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  • 1
    Online Resource
    Online Resource
    A Profiling Float’s Sense of Ice
    American Meteorological Society ; 2007
    In:  Journal of Atmospheric and Oceanic Technology Vol. 24, No. 7 ( 2007-07-01), p. 1301-1308
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 24, No. 7 ( 2007-07-01), p. 1301-1308
    Abstract: The Argo project intends to continuously monitor temperature and salinity of the upper 2000 m of the global ocean by use of autonomous, vertically profiling floats. They are currently generating the largest oceanographic dataset that ever existed, covering most of the world’s oceans. However, the use of these instruments in the polar oceans is seriously impeded by the presence of sea ice, as floats are hindered from transmitting their profile data or, even more seriously, potentially damaged when ascending to, or being at, the ice-covered sea surface. The authors present a cost neutral ice sensing algorithm (ISA), which alerts for the likely presence of sea ice. In this event, the profile is aborted and no surfacing attempted. To retrospectively track floats that actively remained under the sea ice because of ISA, acoustic tracking via the RAFOS technique was tested in the Weddell Sea. Last but not least, the most recent version of floats features the option of interim storage of profiles that could not be transmitted in real time (iStore). With these three developments, the ice-compatible float system to reliably extend Argo into the Antarctic Ocean in the near future was completed. Additional improvement might include using faster satellite communication links (Iridium or Argos 3) to reduce the float’s risk-prone surface drift.
    Type of Medium: Online Resource
    ISSN: 1520-0426 , 0739-0572
    URL: Article
    DOI: 10.1175/JTECH2026.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2007
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 2
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    Evidence that the natal pulse involves the Agulhas Current to its full depth
    American Geophysical Union (AGU) ; 2001
    In:  Geophysical Research Letters Vol. 28, No. 18 ( 2001-09-15), p. 3449-3452
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 28, No. 18 ( 2001-09-15), p. 3449-3452
    Abstract: Natal Pulses are intermittent, solitary meanders on the trajectory of the otherwise remarkably stable northern Agulhas Current. They play disparate roles in the process of inter‐ocean exchange. They have been thought to trigger the spawning of Agulhas Rings at the Agulhas Retroflection, but also to generate an upstream retroflection that prevents Agulhas water from reaching the inter‐ocean boundary. For the Natal Pulse to be such a control it has to extend to considerable depths. We present the first hard evidence that demonstrates that the Natal Pulse is indeed an inherent property of the Agulhas Current throughout its full depth. Our data comprise Eulerian current meter observations and Lagrangian float trajectories in combination with sea‐surface height and sea‐surface temperature data. The results reveal the trapping of water within the Natal Pulse, its southward advection at a phase speed of about 11–12 cm s −1 , and rotation periods of 6 days.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2000GL012639
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 3
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    Path and variability of the Agulhas Return Current
    Elsevier BV ; 2003
    In:  Deep Sea Research Part II: Topical Studies in Oceanography Vol. 50, No. 1 ( 2003-1), p. 35-56
    Details
    In: Deep Sea Research Part II: Topical Studies in Oceanography, Elsevier BV, Vol. 50, No. 1 ( 2003-1), p. 35-56
    Type of Medium: Online Resource
    ISSN: 0967-0645
    URL: Article
    DOI: 10.1016/S0967-0645(02)00377-6
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2003
    detail.hit.zdb_id: 1141627-0
    detail.hit.zdb_id: 1500312-7
    SSG: 14
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  • 4
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    Automatic Round-the-Clock Detection of Whales for Mitigation from Underwater Noise Impacts
    Public Library of Science (PLoS) ; 2013
    In:  PLoS ONE Vol. 8, No. 8 ( 2013-8-12), p. e71217-
    Details
    In: PLoS ONE, Public Library of Science (PLoS), Vol. 8, No. 8 ( 2013-8-12), p. e71217-
    Type of Medium: Online Resource
    ISSN: 1932-6203
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.1371/journal.pone.0071217
    DOI: 10.1371/journal.pone.0071217.g001
    DOI: 10.1371/journal.pone.0071217.g002
    DOI: 10.1371/journal.pone.0071217.g003
    DOI: 10.1371/journal.pone.0071217.g004
