bomb produced radiocarbon in the shell of the chambered nautilus rate of growth and age at maturity abstract the temporal pattern of bomb produced radiocarbon in the oceans provides a chronometer to estimate the rate of growth of marine organisms radiocarbon measurements by tandem accelerator mass spectrometry of samples from the septa and shell wall of a mature specimen of nautilus macromphalus reveal progressively increasing values in more recently formed shell material this pattern is similar to that recorded in a banded coral from surface waters of the great barrier reef australia however the pre bomb values of 14 c are lower in the nautilus than in the coral this offset is probably due to the difference in the respective habitat depths of the two animals taking this difference into account we have used the temporal pattern of 14 c in the coral as a point of reference to help interpret the pattern of 14 c in the nautilus according to our calculations the age of the specimen of n macromphalus is 10 12 years and the timing of septal formation ranges from 80 to 240 days septum

bomb 14c time history recorded in two modern stalagmites importance for soil organic matter dynamics and bomb 14c distribution over continents carbon 14 activity measurements made by accelerator mass spectrometry on two modern stalagmites from the han sur lesse cave belgium and from the postojna cave slovenia permit the construction of 14c activity a14c time series over the last 50 years a high precision chronology is given by annual laminae in the first stalagmite and by a specific mark explosion in the postojna cave in 1944 in the second one in both stalagmites 14c activity increase due to nuclear tests in the atmosphere is remarkable however instead of a sharp peak like the one observed in the atmosphere around 1963 1964 the 14c activities of the stalagmite caco3 show an abrupt increase with an offset of 1 10 years followed by a high activity plateau for the han sur lesse sample and a slight decrease for the postojna sample for both stalagmites the variation of the a14c amplitude between pre and post bomb period is much lower than the atmospheric record which demonstrates the damping effect of the soil carbon reservoir we have modeled the caco3 activities using fractionation processes between atmosphere co2 soil co2 and organic matter om dissolved inorganic carbon and stalagmite caco3 in both cases studied the model and former soil studies suggest that co2 from soil organic matter som decomposition which has a slow turnover i e 1 y is of major importance in winter when the development of speleothem is the most important combined with the fact that 80 90 of the stalagmite carbon comes from soil co2 this produces a damping effect on the speleothem a14c consequently the geochemical time resolution at least for speleothem carbon is much lower than the structural resolution given by annual laminae alternations and is mainly controlled by soil carbon dynamics a14c and 13c are smoothed over several years differences between the 14c time series of the han sur lesse and postojna stalagmites are likely to be due to the double amount of precipitation in postojna which produces a faster soil om turnover and thus a system which is more sensitive to atmospheric changes

plateau versus fissure ridge travertines from quaternary geothermal springs of italy and turkey interactions and feedbacks between fluid discharge paleoclimate and tectonics abstract morphologically different deposits of thermal travertines are known worldwide but what factors controlled their morphology volume and growth for tens of thousands of years is only partially understood two main morphotypes of quaternary thermal travertines are reconsidered here to understand the reasons for their differential growth the fissure ridge travertines of denizli basin western turkey and the travertine plateau of tivoli central italy for comparable longevities and average vertical deposition rates the main differences between the studied travertines are as follows 1 volume of the travertine plateau is about one hundred times larger than each fissure ridge 2 despite a larger volume the travertine plateau does not produce relief whereas the fissure ridges produce a characteristic prominent topography 3 the travertine plateau grew primarily through lateral progradation whereas the fissure ridges through vertical aggradation 4 travertine deposition occurred in different environments principally low energy flat or shallow environments at tivoli and high energy inclined environments at denizli 5 the growth of the tivoli plateau occurred in a subsiding basin whereas the fissure ridges were not influenced by significant subsidence 6 c and o isotope signatures from the two studied travertines are different 7 despite similar annual precipitations the present water discharge in the tivoli area is about ten times greater than that of the denizli basin u series ages from the two deposits are correlated with paleoclimate oscillations at regional and global scales geological field evidence together with paleoclimate correlations suggest that in both the study cases the main body of travertine deposits the bedded travertine grew preferentially when the water table was high warm and or humid periods conversely when the water table was depressed cold and or dry periods the tivoli travertine underwent partial erosion and the denizli ridges were cut by axial veins and lateral sill like structures filled by banded sparitic travertine a comparative model is proposed where the main factor driving the difference in the morphostratigraphic architecture of fissure ridges and travertine plateaus is the volume of water discharge a high discharge rate resulted in the precipitation of caco3 far away from the springs hence driving the lateral progradation of the tivoli plateau a reduced discharge rate caused travertine precipitation close to the springs thus causing the vertical aggradation of the denizli fissure ridges paleoclimate oscillations must have controlled the amount of fluid discharge which in turn must have influenced the opening of the feeding fractures by an increased pore pressure

