Effect of isostatic rebound on modelled ice volume variations during the last 200 kyr

Deformation of the lithosphere under an ice load can be approximated using the hypothesis of local damped isostasy. This simple formulation has been s ystematically compared with a three-dimensional model of the crust-mantle s ystem for simple ice-load scenarios with a period in the range 20-100 kyr. The comparison enables us to introduce the concepts of effective upper mant le density and effective relaxation time into the isostatic model for the r esponse of the Earth to the ice sheets. These parameters depend on the Eart h model considered, ice sheet size and the period of the load cycle. The lo cal damped isostasy model has been implemented in the Louvain-la-Neuve clim ate model to assess the impact of isostasy on continental ice volume variat ions for the last 200 kyr. Results suggest that isostasy acts as a negative feedback for ice volume during the glaciation process and acts as a positi ve feedback during the deglaciation. Moreover, taking isostasy into account is necessary to simulate variations in Northern Hemisphere ice volume duri ng isotopic stage 3. Lastly, the use of effective mantle density and effect ive relaxation time improves the model performance regarding SPECMAP recons tructions. (C) 2001 Elsevier Science B.V. All rights reserved.