Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Vigorous lateral export of the meltwater outflow from beneath an Antarctic ice shelf

Nature volume 542, pages 219–222 (2017)Cite this article

Subjects

Abstract

The instability and accelerated melting of the Antarctic Ice Sheet are among the foremost elements of contemporary global climate change1,2. The increased freshwater output from Antarctica is important in determining sea level rise1, the fate of Antarctic sea ice and its effect on the Earth’s albedo4,5, ongoing changes in global deep-ocean ventilation6, and the evolution of Southern Ocean ecosystems and carbon cycling7,8. A key uncertainty in assessing and predicting the impacts of Antarctic Ice Sheet melting concerns the vertical distribution of the exported meltwater. This is usually represented by climate-scale models3,4,5,6,7,8,9 as a near-surface freshwater input to the ocean, yet measurements around Antarctica reveal the meltwater to be concentrated at deeper levels10,11,12,13,14. Here we use observations of the turbulent properties of the meltwater outflows from beneath a rapidly melting Antarctic ice shelf to identify the mechanism responsible for the depth of the meltwater. We show that the initial ascent of the meltwater outflow from the ice shelf cavity triggers a centrifugal overturning instability that grows by extracting kinetic energy from the lateral shear of the background oceanic flow. The instability promotes vigorous lateral export, rapid dilution by turbulent mixing, and finally settling of meltwater at depth. We use an idealized ocean circulation model to show that this mechanism is relevant to a broad spectrum of Antarctic ice shelves. Our findings demonstrate that the mechanism producing meltwater at depth is a dynamically robust feature of Antarctic melting that should be incorporated into climate-scale models.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Map of the study region.
Figure 2: Transect along the PIIS calving front.
Figure 3: Transect along the main outflow from the PIIS calving front.
Figure 4: Schematic of the meltwater outflow from beneath the PIIS.

Similar content being viewed by others

References

  1. IPCC. Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) (Cambridge Univ. Press, 2014); http://www.climatechange2013.org/report/full-report.

  2. Shepherd, A. et al. A reconciled estimate of ice-sheet mass balance. Science 338, 1183–1189 (2012)

    Article  CAS  PubMed  ADS  Google Scholar 

  3. Rye, C. D. et al. Rapid sea-level rise along the Antarctic margins in response to increased glacial discharge. Nat. Geosci. 7, 732–735 (2014)

    Article  CAS  ADS  Google Scholar 

  4. Richardson, G., Wadley, M. R., Heywood, K. J., Stevens, D. P. & Banks, H. T. Short-term climate response to a freshwater pulse in the Southern Ocean. Geophys. Res. Lett. 32, L03702 (2005)

    Article  ADS  Google Scholar 

  5. Bintanja, R., van Oldenborgh, G. H., Drijfhout, S. S., Wouters, B. & Catsman, C. A. Important role for ocean warming and increased ice-shelf melt in Antarctic sea-ice expansion. Nat. Geosci. 6, 376–379 (2013)

    Article  CAS  ADS  Google Scholar 

  6. Purkey, S. G. & Johnson, G. C. Global contraction of Antarctic Bottom Water between the 1980s and 2000s. J. Clim. 25, 5830–5844 (2012)

    Article  ADS  Google Scholar 

  7. Arrigo, K. R., van Dijken, G. L. & Strong, A. L. Environmental controls of marine productivity hot spots around Antarctica. J. Geophys. Res. 120, 5545–5565 (2015)

    Article  ADS  Google Scholar 

  8. Arrigo, K. R., van Dijken, G. & Long, M. Coastal Southern Ocean: a strong anthropogenic CO2 sink. Geophys. Res. Lett. 35, L21602 (2008)

    Article  ADS  CAS  Google Scholar 

  9. Swart, N. C. & Fyfe, J. C. The influence of recent Antarctic ice sheet retreat on simulated sea ice area trends. Geophys. Res. Lett. 40, 4328–4332 (2013)

    Article  ADS  Google Scholar 

  10. Dutrieux, P. et al. Strong sensitivity of Pine Island Ice Shelf melting to climatic variability. Science 343, 174–178 (2014)

    Article  CAS  PubMed  ADS  Google Scholar 

  11. Hohmann, R., Schlosser, P., Jacobs, S., Ludin, A. & Weppernig, R. Excess helium and neon in the southeast Pacific: tracers for glacial meltwater. J. Geophys. Res. 107, 3198 (2002)

    Article  ADS  CAS  Google Scholar 

  12. Loose, B., Schlosser, P., Smethie, W. M. & Jacobs, S. An optimized estimate of glacial melt from the Ross Ice Shelf using noble gases, stable isotopes, and CFC transient tracers. J. Geophys. Res. 114, C08007 (2009)

