• Behl, R. J., and J. P. Kennett, 1996: Brief interstadial events in the Santa Barbara basin, NE Pacific during the past 60 kyr. Nature,379, 243–246.

  • Berger, A. L., 1978: Long term variations of daily insolation and quaternary climatic changes. J. Atmos. Sci.,35, 2362–2367.

  • Bond, G., W. Broecker, S. Johnsen, J. McManus, L. Labeyrie, J. Jouzel, and G. Bonani, 1993: Correlations between climate records from North Atlantic sediments and Greenland ice. Nature,365, 143–147.

  • Boyle, E. A., and L. Keigwin, 1987: North Atlantic thermohaline circulation during the past 20,000 years linked to high-latitude surface temperature. Nature,330, 35–40.

  • Broecker, W. S., 1992: The strength of the nordic heat pump. The Last Deglaciation: Absolute and Radiocarbon Chronologies, E. Bard and W. S. Broecker, Eds., NATO ASI Series, Vol. 12, Springer-Verlag, 173–181.

  • Bryan, F., 1986: High-latitude salinity effects and interhemispheric thermohaline circulations. Nature,323, 301–304.

  • Budd, W. F., and I. N. Smith, 1981: The growth and retreat of ice sheets in response to orbital radiation changes. Sea-Level, Ice and Climatic Changes, IAHS, Vol. 131, 369–409.

  • CLIMAP Project, 1981: Seasonal Reconstructions of the Earth’s Surface at the Last Glacial Maximum. Map and Chart Series, Geological Society of America, 9 pp.

  • Dansgaard, W., S. J. Johnson, H. B. Clausen, D. Dahl-Jensen, N. Gundestrup, C. U. Hammer, and H. Oeschger, 1984: North Atlantic climatic oscillations revealed by deep Greenland ice cores. Climate Processes and Climate Sensitivity, Geophys. Monogr., No. 29, J. E. Hansen and T. Takahashi, Eds., Amer. Geophys. Union, 288–298.

  • Deblonde, G., and W. R. Peltier, 1991a: A one-dimensional model of continental ice volume fluctuations through the Pleistocene: Implications for the origin of the mid-Pleistocene climatic transition. J. Climate,4, 318–344.

  • ——, and ——, 1991b: Simulations of continental ice sheet growth over the last glacial-interglacial cycle: Experiments with a one level seasonal energy balance model including realistic geography. J. Geophys. Res.,96, 9189–9215.

  • ——, and ——, 1993: Pleistocene ice age scenarios based upon observational evidence. J. Climate,6, 709–727.

  • ——, ——, and W. T. Hyde, 1992: Simulations of continental ice sheet growth over the last glacial–interglacial cycle: Experiments with a one level seasonal energy balance model including seasonal ice albedo feedback. Global Planet. Change.,6, 37–55.

  • Duplessy, J.-C., L. Labeyrie, A. Juillet-Leclerc, F. Maitre, J. Dupart, and M. Sarnthein, 1991: Surface salinity reconstruction of the North Atlantic Ocean during the last glacial maximum. Oceanol. Acta,14, 311–323.

  • GISP2, 1993a: The “flicking switch” of late Pleistocene climate change. Nature,361, 432–436.

  • ——, 1993b: Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event. Nature,362, 527–529.

  • GRIP, 1993a: Climate instability during the last interglacial period recorded in the GRIP ice core. Nature,364, 203–207.

  • ——, 1993b: Evidence for general instability of past climate from a 250-kyr ice-core record. Nature,364, 218–220.

  • Grootes, P. M., M. Stuiver, J. W. C. White, S. Johnsen, and J. Jouzel, 1993: Comparison of oxygen isotope records from the GISP2 and GRIP Greenland ice cores. Nature,466, 552–554.

  • Imbrie, J., and Coauthors, 1992: On the structure and origin of major glacial cycles 1: Linear responses to Milankovitch forcing. Paleoceanography,7, 701–738.

  • ——, and Coauthors, 1993: On the structure and origin of major glacial cycles 2: The 100,000-year cycle. Paleoceanography,8, 699–735.

  • Johnsen, S. J., and Coauthors, 1992: Irregular glacial interstadials recorded in a new Greenland ice core. Nature,359, 311–313.

  • Keigwin, L. D., and G. A. Jones, 1994: Western North Atlantic evidence for millennial-scale changes in ocean circulation and climate. J. Geophys. Res.,99, 12 397–12 310.

  • Kennett, J. P., and B. L. Ingram, 1995: A 20,000-year record of ocean circulation and climate change from the Santa Barbara basin. Nature,377, 510–514.

  • Lorius, C., J. Jouzel, C. Ritz, L. Merlivat, N. I. Barkov, Y. S. Korotkevich, and V. M. Kotlyakov, 1985: A 150,000 year climatic record from Antarctica. Nature,316, 591–596.

  • Meese, D., R. Alley, T. Gow, P. M. Grootes, P. Mayewski, M. Ram, K. Taylor, E. Waddington, and G. Zielinski, 1994: Preliminary depth-age scale of the GISP2 ice core. CRREL Special Report 94-1.

