scholarly journals A model of Fe speciation and biogeochemistry at the Tropical Eastern North Atlantic Time-Series Observatory site

2009 ◽  
Vol 6 (10) ◽  
pp. 2041-2061 ◽  
Author(s):  
Y. Ye ◽  
C. Völker ◽  
D. A. Wolf-Gladrow
Keyword(s):  
Time Series ◽  
Vertical Distribution ◽  
North Atlantic ◽  
Decay Time ◽  
Particle Aggregation ◽  
Dust Particles ◽  
Dimensional Model ◽  
One Dimensional ◽  
Fe Speciation ◽  
Eastern North Atlantic

Abstract. A one-dimensional model of Fe speciation and biogeochemistry, coupled with the General Ocean Turbulence Model (GOTM) and a NPZD-type ecosystem model, is applied for the Tropical Eastern North Atlantic Time-Series Observatory (TENATSO) site. Among diverse processes affecting Fe speciation, this study is focusing on investigating the role of dust particles in removing dissolved iron (DFe) by a more complex description of particle aggregation and sinking, and explaining the abundance of organic Fe-binding ligands by modelling their origin and fate. The vertical distribution of different particle classes in the model shows high sensitivity to changing aggregation rates. Using the aggregation rates from the sensitivity study in this work, modelled particle fluxes are close to observations, with dust particles dominating near the surface and aggregates deeper in the water column. POC export at 1000 m is a little higher than regional sediment trap measurements, suggesting further improvement of modelling particle aggregation, sinking or remineralisation. Modelled strong ligands have a high abundance near the surface and decline rapidly below the deep chlorophyll maximum, showing qualitative similarity to observations. Without production of strong ligands, phytoplankton concentration falls to 0 within the first 2 years in the model integration, caused by strong Fe-limitation. A nudging of total weak ligands towards a constant value is required for reproducing the observed nutrient-like profiles, assuming a decay time of 7 years for weak ligands. This indicates that weak ligands have a longer decay time and therefore cannot be modelled adequately in a one-dimensional model. The modelled DFe profile is strongly influenced by particle concentration and vertical distribution, because the most important removal of DFe in deeper waters is colloid formation and aggregation. Redissolution of particulate iron is required to reproduce an observed DFe profile at TENATSO site. Assuming colloidal iron is mainly composed of inorganic colloids, the modelled colloidal to soluble iron ratio is lower that observations, indicating the importance of organic colloids.

scholarly journals Impact of dust deposition on Fe biogeochemistry at the Tropical Eastern North Atlantic Time-series Observatory site

2009 ◽  
Vol 6 (2) ◽  
pp. 4305-4359 ◽  
Author(s):  
Y. Ye ◽  
C. Völker ◽  
D. A. Wolf-Gladrow
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Organic Ligands ◽  
Particle Aggregation ◽  
Dust Particles ◽  
Dust Deposition ◽  
Colloidal Iron ◽  
Inorganic Particles ◽  
Dissolved Iron ◽  
Eastern North Atlantic

Abstract. A one-dimensional model of iron speciation and biogeochemistry, coupled with the General Ocean Turbulence Model (GOTM) and a NPZD-type ecosystem model, is applied for the Tropical Eastern North Atlantic Time-series Observatory (TENATSO) site. Aimed at investigating the role of organic complexation and dust particles in Fe speciation and bioavailability, the model is extended in this study by a more complex description of the origin and fate of organic ligands and of particle aggregation and sinking. Model results show that the profile of dissolved iron is strongly influenced by the abundance of organic ligands. Modelled processes controlling the source and fate of ligands can well explain the abundance of strong ligands. However, a restoring of total weak ligands towards a constant value is required for reproducing the observed nutrient-like profile of weak ligands, indicating that decay time of weak ligands might be too long for a 1d-model. High dust deposition brings not only considerable input of iron into surface waters but also fine inorganic particles for particle aggregation and Fe scavenging. Simulated profiles of dissolved iron show high sensitivity to re-dissolution of colloidal and particulate iron. The colloidal to soluble iron ratio is underestimated assuming that colloidal iron is mainly composed of inorganic colloids. That strongly argues for introducing organic colloids into the model in future work.

