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

growth and high resolution paleoenvironmental signals of rhodoliths coralline red algae a new biogenic archive we investigated rhodoliths coralline red algae from a subtropical locality in the gulf of california lithothamnium crassiusculum and a subarctic locality in newfoundland lithothamnium glaciale for their potential as paleoenvironmental archives using microanalytical geochemical techniques to measure variations in 18o mg and ca rhodoliths are potentially well suited as recorders of shallow water paleoenvironmental signals because they 1 have worldwide distribution from the tropics to polar regions 2 are long lived from decades to centuries and 3 display well developed growth bands our results indicate that rhodolith growth bands preserve ultrahigh resolution records of paleoceanographic paleoclimatic change and likely constitute an important new archive for reconstructing the paleoenvironmental history of littoral neritic areas in which these algae are found the 18o content of individually sampled rhodolith growth bands ranges from 2 4 to 4 6 in l crassiusculum and from 3 2 to 0 3 in l glaciale in both cases the range of 18o values suggests a slightly lower amplitude of variation in sea surface temperature than that actually measured in the ocean at the two study sites both l crassiusculum and l glaciale show a negative offset from isotopic equilibrium electron microprobe analysis of magnesium and calcium in growth bands reveals cyclic variations with values ranging between 7 7 18 5 mol mgco3 in l glaciale and 13 2 22 5 mol mgco3 in l crassiusculum in addition electron microprobe element maps highlight individual growth bands provide a powerful approach to study rhodolith formation and indicate that the specimens we analyzed have vertical growth rates of 250 450 m yr

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

reprint of comparison of climate signals obtained from encrusting and free living rhodolith coralline algae abstract coralline algae have been used for sclerochronological studies throughout the last decade these studies have focused on two different growth morphologies of the photosynthetic coralline algae massive crusts forming small buildups on hard substrate and free living branching algal nodules known as rhodoliths the latter are generally found on soft substrate where they are frequently overturned by water movement and bottom feeding organisms leaving one side of the rhodolith partially buried in the sediment at any given time here we test whether either of these growth morphologies is more suitable for proxy reconstructions by comparing mg ca ratios a temperature proxy in multiple replicates of rhodoliths of lithothamnion glaciale and in rhodoliths as well as encrusting specimens of clathromorphum compactum with both species being widespread throughout the temperate and arctic regions we have chosen two north atlantic localities at nuuk fjord greenland subarctic and off the southeastern coast of newfoundland canada temperate for this study two to three mg ca ratio transects spanning 18 years of growth were analysed on multiple specimens with encrusting morphologies and along different sides of rhodoliths using laser ablation inductively coupled mass spectrometry and compared to remotely sensed sea surface temperature sst data the length of the common time span used for comparison was limited by growth interruptions in rhodoliths furthermore our comparison is based on the assumption that rhodolith growth increments are annual an assumption that has recently been challenged by mesocosm studies monthly mg ca values from multiple transects within each individual were compared and in samples from nuuk fjord significant correlations were found in 4 of 4 encrusting c compactum 4 of 4 c compactum rhodoliths and 2 of 3 l glaciale rhodoliths in newfoundland significant correlations were found in 6 of 6 encrusting c compactum comparisons average r 0 61 p

a high resolution radiolarian derived paleotemperature record for the late pleistocene holocene in the norwegian sea polycystine radiolarians are used to reconstruct summer sea surface temperatures sssts for the late pleistocene holocene 600 13 400 14c years bp in the norwegian sea at 13 200 14c years bp the ssst wasclose to the average holocene ssst 12 c it then gradually dropped to 7 1 c in the younger dryas nearthe younger dryas holocene transition 10 000 14c years bp the ssst increased 5 c in about 530 years four abrupt cooling events with temperature drops of up to 2 1 c are recognized during the holocene at 9340 7100 8200 calendar years event 6400 and 1650 14 c years bp radiolarian sssts and the isotopic signalfrom the gisp2 ice core are strongly coupled stressing the importance of the norwegian sea as a mediator ofheat precipitation exchange between the north atlantic the atmosphere and the greenland ice sheet radiolarian and diatom derived sssts display similarities with the former not showing the recently reportedholocene cooling trend

