Preprints
https://doi.org/10.5194/tc-2023-122
https://doi.org/10.5194/tc-2023-122
14 Aug 2023
 | 14 Aug 2023
Status: a revised version of this preprint was accepted for the journal TC and is expected to appear here in due course.

The Variability of CryoSat-2 derived Sea Ice Thickness introduced by modelled vs. empirical snow thickness, sea ice density and water density

Imke Sievers, Henriette Skourup, and Till A. S. Rasmussen

Abstract. To derive sea ice thickness (SIT) from CryoSat-2 freeboard (FB) estimates, assumptions about snow thickness, snow density, sea ice density and water density need to be made. These parameters are close to impossible to observe alongside FB, so many existing products use climatologies, or empirical values. A resent study proposed to use model parameters for snow thickness, sea ice density and water density instead. In this study, we are evaluating this values against in situ observations and the commonly used climatologies and empirical values. We show that the snow thickness and water density is in better agreement with observations, and that the sea ice density is overall too light. Analyzing the difference in SIT resulting from the model parameter vs. the empirical values, we find that the snow thickness leads to the largest differences with up to 30 cm, closely followed by the sea ice density with 20 cm. For the water density we find an up to 7.5 cm difference, which is small in comparison to the snow thickness and sea ice density, but not negligible, as most studies currently argue. We find that the origin of the assumption that water density is negligible in the FB to SIT conversion originates from a study investing the seasonal Arctic sea ice density variability, not taking into account the spacial variability. For CryoSat-2 based SIT products we recommend to either use a water density climatology, or an uncertainty value of 2.5 kgm-3 instead of the commonly used value of 0 to 0.5 kgm-3.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Imke Sievers, Henriette Skourup, and Till A. S. Rasmussen

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2023-122', Anonymous Referee #1, 12 Sep 2023
    • AC1: 'Reply on RC1', Imke Sievers, 27 Oct 2023
  • RC2: 'Comment on tc-2023-122', Anonymous Referee #2, 13 Sep 2023
    • AC2: 'Reply on RC2', Imke Sievers, 27 Oct 2023
  • RC3: 'Comment on tc-2023-122', Anonymous Referee #3, 10 Oct 2023
    • AC3: 'Reply on RC3', Imke Sievers, 27 Oct 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2023-122', Anonymous Referee #1, 12 Sep 2023
    • AC1: 'Reply on RC1', Imke Sievers, 27 Oct 2023
  • RC2: 'Comment on tc-2023-122', Anonymous Referee #2, 13 Sep 2023
    • AC2: 'Reply on RC2', Imke Sievers, 27 Oct 2023
  • RC3: 'Comment on tc-2023-122', Anonymous Referee #3, 10 Oct 2023
    • AC3: 'Reply on RC3', Imke Sievers, 27 Oct 2023
Imke Sievers, Henriette Skourup, and Till A. S. Rasmussen
Imke Sievers, Henriette Skourup, and Till A. S. Rasmussen

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Latest update: 08 Dec 2024
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Short summary
To derive sea ice thickness (SIT) from satellite freeboard (FB) observations, assumptions about snow thickness, snow density, sea ice density and water density are needed. These parameters are impossible to observe alongside FB, so many existing products use empirical values. In this study, modeled values are used instead. The modeled values and otherwise commonly used empirical values are evaluated against in situ observations. In a further analysis, the influence on the SIT is quantified.