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Increased ocean heat transport into the Nordic Seas and Arctic Ocean over the period 1993–2016


Warm water of subtropical origin flows northward in the Atlantic Ocean and transports heat to high latitudes. This poleward heat transport has been implicated as one possible cause of the declining sea-ice extent and increasing ocean temperatures across the Nordic Seas and the Arctic Ocean, but robust estimates are still lacking. Here, we use a box inverse model and more than 20 years of volume transport measurements to show that the mean ocean heat transport was 305 ± 26 TW for 1993–2016. A significant increase of 21 TW occurred after 2001, which is sufficient to account for the recent accumulation of heat in the northern seas. Ocean heat transport may therefore have been a major contributor to climate change since the late 1990s. This increased heat transport contrasts with the Atlantic Meridional Overturning Circulation (AMOC) slowdown at mid-latitudes and indicates a discontinuity of the overturning circulation measured at different latitudes in the Atlantic Ocean.

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Fig. 1: Major ocean currents of the region and data coverage.
Fig. 2: Mass-balanced volume transport across the boundary of the Arctic Mediterranean.
Fig. 3: Mass-balanced ocean heat transport across the boundary of the Arctic Mediterranean.
Fig. 4: Filtered ocean heat and temperature transport changes referenced to January 1997.
Fig. 5: Summary of ocean and sea ice heat transport estimates in the North Atlantic and Arctic Mediterranean.

Data availability

The mass-balanced ocean volume and heat transports are available at the Norwegian Marine Data Centre repository at volume transport time series for GSR branches (IF, FSC, NIIC, DS and FBC) are available at Oceansites website The WTR data are available through The objectively mapped sections in Davis Strait are available via The Bering Strait data are available at project website The Arctic Ocean heat transport estimates during 2004–2010 are available at The ERA-Interim reanalysis data were obtained from European Centre for Medium-Range Weather Forecasts ( The PIOMAS were obtained from the Polar Science Centre at University of Washington (


  1. 1.

    Buckley, M. W. & Marshall, J. Observations, inferences, and mechanisms of the atlantic meridional overturning circulation: a review. Rev. Geophys. 54, 5–63 (2016).

    Google Scholar 

  2. 2.

    Eldevik, T. et al. A brief history of climate—the northern seas from the Last Glacial Maximum to global warming. Quat. Sci. Rev. 106, 225–246 (2014).

    Google Scholar 

  3. 3.

    Årthun, M., Kolstad, E., Eldevik, T. & Keenlyside, N. S. Time scales and sources of European temperature variability. Geophys. Res. Lett. 45, 3597–3604 (2018).

    Google Scholar 

  4. 4.

    Mauritzen, C. Production of dense overflow waters feeding the North Atlantic across the Greenland–Scotland Ridge. Part 1. Evidence for a revised circulation scheme. Deep Sea Res. 43, 769–806 (1996).

    Google Scholar 

  5. 5.

    Smedsrud, L. H. et al. The role of the Barents Sea in the Arctic climate system. Rev. Geophys. 51, 415–449 (2013).

    Google Scholar 

  6. 6.

    Aagaard, K., Swift, J. H. & Carmack, E. C. Thermohaline circulation in the Arctic Mediterranean seas. J. Geophys. Res. 90, 4833–4846 (1985).

    Google Scholar 

  7. 7.

    Lozier, M. S. et al. A sea change in our view of overturning in the subpolar North Atlantic. Science 363, 516–521 (2019).

    CAS  Google Scholar 

  8. 8.

    Chafik, L. & Rossby, T. Heat, and freshwater divergences in the subpolar North Atlantic suggest the Nordic Seas as key to the state of the meridional overturning circulation. Geophys. Res. Lett. 46, 4799–4808 (2019).

    Google Scholar 

  9. 9.

    Skagseth, Ø. & Mork, K. A. Heat content in the Norwegian Sea, 1995–2010. ICES J. Mar. Sci. 69, 826–832 (2012).

    Google Scholar 

  10. 10.

    Mork, K. A., Skagseth, Ø. & Soiland, H. Recent warming and freshening of the Norwegian Sea observed by Argo data. J. Clim. 32, 3695–3705 (2019).

