Mechanical and microstructural data from deformation experiments on marine and meteoric ice from the Amery Ice Shelf

Brief description

These data were collected from compressional ice deformation experiments on samples of standard (laboratory-made) ice, and marine and meteoric ice from the Amery Ice Shelf, cores AM01, AM04 and G1. Experiments were performed in the IMAS Ice Mechanics Laboratory between 2018 and 2022, following the methods described in:

Craw, L., Treverrow, A., Fan, S., Peternell, M., Cook, S., McCormack, F., and Roberts, J.: The temperature change shortcut: effects of mid-experiment temp
erature changes on the deformation of polycrystalline ice, The Cryosphere, 15, 2235–2250, https://doi.org/10.5194/tc-15-2235-2021, 2021.

all_experiments.csv contains a list of all experiments performed, and the following fields:
temperature = target temperature of the experiment, in degrees (actual temperature is recorded in the data files for each experiment)
ice_type = string denoting standard, marine or meteoric ice
starting_point = the index of the data point in the raw data file where the experiment begins (i.e. load was applied to the sample)
end_point = the index of the data point in the raw data file where the experiment ends
secondary_rate = secondary minimum strain rate, picked manually from the curve
secondary_strain = the total strain at the secondary minimum
tertiary_rate_1 = first tertiary strain rate, picked manually from the curve
tertiary_strain_1 = the total strain at the first tertiary creep stage
tertiary_rate_2 = second tertiary strain rate, picked manually from the curve (this value only exists in experiments with more than one temperature point)
tertiary_strain_2 = the total strain at the second tertiary creep stage
max_axial_strain = the maximum (final) axial strain reached
max_octahedral_strain = the maximum (final) octahedral strain reached
total_time_hours = total experiment run-time in hours
total_time_days = total experiment run-time in days
undeformed_median_grain_size = median grain size measured in a thin section before the experiment (this was not always recorded)
undeformed_number_of_grains = the number of grains in the section used to calculate the median grain size (for quality control purposes)
deformed_median_grain_size = median grain size measured in a thin section after the experiment (this was not always recorded)
deformed_number_of_grains = the number of grains in the section used to calculate the median grain size (for quality control purposes)
undeformed_jindex = J-index describing the density of c-axis alignment measured in a thin section taken before the experiment (1 denotes random distribution, an infinite value denotes a single orientation)
deformed_jindex = J-index describing the density of c-axis alignment measured in a thin section taken after the experiment (1 denotes random distribution, an infinite value denotes a single orientation)

For each experiment listed in all_experiments.csv, a raw mechanical data file and a processed mechanical data file are supplied, alongside .mat files containing fabric analyser and EBSD data (where collected) from thin sections.

[experiment_number]_raw_data.csv contains the data as logged during the experiment:
time = time in hours
v_dis = vertical diplacement of the top platen (at the top of the sample) relative to its original position
h_dis = not recorded in these experiments
temp = temperature in degrees celsius

[experiment_number]_smoothed.csv contains the processed data used to plot strain rate vs. strain curves:
smoothed_mean_time = the mean time in hours corresponding to the strain rate data
smoothed_axial_strain = the total axial strain calculated over intervals of 250 data points
smoothed_axial_strain_rate = the axial strain rate calculated over intervals of 250 data points
smoothed_octahedral_strain = the total octahedral strain calculated over intervals of 250 data points
smoothed_octahedral_strain_rate = the octahedral strain rate calculated over intervals of 250 data points

[experiment_number]_FA_smoothed.mat contains fabric analyser data (spatially indexed Euler orientations) formatted to be read by the MTEX toolbox (https://mtex-toolbox.github.io/). These were converted from the original .cis data format using methods outlined in Craw et al., 2021 (reference above).

[experiment_number]_ebsd_smoothed.mat contains EBSD data (spatially indexed Euler orientations) formatted to be read by the MTEX toolbox (https://mtex-toolbox.github.io/). These data have been smoothed using a half quadratic filter.

Please direct any questions to lisa.craw@utas.edu.au.

Lineage

Progress Code: completed

Statement: Experiment LC020 is missing a large amount of displacement data due to a malfunctioning dial gauge. Grain sizes from all meteoric ice samples are unreliable, as they are very large relative to the sample/section size. Strain rate data from meteoric ice samples are likely controlled by a small number of grains, for the same reason.

Notes

Purpose
This dataset was collected as part of a project to quantify the rheology of marine ice in comparison with other ice types.