These days, it would be generally accepted that through its northward transport of warm tropical waters, the Atlantic Meridional Overturning Circulation (AMOC) contributes effectively to the anomalous warmth of northern Europe (Large and Nurser 2001; see also Rhines and Hakkinen 2003; Rhines et al., this volume). The oceanic fluxes of mass, heat and salt that pass north across the Greenland–Scotland Ridge from the Atlantic to the Arctic Mediterranean have now been soundly established by direct measurement under the EC VEINS and ASOF/MOEN programmes, as have the corresponding fluxes to the Arctic Ocean (Ingvaldsen et al. 2004a, b; Schauer et al. 2004). We now know that the 8.5 million cubic metres per second of warm salty Atlantic Water that passes north across this Ridge carries with it, on average, some 313 million megawatts of power and 303 million kilograms of salt per second (Østerhus et al. 2005). As it returns south across the Ridge in the form of the two dense overflows from Nordic Seas, its salinity has decreased from about 35.25 to 34.88 and its temperature has dropped from 8.5 °C to 2.0 °C or less. Not surprisingly, surrendering this amount of heat is of more than local climatic importance. To quantify its contribution to climate the AMOC was deliberately* shut down in the HadCM3 Atmosphere-Ocean General Circulation Model by artificially releasing a large pulse of freshwater in the northern North Atlantic (Wood et al. 2003; Vellinga 2004; Wood et al. 2006). The cooling of mean air temperature over the northern Norwegian Sea and Barents Sea in the first 10 years after shutdown exceeds −15 °C, and some lesser degree of cooling is evident over the entire Hemisphere. In addition, significant changes in rainfall are evident (especially at low latitudes, Vellinga and Wood 2002), as well as changes in sea level height (Levermann et al. 2005; Vellinga and Wood 2007). [*note that this is a ‘what if’ experiment. The response of the AMOC to more plausible scenarios of gradual anthropogenic greenhouse gas increase is discussed in Section 12.3.2 of this chapter.]
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Keywords
- Atlantic Meridional Overturning Circulation
- North Atlantic Oscillation
- Thermohaline Circulation
- Freshwater Flux
- Atlantic Meridional Overturning Circulation Variability
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References
Allen MR, WJ Ingram (2002) Constraints on future changes in climate and the hydrologic cycle. Nature 419: 224–232
Banks HT (2000) Ocean heat transport in the South Atlantic in a coupled climate model. J. Geoph. Res. 105(C1): 1071–1091
Banks HT, RA Wood (2002) Where to look for anthropogenic climate change in the ocean? J. Climate 15: 879–891
Barnett TPD, W Pierce, R Schnur (2001) Detection of anthropogenic climate change in the world’s oceans. Science 292: 270–274
Bojariu R, G Reverdin (2002) Large-scale variability modes of freshwater flux and precipitation over the Atlantic. Clim. Dyn. 18: 369–381
Böning CW, FO Bryan, WR Holland, R Döscher (1996) Deep water formation and meridional overturning in a high-resolution model of the North Atlantic. J. Phys. Oceanogr. 26: 515–523
Bony S, R Colman, VM Kattsov, RP Allan, CS Bretherton, JL Dufresne, A Hall, S Hallegate, MM Holland, WJ Ingram, DA Randall, BJ Soden, G Tselioudis, MJ Webb (2006) How well do we understand and evaluate climate change feedback processes? J. Climate 19: 3445–3482
Broecker WS (1997) Thermohaline circulation, the Achilles heel of our climate system: Will man-made CO2 upset the current balance? Science 278: 1582–1588
Bryan F (1986) High-latitude salinity effects and interhemispheric thermohaline circulations. Nature 323: 301–304
Bryden HL, HR Longworth, SA Cunningham (2005) Slowing of the Atlantic meridional Overturning Circulation at 25° N. Nature 438: 655–657
Cayan DR (1992) Latent and sensible heat flux anomalies over the northern oceans: The connection to monthly atmospheric circulation. J. Climate 5: 354–369
Cheng W, PB Rhines (2004) Response of the overturning circulation to high-latitude fresh-water perturbations in the North Atlantic. Clim. Dyn. 22(4): 359–372
Cheng W, R Bleck, C Rooth (2004) Multi-decadal thermohaline variability in an ocean-atmosphere general circulation model. Clim. Dyn. 22: 573–590
Collins M, B Sinha (2003) Predictability of decadal variations in the thermohaline circulation and climate. Geophys. Res. Lett. 30(6): 1413, doi:10.1029/2002GL016776
Collins M, A Botzet, A F Carril, H Drange, A Jouzea, M Latif, S Masina, OH Otteraa, H Pohlmann, A Sorteberg, R Sutton, L Terray (2006) Interannual to decadal climate predictability in the north Atlantic: A multimodel-ensemble study. J. Climate 19: 1195–1203
Cubasch U, GA Meehl, GJ Boer, RJ Stouffer, M Dix, A Noda, CA Senior, SCB Raper, and KS Yap (2001) Projections of future climate change. In JT Houghton, Y Ding, DJ Griggs, M Noguer, P Van der Linden, X Dai, K Maskell, CI Johnson (eds.) Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, pp 525–582
Curry B, GP Lohmann (1982) Carbon isotopic changes in benthic foraminifera from the western South Atlantic: Reconstruction of glacial abyssal circulation patterns, Quat. Res. 18: 218–235
Curry R, C Mauritzen (2005) Dilution of the Northern North Atlantic Ocean in Recent Decades. Science 308 (5729): 1772–1774
Curry R, RR Dickson, I Yashayaev (2003) A change in the freshwater balance of the Atlantic Ocean over the past four decades. Nature 426: 826–829
Dahl K, A Broccoli, R Stouffer (2005) Assessing the role of North Atlantic freshwater forcing in millennial scale climate variability: A tropical Atlantic perspective. Clim. Dyn. 24(4): 325–346
Dai A, A Hu, GA Meehl, WM Washington, WG Strand (2005) Atlantic thermohaline circulation in a coupled general circulation model: unforced variations versus forced changes. J. Climate 18: 3270–3293
Delworth TL, KW Dixon (2000) Implications of the recent trend in the Arctic/N Atlantic Oscillation for the North Atlantic thermohaline circulation. J Climate 13: 3721–3727
Delworth TL, KW Dixon (2006) Have anthropogenic aerosols delayed a greenhouse gas-induced weakening of the North Atlantic thermohaline circulation? Geophys. Res. Lett. 33, LO2606, doi:10.1029/2005Glo24980
—Delworth TL, RJ Greatbatch (2000) Multidecadal thermohaline circulation variability driven by atmospheric flux forcing. J. Climate 13: 1481–1495
Delworth TL, ME Mann (2000) Observed and simulated multidecadal variability in the North Atlantic. Climate Dyn. 16 (9): 661–676
Delworth, TL, S Manabe, RJ Stouffer (1993) Interdecadal variations of the thermohaline circulation in a coupled ocean-atmosphere model. J. Climate 6: 1993–2011
Dickson RR, J Lazier, J Meincke, P Rhines, J Swift (1996) Long-term coordinated changes in the convective activity of the North Atlantic. Prog. Oceanogr. 38: 241–295
Dickson RR, I Yashayaev, J Meincke, W Turrell, S Dye, J. Holfort (2002) Rapid freshening of the deep North Atlantic over the past four decades. Nature 416: 832–837
Dong B, R Sutton (2005) Mechanism of interdecadal thermohaline circulation variability in a coupled ocean-atmosphere GCM. J. Climate 18: 1117–1135
Eden C, T Jung (2001) North Atlantic interdecadal variability: oceanic response to the North Atlantic oscillation (1865–1997). J. Climate 14: 676–691
Eden C, J Willebrand (2001) Mechanism of interannual to decadal variability of the North Atlantic circulation. J. Climate 14: 2266–2280
Gamiz-Fortis SR, D Pozo-Vazquez, MJ Esteban-Parra, Y Castro-Diez (2002) Spectral characteristics and predictability of the NAO assessed through Singular Spectral Analysis. J. Geoph. Res. 107(D23): 4685–4699
Goelzer H, J Mignot, A Levermann, S Rahmstorf (2006) Tropical versus high latitude freshwater influence on the Atlantic circulation. Clim. Dyn. 27(7–8): 715–725
