Drainage and refill of an Antarctic Peninsula subglacial lake reveal an active subglacial hydrological network

Hodgson, Dominic A.; Jordan, Tom A.; Ross, Neil; Riley, Teal R.; Fretwell, Peter T.

doi:https://doi.org/10.5194/tc-16-4797-2022

Articles | Volume 16, issue 12

https://doi.org/10.5194/tc-16-4797-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-16-4797-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 12

Research article

|

30 Nov 2022

Research article |

| 30 Nov 2022

Drainage and refill of an Antarctic Peninsula subglacial lake reveal an active subglacial hydrological network

Dominic A. Hodgson, Tom A. Jordan, Neil Ross, Teal R. Riley, and Peter T. Fretwell

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Final revised paper (published on 30 Nov 2022)
Preprint (discussion started on 21 Jul 2022)

Interactive discussion

Status: closed

RC1:
'Comment on tc-2022-144', Stephen Livingstone, 26 Aug 2022

Please see attached pdf.

Citation: https://doi.org/10.5194/tc-2022-144-RC1
- AC1: 'Reply on RC1', Dominic Hodgson, 13 Sep 2022
  
  Thank you for this constructive review, and for highlighting the additional refences, which will help strengthen our paper.
  1. Constraining/ inferring rapid subglacial lake drainage.
  We are fortunate that the prepublication version of our paper in The Cryosphere prompted a colleague (a UK glaciologist) to examine their photographic archives of overflights of the Mars Glacier. As a result, we now have an image of the site in January 2011 which shows not only the earliest record of collapse, but also surface deformation of the downstream ice revealing the path of the subglacial drainage channel. This latter feature was subsequently infilled by snow and it not visible in later imagery. This photograph also helps address the comment on L191.
  The photograph shows the ice cliffs in the process of collapse into the subglacial cavity due to loss of hydraulic support and will be included into the revised version of the paper.
  We could not find earlier Landsat images of sufficient resolution to aid our interpretations.
  We have compared the feature to that described by Boronina et al 2021; in that example ‘the collapse of the overlying ice was caused by drainage of supraglacial water and nearby epiglacial lakes into an englacial cavity in 2017 causing its overfill and outburst’ (lines 235-237).
  2. Supraglacial meltwater inputs.
  We have no data to separate meltwater inputs from the catchment, glacier surface, seepage through porous firn or a linked cavity network. However, the statement that ‘1.18 m increase in the surface elevation between 22nd and 30th December 2019 substantially exceeds the overall infill trend, confirming the seasonality of meltwater inputs, and coincides with the 32-year record-high surface melt in 2019/2020 recorded on the northern George VI Ice Shelf’ (lines 205-207), suggests that surface melt is likely dominant. We have added this to the revised version.
  The Liang paper, and the Willis (2015) paper that it cites both provide useful analogues from Greenland which we will incorporate into the discussion.
  3. Lake drainage trigger?
  Yes – this is possible. We will include it in the revised text.
  4. Wider implications.
  As suggested, we will rewrite this section with a greater emphasis on surface meltwater getting to the bed of the ice sheet and influencing subglacial hydrological processes. We will also address the comment on Line 255 to better characterise the role of surface melt vs. ocean forcing.
  All other minor observations addressed.
  
  Citation: https://doi.org/10.5194/tc-2022-144-AC1
RC2:
'Comment on tc-2022-144: "Drainage and refill of an Antarctic Peninsula subglacial lake reveals an active subglacial hydrological network" by Hodgson et al.', Anonymous Referee #2, 01 Sep 2022

In their TCD manuscript “Drainage and refill of an Antarctic Peninsula subglacial lake reveals an active subglacial hydrological network” Hodgson et al. combine airborne LiDAR data with time stamped elevation data of the Reference Model of Antarctica (REMA) to investigate surface elevation changes over a potential subglacial lake location on the Antarctic Peninsula. The authors further employ airborne accumulation radar data to investigate the structure of the subglacial bed in the study region. With the help of additional remote sensing data, they broaden the study to other potential subglacial lake locations on the Antarctic Peninsula and discuss their results in a wider context. The paper is interesting to read and presents some new findings about subglacial lakes on the Antarctic Peninsula. In the following, I have two general remarks and a couple of specific comments. However, overall I think this is a nice contribution that is worth to be published after some revisions have been made.

General remarks:

1) Are there any accessible datasets which could be used to investigate the actual lake drainage prior to 2013? Here I am thinking of ICESat-1 data (you need to be lucky), the Antarctic Peninsula DEM derived from ASTER data or any Landsat-7 or ASTER acquisitions? This would certainly strengthen the study.

2) The Authors state that a southerly shift of subglacial lake appearance can be related to a changing glacier regime on the Antarctic Peninsula. This might be true, however, how can the Authors be sure that no subglacial lakes exist in these areas prior to 2013?

Specific comments:

L6-L7: I am not so sure if this is really well understood… please rework this statement.

L21: subglacial water activity has also been monitored by Synthetic Aperture Radar (SAR) satellite data. See for example Joughin et al., 2016, Gray et al., 2005, Neckel et al., 2021.

L23-26: good point. By the way, Capps et al. 2010 also used SAR data to investigate subglacial lakes. I also think many small subglacial lakes are still hidden underneath the East and West Antarctic Ice Sheets (see for example Livingstone et al., 2013).

L46-49: this is an interesting and important point but I am rather skeptical if this canbe answered concerning the limited data situation.

L87: typo: speed.

L100-103: are there any rock outcrops covered by the LiDAR and/or DEM data that can be used for vertical and horizontal alignment and/or validation of the datasets?

L166: according to the oxford dictionary, a catastrophe is defined as: “an event that causes one person or a group of people to suffer, or that makes difficulties” which is not the case here. Please rephrase the term ‘catastrophic’ here and elsewhere in the text.

L200-201: why? Can the authors be sure that the lake was empty in 2013? Or could not have the sealing occurred some time before when no data were available? Not clear from the sentence.

L260-262: I suggest to rethink this statement as active hydrological networks are also common in other parts of Antarctica where surface melt processes are only minor, meaning that surface melt might not the only reason for subglacial water activity (e.g. Ashmore et al., 2014).

Figures

Fig. 1: thin white lines in panel b are rather hard to see. I recommend to zoom in on the study area.

Fig. 5: I think consecutive DEM differences would be more interesting than the single time steps shown here. Are the REMA strips covering the hydrological catchment? If so it might be worth to show it. Also analyzing the DEM differences in the surrounding might be interesting regarding processing biases and/or the detection of actual surface lowering (see for example Palmer et al., 2015).

Fig. 7: please indicate the locations of these profiles in Figure 5. How about combining Figs. 5 and 7?

Additional References

Ashmore, D., & Bingham, R. (2014). Antarctic subglacial hydrology: Current knowledge and future challenges. ( 6), 758-773. doi:10.1017/S0954102014000546.

Gray, L., Joughin, I., Tulaczyk, S., Spikes, V. B., Bindschadler, R., and Jezek, K. (2005), Evidence for subglacial water transport in the West Antarctic Ice Sheet through three-dimensional satellite radar interferometry, , 32, L03501, doi:10.1029/2004GL021387.

Livingstone, S. J., Clark, C. D., Woodward, J., and Kingslake, J.: Potential subglacial lake locations and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets, The Cryosphere, 7, 1721–1740, https://doi.org/10.5194/tc-7-1721-2013, 2013.

Neckel, N., Franke, S., Helm, V., Drews, R., & Jansen, D. (2021). Evidence of cascading subglacial water flow at Jutulstraumen Glacier (Antarctica) derived from Sentinel-1 and ICESat-2 measurements. , 48, e2021GL094472. https://doi.org/10.1029/2021GL094472.

Palmer, S., McMillan, M. & Morlighem, M. Subglacial lake drainage detected beneath the Greenland ice sheet. Nat Commun 6, 8408 (2015). https://doi.org/10.1038/ncomms9408

Citation: https://doi.org/10.5194/tc-2022-144-RC2
- AC2: 'Reply on RC2', Dominic Hodgson, 13 Sep 2022
  
  Thank you for this constructive review, and for highlighting the additional refences, which will help strengthen our paper.
  General remarks
  1) Are there any accessible datasets which could be used to investigate the actual lake drainage prior to 2013?
  We are fortunate that the prepublication of our paper in The Cryosphere prompted a colleague (a UK glaciologist) to examine their photographic archives of overflights of the Mars Glacier. As a result, we now have an image of the site in January 2011 which records the emptying of the basin, collapse of the overlying ice, and formation of the ice cliffs. This will be included in the revised version of the manuscript.
  We could not find earlier publicly available satellite images with sufficient resolution to aid our interpretations.
  2) The Authors state that a southerly shift of subglacial lake appearance…
  We are careful to state that the drainage ‘may indicate the southward expression of this phase of glacier response to regional warming’; i.e., this is speculation. We have not observed similar drainage features elsewhere at these latitudes, but this may be due to under reporting. To address this, we add the sentence: ‘However, the presence of these features has not been systematically mapped and may therefore be underreported.’
  Specific comments
  We will address these constructive observations in the revised version. The suggested additional references are really helpful and will strengthen the discussion.
  
  Citation: https://doi.org/10.5194/tc-2022-144-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to revisions (further review by editor and referees) (23 Sep 2022) by Reinhard Drews

AR by Dominic Hodgson on behalf of the Authors (05 Oct 2022) Author's response Author's tracked changes

ED: Referee Nomination & Report Request started (18 Oct 2022) by Reinhard Drews

RR by Stephen Livingstone (21 Oct 2022)

ED: Publish subject to technical corrections (07 Nov 2022) by Reinhard Drews

Short summary

This paper describes the drainage (and refill) of a subglacial lake on the Antarctic Peninsula resulting in the collapse of the overlying ice into the newly formed subglacial cavity. It provides evidence of an active hydrological network under the region's glaciers and close coupling between surface climate processes and the base of the ice.