variations in magmatic processes along the east greenland volcanic margin summary seismic velocities and the associated thicknesses of rifted and igneous crust provide key constraints on the rifting history the differentiation between non volcanic and volcanic rifted margins the driving force of magmatism at volcanic margins that is active or passive upwelling and the temperature anomaly in the lithosphere this paper presents two new wide angle seismic transects of the east greenland margin and combines the velocity models with a compilation of 30 wide angle seismic velocity models from several publications along the entire east greenland margin compiled maps show the depth to basement depth to moho crustal thickness and thickness of high velocity lower crust hvlc with velocities above 7 0 km s 1 first we present two new wide angle seismic transects which contribute to the compilation at the northeast greenland margin and over the oceanic crust between shannon island and the greenland fracture zone velocity models produced by ray tracing result in total traveltime rms misfits of 100 120 milliseconds and 2 values of 3 7 and 2 3 for the northern and southern profiles with respect to the data quality and structural complexity 2 d gravity modelling is used to verify the structural and lithologic constraints the northernmost profile awi 20030200 reveals a magma starved break up and a rapidly thinning oceanic crust until magnetic anomaly c21 47 1 ma the southern seismic transect awi 20030300 exhibits a positive velocity anomaly associated with the shannon high and a basin of up to 15 km depth beneath flood basalts between shannon island and the continent ocean boundary break up is associated with minor crustal thickening and a rapidly decreasing thickness of oceanic crust out to anomaly c21 the continental region is proposed to be only sparsely penetrated by volcanism and not underplated by magmatic material at all compared to the vast amount of magmatism further south break up is proposed to have occurred at the seaward boundaries of the continent ocean transition zones at between 50 and 54 ma propagating from north to south based on a joint analysis incorporating transects from the kejser franz joseph fjord and godthab gulf secondly the variation of the hvlc along the east greenland margin from 60 to 77 n and from transects of its conjugate margin shows inverted emplacement of prominent landward and seaward hvlc thickness portions from north to south in a distribution chart the differences in the hvlc distribution are attributed to one or more of the following three models in the first model it is inferred that a transfer zone detachment acts as a barrier to northward magma flow in the second model underplating results in thicker and highly intruded lower crust with several small scale feeder dykes that locally increase the lower crustal velocities in the third model a second magmatic event associated with the separation of the jan mayen microcontinent is considered lithospheric scale inhomogeneities might be responsible for the heterogeneous melt generation the inversion of the hvlc distribution in continental and oceanic domains and differences in its velocities

evidence for thin oceanic crust on the extinct aegir ridge norwegian basin ne atlantic derived from satellite gravity inversion 1 satellite gravity inversion incorporating a lithosphere thermal gravity correction has been used to map crustal thickness and lithosphere thinning factor for the ne atlantic predicted oceanic crustal thicknesses in the norwegian basin are between 4 and 7 km on the extinct aegir ridge increasing to 9 14 km at the margins consistent with volcanic margin continental breakup at the end of the paleocene the observation from gravity inversion and seismic refraction studies of thin oceanic crust produced by the aegir ridge in the oligocene may have implications for the temporal evolution of asthenosphere temperature under the ne atlantic during the tertiary thin oligocene oceanic crust may imply cool normal asthenosphere temperatures during the oligocene in contrast to elevated asthenosphere temperatures in the paleocene and miocene recent as indicated by the formation of volcanic margins and iceland respectively

crustal structure across the more margin mid norway from wide angle seismic and gravity data the more margin in the ne atlantic represents a dominantly passive margin with an unusual abrupt transition from alpine morphology onshore to a deep sedimentary basin offshore in order to study this transition in detail three ocean bottom seismometer profiles with deep seismic reflection and refraction data were acquired in 2009 two dip profiles which were extended by land stations and one tie profile parallel to the strike of the more trondelag fault complex the modeling of the wide angle seismic data was performed with a combined inversion and forward modeling approach and validated with a 3d density model modeling of the geophysical data indicates the presence of a 12 15 km thick accumulation of sedimentary rocks in the more basin the modeling of the strike profile located closer to land shows a decrease in crustal velocity from north to south near the coast we observe an intra crustal reflector under the trondelag platform but not under the slorebotn sub basin furthermore two lower crustal high velocity bodies are modeled one located near the more marginal high and one beneath the slorebotn sub basin while the outer lower crustal body is modeled with a density allowing an interpretation as magmatic underplating the inner body has a density close to mantle density which might suggest an origin as an eclogized body formed by metamorphosis of lower crustal gabbro during the caledonian orogeny the difference in velocity and extent of the lower crustal bodies seems to be controlled by the jan mayen lineament suggesting that the lineament represents a pre caledonian structural feature in the basement

