This manuscript reports new 10Be exposure ages from Holocene moraines in the Silvretta Mountains in the Eastern European Alps and puts them into the regional and hemispheric paleoclimatic context. The data is very useful, as Holocene chronologies in the Eastern part of the Alps are still scarce, especially such robust, consistent data sets that allow for meaningful paleoclimatic interpretation. The multi-boulder ages are indeed remarkably consistent for each landform and belong thus to the most valuable data sets from the Alps, which are still relatively rare among the many existing Alpine chronologies.

The manuscript is very well written and illustrated. Also, a new and very promising method is presented that allows low-quartz or low-10Be samples to be analyzed with high precision.

The manuscript is thus worth to be published in Climate of the Past. Before acceptance, a few minor issues should be addressed though.

My main comment relates to the 10Be mean ages of the Early Holocene (EH) moraine sets that are reversed with regard to the stratigraphic order of the landforms. Two EH ice margins were dated in each of the studied valleys. The multiple ages from each ice margin are strikingly consistent with each other, and their mean ages are in perfect agreement between both valleys. But the 10Be ages from the outer (thus older) ice margin are systematically younger, thus leading to a nominal mean age that is younger by ~500 years, in both valleys. This is not discussed nor even mentioned in the manuscript. While from a dating perspective this can be handled relatively easily (see my suggestions below), the major challenge consists in the correlation of the moraine depositions with the independent high-resolution proxies (Discussion). This is particularly notable in section 5.3.2, where the cold spells during the EH warming are discussed, and the timing of the outer moraine formation (MIF 4) is correlated with both the DCP1 (+PBO; ~11.6-11.2 ka) and DCP2 (+related cold spell; ~10.6-10.5 ka). See line 531 for the first (“…evidenced by moraines J4 and L4 dated in this study…”, i.e. MIF 4), and lines 536-537 for the second (“Moraine formation…, concurrent with DCP2, is observed in the Silvretta Massif (MIF 4)…”). Maybe there’s a typo and the authors meant MIF 3 for the first, as the 10Be ages MIF 3 agree with DCP1. But that would of course make no sense, because a stratigraphically older moraine cannot be correlated with a younger paleoclimatic event (also see below my comment on lines 439-440, where this correlation was actually done).

I suggest that the reversed moraine mean ages should be acknowledged and possible reasons discussed. Are there any field observations that might explain a systematic age underestimation, like enhanced exhumation, erosion, cover on the outer moraines? Exhumation seems unlikely, given the big boulder sizes on the supplement pictures. Could the systematic offset just be a coincidence? It can easily be tested, e.g. by using an MSWD, if the dispersion of all MIF 3 and 4 ages is only due to analytical errors. It could be argued that the moraine formation at the two ice margins occurred within such a short interval that their ages are not distinguishable with the 10Be dating method. Logically, the average of all ages from the MIF 3 and 4 ice margins would then provide the best estimate of the two glacier stabilizations. Parts of the discussion will need to adjusted to this.

Minor comments per line:

20-21: According to my above comments, better change by saying that two Early Holocene moraine formation intervals occurred around ~11 ka and that they were close both in space and time.

44: revise grammar

79-80: make two sentences

84: Yes, that’s indeed important, also for the Late Glacial in the rest of the Alps (just a comment).

Legend of Fig. 1: For the light blue shading that’s the ice extent rather than the ice margin. For the national border it might be interesting to indicate to which countries it belongs.

130: something is wrong at the end of this line: “they form” instead of “or”?

176-179: I recommend to at least indicate the potential impact of a possible snow pack scenario, as snow has a higher impact than erosion. The effects of erosion are tested (supplements), but one could argue here as well that it might lead to a higher age dispersion given the various geometries of the boulders. So, testing one but not the other doesn’t seem straightforward.

192-193: J1 is dated to the 18^th, that’s not the end of the LIA. Shouldn’t it therefore say that J0’s age falls between the LIA maximum and the turn of the 20^th century? Or if you just cite Fischer et al. (2019), then phrase the sentence differently (“…is thought to fall…” or similar). The same comment applies to the first line of Fig. 2’s caption.

