residual mean solutions for the antarctic circumpolar current and its associated overturning circulation abstract residual mean theory is applied to the streamwise averaged antarctic circumpolar current to arrive at a concise description of the processes that set up its stratification and meridional overturning circulation on an f plane simple solutions are found in which transfer by geostrophic eddies colludes with applied winds and buoyancy fluxes to determine the depth and stratification of the thermocline and the pattern of associated residual meridional overturning circulation

rationalizing the spatial distribution of mesoscale eddy diffusivity in terms of mixing length theory observations and theory suggest that lateral mixing by mesoscale ocean eddies only reaches its maximum potential at steering levels surfaces at which the propagation speed of eddies approaches that of the mean flow away from steering levels mixing is strongly suppressed because the mixing length is smaller than the eddy scale thus reducing the mixing rates the suppression is particularly pronounced in strong currents where mesoscale eddies are most energetic here a framework for parameterizing eddy mixing is explored that attempts to capture this suppression an expression of the surface eddy diffusivity proposed by ferrari and nikurashin is evaluated using observations of eddy kinetic energy eddy scale and eddy propagation speed the resulting global maps of eddy diffusivity have a broad correspondence with recent estimates of diffusivity based on the rate at which tracer contours are stretched by altimetric derived surface currents finally the expression for the eddy diffusivity is extrapolated in the vertical to infer the eddy induced meridional heat transport and the overturning streamfunction

mapping and facies analysis of paleocene mid eocene seismic sequences offshore southern west greenland abstract new interpretations are reported of the sedimentology and sequence stratigraphy of the palaeogene sediments encountered by the boreholes hellefisk 1 ikermiut 1 kang miut 1 nukik 1 and nukik 2 offshore southern west greenland these interpretations together with new biostratigraphic and palaeoenvironmental interpretations have been used to correlate the boreholes and to calibrate seismic sequences interpreted on a grid of reflection seismic data the interpreted seismic sequences lie between major regional unconformities of danian and mid eocene age the new interpretations show that the area offshore southern west greenland was subject to major uplift and erosion during the danian when latest cretaceous sediments were removed sedimentation restarted in the late danian coevally with major volcanism in central west greenland and the start of sea floor spreading in the labrador sea late paleocene sediments were deposited in a predominantly extensional tectonic environment the extensional stresses continued in most areas during the early eocene but in the northern and northwestern part of the basins a transtensional system developed along the strike slip faults that transferred sea floor spreading movements between the labrador sea and baffin bay sediment input to the basins was predominantly from the north possibly from a major river system flowing out of central greenland lesser amounts of sediment came from the east from the mainland of greenland and minor amounts from the west the thickness of total sediment decreases substantially from north to south the sediments were deposited in environments that ranged from fresh water marginal marine to upper bathyal proximal environments are probably generally sand prone but distal environments probably contain larger amounts of mud some of which could contain a mature source rock for oil basin floor fans syn tectonic wedges and turbidite channel complexes that could act as hydrocarbon reservoirs sealed by surrounding muds have been identified in many of the seismic sequences

isopycnal eddy diffusivities and critical layers in the kuroshio extension from an eddying ocean model abstracthigh spatial resolution isopycnal diffusivities are estimated in the kuroshio extension ke region 28 40 n 120 190 e from a global parallel ocean program pop simulation the numerical float tracks are binned using a clustering approach the number of tracks in each bin is thus roughly the same leading to diffusivity estimates that converge better than those in bins defined by a regular geographic grid cross stream diffusivities are elevated in the southern recirculation gyre region near topographic obstacles and downstream in the ke jet where the flow has weakened along stream diffusivities which are much larger than cross stream diffusivities correlate well with the magnitudes of eddy velocity the ke jet suppresses cross stream mixing only in some longitude ranges this study estimates the critical layer depth both from linear local baroclinic instability analysis and from eddy phase speeds in the pop model using the radon transform the latter is a better predictor of large mixi

