Particle Flux Parameterizations: Quantitative and Mechanistic Similarities and Differences

Cael, B. B.; Bisson, Kelsey

doi:10.3389/fmars.2018.00395

Cited by 36 publications

(53 citation statements)

References 19 publications

(26 reference statements)

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“…A direct comparison of modeled to observed sinking velocities and fluxes is challenging, as scale dissimilarities introduce uncertainty for comparisons between models and observations (Bisson et al, 2018). Furthermore, sediment trap data for POC and mineral fluxes exhibit high uncertainties which complicates model comparisons and even make different parametrizations for vertical fluxes undistinguishable (Cael and Bisson, 2018). As a consequence, we remain with a general evaluation of our model results.…”

Section: Model Tuning and Evaluationmentioning

confidence: 99%

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Maerz¹,

Six²,

Stemmler³

et al. 2019

Preprint

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Abstract. Marine aggregates are the vector for biogenically bound carbon and nutrients from the euphotic zone to the interior of the oceans. To improve the representation of this biological carbon pump in the global biogeochemical HAMburg Ocean Carbon Cycle (HAMOCC) model, we implemented a novel Microstructure, Multiscale, Mechanistic, Marine Aggregates in the Global Ocean (M4AGO) sinking scheme. M4AGO explicitly represents the size, microstructure, heterogeneous composition, density, and porosity of aggregates, and ties ballasting mineral and particulate organic carbon (POC) fluxes together. Additionally, we incorporated temperature-dependent remineralization of POC. We compare M4AGO with the standard HAMOCC version, where POC fluxes follow a Martin curve approach with linearly increasing sinking velocity with depth, and temperature-independent remineralization. Minerals descend separately with a constant speed. In contrast to the standard HAMOCC, M4AGO reproduces the latitudinal pattern of POC transfer efficiency which has been recently constrained by Weber et al. (2016). High latitudes show transfer efficiencies of &#8776;&#8201;0.25&#8201;&#177;&#8201;0.04 and the subtropical gyres show lower values of about 0.10&#8201;&#177;&#8201;0.03. In addition to temperature as a driving factor, diatom frustule size co-determines POC fluxes in silicifiers-dominated ocean regions while calcium carbonate enhances the aggregate excess density, and thus sinking velocity in subtropical gyres. In ocean standalone runs and rising carbon dioxide (CO2) without CO2 climate feedback, M4AGO alters the regional ocean-atmosphere CO2 fluxes compared to the standard model. M4AGO exhibits higher CO2 uptake in the Southern Ocean compared to the standard run while in subtropical gyres, less CO2 is taken up. Overall, the global oceanic CO2 uptake remains the same. With the explicit representation of measurable aggregate properties, M4AGO can serve as a testbed for evaluating the impact of aggregate-associated processes on global biogeochemical cycles, and, in particular, on the biological carbon pump.

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Section: Model Tuning and Evaluationmentioning

confidence: 99%

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Maerz¹,

Six²,

Stemmler³

et al. 2019

Preprint

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“…On the contrary, the available amount of POC, acting as glue, is suggested to limit the uptake capability for ballasting minerals before aggregates disintegrate (Passow, 2004;Passow and De La Rocha, 2006;De La Rocha et al, 2008). Ballasting increases the POC transfer efficiency (Klaas and Archer, 2002;Balch et al, 2010;Cram et al, 2018), defined as the fraction of POC exported out of the euphotic zone that reaches a particular depth, e.g., 1000 m (Francois et al, 2002). As CaCO 3 is significantly denser than opal, CaCO 3 is suggested to be a more effective ballasting material for marine aggregates (Balch et al, 2010), implying higher POC transfer efficiency in CaCO 3production-dominated regions.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

