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  • 2010-2014  (109)
  • 1995-1999  (11)
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  • 1
    In: Journal of geophysical research. C, Oceans, Hoboken, NJ : Wiley, 1978, 116(2011), 2169-9291
    In: volume:116
    In: year:2011
    Description / Table of Contents: There is an incomplete description of the middepth circulation and its link to the oxygen minimum zone (OMZ) in the eastern tropical South Pacific. Subsurface currents of the OMZ in the eastern tropical South Pacific are investigated with a focus at 400 m depth, close to the core of the OMZ, using several acoustic Doppler current profiler sections recorded in January and February 2009. Five profiling floats with oxygen sensors were deployed along 85°50′W in February 2009 with a drift depth at 400 m. Their spreading paths are compared with the model flow field from a 1/10° tropical Pacific model (TROPAC01) and the Simple Ocean Data Assimilation (SODA) model. Overall the mean currents in the eastern tropical South Pacific are weak so that eddy variability influences the flow and ultimately feeds oxygen-poor water to the OMZ. The center of the OMZ is a stagnant area so that floats stay much longer in this region and can even reverse direction. In one case, one float deployed at 8°S, returned to the same location after 15 months. On the northern side of the OMZ in the equatorial current system, floats move rapidly to the west. Most current bands reported for the near-surface layer exist also in the depth range of the OMZ. A schematic circulation flow field for the OMZ core depth is derived which shows the northern part of the South Pacific subtropical gyre south of the OMZ and the complicated zonal equatorial flow field north of the OMZ.
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 2169-9291
    Language: English
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  • 2
    Keywords: Hochschulschrift ; Indischer Ozean ; Thermische Sprungschicht ; Zirkulation
    Type of Medium: Online Resource
    Pages: 159 S , graph. Darst., Kt
    Edition: Elektronische Ausg. 1999
    Language: German
    Note: Hamburg, Univ., FB Geowiss., Diss., 1999
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  • 3
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (28 Seiten = 1,3 MB) , Illustrationen
    Language: German
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  • 4
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (43 Blatt = 4 MB)
    Language: English
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 5
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (35 Blatt = 8 MB) , Illustrationen
    Language: English
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 6
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 43 (4). pp. 805-823.
    Publication Date: 2018-04-12
    Description: Mesoscale anticyclonic eddies in the Irminger Sea are observed using a mooring and a glider. Between 2002 and 2009, the mooring observed 53 anticyclones. Using a kinematic model, objective estimates of eddy length scales and velocity structure are made for 16 eddies. Anticyclones had a mean core diameter of 12 km, and their mean peak observed azimuthal speed was 0.1 m s(-1). They had core salinities and potential temperatures of 34.91-34.98 and 4.488-5.34 degrees C, respectively, making them warm and salty features. These properties represent a typical salinity anomaly of 0.03 and a temperature anomaly of 0.28 degrees C from noneddy values. All eddies had small (〈〈 1) Rossby numbers. In 2006, the glider observed two anticyclones having diameters of about 20 km and peak azimuthal speeds of about 0.3 m s(-1). Similar salinity anomalies were detected throughout the Irminger Sea by floats profiling in anticyclones. Two formation regions for the eddies are identified: one to the west of the Reykjanes Ridge and the other off the East Greenland Irminger Current near Cape Farewell close to the mooring. Observations indicate that eddies formed in the former region are larger than eddies observed at the mooring. A clear increase in eddy salinity is observed between 2002 and 2009. The observed breakup of these eddies in winter implies that they are a source of salt for the central gyre. The anticyclones are similar to those found in both the Labrador Sea and Norwegian Sea, making them a ubiquitous feature of the subpolar North Atlantic basins.
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2019-05-23
    Description: Two consecutive summer upwelling events, each lasting for less than 24 h, were surveyed in high temporal and vertical resolution close to the Boknis Eck time-series station (BE) in the western Belt Sea (Baltic Sea) in summer 2010 with an autonomous glider. Driven only by moderate offshore winds both events resulted in more than 5 K cooling of surface waters, while only for the second event were significant irreversible changes in the vertical stratification observed. Generalizing the glider survey observations with hourly wind data from nearby meteorological stations, it is found that upwelling in the BE area occurs for wind directions between 190 to 260° and wind speed exceeding 4 m s−1. Based on these thresholds the wind-induced summer (June to September) upwelling conditions in the BE area for the period 1982 to 2012 are reconstructed. On average about 18 days of upwelling favourable wind conditions are found for the four summer months, with significant interannual variability ranging from 7.7 days (2006) to more than 28 days (1985). By aligning upwelling favourable wind conditions with the monthly BE surveys it is found that extreme anomalies in BE surveys follow extended periods of upwelling favourable winds.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 8
    Publication Date: 2018-07-04
    Description: The upper ocean, including the biologically productive euphotic zone and the mixed layer, has great relevance for studies of physical, biogeochemical, and ecosystem processes and their interaction. Observing this layer with a continuous presence, sampling many of the relevant variables, and with sufficient vertical resolution, has remained a challenge. Here a system is presented which can be deployed on the top of deep-ocean moorings, with a drive mechanism at depths of 150-200m, which mechanically winches a large sensor float and smaller communications float tethered above it to the surface and back down again, typically twice per day for periods up to 1 year. The sensor float can carry several sizeable sensors, and it has enough buoyancy to reach the near surface and for the communications float to pierce the surface even in the presence of strong currents. The system can survive mooring blow-over to 1000m depth. The battery-powered design is made possible by using a balanced energy-conserving principle. Reliability is enhanced with a drive assembly that employs a single rotating part that has no slip rings or rotating seals. The profiling bodies can break the surface to sample the near-surface layer and to establish satellite communication for data relay or reception of new commands. An inductive pass-through mode allows communication with other mooring components throughout the water column beneath the system. A number of successful demonstration deployments have been completed.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 9
    Publication Date: 2019-09-23
    Description: A deliberate tracer release experiment in 2008–2010 was used to study diapycnal mixing in the tropical northeastern Atlantic. The tracer (CF3SF5) was injected on the isopycnal surface σΘ = 26.88 kg m−3, which corresponds to about 330 m depth. Three surveys, performed 7, 20, and 30 months after the release, sampled the vertically and laterally expanding tracer patch. The mean diapycnal mixing estimate over the entire region occupied by the tracer and the period of 30 months was found to be (1.19 ± 0.18) × 10−5 m2 s−1, or, alternatively, (3.07 ± 0.58) × 10−11 (kg m−3)2 s−1 as computed from the advection-diffusion equation in isopycnal coordinates with the thickness-weighted averaging. The latter method is preferable in the regions of different stratification for it yields local diapycnal mixing estimates varying less with stratification than their Cartesian coordinate counterparts. Results of this study are comparable to the results of the North Atlantic tracer release experiment (NATRE). However, the internal wave-wave interaction models predict reduced mixing from the breaking of internal waves at low latitudes. Thus, the diapycnal diffusivity found in this study is higher than parameterized by the low latitude of the site (4°N–12°N).
    Type: Article , PeerReviewed
    Format: text
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  • 10
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    IFM-GEOMAR
    In:  IFM-GEOMAR, Kiel, Germany, 8 pp.
    Publication Date: 2012-07-19
    Type: Report , NonPeerReviewed
    Format: text
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