F. Lafrenière, Melissa J. Fritz, Michael Heim, Birgit Lantuit, Hugues 2019-11-29 application/pdf https://doi.org/10.5194/bg-16-4535-2019 https://www.biogeosciences.net/16/4535/2019/ eng eng doi:10.5194/bg-16-4535-2019 https://www.biogeosciences.net/16/4535/2019/ eISSN: 1726-4189 Text 2019 ftcopernicus https://doi.org/10.5194/bg-16-4535-2019 2019-12-24T09:48:09Z Climate change is affecting the rate of carbon cycling, particularly in the Arctic. Permafrost degradation through deeper thaw and physical disturbances results in the release of carbon dioxide and methane to the atmosphere and to an increase in lateral dissolved organic matter (DOM) fluxes. Whereas riverine DOM fluxes of the large Arctic rivers are well assessed, knowledge is limited with regard to small catchments that cover more than 40 % of the Arctic drainage basin. Here, we use absorption measurements to characterize changes in DOM quantity and quality in a low Arctic (Herschel Island, Yukon, Canada) and a high Arctic (Cape Bounty, Melville Island, Nunavut, Canada) setting with regard to geographical differences, impacts of permafrost degradation, and rainfall events. We find that DOM quantity and quality is controlled by differences in vegetation cover and soil organic carbon content (SOCC). The low Arctic site has higher SOCC and greater abundance of plant material resulting in higher chromophoric dissolved organic matter (cDOM) and dissolved organic carbon (DOC) than in the high Arctic. DOC concentration and cDOM in surface waters at both sites show strong linear relationships similar to the one for the great Arctic rivers. We used the optical characteristics of DOM such as cDOM absorption, specific ultraviolet absorbance (SUVA), ultraviolet (UV) spectral slopes (S275–295), and slope ratio (SR) for assessing quality changes downstream, at base flow and storm flow conditions, and in relation to permafrost disturbance. DOM in streams at both sites demonstrated optical signatures indicative of photodegradation downstream processes, even over short distances of 2000 m. Flow pathways and the connected hydrological residence time control DOM quality. Deeper flow pathways allow the export of permafrost-derived DOM (i.e. from deeper in the active layer), whereas shallow pathways with shorter residence times lead to the export of fresh surface- and near-surface-derived DOM. Compared to the large Arctic rivers, DOM quality exported from the small catchments studied here is much fresher and therefore prone to degradation. Assessing optical properties of DOM and linking them to catchment properties will be a useful tool for understanding changing DOM fluxes and quality at a pan-Arctic scale. Text Arctic Cape Arctic Climate change Herschel Herschel Island Nunavut permafrost Melville Island Yukon Copernicus Publications: E-Journals Arctic Canada Cape Bounty ENVELOPE(-109.542,-109.542,74.863,74.863) Herschel Island ENVELOPE(-139.089,-139.089,69.583,69.583) Nunavut Yukon Biogeosciences 16 23 4535 4553
institution Open Polar
collection Copernicus Publications: E-Journals
op_collection_id ftcopernicus
language English
description Climate change is affecting the rate of carbon cycling, particularly in the Arctic. Permafrost degradation through deeper thaw and physical disturbances results in the release of carbon dioxide and methane to the atmosphere and to an increase in lateral dissolved organic matter (DOM) fluxes. Whereas riverine DOM fluxes of the large Arctic rivers are well assessed, knowledge is limited with regard to small catchments that cover more than 40 % of the Arctic drainage basin. Here, we use absorption measurements to characterize changes in DOM quantity and quality in a low Arctic (Herschel Island, Yukon, Canada) and a high Arctic (Cape Bounty, Melville Island, Nunavut, Canada) setting with regard to geographical differences, impacts of permafrost degradation, and rainfall events. We find that DOM quantity and quality is controlled by differences in vegetation cover and soil organic carbon content (SOCC). The low Arctic site has higher SOCC and greater abundance of plant material resulting in higher chromophoric dissolved organic matter (cDOM) and dissolved organic carbon (DOC) than in the high Arctic. DOC concentration and cDOM in surface waters at both sites show strong linear relationships similar to the one for the great Arctic rivers. We used the optical characteristics of DOM such as cDOM absorption, specific ultraviolet absorbance (SUVA), ultraviolet (UV) spectral slopes (S275–295), and slope ratio (SR) for assessing quality changes downstream, at base flow and storm flow conditions, and in relation to permafrost disturbance. DOM in streams at both sites demonstrated optical signatures indicative of photodegradation downstream processes, even over short distances of 2000 m. Flow pathways and the connected hydrological residence time control DOM quality. Deeper flow pathways allow the export of permafrost-derived DOM (i.e. from deeper in the active layer), whereas shallow pathways with shorter residence times lead to the export of fresh surface- and near-surface-derived DOM. Compared to the large Arctic rivers, DOM quality exported from the small catchments studied here is much fresher and therefore prone to degradation. Assessing optical properties of DOM and linking them to catchment properties will be a useful tool for understanding changing DOM fluxes and quality at a pan-Arctic scale.
format Text
author Coch, Caroline
Juhls, Bennet
Lamoureux, Scott F.
Lafrenière, Melissa J.
Fritz, Michael
Heim, Birgit
Lantuit, Hugues
spellingShingle Coch, Caroline
Juhls, Bennet
Lamoureux, Scott F.
Lafrenière, Melissa J.
Fritz, Michael
Heim, Birgit
Lantuit, Hugues
Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments
author_facet Coch, Caroline
Juhls, Bennet
Lamoureux, Scott F.
Lafrenière, Melissa J.
Fritz, Michael
Heim, Birgit
Lantuit, Hugues
author_sort Coch, Caroline
title Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments
title_short Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments
title_full Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments
title_fullStr Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments
title_full_unstemmed Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments
title_sort comparisons of dissolved organic matter and its optical characteristics in small low and high arctic catchments
publishDate 2019
url https://doi.org/10.5194/bg-16-4535-2019
https://www.biogeosciences.net/16/4535/2019/
long_lat ENVELOPE(-109.542,-109.542,74.863,74.863)
ENVELOPE(-139.089,-139.089,69.583,69.583)
geographic Arctic
Canada
Cape Bounty
Herschel Island
Nunavut
Yukon
geographic_facet Arctic
Canada
Cape Bounty
Herschel Island
Nunavut
Yukon
genre Arctic Cape
Arctic
Climate change
Herschel
Herschel Island
Nunavut
permafrost
Melville Island
Yukon
genre_facet Arctic Cape
Arctic
Climate change
Herschel
Herschel Island
Nunavut
permafrost
Melville Island
Yukon
op_source eISSN: 1726-4189
op_relation doi:10.5194/bg-16-4535-2019
https://www.biogeosciences.net/16/4535/2019/
op_doi https://doi.org/10.5194/bg-16-4535-2019
container_title Biogeosciences
container_volume 16
container_issue 23
container_start_page 4535
op_container_end_page 4553
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