the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Mar 2025
Reconstruction of mass balance and firn stratigraphy during the 1996–2011 warm period at high-altitude on Mt. Ortles, Eastern Alps: a comparison of modelled and ice core results
Abstract. Paleoclimatic glacial archives in low-latitude mountain regions are increasingly affected by melt, which leads to heavy percolation and can remove snow and firn accumulated across months, seasons or even years. Proxy system models, used for improved interpretation of glacial proxies and paleoclimatic reconstructions, generally do not account for melt because they are optimized for sites where snow layer removal by melting is negligible. In this paper, we present a mass balance model applied to the Mt. Ortles drilling site, at 3859 m a.s.l. in the Eastern Italian Alps, with the aim of building a pseudo proxy of atmospheric conditions during the formation of snow layers survived to ablation. This pseudo proxy is useful for improved dating and environmental interpretation of firn layers (<15 m depth), affected by significant melt in the period 1996–2011, which includes the extremely warm summer 2003. Here we show that the model significantly improves the interpretation of the firn stratigraphy. This is fundamental for detecting melted layers and for refining the dating of the core based on traditional annual layer counting of stable isotope and pollen seasonal oscillations.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-729', Peter Neff, 25 Apr 2025
The authors present a novel approach to surmount the challenge of interpreting altered paleoclimate records such as the ice cores recovered from Mt. Ortles. This is a worthy pursuit, as recovering paleoclimate information from fast changing polar and alpine regions must be done before information is obscured outright by increasing temperatures and increased ablation and meltwater alteration of chemical snow and ice stratigraphy.
Carturan et al make a useful advance in understanding the Ortles records, where some time periods in the core are missing due to less snow accumulation and/or increased melt. The approach models the mass balance history and firn stratigraphy at the site from 1996-2011 to reproduce stratigraphy observed in the firn/ice core records and check interpretation of those samples against their model based expectation of what is preserved in the stratigraphy. The model approach appears well calibrated against accumulation as observed at an automated weather station and the drilling site, despite considerable inter annual variability in mass balance.
This modeling approach importantly provides a somewhat independent verification of the annual layer counting based on water stable isotopes and pollen concentrations. This will help going forward in considering uncertainty in the climate interpretation of the pollen and water isotope data, giving some sense of uncertainty due to dating error.
I have few direct concerns about the approach and manuscript, and indeed consider it a valuable contribution to the discipline that we’d do well to apply to similar sites such as our work at Mount Waddington, British Columbia, Canada.
-Peter Neff
Citation: https://doi.org/10.5194/egusphere-2025-729-RC1 -
AC1: 'Reply on RC1', Luca Carturan, 30 May 2025
We are grateful to the reviewer who finds the manuscript a valuable contribution and the procedure we propose useful and applicable to his study sites in Canada.
Citation: https://doi.org/10.5194/egusphere-2025-729-AC1
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AC1: 'Reply on RC1', Luca Carturan, 30 May 2025
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RC2: 'Comment on egusphere-2025-729', Anonymous Referee #2, 08 May 2025
In this study, the authors used their EIS model to record temperatures during snow accumulation within the model and compared this data with ice core information to provide additional information for reconstructing paleoclimate conditions. Considering the amount of melting, creating a simulated core with temperature records during snow layer formation is scientifically useful research that complements actual ice core information. There are a few areas that need additional explanation or comment. Please consider these when you submit your revised paper.
minor commnets
L152 Possible character-encoding issue. Please verify that all special characters and symbols are displayed correctly.
L205 The snowmelt calculation equation here is expressed as a product of radiation and temperature, but in general heat balance calculations, solar radiation and air temperature are added together to estimate snowmelt. According to the author's previous manuscript, Caturan et al (2012), EISmodel has an option to select additive equations. Is there a reason for using multiplicative equations in this study?
L214-221 SLFT states that redistribution is not included, but according to Caturan et al (2012) paper, the redistribution calculations are included in the EIS model. Was this redistribution calculation deliberately omitted from this analysis?
L252-258 If the annual snowmelt is around 50 cm water equivalent, the effect of water infiltration is also present. Although the main focus of this paper is not to consider infiltration, it is expected that adding a discussion of the effects of infiltration somewhere will provide useful information. If the effects of infiltration can be added to the SLFT model, is there a possibility to remove these effects from the model or to estimate the reliability of the agreement between isotope concentrations and SLFT?
