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  • ACOUSTICAL SOC AMER AMER INST PHYSICS  (2)
  • Wiley  (2)
  • Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung  (1)
  • Bremerhaven : Alfred-Wegener-Inst., Helmholtz-Zentrum für Polar- und Meeresforschung  (1)
  • 1
    Online Resource
    Online Resource
    The expedition of the research vessel "Polarstern" to the Antarctic in 2008/2009 (ANT-XXV/2) (2009)
    Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung
    Details Availability
    Description / Table of Contents: Der Fahrtabschnitt 2 der Antarktisexpedition ANT-XXV führte in das östliche Weddellmeer und diente der Durchführung logistischer und wissenschaftlicher Vorhaben, die sich a)in stationsgebundene, b)vom fahrenden Schiff aus durchführbare, sowie c)helikoptergestützte Arbeiten unterteilen lassen...Zusammenfassend ist festzustellen, dass alle geplanten Aktivitäten in vollem Umfang umgesetzt werden konnten und die Zusammenarbeit zwischen Wissenschaftlern und Schiffsbesatzung über den gesamten Verlauf der Reise stets einvernehmlich und zielgerichtet war.
    Type of Medium: Online Resource
    Pages: Online-Ressource
    Series Statement: Berichte zur Polar- und Meeresforschung 595
    URL: http://hdl.handle.net/10013/epic.33170
    URL: http://hdl.handle.net/10013/epic.33170.d001
    Language: English
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  • 2
    Online Resource
    Online Resource
    The expedition of the research vessel "Polarstern" to the Antarctic in 2012/2013 (ANT-XXIX/2) (2013)
    Bremerhaven : Alfred-Wegener-Inst., Helmholtz-Zentrum für Polar- und Meeresforschung
    Details Availability
    Type of Medium: Online Resource
    Pages: Online-Ressource (99 S.) , Ill., graph. Darst., Kt.
    Series Statement: Berichte zur Polar- und Meeresforschung 671
    URL: http://hdl.handle.net/10013/epic.42735.d001
    Language: English
    Note: Zsfassung in dt. und engl. Sprache
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  • 3
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    Ocean Bottom Pressure Variability: Can It Be Reliably Modeled? (2020)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2023-02-08
    Description: Ocean bottom pressure (OBP) variability serves as a proxy of ocean mass variability, the knowledge of which is needed in geophysical applications. The question of how well it can be modeled by the present general ocean circulation models on time scales in excess of 1 day is addressed here by comparing the simulated OBP variability with the observed one. To this end, a new multiyear data set is used, obtained with an array of bottom pressure gauges deployed deeply along a transect across the Southern Ocean. We present a brief description of OBP data and show large‐scale correlations over several thousand kilometers at all time scales using daily and monthly averaged data. Annual and semiannual cycles are weak. Close to the Agulhas Retroflection, signals of up to 30 cm equivalent water height are detected. Further south, signals are mostly intermittent and noisy. It is shown that the models simulate consistent patterns of bottom pressure variability on monthly and longer scales except for areas with high mesoscale eddy activity, where high resolution is needed to capture the variability due to eddies. Furthermore, despite good agreement in the amplitude of variability, the in situ and simulated OBP show only modest correlation.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Effects of subsampling of passive acoustic recordings on acoustic metrics (2015)
    ACOUSTICAL SOC AMER AMER INST PHYSICS
    In:  EPIC3Journal of the Acoustical Society of America, ACOUSTICAL SOC AMER AMER INST PHYSICS, 138(1), pp. 267-278, ISSN: 0001-4966
    Details
    Publication Date: 2015-07-22
    Description: Passive acoustic monitoring is an important tool in marine mammal studies. However, logistics and finances frequently constrain the number and servicing schedules of acoustic recorders, requiring a trade-off between deployment periods and sampling continuity, i.e., the implementation of a subsampling scheme. Optimizing such schemes to each project's specific research questions is desirable. This study investigates the impact of subsampling on the accuracy of two common metrics, acoustic presence and call rate, for different vocalization patterns (regimes) of baleen whales: (1) variable vocal activity, (2) vocalizations organized in song bouts, and (3) vocal activity with diel patterns. To this end, above metrics are compared for continuous and subsampled data subject to different sampling strategies, covering duty cycles between 50% and 2%. The results show that a reduction of the duty cycle impacts negatively on the accuracy of both acoustic presence and call rate estimates. For a given duty cycle, frequent short listening periods improve accuracy of daily acoustic presence estimates over few long listening periods. Overall, subsampling effects are most pronounced for low and/or temporally clustered vocal activity. These findings illustrate the importance of informed decisions when applying subsampling strategies to passive acoustic recordings or analyses for a given target species.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 5
