massive sand beds attributed to deposition by dense water cascades in the bourcart canyon head gulf of lions northwestern mediterranean sea nowadays the gulf of lions continental shelf and slope are under the influence of dense water cascading wind induced bottom currents and the geostrophic northern current in order to characterize sedimentary activity at the shelf break several interface and piston cores were taken in the bourcart canyon head and a current meter equipped with temperature conductivity pressure and turbidity sensors was moored during the 2003 2004 winter season even if the canyon is not connected directly to continental sources since last glacial maximum detailed grain size x ray and sediment facies analysis of interface cores show that down to 350 m water depth the canyon head is blanketed by up to 1 5 m of structureless muddy medium grained sand 210pbexc activity measurements demonstrate present day sedimentary activity of the canyon head time series of currents with peak velocity reaching 0 37 m s suspended sediment concentration and temperature indicate that dense water cascading is the main process allowing the reworking transport and accumulation of sand within the canyon head even though winter 2003 2004 was characterized by low cascading events compared to other years these sand beds called cascadite constitute a new type of deposit that differs from other typical slope deposits turbidites hyperpycnites contourites in terms of flow duration and sedimentological characteristics they are similar to shallow water contourites they might be time equivalent to the recent turbidites described throughout the deep western gulf of lions basin

microphysical consequences of the spatial distribution of ice nucleation in mixed phase stratiform clouds mixed phase stratiform clouds can persist even with steady ice precipitation fluxes and the origin and microphysical properties of the ice crystals are of interest vapor deposition growth and sedimentation of ice particles along with a uniform volume source of ice nucleation lead to a power law relation between ice water content wi and ice number concentration ni with exponent 2 5 the result is independent of assumptions about the vertical velocity structure of the cloud and is therefore more general than the related expression of yang et al 2013 the sensitivity of the wi ni relationship to the spatial distribution of ice nucleation is confirmed by lagrangian tracking and ice growth with cloud volume cloud top and cloud base sources of ice particles through a time dependent cloud field based on observed wi and ni from indirect and semi direct aerosol campaign a lower bound of 0 006 m 3 s 1 is obtained for the ice crystal formation rate

genesis of the mandongshan gold deposit xinjiang nw china t p ƒs2 and phase equilibria constraints from the au as fe s system abstract the mandongshan gold deposit located in the west junggar xinjiang china is hosted in early carboniferous basalt and tuff ore bodies mainly consist of gold bearing hydrothermal veins mineralized basalt and tuff with disseminated sulfides hydrothermal process could be identified based on ore petrographic studies quartz albite sulfide native gold stage i arsenopyrite calcite native gold ii and pyrite calcite iii microthermometric and laser raman spectroscopic analysis of fluid inclusions in quartz demonstrate the ore forming fluid at stage i was moderate temperature 360 398 c low salinity 0 5 5 1 wt nacl equiv and h 2 o ch 4 dominant which evolved to low salinity 0 2 1 2 wt nacl equiv with insignificant content of ch 4 at 219 267 c stage iii contents of ore elements as au cu sb ba cs rb in mineralized basalt are higher than those in fresh basalt phase analysis for the au as fe s system using supcrt92 software package with the updated database of slop98 dat indicates that a decrease of h 2 s activity and oxygen fugacity caused by phase separation and fluid rock reactions induced native gold precipitation at stage i the decrease of h 2 s activity triggered by arsenopyrite crystallization caused native gold deposition at stage ii