coralline red algae as high resolution climate recorders most high resolution proxy based paleoclimate research has concentrated on tropical oceans while mid and high latitude marine regions have received less attention despite their importance in the global climate system at present sclerochronological analyses of bivalve mollusks supply the bulk of annual to subannual resolution extratropical marine climate data even though interpretation is complicated by a slowdown of growth with increasing shell age hence in order to address the need for additional high resolution proxy climate data from extratropical regions we conducted the first year long in situ field calibration of the coralline red alga clathromorphum compactum in the gulf of maine united states coralline red algae are widely distributed in coastal regions worldwide and individual calcified plants can live continuously for several centuries in temperate and subarctic oceans stable oxygen isotopes extracted at subannual resolution from growth increments of monitored specimens of c compactum relate well to in situ measured sea surface temperatures during the may to december calcification period highlighting the suitability of coralline red algae as an extratropical climate archive furthermore there is a strong correlation between a 30 yr 18 o record of c compactum and an instrumental sea surface temperature record r 0 58 p 0 0008 and a proxy reconstruction derived from the bivalve arctica islandica collected in the central gulf of maine r 0 54 p 0 002

growth rate and potential climate record from a rhodolith using 14c accelerator mass spectrometry rhodoliths free living calcareous red algae create large and diverse habitats worldwide although these plants are abundant and ecologically important little is known about their growth rate we determined the growth rate for an individual rhodolith lithothamnium crassiusculum from the southern gulf of california through 14 c analysis using accelerator mass spectrometry ams to be 0 6 mm yr 21 this growth rate suggests large l crassiusculum which have been found with radii in excess of 6 cm may live over 100 yr declines in the d 14 c record associated with the large el nino events of 1957 1982 and 1992 indicate 14 c analysis may lead to identification of important climate events in the more distant past the ability to determine changes in past ocean circulation related to changes in past climatic conditions through ams 14 c analysis of rhodoliths would increase the geographic range of available climate records from the tropical oceans to the entire global ocean and potentially allow for the determination of past climate conditions from rhodoliths in fossil beds rhodoliths red nongeniculate calcareous algae occupy large areas of the world s oceans forming the basis of di verse and ecologically important communities bosence 1983 foster et al 1997 however little is known about the rate at which these communities develop their rate of re covery after natural or anthropogenic disturbances or their effects on the global carbon budget because some rhodo liths are long lived they also have the potential to provide information on past oceanic conditions as they grow these plants deposit calcium carbonate which should contain chemical and isotopic records reflecting environmental con ditions previous isotopic studies on coral and mollusks found that the amount of 14 c deposited as a part of the total carbon in biogenic carbonate records the 14 c concentration in the ocean water surrounding the organism e g druffel and linick 1978 nozaki et al 1978 druffel and suess 1983 this type of 14 c record should also be found in the carbonate of rhodoliths and can potentially be used as a re cord of climate variation rhodoliths are found in many locations and environ ments around the world ranging from polar deep water to tropical shallows bosence 1983 in the subtropical gulf

reconstructing mid to high latitude marine climate and ocean variability using bivalves coralline algae and marine sediment cores from the northern hemisphere quantifying the role and contribution of the world s oceans in past present and future global change is an essential goal in climate paleoclimate and environmental studies although the global oceans interact and influence climate greatly the marine environment is substantially under represented in key climate assessment reports especially during the last millennium ipcc 2007 see palaeoclimate chapter 6 6 the last 2000 years the under representation of marine records in key climate documents likely results from the often imprecise chronologies associated with many marine based archives which greatly hinders singular climate comparisons lag lead phasing relationships with well dated and or annually resolved archives however several marine archive records have excellent chronological constraint in particular many marine bivalve taxa and coralline algae have annual increments that form within their carbonate framework that can be used to establish an absolutely dated chronology via cross dating techniques from the marine environment additionally in some cases where sedimentation rates are high and alternative chronological dating methods exist e g tephrochronology other than radiocarbon measurements often greater than 40 years uncertainty sediment archives can provide continuous sub decadal records of environmental change for centuries to millennia this brief introductory article and accompanying special issue will focus on the utilization of bivalves coralline algae and high resolution marine sediment cores in paleoclimate and environmental studies within the most recent millennium with a focus on the northern hemisphere

reconstructing greenland ice sheet runoff using coralline algae the greenland ice sheet gris contains the largest store of fresh water in the northern hemisphere equivalent to 7 4 m of eustatic sea level rise but its impacts on current past and future sea level ocean circulation and european climate are poorly understood previous estimates of gris melt from 26 yr of satellite observations and temperature driven melt models over 48 yr show increasing melt trends there are however no runoff data of comparable duration with which to validate the relationship between the spatial extent of melting and runoff or temperature based runoff models further longer runoff records are needed to extend the melt pattern of greenland to centennial timescales enabling recent observations and trends to be put into a better historical context we have developed a new gris runoff proxy by extracting information on relative salinity changes from annual growth bands of red coralline algae we observed significant negative relationships between historic runoff relative salinity and marine summer temperature in sondre stromfjord greenland we produce the first reconstruction of runoff from a section of the gris that discharges into sondre stromfjord over several decades 1939 2002 and record a trend of increasing reconstructed runoff since the mid 1980s in situ summer marine temperatures followed an equivalent trend we suggest that since a d 1939 atmospheric temperatures have been important in forcing runoff these results show that our technique has significant potential to enhance understanding of runoff from large ice sheets as it will enable melt reconstruction over centennial to millennial timescales

a record of mining and industrial activities in new caledonia based on trace elements in rhodolith forming coralline red algae abstract we investigate the ability of coralline red algae to record historical nickel mining activity that occurred between the early 1960s and 1981 in the coulee river watershed southwest new caledonia laser ablation inductively coupled plasma mass spectrometry la icpms was used to determine high resolution sub annual variations of trace metal ratios mn ca fe ca ni ca and co ca in three 45 years old free living forms of the rhodolith coralline red alga sporolithon durum from ricaudy reef in the inner lagoon of new caledonia 15 km from the coulee river mouth we find increased mn ca and fe ca ratio values track the intensity of mining in the coulee river catchment whereas ni ca ratio values appear more sensitive to the ore type saprolite versus laterite that were targeted during two separate stages of mining activity mn ca fe ca and ni ca decrease following the cessation of mining in 1981 but did not reach current values until 10 years after that date surprisingly co ca variations do not correlate with mining activity but rather increase steadily through the record period we argue this relates to nickel refining and smelting activity over the past half century our results further suggest that the local inter annual rainfall variability may influence the metal concentrations recorded in the rhodoliths during the period of intense mining activity but the link between metal uptake and rainfall is not entirely clear for the entire growth period of the rhodoliths

late glacial and holocene palaeoceanography of the north icelandic shelf high resolution gravity cores and box cores from the north icelandic shelf have been studied for palaeoceanographic history based on lithological and biostratigraphical foramin iferal data results from two outer shelf cores covering the last 13 6 k 14 c yr bp are presented in this paper the sediments accumulated in north south trending basins on each side of the kolbeinsey ridge at water depths of ca 400 m sedimentation rates up to 1 5 m kyr 1 are observed during the late glacial and holocene the vedde and saksunarvatn tephras are present in the cores as well as the hekla 1104 a new tephra kol gs 2 has been identified and dated to 13 4 k 14 c yr bp and another tephra geochemically identical to the borrobol tephra has been found at the same level at present the oceanographic polar front is located on the north icelandic shelf which experiences sharp oceanographic surface boundaries between the cold east icelandic current and the warmer irminger current past changes in sedimentological and biological processes in the study area are assumed to be related to fluctuations of the polar front the area was deglaciated before ca 14 kyr bp but there is evidence of ice rafting up to the end of the gs 1 greenland stadial 1 younger dryas period increasing again towards the end of the holocene foraminiferal studies show a relatively strong gs 2 pre 13 kyr bp palaeo irminger current followed by severe cooling and then by unstable conditions during the remainder of the gi 1 greenland interstadial 1 bolling allerod and gs 1 younger dryas another cooling event occurred during the preboreal before the holocene current system was established at about 9 kyr bp after a climatic optimum between 9 and 6 kyr bp the climate began to deteriorate and fluctuate copyright 2000 john wiley sons ltd

coralline algae are global palaeothermometers with bi weekly resolution abstract high resolution palaeoclimate data are required for the holocene to resolve differences recorded by current proxies the pole to pole distribution of rhodoliths coralline algae with their annual and sub annual calcite bands make these attractive candidates for such a role these bands contain climate information in the form of elemental traces in situ temperature ist was recorded at two rhodolith beds for 1 5 years the concentrations of mgco 3 and srco 3 mol deposited in lithothamion glaciale and phymatolithon calcareum over this 18 month period were determined using electron and ion microprobes highly significant linear relationships exist between mg sr and ist as well as sea surface temperature calibration between mg concentration and ist was used to obtain a 2 year temperature profile from a subfossil rhodolith thallus indicating half the seasonal peak to peak temperature amplitude earlier during the holocene than the present day both slow growing species 1 allowed sampling resolutions of 23 year 1 which is equivalent to 1 reading every 2 weeks sub monthly mg and sr records in rhodoliths make them unique globally distributed palaeothermometers which may help refine regional climate histories during the holocene

