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Author
Stukel, M.R. ; Kelly, T.B.
Title
The carbon: (234) Thorium ratios of sinking particles in the California current ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model
Type
$loc['typeJournal Article']
Year
2019
Publication
Marine Chemistry
Abbreviated Journal
Marine Chemistry
Volume
212
Issue
Pages
1-15
Keywords
POC concentration ; sinking particles. ; depth and relationship with water ; phytoplankton
Abstract
Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon: thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.
Address
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Publisher
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Language
Summary Language
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Series Editor
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Series Issue
Edition
ISSN
0304-4203
ISBN
Medium
Area
Expedition
Conference
Funding
Approved
$loc['no']
Call Number
COAPS @ user @
Serial
1002
Permanent link to this record
Author
Stukel, M.R. ; Kelly, T.B.
Title
The carbon: 234Thorium ratios of sinking particles in the California current ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model
Type
$loc['typeJournal Article']
Year
Publication
Marine Chemistry
Abbreviated Journal
Marine Chemistry
Volume
Issue
Pages
Keywords
Abstract
Address
Corporate Author
Thesis
Publisher
Place of Publication
Editor
Language
Summary Language
Original Title
Series Editor
Series Title
Abbreviated Series Title
Series Volume
Series Issue
Edition
ISSN
0304-4203
ISBN
Medium
Area
Expedition
Conference
Funding
Approved
$loc['no']
Call Number
COAPS @ user @
Serial
1037
Permanent link to this record
Author
Stukel, M.R. ; Ohman, M.D. ; Kelly, T.B. ; Biard, T.
Title
The Roles of Suspension-Feeding and Flux-Feeding Zooplankton as Gatekeepers of Particle Flux Into the Mesopelagic Ocean in the Northeast Pacific
Type
$loc['typeJournal Article']
Year
2019
Publication
Frontiers in Marine Science
Abbreviated Journal
Front. Mar. Sci.
Volume
6
Issue
Pages
Keywords
biological pump ; carbon export ; remineralization length scale ; mesozooplankton ecology ; pteropods ; marine biogeochemistry ; sinking particles ; marine snow
Abstract
Zooplankton are important consumers of sinking particles in the ocean's twilight zone. However, the impact of different taxa depends on their feeding mode. In contrast to typical suspension-feeding zooplankton, flux-feeding taxa preferentially consume rapidly sinking particles that would otherwise penetrate into the deep ocean. To quantify the potential impact of two flux-feeding zooplankton taxa [Aulosphaeridae (Rhizaria), and Limacina helicina (euthecosome pteropod)] and the total suspension-feeding zooplankton community, we measured depth-stratified abundances of these organisms during six cruises in the California Current Ecosystem. Using allometric-scaling relationships, we computed the percentage of carbon flux intercepted by flux feeders and suspension feeders. These estimates were compared to direct measurements of carbon flux attenuation (CFA) made using drifting sediment traps and U-238-Th-234 disequilibrium. We found that CFA in the shallow twilight zone typically ranged from 500 to 1000 m mol organic C flux remineralized per 10-m vertical depth bin. This equated to approximately 6-10% of carbon flux remineralized/10 m. The two flux-feeding taxa considered in this study could account for a substantial proportion of this flux near the base of the euphotic zone. The mean flux attenuation attributable to Aulosphaeridae was 0.69%/10 m (median = 0.21%/10 m, interquartile range = 0.04-0.81%) at their depth of maximum abundance (similar to 100 m), which would equate to similar to 10% of total flux attenuation in this depth range. The maximum flux attenuation attributable to Aulosphaeridae reached 4.2%/10 m when these protists were most abundant. L. helicina, meanwhile, could intercept 0.45-1.6% of carbon flux/10 m, which was slightly greater (on average) than the Aulosphaeridae. In contrast, suspension-feeding zooplankton in the mesopelagic (including copepods, euphausiids, appendicularians, and ostracods) had combined clearance rates of 2-81 L m(-3) day(-1) (mean of 19.6 L m(-3) day(-1)). This implies a substantial impact on slowly sinking particles, but a negligible impact on the presumably rapidly sinking fecal pellets that comprised the majority of the material collected in sediment traps. Our results highlight the need for a greater research focus on the many taxa that potentially act as flux feeders in the oceanic twilight zone.
