on the wave number spectrum of oceanic mesoscale variability observed by the seasat altimeter variations of sea surface height measured by the seasat altimeter in nearly repeat orbits during the last 24 days of the mission are used to compute the wave number spectrum of mesoscale variability in various parts of the oceans the instrument noise level 150 cm2 cycles km has limited the resulting oceanic spectrum to wavelengths longer than 100 km we found that the characteristics of the oceanic spectrum are dependent on the energy level of the mesoscale variability in the high energy areas close to major current systems most of the energy is contained at wavelengths longer than 250 km at wavelengths shorter than 250 km the spectrum basically follows a k 5 k is wave number dependence in the low energy areas remote from major current systems the spectrum follows a k 1 dependence at wave lengths from 100 to 1000 km based on the assumption of horizontal isotropy of mesoscale variability scalar wave number spectra of sea surface height and geostrophic kinetic energy are also presented dynamical implications of these spectra are discussed the effects of residual geoid and atmospheric water vapor on the computed oceanic spectra have been rigorously examined it was found that the general characteristics of the oceanic spectra were not significantly affected by them

time scales of submesoscale flow inferred from a mooring array abstractwhile the distribution of kinetic energy across spatial scales in the submesoscale range 1 100 km has been estimated from observations the associated time scales are largely unconstraine

an assessment of the importance of chaotic stirring and turbulent mixing on the west florida shelf application of dynamical systems tools has recently revealed in surface ocean currents produced by a hybrid coordinate ocean model hycom simulation the presence of a persistent large scale lagrangian coherent structure lcs on the southern portion of the west florida shelf wfs consistent with satellite tracked drifter trajectories this lcs constitutes a cross shelf barrier for the lateral transport of passive tracers because of the constraints that the above lcs as well as smaller scale lcss lying shoreside can impose on pollutant dispersal and its potentially very important biological consequences a study was carried out on the nature of the surface ocean lagrangian motion on the wfs the analysis is based on the same simulated surface ocean velocity field that has been able to sustain the aforementioned persistent cross shelf transport barrier examination of several diagnostics suggests that chaotic stirring dominates over turbulent mixing on time scales of up to two months or so more specifically it is found on those time scales that tracer evolution at a given length scale is governed to a nonnegligible extent by coarser scale velocity field features fluid particle dispersion is spatially inhomogeneous and the lagrangian evolution is more irregular than the driving eulerian flow

global wavenumber spectrum with corrections for altimeter high frequency noise the altimetry wavenumber spectra of sea surface height ssh provide a unique dataset for testing of geostrophicturbulence whilesshspectralslopesofk 211 3 andk 25 areexpectedfromtheoriesandnumerical simulations the altimetry spectra from the original unfiltered and instrument noise corrected data often are too shallow falling between k 22 and k 23 in this study the possibility that the flattened spectral slopes are partly due to contamination by unresolved high frequency 10 days motions is tested a spatiotemporal filter based on empirical orthogonal function expansion eof is used to remove the temporally incoherent signals the resulting spectral slopes are much steeper than in the previous studies over 70 of the revised global spectral estimates excluding the tropics are above k 23 moreover in high energy regions like the gulf streamandkuroshio thespectralslopesare aboutk 25 whichis consistentwiththeclassicalquasigeostrophic qg turbulence the spectral slopes are validated with the eddy kinetic energy eke spectra from shipboard acoustic doppler current profiler adcp measurements in the high and low energy regions

relative sea level changes from ne ireland during the last glacial termination deglacial sea level records from ne ireland between 21 and 11 cal ka bp record marine transgressions and sensitive lithospheric responses to ice loading the sawtooth sea level curve contains four intervals characterized by 1 strong net uplift subaerial channelling and a global meltwater pulse 21 19 cal ka bp 2 ice loading isostatic depression and high relative sea level 19 17 5 cal ka bp 3 ice loading renewed isostatic depression and high relative sea level for 1000 years 17 14 5 cal ka bp 4 catastrophic ice wastage rapid uplift and lowstand 14 5 13 cal ka bp geophysical models do not capture these fluctuations

deglacial chronology from county donegal ireland implications for deglaciation of the british irish ice sheet in the north of ireland ice advanced northwards onto the continental shelf from inland centres of dispersion at the last glacial maximum we constrain the timing of three subsequent events by accelerator mass spectrometry 14 c dating of marine microfaunas from muds at corvish county donegal early and rapid deglaciation of the continental shelf off northwestern ireland occurred before 17 1 k 14 c years bp when marine muds formed in trawbreaga bay ice subsequently readvanced into the bay some time between 15 0 and 14 0 k 14 c years bp and compressed contemporary sea stacks and beach cobbles into a ridge at ballycrampsey early deglacial muds were deformed during this ice readvance and redeposited with stratigraphically inverted 14 c ages between 16 0 and 15 2 k 14 c years bp the deformed mud is overlain by undeformed laminae deposited during the final deglaciation of the area after 14 1 k 14 c years bp the early deglaciation in the north at c 17 k 14 c years bp is correlative with deglaciation recorded in the irish sea basin western ireland and northeastern scotland indicating a response of the entire british irish ice sheet to early warming of the north atlantic ocean that resulted in a loss of up to two thirds of its mass subsequent ice sheet readvance between 15 0 and 14 1 k 14 c years bp in the north is part of a widespread response of the british irish ice sheet to heinrich event 1 during the killard point stadial high relative sea levels that accompanied deglaciation at 17 k 14 c years bp and again at 14 1 k 14 c years bp indicate substantial loading and attendant isostatic depression by the british irish ice sheet

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

wavenumber spectrum in the gulf stream from shipboard adcp observations and comparison with altimetry measurements the wavenumber spectra for velocity and temperature in the gulf stream region are calculated from a decade 1994 2004 of shipboard acoustic doppler current profiler adcp measurements taken as part of the oleander project the velocity and temperature spectra have comparable magnitude in terms of the kinetic and potential energy and both indicate a k 23 slope in the mesoscales in contrast the corresponding velocity spectrum determined from satellite altimetry sea surface heights yields a significantly higher energy level and a k 22 slope the discrepancy between altimeter derived and directly measured velocity spectra suggests that altimetric velocity probably is contaminated by noise in sea surface height measurement also the k 23 slope which appears to be in agreement with two dimensional quasigeostrophic turbulence theory does not support the contemporary surface quasigeostrophic theory these results highlight large gaps in the current understanding of the nature of surface geostrophic turbulence

the last glacial maximum in the north sea basin micromorphological evidence of extensive glaciation despite a long history of investigation critical issues regarding the last glacial cycle in northwest europe remain unresolved one of these refers to the extent timing and dynamics of late devensian weichselian glaciation of the north sea basin and whether the british and scandinavian ice sheets were confluent at any time during this period this has been the result of the lack of the detailed sedimentological data required to reconstruct processes and environment of sediments recovered through coring this study presents the results of seismic sedimentological and micromorphological evidence used to reconstruct the depositional processes of regionally extensive seismic units across the north sea basin thin section micromorphology is used here to provide an effective means of discriminating between subglacial and glacimarine sediments from cored samples and deriving process based interpretations from sediment cores on the basis of micromorphology critical formations from the basin have been reinterpreted with consequent stratigraphic implications within the current stratigraphic understanding of the north sea basin a complex reconstruction is suggested with a minimum of three major glacial episodes inferred on at least two occasions during the weichselian devensian the british and scandinavian ice sheets were confluent in the central north sea whilst micromorphology can provide much greater confidence in the interpretation of late quaternary offshore stratigraphic sequences it is noted that a much better geochronology is required to resolve key stratigraphic issues between the onshore and offshore stratigraphic records copyright 2006 john wiley sons ltd

characterizing the transition from balanced to unbalanced motions in the southern california current author s chereskin teresa k rocha cesar b gille sarah t menemenlis dimitris passaro marcello

