Lateral POC transport and consumption in surface and deep waters of the Canary Current region: A box model study

Alonso-González, Iván J.; Arı́stegui, Javier; Vilas, Juan Carlos; Hernández‐Guerra, Alonso

doi:10.1029/2008gb003185

Cited by 50 publications

(66 citation statements)

References 77 publications

(97 reference statements)

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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: 76%

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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Section: Regional Variability In Organic Mattermentioning

confidence: 76%

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

et al. 2010

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“…Modeled POC concentrations have annual mean values between 5 and over 20 mmol C m −3 in the first 100 m depth of the very productive shelf areas, lying therefore in the range of in situ observations (Alonso-González et al, 2009;Arístegui et al, 2003;Santana-Falcón et al, 2016;. Concentrations decline in the offshore direction, with a pattern similar to that of NPP, and have maximum values located between 20 m depth in the shelf area and 70 m depth offshore.…”

Section: Discussionmentioning

confidence: 90%

“…The CanUS therefore constitutes a good potential candidate source region for the organic carbon required to fuel the purportedly heterotrophic conditions in the subtropical North Atlantic. However, despite its potential impact on offshore biological activity (Alonso-González et al, 2009;Álvarez-Salgado et al, 2007), the magnitude and range of the total long-range offshore transport of organic carbon in the CanUS is still poorly quantified.…”

Section: Introductionmentioning

confidence: 99%

On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

Lovecchio¹,

Gruber²,

Münnich³

et al. 2017

Biogeosciences

105

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Abstract. A compilation of measurements of net community production (NCP) in the upper waters of the eastern subtropical North Atlantic had suggested net heterotrophic conditions, purportedly supported by the lateral export of organic carbon from the adjacent, highly productive Canary Upwelling System (CanUS). Here, we quantify and assess this lateral export using the Regional Ocean Modeling System (ROMS) coupled to a nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model. We employ a new Atlantic telescopic grid with a strong refinement towards the northwestern African shelf to combine an eddy-resolving resolution in the CanUS with a full Atlantic basin perspective. Our climatologically forced simulation reveals an intense offshore flux of organic carbon that transports about 19 Tg C yr −1 away from the nearshore 100 km over the whole CanUS, amounting to more than a third of the NCP in this region. The offshore transport extends beyond 1500 km into the subtropical North Atlantic, adding organic carbon along the way to the upper 100 m at rates of between 8 and 34 % of the alongshore average NCP as a function of offshore distance. Although the divergence of this lateral export of organic carbon enhances local respiration, the upper 100 m layer in our model remains net autotrophic in the entire eastern subtropical North Atlantic. However, the vertical export of this organic carbon and its subsequent remineralization at depth makes the vertically integrated NCP strongly negative throughout this region, with the exception of a narrow band along the northwestern African shelf. The magnitude and efficiency of the lateral export varies substantially between the different subregions. In particular, the central coast near Cape Blanc is particularly efficient in collecting organic carbon on the shelf and subsequently transporting it offshore. In this central subregion, the offshore transport adds as much organic carbon as nearly 60 % of the local NCP to the upper 100 m, giving rise to a sharp peak of offshore respiration that extends to the middle of the gyre. Our modeled offshore transport of organic carbon is likely a lower-bound estimate due to our lack of full consideration of the contribution of dissolved organic carbon and that of particulate organic carbon stemming from the resuspension of sediments. But even in the absence of these contributions, our results emphasize the fundamental role of the lateral redistribution of the organic carbon for the maintenance of the heterotrophic activity in the open sea.

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“…5d), through horizontal advection. The role of the horizontal transport in the seasonality of the synthesis and remineralization of organic matter has been previously reported in the Canary region, which is under the influence of the coastal African upwelling (Neuer et al, 2002b;Arístegui et al, 2003;Pelegrí et al, 2005;Alonso-González et al, 2009). Upwelling filaments and Ekman transport export particulate and dissolved organic matter from the coastal upwelling to the open ocean.…”

Section: Distribution Of Biological Sources and Sinksmentioning

confidence: 99%

“…Alonso-González et al (2009) used a box model approach to calculate the lateral transport and consumption of suspended particulate organic matter (POC) in the Canary Current region. They found that lateral POC fluxes, which were up to 3 orders of magnitude higher than vertical fluxes, accounted for 1.42 mmol C m −2 d −1 , what represents 28-59 % of the total mesopelagic (100-700 m) respiration.…”

Section: Remineralization Ratesmentioning

confidence: 99%

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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Lateral POC transport and consumption in surface and deep waters of the Canary Current region: A box model study

Cited by 50 publications

References 77 publications

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

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

On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

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

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