oxygen and carbon isotope record of east pacific core v19 30 implications for the formation of deep water in the late pleistocene north atlantic abstract a detailed oxygen and carbon isotope record has been obtained from benthic foraminifera in core v19 30 from the carnegie ridge on the south side of the panama basin expressing these records and the oxygen and carbon isotope records previously published for atlantic core m 12392 on a common timescale it is apparent that the oxygen isotope records are very similar but that the carbon isotope records are quite different by obtaining the carbon isotope gradient between the two sites as a function of time we show that the production of north atlantic deep water has varied over a wide range during the late pleistocene and that the pattern of variation is not simply related to the well known oxygen isotope record although the two oxygen isotope records are very similar changes in the interoceanic gradient are detectable and support the hypothesis that in the glacial mode the north atlantic was colder and less oxygenated than it is today shackleton s 1 1977 interpretation whereby the carbon isotope record from the atlantic core reflects changes in the terrestrial biomass is an over simplification however the record from the pacific core v19 30 probably can be explained in these terms since it probably approximates the carbon isotope record of global mean oceanic dissolved co 2

the δ15n of nitrate in the southern ocean consumption of nitrate in surface waters we report nitrogen isotope data for nitrate from transects of hydrocast and surface samples collected in the eastern indian and pacific sectors of the southern ocean focusing here on the data from the upper water column to study the effect of nitrate consumption by phytoplankton the 15n of nitrate increases by 1 2 from deep water into the antarctic summertime surface layer due to kinetic isotopic fractionation during nitrate uptake estimation of the nitrate uptake isotope effect from antarctic depth profiles yields values in the range of 5 6 in east indian sector and 4 5 in the east pacific sector surface transect data from the pacific sector also yield values of 4 5 the major uncertainty in the profile based estimation of the isotope effect involves the 15n of nitrate from the temperature minimum layer below the summertime antarctic surface layer which deviates significantly from the predictions of simple models of isotope fractionation for the subantarctic surface it is possible to distinguish between nitrate supplied laterally from the surface antarctic and nitrate supplied vertically from the subantarctic thermocline because of the distinctive relationships between the 15n and concentration of nitrate in these two potential sources our subantarctic samples collected during the summer and fall indicate that nitrate is supplied to the subantarctic surface largely by northward transport of antarctic surface water isotopic data from the pacific sector of the subantarctic suggest an isotope effect of 4 5 indistinguishable from the antarctic estimates in this sector

particulate removal of230th and231pa in the biologically productive northern north pacific settling particles were collected by sediment traps at four stations in the high latitudes of the north pacific and analyzed for234th 232th 230th 228th and231pa in the northern north pacific including the bering sea the average activity ratio of unsupported230th to231pa in settling particles was 5 5 whereas that in the gulf of alaska in the eastern north pacific was about 14 the northern north pacific may be an efficient sink for231pa relative to230th because the average ratio in the world ocean is equal to the production ratio of 10 8 in seawater the activity ratios of230th 231pa of the settling particles agree well with those of the surface sediments at the respective stations this indicates that both nuclides in the surface sediments originated from settling particles and their dissolution or uptake during early diagenesis are not effective the ratio of the particulate nuclide flux f to the overlying water column production rate p did not correlate well with the total mass flux for230th however that for231pa increased almost linearly with increase in total mass flux and reached unity when the total mass flux was about 110 mg m2 d this suggests that231pa transported from oligotrophic regions is being actively removed in the biologically productive northern north pacific

