the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Nov 2025
Assessing the potential for an ice core in the southern Antarctic Peninsula to elucidate Holocene climate history
Abstract. Connecting the West Antarctic Ice Sheet to the southern Antarctic Peninsula, northern Ellsworth Land is a region of enigmatic glacial history now experiencing significant cryospheric change. Large portions of the Bellingshausen-Sea-draining basins have experienced extreme ice thinning and grounding-line change over the satellite observation period. However, the Holocene glacial history of northern Ellsworth Land, which would help to frame the contemporary changes being observed, is poorly constrained. High-resolution ice cores are crucial for reconstructing this past ice-sheet change. We identify a new deep ice-core drilling site at the triple-ice divide point between the Amundsen, Bellingshausen, and Weddell seas (74°34'37" S, 86°54'16" W) that could be utilised to address this knowledge gap. Using a transient ice-thinning model, constrained by shallow-ice-core data and dated englacial radar stratigraphy, we estimate records of accumulation and derive a preliminary age-depth scale for the proposed coring site. Inclusion of dated radar stratigraphy in the model improves our constraints on the long-term climate history, and highlights that these data are not compatible with a steady-state assumption. We also show that there has been a significant change in the accumulation rate regime or ice thickness throughout the Holocene. A deep ice core at this site would provide a climate record up to ∼30 ka with a resolution of 0.58 ka/m at 60 m above the ice-bed interface. An analysis of the model sensitivity to basal melting shows that a record beyond the onset of the Holocene could still be recovered under high basal-melt-rate scenarios. We thus conclude that an ice core at this site would yield a valuable high-resolution climate record and provide precise constraints to reconstruct climatic changes and glacial retreat during the Holocene, to help resolve the onset of the extensive dynamic thinning observed today.
Competing interests: At least one of the (co-)authors is a member of the editorial board of The Cryosphere.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-5467', Frédéric Parrenin, 06 Jan 2026
- CC1: 'Comment on egusphere-2025-5467', Michael Sigl, 10 Feb 2026
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RC2: 'Comment on egusphere-2025-5467', Peter Neff, 24 Feb 2026
The authors present a compelling case for the ABW divide site to provide a full Holocene and late glacial climate record for Ellsworth Land and the Bellingshausen and Weddel Seas (both bodies of water providing primary moisture delivery to the site, per Thomas and Bracegirdle, 2014). The modeling approach here is very reasonable and well-supported by the IRH tracing building on previous work by Bogart and coauthor Bingham, in addition to the existing shallow F10 ice core results. All the data assembled here make a compelling case for the site, although I will note the extraordinary effort required to collect more than 1000 meters of Holocene ice to access a scant ~150 meters of Glacial ice (albeit with annual layers indeed likely interpretable for some part of the very late Pleistocene ice). The authors are appropriately conservative in interpreting depth-age results near the bed, given uncertainty in geothermal heating, melt rates, etc. at depth.
I assume no other potential ice core sites were discussed due to the number of constraints at the F10/ABW site, but it is worth noting that the local triple-dived nearer to the Amundsen Sea (~150km east of Canisteo Peninsula)—although compelling due to its proximity to the fast-changing Amundsen Sea—is home to a subglacial tephra layer visible in 2018 IceBridge RDS data. The presence of such a subglacial feature likely complicates preservation of interpretable snow stratigraphy, at least for a brief period. The authors may wish to note this in their manuscript, and also consider the likelihood and utility of chemical evidence of this layer being identifiable at the ABW site.
Link to 2018 NASA OIB RDS data with (presumed) tephra: https://data.cresis.ku.edu/data/rds/2018_Antarctica_DC8/images/20181116_02/20181116_02_035_1echo.jpg
I hesitate to self-reference, but one important point relating to feasibility/utility of an ice core at ABW is expectations for ice core quality below 400 m given past BAS ice core drilling experience in this zone of increasing bubble pressure and brittle ice fracture. Not only will the top 1000 m of an ABW ice core be restricted to the Holocene (yes, valuable to constrain recent thinning and decreasing snow accumulation) it will also likely exhibit some brittle fracture from 400 or 500 m depth to the bed (e.g. Neff, 2014). This will reduce core quality and the quality of many chemical analyses if mitigating ice core handling procedures aren’t implemented, and then some impacts may still remain. While this isn’t an ice core drilling logistics paper, it is a key factor relating to ice thickness that will degrade the quality of the record.
Additionally, the authors might consider providing a rationale for the particulars of the ABW site with respect to reconstructing past atmospheric composition. What will the characteristics of this site make advantageous for resolving regional discrepancies in greenhouse gas records from Antarctic ice cores? The snow accumulation rate at present may be relatively similar to WAIS Divide, but the shallower ice thickness alters the preservation depth and presence relative to the brittle ice zone so may make ABW more/less advantageous for gas analyses.
I have no specific edits to the paper, I think the methods employed to consider possible depth age distribution for the ABW site are very reasonable and just encourage some broader considerations for the site.
I apologize for the lateness of this comment.
Peter Neff
Minneapolis, Minnesota
February 2026Citation: https://doi.org/10.5194/egusphere-2025-5467-RC2
Model code and software
Model codes and outputs, and plotting code Harry Davis https://github.com/harryjoedavis/ABW_ice_core
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Review of "Assessing the potential for an ice core in the southern Antarctic Peninsula to elucidate Holocene climate history" by H. Davis et al.
This article investigates the potential for an ice core in the Northern Ellsworth Land, at a triple ice divide point between the Amundsen, Bellinghausen and Weddell seas (so called ABW site, 1,200 m ice thickness). This is done with a conjunction of age modeling, radar observations and shallow ice coring. Two IRHs could be traced down to ABW, dated 2.62 and 4.72 ka. Another IRH dated at 6.94 ka could be traced elsewhere in this region but not down to ABW. The model of Martín et al. (2015) was used to evaluate the age-depth relationship at ABW and elsewhere along the radar profiles. It is a 1D model with a steady velocity profile but with a transient surface accumulation forcing. The model is actually able to invert the surface accumulation rate needed to fit some age markers. The accumulation is therefore inverted at ABW for the last ~5 ka with a linear by parts assumptions (there are actually two segments) and before that, it is forced with the Wais Divide scenario. It is found a very strong decrease in accumulation since ~5 ka ago, but the authors also suggest a possible ~600 m Holocene ice thinning explaining these age observations. The maximum age of the ABW profile is also evaluated depending on various estimates of the basal melt rate. It is found that the ABW record probably extends back to at least the onset of the Holocene and possibly back to the Last Glacial Period (LGP), with an acceptable vertical resolution. A spatialisation of this basal age estimate is done along the available radar profiles.
The manuscript is well written and I enjoyed reading it. The figures are generally pleasant and informative, the structure is clear, the references are appropriate.
Major comments
The modeling part is based on the inverse model by Martín et al. (2015). While I appreciate the quality of this model, I think it is only half appropriate in this study. Indeed, as the authors point out, there are two possible explanations of this un-steady age-depth profile: either a change of surface accumulation rate or a change of ice thickness (or a combination of both). While the Martín et al. (2015) model well explores the first option, it is not appropriate to explore the second option. A rough 600 m estimate of a possible ice thickness change is done by keeping the same a-dH/dt term but assuming a is constant. But this is not accounting for the coupling of ice thickness change with ice flow! I put it as a challenge to the authors if they can come up with a more quantitative estimate of ice thickness change, possibly with a figure illustrating possible scenarios.
Minor comments