on the wave number spectrum of oceanic mesoscale variability observed by the seasat altimeter variations of sea surface height measured by the seasat altimeter in nearly repeat orbits during the last 24 days of the mission are used to compute the wave number spectrum of mesoscale variability in various parts of the oceans the instrument noise level 150 cm2 cycles km has limited the resulting oceanic spectrum to wavelengths longer than 100 km we found that the characteristics of the oceanic spectrum are dependent on the energy level of the mesoscale variability in the high energy areas close to major current systems most of the energy is contained at wavelengths longer than 250 km at wavelengths shorter than 250 km the spectrum basically follows a k 5 k is wave number dependence in the low energy areas remote from major current systems the spectrum follows a k 1 dependence at wave lengths from 100 to 1000 km based on the assumption of horizontal isotropy of mesoscale variability scalar wave number spectra of sea surface height and geostrophic kinetic energy are also presented dynamical implications of these spectra are discussed the effects of residual geoid and atmospheric water vapor on the computed oceanic spectra have been rigorously examined it was found that the general characteristics of the oceanic spectra were not significantly affected by them

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

from swallow floats to argo the development of neutrally buoyant floats neutrally buoyant floats have been a vital tool in the exploration of the global ocean circulation and now provide a central element of the in situ ocean observing system through the argo project the paper traces the development of neutrally buoyant floats from their origins in the mid 1950s to the present day and highlights areas of ocean science to which floats made significant contributions

barium partitioning during the transformation of corals from aragonite to calcite examination of fresh aragonite and altered calcite corals from the pleistocene reef terraces exposed on barbados west indies reveals the natural partitioning of ba2 during the aragonite calcite transformation the ba2 decreased from typical values of 8 15 ppm in the aragonites to 1 3 ppm in the calcites a finding consistent with the experimentally determined partition coefficient of ba2 into calcite 0 06 0 02 at 25 c quantitatively the degree of partitioning of ba2 in these samples was compatible with the simultaneous partitioning of sr2

rhenium and molybdenum enrichments in sediments as indicators of oxic suboxic and sulfidic conditions of deposition abstract the trace elements re and mo both behave conservatively in seawater yet are strongly enriched in reducing sediments their potential for authigenic enrichment above crustal concentrations is greater than for many other elements due to the high ratio of metal sw metal crust we present sedimentary re and mo data from box and multi cores spanning a range of redox conditions from well oxygenated sites to locations with substantial sulfide concentrations at the oxic sites re and mo as expected accumulate at concentrations close to their crustal abundances re shows substantial enrichment in suboxic absence of o 2 and h 2 s sediments of the sea of japan in sediments within the oxygen minimum of the pakistan margin as well as in sediments underlying the sulfide bearing waters of the black sea and saanich inlet re enrichment occurs in these cores just below the depths of fe and u reduction only in the sediments underlying the sulfidic waters of the black sea and saanich inlet is there substantial authigenic mo accumulation absence of re and mo enrichments in sediment trap samples from the sulfide bearing basins suggests that the addition of both metals occurs at or below the sediment water interface the re and mo concentration profiles are modeled to hindcast the removal depth of re and mo in the sediments which along with the re mo ratio determine whether oxic suboxic or sulfidic conditions were present in the water column or in the sediments in the past using this approach historical redox conditions can be inferred even in environments such as continental margins where a substantial lithogenic component can obscure authigenic enrichments of other metals

status of the geopotential substantial progress has been made in modeling the geopotential field since the last reporting period anderle 1979a models of the gravity potential show improvement across the entire gravitational spectrum with resolution down to 1 haif wavelength major sources of data utilized for advancing our knowledge of the geopotential field consist of satellite laser ranging smith 1982 wilson 1979 linder 1981 which contributed to the long wavelength portion of the spectrum satellite altimetry geos 3 1979 seasat 1981 and improved surface gravity anomalies rapp 1981b both of which contributed to the intermediate and short wavelength features of the spectrum uniform global distribution of data in combination solutions is generally achieved by using altimeter data over the ocean and terrestrial gravity anomalies over land

comparison data for seasat altimetry in the western north atlantic the radar altimeter flown on seasat in 1978 collected approximately 1000 orbits of high quality data 5 8 cm precision in the western north atlantic these data have been combined with a detailed gravimetric geoid in an attempt to produce profiles of dynamic topography in order to provide a basis for evaluation of these profiles available oceanographic observations in the gulf stream sargasso sea region have been compiled into a series of biweekly maps the data include xbt s satellite infrared imagery and selected trajectories of surface drifters and subsurface sofar floats the maps document the known locations of the gulf stream cyclonic and anticyclonic rings and mid ocean eddies during the period july october 1978

a synthetic geoid validation of geosat mesoscale dynamic topography in the gulf stream region a validation study is carried out for the geosat altimeter in the gulf stream meander and ring region a synthetic geoid containing the medium scales of interest for mesoscale research is constructed by subtracting an independent estimate of the oceanographic mean dynamic topography from the altimetric sea surface the oceanographic mean dynamic topography which is concurrent with the altimetric mean is derived from a year of real time nowcasts and forecasts gulfcast based on assimilating a composite data set into a dynamical model using the synthetic geoid absolute dynamic topography from geosat and gulfcast for a year and 4 months in 1988 and 1989 compare very well in signal shape and feature locations sixteen cases of comparison of dynamic heights derived from axbts along geosat tracks in 1987 are made with geosat absolute topography the rms difference is less than 10 cm thus the comparison of these two independent data sets validates the altimeter and the synthetic geoid within the noise and error levels of the system

