enhanced southward flow over the oregon shelf in 2002 a conduit for subarctic water 1 moored current measurements from the oregon shelf during 1998 2003 are used to estimate time series of anomalous alongshore currents and pseudo displacements after accounting for the mean and seasonal cycle from early january through mid june 2002 currents at 10 m were anomalously strong toward the south by an average 12 cm s producing an anomalous displacement of more than 1500 km over about 5 months this may be compared with the finding by freeland et al 2003 that waters at the same latitude off oregon and off vancouver island were anomalously cool and fresh at depths between 30 and 150 m suggesting displacement from a more northern source anomalous displacements of several hundred kilometers were also found during at least three other periods in the record moored temperature measurements at the same location confirm that local waters were persistently cooler during march to october of 2002 than during the previous two years with the strongest anomaly near 20 m coastal sea levels were lower than usual along the northwest coast during spring and early summer 2003 consistent with a southward current anomaly of large scale local winds near newport did not show strong mean anomalies during this period

the 1997 1998 oceanic el nino signal along the southeast and northeast pacific boundaries an altimetric view changes in the sea surface heights ssh and geostrophic currents along the eastern boundaries of the pacific north central and south america are examined during the 1997 1998 el nino using altimeter data and proxy winds these show that symmetric ssh signals left the equator and propagated into both hemispheres in two episodes with primary periods of high equatorial ssh during may july and october december 1997 these are the distant signals from the mid latitude perspective as the signals spread poleward in each hemisphere their loss of symmetry demonstrates the degree to which they were altered by topographic features local winds and or local currents the first four eofs are calculated for 2 d ssh fields in 10 wide strips along the eastern margins 60 n 60 s and extending out along the equator from the coast to 110 w these account for approximately 40 of the overall variability and represent the main features of the seasonal cycles and el nino interannual variability snapshots of the 2 d ssh fields depict the structure of the el nino signal at different phases of its evolution

identification of tidal mixing fronts from high resolution along track altimetry data abstract coastal fronts can significantly impact the cross shelf material exchange and the marine ecosystem therefore it is important to detect their locations and intensities as well as temporal evolutions in this article we show that coastal tidal mixing front tmf signals can be extracted from both 20 hz and 1 hz along track sea surface height anomalies ssha measured by satellite altimetry the physical mechanism for the existence of the tmf in the ssha data is explained then the hilbert huang transform is applied to selected along track jason 2 data over georges bank the extracted fronts have a cross front sea surface height difference of 13 21 cm over distance of 20 27 5 km the surface geostrophic current anomalies associated with these fronts are estimated to be 0 38 0 45 m s 1 consistent generally with previous studies from in situ observations the present study clearly demonstrates the potential of satellite altimetry for monitoring tmfs it is also shown that tidal fronts can be better extracted from the 20 hz than 1 hz data

uncertainties in altimetry based velocity estimates 1 three methods to estimate ocean geostrophic surface currents from satellite altimetry measurements are evaluated for several single and multiple satellite configurations with specific emphasis on resulting uncertainties altimetric sea surface height measurements are simulated by sampling along satellite ground tracks the surface pressure output from the 1 10 north atlantic run of the los alamos parallel ocean program model and by subsequently adding realistic instrument and orbit errors the effects of both sampling and data errors on the velocity estimates are discussed the satellite orbit configurations considered represent current missions or candidates for future coordinated tandem missions data error budgets are based on those of existing missions and on estimates for new altimetric technology currently under development in midlatitude regions characterized by strong variability such as the gulf stream region velocities estimated at crossovers of interleaved tracks and along a virtual ground track between two parallel tracks with a 0 75 zonal offset are found to be comparable in accuracy and more accurate than velocities estimated from optimally interpolated sea surface height maps error variances as low as 15 25 of the local signal variance can be obtained from all three methods near the gulf stream core larger relative errors are found almost everywhere else with the exact details of the error in the two velocity components depending on data error orbit configuration latitude estimation method and smoothing several scientific applications of the configurations and methods are discussed including the estimation of reynolds stresses momentum fluxes velocity spectra and covariance functions accuracy and applicability suggest that the newly proposed parallel track configuration is a viable option for future tandem missions

time dependent wind driven flow over a shallow midshelf submarine bank 1 during summer 2001 high resolution hydrographic velocity and bio optical surveys were conducted over heceta bank off central oregon north of the bank upwelling over simple bottom topography exhibited a classic response with a midshelf baroclinic coastal jet and upwelled isopycnals the coastal upwelling jet follows the bank topography as it widens offshore before reaching the southern end of the bank where the shelf break turns almost 90 back toward the coast the ensuing adjustment involves the offshelf transport of coastal water and the material it contains the jet meanders anticyclonically in the lee of the bank before resuming its equatorward path seaward of the shelf break a pool of high chlorophyll 15 mg m 3 near surface water is found in the low velocity lee region created by the bank a low temperature high salinity bottom water pool supplied primarily from the south lies over the inshore region of the bank this bottom pool is up to 40 m thick and contains elevated levels of suspended material by creating an east west perturbation in the coastal upwelling front the flow topography interaction introduces an alongshore pressure gradient when southward upwelling favorable winds relax this alongshore pressure gradient can drive flow back to the north this leads to northward flow on the inshore side of the bank ultimately setting up the potential for recirculation around the entire bank complex on a timescale of about 10 days strong northward winds during summer lead to downwelling within 15 km of the coast accompanied by significant 0 2 m s 1 wind driven northward currents

