the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Jun 2024
Impact of short-term atmospheric warming events on the Ice sheet surface and subsurface temperatures of coastal Dronning Maud Land, East Antarctica
Abstract. Short-term, episodic atmospheric warming events over Antarctica have received considerable attention for their direct role in establishing record-high temperatures, surface melting, and their indirect impacts via associated high wind speed and precipitation. However, there is limited knowledge of the effect of these warming events on the ice sheet surface and subsurface temperatures, despite their critical role in firn microphysical properties. Using reanalysis dataset ERA5 and ice sheet surface and subsurface temperature records from an ice core-borehole (71.5 °S, 10.25 °E) from coastal Dronning Maud Land (cDML), we examined the air (T2m) warming, subsurface warming, regional and large scale drivers of 70 short term ice sheet surface warming (ISSW) events covering a period 2014–2018. Out of 70 ISSW events, 60 occurred during periods of strong easterly winds with high snow accumulation and the rest during strong southeasterly winds (katabatic) without any precipitation. The former events resulted from increased downward longwave radiation and warmer air above associated with warm air advection from cyclonic intrusions. With an average frequency of 12 events/year, they established the highest ISSW over the region including the maximum warming of ~11 °C raising the ISST from -34 °C to -25 °C (in 9 days) recorded over the period and penetrating deeper in the snowpack (40–125 cm). Here, the T2m showed a minimum warming of 4.4 °C and a maximum of 24.6 °C, leading the ISSW by two days. The latter events were associated with turbulent mixing from strong, dry and anomalously warm winds from the interior. Although the T2m warmed significantly (4.4–15 °C) without any lead/lag, these events showed modest ISSW (2–5 °C) and shallow heat penetration to snowpack (40–60 cm) but resulted in significant sublimation over the region. Our study suggests that the impact of atmospheric warming events on ice sheet surface and subsurface temperatures varies with meteorological conditions. The frequent occurrence of these events might alter the firn's water-retaining capacity, which becomes crucial when surface melting reaches beyond the grounding line in a continued warming scenario. In the future, it is anticipated that their effects will increase as greenhouse gas concentrations rise.
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RC1: 'Comment on egusphere-2024-1666', Anonymous Referee #1, 08 Jul 2024
This is a manuscript describing sub-surface ice sheet temperatures and their relation to surface temperature extremes, and some of the mechanisms for generating these extremes. It is focused on a region of Dronning Maud Land. I reviewed this paper when it was initially submitted to The Cryosphere and recommended that it was rejected, and the authors take the time to properly improve it and resubmit. I’m afraid that I still think that this ‘revised’ version is full of issues that are beyond a ‘major review’, so I will reject again – fundamentally the revised manuscript comes across as rushed. There is nothing especially wrong with the results or methods, but the structure / organisation / logic of the manuscript and justification of the importance of this work is exceedingly poor. Added to this was that I found the explanation of the Results exceedingly difficult to follow and lacking order and logic (including results situated in the methods section). My judgement is that a reader would genuinely struggle to follow this manuscript due to the aforementioned fundamental issues, and it not at the level expected for The Cryosphere. The authors really need to rethink this paper and produce a focused manuscript on the role of extremes in Dronning Maud Land, and how they affect sub-surface temperatures. The Methods should only focus on the explaining the datasets used. The Results should methodically / systematically explain each Results figure in turn, and not multiple figures at the same time. The Discussion should focus on the implications of the work.
Major comments:
1) The Introduction is poorly written and unconvincing:
- The first paragraph of the Introduction highlights the importance of precipitation, yet this is never a focus of the manuscript. This paragraph also highlights the importance of warming events causing widespread surface melting, yet this is also never a focus of the manuscript as the surface temperatures presented here never approach the melting point (this point is only mentioned in the Discussion). To have such a flaw at the beginning of the paper is genuinely a concern, as to me it highlights that the authors are not able to justify the importance of their work and is misleading to the reader. This paragraph also uses the abbreviation ISST, which has not even been defined at this point. Its also rather puzzling that the March 2022 warming event was not mentioned here (Wille et al., 2024; https://doi.org/10.1175/JCLI-D-23-0175.1).