atmospheric14c changes resulting from fossil fuel co2 release and cosmic ray flux variability a high precision tree ring record of the atmospheric14c levels between 1820 and 1954 is presented good agreement is obtained between measured and model calculated 19th and 20th century atmospheric 14c levels when both fossil fuel co2 release and predicted natural variations in14c production are taken into account the best fit is obtained by using a diffusion model with an oceanic eddy diffusion coefficient of 3 cm2 s a co2 atmosphere ocean gas exchange rate of 21 moles m 2 yr 1 and biospheric residence time of 60 years for trees in the state of washington the measured 1949 1951 atmospheric 14c level was20 0 1 2 below the 1855 1864 level model calculations indicate that in 1950 industrial co2 emissions are responsible for at least 85 of the 14c decline whereas natural variability accounts for the remaining 15

radiocarbon evidence for mid late holocene changes in southwest pacific ocean circulation variability in the southwest sw pacific ocean circulation is influenced by the changes in the south pacific subtropical gyre and its western boundary current the east australian current eac the eac plays a significant role in transporting warm well ventilated nutrient poor waters to more temperate higher latitudes recent climate changes associated with eac intensification have led to anomalous warming in the south tasman with implications for marine ecosystems and environment a clear understanding of the significance of these changes requires knowledge of past natural variability here we have reconstructed a 4500 year record of regional sea surface radiocarbon reservoir ages r and local reservoir effects r our results reveal the centennial scale variability over the last 4500 years with r ranges as large as 390 14c yr older r 410 14c yr between 1610 to 1860 a d in our record corresponding to the little ice age suggests a weaker influence of the eac in the south tasman between 4000 and 1900 cal years b p r and r were significantly younger than the modern with values of 170 and 130 14c yr respectively indicating increased eac transport of tropical waters into the south tasman we propose that the large r variability was influenced by strong and abrupt el nino events which punctuated the muted el nino southern oscillation enso period in the mid late holocene and enabled increased westward flow of gyre waters into the sw pacific the strengthening of the eac extension appears to have been a response to the precession modulated enso southern annular mode interactions

submarine paleoseismology of the northern hikurangi subduction margin of new zealand as deduced from turbidite record since 16 ka abstract paleoseismic studies seek to characterise the signature of pre historical earthquakes by deriving quantitative information from the geological record such as the source magnitude and recurrence of moderate to large earthquakes in this study we provide a 16 000 yr long paleo earthquake record of the 200 km long northern hikurangi margin new zealand using cm thick deep sea turbidites identified in sediment cores cores were collected in strategic locations across the margin within three distinct morphological re entrants the poverty ruatoria and matakaoa re entrants the turbidite facies vary from muddy to sandy with evidence for rare hyperpycnites interbedded with hemipelagites and tephra we use the oxal probabilistic software to model the age of each turbidite using the sedimentation rate of hemipelagite deduced from well dated tephra layers and radiocarbon ages measurements on planktonic foraminifera turbidites are correlated from one core to the other using similarity in sedimentary facies petrophysical properties and ages results show that 46 turbidites are synchronous along the entire margin amongst them 41 are interpreted as originating from the upper continental slope in response to earthquake triggered slope failures between 390 170 to 16 450 310 yr bp using well established empirical relationships that combine peak ground acceleration magnitude and location of earthquakes we calculate that synchronous slope failures were triggered by the rupture of 3 of the 26 known active faults in the region each capable of generating mw 7 3 to 8 4 earthquakes two are crustal reverse faults and one is the subduction interface the 41 mw 7 3 earthquakes occurred at an average recurrence interval of 400 yr over the last 16 000 yr among them twenty are interpreted as subduction interface earthquakes that occurred at an average recurrence interval of 800 yr with alternating periods of high activity and low return times 305 610 yr and quiescence periods with high return times 1480 2650 yr based on turbidite paleoseismology we propose that subduction interface earthquakes were of lower magnitude during active periods mw 7 5 than during quiescence periods mw 8 2

