This paper presents the first reliable record of early Holocene ice in the Alaskan high mountains, where many scientists have attempted to locate it for many years. The finding of this study have the potential to inspire further exploration of Alaskan glaciers as a valuable paleoclimate proxy. Therefore, I strongly recommend the editor to accept this manuscript for publication in The Cryosphere. The manuscript is well-written, and the figures and tables are presented accurately. However,  I would like to suggest the inclusion of several additional references that the authors may have overlooked.

Sasaki, H., Matoba, S., Shiraiwa, T. and Benson, C.S., Temporal variation in iron flux deposition onto the Northern North Pacific reconstructed from an ice core drilled at Mount Wrangell, Alaska, SOLA, 2016, 12, 287-290. DOI:10.2151/sola.2016-056.

https://www.jstage.jst.go.jp/article/sola/12/0/12_2016-056/_pdf/-char/ja

Shiraiwa, T., Goto-Azuma, K., Matoba, S., Yamasaki, T., Segawa, T., Kanamori, S., Matsuoka, K. and Fujii, Y., Ice core drilling at King Col, Mount Logan 2002, Bulletin of Glaciological Research, 2003, 20, 57-63.

https://web.seppyo.org/bgr/pdf/20/BGR20P57.pdf

This manuscript presents the 14C ages of the a 210-meter long ice core drilled to the bottom from the summit plateau of Begguya (Mt. Hunter; Denali National Park, Central Alaska). The authors conclued that the basal ice on Begguya is at least of early Holocene origin, thus providing a potential paleo archive of Holocene climate in the North Pacific region. The results are reliable and the manuscript is well written.

There are a few concerns that the authors may need to consider when revising the manuscript.

(1) In Figure 1, some of the ages below the ice core drilling sites may be misleading. For instance, the Aurora Peak ice core is with a length of 180.17m, while the age of 1734 CE corresponds to the depth of 149.68m w.eq. The authors need to verify if this age of 1734 CE refers to the  basal ice? if not, how far the ice corresponding to 1734 CE is above the bottom? The same kind of verification is necessary for all the other ice cores shown in Figure 1.

(2) Lines 116-117. Please confirm if or not this work provides the first radiometrically dated high latitude Northern Hemisphere ice core chronology?

(3) sections 2.1 and 3.2. Parts of the contents in these two sections duplicate.

(4) The author may want to consider moving section 3.1 into section 2. 

(5) Lines 252-254. Slightly?

General Comments:

This study provides a new radiocarbon-based chronology of an ice core obtained on the Begguya Plateau of Mt. Hunter (2013), located in the Alaska Range. As an application of recently developed radiocarbon dating methods for water-insoluble organic carbon (WIOC) and dissolved organic carbon (DOC), the study is successful in obtaining carbon samples of sufficient size to generate calibrated 14C age probability distributions that are largely in chronostratigraphic order. Further validation of the radiocarbon-based age model is achieved by comparisons with annual layer counting methods and inverse modeling for variable accumulation rates. Strong presentation and interpretation of these methods and results make a compelling argument that the authors have achieved continuous chronological constraint on the ice core through ~4000 to 5000 cal yr BP, or down to ~168 m depth for the ~209 m long core. For the two ages obtained below that depth, and for the author’s interpretation of their significance, there are some additional questions to be addressed (see below). Although the authors provide possible implications for regional Holocene hydroclimate with some good hints shown by a bar diagram in Figure 5, this presentation over-generalizes the depth and breadth of the datasets and in some instances mis-characterizes the aspects of hydroclimate that they represent. Since precipitation records provided by high elevation ice cores combined with lower elevation records are needed to better understand the complex climate history of the Gulf of Alaska region, hopefully there are plans for more thought and exploration on these aspects to come.

Specific Comments:

1. Presentation of the two lowermost ages is currently not sufficient to conclusively support the interpretations and proposed implications.

A prominent feature of the chronostratigraphic results is the abrupt change in ice accumulation rates between samples 232-233 and 234 (Table 1), as shown in Figure 3 (and the age models in Figure 4, although the horizontal log scale of age somewhat masks its appearance). Ages from both depths are from WIOC, but the sample sizes are significantly different (54.8m and 9.8mg, for depths of 206.6 to 208.1 and 208.1 to 208.8, respectively). Notably the value of 9.8mg is just shy of the recommended 10mg threshold described in lines 239-242. Yet, it must be asked why this sample was considered acceptable when, for example, a value of 9.2mg for sample 209 (187.8-188.7 m), which provided an age that is stratigraphically ‘too old’ compared to those above and below it, was not included in the chronostratigraphic analyses. It would seem very possible that the age of 6.2-9.6 cal yr BP provided by the 234 sample is also stratigraphically too old in a similar manner. Additional discussion is needed to explain why this sample was included. If it is a correct age, then the implication is that up to ~4000 years of record is compressed into 1-2 m of ice across this interval. This begs additional questions about the englacial stratigraphy for which lines 197-198 say there is no conclusive evidence for stratigraphic continuity or discontinuity.  If the age data is accepted, then additional investigation-discussion would be helpful to explore either additional evidence, for example related to melt layers or changes in precipitation seasonality, which provide possible explanations for the rapid reduction in accumulation and/or preservation of ice in the core at this time.

