| 1. |
- Björk, Göran, 1956, et al.
(författare)
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Flow of Canadian Basin Deep Water in the Western Eurasian Basin of the Arctic Ocean
- 2010
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Ingår i: Deep Sea Research. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 57:4, s. 577-586
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Tidskriftsartikel (refereegranskat)abstract
- The LOMROG 2007 expedition targeted the previously unexplored southern part of the Lomonosov Ridge north of Greenland together with a section from the Morris Jesup Rise to Gakkel Ridge. The oceanographic data shows that Canadian Basin Deep Water (CBDW) passes the Lomonosov Ridge in the area of the Intra Basin close to the North Pole and then continues along the ridge towards Greenland and further along its northernmost continental slope. The CBDW is clearly evident as a salinity maximum and oxygen minimum at a depth of about 2000 m. The cross slope sections at the Amundsen Basin side of the Lomonosov Ridge and further south at the Morris Jesup Rise show a sharp frontal structure higher up in the water column between Makarov Basin water and Amundsen Basin water. The frontal structure continues upward into the Atlantic Water up to a depth of about 300 m. The observed water mass division at levels well above the ridge crest indicates a strong topographic steering of the flow and that different water masses tend to pass the ridge guided by ridge-crossing isobaths at local topographic heights and depressions. A rough scaling analysis shows that the extremely steep and sharply turning bathymetry of the Morris Jesup Rise may force the boundary current to separate and generate deep eddies.
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| 2. |
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| 3. |
- Dowdeswell, J. A., et al.
(författare)
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High-resolution geophysical observations of the Yermak Plateau and northern Svalbard margin : Implications for ice-sheet grounding and deep-keeled icebergs
- 2010
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:25-26, s. 3518-3531
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution geophysical evidence on the seafloor morphology and acoustic stratigraphy of the Yermak Plateau and northern Svalbard margin between 79°20′ and 81°30′N and 5° and 22°E is presented. Geophysical datasets are derived from swath bathymetry and sub-bottom acoustic profiling and are combined with existing cores to derive chronological control. Seafloor landforms, in the form of ice-produced lineations, iceberg ploughmarks of various dimensions (including features over 80 m deep and down to about 1000 m), and a moat indicating strong currents are found. The shallow stratigraphy of the Yermak Plateau shows three acoustic units: the first with well-developed stratification produced by hemipelagic sedimentation, often draped over a strong and undulating internal reflector; a second with an undulating upper surface and little acoustic penetration, indicative of the action of ice; a third unit of an acoustically transparent facies, resulting from debris flows. Core chronology suggests a MIS 6 age for the undulating seafloor above about 580 m. There are several possible explanations, including: (a) the flow of a major grounded ice sheet across the plateau crest from Svalbard (least likely given the consolidation state of the underlying sediments); (b) the more transient encroachment of relatively thin ice from Svalbard; or (c) the drift across the plateau of an ice-shelf remnant or megaberg from the Arctic Basin. The latter is our favoured explanation given the evidence currently at our disposal.
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| 4. |
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| 5. |
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| 6. |
- Hell, Benjamin, et al.
(författare)
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Gridding heterogeneous bathymetric data sets with stacked continuous curvature splines in tension
- 2011
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Ingår i: Marine Geophysical Researches. - : Springer Netherlands. - 0025-3235 .- 1573-0581. ; 32:4, s. 493-501
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Tidskriftsartikel (refereegranskat)abstract
- Gridding heterogeneous bathymetric data sets for the compilation of Digital bathymetric models (DBMs), poses specific problems when there are extreme variations in source data density. This requires gridding routines capable of subsampling high-resolution source data while preserving as much as possible of the small details, at the same time as interpolating in areas with sparse data without generating gridding artifacts. A frequently used gridding method generalizes bicubic spline interpolation and is known as continuous curvature splines in tension. This method is further enhanced in this article in order to specifically handle heterogeneous bathymetric source data. Our method constructs the final grid through stacking several surfaces of different resolutions, each generated using the splines in tension algorithm. With this approach, the gridding resolution is locally adjusted to the density of the source data set: Areas with high-resolution data are gridded at higher resolution than areas with sparse source data. In comparison with some of the most widely used gridding methods, our approach yields superior DBMs based on heterogeneous bathymetric data sets with regard to preserving small bathymetric details in the high-resolution source data, while minimizing interpolation artifacts in the sparsely data constrained regions. Common problems such as artifacts from ship tracklines are suppressed. Even if our stacked continuous curvature splines in tension gridding algorithm has been specifically designed to construct DBMs from heterogeneous bathymetric source data, it may be used to compile regular grids from other geoscientific measurements.
