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  • 1
    Online Resource
    Online Resource
    DataSheet_1.docx
    Frontiers Media SA ; 2023
    In:  Frontiers in Marine Science Vol. 10 ( 2023-7-27)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 10 ( 2023-7-27)
    Abstract: Antarctic coastal polynyas are persistent and recurrent regions of open water located between the coast and the drifting pack-ice. In spring, they are the first polar areas to be exposed to light, leading to the development of phytoplankton blooms, making polynyas potential ecological hotspots in sea-ice regions. Knowledge on polynya oceanography and ecology during winter is limited due to their inaccessibility. This study describes i) the first in situ chlorophyll fluorescence signal (a proxy for chlorophyll-a concentration and thus presence of phytoplankton) in polynyas between the end of summer and winter, ii) assesses whether the signal persists through time and iii) identifies its main oceanographic drivers. The dataset comprises 698 profiles of fluorescence, temperature and salinity recorded by southern elephant seals in 2011, 2019-2021 in the Cape-Darnley (CDP;67˚S-69˚E) and Shackleton (SP;66˚S-95˚E) polynyas between February and September. A significant fluorescence signal was observed until April in both polynyas. An additional signal occurring at 130m depth in August within CDP may result from in situ growth of phytoplankton due to potential adaptation to low irradiance or remnant chlorophyll-a that was advected into the polynya. The decrease and deepening of the fluorescence signal from February to August was accompanied by the deepening of the mixed layer depth and a cooling and salinification of the water column in both polynyas. Using Principal Component Analysis as an exploratory tool, we highlighted previously unsuspected drivers of the fluorescence signal within polynyas. CDP shows clear differences in biological and environmental conditions depending on topographic features with higher fluorescence in warmer and saltier waters on the shelf compared with the continental slope. In SP, near the ice-shelf, a significant fluorescence signal in April below the mixed layer (around 130m depth), was associated with fresher and warmer waters. We hypothesize that this signal could result from potential ice-shelf melting from warm water intrusions onto the shelf leading to iron supply necessary to fuel phytoplankton growth. This study supports that Antarctic coastal polynyas may have a key role for polar ecosystems as biologically active areas throughout the season within the sea-ice region despite inter and intra-polynya differences in environmental conditions.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2023.1186403
    DOI: 10.3389/fmars.2023.1186403.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 2757748-X
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  • 2
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    Seasonal Variation of the Antarctic Slope Front Occurrence and Position Estimated from an Interpolated Hydrographic Climatology
    American Meteorological Society ; 2021
    In:  Journal of Physical Oceanography Vol. 51, No. 5 ( 2021-05), p. 1539-1557
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 51, No. 5 ( 2021-05), p. 1539-1557
    Abstract: The Antarctic Slope Front (ASF) is a fundamental feature of the subpolar Southern Ocean that is still poorly observed. In this study we build a statistical climatology of the temperature and salinity fields of the upper 380 m of the Antarctic margin. We use a comprehensive compilation of observational datasets including the profiles gathered by instrumented marine mammals. The mapping method consists first of a decomposition in vertical modes of the combined temperature and salinity profiles. Then the resulting principal components are optimally interpolated on a regular grid and the monthly climatological profiles are reconstructed, providing a physically plausible representation of the ocean. The ASF is located with a contour method and a gradient method applied on the temperature field, two complementary approaches that provide a complete view of the ASF structure. The front extends from the Amundsen Sea to the eastern Weddell Sea and closely tracks the continental shelf break. It is associated with a sharp temperature gradient that is stronger in winter and weaker in summer. The emergence of the front in the Amundsen and Bellingshausen sectors appears to be seasonally variable (slightly more westward in winter than in summer). Investigation of the density gradients across the shelf break indicates a winter slowdown of the baroclinic component of the Antarctic Slope Current at the near surface, in contrast with the seasonal variability of the temperature gradient.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    URL: Article
    DOI: 10.1175/JPO-D-20-0186.1
    DOI: 10.1175/JPO-D-20-0186.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 3
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    The Gulf Stream frontal system: A key oceanographic feature in the habitat selection of the leatherback turtle?
