Survival of the Qaidam mega-lake system under mid-Pliocene climates and its restoration under future climates

Scherer, Dieter

doi:https://doi.org/10.5194/hess-24-3835-2020

Articles | Volume 24, issue 7

https://doi.org/10.5194/hess-24-3835-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-24-3835-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 24, issue 7

Research article

| Highlight paper

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29 Jul 2020

Research article | Highlight paper |

| 29 Jul 2020

Survival of the Qaidam mega-lake system under mid-Pliocene climates and its restoration under future climates

Dieter Scherer

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Final revised paper (published on 29 Jul 2020)
Supplement to the final revised paper
Preprint (discussion started on 23 Oct 2019)
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: 'Comments to “Survival of the Qaidam mega-lake system under mid-Pilocene climate and its restoration under future climates” by Scherer', Anonymous Referee #1, 05 Nov 2019
- AC1: 'Replies to Reviewer 1', Dieter Scherer, 06 Nov 2019
RC2: 'Interactive comment on “Survival of the Qaidam Mega-Lake System under Mid-Pliocene Climates and its Restoration under Future Climates”', Anonymous Referee #2, 08 Nov 2019
- AC2: 'Replies to Reviewer 2', Dieter Scherer, 09 Nov 2019
EC1: 'Review comments by referee #3', Bob Su, 09 Jan 2020
- AC3: 'Replies to Reviewer 3', Dieter Scherer, 11 Jan 2020

Peer-review completion

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

ED: Publish subject to minor revisions (further review by editor) (09 Jan 2020) by Bob Su

AR by Dieter Scherer on behalf of the Authors (04 Feb 2020) Author's response Manuscript

ED: Publish subject to revisions (further review by editor and referees) (08 Mar 2020) by Bob Su

ED: Publish subject to revisions (further review by editor and referees) (05 Apr 2020) by Bob Su

AR by Dieter Scherer on behalf of the Authors (11 May 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 May 2020) by Bob Su

RR by Anonymous Referee #2 (27 May 2020)

Suggestions for revision or reasons for rejection

The new version has been improved. I would like to suggest accepting this work if the author can address a major comment and several minor ones below.
Major comment:
I agree that the dependence of precipitation on the change in air temperature and humidity can be physical, as constrained by physical processes in WRF. My point is, however, how evaporation from a mega-lake may alter the dependence of dS (storage change) on meteorological conditions. Current HAR data has included lake evaporation, but the lake area is small and thus its total evaporation amount is small, so the relationship between dS and meteorological conditions is essentially for land. In the mid-Pliocene, the mega-lake area is about 59,000 km^2, as stated in the introduction, which is about 23% of the QB area (254,000 km^2). In such a situation, lake evaporation can be a dominant player of the basin water balance, and current dependence of dS on meteorological conditions in Table 2 is not applicable to the basin scale in the mid-Pliocene. Nevertheless, considering it is applicable to basin land, I suggest the authors to give a semi-empirical analysis through lake water balance, as stated below.
According to water balance of a lake for a long time,
lake evaporation – lake precipitation = runoff into the lake
If we assume the runoff into the lake is approximately the order of magnitude of land water storage in a close basin, as in Table 2, then
Lake area*( lake evaporation – lake precipitation)= Runoff*(basin area – lake area).
We can derive Runoff = Lake area*( lake evaporation – lake precipitation) / (basin area – lake area).
Given basin area=254000km^2, and lake area=59,000km^2 for the mid-Pliocene,
Runoff = 0.3*( lake evaporation – lake precipitation)
Lake evaporation is constrained by energy, and current studies suggest its annual amount is about 800 ~1000m (Lazhu et al., 2016, JGR, doi:10.1002/2015JD024523.; Li et al., 2017, JGR, DOI: 10.1002/2016JD025027).
For the mid-Pliocene, if lake precipitation = 300 mm/year, we can estimate
Runoff=150~210 mm/year.
The derived runoff value is much greater than the estimated dS in Table 2. If lake precipitation is as high as 700 mm/year, the required runoff to sustain the mega-lake is about 30~60 mm/year, which is close to the dS value in Table 2.
If such a high precipitation over the lake is not possible under current climate, then a warmer climate than that assumed here may be needed.
I hope this kind of discussion is helpful to improve our understanding.

Minor comments:
P4, at the end of L101, add “this data is used in the discussion” or similar. I took a long time to see how it is used in section 3, but actually It is used in Section 4.
P6 L163, please confirm the number of 0.25%. Is it not 25%?
P7 L196: Whang et al.. Is this a typo?
P7 L199, it is not true “Tibet tend to warmer but dryer climate”. Overall, the Qinghai-Tibet Plateau is getting warmer and wetter except its southern and eastern edges. See Yang et al. (2014, Global and Planetary Change, 112: 79–91).

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ED: Publish subject to minor revisions (review by editor) (11 Jun 2020) by Bob Su

AR by Dieter Scherer on behalf of the Authors (20 Jun 2020) Author's response Manuscript

ED: Publish as is (26 Jun 2020) by Bob Su

AR by Dieter Scherer on behalf of the Authors (30 Jun 2020)

Short summary

During the Pliocene, the Qaidam Basin on the Tibetan Plateau contained a mega-lake system. During the Pleistocene, it disappeared almost completely. Today, hyperarid climates prevail in the low-altitude parts of the basin. This study reveals that today's mean water balance of the Qaidam Basin is nearly zero and is positive during warmer, less dry years. The results explain how the mega-lake system could survive for a long time in the past and could eventually be restored in the future.