A POTENTIAL CLIMATE SIGNATURE IN REGIONAL SHORELINE BEHAVIOUR, NORTHWEST IRELAND

A potential climate signature in regional shoreline behaviour, Northwest Ireland

Historical shoreline records from 1834 to 2008 provide an impression of coastal behaviour in Northwest Ireland. Instrumental records of wind and wave activity only exist for a few decades and proxies such as the North Atlantic Oscillation are necessary to establish potential past linkages to climate forcing. In northwest Ireland, relative sea level has been stable at the historical period and sandy depositional systems are of finite volume and constrained in coastal re-entrants by bedrock outcrop. With sea level change and sediment supply thus constrained the region is an ideal site to investigate the role of climate change. Analysis of historical shoreline change on pocket beaches and inlet-associated beaches shows a similar overall behavioural pattern that matches instrumental records of climate conditions for the past decade. The relationship of wind and waves to the NAO during this period is quite systematic and the NAO is revealed to be a good proxy of past climate and shoreline behaviour in the pre-instrumental era. For pocket beaches, steepening, dune accumulation and shoreline advance is associated with climatic amelioration while beaches become more gentle in slope (and shorelines retreat) in response to periods of enhanced wave action. Behaviour at inlet-associated beaches involves major shoreline readjustments as sediment transfers from tidal deltas to beach and dunes resulting in shoreline change of tens of metres in scale. The results suggest that both pocket beaches and inlet-associated beache srepond to climate forcing at the regional scale, although the nature of the response is locally specific.