periglacial trimlines and nunataks of the last glacial maximum the gap of dunloe southwest ireland during the last main phase of glaciation 26 13 ka an ice cap developed in southwest ireland and ice from a dispersal centre in the vicinity of kenmare flowed north through the gap of dunloe in the macgillycuddy s reeks on surrounding hillsides a weathering limit separates ice moulded bedrock on low ground from frost weathered terrain above assessment of bedrock dilation joint characteristics schmidt hammer r value data and clay sized mineral contents of basal soil samples demonstrate significant contrasts in the degree of weathering above and below this limit the weathering limit declines in altitude along former ice flow lines and is confluent with morainic deposits on the eastern side of the gap this supports the assertion that the high level weathering limit is a periglacial trimline that marks the former maximum upper limit of the body of ice which occupied the gap of dunloe during the last glacial maximum lgm reconstruction of the former ice surface profile from periglacial trimline limits on the eastern side of the gap yields a mean estimate for basal shear stress of 106 5 kpa this value suggests that the ice mass which occupied the gap of dunloe at the lgm was warm based and flowed on a bedrock substrate copyright 2004 john wiley sons ltd

readvance of the last british irish ice sheet during greenland interstade 1 gi 1 the wester ross readvance nw scotland abstract fourteen samples obtained from torridon sandstone boulders on four moraines marking the limit of the wester ross readvance wrr in nw scotland yielded tightly clustered 10 be exposure ages confirming contemporaneous or penecontemporaneous moraine deposition collectively the 14 samples yield mean ages of 13 5 1 2 ka to 14 0 1 7 ka depending on choice of geomagnetic scaling and sampling surface erosion rates all fourteen moraine ages are significantly younger than an age of ca 16 3 ka previously proposed for the wrr and also younger than most samples obtained from rock outcrops within the wrr limits the ages obtained for the wrr moraines appear to confirm that a substantial cover of glacier ice persisted over low ground in nw scotland during at least the early part of the lateglacial interstade greenland interstade 1 we infer that the wrr probably occurred in response to rapid short lived cooling during the older dryas climatic reversal greenland interstade 1d though the possibilities that the wrr represents ice margin response to a later climatic reversal during the lateglacial interstade or stabilization and readvance of the ice margin following rapid offshore calving cannot be discounted

rock slope failure in the british mountains abstract in this first full review of extant quaternary rock slope failure rsf in the british mountains we provide a near complete inventory of 1082 sites 40 being rock slope deformations 40 arrested rockslides and 20 rock avalanches current rsf activity is negligible and this relict population is predominantly paraglacial with a parafluvial minority its spatial distribution is perplexing with rsf density varying greatly both regionally and locally in the scottish highlands eight main clusters account for 76 of rsf area in 15 of the montane area local concentrations occur in all the british ranges across high and low relief in core and peripheral locations and on varied geological and glaciological domains as conversely do extensive areas of sparsity even in similar lithologies generic interpretations are thus precluded geology is only a secondary control an association with concentrated erosion of bedrock ceb is proposed as a driver of intensified slope stresses ceb is most evident at those glacial breaches of main divides where the most vigorous recent incision is inferred and also in some trough heads a clear association between rsfs and these late developing breaches is demonstrated in the highlands in 42 localities with sparsity away from them it is also seen in seven lake district localities glaciological models identify ice sheet volatility capable of driving breach ramification high magnitude paleoseismic events are generally unlikely to have provoked rsf clusters a few candidates are considered rsf has been underrated as an agent of mountain landscape evolution in britain its spatio temporal incidence may assist in calibrating regional ice sheet models and in assessing climate change impacts we argue that the ceb rsf association has global relevance in identifying primary drivers of mass movement in bedrock

two step deglaciation at the oxygen isotope stage 6 5e transition the zeifen kattegat climate oscillation comparison of marine lacustrine and terrestrial records from twenty four sites suggests the existence of a younger dryas type climate oscillation just prior to the oxygen isotope stage 6 5e boundary these records include results from biostratigraphic pedostratigraphic and speleothem studies as well as analyses of stable isotope compositions of marine records and ice cores the climate oscillation is named after the warm zeifen interstadial and the cold kattegat stadial the zeifen interstadial may be related to a major meltwater pulse in the baffin bay labrador sea norwegian sea region the climate oscillation is presumably in part a result of a variation in ocean circulation especially in the strength of the north atlantic drift but changes in the atmospheric circulation also played an important role the geographically widespread distribution of the oscillation suggests that the two step deglaciation influenced both the northern and southern hemispheres c 1996 elsevier science ltd

rapid fluctuations in the deep north atlantic heat budget during the last glacial period 1 our understanding of past ocean climate interactions has been hampered by a paucity of proxy reconstructions of physical ocean circulation parameters here we present the first detailed record of deepwater temperature variability that resolves dansgaard oeschger climate fluctuations during the last glaciation results indicate a positive coupling between abrupt temperature changes over greenland and in the deep north atlantic that was mediated by perturbations to the atlantic overturning circulation the occurrence of sharp warming events at the center of the heinrich stadials 4 and 5 further indicates that the response of the ocean interior was less static across these major climate events than has been previously apparent

