Sea level, climate change and coastal evolution in Morar, northwest Scotland

Analyses of geomorphologically contrasting sites in Morar, NW Scotland, des cribe the forcing mechanisms of coastal change. Isolation basins (i.e. basi ns behind rock sills and now isolated from the sea following isostatic upli ft) accumulated continuous marine and freshwater sediments from c.12 to 2 k a BP. Raised dune, marsh and wetland sites register breaching, migration an d stability of dunes from c. 9 to 2 ka BP. High-resolution methods designed to address issues of macroscale and microscale sea-level changes and patte rns of storminess include 1-mm sampling for pollen, dinocyst and diatom ana lyses, infra-red photography, X-ray photography and thin-section analysis. The data enhance the record of relative sea-level change for the area. Majo r phases of landward migration of the coast occurred during the period of l ow sea-level rise in the mid-Holocene as the rate of rise decreased from c. 3 to < 1 mm/year. Relative sea-level change controls the broad pattern of coastal evolution at each site; local site-specific factors contribute to s hort-term process change. There is no record of extreme events such as tsun ami. Within a system of dynamic metastable equilibrium, the Holocene records sho w that site-specific factors determine the exact timing of system breakdown , e.g. dune breaching, superimposed on regional sea-level rise. The global average sea-level rise of 3 to 6 mm/yr by AD 2050 predicted by IPCC would o nly partly be offset in the Morar area by isostatic uplift of about 1 mm/yr . A change from relative sea-level fall to sea-level rise, in areas where t he regional rate of uplift no longer offsets global processes, is a critica l factor in the management of coastal resources.