atlantic modulation of el nino influence on summertime rainfall over southeastern south america 1 this study addresses the effect of atlantic sea surface temperature sst anomalies on rainfall over southeastern south america during january february particularly during el nino years using observations as well as model simulations it is found that the state of the equatorial atlantic during el nino years can modulate its influence on rainfall over southeastern south america such that when the equatorial atlantic is warm the el nino influence is weaker this atlantic influence is shown to occur through the response of the low level winds to equatorial sst anomalies the convergence of westerly anomalies onto the warm anomaly decreases the equatorial trades and moisture flow into the amazon and moreover reduces the northerly flow that brings moisture to southeastern south america the total rainfall response in this region can thus be thought as the combination of rainfall anomalies from the equatorial pacific and atlantic oceans

suspended sediment transport in the surf zone response to cross shore infragravity motion a field experiment to investigate the magnitude and temporal and spatial scales of suspended sediment transport in the inner surf zone was conducted at san marine oregon on october 7 13 1984 instrumentation consisted of five electromagnetic current meters three strain gauge type pressure transducers and 25 optical backscatter sensors to measure the concentrations of suspended sediment the instruments were deployed approximately 70 m x seaward of the mean high water line mean depth h 1 1 1 3 m in a closely spaced cross shaped pattern data were collected for 68 min periods spanning high tide during the 7 day experiment during the experiment waves varied in angle of approach from shore normal to southwesterly offshore significant swell heights were 3 5 m with periods of 12 14 s local sea conditions with wind waves of approximately 8 s also occurred a visual estimation of the width of the surf zone indicated it to be approximately 500 m and the breaker pattern suggested that there were two longshore bars at approximately 200 and 500 m offshore the data resulting from the experiment encompass a broad range of wave and current conditions which included periods of extreme infragravity motion 30 t 300 s and weak longshore currents and periods of low infragravity motion and strong longshore currents periods of incident wave dominance also occurred the field study section of this paper qualitatively describes the sediment response to strong 240 cm s 1 low frequency 0 01 hz cross shore fluid motions which dominated the inner surf zone during two of the data runs the infragravity band accounted for 85 of the cross shore velocity variance the peak 0 01 hz of which was associated with shore normal standing waves concentration gradients of suspended sediment appear to be associated with diffusive processes and develop and decay on time scales of the infragravity motions rather than those of incident waves suspension events during times of infragravity dominance often persisted for periods of 30 45 s and reached peak concentrations of 20 40 g l 1 at elevations in excess of 26 cm mean suspended load was 3 4 times larger than that associated with incident wave motions the modeling section of the paper attempts to quantitatively describe the observed time dependent vertical suspended sediment distribution with a one dimensional turbulent diffusion model formulations of eddy diffusion and erosion rate coefficients associated with peak cross shore flows are found to agree with or fall within the range of values from previous laboratory and field studies and are used in the model the model is evaluated by its ability to reproduce the time dependent vertical distribution of suspended sediment and to estimate the observed mean suspended load and the correct direction and magnitude of the mean longshore and cross shore flux level above the bed z 31 cm of suspended sediment

differences in el nino response over the southern hemisphere southern hemisphere sh circulation conditions during austral springs of enso events are examined based on previous knowledge that sst variations over the subtropical south central pacific sscp region are linked to differences among el nino en events a stratification of the springs associated with en events was performed according to sst conditions over the el nino 3 4 sector and over the sscp region the en events associated with cold conditions in the sscp wc exhibit enhanced convection not only in the intertropical convergence zone over the central equatorial pacific but also in the south pacific convergence zone spcz extended south eastward into the subtropical regions the resulting heating forcing intensifies a localized overturning cell which is associated with an anomalous rossby wave source in the central south pacific extratropical region neither the rossby wave source nor the associated wave pattern is evident during en events associated with warm conditions in the sscp and inactive spcz ww the basic features that characterize the differences in the en response over the south pacific can also be identified through the analysis of the spcz activity over the central south pacific the fact that variations in spcz activity lead sst anomaly changes in the sscp would indicate that the differences in the en response over the sh might be mainly driven by atmospheric changes which induces extratropical sst anomalies the differences in the circulation anomalies that characterize both types of en response over the sh were further explored through the analysis of the activity of the three leading modes of circulation variability the combined effect of the three leading patterns describes in some extent the intensification weakening of the cyclonic circulation anomaly observed over the southeastern pacific in wc ww associated with an active inactive spcz in particular the interdecadal variability observed in the pacific by many previous studies influences the circulation response to enso over the sh mainly through changes in the activity of the sh annular mode

past ice sheet flow east of svalbard inferred from streamlined subglacial landforms the pattern of late weichselian ca 20 ka ice flow in the northern barents sea is not well known due mainly to a lack of marine data east of svalbard several years with little summer sea ice have allowed acquisition of swath bathymetric imagery of well preserved subglacial landforms characterizing late weichselian ice flow directions over 150 000 km2 of the northwestern barents sea we show that a major ice dome was located on easternmost spitsbergen or southern hinlopen strait at least 500 km west of its previously inferred position in the northern barents sea this dome controlled the regional flow pattern ice flowed eastward around kong karls land into franz victoria trough and north through hinlopen strait an ice dome west of kong karls land is required to explain the observed ice flow pattern but does not preclude an additional ice dome to the southeast discrepancies with earlier ice sheet reconstructions reflect the lack of previous seafloor observations with evidence limited mainly to past ice loading and postglacial rebound the new pattern of ice flow directions shows predominantly eastward rather than northward flow with franz victoria trough a major drainage pathway with a full glacial balance flux of 40 km3 yr 1

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

control of the south atlantic convergence zone by extratropical thermal forcing the response of the south atlantic convergence zone sacz to an extratropical thermal forcing is investigated in a series of simulations performed with an atmospheric general circulation model coupled to a slab ocean model three sets of experiments are performed varying the extratropical forcing in the first the forcing consists of warming of the northern hemisphere nh and cooling of the southern hemisphere with zero global average in the second and third experiments the former forcing is divided into its northern and southern components to asses their relative roles in affecting the sacz in all the cases realistic surface boundary conditions are implemented we found that during its peak in austral summer the sacz weakens in response to the extratropical forcing and that such weakening is mostly due to the nh component of the forcing we found that 75 of the sacz signal in response to the forcing is linked to the generation of a secondary tropical convergence zone in the atlantic ocean around 20 n 30 n which generates an anomalous hadley circulation with subsidence over the sacz this mechanism appears to be dependent on the upper level changes and tropical ocean response as it weakens significantly when the simulation is repeated not allowing the tropical sea surface temperatures to change in response to the forcing the remaining 25 of the signal can be explained through the development of a walker type of circulation between western tropical africa and the sacz being this mechanism dependent on the african land surface temperature reaction to the remote forcing

numerical modeling of low frequency wave dynamics over a fringing coral reef abstract low frequency infragravity wave dynamics on a fringing coral reef were investigated using the numerical model xbeach roelvink et al 2009 first the skill of the model was evaluated in one and two dimensions based on its predictions of short waves 0 04 0 2 hz infragravity waves 0 004 0 04 hz and water level measurements tidal and wave setup obtained during a 2009 field study at ningaloo reef in western australia the model calibration was sensitive to friction coefficients for short waves and current infragravity bed friction which were assumed independent in this model study although the one dimensional cross shore model captured the gradients in the dominant hydrodynamic processes at the site a high current ig bed friction coefficient was required this resulted in an overestimation and a phase lag between the observed and predicted wave setup signal in the two dimensional model a lower more realistic current infragravity wave friction coefficient was required to achieve optimum performance due to the presence of significant reef and lagoon mean flows in the model which led to reduced setup across the reef the infragravity waves were found to propagate from the surf zone across the reef in a dominantly cross shore direction towards the shore but with substantial frictional damping the infragravity waves were strongly modulated also over the reef by tidal depth variations primarily due to the variability in frictional dissipation rates when the total water depth over the reef varied two mean wave driven circulation cells were observed in the study area with cross shore flow becoming more alongshore dominated before exiting the system via the two channels in the reef the results reveal that short waves dominated bottom stresses on the forereef and near the reef crest however inside the lagoon infragravity waves become increasingly dominant accounting up to 50 of the combined bottom stresses

