Environmental factors controlling the seasonal variability in particle size distribution of modern Saharan dust deposited off Cape Blanc

Friese, Carmen A; Does, Michèlle van der; Merkel, Ute; Iversen, Morten Hvitfeldt; Fischer, Gerhard; Stuut, Jan‐Berend

doi:10.1016/j.aeolia.2016.04.005

Cited by 35 publications

(45 citation statements)

References 75 publications

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“…8) whereas part of the summer dust load is transported further westward and deposited in the Caribbean Sea (Goudie and Middleton, 2001;Prospero and Lamb, 2003). However, the rainfall pattern exhibits elevated precipitation in summer and autumn 2005 when the tropical rainbelt was far north; this might have led to unusual wet deposition of dust in summer over our study site (Friese et al, 2016). As shown earlier, BSi fluxes show positive anomalies in sum- (Fig.…”

Section: Interaction Between Mineral Dust and The Biological Pumpsupporting

confidence: 50%

“…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: 75%

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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: Interaction Between Mineral Dust and The Biological Pumpsupporting

confidence: 50%

Section: Mass Fluxesmentioning

confidence: 75%

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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“…Here, we took advantage of a weather station ideally located on the main pathway of desert aerosols from northern Africa (Léon et al, 2009;Marticorena et al, 2010;Mortier et al, 2016) to explain the effect of meteorological variables on this transition in a region of primary importance worldwide. The interaction of air masses of oceanic origin with dust aerosols are crucial for understanding their fate (e.g., Friese et al, 2016). This study constitutes the first attempt to link the seasonal dynamic of the atmosphere and the vertical distribution of dust aerosol in this region, and it provides the first dynamical explanation of a counterintuitive deposition pattern over the Atlantic Ocean.…”

Section: Discussionmentioning

confidence: 95%

“…The mineral particles suspended in the atmosphere come from different sources and have a nature similar to that of the soil from which they arise (Claquin et al, 1999;Formenti et al, 2008) with a broad spectrum of particle sizes ranging between 0.01 and 300 µm (Wagener, 2008;Ryder et al, 2013). Their impact on the marine ecosystem and particularly on oceanic primary production (Duce and Tindale, 1991;Baker et al, 2003;Mills et al, 2004;Jickells et al, 2005;Mahowald et al, 2009) still remains uncertain and difficult to assess because of the composition of these particles and of physicochemical processes affecting them (e.g., Friese et al, 2016). Mineral dust deposition also has a negative impact on human health and are responsible for meningitis epidemics and cardiac diseases (Thomson et al, 2006;Martiny and Chiapello, 2013;Diokhane et al, 2016;Prospero et al, 2005;Griffin, 2007).…”

Section: Introductionmentioning

confidence: 99%

Seasonal cycle of desert aerosols in western Africa: analysis of the coastal transition with passive and active sensors

et al. 2017

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“…The extinction coefficient maximum of 0.35 -0.4 was observed at 1 -3 Km, suggesting that strong of the synoptic system, dust can be transported to the south and east. This cold front is one of the important synoptic weather systems which are favorable for formation of dust storm [35].…”

Section: Extinction Coefficient Vertical Profilementioning

confidence: 99%

Numerical Studies on a Severe Dust Storm in East Asia Using WRF-Chem

Yu¹,

Wang²,

Liu³

et al. 2017

ACS

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Dust storm is one of the important natural disasters, which can have significant impact on terrestrial ecosystem, global climate, air quality and human health. In Mar. 19-23, 2010, a serious dust storm occurred over East Asia. It started from Mongolia, initially extending to the east, turning to the South of China, then back to the Northeast Asia. About 20% of the areas in China suffered from this severe dust event and the air was heavily polluted with massive airborne particulates. The Air Pollution Index (API) in many cities exceeded 500 when dust storm passed by, while the maximum surface PM 10 concentration reached 1900 µg/m 3 in east area. The coarse particles were dominated in PM 10 , with fine particles named as PM 2.5 only accounting for 5% -20% at cities along the dust moving track in South and East China. MODIS and CALIPSO satellite data were used to investigate the horizontal and vertical patterns of optical parameters of dust aerosol. The average AOD reached 2 -2.5 on dust days in most southeast regions. The dust can be transported up to 5 Km with maximum aerosol extinction coefficient of 0.35 -0.4 at 1 -3 Km in vertical. Synoptic weather was analyzed to understand the meteorological conditions and the backward trajectories were calculated to investigate the movements of air mass. The WRFChem model (Version 3.2) was applied to simulate the transport and deposition of the dust aerosols. The performance of Shaw (2008) and Chin (2002)

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Environmental factors controlling the seasonal variability in particle size distribution of modern Saharan dust deposited off Cape Blanc

Cited by 35 publications

References 75 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

Seasonal cycle of desert aerosols in western Africa: analysis of the coastal transition with passive and active sensors

Numerical Studies on a Severe Dust Storm in East Asia Using WRF-Chem

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