    DOI: 10.1371/journal.pone.0071217.s001
    DOI: 10.1371/journal.pone.0071217.s002
    DOI: 10.1371/journal.pone.0071217.s003
    DOI: 10.1371/journal.pone.0071217.s004
    DOI: 10.1371/journal.pone.0071217.s005
    Language: English
    Publisher: Public Library of Science (PLoS)
    Publication Date: 2013
    detail.hit.zdb_id: 2267670-3
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  • 5
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    DataSheet2.ZIP
    Frontiers Media SA ; 2022
    In:  Frontiers in Remote Sensing Vol. 3 ( 2022-8-29)
    Details
    In: Frontiers in Remote Sensing, Frontiers Media SA, Vol. 3 ( 2022-8-29)
    Abstract: Bowhead whales ( Balaena mysticetus ) of the East Greenland-Svalbard-Barents Sea (Spitsbergen) population are still considered endangered, but knowledge on spatio-temporal distribution patterns and behavioral aspects remains scarce, yet crucial for this population’s conservation. Long-term passive acoustic recordings were collected at five locations in central and eastern Fram Strait (78-79°N, 0-7°E) as part of the Ocean Observing System FRAM (Frontiers in Arctic Marine Monitoring). Data recorded in 2012 and 2016/2017 were analyzed for the acoustic occurrence of bowhead whales at hourly resolution using a combination of automated and manual analyses. Bowhead whales were acoustically present from autumn throughout the winter months (October-February) and occasionally in spring (March-June), supporting hypotheses that Fram Strait is an important overwintering area. Acoustic presence peaked between mid-November and mid-December with bowhead whale calls recorded almost daily, often hourly for several consecutive days. The observed peak in acoustic presence coincided with the presumed mating period of bowhead whales, starting in late winter, indicating that Fram Strait may also serve as a mating area. Detailed analyses of recordings of a single year and location revealed eight distinct bowhead whale song types, comprising simple songs and call sequences. No bowhead whales were recorded in summer (July-September), indicating that they had migrated to summering areas or resided outside the detection range. Compared to previous studies in western Fram Strait, bowhead whale detections in our recordings were less frequent and recorded songs were less complex. The observed regional differences in bowhead whale acoustic behavior across Fram Strait suggest that eastern Fram Strait may represent a less favorable part of the bowhead whale overwintering area.
    Type of Medium: Online Resource
    ISSN: 2673-6187
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/frsen.2022.907105
    DOI: 10.3389/frsen.2022.907105.s001
    DOI: 10.3389/frsen.2022.907105.s002
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 3091289-1
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  • 6
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    The Weddell Gyre heat budget associated with the Warm Deep Water circulation derived from Argo floats
    Copernicus GmbH ; 2023
    In:  Ocean Science Vol. 19, No. 4 ( 2023-07-18), p. 1083-1106
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 19, No. 4 ( 2023-07-18), p. 1083-1106
    Abstract: Abstract. The Weddell Gyre plays an important role in the global climate system by supplying heat to underneath the ice shelves and in the formation of deep and bottom water masses, which have been subject to widespread warming over past decades. In this study, we investigate the re-distribution of heat throughout the Weddell Gyre by diagnosing the terms of the heat conservation equation for a 1000 m thick layer of water encompassing the core of Warm Deep Water. The spatial distributions of the different advective and diffusive terms in terms of heat tendencies are estimated using gridded climatologies of temperature and velocity, obtained from Argo floats in the Weddell Gyre from 2002 to 2016. While the results are somewhat noisy on the grid scale and the representation of the effects of eddy mixing is highly uncertain due to the need to parameterise them by means of turbulent diffusion, the heat budget (i.e. the sum of all terms) closes (within the uncertainty range) when integrated over the open inflow region in the southern limb, whereas the interior circulation cell remains unbalanced. There is an overall balance in the southern limb between the mean horizontal advection and horizontal turbulent diffusion of heat, whereas the vertical terms contribute comparatively little to the heat budget throughout the Weddell Gyre. Heat convergence due to mean horizontal advection balances with divergence due to horizontal turbulent diffusion in the open southern limb of the Weddell Gyre. In contrast, heat divergence due