palaeogene nannofossil biostratigraphy of the kangâmiut 1 and nukik 2 wells offshore west greenland a new palaeogene nannofossil study has been made of the kang miut 1 and nukik 2 wells offshore west greenland the stratigraphy presented herein has been correlated with previously established nannofossil zonation schemes and where possible used to indicate palaeoenvironmental changes during the early and middle eocene the stratigraphy and dating is based upon stratigraphically important species and palaeoenvironmental signals are based upon species influxes a total of 69 samples 26 side wall cores and 43 ditch cuttings samples were examined and where possible were compared with findings from dsdp and odp sites in the labrador sea

the dependence of southern ocean meridional overturning on wind stress an eddy resolving numerical model of a zonal flow meant to resemble the antarctic circumpolar current is described andanalyzedusing the framework of j marshallandt radko in additionto windand buoyancy forcing at the surface the model contains a sponge layer at the northern boundary that permits a residual meridional overturning circulation moc to exist at depth the strength of the residual moc is diagnosed for different strengths of surface wind stress it is found that the eddy circulation largely compensates for the changes in ekman circulation the extent of the compensation and thus the sensitivity of the moc to the winds depend on the surface boundary condition a fixed heat flux surface boundary severely limits the ability of the moc to change an interactive heat flux leads to greater sensitivity to explain the moc sensitivity to the wind strength under the interactive heat flux transformed eulerian mean theory is applied in which the eddy diffusivity plays a central role in determining the eddy response a scaling theory for the eddy diffusivity based on the mechanical energy balance is developed and tested the average magnitude of the diffusivity is found to be proportional to the square root of the wind stress the moc sensitivity to the winds based on this scaling is compared with the true sensitivity diagnosed from the experiments

eddy transport and mixing in a wind and buoyancy driven jet on the sphere abstract the baroclinically unstable wind and buoyancy driven flow in a zonally reentrant pie shaped sector on a sphere is numerically modeled and then analyzed using the transformed eulerian mean tem formalism mean fields are obtained by zonal and time averaging performed at fixed height the very large latitudinal extent of the basin 50 7 s latitude to the equator allows the latitude variation of the coriolis parameter to strongly influence the flow persistent zonal jets are observed in the statistically steady state reynolds stress terms play an important role in redistributing zonal angular momentum convergence of the lateral momentum flux gives rise to a strong eastward jet with an adjacent westward jet equatorward and weaker multiple jets poleward an equally prominent feature of the flow is a strong and persistent eddy that has the structure of a kelvin cat s eye and generally occupies the zonal width of the basin at latitudes 15 10 s a strongly mixed surface diabatic zone overlies the

enhancement of mesoscale eddy stirring at steering levels in the southern ocean abstract meridional cross sections of effective diffusivity in the southern ocean are presented and discussed the effective diffusivity keff characterizes the rate at which mesoscale eddies stir properties on interior isopycnal surfaces and laterally at the sea surface the distributions are obtained by monitoring the rate at which eddies stir an idealized tracer whose initial distribution varies monotonically across the antarctic circumpolar current acc in the absence of observed maps of eddying currents in the interior ocean the advecting velocity field is taken from an eddy permitting state estimate of the southern ocean sose a three dimensional advection diffusion equation is solved and the diffusivity diagnosed by applying the nakamura technique on both horizontal and isopycnal surfaces the resulting meridional sections of keff reveal intensified isopycnal eddy stirring reaching values of 2000 m2 s 1 in a layer deep beneath the acc but rising toward the surface on the equatorward flank

