Doctoral thesis in Marine Geoscience Meddelanden från Stockholms universitets institution för geologiska vetenskaper Nº 344 Mapping bathymetry From measurement to applications Benjamin Hell 2011 Department of Geological Sciences Stockholm University Stockholm Sweden A dissertation for the degree of Doctor of Philosophy in Natural Sciences 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 collec- tion of echo sounding data to the application of Digital Bathymetric Models (DBMs) in Quaternary marine geology and physical oceano- graphy. 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, 130–200ka. 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. Keywords Ocean and coastal mapping · Digital Bathymetric Model · Geogra- phical Information System · Applications of bathymetric data · Baltic Sea · Arctic Ocean · Seafloor morphology · Ocean circulation © 2011 Benjamin Hell ISBN 978-91-7447-309-4 pp. 1–41 Department of Geological Sciences, Stockholm University, 106 91 Stockholm, Sweden Printed by US-AB SU, Stockholm Cover: Three-dimensional bathymetric portrayal of parts of the Fram Strait: Molloy Hole (upper left), Molloy Fracture Zone (center to right) and Hoovgaard Ridge (lower left). Fish tessellation derived from M. C. Escher. This thesis consists of a summary chapter and six appended papers, listed here including my contribution to each of them: Paper 1 B. Hell and M. Jakobsson (2008). A data model and processing environment for ocean-wide bathymetric data compilations. International Hydrographic Review, 9(1): 23–33. Contribution: Developed idea for the presented methods (90%); carried out the technical development (100%); wrote the manuscript (90%, supported by comments from the co-author). Paper 2 B. Hell and M. Jakobsson (unpublished). Gridding heterogeneous bathymetric data sets with stacked continuous curvature splines in tension. To be submitted for publication in Marine Geophysical Research. Contribution: Developed idea for the presented method (90%); carried out the technical development and programming (100%); tested the method (90%); wrote the manuscript (90%, supported by comments from the co-author). Paper 3 B. Hell, B. Broman, L. Jakobsson, M. Jakobsson, Å. Magnusson, and P. Wiberg (in review). The use of bathymetric data in society and science: A review from the Baltic Sea. Submitted for publication in AMBIO. Contribution: Developed idea for study together with co-authors (40%); designed the questionnaire (50%); conducted the questionnaire survey and literature review, and analyzed the results (90%); wrote the manuscript (100%, supported by comments from the co-authors). Paper 4 J. A. Dowdeswell, M. Jakobsson, K. A. Hogan, M. O’Regan, J. Backman, J. Evans, B. Hell, L. Löwemark, C. Marcussen, R. Noormets, C. Ó. Cofaigh, E. Sellén, and M. Sølvsten (2010). High-resolution geophysical observations of the Yermak Plateau and Northern Svalbard margin: Implications for ice-sheet grounding and deep-keeled icebergs. Quarternary Science Reviews, 29: 3518–3531. DOI: 10.1016/j.quascirev.2010.06.002. Contribution: Participated in multibeam and subbottom profiling data collection and processing: Shipboard responsibility for LOMROG 2009 mapping in the for the article relevant areas; collected bathymetric and subbottom profiling data on 2007 and 2009 expeditions; processed bathymetric and subbottom profiling data on both expeditions. Paper 5 M. Jakobsson, J. Nilsson, M. A. O’Regan, J. Backman, L. Löwemark, J. A. Dowdeswell, L. Mayer, L. Polyak, F. Colleoni, L. Anderson, G. Björk, D. Darby, B. Eriksson, D. Hanslik, B. Hell, C. Marcussen, E. Sellén, and Å. Wallin (2010). An Arctic Ocean ice shelf during MIS 6 constrained by new geophysical and geological data. Quarternary Science Reviews, 29: 3505–3517. DOI: 10.1016/j.quas- cirev.2010.03.015. Contribution: Participated in multibeam and subbottom profiling data collection and processing: Shipboard responsibility for LOMROG 2009 mapping in the for the article