Fracturing and deformation along the Amery Ice Shelf

Brief description

Metadata record for data from ASAC Project 2581 See the link below for public details on this project. The break-up of Antarctic ice shelves has highlighted the need for a better understanding of the dominant fracture processes occurring within the ice shelves and whether there is any link to climate variability. Using a combination of in-situ (GPS, seismic) and satellite (optical and radar imagery, synthetic aperture radar (SAR)) measurements and airborne ice radar measurements, we will quantify the deformation and fracture processes in different regions on the Amery Ice Shelf, leading to improved fracture mechanics models. GPS measurements were taken across large crevasses in the shear margins on the eastern side of the Amery Ice Shelf, north of Gillock Is. These measurements will give us an opportunity to measure the three dimensional deformation across active fracture zones, leading to a better understanding of fracture processes on ice shelves. Three GPS networks, each network consisting of 4 GPS units in a quadrilateral shape, were measured over the period 17-28 Jan, 2007. These data will be processed during 2007 to compute the deformation and strain across and within the crevassed areas.

Lineage

Progress Code: completed

Statement: # GPS surface elevation profiles for the Amery Ice Shelf for various campaigns # 1995, 1999, 2000, 2003, 2005/6 # # The raw GPS data were collected under Australian Antarctic Science Advisory Committee (ASAC) funding # to PI Richard Coleman. # The data processing was as described in the paper below. Briefly, these are # 1995: in Leica Ski software, relative to on ice base station, with # coordinates determined relative to rock site at Beaver Lake # subsequent: in Track (GAMIT/GLOBK) relative to base station with coordinates # determined using GIPSY precise point positioning # Coordinate files are in a format to allow easy crossover computations using the GMT supplementary routine # x2sys_crossover using the geoz.def definition provided # e.g., for GPS/GPS crossovers it would be # x2sys_cross file1 file2 -TGEOZ -A0.2 -Ndk -Qe -Ia -V -2 -Ce -Wn6 # col1: time in days since 00:00 Jan 1, 2000. non-integer part of the day may just be a count by epoch rather than actual time. # col2: lon (WGS84 deg) # col3: lat (WGS84 deg) # col4: height (WGS84 ellipsoidal elevation, after removal of ocean tides, ocean tide loading displacement, inverse barometer effect and permanent body tide). See note 1. # Note 1: Corrections applied: # 1. tides (TPXO6.2) # 2. tidal loading displacement (TPXO6.2) # 3. inverse barometer effect (IB corrections are relative to mean pressure (981.2hPa) at the Amery G3 AWS in 1999-2003). # 4. permanent body tide was removed for compatibility to ICESat products (note that ICESat Release 428 products, not included here, are not conventionally on WGS84 ellipsoid so this correction may need to be applied to external datasets for compatibility). This was done by block shifting the GPS time series by -0.10 m # Full details are provided in the paper below. # in using these data please cite King, M.A., R. Coleman, A. Freemantle, H.A. Fricker, R.S. Hurd, B. Legresy, L. Padman and R. Warner 2009. A 4-decade record of elevation change of the Amery Ice Shelf, East Antarctica. Journal of Geophysical Research, 114: F01010, doi:10.1029/2008JF001094. # Matt King, Dec 2012