Lithogenic particle fluxes and grain size distributions in the deep ocean off northwest Africa: Implications for seasonal changes of aeolian dust input and downward transport

Ratmeyer, Volker; Fischer, Gerhard; Wefer, Gerold

doi:10.1016/s0967-0637(99)00008-4

Cited by 127 publications

(99 citation statements)

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“…Some studies have shown a clear linear relationship between lithogenic fluxes and particulate aluminum (e.g. Ratmeyer et al, 1999a), the latter being derived from clay minerals as part of the lithogenic (non-biogenic) component. Grains size studies from Ratmeyer et al (1999a, b) and further microscopic analysis provide evidence that most of the lithogenic material in the study area was derived from quartz grains in the fine silt fraction (10-30 µm, see also Friese et al, 2016).…”

Section: Mass Fluxesmentioning

confidence: 99%

Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

Fischer¹,

Romero²,

Merkel³

et al. 2016

Biogeosciences

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Abstract. A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analysed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales. High winter fluxes of biogenic silica (BSi), used as a measure of marine production (mostly by diatoms) largely correspond to a positive North Atlantic Oscillation (NAO) index (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter and occasionally in summer/autumn enhanced particle sedimentation and carbon export on short timescales via the ballasting effect. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) might have weakened the relationships between fluxes and largescale climatic oscillations. As phytoplankton biomass is high throughout the year, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by incorporating dust into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was observed for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all bulk fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost 1 year during the warm El Niño and high fluxes in the following cold La Niña phase. For decadal timescales, Bakun (1990) suggested an intensification of coastal upwelling due to increased winds ("Bakun upwelling intensification hypothesis"; Cropper et al., 2014) and global climate change. We did not observe an increase of any flux component off Cape Blanc during the past 2 and a half decades which might support this. Furthermore, fluxes of mineral dust did not show any positive or negative trends over time which might suggest enhanced desertification or "Saharan greening" during the last few decades.

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Section: Mass Fluxesmentioning

confidence: 99%

Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

Fischer¹,

Romero²,

Merkel³

et al. 2016

Biogeosciences

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“…11, lower panels). Upper ocean partitioning of Ti into the LSF is notable especially in the mixed layer, despite aeolian inputs nearly entirely into the SSF (Ratmeyer et al, 1999). Short expected residence times (Table 3) relative to input fluxes, indicate that LSF-packaging is occurring both rapidly and continuously in situ.…”

Section: Lithogenic Particle Cycling 1-d Model: Contextmentioning

confidence: 99%

“…away from lithogenic inputs such as aeolian dust and lateral transport of continental margin sediments. The subtropical North Atlantic, however, due to its location beneath perhaps the broadest, most intensely dust-dominated atmospheric regimes on Earth , may well be considered an exception among marine particle regimes: lithogenics account for between 40-72% of the vertical sediment trap flux at productive margin systems near Cape Verde (Ratmeyer et al, 1999), compared to typically less than 20% (and frequently less than 5%) at open ocean stations distant from aeolian dust sources (Francois et al, 2002). The North Atlantic, where 43% of annual dust deposition is estimated to occur (Jickells, 2005), thus provides an opportunity to examine lithogenic particle distributions and behaviors in a basin dominated by lithogenic inputs.…”

Section: Md3 Lab3mentioning

confidence: 99%

“…Fine lithogenic particulates also have a narrower particle size spectrum (1-20 micron-range, if sourced completely from dust (Ratmeyer et al, 1999;Stuut, 2005) compared to particulate organic matter, which spans the full range of sizes from organic polymers, viruses, bacteria, pico-and nano-plankton, etc. (McCave, 1984), (Lal, 1977).…”

Section: Applications Of Inert Particle Model To Other Particle Typesmentioning

confidence: 99%

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The biogeochemistry of marine particulate trace metals

