flow variability at the continental shelf break of the mackenzie shelf in the beaufort sea observations from four yearlong current meter deployments made in 1987 1988 near the shelf break in the canadian beaufort sea are analyzed by statistical and spectral methods to characterize the structure and variability vertical and horizontal of the velocity field and to compare measurements obtained during summer ice free and winter ice covered conditions three main frequency bands are defined low frequencies 0 01 0 07 cpd intermediate or synoptic scale frequencies 0 07 0 7 cpd and high frequencies 0 7 cpd including tides and inertial currents within this division about 65 of the kinetic energy is in the low frequency band 15 in the intermediate band and 20 is in the high frequency band the latter is dominated by tidal motions low frequency variability is well correlated both vertically and horizontally along the shelf for separation distances exceeding 200 km variability in this band appears to be related to wind forcing and topographic wave propagation over large horizontal scales low frequency variability is highest during october and november in association with the occurrence of intense autumn storms and lowest during periods of ice cover due to wind shielding and increased frictional damping by ice cover intermediate scale motions have significant correlation in the vertical but poor correlation in the horizontal motions in this frequency band appear to be associated with mesoscale eddies advected by the mean flow there is also evidence of local generation of intermediate frequency current fluctuations by storms in late autumn and again an apparent damping during winter periods of ice cover finally high frequency motions show significant peaks in diurnal and semidiurnal tidal bands which are well correlated horizontally and vertically however other high frequency motions in this band show no significant correlation in either the vertical or horizontal direction there is no clear evidence in the current meter records of coupling between high frequency motions and direct atmospheric forcing

turbulent mixing near the yermak plateau during the coordinated eastern arctic experiment during the ice camp component of the coordinated eastern arctic experiment cearex in march april 1989 1500 profiles of temperature conductivity and velocity shear microstructure were obtained near the yermak plateau the dominant signal in isopycnal displacements was the diurnal variability near the plateau consistent with the enhanced diurnal currents found in this region previously from the fram iii and fram iv ice camps the dissipation rate of turbulent kinetic energy e reached maximum values of about 10 6 w kg 1 in two distinct regions the surface mixing layer and the pycnocline between 120 and 220 m there was a significant component of diurnal variability in e in each region in the surface layer e was proportional to the cube of the ice relative current speed at 30 m below the ice and it decayed approximately exponentially with increasing depth major mixing events in the pycnocline were correlated with large amplitude short duration isopycnal displacements the lowest dissipation rates were recorded over the deep nansen basin north of the plateau and in the subsurface core of a submesoscale baroclinic eddy in northern fram strait the time averaged vertical eddy diffusivity near the slope of the plateau was about 2 5 10 4 m2 s 1 in the pycnocline above the atlantic layer implying an upward heat flux of 25 w m 2 although only a small fraction of this heat reached the base of the mixed layer the results confirm that current interactions with steep topography are critical to the modification of atlantic water in the eastern arctic ocean

dynamics of the changing near inertial internal wave field in the arctic ocean abstractthe dynamics of the wind generated near inertial internal wave field in the canada basin of the arctic ocean are investigated using the drifting ice tethered profiler dataset for the years 2005 to 2014 during a decade when sea ice extent and thickness decreased dramatically this time series with nearly 10 years of measurements and broad spatial coverage is used to quantify a seasonal cycle and interannual trend for internal waves in the arctic using estimates of the amplitude of near inertial waves derived from isopycnal displacements the internal wave field is found to be most energetic in summer when sea ice is at a minimum with a second maximum in early winter during the period of maximum wind speed amplitude distributions for the near inertial waves are quantifiably different during summer and winter due primarily to seasonal changes in sea ice properties that affect how the ice responds to the wind which can be expressed through the wind factor the ratio of sea ice drift speed to

abrupt change in slope causes variation in the deposit thickness of concentrated particle driven density currents abstract abrupt changes in slope occur frequently in some marine environments laterally confined laboratory experiments show that when dense surge like particulate flows travel over abrupt slope reductions their deposits may have an asymmetric bell shaped thickening near the break of slope this thickening is herein called a slope break deposit and is related to the change in kinetic energy of the flow slope break deposits are particularly pronounced under relatively high velocity flows in our experiments these are flows with high particle concentrations c 5 10 by volume silicon carbide moving down slopes steeper than 3 the experiments were designed such that currents generated by a lock exchange mechanism flowed down a slope variable slope angle onto a flat surface the bodies of the flows became thicker and slower just downstream of the slope break because the flow body slows very rapidly particles are dumped forming the slope break deposit the peak in sediment thickness of the slope break deposit is downstream of the break in slope because falling particles continue to move forward in the flow during settling the slope break deposits may be several tens of percent thicker than deposits from an equivalent flow in which no change in slope occurred the parameters of the slope break deposit correlate with slope angle change

formation and deformation of hyperextended rift systems insights from rift domain mapping in the bay of biscay pyrenees the bay of biscay and the pyrenees correspond to a lower cretaceous rift system including both oceanic and hyperextended rift domains the transition from preserved oceanic and rift domains in the west to their complete inversion in the east enables us to study the progressive reactivation of a hyperextended rift system we use seismic interpretation gravity inversion and field mapping to identify and map former rift domains and their subsequent reactivation we propose a new map and sections across the system illustrating the progressive integration of the rift domains into the orogen this study aims to provide insights on the formation of hyperextended rift systems and discuss their role during reactivation two spatially and temporally distinct rift systems can be distinguished the bay of biscay parentis and the pyrenean basque cantabrian rifts while the offshore bay of biscay represent a former mature oceanic domain the fossil remnants of hyperextended domains preserved onshore in the pyrenean cantabrian orogen record distributed extensional deformation partitioned between strongly segmented rift basins reactivation initiated in the exhumed mantle domain before it affected the hyperthinned domain both domains accommodated most of the shortening the final architecture of the orogen is acquired once the conjugate necking domains became involved in collisional processes the complex 3 d architecture of the initial rift system may partly explain the heterogeneous reactivation of the overall system these results have important implications for the formation and reactivation of hyperextended rift systems and for the restoration of the bay of biscay and pyrenean domains

the results of deep seismic investigations on geotraverse in the barents sea from kola peninsula to franz joseph land abstract in 1995 geophysical investigations in the southern part of the ap 1 geotraverse across the whole barents sea plate were completed the entire profile links the super deep sg 3 well on the kola peninsular town of zapolarny and the base hayes 1 well on franz joseph land the extent of the investigated part of the profile was 700 km the integrated seismic experiment included offshore and onshore wide angle reflection refraction observations referred hereinafter as deep seismic sounding dss with 3 component ocean bottom seismographs obs and air guns and multi channel seismic reflection study mcs at different offsets ranges sufficiently dense deployment of obs 5 20 km and a 250 m shooting interval provided reliable phase correlation and wave identification intensive reflections from the moho have been recorded practically continuously along the profile the dss data processing built a mid point dynamic reflection moho image and produced a general depth section mcs data defined boundaries in the sedimentary layer and the basement surface in the southern part of the profile the lowermost observed boundary the moho occurs at depths between 35 and 40 km the thickness of sedimentary cover varies from zero in the southern part of the profile to 14 16 km in its northern part results of geological interpretation confirm the continental crust in the studied part of the barents sea shelf plate

estimating the mean diapycnal mixing using a finescale strain parameterization abstractfinescale methods are currently being applied to estimate the mean turbulent dissipation rate and diffusivity on regional and global scales this study evaluates finescale estimates derived from isopycnal strain by comparing them with average microstructure profiles from six diverse environments including the equator above ridges near seamounts and in strong currents the finescale strain estimates are derived from at least 10 nearby argo profiles generally 60 km distant with no temporal restrictions including measurements separated by seasons or decades the absence of temporal limits is reasonable in these cases since the authors find the dissipation rate is steady over seasonal time scales at the latitudes being considered 0 30 and 40 50 in contrast a seasonal cycle of a factor of 2 5 in the upper 1000 m is found under storm tracks 30 40 in both hemispheres agreement between the mean dissipation rate calculated using argo profiles and mean from microstructure profiles is wi

