Sea ice thickness retrieval algorithms based on in situ surface elevation and thickness values for application to altimetry

In situ measurements of sea ice thickness (I), snow depth (S), and snow freeboard (Fsn) from drilling profile lines from 15 cruises into the Southern Ocean, Antarctica, were analyzed. Iwas calculated from in situ Fsnand Susing an isostatic approach. Iwas also directly estimated from Fsnas can be obtained from laser altimetry. The root‐mean‐square difference (RMSD) between observed and calculated Ireduces, and the correlation between Fsnand Iincreases substantially, when (1) using values averaged over the survey lines (∼50 m) instead of single drill hole measurements (∼1 m) and (2) treating positive and negative sea ice freeboard (Fi) separately. For small Fi, however, Sapproximates Fsnpointing toward an isostatic balance also between Sand I. Our linear regression analysis between the in situ measurements suggests a direct conversion of Fsninto Iusing a region‐specific set of equations. RMSD values are similar to those obtained employing isostatic balance models and treating positive and negative Fiseparately. However, more data would have been needed to obtain significant differences between most of the various models suggested. Still our new approach gives a viable alternative for Antarctic Iretrieval from altimetric measurements of Fsnalone. Correlation between in situ observations of Fsnand Sis high. RMSD between observed and calculated Sis small. This suggests estimation of Sfrom altimetric Fsnmeasurements. Such Shas an estimated precision of ∼5 cm, and is neither affected by snow wetness or grain size nor limited to S< 50 cm. In situ observations from drilling profiles into Antarctica were analyzed.Statistical relationships between sea ice and snow properties were developed.