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  • AMS (American Meteorological Society)  (22)
  • Springer  (11)
  • Alfred Wegener Institute for Polar and Marine Research  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Trends in Atlantic equatorial current variability (1987)
    Springer
    Ocean dynamics 40 (1987), S. 261-276 
    Details
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Es werden zweimonatliche Bathythermographenschnitte zwischen Europa und Brasilien vom September 1980 bis Mai 1984 vorgestellt. Die Daten werden zur Darstellung eines mehrjährigen Trends im oberflächennahen äquatorialen Stromsystem verwandt, welches senkrecht zu den Schnitten liegt. Unter Ausnutzung einer mittleren Temperatur-Salzgehaltsbeziehung werden die Temperaturprofile in Dichteprofile überführt. Aus diesen wird die dynamische Tiefe (0/300 dbar) errechnet. In Äquatornähe wird eine rechnerische Näherung für die geostrophischen Ströme verwandt. Ferner wird ein Spline-Interpolationsverfahren für die raumzeitliche Herleitung der quasi-meridionalen Strömungsverteilung genutzt. Das äquatoriale Stromsystem wird als eine Zeitserie der dynamischen Tiefe und der geostrophischen Ströme dargestellt.
    Abstract: Résumé Des coupes thermiques au moyen de Bathythermographes à tête perdue (XBT) entre l'Europe et le Brésil environ deux fois par mois de septembre 1980 à mai 1984 sont utilisées pour caracteriser des tendances dans les courants géostrophiques équatoriaux perpendiculaires à ces coupes. Les profils de température dans les couches superficielles sont convertis en profils de densité au moyen de relations temperature-salinité moyennes, et permettent de calculer la hauteur dynamique 0/300 db. Après interpolation (spline) dans le temps et l'espace, on obtient une série spatio-temporelle, présentée sous la forme de cartes trimestrielles de hauteurs dynamiques et de courants géostrophiques.
    Notes: Summary Approximately twice-monthly expendable bathythermograph (XBT) sections between Europe and Brazil, are used to characterize trends in the equatorial geostrophic surface currents orthogonal to the sections between September, 1980 and May, 1984. Using mean temperature-salinity relationships the upper layer temperature profiles are converted to density and used to compute 0/300 db dynamic height. Applying a second derivative method, at and near the equator, geostrophic surface currents are computed along each quasimeridional XBT section and time/space series of the equatorial currents are developed using spline interpolations in both time and space. Equatorial currents are mapped as time series of dynamic height and geostrophic current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02226280
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On simultaneous measurements with rotor, wing and acoustic current meters, moored in shallow water (1980)
    Springer
    Ocean dynamics 33 (1980), S. 1-18 
    Details
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung In zwei benachbarten Verankerungen waren in der Kieler Bucht vier verschiedene Strommessertypen 22 Tage lang verankert. Es handelte sich um zwei Rotorstrommesser vom Typ Aanderaa und VACM (vektormittelnder Strommesser), einen akustischen Strommesser nach Gytre sowie um einen Pendelstrommesser nach Niskin. Das VACM-Gerät mit Auftrieb in 7 m Tiefe wurde als Bezugsinstrument verwendet. Während der ersten 17 Tage befand sich der Auftrieb der zweiten Verankerung in 5 m Tiefe. Um die Verankerung den Oberflächenwellen auszusetzen, wurde der Auftrieb während der letzten 5 Tage auf 2,7 m Tiefe verlegt. Der Niskin-Flügelstrommesser wurde am meisten von der welleninduzierten Verankerungsbewegung beeinflußt. Das Gytre-Instrument zeigte den geringsten Oberflächenwelleneffekt. Die Vektorvarianz dieses Gerätes an der oberflächenbeeinflußten Verankerung in 7,4 m Tiefe war ungefähr dieselbe wie diejenige des VACM-Gerätes auf 10 m Tiefe in der Bezugsverankerung.
