Coast Of Ireland Research Articles

Offshore conversion of wind power to gaseous fuels: Feasibility study in a depleted gas field

A proof-of-concept study is presented of a Power-to-Gas system that is located fully offshore. This paper analyses how such a system would perform if based at the depleted Kinsale Gas Field in the Celtic Sea Basin off the south coast of Ireland. An offshore wind farm is proposed as the power source for the system. Several conversion technologies are examined in detail in terms of resource efficiency, technological maturity, and platform area footprint, the aim being to ascertain their overall applicability to an offshore Power-to-Gas system. The technologies include proton exchange membrane electrolysers for electrolysis of water to release H2. Bipolar membrane electro-dialysis and electronic cation exchange module processes are also considered for the extraction of CO2 from seawater. These technologies provide the feedstock for the Sabatier process for the production of CH4 from H2 and CO2. Simulations of the end-to-end systems were carried out using Simulink, and it was found that the conversion of offshore wind power to hydrogen or methane is a technically feasible option. Hydrogen production is much closer to market viability than methane production, but production costs are too high and conversion efficiencies too low in both cases with present-day technology to be competitive with current wholesale natural gas prices.

An assessment of temporal variation in the low molecular weight phlorotannin profiles in four intertidal brown macroalgae

Phlorotannins are a group of highly bioactive marine polyphenols found exclusively in brown algae (Phaeophyceae) where they play an integral role in chemical defence. Owing to their high degree of reactivity, phlorotannins have attracted recent commercial interest with potential for application in areas such as pharma-, nutra- and cosmeceuticals. However, to date, little is known regarding their biosynthesis and the factors that drive their natural variability, particularly in relation to their chemical properties such as polymerisation and isomerisation - two factors which directly influence their degree of activity. Low molecular weight (LMW; <3.5 kDa) phlorotannin-enriched fractions have exhibited a high level of antioxidant activity yet their degree of natural variability within macroalgae is not known. This study aimed to, for the first time, assess the temporal variation of LMW phlorotannin chemical profiles of four intertidal brown macroalgae dominant along the west coast of Ireland – Pelvetia canaliculata, Fucus vesiculosus, Ascophyllum nodosum and Himanthalia elongata. Samples were collected at six different time points over two years (2014–2015) and assessed for temporal shifts in the chemical profile, content and antioxidant activity. Species-specific profiles were detected, with each species displaying varying degrees of polymerisation and isomerisation, which were linked to the in vitro antioxidant activity observed. While some temporal shifts were observed in the molecular weight composition of the LMW phlorotannin profiles, they, along with the degree of isomerisation, did not appear to correspond with large-scale temporal changes in irradiance or temperature regime of Galway Bay. The results emphasise the strong degree of natural variability associated with phlorotannin profiles which, in situ, are likely to be influenced by several parameters synergistically; future studies should investigate small-scale effects of physio-chemical parameters, as well as biological factors, at microhabitat level, which could be aided by a laboratory-based assessment of individual parameters.

Survivability assessment of fastnet lighthouse

Historic rock lighthouses are unusual structures that are situated in hostile marine environments to provide warning to mariners. Even in an era of satellite navigation their role continues to be an important one, but their survivability into the future is not assured. Out of concern for their ongoing service, the multidisciplinary STORMLAMP project is assessing their survivability under wave loading. This paper presents the various stages of investigations into the structural integrity and stability assessment of the Fastnet lighthouse, situated just off the coast of Ireland. The paper describes: Extreme Bayesian analysis to quantify waves of particular return periods resulting in a 1 in 250 year return period wave with H0.1% of 17.6 m and an associated maximum force of 20,765 kN; logistically challenging field modal tests revealing the key modal parameters, like the modal masses of 1822 t and 1 675 t for 4.8 Hz and 5.0 Hz modes respectively, the cantilevered nature of the overall lighthouse and the directional effects due to the asymmetric contact with the granite rock; and details of a discontinuous finite element model that is used to determine the stability of the tower under the 1 in 250 year return period breaking wave condition, which is well within stability and material strength limits, causing maximum horizontal displacements in the order of 1 mm at the top of the tower. The overall assessment is that the sheer mass of the lighthouse and its interconnected joints are able to withstand the worst of the Atlantic storms.

