surface drifter derived circulation in the northern and middle adriatic sea response to wind regime and season 1 more than 120 satellite tracked drifters were deployed in the northern and middle adriatic nma sea between september 2002 and november 2003 with the purpose of studying the surface circulation at mesoscale to seasonal scale in relation to wind forcing river runoff and bottom topography pseudo eulerian and lagrangian statistics were calculated from the low pass filtered drifter velocity data between september 2002 and december 2003 the structure of the mean circulation is determined with unprecedented high horizontal resolution by the new data in particular mean currents velocity variance and kinetic energy levels are shown to be maximal in the western adriatic current wac separating data into seasons we found that the mean kinetic energy is maximal in fall with high values also in winter while it is significantly weaker in summer high resolution local area model italy winds were used to relate the drifter velocities to the wind fields the surface currents appear to be significantly influenced by the winds the mean flow during the northeasterly bora regime shows an intensification of the across basin recirculating currents in addition the wac is strongly intensified both in intensity and in its offshore lateral extension in the southeasterly sirocco regime northward flow without recirculation dominates in the eastern half of the basin while during northwesterly maestro the wac is enhanced separating the data into low and high po river discharge rates for low wind conditions shows that the wac and the velocity fluctuations in front of the po delta are stronger for high po river runoff lagrangian covariance diffusivity and integral time and space scales are larger in the along basin direction and are maximal in the southern portion of the wac

near surface dynamical structure of the kuroshio extension 1 lagrangian data from 657 svp drifters cnes aviso archiving validation and interpretation of satellite oceanographic data time variable satellite altimeter sea level anomaly and levitus 98 hydrographic data are used to develop 0 25 spatial resolution maps of the mean and eddy circulations in the northwestern pacific during the 1990s drifter velocities at 15 m depth and 200 m temperature data clearly indicate in the kuroshio extension ke jet two prominent meanders that culminate in a 300 km northward deflection east of the shatsky rise at 160 e the interannual trends of aviso mesoscale variance are absent along the path of the meandering ke jet three anticyclonic recirculations can be identified south or southeast of the kuroshio the southernmost around daito island being a new discovery about 3 of the drifters with drogues attached crossed the kuroshio front the aviso currents are correlated at 0 8 with drifter geostrophic velocity the aviso geostrophic currents are adjusted in amplitude to the contemporaneous drifter observations and are further used to compute an unbiased mean geostrophic circulation and the quasi geostrophic reynolds stresses in the ke region the principal axes of the eddy reynolds stresses are oriented along the unbiased mean velocity vectors within the meandering ke jet the time mean horizontal momentum balance that includes both the mean and eddy momentum convergences is used to compute absolute sea level map and its uncertainty at 145 e the 2000 m depth absolute dynamic height referenced to the sea level reveals a heretofore unknown 70 dynamic cm drop from 25 to 42 n

lobal interactions rheologic superposition and implications for a pleistocene ice stream on the continental shelf of british columbia abstract data on structures stone striae clast pavements fabrics morphology provenance and matrix grain size of four pre late wisconsinan diamictons are presented from the lower accessible part of an 855 m long sea cliff at cape ball east coast of graham island queen charlotte archipelago british columbia the data indicate that an ice stream crossed the continental shelf from the british columbian mainland to the queen charlotte islands local queen charlotte piedmont ice coalesced with the western edge of the cordilleran ice sheet resulting in northward flow deflection along the east coast of graham island generally consistent structural and stone data indicate that diamictons were deposited as primary subglacial tills and that subglacial dynamics and rheologic conditions were complex two of the tills can be traced continuously over the cape ball section which provides a north south transect oblique to ice flow each of the two tills reveals five major changes in rheology and genesis ranging from a strong lodgement component to dominantly deformation mainly by subglacial squeeze flow true end member tills are rare and in almost all places the tills are hybrids that formed within a continuum of till forming processes commonly involving stone rotation and superposition of structures and rheologic states this could have occurred mainly in response to fluctuating till pore water content along the transect two dimensional stretches of contrasting till types probably represent a three dimensional patchwork of contrasting till rheologies and pore waters if patches of ductily deforming till were common and or widespread they could have accounted for much of the movement of cordilleran ice over glaciomarine mud on the continental shelf when sea level was much lower than present deforming probably saturated muddy till reconstituted glaciomarine would have possessed negligible shear strength resulting in a thin rapidly moving glacier most likely an ice stream that reached cape ball but failed to remove the record of previous glacial events the ice stream probably issued out of the mainland s skeena valley which is aligned with cape ball and is approximately the size of valleys in antarctica that today conduct small outlet glaciers and ice streams evidence for this and other ice streams on the northwestern continental shelf of north america imply that destabilization and rapid decay of the western edge of the cordilleran ice sheet may have been accomplished by a combination of ice streams sea level rise and extensive calving

interdecadal thermohaline oscillations in a sector ocean general circulation model advective and convective processes abstract oceanic interdecadal thermohaline oscillations are investigated with a coarse resolution version of the geophysical fluid dynamics laboratory modular ocean model the geometry of the model is a box with a depth of 5000 m and a longitudinal width of 60 spanning latitudes from 14 5 to 66 5 n the model ocean is forced by a zonal wind stress a heat flux parameterized by restoring the surface temperature toward a reference value and a specified surface freshwater flux zonal wind stress reference temperature and freshwater flux are all longitudinally uniform time independent and vary meridionally it is shown that the ocean model can be in a state of interdecadal oscillations and a physical mechanism is explained for these oscillatory solutions both surface mean heat flux and basin mean kinetic energy vary with interdecadal periods temperature and salinity budget analyses reveal that these oscillations depend primarily on advective and convective processes horizontal advective heat tran

exploiting coastal altimetry to improve the surface circulation scheme over the central mediterranean sea this work is the first study exploiting along track altimetry data to observe and monitor coastal ocean features over the transition area between the western and eastern mediterranean basins the relative performances of both the aviso and the x track research regional altimetric data sets are compared using in situ observations both products are cross validated with tide gauge records the altimeter derived geostrophic velocities are also compared with observations from a moored acoustic doppler current profiler results indicate the good potential of satellite altimetry to retrieve dynamic features over the area however x track shows a more homogenous data coverage than aviso with longer time series in the 50 km coastal band the seasonal evolution of the surface circulation is therefore analyzed by conjointly using x track data and remotely sensed sea surface temperature observations this combined data set clearly depicts different current regimes and bifurcations which allows us to propose a new seasonal circulation scheme for the central mediterranean the analysis shows variations of the path and temporal behavior of the main circulation features the atlantic tunisian current the atlantic ionian stream the atlantic libyan current and the sidra gyre the resulting bifurcating veins of these currents are also discussed and a new current branch is observed for the first time

ocean drilling program leg 169s surficial geology stratigraphy and geomorphology of the saanich inlet area southeastern vancouver island british columbia abstract this paper provides i a descriptive overview of the late pleistocene and holocene geology and geomorphology of the region surrounding saanich inlet and ii the palaeogeographic setting for discussion of the oceanographic record at odp leg 169s sites 1033 and 1034 the dominant deposits and landforms in the saanich inlet area are similar to those of late pleistocene marine influenced glacial environments and modern fjord inlets dominated by retreating tide water glaciers patterns of ice retreat meltwater drainage and sea level change are reconstructed for the interval 4000 15 000 calendar years before present yrbp the flux of meltwater and sediment into saanich inlet was greatest between ca 12 000 and 15 000 yrbp at that time sea level was up to 90 m higher relative to land than today during deglaciation tidewater glaciers occupying chemainus cowichan and koksilah valleys entered a marine embayment that formed in the vicinity of cowichan bay satellite channel saanich inlet and saanich peninsula in the early holocene relative sea level fell to a low stand perhaps tens of metres below the present datum and the surface area of saanich inlet and satellite channel was much reduced by the middle holocene sea level had risen to near its present position and modern drainage patterns and oceanographic conditions were established

long lived mesoscale eddies in the eastern mediterranean sea analysis of 20 years of aviso geostrophic velocities we analyzed 20 years of aviso data set to detect and characterize long lived eddies which stay coherent more than 6 months in the eastern mediterranean sea in order to process the coarse gridded 1 8 aviso geostrophic velocity fields we optimized a geometrical eddy detection algorithm our main contribution was to implement a new procedure based on the computation of the local and normalized angular momentum lnam to identify the positions of the eddy centers and to follow their lagrangian tra jectories we verify on two mesoscale anticyclones sampled during the egypt campaign in 2006 that our methodology provides a correct estimation of the eddy centers and their characteristic radius corresponding to the maximal tangential velocity our analysis reveals the dominance of anticyclones among the long lived eddies this cyclone anticyclone asymmetry appears to be much more pronounced in eastern mediter ranean sea than in the global ocean then we focus our study on the formation areas of long lived eddies we confirm that the generations of the ierapetra and the pelops anticyclones are recurrent and correlated to the etesian wind forcing we also provide some evidence that the smaller cyclonic eddies formed at the southwest of crete may also be induced by the same wind forcing on the other hand the generation of long lived eddies along the libyo egyptian coast are not correlated to the local wind stress curl but surprisingly their initial formation points follow the herodotus trough bathymetry moreover we identify a new formation area not discussed before along the curved shelf off benghazi

numerical simulation of the interannual variability of the mediterranean sea upper ocean circulation numerical simulations reveal that variations in wind stress and heat fluxes can induce significant interannual fluctuations in the circulation of the upper layers of the mediterranean from january 1980 to november 1988 the atmosphere shows changes in the structure and magnitude of the surface winds and in the air temperatures which induce modifications in the upper ocean structure and currents the model prediction of the interannual fluctuations of the sicily strait baroclinic westward volume transport is in agreement with observations and the variability is explained as a function of the wind curl forcing in the region the current anomalies persist for many months after a winter atmospheric anomalous disturbance has occurred over the basin the eastern mediterranean basin is the area where the interannual ocean response is most pronounced

direct observations reveal the deep circulation of the western mediterranean sea direct observations of the deep water circulation in the western mediterranean sea are presented based on the analysis of autonomous profiling floats drifting at 1200m and 1900m depth during the 1997 2002 period the amount of water circulating in the basin is quantified revealing several distinct gyres and boundary currents it was also possible to follow the spreading of the newly formed western mediterranean deep water nwmdw and tyrrhenian deep water tdw two main components of the deep water in the western mediterranean from their origin based on their temperature and salinity signature both boundary currents and isolated eddies carrying the water into the interior are important for this

