ASIS:Data bed

28/10/08: Below is the combined bed/bathymetry topography datasets. The order of priority is AGASEA, Nitsche bathymetry, BEDMAP. Using the merged ice thickness dataset (see ice thickness page) I did a simple flotation test (thk + 1028/917 * bed). The green areas below are floating, the white areas are grounded, the ice thickness above buoyancy is shown in the third diagram. In the shelf regions of the Amundsen Sea (other than PIG/Thwaites), there is no data whatsoever, so it is just interpolated (see link to a map of BEDMAP datasources).





Impact of firn density: Jon's ice shelf thickness dataset includes a correction in the floatation calculation for changes in firn density. In order to extract a represetative constant value for this, I calculated the freeboard surface using thk + 1028/917 * bed for the ice shelves (using Jon’s shelf thickness) and compared this to Jon’s ice surface. This gave an average difference of ~ 17 m. The diagram below shows the ice thickness above buoyancy using thk + 1028/917 * bed -17.



23/10/08: I've merged AGASEA and BEDMAP thickness (smoothed with a low pass filter) in grounded areas (using a slightly modified ADD mask). The bed topography is then derived by subtracting this thicknesss from the ice surface dataset. In some places I've then added a few metres to the ice thickness where a simple floatation test suggests it is floating (red cells in second diagram).



02/10/08: These are the datasets that I'm going to use in some shape or form to make the bed/bathymetry dataset. The combined picture is just the datsets overlaid, I'm going to hopefully blend them together a bit more neatly!



30/07/08:

This is the dataset provided by Jon Bamber (not the same colour stretch as above - sorry). It is a combination of BEDMAP and AGASEA data, Jon used the BEDMAP bed elevations and updated these with the new AGASEA thickness data and his DEM for the ASE sector only. There is quite a big jump in join areas, and the data was masked using Jon's mask.

I think the join is going to be a bit of a problem, so I'm going to suggest that I should take (grounded) ice thickness from BEDMAP and AGASEA and join them together a bit more smoothly, then create a new bed dataset from this and Jon's surface DEM? Then I'd join this onto the bathymetry data from the original BEDMAP.

Jon's bed data: