Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 12 4 2005 10.5194/npg-12-435-2005 http://www.nonlin-processes-geophys.net/12/435/2005/ http://www.nonlin-processes-geophys.net/12/435/2005/npg-12-435-2005.html http://www.nonlin-processes-geophys.net/12/435/2005/npg-12-435-2005.pdf 435 439 2005-03-24 Effects of the synoptic scale variability on the thermohaline circulation J. J. Taboada M. N. Lorenzo Group of Nonlinear Physics, Faculty of Physics, Univ. of Santiago de Compostela, 15782 Santiago de Compostela, Spain Faculty of Sciences, Campus de Ourense, Univ. of Vigo, 32004 Ourense, Spain In this paper the effect of the synoptic scale variability is analyzed using a simple atmosphere-ocean coupled model. This high frequency variability has been taken into account in the model adding white gaussian noise in variables related to zonal and meridional temperature differences. Results show that synoptic scale frequency variability on longitudinal heating contrast between land and sea can produce a collapse of thermohaline circulation when a threshold of noise is overcome. This result is significant because if synoptic scale variability in the next century increases due to the climatic change an increment of the probability of this collapse could be produced.