This ocean-bottom seismometer deployment is part of an interdisciplinary project examining the Aurora hydrothermal vent field in an attempt to understand its fluid circulation. A total of 8 ocean bottom seismometers modified for the operation in sea ice covered oceans was deployed around Aurora vent field at the intersection of Gakkel Ridge and Lena Trough in the Fram Strait. The aim of the experiment was to monitor seismicity related to the hydrothermal circulation system and to reveal potentially heat reservoirs devoid of seismicity. The network consisted of 8 DEPAS Lobster type broadband OBS. Instruments were free-fall deployed and spaced by about 5-8 km. Their position at the seafloor is known to within few meters from ultrashort baseline positioning system Posidonia. The OBS recorded continuously at 100 Hz for up to 12 months between end of July 2022 and mid July 2023. One instrument (AUR02) had an unreliable seismometer records due to levelling problems. Skew values were obtained for all stations and ranged between -18 s and 12.3 s. Clock drift in this experiment was partially nonlinear. After the skew correction, a nonlinear time drift for stations AUR02, AUR04, AUR06, AUR08 was determined using noise cross-correlation. A best-fit correction was obtained by using skew-corrected station AUR01 as reference station for stations AUR04 and AUR08, while skew-corrected station AUR03 served as reference for stations AUR02 and AUR06. Station specific phase residuals obtained from a manually picked catalog of 492 events were used to further validate the clock drift corrections. For AUR04 a nonlinear phase residual drift was observed and, subsequently, the applied drift polynomial was manually adjusted to minimize resulting residuals. Waveform data are available from the GEOFON data centre under network code 4V.
Seegraswiesen erfüllen wichtige ökologische Dienstleistungen z.B. bei der Sequestrierung von Kohlenstoff, im Bereich von Nährstoffkreisläufen und -filterung sowie bei der Stabilisierung von Sedimenten. Seegraswiesen sind jedoch weltweit durch menschliche Aktivitäten entweder direkt (z.B. durch Gewässerverschmutzung, Habitatzerstörung) oder indirekt, durch sich verändernde Umweltbedingungen, (z.B. erhöhte Wassertemperaturen) stark gefährdet. Eine Schädigung von Seegraswiesen beeinflusst sowohl wichtige ökologische Funktionen als auch assoziierte Dienstleistungen wie z.B. die Primärproduktion und Kohlenstoffsequestrierung sowie den Schutz der Küsten vor Erosion und Bereitstellung von Habitaten für wichtige Fischbestände. Projektziele sind die Untersuchung der Reaktion von zwei Seegrasarten (Halophila stipulacea und Posidonia oceanica) auf zunehmende Wassertemperatur und küstennahe Nährstoffkonzentration, um frühe Warnsignale bereitzustellen mit denen Veränderungen erkannt werden können, lange bevor Zerstörungen irreversibel werden. P. oceanica ist hochproduktiv und kommt entlang der Küsten im gesamten Mittelmeerbereich (1. Untersuchungsgebiet, Küste vor Neapel) vor, ist jedoch auch sehr empfindlich in Bezug auf Störungen und Eutrophierungsprozesse. Das tropische Seegrass H. stipulacea dominiert in der nördlichen Spitze des Golfs von Akaba (2. Untersuchungsgebiet). In beiden Untersuchungsgebieten befinden sich die Seegraswiesen in der Nähe von intensiven Küstenentwicklungen mit erwarteten erhöhten Nährstoffeinträgen. Das Projekt führt Feldexperimente in beiden Regionen durch, um die Reaktion der Seegraswiesen auf erhöhte Nährstoffbelastungen in situ im saisonalen Temperaturverlauf zu untersuchen. Die Ergebnisse werden für die Spezifikation eines ökologischen Simulationsmodells genutzt, um treibenden Kräfte zu analysieren und Implikationen für ein Management abzuleiten.
The OFOBS system consisted of a towed underwater camera system equipped with both a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11) as well as an integrated sidescan sonar system. The cameras were mounted on a steel frame (140L x 92W x 135H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor structures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOBS during deployments, with additional positioning information provided by the integrated INS and DVL systems, which was undergoing testing during this cruise. In this dataset seabed photos from a height of approximately 60 cm from the seafloor, depicting an area of approximately 1.5 m**2, with variations depending on the actual height above ground of the system. Conditions were not optimal, with many particles in the water and considerable ship heave.
The OFOBS system consisted of a towed underwater camera system equipped with both a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11) as well as an integrated sidescan sonar system. The cameras were mounted on a steel frame (140L x 92W x 135H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor structures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOBS during deployments, with additional positioning information provided by the integrated INS and DVL systems, which was undergoing testing during this cruise. In this dataset seabed photos from a height of approximately 60 cm from the seafloor, depicting an area of approximately 1.5 m**2, with variations depending on the actual height above ground of the system. Conditions were not optimal, with many particles in the water and considerable ship heave.