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

annular modes in a multiple migrating zonal jet regime the authors investigate the dynamics of zonal jets in a semihemisphere zonally reentrant ocean model the forcings imposed in the model are an idealized atmospheric wind stress and relaxation to a latitudinal temperature profile held constant in time while there are striking similarities to the observed atmospheric annular modes where the leading mode of variability is associated with the primary zonal jet s meridional undulation secondary weaker jets emerge and systematically migrate equatorward the model output suggests the following mechanism for the equatorward migration while the eddy momentum fluxes sustain the jets the eddy heat fluxes have a poleward bias causing an anomalous residual circulation with poleward equatorward flow on the poleward equatorward flanks by conservation of mass there must be a rising residual flow at the jet from the thermodynamics equation the greatest cooling occurs at the jet core thus creating a tendency to reduce the baroclinicity on the poleward flank while enhancing it on the equatorward flank consequently the baroclinic zone shifts perpetuating the jet migration

enhancement in vertical fluxes at a front by mesoscale submesoscale coupling oceanic frontal instabilities are of importance for the vertical exchange of properties in the ocean submesoscale o 1 rossby number dynamics are particularly relevant for inducing the vertical and lateral flux of buoyancy and tracers in the mixed layer but how these couple with the stratified pycnocline is less clear observations show surface fronts often persist beneath the mixed layer here we use idealized three dimensional model simulations to show how surface fronts that extend deeper into the pycnocline invoke enhanced vertical fluxes through the coupling of submesoscale and mesoscale instabilities we contrast simulations in which the front is restricted to the mixed layer with those in which it extends deeper for the deeper fronts we examine the effect of density stratification on the vertical coupling our results show deep fronts can dynamically couple the mixed layer and pycnocline on time scales that increase with the peak stratification beneath the mixed layer eddies in the interior generate skew fluxes of buoyancy and tracer oriented along isopycnals thus providing an adiabatic pathway for the interior to interact with the mixed layer at fronts the vertical enhancement of tracer fluxes through the mesoscale submesoscale coupling described here is thus relevant to the vertical supply of nutrients for phytoplankton in the ocean a further implication for wind forced fronts is that the vertical structure of the stream function characterizing the exchange between the interior and the mixed layer exhibits significant qualitative differences compared to a linear combination of existing parameterizations of submesoscale eddies in the mixed layer and mesoscale eddies in the interior the discrepancies are most severe within the mixed layer suggesting a potential role for ekman layer dynamics absent in existing submesoscale parameterizations

transformed eulerian mean theory part ii potential vorticity homogenization and the equilibrium of a wind and buoyancy driven zonal flow the equilibrium of a modeled wind and buoyancy driven baroclinically unstable flow is analyzed using the transformed eulerian mean tem approach described in part i within the near adiabatic interior of the flow ertel potential vorticity is homogenized along mean isopycnals a finding readily explained using tem theory given the geometry of the domain the equilibrium zonal mean buoyancy structure at the surface is determined entirely by a balance between imposed surface fluxes and residual mean and eddy buoyancy transport within a surface diabatic layer balance between these same processes and the wind stress determines the stratification and hence potential vorticity immediately below this layer ertel potential vorticity homogenization below then determines the mean buoyancy structure everywhere accordingly the equilibrium structure of this flow can be described and quantitatively reproduced from knowledge of the eddy mixing rates within the surface diabatic zone and the depth of this zone together with potential vorticity homogenization beneath these results emphasize the need to include near surface buoyancy transport as well as interior pv transport in eddy parameterization schemes they also imply that in more realistic models the surface buoyancy balances may be impacted by processes in remote locations that allow diapycnal flow

microfossil biostratigraphy of the palaeogene succession in the davis strait offshore west greenland abstract a new microfossil based biostratigraphy of the paleocene and lower eocene sediments of the hellefisk 1 ikermiut 1 kang miut 1 nukik 1 and nukik 2 boreholes offshore west greenland has been established in general the five boreholes contain fairly well preserved diverse microfossil faunas and floras consisting mainly of foraminifera radiolaria ostracods and diatoms the studied interval was subdivided into three foraminiferid biostratigraphic intervals in ascending stratigraphic order the stensioeina beccariiformis praeglobobulimina ovata and pseudohastigerina wilcoxensis intervals and five biostratigraphic intervals based on additional microfossil groups the thalassiosiropsis wittiana fenestrella antiqua coscinodiscus morsianus ostracod aulacodiscus hirtus and cenodiscus cenosphaera intervals the intervals are more easily recognised in the two basinal boreholes ikermiut 1 and kang miut 1 than in the three more nearshore boreholes nukik 1 nukik 2 and hellefisk 1 due to a higher microfossil diversity and abundance