seasat altimeter determination of ocean current variability radar altimeters of great precision roughly equal10 cm such as the one that flew on the seasat satellite are capable of measuring the small oceanic height variations associated with geostrophic ocean currents an experiment was concluded in the kuroshio current east of japan verifying this capability air expendable bathythermographs axbt s were dropped to coincide with the seasat subtract during flights on september 25 and october 5 and 13 1978 changes in surface dynamic height between flights were inferred from the axbt data they agreed generally to within 10 cm of height changes observed in the altimeter data

the seasat altimeter data and its accuracy assessment the seasat satellite launched on june 27 1978 carried a radar altimeter designed to measure the altitude of the satellite above the ocean surface the surface wave height and the ocean surface backscatter coefficient from which wind speed can be inferred postlaunch engineering assessment indicated that the seasat altimeter met the performance specification for 10 cm precision noise in the altitude measurements however to determine the accuracy of this measurement as well as the accuracy of the wave height and wind speed measurements a significant calibration validation and model development effort was required this summary describes the instrument atmospheric and geophysical effects which influence the radar altimeter measurement accuracies and the attendant correction models adopted for the altimeter geophysical data record also summarized are the activities of the seasat altimeter precision orbit determination experiment team directed towards the validation and improvement of these models as well as the investigations required to assess the accuracy of the altimeter measurement and the computed satellite altitude ephemeris finally an accuracy assessment is made for the various altimeter measurement corrections which are included on the altimeter geophysical data record

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

on the accuracy of marine gravity measurements we have assessed the accuracy of lamont doherty geological observatory s global marine gravity data bank by examining the crossover errors coes at intersecting ship tracks more than 63 000 coes were found having a standard deviation of 22 43 mgal mgal 10 5 m s 2 we use the coes to find and remove linear drifts and dc shifts present in the data set this adjustment reduces the standard deviation to 13 96 mgal coes generally decrease with latitude which we attribute to uncertainties in the eotvos correction high coes occur in areas of high gravity gradients these two features point to poor navigation as the principal source of error in marine gravity surveys coes have generally been decreasing during the last two decades reflecting improvements in instrumentation and quality of navigation a comparison of the shipboard gravity data to seasat derived gravity revealed a 9 mgal bias in the terrestrial data which probably reflects uncertainties in choice of reference field the adjusted data set was used to generate a gravimetric geoid for the nw atlantic ocean by removing this geoid from the seasat sea surface heights a residual geoid was obtained a special feature of this map is an elongate ene trend that appears to correlate with the edge of the gulf stream

spatial variations of ocean wave directional spectra from the seasat synthetic aperture radar seasat synthetic aperture radar ocean wave spectra for a 900 km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers systematic vector wavenumber variations of several times the standard error of determination 1 5 in magnitude and 0 9 in direction occur along the entire 900 km pass the large scale spatial variation of a 200 m swell system can be accurately accounted for as a result of dispersion from a distant storm the more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state there is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east

observations of eddy fields in the northwest atlantic and northwest pacific by seasat altimeter data sea level variability related to the eddy field activity can be calculated from repeating tracks of altimetric data such as the seasat 3 day repeat data september 13 to october 10 1978 if we consider the eddy field in geostrophic balance the geostrophic relation gives the surface eddy velocities also an estimation of the eddy kinetic energy can be deduced under the assumption of quasi isotropy of the velocity variability this approach is used in the northwest atlantic and northwest pacific through the processing of seasat data high variability of sea surface topography up to 20 cm and high eddy kinetic energy 800 1600 cm sup 2 s sup 2 are detected in the vicinity of the gulf stream and the kuroshio power spectra of the observed sea level fluctuations give wavelengths ranging from 100 to 900 km for time scales between 3 and 25 days maps of sea surface topography variability and eddy kinetic energy are presented and discussed

capture of arsenic by pyrite in near shore marine sediments abstract evidence of pyrite formation during diagenesis of suboxic sediments in the laurentian trough canada is presented the process is slower than in salt marsh sediments probably due to the low sulfate reduction rate of 2 3 nmol cm 3 day 1 measured in the st lawrence sediments a strong correlation is observed between arsenic and pyrite suggesting the capture of this element in the lattice sites of pyrite with a fe as ratio of 10 3 it is important to consider this association of as with pyrite in the study of the marine geochemistry of fe and as

seasat derived ocean surface topography comparison with coincident kuroshio hydrographic data during the seasat repeat orbit period a ctd and deep 1800 m xbt hydrographic experiment was conducted across the kuroshio to obtain cotemporaneous surface topography measurements for comparison with the altimeter derived surface height measurements the results showed that the altimeter could detect and measure the change in sea surface topography caused by movement of the kuroshio and the cold rings that were found in the hydrographic data after compensation for the small differences in the time of the measurements the altimeter measured changes in the surface topography that matched those measured by the hydrographic sections with an average difference of 9 6 cm for the 41 comparison points