L260-261 Even if the annual snowmelt is around 20 cm water equivalent, there is a possibility that water infiltration could affect old snow if there is a lot of snowmelt in one event during that season. Was there any evidence that old snow is not affected?
L271-272 If this sentence refers to the isotope amplitude shown in Fig. 7, it would be better to include (Fig. 7).
L304-305 Can you show the scale of seasonal pollen amount in the centre of Fig. 7?
L330-339 Although this is not mandatory, Fig. 8 is a combination of Figs. 6 and 7, so it would be better to combine them into a single figure.
L417-419 I am not familiar with the behaviour of isotopes, but I have a question that comes to mind. If water is ponded here by a capillary barrier or something similar, is it possible that the isotope concentration will increase?
L420 δ appears to be garbled.
L423-424 I think that pollen is a medium that is less susceptible to the effects of water percolation than soluble substances. Can you explain the author's opinion on the extent to which water movement affects pollen movement?
Citation: https://doi.org/10.5194/egusphere-2025-729-RC2 -
AC2: 'Reply on RC2', Luca Carturan, 30 May 2025
Dear Editor,
we would like to thank the Reviewer for the reviews and suggestions that helped us improving our manuscript.
We have addressed all the points highlighted by the reviewer and we modified the manuscript accordingly. In particular, we added a discussion in Section 5 regarding the percolation of meltwater, as suggested.
In the following, we answer in detail to the specific comments made by the reviewers. The author responses are reported in bold italic right below the reviewers’ comments. Line and page numbers indicated by the reviewer are referred to the submitted paper, whereas our replies refer to the revised version of the paper (which will be uploaded when indicated by the editorial service).
In this study, the authors used their EIS model to record temperatures during snow accumulation within the model and compared this data with ice core information to provide additional information for reconstructing paleoclimate conditions. Considering the amount of melting, creating a simulated core with temperature records during snow layer formation is scientifically useful research that complements actual ice core information. There are a few areas that need additional explanation or comment. Please consider these when you submit your revised paper.Minor comments
L152 Possible character-encoding issue. Please verify that all special characters and symbols are displayed correctly.
Reply: thanks for spotting this, the manuscript has been corrected and checked throughout.
L205 The snowmelt calculation equation here is expressed as a product of radiation and temperature, but in general heat balance calculations, solar radiation and air temperature are added together to estimate snowmelt. According to the author's previous manuscript, Caturan et al (2012), EISmodel has an option to select additive equations. Is there a reason for using multiplicative equations in this study?
Reply: there is no particular reason, we used the ‘native’ algorithm of EISModel (Cazorzi and Dalla Fontana, 1996).
Cazorzi F and Dalla Fontana G (1996) Snowmelt modelling by combining air temperature and a distributed radiation index. J. Hydrol., 181(1–4), 169–187.
L214-221 SLFT states that redistribution is not included, but according to Carturan et al (2012) paper, the redistribution calculations are included in the EIS model. Was this redistribution calculation deliberately omitted from this analysis?
Reply: the SRF (snow redistribution factor) implemented in the EISModel accounts for the spatial variability of snow redistribution, not for its variability in time. Because on Mt. Ortles we apply the model to simulate the temporal evolution of the mass balance at single locations (AWS and drilling site), we are not interested in the spatial variability of snow redistribution. The SRF would be a constant for each of the two locations (SRF is a grid where each pixel has a constant SRF value, depending on local topography). For this reason, it makes sense to lump this factor in the PLIF multiplicative factor applied to precipitation data, which includes the two major processes regulating snow accumulation, i.e. the vertical precipitation gradient and the snow redistribution. We are aware that this is a limitation in our approach, as we write at L442-447 in the revised manuscript (L429-434 in the submitted manuscript). Clarified in the text (L218-219 of the revised manuscript).
L252-258 If the annual snowmelt is around 50 cm water equivalent, the effect of water infiltration is also present. Although the main focus of this paper is not to consider infiltration, it is expected that adding a discussion of the effects of infiltration somewhere will provide useful information. If the effects of infiltration can be added to the SLFT model, is there a possibility to remove these effects from the model or to estimate the reliability of the agreement between isotope concentrations and SLFT?
