observational evidence for westward propagation of temperature inversions in the southeastern arabian sea 1 a warm pool forms in the southeastern arabian sea seas prior to the onset of the summer monsoon over india in early june the core of this warm pool is in the lakshadweep sea ls xbt and surface salinity data collected in the ls during may 2002 april 2003 show that temperature inversions occur off the southwest coast of india in early december with the arrival of low salinity waters from the bay of bengal the low salinity waters and the inversions propagate westward along with the downwelling rossby waves that constitute the lakshadweep sea level high inversions occur in the western ls 73 e about 40 days after they occur near the coast in the eastern ls 75 5 e they disappear in april when the tropical convergence zone moves over the seas and the warm pool engulfs the region ocean dynamics and air sea fluxes are together responsible for the formation and westward propagation of the inversions

the late devensian 22 000 bp irish sea basin the sedimentary record of a collapsed ice sheet margin the late devensian 20 ka bp glacial geology of the irish sea basin 4000 km2 is an event stratigraphy recording the entry of marine waters into a glacio isostatically depressed basin and the rapid retreat of the irish sea glacier as a tidewater ice margin marine limits occur up to 140 m o d across much of the central basin the ice margin was uncoupled from its bed exposing a subglacially scoured topography to glaciomarine processes the irish sea glacier was a major drainage conduit of the last british ice sheet calving of the marine ice margin resulted in fast flow surging of ice streams recorded by drumlin fields around the northern basin margin and tunnel valleys rapid evacuation of the basin may have stranded large areas of dead ice in peripheral zones e g cheshire shropshire lowlands and initiated the collapse of the ice sheet thick wedges of ice contact glaciomarine sediments were deposited during ice retreat as morainal bank complexes by successive tidewater ice margins stabilized at pinning points around the irish sea coast where morainal banks occur on the seaward side of drumlin swarms there is a clear sequential relationship between rapid ice loss from calving ice margins the development of fast flowing ice streams drumlinization and the pumping of subglacial sediment to tidewater raised delta complexes are locally associated with marine limits along the high relief coastal margins of wales east central ireland and the lake district associated valley infill complexes record downslope resedimentation of heterogenous sediments into the marine environment during ice retreat co eval offshore deposits are represented by well stratified glaciomarine complexes that infill a subglacially scoured topography that shows networks of tunnel valleys glaciomarine mud drapes occur well to the south of the maximum limit of grounded ice in the basin e g north devon scilly islands southern ireland the age of these distal sediments previously mapped as pre devensian tills is constrained by amino acid ratios basin rebound following deglaciation was rapid with over 100 m recovery in 3 ka and was followed by a low marine still stand peat accumulating in offshore areas now as much as 55 m below sea level has been drowned by the postglacial eustatic rise in sea level the glacio sedimentary model identified in this paper involving rapid ice retreat and related sedimentation triggered by rising relative sea level suggests that isotatic downwarping is an important mechanism for deglaciating continental shelves

the last british ice sheet a review of the evidence utilised in the compilation of the glacial map of britain this paper reviews the evidence presently available as at december 2003 for the compilation of the glacial map of britain see clark c d evans d j a khatwa a bradwell t jordan c j marsh s h mitchell w a bateman m d 2004 map and gis database of glacial landforms and features related to the last british ice sheet boreas 33 359 375 and http www shef ac uk geography staff clark chris britice html in an effort to stimulate further research on the last british ice sheet and promote a reconstruction of ice sheet behaviour based on glacial geology and geomorphology the wide range of evidence that has been scrutinized for inclusion on the glacial map is assessed with respect to the variability of its quality and quantity and the existing controversies in ice sheet reconstructions landforms interpreted as being of unequivocal ice marginal origin moraines ice contact glacifluvial landforms and lateral meltwater channels and till sheet margins are used in conjunction with available chronological control to locate former glacier and ice sheet margins throughout the last glacial cycle subglacial landforms drumlins flutings and eskers have been used to demarcate former flow patterns within the ice sheet the compilation of evidence in a regional map is crucial to any future reconstructions of palaeo ice sheet dynamics and will provide a clearer understanding of ice sheet configuration ice divide migration and ice thickness and coverage for the british ice sheet as it evolved through the last glacial cycle

origins and dynamics of the 90 day and 30 60 day variations in the equatorial indian ocean abstract sea level observations in the equatorial indian ocean show a dominant spectral peak at 90 days and secondary peaks at 30 60 days over an intraseasonal period 20 90 days a detailed investigation of the origins and dynamics of these variations is carried out using an ocean general circulation model namely the hybrid coordinate ocean model hycom two parallel experiments are performed in the tropical indian ocean basin for the period 1988 2001 one is forced by ncep 3 day mean forcing fields together with the climate prediction center cpc merged analysis of precipitation cmap pentad precipitation and the other is forced by monthly mean fields to help to understand the role played by the wind driven equatorial wave dynamics a linear continuously stratified ocean model is also used both the observed and modeled 90 day sea level anomaly fields and hycom surface current clearly show equatorial kelvin and first meridional mode rossby wave structures that are forced by the 90 day winds the

exposure dating and validation of periglacial weathering limits northwest scotland periglacial weathering limits on two mountains in northwest scotland separate zones of contrasting exposure history exposure dating of bedrock below the weathering limits gives ages consistent with late devensian deglaciation but six out of seven samples from above the weathering limits give minimum exposure ages older than late devensian ice expansion these results suggest that mountain summits stood as nunataks above the last ice sheet surface and rule out formation of weathering limits by periglacial rock breakdown since deglaciation trimming of frost debris during an ice sheet readvance or enhanced weathering prior to climatic warming during ice sheet downwastage the dating results do not preclude the possibility that weathering limits mark a former englacial boundary between passive cold based ice on mountain summits and erosive warm based ice at lower elevations although 26 al 10 be ratios for high level bedrock surfaces provide no evidence of prolonged static ice cover

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

vertical dimensions and age of the wicklow mountains ice dome eastern ireland and implications for the extent of the last irish ice sheet abstract patterns of erratic distribution show that the wicklow mountains formerly supported an independent ice cap or ice dome geomorphological mapping of the upper limits of evidence for glaciation ice scoured and moulded bedrock perched boulders and the distribution of features indicative of prolonged periglacial conditions tors frost shattered rock blockfields indicates that along the main axis of high ground erosive warm based ice buried all but the highest 725 m summits and over ran adjacent lower peaks and cols the presence of gibbsite in soil samples from above the inferred upper limit of glacial erosion and its absence in all samples from below this limit is consistent with the geomorphological evidence and implies removal of gibbsitic soils below 725 m by glacial erosion during the last glacial stage cosmogenic 10 be exposure ages for rock outcrops above the inferred upper limit of glacial erosion yield pre last glacial maximum lgm ages of 46 9 3 0 ka to 95 9 6 1 ka whereas rock outcrops on summits over ridden by warm based ice give post lgm ages of 18 2 1 2 to 19 1 1 2 ka all geomorphological and dating evidence thus indicates an lgm age for the ice dome the thickness of the ice dome and limited lateral dispersal of erratics indicate that at the lgm the wicklow ice was encircled by and confluent with thick powerful ice streams moving se from the irish midlands and southwards down the irish sea basin this conclusion is irreconcilable with the traditional view that the last irish ice sheet terminated at the south ireland end moraine but consistent with recent proposals that the last ice sheet was much more extensive than previously believed and over ran the south coast of ireland