    ADS  Google Scholar 

  13. Nicholls, K. W., Østerhus, S., Makinson, K., Gammelsrød, T. & Fahrbach, E. Ice-ocean processes over the continental shelf of the southern Weddell Sea, Antarctica. Rev. Geophys. 47, RG3003 (2009)

    Article  ADS  Google Scholar 

  14. Kim, I. et al. The distribution of glacial meltwater in the Amundsen Sea, Antarctica, revealed by dissolved helium and neon. J. Geophys. Res. 121, 1654–1666 (2016)

    Article  ADS  Google Scholar 

  15. Paolo, F. S., Fricker, H. A. & Padman, L. Volume loss from Antarctic ice shelves is accelerating. Science 348, 327–331 (2015)

    Article  CAS  PubMed  ADS  Google Scholar 

  16. Feldmann, J. & Levermann, A. Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin. Proc. Natl Acad. Sci. 112, 14191–14196 (2015)

    Article  CAS  PubMed  PubMed Central  ADS  Google Scholar 

  17. Pritchard, H. D. et al. Antarctic ice-sheet loss driven by basal melting of ice shelves. Nature 484, 502–505 (2012)

    Article  CAS  PubMed  ADS  Google Scholar 

  18. Joughin, I., Alley, R. B. & Holland, D. M. Ice-sheet response to oceanic forcing. Science 338, 1172–1176 (2012)

    Article  CAS  PubMed  ADS  Google Scholar 

  19. Thoma, M., Jenkins, A. Holland, D. & Jacobs, S. Modelling Circumpolar Deep Water intrusions on the Amundsen Sea continental shelf, Antarctica. Geophys. Res. Lett. 35, L18602 (2008)

    Article  ADS  Google Scholar 

  20. Stewart, A. L. & Thompson, A. F. Eddy-mediated transport of warm Circumpolar Deep Water across the Antarctic shelf break. Geophys. Res. Lett. 42, 432–440 (2015)

    Article  ADS  Google Scholar 

  21. Schmidtko, S., Heywood, K. J., Thompson, A. F. & Aoki, S. Multidecadal warming of Antarctic waters. Science 346, 1227–1231 (2014)

    Article  CAS  PubMed  ADS  Google Scholar 

  22. Pauling, A. G., Bitz, C. M., Smith, I. J. & Langhorne, P. J. The response of the Southern Ocean and Antarctic sea ice to freshwater from ice shelves in an Earth system model. J. Clim. 29, 1655–1672 (2016)

    Article  ADS  Google Scholar 

  23. Thurnherr, A. M., Jacobs, S. S., Dutrieux, P. & Giulivi, C. F. Export and circulation of ice cavity water in Pine Island Bay, West Antarctica. J. Geophys. Res. 119, 1754–1764 (2014)

    Article  ADS  Google Scholar 

  24. St-Laurent, P., Klinck, J. M. & Dinniman, M. S. Impact of local winter cooling on the melt of Pine Island Glacier, Antarctica. J. Geophys. Res. 120, 6718–6732 (2015)

    Article  ADS  Google Scholar 

  25. Hoskins, B. J. The role of potential vorticity in symmetric stability and instability. Q. J. R. Meteorol. Soc. 100, 480–482 (1974)

    Article  ADS  Google Scholar 

  26. Haine, T. W. N. & Marshall, J. Gravitational, symmetric, and baroclinic instability of the ocean mixed layer. J. Phys. Oceanogr. 28, 634–658 (1998)

    Article  ADS  Google Scholar 

  27. Thomas, L. N., Taylor, J. R., Ferrari, R. & Joyce, T. M. Symmetric instability in the Gulf Stream. Deep-Sea Res. Part II 91, 96–110 (2013)

    Article  ADS  Google Scholar 

  28. Nakayama, Y., Timmermann, R., Rodehacke, C. B., Schröder, M. & Hellmer, H. H. Modeling the spreading of glacial meltwater from the Amundsen and Bellingshausen Seas. Geophys. Res. Lett. 41, 7942–7949 (2014)

    Article  ADS  Google Scholar 

  29. Oakey, N. S. Determination of the rate of dissipation of turbulent energy from simultaneous temperature and velocity shear microstructure measurements. J. Phys. Oceanogr. 12, 256–271 (1982)

    Article  ADS  Google Scholar 

  30. Osborn, T. R. Estimates of the local rate of vertical diffusion from dissipation measurements. J. Phys. Oceanogr. 10, 83–89 (1980)

    Article  ADS  Google Scholar 

  31. Padman, L., Fricker, H. A., Coleman, R., Howard, S. & Erofeeva, L. A new tide model for the Antarctic ice shelves and seas. Ann. Glaciol. 34, 247–254 (2002)

    Article  ADS  Google Scholar 

  32. Robertson, R. Tides, the PIG, and ‘warm’ water. IOP Conf. Ser. Earth Environ. Sci. 11, 012002 (2010)

    Article  Google Scholar 

  33. Pawlowicz, R., Beardsley, B. & Lentz, S. Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE. Comput. Geosci. 28, 929–937 (2002)

