middle to late holocene storminess in brittany nw france part i morphological impact and stratigraphical record our study aims to understand the recurring climatic conditions prevailing during the largest storms reaching nw france brittany these storms are responsible for the breaching of coastal barriers and major flooding of lowlands in a first part of our work we examine the morphological impact and stratigraphic record of storm events along western brittany rocky coasts with a special focus on the southern coast of the bay of audierne the most exposed coast of the region in a second paper middle to late holocene storminess in brittany nw france part ii we shall focus on the chronology of storm events and their climate forcing conditions drilling transects and stratigraphic analyses were first undertaken to constrain chronology strength and wind direction during the main holocene storm events new dates observations and a relative sea level rsl curve were then used to inform discussion of the necessary climatic and morphologic conditions leading to destructive storm events most recorded events appear to be linked with cooling episodes of the holocene and a rsl close to present some storms are clearly responsible for breaching and dune building or remobilisation we demonstrate that storm frequency and intensity appear to rise in a stepwise manner during the late holocene maximum efficiency is reached during the little ice age with clustered events probably lasting several days but major storms also occurred immediately prior to the medieval warm period we suggest that recent coastal dune building from c ad 1100 until now despite a sea level close to present and continuously rising may be a direct consequence of the restoration of beaches after periods of recurrent storminess this building activity often occurred during dry negativ

reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk roberts helen plater a j 2007 reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk the holocene 17 4 pp 495 505 rae2008

optically stimulated luminescence osl dating of coastal aeolian sand accumulation in sanday orkney islands scotland optically stimulated luminescence osl dating of sand has been used to identify periods of enhanced aeolian activity at two coastal archaeological sites in orkney that coincide with periods of holocene climatic deterioration recorded elsewhere in both scotland and w europe areas of tofts ness sanday were settled from the neolithic abandoned in the late neolithic early bronze age reoccupied and permanently abandoned in the iron age sand layers above the neolithic soils have been osl dated to about 4000 bp correlating well with a period of increased aeolian activity elsewhere in w europe osl dating of aeolian sands above midden deposits and a bronze age burial at lopness on sanday suggest dune development by 3000 bp although both sites also contain sand that was deposited during the little ice age several possible mechanisms may have contributed to an increase in aeolian activity during the holocene that led to the abandonment of these sites although volcanic eruptions in iceland cannot be disc

climate control on late holocene high energy sedimentation along coasts of the northeastern atlantic ocean abundant sedimentological and geochronological data gathered on european sandy coasts highlight major phases of increased high energy sedimentation in the north atlantic ocean during the late holocene owing to an inconsistent use of the terminology it is often difficult to determine whether studies have described storm built or wave built deposits both deposits can be identified by overall similar coarse grained sedimentary facies but may provide contradictory paleoenvironmental interpretations the aim of this study is to address this issue by analysing a set of published 14c ages recovered from wave built sediment bodies of the pertuis charentais france integration of 14c data highlights seven coarse grained sedimentation pulses csps that reflect a synchronous increase in wave induced sediment supply occurring around 2650 2420 1240 970 800 650 and 450 cal yr b p csps can be matched with geochronological data published on other exposed sandy coasts of the western europe in first order csps were preserved during phases of decreased storm activity and thus limited coastal erosion in the north atlantic ocean from 2700 to 2000 and from 1200 to 600 cal yr b p in second order csps occurred during positive nao and or negative ea wr peaks which are known from previous studies to induce higher waves and to enhance wave induced sediment transport in the pertuis charentais chronological boundaries of csps could be used as a diagnostic tool to differentiate storm deposits indicative of sudden episodic very high energy sedimentation from wave deposits resulting from the sustained action of above average westerly winds blowing across the north atlantic ocean

beach ridges and prograded beach deposits as palaeoenvironment records abstract beach ridges are landforms commonly developed on prograded coasts with beach shorelines a sequence of beach ridges coupled with their subsurface deposits can be regarded as a time series of coastal evolution methodological advances in field surveying and chronology applicable to beach ridges have led to detailed palaeoenvironmental reconstructions to be derived from such sequences this paper reconsiders the basic aspects of beach ridges and deposits which need to be properly understood for their comprehensive interpretation in a palaeo environmental context it also reviews case studies in which beach ridge sequences have been used to unveil past sea level history catastrophic events and climate changes proposed formative processes of beach ridges include 1 progradation of sandy beach and berm formations in relation to fairweather waves coupled with aeolian foredune accumulation 2 building of gravel ridges by storm waves 3 welding of longshore bars beach ridge formation through sea level oscillation is thought to be questionable and caution is suggested for this process when undertaking palaeoenvironmental reconstruction beach deposit stratification is known to dip either landwards or seawards but landward dips are uncommon seaward dipping stratification is formed in relation to beachface progradation and is usually dissected in places by erosion surfaces resulting from episodic beach retreat the boundary between the foreshore and the underlying shoreface is well defined only in the case that longshore bars lead to complex bedding structure relative to that of the foreshore reliable chronology of beach ridges can be determined by radiocarbon and optically stimulated luminescence osl dating radiocarbon dating of articulated shells which are considered not to be extensively reworked provides robust results but osl dating is more useful as it enables direct dating of sediment grains it is noted that there are restrictions in chronological resolution and continuity inherent to beach ridge and beach deposits the plan view geomorphic expression of beach ridges typically consists of ridge sets with multi decadal intervals whereas their internal sedimentary structures define shorter time scales records of beach sedimentation and erosion are likely to be reworked by episodic high magnitude beach retreat and the resultant record of the net progradation is likely to be sporadic and discontinuous the height of sandy beach ridges is often variable due to differing degrees of aeolian sand accumulation and they are thus not used as sea level indicators unless purely wave built gravel ridge height is a relatively reliable indicator of sea level but can vary in response to storminess fluctuations subsurface sediment facies boundaries are preferred as sea level indicators and those proposed include boundaries of aeolian beach foreshore shoreface and upper lower shorefaces catastrophic events are expressed in both erosional and depositional records erosion surfaces or scarp imprints revealed in a cross section of beach deposits indicate storm or tsunami events however erosional events are likely to rework previous records of sedimentation and even other erosional events and thus the apparent history decoded from the resultant deposits tends to be biased several attempts for estimating the frequency and intensity of prehistoric cyclones rely on assumed relationships between the level of coarse sand beach ridges and cyclone inundation the formative process of coarse sand ridges remains uncertain and needs to be clarified as it constitutes the fundamental basis of these attempts the growth rates of beach ridge systems are expected to reflect fluctuations in river sediment discharge to the coast and in aeolian sand flux due to onshore winds both of which are affected by climate change assessment of the growth rate is potentially improved by ground penetrating radar survey of subsurface structure and by detailed chronology orientation of beach ridges reflects long term trends in wave direction inferred relationships between beach ridges and cyclic fluctuations of sea level and climate rely on weak assumptions and are not substantiated by rigid chronological evidence and thus remain highly questionable correlation between the inherently decadal signal of beach ridge intervals and possible climate cycles such as sunspot activity is probably coincidental as it lacks causal explanations