stability in the south pacific surface marine 14c reservoir over the last 750 years evidence from american samoa the southern cook islands and the marquesas abstract although minor climatic and sea level changes have been documented for the south pacific during the late holocene our understanding of the consequent impact of these changes on the marine 14 c reservoir and therefore the 14 c content of shellfish is limited ultimately this has implications for documenting the chronology of human movement and adaptation in this region in this paper we compare marine reservoir r data obtained from tightly controlled archaeological proveniences with known age pre ad 1950 shells from the southern cook islands american samoa and marquesas islands results indicate that there has been no significant change in the near shore marine reservoir in these three locations over the last ca 750 years furthermore known age pre ad 1950 shell samples provide more precise r values for use in sample calibration than archaeological paired shell charcoal samples this is attributed in part to the limitations of assigning provenance and age to material from archaeological sites on the basis of these results we conclude that the known age pre ad 1950 shell derived r values can be used to calibrate shell 14 c results from deposits of late holocene age

fish otoliths in superficial sediments of the mediterranean sea abstract otoliths represent a significant biogenic carbonate component in marine sediments that may provide valuable information for paleoenvironmental and biogeographic reconstructions in spite of their importance relatively little is still known about the taxonomic composition abundance and early taphonomic characteristics of recent otolith death assemblages which would add to their value to interpret situations in the geological record here we present data on the distribution of fish otoliths from bottom sediments collected in the central mediterranean sea ranging in depth from 51 to 3300 m the preservation of otoliths ranges from fresh semi translucent white specimens to dull coloured dark ones although whitish specimens are predominant across all the samples this diversity in lustre and colour and at times texture reflects the degree of early taphonomic processes undergone by these aragonitic bodies post mortem under submarine conditions never being exposed to diagenetic processes on land in general a correlation with depth is observed with best preservation observed in otoliths sampled at depths

pre and post bomb radiocarbon in fish otoliths measurements of radiocarbon in seawater dissolved inorganic carbon dic or suitable proxies such as hermatypic corals are a valuable source of information on carbon flux and ocean circulation however knowledge of the global distribution of both pre and post bomb radiocarbon is limited due to the sources of these data suitable hermatypic corals are restricted to shallow tropical and subtropical waters and oceanographic collections of seawater are prohibitively expensive what is needed is a proxy for ocean radiocarbon that can be collected at most latitudes and depths and which can be reliably aged here i report accelerator mass spectrometry analyses of radiocarbon from selected regions of fish otoliths and show that such measurements are suitable for determining both pre and post bomb radiocarbon in all oceans and at most depths radiocarbon data obtained from otoliths can extend our knowledge of carbon flux in the oceans and atmosphere and help to develop further understanding of the fate of atmospheric co2 and ocean circulation the data presented here represent the first pre and post bomb time series of radiocarbon levels from temperate waters furthermore i demonstrate that the dramatic increase in radiocarbon in the atmosphere and oceans attributable to the atmospheric testing of thermonuclear bombs during the 1950 s and 1960 s provides a chemical mark on fish otoliths that is suitable for the validation of age in fishes

otolith microchemistry of modern versus well dated ancient naked carp gymnocypris przewalskii implication for water evolution of lake qinghai there is ongoing debate over how the water level and composition of the water in lake qinghai changed in the past and might change in future this study of the microchemistry of otoliths from ancient naked carp explores the chemistry of a relict lake isolated from lake qinghai during the little ice age lia a close correlation between the ages measured on fish bone and otoliths by ams 14c and by optically stimulated luminescence on overlying sediments confirms a high water level in lake qinghai before 680 300 years ago the contrasting compositions of the ancient otoliths relative to modern otoliths and waters indicate that the relict lake became enriched in 18o mg li b and to a lesser extent ba but depleted in 13c owing to strong evaporation authigenic carbonates precipitation micro organism activity and less fresh water input after it was isolated if there were long term fresh water input however a reverse trend might occur the most important observation is that because the waters have been supersaturated with respect to carbonates authigenic carbonate precipitation would result in low but consistent sr ca ratios in the lakes as recorded by both the ancient and modern otoliths the geochemical records of ancient versus modern biogenic carbonates provide insights into the long term hydroclimatic evolution processes of an inland water body

distribution of otoliths in surficial sediments of the u s atlantic continental shelf and slope and potential for reconstructing holocene fish stocks we examined more than 1100 surface sediment samples from the atlantic continental margin of the united states to determine the feasibility of using fossil fish otoliths as diagnostic tools in reconstructing paleoenvironments and latitudinal distribution of fish stocks during the holocene although 63 of the 1107 samples collected were from shelf areas 140 m the total number of shelf derived otoliths represents only 0 3 of the entire sampled assemblage the majority of otoliths occurred on the continental slope 400 2000 m with a maximum concentration in sediments at 500 to 600 m water depth otoliths of the most commonly occurring species ceratoscopelus maderensis exhibit a marked distributional boundary just south of cape hatteras north carolina 33 n which mimics the distribution of their living counterparts north of this boundary c maderensis constitutes greater than 70 of the preserved otolith assemblage whereas more southerly regions contain no otoliths of this species although c maderensis typically migrates diurnally over a depth of 300 600 m otoliths taken from live captured c maderensis exhibit 14c values comparable to that of the dissolved inorganic carbon dic of surface seawater in the study area accelerator mass spectrometry radiocarbon analyses of cooccurring otoliths and planktonic foraminifera from a sediment core collected south of martha s vineyard 40 15 n 70 51 w 265 m demonstrate temporal concordance throughout the holocene otoliths appear to be viable underutilized paleoceanographic tools specimens are found in sufficient abundance to permit temporal reconstructions of the distribution of c maderensis and potentially several other icthyospecies along the u s atlantic continental margin

postglacial after 18 ka deep sea sedimentation along the hikurangi subduction margin new zealand characterisation timing and origin of turbidites recent sedimentation along the hikurangi subduction margin off northeastern new zealand is investigated using a series of piston cores collected between 2003 and 2008 the active hikurangi margin lies along the pacific australia subduction plate boundary and contains a diverse range of geomorphologic settings slope basin stratigraphy is thick and complex resulting from sustained high rates of sedimentation from adjacent muddy rivers throughout the quaternary turbidites deposited since c 18 ka in the poverty ruatoria and matakaoa re entrants are central to this study in that they provide a detailed record of the past climatic conditions and tectonic activity here alternating hemipelagite turbidite debrite and tephra layers reflect distinctive depositional modes of marine sedimentation turbidity current debris flow and volcanic eruption respectively turbidites dominate the record ranging in lithofacies from muddy to sandy turbidites and include some basal reverse graded turbidites inferred to be derived from hyperpycnal flows stacked turbidites are common and indicate multiple gravity flows over short time periods the chronology of turbidites is determined by collating an extremely dense set of radiocarbon ages and dated tephra which facilitate sedimentation rate calculation and identification of the origin of turbidites sedimentation rates range from 285 cm ka during late glacial time 18 5 17 ka to 15 to 109 cm ka during postglacial time 17 0 ka turbidite deposition is controlled by 1 the emplacement of slope avalanches reorganising sediment pathways 2 the postglacial marine transgression leading to a five fold reduction in sediment supply to the slope due to disconnection of river mouths from the shelf edge and 3 the holocene pleistocene boundary climate warming resulting in a drastic decrease in the average turbidite grain size flood induced turbidites are scarce nine hyperpycnites are recognised since 18 ka and the youngest is correlated to the largest enso related storm event recorded onland lake tutira other turbidites contain a benthic foraminiferal assemblage which is strictly reworked from the upper slope and which relates to large earthquakes over the last c 7 ka they yield a shorter return time 270 430 years than the published coastal records for large earthquakes c 670 years but the offshore record is likely to be more complete the deep sea sedimentation along the new zealand active margin illustrates the complex interaction of tectonic and climate in turbidite generation climate warming and glacio eustatic fluctuations are well recorded at a millennial timescale 18 ka while tectonic deformation and earthquakes appear predominant in fostering turbidite production at a centennial timescale 270 430 years

investigating bomb radiocarbon transport in the southern pacific ocean with otolith radiocarbon abstract to explore the transport of carbon into water masses from the surface ocean to depths of 1000 m in the southwest pacific ocean we generated time series of radiocarbon c 14 from fish otoliths otoliths carbonate earstones from long lived fish provide an indirect method to examine the bomb pulse of radiocarbon that originated in the 1950s and 1960s allowing identification of changes to distributions of 14c that has entered and mixed within the ocean we micro sampled ocean perch helicolenus barathri otoliths collected at 400 500 m in the tasman sea to obtain measurements of c 14 for those depths we compared our ocean perch c 14 series to published otolith based marine surface water c 14 values australasian snapper chrysophrys auratus and nannygai centroberyx affinis and to published deep water values 800 1000 m orange roughy hoplostethus atlanticus from the southwest pacific to establish a mid water c 14 series the otolith bomb 14c results from these different depths were consistent with previous water mass results in the upper 1500 m of the southwest pacific ocean e g world ocean circulation experiment and geochemical ocean sections study a comparison between the initial c 14 bomb pulse rise at 400 500 m suggested a ventilation lag of 5 to 10 yr whereas a comparison of the surface and depths of 800 1000 m detailed a 10 to 20 yr lag in the time history of radiocarbon invasion at this depth pre bomb reservoir ages derived from otolith 14c located in tasman sea thermocline waters were 530 yr while reservoir ages estimated for tasman antarctic intermediate water were 730 yr

the abandoned ice sheet base at camp century greenland in a warming climate in 1959 the u s army corps of engineers built camp century beneath the surface of the northwestern greenland ice sheet there they studied the feasibility of deploying ballistic missiles within the ice sheet the base and its wastes were abandoned with minimal decommissioning in 1967 under the assumption they would be preserved for eternity by perpetually accumulating snowfall here we show that a transition in ice sheet surface mass balance at camp century from net accumulation to net ablation is plausible within the next 75 years under a business as usual anthropogenic emissions scenario representative concentration pathway 8 5 net ablation would guarantee the eventual remobilization of physical chemical biological and radiological wastes abandoned at the site while camp century and four other contemporaneous ice sheet bases were legally established under a danish u s treaty the potential remobilization of their abandoned wastes previously regarded as sequestered represents an entirely new pathway of political dispute resulting from climate change

late holocene palaeotemperatures and palaeoenvironments in the southeastern brazilian coast inferred from otolith geochemistry abstract holocene palaeoceanography and climatic reconstructions were evaluated based on proxy analyses of fish otoliths from shellmounds located along the coast of rio de janeiro state brazil modern coastal seasonal upwelling is associated with the ascension of a deep and cold water mass as a consequence of persistent ne winds that affect the climate in southeastern brazil however this seasonal influence and the effect of the holocene palaeoenvironment on shallow water are poorly known in this work coastal palaeotemperatures were estimated based on the geochemical analyses of otolith the results of the 18o and 13c analyses from holocene otoliths obtained from coastal shellmounds separated by a distance of almost 200 km show two distinctive otolith derived palaeotemperature signals in a coastal region under upwelling influence additionally this analysis suggests that the fish lived in marine waters showing similar microchemistry values composition when compared with modern marine otoliths

