Improved projections of winds at the crossroads between Antarctica and the Southern Ocean

The coastal region of Antarctica links the Southern Ocean to the Antarctic continent and is where many of the key interactions that govern Antarctica's impact on the global climate system take place. Scientists have studied winds at mid-latitudes over the Southern Ocean and over the Antarctic continent, but much less attention has been paid to the marine winds just offshore from Antarctica. Numerical models of the ocean and atmosphere are now run on small enough grids that these coastal winds can be resolved and represented reliably. However, this needs to be tested in the current generation of climate models. It is important that climate models have a good representation of these coastal winds for the following reasons:
- Coastal winds influence the flow rate of major Antarctic glaciers and their associated impacts on global sea level.
- Winds over coastal polynyas (areas of unfrozen sea within the ice pack) drive cooling and sinking of the densest water in the world ocean, known as Antarctic Bottom Water (AABW), which contributes to storing the extra heat and carbon released into the atmosphere by humans.
- Realistic surface wind fields in climate models are needed to produce realistic distributions of sea ice. This is important in controlling the amount heat and moisture convergence into the Antarctic continent by capping off evaporation and heat loss from the ocean surface. Additionally, since sea ice formation enriches surface waters with salt, it is integral to the formation and sinking of dense AABW.

Reliable projections of future change in AMCWs, and related regional and global impacts, will require their realistic representation in climate models. We will make use of a new collection of state-of-the-art climate model output, the Coupled Model Inter-comparison Project Phase 6 (CMIP6). In collaboration with the Met Office, sensitivity studies using their IPCC-class Unified Model (MetUM) will enable us to understand how sensitive AMCWs are to changes in model configuration. This will tell us which physical processes climate models need to get right to accurately represent the structure and variability of AMCWs.

We will improve the evaluation of observed winds from Antarctic stations, research and supply vessels, drifting buoys, and marine winds from satellites to assess the quality of a range of different gridded wind data products, which are based on both observations and observationally-constrained numerical modelling. The best performing products will be used to evaluate climate model performance. An established framework for model evaluation is the concept of climate model 'metrics', which can quantify a key process or feature of the climate system, usually with a single value, that can be calculated from both model output and observational reference data (in our case observationally-based wind products). We will develop and use metrics to evaluate the performance of CMIP6 models in representing AMCWs, including configurations participating in its high-resolution sub-project HighResMIP. This, along with improved process understanding, will help to reduce uncertainty in projections of future change.

The research outcomes will be:
- Improved 21st century projections of AMCWs from the latest state-of-the-art climate and earth system models.
- Observational metrics of AMCWs that can be applied to gridded climate model output.
- A dataset of historical in-situ meteorological observations of marine coastal Antarctica building on the NERC ORCHESTRA project.
- Identify the best of the current generation of wind products for the Antarctic coastal region.
- Evaluation of the representation of AMCWs in the MetUM which, in combination with planned sensitivity studies, should ultimately facilitate accelerated model development.
- Career development for two early career researchers giving experience in climate modelling, analysing large datasets, networking and communication skills.

- The research proposed here will have a wide range of economic, societal and academic impacts, with the main beneficiaries being:

- The Intergovernmental Panel on Climate Change (IPCC)
The IPCC is the primary focus for assessing past and potential future climate change and its reports are definitive reviews of humankind's current understanding of climate change science. The proposed research on Antarctic coastal winds will help improve estimates of the regional and global impacts of Antarctic climate change and participate in the evaluation of climate model datasets that underpin a large proportion of the climate change science synthesised in the IPCC reports. Peer review papers and datasets generated by the project would therefore be highly relevant to the scientific evidence base of future IPCC reports. To help facilitate strong linkages, researchers involved with the IPCC process will be invited to the proposed scientific workshop.

- Policy makers
Improved projections of centennial time-scale Antarctic climate change are crucial to narrowing estimates of future sea level rise and will aid planning by policy makers. A major source of information for adaptation planning in the UK, the UK Climate Projections (UKCP) projects, are built on output from the UK Met Office models. Anticipated improvements to the Met Office model from the proposed research would likely be carried forward to future updates of projects such as the recently-released UKCP18. As well as adaptation, mitigation plans can be refined and the work will aid the formulation of greenhouse gas emission targets.

More regionally, BAS scientists work closely with the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and have been supplying scientific evidence to support policy and management decisions. We will utilise this existing working relationship to communicate scientific progress from the proposed research and identify future priorities for near-term forecasting capability.

- The general public
Antarctic climatic change has been reported extensively by the media and is of wide public interest. This work will result in increased public awareness of how Antarctic climate may change in the future and the global implications of this.

- Schools
We will give talks on Antarctic climate change to schools which will help to educate young people about climate change and the work of scientists and to inspire the next generation of young scientists to take up climate and environmental research.

- The academic community
Climate projections are of great value to a range of scientific disciplines. Improved knowledge of Antarctic coastal winds and their projections will be highly relevant to oceanographers, ice sheet modellers and ecosystems researchers and the proposed project links to these communities.

- Science and engineering skills
This proposed project would help to develop the next generation of climate scientists with the many opportunities that will be available to the PDRAs. They have the opportunity to develop numerical and analytical skills that are valuable across the science and engineering sectors. They will also improve their collaboration and networking skills by working with the diverse team that has been brought together for this proposal. Related to this, presentation skills will be enhanced by participating in the many project meetings and in more formal settings such as large international conferences.