ice caps existed throughout the lateglacial interstadial in northern scotland we constrain in detail fluctuations of two former ice caps in nw scotland with multibeam seabed surveys geomorphological mapping and cosmogenic 10 be isotope analyses we map a continuous sequence of 40 recessional moraines stretching from 10 km offshore to the wester ross mountains surface exposure ages from boulders on moraine ridges in assynt and the summer isles region show that substantial dynamic ice caps existed in nw scotland between 13 and 14 ka bp we interpret this as strong evidence that large active glaciers probably survived throughout the lateglacial interstadial and that during the older dryas period ca 14 ka bp ice caps in nw scotland were thicker and considerably more extensive than in the subsequent younger dryas stadial by inference we suggest that lateglacial ice cap oscillations in scotland reflect the complex interplay between changing temperature and precipitation regimes during this climatically unstable period ca 15 11 ka bp natural environment research council nerc copyright 2008 reproduced with the permission of nerc published by john wiley sons ltd

reconstructing past glacier dynamics and erosion from glacial geomorphic evidence snowdon north wales bedrock surfaces exposed around llyn llydaw north wales demonstrate contrasting styles of erosion beneath a late devensian ice sheet and a loch lomond stadial lls valley glacier ice sheet erosion involved lee side fracturing surface fracture wear and abrasive wear while lls erosion was primarily by abrasive wear preservation of ice sheet erosional features indicates limited rates of erosion during the lls analysis of the geometry and distribution of erosional markings suggests that the low erosional capacity of the lls glacier was due to a low basal sliding velocity this prevented the formation of lee side cavities reduced the debris flux over the bed and minimised particle bed contact loads reconstructions of the mass balance and geometry of the lls glacier indicate that most of its balance velocity could be achieved by internal deformation alone a combination of low subglacial water pressures and an unusually rough substrate explain the low sliding velocities high bed roughness is due to the absence of leeside cavities and a change in flow orientation between ice sheet and lls times which meant that the lls glacier was in contact with roughness elements which were generated in cavities beneath the ice sheet

sediment evacuation and glacial erosion rates at a small alpine glacier 1 glacial erosion is known to be driven by sliding which occurs in brief episodes in the melt season what is not known is how well this sliding history is reflected in the sediment output from a glacier and to what degree temporary sediment storage in the glacier smoothes the history of sediment production we document sediment evacuation rates for three seasons at bench glacier a small temperate alpine glacier in the chugach range of alaska two lines of evidence suggest that subglacial sediment storage is small strong hysteresis in the relationship between sediment and water discharge argues for sediment exhaustion from the subglacial system on seasonal and flood event timescales uplift of the glacier surface during periods of enhanced basal motion reflects intimate contact of the glacier sole with up glacier inclined stoss slopes of bedrock bumps sediment evacuation rates at bench glacier should therefore closely track glacial erosion rates over annual timescales much of the sediment emerges in a major pulse that closely follows the termination of enhanced sliding each year suggesting that the conduits and well connected cavities that allowed removal of englacial water to terminate sliding also promoted efficient transport of sediment this small glacier efficiently modifies the landscape lowering its bed by 1 2 mm yr while sliding only 1 2 m yr our sparse measurements of instantaneous bed load discharge average 41 of concurrent suspended sediment discharge assuming that half of the suspended load derives from abrasion of subglacially quarried clasts roughly two thirds of the sediment evacuated can be attributed to quarrying

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

glacial deposits in great britain and ireland with the increasing awareness of environmental problems there is a growing desire for a de tailed understanding of superficial deposits in general and glacial deposits in particular this is because these sediments have a profound influence on groundwater protection waste management and nature conservation they are also of vital importance to civil engineering because they provide the foundation for as well as the materials extracted to build our roads and buildings the greater part of the british isles was glaciated at least once during the quater nary era in the regions subjected to glaciation glacial deposits underlie much of the present land surface although there have been many recent publica tions on various quaternary geological topics the present volume is the first dedicated to a detailed assessment of the glacial deposits of britain and ireland after introductory chapters presenting the glacial history the sedimentary sequences in 24 critical regions are discussed these regions include all of ireland the gla ciated area of great britain and the adjoining offshore region of the north sea the controver sial evolution of the irish sea basin during the last glaciation is discussed from various view points a collection of critical topics presented in the later part of the book range from the classification of glacigenic landforms and de posits to the results of geophysical geotechnical and geochemical analyses the book includes 368 figures 40 tables and 51 colour photographs a detailed index and a list of over 1000 references with 45 contributions by 48 scientists this volume represents a truly contemporary view of this field of research to gether with its companion volume the glacial deposits in north west europe this book pro vides an excellent textbook for the advanced student or the amateur as well as an indispen sible source and guidebook for the professional scientist

