Seafloor multibeam backscatter calibration experiment: comparing 45°-tilted 38-kHz split-beam echosounder and 30-kHz multibeam data     

Yoann Ladroit  Geoffroy Lamarche  Arne Pallentin 《Marine Geophysical Researches》2018,39(1-2):41-53

Obtaining absolute seafloor backscatter measurements from hydrographic multibeam echosounders is yet to be achieved. We propose a low-cost experiment to calibrate the various acquisition modes of a 30-kHz Kongsberg EM 302 multibeam echosounder in a range of water depths. We use a 38-kHz Simrad EK60 calibrated fisheries split-beam echosounder mounted at 45° angle on the vessel’s hull as a reference for the calibration. The processing to extract seafloor backscatter from the EK60 requires bottom detection, ray tracing and motion compensation to obtain acceptable geo-referenced backscatter measurements from this non-hydrographic system. Our experiment was run in Cook Strait, New Zealand, on well-known seafloor patches in shallow, mid, and deep-water depths. Despite acquisition issues due to weather, our results demonstrate the strong potential of such an approach to obtain system’s absolute calibration which is required for quantitative use of backscatter strength data.  相似文献   

Spatial constrained inverse rock physics modelling   总被引：1，自引：0，他引：1       下载免费PDF全文

Erling H. Jensen  Tor Arne Johansen 《Geophysical Prospecting》2015,63(1):183-191

Predicting reservoir parameters, such as porosity, lithology, and saturations, from geophysical parameters is a problem with non‐unique solutions. The variance in solutions can be extensive, especially for saturation and lithology. However, the reservoir parameters will typically vary smoothly within certain zones—in vertical and horizontal directions. In this work, we integrate spatial correlations in the predicted parameters to constrain the range of predicted solutions from a particular type of inverse rock physics modelling method. Our analysis is based on well‐log data from the Glitne field, where vertical correlations with depth are expected. It was found that the reservoir parameters with the shortest depth correlation (lithology and saturation) provided the strongest constraint to the set of solutions. In addition, due to the interdependence between the reservoir parameters, constraining the predictions by the spatial correlation of one parameter also reduced the number of predictions of the other two parameters. Moreover, the use of additional constraints such as measured log data at specific depth locations can further narrow the range of solutions.  相似文献   

Zircon fission‐track ages from Newfoundland—A proxy for high geothermal gradients and exhumation before opening of the Central Atlantic Ocean     

Arne P. Willner  Stuart N. Thomson  Johannes Glodny  Hans‐Joachim Massonne  Rolf L. Romer  Cees R. van Staal  Alexandre Zagorevski 《地学学报》2019,31(1):1-10

Following Appalachian orogenesis, metamorphic rocks in central Newfoundland were exhumed and reburied under Tournaisian strata. New zircon fission‐track (ZFT) ages of metamorphic rocks below the Tournaisian unconformity yield post‐depositionally reset ages of 212–235 Ma indicating regional fluid‐absent reheating to at least ≥220°C. Post‐Tournaisian sedimentary thicknesses in surrounding basins show that burial alone cannot explain such temperatures, thus requiring that palaeo‐geothermal gradients increased to ≥30–40°C/km before final late Triassic accelerated cooling. We attribute these elevated palaeo‐geothermal gradients to localized thermal blanketing by insulating sediments overlying radiogenic high‐heat‐producing granitoids. Late Triassic rifting and magmatism before break up of Pangaea likely also contributed to elevated heat flow, as well as uplift, triggering late Triassic accelerated cooling and exhumation. Thermochronological ages of 240–200 Ma are seen throughout Atlantic Canada, and record rifting and basaltic magmatism on the conjugate margins of the Central Atlantic Ocean preceding the onset of oceanic spreading at ~190 Ma.  相似文献   

Differential response at the seafloor during Palaeocene and Eocene ocean warming events at Walvis Ridge,Atlantic Ocean (ODP Site 1262)          下载免费PDF全文

Arne Deprez  Sofie Jehle  André Bornemann  Robert P. Speijer 《地学学报》2017,29(1):71-76