scales and dynamics of submesoscale coherent vortices formed by deep convection in the northwestern mediterranean sea since 2010 an intense effort in the collection of in situ observations has been carried out in the northwestern mediterranean sea thanks to gliders profiling floats regular cruises and mooring lines this integrated observing system enabled a year to year monitoring of the deep waters formation that occurred in the gulf of lions area during four consecutive winters 2010 2013 vortical structures remnant of wintertime deep vertical mixing events were regularly sampled by the different observing platforms these are submesoscale coherent vortices scvs characterized by a small radius 5 8 km strong depth intensified orbital velocities 10 20 cm s 1 with often a weak surface signature high rossby 0 5 and burger numbers o 0 5 1 anticyclones transport convected waters resulting from intermediate 300 m to deep 2000 m vertical mixing cyclones are characterized by a 500 1000 m thick layer of weakly stratified deep waters or bottom waters that cascaded from the shelf of the gulf of lions in 2012 extending down to the bottom of the ocean at 2500 m the formation of cyclonic eddies seems to be favored by bottom reaching convection occurring during the study period or cascading events reaching the abyssal plain we confirm the prominent role of anticyclonic scvs and shed light on the important role of cyclonic scvs in the spreading of a significant amount 30 of the newly formed deep waters away from the winter mixing areas since they can survive until the following winter they can potentially have a great impact on the mixed layer deepening through a local preconditioning effect

thick bottom nepheloid layers in the western mediterranean generated by deep dense shelf water cascading the analysis of a compilation of deep ctd casts conducted in the western mediterranean from 1998 to 2011 has documented the role that dense water formation and particularly deep dense shelf water cascading off the gulf of lions plays in transporting suspended particulate matter from the coastal regions down to the basin deep ctd casts reveal that after the 1999 and 2005 2006 deep cascading events the western mediterranean deep water wmdw was characterized by the presence of a thick bottom nepheloid layer bnl that corresponded in thickness with a thermohaline anomaly generated by the mixture of dense waters formed by deep convection in the open sea and by deep cascading this bnl can be hundreds of meters thick and in the central part of the basin usually exhibits suspended sediment concentrations of 1 mg l after winter 1999 the bnl spread from the gulf of lions and the catalan margin over the northwestern mediterranean basin reaching west of the balearic islands and the ligurian sea while after winters 2005 2006 the bnl covered the entire western mediterranean basin thickness and concentration of the bnl tend to diminish with time but this trend is highly dependent on the volume of dense water generated both by convection and cascading after winter 1999 the bnl signal vanished in one year but after winters 2005 2006 it lasted for longer and the turbidity signal can still be distinguished at present 2011 particle size distribution in the bnl reveals the presence of large aggregates up to 1 mm in size formed by a mixture of single particles with the same bimodal grain size distribution as the surface sediments found in the northwestern mediterranean slope and basin results presented in this paper highlight the fact that the wmdw can be periodically affected by the arrival of new dense waters loaded with suspended particles mainly introduced by resuspension processes during major cascading events being a key process that could ultimately affect deep sea biogeochemical cycles in the western mediterranean

particle fluxes dynamics in blanes submarine canyon northwestern mediterranean abstract within the framework of the multidisciplinary recs project and with the aim of describing the particle flux transfer from the continental shelf to the deep basin an array of five mooring lines equipped with a total of five pairs of pps3 3 sequential sampling sediment traps and rcm 7 8 current meters were deployed 30 m above the bottom from march 2003 to march 2004 inside and outside the blanes canyon one mooring line was located in the upper canyon at 600 m depth one in the canyon axis at 1700 m depth and other two close to the canyon walls at 900 m depth a fifth mooring line was deployed in the continental open slope at 1500 m water depth the highest near bottom downward particle flux 14 50 g m 2 d 1 was recorded at the trap located in the upper canyon m1 where continental inputs associated with the presence of the tordera river are most relevant on the other hand the downward fluxes 4 35 g m 2 d 1 in the canyon axis m2 were of the same order as those found in the western flank m3 of the canyon both values were clearly higher than the value 1 95 g m 2 d 1 recorded at the eastern canyon wall m4 the open slope m5 mass flux 5 42 mg m 2 d 1 recorded by the sediment trap located outside the canyon system was three orders of magnitude lower than the other values registered by the inner canyon stations the relevance of our data is that it explains how the transport pathway in the canyon occurs through its western flank where a more active and persistent current toward the open ocean was recorded over the entire year of the experiment off shelf sediment transport along the canyon axis showed clear differences during the period of the study with some important events leading to strong intensifications of the current coupled with large transport of particle fluxes to the deepest parts of the canyon such events are primarily related to increases in river discharge and the occurrence of strong storms and cascading events during the winter in summary in this study it is shown that the dynamics of the water masses and the currents in the study area convert the sharp western flank of the blanes canyon in a more active region that favors erosion processes than the eastern flank which has a smoother topography and where the absence of erosional conditions yields to steadier sedimentary processes

particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern mediterranean basin abstract the effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern mediterranean basin were studied by near bottom moored instruments recording trapped particle fluxes suspended particle fluxes water properties and hydrodynamics from november 2011 to july 2012 during this period near bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth increasing by more than one order of magnitude the ambient suspended sediment concentrations the trapped particle fluxes and the suspended sediment fluxes during the preconditioning phase of the open sea convection from december 2011 to mid february 2012 currents 1 10 cm s 1 suspended sediment concentrations

an extreme cold surge over the greek peninsula summary this paper is devoted to the detailed description of an extreme cold surge that occurred 3 13 march 1987 over greece this event has been rated as the worst snowfall over the last 100 years and duc to its severily and persistence it paralysed the cconornic and communal life of greece for several days emphasis is given to the initiation phase of this event the structural evolution of the cold surge is analysed using both observations and model results model simulations pcrformed with the colorado state university regional atmospheric modelling system provided the necessary data to diagnose the mesoscale structure of the cold outbreak different mechanisms involved in the structural evolution ofthe cold surge are investigated the gustiness of the observed winds and their significant departure from geostrophy are related to the role of an important isallobaric wind the progression of this surge presented characteristics of a density current while near the eastern slopes of the mountain barriers of continental greece cold air damming occurred leading to an accelerated flow parallcl to the mountains heavy snowfall events over greece are often associated with cold air surges prop agating from northern and central europe through the balkans metaxas 1978 livada tselepidaki 1979 prezerakos and angouridakis 1984 these cold surges are accompanied with the passage of a fast moving cold front from the north towards the south very strong winds especially in the gaps between mountains in northern greece and over the aegean sea a sharp temperature decrease over the whole country and a sharp pressure rise the lifetime of these surges is normally from 1 to 3 days extending up to 10 days in exceptional cases their persistence can cause important problems in economic life since the result ing snowfall can prohibit road transportation on the main traffic routes greek forecasters call these cold fronts balkan fronts due to their origin in the frame of this study this terminology will be retained although the classical term cold surge will also be used interchangeably the forecast of the evolution of these fronts as well as the persistence of cold surges over greece is of great importance not only for the impact of snowfall on economic life but also for the safety of navigation in the aegean sea in gale force winds cold surges accompanied by severe weather phenomena have also been reported in the himalayan region nakamura and murakami 1983 over the usa e g bell and bosart 1988 colle and mass 1995 as well as over central america schultz et al 1997 all the aforementioned studies underlined the fact that cold surges are accompanied by strong lower tropospheric northerly winds sharp decreases in temperature and sharp pressure rises in these studies some interesting features accompanying cold surges were also ad dressed mainly cold air damming near mountain barriers as a result of the interaction of the synoptic scale flow with topography bell and bosart 1988 concluded that the component of the pressure gradient force parallel to the mountain was the primary cause for the appearance of an accelerated flow nearly parallel to the mountains colle and mass 1995 demonstrated that pressure ridging east of the mountain barrier caused ageostrophic northerly winds while cold avection of upslope flow led to the damming of cold air schultz et al 1997 showed that the extraordinary equatorial extent of a cold surge was aided by topographic channelling similar to cold air damming

autumnal mixed phase cloudy boundary layers in the arctic abstract two mixed phase cloudy boundary layer events observed over the arctic ice pack in autumn are extensively analyzed the local dynamic and thermodynamic structure of the boundary layers is determined from aircraft measurements including analysis of turbulence longwave radiative transfer and cloud microphysics the large scale forcing is determined from the national centers for environmental prediction reanalysis fields while mesoscale forcing is estimated from 40 km aircraft box patterns the two cases differed somewhat in their local static stability surface characteristics and large scale forcing one case was characterized by a stably stratified cloudy boundary layer over a heterogeneous surface containing numerous open leads the other case occurred over a fairly homogenous surface of multiyear ice and consisted of a surface based stable layer surmounted by a low level jet and a cloud topped mixed layer an important large scale factor in the development of low clouds appears to have been w

