Intergovernmental Oceanographic Commission Technical Series 63 IMPROVED GLOBAL BATHYMETRY Final Report of SCOR Working Group 107 UNESCO 2001 Intergovernmental Oceanographic Commission Technical Series 63 IMPROVED GLOBAL BATHYMETRY Final Report of SCOR Working Group 107 UNESCO 2001 SCOR Working Group 107 Committee Members Associate Members Albert Gouveia Chris Andreasen John Hall Philippe Blondel Peter Hunter Norman Cherkis Kazuo Kobayashi Nic Flemming Christian Le Provost Peter Killworth Ron Macnab Tony Laughton Hans Schenke Hugh Young Walter Smith Bert Semtner Colin Summerhayes (Chair) Vere Shannon (Rapporteur) Robin Tokmakian David Webb Gleb Udintsev Secretariat Elizabeth Gross Meetings 1. Southampton Oceanography Centre, Southampton, UK, 11-13 November 1996 2. Johns Hopkins University, Baltimore, USA, October 27-28, 1997 Funding This document is based on work partially supported by the U.S. National Science Foundation under Grant No. 0003700. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. National Science Foundation (NSF). Acknowledgements We warmly thank the many people who supported our work on this publication and contributed to its successful completion, notably Harry Yeh, who contributed the section on tsunamis, John Goff, who contributed details about abyssal hills, and Peter Saunders, who contributed the table of sills, Ho Hien Lam for formatting the text and Gualter Soarez for proof reading and arranging the printing. SCOR is thanked for its financial and secretariat support, and IOC for enabling the chairman to take the time to finish editing the report. TABLE OF CONTENTS SUMMARY Page 1. ABSTRACT ............................................................................................................................................ 1 2. INTRODUCTION (by C.P. Summerhayes and W.H.F Smith).................................................................. 2 A. SUBMITTED PAPERS 3. THEGENERAL BATHYMETRIC PERSPECTIVE................................................................................... 5 3.1 THE GENERAL BATHYMETRIC CHART OF THE OCEANS (GEBCO) (P. M. Hunter).......................... 5 3.2 INTERNATIONAL HYDROGRAPHIC ORGANIZATION (IHO) ACTIVITIES RELATED TO BATHYMETRY (by C. Andreasen) ......................................................................................................... 9 3.3 SCIENTIFIC NEEDS AND SPECIFICATIONS FOR BATHYMETRY (by J.H. Hall)............................... 13 3.4 THE ROLE OF SATELLITE ALTIMETRY IN GLOBAL BATHYMETRY (by W.H.F. Smith) ................... 17 4. THE MARINE PHYSICS PERSPECTIVE ............................................................................................ 23 4.1 INACCURACIES IN OUR KNOWLEDGE OF THE OCEAN BATHYMETRY: A LIMITING FACTOR FOR OCEAN TIDE MODELLING (by C. Le Provost ).................................................................................... 23 4.2 NOTE ON A PRIORITIZED LIST OF AREAS WHERE IMPROVEMENTS ARE REQUIRED FOR TIDAL CALCULATIONS (by C.Le Provost)...................................................................................................... 28 4.3 TOPOGRAPHY AND GLOBAL OCEAN MODELS (by R. Tokmakian and A.J. Semtner) ..................... 30 4.4 SENSITIVITY OF OCEAN MODELS TO DIFFERENT BATHYMETRIES (by R.Tokmakian) ................ 37 4.5 TOPOGRAPHIC REQUIREMENTS NEAR SILLS FOR OCEAN MODELS (by P.D. Killworth) ............. 41 4.6 OCEAN TOPOGRAPHY FOR OCEAN MODELLING (by D.J. Webb) .................................................. 49 4.7 THE TSUNAMI PERSPECTIVE (by H.Yeh).......................................................................................... 50 5. THE MARINE GEOLOGICAL PERSPECTIVE..................................................................................... 52 5.1 THE NEEDS OF MARINE GEOLOGY AND BATHYMETRIC CAPABILITY (by A.S. Laughton) ........... 52 5.2 GLOBAL RIDGE BATHYMETRY (by Ph. Blondel)................................................................................ 57 6. THE REGIONAL PERSPECTIVE ......................................................................................................... 62 6.1 AN IMPROVED PORTRAYAL OF OCEANIC BATHYMETRY IN THE ARCTIC, BASED ON A GRID DERIVED FROM GEBCO BATHYMETRIC CONTOURS (by R. Macnab, G. Oakey and D. Vardy) ..... 62 6.2 REGIONAL COMPILATIONS: A LOW-COST APPROACH FOR IMPROVING BATHYMETRIC MAPS IN SELECTED AREAS (by R. Macnab) ................................................................................................ 69 6.3 SOUTHERN OCEAN BATHYMETRY: THE NEW BATHYMETRIC CHART OF THE WEDDELL SEA, ANTARCTICA (by H.W. Schenke) ........................................................................................................ 