the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 18 Oct 2022
Effects of including the adjoint sea ice rheology on estimating Arctic ocean-sea ice state
Armin Koehl
Xinrong Wu
Meng Zhou
Detlef Stammer
Abstract. The adjoint technique has been applied to the coupled ocean and sea ice models for sensitivity studies and Arctic state estimation. However, the accuracy of the adjoint model is degraded by simplifications on the adjoint of the sea ice model, especially adjoint sea ice rheology. As part of ongoing developments of coupled ocean and sea ice estimation system, we incorporate and stabilize the adjoint of viscous-plastic sea ice dynamics (adjoint-VP) and compare it with the adjoint of a free drift sea ice model (adjoint-FD) through assimilation experiments. Using the adjoint-VP resulted in a further cost reduction of 7.9 % in comparison to adjoint-FD with noticeable improvements in ocean temperature over the open water and intermediate layers of the Arctic Ocean. Adjoint-VP more efficiently adjusts uncertain parameters than adjoint-FD by involving different sea ice retreat processes. For instance, adjoint-FD melts sea ice up to 1.0 m in the marginal seas from May to June through over-adjusting air temperature (>8 °C); adjoint-VP reproduces the sea ice retreat with smaller adjustments on the atmospheric state within the prior uncertainty range. The developments of the adjoint model here lay the foundation for further improving Arctic ocean and sea ice estimation through comprehensively adjusting the initial conditions, atmosphere forcings, and model parameters.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(3043 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3043 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Guokun Lyu et al.
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-1099', Anonymous Referee #1, 07 Nov 2022
- AC1: 'Reply on RC1', Guokun Lyu, 27 Jan 2023
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RC2: 'Comment on egusphere-2022-1099', Anonymous Referee #2, 06 Dec 2022
The paper introduces new tangent linear and adjoin model for the Viscous-Plastic parameterization of the sea ice model. The key to this work is the stabilization of the non-linear terms following the paper of Toyoda 2019. The novel contribution of this paper was evaluating of the stabilized adjoint in the framework of an Adjoint (ECCO-like) assimilation over the Arctic domain for the calendar year of 2012. I found the paper relevant to its target audience and is generally well written (see few technical comments in the annotated PDF). However, I found that the paper contains a single (but a key) conclusion that is not substantiated by the presented data (see major points below). I suggest that authors introduce new analysis in the revised paper that addresses my concerns (see specific suggestion in the major points section).
Major concerns:
- Ky finding of this paper is summarized in this citation from the manuscript: “Considering the amplitude of air temperature adjustments, the adjustments of the control variables in adjoint-VP are more reasonable than adjoint-FD, and adjoint-VP seems to project model-data misfits to the control variables more reasonably than adjoint-FD.” Unfortunately, presented analysis does not provide evidence or error bars on what is reasonable and what is not. This is especially true, given that the authors are using a very old and outdated atmospheric analysis. I suggest that authors augment their paper by the analysis of the observation-minus-first guess errors for control variables that do have direct observations (e.g. wind speed, atmospheric temperature, ocean temperature from profiles). I understand that these measurements are very sparse over the Arctic. Nonetheless some are still available for analysis.
- Authors use an obsolete reanalysis product to drive their simulation. While (in it self) their choice does not invalidate their results. I suggest that authors quantify how their choice might impact their conclusions. For example, can the large errors that they report in air temperature corrections can be attributed to a very old reanalysis product?
Minor concearns:
- I have attempted to hioghlight a few typos and rough sentences that authors might choose to improve in the revision (see annotated PDF).
- I find that some of the authors figures are very dense and could use more on-figure annotations (e.g. better panel labels). When appropriate, I provide such suggestions in the annotated pdf.
- AC3: 'Reply on RC2', Guokun Lyu, 27 Jan 2023
-
RC3: 'Comment on egusphere-2022-1099', Anonymous Referee #3, 12 Dec 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1099/egusphere-2022-1099-RC3-supplement.pdf
- AC2: 'Reply on RC3', Guokun Lyu, 27 Jan 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-1099', Anonymous Referee #1, 07 Nov 2022
- AC1: 'Reply on RC1', Guokun Lyu, 27 Jan 2023
-
RC2: 'Comment on egusphere-2022-1099', Anonymous Referee #2, 06 Dec 2022
The paper introduces new tangent linear and adjoin model for the Viscous-Plastic parameterization of the sea ice model. The key to this work is the stabilization of the non-linear terms following the paper of Toyoda 2019. The novel contribution of this paper was evaluating of the stabilized adjoint in the framework of an Adjoint (ECCO-like) assimilation over the Arctic domain for the calendar year of 2012. I found the paper relevant to its target audience and is generally well written (see few technical comments in the annotated PDF). However, I found that the paper contains a single (but a key) conclusion that is not substantiated by the presented data (see major points below). I suggest that authors introduce new analysis in the revised paper that addresses my concerns (see specific suggestion in the major points section).
Major concerns:
- Ky finding of this paper is summarized in this citation from the manuscript: “Considering the amplitude of air temperature adjustments, the adjustments of the control variables in adjoint-VP are more reasonable than adjoint-FD, and adjoint-VP seems to project model-data misfits to the control variables more reasonably than adjoint-FD.” Unfortunately, presented analysis does not provide evidence or error bars on what is reasonable and what is not. This is especially true, given that the authors are using a very old and outdated atmospheric analysis. I suggest that authors augment their paper by the analysis of the observation-minus-first guess errors for control variables that do have direct observations (e.g. wind speed, atmospheric temperature, ocean temperature from profiles). I understand that these measurements are very sparse over the Arctic. Nonetheless some are still available for analysis.
- Authors use an obsolete reanalysis product to drive their simulation. While (in it self) their choice does not invalidate their results. I suggest that authors quantify how their choice might impact their conclusions. For example, can the large errors that they report in air temperature corrections can be attributed to a very old reanalysis product?
Minor concearns:
- I have attempted to hioghlight a few typos and rough sentences that authors might choose to improve in the revision (see annotated PDF).
- I find that some of the authors figures are very dense and could use more on-figure annotations (e.g. better panel labels). When appropriate, I provide such suggestions in the annotated pdf.
- AC3: 'Reply on RC2', Guokun Lyu, 27 Jan 2023
-
RC3: 'Comment on egusphere-2022-1099', Anonymous Referee #3, 12 Dec 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1099/egusphere-2022-1099-RC3-supplement.pdf
- AC2: 'Reply on RC3', Guokun Lyu, 27 Jan 2023
Peer review completion
Journal article(s) based on this preprint
Guokun Lyu et al.
Guokun Lyu et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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