modeling of deep water renewal through cold convective plumes abstract in only a few regions in the world ocean surface water is transformed into deep water by open ocean convection in this paper small areas of vertical flow or plumes are studied using a steady state model integrated in streamline coordinates we use an entrainment hypothesis based on knowledge about in mixing of water across the shear zone from an area of low turbulence into an area of high turbulence this results in a model using conservation equations for momentum heat and salt and a nonlinear equation of state effects of earth rotation are included the depth reached by surface water when moving through stationary plumes is predicted and found strongly dependent on the properties in the surface layer this layer has to be colder but only slightly denser than the water just below it to be a source for steady state plumes the thermobaric effect the dependency of compressibility on the temperature plays a major role for the plume penetration depth in weakly stratified cold water like in the greenland sea deep convection is found to be possible and efficient through steady state plumes initial excess density of less than 5 10 3 kg m 3 caused by low temperature can give convection deeper than 1500 m through plumes with horizontal scales of a few hundred meters and vertical velocities of order a few tens of centimeters per second

chlorine cycling during subduction of altered oceanic crust eclogitic rocks that have experienced devolatilization with little or no interaction with external fluid sources can be viewed as analogues of crustal material which may be transferred back into the mantle during subduction thus they can be used to evaluate the extent of the recycling of volatile elements such as chlorine we report new oxygen isotope ratios of omphacite and fluid inclusion data determined from eclogitic metagabbros of the rocciavre massif italian alps the data are compared with those obtained for the monviso cyclades and the franciscan complex high pressure rocks in all localities relics of early dehydration fluids are preserved as primary fluid inclusions in the cores of omphacite megacrysts rocciavre monviso and franciscan complex or garnet cyclades salinity estimates of the inclusion fluids range from 32 to 45 wt nacl in rocciavre 17 to 21 wt nacl in monviso and are similar to seawater in other areas omphacite and bulk rock 18o values of rocciavre 5 1 6 8 and monviso 3 0 5 3 metagabbros are markedly lower than those of cyclades 6 8 14 3 and the franciscan 6 7 13 1 metabasites the fluid salinity 18o systematics of eclogitic rocks is similar to that documented along a typical section of the altered oceanic crust and unmetamorphosed ophiolites this suggests that high pressure metamorphism and associated processes did not modify significantly the variability in chlorine concentrations and oxygen isotope ratios inherited from a stage of sea floor hydrothermal alteration under low basaltic layer and high temperature gabbroic layer conditions respectively extrapolating the estimated h2o and cl contents of eclogitic rocks to a representative section of the subducted oceanic crust indicates that a minimum of 100 to 200 ppm cl could be recycled into the mantle during subduction this yields a cl h2o ratio of 3 6 to 7 5 10 2 for the subducted oceanic crust which is similar to e morb on the basis of available cl isotopic data we infer that a large proportion 70 of the cl stored in the altered crust should be recycled to the mantle to generate an isotopic composition of the subducted crust equivalent to the source of unaltered mid ocean ridge basalt 37cl 4 7

evolution of the large scale temperature field in the greenland sea during 1988 89 from tomographic measurements the greenland sea ocean acoustic tomography experiment was conducted during 1988 89 as one component of the international greenland sea project to study deep water formation and the response of the gyre to variations in wind stress and ice cover six acoustic transceivers moored in an array 200 km across transmitted to one another at four hour intervals near the end of february 1989 a sub surface temperature maximum at several hundred meters depth disappeared over a surprisingly large area of the central greenland sea while the water column was modified to about 1000 m depth over much of the gyre the surface remained colder than the deeper water contrary to what might be expected from simple models of convective renewal

convective modifications of a geostrophic eddy field ocean convection often occurs in regions of mesoscale eddy activity where convective mixing and geostrophic eddy dynamics interact the authors examine the interactions between a group of geostrophic eddies and convective mixing induced by surface buoyancy loss through a series of numerical simulations using a nonhydrostatic boussinesq model the eddies are initially baroclinic with a surface intensified density anomaly and sheared flow but they are stable to baroclinic instability because of their small size in the absence of buoyancy loss eddy mergers occur much as in previous studies of geostrophic turbulence with the addition of surface buoyancy loss the surface stratification is eroded by small scale convection the convective mixing is highly heterogeneous being deeper in regions of weaker initial stratification and shallower in more strongly stratified regions the deformation radius is reduced in mixing regions and the weakly stratified eddies become baroclinically unstable the barotropic component of kinetic energy increases as convection proceeds largely due to the conversion of the available potential energy of the eddies in the baroclinic instability process the convective forcing therefore provides a means of increasing the barotropic component of the eddy kinetic energy by enabling the baroclinic instability the fluid is efficiently homogenized by the energetic eddy field leading to a few isolated eddies separated by a well mixed fluid these simulations provide a possible explanation for energetic eddy fields observed during convective periods in the labrador sea

data driven and hybrid coastal morphological prediction methods for mesoscale forecasting it is now common for coastal planning to anticipate changes anywhere from 70 to 100 years into the future the process models developed and used for scheme design or for large scale oceanography are currently inadequate for this task this has prompted the development of a plethora of alternative methods some such as reduced complexity or hybrid models simplify the governing equations retaining processes that are considered to govern observed morphological behaviour the computational cost of these models is low and they have proven effective in exploring morphodynamic trends and improving our understanding of mesoscale behaviour one drawback is that there is no generally agreed set of principles on which to make the simplifying assumptions and predictions can vary considerably between models an alternative approach is data driven techniques that are based entirely on analysis and extrapolation of observations here we discuss the application of some of the better known and emerging methods in this category to argue that with the increasing availability of observations from coastal monitoring programmes and the development of more sophisticated statistical analysis techniques data driven models provide a valuable addition to the armoury of methods available for mesoscale prediction the continuation of established monitoring programmes is paramount and those that provide contemporaneous records of the driving forces and the shoreline response are the most valuable in this regard in the second part of the paper we discuss some recent research that combining some of the hybrid techniques with data analysis methods in order to synthesise a more consistent means of predicting mesoscale coastal morphological evolution while encouraging in certain applications a universally applicable approach has yet to be found the route to linking different model types is highlighted as a major challenge and requires further research to establish its viability we argue that key elements of a successful solution will need to account for dependencies between driving parameters such as wave height and tide level and be able to predict step changes in the configuration of coastal systems

variability in the greenland sea as revealed by a repeated high spatial resolution conductivity temperature depth survey this paper deals with the mesoscale variability of water masses in the greenland sea and its implications for bottom water formation the results are based on two conductivity temperature depth surveys performed in successive years the same section in the central greenland basin was sampled in 1989 and 1990 an additional transect across fram strait was carried out in 1990 the transects extended from shelf to shelf with a station spacing of 18 km throughout the data set reveals a surprisingly strong horizontal variability of space scales between 20 and 60 km in the entire greenland sea not only in the frontal zones the area investigated is subdivided into four hydrographical regimes for which mesoscale variability is discussed in detail a noteworthy result is the major change of the deep sea thermal structure within 1 year the classical pattern with upward doming cold waters in the central basin was found in 1989 but was replaced by a capped structure with a warm intermediate layer in 1990 the implications of the observed changes are discussed with respect to deep water formation a mechanism based on differential compressibility is proposed which is able to introduce negative heat input selectively into the bottom layer it is shown that the fine structure of temperature profiles observed in summer can be used as a tracer for the occurrence of deep convection during the preceding winter convective depths are concluded of about 2200 m for 1989 and of only about 250 m for 1990

beach memory and ensemble prediction of shoreline evolution near a groyne abstract in this paper we address the question of estimating the average position of a beach and its inherent variability about this mean it is demonstrated how even in a much simplified situation the ensemble average of beach plan shape involves cross correlation of the beach position and wave conditions this renders the governing equations inimical to analytical treatment a new analytical expression for the mean beach plan shape and its variation are derived for the case of a single groyne exposed to waves varying in direction only this demonstrates that beach memory is directly related to the autocorrelation of wave direction for more general conditions a semi analytical expression for the ensemble average of the shoreline position is derived this solution is estimated with site specific wave conditions using monte carlo simulations the characteristics of the solution are investigated and it is demonstrated that for this case at least the terms involving the wave direction are virtually uncorrelated with the terms that do not it is concluded that in an ensemble sense the morphodynamic impact of wave direction is decoupled from that due to wave height and period

a heton model of the spreading phase of open ocean deep convection abstract a point vortex heton model of the lateral dispersion of cold water formed in open ocean deep convection is developed and studied as an idealized representation of the sinking and spreading phase of open ocean deep convection the overturning and geostrophic adjustment of dense fluid on and below the radius of deformation scale formed by cooling on the large scale are parameterized in the model by introducing paired discrete point vortices hetons of cyclonic sense in the surface layer anticyclonic below driving a cold baroclinic vortex the convection site is imagined to be made up of many such baroclinic vortices each with a vertically homogeneous core carrying cold convectively tainted waters the point vortices are introduced at a rate that depends on the large scale cooling and the intensity assumed for each vortex the interaction of many cold baroclinic vortices making up a cloud is studied using point vortex green s function techniques the current solenoids of the individual ele

a note on seasonal cycles of temperature and salinity in the upper waters of the greenland sea gyre from historical data monthly climatologies of temperature and salinity for two regions in the greenland sea are created by combining historical archives of hydrographie stations with observations from recent cruises the first region corresponds to the gyre center where deepwater formation occurs and a large bay forms in the winter ice pack nordbukta and the second region lies directly to the south in the area usually covered by an ice tongue odden in february and march surface temperature responds primarily to local surface heat fluxes consistently warming in the summer to about 4 c and cooling in the fall to the freezing point interannual variability appears to be greater for salinity than for temperature this coupled with the sparse data coverage makes it more difficult to define a seasonal salinity cycle however in july and august surface salinity in both regions appears to decrease drastically with freshening being more pronounced in the southern region in the fall this mixed layer fresh anomaly is removed probably by brine rejection due to the local formation of ice and its subsequent removal by northerly winds eventually ice formation causes the surface waters to overturn and entrain the warmer water below inhibiting further ice formation the fresh anomaly is smaller in the gyre center than in the odden region so that ice formation will end there earlier resulting in the appearance of a bay to the north of an ice tongue since the disappearance of ice is a necessary precursor to mixing deeper than about 100 m this suggests that large areal changes in ice cover may be used as a proxy for identifying the strength and onset of deep convection

the influence of long waves on macrotidal beach morphology the aim of the following paper is to demonstrate that standing long waves can generate intertidal morphological features in a dissipative macrotidal setting in this environment the tidal excursion can exceed the length scales associated with long waves this extends the work of simmonds et al 1995 in which it was shown that monochromatic long waves could generate sediment convergence patterns that bore a good similarity to observed topographic features namely ridges and runnels from a field site on the belgian coast the simulation is modified to include a band of long waves and it is found that a good correspondence with real topography can still be achieved on a tidally averaged basis by allowing for a degree of uncertainty in the breaking criterion it is also argued why the observed scales are more likely to correspond with the shorter end of the long wave spectrum the simulation helps to shed light on the conditions in which such features are known to form

a probability method for predicting time dependent long term shoreline erosion this paper describes a practical procedure for predicting the probability distributions of long term shoreline erosion it treats the dynamical response of the shoreline over time as that of a time dependent stochastic system the input to the system are the long term wave climate and shoreline properties while the output of the system are the probability distributions of the maximum shoreline recession within any prescribed time period the procedure enables the combined effect of the longshore and cross shore sediment transport processes on the shoreline erosion to be taken into account as both processes are generally responsible for the maximum shoreline recession a series of simulations using idealised long term wave distributions which have relatively narrow directional spread was carried out to evaluate the capability of the method based on these simulations it was found that both the distributions and variability of wave climates have significant influence on the predicted shoreline erosion probability distributions while the chronology effect is less significant especially for long simulation time

acoustic scattering losses in the greenland sea marginal ice zone during the 1988 89 tomography experiment using arrival amplitude data from the 1988 89 greenland sea tomography experiment the effects of ice scattering at 250 hz in the marginal ice zone miz are estimated the resolution of the arrivals is examined first showing that arrivals are resolved as rays from about 8 to 13 launch angle and a normal modes for low angles below about 4 launch angle the under ice reflection losses of resolved rays and modes are then considered using two methods first the ratio of arrival amplitudes during ice free and ice covered periods is estimated second the ratio of members of a ray group with different reflection numbers is used showing similar but not identical results to the first method for higher grazing angle reflections fast field calculations using the program safari are observed to model the data reasonably using a combination of measured and historical ice parameter values for the low angle arrivals the amplitudes of the arrivals are observed to depend strongly upon both the details of th

medium term 2dh coastal area modelling the state of the art in depth averaged mathematical modelling of 3 d coastal morphology is described for the medium term morphodynamic model type in which constituent models of waves currents and sediment transport based on first physical principles are linked together to describe the time evolution of the bed topography various aspects of the combined system of equations are discussed such as its mathematical character its inherent stability and its equilibrium state the results of an intercomparison of different models are shown for two test cases and the potentials and limitations of the model concept are discussed

chlorine isotope chemistry of serpentinites from elba italy as an indicator of fluid source and subsequent tectonic history chlorine concentrations and 37cl and d values are reported for serpentinites in different tectonic positions on elba italy serpentinites from high in the nappe sequence contain 0 01 0 1wt cl with 37cl values from 0 9 to 1 4 samples with positive 37cl values occur beneath gabbro and basalt and are interpreted as having been serpentinized by interaction with seawater samples with negative 37cl values are in direct contact with sedimentary rocks these samples were juxtaposed against and or buried by sediments in response to low angle normal faulting on the seafloor and serpentinization probably occurred by subsequent interaction with sedimentary pore fluids most samples from a structurally lower nappe and from areas affected by contact metamorphism lost their original cl during heating low d values for all samples suggest postserpentinization interaction with meteoric water but neither cl nor o isotope ratios were affected by this interaction our results demonstrate that chlorine can be retained in obducted serpentinites up to low greenschist conditions and that the cl isotope composition of such serpentinites preserves a record of seafloor tectonic processes

tomographic maps of the ocean mesoscale part 1 pure acoustics abstract a field test of ocean acoustic tomography was conducted in 1981 for a two month period in a 300 km square at 26 n 70 w in the north atlantic just south of the mode region nine acoustic deep sea moorings with sea floor transponders for automated position keeping and with provisions for precise time keeping were set and recovered from the measured travel times between moorings various displays of the three dimensional field of sound speed closely related to temperature have been obtained by inversion procedures these procedures use historical ocean data as a reference but all information from the in situ surveys has been withheld the pure tomographic results were then compared to direct in situ observations the tomographically derived spatial mean profile compares favorably to an equivalent profile from the in situ observations both differ significantly from the historical average maps constructed at three day intervals for a two month period show a pattern of eddy structure in agre

chlorine stable isotope composition of the oceanic crust implications for earth s distribution of chlorine abstract this first investigation of the cl stable isotope composition of seafloor rocks reveals systematic variations in 37 cl 35 cl of the oceanic crust and its mantle source s relative to seawater chlorine isotopic measurements expressed as 37 cl relative to the seawater 37 cl 35 cl ratio of fresh morb glass hydrothermally produced amphibole containing whole rocks and smectite veins are presented all the samples analyzed are isotopically enriched 0 2 7 5 relative to seawater 0 uptake of cl into amphibole during axial hydrothermal alteration fractionates cl relative to seawater the isotopic compositions of morb glasses are between 0 2 and 7 2 this range appears to be partially due to the assimilation of cl from hydrothermally altered wallrock into morb magmas samples which are unaffected by assimilation have 37 cl between 3 and 7 2 overall the data imply that cl is isotopically fractionated between the surface and mantle reservoirs of earth calculations based on the degree of fractionation suggest that approximately 40 of the cl originally in the degassed mantle now resides on earth s surface

chloride depletions and enrichments in seafloor hydrothermal fluids constraints from experimental basalt alteration studies na k ca cl fluid was reacted with diabase at 400 and 425 c 400 bars and fluidrock mass ratio of 0 5 to assess the relative mobility of dissolved cl fluids from the present experiments reveal relatively large time and temperature dependent decreases in cl temperature increase enhances cl removal whereas reaction progress has the opposite effect these changes are not due to boiling and or phase separation at 400 and 425 c 400 bars cl removal from solution is accompanied by ca and na fixation respectively both experiments produced mixed layer chlorite smectite clinozoisite and albite olivine was not detected by x ray diffraction or petrographic analysis of run products from either experiment however we propose that the time dependent changes in dissolved cl result from olivine replacement by an fe hydroxy chloride phase followed by hydration effects quenched and washed alteration products however did not reveal anomalous cl which suggests that the cl bearing phase is characterized by retrograde solubility this is consistent with the relative magnitude of cl fixation observed for experiments at both temperatures and from results of an isobaric cooling experiment the experiments provide evidence for the non conservative behavior of cl during hydrothermal alteration of basalt the data are particularly important in light of the cl depleted nature of some ridge crest hot spring fluids and suggest temperatures of formation for these fluids of approximately 410 c assuming sub seafloor pressure of 400 bars in addition the retrograde solubility of the cl bearing phase responsible for cl fixation during high temperature basalt alteration may help to explain cl enrichment in hot spring fluids which have conductively cooled below 350 c

a numerical investigation of the circulation in the greenland and norwegian seas abstract an ocean general circulation model is used to investigate the circulation in the greenland and norwegian seas the primitive equations are solved on 12 levels with a horizontal grid point distance of 20 km this resolution is sufficient to take into account mesoscale topographic structures which according to observations and the model results presented here have a large influence on the distribution of hydrographic variables however the model is not eddy resolving the baroclinic deformation radius in this region is about 5 km only at first a 2 year experiment is run with the forcing functions and the initial stratification derived from climatological annual mean data compared with quasi synoptic data the calculated temperature and salinity distributions show a much better adjustment to the topography than does the climatology the velocities and transports lie within the range of observed long term mean values the model fields obtained by this experiment are used to initialize another e

