a multiproxy approach to reconstructing sea surface conditions using coral skeleton geochemistry 1 we use elemental ratio mg ca sr ca u ca and ba ca and oxygen isotope data from a porites lutea coral head collected from offshore amedee island new caledonia 22 29 s 166 28 e to assess the degree to which changes in these geochemical variables reflect variations in sea surface conditions we have assessed the robustness of each geochemical proxy by comparing 25 years 1992 1968 of monthly geochemical variations with a local record of sea surface temperature sst and with the appropriate 1 by 1 grid box from a global gridded sst data set we conclude from our comparison that the most consistent proxies of monthly sst variations at this site are 18o r2 0 84 p 0001 and sr ca r2 0 84 p 0001 the fidelity of the coral based sr ca sst proxy was assessed via calibration verification exercises at new caledonia and rarotonga the paleoclimate accuracy of the coral sr ca sst technique is judged to be robust and the precision of the technique is estimated to be 0 3 0 5 2 based on the calibration verification exercise in contrast monthly variations in mg ca and u ca ratios are only moderately correlated with monthly sst variations r2 0 55 p 0001 for mg ca and r2 0 47 p 0001 the strength of the correlation between sst and mg ca and u ca varies as a function of time suggesting that variations in these ratios are not a simple function of sst variations this variability in goodness of fit between u ca sst and mg ca sst may ultimately limit the use of these ratios as coral paleothermometers averaging or stacking individual proxy sst records sr ca mg ca and u ca to generate a composite proxy sst record does not necessarily improve the proxy record if the signal to noise ratio in each proxy is highly variable for example stacking of sr ca mg ca u ca records at new caledonia produces a proxy sst time series that has greater standard error than the individual sr ca sst time series cf ordinary least squares standard error of 1 16 c versus 0 86 c ba ca variations have little correlation with sst sr ca mg ca or u ca variations at new caledonia in conclusion variations in oxygen isotopic composition of seawater calculated by removing the sr ca based temperature component of the 18o signal agree reasonably well with observed variations in sea surface salinity especially at the interannual timescale

incorporation of uranium in benthic foraminiferal calcite reflects seawater carbonate ion concentration the chemical and isotopic composition of foraminiferal shells so called proxies reflects the physico chemical properties of the seawater in current day paleoclimate research the reconstruction of past seawater carbonate system to infer atmospheric co2 concentrations is one of the most pressing challenges and a variety of proxies have been investigated such as foraminiferal u ca since in natural seawater and traditional co2 perturbation experiments the carbonate system parameters co vary it is not possible to determine the parameter of the carbonate system causing e g changes in u ca complicating the use of the latter as a carbonate system proxy we overcome this problem by culturing the benthic foraminifer ammonia sp at a range of carbonate chemistry manipulation treatments shell u ca values were determined to test sensitivity of u incorporation to various parameters of the carbonate system we argue that co32 is the parameter affecting the u ca ratio and consequently the partitioning coefficient for u in ammonia sp du we can confirm the strong potential of foraminiferal u ca as a co32 proxy

relative precipitation rates of aragonite and mg calcite from seawater temperature or carbonate ion control the temperature and degree of carbonate mineral supersaturation co3 2 ion concentration of seawater are the two most likely controlling variables on the compositions of recent marine carbonate cements the relative importance of these variables is difficult to assess in nature because they have similar trends with depth 0 1500 m and latitude in modern oceans we carried out laboratory experiments to investigate the relative growth rates of calcite mg calcite and aragonite in seawater as functions of both temperature 5 25 and 37 c and of carbonate ion concentration 2 5 to 15 times supersaturated with respect to calcite the precipitation rates of aragonite relative to those of calcite increase strongly with increasing temperature and are not affected greatly by changes in saturation state at 5 c calcite precipitation rates are nearly equivalent to those of aragonite regardless of the degree of saturation at both 25 and 37 c aragonite precipitation rates are much more rapid than those of calcite up to a factor of 4 except at very low saturation states calcite compositions vary from less than 5 mol mgco3 at 5 c to 14 mol mgco3 at 37 c our results suggest that the well documented shift toward precipitation of lower mol mg calcite and the decrease in abundance of aragonite cements with increasing oceanic depth and latitude can be attributed largely to lower temperatures