Reply: as suggested, we added a discussion in Section 5 (lines 386-396 in the revised manuscript) regarding the percolation of meltwater and the feasibility of including its effects on the pseudo proxy developed in our work. Given the complexity of meltwater infiltration processes and their effect on the isotopic records (still topic of research and discussion in the scientific literature), and considering the type of model we are using, we preferred to keep the pseudo proxy as simple as possible in order to reduce the possible sources of uncertainty.
L260-261 Even if the annual snowmelt is around 20 cm water equivalent, there is a possibility that water infiltration could affect old snow if there is a lot of snowmelt in one event during that season. Was there any evidence that old snow is not affected?
Reply: here we mean that the older layers underneath were not melted, we do not mean that they were not affected by percolation. Rephrased for clarity (L262-263).
L271-272 If this sentence refers to the isotope amplitude shown in Fig. 7, it would be better to include (Fig. 7).
Reply: here we are describing the model output variable SLFT (i.e. the pseudo proxy), and for this reason we only refer to figure 6 and not to figure 7 (which shows the real proxies). Rephrased for clarity (L274).
L304-305 Can you show the scale of seasonal pollen amount in the centre of Fig. 7?
Reply: the seasonal pollen amount in the centre of Fig. 7 is reported as principal component scores (left Y-axis). We have modified the figure caption to clarify.
L330-339 Although this is not mandatory, Fig. 8 is a combination of Figs. 6 and 7, so it would be better to combine them into a single figure.
Reply: in our opinion, even if there is some redundancy, it is better to keep these figure separated to ease understanding.
L417-419 I am not familiar with the behaviour of isotopes, but I have a question that comes to mind. If water is ponded here by a capillary barrier or something similar, is it possible that the isotope concentration will increase?
Reply: We would not expect relative isotope concentration changes (fractionation) to occur in the case illustrated by the reviewer as isotopic fractionation typically occurs when solid-liquid-gas phase changes are involved.
L420 δ appears to be garbled.
Reply: thanks for spotting this, the manuscript has been corrected and checked throughout.
L423-424 I think that pollen is a medium that is less susceptible to the effects of water percolation than soluble substances. Can you explain the author's opinion on the extent to which water movement affects pollen movement?
Reply: Even if literature generally reports that pollen has a low susceptibility to water percolation, there is the possibility that extreme melt events (like the 2003 one in the European Alps) might induce significant relocation of pollen. Ewing et al. (2014), for example, report substantial vertical and horizontal pollen transport during a controlled experiment, following snowmelt. Reference added in the text (L437 in the revised manuscript).
Citation: https://doi.org/10.5194/egusphere-2025-729-AC2
-
AC2: 'Reply on RC2', Luca Carturan, 30 May 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-729', Peter Neff, 25 Apr 2025
The authors present a novel approach to surmount the challenge of interpreting altered paleoclimate records such as the ice cores recovered from Mt. Ortles. This is a worthy pursuit, as recovering paleoclimate information from fast changing polar and alpine regions must be done before information is obscured outright by increasing temperatures and increased ablation and meltwater alteration of chemical snow and ice stratigraphy.
Carturan et al make a useful advance in understanding the Ortles records, where some time periods in the core are missing due to less snow accumulation and/or increased melt. The approach models the mass balance history and firn stratigraphy at the site from 1996-2011 to reproduce stratigraphy observed in the firn/ice core records and check interpretation of those samples against their model based expectation of what is preserved in the stratigraphy. The model approach appears well calibrated against accumulation as observed at an automated weather station and the drilling site, despite considerable inter annual variability in mass balance.
This modeling approach importantly provides a somewhat independent verification of the annual layer counting based on water stable isotopes and pollen concentrations. This will help going forward in considering uncertainty in the climate interpretation of the pollen and water isotope data, giving some sense of uncertainty due to dating error.
I have few direct concerns about the approach and manuscript, and indeed consider it a valuable contribution to the discipline that we’d do well to apply to similar sites such as our work at Mount Waddington, British Columbia, Canada.
-Peter Neff
Citation: https://doi.org/10.5194/egusphere-2025-729-RC1 -
AC1: 'Reply on RC1', Luca Carturan, 30 May 2025
We are grateful to the reviewer who finds the manuscript a valuable contribution and the procedure we propose useful and applicable to his study sites in Canada.
