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  • 1
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: Phytoplankton dynamics and carbon input into Arctic and sub-Arctic ecosystems were investigated around Svalbard, in summer 1991. Phytoplankton biomass, species composition and dissolved nutrient concentrations were analysed from water samples collected along seven transects. Phytoplankton biomass was low especially to the north (Chlorophyll-a mean 0.3 pg 1- '), where flagellates dominated the communities and only ice-diatoms were present. To the west, the phytoplankton composition was representative of a summer Atlantic community, in a post-bloom state. Zooplankton grazing, mainly by copepods, appeared to be the main control on biomass to the west and north of Svalbard.In the Barents Sea (east of Svalbard), an ice edge bloom was observed (Chlorophyll-a max. 6.8 pgl-') and the ice edge receded at a rate of approximately 1 1 km day-'. The phytoplankton community was represented by marginal ice species, especially Phaeocystis poucherii and Chaeroceros socialis. South of the ice edge, Deep Chlorophyll Maxima (DCM) were observed, as surface waters became progressively nutrient-depleted. In these surface waters, the phytoplankton were predominantly auto- and heterotrophic flagellates.Carbon production measurements revealed high net production (new and regenerated) to the north of the Barents Sea Polar Front (BSPF); it was especially high at the receding ice edge (reaching 1.44gC m-'day-'). To the south, a low level of production was maintained, mainly through regenerative processes.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2017-10-04
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung = Reports on polar and marine research, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 724, 66 p., ISSN: 1866-3192
    Publication Date: 2018-11-28
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 5
    Publication Date: 2018-08-10
    Description: Measuring temperature and salinity profiles in the world's oceans is crucial to understanding ocean dynamics and its influence on the heat budget, the water cycle, the marine environment and on our climate. Since 1983 the German research vessel and icebreaker Polarstern has been the platform of numerous CTD (conductivity, temperature, depth instrument) deployments in the Arctic and the Antarctic. We report on a unique data collection spanning 33 years of polar CTD data. In total 131 data sets (1 data set per cruise leg) containing data from 10 063 CTD casts are now freely available at doi:10.1594/PANGAEA.860066. During this long period five CTD types with different characteristics and accuracies have been used. Therefore the instruments and processing procedures (sensor calibration, data validation, etc.) are described in detail. This compilation is special not only with regard to the quantity but also the quality of the data – the latter indicated for each data set using defined quality codes. The complete data collection includes a number of repeated sections for which the quality code can be used to investigate and evaluate long-term changes. Beginning with 2010, the salinity measurements presented here are of the highest quality possible in this field owing to the introduction of the OPTIMARE Precision Salinometer.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    In:  EPIC350th Liège Colloquium on Ocean Dynamics "Long-term studies in oceanography – a celebration of 50 years of science at the Liège Colloquium", Liège, Belgium, 2018-05-28-2018-06-01
    Publication Date: 2018-06-05
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 7
    Publication Date: 2019-03-08
    Description: In May 2018 we towed a new vertical undulator across the equator from 2°S to 2°N along 25°W in the central Atlantic Ocean. Towing the vehicle along a sawtooth path between 5 and 300 m depth a horizontal resolution (wavelength) of 2.5 km was achieved. The vehicle was instrumented in order to bring together marine physics, chemistry and biology. The oceanographic measurements comprised the variables of state (temperature, salinity, pressure, density), and currents as well as solar irradiance. The chemical data collected were dissolved oxygen, nitrate, pH and (indirectly) particulate organic carbon. Biological information on phytoplankton concentration and composition was obtained from fluorometry and hyperspectral radiometry. The major hydrographic feature crossed was the Equatorial Undercurrent (EUC) between roughly 1.8°S and 1.5°N in the depth range 50 to 250 m flowing mainly ENE with maximum velocities of 1 m/s, whereas the slow flow of the nitrate-deplete surface layer was westward. The chlorophyll (phytoplankton) was found concentrated subsurface in the depth range 60 to 90 m on top of the nitracline and within the vertical shear zone of the upper EUC. Horizontally the deep Chl maximum displayed patchiness at scales down to the resolution achieved, hypothetically stimulated by the variable shear-driven vertical supply of nitrate. Below the euphotic zone and both at the southern and northern flank of the EUC patches of increased oxygen concentration were found, which correlate with decreased nitrate concentration and elevated pH.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 8