dynamic topography estimates using geosat data and a gravimetric geoid in the gulf stream region summary a gravimetric geoid undulation on a 3 x 3 grid has been calculated in the gulf stream region 30 5 i 45 278 5 i 5 318 these undulations were calculated using two 360 potential coefficient models land ship and altimeter derived gravity anomalies and bathymetric data least squares collocation and fast fourier transform procedures were used with various data selection and gridding procedures results from five different undulation computations are described with comparisons made with synthetic geoid undulations along geosut tracks in the region the standard deviation of the undulation differences was f14cm when a cubic polynomial was used to model long wavelength errors a point verification of the geoid undulation at the laser tracking station on bermuda was also made with a discrepancy ground truth minus model undulation of 40 cm within the predicted standard deviation the gravimetric geoid undulation was used to compute dynamic topography along geosat tracks for comparison with existing estimates based on hydrographic data in the gulf stream region the agreement between these two estimates is on the order of f15 cm although the discrepancies can reach 60 cm the larger differences are usually associated with a location on a track that passes near a seamount where the gravity data may be inadequate to represent the high frequency variations in the geoid undulations this effect will be represented in the undulation standard deviations that have been calculated using the least squares collocation procedure the average accuracy is fl6cm with the range from f14 to f48cm the dynamic height derived from the gravimetric undulations and altimeter data has been used to calculate characteristics of the gulf stream width velocity centre location height profile using an implied velocity model for the set the results are compared with previous estimates with generally good agreement however the maximum velocities and the jump function are approximately 30 per cent larger than previous studies that used an average of altimeter tracks to define the geoid undulation the dynamic topography was calculated for the entire region using a mean sea surface based on geos 3 seasat and geosat data the results are compared with two hydrographic estimates due to martel wunsch and letraon mercier the agreement is at the f25cm level with the best correlation coefficient reaching 0 72 with the martel wunsch model

uncertainties in the mean ocean dynamic topography before the launch of the gravity field and steady state ocean circulation explorer goce 1 in anticipation of the future observations of the gravity mission gravity field and steady state ocean circulation explorer goce the present day accuracy of mean dynamic topography mdt is estimated from both observations and models a comparison of five observational estimates illustrates that rms differences in mdt vary from 4 2 to 10 5 cm after low pass filtering the fields with a hamming window with wavenumber n 120 corresponding to an effective resolution of 167 km rms differences in observational mdt reduce to 2 4 8 3 cm for n 15 1334 km differences in data sources geoid model in situ data are mostly visible in the small scale oceanic features while differences in processing filtering inverse modeling techniques are reflected at larger scales a comparison of seven different numerical ocean models demonstrates that model estimates differ mostly in western boundary currents and in the antarctic circumpolar current rms differences between modeled and observed mdt are at best 8 8 cm for n 120 and reduce to 6 4 cm for n 15 for models with data assimilation a minimal rms difference of 6 6 cm n 120 to 3 4 cm n 15 is obtained with respect to the observational mdts the reduction of differences between mdts with increasing filtering scales is smaller than expected while it is expected that goce will improve mdt estimates at small spatial scales improvement of mean sea surface estimates from satellite altimetry may be needed to improve mdt estimates at larger scales

calibration of the cryosat 2 interferometer and measurement of across track ocean slope this paper describes the calibration of the cryosat 2 interferometer whose principal purpose is to accurately measure the height of the antarctic and greenland ice sheets a sequence of cryosat 2 data acquisitions over the tropical and midlatitude oceans were obtained between june and september 2010 from the siral a and redundant siral b radars operating in their sarin mode during a sequence of satellite rolls between 0 6 and 0 4 using the arrival angle of the echo relative to the interferometer baseline the attitude of the satellite determined by the star trackers and estimates of the ocean surface across track slope from the egm08 geoid we determined the errors in the interferometer estimate of surface slope as functions of the roll angle and ocean surface waveheight these were found to be in close agreement with the theoretical description the scale factor of the interferometric measurement of angle was determined to be 0 973 0 002 we estimate the accuracy of the across track slope measurement of the interferometer by applying this scale factor to the measured phase in applying this scale factor to the measurements the across track slope of the marine geoid was obtained with an accuracy of 26 rad at 10 km and 10 rad at 1000 km we conclude that the instrument performance considerably exceeds that needed for the accurate determination of height over the sloping surfaces of the continental ice sheets the results also demonstrate that cryosat 2 provides the first observations of the instantaneous vector gradient of the ocean surface and that the normal incidence interferometric configuration has a greater potential for the measurement of the ocean across track slope than has been previously recognized

dynamics of the slope water off new england and its influence on the gulf stream as inferred from satellite ir data abstract the movements of warm core rings and the gulf stream front were studied in the new england slope water region by using both satellite ir data and available in situ sea surface temperature data it is found that 1 the rotating speed of the rings exhibits a marked seasonal variation with the maximum speed occurring in the winter and the minimum in the late fall 2 the surface area of the rings increases monotonically with time and 3 the gulf stream front at the north wall migrates seasonally and attains its northernmost position in the late fall based on these findings we calculated the horizontal eddy viscosity for the rings as 4 10 8 cm 2 5 furthermore by comparing the seasonal variations of the rotational velocity of the rings and the total mass transport of the gulf stream we suggest that the seasonal variation of the slope water hydrography through local air sea interactions could play an important role in the dynamics of the gulf stream system

enzymatic iron and uranium reduction by sulfate reducing bacteria abstract the potential for sulfate reducing bacteria srb to enzymatically reduce fe iii and u vi was investigated five species of desulfovibrio as well as desulfobacterium autotrophicum and desulfobulbus propionicus reduced fe iii chelated with nitrilotriacetic acid as well as insoluble fe iii oxide fe iii oxide reduction resulted in the accumulation of magnetite and siderite desulfobacter postgatei reduced the chelated fe iii but not fe iii oxide desulfobacter curvatus desulfomonile tiedjei and desulfotomaculum acetoxidans did not reduce fe iii only desulfovibrio species reduced u vi u vi reduction resulted in the precipitation of uraninite none of the srb that reduced fe iii or u vi appeared to conserve enough energy to support growth from this reaction however desulfovibrio desulfuricans metabolized h2 down to lower concentrations with fe iii or u vi as the electron acceptor than with sulfate suggesting that these metals may be preferred electron acceptors at the low h2 concentrations present in most marine sediments molybdate did not inhibit fe iii reduction by d desulfuricans this indicates that the inability of molybdate to inhibit fe iii reduction in marine sediments does not rule out the possibility that srb are important catalysts for fe iii reduction the results demonstrate that although srb were previously considered to reduce fe iii and u vi indirectly through the production of sulfide they may also directly reduce fe iii and u vi through enzymatic mechanisms these findings as well as our recent discovery that the so reducing microorganism desulfuromonas acetoxidans can reduce fe iii demonstrate that there are close links between the microbial sulfur iron and uranium cycles in anaerobic marine sediments