Goosse H, T Fichefet, J-M Campin (1997) The effects of the water flow through the Canadian Archipelago in a global ice-ocean model. Geophysical Research Letters 24: 1507–1510, doi:10.1029/97GL01352
Gordon AL (1986) Inter-ocean exchange of thermocline water. J. Geophys. Res. 91: 5037–5046
Gregory JM, HT Banks, PA Stott, JA Lowe, MD Palmer (2004) Simulated and observed decadal variability in ocean heat content. Geophys. Res. Lett. 31: L15312, doi:10.1029/ 2004GL020258
Gregory JM, KW Dixon, RJ Stouffer, AJ Weaver, E Driesschaert, M Eby, T Fichefet, H Hasumi, A Hu, JH Jungclaus, IV Kamenkovich, A Levermann, M Montoya, S Murakami, S Nawrath, A Oka, AP Sokolov, and RB Thorpe (2005) A model intercomparison of changes in the Atlantic thermohaline circulation in response to increasing atmospheric CO2 concentration. Geophys. Res. Lett. 32, L12703, doi:10.1029/2005GL023209
Haak H, J Jungclaus, T Koenigk, D Svein, U Mikolajewicz (2005) Arctic Ocean freshwater budget variability. ASOF Newsletter (3): 6–8. http://asof.npolar.no
Häkkinen S (1999) Variability of the simulated meridional heat transport in the North Atlantic for the period 1951–(1993) J. Geoph. Res. 105(C5): 10, 911–11, 007
Hasselmann K (1976) Stochastic climate models. Part I: Theory. Tellus 28: 473–485
Higuchi K, JP Huang, A Shabbar (1999) A wavelet characterization of the North Atlantic oscillation variation and its relationship to the North Atlantic sea surface temperature. Int. J. Climatol. 19(10), 1119–1129
Hu A, GA Meehl (2005) Reasons for a fresher northern North Atlantic in the late 20th century. Geophys. Res. Lett. 32, doi:10.1029/2005GL022900
Hughes TMC, AJ Weaver (1994) Multiple equilibria of an asymmetric two-basin model. J. Phys. Oceanogr. 24: 619–637
Hunt BG, TI Elliott (2006) Climatic trends. Clim. Dyn. 26: 567–585
Hurrell JW (1995) Decadal trends in the North Atlantic Oscillation: regional temperatures and precipitation. Science 269: 676–679
Hurrell JW, H van Loon (1997) Decadal variations in climate associated with the North Atlantic Oscillation. Clim. Change 36: 301–326
Ingvaldsen RB, L Asplin, H Loeng (2004a) Velocity field of the western entrance to the Barents Sea. J. Geophys. Res. 109, C03021, doi:101029/2003JC001811
Ingvaldsen RB L Asplin, H Loeng (2004b) The seasonal cycle in the Atlantic transport to the Barents Sea during the years 1997–2001. Continent. Shelf Res. 24: 1015–1032
Johannessen, JA, PY Le Traon, I Robinson, K Nittis, MJ Bell, N Pinardi, P Bahurel (2006) Marine environment and security for the European area–Toward operational oceanography. Bull. Am. Met. Soc. 87(8): 1081
Jones PD, T Jonsson, D Wheeler (1997) Extension to the North Atlantic Oscillation using early instrumental pressure observations from Gibraltar and south-west Iceland. Int. J. Climatol. 17: 1433–1450
Jungclaus J, M Haak, H Latif, U. Mikolajewicz (2005) Arctic-North Atlantic interactions and multidecadal variability of the meridional overturning circulation. J. Climate 18: 4013–4031
Knight, JR, RJ Allan, CK Folland, M Vellinga, and ME Mann (2005) A signature of persistent natural thermohaline circulation cycles in observed climate. Geophys. Res. Lett. 32, doi:10.1029/2005GL024233
Knutti R, TF Stocker, F Joos, GK Plattner (2002) Constraints on radiative forcing and future climate change from observations and climate model ensembles. Nature 416: 719–723
Krahmann G, M Visbeck, G Reverdin (2001) Formation and propagation of temperature anomalies along the North Atlantic Current. J. Phys. Oceanogr. 31(5): 1287–1303
Kuzmina SI, L Bengtsson, OM Johannessen, H Drange, LP Bobylev, MW Miles (2005) The North Atlantic Oscillation and greenhouse-gas forcing. Geoph. Res. Let. 32(4), doi:10.1029/2005GL04703
Large WG, AJG Nurser (2001) Ocean surface water mass transformations, pp 317–335. In G Siedler, J Church and J Gould (Eds) Ocean Circulation and Climate. Academic Press International Geophysics Series, 77, 715 pp.
