scholarly journals Vertical Mixing Derived from Surface Chlorophyll-a Concentrations of the North Atlantic Ocean

2016 ◽  
Vol 33 (10) ◽  
pp. 2165-2183
Author(s):  
Lisa Hahn-Woernle ◽  
Henk A. Dijkstra ◽  
Hans J. van der Woerd
Keyword(s):  
Turbulence Model ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Vertical Mixing ◽  
Satellite Observations ◽  
The North ◽  
Model Parameterization ◽  
Standard Configuration ◽  
Eastern North Atlantic ◽  
Calibration Techniques

AbstractVertical mixing is thought to play an essential role in phytoplankton blooms, yet measurements of mixing properties are very sparse. This paper presents a methodology to estimate profiles of the upper-ocean vertical mixing from satellite color observations, using a coupled turbulence–phytoplankton model and data assimilation–based calibration techniques. The method is tested at a location in the eastern North Atlantic for which an integrated set of observations (vertical mixing, phytoplankton, nutrients) is available. Results of identical twin experiments show that the method is very robust and achieves accurate turbulence model parameter calibrations even with noisy or sparsely sampled observations. The application of surface chlorophyll-a (Chl a) concentration to MODIS Aqua satellite observations leads two independent cases (data for the years 2009 and 2011) to a calibration of the model parameterization that produces weaker winter mixing compared to the standard configuration. As a consequence of the weaker mixing, the timing and intensity of increased surface Chl a satellite observations in spring and summer was reproduced by the model. Moreover, the weaker mixing resembles the in situ observations of vertical mixing better than the stronger mixing based on the standard configuration. This shows that the new calibration indeed improves the performance of the turbulence model.

scholarly journals Prochlorococcus Ecotype Abundances in the North Atlantic Ocean As Revealed by an Improved Quantitative PCR Method

2006 ◽  
Vol 72 (1) ◽  
pp. 723-732 ◽  
Author(s):  
Erik R. Zinser ◽  
Allison Coe ◽  
Zackary I. Johnson ◽  
Adam C. Martiny ◽  
Nicholas J. Fuller ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Quantitative Pcr ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Culture Collections ◽  
The North ◽  
Field Samples ◽  
Pcr Method ◽  
Probe Hybridization ◽  
Eastern North Atlantic

ABSTRACT The cyanobacterium Prochlorococcus numerically dominates the photosynthetic community in the tropical and subtropical regions of the world's oceans. Six evolutionary lineages of Prochlorococcus have been described, and their distinctive physiologies and genomes indicate that these lineages are “ecotypes” and should have different oceanic distributions. Two methods recently developed to quantify these ecotypes in the field, probe hybridization and quantitative PCR (QPCR), have shown that this is indeed the case. To facilitate a global investigation of these ecotypes, we modified our QPCR protocol to significantly increase its speed, sensitivity, and accessibility and validated the method in the western and eastern North Atlantic Ocean. We showed that all six ecotypes had distinct distributions that varied with depth and location, and, with the exception of the deeper waters at the western North Atlantic site, the total Prochlorococcus counts determined by QPCR matched the total counts measured by flow cytometry. Clone library analyses of the deeper western North Atlantic waters revealed ecotypes that are not represented in the culture collections with which the QPCR primers were designed, explaining this discrepancy. Finally, similar patterns of relative ecotype abundance were obtained in QPCR and probe hybridization analyses of the same field samples, which could allow comparisons between studies.

scholarly journals The silicon stable isotope distribution along the GEOVIDE section (GEOTRACES GA-01) of the North Atlantic Ocean

2018 ◽  
Vol 15 (18) ◽  
pp. 5663-5676 ◽  
Author(s):  
Jill N. Sutton ◽  
Gregory F. de Souza ◽  
Maribel I. García-Ibáñez ◽  
Christina L. De La Rocha
Keyword(s):  
Stable Isotope ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
North Atlantic Ocean ◽  
Water Masses ◽  
Labrador Sea ◽  
The North ◽  
The North Atlantic ◽  
Eastern North Atlantic

Abstract. The stable isotope composition of dissolved silicon in seawater (δ30SiDSi) was examined at 10 stations along the GEOVIDE section (GEOTRACES GA-01), spanning the North Atlantic Ocean (40–60∘ N) and Labrador Sea. Variations in δ30SiDSi below 500 m were closely tied to the distribution of water masses. Higher δ30SiDSi values are associated with intermediate and deep water masses of northern Atlantic or Arctic Ocean origin, whilst lower δ30SiDSi values are associated with DSi-rich waters sourced ultimately from the Southern Ocean. Correspondingly, the lowest δ30SiDSi values were observed in the deep and abyssal eastern North Atlantic, where dense southern-sourced waters dominate. The extent to which the spreading of water masses influences the δ30SiDSi distribution is marked clearly by Labrador Sea Water (LSW), whose high δ30SiDSi signature is visible not only within its region of formation within the Labrador and Irminger seas, but also throughout the mid-depth western and eastern North Atlantic Ocean. Both δ30SiDSi and hydrographic parameters document the circulation of LSW into the eastern North Atlantic, where it overlies southern-sourced Lower Deep Water. The GEOVIDE δ30SiDSi distribution thus provides a clear view of the direct interaction between subpolar/polar water masses of northern and southern origin, and allow examination of the extent to which these far-field signals influence the local δ30SiDSi distribution.

scholarly journals Factors affecting the distribution of silicate in the North Atlantic Ocean and the formation of North Atlantic deep water

1952 ◽  
Vol 30 (3) ◽  
pp. 511-526 ◽  
Author(s):  
L. H. N. Cooper
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
North Atlantic Ocean ◽  
Phosphorus Compounds ◽  
Mixing Processes ◽  
Factors Affecting ◽  
The North ◽  
Deep Waters ◽  
Eastern North Atlantic ◽  
Straight Lines

In the deep water of the eastern North Atlantic below 2000 m. the variations with depth of salinity, temperature, density, oxygen, phosphorus compounds and nitrate are quite small. By contrast the silicate content is doubled in a descent from 2000 to 4000 m.The distinctive behaviour of silicate is revealed by diagrams (Fig. I) relating it to salinity, temperature, density and total phosphorus at station 2659 worked by R.R.S. Discovery II on 12 May 1950 (Armstrong, 1951; Cooper 1952, Table IV). The temperature-salinity diagram (Cooper, 1952, fig. 15, to 1500 m. only) suggests that between 1200 and 2000 m. we have to deal with simple mixing of the mean Gulf of Gibraltar and North Atlantic Deep waters. If silicate concentration were subject only to mixing processes the curves in Fig. I between these depths would be straight lines. They are not—consequently it would seem that solution of either particulate silica or of aluminosilicates may be occurring. As yet, clear interpretation is not possible. At least five hypotheses may be erected to explain, in whole or in. part, the observed distribution: (i) solution of bottom deposits; (ii) solution of ‘clay’ and of silica in suspension; (iii) concentration by vertical partition; (iv) tundra drainage; (v) sinking of surface water. These are examined in turn.

scholarly journals On the 14C to Tritium Relationship in the North Atlantic Ocean

Radiocarbon ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 636-646 ◽  
Author(s):  
Wolfgang Roether ◽  
Karl-Otto Münnich ◽  
Hildegard Schoch
Keyword(s):  
Surface Water ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Vertical Mixing ◽  
Tritium Concentration ◽  
Time Curve ◽  
The North ◽  
Northern Latitudes ◽  
The North Atlantic ◽  
Relationship Of

Nuclear-weapon produced 14C (or bomb 14C) in the ocean can be traced by simultaneous tritium observations. Data are presented on the general relationship of bomb 14C and tritium in the North Atlantic. For the period 1965 to 1973, the excess 14C to tritium ratios in the surface water vary, systematically, over a factor of 10: the ratios monotonically increase with time, and decrease with latitude, particularly so for the later observations. The sub-surface water ratios show that the mid- and low-latitude water below about the 15° C isothermal horizon (~500m depth) originates from higher northern latitudes, rather than being renewed by local vertical mixing. It is further shown that in the North Atlantic, bomb 14C did not penetrate beyond the horizon where the presently observed 14C concentration is Δ14C = —75‰. Observed concentrations up to about —40‰ can be corrected for a bomb contribution if the tritium concentration is known because the bomb 14C to tritium concentration ratio is rather uniform in this range. A surface water 14C concentration versus time curve is presented for the period since 1957. This curve is based on a North Atlantic mixing model and is fitted to the 14C observations. Making use of a previously published tritium versus time curve obtained by the same model, a time curve for the average excess 14C to tritium ratio in North Atlantic surface water is given. This curve reproduces the observations well. The presented data and theoretical curves show the usefulness of simultaneous 14C and tritium observations for mixing studies and to provide corrections for bomb 14C in sub-surface 14C data in the North Atlantic.

scholarly journals Changes in the CFC Inventories and Formation Rates of Upper Labrador Sea Water, 1997–2001

2006 ◽  
Vol 36 (1) ◽  
pp. 64-86 ◽  
Author(s):  
Dagmar Kieke ◽  
Monika Rhein ◽  
Lothar Stramma ◽  
William M. Smethie ◽  
Deborah A. LeBel ◽  
...  
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Sea Water ◽  
North Atlantic Ocean ◽  
Formation Rate ◽  
Labrador Sea ◽  
The North ◽  
The Mean ◽  
Eastern North Atlantic ◽  
Labrador Sea Water