a semianalytical model of the synthetic aperture interferometric radar altimeter mean echo and echo cross product and its statistical fluctuations this paper develops a model of the synthetic aperture interferometric satellite radar altimeter echo power and echo cross product the model uses the smallness of the satellite pitch and roll angles and the limited range of satellite altitude to provide a semianalytical echo model whose numerical dimensions are limited to two in the synthetic aperture case or three in the interferometric case at large roll angles making its application to extensive data practical by not implementing the synthetic beam formation it is demonstrated that the model recovers the conventional case of a pulse limited altimeter a theoretical description of the fluctuations in the multilooked interferometric cross product and the synthetic aperture and pulse limited powers is given by extending the model to describe correlations between individual looks in each case the model offers the potential to retrieve ocean surface parameters from synthetic aperture and pulse limited altimeter data simultaneously with obvious application to the new generation of altimeters onboard cryosat 2 sentinel 3 and sentinel 6 during the transition to operational synthetic aperture radar altimetry

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

collinear track altimetry in the gulf of mexico from seasat measurements models and surface truth abstract from 17 september to 10 october 1978 seasat made collinear passes over the gulf of mexico altimeter data for eight three day repeat passes over the eastern gulf were examined using an arc segment fitting technique to determine the mesoscale temporal variability of the sea surface the pattern of sea height variability was then compared with sea height data generated by a numerical model of the gulf hurlburt and thompson 1980 from the simulation of a complete cycle of loop current intrusion and shedding of an anticyclonic eddy the model data was found to match that from the seasat altimeter when an anticyclonic eddy separated from the loop current and the loop began to repenetrate into the eastern gulf analysis of sparse ground truth data from ship of opportunity xbt s satellite infrared imagery of the loop current boundary and synthetic aperture radar sar imagery also from seasat tend to confirm the circulation patterns deduced from the altimeter data and the numerical model author

global sea level change determination and interpretation the notion of sea level rise brings to the popular mind the specter of deep inundation of coastal regions one pictures skyscrapers emerging from the waters like so many sleeping flamingos standing in the shallows of a lake of course if all of the world s ice sheets suddenly melted or collapsed this vision would apply to new york city and its coastal counterparts but there is a general consensus that such a calamity is not an immediate threat houghton et al 1990 the actual situation for the recent historical past and near future appears to be more benign but with nonetheless extremely significant even devastating impacts due to erosion and flooding of coastal areas

pyritization of trace metals in anoxic marine sediments the pyritization of reactive trace elements in different anoxic marine sediments was investigated to determine the importance of factors such as h2s reactive fe pyrite content and salinity in controlling this process the areas studied included anoxic sulfidic sediments baffin bay a hypersaline coastal lagoon from texas and green canyon a hemipelagic oil seepage area anoxic nonsulfidic sediments with high sedimentation rates atchafalaya bay mississippi delta system hemipelagic anoxic nonsulfidic sediments with low sedimentation rates gulf of mexico shelf and slope and orca basin an euxinic hypersaline basin and organic rich marsh sediments atchafalaya bay results indicate that the degree of trace metal pyritization dtmp of all trace metals except cd increased with increasing degree of pyritization dop irrespective of the type of sedimentary environment involved however for as hg and mo the dtmpdop values were generally above the 1 1 ratio line whereas the transition metals co cu mn and ni displayed a close to linear increase in dtmp with dop and moderate incorporation into pyrite chromium and the class b metals pb and zn were also gradually incorporated into the pyrite phase but without reaching the dtmp levels exhibited by the transition metals cadmium was not incorporated to a significant extent these results are consistent with the chemical attributes of these different classes of trace elements availability of dissolved trace metals and organic matter content are apparently important factors controlling the incorporation of co cr cu and ni into pyrite in anoxicsulfidic fe poor and h2s rich environments

absolute measurement by satellite altimetry of dynamic topography of the pacific ocean satellites are the only foreseeable possibility for obtaining observations of the ocean circulation on the basin and global scales required to understand it such observations are essential for an understanding of the role of the ocean in various important problems for example climate the 3 month seasat mission1 has demonstrated2 3 that altimetry is capable of providing global observations of oceanic variability we show here that the data from this short sub optimum mission are also adequate for a determination of the absolute sea surface topography of the ocean on large scales a much more difficult4 and even more valuable measurement an absolute determination of the subtropical gyre of the north pacific ocean has been obtained we believe this to be the first direct measurement showing the existence of such a feature that does not depend on conventional hydrography and a series of assumptions

mesoscale ocean eddy measurements by multibeam altimetry a multibeam microwave radar altimeter concept is numerically simulated to evaluate its capability to remotely sense mesoscale oceanographic features and eddies in particular the study tests the sensitivity of the sensor to variations of systematic and environmental parameters including sensor attitude angle sensor position and system errors a novel concept of computing eddy vorticity from the multibeam data is explored application of this concept to the detection of simulated ocean eddies in the presence of tracker noise gives excellent results the technique is shown to be simple and accurate the minimum size of the eddy detectable by the multibeam altimeter is presented for a given performance characteristic of the radar

