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Giant Icebergs of the Ross Sea, in situ Drift and Weather Measurements, Antarctica

Summary

During 2001-2006, 6 giant icebergs (B15A, B15J, B15K, C16 and C25) adrift in the southwestern Ross Sea, Antarctica, were instrumented with global positioning system (GPS) receivers, magnetic compasses and automatic weather stations (AWS), to monitor their behavior in the near-coastal environment and to record their exit into the Southern Ocean. The GPS and AWS data were collected on a 20-minute interval, Many of the station data timeseries are continuous for periods of up to 7 years, with icebergs C16 and B15J having the longest records.

The data is considered useful for examining the processes of iceberg drift (and other behaviors) on time scales that are shorter than what is possible through satellite image iceberg tracking. Data are available in comma-delimited ASCII format and Matlab native mat files. Data are available via FTP.

Citing These Data

The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.

MacAyeal, Douglas, Emile Okal, Richard Aster, and Jeremy Bassis. 2008. Giant Icebergs of the Ross Sea, in situ Drift and Weather Measurements, Antarctica. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5VM496K.

Overview Table

Category Description
Data format comma-delimited ASCII format and Matlab native mat files
Spatial coverage and resolution Southernmost Latitude:78 South
Northernmost Latitude: 60 South
Westernmost Longitude: 178 West
Easternmost Longitude: 110 East
Temporal coverage and resolution 25 January 2001 to 31 June 2008
File size 250 megabytes
Parameter(s) Parameters include iceberg drift, iceberg latitude and longitude, iceberg weather (AWS), ice shelf motion, ice shelf surface temperature, ice shelf weather, iceberg snow accumulation
Procedures for obtaining data

Available via FTP


Table of Contents

  1. Contacts and Acknowledgments
  2. Detailed Data Description
  3. Data Access and Tools
  4. Data Acquisition and Processing
  5. References and Related Publications
  6. Document Information

1. Contacts and Acknowledgments

Investigator(s)

Douglas MacAyeal
Department of Geophysical Sciences
University of Chicago
5734 S. Ellis Ave.
HGS 413
Chicago, Illinois 60637 USA

Emile Okal
Department of Earth and Planetary Sciences
Northwestern University
Evanston, Illinois 60208-2150, USA

Richard Aster
Dept of Earth & Environmental Science
New Mexico Tech
Socorro, New Mexico 87801 USA

Jeremy Bassis
Institute for Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, California, 92093-0225 USA

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgements

This research was supported by National Science Foundation (NSF) Office of Polar Programs (OPP) grant 0229546 awarded to D. MacAyeal.

2. Detailed Data Description

Format

The data are provided in two formats:

All data are interpolated to a common time line for the convenience of comparison (with sample interval of 20 minutes). Look for the "common" substructures under each data heading including time. The second format for data is ascii text files with headers that explain the variables. These files are one per station and are self explanatory.

The first, and recommended, format is a Matlab *.mat file that contains a data structure. This structure is self-explanatory, i.e., the names of the icebergs and the field variables appear in the structured naming convention. For example: the structure "iceberg" consists of the following sub structures:

iceberg =

B15K: [1x1 struct]
B15A: [1x1 struct]
B15J: [1x1 struct]
NIB: [1x1 struct]
DIB: [1x1 struct]
C16: [1x1 struct]
coastline: [1x1 struct]

The substructures are named by the iceberg on which the station that collected the data was located as of July 1 2008, e.g., C16 contains the data for iceberg C16. One exception: the two stations on B15K were originally located on B15A, but broke off as part of B15K when B15A split on 8 October, 2003. NIB stands for Nascent Iceberg on the Ross Ice Shelf, DIB stands for the Drygalski Ice Tongue/iceberg C25 (as the station duration spanned the spawning of a new iceberg when C16 struck the Drygalski Ice Tongue). The structure "coastline" represents a nice digitization of the Antarctic coast provided by Kelly Brunt, of the Raytheon Polar Services Co.

