Offshore advection of particles within the Cape Blanc filament, Mauritania: Results from observational and modelling studies

Fischer, Gerhard; Reuter, Christoph; Karakas, Gokay; Nowald, Nicolas; Wefer, Gerold

doi:10.1016/j.pocean.2009.07.023

Cited by 54 publications

(76 citation statements)

References 27 publications

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“…3b). Fischer et al (2009b) showed that the size of the Cape Blanc filament was small in winter-spring 1997-1998 and unusually high from autumn 1998 to spring 1999 (Figs. 7b, 1e).…”

Section: Large-scale Teleconnections Affecting the Study Areamentioning

confidence: 99%

“…Seasons were defined using the dates of opening and closure of the sampling cups closest to the start of the astronomical seasons (21 March, 21 June, 23 September, 21 December) ( Table 2). Where lower trap data (around 3500 m) were not available, the upper trap data (around 1000 m) were used, which mostly match the lower trap fluxes with respect to seasonality (Fischer et al, 2009b). When plotting all available lower and upper trap total mass fluxes for winter, a close correspondence is observed (r 2 = 0.84, N = 10), with slightly higher fluxes in the deeper trap due to lateral particle advection processes (Fischer et al, 2009b;Karakas et al, 2006Karakas et al, , 2009.…”

Section: Mass Fluxesmentioning

confidence: 99%

“…Helmke et al (2005) correlated these anomalous events with deep-ocean carbon fluxes at the mesotrophic Cape Blanc study site. Using ocean colour data, Fischer et al (2009b) showed a large extension of the Cape Blanc filament from autumn 1998 to spring 1999 when comparing it to the rest of the record (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008). Using remote-sensing data, Nykjaer and Van Camp (1994) found a weak northwest upwelling south of 20 • N during and after the strong 1982-1983 El Niño event.…”

Section: Introductionmentioning

confidence: 99%

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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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“…3b). Fischer et al (2009b) showed that the size of the Cape Blanc filament was small in winter-spring 1997-1998 and unusually high from autumn 1998 to spring 1999 (Figs. 7b, 1e).…”

Section: Large-scale Teleconnections Affecting the Study Areamentioning

confidence: 99%

Section: Mass Fluxesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…If a significant proportion of the particles collected at the coastal station were laterally advected, having a longer residence time in the water column, they might be relatively older compared to the particles traveling vertically. Indeed, recent studies have demonstrated that the lateral transport of particulate material from the African coast is a key process controlling the organic carbon dynamic in this area (Karakas et al, 2006;Alonso-González et al, 2009;Fischer et al, 2009). Another possible explanation for this counterintuitive result could be that in coastal stations the heterotrophic community (particularly mesozooplankton) is more active than in open ocean stations.…”

Section: Regional Variability In Organic Mattermentioning

confidence: 99%

Regional and temporal variability of sinking organic matter in the subtropical northeast Atlantic Ocean: a biomarker diagnosis

et al. 2010

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Abstract. Sinking particles through the pelagic ocean have been traditionally considered the most important vehicle by which the biological pump sequesters carbon in the ocean interior. Nevertheless, regional scale variability in particle flux is a major outstanding issue in oceanography. Here, we have studied the regional and temporal variability of total particulate organic matter fluxes, as well as chloropigment and total hydrolyzed amino acid (THAA) compositions and fluxes in the Canary Current region, between 20-30 • N, during two contrasting periods: August 2006, characterized by warm and stratified waters, but also intense winds which enhanced eddy development south of the Canary Islands, and February 2007, characterized by colder waters, less stratification and higher productivity. We found that the eddyfield generated south of the Canary Islands enhanced by >2 times particulate organic carbon (POC) export with respect to stations (FF; far-field) outside the eddy-field influence. We also observed flux increases of one order of magnitude in chloropigment and 2 times in THAA in the eddy-field relative to FF stations. Principal Components Analysis (PCA) was performed to assess changes in particulate organic matter composition between stations. At eddy-field stations, higher chlorophyll enrichment reflected "fresher" material, while at FF stations a higher proportion of pheophytin indicated greater degradation due to microbes and microzooplankton. PCA also suggests that phytoplankton community structure, particularly the dominance of diatoms versus carbonate-rich plankton, is the major factor influencing the POC export within the eddy field. In February, POC export

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“…In near-coastal areas, particle fluxes can vary dramatically due to productivity events triggered by upwelling and submesoscale frontal processes such as filaments (Fischer et al, 2009b). In the open ocean outside of frontal regions, productivity events are mostly related to the occurrence of mesoscale eddies (Benitez-Nelson and McGillicuddy, 2008).…”

Section: Introductionmentioning

confidence: 99%

Bathypelagic particle flux signatures from a suboxic eddy in the oligotrophic tropical North Atlantic: production, sedimentation and preservation

et al. 2016

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The lithogenic ballasting obviously resulted in high particle settling rates and, thus, a fast transfer of epi-/mesopelagic signatures to the bathypelagic traps. We suspect that the two-to three-fold increase in particle fluxes with depth as well as the tight coupling of mineral dust and organic carbon in the deep trap samples might be explained by particle focusing processes within the deeper part of the eddy. Molar C : N ratios of organic matter during the ACME passage were around 18 and 25 for the upper and lower trap samples, respectively. This suggests that some productivity under nutrient (nitrate) limitation occurred in the euphotic zone of the eddy in the beginning of 2010 or that a local nitrogen recycling took place. The δ 15 N record showed a decrease from 5

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Offshore advection of particles within the Cape Blanc filament, Mauritania: Results from observational and modelling studies

Cited by 54 publications

References 27 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

Regional and temporal variability of sinking organic matter in the subtropical northeast Atlantic Ocean: a biomarker diagnosis

Bathypelagic particle flux signatures from a suboxic eddy in the oligotrophic tropical North Atlantic: production, sedimentation and preservation

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