Fig. 3: Make sure the same language is used in the text and figures (hut/Hütte)

Table 1 and 2: The third to last column has a wrong header in each table. The blanks could be added to the tables, notably for easier comparison of the numbers of atoms 10Be.

308 and 345: Given that there’s just one sample, I would phrase this more cautiously: “might capture” or similar

313-315: Grouping the L3L moraine segments with the other MIF 3 moraine segments seems arbitrary, because the ages of MIF 3 and 4 are statistically the same. Unless you have more convincing arguments, I would attribute these Left-lateral ridges to both MIF 3 and 4.

Fig. 7: According to my main comment above, it would make more sense to compare the kernel plots for MIF 3 and 4 in each valley to show that they are indistinguishable from each other, and show their mean ages and insist that they are the same in both valleys.

364: glacier advance

Fig. 8: It would be convenient to have one of the scales in years before present.

345 + 362 + 395-396 etc: Are the earlier-LIA and pre-LIA boulders in a stratigraphically different (outer) position compared to the ~18^th century boulder? And do you have field evidence that the “LIA” moraines are composite moraines? If yes, it would be good to mention this in the Results – Geomorphology section. Just to interpret this from a few isolated boulder ages is very speculative and should be handle more cautiously.

396: “in the following sections…”

396-398: This sentence probably needs to be revised, it’s unclear. I guess you mean that J1 and L1 mark the MAXIMUM glacier advances and temperature minima SINCE the YD-EH transition?

Revise the title of section 5.2, as it’s the same as for section 5.1

407: Nothing is mentioned about the fact that the nominal ages are systematically reversed, see my main comment above.

410: Concerning the statement about the climate variability in the studied valleys, is this based on specific observations and does it refer to a specific time period? Can you provide a source?

411: “Also, catchments are comparable…”?

413:  It’s not clear to which “variations in the timing of moraine formation” is referred here. The same applies to “age variability among moraines dated in the region”. These variations have not been discussed and cited so far. I guess the statements refer to the Verwall and Ochsental chronologies, but this needs to be clarified.

422: FIG. 9c-f

432 and 435: Were the ELAs in both valleys determined with the same methods? It would be good to give a few more explicit arguments that support the concept that the dated Kartell moraine is not the equivalent of the MIF 3 and 4 moraines and that the age difference is not due to dating uncertainties.

439-440: How can MIF 4, being stratigraphically older than MIF 3, be related to a younger paleoclimatic event??? This needs to be corrected. See my main comment.

446-337: remove “on the one hand” and “on the other hand”

523 and 525: Fig. 9 not 8

531: Fig. 9g-h

535: “which in turn led…”

595: Again, a glacier stabilization that is recorded in the most external position cannot have occurred a few centuries later. Please correct this.

573: this needs to be phrased more cautiously.

Summary of the manuscript

This manuscript presents 27 new Be-10 dates on the timing of Holocene glacial advances in the Eastern Alps of Europe and correlates them with inferred meltwater events within the North Atlantic. Their findings corroborate previous studies from the Western Alps and peripheral regions of the North Atlantic, which is glacial advances in those regions were the result of cold atmospheric temperatures being advected eastward from the Atlantic, and that the Atlantic was cold as a result of a slowdown in AMOC, which was a result of enhanced freshwater input from the Laurentide Ice Sheet.

Summary of my assessment

This manuscript was an absolute delight to read! Scientifically, the results support the conclusions (with a few very minor exceptions, discussed below) and the discussion was beyond interesting, it was enlightening. Aesthetically, the writing was silken, the figures were beautiful, and the logical organization of the manuscript was thoroughly evident. In my opinion, this paper should be published with a few moderate and several minor revisions.

