Anisotropic sea ice mechanics in the Arctic

In response to global warming, the ice covers of the Arctic and Antarctic are changing, with a significant reduction in the summer extent of Arctic sea ice. The observed recent, rapid reduction of Arctic sea ice is more extreme than the predictions of even the most pessimistic of climate models, which suggests that these models do not present the processes controlling the reduction of sea ice adequately. Satellite observations, field work, and modelling all point to the importance of sea ice dynamics in controlling the mass balance of Arctic sea ice. The greatest uncertainty in sea ice dynamics is in the relationship between internal sea ice stresses and the deformation and state of the sea ice cover, known as the sea ice rheology.

The description of sea ice rheology in existing climate models treats the ice cover as isotropic, so that at a given location there is equal resistance to failure in all directions. However, it has been known for over a decade that the ice cover is highly anisotropic, with oriented cracks present at all length scales, and these cracks control the directions of preferential deformation.

While researchers have been aware of the importance of anisotropic mechanics, only recently has a model of anisotropic rheology been constructed and incorporated into the sea ice component of a climate model.

This project aims to eliminate fundamental uncertainty in the processes controlling anisotropy creation and destruction through a combination of recently produced, high-resolution satellite deformation maps and computer modelling. A major result of the research will be a new representation of anisotropic sea ice rheology incorporated into the CICE sea ice model, which is the sea ice model used in many climate models, including the UK Hadley Centre series of climate models. We will use CICE to investigate the role of anisotropic rheology in producing the recent and rapid reduction of Arctic sea ice.

Arctic sea ice reduction has become a totemic indicator of climate change with impacts on iconic species such as polar bears and the Beluga whale, as well as indigenous populations. The reduction of Arctic sea ice extent has generated wide-spread interest with numerous articles in the popular press, radio, television and internet. A major practical impact of this proposal is in the generation of a more realistic, anisotropic treatment of sea ice rheology in the sea ice component of several climate models. The new treatment of sea ice rheology will lead to improved climate and regional prediction studies, used to guide national and international policy on issues related to climate change.

Reduction in the sea ice cover is already opening up shipping routes and the potential for oil exploration has generated political statements and actions including, for example, the placement of the Russian flag at the North Pole and Denmark's declaration of sea bed rights up to the North Pole. Lloyd's of London, with Chatham House, published a report called "Arctic Opening" earlier this year, with business (including insurance) expansion in mind.

Improved predictions of the Arctic sea ice cover will benefit the shipping and insurance industries. The predictions of ice cover evolution and ice stresses will benefit the construction and efficiency of oil exploration platforms.