Get Data

DOWNLOADING DATA VIA FTP

Data can be downloaded through a Web browser or command line via FTP. When using a Web browser, the FTP link first directs you to an Optional Registration Form that if filled out, will allow you to receive notifications about updates or processing changes related to that specific data set. After completing the Optional Registration Form, the FTP directory becomes available. For additional help downloading data through an FTP client, go to the How to access data using an FTP client support page.

FTP

Data Set ID:
NSIDC-0528

Videos of Basal Ice in Boreholes on the Kamb Ice Stream in West Antarctica, Version 1

This data set is a collection of video data of basal ice taken in a borehole on the Kamb Ice Stream in West Antarctica. Ice streams are an expression of the inherent instability of the West Antarctic Ice Sheet, and their behavior is a key control on the overall ice-sheet mass balance. Understanding the response of the ice sheet in a warming climate requires a thorough understanding of the internal dynamics of ice streams, in addition to the relevant ice-atmosphere and ice-ocean interactions in the region. The basal environment of the ice streams and of many glaciers is a key scientific interest, including conditions, mainly basal sliding, that lead to fast flow of the ice. The purpose of this data set is to present a review of the full range of original video recordings from the basal ice of the Kamb Ice Stream. Direct observations at the ice-stream bed are a crucial complement to modeling efforts predicting future scenarios in a warming climate.

Geographic Coverage

Parameter(s):
  • Land Records > Boreholes
Spatial Coverage:
  • N: -82.39955, S: -82.39955, E: -136.404633, W: -136.404633

Spatial Resolution: Not Specified
Temporal Coverage:
  • 14 January 2001
Temporal Resolution: Not specified
Data Format(s):
  • Audio Video Interleave (.avi)
Platform(s) GROUND-BASED OBSERVATIONS
Sensor(s): CAMERAS
Version: V1
Data Contributor(s): Hermann Engelhardt

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Engelhardt, H. and B. Kamb. 2013. Videos of Basal Ice in Boreholes on the Kamb Ice Stream in West Antarctica, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5028PFH. [Date Accessed].

Back to Top

Collapse All / Open All

This data set is a collection of video data of basal ice taken in a borehole on the Kamb Ice Stream in West Antarctica. Ice streams are an expression of the inherent instability of the West Antarctic Ice Sheet, and their behavior is a key control on the overall ice-sheet mass balance. Understanding the response of the ice sheet in a warming climate requires a thorough understanding of the internal dynamics of ice streams, in addition to the relevant ice-atmosphere and ice-ocean interactions in the region. The basal environment of the ice streams and of many glaciers is a key scientific interest, including conditions, mainly basal sliding, that lead to fast flow of the ice. The purpose of this data set is to present a review of the full range of original video recordings from the basal ice of the Kamb Ice Stream. Direct observations at the ice-stream bed are a crucial complement to modeling efforts predicting future scenarios in a warming climate.

Detailed Data Description

This data set is a collection of video data of basal ice taken in a borehole on the Kamb Ice Stream in West Antarctica. The Kamb Ice Stream (82°15'S 145°00'W), a glaciological feature of the West Antarctic Ice Sheet, formerly known as Ice Stream C, was renamed in 2001 in honor of Caltech Glaciologist Dr. Barclay Kamb.

A basal zone tens of meters thick of debris-laden ice was observed on the Kamb Ice Stream, West Antarctica, using a video camera lowered into boreholes made by hot-water drilling. The debris content varies, sometimes abruptly, forming a sequence of layers that reflect the complex history of fast ice flow and bed interaction. In most parts, the concentration of debris is low, a few percent by weight, with particles, often mud clots, dispersed in a matrix of clear ice. The nature of the debris distribution can be interpreted in terms of specific time intervals in the history of fast motion of the Kamb Ice Stream including processes leading up to the termination of its streaming behavior and possible reactivation (Engelhardt & Kamb 2013).