reexposure and advection of 14c depleted organic carbon from old deposits at the upper continental slope represents an additional source of 14 c depleted organic carbon supplied to the ocean in parallel with the weathering of fossil organic carbon delivered by rivers from land to understand the dynamics and implications of this reexposure at the shelf edge a biogeochemical study was carried out in the gulf of lions mediterranean sea where erosive processes driven by shelf dense water cascading are currently shaping the seafloor at the canyon heads mooring lines equipped with sediment traps and current meters were deployed during the cascading season in the southwestern canyon heads whereas sediment cores were collected along the sediment dispersal system from the prodelta regions down to the canyon heads evidence from grain size x radiographs and 210 pb activity indicate the presence in the upper slope of a shelly coarse surface stratum overlying a consolidated deposit this erosive discontinuity was interpreted as being a result of dense water cascading that is able to generate sufficient shear stress at the canyon heads to mobilize the coarse surface layer eroding the basal strata as a result a pool of aged organic carbon d 14 c 944 5 24 7 mean age 23 650 3 321 ybp outcrops at the modern seafloor and is reexposed to the contemporary carbon cycle this basal deposit was found to have relatively high terrigenous organic carbon lignin 1 48 0 14 mg 100 mg oc suggesting that this material was deposited during the last low sea level stand a few sediment trap samples showed anomalously depleted radiocarbon concentrations d 14 c 704 4 62 5 relative to inner shelf d 14 c 293 4 134 0 mid shelf d 14 c 366 6 51 1 and outer shelf d 14 c 384 47 8 surface sediments therefore although the major source of particulate material during the cascading season is resuspended shelf deposits there is evidence that this aged pool of organic carbon can be eroded and laterally advected downslope

the role of the north aegean in triggering the recent eastern mediterranean climatic changes drastic changes have occurred in the vertical structure of the deep waters of the eastern mediterranean in the early 1990s as dense water of aegean origin has displaced lighter waters of adriatic origin at the bottom of the deep basins this work suggests that the initiation of this process took place in the north aegean in the winter of 1986 1987 and was intensified by another formation event in 1992 1993 the available observations from the north aegean support such a scenario furthermore we propose that the outflow of black sea waters into the aegean through the dardanelles could act as an insulator of the deeper layer from the atmosphere thus absorbing a large part of the heat and salt exchange despite this fact the existence of the densest bottom water of the mediterranean in the north aegean and the continuation of density increase for a large period of time suggests that it is a region of formation thus that the insulation layer may at times be penetrated we suggest that reduced black sea outflow into the north aegean could facilitate dense water formation during the passage of cold atmospheric fronts in the winter

evidence of liquid dependent ice nucleation in high latitude stratiform clouds from surface remote sensors 1 ground based lidar radar and microwave radiometer observations at eureka canada barrow alaska and over the western arctic ocean measure physical characteristics and morphology of stratiform clouds despite transition of a cold atmosphere 15 c through ice supersaturated conditions ice is not observed until soon after a liquid layer several cases illustrating this phenomenon are presented in addition to long term observations from three measurement sites characterizing cloud phase frequency this analysis demonstrates that clouds composed entirely of ice occur less frequently than liquid topped mixed phase clouds at temperatures warmer than 25 to 30 c these results indicate ice formation generally occurs in conjunction with liquid at these temperatures and suggest the importance of liquid dependent ice nucleation mechanisms