an avo study of a possible new hydrocarbon play offshore central west greenland since 1992 extensive oil seeps have been discovered in cretaceous sediment and paleogene basalt onshore central west greenland offshore the basalts are buried under younger sediments interpretation of seismic data offshore has shown the presence of a closed structure at top basalt level within the sediments above the closed structure can be seen bright reflections that have strong avo amplitude variation with offset anomalies these features may indicate the presence of hydrocarbons that have migrated through the basalts from deeper source rocks and been trapped in the sediments above the basalts

near surface eddy heat and momentum fluxes in the antarctic circumpolar current in drake passage abstractthe authors present new estimates of the eddy momentum and heat fluxes from repeated high resolution upper ocean velocity and temperature observations in drake passage and interpret their role in the regional antarctic circumpolar current acc momentum balance the observations span 7 yr and are compared to eddy fluxes estimated from a 3 yr set of output archived from an eddy resolving global parallel ocean program pop numerical simulation in both pop and the observations the stream averaged cross stream eddy momentum fluxes correspond to forcing consistent with both a potential vorticity flux into the axis of the subantarctic front saf and a sharpening of all three main acc fronts through drake passage further the pop analysis indicates that the mean momentum advection terms reflect the steering of the mean acc fronts and are not fully balanced by the eddy momentum forcing which instead impacts the strength and number of acc fronts the comparison between pop and observed eddy heat fluxe

estimates and implications of surface eddy diffusivity in the southern ocean derived from tracer transport abstract near surface effective diffusivities associated with geostrophic eddies in the southern ocean are estimated by numerically monitoring the lengthening of idealized tracer contours as they are strained by surface geostrophic flow observed by satellite altimetry the resulting surface diffusivities show considerable spatial variability and are large 2000 m2 s 1 on the equatorward flank of the antarctic circumpolar current and are small 500 m2 s 1 at the jet axis regions of high and low effective diffusivity are shown to be collocated with regions of respectively weak and strong isentropic potential vorticity gradients the maps of diffusivity are used along with climatological estimates of surface wind stress and air sea buoyancy flux to estimate surface meridional residual flows and the relative importance of eulerian and eddy induced circulation in the streamwise averaged dynamics of the antarctic circumpolar current

a model of the upper branch of the meridional overturning of the southern ocean a zonal average model of the upper branch of the meridional overturning circulation of the southern ocean is constructed and used to discuss the processes wind buoyancy eddy forcing and boundary conditions that control its strength and sense of circulation the geometry of the thermocline wedge set by the mapping between the vertical spacing of buoyancy surfaces the stratification on the equatorial flank of the antarctic circumpolar current and their outcrop at the sea surface is seen to play a central role by setting the interior large scale potential vorticity distribution it is shown that the action of eddies mixing this potential vorticity field induces a residual flow in the meridional plane much as is observed with upwelling of fluid around antarctica northward surface flow and subduction to form intermediate water

eddy induced diapycnal fluxes and their role in the maintenance of the thermocline abstract high resolution numerical experiments are diagnosed to study the integral effects of geostrophic eddy fluxes on the large scale ocean circulation three characteristic large scale flows are considered 1 an anticyclonic single gyre 2 a double gyre and 3 an unblocked zonal flow a simple analog of the antarctic circumpolar current it is found that buoyancy and potential vorticity budgets in the presence of eddies are dominated by a balance between vertical advection into the control volume by ekman pumping and eddy transfer across the density surfaces achieved by diapycnal eddy fluxes with small scale mixing making only a minor contribution possible oceanographic implications of the results are discussed