- The second paragraph of the Introduction is an attempt to highlight the importance of the work, i.e., atmospheric warming events on ice sheet surface temperatures. This paragraph crucially fails to quantify the range of temperatures that affect ‘major subsurface processes like refreezing of meltwater, snow metamorphism, and firn densification’ etc. For example, that melting can occur at temperatures lower than 273.15 K (e.g., Liston and Winther, 2005; https://doi.org/10.1175/JCLI3344.1). Without this information, it is not possible to understand whether such processes are occurring for the events examined in this manuscript. This is never made clear. If such effects to the firn are not occurring in the events examined, then again this is never clarified – if this is the case then the emphasis of the paper could be changed to just focusing on the relationship between ice sheet temperatures and surface warming. Also, the terminology ‘atmospheric warming scenarios’ is used to describe climate projections / future warming, which is not a focus of this work – its rather worrying that not a single author of the manuscript picked this up.
- The third paragraph of the Introduction is a rather ad-hoc description of the causes of warming events over Antarctica. This is not a comprehensive description. For example, foehn induced warming is attributed to the Peninsula and McMurdo Dry Valleys, where they occur in many other locations, even though the references by Zou et al. 2021 used in the first paragraph explaining that this mechanism is also important for the Ross Ice Shelf, as well as Pine Island glacier (https://doi.org/10.5194/tc-17-3041-2023). A major issue is that the although the manuscript is focused on Dronning Maud Land in East Antarctica, this paragraph is trying to include all of Antarctica. This is a similar concern for the fourth paragraph, which again is a rather ad-hoc / muddled explanation of trends in extremes.
- Paragraph #6 of the Introduction mentions that a ‘better understanding of relationship between air temperature, ISST and subsurface temperature is required’. This is actually what the manuscript tries to achieve. But this is not clear / unconvincing.
- The final paragraph gives far too much details on the methodology. What was required was to emphasise the use of measurements form ice core boreholes – yet not a single reference is included that discusses this.
2) Section 2
- This is way too late to start describing Dronning Maud Land. Something similar to the first paragraph of section 2.1 should have been in the Introduction. Temperature extremes, subsurface warming etc over this region should have been the focus of the Introduction, so that there was a proper flow to the manuscript. The poor organisation/structure of the manuscript is a huge concern, and evident in every section, making it very difficult to follow.
- Section 2.1 also includes a description of the ‘climatological’ conditions. But this surely be in the ‘Results’ section and not the ‘Methods’ section, and furthermore the case study period should be explained how anomalous it is compared to the climatological conditions.
- The final paragraph of section 2.1 on general conditions in DML is the type of paragraph that should be in the Introduction, as the entire manuscript should be focused on this region.
- Section 2.3 introduces ERA5, despite it already being used in section 2.1. This is a rudimentary organisation failure. 2m temperature has already been defined as T2m, but full name used here. Manuscripts submitted to journals like The Cryosphere should not have these issues. This sub-section also includes Results (Supplementary Figure 2s), which are not appropriate for a methods section – and who is seriously going to stop here and look at panel 2s in the supplementary information. It then goes on in this section to compare ERA5 v model v AWS …. This makes the manuscript so difficult to read. Added to this the structure of paragraphs / paragraph breaks is grammatically wrong here.
- Section 2.4: SEB defined here, despite being mentioned earlier. Variables are defined as ‘parameters’, which is the wrong terminology. Its ‘meteorological variables’, not ‘parameters’. LHF is related to evaporation, condensation, and sublimation – so that is wrong.
- Section 2.5: Again, describes results. Introduces RACMO2 model in ad hoc fashion, and uses to assess annual accumulation, etc. Again – please see my main comment above. There is nothing wrong with any of these approaches, its just that critically they are so poorly explained in the manuscript.
- Section 2.6: Same issues as those raised above. Supplementary Figure 6s (b) is given here as evidence for day to day variability – but what about the previous SF figures, the other panels? None of this follows any logic.
3) Results. The first results figure is Fig. 3a, despite Figure 2 obviously having some key results – so no logic to the structure. The next section then flits between Figures 2 and 4, as well as 5 and 6, rather than systematically explaining each figure in turn – I/the reader are just completely lost. There is also a very poor understanding of how to structure paragraphs and start a new paragraph.