nares strait hydrography and salinity field from a 3 year moored array 1 nares strait to the west of greenland facilitates the exchange of heat and freshwater between the arctic and atlantic oceans this study focuses on salinity temperature and density measurements from nares strait from a mooring array deployed from 2003 to 2006 innovative moorings requiring novel analysis methods measured seawater properties near 80 5 n at spacing sufficient to resolve the internal rossby deformation radius the 3 year mean geostrophic velocity has a surface intensified southward flow of 0 20 m s 1 against the western side of the strait and a secondary core flowing southward at 0 14 m s 1 in the middle of the strait data show warm salty water on the greenland side and cold fresher water on the ellesmere island side especially in the top layers there was a clear difference in hydrographic structure between times when sea ice was drifting and when it was land fast ice was drifting in late summer fall and early winter with a strong surface intensified geostrophic flow in the middle of the strait ice was land fast in late winter spring and early summer when there was a subsurface core of strong geostrophic flow adjacent to the western side of the strait salinity variations of about 2 psu in time and space reflect a variable freshwater outflow from the arctic ocean one particularly strong pulse occurred at the end of july 2005 for several days steeply sloping isohalines indicated strong geostrophic flow down the middle of the strait coinciding with an amplified ice export from the arctic due to strong southward winds

vertical mixing at intermediate depths in the arctic boundary current microstructure and hydrographic observations during september 2007 in the boundary current on the east siberian continental slope document upper ocean stratification and along stream water mass changes a thin warm surface layer overrides a shallow halocline characterized by a 40 m thick temperature minimum layer beginning at 30 m depth below the halocline well defined thermohaline diffusive staircases extended downwards to warm atlantic water intrusions found at 200 800 m depth observed turbulent eddy kinetic energy dissipations are extremely low epsilon 10 6 w m 3 such that double diffusive convection dominates the vertical mixing in the upper ocean the diffusive convection heat fluxes f dc h 1 w m 2 are an order of magnitude too small to account for the observed along stream cooling of the boundary current our results implicate circulation patterns and the influence of shelf waters in the evolution of the boundary current waters

interplay between tectonics climate and fluvial transport during the cenozoic evolution of the ebro basin ne iberia 1 three dimensional modeling that integrates fluvial sediment transport crustal scale tectonic deformation and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the ebro sedimentary basin ne iberia the ebro basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the pyrenees the iberian range and the catalan coastal range in the late oligocene the catalan coastal range underwent extension leading to the formation of the valencia trough nw mediterranean but the ebro basin remained closed for nearly 15 myr more before the ebro river cut through the remnants of the topographic barrier this drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill here we investigate the processes controlling these major drainage changes the modeling results constrained by a large data set on the tectonic and transport evolution of the area predict a closed phase characterized by a large lake in the central eastern ebro basin dry climatic conditions probably lowered the lake level and contributed together with rift flank uplift to prolong this endorheic basin stage the age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8 5 ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions sea level changes in the mediterranean had no major impact in the large scale drainage evolution of the ebro basin index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 3210 mathematical geophysics modeling 3344 meteorology and atmospheric dynamics paleoclimatology 8102 tectonophysics continental contractional orogenic belts keywords pyrenees drainage evolution lake sediment budget erosion flexure

the vertical structure of turbulent dissipation in shelf seas abstract the free fall fly profiler has been used to determine the variation in energy dissipation in the water column over a tidal cycle at mixed and stratified sites in the irish sea it was found that exhibits a strong m4 variation with a pronounced phase lag that increases with height above the bed in mixed conditions this m4 signal which extends throughout the water column is reasonably well reproduced by turbulent closure models of the vertical exchange in the summer stratified situation the m4 signal in is confined to about 40 m above the seabed with phase delays of more than 4 h relative to the seabed the lowest levels of dissipation 10 5 w m 3 measured in the pycnocline are significantly above the system noise level and much higher than predicted by a model using the mellor yamada level 2 closure scheme my2 0 however when allowance is made for the diffusion of tke the model my2 2 simulates the depth time distribution of dissipation in the stratified case satisfactorily if

exhumation of high pressure rocks driven by slab rollback rocks metamorphosed under high pressure hp and ultra high pressure uhp conditions in subduction zones come back to the surface relatively soon after their burial and at rates comparable to plate boundary velocities in the mediterranean realm their occurrence in several belts related to a single subduction event shows that the burial exhumation cycle is a recurrent transient process using the calabria apennine and aegean belts as examples we show that the exhumation of hp rocks is associated in time and space with the subduction of small continental lithosphere blocks that triggers slab rollback creating the necessary space for the exhumation of the buoyant continental crust that was deeply buried just before the buoyancy force of the subducted crust increases until this crust detaches from the downgoing slab it then exhumes at a rate that depends directly on the velocity of trench retreat to become part of the overriding plate heated from below by the asthenosphere that flows into the opening mantle wedge the exhumed crust weakens and undergoes core complex type extension responsible for a second stage of exhumation at a lower rate the full sequence of events that characterizes this model crust mantle delamination slab rollback and trench retreat hp rock exhumation asthenosphere heating and core complex formation arises entirely from the initial condition imposed by the subduction of a small continental block no specific condition is required regarding the rheology and erosion rate of hp rocks the burial exhumation cycle is transient and can recur every time a small continental block is subducted

neogene lake systems of central and south eastern europe faunal diversity gradients and interrelations abstract the gastropod diversity of 12 neogene lake systems is evaluated in total 1184 gastropod taxa from 119 localities are recorded deriving from the early miocene rzehakia lake system the early to middle miocene dinarid lake system lake skopje the paratethyan sarmatian lakes and the south german lakes the late miocene lake pannon the pliocene lakes dacia transylvania slavonia kosovo and sostanj as well as the holocene lake petea each lake system is characterised according to its faunistic inventory and endemism according to their gastropod faunas the lakes may be divided into pyrgulid hydrobiid viviparid and planorbid dominated ones the generally high endemism rate is between 60 and 98 species diversity and generic diversity are strongly correlated in contrast neither endemism nor lake size are tightly linked with diversity outstandingly high diversities such as observed for lake pannon are rather a result of the combined effect of autochthonous evolution in a long lived system and accumulation of inherited elements examples of parallel evolution in lymnaeids and planorbids are presented

microstructure observations of turbulent heat fluxes in a warm core canada basin eddy abstractan intrahalocline eddy was observed on the chukchi slope in september of 2015 using both towed ctd and microstructure temperature and shear sections the core of the eddy was 6 c significa

tide mediated warming of arctic halocline by atlantic heat fluxes over rough topography atlantic water brings heat to the subsurface arctic ocean pan arctic microstructure measurements of energy dissipation suggest that vertical mixing is substantial over the continental slopes tidally induced and insensitive to sea ice cover

wind driven mixing at intermediate depths in an ice free arctic ocean recent seasonal arctic ocean sea ice retreat is a major indicator of polar climate change the arctic ocean is generally quiescent with the interior basins characterized by low levels of turbulent mixing at intermediate depths in contrast under conditions of reduced sea ice cover there is evidence of energetic internal waves that have been attributed to increased momentum transfer from the atmosphere to the ocean new measurements made in the canada basin during the unusually ice free and stormy summer of 2012 show previously observed enhancement of internal wave energy associated with ice free conditions however there is no enhancement of mixing at intermediate depths away from significant topography this implies that contrary to expectations of increased wind induced mixing under declining arctic sea ice cover the stratification in the central canada basin continues to suppress turbulent mixing at intermediate depths and to effectively isolate the large atlantic and pacific heat reservoirs from the sea surface

neogene quaternary structures in the border zone between alps dinarides and pannonian basin hrvatsko zagorje and karlovac basins croatia analysis of neogene quaternary structures from seismic lines surface measurements and geological mapping is presented from the border zone between the alps dinarides and pannonian basin first early miocene extension was possibly characterised by ene directed extension it was partly synchronous with nw se shortening second middle miocene extension was possibly characterised by nw se to wnw ese directed extension again this event was followed by a new generation of thrusts related to end sarmatian shortening the last late miocene e w to wnw ese directed extension was followed by a final shortening that created major map scale folds basement pop ups and inverted former basins geometry onlap and thickness patterns of the youngest syn tectonic basin fill indicate that this last n s to nw se directed shortening started in late pontian and continued up to the present time when taking into account the wider surrounding area it seems that the structures related to this latest shortening are arranged in often perpendicular directions centred at the eastern end of the periadriatic lineament to explain this fan like pattern of synchronous shortenings a kinematic model is proposed combining counter clockwise rotation with north or northwestward shift of the dinaridic block with respect to the more stable alpine buttress

the impact of variable sea ice roughness on changes in arctic ocean surface stress a model study the arctic sea ice cover is thinning and retreating causing changes in surface roughness that in turn modify the momentum flux from the atmosphere through the ice into the ocean new model simulations comprising variable sea ice drag coefficients for both the air and water interface demonstrate that the heterogeneity in sea ice surface roughness significantly impacts the spatial distribution and trends of ocean surface stress during the last decades simulations with constant sea ice drag coefficients as used in most climate models show an increase in annual mean ocean surface stress 0 003 n m2 per decade 4 6 due to the reduction of ice thickness leading to a weakening of the ice and accelerated ice drift in contrast with variable drag coefficients our simulations show annual mean ocean surface stress is declining at a rate of 0 002 n m2 per decade 3 1 over the period 1980 2013 because of a significant reduction in surface roughness associated with an increasingly thinner and younger sea ice cover the effectiveness of sea ice in transferring momentum does not only depend on its resistive strength against the wind forcing but is also set by its top and bottom surface roughness varying with ice types and ice conditions this reveals the need to account for sea ice surface roughness variations in climate simulations in order to correctly represent the implications of sea ice loss under global warming