sand spit rhythmic development a potential record of wave climate variations arcay spit western coast of france abstract this study aims at showing the sedimentary and geomorphological records of wave climate variations by spits the studied spit arcay spit is located on the french atlantic coast and has displayed a rapid elongation since the beginning of the 19th century that potentially represents a two century long wave climate record wave climate and spit growth relationships are studied from two complementary methods 1 numerical modelling of wave and longshore transport temporal and spatial variabilities and 2 morphological monitoring based on the analysis of 4 historical maps 1811 1945 8 aerial photographs 1945 2000 and 17 satellite spot images 1987 2005 results at seasonal to interannual time scales show that the sand spit area gain variations are the result of variations in longshore transport themselves modulated mainly by wave height moreover energetic swells seem to cause massive sand accumulation and spit elongation whereas less energetic swells appear to be responsible for small sand accumulation and spit curvature at longer time scale decades to centuries increasing spit growth phases are also synchronised with periods of energetic swells or high storm surge frequency these results suggest that wave climate variations are the main factor controlling spit morphological evolutions

a mathematical model of spit growth and barrier elongation application to fire island inlet usa and badreveln spit sweden a mathematical model of spit growth and barrier elongation adjacent to an inlet of arbitrary width supplied by sediment coming from longshore sediment transport was developed based on the spit growth model proposed by kraus 1999 the fundamental governing equation is the conservation equation for sand where the width of the spit is assumed constant during growth the portion of the longshore sediment transport feeding the spit has been estimated based on the ratio between the depth of the inlet channel and the depth of active longshore transport sediment transport from the channel due to the inlet flow as well as other sinks of sand e g dredging are taken into account measured data on spit elongation at fire island inlet united states and at badreveln spit sweden were used to validate the model the simulated results agree well with the measured data at both study sites where spit growth at fire island was restricted by the inlet flow and the growth at badreveln spit was unrestricted the model calculation for fire island inlet indicates that the dredging to maintain channel navigation is the major reason for the stable period observed from 1954 to 1994 at the fire island barrier the average annual net longshore transport rate at the eastern side of the fire island inlet obtained in this study was about 220 000 m 3 yr of which approximately 165 000 m 3 yr 75 of the net longshore transport is deposited in the inlet feeding the spit growth whereas the remaining portion 25 is bypassed downdrift through the ebb shoal complex c 2011 elsevier ltd all rights reserved less

late holocene post 4000 years bp coastal dune development in northumberland northeast england the recent environmental history of coastal dune systems in northumberland northeast england has been examined using geomorphological stratigraphical and sedimentological techniques linked to radiocarbon and infrared stimulated luminescence irsl dating stratigraphies were determined from 22 vibracores and three sections and dune chronology was based on 28 14 c dates from peat and soil organic horizons and 26 irsl dates on k feldspar grains from within sand layers almost all dune systems are associated with regressive shorelines consequent upon a fall in relative sea level rsl from its holocene peak and indicate rsl functioned as a macroscale control on dune development where dunes are anchored on terrestrial sediment dune expansion may have been either transgressive or regressive in nature where near shore marine sediments form the dune substrate a regressive prograding dune model seems most likely most dune building occurred during the little ice age lia probably in a

sand invasion along the portuguese coast forced by westerly shifts during cold climate events phases of higher aeolian activity are responsible for the formation and movement of large transgressive dunefields well reported phases of aeolian activity in northwest europe are coincident with global cooling events and were related to enhanced westerly winds and storminess however the extent to which these climatic episodes influenced dunefield dynamics in southwest europe remains an open question ground penetrating radar gpr was used to image the stratigraphy of a cliff top coastal transgressive dunefield in portugal and reconstruct former windfield regimes using optically stimulated luminescence osl five major phases of aeolian activity were dated at 12 6 5 6 1 2 0 4 and 0 3 ka and related to coastal instability and enhanced westerlies these phases were later reconciled to favorable patterns of atmospheric circulation simulated by global and regional climate models at both synoptic and local scales respectively the results prove that major phases of aeolian activity in southwest europe are associated with the onset of cold climate events of global distribution coinciding with aeolian accumulation in northwest europe this implies the dominance of zonal westerlies along the western coast of europe from denmark to portugal during the onset of cold climate events model simulations suggest that the pattern of atmospheric circulation during periods of enhanced aeolian activity is compatible with prolonged negative phases of the north atlantic oscillation nao