Citation: https://doi.org/10.5194/egusphere-2025-729-AC1
-
AC1: 'Reply on RC1', Luca Carturan, 30 May 2025
-
RC2: 'Comment on egusphere-2025-729', Anonymous Referee #2, 08 May 2025
In this study, the authors used their EIS model to record temperatures during snow accumulation within the model and compared this data with ice core information to provide additional information for reconstructing paleoclimate conditions. Considering the amount of melting, creating a simulated core with temperature records during snow layer formation is scientifically useful research that complements actual ice core information. There are a few areas that need additional explanation or comment. Please consider these when you submit your revised paper.
minor commnets
L152 Possible character-encoding issue. Please verify that all special characters and symbols are displayed correctly.
L205 The snowmelt calculation equation here is expressed as a product of radiation and temperature, but in general heat balance calculations, solar radiation and air temperature are added together to estimate snowmelt. According to the author's previous manuscript, Caturan et al (2012), EISmodel has an option to select additive equations. Is there a reason for using multiplicative equations in this study?
L214-221 SLFT states that redistribution is not included, but according to Caturan et al (2012) paper, the redistribution calculations are included in the EIS model. Was this redistribution calculation deliberately omitted from this analysis?
L252-258 If the annual snowmelt is around 50 cm water equivalent, the effect of water infiltration is also present. Although the main focus of this paper is not to consider infiltration, it is expected that adding a discussion of the effects of infiltration somewhere will provide useful information. If the effects of infiltration can be added to the SLFT model, is there a possibility to remove these effects from the model or to estimate the reliability of the agreement between isotope concentrations and SLFT?
L260-261 Even if the annual snowmelt is around 20 cm water equivalent, there is a possibility that water infiltration could affect old snow if there is a lot of snowmelt in one event during that season. Was there any evidence that old snow is not affected?
L271-272 If this sentence refers to the isotope amplitude shown in Fig. 7, it would be better to include (Fig. 7).
L304-305 Can you show the scale of seasonal pollen amount in the centre of Fig. 7?
L330-339 Although this is not mandatory, Fig. 8 is a combination of Figs. 6 and 7, so it would be better to combine them into a single figure.
L417-419 I am not familiar with the behaviour of isotopes, but I have a question that comes to mind. If water is ponded here by a capillary barrier or something similar, is it possible that the isotope concentration will increase?
L420 δ appears to be garbled.
L423-424 I think that pollen is a medium that is less susceptible to the effects of water percolation than soluble substances. Can you explain the author's opinion on the extent to which water movement affects pollen movement?
Citation: https://doi.org/10.5194/egusphere-2025-729-RC2 -
AC2: 'Reply on RC2', Luca Carturan, 30 May 2025
Dear Editor,
we would like to thank the Reviewer for the reviews and suggestions that helped us improving our manuscript.
We have addressed all the points highlighted by the reviewer and we modified the manuscript accordingly. In particular, we added a discussion in Section 5 regarding the percolation of meltwater, as suggested.
In the following, we answer in detail to the specific comments made by the reviewers. The author responses are reported in bold italic right below the reviewers’ comments. Line and page numbers indicated by the reviewer are referred to the submitted paper, whereas our replies refer to the revised version of the paper (which will be uploaded when indicated by the editorial service).
In this study, the authors used their EIS model to record temperatures during snow accumulation within the model and compared this data with ice core information to provide additional information for reconstructing paleoclimate conditions. Considering the amount of melting, creating a simulated core with temperature records during snow layer formation is scientifically useful research that complements actual ice core information. There are a few areas that need additional explanation or comment. Please consider these when you submit your revised paper.Minor comments
L152 Possible character-encoding issue. Please verify that all special characters and symbols are displayed correctly.
Reply: thanks for spotting this, the manuscript has been corrected and checked throughout.
L205 The snowmelt calculation equation here is expressed as a product of radiation and temperature, but in general heat balance calculations, solar radiation and air temperature are added together to estimate snowmelt. According to the author's previous manuscript, Caturan et al (2012), EISmodel has an option to select additive equations. Is there a reason for using multiplicative equations in this study?
Reply: there is no particular reason, we used the ‘native’ algorithm of EISModel (Cazorzi and Dalla Fontana, 1996).
Cazorzi F and Dalla Fontana G (1996) Snowmelt modelling by combining air temperature and a distributed radiation index. J. Hydrol., 181(1–4), 169–187.
L214-221 SLFT states that redistribution is not included, but according to Carturan et al (2012) paper, the redistribution calculations are included in the EIS model. Was this redistribution calculation deliberately omitted from this analysis?