- section 3.2.1 mentions that a warming of 11.7C occurred, but not possible to understand the impacts on firn as the Intro does not explain this. Even if no affects on firn, the Intro should make these temperature thresholds clear. This is a bewildering explanation of the case study, with dates, values, variables just thrown around and no logical progression to systematically explaining the case study. For example, an explanation of the SEB components is drawn out over three paragraphs, when this should have been properly explained in a single paragraph.
- section 3.3.1 seems to be a carbon copy of 3.2.1, which is just overkill and lacking all subtlety. Too explain two case studies in such detail is too much.
4) Much of this is not a Discussion. Most of it is a recap of the Introduction, results, and methods. A discussion should have included what the results tell us about other parts of Antarctica, and perhaps regions that do see changes to firn due to surface warming. It also mentions that ‘had modest ice sheet surface warming’ (despite ISSW being defined) and that ‘air temperature is only one contributor’ - but fundamentally is it not simply that climatologically these extremes are way below the threshold for temperatures that cause melting / impact firn properties?
Citation: https://doi.org/10.5194/egusphere-2024-1666-RC1 -
RC2: 'Comment on egusphere-2024-1666', Anonymous Referee #2, 17 Jul 2024
This is my second time reviewing this manuscript. In response to the first round of review, the authors included a detailed map of the study region and a diagram of the borehole thermistor setup, and they enhanced the discussion of different radiative processes that may contribute to surface and sub-surface warming. However, I find persistent issues in the organization and presentation of the revised manuscript that make the text hard to follow and the results difficult to understand. These aspects of the text were commented on in the initial review, and it is disappointing that not more was done to reconcile these issues prior to re-submission. In its current form, the manuscript still requires major revisions.
My major concern is that there is not enough attention to detail in the composition of text and figures. Much of the text is out of order – for example, the study region is introduced very late (not even in the introduction), results are presented in the methods section, and the model RACMO2 is not introduced in the reanalysis and model data section. The overall organization of the text is poor and requires major improvements for readers to be able to follow the text with ease. Furthermore, there are issues with the choice of colors and display with most figures that make the data presented difficult to interpret. For example, many figures suffer from small font sizes for axis labels, faint coastlines, dark colors overlaid with patterns that are difficult to see, and colors on the figure exceeding values in the colorbar. Much of the analysis is missing references to individual figure panels, which makes the statements difficult to corroborate and the text hard to follow.
Limitations – I am not an expert in ice sheet surface energy balance (SEB), and so I have refrained from commenting on the aspects of the study that focus on the SEB equation and the interpretation of these components when it comes to surface warming. This is a section of the text that was expanded following the first round of review, and I would recommend that if the manuscript were to move forward in the review process, an expert in this area review the methods and interpretation of results.
MAJOR COMMENTS
P9 L256/257 – If I am understanding the text correctly, the authors state that because RACMO2 outputs an average annual surface mass balance of 10 cm water equivalent per year, they assume the thermistors were buried by 10 cm of accumulation each year. There is no mention of converting water equivalent to snow height, which requires assumptions about snow and firn density at the surface. I want to make very clear that the water equivalent of snow is not the same as changes in snow height, and I have the concern that the authors may be incorrectly calculating the burial rate of thermistors by snow.
Introduction – the manuscript is missing an introduction to the study region, coastal Dronning Maud Land, in this section. The introduction jumps around different regions of Antarctica, giving examples of surface warming trends and specific events, but fails to set readers up with a sense of the regional context for this study. The study region is only introduced in section 2.1 (the data and methods section, which should not contain this background information), and the acronym cDML (coastal Dronning Maud Land) is used but not defined.
Section 2.3 Reanalysis and model data – RACMO2 is also used in the study but is not presented in this section. The model is referred to on P9 L250 without any prior introduction.