transformations of mg and ca sulfate hydrates in mars regolith salt hydrates have an active role in regolith development on mars the mg sulfate system with highly variable values of n in the formula mgso 4 n h 2 o is particularly subject to transformations among several crystalline and amorphous forms the ca sulfate system caso 4 n h 2 o is likely to be associated with the mg sulfates in most occurrences but is less susceptible to transformations in n desiccation of mgso 4 n h 2 o occurs in exposed soils at the martian equator in summer where higher daytime temperatures at low relative humidity prevail against sluggish nighttime rehydration at high relative humidity desiccation and rehydration are both accelerated in the finest size fractions particularly in silt size aeolian particles subject to global redistribution by dust storms this redistribution and periodic excursions into long term episodes of high obliquity work to rehydrate desiccated mgso 4 n h 2 o to form epsomite mgso 4 7h 2 o at higher latitudes in the first case and more globally in the latter kieserite a monohydrate form of mgso 4 n h 2 o resistant to desiccation can survive equatorial summer conditions but not protracted high relative humidity preservation of kieserite at the surface may place limits on the equatorial distribution of ice during past episodes of high obliquity deeper horizons in equatorial regolith may preserve hydrated phases through repeated obliquity episodes raising the possibility of an ancient regolith archive of past hydration at shallower depths in the regolith in situ determination of the hydration states of the mg sulfates and possibly the ca sulfates may be used to constrain regolith dynamics if rates and modes of transitions in n can be fully characterized

the last ice sheet in snowdonia in snowdonia there is a marked contrast between weathered summits often with well developed blockfields or tors and lower ice moulded terrain the boundary is interpreted as a trimline marking the upper surface of the last ice sheet this interpretation is supported by the presence of gibbsite an end product of prolonged weathering at the base of soils above but not below the trimline the reconstructed ice surface reaches about 850 m above present sea level along an ice divide running ne sw through the massif there is no evidence to support the popular view that ice centred further south extended over snowdonia and breaching to form the major glacial troughs can be explained by the action of local ice the field evidence presented here demonstrates that most models of the southern british and irish sea ice sheets are significantly flawed the earliest being far too thick and the most recent far too thin copyright 2000 john wiley sons ltd

understanding the origins of interannual thermocline variations in the tropical indian ocean 1 based on the data analysis of the 1000 hpa wind sst and ssh anomalies it is revealed that the atmospheric variations associated with indian ocean dipole iod or referred as indian ocean zonal dipole mode iozdm consist of a pair of anticyclones closely north and south of the equator with accompanying intense equatorial easterly anomalies while the atmospheric variations related to el nino southern oscillation enso include a strong anticyclone in the southeastern tropical indian ocean tio at higher latitudes with strong along shore wind anomalies near java sumatra coast the different atmospheric forcing patterns lead to the fact that oceanic thermocline variations associated with iod iozdm are more closely confined to the region north of 10 s while enso induced thermocline variations are dominant south of 10 s

the last glacial maximum british irish ice sheet a reconstruction using digital terrain mapping the use of digital terrain mapping in determining the anatomy of the late devensian british irish ice sheet at a resolution of 500 m cell size is illustrated for boulton et al s 1985 and 1991 models and lambeck s 1995 model of the ice sheet at its maximum extent as an independent ice mass area and volume of the ice sheet are given for each model and the spatial pattern of ice thickness shown in maps the analyses show that if no account is taken of topography beneath the ice surface models will seriously overestimate ice volume it is suggested that as reconstructions of the ice sheet improve detailed models of ice thickness at the resolution given in this paper may be of value in determining the contribution of the ice sheet to sea surface changes as well as in determining the effects of ice loading on glacio isostasy neotectonics and possibly on paraglacial processes in areas of high relief copyright 2007 john wiley sons ltd

cracks and fins in sulfate sand evidence for recent mineral atmospheric water cycling in meridiani planum outcrops gypsum dunes at white sands national monument new mexico provide an excellent analog to sulfate rich eolian outcrops on meridiani planum mars as characterized by the rover opportunity numerous outcrops imaged by opportunity contain polygonal cracks that crosscut bedding and extend across most surfaces of boulders some of these cracks are associated with millimeter thick platy fins that protrude as much as a few centimeters above outcrops similar cracks crosscut bedding at white sands on erosional stoss slopes and in pedestals of cemented dune sand the cracks at white sands form in response to cementation of damp gypsum sand followed by contraction due to dehydration during warm seasons cracked sand is dry and cracks rarely grow although some may form after rainstorms two types of fins form along cracks and differentially eroded laminae white fins represent subsurface differential cementation along cracks followed by differential erosion tan fins form due to cementation of crack edges and laminae on exposed dune surfaces wind blown sediment adheres to damp tan fins similar processes may be important for crack and fin formation in meridiani planum outcrops implying recent water cycling between sulfate outcrops and the martian atmosphere

periglacial trimlines former nunataks and the altitude of the last ice sheet in wester ross northwest scotland high level weathering limits separating ice scoured topography from frost weathered detritus were identified on 28 mountains in wester ross at altitudes of 700 960 m and a further 22 peaks support evidence of ice scouring to summit level weathering limits are defined most clearly on sandstone and gneiss which have resisted frost shattering during the late devensian lateglacial but can also be distinguished on schists and quartzite schmidt hammer measurements and analyses of clay mineral assemblages indicate significantly more advanced rock and soil weathering above the weathering limits the persistence of gibbsite above weathering limits indicates that they represent the upper limit of late devensian glacial erosion the regular decline of weathering limit altitudes along former flowlines eliminates the possibility that the weathering limits represent former thermal boundaries between protective cold based and erosive warm based ice the weathering limits are therefore interpreted as periglacial trimlines that define the maximum surface altitude of the last ice sheet calculated basal shear stresses of 50 95 kpa are consistent with this interpretation reconstruction of ice sheet configuration indicates that the former ice shed lay above 900 m along the present watershed and that the ice surface descended northwestwards with broad depressions along major troughs and localised domes around independent centres of ice dispersal extrapolation of the ice surface gradient and altitude suggests that the ice sheet did not overrun the outer hebrides but was confluent with the independent outer hebrides ice cap in the north minch basin erratics located up to 140 m above the reconstructed ice surface are inferred to have been emplaced by a pre late devensian ice sheet or ice sheets of unknown age 1997 john wiley sons ltd

rapid thinning of the welsh ice cap at 20 19 ka based on 10be ages abstract new 10 be ages from the summits of three mountain areas of north wales reveal a very similar exposure timing as the welsh ice cap thinned after the global last glacial maximum eight bedrock and one boulder sample gave a combined arithmetic mean exposure age of 19 08 0 80 ka 4 2 1 similar exposure ages over a 320 m vertical range 824 to 581 m altitude show that ice cap thinning was very rapid and spatially uniform using the same production rate and scaling scheme we recalculated six published 10 be exposure ages from the nearby arans which also covered a similar elevation range from 608 to 901 m and obtained an arithmetic mean of 19 41 1 45 ka 7 5 1 the average exposure age of all 15 accepted deglaciation ages is 19 21 1 07 5 6 1 the complete dataset from north wales provides very strong evidence indicating that these summits became exposed as nunataks at 20 19 ka this result provides important insight to the magnitude of ice surface lowering and behavior of the welsh ice cap during the last deglaciation that can be compared to other ice masses that made up the british irish ice sheet

observational evidence for remote forcing of the west india coastal current 1 circulation in the north indian ocean is influenced by both local and remote wind forcing so far however determining the contribution of these two forcing mechanisms at a location has been possible only in numerical experiments here we separate remote and local forcing in observations using field measurements current sea level and wind for a month during march april 2003 off goa in the near coast regime of the west india coastal current wicc we show that the current was driven by local winds only at periods less than 10 days with remote forcing contributing at longer periods the high passed hp period less than 10 days component of the along shore current was strongly correlated with the hp component of the along shore wind the current lagging the wind by half a day the low passed lp components of the wind and current were not correlated the former was unidirectional but the latter reversed during the period of observation the relationship between the hp wind and current was used to estimate the locally forced lp current permitting an estimate of the remote current the lp residual this separation of locally forced and remotely forced currents showed that remote forcing contributed as much as local forcing to the wicc the local current behaved like a classical eastern boundary current forced by local winds the reversal in the remote current was due to winds 700 km farther south along the coast frictional damping had an impact only at periods less than 10 days there being no remotely forced hp current