factors affecting b ca ratios in synthetic aragonite abstract measurements of b ca ratios in marine carbonates have been suggested to record seawater carbonate chemistry however experimental calibration of such proxies based on inorganic partitioning remains limited here we conducted a series of synthetic aragonite precipitation experiments to evaluate the factors influencing the partitioning of b ca between aragonite and seawater our results indicate that the b ca ratio of synthetic aragonites depends primarily on the relative concentrations of borate and carbonate ions in the solution from which the aragonite precipitates not on bicarbonate concentration as has been previously suggested the influence of temperature was not significant over the range investigated 20 40 c however partitioning may be influenced by saturation state and or growth rate based on our experimental results we suggest that aragonite b ca ratios can be utilized as a proxy of co 3 2 boron isotopic composition 11 b is an established ph proxy thus b ca and 11 b together allow the full carbonate chemistry of the solution from which the aragonite precipitated to be calculated to the extent that aragonite precipitation by marine organisms is affected by seawater chemistry b ca may also prove useful in reconstructing seawater chemistry a simplified boron purification protocol based on amberlite resin and the organic buffer tris is also described

a full scale stability experiment on a diaphragm wall trench this paper presents the results of a full scale field experiment on the stability of a slurry filled diaphragm wall trench the objective of this experiment was to observe the failure pattern of a

interlaboratory study for coral sr ca and other element ca ratio measurements the sr ca ratio of coral aragonite is used to reconstruct past sea surface temperature sst twenty one laboratories took part in an interlaboratory study of coral sr ca measurements results show interlaboratory bias can be significant and in the extreme case could result in a range in sst estimates of 7 c however most of the data fall within a narrower range and the porites coral reference material jcp 1 is now characterized well enough to have a certified sr ca value of 8 838 mmol mol with an expanded uncertainty of 0 089 mmol mol following international association of geoanalysts iag guidelines this uncertainty at the 95 confidence level equates to 1 5 c for sst estimates using porites so is approaching fitness for purpose the comparable median within laboratory error is 0 5 c this difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the jcp 1 there are many potential sources contributing to biases in comparative methods but traces of sr in ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty consensus values that fulfil the requirements to be certified values were also obtained for mg ca in jcp 1 and for sr ca and mg ca ratios in the jct 1 giant clam reference material reference values with variable fitness for purpose have also been obtained for li ca b ca ba ca and u ca in both reference materials in future studies reporting coral element ca data should also report the average value obtained for a reference material such as the jcp 1

mg ca sr ca and u ca ratios of a porites coral from sanya bay hainan island south china sea and their relationships to sea surface temperature high resolution mg ca sr ca and u ca ratios are reported in the skeleton of porites sp collected from sanya bay on the south coast of the hainan island china using inductively coupled plasma mass spectrometry combined with isotope dilution technique icp ms id the coralline mg ca ratios covary with sea surface temperatures sst for the 10 year interval giving the relationship between mg ca and sst as t degrees c 14 13 0 31 8 846 0 068 x 10 3 mg ca with the mean square weighted deviation mswd of 9 7 using this equation we are able to reconstruct sst record with a precision better than 0 5 degrees c several sr ca and u ca ratios show poor linear relationships with the measured sst this study indicates that the growth rates of the coral do not significantly affect coralline mg ca sr ca and u ca ratios however the high meteoric precipitation in this area which may cause a heavy run off from the island may change seawater sr ca and u ca ratios and ruin the relationships between coralline sr ca or u ca ratios and sst this implies that in coastal areas like hainan coralline mg ca ratios are valid for reconstructing the sst records but sr ca and u ca ratios may be suspected c 2000 elsevier science b v all rights reserved

δ 18 o values of cave drip water a promising proxy for the reconstruction of the north atlantic oscillation we present cave monitoring data and two drip water 18o models for the herbstlabyrinth adventhohle hl cave system germany winter climate of the cave region is influenced by the north atlantic oscillation nao as documented by the positive correlations between winter temperature winter rainfall 18o values and the winter nao index cave monitoring data show that recharge of the aquifer at the hl cave system mainly occurs during winter months confirming our drip water model which calculates recharge as the difference between precipitation and potential evapo transpiration cave drip water from the hl cave system should thus be a sensitive proxy for reconstruction of the nao the infiltration models accounting for mixing effects occurring in the karst aquifer show a very good agreement with the monitoring data comparison of the modelled and the monitored drip water 18o values suggests a mean residence time of the water in the aquifer of 12 months and a transmission time of 10 months using these parameters a long term dataset from the nearby meteorological station frankfurt am main and the rainfall 18o data from our monitoring program we model the 18o values of the cave drip water for the last 144 years despite of the favourable conditions of the hl cave system for nao reconstruction the modelled drip water 18o time series only shows a moderate correlation with the winter nao index r 0 33 the major reason for the relatively low correlation is the substantial contribution of precipitation from the remaining seasons to the drip water for instance due to heavy precipitation events occurring during summer these rainfall events bias the seasonality of infiltration and weaken the winter nao signal recorded in the drip water 18o values reconstruction of the nao from speleothems is thus challenging in particular considering further complications arising from chronological uncertainties and calcite precipitation under conditions deviating from isotopic equilibrium these problems may at least in part be avoided by multi proxy studies of annually laminated stalagmites

