kinetic control of skeletal sr ca in a symbiotic coral implications for the paleotemperature proxy modeling of past climates is critically dependent on estimates of past sea surface temperatures ssts for which one of the principal techniques used is the measurement of sr ca ratios in corals guilderson et al 1994 mcculloch et al 1999 hughen et al 1999 the link between coral sr ca and sst is not well understood and there have been a number of discrepant observations de villiers et al 1995 alibert 1998 corals with symbiotic zooxanthellae are known to show large diurnal fluctuations in calcification rate associated with the photosynthetic activity of their symbionts using detailed measurements with the ion microprobe we compared the sr ca content of discrete daytime and nighttime skeletal structures in the massive hermatypic coral porties lutea over the course of 1 year and a seasonal temperature range of 4 c the sr ca content of daytime skeleton is always lower than that of adjacent nighttime skeleton while the slope of the nighttime sr ca sst correlation is close to that seen in inorganic aragonite precipitates that of the daytime correlation is 4 times as steep we attribute these differences to the role of photosynthesis in calcification and conclude that bulk sr ca is related principally to daytime calcification rate rather than directly to sst more reliable estimates of past sst may be arrived at through selective analysis of nighttime skeleton

productivity controlled cold water coral growth periods during the last glacial off mauritania abstract article history received 17 june 2010received in revised form 29 october 2010accepted 11 december 2010available online 21 december 2010communicated by g j de langekeywords lopheliacold water coralscarbonate moundsbanda mound provincenw africaprimary productivity cold water corals are widely distributed along the atlantic continental margin with varying growth patternsinrelationtotheirspeci cenvironment here weinvestigatethelong termdevelopmentofcold watercoralsthat once thrived on a low latitude 17 40 n cold water coral mound in the banda mound province offmauritania duringthelastglacial interglacialcycle u thdatesobtained from20specimensofthecold watercoral lophelia pertusa revealed three distinct periods of coral growth during the last glacial at 65 to 57 kyr bp 45 to 32 kyr bp and 14 kyr bp thus comprising the cool periods of marine isotopic stages mis 2 4 thesecoral growth periods occur during periods of increased productivity in the region emphasizing thatproductivity seems to be the major steering factor for coral growth off mauritania which is one of the majorupwelling regions in the world this pattern differs from the well studied coral mounds off ireland where thecurrent regime predominantly in uences the prosperity of the cold water corals moreover coral growth offireland takes place during rather warm interglacial and interstadial periods whereas off mauritania coralgrowth is restricted to glacial and stadial periods however the on mound sedimentation patterns offmauritania largely resemble the observations reported from the irish mounds the bulk of the preservedsediments derives from periods of coral growth whereas during periods without corals hardly any netsedimentation or mound growth took place 2011 elsevier b v all rights reserved

reefs of the deep the biology and geology of cold water coral ecosystems coral reefs are generally associated with shallow tropical seas however recent deep ocean exploration using advanced acoustics and submersibles has revealed unexpectedly widespread and diverse coral ecosystems in deep waters on continental shelves slopes seamounts and ridge systems around the world advances reviewed here include the use of corals as paleoclimatic archives and their biogeological functioning biodiversity and biogeography threats to these fragile long lived and rich ecosystems are mounting the impacts of deep water trawling are already widespread and effects of ocean acidification are potentially devastating

abrupt changes in antarctic intermediate water circulation over the past 25 000 years the formation and circulation of antarctic intermediate water has varied over glacial interglacial timescales a neodymium record from the atlantic ocean basin suggests that changes in circulation may have been driven by changes both in antarctic intermediate water formation in the southern ocean and in the strength of north atlantic meridional overturning

age constraints on the origin and growth history of a deep water coral mound in the northeast atlantic drilled during integrated ocean drilling program expedition 307 sr isotope stratigraphy provides a new age model for the first complete section drilled through a deep water coral mound the 155 m long section from challenger mound in the porcupine sea bight southwest of ireland is on miocene siliciclastics and consists entirely of sediments bearing well preserved cold water coral lophelia pertusa the 87sr 86sr values of 28 coral specimens from the mound show an upward increasing trend correspond to ages from 2 6 to 0 5 ma and identify a significant hiatus from ca 1 7 to 1 0 ma at 23 6 m below seafloor the age of the basal mound sediments coincides with the intensification of northern hemisphere glaciations that set up the modern stratification of the northeast atlantic and enabled coral growth mound growth persisted throughout glacial interglacial fluctuations reached a maximum rate 24 cm k y ca 2 0 ma and ceased at 1 7 ma unlike other buried mounds in porcupine seabight challenger mound was only partly covered during its growth interruption and growth restarted ca 1 0 ma

geomagnetic intensity and 14c abundance in the atmosphere and ocean during the past 50 kyr we have used a new sedimentary record of geomagnetic field intensity combined with published volcanic data to examine the extent to which geomagnetic changes have affected 14c production in the past the production record was then converted into an atmospheric 14c signal using a 4 box model of past oceanic circulation the results indicate that changes in geomagnetic field intensity account for at least 80 of the 14c shift documented by published u th data which are of the order of 500 per mil with respect to a constant production hypothesis model simulations show that changes in past oceanic circulation account for only 100 per mil of 14c variation which is within the uncertainty of the geomagnetic correction in terms of dating these results show that the radiocarbon ages have to be shifted by 2 to 3 5 kyr towards older ages during the 20 40 ka interval

variations in seawater sr ca recorded in deep sea bamboo corals 1 a depth transect of deep sea bamboo corals along the california margin provides evidence that coral strontium to calcium ratios sr cacoral record seawater sr ca ratios sr casw a calibration was constructed utilizing sr cacoral ratios and previously published pacific sr casw data r2 0 53 n 12 p 0 01 sr cacoral mmol mol 4 62 sr casw mmol mol 36 64 sr casw is ultimately governed by the remineralization of sr containing shells of surface water derived marine organisms e g acantharia at intermediate water depths california margin sr cacoral records from 792 and 1295 m document fluctuations in sr casw that appear decadal scale these results suggest that sr casw may not be as stable as previously assumed and may be influenced by surface productivity on short timescales

phosphate defects and apatite inclusions in coral skeletal aragonite revealed by solid state nmr spectroscopy abstract recent development of paleo nutrient proxies based on the phosphorus calcium p ca ratio in tropical and deep water corals also known as cold water corals require an understanding of the processes by which p is incorporated into the coral skeletal aragonite here we apply single and double resonance solid state nuclear magnetic resonance nmr spectroscopy to determine the speciation of p in coral aragonite the results show that the majority of p occurs as phosphate defects in the aragonite structure but in many samples a significant fraction of the p occurs also in crystalline hydroxylapatite inclusions quantification of the amount of hydroxylapatite indicates that its presence is not related simply to external environmental factors and that it can occur at varying abundances in different parts of the same corallite since there is currently no model available to describe the relationship between dissolved inorganic phosphate and its incorporation as apatite inclusions into carbonates careful screening of samples which contain only phosphate in the aragonite structure or selective microsampling could improve proxy development

compositional variations at ultra structure length scales in coral skeleton distributions of mg and sr in the skeletons of a deep sea coral caryophyllia ambrosia and a shallow water reef building coral pavona clavus have been obtained with a spatial resolution of 150 nm using the nanosims ion microprobe at the museum national d histoire naturelle in paris these trace element analyses focus on the two primary ultra structural components in the skeleton centers of calcification coc and fibrous aragonite in fibrous aragonite the trace element variations are typically on the order of 10 or more on length scales on the order of 1 10 mu m sr ca and mg ca variations are not correlated however mg ca variations in pavona are strongly correlated with the layered organization of the skeleton

the 13c suess effect in scleractinian corals mirror changes in the anthropogenic co2 inventory of the surface oceans 1 new 13 c data are presented from 10 coral skeletons collected from florida and elsewhere in the caribbean dominica dominican republic puerto rico and belize these corals range from 96 to 200 years in age and were collected between 1976 and 2002 the change in the 13 c of the skeletons from these corals between 1900 and 1990 has been compared with 27 other published coral records from the atlantic pacific and indian oceans the new data presented here make possible for the first time a global comparison of rates of change in the 13 c value of coral skeletons of these records 64 show a statistically significant p 0 05 decrease in 13 c towards the modem day 23 out of 37 this decrease is attributable to the addition of anthropogenically derived co 2 13 c suess effect to the atmosphere between 1900 and 1990 the average rate of change of the 13 c in all the coral skeletons living under open oceanic conditions is approximately 0 01 o yr 1 in the atlantic ocean the magnitude of the decrease since 1960 0 019 yr 1 0 015 is essentially the same as the decrease in the 13 c of atmospheric co 2 and the 13 c of the oceanic dissolved inorganic carbon 0 023 to 0 029 yr 1 while in the pacific and indian oceans the rate is more variable and significantly reduced 0 007 yr 1 0 013 these data strongly support the notion that i the 13 c of the atmosphere controls ambient 13 c of the dissolved inorganic carbon which in turn is reflected in the coral skeletons ii the rate of decline in the coral skeletons is higher in oceans with a greater anthropogenic co 2 inventory in the surface oceans iii the rate of 13 c decline is accelerating superimposed on these secular variations are controls on the 13 c in the skeleton governed by growth rate insolation and local water masses

