physical controls on biogeochemical zonation in the southern ocean the primary control on the n s zonation of the southern ocean is the wind induced transport of the antarctic circumpolar current acc the acc divides the southern ocean into three major zones the subantarctic zone saz north of the acc the acc transport zone and the zone south of the acc saccz the zone of acc transport is most often subdivided into two zones the polar frontal zone pfz and the antarctic zone aaz but it may be appropriate to define more subzones or indeed only one at some longitudes to maintain geostrophic balance isopycnals must slope upwards to the south across the acc thus raising nutrient rich deep water closer to the surface as one goes polewards in addition silicate concentrations increase polewards along isopycnals because of diapycnic mixing with silicate rich bottom water surface silicate concentrations therefore decrease northwards from high levels in the saccz to low levels in the saz within the saz and pfz and even in the northern part of the aaz silicate levels may drop to limiting levels for siliceous phytoplankton production during summer nitrate concentrations also decrease northwards but only become limiting in the subtropical zone north of the saz the second circumpolar control is the changing balance of stratification with temperature dominating near surface stratification in the saz and salinity dominating further south because of fresh water input to the surface from melting ice this results in circumpolar features such as the subsurface 2 c temperature minimum and the subduction of the salinity minimum of antarctic intermediate water which are often but not always associated with frontal jets and large transports the transport of the acc is dynamically constrained into narrow bands the number and latitudinal location of which are controlled by the bathymetry and so vary with longitude thus it is not the fronts that are circumpolar but the total acc transport and scalar properties of the salinity and temperature fields evidence of summer silicate and nitrate uptake in all zones saz pfz and aaz shows that there is productivity despite their high nutrient low chlorophyll status blooms covering large areas say 400 km across in the pfz and aaz are found in the vicinity of submarine plateaux which suggest benthic iron fertilizatio

eddy forcing of the mean flow in the southern ocean we examine the force or acceleration exerted by eddies on the mean flow of the southern ocean using mapped sea surface height anomalies derived from satellite altimeter measurements we compare this with the position of jets in the mean flow indicated by regions of increased gradient in the mean sea surface temperature the eddy force itself is not of primary importance rather the curl of that force affects the mean flow so the irrotational force due to the gradient of eddy kinetic energy can be ignored leaving a remainder that can be interpreted in terms of the eddy vorticity flux unlike previous modeling and altimetric studies we find that the eddies act to decelerate some of the strongest jets and act as vorticity sources for others the strongest jets are clearly not accelerated by eddies a problem of interpretation does remain however since it is not clear how sea surface temperatures are related to the mean flow this ambiguity can only be completely resolved by measurement of the mean flow requiring a geoid that is accurate at length scales of order 100 km

modulation of rossby waves on the pacific north equatorial current bifurcation associated with the 1976 climate regime shift simulated current velocity and long term reanalysis wind data are used to investigate interannual variations in the bifurcation of the pacific north equatorial current nec after the 1976 climate regime shift wind stress curl anomaly wsca in the region of 10 n 15 n and 160 e 170 e generates rossby waves and affects the nec bifurcation along the philippine coast from 1976 to 1992 following a regime shift to the positive pacific decadal oscillation pdo phase pdo and el nino southern oscillation enso match each other in strength and have a neutralized effect on the wsca from 1993 to 2009 wsca matches pdo well and its correlation with enso is lower using a linear regression model we show that the influence of pdo has nearly 13 times weight over that of enso prior to the 1976 regime shift wsca is closely related to enso from 1961 to 1975 and it does not correlate significantly with pdo our analysis results show that rossby waves are preferentially generated in either the negative pdo phase when the enso signal dominates or in the positive pdo phase when the enso signal is overshadowed in the phase when the positive pdo counteracts with the enso signal neither enso nor pdo has a significant influence on rossby wave generations through the wsca

kuroshio extension variability and forcing of the pacific decadal oscillations responses and potential feedback abstract a forcing mechanism is sought for the large scale circulation changes in the kuroshio extension region of the western north pacific ocean as inferred by topex poseidon sea surface height ssh data the low frequency signal of the kuroshio extension over the last decade was characterized by a modulation in its zonal mean flow intensity the mean kuroshio extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997 the ability to simulate the major trends in the observed ssh signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern north pacific ocean related to the pacific decadal oscillations pdos to be specific the weakening strengthening trend in 1993 96 1997 2001 was caused by westward expansions of negative positive ssh anomalies south of the kuroshio extension and positive negative ssh anomalies north of the kuroshio extension emerg

the large scale horizontal structure of the antarctic circumpolar current from fgge drifters the last decade of research in the southern ocean has shown that the antarctic circumpolar current acc is a complex system composed of narrow high speed currents separated by broad quiescent zones the circumpolar nature of this structure was examined using position and velocity data obtained from approximately 300 surface drifting buoys deployed in the southern ocean during the first garp global experiment fgge the distribution of buoys on 1 1 squares shows that in some regions most notably south of australia the buoys form three coherent bands of high buoy density which are separated by regions of low buoy density the latitudes of these bands coincide with those of the subtropical front subantarctic front and polar front to further examine the relationship between these fronts and buoy distribution locations of the three fronts determined from historical hydrographic data were used to partition the buoys into zonal bands corresponding to front and nonfront regions a mean buoy density and mean near surface speed were then computed for each zonal band high buoy densities were associated with all three fronts in the region south of australia other regions also showed a tendency although not as pronounced for buoys to accumulate in fronts the mean near surface speeds suggest that the subantarctic and polar fronts are circumpolar moreover the mean near surface speeds associated with the three frontal regions differ speeds within the subantarctic and polar front regions are approximately twice that associated with the subtropical front