Major Points

As I said, I have no “major” issues with this paper. I do, however, have three “moderate” points for the authors to consider:

First, there is a slight age inversion between MFI 4 (dated to 10.8 ± 0.7 ka) and MFI 3 (dated to 11.2 ± 0.8 ka). While these two events are indistinguishable in timing from each other based on the Be-10 dates, we know from the geomorphology that MFI 4 must be older than MFI 3. While this apparent age inversion is noted on line 407, it isn’t (as far as I noticed) mentioned again. Thus, the discussion on lines 437-441 seems strange. The authors say MFI 3 falls within the PBO (defined as 11.30-11.15 ka in Europe), but MFI 4 does not. In reality, MFI 4 must have preceded MFI 3, so if only one of them is associated with the PBO, it’s more likely MFI 4. In short, I don’t see how both of the following could be true: (1) MFI 3 correlates with the PBO and (2) MFI 4 postdates the PBO and correlates with a summer cooling detected in Swiss and Austrian lake sediments.

Second, I was surprised that the authors did not acknowledge the possibility that the boulders dating to c. 700-1500 years ago (JAM-18-07, JAM-18-16, and LAR-19-23) were actually deposited more recently (c. the 18^th century?) and contain inherited nuclides from prior exposure. The evidence from these two valleys for glacial advances c. 500 CE and c. 1300 CE is tenuous, in my opinion. The data permit glacial advances at those times, but the evidence is not compelling. I was pretty skeptical of glacial advances at those times in these two drainages—until I read about the evidence elsewhere in the Alps for glacial advances at those times (e.g., the boulder from Ochsental dating to 1500 ± 40 years, the sediment and peat profiles from various glacial forefields in the Eastern Alps, and the documented glacial advances in the Western Alps at those times. In light of the evidence from elsewhere in the Alps for glacial advances at c. 500 CE and 1300 CE, I think the interpretation presented by the authors—that these two valleys also hosted ice advances at those times—is reasonable, but the alternative possibility, that these three samples contain inherited nuclides from prior exposure should be discussed in the text.

Third (and perhaps less importantly than the two previous points), I find it curious that both valleys have moraine ridges just outside the LIA margins that are ~8-10 m wide, rich in fine-grained sediment, and devoid of boulders. While the authors suggest these ridges (J2 and L2) might be equivalent to the c. 10 ka Grüne Kuppe moraine in the adjacent landscape of Ochsental (lines 452-465), the fine-grained nature of these ridges seems anomalous—and suggests to me that they have a different origin from the boulder-rich ridges (moraines) present in these alpine valleys. In particular, I wonder if J2 and L2 might be some sort of push-ridge associated with the LIA advance? That’s speculative, of course, but no more speculative (in my opinion) than their potential association with the Grüne Kuppe moraine. In any event, the true age of the undated J2 and L2 ridges is not an essential point to this manuscript—but their fine-grained nature does seem anomalous and cry out for an explanation.

Minor Points

Line 16: I think there should be a hyphen between ice and margin.

Lines 20-21: I think the MFI should be listed in chronological order, so oldest first.

Line 24: I think “millennial scale” should be hyphenated.

Line 25: I think “contemporaneous” is possibly too strong; I’d suggest “indistinguishable in timing” instead.

Line 32: I think a reference or two should be provided for the duration of the YD and (less importantly) for the beginning of the Holocene. Yes, these dates are common knowledge—but someone(s) did some groundbreaking research at some point to determine those dates and their efforts should be acknowledged, in my opinion.

Line 35: “Centennial scale” should always be linked by a hyphen, I believe, so: “centennial-scale.”

Line 35: I remember Bob Anderson (CU-Boulder) commenting on one of my manuscripts and saying that “to be” was the weakest of all verbs, so to avoid whenever possible. In this case, “to be” can be deleted and the sentence remains grammatically correct (and becomes more concise).

Line 36: Stylistically, I think references should also be cited in chronological order, because that helps me learn the history of the field, but I recognize that some journals prefer/require citations to be in alphabetical order. In this case, it’s neither. Also, the “e.g.” should be followed by a comma (so, “e.g..,”) and there should be a space after the semicolons and before the next name.