Famine on the Coast: The Royal Navy and the Relief of Ireland, 1846–1847

Abstract While the significance of private charity, local organisation and government policy have all been evaluated with respect to Irish famine relief, the role of the Royal Navy in distributing food and assisting ashore has been overlooked within the existing historical literature. Operating from its base at Cork and receiving provisions from Plymouth and Portsmouth, the navy battled against Atlantic storms throughout the winter of 1846–7, and for months thereafter, to supply coastal food depots. It had also to confront a growing lawlessness which placed merchant craft at sea and the movement of aid on shore in peril. Yet the navy was not only a vital means of transport. To assist with medical care, the Admiralty sent surgeons to Ireland who reported at length on the extent of starvation and the worst effects of disease—an initiative which brought the Admiralty into conflict with the authorities in Dublin. Furthermore, naval activities had always to be co-ordinated with the Treasury in London, which had overall responsibility for Irish relief yet often far less understanding of the practicalities of distribution along the south and west coasts of Ireland. The unexplored archival material used allows an original perspective on the efforts made to alleviate the worst effects of Black ’47 and the calamity which overwhelmed so much of Ireland.

Temporal variability in winter wave conditions and storminess in the northwest of Ireland

Winter storms have significant morphological impacts in coastal areas, often leading to extensive infrastructure damage and socio-economic disruption. While storm-dominated coastal environments, such as the northwest coast of Ireland, are generally attuned to highly energetic wave conditions, morphological impacts can be intensified by changes in the frequency and sequencing of storm events, particularly during storm-groups or exceptional winter seasons. Aiming to assess the variability in frequency and sequencing of wintertime wave conditions and storms in the northwest of Ireland, we combine observational records (M4 buoy) with data from two independent wave reanalyses (ERA-Interim and WAVEWATCH III) and perform a statistical analysis of wave conditions over the past six decades. Both reanalyses represent observed wave heights with very good skill. Excellent agreement between modelled data and observations was identified up to the 99th percentile, despite a slight underestimation/overestimation by ERA-Interim/WAVEWATCH III for waves above the 90% exceedance level. The winter of 2014/15 was the most energetic on record (67 years), but not the stormiest. The results show that highly energetic and stormy winters occur in clusters during positive phases of the North Atlantic Oscillation. Significant positive temporal trends for winter wave height, number of storms per winter and average winter storm wave height, suggest that winters are becoming more energetic and stormier, with potential implications for the erosion and recovery of coastal systems in the northwest of Ireland.

Review of DSP Toxicity in Ireland: Long-Term Trend Impacts, Biodiversity and Toxin Profiles from a Monitoring Perspective.

The purpose of this work is to review all the historical monitoring data gathered by the Marine Institute, the national reference laboratory for marine biotoxins in Ireland, including all the biological and chemical data from 2005 to 2017, in relation to diarrheic shellfish poisoning (DSP) toxicity in shellfish production. The data reviewed comprises over 25,595 water samples, which were preserved in Lugol’s iodine and analysed for the abundance and composition of marine microalgae by light microscopy, and 18,166 records of shellfish flesh samples, which were analysed using LC-MS/MS for the presence and concentration of the compounds okadaic acid (OA), dinophysistoxins-1 (DTX-1), dinophysistoxins-2 (DTX-2) and their hydrolysed esters, as well as pectenotoxins (PTXs). The results of this review suggest that DSP toxicity events around the coast of Ireland occur annually. According to the data reviewed, there has not been an increase in the periodicity or intensity of such events during the study period. Although the diversity of the Dinophysis species on the coast of Ireland is large, with 10 species recorded, the two main species associated with DSP events in Ireland are D. acuta and D. acuminata. Moreover, the main toxic compounds associated with these species are OA and DTX-2, but concentrations of the hydrolysed esters are generally found in higher amounts than the parent compounds in the shellfish samples. When D. acuta is dominant in the water samples, the DSP toxicity increases in intensity, and DTX-2 becomes the prevalent toxin. Pectenotoxins have only been analysed and reported since 2012, and these compounds had not been associated with toxic events in Ireland; however, in 2014, concentrations of these compounds were quantitated for the first time, and the data suggest that this toxic event was associated with an unusually high number of observations of D. tripos that year. The areas of the country most affected by DSP outbreaks are those engaging in long-line mussel (Mytilus edulis) aquaculture.

