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  • 1
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    An inverse relationship between production and export efficiency in the Southern Ocean (2013)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 1557–1561, doi:10.1002/grl.50219.
    Description: In the past two decades, a number of studies have been carried out in the Southern Ocean to look at export production using drifting sediment traps and thorium-234 based measurements, which allows us to reexamine the validity of using the existing relationships between production, export efficiency, and temperature to derive satellite-based carbon export estimates in this region. Comparisons of in situ export rates with modeled rates indicate a two to fourfold overestimation of export production by existing models. Comprehensive analysis of in situ data indicates two major reasons for this difference: (i) in situ data indicate a trend of decreasing export efficiency with increasing production which is contrary to existing export models and (ii) the export efficiencies appear to be less sensitive to temperature in this region compared to the global estimates used in the existing models. The most important implication of these observations is that the simplest models of export, which predict increase in carbon flux with increasing surface productivity, may require additional parameters, different weighing of existing parameters, or separate algorithms for different oceanic regimes.
    Description: This work was supported by NASA award number NNX08AB48G.
    Description: 2013-10-23
    Keywords: Biological pump ; Southern Ocean ; Carbon export
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Th-234 sorption and export models in the water column : a review (2006)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 100 (2006): 234-249, doi:10.1016/j.marchem.2005.10.014.
    Description: Over the past few decades, the radioisotope pair of 238U/234Th has been widely and increasingly used to describe particle dynamics and particle export fluxes in a variety of aquatic systems. The present paper is one of five review articles dedicated to 234Th. It is focused on the models associated with 234Th whereas the companion papers (same issue) are focused on present and future methodologies and techniques (Rutgers van der Loeff et al.), C/234Th ratios (Buesseler et al.), 234Th speciation (Santschi et al.) and present and future applications of 234Th (Waples et al.). In this paper, we review current 234Th scavenging models and discuss the relative importance of the non steady state and physical terms associated with the most commonly used model to estimate 234Th flux. Based on this discussion we recommend that for future work the use of models should be accompanied by a discussion of the effect that model and data uncertainty have on the model results. We also suggest that future field work incorporate repeat occupations of sample sites on time scales of 1-4 weeks in order to evaluate steady state versus non steady state estimates of 234Th export, especially during high flux events (〉 ca. 800 dpm m-2 d-1). Finally, knowledge of the physical oceanography of the study area is essential, particularly in ocean margins and in areas of established upwelling (e.g. Equatorial Pacific). These suggestions will greatly enhance the application of 234Th as a tracer of particle dynamics and flux in more complicated regimes.
    Description: This paper grew out of discussion held at the “Future Applications of 234Th in Aquatic Systems” workshop held at Woods Hole Oceanographic Institution in August, 2004 (see: http://www.geol.sc.edu/cbnelson/Thmeeting/). We are grateful to the US National Science Foundation Chemical Oceanography Program (OCE 0354757) for its support of the workshop. We thank the US National Science Foundation, the National Oceanic and Atmospheric Administration and the Belgian Science Policy for their support of many of the field and modeling efforts described in this paper.
    Keywords: Th-234 ; Model ; Scavenging ; Export ; Particle dynamics
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  • 3
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    Pump it Up workshop report (2017)
    Woods Hole Oceanographic Institution
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    Publication Date: 2022-05-25
    Description: Workshop held 28-29 September 2017, Cape Cod, MA
    Description: A two-day workshop was conducted to trade ideas and brainstorm about how to advance our understanding of the ocean’s biological pump. The goal was to identify the most important scientific issues that are unresolved but might be addressed with new and future technological advances.
    Keywords: Biological pump
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Effects of sinking velocities and microbial respiration rates on the attenuation of particulate carbon fluxes through the mesopelagic zone (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 29 (2015): 175–193, doi:10.1002/2014GB004935.