high resolution reconstruction of a holocene coastal sequence nw germany using inorganic geochemical data and diatom inventories abstract holocene deposits of the nw german coastal plain consist of many different lithological facies for example tidal flats brackish water sediments and peat beds the effects of the holocene sea level rise on palaeoenvironmental conditions of this coastal sequence were studied by inorganic geochemical methods in conjunction with diatom analyses three hundred samples from two parallel sediment cores which cover the entire nw german holocene were taken at high resolution and were examined for major and minor elements and bulk parameters selected samples were analysed for redox sensitive trace elements and ree distribution reactive iron and bulk sediment 34 s 32 s ratios chemical parameters for example si al and ca sr ratios and total organic carbon toc contents correlate with depositional factors such as wave energy and lithofacies changes which allow a detailed reconstruction of the palaeoenvironment diatom analyses reveal information about changes between marine brackish and limnic conditions and serve to reconstruct palaeosalinity early diagenetic effects are evident in the toc rich intervals most peat layers are affected by sulphate reduction and resulting pyrite formation as well as by enrichments in redox sensitive trace elements the highest enrichments are seen for as mo re and u indicating a distinct seawater influence s isotope ratios of peat samples are compatible with pyrite formation under both open and closed system conditions depending on exposition to seawater the inorganic geochemical and diatom data suggest limnic conditions at the base of the sequence and repeated changes towards marine conditions within the overlying clastic units on the other hand data obtained from the clastic units yield evidence of a recurrent succession from open to restricted marine brackish lagoonal and finally fen environments clastic sediments overlying peat layers correlate with the increase of marine derived geochemical signatures and pelagic diatoms attest transgressive overlaps the analyses suggest that major controls on the palaeoenvironments were i climate related oscillations of the coast line and ii the morphology of the coastal region allowing marine incursions even into distal semi terrestrial lowlands

degree of pyritization of iron as a paleoenvironmental indicator of bottom water oxygenation abstract a new method is presented for recognizing the degree of bottom water oxygenation in organic carbon bearing rock the method uses the parameter degree of pyritization dop which is the ratio of pyritic fe to pyritic fe acid soluble fe sediments with ages ranging from devonian to cretaceous have been classified on paleoecological and sedimentological criteria as having been deposited in aerobic conditions deposited in fully oxygenated bottom waters restricted marine conditions deposited in waters with low oxygen concentrations or inhospitable bottom conditions where little or no oxygen is present and h2s may be continually or intermittently present aerobic dop

interaction of the antarctic circumpolar current with bottom topography an investigation using satellite altimetry theoretical studies on the interaction of a zonal current with a zonal ridge an isolated bump and a meridional ridge compare favorably with hydrographic observations within the eastward flowing antarctic circumpolar current where it flows over similar topographic features however the existing hydrographic data are insufficient for examining the temporal stability and kinematic behavior of the resulting mesoscale structures in this study some of these transient features have been compared with patterns in sea surface variability derived from collinear satellite altimetric data when these features occurred near the crossing point of two satellite ground traces it was possible to characterize their length scales dynamic height relief and translational and surface geostrophic velocities

a comparison of ocean topography derived from the shuttle laser altimeter 01 and topex poseidon to assess the utility of laser altimetry for studies in dynamical oceanography the authors present a comparison of the shuttle laser altimeter sla 01 and the topex poseidon t p radar altimeter on global and regional scales they compare all spl sim 1 1 million sla 01 range measurements over the oceans to the csrmss95 gridded mean sea surface model and find the overall root mean square rms difference to be 2 33 m the misfit was improved significantly by removing the mean and trend from individual sla 01 profiles often resulting in rms differences less than 1 m they also show that in regions where sea surface height varies dramatically over relatively short horizontal scales such as across major subduction zones sla 01 as capable of resolving rapid changes in sea surface height finally they examine a number of coastal zones and illustrate sla 01 s ability to track continuously across the land sea interface even in regions of dramatic coastal topography the dominant sources of radial error in the sla 01 data are time interval unit tiu error spl plusmn 0 75 m and radial orbit error 1 m rms therefore limitations of the sla 01 data set are caused primarily by system constraints as opposed to instrumentation error their results indicate that future laser altimeters will provide valuable information regarding ocean topography in particular laser altimetry data can be used to supplement orbiting microwave ranging systems in coastal areas where such sensors are incapable of maintaining lock across the continent ocean transition

sampling strategies and model assimilation of altimetric data for ocean monitoring and prediction numerical forecasts using simulated altimeter data are generated in order to examine the assimilation of altimeter derived sea surface heights into numerical ocean circulation models a one layer reduced gravity primitive equation circulation model of the gulf of mexico is utilized the gulf of mexico is chosen because of its amenability to modeling and the ability of low vertical mode models to reproduce many of the observed dynamical features of gulf circulation the simulated data are obtained by flying a hypothetical altimeter over the model ocean and sampling the model sea surface in a manner similar to a real altimeter the data are used to examine spatial sampling requirements for accurate resolution of oceanic eddies and in forecast mode the assimilation of asynoptic altimeter data into numerical models results indicate that for a stationary circular eddy approximately two tracks either ascending or descending across the eddy are sufficient to ensure adequate spatial resolution an irregularly shaped eddy may require three or four tracks in addition the study reveals that if the track spacing is sufficient to resolve the height field of an eddy the along track geostrophic velocity component is determined with equivalent accuracy to that of the cross track component simulated gulf of mexico circulation forecasts suggest that the numerical model can effectively assimilate asynoptic altimeter measurements optimum sampling strategies for a single beam altimeter and intermittent updating of the nowcast forecast are examined

