|Dear Dr. Steni, |
I have reviewed the manuscript referenced below, you can find my comments on-line. I just write here a response to your questions, just in case it is useful for you:
El 05/05/2020 a las 17:00, firstname.lastname@example.org escribió:
"Dear Dr. Moreno,
I am sending you a manuscript by Badaluta and co-authors on a paleoclimate record from an ice cave deposit in Romania. The manuscript is at its second round of revision and I would like to have your opinion on it.
I think that the authors have answered to the relevant questions addressed by the first two reviewers, but I also think that in their revised version they did not introduce some relevant comments on the 14C dating and on the mechanism of excluding or not a sample for dating.
I agree the authors have not yet explained which were their arguments to reject so many 14C samples (and not others). This is to me the main problem with this paper: the robustness of the age model. This issue is specially remarkable since the main idea of this study is to relate d18Oice with AMO variability, at a decadal scale. The uncertainty in the chronology does not allow such comparsion.
Another point on which I would like to have your opinion, if you feel comfortable with this, is related to the text discussing the paleoclimate interpretation, between page 6 and 7 where I found difficult to follow and where some dates should be rounded. Perhaps some parts should be moved up and down, following what is the numbering of the figures instead of going back and forth.
Regarding the paleoclimate interpretation, I find interesting the d18Oice interpretation as summer temperature. This idea would probably require more monitoring data since the authors just present precipitation data for several years, but not any d18O measured in ice formed every year. In additon, temperature measured in the cave will be important to demonstrate water freezes in early fall, thus recording the summer signal in the ice. This is not yet well-demonstrated.
Finally, the comparison with other records requires some statistics. There are many "visual observations" in the manuscript about the correlation among different proxies; that has to be supported by correlation coefficients.
Hoping you can use my comments above and those in my review.
Review of Cave ice stable isotopes suggest summer temperatures in East-Central Europe are linked to AMO variability by Bădăluță et al.
This manuscript presents an interesting record from an ice cave in Rumania where the d18O data are interpreted as summer temperature variations in response to AMO variability during last 1000 years. Although the interest of this type of records is certainly high, the manuscript presents several issues that prevent its publication in Climate of the Past. I outline here my main concerns:
1) The most important problem is the lack of a robust chronology, specially to use this record as a reconstruction of an atmospheric-oceanic phenomenon such as the AMO that changes at a decadal scale. The chronology of this ice sequence, in spite of all the efforts carried out by the authors, is unfortunately not good enough for that comparison. The age-depth model is constructed by just 4 14C dates since up to 8 14C dates had to be discarded. The authors do not explain in detail the reasons to discard those ages but Fig2 shows the difficulties to construct a reliable age model for this sequence. Even if we consider that this is the best possible age model, it certainly lacks the chronological precision and accuracy to be later compared to total solar irradiance or tree-ring chronologies. If the authors decide to keep this chronology, I suggest to use the record to discuss variability at the scale of MCA vs LIA but not use it to compare with AMO variability. I outline here two possible improvements:
- The authors state that since the cave is open many organic remains reach the cave and are incorporated into the ice (they had more than 40 samples with organics). I suggest dating more samples. And, instead of looking for larger pieces of wood or leaves that are for sure more difficult to find, use the WIOC technique that requires a very small amount of carbon in the ice to be dated. Of course, some dates will provide reversals but some others, hopefully, will support the age model and will help to draw it with more certainty.
- the other idea is using the regional summer temperature curve to maximize the correlation with the d18Oice, that is displacing the data from the ice within the chronological uncertainty until the correlation is maxima. Later, the authors can present how much towards the past or towards the present they had to move the d18Oice data and see if this is still coherent with the age model. To do that, better evidences that the d18Oice is a proxy for summer temperatures are needed (see point 2)
2) This record is presented as a summer record instead of a winter one (as A294 ice cave in Spain or Scărișoara cave in Romania). The main argument is that the water that penetrates directly from the open ceiling of the cave freezes during early fall (not late fall-early winter as the other caves do) thus preserving the summer signal in the isotopes. This is probably true, but not demonstrated in the manuscript. I include here some ideas:
- I am pretty sure the authors have some sensors in the cave recording temperatures. Is it possible to see the time of the freezing? Is it always the same every year? Is it changing?
- Have you sampled the ice body surface during last 20 years? In the manuscript there is a sentence that seems to indicate that. If so, it will be excellent to see those data and their relationship with summer temperatures of that year. The comparison during instrumental period presented in Fig. 4 is nice, but the d18Oice from FV ice cave is plotted using the chronology presented here and for the last 150 years, I am afraid there is just one 14C date.
3) Finally, I find very appealing the comparison with other records in CEE during last millennium. This comparison is mostly presented in Fig.7 and in the second part of the Discussion section. I miss there some statistics, specially about the correlation among records. Those correlations are just based on visual observation and this is not enough, I think.