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| 7. |
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| 8. |
- Hell, Benjamin, 1977-
(författare)
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Mapping bathymetry : From measurement to applications
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surface elevation is likely the most fundamental property of our planet. In contrast to land topography, bathymetry, its underwater equivalent, remains uncertain in many parts of the World ocean. Bathymetry is relevant for a wide range of research topics and for a variety of societal needs. Examples, where knowing the exact water depth or the morphology of the seafloor is vital include marine geology, physical oceanography, the propagation of tsunamis and documenting marine habitats. Decisions made at administrative level based on bathymetric data include safety of maritime navigation, spatial planning along the coast, environmental protection and the exploration of the marine resources.This thesis covers different aspects of ocean mapping from the collection of echo sounding data to the application of Digital Bathymetric Models (DBMs) in Quaternary marine geology and physical oceanography. Methods related to DBM compilation are developed, namely a flexible handling and storage solution for heterogeneous sounding data and a method for the interpolation of such data onto a regular lattice. The use of bathymetric data is analyzed in detail for the Baltic Sea. With the wide range of applications found, the needs of the users are varying. However, most applications would benefit from better depth data than what is presently available. Based on glaciogenic landforms found in the Arctic Ocean seafloor morphology, a possible scenario for Quaternary Arctic Ocean glaciation is developed. Our findings suggest large ice shelves around parts of the Arctic Ocean during Marine Isotope Stage 6, 130–200 ka. Steered by bathymetry, deep water from the Amerasian Basin of the Arctic Ocean flows over the central Lomonosov Ridge into the Eurasian Basin. This water mass is traced on its continuing way towards Greenland and the Fram Strait. At the Morris Jesup Rise, bathymetry plays an important role in the partial re-circulation of the water into the Amerasian Basin.
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| 9. |
- Hell, Benjamin, 1977-, et al.
(författare)
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The use of bathymetric data in society and science : A review from the Baltic Sea
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Tidskriftsartikel (refereegranskat)abstract
- Bathymetry, the underwater topography, is a fundamental property of oceans, seas and lakes. As such it is important for a wide range of applications, like physical oceanography, marine geology, geophysics and biology or the administration of marine resources. The exact requirements users may have regarding bathymetric data are, however, unclear. Here, the results of a questionnaire survey and a literature review are presented, concerning the use of Baltic Sea bathymetric data in research and for societal needs. It is demonstrated that there is a great need for detailed bathymetric data, which cannot be satisfied by the digital bathymetric models publicly available, despite of the abundance of high quality bathymetric data that are produced for safety of navigation purposes. Our study shows that DBMs based on such data could substantially improve the base data for administrative decision making as well as the possibilities for marine research in the Baltic Sea.
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| 10. |
- Hell, Benjamin, 1977-, et al.
(författare)
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The Use of Bathymetric Data in Society and Science : A Review from the Baltic Sea
- 2012
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 41:2, s. 138-150
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Forskningsöversikt (refereegranskat)abstract
- Bathymetry, the underwater topography, is a fundamental property of oceans, seas, and lakes. As such it is important for a wide range of applications, like physical oceanography, marine geology, geophysics and biology or the administration of marine resources. The exact requirements users may have regarding bathymetric data are, however, unclear. Here, the results of a questionnaire survey and a literature review are presented, concerning the use of Baltic Sea bathymetric data in research and for societal needs. It is demonstrated that there is a great need for detailed bathymetric data. Despite the abundance of high-quality bathymetric data that are produced for safety of navigation purposes, the digital bathymetric models publicly available to date cannot satisfy this need. Our study shows that DBMs based on data collected for safety of navigation could substantially improve the base data for administrative decision making as well as the possibilities for marine research in the Baltic Sea.
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| 11. |
- Hell, Benjamin, 1977-
(författare)
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Towards the compilation of a new Digital Bathymetric Model of the North Atlantic Ocean
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Topography on land and bathymetry, its underwater depth equivalent, belong to the most fundamental attributes of the solid earth's surface. Over two thirds of the earth is covered by water, with about 90% of this area lying more than 1000m below the sea surface. In contrast to the land area, most of the deep sea remains largely unexplored and to date the topography of the Moon or Mars is much better known than the bathymetry of large parts of our own planet.Deep sea ocean mapping can directly be carried out with ship-bound echo sounders or indirectly through a remote sensing method known as satellite altimetry. Modern echo sounding technology allows for high resolution mapping with unsurpassed accuracy. Due to the vastness of the oceans, however, even after decades of mapping activity, the oceans are far from completely surveyed, and the echo soundings accumulated over the time with different, meanwhile evolving technologies are of highly varying quality. Satellite altimetry, on the contrary, provides virtually complete coverage of the entire globe, although the achieved resolution and accuracy is limited. For the compilation of consistent, ocean spanning Digital Bathymetric Models (DBMs) from raw depth measurements, an appropriate data basis is therefore a heterogeneous mixture of historical and contemporary echo soundings, complemented by satellite altimetry as needed. The North Atlantic is by far the best mapped of all oceans and as such it provides an ideal area to study scientific problems related to ocean mapping and DBM compilation. The heterogeneity and size of the global bathymetric data basis require powerful solutions to handle and process both data and metadata effectively. In this work, a spatial relational database in combination with a geographical information system (GIS) form a flexible tool kit for a DBM compilation, and a data model for the storage and retrieval of both data and metadata is developed. In a case study I show the potential of the available sounding data in the North Atlantic to derive a DBM with significant improvements over the models commonly used today. Many geoscientific applications require that data sets are sampled on a regularly spaced grid, notwithstanding the fact that data acquisition often provides measurements at irregular positions and with incomplete coverage.Several methods exist for interpolating and gridding raw data to obtain gapless grids. In ocean mapping, minimum curvature bicubic splines in tension are a commonly used approach. This work presents a refined technique, multiple resolution splines in tension. The method takes the local data density into consideration during the gridding process, in order to reduce gridding artifacts mainly caused by very inhomogeneous data coverage. It is shown that multiple resolution splines in tension allow for a high maximum grid resolution, without introducing artifacts that appear with regular splines in tension interpolation at the same resolution.
