a lisflood fp hydraulic model of the middle reach of the congo abstract in this paper we attempt to produce a first hydrodynamic model of the middle reach of the congo river system in order to understand what controls this river s unique bimodal flood pulse the model covers the area between kisangani and kinshasa on the main stem and includes the major tributaries and the cuvette centrale wetland one of the world s largest and most understudied lowland regions a mixture of in situ discharges and modelled discharge from a basin wide catchment hydrology model were used to force a four kilometre resolution hydrodynamic simulation developed using the lisflood fp model river channels are represented as sub grid scale features and their width is therefore decoupled from that of the over lying floodplain grid unknown channel friction and bathymetry parameters were calibrated using ers 2 and envisat satellite altimetry measurements of channel water level the calibrated model simulated channel water surface elevations across the domain with a bias and root mean square error of 0 185 and 0 842 m respectively the value for root mean squared error is close to that obtained for comparisons of ers 2 and envisat satellite altimetry to in situ water elevation data in similar basins 0 79 m and 0 47 m respectively the model results imply that the bimodal annual pattern of congo river discharge is predominantly a hydrological rather than hydraulically controlled feature with the channel floodplain interactions and river constrictions having only a modest impact on the flood wave propagation nevertheless and counter to current understanding we find that interactions between channels and floodplains do however occur extensively with over 2100 km of the 13 000 km of channel network in the model identified as zones where water is actively exchanged between channels and floodplains whilst the water volume that is exchanged with the floodplain is substantially less than for other large rivers our results imply that channel floodplain interactions are a significant feature of congo flood wave propagation overall the model provides insights into the hydraulics of this understudied system that can next be tested both in the field and through more detailed modelling studies

calibration of the planktonic foraminiferal mg ca paleothermometer sediment trap results from the guaymas basin gulf of california 1 the mg ca ratio has been measured in two surface dwelling species of planktonic foraminifera globigerinoides ruber and globigerina bulloides from biweekly sediment trap samples collected in guaymas basin gulf of california between august 1992 and november 1997 the guaymas basin experiences significant seasonal changes in sea surface temperature sst 16 33 c and thus is an ideal location for testing the temperature dependence of mg incorporation into foraminiferal calcite the planktonic foraminiferal mg ca ratios are directly compared with concurrent temperature measurements from the study site the results from the sediment trap study reveal a strong positive correlation between sst and the mg ca ratio in both g ruber r2 0 86 and g bulloides r2 0 90 the mg ca ratio increases exponentially by 7 per 1 c change in temperature for g ruber and by 6 for g bulloides these results indicate that the mg ca ratio in g ruber and g bulloides accurately records the measured seasonal surface temperature cycle and interannual variability in the guaymas basin within 1 c the greatest deviation between mg ca estimated sst and observed sst occurs in the spring and fall for both species this variability is attributed to rapidly changing hydrographic conditions and possible offset between the time of calcification and the temperature measurements in addition g ruber and g bulloides exhibit very high mg ca ratios during the strong el nino southern oscillation years of 1992 and 1997 verifying their potential to record sst up to 33 c and 28 c respectively the trace metal data are compared with foraminiferal oxygen isotope and alkenone measurements made on the same suite of sediment trap samples to assess the internal consistency of these temperature proxies strong correlations exist between the 18o and mg ca for g ruber r2 0 86 and g bulloides r2 0 79 similarly sea surface temperature estimates from mg ca ratios are in good agreement with alkenone derived temperature estimates r2 0 89 for g ruber and r2 0 81 for g bulloides

assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures though many studies on the mg contents in the calcitic tests of foraminifers exist the processes controlling its uptake are still a matter of debate laboratory cultures offer an excellent opportunity to reveal these mechanisms the mg concentrations within single chambers of the planktic foraminifer globigerinoides sacculifer brady maintained under controlled laboratory conditions were measured 1 at variable temperatures 19 5 29 5 c and constant salinity and 2 at variable salinity 22 45 and constant temperature the experimental results suggest that under natural conditions temperature is the leading mechanism controlling the mg ca ratio temperature and magnesium are related proportionally a temperature increase of ca 10 c gives rise to an increase of the magnesium concentrations of ca 130 drastic unnatural salinity changes dominate the effects of temperature a 110 change in the mg ca ratio was observed when salinity was elevated or reduced by more than ca 10 specimens which underwent gametogenesis reveal significantly higher mg concentrations than specimens that did not release gametes partition coefficients for mg in foraminiferal calcite are orders of magnitude lower than values from inorganically precipitated calcite when comparing observed mg ca ratios of foraminiferal tests with predicted mg ca ratios calculated according to empirical equations it becomes evident that foraminiferal tests are undersaturated with respect to mg for the water temperature they have experienced apparently foraminifers are capable of controlling their mg concentration the physiological processes presumably responsible for such depressed mg ca ratios appear to be temperature controlled as deduced from the close relationship of the observed mg ca ratios and water temperature this study demonstrates that variations in temperature and salinity are definitely reflected in the mg content of foraminiferal tests magnesium may thus serve as a paleo proxy for past surface water temperatures as long as postdepositional changes and salinity variations are of subordinate importance or can be excluded

the upper end of the uk 37 temperature calibration revisited 1 being able to decipher paleo sea surface temperatures for warm oceanic waters is of the utmost importance to further evaluate the role of the tropics in global climate change the uk 37 index is one of such paleothermometers although the warm range of temperatures often poses serious analytical challenges this paper discusses and reviews several important aspects of the uk 37 index calibration for waters warmer than 26 27 c amongst them insights into the possible existence of a limit above which the uk 37 index is not able to accurately record temperature variations are presented some warnings are also given on the misleading practice and expected consequences of reporting uk 37 index values of unity in the cases when abundances of the minor triunsaturated alkenone below detection limit are encountered future directions toward an improved knowledge of the behaviour of the uk 37 calibration for warm waters are suggested

mg ca ratios of single planktonic foraminifer shells and the potential to reconstruct the thermal seasonality of the water column mg ca ratios of surface and subsurface dwelling foraminifera provide valuable information about the past temperature of the water column planktonic foraminifera calcify over a period of weeks to months therefore the range of mg ca temperatures obtained from single specimens potentially records seasonal temperature changes we present solution derived mg ca ratios for single specimens of the planktonic foraminifera species globigerinoides ruber pink globigerinoides ruber white and globorotalia inflata from a sediment trap off northwest africa 20 45 6 n 18 41 9 w cleaning of single specimens was achieved using a flow through system in order to prevent sample loss mg ca ratios of surface dwelling g ruber pink show strong seasonality linked to sea surface temperature mg ca ratios of g ruber white do not show such seasonality subsurface dwelling g inflata flux is largest during the main upwelling season but mg ca ratios reflect annual temperatures at intermediate water depths the sediment trap time series suggests that changes in the range of mg ca ratios exhibited by single specimens of g ruber pink and g inflata from the sedimentary record should provide information on the past temperature range under which these species calcified statistical analysis suggests detectable changes in the mg ca range are 0 80 mmol mol g ruber pink and 0 34 mmol mol g inflata for g ruber pink such changes would indicate changes in the seasonal sea surface temperature range 4 c or a shift in the main calcification and reproductive period for g inflata such changes would indicate 1 7 c changes in the thermocline temperature or a change in the depth habitat

the effects of temperature salinity and the carbonate system on mg ca in globigerinoides ruber white a global sediment trap calibration abstract the mg ca of planktic foraminifera globigerinoides ruber white is a widely applied proxy for tropical and sub tropical sea surface temperature the accuracy with which temperature can be reconstructed depends on how accurately relationships between mg ca and temperature and the multiple secondary controls on mg ca are known however these relationships remain poorly quantified under oceanic conditions here we present new calibrations based on 440 sediment trap plankton tow samples from the atlantic pacific and indian oceans including 130 new samples from the bay of bengal arabian sea and the tropical atlantic ocean our results indicate temperature salinity and the carbonate system all significantly influence mg ca in g ruber white we propose two calibration models the first model assumes ph is the controlling carbonate system parameter in this model mg ca has a temperature sensitivity of 6 0 0 8 c 2 a salinity sensitivity of 3 3 2 2 psu and a ph sensitivity of 8 3 7 7 0 1 ph units the second model assumes carbonate ion concentration co 3 2 is the controlling carbonate system parameter in this model mg ca has a temperature sensitivity of 6 7 0 8 c a salinity sensitivity of 5 0 3 0 psu and a co 3 2 sensitivity of 0 24 0 11 mol kg 1 in both models the temperature sensitivity is significantly lower than the widely applied sensitivity of 9 0 0 6 c application of our new calibrations to down core data from the last glacial maximum considering whole ocean changes in salinity and carbonate chemistry indicate a cooling of 2 4 1 6 c in the tropical oceans if ph is the controlling parameter and 1 5 1 4 c if co 3 2 is the controlling parameter

surface and subsurface seawater temperature reconstruction using mg ca microanalysis of planktonic foraminifera globigerinoides ruber globigerinoides sacculifer and pulleniatina obliquiloculata laser ablation inductively coupled plasma mass spectrometry microanalyses of mg ca across individual final chambers of three planktonic foraminifera species globigerinoides ruber g sacculifer and pulleniatina obliquiloculata reveal significant interspecies differences in test mg concentrations whereas these three species have similar mg ca values at low sea surface temperatures similar to 22 degrees c they diverge markedly at high sea surface temperatures similar to 29 degrees c explanations for these differences in species mg ca values based on detailed comparison of species intratest mg ca distributions suggest that compositional variability within tests cannot account for the observed deviation of species mg ca values in warm water equatorial regions multiple regression modeling and delta o 18 analysis of globigerinoides sacculifer tests indicate that interspecies differences in mg ca values result from different depth habitats the average mg ca values of g ruber final chambers reflect the temperature of the surface mixed layer 0 25 m whereas those of g sacculifer and pulleniatina obliquiloculata correlate best with subsurface temperatures at 50 75 m and 100 125 m water depths respectively mg ca calibration to the temperatures at these depths reveals a similar temperature control on mg test composition in all species combining our results with mg ca values from published culturing experiments we derive a generalized equation for the effect of temperature and seawater salinity on foraminiferal mg ca we also show that the mg ca composition of specific calcite layers within foraminiferal tests including the low mg ca layers of globigerinoides ruber and g sacculifer and the cortex layer of pulleniatina obliquiloculata correlates with seawater temperature and can be used as an additional proxy for seawater temperature

reach scale floodplain inundation dynamics observed using airborne synthetic aperture radar imagery data analysis and modelling summary in this paper we use an airborne synthetic aperture radar to map river flood inundation synoptically at fine spatial resolution 1 2 m along a 16 km reach of the river severn west central england images were obtained at four times through a large flood event between 8th and 17th november 2000 and processed using a statistical active contour algorithm to yield the flood shoreline at each time intersection of these data with a high vertical accuracy survey of floodplain topography obtained from airborne laser altimetry permitted the calculation of dynamic changes in inundated area total reach storage and rates of reach dewatering in addition comparison of the data to gauged flow rates the measured floodplain topography and map data giving the location of embankments and drainage channels on the floodplain yields new insights into the factors controlling the development of inundation patterns at a variety of scales finally the data were used to assess the performance of a simple two dimensional flood inundation model lisflood fp and allows us for the first time to validate the dynamic performance of the model this process is shown to give new information into structural weaknesses of the model and suggests possible future developments including the incorporation of a better description of floodplain hydrological processes in the hydraulic model to represent more accurately the dewatering of the floodplain

evaluating controls on planktonic foraminiferal geochemistry in the eastern tropical north pacific abstract to explore relationships between water column hydrography and foraminiferal geochemistry in the eastern tropical north pacific we present o 18 and mg ca records from three species of planktonic foraminifera globigerinoides ruber globigerina bulloides and globorotalia menardii collected from a sediment trap mooring maintained in the gulf of tehuantepec from 2006 2012 differences in o 18 between mixed layer species g ruber and g bulloides and thermocline dweller g menardii track seasonal changes in upwelling the records suggest an increase in upwelling during the peak positive phase of el nino and an overall reduction in stratification over the six year period for all three species mg ca ratios are higher than what has been reported in previous studies and show poor correlations to calcification temperature we suggest that low ph 7 6 8 0 and co 3 2 values 70 120 mol kg in the mixed layer contribute to an overall trend of higher mg ca ratios in this region laser ablation inductively coupled mass spectrometry analyses of g bulloides with high mg ca ratios 9 mmol mol reveal the presence of a secondary coating of inorganic calcite that has mg ca and mn ca ratios up to an order of magnitude higher than these elemental ratios in the primary calcite along with elevated sr ca and ba ca ratios some of the samples with abnormally high mg ca are found during periods of high primary productivity suggesting the alteration may be related to changes in carbonate saturation resulting from remineralization of organic matter in oxygen poor waters in the water column although similar shell layering has been observed on fossil foraminifera this is the first time such alteration has been studied in shells collected from the water column our results suggest a role for seawater carbonate chemistry in influencing foraminiferal calcite trace element calcium ratios prior to deposition on the seafloor particularly in high productivity low oxygen environments

field examination of the oceanic carbonate ion effect on stable isotopes in planktonic foraminifera we determined the 18o and 13c of individual globigerinoides ruber and pulleniatina obliquiloculata from sediment traps located from 5 n to 12 s along 140 w in the pacific ocean to evaluate the effects of varying co3 on shell 18o and 13c variations in the offset between shell 13c and 13cdic 13cs dic are attributed to differences in co3 temperature and shell size between sample sites when 13cs dic of g ruber was corrected for variations in co3 using the experimental slope of bijma et al 1998 the residual 13cs dic was correlated with mixed layer temperature 0 10 0 04 c 1 the slope of this temperature effect is consistent with experimental results in p obliquiloculata 13cs dic and temperature were strongly anticorrelated 0 14 0 03 c 1 we are unable to separate the influences of co3 and temperature in this species without independent experimental data correcting for co3 variability on 18os of g ruber improves the accuracy of estimated sea surface temperatures

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

factors controlling the fluoride content of planktonic foraminifera an evaluation of its paleoceanographic applicability abstract this work is an assessment of the effects of seawater salinity and temperature on the incorporation of fluoride into calcitic shells of planktonic foraminifera and of the subsequent modification of shell chemistry by postdepositional dissolution a strong correlation between the fluoride content of most planktonic species and their calcification depth was observed deeper calcifying foraminifera have lower fluoride content and heavier 18o composition perhaps suggesting a temperature control on the partition coefficient however species deviations from this general trend and the absence of correlation between fluoride and sea surface temperature within an individual species suggest that the coprecipitation of fluoride in foraminiferal calcite is more strongly controlled by biological processes rather than by simple chemical relationships foraminiferal fluoride shows weak or no correlation with sea surface salinity core top planktonic foraminifera from the eastern equatorial atlantic sierra leone rise show a substantial decrease of fluoride and to a lesser extent mg content with increasing water depth 2931 5104 m these decreasing trends with depth are attributed to selective dissolution i e removal of the more dissolution susceptible fraction with a different chemical composition than the residual a process which previously has been suggested to account for variations in the isotopic composition of planktonic foraminifera these findings indicate that foraminiferal fluoride cannot serve as a reliable tracer of oceanic paleo temperature or salinity it is possible however that fluoride may be useful for the study of dissolution in deep sea sediments

western equatorial pacific deep water carbonate chemistry during the last glacial maximum and deglaciation using planktic foraminiferal mg ca to reconstruct sea surface temperature and seafloor dissolution 1 we present a reconstruction of deep water carbonate saturation state co32 in the western equatorial pacific for the last glacial maximum lgm and deglaciation based on changes in the mg ca ratio of planktic foraminifers with increased water depth our data suggest there have been changes in bottom water co32 over the past 25 000 years at water depths as shallow as 1 6 km the co32 reconstruction for the lgm suggests co32 was similar or slightly higher than modern values between 1 6 and 2 0 km shifting sharply to lower values an average 30 mol kg lower below 2 5 km the shift in chemistry between 2 0 and 2 5 km supports a hypothesis that pacific overturning circulation occurred deeper during the lgm with a slightly more ventilated water mass above 2 0 km the data are not consistent with enhanced preservation in this region of the deep pacific at depths greater than 2 5 km suggesting that the long held view of better preservation throughout the glacial deep pacific must be reevaluated for the deglaciation we have evidence of a co32 maximum that suggests enhanced deglacial preservation between 1 6 and 4 0 km in comparison to the holocene and the lgm the deglacial co32 was as much as 28 mol kg higher than modern between 1 6 and 4 0 km results suggest carbonate burial rates were 1 5 times greater during the deglacial than the over the past 5 kyr

efficient incorporation of channel cross section geometry uncertainty into regional and global scale flood inundation models this paper investigates the challenge of representing structural differences in river channel cross section geometry for regional to global scale river hydraulic models and the effect this can have on simulations of wave dynamics classically channel geometry is defined using data yet at larger scales the necessary information and model structures do not exist to take this approach we therefore propose a fundamentally different approach where the structural uncertainty in channel geometry is represented using a simple parameterisation which could then be estimated through calibration or data assimilation this paper first outlines the development of a computationally efficient numerical scheme to represent generalised channel shapes using a single parameter which is then validated using a simple straight channel test case and shown to predict wetted perimeter to within 2 for the channels tested an application to the river severn uk is also presented along with an analysis of model sensitivity to channel shape depth and friction the channel shape parameter was shown to improve model simulations of river level particularly for more physically plausible channel roughness and depth parameter ranges calibrating channel manning s coefficient in a rectangular channel provided similar water level simulation accuracy in terms of nash sutcliffe efficiency to a model where friction and shape or depth were calibrated however the calibrated manning coefficient in the rectangular channel model was 2 3 greater than the likely physically realistic value for this reach and this erroneously slowed wave propagation times through the reach by several hours therefore for large scale models applied in data sparse areas calibrating channel depth and or shape may be preferable to assuming a rectangular geometry and calibrating friction alone

calibration of a two dimensional finite element flood flow model using satellite radar imagery the application of numerical models of free surface flow to fluvial flood prediction is currently hampered by the lack of distributed calibration and validation data we address this shortcoming by the use of satellite borne synthetic aperture radar imagery to map a flood on a 15 km reach of the river thames england a finite element numerical model of shallow water flow is constructed over the reach and analysis shows that floodplain friction is the dominant factor affecting inundation extent when compared to channel friction turbulence parameterization and downstream boundary conditions the area of the domain correctly classified by the model is maximized with the constraint of uniform floodplain friction 77 at maximum compared with 70 for a simple planar model of the water free surface a simple distributed calibration scheme is also tested with a minor improvement over the uniform parameterization

seasonal variability in the δ18o and δ13c of planktonic foraminifera from an upwelling environment sediment trap results from the san pedro basin southern california bight stable isotopic analyses 18o and 13crpar on four species of planktonic foraminifera collected from high resolution time series sediment trap sampling indicate that rapid and significant seasonal variability occurred in response to rapid changes in both the hydrographic environment and the isotopic composition of ambient seawater specimens were collected at a depth of 500 m for 28 consecutive 1 week periods in the san pedro basin within the southern california bight a region seasonally influenced by upwelling hydrographic monitoring of the study area revealed a 6 week period late april to mid june during which pulses of upwelling occurred causing significant increases in the oxygen isotopic composition of surrounding waters while decreasing the carbon isotopic composition analyses of globigerina bulloides orbulina universa neogloboquadrina dutertrei and neogloboquadrina pachyderma right coiling indicate that during the upwelling period these species live respectively at the surface in the surface mixed layer within the thermocline and below the thermocline globigerina bulloides ascends from well below the thermocline to the surface at the onset of upwelling and increases production to its maximum simultaneously as its morphology changes to less calcified open forms both n dutertrei and n pachyderma follow isothermal ranges migrating to shallower waters during upwelling and subsequently descending after upwelling ceases neogloboquadrina dutertrei appears to inhabit the region associated with both the thermocline base and chlorophyll maximum when it is most abundant following upwelling orbulina universa increases its depth habitat as solar irradiance increases but this species decreases in abundance during upwelling the 18o signal of o universa appears to be a useful indicator of seasonal temperature variations above the thermocline whereas the 18o of g bulloides documents near surface temperatures during upwelling the 13c signal of both n dutertrei and n pachyderma appears to record the 13c of equilibrium calcite for the regions of the thermocline and just below the thermocline respectively due to the relative preservation potentials of the four species analyzed only n dutertrei and n pachyderma are likely to be preserved in the sedimentary record in regions of oxygenated bottom waters thus an actual record of hydrographic conditions during upwelling as would be found in tests of g bulloides is not preserved instead conditions before n pachyderma and just after n dutertrei are more likely recorded

metabasalts axial hot springs and the structure of hydrothermal systems at mid ocean ridges knowledge of the chemical transfer and mineralogical transformations that occur when sea water reacts with basalt at elevated temperatures and pressures can be used along with geological and geophysical data to deduce the typical structure and evolutionary sequence for hydrothermal systems within the oceanic crust along the axis of a mid ocean ridge studies of metabasalt and metadiabase dredged from fault scarps along the axial valley of the mid atlantic ridge reveal consistent relationships among the bulk chemistry of the altered rocks and their secondary mineralogy mineral abundances and mineral compositions especially for chlorite these relationships can be interpreted in terms of the distribution of alteration with respect to time temperature and water rock ratio in young crust assemblages of chl ab ep act chl ab ep act qtz chl ab qtz and chl qtz are produced at successively higher effective sea water to rock ratios within the temperature range of the greenschist facies 250 to 450 c toward higher ratios chlorites tend to become more mg rich pillow basalts of layer 2 are commonly altered under these conditions by sea water on the descending rather than the ascending limb of a convection system this type of alteration which reflects moderately high water rock ratios may characteristically occur above a still partially molten magma chamber as the magma chamber solidifies and is then penetrated more pervasive alteration of the deeper part of layer 2 and of layer 3 occurs at lower water rock ratios producing solutions such as those recovered from springs on the galapagos rift and the east pacific rise at 21 n localized upwelling limbs of the convection system can produce veins filled with quartz sulfides and fe rich chlorite

