the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Comparison of variables from ocean, sea ice and atmosphere models as forcing data for iceberg drift and deterioration models in the Barents Sea in 2010–2014 and 2020–2021 (Part I)
Abstract. Numerical models of ocean, sea ice and atmosphere supply a wide range of information in the Arctic that are difficult to observe otherwise. Model disagreements emphasise the need to evaluate the suitability of the models for individual applications. This study compares selected ocean, sea ice and atmosphere variables from the models Topaz4b, Barents-2.5, ERA5 and CARRA in the Barents Sea during the years 2010–2014 and 2020–2021. The same data is used in the sequel paper (Herrmannsdörfer et al., 2024) to force simulations of iceberg drift and deterioration and to examine the impact of varied forcing on the iceberg simulations. Comparing Topaz4b and Barents-2.5, it is evident that sea ice is more extensive (larger sea ice concentration, thickness and southward extent) and sea surface temperatures are lower in Barents-2.5 with clear differences in the seasonal and spatial characteristics. Further, sea surface and sea ice drift speeds are larger in Barents-2.5, especially in shallow waters and the sea ice edge. On the side of atmospheric models, CARRA exhibits slightly larger 10 m wind speeds over open water while ERA5 show larger wind speeds over icy water. Those similarities and differences could partly be traced back to similarities and differences in spatial and temporal resolution, model setup, assimilated data and relations between the models. Despite fundamental difference in data assimilation, Barents-2.5 hindcast and forecast showed high similarity for some variables. The large occurrence of sea ice and its deviating representation in the models indicate large relevance for the iceberg pathways in the Barents Sea.
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Status: closed
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RC1: 'Comment on egusphere-2024-3053', Anonymous Referee #1, 15 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3053/egusphere-2024-3053-RC1-supplement.pdf
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AC1: 'Reply on RC1', Lia Herrmannsdörfer, 20 Jan 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3053/egusphere-2024-3053-AC1-supplement.pdf
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AC1: 'Reply on RC1', Lia Herrmannsdörfer, 20 Jan 2025
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RC2: 'Merge into the Part II paper', Anonymous Referee #2, 27 Jan 2025
Review of "Comparison of variables from ocean, sea ice and atmosphere models as forcing data for iceberg drift and deterioration models in the Barents Sea in 2010-2014 and 2020-2021 (Part I)." by Herrmannsdörfer et al.
My background is in Arctic ocean and sea ice modeling and data assimilation. The manuscript presents a comparison of two ocean and sea ice models of the Barents Sea as well as two atmospheric reanalyses, all including data assimilation, in view of their use in iceberg drift simulations (Part 2).
I am reviewing both papers so my reviews are linked.The comparison is opposing the two ocean reanalyses and two atmospheric reanalyses, comparing the variables relevant for iceberg simulations, but does not compare against observations, thereby not taking side about which is preferable. A summary of model validation is given for both models in an Appendix, but not based on coordinated validation, and therefore missing some of the relevant variables.
There are large differences between the reanalyses, which are expected to become important in Part 2, although in line with other model comparisons (Uotila et al. 2019, cited, older results are probably outdated). Many of the differences are unexplained, understandably the reasons are usually very intricate in complex data assimilative models. The products considered in this study are not compared to each other in the published literature, but that alone is not sufficient novelty for a scientific publication.The adaptation of the different datasets is very detailed, even too detailed for the purpose. The results are also very detailed, but not all results are used in Part II, which I will come back to.
The writing style is not very fluid and would deserve a thorough round of polishing with more experienced writers. There are repetitions across different parts of the text and also in the text of Part II. I found the structure of the manuscript confusing because the information about the various reanalyses is scattered between the main text and the annexes.
Another source of duplications is the introduction of "the iceberg pathway" later in the paper, a mask cutting off all areas without icebergs. This mask is a good idea on its own, but all the statistics are then repeated without changing the overall impression. So the authors could have gone directly for the "iceberg pathway" and only that area.
Overall, the only originality of Part I is that there is no recent comparison of reanalysis products in the Barents Sea elsewhere in the recent literature. But the manuscript lacks insights into why these products differ. It also lacks practical recommendations supported by observations and the two models presented may not represent the state of the art either, while several other reanalyses are available (I imagine that all the participants of Uotila et al. 2019 have updated their simulations since then).