Line 77: “State of the art” should be hyphenated, I believe. So, “state-of-the-art.”

Figure 1: Is an absolutely stunning figure, it contains so much information, and is an absolute delight to look at. I hope the person (or people) who made it are proud of their efforts, it is a real accomplishment.

Line 101: “Geographic” can be deleted. (Are their locations that are not geographic? I can’t think of any… so the word can be deleted for greater conciseness without loss of meaning.

Line 112: Delete the “a” before “snow cover.”

Line 126: This might be the previous semester speaking—in which I taught mineralogy/petrology despite being a geomorphologist—but I think “quartz yield” would be a better phrase here than “quartz content.” The lithologies present in these valleys must truly have greater quartz “contents” than these, as some of the quartz was etched away in the cleaning process, was it not? “Quartz content,” to me, suggests some sort of modal norm, potentially applicable to some sort of classification scheme—while “quartz yield” suggests this is how much quartz we got out of the rock.

Line 134: How do you know the boulders were carved out of the bedrock by glacial flow? Why couldn’t they have tumbled onto the glacier’s surface from the adjoining cliffs and been carried to the ice margin. In theory, the boulders were plucked out of the bedrock and never saw “the light of day” until they were deposited on the moraines—but was this really what happened? How do we know?

Line 142: Is there a difference between “complemented” and “updated?” If not, I’d delete complemented and just use updated. I think “updated” is the more commonly used verb.

Line 144: I think the first “historical” should be deleted. First, I’m not sure those moraines are really historical, in the meaning of the word, and second, the sentence is somewhat circular sounding as written.

Lines 150-151: Is the datum for this DEM actually sea level, and not some ellipsoid height? (I know this is nitty-gritty technical, but would you please confirm which the DEM is referencing with regards to its elevation?) See the last two paragraphs of Greg Balco’s blog post here (https://cosmognosis.wordpress.com/2017/03/28/is-a-cheap-gps-ok-for-elevation-measurements-or-do-you-need-a-fancy-one/) for more details, but the gist is that this is a frequent and impactful error on cosmo ages.

Line 157: As above, I think “quartz content” should be “quartz yield.”

Line 171: How can an individual boulder have an arithmetic mean age? (Other than by the counting statistics at the accelerator, which I’m assuming is not being referenced.) If the authors are referring to the counting statistics from the accelerator’s beam line (or whatever it’s called), that should be specified for clarity. My hunch, though, is that this statement (of the boulder ages being arithmetic mean ages) is a typo—and that only the landform ages are arithmetic means. But please, if I’m off the mark with my hunch, just clarify what’s being discussed/reported here.

Line 186: Reviewers don’t often say this (at least I don’t think they do…), but I just want to praise how logical and organized the Results and Discussion are, the thought that the authors have put into this manuscript is clearly evident!

Line 198: As above, I think the fine-grained nature of ridges J2 and L2 is an important observation with regards to their origin(s).

Figure 2: Is absolutely stunning… I really like how the authors have shaded the moraines by color and used the right-angle lines to connect the sample dots with the boxes with their ages and names. The 1-m hillshade background doesn’t hurt either!

Figure 3: Also very nice!

Line 244: The abbreviation “c” shouldn’t be used to start a sentence, even in capitalized form. Instead, I’d recommend using “approximately” instead. Also, in my experience “c.” or “ca.” for “circa” are only used with regards to approximate dates, not approximate distances, or other quantities.

Figure 4: Awesome, just like Figure 2…

Figure 5: Beautiful, just like Figure 3.

Line 276: I think the word “risky” is misleading. At first I thought you were saying that it was too dangerous to sample there, as rocks might fall down as squish you while you’re trying to hammer out a sample, but then the phrase “to tackle with SED of boulders” made me realize that you’re talking about scientific risk, not personal risk. I’d encourage you to preface risky with scientific, so “scientifically risky,” unless you are concerned about being squished, in which case I’d recommend you drop the “to tackle with SED of boulders” part of the sentence.

