Spatial variability in mass loss of glaciers in the Everest region, central Himalayas, between 2000 and 2015

King, Owen; Quincey, Duncan J.; Carrivick, Jonathan L.; Rowan, Ann V.

doi:https://doi.org/10.5194/tc-11-407-2017

Articles | Volume 11, issue 1

https://doi.org/10.5194/tc-11-407-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/tc-11-407-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 11, issue 1

Research article

|

03 Feb 2017

Research article |

| 03 Feb 2017

Spatial variability in mass loss of glaciers in the Everest region, central Himalayas, between 2000 and 2015

Owen King, Duncan J. Quincey, Jonathan L. Carrivick, and Ann V. Rowan

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Final revised paper (published on 03 Feb 2017)
Supplement to the final revised paper
Preprint (discussion started on 23 May 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 - King et al., TCD-2016-99', Joseph Shea, 23 Jun 2016
RC2: 'not ready for publication', Anonymous Referee #2, 08 Jul 2016
AC1: 'Author response to reviewer comments', Owen King, 09 Aug 2016

Peer-review completion

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

AR by Owen King on behalf of the Authors (09 Aug 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Aug 2016) by Tobias Bolch

RR by Joseph Shea (01 Sep 2016)

Suggestions for revision or reasons for rejection

Review - King et al (tc-2016-99-R1)

Summary:
This is an substantially-improved version of the original manuscript. King et al. have addressed most of the comments given by previous reviewers, and Figure 7 (changes in AAR for different glacier types and temperature scenarios) is a great addition. The manuscript is well-written and will be a valuable contribution to ongoing glacier-climate studies in the region.

General comments:
1. Mass loss calculations: how are missing areas in the SRTM dealt with, particularly in accumulation areas? And why not use the slightly lower and generally more accepted density of 850 +/- 60 kg/m3 (Huss, 2013)?

Also: a mass balance can be calculated for the entire glacier/region, but for vertical profiles (e.g. Figure 5 in the revised manuscript) it must be kept as surface elevation differences - the conversion to mass change can only be done if dynamics are taken into account (or they cancel each other out, as in the case for the whole glacier). As Gardelle et al. note in their 2013 paper: "Note, elevation changes over separate sections of a glacier cannot be treated as mass changes due to the disregard of glacier dynamics."

As a result, mass loss rates cannot be compared for different elevations (P10L15-27). This will need to be treated as elevation differences. And ablation gradients should be 'surface lowering' or 'elevation change' gradients (P11L1-10).

2. Derivation of ELA from mass balance (Sec. 3.7). In the previous version of the mansucript, both reviewers pointed to this as a potentially weak point in the methods. The authors have not provided any additional support for the assumption that the ELA can be determined from geodetic mass balance observations (other than Nuth et al., 2007). I think the method of estimating future ELAs/AARs is useful but the method for current ELA calculation needs to be further justified. Also, as the authors calculate mean geodetic mass balance for 100 m elevation bands to estimate ELA the submergence/emergence velocities again become an issue that needs to be considered.

Specific comments:

Abstract: just a suggestion to shorten to the recommended 100 - 200 words

P2L23: Central Himalayan glaciers have less negative mass balances (as opposed to more stable).

P3L24: clarify - do the 40 largest glaciers comprise 70% of the total glacierized area?

P3L29: New paragraph for Tama Koshi.

P4L1: "The Tama Koshi is a poorly studied catchment..."

P4L3: New paragraph for Pumqu catchment.

P9L25: By definition, lapse rates are positive. I'd personally keep it negative and use 'vertical temperature gradient'.

P11L28: Thakuri et al (2014) also examine smaller glaciers, which might help explain the greater rates of area change.

P12L24: 'elevation change' instead of 'mass loss' (and elsewhere)

P12L26: 'here' - be specific again, e.g. 'north of the divide'

P13L1: Measured precipitation is actually low - suggest 'delivers a large proportion of total annual precipitation'

P13L25: Shrestha et al., (1999)

P14L17: (Barundun et al., 2015)

P14L17: 'Our results'...re-state the regional mass loss estimates here for comparison. A table with the current results and those from previous studies would also be helpful.

