Geographical, seasonal, and depth variation in sinking particle speeds in the North Atlantic

Villa-Alfageme, María; Soto, F. C. de; Ceballos, Elvira; Giering, Sarah L. C.; Moigne, Frédéric A.C. Le; Henson, Stephanie A.; Mas, J.L.; Sanders, Richard

doi:10.1002/2016gl069233

Cited by 48 publications

(56 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Martin curve is equivalent to a decreasing remineralization rate with depth or an increasing sinking speed with depth [ Lam et al , ]. Villa‐Alfageme et al [] observed an increase in sinking speed with depth, possibly due to the gradual loss of slow‐sinking particles with depth. Small values of b imply a higher transfer efficiency where more carbon remineralizes at deeper depths.…”

Section: Methodsmentioning

confidence: 99%

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO₂

Gloege

McKinley

Mouw

et al. 2017

Global Biogeochemical Cycles

View full text Add to dashboard Cite

The shunt of photosynthetically derived particulate organic carbon (POC) from the euphotic zone and deep remineralization comprises the basic mechanism of the “biological carbon pump.” POC raining through the “twilight zone” (euphotic depth to 1 km) and “midnight zone” (1 km to 4 km) is remineralized back to inorganic form through respiration. Accurately modeling POC flux is critical for understanding the “biological pump” and its impacts on air‐sea CO2 exchange and, ultimately, long‐term ocean carbon sequestration. Yet commonly used parameterizations have not been tested quantitatively against global data sets using identical modeling frameworks. Here we use a single one‐dimensional physical‐biogeochemical modeling framework to assess three common POC flux parameterizations in capturing POC flux observations from moored sediment traps and thorium‐234 depletion. The exponential decay, Martin curve, and ballast model are compared to data from 11 biogeochemical provinces distributed across the globe. In each province, the model captures satellite‐based estimates of surface primary production within uncertainties. Goodness of fit is measured by how well the simulation captures the observations, quantified by bias and the root‐mean‐square error and displayed using “target diagrams.” Comparisons are presented separately for the twilight zone and midnight zone. We find that the ballast hypothesis shows no improvement over a globally or regionally parameterized Martin curve. For all provinces taken together, Martin's b that best fits the data is [0.70, 0.98]; this finding reduces by at least a factor of 3 previous estimates of potential impacts on atmospheric pCO2 of uncertainty in POC export to a more modest range [−16 ppm, +12 ppm].

show abstract

Section: Methodsmentioning

confidence: 99%

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO₂

Gloege

McKinley

Mouw

et al. 2017

Global Biogeochemical Cycles

View full text Add to dashboard Cite

show abstract

“…There is substantial variation in particle sinking speed in the ocean because particle sizes vary over orders of magnitude (Alldredge & Silver, 1988;Villa-Alfageme et al, 2016) and particle sinking speed has been generally observed to increase as a power law function with particle size (Alldredge & Gotschalk, 1989;Smayda, 1971). For a given equivalent particle size, its shape and roughness can also influence sinking speed (Dietrich, 1982;Johnson et al, 1996).…”

Section: Particle Velocitymentioning

confidence: 99%

The Role of Particle Size, Ballast, Temperature, and Oxygen in the Sinking Flux to the Deep Sea