    Article  ADS  Google Scholar 

  34. Robertson, R. Tidally induced increases in melting of Amundsen Sea Ice Shelves. J. Geophys. Res. 118, 3138–3145 (2013)

    Article  ADS  Google Scholar 

  35. Jenkins, A. The impact of melting ice on ocean waters. J. Phys. Oceanogr. 29, 2370–2381 (1999)

    Article  ADS  Google Scholar 

  36. Rudnick, D. L. On the skewness of vorticity in the upper ocean. Geophys. Res. Lett. 28, 2045–2048 (2001)

    Article  ADS  Google Scholar 

  37. Marshall, J., Adcroft, A., Hill, C., Perelman, L. & Heisey, C. A finite-volume, incompressible Navier–Stokes model for studies of the ocean on parallel computers. J. Geophys. Res. 102, 5753–5766 (1997)

    Article  ADS  Google Scholar 

  38. Daru, V. & Tenaud, C. High order one-step monotonicity-preserving schemes for unsteady compressible flow calculations. J. Comput. Phys. 193, 563–594 (2004)

    Article  MathSciNet  MATH  ADS  Google Scholar 

  39. Depoorter, M. A. et al. Calving fluxes and basal melt rates of Antarctic ice shelves. Nature 502, 89–92 (2013)

    Article  CAS  PubMed  ADS  Google Scholar 

  40. Fabregat Tomàs, A., Poje, A. C., Özgökmen, T. M. & Dewar, W. K. Effects of rotation on turbulent buoyant plumes in stratified environments. J. Geophys. Res. 121, 5397–5417 (2016)

    Article  ADS  Google Scholar 

  41. Randall-Goodwin, E. et al. Freshwater distributions and water mass structure in the Amundsen Sea Polynya region, Antarctica. Elementa Sci. Anthropocene 3, http://dx.doi.org/10.12952/journal.elementa.000065 (2015)

  42. Jenkins, A. & Jacobs, S. Circulation and melting beneath George VI Ice Shelf, Antarctica. J. Geophys. Res. 113, C04013 (2008)

    ADS  Google Scholar 

  43. Herráiz-Borreguero, L. et al. Circulation of modified Circumpolar Deep Water and basal melt beneath the Amery Ice Shelf, East Antarctica. J. Geophys. Res. 120, 3098–3112 (2015)

    Article  ADS  Google Scholar 

  44. Xu, Y., Rignot, E., Menemenlis, D. & Koppes, M. Numerical experiments on subaqueous melting of Greenland tidewater glaciers in response to ocean warming and enhanced subglacial discharge. Ann. Glaciol. 53, 229–234 (2012)

    Article  ADS  Google Scholar 

  45. Cowton, T., Slater, D., Sole, A., Goldberg, D. & Nienow, P. Modeling the impact of glacial runoff on fjord circulation and submarine melt rate using a new subgrid-scale parameterization for glacial plumes. J. Geophys. Res. 120, 796–812 (2015)

    Article  ADS  Google Scholar 

  46. Carroll, D. et al. Modelling turbulent subglacial meltwater plumes: implications for fjord-scale buoyancy-driven circulation. J. Phys. Oceanogr. 45, 2169–2185 (2015)

    Article  ADS  Google Scholar 

  47. Shutts, G. J. & Gray, M. E. B. A numerical modelling study of the geostrophic adjustment process following deep convection. Q. J. R. Meteorol. Soc. 120, 1145–1178 (1994)

    ADS  Google Scholar 

Download references

Acknowledgements

The iSTAR programme is supported by the Natural Environment Research Council of the UK (grants NE/J005703/1, NE/J005746/1 and NE/J005770/1). A.C.N.G. acknowledges the support of a Philip Leverhulme Prize, the Royal Society and the Wolfson Foundation. We are grateful to the scientific party, crew and technicians on the RRS James Clark Ross for their hard work during data collection.

Author information

Authors and Affiliations

  1. Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH, UK

    Alberto C. Naveira Garabato & Alexander Forryan

  2. British Antarctic Survey, Cambridge, CB3 0ET, UK

    Pierre Dutrieux, Adrian Jenkins & Satoshi Kimura

  3. Lamont-Doherty Earth Observatory of Columbia University, Palisades, 10964, New York, USA

    Pierre Dutrieux

  4. Department of Meteorology, Stockholm University, Stockholm, SE-106 91, Sweden

    Liam Brannigan

  5. Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK

    Louise C. Biddle & Karen J. Heywood

  6. National Oceanography Centre, Southampton, SO14 3ZH, UK

    Yvonne L. Firing

Authors
  1. Alberto C. Naveira Garabato
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Alexander Forryan
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Pierre Dutrieux
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Liam Brannigan
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Louise C. Biddle
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Karen J. Heywood
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Adrian Jenkins
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Yvonne L. Firing
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Satoshi Kimura
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

A.C.N.G. and A.F. designed and conducted the data analysis, with contributions from P.D. and L.C.B. L.B. designed and conducted the idealized model experiments. K.J.H. led the JR294/295 research cruise. All authors contributed to the scientific interpretation of the results.