an altimetry based gravest empirical mode south of africa 1 development and validation 1 hydrographic transects of the antarctic circumpolar current acc south of africa are projected into baroclinic stream function space parameterized by pressure and dynamic height this produces a two dimensional gravest empirical mode gem that captures more than 97 of the total density and temperature variance in the acc domain weekly maps of absolute dynamic topography data derived from satellite altimetry are combined with the gem to obtain a 16 year time series of temperature and salinity fields the time series of thermohaline fields are compared with independent in situ observations the residuals decrease sharply below the thermocline and through the entire water column the mean root mean square rms error is 0 15c 0 02 and 0 02 kg m 3 for temperature salinity and density respectively the positions of acc fronts are followed in time using satellite altimetry data these locations correspond to both the observed and gem based positions the available temperature and salinity information allow one to calculate the baroclinic zonal velocity field between the surface and 2500 dbar this is compared with velocity measurements from repeat hydrographic transects at the goodhope line the net accumulated transports of the acc derived from these different methods are within 1 3 sv of each other similarly gem produced cross sectional velocities at 300 dbar compare closely to the observed data with the rms difference not exceeding 0 03 m s 1 the continuous time series of thermohaline fields described here are further exploited to understand the dynamic nature of the acc fronts in the region and which is given by swart and speich 2010

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

location and dynamics of the antarctic polar front from satellite sea surface temperature data the location of the antarctic polar front pf was mapped over a 7 year period 1987 1993 within images of satellite derived sea surface temperature the mean path of the pf is strongly steered by the topographic features of the southern ocean the topography places vorticity constraints on the dynamics of the pf that strongly affect spatial and temporal variability over the deep ocean basins the surface expression of the pf is weakened and the pf meanders over a wide latitudinal range near large topographic features width and temperature change across the front increase and large scale meandering is inhibited elevated mesoscale variability is seen within and downstream of these areas and may be the result of baroclinic instabilities initiated where the pf encounters large topographic features the strong correlations between topography and pf dynamics can be understood in the context of the planetary potential vorticity ppv or f h field mean ppv at the pf varies by more than a factor of 2 along its circumpolar path however at the mesoscale the pf remains within a relatively narrow range of ppv values around the local mean away from large topographic features the pf returns to a preferred ppv value of 25 10 9 m 1 s 1 despite large latitudinal shifts the mean paths of the surface and subsurface expressions of the pf are closely coupled over much of the southern ocean

is there a continuous subtropical front south of africa a 14 3 year series of weekly absolute sea surface height ssh and associated geostrophic velocities is used for a study of the subtropical to subantarctic frontal system in the region south of africa detecting the fronts from surface velocity maxima confirms a two stepped transition in both the southeastern atlantic ocean the northern and southern subtropical fronts nstf sstf and southwestern indian ocean the agulhas front and sstf as proposed previously from hydrographic data an additional front associated with westward flow north of the nstf is indicative of a partial eastern closure of the south atlantic subtropical gyre between 11 e and 17 5 e the role of northwestward propagating agulhas rings in connecting the two fronts explains the varying location the sstf which marks the southern limit of subtropical waters is found continuous from the atlantic to the indian ocean in the time averaged ssh field in the weekly fields however the velocity maximum criterion defining the front is often met at the southern flanks of agulhas rings or agulhas eddies at 12 e 23 e indicating front disruptions such discontinuities suggest that no south atlantic central water is directly advected into the indian ocean instead the eastward limb of the indo atlantic super gyre encompassing the subtropical gyres of both oceans would rest at these longitudes on diffusive processes at the upper levels and possibly be enhanced at depth a schematic diagram of the fronts and their relations to agulhas rings and eddies is proposed

interannual variability in the mid and low latitude western north pacific abstract twenty two years 1967 88 of hydrographic data collected by the japan meteorological agency along the 137 e meridian and surface wind data compiled by florida state university fsu were analyzed to study the interannual variability in the western north pacific in the midlatitude region north of 22 n the dominant signal in the dynamic height field was the interannual path variations of the kuroshio whereas the eastward transport of the kuroshio itself had no significant changes between the straight path and meander path years the net transport of the kuroshio system including recirculations showed a 30 increase during the meander path years in the straight path years when the net transport was small the kuroshio tended to take a straight path with a strong recirculation developed to the south the interannual path variations of the kuroshio strongly influenced the water mass movement in the midlatitudes during the kuroshio meander years we found that a significant portion of the north p

the south atlantic current in this paper we use the historical hydrographic data base for the south atlantic ocean to investigate i the hydrographic boundary between the subtropical gyre and the antarctic circumpolar current acc the sub tropical front stf and ii the southern current band of the gyre which is called the south atlantic current sac the stf begins in the west in the brazil falkland malvinas confluence zone but at locations at and west of 45 w this front is often coincident with the brazil current front east of 45 w the stf appears to be a distinct feature to at least the region south of africa whereupon it continues into the indian ocean the associated current band of increased zonal speed is the sac which except for one instance is found at or north of the surface stf until indian ocean water from the agulhas retroflection is reached a reversal of baroclinicity in the stf is observed south of a highly saline agulhas ring causing the sac to separate from the stf and turn north into the benguela current zonal flow south of the stf is generally weak and serves to separate the south atlantic and circumpolar currents in the argentine basin the sac has a typical volume transport of 30 sv 1 sv 106m3s 1 in the upper 1000 m relative to a deep potential density surface 4 45 87 kg m 3 and can be as high as 37 sv it is thus comparable to or stronger than the brazil current in the cape basin the transport of the sac is reduced to about 15 sy before it turns north to feed the benguela current in late 1983 this flow was joined by about 8 sv of water from the agulhas current

implications of the deep circulation and ventilation of the indian ocean on the renewal mechanism of north atlantic deep water in the indian ocean sector of the great ocean conveyor scheme the north atlantic deep water nadw replacement is realized by the transformation of the sinking circumpolar deep water cdw from the southern ocean to a prevailingly upward flow in the northern indian ocean this water mass transformation scenario has been studied by using hydrographie data including potential temperature salinity dissolved oxygen and nutrients in a water mass mixing model and by calculation of dianeutral velocity the model comprises a mixing system of three major deep water masses nadw cdw and north indian deep water this third water mass is introduced as a virtual water mass to represent the aged cdw the assumption is feasible as the artificial water mass can be eliminated on the deepest n 28 12 neutral surface characterized by isopycnal mixing the experiment is fulfilled when a conservative variable initial phosphate po40 is introduced and all conservative parameters are used in the mixing scheme the n 28 12 surface provides a major isopycnal transition path of cdw to the northern indian ocean and thus cdw is transformed to an upward flow dominant dianeutral up welling is detected on all four neutral surfaces north of 30 s showing increasingly strong dianeutral velocity toward shallower surfaces with the water mass mixing pattern and spreading path dianeutral circulation and dynamical information of the acceleration potential 10 m2 s 2 mapped on neutral surfaces a schematic of deep water circulation and ventilation of the indian ocean emerges from this study the contribution of nadw is largely limited to the southwest indian ocean the northward cdw is found mainly in two paths one in the western indian ocean apparent between 2000 and 3000 m through the western crozet and madagascar basins and farther north into the somali basin and arabian basin and another in the central indian basin apparent below 3000 m where ridge blocking becomes effective in the west and nadw salinity reaches a maximum while the major path switches from west to the central basin in the deeper layer 3000 3500 m the flow in the western indian ocean reverses southward north of the southeast indian ridge the deep path bifurcates from which point the eastern branch feeds the deep western boundary flow in the west australian basin except for part of the transformed cdw which is contributed to the upward flow in the north the return flow of cdw is found on the eastern side of these basins

cross frontal exchange of antarctic intermediate water and antarctic bottom water in the crozet basin abstract the hydrographic survey made across the antarctic circumpolar current acc in the southwestern crozet basin during the april may 1993 antares 1 cruise revealed unprecedented strong cross frontal injections of newly formed antarctic intermediate water aaiw into the subtropical zone north of the acc the acc in this area is mostly associated with the subantarctic front saf and subtropical front stf which are tightly merged into one structure bordered to the north with the eastward extension of the agulhas return current the oxygen and salinity extrema of the newly injected aaiw at a depth of 1200 m well north of the stf reach as high as 6 17 ml l 1 and 34 15 these values coincide almost exactly with those in the aaiw source found at a depth of 500 m just south of the saf but surpass considerably oxygen by 1 35 ml l 1 and salinity by 0 23 psu those values corresponding to the old aaiw at the nearby subtropical stations such spectacular cross frontal injections of new aaiw were not continuous in space and time but were found to be rather local intermittent and impulsive this was closely correlated with the highly perturbed meandering frontal zone due to the frequent passages of strong atmospheric depressions during the cruise there is also clear evidence of the northward penetration of antarctic bottom water aabw through the crozet kerguelen gap and its northward flow along the deep western boundary of the crozet basin supporting previous observations moreover our observations indicate more precisely the bottom water pathway which is concentrated against the continental rise west of 56 e following roughly the 4000 m isobath it is concluded that the crozet basin frontal zone acts as a barrier only for the upper layer water masses and that it is dynamically transparent for the cross frontal exchange of intermediate and deeper layer water masses of potential density anomalies greater than 27 1 including aaiw and aabw

a mean synoptic view of the subantarctic front south of australia abstract a mean synoptic view of the subantarctic front saf is obtained from current meter and hydrographic data by averaging absolute and baroclinic velocity measurements in bins defined by a cross stream coordinate that moves with the current the cross stream coordinate is derived from current meter measurements of vertical shear of the horizontal velocity and is expressed in terms of specific volume anomaly at 780 dbar 780 by averaging absolute and baroclinic velocity measurements in stream coordinates the spatial smoothing that results from eulerian averaging of measurements of a meandering current is avoided the mean saf velocity profile is composed of one central peak and several smaller peaks in the central peak the 2 yr mean absolute velocity from current meters reaches 52 cm s 1 at 420 dbar the mean baroclinic velocity from six ctd sections reaches 34 cm s 1 the saf flow is coherent at all levels reaches the seafloor and is at least 220 km wide the cross stream structure of barocl

support for tropically driven pacific decadal variability based on paleoproxy evidence two independent proxy reconstructions of sea surface temperature reflect a common pattern of pacific decadal sea surface temperature variability over the past two centuries since the pattern extends to both the north ern and southern hemispheres this result supports the idea that pacific decadal variability is a basin wide phenomenon originating in thetropics the causes of pacific decadal climate variability here termed pdv are the subject of much debate most work describing pdv has focused on the north pacific where the leading eof of low pass filtered sea surface temperature

circulation and water properties of the southwest indian ocean spring 1987 abstract the results obtrained during a cruise in the south western indian ocean from south africa to mauritius in september 1987 are presented temperature salinity oxygen and nutrients were measured at 70 ctd station 20 nautical miles apart the data perspective is enhanced by noaa satellite infrared imagery and geosat altimetry the major features encountered on the cruise were two intense cyclonic eddies in the vicinity of the mozambique ridge and the mozambique basin and which seemed to form part of the broader western boundary region of the southern indian ocean evidence was found of a significant equatoward flux at the madagascar ridge which provided input of water from higher latitudes the passage of north atlantic deep water was constrained by the bottom topography south of the madagascar ridge and this led to a reduction of its salinity and oxygen concentration the positive correlation between the ctd results and the altimetry enabled the identification tracking and description of a number of eddies in the region the transition zone of these eddies from east of madagascar to the african continent was identified and so was the apparent closure of the southern entrance of the mozambique channel to migrating eddies

ocean currents and gradients of surface layer properties in the vicinity of the madagascar ridge including seamounts in the south west indian ocean abstract this work is part of the madridge project special issue which aims to describe pelagic ecosystems in the vicinity of three prominent shallow seamounts in the south west indian ocean one here named mad ridge 240 m below the surface plus walters shoal 18 m on the madagascar ridge and la perouse 60 m on the abyssal plain east of madagascar the three span latitudes 20 s and 33 s some 1500 km the study provides the background oceanography for the once off multidisciplinary snapshot cruise studies around the seamounts as life on seamounts is determined by factors such as summit depth proximity to the light layers of the ocean and the ambient circulation a first description of regional spatial field climatologies 16 22 years and monthly along ridge gradients of surface wind driving force water column properties of sea surface temperature mixed layer depth chlorophyll a and eddy kinetic energy plus ocean currents is provided being relevant to many applications in the study domain these properties in particular reveal contrasting environments along the madagascar ridge and between the three seamounts that should drive biological differences relative to the other two seamounts mad ridge is in the more extreme situation being at the end of the east madagascar current where it experiences sturdy albeit variable currents and the frequent passing of mesoscale eddies

spatial and temporal variations of the kuroshio east of taiwan 1982 2005 a numerical study 1 a 1 8 east asian marginal seas model nested to a larger domain north pacific ocean model is implemented over a span of 24 years from 1982 to 2005 to investigate the spatial and temporal variations of the kuroshio east of taiwan between 22 and 25 n the mean state and variability of the kuroshio such as the two paths observed in the trajectories of surface drifters southeast of taiwan and the branching of the kuroshio northeast of taiwan are well reproduced by the model southeast of taiwan the kuroshio is mostly in the top 300 m in the inshore path but extends to 600 m in the offshore path northeast of taiwan the kuroshio follows the shelf edge in the east china sea but may branch along a path south of the ryukyu islands the latter path often meanders southward and a significant portion of the kuroshio transport may be diverted to this path the kuroshio extends from the coast to 123 123 5 e between 22 and 25 n with currents reaching a depth of 1000 m at some latitudes the kuroshio transports averaged over five sections east of taiwan are 28 4 5 0 sv and 32 7 4 4 sv with and without the contribution from the countercurrent respectively

paleogene calcareous nannoplankton biostratigraphy of northwestern europe abstract the classic paleogene stages thanetian cuisian lutetian bartonian ludian and stampian defined in the epicontinental deposits of the anglo paris basin s are placed within a standard biostratigraphic framework based on an analysis of their calcareous nannoplankton floras relatively precise biostratigraphic correlations can be made with some chronostratigraphic units e g lutetian while biostratigraphic resolution of others e g ludian is limited important hiatuses are recognized between certain chronostratigraphic units only the base of the lutetian late np14 and bartonian mid np16 stages can be precisely determined in terms of calcareous nannoplankton zones with the recent study of the magnetic polarity history of the paleogene of southern england and recent advances in magnetobiostratigraphic correlations in deep sea cores it is possible to interpret the paleogene history of the anglo paris basin s in a synoptic global framework in which paleomagnetic stratigraphy provides the chronologic and eustatic variations the graphic units of northwestern europe within rather than at the boundaries of i e at dynamic element redefinition of the boundaries of the standard paleogene chronostratigraphic unconformities eustatically controlled depositional cycles would result in more precise correlations in terms of standard calcareous nannoplankton biostratigraphy

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

fronts transport and weddell gyre at 30 e between africa and antarctica a detailed description of the frontal structure of major currents and estimates of transport between africa and antarctica at 30 e were made on the basis of a finely resolved hydrographic section made during the 1996 civa 2 cruise particular emphasis was put on a refinement of the eastern boundary of the weddell gyre by analyzing also supplementary hydrographic data from the 1993 civa 1 cruise and the best available historical hydrographic data in the weddell and enderby basins contrary to the general belief our results show that the weddell gyre extends far beyond 30 e reaching at least as far east as the enderby land promontory 53 e from this point westward currents along the antarctic continental margin constitute the gyre s southern boundary thus closing the cyclonic circulation of the gyre at its easternmost end as the most convincing evidence for this refined circulation scheme significant westward transport south of 65 s has been identified from the civa 1 acoustic doppler current profiler data we have shown also using an inertial jet model that the blocked feature of the weddell cold regime 57 s to the west of 25 e is due to the topographic control of flow by local bathymetry during the civa 2 cruise 70 of the antarctic circumpolar current acc was concentrated near the polar front 51 s with surface speeds reaching up to 70 cm s 1 the baroclinic current field in the subpolar area south of the weddell front 58 s for civa 2 and 57 s for civa 1 is featureless 3 cm s 1 but yielding a nonnegligible eastward transport of 15 sv 1 sv 106 m3 s 1 this bottom referenced baroclinic transport is entirely compensated by a substantial westward barotropic transport south of 65 s the acc transport across the 30 e section during the civa 2 cruise is estimated to be 160 sv

sequence stratigraphic interpretations from palynofacies dinocyst and lithological data of upper eocene lower oligocene strata in southern mississippi and alabama u s gulf coast abstract this paper presents new information on the sequence stratigraphy of the upper eocene lower oligocene strata in southern mississippi and alabama based on palynological and lithological data from five sections by integrating lithological characteristics with palynofacies assemblages several dinocyst paleoecological groups the deflandrea group and the abundance of reworked dinocysts in samples paleobathymetric curves were reconstructed and used to revise the sequence stratigraphy of the area we identified a maximum flooding surface in the middle of the shubuta clay formation in southern mississippi and dated it as latest eocene in southern alabama the eocene oligocene boundary was placed within a condensed section representing about 0 19 ma and it coincided with the shubuta clay vicksburg group contact this condensed section is equivalent to the accumulation of the upper shubuta and red bluff formations in southern mississippi the forest hill mint spring contact which has been interpreted as a sequence boundary that merged with a transgressive surface does not correlate with the tejas a ta 4 3 4 4 sequence boundary of haq et al 1988 the pachuta marl and lower shubuta clay formations are constituents of a late eocene transgressive systems tract in southern mississippi but this systems tract extended to the shubuta clay vicksburg group contact in southern alabama the overlying early oligocene highstand systems tract consisted of the upper shubuta in mississippi and the red bluff bumpnose forest hill formations a thin sandstone in the mint spring was interpreted as a deposit of a possible lowstand systems tract above the sequence boundary in one southern mississippi section in general the mint spring marl and marianna limestone constituted a transgressive systems tract

vorticity and vertical circulation at an ocean front abstract density and velocity data with 4 km horizontal resolution from a survey of a front during fasinex frontal air sea interaction experiment are combined to describe the structure of the top 300 m of the ocean the geostrophic velocity field is derived and is used to examine the relative importance of stratification relative vorticity and twisting terms in ertel s potential vorticity q tenfold isopycnic changes in q are found across a horizontal scale of only 10 km these changes are confined to isopycnals that outcrop from the seasonal thermocline into the mixed layer the ageostrophic velocity field is quantified by solution of the omega equation and vertical velocities of up to 40 m day 1 are found small 40 km surface trapped top 200 m eddies are found to play a crucial role in the transport and effective diffusion of properties across the thermocline out of the mixed layer

an introduction to the physical oceanography of six seamounts in the southwest indian ocean exploratory surveys of six seamounts in the southwest indian ocean provide a description of physical processes induced by seamounts along the southwest indian ridge mean currents 15 25 cm s 1 in the vicinity of each seamount were dominated by mesoscale eddies the dominant seamount driven process was the generation of internal tides by the barotropic tide interacting with the seamount crests this led to enhanced shear in the vicinity of the crests resulting in mixing where stratification was weak for example in the core of an anticyclonic mesoscale eddy or where there had been a winter mixed layer tidally driven up and downwelling was observed at the seabed with associated variability in bottom temperature of up to 3 c over a tidal cycle vertical displacement of isopycnals by internal tidal waves reached 200 m peak to trough fluorescence in the surface eutrophic layer could thus extend down to the seamount crest on each tidal cycle apparently spatial variations in short conductivity temperature depth sections across each seamount were probably aliased temporal variations from the strong tidal signal evidence for taylor caps or other potential trapped circulations at the seamount crest was weak most likely because currents associated with mesoscale eddies were too strong to allow their formation

multidecadal sea level and gyre circulation variability in the northwestern tropical pacific ocean abstractsea level rise with the trend 10 mm yr 1 has been observed in the tropical western pacific ocean over the 1993 2009 period this rate is 3 times faster than the global mean value of the sea level rise analyses of the satellite altimeter data and repeat hydrographic data along 137 e reveal that this regionally enhanced sea level rise is thermosteric in nature and vertically confined to a patch in the upper ocean above the 12 c isotherm dynamically this regional sea level trend is accompanied by southward migration and strengthening of the north equatorial current nec and north equatorial countercurrent necc using a 1 layer reduced gravity model forced by the ecmwf reanalysis wind stress data the authors find that both the observed sea level rise and the nec necc s southward migrating and strengthening trends are largely attributable to the upper ocean water mass redistribution caused by the surface wind stresses of the recently strengthened atmospheric walker circulation based on the lo

circulation pathways and transports of the southern ocean in the vicinity of the southwest indian ridge circulation pathways and transports of the antarctic circumpolar current acc and agulhas return current arc around the complex bathymetry of the southwest indian ridge and del cano rise have been established from two hydrographic surveys and two year long moorings after crossing the southwest indian ridge in a 110 sv 1 sv 106 m3s 1 flow concentrated at 48 s the acc fragments before being reconcentrated into several branches by the bathymetry in particular 30 40 sv turns north around the eastern flank of the del cano rise turns west as part of anticyclonic flow round the del cano rise finally returning eastward as part of the crozet front eddy variability from both satellite data and moorings is low over the bathymetry of the del cano rise so the strong currents found between the del cano rise and the crozet plateau are believed to be permanent features this largely barotropic time independent transport is the major pathway for the acc to enter the crozet basin the anticyclonic flow also transfers water from the mozambique basin across the southwest indian ridge to the south side of the del cano rise given the evidence for fragmentation of the acc where it crosses the southwest indian ridge and the concentration of several jets into the crozet front from the acc subtropical front and agulhas return current it is misleading to relate standard frontal definitions such as the polar front and subantarctic front to the major transport pathways

phytoplankton pigment distribution from seawifs data in the subtropical convergence zone south of africa a wavelet analysis the agulhas system agulhas current retroflection agulhas return current arc south of africa constitutes a complex energetic system subject to high frequency mesoscale and low frequency variability using chlorophyll pigment concentration data collected by the seawifs ocean color sensor and sea surface height satellite data we demonstrate the utility of wavelet analysis in jointly analyzing ocean color and altimetric signals two distinct dynamical scenarios of the agulhas system october 1997 and january 1998 yield different dominant wavelengths 620 and 500 km for the arc rossby wave they are simultaneously retrieved from the chlorophyll and sea level anomaly signals longitudinal extension of the power resulting from the wavelet analysis also depends on the dynamical regime

mean sea surface height of the antarctic circumpolar current from geosat data method and application the mean sea surface height across the antarctic circumpolar current has been reconstructed from height variability measured by the geosat altimeter without assuming prior knowledge of the geoid for this study an automated technique has been developed to estimate mean sea surface height for each satellite ground track using a meandering gaussian jet model and errors have been estimated using monte carlo simulation the results are objectively mapped to produce a picture of the mean subantarctic and polar fronts which together comprise the major components of the antarctic circumpolar current the meandering jet model explains between 40 and 70 of the height variance along the jet axes the results show that the fronts are substantially steered by topography and that the jets have an average gaussian width of about 44 km in the meridional direction and meander about 75 km to either side of their mean locations the average height difference across the subantarctic front saf is 0 7 m and across the polar front pf 0 6 m the mean widths of the fronts are correlated with the size of the baroclinic rossby radius

structure and transport of the antarctic circumpolar current and agulhas return current at 40 e hydrographic data are presented from a near meridional section across the agulhas return current the subtropical front and the antarctic circumpolar current acc in the southwest indian sector of the southern ocean the location and characteristics of the fronts are examined and the water masses are defined the agulhas return current emerges as a strong current as far east as 40 e which forms a marked front that is separate from the subtropical front and can be distinguished by a separate water mass comparisons are made with a similar hydrographic section at the greenwich meridian and several notable differences are found the subantarctic front at the greenwich meridian is a pronounced feature carrying a large proportion of the geostrophic transport of the acc on the southwest indian section however the subantarctic front is merged with the polar front at 48 s where the flow associated with the acc is concentrated geostrophic calculations show a large volume transport 84 to 103 sverdrup 1 sv 106 m3 s 1 associated with the agulhas return current at 40 s this is quite separate from the transport of the acc which totals 138 sv south of the subantarctic zone and the crozet plateau or 150 sv including flow in the subantarctic zone the transport of the acc out of the south atlantic sector appears to be higher than the transport into the south atlantic sector at drake passage with the extra transport most probably carried by upper layer and intermediate waters eddies are seen to be an important feature of the subantarctic zone where they help to modify the water masses antarctic intermediate water appears in two forms a saline 34 4 indian ocean variety and a fresh 34 2 atlantic ocean variety the atlantic variety is freshest at the polar front and occupies the southern half of the subantarctic zone within the eddies in the central subantarctic zone there is interleaving between these two forms of antarctic intermediate water north atlantic deep water is unable to cross the southwest indian ridge but can pass south of the crozet plateau in the form of circumpolar deep water which is slightly more saline 34 75 than at drake passage 34 73

seasonal nutrient depletion and carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia seasonal surface water nitrate and phosphate depletions were calculated for the subantarctic zone saz and polar frontal zone pfz of the southern ocean along the world ocean circulation experiment sr3 repeat section south of tasmania australia and three other transects slightly to the west the depletions were calculated between a single winter july section and eight other sections from october to march in the years 1991 1998 and corrected for frontal movements and changes in water masses between the cruises using observed quasi linear nutrient salinity relationships arranged in a seasonal progression depletion began in approximately october and continued through march in good agreement with satellite biomass based estimates of production nitrate depletion in the saz 510 mmol n m 2 was approximately twice that of the pfz 250 mmol n m 2 but phosphate depletions were similar 29 and 24 mmol p m 2 for the saz and pfz respectively the saz exhibited a redfield n p depletion ratio 15 1 2 3 but the pfz ratio was much lower 8 3 5 4 while the saz exhibits greater seasonal nutrient depletion the relative magnitudes of export in the two zones remain uncertain because supply of nutrients from south of the polar front may lower the observed nutrient depletions in the pfz however comparisons with sediment trap and production measurements for the region south of australia suggest the saz and pfz differences derive from differences in production assuming a redfield c n ratio 6 6 carbon export for the longest period examined july march averaged 3400 430 mmol c m 2 in the saz with a range between 2700 and 3900 mmol c m 2 depending on latitude in the pfz carbon export averaged 1600 350 mmol c m 2 with a range of 1100 to 2000 mmol c m 2 these averages represent minimum annual export production estimates because neither resupply nor export outside the july march observational period is included

interannual to decadal variability in the bifurcation of the north equatorial current off the philippines satellite altimeter sea surface height ssh data from the past 17 yr are used to investigate the interannualto decadal changes in the bifurcation of the north equatorial current nec along the philippine coast the nec bifurcation latitude migrated quasi decadally between 108 and 158n with northerly bifurcations observed in late 1992 1997 98 and 2003 04 and southerly bifurcations in 1999 2000 and 2008 09 the observed necbifurcationlatitudecanbeapproximatedwellbythesshanomaliesinthe128 148nand1278 1308ebox east of the mean nec bifurcation point using a 1 layer reduced gravity model forced by the ecmwf reanalysis wind stress data the authors find that the ssh anomalies in this box can be simulated favorably to serve as a proxy for the observed nec bifurcation with the availability of the long term reanalysis wind stress data this helps to lengthen the nec bifurcation time series back to 1962 although quasi decadal variability was prominent in the last two decades the nec bifurcation was dominated by changes with a 3 5 yr period during the 1980s and had low variance prior to the 1970s these interdecadalmodulationsin the characteristics of the nec bifurcation reflect similar interdecadal modulations in the wind forcing field over the western tropical north pacific ocean although the nec bifurcation on interannual and longer time

interannual modulation of the pacific decadal oscillation pdo on the low latitude western north pacific to investigate the interannual variability in the northwestern pacific an empirical mode decomposition emd was applied to 17 year absolute dynamic topography adt data west of luzon island the philippines the mean sea surface height in this area is an appropriate index for the kuroshio intrusion into the south china sea scs significant interannual fluctuations were extracted by the emd the interannual variability was strongly correlated with the pacific decadal oscillation pdo index but not the el nino southern oscillation enso this indicated the potential impact of the pdo on the circulation in the area in the warm phase of the pdo positive index a southerly anomalous wind off the philippines causes a northward shift of the north equatorial current bifurcation latitude necbl this leads to a weakened kuroshio off luzon favoring kuroshio intrusion into the scs the northward migration of the necbl also results in a weakened kuroshio off southeast taiwan and a larger kuroshio transport off northeast taiwan the abundant westward propagating eddies impinging on the kuroshio in the subtropical countercurrent region increases this transport although the enso has little effect on monsoonal winds during the warm pdo phase it has a strong impact on the monsoon and meridional migration of the necbl during the cold phase of the pdo therefore necbl variations only show a close correspondence with the enso during the cold pdo phase because the influence of the enso is not stationary the impact of the pdo should be taken into account when examining interannual variability in the low latitude western north pacific

major nutrients and dissolved oxygen as indicators of the frontal zones in the atlantic sector of the southern ocean 1 the chemical tracers of the main frontal zones of the atlantic sector of the southern ocean are considered before the beginning of the spring bloom frontal zones are distinguished by lateral gradients of dissolved oxygen phosphate nitrate and silicate during the spring bloom the smoothing of nutrient concentrations on both sides of the fronts weakens lateral gradients of chemical properties the position of surface gradients of nutrients within the subtropical frontal zone stfz does not coincide with the location of temperature and salinity gradients as a result fronts in this region have a stepped character the best chemical indicator of the northern stfz front is the dissolved oxygen gradient which coincides with the temperature and salinity gradients the southern boundary of the stfz is distinguished by the gradient of nitrate the chemical criterion for identifying the subantarctic front is the gradient of oxygen which ranges from 0 5 to 4 0 mol kg 1 per km the polar front is identified by the gradient of silicate 0 56 to 2 78 m per km at the surface the weddell scotia confluence wsc is distinguished not by the temperature and salinity but by chemical parameters the best year round criterion is the lateral gradient of silicate to phosphate atomic ratio which ranges from 25 to 35 other markers of the wsc are the gradients of silicate at the surface oxygen at the upper boundary of the circumpolar deep water and the depths of its location

oxygen isotope and salinity variations in the indian sector of the southern ocean a combined study of stable oxygen isotopes i 18o and salinity of surface ocean waters collected from the southern indian ocean during the late austral summer and early fall 25th january to 1st april 2006 helped to trace atmospheric and oceanic processes near the equator a very clear signature of the domination of evaporation precipitation process was seen while a precipitation dominated zone was located between two evaporation dominated zones south of the equator the signature of the agulhas front af and the subtropical front stf recognizable by the sharp decrease in salinity and i 18o in the surface waters were identified at 41 s and 44 s in february during the return journey march these two fronts had merged and were located at 41 s south of 45 s the slope of the i 18o salinity relationship was close to zero while north of 62 s could have some precipitation evaporation effect south of 63 s was clearly dominated by freezing melting

physical and biological patchiness of an upper ocean transect from south africa to the ice edge near the greenwich meridian an undulating ctd seasoar was towed from the subtropical front at 42 s 12 e to the ice edge at 57 5 s 2 w the instrument measured temperature salinity pressure and light in the top 400 m of the water column fluorescence and particle counts also were recorded fluorescence was calibrated to chlorophylla and particle counts were converted to biovolume to provide estimates of phyto and zooplankton respectively the size of particles counted covered the range 0 25 8 0 mm three major fronts subtropical subantarctic and polar were intersected and identified by their physical characteristics the polar front showed surface and subsurface signatures separated by nearly 300 km considerable small scale structure was observed between the fronts in particular a large 150 km diameter warm core eddy was found in the northern part of the subantarctic zone both fronts and eddy were associated with significant biological signals phyto and zooplankton correlated well in the frontal regions and south of the polar front the polar frontal zone was associated with elevated concentrations of biomass whereas concentrations were low at the subantarctic front and south of 55 s in contrast the warm core eddy in the subantarctic zone contained the highest zooplankton biovolume of the section while chlorophyll concentration was only moderate we hypothesise that such a distribution results from grazing the overall distribution of phyto and zooplankton changed across the subantarctic front the vertical extent of biomass deepened from north to south across the front zooplankton tended to be concentrated in relatively narrow deep extending bands to the north but were more widely spread to the south the small scale hydrographic structure correlated significantly with the distribution of plankton suggesting strong physical controls on both small zooplankton and phytoplankton

reworked hantkenina specimens at little stave creek alabama abstract abstract the eocene oligocene boundary in mississippi and alabama has been traditionally placed between the shubuta member of the yazoo formation and the overlying red bluff formation or its carbonate facies equivalent the bumpnose formation consequently the presence of eocene planktonic foraminifers in the red bluff and bumpnose has long been attributed to reworking to test the validity of this hypothesis samples were collected on both sides of the boundary from the upper shubuta and bumpnose units at little stave creek alabama and were examined for both calcareous nannofossil and planktonic foraminiferal content the calcereous nannofossil assemblage preserved in the matrix from inside handpicked specimens of hantkenina from both units was demonstrably older than the calcareous nannofossil assemblage from the surrounding sediment thus at least some of the hantkenina specimens in both the shubuta and bumpnose are indeed reworked which not only confirms the original hypothesis regarding reworking within the red bluff and bumpnose but also indicates that the last occurrence of hantkenina the shubuta bumpnose contact and the eocene oligocene boundary in the u s gulf coast may not be equivalent

the south indian ocean current in this paper the historical hydrographic database for the south indian ocean is used to investigate i the hydrographic boundary between the subtropical gyre and the antarctic circumpolar current acc the subtropical front stf and especially ii the southern current band of the gyre a current band of increased zonal speeds in the upper 1000 m is found just north of the stf in the west near south africa and at the surface stf in the open indian ocean until the waters off the coast of australia are reached as neither any other investigation of this current nor a name for it are known the flow has been called the south indian ocean current sioc this name is anologous to the same current band in the south atlantic ocean the south atlantic current the stf is located in the entire south indian ocean near 40 degrees s the associated current band of increased zonal speeds is the sioc which is found at or north of the stf east of 100 degrees e the sioc separates from the stf and continues to the northeast the zonal flow south of the stf is normally weak and serves to separate the south indian ocean and circumpolar currents near africa the sioc has a typical volume transport of 60 sv 1 sv 10 6 m3 s 1 in the upper 1000 m relative to deep potential density surfaces of sigma 4 45 87 kg m 3 2800 3500 m or sigma 2 36 94 kg m 3 1500 2500 m near western australia the sioc is reduced to about 10 sv as it turns to the northeast

an updated examination of the luzon strait transport 1 despite numerous previous estimates of luzon strait transport lst we attempt an update using a fine resolution model with these improvements the circulation in and around luzon strait shows up rather realistically intrusion of a kuroshio meander into the south china sea scs is seasonally varying the lst especially in the upper ocean caused by a small difference between the large meander inflow and outflow is also seasonally varying and subject to large standard deviation the annual mean lst is estimated to be westward 4 0 5 1 sv along 120 75 e we have also conducted process of elimination experiments to assess the relative importance of open ocean inflow outflow wind stress and surface heat flux in regulating lst and its seasonality the east asian monsoon winds stand out as the predominant forcing without it the upper ocean lst changes from westward to eastward ranging up to 4 sv and with misaligned seasonality triggering an inflow from the mindoro strait to the scs to replenish the water mass loss discounting monsoon winds sea level in the sulu sea is generally higher because it receives the indonesian throughflow before the scs which causes an inflow from the sulu sea to the scs on the other hand the annual mean wind from the northeast invites outflow from the scs to the sulu sea or inflow from the luzon strait weighing the two competing factors together we see the cessation of northeast monsoon as a condition favorable for the luzon strait outflow or the mindoro strait inflow