Interannual variations in meltwater input to the Southern Ocean from Antarctic ice shelves

Abstract

Ocean-driven basal melting of Antarctica’s floating ice shelves accounts for about half of their mass loss in steady state, where gains in ice-shelf mass are balanced by losses. Ice-shelf thickness changes driven by varying basal melt rates modulate mass loss from the grounded ice sheet and its contribution to sea level, and the changing meltwater fluxes influence climate processes in the Southern Ocean. Existing continent-wide melt-rate datasets have no temporal variability, introducing uncertainties in sea level and climate projections. Here, we combine surface height data from satellite radar altimeters with satellite-derived ice velocities and a new model of firn-layer evolution to generate a high-resolution map of time-averaged (2010–2018) basal melt rates and time series (1994–2018) of meltwater fluxes for most ice shelves. Total basal meltwater flux in 1994 (1,090 ± 150 Gt yr–1) was similar to the steady-state value (1,100 ± 60 Gt yr–1), but increased to 1,570 ± 140 Gt yr–1 in 2009, followed by a decline to 1,160 ± 150 Gt yr–1 in 2018. For the four largest ‘cold-water’ ice shelves, we partition meltwater fluxes into deep and shallow sources to reveal distinct signatures of temporal variability, providing insights into climate forcing of basal melting and the impact of this melting on the Southern Ocean.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Basal melt rates of Antarctic ice shelves estimated using CryoSat-2 altimetry.
Fig. 2: Vertical structure of melting and refreezing rates for selected ice shelves.
Fig. 3: Variations in Antarctic ice-shelf mass between 1994 and 2018.
Fig. 4: Time-dependent basal melt rates for different modes of melting.

Data availability

ERS‐1, ERS‐2, Envisat and CryoSat‐2 radar altimetry data are available from the European Space Agency (ERS‐1 and ERS‐2 data from ftp://ra-ftp-ds.eo.esa.int/, Envisat data from ftp://ra2-ftp-ds.eo.esa.int/ and CryoSat‐2 level‐2 SARIn‐mode data from ftp://science-pds.cryosat.esa.int/SIR_SIN_L2). We provide two datasets at https://doi.org/10.6075/J04Q7SHT: (1) basal melt rates at high spatial resolution, posted on a 500 m grid, for the period 2010–2018 and (2) changes in height from satellite altimetry, firn air content from GSFC-FDMv0 and precipitation minus evaporation from MERRA-2 at 10-km grid cells and three-month intervals for 1994–2018; (2) can be used to estimate time-varying basal melt rates using Equation (7).

Code availability

The Matlab, Python and shell scripts used for the analyses described in this study can be obtained from the corresponding author upon reasonable request. Code to read and visualize the derived data products described in this manuscript, and to reproduce the major elements of Figs. 1 to 4, is available at https://github.com/sioglaciology/ice_shelf_change.

References

  1. 1.

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

    Google Scholar 

  2. 2.

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

    Google Scholar 

  3. 3.

    Thomas, R. H., Sanderson, T. J. O. & Rose, K. E. Effect of climatic warming on the West Antarctic ice sheet. Nature 277, 355–358 (1979).

    Google Scholar 

  4. 4.

    Jenkins, A. et al. West Antarctic ice sheet retreat in the Amundsen Sea driven by decadal oceanic variability. Nat. Geosci. 11, 733–738 (2018).

    Google Scholar 

  5. 5.

    Nerem, R. S. et al. Climate-change–driven accelerated sea-level rise detected in the altimeter era. Proc. Natl Acad. Sci. USA 115, 2022–2025 (2018).

    Google Scholar 

  6. 6.

    Jacobs, S. S., Helmer, H. H., Doake, C. S. M., Jenkins, A. & Frolich, R. M. Melting of ice shelves and the mass balance of Antarctica. J. Glaciol. 38, 375–387 (1992).

    Google Scholar 

  7. 7.

    Nicholls, K. W. Predicted reduction in basal melt rates of an Antarctic ice shelf in a warmer climate. Nature 388, 460–462 (1997).

    Google Scholar 

  8. 8.

    Lewis, E. L. & Perkin, R. G. Ice pumps and their rates. J. Geophys. Res. Oceans 91, 11756–11762 (1986).

    Google Scholar 

  9. 9.

    Turner, J. et al. Atmosphere-ocean-ice interactions in the Amundsen Sea Embayment, West Antarctica. Rev. Geophys. 55, 235–276 (2017).

    Google Scholar 

  10. 10.

    Rintoul, S. R. The global influence of localized dynamics in the Southern Ocean. Nature 558, 209–218 (2018).

