Atmospheric controls and long range predictability of directional waves in the United Kingdom & Ireland

Abstract

Improved understanding of how our coasts will evolve over a range of time scales (years-decades) is critical for effective and sustainable management of coastal infrastructure. Globally, sea-level rise will result in increased erosion, with more frequent and intense coastal flooding. Understanding of current and future coastal evolution requires robust knowledge of the wave climate. This includes spatial, directional and temporal variability, with recent research highlighting the importance of wave climate directionality on coastal morphological response, for example in UK, Australia and California. However, the variability of the inshore directional wave climate has received little attention, and an improved understanding could drive development of skillful seasonal or decadal forecasts of coastal response. We examine inshore wave climate at 63 locations throughout the United Kingdom and Ireland (1980-2017) and show that 73% are directionally bimodal. We find that winter-averaged expressions of six leading atmospheric indices are strongly correlated with both total and directional winter wave power (peak spectral wave direction) at all studied sites. Coastal classification through hierarchical cluster analysis and stepwise multi-linear regression of directional wave correlations with atmospheric indices defined four spatially coherent regions. We show that combinations of indices have significant skill in predicting directional wave climates (r= 0.45-0.8; p<0.05). We demonstrate for the first time the significant explanatory power of leading winter-averaged atmospheric indices for directional wave climates, and show that leading seasonal forecasts of the NAO skillfully predict wave climate in some regions.

A rules-based shoreface translation and sediment budgeting tool for estimating coastal change: ShoreTrans

“…Note that we have assumed the trend from 1985-2020 will continue for the next 100 years, which may not be the case if long-term climatic variations impact on wave direction [60]. For Start Bay, SLR is a secondary factor, contributing less than a third to the recession forced by the long-term trend in longshore sediment flux.…”

Climate Control of Multidecadal Variability in River Discharge and Precipitation in Western Europe

“…The results of this study imply that the precipitation and river-discharge variability in western Europe is strongly influenced by changes in atmospheric circulation, best described by the WEPA index between latitudes 42 • N to 55 • N, and the NAO index below and above these latitudes. These two indices have already demonstrated a strong ability to explain ocean wave climate and coastal hazards along the Atlantic coast of Europe [57][58][59][60][61], and could help understand and predict other hydrological variables in this region. Future works linking river streamflow at regional or catchment scales with large-scale climate patterns may consider water storage, orographic effects, and the effect of temperature to reduce uncertainties.…”

Modelling of embayed beach equilibrium planform and rotation signal

“…Recent work (e.g. Wiggins et al, 2019aWiggins et al, , 2019b indicate that bimodal wave climate, which is common on many coasts (Scott et al, 2020), can lead to dramatic beach rotation events from the timescale of storm to decades. In such bimodal wave climate, the absence of shorenormal condition resulting in vanishing shoreline diffusivity may also allow for greater-amplitude fluctuations in shoreline curvature.…”