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

relict and other anomalous grains in chondrules implications for chondrule formation we have identified relict olivine and pyroxene grains in chondrules from ordinary and carbonaceous chondrites that probably did not crystallize in situ some of these olivines are clear but others contain fine grained fe ni dusty olivines and resemble previously described occurrences in ordinary chondrites there are also chondrules in which all olivine is dusty we conclude 1 not all relict olivines are dusty 2 not all dusty olivines crystallized outside the chondrule in which they occur and 3 some dusty olivines were produced during chondrule formation by a reduction process that affected the whole chondrule the occurrence of dusty olivines and relict pyroxenes and olivines in chondrules from carbonaceous as well as ordinary chondrites supports the argument that chondrules from all chondrites had similar origins and histories we propose that chondrules and mineral fragments were transported across f o2 gradients in the solar nebula while they were hot or were reheated in an environment different from the one in which they formed partially molten chondrules sometimes incorporated mineral grains or chondrules with different redox states producing compound chondrules and chondrules containing anomalous grains dusty olivines may also have formed when hot chondrules were transported to regions of lower oxygen fugacity

altimeter derived variability of surface velocities in the california current system 2 seasonal circulation and eddy statistics abstract satellite surface height and temperature fields are used to examine the seasonal surface circulation in the california current system in spring and summer an equatorward jet develops next to the coast with an initial latitudinal structure that responds to the latitudinal distribution of equatorward alongshore winds this jet moves offshore from spring to fall and develops meanders and closed eddies that contribute eddy kinetic energy and water mass properties to the nearby deep ocean higher eke appears first in spring near the coast and moves offshore with the seasonal jet along altimeter tracks parallel to the coastline 200 and 400 km offshore the greatest eke is found in summer and fall respectively with wavelengths of approximately 300 km these are the wavelengths of the largest meanders and the distance between the largest eddies visible in altimeter snapshots of the jet at 600 800 km offshore the wavelengths are generally smaller 100 150 km similar to eddy sizes reported by others for the quiescent northeast pacific some energy with longer wavelengths arrives at the track 600 km offshore in winter and 800 km offshore in spring which we interpret as the most offshore extension of the eke generated by the jet and eddy system closer to the coast in the previous spring and summer a sequence of snapshots from october 1992 to october 1993 shows details of the evolution of the jet and eddy system over one complete annual cycle

mesoscale eddies in the south atlantic bight 1 satellite derived sea level anomaly fields constructed by combining measurements from simultaneously operating altimeters are used to quantify properties and propagation characteristics of eddies in the south atlantic bight sab eddy detection and eddy tracking algorithms are applied to 19 years of high resolution observations available at weekly intervals inshore of the 800 m isobath eddies are most frequently observed at and downstream of the charleston bump a major topographic feature located at 31 32 n a region where the amplitude of most eddies is increased the bump is also a preferred region for eddy generation the amplitude of eddies is found to increase with water depth eddies generated in the sab tend to propagate westward toward the coast and to the northeast presumably due to the influence of the strong mean northeastward flow of the gulf stream those eddies are highly nonlinear with potential to trap water in their interior as they propagate since a large fraction of the eddies that at some point in their histories are found inshore of the 800 m isobath experience large bathymetric changes along their trajectories they can potentially serve as efficient mechanisms for cross isobath transport in the sab analysis of temporal variability in eddy activity suggests that cross isobath transport due to nonlinear eddies may be significant during all seasons but will likely be characterized by large interannual variability

extinct i129 in c3 chondrites abstract eight c3 chondrites were examined by the i129 xe129 dating method to see whether their i xe ages better initial i 129 i 127 ratios r0 correlate with any other properties the r0 s range from 1 60 10 4 to 1 09 10 4 corresponding to i xe ages from 2 0 myr before to 6 7 myr after murchison magnetite three c3o s lance felix ornans have essentially indistinguishable r0 s of 1 41 0 13 to 1 17 0 10 10 4 the fourth c3o warrenton is undatable owing to homogenization of radiogenic and trapped xe four c3v s show a distinct spread vigarano and grosnaja are highest r0 1 60 0 07 and 1 57 0 14 10 4 mokoia is intermediate and kaba is lowest r0 1 38 0 06 and 1 09 0 10 10 4 literature values for allende place it near kaba these r0 s correlate inversely with 4 other properties i br and cd content and olivine composition both percent mean deviation pmd and proportion of iron poor olivine grains 2 fayalite it is difficult to accept the 9 myr spread in r0 as a true age reflecting either nebular or parent body processes this time span is more than an order of magnitude longer than the lifetime of the solar nebula inferred from astronomical evidence nor does the degree of thermal metamorphism which is slight for c3 s anyway correlate with r0 a more plausible interpretation is that the variations in r0 reflect mainly isotopic heterogeneity of iodine the simplest model that accounts for the correlations with r0 involves mixing of two iodine components in the solar nebula associated with gas and grains respectively the second of lower i 129 i 127 ratio predominated at later times and thus became enriched in late formed meteorites along with other volatiles such as cd and br the low fe content and large pmd of olivine may reflect either less metamorphism owing to shallow location in the parent body or greater reduction of fe2 during chondrule formation