ostracod assemblages in late quaternary varved glaciomarine clay of the baltic sea yoldia stage in eastern middle sweden abstract four cored sites in eastern middle sweden have been analysed for their content of calcareous fossils the investigated sediments consist of late quaternary varved clay deposited during the baltic sea yoldia stage four regional palaeoecological units a d have been established unit a reflects ice proximal conditions unit b optimal conditions for the benthic fauna and unit c the termination of a saline phase in unit c oxygen deficiency might have occurred in the fourth unit d no fossils were found the fauna recorded is poor in taxa and indicates a weak marine influence the salinity was higher in the western part of the investigated area due to the proximity to the inlet of marine water the meltwater influx was high and the salinity probably fluctuated considerably the ostracod cytheromorpha macchesneyi brady and crosskey is reported for the first time in quaternary deposits from northwestern europe and indicates that a connection could have existed between the baltic and the white sea in late glacial times

comparison study of the modern ostracod associations in the kara and laptev seas ecological aspects recent ostracod assemblages were investigated from coretop sediment samples collected in the eastern kara sea from water depths down to 300 m a total of 45 species were identified 27 of them were reported for the kara sea for the first time the kara sea data were compared with our results on the distribution of ostracods in the eastern laptev sea the spatial distribution of recent taxa and the ecological groupings demonstrate a clear relation to dominant environmental factors which range from estuarine to full marine conditions four assemblages related to average summer bottom water salinities were established 1 a freshwater assemblage from the inner estuaries of the ob and yenisei rivers with salinities less than 2 and from thermokarst lagoons of the southern laptev sea coast with strong salinization in winter 2 a brackishwater assemblage of the outer estuaries of the ob and yenisei rivers with salinities up to 26 3 a mixed euryhaline marine assemblage dominated by euryhaline species paracyprideis pseudopunctillata and heterocyprideis sorbyana from the inner shelf river affected zone of the kara and laptev seas where salinities range between 26 and 32 4 a taxonomically diverse marine assemblage dominated by shallow water marine taxa from the northern parts of the kara and laptev shelves and upper continental slope with stable bottom environments and a salinity higher than 32 abundant euryhaline species found at greater water depths are identified as part of an ice rafted assemblage they are possibly entrained into the newly formed fast ice during autumn storms and freeze up period and then transported to the distal open sea areas during summer

wave current interaction in willapa bay 1 this paper describes the importance of wave current interaction in an inlet estuary system the three dimensional fully coupled coupled ocean atmosphere wave sediment transport coawst modeling system was applied in willapa bay washington state from 22 to 29 october 1998 that included a large storm event to represent the interaction between waves and currents the vortex force method was used model results were compared with water elevations currents and wave measurements obtained by the u s army corp of engineers in general a good agreement between field data and computed results was achieved although some discrepancies were also observed in regard to wave peak directions in the most upstream station several numerical experiments that considered different forcing terms were run in order to identify the effects of each wind tide and wave current interaction process comparison of the horizontal momentum balances results identified that wave breaking induced acceleration is one of the leading terms in the inlet area the enhancement of the apparent bed roughness caused by waves also affected the values and distribution of the bottom shear stress the pressure gradient showed significant changes with respect to the pure tidal case during storm conditions the momentum balance in the inlet shares the characteristics of tidal dominated and wave dominated surf zone environments the changes in the momentum balance caused by waves were manifested both in water level and current variations the most relevant effect on hydrodynamics was a wave induced setup in the inner part of the estuary

swash oscillations on a natural beach run up swash oscillations were measured on a gently sloping beach face for a variety of incident wave conditions run up energy spectra at wind wave frequencies show an 3 dependence and energy levels that are independent of incident wave height this suggests saturation in contrast run up energy at surf beat periods increase approximately linearly with increasing incident wave energy thus in the inner surf zone where wave breaking limits the energy at wind wave frequencies the principal manifestation of large incident wind waves is energetic surf beat

reconstruction of the holocene seismic history of a seabed fault using relative sea level curves reconstructed by ostracode assemblages case study on the median tectonic line in iyo nada bay western japan abstract relative sea level curves of cores k1 k2 s1 and s2 collected from iyo nada bay western japan were reconstructed using ostracode assemblages these curves clearly show a holocene history of seismic subsidence comparing the curves with sea level histories from a tectonically stable area of japan demonstrates that iyo nada bay has undergone subsidence through the holocene this subsidence was probably caused by movements of the median tectonic line mtl fault system in iyo nada bay comparison of relative sea level curves of the lower and upper plates elucidated a detailed seismic history of the kaminada oki kita and shimonada oki minami faults the kaminada oki kita fault moved vertically about 7 m at ca 5500 0 cal yr bp in addition this fault may have moved vertically about 5 m and 9 m at ca 7500 6000 cal yr bp and ca 10 000 9000 cal yr bp respectively the shimonada oki minami fault has moved vertically about 15 m over the last 6500 years this fault also might have had a large movement around 10 000 cal yr bp this study provided a robust method for reconstruction of the holocene seismic history using ostracode assemblages found in seabed drilling cores

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

observations and predictions of run up for a significant range of offshore wave conditions and foreshore slopes run up observations are compared to semiempirical formulations and predictions of an existing numerical model based on the depth averaged one dimensional nonlinear shallow water equations with bore like breaking wave dissipation and quadratic bottom friction the numerical model is initialized with time series of sea surface elevation and cross shore velocity observed in 80 cm mean water depth approximately 50 m offshore of the mean shoreline on a gently sloping beach and in 175 cm water depth 100 m offshore of the shoreline on a steep concave beach run up was measured with a stack of resistance wires at elevations 5 10 15 20 and 25 cm above and parallel to the beach face at sea swell frequencies nominally 0 05 f 0 18 hz run up energy is limited by surf zone dissipation of shoreward propagating waves so that increasing the offshore wave height above a threshold value does not substantially increase the predicted or observed sea swell run up excursions e g run up is saturated existing semiempirical saturation formulations are most consistent with the observations and numerical model predictions of run up excursions nearest the bed in contrast at infragravity frequencies 0 004 f 0 05 hz where surf zone dissipation is relatively weak and reflection from the beach face is strong e g saturation formulas are not applicable the run up excursions increase approximately linearly with increasing offshore wave height the numerical model also accurately predicts that the tongue like shape of the run up results in sensitivity of run up measurements to wire elevation for instance run up excursions and mean vertical superelevation above the offshore still water level increase with decreasing wire elevation and continuous thinning of the run up tongue during the wave uprush can result in large phase differences between run up excursions measured at different wire elevations numerical model simulations suggest that run up measured more than a few centimeters above the bed cannot be used to infer even the sign of the fluid velocities in the run up tongue