Abstract Chlorofluorocarbon (component CFC-11) and hydrographic data from 1997, 1999, and 2001 are presented to track the large-scale spreading of the Upper Labrador Sea Water (ULSW) in the subpolar gyre of the North Atlantic Ocean. ULSW is CFC rich and comparatively low in salinity. It is located on top of the denser “classical” Labrador Sea Water (LSW), defined in the density range σΘ = 27.68–27.74 kg m−3. It follows spreading pathways similar to LSW and has entered the eastern North Atlantic. Despite data gaps, the CFC-11 inventories of ULSW in the subpolar North Atlantic (40°–65°N) could be estimated within 11%. The inventory increased from 6.0 ± 0.6 million moles in 1997 to 8.1 ± 0.6 million moles in 1999 and to 9.5 ± 0.6 million moles in 2001. CFC-11 inventory estimates were used to determine ULSW formation rates for different periods. For 1970–97, the mean formation rate resulted in 3.2–3.3 Sv (Sv ≡ 106 m3 s−1). To obtain this estimate, 5.0 million moles of CFC-11 located in 1997 in the ULSW in the subtropical/tropical Atlantic were added to the inventory of the subpolar North Atlantic. An estimate of the mean combined ULSW/LSW formation rate for the same period gave 7.6–8.9 Sv. For the years 1998–99, the ULSW formation rate solely based on the subpolar North Atlantic CFC-11 inventories yielded 6.9–9.2 Sv. At this time, the lack of classical LSW formation was almost compensated for by the strongly pronounced ULSW formation. Indications are presented that the convection area needed in 1998–99 to form this amount of ULSW exceeded the available area in the Labrador Sea. The Irminger Sea might be considered as an additional region favoring ULSW formation. In 2000–01, ULSW formation weakened to 3.3–4.7 Sv. Time series of layer thickness based on historical data indicate that there exists considerable variability of ULSW and classical LSW formation on decadal scales.

scholarly journals Multi-Iteration Approach to Studying Tracer Spreading Using Drifter Data

2017 ◽  
Vol 47 (2) ◽  
pp. 339-351 ◽  
Author(s):  
Irina I. Rypina ◽  
David Fertitta ◽  
Alison Macdonald ◽  
Sachiko Yoshida ◽  
Steven Jayne
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Irish Sea ◽  
Travel Times ◽  
Tracer Transport ◽  
Mean Flow ◽  
Transport Pathways ◽  
The North ◽  
Geographical Regions ◽  
Eastern North Atlantic

AbstractA novel multi-iteration statistical method for studying tracer spreading using drifter data is introduced. The approach allows for the best use of the available drifter data by making use of a simple iterative procedure, which results in the statistically probable map showing the likelihood that a tracer released at some source location would visit different geographical regions, along with the associated arrival travel times. The technique is tested using real drifter data in the North Atlantic. Two examples are considered corresponding to sources in the western and eastern North Atlantic Ocean, that is, Massachusetts Bay–like and Irish Sea–like sources, respectively. In both examples, the method worked well in estimating the statistics of the tracer transport pathways and travel times throughout the entire North Atlantic. The role of eddies versus mean flow is quantified using the same technique, and eddies are shown to significantly broaden the spread of a tracer. The sensitivity of the results to the size of the source domain is investigated and causes for this sensitivity are discussed.

scholarly journals <i>Syracosphaera noroiticus</i> sp. nov., and <i>S. marginaporata</i> sp. nov., (Syracosphaeraceae, Prymnesiophyta), new coccolithophorids from the Mediterranean Sea and North Atlantic Ocean

1993 ◽  
Vol 12 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Michael Knappertsbusch
Keyword(s):  
Atlantic Ocean ◽  
Mediterranean Sea ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Undescribed Species ◽  
The North ◽  
The North Atlantic ◽  
The Mediterranean ◽  
Eastern North Atlantic ◽  
Scanning Electron

Abstract. During scanning electron microscope investigations of living coccolithophorids from the Mediterranean Sea and the North Atlantic Ocean, two hitherto undescribed species of the genus Syracosphaera Lohmann, 1902 emend. Gaarder (in Gaarder and Heimdal, 1977) were found. The first species, Syracosphaera noroiticus sp. nov., was recorded in the Gulf of Lyons (Mediterranean Sea), and the second, S. marginaporata sp. nov., was found in the eastern North Atlantic.

scholarly journals Vertical and Lateral Mixing Processes Deduced from the Mediterranean Water Signature in the North Atlantic

2008 ◽  
Vol 38 (1) ◽  
pp. 164-176 ◽  
Author(s):  
Jan D. Zika ◽  
Trevor J. McDougall
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Vertical Mixing ◽  
Vertical Direction ◽  
Simple Relation ◽  
Mixing Processes ◽  
The North ◽  
Lateral Mixing ◽  
The North Atlantic ◽  
Mediterranean Water

Abstract The conservation equations of heat, salt, and mass are combined in such a way that a simple relation is found between the known volume flux of Mediterranean Water entering the North Atlantic Ocean and the effects of lateral and vertical mixing processes. The method is a form of inverse method in which the only unknowns are the vertical and lateral diffusivities. For each isohaline contour on each neutral density surface the authors develop one equation in two unknowns, arguing that other terms that cannot be evaluated are small. By considering several such isohaline contours, the method becomes overdetermined for each density layer, and results are found for both the vertical and lateral diffusivity that vary smoothly in the vertical direction, giving some confidence in the method.

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