near coastal satellite altimetry sea surface height variability in the north sea baltic sea area 1 the radiometer wet tropospheric correction is a limiting factor of the application of near coastal altimetry observations in the north sea baltic sea area using an ecmwf model based correction instead we increase the return rate from 70 to 95 with observations as close as 10 km from the coast the altimetry and 39 coastal tide gauges are referenced to the same state of the art regional geoid the two data sets are highly correlated and reveal a consistent mean dynamic topography and two distinct correlation regimes separated by the danish islands the combination of the two data sets in a simple statistical model is shown to estimate the sea surface height with the same error level as state of the art operational models indicating the potential for near coastal applications of satellite altimetry observations

fayalite rich rims veins and halos around and in forsteritic olivines in cais and chondrules in carbonaceous chondrites types compositional profiles and constraints of their formation abstract fayalite rich rims veins and halos around and in forsteritic olivines are a wide spread phenomenon in chondrules ca al rich inclusions cais and single grains in carbonaceous chondrites the presence of fayalite rod like crystals and laths in rims veins in wall of pores and as fluffy network bridging neighbouring olivines pyroxenes feldspars etc is strongly suggestive that the fayalitic olivine was formed by condensation presumably from the solar nebula gas the formation of the fayalitic olivine was probably caused by an increase in the h 2 o h 2 ratio to a ratio between 0 1 1 subsequent to condensation of forsterite at that stage feni inclusions in olivine were also oxidized and fayalitic halos around the metal were then formed by fe diffusion along with addition of sio 2 from the solar gas or loss of mgo to the solar gas the fa rich olivine rims and veins display a narrow compositional variation between fa 34 and fa 46 subsequent to condensation of fa rich olivine and oxidation of feni metal fe diffused in forsterite this diffusion was probably enhanced due to the presence of point defects in olivine or the formation of a nonstoichiometric phase analogous to laihunite enriched in al 2 o 3 and cr 2 o 3 however the presence of al 2 o 3 and cr 2 o 3 rich discrete domains cannot be excluded cooling rates calculated by modelling of the diffusion profiles are indicative of rapid cooling subsequent to the condensation of fayalitic olivines we obtain cooling rates ranging from 2000 c day and 10 c day at an initial temperature of 1200 c and 900 c respectively

altimeter derived surface circulation in the large scale ne pacific gyres part 1 seasonal variability abstract the seasonal variability of sea surface height ssh and currents are defined by analysis of altimeter data in the ne pacific ocean over the region from central america to the alaska gyre the results help to clarify questions about the timing of seasonal maxima in the boundary currents as explained below the long term temporal mean of the ssh values must be removed at each spatial point to remove the temporally invariant and large signal caused by the marine geoid we refer to the resulting ssh values which contain all of the temporal variations as the residual ssh our main findings are 1 the maximum surface velocities around the boundaries of the cyclonic alaska gyre the alaska current and the alaska stream occur in winter at the same time that the equatorward california current is weakest or reversed forming the poleward davidson current the maximum surface velocities in the california current occur in summer these seasonal maxima are coincident with the large scale atmospheric wind forcing over each region 2 most of the seasonal variability occurs as strong residuals in alongshore surface currents around the boundaries of the ne pacific basin directly connecting the boundaries of the subpolar gyre the subtropical gyre and the equatorial current system 3 seasonal variability in the surface velocities of the eastward north pacific current west wind drift is weak in comparison to seasonal changes in the surface currents along the boundaries 4 there is an initial appearance next to the coast and offshore migration of seasonal highs and lows in ssh alongshore velocity and eddy kinetic energy eke in the alaska gyre similar to the previously described seasonal offshore migration in the california current 5 the seasonal development of high ssh and poleward current residuals next to the coast appear first off central america and mainland mexico in may june prior to their appearance in the southern part of the california current in july august and their eventual spread around the entire basin in november december similarly low ssh and equatorward transport residuals appear first off central america and mexico in january february before spreading farther north in spring and summer 6 the maximum values of eke occur when each of the boundary currents are maximum

improved satellite altimetry in coastal systems case study of the corsica channel mediterranean sea 1 the fidelity of corrections and processing are critical for a realistic use of official altimetric products close to the coast a new processing strategy which starts from the topex poseidon gdrs with the addition of improved corrective terms is proposed and evaluated in the area of the corsica channel sea level anomalies agree with the coincident sea truth bottom pressure and tide gauge within 2 3 cm rms for seasonal and longer time scales analysis for almost ten years of coincident mooring and altimetric velocities shows that a substantial reduction of uncertainty to 4 cm s 1 may be possible after reasonable filtering of the noise introduced by more variable coastal sea surface states the conclusion is that the altimetry success is still limited to seasonal time scales and provided that the oceanographic signal ensures an adequate signature to be isolated from background noise

on the spatial structure of coastal circulation off newport oregon during spring and summer 2001 in a region of varying shelf width 1 a time series of hourly surface current maps in the shelf waters off newport oregon was made during april september 2001 using five seasonde hf current mappers during coastal advances in shelf transport coast the surface currents responded rapidly to the changing winds in repeated patterns that were strongly affected by bottom topography an equatorward current jet repeatedly formed in response to upwelling winds its strength but not its trajectory covarying with the meridional wind stress near cape foulweather 44 8 n where the shelf begins to widen the jet rotates weakens and trends offshore to the south first along then across the isobaths below cape foulweather inshore of the jet a lee region of generally weak currents was commonly observed the equatorward jet core was most commonly observed near the 80 m isobath between 45 0 n and 44 4 n but transited offshore between spring and summer over heceta bank at newport 44 6 n it was rarely observed less than 8 km from the coast a second inshore equatorward jet previously unknown was observed repeatedly south of waldport 44 4 n sustained downwelling wind episodes produced poleward currents though less responsively north of cape foulweather strongest poleward flow was generally trapped near the coast surface currents were correlated with the northward wind except regionally far from shore over heceta bank responding within half a day response to the wind varies spatially being intensified in the narrow shelf northern region the equatorward jet persists through periods of zero wind forcing coastal sea level covaries with the meridional wind and the primary mode of ocean current response