insight into the late holocene sea level changes in the nw atlantic from a paraglacial beach ridge plain south of newfoundland constructional sedimentary features can provide insight into past changes in relative sea level rsl in regions where traditional bio stratigraphic markers are absent the paraglacial beach ridge plain at miquelon langlade located 50 km south of newfoundland is an example of a well preserved regressive barrier initiation of this plain correlates with a decrease in the rate of rsl rise from 4 4 mm yr to 1 3 mm yr at around 3000 years ago it developed under conditions of normal regression during a period of slow rsl rise 1 3 mm yr the barrier is composed of two oppositely prograding mixed sand and gravel beach ridge systems which evolved contemporaneously along two open coasts the growth of these features reflects high rates of sediment influx that was sourced from the erosion of proximal glacigenic sediment moraines and reworked alongshore and across shore by wave action the combination of stratigraphic ground penetrating radar and sediment cores topographic rtk gps and chronologic optically stimulated luminescence osl data provide a detailed understanding of the constructional history of the plain the well defined contact between coarse grained wave built facies and overlying aeolian deposits is used to demonstrate the dominant influences of rsl change in the development of the barrier system and produce a rsl curve over the period of its formation a net increase of 2 4 m in the surface elevation of wave built facies is observed across the plain corresponding to the increase in mean sea level during its formation coupled with osl dates trends in elevation of the wave built facies across the plain are used to reconstruct the relative sea level history during this period acknowledging the uncertainties inherent in the method applied in this study three distinct periods of sea level rise can be distinguished 1 an increase from 2 4 to 1 m below modern msl between 2400 and 1500 years average rate of 1 3 mm yr 2 relatively stable or slowly rising rsl 0 2 mm yr from 1400 to 700 years and 3 a rise of ca 0 7 m during the past 700 years 1 1 mm yr this study not only produces the first rsl reconstruction for the saint pierre et miquelon archipelago but also provides i additional details of rsl changes in a region exhibiting great spatial variations in rsl histories newfoundland ii field confirmation that wave built aeolian stratigraphic contacts in beach ridges can provide a powerful tool for sea level reconstructions in mixed clastic systems and iii evidence that sediment influxes can outpace the rate of accommodation creation producing a broad progradational coastal system

timing and climate forcing of volcanic eruptions for the past 2 500 years volcanic eruptions contribute to climate variability but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual to decadal temperature variability in the northern hemisphere during the past 2 500 years our results are based on new records of atmospheric aerosol loading developed from high resolution multi parameter measurements from an array of greenland and antarctic ice cores as well as distinctive age markers to constrain chronologies overall cooling was proportional to the magnitude of volcanic forcing and persisted for up to ten years after some of the largest eruptive episodes our revised timescale more firmly implicates volcanic eruptions as catalysts in the major sixth century pandemics famines and socioeconomic disruptions in eurasia and mesoamerica while allowing multi millennium quantification of climate response to volcanic forcing

aeolian sediment in raised bog deposits halland sw sweden a new proxy record of holocene winter storminess variation in southern scandinavia cores of peat taken from two raised bogs in the near coastal part of halland sw sweden were examined for their content of wind transported clastic material the boarps mosse core has a length of 262 cm and covers the last 2850 years age model based on three radiocarbon dates while the hyltemossen core has a length of 347 cm and records the last 7000 years age model based on eight radiocarbon dates the peat contains aeolian quartz silt and sand from trace amount to more than 10 weight of the dry peat sample and the grain size composition of the minerogenic sediment indicates that the material is composed of both far travelled dust and local wind eroded silt and sand grains larger than 0 2mm are present in many intervals and probably record niveo aeolian transport in connection with severe snowstorms a systematic count of quartz grains between 0 2 0 35mm and larger than 0 35mm was carried out to determine variations in aeolian sand influx asi and winter wind climate with time the boarps m

the east atlantic west russia ea wr teleconnection in the north atlantic climate impact and relation to rossby wave propagation large scale winter teleconnection of the east atlantic west russia ea wr over the atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence a rotated empirical orthogonal function analysis of the upper tropospheric monthly height field captures successfully the ea wr pattern and its interannual variation with the north atlantic oscillation nao as the first mode ea wr s climate impact extends from eastern north america to eurasia the positive negative ea wr produces positive negative temperature anomalies over the eastern us western europe and russia east of caspian sea with negative positive anomalies over eastern canada eastern europe including ural mountains northeastern africa and the middle east these anomalies are largely explained by lower tropospheric temperature advections positive negative precipitation anomalies are found over the mid latitude atlantic and central russia around 60 e where lower level cyclonic anticyclonic circulation anomaly is dominant eastern canada and western europe including the mediterranean region are characterized by negative positive precipitation anomalies the ea wr is found to be closely associated with rossby wave propagation wave activity fluxes show that it is strongly tied to large scale stationary waves furthermore a stationary wave model swm forced with vorticity transients in the mid latitude atlantic 40 n or diabatic heat source over the subtropical atlantic near the caribbean sea produces well organized ea wr like wave patterns respectively sensitivity tests with the swm indicate enhancement of ea wr like blocking over west of scandinavia when the mean state is modified to have a positive nao component that enhances upper level westerlies between 40 and 60 n

late holocene inland dune activity in the uk a case study from breckland east anglia inland dune fields found in breckland east anglia uk have previously been correlated with the widespread late devensian coversands of the region and a seventeenth century sandflood which is known to have inundated the village of santon downham a programme of optically stimulated luminescence and radiocarbon dating undertaken on the dunes at wangford warren and santon downham reveals that episodic aeolian activity has taken place during the last 7000 years five sand depositional phases on breckland dunes are identified c 6500 c 1600 1100 c 500 c 400 335 and from c 200 30 years before present between c 2120 1840 years ago and within the period 1100 300 years ago quiescent periods allowed the development of fen peat and soils local controlling factors on aeolian activity in breckland appear to be related to anthropogenic activities and livestock sheep and rabbits reducing vegetation cover and decreased precipitation and sea levels which led to lowering of water tables breckland aeolian activity when compared to the national and sub continental holocene aeolian activity record shows a high level of concordance the underlying forcing factor for late holocene dune activity in the uk and elsewhere in europe appears to be climatic instability in the north atlantic associated with both the little ice age and previous similar events which led to increased storminess climatic variability and lower temperatures

the impact of north atlantic storminess on western european coasts a review abstract instrumental and documentary records of storminess along the atlantic coast of western europe show that storm activity exhibits strong spatial and temporal variability at annual and decadal scales there is evidence of periods of increased storminess during the little ice age lia ad 1570 1990 and archival records show that these periods are also associated with sand movement in coastal areas independent evidence of sand movement during the lia is derived from dating the coastal sand deposits using luminescence or radiocarbon methods the holocene record of sand drift in western europe includes episodes corresponding to periods of northern hemisphere cooling particularly at 8 2 ka and provides the additional evidence that these periods like the lia were also stormy

evolution of a large baltic beach ridge plain neudarss ne germany a continuous record of sea level and wind field variation since the homeric minimum

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

soret separation of mid ocean ridge basalt magma chemical differentiation of an initially homogeneous mid ocean ridge basalt morb liquid has been experimentally observed in a temperature gradient above the liquidus the magnitude of this effect in producing differences in composition is comparable to that of crystal liquid fractionation for a given temperature difference however the chemical changes produced by the two processes soret and crystal liquid fractionation are different soret separations resemble those observed in a third process silicate liquid immiscibility this similarity is a reflection of the fact that the soret separable components are the same network former network modifier structural components which segregate during silicate liquid immiscibility

spatially explicit bathymetric reconstruction from lead line depth soundings of the late 17th century abstract sequences of repeated bathymetric surveys through time have been successfully used to document the morphodynamical evolution of coastal environments within historical times most chronobathymetric sequences have a restricted temporal coverage as surveys rarely date back earlier than the 19th century the aim of this study is to explore the potential of older lead line depth measurements as a reliable source of bathymetric data a late 17th century marine chart of the pertuis charentais france was used as a test case high resolution scans of the chart sheets were retrieved from a public online digital library a rare manuscript contemporary to the chart was obtained from the french national archives in order to constrain the methodology used to acquire depth measurements a spatially explicit bathymetry covering 1500 km2 was reconstructed from the interpolation of about 4600 georeferenced depth soundings vertical error was estimated by assuming the equivalence of depth values between the late 17th century and the recent 1960 bathymetries above subtidal rocks outcropping on the seafloor documentary data indicated that the chart author did not acquire depth measurements on purpose but instead collected data taken by local sailors and coasting pilots over an unknown period of time probably ranging from a few years to a few decades the large vertical error estimated to 4 5 m mainly resulted from the lack of tide correction bathymetric difference maps could not be computed but despite these weaknesses the large scale sediment infilling of the area and the long term evolution of an estuarine sandbank could be documented in agreement with previous works beyond its utility for local studies this article provides insights into the processing of depth measurements acquired long before modern hydrography surveys and demonstrates that such old marine charts deserve consideration provided conditions are met for their critical assessment

an experimental study of the influence of oxygen fugacity on fe ti oxide stability phase relations and mineral melt equilibria in ferro basaltic systems

meteor observations with the european incoherent scatter uhf radar the european incoherent scatter eiscat uhf radar which operates at a nominal frequency of 930 mhz is introduced as a powerful meteor radar its high sensitivity is utilized to detect transient enhanced ionization trails caused by meteors of all orientations in contrast to conventional hf and vhf backscatter radars which observe only the meteor trails oriented approximately normal to the radar beam a comparison shows that eiscat observes almost as high hourly rates of meteors as meteor radars do in spite of its beamwidth being only 0 5 compared to their 100 two different kinds of echoes are seen in the data about three fourths of them are strongly doppler shifted transient echoes which we interpret as head echoes since they move with meteor velocities the remaining echoes are long lived they come from the ionized trails left behind the meteors which drift slowly or not at all there are fundamental differences between the scattering process producing both types of echoes and the scattering from trails observed with the meteor radars for example we have never seen the trail echoes appear after a head echo all our shower echoes are also strongly nonspecular we postulate that some time is required for the trails to expand and for the ionization within them to approach the thermal equilibrium state in order to give detectable incoherent echoes due to the very small beamwidth our radar cannot follow the motion of an individual meteor as the conventional radars can but we can obtain a statistical profile of what happens at different heights as the meteoroids penetrate the atmosphere the altitude distribution of ionized trails shows that they are observable over the whole measurement range from about 65 to 165 km while the head echoes can be detected only within a narrow altitude range the latter effect is probably related to the radio meteor ceiling effect

late holocene sand invasion and north atlantic storminess along the aquitaine coast southwest france holocene forested coastal dunes of different morphology fringe the atlantic coast of southwest aquitaine infra red stimulated luminescence irsl dating has been applied to sands from these dunes in the aquitaine region in order to test the validity of dune classification theories the ages obtained from the dunes show three phases of sand invasion and dune development during the late holocene 3000 4000 years ago 900 1300 years ago 250 550 years ago the timing of the most recent phase of sand mobilization as dated by irsl is supported by historical maps and records from the fifteenth to the eighteenth centuries ad showing problems for human settlement in the region and village abandonment due to dune drift sand invasion is driven by an increase in frequency of severe storms in the north atlantic associated with the cooler periods of the little ice age and early mediaeval warm period the dunes emplaced 900 1300 years ago were naturally fixed by a mixed deciduous and maritime pine forest durin

holocene storm surge signatures in the coastal dunes of the western netherlands abstract on five different sites along the central netherlands coast one or more sequences of shell deposits in the dunes have been observed they are believed to be the result of storm surge activity on the foreshore either through swash or overwash action and of subsequent preservation due to aeolian coverage of a basically sedimentary coastal system through their stratigraphical positions and radiocarbon dating of shell material their approximate age was determined by interpretation of the role of dynamic wave set up and run up the associated storm surge elevations relative to contemporary mean sea level are reconstructed although our data may not be statistically accurate an increasing level of storm surge elevations over the recent holocene is observed with a particular maximum during the little ice age it is our suggestion that climatic variations on the one hand and foreshore bathymetry on the other hand may be factors of relevance to explain these observations if these findings are correct this would imply that for a proper analysis of exceedance frequencies of extreme storm surge events it would be relevant to base such an analysis not only on present climate and foreshore bathymetry

formation of aeolian dunes on anholt denmark since ad 1560 a record of deforestation and increased storminess abstract sand dunes on the island of anholt denmark in the middle of kattegat form a relatively barren temperate climate aeolian system locally termed the desert the dunes have developed on top of a raised beach ridge system under the influence of dominant winds from westerly directions they are relatively coarse grained with an average mean grain size of 480 m the last phase of aeolian activity and dune formation on anholt started after ad 1560 when the local pine forest was removed historical sources report intense sand mobilization in the 17th century and new optically stimulated luminescence osl dates indicate that dune formation continued until the end of the 19th century this period of sand drift and dune formation took place during the later part of the little ice age which is characterized by increased summer storminess in large parts of nw europe dune stabilization in the beginning of the 20th century probably records a temporary decrease in storminess ground penetrating radar mapping of the internal structures in two dunes in the western part of the desert a parabolic dune and a linear dune indicates the importance of north westerly storm winds during dune formation