haughton impact structure structural and morphological aspects haughton is a complex meteorite impact structure of tertiary age on devon island in the canadian arctic the 20 5 km diameter site was formed in essentially flat lying paleozoic carbonates roughly 1700 m in thickness overlying precambrian gneisses the structure comprises three concentric rings surrounding a central basin with interior peaks the outer ring diameter 20 5 km is an annulus of peaks separating the allen bay dolomites of the regional plateau from the same unit that has been downdropped towards the crater interior along a series of circumferential faults the middle ring of peaks diameter 14 15 km comprises both faulted allen bay dolomites and blocks of the underlying bay fiord formation uplifted 250 m hills of the inner elliptical ring 3 5 5 5 km in diameter are also formed from bay fiord formation and the underlying eleanor river formation brought up 600 m an interconnected series of normal faults occupies most of the annulus between the inner and outer rings within the central b

nd isotopes in deep sea corals in the north eastern atlantic abstract neodymium nd concentrations and isotopic signatures of living and fossil deep sea coral species lophelia pertusa desmophyllum dianthus and madrepora oculata from the northeast atlantic ocean have been investigated in order to test the ability of deep sea corals to reconstruct the seawater nd isotopic signature and past changes of ocean circulation in the eastern north atlantic small quantities of nd less than 45 ng g are incorporated into the aragonite skeleton of living deep sea corals that dwell at upper intermediate depths throughout the northeast atlantic rigorous cleaning techniques are needed in order to avoid nd contamination from manganese oxide and iron hydroxide coatings moreover nd isotopic compositions have been measured using thermal ionization mass spectrometry tims by nd oxide method our data indicate that the isotopic signatures of modern corals are similar to those of adjacent water masses implying that deep sea corals can serve as an archive of the seawater nd isotopic compositions in the past the first results from few fully cleaned fossils corals collected within the porcupine seabight and the southwest rockall bank reveal significantly higher end for corals dated between 150 40 and 3060 90 yrs than those of the living corals located in similar areas this suggests rapid hydrological variations along the eastern margin of the north atlantic ocean at intermediate water depth with higher contribution of the mediterranean overflow waters mow or other temperate atlantic mid depth water masses enacw or nac in the past

the geochemistry of deep sea coral skeletons a review of vital effects and applications for palaeoceanography deep sea corals were discovered over a century ago but it is only over recent years that focused efforts have been made to explore the history of the oceans using the geochemistry of their skeletal remains they offer a promising archive of past oceanic environments given their global distribution layered growth patterns longevity and preservation as well as our ability to date them using radiometric techniques this paper provides an overview of the current state of the art in terms of geochemical approaches to using deep sea coral skeletons to explore the history of the ocean deep sea coral skeletons have a wide array of morphologies e g solitary cup corals branching colonial corals and materials calcite aragonite and proteins as such their biomineralization strategies are diverse leading to complex geochemistry within coral skeletons notwithstanding these complications progress has been made on developing methods for reconstructing the oceanographic environment in the past using trace elements and isotopic methods promising approaches within certain coral groups include clumped isotopes and mg li for temperature reconstructions boron isotopes and radiocarbon for carbon cycling end and radiocarbon for circulation studies and 15 n p ca and ba ca for nutrient tracer studies likewise there is now a range of techniques for dating deep sea corals skeletons e g u series radiocarbon and determining their growth rates e g radiocarbon and 210 pb dating studies on historic coral populations in the atlantic southern ocean and pacific point to climate and environmental changes being dominant controls on coral populations over millennial and orbital timescales this paper provides a review of a range of successes and promising approaches it also highlights areas in which further research would likely provide new insights into biomineralization palaeoceanography and distribution of past coral populations

environmental and biological controls on mg and li in deep sea scleractinian corals abstract deep sea scleractinian corals precipitate aragonite skeletons that provide valuable archives of past ocean conditions during calcification biological mediation causes variability in trace metal incorporation and isotopic ratios of the aragonite such that signals caused by environmental controls can be overwhelmed this complicates the interpretation of geochemical proxies used for paleo reconstructions in this study we examine the environmental controls on the mg li ratio of 34 individuals from seven genera of deep sea scleractinian corals desmophyllum balanophyllia caryophyllia enallopsammia flabellum trochocyanthus and lophelia in addition we examine the microscale distributions of mg and li in desmophyllum and balanophyllia using laser ablation inductively coupled plasma mass spectrometry la icp ms both mg ca and li ca ratios increased by more than a factor of two in the center of calcification regions compared to the outer fibrous regions of the coral skeleton as a result replicate 10 mg subsamples of coral show less variability in the mg li ratio than mg ca microscale mg and li results are consistent with rayleigh type incorporation of trace metals with additional processes dominating the composition within centers of calcification comparison of mg li to seawater properties near the site of collection shows that the ratio is not controlled by either carbonate ion or salinity it appears that temperature is the major control on the mg li ratio for all 34 samples the temperature correlation r2 0 62 is significantly better than for mg ca r2 0 06 for corals of the family caryophyllidae the r2 value increases to 0 82 with the exclusion of one sample that was observed to have an altered chalky texture despite this excellent correlation the scatter in the data suggests that the mg li ratio of deep sea corals cannot be used to reconstruct temperature to better than approximately 1 6 c without better temperature control and additional calibration points on modern coral samples

growth rates of the deep sea scleractinia desmophyllum cristagalli and enallopsammia rostrata with uranium rich skeletons and density bands similar to their surface coral counterparts deep sea scleractinia are a promising archive of past climate to improve the utility of fossil samples as monitors of deep ocean variability we have measured 210 pb and 226 ra activities in a variety of modern specimens to constrain the range of growth rates mechanical and chemical cleaning of each sample are required to isolate the radionuclides trapped in the coral skeleton from surface contaminants however in many cases mechanically cleaned samples show the same overall growth rate as parallel transects of samples subjected to the full chemical and mechanical cleaning but with much higher overall activities three samples of desmophyllum cristagalli show a range of vertical extension rates from 0 5 mm yr to 2 mm yr consistent with previous estimates a single enallopsammia rostrata from the north atlantic is over 100 years old its average radial growth rate is 0 07 mm yr and the clear banding in this direction is not consistent with annual periodicity a minimum vertical extension rate of 5 mm yr is estimated from the 210 pb data both of these species are found in the fossil record and with the growth rates determined here can record about 100 years of climate change the growth rates will allow the reconstruction of climate at subdecadal resolution in d cristagalli and even higher resolution in e rostrata d 2004 elsevier b v all rights reserved

no change in the neodymium isotope composition of deep water exported from the north atlantic on glacial interglacial time scales quantifying past circulation is a vital part of testing our understanding of the modern and future climate system the isotopic composition of neodymium nd in marine precipitates has considerable promise as a recorder of past circulation patterns but its robust application requires knowledge of the end member compositions in order to correctly deconvolute a downstream signal we show here using in situ high temporal resolution analyses of ferro manganese crusts from the north atlantic that the nd isotopic composition of deep water during times of much more extensive northern hemisphere ice cover was no different than the modern day interglacial value this result is surprising but greatly simplifies the use of nd isotopes as tracers of the strength and patterns of circulation in the atlantic in the past

synchronous deglacial overturning and water mass source changes understanding changes in ocean circulation during the last deglaciation is crucial to unraveling the dynamics of glacial interglacial and millennial climate shifts we used neodymium isotope measurements on postdepositional iron manganese oxide coatings precipitated on planktonic foraminifera to reconstruct changes in the bottom water source of the deep western north atlantic at the bermuda rise comparison of our deep water source record with overturning strength proxies shows that both the deep water mass source and the overturning rate shifted rapidly and synchronously during the last deglacial transition in contrast any freshwater perturbation caused by heinrich event 1 could have only affected shallow overturning these findings show how changes in upper ocean overturning associated with millennial scale events differ from those associated with whole ocean deglacial climate events

evaluation of boron isotope ratio as a ph proxy in the deep sea coral desmophyllum dianthus evidence of physiological ph adjustment the boron isotope ratio 11b of foraminifers and tropical corals has been proposed to record seawater ph to test the veracity and practicality of this potential paleo ph proxy in deep sea corals samples of skeletal material from twelve archived modern desmophyllum dianthus d dianthus corals from a depth range of 274 1470 m in the atlantic pacific and southern oceans ambient ph range 7 57 8 05 were analyzed for 11b the 11b values for these corals spanning a range from 23 56 to 27 88 are found to be related to seawater borate 11b by the linear regression 11bcoral 0 76 0 28 11bborate 14 67 4 19 1 standard error se the d dianthus 11b values are greater than those measured in tropical corals and suggest substantial physiological modification of ph in the calcifying space by a value that is an inverse function of seawater ph this mechanism partially compensates for the range of ocean ph and aragonite saturation at which this species grows enhancing aragonite precipitation and suggesting an adaptation mechanism to low ph environments in intermediate and deep waters consistent with the findings of trotter et al 2011 for tropical surface corals the data suggest an inverse correlation between the magnitude of a biologically driven ph offset recorded in the coral skeleton and the seawater ph described by the equation ph ph recorded by coral seawater ph 0 75 0 12 phw 6 88 0 93 1 se error analysis based on 95 confidence interval ci and the standard deviation of the regression residuals suggests that the uncertainty of seawater ph reconstructed from 11bcoral is 0 07 to 0 12 ph units this study demonstrates the applicability of 11b in d dianthus to record ambient seawater ph and holds promise for reconstructing oceanic ph distribution and history using fossil corals