    Google Scholar 

  11. 11.

    Mayer, M., Haimberger, L., Pietschnig, M. & Storto, A. Facets of Arctic energy accumulation based on observations and reanalyses 2000–2015. Geophys. Res. Lett. 43, 10420–10429 (2016).

    Google Scholar 

  12. 12.

    Mayer, M. et al. An improved estimate of the coupled Arctic energy budget. J. Clim. 32, 7915–7934 (2019).

    Google Scholar 

  13. 13.

    Holliday, N. P. et al. Reversal of the 1960s to 1990s freshening trend in the northeast North Atlantic and Nordic Seas. Geophys. Res. Lett. (2008).

  14. 14.

    González-Pola, C., Larsen, K. M. H., Fratantoni, P. & Beszczynska-Möller, A. (eds) ICES Report on Ocean Climate 2017 (ICES, 2018);

  15. 15.

    Hansen, B. et al. Transport of volume, heat, and salt towards the Arctic in the Faroe Current 1993–2013. Ocean Sci. 11, 743–757 (2015).

    Google Scholar 

  16. 16.

    Polyakov, I. V. et al. Greater role for Atlantic inflows on sea-ice loss in the Eurasian basin of the Arctic ocean. Science 356, 285–291 (2017).

    CAS  Google Scholar 

  17. 17.

    Lind, S., Ingvaldsen, R. B. & Furevik, T. Arctic warming hotspot in the northern Barents Sea linked to declining sea-ice import. Nat. Clim. Change 8, 634–639 (2018).

    Google Scholar 

  18. 18.

    Perez-Hernandez, M. D. et al. Structure, transport, and seasonality of the Atlantic water boundary current north of Svalbard: results from a yearlong mooring array. J. Geophys. Res. 124, 1679–1698 (2019).

    Google Scholar 

  19. 19.

    Dickson, R., Meincke, J. & Rhines, P. (eds) Arctic–Subarctic Ocean Fluxes: Defining the Role of the Northern Seas in Climate (Springer, 2008).

  20. 20.

    Østerhus, S. et al. Arctic Mediterranean exchanges: a consistent volume budget and trends in transports from two decades of observations. Ocean Sci. 15, 379–399 (2019).

    Google Scholar 

  21. 21.

    Smeed, D. A. et al. The North Atlantic Ocean is in a state of reduced overturning. Geophys. Res. Lett. 45, 1527–1533 (2018).

    Google Scholar 

  22. 22.

    Hansen, B., Larsen, K. M. H., Hátun, H. & Østerhus, S. A stable Faroe Bank Channel overflow 1995–2015. Ocean Sci. 12, 1205–1220 (2016).

    Google Scholar 

  23. 23.

    Lozier, M. S., Roussenov, V., Reed, M. S. C. & Williams, R. G. Opposing decadal changes for the North Atlantic meridional overturning circulation. Nat. Geosci. 3, 728–734 (2010).

    CAS  Google Scholar 

  24. 24.

    Årthun, M., Eldevik, T. & Smedsrud, L. H. The role of Atlantic heat transport in future Arctic winter sea ice loss. J. Clim. 32, 3327–3341 (2019).

    Google Scholar 

  25. 25.

    Schauer, U. & Beszczynska-Möller, A. Problems with estimation and interpretation of oceanic heat transport—conceptual remarks for the case of Fram Strait in the Arctic Ocean. Ocean Sci. 5, 487–494 (2009).

    Google Scholar 

  26. 26.

    Hansen, B. et al. in Arctic–Subarctic Ocean Fluxes: Defining the Role of the Northern Seas in Climate (eds Dickson, R. R. et al.) 15–43 (Springer, 2008).

  27. 27.

    Eldevik, T. & Nilsen, J. E. O. The Arctic–Atlantic thermohaline circulation. J. Clim. 26, 8698–8705 (2013).

    Google Scholar 

  28. 28.

    Tsubouchi, T. et al. The Arctic Ocean in summer: a quasi-synoptic inverse estimate of boundary fluxes and water mass transformation. J. Geophys. Res. (2012).

  29. 29.

