the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Jul 2026
Isotope-Based Age Scale with Multi-Month Precision for the SE-Dome II Ice Core from Southeast Greenland Over the Past 150 Years
Abstract. Precise age scales are essential for reconstructing past climate variability at high temporal resolution. Here, we present a new oxygen-isotope record for the SE-Dome II ice core from southeast Greenland and construct a multi-month-resolution age scale spanning 1871–2020 CE. The chronology, named SE2025iso, was developed by aligning oxygen-isotope variations in the ice core with isotope-enabled climate-model simulations. High snow accumulation at the SE-Dome site preserved multi-month variations of oxygen isotopes, allowing age determination beyond seasonal extremes. Although absolute validation at the monthly scale is challenging, the chronology has an estimated mean uncertainty of 2.0 months and is supported by multiple consistency evaluations, including melt and tritium horizons, seasonal accumulation comparisons, and also volcanic reference layers. The reconstructed snow accumulation rates correlate well with climate reanalysis data, except in summer. The reconstructed accumulation record shows that the weak seasonality at SE-Dome persisted throughout the past 150 years. This persistence suggests that the balance near the boundary between summer- and winter-dominated accumulation regimes across Greenland remained broadly stable despite recent Arctic warming. Applying the SE2025iso age scale to chemical records shows that hydrogen peroxide concentrations peak approximately 2–3 weeks after the summer solstice and that volcanic sulfate records exhibit reproducible post-eruption peaks at multi-month resolution. Overall, the SE2025iso chronology highlights the potential of high-accumulation ice-core sites for investigating multi-month-scale climate variability and aerosol deposition processes.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-3602', Anders Svensson, 22 Aug 2026
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RC2: 'Comment on egusphere-2026-3602', Giulia Sinnl, 03 Sep 2026
Hamamoto et al. present an excellent contribution to the field of ice-core science and paleoclimatology in terms of a very detailed chronology at sub-annual precision for the period 1871-2020 CE, adding a considerable pre-satellite interval to the previously established SE1 chronology from the same site. By dating the climatic signal of the ice core SE-Dome II in great detail, the authors enable a semi-independent validation of the seasonality of other proxies (e.g. H2O2 and volcanic sulfate), as well as enabling the site-specific assessment of models of precipitation. The scientific quality of the study is high, with plenty of evidence provided of the results and the methods. The general presentation of the work is clear and well-structured, with a good logical flow between sections.
I find myself in agreement with the comments by the other referee (A. Svensson) and I encourage the authors to address those comments carefully. In particular:
- What is the reason behind the correction factor 1.209 (L165)?
- Why is figure 6 is on a depth scale, instead of an age scale? I understand that you want to demonstrate the quality of the dataset and compare the overall properties of d18O at the different sites, but I cannot help but think that NGRIP covers almost your entire age interval at those depths (1880s to 1930s), while Dye-3 only covers 1940s to 1950s. The data from SE2, on the other hand, is from 2000-2010CE. The climate was surely different during these decades. I would suggest to perform the same statistics (variability, how many multi-month peaks there are in a year) and plot figure 6 on a uniform age interval.
- Sigl et al (2015) present an analysis of post-eruptive climate in tree-rings: have you thought of presenting a similar analysis using d18O and layer thickness?
Otherwise, I have a few additional remarks, that I hope you will also consider in your revision:
- Table 1: do you have correlation data between other ice-core datasets and ERA5/IsoGSM20c during the same time interval? Are the values you obtain for your record better or worse?
- Figure 12: given the proximity of DYE 3, the reader might wonder why this core is not included (is there no sulphate data out there? I only know of ECM…)
- L 441: I suggest reminding the reader that you used an automated method of detecting sulphate spikes and that this method is the same used by Sigl et al 2013 (albeit with different RM windows). Did you use the same method for the NGRIP sulphate?
- L 455-462: Can you clarify why the sulphate in the NEEM-S1 and NGRIP cores does not show a narrow peak corresponding to the 5 selected eruptions, if they allegedly passed the threshold testing? What is the temporal resolution of these datasets?
Kind regards,
Giulia Sinnl
Citation: https://doi.org/10.5194/egusphere-2026-3602-RC2
Data sets
Greenland SE2 ice core age scales Saaya Hamamoto, Yoshinori Iizuka, Takuro Aizawa, Kaoru Kawakami, Mai Matsumoto, Sumito Matoba, Hayoung Bong, Kei Yoshimura, Atsushi Okazaki, Laura J. Dietrich, Hans Christian Steen-Larsen, and Ryu Uemura https://doi.org/10.14943/2115.98166
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- 1
The manuscript constructs a monthly-resolved time scale for the Greenland South East Dome II ice core covering the period 1871-2020 CE. The site is among the highest snow accumulation sites in Greenland and therefore uniquely suited for high-resolution studies. The study sets the foundation for interpretation of the highest resolved ice core records from Greenland covering the industrialisation and is thus both timely and important. The manuscript is well written and generally convincing it its argumentation.
I have just a list of minor comments for the authors to consider:
- Considering the pressing issue of global warming and the significant changes currently seen all over the arctic, it is surprising to me that no changes are seen for the SE dome II core in terms of accumulation (Fig. 8) or isotopic warming (Fig. 2 + 5 ). I’m not saying it is wrong, but I think it would be justified to comment on Hörhold et al. (2023) and the trend observed there?
- The authors are carefully comparing their new time scale to that of NEEM-S1, which is fine, but I think it is also relevant to compare to the more recent GICC21 time scale (Sinnl et al., 2022) that is valid for many other Greenland ice cores? GICC21 is mentioned in the manuscript, but there is no comparison or commenting made. For the GICC21 time scale a number of significant ammonium tie points are listed in Sinnl et al., 2022, supplementary folder 3) Tie-points. Are those tie points also present in SE dome II?
- Figure 1 is great, but it is hard to see what exactly is the precipitation at SE-Dome. Maybe you can mention the value in the caption?
- In line 165, a precipitation factor of 1.2 applied for ECHAM6-wiso. Any comment on the reason for this correction? Is it a general issue for the model precipitation over Greenland or is it a local issue, e.g. due to lack of model resolution? If it is a more general issue, it would demonstrate the need for more ice-core based accumulation records to be obtained from Greenland.
- In line 176, the Nye model correction to the accumulation is mentioned. Would be good to mention somewhere how important this correction is for the oldest part of the record, e.g. in terms of percentage change of accumulation.
- In the caption of Figure 2, it would be good to specify which model simulation the red curve shows.
- Comparing the depth and age scales in Fig. 2, it appears there is a large variability in the annual layer thickness for the SE dome cores. Would it make sense to look at the annual layer distribution profile for SE2 and compare it to those of the other cores? I’m thinking along the lines of Fig. 7 in Andersen et al. (2006). Are the SE2 annual layer thicknesses log normal distributed (as we see for many other Greenland ice cores) and is the standard deviation larger for SE2 than for NGRIP as Fig. 2 indicates?
- Around line 240, the visible melt layers in the core are mentioned. The 2012 melt layer is situated in ice corresponding to the month of February. Is this suggesting the melting occurred in February?
- Figure 6 is great, but wouldn’t it make more sense to show the same time period for all the cores, so that we can directly see the better temporal resolution of the SE2 core? E.g to have age on the x-axis rather than depth? The differences shown now for the same depth interval mostly reflects the different snow accumulation at the different sites (as well as thinning)? Maybe you did this already and it was not illustrative for some reason?
- Would a power spectrum comparing the d18O signal of the different cores show us how much better the resolution is for SE2? I’m thinking of something like Bigler et al. (2011), Fig. 7, but in the time domain and for d18O for the different cores. You should be able to resolve much higher frequency signal in SE2 than in the other cores. Just an idea, may not make sense.
- The mentioning of accumulation rates for the various Greenland ice cores in lines 312-315 would be good to have already for the discussion of Figure 6.
- It is mentioned in line 316 that the PCA analysis of the measured seasonal variation is mostly made for evaluating the applicability of the automated layer counting method. However, I would think the analysis is also (or maybe even more so) relevant for understanding the composition of the seasonal signal and maybe also for comparison to model results? How does a similar PCA analysis of the model simulations you are applying for tuning the time scale look like?
- In Fig. 9, again, it is difficult to see the exact position of SE dome, maybe mention the value for SE-dome in the caption ?
- The SE2time2023 time scale is mentioned for the first time in line 426. I think it would make sense to mention this - and if there are other, earlier time scales for the core - already in the introduction? It would also be good to comment on any differences between the two time scales and how important they are.
- In section 3.4.2 is mentioned that 10 volcanic eruptions have been identified in SE II, but only 5 are shown in Figure 12 and applied for the analysis in Figure 13. Please comment also on Katmai 1912 AD that is identified in most other Greenland ice cores (Sinnl et al., 2022, Supplementary folder 3) Tie-points). Do the not-mentioned 5 eruptions follow the same pattern as discussed in Figure 13?
- If you have the time, because you have such high temporal resolution, could it be that you can see a cooling effect of some of the volcanic eruptions in the d18O signal as in Lohmann et al. (2024), Fig. 4d ? Or maybe in the accumulation? I think if you indicate the position of the volcanic eruptions in Fig. 2 (indicate both time of eruption and time of the sulfate spike), it should be quite easy to judge if there is an effect. Likely, you could indicate the position of the melt layers and see if those occurred in ‘warm’ years (Westhoff et al., 2022)? Probably not. Any effects of the large ammonium tie points, if they are related large NH forest fires (Kjær et al., 2022)?
References:
Andersen, K.K., Svensson, A., Rasmussen, S.O., Steffensen, J.P., Johnsen, S.J., Bigler, M., Röthlisberger, R., Ruth, U., Siggaard-Andersen, M.-L., Dahl-Jensen, D., Vinther, B.M., Clausen, H.B., 2006. The Greenland Ice Core Chronology 2005, 15-42 ka. Part 1: constructing the time scale. Quaternary Science Reviews 25, 3246-3257.
Bigler, M., Svensson, A., Kettner, E., Vallelonga, P., Nielsen, M.E., Steffensen, J.P., 2011. Optimization of High-Resolution Continuous Flow Analysis for Transient Climate Signals in Ice Cores. Environmental Science and Technology 45, 4483-4489.
Hörhold, M., Münch, T., Weißbach, S., Kipfstuhl, S., Freitag, J., Sasgen, I., Lohmann, G., Vinther, B., Laepple, T., 2023. Modern temperatures in central–north Greenland warmest in past millennium. Nature 613, 503-507.
Kjær, H.A., Zens, P., Black, S., Lund, K.H., Svensson, A., Vallelonga, P., 2022. Canadian forest fires, Icelandic volcanoes and increased local dust observed in six shallow Greenland firn cores. Clim. Past 18, 2211-2230.
Lohmann, J., Lin, J., Vinther, B.M., Rasmussen, S.O., Svensson, A., 2024. State-dependent impact of major volcanic eruptions observed in ice-core records of the last glacial period. Clim. Past. 20, 313-333.
Sinnl, G., Winstrup, M., Erhardt, T., Cook, E., Jensen, C.M., Svensson, A., Vinther, B.M., Muscheler, R., Rasmussen, S.O., 2022. A multi-ice-core, annual-layer-counted Greenland ice-core chronology for the last 3800 years: GICC21. Clim. Past 18, 1125-1150.
Westhoff, J., Sinnl, G., Svensson, A., Freitag, J., Kjær, H.A., Vallelonga, P., Vinther, B., Kipfstuhl, S., Dahl-Jensen, D., Weikusat, I., 2022. Melt in the Greenland EastGRIP ice core reveals Holocene warm events. Clim. Past. 18, 1011-1034.