observations with moored acoustic doppler current profilers in the convection regime in the golfe du lion abstract in the golfe du lion south of france favorable conditions for deep winter convection exist and were documented by the medoc experiments during 1969 75 a renewed investigation of that regime with upward looking moored acoustic doppler current profilers adcps was carried out during 24 january 5 march 1987 to record the three dimensional currents associated with the deep mixing while in the earlier studies initial deep convection did not begin until fairly late in the winter season a very strong mistral around 10 january 1987 had already generated a 1arge deep mixed patch homogeneous down to around 2000 m at deployment time three adcps two working at 150 khz and one at 75 khz were moored in a triangle of 15 km sidelength at 550 780 m depth full records at 1 hour ensemble time intervals 400 pings per ensemble 8 m bin lengths were obtained by the 75 khz and one of the 150 khz adcps in mid february a second mistral hit the region with the onset of strong winds and surface cooling the

chlorine isotopic composition in seafloor serpentinites and high pressure metaperidotites insights into oceanic serpentinization and subduction processes bulk rock chlorine content and isotopic composition 37 cl were determined in oceanic serpentinites high pressure metaperidotites and metasediments in order to gain constraints on the global chlorine cycle associated with hydrothermal alteration and subduction of oceanic lithosphere the distribution of insoluble chlorine in oceanic serpentinites was also investigated by electron microprobe the hydrothermally altered ultramafic samples were dredged along the south west indian ridge and the mid atlantic ridge the high pressure metamorphic samples were collected in the western alps metaperidotites in the erro tobbio unit and metasediments in the schistes lustres nappe oceanic serpentinites show relatively large variations of bulk rock cl contents and 37 cl values with mean values of 1105 596 ppm and 0 7 0 4 o respectively n 8 1 serpentines formed after olivine meshes show lower cl content than those formed after orthopyroxene bastites in bastites of two different samples cl is positively correlated with al 2 o 3 and negatively correlated with sio 2 these relationships are interpreted as reflecting preferential cl incorporation into the bastite structure distorted by al substituted for si rather than different alteration conditions between olivine and orthopyroxene minerals high pressure metaperidotites display relatively homogeneous cl contents and 37 cl values with mean values of 467 88 ppm and 1 4 0 1 respectively n 7 1 a macroscopic high pressure olivine bearing vein formed from partial devolatilization of serpentinites at 2 5 gpa and 500 600 c shows a cl content and a 37 cl value of 603 ppm and 1 6 o respectively metasediments n 2 show low whole rock cl contents 15 ppm cl that did not allow cl isotope analyses to be obtained the range of negative 37 cl values observed in oceanic serpentinites is likely to result from water rock interaction with fluids that have negative 37 cl values the homogeneity of 37 cl values from the high pressure olivine bearing vein and the metaperidotite samples implies that progressive loss of cl inherited from oceanic alteration throughout subduction did not significantly fractionate cl isotopes chlorine recycled in subduction zones via metaperidotites should thus show a range of 37 cl values similar to the range found in oceanic serpentinized peridotites

beach response to a sequence of extreme storms abstract a sequence of daily beach surveys acquired over one month covering an area larger than 100 000 m 2 was analyzed to study morphological changes resulting from a cluster of storms the beach response was highly variable in both the cross and alongshore a cumulative storm effect was not observed despite one storm being characterized by a 10 year return period that had significant wave height h s of 8 1 m and a peak wave period t p of 17 s instead storms that can potentially cause significant erosion in terms of h s had a limited effect on the morphology because the large wave height was coupled to either neap tides normally incident short waves f 0 04 hz or low levels of infragravity 0 004 f

behavior of li and its isotopes during serpentinization of oceanic peridotites analyses of li and li isotopes in serpentinized peridotites have been performed using thermo ionisation mass spectrometry tims and secondary ion mass spectrometry sims techniques on samples collected from the southwest indian ridge swir in the bulk samples li concentrations range from 0 6 to 8 2 ppm while whole rock 6li values range from 2 9 to 14 in situ analyses display a greater range in both li concentration 0 1 19 5 ppm and li isotopic composition 27 to 19 with the serpentinized portions having higher li concentrations than the associated relict phases these variations may reflect changes in li partitioning and isotopic fractionation between serpentine and fluid with temperature and water rock ratio they may also be explained by changes in the composition of the serpentinizing fluid over the course of serpentinization as the serpentine forms by interaction with a circulating fluid it preferentially removes 6li causing the li in the fluid to become isotopically heavier the isotopic composition of the initial hydrothermal fluid is dominated by basalt derived li which easily overwhelms the very low li content originally present in seawater as this fluid circulates through ultramafic rocks it induces the formation of serpentine that incorporates this mantle derived li hence li in serpentine is mainly derived from oceanic crust rather than from seawater and serpentinization involves li recycling within this crust consequently li isotopes are good tracers of the hydrothermal contribution in serpentinizing fluid these results imply that serpentinized peridotites are probably only a minor sink of oceanic li

numerical modelling of hydrodynamics and sand transport in the tide dominated coastal to estuarine region abstract in order to understand the influences of tide waves and sediment sizes on the sand exchange between an estuary and the adjacent coastal region three estuaries around north west england were chosen for detailed study using a numerical morphological model system telemac hervouet and bates 2000 the numerical model was calibrated against available field measurements for both hydrodynamics and sediment transport simulations on sediment transport under a representative combined waves and tidal condition were carried out comparisons of the model results across the three different estuaries concentrate on effects from seabed bathymetry hydrodynamics and sediment sizes under the complex tide and wave interactions it is clear that the dominant hydrodynamic processes of an estuary are influenced by the tidal asymmetry wave driven currents and wave induced stirring effects which are all affected by the local seabed bathymetry given the same input tide and waves generally it is found that the net sediment transport direction at the estuary mouth depends on the relative strength of landwards transport in the shallow water depths due to tidal asymmetry and seawards transport within the estuary s deep channels in addition the overall sediment flux direction is largely dictated by local and surrounding sediment sizes

effects of sea ice cover on acoustic ray travel times with applications to the greenland sea tomography experiment the travel time effects of a sea ice cover on an acoustic pulse are estimated using generalized ray theory this expands upon the previous work done by jin and wadhams prog oceanogr 22 249 275 1989 by including the effects of frequency dispersion and different sets of ice parameters travel time changes due to single reflections are approximated by plane wave reflection theory and compared to the generalized ray theory results statistical effects for multiple reflections such as the ice thickness probability distribution function fresnel zone averaging and shadowing are considered finally the effects of ice induced travel time changes on tomographic inversions for water column oceanography are considered the implications of this work on the 1988 89 greenland sea tomography experiment are considered in detail

coastal storm characterization and morphological impacts on sandy coasts the present work deals with storm classification using the storm power index and beach morphological response to storm events in the gulf of cadiz sw spain over the 1958 2001 period 377 events divided into five classes ranging from weak to extreme were characterized classes i weak and ii moderate accounted for 60 and 23 of events respectively class iii significant were 9 of the recorded events and classes iv severe and v extreme accounted for 5 and 2 respectively the probability of storm occurrence per year ranged from 93 for class i to 15 for class v in order to characterize beach response to storm events 214 beach profiles carried out with a monthly periodicity over the 1996 1998 period along the chipiona rota littoral were analysed as well as published data different beach types were observed i intermediate beaches underwent important vertical relief changes ranging from 0 3 m to 1 33 m associated with average slope changes from tan 0 06 to tan 0 03 ii the dissipative beaches were characterized by smaller and homogeneous foreshore vertical changes from c 0 36 m to 0 65 m according to the parallel retreat mechanism characterized by small slope variations from tan 0 025 to tan 0 035 and iii intermediate with rock shore platform experienced small morphological and foreshore slope variations related to both beach pivoting and parallel retreat mechanisms the most important morphological changes were due to the impact of usually weak and moderate events during october and november that produced berm erosion and upper foreshore lowering and the impact of severe significant and extreme events in december and january which produced dune escarpment overwash and or damage to coastal structures copyright 2011 john wiley sons ltd