Fig 2 – When looking at the wind direction time series in 2e and 2j, I see very little difference in the wind direction between these two events, but the first is promoted as having surface easterly winds and the other is promoted as having surface southeasterly winds. Both events seem to have southeasterly components of the wind. I understand that all the events are divided between these two wind directions, and one is associated with more precipitation and the other with less, but I am missing explicit discussion of what the deciding degree of wind direction was to separate the two types of events. (see additional comments on Fig 2 below)
MINOR COMMENTS
P1 L18 – “T2m” seems like an unnecessary abbreviation, especially for the abstract but also in the main text.
P1 L22-29 – this section is confusing (sentence structure, length, and order)
P2 L45 – ISST is not yet defined in the main text
P2 L61/62 – give time frame/rate of increase for this statement (needs more context)
P3 L85 – “However, for the subsequent period…” – this sentence is confusing
P3 L91-93 – Second sentence does not follow logically from the first. Also, can you be specific about which types of satellite imagery are/are not limited to clear sky conditions. For example, what about microwave imagery?
P3 L106-108 – “One category” – sentence is out of place
P5 L144 – did not introduce ERA5 yet and yet it is used to present a result on temperatures in the methods section
P6 L146-158 – all of this is results, not methods
P8 L217 – specify which grid point
P10 L272-275 / section 2.6 – the description of how surface warming events are identified lacks clarity and specificity. The authors do not explicitly state which thermistor (the top one?) is used to calculate the surface temperature in this methods section. Furthermore, is there a mathematical way of deciding when temperatures decrease or stabilize, or is this done by eye for each time series? Some of this section belongs in the results.
Fig 2 – the shading is difficult to see when figures are printed. Also, are the units mm or mm water equivalent for 2b and 2g?
P11 L302 – “significant” implies statistical significance, maybe refer to as “top ISSW events” instead
P12 L306 – add “austral”
Fig 3a – this figure is extremely difficult to interpret. The vertical blue dashed lines are so tightly spaced it’s overwhelming, and by eye it is difficult to identify the reported temperature increases in the time series associated with these events, because the events are so narrow in the figure.
P13 L326 – don’t use “preferring”
P13 L328 – 20 deg C – looks like 10 deg C in Fig 2a?
P14 L344 – P15 L356 – need to refer to figure panels in analysis
Fig 5 – I can barely see the Antarctic coastlines in this figure. Also the figure caption is far too brief – need to be specific and state what is shown in each panel.
P16 L376-383 – again, need to refer to figures in analysis
Fig 6c and 6d – the figures are extremely hard to read given the color/hatching choices. In 6c the legend overlaps with one of the bars, and the hatching is nearly impossible to see on the dark blue bars, and difficult to see on the red. Not clear what “maximum penetration depth for easterly wind events” means. Also, how is the “difference in warming” (2m temperature – surface temperature) calculated? This needs to be in the methods.
Fig 7 – I am not sure why there are two different colorbars used for these figures, which show the same variables, but in 7a, there are dark red MSLP anomalies that exceed the color values shown in the colorbar.
P19 L440 – be specific about what is meant by “individual biases”
Fig 8 – again, the coastlines are extremely faint in a-c and I’m curious why the vertical velocity was not shown for the other event?
P23 L523-525 – I’m missing a description of how these r values were calculated.
Citation: https://doi.org/10.5194/egusphere-2024-1666-RC2
Status: closed
-
RC1: 'Comment on egusphere-2024-1666', Anonymous Referee #1, 08 Jul 2024
This is a manuscript describing sub-surface ice sheet temperatures and their relation to surface temperature extremes, and some of the mechanisms for generating these extremes. It is focused on a region of Dronning Maud Land. I reviewed this paper when it was initially submitted to The Cryosphere and recommended that it was rejected, and the authors take the time to properly improve it and resubmit. I’m afraid that I still think that this ‘revised’ version is full of issues that are beyond a ‘major review’, so I will reject again – fundamentally the revised manuscript comes across as rushed. There is nothing especially wrong with the results or methods, but the structure / organisation / logic of the manuscript and justification of the importance of this work is exceedingly poor. Added to this was that I found the explanation of the Results exceedingly difficult to follow and lacking order and logic (including results situated in the methods section). My judgement is that a reader would genuinely struggle to follow this manuscript due to the aforementioned fundamental issues, and it not at the level expected for The Cryosphere. The authors really need to rethink this paper and produce a focused manuscript on the role of extremes in Dronning Maud Land, and how they affect sub-surface temperatures. The Methods should only focus on the explaining the datasets used. The Results should methodically / systematically explain each Results figure in turn, and not multiple figures at the same time. The Discussion should focus on the implications of the work.