Genome Sequence of Paracoccus sp. JM45, a Bacterial Strain Isolated from a Marine Sponge with a Dual Quorum Sensing Inhibition Activity

The draft genome sequence of Paracoccus sp. strain JM45, isolated from a marine sponge harvested off the west coast of Ireland, is reported here. Quorum sensing and quorum sensing inhibition activities have been reported recently for this bacterium, and genomic analysis supports its potential use for novel therapeutic development.

Mis-]managing Fisheries on the West Coast of Ireland in the Nineteenth Century

This study focuses on the cultural heritage of artisan coastal fishing in the west of Ireland in the 19th century. The town and port of Dingle, County Kerry, offers an important case study on the progress of local development and changing British policies. While there was clearly an abundance of fish, the poverty and the lack of capital for improvements in ports, vessels, gear, education, and transportation, left the fishing industry underdeveloped until well after the 1890s. In addition, a growing rift developed between the traditional farmer-fishermen and the new middle-class capitalist companies. After several royal commissions examined the fishing industry, the leading ichthyologists of the day concluded that an abundance of fish could be taken without fear of overfishing. The utilitarian economic principle became dominant, changing the previous non-interventionist policies. In the end, there was little concern for sustainability. The mismanagement of commercial fishing in the west of Ireland stemmed from a series of factors, including the increasing need for protein in Britain, technological developments that allowed greater fish catch, and the Conservative government’s political policy of ‘constructive unionism’ that attempted to develop the Irish economy to preserve the kingdom.

“A Different Sort of Map Altogether”: Reading Hugo Hamilton's Migrant Geographies in &lt;em&gt;Hand in the Fire&lt;/em&gt;

This study analyses how the migrant experience is reflected in the geography of Hugo Hamilton's work of fiction entitled Hand in the Fire (2010). The novel is told from the point of view of Vid, a Serbian immigrant who is trying to settle in Ireland. The young carpenter endeavours to fit in Irish society through his friendship with a young Dublin lawyer, Kevin Concannon, who tells him that a true friend would put his “hand in the fire” for you. Through the portrayal of these displaced characters, Hamilton explores his favourite themes of memory and belonging. This article focuses on the places depicted in the novel, from the Serbia that Vid has left in his past to the modern-day Dublin and the west coast of Ireland, in order to analyse how the settings of the narrative reflect the characters’ state of mind. Using Deleuze and Guattari's concepts of de/re-territorialization and of striated/smooth spaces, the examination of the geographies of the novel allows for a better understanding of the issues at stake for the characters. The liminal, deterritorialized figure of the immigrant represented by Vid is echoed by the smooth islands of the novel. In an archipelagic country where the coastline stands for the visual border, it is no wonder that the transnational protagonist is drawn to the Irish shores. On the edge of two cultures, Vid, who lives in Dún Laoghaire, south of Dublin, is gradually moving west to the striated landscape of Connemara, where he investigates on Kevin's aunt who drowned and was washed ashore the Aran Islands.