intensified diurnal tides along the oregon coast abstractintensified diurnal tides are found along portions of the oregon shelf u s west coast based on analyses of high frequency hf radar surface current data and outputs of a 1 km resolution ocean circulation model the k1 tidal currents with magnitudes near 0 07 m s 1 over a wider part of the shelf heceta bank complex 44 44 5 n previously predicted by erofeeva et al are confirmed here by newly available hf radar data intensified diurnal tides are also found along the narrow shelf south of heceta bank in the close vicinity of cape blanco 42 8 n diurnal tidal currents k1 and o1 constituents combined may reach 0 3 m s 1 appreciable differences in diurnal tide intensity are found depending on whether the model is forced with tides and winds tw or only tides also diurnal variability in wind forcing is found to affect diurnal surface velocities for the case forced by tides alone results strongly depend on whether the model ocean is stratified tides only stratified tos or not t

spatiotemporal variations of mesoscale eddies in the sulu sea mesoscale eddies have been observed in the sulu sea but their characteristics have not been well described this study investigates the eddy population in the sulu sea using 22 years of satellite altimeter data with high spatiotemporal resolution on average there are approximately 1 6 eddies observed in the sulu sea each day and 1 8 eddy tracks generated each month two of the main eddy genesis regions are west of negros island and the zamboanga peninsula the mean radius lifespan and propagation speed of the eddies are 76 6 km 32 days and 4 5 cm s respectively the eddy radius and amplitude are generally large in the central sulu sea but small on its margin the mean eddy kinetic energy and vorticity generally monotonically decrease from south to north consistent with the distributions of background current kinetic energy over the seasonal cycle there are more cyclonic eddies during boreal winter and they tend to have a larger amplitude and radius than the other 3 seasons while there are more anti cyclonic eddies during boreal summer and they tend to have a larger amplitude and radius than the other 3 seasons the instability of the mean current and the island gap wind jets are the two key eddy genesis mechanisms in the sulu sea

the matrices of unequilibrated ordinary chondrites implications for the origin and history of chondrites abstract the matrices of sixteen unequilibrated ordinary chondrites all witnessed falls were studied microscopically in transmitted and reflected light and analyzed by electron microprobe selected specimens were also studied by scanning electron microscopy these studies indicate that the fine grained opaque silicate matrix of type 3 unequilibrated chondrites is compositionally mineralogically and texturally distinct from the chondrules and chondrule fragments and may be the low temperature condensate proposed by larimer and anders 1967 1970 examination of the matrices of unequilibrated chondrites also shows that each meteorite has been metamorphosed with the alteration ranging in intensity from quite mild where the matrix has been only slightly altered to a more severe metamorphism that has completely recrystallized the opaque matrix most of the metamorphic changes in the matrix occurred without significant effects on the compositions or textures of the chondrules the metamorphic alteration probably resulted from a combination of processes including thermal metamorphism and the passage of shock waves the present appearance of each unequilibrated chondrite is a result of the particular temperature and pressure conditions under which it and its components formed plus the subsequent metamorphic alteration it experienced

estimates of sea surface height and near surface alongshore coastal currents from combinations of altimeters and tide gauges 1 present methods used to retrieve altimeter data do not provide reliable estimates of sea surface height ssh in the nearshore region resulting in a measurement gap of 25 50 km next to the coast in the present work gridded ssh fields produced by archiving validation and interpretation of satellite oceanographic data aviso in the offshore region are combined with coastal tide gauge time series of ssh to improve estimation in that gap along the west coast of the united states in the northern california current system between 40 and 45n and 123 8 and 126w to assess the increase in skill provided by this procedure the geostrophic alongshore currents calculated from the new ssh fields in the gap region are compared to three in situ nearshore current measurements resulting in correlation coefficients of 0 73 0 83 and standard deviations of the differences of 11 6 12 6 cm s substantially improved from the aviso only results when the ekman current components are estimated and added to the geostrophic currents comparisons to the 10 m deep acoustic doppler current profiler velocities are only slightly improved the ekman components make a more significant contribution when compared to hf radar surface current measurements providing correlations of 0 94 and standard deviations of the differences of 6 4 9 5 cm s these results represent a dramatic improvement in the quality of the ssh fields and estimated alongshore currents when additional realistic ssh data from the coastal region are added here we use coastal tide gauges to provide the additional ssh data but also discuss more general approaches for altimeter ssh retrievals in coastal regions where tide gauge data are not available

