Arctic Sea Ice Dynamics Using Experiments and Multi-scale Modelling

Satellite and submarine observations reveal the Arctic sea ice cover is thinning at a rapid rate. Recent computer modelling shows that predictions of sea ice export into the Greenland Sea, where it will melt to form a buoyant layer weakening downwelling and hence reducing the strength of the northern extent of the Gulf Stream, are highly sensitive to the treatment of forces in the sea ice cover. The model representation of sea ice forces is uncertain, but the stresses are principally determined by sea ice floes (which are 100 m to 10 km wide and a few metres thick) overiding each other in vertical deformation to form pressure ridges and by in-plane, i.e. horizontal, frictional sliding of sea ice floes past each other. Previous experimental studies and most modelling work has focussed on the role of vertical deformation in determining ice stresses but satellite observations, derived using algorithms for feature tracking, show that almost all the deformation of sea ice is due to in-plane frictional sliding. The proposed research will combine ice tank measurements of the in-plane frictional sliding of an artificial sea ice cover with numerical simulations to give a validated model of in-plane sea ice deformation and the stresses that result. The derived model of sea ice stress will be incorporated into the sea ice model component of an Global Climate Model and its predictions compared with observations of Arctic sea ice motion, extent, concentration, and thickness. The new sea ice stress model will be made available to the Hadley Centre and other climate modelling groups. The proposed programme of research is therefore timely in both its purely scientific and technical modelling aspects.