High frequency monitoring reveals fine scale spatial and temporal dynamics of the deep chlorophyll maximum of a stratified coastal lagoon

Coastal lagoons are a dynamic habitat, with varying marine and freshwater inputs determining the presence and extent of stratification, and the physical and chemical environment of the epi- and hypolimnion. As a result, the biotic assemblages that thrive in such environments are a diverse mix of species, with wide ranges of tolerances. While annual succession and vertical distribution of phytoplankton assemblages in marine and freshwater ecosystems are well documented, few data are available which describe the spatial and temporal variability of phytoplankton in coastal lagoons, even though these are a protected habitat under the European Union's Habitat Directive. In this study, high frequency monitoring (HFM) of chlorophyll fluorescence (ChlF) using a vertical profiling sonde was used to describe the variation in algal biomass over six annual cycles and through the water column of Lough Furnace, a perennially stratified coastal lagoon on the west coast of Ireland. Spot sampling, and species enumeration of phytoplankton were used to confirm the patterns observed in the fluorescence data, which indicated a general pattern of increasing biomass starting in spring, and a deepening of the deep chlorophyll maximum (DCM) over the summer. Typical of a stratified system, the DCM was often situated below the surface mixed layer, in saline hypoxic water. The best predictors of daily maximum ChlF were the depth of the surface mixed layer and daily solar radiation. We conclude that HFM allows an unprecedented glimpse into the substantial variability and complexity of phytoplankton distributions, a key biotic variable.

The effect of arrays of wave energy converters on the nearshore wave climate

The exploitation of wave energy using arrays of wave energy converters (WEC), which contain a large number of devices, could have significant impact on the wave climate in the nearshore region. This research investigates the impact of WEC arrays at the Westwave demonstration commercial site, which is located on the West coast of Ireland. The methodology involves the determination of an appropriate transmission coefficient (Ct) from a computational fluid dynamic (CFD) model of a numerical wave tank (NWT) simulation using ANSYS CFX and the subsequent implementation of WEC arrays using SWAN (Version 41.01). Within this analysis, the Ct value from the CFD NWT model was used in SWAN to represent WEC arrays which are treated as obstacles. Hence, a nested local wave model at the Westwave site have been developed and validated for the period of December 2015 in order to accommodate the simulation of WEC arrays. Three array configurations, which contain 12 WECs (single row, two row arrays and three row arrays), have been simulated and analysed to estimate the impact to the wave conditions at the nearshore area, while also considering the effect of array configuration on power captured. The results of the analysis suggest there is minor impact on the nearshore wave climate for all the scenarios, where the reduction in wave height and wave power was below 1% at a distance of between 1 and 3 km from the shoreline (at water depths varying from 20 to 60 m). At a distance of 100–300 m from the shoreline (at a water depth of approximately 10 m and below), a decrease in wave height and wave power of 0.1% and 0.2%, respectively, was observed. In addition, the methodology can also be applied to other types of WEC and study areas depending on the purpose of the project.

Combined zinc-lead isotope and trace-metal assessment of recent atmospheric pollution sources recorded in Irish peatlands

