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Global ocean heat transport dominated by heat export from the tropical Pacific

Abstract

Heat redistribution is one of the main mechanisms by which oceans regulate Earth’s climate. Analyses of ocean heat transport tend to emphasize global-scale seawater pathways and concepts such as the great ocean conveyor belt. However, it is the divergence or convergence of heat transport within an oceanic region, rather than the origin or destination of seawater transiting through that region, that is most immediately relevant to Earth’s heat budget. Here we use a recent gridded estimate of ocean heat transport to reveal the net effect on Earth’s heat budget, the ‘effective’ ocean heat transport, by removing internal ocean heat loops that have obscured the interpretation of measurements. The result demonstrates the overwhelming predominance of the tropical Pacific, which exports four times as much heat as is imported in the Atlantic and Arctic. It also highlights the unique ability of the Atlantic and Indian oceans to transport heat across the Equator—Northward and Southward, respectively. However, effective inter-ocean heat transports are smaller than expected, suggesting that global-scale seawater pathways play only a minor role in Earth’s heat budget.

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Code availability

The code used to generate the results in the paper can be accessed from public repositories and permanent archives31,35. Maps shown in this paper and Supplementary Information were created using the M_map toolbox41, available at www.eoas.ubc.ca/~rich/map.html.

Data availability

The data that support the findings of this study are available from the corresponding author upon request and via the Harvard Dataverse https://doi.org/10.7910/DVN/AVVGYX. They are publicly available and permanently archived33,34.

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

References

  1. 1.

    Stocker, T. F. in Ocean Circulation and Climate (eds Siedler, G. et al.) Ch. 1 (International Geophysics Vol. 103, Academic Press, 2013).

  2. 2.

    Trenberth, K. E. & Solomon, A. The global heat balance: heat transports in the atmosphere and ocean. Clim. Dyn. 10, 107–134 (1994).

  3. 3.

    Ganachaud, A. & Wunsch, C. Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data. Nature 408, 453–457 (2000).

  4. 4.

    Trenberth, K. E. & Caron, J. M. Estimates of meridional atmosphere and ocean heat transports. J. Clim. 14, 3433–3443 (2001).

  5. 5.

    Macdonald, A. M. & Baringer, M. O. in Ocean Circulation and Climate (eds Gerold Siedler, J. G. et al.) Vol. 103 Ch. 29 (Academic Press, 2013).

  6. 6.

    Fasullo, J. T. & Trenberth, K. E. The annual cycle of the energy budget. part II: meridional structures and poleward transports. J. Clim. 21, 2313–2325 (2008).

  7. 7.

    Trenberth, K. E. & Fasullo, J. T. Atlantic meridional heat transports computed from balancing Earth’s energy locally. Geophys. Res. Lett. 44, 1919–1927 (2017).

  8. 8.

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

  9. 9.

    Döös, K. et al. The coupled ocean–atmosphere hydrothermohaline circulation. J. Clim. 30, 631–647 (2017).

  10. 10.

    Ganachaud, A. & Wunsch, C. Large-scale ocean heat and freshwater transports during the world ocean circulation experiment. J. Clim. 16, 696–705 (2003).

  11. 11.

    Johns, W. E. et al. Continuous, array-based estimates of Atlantic Ocean heat transport at 26.5°N. J. Clim. 24, 2429–2449 (2011).

  12. 12.

    Lumpkin, R. & Speer, K. Global ocean meridional overturning. J. Phys. Oceanogr. 37, 2550–2562 (2007).

  13. 13.

    Talley, L. D. Shallow, intermediate, and deep overturning components of the global heat budget. J. Phys. Oceanogr. 33, 530–560 (2003).

  14. 14.

    Boccaletti, G., Ferrari, R., Adcroft, A., Ferreira, D. & Marshall, J. The vertical structure of ocean heat transport. Geophys. Res. Lett. 32, L10603 (2005).

  15. 15.

    Ferrari, R. & Ferreira, D. What processes drive the ocean heat transport? Ocean Model. 38, 171–186 (2011).

  16. 16.

    Speich, S. et al. Tasman leakage: a new route in the global ocean conveyor belt. Geophys. Res. Lett. 29, 55-1–55-4 (2002).

  17. 17.

    Hirst, A. C. & Godfrey, J. The role of Indonesian throughflow in a global ocean GCM. J. Phys. Oceanogr. 23, 1057–1086 (1993).

  18. 18.

    Sun, C. & Watts, D. R. Heat flux carried by the Antarctic Circumpolar Current mean flow. J. Geophys. Res. C 107, 2-1–2-13 (2002).

  19. 19.

    Tamsitt, V., Talley, L. D., Mazloff, M. R. & Cerovečki, I. Zonal variations in the Southern Ocean heat budget. J. Clim. 29, 6563–6579 (2016).