    Google Scholar 

  11. 11.

    Pauling, A. G., Smith, I. J., Langhorne, P. J. & Bitz, C. M. Time-dependent freshwater input from ice shelves: impacts on Antarctic sea ice and the Southern Ocean in an Earth system model. Geophys. Res. Lett. 44, 10454–10461 (2017).

    Google Scholar 

  12. 12.

    Merino, N. et al. Impact of increasing Antarctic glacial freshwater release on regional sea-ice cover in the Southern Ocean. Ocean Model. 121, 76–89 (2018).

    Google Scholar 

  13. 13.

    Fogwill, C. J., Phipps, S. J., Turney, C. S. M. & Golledge, N. R. Sensitivity of the Southern Ocean to enhanced regional Antarctic ice sheet meltwater input. Earths Future 3, 317–329 (2015).

    Google Scholar 

  14. 14.

    Moffat, C., Beardsley, R. C., Owens, B. & van Lipzig, N. A first description of the Antarctic Peninsula Coastal Current. Deep Sea Res. Part II 55, 277–293 (2008).

    Google Scholar 

  15. 15.

    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).

    Google Scholar 

  16. 16.

    Golledge, N. R. et al. Global environmental consequences of twenty-first-century ice-sheet melt. Nature 566, 65–72 (2019).

    Google Scholar 

  17. 17.

    Eyring, V. et al. Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization. Geosci. Model Dev. 9, 1937–1958 (2016).

    Google Scholar 

  18. 18.

    Jourdain, N. C. et al. A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections. Preprint at https://doi.org/10.5194/tc-2019-277 (2019).

  19. 19.

    Rignot, E., Jacobs, S., Mouginot, J. & Scheuchl, B. Ice-shelf melting around Antarctica. Science 341, 266–270 (2013).

    Google Scholar 

  20. 20.

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

    Google Scholar 

  21. 21.

    Dutrieux, P. et al. Pine Island glacier ice shelf melt distributed at kilometre scales. Cryosphere 7, 1543–1555 (2013).

    Google Scholar 

  22. 22.

    Gourmelen, N. et al. Channelized melting drives thinning under a rapidly melting Antarctic ice shelf. Geophys. Res. Lett. 44, 9796–9804 (2017).

    Google Scholar 

  23. 23.

    Wingham, D. J. et al. CryoSat: A mission to determine the fluctuations in Earth’s land and marine ice fields. Advances in Space Research 37, 841–871 (2006).

    Google Scholar 

  24. 24.

    Lane‐Serff, G. F. On meltwater under ice shelves. J. Geophys. Res. Oceans 100, 6961–6965 (1995).

    Google Scholar 

  25. 25.

    Holland, P. R., Feltham, D. L. & Jenkins, A. Ice shelf water plume flow beneath Filchner-Ronne Ice Shelf, Antarctica. J. Geophys. Res. Oceans 112, C05044 (2007).

    Google Scholar 

  26. 26.

    Foldvik, A. Ice shelf water overflow and bottom water formation in the southern Weddell Sea. J. Geophys. Res. 109, C02015 (2004).

    Google Scholar 

  27. 27.

    Smethie, W. M. & Jacobs, S. S. Circulation and melting under the Ross Ice Shelf: estimates from evolving CFC, salinity and temperature fields in the Ross Sea. Deep Sea Res. Part I 52, 959–978 (2005).

    Google Scholar 

  28. 28.

    Herraiz‐Borreguero, L., Lannuzel, D., Merwe, P., van der, Treverrow, A. & Pedro, J. B. Large flux of iron from the Amery Ice Shelf marine ice to Prydz Bay, East Antarctica. J. Geophys. Res. Oceans 121, 6009–6020 (2016).

    Google Scholar 

  29. 29.

    Schlosser, P. et al. Oxygen 18 and helium as tracers of ice shelf water and water/ice interaction in the Weddell Sea. J. Geophys. Res. 95, 3253–2363 (1990).

    Google Scholar 

  30. 30.

    Reese, R., Gudmundsson, G. H., Levermann, A. & Winkelmann, R. The far reach of ice-shelf thinning in Antarctica. Nat. Clim. Change 8, 53–57 (2018).

    Google Scholar 

  31. 31.

    Goldberg, D. N., Gourmelen, N., Kimura, S., Millan, R. & Snow, K. How accurately should we model ice shelf melt rates? Geophys. Res. Lett. 46, 189–199 (2019).

    Google Scholar 

  32. 32.

    Fürst, J. J. et al. The safety band of Antarctic ice shelves. Nat. Clim. Change 6, 479–482 (2016).

    Google Scholar 

  33. 33.