diatom bound 15n 14n new support for enhanced nutrient consumption in the ice age subantarctic 1 diatom bound 15n 14n was used to reconstruct the glacial nutrient status of the subantarctic zone in the southern ocean down core records from both the pacific and indian sectors show 15n of 5 to 6 during the last glacial maximum and a decrease coincident with the glacial termination to values as low as 2 the effect of either diatom assemblage or physiological change on the diatom bound 15n 14n is unknown and cannot yet be ruled out as a possible explanation for the observed change however the consistency between indian and pacific sector records and with other paleoceanographic data suggests that the glacial interglacial difference in diatom bound 15n 14n was driven by higher consumption of nitrate in the subantarctic surface during the last ice age such a change in nutrient consumption may have resulted from atmospheric iron fertilization and or decreased glacial mixed layer depths associated with sea ice melting enhanced nutrient consumption in the glacial subantarctic would have worked to lower the concentration of co2 in the ice age atmosphere it also would have reduced the preformed nutrient content of the low latitude thermocline leading to decreases in low latitude productivity suboxia and denitrification

diatom productivity in the equatorial pacific ocean from the last glacial period to the present a test of the silicic acid leakage hypothesis 1 the silicic acid leakage hypothesis salh suggests that during glacial periods unused silicic acid escaped the southern ocean into the equatorial oceans causing an ecological shift favoring diatoms relative to coccolithophorids and a drawdown of co2 the 230th normalized opal fluxes and 231pa 230th ratios were measured in eleven equatorial pacific cores to reconstruct diatom productivity over the past 30 kyr and to test the salh holocene spatial patterns of opal flux are strongly correlated with 231pa 230th ratios and with satellite estimates of primary productivity down core opal flux records do not support the salh but show holocene opal burial to exceed that of the late glacial period by 35 or 2 8 gt opal kyr across the equatorial pacific this suggests that the salh may not account for lower atmospheric co2 levels during the late glacial however the data do support results from previous studies that invoke increased el nino like conditions during this time

trapping efficiencies of sediment traps from the deep eastern north atlantic the 230th calibration bottom tethered sediment traps deployed in the deep eastern north atlantic between 54 n 20 w and 33 n 20 w l1 l2 l3 at the european continental margin at 49 n omex and off the canary islands estoc were investigated for the determination of 230th trapping efficiencies the ratios of 230th flux measured in the traps fa to the expected 230th flux from the production rate of 230th in the overlying water column fp ranged between 0 09 and 1 26 for the traps with deployment periods 300 days the interannual variation of fa fp ratios different years but same location and water depth were up to 10 suggesting that the average 230th flux to the sediment traps did not vary significantly the influence of lateral advection on the 230th flux was taken into account either by applying a mass balance of 230th and 231pa or by assuming a constant removal rate of 230th from the water column an assumption based on similar 230th concentration depth profiles observed at most locations investigated 230th trapping efficiencies were between 9 and 143 showing a trend of increasing efficiencies with increasing water depth no relation was found between current velocities and 230th trapping efficiencies our investigations suggest that the observation of constant or even increasing particle flux rates with increasing water depths in several sediment trap arrays investigated may be a result of sediment trap biases the correction for the trapping biases is important for the understanding of the regional differences in the particle flux in the eastern north atlantic

quantitative geomorphological constraints on the landform evolution of the current active boundary of the northeastern tibetan plateau abstract the hexi corridor lies along the northeastern margin of the tibetan plateau forming its northern boundary the late cenozoic tectonic and landscape evolution of this area are key to understanding the growth of the tibetan plateau we investigate the river profile morphology of 36 drainage areas located on the southern flanks of the heli shan which is the outermost range of the hexi corridor here bedrock channels are segmented by steep downstream channels and upper segments with lower gradients a synthesis of tectonics climate lithology and river reorganization indicates that this area has experienced accelerated tectonic uplift we constrain the response times for knickpoint evolution based on a knickpoint celerity model and reconstruct paleo channel profiles combined with onset ages for the growth of the qilian shan 10 ma and yumu shan 4 ma we propose that the hexi corridor and heli shan were affected by the outward growth of the tibetan plateau at 0 6 2 1 ma ago

