the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Nov 2024
Towards ice core sampling by subsea robotic vehicles
Abstract. Ice coring has developed into one of the most frequently used sampling methods across cryospheric sciences. Sea ice, firn and glacial ice are sampled using a range of different coring systems. These systems can retrieve core samples with lengths ranging from several cm to tens of meters when operated by hand or drilling machines, while specialized coring systems have retrieved cores from Antarctica’s ice caps with a length of over 3 km. In the last decade more robotic subsea vehicles like remotely operated vehicles (ROV) and autonomous underwater vehicles (AUV) have ventured into polar waters beneath sea ice and ice shelves, but retrieval of ice samples from the sub-ice environment has not been achieved on a regular basis. Other geophysical investigation methods such as push core sediment coring and rock drilling have been successfully adapted for subsea robotic vehicles. Hence the purpose of this work is to investigate the feasibility of adapting the techniques of retrieving short ice cores from sea ice and glacial research to the subsea environment. We successfully demonstrate the retrieval of an ice sample in a laboratory setting using traditional ice coring systems in conjunction with a subsea manipulator arm. We discuss challenges and further improvements to our experiments towards enabling reliable ice sampling in the subsea environment using generic tooling readily available on subsea vehicles. In conclusion, ice core sampling in the subsea environment seems feasible using industrial work class manipulators particularly when cartesian inverse-kinematic control is available.
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RC1: 'Comment on egusphere-2024-3358', Anonymous Referee #1, 23 Mar 2025
Katlein describes initial coring results from attaching two ice core hand auger drill systems to manipulator arm. He shows that core retrieval can be successful and that a key aspect is keeping the coring axis stable. This is very preliminary work and is a first step towards subsea ice coring.
I found the title to be misleading, "Towards ice core sampling by subsea robotic vehicles" - there is nothing "subsea" in the maunscript. The tests are done on a workbench with no water. A more accurate title would be "autonomous" rather than "subsea" as the manipulator arm could be mounted anywhere - on ice, in water, on the moon (mixed ice/rock), etc. Given the interest in coring on the moon, Mars, and ice moons, I'm surprised that work doesn't already exist in this area, although I admit that I am unfamiliar with it. (https://www.nature.com/articles/d41586-025-00597-z)
The manuscript is missing two key aspects. First, the ice core drill tests should be done in temperate ice such that meltwater can affect the coring. Mechanical coring in temperate ice is much more challenging than in cold ice. Tests should be easily performed and will allow complications of binding to be analyzed.
Second, the description of why subsea drilling is of interest should be greatly expanded. What is the science motivation for this? AWI is full of glaciologists of all types and I'm sure it would take little coaxing to help write a compelling introduction that addresses the sea ice, ice shelf, and iceberg scientific questions that would be addressed with subsea cores.
I would also like to a discussion of the challenges in stabilizing coring in a subsea environment. Given the identified importance of keeping the coring axis unchanged, doing so with a subsea vehicle will be particularly challenging. This work should discuss a path forward for that aspect (i.e. he doesnt' need to do, but he should talk about it).
With the additions of a more complete scientific introduction and the temperature ice tests (and their implications), this work will a nice contribution and starting point for subsea ice coring.
A few other notes:
The amount of references is lacking with only 12. In addition to increasing the scientific motivation, I encourage reading the planetary literature since autonomous ice coring is a significant activity.
Citation: https://doi.org/10.5194/egusphere-2024-3358-RC1 -
RC2: 'Comment on egusphere-2024-3358', James Veale, 15 May 2025
General Comments
This contribution presents a novel investigation into the feasibility of sampling ice cores from beneath ice shelves. It proposes pairing traditional hand ice coring drills with underwater vehicles (ROVs and AUVs). The methodology is well described and results – although largely qualitative – are clear, as is the overall presentation of the manuscript.
Although the work as described is introductory in nature, the community would benefit from its publication. The idea is worth sharing, and the results do warrant further work in this area. I would like to see future testing with an improved setup incorporating an ROV in a test pool environment. I believe the editors of GI are best positioned to decide if the manuscript represents a substantial enough contribution to be published as a short communication or full paper.
I recommend the publication of this contribution, subject to fleshing out with expanded discussion and minor revisions to address the points listed below. I hope these comments will aid in its successful publication.
Specific Comments
- L.29: Evidence of prior scientific interest in sampling ice from the bottom of ice shelves is presented here, but I would like more detail of why there is scientific interest. What are we hoping to learn from these samples? Perhaps the benefit of this sampling method is the opportunity to complement other ROV-based sampling?
- L.76: This is not necessarily a comparison appropriate for assessing available versus required torque. From experience, surface hand drilling requires the torque available from using two arms and would not be possible by the torque available from a single hand/wrist – this would be especially true when cutting solid ice rather than firn.
- L.128: Discussion of available wrist torque (and presentation in Table 1) is good, but it would benefit from reference to known or modelled cutting torque requirements which are available in ice coring literature. Comparing available torque to required torque provides a more robust analysis of feasibility. It would also strengthen the conclusion that commercially available manipulator arms are suitable for a coring process (L.158-159).
- L.135: The discussion section could additionally benefit from discussion of drilling into salt water saturated ice. This was not tested in the described work and may have a significant impact on the drilling process, so it is worth addressing as an area where further exploration is needed.
- L.140: In discussion of controlling the manipulator arm, I would have expected discussion of the limitations of the experimental setup in assessing this. Strapping the arm to a rigid surface is quite different to operating on a vehicle with its own 6 degrees of freedom. Does the manipulator arm’s cartesian inverse-kinematic control account for the motion of the vehicle itself? If not, can the vehicle dynamically hold its position relative to the ice precisely enough to ensure a fixed axis of coring progression while drilling is ongoing? I do not doubt this is achievable, but it would be good to address this as a challenge in the paper.
- L.164: The inclusion of video supplement material is excellent and benefits the contribution significantly, allowing the reader to observe the process and compare their observations to that of the paper.
Technical Corrections
The following technical corrections are suggested to improve clarity of the written language.
- L.28: Rephrase. E.g. “While obtaining ice samples starting from the top surface is a common procedure, ice sampling from the subsea environment is less common.”
- L.42: Rephrase. E.g. “… only a principle of easy operation building on existing vehicle components …”
- L.48: Rephrase. E.g. “As a small coring system comparable in size to a typical sediment push corer …”
- L.106: This approach is commonly referred to as reducing the cutting ‘pitch’, referring to it by this name here may improve clarity.
- L.124: Rephrase. E.g. “… to limit drilling toque, and compensated by …”
- L.130: The reader may benefit from reference to the supplied video supplement here.
- L.147: What is [12] referencing - Sivčev et al., 2018b; Hildebrandt et al., 2008 ?
- L.154: Rephrase. E.g. “… sufficient scientific value remains. Further investigation is required into how best to retrieve samples after an ROV dive, how long they can be conserved during a dive, and which processing methods must be developed to achieve this.”
- Table 1: Missing heading on column 2, needs column width changes and other formatting for readability, Torque units Nm not NM.
Citation: https://doi.org/10.5194/egusphere-2024-3358-RC2
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