The dataset submitted here is 'Sea-ice freeboard derived from airborne laser scanner'. Between 2007 and 2012, the Australian Antarctic program operated a scanning LiDAR system and other scientific instruments for sea-ice geophysical surveys in East Antarctica. For example see Lieser et al. [2013] for the 2012 survey. The dataset here provides the sea-ice freeboard (i.e. elevation above sea level) along various helicopter flight lines of the 2012 survey in the sea-ice zone between 113 degE and 123 degE. The data collection was based on: - Riegl LMS Q240i-60 scanning LiDAR, measuring sea ice elevation above the WGS84 reference ellipsoid; - Hasselblad H3D II 50 camera, taking aerial photographs at about 13 cm resolution every 3-5 seconds (older digital camera used in 2007); - inertial navigation and global positioning system, OxTS RT-4003. The following geophysical corrections were applied to the sea-ice elevations to derive the sea-ice freeboard: - geoid correction (from the EGM2008 Earth gravity model); - mean ocean dynamic topography correction (from the DTU Space model - DTU10MDT); - ocean tide correction (from the Earth and Space Research CATS2008 Antarctic tide model); - atmospheric pressure (inverse barometer effect) correction from ECMWF data (4-year average) and ship-board underway observations. The geophysical corrections have been validated along selected flight lines by extracting ocean surface elevations from leads between ice floes as identified in the aerial photography. Contained in this dataset are the following files: - a netCDF file for 8 selected flights of the 2012 survey containing sea-ice freeboard values; - a postscript file for 4 of the 8 selected flights showing the residuals from the applied geophysical corrections. These 4 flights were selected on the basis of having a good spread of observable leads along the entire flight line that enabled the extraction of ocean surface elevations.

This dataset is a time series of sea ice freeboard proxy estimation based on ASCAT C-band backscatter measurements. File format is unformatted binary, with each file 632*664 pixels, and 32 bits per pixel (floating point). Two datasets are presented here, as detailed in University of Tasmania Honours thesis by Nicola Ramm: "unmasked", i.e., no attempt to mask multiyear and marginal sea ice, and "masked", where these are masked based on backscatter. The grid used by this dataset is described here: https://nsidc.org/data/polar-stereo/ps_grids.html The methods are described in an honours thesis by Nicola Ramm, University of Tasmania.

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.

In situ measurements of ice and snow thickness, and freeboard along an irregular transect on the fast, complementing the repeat ROV (Remotely Operated Vehicle) transects. During our deployment at Davis in 2015 logistics and environmental conditions permitted measurements along 4 transects. The location of the reference grid (ROV box) had its origin (x=0, y=0) at (-68.568904 degrees N,+77.945439 degrees E). Transects 1 – 4 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), respectively. Depending on working conditions the overall transect lengths varied from 128 – 512 m. Sampling dates for in situ ice physcis: Transect ID Date of sampling Zice and FB measured at Ice core taken at Snowpit measured at T1 19/11/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m, 512m 0m, 128m, 512m T2 23/11/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m, 512m 0m, 128m T3 29/11/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m 0m, 128m T4 02/12/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m 0m, 128m Ice cores and snow pits were collected at the 0m, 50m and 100m mark along the transect, where possible. Additionally, ice cores for density analysis were taken at a few of the ice-core sites for independent verification of ice density.

These data have been extracted from an Australian Antarctic Data Centre application, "Sea ice measurements database". The application has now been discontinued. The download file contains the extracted data, plus a sample data entry form. The extracted data are simply database tables that have been converted to csv format. Taken from the main page of the application: This archive contains in-situ measurements of Antarctic sea ice and snow cover properties, collected by many national programs over the past several decades. The data include physical, biological and biogeochemical measurements on ice cores and snow pit samples, as well as ice and snow thickness measurements from drilled transects across ice floes. The data are from all regions of the Antarctic pack ice in many different months of the year. Data can be submitted online using a standard proforma that can be downloaded from this site. The development of this site was a key recommendation from the International Workshop on Antarctic Sea Ice Thickness, held in Hobart, Australia in July 2006.