algorithm for sea surface wind retrieval from terrasar x and tandem x data a geophysical model function gmf which is denoted by xmod2 is developed to retrieve sea surface wind field from x band terrasar x tandem x ts x td x data in contrast to the previously developed xmod1 xmod2 consists of a nonlinear gmf and thus it depicts the difference between upwind and downwind of the sea surface backscatter in x band synthetic aperture radar sar imagery by exploiting 371 collocations with in situ buoy measurements that are used as the tuning data set together with analysis wind model results the retrieved ts x td x sea surface wind speed using xmod2 shows a close agreement with buoy measurements with a bias of 0 32 m s a root mean square error rmse of 1 44 m s and a scatter index si of 16 0 further validation using an independent data set of 52 cases shows a bias of 0 17 m s an rmse of 1 48 m s and an si of 17 0 comparing with buoy measurements to apply xmod2 to ts x td x data acquired at hh polarization we validate three x band sar polarization ratio models that were tuned using ts x dual polarization data by comparing the retrieved sea surface wind speed with buoy measurements

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

wind and wave measurements using complex ers 2 sar wave mode data a global dataset of complex synthetic aperture sar images is processed from wave mode raw data acquired by the ers 2 satellite using these data different algorithms for wind and wave measurements recently developed in view of future envisat asar data are analyzed on a statistical basis different aspects of complex sar wave mode processing with the dlr processor bsar are discussed and global statistics of processing parameters are presented single look complex slc imagettes give the opportunity to apply multilook techniques in range as well as in azimuth such methods are used to reduce speckle noise or to analyze the time evolution of the ocean surface cross section during sar integration time a global analysis of different new algorithms for wind and ocean wave measurements taking advantage of slc data is given wind speed is estimated with the azimuthal cross correlation algorithm cca as a modification of the existing cca range multilooking is used to deal with the speckle bias homogeneity of the imagettes is considered wind speed is derived from mean sar image intensities taking into account wind direction cmod algorithm comparison with collocated ers 2 scatterometer data shows reasonable agreement with the cca and good agreement for the cmod approach using imagettes instead of image power spectra allows the authors to study ocean surface features caused by natural slicks sea ice or atmospheric processes the impact of these phenomena on scat measurements is considered cross spectral methods are used to derive the ocean wave propagation direction from complex imagettes on a global basis comparison with model data provided by the european center for medium range weather forecast ecmwf shows good agreement

do geochemical estimates of sediment focusing pass the sediment test in the equatorial pacific 1 the paleoceanographic recording fidelity of pelagic sediments is limited by chemical diagenesis and physical mixing bioturbation and horizontal sediment transport diagenesis and bioturbation are relatively well studied but the effects of physical sedimentation have been largely ignored modeling u series isotopes e g 230th can potentially quantify horizontal sediment movement but model horizontal sediment focusing often equals or exceeds the vertical particle rain we find no evidence of this level of sediment focusing in the equatorial pacific from geophysical data or sediment core comparisons the overestimate of sediment focusing by 230th is probably caused by poor model assumptions that sediment does not fractionate does not sort according to size during transport and that 230th cannot leak from slowly accumulating sediments both assumptions are weak u series methods do hold promise to quantify sediment focusing if properly calibrated with calibration the trade offs between seeking high sedimentation rates for better time resolution and the blurring by horizontal sediment focusing can be better assessed

silicic acid leakage from the southern ocean a possible explanation for glacial atmospheric pco2 1 using a simple box model we investigate the effects of a reduced si n uptake ratio by antarctic phytoplankton on the marine silica cycle and atmospheric pco2 recent incubation experiments demonstrate such a phenomenon in diatoms when iron is added hutchins and bruland 1998 takeda 1998 franck et al 2000 the southern ocean may have supported diatoms with reduced si n uptake ratios compared to today during the dustier glacial times petit et al 1999 a similar reduction in the uptake ratio may be realized with an increased production of nondiatom phytoplankton such as phaeocystis our model shows that reduced si n export ratios in the southern ocean create excess silicic acid which may then be leaked out to lower latitudes any significant consumption of the excess silicic acid by diatoms that leads to an enhancement in their growth at the expense of coccolithophorids diminishes caco3 production and therefore diminishes the carbonate pump in our box model the combination of a reduced carbonate pump and an open system carbonate compensation draw down steady state atmospheric co2 from the interglacial 277 to 230 242 ppm depending on where the excess silicic acid is consumed by comparison the atmospheric pco2 sensitivity of general circulation models to carbonate pump forcing is 3 5 fold greater which combined with carbonate compensation can account for peak glacial atmospheric pco2 we discuss the importance of the initial rain ratio of caco3 to organic carbon on atmospheric pco2 and relevant sedimentary records that support and constrain this silicic acid leakage scenario

atmospheric boundary layer rolls observed by the synthetic aperture radar aboard the ers 1 satellite two synthetic aperture radar sar images acquired by the european remote sensing satellite ers 1 over the jade weser estuary in the german bight of the north sea on january 2 and 20 1992 are analyzed the images show sea surface manifestations of atmospheric boundary layer rolls this is inferred from the orientation of the quasi periodic sea surface patterns which are aligned approximately with the wind direction from the ratio of the wavelength of the patterns to the height of the boundary layer and from the conditions encountered in the atmospheric boundary layer as measured quasi simultaneously by radiosondes the atmospheric boundary layer rolls were generated by a dynamic instability on january 2 and by a thermal instability on january 20 for the first time quantitative estimates of variations of the wind velocity at the sea surface associated with the atmospheric rolls are extracted from a spaceborne radar sar image it is shown that wind velocities derived from sar image intensity variations are in agreement with theoretical estimates

low level easterly winds blowing through the tsugaru strait japan part i case study and statistical characteristics based on observations abstract this study has investigated structures and diurnal variations of the easterly surface winds blowing throughout the east west passage comprising the tsugaru strait mutsu bay and circumjacent terrestrial gaps in northern japan during the summer months based on observational and reanalysis data a representative case study in june 2003 and supplemental statistical analyses are presented the cool easterly winds accompanied by clouds and fog are blocked by the central mountain range this condition increases an along strait sea level pressure slp gradient which induces strong winds in the west of the strait the along strait slp gradient is enhanced by the developed okhotsk high and by low pressure systems passing along the southern coast of japan or over the japan sea stronger weaker and easterly east northeasterly winds are observed during the nighttime daytime corresponding to the cool air intrusion from the east retreat from west differences in slp observed at meteorological obse

glacial interglacial dynamics of the eastern equatorial pacific cold tongue intertropical convergence zone system reconstructed from oxygen isotope records record mean late holocene lh last glacial maximum lgm d 18 o amplitudes ranging between 1 0 and 1 3 we estimate that mean sea surface temperatures sst in this region during the lgm were on average 1 5 0 5 c lower than the lh larger d 18 o amplitudes are observed in sites north of the equator indicating a spatial pattern of reduced meridional sst gradient across the equator during the lgm this result is supported by comparison of mg ca sst reconstructions from two sites straddling the equator we interpret the reduction of this gradient during the lgm as evidence for a less intense cold tongue intertropical convergence zone itcz frontal system a more southerly position of the itcz and weaker southeast equatorial trades in the eep indexterms 1620 global change climate dynamics 3309 3339 meteorology and atmospheric dynamics ocean atmosphere interactions 0312 4504 3344 meteorology and atmospheric dynamics paleoclimatology 4231 oceanography general equatorial oceanography 4267 oceanography general paleoceanography keywords cold tongue itcz oxygen isotopes tropical pacific

mesoscale wind measurements using recalibrated ers sar images the precision images pri of the synthetic aperture radars sar on board the european remote sensing satellites ers 1 and ers 2 are used to derive mesoscale wind fields over the ocean for calculation of the wind speed the c band model cmod4 is used which was originally developed by stoffelen and anderson 1993 for the european space agency esa to derive wind fields from measurements of the wind scatterometer scat in the case of the ers 1 2 sar the cmod4 is used to compute the wind speed from the normalized radar backscatter cross section nrcs and the incidence angle of the radar beam both computed from the sar pri data the third input variable is the wind direction which is estimated from the wind streaks in the images or from ground truth measurements the sar data are affected by a power loss caused by saturation of the analog to digital converter adc of the sar therefore the images have to be recalibrated errors in the derived wind speed are mainly due to adc saturation and uncertainties of the input wind direction these errors are estimated for various wind conditions mesoscale wind fields computed from ers 1 2 sar pri images taken between the shetland islands and the west coast of norway are compared to ground truth measurements and modeled wind fields from the german weather service dwd wind fields of the nonhydrostatic mesoscale model geesthacht simulation model of the atmosphere gesima are compared to the derived wind field of the ers 1 sar pri image at the island rugen in the baltic sea

