Skip to main content
×
×
Home

Marine ice sheet dynamics: the impacts of ice-shelf buttressing

  • Samuel S. Pegler (a1)
Abstract

Marine ice sheets are continent-scale glacial masses that lie partially submerged in the ocean, as applies to significant regions of Antarctica and Greenland. Such ice sheets have the potential to destabilise under a buoyancy-driven instability mechanism, with considerable implications for future sea level. This paper and its companion present a theoretical analysis of marine ice sheet dynamics under the effect of a potentially dominant control of the buttressing force generated by lateral stresses on the downstream floating component of the ice sheet (the ice shelf). The analysis reveals critical conditions under which ice-shelf buttressing suppresses the buoyancy-driven collapse of an ice sheet and elucidates the implications of lateral stresses on grounding-line control and overall ice-sheet structure. Integrations of a suitably simplified quasi-two-dimensional model are conducted, yielding analytical results that provide a quick assessment of steady-state balances for a given ice-sheet configuration. An analytical balance equation describing the spectrum of marine ice sheet flow regimes spanning zero to strong ice-shelf buttressing is developed. It is determined that the dynamics across this spectrum exhibits markedly different flow regimes and structural characteristics. For sufficient buttressing, the grounding line occurs near to where a lateral-drag controlled section of the ice shelf meets the bedrock, implying an independent control of the grounding line by the ice shelf. The role of basal stresses is relegated to controlling only the thickness of the ice sheet upstream of the grounding line, with no significant control of the grounding line itself. It is further demonstrated that lateral stresses are responsible for inducing additional secondary contacts between the ice shelf and the bedrock downstream of the grounding line, resulting in a rich variety of additional steady states. These inducements generate a further stabilising mechanism that can fully suppress grounding-line retreat and eliminate otherwise irreparable hysteresis effects. The results provide a conceptual framework for numerical and observational interpretation of marine ice sheet dynamics, and clarifies the manner in which ice shelves can control grounding-line positions independently. It is thus indicated that a full resolution of the fine details of the flow of ice shelves and the processes controlling their erosion and disintegration is necessary for the confident forecasting of possible ice-sheet collapse over the course of the next few centuries.