tertiary to recent oblique convergence and wrenching of the central dinarides constraints from a palaeostress study the late eocene to neogene tectonic evolution of the dinarides is characterised by shortening and orogen parallel wrenching superposed on the late cretaceous and eocene double vergent orogenic system the central dinarides exposes nw trending tectonic units which were transported towards the adria apulian microcontinent during late cretaceous palaeogene times these units were also affected by subsequent processes of late palaeogene to neogene shortening neogene extension and subsidence of intramontane sedimentary basins and pliocene quaternary surface uplift and denudation the intramontane basins likely relate to formation of the pannonian basin major dextral se trending strike slip faults are mostly parallel to boundaries of major tectonic units and suggest dextral orogen parallel wrenching of the whole central dinarides during the neogene indentation of the apulian microplate into the alps and back arc type extension in the pannonian basin these fault systems have been evaluated with the standard palaeostress techniques we report four palaeostress tensor groups which are tentatively ordered in a succession from oldest to youngest 1 palaeostress tensor group 1 d1 of likely late eocene age indicates e w shortening accommodated by reverse and strike slip faults 2 palaeostress tensor group 2 d2 comprises n nw trending dextral and w wsw trending sinistral strike slip faults as well as wnw striking reverse faults these indicate ne sw contraction and subordinate nw se extension related to oligocene to early miocene shortening of the dinaric orogenic wedge 3 palaeostress tensor group 3a d3a comprises mainly nw trending normal faults which indicate early middle miocene ne sw extension related to syn rift extension in the pannonian basin the subsequent palaeostress tensor group 3b d3b includes ne trending se dipping normal faults indicating nw se extension which is likely related to further extension in the pannonian basin 4 palaeostress tensor group 4 d4 i s characterised by mainly nw trending dextral and ne trending sinistral strike slip faults together with some e trending reverse faults they indicate roughly n s shortening and dextral wrenching during late miocene to quaternary this is partly consistent with the present day kinematics with motion of the adriatic microplate constrained by gps data and earthquake focal mechanisms the north north westward motion and counterclockwise rotation of the adriatic microplate significantly contribute the shortening and present day wrenching in the central dinarides d 2005 elsevier b v all rights reserved

reduced mixing from the breaking of internal waves in equatorial waters in the oceans heat salt and nutrients are redistributed much more easily within water masses of uniform density than across surfaces separating waters of different densities but the magnitude and distribution of mixing across density surfaces are also important for the earth s climate as well as the concentrations of organisms most of this mixing occurs where internal waves break overturning the density stratification of the ocean and creating patches of turbulence predictions of the rate at which internal waves dissipate were confirmed earlier at mid latitudes here we present observations of temperature and velocity fluctuations in the pacific and atlantic oceans between 42 degrees n and 2 degrees s to extend that result to equatorial regions we find a strong latitude dependence of dissipation in accordance with the predictions in our observations dissipation rates and accompanying mixing across density surfaces near the equator are less than 10 of those at mid latitudes for a similar background of internal waves reduced mixing close to the equator will have to be taken into account in numerical simulations of ocean dynamics for example in climate change experiments

evidence for atmospheric control of sea ice motion through nares strait 1 satellite observations of ice motion are combined with model estimates of low level winds and surface wind stress to provide evidence for atmospheric control of sea ice motion through nares strait between ellesmere island and greenland during two periods in 2004 the results suggest that ice flux through the strait and its shutdown through the formation of a landfast ice mass in the strait can be controlled by wind stress and atmospheric cooling analysis of the model results during these two periods also suggest that the intense low level along strait winds are strongly ageostrophic and may be usefully estimated from pressure differences along the strait

accommodation and supply a dual control on stratigraphic sequences abstract it is widely accepted that both eustatic and tectonically controlled regional changes of sea level have contributed to the record of stratigraphic sequences i suggest that environmental change be added as a third autonomous control sedimentologic principles clearly indicate that sequences and their systems tracts are controlled by the interplay of two rates the rate of change in accommodation space available for sedimentation and the rate of sediment supply sea level has direct control on accommodation but its influence on sediment supply is remote and easily overshadowed by environmental factors for instance the record of the most recent sea level rise is a transgressive systems tract where supply is low it is a prograding highstand systems tract in deltas where the supply is high examples of sequence boundaries generated by changes in sediment supply include tectonically driven shifts in sediment input into basins changes in ocean currents pulsating supply from failure of submarine slopes and drowning of carbonate platforms by environmental stress furthermore the stratigraphic sequences in fluviatile continental basins are physically removed from sea level induced changes in accommodation and must have formed by changes in the rate and pattern of supply subaerial exposure of marine sediments at the sequence boundary is a most important criterion for recognizing sea level cycles as opposed to supply cycles other criteria include downstepping of shelf breaks and characteristic patterns in the spacing of time lines within sequences some third order cycles ca 0 5 3 ma duration meet these criteria others do not cycle stacking patterns and the shifting facies belts on cratons indicate that many second and third order cycles lack pronounced exposure unconformities and represent gradual changes superimposed on more rapid shorter oscillations seismic data yield poor images of these gradational changes because they lack resolution seismic models of outcrops show that near the limits of resolution the seismic tool tends to portray rapid changes in facies and bed thickness i e lateral variations in supply as unconformities seismic unconformities do not necessarily correspond to unconformities in outcrop the succession of stratigraphic sequences is best considered a composite record of sea level and environmental change separating the various controls requires carefully planned experiments work on the oxygen isotope curve another proxy for sea level has set an example in this respect

barotropic and baroclinic tidal currents on the mackenzie shelf break in the southeastern beaufort sea 1 tidal currents near the outer shelf break of the mackenzie shelf in the southern beaufort sea were examined using year long 1987 1988 current measurements from the upper 35 m and lower 150 m layers at four sites along the southeast ss1 northeast ss2 north central ss3 and northwest ss4 perimeter of the shelf at all stations semidiurnal currents were dominant and upper layer currents were approximately double those observed in the lower layer maximum m2 currents were observed above the sharp northeastern corner of the mackenzie shelf 6 0 7 5 cm s 1 while in the mackenzie canyon they were negligible diurnal currents were weaker and depth uniform maximum k1 currents 1 5 3 0 cm s 1 were found in the eastern part of the shelf diurnal and lower layer semidiurnal currents were in good agreement with those computed numerically by kowalik and proshutinsky 1994 indicating that these currents are essentially barotropic in contrast upper layer semidiurnal currents were mainly baroclinic about 74 of the total energy of semidiurnal currents was associated with baroclinic coherent phase locked tidal currents while barotropic 12 baroclinic incoherent 7 and inertial 7 components are the remaining semidiurnal currents in this area high baroclinic generation coefficients the ratio of locally generated baroclinic waves to barotropic waves for stations ss2 and ss3 about 7 0 8 0 in comparison with 0 3 for ss1 and ss4 located near the northeastern mackenzie shelf identify this region as a probable generation source of intensive internal tidal waves which become then locally resonantly trapped between the shelf and the critical latitudes

revisiting internal waves and mixing in the arctic ocean 1 to determine whether deep background mixing has increased with the diminishment of the arctic sea ice we compare recent internal wave energy and mixing observations with historical measurements since 2007 the north pole environmental observatory has launched expendable current probes xcps as a part of annual airborne hydrographic surveys in the central arctic ocean mixing in the upper 500 m is estimated from xcp shear variance and conductivity temperature depth ctd derived brunt vaisala frequency internal wave energy levels vary by an order of magnitude between surveys although all surveys are less energetic and show more vertical modes than typical midlatitude garrett munk gm model spectra survey averaged mixing estimates also vary by an order of magnitude among recent surveys comparisons between modern and historical data reanalyzed in identical fashion reveal no trend evident over the 30 year period in spite of drastic diminution of the sea ice turbulent heat fluxes are consistent with recent double diffusive estimates both mixing and internal wave energy in the beaufort sea are lower when compared to both the central and eastern arctic ocean and expanding the analysis to mooring data from the beaufort sea reveals little change in that area compared to historical results from arctic internal wave experiment we hypothesize that internal wave energy remains lowest in the beaufort sea in spite of dramatic declines in sea ice there because increased stratification amplifies the negative effect of boundary layer dissipation on internal wave energy

