the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Jun 2023
Assessing the potential for ice flow piracy between Totten and Vanderford glaciers, East Antarctica
Abstract. The largest regional drivers of current surface elevation increases in the Antarctic Ice Sheet are associated with ice flow reconfiguration in previously active ice streams, highlighting the important role of ice dynamics in responding to climate change. Here, we investigate controls on the evolution of the flow configuration of the Vanderford and Totten Glaciers – key outlet glaciers of the Aurora Subglacial Basin, the most rapidly thinning region of the East Antarctic Ice Sheet. We review factors that influence the ice flow in this region, and use an ice sheet model to investigate the sensitivity of the catchment divide location to thinning at Vanderford Glacier associated with ongoing retreat, and thickening at Totten Glacier associated with an intensification of the east-west snowfall gradient. The present-day catchment divide between the Totten and Vanderford Glaciers is not constrained by the geology or topography, but is determined by the large-scale ice sheet geometry and its long-term evolution in response to climate forcing. Furthermore, the catchment divide is subject to migration under relatively small changes in surface elevation, leading to ice flow and basal water piracy from Totten to Vanderford Glacier. Our findings show that ice flow reconfigurations do not only occur in regions of West Antarctica like the Siple Coast, but also in the east, motivating further investigations of past, and potential for future, ice flow reconfigurations around the whole Antarctic coastline. Such modelling of ice flow and basal water piracy may require coupled ice sheet thermomechanical and subglacial hydrology models, constrained by field observations of subglacial conditions. Our results also have implications for ice sheet mass budget studies that integrate over catchments, and the validity of the zero flow assumption when selecting sites for ice core records of past climate.
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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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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-872', Anonymous Referee #1, 21 Jun 2023
Review of “Assessing the potential for ice flow piracy between Totten and Vanderford glaciers, East Antarctica”. This paper uses an ice sheet model (ISSM) to study the impact of changing surface elevation on ice and water flow between the Totten and Vanderford glaciers. The changes in surface elevation are not model predictions, but rather reasonable forcing parameters, allowing the impact of such changes to be assessed. The authors find that a proportion of ice and water flow can be switched from Totten to Vanderford Glacier, with the most significant changes driven by increasing the elevation within the Totten Glacier catchment. The authors indicate that these findings are significant as they show that water and ice piracy are possible within East Antarctica. The impact of such piracy on ice flow was not considered by this study, but is put forward as an important factor to be included in future models of the region.
I found the paper clear and well written and that the conclusions are supported by the data and model outputs.
I have a number of minor comments/suggestions which I feel may help the reader to better understand the paper.
L20-21 states “which contains approximately 7m of global sea level equivalent (Morlighem et al., 2020) of which 3.5m is grounded below sea level”. This is a little confusing, what people want to know is what is the actual sea level rise they could experience - maybe split out the end of the sentence to say, "As much of the catchment lies below sea level, the effective impact of total deglaciation of this region would be at least 3.5m of global sea level rise".
L24 states “Paleoclimate evidence suggests markedly reduced ice volumes in the ASB….” Being picky - do you mean "Ice sheet models driven by realistic temperatures derived from paleoclimate evidence.....". Not sure that Paleoclimate evidence can directly suggest reduced ice volumes. Paleo sea-level records would suggest reduced ice volumes, but are hard to attribute to specific basins. Paleoclimate observations close to the ASB/WSB ect showing elevated temperatures could be considered more direct paleoclimate evidence for ice free areas, if so this could be stated.
L37 to L46 I would flag that the work referred to in this paragraph was carried out on the Siple Coast. Later in the paragraph when the authors state “modelling of this system” they could say “modelling of the Siple Coast system”. This would avoid confusion with “this system” being the current study area.
Fig. 1. Sabrina Subglacial Basin (SSB); Sabrina Coast (SC); Knox Coast (KC); and the Elcheikh saddle point (black X) are mentioned in the caption, but not shown on any figure. These are important as they are directly mentioned in the text later, e.g. L78.
Fig. 9 It could be worth showing the ice catchment boundaries from Figs 1 & 2 on these maps for context. Also it might be worth outlining the key hydrological catchments to highlight the significant switch in the area drained.
L435-436 States “We find that the drainage divide between the Totten and Vanderford glaciers is transient and that relatively minor changes in the ice sheet geometry could cause ice flow piracy from Totten to Vanderford Glacier”. It would be nice to say here how far the catchment boundary was shifted for context.