disentangling nebular and asteroidal features of co3 carbonaceous chondrite meteorites abstract analyses of olivines and low ca pyroxenes in a suite of porphyritic chondrules of types ia and ii in each of ten co3 chondrites and comparisons with similar chondrules in ll chondrites suggest that the co3 chondrites may be divided into a metamorphic sequence of subtypes 3 0 to 3 7 chondrules in allan hills a77307 and colony which we classify as type 3 0 show only igneous zoning whereas in the other more metamorphosed type 3 1 3 7 co chondrites chondrule silicates are enriched in feo most markedly in olivine crystals near the rims of type ia chondrules and along cracks the feo enrichments in metamorphosed chondrules result largely from equilibration by solid state diffusion between chondrules and feo rich matrices type 3 1 3 7 co chondrites were formed from chondrites like colony and alh a77307 in heated asteroids or planetesimals we find no evidence for nebular condensation of fayalite rims around these chondrules as reported for cv3 chondrites or nebular modification of chondrule silicates as favored by some workers metallic fe ni in alh a77307 contains up to 0 1 1 wt cr si and p as in the least metamorphosed ordinary chondrites and cm2 chondrites and grains of cohenite fe3c and haxonite fe23c6 these carbides which are the first reported in carbonaceous chondrites are associated with pentlandite and magnetite as in certain ll3 chondrites we assign the following petrologic subtypes to other co chondrites kainsaz 3 1 felix 3 2 alh 82101 and ornans 3 3 lance and alh a77029 3 4 alh a77003 3 5 warrenton 3 6 and isna 3 7

near surface dynamics of a separated jet in the coastal transition zone off oregon 1 three dimensional circulation in the coastal transition zone ctz off oregon is studied using a 3 km resolution model based on the regional ocean modeling system the study period is spring and summer 2002 when extensive observations were available from the northeastern pacific component of the global ocean ecosystems dynamics project our main focus is on near surface transports particularly in an area off cape blanco where an energetic coastal current is separated in the ctz comparisons with available observations velocities from midshelf moorings surface velocities from high frequency radars satellite sea surface temperature maps along track sea surface height altimetry and seasoar hydrography show that the model reproduces qualitatively correctly the flow structure and variability in the study area the near surface flow behavior during 26 july to 21 august a late summer time period of strong time variable southward winds is examined during that period the coastal jet separates from the continental shelf around cape blanco 43 n the energetic separated jet continues to flow southward in a near coastal region between 42 2 n and 43 n it subsequently turns around 42 n to flow westward offshore past 127 w relatively vigorous up and downwelling is found concentrated in the region of the separated jet frontogenesis secondary circulation nonlinear effects of the relative vorticity on the ageostrophic ekman transport and submesoscale instabilities contribute to the vertical circulation within the jet vertical velocities are found to reach 50 m d 1 in the offshore part of the jet and 100 m d 1 in the near coastal part where the jet is aligned with the wind direction

mesoscale structure and its seasonal evolution in the northern california current system abstract during spring and summer 2000 two mesoscale mapping cruises were carried out in the northern california current system between 41 9 n and 44 6 n and between the shallow inner continental shelf and up to 150 km offshore measurements were made using a towed undulating vehicle equipped with a conductivity temperature depth instrument and a chlorophyll fluorometer a shipboard acoustic doppler current profiler adcp measured water velocities and surface drifter trajectories and satellite sea surface temperature imagery provide context for the mesoscale maps nearly identical upwelling favorable wind stresses of up to 0 2 n m 2 existed during both the spring and summer surveys early in the season late may early june the upwelling front and jet followed the continental shelf bottom topography there was cold water inshore of the shelfbreak all along the coast with pockets of elevated phytoplankton biomass chlorophyll chl up to 4 mg m 3 near the coast mesoscale activity was minimal during late summer august the upwelling front and jet were much more convoluted including significant meanders offshore associated with a major submarine bank heceta bank 44 0 44 6 n and a large coastal promontory cape blanco 42 8 n high levels of phytoplankton biomass were found over heceta bank chl 20 mg m 3 and near the coast south of cape blanco chl 10 mg m 3 low velocities inshore of heceta bank measured by both shipboard adcp and surface drifters indicate the potential for retention of water over the bank leading to favorable conditions for phytoplankton biomass accumulation the large offshore meander near cape blanco carried cold nutrient rich high phytoplankton biomass chl of 2 5 mg m 3 water over 100 km offshore this flow topography interaction feature was generated in mid june and remained an important part of the regional circulation for about 2 5 months

eddy induced sea surface temperature gradients in eastern boundary current systems many processes are known to influence the distribution of sea surface temperature sst fronts in eastern boundary current systems ebcs including wind forcing mesoscale activity flow instabilities and flow topography interactions here we used satellite observations to quantify the relative importance of one of these processes mesoscale eddy activity on the distribution of sst gradients in ebcs eddies are characterized by large sst and sst gradient anomalies in all ebcs at the end of the upwelling season eddy induced sst gradients are dominant components of the full sst gradient offshore of 300 km from the coast especially in regions of high eddy activity comparisons between eddy induced and full sst gradients in the california current system indicate that the offshore migration of mesoscale eddies plays a significant role on the seasonal widening of the region of high frontal activity sst gradients associated with anticyclonic eddies are largest within 400 km from shore while the signature of cyclones can extend for up to 700 km from the coast

water masses and circulation in the tropical pacific off central mexico and surrounding areas abstractthe seasonal variations and the interactions of the water masses in the tropical pacific off central mexico tpcm and four surrounding areas were examined based on an extensive new hydrographic database the regional water masses were redefined in terms of absolute salinity sa and conservative temperature according to the thermodynamic equation of seawater 2010 teos 10 hydrographic data and the evaporation minus precipitation runoff balance were used to investigate the origin and seasonality of two salinity minima in the area the shallow 50 100 m salinity minimum originates with the california current system and becomes saltier as it extends southeastward and mixes with tropical subsurface waters while the surface salinity minimum extends farther north in the tpcm in summer and fall because of the northward advection of tropical surface waters the interactions between water masses allow a characterization of the seasonal pattern of circulation of the mexican coastal current mcc