sporadic meteor sources as observed by the jicamarca high power large aperture vhf radar abstract we present for the first time the main sources of sporadic meteors as inferred from meteor head echoes obtained by a high power large aperture radar hplar such results have been obtained at the jicamarca hplar 11 95 s 76 87 w 1 dip angle observations are based on close to 170 000 meteors detected in less than 90 h spread over 14 days between november 2001 and february 2006 meteors with solar orbits are observed to come from basically six previously known sources i e north and south apex helion anti helion and north and south toroidal representing 91 of the observations the other 9 represents meteors with observed velocities greater than the sun s escape velocity at 1 au most of them of extra solar origin results are given before and after removing the earth s velocity and the sources are modeled with two dimensional gaussian distributions in general our results are in very good agreement with previously known sources reported by jones and brown jones j brown p g 1993 mon not r astron soc 265 524 532 using mainly specular meteor radar smr data gathered over many years and different sites however we find slightly different locations and widths that could be explained on the basis of different sensitivities of the two techniques and or corrections needed to our results for example we find that the north and south apex sources are well defined and composed each of them of two collocated gaussian distributions one almost isotropic with 10 width and the other very narrow in ecliptic longitude and wide in ecliptic latitude this is the first time these narrow width sources are reported a careful quantitative analysis is needed to be able to compare the strengths of meteor sources as observed with different techniques we also present speed and initial altitude distributions for selected sources using a simple angular sensitivity function of the combined earth atmosphere radar instrument and an altitude selection criteria the resulting meteor sources are in better qualitative agreement with the results obtained with smrs

modelling the morphology of sandy spits abstract the shape dimensions and growth rate of an accumulating sandy spit is investigated by a theoretical and experimental study the idealised case of a spit growing without change of form under a constant wave forcing is considered the longshore wave driven sediment transport is taken to be dominant in the formation of the spit the shape of the spit is first described by an analytical one line model for the coastline development and by a simple littoral drift model the analytical model is valid for a spit with so large dimensions that quasi uniform conditions can be applied it is found that with this assumption the dimensions of the spit cannot be determined the width and shape of a finite spit is therefore determined from simulations with an area model for the wave driven current and sediment transport along the spit in this case the curvature effects from the spit on the longshore sediment transport inertia of the longshore current wave focussing are includes several solutions for a uniformly growing spit may exist and it is assumed that the fastest growing spit is the one to emerge the simulations indicate the width of the spit to be proportional to the width of the surf zone in experiments conducted in a wave tank an accumulating spit was formed at the down drift end of a uniform stretch of coast exposed to waves approaching at an angle the spit approached equilibrium dimensions when a constant wave climate was applied the radius of curvature of the spit varied according to the height of the incoming waves

results of the first continuous meteor head echo survey at polar latitudes abstract we present the first quasi continuous meteor head echo measurements obtained during a period of over two years using the middle atmosphere alomar radar system maarsy the measurements yield information on the altitude trajectory vector velocity radar cross section deceleration and dynamical mass of every single event the large statistical amount of nearly one million meteor head detections provide an excellent overview of the elevation altitude velocity and daily count rate distributions during different times of the year at polar latitudes only 40 of the meteors were detected within the full width half maximum of the specific sporadic meteor sources our observation of the sporadic meteors are compared to the observations with other radar systems and a meteor input function mif the best way to compare different radar systems is by comparing the radar cross section rcs which is the main detection criterion for each system in this study we aim to compare our observations with a mif which provides information only about the meteoroid mass thus we are using a statistical approach for the elevation and velocity dependent visibility and a specific mass selection the predicted absolute count rates from the mif are in a good agreement with the observation when it is assumed that the radar system is only sensitive to meteoroids with masses higher than one microgram the analysis of the dynamic masses seems to be consistent with this assumption since the count rate of events with smaller masses are low and decrease even more by using events with relatively small errors

extreme wave climate variability in southern europe using satellite data 1 a time dependent generalized extreme value gev model for monthly significant wave height maxima from satellite databases is used to model the seasonal and interannual variability of the extreme wave climate throughout southern europe in order to avoid a misleading use of the maxima time series the classical extreme value model has been modified to cope with nonhomogeneous monthly observations seasonality is represented using intraannual harmonic functions in the model while interannual variability is modeled including north atlantic and mediterranean regional scale sea level pressure predictors such as the north atlantic oscillation nao the east atlantic ea or the east atlantic western russian ea wr patterns the results quantify the strong spatial variability detected in the seasonal location and scale gev parameters in general prominent zonal west east and meridional north south gradients of these location and scale parameters reveal the predominance of low pressure centers located in the nao region e g a gradient of 4 m for the location parameter and 1 5 units for the scale parameter between north south is shown in the month of september the model also quantifies the influence of regional climate patterns on extreme wave climate results show a great influence of nao and ea on the atlantic basin e g every unit of the monthly nao index explains 25 cm of the extreme wave height in the gulf of biscay and the ea index explains 20 cm while the negative phases of ea wr contribute greatly to the western mediterranean basin

a beach ridge progradation complex reflecting periodical sea level and climate variability during the holocene gulf of almeria western mediterranean detailed mapping based on aerial photographs at various scales analysis of morpho sedimentary units and radiocarbon dating of the prograding beach ridge complex of campo de dalias almeria allow the differentiation of six prograding units these are called h1 7400 6000 cal bp h2 5400 4200 cal bp h3 4200 3000 cal bp h4 2700 1900 cal bp h5 1900 1100 cal bp and h6 500 cal bp present h units are deposited during periods of high relative sea level and increased sediment input to the coast they are bounded by large swales or erosional surfaces associated with lower sea levels and reduced input of sediment to the coast these correspond to short periods of increased aridity inside the general arid trend recorded in the western mediterranean since 5 4 ka changes in the flux of atlantic superficial waters into the mediterranean sea and relative strength of the w sw winds account for the recorded oscillations of relative sea level we deduce a decadal periodicity for the deposition of a beach ridge and the adjacent swale and suggest that it is related to fluctuations of the north atlantic oscillation nao index and to variations of solar activity the duration of h units shows a quasi millennial periodicity punctuated by short hundred years episodes of reduced progradation or erosion representing events of increased aridity likely to be related to bond s holocene cold events