The Vertical Distribution of Pelagic Decapods [Crustacea: Natantia] Collected on the Sond Cruise 1965 I. The Caridea

1970 ◽  
Vol 50 (4) ◽  
pp. 939-960 ◽  
Author(s):  
P. Foxton
Keyword(s):  
Vertical Distribution ◽  
Canary Islands ◽  
North Atlantic ◽  
Depth Range ◽  
Main Interest ◽  
Acoustic Characteristics ◽  
Biological Collections ◽  
Eastern North Atlantic ◽  
The Vertical Distribution ◽  
Principal Elements

This study forms a contribution to a series (Angel, 1969; Clarke, 1969; Baker, 1970; Badcock, 1970) describing the biological results of a detailed investigation of the ecology of an oceanic area located in the eastern North Atlantic, close to the island of Fuerteventura (Canary Islands). The scientific background and objectives of the investigation, conducted during September to December 1965, have been described elsewhere (Currie, Boden & Kampa, 1969). Our main interest lay in the biological composition and acoustic characteristics of sonic scattering layers, and it was therefore considered essential to sample the principal elements of the pelagic fauna within the depth range 0–1000 m in as quantitative and detailed a manner as was technically possible. The resulting biological collections represent a unique body of material, the analysis of which is directly pertinent to the vertical distribution, diurnal migration and ecological interrelationships of the mesopelagic fauna.

Observations on the Vertical Distribution of the Genus Acanthephyra (Crustacea: Decapoda) in the eastern North Atlantic, with particular reference to Species of the ‘purpurea’ Group.

1972 ◽  
Vol 73 ◽  
pp. 301-313 ◽  
Author(s):  
P. Foxton
Keyword(s):  
Vertical Distribution ◽  
North Atlantic ◽  
South Atlantic ◽  
The North ◽  
Mesopelagic Zone ◽  
Vertical Distributions ◽  
The North Atlantic ◽  
Eastern North Atlantic ◽  
The Vertical Distribution ◽  
Mesopelagic Species

SynopsisThe vertical distribution of pelagic decapods has been investigated at six positions, each located approximately at 10° interval of latitude between 11°N and 60°N in the eastern North Atlantic. An account of the day and night depth distribution of four mesopelagic species, Acanthephyra purpurea, A. pelagica, A. sexspinosa and A. acanthitelsonis, and four bathypelagic species, A. prionota, A. curtirostris, A. acutifrons and A. stylorostratis, is presented. The four mesopelagic species have vertical distributions which vary latitudinally in association with geographical gradients in temperature, the mesopelagic zone from about the latitude of 28°N cooling both polewards and equatorwards. It is concluded that environmental temperature is a major factor in controlling the vertical ranges of these species although other physical variables, principally light, must also be involved.A faunal boundary exists in the region of 18°N, where the North Atlantic species A. purpurea and A.pelagica are replaced by the Central and South Atlantic species A. sexspinosa and A. acanthitelsonis. The nature of the physical boundary is not clear, but it is tentatively proposed that it represents a relatively broad area where the North Atlantic Central Water and South Atlantic Central Water meet.

scholarly journals The seasonal vertical distribution of the Saharan Air Layer and its modulation by the wind

2013 ◽  
Vol 13 (22) ◽  
pp. 11235-11257 ◽  
Author(s):  
C. Tsamalis ◽  
A. Chédin ◽  
J. Pelon ◽  
V. Capelle
Keyword(s):  
South America ◽  
Vertical Distribution ◽  
North Atlantic ◽  
Deposition Velocity ◽  
Dust Particles ◽  
Dust Aerosols ◽  
Saharan Air Layer ◽  
Western Africa ◽  
The North ◽  
The North Atlantic

