Storminess and vulnerability along the Atlantic coastlines of Europe: analysis of storm records and of a greenhouse gases induced climate scenario

Identification of the distinctive circulation patterns of storminess on the Atlantic margin of Europe forms the main objective of this study; dealing with storm frequency, intensity and tracking. The climatology of the extratropical cyclones that affect this region has been examined for the period 1940–1998. Coastal meteorological data from Ireland to Spain have been linked to the cyclone history for the North Atlantic in the analysis of storm records for European coasts. The study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the North Atlantic Oscillation (NAO). Results indicate a seasonal shift in the wind climate, with regionally more severe winters and calmer summers established. This pattern appears to be linked to a northward displacement in the main North Atlantic cyclone track.

An experiment with the ECHAM4 A-GCM at high resolution (T106) has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region. The experiment consists of (1), a 30-year control time-slice representing present-day equivalent CO₂ concentrations and (2), a 30-year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent CO₂ concentrations. The boundary conditions have been obtained from an atmosphere-ocean coupled OA-GCM simulation at low horizontal resolution. An algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones. For most of the northern part of the study region, covering Ireland and Scotland, results describe the establishment by ca. 2060 of a tendency for fewer but more intense storms.

The impacts of these changes in storminess for the vulnerability of European Atlantic coasts are considered. For low-lying, exposed and ‘soft’ sedimentary coasts, as in Ireland, these changes in storminess are likely to result in significant localised increases in coastal erosion.     

The Elusive AD 1826 Tsunami, South Westland, New Zealand

In AD 1826 sealers reported earthquake and tsunami activity in Fiordland, although, contemporary or near‐contemporary accounts of tsunami inundation at the time are elusive. A detailed analysis of recent sediments from Okarito Lagoon builds on contextual evidence provided by earlier research concerning past tsunami inundation. Sedimentological, geochemical, micropalaeontological and geochronological data are used to determine palaeoenvironments before, during and after what was most probably tsunami inundation in AD 1826. The most compelling chronological control is provided fry a young cohort of trees growing on a raised shoreline bench stranded fry a drop in the lagoon water level following tsunami inundation.     

The morphological response of foredunes at a breached barrier system to winter 2013/2014 storms on the southwest coast of Ireland

The level of storminess in Ireland during the winter of 2013/2014 was exceptional, the effects of which cost the Irish state in excess of €260 million in infrastructure repair and insurance claims. In Ireland, a lack of coastal process data from monitoring programmes means that the response of protective barrier coasts to such events remains largely un‐investigated. This study addresses this issue through an examination of the geomorphic impacts of recent storms, including those that occurred during the winter 2013/2014, on a breached barrier on the southwest coast of Ireland. Data from a two‐year terrestrial laser scanning (TLS) monitoring campaign shows that the winter 2013/2014 events caused a major (>50 m) dune recession at Rossbehy, County Kerry. Results from a simple linear regression analysis indicate storm duration plays an important role in the removal of foredunes at the study site. Given the fact that the frequency of intense storms in the vicinity of Ireland is forecast to increase within the next century, a scientific understanding of barrier response to such events is critical to inform sound management practices. Copyright © 2016 John Wiley & Sons, Ltd.     

Differentiation of MIS 9 and MIS 11 in the continental record: vegetational,faunal, aminostratigraphic and sea-level evidence from coastal sites in Essex,UK

Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 °C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed.     

Late Quaternary relative sea-level changes and the role of glaciation upon continental shelves

Sea levels of the past 20 kyr are largely determined by the response of the Earth to the last ice age. Consequently, sea-level indicators are an important source of information about the interaction between cryosphere and hydrosphere and the solid Earth. Based on the material presented at a recent European Science Foundation conference, the present paper pin-points some of the topics currently under discussion with respect to sea-level evidence found on continental shelves. These topics include possible effects of erosion and changes in palaeotidal ranges on indicators of former relative sea levels as well as the problems involved in the determination of palaeo-water depth in addition to former sea levels. More evidence is being gathered for substantial small-scale patterns in the sea-level changes at or nearby to the former ice margins. These patterns are not reproduced by the available geophysical models, which reconcile on first-order level only the large-scale pattern.     

