the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Feb 2025
Inferring Inherent Optical Properties of Sea Ice Using 360-Degree Camera Radiance Measurements
Abstract. In this work, we demonstrate the utilization of a compact, consumer-grade 360-degree camera for measuring the in-ice spectral angular radiance distribution. This novel technique allows for the instantaneous acquisition of all radiometric quantities at a given depth with a non-intrusive probe. This gives the opportunity to monitor the light field structure (mean cosines) from the atmosphere to the underlying ocean beneath ice. In this study, we report vertical profiles of the light field geometric distribution measured at two sites representative of distinct ice types: High Arctic multi-year ice and Chaleur Bay (Quebec, Canada) landfast first-year ice. We also propose a technique to empirically retrieve the depth-resolved inherent optical properties by matching simulated profiles of spectral irradiances calculated with the HydroLight radiative transfer model to the observed ones. As reported in other studies, the derived reduced scattering coefficients were high (641.57 m-1, 72.85 m-1) in the first (2 cm, 5 cm) for both sites (High Arctic, Chaleur Bay) and lower in the interior part of the ice (0.48 to 4.10 m-1, 0.021 to 7.79 m-1). Due to the inherent underdetermined nature of the inversion problem, we emphasize the importance of using the similarity parameter that considers both the absorption and the reduced scattering coefficients. Finally, we believe that this radiometric device, combined with the proposed inversion technique, will allow to scale up the measurements of the inherent optical properties of different kinds of sea ice enabling to take better account of terrain variability in radiative transfer models.
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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
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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.
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-3819', Anonymous Referee #1, 28 Mar 2025
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AC1: 'Reply on RC1', Bastian Raulier, 09 Apr 2025
We would like to thank reviewer #1 for taking the time to read our research article and to give us his insightful comments. We appreciate the constructive comments enabling us to improve our manuscript. Responses to the comments are attached.
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AC1: 'Reply on RC1', Bastian Raulier, 09 Apr 2025
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RC2: 'Comment on egusphere-2024-3819', Anonymous Referee #2, 18 Apr 2025
The manuscript presents a novel method for measuring the inherent optical properties (IOPs) of sea ice at varying depths, using RGB imagery to capture the light field. This technique is demonstrated on two distinct types of sea ice and shows potential for resolving vertical features such as surface scattering and skeletal layers. The approach is an innovative and compelling adaptation of commercial technology for cryospheric research. It is well-suited for publication in The Cryosphere.
Overall, the paper is clearly written and logically organized. Only minor revisions are needed prior to publication. While I have experience with sea ice AOPs and found the equations and methods clearly presented, I defer to other reviewers with expertise in IOPs and radiative transfer for a more rigorous assessment of the methodological details.
General Comments:
- Clarification of Surface Layers (Chaleur Bay):
The manuscript could more clearly identify whether there is snow, snow-ice, or surface scattering layer (or some combination), particularly at the Chaleur Bay site. For example, Line 394–395 refers to the top ice layer as "snow," whereas elsewhere it is described as a surface scattering layer. Lines 449–452 also reference possible snow-ice. Greater clarity regarding the origin of the surface layer (or acknowledgment of uncertainty) is important for situating the findings in the context of other IOP studies. - Guidance for Future Applications:
The manuscript nicely lays groundwork for future work by sharing code and methodology. However, it would benefit from a more specific summary of practical considerations for field deployment. For example, what engineering challenges remain? A brief section or appendix summarizing guidance for future users of the method would be valuable. - Potential for AOP Validation:
Is there an opportunity to use coincident AOP measurements to validate the derived IOPs? It would be particularly interesting to compare the modeled AOPs to observations from the High Arctic transmission and albedo sites, if feasible.
Minor Comments and Suggested Edits:
- L24: Replace “first” with “top” or “surface.”
- L40: Capitalize “Arctic” (check throughout manuscript).
- L43–49: Consider connecting more explicitly to physical processes mentioned earlier, such as energy partitioning.
- L69: Clarify whether this sentence refers specifically to prior uses of cameras as radiometers.
- L82: Correct “Artic” to “Arctic” and capitalize “North Pole.”
- L95–96: Consider specifying “landfast ice” if appropriate.
- L100: Since variability is discussed later, add brief notes on surface and sub-surface variability at each site here.
- L102: Fix “depth-resolved”
- Figure 1d: No snow is shown at the Chaleur Bay site. Was snow cleared? Descriptions suggest snow-ice may be present—consider revising the structural model.
- L120: Indicate the time required to acquire a full profile at a site.
- L190: Should this be “below” or possibly “drained layer” instead of “skeletal layer”?
- Figure 2: Include RGB color/wavelength labels in the image labels/caption.
- Figure 3: Add “High Arctic” to the caption. Consider making the “HL simulations” line more visible or matching the legend.
- L326: Estimate the percentage of the view impacted by the operator’s shadow. At what depth does this become negligible?
- Figure 4: Add labels for “High Arctic” and “Chaleur Bay.”
- L370: Correct phrasing to “give rise.”