    Elsevier BV ; 2017
    In:  Deep Sea Research Part I: Oceanographic Research Papers Vol. 123 ( 2017-05), p. 35-47
    Details
    In: Deep Sea Research Part I: Oceanographic Research Papers, Elsevier BV, Vol. 123 ( 2017-05), p. 35-47
    Type of Medium: Online Resource
    ISSN: 0967-0637
    URL: Article
    DOI: 10.1016/j.dsr.2017.03.003
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
    detail.hit.zdb_id: 1500309-7
    detail.hit.zdb_id: 1146810-5
    SSG: 14
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  • 4
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    Defining Southern Ocean fronts using unsupervised classification
    Copernicus GmbH ; 2021
    In:  Ocean Science Vol. 17, No. 6 ( 2021-11-02), p. 1545-1562
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 17, No. 6 ( 2021-11-02), p. 1545-1562
    Abstract: Abstract. Oceanographic fronts are transitions between thermohaline structures with different characteristics. Such transitions are ubiquitous, and their locations and properties affect how the ocean operates as part of the global climate system. In the Southern Ocean, fronts have classically been defined using a small number of continuous, circumpolar features in sea surface height or dynamic height. Modern observational and theoretical developments are challenging and expanding this traditional framework to accommodate a more complex view of fronts. Here, we present a complementary new approach for calculating fronts using an unsupervised classification method called Gaussian mixture modelling (GMM) and a novel inter-class parameter called the I-metric. The I-metric approach produces a probabilistic view of front location, emphasising the fact that the boundaries between water masses are not uniformly sharp across the entire Southern Ocean. The I-metric approach uses thermohaline information from a range of depth levels, making it more general than approaches that only use near-surface properties. We train the GMM using an observationally constrained state estimate in order to have more uniform spatial and temporal data coverage. The probabilistic boundaries defined by the I-metric roughly coincide with several classically defined fronts, offering a novel view of this structure. The I-metric fronts appear to be relatively sharp in the open ocean and somewhat diffuse near large topographic features, possibly highlighting the importance of topographically induced mixing. For comparison with a more localised method, we also use an edge detection approach for identifying fronts. We find a strong correlation between the edge field of the leading principal component and the zonal velocity; the edge detection method highlights the presence of jets, which are supported by thermal wind balance. This more localised method highlights the complex, multiscale structure of Southern Ocean fronts, complementing and contrasting with the more domain-wide view offered by the I-metric. The Sobel edge detection method may be useful for defining and tracking smaller-scale fronts and jets in model or reanalysis data. The I-metric approach may prove to be a useful method for inter-model comparison, as it uses the thermohaline structure of those models instead of tracking somewhat ad hoc values of sea surface height and/or dynamic height, which can vary considerably between models. In addition, the general I-metric approach allows front definitions to shift with changing temperature and salinity structures, which may be useful for characterising fronts in a changing climate.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-17-1545-2021
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2183769-7
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  • 5
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    The Thermohaline Modes of the Global Ocean
    American Meteorological Society ; 2019
    In:  Journal of Physical Oceanography Vol. 49, No. 10 ( 2019-10), p. 2535-2552
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 49, No. 10 ( 2019-10), p. 2535-2552
    Abstract: The first 2000 m of the global thermohaline structure of the ocean are statistically decomposed into vertical thermohaline modes, using a multivariate functional principal component analysis (FPCA). This method is applied on the Monthly Isopycnal and Mixed-Layer Ocean Climatology (MIMOC). The first three modes account for 92% of the joint temperature and salinity ( T – S ) variance, which yields a surprisingly good reduction of dimensionality. The first mode (69% of the variance) is related to the thermocline depth and delineates the subtropical gyres. The second mode (18%) is mostly driven by salinity and mainly displays the asymmetry between the North Pacific and Atlantic basins and the salty circumpolar deep waters in the Southern Ocean. The third mode (5%) identifies the low- and high-salinity intermediate waters, covarying with the freshwater inputs of the upper ocean. The representation of the ocean in the space defined by the first three modes offers a simple visualization of the global thermohaline structure that strikingly emphasizes the role of the Southern Ocean in linking and distributing water masses to the other basins. The vertical thermohaline modes offer a convenient framework for model and observation data comparison. This is illustrated by projecting the repeated Pacific section P16 together with profiles from the Array for Real-Time Geostrophic Oceanography (ARGO) global array of profiling floats on the modes defined with the climatology MIMOC. These thermohaline modes have a potential for water mass identification and robust analysis of heat and salt content.