cascades of dense water around the world ocean dense water overflow off continental shelves cascading is one of the contributing processes of shelf deep ocean exchange and of topical interest to climate studies and nutrient fluxes dense water originating from cooling evaporation freezing and salinization on a shallow shelf spills over the shelf edge and may develop as near bottom gravity current or an intermediate depth intrusion it is difficult to observe in nature due to its intermittent character this paper provides an extensive inventory of observed cases of water cascades around the world ocean summarises their locations and individual properties and provides statistics of the identified cases the search for cascading was carried out using oceanographic databases and a literature review this study identified 61 confirmed cases world wide including 25 cases in the arctic seas 12 at mid latitudes seven in sub tropical and tropical regions and 17 off the antarctic shelves eighteen cascades had not been reported before we analyze a set of numerical parameters of dense water cascades allowing us to quantify compare and contrast the properties of water cascades the overall average density contrast between the confirmed cascades and ambient water is 0 37 kg m3 it can be as much as 2 kg m3 on some arctic shelves frequently initiated by strong cooling at the surface cascades often remain colder through the descent thus supplying the deep ocean with colder and fresher water in non dimensional variables the data from all climate zones fit well to a unique curve which represents a relationship between a cascade s internal structure and the parameters describing its forcing on average the down slope volumetric flux provided by dense water cascades is estimated as 0 05 to 0 08 sv per 100 km of shelf edge regional terms arctic antarctic north atlantic ocean barents sea mediterranean sea skagerrak tasman sea sea of okhotsk

comments on cascades of dense water around the world ocean abstract evidences of temperature controlled dense water cascading off the gulf of lion shelf in the northwestern mediterranean and several aegean shelves in the northeastern mediterranean are reported together with the adiatic shelf already listed by ivanov shapiro huthnance aleynik golovin 2004 these zones represent the major coastal areas of the mediterranean sea where dense water is produced

vertical motions in arctic mixed phase stratiform clouds abstract the characteristics of arctic mixed phase stratiform clouds and their relation to vertical air motions are examined using ground based observations during the mixed phase arctic cloud experiment mpace in barrow alaska during fall 2004 the cloud macrophysical microphysical and dynamical properties are derived from a suite of active and passive remote sensors low level single layer mixed phase stratiform clouds are typically topped by a 400 700 m deep liquid water layer from which ice crystals precipitate these clouds are strongly dominated 85 by mass by liquid water on average an in cloud updraft of 0 4 m s 1 sustains the clouds although cloud scale circulations lead to a variability of up to 2 m s 1 from the average dominant scales of variability in both vertical air motions and cloud microphysical properties retrieved by this analysis occur at 0 5 10 km wavelengths in updrafts both cloud liquid and ice mass grow although the net liquid mass growth is usually largest betwee

oceanographic processes and morphosedimentary products along the iberian margins a new multidisciplinary approach abstract our understanding of bottom currents and associated oceanographic processes e g overflows barotropic tidal currents including intermittent processes e g vertical eddies deep sea storms horizontal vortices internal waves and tsunamis is rapidly evolving many deep water processes remain poorly understood due to limited direct observations but can generate significant depositional and erosional features on both short and long term time scales this paper represents a review work which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the iberian continental margins this review explores the implications of the studied processes given their secondary role relative to other factors such as mass transport and turbiditic processes and highlights three major results a contourite depositional and erosional features are ubiquitous along the margins indicating that bottom currents and associated oceanographic processes control the physiography and sedimentation b the position of interfaces between major water masses and their vertical and spatial variation in time specifically appears to exert primary control in determining major morphologic changes along the slope gradient including the contourite terraces development and c contourites deposits exhibit greater variation than the established facies model suggests therefore a consistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development an integrated interpretation of these oceanographic processes requires an understanding of contourites seafloor features their spatial and temporal evolution and the near bottom flows that form them this approach will synthesize oceanographic data seafloor morphology sediments and seismic images to improve our knowledge of permanent and intermittent processes around iberia and evaluate their conceptual and regional role in the margin s sedimentary evolution given their complexes three dimensional and temporally variable nature integration of these processes into sedimentary oceanographic and climatological frameworks will require a multidisciplinary approach that includes geology physical oceanography paleoceanography and benthic biology