experimental determination of factors controlling u ca of aragonite precipitated from seawater implications for interpreting coral skeleton abstract the u ca ratio of aragonite coral skeleton exhibits coherent patterns of seasonal and interannual variability in field sampled corals and those grown in controlled culture experiments strong correlations have been found between coral skeleton u ca and water temperature ph carbonate ion concentration and salinity however the mechanism s underlying these different correlations remain unclear we performed abiogenic precipitation experiments designed to evaluate the sensitivity of u partitioning between aragonite and seawater to temperature ph and the concentration of carbonate ion in seawater aragonite was precipitated from seawater by addition of carbonate alkalinity at rates set to maintain stable carbonate chemistry during precipitation experiments were conducted at 20 40 c with ph 7 8 9 0 and carbonate ion concentrations of 600 2600 mol kg 1 u ca ratios of the bulk precipitate and fluid were determined by inductively coupled plasma mass spectrometry our results show that the u ca ratio of aragonite precipitated from seawater decreases with increasing carbonate ion concentration and is independent of ph and temperature we use these results as a framework to interpret the skeletal composition of coral aragonite precipitated from a calcifying fluid that is semi isolated from the external seawater environment accordingly coral u ca ratios are consistent with calcifying fluid carbonate ion concentrations that are several times greater than those of ambient seawater correlations between coral u ca ratios and seawater temperature carbonate chemistry and other environmental variables arise indirectly via the impacts of these variables on the carbonate ion concentration of the coral calcifying fluid

a high resolution investigation of temperature salinity and upwelling activity proxies in corals we present a high resolution study of five geochemical components of a new caledonia coral core minor and trace elements sr ca u ca mg ca ba ca together with oxygen isotopes 18o were investigated at near fortnightly resolution geochemical measurements were compared to sea surface temperature ssttsg and salinity ssstsg recorded by a thermosalinograph tsg located less than 10 m from the coral results show that sr ca mg ca and 18o are temperature dependent correlation coefficient to local ssttsg between 0 74 and 0 84 their robustness as sst tracers is tested against a satellite based data set for a 4 year validation period u ca has a more complex behavior and appears to be linked to both ssttsg and ssstsg despite relatively small local sss variations for the first time this salinity related imprint is quantified in a u ca coralline ratio in addition to sst and sss tracers ba ca measurements provide a possible way to investigate upwelling activity occurrences

distribution coefficients of trace metals between modern coral lattices and seawater in the northern south china sea species and sst dependencies abstract scleractinian corals provide an excellent archive of geochemical proxies that allow the reconstruction of the oceanographic and climatic changes in the oceans however limited knowledge regarding the distribution coefficients d of trace metals between coral lattices and seawater has complicated efforts to obtain accurate quantitative data for seawater chemistry here we estimated the d values of five trace metals cu zn pb cd and cr for three coral species favia palauensis porites lutea and pavona decussata and in situ seawater around weizhou island in the northern south china sea despite several variations that could not be explained solely by species our results were within the approved ranges of the previous reported estimates and provide the most accurate d values for the these species to date we also focused on the possible effects of surface seawater temperature sst on d vaules finding no significant relationship nevertheless the effects of sst which could impact the distribution behavior of trace metals especially cd should be paid more attention in the context of global climate change the more precise d values for corals provided here represent important basic data for future research on coral reefs and expanded our knowledge of chemical signatures in biogenic lattices with regard to ocean composition

intra and inter annual uranium concentration variability in a belizean stalagmite controlled by prior aragonite precipitation a new tool for reconstructing hydro climate using aragonitic speleothems aragonitic speleothems are increasingly utilised as palaeoclimate archives due to their amenability to high precision u th dating proxy records from fast growing aragonitic stalagmites precisely dated to annual timescales can allow investigation of climatic events occurring on annual or even sub annual timescales with minimal chronological uncertainty however the behaviour of many trace elements such as uranium in aragonitic speleothems has not thus far been as well constrained as in calcitic speleothems here we use uranium concentration shifts measured across primary calcite to aragonite mineralogical transitions in speleothems to calculate the distribution coefficient of uranium in aragonitic speleothems derived du 3 74 1 13 because our calculated du is considerably above 1 increased prior aragonite precipitation due to increased karst water residence time should strongly control stalagmite aragonite u ca values consequently uranium concentrations in aragonitic speleothems should act as excellent proxies for effective rainfall we test this using a high resolution icp ms derived trace element dataset from a belizean stalagmite yok g is an aragonitic stalagmite from yok balum cave in belize with an extremely robust monthly resolved chronology built using annual 13c cycles we interpret seasonal u ca variations in yok g as reflecting changes in the amount and seasonality of prior aragonite precipitation driven by variable rainfall amounts the u ca record strongly suggests that modern drying has occurred in belize and that this drying was primarily caused by a reduction in wet season rainfall this is consistent with published stable isotope data from yok g also very strongly suggesting modern rainfall reductions previously interpreted as the result of southward itcz displacement our results strongly suggest that u ca values in aragonitic speleothems are excellent proxies for rainfall variability this new tool combined with the exceptional chronological control characteristic of aragonitic stalagmites and the high spatial resolution afforded by modern microanalytical techniques should facilitate the construction of new exquisitely resolved rainfall records providing rare insights into seasonality changes as well as long term changes in local recharge conditions