accurate estimation of sea surface temperatures using dissolution corrected calibrations for mg ca paleothermometry 1 paired 18o and mg ca measurements on the same foraminiferal shells offer the ability to independently estimate sea surface temperature sst changes and assess their temporal relationship to the growth and decay of continental ice sheets the accuracy of this method is confounded however by the absence of a quantitative method to correct mg ca records for alteration by dissolution here we describe dissolution corrected calibrations for mg ca paleothermometry in which the preexponent constant is a function of size normalized shell weight 1 for g ruber 212 300 m mg ca ruber 0 025 wt 0 11 e0 095t and b for g sacculifer 355 425 m mg ca sacc 0 0032 wt 0 181 e0 095t the new calibrations improve the accuracy of sst estimates and are globally applicable with this correction eastern equatorial atlantic sst during the last glacial maximum is estimated to be 2 9 0 4 c colder than today

a strong temperature effect on u ca in planktonic foraminiferal carbonates three planktonic foraminiferal species globigerina bulloides neogloboquadrina pachyderma d and globorotalia inflata collected from core tops spanning 35 to 65 n in the north atlantic were used for u ca and mg ca and foraminiferal shell weight analyses except for u ca in g bulloides calcified under warm conditions 13 c u ca ratios in all three studied species increase with decreasing latitude and show strong positive correlations with mg ca ratios a dissolution effect on planktonic u ca is suggested by decreased shell weight and u ca and mg ca ratios for shells from very deep water depth 4 4 km along the latitudinal transect g bulloides from down core samples in the north atlantic show low u ca ratios during the last glacial and high ratios during the holocene similar to the mg ca evolution trend in general our data indicate that the u incorporation into planktonic foraminiferal carbonates is strongly influenced by calcification temperature although u ca in g bulloides may be affected by seawater carbonate ion concentration under warm conditions and or other factors

paleo sea surface temperature calculations in the equatorial east atlantic from mg ca ratios in planktic foraminifera a comparison to sea surface temperature estimates from u37k oxygen isotopes and foraminiferal transfer function we present two 270 kyr paleo sea surface temperature sst records from the equatorial divergence and the south equatorial current derived from mg ca ratios in the planktic foraminifer globigerinoides sacculifer the present study suggests that the magnesium signature of g sacculifer provides a seasonal sst estimate from the upper 50 m of the water column generated during upwelling in austral low latitude fall winter common to both down core records is a glacial interglacial amplitude of 3 3 5 c for the last climatic changes and lower holocene and glacial oxygen isotope stage 2 temperatures compared with interglacial stage 5 5 and glacial stage 6 temperatures respectively the comparison to published sst estimates from alkenones oxygen isotopes and foraminiferal transfer function from the same core material pinpoints discrepancies and conformities between methods

rare earth element redistribution during high pressure low temperature metamorphism in ophiolitic fe gabbros liguria northwestern italy implications for light ree mobility in subduction zones to unravel the rare earth element ree redistribution during high pressure low temperature metamorphism we have analyzed by ion microprobe all the minerals from representative fe gabbros from ligurian metaophiolites northwestern italy contrary to what is observed for fresh fe gabbros the clinopyroxene contribution to the whole rock ree inventory of blueschists and eclogitized fe gabbros is minor or negligible in both blueschists and eclogites ree are redistributed among newly formed minerals in blueschists lawsonite is the major ree carrier and concentrates almost all the light ree lree in the rock whereas titanite plays an important role for middle and heavy ree mree hree in eclogites lree and hree mainly reside in accessory allanite and garnet respectively the development of blueschist and eclogite facies mineral assemblages in mafic oceanic crust due to subduction to 35 65 km depths was not accompanied by release of significant amounts of lree to the overlying mantle wedge owing to the stability of lawsonite and epidote at ultra high pressure conditions subduction of mafic rocks is considered an effective mechanism to bring lree to great depth within the mantle

premelting polymerization of crustal and mantle fluids as indicated by the solubility of albite paragonite quartz in h2o at 1 gpa and 350 620 c abstract the composition and structure of dissolved silicates in model crustal and upper mantle fluids was assessed by measuring the solubility of the assemblage albite paragonite quartz in h 2 o from 350 to 620 c at 1 gpa natural low albite and quartz were equilibrated with h 2 o paragonite grew in all experiments due to incongruent dissolution of albite quartz melting occurred at 635 5 c solute concentrations at subsolidus conditions were determined by analysis of quenched fluids or mineral weight loss and mass balance bulk solubility of the mineral assemblage increased from 1 to 8 oxide wt with rising temperature si al and na all increase in concert the solutions were slightly peralkaline and possess si na al 1 5 molar at all conditions studied extrapolated thermodynamic data were used to predict solubility at the conditions investigated experimentally calculated solubility agreed with that measured from 350 to 500 c however above 500 c the calculations underpredict solubility to an increasing degree as the hydrothermal melting point is approached the excess measured solubility points to increasing abundance of aqueous si al si and na al si polymers polymerized solutes predominate in all near solidus solutions rising to 80 of total dissolved solids at the melting point the observations support a conceptual model in which as the temperature of the system rises isobarically at 1 gpa the silicate components dissolved in the aqueous phase begin to polymerize significantly within 100 c of the melting point the polymerized solutes may facilitate condensation of more polymerized hydrous silicate liquid at the hydrothermal melting point from the perspective of isobaric cooling the fluid crossing the solidus retains na al si o clusters or fragments that are less polymerized than those which comprised the melt but more polymerized than has previously been inferred for the aqueous phase the high concentrations of na al and si in the form of polymeric clusters will yield substantial mass transfer by near solidus metamorphic and magmatic fluids in the crust and mantle and likely promote dissolution transport and precipitation of nominally insoluble refractory rock components

core top calibration of b ca in pacific ocean neogloboquadrina incompta and globigerina bulloides as a surface water carbonate system proxy abstract practical methods for reconstructing past ocean carbonate chemistry are needed to study past periods of ocean acidification and improve understanding of the marine carbonate system s role in the global climate cycles planktic foraminiferal b ca may fill this role but requires better understanding and improved proxy calibrations we used pacific ocean core top sediments to generate new calibrations of the b ca proxy for past carbonate system parameters in two upwelling subpolar species of asymbiotic planktic foraminifera globigerina bulloides and neogloboquadrina incompta both species show significant positive correlation of b ca with calcite saturation calcite and carbonate ion concentration co 3 2 across a broad range of environmental conditions this suggests a calcification rate control on b ca incorporation as calcite regulates calcification rate in agreement with recent inorganic calcite studies this is also consistent with a surface entrapment model of trace element incorporation into caco3 in neither species is b ca significantly correlated with ph suggesting that ph does not directly regulate boron incorporation and that calculation of ph directly from foraminiferal b ca is not suitable correlations between b ca and b oh 4 b oh 4 hco3 and b oh 4 dic are weaker than with calcite boron partition coefficients k d b ca solid b oh 4 hco 3 seawater show little or no correlation with co32 or temperature and vary widely providing no support for application of kd to calculate carbonate system parameters from b ca we also discuss potential effects of depth related dissolution temperature and salinity on b ca these empirical calibrations linking foraminiferal calcite b ca with calcite provide a strong tool for reconstructing the past ocean carbonate system and improve our understanding of the proxy s geochemical basis

the accuracy of sequential aerial photography and sar data for observing urban flood dynamics a case study of the uk summer 2007 floods in this paper we examine for the first time the potential of remote sensing to monitor flood dynamics in urban areas and constrain mathematical models of these processes this is achieved through the development of a unique data set consisting of a series of eight space borne synthetic aperture radar sar and aerial photographic images of flooding of the uk town of tewkesbury acquired over an eight day period in summer 2007 previous observations of urban flooding have used single image and wrack mark data and have therefore been unable to adequately chart the propagation and recession of flood waves through complex urban topography by using a combination of space borne radar and aerial imagery we are able to show that remotely sensed imagery particularly from the new terrasar x radar can reproduce dynamics adequately and support flood modelling in urban areas we illustrate that image data from different remote sensing platforms reveal sufficient information to distinguish between models with varying degrees of channel floodplain connectivity particularly toward the end of the recession phase of the event for this test case our results also show that high resolution sar imagery even when acquired from satellites can reveal important hydraulic characteristics difficult to simulate with current dynamic flood models hence it is established at least for this test case and event that sar imagery from as far as several hundred kilometers from the earth s surface can deliver important information about floodplain dynamics that can be used to identify and help build suitable models even in built up environments

rapid analysis of high precision sr ca ratios in corals and other marine carbonates a method for rapid determination of high precision sr ca ratios in scleractinian corals is presented using an inductively coupled plasma atomic emission spectrophotometer samples are corrected for instrument drift using a reference solution similar to the approach used for analysis of stable isotopes using gas source mass spectrometry further correction for variation of the sr ca ratio with ca concentration is accomplished using internal standards the precision once all corrections have been made is better than 0 1 relative standard deviation 1 for samples of similar ca concentration and better than 0 2 for samples with variable ca concentrations this method increases the sample throughput by approximately a factor of 20 relative to thermal ionization mass spectrometry and significantly reduces instrument and per sample costs comparison of sr ca data for a coral from the galapagos islands with an instrumental temperature record shows excellent agreement and demonstrates the potential for application of this technique to samples of modern and fossil scleractinian corals and other marine carbonates including foraminifera

floodplain channel morphology and networks of the middle amazon river 1 floodplain channels are important components of river floodplain systems and are known to play a key role in hydrodynamic exchange and sediment transport the amazon floodplain exhibits complex networks of these channels and despite their potential importance to this globally important wetland system these floodplain channels are relatively unstudied the research presented here is the first systematic and detailed study of the network and morphologic characteristics of a large number of these channels in the middle reach of the central amazon river using analysis of data derived from landsat enhanced thematic mapper plus etm mosaic and field survey our findings show that the channels are ubiquitous their width varies widely and some of their characteristics can be fitted using power laws potentially much like the self similar or fractal like behavior hypothesized for other types of fluvial networks in all 96 of the floodplain channels are not wide enough to be represented well or at all in the 90 m shuttle radar topography mission data channel depths are tied closely to the local amplitude of the passing main river flood wave p value of 0 75 except where there are local runoff inputs which results in substantially deeper channels which provide preferential flow paths across the floodplain channel networks imply that areas of the floodplain function for large parts of the flood cycle as separate hydrogeomorphic land units here termed floodplain hydrological units fhus these hypothesized fhus also have distinct spatial and pattern characteristics and it is suggested here that their differences could provide the beginnings of a framework for understanding the detailed hydrodynamics of the floodplain in particular different types of fhus have differences in flood water source which will have important implications for biogeochemical studies of the wetlands

incorporation and preservation of mg in globigerinoides sacculifer implications for reconstructing the temperature and 18o 16o of seawater using bathymetric transects of surface sediments underlying similar sea surface temperatures but exposed to increasing dissolution we examined the processes which affect the relationship between foraminiferal mg ca and 18o we found that globigerinoides saccculifer calcifies over a relatively large range of water depth and that this is apparent in their mg content on the seafloor foraminiferal mg ca is substantially altered by dissolution with the degree of alteration increasing with water depth selective dissolution of the chamber calcite formed in surface waters shifts the shell s bulk mg ca and 18o toward the chemistries of the secondary crust acquired in colder thermocline waters the magnitude of this shift depends on both the range of temperatures over which the shell calcified and the degree to which it is subsequently dissolved in spite of this shift the initial relationship between mg ca and 18o determined by their temperature dependence is maintained we conclude that paired measurements of 18o and mg ca can be used for reconstructing 18owater though care must be taken to determine where in the water column the reconstruction applies

agents of low temperature ocean crust alteration 18o and87sr 86sr isotopic data from smectites calcites and whole rocks together with published isotopic age determinations alkali element concentration data and petrographic observations suggest a sequential model of ocean floor alteration the early stage lasts about 3 m y and is characterized by palagonite and smectite formation and solutions with a large basaltic component increasing with temperature which varies from 15 to 80 c at dsdp site 418a most carbonates are depositedafter this stage from solutions with a negligible basaltic sr component and temperatures of 15 to 40 c water of seawater sr and o isotopic composition is shown to percolate to at least 500 m into the basaltic basement no evidence was found for continuing exchange of strontium or oxygen after 3 m y

calibration of the mg ca of globorotalia truncatulinoides r for the reconstruction of marine temperature gradients 1 recent work has provided useful mg ca to water temperature calibrations for shallow dwelling planktonic foraminifer species globorotalia truncatulinoides right coiling r is a deep dwelling species that can serve as a source of information about the temporal variability in the water characteristics of the thermocline we present a temperature calibration for the mg ca in the shell of g truncatulinoides r and examine some of the practical issues associated with evaluating the usefulness of the technique the mg ca in the primary and the secondary calcite of individual g truncatulinoides r correlates exponentially with water column temperatures showing a change of 10 in the mg ca per 1 c r2 0 92 a limited comparison with plankton tow samples demonstrates that the average mg ca temperature was offset 1 c from the average temperature calculated using the 18o calibration of o neil et al 1969 and the mg ca temperatures have a range similar to the 18o temperatures comparisons of the mg in the core top samples to water depth of deposition indicates that dissolution does not alter the measured value of mg in the primary calcite

variations in mg ca and sr ca ratios of planktonic foraminifera caused by postdepositional dissolution evidence of shallow mg dependent dissolution a comparative study has been made of two species of planktonic foraminifera g tumida and g sacculifer in a depth transect on the ontong java plateau western equatorial pacific g tumida tests from core top sediments showed decreasing mg ca 2 65 1 25 mmol mol and sr ca 1 50 1 16 mmol mol ratios with increasing water depth 1600 4400 m while no such variation was found in g sacculifer tests in excess of 355 m average mg ca 3 6 mmol mol sr ca 1 4 mmol mol artificial dissolution of g tumida tests led to a decrease in both mg ca and sr ca but in g sacculifer there was no significant change in the ratios analyses by electron microprobe revealed that mg ca of the inner chamber calcite in g tumida tests was much higher than that of the calcite crust keel whereas sr ca was only slightly elevated there were no consistent spatial differences in either mg ca or sr ca for g sacculifer tests dissolution in the oceans gives rise to the removal of the chamber calcite in g tumida about 30 of the total calcite leaving the keel calcite although g tumida is thought of as a dissolution resistant form the majority of mg ca and sr ca depletion and chamber loss occurs above the lysocline it is also possible that much of the mg enriched gametogenic calcite has been lost by dissolution from g sacculifer above 1600 m mg content has a significant effect on the dissolution susceptibility of planktonic foraminifera calculations show that the saturation horizon for mg rich parts of tests may be elevated by several hundred meters compared with normal calcite

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

an experimental study of trace element fluxes from subducted oceanic crust we have determined experimentally the hydrous phase relations and trace element partitioning behaviour of ocean floor basalt protoliths at pressures and temperatures 3 gpa 750 1000 c relevant to melting in subduction zones to avoid potential complexities associated with trace element doping of starting materials we have used natural pristine mid ocean ridge basalt morb from kolbeinsey ridge and altered oceanic crust aoc from deep sea drilling project leg 46 20 n atlantic approximately 15 wt water was added to starting materials to simulate fluid fluxing from dehydrating serpentinite underlying the oceanic crust the vapour saturated solidus is sensitive to basalt k2o content decreasing from 825 6 25 c in morb 0 04 wt k2o to 750 ci n aoc 0 25 wt k2o textural evidence indicates that near solidus fluids are sub critical in nature the residual solid assemblage in both morb and aoc experiments is dominated by garnet and clinopyroxene with accessory kyanite epidote fe ti oxide and rutile plus quartz coesite phengite and apatite below the solidus trace element analyses of quenched silica rich melts show a strong temperature dependence of key trace elements in contrast to the trace elementdoped starting materials of previous studies we do not observe residual allanite instead abundant residual epidote provides the host for thorium and light rare earth elements lree preventing lree from being released rlree 1500 and la smpum where pum indicates primitive upper mantle 1 most closely matching the geochemical signal of arc lavas worldwide were generated from aoc at 800 850 c

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

crystal chemical controls on rare earth element partitioning between epidote group minerals and melts an experimental and theoretical study we have experimentally determined the partitioning of ree rare earth elements between zoisite and hydrous silicate melt at 1 100 c and 3 gpa all ree behave moderately compatible in zoisite with respect to the melt and all d ree zo melt show a smooth parabolic dependence on ionic radius the partitioning parabola peaks at nd left d nd zo melt 4 9 right and the compatibility slightly decreases towards la left d la zo melt 3 9 right and decreases by half an order of magnitude towards yb left d yb zo melt 1 1 right application of the elastic strain model of blundy and wood 1994 to the available zoisite and allanite ree mineral melt partitioning data and comparison with partitioning pattern calculated from a combination of structural and physical data taken from the literature with the elastic strain model suggest that in zoisite ree prefer the a1 site and that only la and ce are incorporated into the a2 site in significant amounts in contrast in allanite all ree are preferentially incorporated into the large and highly co ordinated a2 site as a result zoisite fractionates the mree effectively from the hree and moderately from the lree while allanite fractionates the lree very effectively from the mree and hree consequently the presence of either zoisite or allanite during slab melting will lead to quite different ree pattern in the produced melt

oceanographic considerations for the application of the alkenone based paleotemperature u37k index in the gulf of california abstract alkenone concentrations were determined in sediment trap samples and surficial sediments collected from guaymas basin gulf of california to investigate the factors that control the relationship between the u37k index and sst the results from the sediment trap study reveal a positive correlation r2 0 5 between alkenone fluxes and satellite avhrr sea surface temperature sst and a strong correlation r2 0 9 between u37k and sst over an annual temperature range of 20 c although sst and u37k are tightly coupled throughout two upwelling seasons the relationship deviates from the expression developed by prahl et al 1988 at temperatures higher than 26 c the possible reasons for this deviation are varied but include the observed changes in the coccolithophore species assemblage and the evolution of the thermocline during periods of high sst the seasonal pattern of alkenone fluxes higher fluxes during warm periods observed throughout the 1996 to 1997 study period causes a bias in the annually averaged u37k record resulting in temperature estimates that are 1 c higher than the annual avhrr sst average furthermore the u37k ratios obtained from core top sediments indicate an additional 2 c warm bias in the sedimentary record that may be related to the lateral inputs of alkenones from other regions of the gulf these results highlight the importance of oceanographic processes in determining the alkenone temperature signal that is preserved in sediments after accounting for such effects u37k ratios from a box core were used to reconstruct a sst record extending back to the 18th century for the guaymas basin these results indicate a steady 2 c warming of the surface waters of the gulf from early 1700s to the 1950s followed by a rapid apparent 1 c cooling between the 1950s and the 1980s

mg ca in the planktonic foraminifera globorotalia inflata and globigerinoides bulloides from western mediterranean plankton tow and core top samples abstract due to its strong gradient in salinity and small temperature gradient the mediterranean provides an ideal setting to study the impact of salinity on the incorporation of mg into foraminiferal tests we have investigated tests of globorotalia inflata and globigerina bulloides in plankton tow and core top samples from the western mediterranean using icp oes for bulk analyses and la icp ms for analyses of individual chambers in single specimens mg ca observed in g inflata are consistent with existing calibrations whereas g bulloides had significantly higher mg ca than predicted particularly in core top samples from the easterly stations scanning electron microscopy and laser ablation icp ms revealed secondary overgrowths on some tests which could explain the observed high core top mg ca we suggest that the mediterranean intermediate and deep water supersaturated with respect to calcite cause these overgrowths and therefore increased bulk mg ca however the different species are influenced by diagenesis to different degrees probably due to different test morphologies our results provide new perspectives on reported anomalously high mg ca in sedimentary foraminifera and the applicability of the mg ca paleothermometry in high salinity settings by showing that 1 part of the signal is generated by precipitation of inorganic calcite on the foraminifer test due to increased calcite saturation state of the water and 2 species with high surface to volume shell surfaces are potentially more affected by secondary mg rich calcite encrustation

quantifying carbonate dissolution and calibration of foraminiferal dissolution indices in the somali basin two sediment traps moored off somalia in 1992 1993 collected similar settling fluxes of carbonate and siliceous shells formed by various plankton groups planktic foraminifera showed large seasonal variations with more than 74 of the total planktic foraminifera flux collected during the sw monsoon summer upwelling when globigerina bulloides was dominating along with globigerinita glutinata and neogloboquadrina dutertrei the intermonsoon and ne monsoon assemblages were dominated by globigerinoides ruber we used the trap records as our no dissolution reference for comparison with three boxcore recorders in order to quantify the carbonate dissolution along a depth transect dissolution increases downslope from station 905 to 907 and 915 at depths of 1567 m 2807 m and 4035 m respectively the carbonate fraction of the sediment at station 915 which is located near the ccd is the most affected by dissolution with more than 97 of the planktic foraminifera dissolved here the planktic foraminifera assemblage is strongly modified with thick walled species such as n dutertrei globorotalia tumida and pulleniatina obliquiloculata as the most resistant it is not representative of the settling assemblage the planktic foraminiferal assemblages of the sediment surface at stations 905 and 907 remain similar to the trap assemblages and the foraminifera are well preserved although only 25 of foraminifera are apparently preserved at station 905 and 8 at station 907 those numbers are surprisingly low and infer that only a small fraction of the foraminiferal carbonate production is buried and removed from the carbon cycle this discrepancy between the export and buried flux is partly be due to bio mechanical destruction by benthic processes and to supralysoclinal dissolution due to metabolic co2 generated by the benthic organisms another important factor is the interannual variability of the productivity well known in the arabian sea the calibration of commonly used foraminiferal dissolution indices percentage of foraminiferal fragments percentage of resistant species foraminiferal dissolution index fdx to our data only shows reliable results for high dissolution levels 97 off somalia the most accurate of the proxies is the percentage of foraminiferal fragments compared to the other methods tested i e fdx planktic foraminiferal loss l percentage of radiolarians and diatoms percentage of benthic foraminifera the species assemblage appears to be not significantly modified by dissolution unless the estimated shell loss is high 92 of the arriving shells in our samples this level is expressed in the percentage of fragmentation the percentage of radiolarians and diatoms the percentage of resistant foraminifera species and fdx as 80 35 25 and 1 8 respectively the relative abundance of globigerina bulloides is a valid sw monsoon upwelling proxy only when dissolution is moderate 92 globigerina bulloides and globigerinoides ruber have similar burial efficiencies and susceptibilities to dissolution thus the ratio g bulloides g ruber is a valid proxy for past changes in the intensity of the sw monsoon even in the strongly dissolved samples in our sediment record the ratio g bulloides g ruber indicates that the sw monsoon was stronger in the recent past than in 1992 93