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

submarine landforms and ice sheet flow in the kvitoya trough northwestern barents sea high resolution geophysical and sediment core data are used to investigate the pattern and dynamics of former ice flow in kvitoya trough northwestern barents sea a new swath bathymetric dataset identifies three types of submarine landform in the study area streamlined landforms meltwater channels and cavities iceberg scours subglacially produced streamlined landforms provide a record of ice flow through kvitoya trough during the last glaciation flow directions are inferred from the orientations of streamlined landforms drumlins crag and tail features ice flowed northward for at least 135 km from an ice divide at the southern end of kvitoya trough a large channel cavity system incised into bedrock in the southern trough indicates that subglacial meltwater was present at the former ice sheet base modest landform elongation ratios and a lack of mega scale glacial lineations suggest that although ice in kvitoya trough was melting at the bed and flowed faster than the likely thin and cold based ice on adjacent banks a major ice stream probably did not occupy the trough retreat was relatively rapid after 14 13 5 14c kyr b p and probably progressed via ice sheet bed decoupling in response to rising sea level there is little evidence for still stands during ice retreat or of ice proximal deglacial sediments relict iceberg scours in present day water depths of more than 350 m in the northern trough indicate that calving was an important mass loss mechanism during retreat

decadal interactions between the western tropical pacific and the north atlantic oscillation the relationship between interdecadal variations of tropical sea surface temperature sst in the last 120 years and circulation anomalies related to the north atlantic oscillation nao is investigated in this study using an atmospheric general circulation model agcm we confirm observational evidence that variations in the sst gradient in the western tropical pacific are related to the nao anomalies on decadal timescale and may be contributing to the shift towards the positive nao phase observed in the late 20th century the role played by the indian ocean nao teleconnection advocated in recent studies focused on the last 50 years is also assessed in the context of the 120 year long record it is suggested that a positive feedback between the pacific sst and the hemispheric circulation pattern embedding the decadal nao signal may act to enhance the internal variability of the coupled ocean atmosphere system and justify the stronger teleconnection found in observational data than in sst forced agcm experiments

relevance of infragravity waves in a wave dominated inlet this study investigates the relevance of infragravity ig waves at albufeira lagoon inlet a shallow wave dominated inlet located on the western coast of portugal a field experiment carried out in september 2010 revealed the occurrence of low frequency oscillations i e 25 300 s in water levels and current velocities while these fluctuations were present over the ebb tidal delta along the whole tidal cycle they only appeared between the beginning of the flood and up to 2 h after high tide inside the lagoon the xbeach modeling system was applied to albufeira lagoon inlet and reproduced the generation and propagation of ig waves and their blocking during the ebb this behavior was explained by blocking due to opposing tidal currents reaching 2 5 m s 1 in shallow water depths numerical results suggest that the breakpoint mechanism and the long bound wave shoaling mechanisms contributed significantly to the generation of ig waves in the inlet ig waves induced fluctuations in flood currents inside the lagoon reaching temporarily 100 of their magnitude the fact that these fluctuations occur mostly at flood and not at ebb could promote flood dominance in the lagoon this hypothesis will have to be verified namely under storm wave conditions

deglacial holocene svalbard paleoceanography and evidence of meltwater pulse 1b abstract better understanding of deglacial meltwater pulses mwps is imperative for future predictions of human induced warming and abrupt sea level change because of their potential for catastrophic damage however our knowledge of the second largest meltwater pulse mwp 1b that occurred shortly after the start of the holocene interglacial remains very limited here we studied fossil ostracods as paleoenvironmental indicators of water depth salinity and temperature in two marine sediment cores from storfjorden svalbard margin the arctic ocean to investigate near field i e areas located beneath continental ice sheets at the last glacial maximum evidence of mwp 1b the depositional environment changed from a cold bathyal environment to a warmer bathyal environment at 11 300 yr bp indicating incursion of warm atlantic water into the nordic seas and eventually to a cold neritic environment by 11 000 yr bp because of melting of the svalbard barents sea ice sheet and resultant isostatic rebound this process corresponds to rapid relative sea level fall of 40 80 m of mwp 1b from 11 300 to 11 000 yr bp

lateglacial and early holocene climatic oscillations on the western svalbard margin european arctic abstract a multi proxy sediment core record on the continental margin off western svalbard european arctic reflects large climatic and oceanographic oscillations at the lateglacial early holocene transition based on studies of planktonic foraminifera their stable oxygen and carbon isotopic composition and ice rafted debris we have reconstructed the last 14 cal ka bp the period 14 13 5 cal ka bp was characterized by highly unstable climatic conditions short lived episodes of warming alternated with meltwater pulses and enhanced iceberg rafting this period correlates to a regional warming of the northern north atlantic an overall decrease in meltwater took place during the deglaciation 14 10 8 cal ka bp the late younger dryas and subsequent transition into the early holocene is characterized by a reduced flux of planktonic foraminifera and increased iceberg rafting a major warming took place from 10 8 to 9 7 cal ka bp the influence of meltwater ceased and the flux of warm atlantic water increased from 9 7 to 8 8 cal ka bp the western svalbard margin surface waters were significantly warmer than today this warm period the thermal maximum was followed by an abrupt cooling at 8 8 cal ka bp caused by an increased influence of arctic water from the arctic ocean the results document that the european arctic was very sensitive to climatic and oceanographic changes at the end of the last glacial and during the holocene

modelling infragravity motions on a rip channel beach a non linear shallow water wave model operating on the time scale of wave groups is compared with measurements of infragravity motions on a rip channel beach to verify the model concepts and assess the model performance the measurements were obtained during the rip current experiment ripex in concert with the steep beach experiment sbe performed at sand city monterey bay ca during the spring of 2001 the nearshore bathymetry was made up of shore connected shoals incised by relatively narrow rip channels spaced approximately 125 m apart the comparison considers a 20 day period during which significant changes in both the offshore wave climate and nearshore bathymetry occurred the temporal variation in infragravity conditions during the experiment is strong with computational results typically explaining 70 to 80 of the observed infragravity motions within the nearshore in contrast to the temporal variation the alongshore spatial variation in infragravity intensity during the experiment is generally weak even though the underlying bathymetry shows strong depth variations model computations suggest preferential coupling between the computed edge wave motions and the quasi periodic bathymetry is present a prerequisite for strong spatial variability however the infragravity field is dominated by cross shore infragravity motions which are only weakly coupled to the quasi periodic bathymetry resulting in a weak alongshore variability of the total infragravity motions

modeling of nonlinear wave propagation over fringing reefs abstract the applicability of existing nonlinear triad spectral models for steep slopes 0 1 0 2 characteristic of reef environments was investigated using both deterministic phase resolving and stochastic phased averaged formulations model performance was tested using laboratory observations of unidirectional wave transformation over steep and smooth bathymetry profiles the models developed for mild slopes were implemented with minimal modifications the inclusion of breaking parametrizations and linear steep slope corrections required by laboratory data the deterministic model produced typically more accurate predictions than the stochastic one but the phase averaged formulation proved fast enough to allow for an inverse modeling search for the optimal breaking parametrization the effects of the additional assumptions of the stochastic approach resulted in a slower than observed evolution of the infragravity band despite the challenge posed by the fast wave evolution and energetic breaking characteristic to the steep reef slopes both formulations performed overall well and should be considered as good provisional candidates for use in numerical investigation of wave current interaction processes on steep reefs