annual cycles of u ca in coral skeletons and u ca thermometry abstract we have discovered annual variations in the 238 u 40 ca ratio of porites coral skeletons measurements were made using thermal ionization mass spectrometric techniques yielding precisions of 2 2 for 238 u 40 ca and l 2 for 88 sr 40 ca coralline aragonite subsamples weighed 2 mg enabling submillimeter sampling resolution corresponding to monthly temporal resolution the annual nature of the cycles was confirmed by comparison with annual banding observable in x radiographs for two modern and one fossil sample the amplitude of the u ca variation ranges from 6 to 23 well outside of analytical error as annual u ca cycles appear to be a general feature of primary coralline aragonite the preservation of such features will be important in identifying unaltered coral for u series dating studies u ca variations mimic and are in phase with annual variations in 88 sr 40 ca for a given fractional shift in sr ca the fractional shift in u ca is about 6 times larger for the two modern corals 238 u 40 ca is strongly anticorrelated with measured temperature suggesting that 238 u 40 ca has potential as a paleothermometer if temperature is the only significant control on coralline 238 u 40 ca we reach the following conclusions from analyses of fossil samples a vanuatu sample which grew halfway through the last deglaciation gives u ca temperatures 4 to 5 c below modern values u ca thermometry applied to published data for barbados corals indicates that 1 temperature generally correlates with sea level 2 glacial temperatures stages 2 and 4 were 4 to 6 c lower than interglacial temperatures stages 7a 5e and 1 and 3 temperatures rose from glacial to interglacial values early in the last deglaciation thermometry applied to papua new guinea corals indicates that 1 temperatures were 5 to 6 c lower than interglacial temperatures from 13 to 10 ky bp then rose to present values 9 ky bp 2 the temperature depression between 13 and 10 ky bp is consistent with low temperatures observed in vanuatu during the same time interval and 3 the papua new guinea deglacial temperature history differs from that of barbados the results generally support estimates of tropical temperatures obtained from sr ca thermometry and snow line elevation data but disagree with those based on foram transfer functions a thermodynamic model suggests that coralline 238 u 40 ca may also be sensitive to marine carbonate ion concentration raising the possibility that some of the observed glacial interglacial 238 u 40 ca variation may result from glacial interglacial carbonate ion changes however the key experiments that might establish a coralline 238 u 40 ca carbonate ion relationship have yet to be performed

quantifying the ph vital effect in the temperate zooxanthellate coral cladocora caespitosa validation of the boron seawater ph proxy boron isotopic and elemental systematics are used to define the vital effects for the temperate shallow water mediterranean coral cladocora caespitosa the corals are from a range of seawater ph conditions pht 7 6 to 8 1 and environmental settings 1 naturally living colonies harvested from normal ph waters offshore levanto 2 colonies transplanted nearby a subsea volcanic vent system and 3 corals cultured in aquaria exposed to high 700 atm and near present day 400 atm pco2 levels b ca compositions measured using laser ablation inductively coupled mass spectrometry la icpms show that boron uptake by c caespitosa cultured at different pco2 levels is independent of ambient seawater ph being mainly controlled by temperature dependent calcification in contrast the boron isotope compositions 11bcarb of the full suite of corals determined by positive thermal ionisation mass spectrometry ptims shows a clear trend of decreasing 11bcarb from 26 7 to 22 2 with decreasing seawater ph reflecting the strong ph dependence of the boron isotope system the 11bcarb compositions together with measurements of ambient seawater parameters enable calibration of the boron ph proxy for c caespitosa by using a new approach that defines the relationship between ambient seawater ph phsw and the internally controlled ph at the site of calcification phbiol c caespitosa exhibits a linear relationship between phsw and the shift in ph due to physiological processes ph phbiol phsw giving the regression phclad 4 80 0 52 phsw for this species we further apply this method ph phsw to calibrate tropical species of porites acropora and stylophora reported in the literature the temperate and tropical species calibrations are all linearly correlated r2 0 9 and the biological fractionation component ph between species varies within 0 2 ph units our ph phsw approach provides a robust and accurate tool to reconstruct palaeoseawater phsw for both temperate and tropical corals further validating the boron fractionation factor b3 b4 1 0272 determined experimentally by klochko et al 2006 and the boron isotope ph proxy both of which have been the foci of considerable debate