exploring some issues in acoustic full waveform inversion the least squares error measures the difference between observed and modelled seismic data because it suffers from local minima a good initial velocity model is required to avoid convergence to the wrong model when using a gradient based minimization method if a data set mainly contains reflection events it is difficult to update the velocity model with the least squares error because the minimization method easily ends up in the nearest local minimum without ever reaching the global minimum several authors observed that the model could be updated by diving waves requiring a wide angle or large offset data set this full waveform tomography is limited to a maximum depth here we use a linear velocity model to obtain estimates for the maximum depth in addition we investigate how frequencies should be selected if the seismic data are modelled in the frequency domain in the presence of noise the condition to avoid local minima requires more frequencies than needed for sufficient spectral coverage we also considered acoustic inversion of a synthetic marine data set created by an elastic time domain finite difference code this allowed us to validate the estimates made for the linear velocity model the acoustic approximation leads to a number of problems when using long offset data nevertheless we obtained reasonable results the use of a variable density in the acoustic inversion helped to match the data at the expense of accuracy in the inversion result for the density

reefal coralline algal build ups within the arctic circle morphology and sedimentary dynamics under extreme environmental seasonality abstract carbonate frameworks secreted by phototrophic organisms within the arctic circle are not well documented underwater surveys of the inner shelf off troms northern norway 70 n reveal extended fixed algal build ups which are fringed by rhodolith belts affected by storms reefd growth by coralline algae under temperature and light regimes of extreme seasonality is made possible because of a decoupling of carbon fixation during summer and utilization of stored carbon during the period of winter darkness although the annual growth of the framework constructing algae is comparatively low the annual carbonate production rate is similar to subtropical tropical counterparts because of a remarkably high standing stock early diagenetic alteration is restricted to intraparticle cementation processes which start in vivo bioerosional destruction is the dominant control on the preservation of high latitude build ups preservation of holocene autochthonous coralline algal biostromes is enhanced by rapid burial during storm events redeposition during storms is the most important process in forming a distinct sedimentary facies zonation

coralline algal growth increment widths archive north atlantic climate variability over the past decade coralline algae have increasingly been used as archives of paleoclimate information encrusting coralline algae which deposit annual growth increments in a high mg calcite skeleton are amongst the longest lived shallow marine organisms in fact a live collected plant has recently been shown to have lived for at least 850 years based on radiometric dating while a number of investigations have successfully used geochemical information of coralline algal skeletons to reconstruct sea surface temperatures less attention has been paid to employ growth increment widths as a temperature proxy here we explore the relationship between growth and environmental parameters in clathromorphum compactum collected in the subarctic northwestern atlantic results indicate that growth increment widths of individual plants are poorly correlated with instrumental sea surface temperatures sst however an averaged record of multiple growth increment width time series from a regional network of c compactum specimens up to 800 km apart reveals strong correlations with annual instrumental sst since 1950 hence similar to methods applied in dendrochronology averaging of multiple sclerochronological records of coralline algae provides accurate climate information a 115 year growth increment width master chronology created from modern collected and museum specimens is highly correlated to multidecadal variability seen in north atlantic sea surface temperatures positive changes in algal growth anomalies record the well documented regime shift and warming in the northwestern atlantic during the 1990s large positive changes in algal growth anomalies were also present in the 1920s and 1930s indicating that the impact of a concurrent large scale regime shift throughout the north atlantic was more strongly felt in the subarctic northwestern atlantic than previously thought and may have even exceeded the 1990s event with respect to the magnitude of the warming

assessing multi site δ18o climate calibrations of the coralline alga clathromorphum across the high latitude northern hemisphere abstract an increased number of climate proxy records and more refined interpretation of proxy data are crucial to improve projections of future climate at high latitudes where internal feedbacks amplify warming and established high resolution climate archives are especially sparse encrusting coralline algae are being developed as a mid to high latitude marine climate archive these long lived algae form a solid high mg calcite skeleton with annual growth bands similar to those of trees and tropical corals the oxygen isotope ratio of the algal skeleton 18oalg records local environmental and climatic factors notably sea surface temperature and seawater 18o here we assess the 18oalg climate relationship in diverse environments across the algal habitat range utilizing two species of coralline algae from the genus clathromorphum clathromorphum is widely distributed from the cold temperate north atlantic and pacific to the arctic ocean and has recently yielded numerous climate reconstructions of up to 650 years in length in this study we calibrate 18oalg of four specimens to gridded temperature and salinity data the latter a proxy for seawater 18o these specimens were collected from a variety of algal growth environments across the high latitude northern hemisphere two specimens from the aleutian archipelago one from the canadian arctic and one from the gulf of maine low winter temperatures and insolation restrict the months when algae record local climate in the 18o of their skeletons we therefore determine these response seasons by correlating monthly temperature and salinity anomalies with annual 18oalg anomalies at each site we then average gridded data over months that correlate significantly 95 confidence interval for regression with 18oalg while the timing and nature of the climate signal vary across sites we find significant relationships between 18oalg and either temperature or salinity averaged over the response season at three sites variation in local climatology among the four sites provides a physical explanation for calibration differences compounded by uncertainties stemming from the proxy chronology biological variability temporal coverage and sparse historical climate data this work takes an essential step toward reconstructing high latitude marine climate patterns with coralline algal 18o and developing algae proxy system models

