|Revision for “A 125-year record of climate and chemistry variability at the Pine Island Glacier ice divide, Antarctica|
I found this new version of the manuscript greatly improved with respect to the first one. But I think that further work is needed. The data presented in this work are so abundant and rich that in order to prepare a balanced paper also a great effort in terms of interpretation and data-analysis are required. This is the weak side of the manuscript. But I am sure that with a little bit more work it will be possible to draw interesting conclusions and evidences. In general I suggest to the authors to shorten a lot of sections. Reading the manuscript sometimes it seems to read a phd-thesis, not a draft of a paper. The space given to references and to their explanations is simply too much. Please consider to resume the most important information taken from literature in a more concise way, not presenting each single reference with an entire sentence which describe it. This is particularly true for chapter 3.2, but also other sections of the work are similar.
Moving to the content I have some doubts about the interpretation. What is lacking is a comprehensive analysis of all the data. At the present state the discussion about elemental fractions, PCA and cluster is completely separated from backtrajectories analysis and from the metorological considerations. TO draw robust conclusions putting all the pieces together is necessary.
Some details about theanalysis of chemical data. At first the equation system presented to distinguish the ss and nss fractions of Al and Na is not convincing. In the equations you show that nss Na depends on nss Al and that ss Al depends on ss Na. Without setting a reference how is it possible to solve this system? Sodium is a function of Aluminum and vice versa, I really could’t understand. You need to take an assumption if you want to solve the problem. I think that the only reasonable possible one is to assume that Al is only crustal and that nss Al is null. Assuming this point it will be possible to distinguish Na ss and nss fractions.
About PCA. I don’t really agree with your interpretation of PC. In addition I think that with suche good results their interpretation should be deepened. My idea about PCA is:
-PC1 is a sort of impurity index. We see that each element is positively correlated with this PC. This means that when the atmospheric load is high (high impurity content) PC1 show high values. At the opposite when impurity concentration reaches minima values PC1 is low. It would be interesting to show the record of PC1 along depth (or age) and see if presents seasonal values, I guess so.
-PC2 and PC3 are related to dust vs marine aerosol deposition. Here we see that Ba, Fe, Ti, Al are positively correlated, while other elements related to marine aerosol as K and Na are negatively correlated. These components distinguish the two fractions. Probably if we look further in deep we could say that PC2 highlights aluminosilicate (Al is the most important element), while PC3 highlights the siliclastic fraction of mineral dust (Fe and Ti).
-PC4 semms related to carbonate content, being Ca and Sr major constituents of CaCo3.
I suggest to the authors to better develop this part, studying the trends related to each component along the core and trying to understand the different seasonal cycles. This could help also for the successive part dedicated to the analysis of atmophseric transport and pathways.
Another important problem concerns the use of elemental concentration instead of fluxes. Since this is a well dated core, with a good seasonal signal, I think that it would be worth to convert all concentrations in fluxes. In this way it would be possible to highlight the real changes of deposition, excluding the effect associated to snow diluition. What is said here is that 3 major periods are recognized in terms of deposition, related to high and low concentration. Maybe such an effect is only related to changes of snow precipitation. Using fluxes such problems would be completely excluded and final interpretation would be improved.
More punctual observations:
102 and 108: class100, add ISO5
110: change to This process is important to guarantee a complete dissolution of particulate and non soluble elemental fractions.
119: applied to, not as
122: (such event occurred in less than 1% of the samples); minor, not less
180-182: Al is not chosen because of its abundance. Al is chosen because in addition to being abundant (and easy to determine) is also quite stable and immobile from a chemical perspective. Thus it can be reliably used as crustal tracer. (see for example nesbitt and young 1982)
190: see my comments about Na and Al
217: I don’t understand which those percentages are related to. In Tab S3 it seems that global volcanic deposition is more important than the local one, but in the text you state the opposite. Is it wrong or am I missing something?
249: specify that while the peak of species associated to marine aerosol is mainly related to winter sea ice peak, the peak of dust deposition is related mainly to atmospheric circulation patterns. In coastal sites such dynamics are greatly influenced by local factors, for this reason the dust peak doesn’t occur in the same season in whole Antarctica, each site presents its peculiarities.
259: associated to