The OFOBS system consisted of a towed underwater camera system equipped with both a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11) as well as an integrated sidescan sonar system. The cameras were mounted on a steel frame (140L x 92W x 135H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor structures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOBS during deployments, with additional positioning information provided by the integrated INS and DVL systems, which was undergoing testing during this cruise. In this dataset seabed photos from a height of approximately 60 cm from the seafloor, depicting an area of approximately 1.5 m**2, with variations depending on the actual height above ground of the system. Conditions were not optimal, with many particles in the water and considerable ship heave.
The OFOBS system consisted of a towed underwater camera system equipped with both a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11) as well as an integrated sidescan sonar system. The cameras were mounted on a steel frame (140L x 92W x 135H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor structures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOBS during deployments, with additional positioning information provided by the integrated INS and DVL systems, which was undergoing testing during this cruise. In this dataset seabed photos from a height of approximately 60 cm from the seafloor, depicting an area of approximately 1.5 m**2, with variations depending on the actual height above ground of the system. Conditions were not optimal, with many particles in the water and considerable ship heave.
The OFOBS system consisted of a towed underwater camera system equipped with both a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11) as well as an integrated sidescan sonar system. The cameras were mounted on a steel frame (140L x 92W x 135H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor structures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOBS during deployments, with additional positioning information provided by the integrated INS and DVL systems, which was undergoing testing during this cruise. In this dataset seabed photos from a height of approximately 60 cm from the seafloor, depicting an area of approximately 1.5 m**2, with variations depending on the actual height above ground of the system. Conditions were not optimal, with many particles in the water and considerable ship heave.
The OFOBS system consisted of a towed underwater camera system equipped with both a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11) as well as an integrated sidescan sonar system. The cameras were mounted on a steel frame (140L x 92W x 135H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor structures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOBS during deployments, with additional positioning information provided by the integrated INS and DVL systems, which was undergoing testing during this cruise. In this dataset seabed photos from a height of approximately 60 cm from the seafloor, depicting an area of approximately 1.5 m**2, with variations depending on the actual height above ground of the system. Conditions were not optimal, with many particles in the water and considerable ship heave. 5 deployments were made during HE502, with all timestamped images collected uploaded here.
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General Information: The dump sites used for the storage of residues from the various phases of steel production have to meet very special criteria. Flue dust and washing-tower sludge contain extremely high proportions of heavy metals and, in accordance with the Council Directive of 20 Match 1978 on toxic and dangerous waste, wastes containing Pb, Cd and As are among those requiring priority consideration. Seepage water in dumps results in the leaching of heavy metals and, if no precautions are taken, in the penetration of pollutants into the earth or groundwater. The base of a dump can act as a barrier against the migration of pollutants into the groundwater and biosphere, if its permeability is low and its sorption capacity high, and if the body of rock has little tendency toward destabilization and is homogenous and thick (20 m). Rocks with these favourable characteristics are generally argillaceous. In order to establish whether a rock would be suitable for a dump base, laboratory tests are normally carried out to check the above characteristics. The laboratory data are then applied to site conditions. However, the modelling of these conditions on laboratory data often involves major uncertainties. In this case we are in the fortunate position of being able to study a flue-dust dump which has been in existence for several decades and is located on a favourable barrier rock, Posidonia shale. A long-term in-situ test which would be very difficult to simulate in a laboratory has been carried out at this dump. When modelling heavy-metal migration the normal process can be reversed. The actual situation is recorded very precisely, and pollutant migration during recent decades reconstructed. Parallel laboratory tests using the same uncontaminated rock and the same pollutants are carried out, and a model is constructed using conventional methods. The validity of such a model can then be checked, and if necessary the model can be corrected so that it corresponds to what has actually happened. In addition to establishing the value of laboratory tests for ascertaining the suitability of a dump site, it will also be possible to show whether Posidonia shale is suitable for flue-dust dumps. Posidonia shale or 'oil shale' (Lias) is often found very near to iron and steel industry works, as it constitutes the under bed of mined dogger ore. From the point of view of infrastructure, Posidonia shale is therefore a favourable site and is in fact often used as such. Furthermore, a better understanding of complex migration processes (hydro-dynamic dispersion, molecular diffusion, ion exchange, adsorption/desorption, solution-precipitation, formation of organometallic complexes, flocculation-peptization, movement of colloid particles, etc) can help to establish whether any pre-treatment of the material to be dumped or the dump base is necessary.
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