Major comments:
1) The Introduction is poorly written and unconvincing:
- The first paragraph of the Introduction highlights the importance of precipitation, yet this is never a focus of the manuscript. This paragraph also highlights the importance of warming events causing widespread surface melting, yet this is also never a focus of the manuscript as the surface temperatures presented here never approach the melting point (this point is only mentioned in the Discussion). To have such a flaw at the beginning of the paper is genuinely a concern, as to me it highlights that the authors are not able to justify the importance of their work and is misleading to the reader. This paragraph also uses the abbreviation ISST, which has not even been defined at this point. Its also rather puzzling that the March 2022 warming event was not mentioned here (Wille et al., 2024; https://doi.org/10.1175/JCLI-D-23-0175.1).
- The second paragraph of the Introduction is an attempt to highlight the importance of the work, i.e., atmospheric warming events on ice sheet surface temperatures. This paragraph crucially fails to quantify the range of temperatures that affect ‘major subsurface processes like refreezing of meltwater, snow metamorphism, and firn densification’ etc. For example, that melting can occur at temperatures lower than 273.15 K (e.g., Liston and Winther, 2005; https://doi.org/10.1175/JCLI3344.1). Without this information, it is not possible to understand whether such processes are occurring for the events examined in this manuscript. This is never made clear. If such effects to the firn are not occurring in the events examined, then again this is never clarified – if this is the case then the emphasis of the paper could be changed to just focusing on the relationship between ice sheet temperatures and surface warming. Also, the terminology ‘atmospheric warming scenarios’ is used to describe climate projections / future warming, which is not a focus of this work – its rather worrying that not a single author of the manuscript picked this up.
- The third paragraph of the Introduction is a rather ad-hoc description of the causes of warming events over Antarctica. This is not a comprehensive description. For example, foehn induced warming is attributed to the Peninsula and McMurdo Dry Valleys, where they occur in many other locations, even though the references by Zou et al. 2021 used in the first paragraph explaining that this mechanism is also important for the Ross Ice Shelf, as well as Pine Island glacier (https://doi.org/10.5194/tc-17-3041-2023). A major issue is that the although the manuscript is focused on Dronning Maud Land in East Antarctica, this paragraph is trying to include all of Antarctica. This is a similar concern for the fourth paragraph, which again is a rather ad-hoc / muddled explanation of trends in extremes.
- Paragraph #6 of the Introduction mentions that a ‘better understanding of relationship between air temperature, ISST and subsurface temperature is required’. This is actually what the manuscript tries to achieve. But this is not clear / unconvincing.
- The final paragraph gives far too much details on the methodology. What was required was to emphasise the use of measurements form ice core boreholes – yet not a single reference is included that discusses this.
2) Section 2
- This is way too late to start describing Dronning Maud Land. Something similar to the first paragraph of section 2.1 should have been in the Introduction. Temperature extremes, subsurface warming etc over this region should have been the focus of the Introduction, so that there was a proper flow to the manuscript. The poor organisation/structure of the manuscript is a huge concern, and evident in every section, making it very difficult to follow.
- Section 2.1 also includes a description of the ‘climatological’ conditions. But this surely be in the ‘Results’ section and not the ‘Methods’ section, and furthermore the case study period should be explained how anomalous it is compared to the climatological conditions.
- The final paragraph of section 2.1 on general conditions in DML is the type of paragraph that should be in the Introduction, as the entire manuscript should be focused on this region.
- Section 2.3 introduces ERA5, despite it already being used in section 2.1. This is a rudimentary organisation failure. 2m temperature has already been defined as T2m, but full name used here. Manuscripts submitted to journals like The Cryosphere should not have these issues. This sub-section also includes Results (Supplementary Figure 2s), which are not appropriate for a methods section – and who is seriously going to stop here and look at panel 2s in the supplementary information. It then goes on in this section to compare ERA5 v model v AWS …. This makes the manuscript so difficult to read. Added to this the structure of paragraphs / paragraph breaks is grammatically wrong here.