ph control on oxygen isotopic composition of symbiotic corals abstract boron carbon and oxygen isotopic compositions were determined at the micrometre scale by high resolution ion microprobe in a sample of modern coral massive hermatypic coral porites lutea the ion probe data show for b and o much larger isotopic variations at the micrometre scale than those measured at the millimetre scale by conventional techniques 18opdb values range from 10 6 0 9 to 0 2 0 5 and 11b values range from 18 6 1 5 to 30 6 1 6 by contrast 13c values show the same range of variations from 4 6 0 65 to 2 2 0 67 at the micrometre and millimetre scales the range of 11b values indicates that significant ph variations from 7 1 to 9 0 are present at the sites of calcification the largest 18o variations correspond to the highest 11b values i e to the highest phs this measurement of ph allows modelling the oxygen isotopic fractionation occurring during aragonite precipitation taking into account the rate of o isotopic equilibrium between dissolved carbonate species h2co3 hco3 and co32 and water via the two reactions of hydration and hydroxylation the full range of 18o values measured at the micrometre scale can be modelled for residence times of dissolved carbonates in the calcifying fluid ranging between 1 h and at maximum 12 h the ph controls the 18o of the growing carbonate through the relative fractions of dissolved carbonate species and through the kinetics of their isotopic equilibration with water via hydration and hydroxylation the so called vital effect systematically observed for 18o in corals can thus be understood as representing an average of rapid ph variations due to coral biology during coral growth selectively measuring 18o values in the zones of coral skeletons that have low 11b values i e formed at low ph should significantly improve the quality of palaeoclimatic reconstructions based on 18o values

late holocene intermediate water variability in the northeastern atlantic as recorded by deep sea corals abstract the nd isotopic composition of the aragonite skeleton of fossil deep sea corals lophelia pertusa madrepora oculata and desmophyllum dianthus located in the northeastern atlantic at water depths between 635 and 1300 m was investigated to reconstruct changes in the atlantic mid depth gyre circulation during the past millennium the coral end values varied systematically from 11 8 to 14 4 during the past 1500 years reflecting variations in seawater end and thus water mass provenance low end values end 14 occurred during the warm medieval climatic anomaly mca between 1000 ad and 1250 ad and during the most recent period 1950 ad to 2000 ad interrupted by a period of significantly higher end values 12 5 during the little ice age lia between 1350 ad and 1850 ad one long lived branching coral even recorded an abrupt systematic rise from low to high end values around 1250 ad over the course of its 10 year growth period these variations are interpreted to result from variable contributions of the subpolar and subtropical atlantic intermediate water masses which today are characterized by end values of 15 and 11 respectively the low end values observed during the warm mca and during recent times imply a strong eastward extension of the mid depth subpolar gyre spg induced by a dominant positive phase of the north atlantic oscillation nao during the lia water from the subtropical gyre stg and potentially from the mediterranean sea water msw propagated further northward as indicated by the higher coral end values this pattern suggests a negative mean state of the nao during the lia with weaker and more southerly located westerlies and a westward contraction of the spg variations in the contributions of the two gyres imply changes in the heat and salt budgets at intermediate depths during the past millennia that may have contributed to changes in the properties of north atlantic inflow into the nordic seas and thus deep water formation

deep sea corals off brazil verify a poorly ventilated southern pacific ocean during h2 h1 and the younger dryas abstract simultaneous 14 c and th u dating of deep sea corals are useful for reconstructing the intensity of deep ocean circulation in the past as they deliver the time between the gas exchange of the water with the atmosphere and the incorporation of the 14 c in the carbonates adkins and boyle 1997 adkins et al 1998 mangini et al 1998 th u ages of deep sea corals sampled in sediment cores from locations off the coast of brazil bathed by antarctic intermediate water at depths between 600 and 800 m group close to heinrich events h2 h1 and the younger dryas the 14 c of the water bathing the corals starts to decrease approximately 2 kyr before the heinrich events and decreases to values 400 lower than the corresponding back tracked atmospheric values the timing and the magnitude of the decrease is similar to that observed in intermediate water in the n pacific off baja california marchitto et al 2007 and in the eastern pacific stott et al 2009 high ventilation ages partly exceeding 4000 years are an unambiguous indication for a reduction of north atlantic deep water formation during h2 h1 and the yd as deduced from higher 231 pa 230 th activity ratios and from end in n atlantic ocean sediments mcmanus et al 2004 pahnke et al 2008 yu et al 1996 they also could indicate a poorly oxygenated southern pacific ocean at the end of the heinrich events

reproducibility of trace element profiles in a specimen of the deep water bamboo coral keratoisis sp abstract bamboo corals order gorgonacea family isididae are attractive prospects for deep sea paleoceanographic reconstruction capturing trace elements in their calcitic skeletons that may serve as environmental proxies with subdecadal resolution over multi century timescales we study the reproducibility and fidelity of trace element profiles ba mg sr mn u pb in a 420 year old specimen of the bamboo coral keratoisis sp from the se usa using laser ablation icp ms to obtain multiple replicate profiles we use spectral techniques to distinguish noise and irreproducible variations from fully reproducible geochemical fluctuations that are candidates for environmental signals by quantifying variability between profiles we assess the fidelity with which the corals potentially record environmental information barium is the most reproducible element in the skeleton with large fluctuations along different growth radii reproducing to within 4 both mg and sr have very uniform levels within the coral but display low amplitude irreproducible variations that might represent an internal biological process in the case of mg which has been proposed as a paleotemperature proxy this irreproducibility would represent an intrinsic uncertainty of 0 1 to 0 4 c both mn and pb contain some irreproducibility superimposed upon broad reproducible profiles that may be environmental signals some of the irreproducible pb fluctuations correlate with cracks and dark bands in the sample suggesting detrital or surface contamination uranium displays large amplitude variations which are not reproducible along different radii this suggests that uranium cannot be used for paleoenvironmental reconstruction and may show signs of early diagenesis a possibility that could complicate attempts to date young keratoisis sp samples by u series geochemistry the highly reproducible ba signal allows precise alignment of profiles and thus we can show that growth rate along one radius can vary by a factor of two relative to growth along a different radius there is no evidence that this large variation in relative growth rate affects either the mg or sr incorporation in addition geochemical anomalies in ba and mg indicate that the very central axis of the specimen may represent a different mode of growth this study suggests that keratoisis sp corals are imperfect recorders of geochemical information but do contain reproducible variations which are good candidates for environmental signals

the holocene occurrence of cold water corals in the ne atlantic implications for coral carbonate mound evolution abstract u series dating of constructional cold water corals is a powerful tool to reconstruct the evolution of corals on carbonate mounds here we have investigated the time framework of corals such as lophelia pertusa and madrepora oculata on five different mound settings of the eastern north atlantic on rockall bank and in porcupine seabight sampled at variable depth and location 610 880 m water depth we have found that the past 11 ka reflect a period generally favourable for coral development we further determined local mound growth rates and identified mound surface erosion framework collapse during times of active coral framework construction local vertical mound growth rates vary between less than 5 cm ka 1 and up to 220 cm ka 1 we interpret rates exceeding 15 cm ka 1 as representative of densely populated coral reefs during times of reduced or absent coral development mound evolution rates are by far smaller 0 to 1 the time resolution achieved here furthermore provides first evidence for reduced coral ecosystem activity at 1 8 2 0 ka 4 2 4 8 ka and between 6 and 8 2 ka within the holocene that may be related to climate driven changes of the coral growth environments during glacial periods coral growth in those areas seems apparently extremely reduced or is even absent on mounds

northeastern atlantic cold water coral reefs and climate u series age patterns obtained on reef framework forming cold water corals collected over a nearly 6000 km long continental margin sector extending from off mauritania 17 degrees n northwest africa to the southwestern barents sea 70 degrees n northeastern europe reveal strong climate influences on the geographical distribution and sustained development of these ecosystems over the past three glacial interglacial cycles framework forming cold water corals lophelia pertusa and madrepora oculata seem to have predominantly populated reefs canyons and patches in the temperate east atlantic and the mediterranean sea above 50 degrees n corals colonize reefs in the northern east atlantic primarily during warm climate periods with the biogeographic limit advancing from similar to 50 degrees n to similar to 70 degrees n we propose that north south oscillations of the biogeographic limit of reef developments are paced by ice ages and may occur synchronously with north south displacement of cold nutrient rich intermediate waters and surface productivity related to changes of the polar front

a near field sea level record of east antarctic ice sheet instability from 32 to 27 myr 1 fossil facies and isotope analyses of an early high paleolatitude 55 s section suggests a highly unstable east antarctic ice sheet from 32 to 27 myr the waxing and waning of this ice sheet from 140 to 40 of its present volume caused sea level changes of 25 m ranging from 30 to 50 m related to periodic glacial 100 000 to 200 000 years and shorter interglacial events the near field gippsland sea level gsl curve shares many similarities to the far field new jersey sea level njsl estimates however there are possible resolution errors due to biochronology taphonomy and paleodepth estimates and the relative lack of lowstand deposits in njsl that prevent detailed correlations with gsl nevertheless the lateral variations in sea level between the gsl section and njsl record that suggest ocean siphoning and antisiphoning may have propagated synchronous yet variable sea levels

gerardia bristlecone pine of the deep sea we measured carbon isotope abundances in the layered proteinaceous skeleton of a zoanthid gerardia collected from 620 m depth off the little bahama bank 27 n 79 w the 14c values decreased from 76 in the outer growth edge to an average of 267 in the center of three portions of the skeleton these 14c data suggest an age for this living organism of 1800 300 years the possibility that the large decrease in 14c reflects the gradual input of bomb 14c over the entire growth of the organism is inconsistent with the post bomb 14c values obtained for the most recent growth tips if the age estimate of two millennia is correct it may be the longest lived animal yet observed in the ocean gerardia may serve as a long lived recorder of ocean chemistry similar to the bristlecone pine tree that has served as a millennial timescale recorder for atmospheric 14co2 suess 1980 and climate in particular there is potential for gerardia to serve as a millennial scale integrator of upper ocean particle flux and possibly reveal past changes in the productivity of the surface ocean