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    MDPI
    In:  EPIC3Remote Sensing, MDPI, 11(9), pp. 1-18, ISSN: 2072-4292
    Publication Date: 2019-05-20
    Description: Real-time quality-controlled surface current data derived from X-Band marine radar (MR) measurements were evaluated to estimate their operational reliability. The presented data were acquired by the standard commercial o�-the-shelf MR-based sigma s6 WaMoS® II (WaMoS® II) deployed onboard the German Research vessel Polarstern. The measurement reliability is specified by an IQ value obtained by the WaMoS® II real-time quality control (rtQC). Data which pass the rtQC without objection are assumed to be reliable. For these data sets accuracy and correlation with corresponding vessel-mounted acoustic Doppler current profiler (ADCP) measurements are determined. To reduce potential misinterpretation due to short-term oceanic variability/turbulences, the evaluation of the WaMoS® II accuracy was carried out based on sliding means over 20 min of the reliable data only. The associated standard deviation �WaMoS = 0.02 m/s of the meanWaMoS® II measurements reflect a high precision of the measurement and the successful rtQC during di�erent wave, current and weather conditions. The direct comparison of 7272 WaMoS® II/ADCP northward and eastward velocity data pairs yield a correlation of r � 0.94, with jbiasDj � 0.06 m/s and �S = 0.05 m/s. This confirms that the MR-based surface current measurements are accurate and reliable.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
    Publication Date: 2019-08-01
    Description: The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide and global modeling efforts – thereby enhancing predictions of the WG in global ocean circulation and climate.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Progress In Oceanography, PERGAMON-ELSEVIER SCIENCE LTD, 175, pp. 263-283, ISSN: 0079-6611
    Publication Date: 2019-11-08
    Description: Argo floats provide both hydrographic and trajectory data, affording the opportunity to investigate surface to mid-depth ocean dynamics. Here, Argo float data are used to determine the absolute geostrophic velocity field of the upper 50–2000 m of the Weddell Gyre, from which the overall circulation pattern is investigated. The Weddell Gyre plays a pivotal role in the modification of climate by advecting heat towards the Antarctic ice shelves and by modifying the water masses that feed into the lowest limb of the global ocean overturning circulation. Warm Deep Water, the source water mass that delivers heat to the Weddell Gyre, is conveniently located within the upper 2000 m domain covered by the floats; we investigate its volume transport as it circulates the gyre. Full depth volume transports are estimated by applying a quadratic function to extrapolate the relative dynamic height field component to the full ocean depth, using CTD profiles from ship-based surveys to determine an extrapolation error. Major new insights are provided by this study. There is an established double-gyre structure to the circulation, with a strong eastern cell and a weaker western cell. Regional variation of the baroclinic component of the flow field is revealed, indicating a northeast-to-southwest reduction in the baroclinic flow, along with a strong meridional gradient of baroclinic flow along the northern limb of the gyre, especially east of ∼25°W. The zonal mean gyre strength away from the shelf edge is 32 ± 5 Sv (1 Sv = 1 × 106 m3 s−1), of which 13 ± 3 Sv are associated with the advection of Warm Deep Water. There is a considerable amount of recirculation within the gyre interior, where water does not traverse the full zonal extent of the gyre. The recirculation is stronger in the eastern cell of the observed double-gyre structure. The interior circulation cells partly explain the large variations in previous gyre strength estimates. We provide an extensive review of previous estimates in context of the new results obtained.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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