Altimetric observation of wave attenuation through the Antarctic marginal ice zone using ICESat-2

Brief description

Data from all ICESat-2 tracks underlying the publication Brouwer et al., 2022:
Brouwer, J., Fraser, A. D., Murphy, D. J., Wongpan, P., Alberello, A., Kohout, A., Horvat, C., Wotherspoon, S., Massom, R. A., Cartwright, J., and Williams, G. D.: Altimetric observation of wave attenuation through the Antarctic marginal ice zone using ICESat-2, The Cryosphere, 16, 2325–2353, https://doi.org/10.5194/tc-16-2325-2022, 2022.

ICESat-2 is a high-precision laser altimeter in a polar orbit. Due to its narrow laser footprint (~17 m) and high measurement repetition rate (firing every 70 cm) it has the capability to resolve the passage of waves (of wavelength ~100 to 1000 m) through sea ice in the Antarctic marginal ice zone. This dataset provides the processed data underlying the ICESat-2 tracks published in Brouwer et al., 2022. The processing is described in that publication, but involves manual and automated filtering to remove inappropriate (cloud-affected) tracks, then a series of steps to convert segment heights into estimates of marginal ice zone width.

Rout
A brief description of the dataset fields is provided below. For more information please see methods section of paper, and the following code: https://github.com/Jill-Brouwer/Brouwer-etal-2022-MIZ-code/blob/main/R-gam3batch.R
• Rows describe FFT and FIRF techniques for calculating significant wave height
o hm0bc: FFT with boxcar window
o hm0hann: FFT with hanning window
o std: 4 times the standard deviation of height
o FXXXX refer to the FIRFs and the wavelengths ranging from 1500m to 38m
• Columns describe the parameters from the segmented regression fits and resulting MIZ width estimate.
o DC_slope_lin: Slope derived from linear regression fit to relevant significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o DC_slope_lin_error: standard error in DC_slope_lin generated by the regression function
o DC_int_lin: Y intercept derived from segmented linear regression fit to relevant significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o DC_int_lin_err: standard error in DC_int_lin generated by the regression function
o DC_bp_lin: break point estimated from R segmented function in corrected distance from ice edge (km units) and linear significant wave height estimates (m)
o DC_miz_lin: Miz width estimated using the attenuation parameters DC_slope_lin and DC_int_lin
o DC_RMSE_lin: RMSE of linear regression fit to relevant significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o DC_miz_lin_err: error in MIZ width estimate calculated by propagating errors in the DC_slope_lin_err and DC_int_lin_err
o DC_slope_exp: Slope derived from exponential regression fit to relevant significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o DC_slope_exp_err: standard error in DC_slope_exp generated by the regression function
o DC_exp_lin: Y intercept derived from exponential segmented regression fit to relevant significant wave height estimate (row value) and corrected distance of the section midpoint from ice edge (km units) for the outer/attenuation dominated segment.
o DC_int_exp_err: standard error in DC_exp_lin generated by the regression function
o DC_bp_exp: break point estimated from R segmented function in corrected distance from ice edge (km units) and log-transformed significant wave height estimates; exponential fit.
o DC_miz_exp: Miz width estimated using the attenuation parameters DC_slope_exp and DC_exp_lin
o DC_RMSE_exp: RMSE of exponential regression fit to relevant significant wave height estimate (row value) and corrected distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o DC_miz_exp_err: error in MIZ width estimate calculated by propagating errors DC_slope_exp_err and DC_int_exp_err.
o D_slope_lin: Slope derived from linear regression fit to relevant significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o D_slope_lin_err: standard error in D_slope_lin generated by the regression function
o D_int_lin: Y intercept derived from segmented linear regression fit to relevant significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o D_int_lin_err: standard error in D_int_lin generated by the regression function
o D_bp_lin: break point estimated from R segmented function in distance from ice edge (km units) and significant wave height estimates (m)
o D_miz_lin: Miz width estimated using the attenuation parameters D_slope_lin and D_int_lin
o D_RMSE_lin: RMSE of linear regression fit to relevant significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the outer/attenuation dominated segment.
o D_miz_lin_err: error in MIZ width estimate calculated by propagating errors in the D_slope_lin_err and D_int_lin_err
o D_slope_exp: Slope derived from exponential regression fit to relevant significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the outer/attenuation dominated segment.
o D_slope_exp_err: standard error in D_slope_exp generated by the regression function
o D_exp_lin: Y intercept derived from exponential segmented regression fit to relevant significant wave height estimate (row value) and corrected distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o D_int_exp_err: standard error in DC_exp_lin generated by the regression function
o D_bp_exp: break point estimated from R segmented function in corrected distance from ice edge (km units) and log-transformed significant wave height estimates; exponential fit.
o D_miz_exp: Miz width estimated using the attenuation parameters D_slope_exp and D_exp_lin
o D_RMSE_exp: RMSE of exponential regression fit to relevant significant wave height estimate (row value) and corrected distance of the section midpoint from ice edge (km units) for the outer (attenuation-dominated) segment.
o D_miz_exp_err: error in MIZ width estimate calculated by propagating errors D_slope_exp_err and D_int_exp_err.
• The final column parameters provide some extra values from the broken regression function that describe the inner ice-structure dominated fit:
o DC_sgslop_lin: Slope derived from linear regression fit to relevant significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o DC_segslop_lin_err: standard error in DC_sgslope_lin generated by the regression function
o DC_segint_lin: Y intercept derived from segmented linear regression fit to relevant significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o DC_bp_lin_err: standard error in DC_bp_lin generated by the regression function
o DC_segslop_exp: Slope derived from exponential regression fit to relevant significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o DC_segslop_exp_err: standard error in DC_segslope_exp generated by the regression function
o DC_segint_exp: Y intercept derived from segmented regression fit to log-transformed significant wave height estimate (row value, m units) and corrected distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o DC_bp_exp_err: standard error in DC_bp_exp generated by the regression function
o D_segslop_lin: Slope derived from linear regression fit to relevant significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o D_segslop_lin_err: standard error in D_segslope_lin generated by the regression function
o D_segint_lin: Y intercept derived from segmented linear regression fit to relevant significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o D_bp_lin_err: standard error in D_bp_lin generated by the regression function
o D_segslop_exp: Slope derived from exponential regression fit to relevant significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o D_segslop_exp_err: standard error in D_segslope_exp generated by the regression function
o D_segint_exp: Y intercept derived from segmented regression fit to log-transformed significant wave height estimate (row value, m units) and distance of the section midpoint from ice edge (km units) for the inner (ice-structure-dominated) segment.
o D_bp_exp_err: standard error in D_bp_exp generated by the regression function
• The final column, SIC_dist, lists the MIZ width derived from sea ice concentration data in km.