The lowermost age, sample 235 at 208.8-209.4 m depth, was the only age from the core obtained from DOC. Although it does not suffer from sample size issue as the WICO age above, it does raise the question about the propensity for DOC ages to be stratigraphically “too old” due to old carbon sources. One way to address this concern would be to date a few other intervals down the core with both DOC and WIOC to establish that the two materials can be confidently compared in this core. Due to the large sample sizes needed for the analyses, it is understandable that this may not be readily feasible.  However, without such a data comparison, it would strengthen the quality of the discussion to include an acknowledgement of this possibility and add a more parsimonious evaluation of the implications.

In summary, there is a reasonable possibility that the lowermost two ages are stratigraphically “too old” due to analytical and source carbon reasons and the manuscript could be improved to account for and acknowledge this possibility with corresponding adjustments to the certainty for which the implications are presented.  For example, lines 440-442 that states the results ‘clearly indicates’ ice of early Holocene age are rather more suggestive and therefore to be developed further. A reconsideration of the statement that the results ‘confirm that at least some glacier ice… survived… the Holocene thermal maximum’ (lines 397-398) could include addressing if there is any evidence to doubt that glacier ice at 3900 m elevation persisted during the early Holocene. Furthermore, the stated conclusion also raises questions about how basal ages of mountain glaciers serve to provide evidence for ice presence (or not) when they may be in constant downward motion.

1. Regional paleoclimate

The primary subject of this paper is the radiocarbon data, and the context is regional paleoclimate. So, although it is not a focus or objective to deeply survey the regional paleoclimatic data, there are some important general aspects that could be better clarified. First, while the notion of a “early Holocene thermal maximum” may have meaning for the cryosphere on a pan-Arctic scale, in Alaska a thermal expression is vague, if at all, by low elevation terrestrial proxies, including pollen. Rather, corresponding changes in effective moisture are more commonly reflected by the proxy records. Prominent oxygen isotope studies document changes in atmospheric circulation patterns related to the strength and position of the Aleutian Low (Jellybean with the PRCol record from Logan summarized by Anderson et al., 2016, Takahula and more recently Tangled Up in the Brooks Range by Anderson et al., 2018: these records should not be primarily characterized as ‘lake level’ such as in Figure 5). Subsequent studies show how those changes in atmospheric circulation may be related to changes in effective moisture on the leeward sides of the major mountain barriers, ie., lake level (Marcella, Seven Mile Lake by Anderson et al., 2011, and more recently Track Lake in the Yukon Flats by Anderson et al. 2018 and Squanga Lake in the interior Yukon by Lasher et al., 2021). However, much like the complexities discovered when comparing the ice cores from Logan with Hunter by Osterberg et al., 2017, it may not always be a correct assumption that the hydroclimate of the SW Yukon and Alaska Range are always the same.

Most closely located to Hunter is a carbon isotope record from Dune Lake, on the north (leeward) slope of the Alaska Range (Finney et al., 2012), which suggests that late Holocene changes to winter precipitation seasonality has played a role in lake level through groundwater, which could in theory be related to Alaska Range glacial ice. For the windward side of the range, on the Kenai Peninsula, there is currently the Horse Trail Fen peat oxygen isotope record (Jones et al., 2019) with additional work on lake isotope records currently underway in Upper Cook Inlet (IALIPA abstract by Anderson et al., 2022).  In summary, while there is a rich and growing record of the hydroclimatic changes in Alaska during the Holocene, many questions remain about the role of temperature, moisture and precipitation seasonality in relation to the complex topography of the region. With an improved characterization of the state of knowledge, the contributions made by this study of the Holocene ice accumulation on Mt. Hunter will be more clear. This paper has begun to provide the needed chronology for additional contributions and it is hoped that more in depth comparative analyses are planned.

Fang et al. present new 14C ages measured on WIOC and DOC from an ice core from the Begguya plateau. I think this is a very interesting study that explains well the new measurements and results. I have just a few minor comments that the authors should consider in an updated version of the manuscript.

I am wondering about the modelling approach with the variable accumulation rate (figure S2). I understand the approach the authors did but less thinning at the bottom would directly lead to lower accumulation rates. How realistic is the assumption of constant thinning and are the uncertainty bands in the accumulation rate (figure S2) realistic?

It would be nice to have an explanation why sample "Denali215-216" was excluded but sample "Denali234" not. The latter sample is very important for the age model but it has a lower WIOC content than "Denali215-216".  I see the reason for excluding "Denali215-216" as it does not fit into the 14C age sequence but I am wondering if this questions the robustness of the "Denali234" result.

Why was the "in-situ" correction done with an accumulation rate that is lower than the reconstructions based on the modelling in this study (Figure S2 lower panel)?  The authors write that they take the average accumulation rate from Winski et al., (2017) but figure S2 shows lower values for the Winski model. Please explain.

In the conclusion the authors write: "These were achieved by a slight adaptation of the WIOC 14C-dating method, allowing for larger ice samples of up to around 1 kg of ice and the use of a new technique for 14C dating of the DOC fraction. From the text it was not clear to me what exactly this "adaptation" was. Similarly, it would be good to write clearly what the ”new technique” for DOC measurements includes in comparison to previous measurements?

The basis for preferring WIOC over DOC 14C measurements could be very briefly mentioned for the non-experts in the method.