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.

These data are contained within a netcdf file of the multi-model mean (MMM) calculated as part of the Realistic ice-shelf/ocean state estimates (RISE) project, with the following variables calculated on a 2 kilometer grid, from the ten contributing models: - longitude degrees east EPSG:4326 - latitude: degrees north EPSG:4326 - easting: meters east EPSG:3031 - northing: meters_north EPSG:3031 - mask: grounded=1,iceshelf=2,conshelf=3,ocean=4 - iceshelf_id: NSIDC iceshelf-id - h: Depth (m) - zice: Ice draft depth (m) - ismr: Average basal iceshelf melt (m/year) - salt_bar: Depth averaged practical salinity (psu) - salt_zice: Average practical salinity (icedraft) (psu) - salt_zice_sa: Average absolute salinity (icedraft) (g/kg) - temp_bar: Average potential temperature - \"theta\" (water column) (degrees C) - temp_tw_zice: Average in-situ temperature (icedraft) (degrees C) - temp_tf_zice: Average in-situ temperature which seawater freezes (icedraft) (degrees C) - tstar_zice: Average thermal driving (degrees C) - u_bar: Average East-west velocity (u) ocean current speed (m/s) - v_bar: Average North-south velocity (v) ocean current speed (m/s) - u_zice: Average East-west velocity (u) ocean current speed (icedraft) (m/s) - v_zice: Average North-south velocity (v) ocean current speed (icedraft) (m/s) - rho_zice: Average in-situ seawater density (icedraft) (kg/m3) - ustar_zice: Average ice-water friction velocity Contextual information taken from the abstract of the referenced paper: Societal adaptation to rising sea levels requires robust projections of the Antarctic Ice Sheet’s retreat, particularly due to ocean-driven basal melting of its fringing ice shelves. Recent advances in ocean models that simulate ice-shelf melting offer an opportunity to reduce uncertainties in ice–ocean interactions. Here, we compare several community-contributed, circum-Antarctic ocean simulations to highlight inter-model differences, evaluate agreement with satellite-derived melt rates, and examine underlying physical processes. All but one simulation use a melting formulation depending on both thermal driving (T ⋆) and friction velocity (u⋆), which together represent the thermal and ocean current forcings at the ice–ocean interface. Simulated melt rates range from 650 to 1277 Gt year−1 (m = 0.45 − 0.91 m year−1), driven by variations in model resolution, parameterisations, and sub-ice shelf circulation. Freeze-to-melt ratios span 0.30 to 30.12 %, indicating large differences in how refreezing is represented. The multi-model mean (MMM) produces an averaged melt rate of 0.60 m year−1 from a net mass loss of 842.99 Gt year−1 (876.03 Gt year−1 melting and 33.05 Gt year−1 refreezing), yielding a freeze-to-melt ratio of 3.92 %. We define a thermo-kinematic melt sensitivity, ζ = m/(T ⋆ u⋆) = 4.82 × 10−5 °C−1 for the MMM, with individual models spanning 2.85 × 10−5 to 19.4 × 10−5 °C−1. Higher melt rates typically occur near grounding zones where both T ⋆ and u⋆ exert roughly equal influence. Because friction velocity is critical for turbulent heat exchange, ice-shelf melting must be characterised by both ocean energetics and thermal forcing. Further work to standardise model setups and evaluation of results against in situ observations and satellite data will be essential for increasing model accuracy, reducing uncertainties, to improve our understanding of ice-shelf–ocean interactions and refine sea-level rise predictions.

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).

The data sets consist of static GPS data collected on the Amery Ice Shelf using Leica CRS1000 receivers. Additional data at Landing Bluff, Dalton Corner and Beaver Lake were collected by ANU (see ASAC project 1112). All data are provided in UNIX Z compressed RINEX (Receiver INdependent EXchange) format, as described in the IGS standards - see http://www.igs.org/products The standard RINEX file naming convention is used, i.e., an eight digit file name as bbbbddds.yyt, where bbbb refers to a four digit station name, ddd refers to the day number of the year, s refers to a session number and yyt is the file extension number where yy refers to the year and t defines the file type (o for observation file and n for navigation file). All files are compressed using the UNIX Z compression scheme, as shown by the extension .Z. For example, base0010.00o.Z and base0010.00n.Z. The files are set out in the following directories on the ftp site: season1999_2000 \amery \land \raw Data are also available for download from the Australian Antarctic Data Centre at the provided URL. Raw data, where available, is stored in the aw directory in standard Leica LB2 Binary format. Conversion routines are available: http://www.unavco.org/software/software.html GPS data collected at the permanent stations at Casey, Davis and Mawson are available from Geoscience Australia (previously AUSLIG) - see http://www.ga.gov.au/geodesy/antarc/antgps.jsp The fields in this dataset are: GPS marker number marker name observer/agency approximate position antenna wavelength interval

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.

