The SOLAS air-sea gas exchange experiment (SAGE) 2004
The SOLAS air-sea gas exchange experiment (SAGE) was a multiple-objective study investigating gas-transfer processes and the influence of iron fertilisation on biologically driven gas exchange in high-nitrate low-silicic acid low-chlorophyll (HNLSiLC) Sub-Antarctic waters characteristic of the expan...
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Format: | Article in Journal/Newspaper |
Language: | unknown |
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Pergamon-Elsevier Ltd
2015
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Online Access: | http://hdl.handle.net/1885/51834 |
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ftanucanberra:oai:digitalcollections.anu.edu.au:1885/51834 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
Australian National University: ANU Digital Collections |
op_collection_id |
ftanucanberra |
language |
unknown |
description |
The SOLAS air-sea gas exchange experiment (SAGE) was a multiple-objective study investigating gas-transfer processes and the influence of iron fertilisation on biologically driven gas exchange in high-nitrate low-silicic acid low-chlorophyll (HNLSiLC) Sub-Antarctic waters characteristic of the expansive subpolar zone of the southern oceans. This paper provides a general introduction and summary of the main experimental findings. The release site was selected from a pre-voyage desktop study of environmental parameters to be in the south-west Bounty Trough (46.5°S 172.5°E) to the south-east of New Zealand and the experiment was conducted between mid-March and mid-April 2004. In common with other mesoscale iron addition experiments (FeAX's), SAGE was designed as a Lagrangian study, quantifying key biological and physical drivers influencing the air-sea gas exchange processes of CO2, DMS and other biogenic gases associated with an iron-induced phytoplankton bloom. A dual tracer SF6/3He release enabled quantification of both the lateral evolution of a labelled volume (patch) of ocean and the air-sea tracer exchange at tenths of kilometer scale, in conjunction with the iron fertilisation. Estimates from the dual-tracer experiment found a quadratic dependency of the gas exchange coefficient on windspeed that is widely applicable and describe air-sea gas exchange in strong wind regimes. Within the patch, local and micrometeorological gas exchange process studies (100m scale) and physical variables such as near-surface turbulence, temperature microstructure at the interface, wave properties and windspeed were quantified to further assist the development of gas exchange models for high-wind environments. There was a significant increase in the photosynthetic competence (Fv/Fm) of resident phytoplankton within the first day following iron addition, but in contrast to other FeAX's, rates of net primary production and column-integrated chlorophyll a concentrations had only doubled relative to the unfertilised surrounding waters by the end of the experiment. After 15 days and four iron additions totalling 1.1ton Fe2+, this was a very modest response compared to other mesoscale iron enrichment experiments. An investigation of the factors limiting bloom development considered co-limitation by light and other nutrients, the phytoplankton seed-stock and grazing regulation. Whilst incident light levels and the initial Si:N ratio were the lowest recorded in all FeAXs to date, there was only a small seed-stock of diatoms (less than 1% of biomass) and the main response to iron addition was by the picophytoplankton. A high rate of dilution of the fertilised patch relative to phytoplankton growth rate, the greater than expected depth of the surface mixed layer and microzooplankton grazing were all considered as factors that prevented significant biomass accumulation. In line with the limited response, the enhanced biological draw-down of pCO2 was small and masked by a general increase in pCO2 due to mixing with higher pCO2 waters. The DMS precursor DMSP was kept in check through grazing activity and in contrast to most FeAX's dissolved dimethylsulfide (DMS) concentration declined through the experiment. SAGE is an important low-end member in the range of responses to iron addition in FeAX's. In the context of iron fertilisation as a geoengineering tool for atmospheric CO2 removal, SAGE has clearly demonstrated that a significant proportion of the low iron ocean may not produce a phytoplankton bloom in response to iron addition. |
format |
Article in Journal/Newspaper |
author |
Harvey, Michael Law, Cliff S Smith, Murray J. Hall, Julie A Abraham, E R Stevens, C L Hadfield, Mark G Ho, David T. Ward, Brian Archer, Stephen D. Cainey, Jill M Currie, Kim Devries, Dawn Ellwood, Michael Hill, Peter Jones, Graham Barry Katz, D. Kuparinen, J. Macaskill, Burns Main, William Marriner, A McGregor, John McNeil, Craig Minnett, Peter J. Nodder, Scott D Peloquin, J. Pickmere, Stuart Pinkerton, Matthew H Safi, Karl A Thompson, Rona Walkington, Matthew Wright, Simon Ziolkowski, Lori |
spellingShingle |
Harvey, Michael Law, Cliff S Smith, Murray J. Hall, Julie A Abraham, E R Stevens, C L Hadfield, Mark G Ho, David T. Ward, Brian Archer, Stephen D. Cainey, Jill M Currie, Kim Devries, Dawn Ellwood, Michael Hill, Peter Jones, Graham Barry Katz, D. Kuparinen, J. Macaskill, Burns Main, William Marriner, A McGregor, John McNeil, Craig Minnett, Peter J. Nodder, Scott D Peloquin, J. Pickmere, Stuart Pinkerton, Matthew H Safi, Karl A Thompson, Rona Walkington, Matthew Wright, Simon Ziolkowski, Lori The SOLAS air-sea gas exchange experiment (SAGE) 2004 |
author_facet |