thorium abundances of basalt ponds in south pole aitken basin insights into the composition and evolution of the far side lunar mantle 1 imbrian aged basalt ponds located on the floor of south pole aitken spa basin are used to provide constraints on the composition and evolution of the far side lunar mantle we use forward modeling of the lunar prospector gamma ray spectrometer thorium data to suggest that at least five different and distinct portions of the far side lunar mantle contain little or no thorium as of the imbrian period we also use spatial correlations between local thorium enhancements and nonmare material on top of the basalt ponds to support previous assertions that lower crustal materials exposed in spa basin have elevated thorium abundances consistent with noritic to gabbronoritic lithologies we suggest that the lower crust on the far side of the moon experienced multiple intrusions of thorium rich basaltic magmas prior to the formation of spa basin the fact that many of the ponds on the lunar far side have elevated titanium abundances indicates that the far side of the moon experienced extensive fractional crystallization that likely led to the formation of a kreep like component however because the imbrian aged basalts contain no signs of elevated thorium we propose that the spa impact event triggered the transport of a kreep like component from the lunar far side and concentrated it on the nearside of the moon because of the correlation between basaltic ponds and basins within spa we suggest that imbrian aged basaltic volcanism on the far side of the moon was driven by basin induced decompressional melting

experimental constraints on sulphur behaviour in subduction zones implications for ttg and adakite production and the global sulphur cycle since the archean we performed crystallization experiments at 2 3 gpa at 700 9508c on basaltic and pelitic lithologies with added water and sulphur to constrain the factors controlling sulphur behaviour in subduction zones and how it may have varied through geological time the resulting hydrous silicic melts have up to 20 times more dissolved sulphur up to 1wt than at 0 2 0 4 gpa when moderately oxidized conditions prevail such high solubilities appear to result from the combined effects of enhanced solubility of water in high pressure silicate melts 10 20 wt h2o which acts to decrease silica activity and oxidizing conditions the results confirm previous findings that high sulphur contents in silicate melts do not necessarily require iron rich compositions suggesting instead that sulphur water complexes play a fundamental role in sulphur dissolution mechanisms in iron poor silicic melts in agreement with recent spectroscopic data the experimental melts reproduce phanerozoic slab derived magmas in particular their distinct ca and mg rich composition the results also show that sulphur increases the degree of melting of basalt lithologies hence we suggest that subducted slabs will preferentially melt where sulphur is present in abundance and that the variability in arc magma sulphur output reflects in part the vagaries of sulphur distribution in the slab source in contrast comparison with the composition of archean felsic rocks suggests that in the early earth much less sulphur was present in subducted slabs in agreement with a number of independent lines of evidence showing that the archean ocean hence the hydrothermally altered subducted archean oceanic crust was considerably poorer in sulphur than at present volcanic degassing of sulphur was thus probably much weaker during the archean than in proterozoic phanerozoic times

cadmium zinc copper and barium in foraminifera tests the concentrations of cadmium zinc copper and barium have been determined on 2 mg samples of single species foraminifera populations cleaning techniques were tested using north atlantic core tops and followed by a detailed downcore study for the last 30 000 years in south atlantic core v22 174 raw foram tests cleaned by crushing followed by ultrasonic removal of fine grained material and dissolved in a ph 5 5 acetate buffer contain appreciable amounts of trace elements associated with ferromanganese and alumino silicate contaminants a reductive complexing cleaning treatment reduces ferromanganese contamination by 1 2 orders of magnitude acetate buffers at ph 5 5 complex iron and raise the solubility of ferromanganese oxides these buffers are unsuitable for separating carbonate lattice bound trace elements from the fraction associated with ferromanganese phases improved mechanical and ultrasonic reductive cleaning combined with a mild dissolution in distilled water under 1 atm pco2 reduces contaminant levels another order of magnitude the cd and zn concentrations order 10 8 mole cd mole ca and 10 5 mole zn mole ca of species with low surface area show an increase with decreasing isotopic temperatures this increase is consistent with the increasing concentrations of these metals from low values in surface waters to higher values at depth the variance of cd and zn over the last 30 000 years in the central south atlantic is consistent with the probable variability of the dissolved trace elements at the calcification levels of the species analyzed cu and ba are irreproducible and probably sensitive to residual contaminant phases the trace element content of the tests differs from levels observed in a recent coprecipitation study foraminifera may be a significant vector in zinc cycling in the ocean

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

a multiproxy assessment of the western equatorial pacific hydrography during the last 30 kyr foraminiferal species assemblages and uk37 0 1 2 c these estimates are consistent with estimates from other wpwp cores thereby suggesting that the discrepancy is due to proxy compatibility rather than differences in cores qualitity postdepositional dissolution above the lysocline might have altered the mg ca based temperature estimates in our site but this effect is insufficient to resolve discrepancies between mg ca in g ruber and the other proxies we suggest that the lower estimates obtained from mg ca in g sacculifer faunal transfer functions and uk37 0 might reflect subsurface temperature changes rather than strict surface estimates accounting for potential artefacts including dissolution and bioturbation we suggest that the glacial wpwp sst was about 2 5 0 7 c cooler than during the holocene whereas the subsurface upper thermocline temperature change was only about 1 8 0 7 c interpreting variations in d 18 osw in terms of salinity changes suggests a possibly slight decrease in surface salinity at the site of md97 2138 during the lgm though lgm freshening in md97 2138 is not robust to postdeposition dissolution effects this inferred freshening appears to be a general feature of the western equatorial pacific

validation of a full hydrodynamic model for large scale hydrologic modelling in the amazon a key aspect of large river basins partially neglected in large scale hydrological models is river hydrodynamics large scale hydrologic models normally simulate river hydrodynamics using simplified models that do not represent aspects such as backwater effects and flood inundation key factors for some of the largest rivers of the world such as the amazon in a previous paper we have described a large scale hydrodynamic approach resultant from an improvement of the mgb iph hydrological model it uses full saint venant equations a simple storage model for flood inundation and gis based algorithms to extract model parameters from digital elevation models in the present paper we evaluate this model in the solimoes river basin discharge results were validated using 18 stream gauges showing that the model is accurate it represents the large delay and attenuation of flood waves in the solimoes basin while simplified models represented here by muskingum cunge provide hydrographs are wrongly noisy and in advance validation against 35 stream gauges shows that the model is able to simulate observed water levels with accuracy representing their amplitude of variation and timing the model performs better in large rivers and errors concentrate in small rivers possibly due to uncertainty in river geometry the validation of flood extent results using remote sensing estimates also shows that the model accuracy is comparable to other flood inundation modelling studies results show that i river floodplain water exchange and storage and ii backwater effects play an important role for the amazon river basin hydrodynamics copyright 2011 john wiley sons ltd

fluid present melting of ocean crust in subduction zones phase equilibria were investigated in the pressure range 400 2000 mpa on the pinatubo dacite a representative example of natural cenozoic adakites slab melts to constrain the temperature versus wt h 2 o conditions of magma genesis the experimental results suggest that water contents of the melt were at least 10 wt and temperatures were 900 c during magma ascent from the slab natural aluminous amphiboles present in the dacite crystallized at pressures of 1000 mpa fixing an upper temperature limit of 950 c for the slab melts at the crust mantle boundary amphiboles experimentally crystallized at 1000 mpa are identical to those found in melt inclusions in metasomatized mantle xenoliths these natural inclusions represent samples of slab melts and contain glasses with a dacitic bulk composition which requires an h 2 o content in the melt of 10 wt at 1000 mpa and 900 c for conditions of magma generation of 800 900 c at 2000 2300 mpa melt h 2 o contents close to 15 wt are needed to generate melts with dacitic bulk composition overall these constraints are inconsistent with slab melts being produced by dehydration melting of amphibolite a mechanism unable to produce dacite melt compositions that are both hydrous and cool slab melting in modern subduction zones must occur under fluid present conditions at temperatures below 900 c in agreement with the thermal regime of subducted oceanic crust as deduced from numerical simulation of heat transfer using the present day mantle geotherm at such low temperatures ti bearing phases are stable during melting thus any metasomatizing slab melt will be strongly depleted in nb ta and ti a major characteristic of arc magmas produced in the mantle wedge

applicability of the local inertial approximation of the shallow water equations to flood modeling 1 recent studies have demonstrated the improved computational performance of a computer algorithm based on a simplification of the shallow water equations the so called local inertial approximation which has been observed to provide results comparable to the full set of equations in a range of flood flow problems this study presents an extended view on the local inertial system shedding light on those key elements necessary to understand its applicability to flows of practical interest first the properties of the simplified system with potential impact on the accuracy of the solutions are described and compared to the corresponding full dynamic counterparts in light of this discussion the behavior of the solutions is then analyzed through a set of rigorously designed test cases in which analytical solutions to the shallow water system are available results show a general good agreement between the local inertial and full dynamic models especially in the lower range of subcritical flows fr 0 5 in terms of steady nonuniform flow water profiles the error introduced by the local inertial approximation leads to milder water depth gradients which results in attenuated spatial changes in depth in unsteady problems the local inertial approximation leads to slower flood propagation speeds than those predicted by the full dynamic equations even though our results suggest that the magnitude of these errors is small in a range of floodplain and lowland channels it becomes increasingly relevant with increasing fr and depth gradients

timing and mechanism for intratest mg ca variability in a living planktic foraminifer abstract geochemical observations indicate that planktic foraminifer test mg ca is heterogeneous in many species thereby challenging its use as a paleotemperature proxy for paleoceanographic reconstructions we present mg ca and ba ca data collected by laser ablation icp ms from the shells of orbulina universa cultured in controlled laboratory experiments test calcite was labeled with ba spiked seawater for 12 h day or night calcification periods to quantify the timing of intratest mg banding across multiple diurnal cycles results demonstrate that high mg bands are precipitated during the night whereas low mg bands are precipitated during the day data obtained from specimens growing at 20 c and 25 c show that mg ca ratios in both high and low mg bands increase with temperature and average test mg ca ratios are in excellent agreement with previously published empirical calibrations based on bulk solution icp ms analyses in general mg band concentrations decrease with increasing ph and or co2 3 but this effect decreases as experimental temperatures increase from 20 c to 25 c we suggest that mitochondrial uptake of mg2 from the thin calcifying fluid beneath streaming rhizopodial filaments may provide the primary locus for mg2 removal during test calcification and that diurnal variations in either mitochondrial density or activity produce mg banding these results demonstrate that mg banding is an inherent component of test biomineralization in o universa and show that the mg ca paleothermometer remains a fundamental tool for reconstructing past ocean temperatures from fossil foraminifers

