Thresholds, Reversibility, and Hysteresis

© 2005 Eugene S. Takle

Unit 2-14 on sea-level rise contains a brief description of a "hysteresis" caused by the ice-albedo feedback in the climate system. Hysteresis is a process in which once a threshold of some driving variable is exceeded, the system will not reverse until the driving variable passes a second threshold in the opposite direction. Maslin (2004) discusses this phenomenon in relation to tropical vegetation (Jennerjahn et al., 2004) and forest stages in southern Europe (Tzedakis, 2004) and notes that analogous thresholds exist for the relationship between surface ocean salinity and the rate of deep-ocean circulation (Ramnstorf, 1995). There is a possibility that high altitude cloud forests at low latitude also may exhibit this behavior (Asbjornsen, pers. Comm.).

References

Jennerjahn, T.C., V. Ittekkot, H.W. Arz, H. Behling, J. Patzold, and G. Wefer, 2004: Asynchronous terrestrial and marine signals of climate change during Heinrich events. Science, 306, 2236-2239.

Maslin, M, 2004: Ecological versus climatic thresholds. Science, 306, 2197-2198.

Tzedakis, P.C., K.H. Roucoux, L. de Abreau, and N.J. Shackleton, 2004: The duration of forest stages in southern Europe and interglacial climate variability. Science, 306, 2231-2235.

Ramstorf, S., 1995: Nature, 378, 145.