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    Estimating the spatial distribution of vocalizing animals from ambient sound spectra using widely spaced recorder arrays and inverse modelling (2019)
    ACOUSTICAL SOC AMER AMER INST PHYSICS
    In:  EPIC3Journal of the Acoustical Society of America, ACOUSTICAL SOC AMER AMER INST PHYSICS, 146, pp. 4699, ISSN: 0001-4966
    Details
    Publication Date: 2020-07-07
    Description: The sound energy from marine mammal populations vocalizing over extended periods of time adds up to quasi-continuous “choruses” which create characteristic peaks in marine sound spectra. We present an approach to estimate animal distribution that uses chorus recordings from very sparse unsynchronized arrays in ocean areas that are too large or remote to survey with traditional methods. To solve this underdetermined inverse problem, we use simulated annealing to estimate the distribution of vocalizing animals on a geodesic grid. This includes calculating a transmission loss matrix, which connects all grid nodes and recorders. Geometrical spreading and the ray trace model BELLHOP were implemented. The robustness of the proposed method was tested with simulated marine mammal distributions in the Atlantic sector of Southern Ocean using both drifting acoustic recorders (Argo floats) and a moored array as acoustic receivers. The results show that inversion accuracy mainly depends on the number and location of the recorders and can be predicted using the entropy and range of the estimated source distribution. Tests with different transmission loss models indicated that inversion accuracy is affected only slightly by inevitable inaccuracies in transmission loss models. The presented method could also be applied to bird, crustacean and insect choruses.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 6
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    Dynamic species distribution models of Antarctic blue whales in the Weddell Sea using visual sighting and passive acoustic monitoring data (2024)
    Wiley
    In:  EPIC3Diversity and Distributions, Wiley, 30(1), pp. 87-105, ISSN: 1366-9516
    Details
    Publication Date: 2024-02-12
    Description: Aim: Species distribution models (SDMs) are essential tools in ecology and conservation. However, the scarcity of visual sightings of marine mammals in remote polar areas hinders the effective application of SDMs there. Passive acoustic monitoring (PAM) data provide year-round information and overcome foul weather limitations faced by visual surveys. However, the use of PAM data in SDMs has been sparse so far. Here, we use PAM-based SDMs to investigate the spatiotemporal distribution of the critically endangered Antarctic blue whale in the Weddell Sea. Location: The Weddell Sea. Methods: We used presence-only dynamic SDMs employing visual sightings and PAM detections in independent models. We compared the two independent models with a third combined model that integrated both visual and PAM data, aiming at leveraging the advantages of each data type: the extensive spatial extent of visual data and the broader temporal/environmental range of PAM data. Results: Visual and PAM data prove complementary, as indicated by a low spatial overlap between daily predictions and the low predictability of each model at detections of other data types. Combined data models reproduced suitable habitats as given by both independent models. Visual data models indicate areas close to the sea ice edge (SIE) and with low-to-moderate sea ice concentrations (SIC) as suitable, while PAM data models identified suitable habitats at a broader range of distances to SIE and relatively higher SIC. Main Conclusions: The results demonstrate the potential of PAM data to predict year-round marine mammal habitat suitability at large spatial scales. We provide reasons for discrepancies between SDMs based on either data type and give methodological recommendations on using PAM data in SDMs. Combining visual and PAM data in future SDMs is promising for studying vocalized animals, particularly when using recent advances in integrated distribution modelling methods.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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