Copyright
Corresponding author
Email address for correspondence: S.Pegler@leeds.ac.uk
References
Hide All
Bamber, J. L., Riva, R. E. M., Vermeersen, B. L. A. & LeBrocq, A. M. 2009 Reassessment of the potential sea-level rise from a collapse of the West Antarctic Ice Sheet. Science 324 (5929), 901903.
Chugunov, V. A. & Wilchinsky, A. V. 1996 Modelling of marine glacier and ice-sheet–ice-shelf transition zone based on asymptotic analysis. Ann. Glaciol. 23, 5967.
Cuffey, K. M. & Paterson, W. S. B. 2010 The Physics of Glaciers, 4th edn. Academic Press.
DeConto, R. M. & Pollard, D. 2016 Contribution of Antarctica to past and future sea-level rise. Nature 531, 591597.
DiPietro, N. D. & Cox, R. G. 1979 The spreading of a very viscous liquid on a quiessent water surface. Q. J. Mech. Appl. Maths 32, 355381.
Dupont, T. K. & Alley, R. B. 2005 Assessment of the importance of ice-shelf buttressing to ice-sheet flow. Geophys. Res. Lett. 32, F03009.
Favier, L., Durand, G., Cornford, S. L., Gudmundsson, G. H., Gagliardini, O., Gillet-Chaulet, F. & Brocq, M. L. 2014 Retreat of Pine Island Glacier controlled by marine ice-sheet instability. Nat. Clim. Change 5 (2), 117121.
Fowler, A. C. & Larson, D. A. 1978 On the flow of polythermal glaciers. Part I. Model and preliminary analysis. Proc. R. Soc. Lond. A 363, 217242.
Fretwell, P., Pritchard, H. D. et al. 2013 Bedmap2: improved ice bed, surface and thickness datasets for Antarctica. The Cryosphere 7, 375393.
Gagliardini, O., Durand, G., Zwinger, T., Hindmarsh, R. C. A. & Meur, E. L. 2010 Coupling of ice-shelf melting and buttressing is a key process in ice-sheets dynamics. Geophys. Res. Lett. 37, L14501.
Goldberg, D., Holland, D. M. & Schoof, C. 2009 Grounding line movement and ice shelf buttressing in marine ice sheets. J. Geophys. Res. 114, F0402.
Gudmundsson, G. H. 1997 Basal-flow characteristics of a non-linear flow sliding frictionless over strongly undulating bedrock. J. Glaciol. 43 (143), 8089.
Gudmundsson, G. H. 2013 Ice-shelf buttressing and the stability of marine ice sheets. The Cryosphere 7, 647655.
Gudmundsson, G. H., Krug, J., Durand, G., Favier, L. & Gagliardini, O. 2012 The stability of grounding lines on retrograde slopes. The Cryosphere 6, 14971505.
Hanna, E., Navarro, F. J., Pattyn, F., Domingues, C. M., Fettweis, X., Ivins, E. R., Nicholls, R. J., Ritz, C., Smith, B., Tulaczyk, S., Whitehouse, P. L. & Zwally, H. J. 2013 Ice-sheet mass balance and climate change. Nature 498, 5159.
Hindmarsh, R. C. A. 2012 An observationally validated theory of viscous flow dynamics at the ice-shelf calving front. J. Glaciol. 58, 375387.
Hughes, T. J. 1981 The weak underbelly of the West Antarctic ice sheet. J. Glaciol. 27 (97), 518525.
Jenkins, A. 1991 A one-dimensional model of ice shelf–ocean interaction. J. Geophys. Res. 96, 2067120677.
Katz, R. F. & Worster, M. G. 2010 Stability of ice-sheet grounding lines. Proc. R. Soc. Lond. A 466, 15971620.
Kowal, K. N., Pegler, S. S. & Worster, M. G. 2016 Dynamics of laterally confined marine ice sheets. J. Fluid Mech. 790, R2.
Lliboutry, L. 1987 Realistic, yet simple bottom boundary conditions for glaciers and ice sheets. J. Geophys. Res. 92, 91019109.
MacAyeal, D. R. 1989 Large-scale ice flow over a viscous basal sediment: theory and application to Ice Stream B, Antarctica. J. Geophys. Res. 94, 40714087.
MacAyeal, D. R. & Barcilon, V. 1988 Ice-shelf response to ice-stream discharge fluctuations. Part I. Unconfined ice tongues. J. Glaciol. 34, 121127.
Morland, L. W. 1987 Unconfined ice-shelf flow. Dynamics of the West Antarctic Ice Sheet: Proceedings of a Meeting Held in Utrecht, May 6–8, 1985. D. Reidel.
Muszynski, I. & Birchfield, G. E. 1987 A coupled marine ice-stream–ice-shelf model. J. Glaciol. 33, 315.
Nick, F. M., van der Veen, C. J., Vieli, A. & Benn, D. I. 2010 A physically based calving model applied to marine outlet glaciers and implications for the glacier dynamics. J. Glaciol. 56 (199), 781794.
Nowicki, S. M. J. & Wingham, D. J. 2008 Conditions for a steady ice sheet–ice shelf junction. Earth Planet. Sci. Lett. 265, 246255.
Pegler, S. S. 2016 The dynamics of confined extensional flows. J. Fluid Mech. 804, 2457.
Pegler, S. S. 2018 Suppression of marine ice sheet instability. J. Fluid Mech. 857, 648680.
Pegler, S. S., Kowal, K. N., Hasenclever, L. Q. & Worster, M. G. 2013 Lateral controls on grounding-line dynamics. J. Fluid Mech. 722, R1.
Pegler, S. S. & Worster, M. G. 2012 Dynamics of a viscous layer flowing radially over an inviscid ocean. J. Fluid Mech. 696, 152174.
Pegler, S. S. & Worster, M. G. 2013 An experimental and theoretical study of the dynamics of grounding lines. J. Fluid Mech. 728, 528.
Rignot, E., Casassa, G., Gogineni, P., Krabill, W., Rivera, A. & Thomas, R. 2004 Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen B ice shelf. Geophys. Res. Lett. 31, L18401.
Rignot, E., Mouginot, J. & Scheuchl, B. 2011 MEaSUREs InSAR-Based Antarctica Ice Velocity Map. NASA DAAC at the National Snow and Ice Data Center.
Robison, R. A. V., Huppert, H. E. & Worster, M. G. 2010 Dynamics of viscous grounding lines. J. Fluid Mech. 648, 363380.
de Rydt, J., Gudmundsson, G. H., Rott, H. & Bamber, J. L. 2015 Modeling the instantaneous response of glaciers after the collapse of the Larsen B Ice Shelf. Geophys. Res. Lett. 42 (13).
Scambos, T. A., Bohlander, J. A., Shuman, C. A. & Skvarca, P. 2004 Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophys. Res. Lett. 31, L18402.
Schoof, C. 2007a Ice sheet grounding line dynamics: steady states, stability, and hysteresis. J. Geophys. Res. 112, F03S28.
Schoof, C. 2007b Marine ice sheet dynamics. Part 1. The case of rapid sliding. J. Fluid Mech. 573, 2755.
Schoof, C., Davis, A. D. & Popa, T. V. 2017 Boundary layer models for calving marine outlet glaciers. The Cryosphere 11, 22832303.
Stuiver, M., Denton, G. H., Hughes, T. J. & Fastook, J. L. 1981 History of the Marine Ice Sheet in West Antarctica During the Last Glaciation: A Working Hypothesis, pp. 319436. Wiley-Interscience.
Thomas, R. H. 1973 The creep of ice shelves: theory. J. Glaciol. 12, 4553.
Thomas, R. H. & Bentley, C. R. 1978 A model for Holocene retreat of the West Antarctic ice sheet. Quaternary Res. 2, 150170.
Tsai, V. C., Stewart, A. L. & Thompson, A. F. 2015 Marine ice-sheet profiles and stability under Coulomb basal conditions. J. Glaciol. 61, 205221.
van der Veen, C. J.1983 A note on the equilibrium profile of a free floating ice shelf. IMOU Report V83(15), State University Utrecht.
van der Veen, C. J. 1999 Fundamentals of Glacier Dynamics. CRC Press.
Walker, R. T., Holland, D. M., Parizek, B. R., Alley, R. B., Nowicki, S. M. J. & Jenkins, A. 2013 Efficient flowline simulations of ice shelf–ocean interactions: sensitivity studies with a fully coupled model. J. Phys. Oceanogr. 43, 22002210.
Weertman, J. 1957 On the sliding of glaciers. J. Glaciol. 3, 3338.
Weertman, J. 1974 Stability of the junction of an ice sheet and an ice shelf. J. Glaciol. 31, 311.
Wilchinsky, A. V. & Chugunov, V. A. 2000 Ice stream–ice shelf transition: theoretical analysis of two-dimensional flow. Ann. Glaciol. 30, 153162.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Journal of Fluid Mechanics
  • ISSN: 0022-1120
  • EISSN: 1469-7645
  • URL: /core/journals/journal-of-fluid-mechanics
Please enter your name
Please enter a valid email address
Who would you like to send this to? *
×
MathJax

JFM classification

Type Description Title
PDF
Supplementary materials

Pegler supplementary material
Supplementary data

 PDF (839 KB)
839 KB

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed