Anisotropic sea ice mechanics in the Arctic

Lead Research Organisation: University of Reading
Department Name: Meteorology

Abstract

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.

Planned Impact

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.

Publications

10 25 50
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Feltham D (2015) Arctic sea ice reduction: the evidence, models and impacts. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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Heorton HDBS (2018) Stress and deformation characteristics of sea ice in a high-resolution, anisotropic sea ice model. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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Sammonds PR (2017) Micromechanics of sea ice frictional slip from test basin scale experiments. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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Stroeve J (2018) Warm Winter, Thin Ice?

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Tsamados M (2015) Processes controlling surface, bottom and lateral melt of Arctic sea ice in a state of the art sea ice model. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

 
Description 1. 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.

2. Note: appointment started on 1 April 2014.

Initial work has focussed on procuring and analysing GLOBICE and RADARSAT data on sea ice deformation and analysis of this data to produce gridded fields of the anisotropy tensor.

Trials simulations of the Arctic sea ice cover have been performed with a model accounting for anisotropy.
Exploitation Route Improved representation of the physics of sea ice anisotropy will affect sea ice predictions in climate models and local predictions.

The project is designed so that new physics developments will be included in the sea ice climate model CICE, where they will be used by other modelling and climate prediction groups including the Met Office, NOC and BAS.

A new optimised anisotropic plastic (EAP) rheology routines has been developed, improving the efficiency of the anisotropic EAP rheology for sea ice within a numerical climate model. These routines have been improved to give more accurate numerical solutions to the sea ice stress equations. This year (2019) the new improved code has been incorporated into both the new Los Alamos National Laboratory CICE model community code on GitHub https://github.com/CICE-Consortium/CICE and also supplied for the development of the UK Met Office Hadley Centre climate model HadGEM.
Sectors Aerospace, Defence and Marine,Education,Environment

URL https://climatemodeling.science.energy.gov/technical-highlights/icepack-essential-physics-sea-ice-models
 
Description A more numerically efficient anisotropic rheology model has been produced and disseminated to the Met Office, our project Partner. Papers are in progress.
First Year Of Impact 2017
Sector Aerospace, Defence and Marine,Education,Environment
 
Description Input to Arctic Select Committee of House of Lords - oral and written evidence
Geographic Reach Australia 
Policy Influence Type Gave evidence to a government review
URL http://www.parliament.uk/business/committees/committees-a-z/lords-select/arcticcom/publications/
 
Title Input to CICE sea ice climate model 
Description Research projects have developed new physics of sea ice processes. Under separate funding, but in collaboration with research projects, this has been turned into new physics modules in the sea ice climate model CICE. 
Type Of Technology Physical Model/Kit 
Year Produced 2017 
Impact The CICE sea ice model is used by climate modelling groups worldwide. In the UK this includes the UK Met Office, NOC and BAS.