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

the long lived mollusc arctica islandica a new paleoceanographic tool for the reconstruction of bottom temperatures for the continental shelves of the northern north atlantic ocean the carbonate shell of the bivalve arctica islandica has been recognized for more than a decade as a potentially important marine geochemical biorecorder owing to this species great longevity 200 years and wide geographic distribution throughout the northern north atlantic ocean a region vital to global climate and ocean circulation however until now this potential has not been realized owing to the difficulty of precisely sampling the shell of this slow growing species using newly available automated microsampling techniques combined with micromass stable isotope mass spectrometry a stable oxygen isotope record 1956 1957 and 1961 1970 has been obtained from a live captured 38 year old a islandica specimen collected near the former position of the nantucket shoals lightship 41 n 69 w the shell s 18o signal is compared with an expected signal derived from ambient bottom temperature and salinity data recorded at the lightship for the same period the results show that a islandica s 18o record 1 is in phase with its growth banding confirming the annual periodicity of this species growth bands 2 is in oxygen isotopic equilibrium with the ambient seawater 3 shows a consistent shell growth shutdown temperature of 6 c which translates into an 8 month may december shell growth period at this location and 4 records the ambient bottom temperature with a precision of 1 2 c these results add important information on the life history of this commercially important shellfish species and demonstrate that a islandica shells can be used to reconstruct inter and intra annual records of the continental shelf bottom temperature

b ca in planktonic foraminifera as a proxy for surface seawater ph boron isotope systematics indicate that boron incorporation into foraminiferal caco3 is determined by the partition coefficient k d frac left rm b rm ca right rm caco3 left rm b left rm oh right 4 rm hco 3 right rm seawater and b oh 4 hco3 seawater providing in principle a method to estimate seawater ph and pco2 we have measured b ca ratios in globigerina bulloides and globorotalia inflata for a series of core tops from the north atlantic and the southern ocean and in globigerinoides ruber white from ocean drilling program odp site 668b on the sierra leone rise in the eastern equatorial atlantic b ca ratios in these species of planktonic foraminifera seem unaffected by dissolution on the seafloor k d shows a strong species specific dependence on calcification temperature which can be corrected for using the mg ca temperature proxy a preliminary study of g inflata from southern ocean sediment core chat 16k suggests that temperature corrected b ca was 30 higher during the last glacial correspondingly ph was 0 15 units higher and aqueous pco2 was 95 atm lower at this site at the last glacial maximum the covariation between reconstructed pco2 and the atmospheric pco2 from the vostok ice core demonstrates the feasibility of using b ca in planktonic foraminifera for reconstructing past variations in ph and pco2

mg fractionation in crustose coralline algae geochemical biological and sedimentological implications of secular variation in the mg ca ratio of seawater the mg ca ratio of seawater has varied significantly throughout the phanerozoic eon primarily as a function of the rate of ocean crust production specimens of the crustose coralline alga neogoniolithon sp were grown in artificial seawaters encompassing the range of mg ca ratios shown to have existed throughout the phanerozoic significantly the coralline algae s skeletal mg ca ratio varied in lockstep with the mg ca ratio of the artificial seawater specimens grown in seawater treatments formulated with identical mg ca ratios but differing absolute concentrations of mg and ca exhibited no significant differences in skeletal mg ca ratios thereby emphasizing the importance of the ambient mg ca ratio and not the absolute concentration of mg in determining the mg ca ratio of coralline algal calcite specimens grown in seawater of the lowest molar mg ca ratio mmg ca 1 0 actually changed their skeletal mineralogy from high mg skeletal mmg ca 0 04 to low mg calcite skeletal mmg ca 0 04 suggesting that ancient calcitic red algae which exhibit morphologies and modes of calcification comparable to neogoniolithon sp would have produced low mg calcite from the middle cambrian to middle mississippian and during the middle to late cretaceous when oceanic mmg ca approached unity by influencing the original mg content of carbonate facies in which these algae have been ubiquitous this condition has significant implications for the geochemistry and diagenesis of algal limestones throughout most of the phanerozoic the crustose coralline algae s precipitation of high mg calcite from seawater that favors the abiotic precipitation of aragonite indicates that these algae dictate the precipitation of the calcitic polymorph of caco3 however the algae s nearly abiotic pattern of mg fractionation in their skeletal calcite suggests that their biomineralogical control is limited to polymorph specification and is generally ineffectual in the regulation of skeletal mg incorporation therefore the mg ca ratio of well preserved fossils of crustose coralline algae when corrected for the effect of seawater temperature may be an archive of oceanic mg ca throughout the phanerozoic magnesium fractionation algorithms that model algal skeletal mg ca as a function of seawater mg ca and temperature are presented herein the results of this study support the empirical fossil evidence that secular variation of oceanic mg ca has caused the mineralogy and skeletal chemistry of many calcifying marine organisms to change significantly over geologic time