    Tsubouchi, T. et al. The Arctic Ocean seasonal cycles of heat and freshwater fluxes: observation-based inverse estimates. J. Phys. Oceanogr. 48, 2029–2055 (2018).

    Google Scholar 

  30. 30.

    Tsubouchi, T. et al. The Arctic Ocean volume, heat and fresh water transports time series from October 2004 to May 2010. PANGAEA (2019).

  31. 31.

    Berx, B. et al. Combining in situ measurements and altimetry to estimate volume, heat and salt transport variability through the Faroe–Shetland Channel. Ocean Sci. 9, 639–654 (2013).

    Google Scholar 

  32. 32.

    Jónsson, S. & Valdimarsson, H. Water mass transport variability to the North Icelandic shelf, 1994–2010. ICES J. Mar. Sci. 69, 809–815 (2012).

    Google Scholar 

  33. 33.

    Jochumsen, K. et al. Revised transport estimates of the Denmark Strait overflow. J. Geophys. Res. 122, 3434–3450 (2017).

    Google Scholar 

  34. 34.

    Sherwin, T. J., Griffiths, C. R., Inall, M. E. & Turrell, W. R. Quantifying the overflow across the Wyville Thomson Ridge into the Rockall Trough. Deep Sea Res. 55, 396–404 (2008).

    Google Scholar 

  35. 35.

    Hansen, B. et al. Overflow of cold water across the Iceland–Faroe Ridge through the Western Valley. Ocean Sci. 14, 871–885 (2018).

    CAS  Google Scholar 

  36. 36.

    Curry, B., Lee, C. M., Petrie, B., Moritz, R. E. & Kwok, R. Multiyear volume, liquid freshwater, and sea ice transports through Davis Strait, 2004–10. J. Phys. Oceanogr. 44, 1244–1266 (2014).

    Google Scholar 

  37. 37.

    de Steur, L. et al. Liquid freshwater transport estimates from the East Greenland Current based on continuous measurements north of Denmark Strait. J. Geophys. Res. 122, 93–109 (2017).

    Google Scholar 

  38. 38.

    Woodgate, R. A. Increases in the Pacific inflow to the Arctic from 1990 to 2015, and insights into seasonal trends and driving mechanisms from year-round Bering Strait mooring data. Prog. Oceanogr. 160, 124–154 (2018).

    Google Scholar 

  39. 39.

    Rudels, B. et al. The interaction between waters from the Arctic Ocean and the Nordic Seas north of Fram Strait and along the East Greenland Current: results from the Arctic Ocean-02 Oden expedition. J. Mar. Sys. 55, 1–30 (2005).

    Google Scholar 

  40. 40.

    Wunsch, C. The Ocean Circulation Inverse Problem (Cambridge Univ. Press, 1996).

  41. 41.

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

    Google Scholar 

  42. 42.

    Lanzante, J. R. Resistant, robust and non-parametric techniques for the analysis of climate data: theory and examples, including applications to historical radiosonde station data. Int. J. Climatol. 16, 1197–1226 (1996).

    Google Scholar 

  43. 43.

    Emery, W. J. & Thomson, R. E. Data Analysis Methods in Physical Oceanography (Elsevier Science, 2014).

  44. 44.

    Segtnan, O. H., Furevik, T. & Jenkins, A. D. Heat and freshwater budgets of the Nordic seas computed from atmospheric reanalysis and ocean observations. J. Geophys. Res. (2011).

  45. 45.

    Smedsrud, L. H., Ingvaldsen, R., Nilsen, J. E. O. & Skagseth, Ø. Heat in the Barents Sea: transport, storage, and surface fluxes. Ocean Sci. 6, 219–234 (2010).

    Google Scholar 

  46. 46.

    Mauritzen, C. Production of dense overflow waters feeding the North Atlantic across the Greenland–Scotland Ridge. Part 2. An inverse model. Deep Sea Res. 43, 807–835 (1996).

    Google Scholar 

  47. 47.

    Håvik, L. et al. Evolution of the east Greenland current from Fram Strait to Denmark Strait: synoptic measurements from summer 2012. J. Geophys. Res. 122, 1974–1994 (2017).

    Google Scholar 

  48. 48.