    Abstract: Résumé Sur deux sites très voisins de la Baie de Kiel, quatre courantomètres de types différents ont été mouillés pendant 22 jours: Deux à rotor (Aanderaa et à «intégration vectorielle» (VACM)), un acoustique (conçu par Gytre) et un à ailettes (conçu par Niskin). Le courantomètre VACM fut utilisé sur le premier site comme instrument de référence avec une immersion de 7 m. Sur le second site, l'immersion a été de 5 m pendant les 17 premiers jours de l'expérience mais ramenée à 2,7 m dans les 5 derniers jours pour rendre les mouillages plus sensibles aux mouvements de surface. Le courantomètre à ailettes Niskin se révèla le plus sensible aux effets dûs à la houle. Le Gytre se montra le moins sensible à ces mouvements. Les fluctuations de cet instrument à l'immersion 7,4 m étaient à peu près égales à celles du VACM à 10 m, sur le site de référence.
    Notes: Summary In two closely spaced moorings in the Kiel Bight, four different current meterstwo rotor current meters (Aanderaa and Vector averaging), an acoustic current meter (designed by Gytre), and a pendulum current meter (designed by Niskin) were moored for 22 days. The Vector averaging current meter (VACM) was used as reference instrument on one mooring with the floatation at 7 m depth. The floatation of the second mooring was at 5 m depth in the first 17 days of the experiment, but in 2.7 m depth in the last 5 days to make their mooring more effected by surface waves. The Niskin wing current meter was most effected by wave-induced mooring motion. The Gytre instrument showed the smallest surface-wave effects. The vector variances of this instrument in 7.4 m depth on the surface-wave effected mooring and those of the VACM in 10 m depth on the reference mooring were about equal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02225955
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Some XBT-observations on the thermal structure of theWarmwassersphäre in equatorial and lower latitudes of the eastern Atlantic (1982)
    Springer
    Ocean dynamics 35 (1982), S. 73-81 
    Details
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zussaenfassung Im November 1980 und März 1981 wurden auf Versorgungsfahrten zur Antarktis zwei lange XBT-Schnitte gewonnen. Sie verlaufen zwischen der Iberischen Halbinsel und dem äquatorialen brasilianischen Schelf beziehungsweise der Kapregion von Südafrika. Die meisten Sonden reichten bis zu einer Meßtiefe von 800 m, so daß Aussagen zur thermischen Schichtung und horizontalen Gliederung der Warmwassersphäre im offenen Ozean möglich wurden. Wir vergleichen unsere neuen Daten mit einer Reihe von früher gewonnenen Schnitten. Als Ergebnis erhalten wir fünf unterschiedliche hydrographische Regionen. Zone 1 ist gekennzeichnet durch den klaren Einfluß des Mittelmeerausstromes, der an der Unterseite der Warmwassersphäre westlich Portugals unterhalb von 300 m nahezu thermostatische Bedingungen schafft. Die anschließende Zone 2 ist identisch mit der Subtropenkonvergenz, innerhalb derer die Warmwasserphäre ihre Maximaltiefe (15-°C-Isotherme bei etwa 300 m) erreicht. Die äquatoriale Region nennen wir Zone 3. Es wird eine überarbeitete Darstellung der Strömungs- und Temperaturschichtungsverhältnisse dieser Region gegeben. Die Zone 4 ist durch den Benguela Strom und seine nördlichen Ausläufer geprägt. In der letzten Zone 5 wird der Einfluß des Agulhas-Strom-Ausläufers auf die Schichtung vorgestellt.
    Abstract: Résumé En novembre 1980 et mars 1981 on a obtenu deux longues sections XBT pendant des voyages d'approvisionnement à l'Antarctique. Les sections passent entre la péninsule Ibérique et le plateau équatorial brasilien et entre la péninsule Ibérique et la région du Cap de l'Afrique du Sud respectivement. La plupart des sondes descendaient jusqu' à 800 m, ce qui a permis d'obtenir des renseignements sur la stratification thermique et la structure horizontale de laWarmwassersphäre en haute mer. Nous avons comparé nos nouvelles données avec une série de sections obtenues plus tôt. Nous en avons obtanu comme résultat cinq zones hydrographiques. La zone 1 est caractérisée par l'influence évidente du courant profond de la Méditerranée sur la côté inférieure de laWarmwassersphäre, ce qui crée des conditions presque thermostatiques aux profondeurs excédant 300 m à l'ouest du Portugal. La zone 2 adjacente est identique à la convergence subtropicale, où laWarmwassersphäre atteint sa profondeur maximale (isotherme de 15°C à environ 300 m). Nous désignons la région équatoriale la zone 3, et nous présentons un schéma révisé des systèmes des courants et des stratifications thermiques de cette zone. La zone 4 est marquée par le courant Benguela et son extension vers le nord. Dans la zone 5 nous présentons l'influence de l'extension du courant Agulhas sur la stratification.