Harvey, Michael Law, Cliff S Smith, Murray J. Hall, Julie A Abraham, E R Stevens, C L Hadfield, Mark G Ho, David T. Ward, Brian Archer, Stephen D. Cainey, Jill M Currie, Kim Devries, Dawn Ellwood, Michael Hill, Peter Jones, Graham Barry Katz, D. Kuparinen, J. Macaskill, Burns Main, William Marriner, A McGregor, John McNeil, Craig Minnett, Peter J. Nodder, Scott D Peloquin, J. Pickmere, Stuart Pinkerton, Matthew H Safi, Karl A Thompson, Rona Walkington, Matthew Wright, Simon Ziolkowski, Lori |
author_sort |
Harvey, Michael |
title |
The SOLAS air-sea gas exchange experiment (SAGE) 2004 |
title_short |
The SOLAS air-sea gas exchange experiment (SAGE) 2004 |
title_full |
The SOLAS air-sea gas exchange experiment (SAGE) 2004 |
title_fullStr |
The SOLAS air-sea gas exchange experiment (SAGE) 2004 |
title_full_unstemmed |
The SOLAS air-sea gas exchange experiment (SAGE) 2004 |
title_sort |
solas air-sea gas exchange experiment (sage) 2004 |
publisher |
Pergamon-Elsevier Ltd |
publishDate |
2015 |
url |
http://hdl.handle.net/1885/51834 |
long_lat |
ENVELOPE(178.070,178.070,-45.499,-45.499) |
geographic |
Antarctic New Zealand Bounty Trough |
geographic_facet |
Antarctic New Zealand Bounty Trough |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
Deep-Sea Research Part II: Tropical studies in oceanography |
op_relation |
0967-0645 http://hdl.handle.net/1885/51834 |
_version_ |
1766265311003148288 |
spelling |
ftanucanberra:oai:digitalcollections.anu.edu.au:1885/51834 2023-05-15T13:57:36+02:00 The SOLAS air-sea gas exchange experiment (SAGE) 2004 Harvey, Michael Law, Cliff S Smith, Murray J. Hall, Julie A Abraham, E R Stevens, C L Hadfield, Mark G Ho, David T. Ward, Brian Archer, Stephen D. Cainey, Jill M Currie, Kim Devries, Dawn Ellwood, Michael Hill, Peter Jones, Graham Barry Katz, D. Kuparinen, J. Macaskill, Burns Main, William Marriner, A McGregor, John McNeil, Craig Minnett, Peter J. Nodder, Scott D Peloquin, J. Pickmere, Stuart Pinkerton, Matthew H Safi, Karl A Thompson, Rona Walkington, Matthew Wright, Simon Ziolkowski, Lori 2015-12-10T22:20:14Z http://hdl.handle.net/1885/51834 unknown Pergamon-Elsevier Ltd 0967-0645 http://hdl.handle.net/1885/51834 Deep-Sea Research Part II: Tropical studies in oceanography Journal article 2015 ftanucanberra 2015-12-28T23:27:38Z The SOLAS air-sea gas exchange experiment (SAGE) was a multiple-objective study investigating gas-transfer processes and the influence of iron fertilisation on biologically driven gas exchange in high-nitrate low-silicic acid low-chlorophyll (HNLSiLC) Sub-Antarctic waters characteristic of the expansive subpolar zone of the southern oceans. This paper provides a general introduction and summary of the main experimental findings. The release site was selected from a pre-voyage desktop study of environmental parameters to be in the south-west Bounty Trough (46.5°S 172.5°E) to the south-east of New Zealand and the experiment was conducted between mid-March and mid-April 2004. In common with other mesoscale iron addition experiments (FeAX's), SAGE was designed as a Lagrangian study, quantifying key biological and physical drivers influencing the air-sea gas exchange processes of CO2, DMS and other biogenic gases associated with an iron-induced phytoplankton bloom. A dual tracer SF6/3He release enabled quantification of both the lateral evolution of a labelled volume (patch) of ocean and the air-sea tracer exchange at tenths of kilometer scale, in conjunction with the iron fertilisation. Estimates from the dual-tracer experiment found a quadratic dependency of the gas exchange coefficient on windspeed that is widely applicable and describe air-sea gas exchange in strong wind regimes. Within the patch, local and micrometeorological gas exchange process studies (100m scale) and physical variables such as near-surface turbulence, temperature microstructure at the interface, wave properties and windspeed were quantified to further assist the development of gas exchange models for high-wind environments. There was a significant increase in the photosynthetic competence (Fv/Fm) of resident phytoplankton within the first day following iron addition, but in contrast to other FeAX's, rates of net primary production and column-integrated chlorophyll a concentrations had only doubled relative to the unfertilised surrounding waters by the end of the experiment. After 15 days and four iron additions totalling 1.1ton Fe2+, this was a very modest response compared to other mesoscale iron enrichment experiments. An investigation of the factors limiting bloom development considered co-limitation by light and other nutrients, the phytoplankton seed-stock and grazing regulation. Whilst incident light levels and the initial Si:N ratio were the lowest recorded in all FeAXs to date, there was only a small seed-stock of diatoms (less than 1% of biomass) and the main response to iron addition was by the picophytoplankton. A high rate of dilution of the fertilised patch relative to phytoplankton growth rate, the greater than expected depth of the surface mixed layer and microzooplankton grazing were all considered as factors that prevented significant biomass accumulation. In line with the limited response, the enhanced biological draw-down of pCO2 was small and masked by a general increase in pCO2 due to mixing with higher pCO2 waters. The DMS precursor DMSP was kept in check through grazing activity and in contrast to most FeAX's dissolved dimethylsulfide (DMS) concentration declined through the experiment. SAGE is an important low-end member in the range of responses to iron addition in FeAX's. In the context of iron fertilisation as a geoengineering tool for atmospheric CO2 removal, SAGE has clearly demonstrated that a significant proportion of the low iron ocean may not produce a phytoplankton bloom in response to iron addition. Article in Journal/Newspaper Antarc* Antarctic Australian National University: ANU Digital Collections Antarctic New Zealand Bounty Trough ENVELOPE(178.070,178.070,-45.499,-45.499) |