Point by point response (Review 1):

Review of "Characterization of Marine Heat Waves in the IBI Region in 2022", by Lluís Castrillo-Acuña, Axel Alonso-Valle, Álvaro de Pascual-Collar.

Dear Anonymous referee #1,

We would like to thank you for your comments and time dedicated to make this contribution useful and clear for the community. We all agree with most of your appreciations, in fact, we believe that some of them will help to improve some parts relevantly.

The article details MHW events occurring at the large IBI region, using data from 1981 to 2022 from various sources (satellite reanalysis, models and in situ data for the 2022 events). The paper reads well and is well organized. I have two major comments, which could be summarized as follows:

- Q:Some analysis are presented for 2022 (like in figure 3) and the text that refers to it, but the satellite data only covers until September of that year. I think it can be misleading to discuss about variables like maximum intensity, annual total days and so on, when the statistics do not cover the whole year. As it's necessary for these data to become available, I would encourage the authors to limit this kind of analysis and instead go more in depth with specific events that occurred during that year. This takes me to my second major comment:

R: You are completely right; we all agree that this is probably the major issue in this contribution. In this way we have been able to update our dataset covering all the year 2022, consequently, the affected figures and text will be corrected in the main document.

-Q: The authors present some analysis of the effect of the MHWs at depth, but in my opinion these results are not fully exploited. In situ profiles are only presented for one region, and the figure (figure 4) is quite crammed and therefore unclear. I would expand this part of the paper to provide more insight into the effects of MHWs at depth in different regions, as this is something that needs more insight in order to understand the effects of MHWs in the ecosystem.

R: We only select one region to perform the subsurface assessment for different reasons. First, this contribution is expected to be relatively short in comparison to a common paper, so, doing this analysis for all the subregions and events could be probably enough to a single contribution. Second, there are substantial data limitations. We chose the BSC region to be the one with more quantity of in situ data and a substantia number of MHW events, even thought, as shown in figure 4, the confidence intervals are too wide, even crossing to 0 sometimes. Meaning that conclusions by using this data must be conservative.

It is true that this figure might look a bit crammed, specially in the range from 20 to 70 meters depth, but, on the other side, we think that it is clear enough to see the conclusions that we extract from it. It would probably look much clear without the confidence intervals, but we believe that it is important the show how subsurface in situ data is still far from being an accurate way to assess MHWs.

We should consider that, despite this work provides some descriptive results of the vertical propagation of MHW, the effects or impacts regarding MHWs in depth is something completely out of the scope of our study. Our work tries to do a first look into how MHWs behave or evolve with depth and time.

In summary, according to the expected contribution length and the fragile robustness of the results looking into the data limitations, we consider that we cannot (despite it is truly interesting) expand this analysis (figure 4) until there is more in situ subsurface data. We also consider that expanding the conclusions regarding these specific results could be too adventurous, as one of our main conclusions is that subsurface MHWs assessment through ARGO data is currently strongly limited (which we try to demonstrate by putting the confidence intervals of the 4 MHWs events with more available ARGO data). On the other hand, we can expand subsurface results through Figure 5 (the Hovmöller diagram). It has other limitations, but we think that we can extract more information from it.

Detailed comments;

Q: line 20: which perform extreme temperatures -> which show/result in

R: We will take care of it.

Q: line 22: the authors mention the global temperature trend but not the fact that because of it, the number of MHWs and their intensity is rising, which I guess is the point they want to make here?

R: You are right. We will add a clarification at the end of the sentence.

Q: line 33: again the authors say something but don’t explain it fully, which for non-experts might be confusing. The discussion on removing the SST trend before detecting MHWs and the effect this has on the results obtained should be detailed more carefully.

R: We will reorder an add a sentence trying to clarify this point. The issue is, there are a few studies that demonstrate or look into the influence of long-term trends in MHW results (mainly the ones we cite) but generally this influences its assumed as a “natural process” of the MHW formation. What we try to do with this contribution is to address this issue to the scientific community.

Q: line 141: (5-8): not sure what these numbers refer to.   

R: It is an error. Corrected.

Q: line 146: "used to take place" when?

R: We will add a clarification on the text.

Q: line 151: outliers in inland waters. Why are inland waters, not addressed in this work, not masked out? Are these really outliers? and are they removed from the analysis before MHW assessment? (if yes, I would take them out of the figures, if not, they might be influencing the results which is not good)

R:

• Why are inland waters, not addressed in this work, not masked out?:

• Are these really outliers? We did not perform a statistical test of the confidence interval for the mean value for all the IBI domain to say that, for instance, the value of 5 events per year of the Humber estuary lies out of the 95% confidence interval of the mean for all the region. To be more robust in our writing we will change from outlier to abnormal value.

• and are they removed from the analysis before MHW assessment? (if yes, I would take them out of the figures, if not, they might be influencing the results which is not good) We do not remove anything before neither after the MHW assessment, we take all the quality-controlled data that the data source can give, and we process it. Each grid point is treated independent of each other, so there is no horizontal influence. The workflow goes: 1. select a grid point (time series), 2. Compute its own climatology and threshold, 3. Compute the MHWs properties, and 4. Plot. Another situation is when we do spatial averages in the cases of tables 2 and 3 where these special cases could affect, but as you can see in figure 1 and 2, we try to avoid these cases.