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| 12. |
- Jakobsson, Martin, 1966-, et al.
(författare)
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An Arctic Ocean ice shelf during MIS 6 constrained by new geophysical and geological data
- 2010
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:25-26, s. 3505-3517
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis of floating ice shelves covering the Arctic Ocean during glacial periods was developed in the 1970s. In its most extreme form, this theory involved a 1000 m thick continuous ice shelf covering the Arctic Ocean during Quaternary glacial maxima including the Last Glacial Maximum (LGM). While recent observations clearly demonstrate deep ice grounding events in the central Arctic Ocean, the ice shelf hypothesis has been difficult to evaluate due to a lack of information from key areas with severe sea ice conditions. Here we present new data from previously inaccessible, unmapped areas that constrain the spatial extent and timing of marine ice sheets during past glacials. These data include multibeam swath bathymetry and subbottom profiles portraying glaciogenic features on the Chukchi Borderland, southern Lomonosov Ridge north of Greenland, Morris Jesup Rise, and Yermak Plateau. Sediment cores from the mapped areas provide age constraints on the glaciogenic features. Combining these new geophysical and geological data with earlier results suggests that an especially extensive marine ice sheet complex, including an ice shelf, existed in the Amerasian Arctic Ocean during Marine Isotope Stage (MIS) 6. From a conceptual oceanographic model we speculate that the cold halocline of the Polar Surface Water may have extended to deeper water depths during MIS 6 inhibiting the warm Atlantic water from reaching the Amerasian Arctic Ocean and, thus, creating favorable conditions for ice shelf development. The hypothesis of a continuous 1000 m thick ice shelf is rejected because our mapping results show that several areas in the central Arctic Ocean substantially shallower than 1000 m water depth are free from glacial influence on the seafloor.
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| 13. |
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| 14. |
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| 15. |
- Jakobsson, Martin, et al.
(författare)
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The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0
- 2012
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 39
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Tidskriftsartikel (refereegranskat)abstract
- The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded bathymetric compilation in 1999. The IBCAO bathymetric portrayals have since supported a wide range of Arctic science activities, for example, by providing constraint for ocean circulation models and the means to define and formulate hypotheses about the geologic origin of Arctic undersea features. IBCAO Version 3.0 represents the largest improvement since 1999 taking advantage of new data sets collected by the circum-Arctic nations, opportunistic data collected from fishing vessels, data acquired from US Navy submarines and from research ships of various nations. Built using an improved gridding algorithm, this new grid is on a 500 meter spacing, revealing much greater details of the Arctic seafloor than IBCAO Version 1.0 (2.5 km) and Version 2.0 (2.0 km). The area covered by multibeam surveys has increased from similar to 6% in Version 2.0 to similar to 11% in Version 3.0. Citation: Jakobsson, M., et al. (2012), The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0, Geophys. Res. Lett., 39, L12609, doi:10.1029/2012GL052219.
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| 16. |
- Lantz, Patrik, et al.
(författare)
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Visual Cryptography and Obfuscation: A Use-Case for Decrypting and Deobfuscating Information using Augmented Reality
- 2015
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Ingår i: Financial Cryptography and Data Security. San Juan, Puerto Rico. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. - 9783662480519 ; 8976, s. 261-273
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Konferensbidrag (refereegranskat)abstract
- As new technologies emerge such as wearables, it opens up for new challenges, especially related to security and privacy. One such recent technology is smart glasses. The use of glasses introduces security and privacy concerns for the general public but also for the user itself. In this paper we present ongoing theoretical work which focus on privacy of the user during authentication. We propose and analyze two methods, visual cryptography and obfuscation for protecting the user against HUD and camera logging adversaries as well as shoulder-surfing.
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