late weichselian local ice dome configuration and chronology in northwestern svalbard early thinning late retreat the chronology and configuration of the svalbard barents sea ice sheet sbsis during the late weichselian lw are based on few and geographically scattered data thus the timing and configuration of the sbsis has been a subject of extensive debate we present provenance data of erratic boulders and cosmogenic 10be ages of bedrock and boulders from northwest spitsbergen nws svalbard to determine the thickness configuration and chronology during the lw we sampled bedrock and boulders of mountain summits and summit slopes along with erratic boulders from coastal locations around nws we suggest that a local ice dome over central nws during lw drained radially in all directions provenance data from erratic boulders from northern coastal lowland reinsdyrflya suggest northeastward ice flow through liefdefjorden 10be ages of high elevation erratic boulders in central nws 687 836 m above sea level ranging from 18 3 1 3 ka to 21 7 1 4 ka indicate that the centre of a local ice dome was at least 300 m thicker than at present 10be ages of all high elevation erratics 400 m above sea level central and coastal locations indicate the onset of ice dome thinning at 25 20 ka 10be ages from erratic boulders on reinsdyrflya ranging from 11 1 0 8 ka to 21 4 1 7 ka indicate an ice cover over the entire reinsdyrflya during lw and a complete deglaciation prior to the holocene but apparently later than the thinning in the mountains lack of moraine deposits but the preservation of beach terraces suggest that the ice covering this peninsula possibly was cold based and that reinsdyrflya was part of an inter ice stream area covered by slow flowing ice as opposed to the adjacent fjord which possibly was filled by a fast flowing ice stream despite the early thinning of the ice sheet 25 20 ka we find a later timing of deglaciation of the fjords and the distal lowlands several bedrock samples 10be from vertical transects in the central mountains of nws pre date the lw and suggest either ice free or pervasive cold based ice conditions our reconstruction is aligned with the previously suggested hypothesis that a complex multi dome ice sheet configuration occupied svalbard and the barents sea during lw with numerous drainage basins feeding fast ice streams separated by slow flowing possibly cold based inter ice stream areas

holocene paleoceanography and glacial history of the west spitsbergen area euro arctic margin two sediment cores from the west spitsbergen area euro arctic margin md99 2304 and md99 2305 have been investigated for paleoceanographic proxies including benthic and planktonic foraminifera benthic foraminiferal stable isotopes and ice rafted debris core md99 2304 is located on the upper continental margin reflecting variations in the influx of atlantic water in the west spitsbergen current core md99 2305 is located in van mijenfjord picturing variations in tidewater glacier activity as well as fjordocean circulation changes surface water warmer than today was present on the margin as soon as the van mijenfjord was deglaciated by 11 200 cal years bp relatively warm water invaded the fjord bottom almost immediately after the deglaciation a relatively warm early holocene was followedby an abrupt cooling at 8800 cal years bp on the continental margin another cooling in the fjord record 8000 4000 cal years bp is documented by an increase in ice rafted debris and an increase in benthic foraminiferal d 18 o the ird record indicates that central spitsbergen never was completely deglaciated during the holocene relatively cool andstable cond itions similar to the present were establishedabout 4000 cal years bp

depth and current induced effects on wave propagation into the altamaha river estuary georgia abstract a study of sea surface wave propagation and its energy deformation was carried out using field observations and numerical experiments over a region spanning the midshelf of the south atlantic bight sab to the altamaha river estuary ga wave heights on the shelf region correlate with the wind observations and directional observations show that most of the wave energy is incident from the easterly direction comparing midshelf and inner shelf wave heights during a time when there was no wind and hence no wave development led to an estimation of wave energy dissipation due to bottom friction with corresponding wave dissipation factor of 0 07 for the gently sloping continental shelf of the sab after interacting with the shoaling region of the altamaha river the wave energy within the estuary becomes periodic in time showing wave energy during flood to high water phase of the tide and very little wave energy during ebb to low water this periodic modulation inside the estuary is a direct result of enhanced depth and current induced wave breaking that occurs at the ebb shoaling region surrounding the altamaha river mouth at longitude 81 23 w modelling results with stwave showed that depth induced wave breaking is more important during the low water phase of the tide than current induced wave breaking during the ebb phase of the tide during the flood to high water phase of the tide wave energy propagates into the estuary measurements of the significant wave height within the estuary showed a maximum wave height difference of 0 4 m between the slack high water shw and slack low water slw in this shallow environment these wave current interactions lead to an apparent bottom roughness that is increased from typical hydraulic roughness values leading to an enhanced bottom friction coefficient

two leading modes of the interannual variability in south american surface air temperature during austral winter the first two empirical orthogonal function eof modes of the surface air temperature sat interannual variability in the south american sa continent have been revealed in several previous studies this presentation focuses on winter season and furtherly investigates the detailed advection and cloud radiation processes and teleconnections from tropical sea surface temperature anomalies ssta combining statistical analysis with rossby wave dynamics and modelling experiments the eof1 featured with the anomalous center in the central part is related to the tropical eastern pacific ssta which may impact on the sa sat variability through the walker circulation and a regional hadley cell the anomalous center is largely attributed to low level advection transported by the hadley cell the eof2 as a fluctuation between anomalies in the southeast brazil and the southern tip is related to the ssta surrounding the maritime continent which may generate a barotropic wave train propagating to the sa continent this wave train can strengthen high latitude westerly flow transporting warm advection to the southern tip and generate southeast anomalous flow transporting cold advection to the southeast brazil meanwhile the cloud radiation processes are also involved to enhance the advection induced sat anomalies in both areas

comparison between the wintertime and summertime dynamics of the misa river estuary abstract the misa river on the italian adriatic coast is typical of the rivers that drain the apennine mountain range the focus of this study conducted in the late summer of 2013 and mid winter of 2014 was to contrast the general wintertime summertime dynamics in the misa river estuarine system rather than investigate specific dynamical features e g offshore sediment transport channel seiche and flocculation mechanisms summertime conditions of the misa river estuary are characterized by low freshwater discharge and net sediment deposition whereas in the wintertime the misa river and estuary is characterized by high episodic freshwater discharge and net erosion and sediment export major observed differences between wintertime summertime dynamics in the misa river and estuary are a result of seasonal scale differences in regional precipitation and forcing conditions driven largely by the duration and intensity of prevailing wind patterns that frequently change direction in summertime while keep almost constant directions for much longer periods in wintertime thus generating major sea storms sediment deposition was observed in the final reach of the misa river and estuary in the summertime however in the wintertime large flood events led to sediment erosion and export in the final reach of the misa river and estuary that in conjunction with storm wave induced mud transport led to sediment deposition at the river entrance and in the adjacent nearshore region the seasonal cyclic pattern of erosion and deposition was confirmed with bathymetric surveys of the final reach of the estuarine region a critical component for the balance between summertime deposition and wintertime erosion was the presence of an underlying mat of organic deposits that limited the availability of sediments for erosion in winter when massive debris transport occurs further suspended cohesive sediments flocs were subjected to smaller hydrodynamic stresses in the summertime favoring deposition within the estuary conversely during wintertime storms flocs were subjected to larger hydrodynamic stresses favoring breakup into smaller flocs and deposition outside the estuary

the influence of nonlinearities and different sst spatial patterns on the summertime anomalies in subtropical south america during strong enso events in this study we analyze the impacts of the strongest enso events on subtropical south america ssa rainfall during the austral summer in the period 1979 2014 we consider reanalysis data and model experiments for the strongest el nino events the precipitation pattern over ssa presents a monopole structure the reanalysis shows a short rossby wave train that causes an increase of the baroclinicity and advection of cyclonic vorticity toward ssa together with an increase in the moisture transport by the south american low level jet sallj they induce strong positive precipitation anomalies over ssa the model reproduces this rainfall anomaly as consequence of a strengthening of the upper level jet and of the sallj although it does not simulate the short wave train from the pacific for the strongest la nina events the precipitation pattern presents a tripole like structure with centers located over 1 uruguay 2 the continental part of the south atlantic convergence zone c sacz and 3 the northwestern argentina nw arg in both cases reanalysis and model experiments the tripole is associated with a weakening of the sallj that increases reduces rainfall anomalies over c sacz uruguay and with an anomalous increase of the lower level moisture convergence over nw arg that increases precipitation over there differences in precipitation responses to the strongest enso events are mainly associated to changes in the spatial pattern of the sea surface temperature anomalies however there is also a contribution of nonlinearities