propagation and vertical structure of the tidal flow in nares strait the southward freshwater flux through nares strait is an important component of the arctic s freshwater budget on short time scales flow through the strait is dominated by the tides and tidal dynamics may be important for the magnitude of the freshwater flux over longer periods here we build upon our existing knowledge of the tides in the region by exploring their propagation and vertical structure using data from four bottom mounted acoustic doppler current profilers deployed in nares strait between 2003 and 2006 we observe that propagating barotropic semidiurnal tidal waves interact to create a standing wave pattern explaining the abnormally large tidal amplitudes that are observed in this region in the along strait direction semidiurnal tidal currents exhibit strong variations with depth in contrast the diurnal tides propagate northward through the strait as progressive waves and the tidal currents are broadly depth invariant proximity of nares strait to the semidiurnal critical latitude and the topographical restriction imposed by the steep side wall of ellesmere island are primary drivers behind the observed vertical variability in the upper part of the water column baroclinic activity increases the tidal current amplitude by up to 25 in the across strait direction a two layer structure exists in both the diurnal and semidiurnal tidal flow with a phase lag of approximately a quarter of a tidal cycle across the strait for the semidiurnal tide our results suggest that strong vertical motion exists against the side walls of nares strait as the across strait flow interacts with the steeply sloping bathymetry

vertical diffusivity of the western arctic ocean halocline a nearly year long series of upper ocean temperature conductivity and temperature microstructure profiles were collected from an ice camp drifting in the beaufort gyre as part of the 1997 1998 surface heat budget of the arctic experiment sheba geographically the record includes portions over the deep canada basin and the steep bathymetry of the chukchi borderlands region hydrographically the record includes cool pacific origin haloclines which contain a variety of subsurface temperature maxima and cold haloclines typical of the eurasian basins we present estimates of the vertical turbulent diffusivity derived from the dissipation rate of thermal variance and calculations of the associated vertical heat fluxes we find that vertical diffusion proceeds at molecular rates in the deep basins and away from topographic features while still relatively small diffusivity is enhanced by 1 order of magnitude near and above the chukchi borderlands the enhanced diffusivity is correlated to an increase in water column strain variance above the borderlands providing a linkage between bathymetry internal wave activity and turbulence the chukchi borderlands play a significant role in heat transport in the western arctic they are a pathway for horizontal heat transport and a hot spot for vertical heat transport vertical fluxes make a substantial contribution to the energy balance of the sea ice cover in this region heat fluxes between the halocline and underlying atlantic water are shown to be small and lacking vertical connection near surface waters

origin and fate of particulate organic matter in the southern beaufort sea amundsen gulf region canadian arctic canadian arctic shelf exchange study cases natural sciences and engineering research council of canada nserc fonds quebecois de la recherche sur la nature et les technologies fqrnt department of earth and planetary sciences at mcgill university

changing lake dynamics and sequence stratigraphy of synrift lacustrine strata in a half graben an example from the triassic ischigualasto villa union basin argentina well exposed triassic rift strata from the ischigualasto villa union basin nw argentina include a 80 to ca 515 m thick lacustrine dominated package that can be correlated across a half graben using key stratigraphic surfaces sequence boundaries lacustrine flooding surfaces and forced regressive surfaces the characteristics of the synrift lacustrine fill in different parts of the half graben have been examined and the mechanisms controlling sedimentation inferred a variety of sedimentary environments are recognized including volcaniclastic floodplain mildly saline lake and playa lake offshore lacustrine delta front to fluvial dominated and wave dominated deltas distributary and fluvial channel and interdistributary bay the succession can be divided into four stratigraphic sequences ss1 to ss4 the oldest of which ss1 contains volcaniclastic fluvial and saline lake deposits it is thickest close to the western border fault zone reflecting more rapid subsidence here accommodation exceeded sediment and water input during ss1 the second and third sequences ss2 and ss3 mark the onset of widespread lacustrine sedimentation reflecting a balance between accommodation creation and water and sediment fluxes sequences ss2 and ss3 are represented by offshore meromictic lacustrine and deltaic deposits the latter mostly sourced from the flexural and southern axial margins of the half graben the presence of stacked parasequences bound by lacustrine flooding surfaces is related to climatically induced lake level fluctuations superimposed on variable rates of subsidence on the controlling rift border fault zone the youngest sequence ss4 is represented by the deposits of littoral lacustrine and shallow shelf deltas distinguished by a change in lithofacies palaeocurrents and sandstone composition suggesting a switch in sediment supply to the footwall margin to the nw the change in the sediment source is related to reduced footwall uplift the possible presence of a relay ramp and or supply from a captured antecedent drainage network during ss4 the rate of creation of accommodation was exceeded by the sediment and water discharge the stratigraphic evolution of lacustrine strata in the half graben was mainly controlled by tectonic processes including subsidence rate and the growth and evolution of the border fault zone but changing climate inducing changes in water balance and lake level and autocyclic processes delta lobe switching were also important

spatial variability of the arctic ocean s double diffusive staircase the arctic ocean thermohaline stratification frequently exhibits a staircase structure overlying the atlantic water layer that can be attributed to the diffusive form of double diffusive convection the staircase consists of multiple layers of o 1 m in thickness separated by sharp interfaces across which temperature and salinity change abruptly through a detailed analysis of ice tethered profiler measurements from 2004 2013 the double diffusive staircase structure is characterized across the entire arctic ocean we demonstrate how the large scale arctic ocean circulation influences the small scale staircase properties these staircase properties layer thicknesses and temperature and salinity jumps across interfaces are examined in relation to a bulk vertical density ratio spanning the staircase stratification we show that the lomonosov ridge serves as an approximate boundary between regions of low density ratio approximately 3 to 4 on the eurasian side and higher density ratio approximately 6 to 7 on the canadian side we find that the eurasian basin staircase is characterized by fewer thinner layers than that in the canadian basin although the margins of all basins are characterized by relatively thin layers and the absence of a well defined staircase a double diffusive 4 3 flux law parametrization is used to estimate vertical heat fluxes in the canadian basin to be o 0 1 wm 2 it is shown that the 4 3 flux law may not be an appropriate representation of heat fluxes through the eurasian basin staircase here molecular heat fluxes are estimated to be between o 0 01 wm 2 and o 0 1 wm 2 however many uncertainties remain about the exact nature of these fluxes this article is protected by copyright all rights reserved

the distribution of nutrients in the southeastern beaufort sea implications for water circulation and primary production hydrographic data collected above the shelf and slope in the southeastern beaufort sea show marked contrast in surface properties of nutrients temperature salinity and oxygen between august 1974 a year when ice remained close to shore and august 1975 a year with much open water the near surface properties are dominated by river inputs biological activity and the ice regime below the winter mixed zone 40 50 m properties are similar to those observed elsewhere in the arctic ocean bering sea water is detected at 50 60 m as a very weak signal in temperature nutrients and oxygen upwelling in both years was observed at the eastern side of mackenzie canyon this upwelling likely results from the interaction of coastal circulation with topography estimates of new productivity based on nutrient budgets are low 20 g c m 2 yr 1 compared to temperate coastal waters but fall in the range expected for the arctic in 1974 the heavy ice year turbid water and ice cover appear to have reduced new production by about 30 calculations show that this production over the shelf could potentially supply a significant portion of the nutrients found in the upper halocline over a wide region of the arctic ocean by regeneration at the shelf bottom and transport off the shelf in brine drainage

sea ice draft observations in nares strait from 2003 to 2012 time series observation of sea ice draft and velocity from nares strait between 2003 and 2012 provides new insights on the statistical properties of sea ice leaving the arctic for the atlantic oceans median ice draft is 0 8 m but it varies annually from 1 5 m in 2007 2008 to 0 5 m in 2008 2009 probability density distributions of sea ice draft depend on location across the channel with thicker ice near canada and thinner ice near greenland nevertheless sea ice motion stops seasonally due to arching land fast ice that spans the 30 40 km wide channel for up to 190 days per year such as during the 2011 2012 winter in contrast the 2006 2010 period exhibits a single ice arch lasting 47 days in april may 2008 hence sea ice statistics are weighted by space not by time using sea ice velocities estimated from colocated velocity observations multiyear sea ice with drafts exceeding 5 m constitute between 9 2003 2004 and 16 2007 2008 of the observed sea ice the probability g d of this thick ridged multiyear ice decays exponentially with draft d at an e folding scale d0 of 3 0 0 2 m the trend of d0 with time is statistically indistinguishable from zero this observation suggests a steady export of multiyear sea ice at decadal time scales we speculate that our observations document the draining of the last reservoir of thick ice from the arctic ocean found to the north of ellesmere island and greenland