deglacial variability of antarctic intermediate water penetration into the north atlantic from authigenic neodymium isotope ratios 1 understanding intermediate water circulation across the last deglacial is critical in assessing the role of oceanic heat transport associated with atlantic meridional overturning circulation variability across abrupt climate events however the links between intermediate water circulation and abrupt climate events such as the younger dryas yd and heinrich event 1 h1 are still poorly constrained here we reconstruct changes in antarctic intermediate water aaiw circulation in the subtropical north atlantic over the past 25 kyr by measuring authigenic neodymium isotope ratios in sediments from two sites in the florida straits our authigenic nd isotope records suggest that there was little to no penetration of aaiw into the subtropical north atlantic during the yd and h1 variations in the northward penetration of aaiw into the florida straits documented in our authigenic nd isotope record are synchronous with multiple climatic archives including the greenland ice core 18o record the cariaco basin atmosphere 14c reconstruction the bermuda rise sedimentary pa th record and nutrient and stable isotope data from the tropical north atlantic the synchroneity of our nd records with multiple climatic archives suggests a tight connection between aaiw variability and high latitude north atlantic climate change

loss of carbon from the deep sea since the last glacial maximum deep ocean carbonate ion concentrations co32 and carbon isotopic ratios 13c place important constraints on past redistributions of carbon in the ocean land atmosphere system and hence provide clues to the causes of atmospheric co2 concentration changes however existing deep sea co32 reconstructions conflict with one another complicating paleoceanographic interpretations here we present deep sea co32 for five cores from the three major oceans quantified using benthic foraminiferal boron calcium ratios since the last glacial period combined benthic 13c and co32 results indicate that deep sea released co2 during the early deglacial period 17 5 to 14 5 thousand years ago was preferentially stored in the atmosphere whereas during the late deglacial period 14 to 10 thousand years ago besides contributing to the contemporary atmospheric co2 rise a substantial portion of co2 released from oceans was absorbed by the terrestrial biosphere

late holocene radiocarbon and aspartic acid racemization dating of deep sea octocorals abstract primnoa resedaeformis is a deep sea gorgonian coral with a two part skeleton of calcite and gorgonin a fibrillar protein potentially containing long term records of valuable paleo environmental information for various reasons both radiocarbon and u th dating of these corals is problematic over the last few centuries this paper explores aspartic acid racemization dating of the gorgonin fraction in modern and fossil specimens collected from the nw atlantic ocean radiocarbon dating of the fossil specimen indicates a lifespan of 700 100 years the longest yet documented for any octocoral gorgonin amino acid compositions were identical in the fossil and modern specimens indicating resistance to organic diagenesis similar to bone collagen the fibrillar protein of gorgonin may impose conformational constraints on the racemization of asp at low temperatures the rate of racemization of aspartic acid d l asp was similar to previously published results from an 1800 year old anemone gerardia the age equation was age years bp 2000 ad d l 0 020 002 0011 0001 2 r2 0 97 p d l asp was marginally better than that for 14c dating over the most recent 50 200 years although the dating error may be improved by inclusion of more samples over a broader time range these results suggest that d l asp dating may be useful in augmenting 14c dating in cases where 14c calibrations yield two or more intercept ages or in screening samples for further 14c or u th dating

precise th u dating of small and heavily coated samples of deep sea corals marine carbonate skeletons like deep sea corals are frequently coated with iron and manganese oxides hydroxides which adsorb additional thorium and uranium out of the sea water a new cleaning procedure has been developed to reduce this contamination in this further cleaning step a solution of na2edta na2h2tb and ascorbic acid is used which composition is optimised especially for samples of 20 mg of weight it was first tested on aliquots of a reef building coral which had been artificially contaminated with powdered ferromanganese nodule applied on heavily contaminated deep sea corals scleractinia it reduced excess 230th by another order of magnitude in addition to usual cleaning procedures the measurement of at least three fractions of different contamination together with an additional standard correction for contaminated carbonates results in th u ages corrected for the authigenic component a good agreement between th u and 14c ages can be achieved even for extremely coated corals

deep sea coral evidence for rapid change in ventilation of the deep north atlantic 15 400 years ago coupled radiocarbon and thorium 230 dates from benthic coral species reveal that the ventilation rate of the north atlantic upper deep water varied greatly during the last deglaciation radiocarbon ages in several corals of the same age 15 41 0 17 thousand years and nearly the same depth 1800 meters in the western north atlantic ocean increased by as much as 670 years during the 30 to 160 year life spans of the samples cadmium calcium ratios in one coral imply that the nutrient content of these deep waters also increased our data show that the deep ocean changed on decadal centennial time scales during rapid changes in the surface ocean and the atmosphere

glacial water mass geometry and the distribution of δ13c of σco2 in the western atlantic ocean 1 oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa cibicidoides and planulina from 25 new piston cores gravity cores and multicores from the brazil margin the cores span water depths from about 400 to 3000 m and intersect the major water masses in this region these new data fill a critical gap in the south atlantic ocean and provide the motivation for updating the classic glacial western atlantic 13c transect of duplessy et al 1988 the distribution of 13c of co2 requires the presence of three distinct water masses in the glacial atlantic ocean a shallow 1000 m southern source water mass with an end member 13c value of about 0 3 0 5 vpdb a middepth 1500 m northern source water mass with an end member value of about 1 5 and a deep 2000 m southern source water with an end member value of less than 0 2 and perhaps as low as the 0 9 values observed in the south atlantic sector of the southern ocean ninnemann and charles 2002 the origins of the water masses are supported by the meridional gradients in benthic foraminiferal 18o a revised glacial section of deep water 13c documents the positions and gradients among these end member intermediate and deep water masses the large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation

proliferation and demise of deep sea corals in the mediterranean during the younger dryas abstract uranium series and radiocarbon ages are reported for deep sea corals madrepora oculata desmophyllum dianthus lophelia pertusa and caryophyllia smithii from the mediterranean sea u series dating indicates that deep sea corals have persisted in the mediterranean for over 480 000 years especially during cool interstadial periods the most prolific period of growth however appears to have occurred within the younger dryas yd period from 12 900 to 11 700 years bp followed by a short 330 years phase of post yd coral growth from 11 230 to 10 900 years bp this indicates that deep sea corals were prolific in the mediterranean not only during the return to the more glacial like conditions of the yd but also following the rapid deglaciation and transition to warmer conditions that followed the end of the yd surprisingly there is a paucity last glacial maximum lgm coral ages implying they were largely absent during this period when cold water conditions were more prevalent radiocarbon ages show that the intermediate depth waters of the mediterranean generally had 14 c compositions similar to surface waters indicating that these waters were extremely well ventilated the only exception is a narrow period in the yd 12 500 100 years bp when several samples of lophelia pertusa from the ionian sea had 14 c values falling significantly below the marine curve using a refined approach isolation ages isol of 300 years to 500 years are estimated for these intermediate 800 1000 m depth waters relative to surface marine waters indicating a reduction or absence of deep water formation in the ionian and adjacent adriatic seas during the yd contrary to previous findings we find no evidence for widespread intrusion of low 14 c atlantic waters into the mediterranean prolific growth of deep sea corals in the mediterranean ended abruptly at 10 900 years bp with many of the coral bearing mounds on the continental slopes being draped in a thin veneer of mud their demise is attributed to a number of factors including the direct loss of habitat due to high sedimentation that accompanied glacial meltwater pulses together with rising temperatures that would have finally pervaded the deeper water of the mediterranean following the onset of holocene warming

effect of environmental conditions and skeletal ultrastructure on the li isotopic composition of scleractinian corals the lithium isotope compositions li 7 li 6 and li ca ratios of shallow water and deep sea corals porites lutea cladocora caespitosa lophelia pertusa and desmophyllum cristagalli were measured using a cameca ims 1270 ion microprobe the two c caespitosa samples were grown under controlled conditions at co2 partial pressures pco 2 of 416 29 mu atm and 729 30 mu atm respectively in situ analyses show that all samples are isotopically homogeneous within analytical precision 1 1 parts per thousand 1 sigma and display significantly lower delta li 7 values relative to seawater indicating a significant isotope fractionation during aragonite formation in contrast to all other elements analysed so far there is no relationship between the li isotopic compositions and the skeletal ultrastructure however li ca does show variation correlated with ultrastructure albeit with significant differences between species this implies that the bio mineralization mechanisms which are supposed to be different for the different skeletal components do not influence the li isotopic composition in corals in particular the model of rayleigh fractionation in a semi enclosed calcifying fluid is incompatible with the homogeneity of the li isotope compositions at the micrometer scale we also show that changes in pco 2 and ph do not significantly affect the li isotope signature nevertheless a small but significant and systematic difference in li isotopic composition is observed between deep sea azooxanthellate and shallow water zooxanthellate corals the lack of dependence on ph and pco 2 and on skeletal ultrastructure indicates that the u isotopic signature of corals could be used as a proxy for reconstructing the paleo delta li 7 of seawater and potentially for deconvolving past continental weathering rates c 2009 elsevier b v all rights reserved

intensification and variability of ocean thermohaline circulation through the last deglaciation neodymium isotope ratios in the authigenic ferromanganese oxide component in a southeastern atlantic core reveal a history of the global overturning circulation intensity through the last deglaciation from a minimum during the last glacial maximum lgm north atlantic deep water nadw began to strengthen between 18 and 17 kyr cal bp approximately 2000 3000 years before the bolling warming it exhibits a gradually increasing baseline intensity that plateaus in the early holocene tracks increasing northern hemisphere insolation and parallels atmospheric co2 concentration millennial scale fluctuations are superimposed on this baseline nadw increase corresponding to events in northern hemisphere climate records the millennial excursions show sharp increases associated with the pre bolling retreat of continental glaciers and the bolling warming itself a decrease with allerod cooling and a recovery through the younger dryas and early holocene the data confirm a close link between deep ocean circulation and north atlantic climate changes there is no clear linkage with meltwater pulses indicating that rapid meltwater additions did not trigger observable mode changes in nadw production however rapid changes in north atlantic sea ice cover show a strong relationship with the millennial perturbations of nadw flux to the deep southern ocean the data indicate that the baseline intensity of nadw reaching the cape basin is paced by northern hemisphere insolation and that north atlantic sea ice coverage acts as a major amplifying link between the oceans and the atmosphere d 2004 elsevier b v all rights reserved

a deep sea coral record of north atlantic radiocarbon through the younger dryas evidence for intermediate water deepwater reorganization requires the existence of large mobile gradients of d 14 c in the ocean during the younger dryas the d 14 c water column profile from keigwin 2004 provides direct evidence for the presence of one such gradient at the beginning of the younger dryas 12 9 ka with a 100 offset between shallow 2400 m and deep water our early younger dryas data are consistent with this profile and also show a d 14 c inversion with 35 more enriched water at 2400 m than at 1700 m this feature is probably the result of mixing between relatively well 14 c ventilated northern source water and more poorly 14 c ventilated southern source intermediate water which is slightly shallower over the rest of the younger dryas our intermediate water deepwater coral d 14 c data gradually increase while the atmosphere d 14 c drops for a very brief interval at 12 0 ka and at the end of the younger dryas 11 5 ka intermediate water d 14 c 1200 m approached atmospheric d 14 c these enriched d 14 c results suggest an enhanced initial d 14 c content of the water and demonstrate the presence of large lateral d 14 c gradients in the intermediate deep ocean in addition to the sharp vertical shift at 2500 m the transient d 14 c enrichment at 12 0 ka occurred in the middle of the younger dryas and demonstrates that there is at least one time when the intermediate deep ocean underwent dramatic change but with much smaller effects in other paleoclimatic records

seawater 234 u 238 u during the last 800 thousand years abstract constraining the history of seawater 234u 238u is important because this ratio is used to assess the validity of u th ages and because it provides information about the past rate of physical weathering on the continents this study makes use of u rich slope sediments from the bahamas in an attempt to reconstruct seawater 234u 238u for the last 800 kyr for the last 360 kyr u th dating of these sediments provides ages and initial 234u 238u values sixty seven samples largely from marine highstands have initial 234u 238u which scatter somewhat about the modern seawater value 1 145 but neither this scatter nor the average value increases with age of sample these data contrast with published coral data and suggest that seawater 234u 238u has remained within 15 of the modern value for the last 360 kyr this confirms the rejection of coral u th ages where the initial 234u 238u is significantly different from modern seawater data from older highstands dated with 18o stratigraphy or by the presence of the brunhes matuyama b m reversal at 780 kyr allow seawater 234u 238u to be assessed prior to the range of the 230th chronometer unfortunately diagenetic scatter in the data between the b m reversal and 360 kyr is rather large probably relating to low u concentrations for these samples but there is no indication of a trend in seawater 234u 238u with age high u samples from close to the b m reversal show less diagenetic scatter and an initial 234u 238u that averages 1 102 this lower value can be explained by lower seawater 234u 238u at the time of the b m reversal or by progressive loss of 234u from the sediment by recoil a simple box model is presented to illustrate the response of seawater 234u 238u to variations in riverine input such as might be caused by changes in continental weathering comparison of the bahamas 234u 238u data with model results indicates that riverine 234u 238u has not varied by more than 65 for any 100 kyr period during the last 360 kyr it also indicates that the ratio of physical to chemical weathering on the continents has not been higher than at present for any extended period during the last 800 kyr

rapid and accurate u th dating of ancient carbonates using inductively coupled plasma quadrupole mass spectrometry here the potential for rapid and accurate u th dating technique of marine aragonite skeletons deep sea corals lophelia pertusa and secondary calcite deposits speleothems and stalagmites has been explored using inductively coupled plasma quadrupole mass spectrometry icp qms the analytical procedure includes a largely simplified chemical separation technique for uranium u and thorium th using uteva resin the developed technique permits simultaneous quantification of uranium 238u and thorium 232th concentrations and their respective isotopic composition required for u series disequilibrium dating up to 50 u th dates per day can be achieved through icp qms with 234u and 230th reproducibility 2 of 3 4 and 1 respectively the high sensitivity 3 0 105 cps ppb together with low background 0 5 cps on each mass between 228 and 236 amu allowed u th dating of ancient deep water corals 15 260 kyr and stalagmites 30 85 kyr at precision levels of less than 2 consequently the combination of simplified chemistry using uteva with state of the art icp qms isotopic measurements that do not require a u th separation step now provides an extremely rapid and low cost u series dating technology the level of precision is most convenient for numerous geochronological applications such as the determination of climatic influences on ecosystem development and carbonate precipitation as a first example application we present icp qms u th dates of north atlantic deep water coral fragments retrieved in the southeastern porcupine seabight md01 2463g mound therese indicating a purely interglacial growth of deep water corals on so called carbonate mounds over several climate cycles

glacial cold water coral growth in the gulf of cadiz implications of increased palaeo productivity a set of 40 uranium series datings obtained on the reef forming scleractinian cold water corals lophelia pertusa and madrepora oculata revealed that during the past 400 kyr their occurrence in the gulf of cadiz goc was almost exclusively restricted to glacial periods this result strengthens the outcomes of former studies that coral growth in the temperate ne atlantic encompassing the french iberian and moroccan margins dominated during glacial periods whereas in the higher latitudes irish and norwegian margins extended coral growth prevailed during interglacial periods thus it appears that the biogeographical limits for sustained cold water coral growth along the ne atlantic margin are strongly related to climate change by focussing on the last glacial interglacial cycle this study shows that palaeo productivity was increased during the last glacial this was likely driven by the fertilisation effect of an increased input of aeolian dust and locally intensified upwelling after the younger dryas cold event the input of aeolian dust and productivity significantly decreased concurrent with an increase in water temperatures in the goc this primarily resulted in reduced food availability and caused a widespread demise of the formerly thriving coral ecosystems moreover these climate induced changes most likely caused a latitudinal shift of areas with optimum coral growth conditions towards the northern ne atlantic where more suitable environmental conditions established with the onset of the holocene

coral provides way to age deep water we propose a new method for computing the ratio of the isotopes carbon 14 to carbon 12 in deep water from the past and for testing the results derived from the normal method of age difference between benthic and planktic foraminifera in deep sea sediments1

deep sea corals evidence periodic reduced ventilation in the north atlantic during the lgm holocene transition abstract nine new intermediate water ages estimated with coupled uranium series and radiocarbon measurements on deep sea corals from the northeastern atlantic are presented together with six intermediate and deep water ages from the western north atlantic adkins et al science 280 1998 725 728 and one from the equatorial atlantic mangini et al nature 392 1998 347 348 they span the time period from 15 400 to 560 yr ago and show abrupt variations of intermediate and deep water ages from 270 up to 2320 yr both major pulses of meltwater discharge mwp 1a following heinrich event 1 and mwp 1b after the younger dryas cold event are followed by enhanced supply of southern source water at intermediate depths in the north atlantic together with reduced formation of well ventilated glacial north atlantic intermediate water 1000 2000 m this result gives strong support to numerical models predicting fast and sharp increase of bottom water age in the atlantic triggered by pulses of freshwater discharge into the north atlantic rahmstorf nature 372 1994 82 85 stocker and wright radiocarbon 40 1998 359 366

rapid climate change in the north atlantic during the younger dryas recorded by deep sea corals research on global climate change has increasingly focused on rapid century scale and decadal changes one such climate shift the younger dryas cooling event1 took place during the last deglaciation from 13 000 to 11 700 years bp climate records from greenland ice cores and north atlantic sediment cores show high frequency fluctuations implying significant 5 c shifts in temperature at this time taking place within 50 100 years ref 2 the origin of the younger dryas has recently been attributed to a reduction or cessation of deep water production in the north atlantic and a concurrent lessening of the heat flux from low latitudes3 4 the role of intermediate waters 1 000 2 000 m depth is less certain however because climate proxies for this ocean reservoir are rare and ambiguous here we report on the use of a new climate archive deep sea corals from orphan knoll 1 600m depth in the northwestern atlantic ocean the oxygen isotope ratios in the coral skeletons accurately dated by the 230th 234u chronometric method change markedly coincident with the initiation of the younger dryas suggesting that there were profound changes in intermediate water circulation at this time

continental weathering fluxes during the last glacial interglacial cycle insights from the marine sedimentary pb isotope record at orphan knoll nw atlantic abstract regional weathering intensity must have changed dramatically at high latitudes during the quaternary as a consequence of repeated continental glaciation investigation of these glacial interglacial changes at high temporal resolution is possible with the recent development of pb isotopes in femn oxyhydroxide phases as a proxy for region specific weathering intensity where increases in the radiogenic component are thought to correspond to increased continental weathering fluxes here we present a pb isotope record sourced from the femn oxyhydroxide fraction in marine sediments from iodp sites u1302 3 on orphan knoll 3500 mbsl nw atlantic spanning the last 37 ka located at the eastern edge of the laurentide ice sheet lis site u1302 3 is well placed to monitor changes in weathering intensity associated with lis glacial history overall the data show a close correspondence to local surface water 18o with least radiogenic values during times of heavy 18o glacial maximum and most radiogenic values during times of light 18o holocene this supports the prediction that weathering intensity in glaciated regions of the north atlantic correlates with the exposure age of glacial debris superimposed on these background trends are extreme radiogenic excursions e g variation in 206pb 204pb from 19 2 21 0 contemporaneous with heinrich events and the younger dryas these data are substantially more radiogenic than existing records from the nw atlantic and most likely represent episodes of exceptionally high inputs of pre formed femn oxyhydroxides during drainage of the lis due to its extreme isotope composition at least in the nw atlantic region pb would appear to be a good proxy for the fluxes of weathered continental material and perhaps by inference nutrients to the surface ocean