The substructures below the iceberg name contain the data in various raw and processed forms:

>> iceberg.B15A

ans =

desc: 'Iceberg data: constructed on 30-Jul-2008 13:33:24'
raw: [1x1 struct]
time: [1x1 struct]
pos: [1x1 struct]
T: [1x1 struct]
RH: [1x1 struct]
pressure: [1x1 struct]
windspeed: [1x1 struct]
solar: [1x1 struct]
winddirection: [1x1 struct]

orientation: [1x1 struct]
snowdistance: [1x1 struct]
errors: [1x1 struct]
station: [1x1 struct]
square_of_wind_speed: [1x1 struct]

The "raw" substructure contains the raw data processed from the ARGOS data transmission (including the hexidecimal ARGOS code):

>> iceberg.B15A.raw

ans =
desc: 'Raw unprocessed data from one hex file, split into ARGOS data and station data'
hex: [1x1 struct]
cr10x: [1x1 struct]
station_month: {1x50 cell}
station_year: {1x50 cell}
file: [1x1 struct]
argos: [1x1 struct]

The "raw.cr10x" data contains the data that has been decoded from the ARGOS (including engineering data transmitted on a less frequent basis), but no data processing and quality control have been provided:

>> iceberg.B15A.raw.cr10x

ans =
desc: 'Raw Decimal data converted from HEX'
engineering: [1x1 struct]
output: [212024x16 double]
data: [2689x16 double]

The processed data is located in the following structures: time, pos (position), T (temperatures), RH (relative humidity), pressure, windspeed, solar (if available), winddirection, orientation, snowdistance, square of wind speed. The "error" structure contains a flag set where original hex data is suspected of having an error.

>> iceberg.B15A
ans =
desc: 'Iceberg data: constructed on 30-Jul-2008 13:33:24'
raw: [1x1 struct]
time: [1x1 struct]
pos: [1x1 struct]
T: [1x1 struct]
RH: [1x1 struct]
pressure: [1x1 struct]
windspeed: [1x1 struct]
solar: [1x1 struct]
winddirection: [1x1 struct]
orientation: [1x1 struct]
snowdistance: [1x1 struct]
errors: [1x1 struct]
station: [1x1 struct]
square_of_wind_speed: [1x1 struct]

Units for data are as follows:

Time: either Matlab time (in days) or standard y m d h m s format
Temperature: degrees centigrade
Lat/lon: degrees, degrees minutes decimal minutes
RH: non-dimensional (percent)
Pressure: millibars
Windspeed: m/s
Winddirection: radians (unwrapped)
Orientation: radians (unwrapped)
Snow distance: meters
Solar: watts per meter squared per whole sky (downward flux) integrated over all band.

Iceberg C16 has two epochs. Epoch 1 represents data that was collected by storage module (no ARGOS transmission involved), Epoch 2 represents data that was only collected by ARGOS transmission)

Iceberg B15J (originally B15A prior to 8 October 2003) contains two stations: M1 and M2.

Nascent Iceberg is located on the Ross Ice Shelf, and is not an iceberg.

File Size

250 megabytes (MB)

Spatial Coverage

Southernmost Latitude: 78 S
Northernmost Latitude: 60 S
Westernmost Longitude: 178 W
Easternmost Longitude: 110 E

Spatial Resolution

GPS data ~10 meters

Temporal Coverage

25 January, 2001 to 31 June, 2008

Parameter or Variable

Parameters include iceberg drift, iceberg latitude and longitude, iceberg weather (AWS), ice shelf motion, ice shelf surface temperature, ice shelf weather, iceberg snow accumulation

Sample Data Record

The first, and recommended, format is a Matlab *.mat file that contains a data structure. See Format section above.
This structure is self-explanatory, i.e., the names of the icebergs and the field variables appear in the structured naming convention.

Units for data are as follows:
Time: either Matlab time (in days) or standard y m d h m s format
Temperature: degrees centigrade
Lat/lon: degrees, degrees minutes decimal minutes
RH: non-dimensional (percent)
Pressure: millibars
Windspeed: m/s
Winddirection: radians (unwrapped)
Orientation: radians (unwrapped)
Snow distance: meters
Solar: watts per meter squared per whole sky (downward flux) integrated over all band.

Error Sources

Wind direction data have a highly variable uncertainty due to the difficulty of correcting for iceberg rotation. Users are recommended to contact the Antarctic Meteorological Research Center (AMRC) for assistance in accessing the raw unprocessed data. Data precision is as listed for the instruments used (Garmin GPS36, Campbell Scientific weather instruments). Wind direction data is very poorly constrained due to difficulty working with magnetic compasses (which were inaccurate and unstable) and the difficulty of correcting iceberg orientation. For scientists interested in using the wind direction data, we recommend that the data be re-processed from the original ARGOS hex stream.