break up and seafloor spreading domains in the ne atlantic an updated magnetic anomaly grid of the ne atlantic and an improved database of magnetic anomaly and fracture zone identifications allow the kinematic history of this region to be revisited at break up time continental rupture occurred parallel to the mesozoic rift axes in the south but obliquely to the previous rifting trend in the north probably due to the proximity of the iceland plume at 57 54 ma the new oceanic lithosphere age grid is based on 30 isochrons c from c24n old 53 93 ma to c1n old 0 78 ma and documents ridge reorganizations in the se lofoten basin the jan mayen fracture zone region in iceland and offshore faroe islands updated continent ocean boundaries including the jan mayen microcontinent and detailed kinematics of the eocene present greenland eurasia relative motions are included in this model variations in the subduction regime in the ne pacific could have caused the sudden northwards motion of greenland and subsequent eurekan deformation these events caused seafloor spreading changes in the neighbouring labrador sea and a decrease in spreading rates in the ne atlantic boundaries between major oceanic crustal domains were formed when the european plate changed its absolute motion direction probably caused by successive adjustments along its southern boundary supplementary material figures showing the long wavelength of the nag tec magnetic anomaly grid detailed magnetic anomalies and isochrons and a table documenting aeromagnetic surveys for nag tec magnetic compilation are available at https doi org 10 6084 m9 figshare c 3661925

an upper mantle s wave velocity model for northern europe from love and rayleigh group velocities summary a model of upper mantle s wave velocity and transverse anisotropy beneath northwestern europe is presented based on regional surface wave observations group velocities for both love and rayleigh surface waves are measured on waveform data from international and regional data archives including temporary deployments and then inverted for group velocity maps using a method accounting for fresnel zone sensitivity the group velocity variations are larger than in global reference maps and we are able to resolve unprecedented details we then apply a linear inversion scheme to invert for local 1 d shear wave velocity profiles which are consequently assembled to a 3 d model by choosing conservative regularization parameters in the 2 d inversion we ensure the smoothness of the group velocity maps and hence of the resulting 3 d shear wave speed model to account for the different tectonic regimes in the study region and investigate the sensitivity of the 1 d inversions to inaccuracies in crustal parameters we analyse inversions with different reference models of increasing complexity pure 1 d 3 d crust 1 d mantle and pure 3 d we find that all inverted models are very consistent at depths below 70 km at shallower depths the constraints put by the reference models primarily moho depth which we do not invert for remain the main cause for uncertainty in our inversion the final 3 d model shows large variations in s wave velocity of up to 12 per cent we image an intriguing low velocity anomaly in the depth range 70 150 km that extends from the iceland plume beneath the north atlantic and in a more than 400 km wide channel under southern scandinavia beneath southern norway the negative perturbations are around 10 per cent with respect to ak135 and a shallowing of the anomaly is indicated which could be related to the sustained uplift of southern scandinavia in neogene times furthermore our upper mantle model reveals good alignment to ancient plate boundaries and first order crustal fronts around the triple junction of the baltica avalonia laurentia collision in the north sea

effect of thermal contrasts on gravity modeling at passive margins results from the western barents sea the western barents sea passive margin is a key locality to demonstrate the effect of the thermal structure of the lithosphere on forward gravity modeling this margin developed by shear motion between the eurasian and greenland plates during the early tertiary and it is a significant border zone between young hot oceanic lithosphere and cooler continental lithosphere we construct two dimensional gravity models of 125 km thick lithosphere based on expansion of mantle rocks determined from thermal modeling the approach has a substantial impact over traditional shallow gravity models here demonstrated on a previously published model on the basis of a 140 mgal free air anomaly the old model proposes an anomalous high density oceanic crust emplaced in a leaky transform adjacent to the continent during early margin development however the lithospheric models predict a homogeneous oceanic crust while preserving regional isostasy at base lithosphere from continent to ocean two further tests agree with this conclusion a map of bouguer corrected ers 1 satellite data reveals no residual anomalies originating from the oceanic crust at the margin admittance analysis shows a strong oceanic lithosphere and the high coherence between bathymetry and free air gravity discounts a significant subsurface load the high gravity anomalies at the margin are thus an edge effect enhanced by sedimentation onto the strong oceanic lithosphere and shaped by the effect of the lithospheric thermal field other results of this work include a new continent ocean boundary map and two crustal transects across the margin

a first description of the summer upwelling off the bay of algeciras and its role in the northwestern alboran sea abstract a local upwelling process is observed in the mouth of the bay of algeciras showing a singular pattern partially disengaged of the neighboring coastal upwelling variability the physical mechanisms which drive this local upwelling are not clear but the ekman pumping seems to be the most important forcing factor the surface chlorophyll a variability associated with this local upwelling is uncorrelated with the concentration registered in the inner bay of algeciras or in the surrounding coastal and shelf waters secondary the emerged waters in the mouth of the bay of algeciras flow eastwards into the northwestern alboran sea dragged by the northern edge of the atlantic jet forming a narrow and elongated nutrient enriched area hereafter called filament usually detached from the coast a sampling station located at 14 6 km from the coastline and 68 km far from the mouth of the bay of algeciras was employed to monitor the presence of the filament in the alboran sea the filament is most frequently presented during the summer in fact it was detectable in more than 50 of the days of august when the filament is distinguishable its chlorophyll a concentration doubles in average the values registered in neighboring locations and in annual average also higher nitrate and phosphate surface concentrations about 30 are registered at the filament location these results indicate that the filament provides nutrients to the surface waters of alboran not only when it is optically detected our analyses indicate that the trajectory of the filament follows the northern edge of the western gyre of alboran although its width and speed are variable depending on the atlantic jet properties and the related sub mesoscale activity

structure of the jan mayen microcontinent and implications for its evolution an extensive seismic survey using ocean bottom seismographs obs was performed in the area across the jan mayen basin north atlantic from the jan mayen ridge to the iceland plateau the jan mayen ridge and surrounding area are considered to be a fragment of a continent which was separated from greenland just prior to magnetic anomaly 6 this study presents the crustal structure of the jan mayen microcontinent and the ocean continent transition to the west of the jan mayen ridge the crustal structures from the centre of the jan mayen ridge to the jan mayen basin are characterized by a deep sedimentary basin a thin basaltic layer within the sedimentary section and extreme thinning of the continental crust towards the iceland plateau the obs data indicate that a continental upper crust v p 5 8 6 1 km s 1 and lower crust v p 6 7 6 8 km s 1 underlie the deep sedimentary basin the thickness of the continental lower crust varies significantly from 12 km beneath the jan mayen ridge to almost zero thickness beneath the northwestern part of the jan mayen basin an ocean continent transition zone is found at the western edge of the jan mayen basin within the 10 km wide transition zone crustal velocities increase towards the iceland plateau and approach the velocities of the oceanic crust obtained at the iceland plateau that is 3 8 5 1 km s 1 oceanic layer 2a 5 9 6 5 km s 1 oceanic layer 2b and 6 8 7 3 km s 1 oceanic layer 3 the crustal model indicates very thin oceanic crust 5 km immediately oceanwards of the ocean continent transition zone beneath the iceland plateau the oceanic crust is thicker 9 km than the typical thickness of normal oceanic crust this might imply that the oceanic crust at the iceland plateau has been generated by asthenospheric material slightly hotter than normal from the crustal structure obtained by the present study it is proposed that the western part of the jan mayen ridge may be referred to as a non volcanic continental margin generated by a long duration of rifting even if the asthenospheric material upwelling along the margin were hotter than normal only small amounts of magmatic intrusions and extrusions would have been generated because of significant conductive cooling under the long duration of rifting

a review of the ne atlantic conjugate margins based on seismic refraction data the ne atlantic region evolved through several rift episodes leading to break up in the eocene that was associated with voluminous magmatism along the conjugate margins of east greenland and nw europe existing seismic refraction data provide good constraints on the overall tectonic development of the margins despite data gaps at the ne greenland shear margin and the southern jan mayen microcontinent the maximum thickness of the initial oceanic crust is 40 km at the greenland iceland faroe ridge but decreases with increasing distance to the iceland plume high velocity lower crust interpreted as magmatic underplating or sill intrusions is observed along most margins but disappears north of the east greenland ridge and the lofoten margin with the exception of the vestbakken volcanic province at the sw barents sea margin south of the narrow lofoten margin the european side is characterized by wide margins the opposite trend is seen in greenland with a wide margin in the ne and narrow margins elsewhere the thin crust beneath the basins is generally underlain by rocks with velocities of 7 km s 1 interpreted as serpentinized mantle in the porcupine and southern rockall basins while off norway alternative interpretations such as eclogite bodies and underplating are also discussed

