Mechanical and microstructural data from ice deformation experiments with a change in temperature partway
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This dataset contains data collected during and after a series of ice deformation experiments. Seven of the experiments are controls, run at a constant temperature of either -2, -7 or -10 degrees celsius, and four involve a change in temperature partway through the experiment. Vertical displacement and temperature data were collected during the experiments, and microstructural data (fabric analyser thin sections) were collected at the conclusion of each experiment. The experimental methods and our interpretations are described thoroughly in Craw, et al. (in prep). In folder mechanical_data: - One .csv file for each experiment containing a header with information on experimental conditions, and columns of data corresponding to time (hours), vertical displacement (mm), and temperature (degrees celsius) throughout the experiment. This is raw data, there will be points recorded from before weights were added at the beginning of the experiment, and after the temperature was lowered at the end. in folder microstructural_data: - One .mat file for each experiment, containing microstructural data (spatially indexed Euler orientations) formatted to be read by the MTEX toolbox (https://mtex-toolbox.github.io/). There is also a file for an example of the starting material, "standard" laboratory ice. These data are converted from the .cis files which are generated by the G50 fabric analyser. - One .m script (plot_microstructural_data.m) containing commands for plotting spatial maps, histograms of grain size distribution and pole figures of c-axis orientation from the .mat files in this directory.
Sea ice data - Bio-optics and physics measurements from Scott Base and McMurdo Sound 2014
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As part of Australian Antarctic Science project # 4298 and Antarctica New Zealand project K131A, a total number of 24 sea ice sites were sampled for bio-optical measurements along 2 transects on land-fast sea ice in McMurdo Sound (Antarctica) during November 2014. Measurements included hyperspectral surface irradiance measurements (TriOS ASS) as well as under-ice radiance measurements using a TriOS ARC (350 – 900 nm, 3.3 nm resolution) radiometer mounted to an L-arm. After completion of radiometric measurements, snow thickness was measured with a ruler and an ice core was collected directly above the radiometer location. Sea-ice freeboard (tape measure) and ice thickness (ice core length) were recorded. Ice core (9 cm internal diameter) bottom sections (lowermost 0.1 m of ice cores) were collected and were used for determination of algal pigment content (using HPLC) and spectral ice algal absorption coefficients (ap, ad, aph). Sea ice physical properties including vertical profiles of ice temperature and salinity profiles were collected at some specific locations along the transects, which were sampled near Little Razorback Island and near Cape Evans, McMurdo Sound.
Sea ice bio-optical measurements
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Field-based sampling: As part of Australian Antarctic Science project # 4298, a total number of 44 sea ice sites were sampled for bio-optical measurements along 4 transects on land-fast sea ice off Davis Station (Antarctica) during November – December 2015. Measurements included simultaneous hyperspectral down-welling (ice surface) irradiance (triplicate) and under-ice radiance (triplicate) measurements (320 – 900 nm, 3.3 nm resolution) with a TriOS ACC and Trios ARC radiometer, respectively. The radiance measurements were conducted with the TriOS ARC radiometer mounted onto an L-shaped arm (for deployment details see Melbourne-Thomas et al. 2015). Subsequently, snow thickness was measured with a ruler and an ice core was collected directly above the radiometer location. Sea-ice freeboard (tape measure) and ice thickness (ice core length) were also recorded. Ice cores (9 cm internal diameter) were cut into sections, and these were melted in the dark at +4 degrees C, filtered onto GFF filters and then used to measure ice algal pigment content (using High Performance Liquid Chromatography (HPLC) and spectral ice algal absorption coefficients (ap, ad, aph) for entire vertical profiles or for the lower-most 0.1 m of ice cores. The location of the sampling grid had its origin (x=0, y=0) at GPS position: -68.568904, 77.945439. Transects (128m – 512 m in length) started at x=60, x=70, x=80 and x=90 m and were sampled at y-positions of 0m, 0.5m, 1m, 2m, 4m, 8m, 16m, 32m, 64m, 128m, (256m, and 512m) on 19/11/2015, 23/11/2015, 29/11/2015 and 02/12/2015, respectively. Analysis of ice algal chlorophyll a concentration: For pigment analysis, 0.25 to 1.0 litres of melted ice core subsamples were passed through 25 mm diameter glass-fiber (Whatman GF/F) filters. The filters were then frozen and stored below −80 degrees C prior to analysis using HPLC. Samples were extracted over 15 to 18 hours in acetone before analysis by HPLC using a modified C8 column and binary gradient system with an elevated column temperature [Van Heukelem and Thomas, 2001]. Pigments were identified by retention time and absorption spectra from a photo-diode array (PDA) detector, and concentrations were determined from commercial and international standards (Sigma; DHI, Denmark). Analysis of particulate (algal and non-algal) absorption: The optical density (OD) spectra of the particulate material on these filters (see section above) were measured over the 350 to 750 nm spectral range in 0.9 nm increments, using a Cintra 404 UV/VIS dual-beam spectrophotometer equipped with an integrating sphere. The pigments on the sample filter were then extracted using the method of Kishino et al. [1985]'s method to determine the OD of the non-algal particles in a second scan. The OD due to ice algae was then obtained by calculating the difference between the optical density of the total particulate and non-algal fractions. The OD measurements were converted to absorption spectra using blank filter measurements, and by first normalizing the scans to zero at 750 nm and then correcting for the path length amplification using the coefficients of Mitchell [1990]. A detailed description of the method is given in Clementson et al. [2001], and followed SeaWiFS protocols [Muller et al., 2003]. An exponential function was fitted to all spectra of non-algal particulate material: ad(λ) = ad(350 nm) exp[−S(λ − 350 nm)] + b, (1) where ad(λ) is the residual absorption coefficient over the wavelength (λ) range 350 to 750 nm of the particles after methanol extraction, also referred to as absorption of detritus [m−1] although this may include absorption of non-extractable pigments and heterotrophic protists. A non-linear least-squares technique was used to fit Equation 1 to the untransformed data, where S and b are empirically-determined constants. The inclusion of an offset b allows for any baseline correction. In some samples, pigment extraction was incomplete, leaving small residual peaks in
Sea ice micro-zooplankton in ice cores and the water column (LOPC) observed during the SIPEX II voyage of the Aurora Australis, 2012
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This data set includes abundance and distribution of sea ice and water column micro-invertebrates. Data was collected form 8 stations over the course of the SIPEX 2 voyage. The data for this project consists of 2 separate collection regimes: Ice cores - a number of ice were taken at stations 1-6, using a 15cm corer, they were sectioned and dissolved in filtered seawater before being fixed in formalin. At Station 6 sufficient biomass was present in the bottom 10cm of some cores to allow microscopic separation of copepod species, which were then frozen for stable isotope analysis (SIA). Lazer optical plankton counter (LOPC) was deployed at stations 2 to 7 either from ice holes (IH) or from the trawl Deck (TD) to depths of 60m or 100m. These deployments were made throughout the day where possible and were accompanied by a 100um plankton net . Each deployment consisted of 2 drops for both the LOPC and the net. Collected plankton were filtered onto 50um mesh and backwashed into vials before being fixed in 5% formalin. All LOPC files .bin will require LOPC program manufactured by ODIM Rolls Royce Nova Scotia. These files are read to format .dat which maybe opened as a .txt file