mg ca ratios in coralline algae record northwest atlantic temperature variations and north atlantic oscillation relationships climate variability in the north atlantic has been linked in part to the north atlantic oscillation nao the nao influences marine ecosystems in the northwestern atlantic and transport variability of the cold labrador current understanding historic patterns of nao variability requires long term and high resolution climate records that are not available from instrumental data here we present the first century scale proxy record of sea surface temperature sst variability from the newfoundland shelf a region from which other annual resolution shallow marine proxies are unavailable the 116 year record was obtained from three sites along the eastern newfoundland shelf using laser ablation inductively coupled mass spectrometry determined mg ca ratios in the crustose coralline alga clathromorphum compactum the alga is characterized by a high mg calcite skeleton exhibiting annual growth increments and a century scale lifespan results indicate positive correlations between interannual variations in mg ca ratios and both station based and gridded instrumental sst in addition the record shows high spatial correlations to sst across the newfoundland shelf and the gulf of st lawrence before 1950 the mg ca proxy record reveals significant departures from gridded temperature records while the newfoundland shelf is generally considered a region of negative correlations to the nao the algal time series as well as a recent modeling study suggest a variable negative relationship with the nao which is strongest after 1960 and before the mid 1930s

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

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

high resolution analysis of trace elements in crustose coralline algae from the north atlantic and north pacific by laser ablation icp ms we have investigated the trace elemental composition in the skeleta of two specimens of attached living coralline algae of the species clathromorphum compactum from the north atlantic newfoundland and clathromorphum nereostratum from the north pacific bering sea region amchitka island aleutians samples were analyzed using laser ablation inductively coupled plasma mass spectrometry la icp ms yielding for the first time continuous individual trace elemental records of up to 69 years in length the resulting algal mg ca sr ca u ca and ba ca ratios are reproducible within individual sample specimens algal mg ca ratios were additionally validated by electron microprobe analyses amchitka sample algal sr ca u ca and ba ca ratios were compared to algal mg ca ratios which previously have been shown to reliably record sea surface temperature sst ratios of sr ca from both clathromorphum species show a strong positive correlation to temperature dependent mg ca ratios implying that seawater temperature plays an important role in the incorporation of sr into algal calcite linear sr ca sst regressions have provided positive but weaker relationships as compared to mg ca sst relationships both algal mg ca and sr ca display clear seasonal cycles inverse correlations were found between algal mg ca and u ca ba ca and correlations to sst are weaker than between mg ca sr ca and sst this suggests that the incorporation of u and ba is influenced by other factors aside from temperature

new research on the development of high resolution palaeoenvironmental proxies from geochemical properties of biogenic carbonates abstract geochemical signatures from biogenic carbonates are being increasingly employed as palaeoenvironmental proxies in turn many of these proxy archives including mollusc shells corals and otoliths have periodic growth structures which allow the reconstruction of chronologically constrained records of palaeoenvironmental variability at unparalleled high temporal resolution studying the growth and chemistry of these periodic growth structures is known as sclerochronology biogenic hard parts accumulate in geological or archaeological deposits and can be directly dated using radiometric and racemisation methods they therefore offer the opportunity for high resolution palaeoenvironmental reconstructions across many time intervals all over the globe such data are important for several reasons 1 understanding past climate and environmental change provides a means of contextualising current and future climate change and ecological disturbance 2 high resolution palaeoenvironmental records are essential for constraining testing and validating global and regional numerical climate models 3 palaeoenvironmental records from biogenic carbonates can provide an environmental framework from which to understand the behavioural changes and interactions of peoples with their environment however inter and intra species differences in growth rate physiology and environmental response can cause variations in the chemical profiles of biogenic carbonates before geochemical data is employed for palaeoenvironmental reconstructions it is thus necessary to examine modern specimens of the target species or related taxa to understand how geochemical variations are influenced by local environmental conditions kinetic and vital effects this allows the generation of quantitative and more reliable proxy records of environmental change this special issue brings together the latest research on palaeoenvironmental proxy development and validation in biogenic carbonates it includes studies on marine freshwater and estuarine organisms molluscs corals and echinoderms and on traditional as well as novel geochemical proxies the papers presented here include in situ field calibration studies laboratory growth experiments as well as methodological studies into the effects of sampling and pre treatment the geographical scope is broad encompassing both the northern and southern hemispheres including south africa south america australia asia the mediterranean sea and the north atlantic