- L375: Clarify whether “surface slab” refers to snow or a surface scattering layer.
- L384: Should “sea ice” be “water” here?
- L407: Fix typo: “the in”
- L407: Consider changing “episodes” to “cycles.”
- L418: Reword for clarity: the phrase “where contamination sediment sources is far away” is awkward. Perhaps rephrase to emphasize the likely absence of sediment due to MYI origin or absence in cores.
- L425: Replace “wrong” with a more scientific term such as “nonphysical.”
- L481: Capitalize “High” for consistency with “High Arctic.”
- L515–517: Could this issue be addressed in future work by increasing the number of measurements within a site?
Citation: https://doi.org/10.5194/egusphere-2024-3819-RC2 -
AC2: 'Reply on RC2', Bastian Raulier, 16 May 2025
We would like to thank the reviewer for taking the time to read and provide valuable
comments on our article. The comments initiated interesting discussions among the
authors of this article and, we believe, helped improve the quality of the outcome.
General comments are discussed in attached document, along with minor comments and editing
suggestions.
- Clarification of Surface Layers (Chaleur Bay):
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-3819', Anonymous Referee #1, 28 Mar 2025
This manuscript presents a novel technique for investigating in situ magnitude and shape of the radiation field within a sea ice cover. Application of a commercially available 360 deg camera, along with sophisticated radiative transfer modeling, is demonstrated to yield detailed, vertically-resolved inherent optical properties of sea ice. The topic of this manuscript is of high interest to the TC readership and the manuscript is clear and concise, with appropriately illustrative figures. I found the manuscript a pleasure to read and think it is publishable in something very close to its present form. My only comments are minor, as detailed below. I found it particularly interesting to see the skeletal layer resolved in this study.
Fig 1c: Could be a bit more clear about the camera FOV and what it is seeing. The fact that the FOV is reduced to 76 deg (water, compared to air) should be mentioned in the text, not strictly relegated to a figure caption. It’s not clear from the drawing in Fig. 1c where exactly the two fish-eye lenses view, nor is it clear what the solid angle 2*pi sr refers to.
167: “In ice…”, would be good to be more explicit, “In sea ice…”
Figure 2: lots packed in here, would be helpful to have a bit more orientation (authors have been looking at these distributions, but they are new to us readers). E.g. line 274, help me see “is apparent” by walking me through the distribution in the figure.
245: Eqn 9 exponent is – ½ (difficult to see negative sign, but so important!)
305: “imply fieldwork error” how about “likely derive from large observational uncertainties”?
347: is “zenithal” a word?
354: “Gershun’s law”
395: “The first two centimetres of pack ice are a special case, as they are made up of snow…” Snow or surface scattering layer?
409: winters? Or previous summer? Multiple melt seasons? Or one previous melt season?
556: spectral bands centered on 480, 540, 600 (since they likely aren’t strictly at those wavelengths)
563 – 564: “significantly higher light attenuation was assessed, due to both larger absorption, 0.32 – 2.11 m-1, and reduced scattering coefficients, 0.021 – 7.79 m-1,” . Here “reduced scattering coefficients” is confusing—it refers to b’, but it also sounds like the b’ values are lower, when I don’t think that’s the intent. Rewrite for improved clarity.
Citation: https://doi.org/10.5194/egusphere-2024-3819-RC1 -
AC1: 'Reply on RC1', Bastian Raulier, 09 Apr 2025
We would like to thank reviewer #1 for taking the time to read our research article and to give us his insightful comments. We appreciate the constructive comments enabling us to improve our manuscript. Responses to the comments are attached.
-
AC1: 'Reply on RC1', Bastian Raulier, 09 Apr 2025
-
RC2: 'Comment on egusphere-2024-3819', Anonymous Referee #2, 18 Apr 2025
The manuscript presents a novel method for measuring the inherent optical properties (IOPs) of sea ice at varying depths, using RGB imagery to capture the light field. This technique is demonstrated on two distinct types of sea ice and shows potential for resolving vertical features such as surface scattering and skeletal layers. The approach is an innovative and compelling adaptation of commercial technology for cryospheric research. It is well-suited for publication in The Cryosphere.
Overall, the paper is clearly written and logically organized. Only minor revisions are needed prior to publication. While I have experience with sea ice AOPs and found the equations and methods clearly presented, I defer to other reviewers with expertise in IOPs and radiative transfer for a more rigorous assessment of the methodological details.
General Comments:
- Clarification of Surface Layers (Chaleur Bay):
The manuscript could more clearly identify whether there is snow, snow-ice, or surface scattering layer (or some combination), particularly at the Chaleur Bay site. For example, Line 394–395 refers to the top ice layer as "snow," whereas elsewhere it is described as a surface scattering layer. Lines 449–452 also reference possible snow-ice. Greater clarity regarding the origin of the surface layer (or acknowledgment of uncertainty) is important for situating the findings in the context of other IOP studies. - Guidance for Future Applications:
The manuscript nicely lays groundwork for future work by sharing code and methodology. However, it would benefit from a more specific summary of practical considerations for field deployment. For example, what engineering challenges remain? A brief section or appendix summarizing guidance for future users of the method would be valuable. - Potential for AOP Validation:
Is there an opportunity to use coincident AOP measurements to validate the derived IOPs? It would be particularly interesting to compare the modeled AOPs to observations from the High Arctic transmission and albedo sites, if feasible.