relevant areas; collected bathymetric and subbottom profiling data on 2007 and 2009 expeditions; processed bathymetric and subbottom profiling data on both expeditions. Positioning/navigation in the ice drift for sampling GC10. Paper 6 G. Björk, L. G. Anderson, M. Jakobsson, D. Antony, B. Eriksson, P. B. Eriksson, B. Hell, S. Hjalmarsson, T. Janzen, S. Jutterström, J. Linders, L. Löwemark, C. Marcussen, K. A. Olsson, B. Rudels, E. Sellén, and M. Sølvsten (2010). Flow of Canadian basin deep water in the Western Eurasian Basin of the Arctic Ocean. Deep-Sea Research I, 57: 577–586. DOI: 10.1016/j.dsr.2010.01.006. Contribution: Participated in bathymetric data collection and processing; commented on the manuscript. Paper 1 is reprinted with permission by the International Hydrographic Organisation. Paper 4, 5 and 6 are reprinted with permission from Elsevier. Publication status of the papers as of May 3, 2011. 3 Contents Summary: Mapping bathymetry 0.1 Introduction . 7 0.1.1 Measuring bathymetry . 7 0.1.2 What bathymetric data are being used for . 8 0.2 Aims of this study . 9 0.3 Ocean mapping from data collection to the use of DBMs . 10 0.3.1 Measuring and mapping bathymetry . 10 0.3.2 Hydrographic data processing . 14 0.3.3 The compilation of Digital Bathymetric Models . 15 0.3.4 The use of bathymetric data . 20 0.4 Discussion . 27 0.4.1 Tools for DBM compilations . 28 0.4.2 Gridding of heterogeneous bathymetric data sets . 28 0.4.3 The use of bathymetric data for research and other purposes . 30 0.4.4 Quaternary glaciation history of the Arctic Ocean . 30 0.4.5 The importance of bathymetry for ocean circulation . 32 0.5 Conclusions . 32 0.6 Outlook . 35 0.7 References . 36 Paper 1: Data model and processing environment — Hell and Jakobsson (2008) 1.1 Introduction and background . 45 1.2 Errors and uncertainty of bathymetric data . 46 1.2.1 Systematic errors . 46 1.2.2 Random uncertainty . 47 1.3 Metadata: Critical information for error tracking and uncertainty estimation . 47 1.4 Data storage and analysis capabilities . 47 1.4.1 A multi-dimensional data structure . 47 1.4.2 Relational database storage . 48 1.4.3 Data to be stored . 49 1.4.4 Database schema . 49 1.5 Database-GIS coupling . 51 1.6 Software implementation . 51 1.7 Application and outlook: A Digital Bathymetric Model of the North Atlantic . 51 1.7.1 Tracing DBM problems to their origins . 54 1.7.2 The power of an up-to-date sounding database . 54 1.8 Conclusions . 56 1.9 References . 56 Paper 2: Gridding with stacked splines in tension — Hell and Jakobsson (unpublished) 2.1 Introduction . 61 4 Contents 2.1.1 Background . 62 2.1.2 Variable grid cell sizes . 63 2.2 Methods . 64 2.2.1 Gridding with stacked continuous curvature splines in tension . 64 2.2.2 Study area and bathymetric source data . 64 2.3 Results . 66 2.4 Discussion . 69 2.5 Conclusions . 69 2.6 References . 70 Paper 3: Use of bathymetric data from the Baltic Sea — Hell et al. (in review) 3.1 Introduction . 75 3.1.1 Available bathymetric data for the Baltic Sea . 76 3.2 Methods . 78 3.2.1 Questionnaire survey . 78 3.2.2 Literature analysis . 78 3.3 Results . 78 3.3.1 Questionnaire survey response . 78 3.3.2 Countries performing research involving bathymetric data . 79 3.3.3 The present use of depth data . 79 3.3.4 Needs regarding bathymetric data . 82 3.3.5 The capabilities of high-resolution DBMs . 83 3.4 Discussion . 84 3.4.1 Possibilities in data collection . 86 3.5 Conclusions . 86 3.6 References . 87 Paper 4: Ice grounding on the Yermak Plateau — Dowdeswell et al. (2010) 4.1 Introduction . 93 4.2 Methods . 94 4.3 Submarine landforms from swath bathymetry . 95 4.3.1 Lineations — streamlined subglacial landforms . 95 4.3.2 Large- and small-scale curvilinear features . 96 4.3.3 Moat — current overflow channel . 97 4.3.4 Largely featureless seafloor — hemipelagic deposits . 98 4.3.5 Distribution of landform types . 98 4.4 Acoustic stratigraphy of the Yermak Plateau . 99 4.4.1 Description . ..