the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Sep 2025
Review Article: The Foundation-Patuxent-Academy ice stream system, Antarctica
Abstract. The Foundation-Patuxent-Academy system (FPAS) is a major Antarctic ice stream system with a global sea level potential of ~3 m. Draining both East and West Antarctica, the FPAS has been understudied compared with other major Antarctic ice streams. We provide a holistic catchment-scale overview of the FPAS reviewing its glaciological and hydrological systems, its glacial history, and its modelled response to past and future climate change. FPAS may be vulnerable to future change because of: (i) a deep (~2.4 km below sea level) low-gradient retrograde bed that encourages grounding-zone retreat; (ii) a low-gradient ice surface and high tidal range, which are likely to promote flotation of grounded ice and seawater intrusion; (iii) an active and dynamic subglacial hydrological system; (iv) complex ice-meltwater-ocean interactions at the grounding zone; (v) potential for substantive expansion of the across-flow length – and cross sectional area – of the grounding zone; and (vi) susceptibility to ice flow-switching and water piracy. Despite such potential vulnerabilities, existing numerical model simulations of FPAS grounding-zone retreat produce a wide and divergent range of past and future scenarios. Uncertainties in the future response of the FPAS to a warming climate result from poor constraints on its topography and hydrology, processes of ice-ocean interaction, interlinkages with the surrounding ice sheet and ice shelf, and a shortage of FPAS-specific modelling experiments. This review outlines and evaluates these critical gaps in our knowledge of the FPAS and develops a strategy to address them. This strategy would provide: (i) the first robust and comprehensive evaluation of the FPAS’s vulnerability to current and near-future climate forcing; and (ii) improved constraints on projections of the future contribution of the Antarctic Ice Sheet to sea-level rise.
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Status: open (until 26 Nov 2025)
- RC1: 'Comment on egusphere-2025-3625', Duncan Young, 14 Oct 2025 reply
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Review of Ross et al., 2025 (doi:10.5194/egusphere-2025-3625)
"Review Article: The Foundation-Patuxent-Academy ice stream system, Antarctica"
Overview:
This review paper is a call to arms to focus on the sprawling Foundation-Patuxent-Academy System, a collection of ice stream catchments that flow from Dome A into the intersection of the Filchner and Ronne Ice Shelves. In general, it is a fine and timely overview, but there are gaps, and places where things could be clearer. There are elements of a proposal in here, so forgive me if I approach it with that mindset.
Major issues:
Section 1:
It appears a key point this paper is trying to make is a shift from an ice shelf oriented view to a grounded ice point of view of the system (the historical priority of the ice shelf is a natural outcome of the evolution in satellite remote sensing described in the discussion of Section 3 below). Authors could be more explicit in why they want to make this contrast. Figure 1 is not clear. The forest of overlapping red boxes with letter pointers to numeric pointers to other figures does not add much value. You could combine a simple insert map of all Antarctica, showing simply the major subcatchments you describe here, with Figure 10 (the block diagram), and it would be clearer what you are talking about. There is talk of flux gates which are not shown.
Section 2:
The numbered 'insights' (eg "Bed geometry near the grounding zone" here are titled as generic targets. I think those targets could be phrased as actual insights. Why do we care about the bed geometry near the grounding zone? etc etc. Frame them as a provocation. A pithier version of the first sentence of each section. Alternatively, you could refer to them as 'targets of investigation' instead of 'insights'.
Section 3:
There is a good historical section that goes into the detail of the early exploration of this issue. However, it is missing a discussion an element that has profoundly shaped the understanding of this region - the remote sensing 'pole hole' that meant we didn't have good topography of much of this region before IceSat-1 in 2003 (DiMarzio et al., 2003), which was significantly, but not totally advanced by Cryosat-2 in 2014 (Helm et al., 2014), and then it wasn't until TanDEM-X (Wessel et al., 2021) that we managed to fill in the key intersection between Foundation and Academy (and event then there are issues with the accessibility of that dataset).
Surface velocity is a similar story: image based velocity tracking (Gardner et al., 2019) - the only data we have for much of the system is from Radarsat-2 coverage from ~ 2015 (Mouginot et al 2019), with significant errors in key parts of the onset of this system. NiSAR should address a lot of the surface velocity issues. The role of intuition on this system from balance velocities derived from incomplete surface topography data is a key part of the story (which was acknowledged as an issue at the time (eg Bingham et al. 2007)).
On the airborne geophysics side, it's probably worth mentioning the SOAR/Pensacola-Pole Transect (Studinger et al., 2006, Holt et al., 1998, Blankenship et al., 2025) which first traversed this system at the South Pole.