environmental constraints on holocene cold water coral reef growth off norway insights from a multiproxy approach high latitude cold water coral cwc reefs are particularly susceptible due to enhanced co2 uptake in these regions using precisely dated u th cwcs lophelia pertusa retrieved during research cruise pos 391 lopphavet 70 6 n oslofjord 59 n we applied boron isotopes 11b ba ca li mg and u ca ratios to reconstruct the environmental boundary conditions of cwc reef growth the sedimentary record from these cwc reefs reveals a lack of corals between 6 4 and 4 8 ka the question remains if this phenomenon is related to changes in the carbonate system or other causes the initial postglacial setting had elevated ba ca ratios indicative of meltwater fluxes showing a decreasing trend towards cessation at 6 4 ka with a oscillation pattern similar to continental glacier fluctuations downcore u ca ratios reveal an increasing trend which is outside the range of modern u ca variability in l pertusa suggesting changes of seawater ph near 6 4 ka the reconstructed bwt at lopphavet reveals a striking similarity to barent sea surface and sub sea surface temperature records we infer that meltwater pulses weakened the north atlantic current system resulting in southward advances of cold and co2 rich arctic waters a corresponding shift in the 11b record from 25 0 to 27 0 probably implies enhanced ph up regulation of the cwcs due to the higher pco2 concentrations of ambient seawater which hastened mid holocene cwc reef decline on the norwegian margin

geochemical perspectives on coral mineralization corals open an exceptional window into many phenomena of geological geochemical climatic and paleontological interest from the paleozoic to the present corals provide some of the finest high resolution archives of marine conditions corals are likewise exceptional for chronometric purposes and even the terrestrial 14c timescale has now been calibrated against coral 230th 234u corals also represent a testing ground for basic ideas about mineralogy and geochemistry the shapes sizes and organization of skeletal crystals have been attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth the coupling between calcification and photosynthesis in symbiotic corals is likewise attributed to everything from photosynthetic alkalinization of the water to efforts by the coral to prevent photosynthetic alkalinization corals also leave a significant geochemical imprint on the oceans their aragonite skeletons accept about 10 times more strontium than does calcite hence the proportion of marine aragonite precipitation affects the oceanic chemical balance biological carbonates represent the biosphere s largest carbon reservoir hence calcareous organisms affect the ocean s ph co2 content and ultimately global temperatures through the greenhouse gas connection finally corals present some geochemical puzzles for ecology and conservation how do symbiotic corals obtain nutrients in some of the most nutrient deficient parts of the planet are global geochemical changes partially responsible for the widespread declines in coral reefs during recent decades we will address many of these issues but will concentrate on coral skeletal structure and calcification mechanism these topics bear most directly on the biomineralization process and generally affect the choice of skeletal materials and analytical techniques used in geochemical investigations the coral reef is probably the planet s most spectacular biomineralization product these grand and complex ecosystems build on the accumulated skeletal debris of countless generations of organisms especially calcareous algae and symbiotic

relationship between water and aragonite barium concentrations in aquaria reared juvenile corals abstract coral barium to calcium ba ca ratios have been used to reconstruct records of upwelling river and groundwater discharge and sediment and dust input to the coastal ocean however this proxy has not yet been explicitly tested to determine if ba inclusion in the coral skeleton is directly proportional to seawater ba concentration and to further determine how additional factors such as temperature and calcification rate control coral ba ca ratios we measured the inclusion of ba within aquaria reared juvenile corals favia fragum at three temperatures 27 7 24 6 and 22 5 c and three seawater ba concentrations 73 230 and 450 nmol kg 1 coral polyps were settled on tiles conditioned with encrusting coralline algae which complicated chemical analysis of the coral skeletal material grown during the aquaria experiments we utilized sr ca ratios of encrusting coralline algae as low as 3 4 mmol mol 1 to correct coral ba ca for this contamination which was determined to be 26 11 using a two end member mixing model notably there was a large range in ba ca across all treatments however we found that ba inclusion was linear across the full concentration range the temperature sensitivity of the distribution coefficient is within the range of previously reported values finally calcification rate which displayed large variability was not correlated to the distribution coefficient the observed temperature dependence predicts a change in coral ba ca ratios of 1 1 mol mol 1 from 20 to 28 c for typical coastal ocean ba concentrations of 50 nmol kg 1 given the linear uptake of ba by corals observed in this study coral proxy records that demonstrate peaks of 10 25 mol mol 1 would require coastal seawater ba of between 60 and 145 nmol kg 1 further validation of the coral ba ca proxy requires evaluation of changes in seawater chemistry associated with the environmental perturbation recorded by the coral as well as verification of these results for porites species which are widely used in paleo reconstructions