influences on the fractionation of calcium isotopes in planktonic foraminifera for paleoceanographic studies it is important to understand the processes that influence the calcium ca isotopic composition of foraminiferal calcite tests preserved in the sediment record seven species of planktonic foraminifera from coretop sediments collectively exhibited a ca temperature dependent fractionation of 0 013 per c thisisin agreement with previously published estimatesformostspecies ofplanktonic foraminifera as well asbiogenicandinorganiccalciteandaragonite fourspeciesofplanktonicforaminiferacollectedfromasedimenttrapshowedaconsiderableamountof scatterandnoconsistenttemperaturedependentfractionation analyzedsizefractionsofcoretopsamplesshownosignificantrelationshipwith 44 40 ca however preliminary results suggest that the symbiotic and spinose foraminifera globigerinoides sacculifer might exhibit a relationship between test size and 44 40 ca a one box model in which ca isotopes are allowed to fractionate by rayleigh distillation from a biomineralization reservoir internal pool was used to constrain the isotopic composition of the original biomineralization ca reservoir assuming around 85 of the ca reservoir is precipitatedandthefractionationfactorduringprecipitationis0 9985 0 00002 t c toexplaintheforaminiferalcaisotopedata thismodelindicates

fluvial processes in a forested anastomosing river flood partitioning and changing flow patterns in an effort to further our understanding of multiple channel systems this paper presents data on the flood response of channels in one of the last wooded semi natural anastomosing systems in europe the gearagh ireland is characterized by hundreds of small islands separated by interconnected channels of low slope these include channels that cross islands at right angles to the main flow and blind anabranching channels islands are relatively stable and wooded with evidence of division by channel erosion and growth by in channel sedimentation four active zone cross profiles were surveyed each containing between seven and 13 channels velocities were measured in several channels before and during two separate floods from these observations channels have been categorised into three types fast shallow and trapezoidal slow deep and more irregular and flood channels during the floods interchannel flows were caused by variations in water surface elevations due to backing up behind debris dams and it is suggested that this is the origin of the anomalous cross island channels and one cause of island division another potential cause of island division blind anabranching channels is the result of concentrated bank scour between root masses biotic components such as debris dams tree root masses and tree throw pits play a key role in the partitioning of flow and cause variations in channel velocities and the overbank velocity distribution the implications of these observations for channel pattern maintenance are briefly discussed

mg ca in foraminifera from plankton tows evaluation of proxy controls and comparison with core tops abstract calibrations and validations of the mg ca paleothermometer in planktic foraminifera have traditionally been performed by means of core tops sediment trap samples and culture experiments in this study mg ca ratios have been measured in 8 species of planktic foraminifera non globorotaliids globigerina bulloides neogloboquadrina incompta orbulina universa globigerinoides ruber white and g sacculifer and globorotaliids globorotalia inflata g hirsuta and g truncatulinoides collected live from the north atlantic the southeast atlantic the northeast pacific and the norwegian sea mg ca ratios for n incompta o universa g ruber g sacculifer and g truncatulinoides are similar to available north atlantic core top studies and consistent with previous calibration equations in contrast some g bulloides g inflata and g hirsuta mg ca ratios are higher than predicted based on 18 o values and exhibit considerable scatter this elevation may be in part related to the impact of potential isotopic disequilibrium effects on 18 o derived temperatures which the mg ca ratios are compared to another factor that may affect mg ca ratios in some plankton samples is the lack of low mg test components e g final chambers or gametogenic calcite because of the incompleteness of the life cycle at the time of collection n incompta mg ca ratios are correlated with salinity with mg ca changing about 16 per salinity unit suggesting that salinity may have an important influence on mg ca of some species even in non extreme salinity environments this is the first extensive multispecific plankton tow mg ca data set from different oceanographic regions which has been used to test the mg ca temperature proxy in the context of published calibration data highlighting the complex physiological ecological controls on the acquisition of the proxy signal

distribution of alteration zones in the upper oceanic crust aging of the upper oceanic crust produces alteration zones that have distinct mineralogical and geochemical characteristics five zones are recognized in the troodos ophiolite and in situ oceanic crust 1 a sea floor weathering zone swz 2 a low temperature zone ltz 3 a transition zone tz 4 an upper dike zone udz and 5 a mineralized zone mz the mz may be overlain by the swz ltz or tz but in the known examples it is always underlain by the udz the development of the swz is dependent upon the duration of cold seawater circulation which is dependent upon seafloor topography and the rate and nature of sedimentation the boundary between the low and high temperature zones is largely controlled by permeability contrasts lateral variation in the depth of this boundary indicates that the thermal gradient is not uniform within the crust this along with the evidence for disequilibrium assemblages implies that regional metamorphic zones are not appropriate to describe the distribution of alteration effects

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

experimentally based water budgets for dehydrating slabs and consequences for arc magma generation phase diagrams of hydrous mid ocean ridge mor basalts to 330 km depth and of hydrous peridotites to 250 km depth are compiled for conditions characteristic for subduction zones a synthesis of our experimentally determined phase relations of chlorite lawsonite epidote zoisite amphibole paragonite chloritoid talc and phengite in basalts and of phase relations from the literature of serpentine talc chlorite amphibole and phase a in ultramafics permits calculation of h2o contents in hydrous phase assemblages that occur in natural compositions this yields the information necessary to calculate water budgets for descending slabs starting from low grade blueschist conditions 10 20 km depth with h2o contents between 5 and 6 wt for hydrated oceanic crust complete dehydration is achieved between 70 and 300 km depth as a function of individual slab geotherms hydrous phases which decompose at depth below volcanic arcs are lawsonite zoisite chloritoid and talc phengite in mafic compositions and chlorite and serpentine in peridotite approximately 15 35 of the initially subducted h2o are released below volcanic arcs the contribution of amphibole dehydration to the water budget is small 5 20 and occurs at relatively shallow depth 65 90 km in any predicted thermal structure dehydration is a combination of a stepwise and a continuous process through many different reactions which occur simultaneously in the different portions of the descending slab such a dehydration characteristic is incompatible with single phase dehydration models which focus fluid flow through a unique major dehydration event in order to explain volcanic fronts as a consequence of continuously progressing dehydration water ascending from the slab will be generally available to depth of ca 150 200 km the fluid rising from the subducting lithosphere will cause partial melting in the hot portion of the mantle wedge we propose that the volcanic front simply forms above the mantle wedge isotherm where the extent of melting is sufficient to allow for the mechanical extraction of parental arc magmas thermal models show that such an isotherm ca 1300oc locates below volcanic fronts slab surface depths below such an isotherm are compatible with the observed depths of the slab surface below volcanic fronts 1998 elsevier science b v all rights reserved

late holocene 0 2 4 ka bp surface water temperature and salinity variability feni drift ne atlantic ocean abstract planktonic foraminiferal mg ca ratios and oxygen isotopic compositions of a spliced sediment record from feni drift ne atlantic ocean box core m200309 and piston core enam9606 trace late holocene sea surface temperature sst and salinity changes over the past 2400 years at this location the variability of sst and oxygen isotopic composition of seawater 18 o w reflects variable northward advection of warm and saline surface waters which appears linked to climate variability over the adjacent european continent our records reveal a general long term cooling trend superimposed on this overall trend partly higher temperatures and salinities from 180 to 560 ad and 750 to 1160 ad may be ascribed to the roman and medieval warm periods respectively subsequently our record displays highly variable surface water conditions the main little ice age sst minimum is restricted to the 15th and 16th centuries ad pervasive multidecadal to centennial scale variability throughout the sedimentary proxy records can be partly attributed to solar forcing and or variable heat extraction from the surface ocean caused by shifts in the prevailing state of the north atlantic oscillation nao high salinities in the 17th and 18th centuries are considered to reflect tropical anomalies linked to a southward shift of the intertropical convergence zone propagating across the north atlantic ocean

the lower atmosphere over the gulf of california automated meteorological observations at coastal and island stations instrumented aircraft flights and coastal soundings were made between july 1983 and june 1985 to define the variations of the lower atmosphere over the northern half of the gulf of california during the two important climatic seasons the mid latitude winter and the subtropical summer a marine layer is well defined over water during both seasons but dissipates within a few kilometers inland the winter large scale pressure field is dominated by the great basin high over the southwestern united states modulated by upper level synoptic activity it causes 3 to 6 days events of northwesterly winds 8 12 m s 1 directed along the gulf s axis which are coherent over basin scales and bring cool dry desert air over the gulf the vertical scale of these winds is 700 1000 m over land on the western side of the gulf close to the height of the baja california mountains but only 100 400 m over water defined by the wintertime inversion cross gulf winds related to topographic effects during upper level trough passages over baja california are particularly intense in the northwestern portion of the gulf the winter marine layer is defined by a 1 to 4 5 c temperature inversion and a dew point temperature of 6 11 c a moisture content of 6 8 g kg 1 weak subsidence reduces dew point values to 4 c above the inversion winter winds above the marine layer are coherent 0 8 across the width of the gulf the summer large scale pressure field is dominated by a thermal low over the southwestern united states and drives weak 2 5 m s 1 southeasterly winds also directed primarily along the gulf which are less spatially uniform than winter winds air temperature and moisture content are rather constant and topographic effects are absent the summer marine layer is on the order of 200 300 m thick with dew point temperatures of 26 28 c 21 24 g kg 1 and capped by a weak temperature inversion 1 2 c over water aloft the dew point temperature is 17 21 c and winds are weak and uncorrelated across the width of the gulf during june and early july 1984 four week long pulses of southeasterly winds 10 m s 1 support the existence reported previously of moisture surges from the gulf into the sonoran desert a dynamical analysis of subdiurnal motions shows that the cross gulf momentum balance is geostrophic the along gulf balance is ageostrophic with the along gulf pressure gradient opposed by friction at the surface these results are consistent with a scale analysis of the equations of motion in the marine layer over the gulf of california

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

excess dissolved ca in the deep ocean a hydrothermal hypothesis abstract variations in seawater alkalinity and dissolved calcium provide information essential to establishing the integrated deep ocean calcium carbonate dissolution flux high precision ca measurements reported here confirm earlier suggestions that the deep ocean contains higher levels of dissolved ca than expected from calcium carbonate dissolution only i propose that the mid depth ca excess is a manifestation of the circulation of seawater through hydrothermal systems at mid ocean ridges qualitative agreement with 3 he distributions and evidence for deep water mg depletions support this hypothesis the magnitude of the mid depth ca excess implies a total hydrothermal flux larger than expected from the corresponding excess in 3 he and points to the relative importance of low temperature diffuse fluxes versus high temperature discrete fluxes for elements such as ca the implied total hydrothermal flux for ca is consistent with its oceanic mass balance requirements and resolves several long standing problems associated with our understanding of the chemical evolution of the ocean and in particular its low alkaline content

estimation of river discharge propagation speed and hydraulic geometry from space lena river siberia 1 moderate resolution imaging spectroradiometer modis derived measurements of lena river effective width we display a high predictive capacity r2 0 81 mean absolute error 60 90 km 2 3 time valley width satellite derived we q rating curves and hydraulic geometry b exponents converge upon stable values b 0 48 indicating transferability of the discharge retrieval method between different locations put another way at length scales exceeding 60 90 km all subreaches display similar behavior everywhere at finer reach length scales e g 0 25 1 km longitudinal extraction of b exponents represents the first continuous mapping of a classical hydraulic geometry parameter from space while at least one gauging station is required for calibration results suggest that multitemporal satellite data can powerfully enhance our understanding of water discharge and flow conveyance in remote river systems

