Contribution of topographically generated submesoscale turbulence to Southern Ocean overturning

Abstract

The ocean’s global overturning circulation regulates the transport and storage of heat, carbon and nutrients. Upwelling across the Southern Ocean’s Antarctic Circumpolar Current and into the mixed layer, coupled to water mass modification by surface buoyancy forcing, has been highlighted as a key process in the closure of the overturning circulation1,2. Here, using twelve high-resolution hydrographic sections in southern Drake Passage, collected with autonomous ocean gliders, we show that Circumpolar Deep Water originating from the North Atlantic, known as Lower Circumpolar Deep Water, intersects sloping topography in narrow and strong boundary currents. Observations of strong lateral buoyancy gradients, enhanced bottom turbulence, thick bottom mixed layers and modified water masses are consistent with growing evidence that topographically generated submesoscale flows over continental slopes enhance near-bottom mixing3,4, and that cross-density upwelling occurs preferentially over sloping topography5,6. Interactions between narrow frontal currents and topography occur elsewhere along the path of the Antarctic Circumpolar Current, which leads us to propose that such interactions contribute significantly to the closure of the overturning in 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.

Figure 1: Overview of the ChinStrAP (Changes in Stratification at the Antarctic Peninsula) field programme.
Figure 2: Stratification and flow characteristics from a typical glider section (transect 5 in Fig. 1).
Figure 3: Bottom mixed layer (BML) properties over continental shelf and slope.
Figure 4: Water mass transformation over the continental slope and schematics of the upper overturning closure in the Southern Ocean.

References

  1. 1

    Marshall, J. & Radko, T. Residual-mean solutions for the Antarctic Circumpolar Current and its associated overturning circulation. J. Phys. Oceanogr. 33, 2341–2354 (2003).

  2. 2

    Marshall, J. & Speer, K. Closure of the meridional overturning circulation through Southern Ocean upwelling. Nat. Geosci. 5, 171–180 (2012).

  3. 3

    Molemaker, M. J., McWilliams, J. C. & Dewar, W. K. Submesoscale instability and generation of mesoscale anticyclones near a separation of the California Undercurrent. J. Phys. Oceanogr. 45, 613–629 (2015).

  4. 4

    Gula, J., Molemaker, J. & McWilliams, J. C. Topographic generation of submesoscale centrifugal instability and energy dissipation. Nat. Commun. 7, 12811 (2016).

  5. 5

    De Lavergne, C., Madec, G., Le Sommer, J., Nurser, A. G. & Naveira Garabato, A. C. On the consumption of Antarctic Bottom Water in the abyssal ocean. J. Phys. Oceanogr. 46, 635–661 (2016).

  6. 6

    Ferrari, R., Mashayek, A., McDougall, T. J., Nikurashin, M. & Campin, J.-M. Turning ocean mixing upside down. J. Phys. Oceanogr. 46, 2239–2261 (2016).

  7. 7

    Speer, K., Rintoul, S. R. & Sloyan, B. The diabatic Deacon cell. J. Phys. Oceanogr. 30, 3212–3222 (2000).

  8. 8

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

  9. 9

    Munk, W. H. Abyssal recipes. Deep-Sea Res. 13, 707–730 (1966).

  10. 10

    Wolfe, C. L. & Cessi, P. The adiabatic pole-to-pole overturning circulation. J. Phys. Oceanogr. 41, 1795–1810 (2011).

  11. 11

    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).

  12. 12

    Talley, L. D. Closure of the global overturning circulation through the Indian, Pacific, and Southern Oceans: schematics and transports. Oceanography 26, 80–97 (2013).

  13. 13

    Ferrari, R. et al. Antarctic sea ice control on ocean circulation in present and glacial climates. Proc. Natl Acad. Sci. USA 111, 8753–8758 (2014).

  14. 14

    Orsi, A. H. & Whitworth III, T. Hydrographic Atlas of the World Ocean Circulation Experiment (WOCE): Volume 1: Southern Ocean (WOCE International Project Office, 2005).

  15. 15

    Naveira Garabato, A. C., Stevens, D. P., Watson, A. J. & Roether, W. Short-circuiting of the overturning circulation in the Antarctic Circumoplar Current. Nature 447, 194–197 (2007).

  16. 16

    Silvester, J. M., Lenn, Y.-D., Polton, J. A., Rippeth, T. P. & Maqueda, M. M. Observations of a diapycnal shortcut to adiabatic upwelling of Antarctic Circumpolar Deep Water. Geophys. Res. Lett. 41, 7950–7956 (2014).

  17. 17

    Orsi, A. H., Smethie, W. M. & Bullister, J. L. On the total input of Antarctic waters to the deep ocean: a preliminary estimate from chlorofluorocarbon measurements. J. Geophys. Res. 107, 31-1–31-14 (2002).

  18. 18

    Armi, L. Some evidence for boundary mixing in the deep ocean. J. Geophys. Res. 83, 1971–1979 (1978).

  19. 19

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

  20. 20

    Orsi, A. H., Whitworth III, T. & Nowlin, W. D. On the meridional extent and fronts of the Antarctic Circumpolar Current. Deep-Sea Res. 42, 641–673 (1995).

  21. 21

    Gill, A. E. Circulation and bottom water production in the Weddell Sea. Deep-Sea Res. 20, 111–140 (1973).

  22. 22

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

  23. 23

    Lozovatsky, I., Fernando, H. & Shapovalov, S. Deep-ocean mixing on the basin scale: inference from North Atlantic transects. Deep-Sea Res. I 55, 1075–1089 (2008).

  24. 24

    Todd, R. E. High-frequency internal waves and thick bottom mixed layers observed by gliders in the Gulf Stream. Geophys. Res. Lett. 44, 6316–6325 (2017).

  25. 25

    Phillips, O. M., Shyu, J.-H. & Salmun, H. An experiment on boundary mixing: mean circulation and transport rates. J. Fluid Mech. 173, 473–499 (1986).

  26. 26

    Garrett, C., MacCready, P. & Rhines, P. Boundary mixing and arrested Ekman layers: rotating stratified flow near a sloping boundary. Annu. Rev. Fluid Mech. 25, 291–323 (1993).

  27. 27

    Flexas, M. M., Schodlok, M., Padman, L., Menemenlis, D. & Orsi, A. Role of tides on the formation of the Antarctic Slope Front at the Weddell–Scotia Confluence. J. Geophys. Res. 120, 3658–3680 (2015).

  28. 28

    Rosso, I., Hogg, A. M., Kiss, A. E. & Gayen, B. Topographic influence on submesoscale dynamics in the Southern Ocean. Geophys. Res. Lett. 42, 1139–1147 (2015).

  29. 29

    Thompson, A. F., Stewart, A. L. & Bischoff, T. A multi-basin residual-mean model for the global overturning circulation. J. Phys. Oceanogr. 46, 2583–2604 (2016).

  30. 30

    Tamsitt, V. et al. Spiraling pathways of global deep waters to the surface of the Southern Ocean. Nat. Commun. 8, 172 (2017).

  31. 31

    Thorpe, S. A. The Turbulent Ocean (Cambridge Univ. Press, 2005).

Download references

Acknowledgements

X.R., A.F.T. and M.M.F. received support from NSF grant OPP-1246460. J.S. received support from NSF grant OPP-1246160. A.F.T. also received support from the David and Lucille Packard Foundation.

Author information

A.F.T. and J.S. conceived and designed the field programme; X.R., A.F.T. and J.S. collected the data; X.R., A.F.T. and M.M.F. analysed the data; X.R., A.F.T., M.M.F. and J.S. co-wrote the paper.

Correspondence to Xiaozhou Ruan.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 2568 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Ruan, X., Thompson, A., Flexas, M. et al. Contribution of topographically generated submesoscale turbulence to Southern Ocean overturning. Nature Geosci 10, 840–845 (2017). https://doi.org/10.1038/ngeo3053

Download citation

Further reading