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1 KNMI - Royal Netherlands Meteorological Institute 2 Department of Earth Sciences

Abstract : Climate variability at sub-Milankovitch periods between 2 and 15 kyr is studied in a set of transient simulations with a coupled atmosphere-ocean-vegetation model of intermediate complexity Climber-2. Focus is on the region influenced by the African and Asian summer monsoon. Pronounced variations at sub-Milankovitch periods of about 10 kyr Asia and Africa and about 5 kyr Asia are found in the monsoonal runoff in response to the precessional forcing. This is caused by the dynamic response of the vegetation. For low summer insolation precession maximum precipitation is low and desert expands at the expense of grass, while for high insolation precession minimum precipitation is high and the tree fraction increases thus reducing the grass fraction. This induces sub-Milankovitch variations in the grass fraction and associated variations in the water holding capacity of the soil. No sub-Milankovitch variability occurs in the runoff when vegetation is kept fixed. The high-latitude vegetation coverage also exhibits sub-Milankovitch variability under both obliquity as well as precessional forcing. We hypothesize that sub-Milankovitch variations found in terrestrial and marine records are related to variations in vegetation, soil characteristics and runoff influencing ocean salinity and circulation.

Autor: E. Tuenter - S. L. Weber - F. J. Hilgen - L. J. Lourens -



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