medium term frequency distributions of cross shore suspended sediment transport rates in water depths of 3 to 9 m abstract a data set of several thousands of hours of near bed flow obtained at three cross shore positions in 3 to 9 m water depth in the multiple bar system of terschelling netherlands was used to estimate the medium term years frequency distribution of the cross shore suspended sediment transport rates induced by short waves infragravity waves and cross shore mean flows predictions of an energetics based transport model were categorised into groups of the local height over depth ratio with a width of 0 02 and were subsequently coupled to the discrete medium scale probability distribution of this ratio at all depths the estimated medium scale sediment transport rate by the short waves q ms h and mean flows q ms mf were of approximately equal magnitude and were about three times as large as that of the infragravity waves in general the medium term sediment transport rates were dominated neither by the most extreme conditions nor by day to day situations this was related to the infrequent recurrence of the most energetic events and by the predicted negligible transport rates under daily conditions in 9 m depth breaking conditions contributed to about 90 of both q ms h and q ms mf in shallower water 3 5 m non breaking conditions became increasingly important for q ms h whereas q ms mf remained fully dominated by surf zone conditions this observation as well as literature findings for water depths less than about 3 m suggest that the range of small scale conditions that contribute most to q ms h and q ms mf changes in the onshore direction from mainly breaking conditions at depths in excess of 5 7 m towards prolonged non breaking periods for q ms h and short breaking events for q ms mf on the beach

open ocean deep convection due to thermobaricity 1 scaling argument properties of open ocean deep convection due to thermobaricity at high latitudes have been investigated by the scaling argument two types of open ocean deep convection are found the first type appears in a homogeneous ocean or in a deepening mixed layer the increased apparent buoyancy flux due to thermobaricity makes scales of convective properties larger than those without thermobaricity the ratio of thermobaric to nonthermobaric scales is determined only by l0 h where l0 and h are the size of nonthermobaric convection and the characteristic depth for thermobaricity to be effective respectively in a nonrotating frame then thermobaricity becomes effective when the ocean depth h is comparable with h as previous studies show in a rotating frame thermobaricity is most effective with slow rotation the coriolis parameter 10 4 s 1 and low temperatures approximately the freezing point of seawater since l0 h becomes largest in the actual situation 10 4 s 1 thus thermobaricity is not so effective because the earth rotation confines l0 to a smaller level i e l0 h 1 the second type of deep convection is driven by pure thermobaric instability in a two layer ocean where a cold fresh mixed layer overlies a warm saline deep layer as often observed in polar oceans it causes an abrupt overturning of the water column scales of convective properties are dependent on the difference of water temperature between the two layers the initial size of plume and the coriolis parameter or time but not on the surface cooling rate directly with actual parameters convective properties and the associated buoyancy flux are much larger than those of the first type observed vertical profiles of water temperature and salinity suggest that the first type of deep convection could occur in the greenland basin while the second type could occur in the weddell sea

localization of deep ocean convection by a mesoscale eddy abstract observations of open ocean deep convection indicate that it is a highly localized phenomenon occurring over areas of tens of kilometers in diameter the cause of this localization has been ascribed to preconditioning the local weakening of the stable density stratification associated with upwardly domed isopycnal surfaces in a surface intensified cyclonic circulation however most numerical and laboratory studies of localized convection have prescribed the localization artificially by confining the surface buoyancy loss to a circular disk in contrast in the numerical simulations described here deep convection forced by horizontally uniform buoyancy loss is localized within a region of initially weaker stratification than its surroundings the preconditioned region is associated with a cold core cyclonic eddy in geostrophic and cyclostrophic balance as in previous studies of disk shaped cooling the localized convection region undergoes baroclinic instability at late times causing the br

deterministic profile modelling of nearshore processes part 1 waves and currents abstract this is the first of two companion papers concerned with the modelling of beach profile response to wave and tidal action the present paper concentrates on wave and current modelling while the companion paper deals with sediment transport and beach profile development the papers describe summaries of the relevant theory model structure and comparisons with laboratory and field data including plane and barred beaches in the present paper wave heights fraction of broken waves bottom orbital velocities longshore wave driven currents undertow currents and bottom wave velocity moments are compared with measured data in these tests generally with good agreement due to lack of suitable data tidal effects have not been included in these comparisons the model is at present designed for application to beach erosion during storm events lasting several days and longer wave sequences of several months using hydrodynamic timesteps of the order of 0 5 to 3 hours wave sequences covering very long timespans several years may require further studies of filtering of input data

storm response and beach rotation on a gravel beach slapton sands u k abstract continuous argus video data and fortnightly measurements of subaerial morphology were obtained over a 3 year period from a steep macrotidal gravel beach on the southwest coast of the u k concurrent wave and water level data were also collected enabling the correlation of the observed morphological changes to the hydrodynamic forcing wave conditions are generally low h s 0 5 1 m but the beach is affected by frequent storm wave activity c 15 storms per year with h s 2 4 m with waves either approaching from the south swell waves or from the east wind waves an assessment of the three dimensional morphological response of the beach to the two typical storm types was carried out by analysing the impact of 27 storms that occurred from april 2007 to april 2009 southerly storms cause accretion of the supratidal zone and erosion of the intertidal zone and a significant loss in overall beach volume easterly storms on the other hand induce supratidal erosion and intertidal accretion and a significant gain in overall beach volume during the intervening calm periods a small supratidal berm is constructed and a modest gain in overall beach volume occurs wave modelling indicated that opposing longshore energy fluxes occur for the different storm types with a northerly energy flux during southerly storms and a southerly flux during easterly storms weekly shorelines derived from the argus images revealed that the northern end of the beach widened by c 30 m and the middle beach receded by c 40 m over a relatively brief period a few months the occurrence of this beach rotation event is attributed to a higher frequency of southerly storms and or a lower frequency of easterly storms over this period thus the development and stability of the beach on annual time scales depend on the relative contributions of the two storm types and their sequencing longshore sediment transport lst rates derived from the data on beach morphological change were compared with several littoral drift formulae previously applied to gravel beaches the cerc equation with a proportionality factor k between littoral drift rate i l and longshore wave energy flux p l of k 0 054 yielded the best results

observations of shoreline sandbar coupling on an embayed beach we analyse a seven year dataset 1999 2005 of shoreline and sandbar variations derived from video observations at the embayed tairua beach new zealand to explore sandbar shoreline coupling and to determine how this coupling is related to alongshore averaged sandbar shoreline separation and beach rotation our results quantify the coupling between the sandbar and the shoreline which is directly related to the reduced separation between the sandbar and the shoreline using a simple predictive shoreline model we show that this behaviour is related to the energy of the incoming waves our observations are obtained from a headland enclosed beach and show aspects of the morphological state that relate to the existence of headlands that are not considered in the wright and short beach state classification both the sandbar and shoreline at tairua beach rotate relatively quickly 1 month during the winter storm events when the storms are accompanied by strong alongshore components gradually returning during the summer months the sandbar shoreline coupling length scale is controlled by this rotation with large wavelengths occurring when the sandbar is strongly rotated

alpine olivine and titanian clinohumite bearing assemblages in the erro tobbio peridotite voltri massif nw italy the microstructures in the erro tobbio peridotite indicate several stages of recrystallization of olivine titanian clinohumite bearing assemblages the development of these assemblages is closely associated with serpentinite mylonites in which they occur in shear bands and foliations and are inferred to have grown synkinematically in veins and as post kinematic radial aggregates in the peridotite wall rock adjacent to these mylonites the same assemblages have recrystallized statically at the expense of original olivine and pyroxenes mesh textured chrysotile and antigorite veins in addition the olivine bearing assemblage occurs in widespread vein systems the brittle deformation of the peridotite resulting in the development of these vein systems is closely related to ductile deformation of metagabbroic dykes in the peridotite although early metasomatism resulted in extensive rodingitization of the gabbros some dykes show an eclogitic assemblage of na clinopyroxene garnet chloritoid chlorite f talc these observations the microstructures and the mineral chemistry all suggest that the assemblages in the ultramafic rocks and metagabbros developed during a prograde evolution towards high pressures 13 16 kbar 450 550 c and during subsequent decompression this metamorphic evolution is considered to be related to late cretaceous intraoceanic subduction in the alps apennine system and closure of the piedmont ligurian basin

the predictability of cross shore bed evolution of sandy beaches at the time scale of storms and seasons using process based profile models deterministic and probabilistic profile models have been compared with hydrodynamic and morphodynamic data of laboratory and field experiments on the time scale of storms and seasons the large scale laboratory experiment is a pure 2d case and offers and ideal test case for cross shore profile models as disturbing alongshore non uniformities are absent the field experiments are performed at the egmond site the netherlands during the eu coast3d project and represent storm time scale oct nov 1998 as well as seasonal time scale conditions may 1998 sep 1999 the objective of the paper is to present information of coastal processes on these time scales and to assess the predictive capabilities coastal process based profile models with respect to hydrodynamics and morphodynamics at sandy beaches on the time scales of storms and seasons profile models can quite accurately errors smaller than 10 represent the cross shore significant wave height distribution in the surf zone if the wave breaking model is properly calibrated the wave breaking coefficient should be a function of local wave steepness and bottom slope for most accurate results profile models can reasonably represent the cross shore and longshore currents undertow in a pure 2d case and in 3d field conditions profile models including cross shore mixing effects and breaker delay effects do not produce better predictions of the longshore and cross shore current velocities profile models using default settings can quite reasonably simulate the behaviour of the outer and inner bars on the storm time scale the behaviour of the beach cannot be modelled with sufficient accuracy on the storm time scale profile models can reasonably simulate the post storm onshore bar migration provided that the near bed orbital velocities and wave asymmetry related sand transport are represented in a sufficiently accurate way using non linear wave theories profile models cannot simulate the beach recovery processes on the post storm time scale because these essentially 3d processes are not sufficiently known to be included in the models profile models using default settings cannot simulate the behaviour of the outer and inner bars and the beach on the seasonal time scale the behaviour of the outer bar on the seasonal time scale can only be represented properly after tuning using measured bed profiles the simulation of the inner bar and beach morphology on the seasonal time scale could not be improved by tuning