    Description: The attenuation of sinking particle fluxes through the mesopelagic zone is an important process that controls the sequestration of carbon and the distribution of other elements throughout the oceans. Case studies at two contrasting sites, the oligotrophic regime of the Bermuda Atlantic Time-series Study (BATS) and the mesotrophic waters of the west Antarctic Peninsula (WAP) sector of the Southern Ocean, revealed large differences in the rates of particle-attached microbial respiration and the average sinking velocities of marine particles, two parameters that affect the transfer efficiency of particulate matter from the base of the euphotic zone into the deep ocean. Rapid average sinking velocities of 270 ± 150 m d−1 were observed along the WAP, whereas the average velocity was 49 ± 25 m d−1 at the BATS site. Respiration rates of particle-attached microbes were measured using novel RESPIRE (REspiration of Sinking Particles In the subsuRface ocEan) sediment traps that first intercepts sinking particles then incubates them in situ. RESPIRE experiments yielded flux-normalized respiration rates of 0.4 ± 0.1 day−1 at BATS when excluding an outlier of 1.52 day−1, while these rates were undetectable along the WAP (0.01 ± 0.02 day−1). At BATS, flux-normalized respiration rates decreased exponentially with respect to depth below the euphotic zone with a 75% reduction between the 150 and 500 m depths. These findings provide quantitative and mechanistic insights into the processes that control the transfer efficiency of particle flux through the mesopelagic and its variability throughout the global oceans.
    Description: Funding was provided by the University of Alaska Fairbanks, Woods Hole Oceanographic Institution (WHOI) Rinehart Access to the Sea Program, the WHOI Coastal Oceans Institute, WHOI Academic Programs Office, and the National Science Foundation (NSF) for support of PAL (ANT-0823101), FOODBANCS, and WAPflux (ANT- 83886600) projects. A grant from the NSF Carbon and Water Program (06028416) supported the development of these methods.
    Description: 2015-08-25
    Keywords: Biological pump ; Marine particles ; Carbon flux ; Sinking velocity ; Microbial respiration
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Fukushima 137Cs at the base of planktonic food webs off Japan (2016)
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 106 (2015): 9-16, doi:10.1016/j.dsr.2015.09.006.
    Description: The potential bioaccumulation of 137Cs in marine food webs off Japan became a concern following the release of radioactive contaminants from the damaged Fukushima nuclear power plant into the coastal ocean. Previous studies suggest that 137Cs activities increase with trophic level in pelagic food webs, however, the bioaccumulation of 137Cs from seawater to primary producers, to zooplankton has not been evaluated in the field. Since phytoplankton are frequently the largest component of SPM (suspended particulate matter) we used SPM concentrations and particle-associated 137Cs to understand bioaccumulation of 137Cs in through trophic pathways in the field. We determined particle-associated 137Cs for samples collected at 20 m depth from six stations off Japan three months after the initial release from the Fukushima nuclear power plant. At 20 m SPM ranged from 0.65 to 1.60 mg L-1 and rapidly declined with depth. The ratios of particulate organic carbon to chlorophyll a suggested that phytoplankton comprised much of the SPM in these samples. 137Cs activities on particles accounted for on average 0.04% of the total 137Cs in seawater samples, and measured concentration factors of 137Cs on small suspended particles were comparatively low (~102). However, when 137Cs in crustacean zooplankton was derived based only on modeling dietary 137Cs uptake, we found predicted and measured 137Cs concentrations in good agreement. We therefore postulate the possibility that the dietary route of 137Cs bioaccumulation (i.e., phytoplankton ingestion) could be largely responsible for the measured levels in the copepod-dominated (%) zooplankton assemblages in Japanese coastal waters. Finally, our data did not support the notion that zooplankton grazing on phytoplankton results in a biomagnification of 137Cs.
    Description: This project was funded by the Gordon and Betty Moore Foundation through Grants GBMF3007 and GBMF 3423, and JSPS KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas Grant Number 24110005.
    Description: 2016-09-25
    Keywords: Fukushima ; Cesium ; Trophic transfer ; Phytoplankton ; Zooplankton
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Revisiting carbon flux through the ocean's twilight zone (2010)
    American Association for the Advancement of Science
    Details
    Publication Date: 2017-01-04
    Description: Citation only. Published in Science 316: 567-570, doi: 10.1126/science.1137959
    Description: Funding was obtained primarily through the NSF, Ocean Sciences Programs in Chemical and Biological Oceanography, with additional support from the U.S. Department of Energy, Office of Science, Biological and Environmental Research Program, and other national programs, including the Australian Cooperative Research Centre program and Australian Antarctic Division.
    Keywords: Carbon flux ; Carbon sequestration ; Biological pump
    Repository Name: Woods Hole Open Access Server
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  • 7
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    Concentrations, ratios, and sinking fluxes of major bioelements at Ocean Station Papa (2021)
    University of California Press
    Details
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Roca-Marti, M., Benitez-Nelson, C. R., Umhau, B. P., Wyatt, A. M., Clevenger, S. J., Pike, S., Horner, T. J., Estapa, M. L., Resplandy, L., & Buesseler, K. O. Concentrations, ratios, and sinking fluxes of major bioelements at Ocean Station Papa. Elementa: Science of the Anthropocene, 9(1), (2021): 00166, https://doi.org/10.1525/elementa.2020.00166.
    Description: Fluxes of major bioelements associated with sinking particles were quantified in late summer 2018 as part of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign near Ocean Station Papa in the subarctic northeast Pacific. The thorium-234 method was used in conjunction with size-fractionated (1–5, 5–51, and 〉51 μm) concentrations of particulate nitrogen (PN), total particulate phosphorus (TPP), biogenic silica (bSi), and particulate inorganic carbon (PIC) collected using large volume filtration via in situ pumps. We build upon recent work quantifying POC fluxes during EXPORTS. Similar remineralization length scales were observed for both POC and PN across all particle size classes from depths of 50–500 m. Unlike bSi and PIC, the soft tissue–associated POC, PN, and TPP fluxes strongly attenuated from 50 m to the base of the euphotic zone (approximately 120 m). Cruise-average thorium-234-derived fluxes (mmol m–2 d–1) at 120 m were 1.7 ± 0.6 for POC, 0.22 ± 0.07 for PN, 0.019 ± 0.007 for TPP, 0.69 ± 0.26 for bSi, and 0.055 ± 0.022 for PIC. These bioelement fluxes were similar to previous observations at this site, with the exception of PIC, which was 1 to 2 orders of magnitude lower. Transfer efficiencies within the upper twilight zone (flux 220 m/flux 120 m) were highest for PIC (84%) and bSi (79%), followed by POC (61%), PN (58%), and TPP (49%). These differences indicate preferential remineralization of TPP relative to POC or PN and larger losses of soft tissue relative to biominerals in sinking particles below the euphotic zone. Comprehensive characterization of the particulate bioelement fluxes obtained here will support future efforts linking phytoplankton community composition and food-web dynamics to the composition, magnitude, and attenuation of material that sinks to deeper waters.
    Description: The authors would like to acknowledge support from the National Aeronautics and Space Administration as part of the EXport Processes in the Ocean from RemoTe Sensing program awards 80NSSC17K0555 and 80NSSC17K0662. They also acknowledge the funding from the Woods Hole Oceanographic Institution’s Ocean Twilight Zone study for MRM and KOB, the National Science Foundation Graduate Research Fellowship Program for AMW, and the Ocean Frontier Institute for MRM.
    Keywords: Biological pump ; Bioelements ; Particulate fluxes ; Transfer efficiency ; Size-fractionated particles ; EXPORTS
    Repository Name: Woods Hole Open Access Server
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  • 8
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    Th-234 deficit and excess in the Southern Ocean during spring 2001 : particle export and remineralization (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 31 (2004): L12301, doi:10.1029/2004GL019744.
    Description: 234Th deficit and excess were examined in the upper 500 m of the Southern Ocean from Sub-Antarctic to Seasonal Ice Zones (Australian sector) during austral spring 2001. 234Th fluxes at 100 m indicate that particle export was low in the North (46.9–51.0°S), minimal in the Polar and Inter-Polar Frontal Zones and high in the South (≥61°S). These results are in tight agreement with new production estimates from the same cruise. Our data indicate that Polar and Inter-Polar Frontal Zones were not zones of intense export in the Australian sector at this time of year, in contrast with other sectors of the Southern Ocean. Also, we highlight the usefulness of 234Th excess below the mixed layer as a tool to study mesopelagic remineralization.
    Description: K.O. Buesseler was supported by WHOI Ocean Life Institute Fellowship and US National Science Foundation.
    Keywords: Th-234
    Repository Name: Woods Hole Open Access Server
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  • 9
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    A review of present techniques and methodological advances in analyzing Th-234 in aquatic systems (2006)
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    Publication Date: 2022-05-26
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 100 (2006): 190-212, doi:10.1016/j.marchem.2005.10.012.
    Description: The short-lived thorium isotope 234Th (half-life 24.1 days) has been used as a tracer for a variety of transport processes in aquatic systems. Its use as a tracer of oceanic export via sinking particles has stimulated a rapidly increasing number of studies that require analyses of 234Th in both marine and freshwater systems. The original 234Th method is labour intensive. Thus, there has been a quest for simpler techniques that require smaller sample volumes. Here, we review current methodologies in the collection and analysis of 234Th from the water column, discuss their individual strengths and weaknesses, and provide an outlook on possible further improvements and future challenges. Also included in this review are recommendations on calibration procedures and the production of standard reference materials as well as a flow chart designed to help researchers find the most appropriate 234Th analytical technique for a specific aquatic regime and known sampling constraints.
    Description: Individuals and science efforts discussed herein were supported by many national science programs, including the U.S. National Science Foundation and U.S. Department of Energy and the Ministerio de Educación y Ciencia of Spain. The Agency is grateful for the support provided to its Marine Environment Laboratory by the Government of the Principality of Monaco".
    Keywords: Th-234 ; Methodology ; Sampling ; Analytical techniques, ; Export
    Repository Name: Woods Hole Open Access Server
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  • 10
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    Global assessment of ocean carbon export by combining satellite observations and food-web models (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 28 (2014): 181-196, doi:10.1002/2013GB004743.
    Description: The export of organic carbon from the surface ocean by sinking particles is an important, yet highly uncertain, component of the global carbon cycle. Here we introduce a mechanistic assessment of the global ocean carbon export using satellite observations, including determinations of net primary production and the slope of the particle size spectrum, to drive a food-web model that estimates the production of sinking zooplankton feces and algal aggregates comprising the sinking particle flux at the base of the euphotic zone. The synthesis of observations and models reveals fundamentally different and ecologically consistent regional-scale patterns in export and export efficiency not found in previous global carbon export assessments. The model reproduces regional-scale particle export field observations and predicts a climatological mean global carbon export from the euphotic zone of ~6 Pg C yr−1. Global export estimates show small variation (typically 〈 10%) to factor of 2 changes in model parameter values. The model is also robust to the choices of the satellite data products used and enables interannual changes to be quantified. The present synthesis of observations and models provides a path for quantifying the ocean's biological pump.
    Description: D.A.S. and K.O.B. acknowledge support from the National Aeronautics and Space Administration (NNX11AF63G). S.C.D. and S.F.S. acknowledge support from the National Science Foundation through the Center for Microbial Oceanography: Research and Education (C-MORE) (NSF EF-0424599).
    Description: 2014-09-10
    Keywords: Carbon cycle ; Biological pump ; Carbon export ; Remote sensing ; Food webs
    Repository Name: Woods Hole Open Access Server
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