ice tethered profiler observations of the double diffusive staircase in the canada basin thermocline vertical heat fluxes through the staircase are in the range 0 05 0 3 w m 2 only about one tenth of the estimated mean surface mixed layer heat flux to the sea ice it is thus concluded that the vertical transport of heat from the atlantic water in the central basin is unlikely to have a significant impact to the canada basin ocean surface heat budget icebreaker conductivity temperature depth data from the beaufort gyre freshwater experiment show that the staircase is absent at the basin periphery turbulent mixing that presumably disrupts the staircase might drive greater flux from the atlantic water at the basin boundaries and possibly dominate the regionally averaged heat flux

the interplay between eustacy tectonics and surface processes during the growth of a fault related structure as derived from sequence stratigraphy the govora ocnele mari antiform south carpathians abstract orogenic collision represents a moment when typical rules of thin skinned development are at odds with the generalized interaction between the upper and buoyant lower plate deriving the kinematics of these collisional features is usually difficult because of the large amounts of subsequent erosion study areas such as those that exist along the south carpathians foredeep where the syn and post collisional sediments are still preserved are important places to identify record and quantify out of sequence deformation here sequence stratigraphic techniques may be used in order to detect tectonic movements which are an order of magnitude higher resolution than those routinely identified by either standard structural analysis or isotope geochronology this study proves that what has been previously interpreted as a one stage growing anticline situated at the contact with the core of the orogen is in fact a gradually evolving antiform structure with at least four quantifiable pulses of vertical movements associated with various amounts of orogenic uplift during collision the interplay between the orogenic core and the anticline uplift controls the depositional area the effects of sea level variations being subordinated transversal shear zones such as strike slip faults are used as transport corridors by the progressive infill of large quantities of sediments from the source area towards the larger basins situated more to the foreland

cenozoic granitoids in the dinarides of southern serbia age of intrusion isotope geochemistry exhumation history and significance for the geodynamic evolution of the balkan peninsula two age groups were determined for the cenozoic granitoids in the dinarides of southern serbia by high precision single grain u pb dating of thermally annealed and chemically abraded zircons 1 oligocene ages kopaonik drenje eljin ranging from 31 7 to 30 6 ma 2 miocene ages golija and polumir at 20 58 20 17 and 18 06 17 74 ma respectively apatite fission track central ages modelling combined with zircon central ages and additionally local structural observations constrain the subsequent exhumation history of the magmatic rocks they indicate rapid cooling from above 300 c to ca 80 c between 16 and 10 ma for both age groups induced by extensional exhumation of the plutons located in the footwall of core complexes hence miocene magmatism and core complex formation not only affected the pannonian basin but also a part of the mountainous areas of the internal dinarides based on an extensive set of existing age data combined with our own analyses we propose a geodynamical model for the balkan peninsula the late eocene to oligocene magmatism which affects the adria derived lower plate units of the internal dinarides was caused by delamination of the adriatic mantle from the overlying crust associated with post collisional convergence that propagated outward into the external dinarides miocene magmatism on the other hand is associated with core complex formation along the southern margin of the pannonian basin probably associated with the w directed subduction of the european lithosphere beneath the carpathians and interfering with ongoing dinaridic hellenic back arc extension

the tectonic evolution of a critical segment of the dinarides alps connection kinematic and geochronological inferences from the medvednica mountains ne croatia the transition zone between the alps and dinarides is a key area to investigate kinematic interactions of neighboring orogens with different subduction polarities a study combining field kinematic and sedimentary data microstructural observations thermochronological data rb sr and fission track and regional structures in the area of medvednica mountains has revealed a complex polyphase tectonic evolution we document two novel stages of extensional exhumation the first stage of extension took place along a late cretaceous detachment following the late early cretaceous nappe stacking burial and greenschist facies metamorphism two other shortening events that occurred during the latest cretaceous oligocene were followed by a second event of extensional exhumation characterized by asymmetric top ne extension during the miocene top nw thrusting took place subsequently during the pliocene inversion of the pannonian basin the cretaceous nappe burial late cretaceous extension and the oligocene earliest miocene contraction are events driven by the alps evolution in contrast the latest cretaceous eocene deformation reflects phases of dinaridic contraction furthermore the miocene extension and subsequent inversion display kinematics similar with observations elsewhere in the dinarides and eastern alps all these processes demonstrate that the medvednica mountains were affected by alpine phases of deformations to a much higher degree than previously thought similarly with what has been observed in other areas of contractional polarity changes such as the mediterranean black sea or new guinea systems the respective tectonic events are triggered by rheological weak zones which are critical for localizing the deformation created by both orogens

turbulent kinetic energy dissipation in barrow canyon pacificwaterflowsacross theshallowchukchisea beforereachingthe arctic ocean where it isa sourceof heat freshwater nutrients and carbon a substantial portion of pacific water is routed through barrow canyon located in the northeast corner of the chukchi barrow canyon is a region of complex geometry and forcing where a variety of water masses have been observed to coexist these factors contribute to a dynamic physical environment with the potential for significant water mass transformation the measurements of turbulent kinetic energy dissipation presented here indicate diapycnal mixing is important in the upper canyon elevated dissipation rates were observed near the pycnocline effectively mixing winter and summer water masses as well as within the bottom boundary layer the slopes of shear stratification layers combined with analysis of rotary spectra suggest that near inertial wave activity may be important in modulating dissipation near the bottom because the canyon is known to be a hotspot of productivity with an active benthic community mixing may be an important factor in maintenance of the biological environment

observations of a diapycnal shortcut to adiabatic upwelling of antarctic circumpolar deep water in the southern ocean small scale turbulence causes diapycnal mixing which influences important water mass transformations in turn impacting large scale ocean transports such as the meridional overturning circulation moc a key controller of earth s climate we present direct observations of mixing over the antarctic continental slope between water masses that are part of the southern ocean moc a 12 h time series of microstructure turbulence measurements hydrography and velocity observations off elephant island north of the antarctic peninsula reveals two concurrent bursts of elevated dissipation of o 10 6 w kg 1 resulting in heat fluxes 10 times higher than basin integrated drake passage estimates this occurs across the boundary between adjacent adiabatic upwelling and downwelling overturning cells ray tracing to nearby topography shows mixing between 300 and 400 m is consistent with the breaking of locally generated internal tidal waves since similar conditions extend to much of the antarctic continental slope where these water masses outcrop diapycnal mixing may contribute significantly to upwelling

graben width controlling syn rift sedimentation the palaeogene southern upper rhine graben as an example eocene to early oligocene syn rift deposits of the southern upper rhine graben urg accumulated in restricted environments sedimentation was controlled by local clastic supply from the graben flanks as well as by strong intra basinal variations in accommodation space due to differential tectonic subsidence that in turn led to pronounced lateral variations in depositional environment three large scale cycles of intensified evaporite sedimentation were interrupted by temporary changes towards brackish or freshwater conditions they form three major base level cycles that can be traced throughout the basin each of them representing a stratigraphic sub unit a relatively constant amount of horizontal extension l in the range of 4 5 km has been estimated for the urg from numerous cross sections the width of the rift lf however varies between 35 and more than 60 km resulting in a variable crustal stretching factor between the bounding masterfaults apart from block tilting tectonic subsidence was therefore largely controlled by changes in the initial rift width l0 the along strike variations of the graben width are responsible for the development of a deep trough like evaporite basin potash basin in the narrowest part of the southern urg adjacent to shallow areas in the wider parts of the rift such as the colmar swell in the north and the rhine bresse transfer zone that delimits the urg to the south under a constant amount of extension the along strike variation in rift width is the principal factor controlling depo centre development in extensional basins

water mass structure and boundaries in the mackenzie shelf estuary the mackenzie shelf is a broad estuarine region bordering the southeastern beaufort sea in the arctic ocean its fields of temperature and salinity result from the modification of offshore water masses by river inflow ice melting and freezing solar insolation and air sea exchange we here relate water masses resident on the mackenzie shelf to the large scale oceanography of the arctic mediterranean the summertime exchange between the shelf and open ocean is largely confined to waters lying above the main halocline s 34 2 psu cross shelf property distributions show that individual water masses maintain their structural identity i e core properties and buoyancy frequency as they move across the shelf and participate in the estuarine circulation shelf waters are strongly influenced by river inflow however the concept of a single plume issuing from the incoming river and forming a strictly two layered structure over uniform shelf water is misleading since a variety of temperature salinity and turbidity fronts co exist on the shelf at any given time

