Brief communication: Glacier run-off estimation using altimetry-derived basin volume change: case study at  Humboldt Glacier, northwest Greenland

Gray, Laurence

doi:https://doi.org/10.5194/tc-15-1005-2021

Articles | Volume 15, issue 2

https://doi.org/10.5194/tc-15-1005-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-15-1005-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 2

Brief communication

|

25 Feb 2021

Brief communication |

| 25 Feb 2021

Brief communication: Glacier run-off estimation using altimetry-derived basin volume change: case study at Humboldt Glacier, northwest Greenland

Laurence Gray

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Final revised paper (published on 25 Feb 2021)
Supplement to the final revised paper
Preprint (discussion started on 04 Sep 2020)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of Gray, Brief Communication...', Anonymous Referee #1, 23 Oct 2020
- AC1: 'Response to reviewer 1', Laurence Gray, 01 Dec 2020
RC2: 'Review of tc-2020-220', Anonymous Referee #2, 12 Nov 2020
- AC2: 'response to reviewer 2', Laurence Gray, 01 Dec 2020

Peer-review completion

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

ED: Publish subject to revisions (further review by editor and referees) (14 Dec 2020) by Kenichi Matsuoka

AR by Laurence Gray on behalf of the Authors (15 Dec 2020) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (21 Dec 2020) by Kenichi Matsuoka

RR by Anonymous Referee #1 (26 Dec 2020)

RR by Anonymous Referee #2 (04 Jan 2021)

Suggestions for revision or reasons for rejection

Thanks for your edits in response to my first set of comments. I'd just like to revisit my comments about the surface-elevation losses during the summer. Even after the revisions from version 1, the manuscript implies that the only reasons why the surface would have decreased in height during the summer would be runoff or firn-densification anomalies. It is completely normal for the surface height to decrease during the summer, simply due to the reduced accumulation during the summer not keeping pace with ice flow. What is unusual in this case is the magnitude of the changes. I think the approach of removing the summers from the mass-change total is reasonable in this case, but it's important to say why the correction is being made. After the sentence "Consequently, the anomalous height decreases in this area can be linked to the unusually warm summers in 2012, 2015 and 2019." I'd recommend adding something like: "These decreases are much larger than would be expected due to the normal reduced accumulation during the summer."

Towards the end of the paragraph, Dr. Gray says:
"When calculating the volume change to mass change I assume, therefore, that the height losses of 0.42 ±0.08 m (2012), 0.45 ±0.08 m (2015) and 0.4 ±0.08 m (2019) were due to firn densification and I correct the yearly volume change accordingly."

I think it would be good to account for the changes by modifying the mass associated with the changes, rather than by modifying the volume change-- CRYOSAT-2 presumably measured the volume change correctly, but Dr. Gray's insight here is that the mass change does not reflect a change in the amount of ice present, but rather a change in the amount of air.

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ED: Publish subject to technical corrections (14 Jan 2021) by Kenichi Matsuoka

Short summary

A total of 9 years of ice velocity and surface height data obtained from a variety of satellites are used to estimate the water run-off from the northern arm of the Humboldt Glacier in NW Greenland. This represents the first direct measurement of water run-off from a large Greenland glacier, and it complements the iceberg calving flux measurements also based on satellite data. This approach should help improve mass loss estimates for some large Greenland glaciers.