• Baumgartner, A., and E. Reichel, 1975: The World Water Balance. Elsevier, 179 pp.

  • Broecker, W. S., T.-P. Peng, J. Houzel, and G. Russell, 1990: The magnitude of global freshwater transports of importance to ocean circulation. Climate Dyn.,4, 73–79.

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

  • Gordon, A. L., 1986: Interocean exchange of thermocline water. J. Geophys. Res.,91, 5037–5046.

  • Hughes, T. C. M., and A. J. Weaver, 1994: Multiple equilibrium of an asymmetric two-basin model. J. Phys. Oceanogr.,24, 619–637.

  • Klinger, B. A., and J. Marotzke, 1999: Behavior of double-hemisphere thermohaline flows in a single basin. J. Phys. Oceanogr.,29, 382–399.

  • Krasovskiy, Y., and P. H Stone, 1998: Destabilization of the thermohaline circulation by atmospheric transports: An analytic solution. J. Climate,11, 1803–1811.

  • Levitus, S., 1982: Climatological Atlas of the World Ocean. NOAA Prof. Paper No. 13, U.S. Dept. of Commerce, NOAA, Washington, D.C., 173 pp.

  • Lohmann, G., R. Gerdes, and D. Chen: 1996. Stability of the thermohaline circulation in a simple coupled model. Tellus,48A, 465–476.

  • Macdonald, A. M., and C. Wunsch, 1996: An estimate of global ocean circulation and heat fluxes. Nature,382, 436–439.

  • Manabe, S., and R. J. Stouffer, 1988: Two stable equilibria of a coupled ocean–atmosphere model. J. Climate,1, 841–866.

  • ——, and ——, 1995: Simulation of abrupt climate change induced by freshwater input to the North Atlantic Ocean. Nature,378, 165–167.

  • Marotzke, J., 1989: Instabilities and multiple steady states of the thermohaline circulation. Ocean Circulation Models: Combining Data and Dynamics. D. L. T. Anderson and J. Willebrand, Eds., Kluwer, 501–511.

  • ——, 1990: Instabilities and multiple equilibria of the thermohaline circulation. Ph.D. thesis, Ber. Inst. Meeresk., Kiel, Germany, 126 pp.

  • ——, 1996: Analysis of thermohaline feedbacks. Decadal Climate Variability: Dynamics and Predictability. D. L. T. Anderson and J. Willebrand, Eds., Springer-Verlag, 333–378.

  • ——, and J. Willebrand, 1991: Multiple equilibria of the global thermohaline circulation. J. Phys. Oceanogr.,21, 1372–1385.

  • ——, and P. H. Stone, 1995: Atmospheric transports, the thermohaline circulation, and flux adjustments in a simple coupled model. J. Phys. Oceanogr.,25, 1350–1364.

  • Mikolajewicz, U., and E. Maier-Reimer, 1994: Mixed boundary conditions in ocean general circulation models and their influence on the stability of the model’s conveyor belt. J. Geophys. Res.,99, 22 633–22 644.

  • Nakamura, M., P. H. Stone, and J. Marotzke, 1994: Destabilization of the thermohaline circulation by atmospheric eddy transports. J. Climate,7, 1870–1882.

  • Peixoto, J. P., and A. H. Oort: 1992. Physics of Climate. Amer. Inst. Phys., 520 pp.

  • Rahmstorf, S., 1996: On the freshwater forcing and transport of the Atlantic thermohaline circulation. Climate Dyn.,12, 799–811.

  • ——, and J. Willebrand, 1995: The role of temperature feedback in stabilizing the thermohaline circulation. J. Phys. Oceanogr.,25, 787–805.

  • ——, J. Marotzke, and J. Willebrand, 1996: Stability of the thermohaline circulation. The Warm Water Sphere of the North Atlantic Ocean, W. Krauss, Ed., Borntraeger, 129–157.

  • Rooth, C., 1982: Hydrology and ocean circulation. Progress in Oceanography, Vol. 11, Pergamon, 131–149.

  • Saravan, R., and J. C. McWilliams, 1995: Multiple equilibria, natural variability, and climate transitions in an idealized ocean–atmosphere model. J. Climate,8, 2296–2323.

  • Schiller, A., U. Mikolajewicz, and R. Voss, 1997: The stability of the thermohaline circulation in a coupled ocean–atmosphere general circulation model. Climate Dyn.,13, 325–347.

  • Stocker, T. F., and D. G. Wright, 1991: Rapid transitions of the ocean’s deep circulation induced by changes in surface water fluxes. Nature,351, 729–732.

  • Stommel, H., 1961: Thermohaline convection with two stable regimes of flow. Tellus,13, 224–230.

  • Stone, P. H., and D. A. Miller, 1980: Empirical relations between seasonal changes in meridional temperature gradients and meridional fluxes of heat. J. Atmos. Sci.,37, 1708–1721.

  • ——, and M.-S. Yao, 1990: Development of a two-dimensional zonally averaged statistical–dynamical model. Part III: The parameterization of the eddy fluxes of heat and moisture. J. Climate,3, 726–740.

  • Tziperman, E., 1997: Inherently unstable climate behavior due to weak thermohaline ocean circulation. Nature,386, 592–595.