interface scattering versus body scattering in subbasalt imaging and application of prestack wave equation datuming the presence of high velocity highly heterogeneous layers such as basalt have a detrimental effect on imaging below those structures internal characteristics of the basalt itself can also degrade the subbasalt image quality in many cases the boundary surfaces of a basalt sequence are not smooth but contain some roughness at a scale similar to the seismic wavelength interface scattering resulting from interface roughness can be a serious problem in this paper body and interface scattering problems are addressed through acoustic finite difference modeling interface scattering seems to have the most detrimental effect on imaging at depth a wave equation prestack datuming procedure is applied to synthetic acoustic data to remove the effects of rough interfaces this computational process transforms seismic data to a new datum plane in the subsurface eliminating propagation effects between the surface and the new datum plane the technique leads to a much improved image of below the basalt with the g

moho and basement depth in the ne atlantic ocean based on seismic refraction data and receiver functions seismic refraction data and results from receiver functions were used to compile the depth to the basement and moho in the ne atlantic ocean for interpolation between the unevenly spaced data points the kriging technique was used free air gravity data were used as constraints in the kriging process for the basement that way structures with little or no seismic coverage are still presented on the basement map in particular the basins off east greenland the rift basins off nw europe are mapped as a continuous zone with basement depths of between 5 and 15 km maximum basement depths off ne greenland are 8 km but these are probably underestimated plate reconstructions for chron c24 c 54 ma suggest that the poorly known ammassalik basin off se greenland may correlate with the northern termination of the hatton basin at the conjugate margin the most prominent feature on the moho map is the greenland iceland faroe ridge with moho depths 28 km crustal thickness is compiled from the moho and basement depths the oceanic crust displays an increased thickness close to the volcanic margins affected by the iceland plume

new gravity data in the arctic ocean comparison of airborne and ers gravity new gravity fields from airborne gravimetry and from ers 1 and 2 satellite altimetry cover extensive portions of the arctic ocean these two data sets may constitute as much as 60 of the data contributions to the arctic gravity project compilation here we evaluate the accuracy and resolution of these data and quantify their impact on the compilation both gravity determinations compare favorably with geological survey of canada surface measurements in the beaufort sea airborne 1 86 2 09 mgal rms ers 2 64 3 11 mgal rms comparisons between the airborne and ers data over the chukchi borderlands reveal a 4 38 mgal rms difference over the smoother region of the field and 7 36 mgal rms over the rugose field generated by the shallow ridges and deep troughs coherency between the two data sets in the chukchi region implies a resolution of 19 km comparison with science ice expedition submarine measurements over chukchi plateau suggests that the ers field resolves even shorter wavelength signal than the airborne data whereas in the beaufort sea the airborne data showed better coherence to ground truth data long wavelength differences exist between the two data sets expressed as a 2 3 mgal offset over the chukchi region this study highlights the respective strengths of the two data sets the ers gravity field has the advantage of ubiquitous coverage of the ocean south of 81 5 degreesn a denser sampling of the gravity field and a recovery of signal down to similar to 15 km the airborne data cover a significant portion of the polar hole in the satellite coverage have lower measurement noise and recover somewhat higher anomaly amplitudes in the 25 100 km wavelength range