    Malyarenko, A., Robinson, N. J., Williams, M. J. M. & Langhorne, P. J. A wedge mechanism for summer surface water inflow into the Ross Ice Shelf cavity. J. Geophys. Res. Oceans 124, 1196–1214 (2019).

    Google Scholar 

  34. 34.

    Porter, D. F. et al. Evolution of the seasonal surface mixed layer of the Ross Sea, Antarctica, observed with autonomous profiling floats. J. Geophys. Res. Oceans 124, 4934–4953 (2019).

    Google Scholar 

  35. 35.

    Stewart, C. L., Christoffersen, P., Nicholls, K. W., Williams, M. J. M. & Dowdeswell, J. A. Basal melting of Ross Ice Shelf from solar heat absorption in an ice-front polynya. Nat. Geosci. 12, 435–440 (2019).

    Google Scholar 

  36. 36.

    Tinto, K. J. et al. Ross Ice Shelf response to climate driven by the tectonic imprint on seafloor bathymetry. Nat. Geosci. 12, 441–449 (2019).

    Google Scholar 

  37. 37.

    The IMBIE team Mass balance of the Antarctic Ice Sheet from 1992 to 2017. Nature 558, 219–222 (2018).

    Google Scholar 

  38. 38.

    Smith, B. E. et al. Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes. Science 368, 1239–1242 (2020).

    Google Scholar 

  39. 39.

    Castagno, P. et al. Rebound of shelf water salinity in the Ross Sea. Nat. Commun. 10, 5441 (2019).

    Google Scholar 

  40. 40.

    Nicholls, K. W. & Østerhus, S. Interannual variability and ventilation timescales in the ocean cavity beneath Filchner-Ronne Ice Shelf, Antarctica. J. Geophys. Res. Oceans 109, C04014 (2004).

    Google Scholar 

  41. 41.

    Smith, B. E., Fricker, H. A., Joughin, I. R. & Tulaczyk, S. An inventory of active subglacial lakes in Antarctica detected by ICESat (2003–2008). J. Glaciol. 55, 573–595 (2009).

    Google Scholar 

  42. 42.

    Motyka, R. J., Dryer, W. P., Amundson, J., Truffer, M. & Fahnestock, M. Rapid submarine melting driven by subglacial discharge, LeConte Glacier, Alaska. Geophys. Res. Lett. 40, 5153–5158 (2013).

    Google Scholar 

  43. 43.

    Washam, P., Nicholls, K. W., Münchow, A. & Padman, L. Summer surface melt thins Petermann Gletscher Ice Shelf by enhancing channelized basal melt. J. Glaciol. 65, 662–674 (2019).

    Google Scholar 

  44. 44.

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

    Google Scholar 

  45. 45.

    Paolo, F. S. et al. Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation. Nat. Geosci. 11, 121–126 (2018).

    Google Scholar 

  46. 46.

    Kimura, S. et al. Oceanographic controls on the variability of ice-shelf basal melting and circulation of glacial meltwater in the Amundsen Sea Embayment, Antarctica. J. Geophys. Res. Oceans 122, 10131–10155 (2017).

    Google Scholar 

  47. 47.

    Holland, P. R., Bracegirdle, T. J., Dutrieux, P., Jenkins, A. & Steig, E. J. West Antarctic ice loss influenced by internal climate variability and anthropogenic forcing. Nat. Geosci. 12, 718–724 (2019).

    Google Scholar 

  48. 48.

    Budillon, G., Castagno, P., Aliani, S., Spezie, G. & Padman, L. Thermohaline variability and Antarctic bottom water formation at the Ross Sea shelf break. Deep Sea Res. Part I 58, 1002–1018 (2011).

    Google Scholar 

  49. 49.

    Williams, G. D. et al. The suppression of Antarctic bottom water formation by melting ice shelves in Prydz Bay. Nat. Commun. 7, 12577 (2016).

    Google Scholar 

  50. 50.

    Petty, A. A., Holland, P. R. & Feltham, D. L. Sea ice and the ocean mixed layer over the Antarctic Shelf seas. Cryosphere 8, 761–783 (2014).

    Google Scholar 

  51. 51.

    Moholdt, G., Padman, L. & Fricker, H. A. Basal mass budget of Ross and Filchner-Ronne ice shelves, Antarctica, derived from Lagrangian analysis of ICESat altimetry. J. Geophys. Res. Earth Surf. 119, 2361–2380 (2014).

    Google Scholar 

  52. 52.