79 6.4 THE JAPANESE PERSPECTIVE: NEW ASPECTS OF IMPROVED GLOBAL BATHYMETRY (by K. Kobayashi).................................................................................................................................. 87 6.5 RUSSIAN INITIATIVES FOR IMPROVED OCEAN BATHYMETRY: A BRIEF REVIEW (by G. Udintsev ) ................................................................................................................................... 95 6.6 THE INDIAN OCEAN PERSPECTIVE (by A. Gouveia) ........................................................................ 98 7. THE COMMERCIAL PERSPECTIVE ................................................................................................... 99 7.1 COMMERCIAL DRIVERS FOR IMPROVED WORLDWIDE BATHYMETRY (by H.W. Young)............. 99 B. CONCLUSIONS AND R ECOMMENDATIONS 8. SCIENTIFIC REQUIREMENTS FOR IMPROVED GLOBAL BATHYMETRY .................................... 104 8.1 TOPICS WITH SCIENTIFIC NEEDS FOR IMPROVED BATHYMETRY............................................. 104 8.2 QUANTITATIVE SCIENTIFIC REQUIREMENTS................................................................................ 105 -i- 9. KEY ISSUES AND ASSOCIATED RECOMMENDATIONS ............................................................... 110 9.1 DATA GAPS ....................................................................................................................................... 110 9.2 DATA POLICY .................................................................................................................................... 113 9.3 DIGITIZING DATA .............................................................................................................................. 114 9.4 GETTING DATA INTO DATA CENTRES............................................................................................ 114 9.5 ACCESSING ALREADY COLLECTED BUT ‘UNAVAILABLE’ DATA.................................................. 114 9.6 STANDARDS...................................................................................................................................... 115 9.7 EDUCATION/AWARENESS ............................................................................................................... 115 10. PRINCIPAL PRIORITIES ................................................................................................................... 118 ANNEXES 1. LIST OF RECOMMENDATIONS................................................................................................................. 120 2. LIST OF ACRONYMS ................................................................................................................................122 -ii- 1. ABSTRACT Accurate and detailed knowledge of global bathymetry is a prerequisite for progress in the scientific understanding of the different components of the earth’s global systems, and for intelligent management of global resources. Data on the shape of the sea bed are necessary to select sites for communications cables and fisheries, to make inferences about the energy and mineral resource potential of ocean floor structures, to guide computer simulations of the behaviour of the oceans and of climate, and to forecast tsunamis. Improved knowledge of the shape of the seabed is one of the factors required for success of the planetary scale global observing systems (GOOS, the Global Ocean Observing System, and GCOS, the Global Climate Observing System) whose operations will help a larger human population to manage sustainably on an increasingly crowded Earth. SCOR Working Group 107 on Improved Global Bathymetry was charged with: (i) establishing the scientific needs for improved knowledge of ocean depths (i.e., what scientific problems need what measurements?); (ii) specifying the accuracy and resolution requirements needed in different geographical and research areas (e.g. identifying limitations and gaps to be filled); (iii) recommending actions and priorities (such as what parts of the oceans should be tackled first). The group identified a range of topics for which improvements in bathymetry were considered important, and quantified the scientific requirements in terms of horizontal and vertical resolution for a number of them. In the open ocean seawards of the continental shelf and slope there is a progressive increase in the requirement for horizontal (H) and vertical (V) resolutions from 5-10 km (H) and 10-50 m (V) over the open ocean, to 1-5 km (H) and 20 m (V) over open ocean sills, to 250 m (H) and 10 m (V) for abyssal hills, and finally to 100 m (H) and a few metres (V) in rift valleys. On the continental slope there is a requirement for 1 km (H), decreasing to 500 m (H) over canyons and ridges. On