Internal layers in the Antarctic Ice Sheet


			Internal layers in the Antarctic Ice Sheet: electronic repository including three-dimensional visualisation

Data summary

We present three forms of the internal layering data:

A spreadsheet database containing all picked internal layers.
>> To the spreadsheet database
A 3-D visualisation containing all scanned images of the raw Z-scope radargrams as �vertical curtains� (must be viewed using IVS Fledermaus^TM or IVS iView3D^TM freeware).
>> To the 3-D Z-scopes
A 3-D visualisation containing all picked internal layers as surface-corrected 3-D lines (must be viewed using IVS Fledermaus^TM or IVS iView3D^TM freeware).
>> To the 3-D internal layers

>> Back to the introduction

How to locate from where data were collected

RES surveys were conducted along all the lines shown (right) between 1974 and 1979. In each case, the identifier given to each line in the respective season the data were acquired is used here:

Line identifiers beginning with the number �1� were collected in the 1974/75 season.

Line identifiers beginning with the numbers �00� or �01� were collected in the 1977/78 season.

Line identifiers beginning with the numbers �03� or �04� were collected in the 1974/75 season.

In order to locate an individual RES line, we have provided an interactive line locator.

>> Load the line locator

SPRI-NSF-TUD RES coverage (click on figure to load line locator)

Spreadsheet database of picked internal layers

The spreadsheets provided for download here represent the clear internal layers that have been traced from scanned 'jpegs' or 'tiffs' of the raw Z-scope radargrams. Where spreadsheets are not provided for individual lines, it may be assumed that clear internal layers are not traceable in those profiles.

>> Download all spreadsheets

Available spreadsheets (click on relevant links to access):

1974-75

1977-78

1978-79

102
104
106
108
109
110

111
112
116
121
122
123

131
133
134
135
136
137

138
139
144
147
148

001
002
005
007

033
035
037

The traced internal layers given in these spreadsheets may also be visualised in a 3-D context as provided below.

>> To the 3-D internal layers

Example of spreadsheet containing picked internal layers from SPRI-NSF-TUD RES surveys

3-D visualisation of Z-scope radargrams

We provide here visualisations of the original Z-scope radargrams (pseudo cross-sections with internal layers) within a 3-D environment representing the Antarctic Ice Sheet.

To view the data it is necessary to use either the freeware IVS iView3D^TM or the software IVS Fledermaus^TM. It is also essential that your computer holds a graphics card. iView3D^TM is free and useful for basic visualisations; Fledermaus however provides a much greater degree of control and allows manipulation of the data. The programmes may be accessed/ordered from the IVS website by following the links below:

>> Download IVS iView3D^TM from IVS website

>> Purchase IVS Fledermaus^TM via IVS website

Internal layers viewed in their typical 2-D context: a "Z-scope" radargram

Radargrams are available for viewing as SCENES or SEGMENTS:

SCENES show all the radargrams along a particular RES profile, emplaced in their 3-D context. All SCENES load with the radargrams placed in their horizontally (xy) georectified locations, superimposed over subglacial topography provided by BEDMAP. SCENES consist of a number of SEGMENTS, which are sub-sections of the radargrams and coverages of basal and surface topography. Using iView3D^TM, once a SCENE has been loaded, individual SEGMENTS may be switched on/off via the 'View' command in the taskbar. Thus, to better view an individual radargram, you might wish temporarily to remove subglacial topography from the SCENE; where SEGMENTS obscure one another you can remove some; and in some applications you may wish to add in the 'surface topography' SEGMENT.

Note that whilst these visualisations are useful for data interpretation and visual inspection of trends, the scanned nature of the radargrams means that they are not truly vertically georectified. In fact, for clarity of viewing, the radargrams are artificially raised above the bedrock topography segment, and all scenes are vertically exaggerated by 60. However, the 3-D database of internal layers (below) incorporates full xyz georectification.

Internal layering radargram emplaced in 3-D scene (see inset for profile location)

Available scenes (click on relevant links to access):

1974-75

1977-78

1978-79

101
102
104
105
106
108
109
110
111

112
113
116
117
119
121
122
123
124

129
130
131
132
133
134
135
136

137
138
139
144
145
147
148
149

001
002
003
004
005
006
007
008
009
010
012
013

032
033
035
037
040

>> Download all scenes

>> Download all individual segments

Selected segments viewed in iView3d^TM

The power of 3-D visualisation: some examples

3-D visualisation aids data interpretation through the ability to view radargrams from all angles. We provide here 2 small animations which indicate the level to which data can be viewed and manipulated within IVS Fledermaus^TM.

Animation 1: radargrams across Ellsworth Land, West Antarctica
In this short animation we zoom in on, and rotate around, several intersecting radargrams collected across Ellsworth Land, West Antarctica. The animation finishes towards the head of Rutford Ice Stream.

>> Load the animation [10.5 Mb]

Animation 2: Insights into the geometry of subglacial Lake Ellsworth
Subglacial Lake Ellsworth, West Antarctica, has been identified as a suitable site for a drilling investigation of a subglacial lake. The lake was originally identified from a bright reflecting surface on the basal reflector from the SPRI-NSF-TUD RES programme. More recently, the British Antarctic Survey cartried out an airborne survey of the lake site in 2004/05. This animation shows an amalgamation of the SPRI-NSF-TUD and the BAS RES data. We first zoom into the region and focus on the SPRI-NSF-TUD profile, from which the lake was originally identified. Subglacial topography is removed, so as not to obscure the profile, and then the BAS profiles are added. We the rotate around the location, and clear lake reflectors can be viewed in most of the radargrams, confirming the location of the lake and adding to our understanding of its geometry.

>> Load the animation [28.9 Mb]