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  • 1
    Book
    Book
    Kiel : Inst. für Meereskunde [u.a.]
    Keywords: Statistik ; Atlantischer Ozean Süd ; Agulhasstrom ; Meeresströmung ; Meerwasser ; Austausch ; Geschichte 1997-1999
    Type of Medium: Book
    Pages: 194 S , zahlr. graph. Darst., Kt
    Series Statement: KAPEX RAFOS Float Data Report : 1997 - 1999 pt. A
    Language: English
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  • 2
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    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 318 . Institut für Meereskunde, Kiel, Germany, 194 pp.
    Publication Date: 2019-09-23
    Type: Report , NonPeerReviewed
    Format: text
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  • 3
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    Godae Project Office, Bureau of Meteorology
    In:  In: Observing the Oceans in the 21st Century. , ed. by Koblinsky, C. J. and Smith, N. R. Godae Project Office, Bureau of Meteorology, Melbourne, pp. 248-258. ISBN 064270618 2
    Publication Date: 2012-07-13
    Type: Book chapter , NonPeerReviewed
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  • 4
    Publication Date: 2019-07-17
    Description: Combining in-situ Lagrangian intermediate depth velocity measurements from the KAPEX (Cape of Good Hope Experiments) float program with sea-surface height data, this study reviews the inter-ocean exchange mechanisms around southern Africa. In the southeastern Cape Basin, a highly energetic field of coexisting anticyclonic and cyclonic eddies is documented. Agulhas Rings of typically 200 km diameter are observed to merge, split, deform, and to reconnect to the Agulhas Retroflection. Concomitant, slightly smaller cyclones are observed to drift across the northwestward migration path of the Agulhas Rings. These cyclones, with typical diameters of 120 km, are formed within the Cape Basin along the African shelf, inshore of the Agulhas Current, and in the subantarctic region south of Africa.The data suggests the annual formation of 3-6 long-lived Agulhas Rings, that eventually cross 5°E longitude, while approximately twice the number of rings occur in the southeastern Cape Basin. Within this region, cyclones outnumber anticyclones by a factor of 3:2. Both cyclones and anticyclones extend through the upper thermocline into the intermediate depth layer. Mean drifts of anticyclones are 3.8 ± 1.2 cm s-1 to the northwest, while cyclones follow a west-southwestward route at 3.6 ± 0.8 cm s-1. Transport estimates suggest that the intermediate depth layer in the southeastern Cape Basin is primarily supplied from the east (approximately 9 Sv) with minor direct inflow from the Atlantic to the west and south.Cyclone/anticyclone interaction is surmised to result in vigorous stirring and mixing processes in the southeastern Cape Basin, which necessitates a review of the traditional concept of Indo-Atlantic inter-ocean exchange. We propose to limit the concept of ?isolated Agulhas Rings embedded in a sluggish Benguela Drift? to the northwestern Cape Basin and beyond, while linking this regime to the Agulhas Retroflection proper through a zone of turbulent stirring and mixing in the southeastern Cape Basin, named for the first time the ?Cape Cauldron? hereinafter.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    In:  EPIC3Deep-sea research ii, 50(1), pp. 35-56
    Publication Date: 2019-07-17
    Description: The combined analysis of hydrographic, kinematic and dynamic data collected during the 1997-1999 KAPEX (CAPe of Good Hope EXperiments) reveals a quasi-stationary meandering pattern of the Agulhas Retroflection Current east and upstream of the Southwest-Indian Ridge. The current meanders between 38°S and 40°S in a spatially and temporally continuous fashion and has a core width of approximately 70 km with an associated transport of 44 ± 5 106 m3 s-1 in the upper 1000 m. Peak surface velocities decrease from 2.1 m s?1 near the Agulhas Retroflection to 1.1 m s-1 around 32°E. Meander troughs (northward extremes) are found predominantly near 26.8°E, 32.6°E and 38.9°E, while crests (southward extremes) are located with high probability near 29.7°E, 35.5°E and 42.9°E, resulting in a typical wavelength of 500 km. Cold eddies are shed along the northern boundary of the current from meander troughs into the recirculation regime between the Agulhas Current proper and the Agulhas Return Current. Strongest cyclonic eddies are preferably shed in austral autumn. The cyclonic eddies so formed propagate westward at an average phase-speed of 5.4 cm s-1, with however, a variability of at least the same magnitude. Subsequently, the cyclones are absorbed by the next meander trough located upstream and to the west of the shedding trough.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    In:  EPIC3Deep-sea research ii, 50(19), pp. 119-139
    Publication Date: 2019-07-17
    Description: Satellite borne altimetric data are of increasing prominence for assimilation in ocean circulation models and interpretation of localized in-situ measurements. Physically, geo-referenced sea surface height (SSH) data products are mostly referenced relative to a long-term SSH mean, and consequently called SSH-anomalies. The Modular Ocean Data Assimilation System (MODAS) adds climatological SSH fields to provide space-time interpolated absolute steric SSH fields. This, in theory, should provide realistic geostrophic surface velocities and flow patterns, including quasi-permanent features such as western boundary currents or free jets. This study compares such data for the wider Agulhas Retroflection region with co-located, simultaneous velocity measurements from KAPEX (Cape of Good Hope Experiments). KAPEX used ship-borne Acoustic Doppler Current Profiles (ADCP) and neutrally buoyant RAFOS (Ranging And Fixing Of Sound) floats at intermediate depths to obtain in-situ velocity data.Correlation coefficients of MODAS-2D geostrophic and RAFOS subsurface flow directions fall between 0.8 and 0.9 with a typical error less than 0.05. The high correlation suggests that MODAS-2D provides a correct depiction of anticyclonic/cyclonic flow patterns in this region, making it a useful tool to describe the Agulhas Retroflection. Root-mean-square differences between velocities as measured by the various data sources rage between 20-30 cm s-1, lying between the natural variability observed for the intermediate and surface layers. Decreasing slope parameters of linear regressions between MODAS, RAFOS and ADCP velocities reflect the baroclinic velocity shear. Slope equals 1 at surface and decreases to 0.4 at depths below 1000 m. Offsets of linear regression of these fits are not significantly different from zero, except for the zonal component in the Agulhas Return Current (5 to 10 cm s-1). This discrepancy suggests a missing meridional gradient in this region?s climatological signal that is added to the SSH anomaly field within MODAS.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    In:  EPIC3Deep-sea research ii, 50(1), pp. 141-166, ISSN: 0967-0645
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    In:  EPIC3International WOCE Newsletter, Number 42, pp., pp. 22-24
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev
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  • 9
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    In:  EPIC3Workshop to promote the development of instrumentation for Arctic Ocean exploration: Technology for assessing the water column and the seafloor, Moss Landing, California, USA.-18.10.2002.., 16
    Publication Date: 2014-09-17
    Description: Being one of the leading polar research organizations in Europe, the Alfred Wegener Institute for Polar and Marine Research (AWI) acts as a motor for the development of polar research technologies. A couple of scheduled Arctic projects has been selected out of a large variety of future activities to be presented here:1) Subsequent to the AMORE expedition to the Gakkel Ridge jointly performed in 2001 by the two research icebreakers USCGC ?Healy? and RV ?Polarstern? a further two ship mission is scheduled for 2004. AWI will participate again with RV ?Polarstern? and will host the remotely operating vessel (ROV) ?Victor6000?. The main focus will be laid on a detailed sampling of the Gakkel Ridge system by means of the ROV which is well appropriate for visual and experimental investigations of ridge structures. The vehicle will take samples at sites surveyed and pre-investigated by geophysical techniques in 2001. Besides, it is also envisaged to conduct ROV-based experiments and sampling on the Siberian Shelf. Based on the results of the joint Russian-German project on "Siberian River Run-off (SIRRO) the river fans of Ob and Yenesei are targeted. Geological, geochemical and biological processes relevant for the understanding of the input of fresh water, sediments, and organic matter from the rivers to the Kara Sea and the adjacent Arctic Ocean will be subject to ROV investigations.2) AWI is currently purchasing an autonomous underwater vehicle (AUV) for under-ice research, seafloor and water column surveys. Equipped with acoustic tools like side scan sonar, sub-bottom profiler, swath bathymetry as well as with visual imaging systems the vessel shall perform e.g. autonomous pre-site surveys for future Arctic drill campaigns and further seismic investigations at Arctic ridge systems. Moreover, the AUV is planned to be used for surveying arctic sediment and fauna distribution and tracks of grounded icebergs. In addition, special payload modules capable to trace geochemical parameters in the water column will be developed for the AUV in order to quantify submarine fluid discharge plumes etc.3) The ARGO system of vertically profiling floats is expected to become the backbone of a global ocean observing system. However, their use under Arctic conditions remains difficult, since the floats have to get to the sea surface to be located and to transmit the measured data via satellite. Instead, AWI promotes a Hybrid Arctic/Antarctic Float Observation System (HAFOS) which shall combine different technologies. It comprises ice resistant profiling subsurface floats, surface drifters on the ice and moored stations. The envisaged system consists of RAFOS (ranging and fixing of sound) type subsurface profiling floats which obtain their position by ranging of sound sources on moored stations. The floats measure vertical profiles of temperature and conductivity/salinity, but do not surface while floating under the ice. As a first stage of development, data will be stored until the floats reach ice-free waters. Later, the floats will be able to communicate with receivers installed on moorings and ice drifters allowing fast satellite data transmission.4) The central Arctic Ocean has hitherto not been visited by a deep-drilling research vessel (DSDP/ODP) and therefore its long-term environmental history as well as the tectonic structure are poorly known. A European contribution to IODP is needed. A newly designed research ice breaker with a deep ocean drilling capability would provide the opportunity to conduct international, interdisciplinary expeditions during all seasons of the year and to penetrate into permanently ice-covered basins of the central Arctic Ocean. AWI promotes a European consortium of interested institutes/countries to share responsibilities for the planning and construction of a multi-purpose Arctic ice breaker and to coordinate scientific programs.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 10
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    In:  EPIC3Deep-Sea Research II, 50(1), pp. 1-12
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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