Autori: Dima, M, and G. Lohmann

Editorial: Climate Dynamics, 32(2-3), p.301-311, 2008.

Rezumat:

Dansgaard-Oeschger and Heinrich events are the most pronounced climate changes over the last 120,000 years. Although many of their properties were derived from climate reconstructions, the associated physical mechanisms are not yet fully understood. These events are paced by a ~1500 year periodicity whose origin remains unclear. In a conceptual model approach, we show that this millennial variability can originate from rectification of an external (solar) forcing, possibly through a threshold response of the thermohaline circulation. We argue that internal threshold response of the THC to solar forcing is more likely to produce the observed DO/H cycles than amplification by THC of weak, direct ~1500 year forcing of an unknown origin. As one consequence of our concept, the millennial variability is viewed as a derived mode without physical processes on its characteristic time scale. In contrast, the mode results from the linear representation in the Fourier space of nonlinearly transformed fundamental modes.

Cuvinte cheie: Rectification, Solar forcing, Thermohaline circulation, Millennial variability, Fundamental - Derived climate modes

URL: http://www.springerlink.com/content/24rm14413xx883p2/