The Latest Danian Event (LDE, c. 62.1 Ma) is an early Palaeogene hyperthermal or transient (<200 ka) ocean warming event. We present the first deep‐sea benthic foraminiferal faunal record to study deep‐sea biotic changes together with new benthic (Nuttallides truempyi) stable isotope data from Walvis Ridge Site 1262 (Atlantic Ocean) to evaluate whether the LDE was controlled by similar processes as the minor early Eocene hyperthermals. The spacing of the double negative δ¹³C and δ¹⁸O excursion and the slope of the δ¹⁸O–δ¹³C regression are comparable, strongly suggesting a similar orbital control and pacing of eccentricity maxima as well as a rather homogeneous carbon pool. However, in contrast to early Eocene hyperthermals, the LDE exhibits a remarkable stability of the benthic foraminiferal fauna. This lack of benthic response could be related to the absence of threshold‐related circulation changes or better pre‐adaptation to elevated deep‐sea temperatures, as the LDE was superimposed on a cooling trend, in contrast to early Eocene warming.  相似文献   

Modelling the effect of climate change on the wave climate of the world’s oceans     

Erik Vanem  Bent Natvig  Arne Bang Huseby 《Ocean Science Journal》2012,47(2):123-145

This paper analyses the trends and the future projections of significant wave height in several ocean areas at different parts of the world. It uses a stochastic Bayesian hierarchical space-time model, with a regression component with atmospheric levels of CO₂ as covariates in order to estimate the expected long-term trends and make future projections towards the year 2100. The model was initially developed for an area in the North Atlantic ocean, and has been found to perform reasonably well there, and it is now investigated how the model performs for other ocean areas. 11 new ocean areas have been analysed with the model, and this paper presents the results pertaining to the estimated long-term trends and future projections of monthly maximum significant wave height for each of the 12 ocean areas.  相似文献   

Exposure of phytoplankton to ekofisk crude oil     

Kjetill Østgaard  Ingvar Eide  Arne Jensen 《Marine environmental research》1984,11(3):183-200

Solutions of Ekofisk crude oil in sea water were prepared by slow stirring for 21h in a closed system. Headspace and GC/MS techniques were applied to establish dose composition and levels. The standardized test medium produced in a closed system contained approximately 14 mg oil per litre and was dominated by low molecular weight aromatic hydrocarbons and phenols.The toxicity of the standarized oil-containing medium to three marine diatoms was studied in a cage culture turbidostat and by conventional batch culture technique. The three algal species differed in sensitivity to the oil compounds, but showed identical ranking in both test systems.Standardized test medium diluted to 50% with respect to oil content stopped the growth of the most sensitive alga, Skeletonema costatum. For comparison naphthalene was applied and gave 50 % growth reduction at a concentration of 400 μg litre^?1. The growth of Chaetoceros ceratosporum was only slighty affected by the full strength standard test medium, which had no influence on the growth of Phaeodactylum tricornutum, the least sensitive organism. The presence of an oil layer on the surface of the standard test medium during the growth test greatly increased its toxicity and blocked completely the photosynthesis even of P. tricornutum after 4 days.  相似文献   

Salmon lice, Lepeophtheirus salmonis (Kroyer), infestation in sympatric populations of Arctic char, Salvelinus alpinus (L.), and sea trout, Salmo trutta (L.), in areas near and distant from salmon farms     

Bjorn  Pal Arne; Finstad  Bengt 《ICES Journal of Marine Science》2002,59(1):131-139

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Influence of seismic shooting on the lesser sandeel (Ammodytes marinus)     

Hassel  Arne; Knutsen  Tor; Dalen  John; Skaar  Kristian; Lokkeborg  Svein; Misund  Ole Arve; Ostensen  Oivind; Fonn  Merete; Haugland  Eli Kyrkjebo 《ICES Journal of Marine Science》2004,61(7):1165-1173

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What is good for the fishermen, is good for the nation: co-management in the Norwegian fishing industry in the 1990s     

Bjrn Hersoug  Stein Arne Rnes 《Ocean & Coastal Management》1997,35(2-3)

This paper analyses the concept of ‘co-management’ and tries to explain why co-management has recently become important to different types of fisheries administration. A preliminary analytical framework is sketched, before going on to describe the Norwegian co-management system, known as ‘centrally directed consultation’, where fishermen's representatives are established on a wide range of organisations that exert a direct influence on fisheries policy, including not only quota management but grant aid, sales, research and education. The final section is devoted to the lessons that may be learned from the Norwegian experience, bearing in mind the particular background of Norway and its historical setting.  相似文献   

The behaviour of spawning herring in relation to a survey vessel     

Skaret  Georg; Axelsen  Bjorn Erik; Nottestad  Leif; Ferno  Anders; Johannessen  Arne 《ICES Journal of Marine Science》2005,62(6):1061-1064

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