last glacial maximum cirque glaciation in ireland and implications for reconstructions of the irish ice sheet abstract reconstructions of the extent and height of the irish ice sheet iis during the last glacial maximum lgm 19 26 ka are widely debated in large part due to limited age constraints on former ice margins and due to uncertainties in the origin of the trimlines a key area is southwestern ireland where various lgm reconstructions range from complete coverage by a contiguous iis that extends to the continental shelf edge to a separate more restricted southern sourced kerry cork ice cap kcic we present new 10be surface exposure ages from two moraines in a cirque basin in the macgillycuddy s reeks that provide a unique and unequivocal constraint on ice thickness for this region nine 10be ages from an outer moraine yield a mean age of 24 5 1 4 ka while six ages from an inner moraine yield a mean age of 20 4 1 2 ka these ages show that the northern flanks of the macgillycuddy s reeks were not covered by the iis or a kcic since at least 24 5 1 4 ka if there was more extensive ice coverage over the macgillycuddy s reeks during the lgm it occurred prior to our oldest ages

ice sheet variability around the north atlantic ocean during the last deglaciation millennial scale variability in the flux of ice rafted detritus to north atlantic sediments during the last glacial period has been interpreted to reflect a climate forced increase in the discharge of icebergs from ice sheet margins surrounding the northern north atlantic ocean 1 but the relationship between ice sheet variability and climate change is not clear as both the sources of ice rafted detritus and the ice marginal processes are varied and complex 2 4 terrestrial records are helpful in unravelling this complexity because they can demonstrate the scale of ice sheet oscillations and whether the ice sheet or sector was advancing or retreating with respect to climate change here we constrain the age and anatomy of a prominent readvance of the british ice sheet in the northern irish sea region at similar to 14 14 c kyr bp similar to 16 4 calendar kyr bp the analysis indicates that the british ice sheet participated in an iceberg discharge episode known as heinrich event 1 comparison with other terrestrial and marine ice sheet records suggests that the dynamic collapse of the laurentide ice sheet beginning at 14 6 15 0 c 14 kyr bp1 4 similar to 17 2 17 6 calendar kyr bp 5 initiated varied responses from other ice sheet margins around the northern north atlantic region these observations support the argument that the release of icebergs and meltwater during heinrich event 1 disrupted the north atlantic thermohaline circulation 6 8 leading to a delay or reversal of deglaciation of the northern hemisphere and at least as far south as 40 degrees s for two to three thousand years 5 9 10 suggesting a climate forcing and response similar to that of the ensuing younger dryas cold snap 11 12

persistent millennial scale glacier fluctuations in ireland between 24 ka and 10 ka we report 80 10be ages on 14 moraines from irish cirques that show a previously unrecognized signal of at least eight millennial scale fluctuations between 24 5 0 7 ka and 11 0 0 3 ka several moraine ages may be correlative with abrupt warming at the onset of the bolling 14 7 ka and the end of the younger dryas 11 7 ka suggesting a forced response our ages also identify glacier fluctuations that occurred when regional temperatures were relatively stable this finding is consistent with modeling results showing several hundred meter scale glacier fluctuations in response to interannual variability at the same time our composite record of cirque glacier average equilibrium line altitudes elas shows a response to warming due to increasing greenhouse gases and summer insolation modulated by abrupt climate changes our new 10be chronology thus records both forced and unforced millennial scale glacier fluctuations superimposed on a lower frequency ela signal of forced response to climate change

holocene alluvial fan development in the macgillycuddy s reeks southwest ireland holocene alluvial landforms in the macgillycuddy9s reeks southwest ireland were investigated to determine the controls and timing of postglacial geomorphic activity detailed geomorphologic analysis of three alluvial fan and debris cones within high level cirque basins demonstrates evidence of episodic phases of late holocene surface aggradation and incision radiocarbon dates from peat horizons above and below inorganic units show that phases of aggradation cluster into two distinct periods the first after 230 790 calibrated cal yr a d and the second from 1510 cal yr a d to the present an additional phase of fan aggradation at one site is dated after 1040 1280 cal yr a d all three phases coincide with episodes of enhanced late holocene valley floor alluviation and debris flow activity from upland britain alluvial fans and debris cones have developed primarily as a result of the resedimentation of late midlandian wisconsin drift and talus slopes and mobilization of materials involved flooding transitional flow and debris flow processes pollen analysis of peat horizons interbedded with alluvial fan and debris cone sediments indicates that land use changes were an important factor in lowering the threshold for local slope erosion phases of aggradation also coincide with well documented episodes of climate change and hence fan development is probably a function of both anthropogenic and climatic forcing a sequence of events may have involved initial slope destabilization due to overgrazing and removal of vegetation that was followed by debris mobilization and fan aggradation during intense rainstorms associated with climate change

