Abstract:
The Antarctic megadune research was conducted during two field seasons, one in November 2002 and the other during the period of December 2003 through January 2004. The megadune field site is located on the East Antarctic Plateau, southeast of Vostok station. The objectives of this multi-facetted research are 1) to determine the physical characteristics of the firn across the dunes including ... typical climate indicators such as stable isotopes and major chemical species and 2) to install instruments to measure the time variation of near-surface wind and temperature with depth, to test and refine hypotheses for megadune formation. It is important to improve our current understanding of the megadunes because of their extreme nature, their broad extent, and their potential impact on the climate record. Megadunes are a manifestation of an extreme terrestrial climate and may provide insight on the past terrestrial climate or on processes active on other planets. Snow megadunes are undulating variations in accumulation and surface texture with wavelengths of 2 to 5 km and amplitudes up to 5 meters. The features cover 500,000 km^2 of the East Antarctic plateau, occurring in areas of moderate regional slope and low accumulation on the flanks of the ice sheet between 2500 and 3800 meters elevation. Landsat images and aerial photography indicate the dunes consist of alternating surfaces of glaze and rough sastrugi, with gradational boundaries. This pattern is oriented perpendicular to the mean wind direction, as modeled in katabatic wind studies. Glazed surfaces cover the leeward faces and troughs; rough sastrugi cover the windward faces and crests. The megadune pattern is crossed by smooth to eroded wind-parallel longitudinal dunes. Wind-eroded longitudinal dunes form spectacular 1-meter-high sastrugi in nearby areas. This data set contains automated weather station (AWS) data from two sites. The Mac site was oriented on the rough sastrugi-covered windward face and the Zoe site was on the glazed leeward face. The AWSs collected data throughout the year from 16 January 2004 to 17 November 2004. Investigators received data from the two field sites via the ARGOS Satellite System (http://www.argosinc.com/). Data are provided in space-delimited ASCII text format and are available via FTP.
Quality
The 10 meter firn temperature reading did not work much of the time at the Zoe site (mostly not a number (NAN) values). Not all ARGOS satellite passes caught both a Block 1 and a Block 2 corresponding to the same set of measurements, so they are not coincident measurements unless their julian day values match to within about 0.007 days (about 10 minutes). There are a few spurious points because of ... the communication link: sometimes the data logger and satellite transmitter would get out of sync, and values ended up in the wrong columns, etc. Investigators filtered out the obvious spurious values, but a few still exist in the data. Investigators estimated the wind direction margin of error at the Mac site to be ±1 degree clockwise from true north with no measurable offset. They estimated wind direction margin of error at the Zoe site to be ± 4 degrees clockwise from true north, but believe the measurements appeared to be approximately 4 degrees too high.
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
City:
Boulder
Province or State:
CO
Postal Code:
80309-0449
Country:
USA
Publications/References
Albert, M. R., C. A. Shuman, Z. R. Courville, R. Bauer, M. A. Fahnestock, and T. A. Scambos. 2004. Extreme firn metamorphism: impact of decades of vapor transport on near-surface firn at a low-accumulation glazed site on the East Antarctic Plateau. Annals of Glaciology 39: 73-78.
Campbell Scientific, Inc. 2002. CR10X Measurement and Control Module Operator's Manual.
Courville, Z. R., M. R. ... Albert, and J. Severinghaus. 2002. Firn physical characteristics and impact on interstitial convection and diffusion in the megadunes of East Antarctica. Eos. Trans. AGU 85(47). Fall Meeting Suppl., Abstract C31C-06.
Courville, Z. R., M. R. Albert, M. A. Fahnestock, and L. Cathles. 2005. Impact of accumulation rate on firn properties. Eos. Trans. AGU 86(52). Fall Meeting Suppl., Abstract C21B-1108.
Courville, Z. R., M. Albert, M. Fahnestock, L. M. Cathles. 2006. Impact of accumulation hiatus on the physical properties of firn at a low accumulation site. Journal of Geophysical Research. In review.
Fahnestock, M. A., T. A. Scambos, C. A. Shuman, et. al. 2000. Snow megadune fields on the East Antarctic Plateau: extreme atmosphere-ice interaction. Geophysical Research Letters 27(22): 3719-3722.
Fahnestock, M. A., C. A. Shuman, M. R. Albert, and T. A. Scambos. 2002. Satellite, observational, meteorological and thermal records from two sites in the Antarctic megadunes stability of atmospheric forcing, thermal cracking, and the seasonal evolution of the thermal profile. Eos. Trans. AGU 85(47). Fall Meeting Suppl., Abstract C31C-03.
Fahnestock, M. A., C. A. Shuman, T. A. Scambos, M. R. Albert, T. Haran, Z. R. Courville, and R. Bauer. 2005. Mapping Antarctic megadunes and other accumulation-related features on the East Antarctic Plateau. Eos. Trans. AGU 86(52). Fall Meeting Suppl., Abstract C13A-06.
Frezzotti, M., S. Gandolfi, F. La Marca, and S. Urbini. 2002. Snow dunes and glazed surfaces in Antarctica: new field and remote sensing data. Annals of Glaciology 34: 81-88.
Frezzotti, M., S. Gandolfi, and S. Urbini. 2002. Snow megadunes in Antarctica: sedimentary structure and genesis. Journal of Geophysical Research 107(D18), 4344: doi:10.1029/2001JD000673.
Kawamura, K., and J. P. Severinghaus. 2005. Krypton and Xenon as indicators of convective zone thickness in firn at Megadunes, Antarctica. Eos. Trans. AGU 86(52). Fall Meeting Suppl., Abstract PP33C-1590.
Scambos, T. A., M. A. Fahnestock, C. A. Shuman, and R. Bauer. 2002. Antarctic megadunes: characteristics and formation. Eos. Trans. AGU 85(47). Fall Meeting Suppl., Abstract C31C-04.
Suchdeo, V. P., C. A. Shuman, T. A. Scambos, M. A. Fahnestock, M. R. Albert, and R. Bauer. 2002. Precise elevation profiles across Antarctic megadunes. Eos. Trans. AGU 85(47). Fall Meeting Suppl., Abstract C33C-0357.
Suwa, M., and J. Severinghaus. 2002. Firn density profile at Megadunes, East Antarctica, calls for an improved densification model for low accumulation sites. Eos. Trans. AGU 85(47). Fall Meeting Suppl., Abstract C33C-0359.