the climate influence on the mid depth northeast atlantic gyres viewed by cold water corals 1 the neodymium nd isotopic composition expressed in epsilon units nd of reef framework forming cold water corals provides unique measures of water mass provenance and mixing within the northeast atlantic today and in the past a reconstruction of near thermocline water nd from cold water corals of the gulf of cadiz and porcupine seabight spanning over the past 300 000 years now revealed that climate cooling during marine isotope stages mis 7 2 and mis 8 9 led to a retraction of the mid depth subpolar gyre mspg to the west conversely northern hemisphere warming and increasing fresh water fluxes to the northwest labrador sea favor a stronger eastward extension of the mspg blocking the northward flow of temperate atlantic water as observed during the early mis 1 and the early stage mis 5 5 these changes are likely the result of large scale south north displacement of the westerlies similar to present day observations that the north atlantic oscillation nao is linked with mid depth ocean circulation based on these observations we hypothesize that further climate warming will also strengthen the mspg leading to a salt and temperature decrease in the northeast atlantic whereas salinity and temperature will increase in the temperate atlantic however the amplitude of such changes on north atlantic overturning remains to be tested

temporal stability of the neodymium isotope signature of the holocene to glacial north atlantic the neodymium isotopic composition of marine precipitates is increasingly recognized as a powerful tool for identifying changes in ocean circulation and mixing on million year to millennial timescales unlike nutrient proxies such as 13 c or cd ca nd isotopes are not thought to be altered in any significant way by biological processes and thus they can serve as a quasi conservative water mass tracer however the application of nd isotopes in understanding the role of thermohaline circulation in rapid climate change is currently hindered by the lack of direct constraints on the signature of the north atlantic end member through time here we present the first results of nd isotopes measured in u th dated deep sea corals from the new england seamounts in the northwest atlantic ocean our data are consistent with the conclusion that the nd isotopic composition of north atlantic deep and intermediate water has remained nearly constant through the last glacial cycle the results address long standing concerns that there may have been significant changes in the nd isotopic composition of the north atlantic end member during this interval and substantiate the applicability of this novel tracer on millennial timescales for paleoceanography research

in situ measurements of oxygen isotopic composition in deep sea coral lophelia pertusa re examination of the current geochemical models of biomineralization abstract we present ion microprobe measurements of oxygen isotopic compositions in the deep sea coral lophelia pertusa compared to bulk skeletal aragonite fibres the emz early mineralization zone near the inside of the calyx was systematically depleted in 18 o rayleigh fractionation from a semi closed fluid reservoir does not explain this and other geochemical differences furthermore ph values estimated from skeletal 11 b data are inconsistent with the idea that emz or centres of calcification 18 o depletion reflects a more alkaline calcification environment our data combined with microstructural and geochemical observations indicate that the aragonitic fibres and emz are formed by a compartmentalized mineralization calicoblastic ectoderm which exerts strong biological control on the composition of the skeleton hence we propose a new model whereby amorphous calcium carbonates acc are precursors to the emz whereas the fibre precipitation is probably governed by kinetic processes

preboreal onset of cold water coral growth beyond the arctic circle revealed by coupled radiocarbon and u series dating and neodymium isotopes cold water coral mounds of lophelia pertusa are widespread across the scandinavian shelf which was completely ice covered during the last glacial maximum between 22 to 18 ka bp rapid deglacial meltdown of the fennoscandian inland ice and the retreat of its ice streams freed most of the shelf of ice by 15 ka bp however cold water coral growth commenced only after the pleistocene holocene transition at 11 65 ka bp when modern like climatic patterns and oceanographic conditions were established a tight climatic coupling has been constrained with u series ages coupled 14c ages provide local reservoir ages from various gravity cores in a fjord setting in stjernsund at 70 n and on the open shelf in traenadjupet at 66 n reinvestigation of earlier 14c coral chronologies suggests that coral ecosystems widely established themselves across the entire 3000 km long scandinavian shelf prior to 10 ka bp the earliest occurrence of madrepora oculata at 2 4 ka bp suggests a late holocene colonization of the norwegian shelf which is linked to a prominent mound growth hiatus in traenadjupet 64 n mound growth rates near the northern biogeographic boundary of l pertusa with up to 614 cm ka 1 during certain growth periods are much higher than the previously reported fastest rates of 220 cm ka 1 from the irish margin contemporaneous rapid fjordbasin sedimentation is slower with 63 cm ka 1 matrix 14c ages overlap with coral 14c ages from the same horizon this indicates rapid framework construction and efficient trapping of background sediment hiatuses are frequent in on mound sediments and only short periods of coral growth are recorded coupled 14c and end values indicate a persistent holocene inflow of the north atlantic current in stjernsund but also deglacial meltwater mixing during the early holocene prior to 9 5 ka bp reservoir ages are overall close to the surface marine reservoir age but r is highly localized

deep sea coral geochemistry implication for the vital effect abstract deep sea corals hold a great potential as a key to important aspects of paleoceanography for at least two reasons 1 they offer temporal high resolution records of deep sea environment because they have growth banding structures 2 and they are well suited for studying vital effects because the deep sea environment does not change over short time scales however the relationship between the chemical composition of deep sea coral skeletons and environmental factors is not well understood in this study the chemical composition of deep sea corals was measured in bulk individuals and along skeletal micro structures among the bulk individuals 18 o value and sr ca ratio show a negative but weak correlation with ambient temperature on the other hand the mg ca ratio has a positive weak correlation with the temperature large variations were found among samples collected from similar temperature the variation is up to 3 8 for 18 o 0 9 mmol mol for sr ca ratios and 0 78 mmol mol for mg ca ratios among samples with ambient average temperature within 1 c this variation may be due to a large vital effect the centers of calcification cocs which were formed at high calcification rate have lower sr ca u ca and higher mg ca ratios than surrounding fasciculi this chemical distribution supports the model that elemental incorporation depends on calcification rate this suggests that calcification rate is a very important factor for the chemical composition in deep sea corals and is one of the most significant mechanisms of the vital effect because of this large vital effect further investigations are essential to use the deep sea coral as a temperature proxy

eastern north atlantic deep sea corals tracing upper intermediate water δ14c during the holocene abstract paired 230th u and 14c dating were performed on deep sea corals lophelia pertusa and madrepora oculata from the northeastern north atlantic at 730 m bsl to investigate past changes of the thermohaline circulation these were estimated using the 14c value of the upper intermediate waters based on the 14c ages of the top and base of each coral where possible and the 230th u dating the reliability of these estimates was checked by dating two very young corals of the species l pertusa one of these corals collected alive in 1999 ad gave a 230th u age of 1995 4 ad after correction for non radiogenic 230th another coral the top of which dated to 1969 6 ad recorded the atmospheric 14c 12c increase due to the nuclear tests in the early 1960s the calculated 14c values from these two corals agree with those measured at geosecs station 23 in 1972 1973 ostlund et al earth planet sci lett 23 1974 69 86 and 1991 1992 nydal and gisfelos radiocarbon 38 1996 389 406 this together with the 100 aragonite content and the 234u and 230th 232th values of all the dated corals indicates that none of the corals behaved as open systems with respect to their u series nuclides and that they closely represent the water mass properties in which they lived the pre anthropogenic 14c value of the north atlantic intermediate waters was estimated at 69 4 the reservoir age varies from 400 years to 600 years and this variation is due to atmospheric 14c 12c changes a reservoir age of 610 80 years close to the pre anthropogenic value was determined from one coral dated at 10 430 120 cal yr bp when the global sea level was approximately at 35 m bard et al nature 382 1996 241 244 this suggests a modern like pattern of the oceanic circulation prevailed in the northeast atlantic ocean at this time although the deglaciation was not completely achieved

solution and laser ablation inductively coupled plasma mass spectrometry measurements of br i pb mn cd zn and b in the organic skeleton of soft corals and black corals proxy records can be derived from soft corals and black corals using minor and trace element measurements of the organic skeleton of these corals here concentrations of br i pb mn cd zn and b in the organic skeleton were determined using solution inductively coupled plasma mass spectrometry icp ms in one black coral from 5 m depth and two soft corals from 85 and 105 m depth collected from a reef offshore of palau in the western tropical pacific solution icp ms results indicate that concentrations of some elements vary as expected with depth cd and mn while others are taxa specific i or colony specific br pb zn and b the intensities of the same elements normalized to 13c were also measured at high resolution using laser ablation la icp ms along radial transects covering the lifespan of the colonies the results here indicate that high resolution la icp ms elemental records in black corals could be more fully developed for paleoceanographic reconstructions in contrast results of the laser transects from the two soft corals were not reproducible for any of the elements and no discernible patterns were detected that could be developed into reliable proxy records using the current la icp ms method