late quaternary sea level changes crustal movements and coastal evolution in northumberland uk northumberland lies in the transition between holocene emergence and submerg ence and is thus a critical zone for testing models of isostatic rebound we have collected data from this area to reconstruct relative sea level changes and lateral coastline movements for the last 14000 y these are deposits from tidal marsh back barrier wetland and terrestrial environ ments producing 47 sea level index points from 12 sites there is no unequivocal evidence for late devensian sea levels above present and the reliable sea level index points are restricted between 26 m and 12 5 m relative to present and 9 0 2 5 kyr cal bp analysis of these quantifies differential responses to glacio and hydroisostatic rebound with the northern sites recording a mid holocene sea level maximum ca 2 5 m above present whereas the southern sites show a maximum ca 0 5 m above present these observations show a reasonable fit with the predictions from quantitative models of glacio and hydroisostatic rebound but there is currently no unique solution of earth and ice model parameters that will explain all the sea level observations copyright 2000 john wiley sons ltd

sedimentary evidence for deforming bed conditions associated with a grounded irish sea glacier southern ireland along the south coast of ireland a shelly diamict facies the irish sea till has been variously ascribed to subglacial deposition by a grounded irish sea glacier or to glacimarine sedimentation by suspension settling and iceberg rafting observations are presented here from five sites along the south coast to directly address this question at these sites sedimentary evidence is preserved for the onshore advance of a grounded irish sea glacier which glacitectonically disturbed and eroded pre existing sediments and redeposited them as deformation till recession of this irish sea glacier resulted in the damming of ice marginal lakes in embayments along the south coast into which glacilacustrine sedimentation then took place these lake sediments were subsequently glacitectonised and reworked by overriding glacier ice of inland origin which deposited deformation till on top of the succession there is no evidence for deposition of the irish sea diamicts by glacimarine sedimentation at these sites the widespread development of subglacial deforming bed conditions reflected the abundance of fine grained marine and lacustrine sediments available for subglacial erosion and reworking stratigraphical and chronological data suggest that the advance of a grounded irish sea glacier along the south coast occurred during the last glaciation and this is regionally consistent with marine geological data from the celtic sea these observations demonstrate extension of glacier ice far beyond its traditional limits in the celtic sea and on land in southern ireland during the last glaciation and remove the stratigraphical basis for chronological differentiation of surficial glacial drifts and thus the munsterian glaciation in southern ireland copyright 2001 john wiley sons ltd

diagnosing lateral mixing in the upper ocean with virtual tracers spatial and temporal resolution dependence several recent studies diagnose lateral stirring and mixing in the upper ocean using altimetry derived velocity fields to advect virtual particles and fields offline however the limited spatiotemporal resolution of altimetric maps leads to errors in the inferred diagnostics because unresolved scales are necessarily imperfectly modeled the authors examine a range of tracer diagnostics in two models of baroclinic turbulence the standard phillips model in which dispersion is controlled by large scale eddies and the eady model where dispersion is determined by local scales of motion these models serve as a useful best and worst case comparison and a valuable test of the resolution sensitivity of tracer diagnostics the effect of unresolved scales is studied by advecting tracers using model velocity fields subsampled in space and time and comparing the derived tracer diagnostics with their true value obtained from the fully resolved flow the authors find that eddy diffusivity and absolute dispersion which are governed by largescaledynamics areinsensitivetospatialsamplingerrorin eitherflow measuresthatdependstronglyonsmall scales such as relative dispersion andfinite timelyapunov exponents are highly sensitive to spatial sampling in the eady model temporal sampling error is found to have a more complicated behavior because of the onset of particle overshoot leading to scrambling of lagrangian diagnostics this leads to a potential restrictionontheutilityofrawaltimetrymapsforstudyingmixingintheupperocean theauthorsconcludethat offline diagnostics of mixing in ocean flows with an energized submesoscale should be viewed with some caution

the role of mixed layer instabilities in submesoscale turbulence upper ocean turbulence at scales smaller than the mesoscale is believed to exchange surface and thermocline waters which plays an important role in both physical and biogeochemical budgets but what energizes this submesoscale turbulence remains a topic of debate two mechanisms have been proposed mesoscale driven surface frontogenesis and baroclinic mixed layer instabilities the goal here is to understand the differences between the dynamics of these two mechanisms using a simple quasi geostrophic model the essence of mesoscale driven surface frontogenesis is captured by the well known surface quasi geostrophic model which describes the sharpening of surface buoyancy gradients and the subsequent breakup in secondary roll up instabilities we formulate a similarly archetypical eady like model of submesoscale turbulence induced by mixed layer instabilities the model captures the scale and structure of this baroclinic instability in the mixed layer a wide range of scales are energized through a turbulent inverse cascade of kinetic energy that is fuelled by the submesoscale mixed layer instability major differences to mesoscale driven surface frontogenesis are that mixed layer instabilities energize the entire depth of the mixed layer and produce larger vertical velocities the distribution of energy across scales and in the vertical produced by our simple model of mixed layer instabilities compares favourably to observations of energetic wintertime submesoscale flows suggesting that it captures the leading order balanced dynamics of these flows the dynamics described here in an oceanographic context have potential applications to other geophysical fluids with layers of different stratifications

radiocarbon constraints on the history of the western irish ice sheet prior to the last glacial maximum accelerator mass spectrometer c 14 dating of in situ monospecific marine microfaunas and reworked shells records high relative sea level on the western coast of ireland between ca 40 and 19 call calibrated ka requiring substantial isostatic loading by the irish ice sheet iis during that interval glacial and marine deposits also record a rapid fluctuation of the us margin onto the continental shelf ca 28 cal ka evidence that the coast was not subsequently overridden by the iis indicates that at least for this sector of the ice sheet the ice margin during the last glacial maximum lgm was less extensive than the 28 cal ka event our data from western ireland support c 14 and cl 36 chronologies from the irish sea basin in identifying an us that was as extensive and thick as the lgm iis for much of the 20 k y interval prior to the lgm

subglacial bedform geomorphology of the irish ice sheet reveals major configuration changes during growth and decay the belated realisation that ribbed rogen moraines form such an integral part of irish geomorphology and the piecemeal approach to previous drumlin mapping is probably responsible for the highly contrasting views of palaeoflow patterns of the irish ice sheet using a high resolution 25 m digital elevation model we present morphological maps of a large part 100 100 km of the so called drumlin belt of north central ireland the landforms comprise mostly ribbed moraine much larger than found elsewhere up to 16 km in length which in places are superimposed on each other contrary to most prior assessments we find the bedform record to contain numerous and overlapping episodes of bed formation ribbed moraine drumlins and crag and tails that provide a palimpsest record of changing flow geometries these demonstrate an ice sheet with a centre of mass and flow geometry that changed during growth and decay using distinctive flow patterns and relative age relationships between them we reconstruct ice sheet evolution into four phases during a single glacial cycle in phase 1 early in the glacial cycle scottish and local ice coalesced to form a northeast centred irish ice sheet as it grew its centre of mass migrated southwards culminating in a major n s divide positioned down the east of ireland phase 2 ca last glacial maximum during retreat the centre of mass migrated at least 120 km northwards and became established in northwest ireland and at this point a dramatic bedforming event produced one of the world s largest and most contiguous ribbed moraine fields phase 3 final deglaciation is thought to be by fragmentation into many topographically controlled minor ice caps phase 4 rather than any dramatic or unexpected behaviour the reconstructed phases indicate a relatively predictable pattern of ice sheet growth and decay with changes in centres of mass and does not require major readvances or ice stream events copyright 2001 john wiley sons ltd

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

on the transfer function between surface fields and the geostrophic stream function in the mediterranean sea abstractthe real transfer function and the phase shift between sea surface height ssh and sea surface buoyancy ssb were estimated from the output of a realistic eddy resolving model of the mediterranean sea circulation the analysis of their temporal evolution unveiled the existence of a clear seasonal cycle closely related to that of the mixed layer depth the phase shifts between ssh and ssb attain their minimum for deep mixed layers which is different from zero besides the spectral slope of the transfer function at scales shorter than 100 km fluctuates between k 1 and k 2 for deep mixed layers it is close to k 1 as predicted by the surface quasigeostrophic sqg solution at longer wavelengths it is approximately constant under the different environmental conditions in all of the subbasins analyzed with the exception of the gulf of lions the capability to observe sea surface temperature sst from satellites motivated the extension of this analysis to sst and ssh results showed a similar q

computing ocean surface currents over the coastal california current system using 30 min lag sequential sar images as compared with conventional methods for measuring ocean surface currents spaceborne synthetic aperture radar sar offers cloud penetrating ocean current observation capability at high spatial resolution while some studies have shown the potential of sar for studying ocean surface currents through feature tracking they have only analyzed a few images to demonstrate the basic measurement technique and no concise general technique has been developed this paper shows the application of the maximum cross correlation mcc method to generate ocean surface currents from nearly two years of available sequential spaceborne c band sar imagery from the envisat asar and ers 2 advanced microwave instrument sar sensors over the coastal california current system the data processing strategies are discussed in detail and results are compared with hf radar measured currents one dimensional wavenumber spectra of the sar derived surface currents agree with the k 2 power law as predicted by submesoscale resolution models comparisons with hf radar currents show encouraging results with mcc sar vectors oriented slightly counterclockwise relative to hf radar vectors mcc sar surface currents are found to have larger magnitudes than hf radar currents approx 11 cm s which may be due to the fact that sar penetrates only a few centimeters into the ocean surface whereas hf radar currents are averaged over the top 1 m of the ocean surface the larger part of this magnitude difference is contained in the along shore component which can be attributed to higher hf radar accuracy in the direct radial cross shore measurements as compared with along shore components derived from multiple cross shore radial measurements

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

pleistocene glacial history of the nw european continental margin abstract in this paper new and previously published data on the pleistocene glacial impact on the nw european margin from ireland to svalbard between c 48 n 80 n are compiled the morphology of the glaciated part of the european margin strongly reflects repeated occurrence of fast moving ice streams creating numerous glacial troughs channels that are separated by shallow bank areas end moraines have been identified at several locations on the shelf suggesting shelf edge glaciation along the major part of the margin during the last glacial maximum deposition of stacked units of glacigenic debris flows on the continental slope form fans at a number of locations from 55 n and northwards whereas the margin to the south of this is characterised by the presence of submarine canyons glaciation curves based primarily on information from the glacial fed fan systems that depict the pleistocene trends in extent of glaciations along the margin have been compiled these curves suggest that extensive shelf glaciations started around svalbard at 1 6 1 3 ma while repeated periods of shelf edge glaciations on the uk margin started with mis 12 c 0 45 ma the available evidence for mis 2 suggest that shelf edge glaciation for the whole margin was reached between c 28 and 22 14 c ka bp and maximum positions after this were more limited in some regions north sea and lofoten the last glacial advance on the margin has been dated to 15 13 5 14 c ka bp and by c 13 14 c ka bp the shelf areas were completely deglaciated the younger dryas loch lomond advance reached the coastal areas in only a few regions

mapping the nonstationary internal tide with satellite altimetry temporal variability of the internal tide has been inferred from the 23 year long combined records of the topex poseidon jason 1 and jason 2 satellite altimeters by combining harmonic analysis with an analysis of along track wavenumber spectra of sea surface height ssh conventional harmonic analysis is first applied to estimate and remove the stationary components of the tide at each point along the reference ground tracks the wavenumber spectrum of the residual ssh is then computed and the variance in a neighborhood around the wavenumber of the mode 1 baroclinic m2 tide is interpreted as the sum of noise broadband nontidal processes and the nonstationary tide at many sites a bump in the spectrum associated with the internal tide is noted and an empirical model for the noise and nontidal processes is used to estimate the nonstationary semidiurnal tidal variance the results indicate a spatially inhomogeneous pattern of tidal variability nonstationary tides are larger than stationary tides throughout much of the equatorial pacific and indian oceans

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

surface quasigeostrophic solutions and baroclinic modes with exponential stratification abstractthe author derives baroclinic modes and surface quasigeostrophic sqg solutions with exponential stratification and compares the results to those obtained with constant stratification the sqg solutions with exponential stratification decay more rapidly in the vertical and have weaker near surface velocities this then compounds the previously noted problem that sqg underpredicts the velocities associated with a given surface density anomaly the author also examines how the sqg solutions project onto the baroclinic modes with constant stratification sqg waves larger than deformation scale project primarily onto the barotropic mode and to a lesser degree onto the first baroclinic mode however with exponential stratification the largest projection is on the first baroclinic mode the effect is even more pronounced over rough bottom topography therefore large scale sqg waves will look like the first baroclinic mode and vice versa with realistic stratification

on post glacial sea level i general theory summary modern analyses of sea level changes due to glacial isostatic adjustment gia are based on the classic sea level equation derived by farrell clark 1976 geophys j r astr soc 46 647 667 the connection between global sea level variations and changes to ocean height that is assumed within this equation breaks down in the presence of a time varying shoreline geometry we present a generalized sea level equation that overcomes this difficulty we also derive analytic expressions for and present schematic illustrations of the error in the ocean height change over finite time intervals introduced in published efforts to incorporate shoreline evolution into the theory of gia induced sea level change this comparison includes studies of shoreline migration due to either local sea level changes or the growth and ablation of marine based ice we conclude that the theories applied by johnston 1993 geophys j int 114 615 634 milne 1998 phd thesis university of toronto toronto and co workers are more accurate than the procedure advocated by peltier 1994 science 265 195 201 1998a geophys res lett 25 3955 3958 1998b rev geophys 114 615 634 although an improvement in the latter has recently been reported peltier drummond 2002 geophys res lett 29 10 1029 2001gl014273 our generalized theory is valid for any earth model in a companion paper we derive the equations necessary to treat the special case of a spherically symmetric linear viscoelastic and rotating earth and we quantify errors associated with previous work

impact of horizontal resolution 1 12 to 1 50 on gulf stream separation penetration and variability abstractthe impact of horizontal resolution 1 12 to 1 50 6 to 1 5 km at midlatitudes on gulf stream separation penetration and variability is quantified in a series of identical north atlantic experiments the questions the authors seek to address are twofold 1 is the realism of the modeled solution increased as resolution is increased 2 how robust is the modeled mesoscale and submesoscale eddy activity as a function of grid spacing and how representative is it of interior quasigeostrophic qg or surface quasigeostrophic sqg turbulence this study shows that i the representation of gulf stream penetration and associated recirculating gyres shifts from unrealistic to realistic when the resolution is increased to 1 50 and when the nonlinear effects of the submesoscale eddies intensifies the midlatitude jet and increases its penetration eastward ii the penetration into the deep ocean drastically increases with resolution and closely resembles the observations and iii surface power spec

interpreting energy and tracer spectra of upper ocean turbulence in the submesoscale range 1 200 km submesoscale 1 200km wavenumber spectra of kinetic and potential energy and tracer variance are obtained from in situ observations in the gulf stream region and in the eastern subtropical north pacific in the gulf stream region steep kinetic energy spectra at scales between 200 and 20km are consistent with predictions of interior quasigeostrophic turbulence theory both in the mixed layer and in the thermocline at scales below 20km the spectra flatten out consistent with a growing contribution of internal wave energy at small scales in the subtropical north pacific theenergyspectraareflatterand inconsistentwith predictionsofinteriorquasigeostrophic turbulence theory the observed spectra and their dependence on depth are also inconsistent with predictions of surface quasigeostrophic turbulencetheoryfortheobservedoceanstratification itappearsthatunbalancedmotions most likely internal tides at large scales and the internal wave continuum at small scales dominate the energy spectrum throughout the submesoscale range spectra of temperature variance along density surfaces which are not affected by internal tides are also inconsistent with predictions of geostrophic turbulence theories reasons for this inconsistency could be the injection of energy in the submesoscale range by small scale baroclinic instabilities or modifications of the spectra by coupling between surface and interior dynamics or by ageostrophic frontal effects

the scales and equilibration of midocean eddies freely evolving flow quasigeostrophic turbulence theory and numerical simulation are used to study the mechanisms determining the scale structure and equilibration of mesoscale ocean eddies the present work concentrates on using freely decaying geostrophic turbulence to understand and explain the vertical and horizontal flow of energy through a stratified horizontally homogeneous geostrophic fluid it is found that the stratification profile in particular the presence of a pycnocline has significant qualitative effects on the efficiency and spectral pathways of energy flow specifically with uniform stratification energy in high baroclinic modes transfers directly quickly within a few eddy turnaround times and almost completely to the barotropic mode by contrast in the presence of oceanlike stratification kinetic energy in high baroclinic modes transfers intermediately to the first baroclinic mode whence it transfers inefficiently and incompletely to the barotropic mode the efficiency of transfer to the barotropic mode is reduced as the pycnocline is made increasingly thin the b effect on the other hand improves the efficiency of barotropization but for oceanically realistic parameters this effect is relatively unimportant compared to the effects of nonuniform stratification finally the nature of turbulent cascade dynamics is such as to lead to a concentration of first baroclinic mode kinetic energy near the first radius of deformation which in the case of a nonuniform and oceanically realistic stratification has a significant projection at the surface this may in part explain recent observations of surface eddy scales by topex poseidon satellite altimetry which indicate a correlation of surface height variance with the scale of the first deformation radius

relative sea level observations in western scotland since the last glacial maximum for testing models of glacial isostatic land movements and ice sheet reconstructions observations of relative sea level change and local deglaciation in western scotland provide critical constraints for modelling glacio isostatic rebound in northern britain over the last 18 000 years the longest records come from skye arisaig and knapdale with a shorter holocene record from kintail biostratigraphic diatom pollen dinoflagellate foraminifera and thecamoebian lithological and radiocarbon analyses provide age and elevation parameters for each sea level index point all four sites reveal relative sea level change that is highly non monotonic in time as the local vertical component of glacio isostatic rebound and eustasy or global meltwater influx dominate at different periods copyright 2006 john wiley sons ltd

spatial scales of mesoscale variability in the north atlantic as deduced from geosat data two years of geosat data were used to systematically investigate the mesoscale variability and spatial scales of the north atlantic we first calculated sea surface height variability and eddy kinetic energy these compare well with the eddy kinetic energy obtained with surface drifters then the spatial scales of mesoscale variability were characterized in 10 latitude 10 longitude areas by their wave number spectra and autocorrelation functions comparison with existing in situ data shows good agreement and it is believed that the total error budget is globally below that of the oceanic signal the wave number spectra show significant differences as a function of latitude and longitude and these can be related to different types of forcing instability of a mean current or fluctuating wind scales typically decrease from west to east and south to north simple proportionality with respect to the first internal rossby radii does not apply everywhere

exploring the mesoscale activity in the solomon sea a complementary approach with a numerical model and altimetric data the solomon sea is an area of high level of eddy kinetic energy eke and represents a transit area for the low latitude western boundary currents llwbcs connecting the subtropics to the equatorial pacific and playing a major role in enso dynamics this study aims at documenting the surface mesoscale activity in the solomon sea for the first time our analysis is based on the joint analysis of altimetric data and outputs from a 1 12 model simulation the highest surface eke is observed in the northern part of the basin and extends southward to the central basin an eddy tracking algorithm is used to document the characteristics and trajectories of coherent mesoscale vortices cyclonic eddies generated in the south basin are advected to the north by the llwbcs before merging with stationary mesoscale structures present in the mean circulation anticyclonic eddies are less numerous they are generated in the southeastern basin propagate westward reach the llwbcs and dissipate the seasonal and interannual modulations of the mesoscale activity are well marked at seasonal time scale maximum minimum activity is in may june september at interannual time scale the mesoscale activity is particularly enhanced during la nina conditions if instabilities of the regional circulations seem to explain the generation of mesoscale features the modulation of the mesoscale activity seems to be rather related with the intrusion at solomon strait of the surface south equatorial current rather than to the llwbcs by modulating the horizontal and vertical shears suitable for instabilities

sea level change and inner shelf stratigraphy off northern ireland new seismic stratigraphic vibracore and ams c 14 dates from two sites off the northern ireland coast yield information on the deglacial to present sea level history and shelf evolution of the region a lowstand of sea level at about 30 m below present sea level recorded by fossils in a lowstand shoreline deposit occurred around 13 4 cal ka b p following a period of rapid isostatic uplift associated with a rsl fall of 6 7 cm yr following the lowstand contrasting styles of sedimentation characterized the two study sites in the sheltered environment of belfast lough the lowstand shoreline was overtopped and buried by transgressive facies of intertidal and shallow sub tidal mud and sandy mud on the high energy portrush coast the inner shelf sedimentary sequence is characterized by a basal conglomerate overlain by well sorted sands with occasional interbedded gravel c 2006 elsevier b v all rights reserved

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

diagnosis of high resolution upper ocean dynamics from noisy sea surface temperatures 1 the noise present in infrared satellite measurements of sea surface temperature sst hampers the use of surface quasi geostrophic sqg equations to diagnose ocean dynamics at high resolutions here we propose a methodology to reduce the contribution of noise when diagnosing surface vorticity divergence and vertical velocity from sst able to retain the dynamics at scales of a few kilometers it is based on the use of denoising techniques with curvelets as basis functions and the application of a selective low pass filters to improve the reconstruction of surface upwelling downwelling patterns first it is tested using direct numerical simulations of sqg turbulence and then applied to diagnose low frequency vertical velocity patterns from real modis moderate resolution imaging spectroradiometer images the methodology here presented which is not tied to the validity of sqg equations nor to the use of sst is quite general and can be applied to a wide range of measurements and dynamical frameworks

the lithostratigraphy and biostratigraphy of a holocene coastal sediment sequence in marazion marsh west cornwall u k with reference to relative sea level movements abstract a holocene sedimentary sequence at marazion marsh mount s bay west cornwall u k is examined with reference to coastal evolution and relative sea level change a sample core analyzed in this paper shows the base of the sedimentary sequence rests on weathered bedrock material basal organic rich deposits are overlain by minerogenic materials dominated by sand a sharp contact separates these two sedimentary units changing coastal conditions are reconstructed using lithostratigraphic biostratigraphic and chronometric data from this sequence the lower organic rich unit accumulated between ca 5420 60 and 4380 55 yrs b p substantial changes in the marsh environment involving vegetation succession from initial herb domination to mesophytic woodland and eventually to fen carr reed marsh development is indicated by pollen records from this unit diatom data show increased salinity within the basal sequence as arboreal pollen values decline and fen carr reed marsh becomes established radiocarbon dates from this and other cores from west cornwall are used to construct a local time altitude plot of relative sea level rsl it is concluded that the sediment sequence at marazion marsh appears to have accumulated in an embayed environment the sequence was both indirectly and directly affected by changes in relative sea level position and the influence of protective transgressive coastal morpho sedimentary structures and associated processes of sedimentation during the mid holocene period

late pleistocene tidewater glaciers and glaciomarine sequences from north county mayo republic of ireland late pleistocene deposits in north county mayo were deposited in three main glacigenic environments 1 drumlins and basal tills were formed when ice moved from the irish lowlands and local mountain catchments into donegal bay 2 gilbert type deltas accumulated up to 80m i o d on the lowlands and subaqueous moraines formed across minor valleys when marine based ice grounded inland 3 a thick drape of fossiliferous glaciomarine mud along the coastal fringe was deposited from meltwater plumes and by ice rafting immediately outside of these ice limits the muds contain an elphidium clavatum dominated low diversity microfauna which is characteristic of cold water conditions adjacent to glacier termini valves of macoma calcarea from the mud have been 14c dated at 16940 120 and 17300 100 bp the high level delta complex was deposited from tidewater glaciers in a peripheral depression adjacent to the drumlin ice limits of north county mayo although the field evidence cannot be used to determine former sea level history with any accuracy it poses general problems for sea level history and isostatic effects of the last major ice sheet in the west of ireland raised glaciomarine sequences commonly occur in close association with drumlin ice limits elsewhere in ireland and represent marine transgressions prior to glacial unloading it is suggested that the magnitudes and patterns of crustal depression are greater and geometrically more complex at the margins of ice sheets in ireland than hitherto realised

submesoscale impacts on horizontal and vertical transport in the gulf of mexico 1 impacts of submesoscale processes on transport are investigated numerically in an energetic mesoscale flow with an ocean model run at two horizontal resolutions 1 and 5 km the focus is the northwestern gulf of mexico where the loop current eddies are surrounded by smaller vortices by increasing the horizontal resolution the number and strength of submesoscale eddies and vorticity filaments within the mixed layer increase dramatically and with them the vertical velocities inside the coherent eddies and at their peripheries increased vertical velocities for increasing resolution are associated to near inertial motions and they are not limited to the mixed layer but are found at all depths horizontal velocities on the contrary are similar lagrangian isobaric tracers are deployed close to the surface and at 100 m and three dimensional neutrally buoyant particles are released close to the surface at the base of the mixed layer and at 100 m the modeled horizontal dispersion curves for each deployment depth are independent of the kind of particles and of horizontal resolution close to the ocean surface however convergence zones generated by submesoscale ageostrophic motions and resolved at 1 km resolution influence the details of the tracer distributions vertical dispersion increases by several folds for increasing resolution at all depths explored with the largest differences found close to the surface therefore submesoscales processes play a fundamental role in driving vertical transport in eddy dominated flows both within and below the mixed layer for times comparable to the eulerian time scale

three dimensional reconstruction of oceanic mesoscale currents from surface information the ability to reconstruct the three dimensional 3d dynamics of the ocean by an effective version of surface quasi geostrophy esqg is examined using the fact that surface density plays an analogous role as interior potential vorticity pv the esqg method consists in inverting the qg pv generated by sea surface density only we also make the extra assumption that sea surface temperature sst anomalies fully represent surface density anomalies this approach requires a single snapshot of sst and the setup of two parameters the mean brunt vaisala frequency and a parameter that determines the energy level at the ocean surface the validity of this approach is tested using an ocean general circulation model simulation representing the north atlantic in winter it is shown that the method is quite successful in reconstructing the velocity field at the ocean surface for mesoscales between 30 and 300 km the esqg framework can also be applied to reconstruct subsurface fields using surface information results show that the reconstruction of velocities and vorticity from surface fields is reasonably good for the upper 500 m and that the success of the method mainly depends on the quality of the sst as a proxy of the density anomaly at the base of the mixed layer this situation happens after a mixed layer deepening period therefore the ideal situation for the application of this method would be after strong wind events

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

surface drifter pair spreading in the north atlantic 1 this study examines spreading of surface drifter pairs deployed as part of the clivar mode water dynamic experiment climode project in the gulf stream region the spreading is resolved at hourly resolution and quantified by relative dispersion and finite scale lyapunov exponents at scales from 1 3 km to 300 500 km the dispersion follows richardson s law indicating stirring by eddies comparable in scale to the pair separation distance at larger scales the spreading becomes a random walk described by a constant diffusivity the behavior from 1 3 km to the local deformation radius is inconsistent with the enstrophy cascade of 2 d quasigeostrophic turbulence to test various hypotheses for this result drifter pair spreading is examined for pairs that were not launched together pairs deployed in the eastern subtropical north atlantic and climode pairs subsampled to daily temporal resolution our results indicate the presence of significant energy at the submesoscale in the gulf stream region which flattens the wave number spectrum and dominates surface stirring at this scale range results in the less energetic subtropical eastern atlantic are more equivocal

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

ice marginal depositional responses to readvance episodes in the late devensian deglaciation of the isle of man abstract remapping of the quaternary geology of the isle of man and consequent revision of the stratigraphic succession identifies three glacigenic formations each separated by a major unconformity the oldest formation the shellag represents an extensive ice advance beyond the island limits to the last glacial maximum lgm the overlying formation the orrisdale represents a major readvance episode during retreat from the lgm and is associated with the construction of the bride moraine and the deposition of extensive proglacial subaqeous sediment examination of the sedimentology and micropalaeontology of these sediments indicates that the water body was most likely lacustrine and not marine application of sequence stratigraphy to the overlying jurby formation identifies evidence for three further phases of readvance each off lapping one another into the margin of the lake basin via a complex system of ice contact subaqueous fans and outwash fan deltas the jurby formation is dated by organic sediments overlying it as older than 18 5 14 4 kyr bp and provides an ice marginal correlative for heinrich event 1 readvance limits identified 50 km to the west in eastern ireland

robustness of an effective diffusivity diagnostic in oceanic flows the robustness of nakamura s effective diffusivity diagnostic for quantifying eddy diffusivities of tracers within a streamwise average framework is carefully examined in an oceanographic context and the limits of its applicability are detailed the near surface southern ocean geostrophic flow obtained from altimetric observations is chosen for particular examination since it exhibits strong eddy activity careful analysis indicates that the effective diffusivity calculation is not strongly sensitive to the resolution of the velocity field or to the tracer initial conditions after a spinup time of 3 months and that a numerical diffusivity of 50 m 2 s 21 is appropriate to resolve the batchelor scale at a computational resolution of 1 208 the spatial variability of the effective diffusivity is examined and shown to be related to the eddy kinetic energy eke mean zonal current u and phase speed of the eddies c following the streamwise averge of eke u 2 c 2 in agreement with linear baroclinic instability theory the temporal variability of the effective diffusivity over the period 1996 2001 indicates significant variability on seasonal time scales with a magnitude of 610 215 interannual variations are investigated and discussed in the context of changes in the wind stress associated with the southern annular mode

characterizing meso to submesoscale features in the south china sea abstract in this study the mesoscale and submesoscale features in the south china sea scs are characterized based on a submesoscale permitting numerical simulation mitgcm llc4320 with nominal horizontal grid spacing of 1 48 2 2 km in the scs the simulation includes tidal forcing which is particularly crucial in the scs where tides play a key role in many aspects of regional dynamics evaluation against observations demonstrates that the simulation is capable of reproducing a wide spectrum of dynamical features in the scs the simulation is then used to characterize meso to submesoscale features in the scs and the key findings are summarized as follows i the scs is rich in submesoscale features e g vortices filaments which undergo significant seasonal variations in many regions ii there is a clear dominance of positive surface relative vorticity in most regions of the scs presumably due to the centrifugal instability but large negative also emerges in areas with strong flow topography interactions iii the vertical motions in the upper scs are dominated by tidal modulations with strong vertical velocities up to 0 01 m s 1 about an order of magnitude larger than those due to the quasi balanced sub inertial motions and iv both the wintertime and summertime horizontal wavenumber spectra of kinetic energy scale roughly as k 2 with k being the horizontal wavenumber for wavelengths below 100 km in addition four key regions are highlighted with distinctive characteristics of submesoscale turbulence including the northern scs luzon strait the scs western boundary current region in winter and east of vietnam in summer a number of model deficiencies are noted along with suggestions for improving model accuracy in order to better characterize the local submesoscale features as well as the underlying dynamics

flandrian sea level changes in the fenland i the geographical setting and evidence of relative sea level changes the flandrian sediments of the fenland record the infilling of the wash embayment on the east coast of england uk since at least 6500 bp changes in sea level have been a major control on the rate and pattern of sediment accumulation new data are presented from the area which together with published information allow the reconstruction of palaeoenvironments from 6500 to 2500 bp the major environmental changes involved alternations between freshwater fen and intertidal marine sedimentation each episode was characterised by transitional changes as vegetation and sediment zones shifted over large areas marine brackish sediments are found up to 45 km inland of the present coast radiocarbon dated sea level index points with relevant stratigraphic and micropalaeontological data ranging from 6415 bp at 8 17m od to 2595 bp at 1 45m od are described

surface ocean mixing inferred from different multisatellite altimetry measurements abstract two sea surface height ssh anomaly fields distributed by archiving validation and interpretation of satellite oceanographic aviso altimetry are evaluated in terms of the effects that they produce on mixing one ssh anomaly field tagged ref is constructed using measurements made by two satellite altimeters the other ssh anomaly field tagged upd is constructed using measurements made by up to four satellite altimeters advection is supplied by surface geostrophic currents derived from the total ssh fields resulting from the addition of these ssh anomaly fields to a mean ssh field emphasis is placed on the extraction from the currents of lagrangian coherent structures lcss which acting as skeletons for patterns formed by passively advected tracers entirely control mixing the diagnostic tool employed to detect lcss is provided by the computation of finite time lyapunov exponents it is found that currents inferred using upd ssh anomalies support mixing with characteristics similar t

connecting antarctic cross slope exchange with southern ocean overturning previous idealized investigations of southern ocean overturning have omitted its connection with the antarctic continental shelves leaving the influence of shelf processes on antarctic bottom water aabw export unconsidered in particular the contribution of mesoscale eddies to setting the stratification and overturning circulation in the antarctic circumpolar current acc is well established yet their role in cross shelf exchange of water masses remains unclear this study proposes a residual mean theory that elucidates the connection between antarctic cross shelf exchange and overturning in the acc and the contribution of mesoscale eddies to the export of aabw the authors motivate and verify this theory using an eddy resolving process model of a sector of the southern ocean the strength and pattern of the simulated overturning circulation strongly resemble those of the real ocean and are closely captured by the residualmean theory over the continental slope baroclinic instability is suppressed and so transport by mesoscale eddies is reduced this suppression of the eddy fluxes also gives rise to the steep v shaped isopycnals that characterize the antarctic slope front in aabw forming regions of the continental shelf furthermore to produce water on the continental shelf that is dense enough to sink to the deep ocean the deep overturning cell must be at least comparable in strength to wind driven mean overturning on the continental slope this results in a strong sensitivity of the deep overturning strength to changes in the polar easterly winds

non stationary internal tides observed with satellite altimetry 1 temporal variability of the internal tide is inferred from a 17 year combined record of topex poseidon and jason satellite altimeters a global sampling of along track sea surface height wavenumber spectra finds that non stationary variance is generally 25 or less of the average variance at wavenumbers characteristic of mode 1 tidal internal waves with some exceptions the non stationary variance does not exceed 0 25 cm2 the mode 2 signal where detectable contains a larger fraction of non stationary variance typically 50 or more temporal subsetting of the data reveals interannual variability barely significant compared with tidal estimation error from 3 year records comparison of summer vs winter conditions shows only one region of noteworthy seasonal changes the northern south china sea implications for the anticipated swot altimeter mission are briefly discussed

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

mesoscale to submesoscale transition in the california current system part i flow structure eddy flux and observational tests in computational simulations of an idealized subtropical eastern boundary upwelling current system similar to the california current a submesoscale transition occurs in the eddy variability as the horizontal grid scale is reduced to o 1 km this first paper in a series of three describes the transition in terms of the emergent flow structure and the associated time averaged eddy fluxes in addition to the mesoscale eddies that arise from a primary instability of the alongshore wind driven currents significant energy is transferred into submesoscale fronts and vortices in the upper ocean the submesoscale arises through surface frontogenesis growing off upwelled cold filaments that are pulled offshore and strained in between the mesoscale eddy centers in turn some submesoscale fronts become unstable and develop submesoscale meanders and fragment into roll up vortices associated with this phenomenon are a large vertical vorticity and rossby number a large vertical velocity relatively flat horizontal spectra contrary to the prevailing view of mesoscale dynamics a large vertical buoyancy flux acting to restratify the upper ocean a submesoscale energy conversion from potential to kinetic a significant spatial and temporal intermittency in the upper ocean and material exchanges between the surface boundary layer and pycnocline comparison with available observations indicates that submesoscale fronts and instabilities occur widely in the upper ocean with characteristics similar to the simulations

mixing by low and high resolution surface geostrophic currents 1 the nature of mixing near the ocean s surface is investigated by considering passive tracer advection by currents derived geostrophically using sea surface height fields that differ in their spatiotemporal resolution one is a low resolution field that can be thought of as being derived using current generation groundtrack altimetric measurements the other is a high resolution field that may be envisioned as derived using hypothetical next generation wideswath altimetric measurements the investigation is carried out in two world ocean regions with quite distinct characteristics and which have been the focus of recent studies on mixing by altimetry derived currents one region corresponds to an ample domain in the south atlantic which is traversed by vortices shed from the agulhas current the other region corresponds to a portion of the pacific sector of the southern ocean which is dominated by multiple zonal jets associated with the antarctic circumpolar current it is argued that while altimetry derived currents capture the most salient characteristics of surface ocean mixing deterministic lagrangian calculations may be improved by considering surface geostrophic currents with greater spatiotemporal resolution this is supported on analysis of probability distribution functions of finite time lyapunov exponents ftles inspection of lagrangian coherent structures or lcss which constitute distinguished material fluid curves that organize mixing computation of kinetic energy and ftle variance spectra and realization of explicit passive tracer advection experiments

sedimentology and micropalaeontology of glacimarine sediments from the central and southwestern celtic sea thin discontinuous glacigenic sediments occur at or close to the sea bed as far south as 49 n in the celtic sea the northern samples facies a are clast rich overconsolidated lodgement tills or proximal glacimarine sediments containing sparse reworked microfaunas the southern samples facies b are distal glacimarine plastic silty clays containing abundant cold water microfaunas both these facies are correlated with the late devensian scilly till enabling a quantitative reconstruction of ice thicknesses grounding line sea level and shoreline elevations in the celtic sea at 19 000 years bp the ice advance terminated in marine waters towards the shelf edge break and is likely to have constituted a thin lobate surge over deformable marine sediments 1990 the geological society

sea level change in the irish sea since the last glacial maximum constraints from isostatic modelling models of glacio hydroisostatic sea level change have been published for the british isles that are broadly consistent with the observational evidence as well as with glaciological constraints it has been argued however that the models fail to represent sea level change along the irish sea margins and in southern ireland for the post deglaciation period the argument rests on the interpretation of the depositional environment of the elevated irish sea drift on both sides of the irish sea whether this is terrestrial or glaciomarine the isostatic models for the british isles are consistent with the former interpretation in that sea levels on either side of the irish sea south of about the isle of man are not predicted to have risen above present sea level at any time since the deglaciation of the irish sea this implies that ice over both the irish sea and ireland was relatively thin ca 600 700 m over ireland if the glaciomarine interpretation of the elevated irish sea drift is correct then the maximum ice thickness over central and southern ireland would have to reach 2000 m exceeding that over scotland furthermore for the resulting sea level change to be consistent with the holocene evidence this thick ice sheet could not have extended to the eastern side of the irish sea nor could it have been very thick at its northern and western limits if such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the irish sea drift as terrestrial in origin copyright 2001 john wiley sons ltd

ssh wavenumber spectra in the north pacific from a high resolution realistic simulation abstractfollowing recent studies based on altimetric data this paper analyses the spectral characteristics of the sea surface height ssh using a new realistic simulation of the north pacific ocean with high resolution in the horizontal and 100 vertical levels this simulation resolves smaller scales down to 10 km than altimetric data limited to 70 km because of the noise level in high eddy kinetic energy eke regions as in the western part ssh spectral slope almost follows a k 4 with k the wavenumber or slightly steeper law in agreement with altimeter studies the new result is that unlike altimeter studies such a k 4 slope is also observed in low eke regions as in the eastern part in these regions this slope mostly concerns scales not well resolved by altimetric data such k 4 ssh spectral slopes are weaker from what is expected from quasigeostrophic turbulence theory but closer to surface quasigeostrophic sqg turbulence theory the consequence is that the small scales concerned

do altimeter wavenumber spectra agree with the interior or surface quasigeostrophic theory in high eddy energy regions it is generally assumed that sea level wavenumber spectra compare well with quasigeostrophic qg turbulence models and that spectral slopes are close to the expected k 5 law this issue is revisited here sea level wavenumber spectra in the gulf stream kuroshio and agulhas regions are estimated using the most recent altimeter datasets the ocean topography experiment topex poseidon jason 1 the environmental satellite envisat and the geosat follow on the authors show that spectral slopes in the mesoscale band are significantly different from a k 5 law in disagreement with the qg turbulence theory however they very closely follow a k 11 3 slope which indicates that the surface quasigeostrophic theory sqg is a much better dynamical framework than the qg turbulence theory to describe the ocean surface dynamics because of the specific properties of the sqg theory these results offer new perspectives for the analysis and interpretation of satellite data

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

nonstationary internal tides observed using dual satellite altimetry abstractdual satellite crossover data from the jason 2 and cryosat 2 altimeter missions are used in a novel approach to quantify stationary and nonstationary tides from time lagged mean square sea surface height ssh differences computed for lags from 1 to 1440 h 60 days the approach is made feasible by removing independent estimates of the stationary tide and mesoscale ssh variance which greatly reduces the sampling error of the ssh statistics for the semidiurnal tidal band the stationary tidal variance is approximately 0 73 cm2 and the nonstationary variance is about 0 33 cm2 or 30 of the total the temporal correlation of the nonstationary tide is examined by complex demodulation and found to be oscillatory with first 0 crossing at 400 h 17 days because a significant fraction of the time variable mesoscale signal is resolved at time scales of roughly 150 h by the present constellation of satellite altimeters the results suggest that it may be feasible to predict the nonstationary tide fr

high resolution reconstruction of the last ice sheet in nw scotland reconstructions of the last late devensian british ice sheet have hitherto been based on assumptions regarding its extent and form here we employ observational evidence for the maximum altitude of glacial erosion trimlines on mountains that protruded through the ice palaeonunataks to reconstruct the form of the ice sheet over 10 000 km2 of nw scotland contrasts in the clay mineralogy of soils and exposure ages of rock surfaces above and below these trimlines confirm that they represent the upper limit of late devensian glacial erosion the reconstruction yields realistic values of basal shear stress and is consistent with independent evidence of ice movement directions the ice sheet reached 950 m altitude over the present n s watershed descended northwards and north westwards was deflected around an ice dome on skye and an independent outer hebrides ice cap and probably extended across the adjacent shelf on a bed of deforming sediments

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

multiscale dynamical analysis of a high resolution numerical model simulation of the solomon sea circulation a high 1 36 resolution numerical model is used to study the ocean circulation in the solomon sea an evaluation of the model with the few available observation shows that the 1 36 resolution model realistically simulates the solomon sea circulations the model notably reproduces the high levels of mesoscale eddy activity observed in the solomon sea with regard to previous simulations at 1 12 resolution the average eddy kinetic energy levels are increased by up to 30 40 in the present 1 36 simulation and the enhancement extends at depth at the surface the eddy kinetic energy level is maximum in march april may and is minimum in december january february the high subsurface variability is related to the variability of the western boundary current new guinea coastal undercurrent moreover the emergence of submesoscales is clearly apparent in the present simulations a spectral analysis is conducted in order to evidence and characterize the modeled submesoscale dynamics and to provide a spectral view of scales interactions the corresponding spectral slopes show a strong consistency with the surface quasi geostrophic turbulence theory

spectral decomposition of internal gravity wave sea surface height in global models two global ocean models ranging in horizontal resolution from 1 12 to 1 48 are used to study the space and time scales of sea surface height ssh signals associated with internal gravity waves igws frequency horizontal wavenumber ssh spectral densities are computed over seven regions of the world ocean from three simulations of the hybrid coordinate ocean model hycom and two simulations of the massachusetts institute of technology general circulation model mitgcm high wavenumber high frequency ssh variance follows the predicted igw linear dispersion curves the realism of high frequency motions 0 87cpd in the models is tested through comparison of the frequency spectral density of dynamic height variance computed from the highest resolution runs of each model 1 25 hycom and 1 48 mitgcm with dynamic height variance frequency spectral density computed from 9 in situ profiling instruments these high frequency motions are of particular interest because of their contributions to the small scale ssh variability that will be observed on a global scale in the upcoming surface water and ocean topography swot satellite altimetry mission the variance at supertidal frequencies can be comparable to the tidal and low frequency variance for high wavenumbers length scales smaller than 50km especially in the higher resolution simulations in the highest resolution simulations the high frequency variance can be greater than the low frequency variance at these scales

reconstruction of ocean s interior from observed sea surface information observational surface data are used to reconstruct the ocean s interior through the interior surface quasigeostrophic isqg method the input data include the satellite derived sea surface height satellite derived sea surface temperature satellite derived or argo based sea surface salinity and an estimated stratification of the region the results show that the isqg retrieval of subsurface density anomalies is quite promising compared to argo profile data at 1000 m depth the directions of retrieved velocity anomalies are comparable to those derived from argo float trajectories the reconstruction using surface density input field approximated only by sst with constant sss performs less satisfactorily than that taking into account the contribution of sss perturbations suggesting that the observed sss information is important for the application of the isqg method better reconstruction is obtained in the warm season than in the cold season which is probably due to the stronger stratification in the warm season that confines the influence of the biases in the surface input data especially sss in a shallow layer the comparison between the performance of isqg with argo based sss input and that with satellite derived sss input suggests that the biases in the sss products could be a major factor that influences the isqg performance with reduced biases in satellite derived sss in the future the measurement based isqg method is expected to achieve better reconstruction of ocean interior and thus is promising in practical application

inferring dynamics from the wavenumber spectra of an eddying global ocean model with embedded tides 1 the slopes of the wavenumber spectra of sea surface height ssh and kinetic energy ke have been used to infer interior or surface quasi geostrophic qg or sqg dynamics of the ocean however inspection of spectral slopes for altimeter ssh in the mesoscale band of 70 to 250 km shows much flatter slopes than the qg or sqg predictions over most of the ocean comparison of altimeter wavenumber spectra with spectra from an eddy resolving global ocean circulation model the hybrid coordinate ocean model hycom at 1 12 5 equatorial resolution which has embedded tides suggests that the flatter slopes of the altimeter ssh may arise from three possible sources 1 presence of strong internal tides 2 shift of the inertial sub range to smaller scales and 3 altimeter noise artificially adding noise to the model tends to flatten the spectra for low ke regions near internal tide generating regions spectral slopes in the presence of internal waves are much flatter than qg or sqg predictions separating the variability into high and low frequency around periods of 2 days then a different pattern emerges with a flat high frequency wavenumber spectrum and a steeper low frequency wavenumber spectrum for low mesoscale ke the inertial sub range defined by the nearly flat enstrophy band moves to smaller scales and the mesoscale band of 70 to 250 km no longer represents the inertial sub range the model wavenumber spectra are consistent with qg and sqg theory when internal waves and inertial sub range shifts are taken into consideration