seasonal cycles of currents temperatures winds and sea level over the northeast pacific continental shelf 35 n to 48 n seasonal cycles of coastal wind stress adjusted sea level asl shelf currents and water temperatures off the west coast of north america 35 n to 48 n are estimated by fitting annual and semiannual harmonics to data from 1981 1983 longer records 9 34 years of monthly asl indicate that these two harmonics adequately represent the long term monthly average seasonal cycle and that the current measurement period is long enough to estimate the seasonal cycles we characterize the differences between fall winter and spring summer as follows for fall winter monthly mean winds north of 35 n are northward for 3 6 months longer in the north than in the south south of 35 n the mean winds are near zero or weakly southward monthly mean alongshore currents are northward over midshelf and shelf break at all locations sampled at depths of 35 m and deeper and are associated with high coastal sea levels and relatively warm water temperatures for spring summer monthly mean wind stresses are southward at all latitudes for 3 6 months longer in the south than in the north sea levels are low and water temperatures are relatively cool monthly mean currents at 35 m depth over the shelf are southward for 1 6 months longer at the shelf break than over midshelf and longer in the north than in the south while the deeper currents are less southward or northward the magnitudes of the seasonal cycles of all variables are maximum between approximately 38 n and 43 n generally decreasing slightly to the north and greatly to the south at each location the seasonal cycle of the alongshore current from 35 m depth at midshelf leads the sea level slightly and both lead the wind stress and temperatures by 1 2 months the seasonal cycles of all variables show a south to north progression south leads north by 1 2 months at 48 n annual mean currents at 50 m depth over the shelf break oppose the annual mean wind northward wind and southward current similarly at 35 n annual mean currents at 35 m depth over both midshelf and shelf break are opposed to the annual mean wind southward wind and northward current from 35 n to 43 n both summer and winter regimes are dominated by strongly fluctuating currents

improving the quality of satellite altimetry data over continental shelves 1 satellite altimetry has proven to be a useful tool to study oceanic processes in the deep ocean over continental shelves however the aliasing of unresolved high frequency signals of tidal and wind induced origin is the source of long wavelength errors that corrupt altimetry measurements and limit their use in shallow waters in 2005 ssalto duacs performed a complete reanalysis of altimeter data to accommodate the latest tidal model got2000 and a correction for the aliased high frequency signals using a hydrodynamic model mog2d g this paper examines the quality and the performance of the newly released altimetry data over the northwest european shelf this region is known for complex tides and for frequent storm surges the newly corrected maps of sea level anomalies were compared with a previous altimetry product residual tidal aliasing was analyzed and the impact of mog2d g and got2000 models was assessed altimeter records were compared with tide gauge measurements this research showed a significant reduction in the contamination of data by high frequency aliasing achieved through the use of the aforementioned models however aliased shallow water tidal constituents pose a serious problem and it is obvious that future tidal corrections should feature local tides nonaliased physical sea level variability was also studied focusing on interannual seasonal and intra annual periods from 20 days to 1 year modes the magnitudes and the contributions of each mode to the total variance were estimated it was demonstrated that the newly corrected data can successfully be used to study the variability of sea level over continental shelves

evaluating the use of high frequency radar coastal currents to correct satellite altimetry 1 coastal altimeter waveforms may differ from the ones in the open ocean either from rapid changes in the sea state or the presence of land within the satellite altimeter footprint the optimal retracking method for an individual track may turn out to be a combination of several retrackers and may depend on the sea state the coastal high frequency radar hfr ocean surface currents hourly interpolated with a resolution up to 2 km and an offshore range up to 150 km are evaluated to validate the altimeter sea surface height ssh measurements a method to derive hfr ssh mapped with a varying spatial scale optimal interpolation from the hfr velocities has been implemented evaluated mainly in the regions farther than 25 km off the u s west coast the hfr ssh shows good agreement with jason 1 2 altimetry products over the years 2008 and 2009 three jason 2 pistach retrackers and one generic open ocean retracker have been analyzed using the traditional 1 hz sampling rate nearshore an experimental reprocessing of the 20 hz range measurements is also tested to check for a gain in along track spatial resolution referencing to the hfr ssh indicate the need to have several retrackers available even over the continental shelf with ice3 fitting better during bloom events and mle 4 or red3 for high sea states these studies demonstrate the value of hfr as a potential tool to correct coastal altimeter ssh refine their spatial resolution and provide some insight into the altimeter behavior as a function of ocean conditions