western north atlantic evidence for millennial scale changes in ocean circulation and climate two late quaternary series of high resolution percent carbonate data from western north atlantic sediment drifts bermuda rise and bahama outer ridge show millennial scale oscillations superimposed on the familiar longer period oscillations of orbital origin the dominant high frequency oscillation in these records has a quasi period of about 4000 years these percent caco3 changes most likely result from the influence of climate change on the flux of terrigenous material from eastern canada the resuspension of continental margin sediment by deep eddy kinetic energy and carbonate dissolution sediment is transported to the bermuda rise by deep recirculating gyres and to the bahama outer ridge by the deep western boundary current system stable isotope results on foraminifera across several of these oscillations from interstadial climate conditions and from a glacial inception display variability similar to that of percent caco3 oxygen isotope ratios of planktonic foraminifera suggest large variations in near surface temperature and or salinity and carbon isotope ratios of benthic foraminifera indicate that there were significant oscillations in the flux of north atlantic deep water nadw these data support models which couple surface ocean conditions in the north atlantic production of nadw north atlantic heat flux and evidence for temperature oscillations in ice cores

response of global deep water circulation to earth s climatic change 135 000 107 000 years ago the response of deep ocean circulation to major climatic events of the past 135 000 years is inferred using carbon 13 analyses of benthic foraminifera from the major ocean basins the results demonstrate that the circulation of the world ocean deep water is very sensitive to climate and that it changes drastically during climatic transitions

periglacial trimlines and the extent of the kerry cork ice cap sw ireland abstract periglacial trimlines on the mountains of sw ireland demarcate a contrast between glacially scoured bedrock on lower ground and thick periglacial regolith covers on summits and plateaus and have previously been interpreted as marking the maximum altitude of the kerry cork ice cap kcic glacially eroded bedrock extends to the highest points on the beara peninsula but the highest summits on the iveragh peninsula support thick regolith covers trimline altitudes on the iveragh peninsula decline radially from a former ice divide near the head of kenmare river from 700 m altitude near the divide to 470 m near dingle bay contrasts in the clay mineral content of above and below trimline soils and cosmogenic isotope exposure ages indicate a lgm age for the trimlines assumption that the trimlines represent the maximum thickness of the kcic implies an ice divide altitude of 825 m however modelling of ice surface profiles demonstrates that an ice divide at 825 m is irreconcilable with stratigraphic evidence for extension of the kcic at least as far as garryvoe 115 km east of the divide we infer that the iveragh trimlines represent a former englacial transition between warm based sliding ice on low ground and cold based ice on high ground rather than delimiting nunataks as previously interpreted modelling of ice surface altitudes suggests that during the lgm the kcic probably overtopped all of the mountains in sw ireland the trimlines of sw ireland thus define the minimum rather than maximum altitude of the kcic at the lgm as well as the sites of former cold patches within the kcic

climatic pause during termination ii identified in shallow and intermediate waters off the iberian margin the sequence of termination ii from the end of marine isotopic stage 6 mis 6 to mis 5e is observed through an isotopic study 18o of planktic and benthic foraminifera in core md99 2331 42 09 n 09 41 w collected in the north atlantic on the iberian margin first to build an approximate time scale a record of the planktic 18o signal is achieved from the top of the core holocene to mis 6 the remarkable similarity of this planktic record to the greenland ice core project ice core 18o record allows a rough dating of our core a focus on termination ii reveals one standstill in the benthic record this pause can be linked either to a perturbation of north atlantic oceanic circulation pattern as a slowing down of the north atlantic deep water formation or to an interruption in polar ice sheet melting which could be a more global phenomenon

10be ages of late pleistocene deglaciation and neoglaciation in the north central brooks range arctic alaska we present a chronology of late pleistocene deglaciation and neoglaciation for two valleys in the north central brooks range alaska using cosmogenic 10be exposure dating the two valleys show evidence of ice retreat from the northern range front before 16 15 ka and into individual cirques by 14 ka there is no evidence for a standstill or re advance during the lateglacial period indicating that a glacier advance during the younger dryas if any was less extensive than during the neoglaciation the maximum glacier expansion during the neoglacial is delimited by moraines in two cirques separated by about 200 km and dated to 4 6 0 5 and 2 7 0 2 cal ka bp both moraine ages agree with previously published lichen inferred ages and confirm that glaciers in the brooks range experienced multiple advances of similar magnitude throughout the late holocene the similar extent of glaciers during the middle holocene and the little ice age may imply that the effect of decreasing summer insolation was surpassed by increasing aridity to limit glacier growth as neoglaciation progressed copyright 2012 john wiley sons ltd

younger dryas glaciers and climate in the mourne mountains northern ireland here we present evidence to suggest that the mourne mountains northern ireland were last occupied by glaciers during the younger dryas stadial the margins of these glaciers are marked by moraines chronologically constrained to the younger dryas by schmidt hammer exposure dating reconstructions indicate that these glaciers had equilibrium line altitudes elas ranging from 356 33 m a s l to 570 9 m a s l with a mean of 475 36 m a s l elas rise from west to east probably reflecting the contribution of windblown snow and ice to the accumulation of younger dryas glaciers in the western mournes taking this into consideration a mean climatic ela of 529 4 m a s l is calculated for the mountains as a whole assuming a mean annual sea level air temperature of 8 c and an annual temperature range of 34 c degree day modelling suggests that during the younger dryas accumulation at the climatic ela of glaciers in the mournes was 846 990 mm a 1 this suggests increased aridity relative to present and is consistent with other parts of nw europe where reduced precipitation alongside notable cooling is thought to reflect increased north atlantic sea ice extent during the younger dryas