Latif M, E Roeckner, U Mikolajewicz, R Voss (2000) Tropical stabilisation of the thermohaline circulation in a greenhouse warming simulation. J. Climate 13: 1809–1813
Latif M, E Roeckner, M Botzet, M Esch, H Haak, S Hagemann, J Jungclaus, S Legutke, S Marsland, U Mikolajewicz, J. Mitchell (2004) Reconstructing, monitoring and predicting multidecadal-scale changes in the North Atlantic thermohaline circulation with sea surface temperature. J. Climate 17: 1605–1614
Latif M, C Böning, J Willebrand, A Biastoch, J Dengg, N Keenlyside, Schweckendiek (2006) Is the themohaline circulation changing? J. Climate 19: 4632–4637
Levermann AA, M Griesel, M Hofmann, M Montoya, S Rahmstorf (2005) Dynamic sea level changes following changes in the thermohaline circulation. Clim. Dyn. 24: 347–354
Maltrud ME, JL McClean (2005) An eddy resolving global ocean simulation. Ocean Model 8: 31–54
Mikolajewicz U, M Groger, E Maier-Reimer, G Schurgers, M Vizcaino and AME Winguth (2007) Long-term effects of anthropogenic CO2 emissions simulated with a complex earth system model. Clim Dyn., doi 10.1007/s00382–006-0204-y
Manabe S, RJ Stouffer (1988) Two stable equilibria of a coupled ocean-atmosphere model. J. Climate 1: 841–866
Manabe S, RJ Stouffer (1993) Century-scale effects of increased atmospheric C02 on the ocean–atmosphere system. Nature 364: 215–218, doi:10.1038/364215a0
Manabe S, RJ Stouffer (1994) Multiple century response of a coupled ocean-atmosphere model to an increase of atmospheric carbon dioxide. J. Climate 7: 5–23
Manabe S, RJ Stouffer (1997) Coupled ocean-atmosphere model response to freshwater input: comparison with Younger Dryas event. Paleoceanography 12: 321–336
Marotzke J, J Willebrand (1991) Multiple equilibria of the global thermohaline circulation. J. Phys. Oceanogr. 21: 1372–1385
Mignot J, C Frankignoul (2005) On the variability of the Atlantic meridional overturning circulation, the NAO and the ENSO in the Bergen Climate Model. J. Climate 18: 2361–2375
Murphy JM, DMH Sexton, DN Barnett, GS Jones, MJ Webb, M Collins, DA Stainforth (2004) Quantification of modelling uncertainties in a large ensemble of climate change simulations. Nature 430: 768–772
Myers PG (2005) Impact of freshwater from the Canadian Arctic Archipelago on Labrador Sea Water formation. Geophys. Res. Lett. 32, L06605, doi:10.1029/2004GL022082
Oka A, H Hasumi (2006) Effects of model resolution on salt transport through northern high-latitude passages and Atlantic meridional overturning circulation. Ocean Model 13: 126–147
Osborn TJ (2004) Simulating the winter North Atlantic Oscillation: the roles of internal variability and greenhouse gas forcing. Clim. Dyn. 22: 605–623
Østerhus S, WR Turrell, S Jonsson and B Hansen (2005) Measured volume, heat and salt fluxes from the Atlantic to the Arctic Mediterranean. Geophys. Res. Lett. 32, L07603, doi:10.1029/2004GL022188
Ottera OH, H Drange, M Bentsen, NG Kvamsto, DB Jiang (2004) Transient response of the Atlantic meridional overturning circulation to enhanced freshwater input to the Nordic Seas-Arctic Ocean in the Bergen Climate Model. Tellus (A) 56(4): 342–361
