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| Registros recuperados: 15 | |
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| Ardhuin, Fabrice; Lavanant, Thibaut; Obrebski, Mathias; Marie, Louis; Royer, Jean-yves; D'Eu, Jean-francois; Howe, Bruce M.; Lukas, Roger; Aucan, Jerome. |
| The generation of ultra-low frequency acoustic noise (0.1 to 1 Hz) by the nonlinear interaction of ocean surface gravity waves is well established. More controversial are the quantitative theories that attempt to predict the recorded noise levels and their variability. Here a single theoretical framework is used to predict the noise level associated with propagating pseudo-Rayleigh modes and evanescent acoustic-gravity modes. The latter are dominant only within 200 m from the sea surface, in shallow or deep water. At depths larger than 500 m, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii and the Kerguelen islands reveal: (a) Deep ocean acoustic noise at frequencies 0.1 to 1 Hz is consistent with the... |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00176/28748/27211.pdf |
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| Maia, Marcia; Pessanha, Ivo; Courreges, Esther; Patriat, Martin; Gente, Pascal; Hemond, Christophe; Janin, Myriam; Johnson, Kevin; Roest, Walter; Royer, Jean-yves; Vatteville, Judith. |
| The Amsterdam-Saint Paul plateau results from a 10 Myr interaction between the South East Indian Ridge and the Amsterdam-Saint Paul hot spot. During this period of time, the structure of the plateau changed as a consequence of changes in both the ridge-hot spot relative distance and in the strength of the hot spot source. The joint analysis of gravity-derived crust thickness and bathymetry reveals that the plateau started to form at similar to 10 Ma by an increase of the crustal production at the ridge axis, due to the nearby hot spot. This phase, which lasted 3-4 Myr, corresponds to a period of a strong hot spot source, maybe due to a high temperature or material flux, and decreasing ridge-hot spot distance. A second phase, between similar to 6 and... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00047/15865/13284.pdf |
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| Louis, Gilles; Lequentrec-lalancette, Marie-françoise; Royer, Jean-yves; Rouxel, Didier; Géli, Louis; Maïa, Marcia; Faillot, Mathilde. |
| Over the past 3 decades, satellite altimetry has been a key tool for dynamic ocean studies and for accurately estimating sea surface heights. The geodetic reference surface—the “geoid”—can be approximated as the mean sea surface height of an ocean corrected for dynamic terms such as tides and currents. It is an equipotential surface of the gravity field; and variations of this field are quantified as free‐air anomalies, from which density heterogeneities of the oceanic basement can be inferred. Using such data in combination with other geophysical data, scientists have improved their knowledge of the nature of submarine relief and underlying structures. In solid Earth geophysics, major breakthroughs came from the development of high‐resolution marine... |
| Tipo: Text |
Palavras-chave: Altimetry; High resolution; SWAT soil and water assessment tool. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00451/56260/57829.pdf |
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| Royer, Jean-yves; Çakir, Ziyadin; Lange, Dietrich; Henry, Pierre. |
| The objective of the cruise was to download data from the sea-bottom distancemeter stations in the Kumburgaz Basin, Marmara Sea. The stations were installed by the Marine Geosciences Laboratory in Brest and Geomar Institute in Khiel during RV Pourquoi Pas ? Marsite cruise late October 2014. The first data set was downloaded during the 3rd leg of the Marsite cruise, after only 15 days of operations. A 2nd cruise was organized in April 2015 by GEOMAR using RV Poseidon (POS484) to collect the data after 6 months of operation. A 3rd download was performed in April 2016 using again RV Poseidon (POS497). This cruise was the 4th data collection and was organized by the Technical University of Istanbul (ITU) using RV Yunus. The stations have been ranging on the... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00630/74227/73861.pdf |
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| Tsang-hin-sun, Eve; Royer, Jean-yves; Perrot, Julie. |
| Volcanic and tectonic events are the main processes involved in the generation of the oceanic crust and responsible for the seismicity associated with seafloor spreading. To monitor this activity, usually not or poorly detected by land-based seismological stations, we deployed from February 2012 to February 2013 a network of autonomous hydrophones to compare the behaviour of the ultraslow-spreading Southwest (SWIR) with that of the intermediate-spreading Southeast Indian ridges (SEIR). The rate of seismicity is similar for both ridges, suggesting that there is no systematic relationship between seismicity and spreading rates. The along-axis distribution of the seismic events, however, does differ, reflecting the rate-dependence of accretion modes.... |
