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.

A mathematical model (Bennetts and Meylan, 2021, doi.org/10.1137/20M13851) has been used to make predictions of ocean wave transfer to Ross Ice Shelf flexure. The transfer is considered along transects of the Ross Ice Shelf and adjoining open ocean, where the ice shelf thickness and seabed profiles along the transects are sampled from the Bedmap2 dataset (Fretwell et al, 2013, doi.org/10.5194/tc-7-375-2013). Our dataset consists of MAT-files, where each file is for a particular transect and holds two structures: 'data_I' as input data and 'data_o' for the model output data. The input data are the profiles from Bedmap2: 'thick' is the shelf thickness, 'draft' is the shelf draught; and 'bed' is the seabed elevation. They are all in vector form with 2001 sample points along the shelf, which was found to give model outputs accurate to 95%. The input data also contains: a 1x2 vector 'L_vec', for which the first entry is the shelf length, and the second entry is the length of the adjoining open ocean, where both values are in metres; and a 1x2 vector 'Int_vec', for which the first entry is the total number of sample points (ocean + shelf) and the second entry is the number of points in the shelf only. The output date are the three matrices where the rows correspond to different wave period and columns are distances along the transect: 'eta_w' is the water displacement (dimensionless); 'eta_s' is the shelf displacement (dimensionless); and 'str' is the flexural shelf strain (1/metres). All three outputs are normalised by the incident amplitude, noting that the model is linear. The output data also contains: a 1x300 vector containing the wave periods 'T', which are log-spaced between 10s and 1000s. The data are divided into two folders: validation/ and transects/. The first group (validation/) are used to validate the model predictions against the observations of Chen et al (Geophysical Research Letters, 2019, doi.org/10.1029/2019GL084123) close to 2 km away from the shelf front, where the results of Chen et al (2019) have been digitised and are contained in 'Chen_paper.mat'. The second group (transects/) can be used to study transfer over a 500km wide region of the Ross Ice Shelf. There are 101 transects with 5 km spacing. We also analysed the shelf displacement and strain over different wave periods at 10 km away from shelf front for all transects to investigate the relations between strain and wave period, these data have stored in 'Transfer_function_x_10km.mat'. Three MATLAB scripts (Fig1.m, Fig2.m, Fig3.m) are included to recreate results from Bennetts et al (submitted). Fig1.m produces plots from observation (Chen et al) and our models. Fig2.m performs strain transfer function analysis for different profiles and Fig3.m generate the strain map and selected region of Ross Ice Shelf for given incident ocean wave. For Fig1.m, it requires “Bedmap2 Toolbox for Matlab” to access the bedmap2 for producing Ross Ice Shelf on the Antarctica map. A link to download this software will be stated in the MATLAB scripts. An updated dataset was provided on 2022-10-25.

Direct Numerical Simulation (DNS) was used to study the effect of sloping the ice-shelves on the dissolution/melt rate at the ice-ocean interface. The simulations were done on the HPC Raijin at NCI, Canberra over March 2015 to June 2017. Numerical experiments were carried out over a range of slope angle (5 degrees – 90 degrees) of the ice-shelves measured from the horizon. Turbulent flow field is simulated over the domain length of 1.8 m, (for slope angle greater than or equal to 50 degrees) and 20 m (for slope angle less than or equal to 20 degrees) respectively; the flow-field is laminar otherwise. A constant ambient temperature 2.3 degrees C and salinity 35 psu is maintained throughout the simulations. The DNS successfully resolved all possible turbulence length scales and relative contributions of diffusive and turbulent heat transfer into the ice wall is measured. Data available: Excel file Meltrate_vs_slopeangle_lam_turb.xlsx contains both simulated laminar and turbulent dissolution/melt rate as a function of slope angle along with their analytical values based on laminar and turbulent scaling theory respectively.

This is a derived product containing two products blended together that describes the elevation of the seafloor beneath and out to approximately seaward of the Totten Glacier Ice Shelf cavity as well as the elevation of the ice bottom beneath the ice sheet immediately sounding the ice shelf cavity. The seafloor was inferred by inverting airborne gravity observations; the terrain beneath grounded ice was observed with airborne ice sounding radar measurements. The two products were blended along the grounding line observed with satellite observations [Rignot, E., Mouginot, J. and Scheuchl, B. Antarctic grounding line mapping from differential satellite radar interferometry. Geophys. Res. Lett. 38, L10504 (2011)]. We have provided a text file that contains three columns that may be used to produce a gridded bathymetry of the Totten Glacier Ice Shelf and surrounding area with a cell size of 1-km. The first two columns contain grid coordinates using the Polar Stereographic projection based on WGS84 with true scale at 71 degrees S. The third column contains the vertical coordinate representing the seafloor beneath and the ice-bottom elevation around the Totten Glacier Ice Shelf cavity. The center of the region is located near 115E and 67S and spans an area about 217 km by 131 km. The data are described in detail in the publication and supplementary materials that can be found by following this link: http://www.nature.com/ngeo/journal/v8/n4/abs/ngeo2388.html#supplementary-information

