Looking for evidence of climate change impacts in the eastern Irish Sea

Abstract

Abstract. Although storminess is often cited as a driver of long-term coastal erosion, a lack of suitable datasets has only allowed objective assessment of this claim in a handful of case studies. This reduces our ability to understand and predict how the coastline may respond to an increase in "storminess" as suggested by global and regional climate models. With focus on 16 km of the Sefton coastline bordering the eastern Irish Sea (UK), this paper analyses available measured datasets of water level, surge level, wave height, wind speed and barometric pressure with the objective of finding trends in metocean climate that are consistent with predictions. The paper then examines rates of change in shoreline position over the period 1894 to 2005 with the aim of establishing relationships with climatic variability using a range of measured and modelled metocean parameters (with time spans varying from two to eight decades). With the exception of the mean monthly wind speed, available metocean data do not indicate any statistically significant changes outside seasonal and decadal cycles. No clear relationship was found between changes in metocean conditions and rates of shoreline change along the Sefton coast. High interannual variability and the lack of long-term measurements make unambiguous correlations between climate change and shoreline evolution problematic. However, comparison between the North Atlantic Oscillation winter index (NAOw) and coastline changes suggest increased erosion at times of decreasing NAOw values and reduced erosion at times of increasing NAOw values. Erosion tends to be more pronounced when decreasing NAOw values lead to a strong negative NAO phase. At present, anthropogenic changes in the local sediment budget and the short-term impact of extreme events are still the largest threat likely to affect coastal flooding and Correspondence to: L. S. Esteves (l.slompesteves@londonmet.ac.uk) erosion risk in the short-and medium-term. Nevertheless, the potential impacts of climate change in the long-term should not be ignored.

Regional modelling of the 21st century climate changes in the Irish Sea

“…The ECHAM5 model under the A1B scenario projects a slight (c. 2%) increase in winter wind speeds and decreases of 1.2, 4.5 and 2.2% in spring, summer and autumn, respectively. These trends are in line with those found from ensemble simulations for Ireland ) and with observations (Esteves et al, 2011).…”

Recent Change—Atmosphere

“…Red, blue and green colours indicate positive, negative or no trend, respectively high water for the period 1768-1999 (Woodworth and Blackman 2002) but no trend in the annual maximum high water level or the surges at annual maximum high water for this period. For shorter periods, no trends are found for maximum monthly wind speed observations for the Irish Sea 1929-2002 (Ciavola et al 2011) while Esteves et al (2011) found a weak but significant negative trend for monthly mean wind speeds at the Bidston observatory on the northern Irish Sea coast over the same period.…”

Remote sensing of geomorphological and ecological change in response to saltmarsh managed realignment, The Wash, UK

“…The distance from each linear feature to a fixed baseline is found for a user-specified distance along that baseline, allowing the rate of change to be determined at a very high level of spatial densification. This study is concerned with shoreline change, which is the most commonly found application of the DSAS methodology (Thieler et al, 2005;Addo et al, 2008;Esteves et al, 2009). While DSAS has been applied to a range of scales and coastal settings, it has not previously been applied to boundaries between vegetation communities in upper intertidal environments.…”