An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data

Jordan, T. M.; Bamber, J. L.; Williams, C. N.; Paden, J. D.; Siegert, M. J.; Huybrechts, P.; Gagliardini, O.; Gillet-Chaulet, F.

doi:https://doi.org/10.5194/tc-10-1547-2016

Articles | Volume 10, issue 4

https://doi.org/10.5194/tc-10-1547-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/tc-10-1547-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 10, issue 4

Research article

|

20 Jul 2016

Research article |

| 20 Jul 2016

An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data

T. M. Jordan, J. L. Bamber, C. N. Williams, J. D. Paden, M. J. Siegert, P. Huybrechts, O. Gagliardini, and F. Gillet-Chaulet

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Final revised paper (published on 20 Jul 2016)
Supplement to the final revised paper
Preprint (discussion started on 22 Jan 2016)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'review of Jordan et al. (2016, TCD)', Joseph MacGregor, 11 Feb 2016
- AC1: 'Author comments to RC1', Thomas Jordan, 04 Apr 2016
RC2: 'Review: “An ice-sheet wide framework for englacial attenuation and basal reflection from ice penetrating radar data”', Michael Wolovick, 18 Feb 2016
- AC2: 'Author comments to RC2', Thomas Jordan, 04 Apr 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Thomas Jordan on behalf of the Authors (29 Apr 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (19 May 2016) by Kenichi Matsuoka

RR by Michael Wolovick (03 Jun 2016)

RR by Joseph MacGregor (06 Jun 2016)

Suggestions for revision or reasons for rejection

Review of “An ice sheet wide framework for englacial attenuation from ice penetrating radar data” by T.M. Jordan et al.

Joseph A. MacGregor
5 June 2016

This manuscript continues to impress. I have only a few minor editorial comments and suggested edits.

20: A paper that the authors don’t cite but is somewhat related to their undertaking is Schroeder et al. [2016, Geophysics, 81(1), WA35-WA43]. The present authors’ is arguably more sophisticated, but Schroeder et al. [2016] also undertook an analogous strategy of leveraging the reasonably predicted behavior of the attenuation rate to better constrain basal conditions.

25: Mor -> Morlighem et al. [2014], I assume

42: expected to be low

54: uniform: same in space; constant: same in time. Here “uniform” makes more sense than “constant”.

55: “constancy” adds nothing here

59-60: “A central feature of our algorithm is to use an Arrhenius model to estimate the attenuation rate.” Expand upon this statement, because in its present form it does not distinguish the present study clearly from many other studies.

308: 20 measurements

527-9: Here and elsewhere in the manuscript, there is a mild confusion regarding the nature of the variable depth range sampled by MacGregor et al. [2015b]. While we reported depth-averaged temperatures, we made no attempt to restrict our analysis to the approximately isothermal portion of the ice sheet. We simply considered our inferred values to represent the mean temperature within the sampled depth range, even at borehole intersections where the temperature is known not to be isothermal within that range.

652-9: I think this is fair description of the problem and the route selected by the authors is a wise one (evaluation of bed-reflectivity/ice-thickness correlation for each model in Figure 14). While MacGregor et al. [2015b] expected the inferred frequency dependence to be somewhat lower than they reported, I am surprised at how well 1.7 does vs. 2.6 in Figure 14. I cannot reconcile why 2.6 works for the partial-thickness borehole-radar comparison in MacGregor et al. [2015b], but not for the entire ice column as considered here. To do so would require discounting the authors’ otherwise reasonable assumption. Note that, from the perspective of the lab measurements of Stillman et al. [2013] and their interpretation by MacGregor et al. [2015b], the M07 model is “right for the wrong reasons”. While I do not expect it as a revision, I would have preferred for W97C-1.7 to be used with the 3-D temperature models and subsequent analysis, rather than M07.

681: Here I believe W97 is meant, not W97C.

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ED: Publish subject to minor revisions (Editor review) (20 Jun 2016) by Kenichi Matsuoka

AR by Thomas Jordan on behalf of the Authors (23 Jun 2016) Author's response Manuscript

ED: Publish as is (24 Jun 2016) by Kenichi Matsuoka

AR by Thomas Jordan on behalf of the Authors (27 Jun 2016)

Short summary

Ice penetrating radar enables determination of the basal properties of ice sheets. Existing algorithms assume stationarity in the attenuation rate, which is not justifiable at an ice sheet scale. We introduce the first ice-sheet-wide algorithm for radar attenuation that incorporates spatial variability, using the temperature field from a numerical model as an initial guess. The study is a step toward ice-sheet-wide data products for basal properties and evaluation of model temperature fields.