seasat altimeter observations of dynamic topography in the gulf stream region individual seasat altimeter profiles in the western north atlantic have been differenced with the best available geoid model to remove the gravitational component the resulting sea surface height profiles compare remarkably well with independent oceanographic observations the gulf stream is clearly apparent in each profile as a 1 to 2 m step and known positions of cyclonic and anticyclonic rings correspond with depressions and elevations respectively with amplitudes as large as 95 cm some of the most important altimeter data for analyzing the dynamic ocean signal were gathered during the last month of the mission when the same ground track was repeated every 3 days these data allow detailed examination of time varying ocean phenomena since the gravitational component is time invariant one set of collinear passes clearly shows a cyclonic ring as it moves out from underneath the spacecraft s track an event which was simultaneously observed with the aid of a satellite tracked surface buoy another striking feature seen in the altimeter data set is the apparent variability exhibited by the gulf stream on time scales of a few days surface transport indicated by the sea surface height difference across the stream varied by nearly 30 and over the entire 3 month period much larger fluctuations were observed suggesting significant changes in total mass transport altimetry may provide an effective means of determining the time and space scales associated with these variations

wind driven currents in the tropical pacific abstract an analysis is made of the ensemble mean ageostrophic near surface circulation measured by 1503 lagrangian drifters drogued to 15 m depth in the tropical pacific between 1987 and 1994 it was found that the physical model of the wind driven currents in a weakly stratified upper layer in which the richardson number remains near unity accounts for 40 of the vector variance of the observations in such a model the amplitude of the current is proportional to u n f 1 2 and the depth scale of the wind driven layer is proportional to u n f 1 2 when the ageostrophic currents at 15 m depth are binned by the scaled ekman depth a net rotation of 0 87 radians was observed through the layer depth these measurements suggest that the vertical austausch coefficient of the upper ocean is proportional to u2 n ekman proposed such a model based on two reports of wind driven currents in 1905 at widely separated latitudes

surface geostrophic circulation of the mediterranean sea derived from drifter and satellite altimeter data abstractdrifter observations and satellite derived sea surface height data are used to quantitatively study the surface geostrophic circulation of the entire mediterranean sea for the period spanning 1992 2010 after removal of the wind driven components from the drifter velocities and low pass filtering in bins of 1 1 1 week maps of surface geostrophic circulation mean flow and kinetic energy levels are produced using the drifter and or satellite data the mean currents and kinetic energy levels derived from the drifter data appear stronger higher with respect to those obtained from satellite altimeter data the maps of mean circulation estimated from the drifter data and from a combination of drifter and altimeter data are however qualitatively similar in the western basin they show the main pathways of the surface waters flowing eastward from the strait of gibraltar to the sicily channel and the current transporting waters back westward along the italian french and spanish coasts intermi

the controversial path of atlantic water in the eastern mediterranean abstract the atlantic water aw path suggested by two decades of thermal satellite data observations in the eastern mediterranean is similar to the path followed by the aw in the western mediterranean but is in contrast with the scheme proposed after the physical oceanography of the eastern mediterranean poem experiment during the 1990s evidence of the aw path along the libyo egyptian coast libyo egyptian current lec and around anti cyclonic eddies of variable size and position libyo egyptian eddies lees is reported in xbt transects high resolution models and drifter trajectories in the poem scheme the aw was carried eastwards by the mid mediterranean jet mmj flowing in the middle of the levantine basin the mmj is still noted in recent drifter trajectory analyses and seasonal surveys and glider missions report that the aw is transferred towards the levantine basin by the mmj in subsurface layers the issue is investigated in this study by considering whether the determination of the aw path and the resolution of the surface circulation are unlike in the western mediterranean two distinct problems historical hydrographic datasets and numerical experiments illustrated in this study demonstrate that satellite observations in the eastern mediterranean reveal the path of the surface water of atlantic origin which is modified by heating and evaporation into the saltier and warmer levantine surface water lsw but do not reveal the path of the submerged aw that maintains the distinctive character of fresh aw in the levantine basin differences between the surface and the submerged circulation in the mersa matruh area explain the reason for the discrepancy in summer the aw departs from the sicily channel at the sea surface and crosses the ionian sea in a surface layer 30 m deep at the entrance to the levantine basin part of the aw re circulates westwards in two separate branches one directed to the southern ionian and the other towards the central ionian causing meanders in the incoming aw in the levantine basin before the cretan passage the aw is close to the libyan coast with surface layers already modified into lsw and a subsurface fresh aw core centered at 50 m depth surface and subsurface flows diverge within the cretan passage as they approach the mersa matruh area according to satellite observations the lsw flows along the libyo egyptian coast lec and around anti cyclonic lees of variable size and position in the subsurface layers the blend and fragmented anti cyclonic circulation found at the surface is augmented by the aw itself which becomes saltier and negatively buoyant and veers offshore joining the mmj in summer the jet assumes the aspect of a submerged injection of fresh aw into the levantine basin below a depth of 60 70 m from the ionian eastwards the depth of the fresh core of aw sinks by tens of meters from the beginning to the end of summer in the sicily channel the aw in winter is saltier than in other periods of the year due to evaporation and mixing occurring between the fresh aw and the saltier ionian surface water intruding into the southern side of the channel in summer

seismic stratigraphy of upper quaternary shallow water contourite drifts in the gulf of taranto ionian sea southern italy abstract the occurrence of articulated seafloor morphology over continental shelf upper slope environments may result in a significant change in the patterns and intensity of basin scale thermohaline circulation during eustatic sea level fluctuations these changes may cause in turn erosion deposition and or transport of sediments at the seafloor to form shallow water contourite drifts here we investigate this process in the nw sector of the gulf of taranto ionian sea during and following the last glacial maximum lgm by integrating multibeam bathymetric data ultra high resolution seismic reflection data and gravity core data sea level fall caused subaerial exposure of the summit of the amendolara bank forming a short lived island off the eastern coast of calabria and also creating a narrow passageway between the island and the northern calabria mainland integrated seismic stratigraphic data show that upper quaternary shallow water contourite drifts and associated erosional features locally formed both around the flanks of the amendolara bank ambk and the continental shelf and upper slope off the amendolara village contourite drifts are bounded at the bottom and at the top by two major unconformities indicating that the formation of the sediments drifts occurred between the onset of the lgm and the gs 1 younger dryas event the stratal architecture suggests the occurrence of various types of contourite deposits mostly represented by a axial and lateral channel patch drifts and channel related drifts along the incision to the ne of the ambk b sheeted drifts along the northeastern slope of the ambk c elongated drifts along the continental shelf and upper slope off the coast of amendolara village erosional features also developed on the south eastern flank of the ambk where the levantine intermediate water flows from the central ionian sea towards the gulf of taranto until the present day both processes and timing responsible for erosion of the seafloor and the formation of sediment drifts in the gulf of taranto may be similar to that occurred in the tyrrhenian margins during the late quaternary

the dwyka group in the northern part of kwazulu natal south africa sedimentation during late palaeozoic deglaciation abstract multiple sedimentary sequences up to and over 300 m thick and comprising the late palaeozoic dwyka group in the southeastern part of the african subcontinent were deposited during deglaciation of the gondwana ice sheet attention is focused on the northern part of kwazulu natal in south africa where the dwyka group represented by glaciogenic deposits rests on an uneven surface of archaean basement rocks these deposits occur on the northwestern flank of an elongate pre dwyka crustal downwarp which had a significant influence on the mode of sedimentation as it progressively subsided stratigraphic sections from selected localities in northern kwazulu natal display the thickness variations and marked vertical and lateral lithofacies changes that characterise the dwyka group of this region diamictite consistently occurs at the base of the dwyka sequences but is also interstratified with mainly arenaceous and conglomeratic lithotypes which predominate in the upper 60 160 m these heterolithic sequences reflect sedimentation from a retreating marine ice sheet during a rise in relative sea level which commenced towards the close of the carboniferous period in southwestern gondwana as the margin of the ice sheet receded towards an archaean upland region in the northwest this ice mass was locally grounded and stabilised on bathymetric highs of the irregular basement topography release of glacial debris produced diachronous sedimentary sequences as the ice sheet was temporarily pinned on successive basement highs during its episodic retreat matrix and clast supported conglomerates and associated sandstones testify to a plexus of sediment gravity flow and subaqueous outwash processes that occurred near the grounding line thick homogeneous blanket like diamictite facies in the southeastern and southern part of the region suggest an unimpeded retreat of the sediment laden marine sheet in the deeper parts of the basin rapid dissipation of the ice in the closing stages of deglaciation was followed by accumulation of postglacial muds which mantled the glaciogenic sediments in the northernmost part of the study area proximal products of deglaciation represented by conglomeratic deposits and associated sandstones are preserved in deep partly exhumed glaciated valleys and depressions along the southern periphery of the archaean upland the distinctive character of the dwyka group in northern kwazulu natal is partly attributable to the complex tectonic setting in which it occurs and reflects an interplay of various factors that controlled the styles of sedimentation during deglaciation

decadal variations of circulation in the central mediterranean and its interactions with mesoscale gyres abstract the most prominent oceanographic features in the central mediterranean are decadal reversals of the northern ionian gyre nig interpreted in terms of internal processes altimetry data drifter data and model surface salinity products are used in this paper to define some specific features of the circulation related to the anticyclonic or cyclonic nig modes results not only highlight different shapes and intensities of the mid ionian jet and northern ionian meander among the two circulation mode but emphasize distinct behaviour within the same mode imputable to the variability of the mesoscale quasi permanent features the wind driven messina rise vortex on the western side of the northern ionian and the pelops gyre on the eastern side of the northern ionian show different behaviour during the first 1993 1996 and the second 2006 2010 anticyclonic periods related to the cyclonic activity along the dense water pathway when the dense water was of aegean origin 1993 1996 aegean anticyclone the cyclonic mesoscale activity on the eastern flank of the ionian overwhelmed the anticyclonic wind forcing and led to the disappearance of the pelops gyre when the dense water was of adriatic origin 2006 2010 adriatic anticyclone the strengthening of cyclonic mesoscale activity on the western flank of the ionian caused the shape change of the messina rise vortex favouring its longitudinal extension the zonally elongated messina rise vortex reduced the inflow of atlantic water in the northern ionian and induced a strengthening of the eastward flowing mid ionian jet in the southern ionian and cretan passage from these results it emerges that the interannual variability of the wind driven quasi permanent mesoscale gyres in the ionian is influenced by internal forcing location of the deep water formation site aegean or adriatic sea in turn related to the major local climatic shift occurred in the last decades the eastern mediterranean transient we show that the interplay between decadal and interannual variability or rather between basin wide and mesoscale circulation affected the intrinsic characteristics of the nig reversals