The Kamb Ice Stream is interesting because it was very active in the past until it stopped flowing fast approximately 150 years ago (Retzlaff and Bentley 1993); (Smith et al. 2002). The timing of the stoppage can be determined from the depths of buried crevasses about 22 m below surface, but also from the thickness of a distinct frozen-on layer at the bottom of the ice. A velocity profile was measured from North to South across the ice stream, using repeat GPS location fixes at 86 stakes. It started at km 0 with coordinates S 81° 49.70', W 135° 59.99' and ended at km 102.97 (S 82° 45.30', W 135° 46.39'). The velocity and the corresponding ice-thickness profile (Conway et al. 2002) was the basis for choosing specific drill sites to capture a variety of basal situations. From a total of 11 boreholes at three drill sites, three were dedicated for video camera deployment, borehole three, five, and nine. However, the nine image files that makeup this data set were all taken in borehole number nine at drill site number three except for one image file, SLDL5-1220-1226.avi, that was taken in borehole number five at drill site number two. Drill site two is 3.64 km South of drill site three.

Format

Data are provided in Audio Video Interleave (.avi) format, which was converted from Mini-DV tape format.

Background color on
File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0528_engelhardt_V01 directory. Within this directory, there are nine video files:

DL9-1053.76-1055.70.avi
SL9-1057.67-1053.00.avi.
SL9-1062.59(Big-Rock).avi
SL9-1065.25.avi
SLDL5-1220-1226.avi
SLDL9-1062.47-1062.00.avi
SL9-1057.00-1059.25.avi
SL9-1059.25-1060.50.avi
SL9-1060.51-1063.32.avi

The SL9 in the file name stands for the side-looking camera in borehole nine, and the DL9 in the file name stands for the down-looking camera in borehole nine. The numbers indicate the nominal depth range in the borehole. In the SLDL9 file, both views are shown in the same video.

Background color on
File Size

The DL9-1053.76-1055.70.avi file is 529.16 MB in size.
The SL9-1057.67-1053.00.avi. file is 1262.10 MB in size.
The SL9-1062.59(Big-Rock).avi file is 10.316 MB in size.
The SL9-1065.25.avi file is 469.2 in size.
The SLDL5-1220-1226.avi file is 1.63 GB in size.
The SLDL9-1062.47-1062.00.avi file is 175.1 MB in size. 
The SL9-1057.00-1059.25.avi file is 335.54 MB in size.
The SL9-1059.25-1060.50.avi file is 94.31 MB in size.
The SL9-1060.51-1063.32.avi file is 789.32 MB in size.

Background color on
Spatial Coverage

Southernmost Latitude: 82° 23.973' S
Northernmost Latitude: 82° 23.973' S
Westernmost Longitude: 136° 24.278' W
Easternmost Longitude: 136° 24.278' W

Spatial Resolution

The elevation of borehole nine, drill site three is 503 m, and the ice thickness is 952 m. The elevation at borehole five, drill site two is 510 m, and the ice thickness is 1192 m. Drill site two is 3.64 km South of drill site three.

Background color on
Temporal Coverage

These data were collected on 14 January 2001.

Background color on
Parameter or Variable

This data set contains the following parameters:
Kamb Ice Stream
Basal Ice
Basal Debris 
Basal Freeze-on
Basal Water
Borehole Video
Ice Stream Flow
West Antarctic Ice Sheet Instability

Parameter Description

  1. The Kamb Ice Stream is the central ice stream flowing out of the West Antarctic Ice Sheet.
  2. Basal Ice is accreted at the base of the ice stream by freeze-on and tectonic mechanisms.
  3. Basal Debris is incorporated into the basal ice by various freeze-on mechanisms from the basal till.
  4. Basal Freeze-on is the process of incorporating debris into basal ice.
  5. Basal Water is present under ice streams providing lubrication for fast flow.
  6. Borehole Video is taken in boreholes drilled by hot-water jet.
  7. Ice Stream Flow is 10 to 100 times faster than the surrounding ice sheet.
  8. West Antarctic Ice Sheet Instability is possible by fast moving, water lubricated ice steams based far below sea level.

Sample Data Record

Figures 1 and 2 are sample video images taken from the video data files showing both a side-looking camera and a down-looking camera image.

side-looking borehole image
Figure 1. Sample Video Image Showing a Side-looking Camera Image
down-looking borehole image
Figure 2. Sample Video Image Showing a Side-looking Image with an Inserted Down-looking Image

Background color on

Software and Tools

Background color on

Data Acquisition and Processing

Data Acquisition Methods

The boreholes were drilled with the Caltech hot-water drilling system, which is capable of drilling a 1000 m deep hole in less than a day (Kamb et al. 2004). The water filled borehole was initially 17.5 cm in diameter to accommodate the video camera case of 12.5 cm outer diameter and to allow for the gradual refreezing of the borehole during downhole camera deployment. Because the ice temperature is -26°C in the upper half of the borehole, the camera could be safely used for about four hours in the borehole without getting stuck. After four hours, the borehole needed to be widened again using a hot-water reamer.