satellite microwave and in situ observations of the weddell sea ice cover and its marginal ice zone the radiative and physical characteristics of the weddell sea ice cover and its marginal ice zone are studied using multichannel satellite passive microwave data in conjunction with in situ observations during the 1983 antarctic marine ecosystem research at the ice edge zone experiment time series studies from winter through spring using every other day observations from the nimbus 7 scanning multichannel microwave radiometer reveal significant spatial variability of the brightness temperatures of consolidated ice in winter and a recurring temporal and oftentimes larger spatial variability in spring the recurring effect in spring was found to be strongly correlated with observed surface air temperatures and is apparently associated with the cyclic changes in wetness of the snow cover of the ice while experiencing the freeze thaw cycle analysis of scatter plots of observed brightness temperatures from selected study regions using two or three frequencies and or polarizations shows that to effectively discriminate ice from open water within the ice pack a minimum of two channels at different frequencies preferably 18 ghz and 37 ghz is required serious problems associated with using only one frequency even at two polarizations i e 37 ghz and perhaps higher frequencies have been observed ice concentrations derived from the sensor are compared with helicopter and ship observations and results show consistency but a relatively low correlation coefficient partly due to the quasi qualitative nature of the in situ observations and uncertainties in ice emissivity in spring the character and the northernmost extent of the ice margin are quantified using radial plots of ice concentration across the ice pack and into ice free ocean temporal changes in the ice margin structure are compared with ship data of physical temperature ice characteristics wind and weather studies of the mass balance of fresh water and of biological features of the marginal ice zone are shown to benefit from time series information concerning the position of the ice edge as derived from satellite remote sensing

deterministic profile modelling of nearshore processes part 2 sediment transport and beach profile development abstract this is the second of two companion papers concerned with the modelling of sediment transport and beach profile response to wave and tidal action part i was concerned with the wave and current modelling aspects whilst the present paper considers the sediment transport and profile development predictions particular adaptations of well known theoretical developments that distinguish the present modelling work are described both cross shore and alongshore sediment transport processes the latter including the influence of tides are represented the alongshore transport description is included to allow this quasi 2dv model to act as a module to a quasi 3dh morphodynamic model the q3dh model is not described here the beach profile evolution phase of the model is capable of considering a fixed boundary such as a seawall the fixed boundary may also be erodible as in the case of a sandy beach overlying a cohesive till substratum in both parts i and ii the validity of each individual predictive phase of the model has been assessed where the accuracy was found to be insufficient additional processes were considered until the level of accuracy could be considered suitable for input to the next predictive phase of the model whilst free variables exist within the formulation of the model these have been considered to be fixed in almost every application of the model the consideration of additional processes is the approach used to achieve improved model prediction not the arbitrary tuning of free variables some of the validation tests for the sediment transport phases alongshore and cross shore are presented in this paper along with evaluations of the integrated model for profile change the foremost value of the model rests with the ability to identify links between observed beach changes and the underlying coastal processes

identification of modeled ocean plumes in greenland gyre ers 1 sar data oceanic convective plumes modeled with a thermobaric large eddy simulation and driven by conditions similar to those of the greenland sea are compared to observations from ers 1 synthetic aperture radar sar data from the greenland sea for the winter of 1992 in both form and size the two representations are seen to compare favorably the plume filled area of the sar image occupies a region about 20 km by 90 km at the ice edge of the open water in nordbukta the large seasonal ice retreat in the odden ice protuberance in the southern greenland gyre in the sar data the plumes appear to be ice covered while the convective return areas are open

how to identify winter convection in the greenland sea from hydrographic summer data 1 the identification of winter convection depths from later field observations is an often required but not trivial task we show from field measurements that the effects of winter convection in the greenland sea can vary enormously including such opposite changes as an increase or decrease of temperature salinity or stability also small scale fluctuations in the vertical can grow larger or cease commonly used indicators for past convection in the greenland sea like overall vertical homogeneity or a freshwater input to deeper layers alone are therefore not reliable to construct a time series of winter convection we explain this variety of effects with the occurrence of two rather different ventilation scenarios possible in the greenland sea they are exemplified by two winters using mainly hydrographic observations of the adjoining summers the observed differences are substantiated by the results of a one dimensional model out of this a multicriteria catalogue is developed which can be used to determine unambiguously convection depths in the greenland sea the fulfillment of one of the criteria is sufficient to evidence convection but the suitable criterion may differ from winter to winter a straightforward indicator proving the absence of winter convection does not exist

ocean mixed layers and acoustic pulse propagation in the greenland sea a simple one dimensional ocean mixed layer model is used to study the effect of the transition between summer and winter conditions in the greenland sea on range independent acoustic propagation acoustic normal modes propagated through the evolving sound speed profile simulate broadband acoustic receptions from the greenland sea tomography experiment the resulting changes in arrival structure and travel time are compared with data recorded between two of the tomographic moorings the starting state for the model is the average of measured summer temperature and salinity profiles at each time step the surface layer is modified by the removal of heat modeling heat loss to the atmosphere and the removal of fresh water modeling evaporation minus precipitation when necessary static stability is maintained by mixing the surface layer into deeper layers the acoustic normal modes exhibit large changes in behavior as the profile changes in both summer seasonal thermocline and winter adiabatic sound speed profile individual modes show minimal frequency dispersion intermediate profiles with a shallow surface mixed layer give highly dispersive modes delaying the final acoustic energy cutoff by several hundred milliseconds relative to the summer and winter cases this is the largest travel time signal observed in the data the largest peak in the late continuous acoustic energy is due to minimally dispersed modes and corresponds to ray arrivals with near horizontal receiver angles the amplitude of the arrival is low when significant dispersion is present

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

origin and evolution of fluids from mud volcanoes in the barbados accretionary complex a large collection of fluids 54 interstitial fluids and four expelled fluids were sampled at the manon site at the outer edge of the barbados accretionary complex these warm fluids up to 20 c are expelled by sub marine 5000 mbsl mud volcanoes consisting of diapirs unchanneled flow and diatremes channeled chlorine stable isotope ratios of these fluids were measured by irms with a reproducibility of 0 05 1 versus smoc standard mean ocean chloride a large range of 37cl between 5 3 and 0 1 is observed data from each volcanic structure describe a mixing between seawater and a low 37cl fluid the whole set of data is interpreted as the result of a mixing between two deep components and seawater the two deep fluids are chemically distinct e g in ca mg k li sr and br contents and br cl ratio they display low and significantly different 87sr 86sr ratios 0 707790 and 0 707892 respectively and 37cl values 4 51 and 5 24 respectively physicochemical processes such as mineralogical transformation diffusion compaction or ion filtration are known to fractionate chlorine stable isotopes and can produce fluids with negative 37cl values ion filtration due to sediment compaction appears to be the more likely process to explain the negative 37cl values observed at the manon site a model for the generation of these signatures is proposed where a residual negative 37cl fluid reservoir is created at the bottom of the prism or the sediment pile further compaction fracturing and or dewatering of the slab may flush out these fluids and focus them towards the decollement zone mixing between the fluids and ultimately with seawater and water released during gas hydrate destabilizations may explain the data set within the individual cores and between the different structures

tomographic resolution of mesoscale eddies in the marginal ice zone a preliminary study the adequacy of ocean acoustic tomography to resolve mesoscale eddies in the marginal ice zones miz in the vertical plane containing the acoustic multipaths connecting a pair of transceivers is studied using simulation inversions based on realistic eddy profiles obtained from conductivity temperature depth data resolution in this plane is seen to be strongly dependent upon the characteristics of the sound channel for optimal minimum mean square error estimators resolution is directly related to accuracy with better resolution implying higher accuracy for unaided acoustic tomography i e no supplementary measurements using only non bottom interacting paths horizontal and vertical resolution lengths of the order of 40 km and 200 m respectively are found in the upper water column for a transmission range of 150 km the implication is that the horizontal resolution is marginally adequate to resolve miz eddies but the vertical resolution is not since the horizontal scale of the eddies is of the same order whereas the vertical scale is much shorter the incorporation of bottom reflected arrivals is found to improve resolution significantly however the improvement only occurs in the horizontal direction and saturates when more than 14 of these arrivals are included beyond this point additional travel time observations give mostly redundant information on the other hand the disappearance of less stable non bottom interacting ray paths can result in a significant loss of resolution but only vertically the deficiency in vertical resolution is a result of the upward refracting nature of the miz sound channel it is also demonstrated that the inclusion of point temperature measurements on the acoustic transceiver moorings can dramatically increase the vertical resolution of the overall system particularly within a horizontal correlation length of the mooring with the inclusion of satellite radiometry surface temperature measurements adequate vertical resolution is achieved over the entire range considered