Q: line 153: "This is" probably due to (otherwise sentence non complete)

Q: line 155: refer to figure 3 in the first sentence of this paragraph.

Q:  line 156: "positive anomalies": of what. And later in this line, "negative values": of what?

R: We will correct them.

Q: line 159: "Drastic" positive anomalies. Define drastic, or use another, more quantifiable word

R: Drastic to severe.

Q: line 163, I would turn the last sentence the other way round: indicate the number of days of MHW, as you have just given the number of days of the analysed time series.

R:We will remove this sentence. It was though to emphasize the results in relation to the 2022 data limitation; as this limitation will be removed, we understand that this sentence has lost sense.

Q: line 183: incomplete sentence

Q: line 207: "cold and warm seasonal events" -> events during cold and warm seasons.

R: We will take care of them.

Q: Figure 2. The colors are completely saturated, and there is no reason to start the minimum values where they stand now (minimum intensity of MHW at 0degC?, Annual total days at 10 days?) It would improve the clarity of the figure if these were adjusted. Also decreasing the number of colours in panels C and D, as it is done in panels A and B. It is not possible to differentiate between 25 and 32 days in panel C for example.

R: We completely agree with this comment. We will work to find a better way of representation in order to minimise loosing information and maximise the visualization.



Q: Figure 3. I am not sure highlighting 2022, for which there is not a complete year of data available in this paper, is a good idea. Wouldn’t it make more sense to wait until the whole 2022 is available (it isn’t yet?) so that numbers can be compared to other years? 

R: You are right, we will upload the dataset including all the year 2022. In this way we will assess the 2022 anomaly or deviation from the climatological normal values in relation to the MHWs properties.

Q: Figure 4. Mention in the caption that these are 2022 data. A small insert with the position of these profiles would be interesting. Why only profiles in one region are shown? It would be interesting to compare with what happened at the more coastal IBE region, or the shallow CEL region... As I mentioned above, figure 3 is not complete as the data used do not cover the whole year, therefore the authors could choose to leave maybe this figure out (and put average numbers in a table for example?) and use the extra figure to look more in detail at the depth variations in different regions.

R: We will add a small insert with the position of the ARGO profiles used to obtain the figure 4 results in figure 1.

We only select one region to perform the subsurface assessment for different reasons. First, this contribution is expected to be relatively short in comparison to a common paper, so, doing this analysis for all the subregions could be probably enough to a single contribution. Second, there are substantial data limitations. We chose the BSC region to be the one with more quantity of in situ data per MHW event, even thought, as shown in figure 4, the confidence intervals are too wide, even crossing to 0 sometimes. Meaning that conclusions by using this data must be conservative.

Q: Figure 5. Only one paragraph is dedicated to this figure, which is surprising. Authors should add perhaps a time series of the intensity of the MHW at the surface, and indicate up to which depth these anomalies are still considered a MHW. Since these come from a model, looking at water currents at different depths could be also of interest, or wind intensity… Compare with other regions... There is a need to assess what the impact of the MHWs is in the subsurface and this work could help improving our knowledge on that.

R: We partially agree with this comment. We believe also that these results should be more exploited; in order to do so, we will add a time series from the truly MHWs result, the surface assessment through the L4 reprocessed data. Also, we will discuss about different topics opened by these results. On the other side, we must be very careful to not miss crossing ideas, as they are results from different products, with different reference periods and do not represent exactly the same. One has passed through the MHWs definition and the other represents the anomaly in depth. Expanding to the possible impacts or drivers of the detected events it is something very interesting for future contributions but out of our scope in this one.

Dear Anonymous referee #1,

This additional comment is due to a missing paragraph on the first reply. When copying the answers a part went missing, specifically the first section of your comment:

Q: line 151: outliers in inland waters. Why are inland waters, not addressed in this work, not masked out? Are these really outliers? and are they removed from the analysis before MHW assessment? (if yes, I would take them out of the figures, if not, they might be influencing the results which is not good)

And here the missing part:

Why are inland waters, not addressed in this work, not masked out?

We understand that the terminology of inland waters may be confusing in some cases, also corroborated by the FAO (https://www.fao.org/cwp-on-fishery-statistics/handbook/general-concepts/main-water-areas/es/). We understood as inland waters the ones located in a particular national sovereignty, inside the “imaginary” line drawn by the shore which divides the marine waters and the inland waters, and consequently the waters that have very particular and local bio-geo-chemical properties. In any case, we will avoid this terminology in order to simplify and not lead to misunderstandings. They are not masked out as they are results as any other, abnormal or particular as the physical system which represents, yes, but we do not find any reason to remove them. 

Sorry for any possible inconvenience,

Lluís

Dear referee,

Tanks for your time dedicated into this contribution, here we attach our response.