Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation

Abstract

The lower limb of the Atlantic overturning circulation is resupplied by the sinking of dense Antarctic Bottom Water (AABW) that forms via intense air–sea–ice interactions next to Antarctica, especially in the Weddell Sea1. In the last three decades, AABW has warmed, freshened and declined in volume across the Atlantic Ocean and elsewhere2,3,4,5,6,7, suggesting an ongoing major reorganization of oceanic overturning8,9. However, the future contributions of AABW to the Atlantic overturning circulation are unclear. Here, using observations of AABW in the Scotia Sea, the most direct pathway from the Weddell Sea to the Atlantic Ocean, we show a recent cessation in the decline of the AABW supply to the Atlantic overturning circulation. The strongest decline was observed in the volume of the densest layers in the AABW throughflow from the early 1990s to 2014; since then, it has stabilized and partially recovered. We link these changes to variability in the densest classes of abyssal waters upstream. Our findings indicate that the previously observed decline in the supply of dense water to the Atlantic Ocean abyss may be stabilizing or reversing and thus call for a reassessment of Antarctic influences on overturning circulation, sea level, planetary-scale heat distribution and global climate2,3,8.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Pathways of AABW from the Weddell Sea into the world ocean.
Fig. 2: Area of LWSDW from hydrographic sections.
Fig. 3: Normalized areas of water masses on hydrographic sections.
Fig. 4: Northward transport of LWSDW through Orkney Passage.

Data availability

CTD data were collected on UK, US and German research cruises; these data are available at CCHDO (http://cchdo.ucsd.edu) for US and some UK cruises, BODC (http://www.bodc.ac.uk) for UK cruises and PANGAEA (http://www.pangaea.de) for German cruises46,47,48,49,50,51,52,53,54; links to the data are given in Supplementary Table 1. Mooring data from Orkney Passage are available from BODC at https://www.bodc.ac.uk/data/bodc_database/nodb/data_collection/6565/.

The altimeter products were produced by Ssalto/Duacs and distributed by Aviso, with support from CNES (https://www.aviso.altimetry.fr). ERA-interim reanalysis data are available from the ECMWF (https://www.ecmwf.int/en/research/climate-reanalysis/era-interim). SOSE data are available from http://sose.ucsd.edu/. GEBCO_2014 bathymetry data are available from https://www.gebco.net/.

References

  1. 1.

    Orsi, A. H., Johnson, G. C. & Bullister, J. L. Circulation, mixing, and production of Antarctic Bottom Water. Prog. Oceanogr. 43, 55–109 (1999).

  2. 2.

    Johnson, G. C., McTaggart, K. E. & Wanninkhof, R. Antarctic Bottom Water temperature changes in the western south Atlantic from 1989 to 2014. J. Geophys. Res. Oceans 119, 8567–8577 (2014).

  3. 3.

    Purkey, S. G. & Johnson, G. C. Antarctic Bottom Water warming and freshening: contributions to sea level rise, ocean freshwater budgets, and global heat gain. J. Clim. 26, 6105–6122 (2013).

  4. 4.

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

  5. 5.

    Menezes, V. V., Macdonald, A. M. & Schatzman, C. Accelerated freshening of Antarctic Bottom Water over the last decade in the Southern Indian Ocean. Sci. Adv. 3, e1601426 (2017).

  6. 6.

    Rintoul, S. R. Rapid freshening of Antarctic Bottom Water formed in the Indian and Pacific oceans. Geophys. Res. Lett. 34, L06606 (2007).

  7. 7.

    Bindoff, N. L. & Hobbs, W. R. Oceanography: deep ocean freshening. Nat. Clim. Change 3, 864–865 (2013).

  8. 8.

    Patara, L. & Böning, C. W. Abyssal ocean warming around Antarctica strengthens the Atlantic overturning circulation. Geophys. Res. Lett. 41, 3972–3978 (2014).

  9. 9.

    Johnson, G. C., Purkey, S. G. & Toole, J. M. Reduced Antarctic meridional overturning circulation reaches the North Atlantic ocean. Geophys. Res. Lett. 35, L22601 (2008).

  10. 10.

    Johnson, G. C. Quantifying Antarctic Bottom Water and North Atlantic deep water volumes. J. Geophys. Res. Oceans 113, C05027 (2008).

  11. 11.

    Sloyan, B. M. & Rintoul, S. R. The Southern Ocean limb of the global deep overturning circulation. J. Phys. Oceanogr. 31, 143–173 (2001).

  12. 12.

    Jullion, L. et al. Decadal freshening of the Antarctic Bottom Water exported from the Weddell Sea. J. Clim. 26, 8111–8125 (2013).

  13. 13.

    Meredith, M. P., Garabato, A. C. N., Gordon, A. L. & Johnson, G. C. Evolution of the deep and bottom waters of the Scotia Sea, Southern Ocean, during 1995–2005. J. Clim. 21, 3327–3343 (2008).

  14. 14.

    Heywood, K. J., Naveira Garabato, A. C. & Stevens, D. P. High mixing rates in the abyssal Southern Ocean. Nature 415, 1011–1014 (2002).

  15. 15.

    Jackett, D. R. & McDougall, T. J. A neutral density variable for the world’s oceans. J. Phys. Oceanogr. 27, 237–263 (1997).

  16. 16.

    Naveira Garabato, A. C., McDonagh, E. L., Stevens, D. P., Heywood, K. J. & Sanders, R. J. On the export of Antarctic Bottom Water from the Weddell Sea. Deep Sea Res. Pt II 49, 4715–4742 (2002).

  17. 17.

    Naveira Garabato, A. C., Williams, A. P. & Bacon, S. The three-dimensional overturning circulation of the Southern Ocean during the WOCE era. Prog. Oceanogr. 120, 41–78 (2014).

  18. 18.

    Firing, Y. L., McDonagh, E. L., King, B. A. & Desbruyères, D. G. Deep temperature variability in Drake Passage. J. Geophys. Res. Oceans 122, 713–725 (2017).

  19. 19.

    Meijers, A. J. S. et al. Wind-driven export of Weddell Sea slope water. J. Geophys. Res. Oceans 121, 7530–7546 (2016).

  20. 20.

    Fahrbach, E., Hoppema, M., Rohardt, G., Schröder, M. & Wisotzki, A. Decadal-scale variations of water mass properties in the deep Weddell Sea. Ocean Dynam. 54, 77–91 (2004).

  21. 21.

    Sheen, K. L. et al. Rates and mechanisms of turbulent dissipation and mixing in the Southern Ocean: results from the diapycnal and isopycnal mixing experiment in the Southern Ocean (DIMES). J. Geophys. Res. Oceans 118, 2774–2792 (2013).

  22. 22.

    Sheen, K. L. et al. Eddy-induced variability in Southern Ocean abyssal mixing on climatic timescales. Nat. Geosci. 7, 577–582 (2014).

  23. 23.

    Meredith, M. P. et al. Synchronous intensification and warming of Antarctic Bottom Water outflow from the Weddell Gyre. Geophys. Res. Lett. 38, L03603 (2011).

  24. 24.

    Su, Z., Stewart, A. L. & Thompson, A. F. An idealized model of Weddell Gyre export variability. J. Phys. Oceanogr. 44, 1671–1688 (2014).

  25. 25.

    Polzin, K. L., Naveira Garabato, A. C., Abrahamsen, E. P., Jullion, L. & Meredith, M. P. Boundary mixing in Orkney Passage outflow. J. Geophys. Res. Oceans 119, 8627–8645 (2014).

  26. 26.

    Thompson, A. F., Heywood, K. J., Schmidtko, S. & Stewart, A. L. Eddy transport as a key component of the Antarctic overturning circulation. Nat. Geosci. 7, 879–884 (2014).