the role of morphology and wave current interaction at tidal inlets an idealized modeling analysis the outflowing currents from tidal inlets are influenced both by the morphology of the ebb tide shoal and interaction with incident surface gravity waves likewise the propagation and breaking of incident waves are affected by the morphology and the strength and structure of the outflowing current the 3 d coupled ocean atmosphere wave sediment transport coawst modeling system is applied to numerically analyze the interaction between currents waves and bathymetry in idealized inlet configurations the bathymetry is found to be a dominant controlling variable in the absence of an ebb shoal and with weak wave forcing a narrow outflow jet extends seaward with little lateral spreading the presence of an ebb tide shoal produces significant pressure gradients in the region of the outflow resulting in enhanced lateral spreading of the jet incident waves cause lateral spreading and limit the seaward extent of the jet due both to conversion of wave momentum flux and enhanced bottom friction the interaction between the vorticity of the outflow jet and the wave stokes drift is also an important driving force for the lateral spreading of the plume for weak outflows the outflow jet is actually enhanced by strong waves when there is a channel across the bar due to the return current effect for both strong and weak outflows waves increase the alongshore transport in both directions from the inlet due to the wave induced setup over the ebb shoal wave breaking is more influenced by the topography of the ebb shoal than by wave current interaction although strong outflows show intensified breaking at the head of the main channel

post glacial relative sea level history of northwestern spitsbergen svalbard the late weichselian and holocene raised beach sequences on northwestern spitsbergen provide a detailed record of sea level oscillations during the last deglacial hemicycle initial emergence commenced at 13 ka coincident with local deglaciation and until 10 5 ka was characterized by a relative slow rate of emergence 1 5 to 5 m ka interrupted by minor stillstands or transgressions associated with possible glacier re advances the orientation of paleo spits and the paucity of whale remains at the late weichselian marinelimit indicate that the prevailing westerly fetch was dampened by a semi permanent sea ice cover allowing long shore drift to predominate a period of accelerated emergence 15 to 30 m ka between 10 5 and 9 ka is correlative with rapid deglaciation of fiords the middle and late holocene is characterized by two brief transgressions one between 6 5 and 5 0 ka that did not exceed 7 m asl and a present probable slow rise in sea level that commenced 2 to 1 ka the strandline tilts in northwestern spitsbergen and the pattern and rate of emergence on svalbard indicate that the maximum glacier loads during the late weichselian were centered on nordaustlandet and on the central and eastern part of the archipelago northwestern and southwestern spitsbergen were marginal to glacial loading and were deglaciated early 13 ka which is presently incompatible with maximum ice sheet extent and the timing and position of deglacial margins recently reconstructed for the barents sea and svalbard mountain ranges and large fiords probably confined major outlet glaciers to the central part of the archipelago preventing inundation of much of western spitsbergen by an inferred large ice sheet based in eastern svalbard and the barents sea

brine formation in relation to climate changes and ice retreat during the last 15 000 years in storfjorden svalbard 76 78 n storfjorden svalbard is an area of intense brine formation the brine is cold dense rich in oxygen and co2 and has reduced ph storfjorden is unique because it contains well preserved agglutinated foraminifera dating back to the beginning of the last deglaciation we have investigated the distribution of calcareous and agglutinated benthic foraminifera benthic oxygen and carbon isotopes calcium carbonate total organic carbon and ice rafted debris in five cores from storfjorden comprising the holocene and the deglaciation the purpose of the study is to reconstruct brine formation in the past under different climate scenarios the data indicate that in storfjorden the ratio of agglutinated to calcareous benthic foraminifera can be taken as a measure of the strength of brine formation the foraminiferal data which are supported by stable isotopes degree of fragmentation and geochemical parameters signify that brine formation intensified during cold periods and weakened during warm periods during the deglaciation increased brine flow coincides with the older dryas the intra allerod cold period and the younger dryas brine formation increased from circa 8200 years b p reaching periodic maxima during the last 4000 years b p in response to the unstable climate maximum brine production correlates with the dark ages cold period circa 1500 1100 years b p and the little ice age circa 600 100 years b p lower production correlates with the roman warm period circa 2500 2000 years b p and the medieval warm period circa 1000 700 years b p

a review of postglacial emergence on svalbard franz josef land and novaya zemlya northern eurasia the pattern of postglacial emergence in the barents sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern eurasia this review unites records of holocene relative sea level from svalbard franz josef land and novaya zemlya to better understand the geometries of past ice sheet loads emergence data from northern eurasia confine the maximum area of glacier loading to the northwestern barents sea where 100 m of emergence is measured on kongs ya deglacial unloading commenced on western and northern spitsbergen c 13 12 14 c ka ago and by c 10 5 14 ck a on eastern svalbard and more distal sites on franz josef land and novaya zemlya the marine limit phase c 13 12 14 c ka on western and northern spitsbergen is characterized by the construction of spits indicating a dominance of long shore drift over stormgenerated fetch reflecting extensive sea ice coverage of coastal areas at sites in proximity to the ice sheet margin on western and northern spitsbergen there is evidence for a transgressive regressive cycle c 6 4 14 c ka possibly reflecting back migration of displaced mantle material a modern transgression is inferred from the marine erosion of 17th century cultural features and 14 c ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c 2 to 1 ka ago the greatest observed emergence on franz josef land occurs on bell island with a marine limit at 49 m aht formed c 10 14 c ka available emergence data since 9 ka show rising strandlines toward the southwest at b0 3 m km the northern limit of emergence on franz josef land is poorly constrained because relative sea level data is sparse north of 80 30 0 n in contrast to svalbard and franz josef land the marine limit on northern novaya zemlya is only 10 15 m above high tide and formed between 6 5 and 5 0 14 c ka when global sea level was stabilizing all sites show little apparent emergence during the past 2 ka with the youngest raised landforms at identical heights to storm beaches this minimal glacio isostatic signature on novaya zemlya and on vaygach island where deglaciation commenced 10 ka ago indicates ice sheet thicknesses of o1 5 km the spatial variation in emergence for the barents sea indicates that western and northern spitsbergen and novaya zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage 2 6 ka and were probably not in isostatic equilibrium in contrast central and eastern svalbard and southern franz josef land were beneath a substantial ice load and probably sustained this load for c 10 14 c ka and achieved isostatic equilibrium isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets but deviates substantial at the ice sheet margin or areas covered by thin ice like novaya zemlya

observations of infragravity waves infragravity wave periods of one half to a few minutes energy levels observed for about 1 year in 8 m water depth in the pacific and in 8 and 13 m depths in the atlantic are highly correlated with energy in the swell frequency band 7 to 20 s periods suggesting the infragravity waves were generated locally by the swell the amplification of infragravity wave energy between 13 and 8 m depth separated by 1 km in the cross shore is about 2 indicating that the observed infragravity motions are dominated by free waves not by group forced bound waves which in theory are amplified by an order of magnitude in energy between the two locations however bound waves are more important for the relatively few cases with very energetic swell when the observed amplification between 13 and 8 m depth of infragravity wave energy was sometimes 3 times greater than expected for free waves bispectra are consistent with increased coupling between infragravity waves and groups of swell and sea for high energy incident waves

intraseasonal predictions for the south american rainfall dipole the south american rainfall dipole sad is a renowned spatial structure present in the austral summer as part of the south american monsoon system sad phases have been related with extreme precip

northern north sea benthic ostracoda modern distribution and palaeoenvironmental significance the ostracod faunas of the northern north sea exhibit a depth related distribution that is controlled by substrate and hydrographic conditions four biofacies are defined on the basis of total live dead counts sandy substrates shallower than 110 m are characterized by robertsonites tuberculatus and cytheropteron latissimum these species are replaced by acanthocythereis dunelmensis and palmenella limicola on sandy muds in the fladen ground 110 150 m muellerina abyssicola dominates from 175 250 m in the norwegian channel giving way to krithe praetexta at greater depths on soft bottom substrates the results are compared with data from the skagerrak and the western european shelf area temperature ranges for the commonest taxa show that north sea faunas contain endemic western european species temperature range on average 2 20 c some southern species 5 26 c and taxa that range to high latitudes 2 to 14 c southern species are confined to the southern and western margins of the north sea

recent ostracoda from the laptev sea arctic siberia species assemblages and some environmental relationships ostracod assemblages from coretop sediments collected at 26 localities at different depths of the laptev sea shelf and upper continental slope were investigated for assemblage studies a total of 41 species belonging to 19 genera and 12 families have been identified three assemblages have been established that could be linked to environmental factors such as water depth bottom salinities water mass circulation and sea ice transportation the species rich and abundant assemblages of the western and central laptev sea were related to the atlantic waters occupying the upper continental slope these include relatively deep water forms that show clear affinities to north atlantic and arctic ocean assemblages cytheropteron biconvexa c testudo c simplex c nodosoalatum c inflatum c porterae krithe glacialis k minima pseudocythere caudata polycope punctata p orbicularis in the eastern middle shelf region the assemblage is comprised of acanthocythereis dunelmensis together with other normal marine species semicytherura complanata elofsonella concinna cluthia cluthae this assemblage seems connected to the winter flaw polynya which is believed to be the main area of sediment entrainment into sea ice the inner shelf assemblage of the southern laptev sea is dominated by shallow water euryhaline species paracyprideis pseudopunctillata and heterocyprideis sorbyana with admixture of the brackish water species roundstonia macchesneyi the unusual occurrence of a number of shallow water ostracod species on the upper continental slope may be explained by ice rafting which these ostracods are probably able to survive

midsummer low level circulation and precipitation in subtropical south america and related sea surface temperature anomalies in the south atlantic abstract the midsummer interannual variability of the low level tropospheric circulation and of the precipitation field in subtropical south america sa associated to the sea surface temperature sst anomalies in the western subtropical south atlantic ocean wssa is investigated using reanalyses regional precipitation datasets and monthly ssts the region of the wssa where sst has the strongest relation with precipitation in subtropical sa was identified using canonical correlation analysis this region extends from 20 to 30 s and from 30 to 50 w composites corresponding to extreme ssts in this area show two well differentiated patterns in the low level circulation and in the precipitation fields in the composite corresponding to the more positive sst anomalies in this area the mainstream of the low level flow and of the moisture transport from the continental low latitudes starts to follow a southeastward direction at 10 s and converges with the west flow at 35 s over the atlantic ocean on t

reconstruction of glacier variability from lake sediments reveals dynamic holocene climate in svalbard abstract the arctic is warming faster than anywhere else on earth holocene proxy time series are increasingly used to put this amplified response in perspective by understanding arctic climate processes beyond the instrumental period however available datasets are scarce unevenly distributed and often of coarse resolution glaciers are sensitive recorders of climate shifts and variations in rock flour production transfer this signal to the lacustrine sediment archives of downstream lakes here we present the first full holocene record of continuous glacier variability on svalbard from glacier fed lake hajeren this reconstruction is based on an undisturbed lake sediment core that covers the entire holocene and resolves variability on centennial scales owing to 26 dating points a toolbox of physical geochemical xrf and magnetic proxies in combination with multivariate statistics has allowed us to fingerprint glacier activity in addition to other processes affecting the sediment record evidence from variations in sediment density validated by changes in ti concentrations reveal glaciers remained present in the catchment following deglaciation prior to 11 300 cal bp culminating in a holocene maximum between 9 6 and 9 5 ka cal bp correspondence with freshwater pulses from hudson strait suggests that early holocene glacier advances were driven by the melting laurentide ice sheet lis we find that glaciers disappeared from the catchment between 7 4 and 6 7 ka cal bp following a late hypsithermal glacier reformation around 4250 cal bp marks the onset of the neoglacial supporting previous findings between 3380 and 3230 cal bp we find evidence for a previously unreported centennial scale glacier advance both events are concurrent with well documented episodes of north atlantic cooling we argue that this brief forcing created suitable conditions for glaciers to reform in the catchment against a background of gradual orbital cooling these findings highlight the climate sensitivity of the small glaciers studied which rapidly responded to climate shifts the start of prolonged neoglacial glacier activity commenced during the little ice age lia around 700 cal bp in agreement with reported advances from other glaciers on svalbard in conclusion this study proposes a three stage holocene climate history of svalbard successively driven by lis meltwater pulses episodic atlantic cooling and declining summer insolation

deglacial meltwater pulse 1b and younger dryas sea levels revisited with boreholes at tahiti reconstructing sea level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets the resolution of the few sea level records covering the critical time interval between 14 000 and 9 000 calendar years before the present is still insufficient to draw conclusions about sea level changes associated with the younger dryas cold event and the meltwater pulse 1b mwp 1b we used the uranium thorium method to date shallow living corals from three new cores drilled onshore in the tahiti barrier reef no significant discontinuity can be detected in the sea level rise during the mwp 1b period the new tahiti sea level record shows that the sea level rise slowed down during the younger dryas before accelerating again during the holocene

seasonal dependence of enso teleconnections over south america and relationships with precipitation in uruguay the el nino southern oscillation enso has an established impact on precipitation in uruguay during austral spring october december this impact is absent in peak summer january february and returns weakly in fall winter march july interannual and intraseasonal variability of the atmospheric circulation over south america and the south pacific is investigated using the ncep ncar reanalysis data for these seasons the leading empirical orthogonal function eof of seasonally averaged 200 hpa winds over south america is found to be associated with enso through a pronounced walker cell component in all seasons however during spring this pattern acquires an extratropical teleconnection that links the circulation over southeastern south america sesa with enso this extratropical teleconnection disappears in summer when the circulation over sesa is dominated by variability in the south atlantic convergence zone in fall extratropical south america again becomes affected by a wavelike pattern that extends over the south pacific but it is uncorrelated with enso on intraseasonal timescales a cluster analysis of daily geopotential height fields over the south pacific sector reveals three wave train like circulation regimes with similar structures in all seasons during the transition seasons but not summer the frequencies of occurrence of two of these regimes are found to be significantly different from normal in years when the interannual wavelike eofs are pronounced interannual anomaly patterns are constructed from the intraseasonal regimes according to these changes in their frequency of occurrence and shown to resemble quite closely the interannual eofs over the south pacific sector these results provide evidence that the interannual teleconnection patterns seen over the south pacific in austral spring and fall winter are due to changes in the frequency of occurrence and amplitude of intraseasonal circulation regimes the rossby wave source composited over enso years suggests that enso heating anomalies are able to trigger these changes in regime occurrence and amplitude during october december through rossby wave propagation leading to the known enso teleconnection in austral spring by contrast the interannual teleconnection over the south pacific during fall winter appears to be due to essentially random changes in the frequency of occurrence of the intraseasonal circulation regimes which are found to be much larger than during austral summer when no extratropical teleconnection pattern exists