carbon transfer dynamics from bomb 14c and δ13c time series of a laminated stalagmite from sw france modelling and comparison with other stalagmite records twenty two ams 14c measurements have been made on a modern stalagmite from sw france in order to reconstruct the 14c activity history of the calcite deposit annual growth laminae provides a chronology up to 1919 a d results show that the stalagmite 14c activity time series is sensitive to modern atmosphere 14c activity changes such as those produced by the nuclear weapon tests the comparison between the two 14c time series shows that the stalagmite time series is damped its amplitude variation between pre bomb and post bomb values is 75 less and the time delay between the two time series peaks is 16 years 3 a model is developed using atmosphere 14c and 13c data fractionation processes and three soil organic matter components whose mean turnover rates are different the linear correlation coefficient between modeled and measured activities is 0 99 these results combined with two other stalagmite 14c time series already published and compared with local vegetation and climate demonstrate that most of the carbon transfer dynamics are controlled in the soil by soil organic matter degradation rates where vegetation produces debris whose degradation is slow the fraction of old carbon injected in the system increases the observed 14c time series is much more damped and lag time longer than that observed under grassland sites the same mixing model applied on the 13c shows a good agreement r2 0 78 between modeled and measured stalagmite 13c and demonstrates that the suess effect due to fossil fuel combustion in the atmosphere is recorded in the stalagmite but with a damped effect due to som degradation rate the different sources of dead carbon in the seepage water are calculated and discussed

late holocene radiocarbon variability in northwest atlantic slope waters abstract deep sea gorgonian corals secrete a 2 part skeleton of calcite derived from dissolved inorganic carbon at depth and gorgonin derived from recently fixed and exported particulate organic matter radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters respectively using specimens collected from northwest atlantic slope waters we generated radiocarbon records for surface and upper intermediate water layers spanning the pre and post bomb 14 c eras in labrador slope water lsw convective mixing homogenizes the pre bomb 14 c signature 67 4 to at least 1000 m depth surface water bomb 14 c signals were lagged and damped peaking at 45 in the early 1980s relative to other regions of the northwest atlantic and intermediate water signals were damped further off southwest nova scotia the vertical gradient in 14 c is much stronger in surface water pre bomb 14 c averaged 75 5 at 250 475 m depth pre bomb 14 c oscillated quasi decadally between 80 and 100 likely reflecting interannual variability in the presence of labrador slope water vs warm slope water wsw finally subfossil corals reveal no systematic changes in vertical 14 c gradients over the last 1200 yr

the distribution of bomb radiocarbon in the ocean water column inventories are calculated for bomb radiocarbon at all the stations occupied during the geosecs and norpax expeditions and for the available tto stations the pattern of global inventories obtained in this way suggests that a sizable portion of the bomb radiocarbon that entered the antarctic the northern pacific and the tropical ocean has been transported to the adjacent temperate zones a strategy for utilizing these inventory anomalies as constraints on global ocean circulation models is presented essential to this strategy are the improvement of our knowledge of the pattern of wind speed over the ocean the establishment of the wind speed dependence of the rate of gas exchange between the atmosphere and sea and the continued mapping of the distribution of bomb produced radiocarbon in the sea

persistent englacial drainage features in the greenland ice sheet 1 surface melting on the greenland ice sheet is common up to 1400 m elevation and in extreme melt years even higher water produced on the ice sheet surface collects in lakes and drains over the ice sheet surface via supraglacial streams and through the ice sheet via moulins water delivered to the base of the ice sheet can cause uplift and enhanced sliding locally here we use ice penetrating radar data to observe the effects of significant basal melting coincident with moulins and calculate how much basal melt occurred we find that more melting has occurred than can be explained by the release of potential energy from the drainage of surface meltwater during one melt season suggesting that these moulins are persistent for multiple years we find only a few persistent moulins in our study area that drain the equivalent of multiple lakes per year and likely remain active over several years our observations indicate that once established these persistent moulins might be capable of establishing well connected meltwater drainage pathways