assessing the effect of different bathymetric models on hydraulic simulation of rivers in data sparse regions abstract river bathymetry which is vital for accurate hydraulic modeling is not readily available at large scales because of the logistical difficulties in field surveys and uncertainties associated with remote sensing techniques several studies have explored the potential of conceptual models and interpolation algorithms to estimate bathymetry these models have certain underlying assumptions that limit their accuracy and widespread implementation this study aims to provide insights into the choice of bathymetric model for different hydraulic applications by analyzing the effect of different bathymetric models on hydraulic modeling under different geomorphologic and flow settings this study does not aim to reinforce the importance of bathymetry rather its objective is to identify the bathymetric properties that are critical to accurate estimation of different hydraulic outputs the study accomplishes its objectives by implementing three different bathymetric models with varying cost and efficiency at four sites with diverse bathymetric characteristics five hydraulic outputs namely wetted cross sectional area water surface elevation inundation extents velocity and shear are estimated at three characteristic low and high flows and the results from the four sites are grouped together to perform an unbiased and robust evaluation the performance of these models is evaluated using the best available bathymetric representation generated from detailed field surveys as a benchmark the results indicate that 1d flood modeling is somewhat insensitive to channel shape as long as the estimated shape reflects the channel storage accurately velocity and shear related applications should incorporate bathymetry that represent both the cross sectional area and channel thalweg accurately reaches with low sinuosity

varve formation in the gulf of california insights from time series sediment trap sampling and remote sensing the varved sediments that accumulate in the central gulf of california guaymas and carmen basins provide a record that allows for the resolution of annual to decadal scale climate variability in this region time series sediment trapping combined with remotely sensed observations of sea surface temperature avhrr and color czcs have been used to examine the mechanism of varve formation in the central gulf sst and surface pigment concentration records for both the mainland and baja sides of the gulf display similar seasonal trends high temperatures and low pigment concentrations occur synchronously on both sides of the central gulf from june through to october in association with the 1991 92 el nino warm temperatures persist in the central gulf until december low ssts typically occur from december through may with high pigment concentrations marking the period from november through april the summer early fall june october is a time of high terrigenous and biogenic sediment fluxes during this time of year the total flux is dominated by eolian transported lithogenic material and dark laminae are deposited during this period during el nino years high terrigenous fluxes may extend into winter light laminae represent deposition from november through may during which time biogenic material dominates the total sediment flux high opal fluxes beginning in november are attributed to seasonal cooling of surface water and upward mixing of nutrients true upwelling conditions do not develop in the gulf until late winter spring during this time the total flux is still dominated by opal but the magnitude of the flux is reduced this may be an artifact of phytoplankton grazing and not lower production rates

large scale hydrologic and hydrodynamic modeling using limited data and a gis based approach summary in this paper we present a large scale hydrologic model with a full one dimensional hydrodynamic module to calculate flow propagation on a complex river network the model uses the full saint venant equations and a simple floodplain storage model and therefore is capable of simulating a wide range of fluvial processes such as flood wave delay and attenuation backwater effects flood inundation and its effects on flood waves we present the model basic equations and gis algorithms to extract model parameters from relatively limited data which is globally available such as the srtm dem gis based algorithms include the estimation of river width and depth using geomorphological relations river cross section bottom level and floodplain geometry extracted from dem etc we also show a case study on one of the major tributaries of the amazon the purus river basin a model validation using discharge and water level data shows that the model is capable of reproducing the main hydrological features of the purus river basin also realistic floodplain inundation maps were derived from the results of the model our main conclusion is that it is possible to employ full hydrodynamic models within large scale hydrological models even using limited data for river geometry and floodplain characterization

li sr mg and na in foraminiferal calcite shells from laboratory culture sediment traps and sediment cores abstract constant temperature laboratory culture experiments of the planktonic foraminiferal species globigerinoides sacculifer brady suggest that the ratios of li and sr to ca in the shells are a function of these ratios in the culture solutions mg ca and na ca in the shells did not vary with changes of these ratios in the culture solution these are the first direct determinations of the relationship between foraminiferal shell chemistry and solution composition the possibility of temperature dependence for the minor elemental composition of foraminiferal shells was also investigated in the laboratory and by analysis of several planktonic and one benthic foraminiferal species from sediment trap and sediment core samples the sr ca mg ca and na ca ratios in the natural samples roughly correlate with calcification temperature whereas differences in the li ca ratios are small and not systematically related to temperature however laboratory culture experiments at 20 c and 30 c showed no variation in the li ca sr ca mg ca and na ca ratios with calcification temperature for the planktonic foraminifera g sacculifer and orbulina universa therefore observed differences in the sr ca mg ca and na ca ratios for the sediment trap and core foraminiferal samples cannot be ascribed to direct effects of calcification temperature but may be due to some other environmental factor which is correlated with temperature

experimental constraints on phase relations in subducted continental crust synthesis piston cylinder experiments were carried out in the range 2 0 4 5 gpa and 680 1 050 c to investigate phase relations in subducted continental crust a model composition kcmash has been used because all major ultrahigh pressure uhp minerals of the whole range of rock types typical for continental crust can be reproduced within this system the combination of experimental results with phase petrologic constraints permits construction of a uhp petrogenetic grid the phase relations demonstrate that the most important uhp paragenesis consists of coesite kyanite phengite clinopyroxene and garnet in subducted continental crust below 700 c talc is stable instead of garnet as most of these minerals are also stable at much lower pressure and temperature conditions it is thus not easy to recognize uhp metamorphism in subducted crust a general feature however is the absence of feldspars at h2o saturated conditions plagioclase is never stable at uhp conditions but k feldspar can occur in h2o undersaturated rocks mineral compositions in the experiments are fully buffered by coexisting phases the si content of phengite and biotite increase with increasing pressure at 4 0 gpa 780 c biotite contains 3 28 si per formula unit which is most probably caused by solid solution of biotite with talc above 800 c the caal2sio6 component in clinopyroxene buffered with kyanite coesite and a mg phase increases with increasing temperature providing a tool to distinguish between cold and hot eclogites up to 10 ca eskolaite ca0 5 0 5alsi2o6 in clinopyroxene has been found at the highest temperature and pressure investigated 900 c 4 5 gpa garnet buffered with coesite kyanite and clinopyroxene displays an increase of grossular component with increasing pressure for a given temperature although the investigated system represents a simplification with respect to natural rocks it helps to constrain general features of subducted continental crust the observed phase relations and phase compositions demonstrate that at pressures 3 0 gpa and temperatures 800 c continental crust can retain significant amounts of h2o 1 wt whereas k free mafic or ultramafic rocks are dry at these conditions uhp parageneses are only preserved if the whole exhumation path is situated within the stability field of phengite i e if there is cooling during exhumation or if the whole exhumation occurred at t 700 c in contrast break down of phengite and concomitant partial melting in terranes that show isothermal decompression may lead to a complete recrystallization of the subducted crust during exhumation the density of uhp rocks can be estimated on the basis of the established phase relations pelitic rocks are likely to have a density close to mantle rocks 3 3 g cm3 because of significant amounts of dense garnet and kyanite whereas granitic rocks are less dense 3 0 g cm3 hence subducted average continental crust is most probably buoyant with respect to mantle rocks and tends to get exhumed as soon as it is detached from the down going slab electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00410 001 0336 3

glacial interglacial changes in subantarctic sea surface temperature and δ18o water using foraminiferal mg laboratory culturing experiments with living globigerina bulloides indicate that mg ca is primarily a function of seawater temperature and suggest that mg ca of fossil specimens is an effective paleotemperature proxy using culturing results and a core top neogloboquadrina pachyderma calibration we have estimated glacial interglacial changes in sea surface temperature sst using planktonic mg ca records from core rc11 120 in the subantarctic indian ocean 43 s 80 e and core e11 2 in the subantarctic pacific ocean 56 s 115 w our results suggest that glacial sst was about 4 c cooler in the subantarctic indian ocean and 2 5 c cooler in the subantarctic pacific comparison of sst and planktonic 18o records indicates that changes in sst lead changes in 18o by on average 1 3 kyr the glacial interglacial temperature change indicated by the subantarctic mg ca records suggests that temperature accounts for 40 60 of the foraminiferal 18o change we have used the mg ca based sst estimates and 18o determinations to generate site specific seawater 18o records which suggest that seawater 18o was on average 1 more positive during glacial episodes compared with interglacial episodes

compositional variations of granitic rocks in continental margin arc constraints from the petrogenesis of eocene granitic rocks in the tengchong block sw china abstract in order to address the causes of compositional variations of crust derived granitic rocks in continental margin arc we focused on the petrogenesis of eocene granitic host rocks with enclosed mmes associated metagabbro fine grained quartz diorite in xima tongbiguan area the tengchong block which is a continental margin arc related to the subduction of neo tethys both the eocene granitic and mafic rocks are characterized by gradual increment in enriched compositions such as k rb th lree initial 87sr 86sr end t and ehf t but decreasing pb isotopic ratios from the west to the east of the tengchong block zircon u pb age data of granitic host rocks mmes metagabbro and fine grained quartz diorite reveal a similar age range of 55 50 ma the lithologies zircon hf compositions geochemical and isotopic signatures of host granitic rocks show that the origin of these host rocks are mainly controlled by magma mixing between felsic and mafic magma the products of the mafic magma are dominated by metagabbro fine grained quartz diorite and mmes enclosed in granitic rocks which are all resulted from the reaction and mixture between different mafic magmatic products and felsic magma the metagabbros could be the products of felsic magma mixing with early crystallized mafic magma and the fine grained quartz diorites could be the products of felsic magma mixing with crystal rich mafic magma and the mmes could be the products of felsic magma mixing with crystal poor mafic magma or melt the metagabbro has positive ehf t values of 1 8 to 10 9 which could provide the relative primitive lu hf isotopic compositions of mafic magma indicating that the mafic magma is derived from a depleted mantle the host granitic rocks have negative end t values of 5 2 to 6 5 indicating that the felsic magma is derived from partial melting of an ancient mafic lower crust furthermore there are excess reactions after magma mixing between the mafic and felsic magma such as multi stage reactions between solidified mmes and felsic magma and the disaggregation of mmes finally resulting in the basification of felsic magma magma mixing is therefore the main mechanism of the formation of granitic rocks in the tengchong block the compositional variation of intermediate to acid igneous rock in a continental margin arc is likely dominated by the characteristics of mafic magma because the intermediate to acid igneous rock is derived from mixing of crust derived granitic and different mantle sources derived mafic magma

the mid pleistocene transition in the subtropical southwest pacific 1 reconstructions of subtropical southwest pacific climate variability over the pleistocene were derived from coupled planktic foraminiferal 18o mg ca measurements taken from a southern coral sea sediment core a clear shift from 40 kyr to 100 kyr modes of reconstructed glacial interglacial sea surface temperature sst variability is seen over the mid pleistocene transition and these fluctuations are shown to have remained coherent with the orbital obliquity cycle across the transition the likely origin of this strong obliquity signal in subtropical southwest pacific sst is shown to be the southern high latitudes and comparison with existing sst reconstructions from the equatorial pacific is consistent with the communication of the signal occurring principally by greenhouse gas forcing in contrast to the sst reconstruction regional hydrological cycle variability based on the calculated local component of 18osw change does not show significant coherence with obliquity after 1000 ka the decoupling of the sst and hydrological cycle responses over the mid pleistocene transition allows constraints to be placed on the evolution and extent of orbitally paced fluctuations within the coupled low latitude ocean atmosphere system

influence of temperature on the composition of magnesian calcite overgrowths precipitated from seawater a constant disequilibrium technique was used to determine the composition of magnesian calcite overgrowths precipitated on pure calcite seeds from artificial seawater at 5 25 and 40 c the amount of magnesium incorporated in the overgrowths at a given temperature is independent of the precipitation rate over a wide range of saturation states and is believed to correspond to a composition in true equilibrium with seawater the distribution coefficient of magnesium dmg2 c in the magnesian calcite overgrowths increases almost linearly with temperature being 0 0121 0 0013 at 5 c 0 0172 0 0022 at 25 c and 0 0271 0 0013 at 40 c these values apply only to magnesian calcites precipitated from standard composition seawater since a previous study has shown dmg2 c to be a function of the mg2 ca2 ratio in the parent solution results of this study are compared with values reported previously by other workers and with the compositional distribution of naturally occurring magnesian calcite cements and ooids found in seawater it appears that variations in temperature are not sufficient to account for the compositional variability of naturally occurring inorganic marine magnesian calcite cements