on the transfer function between surface fields and the geostrophic stream function in the mediterranean sea abstractthe real transfer function and the phase shift between sea surface height ssh and sea surface buoyancy ssb were estimated from the output of a realistic eddy resolving model of the mediterranean sea circulation the analysis of their temporal evolution unveiled the existence of a clear seasonal cycle closely related to that of the mixed layer depth the phase shifts between ssh and ssb attain their minimum for deep mixed layers which is different from zero besides the spectral slope of the transfer function at scales shorter than 100 km fluctuates between k 1 and k 2 for deep mixed layers it is close to k 1 as predicted by the surface quasigeostrophic sqg solution at longer wavelengths it is approximately constant under the different environmental conditions in all of the subbasins analyzed with the exception of the gulf of lions the capability to observe sea surface temperature sst from satellites motivated the extension of this analysis to sst and ssh results showed a similar q

late wisconsinan glaciomarine deposition and isostatic rebound northern puget lowland washington the distribution and age of glaciomarine and marine sediment in the northern puget lowland washington demonstrate that rapidretreatofcontinentalice theeverson marineincursion andhighratesofisostatic reboundoccurredbetweenabout13 600and 11 300 14 c yr b p 11 3 ka glaciomarine and marine deposits are thickest in zones where retreating ice lobes grounded in the northeast puget lowland and near large drainages glaciomarine sediment was depositedmainlyfrom 1 submarineoutwash in ice proximal zones 2 turbid underflows dispersed melt water icebergs and resedimentation in transitional zones and 3 dispersedmeltwaterandcurrentsinicedistal zones marine estuarine and emergence intertidalandbeach faciesaccumulated in areas more than 10 km from ice margins particularly near major rivers molluscan and foraminiferal assemblages intheglaciomarineandmarinedepositsindicate that turbid cool brackish water covered much of the puget lowland during the everson interval water was generally shallower 30 m in the southern part of the area and deeper 15 60 m to the north mineralogy and geochemical properties such as boron or sodium content of the gravel free fraction do not clearly distinguish glaciomarine and marine deposits from terrestrial deposits isostatic rebound rapidly lifted the glaciomarine and marine deposits through sea level between about 13 5 and 11 3 ka the presentaltitudesofradiocarbon datedshell and the marine limit show that initial rates of isostatic rebound exceeded 10 cm yr 21 in thenorthernpugetlowland butdroppedto 2cmyr 21 before 11 ka the uplift gradient is about 0 6 m km 21 to the north and steepens locally to at least 1 3 m km 21 the pattern of emergence in the northern puget lowland is anomalous locally perhaps as a result of complex isostatic effects near the glacier margin rapid rise of sea level or tectonic deformation

gravity and magnetic study of the crustal structure of the san francisco volcanic field arizona usa abstract bouguer gravity residual aeromagnetic high and strike passed filtered gravity and magnetic anomaly maps are analyzed to model the general crustal structure of the san francisco volcanic field in northern arizona analysis of these maps indicate that the sources of the gravity and magnetic anomalies reflect predominately precambrian tectonic cenozoic volcanic and possibly laramide age cretaceous tertiary tectonic events northeast and north trending gravity and magnetic maxima and minima are thought to be caused by precambrian metavolcanics and granites intruded along regional fault systems although the gravity minima may be caused by laramide age igneous intrusions known to exist southwest of the study area a strike pass filtered gravity anomaly map and seismic tomographic models roughly delineate the lateral extent of a high density velocity zone which may represent the crystallized source material of the san francisco volcanic field two gravity and magnetic models constrained by magnetotelluric models seismic tomographic models petrologic studies and geologic mapping indicate that surficial volcanic material of up to 1 5 km in thickness overlie a silicic intermediate body which may be the part of the san francisco volcanic field source this body is approximately 3 km below the earth s surface and extends to 8 km with a width of 15 km below this now crystallized body is a low density zone extending to 34 km which is interpreted as a partially melted zone and may ultimately be the source of the volcanic field

evolution of dynamics in the eastern mediterranean affecting water mass structures and properties in the ionian and adriatic seas 1 basin wide hydrographic observations performed in the eastern mediterranean during the past 2 decades attest changes in the thermohaline circulation as well as new aspects concerning the onset and the follow up of the major transient event that occurred at the beginning of the 1990s i e the change of the dense water formation site from the adriatic to the aegean sea since 1999 the upper thermohaline circulation has indicated the restoring of the opposite flows of the atlantic water and the levantine intermediate water which were greatly reduced in the period 1987 1995 in the deep layer the comparison between water mass structures observed in 1995 during the mature status of the transient and those observed in 1999 shows a damping of the event and a regained role of the adriatic sea as a primary source of dense waters separate calculations of the salt content in the ionian and in the levantine seas show an overall salt redistribution during 1987 1995 a salt loss of about 25 1012 kg was computed for the upper 800 m constituting only 27 of the salt gain in the deep layer over most of the eastern mediterranean on the contrary during 1995 1999 the restored upper thermohaline circulation caused a salt redistribution between the two basins of about the same amount but in the opposite sense while an extra quantity of 12 1012 kg was deposited in the deep layer in addition calculations of the salt concentration in the convection region of the southern adriatic reveal a remarkable amount of the salt not yet totally transferred into the deep layers by its interior dynamics because of mild winters

microstructures within a modern debris flow deposit derived from quaternary glacial diamicton a comparative micromorphological study abstract examination of a modern debris flow in comparison with a quaternary diamicton from which it has been derived reveals significant differentiating sedimentological characteristics the two sediments were examined using micromorphological analyses thin sections of the debris flow show distinct primary microstructure sets that appear indicative of debris flow processes of turbate micro deformation during flow and subsequent flow deceleration comparison of the micromorphological character of both sediments reveal many similarities but the differences seem indicative of flow processes within the active debris flow large turbate structures are common within the debris flow sediment and although many more turbate structures occur within the in situ diamicton they are smaller in size possibly indicative that those structures within the debris flow sediment are not inherited but are neo formed perhaps the most distinctive and individual characteristic separating the debris flow sediment from the older diamicton is the presence of tiled structures these structures result from downslope flow deceleration and dewatering resulting in transverse bands of clays developing in rhythmic like patterns likewise the debris flow sediment exhibits a marbled appearance presumably indicative of intense deformation a characteristic not found in the in situ quaternary diamicton

the mid mediterranean jet artefact 1 the mid mediterranean jet has been considered to be since the 1990s a more or less continuous surface current meandering across most of the eastern basin of the mediterranean sea generating a series of eddies this relatively recent view of the current which was not found in earlier circulation diagrams and does not have any theoretical support emerges more or less from simple statistics applied to any kind of in situ data here we use a relatively large set of surface drifter trajectories which provide reasonable sampling of the area of interest to show how mesoscale anticyclonic eddies generated elsewhere with specific diameters locations and displacements can provide a misleading picture by suggesting the occurrence of a mid basin jet which is actually nothing more than a data analysis artefact

satellite images of upwellings and cold filament dynamics as transient effects of violent air sea interactions downstream from the island of sardinia western mediterranean sea a systematic analysis of thermal satellite images of upwellings and cold filament dynamics downstream from the island of sardinia western mediterranean sea covering the years 1984 1985 1989 1990 1993 and 1994 is discussed for this sea the main transient atmospheric forcing comes from bursts of the mistral a north western wind which downstream from sardinia affects a rather calm basin the tyrrhenian sea in early summer particularly clear effects of atmospheric forcings such as gyres upwellings and cold filaments can be observed our analysis provides not only a systematic insight into these phenomena but also some experimental evidence of a novel mechanism of cold filament formation and evolution indeed in july 1989 a nice set of satellite images shows a cold filament rooted to the shallowest part of the wide shelf off olbia which meanders offshore for a few days under the effect of the mistral and of the general circulation it is of interest to underline how stably the filament is rooted to the shelf so that in only one image it appears as an elongated straight segment also the filament s potential vorticity is discussed in order to gain some insight into shelf water fluxes detachment depths and velocities relative to such phenomena

a systematic classification of glacial and periglacial environments facies and deposits abstract several aspects of the deposits formed in the glacial and periglacial environments are presented in order to establish a framework that can be used in various disciplines dealing with sedimentation under glacial and periglacial conditions the almost unlimited number of different deposits are grouped into 37 types that are all described briefly most of them are also illustrated by field examples mainly from poland these 37 types are grouped within 23 facies belonging to 3 continental glacial 3 continental periglacial and 3 marine periglacial subenvironments all environments subenvironments facies and deposits are defined and presented with a hierarchic code that enables unambiguous definition attention is paid to both the general characteristics of the various deposits as they have been described by previous investigators and to specific deposits that have been studied by the present authors the factors influencing peri glacial sedimentation are discussed briefly

a new hypothesis about the surface circulation in the eastern basin of the mediterranean sea abstract in time the circulation of the atlantic water aw in the eastern basin of the mediterranean sea has been described differently according to two major representations the historical one which began with the scheme from nielsen in 1912 and has been refined up to the 1980s favours a counterclockwise circulation in the whole basin with aw flowing in its southern part as a broad flow off libya and egypt from the ionian to the levantine subbasins then continuing along middle east and turkey before flowing back westwards the more recent one issued in the 1990s favours a clockwise circulation in the northern part of the ionian continuing offshore across the basin from the cretan to the central part of the levantine as the so called mid mediterranean jet this jet is depicted then as splitting both clockwise in the southeastern part of the basin and counterclockwise off turkey where this representation agrees with the former because the recent representation cannot be considered as a refinement of the historical ones we have been interested in understanding why a given data set available to everybody is interpreted in such different ways in the algerian subbasin the combined use of satellite infrared images and a significant amount of in situ data sets hydrology and both eulerian and lagrangian current measurements allowed us to solve a similar controversy therefore we examined the circulation features in the eastern basin undertaking the detailed analysis of 1000 daily and weekly composite images spanning the period 1996 2000 and of monthly composite images available since 1985 whenever in situ observations were available we have confronted them with the satellite thermal signatures and have shown that both are consistent this paper focuses on the overall basin scale results while the detailed ones are published in an other paper the new scheme we propose is basically a refined version of the historical ones the circulation of aw is counterclockwise in the whole eastern basin but it is more constrained alongslope than previously thought and the broadening historically schematised appears to be due to intense mesoscale eddies mainly generated by the instability of this circulation

