Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat
The seasonality of sea ice in the Southern Ocean has profound effects on the life cycle (phenology) of phytoplankton residing under the ice. The current literature investigating this relationship is primarily based on remote sensing, which often lacks data for half of the year or more. One prominent...
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ftcopernicus:oai:publications.copernicus.org:bg86823 2023-05-15T13:31:39+02:00 Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat Hague, Mark Vichi, Marcello 2021-01-04 application/pdf https://doi.org/10.5194/bg-18-25-2021 https://bg.copernicus.org/articles/18/25/2021/ eng eng doi:10.5194/bg-18-25-2021 https://bg.copernicus.org/articles/18/25/2021/ eISSN: 1726-4189 Text 2021 ftcopernicus https://doi.org/10.5194/bg-18-25-2021 2021-01-11T17:22:15Z The seasonality of sea ice in the Southern Ocean has profound effects on the life cycle (phenology) of phytoplankton residing under the ice. The current literature investigating this relationship is primarily based on remote sensing, which often lacks data for half of the year or more. One prominent hypothesis holds that, following ice retreat in spring, buoyant meltwaters enhance available irradiance, triggering a bloom which follows the ice edge. However, an analysis of Biogeochemical Argo (BGC-Argo) data sampling under Antarctic sea ice suggests that this is not necessarily the case. Rather than precipitating rapid accumulation, we show that meltwaters enhance growth in an already highly active phytoplankton population. Blooms observed in the wake of the receding ice edge can then be understood as the emergence of a growth process that started earlier under sea ice. Indeed, we estimate that growth initiation occurs, on average, 4–5 weeks before ice retreat, typically starting in August and September. Novel techniques using on-board data to detect the timing of ice melt were used. Furthermore, such growth is shown to occur under conditions of substantial ice cover ( >90 % satellite ice concentration) and deep mixed layers ( >100 m), conditions previously thought to be inimical to growth. This led to the development of several box model experiments (with varying vertical depth) in which we sought to investigate the mechanisms responsible for such early growth. The results of these experiments suggest that a combination of higher light transfer (penetration) through sea ice cover and extreme low light adaptation by phytoplankton can account for the observed phenology. Text Antarc* Antarctic Sea ice Southern Ocean Copernicus Publications: E-Journals Antarctic Southern Ocean Biogeosciences 18 1 25 38 |
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Copernicus Publications: E-Journals |
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English |
description |
The seasonality of sea ice in the Southern Ocean has profound effects on the life cycle (phenology) of phytoplankton residing under the ice. The current literature investigating this relationship is primarily based on remote sensing, which often lacks data for half of the year or more. One prominent hypothesis holds that, following ice retreat in spring, buoyant meltwaters enhance available irradiance, triggering a bloom which follows the ice edge. However, an analysis of Biogeochemical Argo (BGC-Argo) data sampling under Antarctic sea ice suggests that this is not necessarily the case. Rather than precipitating rapid accumulation, we show that meltwaters enhance growth in an already highly active phytoplankton population. Blooms observed in the wake of the receding ice edge can then be understood as the emergence of a growth process that started earlier under sea ice. Indeed, we estimate that growth initiation occurs, on average, 4–5 weeks before ice retreat, typically starting in August and September. Novel techniques using on-board data to detect the timing of ice melt were used. Furthermore, such growth is shown to occur under conditions of substantial ice cover ( >90 % satellite ice concentration) and deep mixed layers ( >100 m), conditions previously thought to be inimical to growth. This led to the development of several box model experiments (with varying vertical depth) in which we sought to investigate the mechanisms responsible for such early growth. The results of these experiments suggest that a combination of higher light transfer (penetration) through sea ice cover and extreme low light adaptation by phytoplankton can account for the observed phenology. |
format |
Text |
author |
Hague, Mark Vichi, Marcello |
spellingShingle |
Hague, Mark Vichi, Marcello Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat |
author_facet |
Hague, Mark Vichi, Marcello |
author_sort |
Hague, Mark |
title |
Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat |
title_short |
Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat |
title_full |
Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat |
title_fullStr |
Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat |
title_full_unstemmed |
Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat |
title_sort |
southern ocean biogeochemical argo detect under-ice phytoplankton growth before sea ice retreat |
publishDate |
2021 |
url |
https://doi.org/10.5194/bg-18-25-2021 https://bg.copernicus.org/articles/18/25/2021/ |
geographic |
Antarctic Southern Ocean |
geographic_facet |
Antarctic Southern Ocean |
genre |
Antarc* Antarctic Sea ice Southern Ocean |
genre_facet |
Antarc* Antarctic Sea ice Southern Ocean |
op_source |
eISSN: 1726-4189 |
op_relation |
doi:10.5194/bg-18-25-2021 https://bg.copernicus.org/articles/18/25/2021/ |
op_doi |
https://doi.org/10.5194/bg-18-25-2021 |
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Biogeosciences |
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18 |
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1 |
container_start_page |
25 |
op_container_end_page |
38 |
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1766019945391456256 |