  20. 20.

    Godfrey, J. S. A sverdrup model of the depth-integrated flow for the world ocean allowing for island circulations. Geophys. Astrophys. Fluid Dyn. 45, 89–112 (1989).

  21. 21.

    Song, Q., Vecchi, G. A. & Rosati, A. J. The role of the Indonesian throughflow in the Indo-Pacific climate variability in the GFDL coupled climate model. J. Clim. 20, 2434–2451 (2007).

  22. 22.

    Corell, H., Nilsson, J., Döös, K. & Broström, G. Wind sensitivity of the inter-ocean heat exchange. Tellus A 61, 635–653 (2009).

  23. 23.

    Speer, K. & Forget, G. in Ocean Circulation and Climate (eds Siedler, G. et al.) Vol. 103 Ch. 9 (Academic Press, 2013).

  24. 24.

    Balmaseda, M. et al. The Ocean Reanalyses Intercomparison Project (ORA-IP). J. Oper. Oceanogr. 8, s80–s97 (2015).

  25. 25.

    Bryan, K. Measurements of meridional heat transport by ocean currents. J. Geophys. Res. 67, 3403–3414 (1962).

  26. 26.

    Warren, B. A. Approximating the energy transport across oceanic sections. J. Geophys. Res. C 104, 7915–7919 (1999).

  27. 27.

    Vranes, K., Gordon, A. L. & Ffield, A. The heat transport of the Indonesian throughflow and implications for the indian ocean heat budget. Deep Sea Res. II 49, 1391–1410 (2002).

  28. 28.

    Watterson, I. G. Decomposition of global ocean currents using a simple iterative method. J. Atmos. Ocean. Technol. 18, 691–703 (2001).

  29. 29.

    Chen, T.-C. Global water vapor flux and maintenance during FGGE. Mon. Weather Rev. 113, 1801–1819 (1985).

  30. 30.

    Forget, G. et al. ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation. Geosci. Model Dev. 8, 3071–3104 (2015).

  31. 31.

    Forget, G. gcmfaces: A Matlab Toolbox Designed to Handle Gridded Earth Variables Using Compact and Generic Codes (Massachusetts Institute of Technology, 2017); https://doi.org/10.5281/zenodo.834079

  32. 32.

    Forget, G. et al. ECCO Version 4: Second Release (DSpace@MIT, 2019); http://hdl.handle.net/1721.1/102062

  33. 33.

    Forget, G. ECCO Version 4 Release 2: Monthly 1992–2011 Time Series (Massachusetts Institute of Technology, 2016); https://doi.org/10.7910/DVN/NXYKDW

  34. 34.

    Forget, G. ECCO Version 4 Release 2: Three Daily Tendency Terms for Temperature (Massachusetts Institute of Technology, 2016); https://doi.org/10.7910/DVN/T093T1

  35. 35.

    Forget, G. ECCO Version 4: An Ocean State Estimation Framework Based on the MITgcm and its Adjoint (Massachusetts Institute of Technology, 2018); https://doi.org/10.5281/zenodo.1211363

  36. 36.

    Davies, J. H. Global map of solid Earth surface heat flow. Geochem. Geophys. Geosyst. 14, 4608–4622 (2013).

  37. 37.

    Forget, G. & Ponte, R. The partition of regional sea level variability. Prog. Oceanogr. 137, 173–195 (2015).

  38. 38.

    Forget, G., Ferreira, D. & Liang, X. On the observability of turbulent transport rates by Argo: supporting evidence from an inversion experiment. Ocean Sci. 11, 839–853 (2015).

  39. 39.

    Large, W. & Yeager, S. The global climatology of an interannually varying air–sea flux data set. Clim. Dyn. 33, 341–364 (2009).

  40. 40.

    Sverdrup, H. U. in Handbuch der Physik (ed. Bartels, J.) Vol. 48 608–670 (Springer, 1957).

  41. 41.

    Pawlowicz, R. M_Map: A Mapping Package for MATLAB Version 1.4j (University of British Columbia, 2018).

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Acknowledgements

J. Chapin is acknowledged for helping proofread the manuscript. G.F. acknowledges support from NASA (6937342) and the Simons Foundation (549931).

Author information

G.F. performed the analyses and wrote the manuscript. Both authors contributed to the design of the study and interpretation of the results.

Competing interests

The authors declare no competing interests.

Correspondence to Gaël Forget.

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DOI

https://doi.org/10.1038/s41561-019-0333-7

Fig. 1: OHT as estimated through sections that separate ocean basins and delimit the tropics for the 1992–2011 time average.
Fig. 2: Meridional effective OHT.
Fig. 3: Scalar potential and vector potential as derived from the global vector field of OHT0 for the 1992–2011 time average.