- Section 2.4: SEB defined here, despite being mentioned earlier. Variables are defined as ‘parameters’, which is the wrong terminology. Its ‘meteorological variables’, not ‘parameters’. LHF is related to evaporation, condensation, and sublimation – so that is wrong.
- Section 2.5: Again, describes results. Introduces RACMO2 model in ad hoc fashion, and uses to assess annual accumulation, etc. Again – please see my main comment above. There is nothing wrong with any of these approaches, its just that critically they are so poorly explained in the manuscript.
- Section 2.6: Same issues as those raised above. Supplementary Figure 6s (b) is given here as evidence for day to day variability – but what about the previous SF figures, the other panels? None of this follows any logic.
3) Results. The first results figure is Fig. 3a, despite Figure 2 obviously having some key results – so no logic to the structure. The next section then flits between Figures 2 and 4, as well as 5 and 6, rather than systematically explaining each figure in turn – I/the reader are just completely lost. There is also a very poor understanding of how to structure paragraphs and start a new paragraph.
- section 3.2.1 mentions that a warming of 11.7C occurred, but not possible to understand the impacts on firn as the Intro does not explain this. Even if no affects on firn, the Intro should make these temperature thresholds clear. This is a bewildering explanation of the case study, with dates, values, variables just thrown around and no logical progression to systematically explaining the case study. For example, an explanation of the SEB components is drawn out over three paragraphs, when this should have been properly explained in a single paragraph.
- section 3.3.1 seems to be a carbon copy of 3.2.1, which is just overkill and lacking all subtlety. Too explain two case studies in such detail is too much.
4) Much of this is not a Discussion. Most of it is a recap of the Introduction, results, and methods. A discussion should have included what the results tell us about other parts of Antarctica, and perhaps regions that do see changes to firn due to surface warming. It also mentions that ‘had modest ice sheet surface warming’ (despite ISSW being defined) and that ‘air temperature is only one contributor’ - but fundamentally is it not simply that climatologically these extremes are way below the threshold for temperatures that cause melting / impact firn properties?
Citation: https://doi.org/10.5194/egusphere-2024-1666-RC1 -
RC2: 'Comment on egusphere-2024-1666', Anonymous Referee #2, 17 Jul 2024
This is my second time reviewing this manuscript. In response to the first round of review, the authors included a detailed map of the study region and a diagram of the borehole thermistor setup, and they enhanced the discussion of different radiative processes that may contribute to surface and sub-surface warming. However, I find persistent issues in the organization and presentation of the revised manuscript that make the text hard to follow and the results difficult to understand. These aspects of the text were commented on in the initial review, and it is disappointing that not more was done to reconcile these issues prior to re-submission. In its current form, the manuscript still requires major revisions.
My major concern is that there is not enough attention to detail in the composition of text and figures. Much of the text is out of order – for example, the study region is introduced very late (not even in the introduction), results are presented in the methods section, and the model RACMO2 is not introduced in the reanalysis and model data section. The overall organization of the text is poor and requires major improvements for readers to be able to follow the text with ease. Furthermore, there are issues with the choice of colors and display with most figures that make the data presented difficult to interpret. For example, many figures suffer from small font sizes for axis labels, faint coastlines, dark colors overlaid with patterns that are difficult to see, and colors on the figure exceeding values in the colorbar. Much of the analysis is missing references to individual figure panels, which makes the statements difficult to corroborate and the text hard to follow.
Limitations – I am not an expert in ice sheet surface energy balance (SEB), and so I have refrained from commenting on the aspects of the study that focus on the SEB equation and the interpretation of these components when it comes to surface warming. This is a section of the text that was expanded following the first round of review, and I would recommend that if the manuscript were to move forward in the review process, an expert in this area review the methods and interpretation of results.
MAJOR COMMENTS
P9 L256/257 – If I am understanding the text correctly, the authors state that because RACMO2 outputs an average annual surface mass balance of 10 cm water equivalent per year, they assume the thermistors were buried by 10 cm of accumulation each year. There is no mention of converting water equivalent to snow height, which requires assumptions about snow and firn density at the surface. I want to make very clear that the water equivalent of snow is not the same as changes in snow height, and I have the concern that the authors may be incorrectly calculating the burial rate of thermistors by snow.
