Dust deposition pulses to the eastern subtropical North Atlantic gyre: Does ocean's biogeochemistry respond?

Neuer, Susanne; Torres-Padrón, M. E.; Gelado-Caballero, M. D.; Rueda, M. J.; Hernández‐Brito, J. J.; Davenport, Robert; Wefer, Gerold

doi:10.1029/2004gb002228

Cited by 73 publications

(69 citation statements)

References 45 publications

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“…A recent study demonstrated that the most frequent and intense response of the microbial plankton to atmospheric dust deposition in the Tropical Atlantic is the stimulation of the bacterial activity rather than phytoplankton primary production (Marañón et al, 2010). This is consistent with the results found at ESTOC, which is strongly influenced by the natural atmospheric deposition of Saharan dust, and where phytoplanktonic production seems not to be affected by aerosol inputs (Neuer et al, 2004).…”

Section: Introductionsupporting

confidence: 81%

Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

et al. 2012

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Abstract. We used 5-yr concomitant data of tracer distribution from the BATS (Bermuda Time-series Study) and ES-TOC (European Station for Time-Series in the Ocean, Canary Islands) sites to build a 1-D tracer model conservation including horizontal advection, and then compute net production and shallow remineralization rates for both sites. Our main goal was to verify if differences in these rates are consistent with the lower export rates of particulate organic carbon observed at ESTOC. Net production rates computed below the mixed layer to 110 m from April to December for oxygen, dissolved inorganic carbon and nitrate at BATS (1.34 ± 0.79 mol O 2 m −2 , −1.73 ± 0.52 mol C m −2 and −125±36 mmol N m −2 ) were slightly higher for oxygen and carbon compared to ESTOC (1.03 ± 0.62 mol O 2 m −2 , −1.42 ± 0.30 mol C m −2 and −213 ± 56 mmol N m −2 ), although the differences were not statistically significant. Shallow remineralization rates between 110 and 250 m computed at ESTOC (−3.9 ± 1.0 mol O 2 m −2 , 1.53 ± 0.43 mol C m −2 and 38 ± 155 mmol N m −2 ) were statistically higher for oxygen compared to BATS (−1.81 ± 0.37 mol O 2 m −2 , 1.52 ± 0.30 mol C m −2 and 147 ± 43 mmol N m −2 ). The lateral advective flux divergence of tracers, which was more significant at ESTOC, was responsible for the differences in estimated oxygen remineralization rates between both stations. According to these results, the differences in net production and shallow remineralization cannot fully explain the differences in the flux of sinking organic matter observed between both stations, suggesting an additional consumption of nonsinking organic matter at ESTOC.

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Section: Introductionsupporting

confidence: 81%

Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

et al. 2012

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“…Towards 12 • N, upwelling is also fed by the North Equatorial Undercurrent (Hagen and Schemainda, 1984). Moreover, the entire northwest African coast is also influenced by the African desert dust transport by the midtropospheric Harmattan winds originating from the central Sahara, which supplements the levels of micronutrients (such as iron) to the adjacent marine ecosystem (Mittelstaedt, 1983;Neuer et al, 2004). The study area is also affected by the migration of the Intertropical Convergence Zone (ITCZ), related to maximum precipitation rates (Hastenrath, 1995).…”

Section: Physical Propertiesmentioning

confidence: 99%

Changes in the partial pressure of carbon dioxide in the Mauritanian–Cap Vert upwelling region between 2005 and 2012

2017

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Abstract. Coastal upwellings along the eastern margins of major ocean basins represent regions of large ecological and economic importance due to the high biological productivity. The role of these regions for the global carbon cycle makes them essential in addressing climate change. The physical forcing of upwelling processes that favor production in these areas are already being affected by global warming, which will modify the intensity of upwelling and, consequently, the carbon dioxide cycle. Here, we present monthly high-resolution surface experimental data for temperature and partial pressure of carbon dioxide in one of the four most important upwelling regions of the planet, the Mauritanian-Cap Vert upwelling region, from 2005 to 2012. This data set provides direct evidence of seasonal and interannual changes in the physical and biochemical processes. Specifically, we show an upwelling intensification and an increase of 0.6 Tg yr −1 in CO 2 outgassing due to increased wind speed, despite increased primary productivity. This increase in CO 2 outgassing together with the observed decrease in sea surface temperature at the location of the Mauritanian Cap Blanc, 21 • N, produced a pH rate decrease of −0.003 ± 0.001 yr −1 .

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“…iron) and macronutrients to the ocean surface waters (e.g. Jickells et al, 2005;Neuer et al, 2004). Additionally, dust acts as ballast mineral (Armstrong et al, 2002;Klaas and Archer, 2002) for organic carbon-rich particles (e.g.…”

Section: Introductionmentioning

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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Dust deposition pulses to the eastern subtropical North Atlantic gyre: Does ocean's biogeochemistry respond?

Cited by 73 publications

References 45 publications

Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

Changes in the partial pressure of carbon dioxide in the Mauritanian–Cap Vert upwelling region between 2005 and 2012

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

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