|I thank the authors for thoughtfully addressing the concerns raised in the first round of reviews. While I am generally satisfied with the revised manuscript, which has substantially improved, I think there are several issues that need to be addressed before publication can be recommended. My main issue is with the revised Introduction section, where the authors attempt to summarize the oceanographic literature on polynya formation. As I detail below, the authors introduced statements that I view as misleading and inaccurate. |
That said, I think the issues mentioned above are relatively minor and the scientific core of the paper remains valuable. While this new sea ice thickness retrieval comes with many caveats, the authors are clear about its limitations and demonstrate that it provides information that is distinct and independent of existing sea ice area information. Future work is needed to validate these retrievals and quantify their uncertainties, but this study is a good start.
- Title: This title is fine but many people in the ocean community understand "Weddell Sea Polynya" to mean large open-ocean polynyas that span *most* of the Weddell Sea, which this paper does not analyze. I would suggest a more general title, such as "Analysis of open-ocean polynyas in the Weddell Sea using SMOS-SMAP apparent sea ice thickness retrieval"
- Line 2 (abstract): Related to the above comment, this definition of "Weddell Sea open-ocean polynyas" does not quite align with definitions found in the literature. While open-ocean polynyas are often found near the Maud Rise seamount, they are not exclusive to this specific region. Perhaps an opening sentence like the following would suffice, "The Weddell Sea is known to feature large openings in its winter sea ice field, otherwise known as open-ocean polynyas...."
- Lines 3-4 (abstract): "2017, however, is far from the only year that the imprint of a polynya can be identified at this location." This is an odd sentence considering the previous sentence states that these polynyas have intermittently appeared over the past 40 years. Perhaps the authors wish to communicate that their new estimates of sea ice thickness reveal periods of the substantial thinning that are not apparent in existing observations of sea ice area/concentration.
- Lines 23-34: I would delete "surprisingly".
- Lines 26-28: I would suggest referring to these openings as "open-ocean polynyas". I think the use of lower-case "p" in the term "Weddell Sea polynya" only makes things more confusing.
- Line 29: "The Weddell Sea polynya is an anomalous opening in sea ice that is generally classified as an open-ocean polynya" See above comment.
- Line 32: "ocean processes" is rather vague. I prefer the original description that mentions the upwelling of warm water.
- Lines 32-34: "The main mechanism that preconditions the Weddell Sea polynya is described by Martinson et al. (1981) as destratification of water masses leading to a raised pycnocline. The raised pycnocline compresses the winter surface mixed layer that is made dense through heat loss and brine rejection from ice formation, resulting in density overturning." This explanation is rather muddled and arguably incorrect. I would delete this sentence since the one that follows gets right message across.
- Lines 37-45: This section contains several statements that are confusing, misleading, and at times inaccurate. This is perplexing since the section was mostly fine in the original submission. To give a few specific examples: I don't understand what is meant by "...destratification of water masses leading to a raised pycnocline..." or the idea that a raised pycnocline "compress[es]" the mixed layer. Additionally, the authors appear to use "weak stratification" and "lack of stratification" inter-changeably, which are very different.
Martinson et al. (1981), which the authors try to summarize, proposes that open-ocean polynyas in the Weddell Sea may be initiated when the winter mixed layer becomes sufficiently dense that it triggers deep convection, which results in the upward mixing of warm deep water. These events may be preconditioned by processes that weaken the upper ocean stratification, such as the anomalous upwelling or advection of high salinity water into the surface mixed layer. I don't think the authors need to spend more than a couple sentences reviewing these mechanisms. Like I mentioned before, the initial text was mostly fine.
- Lines 44-53: Reading this for a second time, I think this extended discussion about Taylor columns and flow-topography interactions lacks appropriate nuance and does not add much to the paper. With my previous comment in mind, I would also suggest reducing this entire paragraph to a 1-2 sentences. For the purposes of this study, I think it is fine to simply state (with supporting citations) that interactions between the mean flow and topography preconditions the area above Maud Rise for anomalously high vertical heat fluxes, which favors thinner sea ice.
- Lines 58-59: "Direct atmospheric forcing" and "large-scale climate processes" are framed as two separate entities but the former is a subset of the latter.
- Lines 117-118: "Patilea et al. (2019) estimated the uncertainty at 90% SIC from SIT values up to 50%." While I get the gist of this discussion, I'm a bit confused by this line.
- Lines 123-124: "...this compromises the validity the of the sea ice thicknesses retrieved..." Typo. "the" after validity is not necessary.
- Lines 125-126: "While the degree by which the ice thins is difficult to quantify in terms of uncertainty, our analysis has shown that the pattern of thin ice anomalies above Maud Rise is not random nor is it identical to the distribution of low SIC areas..."
Is there a simple, quantifiable way of demonstrating this statement? I wish I suggested this in my first review, but it would be interesting to compare these SIT measurements with available in situ ocean salinity measurements or perhaps a data-assimilative model such as the Southern Ocean State Estimate. Periods of thinning should correspond to periods of mixed layer freshening. In fairness to the authors, I will not demand that they do this validation but I hope they consider doing so in the future.
Lines 294-295: "anomalous episode of sea ice" is a bit vague. How about "...episodes of anomalous wintertime sea ice loss..."?
Line 321-322: "In the end, strength of the wind magnitude present above the region is most directly connected with drops in ASIT and SIC." This is an interesting finding!