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

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

a high resolution record of atmospheric 14c based on hulu cave speleothem h82 abstract the development of a calibration of atmospheric radiocarbon 14c is a significant scientific goal because it provides the means to link the numerous 14c dated paleoclimate records to a common timescale with absolutely dated records and thereby improve our understanding the relationships between the carbon cycle and climate change currently few calibration datasets that directly sample the atmospheric 14c reservoir are available beyond the end of the dendro dated holocene tree ring record at 12 6 kyr bp before 1950 ad in the absence of suitable true atmospheric records 14c calibrations beyond this age limit are based largely on marine data that are complicated by the marine reservoir effect which may have varied over the glacial cycle in this paper we present a high resolution record of u th series and 14c measurements from hulu cave speleothem h82 spanning 10 6 26 8 kyr bp corrections for detrital 230th are negligible and the contribution of 14c free geologic carbon to the speleothem calcite is small 5 6 and is stable across major climate shifts the time series provides a 16 kyr record of atmospheric 14c as well as an updated age model for the existing hulu cave 18o record the 14c data are in good overall agreement with existing marine and terrestrial 14c records but comparisons with the cariaco basin marine 14c record through the deglacial interval reveal that the cariaco reservoir age appears to have varied during parts of the younger dryas and heinrich stadial 1 cold events this highlights the importance of developing extended high resolution marine and terrestrial 14c records as a means of detecting changes in ocean circulation over the glacial cycle

uranium series dating and growth characteristics of the deep sea scleractinian coral enallopsammia rostrata from the equatorial pacific the deep sea coral enallopsammia rostrata a member of the dendrophylliidae family is a major structure forming species that creates massive dendroid colonies up to 1 m wide and 0 5 m tall living colonies of e rostrata have been collected using the pisces submersibles from three locations from 480 to 788 m water depth in the line islands similar to 160 degrees w in the equatorial pacific we have applied to these colonies a high sensitivity low blank technique to determine u series ages in small quantities 70 15 mg of modern and near modern calcareous skeletons using mc icp ms multi collector inductively coupled plasma mass spectrometer the application of this method to living slow growing colonies from a range of sites as well as the observations of axial growth patterns in thin sections of their skeletons offer the first expanded and well constrained data on longevity growth pattern and mean growth rates in e rostrata absolute dated specimens indicate life spans of colonies ranging from 209 8 yrs to 605 7 yrs with radial growth rates from 0 012 to 0 072 mm yr 1 and vertical extension rates from 0 6 to 1 9 mm yr 1 the linear growth rates reported here are lower than those reported for other deep sea scleractinian corals lophelia pertusa and madrepora oculata the u series dating indicates that the growth ring patterns of e rostrata are not consistent with annual periodicity emphasizing the importance of absolute radiometric dating methods to constrain growth rates slow accretion and extreme longevity make this species and its habitat especially vulnerable to disturbances and impacts from human activities this dating method combined with observation of growth patterns opens up new perspectives in the field of deep sea corals since it can provide quantitative estimates of growth rates and longevity of deep sea corals in general

rapid radiocarbon 14c analysis of coral and carbonate samples using a continuous flow accelerator mass spectrometry cfams system 1 radiocarbon analyses of carbonate materials provide critical information for understanding the last glacial cycle recent climate history and paleoceanography methods that reduce the time and cost of radiocarbon 14c analysis are highly desirable for large sample sets and reconnaissance type studies we have developed a method for rapid radiocarbon analysis of carbonates using a novel continuous flow accelerator mass spectrometry cfams system we analyzed a suite of deep sea coral samples and compared the results with those obtained using a conventional ams system measurement uncertainty is 0 02 fm or 160 ryr for a modern sample and the mean background was 37 800 ryr radiocarbon values were repeatable and in good agreement with those from the conventional ams system sample handling and preparation is relatively simple and the method offered a significant increase in speed and cost effectiveness we applied the method to coral samples from the eastern pacific ocean to obtain an age distribution and identify samples for further analysis this paper is intended to update the paleoceanographic community on the status of this new method and demonstrate its feasibility as a choice for rapid and affordable radiocarbon analysis

growth rate of a deep sea coral using 210pb and other isotopes abstract a deep sea coral was studied to determine its growth rate and to reconstruct time histories of isotope distributions in the deep ocean the specimen was collected at a depth of 600 m off little bahama banks using the deep submergence vehicle dsv alvin the growth rate of the calcitic coral trunk was determined using excess 210pb measured in concentric bands excess 210pb was found in the outer half of the coral s radius and a growth rate of 0 11 0 02 mm a is calculated assuming a constant growth rate during formation of the entire trunk an age of 180 40 a is estimated for the coral the decrease observed in radiocarbon activities measured on the same bands griffin and druffel 1989 concurred with the growth rate estimated from excess 210pb activity 239 240pu activities measured by mass spectrometry were also detected in the outer two bands of the coral as expected from the 210pb chronology stable oxygen and carbon isotopes measured in samples collected by a variety of techniques are positively correlated this is evidence of a variable kinetic isotope effect most likely caused by variations in the skeletal growth rate long lived corals such as this specimen have the potential for serving as integrators of seawater chemistry in the deep sea over several century timescales

nd isotopic composition of water masses and dilution of the mediterranean outflow along the southwest european margin nd isotopic compositions epsilon nd of seawater profiles and deep sea corals collected off the coast of iberia and from the bay of biscay were measured 1 to constrain the nd isotopic composition of water masses along the southwest european margin 2 to track the mediterranean outflow water mow during its northward propagation and 3 to establish hydrological changes during the last 1500 years the eastern north atlantic central water enacw is characterized by nd isotopic composition of around 12 0 mediterranean sea water msw is collected from 800 and 1200 m depth and is characterized by epsilon nd values ranging from 10 9 off the coast of iberia to 11 6 in the bay of biscay these epsilon nd results suggest a strong dilution of the pure mow at the strait of gibraltar epsilon nd 9 4 of approximately 40 and 30 along its northward circulation pathway essentially with a contribution from enacw at around 2000 m depth epsilon nd water profiles display the occurrence of a nonradiogenic water mass epsilon nd 13 originating from the labrador sea labrador sea water fossil deep sea corals dated between 84 and 1500 years display nd isotopic compositions that vary moderately from present day seawater values suggesting a weaker influence of mow in the formation of msw during the dark ages and the little ice age these recent cold events seem to be associated with a reduction in the northward penetration of msw which may result from a greater eastward extension of the middepth subpolar gyre and or a reduction of msw formation likely tied to a variation in deep mediterranean water production

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

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

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

uranium series and radiocarbon geochronology of deep sea corals implications for southern ocean ventilation rates and the oceanic carbon cycle we present new uranium series and radiocarbon measurements for deep sea corals from the southern ocean these data are used to reconstruct ventilation ages both at present and at the end of the last glacial period approximately 16 500 years ago we apply an improved two component mixing approach to correct uranium series dates for contaminant thorium and protactinium present in oxide coatings calculated seawater radiocarbon values for contemporary samples decrease with depth in the water column and agree with direct seawater radiocarbon measurements for this area this indicates that deep sea corals can accurately record seawater radiocarbon distributions two of three glacial samples experienced open system uranium series systematics however a third sample from the drake passage yields concordant thorium and protactinium dates as well as seawater values for initial 234u 238u this coral yields a ventilation age that is approximately 20 40 greater than modern values for its location this increase is consistent with published deep sea coral and calibrated planktonic benthic foraminifera radiocarbon data suggesting that the glacial oceans as a whole may have been substantially less ventilated presumably due to decreased formation of north atlantic deep water an overall decrease in oceanic mixing rates could have contributed to lower dissolved carbon in surface ocean water and lower atmospheric pco2 during the past glacial period

primary u distribution in scleractinian corals and its implications for u series dating in this study we use microsampling techniques to explore diagenetic processes in carbonates these processes are important as they can affect the accuracy of u series chronometry fission track maps of deep sea scleractinian corals show a threefold difference between the minimum and maximum u in modern corals which is reduced to a factor of 2 in fossil corals we use micromilling and mc icp ms to make detailed analyses of the u and 234uinitial distributions in corals from 218 ka to modern within each fossil coral we observe a large range of 234uinitial values with high 234uinitial values typically associated with low u a simple model shows that this observation is best explained by preferential movement of alpha decay produced 234u atoms alpha recoil diffusion open system addition of 234u may occur when alpha recoil diffusion is coupled with a high u surface layer such as organic material this process can result in large whole coral 234uinitial elevations with little effect on the final age the diagenetic pathways that we model are relevant to both shallow water and deep sea scleractinian corals since both exhibit primary u heterogeneity and may be subject to u addition

neodymium isotopic composition of deep sea corals from the ne atlantic implications for past hydrological changes during the holocene the nd isotopic composition of deep sea corals lophelia pertusa and madrepora oculata located on the rockall bank at a depth of 747 m was investigated to reconstruct past hydrological changes of the north atlantic the coral 3nd values ranged from 15 4 to 11 9 and demonstrate strong and systematic changes during the holocene most likely reflecting changes in seawater 3nd the 3nd record displays a general trend with a small decrease from 14 1 to 15 2 during the time interval from 9400 to 6000 yrs followed by an abrupt increase in 3nd towards more radiogenic 3nd values ranging from 13 9 to 11 9 these variations imply strong changes in the relative proportions of upper intermediate waters originating in the subtropical and subpolar atlantic which are characterised today by 3nd of 10 4 11 5 and 15 respectively therefore we suggest that the 3nd of reef frameworks forming deep sea corals reveals strong evidence of systematic mid holocene changes in mid depth subpolar gyre circulation a wider eastward extension of the subpolar gyre induced by stronger westerlies and a less intense deepwater formation in the labrador sea occurred during the early mid holocene supposedly larger amounts of freshwater from the subpolar gyre were carried eastward underneath the nordic seas similar to today a freshening of the subpolar gyre may have been offset by a reinforcement of the nac and higher salinities of water masses contributing to the nordic inflow beyond 6000 yrs a weakening of the subpolar gyre triggered an extension of saline subtropical water masses to the eastern north atlantic increasing the potential for labrador sea deep convection and reducing the contribution of subpolar atlantic waters to the basin scale re circulation at the upper intermediate depth and to the nordic seas inflow such modifications could have affected deep water convective activity in the northern hemisphere through a redistribution of freshwater from the early holocene melting of northern hemisphere ice sheets

