The New Bathymetric Charts Of The Weddell Sea: AWI BCWS

The Weddell Sea, southernmost part of the Atlantic Ocean and located between the Antarctic Peninsula, the South Shetland Islands, and East Antarctica, is difficult to sail, since much of the Weddell Sea is covered with multi-year sea ice. Data on bathymetry are patchy, varying in type, source, and quality, resulting in different approaches for mapping the seafloor. Since about one decade, large amounts of bathymetric data have been collected by polar research expeditions, such as the German research vessel Polarstern. Being part of the vital interest of research and development programmes at the Alfred Wegener Institute for Polar and Marine Research (AWI), all available bathymetric data in this region were collected, compiled, and analyzed, resulting in new and completely revised bathymetric charts of the southern part of the Weddell Sea.

Six sheets of the AWI BCWS series in the scale of 1:1,000,000 covering the southern Weddell Sea from 66°S to 78°S and from 68°W to 0°E were recently completed and included in the 1997 General Bathymetric Chart of the Oceans (GEBCO) Digital Atlas CD-ROM (GEBCO GDA).

Features and structures revealed by the bathymetric mapping process are described with regard to their significance to other disciplines, e.g. oceanography, geology, glaciology.
On the basis of these sheets and in addition of further depth data a generalized bathymetric chart in scale 1:3,000,000 was compiled for the entire southern Weddell Sea. The latter is one of the enclosures of the AGU Antarctic Research Series volumne 75.

Figure:
AWI BCWS sheet index for scale 1:1,000,000. The sheets 551, 552, 553, 566, 567, 568 are in press; the other sheets are in preparation. The map in scale 1:3,000,000 covers an area slightly larger than the area covered by the sheets in scale 1:1,000,000 which are in press.

The 1:1,000,000 Bathymetric Chart of the Weddell Sea (AWI BCWS) series has been developed at AWI. The charts are based upon depth data collected by RV Polarstern, additional echosoundings provided by national hydrographic offices, research institutions and the International Hydrographic Organization (IHO) Digital Bathymetric Data Center. Digital and analogue data were supplied by the Hydrographic Offices of Argentina, Brazil, Japan, Norway, South Africa, United Kingdom, the United States, the Russian Federation, and by the IHO Data Centre for Digital Bathymetry. Data also were supplied by the British Antarctic Survey, Bureau Gravimetrique International, Institute of Geophysics at the University of Texas-Austin, Japan Oceanographic Data Centre, Lamont-Doherty Earth Observatory (USA), National Institute of Polar Research of Japan, Norwegian Polar Research Institute, Sevmorgeologia in St. Petersburg (Russia), and the World Data Center A in Boulder (USA). Additional data were extracted from various publications as detailed on the charts.

Credits have to be given to individuals for providing data, for fruitful discussions on bathymetry and cartography, and for other substantial contributions and support they gave to the AWI BCWS charting project: Christian Andreasen, Guiseppe Angrisano, Barbara Bond, Brian Harper, Bruce Huber, Meirion T. Jones, Andrev Popov, Vital Pozdeev, Günter Seeber, K. Shibuya, Jörn Sievers, Brian Skittrall, Bruce Sloan, Nick M. Smit, Anders Solheim, S. Tani, Pauline Weatherall.

For terrain modelling and contouring a new semi-automatic procedure was developed and applied. The methods applied yield the most recent state-of-the-art picture of the sea and coastal zone of this part of Antarctica.
The incorporation of supplementary geophysical and geographical information was necessary due to the heterogeneity of bathymetric data and the lack of observations for ice-covered areas. To model the bathymetry of the transition zone along the Antarctic ice edge in coastal regions, also adjacent sub-glacial information was included.
Sheets 551, 553, 554, 566, 567, 568 of the 1:1,000,000 chart series substantially were supported by such kind of information, since the sea floor continues below the ice shelves, where it still is covered by water on which the ice self is floating, and it also continues below the ice sheets, where the ice is resting on the ground may it be below or above the mean sea level.
Figure:
Sheet 567 (when it was within the draft process): Light grey areas are ice shelves (Ronne Ice Shelf, Filchner-Schelfeis, Brunt Ice Shelf) and darker grey areas are ice sheets (Berkner Island, Coats Land). The feature off and below the Filchner-Schelfeis is the Filchner Trough with depths excceding 1200 m just at the front of the ice shelf. Two generations of research stations are displayed at the right side of the image: Halley II and III, the latter the newer UK permanent station on the Brunt Ice Shelf. The German research station Filchner on the Ronne Ice Shelf, only operating in austral summers, is just by a hair's breadth to the lower left side of the image.

Chapters of the article:
1.    Introduction
2.    Bathymetric Database
2.1.     Data Aquisition
2.2.     Data and Chart Datum
2.3.     Data Validation
3.    Seafloor Modelling
3.1.     Digital Terrain Model (DTM) Calculation
3.2.     DTM Verification and Bathymetric Modelling
3.2.1.       Major structures
3.2.2.       Minor structures
3.3.     Bathymetric Model Accuracy
4.    Seafloor Topographic Features
4.1.     Deep Sea
4.2.     Continental Margin
4.3.     Continental Shelf
5.    Printed and Digital Bathymetry Products
5.1.     Oceanographic Cartography
5.2.     Undersea Feature and Geographic Names
5.3.     Digital Depth Data and GEBCO GDA
Acknowledgements
References

*)
For my own summary of the paper the sequence of authors may differ from the original article. The Paper including the bathymetric chart in scale 1:3,000,000 is published in:
Stan Jacobs, Ray Weiss (eds.): Ocean, Ice and Atmosphere: Interactions at the Antarctic Continental Margin. AGU Antarctic Research Series 75, Washington D.C.
Copyright © 1998 by American Geophysical Union (AGU).

Author's affiliations:
   *     Dijkstra, Niederjasper, Schenke, Schöne:
          Alfred Wegener Institute for Polar and Marine Research, Bremerhaven
   **    Hinze: Geodäsie & Meer, Meine
   ***   Hoppmann: Media Factory, Bremerhaven

If you are interested in the AWI BCWS bathymetric charts, please write to:

   Dr. Hans Werner Schenke
   Alfred-Wegener-Institut fuer Polar- und Meeresforschung
   D - 27515 Bremerhaven, Germany
   Phone: ++49 (0)471 - 4831 - 1222
   Fax:     ++49 (0)471 - 4831 - 1149
   Email:   schenke@awi-bremerhaven.de