3. Data Access and Tools

Data Access

Available via FTP

Volume

250 megabytes

Software and Tools

An example of Matlab code used to read the data is provided in the Data Format section.

Please visit The Incorporated Research Institutions for Seismology (IRIS) for more information.

Related Data Collections

4. Data Acquisition and Processing

Sensor or Instrument Description

The station is set on a 10 meter tower which is dug into the firn surface about 2 meters. At the top of the station are GPS, windspeed and wind direction (RM Young instrument), pyranometer and downward looking snow distance sensor. Two thermometers (one with a relative humidity (RH) sensor) are mounted on the tower at different heights typically separated by 2-3 meters. Barometric pressure is sensed in an environmental enclosure that (in the case of C16) was buried at times.

Data Acquisition Methods

Automatic weather stations (AWS) were deployed on icebergs and on a nascent iceberg on the Ross Ice Shelf. These stations were equipped with normal weather instrumentation (e.g., temperature at two levels above the surface, atmospheric surface pressure, wind direction and speed, relative humidity, snow accumulation via ground surface distance measurement, solar radiation influx) as well as "navigation style" (single frequency) global positioning system (GPS) receivers, magnetic (flux gate) compasses, firn thermistor strings and automated cameras. Seismometers were deployed at several sites for limited campaign purposes (seismic data is stored in the IRIS data archive). Geodetic GPS and tiltmeter data were also collected over limited time periods. The GPS-augmented AWS data were collected on a 20 minute interval and transmitted via ARGOS satellite data transmission.

5. References and Related Publications


MacAyeal, D. R., M. H. Okal, J. E. Thom, K. M. Brunt, Y.-J. Kim and A. K. Bliss, 2008. Tabular iceberg collisions within the coastal regime. J. Glaciol., Vol. 54, No. 185, p. 371-386.

MacAyeal, D. R., E. A. Okal, R. C. Aster and J. N. Bassis, 2008. Seismic and hydroacoustic tremor generated by colliding icebergs. J. Geophys. Res., Vol 13, doi: 10.1029/2008JF001005.

MacAyeal, D. R., E. A. Okal, R. C. Aster, J. N. Bassis, K. M. Brunt, L. M. Cathles, R. Drucker, H. A. Fricker, Y.-J. Kim, S. Martin, M. H. Okal, O. V. Sergienko, M. P. Sponsler, J. E. Thom, 2006. Transoceanic wave propagation links iceberg calving margins of Antarctica with storms in tropics and Northern Hemisphere. Geophys. Res. Lett., Vol 33, doi: 10.1029/2006GL027235.

Sergienko, O. V., D. R. MacAyeal and J. E. Thom, 2008. Reconstruction of snow/firn thermal diffusivities from observed temperature variation: application to iceberg C16 (Ross Sea, Antarctica), 2004-07. Ann. Glaciol., Vol. 49, in press.

K. M. Brunt, 2008. Tidal Motion of the Ross Ice Shelf and its Interaction with the Siple Coast Ice Streams, Antarctica. (PhD dissertation, University of Chicago, Chicago, IL, 202 pages).

The following related documents are available on NSIDC's Web site.

Table X. Related Documents
Document Description URL
Continuous GPS (static) Data from the Ross Ice Shelf, Antarctica related Iceberg data http://nsidc.org/data/nsidc-0347.html
Iceberg Harmonic Tremor Seismometer Data, Antarctica related Iceberg data http://nsidc.org/data/nsidc-0349.html

6. Document Information

Acronyms

The following acronyms are used in this document.

Table X. Acronyms and Abbreviations
Acronym Description
FTP File Transfer Protocol
NSIDC National Snow and Ice Data Center
MB Megabytes
m/s meters per second
GPS Global positioning System
AWS automatic weather stations
RH Relative Humidity
AMRC Antarctic Meteorological Research Center
URL Uniform Resource Locator

Document Creation Date

November 2008

Document URL

http://nsidc.org/data/docs/agdc/nsidc0350_macayeal/index.html