Introduction – the manuscript is missing an introduction to the study region, coastal Dronning Maud Land, in this section. The introduction jumps around different regions of Antarctica, giving examples of surface warming trends and specific events, but fails to set readers up with a sense of the regional context for this study. The study region is only introduced in section 2.1 (the data and methods section, which should not contain this background information), and the acronym cDML (coastal Dronning Maud Land) is used but not defined.
Section 2.3 Reanalysis and model data – RACMO2 is also used in the study but is not presented in this section. The model is referred to on P9 L250 without any prior introduction.
Fig 2 – When looking at the wind direction time series in 2e and 2j, I see very little difference in the wind direction between these two events, but the first is promoted as having surface easterly winds and the other is promoted as having surface southeasterly winds. Both events seem to have southeasterly components of the wind. I understand that all the events are divided between these two wind directions, and one is associated with more precipitation and the other with less, but I am missing explicit discussion of what the deciding degree of wind direction was to separate the two types of events. (see additional comments on Fig 2 below)
MINOR COMMENTS
P1 L18 – “T2m” seems like an unnecessary abbreviation, especially for the abstract but also in the main text.
P1 L22-29 – this section is confusing (sentence structure, length, and order)
P2 L45 – ISST is not yet defined in the main text
P2 L61/62 – give time frame/rate of increase for this statement (needs more context)
P3 L85 – “However, for the subsequent period…” – this sentence is confusing
P3 L91-93 – Second sentence does not follow logically from the first. Also, can you be specific about which types of satellite imagery are/are not limited to clear sky conditions. For example, what about microwave imagery?
P3 L106-108 – “One category” – sentence is out of place
P5 L144 – did not introduce ERA5 yet and yet it is used to present a result on temperatures in the methods section
P6 L146-158 – all of this is results, not methods
P8 L217 – specify which grid point
P10 L272-275 / section 2.6 – the description of how surface warming events are identified lacks clarity and specificity. The authors do not explicitly state which thermistor (the top one?) is used to calculate the surface temperature in this methods section. Furthermore, is there a mathematical way of deciding when temperatures decrease or stabilize, or is this done by eye for each time series? Some of this section belongs in the results.
Fig 2 – the shading is difficult to see when figures are printed. Also, are the units mm or mm water equivalent for 2b and 2g?
P11 L302 – “significant” implies statistical significance, maybe refer to as “top ISSW events” instead
P12 L306 – add “austral”
Fig 3a – this figure is extremely difficult to interpret. The vertical blue dashed lines are so tightly spaced it’s overwhelming, and by eye it is difficult to identify the reported temperature increases in the time series associated with these events, because the events are so narrow in the figure.
P13 L326 – don’t use “preferring”
P13 L328 – 20 deg C – looks like 10 deg C in Fig 2a?
P14 L344 – P15 L356 – need to refer to figure panels in analysis
Fig 5 – I can barely see the Antarctic coastlines in this figure. Also the figure caption is far too brief – need to be specific and state what is shown in each panel.
P16 L376-383 – again, need to refer to figures in analysis
Fig 6c and 6d – the figures are extremely hard to read given the color/hatching choices. In 6c the legend overlaps with one of the bars, and the hatching is nearly impossible to see on the dark blue bars, and difficult to see on the red. Not clear what “maximum penetration depth for easterly wind events” means. Also, how is the “difference in warming” (2m temperature – surface temperature) calculated? This needs to be in the methods.
Fig 7 – I am not sure why there are two different colorbars used for these figures, which show the same variables, but in 7a, there are dark red MSLP anomalies that exceed the color values shown in the colorbar.
P19 L440 – be specific about what is meant by “individual biases”
Fig 8 – again, the coastlines are extremely faint in a-c and I’m curious why the vertical velocity was not shown for the other event?
P23 L523-525 – I’m missing a description of how these r values were calculated.
Citation: https://doi.org/10.5194/egusphere-2024-1666-RC2
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