Case Study: Satellite Oceanographic Consultants Ltd – Sea Level SpaceWatch

This project set out to establish a sea level monitoring service for UK seas to assess sea level variability using space-borne altimeter data combined with tide gauge data. The intention was to devise a service which would be able to:

1. Advise the UK’s Committee on Climate Change in the production of their 5-yearly Climate Change Risk Assessment
2. Support the planning of national flood defences and adaptation plans, and the maintenance of coastal habitats
3. Provide supplementary information of seasonal and regional variations in sea level to the UK Climate Projections – following on from the UK Climate Predictions 2009 (UKCP09) and the Marine Climate Change Impacts Partnership (MCCIP)

This would require the following information:

• Time series of sea-level data in UK coastal seas
• Analyses to derive regional trends in mean sea level around the UK
• Detailed validation and error analysis to provide guidance on the interpretation and use of these data
• Comparison of current trends in sea level with climate model projections

New leaps have recently been made in the processing of coastal altimetry from satellite data. The National Oceanography Centre is the global leader in this field. With this advancement it will be possible to recover altimetry data along the coastal strip of the UK for the past 20 years. Additionally, new developments in altimeter design – as implemented on the new series of ESA Sentinel satellites – will in future provide higher resolution and higher precision measurements close to the coast.

Together these developments support the generation of new sea level products which will provide end-users with a much greater understanding of mean sea level change which will strongly govern future flood probabilities, and of observed sea level trends vs predicted trajectories. This in turn allows more timely and insightful decisions to be made on when and where to direct investments to maximise the reduction in unacceptable flood risk.

The aim of the Sea Level SpaceWatch service is to make this data available to the end-users. It will provide access to 14 years’ altimetry data from a series of altimeter missions, with more years to come, and has generated a range of data products which are free to download.

Lessons Learned

Early and continued engagement with the user agencies has been essential, to ensure that the service met their needs. Some flexibility is needed on both sides as understanding of the needs of the users and the capabilities of the data developed.

14 years’ altimeter data have now been processed. Ideally a longer time series is still needed to bring down the uncertainties on estimates of long-term trends. Analysis has yielded new insights, such as a link between open ocean sea level with shelf seas and the coastal zone; regional variability in trends and annual cycles; and the timing of peak annual cycles occurring more than a month later in the west and north of the UK.

Some final service developments are proposed, such as the provision of regionally averaged information.

Costs and Benefits

The initial implementation costs for an operational Sea Level SpaceWatch service are estimated to be in the region of £12k-£15k, with an annual operating cost of ~£35k, depending on the exact specification.

These costs would be recouped if the service could provide a 0.01% improvement in the efficiency of decisions on the investment in coastal flooding infrastructure.

Next Steps

The potential value of this service has been widely recognised and generated considerable interest amongst its intended end-users.

It is intended to continue discussions with the user agencies to agree final service specifications and Business Plan, with an aim of implementing an operational service in the autumn of 2016.

This service could also be extended for coastal regions across Europe and beyond, especially in flood-sensitive areas which currently lack accurate ground based data. It is anticipated that there are various funding sources available to explore such applications.