P14L27: 'surface lowering' instead of 'mass loss'

P15L26: awkward phrasing. Perhaps: '...suggests large glacier mass losses."

P16L5-120: Expand on Figure 7! E.g. at high-end temperature projections, AARs go to zero and ELAs are above the head of glaciers in the Tama Kosi. Initial response to temperature change is greater for Dudh Kosi...

P18L3. "Projected warming in the Everest region will lead to increased ELAs and, depending on glacier hyspometry, substantial increases in ablation areas.'

Figure 1: Glacier names still too small to read.

Figure 2: Glacier names too small, and are the grey regions on the glaciers areas with no data?

Figure 7: What does each point represent?

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RR by Anonymous Referee #2 (05 Sep 2016)

ED: Reconsider after major revisions (12 Sep 2016) by Tobias Bolch

Dear authors,

I have received the reviews and studied your revision by myself carefully. Although both reviewers differ with the overall recommendation they both point out one major shortcoming which was not addressed: Using a geodetic approach, glacier mass balance can only be calculated for an entire glacier or region. However you used the SRTM DEM which has several data voids. Hence, it needs to be clearly written how you dealt with this problem. You need also provide more information about how you tackled outliers. If these issues are not treated adequately I cannot accept this paper.

In addition, the other reviewers comments I ask you to consider the following:
- Shorten the Abstract: A good word count is 250 words.
- P2, L5: Wrong statement. What is about Alaska? Lease also consider that the % of the volume of the glaciers is much lower than the area.
- L. 22 Eastern Nyainqentanglha is not considred as being part of the Himalaya
- L. 30: Although the sample is quite limited you may think about considering Basnet et al. 2013.
- P. 3, L 17: Hambrey et al. 2008 does only study Khumbu Glacier to my knowledge. Please check.
- P. 4, L. 5: Is it really only terminus recession? Please check.
- L. 13: This number is difficult to interpret without knowing the extent of “Everest region”. Please also consider other publications on glacial lakes in this region, e.g. those by Franco Salerno
- L. 21/23: supraglacial ≠proglacial…
- P. 8, L. 5: Should be 2011.
- Section 4.2: What is about the uncertainty in area and area changes?
- Sections 4.2.2 and 2.3 are rather short. I suggest to combine. A very interesting addition would be to the the hypsometry of the debirs-covered vs. the debris-free glaciers.
- P. 14 L. 5ff: Rather speculative. What is about the influence of the overall topography and debris-cover?
- Section 5.2: What is about Gardelle et al. 2013, Ye et al. 2015, Bolch et al. 2011 (latest period in this study)?
- Section 5.3: You may consider Thakuri et al. 2016, Ann. Glaciol.
- Section 5.4: L. 11 There are also other studies Who measured the velocity. Include at least one more (not necessarily mine) which would make the statement stronger. You may also be interested to read Ragettli et al. 2016 TCD. It is now accepted for TC.
- P. 16, ~L. 20. A word about the estimated distribution of the volume possible?

Please address all comments carefully in the revised version. The revision should contain a response to each of the comments above and the comments from the reviewers and explain how the comment was handled. If you disagree with a comment, please explain why. If the text was modified as a response to a comment, please indicate how the text was modified, including the new text and its position in the manuscript (line numbers) and/or highlight the changes in the manuscript.
I am looking forward to the new version of your manuscript.

Best regards,

Tobias Bolch –Editor TC-

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AR by Owen King on behalf of the Authors (21 Oct 2016) Manuscript

ED: Referee Nomination & Report Request started (03 Nov 2016) by Tobias Bolch

RR by Joseph Shea (24 Nov 2016)

Suggestions for revision or reasons for rejection

King et al - TCD-2016-99-V5.

This is a review of the revised manuscript submitted by King et al (version 5). Below I provide some general and specific comments on both the revised manuscript and the response to reviewers.

General comments:
1) The authors have responded to most of the comments from reviewers 1 and 2. The biggest reviewer concerns about the confusion between mass balance and surface lowering (dH/dT) appears to have been resolved. Figures 5 and 6 show surface lowering rates versus elevation, while overall basin and glacier changes are given as mass change (m w.e./yr). Uncertainty in dH/dT and area change estimates, a large concern from Reviewer 2, have been addressed in section 3.3.