et al. 2020

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Abstract. Marine aggregates are the vector for biogenically bound carbon and nutrients from the euphotic zone to the interior of the oceans. To improve the representation of this biological carbon pump in the global biogeochemical HAMburg Ocean Carbon Cycle (HAMOCC) model, we implemented a novel Microstructure, Multiscale, Mechanistic, Marine Aggregates in the Global Ocean (M4AGO) sinking scheme. M4AGO explicitly represents the size, microstructure, heterogeneous composition, density and porosity of aggregates and ties ballasting mineral and particulate organic carbon (POC) fluxes together. Additionally, we incorporated temperature-dependent remineralization of POC. We compare M4AGO with the standard HAMOCC version, where POC fluxes follow a Martin curve approach with (i) linearly increasing sinking velocity with depth and (ii) temperature-independent remineralization. Minerals descend separately with a constant speed. In contrast to the standard HAMOCC, M4AGO reproduces the latitudinal pattern of POC transfer efficiency, as recently constrained by Weber et al. (2016). High latitudes show transfer efficiencies of ≈0.25±0.04, and the subtropical gyres show lower values of about 0.10±0.03. In addition to temperature as a driving factor for remineralization, diatom frustule size co-determines POC fluxes in silicifier-dominated ocean regions, while calcium carbonate enhances the aggregate excess density and thus sinking velocity in subtropical gyres. Prescribing rising carbon dioxide (CO2) concentrations in stand-alone runs (without climate feedback), M4AGO alters the regional ocean atmosphere CO2 fluxes compared to the standard model. M4AGO exhibits higher CO2 uptake in the Southern Ocean compared to the standard run, while in subtropical gyres, less CO2 is taken up. Overall, the global oceanic CO2 uptake remains the same. With the explicit representation of measurable aggregate properties, M4AGO can serve as a test bed for evaluating the impact of aggregate-associated processes on global biogeochemical cycles and, in particular, on the biological carbon pump.

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“…6a). We suggest this offset is likely caused by a non-linear relationship between b and the amount of organic matter reaching the deep ocean (as measured by the e-folding depth: depth at which ∼63% of exported POC has been remineralised) following from the fact that the Martin curve represents the scenario of a fixed remineralisation rate and an increasing sinking rate (Kriest and Oschlies, 2008;Cael and Bisson, 2018) To demonstrate this, we find the equivalent e-folding depths for each Latin hypercube sample, which form a skewed distribution due to higher occurrence of shallower remineralisation, calculate the area-weighted geometric mean efolding depth for each sample, and re-arrange again for b (see Supplementary Material for details). The distributions in Figure 6b now fall along the line of globally uniform experiments.…”

Section: Regional Versus Global Sensitivitymentioning

confidence: 99%

“…as the depth at which ∼63% of POC has been remineralised (Kwon et al, 2009), to refer to changes in POC remineralisation as it is relatable to alternative mathematical functions also used (e.g., Cael and Bisson, 2018).…”

mentioning

confidence: 99%

Sensitivity of atmospheric CO2 to regional variability in particulate organic matter remineralization depths

Wilson¹,

Barker²,

Edwards³

et al. 2018

Preprint

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Abstract. The concentration of CO2 in the atmosphere is sensitive to changes in the depth at which sinking particulate organic matter is remineralised: often described as a change in the exponent "b" of the Martin curve. Sediment trap observations from deep and intermediate depths suggest there is a spatially heterogeneous pattern of b, particularly varying with latitude, but disagree over the exact spatial patterns. Here we use a biogeochemical model of the phosphorus cycle coupled with a steady-state representation of ocean circulation to explore the sensitivity of preformed phosphate and atmospheric CO2 to spatial variability in remineralisation depths. A Latin hypercube sampling method is used to simultaneously vary the Martin curve indepedently within 15 different regions, as a basis for a regression-based analysis used to derive a quantitative measure of sensitivity. Approximately 30&#8201;% of the sensitivity of atmospheric CO2 to changes in remineralisation depths is driven by changes in the Subantarctic region (36&#176;&#8201;S to 60&#176;&#8201;S), simliar in magnitude to the Pacific basin despite the much smaller area and lower productivity. Overall, the absolute magnitude of sensitivity is controlled by export production but the relative spatial patterns in sensitivity are predominantly constrained by ocean circulation pathways. The high sensitivity in the Subantarctic regions is driven by a combination of high export production and the high connectivity of these regions to regions important for the export of preformed nutrients such as the Southern Ocean and North Atlantic. Overall, regionally varying remineralisation depths contribute to variability in CO2 of between &#177;5&#8211;15 ppm relative to a global mean change in remineralisation depth. Future changes in the environmental and ecological drivers of remineralisation, such as temperature and ocean acidification, are expected to be most significant in the high latitudes where CO2 sensitivity to remineralisation is also highest. The importance of ocean circulation pathways to the high sensitivity in Subantarctic regions also has significance for past climates given the importance of circulation changes in the Southern Ocean.

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Particle Flux Parameterizations: Quantitative and Mechanistic Similarities and Differences

Cited by 36 publications

References 19 publications

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Sensitivity of atmospheric CO<sub>2</sub> to regional variability in particulate organic matter remineralization depths

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Particle Flux Parameterizations: Quantitative and Mechanistic Similarities and Differences

Cited by 36 publications

References 19 publications

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Microstructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global ocean

Sensitivity of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; to regional variability in particulate organic matter remineralization depths

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Sensitivity of atmospheric CO<sub>2</sub> to regional variability in particulate organic matter remineralization depths