a high resolution study of holocene paleoclimatic and paleoceanographic changes in the nordic seas 1 high resolution records from images core md95 2011 in the eastern norwegian sea provide evidence for relatively large and small scale high latitude climate variability throughout the holocene during the early and mid holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of arctic intermediate and near surface waters for the late holocene a relaxation of the atmospheric forcing resulted in increased influence of atlantic water the main changes in holocene climate show no obvious connection to changing solar irradiance and spectral analysis reveals no consistent signature for any periodic behavior of holocene climate at millennial or centennial timescales there are however indications of consistent multidecadal variability

sea surface temperatures and ice rafting in the holocene north atlantic climate influences on northern europe and greenland abstract the oceanographic conditions in the high latitude north atlantic ocean during the holocene were reconstructed through analyses of sea surface temperature sst alkenone unsaturation ratios and ice rafting mineralogy and grain size from two sediment sequences one recovered from the reykjanes ridge at 59 n and the other from the norwegian sea at 68 n comparison of our records to published ice core and terrestrial proxy climate data sets suggests that atmospheric temperature changes over northern europe and greenland were coupled to sst variability and ice rafting the records outline four major climatic phases i an early holocene thermal maximum that lasted until approximately 6 7 kyr bp ii a distinctly cooler phase associated with increased ice rafting between 6 5 and 3 7 kyr bp iii a transition to generally warmer but relatively unstable climate conditions between 3 7 and 2 kyr bp and iv a second distinct sst decline that took place between 2 and 0 5 kyr bp in contrast to the dominant control of northern hemisphere summer insolation on early holocene climate development via strong seasonality the trigger for the onset of relatively unstable climatic conditions in the north atlantic at 3 7 kyr bp is not straightforward however it is possible that this change was triggered by late holocene winter insolation increase at high northern latitude and or by inter hemispheric changes in orbital forcing the late holocene neoglaciation trend which is characteristic of numerous terrestrial archives in northern europe may not only be attributed to a gradual decrease in orbitally forced summer temperature but also to increase snow precipitation at high northern latitudes during generally milder winters

using coralline algae to understand historic marine cloud cover abstract free living coralline algae lay down growth bands formed by areas of more and less calcified cells which in certain species are associated with winter and summer growth respectively band width and cell calcification of lithothamnion glaciale from scotland were compared to annual and seasonal cloud cover and sea surface temperature sst there was a negative relationship between summer calcification the degree of cellular carbonate infilling and winter cloud cover annual and summer sst were also negatively related to summer calcification this indicates that summer calcification may be affected by the previous winter s cloud cover and that summer s year s sst no relationships between band width and cloud cover were observed a cloud cover hindcast using summer calcification and sst indicated a modest rise in cloud cover trends from 1910 to 2006 and a 12 mean year cyclicity in cloud cover however the latter may be associated with other site specific factors this study demonstrates the utility of densitometric algochronology in understanding marine temperature and cloud cover histories

comparison of climate signals obtained from encrusting and free living rhodolith coralline algae abstract coralline algae have been used for sclerochronological studies throughout the last decade these studies have focused on two different growth morphologies of the photosynthetic coralline algae massive crusts forming small buildups on hard substrate and free living branching algal nodules known as rhodoliths the latter are generally found on soft substrate where they are frequently overturned by water movement and bottom feeding organisms leaving one side of the rhodolith partially buried in the sediment at any given time here we test whether either of these growth morphologies is more suitable for proxy reconstructions by comparing mg ca ratios a temperature proxy in multiple replicates of rhodoliths of lithothamnion glaciale and in rhodoliths as well as encrusting specimens of clathromorphum compactum with both species being widespread throughout the temperate and arctic regions we have chosen two north atlantic localities at nuuk fjord greenland subarctic and off the southeastern coast of newfoundland canada temperate for this study two to three mg ca ratio transects spanning 18 years of growth were analysed on multiple specimens with encrusting morphologies and along different sides of rhodoliths using laser ablation inductively coupled mass spectrometry and compared to remotely sensed sea surface temperature sst data the length of the common time span used for comparison was limited by growth interruptions in rhodoliths furthermore our comparison is based on the assumption that rhodolith growth increments are annual an assumption that has recently been challenged by mesocosm studies monthly mg ca values from multiple transects within each individual were compared and in samples from nuuk fjord significant correlations were found in 4 of 4 encrusting c compactum 4 of 4 c compactum rhodoliths and 2 of 3 l glaciale rhodoliths in newfoundland significant correlations were found in 6 of 6 encrusting c compactum comparisons average r 0 61 p

holocene centennial to millennial scale climatic variability evidence from high resolution magnetic analyses of the last 10 cal kyr off north iceland core md99 2275 abstract high resolution magnetic analysis has been performed on the top 25 m of core md99 2275 66 33 06 n 17 41 59 w 440 m water depth from the mid outer shelf off north iceland this is a key boundary region for climate changes related to atmospheric and oceanographic variations influenced by the moving limit between the cold and warm water masses at the polar front and the low depression track with its associated westerlies situated across iceland an age model based on tephrochronology was previously reported for this core and has allowed precise timing of significant variations in the magnetic mineral concentration and grain size over the last 10 cal kyr the holocene climatic optimum identified in north iceland between 10 and 6 cal kyr bp is characterized by minor variations in the magnetic record while there is a clear increase in oceanographic instability from 6 cal kyr bp to the present at large scale a decreasing trend in the magnetic mineral content toward the present is presumably associated with a change in the circulation pattern and coincides in time with decreasing north atlantic deep water formation short term intervals of decreased magnetic mineral content are also identified at 5 2 4 9 3 77 3 41 3 01 2 7 and 0 93 0 62 cal kyr bp the youngest one ad 1020 to 1330 corresponding in time to the medieval warm period these events are interpreted to reflect periods of increased activity of the relatively warm high salinity surface irminger current related to stronger input of north atlantic waters into the nordic seas in addition spectral analysis of selected magnetic parameters demonstrates centennial scale periodicities of 715 240 170 and 100 yr which are more clearly expressed in the last 6 cal kyr bp than in the previous period these periodicities might be attributed to intervals of persistence in the north atlantic oscillation nao mode at centennial timescales this record therefore indicates that the holocene climate was more unstable than is often assumed and it demonstrates the importance of high resolution climatic studies for this recent time period to improve climate model predictions

coralline algal mg o bond strength as a marine pco2 proxy past ocean acidification recorded in the geological record facilitates the understanding of rates and influences of contemporary pco 2 enrichment most ph reconstructions are made using boron however there is some uncertainty associated with vital effects and isotopic fractionation here we present a new structural proxy for carbonate chemistry mg o bond strength in coralline algae coralline algae were incubated in control 380 matm pco 2 moderate 750 matm pco 2 and high 1000 matm pco 2 acidification conditions for 24 months raman spectroscopy was used to determine skeletal mg o bond strength there was a positive linear relationship between pco 2 concentration and bond strength mediated by positional disorder in the calcite lattice when accounting for seasonal temperature the structural preservation of the carbonate chemistry system in coralline algal high mg calcite represents an alternative approach to reconstructing marine carbonate chemistry significantly it also provides an important mechanism for reconstructing historic atmospheric co 2 concentrations

high cr and high al chromitites from the sagua de tanamo district mayari cristal ophiolitic massif eastern cuba constraints on their origin from mineralogy and geochemistry of chromian spinel and platinum group elements article i nfo several chromitite bodies of variable sizes are hosted in dunite harzburgite of the small b3 km mining district of sagua de tanamo in the mayari cristal ophiolitic massif eastern of cuba the chromian spinel in these bodies displays a large range in cr cr cr al atomic ratio from 0 74 to 0 45 in high cr chromitites cr and ti contents increase from harzburgite to dunite to chromitite a roughly opposite trend of variation in cr is observed in high al chromitites although in this case ti distributes randomly the differences in the type of chromian spinel i e high cr or high al in the chromitite coincide with a different behavior of the platinum group elements pge whereas high cr chromitites are rich in pge and contain abundant grains of platinum group minerals pgm high al chromitites are systematically poor in pge and in pgm the calculated melts in equilibrium with chromian spinel of high cr chromitite are island arc thoeliites iat with boninitic affinity whereas those in equilibrium with chromian spinel of high al chromitites are back arc basin basalts babb the formation of high cr chromitites is interpreted as a result of the extensive reaction of harzburgite with migrating island arc tholeiite melts of boninitic affinity melt rock reaction produces boninitic melts with variable composition and porous dunitic channels in which the mixing mingling of melts promotes crystallization of mononomineralic high cr chromian spinel in contrast high al chromitites formed by the mixing mingling of babb melts within conduits not in equilibrium with dunite percolation of primitive babb melts through pre existing dunite dissolved olivine producing melt conduits in which babb melts mixed and formed high al chromian spinel the higher pge and pgm in high cr chromitites is not only a function of the degree of partial melting but is linked to interaction between the migrating melt and mantle harzburgite during the formation of the chromitite the coexistence of both types of chromitites in one small mining district reflects the temporal and or spatial variations of separate melt intrusions emplaced in different subarc mantle domains during the opening of a back arc basin in a supra subduction zone environment