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.

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).

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.

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

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.

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 Profile_salinity_temperature_velocity.xlsx contains along-slope velocity, temperature and salinity as a function of wall normal distance for slope angle 50 degrees, 65 degrees and 90 degrees respectively for the domain length 1.8 m.

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.

AM03 borehole drilled December 2005. Current meter data dips collected during routine CTD operations over a period of 4 days upon completion of borehole. Consult Readme file for detail of data files and formats.

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.