Simultaneous tracking of multiple whales using two fiber-optic cables in the Arctic

Climate change is impacting the Arctic faster than anywhere else in the world. As a response, ecosystems are rapidly changing. As a result, we can expect rapid shifts in whale migration and habitat use concurrent with changes in human patterns. In this context, responsible management and conservation requires improved monitoring of whale presence and movement over large ranges, at fine scales and in near-real-time compared to legacy tools. We demonstrate that this could be enabled by Distributed Acoustic Sensing (DAS). DAS converts an existing fiber optic telecommunication cable into a widespread, densely sampled acoustic sensing array capable of recording low-frequency whale vocalizations. This work proposes and compares two independent methods to estimate whale positions and tracks; a brute-force grid search and a Bayesian filter. The methods are applied to data from two 260 km long, nearly parallel telecommunication cables offshore Svalbard, Norway. First, our two methods are validated using a dedicated active air gun experiment, from which we deduce that the localization errors of both methods are 100 m. Then, using fin whale songs, we demonstrate the methods' capability to estimate the positions and tracks of eight fin whales over a period of five hours along a cable section between 40 and 95 km from the interrogator unit, constrained by increasing noise with range, variability in the coupling of the cable to the sea floor and water depths. The methods produce similar and consistent tracks, where the main difference arises from the Bayesian filter incorporating knowledge of previously estimated locations, inferring information on speed, and heading. This work demonstrates the simultaneous localization of several whales over a 800 km area, with a relatively low infrastructural investment. This approach could promptly inform management and stakeholders of whale presence and movement and be used to mitigate negative human-whale interaction.publishedVersio

Using DAS-Fibres for Lunar Seismic Imaging

A set of major mission themes has emerged from the 2020 ESA Call for Ideas, "Exploring the Moon with a large European lander", with a polar ice prospecting mission identified and currently being studied as a candidate EL3 science mission. A combination of Ground-Penetrating Radar (GPR), Magnetic Induc-tion Spectroscopy (MIS) and Distributed Acoustic Sensing (DAS) has been proposed to localize and 3D-map water ice and volatiles in the subsurface. In 2020 CGF (Centre for Geophysical Forecasting at NTNU) conducted a DAS field test using one DAS (Distributed Acoustic Sensing) interrogator located in Longyearbyen. An interrogator is a laser instru-ment that sends light into a fiber optic cable to perform real-time measurements of strain. This operation was a cooperation between CGF/NTNU, and industry. 40 days of continuous DAS recording was successfully completed, and the results demonstrate the huge potential of using telecommunication fibre cables for underwater sensing. We recorded more than 800 whale soundings, several earthquakes, ship passing and long distance Atlantic storms in 2020. In another field test in 2021 CGF established a field station in a quick clay area in Rissa, Norway for the purpose of acoustic monitoring of the clay proper-ties. Both these experiments were successful and proved that good DAS-data can be acquired using the newly developed high-energy interrogator

Evolution and Character of Supra-Salt Faults in the Easternmost Hammerfest Basin, SW Barents Sea

Research analyzed the influence of parameters derived from urban planning, architecture, building materials and technology, building physics, users and patterns of use, the measured thermal performance of the envelope and thermal comfort parameters on the energy performance indicators of two representative kindergartens. The paper presents an energy performance indicator through design and measured parameters of representative samples of old and new kindergartens located in the temperate climate zone of Banja Luka (northern Bosnia and Herzegovina). When the data presented in EN 13790 concerning the patterns of use and design temperatures for residential buildings or educational and cultural buildings is compared with the measured, surveyed, analyzed and estimated kindergarten data, the design parameters are found to deviate from the measured parameters. On the basis of the presented analysis, it is recommended that measurement of the thermal performance of envelopes of old buildings become a mandatory part of energy audit, and that an appropriate set of parameter values be used in the calculation of the energy performance indicator of kindergartens. Kindergartens must be introduced as a specific type of buildings in policies related to the minimum requirements for the energy performance of buildings and rational use of energy, energy audit and certification of buildings

Morphometric analysis of sediment conduits on a bathymetric high: Implications for palaeoenvironment and hydrocarbon prospectivity