rapid changes in mixed layer stratification driven by submesoscale instabilities and winds 1 submesoscale eddies generated by baroclinic instability of upper ocean fronts lead to rapid restratification of the mixed layer on a time scale of days this restratification can be opposed by a down front wind stress acting in the direction of the geostrophic velocity that drives a surface ekman flow from the dense side to the light side of the front to arrest the slumping of isopycnals a scaling diagnostic is suggested to determine whether the effect of eddies or wind dominates under different conditions using a numerical model we investigate the juxtaposition of submesoscale eddies and down front winds acting on the mixed layer by estimating the eddy induced overturning stream function in the mixed layer we separate the along and cross isopycnal fluxes of buoyancy associated with submesoscale mixed layer eddies and demonstrate the need for parameterization of the advective along isopycnal flux though the cross front transport of buoyancy induced by the down front component of the wind opposes restratification by mixed layer eddies it becomes diminished as the eddies and growth of the frontal instability disrupt alignment between the wind and frontal axis

a mid cretaceous prograding sedimentary complex in the sisimiut basin offshore west greenland stratigraphy and hydrocarbon potential a prograding and aggrading depositional system has been mapped from seismic data in the sisimiut basin offshore west greenland seismic stratigraphic analysis resulted in mapping of three seismic sequences and internal boundaries mounds at the base of the prograding sequences may represent massflows which could be prospective the sealing deposits are cretaceous claystone indicated by correlation to the ikermiut 1 well local closures of mounds regional seal and hydrocarbon traces in the region indicate a potential for stratigraphic hydrocarbon leads amplitude interpretation indicates possible mass flow deposits within the sequences as well as half graben syn rift deposits below both of which may be prospective

late quaternary marginal marine palaeoenvironments of northern australia as inferred from cluster analysis of coccolith assemblages abstract cluster analyses r and q mode were applied to upper quaternary coccolith assemblages in a sediment core md972132 collected in the gulf of carpentaria northern australia this shallow gulf is influenced by the australian monsoon is tectonally stable and represents an important link between marine and terrestrial palaeoenvironments the gulf of carpentaria is linked to the pacific ocean to the east by torres strait 12 m water depth and to the indian ocean to the west by the arafura sill 53 m water depth and therefore has been separated from both oceans during sea level low stands resulting in the formation of lake carpentaria coccolith assemblages in the gulf are similar to modern assemblages in the region and correspond to typical assemblages in marginal seas the cluster analysis defines six species assemblages r mode and six groups of samples i e defined by depth in core depth q mode some with sub groups which were deposited under similar environmental conditions we thus recognised four major environmental facies over the past 125 ka corresponding to closed lake carpentaria stages the transitional periods while active channels sporadically connected lake carpentaria to the indian ocean and the opening of the gulf of carpentaria to the ocean over either one or both of the sills lake carpentaria was isolated from both oceans through marine isotope stages mis 5d mis 4 and mis 2 and the gulf of carpentaria was connected to both oceans during mis 5c and mis 1 torres strait was emergent during mis 5b was flooded again during mis 5a and persisted as land bridge from mis 4 to mis 1 the arafura sill was opened from mis 5c to mis 5a and episodically connected the gulf to the indian ocean during mis 3

isopycnal diffusivities in the antarctic circumpolar current inferred from lagrangian floats in an eddying model average 750 250 m 2 s 1 around the polar frontal zone the results imply that parameterizations that only use eddy kinetic energy to parameterize the diffusivities are incomplete we suggest that dominant correlations of lagrangian eddy diffusivities with eddy kinetic energy found in previous studies may have been due to the use of too short time lags in the integration of the velocity autocovariance used to infer the diffusivities we find evidence that strong mean flow inhibits cross stream mixing within the acc but there are also areas where cross stream diffusivities are large in spite of strong mean flows for example in regions close to topographic obstacles such as the kerguelen plateau