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

ocean mesoscale variability from repeat tracks of geos 3 altimeter data the geos 3 satellite altimeter observed numerous sea surface profiles along nearly repeated tracks in the western north atlantic during its 3 5 year lifetime enabling observation of the variation of sea surface topography along these tracks analysis of 14 north going and 13 south going sets of repeated tracks has yielded the variability of the surface at a resolution of 1 from 25 to 41 n latitude and from 60 to 80 w longitude the observed rms variation of surface topography ranges from about 8 cm in the sargasso sea to a maximum of 48 cm in the gulf stream meander region in agreement with known mesoscale energetics of this region

the history of quaternary sedimentation in the uk sector of the north sea basin reconnaissance seismic and sampling surveys have shown that up to 500 m of lower and early middle pleistocene deltaic sediments are preserved in the uk sector of the north sea the distributions of delta related facies record the progressive expansion of peripheral delta systems northwards across the southern north sea during the early pleistocene a late middle pleistocene unconformity is present throughout the uk sector and sedimentation above the unconformity was dominated by glacial erosional and depositional processes a complex system of deeply incised valleys was eroded during each of three regional middle and upper pleistocene glaciations and the valleys have been filled or partially filled by glaciolacustrine or glaciomarine and interglacial marine sediments the valleys of the earliest elsterian glaciation are up to 400 m deep in the southern north sea the saalian and weichselian valleys are commonly more than 100 m deep they are eroded through their contemporary tills nearshore but occur well beyond the limits of these tills offshore the origins of these valleys are attributed to a combination of fluvial subglacial and periglacial processes

the branching of the gulf stream southeast of the grand banks during march april 1987 101 hydrographic stations were occupied on three sections spanning a triangle between the azores faial the southern tip of the grand banks of newfoundland and bermuda information on the near surface processes in the interior of the triangle were obtained from 32 satellite tracked buoys deployed during the cruise and a composite infrared image based on cloud free noaa 9 data during april 1987 the data were combined to analyze the eddy field and the branching of the gulf stream into the north atlantic current and the azores current calculations of mass transports through the legs of the triangle gave a total of 46 sv supplied by the gulf stream 31 sv of which left the area as the north atlantic current and westwind drift north of the azores the remaining 14 sv continued towards east southeast as the azores current and southern recirculation additional conductivity temperature depth stations from a cruise in april 1986 into the same area allowed also study of the large scale circulation within that triangle in deeper layers the azores current appears as a baroclinic stream which reaches down to approximately 1000 m intensive mixing was observed at the continental slope of newfoundland between water of the labrador current and the gulf stream mixed water owing to cabbeling and consecutive convective mixing this water penetrates down to 2000 m depth and creates horizontal density gradients to the surrounding gulf stream water which intensifies the north atlantic current this process is considered to be an important energy source for this current

life history of a cyclonic ring detached from the kuroshio extension as seen by the geosat altimeter the sea surface dynamic topography ssdt sea surface height relative to the geoid is approximately estimated by combining the temporal fluctuation of ssdt determined from altimetry data with the climatological mean ssdt calculated from hydrographic data this approximated ssdt or composite ssdt is obtained in the area southeast of japan for the first year 1986 1987 of the geosat exact repeat mission variations in the kuroshio current system are well described by the composite ssdt in particular a complete life history of a cyclonic ring is observed for the first time in this region namely westward propagation of a southward meander of the kuroshio extension its pinching off to form a cyclonic ring the ring s westward movement its coalescence with the kuroshio and its eastward advection all available hydrographic data and cloud free satellite infrared images support the existence of this series of phenomena

preliminary estimates of gulf stream characteristics from topex data and a precise gravimetric geoid topex sea surface height data has been used with a gravimetric geoid to calculate sea surface topography across the gulf stream this topography was initially computed for nine tracks seven descending and two ascending on cycles 21 to 29 due to inaccurate geoid undulations on one track results for eight tracks are reported in the paper the sea surface topography estimates were used to calculate parameters that describe gulf stream characteristics from two models of the gulf stream one model was based on a gaussian representation of the velocity while the other was a hyperbolic representation of velocity or the sea surface topography the parameters of the gaussian velocity model fit were a width parameter a maximum velocity value and the location of the maximum velocity the parameters of the hyperbolic sea surface topography model were the width the height jump position and the sea surface topography at the center of the stream both models were used for the eight tracks and nine cycles studied comparisons were made between the width parameters the maximum velocities and the height jumps for one track d04 near 36 n 73 w the average width parameter was 69 15 km based on the gaussian velocity fitting and 75 14 km based on the hyperbolic sea surface topography fit with a 10 km smoothing function along the same track the average maximum velocity was 164 30 cm s using the velocity fit and 163 37 cm s with the hyperbolic sea surface topography fit some of the parameter estimates were found to be highly 0 9 correlated when the hyperbolic sea surface topography fit was carried out but such correlations were reduced for either the gaussian velocity fits or the hyperbolic velocity model fit a comparison of the parameters derived from 1 year of topex data showed good agreement with values derived by kelly 1991 using 2 5 years of geosat data near 38 n 66 w longitude width 78 22 km this paper 82 25 km kelly height jump 115 28 cm 123 19 cm maximum velocity 171 59 cm s 1 179 46 cm s 1 the accuracy of the geoid undulations used in the calculations was of the order of 16 cm with the accuracy of a geoid undulation difference equal to 15 cm over a 100 km line in areas with good terrestrial data coverage the north edge of the gulf stream was studied with topex data from cycles 1 to 37 the north edge was located at the position corresponding to the half width of the gulf stream north of the center of the stream along each track with all parameters estimated from the gaussian velocity fit procedure the location of the north edge along one track generally agreed with the location defined by national oceanic and atmospheric administration national ocean survey noaa nos maps based on advanced very high resolution radiometer avhrr data and with a north wall location provided by cornillon at 2 day intervals the results for this topex track showed the north edge at the highest 37 8 n latitude in october november 1992 falling to the lowest 36 9 n latitude in february march 1993 after which the stream moves north a second track 550 km to the east of the first track showed consistent agreement with the cornillon data for the edge location when such data were available in one case with the noaa data there was a 77 km discrepancy between the topex and noaa estimates of the north edge analysis of the sea surface topography suggested the noaa avhrr location may be inaccurate at this one location and time this paper demonstrates that our knowledge of geoid undulations and undulation differences in a portion of the gulf stream region is sufficiently accurate to determine characteristics of the jet when used with topex altimeter data the method used here has not been shown to be more accurate than methods that average altimeter data to form a reference surface used in analysis to obtain the gulf stream characteristics however the results in the paper show the geoid approach may be used in areas where lack of current meandering reduces the accuracy of the average surface procedure

