the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Jan 2026
Improved recovery of sub ice shelf bathymetry from gravity data using an isostatic correction: A case study from the Dotson and Crosson ice shelves, West Antarctica
Abstract. Bathymetry beneath ice shelves is challenging to observe yet is vitally important for modelling how ice sheets will evolve into the future. An alternative to direct observation of bathymetry is to invert airborne gravity data for the bathymetric signal. Appropriate gravity data can be collected via remote sensing above the ice shelf and be used to provide an initial estimate of sub-ice-shelf bathymetry, typically at wavelengths of ~5 km and above. However, lateral variations in density associated with the underlying geology can distort the gravity field biassing the results. We show that techniques which tie inversion results to known bathymetry and topography, although solving some of these issues, may be insufficient in the case of large and deep basins lacking centrally located tie points. Using new direct observations of the Dotson and Crosson ice shelves as a case study, we show that gravity inversion for bathymetry can be improved by considering and removing a model of the gravity field due to crustal isostatic compensation prior to inversion. We finally present our updated and improved bathymetric model for the Dotson-Crosson and Thwaites Glacier Ice Shelf system and discuss where our method can be best applied in future.
- Preprint
(2176 KB) - Metadata XML
- BibTeX
- EndNote
Status: open (until 01 Apr 2026)
- RC1: 'Comment on egusphere-2025-6001', Matthew Tankersley & Jörg Ebbing (co-review team), 19 Feb 2026 reply
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 118 | 60 | 18 | 196 | 21 | 27 |
- HTML: 118
- PDF: 60
- XML: 18
- Total: 196
- BibTeX: 21
- EndNote: 27
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
General comments:
This work provides a novel addition to the field of sub-ice shelf bathymetry modelling. It addresses the major limitation of this technique, the effective removal of the often long-wavelength signal associated with crustal gravity effects. I think the paper can be improved with a better explanation or justification of some of the methods, and some more discussion added about the assumptions made and their limitations.
Calculation of the isostatic Moho: I have a few reservations about the methods used to calculate the isostatic Moho model. I'm not entirely sure why the free-air gravity was used with a Bouguer slab correction to define the topography used in the isostatic calculation. Why not just use an initial (interpolated) topography model like BedMap2? I assume the differences would be small, but you would be removing what seems to be the most tenuous step in this process. If you retain the Bouguer slab correction, it would be good to have some more clarity on how you calculated the topography from the Bouguer slab, as I don't follow how you accounted for locations where the topography is a density contrast between rock and water, rock and ice, or rock and air. As the isostatic gravity correction is the main novel concept in this paper, I think a slightly more thorough discussion of the assumptions is required so future users of the method understand the limitations. For example, how does the assumption of no lateral strength affect the results? With some lateral strength (as expected for a small study region), the Moho model would likely be more subdued, and therefore less of the shorter-wavelength gravity signal would be accounted for by the Moho model, meaning the inverted bathymetry model may contain more short-to-mid wavelength features than if no lateral strength is assumed. If your ice shelf basin contained some sediments, how much would this affect the isostatic Moho and the resulting bathymetry?
Gravity processing: It would be nice to have some more details on the gravity reduction. Did you remove the effects of the ice and water loads from the free-air gravity before the inversion, or before the preliminary topography estimate? It would be helpful to understand how the method works to include more figures of the intermediate steps, mainly the isostatic gravity anomaly, but maybe also the preliminary topography and the initial gravity-derived topography. For the various Bouguer calculations, did you use a density of 2670, and if so, why?
Specific comments:
Line 39: bathymetry only dominates for the free-air anomaly, so I would either change gravity to free-air gravity or change dominates to contains.
Line 64 and 68: with "initial" clarify if you are talking about past published inversion (and which ones, Jordan et al 2020?) or the first attempt of your inversion in this paper.
Line 70: possible rewording: which is changing the observed gravity -> which is a component of the observed gravity
Line 71: reword for clarity: The underestimate of the bathymetry suggests that the expected negative gravity anomaly associated with deep bathymetry is being offset by something causing a positive gravity anomaly.
Fig 3: can you include flight lines over the gravity data? For the gravity, since it is a free air anomaly, the sign is important. Could you use a linear diverging colormap (i.e., blue to red) that is centered on 0 and has the same positive and negative limits (-70 to +70 mGal) just like the colormap in Fig 2a. I'd also suggest a linear colormap for the topography in b, the current colormap exaggerates the difference between 0 and 100 m, and 0 m is relatively meaningless in Antarctica since neither groundingline or coastline is at 0 m.
Line 103: It would be good to have additional details on the gravity processing. What was the general flight line spacing, speed, altitude etc. Cross over errors? Levelling procedure. Was the free-air anomaly corrected for the gravity effects of the ice sheet or the water thickness? In typical inversions, the water layer is included in the initial model and therefore accounted for. But with your technique, I don't see where the gravity effect of the water column is accounted for.
Line 147: Maybe replace reference elevation model with starting elevation model for clarity.
Line 165: For such a small region it is harder to justify assuming 0 lateral strength in the lithosphere. Given some lateral strength is expected, this would essentially smooth out your isostatic Moho. A smooth Moho would account for less short wavelength gravity variations, leaving those shortwavelength anomalies within your signal used in the inversion. Therefore a smoother Moho will result in more variation in your topography and vice versa. Due to this, your assumption about lateral strength has a direct effect on the amplitude of your bathymetry variation. By assuming no strength, you are putting much more of the short-wavelength variation into Moho, and therefore less into the bathymetry. While I agree it is a fine assumption, I think this aspect of it is important for you to state.
Line 173: Please describe how you did the Bouguer slab transformation. Did you take free air gravity (not corrected for ice or water) and divided it by (2 pi G (2670 (crust) - 1 (air)). Wouldn't you need to use a spatially variable density contrast, where it is 2670 - 1 on land, and 2670-1040 for regions of topography<0. By using density of air instead of water, you are increasing the density contrast, which should result in more subdued topography, not amplified as I think you stated. Where did you get 1.6 from?
Line 174: The max underestimate is ~400 m, and only in the ice shelf region, as other regions are much better constrained. So does a maximum of 400 m really justify creating a new topography from the Bouguer slab equation?
Fig. 4: replace isostatic moho gravity anomaly with isostatic moho gravity effect.
Fig. 7: for b, you should use the same magnitude of upper and lower limits for the colorbar, and currently it distorts it to make it seem like the grid is dominated by negative values.
Line 284: Change from Moho gravity anomaly to Moho gravity effect, or isostatic gravity effect.
Technical corrections:
Ensure consistent use of either sub ice shelf or sub-ice-shelf in title and text
Line 25: add word "bathymetry": Using new direct bathymetry observation ... to clarify.
Line 75: by basin do you mean ice shelf region?
Line 94: add 'past' before gravity-derived to clarify these are not the inversion results from this paper.
Line 170: Mantle should be lowercase