Corresponding author

Correspondence to Alberto C. Naveira Garabato.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Additional information

Reviewer Information Nature thanks C. Stevens and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Figure 1 Tidal flows near the PIIS calving front.

Major axis of tidal ellipse for each individual tidal constituent from a mooring deployed in the area of the main meltwater outflow from the PIIS (Fig. 1), at nominal depths of 310 m (measured with an acoustic Doppler current profiler, black symbols) and 671 m (measured with a current meter, red symbols). Tidal ellipses are computed using harmonic analysis33. The amplitude of each ellipse’s major axis is shown by dots, and error estimates are displayed as bars. The 2-year-record-mean flow speed for each of the two instruments is indicated in the inset.

Extended Data Figure 2 Turbulent dissipation along the PIIS calving front.

Rate of dissipation of turbulent kinetic energy (ε, colour scale) along transects S1A and S1B, displayed as a function of potential temperature θ and salinity S. The loci of the three distinct water masses in the region are indicated by the labels in italics (CDW, Circumpolar Deep Water; GMW, glacially modified water; WW, Winter Water).

Extended Data Figure 3 Cross-transect velocity and relative vorticity along the main outflow from the PIIS calving front.

a, Cross-transect velocity (v, colour scale) along transect S2, with positive values directed northeastward. Potential temperature contours are shown at intervals of 0.2 °C (see Fig. 3a). b, Ratio of relative vorticity ζ to planetary vorticity f along the same transect (colour scale), where . Areas of positive potential vorticity (indicative of overturning instabilities) are outlined as in Fig. 3e. The outline shading denotes the instability type (GRV, gravitational; SYM, symmetric; CTF, centrifugal; see Methods). The characteristic vertical extent of the PIIS is shown by the grey rectangle at the right-hand axis of each panel.

Extended Data Figure 4 Assessment of geostrophic balance along the main outflow from the PIIS calving front.

a, Cross-transect velocity (v, colour scale) along transect S2, with positive values directed norththeastward. Neutral density (in kg m−3) is indicated by black contours. b, Profiles of transect-mean cross-transect velocity v and geostrophic velocity gvel, relative to the depth-averaged velocity.

Extended Data Figure 5 Initial condition in the Main simulation of an idealized meltwater outflow from beneath an Antarctic ice shelf.

The initial temperature distribution is shown by the colour shading, and the locations of the unstable restoring region (representing the meltwater outflow) and of the stable restoring region (representing ambient offshore conditions) are indicated.

Extended Data Figure 6 Evolution of the idealized meltwater outflow in the Main experiment.

Distributions of the along-domain velocity (a), relative vorticity normalized by the planetary vorticity (c), potential vorticity (e) and passive tracer concentration (g), 2 h after the start of the simulation. Panels b, d, f and h show the same variables as a, c, e and g, respectively, 120 h after the start of the simulation. Temperature contours are shown at intervals of 0.2 °C in all panels. Units are indicated next to the colour bars.

Extended Data Figure 7 Evolution of the idealized meltwater outflow in the Perturbation experiments with reduced and enhanced forcings.

Distributions of the along-domain velocity (a), relative vorticity normalized by the planetary vorticity (c), potential vorticity (e) and passive tracer concentration (g), 120 h after the start of the reduced forcing (0.5 K) simulation. Panels b, d, f and h show the same variables as a, c, e and g, respectively, 120 h after the start of the enhanced forcing (1.5 K) simulation. Temperature contours are shown at intervals of 0.2 °C in all panels. Units are indicated next to the colour bars.

Extended Data Figure 8 Vertical distribution of passive tracer on day 1 for varying planetary rotation.

a, Horizontally integrated tracer concentration (A) (normalized to a common value, A0) as a function of depth for the Main experiment with realistic rotation ( f = 1.4 × 10−4 s−1), and for the two Rotation experiments with weak ( f = 1 × 10−5 s−1) and no ( f = 0) rotation. b, Domain-mean tracer concentration (normalized to a common value) in temperature bins of width 0.05 K. The depth (a) or temperature (b) of neutral buoyancy for the simulated outflow is shown as a horizontal black line.

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Garabato, A., Forryan, A., Dutrieux, P. et al. Vigorous lateral export of the meltwater outflow from beneath an Antarctic ice shelf. Nature 542, 219–222 (2017). https://doi.org/10.1038/nature20825

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature20825

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing