the knudsen theorem and the total exchange flow analysis framework applied to the baltic sea abstract the knudsen theorem for estuarine exchange flow based on mass conservation of water and salt and its generalization with resolution in salinity coordinates the total exchange flow tef analysis framework are reviewed here the former had been developed and applied to quantify exchange flow between the north sea and the baltic sea more than a century ago in this paper the underlying short research paper published in 1900 by martin knudsen originally written in german is translated into english reaching far beyond the knudsen relation in particular the extensive scientific achievements of martin knudsen on the salinity of seawater are reviewed using the knudsen theorem and the tef analysis framework validated multi decadal years 1949 2013 model simulations are analyzed in terms of exchange flow through straits of the western baltic sea when comparing the model results to the original findings of martin knudsen it is impressive to see how relevant his analysis of ratios of averaged inflowing and outflowing water masses still is today given that they were based on just a few salinity observations the model based long term knudsen and tef analyses of exchange flow in the western baltic sea reproduces the major baltic inflows mbis that have occurred since the 1950s for the complex inflow years 2002 2003 with two baroclinic summer inflows and one barotropic winter inflow in between the strong underestimation of the exchange flow by eulerian analysis as compared to tef analysis is demonstrated

a numerical investigation of circulation in the arabian gulf a three dimensional hydrodynamic model is developed to study the circulation in the arabian gulf the model contains realistic basin geometries and bathymetries of the arabian gulf and a good portion of the gulf of oman and is driven by monthly climatological winds evaporation and net ocean heat gain in both gulfs and the shatt al arab discharge it is found that the cyclonic circulation in the southern portion of the gulf is primarily driven by the evaporation induced freshening from the strait of hormuz in the northwestern corner of the gulf the shatt al arab discharge maintains the cyclonic circulation which would otherwise be anticyclonic the northwestward intrusion of fresher water along the iranian coast is weakened by northwesterly winds in winter but strengthens and extends almost to the head of the gulf in summer owing to the warming of the gulf of oman waters the development of the summer thermocline in the arabian gulf and diminishing winds the southward coastal current along the arabian coast is most prominent between the head of the gulf and qatar the model also predicts a strong southward coastal jet east of qatar which is primarily wind driven no similar coastal jet can be developed in the gulf of salwa west of qatar

eddy topography interactions and the fate of the persian gulf outflow the persian gulf feeds a warm and salty outflow in the gulf of oman northern arabian sea the salt climatological distribution is relatively smooth in the gulf of oman and the signature of a slope current carrying salty waters is difficult to distinguish hundreds of kilometers past the strait of hormuz in contrast to other outflows of the world ocean this study focuses on the mechanisms involved in the spreading of persian gulf water pgw in the gulf of oman using a regional primitive equation numerical simulation the authors show that the dispersion of pgw occurs through a regime that is distinct from for example the one responsible for the mediterranean outflow dispersion the background mesoscale eddy field is energetic and participates actively to the spreading of pgw remotely formed eddies propagate into the gulf of oman and interact with the topography leading to submesoscales formation and pgw shedding eddy topography interactions are isolated in idealized simulations and reveal the formation of intense frictional boundary layers generating submesoscale coherent vortices scvs interactions take place at depths encompassing the pgw depth thus scvs trap pgw and contribute to its redistribution from the boundaries to the interior of the gulf of oman the overall efficiency of these processes is confirmed by a strong contribution of eddy salt fluxes in the interior of the basin and is quantified using particle statistics it is found to be a highly dispersive regime with an approximated eddy diffusivity of inline image

vertical heat transport by ocean circulation and the role of mechanical and haline forcing abstractvertical transport of heat by ocean circulation is investigated using a coupled climate model and novel thermodynamic methods using a streamfunction in temperature depth coordinates cells are identified by whether they are thermally direct flux heat upward or indirect flux heat downward these cells are then projected into geographical and other thermodynamic coordinates three cells are identified in the model a thermally direct cell coincident with antarctic bottom water a thermally indirect deep cell coincident with the upper limb of the meridional overturning circulation and a thermally direct shallow cell coincident with the subtropical gyres at the surface the mechanisms maintaining the thermally indirect deep cell are investigated sinking water within the deep cell is more saline than that which upwells because of the coupling between the upper limb and the subtropical gyres in a broader thermohaline circulation despite the higher salinity of its sinking water the deep cell tr

a modeling study of circulation and eddies in the persian gulf abstract the circulation and mesoscale eddies in the persian gulf are investigated using results from a high resolution 1 km hybrid coordinate ocean model hycom the circulation in the persian gulf is composed of two spatial scales basin scale and mesoscale the progression of a cyclonic circulation cell dominates the basin scale circulation in the eastern half of the gulf 52 55 e during march july this is primarily the consequence of density driven outflow inflow through the strait of hormuz and strong stratification a northwestward flowing iranian coastal current icc 30 40 cm s 1 between the strait of hormuz and north of qatar 52 e forms the northern flank of the cell between july and august the icc becomes unstable because of the baroclinic instability mechanism by releasing the potential energy stored in the cross shelf density gradient as a result the meanders in the icc evolve into a series of mesoscale eddies which is denoted as the iranian coastal eddies ice the ice have a

a hycom modeling study of the persian gulf 1 model configurations and surface circulation 1 the circulation and water mass transformation processes in the persian gulf and the water exchange with the indian ocean through the strait of hormuz are studied using the hybrid coordinate ocean model hycom model results show that the indian ocean surface water iosw propagates in two branches into the gulf one along the iranian coast toward the northern gulf and the other one onto the southern banks driven by the ekman drift due to the prevailing northwesterly winds these two branches of inflow form two cyclonic gyres in the northern and in the southern gulf a salinity front separates the fresher intruding iosw from the saltier waters in the gulf eddies with size of about 100 km are fully developed along the salinity front in summer the intrusion of the iosw in the model extends much farther into the gulf in summer than in winter by analyzing the salt balance in the basin and conducting sensitivity experiments we show that it is the balance between the advection of iosw and vertical salt flux induced by mixing that mainly controls the seasonal variation of the surface salinity surface wind stress plays a secondary role in modulating the seasonal intrusion of the iosw high frequency atmospheric forcing produces more realistic surface temperatures than obtained from climatological forcing as a result of increased heat loss in winter however the high frequency forcing does not change significantly the general features of the circulation

interpretation of heat flow density of the apennine chain italy the apennine chain is a consequence of the continental collision between europe and africa characterized by several compressive phases with events of intense shortening during one of these phases from early oligocene to early miocene the continental crust broke into various segments which became packed one over the other forming an adriatic verging structure of imbricated listric wedges this event is thermally modeled in the southern apennines by the successive overthrust of two slabs of 7 km total thickness and explains the low heat flow density hfd 40 mw m 2 observed there in the northwestern apennines modeling is on the basis of the overthrusting of a slab 10 km thick which reduced the hfd of the steady lithosphere 63 mw m 2 observed on the iblean platform to 50 4 mw m 2 from the late miocene onwards tensional tectonism developed in the internal areas of the chain application of mckenzie s simple stretching model shows that the high regional heat flow 100 mw m 2 obtaining by filtering the observed data is explained by a stretching of the lithosphere of a factor 3 1

hydrology and circulation in the strait of hormuz and the gulf of oman results from the gogp99 experiment 1 strait of hormuz in october and early november 1999 the gogp99 experiment collected hydrological currentmeter tide recorder thermistor and drifting buoy data near the strait of hormuz data analysis provides the water mass structure in the strait persian gulf water pgw core is banked against the omani coast while indian ocean surface water iosw lies near the iranian coast these water masses are most often covered by a homogeneous surface layer thermohaline characteristics of the pgw core decrease substantially downstream from the persian arabian gulf to the gulf of oman pgw and iosw thermohaline characteristics and distribution also exhibit notable changes at periods shorter than a month as shown by repeated hydrological sections the tidal signal measured south of the strait by moored adcp and thermistor chains has predominant semi diurnal m2 and s2 and diurnal k1 components and possesses a complex vertical structure tidal intensification near the surface pycnocline is associated with noticeable internal waves at subtidal timescale mooring recordings confirm the water mass variability observed in the repeated hydrological sections the mixed layer also deepens substantially during the 1 month period finally trajectories of surface buoys drogued at 15 m exhibit reversals over periods characteristic of changes in wind direction

modeling of circulation in the arabian gulf and the sea of oman skill assessment and seasonal thermohaline structure hindcast simulations of the arabian gulf and the sea of oman using the regional ocean modeling system roms are quantitatively evaluated with basin wide hydrographic data and time series measurements the model shows comparable skill in reproducing moored observations of current velocities structure in upper and bottom depths the skill in simulating observed temperature is higher of 0 93 scale 0 1 in upper depths compared to 0 52 in bottom depths model results are sensitive to parameterization of water clarity a lower sensitivity was noticed to kpp gls and my2 5 turbulence closures when coastal turbid water parameterization is used accuracy of the model in reproducing seasonal and spatial variations of temperature and salinity increased by 25 compared to the clear water case whereas only 10 increase was noticed when applying kpp turbulent closure the model reproduces well anticlockwise circulation in the gulf a stronger surface inflow of fresher water to the arabian gulf through the strait of hormuz is simulated in summer compared to winter conditions mainly due to upper layer horizontal gradient of density between the arabian gulf and the sea of oman less seasonal variability of outflow between 0 15 and 0 20 m s 1 at 50 m to bottom depth around the strait of hormuz was noticed in the model results modeled surface layer stratification is stronger in summer than winter and varies spatially in the arabian gulf with highest stratification near the strait of hormuz overall the stratification in shallow water area of the arabian gulf remains low throughout the year

observations of seasonal exchange through the straits of hormuz and the inferred heat and freshwater budgets of the persian gulf the exchange between the persian arabian gulf and the indian ocean is investigated using hydrographic and moored acoustic doppler current profiler data from the straits of hormuz during the period december 1996 to march 1998 the moored time series records show a relatively steady deep outflow through the strait from 40 m to the bottom with a mean speed of approximately 20 cm s a variable flow is found in the upper layer with frequent reversals on timescales of several days to weeks the annual mean flow in the near surface layer is found to be northeastward out of the persian gulf in the southern part of the strait suggesting a mean horizontal exchange with the indian ocean that is superimposed on the vertical overturning exchange driven by evaporation over the gulf the salinity of the deep outflow varies from 39 3 to 40 8 psu with highest outflow salinities occurring in the winter months december march the annual mean deep outflow through the strait is estimated to be 0 15 0 03 sv calculation of the associated heat and freshwater fluxes through the strait yields estimates for the annual heat loss over the surface of the gulf of 7 4 w m2 and an annual water loss e p r of 1 68 0 39 m yr these values are shown to be in relatively good agreement with climatological surface fluxes derived from the southampton oceanography centre global flux climatology after known regional biases in the radiative budget are taken into account

crustal and velocity structure of the valencia trough western mediterranean part i a combined refraction wide angle reflection and near vertical reflection study abstract in november 1988 a 2 ship seismic survey was carried out in the valencia trough western mediterranean to collect normal incidence seismic reflection profile data and six expanding spread profiles along the continental shelf and trough velocity depth solutions derived from the analysis of the esp show a pattern that corresponds with that of continental type crust except in the northeastern part of the basin where oceanic type crust is present along the iberian margin and centre of the trough the seismic data show a well developed neogene and quaternary sequence with velocities ranging from 1 6 to 4 8 km s 1 whereas along the mallorca margin these deposits are absent at the base of the neogene there is a tertiary unconformity which marks the top of the pre rift mesozoic carbonate platform the carbonates which have velocities from 5 4 to 5 9 km s 1 thin towards the axis of the trough along both margins the upper and middle crust is characterised by an almost transparent layer of variable thickness 6 9 km with velocities ranging from 6 1 to 6 4 km s 1 dipping reflections are observed however in the southern part of the trough these reflections are the result of a locally thick mesozoic sequence a 6 km thick highly reflective lower crust with velocities from 6 4 to 7 0 km s 1 is seen beneath the iberian margin along the mallorca margin the lower crust is variably reflective with a velocity of about 6 6 km s 1 in the centre of the trough the total crustal thickness is less than 14 km which thickens asymmetrically towards the flanks reaching values of 20 21 km off shore the iberian peninsula and 23 km in the mallorca margin the seismic moho increases in depth from 13 to 16 km in a ne sw direction relatively low upper mantle velocities from 7 6 to 8 0 km s 1 have been found throughout the basin indicating a slightly anomalous uppermost mantle or a crust mantle transitional layer in the northeast the velocities for the sediments are similar to those described above however the crustal velocity solution can be characterised by three velocity gradient layers ranging from 4 8 6 1 6 1 6 7 to 6 7 7 2 km s 1

heat flow data and shallow thermal regime on mallorca and menorca western mediterranean abstract the first heat flow density values acquired on the balearic islands are presented a total of 39 thermal gradient determinations were carried out 23 on mallorca and 16 on menorca the sampling points consist of water exploration wells whose depths range between 100 m and 250 m most of the thermometric logs are strongly affected by water circulation through the formation and or through the borehole heat flow density measurements have been performed from 18 boreholes where conductive heat transport is inferred thermal conductivity values were obtained from 52 available well core samples covering the main lithologies present in the area after topographic and paleoclimatic corrections surface heat flow values ranging from 24 13 mw m 2 to 88 23 mw m 2 for mallorca and from 46 6 mw m 2 to 92 20 mw m 2 for menorca are obtained a well defined positive thermal anomaly associated to upward ground water flow is described on mallorca water flowing through the mesozoic basement would be responsible for an overall cooling effect affecting the northeastern half of the island where the lower heat flow values are measured water perturbations on menorca are mainly due to hydraulic connection through the borehole taking into account the effects of the regional ground water flow background heat flow densities of about 70 80 mw m 2 for mallorca and 75 90 mw m 2 for menorca are proposed

a hycom modeling study of the persian gulf 2 formation and export of persian gulf water 1 the circulation and water mass transformation processes in the persian gulf and the water exchange with the indian ocean through the strait of hormuz are studied using the hybrid coordinate ocean model hycom model results suggest that intruding indian ocean surface water iosw is transformed into hypersaline waters with salinity 41 practical salinity unit by the fresh water loss in the northern end of the gulf and in the southern shallow banks during wintertime intense heat loss from sea to air leads to the formation of cold and saline waters both in the northern gulf and in the southern gulf dense waters formed in the southern gulf have higher salinity and spill into the axial deep trough of the gulf as a sporadic bottom outflow in winter which leads to high salinity pulses in the strait as observed whereas in summer their buoyancy is increased due to heating and they are exported as a warm yet salty intermediate depth flow through the strait dense waters formed in the northern gulf propagate toward the strait along the axial trough throughout the year correspondingly there are two branches of seasonal overturning circulation in density classes the northern branch peaking in august with strength of 0 13 sv and the southern branch peaking in february and december with strength of 0 08 sv these two branches outflow together feed a seasonally varying deep outflow through the strait with an annual mean volume transport of 0 12 sv

the deacon cell and the other meridional cells of the southern ocean abstract the meridional circulation cells of the southern ocean are investigated using the results from a fine resolution primitive equation model zonal integration along depth levels shows the classical series of meridional cells but integration along density layers shows a number of differences including the virtual disappearance of the deacon cell to investigate the differences the meridional transport is calculated as a function of both density and depth the results show that the deacon cell is associated with systematic changes in the depth of density surfaces between the western boundary current region off south america and the return flow in the interior of the ocean water flowing on each density surface produces a meridional cell with a vertical excursion of a few hundred meters thew cells combine without water crossing density surfaces to produce a single integrated deacon cell extending from the surface to below 2000 m the results also show that at each latitude water on each of the

the stacking of thrust slices in collision zones and its thermal consequences the thermal consequences of stacking up thrust slices in collision zones are investigated using simple one dimensional thermal models the metamorphic evolution geotherms and p t time paths of a given tectonic unit belonging to a crustal stacking wedge made of more than two units is governed by three effects cooling and pressure decrease associated with erosion cooling by the lowest units screen effect heating by the upper units cover effect it is shown that the efficiency of these effects are dependent on the tectonic evolution of the collision zone the metamorphic evolutions are very sensitive to the following tectonic parameters the number of thrusted units involved in thickening the time delay between each thrust and finally the mode of stacking of the different units over and understacking it appears that for a given depth of burial the temperature increase during uplift is less important in a crust thickened by three or four units than in the case of two units the screen effect during understacking is more efficient for a short time delay 10 ma between each thrust overstacking leads to higher temperatures before uplift when compared to understacking it is also shown that the thermal perturbation induced in an intermediate unit of the pile is more efficiently recorded when its thickness is rather small 10 km it is shown that for an erosion controlled uplift the shape of the p t t path depends on the position of the rocks within a given unit and on the unit position within the pile finally the general metamorphic evolutions during crustal thickening hp lt metamorphism and subsequent overprint are discussed in terms of the previously mentioned parameters in the case of the western alps it appears that the more or less efficient greenschist overprint of the units involved in thickening can be explained by different time intervals between the thrust events

mixing estimates for estuaries abstractthe well known knudsen relations and the total exchange flow tef analysis framework provide quantifications of exchange flow across an open boundary to the adjacent ocean in terms of bulk

deep crustal configuration of the valencia trough and its iberian and balearic borders from extensive refraction and wide angle reflection seismic profiling abstract new constraints on the crustal structure of the valencia trough and its iberian and balearic borders have been obtained from a seismic experiment carried out in autumn 1989 a total of 290 sea shots were fired along three refraction wide angle reflection profiles recorded by 10 ocean bottom seismometers obss in the valencia trough and 110 land stations distributed on both flanks the huge amount of recorded data in each profile has been integrated and jointly interpreted to obtain a single 2 d velocity depth model along each line the geometry and deep crustal structure of the basin are fairly well defined in terms of laterally inhomogeneous layered media the sedimentary cover shows a layer of consolidated sediments overlain by neogene and quaternary sediments with a velocity of 5 1 km s interpreted as mesozoic carbonates at the northwestern side of the valencia trough a fairly homogeneous crystalline basement is found on all profiles at a mean depth of 4 km below sea level with a velocity of 6 0 6 1 km s the observed critical distances and arrival times of the moho reflected waves are firm evidence supporting a thinning of the crust towards the centre of the basin the moho rises up to 13 km in the axis of the trough in the nw se and e w profiles and up to 15 km in the ne sw profile moreover the analysis of the well defined pmp phase shows differences between the deep structure of the flanks and the trough respectively a sharp velocity contrast at the moho from a fairly uniform lower crust of 6 4 km s velocity is proposed in both flanks in contrast to a high velocity gradient within the lower crust interpreted near the axis of the trough an anomalous upper mantle velocity of 7 8 km s fits the data throughout the valencia trough and mallorca with slightly higher values of 7 9 km s required towards the continent these velocity values do not favour an interpretation in terms of underplating the geometry of the moho discontinuity shows a gradual deepening towards the iberian peninsula in contrast to a more abrupt slope towards mallorca depth values of 30 32 km typical of a continental crust are inferred about 40 km inland on the iberian peninsula in agreement with the crustal thicknesses already reported for the iberian range and the ebro basin the present crustal thinning resulting from rift episodes in the valencia trough and the iberian border is thus confirmed and constrained from our seismic results of the deep crust and upper mantle

on the mechanisms of episodic salinity outflow events in the strait of hormuz abstract observations in the strait of hormuz 26 26 n 56 08 e during 1997 98 showed substantial velocity fluctuations accompanied by episodic changes in the salinity outflow events with amplitude varying between 1 and 2 psu on time scales of several days to a few weeks these events are characterized by a rapid increase in salinity followed by an abrupt decline the mechanisms behind these strong pulses of salinity events are investigated with a high resolution 1 km hybrid coordinate ocean model hycom with particular reference to the year 2005 in accordance with the observations the simulated salinity events are characterized by strong coherence between the enhanced flows in zonal and meridional directions it is inferred that most of the simulated and observed outflow variability is associated with the continuous formation of strong mesoscale cyclonic eddies whose origin can be traced upstream to around 26 n 55 5 e these cyclonic eddies have a diameter of about 63 km and have a remnant of p

