Sea level trend reversal: Land uplift outpaced by sea level rise on Scotlandʹs coast

A widely held belief persists that rising land levels since the latter part of the last glaciation will help safeguard much of the Scottish coast from the impact of global sea level rise. Although the landforms of much of Scotlandʹs coast reflect long-term land uplift, recent investigations show that uplift rates are now modest and are less than rising sea levels. When comparisons are made between long-term land-level changes using Glacio-Isostatic Adjustment models, representative of the last few thousand years (Shennan and Horton, 2002; Shennan et al., 2009), and recent land-level changes using Continuous GPS records, representative of the last decade (Bradley et al., 2006), it is apparent that recent rates of uplift are slower than longer-term averages. We show here that when tidal records are considered, they show marked increases over recent decades although the extent to which these are part of a longer-term trend is uncertain. When considered alongside the UKCP09 climate projections, these tidal observations are of value in narrowing or calibrating the wide choice of sea level projections under various climate change scenarios. It appears that Scotlandʹs observed tidal record now lies close to the 95% projection of the UKCP09 High Emission Scenario and isostatic uplift now contributes little towards mitigating the effect of relative sea level rise on the Scottish coast. If the observed recent patterns are maintained, this has significant implications for strategic planning, flood risk management and sustainable development on Scotlandʹs coast, and particularly on low-lying coastal zones around the major cities.