gravity modeling of the ocean continent transition along the south atlantic margins 1 gravity magnetic and seismic data have been used to examine changes in crustal structure of conjugate portions of the south atlantic volcanic margins south of the walvis ridge rio grande rise hot spot tracks we have constructed 18 seismically constrained crustal scale gravity models of the ocean continent transition 12 across the african margin and 6 across the south american margin we attribute changes in character of the gravity anomalies to variations in crustal thickness sedimentation and magmatic underplating to investigate variations in the lower crust and upper mantle we have removed the relatively well constrained contributions to the gravity field from shallow sources the resulting residual anomalies delineate distinct crustal domains associated with crustal thinning and regions of underplating that correspond well with those independently identified from limited seismic refraction data near the hot spot tracks we find underplated crust to be symmetrically distributed with a horizontal extent of 240 km for each margin further south however the underplated region is asymmetric with significantly more beneath the african than the corresponding south american margin residual gravity anomalies indicate that the width of underplated crust decreases from 240 km to 150 km at 33 s on the african side and to 100 km at 38 s on the south american side the wider underplated region on the african side suggests an asymmetric rifting mechanism in which greater melts accumulate beneath an upper plate margin our results are consistent with recently proposed asymmetric rifting models that involve strain softening of a coupled cold frictional upper lithosphere at low rifting velocities such models also predict greater symmetry for areas with more heat such as those associated with the hot spot

mantle thermal structure and active upwelling during continental breakup in the north atlantic seismic reflection and refraction data acquired on four transects spanning the southeast greenland rifted margin and greenland iceland ridge gir provide new constraints on mantle thermal structure and melting processes during continental breakup in the north atlantic maximum igneous crustal thickness varies along the margin from s 30 km in the near hotspot zone 6 500 km from the hotspot track to v18 km in the distal zone 500 1100 km magmatic productivity on summed conjugate margins of the north atlantic decreases through time from 1800 300 to 600 50 km 3 km ma in the near hotspot zone and from 700 200 to 300 50 km 3 km ma in the distal zone comparison of our data with the british faeroe margins shows that both symmetric and asymmetric conjugate volcanic rifted margins exist joint consideration of crustal thickness and mean crustal seismic velocity suggests that along margin changes in magmatism are principally controlled by variations in active upwelling rather than mantle temperature the thermal anomaly vt at breakup was modest v100 125 c varied little along the margin and transient data along the gir indicate that the potential temperature anomaly 125 50 c and upwelling ratio v4 times passive of the iceland hotspot have remained roughly constant since 56 ma our results are consistent with a plume impact model in which 1 a plume of radius v300 km and vt of v125 c impacted the margin around 61 ma and delivered warm material to distal portions of the margin 2 at breakup 56 ma the lower half of the plume head continued to feed actively upwelling mantle into the proximal portion of the margin and 3 by 45 ma both the remaining plume head and the distal warm layer were exhausted with excess magmatism thereafter largely confined to a narrow 6 200 km radius zone immediately above the iceland plume stem alternatively the warm upper mantle layer that fed excess magmatism in the distal portion of the margin may have been a pre existing thermal anomaly unrelated to the plume fl 2001 elsevier science b v all rights reserved

integrated geophysical modelling of a lateral transition zone in the lithospheric mantle under norway and sweden summary the scandinavian mountain chain the scandes exhibits characteristics that are unusual for an old palaeozoic mountain belt these include renewed neogene uplift in a passive margin setting and the lack of a pronounced crustal root we investigate the influence of present day thermal compositional and geometric structures in the crust and mantle on the topography of the southern scandes and the resulting implications for the tectonic history of fennoscandia a self consistent 3 d subsurface model of southern norway and sweden is constructed from recent geophysical data sets that constrain the crustal architecture lithosphere geometry density distributions and thermal properties recent seismological studies show evidence for a relatively abrupt transition from seismically slower lithospheric mantle underneath southern norway to seismically faster lithospheric mantle underneath southern sweden we find that a transition from thin subcontinental lithospheric mantle sclm underneath southern norway to a significantly thicker sclm beneath southern sweden can explain this velocitytrend adifferenceincompositionbetweenthetwosclmdomains owingtodifferent depletion refertilization is required to satisfy the gravity field and isostatically compensated topography but contributes only slightly to the observed velocity contrast such a lateral transition zone constituting a major change in the lithospheric structure in southwestern fennoscandia can be related to several major proterozoic and phanerozoic tectonic events such as the sveconorwegian orogeny the permian oslo rift and perhaps even the opening of the atlantic