terrigenous fe input and biogenic sedimentation in the glacial and interglacial equatorial pacific ocean many ocean regions important to the global carbon budget including the equatorial pacific ocean have low chlorophyll concentrations despite high levels of conventional nutrients iron may instead be the limiting nutrient and elevated input of terrigenous fe during windy glacial episodes has been hypothesized to stimulate oceanic productivity through time and thus regulate the oceanic and atmospheric co2 balance to test whether particulate fe input is related to the accumulation of biogenic matter in one important low chlorophyll high nutrient area that is the equatorial pacific ocean we present results from a suite of sediment cores that collectively record biogenic deposition through the last six glacial interglacial cycles 600 000 years our data set includes new chemical data on total fe terrigenous and biogenic components in three cores as well as previously published mineralogic records of coljan input to the region chemical spectral and stratigraphic analysis indicates that 1 terrigenous input to the region shows no consistent pattern of either glacial or interglacial maxima 2 the accumulation of particulate fe is closely related to the accumulation of terrigenous matter linear r 2 0 81 0 98 3 there are no coherent spectral relationships between fe input and glacial periodicity i e 5180 in any of the orbital frequency bands 4 the linear and cross spectral correlations between fe or coljan input and caco3 concentration are most commonly the strongest observed relationships between fe and any biogenic component yet indicate a largely inverse pattern with higher fe being associated with low caco3 5 there is no consistent linear r 2 correlation or spectral coherence between the accumulation of fe and that of caco3 corg or opal thus in total there is no relationship between terrigenous fe input and sedimentary sequestering of carbon additionally although we cannot specifically address the potential for changes in solubility of the terrigenous fraction that may be driven by a terrigenous compositional change the fe ti ratio which monitors first order mineralogic changes records only slight variations that also are linearly and spectrally unrelated to glacial periodicity the bulk fe flux and the accumulation of any biogenic component finally we find that the paleoceanographic flux of fe is several order of magnitudes larger than modem observations of coljan fe input suggesting that the long term importance of fe input by dust storms which deliver fe on the order of the sedimentary burial may be underestimated the removal of particulate terrigenous fe from the recently discovered source within the equatorial undercurrent however remains unquanfified and may also prove significant

assessing the collection efficiency of ross sea sediment traps using 230th and 231pa abstract annual fluxes of particulate 230th and 231pa collected by sediment traps deployed at two locations in the ross sea are compared to expected fluxes derived by combining the seasonal depletion of 230th and 231pa in surface waters with the steady state production of each nuclide by radioactive decay of its respective dissolved uranium parent conservative minimum estimates of the expected 230th flux are greater than the flux collected by sediment traps deployed at 200 m by factors of 3 and 6 at the two sites the actual discrepancy may be much larger the discrepancies between expected and measured fluxes of 231pa are slightly smaller but comparable in magnitude to those for 230th the discrepancies between expected and measured fluxes for these natural radionuclides are similar in magnitude to those determined previously using the same sediment traps for particulate organic carbon which suggests that the sediment traps undercollected the actual flux of sinking particles