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    URL: Article
    DOI: 10.1175/JPO-D-19-0120.1
    DOI: 10.1175/jpo-d-19-0120.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2019
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 6
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    A Correction for the Thermal Mass–Induced Errors of CTD Tags Mounted on Marine Mammals
    American Meteorological Society ; 2018
    In:  Journal of Atmospheric and Oceanic Technology Vol. 35, No. 6 ( 2018-06), p. 1237-1252
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 35, No. 6 ( 2018-06), p. 1237-1252
    Abstract: The effect of thermal mass on the salinity estimate from conductivity–temperature–depth (CTD) tags sensor mounted on marine mammals is documented, and a correction scheme is proposed to mitigate its impact. The algorithm developed here allows for a direct correction of the salinity data, rather than a correction of the sample’s conductivity and temperature. The amplitude of the thermal mass–induced error on salinity and its correction are evaluated via comparison between data from CTD tags and from Sea-Bird Scientific CTD used as a reference. Thermal mass error on salinity appears to be generally O (10 −2 ) g kg −1 , it may reach O (10 −1 ) g kg −1 , and it tends to increase together with the magnitude of the cumulated temperature gradient ( T HP ) within the water column. The correction we propose yields an error decrease of up to ~60% if correction coefficients specific to a certain tag or environment are calculated, and up to 50% if a default value for the coefficients is provided. The correction with the default coefficients was also evaluated using over 22 000 in situ dive data from five tags deployed in the Southern Ocean and is found to yield significant and systematic improvements on the salinity data, including for profiles whose T HP was weak and the error small. The correction proposed here yields substantial improvements in the density estimates, although a thermal mass–induced error in temperature measurements exists for very large T HP and has yet to be corrected.
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    DOI: 10.1175/JTECH-D-17-0141.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 7
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    Correction and Accuracy of High- and Low-Resolution CTD Data from Animal-Borne Instruments
    American Meteorological Society ; 2019
    In:  Journal of Atmospheric and Oceanic Technology Vol. 36, No. 5 ( 2019-05), p. 745-760
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 36, No. 5 ( 2019-05), p. 745-760
    Abstract: Most available CTD Satellite Relay Data Logger (CTD-SRDL) profiles are heavily compressed before satellite transmission. High-resolution profiles recorded at the sampling frequency of 0.5 Hz are, however, available upon physical retrieval of the logger. Between 2014 and 2018, several loggers deployed on elephant seals in the Southern Ocean have been set in continuous recording mode, capturing both the ascent and descent for over 60 profiles per day during several months, opening new horizons for the physical oceanography community. Taking advantage of a new dataset made of seven such loggers, a postprocessing procedure is proposed and validated to improve the quality of all CTD-SRDL data: that is, both high-resolution profiles and compressed low-resolution ones. First, temperature and conductivity are corrected for a thermal mass effect. Then salinity spiking and density inversion are removed by adjusting salinity while leaving temperature unchanged. This method, applied here to more than 50 000 profiles, yields significant and systematic improvements in both temperature and salinity, particularly in regions of rapid temperature variation. The continuous high-resolution dataset is then used to provide updated accuracy estimates of CTD-SRDL data. For high-resolution data, accuracies are estimated to be of ±0.02°C for temperature and ±0.03 g kg −1 for salinity. For low-resolution data, transmitted data points have similar accuracies; however, reconstructed temperature profiles have a reduced accuracy associated with the vertical interpolation of ±0.04°C and a nearly unchanged salinity accuracy of ±0.03 g kg −1 .