biological and geochemical signatures associated with the water circulation through the strait of gibraltar and in the western alboran sea previous hydrological investigations of the gibraltar strait have left some questions unanswered as regards the composition of the mediterranean outflow into the atlantic ocean in the present study nutrient oxygen and chlorophyll distributions are used to characterize the main water masses flowing through the strait of gibraltar and the alboran sea with particular reference to levantine intermediate water liw and western mediterranean deep water wmdw high chlorophyll a concentrations reaching 3 g l 1 at the subsurface are observed in the northern part of the anticyclonic alboran sea gyre the salinity subsurface minimum 36 located temporarily in the strait corresponds to high nutrient concentrations 7 8 g at l 1 diagram analysis shows that in the upwelling area off the spanish coast nutrients are largely transported into the photic zone and that photosynthetic nitrate consumption actually takes place consequently the formation of the alboran sea o2 extraminimum can be related to the enhanced new production most of the lowest o2 values 4 00 ml l 1 also correspond to a slight nutrient maximum po4 and no3 comparative diagram analysis of biologically affected parameters oxygen and nutrients versus salinity as a conservative property confirms and expands results from the classical s analysis oxygen and silicate exhibit the best tracer qualities for the circulation pattern demonstrating in particular that during the period of observations water rich in liw feeds the mediterranean outflow

crustal structure beneath the faroe islands and the faroe iceland ridge abstract we have mapped the transition from the continental faroe block the faroe islands and surrounding shelf to the thickened oceanic crust of the faroe iceland ridge in the north atlantic using the results of a detailed sea to land seismic profile with wide angle to normal incidence recordings of explosive and airgun shots fired at sea along the faroe iceland ridge interpretation of all available seismic and gravity data indicates that this aseismic ridge is composed of 30 3 km thick oceanic crust with a gradual transition to ancient continental crust from 100 to 40 km northwest of the faroe islands close to the shelf edge this confirms that the crust beneath the faroe islands which may be up to 46 km thick comprises continental material in agreement with previous seismic and geochemical results results suggest that the upper 5 2 0 7 km of the faroe crust consists of tertiary basalts generated during continental breakup overlying the continental crust beneath the lower crust where seismic constraint is poor may exhibit high seismic velocities 7 1 7 6 km s 1 which we attribute to underplating or intrusion by mafic melts during continental breakup in the early tertiary

palaeocene recent plate boundaries in the ne atlantic and the formation of the jan mayen microcontinent abstract breakup and sea floor spreading between greenland and eurasia established a series of new plate boundaries in the north atlantic region since the late palaeocene a conventional kinematic model from pre breakup to the present day assumes that eurasia and greenland moved apart as a two plate system however new regional geophysical datasets and quantitative kinematic parameters indicate that this system underwent several adjustments since its inception and suggest that additional short lived plate boundaries existed in the ne atlantic among the consequences of numerous plate boundary relocations is the formation of a highly extended or even fragmented jan mayen microcontinent and subsequent deformation of its margins and surrounding regions the major oligocene plate boundary reorganization and microcontinent formation might have been precluded by various ridge propagations and or short lived triple junctions ne and possibly sw of the jan mayen microcontinent from the inception of sea floor spreading 54 ma to c18 40 ma our model implies a series of failed ridges offshore the faeroe islands a northern propagation of the aegir ridge ne of the jan mayen microcontinent and a series of triple junctions and or propagators in the southern greenland basin

auroral disturbances during the january 10 1997 magnetic storm it is well known that intense and frequent auroral zone disturbances often attributed to substorms occur during magnetic storms we examine observations during the january 10 1997 main phase and find that observed auroral zone activity was dominated by a combination of global auroral and current enhancements which are a direct response to solar wind dynamic pressure enhancements and poleward boundary intensifications which are localized in longitude and have an auroral signature that moves equatorward from the magnetic separatrix poleward and azimuthally expanding regions of auroral activity which accompany substorms are found to contribute significantly less to the observed activity this suggests that poleward boundary intensifications and dynamic pressure responses may be an important cause of disturbances during periods of enhanced convection such as magnetic storms and convection bays

a 3d regional crustal model of the ne atlantic based on seismic and gravity data abstract we present a 3d regional crustal model for the north atlantic which is based on the integration of seismic constraints and gravity data the model addresses the crustal thickness geometry and includes information on sedimentary thickness the presence of high velocity zones in the lower crust and information on the crustal density distribution in the continental and oceanic domains using an iterative forward and inverse modelling approach we adhere to the seismic constraints within their uncertainty but manage to enhance the crustal geometry in areas where seismic data are sparse or absent a number of basins are resolved with more detail recently released seismic reflection data beneath the ne greenland shelf allowed for a major improvement of the crustal thickness estimates estimated moho depths beneath the basins there vary between 15 and 25 km which is compatible with the conjugate norwegian margin a major lower crustal seismic velocity anomaly in the vicinity of the greenland iceland faroe ridge complex is supported by density modelling we discuss the validity and uncertainties of our model assumptions and discuss the correlation with the main structural elements of the north atlantic

