the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Jun 2025
A new coastal ice-core site identified in Dronning Maud Land, Antarctica, for high-resolution climate reconstructions to the Last Glacial Maximum
Abstract. High-resolution ice cores from the Antarctic Ice Sheet margin are crucial for reconstructing the climate history of Antarctica and the Southern Ocean. Ice-rise summits with stable positions and substantial snow accumulation can be ideal sites for such ice cores. We surveyed two ice rises at 16° E, at the eastern edge of the Lazarev Ice Shelf. Kupol Verbljud (VER) is an isle at the calving front, and Kamelryggen (KAM) is a promontory landward of VER. Radar survey reveals ice thicknesses of 560 m under VER's summit and 525 m under KAM's summit. The long-term stable englacial features, Raymond Arches, are observed in both ice rises, but while VER's arches are tilted, KAM exhibits vertically-aligned arches within its summit, indicating a more stable summit position. We find KAM's summit area better suited for a long ice core, given its gentler bed slope and simpler ice stratigraphy. Surface mass balance derived from dated reflectors show consistent spatial patterns over recent decades. Using a one-dimensional age-depth model we consider the local ice flow as a combination of two extreme cases: diverging divide flow and shear-dominated flank flow. We determine which combination of these flow regimes best reproduces the mapped englacial radar stratigraphy and use it to estimate the age of ice. We conclude that KAM's summit is well-suited for obtaining a high-resolution ice core record beyond the Last Glacial Maximum with expected ~20 kiloyear-old ice at a depth 80 m above the bed where the resolution is expected to be 2.5 a cm-1.
Competing interests: Co-author Carlos Martin 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: open (until 10 Oct 2025)
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RC1: 'Comment on egusphere-2025-2037', Frédéric Parrenin, 08 Sep 2025
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Review of "A new coastal ice-core site identified in Dronning Maud Land, Antarctica, for high-resolution climate reconstructions to the Last Glacial Maximum" by Goel et al.
This manuscript presents a study of several ice rises in the Dronning Maud Land region, all being accessible from the Indian Maitri station.
While the DJU and LEN ice rises are briefly mentioned, the focus is then made on the more promising KAM and VER ice rises.
For these two rises, a detailed radar survey has been performed.
These radar surveys are used to map the SMB from a shallow horizon and firn cores at the summits.
The deeper horizons show Raymond bumps, characteristic of stable ice rises.
A simple 1D age model is then fitted onto observed isochrones dated by a Lliboutry-type 1D model at the flanks where the flow is better known.
From this 1D model, a 3D mapping of the age can be done and shows that KAM is the most promising site and should hold LGM ice at an acceptable resolution.I enjoyed reading this manuscript and I think it is an important contribution for glaciology and ice core science.
In my opinion, this manuscript should be accepted after a few minor corrections and improvements.General comments:
- The age model used is said to be pseudo-steady, but I have the impression that it is just steady.
The difference between the two just comes from a change of the time variable based on SMB variations (see Parrenin et al., JG, 2006 and Parrenin and Hindmarsh, JG, 2007 for details).
Here, the temporal variations of SMB could be taken into account by using, e.g., the EDML SMB temporal variations.
This would affect the age and resolution of the deepest layer, close to the LGM, where SMB was probably ~2 times smaller.
Numerically, this is really easy to do so I suggest to do it if it has not been done.
- The value of the Lliboutry exponent (p) is taken between 2 and 4. I am not sure where these values come from, so proper references would help.
From the original 1979 Lliboutry article, an estimate of p can be done using the Shallow Ice Approximation and an estimate of the temperature gradient at the base.
If I remember correctly, the p value for Vostok is more around 8.
Not sure what is the temperature gradient at the base here, so the value might be different.
- From the radargrams, it seems Raymond bumps are surrounded by troughs, at least on one side.
Parrenin and Hindmarsh (JG, 2007), showed that horizontal advection of the ice can create these troughs.
Not sure it is the correct explanation here, but at least it could be worth mentioning.
By the way, using a flow tube model like in Parrenin et al. (GMD, in press) and Chung et al. (TC, in press) could be a possible perspective for the modeling exercise to take into account horizontal advection.Minor comments:
- l. 66: Maybe introduce the "LEN" notation here.
- l. 134: Not sure your model is really pseudo-steady, see comment above.
- l. 142: "isn't" -> "is not"
- l. 144: "p values lie between 2-4" -> see comment above
- section 4.1: I am not sure to understand the comparison of this section. It is said in the beginning that the comparison will be done at 0.2H over the bed. Then the comparison is made at 0.12H for DJU and VER and 0.16H for KAM.
- Figure 2: I would rather use dark colours for troughs and light colours for highs.
- l. 407: Should not is be Fig. 1a and 1b instead of Fig. 1b and 1c?
- Figure 3: The labels of the sub-figures do not seem to correspond to the legend. They are also ordered from top to bottom, which is not consistent with Figure 2.
- Figure 6d: There is a model-obs discrepancy, which could be due to horizontal advection (see comment above) or to non-steady features such as varying accumulation pattern.Citation: https://doi.org/10.5194/egusphere-2025-2037-RC1
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