environmental controls on coastal dune formation skallingen spit denmark abstract many coastal dune systems in western europe were emplaced during the little ice age lia the formation of such dune fields has generally been ascribed to a combination of low sea level and strong winds during that time period providing a supply of sand from the exposed shoreface and sufficient wind energy to transport this sand landward however little information exists on the processes that controlled sediment supply to the beach and why this onshore supply was initiated at all in this contribution we consider the origin and development of older dune fields on a barrier spit complex skallingen located in the northern part of the danish wadden sea maps and new data on dune litho and chrono stratigraphy the latter based on osl dating allow a precise estimate of the initiation and termination of dune emplacement dune formation at skallingen started at a relatively late stage of the lia and it can be temporally correlated with a phase of relative sea level rise in north western europe and with a high frequency of storm surges along the danish west coast these are the conditions during which nearshore bars currently migrate onshore across the shoreface off skallingen the bars eventually merge with the beach and constitute a source of sand for modern foredune accretion it is probable that the onshore bar migration occurred under similar conditions in the past and the migration was triggered or enhanced by the sea level recovery from the mid lia low stand and the associated frequent storm surge activity consequently at skallingen onshore sand supply was caused by marine rather than aeolian agents this supply provided the basis for subsequent dune formation indications are however that the sediment supply to the beach dunes was a factor of 2 3 larger in the past dune aggradation eventually ceased around 1900ad because of dyke construction hence the association between dune formation and sea level surge variation at skallingen is somewhat contrary to other statements of coastal dune development during the lia in north western europe

ocean waves and teleconnection patterns in the northern hemisphere abstractunderstanding long term ocean wave climate variability is important to assess climate change impacts on coastal and ocean physics and engineering teleconnection patterns can represent wave climate variability in the context of climate change the objective of this study is to identify how large scale spatial distributions of wave heights vary on a monthly basis and how they are influenced by various teleconnection patterns using reanalysis datasets the wave height climate responses to teleconnection patterns in the eastern part of the north pacific and north atlantic are more sensible than in the corresponding western parts the dominant spatial patterns of monthly averaged wave height variability in winter were obtained by empirical orthogonal function analysis the three dominant patterns in the north pacific and north atlantic are similar it is remarkable that one of the three dominant patterns a band shaped pattern exhibits a strong relation to the teleconnection pattern in each ocean t

a well verified multiproxy reconstruction of the winter north atlantic oscillation index since a d 1400 abstract a new well verified multiproxy reconstruction of the winter north atlantic oscillation nao index is described that can be used to examine the variability of the nao prior to twentieth century greenhouse forcing it covers the period a d 1400 1979 and successfully verifies against independent estimates of the winter nao index from european instrumental and noninstrumental data as far back as 1500 the best validation occurs at interannual timescales and the weakest at multidecadal periods this result is a significant improvement over previous proxy based estimates which often failed to verify prior to 1850 and is related to the use of an extended reconstruction model calibration period that reduced an apparent bias in selected proxies associated with the impact of anomalous twentieth century winter nao variability on climate teleconnections over north atlantic sector land areas although twentieth century nao variability is somewhat unusual comparable periods of persistent positive phase

radar interferometric imaging studies of long duration meteor echoes observed at jicamarca a large number of long duration 15 s meteor echoes were detected at the jicamarca radio observatory on two nights in early august 1990 during an evening electrojet experiment using an interferometric imaging technique we were able to measure a zonal velocity profile for each meteor trail our analysis procedure differs from conventional meteor wind methods in that it provides instantaneous profiles rather than long term average information significant altitudinal and temporal variabilities of the horizontal velocities were noted zonal speeds of up to 100 m s 1 large vertical shears of up to 20 m s 1 km and rapid temporal variations of up to 50 m s 1 over an hour interval were observed spectral analysis indicates the presence and decay of asymmetrical high frequency signal components possible explanations for the observed high frequency components are discussed as are the angle of arrival of and the scattering mechanism responsible for the meteor echoes

multi static common volume radar observations of meteors at jicamarca 1 multi static common volume radar mscvr observations have long been considered necessary for meteor observations especially for the study of range spread trail echoes rste we present preliminary results in the form of a case study from the first mscvr observations that were carried out at the jicamarca radar observatory jro in june 2007 a second antenna array of similar sensitivity to a single jro receive module was constructed and operated at carapongo approximately 5 kilometers geomagnetically south of jro the jro main array was used for transmission receiving was done using sub arrays at jro and with the array at carapongo the results provide new insights not only into the aspect sensitivity of rstes but also into the physical structure of the plasma giving rise to these echoes these observations also establish a firmer basis for the modeling of the plasma processes that cause meteor trails to become field aligned

depositional controls on a hypertidal barrier spit system architecture and evolution pointe du banc spit north western france physical stratigraphy architecture and evolution of barrier systems in hypertidal environments tidal range above 6 m are understudied and depositional controls are poorly understood compared with wave dominated barrier systems and barrier spits in microtidal mesotidal and macrotidal settings based on vibracores ground penetrating radar radiocarbon and optically stimulated luminescence age data the formation and evolution of the hypertidal barrier system of pointe du banc north western france has been reconstructed the study shows that the barrier spit has a complex composite sedimentary architecture consisting of wave dominated and tide dominated sedimentary bodies a morpho sedimentary model is presented that demonstrates how barrier spit progradation resulting from littoral drift was the main manner of spit elongation whereas sediment convergence caused by landward migration of swash bars and seaward migration of tidal dunes caused the spit terminus to grow in height and width these results suggest that long term accretion rates varied considerably in response to changes in sediment supply variations in storminess together with the large scale topography of the coast controlled the sediment supply and thus the evolution of the barrier system during latest holocene despite architectural complexity hypertidal barrier systems preserve records of past climate changes