holocene sea levels last glacial maximum glaciomarine environments and geophysical models in the northern irish sea basin uk newly acquired geological records from the isle of man reveal intercalated intertidal and terrestrial sediments that record a relative sea level rise from ca 3 86 m in the early holocene up to a mid holocene maximum between ca 6 6 and 4 5 cal kyr bp at ca 2 25 m when compared with similar marine records from elsewhere in the northern irish sea basin the sea level data confirm a strong north south trend in glacioisostatic loading but little east to west difference in loading this pattern results from the central northern sectors of the british ice sheet over scotland strongly influencing the glacioisostatic downwarping throughout the northern irish sea basin differential ice thicknesses over the irish sea the lake district and ireland did not cause perturbations of local glacioisostatic signatures the holocene marine data in the central irish sea record a slow termination of global eustatic sea level rise during the early holocene geophysical predictions of relative sea level partially constrained by the holocene rsl observations but extrapolated to the last glacial maximum show the potential for shallow marine conditions in the central irish sea basin and in northeast ireland between ca 21 0 16 0 cal kyr bp however glaciomarine deposits in northeast ireland suggest the model relative sea level predictions are too low and require increased ice loading or a thinner lithosphere to generate extra glacioisostatic depression at the time of deglaciation furthermore predicted deglacial relative sea level for northeast ireland does not match the geological record highlighting complex ice margin ocean interaction during deglaciation on the isle of man where glacioisostatic loading is of a similar magnitude to that across northeast ireland the presence of grounded ice inhibited marine incursion during early deglaciation but the occurrence of glaciolacustrine conditions along the ice margin as it moved northwards supports model predictions that relative sea level fell below present during the late glacial early holocene due to rapid glacioisostatic rebound

dynamics of the upper oceanic layers in terms of surface quasigeostrophy theory in this study the relation between the interior and the surface dynamics for nonlinear baroclinically unstable flows is examined using the concepts of potential vorticity first it is demonstrated that baroclinic unstable flows present the property that the potential vorticity mesoscale and submesoscale anomalies in the ocean interior are strongly correlated to the surface density anomalies then using the invertibility of potential vorticity the dynamics are decomposed in terms of a solution forced by the three dimensional 3d potential vorticity and a solution forced by the surface boundary condition in density it is found that in the upper oceanic layers the balanced flow induced only by potential vorticity is strongly anticorrelated with that induced only by the surface density with a dominance of the latter the major consequence is that the 3d balanced motions can be determined from only the surface density and the characteristics of the basin scale stratification by solving an elliptic equation these properties allow for the possibility to reconstruct the 3d balanced velocity field of the upper layers from just the knowledge of the surface density by using a simpler model that is an effective surface quasigeostrophic model all these results are validated through the examination of a primitive equation simulation reproducing the dynamics of the antarctic circumpolar current

the effects of altimeter instrument noise on the estimation of the wavenumber spectrum of sea surface height the wavenumber spectrum of sea surface height ssh observed by satellite altimetry was analyzed by xu and fu the spectral shape in the wavelength range of 70 250 km was approximated by a power law representing a regime governed by geostrophic turbulence theories the effects of altimeter instrument noise were assumed insignificant at wavelengths longer than 70 km the authors reexamined the assumption in the study using nearly simultaneous observations made by jason 1 and jason 2 during their cross calibration phase this study found that the white noise level of altimetry measurement was best estimated from the spectral values at wavelengths from 25 to 35 km after removing a white noise level based on such estimate from the ssh spectrum the spectral slope values changed significantly over most of the oceans a keyfinding is that the spectral slopes are generally steeper than k 22 k is wavenumber poleward of the 208 latitudes where flatter spectral slopes in some regions have previously caused problems for dynamic interpretations the new results indicate that the spectral slopes in the core regions of the major ocean current systems have values between the original geostrophic turbulence theory and the surface quasigeostrophic theory the near k 24 spectrum suggests that the sea surface height variability at these wavelengths in the high eddy energy regions might be governed by frontogenesis

a model of subaqueous sedimentation at the margin of the late midlandian irish ice sheet connemara ireland and its implications for regionally high isostatic sea levels abstract the geomorphology and sedimentology of a series of late midlandian glacigenic sites in connemara western ireland are described and a set of commonly occurring sedimentary assemblages identified these form components of a simple model of ice contact subaqueous sedimentation involving progressive down current transition from subglacial esker tunnel fill through proximal tunnel mouth fans proximal and distal subaqueous fans into basin floor sediments in two of the sites aggradation to the water line passes into fan delta topsets and foresets all sites abut into inferred water bodies to their west and imply minimum water surface heights of between 35 and 65 m irish od or in the case of the two deltaic sites shoreline heights of between 75 and 80 m these high water levels very close to and facing directly into the immediately adjacent open atlantic ocean are difficult to explain as ice dammed glaciolacustrine water bodies without invoking improbable ice sheet marginal geometries they may however be explained as a set of successive fjord head grounding line depositional systems that trace temporary still stands in the phased retreat of the irish ice sheet from its offshore maximum this possibility not yet confirmed by the discovery of in situ marine fauna implies a degree of late midlandian isostatic depression and subsequent response unexplained by currently applied crustal response models but supported by previously constructed glacio sedimentary models

global variability of the wavenumber spectrum of oceanic mesoscale turbulence abstractthe wavenumber spectra of sea surface height from satellite altimeter observations have revealed complex spatial variability that cannot be explained by a universal theory of mesoscale turbulence near the edge of the core regions of high eddy energy agreement is observed with the prediction of the surface quasigeostrophic sqg turbulence theory which has fundamental differences from that of the traditional quasigeostrophic qg turbulence theory in the core regions of high eddy energy the spectra are consistent with frontogenesis that is not fully accounted for by the sqg theory however the observations in the vast ocean interior of low eddy energy exhibit substantial differences from the predictions of existing theories of oceanic mesoscale turbulence the spectra in these regions may reflect the ocean s response to short scale atmospheric forcing and air sea interaction the observations presented in this paper serve as a test bed for new theories and ocean general circulation models

a multidimensional spectral description of ocean variability abstractan updated empirical analytical model for the frequency and wavenumber distribution of balanced motion in the ocean is presented the spectrum model spans periods longer than the inertial but shorter than a decade and wavelengths between 100 and 10 000 km assuming geostrophic dynamics a spectrum model for the streamfunction is constructed to be consistent with a range of observations including sea surface height from satellite altimetry velocity from moored and shipboard instruments and temperature from moorings first order characteristics of the observed spectra including amplitude and spectral moments vary slowly geographically the spectrum model is horizontally anisotropic accommodating observations that zonal wavenumber frequency spectra are dominated by a nondispersive line qualitative and quantitative agreement is found with one dimensional frequency and wavenumber spectra and observed vertical profiles of variance illustrative application is made of the model spectrum to obse

a late pleistocene intertidal boulder pavement from an isostatically emergent coast dundalk bay eastern ireland late pleistocene sequences around dundalk bay eastern ireland record glaciomarine sedimentation near the margin of a grounded ice lobe around 15 ka sp a coastal exposure at cooley point consists of four major facies deposited outside this ice limit 1 a basal mud facies deposited from sediment plumes accumulated following the initial ice marginal retreat inland it contains a well preserved arctic microfauna dominated by the foram elphidium clavatum and the ostracod roundstonia globulifera 2 a flat to undulating boulder facies pavement mostly one clast thick is found pressed into the mud and is characterized by bevelled and striated upper clast surfaces pavement attributes are a result of intertidal activity in a cold climate the boulder source is due to rafting by ice flees from glacigenic debris deposited during an ice advance 3 laminated sand facies drape the pavement and are a result of variable current activity 4 the overlying gravel facies is separated from the sand facies by a marine erosion surface the gravel facies is subaqueous channelized and is overlain by late glacial raised beach ridges locally the gravels have been deformed by ice pressure from partially floating ice flees facies changes record terrestrial submergence and provide evidence for changes in relative sea level during part of the last deglacial cycle the boulder pavement and deformed gravel facies suggest that ice flees and sea ice effects may be more common within stratigraphies along emergent coasts than previously thought though they have a low preservation potential extreme conditions during the deglacial favoured opportunistic microfaunas during mud deposition this event may be related to a major meltwater event within the irish sea basin