sedimentation in a subglacial lake enniskerry eastern ireland abstract field relationships between a subglacial lake fill from the enniskerry basin eastern ireland provide evidence for dynamic links between the sedimentary fill regional subglacial meltwater flow and regional ice dynamics the basin fill 6 7 km2 forms an integral part of an extensive 30 km subglacial meltwater system which developed parallel to north south ice flow along the western marginal sector of the late pleistocene irish sea glacier high magnitude sediment fluxes were directed into the subglacial lake southwards across the northern basin rim from two nye type channels and westwards by a rothlisberger type channel the resulting subaqueous fans typically consist of cones of coarse boulder gravels deposited by jet effluxes overlain by cross bedded sands and foreset gravels in places these are eroded and overlain by multistorey dish shaped channels cut and filled by subglacial meltwaters driven by a high hydrostatic head a variety of gravelly and sandy bedforms indicate that sediment migrated over efflux cores towards deeper parts of the basin facies variability within the ice proximal fans and spreads record deposition from a wide range of high and low density turbulent flows traction currents density underflows suspension and sediment gravity flows a surficial drape of winnowed diamict is related to areal resedimentation as jet effluxes closed down at one site the gravelly sequence shows a largely conformable transition upwards into glaciotectonised gravel and basal till in the lee of the basin rim elsewhere the upper part of the sediment pile is occasionally deformed by the drag of the ice roof a series of sequential events is postulated for the evolution of the subglacial drainage system and subglacial lake development initially a rock ridge transverse to ice flow resulted in the development of a relatively low pressure lee zone along the northern margin of the basin ice sheet decoupling within the basin was enhanced by water migration into this low pressure lee zone which also melted an ice roof cavity closure and maintenance of the ice roof was prevented by a fast ice flux generated by intense marine downdraw in the main ice lobe centred in the irish sea basin regional ice directed meltwater pressure gradients and erosion enhanced subglacial lake development in the lowest topographic point of the system major inlet and outlet nye type channels incised transverse to the rims of the basin testify to the intensity of ice directed drainage along the marginal sector of the irish sea glacier in a wider context the concepts of high magnitude subglacial meltwater flow coupled with high rates of debris flux invoked for the subglacial basin fill are also necessary to explain the thick tidewater sequences present in adjacent sectors of the irish sea basin

mediterranean sea large scale low frequency ocean variability and water mass formation rates from 1987 to 2007 a retrospective analysis abstract we describe a synthesis of the mediterranean sea circulation structure and dynamics from a 23 year long reanalysis of the ocean circulation carried out by adani et al 2011 this mesoscale permitting dynamical reconstruction of past ocean variability in the mediterranean sea allows the study of the time mean circulation and its low frequency decadal components it is found that the time mean circulation is composed of boundary and open ocean intensified jets at the border of cyclonic and anticyclonic gyres the large scale basin circulation is generally characterized in the northern regions by cyclonic gyres and in its southern parts by anticyclonic gyres and eddy dominated flow fields with the exception of the tyrrhenian and the northern ionian sea the time mean tyrrhenian sea circulation is dominated by cyclonic gyres of different intensity and intermittency the northern ionian sea circulation however reverses in sign in two ten year periods the first in 1987 1996 and the second in 1997 2006 which is here called the northern ionian reversal phenomenon this reversal is provoked by the excursion of the atlantic ionian stream from the middle to the northern parts of the basin the decadal variability of other parts of the basin is characterized by changes in strength of the basin scale structures the water mass formation rates and variability are dominated by event like periods where the intermediate and deep waters are formed for 2 3 years at higher rates the largest deep water formation events of the past 23 years occurred separately in the western and eastern mediterranean basin the first coincided with the eastern mediterranean transient roether et al 1996 and the second with the western mediterranean deep water formation event in 2005 2006 smith et al 2008 a new schematic of the basin scale circulation is formulated and commented

aegean surface circulation from a satellite tracked drifter array a pilot experiment using an array of 45 drifters to explore the circulation in the north and central aegean sea is described the global positioning system drifters with holey sock drogues provide positions every hour with data recovery through the argos system the drifters were launched in four separate deployments over a 1 yr period the resulting trajectories confirm the existence of a current around the rim of the basin consistent with a buoyancy plume created by the outflow of black sea waters through the dardanelles strait of canakkale in turkish the degree to which this is augmented by an ekman response to the dominant northerly winds is not obvious in the dataset owing to mesoscale dynamics that obscure the existence of any westward ekman flow the mesoscale eddy field involves anticylonic eddies in the current around the rim of the basin consistent with eddies with low salinity water cores cyclones are also seen with the most prominent forming over deep regions in the basin topography the array also documents the interaction of the currents with the straits through the sporades and cyclades island groups these interactions are complicated by the nature of the mesoscale flow and in some trajectories suggest a bernouilli acceleration in straits in others the flow through the island groups appears to be more diffusive and involves deceleration and eddy motions the rapid sampling by the drifters reveals an extremely nonlinear submesoscale eddy field in the basin with length scales less than 4 km and rossby numbers of order 1 a better understanding of the dynamics of these features is of importance for understanding the circulation of the basin

dense intermediate water outflow from the cretan sea a salinity driven recurrent phenomenon connected to thermohaline circulation changes data collected from different platforms in the cretan sea during the 2000s decade present evidence of gradually increasing salinity in the intermediate and deep intermediate layers after the middle of the decade the observed gradual salt transport toward the deeper layers indicates contributions of dense water masses formed in various aegean sea subbasins the accumulation of these saline and dense water masses in the cretan sea finally led to outflow from both cretan straits with density greater than typical levantine cretan intermediate water but not dense enough to penetrate into the deep layers of the eastern mediterranean we name this outflowing water mass as dense cretan intermediate water dciw a retrospective analysis of in situ data and literature references during the last four decades shows that similar events have occurred in the past in two occasions a in the 1970s and b during the eastern mediterranean transient emt onset 1987 1991 we argue that these salinity driven aegean outflows are mostly attributed to recurrent changes of the eastern mediterranean upper thermohaline circulation that create favorable dense water formation conditions in the aegean sea through salinity preconditioning we identify these phenomena as emt like events and argue that in these cases internal thermohaline mechanisms dominate over atmospheric forcing in dense water production however intense atmospheric forcing over an already salinity preconditioned basin is indispensable for creating massive deep water outflow from the cretan sea such as the emt event

on the relationship between the decadal oscillations of the northern ionian sea and the salinity distributions in the eastern mediterranean 1 we study the impact of decadal inversions of the ionian upper layer circulation denominated as adriatic ionian bimodal oscillation system on thermohaline properties of the levantine and cretan seas lagrangian drifter data and surface geostrophic currents show that the atlantic water aw flow is well organized and most intense when the ionian circulation is cyclonic during the ionian anticyclonic phase the aw spreading pathway is the longest contributing to its prolonged mixing and higher salinity once it reaches the levantine thus the levantine basin is subject to less dilution by aw during the anticyclonic surface circulation phase empirical orthogonal function analysis of the sea level shows a large amplitude circular feature in the northern ionian which matches the cyclonic anticyclonic gyre obtained from lagrangian measurements furthermore it reveals the out of phase variability of the north ionian gyre and the aegean and levantine sea levels we further show that the surface salinity of the levantine basin variation is out of phase with that of the ionian surface layers salinity variations of the deepwater column in the aegean are out of phase with the ionian surface salinity values owing probably to a fast transfer of the surface salinity changes via winter deep convection the changing of the levantine and cretan seas salinity parallel to the ionian circulation inversions suggests that the preconditioning for the eastern mediterranean transient emt is driven by internal processes as the ionian inversions are cyclical events we conclude that the emt is not an isolated episode but potentially a recurrent phenomenon

recent progress in the application of satellite altimetry to observing the mesoscale variability and general circulation of the oceans recent progress in the application of satellite altimetry from seasat and geos 3 to the observation of the oceanic mesoscale variability and general circulation is reviewed the lack of accurate geoid models has been the major obstacle in the study of the general ocean circulation from altimetry the use of geoid independent methods that utilize the temporal differences in altimetric measurements taken at fixed locations however has made significant contributions to our knowledge of the mesoscale variability of the ocean the mesoscale energies of the sea surface height and geostrophic current have been mapped on a global basis their distributions in wave number space have also been analyzed because of many of the deficiencies of existing altimeter data short duration inadequate orbit poor accuracy etc most of these results describe only a small portion of the frequency wave number spectrum of the variability but they have nonetheless demonstrated the great value of an optimally designed altimetric mission in advancing our knowledge of the global mesoscale variability the current technology allows satellite altimetry to detect oceanic variability at periods from a few days to 3 5 years and wavelengths from 50 to 10 000 km determining the time averaged general ocean circulation from altimetry is more problematic because an accurate geoid is indispensable the currently available global geoid models have useful accuracies only at wavelengths greater than about 7000 km there have been several attempts at mapping the global ocean circulation at those scales using existing altimeter data and geoids when these results are compared with hydrographic surveys some qualitative agreement can be observed but the quantitative differences are mostly inconclusive because of the geoid and orbit errors it has been suggested however that an altimetric mission that is optimally designed with the current technology when complemented by a state of the art gravimetric mission to map the earth s gravity field is able to determine the ocean circulation quantitatively at scales from the ocean basin to about 200 km

the new esa satellite only gravity field model via the direct approach 1 reprocessed gravity field and steady state ocean circulation explorer goce gravity gradient data were combined with data from laser geodynamics satellite lageos 1 2 and gravity recovery and climate experiment grace to generate a satellite only gravity field model to degree 260 using the direct approach named dir r4 when compared to earth gravitational model 2008 egm2008 it is more accurate at low to medium resolution thanks to goce and grace data when compared to earlier releases of esa goce models it is more accurate at high degrees owing to the larger amount of data ingested it is also slightly more accurate than esa s fourth release of the time wise model tim r4 as demonstrated by gps leveling orbit determination tests and an oceanographic evaluation according to the formal probably too optimistic by a factor of 2 2 5 cumulated geoid 1 3 cm and gravity anomaly 0 4 mgal errors at 100 km resolution the goce mission objectives have been reached