measurements of dynamic topography during synop utilizing a geosat synthetic geoid dynamic topography estimates were obtained for the gulf stream region employing a previously derived synthetic geoid and geosat radar altimeter measurements ascending tracks passed through the central and eastern arrays of the synoptic ocean prediction experiment by utilizing the geoid estimate instead of the mean altimetric signal the axis position and velocity can be computed a time series of the dynamic height profiles crossing the gulf stream and a table of the positions of the axis of the stream along two tracks are given time series of the maximum velocity perpendicular to the ground track were computed for both arrays it was found that there was a seasonal cycle in this time series with a maximum in november

southern ocean mean monthly waves and surface winds for winter 1978 by seasat radar altimeter data acquired by the seasat radar altimeter during the 3 month satellite lifetime are analyzed in a study of the sea state of the southern hemisphere oceans the lifetime of the seasat satellite july 7 to october 10 1978 corresponds to the antarctic winter mean monthly maps of wind speed significant wave height and swell have been generated from the altimeter measurements along the satellite tracks these maps delineate spatial and temporal differences of these parameters in the atlantic indian and pacific oceans several features of the southern ocean wind and wave fields agree with conventional descriptions for example the principle zonal wind regimes established by the southeast trades and westerlies are clearly evident in the monthly averages significant wave height and swell also exhibit minima near the doldrums at low latitudes with steady increases southward to the latitudes of the westerlies however superimposed on these general patterns is significant variability with horizontal scales as small as 1000 km the maps also document a gradual migration of the region of absolute maximum wind and wave from the atlantic eastward to the indian ocean and finally into the pacific

seasat altimeter height calibration the seasat altimeter has been calibrated for height bias using four overflight passes of bermuda that were supported by the bermuda laser the altimeter data was corrected for tides by using recorded tide gage data for propagation effects by using meteorological data taken around the time of each pass for acceleration lag and for sea state bias including both surface effects and instrumental effects altimeter data for each of the four passes was smoothed and extrapolated across the island interpolation between passes then produced an equivalent altimeter measurement to the geoid at the laser site so that the altimeter bias could be estimated without the use of a geoid model the estimated height bias was 0 0 0 07 m

sulfur distribution and isotopic composition in peats from the okefenokee swamp georgia and the everglades florida abstract peat cores from three aquatic environments freshwater brackish and marine have been analyzed for organic pyritic and sulfatic sulfur contents and isotope ratios peat collected from each environment has a unique combination of sulfur content distribution and isotope ratio freshwater peat from the okefenokee swamp contains the least sulfur 0 26 to 0 48 primarily organic sulfur and is vertically uniform in sulfur content and isotope ratio the organic sulfur isotope ratio of the okefenokee pear 12 3 to 12 8 per mil is similar to that of sulfate in associated surface waters cores from presently brackish and marine peats from the florida everglades have high organic pyritic and sulfatic sulfur contents with vertical variability in sulfur content and isotope ration the isotope ratio of organic sulfur in the brackish and marine peat is lighter than that of sulfate associated with their respective peat forming environments organic sulfur in the marine peat is isotopically lighter than in the brackish peat freshwater peats subsequently overlain by sediment associated with brackish to marine waters may have a sulfur content distribution and isotopic ratio indistinguishable from peats derived under brackish or marine conditions the primary source of sulfur in peats is dissolved sulfate associated with the peat forming system the sulfate concentration of the waters in which a peat forms is of major importance in determining the isotopic composition of the sulfur form found in peat the content distribution and isotopic ratio of low and high sulfur peats are similar to those reported for coals indicating that the fundamental sulfur geochemistry of coals may have been established during the peat forming stage of coalification the organic sulfur content and isotope ratio of a coal may be useful in estimating the relative sulfate ion concentration of the waters present during the peat forming stage of coalification where transgressive sequences are not involved the sulfate ion concentration of paleowaters could be used to interpret the paleoenvironment during the peat forming stage of coalification and thus information about the organic sulfur content and isotope ratio of coals may prove useful in helping to assess coal quality in advance of mining

altimetry ship gravimetry and the general circulation of the north atlantic gravity accelerations estimated from satellite altimetric mean sea surfaces seasat and geos 3 are compared to ship gravity measurements ship gravity are closer to an estimate based on least squares collocation orbit perturbations altimetry and terrestrial gravity than to an estimate based on fourier transforms orbit perturbations and altimetry only both altimetric estimates yield a smoothed picture of the geostrophic component of sea surface currents in the north atlantic when gravity acceleration data from only nine cruises are subtracted from the altimetric gravity

