Antarctic-Sea-ice-thickness: a repository of algorithms to reconstruct Antarctic Sea-ice thickness with satellite observations

Authors: Magata J Mangatane , Marcello Vichi

This is a repository containing scripts to estimate Antarctic Sea-ice thickness with three algorithms. The algorithms have been used for the data analysis in Mangatane and Vichi (Submitted to the Journal of Geophysical Research)

Brief description

This collection of scripts reconstructs the Antarctic circumpolar seasonal Sea-ice thickness (SIT) with three innovative algorithms, namely, the improved One-Layer Method (OLMi), the improved Buoyancy equation (BOC), and the freeboard differencing method (Diff method). The sea-ice freeboard data used are from the ICESat-2 and CryoSat-2 satellites covering the period 2019-2022 and 2019 only, respectively (see Data sources below)

Workflow

The workflow is divided into the preprocessing of the data and the analysis. The raw data and preprocessed data are not provided due to their size but would be located in the data/ directory of this repository. These data are publicly available for download.

The scripts are provided in the scripts/ directory. This directory is divided into two sub-directories, preprocessing/ and analysis/ to preprocess the raw data and to estimate the Sea-ice thickness, respectively.

Preprocessing of data

The preprocessing scripts are found in scripts/preprocessing/

This is the sequence of operations:

1. Extract ICESat-2 freeboard data from HDF files to NetCDF file format (extract_IS2_freeboards.py)
2. Extract AMSR Sea-ice concentration data from He5 to NetCDF file format (extract_amsr_sic_to_nc.py)
3. Grid CryoSat-2 data to a daily 25 km polar stereographic grid (grid_CS2_freeboards.py)
4. Weigh CryoSat-2 data with AMSR data (weigh_cs2_freeboards.py)

Analysis

The scripts to estimate Sea-ice thickness are found in scripts/analysis/

These are the different algorithms used:

1. Estimation of SIT with the improved One-Layer Method (OLMi_sit_estimation.py)
2. Estimation of SIT with the improved Buoyancy equation (BOC_sit_estimation.py)
3. Estimation of SIT with the freeboard differencing method (diff_method_sit_estimation.py)

Data sources

The raw data required to complete the reconstruction of Antarctic Sea-ice thickness demonstrated here are publicly available as follows:

• Kwok, R., A. A. Petty, G. Cunningham, T. Markus, D. Hancock, A. Ivanoff, J. Wimert, M. Bagnardi, N. Kurtz, and the ICESat-2 Science Team. (2021). ATLAS/ICESat-2 L3A Sea Ice Height, Version 5 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/ATLAS/ATL07.005. Date Accessed 09-25-2023.
• European Space Agency, 2019, L2 SAR Precise Orbit. Baseline D. https://doi.org/10.5270/CR2-53hztdl
• Markus, T., J. C. Comiso, and W. N. Meier. (2018). AMSR-E/AMSR2 Unified L3 Daily 25 km Brightness Temperatures & Sea Ice Concentration Polar Grids, Version 1 [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/TRUIAL3WPAUP. Date Accessed 09-24-2023

References

Below are references to public repositories that were adopted to the methods presented in this repository.

• Anthony Arendt, Ben Smith, David Shean, Amy Steiker, Alek Petty, Fernando Perez, Scott Henderson, Fernando Paolo, Johan Nilsson, Maya Becker, Susheel Adusumilli, Daniel Shapero, Bruce Wallin, Axel Schweiger, Suzanne Dickinson, Nicholas Hoschuh, Matthew Siegfried, Thomas Neumann. (2019). ICESAT-2HackWeek/ICESat2_hackweek_tutorials (Version 1.0). Zenodo. http://doi.org/10.5281/zenodo.3360994
• Jack Landy (2022) “jclandy/CryoSat2_Summer_SIT: CryoSat2_Summer_SIT_2022”. Zenodo. doi: 10.5281/zenodo.6558483.