Tides are one of the most persistent and dominant forces on our planet. Tides influence coastal flooding and erosion, navigation, sediment transport, mixing and dissipation. Therefore, any changes to tides have wide ranging and important implications. Changes in tides are known to have occurred over thousands of years and longer, but tides have generally been considered to have been a stationary phenomenon over centennial time-scales. However, an increasing body of evidence demonstrates that there have been significant and widespread changes in tides over at least the last 150 years at a number of locations worldwide. Furthermore, several studies indicate that tides will alter considerably over the 21st century and beyond in response to future mean sea-level rise, including in many coastal mega cites. Pickering et al. (2017) estimated that with 2m sea-level rise, mean high water is projected to increase or decrease by 10% of the sea-level rise at around a tenth of global coastal megacities. There is currently, however, a crucial lack of understanding of why widespread changes in tidal levels have occurred over the last 150 years with relatively small variations in water depth. This severely limits our ability to: (1) understand and interpret recent observed changes in tidal level; (2) isolate changes due to mean sea-level rise from other natural/anthropogenic factors; (3) accurately project future changes in tidal levels; and (4) quantify how predicted changes in tides will impact coastal and shelf seas.
The overall aim of this PhD will be to undertake an ambitious, integrated and ground-breaking assessment of future changes in tides on global and local scales. Objective 1 is to accurately predict future changes in tides using a suite of global numerical models. Efforts to directly compare and contrast modelling studies on future tidal characteristics are complicated by differences in numerical software across studies, boundary conditions, configuration settings, horizontal resolutions, forcing tidal constituents, mean sea-level rise scenarios, and analytical tidal metrics. In this objective the PhD candidate will run global simulations of tides, consistently accounting for projections of sea-level rise (considering UKCP18 and IPCC projections and high end estimates), across a range of different global tidal models, carefully assessing the uncertainties associated with key model settings and inputs. This will contextualise previous projections and bound the uncertainty of tidal projections informing policy and coastal management. Objective 2 will be to assess changes in future tides from the models at global coastal mega cities around the world. In objective 3, a series of case study locations will be selected (such as the Thames Estuary and Bristol Chanel). The PhD candidate will undertake a detailed analysis, at these case study sites to assess how climate, and other anthropogenic changes (e.g., dredging) are likely to influence tides and extreme sea levels at this location.
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for PhD candidates to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The PhD candidate will be registered at the University of Southampton and hosted at the National Oceanography Centre, with regular visits to the Met Office. Specific training will include hydrodynamic modelling; Big Data analysis in Python or MATLAB; CFD on leading high performance computing platforms; operation and management of storm surge barriers; and coastal management. The PhD candidate will join the physical oceanography research group, working alongside other PhD candidates researching complementary coastal flood problems.
Please see https://inspire-dtp.ac.uk/how-apply for details.
[1] Pickering, M. D., Horsburgh, K. J., Blundell, J. R., Hirschi, J. J.-M., Nicholls, R. J., Verlaan, M., & Wells, N. C. (2017). The impact of future sea-level rise on the global tides. Continental Shelf Research, 142, 50– 68. https://doi.org/10.1016/j.csr.2017.02.004
[2] Mawdsley, R. J., Haigh, I. D., & Wells, N. C. (2015). Global secular changes in different tidal high water, low water and range levels. Earth's Future, 3(2), 66– 81. https://doi.org/10.1002/2014EF000282
[3] Haigh, I.D., Pickering, M.D., et al. (2019). The tides they are a’ changing: A comprehensive review of past and future non-astronomical changes in tides, their driving mechanisms and future implications. Reviews of Geophysics, 58 (1), e2018RG000636. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018RG000636