high frequency response of wind driven currents measured by drifting buoys and altimetry over the world ocean 1 we investigate the wind driven current response over the world ocean using svp drifting buoys ers 1 and ers 2 and topex altimetry data and ecmwf wind stress fields wind driven ageostrophic currents are estimated from drifting buoys by removing altimetry deduced geostrophic currents from observed drifting velocities removing the geostrophic signal enhances the coherence with wind stress at periods longer than 10 days for superinertial periods lower than 20 days a two parameter i e angle and amplitude model is fitted to the isolated ageostrophic signal to study the upper ocean response to surface wind stress in that frequency band the model which can explain up to 30 of the variance in some areas indicates that the currents spiral to the right left of the wind with depth in the northern southern hemisphere in agreement with the ekman theory the absolute value of the angle parameter is found to exhibit significant spatial and seasonal variability the vertical eddy viscosity and the ekman layer depth as deduced from ekman theory are compared to previous results their seasonal variability is also studied model results are then used to compute the mean and standard deviation of ageostrophic currents in 5 boxes over the world ocean the equatorial divergence and the subpolar and subtropical convergence zones are well reproduced

lagrangian and eulerian observations of the surface circulation in the tyrrhenian sea 1 this paper focuses on the study of the tyrrhenian sea a subbasin of the western mediterranean whose surface and near surface dynamics are still relatively poorly known in particular its southern region its circulation is described first by a set of 53 surface drifters deployed in the area between december 2001 and february 2004 in order to supplement the drifter data with continuously and uniformly sampled observations and to characterize the seasonal as well as higher frequency variability of the surface circulation the lagrangian analysis was associated to simultaneous satellite remotely sensed altimeter covering the period 2001 2004 the investigation was based on trajectory analysis and on the computation of the pseudo eulerian statistics using the same binning and space time averaging for drifter and altimeter data the data reveal a complex pattern of the circulation especially in the southern region of the tyrrhenian dominated by semipermanent recirculations and transient features which sometimes makes it difficult to identify a consistent mean flow while the northern subbasin is characterized by a pair composed of cyclonic and anticyclonic circulations known in the literature as the north tyrrhenian cyclone and north tyrrhenian anticyclone the pseudo eulerian statistics computed with the two data sets evidenced the representativeness of a joint analysis of altimeter and drifter data and yielded useful indications about proper preliminary preprocessing and resampling procedures so as to make the comparison statistically sound

multiple flow and support mechanisms and the development of inverse grading in a subaquatic glacigenic debris flow subaquatic glacigenic debris flows of late wisconsinan age occur as lobes within an ice marginal glaciomarine lithofacies at victoria british columbia flow was initiated by release of supraglacial debris during an interval of glacial ablation prior to advance and deposition of lodgement till many of the lobes developed a common morphology during deposition consisting of an outer layer surrounding an inner core of rafted material in the largest lobe reworking of the sediment during flow produced improved sorting a coarsening of mean grain size and a shift in skewness toward the negative this occurred simultaneously within the core and outer layer as a result of different transformations in mechanisms of flow and support normal grading produced in the outer layer was conveyed around the nose and buried in an inverse position along the base of the flow these data enable us to present a model that may be applicable to similar flows elsewhere the flow studied demonstrates that transformations between flow types and sediment support mechanisms can occur simultaneously and serially in subaquatic debris flows

late quaternary stratigraphy and seafloor geology of eastern juan de fuca strait british columbia and washington abstract a combination of shallow sediment cores and high resolution seismic reflection data were used to identify and map four main surficial geologic units in eastern juan de fuca strait these units comprise bedrock unit 1 till diamict unit 2 glacial marine unit 3 and post glacial sediments unit 4 bedrock crops out only in nearshore environments off vancouver island diamicton forms the numerous morainal and drumlin like banks in the region a series of banks including middle and hein banks and the offshore extension of dungeness spit divide the strait into two major areas based on the dominant surficial sedimentary units post glacial sediments are most common to the east and glacial marine sediments to the west glacial marine sediments are represented by several seismo lithologic subunits that suggest progression from ice proximal to ice distal depositional environments radiocarbon dates indicate these sediments are a product of the last phase of glacier retreat there is relatively little modern sediment input to eastern juan de fuca strait so most post glacial sediments are thought to consist of material reworked from glacial outwash or eroded from shallow bank deposits this conclusion is supported by radiocarbon ages from the post glacial sediments most of which are early holocene or younger also there are sandwave fields sediment drifts and barrier spits that appear to be actively maintained the source of sediment to these features is probably the pre existing deposits that occur in banks and extensive coastal exposures

sediment characteristics and sea level history of royal roads anchorage victoria british columbia high resolution and airgun seismic reflection mapping of the approaches to esquimalt harbour juan de fuca strait reveal that offshore sea floor sediments consist of a widespread glaciomarine unit recognizable to the entrance of the strait the upper part of the unit has been dated at approximately 10 000 radiocarbon years bp an early postglacial sea level low of at least 50 m appears to have formed a widespread unconformity nearshore sediments above the unconformity consist of sands muddy fine sands and minor gravel that were deposited in a prograding marine environment sediments have been accumulating off esquimalt harbour at a rate of approximately 1 9 cm per 100 years

eddy properties in the western mediterranean sea from satellite altimetry and a numerical simulation three different eddy detection and tracking methods are applied to the outputs of a high resolution simulation in the western mediterranean sea in order to extract mesoscale eddy characteristics the results are compared with the same eddy statistics derived from satellite altimetry maps over the same period eddy radii are around 30 km in altimetry maps whereas in the model they are around 20 km this is probably due to the inability of altimetry maps to resolve the smaller mesoscale in the region about 30 eddies are detected per day in the basin with a very heterogeneous spatial distribution and relatively short lifespans median life around 13 days unlike other areas of the open ocean they do not have a preferred direction of propagation but appear to be advected by mean currents the number of detected eddies seems to present an annual cycle when separated according to their lifespan with the numerical simulation we show that anticyclones extend deeper in the water column and have a more conic shape than cyclones

scales and variability of the sea surface temperature distribution in the adriatic sea 1 scales and variability of the adriatic sea surface temperature sst distribution in the period january 1991 to december 2000 are studied by means of 8 day composite 4 km resolution sst data scales of the sst are defined as scales of the sst autocorrelation function assuming an exponential correlation model scales of the sst are quantified as e folding times and distances of the sst autocorrelation function variability in the sst is analyzed through empirical orthogonal function eof analysis from summer to winter spatial scales of the sst in the along basin direction remain unchanged while in the across basin direction they decrease resulting in scales that are slightly shorter 10 15 in winter than in summer the spatial distribution of temporal scales displays two patterns the first characterized by low values is located in the northern part of the basin and along the italian coast and the second characterized by high values covers the rest of the basin the sst variability is dominated by the annual signal which explains 45 of the overall variance the main structures of the adriatic circulation leave their signature on the first three eofs whose spatial variability occurs on wavelengths longer than 200 km in the along basin direction and in the across basin direction in the band 25 50 km and at 80 and 100 km eof coefficients are characterized by oscillating components with periods of 20 days to 6 months

multiscale variability in the balearic sea an altimetric perspective 1 the present day availability of an 18 year record of 1 8 merged mediterranean sea sea level anomaly sla data enables a contemporary description of long term mesoscale activity in the balearic sea sla data from satellite altimetry are used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales within this complex and relatively understudied region in the western mediterranean wmed we find that the mean northern current along the iberian slope is strongest in autumn although higher variability in winter leads to stronger peaks in kinetic energy the balearic current which flows along the northern slopes of the balearic islands also has its maximum expression in autumn across the two balearic channels ibiza and mallorca key locations that partly regulate meridional exchange in the wmed observed seasonal variability in geostrophic velocity anomalies conforms rather well to prior descriptions suggesting cautious confidence in the use of the mediterranean merged altimeter product in nearshore regions circulation through the channels is maximum in winter the channel data support the hypothesis that the channel circulation may be hindered by the intermittent presence of the western intermediate water mass which sometimes forms in winter in the gulf of lions this is the first time that an analysis of variability in the balearic channels has been performed using altimetric data

nature and classification of waterlain glaciogenic sediments exemplified by pleistocene late paleozoic and late precambrian deposits this study of waterlain glaciogenic sediments is designed to present both a review and new information on glaciogenic subaquatic deposits of differing age in a number of localities in north and south america and south africa the late paleozoic glaciogenic deposits of the parana basin in brazil and the karoo basin of south africa are singled out for special attention as they show a reasonably complete lateral sequence of terrestrial to off shore glaciogenic sedimentation although the environment of subaquatic glaciogenic sedimentation varies from one area to the next certain common elements are found which can be used to develop a generalized model for both glaciomarine and glaciolacustrine sedimentation for descriptive purposes the model is divided into two broad categories a shelf facies and a basinal facies the shelf facies is marked by massive diamicton ite which may be 200 m or more in thickness and which is frequently overlain by a complex of clastic sediments consisting primarily of gravity and fluid flows the basinal facies is marked by products of subaquatic slumps and more distal turbidites and glaciomarine sediments new terminology is introduced the massive diamicton ite which is diagnostic of the shelf facies probably represents deposition from the base of active ice in a subaquatic environment and is termed undermelt diamicton ite the gravity and fluid flows which are usually found overlying undermelt diamicton ite and in the basinal facies are subdivided into six categories glaciogenic subaquatic outwash glaciogenic suspension flow glaciogenic chaotic debris flow glaciogenic subaquatic debris flow glaciogenic slurry flow and glaciogenic turbidity flow the relative abundance of undermelt diamicton ite and the various types of gravity and fluid flows can be used to define inner shelf outer shelf inner basin and outer basin facies of glaciomarine sedimentation

submarine flow tills at victoria british columbia sea cliffs at victoria expose submarine flow tills within an ice contact complex of flow till outwash proglacial cones interbedded with dinoflagellate bearing glaciomarine fine sediments glacial debris flow lobes mainly flow tills were formed by supraglacially englacially and basally transported sediment slumping off an ice margin grounded in the strait of juan de fuca the structures and textures reveal that lobes formed by a conveyor mechanism in some lobes a double sorting phenomenon apparently developed involving an outer winnowed layer of pseudo plastic flow around an inner core of till that was sorted by dewatering and expulsion of fines outward from the centre during flow structures and fabric data indicate lobe travel was gravitationally controlled down cone flanks and independent of ice movement a depositional model for the complex proposes the ice margin produced a proglacial apron of interdigitating cones which accumulated on the sea floor sediment facies variations were probably c

a synthesis of the ionian sea hydrography circulation and water mass pathways during poem phase i abstract in this paper we revisit with a thorough in depth analysis the dataset collected in the hydrographic surveys of the international collaborative programme poem physical oceanography of the eastern mediterranean in the period 1986 1987 the work has two major objectives the first is to refine the dynamic picture of the ionian upper thermocline sub basin scale circulation rather less definitive than the dynamic picture of the levantine sea circulation the second is to identify the pathways of the major water masses of the basin not only in the near surface but also in the intermediate and deep layers to our knowledge this is the first work defining the pathways of the levantine intermediate water liw and of the adriatic deep water adw eastern mediterranean deep water emdw that characterize the intermediate and deep circulations the major novel results can be summarized as follows in the upper thermocline 1 the atlantic ionian stream ais jet entering the sicily straits bifurcates into two main branches at 37 n 17 e it advects the modified atlantic water maw into the ionian sea interior the first branch turning directly southward encloses an overall anticyclonic area comprising multiple centers around which the maw is advected 2 the second ais branch extends further into the northeastern ionian where it too turns southward before crossing the entire ionian sea meridionally advecting maw on its left side and ionian surface water isw on its right this branch of the jet is confined to the ionian margin and does not pass around the pelops gyre 3 a new water mass the lsw is formed in the levantine basin and enters the cretan passage then is first veered cyclonically south of crete by the cretan gyre and successively is entrained anticyclonically around the pelops gyre and then enters the aegean sea 4 a permanent cyclone located in the northeastern ionian determines the pathway of mixed adriatic surface water ionian surface water asw isw 5 a permanent cyclone is found in all the surveys near the tip of the italian boot this novel analysis of the liw pathways shows that 1 the major source of intermediate liw during the period 1986 1987 was actually in the levantine sea liw formed there entered the cretan passage was veered cyclonically by the cretan gyre south of crete and then entered the southern ionian sea the major liw pathway was westward directly to the sicilian straits 2 secondary important liw pathways were determined by the interior structures the strong pelops anticyclone was entraining liw around its periphery and was determining the liw northward pathway that closely followed the eastern greek coastline it was along this pathway that liw entered the otranto strait a further branch of liw was entrained and recirculated around the multiple ionian anticyclones ia of the western ionian sea 3 the cretan cyclone is a feature confined to the upper thermocline intermediate layer it disappears at 400 dbar while the pelops anticyclone is strongly barotropic below the upper 100 dbar and penetrates quite intense down to 800 dbar 4 a further completely novel result concerns the new water mass found in the deep layer that spreads on the 29 15 kg m3 isopycnal surface this water mass characterized by high salinity and high oxygen content is formed inside the aegean sea and is observed to spread out all around the cretan arc straits the final fully novel result is the demonstration of a second pathway for the adw exiting from the otranto strait that is transformed into emdw and occupies the abyssal layers of the ionian sea interior the traditional pathway for emdw is along the isobaths along the western side of italy but adw was observed to be exiting from the otranto strait in the eastern hellenic trench at 39 5 n both during poem on86 and poem as87 this second pathway for emdw follows isobath contours along the western side of greece the two emdw routes converge and merge between 36 n and 35 n so producing a deep layer of emdw that occupies uniformly the abyssal plain of the interior of the ionian sea

spreading of levantine intermediate waters by submesoscale coherent vortices in the northwestern mediterranean sea as observed with gliders since 2007 gliders have been regularly deployed in the northwestern mediterranean sea a crucial region regarding the thermohaline circulation of the mediterranean sea it revealed for the first time very warm 10 48c and saline 10 1 submesoscale anticyclones at intermediate depth characterized by a small radius 5 km high rossby 0 3 and burger 0 7 numbers they are likely order of 10 to be formed each year have a life time order a year and certainly contribute significantly to the spreading of the levantine intermediate waters liw toward the whole subbasin thus potentially impacting wintertime vertical mixing through hydrographical and dynamical preconditioning they could be mainly formed by the combined action of turbulent mixing and flow detachment of the northward flow of liw at the northwestern headland of sardinia upwelling conditions along the western coast of sardinia associated with a southward geostrophic flow within the upper layers seem to play a key role in their formation process

glacimarine processes and inductive lithofacies modelling of ice shelf and tidewater glacier sediments based on quaternary examples abstract three variables control the type of glacial debris source and where and when debris is introduced to an ocean 1 type of glacial ice source ice sheet or valley glacier 2 condition of a grounded glacier melting freezing or frozen base and cold or warm internal ice and 3 type of glacier front ice shelf or tidewater using these variables in different combinations eight glacimarine regimes are postulated to exist by integrating information from holocene sediment and pleistocene glacimarine sequences with the eight inductive regimes lithofacies relationships are predicted and modelled the models show a complexity of glacimarine lithofacies the importance of recognizing this complexity lies in realistic interpretations of ancient sequences ice shelf sediment may be limited in the geologic record because of tectonic and climatic constraints required for ice shelf formation alternatively in some tidewater glacier regimes larger volumes of glacimarine sediment are produced than in ice shelf regimes ice proximal sediment is distinctive especially near subglacial meltwater stream effluxes ice shelves and tidewater glaciers may produce similar ice proximal lithofacies e g morainal bank associations and laminites in certain regimes however details of lithofacies may aid in distinguishing ice shelf from tidewater regimes ice shelf and tidewater iceberg zone sediment can be distinguished from each other if basal and high level englacial debris can be distinguished ice shelf zone sediment out from the grounding line has a basal debris source high level englacial debris is deposited in more distal ice shelf zones resulting in sediment by pass in corresponding positions of a tidewater glacier regime iceberg rafted debris comprises mixed basal and high level englacial debris deeper water zones receive large volumes of sediment when a melting freezing base grounding line is at the edge of a continental shelf when the grounding line retreats sediment supply may be drastically reduced because of a back sloping continental shelf and trapping by morainal banks cool water bioclastic carbonates may accumulate once a grounding line has retreated although ice shelf iceberg zones are more extensive than those in tidewater regimes ice shelf icebergs have low debris content and resulting ice rafted debris may be scarce the smallest volume of sediment is produced by a frozen base ice sheet ending as a tidewater front and the largest volume by a melting freezing base valley tidewater glacier glacimarine sediment has a relatively high preservation potential near continental interiors or margins however at continental margins mass flow olistostrome and tectonic melange deposits may be preserved with glacimarine diamictites these deposits may be difficult to distinguish from each other especially if metamorphosed such as at a convergent margin the models presented do not fully represent the glacimarine environment because many other variables are omitted however the principal concepts of generating glacimarine lithofacies associations are considered continued research will verify if each regime exists and will provide data on those regimes that exist today to compare and modify these models

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

terrestrial or waterlain glacial diamictites three case studies from the late precambrian and late ordovician glacial drifts in west africa abstract three examples of extensive diamictites within glacial sequences well exposed in the sedimentary cover of the west african cratonic platform are described they belong to the late precambrian and upper ordovician glacial periods and the paleogeography is summarized the late precambrian diamictites of the jbeliat group in adrar of mauritania displays characteristics of tillite deposited as lodgement or melt out till detail studies on structure clast shape nature and fabric texture in thin section clay mineralogy and carbonate content are given and discussed in order to delimitate useful criteria for tillite identification compared to this first example the two other diamictites from the late precambrian bakoye group in western mali and from the upper ordovician tichit group in southeastern mauritania have obviously been deposited in an aquatic environment waterlain glacial diamictites by the action of ice rafting bottom current and flow processes these examples show that for such ancient deposits sedimentological interpretations are partly solved by broad scale stratigraphical relationships however detailed sedimentological analyses remain essential for precise facies identification especially structural and petrographic studies must be encouraged in the lights of modern glaciodynamic processes

transient eastern mediterranean deep waters in response to the massive dense water output of the aegean sea in the 1990s abstract we present a detailed account of the changing hydrography and the large scale circulation of the deep waters of the eastern mediterranean emed that resulted from the unique high volume influx of dense waters from the aegean sea during the 1990s and of the changes within the aegean that initiated the event the so called eastern mediterranean transient emt the analysis uses repeated hydrographic and transient tracer surveys of the emed in 1987 1991 1995 1999 and 2001 2002 hydrographic time series in the southern aegean and southern adriatic seas and further scattered data aegean outflow averaged nearly 3 10 6 m 3 s 1 between mid 1992 and late 1994 and was largest during 1993 when south and west of crete aegean influenced deep waters extended upwards to 400 m depth emt related aegean outflow prior to 1992 confined to the region around crete and to 1800 m depth wise amounted to about 3 of the total outflow outflow after 1994 up to 2001 2002 derived from the increasing inventory of the tracer cfc 12 contributed 20 to the total of 2 8 10 14 m 3 densities in the southern aegean sea deep waters rose by 0 2 kg m 3 between 1987 and 1993 and decreased more slowly thereafter the aegean waters delivered via the principal exit pathway in kasos strait east of crete propagated westward along the cretan slope such that in 1995 the highest densities were observed in the hellenic trench west of crete aegean influenced waters also crossed the east mediterranean ridge south of crete and from there expanded eastward into the southeastern levantine sea transfer into the ionian mostly followed the hellenic trench largely up to the trench s northern end at about 37 n from there the waters spread further west while mixing with the resident waters additional transfer occurred through the herodotus trough in the south levantine waters after 1994 consistently showed temperature salinity t s inversions in roughly 1000 1700 m depth with amplitudes decreasing in time the t s distributions in the ionian sea were more diverse one cause being added aegean outflow of relatively lower density through the antikithira strait west of crete spreading of the aegean influenced waters was quite swift such that by early 1995 the entire emed was affected and strong mixing is indicated by near linear t s relationships observed in various places referenced to 2000 and 3000 dbar the highest aegean generated densities observed during the event equaled those generated by adriatic sea outflow in the northern ionian sea prior to the emt a precarious balance between the two dense water source areas is thus indicated a feedback is proposed which helped triggering the change from a dominating adriatic source to the aegean source but at the same time supported the previous long year dominance of the adriatic the emed deep waters will remain transient for decades to come

basin to mesoscale surface circulation of the western mediterranean manifested by satellite derived data products abstract in this article there is an overview of the potential of different mostly altimetry derived products for manifesting features of basin and mesoscale circulation of the western mediterranean basin in terms of detection of mesoscale eddies and larger gyres the comparison was performed between eddy statistics extracted directly from fields of sea surface temperature sst on the one hand and reconstructed from different scalar and vector altimetry derived fields on the other hand among the products being analysed there are fields of i sea level anomaly sla ii geostrophic currents and iii finite size lyapunov exponents fsle comparison of the eddy statistics provided by such different data sources revealed that altimetry based techniques tended to overestimate the number of big cyclones and thus failed to reproduce cyclonic anticyclonic eddy asymmetry which was shown by fields of sst defining the spatial scale of eddies via altimetry based techniques seemed particularly problematic fsle product analysed in the study showed significant disagreements with vortical structures observed in fields of sst both in terms of the spatial scale and the sign of rotation in order to scrutinize basin scale features of surface circulation in the region of interest fields of i geostrophic currents ii total currents reconstructed by the globcurrent project and iii surface currents provided by the reanalysis technique were analysed as a result of the comparison performed a conclusion was made on the complementarity of the datasets analysed