  • Wang, X., P. H. Stone, and J. Marotzke, 1999a: Global thermohaline circulation. Part I: Sensivity to atmospheric moisture transport. J. Climate,12, 71–82.

  • ——, ——, and ——, 1999b: Global thermohaline circulation. Part II: Sensivity with interactive atmospheric transports. J. Climate,12, 83–91.

  • Warren, B. A., 1993: Why is no deep water formed in the North Pacific? J. Mar. Res.,41, 327–347.

  • Weaver, A. J., and E. S. Sarachik, 1991: The role of mixed boundary conditions in numerical models of the ocean’s climate. J. Phys. Oceanogr.,21, 1470–1493.

  • ——, J. Marotzke, P. F. Cummins, and E. S. Sarachik, 1993: Stability and variability of the thermohaline circulation. J. Phys. Oceanogr.,23, 39–60.

  • Welander, P., 1986: Thermohaline effects in the ocean circulation and related simple models. Large-Scale Transport Processes in Oceans and Atmosphere, J. Willebrand and D. L. T. Anderson, Eds., NATO ASI Series, D. Reidel, 163–200.

  • Zhang, S., R. J. Greatbatch, and C. A. Lin, 1993: A re-examination of the polar halocline catastrophe and implications for coupled ocean–atmosphere modeling. J. Phys. Oceanogr.,23, 287–299.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 414 191 4
PDF Downloads 314 221 1

Interhemispheric Thermohaline Circulation in a Coupled Box Model

View More View Less
  • 1 Program in Atmospheres, Oceans, and Climate, Massachusetts Institute of Technology, Cambridge, Massachusetts
Restricted access

Abstract

The interhemispheric thermohaline circulation is examined using Rooth’s three-box ocean model, whereby overturning strength is parameterized from density differences between high-latitude boxes. Recent results with general circulation models indicate that this is a better analog of the Atlantic thermohaline circulation than a single-hemisphere box model. The results are compared with those of hemispheric box model studies, where possible, and the role of asymmetrical freshwater forcing is explored.

Using both analytical and numerical methods, the linear and nonlinear stability of the model is examined. Although freshwater forcing in the Southern Hemisphere alone governs overturning strength, increasing freshwater forcing in the Northern Hemisphere leads to a heretofore unrecognized instability in the northern sinking branch due to an increasingly positive ocean salinity feedback. If the northern forcing is instead made weaker than the southern forcing, this feedback becomes negative. In contrast, the ocean salinity feedback is always positive in single-hemisphere models. Nonlinear stability, as measured by the size of the perturbation necessary to induce a permanent transition to the southern sinking equilibrium, is also observed to depend similarly on the north–south forcing ratio.

The model is augmented with explicit atmospheric eddy transport parameterizations, allowing examination of the eddy moisture transport (EMT) and eddy heat transport (EHT) feedbacks. As in the hemispheric model, the EMT feedback is always destabilizing, whereas the EHT may stabilize or destabilize. However, in this model whether the EHT stabilizes or destabilizes depends largely on the sign of the ocean salinity feedback and the size of the perturbation. Since oceanic heat transport in the Southern Hemisphere is weak, the Northern Hemisphere EMT and EHT feedbacks dominate.

Corresponding author address: Jeffery R. Scott, Dept. of Earth, Atmospheric, and Planetary Sciences, MIT, Room 54-1711, Cambridge, MA 02139.

Email: jscott@mit.edu

Abstract

The interhemispheric thermohaline circulation is examined using Rooth’s three-box ocean model, whereby overturning strength is parameterized from density differences between high-latitude boxes. Recent results with general circulation models indicate that this is a better analog of the Atlantic thermohaline circulation than a single-hemisphere box model. The results are compared with those of hemispheric box model studies, where possible, and the role of asymmetrical freshwater forcing is explored.

Using both analytical and numerical methods, the linear and nonlinear stability of the model is examined. Although freshwater forcing in the Southern Hemisphere alone governs overturning strength, increasing freshwater forcing in the Northern Hemisphere leads to a heretofore unrecognized instability in the northern sinking branch due to an increasingly positive ocean salinity feedback. If the northern forcing is instead made weaker than the southern forcing, this feedback becomes negative. In contrast, the ocean salinity feedback is always positive in single-hemisphere models. Nonlinear stability, as measured by the size of the perturbation necessary to induce a permanent transition to the southern sinking equilibrium, is also observed to depend similarly on the north–south forcing ratio.

The model is augmented with explicit atmospheric eddy transport parameterizations, allowing examination of the eddy moisture transport (EMT) and eddy heat transport (EHT) feedbacks. As in the hemispheric model, the EMT feedback is always destabilizing, whereas the EHT may stabilize or destabilize. However, in this model whether the EHT stabilizes or destabilizes depends largely on the sign of the ocean salinity feedback and the size of the perturbation. Since oceanic heat transport in the Southern Hemisphere is weak, the Northern Hemisphere EMT and EHT feedbacks dominate.

Corresponding author address: Jeffery R. Scott, Dept. of Earth, Atmospheric, and Planetary Sciences, MIT, Room 54-1711, Cambridge, MA 02139.

Email: jscott@mit.edu

Save