CONTENTS 1 DRIVERS ..................................................................................................................... 341 a) Slow and incremental change ............................................................................................................ 341 b) Event-driven change ........................................................................................................................... 341 1.1 Climatic drivers ............................................................................................................ 341 a) Natural cycles and variability ............................................................................................................. 341 b) External forcings ................................................................................................................................. 341 c) Internal forcings ................................................................................................................................... 341 d) NAO (North Atlantic Oscillation) ................................................................................................... 342 e) ACC (anthropogenic climate change) .............................................................................................. 342 1.2 Non-climatic drivers .................................................................................................... 342 a) Planetary forcings: lunar cycles .......................................................................................................... 342 b) Geology ................................................................................................................................................. 343 1.3 Greenhouse gas emissions ........................................................................................... 343 1.4 Extreme sea levels ........................................................................................................ 343 a) Concurrent events ............................................................................................................................... 344 1.4.1 Long term sea level variability & trends ..............................................................................344 a) Halosteric SLC ..................................................................................................................................... 344 b) Isostatic subsidence ............................................................................................................................ 344 c) Changes in hydrological cycle ............................................................................................................ 345 d) Thermosteric SLC ............................................................................................................................... 345 e) Sediment compaction.......................................................................................................................... 345 f) Changes in Geoid ................................................................................................................................. 345 g) Changes in atmospheric surface pressure & ocean circulation .................................................... 345 1.4.1.1 Glacio-eustacy ............................................................................................................... 346 a) Glacio-eustacy: small glaciers and ice caps ...................................................................................... 346 b) Glacio-eustacy: large ice sheets ......................................................................................................... 346 1.4.2 Short term SLC .....................................................................................................................346 1.4.2.1 Non-climatic causes of short-term SLC .......................................................................... 347 a) Tides ...................................................................................................................................................... 347 b) Severn bore .......................................................................................................................................... 347 c) Tsunamis ............................................................................................................................................... 347 1.4.2.2 Climatic causes of short-term SLC ................................................................................. 347 a) Storms .................................................................................................................................................... 348 335 b) Precipitation ......................................................................................................................................... 348 c) Surges..................................................................................................................................................... 348 d) Waves .................................................................................................................................................... 349 e) Storm typology & track ...................................................................................................................... 350 f) Meteotsunamis...................................................................................................................................... 350 1.5 Unknowns .................................................................................................................... 350 1.6 Other climatic and non-climatic factors ...................................................................... 350 2 PHYSICAL IMPACTS ................................................................................................. 351 a) Recovery? .............................................................................................................................................. 351 b) Slow and incremental or event-driven ............................................................................................. 351 2.1 Pathways....................................................................................................................... 352 a) Overtopping/failure of natural & engineered defences ................................................................ 352 b) Inundation (permanent/temporary) ................................................................................................ 352 c) Pollution ................................................................................................................................................ 352 d) Landscape changes .............................................................................................................................. 352 e) Impacts on water resources ............................................................................................................... 352 2.2 Hydrological change .................................................................................................... 352 a) Changes in tidal regime & curve ....................................................................................................... 353 b) Changes in surge characteristics........................................................................................................ 353 c) Changes in wave characteristics ........................................................................................................ 353 2.2.1 Saltwater intrusion & waterlogging .....................................................................................354 a) Saltwater intrusion into rivers & changes in saltwater wedge ...................................................... 354 b) Saltwater intrusion into groundwater ............................................................................................... 354 2.2.2 Flooding: changes in frequency/magnitude/likelihoods ...................................................354 a) Surface water flooding ........................................................................................................................ 354 b) Groundwater flooding ........................................................................................................................ 354 c) Coastal flooding ................................................................................................................................... 355 d) Fluvial flooding .................................................................................................................................... 355 e) Tide locking .......................................................................................................................................... 355 2.3 Morphological change ................................................................................................. 356 a) Sediment supply ................................................................................................................................... 356 b) Changes in biochemical cycling ........................................................................................................ 356 c) Changes in the supratidal environment............................................................................................ 356 d) Changes in the subtidal environment..............................................................................................