intermittent intense turbulent mixing under ice in the laptev sea continental shelf vertical mixing in the bottom boundary layer and pycnocline of the laptev sea is evaluated from a rapidly sampled 12 h time series of microstructure temperature conductivity and shear observations collected under 100 sea ice during october 2008 the bottom boundary turbulent kinetic energy dissipation was observed to be enhanced 10 4 w m 3 beyond background levels 10 6 w m 3 extending up to 10 m above the seabed when simulated tidal currents were directed on slope upward heat fluxes into the halocline class waters along the laptev sea seabed peaked at 4 8 w m 2 averaging out to 2 w m 2 over the 12 h sampling period in the laptev sea pycnocline an isolated 2 h episode of intense dissipation 10 3 w m 3 and vertical diffusivities was observed that was not due to a localized wind event observations from an acoustic doppler current meter moored in the central laptev sea near the m2 critical latitude are consistent with a previous model in which mixing episodes are driven by an enhancement of the pycnocline shear resulting from the alignment of the rotating pycnocline shear vector with the under ice stress vector upward cross pycnocline heat fluxes from the arctic halocline peaked at 54 w m 2 resulting in a 12 h average of 12 w m 2 these results highlight the intermittent nature of arctic shelf sea mixing processes and how these processes can impact the transformation of arctic ocean water masses the observations also clearly demonstrate that absence or presence of sea ice profoundly affects the availability of near inertial kinetic energy to drive vertical mixing on the arctic shelves

global abyssal mixing inferred from lowered adcp shear and ctd strain profiles abstract internal wave wave interaction theories and observations support a parameterization for the turbulent dissipation rate e and eddy diffusivity k that depends on internal wave shear vz2 and strain z2 variances its latest incarnation is applied to about 3500 lowered adcp ctd profiles from the indian pacific north atlantic and southern oceans inferred diffusivities k are functions of latitude and depth ranging from 0 03 10 4 m2 s 1 within 2 of the equator to 0 4 0 5 10 4 m2 s 1 at 50 70 diffusivities k also increase with depth in tropical and subtropical waters diffusivities below 4500 m depth exhibit a peak of 0 7 10 4 m2 s 1 between 20 and 30 latitudes where semidiurnal parametric subharmonic instability is expected to be active turbulence is highly heterogeneous though the bulk of the vertically integrated dissipation e is contributed from the main pycnocline hotspots in e show some correlation with small scale bottom roughness and near bottom flow at sites where st

mixing across the arctic ocean microstructure observations during the beringia 2005 expedition 1 turbulent scale temperature and conductivity were measured during the pan arctic beringia 2005 expedition the rates of dissipation of thermal variance and diapycnal diffusivities are calculated along a section from alaska to the north pole across deep flat basins canada and makarov basins and steep ridges alpha mendeleev and lomonosov ridges the mixing rates are observed to be small relative to lower latitudes but also remarkably non uniform relatively elevated turbulence is found over deep topography confirming the dominant role of bottom generated internal waves measured patterns of mixing in the arctic are also associated with other mechanisms such as double diffusive structures and deep overflows a better knowledge of the distribution of mixing is essential to understand the dynamics of the changing arctic environment

meteorological forcing of sea ice concentrations in the southern beaufort sea over the period 1979 to 2000 1 northern hemisphere sea ice areal extent and perhaps thickness have shown a detectable reduction over the past several decades this situation is particularly apparent in the southern beaufort sea the region encompassing the mackenzie shelf the cape bathurst polynya and the canada basin mobile pack ice all occur in a region referred to here as the canadian arctic shelf exchange study area cases in this paper we present results from an analysis of atmosphere sea ice and ocean coupling over the period 1979 to 2000 as a means of setting a physical science context for the cases research network operating over the period 2001 2005 results show that the cape bathurst polynya complex can be considered as a recurrent polynya particularly the flaw leads associated with the early opening of the polynya the polynya appears to be a consequence of the beaufort sea gyre acting like an ice bridge and a series of flaw leads creating conditions conducive to oceanic upwelling the sea ice average areal extent has been decreasing in this region over the period 1979 to 2000 large regional reductions are found i north of the yukon and alaska coasts in the region between the canada basin pack ice and the landfast sea ice and 2 at the eastern limit of the cape bathurst polynya in amundsen gulf the meteorological forcing of sea ice anomalies occurs through a full range of timescales and space scales at hemispheric scales a statistical cross correlation analysis between weekly sea ice concentration anomalies and the arctic oscillation accounts for a maximum of about 25 percent of the explained variance and show a surprising spatial coherence in correlation magnitudes both within the study area and northward along the canadian archipelago coast at local scales positive and negative concentration anomaly periods can be explained through local scale advective processes associated with regional scale sea level pressure 500 hpa geopotential heights and surface temperature anomalies

turbulent nitrate fluxes in the amundsen gulf during ice covered conditions 3 2 5 10 3 m 2 s 1 and decreased exponentially to a depth of 50 m below which it was roughly constant at the background value kb 3 2 5 1 0 6 m 2 s 1 t he nitracline centered around 62 m depth was subject to an eddy diffusivity close to the background value kb and the mean diffusive nitrate flux across the nitracline was fnit 0 5 0 3 0 8 mmol m 2 d 1 these observations are compared with other regions and the role of vertical mixing on primary production in the amundsen gulf is discussed citation bourgault d c hamel f cyr j e tremblay p s galbraith d dumont and y gratton 2011 turbulent nitrate fluxes in the amundsen gulf during ice covered conditions geophys res lett 38 l15602 doi 10 1029 2011gl047936

tectonic control on sedimentary facies pattern and sediment accumulation rates in the miocene foreland basin of the southern alborz mountains northern iran 1 the southern alborz mountains of northern iran are an integral part of the arabia eurasia collision zone a magnetostratigraphic and rock magnetic investigation of the eyvanekey stratigraphic section in the southern alborz mountains reveals the spatiotemporal character of sedimentary facies migration in the alborz foreland basin the section constitutes three coarsening upward units units 1 2 and 3 comprising the upper red and hezardarreh formations our data reveal that the upper red formation was deposited between 17 5 and 7 5 ma while the depositional age of the top of the hezardarreh formation can be extrapolated to 6 2 ma slow sediment accumulation rates correlate with sedimentary facies comprising prograding coarsening upward units this is likely the result of intraforeland uplift units 1 and 2 and basin inversion probably associated with a growth syncline located in the proximal foreland unit 3 in contrast fine grained strata at the bottom of each cycle are associated with faster sediment accumulation rates testifying to enhanced flexural basin subsidence in the course of thrust loading progradation of coarse grained facies also occurred during relatively fast sediment accumulation top of unit 2 suggesting that the influx of coarse grained sediment outpaced the storage capacity of the proximal foreland thus despite an overall southward propagation of deformation into the southern alborz foreland the locus of active deformation must have migrated back and forth on a time scale of circa 0 7 to 2 ma

observations of turbulent mixing and hydrography in the marginal ice zone of the barents sea 1 measurements of hydrography currents microstructure shear and temperature were made at ice drift stations in the marginal ice zone miz of the northern barents sea highly variable mixing regimes were observed within and below the pycnocline elevated turbulent dissipation 5 15 10 7 w kg 1 was associated with strong vertical shear between the surface layer and the subsurface currents as well as strong tidal flow over shallow topography dissipation in the pycnocline was enhanced at stations with strong wind forcing during drifts under relatively calm wind and away from strong fronts and abrupt topography station mean dissipation values were up to a factor 50 lower and double diffusion contributed significantly to the vertical heat flux where hydrography favored diffusive layering independent measures of turbulent length scale from density overturns compared well with those inferred from the dissipation measurements the variability of dissipation was better captured using a scaling by shear suggested for shelves rather than shear variance models appropriate to the deep open ocean sufficiently resolved patches of enhanced temperature microstructure used in combination with dissipation measurements suggest mixing efficiency of rf 0 2 for patches stable to double diffusion comparable to the conventional upper bound of rf 0 17 mixing efficiency for double diffusive convection favorable cases is found to be significantly larger rf 0 36 water mass modification and fluxes of nutrients and dissolved carbon were found to have large local variability in accordance with the observed variability of vertical mixing in the miz

eddy induced modulation of turbulent dissipation over rough topography in the southern ocean abstractmesoscale eddies are universal features of the ocean circulation yet the processes by which their energy is dissipated remain poorly understood one hypothesis argues that the interaction of strong geostrophic flows with rough bottom topography effects an energy transfer between eddies and internal waves with the breaking of these waves causing locally elevated dissipation focused near the sea floor this study uses hydrographic and velocity data from a 1 yr mooring cluster deployment in the southern ocean to test this hypothesis the moorings were located over a small 10 km topographic obstacle to the east of drake passage in a region of high eddy kinetic energy and one was equipped with an adcp at 2800 m depth from which internal wave shear variance and dissipation rates were calculated examination of the adcp time series revealed a predominance of upward propagating internal wave energy and a significant correlation r 0 45 between shear variance levels and subinertial near bottom cur