Readme file for the AAD 4528 dataset on the Wilkins and Voykeykov calving events in 2007--2008 (paper pending) Uploaded 01/02/2024 CL, RC and Voyeykov daily transects folders contain the daily ice cover for each shelf face with the data sorted as: Date_List,pack ice length (km), annual fast ice length (km), per annual fast ice length (km), sea ice length (km). Data was calculated with a shelf latitude mean + 10 degree latitude boundary and a shelf longitude mean +7, or -12 for the east/west boundary. Pack ice length was calculated using the ASMR2 ASI sea ice concentration dataset and fast ice was calculated via the outputs from Fraser et al., 2012 landfast ice dataset. Strain outputs folder contains both the strain calculated off the ice cover timeseries and the strain using a climatological average for ice cover. Each file contains Date_List,LowIce_Strain_Shelf_timeseries,w10d_strain_sum,w30d_strain_sum,w60d_strain_sum,w90d_strain_sum,w120d_strain_sum as its' file headers, with w##d indicating how many days there was a weighted flexural window applied to each timeseries, and the LowIce_Strain_Shelf_timeseries being the daily outputs. Wave statistics are present in ##_corridor_data.txt which provides the daily maximum from each idealised corridor output and ##_icelengths.txt is a summary file for average ice lengths. Fast_Ice_Composites are a combination of Fraser et al., 2012 landfast ice dataset and ASMR_2 ASI dataset used to calculate ice cover. Flags are 0 - open ocean, 1 - ice sheet, 2 - islands, 3 - ice shelf, 4 - pack ice, 5 - annual fast ice, 6 - perennial fast ice, 7 - ice shelf edge. Figure_outputs is the planned figures for this paper.

This indicator is no longer maintained, and is considered OBSOLETE. INDICATOR DEFINITION Regular measurements of the thickness of the fast ice, and of the snow cover that forms on it, are made through drilled holes at several sites near both Mawson and Davis. TYPE OF INDICATOR There are three types of indicators used in this report: 1.Describes the CONDITION of important elements of a system; 2.Show the extent of the major PRESSURES exerted on a system; 3.Determine RESPONSES to either condition or changes in the condition of a system. This indicator is one of: CONDITION RATIONALE FOR INDICATOR SELECTION Each season around the end of March, the ocean surface around Antarctica freezes to form sea ice. Close to the coast in some regions (e.g. near Mawson and Davis stations) this ice remains fastened to the land throughout the winter and is called fast ice. The thickness and growth rate of fast ice are determined purely by energy exchanges at the air-ice and ice-water interfaces. This contrasts with moving pack ice where deformational processes of rafting and ridging also determine the ice thickness. The maximum thickness that the fast ice reaches, and the date on which it reaches that maximum, represent an integration of the atmospheric and oceanic conditions. Changes in ice thickness represent changes in either oceanic or atmospheric heat transfer. Thicker fast ice reflects either a decrease in air temperature or decreasing oceanic heat flux. These effects can be extrapolated to encompass large-scale ocean-atmosphere processes and potentially, global climate change. DESIGN AND STRATEGY FOR INDICATOR MONITORING PROGRAM Spatial Scale: At sites near Australian Antarctic continental stations: Davis; Mawson. Frequency: at least weekly, reported annually Measurement Technique: Tape measurements through freshly drilled 5 cm diameter holes in the ice at marked sites. RESEARCH ISSUES To more effectively analyse the changes in Antarctic fast ice a detailed long-term dataset of sea ice conditions needs to be established. This would provide a baseline for future comparisons and contribute important data for climate modelling and aid the detection of changes that may occur due to climate or environmental change. LINKS TO OTHER INDICATORS SOE Indicator 1 - Monthly mean air temperatures at Australian Antarctic stations SOE Indicator 40 - Average sea surface temperatures in latitude bands 40-50oS, 50-60oS, 60oS-continent SOE Indicator 41 - Average sea surface salinity in latitude bands: 40-50oS, 50-60oS, 60oS-continent SOE Indicator 42 - Antarctic sea ice extent and concentration The fast ice data are also available as a direct download via the url given below. The data are in word documents, and are divided up by year and site (there are three sites (a,b,c) at each station). Snow thickness data have also been included. A pdf document detailing how the observations are collected is also available for download.