neodymium isotopic composition of the oceans a compilation of seawater data a global compilation of the neodymium isotopic composition of seawater is presented with 880 data points it confirms the gradual end increase for intermediate deep water masses from the northwest north atlantic via the austral and indian oceans to the pacific this confirms the usefulness of this tracer for studying large scale oceanic circulation the compilation stresses the need for documenting the oceans south of 30 s from which less than 4 of the data are derived the associated neodymium concentrations display heterogeneous vertical gradients among major oceanic basins in addition to particle remineralization along the global thermohaline circulation the database suggests that basin size differences also contribute to that heterogeneity

southern ocean evidence for reduced export of north atlantic deep water during heinrich event 1 deep sea corals form unique high resolution archives of ocean circulation that can be dated using the decay of uranium to thorium they are abundant in the southern ocean and can provide unprecedented insights into ocean circulation and ocean chemistry on sub millennial time scales in areas where application of traditional paleoceanographic proxies is difficult here we present the first coupled neodymium nd isotope and radiocarbon data from deep sea corals in the drake passage southern ocean adding new constraints on ocean circulation during the last heinrich event h1 16 7 ka the modern day drake passage water column is homogeneous with respect to nd isotopes expressed in epsilon units nd its isotopic value of close to 9 is largely controlled by the mixture of north atlantic deep water and pacific deep water the aragonite of modern drake passage corals reflects this water column value whereas a fossil coral from h1 is significantly higher at 6 4 0 4 we interpret this 2 5 unit shift as a reduction in the influence of north atlantic sourced nd in the southern ocean during h1 this interpretation is supported by a series of radiocarbon analyses on the same sample and is consistent with a twofold or greater reduction in export of north atlantic waters from the atlantic basin combining analyses of radiocarbon and nd isotopes on u series dated deep sea coral skeletons holds great potential for quantification of past ocean ventilation rates

dating the death of mediterranean deep sea scleractinian corals abstract several c 14 datings of deep sea scleractinians indicate that the major decline of this coral population in the mediterranean sea took place around 30 000 15 000 yrs b p it is probable that the most important factor causing such an event was the rise of temperature that either directly affected the physiology of the corals or more likely triggered unfavorable hydrological conditions

movement of deep sea coral populations on climatic timescales during the past 40 000 years global climate has moved into and out of a full glacial period with the deglaciation marked by several millennial scale rapid climate change events here we investigate the ecological response of deep sea coral communities to both glaciation and these rapid climate change events we find that the deep sea coral populations of desmophyllum dianthus in both the north atlantic and the tasmanian seamounts expand at times of rapid climate change however during the more stable last glacial maximum the coral population globally retreats to a more restricted depth range holocene populations show regional patterns that provide some insight into what causes these dramatic changes in population structure the most important factors are likely responses to climatically driven changes in productivity o 2 and co 3 2

a biological origin for climate signals in corals trace element vital effects are ubiquitous in scleractinian coral skeletons 1 laser ablation icp ms was used to analyze mg sr and u at fine hundreds of microns and seasonal spatial scales in the reef coral porites and the non photosynthetic deep sea corals lophelia oculina and desmophyllum tropical corals display strong seasonal correlations between mg sr and u even when normal cycles are perturbed by unknown factors an inverse relationship between mg and u is a universal feature of all the corals but is much larger in deep corals despite stable environmental conditions this correlation originates from two aragonitic skeletal types mg rich opaque centers of calcification and u rich large translucent crystals the mg rich material probably precipitates rapidly and corresponds to materials strongly deficient in 18o and 13c compared to isotopic equilibrium combined these observations imply that varying proportions of the two skeletal types may account for most of the temperature or climate signal in tropical corals as well as anomalous vital effects

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

temporal variability of the atlantic meridional overturning circulation at 26 5 n the vigor of atlantic meridional overturning circulation moc is thought to be vulnerable to global warming but its short term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain we combine continuous measurements of the moc beginning in 2004 using the purposefully designed transatlantic rapid climate change array of moored instruments deployed along 26 5 n with time series of gulf stream transport and surface layer ekman transport to quantify its intra annual variability the year long average overturning is 18 7 5 6 sverdrups sv range 4 0 to 34 9 sv where 1 sv a flow of ocean water of 106 cubic meters per second interannual changes in the overturning can be monitored with a resolution of 1 5 sv

radiocarbon variability in the western north atlantic during the last deglaciation we present a detailed history of glacial to holocene radiocarbon in the deep western north atlantic from deep sea corals and paired benthic planktonic foraminifera the deglaciation is marked by switches between radiocarbon enriched and depleted waters leading to large radiocarbon gradients in the water column these changes played an important role in modulating atmospheric radiocarbon the deep ocean record supports the notion of a bipolar seesaw with increased northern source deep water formation linked to northern hemisphere warming and the reverse in contrast the more frequent radiocarbon variations in the intermediate deep ocean are associated with roughly synchronous changes at the poles

synchronous radiocarbon and climate shifts during the last deglaciation radiocarbon data from the cariaco basin provide calibration of the carbon 14 time scale across the period of deglaciation 15 000 to 10 000 years ago with resolution available previously only from holocene tree rings reconstructed changes in atmospheric carbon 14 are larger than previously thought with the largest change occurring simultaneously with the sudden climatic cooling of the younger dryas event carbon 14 and published beryllium 10 data together suggest that concurrent climate and carbon 14 changes were predominantly the result of abrupt shifts in deep ocean ventilation

the southern ocean s role in carbon exchange during the last deglaciation changes in the upwelling and degassing of carbon from the southern ocean form one of the leading hypotheses for the cause of glacial interglacial changes in atmospheric carbon dioxide we present a 25 000 year long southern ocean radiocarbon record reconstructed from deep sea corals which shows radiocarbon depleted waters during the glacial period and through the early deglaciation this depletion and associated deep stratification disappeared by 14 6 ka thousand years ago consistent with the transfer of carbon from the deep ocean to the surface ocean and atmosphere via a southern ocean ventilation event given this evidence for carbon exchange in the southern ocean we show that existing deep ocean radiocarbon records from the glacial period are sufficiently depleted to explain the 190 per mil drop in atmospheric radiocarbon between 17 and 14 5 ka

correlation of boron isotopic composition with ultrastructure in the deep sea coral lophelia pertusa implications for biomineralization and paleo ph using the crpg cnrs cameca 1270 ion microprobe facility we have measured boron isotopic compositions b 11 b 10 in different ultrastructural components of the deep sea aragonitic scleractinian coral lophelia pertusa we observe a systematic difference in b isotopic composition between the early mineralization zone emz and adjacent fibrous skeleton in emz the measured delta 11 b values are consistently low fibrous aragonite is characterized by systematically higher delta 11 b values but also displays b isotopic heterogeneity associated with specific growth bands in the calyx wall the magnitude of the observed b isotopic variations cannot be explained by changes in environmental conditions and is likely caused by biological processes involved in the biomineralization of new skeleton i e vital effects the observed b isotopic variations are opposite to the predictions of geochemical models for vital effects these models are based on the idea that stable isotopic fractionations including c and o in coral skeleton are driven by changes in ph of the fluid from which the skeleton is presumed to precipitate our data indicate that ph variations are not responsible for the observed stable isotopic fractionations geochemical models therefore do not provide an adequate framework within which to understand coral skeletal formation without a better understanding of these processes the use of b isotopic composition to reconstruct paleo ph variations in the oceans must be considered problematic at least as far as lophelia pertusa is concerned

bamboo coral ba ca calibration of a new deep ocean refractory nutrient proxy abstract it is poorly understood how intermediate water masses are affected by decadal scale climate via biogeochemical cycling export production and changes in circulation ventilation to this end a geochemical nutrient proxy from deep sea bamboo corals would provide decadal to centennial scale records of deep and intermediate water nutrient dynamics seawater barium basw has a nutrient like distribution in the water column similar to silicate so ba ca records in foraminifera shallow water surface corals and other deep sea corals have been used to trace refractory nutrients here we present the first calibration of a nutrient proxy from skeletal barium preserved in the calcitic internodes of deep sea bamboo corals collected from intermediate water depths a calibration was calculated from a broadly distributed suite of isidella and keratoisis corals spanning a silicate and basw gradient n 33 corals 300 2800 m ba ca b a m b o o c o r a l mol mol 0 079 0 008 ba sw nmol kg 4 205 0 870 r 2 0 77 n 33 the strong linear correlation between ba cabamboo coral and basw suggests that coral ba ca is a reliable recorder of seawater barium and therefore silicate we find a distribution coefficient dba for ba cabamboo coral of 1 3 0 2 similar to that of other corals surface and deep sea dwelling and inorganic calcium carbonate precipitation experiments dba 1 2 1 5 this suggests that ba incorporation is primarily driven by cationic substitution in bamboo corals and holds promise as a globally applicable refractory nutrient proxy we find interannual decadal scale variability in a ba cabamboo coral timeseries from a california margin coral san juan seamount 1295 m these data suggest that additional high resolution ba cabamboo coral records may reveal a connection between regional scale intermediate water biogeochemistry and low latitude surface ocean atmospheric climate