Ohnemus¹

2014

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Marine particles include all living and non-living solid components of seawater, representing an extremely dynamic and chemically diverse mixture of phases. The distributions of these phases are poorly constrained and undersampled in the oceans, despite interactions between living organisms and non-living minerals having central roles within many globally relevant biogeochemical processes. Through a combination of method development, basin-scale particulate collection and analyses, modeling, and field experiments, this thesis examines both the distributions of marine particulate trace metals and the underlying processesinputs, scavenging, vertical and horizontal transport, and biotic uptake-in which marine particles participate.I first present the results of an intercalibration exercise among several US laboratories that analyzed filtered particles on shared polyethersulfone filters. We use inter-lab and intra-lab total elemental recoveries of these particles to determine our state of our intercalibration (521% one-sigma inter-lab uncertainty for most elements; 9% intra-lab) and to identify means of future improvement. We also present a new chemical method for complete dissolution of polyethersulfone filters and compare it to other total particle digestion procedures. I then present the marine particulate distributions of the lithogenic elements Al, Fe, and Ti in the North Atlantic GEOTRACES section. Inputs of lithogenic particles from African dust sources, hydrothermal systems, benthic nepheloid layers and laterally-sourced margin influences are observed and discussed. Lithogenic particle residence times, size-fractionation patterns, Ti-mineral speciation, and relationships to biological aggregation processes are calculated and described. A one-dimensional, sizefractionated, multi-box model that describes lithogenic particle distributions is also proposed and its parameter sensitivities and potential implications are discussed.The thesis concludes with the presentation of results from a series of bottle incubations in naturally iron-limited waters using isotopically labeled Fe-minerals. We demonstrate both biotic and abiotic solubilization of the minerals ferrihydrite and fayalite via transfer of isotopic label into suspended particles. These results are the first of their kind to demonstrate that minerals can be a source of bioavailable iron to euphotic communities and that spatial and ecological variations in mineral Fe-bioavailability may exist.Thesis supervisor: Phoebe J. Lam Title: Associate Scientist AcknowledgementsAlthough this thesis has my name on it, every page bears the watermark of my brilliant and ever thoughtful advisor, Phoebe (J.) Lam. Thank you so much for providing me with exciting projects, invigorating afternoon data conversations, prompt and thoughtful written feedback, and what I'm sure was a lifetime's worth of patience over the years. Together we've travelled to the bottom of the world, sampled oceans, and spent nights by the hum of a synchrotron; it's hard to imagine doing rese...

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“…Most of the data concern shortterm periods (usually dust storms or other events of high dust activity) [5,8,[13][14][15]17] or medium-term data evolution [9][10][11]19]. As for horizontal dust flux, published long-term information for dust grain size is only available via indirect studies, for example, dust in oceanic sediment cores [3,6,21], in ice cores [12,22,23], or in loess deposits [1,4,7,26]. Arimoto et al [2] performed grain size measurements of airborne dust collected over the Atlantic and Pacific oceans.…”

Section: Introductionmentioning

confidence: 99%

Airborne particle granulometry and micromorphology during working and not working days in the Brussels environment

Vanderstraeten¹,

Lénelle²,

Meurrens³

et al. 2006

WIT Transactions on Ecology and the Environment, Vol 86

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We report and analyze here data on airborne particles up to PM10, measured in the Brussels region from October 2002 through to September 2003.The purpose of this study was to measure the impact of urban activities on airborne particles. Differences in the granulometry and micromorphology of particles sampled on working days and weekends were studied. Two parameters are computed for a large number of collected particles. The first parameter is the isoperimetric quotient, IQ, defined as the area A of the planar projection of the particle divided by the square of its perimeter (rescaled by 4π), i.e. IQ=4π A/p 2 . This parameter is smaller or equal to one (for a circular planar projection) and measures the particle surface irregularity or roughness.The second parameter, β, corresponds to the ratio L 1 /L 2 between the projected major and minor axis of the particle. It is larger or equal to one and represents the particle elongation.We observed significant tendencies in the particles distributions in terms of IQ and β.

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Lithogenic particle fluxes and grain size distributions in the deep ocean off northwest Africa: Implications for seasonal changes of aeolian dust input and downward transport

Cited by 127 publications

References 0 publications

Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

The biogeochemistry of marine particulate trace metals

Airborne particle granulometry and micromorphology during working and not working days in the Brussels environment

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