    Förste, C. et al. EIGEN-6C4 The latest combined global gravity field model including GOCE data up to degree and order 2190 of GFZ Potsdam and GRGS Toulouse (GFZ Data Services, 2014); http://doi.org/10.5880/icgem.2015.1

  53. 53.

    Andersen, O., Knudsen, P. & Stenseng, L. in IGFS 2014 (eds Jin, S. & Barzaghi, R.) 111–121 (Springer, 2016).

  54. 54.

    Howard, S. L., Padman, L. & Erofeeva, S. Y. CATS2008: Circum-Antarctic Tidal Simulation version 2008 (USAP Data Center, 2019); https://doi.org/10.15784/601235

  55. 55.

    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).

    Google Scholar 

  56. 56.

    Carrère, L. & Lyard, F. Modeling the barotropic response of the global ocean to atmospheric wind and pressure forcing—comparisons with observations. Geophys. Res. Lett. 30, 1275 (2003).

    Google Scholar 

  57. 57.

    Egbert, G. D. & Erofeeva, S. Y. Efficient inverse modeling of barotropic ocean tides. J. Atmos. Ocean. Technol. 19, 183–204 (2002).

    Google Scholar 

  58. 58.

    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).

    Google Scholar 

  59. 59.

    Gardner, A. S. et al. Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years. Cryosphere 12, 521–547 (2018).

    Google Scholar 

  60. 60.

    Rignot, E., Mouginot, J. & Scheuchl, B. MEaSUREs InSAR-Based Antarctica Ice Velocity Map, Version 2 (NSIDC, 2017); https://nsidc.org/data/NSIDC-0484/versions/2

  61. 61.

    Adusumilli, S. et al. Variable basal melt rates of Antarctic Peninsula ice shelves, 1994–2016. Geophys. Res. Lett. 45, 4086–4095 (2018).

    Google Scholar 

  62. 62.

    Alley, K. E. et al. Continent-wide estimates of Antarctic strain rates from Landsat 8-derived velocity grids. J. Glaciol. 64, 321–332 (2018).

    Google Scholar 

  63. 63.

    Gelaro, R. et al. The modern-era retrospective analysis for research and applications, version 2 (MERRA-2). J. Clim. 30, 5419–5454 (2017).

    Google Scholar 

  64. 64.

    Arthern, R. J., Vaughan, D. G., Rankin, A. M., Mulvaney, R. & Thomas, E. R. In situ measurements of Antarctic snow compaction compared with predictions of models. J. Geophys. Res. Earth Surf. 115, F03011 (2010).

    Google Scholar 

  65. 65.

    Stevens, C. M. et al. The Community Firn Model (CFM) v1.0. Preprint at https://doi.org/10.5194/gmd-2019-361 (2020).

  66. 66.

    Morlighem, M. et al. Deep glacial troughs and stabilizing ridges unveiled beneath the margins of the Antarctic ice sheet. Nat. Geosci. 13, 132–137 (2020).

    Google Scholar 

  67. 67.

    Boyer, T. P. et al. World Ocean Database (WOD) 2018 (NCEI, 2018); https://www.nodc.noaa.gov/OC5/WOD/pr_wod.html

  68. 68.

    McDougall, T. J., Barker, P. M., Feistel, R. & Galton-Fenzi, B. K. Melting of ice and sea ice into seawater and frazil ice formation. J. Phys. Oceanogr. 44, 1751–1775 (2014).

    Google Scholar 

  69. 69.

    McDougall, T. J. & Barker, P. M. Getting Started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox (SCOR/IAPSO, 2011).

  70. 70.

    Schaffer, J. et al. A global, high-resolution data set of ice sheet topography, cavity geometry, and ocean bathymetry. Earth Syst. Sci. Data. 8, 543–557 (2016).

    Google Scholar 

  71. 71.

    Dunn, J. R. & Ridgway, K. R. Mapping ocean properties in regions of complex topography. Deep Sea Res. Part I 49, 591–604 (2002).

    Google Scholar 

  72. 72.

    Dinniman, M. S., Klinck, J. M. & Smith, W. O. A model study of circumpolar deep water on the West Antarctic Peninsula and Ross Sea continental shelves. Deep Sea Res. Part II 58, 1508–1523 (2011).

    Google Scholar 

  73. 73.

    Brockley, D. J. et al. REAPER: reprocessing 12 years of ERS-1 and ERS-2 altimeters and microwave radiometer data. IEEE Trans. Geosci. Remote Sens. 55, 5506–5514 (2017).

    Google Scholar 

  74. 74.

    Soussi, B. et al. ENVISAT Altimetry Level 2 Product Handbook (ESA, 2018).

  75. 75.