the interior shelves of the arctic ocean physical oceanographic setting climatology and effects of sea ice retreat on cross shelf exchange abstract the interior shelves of the arctic mediterranean are the shelves of the kara sea laptev sea east siberian sea and beaufort sea they comprise approximately 40 of the total arctic shelf area 2 5 10 6 km 2 and are distinguished from inflow and outflow shelves by their principal forcing dynamics along their southern continental boundary the interior shelves are dominated by the major arctic rivers receiving over 80 of the total freshwater input to the arctic ocean in the mid shelf region wind and ice motion surface stresses dominate mixing and circulation resulting in high variability along their northern seaward boundary they are forced by upwelling and downwelling favourable surface stresses which drive shelf basin exchanges with atlantic and pacific origin cyclonic boundary currents over the upper slope shelf basin exchange is further modified by shelf break morphometry e g canyons valleys headlands and bottom slope here we review the physical oceanographic settings and forcing of the interior shelves and then focus on shelfbreak exchange and supply of nutrients for new primary production due to upwelling across the shelfbreak as a proxy for this nutrient supply we show seasonal and annual time series of along shelfbreak surface stress due to wind and ice motion from 1979 to 2011 we apply this analysis to the shallow shelves from the kara sea to the beaufort sea and comment on recent increases due to atmospheric changes and sea ice retreat

enhanced diapycnal mixing due to near inertial internal waves propagating through an anticyclonic eddy in the ice free chukchi plateau abstractthe arctic ocean is known to be quiescent in terms of turbulent kinetic energy tke associated with internal waves to investigate the current state of tke in the seasonally ice free chukchi plateau arctic ocean this study performed a 3 week fixed point observation fpo using repeated microstructure hydrographic and current measurements in september 2014 during the fpo program the microstructure observation detected noticeable peaks of tke dissipation rate e during the transect of an anticyclonic eddy moving across the fpo station particularly e had a significant elevation in the lower halocline layer near the critical level reaching the order of 10 8 w kg 1 the adcp measured current displayed energetic near inertial internal waves niws propagating via the stratification at the top and bottom of the anticyclone according to spectral analyses of horizontal velocity the waves had almost downward energy propagation and its current amplitude reached 10 cm s 1 the wkb scaling inco

evolution of near surface ramp flat ramp normal faults and implication during intramontane basin formation in the eastern betic cordillera the huercal overa basin se spain 1 the nucleation propagation and associated folding of ramp flat ramp normal faults were analyzed from field examples developed in a brittle ductile multilayer sequence of the huercal overa basin se spain gently dipping sandy silt layers which display a low cohesive strength c0 7 kpa 34 favor the development of extensional detachments a tectonic origin instead of a possible gravitational origin is supported by the perpendicularity between the paleoslope direction of the fluvial deltaic environment inferred from imbricated pebbles and the senses of movement deduced from fault slicken lines the link between high angle normal faults hanfs formed at different levels in the layered sequence with horizontal fault segments comes to develop ramp flat ramp normal faults with associated roll over in the hanging wall observed extensional duplexes are formed by parallel detachments connected through synthetic riedel faults these riedel faults would produce the back rotation of the individual blocks horses i e extensional folding of the originally subhorizontal layers there is no correlation between the analyzed ramp flat ramp normal faults accommodating south southeastward extension during serravallian lower tortonian and either the regional alpujarride nevado filabride west directed extensional shear zone or the top to the north detachments within alpujarride units which are clearly sealed by serravallian lower tortonian sediments therefore the studied normal faults are restricted to the brittle ductile multilayer fluvio deltaic sequence and accommodate moderate late extension instead of belonging to a large crustal extensional system connected with a regional detachment at depth therefore the basin formed in a moderate crustal thickness context where small and medium scale extensional systems were subordinate structures these natural examples support the development of low angle normal faults at very shallow crustal levels in multilayer sequences with suitable rheological conditions

internal waves and mixing in the marginal ice zone near the yermak plateau observations were made of oceanic currents hydrography and microstructure in the southern yermak plateau in summer 2007 the location is in the marginal ice zone at the arctic front northwest of svalbard where the west spitsbergen current wsc carries the warm atlantic water into the arctic ocean time series of approximately 1 day duration from five stations upper 520 m and of an 8 day duration from a mooring are analyzed to describe the characteristics of internal waves and turbulent mixing the spectral composition of the internal wave field over the southern yermak plateau is 0 1 0 3 times the midlatitude levels and compares with the most energetic levels in the central arctic dissipation rate and eddy diffusivity below the pycnocline increase from the noise level on the cold side of the front by one order of magnitude on the warm side where 100 m thick layers with average diffusivities of 5 3 10 25 m 2 s 21 lead to heat loss from the atlantic water of 2 4 w m 22 dissipation in the upper 150 m is well above the noise level at all stations but strong stratification at the cold side of the front prohibits mixing across the pycnocline close to the shelf at the core of the svalbard branch of the wsc diffusivity increases by another factor of 3 6 here nearbottom mixing removes 15 w m 22 of heat from the atlantic layer internal wave activity and mixing show variability related to topography and hydrography thus the path of the wsc will affect the cooling and freshening of the atlantic inflow when generalized to the arctic ocean diapycnal mixing away from abyssal plains can be significant for the heat budget around the yermak plateau it is of sufficient magnitude to influence heat anomaly pulses entering the arctic ocean however diapycnal mixing alone is unlikely to be significant for regional cooling of the wsc

the link between tectonics and sedimentation in asymmetric extensional basins inferences from the study of the sarajevo zenica basin abstract the coupled tectonic and depositional history of extensional basins is usually described in terms of stratigraphic sequences linked with the activity of normal faults this depositional kinematic interplay is less understood in basins bounded by major extensional detachments or normal fault systems associated with significant exhumation of footwalls of particular interest is the link between tectonics and sedimentation during the migration of normal faulting in time and space across the basin one area where such coupled depositional kinematic history can be optimally studied is the late oligocene miocene sarajevo zenica basin located in the dinarides mountains of bosnia and herzegovina this intra montane basin recorded oligocene pliocene sedimentation in an endemic and isolated lake environment we use field kinematic and sedimentological mapping in outcrops correlated with existing local and regional studies to derive a high resolution evolutionary model of the basin the novel results demonstrate a close correlation between moments of normal faulting and high order sedimentological cycles while the overall extensional basin was filled by a largely uni directional sediment supply from the neighbouring mountain chain the migration in time and space of listric ne dipping normal faults was associated with a gradual shift of the sedimentological environment transgressive regressive cycles reflect sequential displacements on normal faults and their footwall exhumation defining a new sedimentological model for such basins this early middle miocene extension affected the central part of the dinarides and was associated with the larger opening of the neighbouring pannonian basin the extension was preceded and followed by two phases of contraction the oligocene early miocene thrusting took place during the final stages of the dinarides collision while the post middle miocene contraction is correlated with the regional indentation of the adriatic continental unit this latter phase inverted the extensional basin by reactivating the inherited basal listric detachment

spatial and temporal variability of global ocean mixing inferred from argo profiles 1 the influence of turbulent ocean mixing transcends its inherently small scales to affect large scale ocean processes including water mass transformation stratification maintenance and the overturning circulation however the distribution of ocean mixing is not well described by sparse ship based observations since this mixing is both spatially patchy and temporally intermittent we use strain information from argo float profiles in the upper 2 000 m of the ocean to generate over 400 000 estimates of the energy dissipation rate indicative of ocean mixing these estimates rely on numerous assumptions and do not take the place of direct measurement methods temporally averaged estimates reveal clear spatial patterns in the parameterized dissipation rate and diffusivity distribution across all the oceans they corroborate previous observations linking elevated dissipation rates to regions of rough topography we also observe heightened estimated dissipation rates in areas of high eddy kinetic energy as well as heightened diffusivity in high latitudes where stratification is weak the seasonal dependence of mixing is observed in the northwest pacific suggesting a wind forced response in the upper ocean