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

the svalbard barents sea ice sheet historical current and future perspectives abstract the history of research on the late quaternary svalbard barents sea ice sheet mirrors the developments of ideas and the shifts of paradigms in glacial theory over the past 150 years since the onset of scientific research there in the early 19th century svalbard has been a natural laboratory where ideas and concepts have been tested and played an important but rarely acknowledged role in the break through of the ice age theory in the 1870 s the history of how the scientific perception of the svalbard barents sea ice sheet developed in the mid 20th century also tells a story of how a combination of fairly scattered and often contradictory observational data and through both deductive and inductive reasoning could outline a major ice sheet that had left but few tangible fingerprints since the 1980 s with increased terrestrial stratigraphical data ever more marine geological evidence and better chronological control of glacial events our perception of the svalbard barents sea ice sheet has changed the first reconstructions depicted it as a static concentric single domed ice sheet with ice flowing from an ice divide over the central northern barents sea that expanded and declined in response to large scale late quaternary climate fluctuations and which was more or less in tune with other major northern hemisphere ice sheets we now increasingly perceive it as a very dynamic multidomed ice sheet controlled by climate fluctuations relative sea level change as well as subglacial topography substrate properties and basal temperature in this respect the svalbard barents sea ice sheet will increasingly hold the key for understanding the dynamics and processes of how marine based ice sheets build up and decay

hydrodynamics at a microtidal inlet analysis of propagation of the main wave components abstract the evolution of different wave components as they propagate within a microtidal inlet during a storm occurring from 24 26 january 2014 is analysed in order to improve knowledge on how microtidal river mouths typical of the adriatic sea behave for the first time the low pass filter mechanism previously ascertained at several macrotidal oceanic inlets around the world has been observed in the field with remarkably specific hydrodynamic conditions i e low tide excursion permanent connection with the sea and generally milder wave climate than in the ocean sea swell ss waves were strongly dissipated before entering the river mouth through the combined action of wave breaking due to reducing depths and opposing river currents enhanced by rainfall infragravity ig waves propagated upstream and significant ig wave heights of up to 0 4 m about 13 of the local water depth have been observed 400 m upriver about 10 times the local ss peak wavelength during storm climax the ig wave energy here represented over 4 of the maximum offshore storm energy ig wave components travelled upriver at estimated velocities between 3 6 m s and 5 5 m s comparable with speeds of nonlinear long waves during intense storm stages up to 600 m into the river channel about 15 times the local ss peak wavelength and are enhanced by tide induced increase in water depths it is estimated that tide induced excursion accounted for about 80 of the total mean water elevation at storm peak at about 400 m into the river finally tidal oscillations are detected up to 1 5 km upstream about 40 times the local ss peak wavelength this study highlights the dominance of astronomical tide over both wave setup and storm surge in controlling the upriver propagation of ig waves even in a microtidal environment

deep arctic ocean warming during the last glacial cycle in the arctic ocean the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier atlantic layer by a halocline ongoing sea ice loss and warming in t

wave current interactions in a wave dominated tidal inlet 1 wave current interactions play a major role in the dynamics of shallow tidal inlets this study investigates these interactions at a natural inlet with a strong focus on current induced changes on wave propagation the analysis of hydrodynamic data collected at the albufeira lagoon portugal revealed spatiotemporal variations of water levels and wave heights along the inlet attributed to wave current interaction processes we compared the simulations of a coupled wave circulation modeling system computed with and without waves and propagated with and without current feedback the wave induced setup inside the lagoon represented 7 15 of the offshore significant wave height the accuracy of the wave s predictions improved when current feedback was included during ebb the currents increased the wave height at the mouth of the inlet up to 20 and decreased the wave height in the inlet up to 40 due to current induced refraction steepness dissipation and partial blocking during flood the currents decreased the wave height in the inlet up to 10 and increased the wave height at the exterior parts of the ebb shoal up to 10 due to current induced refraction these effects significantly attenuate seaward sediment fluxes during ebb and contribute to the sediment accretion in the inlet

some overlooked features of tropical atlantic climate leading to a new nino like phenomenon abstract the atlantic nino an equatorial zonal mode akin to the pacific el nino southern oscillation enso is phase locked to boreal summer when the equatorial easterly winds intensify and the thermocline shoals in the gulf of guinea a suite of satellite and in situ observations reveals a new mode of tropical atlantic variability that displays many characteristics of the zonal mode but instead peaks in november december nd this new mode is found to be statistically independent from both the atlantic nino in the preceding summer and the pacific enso the origin of this nd zonal mode lies in an overlooked aspect of the seasonal cycle in the equatorial atlantic in november the equatorial easterly winds intensify for the second time increasing upwelling and lifting the thermocline in the gulf of guinea an analysis of high resolution climatological data shows that these dynamical changes induce a noticeable sst cooling in the central equatorial atlantic the shoaling thermocline and increased upwelli

infragravity currents in a small ria estuary amplified coastal edge waves abstract observations are presented of estuarine infragravity oscillations in a very small estuary the ria de santiuste northern spain that discharges into a bay time scale calculations and measurements indicate that the most likely source of amplified infragravity waves within the estuary are coastal edge waves which appear to be resonating between the headlands of the bay and onshore offshore seiching of waters that may be resonating between the beach and the bay s seaward limit infragravity waves in the estuary have a narrow power dominant periodicity range of 4 3 4 8 min generally only very weak waves and at other periodicities occur within the tidal river when it is unaffected by the tide although infragravity water level amplitudes are small in the tidal river typically 0 01 m during high water the corresponding velocity amplitudes are significant typically 0 1 m s 1 despite the occurrence of high runoff conditions during these measurements within the estuary and close to the mouth near bed salinity shows considerable variability that is a consequence of salt wedge oscillations with periodicities that are within the range of 4 3 4 8 min model results for simulated neap to spring high water water levels show that wave periodicities in the range 3 5 4 5 min correspond approximately to 3 4 resonances the model also indicates that an effect of low runoff is to greatly enhance resonant behaviour within the estuary such that water level amplitudes of 0 02 m at the mouth can produce wave currents as fast as 0 4 m s 1 within the estuary compared with 0 1 m s 1 during high runoff

wave run up on a high energy dissipative beach 1 because of highly dissipative conditions and strong alongshore gradients in foreshore beach morphology wave run up data collected along the central oregon coast during february 1996 stand in contrast to run up data currently available in the literature during a single data run lasting approximately 90 min the significant vertical run up elevation varied by a factor of 2 along the 1 6 km study site ranging from 26 to 61 of the offshore significant wave height and was found to be linearly dependent on the local foreshore beach slope that varied by a factor of 5 run up motions on this high energy dissipative beach were dominated by infragravity low frequency energy with peak periods of approximately 230 s incident band energy levels were 2 5 to 3 orders of magnitude lower than the low frequency spectral peaks and typically 96 of the run up variance was in the infragravity band a broad region of the run up spectra exhibited an f 4 roll off typical of saturation extending to frequencies lower than observed in previous studies the run up spectra were dependent on beach slope with spectra for steeper foreshore slopes shifted toward higher frequencies than spectra for shallower foreshore slopes at infragravity frequencies run up motions were coherent over alongshore length scales in excess of 1 km significantly greater than decorrelation length scales on moderate to reflective beaches

