Reconstructed Centennial Mass Balance Change for Golubin Glacier, Northern Tien Shan

Round 1

Reviewer 1 Report

 

Please find my comments and suggestions for the authors in the annotated pdf

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for the good feedback and minor comments. We accounted for all changes as proposed by the reviewer and resign from uploading a point-by-point answer, since the corrections only addresses style or English corrections. We hope this meets the reviewer’s expectation and would like again to thank for the positive feedback on our article.

Reviewer 2 Report

This manuscript presents a reconstruction of annual mass balance time series on Golubin at the centurial scale, using multisource data and methods, based on repeated meteorological analyses, current and historical glaciological measurements, and observations of length change. The authors find a shift to a more negative/less positive regime with time, with a steepening of the ablation and accumulation gradients, especially for the past two decades. This result provides evidence for the first time of changes in the glacier regime of Golubin. This reconstruction is interesting and  meaningful to enhance our understanding of glacier changes in High Mountain Asia. The manuscript is also well recognized, and its figures are important and easy to follow. Thus, it deserves publication in Atmosphere. However, there are different points of the paper that require some explanation from the authors, and I do have some feedback that can be used to improve the paper:

1. There is a spelling error in the title of the manuscript, misspelled Balance as Malance.

2. Line 59, Whether there is any difference between manually delineated glacier outlines data and data before 1962, the accuracy of data needs to be explained.

3. What is the significance of Figure 4 in the passage? And Figure 4 also lacks trend lines and so on.

4. Section 2, description of data and data sources are not clear and detailed enough.

5. Line 67, only the Alplager weather station was used in this study, whether it would make a difference to the results.

6. Line 105-108, I do not understand the SMB interpolation method, please further explain how you do SMB interpolation.

7. Some of the details: (1) line 61, I judge that 1990 should be changed to 1900 from the context; (2) In Figure 2, the text marked on the figure is too small; (3) The abbreviation TAP is not marked in the title of Figure 4.

Author Response

 

We thank the reviewer for the good feedback and minor comments. We tried to account for all changes proposed by the reviewer. Below you find the point-by-point answer to the reviewer’s comments and the relevant section of the paper in “ ”:

 

1. There is a spelling error in the title of the manuscript, misspelled Balance as Malance.

We corrected for the spelling mistake.

2. Line 59, Whether there is any difference between manually delineated glacier outlines data and data before 1962, the accuracy of data needs to be explained.

We added uncertainty statement to the outlines used.

“Uncertainties are expected to be similar for the different data sources and to range withing 5\% to 10\% of the total glacier area Paul et al., 2013.”

3. What is the significance of Figure 4 in the passage? And Figure 4 also lacks trend lines and so on.

We moved the figure down in the text and added the trendlines. We highlighted in caption the use of this data and improved the description.

“Bias corrected ERA20C Mean Annual Air Temperature (MAAT) and Total Annual Precipitation (TAP) for the study area. The time series is used to run the mass balance model.”

4. Section 2, description of data and data sources are not clear and detailed enough.

We added details and tried to clarify the data and their sources. We also provide all the references belonging to the different datasets and stated how we obtained the data.

“Historical seasonal mass balance measurements (Figure 2) are available from the World Glacier Monitoring Service (WGMS) from 1968/69 to 1993/94 (WGMS 2021, Figure 2). This data collection contains winter, summer and annual glacier-wide mass balances as well as the mass balance for each elevation bin for Golubin. For more details please refer to WGMS. In 2010, glacier monitoring was reestablished Hoelzle et al., 2017. The modern monitoring network consists of 15 ablation stakes and 3 snow pit sites in the accumulation zone (Hoelzle et al., 2019, Barandun et al., 2020). All point measurement as well as annual glacier-wide mass balances and the mass balance for each elevation bin are accessible through the WGMS. In 2013, an automatic meteorological station and two automatic cameras for snowline monitoring were installed near the glacier (Schöne et al., 2013, Hoelzle et al., 2017). This data is accessible on an open-data platform (http://sdss.caiag.kg/sdss). Camera images are taken 6 times a day and meteorological data have 5min intervals. We used the Shuttle Radar Topography Mission (SRTM, Jarvis et al., 2018) digital elevation model (DEM) for the model runs. Glacier outlines used for modeling were manually delineated from 1962 to 2018 from aerial photographs and WorldView-2 that were available to the authors and from freely accessible Landsat and Sentinel-2 satellite images. Prior to 1962, outlines were obtained from Venukov, 1861, Aizen et al., 1988 and Aizen et al., 2006. Uncertainties are expected to be similar for the different data sources and to range withing 5% to 10% of the total glacier area Paul et al., 2013. Glacier outlines were available or generated for 1861, 1883, 1905, 1927, 1949, 1955, 1962, 1967, 1972, 1975, 1976, 1977, 1978, and 1989 and annually after 1990. For years with no observations, we used the outline of the year dating closest to the modeled year. Glacier length change data were obtained from the WGMS. The observed Golubin glacier length change is available since 1861, with a 20-year step between subsequent measurements until the mid 20th century and more frequent after that. We did not adjust the glacier thickness. In the Ala-Archa Valley, the Alplager weather station --located at an altitude of 2145 m a.s.l.-- provides daily temperature and precipitation measurements from 1980 to present. This data was provided by the KyrgyzHydromet. Meteorological reanalysis data were used to complete the meteorological time series needed as input data to drive the mass balance model. We used the daily ERA20C reanalysis data (Poli et al., 2016) at the 0.125° resolution extracted at the Golubin location. For consistency we only used direct meteorological observations from the Alplager station for bias correction and model forcing.”

 

5. Line 67, only the Alplager weather station was used in this study, whether it would make a difference to the results.

The Alplager weather station was used to debias the ERA20C data. We have run the model with both data set and compared the results for which both datasets are available. The difference was interpreted as uncertainty related to the meteorological input. This is described in the Subsection “Model Mass Balance Uncertainty”.

6. Line 105-108, I do not understand the SMB interpolation method, please further explain how you do SMB interpolation.

We clarified.

“For this homogenization, we applied the approach used in Huss et al., 2008. Thereby, a mass balance model is used as an interpolation tool to obtain SMB values for each grid cell at daily temporal resolution from in situ field data. With the model spatially distributed accumulation and ablation processes can be better captured when extrapolating direct observations using physical relations. With the mass balance model we furthermore provide mass balances at the end of the mass balance year. Thus, modelled distributed mass balances represent the direct observations as closely as possible. This method has been widely-used in literature (Huss et al 2008, 2009; Barandun et al., 2015, Kronenberg et al., 2016) and details can be found in Kenzhebaev et al, 2017.”

7. Some of the details: (1) line 61, I judge that 1990 should be changed to 1900 from the context; (2) In Figure 2, the text marked on the figure is too small; (3) The abbreviation TAP is not marked in the title of Figure 4.

We corrected for this also following the comments of reviewer 1.