Line 293: I’m not seeing the gray-shaded bars… do you mean the thin black lines instead, for each individual sample? Perhaps “bars” should be singular, “bar,” instead? Also, the vertical uncertainty bar in the background—which I’m guessing is what you’re talking about—seems kind of greenish, but perhaps that’s me.

Figure 6: Also, while we’re talking about Fig. 6, I don’t really understand the differences between the three types of uncertainty you report on the mean age, and I think other readers might also struggle. I understand total uncertainty (reported in red) is the production rate and spike uncertainty added in quadrature, but I don’t really understand the importance of the difference between the 1-sigma uncertainty (±16 years) and the standard error of the mean (±9). I guess I would have thought they were the same thing, with the “standard error of the mean” being the correct term and the “1-sigma uncertainty” being the not-really-100%-approved-by-statisticians version of the “standard error of the mean.” Your paper isn’t the place to teach readers about statistics—but a few sentences somewhere in the text about the differences between these things would help me (and I think others) out. (Thanks for considering this request!)

Line 300: I think “supplements” should be capitalized, and the final “s” in it dropped. So, “Supplement.”

Table 1: Are the elevations really meters above sea level, or meters about some ellipsoid? (As above, what is really 0 m elevation in the DEM?) Also, “quartz weight” would be better reported as “quartz mass.” Also, I think the 10^th column from the left (3^rd from the right) is mislabeled. It says it’s a ratio of Be-10 to Be-9, but that’s what the column to the left reports and the units in this column are atoms, and a ratio shouldn’t have units. Finally, how can we possibly know the average thickness of the samples to a 10^th of a millimeter? While you could just reduce the reported precision (as I suspect the true precision of these measurements is being overstated)—I’m also curious as to what method you used to calculate these numbers, as it’s not stated in the text (that I saw) and I’d potentially like to use the same method in my own research.

Line 313: “11 230” should be reported as “11,230” or, alternatively, all the other 5-digit ages should be reported in the same fashion, with a space between the 3^rd and 4^th digits.

Lines 323-327: This advancement—of adding a late spike of Fe to help process small-volume samples—seems worth of a sentence in the abstract, in my opinion. It’s a really methodological advancement for cosmo, I think, and well worth highlighting, in my assessment.

Table 2: Same 4 points as for Table 1 above.

Figure 7: Same comment about the meaning of the reported statistics (i.e., what’s the difference between the 1 sigma uncertainty and the standard error of the mean) as for Figure 6. In other words (in case my point/uncertainty has been unclear), what are these two statistical calculations telling us? When would/should we refer to one and when should we refer to the other?

Lines 344-345: I think 1-3 references would be appropriate here. Who did the work that leads us to expect LIA moraine formation between 1250 and 1850 CE?

Line 345: As discussed above in the “moderate points” section, I think “recorded” is too strong a word for the evidence this manuscript presents, “suggested” might be a good alternative.

Line 361: While you interpret JAM-18-16’s 1070 yr age as a minimum age, because that dates to the beginning of the MWP and the boulder might have toppled. The boulder might, alternatively, host inherited nuclides, in which case the 1070 yr age would be a maximum age. I think this possibility should be acknowledged in the text.

Line 377: “Centennial scale” should be hyphenated.

Figure 8: There isn’t a year 0 in the CE chronologic system, as far as I know. I believe the “CE” dating convention is the same as the “AD” dating convention, with the years matching one-to-one and the meaning ascribed to them (the two-letter abbreviation) being the only difference. Because the Roman’s didn’t have the concept of zero, the numbering goes directly from 1 BC to 1 AD. Thus, as far as I know, the CE system also goes from -1 to 1 with no zero (but feel free provide a citation correcting me if you think I’m wrong). Also, on a much less nit-picky note, Figure 8 is really well designed! I like your use of color—and how time runs from left to right, that makes it easier to read in my opinion.