valley glaciers persisted in the lake district north west england until 16 15 ka as revealed by terrestrial cosmogenic nuclide 10be dating a response to heinrich event 1

late quaternary stage 2 and 3 meltwater and heinrich events northwest labrador sea two major meltwater events are documented in cores from the nw labrador sea one occurred ca 20 000 14c yr b p in association with deposition of a major detrital carbonate unit both prior to and after this event 18o values of near surface planktonic foraminifera were 4 5 indicating fully enriched glacial values a younger event ca 14 000 14 c yr b p is characterized by a dramatic change in 18o from 4 5 to 2 0 and coincided with the retreat of ice from the outer se baffin shelf possibly into hudson strait these meltwater events coincide with heinrich h layers 1 and 2 from north atlantic sediments the 14 000 14c yr b p meltwater event indicates that the eastern margin of the laurentide ice sheet also underwent rapid retreat at approximately the same time as other ice sheet margins around the ne north atlantic a third major detrital carbonate event at the base of hu87 033 009 possibly correlative with heinrich layer 3 occurred ca 33 960 675 14 c yr b p however this is older than the accepted date for h 3 of 27 000 14c yr b p and may be h 4

late glacial warming prior to heinrich event 1 the influence of ice rafting and large ice sheets on the timing of initial warming high resolution faunal isotopic and sedimentologic data from north atlantic core v29 191 show that sea surface temperatures increased from 17 5 to 17 3 ka prior to the heinrich event 1 h1 ice rafting event ca 17 16 ka these new data support previous studies that showed that warming predated the extensive climatic warming ca 15 9 ka this relationship indicates that h1 occurred after warming had begun loss of latent heat during iceberg melting created near glacial sea surface temperatures during h1 and kept much of the subpolar north atlantic cold despite increasing northern hemisphere insolation the cold ocean conditions influenced proximal terrestrial climates and may also have affected remote regions

late pleistocene mountain glacier response to north atlantic climate change in southwest ireland stephan harrison neil glasser ed anderson susan ivy ochs peter w kubik 2010 late pleistocene mountain glacier response to north atlantic climate change in southwest ireland quaternary science reviews 29 27 28 3948 3955

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

geomagnetic effects on time integrated cosmogenic nuclide production with emphasis on in situ 14c and 10be abstract production of cosmogenic nuclides cns in geologic material is a function of the cosmic ray flux at the earth s surface which in turn is a function of the intensity and orientation of the earth s geomagnetic field temporal variations in the intensity of the geomagnetic field and the position of the geomagnetic dipole axis i e polar wander must be considered when calculating production rates that are integrated through time we have developed a model based in part on protocols set forth by desilets and zreda earth planet sci lett 206 2003 21 42 that accounts for these variations in an effort to systematically determine their impact on time integrated production of short lived in situ 14c t1 2 5 73 ka and long lived in situ 10be t1 2 1 5 ma cns our modeling results show that for samples exposed for the last 3 ka integrated in situ 14c and 10be production rates that account for temporal variations in the intensity of the earth s geomagnetic field are up to 13 lower than modern rates at the same location modern rates are referenced to the 1945 0 definitive geomagnetic reference field dgrf in contrast intensity corrected 10be rates are up to 30 higher than modern for samples exposed for 25 30 ka intensity variations have little effect our modeling results also show that the impact of polar wander on integrated cn production is secondary compared to intensity variations accounting for polar wander is critical however when determining modern production rates at midlatitudes 30 40 because of the current offset between the geomagnetic and geographic poles at sea level integrated in situ 14c production rates that account for both intensity variations and polar wander range from 27 higher to 24 lower than modern rates at the same location and integrated in situ 10be rates range from 48 higher to 26 lower than modern differences between integrated and modern rates increase significantly at higher altitudes based on these results we recommend correcting the modern production rate referenced to the 1945 0 dgrf or another specific geomagnetic reference field at site latitudes

timing of glacial retreat in the wicklow mountains ireland conditioned by glacier size and topography this paper presents 170 schmidt hammer exposure ages from moraine boulders and glacially sculpted bedrock to reveal the post last glacial maximum lgm history of the wicklow mountains ireland these data suggest that large ice masses survived for 4 7 ka after retreat of the irish sea ice stream and were sustained by summit ice fields until 16 6 ka post lgm retreat was dynamic with re advance moraines deposited in response to heinrich stadial 1 however these events reflect short term ice front oscillations 1 ka during the long term retreat phase retreat from re advance positions was synchronous across the range and paced by climate with time progressive deglaciation from low to high elevation in contrast marked asynchroneity in the timing of younger dryas deglaciation is closely linked to snow redistribution and indicates that for small cirque glaciers 1 km2 topography can exert the primary control on glacier survival this result has important implications for palaeoclimate econstructions as cirque glacier dynamics may be unrelated to climate this is further complicated by post depositional processes which can result in moraine ages e g 10be which post date retreat future palaeoclimate studies should prioritise cirque glaciers where snow contributing areas are small and where postdepositional disturbance is limited matrix poor boulder rich moraines

