Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage
A combination of in situ and satellite data is used to examine the effects of horizontal advection, diapycnal mixing, and mixed-layer entrainment on natural iron fertilization in a region near the Shackleton Fracture Zone in southern Drake Passage. Results from Optimal Multiparameter analysis of tem...
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ftcdlib:oai:escholarship.org/ark:/13030/qt2dk269wh 2023-05-15T14:02:05+02:00 Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage Frants, Marina 2011-01-01 application/pdf https://escholarship.org/uc/item/2dk269wh unknown eScholarship, University of California qt2dk269wh https://escholarship.org/uc/item/2dk269wh public UCSD Dissertations Academic Oceanography. (Discipline) etd 2011 ftcdlib 2020-06-06T07:56:45Z A combination of in situ and satellite data is used to examine the effects of horizontal advection, diapycnal mixing, and mixed-layer entrainment on natural iron fertilization in a region near the Shackleton Fracture Zone in southern Drake Passage. Results from Optimal Multiparameter analysis of temperature, salinity, oxygen and nutrient data are consistent with a scenario in which iron-rich shelf waters from the South Shetland Islands and the Antarctic peninsula are advected northward on the eastern side of the Shackleton Transverse Ridge (STR), where they interact with the low-iron waters of the Antarctic Circumpolar Current (ACC) in the Ona Basin. However, comparisons between sea surface height and Chlorophyll-a (Chl-a) levels in the region for the years 1997-2010 indicate that this advection process is significantly correlated with biological productivity only during the months of November and December, while high Chl -a concentrations persist through March. Enhanced diapycnal mixing and mixed-layer entrainment are considered as alternative mechanisms for delivering iron into the Ona Basin mixed layer. While fine-scale mixing estimates lack the vertical resolution to fully resolve the small-scale density fluctuations in the low- stratification regime of the Southern Ocean, microstructure measurements indicate that diapycnal diffusivities in Drake Passage are on the order of 10⁻⁴ m² s⁻¹. Based on these diffusivities, estimates of iron flux from iron concentrations measured during the summer of 2004 and winter of 2006 suggest that diapycnal mixing alone can supply iron ito the mixed layer at a rate of approximately 96±9 nmol m⁻² day⁻¹ during the winter and approximately 64±2 nmol m⁻² day⁻¹ during the summer. In addition, the Ona Basin mixed layer deepens from January into April, allowing for iron to be steadily entrained from below. Simulation of these vertical processes with a simple one-dimensional model yields an estimated mixed- layer entrainment rate of 12±9 nmol m⁻² day⁻¹, while the combined effect of mixing and entrainment can supply 176±44ñmol m⁻² day⁻¹ into the top 30 m from January to April, which is sufficient to sustain the phytoplankton bloom that persists in the basin throughout the summer months Other/Unknown Material Antarc* Antarctic Antarctic Peninsula Drake Passage South Shetland Islands Southern Ocean University of California: eScholarship Antarctic Antarctic Peninsula Drake Passage Ona Basin ENVELOPE(-56.000,-56.000,-59.250,-59.250) Shackleton Shackleton Fracture Zone ENVELOPE(-60.000,-60.000,-60.000,-60.000) South Shetland Islands Southern Ocean The Antarctic |
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University of California: eScholarship |
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UCSD Dissertations Academic Oceanography. (Discipline) |
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UCSD Dissertations Academic Oceanography. (Discipline) Frants, Marina Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage |
topic_facet |
UCSD Dissertations Academic Oceanography. (Discipline) |
description |
A combination of in situ and satellite data is used to examine the effects of horizontal advection, diapycnal mixing, and mixed-layer entrainment on natural iron fertilization in a region near the Shackleton Fracture Zone in southern Drake Passage. Results from Optimal Multiparameter analysis of temperature, salinity, oxygen and nutrient data are consistent with a scenario in which iron-rich shelf waters from the South Shetland Islands and the Antarctic peninsula are advected northward on the eastern side of the Shackleton Transverse Ridge (STR), where they interact with the low-iron waters of the Antarctic Circumpolar Current (ACC) in the Ona Basin. However, comparisons between sea surface height and Chlorophyll-a (Chl-a) levels in the region for the years 1997-2010 indicate that this advection process is significantly correlated with biological productivity only during the months of November and December, while high Chl -a concentrations persist through March. Enhanced diapycnal mixing and mixed-layer entrainment are considered as alternative mechanisms for delivering iron into the Ona Basin mixed layer. While fine-scale mixing estimates lack the vertical resolution to fully resolve the small-scale density fluctuations in the low- stratification regime of the Southern Ocean, microstructure measurements indicate that diapycnal diffusivities in Drake Passage are on the order of 10⁻⁴ m² s⁻¹. Based on these diffusivities, estimates of iron flux from iron concentrations measured during the summer of 2004 and winter of 2006 suggest that diapycnal mixing alone can supply iron ito the mixed layer at a rate of approximately 96±9 nmol m⁻² day⁻¹ during the winter and approximately 64±2 nmol m⁻² day⁻¹ during the summer. In addition, the Ona Basin mixed layer deepens from January into April, allowing for iron to be steadily entrained from below. Simulation of these vertical processes with a simple one-dimensional model yields an estimated mixed- layer entrainment rate of 12±9 nmol m⁻² day⁻¹, while the combined effect of mixing and entrainment can supply 176±44ñmol m⁻² day⁻¹ into the top 30 m from January to April, which is sufficient to sustain the phytoplankton bloom that persists in the basin throughout the summer months |
format |
Other/Unknown Material |
author |
Frants, Marina |
author_facet |
Frants, Marina |
author_sort |
Frants, Marina |
title |
Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage |
title_short |
Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage |
title_full |
Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage |
title_fullStr |
Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage |
title_full_unstemmed |
Effects of horizontal advection and vertical mixing on natural iron fertilization in Southern Drake Passage |
title_sort |
effects of horizontal advection and vertical mixing on natural iron fertilization in southern drake passage |
publisher |
eScholarship, University of California |
publishDate |
2011 |
url |
https://escholarship.org/uc/item/2dk269wh |
long_lat |
ENVELOPE(-56.000,-56.000,-59.250,-59.250) ENVELOPE(-60.000,-60.000,-60.000,-60.000) |
geographic |
Antarctic Antarctic Peninsula Drake Passage Ona Basin Shackleton Shackleton Fracture Zone South Shetland Islands Southern Ocean The Antarctic |
geographic_facet |
Antarctic Antarctic Peninsula Drake Passage Ona Basin Shackleton Shackleton Fracture Zone South Shetland Islands Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Antarctic Peninsula Drake Passage South Shetland Islands Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctic Peninsula Drake Passage South Shetland Islands Southern Ocean |
op_relation |
qt2dk269wh https://escholarship.org/uc/item/2dk269wh |
op_rights |
public |
_version_ |
1766272165959696384 |