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

horizontal ocean circulation forced by deep water formation part ii a quasi geostrophic simulation abstract this numerical experiment aims to investigate the dynamical effects of the vertical convection of waters occurring in regions where the cooling of the upper ocean is due to periodical local rough winter atmospheric conditions the simulation is performed with a 2 layer quasi geostrophic model which configuration yields a small internal radius of deformation 10 km and a high spatial resolution 5 km the sinking of waters is parametrized by a conversion in a limited area of some of the upper layer fluid into lower layer fluid this forcing is continuously active for the first 3 months of the year and is zero otherwise this cycle is repeated for several years the model response results in an elevation of the interface a dome which generates a geostrophic circulation first limited to the region where the forcing is active the dome grows and reaches a critical amplitude where it becomes baroclinically unstable and breaks into eddies of smaller size in a way very comparable to what h

long term morphological modeling of a tidal inlet the arcachon basin france abstract the arcachon lagoon on the french atlantic coast is a triangular shaped lagoon of 20 km on a side connected to the ocean by a 3 km wide inlet between the mainland and an elongated sand spit this tidal inlet exhibits a particularly active morphology due to locally strong tidal currents and rough wave conditions during the past 300 years minimum and maximum spatial extents of the cap ferret sand spit have varied by 8 km while one or two channels have alternately allowed circulation between the lagoon and the ocean these impressive morphological changes have never prevented regular flushing of the lagoon eventhough the spit came as close as 300 m from the coast during the 18th century according to bruun s concept of tidal inlet stability theory and engineering 1978 510 pp the balance between longshore littoral transport and the tidal prism ensures the perpetuity of the inlet process modeling was believed to give better insight into the respective roles of tides and waves in driving the long term morphological changes of the inlet a two dimensional horizontal morphodynamic model was therefore developed combining modules for hydrodynamics waves sediment transport and bathymetry updates the use of process models at a scale of decades requires a schematization of the input conditions we defined representative mean annual wave and tide conditions with respect to sediment transport i e conditions that induce the same annual transport as measured in the field driven by these representative conditions simulations run from the 1993 bathymetry show that the tide is responsible for the opening of a new channel at the extremity of the sand spit where tidal currents are the strongest while waves induce a littoral transport responsible for the longshore drift of sand bodies across the inlet one particular simulation consisted in running the model from a hypothetical initial topography where the channels are filled with sand and the entire inlet is set to a constant depth 3 m the results show the reproduction of a channel and bar system comparable to historical observations which supports the idea that the lagoon is unlikely to be disconnected from the ocean provided tide and wave conditions remain fairly constant in the following decades

convection with rotation in a neutral ocean a study of open ocean deep convection abstract the intensity and scale of the geostrophically adjusted end state of the convective overturning of a homogeneous rotating ocean of depth h at a latitude where the coriolis parameter is f induced by surface buoyancy loss of magnitude b0 are studied by numerical experiment the experiments are related to observations and laboratory studies of open ocean deep convection a numerical model based on the nonhydrostatic boussinesq equations is used the grid spacing of the model is small enough that gross aspects of convective plumes themselves can be resolved yet the domain of integration is sufficiently large to permit study of the influence of plumes on the large scale and geostrophic adjustment of the convected water numerical simulations suggest that cooling at the sea surface is offset by buoyancy drawn from depth through the agency of convective plumes these plumes efficiently mix the water column to generate a dense chimney of fluid which subsequently breaks up through the mechanism of bar

a coupled dynamic thermodynamic model of an ice ocean system in the marginal ice zone wind driven ice ocean processes in the marginal ice zone are studied when thermodynamics is included into a coupled ice ocean model the ocean is considered to be a two layer ocean where a fresh and cold freezing mixed layer is lying above the stagnant warm and saline lower layer the essential part of the thermodynamics is the entrainment between the mixed layer and the lower layer which is parameterized using the frictional velocity at the ocean surface a kraus turner type parameterization it is shown that upwelling at the ice edge which is generated by the difference in the air ice and air water surface stresses will give rise to a strong entrainment by bringing the pycnocline nearer to the surface furthermore the entrainment is negligible outside the areas affected by the ice edge upwelling when cooling at the top is included the heat and salt exchange are further enhanced in the upwelling areas because the entrainment depends inversely on the density difference between the layers new ice formation occurs in the area which is not affected by ice edge upwelling that is no entrainment of the warm lower layer fluid so the mixed layer temperature stays at the freezing point the ice growth will give rise to a large salt flux to the upper layer but the subsequent salinity change is not as large as that due to the entrainment of the lower layer fluid the mixed layer in the areas affected by the ice edge upwelling is only slightly less saline than the lower layer it is suggested that these high salinity mixed layer regions with a scale of a few rossby radii of deformation 10 km will overturn due to cooling possibly as a plume and may this contribute to the formation of deep water

stable cl isotopes in subduction zone pore waters implications for fluid rock reactions and the cycling of chlorine stable cl isotope ratios measured in marine pore waters associated with the barbados and nankai subduction zones extend significantly to 8 the range of 37 cl values reported for natural waters these relatively large negative values together with geologic and chemical evidence from barbados and nankai and recent laboratory data showing that hydrous silicate minerals i e those with structural oh sites are enriched up to 7 5 in 37 cl relative to seawater strongly suggest that the isotopic composition of cl in pore waters from subduction zones reflects diagenetic and metamorphic dehydration and transformation reactions these reactions involve clays and or other hydrous silicate phases at depth in the fluid source regions chlorine therefore cannot be considered geochemically conservative in these systems the uptake of cl by hydrous phases provides a mechanism by which cl can be cycled into the mantle through subduction zones thus stable cl isotopes should help in determining the extent to which cl and companion excess volatiles like h 2 o and co 2 cycle between the crust and mantle

storm driven variability of the beach nearshore profile at duck north carolina usa 1981 1991 the us army corps of engineers field research facility frf at duck north carolina has collected approximately biweekly beach nearshore profile data to 8 m depth and associated wave data since 1981 sediment budget analysis was used to examine the medium scale years to a decade variability of the beach nearshore profile from 1981 to 1991 significant changes occurred during four groups of energetic storm events during february march of 1983 1987 1989 and december 1989 each group was comprised of at least two storms within a period of less than 39 days both with hmo 4 m during each storm group offshore sediment movement caused a distinct outer bar to migrate offshore and grow in size resulting in an abrupt increase in the volume of sediment on the upper shoreface the net profile changes were much larger than the changes due to single storms and the cumulative effect of the storms can be considered as one event during these events the first storm appears to have a destabilizing effect on the profile which has insufficient time to recover before the second and subsequent storm s as a result several storms in quick succession are able to have a large impact on the morphology the intervening periods between the groups of storm events termed fairweather conditions lasted up to 4 years they are characterized by slow but steady sediment redistribution averaging 33 m3 m 1 year 1 from the upper shoreface 5 m depth toward the shore while the total sediment volume was effectively constant the onshore feed of sediment was not significantly affected by individual storms during the fairweather conditions these two processes of 1 morphologic change during groups of storm events and 2 the steady onshore feed of sediments from the shoreface during fairweather conditions appear to play an important role on medium and long term profile evolution at least at duck

modeled radar surface signature of deep ocean convection deep ocean convection the process by which the deep waters of the world s oceans are created and renewed plays a key role in the global thermohaline circulation and hence the world s heat balance the process of deep ocean convection involves a vigorous overturning of the ocean water column down to depths of 2000 3000 m in an area probably not larger than 50 km in diameter this paper details the results of a theoretical study to identify remotely sensible surface signatures for deep ocean convection due to the all weather capability efforts have focused on the microwave part of the spectrum particularly the high resolution imaging capability of synthetic aperture radar sar the goal of this research is to use the sar surface signature or fingerprint to identify and characterize areas of convection in the open ocean this information is then used to improve model parameterizations for deep convection used in general circulation models electromagnetic simulations of remote sensing signatures of deep ocean convection have been performed based on existing hydrodynamic models simulated surface signatures of deep convection are presented for various hydrodynamic and imaging conditions along with a discussion of applicability of these simulations to real sar data key findings are the existence of a definite identifiable radar surface signature in convective regions and a set of conditions under which one would expect to observe these signatures