Canyons and other sediment conduits are important components of the deep-water environment and are the main pathways for sediment transport from the shelf to the basin floor. Using 3-D and 2-D seismic reflection data, seismic facies and statistical morphometric analyses, this study showed the architectural evolution of five canyons, two slide scars and four gullies on the southern part of the Loppa High, Barents Sea. Morphometric parameters such as thalweg depth (lowest point on a conduit’s base), wall depth (middle point), height, width and base width, sinuosity, thalweg gradient, aspect ratio (width/height) and cross-sectional area of the conduits were measured at intervals of 250-m perpendicular to the conduits’ pathways. Our results show that the canyons and slide scars in the study area widen down slope, whereas the gullies are narrow and short with uniform widths. The sediment conduits in the study area evolved in three stages. The first stage is correlated with a time when erosion and bypass were dominant in the conduits, and sediment transferred to the basin in the south. The second stage occurred when basin subsidence was prevalent, and a widespread fine-grained sequence was deposited as a drape blanketing the canyons and other conduits. A final stage occurred when uplift and glacial erosion configured the entire southern Loppa High into an area of denudation. Our work demonstrates that the morphometric parameters of the canyons, slide scars and gullies generally have increasing linear trends with down-slope distance, irrespective of their geometries. The morphometric analysis of the sediment conduits in the study area has wider applications for understanding depositional processes, reservoir distribution and petroleum prospectivity in frontier basins

New interpretation of the spreading evolution of the Knipovich Ridge derived from aeromagnetic data

Insights into the spreading evolution of the Knipovich Ridge and development of the Fram Strait are revealed from a recent aeromagnetic survey. As an ultraslow spreading ridge in an oblique system located between the Svalbard–Barents Sea and the Northeast Greenland rifted margins, the dynamics of the Knipovich Ridge opening has long been debated. Its 90° bend with the Mohns Ridge, rare in plate tectonics, affects the evolution of the Fram Strait and motivates the study of crustal deformation with this distinctive configuration. We identified magnetic isochrons on either side of the present-day Knipovich Ridge. These magnetic observations considerably reduce the mapped extent of the oceanic domain and question the present understanding of the conjugate rifted margins. Our analysis reveals a failed spreading system before a major spreading reorganization of the Fram Strait gateway around magnetic chron C6 (circa 20 Ma)

Deep-seated faults and hydrocarbon leakage in the Snøhvit Gas Field, Hammerfest Basin, Southwestern Barents Sea

High-quality 3D seismic data are used to analyze the history of fault growth and hydrocarbon leakage in the Snøhvit Field, Southwestern Barents Sea. The aim of this work is to evaluate tectonic fracturing as a mechanism driving hydrocarbon leakage in the study area. An integrated approach was used which include seismic interpretation, fault modeling, displacement analysis and multiple seismic attribute analysis. The six major faults in the study area are dip-slip normal faults which are characterized by complex lateral and vertical segmentation. These faults are affected by three main episodes of fault reactivation in the Late Jurassic, Early Cretaceous and Paleocene. Fault reactivation in the study area was mainly through dip-linkage. The throw-distance plots of these representative faults also revealed along-strike linkage and multi-skewed C-type profiles. The faults evolved through polycyclic activity involving both blind propagation and syn-sedimentary activity with their maximum displacements recorded at the reservoir zone. The expansion and growth indices provided evidence for the interaction of the faults with sedimentation throughout their growth history. Soft reflections or hydrocarbon-related high-amplitude anomalies in the study area have negative amplitude, reverse polarity and are generally unconformable with structural reflectors. The interpreted fluid accumulations are spatially located at the upper tips of the major faults and gas chimneys. Four episodes of fluid migration are inferred and are linked to the three phases of fault reactivation and Neogene glaciations. Hydrocarbon leakage in the Snøhvit Gas Field is driven by tectonic fracturing, uplift, and erosion. The interpreted deep-seated faults are the main conduits for shallow hydrocarbon accumulations observed on seismic profiles

Recurrent mass-wasting in the Sørvestsnaget Basin Southwestern Barents Sea: A test of multiple hypotheses

