Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 2 5 2006 10.5194/cpd-2-745-2006 http://www.clim-past-discuss.net/2/745/2006/ http://www.clim-past-discuss.net/2/745/2006/cpd-2-745-2006.html http://www.clim-past-discuss.net/2/745/2006/cpd-2-745-2006.pdf 745 769 2006-09-11 Simulating sub-Milankovitch climate variations associated with vegetation dynamics E. Tuenter S. L. Weber F. J. Hilgen L. J. Lourens Royal Netherlands Meteorological Institute (KNMI), P.O. Box 201, 3730 AE De Bilt, The Netherlands Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands 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.