Atmospherically-fed Earth surface archives such as ombrotrophic peatlands, lake sediments, and ice consistently show an upward increase in Zn concentrations of hitherto unclear origin. Here, we present a combined stable Zn isotope and trace element (Zn, Cd, Ni, Cu, Cr, V, Ta, Pb) dataset for a historically polluted, near-urban bog (Liffey Head) from the east coast of Ireland. This peat record is compared to an archive from a rural site at the west coast of Ireland (Brackloon Wood). Both archives show a clear near-surface increase in Zn deposition, accompanied by periodic deposition in Cr, Ni, Mo, and V suggesting a co-genetic origin of these elements. In the Liffey Head site, biologic upward distillation of nutrients can be excluded as the origin of the elemental enrichments. The differences in the excess metal ratios between the two sites (e.g., Zn/Cd of 426–1564, east, and 77–106, west) are attributed to a higher contribution from traffic emissions (diesel, petrol) and oil-burning at the near-urban site, and dominant atmospheric influence from solid fossil fuel combustion emissions (e.g., mixed fuel, coal and wood) at the rural site.The Zn isotope composition in the historically-polluted Liffey Head bog evolved from δ66/64ZnJMC-Lyon values of 0.72 ± 0.03‰ in the peat accumulated during the 19th century to lighter ratios (0.18 ± 0.03‰) towards the top of the monolith (i.e., recent). Zinc-isotope ratios are positively correlated with excess metal/Cd ratios and also with 206Pb/207Pb, collectively fingerprinting the gradual change from a mining-dominated to a traffic-dominated atmospheric pollution at the east coast over the past century. A prevalent input, interpreted to represent combustion emissions from diesel engines, is observed for the past 15 years. Combined with trace elements and radiogenic Pb isotopes, the information obtained with the Zn isotope systematics adds towards an in-depth characterisation of the pollution signals.

“The place is full of cabbages”: An analysis of the Irish Late Mesolithic stone tool technology from Kenure, Co. Dublin

This paper examines the stone tool technology from the site of Kenure, Co. Dublin, on the East coast of Ireland. Collected in the 1940s by the avocational archaeologist Gwendoline C. Stacpoole, Kenure represents an extremely large surface assemblage likely belonging to the later phase of the Irish Late Mesolithic period (~7000–5500 BP). The results of this analysis affirm the likelihood that the Kenure lithic assemblage does, in fact, date to the Late Mesolithic. Core reduction was conducted using hard hammers and was generally expedient, usually involving the splitting of locally occurring glacial till chert cobbles followed by the use of single platform core reduction strategies. Retouched tools were characterized by a range of scraper, notch, denticulate, and borer forms. Moderate frequencies of convergent flakes were also present, with many fitting the typological definition of Bann flakes. In addition, there were noticeable numbers of small blades, though these generally lack the specialized technical features of Mesolithic blades from the Irish Early Mesolithic and Mesolithic sites in other regions of Western Europe. Moderate frequencies of pieces derived from bipolar percussion were also present in the Kenure assemblage and this paper offers an explanation of the use of bipolar percussion in relation to the small size of locally available lithic raw materials. Finally, this paper concludes with a consideration of the implications of the technological features of the Kenure assemblage for the organization of Irish Late Mesolithic foraging technology, as well as the potential for future research on the Kenure collection.

Historical Evolution of the Wave Resource and Energy Production off the Chilean Coast over the 20th Century

The wave energy resource in the Chilean coast shows particularly profitable characteristics for wave energy production, with relatively high mean wave power and low inter-annual resource variability. This combination is as interesting as unusual, since high energetic locations are usually also highly variable, such as the west coast of Ireland. Long-term wave resource variations are also an important aspect when designing wave energy converters (WECs), which are often neglected in resource assessment. The present paper studies the long-term resource variability of the Chilean coast, dividing the 20th century into five do-decades and analysing the variations between the different do-decades. To that end, the ERA20C reanalysis of the European Centre for Medium-Range Weather Forecasts is calibrated versus the ERA-Interim reanalysis and validated against buoy measurements collected in different points of the Chilean coast. Historical resource variations off the Chilean coast are compared to resource variations off the west coast in Ireland, showing a significantly more consistent wave resource. In addition, the impact of historical wave resource variations on a realistic WEC, similar to the Corpower device, is studied, comparing the results to those obtained off the west coast of Ireland. The annual power production off the Chilean coast is demonstrated to be remarkably more regular over the 20th century, with variations of just 1% between the different do-decades.