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Series Editor
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Edition
ISSN
2296-7745
ISBN
Medium
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Approved
$loc['no']
Call Number
COAPS @ user @
Serial
1066
Permanent link to this record
Author
Subrahmanyam, B, J.J. O'Brien, V. Manghanani, L. Xie, and J.M. Morrison
Title
Estimation of Heat Transports in the Indian Ocean uisng Altimetry and MICOMi
Type
$loc['typeConference Article']
Year
2003
Publication
WMO WORLD Climate Research Programme, CAS/JSC Working Group on Numerical Experimentation, Research Activities in Atmospheric and Oceanic Modelling
Abbreviated Journal
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Issue
Pages
Keywords
Abstract
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Series Editor
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Series Issue
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ISSN
ISBN
Medium
Area
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Approved
$loc['no']
Call Number
COAPS @ mfield @
Serial
866
Permanent link to this record
Author
Subrahmanyam, B. ; Babu, V.R. ; Murty, V.S.N. ; Rao, L.V.G.
Title
Surface circulation off Somalia and western equatorial Indian Ocean during summer monsoon of 1988 from Geosat altimeter data
Type
$loc['typeJournal Article']
Year
1996
Publication
International Journal of Remote Sensing
Abbreviated Journal
International Journal of Remote Sensing
Volume
17
Issue
4
Pages
761-770
Keywords
Abstract
Address
Corporate Author
Thesis
Publisher
Place of Publication
Editor
Language
Summary Language
Original Title
Series Editor
Series Title
Abbreviated Series Title
Series Volume
Series Issue
Edition
ISSN
0143-1161
ISBN
Medium
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$loc['no']
Call Number
COAPS @ mfield @
Serial
713
Permanent link to this record
Author
Subrahmanyam, B. ; Legler, D. M. ; Barnier, B. ; de Miranda, A. P. ; O'Brien, J. J.
Title
Sensitivity of the North Atlantic circulation to momentum forcing using SPEM
Type
$loc['typeConference Article']
Year
2000
Publication
IGARSS 2000, Honolulu, Hawaii, USA
Abbreviated Journal
Volume
Issue
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ISBN
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$loc['no']
Call Number
COAPS @ mfield @
Serial
797
Permanent link to this record
Author
Subrahmanyam, B. ; Legler, D. M. ; Barnier, B. ; O'Brien, J. J. ; de Miranda, A. P. ; Bourassa, M.
Title
Sensitivity of an ocean general circulation model to changes in surface momentum forcing
Type
$loc['typeConference Article']
Year
2001
Publication
Abbreviated Journal
Volume
Issue
Pages
Keywords
Abstract
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Editor
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Summary Language
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Series Editor
Series Title
WMO WORLD Climate Research Programme, CAS/JSC Working Group on Numerical Experimentation, Research Activities in Atmospheric and Oceanic Modeling
Abbreviated Series Title
Series Volume
Series Issue
Edition
ISSN
ISBN
Medium
Area
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Conference
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$loc['no']
Call Number
COAPS @ mfield @
Serial
822
Permanent link to this record
Author
Subrahmanyam, B. ; Legler, D. M. ; O'Brien, J. J.
Title
Response of the North Atlantic circulation with surface momentum forcing using SPEM Model
Type
$loc['typeReport']
Year
2000
Publication
Abbreviated Journal
Volume
Issue
Pages
9.13-9.14
Keywords
Abstract
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Thesis
Publisher
Place of Publication
Editor
Ritchie, H.
Language
Summary Language
Original Title
Series Editor
Series Title
WMO World Climate Research Programme, CAS/JSC Working Group on Numerical Experimentation, Research Activities in Atmospheric and Oceanic Modeling, Report No. 30 (WMO/TD-No.987)
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$loc['no']
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COAPS @ mfield @
Serial
801
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Author
Subrahmanyam, B. ; Legler, D. M. ; O'Brien, J. J.
Title
), Indian Ocean Circulation using TOPEX/POSEIDION Altimetry and Model Simulations
Type
$loc['typeReport']
Year
1999
Publication
Abbreviated Journal
Volume
28
Issue
Pages
Keywords
Abstract
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Corporate Author
Thesis
Publisher
Place of Publication
Editor
Ritchie, H.
Language
Summary Language
Original Title
Series Editor
Series Title
Research activities in Atmospheric and Oceanic Modeling
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ISBN
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$loc['no']
Call Number
COAPS @ mfield @
Serial
776
Permanent link to this record
Author
Subrahmanyam, B. ; Manghanai, V. ; O'Brien, J. J. ; Morrison, J. M. ; Xie, L.
Title
A study of the Indian Ocean Dipole Mode Dynamics using satellite observations and MICOM simulations
Type
$loc['typeConference Article']
Year
2001
Publication
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Volume
Issue
Pages
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Abstract
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Place of Publication
San Diego, California, USA
Editor
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Series Issue
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ISBN
Medium
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Approved
$loc['no']
Call Number
COAPS @ mfield @
Serial
823
Permanent link to this record