on determining the large scale ocean circulation from satellite altimetry to determine the surface geostrophic currents which are proportional to the slope of the dynamic topography from satellite altimetry one needs an accurate and independent estimate of the geoid currently these estimates are given in terms of spherical harmonics while the high degree terms short wavelengths are either uncertain or completely unknown the low degree terms long wavelengths are reasonably accurate furthermore in terms of spherical harmonics most of the dynamic topography s power is contained in the low degree terms if the dynamic topography is treated as the signal and the geoid uncertainty as the noise the signal to noise ratio is the highest for these low degree terms therefore a spherical harmonic expansion of the difference between the altimeter derived mean sea surface and the geoid estimate should reveal the large scale circulation of the ocean surface layer when one examines the low degree terms methods based on this principle are proposed and partially demonstrated over the pacific ocean using the mean sea surface derived from the seasat altimeter and the goddard earth model 9 earth gravity model the preliminary results show a well defined clockwise gyre in the north pacific and a much less well defined counterclockwise gyre in the south pacific when the dynamic topography so obtained is compared to wyrtki s 1975 dynamic topography derived from hydrographic data the agreement is within the limit of geoid uncertainties and satellite orbital errors to fully determine the three dimensional ocean circulation one still needs hydrography the three dimensional density distribution of the ocean a method is presented for the determination of the ocean circulation and the improvement of the geoid in the combined problem of geodesy hydrography and satellite altimetry

the geochemical cycle of rhenium a reconnaissance rhenium re is one of a suite of elements including uranium and molybdenum that display conservative behavior in seawater and are enriched in anoxic sediments the decay of187re to187os provides a geochronometer in ancient sedimentary rocks and gives rise to os isotopic variations in nature in order to better characterize its sources to seawater re was measured in three major rivers amazon orinoco ganges brahmaputra and some of their tributaries re concentrations span four orders of magnitude from 0 02 to 400 pmol kg with the highest concentrations found in rivers draining black shales in the venezuelan andes mainstream re levels in the three rivers are between 1 and 10 pmol kg with a flux weighted average of 2 3 pmol kg the residence time for re in the oceans is estimated to be 750 000 yr with respect to river inputs re profiles from the atlantic and pacific oceans confirm that re behaves conservatively in seawater with no significant uptake onto particles and or recycling within the water column this is also true in the anoxic water column of the black sea re removal into anoxic sediments occurs at or below the sediment water interface as demonstrated in sediment pore waters from chesapeake bay in oxic sediments re is not cycled with manganese oxides and it is not enriched in very slowly accumulating pelagic sediments with a large hydrogenous iron and manganese component or in manganese nodules burial of re in anoxic sediments which accumulate on 0 3 of the ocean floor removes approximately 50 of the riverine re flux to the oceans hence oceanic re concentrations may be very sensitive to changes in the area of anoxic sedimentation

geochemical and microfacies characterization of a holocene depositional sequence in northwest germany abstract holocene depositional sequences in the coastal zone of the north sea reflect climate driven sea level changes that led to lateral interfingering of marine brackish lagoonal and limnic sediments and peat layers this succession is reflected in an 18 m sediment core drilled in the marsh lands of the river weser the core spanning the entire holocene was analyzed at high stratigraphic resolution for major and minor elements bulk and molecular constituents and microfacies characteristics abundant triterpenoids in sediments of the basal organic unit indicate nutrient rich limnic paleoconditions not yet influenced by the rising sea level lithological description of several sedimentary units overlying the basal sequence initially suggested a mainly lagoonal setting with occasional influence by tidal channel activities geochemical and microfacies analyses confirmed repeated marine ingression marine conditions are indicated by pyrite enrichment the presence of sterathiols formed by the reaction of sterols with reduced sulfur species and the occurrence of marine pelagic diatoms towards the top of the sedimentary sequence estuarine conditions become more and more pronounced as the river weser established its modern course whereas it had been quite variable previously estuarine conditions are reflected by sterol and amino acid distributions and by limnic diatom species that are mixed with marine pelagic forms although the majority of the clastic units consist of silty to clayey sediments some intercalated quartz sand layers reflect the increase of hydrodynamic energy characteristic of lower tidal flats and channels lumps of reworked peat within fine clastic deposits also reflect high energy events even a dark layer within the upper clastic unit formerly considered a fossil soil horizon is not the direct result of regression induced soil development but originates mainly from eroded fossil organic material from the basal unit this interpretation was established by biomarker analysis and radiocarbon dating

the geoid edin2000 and mean sea surface topography around the british isles summary this paper describes a new rationale for computing a gravimetric geoid and reports that the resulting geoid model edin2000 is now good enough to resolve previously contradictory estimates for mean sea surface topography msst around great britain for at least 30 yr it has been known that msst derived from tide gauges levelling and oceanography were mutually inconsistent and differed by an order of magnitude when combined with an altimetric mean sea surface edin2000 is also able to map realistic msst over the northwest european shelf and identify and quantify mean currents flowing in the deep ocean parallel to the shelf edge when compared with 11 gps referenced tide gauges on the british mainland our estimate of msst has a standard deviation of only 0 03 m and its variation with latitude is not significantly different from zero for these sites long distance levelling errors are larger than geoid errors we identify a systematic jump by 0 24 0 05 m in the levelled transfer of ordnance datum newlyn affecting all sites in great britain to the north of latitude 53 n even after this correction the variability of levelling remains larger than that of the geoid and gps implying a more complex structure to the levelling error than a simple step away from coasts we find that the best way to validate marine gravity data is their ability to predict msst with low local variability when combined with altimetric mean sea level there is a large reduction in msst variability when marine gravity data are subjected to an anti aliased adjustment of the mismatch where ship tracks cross we also report two msst model comparisons from a shelf seas and a deep ocean model both of high resolution there is quantitative and qualitative agreement between our geoid derived msst and the model predictions indicating significant improvements compared with earlier geoid models we also show that with the improved accuracy of geoid based msst it will become necessary to validate models and observations at matching epochs