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

grain size variations in north atlantic non carbonate sediments and sources of terrigenous components abstract fine silt to medium sand grain size spectra of the carbonate free fractions of 115 sea bed samples from the northern north atlantic the labrador sea and baffin bay can be explained as mixtures of five distinct end members the five end members resemble combinations of grain size modes which are characteristic of till matrix dreimanis and vagners 1972 therefore the ultimate source of most of the terrigenous deep sea sediments in the study area is probably the veneer of glacial comminution products on the surrounding continents three sand rich end members exhibit patterns of distribution that are largely compatible with the modern transport of ice rafted debris as inferred from iceberg drift observations the best sorted of those sandy end members however also appears to be concentrated in regions characterized by high energy turbidity and contour currents and so may also represent hydraulically winnowed sediment the distribution of two lutite end members appears in general to reflect the transport of fines by moderate to low energy thermohaline currents although in baffin bay and the northeastern north atlantic the lutite could have accumulated primarily in turbidites ice rafting by icebergs calved from greenland glaciers the reworking of glacigenic sediments on the iceland faeroes ridge and injection of turbid glacial meltwater into deep baffin bay from west greenland fiords are suggested as the principal means of introduction of clastic particles into the sediment distribution redistribution budget of the deep north atlantic

late pleistocene glaciolacustrine sedimentation and paleogeography of southeastern michigan usa abstract the geomorphic stratigraphic and sedimentological characteristics of glaciolacustrine sediments in the metropolitan detroit michigan area were studied to determine environments of deposition and make paleogeographic reconstructions nine lithofacies were identified and paleoenvironments interpreted based on their morphostratigraphic relationships with relict landforms the sediments studied are found southeast of the defiance and birmingham moraines lying beneath a lowland characterized by a low morainal swell detroit moraine and a series of lacustrine terraces that descend progressively in elevation southeastward the glaciolacustrine sediments were deposited approximately 14 3 12 4 ka bp during the port bruce and port huron glacial phases of late wisconsinan time and are related to proglacial paleolakes maumee arkona whittlesey warren wayne grassmere lundy and rouge the glaciolacustrine section is typically 2 4 m thick and consists of a basal unit of wavy bedded clayey diamicton overlain by a surficial deposit of stratified and cross stratified sand and gravel the basal unit is comprised of subaqueous debris flow deposits that accumulated as subaqueous moraine in paleolake maumee along the retreating front of the huron lobe the surficial deposits of sand and gravel were formed by traction resulting from lacustrine wave activity and fluvial processes in lakebed plain beach ridge and deltaic depositional settings much of the lake margin sand and gravel was derived from clayey diamicton by lacustrine wave action and winnowing and that associated with paleolakes of the port huron phase is largely reworked port bruce sediment paleogeographic reconstructions show that the defiance birmingham and detroit moraines defiance and rochester channels and the rochester delta were deposited penecontemporaneously as paleolake maumee expanded northward across the map area a unique type of wavy bedform is characteristic of clayey diamicton deposited by subaqueous mass flow in the study area that is useful for differentiating sediment 1 deposited by mass flow in subaqueous vs subaerial settings and 2 deposited by subaqueous mass flow vs basal till these bedforms are a useful tool for identifying subglacial meltwater deposits and facilitate the mapping and correlation of glacial sediments based on till sheets the map area provides a continental record of ice sheet dynamics along the southern margin of the laurentide ice sheet during heinrich event h 1 the record reveals rapid glacial retreat 0 8 km yr contemporaneous with the discharge of a large volume of meltwater evidence in the study area for subglacial meltwater is problematic but indications that periglacial conditions persisted in the map area until 12 7 ka bp and extended for 200 km or more south of the ice front suggest that a frozen substrate may have contributed to instability of the lis

coeval brittle and ductile deformation beneath the late wisconsinan puget lobe washington state usa late wisconsinan glacial sediments exposed on whidbey island and camano island puget sound washington state usa were deposited in a proglacial shallow marine outwash environment during northward retreat of the puget lobe of the cordilleran ice sheet sediments mainly comprise massive and cross bedded sand and gravels and rhythmically bedded clay and silt fine sand couplets interbedded with diamictons that were deposited by a range of mass flows of different viscosities although sediment stratigraphy and ice advance retreat patterns are well established for the puget lobe brittle and ductile deformation structures within and separating these sediment units are less well understood these structures record the nature of ice bed interactions taking place in subglacial and proglacial environments this study examines evidence for these processes and environments key deformation structures identified include open to overturned folds normal and reverse faults clastic dikes and hydrofractures and passive loading structures evidence for coeval development of ductile and brittle deformation structures shows the close relationship between porewater changes sediment rheology and sediment system responses to changes in strain caused by ice bed interactions

observations of recurrent mesoscale eddies in the eastern mediterranean a mediterranean sea observation program conducted in the early 1990s by the naval oceanographic office included temperature aerial surveys the deployment of satellite tracked drifting buoys and the real time analysis of satellite infrared imagery over 4 years of weekly front and eddy analyses generated from the satellite imagery and over 100 drifting buoy trajectories were examined here for recurrent eddies in the eastern mediterranean five recurrent mesoscale eddies found in the satellite imagery remained relatively stationary with the standard deviation of the eddy center locations comparable to the mean eddy diameter three of the recurrent eddies were seeded with satellite tracked drifting buoys one buoy circulated within each of two anticyclones for several weeks allowing application of a kinematic feature model to the buoy trajectories for the extraction of propagation and circulation characteristics the ierapetra anticyclone remained southwest of the mean satellite derived center rotating slowly clockwise about 1 2 d 1 with a swirl velocity that increased linearly with distance from the center nearly to its outer edge the pelops anticyclone exhibited a slight westward propagation tendency its major axis rotated clockwise about 4 d 1 and the swirl velocity had a broad maximum well inside the eddy that was nearly independent of radius inertial waves were observed in two of the buoy trajectories with the differences in the observed inertial periods consistent with the effects of eddy circulation on near inertial waves

lago mare and the messinian salinity crisis evidence from the alboran sea s spain this paper provides a new environmental sedimentological and stratigraphic context of the lago mare deposits from the north alboran region and clarifies their chronologic location with respect to the messinian salinity crisis we present new micropaleontological data dinoflagellate cysts calcareous nannoplankton planktonic foraminifers correlated with field observations and offshore seismic interpretations we show that the lago mare event known in three onshore localities rio mendelin near malaga zorreras near sorbas gafares near nijar follows the marine reflooding of the mediterranean basin which ended the messinian salinity crisis chronologically these lago mare deposits last from the latest messinian to the early zanclean in fact the first influx of paratethyan organisms is revealed by the dinoflagellate cyst record from near malaga within a gilbert type fan delta overlying the messinian erosional surface invading molluscs and or ostracods may have persisted in lagoonal coastal areas more or less affected by discontinuous marine influxes sorbas and nijar the malaga area is convenient for a paleogeographic and sedimentary reconstruction which shows the prevalent forcing of sea level changes during the time interval 5 600 5 332 ma at the difference of the usually solicited prevalent tectonics the studied lago mare event is the third episode resulting in such a paleobiological assemblage in the mediterranean region and corresponds to the final two way water exchange at high sea level between the mediterranean and the former paratethys it documents the onset of the modern marine circulation in the mediterranean after the reflooding ending the messinian salinity crisis

mediterranean surface geostrophic circulation from satellite gravity and altimetry observations we present a data based approach to study the mean and the climatology of the surface geostrophic currents sgc for the mediterranean sea using satellite ocean surface altimetry observations for 22 years 1993 2014 in conjunction with the geoid solution derived from the space mission of goce gravity field and steady state ocean circulation explorer release 4 the resultant product is the mediterranean sgc velocity field that we denote by sgc goce alt given in spatial resolution of 1 4 circ and monthly time resolution it exhibits smaller scales and lower dynamic intensities in comparison with open oceans making the mediterranean sea a challenging test case for our satellite based analysis the mean sgc goce alt is largely consistent with previous findings but with additional circulation features in time and space we also compare our results with the sgc output from the regional hydrodynamic model of mercator that assimilates satellite altimetry satellite sea surface temperature and in situ observations the prominent sgc features agree well not only on the large and subbasin scales but also in the widespread mesoscale dynamics we find however comparatively lower intensities than the mercator model in general with differences that are on average around 7 cm s but might reach 13 cm s in some coastal areas

submarine flow tills at victoria british columbia reply during winter to maintain the same average position over a year perhaps these cones originated by slumps on the foreslope of subaquatic outwash fans similar to those postulated by aario 1972 and rust and romanelli 1975 for a glacimarine setting the small proportion of traction current deposits may be due to subglacial streams not having a sufficiently high sediment concentration to maintain an underflow away from the efflux occasionally the streams were sufficiently dense to deposit outwash sand and gravel in the foreslope area the gravity flows may have incorporated the stream gravel sand and mud as well as melt out debris from englacial and basal debris layers mixing of these sources during liquefaction perhaps induced by iceberg calving powell 1980 p 70 may produce poorly sorted sediment flows thick accumulation by supraglacial melt out from debris layers in a tidewater glacier may best occur where the glacier has almost retreated from the sea and ablation occurs primarily by surface melting rather than iceberg calving the situation in facies association 111 of powell 1981 a similar situation of ice in shallow water under mid latitude temperature conditions was envisaged by evenson et al 1977 to explain stratified quaternary tills although their interpretation has been questioned gibbard 1980 here the glacial regime and processes are similar to those of the terrestrial environment mudflows and debris flows may occur from the ice surface and retain their integrity whilst flowing down a shallower though still relatively steep slope into shallow water if such deposits are not modified by wave action and remain preserved then they may indicate proximity to sea level in a similar way to deltaic plains

