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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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 |
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Open Polar |
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Copernicus Publications: E-Journals |
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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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1766303611732623360 |