numerical simulation of remote acoustic sensing of ocean temperature in the fram strait environment an important part of the general problem of the arctic climate change is the monitoring of the fram strait which lies between greenland and spitsbergen for this reason it is reasonable to apply acoustic methods which are proven to be effective in acoustic ocean thermometry acoustic tomography etc knowledge of the main peculiarities of sound signal propagation in this region is needed to estimate the feasibility of applying remote acoustic methods to this end computer simulation of sound signal propagation in the fram strait environment was performed based on oceanographic data obtained by the r v polarstern expedition the presence of stable eigenrays in fram strait environmental conditions is demonstrated typical values of acoustic signal travel time fluctuations due to environmental variations are determined and the temperature effect on the signal travel time variation is considered sensitivity estimates for measurement of the average ocean temperature across fram strait is considered in two approaches by calculating travel time changes along selected stable eigenrays and by determining the cumulative sum of the whole envelope of the signals passed along water borne paths

observations of vertical currents and convection in the central greenland sea during the winter of 1988 1989 during the winter of 1988 1989 five acoustic doppler current profilers adcps were moored in the central greenland sea to measure vertical currents that might occur in conjunction with deep mixing and convection two adcps were looking up from about 300 m and combined with thermistor strings in the depth range 60 260 m two were looking downward from 200 m and one was looking upward from 1400 m first maxima of vertical velocity variance occurred at two events of strong cold winds in october and november when cooling and turbulence in the shallow mixed layer generated internal waves in the thermocline beginning in late november the marginal ice zone expanded eastward over the central greenland sea reaching its maximum extent in late december in mid january a bay of ice free water opened over the central greenland sea leaving a wedge of ice the is odden curled around it along the axis of the jan mayen current and then northeastward and existing well into april 1989 below the ice a mixed layer at freezing temperatures developed that increased in thickness from 60 to 120 m during the period of ice cover corresponding to an average heat loss of about 40 w m 2 through brine rejection mixed layer salinity increased steadily reducing stability to underlying weakly stratified layers roach et al 1993 during the ice cover period vertical currents were at a minimum after the opening of the ice free bay successive mixed layer deepening to 350 m occurred in conjunction with cooling events around february 1 and 15 accompanied by strong small scale vertical velocity variations upward mixing of more saline waters of atlantic origin during this phase reduced the stability further generating a pool of homogeneous water of 50 km horizontal extent in the central greenland sea preconditioned for subsequent convection to greater depths individual convection events were observed during march 6 16 associated with downward velocities at the 1400 m level of about 3 cm s l one event was identified as a plume of about 300 m horizontal scale in agreement with recently advanced scaling arguments and model results and with earlier similar observations in the gulf of lions western mediterranean the deep convection occurred in the center of the ice free bay hence brine rejection did not seem necessary for its generation plume temperatures at 1400 m were generally higher than that of the homogeneous surface pool suggesting entrainment of surrounding warmer waters on the way down mean vertical velocity over a period of convection events was indistinguishable from zero suggesting that plumes served as a mixing agent rather than causing mean downward transport of water masses however different from the surface pool that was governed by mixed layer physics the water between 400 and 1400 m was not horizontally homogenized in a large patch by the sporadic plumes overall and compared to results from the gulf of lions convection activity in the central greenland sea was weak and limited to intermediate depths in winter 1988 1989

the effects of wave chronology on medium and long term coastal morphology the sequencing or chronology of wave events plays an important role in determining how coastlines and nearshore regions evolve over medium and long timescales from weeks to decades however present day computer models of coastal morphology treat the input wave conditions in either a deterministic i e a single wave sequence or a probabilistic manner in neither method are the effects of the full range of possible future wave sequences for given overall statistical values calculated the methodology presented here addresses this problem by multiple model runs using different re orderings of a wave sequence a series of tests demonstrate different aspects of wave chronology and its importance in the prediction of seabed and beach levels the method provides a means both for understanding wave chronology effects and for predicting these effects in practical engineering problems involving medium and long timescale changes to coastal morphology

thermal evolution of the greenland sea gyre in 1988 1989 slice inverses of temperature and heat content from the 1988 1989 greenland sea tomography experiment and other observations including standard conductivity temperature depth stations moored thermistors surface meteorological variables and surface ice cover are combined to better understand the thermodynamics of the greenland sea gyre thermal evolution of the gyre center seems to divide naturally into the following three periods a preconditioning phase november january during which surface salinity is increased by brine rejection from ice formation and by entrainment but in which the mixed layer deepens only slowly to a depth of some 150 200 m a deep mixing phase february march during which the surface mixed layer deepens rapidly to approximately 1500 m in the gyre center purely under the influence of local surface cooling and a restratification phase during which the products of deep mixing are replaced by arctic intermediate water flowing in from the gyre edges the onset of the deep mixing phase occurs after ice formation in the gyre center stops resulting in an area of open water where large heat fluxes can occur in surrounding regions including the odden region to the south ice is still being formed to the north and west closer to the steep topography of the continental shelf the inverse results show significant variability due to advection and large temperature and heat content fluctuations with a period of about 50 days are seen

on the morphological development of embayed beaches abstract the typically curved and stable planform shape of embayed beaches is often observed in the presence of rigid headlands the long term alongshore equilibrium shape is variable and is controlled by headland geometry cellular circulation patterns and wave obliquity at the shoreline we use a process based morphological model to simulate the development of embayed beaches depending on different environmental conditions and geological settings i e topography and geometry the embayment is allowed to develop from an initially straight beach to one which is curved under idealized wave forcing conditions and without external sediment input bay development can be approximated with an exponential function with coefficients representing rate of growth and bay size long term shoreline cutback is both uniform shoreline translation and non uniform shoreline rotation and is parameterized alongshore gradients in flow and transport patterns are related to long term non uniform shoreline cutback rotation of the beach ceases as the bay matures leading to a curved shoreline planform which is a remnant of decaying erosion processes

temperature evolution of the upper ocean in the greenland sea january to march 1989 tomographic data obtained during early 1989 in the greenland sea have been analyzed at 4 8 hour resolution to give the range averaged vertical temperature evolution in the upper 500m for a 106km path the tomographic inversions used both ray travel time data and normal mode group velocity data in order to maximize near surface resolution two major events are apparent in the results the first is the warming of a cold 1 9 c 100m thick surface layer and the second 10 days later is the cooling of a relatively warm 0 9 c subsurface layer between 300m and 500m depth this warm subsurface layer is a critical source of salinity and buoyancy for deep convection the surface layer warming is consistent with a mixed layer deepening over a portion of the path bringing up water from below special sensor microwave imager ssm i ice data indicate that the local ice field disappears 3 4 days after the surface warming the cooling of the warm 300m to 500m layer is also consistent with a vertical process there is no ice cover at this time and so surface heat fluxes are large a northerly wind event occurs at the onset of the cooling of the 300 500 m layer suggesting that wind induced mixing may have played a role in initiating the process there is evidence of southward flow advecting warm water into the area both before and after the two events studied in detail here

investigation of a self organization model for beach cusp formation and development a recent numerical investigation of self organization werner and fink 1993 suggests that the feedback process between currents and sediment response can result in self organized patterns and can be used to predict beach cusp formation and spacing a similar model based on self organization is tested here in order to understand the processes occurring during beach cusp formation and development to evaluate the sensitivity toward the parameters used and to examine how the model might relate to field observations results obtained confirm the validity of the self organization approach and its capacity to predict beach cusp spacing with values in fair agreement with the available field measurements with most of the input parameters primarily affecting the rate of the process rather than the final spacing however changes in the random seed and runs for large numbers of swash cycles reveal a dynamical system with significant unpredictable behavior cusp spacing tends to change with time and cusp regularity shows large long term variations cusps are found to be accretionary in the swash zone and in agreement with most observations mean flows are horn divergent over developed topography simulations over nonplanar slopes characterized by the presence of preexisting nonrhythmic or cuspate features have been performed results indicate that preexisting large amplitude cusps are destroyed if their spacing is substantially different from that expected under self organization and that the final spacing is consistent with that predicted by the model for an equivalent plane beach these findings support the hypothesis that self organization is a robust mechanism for beach cusp formation

alteration of oceanic crust and geologic cycling of chlorine and water we report new estimates of transport rates for h2o and cl between the mantle and surface reservoirs our estimates take into consideration alteration of oceanic crust especially that of plutonic rocks and possible subduction of sediments the effect of hydrothermal alteration on the cl budget seems to be negligible but the effect on the h2o budget is significant altered oceanic crust excluding sediments contains about 10 times as much h2o as the unaltered crust and its subduction may result in a net transport of h2o to the upper mantle in subduction zones however the rate of expulsion of h2o from the mantle by subduction zone magmatism is comparable to the amount released by ridge magmatism and is only about 10 of the amount subducted therefore about 90 of the subducted h2o must be returned to the mantle or returned to the crust by other processes in addition subduction of oceanic sediments to mantle depths will result in 1 1 a further increase in the return rate of h2o to the mantle reservoir 2 2 possible net transfer of cl to the mantle depending on the rate of pore water expulsion