flexural partitioning of the late archaean witwatersrand foreland system south africa abstract the witwatersrand basin is part of a retroarc foreland system formed during the late archaean in response to crustal thickening along the northern margin of the kaapvaal craton this foreland system may be partitioned into foredeep forebulge and back bulge flexural provinces the preserved sedimentary fill occupies the region of the flexural foredeep and displays a typical transition from underfilled deep and shallow marine to overfilled fluvial and alluvial fan phases loading in the witwatersrand thrust belt took place in relation to the oblique convergence of two compressional stress fields as a result the foredeep is restricted along the strike to a distance of the witwatersrand foreland system formed on a newly cratonized continental lithosphere which gave the basin a small flexural wavelength i e 490 km from the center of orogenic loading to the axis of the back bulge relative to most phanerozoic counterparts the forebulge unconformity may be associated with the lack of dynamic loading which is probably a common feature for all precambrian retro foreland systems due to the lower rates of subduction associated with the early stage of plate tectonic processes

seasonal variability of water mass distribution in the southeastern beaufort sea determined by total alkalinity and δ18o 1 we examined the seasonal variability of water mass distributions in the southeastern beaufort sea from data collected between september 2003 and august 2004 salinity total alkalinity ta and isotopic composition 18o of seawater were used together as tracers of freshwater input i e meteoric water and sea ice meltwater we used an optimum multiparameter analysis to identify the different water masses including the mackenzie river sea ice melt sim winter polar mixed layer pml upper halocline water uhw with core salinity of 33 1 psu pacific origin and atlantic water computed values of co2 fugacity in seawater fco2 sw show that the surface mixed layer sml remains mostly undersaturated 328 55 atm n 552 with respect to the average atmospheric co2 concentration 380 5 atm over the study period the influence of the mackenzie river fco2 sw 500 atm was relatively small in the southeastern beaufort sea and significant fractions were only observed on the inner mackenzie shelf the contribution of sea ice melt fco2 sw 600 atm was usually located between 120 and 180 m depth but could contribute to the sml during wind driven upwelling events in summer and autumn and during brine driven eddies in winter

dynamic processes controlling evolution of rifted basins abstract the extension of the lithosphere controlling the development of rifted basins is driven by a combination of plate boundary forces frictional forces exerted on the base of the lithosphere by the convecting asthenosphere and deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system although mantle plumes are not a primary driving force of rifting they play an important secondary role by weakening the lithosphere and by controlling the level of rift related volcanic activity a distinction between active and passive rifting is only conditionally justified the extension of the lithosphere depending on its rate and magnitude and the potential temperature of the asthenosphere can cause by adiabatic decompression partial melting of the lower lithosphere and upper asthenosphere in rift systems the level and timing of volcanic activity is highly variable the lack of volcanic activity implies passive rifting an initial passive rifting stage can be followed by a more active one during which magmatism plays an increasingly important role magmatic destabilization of the moho may account for the frequently observed discrepancy between upper and lower crustal extension factors combined with evidence for thermal thinning of the mantle lithosphere this suggest that the volume of the lithosphere is not necessarily preserved during rifting as advocated by conventional stretching models the structural style of rifts is controlled by the rheological structure of the lithosphere the availability of crustal discontinuities that can be tensionally reactivated the mode orthogonal or oblique and amount of extension and the lithological composition of pre and syn rift sediments simple shear extension prevails in rifts that subparallel the structural grain of the basement pure shear extension is typical for rifts cross cutting the basement grain pre existing crustal and mantle lithospheric discontinuities contribute to the localization of rift systems the duration of the rifting stage of extensional basins is highly variable stress field changes can cause abrupt termination of rifting in major rift systems progressive strain concentration on the zone of future crustal separation entails abandonment of lateral rifts depending on constraints on lateral block movements crustal separation can be achieved after as little as 9 my and as much as 280 my of rifting activity syn rift basin subsidence is controlled by isostatic adjustment of the crust to mechanical stretching of the lithosphere its magmatic inflation and thermal attenuation of the mantle lithosphere post rift basin subsidence is governed by thermal reequilibration of the lithosphere asthenosphere system deep seated thermal anomalies related to syn rift pull up of the asthenosphere lithosphere boundary have decayed after 60 my by about 65 and after 180 my by about 95 the magnitude of post rift subsidence is a function of the rift induced thermal anomaly and crustal density changes the potential temperature of the asthenosphere and initial water depths intraplate stresses can have an overprinting effect on post rift subsidence stretching factors derived from post rift subsidence analyses must be corrected for such effects

diffusive vertical heat flux in the canada basin of the arctic ocean inferred from moored instruments 1 observational studies have shown that an unprecedented warm anomaly has recently affected the temperature of the atlantic water aw layer lying at intermediate depth in the arctic ocean using observations from four profiling moorings deployed in the interior of the canada basin between 2003 and 2011 the upward diffusive vertical heat flux from this layer is quantified vertical diffusivity is first estimated from a fine scale parameterization method based on ctd and velocity profiles resulting diffusive vertical heat fluxes from the aw are in the range 0 1 0 2 w m 2 on average although large over the period considered the variations of the aw temperature maximum yields small variations for the temperature gradient and thus the vertical diffusive heat flux in most areas variations in upward diffusive vertical heat flux from the aw have only a limited effect on temperature variations of the overlying layer however the presence of eddies might be an effective mechanism to enhance vertical heat transfer although the small number of eddies sampled by the moorings suggest that this mechanism remains limited and intermittent in space and time finally our results suggest that computing diffusive vertical heat flux with a constant vertical diffusivity of 2 10 6 m2 s 1 provides a reasonable estimate of the upward diffusive heat transfer from the aw layer although this approximation breaks down in the presence of eddies

sedimentology and sequence stratigraphy of a transfer zone coarse grained delta miocene suez rift egypt this study focuses on miocene sedimentation and stratigraphic evolution in a major transfer zone at the northern tip of the thal fault segment gulf of suez the succession generally shoals upwards from offshore mudstone containing pro delta turbidites into conglomeratic delta foresets and topsets with sandstone dominated shoreface facies coexisting laterally despite this upward shoaling key stratal surfaces marking abrupt changes in relative sea level allow the succession to be divided into four stratal units the stacking pattern of the stratal units suggests an initial relative sea level rise that generated a major marine flooding surface a relative sea level fall followed resulting in widespread exposure and incision during the ensuing relative sea level rise a lowstand coarse grained delta and coeval shoreface succession prograded several kilometres basinward the stratigraphic development of the transfer zone delta is in marked contrast to that of aggradationally stacked deltas that occur near the centre of the baba sidri fault segment further south at the transfer zone low rates of subsidence and accommodation development coupled with a high sediment supply derived from a large fault tip drainage catchment have produced a strongly progradational delta subject to marked changes in relative sea level in the fault centre location however higher rates of accommodation development coupled with lower rates of sediment supply from footwall catchments have produced aggradationally stacked deltas the results from this study have implications for sequence stratigraphic models and hydrocarbon exploration within extensional basins

temporal variability of diapycnal mixing in shag rocks passage diapycnal mixing rates in the oceans have been shown to have a great deal of spatial variability but the temporal variability has been little studied here results are presented from a method developed to calculate diapycnal diffusivity from moored acoustic doppler current profiler adcp velocity shear profiles an 18 month time series of diffusivity is presented from data taken by a longranger adcp moored at 2400 m depth 600 m above the seafloor in shag rocks passage a deep passage in the north scotia ridge southern ocean the polar front is constrained to pass through this passage and the strong currents and complex topography are expected to result in enhanced mixing the spatial distribution of diffusivity in shag rocks passage deduced from lowered adcp shear is consistent with published values for similar regions with diffusivity possibly as large as 90 3 10 24 m 2 s 21 near the seafloor decreasing to the expected background level of 0 1 3 10 24 m 2 s 21 in areas away from topography the moored adcp profiles spanned a depth range of 2400 1800 m thus the moored time series was obtained from a region of moderately enhanced diffusivity the diffusivity time series has a median of 3 3 3 10 24 m 2 s 21 and a range from 0 5 3 10 24 to 57 3 10 24 m 2 s 21 there is no significant signal at annual or semiannual periods but there is evidence of signals at periods of approximately 14 days likely due to the spring neap tidal cycle and at periods of 3 8 and 2 6 days most likely due to topographically trappedwaves propagating around the local seamount using the observed stratification and an axisymmetric seamount of similar dimensions to the one west of the mooring in a model of baroclinic topographically trapped waves produces periods of 3 8 and 2 6 days in agreement with the signals observed the diffusivity is anticorrelated with the rotary coefficient indicating that stronger mixing occurs during times of upward energy propagation which suggests that mixing occurs due to the breaking of internal waves generated at topography

late neogene stratigraphy and tectonic control on facies evolution in the laguna salada basin northern baja california mexico abstract the laguna salada basin lsb in northeastern baja california records late neogene marine incursions in the salton trough and progradation of the colorado river delta early subsidence and subsequent tectonic erosion are related to evolution of the sierra el mayor detachment fault during late miocene time