The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle
The Southern Ocean plays a critical role in the air-sea CO2 balance through biological and physical mechanisms. Vertical supply of deep waters returns nutrients and CO2 to the surface and stimulates phytoplankton growth. Photosynthesis in the Southern Ocean is limited by iron and only a fraction of...
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ftunivrhodeislan:oai:digitalcommons.uri.edu:gsofacpubs-3177 2024-02-11T09:58:51+01:00 The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle Robinson, Rebecca S. Brzezinski, Mark A. Beucher, Charlotte P. Horn, Matthew G.S. Bedsole, Patrick 2014-12-01T08:00:00Z https://digitalcommons.uri.edu/gsofacpubs/2208 https://doi.org/10.1002/2014PA002686 unknown DigitalCommons@URI https://digitalcommons.uri.edu/gsofacpubs/2208 doi:10.1002/2014PA002686 https://doi.org/10.1002/2014PA002686 Graduate School of Oceanography Faculty Publications Fe fertilization nutrient utilization overturning Southern Ocean text 2014 ftunivrhodeislan https://doi.org/10.1002/2014PA002686 2024-01-15T19:10:03Z The Southern Ocean plays a critical role in the air-sea CO2 balance through biological and physical mechanisms. Vertical supply of deep waters returns nutrients and CO2 to the surface and stimulates phytoplankton growth. Photosynthesis in the Southern Ocean is limited by iron and only a fraction of the carbon and nutrients that return to the surface are consumed for potential sequestration in the deep sea. Here we present the most spatially extensive data set of silicon and nitrogen isotope measurements from diatom frustules to date to examine the controls on nutrient drawdown during the last glacial period and across the glacial termination in both the Antarctic and Subantarctic zones. The new data confirm existing views that differing silicon and nitrate consumption patterns in the Antarctic zone are likely the result, at least in part, of iron addition during the last glacial maximum (LGM). However, earlier in the glacial, a more coordinated response in the two proxy records, with both reflecting enhanced consumption during episodes of increased iron accumulation and export production, implies a different system response than observed for the LGM. A collapse of the expected equatorward gradient in silicon isotope values and contraction of the nitrogen isotope gradient during the deglaciation suggests that nutrient supply increased not only in the Antarctic Zone, but also in the Subantarctic, perhaps due to enhanced deep mixing locally. Enhanced deep water ventilation across the Southern Ocean likely increased the nutrient content of mode waters during the deglaciation. Key Points Decoupling of Si and N consumption is related to iron addition during the LGM Subantarctic data indicates persistent local vertical mixing of new nutrients Enhanced Si and N consumption occurs during iron peaks prior to the LGM Text Antarc* Antarctic Southern Ocean University of Rhode Island: DigitalCommons@URI Antarctic Southern Ocean The Antarctic Paleoceanography 29 12 1179 1195 |
institution |
Open Polar |
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University of Rhode Island: DigitalCommons@URI |
op_collection_id |
ftunivrhodeislan |
language |
unknown |
topic |
Fe fertilization nutrient utilization overturning Southern Ocean |
spellingShingle |
Fe fertilization nutrient utilization overturning Southern Ocean Robinson, Rebecca S. Brzezinski, Mark A. Beucher, Charlotte P. Horn, Matthew G.S. Bedsole, Patrick The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle |
topic_facet |
Fe fertilization nutrient utilization overturning Southern Ocean |
description |
The Southern Ocean plays a critical role in the air-sea CO2 balance through biological and physical mechanisms. Vertical supply of deep waters returns nutrients and CO2 to the surface and stimulates phytoplankton growth. Photosynthesis in the Southern Ocean is limited by iron and only a fraction of the carbon and nutrients that return to the surface are consumed for potential sequestration in the deep sea. Here we present the most spatially extensive data set of silicon and nitrogen isotope measurements from diatom frustules to date to examine the controls on nutrient drawdown during the last glacial period and across the glacial termination in both the Antarctic and Subantarctic zones. The new data confirm existing views that differing silicon and nitrate consumption patterns in the Antarctic zone are likely the result, at least in part, of iron addition during the last glacial maximum (LGM). However, earlier in the glacial, a more coordinated response in the two proxy records, with both reflecting enhanced consumption during episodes of increased iron accumulation and export production, implies a different system response than observed for the LGM. A collapse of the expected equatorward gradient in silicon isotope values and contraction of the nitrogen isotope gradient during the deglaciation suggests that nutrient supply increased not only in the Antarctic Zone, but also in the Subantarctic, perhaps due to enhanced deep mixing locally. Enhanced deep water ventilation across the Southern Ocean likely increased the nutrient content of mode waters during the deglaciation. Key Points Decoupling of Si and N consumption is related to iron addition during the LGM Subantarctic data indicates persistent local vertical mixing of new nutrients Enhanced Si and N consumption occurs during iron peaks prior to the LGM |
format |
Text |
author |
Robinson, Rebecca S. Brzezinski, Mark A. Beucher, Charlotte P. Horn, Matthew G.S. Bedsole, Patrick |
author_facet |
Robinson, Rebecca S. Brzezinski, Mark A. Beucher, Charlotte P. Horn, Matthew G.S. Bedsole, Patrick |
author_sort |
Robinson, Rebecca S. |
title |
The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle |
title_short |
The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle |
title_full |
The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle |
title_fullStr |
The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle |
title_full_unstemmed |
The changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the Southern Ocean over the last glacial cycle |
title_sort |
changing roles of iron and vertical mixing in regulating nitrogen and silicon cycling in the southern ocean over the last glacial cycle |
publisher |
DigitalCommons@URI |
publishDate |
2014 |
url |
https://digitalcommons.uri.edu/gsofacpubs/2208 https://doi.org/10.1002/2014PA002686 |
geographic |
Antarctic Southern Ocean The Antarctic |
geographic_facet |
Antarctic Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Southern Ocean |
genre_facet |
Antarc* Antarctic Southern Ocean |
op_source |
Graduate School of Oceanography Faculty Publications |
op_relation |
https://digitalcommons.uri.edu/gsofacpubs/2208 doi:10.1002/2014PA002686 https://doi.org/10.1002/2014PA002686 |
op_doi |
https://doi.org/10.1002/2014PA002686 |
container_title |
Paleoceanography |
container_volume |
29 |
container_issue |
12 |
container_start_page |
1179 |
op_container_end_page |
1195 |
_version_ |
1790594656779632640 |