Data description for output .csv files containing processed AltiKa data to support Fraser et al., 2026 (Nature Communications).

first_meas_time: This is the datetime of the start of each SARAL orbit. SARAL L2 data are distributed as pole-to-pole half-orbits, so this time will correspond to a measurements close to the turning latitude (+/- ~81.5 degrees N).

swhAtMyEdge: The AltiKa-reported significant wave height at the NOAA/NSIDC CDR of sea ice concentration-reported ice edge (not the AltiKa flag-reported ice edge), in metres.

latAtMyEdge: The latitude of the NOAA/NSIDC CDR of sea ice concentration-reported ice edge under this satellite pass (SIC > 15%), in degrees N.

lonAtMyEdge: The longitude of the NOAA/NSIDC CDR of sea ice concentration-reported ice edge under this satellite pass (SIC > 15%), in degrees E.

latAtAltiKaEdge: The latitude of the ice edge under this pass, as reported by AltiKa flags (open_sea_ice_flag between 1 and 4, inclusive), in degrees N.

lonAtAltiKaEdge: The longitude of the ice edge under this pass, as reported by AltiKa flags (open_sea_ice_flag between 1 and 4, inclusive), in degrees E.

latAtInnerMIZ: This (together with the "lonAtInnerMIZ") is the primary output of this work. This is the middle value of five chosen to assess the sensitivity of inner MIZ location to the choice of thresholds of "Slope of leading edge" (SLE) times waveform peakiness, as described in the Nature Communications paper. It can be considered the best guess of the latitude of the point at which waves become undetectable from AltiKa. Degrees N.

lonAtInnerMIZ: This (together with the "latAtInnerMIZ") is the primary output of this work. This is the middle value of five chosen to assess the sensitivity of inner MIZ location to the choice of thresholds of "Slope of leading edge" (SLE) times waveform peakiness, as described in the Nature Communications paper. It can be considered the best guess of the longitude of the point at which waves become undetectable from AltiKa. Degrees E.

mizWidthAlongTrackFromMyEdge: This is the north-south distance (in km) between the "inner MIZ" location (lat/lon given in previous two header columns) and the NOAA/NSIDC CDR-derived ice edge.

mizWidthAlongTrackFromAltikaEdge: As above, but the north-south distance from the AltiKa-defined ice edge to the inner MIZ location (in km). 

ice_edge_diff_flag: "1" if the difference between the latitude of the AltiKa-reported ice edge latitude differs from that reported by the NOAA/NSIDC CDR product by more than 1 degree, otherwise "0".

too_many_switches_flag: "1" if there exists a stretch of open water (as defined by the AltiKa open_sea_ice_flag) between the ice edge and the inner MIZ, "0" otherwise.

hit_continent_flag: "1" if the continent is intercepted by the satellite track prior to full attenuation of the wave, "0" otherwise.

inner_miz_sd_km: The standard deviation, in km, of the location of the inner MIZ when using the five threshold candidates. "0" indicates that the inner MIZ location is the same in all 5 candidates, as described in the main text.

"sicedge_lat_p2": The latitude of the sea ice edge, in degrees N, at the longitude of the satellite track plus 2 degrees (as reported by the NOAA/NSIDC CDR). This is used to assess the complexity of the ice edge.

"sicedge_lat_m2": The latitude of the sea ice edge, in degrees N, at the longitude of the satellite track minus 2 degrees (as reported by the NOAA/NSIDC CDR). This is used to assess the complexity of the ice edge.

ice_edge_complex_flag: "True" if the ice edge varies in latitude by more than 1 degree across a longitude baseline of +/- 2 degrees, "False" otherwise.

"sic_at_inner_miz": The fraction (0-1) of sea-ice concentration at the inner MIZ location, according to the NOAA/NSIDC CDR.

latAtHitContinentPoint: The latitude (degrees N) at which the satellite track intercepts the Antarctic continent (all tracks touch the continent).

lonAtHitContinentPoint: The longitude (degrees E) at which the satellite track intercepts the Antarctic continent (all tracks touch the continent).

latAtSouthernmostSeaIce: The latitude (degrees N) of the southernmost sea ice encountered along this track (as defined by the AltiKa open_sea_ice_flag flag).

lonAtSouthernmostSeaIce: The longitude (degrees E) of the southernmost sea ice encountered along this track (as defined by the AltiKa open_sea_ice_flag flag).

latAtSICge80: The northernmost latitude (in degrees N) at which a sea-ice concentration greater than 80% is encountered.

lonAtSICge80: The northernmost longitude (in degrees E) at which a sea-ice concentration greater than 80% is encountered.
