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

L S Esteves,J J Williams,J M Brown

doi:10.5194/nhess-11-1641-2011

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 erosion risk in the short- and medium-term. Nevertheless, the potential impacts of climate change in the long-term should not be ignored.

Highlights

Climate change is expected to affect the frequency, trajectory and intensity of storms (IPCC, 2007) which in turn may increase the occurrence of extreme water levels through the combined effect of rising sea level and higher storm surges (e.g. Wang et al, 2008)
Woodworth and Blackman (2002) found that values of annual maximum surge at high water were larger at the end of the last three centuries than for most of the 20th century, and suggest: (a) the findings are consistent with known variations in storminess in the region; and (b) there is a secular trend in the distribution shape of storminess, with enhanced storminess at the beginning and end of centuries in comparison to mid-century
Model projections indicate that climate change might result in increased storm surge heights at most locations in the UK by the end of this century and higher sea level will lead to higher extreme water levels (e.g. Lowe and Gregory, 2005)

Summary

Introduction

Climate change is expected to affect the frequency, trajectory and intensity of storms (IPCC, 2007) which in turn may increase the occurrence of extreme water levels through the combined effect of rising sea level and higher storm surges (e.g. Wang et al, 2008). Climate change is expected to affect the frequency, trajectory and intensity of storms (IPCC, 2007) which in turn may increase the occurrence of extreme water levels through the combined effect of rising sea level and higher storm surges A number of studies have examined long-term trends of storm surges and sea level Model projections indicate that climate change might result in increased storm surge heights at most locations in the UK by the end of this century and higher sea level will lead to higher extreme water levels The projected increases in storm surges and extreme water levels are expected to intensify coastal erosion

Objectives

Methods

Conclusion