Minor Comments and Suggested Edits:
- L24: Replace “first” with “top” or “surface.”
- L40: Capitalize “Arctic” (check throughout manuscript).
- L43–49: Consider connecting more explicitly to physical processes mentioned earlier, such as energy partitioning.
- L69: Clarify whether this sentence refers specifically to prior uses of cameras as radiometers.
- L82: Correct “Artic” to “Arctic” and capitalize “North Pole.”
- L95–96: Consider specifying “landfast ice” if appropriate.
- L100: Since variability is discussed later, add brief notes on surface and sub-surface variability at each site here.
- L102: Fix “depth-resolved”
- Figure 1d: No snow is shown at the Chaleur Bay site. Was snow cleared? Descriptions suggest snow-ice may be present—consider revising the structural model.
- L120: Indicate the time required to acquire a full profile at a site.
- L190: Should this be “below” or possibly “drained layer” instead of “skeletal layer”?
- Figure 2: Include RGB color/wavelength labels in the image labels/caption.
- Figure 3: Add “High Arctic” to the caption. Consider making the “HL simulations” line more visible or matching the legend.
- L326: Estimate the percentage of the view impacted by the operator’s shadow. At what depth does this become negligible?
- Figure 4: Add labels for “High Arctic” and “Chaleur Bay.”
- L370: Correct phrasing to “give rise.”
- L375: Clarify whether “surface slab” refers to snow or a surface scattering layer.
- L384: Should “sea ice” be “water” here?
- L407: Fix typo: “the in”
- L407: Consider changing “episodes” to “cycles.”
- L418: Reword for clarity: the phrase “where contamination sediment sources is far away” is awkward. Perhaps rephrase to emphasize the likely absence of sediment due to MYI origin or absence in cores.
- L425: Replace “wrong” with a more scientific term such as “nonphysical.”
- L481: Capitalize “High” for consistency with “High Arctic.”
- L515–517: Could this issue be addressed in future work by increasing the number of measurements within a site?
Citation: https://doi.org/10.5194/egusphere-2024-3819-RC2 -
AC2: 'Reply on RC2', Bastian Raulier, 16 May 2025
We would like to thank the reviewer for taking the time to read and provide valuable
comments on our article. The comments initiated interesting discussions among the
authors of this article and, we believe, helped improve the quality of the outcome.
General comments are discussed in attached document, along with minor comments and editing
suggestions.
- Clarification of Surface Layers (Chaleur Bay):
Peer review completion
Journal article(s) based on this preprint
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- 1
Cited
Raphaël Larouche
Bastian Raulier
Christian Katlein
Simon Lambert-Girard
Simon Thibault
Marcel Babin
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
This manuscript presents a novel technique for investigating in situ magnitude and shape of the radiation field within a sea ice cover. Application of a commercially available 360 deg camera, along with sophisticated radiative transfer modeling, is demonstrated to yield detailed, vertically-resolved inherent optical properties of sea ice. The topic of this manuscript is of high interest to the TC readership and the manuscript is clear and concise, with appropriately illustrative figures. I found the manuscript a pleasure to read and think it is publishable in something very close to its present form. My only comments are minor, as detailed below. I found it particularly interesting to see the skeletal layer resolved in this study.
Fig 1c: Could be a bit more clear about the camera FOV and what it is seeing. The fact that the FOV is reduced to 76 deg (water, compared to air) should be mentioned in the text, not strictly relegated to a figure caption. It’s not clear from the drawing in Fig. 1c where exactly the two fish-eye lenses view, nor is it clear what the solid angle 2*pi sr refers to.
167: “In ice…”, would be good to be more explicit, “In sea ice…”
Figure 2: lots packed in here, would be helpful to have a bit more orientation (authors have been looking at these distributions, but they are new to us readers). E.g. line 274, help me see “is apparent” by walking me through the distribution in the figure.
245: Eqn 9 exponent is – ½ (difficult to see negative sign, but so important!)
305: “imply fieldwork error” how about “likely derive from large observational uncertainties”?
347: is “zenithal” a word?
354: “Gershun’s law”
395: “The first two centimetres of pack ice are a special case, as they are made up of snow…” Snow or surface scattering layer?
409: winters? Or previous summer? Multiple melt seasons? Or one previous melt season?
556: spectral bands centered on 480, 540, 600 (since they likely aren’t strictly at those wavelengths)
563 – 564: “significantly higher light attenuation was assessed, due to both larger absorption, 0.32 – 2.11 m-1, and reduced scattering coefficients, 0.021 – 7.79 m-1,” . Here “reduced scattering coefficients” is confusing—it refers to b’, but it also sounds like the b’ values are lower, when I don’t think that’s the intent. Rewrite for improved clarity.