Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study
Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to constr...
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Copernicus Publications
2014
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00019668 2023-05-15T13:41:02+02:00 Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study Chang, C.-H. Johnson, N. C. Cassar, N. 2014-06 electronic https://doi.org/10.5194/bg-11-3279-2014 https://noa.gwlb.de/receive/cop_mods_00019668 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00019623/bg-11-3279-2014.pdf https://bg.copernicus.org/articles/11/3279/2014/bg-11-3279-2014.pdf eng eng Copernicus Publications Biogeosciences -- http://www.bibliothek.uni-regensburg.de/ezeit/?2158181 -- http://www.copernicus.org/EGU/bg/bg.html -- 1726-4189 https://doi.org/10.5194/bg-11-3279-2014 https://noa.gwlb.de/receive/cop_mods_00019668 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00019623/bg-11-3279-2014.pdf https://bg.copernicus.org/articles/11/3279/2014/bg-11-3279-2014.pdf uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2014 ftnonlinearchiv https://doi.org/10.5194/bg-11-3279-2014 2022-02-08T22:52:33Z Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to construct weekly gridded (1° × 1°) maps of organic carbon export for the Southern Ocean from 1998 to 2009. The SOM is trained with in situ measurements of O2 / Ar-derived net community production (NCP) that are tightly linked to the carbon export in the mixed layer on timescales of one to two weeks and with six potential NCP predictors: photosynthetically available radiation (PAR), particulate organic carbon (POC), chlorophyll (Chl), sea surface temperature (SST), sea surface height (SSH), and mixed layer depth (MLD). This nonparametric approach is based entirely on the observed statistical relationships between NCP and the predictors and, therefore, is strongly constrained by observations. A thorough cross-validation yields three retained NCP predictors, Chl, PAR, and MLD. Our constructed NCP is further validated by good agreement with previously published, independent in situ derived NCP of weekly or longer temporal resolution through real-time and climatological comparisons at various sampling sites. The resulting November–March NCP climatology reveals a pronounced zonal band of high NCP roughly following the Subtropical Front in the Atlantic, Indian, and western Pacific sectors, and turns southeastward shortly after the dateline. Other regions of elevated NCP include the upwelling zones off Chile and Namibia, the Patagonian Shelf, the Antarctic coast, and areas surrounding the Islands of Kerguelen, South Georgia, and Crozet. This basin-scale NCP climatology closely resembles that of the satellite POC field and observed air–sea CO2 flux. The long-term mean area-integrated NCP south of 50° S from our dataset, 17.9 mmol C m−2 d−1, falls within the range of 8.3 to 24 mmol C m−2 d−1 from other model estimates. A broad agreement is found in the basin-wide NCP climatology among various models but with significant spatial variations, particularly in the Patagonian Shelf. Our approach provides a comprehensive view of the Southern Ocean NCP climatology and a potential opportunity to further investigate interannual and intraseasonal variability. Article in Journal/Newspaper Antarc* Antarctic Southern Ocean Niedersächsisches Online-Archiv NOA Antarctic Indian Kerguelen Pacific Southern Ocean The Antarctic Biogeosciences 11 12 3279 3297 |
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Niedersächsisches Online-Archiv NOA |
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ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Chang, C.-H. Johnson, N. C. Cassar, N. Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study |
topic_facet |
article Verlagsveröffentlichung |
description |
Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to construct weekly gridded (1° × 1°) maps of organic carbon export for the Southern Ocean from 1998 to 2009. The SOM is trained with in situ measurements of O2 / Ar-derived net community production (NCP) that are tightly linked to the carbon export in the mixed layer on timescales of one to two weeks and with six potential NCP predictors: photosynthetically available radiation (PAR), particulate organic carbon (POC), chlorophyll (Chl), sea surface temperature (SST), sea surface height (SSH), and mixed layer depth (MLD). This nonparametric approach is based entirely on the observed statistical relationships between NCP and the predictors and, therefore, is strongly constrained by observations. A thorough cross-validation yields three retained NCP predictors, Chl, PAR, and MLD. Our constructed NCP is further validated by good agreement with previously published, independent in situ derived NCP of weekly or longer temporal resolution through real-time and climatological comparisons at various sampling sites. The resulting November–March NCP climatology reveals a pronounced zonal band of high NCP roughly following the Subtropical Front in the Atlantic, Indian, and western Pacific sectors, and turns southeastward shortly after the dateline. Other regions of elevated NCP include the upwelling zones off Chile and Namibia, the Patagonian Shelf, the Antarctic coast, and areas surrounding the Islands of Kerguelen, South Georgia, and Crozet. This basin-scale NCP climatology closely resembles that of the satellite POC field and observed air–sea CO2 flux. The long-term mean area-integrated NCP south of 50° S from our dataset, 17.9 mmol C m−2 d−1, falls within the range of 8.3 to 24 mmol C m−2 d−1 from other model estimates. A broad agreement is found in the basin-wide NCP climatology among various models but with significant spatial variations, particularly in the Patagonian Shelf. Our approach provides a comprehensive view of the Southern Ocean NCP climatology and a potential opportunity to further investigate interannual and intraseasonal variability. |
format |
Article in Journal/Newspaper |
author |
Chang, C.-H. Johnson, N. C. Cassar, N. |
author_facet |
Chang, C.-H. Johnson, N. C. Cassar, N. |
author_sort |
Chang, C.-H. |
title |
Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study |
title_short |
Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study |
title_full |
Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study |
title_fullStr |
Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study |
title_full_unstemmed |
Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study |
title_sort |
neural network-based estimates of southern ocean net community production from in situ o2 / ar and satellite observation: a methodological study |
publisher |
Copernicus Publications |
publishDate |
2014 |
url |
https://doi.org/10.5194/bg-11-3279-2014 https://noa.gwlb.de/receive/cop_mods_00019668 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00019623/bg-11-3279-2014.pdf https://bg.copernicus.org/articles/11/3279/2014/bg-11-3279-2014.pdf |
geographic |
Antarctic Indian Kerguelen Pacific Southern Ocean The Antarctic |
geographic_facet |
Antarctic Indian Kerguelen Pacific Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Southern Ocean |
genre_facet |
Antarc* Antarctic Southern Ocean |
op_relation |
Biogeosciences -- http://www.bibliothek.uni-regensburg.de/ezeit/?2158181 -- http://www.copernicus.org/EGU/bg/bg.html -- 1726-4189 https://doi.org/10.5194/bg-11-3279-2014 https://noa.gwlb.de/receive/cop_mods_00019668 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00019623/bg-11-3279-2014.pdf https://bg.copernicus.org/articles/11/3279/2014/bg-11-3279-2014.pdf |
op_rights |
uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/bg-11-3279-2014 |
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Biogeosciences |
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11 |
container_issue |
12 |
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3279 |
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3297 |
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1766144849737678848 |