The value of Figure 3 is not clear, especially panels c-e. It might be clearer just to show the various bedmaps (including bedmap1) to show synoptic scale changing in configuration. To make the point about poorly optimized collection, maybe using the ILCI figure (Fig 6 in Bingham, Bodart, Cavitte, Chung, Sanderson and Sutter et al., in press) might make the point better.
Lastly, there now has been an very extensive recent survey of the onset region of this system through NSF COLDEX; data has been out for a while (Young, Paden et al., 2024), and now actually a paper (Young et al., 2025), which has implications for how this system is initiating (obviously this came out after the paper was submitted, but is relevant to this review paper).
Section 4:
This section starts with two paragraphs which are a half page long, which makes it a little hard to parse. Names are introduced that are not in the Antarctic Gazette (eg "Foundation Trough") - the authors should make it clear what is official and what is not, and maybe consider a plan for getting them approved if not.
The discussion of Joughin et al 2006 in the context of in Academy roughness is a little indirect, since that paper does not explicitly mention Academy Ice Stream or roughness. It does seem that what Joughin's inversion is picking up is the prominent cross flow ridges visible in MOA imagery, which the FISS and Polargap survey lines in Figure 4 are not well oriented to detect (which does go to the authors' point on coverage in Section 3).
On the roughness trend inland - at least with the color map in Figure 4a, it's still looking fairly smooth on the rebounded bed >0 elevation topography.
Figure 4. Using consistent colours between panels a and b for the bed contours will make it easier to compare. For FAIR purposes, include the granule/flight information for the radargram in the caption.
Figure 6 has some issues. In a) The higher discharge values are hard to distinguish from the background color map. In the legend the text Subglacial Lakes bleeds directly into Channel Discharge. 6a also needs a scalebar. 6b (directly taken from Siegfried and Fricker, 2021) should be located on 6a, not on a separate figure on a separate page. The box for 6d should be shown on 6a, or the catchment boundaries should be added to 6d for reference.
The Jordan 2018 downdraw is shown on Figure 5, but not fully discussed in the text until after the subglacial hydrology section - I would suggest adding it to the subglacial hydrology figures. Would it be possible to add the Jordan flow routes (yellow line their Fig 3) to these figures?
line 426: It’s not clear that the dynamic summit migration seen at Dome C, which is solely a function of velocity, would have any direct bearing on ice sheet geometry.
The Hydrogeology section could use some paragraph breaks.
Section 5:
It seems there is a missed opportunity to directly tie the targeted activities in Section 5 to the insights in Section 2.
Figure 9: Put titles of panels on the panels.
line 678: "For example, some reported ‘Academy Glacier’ active subglacial lakes (i.e. A14 and A16) could be located beneath Support Force Glacier instead. " This does not make sense as written. You have defined the margins of these features in this paper, and the locations of the active lakes is well determined. Are you suggesting that there are Academy Glacier and Support Force Glacier hydrological catchments that do not correspond to the ice declared ones?
Minor issues:
In general - more paragraph breaks. Also for radargrams add more granularity to the reference - allow readers to go directly to the Polar Airborne Geophysics Data Portal or equivalent and look at the same radargram at full resolution.
line 366: sub-iice -> sub-ice
line 373: "Based on overburden hydraulic potential calculations, but not model results (Dow et al.,2022)," Awkwardly phrased - does Dow and GLADS imply that water-route switching is unlikely?
line 696: "Aurora Basin" -> "Aurora Subglacial Basin"
References in this review:
Bingham, R. G., M. J. Siegert, D. A. Young, and D. D. Blankenship (2007), Organized flow from the South Pole to the Filchner-Ronne ice shelf: an assessment of balance velocities in interior East Antarctica using radio-echo sounding data, Journal of Geophysical Research, 112(F03S27), doi:https://doi.org/10.1029/2006JF000556.