the gulf stream front a comparison between seasat altimeter observations and theory in a recent paper by cheney and marsh 1981 seasat altimeter data were used to derive quantitative information on sea surface height anomalies across the gulf stream in another recent paper by kao 1980 the dynamics of the gulf stream front was investigated and a similarity solution was obtained the model gives a universal shape of the sea surface height rise and the width of that anomaly across the gulf stream in this paper we present a quantitative comparison between the model and six gulf stream altimeter profiles representing a broad range of conditions the remarkable closeness of fit is mutually reinforcing to both the model and to the role of satellite altimetry in ocean dynamics comparisons of the data with the well known theories of stommel 1966 and charney 1955 are also made and implications of these comparisons are explored

ice marginal sedimentation and processes of diamicton deposition in large proglacial lakes lake erie ontario canada detailed studies of coastal cliff exposures through two end moraines form the basis for a model of ice marginal sedimentation in large ice contact glacier fed lakes the input to the ice marginal environment directly from the glacier included subglacial till and subaquatic flow tills the subaquatic flow till thinly bedded diamicton was deposited in an apron up to 1 km wide along the ice margin an upward gradient of pore water pressure immediately beyond the ice margin causing heaving and dilation of the sediments initiated debris flows of glacially derived debris subaquatic flow tills most of the stratified sediments in the ice marginal zone entered the lake by way of a large proglacial stream sedimentation was dominated by quasi or near continuous density underflows that resulted in the deposition of a sequence of thick rhythmites the glacier in the lake erie basin most likely behaved like an ice stream with its movement controlled predominantly by a deforming bed of glacial debris separa

seasonal variability of the tyrrhenian sea surface geostrophic circulation as assessed by altimeter data abstractnew insights into the structure and variability of the tyrrhenian sea s surface circulation are obtained through the analysis of a very long series of altimetric observations 1993 2010 in late winter and part of spring a consistent mean flow is individuated in the eastern tyrrhenian sea formed by a stream of atlantic water that meanders around four anticyclonic structures located along the italian coast which have smaller cyclonic companions offshore the signatures of these vortices are also found in images of chlorophyll and sea surface temperature as well as in modeling results both from a high resolution operational model of the tyrrhenian sea s circulation and from a dedicated numerical simulation analysis of the energy exchange between eddies and mean flow together with numerical evidence suggests that this winter spring circulation pattern may result from basin scale instability of the atlantic stream in summer the dynamic is dominated by a well known dipole located to the east

glacial and postglacial stratigraphy of dinosaur provincial park and surrounding plains southern alberta canada abstract thirty one stratigraphic logs from the dinosaur provincial park area reveal seven major lithofacies associations lfa s lfa 1 is a preglacial fluvial deposit recording deposition on a sandy braided floodplain this lfa fines upwards to lfa 2 a glacilacustrine deposit which records the first advance of laurentide glacier ice into the region erosional contacts between lfa s 1 and 2 and bedrock suggest that large expanses of badlands may have existed prior to glaciation lfa 3 is a grey till which together with glacitectonized bedrock records ice movement from the northeast lfa 4 represents supraglacially derived diamictons and outwash its oxidized colour indicates either a considerable period of subaerial weathering or groundwater activity and the deposit is tentatively assigned an interstadial or interglacial age a second glaciation is recorded by lfa 5 heterogeneous diamicton and lfa 6 homogeneous diamicton lfa 5 records a period of subglacial molding and then cavity filling by fluvial and debris flow deposits lfa 6 records lodgement and melt out of the same glacier ice after it had glacitectonically thrust large rafts of older lfa s the sequence of molding cavity fill tectonism melt out represents large scale decoupling of the glacier from its bed and later surges creating extensive deformation of the substrate melt out was interrupted in some places by remobilization caused by surges which continued throughout ice retreat lfa s 7a 7e record deposition in glacilacustrine fluvial pond and aeolian environments after deglaciation some previously reported and new radiocarbon dates on regional and local surface drainage are discussed with reference to fluvial incision and holocene climate all lfa s are tentatively correlated with stratigraphic sequences reported from adjacent areas of southern alberta and former regional glaciodynamics are assessed

sea surface transport in the western mediterranean sea a lagrangian perspective 2 we study the sea surface transport in the western mediterranean sea from a lagrangian point of view in particular the alboran and the north western subbasins the study is carried out through the analysis of 3 years of surface velocity model data through finite size lyapunov exponents residence time and virtual particle trajectories complementing the classical eulerian approach the spatiotemporal variability of the main transport processes is inferred from the empirical orthogonal function modes of the lyapunov exponents being the most relevant modes discussed and physically interpreted results indicate that some of the variability in the surface transport patterns in the western mediterranean can be explained by specific modes which provide an indication of connectivity among subbasins like the inflow of atlantic waters through the ibiza channel

submarine debris flow deposits from the upper carboniferous dwyka tillite formation in the kalahari basin south africa four types of sediment gravity flow deposits occur interbedded with rhythmite shale siltsone mudstone and minor diamictite in a 230 m thick carboniferous glacial sequence shear and plug zones are present in the cohesive debris flow deposits which have a diamictic texture the high density turbidity flow deposits which consist of coarse to medium grained clastics are characterized by both normal and reverse grading the medium to fine grained low density turbidity flow deposits show normal grading and consist of bouma units a b d and e deposition occurred by gravity flow suspension settling and minor basal melt out during ice retreat along the southern margin of the kalahari basin immediately basinwards of the ice grounding line a proximal diamictite facies consisting predominantly of cohesive and high density turbidity flow deposits and minor melt out tills formed a distal sedimentary facies of graded sandstone and siltstone units deposited by low density turbidity flows and suspension settling of muds with ice rafted debris is located basinwards

storm related sedimentation influenced by coastal configuration in the stratigraphic record of a tectonically active shelf upper pleistocene le castella terrace italy abstract analysis of patterns of coastal circulation and sediment dispersal is an essential step for the study of controlling factors influencing the long term dynamics of coastal systems modern settings offer the possibility to monitor relevant parameters over relatively short time spans however geological examples complement this perspective by providing a time averaged record where longer trends and stratigraphically significant processes can be evaluated this study investigates the shallow marine deposits of le castella terrace upper pleistocene southern italy to document how patterns of circulation influenced by coastline configuration can affect the preserved millennial scale depositional record of a progradational shoreline system the regressive portion of the le castella terrace deposits developed during a relative sea level highstand and falling stage consists of a progradational wedge mainly composed of redistributed skeletal particles of a coeval shallow water carbonate factory preservation of the morphology of the paleocoastline and abundant current related sedimentary structures allow reconstruction of the predominant sediment dispersal dynamics responsible for the formation of this sedimentary wedge facies and paleocurrent analysis indicate offshore and alongshore sediment transport modes consistent with coastal circulation driven by storms normally incident to the shoreline and a sharp change in coastline orientation this coastal inflection influenced circulation patterns causing flow separation and eddy formation in the lee of the curved coastline syndepositional tectonic deformation also affected the architecture of the preserved deposits controlling the nucleation and development of a clinostratified body and determining localized lateral stratigraphic variability this study illustrates how transient but recurrent circulation patterns associated with changes in coastal orientation and related to high energy storm events can leave a predominant signature in the stratigraphic record of microtidal shallow marine successions

surface connectivity and interocean exchanges from drifter based transition matrices global surface transport in the ocean can be represented by using the observed trajectories of drifters to calculate probability distribution functions the oceanographic applications of the markov chain approach to modeling include tracking of floating debris and water masses globally and on yearly to centennial time scales here we analyze the error inherent with mapping trajectories onto a grid and the consequences for ocean transport modeling and detection of accumulation structures a sensitivity analysis of markov chain parameters is performed in an idealized stommel gyre and western boundary current as well as with observed ocean drifters complementing previous studies on widespread floating debris accumulation focusing on two key areas of interocean exchange the agulhas system and the north atlantic intergyre transport barrier we assess the capacity of the markov chain methodology to detect surface connectivity and dynamic transport barriers finally we extend the methodology s functionality to separate the geostrophic and nongeostrophic contributions to interocean exchange in these key regions

eastern mediterranean transient and reversal of the ionian sea circulation 1 maps of the remotely sensed absolute dynamic topography adt and sea surface temperature sst over the eastern mediterranean in the period june 1993 to june 2001 show a dramatic and sudden change in the sea surface structure this change which is presumably associated with the relaxation of the eastern mediterranean transient emt had taken place by the middle of 1997 and consisted of a complete reversal of the ionian upper layer circulation from anticyclonic to cyclonic in the emt phase sst and adt maps suggest enhanced communication between the ionian and the aegean basins as well as aegean waters spreading northward along the eastern ionian flank negative wind vorticity in the ionian suggests that the switch of the upper layer circulation from anticyclonic to cyclonic cannot be explained in terms of the wind forcing therefore we suggest the predominance of the baroclinic vorticity production term in determining the upper layer circulation inversion

occurrence of microplastics in surface waters of the gulf of lion nw mediterranean sea abstract between 2014 and 2016 a total of 43 microplastic samples were collected at six sampling stations in the eastern section of the gulf of lion located in the northwestern mediterranean sea as well as upstream of the rhone river microplastics were found in every sample with highly variable concentrations and masses concentrations ranged from 6 103 items km 2 to 1 106 items km 2 with an average of 112 103 items km 2 and mass ranged from 0 30 g km 2 to 1018 g km 2 dw mean 61 92 178 03 g km 2 the samples with the highest and lowest microplastic count originate both from the bay of marseille for the bay of marseille it is estimated that the total microplastic load consist of 519 103 101 106 items weighing 0 07 118 kg estimations for daily microplastic transport by the northern current and the rhone river two important hydrologic features of the northwestern mediterranean sea range from 0 18 to 86 46 t and from 0 20 to 21 32 kg respectively particles

near surface circulation in the south china sea during the winter monsoon 1 original velocity measurements at 15 m depth from surface velocity program drifters are used to calculate the circulation in the south china sea during the winter monsoon the ekman currents are computed with a new method and subtracted from drifter s velocity to calculate the residual circulation which is approximately in geostrophic balance the ekman flow is nearly zonal and comparable to the zonal geostrophic flow in the northern basin the geostrophic flow is cyclonic and extends into the southern luzon strait strong jets occur south of hainan off vietnam and to the south off peninsular malaysia the vietnam jet is concentrated inshore of the 200 m isobath with mean speeds in excess of 1 m s 1 the onshore ekman transport and pumping velocity computed from the wind stress curl offer a qualitative explanation of the existence and behavior of such jets