to mean horizontal advection is much weaker than convergence due to horizontal turbulent diffusion in the interior circulation cell of the Weddell Gyre, due to large values in the latter along the northern boundary due to large meridional temperature gradients. Heat is advected into the Weddell Gyre along the southern limb, some of which is turbulently diffused northwards into the interior circulation cell, while some is likely turbulently diffused southwards towards the shelf seas. This suggests that horizontal turbulent diffusion plays a role in transporting heat both towards the gyre interior where upwelling occurs and towards the ice shelves. Horizontal turbulent diffusion is also a mechanism by which heat can be transported into the Weddell Gyre across the open northern boundary. Temporal deviations from the mean terms are not included due to study limitations. In order to appreciate the role of transient eddying processes, a continued effort to increase the spatial and temporal coverage of observations in the eastern Weddell Sea is required.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    URL: Article
    DOI: 10.5194/os-19-1083-2023
    DOI: 10.5194/os-19-1083-2023-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2183769-7
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  • 7
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    Presentation_1.pdf
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 8 ( 2021-12-23)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-12-23)
    Abstract: Species distribution models (SDMs) relate species information to environmental conditions to predict potential species distributions. The majority of SDMs are static, relating species presence information to long-term average environmental conditions. The resulting temporal mismatch between species information and environmental conditions can increase model inference’s uncertainty. For SDMs to capture the dynamic species-environment relationships and predict near-real-time habitat suitability, species information needs to be spatiotemporally matched with environmental conditions contemporaneous to the species’ presence (dynamic SDMs). Implementing dynamic SDMs in the marine realm is highly challenging, particularly due to species and environmental data paucity and spatiotemporally biases. Here, we implemented presence-only dynamic SDMs for four migratory baleen whale species in the Southern Ocean (SO): Antarctic minke, Antarctic blue, fin, and humpback whales. Sightings were spatiotemporally matched with their respective daily environmental predictors. Background information was sampled daily to describe the dynamic environmental conditions in the highly dynamic SO. We corrected for spatial sampling bias by sampling background information respective to the seasonal research efforts. Independent model evaluation was performed on spatial and temporal cross-validation. We predicted the circumantarctic year-round habitat suitability of each species. Daily predictions were also summarized into bi-weekly and monthly habitat suitability. We identified important predictors and species suitability responses to environmental changes. Our results support the propitious use of dynamic SDMs to fill species information gaps and improve conservation planning strategies. Near-real-time predictions can be used for dynamic ocean management, e.g., to examine the overlap between habitat suitability and human activities. Nevertheless, the inevitable spatiotemporal biases in sighting data from the SO call for the need for improving sampling effort in the SO and using alternative data sources (e.g., passive acoustic monitoring) in future SDMs. We further discuss challenges of calibrating dynamic SDMs on baleen whale species in the SO, with a particular focus on spatiotemporal sampling bias issues and how background information should be sampled in presence-only dynamic SDMs. We also highlight the need to integrate visual and acoustic data in future SDMs on baleen whales for better coverage of environmental conditions suitable for the species and avoid constraints of using either data type alone.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2021.802276
    DOI: 10.3389/fmars.2021.802276.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2757748-X
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  • 8
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    Marine soundscape planning: Seeking acoustic niches for anthropogenic sound
    MDPI AG ; 2018
    In:  Journal of Ecoacoustics Vol. 2, No. 1 ( 2018-3-29), p. 1-1
    Details
    In: Journal of Ecoacoustics, MDPI AG, Vol. 2, No. 1 ( 2018-3-29), p. 1-1
    Abstract: Both marine mammals and hydroacoustic instruments employ underwater sound to communicate, navigate or infer information about the marine environment. Concurrent timing of acoustic activities using similar frequency regimes may result in (potentially mutual) interference of acoustic signals when both sources are within audible range of the recipient. While marine mammal fitness might be negatively impacted upon, both on individual and population level, hydroacoustic studies may generate low quality data or suffer data loss as a result of bioacoustic interference. This article pursues, in analogy to landscape planning, the concept of marine soundscape planning to reconcile potentially competing uses of acoustic space by managing the anthropogenic sound sources. We here present a conceptual framework exploring the potential of soundscape planning in reducing (mutual) acoustic interference between hydroacoustic instrumentation and marine mammals. The basis of this framework is formed by the various mechanisms by which acoustic niche formation (i.e., the partitioning of the acoustic space) occurs in species-rich communities that acoustically coexist while maintaining high fidelity (hi-fi) soundscapes, i.e., by acoustically partitioning the environment on the basis of time, space, frequency and signal structure. Hydroacoustic measurements often exhibit certain flexibility in their timing, and even instrument positioning, potentially offering the opportunity to minimize the ecological imprint of their operation. This study explores how the principle of acoustic niches could contribute to reduce potential (mutual) acoustic interference based on actual acoustic data from three recording locations in polar oceans. By employing marine soundscape planning strategies, entailing shifting the timing or position of hydroacoustic experiments, or adapting signal structure or frequency, we exemplify the potential efficacy of smart planning for four different hydroacoustic instrumentation types: multibeam echosounders, air guns, RAFOS (Ranging and Fixing of Sound) and tomographic sound sources.
    Type of Medium: Online Resource
    ISSN: 2516-1466
    URL: Article
    DOI: 10.22261/JEA.5GSNT8
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
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  • 9
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    Corrigendum to “Horizontal circulation and volume transports in the Weddell Gyre derived from Argo float data” [Progr. Oceanogr. 175 (2019) 263–283]
    Elsevier BV ; 2020
    In:  Progress in Oceanography Vol. 184 ( 2020-05), p. 102294-
    Details
    In: Progress in Oceanography, Elsevier BV, Vol. 184 ( 2020-05), p. 102294-
    Type of Medium: Online Resource
    ISSN: 0079-6611
    URL: Article
    DOI: 10.1016/j.pocean.2020.102294
    RVK:
    RB 10402
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 1497436-8
    detail.hit.zdb_id: 4062-9
    SSG: 21,3
    SSG: 14
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  • 10
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    Ice platelets below Weddell Sea landfast sea ice
    International Glaciological Society ; 2015
    In:  Annals of Glaciology Vol. 56, No. 69 ( 2015), p. 175-190
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 56, No. 69 ( 2015), p. 175-190
    Abstract: Basal melt of ice shelves may lead to an accumulation of disc-shaped ice platelets underneath nearby sea ice, to form a sub-ice platelet layer. Here we present the seasonal cycle of sea ice attached to the Ekström Ice Shelf, Antarctica, and the underlying platelet layer in 2012. Ice platelets emerged from the cavity and interacted with the fast-ice cover of Atka Bay as early as June. Episodic accumulations throughout winter and spring led to an average platelet-layer thickness of 4 m by December 2012, with local maxima of up to 10 m. The additional buoyancy partly prevented surface flooding and snow-ice formation, despite a thick snow cover. Subsequent thinning of the platelet layer from December onwards was associated with an inflow of warm surface water. The combination of model studies with observed fast-ice thickness revealed an average ice-volume fraction in the platelet layer of 0.25 ± 0.1. We found that nearly half of the combined solid sea-ice and ice-platelet volume in this area is generated by heat transfer to the ocean rather than to the atmosphere. The total ice-platelet volume underlying Atka Bay fast ice was equivalent to more than one-fifth of the annual basal melt volume under the Ekström Ice Shelf.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/2015AoG69A678
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2015
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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