Abstract
The global thermohaline circulation is the oceanic overturning mode, which is manifested in the North Atlantic Ocean as northward-flowing surface waters which sink in the Nordic (Greenland, Iceland and Norwegian) seas and return southwards—after overflowing the Greenland–Scotland ridge—as deep water. This process has been termed the ‘conveyor belt’, and is believed to keep Europe 5–8 °C warmer than it would be if the conveyor were to shut down1. The variability of today's conveyor belt is therefore an important component of climate regulation. The Nordic seas are the only Northern Hemisphere source of deep water and a previous study3 has revealed no long-term variability in the outflow of deep water from the Nordic seas to the Atlantic Ocean. Here I use flows derived from hydrographic data to show that this outflow has approximately doubled, and then returned to previous values, over the past four decades. I present evidence which suggests that this variability is forced by variability in polar air temperature, which in turn may be connected to the recently reported Arctic warming4.
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References
Broecker, W. S. The great ocean conveyor. Oceanography 4, 79–89 (1991).
Warren, B. A. in Evolution of Physical Oceanography (eds Warren, B. A. & Wunsch, C.) 6–41 (MIT Press, Cambridge, MA, (1981)).
Dickson, R. R. & Brown, J. The production of North Atlantic Deep Water: sources, rates and pathways. J. Geophys. Res. 99, 12319–12341 (1994).
Macdonald, R. Awakenings in the Arctic. Nature 380, 286–287 (1996).
Swift, J. H. The circulation of the Denmark Strait and Iceland-Scotland overflow waters in the North Atlantic. Deep-Sea Res. 31, 1339–1355 (1984).
Dickson, R. R., Gmitrowicz, E. M. & Watson, A. J. Deep-water renewal in the northern North Atlantic. Nature 344, 848–850 (1990).
McCartney, M. S. Recirculating components to the deep boundary current of the northern North Atlantic. Proc. Oceanogr. 29, 283–383 (1992).
Price, J. F. & Baringer, M. O. Outflows and deep water production by marginal seas. Prog. Oceanogr. 33, 161–200 (1994).
Clarke, R. A. Transport through the Cape Farewell–Flemish Cap section. Rapp. P.-v. Réun. Cons. Int. Explor. Mer. 185, 120–130 (1984).
Pearson, E. S. & Hartley, H. O. Biometrika Tables for StatisticiansVol. 2 (Biometrika Trust, London, (1976)).
Bryan, F. O., Böning, C. W. & Holland, W. R. On the midlatitude circulation in a high-resolution model of the North Atlantic. J. Phys. Oceanogr. 25, 289–305 (1995).
Redler, R. & Böning, C. W. Effect of the overflows on the circulation in the subpolar North Atlantic: aregional model study. J. Geophys. Res. 102, 18529–18552 (1997).
Bacon, S. Circulation and fluxes in the North Atlantic between Greenland and Ireland. J. Phys. Oceanogr. 27, 1420–1435 (1997).
Schmitz, W. J. & McCartney, M. S. On the North Atlantic circulation. Rev. Geophys. 31, 29–49 (1993).
Reid, J. L. On the total geostrophic circulation of the North Atlantic Ocean: flow patterns, tracers, and transports. Prog. Oceanogr. 33, 1–92 (1994).
Talley, L. D. North Atlantic circulation and variability. Physica D 98, 625–646 (1996).
Ross, C. K. Temperature–salinity characteristics of the “overflow” water in Denmark Strait during “OVERFLOW ‘73”. Rapp. P.-v. Réun. Cons. Int. Explor. Mer. 185, 111–119 (1984).
Read, J. F. & Gould, W. J. Cooling and freshening of the subpolar North Atlantic Ocean since the 1960s. Nature 360, 55–57 (1992).
Dickson, R. R., Lazier, J. R. N., Meincke, J., Rhines, P. & Swift, J. Long-term coordinated changes in the convective activity of the North Atlantic. Proc. Oceanogr. 38, 241–295 (1997).
Sy, A. et al. Surprisingly rapid spreading of newly formed intermediate waters across the North Atlantic Ocean. Nature 386, 675–679 (1997).
Turner, J. S. Turbulent entrainment: the development of the entrainment assumption, and its application to geophysical flows. J. Fluid Mech. 173, 431–471 (1986).
Swift, J. H., Aagaard, K. & Malmberg, S.-A. The contribution of the Denmark Strait overflow to the deep North Atlantic. Deep-Sea Res. 27, 29–42 (1980).
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. I 43, 769–806 (1996).
Strass, V. H., Fahrbach, E., Schauer, U. & Sellman, L. Formation of Denmark Strait Overflow water by mixing in the East Greenland Current. J. Geophys. Res. 98, 6907–6919 (1993).
Bönisch, G., Blindheim, J., Bullister, J. L., Schlosser, P. & Wallace, D. W. R. Long-term trends of temperature, salinity, density and transient tracers in the central Greenland Sea. J. Geophys. Res. 102, 18553–18571 (1997).
Mysak, L. A., Manak, D. K. & Marsden, R. F. Sea-ice anomalies observed in the Greenland and Labrador Seas during 1901–1984 and their relation to an interdecadal Arctic climate cycle. Clim. Dyn. 5, 111–133 (1990).
Häkkinen, S. An Arctic source for the Great Salinity Anomaly: a simulation of the Arctic Ice-Ocean system for 1955–75. J. Geophys. Res. 98, 16397–16410 (1993).
Dickson, R. R., Meincke, J., Malmberg, S-A. & Lee, A. J. The “Great Salinity Anomaly” in the northern North Atlantic 1968–1982. Prog. Oceanogr. 20, 103–151 (1988).
Rahmstorf, S. Rapid climate transitions in a coupled ocean–atmosphere model. Nature 372, 82–85 (1994).
Webb, R. S., Rind, D. H., Lehman, S. J., Healy, R. J. & Sigman, D. Influence of ocean heat transport on the climate of the last glacial maximum. Nature 385, 695–699 (1997).
Acknowledgements
I thank R. Hendry (BIO) for the Hudson 1991 data; A. Sy (BSH) for the Meteor 1994 data; R. Pollard and P. Holliday (SOC) and H. Leach (LUDO) for the Discovery 1996 data; S. Cunningham for the Discovery 1997 data; the German Oceanographic Data Centre (BSH, Hamburg) for the Poseidon 1988 data. The Jan Mayen data were obtained from the Climatic Research Unit at UEA. (All other pre-1990 da
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Bacon, S. Decadal variability in the outflow from the Nordic seas to the deep Atlantic Ocean. Nature 394, 871–874 (1998). https://doi.org/10.1038/29736
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DOI: https://doi.org/10.1038/29736
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