Reply: the SRF (snow redistribution factor) implemented in the EISModel accounts for the spatial variability of snow redistribution, not for its variability in time. Because on Mt. Ortles we apply the model to simulate the temporal evolution of the mass balance at single locations (AWS and drilling site), we are not interested in the spatial variability of snow redistribution. The SRF would be a constant for each of the two locations (SRF is a grid where each pixel has a constant SRF value, depending on local topography). For this reason, it makes sense to lump this factor in the PLIF multiplicative factor applied to precipitation data, which includes the two major processes regulating snow accumulation, i.e. the vertical precipitation gradient and the snow redistribution. We are aware that this is a limitation in our approach, as we write at L442-447 in the revised manuscript (L429-434 in the submitted manuscript). Clarified in the text (L218-219 of the revised manuscript).
L252-258 If the annual snowmelt is around 50 cm water equivalent, the effect of water infiltration is also present. Although the main focus of this paper is not to consider infiltration, it is expected that adding a discussion of the effects of infiltration somewhere will provide useful information. If the effects of infiltration can be added to the SLFT model, is there a possibility to remove these effects from the model or to estimate the reliability of the agreement between isotope concentrations and SLFT?
Reply: as suggested, we added a discussion in Section 5 (lines 386-396 in the revised manuscript) regarding the percolation of meltwater and the feasibility of including its effects on the pseudo proxy developed in our work. Given the complexity of meltwater infiltration processes and their effect on the isotopic records (still topic of research and discussion in the scientific literature), and considering the type of model we are using, we preferred to keep the pseudo proxy as simple as possible in order to reduce the possible sources of uncertainty.
L260-261 Even if the annual snowmelt is around 20 cm water equivalent, there is a possibility that water infiltration could affect old snow if there is a lot of snowmelt in one event during that season. Was there any evidence that old snow is not affected?
Reply: here we mean that the older layers underneath were not melted, we do not mean that they were not affected by percolation. Rephrased for clarity (L262-263).
L271-272 If this sentence refers to the isotope amplitude shown in Fig. 7, it would be better to include (Fig. 7).
Reply: here we are describing the model output variable SLFT (i.e. the pseudo proxy), and for this reason we only refer to figure 6 and not to figure 7 (which shows the real proxies). Rephrased for clarity (L274).
L304-305 Can you show the scale of seasonal pollen amount in the centre of Fig. 7?
Reply: the seasonal pollen amount in the centre of Fig. 7 is reported as principal component scores (left Y-axis). We have modified the figure caption to clarify.
L330-339 Although this is not mandatory, Fig. 8 is a combination of Figs. 6 and 7, so it would be better to combine them into a single figure.
Reply: in our opinion, even if there is some redundancy, it is better to keep these figure separated to ease understanding.
L417-419 I am not familiar with the behaviour of isotopes, but I have a question that comes to mind. If water is ponded here by a capillary barrier or something similar, is it possible that the isotope concentration will increase?
Reply: We would not expect relative isotope concentration changes (fractionation) to occur in the case illustrated by the reviewer as isotopic fractionation typically occurs when solid-liquid-gas phase changes are involved.
L420 δ appears to be garbled.
Reply: thanks for spotting this, the manuscript has been corrected and checked throughout.
L423-424 I think that pollen is a medium that is less susceptible to the effects of water percolation than soluble substances. Can you explain the author's opinion on the extent to which water movement affects pollen movement?
Reply: Even if literature generally reports that pollen has a low susceptibility to water percolation, there is the possibility that extreme melt events (like the 2003 one in the European Alps) might induce significant relocation of pollen. Ewing et al. (2014), for example, report substantial vertical and horizontal pollen transport during a controlled experiment, following snowmelt. Reference added in the text (L437 in the revised manuscript).
Citation: https://doi.org/10.5194/egusphere-2025-729-AC2
-
AC2: 'Reply on RC2', Luca Carturan, 30 May 2025
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- 1
Luca Carturan
Alexander C. Ihle
Federico Cazorzi
Tiziana Lazzarina Zendrini
Fabrizio De Blasi
Giancarlo Dalla Fontana
Giuliano Dreossi
Daniela Festi
Bryan Mark
Klaus Dieter Oeggl
Roberto Seppi
Barbara Stenni
Paolo Gabrielli
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3951 KB) - Metadata XML