whales and waves humpback whale foraging response and the shoaling of internal waves at stellwagen bank we tested the hypothesis that humpback whales aggregate at the southern flank of stellwagen bank sb in response to internal waves iws generated semidiurnally at race point rp channel because of the presence of their preferred prey planktivorous fish which in turn respond to zooplankton concentrated by the predictable iws analysis of synthetic aperture radar sar images indicates that rp iws approach the southern flank of sb frequently 62 of the images published reports of whale sighting data and archived sar images point to a coarse spatial coincidence between whales and race point iws at sb s southern flank the responses of whales to iws were evaluated via sightings and behavior of humpback whales and iws were observed in situ by acoustic backscatter and temperature measurements modeling of iws complemented the observations and results indicate a change of 0 4 m s in current velocity and 1 5 pa in dynamic pressure near the bottom which may be sufficient for bottom fish to detect the iws however fish were rare in our acoustic observations and fish response to the iws could not be evaluated rp iws do not represent the leading edge of the internal tide and they may have less mass transport potential than typical coastal iws there was large interannual variability in whale sightings at sb s southern flank with decreases in both numbers of sightings and proportion of sightings where feeding was observed from 2008 to 2013 coincidence of whales and iws was inconsistent and results do not support the hypothesis

combined satellite gravity field model goco01s derived from goce and grace 1 the satellite only gravity field model goco01s is a combination solution based on 61 days of goce gravity gradient data and 7 years of grace gps and k band range rate data resolved up to degree order 224 of a harmonic series expansion the combination was performed consistently by addition of full normal equations and stochastic modeling of goce and grace observations the model has been validated against external global gravity models and regional gps leveling observations while low to medium degrees are mainly determined by grace significant contributions by the new measurement type of goce gradients can already be observed at degree 100 beyond degree 150 goce becomes the dominant contributor correspondingly with goco01s a global gravity field model with high performance for the complete spectral range up to degree order 224 is now available this new gravity model will be beneficial for many applications in geophysics oceanography and geodesy

insights from the jan mayen system in the norwegian greenland sea i mapping of a microcontinent summary in this contribution we present a model of microcontinent architecture within a system that involves a complex rifted margin setting and different phases of deformation and continental breakup our case study is the jan mayen microcontinent jmmc located in the central part of the norwegian greenland sea we have revised its basement and sedimentary geometries using modern and vintage seismic reflection profiles and updated potential field data the northern part of the jmmc consists of a 10 15 km thick continental crust body flanked by two major sedimentary basins we propose that the microcontinent is divided into six distinct segments characterized by different basement and sedimentary architectures the shallow stratigraphy is well imaged and has been detailed three distinct sedimentary units have been defined together with pronounced reflectors ja red jo and f related to erosional magmatic thermal or uplift events the continent ocean boundary has been revised together with the mapping of the distinct volcanic events that characterize the evolution of the microcontinent a companion paper aims to further detail the interpretation of the jmmc structure presented here by constraining the conjugated mid norwegian and mid east greenland structures

structure of the scandes lithosphere from surface to depth abstract in this review we give an overview of geophysical data and models available for the scandinavian mountains and adjacent areas as they are of relevance to the debate about the existence and cause of neogene uplift emphasis is given to potential field and petrophysical data of which the earth science communities of norway and sweden have a long tradition of acquisition and interpretation this is reflected in the wealth and dense coverage of data available the topography of the scandes mountain chain correlates to a large degree with a bouguer gravity low which suggests isostatic compensation but comparison with magnetic and petrophysical data shows that the gravity low is partly influenced by the trans scandinavian igneous belt signals due to the effects of surface geology can be further eliminated by considering the near surface density distribution as provided by petrophysical sampling to illuminate the entire lithospheric structure active and passive seismic and magnetotelluric data can be used recent and ongoing experiments are aimed at improving the existing models of the lithosphere integration of these different geophysical data sets allows the structure of the lithosphere of the scandes and its surroundings to be addressed seismic models show no pronounced crustal root below the scandes which could provide isostatic compensation but instead an increase of crustal thickness towards the central fennoscandian shield from the integrated model isostatic compensation is inferred to be largely controlled by the density distribution of the crust and that a high density lower crust to the east of the scandes is necessary to achieve isostatic equilibrium on a regional scale we demonstrate the typical crustal structure with profiles crossing from the scandes into the shield and a combined onshore offshore basement map