morphological and compositional changes in the skeletons of new coral recruits reared in acidified seawater insights into the biomineralization response to ocean acidification 1 we reared primary polyps new recruits of the common atlantic golf ball coral favia fragum for 8 days at 25 c in seawater with aragonite saturation states ranging from ambient 3 71 to strongly undersaturated 0 22 aragonite was accreted by all corals even those reared in strongly undersaturated seawater however significant delays in both the initiation of calcification and subsequent growth of the primary corallite occurred in corals reared in treatment tanks relative to those grown at ambient conditions in addition we observed progressive changes in the size shape orientation and composition of the aragonite crystals used to build the skeleton with increasing acidification densely packed bundles of fine aragonite needles gave way to a disordered aggregate of highly faceted rhombs the sr ca ratios of the crystals measured by sims ion microprobe increased by 13 and mg ca ratios decreased by 45 by comparing these variations in elemental ratios with results from rayleigh fractionation calculations we show that the observed changes in crystal morphology and composition are consistent with a 80 decrease in the amount of aragonite precipitated by the corals from each batch of calcifying fluid this suggests that the saturation state of fluid within the isolated calcifying compartment while maintained by the coral at levels well above that of the external seawater decreased systematically and significantly as the saturation state of the external seawater decreased the inability of the corals in acidified treatments to achieve the levels of calcifying fluid supersaturation that drive rapid crystal growth could reflect a limit in the amount of energy available for the proton pumping required for calcification if so then the future impact of ocean acidification on tropical coral ecosystems may depend on the ability of individuals or species to overcome this limitation and achieve the levels of calcifying fluid supersaturation required to ensure rapid growth

northern galapagos corals reveal twentieth century warming in the eastern tropical pacific models and observations disagree regarding sea surface temperature sst trends in the eastern tropical pacific we present a new sr ca sst record that spans 1940 2010 from two wolf island corals northern galapagos trend analysis of the wolf record shows significant warming on multiple timescales which is also present in several other records and gridded instrumental products together these data sets suggest that most of the eastern tropical pacific has warmed over the twentieth century in contrast recent decades have been characterized by warming during boreal spring and summer especially north of the equator and subtropical cooling during boreal fall and winter especially south of the equator these sst trends are consistent with the effects of radiative forcing mitigated by cooling due to wind forcing during boreal winter as well as intensified upwelling and a strengthened equatorial undercurrent

sr ca and mg ca vital effects correlated with skeletal architecture in a scleractinian deep sea coral and the role of rayleigh fractionation deep sea corals are a new tool in paleoceanography with the potential to provide century long records of deep ocean change at sub decadal resolution complicating the reconstruction of past deep sea temperatures mg ca and sr ca paleothermometers in corals are also influenced by non environmental factors termed vital effects to determine the magnitude pattern and mechanism of vital effects we measure detailed collocated sr ca and mg ca ratios using a combination of micromilling and isotope dilution icp ms across skeletal features in recent samples of desmophyllum dianthus a scleractinian coral that grows in the near constant environment of the deep sea sr ca variability across skeletal features is less than 5 2 relative standard deviation and variability of sr ca within the optically dense central band composed of small and irregular aragonite crystals is significantly less than the surrounding skeleton the mean sr ca of the central band 10 6 0 1 mmol mol 2 standard error and that of the surrounding skeleton 10 58 0 09 mmol mol are statistically similar and agree well with the inorganic aragonite sr ca temperature relationship at the temperature of coral growth in the central band mg ca is greater than 3 mmol mol more than twice that of the surrounding skeleton a general result observed in the relative mg ca ratios of d dianthus collected from separate oceanographic locations this large vital effect corresponds to a 10 c signal when calibrated via surface coral mg ca temperature relationships and has the potential to complicate paleoreconstructions outside the central band mg ca ratios increase with decreasing sr ca we explain the correlated behavior of mg ca and sr ca outside the central band by rayleigh fractionation from a closed pool an explanation that has been proposed elsewhere but which is tested in this study by a simple and general relationship we constrain the initial solution and effective partition coefficients for a rayleigh process consistent with our accurate metal ca measurements a process other than rayleigh fractionation influences mg in the central band and our data constrain a number of possible mechanisms for the precipitation of this aragonite understanding the process affecting tracer behavior during coral biomineralization can help us better interpret paleoproxies in biogenic carbonates and lead to an improved deep sea paleothermometer