assessing the accuracy of satellite derived ocean currents by comparing observed and virtual buoys in the greater agulhas region abstract in this study we assess the accuracy of a combined geostrophic and ekman current product globcurrent that estimates ocean currents at 15 m depth by coupling it to a synthetic particle tracking tool and comparing the virtual trajectories to those of surface drifting buoys drogued at 15 m in the greater agulhas current region the velocities from a total of 1041 drifters are compared and evaluated to the synthetic particle derived velocities for the period 1993 2015 on average the globcurrent underestimates the velocity in the greater agulhas current by approximately 27 the underestimation ranges from 4 to 64 in different regions with the smallest error found in the agulhas retroflection region and the highest in the benguela upwelling system furthermore we compare the time taken for the separation between the virtual and real drifters to reach 35 km the mean separation time was found to be 78 h with the shortest time 35 h found in the agulhas current and the longest time 116 h located in the agulhas return current deploying 10 000 virtual drifters in a 1 1 box within the southern agulhas current shows a convergence of trajectories towards the core of the current while higher divergence is evident in the agulhas retroflection to evaluate the utility of this synthetic particle tracking tool coupled with globcurrent in open ocean search and rescue operations two test cases are examined 1 a capsized catamaran spotted south of cape recife and recovered 5 days later south of cape agulhas and 2 a drifter trajectory in the same region the comparison suggests that the globcurrent forced synthetic particle tracking tool is not appropriate for predicting the trajectory of a capsized catamaran that does not have the same drift characteristics as a surface drifting buoy drogued to 15 m

chemical and physical studies of type 3 chondrites viii thermoluminescence and metamorphism in the co chondrites the thermoluminescence properties of nine co chondrites have been measured with the exception of colony and allan hills a77307 alha 77307 whose maximum induced tl emission is at approximately 350 c co chondrites exhibit two tl peaks one at 124 7 c 130 c peak and one at 252 7 c 250 c peak the 130 c peak shows a 100 fold range in tl sensitivity 0 99 0 21 for isna to 0 010 0 004 for colony and correlates with various metamorphism related phenomena such as silicate heterogeneity metal composition and mcsween s metamorphic subtypes the peak at 250 c does not show these correlations and colony excepted varies little throughout the class 0 3 to 0 07 colony 0 018 0 004 mineral separation experiments and a series of annealing experiments on isna suggest that the tl properties for co chondrites reflect the presence of feldspar in two forms 1 a form produced during metamorphism and analogous to the dominant form of feldspar in type 3 ordinary chondrites and 2 a primary metamorphism independent form perhaps associated with the amoeboid inclusions if this interpretation is correct then the co chondrites have not experienced temperatures above the order disorder temperature for feldspar 500 600 c and they cooled more slowly than comparable i e type 3 5 type 3 ordinary chondrites colony and alha 77307 have atypical tl properties including very low tl sensitivity suggesting that phosphors other than feldspar are important they have apparently experienced less metamorphism than the others and may have also been aqueously altered

large scale forcing of environmental conditions on subarctic copepods in the northern california current system in the ocean dominant physical processes often change at various spatial and temporal scales here we examined associations between large scale physical forcing indexed by the pacific decadal oscillation pdo regional ocean conditions including alongshore currents in relation to the abundance of two subarctic oceanic copepods neocalanus plumchrus and n cristatus in the offshore portions of the northern california current ncc system in spring of 1998 2008 we found significant relationships between the abundance of copepods water temperature and alongshore currents with a lag of two or four months in response to the pdo in the ncc system during the growth season in march april both subarctic copepod species displayed consistent cross shelf patterns with shoreward decreasing gradient in abundance and were negatively correlated with the pdo sea water temperature and alongshore currents our studies highlight the responses of regional ocean conditions to large scale physical forcing and illustrate the potential for neocalanus copepods as unique vectors for a new understanding of the ecological response in the offshore oceanic waters of the ncc system to climate variability

altimeter derived surface circulation in the large scale ne pacific gyres part 2 1997 1998 el nino anomalies abstract changes in the sea surface heights ssh and geostrophic transports in the ne pacific are examined during the 1997 1998 el nino using altimeter data sea level pressure slp fields proxy winds and satellite sea surface temperature sst most of the signal occurs along the boundaries of the basin from panama to the alaska peninsula changes in the ssh and alongshore transports along the boundaries are caused both by propagation of signals from the south stronger between the equator and the gulf of california and by local and basin scale winds stronger between the pacific northwest and the alaska peninsula two periods of high ssh occur at the equator may july 1997 and october 1997 january 1998 the first coastal ssh signal moved quickly polewards to approximately 24 n in early june then stalled and moved farther north during transient events in july september large scale wind forcing combined with the equatorial signals during the second period of high equatorial ssh fall 1997 to move the high ssh and poleward transports quickly around the alaska gyre a connection between the boundary currents and the interior north pacific developed as part of the large scale response to the basin scale winds after changes in the boundaries decreases in anomalies of ssh and poleward transports began in january 1998 south of 40 n and in february 1998 farther north

measurements of upper ocean surface current shear with high frequency radar estimates of the variation with depth of both the speed and direction of near surface ocean currents within the top meter have been made using time series data collected from a dual frequency high frequency radar located on the california coast south of monterey long term averages derived from this data set over 3 different years consistently revealed an expected reduction in the speed of the near surface current as a function of depth consistent with a logarithmic vertical current profile an unexpected and previously unmeasured clockwise rotation with increasing depth of the near surface current was also observed hypotheses are suggested for the apparent rotation