Figure A1. Does not appear to be referenced in the text.
Citation: https://doi.org/10.5194/egusphere-2023-872-RC1 -
AC1: 'Reply on RC1', Felicity McCormack, 21 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-872/egusphere-2023-872-AC1-supplement.pdf
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AC1: 'Reply on RC1', Felicity McCormack, 21 Aug 2023
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RC2: 'Comment on egusphere-2023-872', Anonymous Referee #2, 04 Aug 2023
Review of 'Assessing the potential for ice flow piracy between Totten and Vanderford glaciers, East Antarctica'
This is a very well written manuscript that highlights the potential for ice flow reconfiguration for a paor of glaciers in East Antarctica, a phenomenon that has happened for glaciers on Siple Coast.
The authors summarize the state of knowledge needed to motivate and support the work undertaken in this study. The project is well described, results are discussed in sufficient detail and provide a clear set of conclusions.
Model based as well as remote sensing based inputs are used, they all are discussed and evaluated for strengths, shortcomings, and needed improvements. Equally important to the actual findings of the study is the discussion of the information needs for the region:
“Improved knowledge of the bed geometry and sediment characteristics in these regions is essential, and should be a focus of future airborne surveys”
Potential improvements for SMB estimates
“Given that accurate knowledge of ocean melt rates is critical for ice sheet model simulations of retreat, and the evidence for a strong observed warming trend of mCDW in this region of East Antarctica “… “, this emphasises the need for long-term ocean state monitoring in this region.”
I highlight these because rather than bemoaning the quality of available products, which are the current state of knowledge, the authors make due with what is available, and discuss the impact of accuracies and errors in the input data. In addition, the authors highlight needed improvements and challenge the community as well as funding agencies with a very clear set of information needs from both regional climate models and remote sensing campaigns.
Figure 1:
Areas mentioned in the caption are not shown in the figures (SBB, SC, the X for Elcheikh Saddle Point)
You mention Law Dome multiple times in the text, this should accordingly also be indicated in one of the figures.
Highland C: The “C” is not well legible
Figure 8
Are catchment divide changes only happening between Totten and Vanderford glaciers? Figure 9 indicates very few changes in the water routing between Totten and Moscow University glaciers, but did you look at divide changes there?
Citation: https://doi.org/10.5194/egusphere-2023-872-RC2 -
AC2: 'Reply on RC2', Felicity McCormack, 21 Aug 2023
Please note that our response to RC2 was combined in the response to RC1.
Citation: https://doi.org/10.5194/egusphere-2023-872-AC2 -
AC1: 'Reply on RC1', Felicity McCormack, 21 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-872/egusphere-2023-872-AC1-supplement.pdf
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AC2: 'Reply on RC2', Felicity McCormack, 21 Aug 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-872', Anonymous Referee #1, 21 Jun 2023
Review of “Assessing the potential for ice flow piracy between Totten and Vanderford glaciers, East Antarctica”. This paper uses an ice sheet model (ISSM) to study the impact of changing surface elevation on ice and water flow between the Totten and Vanderford glaciers. The changes in surface elevation are not model predictions, but rather reasonable forcing parameters, allowing the impact of such changes to be assessed. The authors find that a proportion of ice and water flow can be switched from Totten to Vanderford Glacier, with the most significant changes driven by increasing the elevation within the Totten Glacier catchment. The authors indicate that these findings are significant as they show that water and ice piracy are possible within East Antarctica. The impact of such piracy on ice flow was not considered by this study, but is put forward as an important factor to be included in future models of the region.
I found the paper clear and well written and that the conclusions are supported by the data and model outputs.
I have a number of minor comments/suggestions which I feel may help the reader to better understand the paper.
L20-21 states “which contains approximately 7m of global sea level equivalent (Morlighem et al., 2020) of which 3.5m is grounded below sea level”. This is a little confusing, what people want to know is what is the actual sea level rise they could experience - maybe split out the end of the sentence to say, "As much of the catchment lies below sea level, the effective impact of total deglaciation of this region would be at least 3.5m of global sea level rise".