  27. 27.

    Coles, V. J., McCarney, M. S., Olson, D. B. & Smethie, W. M. Jr. Changes in Antarctic Bottom Water properties in the western South Atlantic in the late 1980s. J. Geophys. Res. Oceans 101, 8957–8970 (1996).

  28. 28.

    Armitage, T. W. K., Kwok, R., Thompson, A. F. & Cunningham, G. Dynamic topography and sea level anomalies of the Southern Ocean: variability and teleconnections. J. Geophys. Res. Oceans 123, 613–630 (2018).

  29. 29.

    Hellmer, H. H., Huhn, O., Gomis, D. & Timmermann, R. On the freshening of the northwestern Weddell Sea continental shelf. Ocean Sci. 7, 305–316 (2011).

  30. 30.

    Haumann, F. A., Gruber, N., Münnich, M., Frenger, I. & Kern, S. Sea-ice transport driving Southern Ocean salinity and its recent trends. Nature 537, 89–92 (2016).

  31. 31.

    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).

  32. 32.

    Daae, K., Darelius, E., Fer, I., Østerhus, S. & Ryan, S. Wind stress mediated variability of the Filchner Trough overflow, Weddell Sea. J. Geophys. Res. Oceans 123, 3186–3203 (2018).

  33. 33.

    Kerr, R., Dotto, T. S., Mata, M. M. & Hellmer, H. H. Three decades of deep water mass investigation in the Weddell Sea (1984-2014): temporal variability and changes. Deep Sea Res. Pt II 149, 70–83 (2018).

  34. 34.

    Sutherland, W. J. et al. A horizon scan of global conservation issues for 2012. Trends Ecol. Evol. 27, 12–18 (2012).

  35. 35.

    Arhan, M., Heywood, K. J. & King, B. A. The deep waters from the Southern Ocean at the entry to the Argentine basin. Deep Sea Res. Pt II 46, 475–499 (1999).

  36. 36.

    Stramma, L. & England, M. On the water masses and mean circulation of the south Atlantic ocean. J. Geophys. Res. Oceans 104, 20863–20883 (1999).

  37. 37.

    Locarnini, R. A. et al. World Ocean Atlas 2013 Vol. 1 (eds Levitus, S. & Mishonov, A.) (NOAA Atlas NESDIS Vol. 73, NOAA, 2013).

  38. 38.

    Zweng, M. M. et al. World Ocean Atlas 2013 Vol. 2 (eds Levitus, S. & Mishonov, A.) (NOAA Atlas NESDIS Vol. 74, NOAA, 2013).

  39. 39.

    Garcia, H. E. et al. World Ocean Atlas 2013 Vol. 3 (eds Levitus, S. & Mishonov, A.) (NOAA Atlas NESDIS Vol. 75, NOAA, 2014).

  40. 40.

    Garcia, H. E. et al. World Ocean Atlas 2013 Vol. 4 (eds Levitus, S. & Mishonov, A.) (NOAA Atlas NESDIS Vol. 76, NOAA, 2014).

  41. 41.

    Kawano, T. et al. The latest batch-to-batch difference table of standard seawater and its application to the WOCE onetime sections. J. Oceanogr. 62, 777–792 (2006).

  42. 42.

    Smith, W. H. F. & Sandwell, D. T. Global sea floor topography from satellite altimetry and ship depth soundings. Science 277, 1956–1962 (1997).

  43. 43.

    Mazloff, M. R., Heimbach, P. & Wunsch, C. An eddy-permitting Southern Ocean state estimate. J. Phys. Oceanogr. 40, 880–899 (2010).

  44. 44.

    Dee, D. P. et al. The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q. J. R. Meteorol. Soc. 137, 553–597 (2011).

  45. 45.

    Naveira Garabato, A. C., Heywood, K. J. & Stevens, D. P. Modification and pathways of Southern Ocean deep waters in the Scotia Sea. Deep Sea Res. Pt II 49, 681–705 (2002).

  46. 46.

    Fahrbach, E. & Rohardt, G. Physical Oceanography during POLARSTERN Cruise ANT-VIII/2 (WWGS) on Section SR02 and SR04. PANGAEA https://doi.org/10.1594/PANGAEA.742580 (1990).

  47. 47.

    Fahrbach, E. & Rohardt, G. Physical Oceanography during POLARSTERN Cruise ANT-IX/2 on Section SR04. PANGAEA https://doi.org/10.1594/PANGAEA.735277 (1991).

  48. 48.

    Fahrbach, E. & Rohardt, G. Physical Oeanography during POLARSTERN Cruise ANT-X/7 on Section SR04. PANGAEA https://doi.org/10.1594/PANGAEA.742651 (1993).

  49. 49.

    Fahrbach, E. & Rohardt, G. Physical Oceanography during POLARSTERN Cruise ANT-XIII/4 on Section S04A. PANGAEA https://doi.org/10.1594/PANGAEA.738489 (1996).

  50. 50.

    Fahrbach, E. & Rohardt, G. Physical Oceanography during POLARSTERN Cruise ANT-XV/4 (DOVETAIL) on Section SR04. PANGAEA https://doi.org/10.1594/PANGAEA.742626 (1998).

  51. 51.

    Rohardt, G. Physical Oceanography during POLARSTERN Cruise ANT-XXII/3. PANGAEA https://doi.org/10.1594/PANGAEA.733664 (2010).

  52. 52.

    Fahrbach, E. & Rohardt, G. Physical Oceanography during POLARSTERN Cruise ANT-XXIV/3. PANGAEA https://doi.org/10.1594/PANGAEA.733414 (2008).

  53. 53.

    Rohardt, G., Fahrbach, E. & Wisotzki, A. Physical Oceanography during POLARSTERN Cruise ANT-XXVII/2. PANGAEA https://doi.org/10.1594/PANGAEA.772244 (2011).

  54. 54.

    Rohardt, G. Physical Oceanography during POLARSTERN Cruise ANT-XXIX/2. PANGAEA https://doi.org/10.1594/PANGAEA.817255 (2013).

Download references

Acknowledgements

E.P.A., A.C.N.G. and M.P.M. were supported by Natural Environment Research Council (NERC) grant nos. NE/K012843/1 and NE/K013181/1 (Dynamics of the Orkney Passage Outflow). E.P.A., A.S.M., B.A.K., Y.L.F. and M.P.M. were supported by NERC grant no. NE/N018095/1 (Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports, ORCHESTRA). K.P. was supported by NSF grant no. OCE-1536779. A.C.N.G. was supported by the Royal Society and the Wolfson Foundation. Collection of data on A23 and SR1b was supported by NERC National Capability funding including ORCHESTRA. Collection of data in Orkney Passage was supported by NERC National Capability funding including ORCHESTRA and was funded in part by the Climate Observation Division, Climate Program Office (FundRef no. 100007298), National Oceanic and Atmospheric Administration, US Department of Commerce. Computational resources for SOSE were provided by NSF XSEDE resource grant no. OCE130007.

Author information

E.P.A., A.S.M., M.P.M., B.A.K., Y.L.F., J.B.S. and B.A.H. contributed to data collection and interpretation. K.P. instigated this study with questions concerning the interpretation of the diminishing area of LWSDW along SR1b and A23. K.L.S. performed the kinetic energy anomaly analysis and generated Supplementary Fig. 3. E.P.A., A.S.M. and M.P.M. made the remaining figures and wrote the manuscript with contributions from all the remaining authors.

Correspondence to E. Povl Abrahamsen.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information: Nature Climate Change thanks Viviane Menezes and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Supplementary information

Supplementary Information

Supplementary Table 1 and Supplementary Figs. 1–4

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark