the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Dec 2023
Climate and ablation observations from automatic ablation and weather stations at A. P. Olsen Ice Cap transect, NE Greenland, May 2008 through May 2022
Abstract. The negative surface mass balance of glaciers and ice caps under a warming climate impacts local ecosystems, influencing the volume and timing of water flow in local catchments, while also contributing to global sea level rise. Peripheral glaciers distinct to the Greenland ice sheet respond faster to climate change than the main ice sheet. Accurate assessment of surface mass balance depends on in-situ observations of near-surface climate and ice ablation, but very few in-situ observations of near-surface climate and ice ablation are freely available for Greenland’s peripheral glaciers. The transect of three automated weather and ablation stations on the peripheral A. P. Olsen ice cap in northeast Greenland is an example of this much needed data. The transect has been monitored since 2008, and in 2022 the old weather and ablation stations were replaced by a new standardized setup. In order to ensure comparable data quality from the old and new monitoring station setups, it was necessary to re-evaluate the data collected between 2008 and 2022. This paper presents the fully reprocessed near-surface climate and ablation data from the A. P. Olsen ice cap transect from 2008 to 2022, with a focus on data quality and the usability for ice ablation process studies. The usability and some quality issues are exemplified by using the data in an energy balance melt model for two different years. We showed that the inherent uncertainties of the data resulted in an accurate reproduction of ice ablation for just one of the two years. A transect of three automatic ablation and weather stations of this length is unique for Greenland’s peripheral glaciers and it has a broad scale of usage from input to climate reanalysis to detailed surface ablation studies. The dataset can be downloaded here: https://doi.org/10.22008/FK2/X9X9GN (Larsen and Citterio, 2023). Future refinements will be uploaded as new versions and the continuation of the transect time series are available via https://doi.org/10.22008/FK2/IW73UU (How et al., 2022).
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Status: final response (author comments only)
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RC1: 'Review of essd-2023-444', Anonymous Referee #1, 24 Jan 2024
Review of: „Climate and ablation observations from automatic ablation and weather stations at A. P. Olsen Ice Cap transect, NE Greenland, May 2008 through May 2022 “ by Signe Hillerup Larsen, Daniel Binder, Anja Rutishauser, Bernhard Hynek, Robert Fausto and Michele Citterio
Summary and major points
The manuscript by Hillerup-Larsen end co-authors presents a 14-year meteorological record from a transect of three automatic weather stations on the A.P. Olsen Ice Cap, peripheral to the Greenland Ice Sheet and located on Greenland’s north-east coast. The authors present the 14-year record and data post-processing because AWS design and data processing has recently been changed, necessitating to thoroughly rework the previously collected data.
The authors present a very valuable and unique dataset. The efforts of maintaining the remote installations over such a long time period, under challenging conditions, and making data publicly available, are highly appreciated. It is excellent that the authors post-process the data and clearly demonstrate strength and limitations of the data. While the manuscript addresses all relevant points for a data paper, I do have two major concerns.
Firstly, I suggest revising the structure in Section 3, to a lesser degree in Sections 2 and 4. I suggest structuring Section 3 by describing sensors and the field tasks of all variables first as subsections under Section 3.1 (Subsection 3.2 would become 3.1.1 "Temperature ...", followed by 3.1.2 Radiation measurements, and so on). Any data processing would then be placed in a Section 3.2, which could be entitled "Data Processing" or similar. Currently, the text jumps forth and back between basic field tasks and post-processing. Information on data availability and submission (e,g. to the WGMS) is found at various locations throughout the text. I suggest to first describe the complete data, including post processing and derived parameters, then to state what was done with which data product.
Secondly, I am not convinced by the use case. While I believe that the example is valid, I disagree with the conclusions. The use case shows that measured and modelled melt agree within the bounds of uncertainty, for both years. Likely this would become even clearer if a more complete uncertainty assessment of model input parameters and measured ablation would be done. I am not asking for an uncertainty analysis, but interpretation of the use case needs to be modified. The use case also needs a more thorough discussion.
Detailed remarks
Line 12: Not sure, but abstract is typically written in present tense?
Lines 15 -17: Consider mentioning only one link in the abstract? The two links are slightly confusing.
Line 32: “Data” in plural, in particular as you present various parameters?
Lines 57-62: This appears, at least partially, to be a repetition of statements made earlier, consider merging?
Line 70: Units not in italic.
Line 74: “fullest data record”: unclear, do you mean the most complete record? Or the record with most parameters?
Line 79: "Zackenberg Research station", if a name then capitalize all three words
Line 80: “sunrise”, replace with “end of the polar night”
Lines 82-85: Consider moving to a proposed section that details where and how the data are made available (see major comments)
Line 90: As mentioned in the major comments, the structure needs revision. In the current structure this title mentions something (automatic ablation) that does not appear in the text of 3.1 (it appears then in another section).
Line 92-93: Unclear, do the authors mean that during the melt season the distance to the surface is at its maximum (approx. the height of sensors above the feet of the tripod)? Please rephrase.
Lines 97-98, structure: This statement (“The data is published...”) does not fit with the title of the subsection. Consider adding such a statement to where you describe which data are published where and how.
Figure 2: Poor graphical quality of both photos. Both are underexposed, (b) is strongly underexposed. This can be corrected in image adjustment software.
Table 3: This table appears not to be referenced in the text. Please check all other items too.
Section 3.2 and following: I suggest describing the sensors and the field tasks related to all variables first as subsections under Section 3.1 (3.2 would become 3.1.1 "Temperature ...", followed by 3.1.2 Radiation measurements, and so on). Any data processing would then be placed in a Section 3.2, which could be entitled "Data Processing" or similar. Data submission and publication could go into a section 3.3. I consider it important that the reader first gets a complete overview which products have been generated before it is explained where these are submitted to / published.
Lines 118/119: Sensor replacement: is this the case for other sensors as well? Table 3 suggests yes, but this appears to be mentioned only here.
Line 121: “making us able” -> “enabling us”
Line 166: All sensors are subject to measuring uncertainty. Why is this mentioned here and not in the text for some of the other sensors? Table 3 provides measuring accuracy for all sensors.
Line 168: Height of installation: Information is given for this sensor but not for the others?
Line 182: “is converted and can be converted” - reword.
Line 187: Unclear, what does mean "contains some noise", how does this relate to the 4 cm? Are the 4 cm independent of the pressure levels?
Line 188: how is the start of melt defined?
Lines 196-197: “should be in a state to be used directly for the continued monitoring of the A. P. Olsen transect.” Reword, unclear also with added explanations in the following sentence.
Line 198: “and this is” should this read "and are therefore included"? Even if so, I do not fully understand what is meant.
Figure 4: As with other figures or tables, this item appears before it is referenced in the text.
Line 244/245: “after snow cover” What is meant, after melting of the snow cover? “... non-tilt corrected data could potentially provide information discerning cloud cover variations, but using this should be approached with caution as absolute values are not reliable.” I do not understand. Is this relevant? Consider removing or reword.
Lines 251/252: The years cannot be corrected, consider rewording, making clear what exactly is corrected.
Lines 261/262: Add a very brief justification for these thresholds. Have these thresholds been used elsewhere? Literature sources?
Figure 8: Top of atmosphere radiation is shown as a line in the legend but seems to refer to the grey background shading. How is this to be interpreted? I understand the upper threshold but not the lower one.
Figure 11, x-axis: While described, the axis is confusing. Could this be improved, showing ticks for the start of the individual months and labelling at least one of the months for every year (e.g. 1-7-2011 instead of only 2017)? Maybe a discrete vertical grid would improve readability of the figure.
Line 285: snow -> snowfall
Line 290: Snow-> Snowfall; is -> are
Lines 294/295: “how a point energy budget melt model is evaluated with the observed ice ablation.” Is the model evaluated? Or are the data evaluated using the model? This might be somewhat of an open question. The abstract suggests rather that the model is used to evaluate the data ("We showed that the inherent uncertainties of the data resulted in an accurate reproduction of ice ablation for just one of the two years."), while here you state the opposite.
Line 303: It might be fine to neglect G, but this needs to be justified, at least to a minimal degree, e.g. citation of relevant literature. Same for sublimation further below.
Line 320, citation: Broeke -> van den Broeke.
Line 322: somewhat unclear, maybe instead "day n-1 to day n"?
Line 333: accumulated -> cumulative
Line 325: “..., while the model performs poorly in 2016 for all three roughness factors.” This statement cannot remain as it is. I agree that none of the three match, but the three z0w values do define a range of uncertainty in the parameter, not the only three discrete and possible values. Hence, the question is not whether one of the three calculated melt curves coincides with the measurements, the question is whether the measurements fall within the range of the three simulated melt curves. This is the case for both years.
Line 327/328: “In conclusion...” please reword, consider making two sentences.
Line 331: “all major components” This is not correct as the data do not include the turbulent fluxes which are a key component of the energy balance. They can be calculated from the measurements, hence slightly reformulate: The dataset does not comprise the components of surface energy balance directly, but all meteorological parameters relevant to calculate the surface energy balance.
Conclusions of Section 5; interpretation of the results from Section 5 in the abstract: I do not agree to these conclusions. I understand that this is a data paper and that the use case should be kept short. However, some more discussion is needed. In both years, the measured melt lies well within the range of model output. At the same time, the model relies on various simplifications and there is no appropriate uncertainty calculation, neither in model output, nor in measured melt. The coinciding value for z0w =0.001 in 2009 could be a coincidence. How good is the agreement that one typically expects from an energy balance model, consider citing other studies? Is there a reason that you mainly look at the results from z0w = 0.001? If yes, please justify.
I do not expect the authors to carry out a complete uncertainty analysis like, e.g., Machguth et al. (2008) or Zolles et al. (2019). However, uncertainties in energy balance modelling are considerable and even without any complete uncertainty analysis, modelled and simulated melt overlap in this case. Hence, I am not sure that this analysis tells anything else than that model and measurements agree within their simple bounds of uncertainty (simple referring to the fact that only one parameter was varied within bounds of uncertainty).
Cited literature
Machguth, H., Purves, R. S., Oerlemans, J., Hölzle, M., & Paul, F. (2008). Exploring uncertainty in glacier mass balance modelling with Monte Carlo simulation. The Cryosphere, 2, 191–204. https://doi.org/10.5194/tc-2-191-2008
Zolles, T., Maussion, F., Galos, S. P., Gurgiser, W., & Nicholson, L. (2019). Robust uncertainty assessment of the spatio-temporal transferability of glacier mass and energy balance models. The Cryosphere, 13(2), 469–489. https://doi.org/10.5194/tc-13-469-2019
Citation: https://doi.org/10.5194/essd-2023-444-RC1 -
RC2: 'Comment on essd-2023-444', Anonymous Referee #2, 26 Feb 2024
The reviewed manuscript establishes a quality-assured near-surface climate and ablation data collected by three Automatic Ablation and Weather Stations in northern Greenland. This manuscript focuses on the quality of the data and its usability in the study of ice ablation processes, emphasizing the unique value of this long-term dataset in understanding the response of peripheral glaciers to climate change.
In principle, this work is important as it provides a very valuable long-term series monitoring dataset of Greenland’s peripheral glaciers which are sensitive to climate warming. The manuscript detailly outlines the quality control procedures, assesses data integrity, and provides explanations for data gaps. The dataset of this study would be of interest to the community of geomorphology and cryosphere stakeholders, especially in the context of modern climate change. Overall, I find the paper to be well-organized with clear logic.
My main concern is the readability of the articles, as they can be difficult for readers to follow. Particularly troubling are the diagrams within the manuscript, which lack clear legends and can consequently confuse readers. Additionally, the figure captions are too brief and fail to provide a detailed description of the figures they represent. Furthermore, I have concerns regarding the representativeness of the chosen sampling points. To address this, I suggest including an explanation that details the rationale behind the selection of these specific points.
Overall, I think this is a nice and important work that is suitable for ESSD. I would recommend a minor revision.
Major comment:
While Figure 1 shows the locations of the three AAWSs on the A.P. Olsen ice cap, and Table 1 provides their coordinates, readers may be interested in the broader context of the sites' location within Greenland. It is suggested to add an inset map of Greenland in Figure 1 to show the distribution of the sites.
The melting of marginal glaciers is a major contributor to sea level rise. In addition, what are the other important ecological and social implications of marginal glaciers compared to the Greenland ice sheet? It is suggested to add this in the first paragraph of the introduction to highlight the importance of this study.
Lines 211-214: A more logical explanation is needed here as to why the inability to recharge a battery does not affect temperature observations during the winter months.
Minor comments:
Figure 4: Differences in gradients between sites need to be added to the figure caption in more detail, such as the difference between gray and red curves.
Figure 11: The Zstake-curve of 2013 is significantly different from other years. There is a suspected case of multiple m ice values corresponding to one date, and a reasonable explanation needs to be given.
Figure 12：Resolution is significantly lower than the other figures.
Line 8: Improving the comparability of data from the old and new monitoring stations is mentioned here, but not discussed in detail in the text.
Line 226: How to assess whether data has been affected.
Section 5 shows a successful application of the point energy budget melt model. But in Figure 12, a and b, the deviation of the simulated values from the observed values is not given. It is suggested to add the specific values for the quality assessment.
Citation: https://doi.org/10.5194/essd-2023-444-RC2 -
AC1: 'Response to comments from Referee #1 and Referee #2', Signe Hillerup Larsen, 23 Mar 2024
The comment was uploaded in the form of a supplement: https://essd.copernicus.org/preprints/essd-2023-444/essd-2023-444-AC1-supplement.pdf
Data sets
GlacioBasis Zackenberg - Level 1 data 2008 - 2022 Signe Hillerup Larsen and Michele Citterio https://doi.org/10.22008/FK2/X9X9GN
Model code and software
Point energy balance model Signe Hillerup Larsen https://github.com/GEUS-Glaciology-and-Climate/GlacioBasis_essd_point_energy_balance_model
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