recent shifts in coastline change and shoreline stabilization linked to storm climate change since cuspate coastlines are especially sensitive to changes in wave climate they serve as potential indicators of initial responses to changing wave conditions previous work demonstrates that cape hatteras and cape lookout north carolina which are largely unaffected by shoreline stabilization efforts have become increasingly asymmetric over the past 30 years consistent with model predictions for coastline response to increases in atlantic ocean summer wave heights and resulting changes in the distribution of wave approach angles historic and recent shoreline change observations for cape fear north carolina and model simulations of coastline response to an increasingly asymmetric wave climate in the presence of beach nourishment produce comparable differences in shoreline change rates in response to changes in wave climate results suggest that the effect of beach nourishment is to compensate for and therefore to mask natural responses to wave climate change that might otherwise be discernible in patterns of shoreline change alone therefore this case study suggests that the effects of wave climate change on human modified coastlines may be detectable in the spatial and temporal patterns of shoreline stabilization activities similar analyses of cuspate features in areas where the change in wave climate is less pronounced i e fishing point maryland virginia and where local geology appears to exert control on coastline shape i e cape canaveral florida suggest that changes in shoreline configuration that may be arising from shifting wave climate are currently limited to sandy wave dominated coastlines where the change in wave climate has been most pronounced however if hurricane generated wave heights continue to increase large scale shifts in patterns of erosion and accretion will likely extend beyond sensitive cuspate features as the larger scale coastline shape comes into equilibrium with changing wave conditions copyright 2014 john wiley sons ltd

sea ice impact on long term particle flux in the greenland sea s is odden nordbukta region 1985 1996 five sediment traps deployed in the greenland sea at a depth of 500 m between 72 n and 75 n by the sonderforschungsbereich 313 kiel germany provide the necessary data to compare particle flux with ambient ice regimes sedimentation in this seasonally ice covered region is dependent upon the following three basic parameters 1 ice concentration 2 duration of ice cover and 3 distance from the ice edge these factors vary significantly with time and space we develop algorithms that provide annual sedimentation amounts for the area contained by 71 n to 76 n the greenland coast and 10 e for a severe ice year the area of seasonal ice cover and an 80 km wide band extending along the maximum extent of the ice edge the biological marginal ice zone bmiz combine to provide 92 of the total sedimentation for particulate organic carbon and silica this zone accounts for 89 each of the total sedimentation in a light ice year the respective percentages are 84 for dry weight 87 for particulate organic carbon and 81 for biogenic particulate silica these figures are slightly less than sedimentation for a severe ice year if the is odden nordbukta region is replaced by open ocean for purposes of comparison the bmiz out produces the open ocean for poc by a factor of 3 2 projecting the algorithms for the is odden nordbukta region to the rest of the greenland sea we conclude that the is odden nordbukta region is a substantial producer of sedimentation

on the deep and bottom waters of the greenland sea from summer 1989 and 1990 data the deep waters of the central and southern greenland sea are examined using bartlett 1989 and 1990 summer data displayed at very high temperature and salinity resolutions the mixing of arctic ocean deep water aodw with greenland sea deep water gsdw in proportions of about 1 1 to form new norwegian sea deep water nsdw is confirmed however the previously accepted route of this new nsdw through the ridge system into the norwegian sea the jan mayen channel is shown to pass deep water only intermittently a passage through mohn s ridge farther north beginning near 72 06 n 2 w is identified as a more likely route part of the ultimate aodw gsdw mixture is shown to continue on along the greenland continental slope into the iceland sea a peculiar isothermal condition was found in the deeper parts of the gsdw this is postulated to result from upward diffusion of temperature from a layer initially having the adiabatic temperature gradient above the isothermal layer is one of warming and decreasing salinity the result of recent successive deep convections to different depths

chlorine stable isotopic composition of basement fluids of the eastern flank of the juan de fuca ridge odp leg 168 abstract this paper presents chlorine stable isotope compositions 37cl of sediment pore waters collected by squeezing sediment cores from the sediment basement interface along an east west transect through the eastern flank of the juan de fuca ridge odp leg 168 these near basement fluids nbf are generally thought to be representative of low temperature fluids circulating in the off axis basaltic crust the 37cl value of the fluid directly sampled from a flow at the base of site 1026 wstp1026 is also reported nbf display 37cl values between 2 09 and 0 12 relative to the standard mean ocean chloride smoc defined as 0 and small variations in chlorinity 4 these data contrast with the homogeneity of 37cl values associated with highly variable chlorinities observed in high temperature on axis fluids m bonifacie j l charlou n jendrzejewski p agrinier j p donval chlorine isotopic compositions of ridge axis high temperature hydrothermal vent fluids chem geol 221 2005 279 288 the nbf 37cl values show a general decreasing trend with distance from the ridge axis except for two fluids when plotted against 18o values the 37cl of the nbf show two different trends this paper discusses the possible contributions on nbf 37cl values of fluid mixing water rock interactions and transport processes diffusion ion membrane filtration that can occur in the igneous basement however as none of these processes can fully explain the observed 37cl variations the potential effect of the sediment cover is also investigated at site 1026 the interstitial pore fluid displays a 37cl signature significantly lower than that of the fluid discharge sample 1 90 and 0 28 respectively this difference demonstrated here cannot be an artifact of the sampling method rather indicates the influence of the sediment cover on nbf 37cl values the potential contributions of physical processes associated with transport compaction e g diffusion ion membrane filtration adsorption ion exchange on nbf 37cl values are qualitatively discussed here but require additional studies for further insights however this study indicates that near basement fluids nbf are not at least for cl isotopic compositions necessarily as representative of fluids circulating in the basaltic crust as initially thought these results add new constraints on cl geodynamics and show that cl isotopes fractionate during low temperature circulation of fluids in off axis and off margin flow contexts but not to the extent observed for active margins fluids circulating at low temperature in the magmatic and or the sedimentary part of the oceanic crust might have played a major role on the 37cl evolution of seawater over geologic time

incorporation of acoustic normal mode data into tomographic inversions in the greenland sea acoustic normal mode group velocity data are extracted from tomographic receptions in the greenland sea using a combination of spatial filtering with data from a six element hydrophone array and variable time windowing the mode group velocity data together with ray travel time data are used in inversions to obtain the range average sound speed profile the modal data significantly improve near surface resolution which is where the largest oceanographic signals occur inverse results using only acoustic data are consistent with point measurements a seasoar section and sparse conductivity temperature depth data

subduction of water into the mantle history of an alpine peridotite the erro tobbio peridotite western alps is a slice of subcontinental mantle that underwent pre jurassic passive rifting followed by sea floor hydration and cretaceous alpine subduction analysis of its extension and subduction related structures and metamorphism suggest the dip below the adria plate of both the extensional detachments and the subduction plane high pressure boudinage structures of rigid metarodingite within ductile antigorite serpentinite prove that antigorite survived subduction and remained stable at eclogite facies conditions subduction of serpentinized peridotites from ophiolite slabs is here considered the most effective mechanism of bringing water to great depth within the mantle

antarctic sea ice microwave signatures and their correlation with in situ ice observations the general characteristics and microwave radiative properties of sea ice in the weddell sea region during the onset of spring are studied by using the nimbus 7 scanning multichannel microwave radiometer smmr and other satellite sensors in conjunction with in situ observations from the mikhail somov the position of the ice edge the gradient of ice concentration and the width of the marginal ice zone are inferred from the microwave data and are found to be consistent with ship observations especially at 18 ghz the sensitivities of the various smmr frequencies to surface and other effects are investigated by using multi spectral cluster analysis the results show considerable variability in emissivity especially at 37 ghz likely associated with varying degrees of surface wetness ice concentrations are derived by using two methods one that assumes fixed emissivities for consolidated ice and an iterative procedure that accounts for the variable emissivities observed by using the procedure that allows the emissivities to be variable gives ice concentrations that are more consistent with qualitative field observations

fractal properties of coastal profile evolution at duck north carolina observed variations in coastal morphology on monthly to decadal timescales are often difficult to explain in terms of physical processes operating on shorter timescales one reason could be that the morphology evolves to high dimensional self organized states circumstantial evidence for this would be indicated by fractal distributions of the dynamical variables fractal analysis techniques are applied to beach level time series collected at duck north carolina united states after processing for this study the data set consists of time series of monthly beach and nearshore levels at up to 86 locations at 10 m spacing along each of four shore normal profile lines over a period of 10 5 years time series of shoreline positions are also analyzed several fractal analysis techniques are used based on the hurst exponent h and various sources of error are considered and quantified results indicate different fractal behavior in different cross shore zones h values of around 0 5 are found in the nearshore bar zones and are thus consistent with a random gaussian process while values around 0 8 are found farther offshore and on upper parts of the beach indicating long range persistency further analyses are done to determine time spans over which fractal behavior occurs generally fractal responses are found at locations and timescales where the temporal variations of wave forcing are relatively weak suggestions are made to interpret these findings in terms of forced and self organized morphodynamic change in different cross shore zones and over different timescales some possible implications for predicting future coastal morphology are discussed