| Tipo: Text |
Palavras-chave: Seismicity and tectonics; Acoustic properties; Mid-ocean ridge processes; Indian Ocean. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00340/45165/44559.pdf |
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| Gutscher, Marc-andre; Royer, Jean-yves; Graindorge, David; Murphy, Shane; Klingelhoefer, Frauke; Aiken, Chastity; Cattaneo, Antonio; Barreca, Giovanni; Quetel, Lionel; Riccobene, Giorgio; Petersen, Florian; Urlaub, Morelia; Krastel, Sebastian; Gross, Felix; Kopp, Heidrun; Margheriti, Lucia; Beranzoli, Laura. |
| Laser reflectometry (BOTDR), commonly used for structural health monitoring (bridges, dams, etc.), will for the first time be applied to study movements of an active fault on the seafloor 25 km offshore Catania Sicily. The goal of the European funded FOCUS project (ERC Advanced Grant) is to connect a 6-km long strain cable to the EMSO seafloor observatory in 2100 m water depth. Laser observations will be calibrated by seafloor geodetic instruments and seismological stations. A long-term goal is the development of dual-use telecom cables with industry partners. |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00493/60430/63872.pdf |
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| Samaran, Flore; Stafford, Kathleen M.; Branch, Trevor A.; Gedamke, Jason; Royer, Jean-yves; Dziak, Robert P.; Guinet, Christophe. |
| Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp) are an endangered species found in the Southern and Indian Oceans. Here two recognized subspecies of blue whales and, based on passive acoustic monitoring, four "acoustic populations" occur. Three of these are pygmy blue whale (B. m. brevicauda) populations while the fourth is the Antarctic blue whale (B. m. intermedia). Past whaling catches have dramatically reduced their numbers but recent acoustic recordings show that these oceans are still important... |
| Tipo: Text |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00274/38490/36960.pdf |
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| Leroy, Emmanuelle C.; Samaran, Flore; Stafford, Kathleen M.; Bonnel, Julien; Royer, Jean-yves. |
| The southern Indian Ocean is believed to be a natural territory for blue and fin whales. However, decades after commercial and illegal whaling decimated these populations, little is known about their current status, seasonal habitat or movements. Recent passive acoustic studies have described the presence of 4 acoustic populations of blue whales (Antarctic and 3 'pygmy' types), but are generally limited temporally and geographically. Here, we examine up to 7 yr of continuous acoustic recordings (2010-2016) from a hydrophone network of 6 widely spaced sites in the southern Indian Ocean, looking for the presence of Antarctic and pygmy blue and fin whales. Power spectral density analyses of characteristic and distinct frequency bands of these species show... |
| Tipo: Text |
Palavras-chave: Pygmy blue whales; Antarctic blue whales; Fin whales; Southern Indian Ocean; Passive acoustic monitoring; Sympatry. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00516/62731/67110.pdf |
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| Lange, Dietrich; Kopp, Heidrun; Royer, Jean-yves; Henry, Pierre; Cakir, Ziyadin; Petersen, Florian; Sakic, Pierre; Ballu, Valerie; Bialas, Joerg; Ozeren, Mehmet Sinan; Ergintav, Semih; Geli, Louis. |
| Using offshore geodetic observations, we show that a segment of the North Anatolian Fault in the central Sea of Marmara is locked and therefore accumulating strain. The strain accumulation along this fault segment was previously extrapolated from onshore observations or inferred from the absence of seismicity, but both methods could not distinguish between fully locked or fully creeping fault behavior. A network of acoustic transponders measured crustal deformation with mm-precision on the seafloor for 2.5 years and did not detect any significant fault displacement. Absence of deformation together with sparse seismicity monitored by ocean bottom seismometers indicates complete fault locking to at least 3 km depth and presumably into the crystalline... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00507/61838/65897.pdf |
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| Leroy, Emmanuelle; Royer, Jean-yves; Alling, Abigail; Maslen, Ben; Rogers, Tracey L.. |