Very large boulders were moved by storm waves on the west coast of Ireland in winter 2013–2014

Erdmann and co-authors (2018) present interesting observations of coastal boulder deposits along Ireland's western seaboard, Unfortunately, some of their interpretations are undermined by inaccurate information; and two of their main conclusions—that boulders greater >50 t were not moved during the recent strong storms, and that boulders 20–30 t were not moved significantly against gravity—are incorrect. Field records from before and after the storm events clearly show that boulders weighing 10 s to 100 s of tonnes were moved inland and uphill.

Case study of the winter 2013/2014 extreme wave events off the west coast of Ireland

Abstract. Using the third generation WAVEWATCH III wave model in an unstructured formulation, and driven by HARMONIE-AROME mesoscale model hourly winds with a 2.5 km horizontal resolution, we reproduce the winter storms of 2013/2014 and analyse their effect on the western coastline of Ireland. WAVEWATCH III was forced at its ocean boundaries by directional wave spectra obtained from the ECMWF ERA-Interim re-analysis dataset. The wave model has a high resolution grid (up to 225 m resolution in the nearshore) with around 20 000 nodes, producing an abundance of important wave parameters outputted hourly, enabling a high quality, high-resolution analysis of the winter storms of 2013/2014.

Trace element and Pb isotope fingerprinting of atmospheric pollution sources: A case study from the east coast of Ireland

Unravelling inputs of multiple air pollution sources and reconstructing their historic contribution can be a difficult task. Here, new trace metal concentrations and Pb isotope data were combined for a radionuclide (210Pb-241Am) dated peat core from the Liffey Head bog (LHB) in eastern Ireland in order to reconstruct how different sources contributed to the atmospheric pollution over the past century. Highest enrichments in the heavy metals Pb, Cu, Ag, Sn, and Sb, together with a Pb isotope composition (206Pb/204Pb: 18.351 ± 0.013; 206Pb/207Pb: 1.174 ± 0.012) close to that of the Wicklow mineralisation demonstrates significant aerial influx of heavy metals from local mining and smelting activities during the 19th century until ca. 1940s. A dramatic compositional shift defined by elevated Co, Cr, Ni, Mo, Zn, and V enrichments and a sharp transition towards unradiogenic 206Pb values (206Pb/204Pb: 18.271 ± 0.013–17.678 ± 0.006; 206Pb/207Pb: 1.170 ± 0.012–1.135 ± 0.007) is documented from the 1940s until ca. 2000. These are attributed to the atmospheric impact of fossil fuels and especially leaded petrol, modelled to have contributed between 6 and 78% to the total Pb pollution at this site. The subsequent turn to a more radiogenic Pb isotope signature since 2000 in Ireland is clearly documented in the investigated archive (206Pb/204Pb: 17.930 ± 0.006; 206Pb/207Pb: 1.148 ± 0.007) and reflects the abolishment of leaded petrol. However, there remains a persisting and even increasing pollution in Ni, Mo, Cu, and especially Zn, collectively originating from countrywide use of fossil fuels (peat, coal, heating oil, and unleaded vehicle fuels) for domestic and industrial purposes. This illustrates the continued anthropogenic influence on important natural archives such as bogs in Ireland despite the phase-out of leaded petrol.