    Årthun, M. & Eldevik, T. On anomalous ocean heat transport toward the Arctic and associated climate predictability. J. Clim. 29, 689–704 (2016).

    Google Scholar 

  49. 49.

    Asbjørnsen, H., Årthun, M., Skagseth, Ø. & Eldevik, T. Mechanisms of oean heat anomalies in the Norwegian Sea. J. Geophys. Res. (2019).

  50. 50.

    IPCC Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) (Cambridge Univ. Press, 2013).

  51. 51.

    Zhang, J. L. & Rothrock, D. A. Modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates. Monthly Weather Rev. 131, 845–861 (2003).

    Google Scholar 

  52. 52.

    Bacon, S., Aksenov, Y., Fawcett, S. & Madec, G. Arctic mass, freshwater and heat fluxes: methods and modelled seasonal variability. Phil. Trans. R. Soc. A (2015).

  53. 53.

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

    Google Scholar 

  54. 54.

    Shepherd, A. et al. Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature 579, 233–239 (2020).

    Google Scholar 

  55. 55.

    Armitage, T. W. K. et al. Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003–2014. J. Geophys. Res. 121, 4303–4322 (2016).

    Google Scholar 

  56. 56.

    Fukumori, I., Wang, O., Llovel, W., Fenty, I. & Forget, G. A near-uniform fluctuation of ocean bottom pressure and sea level across the deep ocean basins of the Arctic Ocean and the Nordic Seas. Prog. Oceanogr. 134, 152–172 (2015).

    Google Scholar 

  57. 57.

    Haine, T. W. N. et al. Arctic freshwater export: status, mechanisms, and prospects. Glob. Planet. Change 125, 13–35 (2015).

    Google Scholar 

  58. 58.

    Jochumsen, K., Quadfasel, D., Valdimarsson, H. & Jónsson, S. Variability of the Denmark Strait overflow: moored time series from 1996–2011. J. Geophys. Res. (2012).

  59. 59.

    Hátun, H., Sandø, A. B., Drange, H. & Bentsen, M. in The Nordic Seas: An Integrated Perspective (Drange, H. et al.) 239–250 (AGU, 2005).

  60. 60.

    Harden, B. E. et al. Upstream sources of the Denmark Strait overflow: observations from a high-resolution mooring array. Deep Sea Res. 112, 94–112 (2016).

    Google Scholar 

  61. 61.

    Evaluation of Measurement Data—Guide to the Expression of Uncertainty in Measurement. Vol. 100 (JCCM, 2008).

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Support for this work was provided by the Trond Mohn Foundation under grant no. BFS2016REK01 (T.T. and K.V.), the European Union’s FP7 grant no. 308299, NACLIM project (C.J.) and the European Union’s Horizon 2020 research and innovation programme under grant no. 727852, Blue-Action project (B.H., K.M.H.L., S.Ø., S.J. and H.V.). We acknowledge R. Dickson’s active role in initiating and promoting the integration of the Nordic Seas and Arctic Ocean boundary observation arrays over recent decades. The sustained mooring observations across GSR during 1993–2016 were funded through many national and international research projects including EU research projects such as VEINS (EU contract no. MAST-III MAS3960070), THOR (EU grant no. 212643) and NACLIM (EU grant no. 308299). Bering Strait data and analysis were supported by various NSF, NOAA and ONR grants, including NSF grant no. NFS-0856786 and the NOAA-RUSALCA programme. The Davis Strait programme was supported by the US National Science Foundation under grant nos. ARC0632231 and ARC1022472.

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T.T. and K.V. conceived and developed the study. T.T. integrated and analysed the data with inputs from all authors. T.T. and K.V. wrote the paper. All authors interpreted the results and clarified the implications.

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Correspondence to Takamasa Tsubouchi.

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Peer review information Nature Climate Change thanks Andrea Storto and Andrey Pnyushkov for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Tables 1–3 and Figs. 1–5.

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Tsubouchi, T., Våge, K., Hansen, B. et al. Increased ocean heat transport into the Nordic Seas and Arctic Ocean over the period 1993–2016. Nat. Clim. Chang. 11, 21–26 (2021).

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