  • Paterson, W. S. B., 1981: The Physics of Glaciers. 2d ed. Pergamon Press, 380 pp.

  • Peltier, W. R., and S. Marshall, 1995: Coupled energy-balance/ice-sheet model simulations of the glacial cycle: A possible connection between terminations and terrigenous dust. J. Geophys. Res.,100, 14 269–14 289.

  • Pollard, D., 1980: A simple parameterization for ice sheet ablation rate. Tellus,32, 384–388.

  • Sakai, K., and W. R. Peltier, 1995: A simple model of the Atlantic thermohaline circulation: Internal and forced variability with paleoclimatological implications. J. Geophys. Res.,100, 13 455–13 479.

  • ——, and ——, 1996: A multi-basin reduced model of the global thermohaline circulation: Paleoceanographic analyses of the origins of ice-age climate variability. J. Geophys. Res., in press.

  • Schutz, C., and W. L. Gates, 1971: Global climatic data for surface, 800 mb, 400 mb, January, July. Advanced Research Projects Agency Rep.

  • Stuiver, M., P. M. Grootes, and T. F. Braziunas, 1995: The GISP2 δ18O climate record of the past 16,500 years and the role of the sun, ocean, and volcanoes. Quat. Res.,44, 341–354.

  • Winton, M., and E. S. Sarachik, 1993: Thermohaline oscillations induced by strong steady salinity forcing of an ocean general circulation model. J. Phys. Oceanogr.,23, 1389–1410.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 231 68 9
PDF Downloads 124 49 5

Dansgaard–Oeschger Oscillations in a Coupled Atmosphere–Ocean Climate Model

View More View Less
  • 1 Department of Physics, University of Toronto, Toronto, Ontario, Canada
Restricted access

Abstract

A reduced model of the global thermohaline circulation has been asynchronously coupled to a simple energy balance climate model in order to investigate the natural variability of the overturning circulation that may have been characteristic of late glacial conditions. Previous analyses with the ocean-only component of the model have suggested that the nature of the internal variability of the thermohaline circulation was a strong function of the surface boundary conditions on temperature and salinity flux. When the boundary conditions were altered from those corresponding to modern conditions to those appropriate to full glacial conditions, then the internal variability was shown to be radically transformed. Under modern conditions the ocean-only version of the model delivered an overturning circulation that was only weakly time dependent with a characteristic period of centuries. Under full glacial boundary conditions, however, the circulation became strongly time dependent with a characteristic period of millennia. This timescale corresponds to that of the Dansgaard–Oeschger oscillation, which is a prominent feature of the proxy climate records that have been derived on the basis of oxygen isotope data from Summit, Greenland, ice cores by the GRIP and GISP2 collaborations. By coupling the reduced model of the global thermohaline circulation to a simple model of the atmosphere, the authors are able to address the issue of whether the amplitude of the millennium timescale oscillation of atmospheric temperature matches that inferred on the basis of the ice core records. The results reported herein demonstrate that model and observations agree extremely well in this regard. The authors construe this to provide strong further support for the idea that the Dansgaard–Oeschger oscillation is a natural mode of internal variability that would exist even with time-independent boundary conditions appropriate to the full glacial state.

Corresponding author address: Dr. W. R. Peltier, University of Toronto, Department of Physics, 60 St. George Street, Toronto, ON M5S 1A7, Canada.

Email: peltier@atmosp.physics.utoronto.ca

Abstract

A reduced model of the global thermohaline circulation has been asynchronously coupled to a simple energy balance climate model in order to investigate the natural variability of the overturning circulation that may have been characteristic of late glacial conditions. Previous analyses with the ocean-only component of the model have suggested that the nature of the internal variability of the thermohaline circulation was a strong function of the surface boundary conditions on temperature and salinity flux. When the boundary conditions were altered from those corresponding to modern conditions to those appropriate to full glacial conditions, then the internal variability was shown to be radically transformed. Under modern conditions the ocean-only version of the model delivered an overturning circulation that was only weakly time dependent with a characteristic period of centuries. Under full glacial boundary conditions, however, the circulation became strongly time dependent with a characteristic period of millennia. This timescale corresponds to that of the Dansgaard–Oeschger oscillation, which is a prominent feature of the proxy climate records that have been derived on the basis of oxygen isotope data from Summit, Greenland, ice cores by the GRIP and GISP2 collaborations. By coupling the reduced model of the global thermohaline circulation to a simple model of the atmosphere, the authors are able to address the issue of whether the amplitude of the millennium timescale oscillation of atmospheric temperature matches that inferred on the basis of the ice core records. The results reported herein demonstrate that model and observations agree extremely well in this regard. The authors construe this to provide strong further support for the idea that the Dansgaard–Oeschger oscillation is a natural mode of internal variability that would exist even with time-independent boundary conditions appropriate to the full glacial state.

Corresponding author address: Dr. W. R. Peltier, University of Toronto, Department of Physics, 60 St. George Street, Toronto, ON M5S 1A7, Canada.

Email: peltier@atmosp.physics.utoronto.ca

Save