| Blue whales were brought to the edge of extinction by commercial whaling in the twentieth century and their recovery rate in the Southern Hemisphere has been slow; they remain endangered. Blue whales, although the largest animals on Earth, are difficult to study in the Southern Hemisphere, thus their population structure, distribution and migration remain poorly known. Fortunately, blue whales produce powerful and stereotyped songs, which prove an effective clue for monitoring their different ‘acoustic populations.’ The DGD-Chagos song has been previously reported in the central Indian Ocean. A comparison of this song with the pygmy blue and Omura’s whale songs shows that the Chagos song are likely produced by a distinct previously unknown pygmy blue whale... |
| Tipo: Text |
Palavras-chave: Animal migration; Biogeography; Marine biology; Marine mammals. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00691/80280/83365.pdf |
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| Yatheesh, V.; Dyment, J.; Bhattacharya, G. C.; Royer, Jean-yves; Raju, K. A. Kamesh; Ramprasad, T.; Chaubey, A. K.; Patriat, P.; Srinivas, K.; Choi, Y.. |
| The Central Indian Ocean, namely the Central Indian, Crozet, and Madagascar basins, formed by rifting and subsequent drifting of India (now Capricorn), Antarctica, and Africa (now Somalia). We gathered a comprehensive set of sea surface magnetic anomaly profiles over these basins and revisited location and identification of magnetic isochrons between C34ny (83.0 Ma) and C20ny (42.536 Ma) using the objective analytic signal technique. We present high-resolution magnetic isochrons for 29 periods based on similar to 1,400 magnetic anomaly picks. From the conjugate sets of picks, we derive two-plate finite rotation parameters for both the Capricorn-Antarctica and Capricorn-Somalia motions. These finite rotations are compared to three-plate reconstructions of... |
| Tipo: Text |
Palavras-chave: Magnetic isochrons; Central Indian Basin; Crozet Basin; Madagascar Basin; Plate reconstruction. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74935/76014.pdf |
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| Leroy, Emmanuelle C; Royer, Jean-yves; Bonnel, Julien; Samaran, Flore. |
| In the past decades, in the context of a changing ocean submitted to an increasing human activity, a progressive decrease in the frequencies (pitch) of blue whale vocalizations has been observed worldwide. Its causes, of natural or anthropogenic nature, are still unclear. Based on 7years of continuous acoustic recordings at widespread sites in the southern Indian Ocean, we show that this observation stands for five populations of large whales. The frequency of selected units of vocalizations of fin, Antarctic, and pygmy blue whales has steadily decreased at a rate of a few tenths of hertz per year since 2002. In addition to this interannual frequency decrease, blue whale vocalizations display seasonal frequency shifts. We show that these intra-annual... |
| Tipo: Text |
Palavras-chave: Large baleen whales; Blue whale calls; Frequency shifts; Frequency decrease; Ambient noise; Bioacoustics. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00516/62730/67109.pdf |
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| Lecoulant, Jean; Guennou, Claude; Guillon, Laurent; Royer, Jean-yves. |
| The low-frequency (4-40 Hz) acoustic waves generated by undersea earthquakes are of great importance to monitor the low-level seismic activity associated with seafloor spreading ridges. To better understand the near-source interaction of seismic waves with the seafloor and the resulting generation of low-frequency acoustic waves, the wave propagation in a solid medium (the Earth's crust) and in the overlaying fluid medium (the ocean) were jointly simulated using a three-dimensional (3D) spectral finite-element code (SPECFEM3D). Due to numerical limitations of 3D simulations, the focus was on simple model configurations with a 1 Hz source located below a Gaussian seamount or ridge. The simulated acoustic waves (0-2.5 Hz) propagate as Rayleigh modes and are... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00637/74914/75768.pdf |
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| Leroy, Emmanuelle C.; Samaran, Flore; Bonnel, Julien; Royer, Jean-yves. |
| Passive acoustic monitoring is an efficient way to provide insights on the ecology of large whales. This approach allows for long-term and species-specific monitoring over large areas. In this study, we examined six years (2010 to 2015) of continuous acoustic recordings at up to seven different locations in the Central and Southern Indian Basin to assess the peak periods of presence, seasonality and migration movements of Antarctic blue whales (Balaenoptera musculus intermedia). An automated method is used to detect the Antarctic blue whale stereotyped call, known as Z-call. Detection results are analyzed in terms of distribution, seasonal presence and diel pattern of emission at each site. Z-calls are detected year-round at each site, except for one... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00357/46828/46699.pdf |
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| Registros recuperados: 15 | |
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