a synthesis of the circulation and hydrography of the south aegean sea and the straits of the cretan arc march 1994 january 1995 abstract four seasonal oceanographic cruises were carried out in the eastern mediterranean sea within the framework of the cec mast mtp project pelagos during 1994 1995 the surveys covered the south aegean sea and the adjacent open sea regions southeastern ionian northwestern levantine analysis of ctd data revealed that a multiscaled circulation pattern prevails in the area it differs from the circulations detected during the 1986 87 thus indicating interannual variability cyclonic and anticyclonic gyres and eddies are interconnected by currents and jets variable in space and time most of the features are persistent others seem transitional or recurrent the hydrological structure is also complex and apart from the upper layer does not present basinwide any significant seasonality dynamical and hydrological regimes are variable in the upper and intermediate layers at the straits of the cretan arc while the deep regime seems rather constant topographic control is evident on the flows through the straits the new very dense deep water mass namely the cretan deep water cdw and a well defined intermediate layer of minimum temperature and salinity the so called transition mediterranean water tmw consists the new important structural elements of the south aegean sea the cdw outflows towards the deep and bottom layers of the eastern mediterranean thus considerably contributing to the formation of the new denser deep and bottom water of the eastern mediterranean which sinks and displaces the eastern mediterranean deep water of adriatic origin in the adjacent sea regions outside the aegean sea

large sediment waves over the gulf of roses upper continental slope nw mediterranean recently acquired swath bathymetry and seismic datasets on the gulf of roses continental slope revealed the presence of large sediment waves that have developed between 200 and 400 m water depth geometric parameters were computed from the multibeam dataset and the obtained results showed mean sediment wave lengths of 2000 m and maximum heights of 60 m the analysis of seismic profiles showed the general architecture of the late quaternary deposits over the gulf of roses outer shelf and slope the outer continental shelf is characterized by morphological erosional features affecting the upper part of the most recent seismic unit over the continental slope five main unconformity bounded seismic units are differentiated with sediment waves developed in all of them the sediment waves observed over the continental slope are presumably generated by bottom currents intensified during major dense shelf water cascading events flowing downslope at an oblique angle with respect to the main bathymetry

modeling immersion freezing with aerosol dependent prognostic ice nuclei in arctic mixed phase clouds while recent laboratory experiments have thoroughly quantified the ice nucleation efficiency of different aerosol species the resulting ice nucleation parameterizations have not yet been extensively evaluated in models on different scales here the implementation of an immersion freezing parameterization based on laboratory measurements of the ice nucleation active surface site density of mineral dust and ice nucleation active bacteria accounting for nucleation scavenging of ice nuclei into a cloud resolving model with two moment cloud microphysics is presented we simulated an arctic mixed phase stratocumulus cloud observed during flight 31 of the indirect and semi direct aerosol campaign near barrow alaska through different feedback cycles the persistence of the cloud strongly depends on the ice number concentration it is attempted to bring the observed cloud properties assumptions on aerosol concentration and composition and ice formation parameterized as a function of these aerosol properties into agreement depending on the aerosol concentration and on the ice crystal properties the simulated clouds are classified as growing dissipating and quasi stable in comparison to the default ice nucleation scheme the new scheme requires higher aerosol concentrations to maintain a quasi stable cloud the simulations suggest that in the temperature range of this specific case mineral dust can only contribute to a minor part of the ice formation the importance of ice nucleation active bacteria and possibly other ice formation modes than immersion freezing remains poorly constrained in the considered case since knowledge on local variations in the emissions of ice nucleation active organic aerosols in the arctic is scarce