Clast abrasion of a rock shore platform on the Atlantic coast of Ireland

AbstractThe abrasion of coastal rock platforms by individual or clusters of clasts during transport has not been quantitatively assessed. We present a study which identifies the types of abrasion and quantifies erosion due to the transport of clasts during three storms in February and March 2016. We explore relationships between platform roughness, determined by the fractal dimension (D) of the topographic profiles, geomorphic controls and the type and frequency of abrasion feature observed. Clast transport experiments were undertaken in conjunction with the measurement of wave energy to assess transport dynamics under summer and winter (non‐storm) conditions.Platform abrasion occurred extensively during the storms. We identify two types of clast abrasion trails: simple and complex. In addition, we find two forms of erosion occur on these trails: Scratch marks and Percussion marks. An estimated 13.6 m2 of the platform surface was eroded by clast abrasion on simple abrasion trails during the three storms. We attribute approximately two thirds of this to scratch‐type abrasion. The total volume of material removed by abrasion was 67 808 cm3. Despite the larger surface area affected by scratch marks, we find that the volume of material removed through percussion impact was almost seven times greater. We also find that the type and frequency of abrasion features is strongly influenced by the effect of platform morphometry on transport mode, with impact‐type abrasion dominating areas of higher platform roughness. Results of the clast transport experiments indicate that abrasion occurs under non‐storm wave energy conditions with observable geomorphological effects. We suggest that abrasion by clasts is an important component of platform erosion on high energy Atlantic coastlines, particularly over longer timescales, and that the morphogenetic link between the cliff and the platform is important in this context as the sediment supplied by the cliff is used to abrade the platform. © 2018 John Wiley &amp; Sons, Ltd.

Trans-performance

In response to the PR issue on ‘Trans/Performance’, this essay explores the multiple dimensions of performances which cross corporealities, topographies, languages, and other sites or locations. To extend this exploration of a performative crossing of unknown and dangerous terrain, the essay examines the journey which the performance theorist Antonin Artaud made to the island of Inishmore, off the western coast of Ireland, in 1937. The journey encompassed a transmutation of Artaud's work from the writing of manifestoes to the writing of letters and magic spells. It also propelled him into an alien and perilous interzone; at the conclusion of his journey, he was arrested, imprisoned, deported back to France and then interned in psychiatric hospitals for nine years. Artaud's letters were always written at speed, and imagine immense conspiracies and apocalyptic world events imminently to take place both in Ireland and France. Many of his letters were lost in the transitional interval between sending and receipt (or were discarded by their recipients), and this essay is based on archival examinations of the surviving letters, often in the form of one surviving page from an otherwise lost letter. Several of Artaud's letters were written to the head of the Surrealist art movement, André Breton, and the essay concludes with a translation of one of Artaud's letters to Breton, taken from a volume of translations - Artaud 1937 Apocalypse - published earlier in 2018 and marking the seventieth anniversary of Artaud's death in 2018.

Trough geometry was a greater influence than climate-ocean forcing in regulating retreat of the marine-based Irish-Sea Ice Stream

Marine terminating ice streams are a major component of contemporary ice sheets and are likely to have a fundamental influence on their future evolution and concomitant contribution to sea-level rise. To accurately predict this evolution requires that modern day observations can be placed into a longer-term context and that numerical ice sheet models used for making predictions are validated against known evolution of former ice masses. New geochronological data document a stepped retreat of the paleo−Irish Sea Ice Stream from its Last Glacial Maximum limits, constraining changes in the time-averaged retreat rates between well-defined ice marginal positions. The timing and pace of this retreat is compatible with the sediment-landform record and suggests that ice marginal retreat was primarily conditioned by trough geometry and that its pacing was independent of ocean-climate forcing. We present and integrate new luminescence and cosmogenic exposure ages in a spatial Bayesian sequence model for a north-south (173km) transect of the largest marine-terminating ice stream draining the last British−Irish Ice Sheet. From the south and east coasts of Ireland, initial rates of ice margin retreat were as high as 300−600 m a−1, but retreat slowed to 26 m a−1 as the ice stream became topographically constricted within St George’s Channel, a sea channel between Ireland to the west and Great Britain to the east, and then stabilized (retreating at only 3 m a−1) at the narrowest point of the trough during the climatic warming of Greenland Interstadial 2 (GI-2: 23.3−22.9 ka). Later retreat across a normal bed-slope during the cooler conditions of Greenland Stadial 2 was unexpectedly rapid (152 m a−1). We demonstrate that trough geometry had a profound influence on ice margin retreat and suggest that the final rapid retreat was conditioned by ice sheet drawdown (dynamic thinning) during stabilization at the trough constriction, which was exacerbated by increased calving due to warmer ocean waters during GI-2.