The ice stream thickness at the borehole sites were measured from the snow surface with the video-camera cable, which is a Kevlar-reinforced fiber-optic cable with little stretch, which was calibrated with a tape measure. It was estimated that the uncertainty in the absolute depth is 0.5 m, and the repeatability and the precision on any particular logging run is 0.01 m at 1 km depth. The nominal ice stream thickness at borehole three, site one was 951.7 m; at borehole five, site two it was 1191.8 m; at borehole nine, site three it was 1033.9 m. Between the base of the ice at borehole nine and the top of the till we discovered a water-filled gap 1.4 m thick. In borehole five the basal gap was approximately 1 - 2 cm. The best way to know the depth of the ice and to ascertain that the bed was reached was to use the camera to see the actual basal edge of the ice. This was possible in boreholes five and nine, not in borehole three where the ice was frozen to the bed. During hot-water drilling, the borehole is filled with water up to the permeable firn layer about 30 m below the surface. At that moment the hot-water drill breaks through from the ice to a wet bed, the borehole in most cases makes a good hydraulic connection and water rushes out of the boreholes into the basal water system. The water level in the borehole drops from 30 m to a level about 100 m below the surface for a 1000 m deep borehole. The new lower level corresponds to a water pressure at the base, which is near the ice overburden pressure. A typical water level drop starts very rapidly and it is completed within one to two minutes depending on the efficiency of the basal hydraulic connection. Occasionally the water pressure oscillates two to three times around the overburden pressure (Engelhardt & Kamb 1997). This vigorous outflow of water helps in cleaning out turbidity from the borehole that unavoidably forms when the drill is melting out debris-laden ice or is stirring up basal debris. High turbidity prevented clear pictures with the video camera. In order to remove any lingering turbidity, pumping additional clean water into the borehole was sometimes necessary to prepare the boreholes for camera work. The situation is more difficult when the base of the ice is frozen to the bed and into the till so that no water can run out. This was the case for site one boreholes. No break-through occurred and the water level in the borehole did not drop. Camera work would have been impossible, had we drilled all the way to the bottom and filled the borehole with turbid water. Instead, we initially drilled only into the upper 1.6 m of the basal ice. Clean water was pumped to the bottom of the borehole that stopped about 24 m short of the base of the ice, in order to displace the turbid water. Turbidity could not be eliminated completely, but enough to see the debris-laden ice with the side-looking camera. After we drilled all the way to the bed, the bottom could be seen only when the down-looking camera window directly touched the melted-out debris collected at the base (Engelhardt & Kamb 2013).

Background color on
Sensor or Instrument Description

A Caltech/JPL borehole video camera system with modified Sony Mini-DV recorder was used to take the images for this data set. The system can take continuous videos with a rate of 30 frames per second and a resolution of 720 x 480 pixels per frame in NTSC format. The Caltech/JPL Antarctic Ice Borehole Probe was developed by a collaboration of Caltech and NASA's JPL engineers to study the basal zone of the ice streams, where the fast-flow mechanism is believed to operate. The probe carries two video cameras, one looking straight down and the other looking to the side. The probe is lowered down boreholes drilled through the ice to the bottom, and can then observe features and processes in the basal zone. The boreholes, about 1000 m deep, are drilled with a hot-water jet drill developed by Caltech (CIT). The drill development and the Antarctic field work and interpretation of the probe results were carried out by a Caltech/JPL team with support of the National Science Foundation (NSF) Office of Polar Programs (OPP).

Background color on

References and Related Publications

Contacts and Acknowledgments

Dr. Hermann Engelhardt
University of Maryland
Center of Environmental Sciences
Appalachian Laboratory
301 Braddock Road
Frostburg, MD 21532-2307
E-mail: engel@caltech.edu
Telephone: 301 689 3405

Acknowledgments: 

This research was supported by NSF OPP Grant Number 9615420.

Document Information

DOCUMENT CREATION DATE

January 2013

No technical references available for this data set.
No FAQs or How Tos available for this data set.

Access complete Knowledge Base

Questions? Please contact:
NSIDC User Services
Phone: 1 303 492-6199
Email: nsidc@nsidc.org