bomb produced radiocarbon validation of growth increment crossdating allows marine paleoclimate reconstruction abstract the bivalve pacific geoduck panopea generosa has been used in the eastern north pacific ocean to create proxies for environmental factors such as temperature and oceanographic conditions this type of research depends upon accurate age determination of pacific geoducks which historically was based on shell growth increment counts a recent study comparing age estimates generated by the dendrochronology tree ring science procedure of crossdating to those estimated from growth increment counts found a significant difference between the methods for geoduck older than 30 years compared to the traditional age determination method of counting growth increments the crossdating method estimates a greater longevity in this species with some individuals living in excess of 150 years in the present study the accuracy of each method was independently assessed using bomb produced radiocarbon 14c techniques specimens whose birth years were estimated to be within the era of the bomb produced marine 14c increase and where the differences between ages estimated by the two methods were greatest were selected for 14c analysis the difference between age estimates from traditional growth increment counts and those from crossdating was evaluated using their respective 14c chronologies in comparisons to a reference chronology as a standard the comparisons relied on bayesian nonlinear models using markov chain monte carlo simulation this method of analysis showed that with a 50 probability geoducks were aged correctly when using the crossdating method compared to the growth increment counts which had a 50 probability of underestimating the age by 4 years therefore the crossdated age estimates were found to be more accurate than increment counts furthermore these results provide new confidence in using pacific geoduck biochronologies for paleoclimate and paleoenvironmental reconstruction

modern tasman sea surface reservoir ages from deep sea black corals abstract marine reservoir ages are a key element in calculating and constraining uncertainty in radiocarbon age estimates and are also essential to better understand regional ocean circulation in this study we present a new method to reconstruct long term high resolution sea surface reservoir ages based on analysis of the organic skeleton of deep sea 560 m black coral anthozoa antipatharia our results confirm that antipatharians are extremely slow growing typical radial growth rate for a south pacific specimen around 0 03 mm yr coupled uranium series and radiocarbon measurements were made on black coral collected live from the norfolk ridge north tasman sea to provide the first modern reservoir ages for this region at the norfolk ridge the average reservoir age between 1790 ad and 1900 ad was 330 years this was followed by a steep decrease over time of about 70 years to 1950 ad our most modern value this indicates an increase in surface ocean ventilation of water masses in this region these results are consistent with observational studies for the early twentieth century which suggest significant changes in regional circulation of the southwest pacific

bomb produced radiocarbon in the western tropical pacific ocean guam coral reveals operation specific signals from the pacific proving grounds high resolution radiocarbon 14c analyses on a coral core extracted from guam a western tropical pacific island revealed a series of early bomb produced 14c spikes the typical marine bomb 14c signal phase lagged and attenuated relative to atmospheric records is present in the coral and is consistent with other regional coral records however 14c levels well above what can be attributed to air sea diffusion alone punctuate this pattern this anomaly was observed in other indo pacific coral records but the guam record is unmatched in magnitude and temporal resolution the guam coral 14c record provided three spikes in 1954 1955 1956 1957 and 1958 1959 that are superimposed on a normal 14c record relative to mean prebomb levels the first peak rises an incredible 700 and remained elevated for 1 2 years a follow up assay with finer resolution increased the peak by 300 subsequent spikes were less intense with a rise of 35 and 70 each can be linked to thermonuclear testing in the pacific proving grounds at bikini and enewetak atolls in operations castle 1954 redwing 1956 and hardtack i 1958 these 14c signals can be explained by vaporization of coral reef material in the nuclear fireball coupled with neutron activation of atmospheric nitrogen 14c production and subsequent absorption of 14co2 to form particulate carbonates of close in fallout the lag time in reaching guam and other coral records abroad was tied to ocean surface currents and modeling provided validation of 14c arrival observations