2) However, the authors have disagreed with both reviewers and continue to assert that the elevation where dH/dT = 0 can be used to approximate the equilibrium line altitude (ELA). In their response the authors argue that the ELA should coincide more or less with the elevation where emergence and submergence are equal - but this is not equivalent to the elevation where surface elevation changes are zero! As this disagreement cannot (and should not) be resolved within the current manuscript, perhaps the authors could use the median glacier elevation of the individual glaciers as a proxy of the ELA (e.g. Braithwaite and Raper, 2010), and recalculate their mass changes. If they wanted to compare the median elevation with the elevation where dH/dT = 0 that could be a very useful additional analysis.

Specific comments:
Response-P2: Snowlines reported in Thakuri et al. (2014) should be treated cautiously as they are snapshot only. Transient snowline elevations are (a) difficult to determine due to cloud cover and (b) can vary dramatically at the end of the monsoon season. They do not likely reflect the true glaciological ELA (as noted in Sec. 5.1), and should probably not be used to justify your ELA proxy.

Manuscript-P1L21. "Our results suggest that glacial lake expansion..."

Figure 1: Font sizes are generally still too small to read clearly...

References: Cherkasov et al. reference should include the third author (Hastenrath)

References:
Braithwaite, R.J. and Raper, S.C.B., 2010. Estimating equilibrium-line altitude (ELA) from glacier inventory data. Annals of Glaciology, 50(53), pp.127-132.

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RR by Anonymous Referee #2 (06 Dec 2016)

ED: Publish subject to minor revisions (Editor review) (08 Dec 2016) by Tobias Bolch

AR by Owen King on behalf of the Authors (16 Dec 2016) Author's response Manuscript

ED: Publish subject to minor revisions (Editor review) (23 Dec 2016) by Tobias Bolch

Dear authors,

Thank you very much for the revision. The manuscript can be accepted after the following minor issues have been addressed:

- As recommended you use now the median elevation as a proxy for the ELA. You should however, be a bit more careful when presenting and also discussing the methodology and results. Raper and Braithwaite show that the median elevation is a good proxy for balanced budget ELAs. Nuimura et al. (2015) use the median elevation for comparison different glacier inventories but I think they do not explicitly refer to the ELA. Please check.

- Although frequently used the term “climate warming” is physical not correct. Climate is much more than temperature. I recommend to use “atmospheric warming” or “temperature increase” instead but leave it up to you.

- A minor remark regarding the names of the regions. I’d suggest to name the region you call “Tibetan Plateau” (with glaciers on the northern slopes of the Himalaya) “Pumqu river” to be consistent with the regions of the southern slope of the Himalaya.

- Table 3: Bolch et al. 2011 investigate the periods 1970 – 2007 (not 2008) and also 2002-2007. I suggest to include also the value for the latter period as there is a discussion in the literature of possibly increased mass loss or not.

- References: Please check carefully that all references are in the Copernicus style. I did not check in detail, but the style of the newly added is mostly incorrect.

Please address these comments carefully in the revised version. The revision should contain a response to each of the comments above and the comments from the reviewers and explain how the comment was handled. If you disagree with a comment, please explain why. If the text was modified as a response to a comment, please indicate how the text was modified, including the new text and its position in the manuscript (line numbers) and/or highlight the changes in the manuscript.

I am looking forward to the new version of your manuscript.

Have some nice and relaxing Christmas days and a good start in the New Year,

Tobias

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AR by Owen King on behalf of the Authors (27 Dec 2016) Author's response Manuscript

ED: Publish as is (09 Jan 2017) by Tobias Bolch

AR by Owen King on behalf of the Authors (18 Jan 2017) Manuscript

Short summary

We used multiple digital elevation models to quantify melt on 32 glaciers in the Everest region of the Himalayas. We examined whether patterns of melt differed depending on whether the glacier terminated on land or in water. We found that glaciers terminating in large lakes had the highest melt rates, but that those terminating in small lakes had comparable melt rates to those terminating on land. We carried out this research because Himalayan people are highly dependent on glacier meltwater.