L24 states “Paleoclimate evidence suggests markedly reduced ice volumes in the ASB….” Being picky - do you mean "Ice sheet models driven by realistic temperatures derived from paleoclimate evidence.....". Not sure that Paleoclimate evidence can directly suggest reduced ice volumes. Paleo sea-level records would suggest reduced ice volumes, but are hard to attribute to specific basins. Paleoclimate observations close to the ASB/WSB ect showing elevated temperatures could be considered more direct paleoclimate evidence for ice free areas, if so this could be stated.
L37 to L46 I would flag that the work referred to in this paragraph was carried out on the Siple Coast. Later in the paragraph when the authors state “modelling of this system” they could say “modelling of the Siple Coast system”. This would avoid confusion with “this system” being the current study area.
Fig. 1. Sabrina Subglacial Basin (SSB); Sabrina Coast (SC); Knox Coast (KC); and the Elcheikh saddle point (black X) are mentioned in the caption, but not shown on any figure. These are important as they are directly mentioned in the text later, e.g. L78.
Fig. 9 It could be worth showing the ice catchment boundaries from Figs 1 & 2 on these maps for context. Also it might be worth outlining the key hydrological catchments to highlight the significant switch in the area drained.
L435-436 States “We find that the drainage divide between the Totten and Vanderford glaciers is transient and that relatively minor changes in the ice sheet geometry could cause ice flow piracy from Totten to Vanderford Glacier”. It would be nice to say here how far the catchment boundary was shifted for context.
Figure A1. Does not appear to be referenced in the text.
Citation: https://doi.org/10.5194/egusphere-2023-872-RC1 -
AC1: 'Reply on RC1', Felicity McCormack, 21 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-872/egusphere-2023-872-AC1-supplement.pdf
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AC1: 'Reply on RC1', Felicity McCormack, 21 Aug 2023
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RC2: 'Comment on egusphere-2023-872', Anonymous Referee #2, 04 Aug 2023
Review of 'Assessing the potential for ice flow piracy between Totten and Vanderford glaciers, East Antarctica'
This is a very well written manuscript that highlights the potential for ice flow reconfiguration for a paor of glaciers in East Antarctica, a phenomenon that has happened for glaciers on Siple Coast.
The authors summarize the state of knowledge needed to motivate and support the work undertaken in this study. The project is well described, results are discussed in sufficient detail and provide a clear set of conclusions.
Model based as well as remote sensing based inputs are used, they all are discussed and evaluated for strengths, shortcomings, and needed improvements. Equally important to the actual findings of the study is the discussion of the information needs for the region:
“Improved knowledge of the bed geometry and sediment characteristics in these regions is essential, and should be a focus of future airborne surveys”
Potential improvements for SMB estimates
“Given that accurate knowledge of ocean melt rates is critical for ice sheet model simulations of retreat, and the evidence for a strong observed warming trend of mCDW in this region of East Antarctica “… “, this emphasises the need for long-term ocean state monitoring in this region.”
I highlight these because rather than bemoaning the quality of available products, which are the current state of knowledge, the authors make due with what is available, and discuss the impact of accuracies and errors in the input data. In addition, the authors highlight needed improvements and challenge the community as well as funding agencies with a very clear set of information needs from both regional climate models and remote sensing campaigns.
Figure 1:
Areas mentioned in the caption are not shown in the figures (SBB, SC, the X for Elcheikh Saddle Point)
You mention Law Dome multiple times in the text, this should accordingly also be indicated in one of the figures.
Highland C: The “C” is not well legible
Figure 8
Are catchment divide changes only happening between Totten and Vanderford glaciers? Figure 9 indicates very few changes in the water routing between Totten and Moscow University glaciers, but did you look at divide changes there?
Citation: https://doi.org/10.5194/egusphere-2023-872-RC2 -
AC2: 'Reply on RC2', Felicity McCormack, 21 Aug 2023
Please note that our response to RC2 was combined in the response to RC1.
Citation: https://doi.org/10.5194/egusphere-2023-872-AC2 -
AC1: 'Reply on RC1', Felicity McCormack, 21 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-872/egusphere-2023-872-AC1-supplement.pdf
-
AC2: 'Reply on RC2', Felicity McCormack, 21 Aug 2023
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Felicity S. McCormack
Jason L. Roberts
Bernd Kulessa
Alan Aitken
Christine F. Dow
Lawrence Bird
Ben K. Galton-Fenzi
Katharina Hochmuth
Richard S. Jones
Andrew N. Mackintosh
Koi McArthur
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(28678 KB) - Metadata XML