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

a seasonal climatology of effective diffusivity in the stratosphere a 7 year 1992 1998 seasonal climatology of effective horizontal diffusivity is presented for the stratosphere 350 1900 k as in previous studies the diagnosis is based on the equivalent length of a test tracer advected on isentropic surfaces in this case using the van leer flux limiting scheme driven by the united kingdom meteorological office assimilated winds although the magnitude of equivalent length is resolution dependent its structure is shown to be reasonably robust for quantifying the inhomogeneous mixing in the stratosphere the van leer calculation agrees well with a more expensive spectral transform calculation at a comparable resolution suggesting that the diagnostic is not sensitive to the advection scheme or subgrid representation of the models a first attempt is also made at estimating the implicit numerical diffusion of the van leer scheme which is necessary to convert equivalent length to effective diffusivity compared with the spectral calculations with a constant diffusion coefficient the van leer results show notably greater diffusivity within the winter polar vortices despite the comparable equivalent lengths suggesting that the scheme may be overdiffusing in the vicinities of mobile tracer extrema the climatology of equivalent length is then presented and the seasonal evolution is discussed in detail for the lower middle and upper stratosphere the major mixing barriers winter and summer polar vortices and tropical eddy transport barrier are easily identified as well as the strong mixing regions surf zones generally equivalent length tends to be small in regions of strong zonal wind and large in regions of weak wind large values of equivalent length are observed in the summer lower stratosphere and in the middle stratosphere during the breakup of the polar vortices interhemispheric asymmetry is observed both after the winter polar vortex breakup where in the middle stratosphere the southern hemisphere shows much larger equivalent lengths and in the summer tropical region where larger equivalent lengths are observed in the northern hemisphere likely related to the monsoon circulation a monthly averaged equivalent length climatology is presented and implications for two dimensional stratospheric chemistry transport modeling are discussed

mesoscale eddy buoyancy flux and eddy induced circulation in eastern boundary currents abstracta dynamical interpretation is made of the mesoscale eddy buoyancy fluxes in the eastern boundary currents off california and peru chile based on regional equilibrium simulations the eddy fluxes are primarily shoreward and upward across a swath several hundred kilometers wide in the upper ocean as such they serve to balance mean offshore air sea heating and coastal upwelling in the stratified interior the eddy fluxes are consistent with the adiabatic hypothesis associated with a mean eddy induced velocity advecting mean buoyancy and tracers furthermore with a suitable gauge choice the horizontal fluxes are almost entirely aligned with the mean horizontal buoyancy gradient consistent with the advective parameterization scheme of gent and mcwilliams the associated diffusivity is surface intensified matching the vertical stratification profile the fluxes span the across shore band of high eddy energy but their alongshore structure is unresolved because of sampling limitations in the sur

the surface branch of the zonally averaged mass transport circulation in the troposphere the near surface branch of the overturning mass transport circulation in the troposphere containing the equatorward flow is examined in isentropic and geometric coordinates a discussion of the zonal momentum balance within isentropic layers shows that the equatorward flow at a given latitude is confined to isentropic layers that typically intersect the surface at that latitude as a consequence of mass transport within the surface mixed layer much of the equatorward flow occurs in layers with potential temperatures below the mean surface potential temperature in the conventional transformed eulerian mean formulation for geometric coordinates the surface branch of the overturning circulation is represented in an unrealistic manner streamlines of the residual circulation do not close above the surface a modified residual circulation is introduced that is free from this defect and has the additional advantage that its computation unlike that of the conventional residual circulation does not require division by the static stability which may approach zero in the planetary boundary layer it is then argued that cold air advection by the residual circulation is responsible for the formation of surface inversions at all latitudes in idealized gcms with weak thermal damping also included is a discussion of how a general circulation theory for the troposphere must be built upon a theory for the near surface meridional mass fluxes

dinoflagellate cyst stratigraphy of the palaeogene strata from the hellefisk 1 ikermiut 1 kangâmiut 1 nukik 1 nukik 2 and qulleq 1 wells offshore west greenland abstract a new palaeogene dinoflagellate cyst stratigraphy from offshore west greenland has been described based on the strata from the hellefisk 1 ikermiut 1 kang miut 1 nukik 1 nukik 2 and qulleq 1 wells twenty one palynological intervals are defined from the late eocene to the late early paleocene this stratigraphy has been correlated with a new microfossil zonation and previous established north sea zonations the stratigraphy and well correlation are based on last appearance datum events and abundances of stratigraphically important species from 355 samples 148 of which are sidewall core samples a major middle eocene hiatus spanning the early lutetian and a major early paleocene hiatus spanning the late santonian late cretaceous to the early danian have been recognised from the offshore deposits