Reworking Part I into a valuable scientific paper would require significant efforts: either by validating all relevant variables against satellite or in situ observations, or by including additional reanalyses that would put the differences in the context of the international state of the art. Both options are probably out of the scope of the authors, whose main expertise resides in iceberg dynamics.
My recommendation is therefore to merge Part I into Part II: extract the elements re-used in Part II (there are not that many of them, see below) and make it a section of Part II, instead of some technical details.As far as I have seen, the only Figures cited in Part II are the following:
- Figure 5, the map of SST differences.
- Figure 9, maps of SIC differences. There are details in the maps that can also be omitted because they are not discussed in the text.
- Figure 10, maps of SIT differences, also removing the details that are not exploited.Minor points:
- Section 2.1.1: If TOPAZ and Barents2.5 are ensemble systems, are the reanalysis products an ensemble average? An average of a large ensemble smoothes the fields compared to an individual member of the ensemble, leading to more accurate but less realistic results, for example slowing down the current velocity.
- Section 2.1.3: Comparing Topaz to Barents2.5 is too early: their main characteristics are not yet given. Similarly for Section 2.2.3, the comparison of ERA5 and CARRA comes before we even know which models and data assimilation techniques are used.
- L. 176: Mention that the 2-hours sampling is necessary with Barents2.5 in order to resolve the tidal cycle.
- Figure 2 is unnecessary and the caption is repeated in the text. Figures 3 and 4 can also be removed.
- The shading for the 5%-95% percentiles on the time series is not exploited in the text and should be removed for clarity.
- Figure 7 shows currents diverging from the coast, which seems impossible for an incompressible fluid. Have the current vectors
been rotated correctly from the model output grid to the projection used in the Figure?
- Averaging current speeds can give a false indication of iceberg movements: the tides are included in Barents2.5, not in Topaz, and therefore the average of current magnitude is faster with tides, but the residual displacement from one tidal cycle is close to zero.
- Figure 12: The figure is difficult to read with many small vectors and misses a scale for the vectors length. The question of their rotation also applies here, like in the surface currents above. Are the sea ice drifts masked in grid cells where very little ice is present (CI<5%)? Also how are the differences computed when/where one model is ice-covered but not the other?Vocabulary:
- "Large occurence of sea ice". Replace by "sea ice extent"
- L. 32: "inexcusably justified", I am not sure what is meant here.
- "Data Assimilation" is often confused with "model forcing" in the main text although the Annexes 1.3 and 1.4 make a correct distinction between the two.
- l. 165: "preliminary version" implies that a more mature version of Barents2.5 would come later, but not that the data will be remapped.
- "larger SST" -> "warmer SST"
- Replace "Following," by an preposition like "Furthermore"References:
Citations do not always respect the recommendations from The Cryosphere:
- Notz and Community (2020)
- For the TOPAZ reanalysis, cite Xie et al. (2017) instead of MDS.
- Röhrs et al. (2023) is cited as a GMD discussions paper, the final paper should be cited instead.Typos:
- l.99: "the an EPS".Citation: https://doi.org/10.5194/egusphere-2024-3053-RC2
Status: closed
-
RC1: 'Comment on egusphere-2024-3053', Anonymous Referee #1, 15 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3053/egusphere-2024-3053-RC1-supplement.pdf
-
AC1: 'Reply on RC1', Lia Herrmannsdörfer, 20 Jan 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-3053/egusphere-2024-3053-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Lia Herrmannsdörfer, 20 Jan 2025
-
RC2: 'Merge into the Part II paper', Anonymous Referee #2, 27 Jan 2025
Review of "Comparison of variables from ocean, sea ice and atmosphere models as forcing data for iceberg drift and deterioration models in the Barents Sea in 2010-2014 and 2020-2021 (Part I)." by Herrmannsdörfer et al.
My background is in Arctic ocean and sea ice modeling and data assimilation. The manuscript presents a comparison of two ocean and sea ice models of the Barents Sea as well as two atmospheric reanalyses, all including data assimilation, in view of their use in iceberg drift simulations (Part 2).
I am reviewing both papers so my reviews are linked.The comparison is opposing the two ocean reanalyses and two atmospheric reanalyses, comparing the variables relevant for iceberg simulations, but does not compare against observations, thereby not taking side about which is preferable. A summary of model validation is given for both models in an Appendix, but not based on coordinated validation, and therefore missing some of the relevant variables.
