Tuesday, 24 August 1999
From: Matthew Lythe, BEDMAP Database Manager

Completion of Phase 1 - data collection and storage
The first Phase of the BEDMAP programme is now complete. Over the past 12 months almost 2 million observations of ice thickness have been assembled within the BEDMAP relational database. These data have been collected on over 100 separate expeditions conducted by 12 countries over the past fifty years. The most comprehensive compilation of its type, we estimate that this data set represents about 90% of all ice thickness measurements over Antarctica. A summary of the data sets in BEDMAP, a list of contributors, as well as several maps describing the coverage and density of data is available on the BEDMAP web site at; http://www.nerc-bas.ac.uk/public/aedc/bedmap/

The BEDMAP programme is now entering the second phase of work, which includes the validation of the database and the generation of the final gridded data sets. Although the deadline for submission of data to BEDMAP has passed, the submission of additional data will be received gratefully. It is likely that if these data are submitted within the next month they can be incorporated within the final gridded data sets.

Second BEDMAP Workshop
On 24 and 25 July 1999, a working group of 21 scientists and data management specialists from seven countries met at the British Antarctic Survey (BAS), Cambridge, UK in the second BEDMAP workshop. Under the sponsorship of the Scientific Committee on Antarctic Research (SCAR), they met to discuss the generation of a new topographic model of the bed beneath the Antarctic Ice Sheet and the seabed of the surrounding continental shelf. Scheduled at the conclusion of Phase 1 the workshop was able to evaluate the suitability of the ice thickness database, compiled over the past year, to meet this objective. Other issues addressed included recent developments in Digital Elevation Models (DEMs), the status of bathymetry over the Antarctic continental shelf, upcoming ice thickness surveys and the establishment of a long term ice thickness data archive for Antarctica. The report from this meeting is available from the BEDMAP web site in several formats or alternatively a hard-copy version can be requested from Matt Lythe (matt.lythe@bas.ac.uk). The key outputs from the meeting may be found at; http://www.nerc-bas.ac.uk/public/aedc/bedmap/workshop/summary.html

BEDMAP Products
The generation of a new bed elevation grid for the continent and continental shelf will involve the construction of a number of intermediate products. The principal output from the assembled database will be a grid of ice thickness for the grounded ice sheet and ice shelves. This data set will be generated through the application of a spatial interpolation procedure to the input ice thickness and other relevant data. Note; this model will not describe absolute heights. The bed elevation grid will be derived through the subtraction of the ice thickness grid from the best available Digital Elevation Model (DEM). Resources and time permitting a digital terrain model of seabed elevation will then be generated using available bathymetric data and the seismic reflection derived sub ice shelf sea bed depths. If we do not have the time to achieve this, the best of the currently available data sets will be used to describe seabed elevation. Finally the two bed elevation grids will be combined to produce the complete bed elevation grid.

BEDMAP will therefore generate four principal products;
1. an ice thickness grid for the grounded ice sheet and ice shelves,
2. a bed elevation model for the grounded ice sheet
3. a sub ice shelf bed and seabed topographic model,
4. a final combined bed elevation grid incorporating the grounded ice sheet, sub ice shelf and continental shelf.

It is expected that the first BEDMAP products will be completed in March 2000.