modulation of chlorophyll concentration by downwelling rossby waves during the winter monsoon in the southeastern arabian sea abstract signatures of rossby waves that are evident in satellite ocean colour data in the southeastern arabian sea seas are more prominent during the winter than the summer monsoon during the winter the sea level is high and the conditions are less conducive for the injection of nutrients through the eddy pumping mechanism in this study we use satellite observations and a physical ecosystem model to examine the role of horizontal advection associated with rossby waves in enhancing chlorophyll concentration in the seas zonal advection dominates over meridional advection and its effect is more prominent in the south of indian subcontinent and west of the maldives except along the coast and around the islands the vertical processes are weak and do not lead to a substantial increase in chlorophyll model simulations show that the currents associated with the rossby wave also transport nutrients and other physicochemical properties of water along the path of the wave the advected water decreases the concentration of arabian sea high salinity water mass and replenishes the oxygen in the oxygen minimum zone in the seas

the donegal ice dome northwest ireland dimensions and chronology geomorphological evidence indicates that donegal was formerly occupied by an ice dome that extended offshore to the west northwest and north and was confluent with adjacent ice masses to the east and south erosive warm based ice over rode almost all the highest mountains implying an ice divide altitude greater than 700 m only six peripheral summits escaped glacial modification implying either that they remained above the ice surface as nunataks or supported a thin cover of protective cold based ice gibbsite a pre last glacial weathering product is preferentially represented on summits that escaped glacial modification cosmogenic 10be exposure ages of 18 6 1 4 to 15 9 1 0 k yr for coastal sites confirm that donegal ice extended offshore at the last glacial maximum reconstruction of the form of the donegal ice dome suggests a former minimum ice thickness of 500 m close to the present coastline in the west and northwest and 400 m near the coast of the inishowen peninsula in the north with the ice extending at least 20 km across the adjacent shelf to the west and northwest copyright 2007 john wiley sons ltd

effects of islands on equatorial waves the effects of islands on equatorially trapped waves induced by the sudden onset of zonal wind are investigated by solving the shallow water equations numerically the energy propagation associated with an equatorial kelvin wave is almost unaffected by an island on the equator the energy transmission ratio is over 0 8 even when the north south extent of the island is the same as the rossby deformation radius it is also shown that the maldive islands in the indian ocean and the gilbert islands in the pacific ocean do not affect the energy flux associated with kelvin waves significantly the sea level near the island however differs significantly from the sea level associated with an equatorial kelvin wave in the absence of an island this result has important implications for the interpretation of sea level measurements at equatorial islands on the other hand the energy propagation of equatorial rossby waves the lowest mode in the north south direction is greatly affected by an island on the equator the energy transmission ratio is less than 0 3 when the north south extent of the island is the same as the radius of deformation

the last ice sheet in north west scotland reconstruction and implications recent models of the last scottish ice sheet suggest that nunataks remained above the ice surface in areas peripheral to the main centres of accumulation this proposition has been investigated on 140 mountains over an area of 10 000 km2 in nw scotland outside the limits of the later loch lomond readvance in this area there is evidence for a single high level weathering limit that separates glacially eroded terrain from higher areas of in situ frost debris this limit occurs at altitudes ranging from 425 to 450 m in the outer hebrides to 950 m on the mainland and is best developed on lithologies that resisted breakdown after ice sheet downwastage interpretation of this weathering limit as a periglacial trimline cut by the last ice sheet at its maximum thickness is supported by 1 joint depth and schmidt hammer measurements that indicate significantly more advanced rock breakdown above the weathering limit 2 a much greater representation of gibbsite a pre late devensian weathering product in the clay fraction of soils above the limit 3 cosmogenic isotope dating of the exposure ages of rock outcrops above and below the limit 4 the sharpness of the limit at some sites and its regular decline along former ice flowlines and 5 shear stress calculations based on the inferred altitude and gradient of the former ice surface reconstruction of the ice surface based on trimline evidence indicates that the mainland ice shed lay near or slightly east of the present watershed and descended northwards from 900 m to ca 550 m at the north coast independent dispersion centres fed broad ice streams that occupied major troughs on skye an ice dome 800 m deflected the northwestwards movement of mainland ice but the mountains of rum were over ridden by mainland ice up to an altitude of ca 700 m the outer hebrides supported an independent ice cap that was confluent with mainland ice in the minches extrapolation of the trimline evidence indicates that most reconstructions of ice extent are too conservative and suggests that low gradient ice streams extended across the hebridean shelf offshore wider implications of this research are 1 that blockfields and other periglacial weathering covers are not all of the same age or significance depending on the resistance of different lithologies to frost weathering 2 that the contrasting degree of glacial modification in the western and eastern highlands of scotland may reflect a former cover of predominantly warm based ice in the former and predominantly cold based ice in the latter and 3 that the approach and techniques developed in this study have potential application for constraining ice sheet models not only in areas peripheral to the main centres of ice accumulation in britain and ireland but also in other mountain areas where nunataks protruded through warm based late pleistocene ice masses

extent and timing of the last glacial maximum lgm in britain and ireland a review the last glacial maximum lgm of marine isotope stage mis 2 is defined here as the period either of maximum global ice volume or in which major ice sheets reached their maximum extent both definitions lack clarity as there is no reason to suppose that maximum volumes or limits were reached simultaneously at either all ice sheets or around the margins of individual ice sheets here we review the traditional terrestrial limits of the biis british irish ice sheet examine developments in understanding the offshore record and attempt a redefinition of the extent and timing of the mis 2 maximum as a working chronological model the build up of the biis is assigned to after 35 32 ka the maximum to the period 27 21 ka and a more limited readvance after 19 ka as marginal oscillations driven by ice sheet dynamics appear to have characterised much of the advance and especially the retreat of the biis caution should be exercised in assigning climatic significance to the many identified ice limits or still stands while much of the terrestrial limit in britain remains relatively unaltered significant revision is required offshore around britain and ireland to portray an extensive ice advance to the shelf edge and a period when the biis was conjoined with the adjacent fenno scandinavian ice sheet although there appears to be a broad synchrony between the biis and other major ice sheets local controls have produced some variation in the timing of advance to and retreat from maximum limits for particular ice streams or lobes but much of the offshore limit remains very poorly age constrained consequently a key objective in future research should be to improve and refine the chronological control for all portions of the maximum margin of the biis and its subsequent retreat stages copyright 2010 john wiley sons ltd

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

the dynamics of the southwest monsoon current in 2016 from high resolution in situ observations and models abstractthe strong stratification of the bay of bengal bob causes rapid variations in sea surface temperature sst that influence the development of monsoon rainfall systems this stratification

hydrated mineral stratigraphy of ius chasma valles marineris new high resolution spectral and morphologic imaging of deposits on walls and floor of ius chasma extend previous geomorphic mapping and permit a new interpretation of aqueous processes that occurred during the development of valles marineris we identify hydrated mineralogy based on visible near infrared vnir absorptions we map the extents of these units with crism spectral data as well as morphologies in ctx and hirise imagery three cross sections across ius chasma illustrate the interpreted mineral stratigraphy multiple episodes formed and transported hydrated minerals within ius chasma polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma they may have been precipitates in a closed basin or diagenetically altered after deposition fluvial or aeolian processes then deposited layered fe mg smectite and hydrated silicate on the chasma floor postdating the sulfates the smectite apparently was weathered out of noachian age wallrock and transported to the depositional sites the overlying hydrated silicate is interpreted to be an acid leached phyllosilicate transformed from the underlying smectite unit or a smectite jarosite mixture the finely layered smectite and massive hydrated silicate units have an erosional unconformity between them that marks a change in surface water chemistry landslides transported large blocks of wallrock some altered to contain fe mg smectite to the chasma floor after the last episode of normal faulting and subsequent landslides opal was transported short distances into the chasma from a few m thick light toned layer near the top of the wallrock by sapping channels in louros valles alternatively the material was transported into the chasma and then altered to opal the superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential distinct aqueous environments characterized by alkaline then circum neutral and finally very acidic surface or groundwater chemistry

10be and 26al exposure age dating of bedrock surfaces on the aran ridge wales evidence for a thick welsh ice cap at the last glacial maximum this paper presents results of the analysis of paired cosmogenic isotopes 10be and 26al from eight quartz rich samples collected from ice moulded bedrock on the aran ridge the highest land in the british isles south of snowdon on the aran ridge comprising the summits of aran fawddwy 905 m a s l and aran benllyn 885 m a s l 26al and 10be ages indicate complete ice coverage and glacial erosion at the global last glacial maximum lgm six samples from the summit ridge above 750 800 m a s l yielded paired 10be and 26al ages ranging from 17 2 to 34 4 ka respectively four of these samples are very close in age 10be ages of 17 5 0 6 17 5 0 7 19 7 0 8 and 20 0 0 7 ka and are interpreted as representing the exposure age of the summit ridge two other summit samples are much older 10be ages of 27 5 1 0 and 33 9 1 2 ka and these results may indicate nuclide inheritance the 26al 10be ratios for all samples are indistinguishable within one sigma uncertainty from the production rate ratio line indicating that there is no evidence for a complex exposure history these results indicate that the last welsh ice cap was thick enough to completely cover the aran ridge and achieve glacial erosion at the lgm however between c 20 and 17 ka ridge summits were exposed as nunataks at a time when glacial erosion at lower elevations below 750 800 m a s l was achieved by large outlet glaciers in the valleys surrounding the mountains copyright 2011 john wiley sons ltd

glaciation and sea level change for ireland and the irish sea since late devensian midlandian time the sea level change around the coast of ireland and the irish sea for the past 20 000 years is primarily the combined result of the glacio isostatic adjustment of the crust to the removal of ice over the british isles and the total eustatic change from the global ice sheets however the isostatic effects due to the removal of ice from northern europe and north america and the addition of meltwater into the oceans also make a significant contribution predictions of sea level change based on glacio hydro isostatic models are compared with observations to constrain the ice volume over ireland at the time of the last glacial maximum and the maximum ice height appears to have been of the order of 600 m the models predict well the spatial variability in sea level change observed across the region for holocene and lateglacial time with levels above present being predicted only for northeastern ireland and north of about morecambe bay the models do not support suggestions that lateglacial levels along the east coast of ireland or the coast of wales were 50 150 m above their present levels consistent models that would produce such large lateglacial highstands are incompatible with all other sea level and glacial evidence for the british isles palaeobathymetry and palaeoshoreline reconstructions for the irish sea indicates that a tenuous landbridge between britain and ireland developed only across the celtic sea between about 18000 and 14000 years bp

an improved technique for the reconstruction of former glacier mass balance and dynamics abstract the recognition of past glacier extent and dynamics is a fundamental aspect of investigations of the climatic sensitivity of glaciers especially when examining short lived climate events such as the younger dryas or little ice age existing approaches to the reconstruction of glacier form and dynamics depend on speculative reasoning of key glacier dynamic parameters including the role of basal slip and subglacial deformation in glacier mass transfer this study reviews approaches to glacier reconstruction derivation of former glacier equilibrium line altitudes ela s and estimation of mass balance and dynamics concluding that most reconstructions of glacier mass balance are compromised by a lack of glaciological considerations an alternative approach to glacier reconstruction is presented demonstrated and discussed by which an empirical relationship between ablation gradient and mass loss at the ela is used to derive mass balance mass flux through the ela and average balance velocity at the ela this glaciological approach is applied to four reconstructed glaciers to test previous interpretations that each reflects younger dryas glaciation in the uk the study concludes that this approach provides a more robust technique for reconstructing former glacier dynamics and may be applied to test geomorphological interpretations of former mountain glaciation

the thermal stability of near surface ground ice on mars the existence of subsurface water ice on mars has been predicted in several theoretical studies1 5 but there are no definitive observations of its present distribution geomorphic features on the surface of mars have been widely interpreted as evidence for the presence of ground ice6 12 but many of these features are found at near equatorial latitudes where thermal models have predicted that near surface water ice should not be stable under present climate conditions3 13 14 here i present the results of thermal calculations which show that observed geographic variations in the thermal and reflectance properties of martian soils significantly affect subsurface temperatures my results indicate that in certain regions ground ice deposits could exist much closer to the surface and much closer to the equator than previously thought in the future these deposits could be a valuable resource for human exploration15

evidence for heinrich event 1 in the british isles in the north irish sea basin isb sedimentary successions constrained by ams 14c dates obtained from marine microfaunas record three major palaeoenvironmental shifts during the last deglacial cycle i marine muds cooley point interstadial dated to between 16 7 and 14 7 14c kyr bp record a major deglaciation of the isb following the late glacial maximum lgm ii terminal outwash and ice contact landforms killard point stadial were deposited during an extensive ice readvance which occurred after 14 7 14c kyr bp and reached a maximum extent at ca 14 14c kyr bp at this time the lowlands surrounding the north isb were drumlinised coeval flowlines reconstructed from these bedforms end at prominent moraines killard point bride st bees and indicate contemporaneity of drumlinisation from separate ice dispersal centres substrate erosion by fast ice flow and subglacial sediment transfer to ice sheet margins in north central ireland bed reorganisation associated with this fast ice flow phase involved overprinting and drumlinisation of earlier transverse ridges rogen type moraines by headward erosion along ice streams that exited through tidewater ice margins this is the first direct terrestrial evidence that the british ice sheet bis participated in heinrich event 1 h1 iii regional mud drapes directly overlying drumlins record high relative sea level rsl with stagnation zone retreat after 13 7 14c kyr bp rough island interstadial elsewhere in lowland areas of northern britain ice marginal sediments and morainic belts record millennial scale oscillations of the bis which post date the lgm advance on to the continental shelf and pre date the loch lomond stadial younger dryas advance in the highlands of western scotland ca 11 10 14c kyr bp in western northwestern and northern ireland killard point stadial h1 ice limits are reconstructed from ice flow lines that are coeval with those in the north isb and end at prominent moraines on the scottish continental shelf possible h1 age ice limits are reconstructed from dated marine muds and associated ice marginal moraines it is argued that the last major offshore ice expansion from the scottish mountains post dated ca 15 14c kyr bp and is therefore part of the h1 event in eastern england the stratigraphic significance of the dimlington silts is re evaluated because evidence shows that there was only one major ice oscillation post dating ca 18 14c kyr bp in these lowlands in a wider context the sequence of deglacial events in the isb widespread deglaciation of southern part of the bis major readvance during h1 ice sheet collapse is similar to records of ice sheet variability from the southern margins of the laurentide ice sheet lis well dated ice marginal records however show that during the killard point readvance the bis was at its maximum position when retreat of the lis was well underway this phasing relationship supports the idea that the bis readvance was a response to north atlantic cooling induced by collapse of the lis 1998 john wiley sons ltd

a critical review of the glaciomarine model for irish sea deglaciation evidence from southern britain the celtic shelf and adjacent continental slope in support of their glaciomarine model for the deglaciation of the irish sea basin eyles and mccabe cited the occurrence of distal glaciomarine mud drapes onshore in the isles of scilly and north devon and of arctic beach face gravels and sands around the shores of the celtic sea glacial and sea level data from the southern part of the irish sea in the terminal zone of the ice stream and the adjacent continental slope are reviewed here to test this aspect of the model the suggestion that the glacial sequences of both the isles of scilly and fremington in north devon are glaciomarine mud drapes is rejected an actively calving tidewater margin only occurred early in the deglacial sequence close to the terminal zone in the south central celtic sea relative sea levels were lower and therefore glacio isostatic depression less than envisaged in the glaciomarine model geochronological sedimentological and biostratigraphical data indicate that the raised beach sequences around the shores of the celtic sea and english channel were deposited at or during regression soon after interglacial eustatic highstands evidence for ice rafting at a time of high relative sea levels is restricted to a phase s earlier than the late devensian these data indicate that the raised beach sequences have no bearing on the style of irish sea deglaciation copyright 2001 john wiley sons ltd