Bingham, R. G., J. A. Bodart, M. G. P. Cavitte, A. Chung, R. J. Sanderson, J. Sutter, O. Eisen, N. B. Karlsson, J. A. MacGregor, N. Ross, D. A. Young, D. W. Ashmore, A. Born, W. Chu, R. Drews, S. Franke, V. Goel, J. W. Goodge, A. C. J. Henry, A. Hermant, B. H. Hills, N. Holschuh, M. R. Koutnik, G. J.-M. C. L. Vieli, E. J. MacKie, E. Mantelli, C. Mart´ın, F. S. L. Ng, F. M. Oraschewski, F. Napoleoni, F. Parrenin, S. V. Popov, T. Rieckh, R. Schlegel, D. M. Schroeder, M. J. Siegert, T. O. Teisberg, K. Winter, X. Cui, X. Tang, S. Yan, H. Davis, C. F. Dow, T. J. Fudge, T. A. Jordan, B. Kulessa, K. Matsuoka, C. J. Nyqvist, M. Rahnemoonfar, M. R. Siegfried, S. Singh, V. Viˇsnjevi´c, R. Zamora, and A. Zuhr (accepted), Review Article: Antarctica’s internal architecture: Towards a radiostratigraphicallyinformed age–depth model of the Antarctic ice sheets, The Cryosphere, doi:https://doi.org/10.5194/egusphere-2024-2593.
Blankenship, D., J. Holt, S. Kempf, D. L. Morse, M. Davis, R. Bell, and R. Arko (2025), SOAR PPT (Pensacola-Pole Transect) gridded aerogeophysical observations, doi:https://doi.org/10.18738/T8/QMEWFA. [DiMarzio et al.(2003)DiMarzio, Zwally, Brenner, and Sidel] DiMarzio, J. P., H. J. Zwally, A. C. Brenner, and T. Sidel (2003), Ice Sheet Surface Topography of Greenland and Antarctic from ICESat Altimetry, AGU Fall Meeting Abstracts, pp. A420+.
Gardner, A. S., M. A. Fahnestock, and T. A. Scambos (2019), ITS_LIVE Regional glacier and ice sheet surface velocities: Version1.,doi: https ://doi :10.5067/6II6V W8LLWJ7.
Helm, V., A. Humbert, and H. Miller (2014), Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2, The Cryosphere, 8(2), 1539–1559, doi:https://doi.org/10.5194/tc-8-1539-2014.
Holt, J. W., S. L. Magsino, M. E. Peters, S. D. Kempf, R. R. Giggs, D. D. Blankenship, and R. E. Bell (1999), Soar annual report 1998/99. antarctica, Technical Report 185, University of Texas Institute for Geophysics.
Joughin, I., J. Bamber, T. Scambos, S. Tulaczyk, M. Fahnestock, and D. MacAyeal (2006), Integrating satellite observations with modelling: basal shear stress of the Filcher-Ronne ice streams, Antarctica, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 364(1844), 1795–1814.
Mouginot, J., E. Rignot, and B. Scheuchl (2019), Continent-wide, interferometric SAR phase, mapping of Antarctic ice velocity, Geophysical Research Letters, 46(16), 9710–9718, doi: https://doi.org/10.1029/2019GL083826.
Siegfried, M. R., and H. A. Fricker (2021), Illuminating active subglacial lake processes with icesat-2 laser altimetry, Geophysical Research Letters, 48(14), e2020GL091,089, doi:https://doi.org/10.1029/2020GL091089, e2020GL091089 2020GL091089.
Studinger, M., R. E. Bell, P. G. Fitzgerald, and W. R. Buck (2006), Crustal architecture of the Transantarctic Mountains between the Scott and Reedy Glacier region and South Pole from aerogeophysical data, Earth and Planetary Science Letters, 250(1-2), 182–199, doi:https://doi.org/10.1016/j.epsl.2006.07.035.
Wessel, B., M. Huber, C. Wohlfart, A. Bertram, N. Osterkamp, U. Marschalk, A. Gruber, F. Reuß, S. Abdullahi, I. Georg, and A. Roth (2021), TanDEM-X PolarDEM 90 m of Antarctica: generation and error characterization, The Cryosphere, 15(11), 5241–5260, doi:https://doi.org/10.5194/tc-15-5241-2021.
Young, D. A., J. D. Paden, J. S. Greenbaum, D. D. Blankenship, M. E. Kerr, S. Singh, S. R. Kaundinya, K. Chan, D. P. Buhl, G. Ng, and S. D. Kempf (2024), COLDEX Open Polar Radar MARFA Airborne Radar Data, doi:https://doi.org/10.18738/T8/J38CO5.
Young, D. A., J. D. Paden, S. Yan, M. E. Kerr, S. Singh, A. Vega Gonzalez, S. R. Kaundinya, J. S. Greenbaum, G. Ng, D. P. Buhl, S. D. Kempf, and D. D. Blankenship (2025), Coupled ice sheet structure and bedrock geology in the deep interior of East Antarctica: Results from Dome A and the South Pole Basin, Geophysical Research Letters, 52(e2025GL115729), doi:https://doi.org/10.1029/2025GL115729.