The problem of a late quaternary landbridge between Britain and Ireland

The question of whether a possible landbridge(s) existed between Britain and Ireland during Devensian (Midlandian) Late-glacial and Holocene time is analysed in the light of new geological and related environmental information. The problem of landbridge definition as a whole and related palaeogeographic reconstruction is reviewed briefly, particularly in relation to present understanding of the mechanisms conditioning sea-level movements and marine inundation of former land areas. A tentative palaeoenvironmental reconstruction is made for the Irish Sea and neighbouring seas from Late-glacial time onwards. Suggestions are put forward for the lack of a long Quaternary sedimentary record in Ireland. From the palaeoenvironmental data, it is concluded that no land links are likely to have existed via routeways across the southern continental shelf or Irish Sea zones. If any landbridge existed, it could only have operated between the north of Ireland and South West Scotland as a discontinuous linkage, formed by temporary islands at levels >?46 m O.D. The timing of its operation, if at all, is placed at ～11,400 to 10,200 ± 200 BP.     

Lagoon subsidence and tsunami on the West Coast of New Zealand

Sediment core and trench data from a coastal lagoon on the West Coast of the South Island, New Zealand are used to investigate evidence for co-seismic subsidence and associated tsunami inundation. Physical data are used to document a salt marsh soil buried  80 cm below the modern sediment surface that is locally covered by a gravelly sand bed. The sediment record also contains geochemical and biological (diatom and foram) evidence for abrupt changes in salinity of lagoon waters that link to subsidence, tsunami flooding and to the open versus closed state of the lagoon tidal entrance. At the local scale, these relationships allow for separation of tsunami evidence from other agents of environmental change in the lagoon. We also propose a conceptual connection between these local changes and regional drivers of landscape development, most notably major earthquakes and resultant pulses in sediment supply to the coast.     

Sea-level applications and management

The development of the International Geological Correlation Programme's Project 61 and other international sea-level studies have led to a wealth of new publications since 1975. Part of this growth stems from a widening in understanding of the real problems that would result from a continued rise in global sea-level, whilst part comes from the subject's present popularity in the earth sciences. The potential for the application of sea-level data is wide. The publications in 1977 of VAIL, MITCHUM, TODD, WIDMEIR, THOMPSON, SANGREE, BUBB and HATLEHID's approach to ‘seismic stratigraphy’ stimulated an expansion in commercial and geological applications of sea-level data. Further, the value of shoreline data in testing models of earth crustal behaviour and mantle rheology is well established. In biogeography, data may be used to test the feasibility of land bridge development and the consequential movements of plants and animals. In the coastal zone, the probable continuing and even accelerating rise of sea-level, resulting from man-induced changes of the environment, has thrown a scare into all those concerned with shoreline management. Ingeneous solutions have been developed to cope with the sea-level problem, ranging from physical barrages to proposals for large-scale water mass transfers. But how technically able, or more importantly, prepared, is mankind to manage a long-term progressively rising sea-level? The aims of Project 61 were found to be unattainable, will the results of Project 200 be of greater practical relevance?     

Contemporary process controls on the evolution of sedimentary coasts under low to high energy regimes: western Ireland

Sedimentary environments, representative of the Irish west coast, have been studied to examine their responses at the microscale (10^-1–10⁰ yr). This was achieved using a variety of techniques, including grain-size analysis, measurement of accretionary responses and radiometric dating. Monthly elevation monitoring of silt-dominated marshes shows an annual pattern in sediment accumulation. This reflects two processes: a) winter accretion attributable to storm events, and b) summer consolidation and contraction of the marsh sediments. Together, the results suggest that intertidal sedimentation is likely to be dominated by episodic processes, primarily storms. Examination of the tidal regime shows a weaker than expected influence of hydroperiodicity on intertidal accretion, although this influence remains distinctive, as expressed by a landward textural fining. Storms were also identified as of major importance in the functioning of higher-energy sandy coastal systems, again having a largely accretional influence, primarily through aeolian transport. Erosion at such study sites is probably controlled by the attainment of a critical threshold surface elevation, or by exceptional storm action, or a combination of both. The linking of microscale sedimentation rates with those at the meso- to macroscale, and assessment of their importance for coastal functioning, is difficult due to the geological averaging effect of the sedimentary record. Human impacts on this coast in historical times are large but difficult to quantify.