Pain CC, MD Piggott, AJH Goddard, F Fang, GJ Gorman, DP Marshall, MD Eaton, PW Power, CRE de Oliveira (2005) Three-dimensional unstructured mesh ocean modelling. Ocean Model 10(1–2): 5–33
Rahmstorf S (1995) Bifurcations of the Atlantic thermohaline circulation in response to changes in the hydrological cycle. Nature 378: 145–149
Rahmstorf S (1996) On the freshwater forcing and transport of the Atlantic thermohaline circulation. Clim. Dyn. 12: 799–811
Rahmstorf S (2003) Thermohaline Circulation: The current climate. Nature 421: 699
Rahmstorf S, A Ganopolski (1999) Long term global warming scenarios, computed with an efficient climate model. Clim. Change 43: 353–367
Rhines P, S Hakkinen (2003) Is the Oceanic heat transport in North Atlantic irrelevant to the climate in Europe? ASOF Newsletter #2: 13–17
Ridley J, Huybrechts P, Gregory JM, Lowe JA (2005) Elimination of the Greenland ice sheet in a high CO2 climate. J. Climate 18: 3409–3427
Roberts MJ, RA Wood (1997) Topography sensitivity studies with a Bryan-Cox type ocean model. J. Phys. Oceanogr. 27: 823–836
Roberts, MJ, H Banks, N Gedney, J Gregory, R Hill, S Mullerworth, A Pardaens, G Rickard, R Thorpe, R Wood (2004) Impact of an eddy-permitting ocean resolution on control and climate change simulations with a global coupled GCM. J. Climate 17: 3–20
Schauer U, E Fahrbach, S Østerhus, G Rohardt (2004) Arctic warming through the Fram strait: Oceanic heat transports from 3 years of measurements. J. Geophys Res. 109, C06026, doi:10.1029/2003JC001823
Schiller A, U Mikolajewicz, R Voss (1997) The stability of the thermohaline circulation in a coupled ocean-atmosphere general circulation model. Clim. Dyn. 13: 325–347
Schmittner A, M Latif, B Schneider (2005) Model projections of the North Atlantic thermohaline circulation for the 21st century assessed by observations. Geophys. Res. Lett. 32, doi:10.1029/2005GL024368
Smith RD, ME Maltrud, FO Bryan, MW Hecht (2000) Numerical simulations of the North Atlantic Ocean at 1/10 degree. J. Phys. Oceanogr. 30: 1532–1561
Schneider von Deimling T, H Held, A Ganapolski, S Rahmstorf (2006) Climate sensitivity estimated from ensemble simulations of glacial climate. Clim. Dyn. 27: 149–163, doi:10.1007/s00382–006-0126–8
Stephenson DB, V Pavan, M Collins, MM Junge, R Quadrelli (2006) North Atlantic oscillation response to transient greenhouse gas forcing and the impact on european winter climate: a cmip2 multi-model assessment. Clim. Dyn. 27: 401–420
Stommel HM (1961) Thermohaline convection with two stable regimes of flow. Tellus 13: 224–230
Stouffer RJ, J Yin, JM Gregory, KW Dixon, MJ Spelman, W Hurlin, AJ Weaver, M Eby, GM Flato, H Hasumi, A Hu, J Jungclaus, IV Kamenkovich, A Levermann, M Montoya, S Murakami, S Nawrath, A Oka, WR Peltier, DY Robitaille, A Sokolov, G Vettoretti, N Weber (2006) Investigating the causes of the response of the thermohaline circulation to past and future climate changes. J. Climate 19: 1365–1387
Swingedouw D, P Braconnot, O Marti (2006) Sensitivity of the Atlantic meridional overturning circulation to the melting from northern glaciers in climate change experiments. Geophys. Res. Lett. 33, L07711, doi:10.1029/2006GL025765
Thorpe, RB, JM Gregory, TC Johns, RA Wood, and JFB Mitchell (2001) Mechanisms determining the Atlantic thermohaline circulation response to greenhouse gas forcing in a non-flux-adjusted coupled climate model. J. Climate 14: 3102–3116
Timmermann, A, M Latif, RVA Grötzner (1998) Northern Hemisphere interdecadal variability: a coupled air-sea mode. J. Climate 11: 1906–1931
Vellinga M (2004) Robustness of climate response in HadCM3 to various perturbations of the Atlantic meridional overturning circulation. Hadley Centre Technical Note CRTN 48, Met Office Hadley Centre, FitzRoy Road, Exeter EX1 3PB, United Kingdom (available via: URL http://www.metoffice.gov.uk/research/hadleycentre/pubs/HCTN/HCTN_48.pdf)
Vellinga M, RA Wood (2004) Timely detection of anthropogenic change in the Atlantic meridional overturning circulation. Geophys. Res. Lett. 31, doi:10.1029/2004GL020306
Vellinga M, RA Wood (2007) Impacts of thermohaline circulation shutdown in the twenty-first century. Clim. Change, doi:10.1007/s10584–006-9146-y
Vellinga M, P Wu (2004) Low-latitude fresh water influence on centennial variability of the thermohaline circulation. J. Climate 17: 4498–4511
Vellinga M, RA Wood, JM Gregory (2002) Processes governing the recovery of a perturbed thermohaline circulation in HadCM3. J. Climate 15: 764–780
Wadley MR, GR Bigg (2002) Impact of flow through the Canadian Archipelago and Bering Strait on the North Atlantic and Arctic circulation: An ocean modelling study. Q. J. Roy. Met. Soc. 128: 2187–2203
Welander P (1982) A simple heat salt oscillator. Dyn. Atmos. Oceans 6: 233–242
Whitehead JA (1998) Topographic control of oceanic flows in deep passages and straits. Rev. Geophys. 36: 423–440
Wood RA, M Vellinga, R Thorpe (2003) Global warming and thermohaline circulation stability, Phil. Trans. R. Soc. Lond. (A) 361: 1961–1975
Wood RA, M Collins, J Gregory, G Harris, M Vellinga (2006) Towards a risk assessment for shutdown of the Atlantic Thermohaline Circulation. In HJ Schellnhuber et al. (eds.)‘Avoiding Dangerous Climate Change. Cambridge University Press, Cambridge, 392 pp.
Wu P, RA Wood (2007) Convection-induced long term freshening of the Subpolar North Atlantic Ocean. Climate Dyn. submitted
Wu P, RA Wood, P Stott (2004) Does the recent freshening trend in the North Atlantic indicate a weakening thermohaline circulation? Geophys. Res. Lett. 31, Lo2301, doi: 0.1029/ 2003GLO18584
Wunsch C, P Heimbach (2006) Estimated decadal changes in the North Atlantic Meridional overturning circulation and heat flux 1993–2004. J. Phys. Oceanogr. 36: 2012–2024
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Vellinga, M., Dickson, B., Curry, R. (2008). The Changing View on How Freshwater Impacts the Atlantic Meridional Overturning Circulation. In: Dickson, R.R., Meincke, J., Rhines, P. (eds) Arctic–Subarctic Ocean Fluxes. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-6774-7_13
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