middle to late holocene storminess in brittany nw france part ii the chronology of events and climate forcing this study focuses on the recurring climate conditions required for the largest storms occurring in nw france brittany it is based on the analysed records of storm events along western brittany coast see part i in this manuscript part ii storm recurrence is explored along with forcing mechanisms periods of more frequent storm events over the two last centuries are analysed first in order to link these events with possible forcing mechanisms north atlantic oscillation nao and atlantic multidecadal oscillation amo modes triggering the most destructive storms then palaeostorm events are discussed at the holocene scale from 6000 yr bp to present to verify the forcing mechanisms most recorded events appear to be linked with cooling episodes mostly in winter a transition to or from a negative winter nao mode a positive amo mode extreme storms occur immediately prior to the medieval warm period mwp maximum effects are reached prior to the onset of the mwp and during the maunder and dalton solar minima low storm activity occurred during the sporer minimum linked to an acceleration of the atlantic meridional overturning circulation amoc main storm triggers seem to correspond to a positive amo mode with an unstable jetstream configuration driving a negative nao in this study four specific weather configurations were defined to explain each type of recorded storminess the strongest storms correspond to low amo and decennial negative nao modes e g little ice age or high amo in association with dominant low nao modes as during the early middle age and present day period fresh or warm oceans in association with a positive nao mode are stormy but with very low sting storms frequency although in agreement with the orbital forcing and the holocene glacial history increasing storm frequency and intensity is most probably partly biased by continuous sea level rise and resulting erosion

spatial and temporal patterns of shoreline change of a 280 km high energy disrupted sandy coast from 1950 to 2014 sw france abstract a dataset of 15 geo referenced orthomosaics photos was generated to address long term shoreline change along approximately 270 km of high energy sandy coast in sw france between 1950 and 2014 the coast consists of sandy beaches backed by coastal dunes which are only disrupted by two wide tidal inlets arcachon and maumusson a wide estuary mouth gironde and a few small wave dominated inlets and coastal towns a time and spatially averaged erosion trend of 1 12 m year is found over 1950 2014 with a local maximum of approximately 11 m year and a maximum local accretion of approximately 6 m year respectively maximum shoreline evolutions are observed along coasts adjacent to the inlets and to the estuary mouth with erosion and accretion alternating over time on the timescale of decades the two inlet sandspit systems of arcachon and maumusson show a quasi synchronous behaviour with the two updrift coasts accreting until the 1970s and subsequently eroding since then which suggests that shoreline change at these locations is controlled by allocyclic mechanisms despite sea level rise and the well established increase in winter wave height over the last decades there is no capture of significant increase in mean erosion rate this is hypothesized to be partly the result of relevant coastal dune management works from the 1960s to the 1980s after a long period of coastal dune disrepair during and after the second world war this study suggests that long term shoreline change of high energy sandy coasts disrupted by inlets and or estuaries is complex and needs to consider a wide range of parameters including non extensively waves tides inlet dynamics sea level rise coastal dune management and coastal defences which challenges the development of reliable long term coastal evolution numerical models

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

incremental dilation of magma filled fractures evidence from dykes on the isle of skye scotland abstract localised swarms of narrow 10 120 mm basaltic dykes occur at offsets and terminations of some larger basaltic dykes in skye scotland these narrow dykes cut and chill against each other and the larger dyke and its country rock the narrow dykes can only be traced a short distance into the larger dyke before terminating some of these terminations show the central parts of both dykes merging as the chilled margins vanish at other terminations the later dyke outcrop narrows progressively to a point these all show that after initial dilation and some crystallisation of material in the dyke fissure there were additional up to 11 increments of dilation increments were sufficiently spaced in time for preceding injections to have become solid time spans separating initial and later dilation may be sufficient for local crystallisation of dykes up to 3 2 m thick away from these terminations the dyke fissure remained an open void occupied by flowing magma during the successive increments of dilation this paper demonstrates that fluid filled dyke fissures can vary in width with time an observation consistent with the modern theoretical models of dyke emplacement that relate dyke width to magma input pressures and other magmatic parameters dyke offsets and terminations with late dilational increments are shown to provide a variety of other information on flow crystallisation and sealing of dyke fissures

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

low frequency storminess signal at bermuda linked to cooling events in the north atlantic region north atlantic climate archives provide evidence for increased storm activity during the little ice age 150 to 600 calibrated years cal years b p and centered at 1700 and 3000 cal years b p typically in centennial scale sedimentary records meteorological tropical versus extratropical storms and climate forcings of this signal remain poorly understood although variability in the north atlantic oscillation nao or atlantic meridional overturning circulation amoc are frequently hypothesized to be involved here we present records of late holocene storminess and coastal temperature change from a bermudian submarine cave that is hydrographically circulated with the coastal ocean thermal variability in the cave is documented by stable oxygen isotope values of cave benthic foraminifera which document a close linkage between regional temperature change and nao phasing during the late holocene however erosion of terrestrial sediment into the submarine cave provides a storminess signal that correlates with higher latitude storminess archives and broader north atlantic cooling events understanding the driver of this storminess signal will require higher resolution storm records to disentangle the contribution of tropical versus extratropical cyclones and a better understanding of cyclone activity during hemispheric cooling periods most importantly however the signal in bermuda appears more closely correlated with proxy based evidence for subtle amoc reductions than nao phasing

basal reversals in layered intrusions are evidence for emplacement of compositionally stratified magma basal reversals in layered intrusions are evidence for emplacement of compositionally stratified magma

evidence of episodic coastal change during the late holocene the dungeness barrier complex se england plater a j stupples p roberts h m 2009 evidence of episodic coastal change during the late holocene the dungeness barrier complex se england geomorphology 104 1 2 47 58