diagenetic effects on uranium isotope fractionation in carbonate sediments from the bahamas abstract uranium isotope variations 238u recorded in sedimentary carbonate rocks are a promising new proxy for the extent of oceanic anoxia through geological time however the effects of diagenetic alteration on the u isotopic composition in carbonate sediments which are crucial to understand the accurate reconstruction of marine 238u are currently poorly constrained here we examine the effects of the aragonite to calcite transition in the pleistocene key largo limestone of south florida and assess the effects of vadose meteoric phreatic meteoric and phreatic marine diagenesis on u isotope fractionation in carbonate sediments from the bahamas transect including the well studied clino unda and odp site 1006 drill cores our results suggest that early diagenetic processes in bahamas carbonate sediments fractionate u isotopes by an average of 0 27 0 14 1 sd heavier than contemporaneous seawater downcore variations of 238u in slope and basin sediments display little if any correlation with u concentration and common geochemical indicators of diagenesis 13c 18o mn sr mg ca sr ca enrichments of redox sensitive elements or rare earth elements anomalies we propose two possible mechanisms to interpret the positive change in the 238u during carbonate diagenesis authigenic enrichment of isotopically positive u iv in carbonates and preferential incorporation of isotopically positive aqueous u vi species into carbonates these processes likely operate during early syndepositional diagenesis on the banktop further diagenesis during deeper burial is limited by the low solubility of u iv under reducing pore water conditions the early diagenetic behavior of u isotopes in bahamas carbonate sediments is likely broadly representative of carbonate diagenesis in the geological past we suggest that the mean diagenetic offset determined in this study be applied when reconstructing seawater 238u from ancient carbonates furthermore early diagenesis induces significant statistical variability in sediment 238u values pointing to the need for large high resolution data sets in order to average out stochastic variations in individual bulk sediment samples

uranium isotope compositions of biogenic carbonates implications for u uptake in shells and the application of the paleo ocean oxygenation proxy abstract the application of u isotopes in carbonates as a paleo ocean oxygenation proxy is based on the critical assumption that the carbonaceous shell building organisms incorporate u into their shells without fractionating the u isotopic composition of the ambient seawater recent studies claim a small but resolvable isotopic offset during abiotic and biogenic aragonite precipitation whereas no isotope fractionation has been recorded during calcite precipitation although aragonite is meta stable and not preserved over geological timescales 1 myr and u precipitates during diagenesis the u isotope composition of biogenic aragonite is important because aragonite precipitation is an important u flux to carbonate sediments in contrast low magnesium calcite is preserved over geological timescales and may provide a reliable fingerprint of ancient ocean chemistry therefore a more general study is needed that compares u isotope compositions of primary marine biogenic carbonate precipitates we report the u isotope compositions of 32 modern samples from geographically distinct localities in the atlantic oceans including corals scleractinia octocorallia brachiopods articulata molluscs tellina listeri codahia obicularis and barnacles as well as one fossil mollusc these samples reflect variable primary minerals water temperatures water depths ph values of ambient water and u concentrations several seawater samples have also been measured to compare our methods with those of previously published studies the analyzed modern corals and brachiopods display u isotopic compositions that are indistinguishable from modern seawater this suggests that these carbonates have the potential to faithfully record the u isotopic composition of the surrounding seawater in which they form the analyzed brachiopods are of particular interest as they are composed of the calcium carbonate polymorph low mg calcite lmc that is stable over geological timescales while this study shows for the first time that lmc phases are robust targets in ancient samples their low u abundance presents analytical challenges for precise u isotope analyses we also show that two barnacle shells collected with ambient seawater have u isotopic compositions that are both lighter and heavier than the ambient seawater the mechanism to explain this offset is not determined but it demonstrates that at least barnacle shells are not representative of the seawater in which they last lived two of three partially fossilized mollusc shells also show resolvable offsets from seawater likely indicating secondary processes that are known to shift or fractionate u isotopes collectively our new data indicate that 1 aragonite delivers u with seawater composition to carbonate sediments and 2 lmc shells of brachiopods that are stable over geological timeframes may be more suitable for reconstructing the u isotope composition of ancient oceans

seawater transport during coral biomineralization cation transport during skeletal growth is a key process controlling metal calcium me ca paleoproxy behavior in coral to characterize this transport cultured corals were transferred into seawater enriched in the rare earth element tb 3 as well as stable isotopes of calcium strontium and barium subsequent nanosims ion images of each coral skeleton were used to follow uptake dynamics these images show a continuous region corresponding to new growth that is homogeneously enriched in each tracer isotope ratio profiles across the new growth boundary transition rapidly from natural abundance ratios to a ratio matching the enriched culture solution the location of this transition is the same for each element within analytical resolution the synchronous incorporation of all these cations including the dissimilar ion terbium which has no known biological function in coral suggests that 1 there is cation exchange between seawater and the calcifying fluid and 2 these elements are influenced by similar transport mechanisms consistent with direct and rapid seawater transport to the site of calcification measured using isotope ratio profiles seawater transport rates differ from place to place on the growing coral skeleton with calcifying fluid turnover times from 30 min to 5 7 h despite these differences all the elements measured in this study show the same transport dynamics at each location using an analytical geochemical model of biomineralization that includes direct seawater transport we constrain the role of active calcium pumping during calcification and we show that the balance between seawater transport and precipitation can explain observed me ca variability in deep sea coral