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

a subgrid channel model for simulating river hydraulics and floodplain inundation over large and data sparse areas 1 this paper presents a new computationally efficient hydraulic model for simulating the spatially distributed dynamics of water surface elevation wave speed and inundation extent over large data sparse domains the numerical scheme is based on an extension of the hydraulic model lisflood fp to include a subgrid scale representation of channelized flows which allows river channels with any width below that of the grid resolution to be simulated the scheme is shown to be numerically stable and scalable before being applied to an 800 km reach of the river niger in mali the niger application focused on the performance of four different model structures a model without channels two dimensional 2 d model a model without a floodplain one dimensional 1 d model a model of the main channels and floodplain 1 d 2 d model and the subgrid approach developed here inclusion of both the channel network and the floodplain was shown to be essential meaning that large scale models of this region including routing models for land surface schemes will require a floodplain component including subgrid scale channels on the floodplain changed inundation dynamics over the delta significantly and increased simulation accuracy in terms of water level wave propagation speed and inundation extent furthermore only the subgrid model showed a consistent parameterization when calibrated against either gauge or icesat water level data suggesting that connectivity provided by small channels is a strong control on the hydraulics of the floodplain or at the very least that low resolution gridded hydraulic models require additional connectivity to represent the delta flow dynamics

orbital and suborbital climate variability in the sulu sea western tropical pacific 1 a detailed record of planktic 18o from a sediment core in the sulu sea located between the south china sea and the western pacific warm pool reveals that for the past 400 kyr 1 kyr 1000 years 18o variability on orbital timescales is similar to that caused by changes in ice volume alone this result indicates that in the sulu sea temperature driven changes in planktic 18o on orbital times scales were generally compensated for by the effects of sea level and changes in seasonal monsoon intensity on the local freshwater budget as well as by other changes in the tropical hydrologic cycle and their attendant effects on surface water 18o increased freshening of the western tropical pacific warm pool is reminiscent of la nina conditions however we argue that the mean tropical climate state was not more la nina like than today on broader spatial scales suborbital variability occurred in the sulu sea throughout the past 400 kyr suggesting little sensitivity to ice volume or to glacial interglacial changes in tropical hydrology variations on 4 10 kyr timescales appear to be linked to those in the north atlantic region suggesting a common forcing of that variability we suggest that sulu sea salinity variations were a response to suborbital climate variability in the north atlantic region transmitted via changes in the intensity of the east asian summer monsoon we suggest that a north atlantic origin of that tropical suborbital variability can be reconciled with weak glacial amplification in the tropics if the tropical response is nonlinear

hydraulic correction method hcm to enhance the efficiency of srtm dem in flood modeling abstract digital elevation model dem is one of the most important controlling factors determining the simulation accuracy of hydraulic models however the currently available global topographic data is confronted with limitations for application in 2 d hydraulic modeling mainly due to the existence of vegetation bias random errors and insufficient spatial resolution a hydraulic correction method hcm for the srtm dem is proposed in this study to improve modeling accuracy firstly we employ the global vegetation corrected dem i e bare earth dem developed from the srtm dem to include both vegetation height and srtm vegetation signal then a newly released dem removing both vegetation bias and random errors i e multi error removed dem is employed to overcome the limitation of height errors last an approach to correct the multi error removed dem is presented to account for the insufficiency of spatial resolution ensuring flow connectivity of the river networks the approach involves a extracting river networks from the multi error removed dem using an automated algorithm in arcgis b correcting the location and layout of extracted streams with the aid of google earth platform and remote sensing imagery and c removing the positive biases of the raised segment in the river networks based on bed slope to generate the hydraulically corrected dem the proposed hcm utilizes easily available data and tools to improve the flow connectivity of river networks without manual adjustment to demonstrate the advantages of hcm an extreme flood event in huifa river basin china is simulated on the original dem bare earth dem multi error removed dem and hydraulically corrected dem using an integrated hydrologic hydraulic model a comparative analysis is subsequently performed to assess the simulation accuracy and performance of four different dems and favorable results have been obtained on the corrected dem

paleosecular variation of brunhes age lava flows from british columbia canada 1 brunhes age lava flows have been sampled for paleosecular variation studies from several volcanic fields of southern british columbia silverthrone garibaldi lake mt meager clearwater wells gray park and kelowna area a total of 52 lava flows were sampled and 7 to 10 samples were drilled at each site previous radiometric studies indicate that the ages of these lava flows range from 2 3 to 760 ka stepwise thermal demagnetization 14 to 21 steps was carried out for all the samples in each site and af demagnetization was performed on one sample per site forty five sites were selected based on rigorous criteria 95 5 to calculate a mean direction d 356 9 i 70 2 95 2 8 that is statistically indistinguishable from the direction of the dipole field at the area i 68 3 virtual geomagnetic poles vgps do not show the far sided effect and the angular standard deviation is 17 5 a value in agreement with the paleomagnetic field dispersion for that latitude these high quality results are expected to improve the time averaged field taf and secular variation models

foraminiferal magnesium in globeriginoides sacculifer as a paleotemperature proxy foraminiferal magnesium shows increasing promise as a paleothermometer but the accuracy and precision are limited by biases introduced by partial dissolution salinity variations mg rich gametogenic calcite and contaminant phases we improved cleaning methods and reduced errors introduced by partial dissolution by sampling from well preserved cores in the equatorial atlantic and the caribbean sea with different dissolution histories all cores reveal a synchronous 25 increase in mg ca from the stage 2 3 boundary to the holocene core top indicating that dissolution is not a controlling factor modern temperatures estimated from core top mg ca are 24 5 25 0 c equal to mean annual water temperatures at 50 100 m we estimate that sea surface temperature increased by 2 6 c 1 3 from the last glacial maximum to the holocene holocene values were comparable to those during isotope stage 5e our data indicate that biases from contaminant phases and partial dissolution can be reduced this paleothermometer holds promise if uncertainties introduced by salinity variations and gametogenic calcite can be constrained

coccolithophore export production in guaymas basin gulf of california response to climate forcing abstract the flux and taxonomic composition of coccolithophores has been determined for sediment trap samples collected over a two year period from guaymas basin central gulf of california the gulf of california is a subtropical marginal sea with exceptionally high rates of primary productivity the annual biogenic sediment fluxes are largely dominated by silica with diatoms as the major contributor to the opal flux for the july 1990 through november 1992 study period the total coccolithophore export production in guaymas varied in response to the strength of el nino southern oscillation enso coccolithophore production follows the general surface primary productivity pattern with relatively high fluxes from late fall to late winter and low production in the summer when the water column is highly stratified and nutrient depleted high fluxes of up to 10 9 coccoliths m 2 day 1 and 3 10 6 coccospheres m 2 day 1 indicate that coccolithophores are an important component of the phytoplankton population in guaymas basin the intensification of enso conditions during 1992 altered the typical hydrography of the gulf of california by increasing sst and reducing the strength of spring upwelling this is reflected in reduced opal and diatom fluxes during this period conversely these more oligotrophic conditions resulted in higher total coccolithophore fluxes during spring and summer 1992 gephyrocapsa oceanica is present in the gulf throughout the study period but is dominant during weak or non enso times emiliania huxleyi and to a lesser degree florisphaera profunda are abundant during strong enso periods two major coccolithophore signals are indicative of strong enso conditions and could be used as paleo enso indicators in the gulf of california a the switch in dominance between g oceanica and e huxleyi and b high abundances of the deep dwelling species f profunda the abundance of this latter species shows a strong inverse relationship with opal fluxes a comparison of the annual coccolith flux with coccolith accumulation rates in the surface sediments indicates that only about 10 20 of the coccolith export production is preserved in the anoxic sediments of guaymas basin this very low level of preservation is probably due to bacterial processes on the sea floor which cause acidification of the bottom waters at the sediment water interface coccolith accumulation rates are higher in surface sediments from the western coast of the central gulf suggesting both higher coccolithophore production and better preservation in this region probably associated with lower diatom production tintinnids which agglutinate coccoliths are strongly selective for both coccolith size and species

experimental constraints on recycling of potassium from subducted oceanic crust petrological experiments on oceanic crust samples characterize the recycling of potassium from mid ocean ridge basalts and sediments metasomatism could develop directly and continuously from subducted potassium bearing crust from shallow levels to a maximum depth of 300 kilometers phengite a potassium rich mica is the principal potassium host at subsolidus conditions it transports potassium and water to depths of up to 300 kilometers and could yield over the entire depth range potassium rich fluids or melts depending on the specific geotherm which are likely to constitute one of the primary metasomatic agents for generation of calc alkaline magmas

sea surface temperature anomalies associated with the 1997 1998 el nino recorded in the oxygen isotope composition of planktonic foraminifera anomalously warm sea surface temperatures and associated high rainfall propagated northward from the eastern equatorial pacific along the western margin of north america during the 1997 1998 el nino we present data from the guaymas basin gulf of california and the santa barbara basin southern california borderlands that clearly demonstrate that the oxygen isotope composition of planktonic foraminifera accurately records the local sea surface temperature changes related to the el nino phenomenon on the basis of this observation the varved sediments accumulating in these basins should contain a detailed history of both the occurrence and intensity of past el nino events

the mg ca temperature relationship of benthic foraminiferal calcite new core top calibrations in the 4 c temperature range abstract calcite magnesium calcium ratios were determined for four species of benthic foraminifera cibicidoides wuellerstorfi cibicidoides mundulus oridorsalis umbonatus and pyrgo murrhina from core top samples collected from the atlantic indian and pacific oceans where modern bottom water temperatures are less than 4 c mg ca of all four species increase with increasing temperature and the mg ca temperature relationship does not appear to be necessarily exponential mg ca of c mundulus is consistently higher than c wuellerstorfi implying differences in the uptake of mg by different species within this genus the observed mg ca for c wuellerstorfi at temperatures less than 3 c is lower than those predicted from published mg ca temperature relationships derived for cibicidoides spp at higher temperatures previous studies have attributed this change in the mg ca temperature relationship of c wuellerstorfi to the effect of decreased carbonate ion saturation co32 on mg ca at low temperatures a relationship between the co32 and mg ca of 0 0083 0 002 mmol mol mol kg has been established for c wuellerstorfi from this study