decadal changes in north atlantic atmospheric circulation patterns recorded by sand spits since 1800 ce abstract present day coastal barriers represent around 15 of the world s oceanic shorelines and play an important role as early warning indicators of environmental change among them wave dominated barriers are dynamic landforms that tend to migrate landward in response to storms and sea level change high rates of sediment supply can locally offset the global retrogradation trend providing valuable records of past environmental change occurring on transgressive coasts however geochronological control limits the temporal resolution of such records to millennial or centennial timescales and the decadal or even faster response of wave built barriers to historical climate changes is therefore poorly understood in this study we show that shoreline dynamics of sand spits reconstructed from old cartographic documents has been synchronous on both margins of the north atlantic ocean since about 1800 ce spit growth accelerated drastically during three periods lasting about 15 years characterised by positive north atlantic oscillation nao and negative east atlantic west russia ea wr atmospheric circulation patterns these changes are in phase with periods of increased volcanic activity we use a high resolution wave hindcast 1948 2014 ce in a reference area to confirm the association between nao and ea wr as a proxy for offshore and nearshore wave height and for associated longshore sediment transport lst involved in spit growth a 24 month lagged correlation between sediment transport and volcanic aerosol optical thickness concentration of ashes in the atmosphere is observed suggesting that spit shoreline dynamics at the decadal timescale is partially forced by external climate drivers via cascading effects on atmospheric circulation patterns and wave climate our results imply that nao variability alone is not sufficient to understand the evolution of wave built coastal environments the associated sediment record can be used to reconstruct multi decadal variability of other climate patterns

nonspecular meteor trail altitude distributions and durations observed by a 50 mhz high power radar 1 high power large aperture hpla radars frequently observe nonspecular meteor trail echoes that result from plasma turbulence driven by the intense pressure gradients on the trail edges this paper analyzes the altitude range duration and dependence on head echo strength of nonspecular trails using two large data sets from the 50 mhz hpla radar at the jicamarca radio observatory over 2100 trails were used to build altitude profiles that extend from 86 km to 120 km altitude with 97 of events occurring between 90 km and 110 km longer duration trails tend to form at lower altitudes than shorter duration echoes the peak of the altitude distribution of trails lasting at least 5 s can be up to 12 km lower than the peak of the distribution of trails shorter than 5 s further the data show a clear power law relationship for the frequency of both head echo and nonspecular trail power an improved knowledge of nonspecular trails will allow researchers to better understand meteor trail evolution and their use in monitoring lower thermospheric winds

buried sandbodies within present day estuaries atlantic coast of france revealed by very high resolution seismic surveys abstract studies of sandbanks within estuaries and macrotidal bays are critical for management of those coastal environments where human activity concentrates they are also excellent analogues of reservoirs new very high resolution vhr seismic profilers are now available for studying at the outcrop resolution scale sandbodies in very shallow water we present here a vhr seismic study constrained by vibrocores repetitive bathymetric surveys and radiocarbon dating which provide evidence of buried sandbodies in mixed tide and wave influenced estuaries of the french atlantic coast the three selected buried sandbodies are chosen because they are located at various water depths and have different internal architecture and outer shape they include 1 a very shallow water around 2 m under low tide elongated nearshore sandbody emplaced during the last centuries 2 a 6 to 7 m deep elongated nearshore sandbody dated to 2965 30 bp and 3 sandwaves lying around 17 m of water depth over the top of a large rounded shape sandbody dated to 5260 30 bp deepest 6 and 17 m sandbodies are interpreted as remnants of lower sea levels and thus transgressive sandbodies all those sandbodies are buried under estuarine mud which have been mainly emplaced during the last millenium such major sedimentary transition from basal sand to upper mud is assumed to record a major environmental change in relation to both natural infilling of estuaries climate change and increasing human activities anthropogenic perturbations are however believed to be the most important factor they have mainly consisted of land reclamation and are responsible for 1 rapid infilling of tidal bays 2 tidal prism and tidal current energy decreases and 3 deposition of muddy sediments upon sandbodies

variability and predictability of the north atlantic wave climate wave climate across the ocean basins can be described using satellite altimetry here we concentrate on the north atlantic region waves in the north atlantic are strongly seasonal and peak in the winter season the northeastern sector of the atlantic and adjoining shelf seas also exhibit exceptionally high interannual variability in the winter with monthly average significant wave height varying by up to a factor of 2 from one year to the next the strength and geographical distribution of variability is broadly consistent throughout the winter months december march a large fraction of these wave height anomalies is associated with a single pattern of pressure anomalies that resembles the north atlantic oscillation nao a predictor based on nao dependence is trained from relatively recent satellite data and then tested against earlier satellite and in situ data the predictor is successful in large areas of the north atlantic confirming a robust relationship between wave height anomalies and the nao over the last few decades a substantial rise up to 0 6 m in monthly mean wave heights on the northeastern atlantic during the latter part of the twentieth century is attributable to changes in the nao substantial residual anomalies in wave heights exist after the influence of the nao has been subtracted these are partly explained by a second pair of north atlantic patterns in wave height anomalies and sea level pressure anomalies this east atlantic pattern is particularly influential in midwinter and affects the southern part of the northeastern sector including the region of seven stones light vessel

fine scale chemical zonation in small mafic dykes kestio island sw finland detailed centimetre scale sampling across two small dolerite dykes 7 and 21 cm wide of kestio island sw finland has revealed a well developed internal zonation with surprisingly systematic compositional variations from the margins inwards the dykes exhibit a steady decrease in whole rock mgo mg number 100mg mg fe total and normative opx indicating a normal fractionation trend with simultaneous increase in normative an 100an an ab and decrease in incompatible zr y tio 2 and p 2 o 5 indicating a reverse fractionation trend in addition marginal rocks of dykes contain normative corundum that is apparently associated with their significant depletion in whole rock cao the extent of margin to centre differentiation of dykes in terms of most components is slight to modest although in some petrochemical parameters it is quite high e g 15 mol of normative an the dykes are almost glassy and uncontaminated by host rocks suggesting that their compositional profiles are primary and most likely reflect temporal changes in composition of magma filling the dykes a mechanism responsible for the systematic changes in composition of inflowing magma remains elusive however since no known processes are able to force magma to evolve simultaneously along both normal and reverse fractionation trends the study thus appears to indicate some not yet specified process of magma differentiation