reconstruction of inflow of atlantic water to isfjorden svalbard during the holocene correlation to climate and seasonality abstract the distribution patterns of benthic foraminifera faunas stable isotopes and ice rafted debris ird have been studied in piston core jm98 845 pc from isfjorden western svalbard to reconstruct changes in the flow of atlantic water during the holocene interglacial the paleoenvironmental conditions in isfjorden and the inflow of the atlantic water followed closely the changes in insolation with strong seasonality in the early holocene and weaker seasonality in the middle to late holocene a summer temperature maximum of the bottom water occurred in the early holocene 10 500 c 8200 years bp cooling began at 9000 years bp with stepwise coolings at c 8200 7400 and 4000 years bp the cooling correlated with an increase in ice rafting and increased influence of polar water and seasonal sea ice cover between 4000 and 2000 years bp bottom water temperatures reached a minimum after 2000 years bp episodic inflow of warmer atlantic water at the bottom of the fjord occurred and conditions became more unstable the data indicate close interaction of the flow of atlantic water with the development of the terrestrial climate and the amount of polar meltwater and sea ice

cross shore sand transport by infragravity waves as a function of beach steepness two field data sets of near bed velocity pressure and sediment concentration are analyzed to study the influence of infragravity waves on sand suspension and cross shore transport on the moderately sloping sand motor beach 1 35 the local ratio of infragravity wave height to sea swell wave height is relatively small hig hsw 0 4 most sand is suspended during negative infragravity velocities and qig is offshore directed the infragravity contribution to the total sand flux is considerably larger and reaches up to 60 during energetic conditions on the whole hig hsw is a good indicator for the infragravity related sand suspension mechanism and the resulting infragravity sand transport direction and relative importance

dating high arctic holocene relative sea level changes using juvenile articulated marine shells in raised beaches high arctic raised beaches provide evidence for changes in relative sea level rsl sea ice extent storminess and variations in sediment supply in many high arctic areas driftwood and whale bone are usually the preferred targets for radiocarbon dating with marine shells a third choice because of their often large age and height uncertainties with respect to former sea level here we detail a new approach to sampling marine shells that reduces these problems by targeting juvenile articulated specimens of astarte borealis that are washed onto the beach under storm conditions and become incorporated into the beach crest radiocarbon dates from articulated valves of a borealis from eight raised beaches from billefjorden svalbard provide a chronology for holocene beach ridge formation and rsl change that compares favourably to the most precise records developed from elsewhere in svalbard using driftwood or whale bone we demonstrate the value of this new approach by comparing our record with previously published rsl data from eastern svalbard to test different models of late weichselian ice load in this region we find support for a major ice dome centred south and east of kong karls land but no evidence for a significant ice dome located over easternmost spitsbergen or southern hinlopen strait as proposed from recent marine geophysical survey the approach is potentially applicable elsewhere in svalbard and the high arctic to address questions of rsl change and beach ridge chronology and hence wider questions regarding palaeoclimate and ice load history

sediment transport and beach morphodynamics induced by free long waves bound long waves and wave groups new laboratory data are presented on the influence of free long waves bound long waves and wave groups on sediment transport in the surf and swash zones as a result of the very significant difficulties in isolating and identifying the morphodynamic influences of long waves and wave groups in field conditions a laboratory study was designed specifically to enable measurements of sediment transport that resolve these influences the evolution of model sand beaches each with the same initial plane slope was measured for a range of wave conditions firstly using monochromatic short waves subsequently the monochromatic conditions were perturbed with free long waves and then substituted with bichromatic wave groups with the same mean energy flux the beach profile changes and net cross shore transport rates were extracted and compared for the different wave conditions with and without long waves and wave groups the experiments include a range of wave conditions e g high energy moderate energy low energy waves which induce both spilling and plunging breakers and different turbulent intensities and the beaches evolve to form classical accretive erosive and intermediate beach states the data clearly demonstrate that free long waves influence surf zone morphodynamics and promote increased onshore sediment transport during accretive conditions and decreased offshore transport under erosive conditions in contrast wave groups which can generate both forced and free long waves generally reduce onshore transport during accretive conditions and increase offshore transport under erosive conditions the influence of the free long waves and wave groups is consistent with the concept of the relative fall velocity h wst as a dominant parameter controlling net beach erosion or accretion free long waves tend to reduce h wst promoting accretion while wave groups tend to increase the effective h wst promoting erosion

what are the climate controls on δd in precipitation in the zongo valley bolivia implications for the illimani ice core interpretation abstract controversy has surrounded the interpretation of the water isotopic composition d or 18o in tropical and subtropical ice cores in south america although recent modeling studies using agcm have provided useful constraints at interannual time scales no direct calibration based on modern observations has been achieved in the context of the recent ice core drilling at nevado illimani 16 39 s 67 47 w in bolivia we examine the climatic controls on the modern isotopic composition of precipitation in the zongo valley located on the northeast side of the cordillera real at about 55 km from nevado illimani monthly precipitation samples were collected from september 1999 to august 2004 at various altitudes along this valley first we examine the local and regional controls on the common d signal measured along this valley we show that 1 local temperature has definitely no control on d variations and 2 local rainout is a poor factor to explain d variations we thus seek regional controls upstream the valley potentially affecting air masses distillation based on backtrajectory calculations and using satellite data trmm precipitation noaa olr and direct observations of precipitation iaea gnip we show that moisture transport history and the degree of rainout upstream are more important factors explaining seasonal d variations analysis of a 92 yr simulation from the echam 4 model t30 version implemented with water stable isotopes confirms our observations at seasonal time scale and emphasize the role of air masses distillation upstream as a prominent factor controlling interannual d variations lastly we focus on the isotopic depletion along the valley when air masses are lifted up our results suggest that if the temperature gradient between the base and the top of the andes was higher by a few degrees during the last glacial maximum lgm less than 10 of the glacial to interglacial isotopic variation recorded in the illimani ice core could be accounted for by this temperature change it implies that the rest of the variation would originate from wetter conditions along air masses trajectory during lgm

tidally discontinuous ocean forcing in bar built estuaries the interaction of tides infragravity motions and frictional control shallow bar built estuaries on wave dominated coasts in mediterranean climates experience an intermittent connection to the ocean in the presence of low streamflow their inlets may completely close as a result of nearshore sand transport but even in the open condition these inlets remain constricted extensive field measurements in the highly salt stratified pescadero estuary in northern california show that the shallow mouth causes these estuaries to experience discontinuous tidal forcing while the ocean and estuary are fully connected with near equal water levels tidal velocities are slow but infragravity motions in the nearshore induce large velocity oscillations within the estuary as the ocean tide falls infragravity forcing is cut off because the estuarine mouth is perched above the low tide ocean water level and ebbing velocities are set by bed friction observations reveal this oscillation between ocean forced and frictionally controlled conditions characterizes and sets estuarine hydrodynamics additional wave setup of the lagoon emphasizes the dependence of these estuaries on nearshore ocean conditions but the diurnal or semidiurnal retreat of the ocean below the mouth cuts off this nearshore influence so it too is tidally varying here we present detailed observations and a framework for understanding hydrodynamics in small shallow bar built estuaries

water levels in a dual basin harbour in response to infragravity and edge waves abstract seiche modes in a compound harbour an outer harbour connected both to the sea and to an inner harbour were studied using water level data and a numerical model a variety of harbour oscillations are present with periods up to 67 min periods longer than 25 min exceed resonant modes of the harbour this paper addresses the characteristics and causes of the open basin modes the dual harbour open basin mode is modified by constriction at the connection between harbours by partial reflection at the antinode and by the geometry of the entrance the single harbour open basin mode excites the dual harbour closed basin mode which has nearly the same period this forcing moves the closed basin antinode and slightly changes the modal period but the coupling permits the amplitude to increase through the closed basin resonance the water level response to wind stress is weak but significant residual currents can occur which take the form of clockwise gyres in each basin energetic peaks in the water level spectrum at 26 35 and 67 min are shown to correspond to possible edge waves on the local shelf the work has practical implications to port design e g towards minimisation of ship ranging while at anchor