global to local scale parameters determining relative sea level changes and the post glacial isostatic adjustment of great britain abstract observations of relative sea level rsl change in great britain since 16 kyr bp and models of post glacial isostatic adjustment provide constraints on reconstructions of the british and antarctic ice sheets from the last glacial maximum to the present we use the global model from an earlier investigation modified ice 4g vm2 with lithospheric thickness 90 km which gives good rsl fits globally as well as for much of the british data a revised ice model for great britain that fits with recently published observations on ice limits and heights fails to explain all the misfits between rsl observations and predictions much more significant improvements result from models that incorporate a different chronology for the partial deglaciation of antarctica while keeping the total ice melt 17 m the same as in ice 4g vm2 the results suggest antarctic melting of 3 m ice equivalent sea level by 15 kyr bp only 1 m contribution to the 24 m rise of mwp1a with the major melting 12 5 kyr bp and a small amount of melting 1 0 0 3 m between then and 3 or 2 kyr bp these modifications produce rsl predictions for barbados that show the major changes in rate of sea level rise but with an offset up to 1 kyr compared to the observations possible explanations that remain to be investigated further are a delay in the melting of ice from some other region a reduction in the total melt derived from antarctica and a refinement of the 1 kyr temporal resolution assumed in the construction of the theoretical solution

exposure age constraints on the extent timing and rate of retreat of the last irish sea ice stream abstract we report 23 cosmogenic isotope exposure ages 10be and 36cl relating to the maximum extent and deglaciation chronology of the irish sea ice stream isis which drained the sw sector of the last british irish ice sheet these show that the isis failed to reach the preseli hills of north pembrokeshire yet extended southwards to impinge on northern isles of scilly 50 n during the last glacial maximum four samples from western anglesey demonstrate deglaciation of the southern irish sea basin by c 20 18 ka and two from the ll n peninsula in northwest wales if valid suggest deglaciation by c 23 22 ka followed by gradual oscillatory northwards retreat of the ice margin for over 3000 years an alternative interpretation of our data suggests that ice reached scilly as late as 22 21 ka then retreated 450 km northwards within the following three millennia possibly in response to sea level rise and or intrinsic reorganisation within the last british irish ice sheet samples from upland source areas of the isis in nw england and sw scotland produced exposure ages 14 3 ka suggesting possible persistence of ice in such areas into the lateglacial interstade of 14 7 12 9 ka

modification of peripheral mountain ranges by former ice sheets the brecon beacons southern uk abstract the brecon beacons in southern wales is a large upland area 900 km 2 close to the periphery of the former british irish ice sheet the geomorphology of the brecon beacons highlands and surrounding areas was mapped using satellite imagery and a digital elevation model dem a fragmentary pattern of glacial lineations is inferred to represent ice build up in the mountains a more coherent set of glacial lineations formed by southward ice flow across the area from the welsh ice cap represents recession from the last glacial maximum lgm during this phase the brecon beacons acted as an obstacle deflecting the ice around higher terrain most of the higher terrain in the brecon beacons therefore appears to have escaped significant glacial erosion during both phases of ice flow due to cold based ice or low basal ice velocities beneath a local ice cap landforms previously interpreted as cirques in fact have v shaped profiles and lack evidence of major over deepening they are interpreted to have been formed primarily by processes other than glacial erosion the overall impact of glaciation in the brecon beacons appears to be limited primarily to the time when the area was over run by the welsh ice cap and the influence of local glaciation has been minimal this study has two main implications for landscape evolution in mountain ranges that lie at the periphery of former ice sheets first due to the presence of cold based ice or low basal ice velocities beneath a local ice cap it may be possible to find fragmentary traces of pre lgm ice flow second the pattern of glacial lineations in and around the brecon beacons indicates that peripheral mountain ranges may have deflected ice flow at the lgm resulting in low basal ice flow velocities and possible frozen bed conditions over higher terrain which consequently resulted in ineffective glacial erosion within the mountains themselves

paleoclimate of mars as captured by the stratigraphic record in gale crater a kilometers thick sedimentary sequence in gale crater exhibits stratigraphic changes in lithology that are consistent with transitions in aqueous and climatic conditions purported to be global in scale the sequence is divided into two formations where the lower formation exhibits a net transition in mineralogy from clay sulfate to sulfate oxide assemblages and is separated from the overlying upper formation by an erosional unconformity superposition and crater counts suggest strata in the lower formation lie along the noachian hesperian time stratigraphic boundary whereas beds in the upper formation which lack signatures indicative of clay minerals or sulfates are thinner more regularly spaced and clearly younger the observed stratigraphic trends are consistent with the rocks at gale crater recording a global transition from a climate favorable to clay mineral formation to one more favorable to forming sulfates and other salts

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

structural and depositional evidence for repeated ice marginal oscillation along the eastern margin of the late devensian irish sea ice stream abstract late devensian glacigenic sediments and landforms along the north west coast of wales document the advance and subsequent retreat of the eastern margin of an irish sea ice stream that met coalesced and ultimately uncoupled from ice radiating outwards from the adjacent welsh ice cap centred over snowdonia across the boundary between the two former ice masses is a set of sediment landform assemblages that reflect rapidly changing erosional and depositional conditions during ice interaction from the inner part of the ice stream the assemblages range outwards from a subglacial depositional assemblage characterised by drumlin swarms through a subglacial erosional assemblage marked by prominent bedrock scours and large subglacial rock channels through an ice marginal assemblage identified by closely spaced glaciotectonised push moraines and intervening marginal sandur troughs into a freely expanding proglacial sandur and lacustrine delta assemblage the ice marginal assemblage provides evidence for numerous oscillatory episodes during retreat and at least 20 ice marginal limits can be identified at least 11 of these display multiple criteria for identifying readvance and in the ideal case is characterised by a moraine form built by localised tectonic stacking of diamict to the rear fronted by a clastic wedge of ice front alluvial fan gravel and intercalated flow till the distribution of sediment landform assemblages suggests a highly dynamic convergent ice stream flow pattern with high ice velocity a sharply delineated lateral shear margin pervasive ice marginal glaciotectonic deformation and a tightly focused ice marginal sediment delivery system all signature characteristics of contemporary ice streams

glaciotectonized quaternary sediments at dinas dinlle gwynedd north wales and their bearing on the style of deglaciation in the eastern irish sea abstract the sedimentology and structure of late quaternary sediments exposed in a coastal section at dinas dinlle north wales are described the deposits from two small hills the northern one being more prominent and containing northward dipping units of gravel and diamicton bounded by clay lined thrust faults the southern hill comprises complex folded sands and gravels overlying a basal till surface high resolution seismic surveys along the beach 50 m west of the cliffs show a roughly horizontal rockhead lying some 35 m below beach level and demonstrate that thrust faults penetrate the entire quaternary sequence to a detachment immediately above rockhead thrust units in the exposed cliff section show excellent correlation with the seismic sequence 50 m to the west indicating a strike of 080 260 balanced cross section techniques were applied to an initial simple layered sequence comprising a lower irish sea till overlain by a coarsening upwards sand to gravel unit followed by upper till mixed lithology including welsh and northern provenance and finally an upper gravel unit shortening of approximately 54 is estimated within the thrust sequence it is concluded that the two isolated hills at dinas dinlle are erosional remnants of a formerly more extensive push moraine extending westwards into caernarfon bay which has now been truncated by coastal retreat deglaciation of the area was interrupted by ice sheet readvance towards 170 across a proglacial surface

periglacial trimlines in the scottish highlands abstract two periglacial weathering limits have been identified on mountains in the highlands of scotland the lower has been interpreted as a periglacial trimline marking the upper limits of loch lomond younger dryas stade glaciers and has been employed to reconstruct the dimensions of parts of the main west highland icefield and certain smaller glaciers and icefields interpretation of the upper weathering limit has been more contentious but recent research has demonstrated 1 significant contrasts in the degree of bedrock weathering above and below this limit 2 that gibbsite a pre devensian weathering product is abundant above the limit but rare in soils farther downslope 3 that the isotopic 26al age of bedrock exposures above the limit greatly exceeds that at lower altitudes and 4 that the altitude of the weathering limit descends regularly along former ice sheet flowlines collectively these attributes suggest that the upper weathering limit is a periglacial trimline defining the maximum altitude of the last ice sheet calculated basal shear stress values are consistent with this interpretation which implies that the mainland ice shed lay at ca 900 m in wester ross and descended gently northwards whilst harris and lewis in the outer hebrides supported an independent ice cap that achieved a maximum altitude of ca 700 m wider implications of this interpretation and the future potential for ice sheet reconstruction are explored

trimlines blockfields mountain top erratics and the vertical dimensions of the last british irish ice sheet in nw scotland periglacial trimlines separating glacially eroded lower slopes from blockfield covered plateaus on british and irish mountains have been interpreted either 1 in terms of representing the maximum altitude of the last ice sheet during the last glacial maximum lgm or 2 as a thermal boundary separating wet based ice at pressure melting point from cold based ice on summit plateaus we test these competing hypotheses through 10be exposure dating of high level erratic boulders above trimlines on five mountains in nw scotland nine out of 14 erratics yielded post lgm exposure ages ranging from 14 0 0 7 ka to 16 5 0 9 ka or from 14 9 0 9 ka to 17 6 1 1 ka depending on the 10be production rate employed in exposure age calculation these ages refute hypothesis 1 as they imply that the last ice sheet overtopped the mountains preservation of apparently intact blockfields on the summits implies cold based ice cover supporting hypothesis 2 as altitudinally consistent high level trimlines extend from our sampled sites across much of nw scotland and the hebrides our conclusions apply to all trimlines in this broader area and probably to all high level trimlines elsewhere in the british isles preservation of blockfields under cold based ice is consistent with blockfield evolution on plateaus throughout much or all of the quaternary averaged exposure ages of 15 16 ka for plateau top erratics implies nunatak emergence from the downwasting ice sheet prior to a regional readvance of the ice margin the wester ross readvance and before rapid warming at 14 7 ka at the onset of the lateglacial interstade but after the timing of ice sheet thinning as retrodicted by recent proxy climate driven thermo mechanical coupled models our findings provide an additional constraint on the future development of such models by implying that high level trimlines represent the altitude of a former transition zone between ice at pressure melting point and ice below pressure melting point

weathering patterns in high latitude regolith 1 large areas distributed on the earth s surface are covered by regolith an unconsolidated heterogeneous material overlying bedrock in high latitude areas most of the land surface has been reworked and eroded by both glacial and fluvial processes leaving only remnants of formerly extensive regolith covers in an effort to further the understanding of weathering patterns and processes in old regolith covers a comprehensive study of localities spread across norway was carried out on the basis of the distribution of minerals and elements within regolith as well as its internal structure and geomorphologic setting we ascertained that it was formed in situ and originated in pre quaternary times there are similarities between the study sites with respect to regolith thickness zonation and composition the chemical index of alteration cia and the weathering index of parker wip suggests that the degree of chemical weathering in the regolith is advanced compared to the parental bedrock with a maximum change of over 80 which indicates a substantial increase in the proportion of secondary versus primary minerals mineral analysis identified kaolinite and gibbsite which are considered indicative of advanced weathering and therefore support this observation on the basis of statistical relationships between different grain size fractions 125 m we observed a consistent pattern which revealed that physical weathering becomes progressively less important in the production of grains smaller than 32 m on the basis of this finding we infer that chemical weathering progressively dominates the production of fine silt very fine silt and clay whereas physical weathering primarily controls the production of grain size fractions larger than 32 m this particular pattern is suggested to be an intrinsic feature in the formation of weathered high latitude regolith

devensian glacigenic sedimentation and landscape evolution in the cardigan area of southwest wales hambrey michael davies j r glasser n f waters r a 2001 devensian glacigenic sedimentation and landscape evolution in the cardigan area of southwest wales journal of quaternary science 16 5 pp 455 482 rae2008

extent and deglacial chronology of the last british irish ice sheet implications of exposure dating using cosmogenic isotopes over 160 10be and 36cl exposure ages pertaining to the extent and chronology of the last british irish ice sheet biis are critically reviewed despite uncertainties inherent in the use of exposure ages this approach has demonstrated that at the last glacial maximum lgm ca 26 21 ka the biis extended over all low ground in scotland and all or almost all of ireland consistent with recent models depicting extension of the last biis to the atlantic shelf edge all exposure ages obtained for high level sites above trimlines on the mountains of northwestern scotland and ireland pre date the lgm this finding confirms that high plateaux in these areas escaped significant glacial erosion probably under a protective cover of cold based glacier ice that remained frozen to the underlying substrate in terms of deglaciation chronology the southern irish sea basin was probably deglaciated by 19 18 ka with extensive deglaciation of low ground in ireland and northeastern scotland prior to ca 14 5 ka ice cover on low ground in northwestern scotland apparently persisted after 14 0 ka suggesting survival of ice in favourable locations during the lateglacial interstade ca 14 5 12 9 ka attempts to date readvances have had mixed success the wester ross readvance in northwestern scotland was initially dated to ca 16 3 ka but more recent research implies a much younger age ca 14 0 13 5 ka exposure ages indicating a prolonged stillstand during ice sheet retreat in the cairngorms at ca 14 5 14 0 ka conflict with ages obtained on postglacial rockslides and basal radiocarbon dates which indicate deglaciation before ca 15 5 15 0 ka exposure dating has been successfully employed to confirm a loch lomond stadial ca 12 9 11 5 ka age for moraines in several mountain areas and to constrain the minimum altitude of the ice cap that extended over the western grampians at that time copyright 2009 john wiley sons ltd

observational evidence from direct current measurements for propagation of remotely forced waves on the shelf off the west coast of india 1 we use data from six acoustic doppler current profiler adcp moorings deployed during march september 2008 on the continental shelf and slope off bhatkal goa and jaigarh on the central west coast of india to present evidence for poleward propagation of shelf or coastal trapped waves ctws wave propagation is seen on the shelf in the 20 40 day 10 14 day and 3 5 day period bands the lag from south to north indicates that remote forcing is important even at periods as short as 4 days using quikscat wind data we show that the contribution of remote forcing to the shelf west indian coastal current wicc is significant even when the local alongshore wind is strong as during the summer monsoon onset during may june and forces a strong local response that masks the effect of remote forcing forced wave calculations using ctw theory show that remote forcing of the wicc is present at all times but is most striking when the local winds are weak as during march april the ctw calculations show that the source region for the remote forcing may extend beyond the west coast into the gulf of mannar between india and sri lanka on the slope propagation is seen only at the 4 day period at higher periods the slope wicc decorrelates rapidly along the coast but upward phase propagation implying downward propagation of energy associated with poleward propagation is evident even at these higher periods

dimensions and chronology of the last ice sheet in western ireland abstract on the mountains of western ireland the upper limit of glacial evidence descends from 730 m in the connemara mountains to 400 m on achill island this limit is interpreted as a trimline marking the upper limit of erosive warm based ice implying that higher summits remained above a former ice sheet as nunataks or supported a cover of cold based ice significantly greater representation of gibbsite in soils above the trimline indicates that it relates to the last glacial stage 10 be exposure ages for bedrock samples above the trimline fall within the range 36 0 2 3 ka to 61 6 4 0 ka whereas ice scoured bedrock below the trimline yielded 10 be exposure ages 24 0 1 6 ka and in all but two cases 17 2 1 1 ka consistent with deglaciation after the lgm reconstruction of the minimum altitude of the lgm ice surface implies that inland ice was diverted northwestwards by an ice dome on the connemara mountains and extended at least 25 km offshore this evidence conflicts with previous accounts that place the lgm ice limit onshore and implies that recent models underestimate lgm ice thickness in western ireland

deglaciation of the irish sea basin a critique of the glaciomarine hypothesis the glaciomarine model for deglaciation of the irish sea basin suggests that the weight of ice at the last glacial maximum was sufficient to raise relative sea levels far above their present height destabilising the ice margin and causing rapid deglaciation glacigenic deposits throughout the basin have been interpreted as glaciomarine the six main lines of evidence on which the hypothesis rests sedimentology deformation structures delta deposits marine fauna amino acid ratios and radiocarbon dates are reviewed critically the sedimentological interpretation of many sections has been challenged and it is argued that subglacial sediments are common rather than rare and that there is widespread evidence of glaciotectonism density driven deformation associated with waterlain sediments is rare and occurs where water was ponded locally sand and gravel deposits interpreted as gilbert type deltas are similarly the result of local ponding or occur where glaciers from different source areas uncoupled they do not record past sea levels and the ad hoc theory of piano key tectonics is not required to explain the irregular pattern of altitudes the cold water foraminifers interpreted as in situ are regarded as reworked from irish sea sediments that accumulated during much of the late quaternary when the basin was cold and shallow with reduced salinities amino acid age estimates used in support of the glaciomarine model are regarded as unreliable radiocarbon dates from distinctive foraminiferal assemblages in northeast ireland show that glaciomarine sediments do occur above present sea level but they are restricted to low altitudes in the north of the basin and record a rise rather than a fall in sea level it is suggested here that the oldest dates around 17 000 yr bp record the first late devensian weichselian marine inundation above present sea level this accords with the pattern but not the detail of recent models of sea level change copyright 2001 john wiley sons ltd

sulfur species and biosignatures in sulphur springs valles caldera new mexico implications for mars astrobiology abstract a biogeochemical so 4 2 cycle was investigated in the acid hot springs of valles caldera new mexico using s isotopes and distribution of amino acids in 2007 a major contribution of so 4 2 in this modern volcanic setting came from oxidation of h 2 s from hydrothermal sources which largely increased so 4 2 concentrations up to 2550 mg l 1 and decreased ph down to 2 27 in surface water a relatively small variation of 34 s among the analyzed s bearing minerals 2 1 to 4 0 fumarole h 2 s 1 7 to 4 6 and dissolved so 4 2 in modern surface and groundwater 2 5 to 7 9 indicates poor evidence of s isotope biosignatures related to microbial disproportionation of elemental s to h 2 s and so 4 2 which in turn are not effectively captured in the hydrothermal minerals of the studied volcanic setting this is mainly due to prevailing contribution of reduced s forms from magmatic hydrothermal sources and considerably smaller microbial activity in acid hot spring areas although hydrothermal gypsum and elemental s effectively trap amino acids their preservation lifetimes in s bearing hydrothermal minerals appear to be small the minimal lifetimes are inferred to be the result of increased temperatures and rapid recycling time of s materials in hydrothermal settings landed missions to the martian surface at sites inferred to have experienced active hydrothermal activity similar to the one studied in valles caldera e g elevated volcanic s flux may provide valuable insight into geological and geochemical processes that have influenced the martian surface but may provide minimal potential for recording either amino acid or s isotopic biosignatures of an extinct martian ecosystem

sea level interannual variability along the west coast of india interannual sea level anomalies sla and the related thermocline variations along the west coast of india wci strongly impact the ecosystems fisheries and potentially the monsoon rainfall here we investigate the mechanisms driving the wci interannual sla using a linear continuously stratified ocean model which realistically simulates the leading northern indian ocean sla mode associated with the indian ocean dipole iod during for example positive iod events easterly wind anomalies near sri lanka in late summer and fall force downwelling coastal kelvin waves which induce positive wci sla within days meanwhile equatorial easterlies force upwelling kelvin waves that travel to wci through the bay of bengal coastal waveguide part of this opposite signal also transits slowly through the bay of bengal interior as rossby waves eventually yielding negative sla along the wci in winter the wci sla thus shifts from positive in fall to negative in winter during positive iod events

gibbsitic soils on former nunataks implications for ice sheet reconstruction x ray diffraction analyses of soils above and below a periglacial trimline developed across the basalts of the trotternish escarpment isle of skye scotland demonstrate that gibbsite is restricted to soils above the trimline this suggests that the gibbsite is a relict of pre late devensian weathering and that the trimline did not develop after the last ice sheet achieved its maximum thickness the sharpness of the boundary between frost weathered regolith and gibbsitic soils upslope and ice scoured bedrock associated with gibbsite free soils downslope suggests that the trimline represents the altitude of the last ice sheet at its maximum thickness rather than a former boundary between passive cold based ice and erosive warm based ice these findings illustrate how identification of high level periglacial trimlines and associated contrasts in clay mineralogy provide a means for constraining reconstructions of the form of the last ice sheets

the vertical dimensions of late devensian glaciation on the mountains of harris and southeast lewis outer hebrides scotland on north harris and southeast lewis a weathering limit separates glacially moulded bedrock on low ground from frost shattered bedrock and blockfields on high plateaux analysis of the depths of horizontal stress release joints demonstrates significant contrasts in bedrock weathering above and below this boundary and the survival of gibbsite only in soils above the weathering limit indicates that it represents the upper limit of late devensian glacial erosion the weathering limit declines regularly in altitude on either side of the former ice shed and is therefore interpreted as a periglacial trimline defining the upper limit of a locally nourished ice mass at its maximum extent rather than a former thermal boundary between protective cold based and erosive warm based ice calculated basal shear stress values are consistent with this interpretation the configuration of the trimline indicates that at the last glacial maximum the area supported an ice cap that achieved a maximum altitude of ca 700 m above present sea level and declined in altitude to the west northwest and east southeast at an average gradient of ca 20 m km 1 extrapolation of the dimensions of this ice cap suggests that it terminated ca 7 10 km west of the present coast of harris and was confluent with mainland ice a short distance east of the present coastline

postglacial relative sea level observations from ireland and their role in glacial rebound modelling the british isles have been the focus of a number of recent modelling studies owing to the existence of a high quality sea level dataset for this region and the suitability of these data for constraining shallow earth viscosity structure local to regional ice sheet histories and the magnitude timing of global meltwater signals until recently the paucity of both glaciological and relative sea level rsl data from ireland has meant that the majority of these glacial isostatic adjustment gia modelling studies of the british isles region have tended to concentrate on reconstructing ice cover over britain however the recent development of a sea level database for ireland along with emergence of new glaciological data on the spatial extent thickness and deglacial chronology of the irish ice sheet means it is now possible to revisit this region of the british isles here we employ these new data to constrain the evolution of the irish ice sheet we find that in order to reconcile differences between model predictions and rsl evidence a thick spatially extensive ice sheet of 600 700 m over much of north and central ireland is required at the lgm with very rapid deglaciation after 21 k cal yr bp copyright 2007 john wiley sons ltd

sulfate minerals and organic compounds on mars strong evidence for evaporitic sulfate minerals such as gypsum and jarosite has recently been found on mars although organic molecules are often codeposited with terrestrial evaporitic minerals there have been no systematic investigations of organic components in sulfate minerals we report here the detection of organic material including amino acids and their amine degradation products in ancient terrestrial sulfate minerals amino acids and amines appear to be preserved for geologically long periods in sulfate mineral matrices this suggests that sulfate minerals should be prime targets in the search for organic compounds including those of biological origin on mars

observed anomalous upwelling in the lakshadweep sea during the summer monsoon season of 2005 1 repeat near fortnightly expendable bathythermograph xbt transects made along kochi kavaratti kk shipping lane in the lakshadweep sea ls during 2002 2006 are examined to describe the observed year to year variability of upwelling during summer monsoon season sms among all the years the upwelling characterized by up sloping of 25 c isotherm is relatively weaker and persisted until november during sms of 2005 and is stronger during the sms of 2002 as a result of prolonged upwelling the sea surface temperature has shown cooling extending into the postmonsoon season the estimated marine pelagic fish landings along the southwest coast of india swci have also shown increase until december the governing mechanisms both in terms of local and remote forcings are examined to explain the observed anomalous upwelling during sms of 2005 the equatorward alongshore wind stress ws along the kk xbt transect persisted in a transient manner beyond september only during sms of 2005 the westerly wind bursts over the equator during the winter of 2004 2005 are both short lived and relatively weaker triggering weaker upwelling kelvin waves that propagated into ls in the following sms of 2005 the observed distribution of negative sea surface height anomaly in the ls is relatively weaker during the sms of 2005 and lasted longer the correlation analysis suggests that the local alongshore ws off the swci and the remote forcing from the southern coast of sri lanka has greater influence on the observed interannual variability of upwelling in the ls when compared to the remote forcing from the equator

formation of gypsum and bassanite by cation exchange reactions in the absence of free liquid h2o implications for mars 1 smectites and hydrated mg sulfate minerals have been identified in close association at various locations on the martian surface the hydration states of sulfates and smectites are dependent on temperature and relative humidity rh and therefore these minerals have the potential to affect cycling and bioavailability of h2o on mars we have conducted x ray powder diffraction experiments to investigate cycling of h2o within mixtures of ca bearing smectites and hydrated mg sulfate minerals under conditions of varying rh similar to those that exist at or just beneath the martian surface our experiments show that under conditions of varying rh cation exchange reactions occur between these two potential components of the martian regolith producing gypsum caso4 2h2o and bassanite caso4 0 5h2o in the absence of free liquid h2o cation exchange reactions were accompanied by significant loss of porosity warping of the sample surface and in some cases volume expansion the formation of ca sulfate minerals in these experiments provides evidence for the development of thin films of h2o at mineral surfaces and suggests that similar processes may operate at the arid surface of mars humidity driven cation exchange reactions between smectites and hydrated mg sulfate minerals may therefore play a role in shaping the present day martian surface and could have provided a transient source of h2o and nutrients e g major and trace elements and possibly organic micro macronutrients for putative microorganisms

glacial rebound of the british isles ii a high resolution high precision model summary observations of ice movements across the british isles and of sea level changes around the shorelines during late devensian time after about 25 000 yr bp have been used to establish a high spatial and temporal resolution model for the rebound of great britain and associated sea level change the sea level observations include sites within the margins of the former ice sheet as well as observations outside the glaciated regions such that it has been possible to separate unknown earth model parameters from some ice sheet model parameters in the inversion of the glaciohydro isostatic equations the mantle viscosity profile is approximated by a number of radially symmetric layers representing the lithosphere the upper mantle as two layers from the base of the lithosphere to the phase transition boundary at 400 km the transition zone down to 670 km depth and the lower mantle no evidence is found to support a strong layering in viscosity above 670 km other than the high viscosity lithospheric layer models with a low viscosity zone in the upper mantle or models with a marked higher viscosity in the transition zone are less satisfactory than models in which the viscosity is constant from the base of the lithosphere to the 670 km boundary in contrast a marked increase in viscosity is required across this latter boundary the optimum effective parameters for the mantle beneath great britain are a lithospheric thickness of about 65 km a mantle viscosity above 670 km of about 4 5 lo2 pa s and a viscosity below 670 km greater than 4 x lo2 pas

palaeoglaciology of the welsh sector of the british irish ice sheet this palaeoglaciological reconstruction based on the distribution of glacial lineations interpreted from satellite imagery considers the extent thickness and dynamics of the welsh ice cap and its interaction with the british irish ice sheet two major ice flow events were identified the oldest phase of ice flow event i is characterized by ice flowing from an ice dispersal centre situated over the higher terrain in north central wales and by ice thick enough to cover the mountain summits at this time the interior of the ice cap is inferred to have been dominated by cold based ice during the growth of the welsh ice cap it became confluent with the british irish ice sheet the welsh ice cap at this time was again sufficiently thick to submerge the highest mountain summits the youngest detected phase of ice flow event ii was marked by an abrupt change in the dynamics of the welsh ice cap during event ii the welsh ice cap was drained by at least four ice streams which followed major troughs in northern and eastern wales

stability of mg sulfate minerals in the presence of smectites possible mineralogical controls on h2o cycling and biomarker preservation on mars abstract martian layered deposits and regolith at gale crater may contain multiple hydrated mineral phases tentatively identified as hydrated mg sulfate minerals and smectites we have used humidity buffer experiments to assess the stability of hydrated mg sulfate minerals in the presence of smectites in order to improve our understanding of the probable behavior of mg sulfate minerals within multiphase geological materials on mars a series of long term experiments employed temperature 25 to 23 c and relative humidity rh conditions 7 100 that emulate near equatorial martian surface conditions our results indicate that the hydration state of mg sulfate minerals is affected by the presence of rh sensitive clay minerals i e smectites the formation of gypsum and bassanite in dry mineral mixtures via cation exchange between ca bearing smectite and mg sulfate minerals indicates that ca sulfate minerals may be useful indicators of h 2 o and metal mobility at mars relevant temperatures 25 to 23 c the presence of smectites also suppresses deliquescence of mg sulfate minerals at 100 rh and low but non freezing temperatures co existence of smectites and mg sulfate minerals appears to buffer rh within mixtures of these minerals which can result in production or preservation of mg sulfate phases that are inconsistent with measured values of atmospheric rh consequently hydrated mg sulfate minerals may persist beyond their expected t rh equilibrium fields on longer timescales within smectite mgso 4 mixtures than in the pure mgso 4 h 2 o system dehydration of highly hydrated mg sulfate minerals appears to slow in the presence of smectite which may have important implications for long term preservation of organic biosignatures within mg sulfate crystals on mars together these observations suggest that mg sulfate mineral behavior and thus cycling and bioavailability of h 2 o and metals may be impacted by the presence of smectites within mineralogically complex martian layered deposits and regolith

crystal molds on mars melting of a possible new mineral species to create martian chaotic terrain images sent back by the mars exploration rover opportunity from the meridiani planum show sulfate rich rocks containing plate shaped voids with tapered edges that are interpreted as crystal molds formed after a late stage evaporite mineral has been removed experimental studies of the mgso4 h2o system at low temperatures reveal that the triclinic phase mgso4 11h2o exhibits a crystal morphology that matches the shapes of these molds mgso4 11h2o melts incongruently above 2 c to a mixture of 70 epsomite mgso4 7h2o and 30 h2o by volume when this occurs while crystals are encased in sediment plate shaped voids remain the existence of ice low surface temperatures and the high sulfate content of surface rocks and soil on mars makes mgso4 11h2o a possible mineral species near the surface at high latitudes or elsewhere in the subsurface if an evaporite layer contained a significant amount of this phase incongruent melting would result in a rapid release of a large volume of water and could explain some of the landform features on mars that are interpreted as outflow channels mgso4 11h2o would not survive a sample return mission unless extraordinary precautions were taken

glacial trimlines to identify former ice margins and subglacial thermal boundaries a review and classification scheme for trimline expression abstract reconstructions of former ice sheets and glaciers provide important palaeoglaciological information about their behaviour in response to climate changes glacial trimlines record both the margin positions and palaeo ice thickness enabling the production of empirically constrained 3 dimensional reconstructions however the literature review into the characteristics interpretation and use of glacial trimlines here presented shows that these features have been under utilised and are poorly described in the existing literature with a confusing terminology currently in use a new classification scheme and terminology for trimline identification and interpretation is developed to better facilitate further research into these common features of glacierised and formerly glaciated landscapes

allometric development of glacial cirque form geological relief and regional effects on the cirques of wales headward and downward erosion near glacier sources at rates exceeding fluvial erosion is important in recent discussions of orogen development and the limits to relief this relates to a long history of debate on how the form of glacial cirques develops which can be advanced by relating shape to size in large data sets for 260 cirques in wales this confirms different rates of enlargement in the three dimensions faster in length than in width and slower in vertical dimension whether expressed as overall height range axial height range or wall height maximum gradient plan closure and number of cols increase with overall size this allometric development applies over different cirque types regions and rock types headwall retreat often by collapse following glacial erosion at the base is faster than downward erosion welsh cirques form a scale specific population and as in other regions size variables follow gaussian distributions on a logarithmic scale as in england width commonly exceeds length vertical dimensions correlate with length more than with width cirque form varies with geology but also with relief as both vary between mountain groups the main contrast is between larger better developed cirques and higher relief on volcanic rocks in the north west and smaller less developed cirques and lower relief on sedimentary rocks in the south