Remote sensing of phytoplankton in the Southern Ocean
One of the greatest challenges for Southern Ocean and Antarctic research is the development of robust methods for assessing the current and future impacts of climate change, and for evaluating regional differences in the rate and direction of that change. The Southern Ocean has been changing rapidly...
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ftunivtasmania:oai:eprints.utas.edu.au:23452 2023-05-15T14:04:48+02:00 Remote sensing of phytoplankton in the Southern Ocean Johnson, R 2016 application/pdf https://eprints.utas.edu.au/23452/ https://eprints.utas.edu.au/23452/1/Johnson_whole_thesis.pdf en eng https://eprints.utas.edu.au/23452/1/Johnson_whole_thesis.pdf Johnson, R 2016 , 'Remote sensing of phytoplankton in the Southern Ocean', PhD thesis, University of Tasmania. cc_utas remote sensing ocean colour bio-optics chlorophyll calcite satellite phytoplankton southern ocean Thesis NonPeerReviewed 2016 ftunivtasmania 2020-05-30T07:38:00Z One of the greatest challenges for Southern Ocean and Antarctic research is the development of robust methods for assessing the current and future impacts of climate change, and for evaluating regional differences in the rate and direction of that change. The Southern Ocean has been changing rapidly for at least the last 30 years, including measurable changes to phytoplankton communities. Climate projections suggest that they will continue to change. It is predicted that there will be continued southward movement of oceanographic fronts, in- creased warming and freshening (increased precipitation) of the surface ocean, shallowing of the mixed layer (increased stratification) and increased carbon dioxide enrichment and ab- sorption of the upper ocean. In order to capture and monitor the response of phytoplankton across the Southern Ocean, an economical observing system with high resolution in time and space is needed. This thesis examines the ability of ocean colour remote sensing to meet this challenge by accurately assessing and monitoring climate change impacts on phytoplankton. The ever-increasing number of in situ samples from the Southern Ocean, which can be used to calibrate and validate remote sensing algorithms, have the potential to make ocean colour radiometry a robust method for assessing climate change impacts on the Southern Ocean ecosystem. We investigated both calcite and chlorophyll products, two measurements that are key for assessing the impact of climate change on phytoplankton. Chlorophyll is used as a proxy for biomass and calcite is used to identify calcifying plankton, and to detect changes in calcification rates and carbon sequestration impacted by ocean acidification. We found that current satellite algorithms underestimate chlorophyll by as much as 50% and overestimate calcite by up to 400% in the Southern Ocean. Much of the in situ data used in this thesis were collected by ships transiting to and from the Antarctic on station re-supply missions that collected surface samples while the ship was sailing. This methodology naturally raised the question of how well does surface sampling capture the variability with depth in the euphotic zone. We determined that surface sampling of chlorophyll, either from ships or satellites, is an adequate representation of the ecologically important euphotic zone in the well-mixed regions of the Southern Ocean. This thesis concludes that customised ocean colour algorithms can be a robust method for assessing Southern Ocean phytoplankton and presents several methods and improved satellite products for doing so. Thesis Antarc* Antarctic Ocean acidification Southern Ocean University of Tasmania: UTas ePrints Antarctic Southern Ocean The Antarctic |
institution |
Open Polar |
collection |
University of Tasmania: UTas ePrints |
op_collection_id |
ftunivtasmania |
language |
English |
topic |
remote sensing ocean colour bio-optics chlorophyll calcite satellite phytoplankton southern ocean |
spellingShingle |
remote sensing ocean colour bio-optics chlorophyll calcite satellite phytoplankton southern ocean Johnson, R Remote sensing of phytoplankton in the Southern Ocean |
topic_facet |
remote sensing ocean colour bio-optics chlorophyll calcite satellite phytoplankton southern ocean |
description |
One of the greatest challenges for Southern Ocean and Antarctic research is the development of robust methods for assessing the current and future impacts of climate change, and for evaluating regional differences in the rate and direction of that change. The Southern Ocean has been changing rapidly for at least the last 30 years, including measurable changes to phytoplankton communities. Climate projections suggest that they will continue to change. It is predicted that there will be continued southward movement of oceanographic fronts, in- creased warming and freshening (increased precipitation) of the surface ocean, shallowing of the mixed layer (increased stratification) and increased carbon dioxide enrichment and ab- sorption of the upper ocean. In order to capture and monitor the response of phytoplankton across the Southern Ocean, an economical observing system with high resolution in time and space is needed. This thesis examines the ability of ocean colour remote sensing to meet this challenge by accurately assessing and monitoring climate change impacts on phytoplankton. The ever-increasing number of in situ samples from the Southern Ocean, which can be used to calibrate and validate remote sensing algorithms, have the potential to make ocean colour radiometry a robust method for assessing climate change impacts on the Southern Ocean ecosystem. We investigated both calcite and chlorophyll products, two measurements that are key for assessing the impact of climate change on phytoplankton. Chlorophyll is used as a proxy for biomass and calcite is used to identify calcifying plankton, and to detect changes in calcification rates and carbon sequestration impacted by ocean acidification. We found that current satellite algorithms underestimate chlorophyll by as much as 50% and overestimate calcite by up to 400% in the Southern Ocean. Much of the in situ data used in this thesis were collected by ships transiting to and from the Antarctic on station re-supply missions that collected surface samples while the ship was sailing. This methodology naturally raised the question of how well does surface sampling capture the variability with depth in the euphotic zone. We determined that surface sampling of chlorophyll, either from ships or satellites, is an adequate representation of the ecologically important euphotic zone in the well-mixed regions of the Southern Ocean. This thesis concludes that customised ocean colour algorithms can be a robust method for assessing Southern Ocean phytoplankton and presents several methods and improved satellite products for doing so. |
format |
Thesis |
author |
Johnson, R |
author_facet |
Johnson, R |
author_sort |
Johnson, R |
title |
Remote sensing of phytoplankton in the Southern Ocean |
title_short |
Remote sensing of phytoplankton in the Southern Ocean |
title_full |
Remote sensing of phytoplankton in the Southern Ocean |
title_fullStr |
Remote sensing of phytoplankton in the Southern Ocean |
title_full_unstemmed |
Remote sensing of phytoplankton in the Southern Ocean |
title_sort |
remote sensing of phytoplankton in the southern ocean |
publishDate |
2016 |
url |
https://eprints.utas.edu.au/23452/ https://eprints.utas.edu.au/23452/1/Johnson_whole_thesis.pdf |
geographic |
Antarctic Southern Ocean The Antarctic |
geographic_facet |
Antarctic Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Ocean acidification Southern Ocean |
genre_facet |
Antarc* Antarctic Ocean acidification Southern Ocean |
op_relation |
https://eprints.utas.edu.au/23452/1/Johnson_whole_thesis.pdf Johnson, R 2016 , 'Remote sensing of phytoplankton in the Southern Ocean', PhD thesis, University of Tasmania. |
op_rights |
cc_utas |
_version_ |
1766276122372210688 |