There are large differences between the reanalyses, which are expected to become important in Part 2, although in line with other model comparisons (Uotila et al. 2019, cited, older results are probably outdated). Many of the differences are unexplained, understandably the reasons are usually very intricate in complex data assimilative models. The products considered in this study are not compared to each other in the published literature, but that alone is not sufficient novelty for a scientific publication.The adaptation of the different datasets is very detailed, even too detailed for the purpose. The results are also very detailed, but not all results are used in Part II, which I will come back to.
The writing style is not very fluid and would deserve a thorough round of polishing with more experienced writers. There are repetitions across different parts of the text and also in the text of Part II. I found the structure of the manuscript confusing because the information about the various reanalyses is scattered between the main text and the annexes.
Another source of duplications is the introduction of "the iceberg pathway" later in the paper, a mask cutting off all areas without icebergs. This mask is a good idea on its own, but all the statistics are then repeated without changing the overall impression. So the authors could have gone directly for the "iceberg pathway" and only that area.
Overall, the only originality of Part I is that there is no recent comparison of reanalysis products in the Barents Sea elsewhere in the recent literature. But the manuscript lacks insights into why these products differ. It also lacks practical recommendations supported by observations and the two models presented may not represent the state of the art either, while several other reanalyses are available (I imagine that all the participants of Uotila et al. 2019 have updated their simulations since then).
Reworking Part I into a valuable scientific paper would require significant efforts: either by validating all relevant variables against satellite or in situ observations, or by including additional reanalyses that would put the differences in the context of the international state of the art. Both options are probably out of the scope of the authors, whose main expertise resides in iceberg dynamics.
My recommendation is therefore to merge Part I into Part II: extract the elements re-used in Part II (there are not that many of them, see below) and make it a section of Part II, instead of some technical details.As far as I have seen, the only Figures cited in Part II are the following:
- Figure 5, the map of SST differences.
- Figure 9, maps of SIC differences. There are details in the maps that can also be omitted because they are not discussed in the text.
- Figure 10, maps of SIT differences, also removing the details that are not exploited.Minor points:
- Section 2.1.1: If TOPAZ and Barents2.5 are ensemble systems, are the reanalysis products an ensemble average? An average of a large ensemble smoothes the fields compared to an individual member of the ensemble, leading to more accurate but less realistic results, for example slowing down the current velocity.
- Section 2.1.3: Comparing Topaz to Barents2.5 is too early: their main characteristics are not yet given. Similarly for Section 2.2.3, the comparison of ERA5 and CARRA comes before we even know which models and data assimilation techniques are used.
- L. 176: Mention that the 2-hours sampling is necessary with Barents2.5 in order to resolve the tidal cycle.
- Figure 2 is unnecessary and the caption is repeated in the text. Figures 3 and 4 can also be removed.
- The shading for the 5%-95% percentiles on the time series is not exploited in the text and should be removed for clarity.
- Figure 7 shows currents diverging from the coast, which seems impossible for an incompressible fluid. Have the current vectors
been rotated correctly from the model output grid to the projection used in the Figure?
- Averaging current speeds can give a false indication of iceberg movements: the tides are included in Barents2.5, not in Topaz, and therefore the average of current magnitude is faster with tides, but the residual displacement from one tidal cycle is close to zero.
- Figure 12: The figure is difficult to read with many small vectors and misses a scale for the vectors length. The question of their rotation also applies here, like in the surface currents above. Are the sea ice drifts masked in grid cells where very little ice is present (CI<5%)? Also how are the differences computed when/where one model is ice-covered but not the other?Vocabulary:
- "Large occurence of sea ice". Replace by "sea ice extent"
- L. 32: "inexcusably justified", I am not sure what is meant here.
- "Data Assimilation" is often confused with "model forcing" in the main text although the Annexes 1.3 and 1.4 make a correct distinction between the two.
- l. 165: "preliminary version" implies that a more mature version of Barents2.5 would come later, but not that the data will be remapped.
- "larger SST" -> "warmer SST"
- Replace "Following," by an preposition like "Furthermore"References:
Citations do not always respect the recommendations from The Cryosphere:
- Notz and Community (2020)
- For the TOPAZ reanalysis, cite Xie et al. (2017) instead of MDS.
- Röhrs et al. (2023) is cited as a GMD discussions paper, the final paper should be cited instead.Typos:
- l.99: "the an EPS".Citation: https://doi.org/10.5194/egusphere-2024-3053-RC2
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