rapid changes in the mechanism of ocean convection during the last glacial period high amplitude rapid climate fluctuations are common features of glacial times the prominent changes in air temperature recorded in the greenland ice cores1 2 are coherent with shifts in the magnitude of the northward heat flux carried by the north atlantic surface ocean3 4 changes in the ocean s thermohaline circulation are a key component in many explanations of this climate flickering5 here we use stable isotope and other sedimentological data to reveal specific oceanic reorganizations during these rapid climate change events deep water was generated more or less continuously in the nordic seas during the latter part of the last glacial period 60 to 10 thousand years ago but by two different mechanisms the deep water formation occurred by convection in the open ocean during warmer periods interstadials but during colder phases stadials a freshening of the surface ocean reduced or stopped open ocean convection and deep water formation was instead driven by brine release during sea ice freezing these shifting magnitudes and modes nested within the overall continuity of deep water formation were probably important for the structuring and rapidity of the prevailing climate changes

climate change in the circum north atlantic region during the last deglaciation a survey of new and published palaeoclimate data indicates that both the high and low latitude north atlantic regions were characterized by at least three synchronous periods of abrupt climate change during the last glacial to interglacial transi tion climate model results suggest that changes in the melting history of the laurentide ice sheet may explain much of this nonlinear response of the climate system to astronomical milankovitch forcing

a heinrich like event h 0 dc 0 source s for detrital carbonate in the north atlantic during the younger dryas chronozone in the north atlantic we define h 0 as a heinrich like event which occurred during the younger dryas chron on the se baffin shelf prior to 11 ka surface water productivity was reasonably high as measured by the numbers of diatom and planktic foraminifera per gram but an abrupt increase in detrital carbonate dc 0 event from approximately 15 up to 50 carbonate by weight occurred at 11 14c ka and continued to circa 10 ka these deposits 2 6 m thick are dominated by detrital calcite and silt and clay sized sediments during this event dc 0 h 0 ice extended onto the inner shelf but did not reach the shelf break and probably originated from a center over labrador ungava as a consequence the pattern of ice rafted debris and sediment provenance shown by h o in the north atlantic is different from that during h 1 14 5 ka or h 2 20 ka when the ice sheet extended along the axis of hudson strait and may have reached the shelf break for example there is no concrete evidence for dc o is cores on the floor of the labrador sea due east of hudson strait hu75 55 56 but h o has been noted in cores off newfoundland and west of ireland a coeval carbonate event to dc 0 but this one dominated by dolomite occurs in hu82 su5 on the west side of davis strait with a source either from northern baffin bay or cumberland sound although other sources for north atlantic detrital carbonate cannot be totally excluded our evidence suggests that h 0 represents the expression of glaciological instability of the laurentide ice sheet within the general region of hudson strait and probably to the north cumberland sound and northernmost baffin bay there is one younger dc event dated circa 8 4 ka present in sediments along the labrador margin and in hudson strait which represents the final collapse of the ice sheet within hudson strait and hudson bay

oily old ores evidence for hydrothermal petroleum generation in an archean volcanogenic massive sulfide deposit oil is formed in some modern seafloor vent systems after rapid thermal maturation of sedimentary organic matter by hydrothermal fluids although most of this petroleum escapes into the ocean some hydrocarbons may be trapped as fluid inclusions in hydrothermal precipitates or as bituminous residues in cavities however the geological record lacks evidence of this phenomenon which is unfortunate because it could be significant for understanding the history of petroleum genesis the processes of hydrothermal mineralization and perhaps the origin and early evolution of life from the pilbara craton of australia we report the discovery of pyrobitumen and oil in an early archean ca 3235 ma deep sea volcanogenic massive sulfide deposit the oil occurs in fluid inclusions within hydrothermal barite and pyrobitumen is intergrown with polymetallic sulfides petrographic textures show that the oil was emplaced and thermally altered coked before late stage sulfide mineralization the results demonstrate that subseafloor hydrothermal petroleum generation was active during the early archean possibly providing an energy and carbon source for a subsurface microbiota metabolizing hydrothermal sulfur species

late quaternary river terrace development in the macgillycuddy s reeks southwest ireland abstract geomorphological sedimentological pedostratigraphical and palaeoecological analyses of fluvial and glacigenic deposits infilling the gaddagh valley macgillycuddy s reeks southwest ireland are used to elucidate the patterns and controls of late quaternary valley floor development in a 3 km reach of the catchment lying immediately downvalley of two mid basin lakes lough gouragh and lough callee a total of four holocene alluvial terraces terrace level tl 2 5 and a modern floodplain tl 6 have been identified and lie inset within a strath terrace comprising late quaternary midlandian till tl 1 the combination of mid basin lakes and flanking strath terraces acted to decouple the gaddagh channel from upper catchment and valley side debris sources shortly after regional deglaciation postglacial fluvial terrace development in the study reach has therefore occurred primarily in response to hydrological changes and reworking of local valley floor deposits rather than catchment wide debris supply changes pollen analyses of valley floor peat deposits interbedded with minerogenic alluvium indicate that anthropogenic disturbance of catchment tree cover had commenced by c a 1690 1450 cal bc and that the catchment was largely cleared of woodland by later prehistoric times major phases of incision and alluviation represented by terraces tl 3 5 however have been radiocarbon dated to the period after 250 530 cal ad and broadly correspond with holocene fluvial records elsewhere in the region upland britain and northwest europe although fluvial system responses to hydrological changes will have been promoted by anthropogenic disturbances of catchment vegetation cover the timing of late holocene incision and alluviation episodes are interpreted as reflecting enhanced flood frequencies and or magnitudes associated with late holocene climatic shifts in the gaddagh valley however we hypothesise that the headwater lakes lough gouragh and lough callee may also have exerted a critical control on the postglacial evolution of the valley floor in particular high magnitude flooding is likely to have been instrumental in valley floor entrenchment and formation of tl 3 tl 4 and tl 5 terraces

new data for the last glacial maximum in great britain and ireland abstract understanding the history of the british and irish ice sheet biis at the last glacial maximum lgm has been advanced by new approaches in particular by cosmogenic nuclide surface exposure dating aminostratigraphy of shelly glacial deposits ams radiocarbon dating and the evidence from continental margin marine cores all of which supersede the previously weak geochronologic control it was formerly believed that great britain and ireland was largely ice free between the last interglacial oxygen isotope sub stage 5e and the late devensian when the lgm occurred as such the biis was effectively out of phase with laurentide and scandinavian ice sheets as well as inferences of ice volume from oxygen isotope stratigraphy the biis during the late devensian maximum was also perceived as having been relatively stationary new evidence shows that the lgm was an important event during the evolution of an earlier biis when the extent of ice was greater repeated iceberg rafting events over the past 50 ka are shown by marine cores while the derivative inference of numerous corresponding glacial advances is supported by several clusters of 36 cl ages on glaciated surfaces and glacial boulders that are indicative of deglacial events between 40 and 12 ka these appear to be associated with heinrich events the earliest being inferred as heinrich 4 at about 40 ka during this advance the biis and scandinavian ice sheet sis were in contact and all of ireland was glaciated the ice sheet appears to have fluctuated several times between 40 and 25 ka although evidence for this is poorly preserved but the 36 cl and 14 c evidence is clear that the biis reached its lgm maximum size about 22 ka soon after heinrich event 2 when the biis and sis were not in contact one cluster of 36 cl and 14 c ages at 21 4 1 3 ka records an initial pulse of deglaciation that was followed by extensive deglaciation about 17 4 0 4 ka just before heinrich event 1 when the ice sheet readvanced contrary to previous views the biis probably existed throughout much of devensian time as a mobile and sensitive ice sheet during which the lgm advance was but one important event in places glacial deposits of the earlier devensian glaciation have previously been incorrectly identified as products of the later lgm glaciation

relation of subtropical atlantic temperature high latitude ice rafting deep water formation and european climate 130 000 60 000 years ago abstract a new high resolution record of sea surface temperature from the subtropical western north atlantic documents a series of abrupt coolings within marine isotope stage 5 which can be objectively correlated with marine core evidence for increased ice sheet discharge at subpolar latitudes and reduced north atlantic deep water formation these results indicate that ice sheet forcing of deep ocean circulation influenced surface temperatures over much of the north atlantic a proposed correlation to the pollen record of grande pile france indicates that each cold event seen in the pollen sequence has a unique counterpart in the record of subtropical ocean temperature if this correlation is correct it suggests that the warmest part of the european eemian ended suddenly in response to oceanographic changes and that the subsequent post temperate phase of the eemian extended well into the interval of ice sheet growth corresponding to marine isotope substage 5d