subtropical coral reveals abrupt early twentieth century freshening in the western north pacific ocean instrumental climate observations provide robust records of global land and ocean temperatures during the twentieth century unlike for temperature continuous salinity observations in the surface ocean are scarce prior to 1970 and the magnitude of salinity changes during the twentieth century is largely unknown surface ocean salinity is a major component in climate dynamics as it influences ocean circulation and water mass formation here we present an annually resolved reconstruction of salinity variations in the surface waters of the western subtropical north pacific ocean since 1873 based on bimonthly records of 18o sr ca and u ca in a coral from the ogasawara islands the reconstruction indicates that an abrupt regime shift toward fresher surface ocean conditions occurred between 1905 and 1910 observational atmospheric data suggest that the abrupt freshening was associated with a weakening of the winds that drive the kuroshio current system and the associated subtropical gyre circulation we note that the abrupt early twentieth century freshening in the western subtropical north pacific precedes abrupt climate change in the northern north atlantic by a few years the potential for abrupt regime shifts in surface ocean salinity should be considered in climate predictions for the coming decades

seawater nutrient and carbonate ion concentrations recorded as p ca ba ca and u ca in the deep sea coral desmophyllum dianthus as paleoceanographic archives deep sea coral skeletons offer the potential for high temporal resolution and precise absolute dating but have not been fully investigated for geochemical reconstructions of past ocean conditions here we assess the utility of skeletal p ca ba ca and u ca in the deep sea coral d dianthus as proxies of dissolved phosphate remineralized at shallow depths dissolved barium trace element with silicate type distribution and carbonate ion concentrations respectively measurements of these proxies in globally distributed d dianthus specimens show clear dependence on corresponding seawater properties linear regression fits of mean coral element ca ratios against seawater properties yield the equations p cacoral lmol mol 0 6 0 1 p casw lmol mol 23 18 r 2 0 6 n 16 and ba cacoral lmol mol 1 4 0 3 ba casw lmol mol 0 2 r 2 0 6 n 17 no significant relationship is observed between the residuals of each regression and seawater temperature salinity pressure ph or carbonate ion concentrations suggesting that these variables were not significant secondary dependencies of these proxies four d dianthus specimens growing at locations withoarag 6 0 6 displayed markedly depleted p ca compared to the regression based on the remaining samples a behavior attributed to an undersaturation effect these corals were excluded from the calibration coral u ca correlates with seawater carbonate ion u cacoral lmol mol 0 016 0 003 co 2 3 lmol kg 3 2 0 3 r 2 0 6 n 17 the residuals of the u ca calibration are not significantly related to temperature salinity or pressure scatter about the linear calibration lines is attributed to imperfect spatialtemporal matches between the selected globally distributed specimens and available water column chemical data and potentially to unresolved additional effects the uncertainties of these initial proxy calibration regressions predict that dissolved phosphate could be reconstructed to 0 4 lmol kg for 1 3 1 9 lmol kg phosphate and dissolved ba to 19 nmol kg for 41 82 nmol kg basw carbonate ion concentration derived from u ca has an uncertainty of 31lmol kg for 60 120 lmol kg co 2 3

sr ca u ca and δ18o records in recent massive corals from bermuda relationships with sea surface temperature abstract high resolution records of sr ca u ca ratios and 18o have been obtained in two recent colonies of massive corals diploria labyrinthiformis from bermuda the three geochemical proxies display regular seasonal variations and are well correlated with each other however some important discrepancies are observed between the two colonies the average seasonal variations of the three geochemical proxies are lower by almost 50 in one of the profiles where the seasonal oscillation also displays a strong asymmetry with narrower summer maxima different calculations are discussed for calibrating sr ca and 18o with sea surface temperatures sst we show that the method using only temperature minima and maxima is slightly more accurate and is also more reliable our results from bermuda corals confirm that the temperature dependency of sr ca u ca and 18o is species dependent as previously shown by others and that vital effects are clearly involved in the geochemical incorporation of trace elements in the coral skeleton finally a simple model involving seasonal variation of the growth rate and a kinetic fractionation related to growth rate is presented to explain the differences between the two bermuda colonies it is shown that these factors may prevent corals from recording the complete temperature seasonality and could be the cause for the discrepancies observed between profiles resulting in significant biases of the sst reconstructions