spatial and temporal variability of downward particle fluxes on a continental slope lessons from an 8 yr experiment in the gulf of lions nw mediterranean abstract a long term experiment of downward particle fluxes and currents has been initiated in 1993 on the continental slope of the gulf of lions nw mediterranean and pursued within the frame of several french and european projects pnec euromarge nb mtp ii mater eurostrataform sediment traps and current meters were deployed at several locations on this slope deeply incised by numerous canyons with an extensive spatial coverage for the first 2 years canyons at the entrance middle and exit of the gulf with respect to the general along slope circulation head and mid canyon depths adjacent open slope from late 1995 onwards this design was reduced to the two mid canyon moorings at the entrance and exit of the gulf monthly fluxes and hourly temperatures and currents were recorded at 500 m 30 m above bottom mab in the canyon heads at 500 and 1000 m respectively 530 and 30 mab nominal depths at the mid canyon sites and at 750 m 30 mab open slope this study aims at describing the spatial seasonal and interannual variability of flux intensity and composition of settling particles and at analyzing the role of diverse forcings in the control of particle exchange across the margin results from the first 8 years 1993 2001 show that total mass fluxes in the 101 104 mg m 2 d 1 range increase along slope particularly for the near bottom traps between the ne planier canyon and the sw lacaze duthiers canyon limits of the gulf of lions indicating an increased shelf export of particulate matter in the western part of the system bulk chemical composition organic matter carbonate opal and lithogenic fraction remained rather stable during the course of the experiment tending towards values typical of superficial shelf sediments at higher mass fluxes first order calculations using a simple two component mixing model suggest a decreasing contribution of primary particles settling out of the overlying waters to the total flux from the entrance towards the exit of the system particulate material transferred to the deeper slope in the southwestern part of the gulf of lions appears therefore to predominantly originate in resuspended shelf and or upper slope sediment downward particle fluxes and potential forcing parameters exhibit a high seasonal variability with higher values from late autumn to early spring furthermore unprecedented winter flux peaks observed in 1999 dominated the interannual differences which otherwise were quite limited correlations between sources of particulate material on the shelf i e river and atmospheric inputs phytoplankton biomass and sediment resuspension cross slope exchange mechanisms derived from in situ temperature and current records and flux data indicate a predominant effect of dense cold water cascading on the exchange of particulate matter between the shelf and the slope

megafauna of vulnerable marine ecosystems in french mediterranean submarine canyons spatial distribution and anthropogenic impacts abstract vulnerable marine ecosystems vme in the deep mediterranean sea have been identified by the general fisheries commission for the mediterranean as consisting of communities of scleractinia lophelia pertusa and madrepora oculata pennatulacea funiculina quadrangularis and alcyonacea isidella elongata this paper deals with video data recorded in the heads of french mediterranean canyons quantitative observations were extracted from 101 video films recorded during the medseacan cruise in 2009 aamp comex qualitative information was extracted from four other cruises two marum comex cruises in 2009 and 2011 and two ifremer cruises in 1995 and 2010 to support the previous observations in the cassidaigne and lacaze duthiers canyons all the species fishing impacts and litter recognized in the video films recorded from 180 to 700 m depth were mapped using gis the abundances and distributions of benthic fishing resources marketable fishes aristeidae octopodidae vulnerable marine species trawling scars and litter of 17 canyons were calculated and compared as was the open slope between the stoechades and toulon canyons funiculina quadrangularis was rarely observed being confined for the most part to the marti canyon and i elongata was abundant in three canyons bourcart marti petit rhone these two cnidarians were encountered in relatively low abundances and it may be that they have been swept away by repeated trawling the lacaze duthiers and cassidaigne canyons comprised the highest densities and largest colony sizes of scleractinian cold water corals whose distribution was mapped in detail these colonies were often seen to be entangled in fishing lines the alcyonacean callogorgia verticillata was observed to be highly abundant in the bourcart canyon and less abundant in several other canyons this alcyonacean was also severely affected by bottom fishing gears and is proposed as a vulnerable marine species our studies on anthropogenic impacts show that seafloor disturbance by benthic fishing is mainly attributable to trawling in the gulf of lion and to long lines where rocky substrates are present the bauxite residue red mud expelled in the cassidaigne canyon was seen to prevent fauna from settling at the bottom of the canyon and it covered much of the flanks litter was present in all of the canyons and especially in considerable quantities in the ligurian sea where the heads of the canyons are closer to the coast three marine protected areas and one fishing area with restricted access have recently been established and should permit the preservation of these deep ecosystems