    Notes: Summary Two megameter long XBT sections passing through the Atlantic between the Iberian Peninsula and the equatorial Brazilian shelf, and between the Peninsula and the Cape region of South Africa were obtained during supply cruises to the antarctic in November 1980 and March 1981. Most of the individual probes reached an observation depth of nearly 800 m allowing statements on the thermal stratification and zonation of theWarmwassersphäre in the open ocean. Our new data are compared with a number of earlier long sections. As a general result we identify five zones dividing different hydrographic regions. Zone 1 is characterized by the clear influence of the Mediternean Undercurrent on the lower boundary of theWarmwasserphäre creating nearly thermostatic conditions below 300 m off Portugal. The adjacent zone 2 is identical with the Subtropical Convergence, where theWarmwassersphäre reaches its maximum depth (15°C isotherm at about 300 m). We call the equatorial region zone 3 and present an improved scheme of its current system and its thermal stratification. Zone 4 is marked by the Benguela Current and its northern extension. In a final zone 5 we show the influence of the Agulhas Current extension on the stratification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02226270
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    Paper (German National Licenses)
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  • 4
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    Calculation of Salinity from Neutrally Buoyant RAFOS Floats (1995)
    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 12 (4). pp. 923-934.
    Details
    Publication Date: 2020-08-04
    Description: A method to derive salinity data from RAFOS float temperature and pressure measurements is described. It is based on evaluating the float's in situ density from its mechanical properties and in situ pressure and temperature data. The salinity of the surrounding water may then be determined, assuming that the float has reached equilibrium with its environment. This method, in comparison with the possible use of floatborne salinity cells, has the advantage of being both cost and energy neutral and highly stable in the long term. The effect on the estimated salinity of various parameters used in the determination of the float's in situ density is discussed. Results of seven RAFOS Boats deployed in the Brazil Basin are compared with corresponding CTD data to estimate the magnitude of these errors. At present, an accuracy of 0.3 psu is achieved. The accuracy may be improved to 0.02 psu by referring the float's calculated density to a reference density established by a CTD cast at the time of launch. Results from five floats deployed in the heterogeneous water masses of the Iberian Basin are compared with the corresponding CM casts to demonstrate the variability and interpretation of p-T-S float datasets from different areas.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0426(1995)012〈0923:COSFNB〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Large Lenses of Highly Saline Mediterranean Water (1984)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 14 (10). pp. 1560-1576.
    Details
    Publication Date: 2016-05-10
    Description: Isolated compact anticyclonic eddies or salt lenses were found in the Canary Basin. Hydrographic surveys of three such lenses show large anomalies of salinity and temperature (∼0.8, 2.5°C). They are centered at ∼1100 m, have a vertical extent of up to 900 m and radii of ∼50 km. Current meter records indicate anticyclonic velocities up to 29 cm s−1. Fine structure with vertical scales of ∼20 m and less, possibly due to intrusive decay, appears at the outer edges of the lenses whereas the centers are free of such structure. The probability of finding a salt lens at any station in the Canary Basin is fairly high (∼0.08).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(1984)014〈1560:LLOHSM〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    A Low-Cost Digital XBT System and its Application to the Real-Time Computation of Dynamic Height (1986)
    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 3 (1). pp. 75-83.