Balance Ice Fluxes for the Antarctic ice sheet. These ice fluxes (in km^2/yr)represent the (hypothetical) distribution of ice flux that would keep the Antarctic ice sheet in its present shape (i.e. surface topography), under the influence of a prescribed accumulation distribution. The present fluxes were computed using computer code BalanceV2 (by Warner) (outlined in Budd and Warner 1996, and detailed in Fricker, Warner and Allison 2000), using the surface accumulation dataset of Vaughan et al (1999), and the ice sheet surface elevation dataset distributed by BEDMAP (attributed to Liu et al 1999). This ice flux dataset represents the (hypothetical) distribution of ice flux that would keep the ice sheet topography in its present shape, under the influence of the given accumulation distribution.

Balance Ice Velocities for the Antarctic ice sheet. These ice velocities (in m/yr) represent the (hypothetical) distribution of depth-averaged ice velocities that would keep the Antarctic ice sheet in its present shape (i.e. surface topography and thickness), under the influence of a prescribed accumulation distribution. The present fluxes were computed using computer code BalanceV2 (by Warner) (outlined in Budd and Warner 1996, and detailed in Fricker, Warner and Allison 2000), using the surface accumulation dataset of Vaughan et al (1999), the ice sheet surface elevation dataset distributed by BEDMAP (attributed to Liu et al 1999), and the ice sheet thickness compilation distributed by the BEDMAP consortium (Lythe et al 2001).

AM06 borehole drilled January 2010. Data collected in series of files following production of borehole. Consult Readme file for detail of data files and formats.

AM05 borehole drilled December 2009. See the pdf file as part of the download for more information on the work carried out as part of this borehole.

AM04 borehole drilled January 2006. Data collected in series of files over a period of 4 days during production of borehole. Consult Readme file for detail of data files and formats.

Metadata record for data from ASAC Project 291 See the link below for public details on this project. From the abstracts of the referenced papers: Ground surveys of the ice sheet in Wilkes Land, Antarctica, have been made on oversnow traverses operating out of Casey. Data collected include surface elevation, accumulation rate, snow temperature, and physical surveys, the data are mostly restricted to line profiles. In some regions, aerial surveys of surface topology have been made over a grid network. Satellite imagery and remote sensing are two means of extrapolating the results from measurements along lines to an areal presentation. They are also the only source of data over large areas of the continent. Landsat images in the visible and near infra-red wavelengths clearly depict many of the large- and small-scale features of the surface. The intensity of the reflected radiation varies with the aspect and magnitude of the surface slope to reveal the surface topography. The multi-channel nature of the Landsat data are exploited to distinguish between different surface types through their different spectral signatures, e.g. bare ice, glaze, snow, etc. Additional information on surface type can be gained at a coarser scale from other satellite-borne sensors such as the ESMR, SMMR, etc. Textural enhancement of the Landsat images reveals the surface micro-relief. Features in the enhanced images are compared to ground-truth data from the traverse surveys to produce a classification of the surface types across the images and to determine the magnitude of the surface topography and micro-relief observed. The images can then be used to monitor changes over time. Landsat imagery of the Antarctic ice sheet and glaciers exhibit features that move with the ice and others that are fixed in space. Two images covering the same area but acquired at different times are compared to obtain the displacement of features. Where the time lapse is large, the displacement of obvious features can be scaled from photographic prints. When the two images are co-registered finer features and displacements can be resolved to give greater detail. Remote sensing techniques can be used to investigate the dynamics and surface characteristics of the Antarctic ice sheet and its outlet glaciers. This paper describes a methodology developed to map glacial movement velocities from LANDSAT MSS data, together with an assessment of the accuracy achieved. The velocities are derived by using digital image processing to register two temporally separated LANDSAT images of the Denman glacier and Shackleton Ice Shelf region. A derived image map is compared with existing maps of the region to substantiate the measured velocities. The velocity estimates from this study were found to correspond closely with ground-based measurements in the study area.