Realistic sea ice melt in climate models using field observations and theory

In response to global warming, the ice covers of the Arctic and Antarctic are changing, with a significant, and accelerated, reduction in the summer extent of Arctic sea ice. The observed 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 represent the processes controlling the reduction of sea ice adequately. Satellite observations, field work, and modelling all point to the importance of melt ponds in controlling the summer melt of Arctic sea ice but climate models do not explicitly represent melt ponds.
Melt ponds form when surface snow and sea ice meltwater accumulates on the sea ice surface. Since pond-covered ice has a lower reflectivity (albedo) than bare sea ice, pond-covered ice melts up to 3 times more rapidly than bare ice. This project aims to eliminate fundamental uncertainty in the processes controlling the melt of Arctic sea ice through a combination of recently collected, closely controlled field observations and computer modelling. This project will identify the contribution of melt ponds to the rapid reduction in Arctic sea ice. A result of the research will be a new representation of sea ice melt incorporated into the CICE sea ice model, which is the sea ice model used in many climate models, including the UK Meteorological Office climate model.

Specific users who will benefit from this proposal

This proposal will generate new scientific knowledge and insight into the thermodynamic and radiative processes, including the role of melt ponds, that determine sea ice melt and thus the heat and mass budget of the Arctic Ocean. In particular, this new knowledge will benefit sea ice geophysicists and polar oceanographers seeking to understand the role of sea ice melt in recent remarkable changes in the Arctic ice cover.

A major practical impact of this proposal is in the generation of a more realistic treatment of sea ice melt in the sea ice component (CICE) of a Global Climate Model (GCM). The CICE sea ice component is used in the HadGEM3 GCM developed in the Hadley Centre UK Meteorological Office (UKMO) and the Community Climate System Model at the (US) National Center for Atmospheric Research.

CICE is also used in many sea ice-ocean models, e.g. within the UK, CICE is used in the National Oceanography Centre Southampton, the National Oceanography Centre Liverpool, the British Antarctic Survey, and the National Centre for Earth Observation.

Engagement with the user group

The PI plays a leading role in organising annual meetings of the UK Sea ice group, which regularly attracts the leading UK climate and polar modelling groups (and experimental and observational groups). This is an informal environment allowing for practical difficulties and issues to be discussed. The project results, and guidance on use of the new sea ice melt module, will be presented in a special session of this forum to the potential UK users.

In order to maximise user take up of the sea ice melt module, several multi-day visits to both NOC sites will be arranged.

The Met Office Hadley Centre climate model HadGEM3 uses a non-standard configuration of CICE to allow close coupling with the atmosphere model, with the surface ice heat budget being incorporated into the atmosphere model. For this reason, we will arrange two mid-project meetings in order to discuss the most practical way for the Hadley Centre to incorporate the new sea ice melt treatment into their model.

The PI convenes an annual session on sea ice processes and models at the European Geosciences Union meeting, and occasional sessions at the American Geophysical Union meeting, both of which would provide ideal forums to make the project work widely known to the international community.

As part of core NCEO activity, the new sea ice melt module will be tested and uploaded to the Los Alamos National Laboratory, who develop and maintain the CICE code, and incorporated into the latest version of CICE. This will maximise the impact of the project, since every user group downloading the latest version of CICE will automatically be using the new sea ice melt module.

We will expand the existing CPOM web site. This web site will provide illustrated information on sea ice melt and melt ponds for a more general audience, and will provide links to documentation of the sea ice melt module and the module itself.

In addition to the various meetings, conferences, and website, the results of the project will be published in high quality journals with a wide readership in the user community.

Wider user interest

The new treatment of sea ice melt will have implications for climate change prediction by affecting atmosphere and ocean coupling and the sea ice heat and mass balance. In particular, the GCMs affected by the new sea ice model are used to provide results for the Intergovernmental Panel on Climate Change, the reports of which are used to guide national and international policy on issues related to climate change.

The demonstrated impact of melt ponds will affect the climate model simulations used to inform government policy and those with financial and societal interest, such as the insurance and oil industries, and Inuit community groups.