evidence for the existence of persian gulf water and red sea water in the bay of bengal the high salinity water masses that originate in the north indian ocean are arabian sea high salinity water ashsw persian gulf water pgw and red sea water rsw among them only ashsw has been shown to exist in the bay of bengal we use ctd data from recent cruises to show that pgw and rsw also exist in the bay the presence of rsw is marked by a deviation of the salinity vertical profile from a fitted curve at depths ranging from 500 to 1000 m this deviation though small of the order of similar to 0 005 psu and therefore comparable to the ctd accuracy of 0 003 psu is an order of magnitude larger than the similar to 0 0003 psu fluctuations associated with the background turbulence or instrument noise in this depth regime allowing us to infer the existence of rsw throughout the bay pgw is marked by the presence of a salinity maximum at 200 450 m in the southwestern bay pgw can be distinguished from the salinity maximum due to ashsw because of the intervening arabian sea salinity minimum this salinity minimum and the maximum associated with ashsw disappear east and north of the south central bay 85a degrees e 8a degrees n owing to mixing between the fresher surface waters that are native to the bay bay of bengal water or bbw with the high salinity ashsw hence ashsw is not seen as a distinct water mass in the northern and eastern bay and the maximum salinity over most of the bay is associated with pgw the surface water over most of the bay is therefore a mixture of ashsw and the low salinity bbw as a corollary we can also infer that the weak oxygen peak seen within the oxygen minimum zone in the bay at a depth of 250 400 m is associated with pgw the hydrographic data also show that these three high salinity water masses are advected into the bay by the summer monsoon current which is seen to be a deep current extending to 1000 m these deep currents extend into the northern bay as well providing a mechanism for spreading ashsw pgw and rsw throughout the bay

late quaternary climatic changes on the southwestern balearic slope western mediterranean isotopic faunal and mineralogical relationships abstract we report the results of a research on the carbonate mineralogy planktonic foraminifera distribution and oxygen and carbon isotope composition of g bulloides in hemipelagic carbonate oozes of the southwestern balearic slope western mediterranean to contribute to the understanding of climatic and ecological variations during the last quaternary interglacial glacial cycle and their influences on the carbonate sedimentary processes of the western mediterranean oxygen isotope stages 1 2 and 3 have been identified and correlated to those established in tyrrhenian cores the carbon isotope records display several anomalies which are explained by productivity variations and diagenetic processes pelagic carbbonates low mg calcite and aragonite and detrital minerals quartz high mg calcite and dolomite display variations that are climate related pelagic carbonates increase during warm intervals while intense low mg calcite dissolution and greater quantities of detrital minerals are found in colder intervals our results suggest that the carbonate distribution of the western mediterranean correlates to the reported from the atlantic ocean nevertheless the molar mgco3 content in low mg calcite disagree to the established temperature relationship in other oceans

formation and circulation of dense water in the persian arabian gulf 1 the nature and circulation of water masses in the persian arabian gulf hereinafter referred to as the gulf is investigated by examination of a historic database of hydrographic observations the densest water forms in winter at the northern end of the gulf rather than along the warmer southern and western coasts with the exception of small amounts of water directly above the seafloor most water flowing out of the gulf mixes across a density front that separates gulf deep water within the gulf from the indian ocean surface water iosw contrary to previous inferences the seasonally variable incursion of iosw into the gulf peaks in late spring this timing may be due to seasonal changes in sea surface slope driven by variations in evaporation rate in order to explain mooring results published elsewhere that show relatively small seasonal changes in the volume flux through the strait of hormuz hereinafter referred to as the strait we suggest that this flux is driven by the difference between the density of gulf deep water in the interior of the basin and water at comparable depths outside the gulf this density difference varies less than 15 during the year high rates of vertical mixing in the strait extend about 200 km westward in response to topographic constriction of tidal flows by islands and shoals