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    URL: Article
    DOI: 10.1175/JTECH-D-18-0170.1
    DOI: 10.1175/jtech-d-18-0170.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2019
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 8
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    Acoustic seascape partitioning through functional data analysis
    Wiley ; 2023
    In:  Journal of Biogeography Vol. 50, No. 9 ( 2023-09), p. 1546-1560
    Details
    In: Journal of Biogeography, Wiley, Vol. 50, No. 9 ( 2023-09), p. 1546-1560
    Abstract: Water column acoustic backscatter is regularly registered during oceanographic surveys, providing valuable information on the composition and distribution of pelagic life in the ocean. We propose an objective approach based on functional data analysis to classify these acoustic seascapes into biogeographical regions. Location Tropical South Atlantic Ocean off northeastern Brazil. Taxon Sound‐scattering pelagic fauna detected with acoustic echosounders, principally small fish, crustaceans, squid and diverse gelatinous life‐forms. Methods We use acoustic backscatter as a function of depth, simultaneously at three frequencies, to numerically describe the vertical distribution and composition of sound‐scattering organisms in the water column. This information is used to classify the acoustic seascape through functional principal component analysis. The analysis routine is tested and illustrated with data collected at 38, 70 and 120 kHz in waters affected by contrasting environmental conditions. Results Acoustic seascape partitioning mirrored the distribution of current systems, fronts and taxonomically based regionalization. The study area was divided between slope‐boundary and open‐ocean waters, and between spring and fall hydrological regimes. Main Conclusions The acoustic seascape consistency and the spatiotemporal coherence of the regions classified show that the method is efficient at identifying homogeneous and cohesive sound‐scattering communities. Comparisons against hydrological and biological regionalization prove that the method is reliable at delineating distinct pelagic ecosystems in a cost‐efficient and non‐intrusive way.
    Type of Medium: Online Resource
    ISSN: 0305-0270 , 1365-2699
    URL: Issue
    URL: Article
    DOI: 10.1111/jbi.v50.9
    DOI: 10.1111/jbi.14534
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2020428-0
    detail.hit.zdb_id: 188963-1
    SSG: 12
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  • 9
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    A Linear Decomposition of the Southern Ocean Thermohaline Structure
    American Meteorological Society ; 2017
    In:  Journal of Physical Oceanography Vol. 47, No. 1 ( 2017-01), p. 29-47
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 47, No. 1 ( 2017-01), p. 29-47
    Abstract: The thermohaline structure of the Southern Ocean is deeply influenced by the presence of the Antarctic Circumpolar Current (ACC), where water masses of the World Ocean are advected, transformed, and redistributed to the other basins. It remains a challenge to describe and visualize the complex 3D pattern of this circulation and its associated tracer distribution. Here, a simple framework is presented to analyze the Southern Ocean thermohaline structure. A functional principal component analysis (PCA) is applied to temperature θ and salinity S profiles to determine the main spatial patterns of their variations. Using the Southern Ocean State Estimate (SOSE), this study determines the vertical modes describing the Southern Ocean thermohaline structure between 5 and 2000 m. The first two modes explain 92% of the combined θ – S variance, thus providing a surprisingly good approximation of the thermohaline properties in the Southern Ocean. The first mode (72% of total variance) accurately describes the north–south property gradients. The second mode (20%) mostly describes salinity at 500 m in the region of Antarctic Intermediate Water formation. These two modes present circumpolar patterns that can be closely related with standard frontal definitions. By projecting any given hydrographic profile onto the SOSE-based modes, it is possible to determine its position relative to the fronts. The projection is successfully applied on the hydrographic profiles of the WOCE SR3 section. The Southern Ocean thermohaline decomposition provides an objective way to define water mass boundaries and their spatial variability and has useful application for comparing model output with observations.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    URL: Article
    DOI: 10.1175/JPO-D-16-0083.1
    DOI: 10.1175/JPO-D-16-0083.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2017
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 10
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    Impact of Thermohaline Variability on Sea Level Changes in the Southern Ocean
    American Geophysical Union (AGU) ; 2021
    In:  Journal of Geophysical Research: Oceans Vol. 126, No. 9 ( 2021-09)
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 126, No. 9 ( 2021-09)
    Abstract: Variability of vertical thermohaline modes induces regional patterns in steric height trends in the Southern Ocean Steric height has risen north of the Polar Front and fallen south of it due to both thermo‐ and halosteric changes The halosteric effect in the Southern Ocean is nowhere negligible and significantly reduces the rate of sea level rise around Antarctica
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2021JC017381
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2021
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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