How to define extreme sea level scenarios in the Pacific Islands?

The second technical workshop on Best Practices for the Formulation of Localized Sea Level Rise/Coastal inundation ‘Extremes’ Scenarios in the Pacific Islands was held in November at the University of Hawaii, Honolulu.

The key aims were to outline: (1) best practices and methodologies for the formulation of probabilistic estimates of extreme water levels under a changing climate for specific locations in the Pacific Islands; and (2) key issues that need to be addressed with future research.

The workshop involved a team of international experts. Dr Shari Gallop, Research Fellow in G&G, attended the workshop to discuss recent research on extreme sea levels and waves in Western Australia, and impacts on the reefed coastline. This research also involved UoS Lecturer Dr Ivan Haigh (Physical Oceanography), Cyprien Bosserelle, Ian Eliot and Chari Pattiaratchi in Western Australia.

Key discussions included how to estimate and combine uncertainties in estimating extreme sea level scenarios, such as due to uncertainty in projections of sea level rise; and how storms and tropical cyclones frequency and intensities might change with climate change. In addition, it was discussed how to use traditional techniques of extreme value analysis such as using Gumbel distributions, in areas where tropical cyclones occur because the magnitudes and recurrence intervals of tropical-cyclone and non-tropical cyclone events are very different. Measurements of the effect of tropical cyclones on sea levels and wave conditions are relatively rare, due to relatively short records; gauges that are not capable of measuring waves; and well as the often localised nature of tropical cyclones so that the likelihood of one passing directly past a gauge is relatively low.  Another key discussion point was that the geographical location of an area of interest needs to play a key role in determining what method of extreme value analysis is required e.g. is it in the region affected by tropical cyclones? And therefore, is stochastic tropical cyclone modelling required? Also, how to understand and include effects of sea level rise and climate change on reef structures themselves is an area requiring urgent research.