    Details
    Publication Date: 2016-05-10
    Description: An XBT interface is described for use with Commodore and other 6502 based microprocessors. This interface takes the form of a single circuit board mounted inside the microcomputer and is completely software controlled. The application of this digital XBT system to the real-time computation of density and dynamic height, using historical or recent temperature-salinity relationships, is also described. Comparison between XBT and CTD measured temperatures from the Northeast Atlantic yield a mean temperature difference of −0.08°C and an rms temperature difference of 0.33°C for the upper 800 m. Examples of dynamic topography maps and a temperature section computed using this technique are also presented and comparison between objectively analyzed XBT and CTD dynamic topographies demonstrates the reliability of the method for mapping the baroclinic flow.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0426(1986)003〈0075:ALCDXS〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    The Volunteer Observing Ship and Future Ocean Monitoring (1995)
    AMS (American Meteorological Society)
    In:  Bulletin of the American Meteorological Society, 76 (1). pp. 5-11.
    Details
    Publication Date: 2019-01-21
    Description: Widespread and sustained in situ ocean measurements are essential to an improved understanding of the state of the ocean and its role in global change. Merchant marine vessels can play a major role in ocean monitoring, yet apart from routine weather observations and upper-ocean temperature measurements, they constitute a vastly underutilized resource due to lack of suitable instrumentation. Examples of ways in which vessels can assist include profiling techniques of physical properties, chemical sampling via automated water samplers, optical techniques to measure various biological parameters, and ground truth measurements for remote sensing from orbiting and geostationary satellites. Further, ships can act as relays between subsurface instrumentation and satellite communication services. To take advantage of the opportunities that the maritime industry can provide, two steps must be taken. The first is to initiate an instrumentation development program with emphasis on techniques optimized for highly automated use onboard ships at 15-20-kt speeds. The second is to forge partnerships or links between academic and government laboratories and the maritime industry for the institution and maintenance of such monitoring programs. No doubt significant resources will be required, but in the long run the improved ability to monitor the state of ocean in situ will make the effort more than worthwhile.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0477(1995)076〈0005:TVOSAF〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    The Madeira Mode Water (1987)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 17 (10). pp. 1561-1570.
    Details
    Publication Date: 2020-08-04
    Description: Quasi-homogeneous layers in vertical profiles of temperature and salinity in the eastern North Atlantic near Madeira indicate the existence of a subtropical Mode Water in the Eastern Basin. Temperature sections show a maximum horizontal extent of at least 500 km. The frequency distribution analysis of homogeneous layers in a historical XBT dataset shows a Mode Water formation region near and to the north of Madeira. This Mode Water is found at increasing depths and displaced to the west and southwest during the course of the year after its formation by wintertime convection. It disappears almost completely, due to mixing, before the next winter. Volume estimates suggest that this Madeira Mode Water in the eastern Atlantic accounts for 15–20% of the total Central Water formation in the corresponding density range as obtained from tracer studies in the North Atlantic gyre.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(1987)017〈1561:TMMW〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    The float park: A new tool for a cost-effective collection of Lagrangian time-series with dual release RAFOS floats (2000)
    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 17 . pp. 1439-1443.
    Details
    Publication Date: 2020-08-04
    Description: The World Ocean Circulation Experiment has established Lagrangian observations with neutrally buoyant floats as a routine tool in the study of deep-sea currents. Here a novel variant of the well-proven RAFOS concept for seeding floats at locations where they can be triggered on a timed basis is introduced. This cost-effective method obviates the need to revisit sites with a high-priced research vessel each time floats are to be deployed. It enables multiple Lagrangian time series, for example, for the observation of intermediate point sources of water masses, which are independent but have identical start points. This can be done even in environmentally challenging regions such as below the ice. The successfully tested autonomous float park concept does not rely on a release carousel moored on the seafloor. Instead, a second release was added to the standard RAFOS float for optional delay of regular drift missions. A float park can easily be installed by a conductivity–temperature–depth recorder system with a slightly modified rosette sampler.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0426(2000)017〈1439:TFPANT〉2.0.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Changes in the CFC inventories and formation rates of upper Labrador Sea Water, 1997-2001 (2006)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 36 (1). pp. 64-86.
    Details
    Publication Date: 2018-04-11
    Description: 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.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/JPO2814.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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