    Paolo, F. S., Fricker, H. A. & Padman, L. Constructing improved decadal records of Antarctic ice shelf height change from multiple satellite radar altimeters. Remote Sens. Environ. 177, 192–205 (2016).

    Google Scholar 

  76. 76.

    Wessem, J. M. et al. Modelling the climate and surface mass balance of polar ice sheets using RACMO2—Part 2: Antarctica (1979–2016). Cryosphere 12, 1479–1498 (2018).

    Google Scholar 

  77. 77.

    Nicolas, J. P. et al. January 2016 extensive summer melt in West Antarctica favoured by strong El Niño. Nat. Commun. 8, 15799 (2017).

    Google Scholar 

  78. 78.

    McMillan, M. et al. Increased ice losses from Antarctica detected by CryoSat-2. Geophys. Res. Lett. 41, 3899–3905 (2014).

    Google Scholar 

  79. 79.

    Mouginot, J., Rignot, E. & Scheuchl, B. Sustained increase in ice discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013. Geophys. Res. Lett. 41, 1576–1584 (2014).

    Google Scholar 

  80. 80.

    Mouginot, J., Rignot, E., Scheuchl, B. & Millan, R. Comprehensive annual ice sheet velocity mapping using Landsat-8, Sentinel-1, and RADARSAT-2 data. Remote Sens. 9, 364 (2017).

    Google Scholar 

  81. 81.

    Ligtenberg, S. R. M., Helsen, M. M. & Broeke, M. Rvanden An improved semi-empirical model for the densification of Antarctic firn. Cryosphere 5, 809–819 (2011).

    Google Scholar 

  82. 82.

    Joughin, I. & Vaughan, D. G. Marine ice beneath the Filchner–Ronne Ice Shelf, Antarctica: a comparison of estimated thickness distributions. Ann. Glaciol. 39, 511–517 (2004).

    Google Scholar 

  83. 83.

    Fricker, H. A., Popov, S., Allison, I. & Young, N. Distribution of marine ice beneath the Amery Ice Shelf. Geophys. Res. Lett. 28, 2241–2244 (2001).

    Google Scholar 

  84. 84.

    Lambrecht, A., Sandhäger, H., Vaughan, D. G. & Mayer, C. New ice thickness maps of Filchner–Ronne Ice Shelf, Antarctica, with specific focus on grounding lines and marine ice. Antarct. Sci. 19, 521–532 (2007).

    Google Scholar 

  85. 85.

    Cook, A. J. & Vaughan, D. G. Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years. Cryosphere 22 (2010).

  86. 86.

    MacGregor, J. A., Catania, G. A., Markowski, M. S. & Andrews, A. G. Widespread rifting and retreat of ice-shelf margins in the eastern Amundsen Sea Embayment between 1972 and 2011. J. Glaciol. 58, 458–466 (2012).

    Google Scholar 

  87. 87.

    Griggs, J. A. & Bamber, J. L. Antarctic ice-shelf thickness from satellite radar altimetry. J. Glaciol. 57, 485–498 (2011).

    Google Scholar 

  88. 88.

    Scambos, T. A., Bohlander, J. A., Shuman, C. A. & Skvarca, P. Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica. Geophys. Res. Lett. 31, L18402 (2004).

    Google Scholar 

  89. 89.

    Scambos, T. et al. Ice shelf disintegration by plate bending and hydro-fracture: satellite observations and model results of the 2008 Wilkins ice shelf break-ups. Earth Planet. Sci. Lett. 280, 51–60 (2009).

    Google Scholar 

Download references

Acknowledgements

This study was funded by NASA grants NNX17AI03G and NNX17AG63G, and NSF grant 1744789. S.A. was also supported by the NASA Earth and Space Science Fellowship. B.M was supported by the ICESat-2 Project Science Office. We thank members of the Scripps Polar Center, S. Howard, and K. Nicholls for their important contributions to this manuscript.

Author information

Affiliations

Authors

Contributions

S.A., H.A.F., L.P. and M.R.S. conceptualized the study. S.A. and M.R.S. performed altimetry data processing. B.M. conducted climate and firn modelling. All authors contributed to the writing and editing of the manuscript. H.A.F., B.M., L.P. and M.R.S. contributed equally to this work.

Corresponding author

Correspondence to Susheel Adusumilli.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Primary Handling Editors: James Super; Heike Langenberg.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–8 and Table 1.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Adusumilli, S., Fricker, H.A., Medley, B. et al. Interannual variations in meltwater input to the Southern Ocean from Antarctic ice shelves. Nat. Geosci. 13, 616–620 (2020). https://doi.org/10.1038/s41561-020-0616-z

Download citation

Further reading

Search

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