Regional variability in the vertical flux of particulate organic carbon in the ocean interior

Lutz, M.J.; Dunbar, Robert B.; Caldeira, K.

doi:10.1029/2000gb001383

Cited by 244 publications

(251 citation statements)

References 109 publications

(166 reference statements)

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“…More recently, the analyses of deep trap data have confirmed this variability in "b", and have led to the suggestion of carbonate ballast or sinking rate controls on particle export efficiency (Armstrong et al, 2002;Klaas and Archer, 2002;Lutz et al, 2002). However, our data do not support a primary role for carbonate in controlling mesopelagic or deep-ocean POC flux, since at least at K2, the "silicate pump" appears to lead to enhanced POC delivery to the deep sea.…”

Section: Discussioncontrasting

confidence: 51%

VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific

Buesseler

Trull

Steinberg

et al. 2008

Deep Sea Research Part II: Topical Studies in Oceanography

121

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The VERtical Transport In the Global Ocean (VERTIGO) study examined particle sources and fluxes through the ocean's "twilight zone" (defined here as depths below the euphotic zone to 1000 m). Interdisciplinary process studies were conducted at contrasting sites off Hawaii (ALOHA) and in the NW Pacific (K2) during 3 week occupations in 2004 and 2005, respectively. We examine in this overview paper the contrasting physical, chemical and biological settings and how these conditions impact the source characteristics of the sinking material and the transport efficiency through the twilight zone. A major finding in VERTIGO is the considerably lower transfer efficiency (T eff ) of particulate organic carbon (POC), POC flux 500 / 150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatom-dominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, and where zooplankton and their pellets are larger. At K2, the drawdown of macronutrients is used to assess export and suggests that shallow remineralization above our 150 m trap is significant, especially for N relative to Si. We explore here also surface export ratios (POC flux/primary production) and possible reasons why this ratio is higher at K2, especially during the first trap deployment. When we compare the 500 m fluxes to deep moored traps, both sites lose about half of the sinking POC by >4000 m, but this comparison is limited in that fluxes at depth may have both a local and distant component.Certainly, the greatest difference in particle flux attenuation is in the mesopelagic, and we highlight other VERTIGO papers that provide a more detailed examination of the particle sources, flux and processes that attenuate the flux of sinking particles. Ultimately, we contend that at least three types of processes need to be considered: heterotrophic degradation of sinking particles, zooplankton migration and surface feeding, and lateral sources of suspended and sinking materials. We have evidence that all of these processes impacted the net attenuation of particle flux vs. depth measured in VERTIGO and would therefore need to be considered and quantified in order to understand the magnitude and efficiency of the ocean's biological pump.

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Section: Discussioncontrasting

confidence: 51%

VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific

Buesseler

Trull

Steinberg

et al. 2008

Deep Sea Research Part II: Topical Studies in Oceanography

121

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“…This finds confirmation in our observations of the appearance and disappearance of large fecal material in the 100-m depth interval below the euphotic zone, the interval of the highest gradient in POC (Figure 7c,d). The abundance of zooplankton activity high in the twilight zone explains why exponential or power law fits that capture the region of the highest concentration gradient underpredict deep POC fluxes (Armstrong et al 2002;Lutz et al 2002), since loss rates are much higher where zooplankton graze.…”

Section: Dominance Of Biological Loss Processes In the Upper Twilightmentioning

confidence: 99%

High biomass, low export regimes in the Southern Ocean

Lam

Bishop

2007

Deep Sea Research Part II: Topical Studies in Oceanography

109

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2 AbstractThis paper investigates ballasting and remineralization controls of carbon sedimentation in the twilight zone (100-1000 m) of the Southern Ocean. Size-fractionated (<1 μm, 1-51 μm, >51 μm) suspended particulate matter was collected by large volume in-situ filtration from the upper 1000 m in the Subantarctic (55°S, 172°W) and Antarctic (66°S, 172°W) zones of the Southern Ocean during the Southern Ocean Iron Experiment (SOFeX) in January-February 2002.Particles were analyzed for major chemical constituents (POC, P, biogenic Si, CaCO 3 ), and digital and SEM image analyses of particles were used to aid in the interpretation of the chemical profiles.Twilight zone waters at 66°S in the Antarctic had a steeper decrease in POC with depth than at 55°S in the Subantarctic, with lower POC concentrations in all size fractions at 66°S than at 55°S, despite up to an order of magnitude higher POC in surface waters at 66°S. The decay length scale of >51 μm POC was significantly shorter in the upper twilight zone at 66°S ( e =26 m) compared to 55°S ( e =81 m).Particles in the carbonate-producing 55°S did not have higher excess densities than particles from the diatom-dominated 66°S, indicating that there was no direct ballast effect that accounted for deeper POC penetration at 55°S. An indirect ballast effect due to differences in particle packaging and porosities cannot be ruled out, however, as aggregate porosities were high (~97%) and variable.Image analyses point to the importance of particle loss rates from zooplankton grazing and remineralization as determining factors for the difference in twilight zone POC 3 concentrations at 55°S and 66°S, with stronger and more focused shallow remineralization at 66°S. At 66°S, an abundance of large (several mm long) fecal pellets from the surface to 150 m, and almost total removal of large aggregates by 200 m, reflected the actions of a single or few zooplankton species capable of grazing diatoms in the euphotic zone, coupled with a more diverse particle feeding zooplankton community immediately below.Surface waters with high biomass levels and high proportion of biomass in the large size fraction were associated with low particle loading at depth, with all indications implying conditions of low export. The 66°S region exhibits this "High Biomass, Low Export" (HBLE) condition, with very high >51 μm POC concentrations at the surface (~2.1 μM POC), but low concentrations below 200 m (<0.07 μM POC). The 66°S region remained HBLE after iron fertilization. Iron addition at 55°S caused a ten fold increase in >51 μm biomass concentrations in the euphotic zone, bringing surface POC concentrations to levels found at 66°S (~3.8 μM), and a concurrent decrease in POC concentrations below 200 m. The 55°S region, which began with moderate levels of biomass and stronger particle export, transitioned to being HBLE after iron fertilization. We propose that iron addition to already HBLE waters will not cause mass sedimentation events. The stability of an iron-induced HBLE condition is unknow...

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“…Buesseler, 1998;Laws et al, 2000;Antia et al, 2001;Armstrong et al, 2002;Francois et al, 2002;Lutz et al, 2002;Schlitzer, 2002b), the export production in 1000 m water depth is probably not well suited as an environmental input parameter for a planktic foraminiferal flux model. We decided to still use export production, because it was the only productivity-related parameter being available in the temporal resolution of sediment trap samples.…”

Section: Pitfalls and Potential Of The Modelmentioning

confidence: 99%

Global prediction of planktic foraminiferal fluxes from hydrographic and productivity data

2006

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Abstract. Understanding and quantifying the seasonal and spatial distribution of planktic foraminiferal fluxes reflected in sedimentary assemblages is key to interpret foraminiferabased proxies in paleoceanography. Towards this goal we present an empirical model to predict foraminiferal fluxes on a global scale.A compilation of planktic foraminiferal flux and export production data from globally distributed sediment traps together with environmental data of sea-surface temperature and mixed-layer depth from online databases is used to calibrate the model that calculates monthly foraminiferal fluxes for the 18 most common species. The calibrated model is then forced with a global data set of hydrographic and productivity data to predict monthly foraminiferal fluxes worldwide. The predictive skills of the model are assessed by comparing the model output with planktic foraminiferal assemblages from globally distributed surface sediments as well as with measured foraminiferal fluxes of sediment traps not included in the calibration data set.Many general distribution patterns of foraminiferal species recognized from the model output compare favorably with observations from coretops or sediment traps, even though the model still produces problematic results in some places. Among others, meridional gradients in species richness and diversity, increased relative abundances of Neogloboquadrina pachyderma (dex.) in upwelling areas, and peak abundances of Globigerinella siphonifera in oligotrophic subtropical gyres show good agreement between model and coretops. Absolute foraminiferal fluxes are significantly underestimated in most cases, while seasonal variations can be reproduced for some species. Interannual differences in foraminiferal fluxes are not reflected by the model which might partly be due to a lack of actual environmental data for the calibration and model experiments.Correspondence to: S.Žarić (zaric@uni-bremen.de)The limited predictive skills of the model suggest that additional parameters should be considered. Export production should probably be replaced by a more realistic representation of food availability for planktic foraminifera. This could be achieved by adding a dynamic component to the model and linking it to an ecosystem model.

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Regional variability in the vertical flux of particulate organic carbon in the ocean interior

Cited by 244 publications

References 109 publications

VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific

VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific

High biomass, low export regimes in the Southern Ocean

Global prediction of planktic foraminiferal fluxes from hydrographic and productivity data

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