eddy mixing of potential vorticity versus thickness in an isopycnic ocean model abstract parameterizations of the eddy induced velocity that advects tracers in addition to the eulerian mean flow are traditionally expressed as a downgradient fickian diffusion of either isopycnal layer thickness or large scale potential vorticity pv there is an ongoing debate on which of the two closures is better and how the spatial dependence of the eddy diffusivity should look like to increase the physical reasoning on which these closures are based the authors present a systematic assessment of eddy fluxes of thickness and pv and their relation to mean flow gradients in an isopycnic eddy resolving model of an idealized double gyre circulation in a flat bottom closed basin the simulated flow features strong nonlinearities such as tight inertial recirculations a meandering midlatitude jet pools of homogenized pv and regions of weak flow where h dominates the pv gradient it is found that the zonally averaged eddy flux of thickness scales better with the zonally averaged meridional thickn

parameterization of mixed layer and deep ocean mesoscales including nonlinearity abstractin 2011 chelton et al carried out a comprehensive census of mesoscales using altimetry data and reached the following conclusions essentially all of the observed mesoscale features are nonlinear and mesoscales do not move with the mean velocity but with their own drift velocity which is the most germane of all the nonlinear metrics accounting for these results in a mesoscale parameterization presents conceptual and practical challenges since linear analysis is no longer usable and one needs a model of nonlinearity a mesoscale parameterization is presented that has the following features 1 it is based on the solutions of the nonlinear mesoscale dynamical equations 2 it describes arbitrary tracers 3 it includes adiabatic a and diabatic d regimes 4 the eddy induced velocity is the sum of a gent and mcwilliams gm term plus a new term representing the difference between drift and mean velocities 5 the new term lowers the transfer of mean potential energy to mesoscales 6 th

development of the continental margins of the labrador sea a review abstract the labrador sea is a small oceanic basin that developed when the north american and greenland plates separated an initial period of stretching in early cretaceous time formed sedimentary basins now preserved under the continental shelves and around the margins of the oceanic crust the basins subsided thermally during late cretaceous time and a second episode of tectonism took place during latest cretaceous and early paleocene time before the onset of sea floor spreading in mid paleocene time around the northern labrador sea davis strait and in southern baffin bay voluminous picrites and basalts were erupted at and shortly after the commencement of sea floor spreading volcanism occurred again in early eocene time at the same time as sea floor spreading commenced in the northern north atlantic farther southeast along the labrador and southern west greenland margins oceanic crust is separated from continental crust by highly stretched but non magmatic transition zones which developed before sea floor spreading a complex transform zone which developed during sea floor spreading in late paleocene and early eocene time separates continental and oceanic crust along the baffin island margin the greenland and labrador ocean continent transitions are asymmetric across the only available conjugate cross sections however a cross section through the labrador margin farther north resembles the greenland cross section in the conjugate pair more than it does the labrador cross section of this pair consideration of the geological history of the area suggests that the non magmatic transition zones may have formed by slow extension of a few millimetres per year through a period of 53 ma during cretaceous and early paleocene time

the role of eddy transfer in setting the stratification and transport of a circumpolar current abstract high resolution numerical experiments of a circumpolar current are diagnosed to study how lateral and vertical transfer of buoyancy by geostrophic eddies balances advection by a meridional circulation driven by surface wind stresses and buoyancy fluxes a theory is developed in the framework of the residual circulation to relate the vertical and horizontal stratification set up to the transfer properties of eddies and the patterns of imposed wind and buoyancy forcing simple expressions are found for the depth of penetration stratification baroclinic transport and residual circulation of the current finally the ideas are applied to the antarctic circumpolar current acc and yield predictions for how its properties depend on wind and buoyancy forcing