lower export production during glacial periods in the equatorial pacific derived from 231pa 230th xs 0 measurements in deep sea sediments 1 the 231pa 230th xs 0 records obtained from two cores from the western md97 2138 1 25 s 146 24 e 1900 m and eastern ocean drilling program leg 138 site 849 0 11 59 n 110 31 18 w 3851 m equatorial pacific display similar variability over the last 85 000 years i e from isotopic stages 1 to 5a with systematically higher values during the holocene isotopic stage 3 and isotopic stage 5a and lower values approaching the production rate ratio of the two isotopes 0 093 during the colder periods corresponding to isotopic stages 2 and 4 we have also measured the 230th normalized biogenic preserved and terrigenous fluxes as well as major and trace elements concentrations in both cores the 231pa 230th xs 0 results combined with the changes in preserved carbonate and opal fluxes at the eastern site indicate lower productivity in the eastern equatorial pacific during glacial periods the 231pa 230th xs 0 variations in the western equatorial pacific also seem to be controlled by productivity carbonate and or opal the generally high 231pa 230th xs 0 ratios 0 093 of the profile could be due to opal and or mno2 in the sinking particles the profiles of 231pa 230th xs 0 and 230th normalized fluxes indicate a decrease in exported carbonate and possibly opal during isotopic stages 2 and 4 in md97 2138 using 230th normalized flux we also show that sediments from the two cores were strongly affected by sediment redistribution by bottom currents suggesting a control of mass accumulation rates by sediment focusing variability

the polarization dependent relation between radar backscatter from the ocean surface and surface wind vector at frequencies between 1 and 18 ghz a series of airborne scatterometer measurements carried out with the dutscat multifrequency airborne scatterometer are discussed this study deals with the first results obtained from the analysis of these measurements the objective of this activity is to establish a multifrequency dual polarization radar signature database and with it a multidimensional version of the current cmod1 model the main features of the data set are the following the wind exponent of the upwind normalized radar cross section nrcs increases with frequency and incidence angle in the case of hh polarization the upwind downwind ratio is mainly negative at 20 degrees of incidence angle always at c x and ku1 bands

a switch from si oh 4 to no 3 depletion in the glacial southern ocean 1 phytoplankton in the antarctic deplete silicic acid si oh 4 to a far greater extent than they do nitrate no3 this pattern can be reversed by the addition of iron which dramatically lowers diatom si oh 4 no3 uptake ratios higher iron supply during glacial times would thus drive the antarctic towards no3 depletion with excess si oh 4 remaining in surface waters new 30si and 15n records from antarctic sediments confirm diminished si oh 4 use and enhanced no3 depletion during the last three glaciations the present low si oh 4 water is transported northward to at least the subtropics we postulate that the glacial high si oh 4 water similarly may have been transported to the subtropics and beyond this input of si oh 4 may have caused diatoms to displace coccolithophores at low latitudes weakening the carbonate pump and increasing the depth of organic matter remineralization these effects may have lowered glacial atmospheric pco2 by as much as 60 ppm

removal of 230th and 231pa at ocean margins abstract uranium thorium and protactinium isotopes were measured in particulate matter collected by sediment traps deployed in the panama basin and by in situ filtration of large volumes of seawater in the panama and guatemala basins concentrations of dissolved th and pa isotopes were determined by extraction onto mno 2 adsorbers placed in line behind the filters in the in situ pumping systems concentrations of dissolved 230 th and 231 pa in the panama and guatemala basins are lower than in the open ocean whereas dissolved 230 th 231 pa ratios are equal to or slightly greater than ratios in the open ocean particulate 230 th 231 pa ratios in the sediment trap samples ranged from 4 to 8 in contrast to ratios of 30 or more at the open ocean sites previously studied particles collected by filtration in the panama basin and nearest to the continental margin in the guatemala basin contained 230 th 231 pa ratios similar to the ratios in the sediment trap samples the ratios increased with distance away from the continent suspended particles near the margin show no preference for adsorption of th or pa and therefore must be chemically different from particles in the open ocean which show a strong preference for adsorption of th ocean margins as typified by the panama and guatemala basins are preferential sinks for 231 pa relative to 230 th furthermore the margins are sinks for 230 th and to a greater extent 231 pa transported by horizontal mixing from the open ocean