Cram

Weber

Leung

et al. 2018

Global Biogeochemical Cycles

115

View full text Add to dashboard Cite

The “transfer efficiency” of organic particles from the surface to depth is a critical determinant of ocean carbon sequestration. Recently, direct observations and geochemical analyses have revealed a systematic geographical pattern of transfer efficiency, which is highest in high latitude regions and lowest in the subtropical gyres. We evaluate the possible causes of this pattern using a mechanistic model of sinking particle dynamics. The model represents the size distribution of particles, the effects of mineral ballast, seawater temperature (which influences both particle settling velocity and microbial metabolic rates), and O2. Parameters are optimized within reasonable ranges to best match the observational constraints. Our model shows that no single factor can explain the observed pattern of transfer efficiency, but the biological effect of temperature on remineralization rate and particle size effects together can reproduce most of the regional variability with both factors contributing to low transfer efficiency in the subtropical gyres and high transfer efficiency in high latitudes. Particle density from mineral ballast has a similar directional effect to temperature and size but plays a substantially smaller role in our optimum solution, due to the opposing patterns of silicate and calcium carbonate ballasting. Oxygen effects modestly improved model fit by depressing remineralization rates and thus increasing transfer efficiency in the Eastern Tropical Pacific. Our model implies that climate‐driven changes to upper ocean temperature and associated changes in surface plankton size distribution would reduce the carbon sequestration efficiency in a warmer ocean.

show abstract

“…This result implies that a parameterization of particle SV with a Stokes' model could be more robust in the mesopelagic layer and deeper ocean. Increase of particle SV with depth (Berelson ; Trull et al ; Villa‐Alfageme et al ) could thus be potentially simulated through compositional changes in addition to depth‐varying size classes (SV strictly size‐dependent; Kriest and Oschlies ) or a prescribed linear SV increase with depth (Gehlen et al ; Kriest and Oschlies ; Aumont et al ).…”

Section: Concluding Remarks: Implications For Biogeochemical Model Pamentioning

confidence: 99%

New guidelines for the application of Stokes' models to the sinking velocity of marine aggregates

Laurenceau-Cornec

Moigne

Gallinari

et al. 2019

Limnology & Oceanography

View full text Add to dashboard Cite

Numerical simulations of ocean biogeochemical cycles need to adequately represent particle sinking velocities (SV). For decades, Stokes' Law estimating particle SV from density and size has been widely used. But while Stokes' Law holds for small, smooth, and rigid spheres settling at low Reynolds number, it fails when applied to marine aggregates complex in shape, structure, and composition. Minerals and zooplankton can alter phytoplankton aggregates in ways that change their SV, potentially improving the applicability of Stokes' models. Using rolling cylinders, we experimentally produced diatom aggregates in the presence and absence of minerals and/or microzooplankton. Minerals and to a lesser extent microzooplankton decreased aggregate size and roughness and increased their sphericity and compactness. Stokes' Law parameterized with a fractal porosity modeled adequately size‐SV relationships for mineral‐loaded aggregates. Phytoplankton‐only aggregates and those exposed to microzooplankton followed the general Navier‐Stokes drag equation suggesting an indiscernible effect of microzooplankton and a drag coefficient too complex to be calculated with a Stokes' assumption. We compared our results with a larger data set of ballasted and nonballasted marine aggregates. This confirmed that the size‐SV relationships for ballasted aggregates can be simulated by Stokes' models with an adequate fractal porosity parameterization. Given the importance of mineral ballasting in the ocean, our findings could ease biogeochemical model parameterization for a significant pool of particles in the ocean and especially in the mesopelagic zone where the particulate organic matter : mineral ratio decreases. Our results also reinforce the importance of accounting for porosity as a decisive predictor of marine aggregate SV.

show abstract

Geographical, seasonal, and depth variation in sinking particle speeds in the North Atlantic

Cited by 48 publications

References 46 publications

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO₂

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO₂

The Role of Particle Size, Ballast, Temperature, and Oxygen in the Sinking Flux to the Deep Sea

New guidelines for the application of Stokes' models to the sinking velocity of marine aggregates

Contact Info

Product

Resources

About

Geographical, seasonal, and depth variation in sinking particle speeds in the North Atlantic

Cited by 48 publications

References 46 publications

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO2

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO2

The Role of Particle Size, Ballast, Temperature, and Oxygen in the Sinking Flux to the Deep Sea

New guidelines for the application of Stokes' models to the sinking velocity of marine aggregates

Contact Info

Product

Resources

About

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO₂

Global evaluation of particulate organic carbon flux parameterizations and implications for atmospheric pCO₂