observation of a western alboran gyre migration event abstract in the western alboran sea light atlantic water and dense mediterranean waters meet this gives rise to intense density fronts and energetic mesoscale features such as two semi permanent anticyclonic vortices the western and eastern alboran gyres however the circulation in the alboran sea is strongly varying in time with episodes where neither the western alboran gyre nor the eastern alboran gyre are present in october 1996 four consecutive high resolution surveys of the western alboran gyre wag were carried out and lagrangian floats were released during the first survey the western alboran sea was occupied by the wag surrounded by the atlantic jet the following surveys showed the wag drifting eastward beginning a wag migration event as confirmed 15 days later by the lagrangian float tracks and the sst images to replace the old gyre one month later a new gyre was formed analysis of adcp velocities sst images and ts properties show a change between the first and the second survey in the atlantic inflow through the strait of gibraltar the relationships between this change in the atlantic inflow a drop in the atmospheric pressure at ceuta the tidal regime and the wag migration are discussed the existence of a high resolution sampling in space together with the possibility of addressing the temporal variability has allowed us to describe in detail and for the first time the time evolution of the western alboran sea during a wag migration event relating the migration to changes in the inflow through the strait of gibraltar

crustal structure and evolution of the outer more margin ne atlantic abstract five regional ocean bottom seismic profiles from the northwestern part of the more margin ne atlantic have been modeled with regard to crustal structure and the interpretations have been supported by the use of multi channel seismic and potential field data the chi squared values uncertainty for the studied profiles are generally in the range 1 3 and the uncertainty in the moho depth is estimated to 1 km the continent ocean transition is found to be relatively sharp 10 40 km wide expressing a change in physical properties corresponding to felsic continental crust along the landward part of the marginal high vp 6 2 6 5 km s and thick mafic oceanic crust further northwestwards the early eocene breakup was associated with excessive magmatism and the models document direct continuity between this magmatism and a lower crustal high velocity layer in the more basin vp 7 1 7 3 km s suggesting a genetic link the jan mayen lineament is observed across the entire study area as northeastward termination of the lower crustal body as well as structuring in the top of the crystalline basement and the moho we present a speculative model involving lower crustal bodies of eclogites vp 8 km s inferred in the easternmost part of the more basin linking the jan mayen lineament to the post caledonian nordfjord sogn detachment

lower crustal bodies in the more volcanic rifted margin geophysical determination and geological implications abstract understanding nature structure and age of lower crustal bodies lcbs and their relation to the crustal structure of the more margin mid norwegian margin and in a more general way of magma rich rifted margins is a key issue to decipher the tectono magmatic processes found in volcanic rifted margins in light of 2d potential field modelling combined with reflection and refraction seismic data we reinvestigated the crustal nature of the more margin and adjacent jan mayen corridor in the proximal domain our study shows that the lcbs most likely represent inherited crustal bodies and not necessarily rift related serpentinised mantle as previously proposed to fit all geophysical observations both lower and middle crustal layers need to be preserved over a large part of the more basin for the distal margin the interpretation of the lcbs is more difficult our preferred interpretation is that they are mainly made of boudins of hyper extended pre rift lower continental crustal rocks more or less intruded by early tertiary magmatic material our seismic magnetic and gravity data does not easily support large scale exhumation of serpentinised mantle in the inner and is unlikely in the outer parts of the more basin the deep structures of the mid norwegian magma rich rifted margin result from the poly phase stretching and thinning of complex inherited crustal structures locally intruded by early tertiary magmatic material

the ne atlantic region a reappraisal of crustal structure tectonostratigraphy and magmatic evolution an introduction to the nag tec project the ne atlantic region and its continental margins fig 1 hold unique information for understanding many aspects of earth science from global geodynamics to palaeoceanography and global environmental change it also holds some of the world s most important hydrocarbon reserves from the north sea along the atlantic margins of ireland britain and norway and into the arctic in the barents sea historically studies in the ne atlantic were important for establishing many of the key ideas during the early part of the plate tectonic revolution