Atmosphere to ocean momentum transfer by sea ice

Lead Research Organisation: University of Reading
Department Name: Meteorology


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 reduction of Arctic sea ice is more rapid and extreme than climate models predict, suggesting that these models do not adequately represent the processes controlling this reduction.
The reduced summer Arctic sea ice cover, and changes to the winter sea ice cover, affect the mechanical and thermodynamic coupling between the air and ocean. In fact, observations show that the sea ice cover has become more mobile in the last 15 years and that there has been an increase in the mean ocean circulation beneath the sea ice. Since, over the same period, there has not been an observed increase in wind strength, this suggests that changes to the sea ice cover itself are responsible for an enhanced ice motion and transfer of wind stress to the ocean beneath sea ice.
Our project hypothesis is: Changes in the Arctic sea ice cover have resulted in a more efficient transfer of momentum between the air and ocean, resulting in spin up of sea ice and the Arctic Ocean. We will test this hypothesis with a combination of new data, theory and numerical modelling.
We will investigate how changes in the roughness of the ice cover, e.g. through a more dilute ice cover having more floe edges exposed, change the drag forces exerted by the air on the ice and the ice on the ocean. We will investigate how a reduction in the ice cover may reduce the resistance of the ice cover to the wind, allowing it to move more easily. In particular we address the question: to what extent is acceleration of the Arctic sea ice gyre the result of decreased ice forces versus increased drag?
We will use climate models containing new physics calibrated with, and derived from, new observations, to examine the prediction that: Changes in the sea ice cover will continue to lead to enhanced momentum transfer between the air and ocean, resulting in a more mobile and responsive ice cover and enhanced flow and mixing in the Arctic Ocean.
Although we focus our analysis on the Arctic Ocean, where sea ice changes have been more dramatic, we will also examine air-ice-ocean momentum exchanges in the Southern Ocean.
This proposal brings together leading researchers in sea ice dynamics, remote sensing, ocean and climate modelling, and builds upon existing expertise in satellite observation, theory, and modelling of sea ice in the Centre for Polar Observation and Modelling.
In addition to the scientific outcomes, the proposed work will result in new sea ice drag physics being incorporated into a sea ice climate model and delivered to climate modelling groups. This will directly help scientists investigating and predicting future changes to the sea ice cover in the Arctic and Southern Oceans and also help scientists trying to understand and predict changes in the global climate system.

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 human populations. The reduction of Arctic sea ice extent has generated widespread interest with numerous articles in the popular press, radio, television and internet.

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" in 2012, with business (including insurance) expansion in mind. A Royal Society meeting on Arctic sea ice: the evidence, models, and global impacts is being organised by the PI in September 2014.

Continued reduction of the sea ice cover is expected to cause enhanced ocean mixing with a consequent impact on water mass transformation and supply of nutrients to the euphotic zone, which are necessary for primary production. The change in ocean and ice is expected to have implications for climate in NW Europe.

A major practical impact of this proposal is in the generation of a more realistic treatment of air to ice to ocean momentum transfer by form drag in the sea ice component of several climate models. The new treatment of air-sea ice-ocean momentum transfer will affect regional ice predictions used to inform government policy and those with financial and societal interest, such as the insurance, shipping and oil industries, as well as Inuit community groups.

The new treatment of form drag will also lead to improved climate prediction studies, used to guide national and international policy on issues related to climate change.


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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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Stroeve J (2018) Warm Winter, Thin Ice?

Description An internal wave drag parameterisation for sea ice--ocean drag has been developed and incorporated into a climate sea ice model. In addition to its intrinsic interest and importance, the modified drag routine will be made available to our Project Partners and other stakeholders.
Exploitation Route Drag routine made available to various modelling groups including Met Office, where it will affect sea ice predictions.
Publication detailing the model development and its impact in progress.
Sectors Aerospace

Defence and Marine

Description CANARI: Climate change in the Arctic-North Atlantic Region and Impacts on the UK
Amount £9,047,608 (GBP)
Funding ID NE/W004984/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 03/2022 
End 03/2027
Title ARC36 stand-alone SI3 Arctic configuration 
Description SI3 regional configuration of the Arctic This is a configuration of the NEMO community ocean model based on the ORCA2_SAS_ICE reference configuration. The NEMO code is available from This configuration has a resolution of 1/36 degree and is a cut-out of the global 1/36 configuration: The code base is a pre-4.2.0 NEMO version, the model source code can be found in the file src_tar. Model setup Follow the instructions on to download and install the NEMO model version 4.2.0. Swap the src directory for the one in the tar file src_tar. Compile the ORCA2_SAS_ICE reference configuration. Put the rest of the files in this zenodo archive in the EXP00 directory, except the namelist_cfg_for_DOMAINcfg file which goes into tools/DOMAINcfg along with the grid files to be downloaded later. The files provided include example configuration namelist files namelist_cfg and namelist_ice_cfg. The atmospheric forcing used is the Drakkar forcing set (DFS) version 5.2, year 2008. The atmospheric forcing is interpolated on-the-fly, using the weights files. The weights were calculated using the nemo WEIGHTS tool. For the ocean (bottom) boundary the World Ocean Atlas 2018 multidecadal monthly averages are used. The data is already interpolated onto the ARC36 grid. Interpolation was done using the SOSIE tool. Files provided are monthly averages of sea surface salinity and temperature. Finally, the model grid needs to be created. Download the ORCA36 files from, see the ORCA36 demonstrator github page. The necessary files are the coordinates and bathymetry files. To cut out the Arctic domain use ncks -F -d y,7000,,1 Put in tools/DOMAINcfg and use the DOMAINcfg NEMO tool to create the file using the file namelist_cfg_for_DOMAINcfg as namelist_cfg. The resulting file is large (122GB) therefore executing in parallel mode is required. The individual processor files need to be merged into one, use the REBUILD_NEMO tool. Put the resulting file into EXP00 and run NEMO following the instructions. The ARC36 configuration was set up and run on ARCHER2 using 594 NEMO processors and 12 XIOS processors. Animation The animation has been created from daily average of sea ice fraction from the 1/36° Arctic NEMO-SI3 model integrations with the EAP rheology. The animation has started on the 00:00 of the 1st January 2008 and carried out through the January. It shows a limited area of the model domain north of Fram Strait. The lower concentrations correspond to the opening leads, with "blurred" leads and some multiple signatures due to ice displacement and data averaging over 1-day periods. Acknowledgements: EU IMMERSE (Grant agreement ID: 821926), NERC APEAR project (NE/R012865/1, NE/R012865/2, #03V01461), part of the Changing Arctic Ocean programme; EU H2020 COMFORT (no. 820989); NERC PRE-MELT (NE/T000546/1), and LTS-S CLASS (NE/R015953/1). ARCHER UK National Supercomputing and JASMIN facilities. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
Impact Improved air to ocean momentum coupling in presence of sea ice cover. 
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. 
Description Are we waking up the sleeping Arctic Ocean youtube broadcast. 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A talk on broadcast on YouTube describing changes in Arctic Ocean as sea ice retreats.
Year(s) Of Engagement Activity 2016