ams c 14 dating of deglacial events in the irish sea basin and other sectors of the british irish ice sheet sedimentary sequences deposited by the decaying marine margin of the british irish ice sheet biis record isostatic depression and successive ice sheet retreat towards centres of ice dispersion radiocarbon dating by accelerator mass spectrometry ams of in situ marine microfaunas that are commonly associated with these sequences constrain the timing of glacial and sea level fluctuations during the last deglaciation enabling us to evaluate the dynamics of the bus and its response to north atlantic climate change here we use our radiocarbon dated stratigraphy to define six major glacial and sea level events since the last glacial maximum 1 initial deglaciation may have occurred 18 3 kyr c 14 bp along the northwestern irish coast in agreement with a deglacial age of similar to 22 cl 36 kyr bp for southwestern ireland ice retreated to inland centres and areas of transverse moraine began to form across the north irish lowlands 2 channels cut into glaciomarine deglacial sediments along the western irish sea coast are graded to below present sea level identifying a fall of relative sea level rsl in response to isostatic emergence of the coast 3 marine mud that rapidly infilled these channels records an abrupt rise in global sea level of 10 15 m similar to 16 7 c 14 kyr bp that flooded the irish sea coast and may have triggered deglaciation of a marine based margin in donegal bay 4 intertidal boulder pavements in dundalk bay indicate that rsl similar to 15 0 c 14 kyr bp was similar to present 5 a major readvance of all sectors of the biis occurred between 14 and 15 kyr 14 c bp which overprinted subglacial transverse moraines and delivered a substantial sediment flux to tidewater ice sheet margins this event the killard point stadial indicates that the bus participated in heinrich event 1 6 subsequent deposition of marine muds on drumlins 12 7 c 14 kyr bp indicates isostatic depression and attendant high rsl resulting from the killard point readvance these events identify a dynamic biis during the last deglaciation as well as significant changes in rsl that reflect a combination of isostatic loading and eustatic changes in global sea level c 2005 elsevier ltd all rights reserved

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

the use of hypsometry to indicate long term stability and response of valley glaciers to changes in mass transfer a simple equation is derived relating the net mass balance and hypsometric curves of a steady state valley glacier it is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions examples are given which show that area based indices e g aar for estimating the equilibrium line altitude ela may be subject to a substantial built in variance because they implicitly rely upon similarity of glacier shape and regimen over a region if accurate topographic maps are available the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass balance gradients alternatively if similar information is available concerning regional glacier regimen disparate extents and responses may be collectively utilized to estimate values of ela or to infer climatic influence taking glacier hypsometry into account

loch lomond stadial glaciers in north harris outer hebrides north west scotland glacier reconstruction and palaeoclimatic implications abstract geomorphological mapping of north harris provides evidence for the former existence of 10 glaciers with a total area of ca 35 km2 a loch lomond younger dryas stadial age ca 12 9 11 5 kyr bp for this glacial episode is inferred from glacier configuration landsystems dominated by hummocky recessional moraines and relationships with lateglacial periglacial phenomena equilibrium line altitudes elas of 150 289 m were calculated for individual glaciers ela variability mainly reflects differences in snow contributing area the area weighted mean ela 204 m is consistent with a northwards decline in elas along the western seaboard of the british isles of 69 5 m 100 km 1 equivalent to a northwards ablation season temperature decrease of 0 42 c 100 km 1 this latitudinal temperature gradient implies a mean july sea level temperature of ca 7 2 c for the coldest part of the stade roughly 6 c lower than at present sea level precipitation at the time of the lls glacial maximum is inferred to have been between ca 1970 200 and 2350 200 mm yr 1 implying that lls precipitation was up to 25 greater than now patterns of recessional moraines indicate that the glaciers remained close to climatic equilibrium as they retreated to their sources though moraine belts implying near stationary or readvancing ice margins on flat valley floors are separated by moraine free zones indicating uninterrupted retreat calculation of elas for residual glaciers in former source areas suggests that summer warming of 1 0 c would have resulted in shrinkage of the glaciers to their sources

reply to comment received from j c knight regarding last glacial maximum cirque glaciation in ireland and implications for reconstructions of the irish ice sheet by barth et al 2016 quaternary science reviews 141 85 93

comment on last glacial maximum cirque glaciation in ireland and implications for reconstructions of the irish ice sheet quaternary science reviews 141 85 93

paleoenvironmental changes in the norwegian sea and the northeast atlantic during the last 2 8 m y deep sea drilling project ocean drilling program sites 610 642 643 and 644 sedimentological isotopic and magnetostratigraphic investigations of ocean drilling program and deep sea drilling project sites 642 643 644 and 610 document the oceanographic and climatic evolution of the norwegian sea and the northeastern atlantic over the last 2 8 m y the results show that a major expansion of the scandinavian ice sheet to the coastal areas took place at about 2 56 ma relatively severe glacials appeared until about 2 ma the period 2 6 1 2 ma experienced in general cold surface water conditions with only a weak influx of temperate atlantic water as compared with late quaternary interglacials the norwegian sea was a sink of deep water through this period but deepwater ventilation was reduced and calcite dissolution was high compared with the holocene deep water formed by other mechanisms than it does today between 2 and 1 2 ma the glaciations in scandinavia were small a transition toward larger glacials took place during the period 1 2 to 0 6 ma corresponding to warmer interglacials and reduced calcite dissolution only during the last 0 6 m y has the oceanographic and climatic system of the norwegian sea varied in the manner described in previous studies of the late quaternary a strong thermal gradient was present between the norwegian sea and the northeastern atlantic during the matuyama 2 5 0 7 ma this is interpreted as a sign of a more zonal and less meridional climatic system over the region compared with the present situation