variability of the near surface eddy kinetic energy in the california current based on altimetric drifter and moored current data low pass filtered velocities obtained from world ocean circulation experiment woce surface drifters deployed in the california current off northern california during 1993 1995 have been compared with surface geostrophic velocity estimates made along subtracks of the topex poseidon altimeter and with moored acoustic doppler current profiler adcp data to obtain absolute geostrophic velocities a mean sea surface height ssh field was estimated using the mean drifter velocities and historical hydrographic data and was added to the altimetric ssh anomalies the correlation between collocated drifter and altimetric velocities is 0 73 significant at the 95 level the component of the drifter velocity which was uncorrelated with the altimetric velocity was correlated with the wind in the ekman transport sense monthly averages of eddy kinetic energy eke estimated using all drifter and altimeter data within the domain 124 132 w 33 40 5 n show energy levels for the drifters that are about 13 greater than those for the altimeter drifter altimeter and adcp measurements all exhibit similar seasonal cycles in eke with the altimeter data reaching maximum values of about 0 03 m 2 s 2 in late summer fall wavenumber spectra of the altimeter velocity indicate that the velocity fluctuations were dominated by features with wavelengths of 240 370 km while the adcp data suggest that the temporal scales of these fluctuations are at least several months between 36 and 40 5 n the region of monthly maximum eke migrates westward to about 128 w on a seasonal timescale this region of maximum eke coincides with the maximum zonal ssh gradient with increased eke associated with increased southward flow a simple model shows that much of the seasonal cycle of the ssh anomalies can be produced by linear processes forced by the curl of the wind stress although the model cannot explain the offshore movement of the front

a coastal retracking system for satellite radar altimeter waveforms application to ers 2 around australia 1 satellite radar altimeter derived sea surface heights ssh are in error in coastal regions due in part to the complex nature of echoes returned from rapidly varying land and sea surfaces this paper presents improved altimeter derived ssh results in australian coastal regions using the waveform retracking technique which reprocesses the waveform data through a coastal retracking system the system based upon a systematic analysis of satellite radar altimeter waveforms around australia improves ssh data from several retrackers depending on the waveforms characteristics central to the system is the use of two techniques the least squares fitting and the threshold retracking algorithms to overcome the problem of fading noise the fitting algorithm has been developed to include a weighted iterative scheme the retrackers include five fitting models and the threshold method with varying threshold levels a waveform classification procedure has also been developed which enables the waveforms to be sorted and then retracked by an appropriate retracker two cycles of 20 hz waveform data from ers 2 have been reprocessed using this system to obtain the improved ssh estimates using the ausgeoid98 gravimetric geoid model as a quasi independent reference the system improves ssh estimates from beyond 22 km to beyond 5 km from the coastline

a separating coastal upwelling jet at cape blanco oregon and its connection to the california current system the coastal upwelling region near cape blanco oregon 433n o the west coast of the united states was studied using a towed ctd on seasoar a shipboard acoustic doppler current pro ler adcp satellite sea surface temperature maps and surface drifters during august 1995 the equatorward upwelling jet was inshore of the shelfbreak north of cape blanco meandered gently o shore around the cape and then veered sharply o shore just to the south of the cape analysis of vertical sections of density velocity and spicinessa con rmed the separation of an upwelling jet and front the jet was followed from over the shelfbreak north of the cape to 100 km o shore downstream of the cape the separating jet originates from the coastal upwelling jet leaving the shelf but is augmented by an o shore branching of the poleward undercurrent by combining information from adcp streamfunction maps with analysis of hydrographic data including distributions of the tracer like quantity spicinessa a conceptual model of the three dimensional circulation near the cape emerges a mid shelf upwelling jet encounters a coastal promontory then turns o shore stretching and deepening as it crosses the continental margin the jet then turns back shoreward cyclonically where the deepened equatorward ow encounters the top of the poleward undercurrent owing along the continental slope this causes a portion of the undercurrent to turn o shore to join and strengthen the equatorward transport in the separated jet throughout the separation process the coastal upwelling front and jet are continuous robust features separation of a coastal upwelling jet is an important mechanism for cross shelf transport from the coast to the deep ocean cape blanco appears to be the northernmost point where an equatorward jet regularly separates from the coast to become an oceanic jet and thus serves as the northern boundary of the region where an intense meandering current characteristic of the california current system

spinel compositions of mantle hosted chromitite from the eastern anatolian ophiolite body turkey implications for deep and shallow magmatic processes abstract the eastern anatolian accretionary complex includes several ophiolitic megablocks and or tectonic slivers within a 150 180 km long east west trending complex formed during the late cretaceous tertiary in eastern turkey the alabayir mollatopuz yukaribalcikli and mehmetalan ophiolites are megablocks or tectonic slivers containing locally massive nodular or schlieren banded chromitite layers these podiform chromitites formed in mantle sequences and are classified as high cr chromitites cr 0 63 0 88 mg 0 50 0 64 0 01 0 5 wt tio 2 5 7 18 8 wt al 2 o 3 calculated parental melt compositions of these chromitites indicate boninite magma characteristics 8 2 13 4 wt al 2 o 3 0 64 1 50 feo mgo the pge patterns also support the view that they crystallized from a boninitic melt the total pge contents of chromitites vary between 79 and 390 ppb pd ir ratios of chromitites vary from 0 07 to 0 28 and are consistent with an ipge fractionated nature the examined chromitites were divided into two groups in terms of their mineral chemistry group i alabayir mollatopuz yukaribalcikli and mehmetalan i chromitites group ii mehmetalan ii chromitites mineral chemistry of these chromitites and their parental melt composition indicate that group i chromitites were probably formed at shallow mantle depths and that group ii chromitites formed in deeper parts of the mantle mineral chemistry of these eastern anatolia high cr chromitites indicate that they formed not only in the deeper mantle but also in shallower parts of the moho transition zone