Rawheight
Describes distance from ice edge in meters at 8m intervals and the matching height values interpolated from IS-2 altimeter heights with cubic spline.

Csv (mizfind)
This is the data that was used in fitting the linear and exponential fits to significant wave height and distance from the ice edge for each 6.25km section midpoint, for final estimation of MIZ width. For more information please see methods section of paper and source code available here: https://github.com/Jill-Brouwer/Brouwer-etal-2022-MIZ-code/tree/main.

The following variables are for section midpoints with suitable significant wave height estimates:
• Dist: midpoint distance from ice edge (in kilometers)
• CDist: midpoint corrected distance from ice edge (in kilometers)
• Hm0bc: significant wave height from spectral analysis of Icesat-2 interpolated height data using boxcar window
• Hm0hann: significant wave height from spectral analysis of Icesat-2 interpolated height data using hann window
• Std: significant wave height from the standard deviation (SD) of the Icesat-2 interpolated height data
• FXXXX: significant wave height from spatial domain filters where XXXX corresponds to the wavelength used (in meters).
• hm0bcerr: hm0bc error
• hm0hannerr: hm0hann error
• stderr: std error
• FXXXXerr: error in FXXXX
• Mplat, mplon: Latitude and longitude of section midpoint
• Mpsic: sea ice concentration of section midpoint
• Good_mpinds: lookup table of corresponding section midpoint indexes that had acceptable significant wave height estimates

The below variables are for all section midpoints from the ice edge - including those that do not have suitable significant wave height estimates.
• all_sic_dist: Distance from ice edge in km for section midpoint
• all_sic_corrdist: Corrected distance from ice edge in km for section midpoint
• all_sic_vals: sea ice concentration value for section midpoint
• all_lat, all_lon: latitude and longitude of all section midpoints
• beam2mp_time: midpoint time extracted from IS-2 dataset

Lineage

Progress Code: completed

Statement: Track quality is annotated for each track in the "goodlog.txt" in each month's directory.