effects of ice number concentration on dynamics of a shallow mixed phase stratiform cloud 1 previous modeling studies have shown high sensitivity of mixed phase clouds to ice number concentration ni with simulated clouds often transitioning from mixed phase to ice only regime within a narrow range of ni to better understand the mechanisms behind this transition we analyze several simulations of a mixed phase stratiform arctic cloud observed on 26 april 2008 during the indirect and semi direct aerosol campaign isdac in the base run ni is constrained to match the measured value and a persistent mixed phase cloud is formed with properties similar to those observed when ni is quadrupled hi ice the liquid water path is reduced by half within two hours the changes in liquid water are accompanied by diminishing radiative cooling and slowing vertical mixing exposing complex interactions among microphysics radiation and dynamics deviations of base and hi ice from a simulation without ice are used to explore the linearity of the model response to variation in ni it is shown that early changes in cloud condensate amount and radiative cooling rate are proportional to ni while changes in the vertical buoyancy flux and dynamics are qualitatively different in hi ice compared to base the nonlinear with respect to ni reduction in buoyancy flux drives the initial response of the mixed layer dynamics to the appearance of ice and subsequently determines the sustainability of liquid water in the cloud in this case two additional sensitivity experiments link the decreased buoyancy production to the latent heat release from the depositional ice growth while confirming the importance of the cloud radiation feedback

sediment transport processes at the head of halibut canyon eastern canada margin an interplay between internal tides and dense shelf water cascading abstract to investigate the processes by which sediment is transported through a submarine canyon incised in a glaciated margin the bottom boundary layer quadrapod ralph was deployed at 276 m depth in the west halibut canyon off newfoundland during winter 2008 2009 two main sediment transport processes were identified throughout the deployment firstly periodic increases of near bottom suspended sediment concentrations ssc were recorded associated with the up canyon propagation of the semidiurnal internal tidal bore along the canyon axis carrying fine sediment particles resuspended from deeper canyon regions the recorded ssc peaks lasting less than 1 h were observed sporadically and were linked to bottom intensified up canyon flows 40 cm s 1 concomitant with sharp drops in temperature secondly sediment transport was also observed during events of intensified down canyon current velocities that occurred during periods of sustained heat loss from surface waters but were not associated with large storm waves high resolution velocity profiles throughout the water column during these events revealed that the highest current speeds 1 m s 1 were centered several meters above the sea floor and corresponded to the region of maximum velocities of a gravity flow such flows had associated low ssc and cold water temperatures and are interpreted as dense shelf water cascading events channelized along the canyon axis sediment transport during these events was largely restricted to bedload and saltation producing winnowing of sands and fine sediments around larger gravel particles analysis of historical hydrographic data suggests that such gravity flows are not related to the formation of coastal dense waters advected towards the outer shelf that reached the canyon head rather the dense shelf waters appear to be generated around the outer shelf where convection during winter is able to reach the sea floor and generate a pool of near bottom dense water that cascades into the canyon during one or two tidal cycles a similar transport mechanism is likely to occur in other submarine canyons along the eastern canadian margin as well in other canyoned margins where winter convection can reach the shelf edge

long lifetime ice particles in mixed phase stratiform clouds quasi steady and recycled growth ice particles play an important role in precipitation and radiation transfer in stratiform mixed phase clouds lagrangian ice particle tracking in mixed phase clouds is applied in both a 3 d time dependent velocity field produced by a large eddy simulation cloud model and a 2 d idealized field it is found that more than 10 of ice particles have lifetimes longer than 1 5 h much longer than the large eddy turnover time or the time for a crystal to fall through the depth of a nonturbulent cloud an analysis of trajectories in a 2 d idealized field shows that there are two types of long lifetime ice particles quasi steady and recycled growth for quasi steady growth ice particles are suspended in the updraft velocity region for a long time for recycled growth ice particles are trapped in the large eddy structures and whether ice particles grow or sublimate depends on the ice relative humidity profile within the boundary layer some ice particles can grow after each cycle in the trapping region until they are too large to be trapped and thus have long lifetimes the relative contribution of the recycled ice particles to the cloud mean ice water content depends on both the dynamic and thermodynamic properties of the mixing layer in particular the total ice water content of a mixed phase cloud in a decoupled boundary layer can be much larger than that in a fully coupled boundary layer