Mass-wasting on the NE Atlantic Margin is generally attributed to Cenozoic glaciations. Using high-quality 2D seismic datasets and two exploration wells, this study investigates the types and driving mechanisms of mass-wasting in the Sørvestsnaget Basin, Southwestern Barents Sea. The methods include seismic interpretation of shelf margin clinoforms, mass-transport deposits (MTDs), submarine channels and V-shaped canyons. The shelf-edge trajectory provided information about sea-level conditions, paleo-sediment routes, and dispersal patterns during the evolution of the basin. In terms of the internal geometry of seismic reflectors, the major depositional units are five sedimentary packages (P1 to P5) characterized by distinct southwest dipping shelf margin clinoforms. Seven identified MTDs have Late Miocene to Pleistocene ages. Miocene and Early Pliocene MTDs in the basin demonstrate a tendency for initial translation through canyons and channels. The youngest MTDs are composed of glaciogenic sediments remobilized by ice streams during large-scale Neogene and Quaternary glaciations. This work shows that mass-wasting has been a recurrent and inherent process in the Sørvestsnaget Basin from the Miocene until recent times. The main triggering mechanisms for slope failure in the basin are interpreted to be increased pore pressure from sea-level fall and high sedimentation rate. Mass-wasting in the study area occurred through progressive, retrogressive and coherent downslope failures

Seismic geomorphology of submarine channel-belt complexes in the Pliocene of the Levant Basin, offshore central Israel

In this study, analyses of a high-resolution, three-dimensional seismic reflection dataset and well-log data were combined to characterize a distinct Pliocene interval in the Levant Basin offshore central Israel. This succession is characterised by moderate to high-amplitude, discontinuous to continuous seismic reflections between a mass transport deposit above and an undeformed basin series below. The studied interval contains two separate channelised subunits. Morphologically, the channels trend in a north to northwest direction, are incised 230 m and higher sinuosity, >1.1). The mechanisms that control the interplay between sedimentary processes and channel evolution show a cyclic pattern. Due to the cyclic occurrence of different channel types and the estimated age of the studied interval, formation and evolutionary processes of the submarine channels in the study area are likely to be controlled by relative sea level fluctuations and increased Nile River sediment supply, which is associated with rapid uplift of the Ethiopian plateau and increased African Monsoon rainfall during the Pliocene

Self-similarity of intrasalt thrust faults: Lessons from offshore Levant Basin and the Dead Sea

The Levant Basin in the eastern Mediterranean Sea developed during rifting episodes occurring from Permian to the Early Jurassic (Netzeband et al. 2006; Gardosh et al. 2010), and has been a deep-water basin with a passive continental margin at least since the Cretaceous (Gardosh et al. 2008). Thick sequences of halite and interbedded shales (stringers) were deposited during the infamous Messinian Salinity Crisis (5.96-5.33 Ma). Salt-rich passive continental margins facilitate complex deformation of both the mobile salt and the surrounding rock mass (Allen et al. 2016, Cartwright et al. 2012). The weak salt will mobilize as a response to differential loading (gravity spreading) or tilting of the basin (gravity gliding), and intricate strains within the package may be observed due to the difference in AI between the halite and the stringers. This study compares large-scaled intrasalt thrust systems interpreted on high quality 3D seismic data from offshore Israel (Kartveit et al. under review) with recently published outcrop analogies in gravity-driven mass transport systems near the Dead Sea (Alsop et al. 2017a, Alsop et al. 2017b) in order to evaluate the multi-phase deformation history in the basin

Multiphase structural evolution and geodynamic implications of Messinian salt-related structures, Levant Basin, offshore Israel

Speculations surround salt deformation in the Mediterranean Basins, both related to the deformation history and the triggers for halokinesis since the onset of the Messinian Salinity Crisis (MSC). This work presents a detailed description of the mechanisms driving internal and external deformation of a salt giant from the Levant Basin, offshore Israel. The intrasalt siliciclastic layers generate good internal reflectivity within the Messinian evaporites, allowing a thorough elucidation of the complex evolution and nature of syn- and post-Messinian structures. We have identified three distinct phases of deformation in the deep basin, based on the orientation, timing and geometry of their related structures: The first phase is characterized by small-scaled, gravity-driven, contractional faults and folds oriented N-S that have been overprinted by a second syn-Messinian, NW-SE trending, deformation phase affecting the clastic bundles. This latter deformation phase is the cause of truncation of the intrasalt stringers on the intra-Messinian erosional surface (IMTS). The third deformation phase occurred in the Pleistocene and affected all strata from the Messinian salt to the seabed. This deformational phase produced thrust, strike-slip- and normal faults, but the dominant orientation of the thrust faults and folds is NNW-SSE. Our study demonstrates that the first deformation phase was caused by regional uplift along the Levant margin during the Messinian, the second is a response to basin subsidence toward the Cyprus Arc, also syn-Messinian, and the third phase is likely related to the reorganization of the African-Eurasian plate boundary and activity along the Dead Sea Transform after the MSC