iron and silicic acid concentrations regulate si uptake north and south of the polar frontal zone in the pacific sector of the southern ocean abstract we investigated the relative roles of fe and silicic acid availabilities in regulating si uptake rates across the polar frontal zone in the pacific sector of the southern ocean 59 68 s 170 w during the us jgofs antarctic environment southern ocean process study aesops meridional gradients in silicic acid concentration si oh 4 of about 0 25 0 56 m km 1 were observed in this area during austral spring and summer 1997 1998 with si oh 4 ranging from 32 si oh 4 and 15 no 3 uptake rates biogenic silica concentrations and si oh 4 no3 uptake ratios fe addition had little or no effect on si uptake rates in enrichments conducted in the low si waters north of the si gradient however fe addition increased si uptake rates 3 5 times over controls in enrichments conducted in the high si waters south of the gradient in both spring and summer fe addition decreased si oh 4 no3 uptake ratios by 2 5 times largely due to stimulation of no3 uptake rates zn addition had no effect on si oh 4 and no3 uptake rates short term 24 h si additions had varying effects on si uptake rates depending on season and location in spring additions of 40 m si to water from bottle enrichments conducted north of the si gradient in situ si oh 4 15 m did not increase si uptake rates initially but did increase uptake rates after 8 days in the summer enrichment north of the si gradient in situ si oh 4 5 m 50 m si additions doubled in situ si uptake rates in the initial water collected for the enrichment and increased si uptake rates as much as 16 fold during the experiment south of the si gradient where in situ si oh 4 was 40 m in both spring and summer si addition had no effect on in situ si uptake rates in the initial enrichment water nor on any si uptake rates measured during the experiment our results indicate that both fe and si availabilities regulate si uptake rates and silica production in the southern ocean along 170 w fe limitation appears to restrict si uptake rates south of the si gradient and plays a role in preventing si depletion south of the acc where ambient si oh 4 never fell below 40 m during 1997 1998 our experiments in the seasonal ice zone at 62 suggest that si uptake in this area switched from being fe limited in the spring when in situ si oh 4 was 40 m to si limited in the summer when si oh 4 was

wind retrieval over the ocean using synthetic aperture radar with c band hh polarization the high spatial resolution and large coverage of satellite based synthetic aperture radars sar offers a unique opportunity to derive mesoscale wind fields over the ocean surface providing high resolution wind fields near the shore for this purpose algorithms were developed and tested using the scansar aboard the canadian satellite radarsat 1 operating at c band with horizontal polarization in transmit and receive wind directions are extracted from wind induced streaks visible on most sar images wind speeds are derived from normalized radar cross sections nrcs using empirical models the models were developed for scatterometers scat operating at c band with vertical polarization and must be modified for horizontal polarization several available c band polarization ratios were considered including theoretical and empirical forms to verify and improve the algorithm wind speeds were computed from several radarsat 1 scansar images and compared to colocated measurements from the scat aboard the european remote sensing satellite ers 2 and to the results of the danish high resolution limited area model hirlam using the colocated measurements the polarization ratio was estimated and applied to improve the wind retrieval algorithm in addition the main error sources in sar wind field extraction are discussed with respect to the radarsat 1 scansar data sensitivity studies were performed under different atmospheric situations using the modified c band model to compute the errors due to wind direction and inaccuracies in nrcs

particulate fluxes of 230th 231pa and 10be in the northeastern pacific ocean abstract measurements of 230th 231pa and 10be in sediment trap samples and holocene sediments collected along a transect in the northeastern pacific indicate that the removal of these nuclides from the ocean is greatly influenced by boundary scavenging more than 35 of the 230th at least 70 of the 231pa and as much as 85 of the 10be fluxes collected by sediment traps at a nearshore site located 120 km off shore are supplied by lateral transport of the dissolved nuclides from the open ocean these findings are consistent with the hypothesis that boundary scavenging is proportional to the oceanic residence times of the nuclides 10 40 y for 230th 100 y for 231 pa and 1000 y for 10be results of this study indicate that particle flux is a principal factor influencing scavenging of 230th 231pa and 10be from the water column the marine geochemistry of 10be in ocean margins is fundamentally different from that in the open ocean scavenging of 10be occurs throughout the water column at the margin area in this study in contrast to the pattern of 10be being removed only in the surface waters and then remineralized at depth in the open ocean aluminosilicate may be a major phase removing 10be from the water column in the open ocean but not at ocean margins nuclide accumulation rates in the underlying holocene sediments are all higher than the corresponding fluxes collected by sediment traps several possibilities that could account for this observation include downslope sediment transport deployment of the traps during a period when the particle flux was not representative of long term average conditions and scavenging of the nuclides from near bottom waters the high accumulation rate of authigenic mn in some holocene sediments which can be attributed to redox cycling of mn may have caused near bottom scavenging of 230th and 231pa as well as certain other trace elements such as ba cu and zn

core top 14c ages as a function of latitude and water depth on the ontong java plateau radiocarbon measurements on core tops from the ontong java plateau confirm a previous finding by berger and killingley 1982 that at any given water depth cores taken on the equator have higher accumulation rates and younger core top ages than their off equator counterparts further these new results fortify the conclusion by broecker et al 1991 that the increase in core top radiocarbon age with water depth rules out homogeneous dissolution within the pore waters as the dominant mechanism either most of the dissolution must occur prior to burial or it must occur during the first pass through the respiration co2 rich upper pore waters after which the calcite grains become armored against further dissolution a puzzling aspect of this new data set is that despite the sizable difference in accumulation rate the extent of dissolution as measured by either the caco3 content or the ratio of caco3 in the 150 m size fraction to that in the 63 m fraction is no different off than on the equator in order to reconcile the results of this study with those obtained by hales and emerson 1996 using in situ electrodes it is necessary to call upon calcite armoring

wind vector retrieval using ers 1 synthetic aperture radar imagery an automated algorithm intended for operational use is developed and tested for estimating wind speed and direction using ers 1 sar imagery the wind direction comes from the orientation of low frequency linear signatures in the sar imagery that the authors believe are manifestations of roll vortices within the planetary boundary layer the wind direction thus has inherently a 180 spl deg ambiguity since only a single sar image is used wind speed is estimated by using a new algorithm that utilizes both the estimated wind direction and spl sigma sub 0 values to invert radar cross section models the authors show that 1 on average the direction of the roll vortices signatures is approximately 11 spl deg to the right of the surface wind direction and can be used to estimate the surface wind direction to within spl plusmn 19 spl deg and 2 utilizing these estimated wind directions from the sar imagery subsequently improves wind speed estimation generating errors of approximately spl plusmn 1 2 m s for ers 1 sar data collected during the norwegian continental shelf experiment in 1991

a new approach to ocean wave parameter estimates from c band scansar images because of their large swath widths of about 400 500 km the scansar modes of radarsat 1 and 2 and of the advanced sar asar system on envisat have been the preferred modes of operation for hurricane and typhoon observations and similar applications while c band scansar images have been demonstrated to be well suitable for wind retrievals ocean wave retrievals are a more challenging problem because of the limited spatial resolution of 100 m radarsat 150 m envisat only long waves can get imaged directly and many images of tropical storm scenarios do not exhibit clear signatures of any waves in large areas the interpretation of wave patterns that exist in an image is difficult because of the imaging mechanism s nonlinearities we think we have found a promising new technique for wave parameter retrievals from c band scansar images which determines peak wavelengths and directions from image spectra where possible but uses an empirically determined relation to estimate significant wave heights swhs from local mean image intensities which is similar to the method used for wind retrievals this way it is possible to obtain swh estimates for the entire image and to account for the contributions of subresolution scale waves we explain how the algorithm works and how the empirical swh model function has been determined from a set of hurricane images from radarsat 1 and reference wave spectra from a numerical wave model the first independent test with a set of radarsat 2 and envisat images from the 2010 impact of typhoons on the ocean in the pacific itop experiment reveals a few weaknesses but essentially confirms the feasibility of the concept