Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis
We examine 20 years of monthly global ocean color data and modeling outputs of nutrients using self-organizing map (SOM) analysis to identify characteristic spatial and temporal patterns of high-nutrient low-chlorophyll (HNLC) regions and their association with different climate modes. The global ni...
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ftcopernicus:oai:publications.copernicus.org:egusphere106008 2023-07-30T04:07:03+02:00 Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis Basterretxea, Gotzon Font-Muñoz, Joan S. Hernández-Carrasco, Ismael Sañudo-Wilhelmy, Sergio 2023-07-06 application/pdf https://doi.org/10.5194/egusphere-2022-827 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-827/ eng eng doi:10.5194/egusphere-2022-827 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-827/ eISSN: Text 2023 ftcopernicus https://doi.org/10.5194/egusphere-2022-827 2023-07-10T16:24:18Z We examine 20 years of monthly global ocean color data and modeling outputs of nutrients using self-organizing map (SOM) analysis to identify characteristic spatial and temporal patterns of high-nutrient low-chlorophyll (HNLC) regions and their association with different climate modes. The global nitrate-to-chlorophyll ratio threshold of NO 3 : Chl > 17 (mmol NO 3 mg Chl −1 ) is estimated to be a good indicator of the distribution limit of this unproductive biome that, on average, covers 92 × 10 6 km 2 ( ∼ 25 % of the ocean). The trends in satellite-derived surface chlorophyll (0.6 ± 0.4 % yr −1 to 2 ± 0.4 % yr −1 ) suggest that HNLC regions in polar and subpolar areas have experienced an increase in phytoplankton biomass over the last decades, but much of this variation, particularly in the Southern Ocean, is produced by a climate-driven transition in 2009–2010. Indeed, since 2010, the extent of the HNLC zones has decreased at the poles (up to 8 %) and slightly increased at the Equator ( < 0.5 %). Our study finds that chlorophyll variations in HNLC regions respond to major climate variability signals such as the El Niño–Southern Oscillation (ENSO) and Meridional Overturning Circulation (MOC) at both short (2–4 years) and long (decadal) timescales. These results suggest global coupling in the functioning of distant biogeochemical regions. Text Southern Ocean Copernicus Publications: E-Journals Southern Ocean |
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Copernicus Publications: E-Journals |
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English |
description |
We examine 20 years of monthly global ocean color data and modeling outputs of nutrients using self-organizing map (SOM) analysis to identify characteristic spatial and temporal patterns of high-nutrient low-chlorophyll (HNLC) regions and their association with different climate modes. The global nitrate-to-chlorophyll ratio threshold of NO 3 : Chl > 17 (mmol NO 3 mg Chl −1 ) is estimated to be a good indicator of the distribution limit of this unproductive biome that, on average, covers 92 × 10 6 km 2 ( ∼ 25 % of the ocean). The trends in satellite-derived surface chlorophyll (0.6 ± 0.4 % yr −1 to 2 ± 0.4 % yr −1 ) suggest that HNLC regions in polar and subpolar areas have experienced an increase in phytoplankton biomass over the last decades, but much of this variation, particularly in the Southern Ocean, is produced by a climate-driven transition in 2009–2010. Indeed, since 2010, the extent of the HNLC zones has decreased at the poles (up to 8 %) and slightly increased at the Equator ( < 0.5 %). Our study finds that chlorophyll variations in HNLC regions respond to major climate variability signals such as the El Niño–Southern Oscillation (ENSO) and Meridional Overturning Circulation (MOC) at both short (2–4 years) and long (decadal) timescales. These results suggest global coupling in the functioning of distant biogeochemical regions. |
format |
Text |
author |
Basterretxea, Gotzon Font-Muñoz, Joan S. Hernández-Carrasco, Ismael Sañudo-Wilhelmy, Sergio |
spellingShingle |
Basterretxea, Gotzon Font-Muñoz, Joan S. Hernández-Carrasco, Ismael Sañudo-Wilhelmy, Sergio Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis |
author_facet |
Basterretxea, Gotzon Font-Muñoz, Joan S. Hernández-Carrasco, Ismael Sañudo-Wilhelmy, Sergio |
author_sort |
Basterretxea, Gotzon |
title |
Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis |
title_short |
Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis |
title_full |
Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis |
title_fullStr |
Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis |
title_full_unstemmed |
Global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis |
title_sort |
global variability of high nutrient low chlorophyll regions using neural networks and wavelet coherence analysis |
publishDate |
2023 |
url |
https://doi.org/10.5194/egusphere-2022-827 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-827/ |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
eISSN: |
op_relation |
doi:10.5194/egusphere-2022-827 https://egusphere.copernicus.org/preprints/2022/egusphere-2022-827/ |
op_doi |
https://doi.org/10.5194/egusphere-2022-827 |
_version_ |
1772820132091920384 |