Line 399: This is the same section heading as 5.1. I think you might mean “The moraine record of the early Holocene” here.

Line 462: I don’t think the word “evolving” should be used with regards to species, except in the case of evolution in the Darwinian sense. I think you might be thinking of an upward migration in the treeline, is that right? Also, pinus cembra should be italicized, I think, and shouldn’t pinus be capitalized as well?

Figure 9: I’m not familiar with the word “warves.” It’s at the top of the figure, sideways, in association with PBO. Do you mean varves instead? And if so, what do varves have to do with the PBO? Also, with regards to (g) and (h), what do the uncertainty bars represent, 1-sigma uncertainties?

Line 467: I’m not familiar with the word “detrical.” Do you mean “detrital” instead?

Line 491: I had a stats prof who said the word “significant” should only be used in scientific writing to mean “statistically significant” (at a specified threshold). That might be a stats professor’s view of the world—but I see no reason why “substantial” couldn’t be used here instead.

Line 491: “large scale” should be hyphenated, I believe.

Line 493: Was the Icelandic ice mass really an ice sheet (>50,000 km2) vs. an ice cap (<50,000 km2)?

Line 501: I believe “hemisphere” should be capitalized.

Line 502: Essentially the same point, I think “northern hemisphere” should be capitalized.

Line 508-509: I have two minor points about “there is evidence of more subdued glacial discharge during the EH that results in a deceleration of the thermohaline circulation.” First, I think 1-3 references should be cited here, in support of that statement. Second, the term “thermohaline circulation” seems to have gone out of fashion, so I’d recommend you use “AMOC,” meridional overturning circulation, or something of that nature.

Line 513: I think “glaciated” should be deleted, because it is redundant with “glaciers” two words previous.

Line 517: “ice bergs” should be one word, “icebergs.”

Line 518: I don’t know if you need to introduce the term/concept “H0” into the paper. Its fine if you want to—but, if I’m not mistaken, the term is only used in this paragraph (lines 515-531) and “H0” does not appear on Fig. 9 (YD is used there instead).

Line 519: I’m not familiar with the word “detrical,” do you mean “detrital” instead?

Line 521-522: The sentence says Jennings et al. (2015) found 6 DCPs, but Fig. 9 shows 7. Maybe someone discovered a 7^th one later (I don’t know that literature well enough), but it seems like possibly a typo so I thought I’d mention it.

Line 523: The reference to “Fig. 8a” should be to Fig. 9a.

Line 531: A figure number is missing from “Fig. g-h.”

Line 534: I think “Resulting” should be preceded by “The,” so “The resulting freshwater…”

Line 543: “sea ice” should be hyphenated.

Line 555: I think there’s a typo here… do you mean the western margin of the North Atlantic? Or the eastern margin of the LIS? The “western” margin of the LIS would be in the Canadian prairie... at least, that’s the thought that comes to my mind as I read the sentence.

Line 556: I think “perturbated” should be replaced with “reduced,” as “perturbed” (note the spelling difference) means changed or altered, while “reduced” specifies the direction of change.

Line 573: Delete “have,” it’s not necessary.

Appendix A: I think it’s great that you included so many photos of the sampled landscapes, that really helps the curious reader understand each boulder’s context within the landscape.

Line 612: “unweatherd” should be “unweathered.”

Line 617: I looked for your samples on the ICE-D Alpine database and was unable to find them. What’s the timeline for getting the samples posted?

Line 632: Is “inatura” supposed to be capitalized? (I don’t know… but it seems likely to me.)

The Supplement: Once again, it’s really nice that you included multiple photos of every boulder, I like your thoroughness!

Supplement, 5^th line to the caption for Table A2: I think the “therefore” in “and was therefore used to quantify” should be deleted, its unnecessary (the sentence makes sense without it).

One final note: thanks so much for submitting this manuscript to Climate of the Past. I know reviewers don’t often tack on such comments—but your manuscript was such a delight to read, and the figures were so well made!