Abstract. The Saharan Air Layer (SAL) influences large-scale environment from western Africa to eastern tropical Americas, by carrying large amounts of dust aerosols. However, the vertical distribution of the SAL is not well established due to a lack of systematic measurements away from the continents. This can be overcome by using the observations of the spaceborne lidar CALIOP onboard the satellite CALIPSO. By taking advantage of CALIOP's capability to distinguish dust aerosols from other types of aerosols through depolarization, the seasonal vertical distribution of the SAL is analyzed at 1° horizontal resolution over a period of 5 yr (June 2006–May 2011). This study shows that SAL can be identified all year round displaying a clear seasonal cycle. It occurs higher in altitude and more northern in latitude during summer than during winter, but with similar latitudinal extent near Africa for the four seasons. The south border of the SAL is determined by the Intertropical Convergence Zone (ITCZ), which either prohibits dust layers from penetrating it or reduces significantly the number of dust layers seen within or south of it, as over the eastern tropical Atlantic. Spatially, near Africa, it is found between 5° S and 15° N in winter and 5–30° N in summer. Towards the Americas (50° W), SAL is observed between 5° S and 10° N in winter and 10–25° N in summer. During spring and fall, SAL is found between the position of winter and summer not only spatially but also vertically. In winter, SAL occurs in the altitude range 0–3 km off western Africa, decreasing to 0–2 km close to South America. During summer, SAL is found to be thicker and higher near Africa at 1–5 km, reducing to 0–2 km in the Gulf of Mexico, farther west than during the other seasons. SAL is confined to one layer, of which the mean altitude decreases with westward transport by 13 m deg−1 during winter and 28 m deg−1, after 30° W, during summer. Its mean geometrical thickness decreases by 25 m deg−1 in winter and 9 m deg−1 in summer. Spring and fall present similar characteristics for both mean altitude and geometrical thickness. Wind plays a major role not only for the transport of dust within the SAL but also by sculpting it. During winter, the trade winds transport SAL towards South America, while in spring and summer they bring dust-free maritime air masses mainly from the North Atlantic up to about 50° W below the SAL. The North Atlantic westerlies, with their southern border occurring between 15 and 30° N (depending on the season, the longitude and the altitude), prevent the SAL from developing further northward. In addition, their southward shift with altitude gives SAL its characteristic oval shape in the northern part. The effective dry deposition velocity of dust particles is estimated to be 0.07 cm s−1 in winter, 0.14 cm s−1 in spring, 0.2 cm s−1 in summer and 0.11 cm s−1 in fall. Finally, the African Easterly Jet (AEJ) is observed to collocate with the maximum dust load of the SAL, and this might promote the differential advection for SAL parts, especially during summer.

The Vertical Distribution of Pelagic Decapods [Crustacea: Natantia] Collected on the Sond Cruise 1965 II. The Penaeidea and General Discussion

1970 ◽  
Vol 50 (4) ◽  
pp. 961-1000 ◽  
Author(s):  
P. Foxton
Keyword(s):  
Vertical Distribution ◽  
North Atlantic ◽  
Depth Distribution ◽  
Final Part ◽  
Decapod Crustaceans ◽  
Eastern North Atlantic ◽  
And Migration ◽  
The Vertical Distribution ◽  
Diurnal Migration

This paper represents the second and final part of a study of the depth distribution and diurnal migration of pelagic decapod crustaceans in an area of the eastern North Atlantic. Part I (Foxton, 1970) dealt with the Caridea; Part II now considers the Penaeidea. In the discussion the data as a whole are analysed and the resulting patterns of vertical distribution and migration discussed.

scholarly journals Seasonality of intermediate waters hydrography west of the Iberian Peninsula from an 8 yr semiannual time series of an oceanographic section

Ocean Science ◽  
2013 ◽  
Vol 9 (2) ◽  
pp. 411-429 ◽  
Author(s):  
E. Prieto ◽  
C. González-Pola ◽  
A. Lavín ◽  
R. F. Sánchez ◽  
M. Ruiz-Villarreal
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Large Scale ◽  
Seasonal Migration ◽  
Ekman Transport ◽  
Wind Stress Curl ◽  
Pressure System ◽  
Vertical Displacements ◽  
Eastern North Atlantic ◽  
Mediterranean Water

Abstract. Seasonality of hydrographical properties at depth in the western Iberian margin (eastern North Atlantic) is analysed from a 2003–2010 time series of a semiannual oceanographic section extending ∼200 nm off Cape Finisterre (43° N). All water masses down to the permanent thermocline (2000 dbar) show a consistent seasonal signature in their thermohaline properties and there is a notable asymmetry between the slope region and the outer ocean (in the surroundings of the Galicia Bank). There is overall cooling and freshening of eastern North Atlantic central waters in summertime, which is larger and deeper-reaching on the slope. In summertime, Mediterranean Water (MW) gets tightly attached against the slope and is uplifted, reinforcing its thermohaline signature and diminishing its presence at the outer ocean. In wintertime the situation reverses, MW seems to detach from the slope and spreads out to the open ocean, even being observed a secondary branch around the Galicia Bank. Thermohaline seasonality at depth shows values up to 0.4 °C and 0.08 in salinity at the lower MW, of the order of 20% of the overall interannual variability observed during the whole period. Decomposition of thermohaline changes at isobaric levels to changes along isoneutral surfaces and changes due to vertical displacements help analyse the physical processes behind the observed seasonality in terms of (1) the large-scale seasonality of the subtropical gyre in response to the seasonal migration of the subtropical high pressure system and subsequent anomalies in Ekman transport and wind stress curl, (2) the continental slope dynamics, characterized by summer upwelling, winter development of the Iberian Poleward Current and Mediterranean water spreading, and (3) the possible influence of seasonal changes of water mass properties at their formation sources.

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