miocene sea level falls related to the geologic history of midway atoll a period of atoll emergence results in the development of a karst surface on the atoll upon resubmergence this surface is preserved as a subsurface solution unconformity that can be identified by petrographic characteristics and a distinctive stable isotope signature imprinted by subaerial or phreatic diagenesis determination of the magnitude of miocene sea level falls by considering subsidence rates and depths to solution unconformities must take into account the lowering of the emergent atoll surface by dissolution previously the depth to a miocene solution unconformity below midway atoll was assumed to record a maximum highstand of sea level that preceded a period of island emergence however because of surface dissolution the solution unconformity must represent some elevation between a past highstand and a subsequent lowstand the subsurface stratigraphy of midway atoll shows that a late miocene sea level fall of 75 125 m below present sea level took place the magnitude of this fall is greater than that previously determined on the basis of stable isotope data from midway atoll but approximates miocene sea level falls determined by seismic stratigraphic methods

a potential bias in coral reconstruction of sea surface temperature 1 isotopic measurements in corals are used to reconstruct past sea surface temperature these reconstructions are based on calibration regression analyses using paired measurements of modern isotopic composition and sea surface temperature it is shown that error in these measurements of sea surface temperature can lead to substantial bias in reconstruction provided the variance of the measurement error is known or can be estimated a simple correction can eliminate this bias

source dependent biomarker properties of five crude oils from the gulf of suez egypt abstract five crude oils from some producing wells in the southern part of the gulf of suez were characterized using a variety of organic geochemical parameters the results reveal significant differences within the oils from the gulf of suez basin that suggest two oil types and one mixed type type 1 oils from ras fanar and east zeit fields show a high relative abundance of gammacerane indicating a marine saline source depositional environment another related feature of these oils is the predominance of c 35 over c 34 17 h homohopanes type 2 oils from gama and amal 9 wells show oleanane indices over 20 indicating that they originated from an angiosperm rich tertiary source rock type 3 oil from amal 10 well has geochemical characteristics intermediate between those of types 1 and 2 this may reflect mixing of oils from the sources of both types 1 and 2 the geochemical characteristics of the oils vary sufficiently to suggest multiple sources the type 1 oils possess geochemical characteristics consistent with upper cretaceous brown limestone or lower eocene thebes formation carbonate source rocks type 2 oils are very similar in geochemical character to the lower miocene rudeis formation source rocks

strontium calcium ratios in modern porites corals from the great barrier reef as a proxy for sea surface temperature calibration of the thermometer and monitoring of enso high precision sr ca ratios are reported for porites corals from davies reef at 19 s on the midshelf of the great barrier reef australia skeletal growth parameters were also determined from coral slabs using x ray photographs and densitometry measurements a calibration of the sr ca thermometer has been obtained using in situ measured sea surface temperatures which gives sr ca 10 10 48 0 01 0 0615 0 0004 t wheret is in c this calibration applies to different species of porites and a large range of annual extension and calcification rates provided sampling follows a major growth axis biases of 1 2 c have been observed in the low density margins where growth is hampered by interfering fans of corallites the analytical and the long term reproducibility of sr ca derived temperatures are both better than 0 3 c 2 coral growth parameters such as the extension rate or density generally appear to respond to environmental changes such as rainfall but do not affect the sr ca partitioning between coralline aragonite and seawater no correlation has been found between calcification rate and sr ca variations consistent with sr ca being mainly controlled by temperature in the great barrier reef the interannual variability in sst is primarily related to the el nino southern oscillation phenomenon and is typically marked by a cold anomaly during the winter preceding the mature warm phase instrumental records show that the surface waters of the coral sea around 19 s have experienced a significant cooling associated with the el ninos of 1965 1972 and 1982 1983 which the porites corals record faithfully the coral derived temperatures for the period from 1965 to 1993 show an increase of 1 3 c which has occurred mainly since 1979 this warming is larger in magnitude but consistent with the trend for the southern hemisphere land and marine temperature records which shows an increase of around 0 4 c

coral microatolls from the central pacific record late holocene el nino microatolls are discoid corals that have grown laterally because vertical growth is constrained by exposure at lowest tides we demonstrate that a modern reef flat porites microatoll from christmas kiritimati island preserves an oxygen isotope record of substantial sea surface temperature variations related to el nino southern oscillation enso we also show that a late holocene fossil microatoll from the centre of the island contains interannual oxygen isotope variations over an approximate 20 year period three pronounced negative isotope anomalies attributed to warm el nino events are superimposed on an annual cycle el nino events similar to those seen in recent decades appear to have been a feature of mid pacific climate in the late holocene analysis of further microatolls offers a source of pre instrumental el nino tropical climate data it may be possible to extend the nino c proxy to indicate intensity and frequency of enso over the past three millennia

geochemistry based coral palaeoclimate studies and the potential of non traditional non massive porites corals recent developments and future progression understanding the natural variability of the earth s climate system and accurately identifying potential anthropogenic influences requires long term geographically distributed records of key climate indicators such as temperature and precipitation that extend prior to the last 400 years of the holocene reef corals provide an excellent source of high resolution climate records and importantly represent the tropical marine environment where palaeoclimate data are urgently required recent decades have seen significant improvement in our understanding of coral biomineralisation the associated uptake of geochemical proxies and methods of identifying and understanding the effects of both early and late post depositional diagenetic alteration these processes all have significant implications for interpreting geochemical proxies relevant to palaeoclimatic reconstructions this paper reviews the current state of the art in terms of coral based palaeoclimate reconstructions and highlights a key remaining problem the majority of coral based palaeoclimate research has been derived from massive colonies of porites however massive porites are not globally abundant and may not provide material of a particular age of interest in those regions where they are present therefore there is great potential for alternate coral genera to act as complimentary climate archives while it remains critical to consider five key factors vital effects differential growth morphologies geochemical heterogeneity in the skeletal ultrastructure transfer equation selection and diagenetic screening of skeletal material in order to allow the highest level of accuracy in coral palaeoclimate reconstructions it is also important to develop alternate taxa for palaeoclimate studies in regions where porites colonies are absent or rare currently as many as nine genera other than porites have proven at least limited utility in palaeothermometry most of which are found in the atlantic caribbean region where massive porites do not exist even branching taxa such as acropora have significant potential to preserve environmental archives increasing this capability will greatly expand the number of potential geochemical archives available for longer term temporal records of palaeoclimate

a 170 year sr ca and ba ca coral record from the western pacific warm pool 1 what can we learn from an unusual coral record 1 a long lived porites coral from new ireland 2 5 s 150 5 e papua new guinea has been analyzed for sr ca and ba ca by laser ablation inductively coupled plasma mass spectrometry la icpms the top 50 years of the core are examined here and compared with instrumental sea surface temperatures ssts for the small range of sst in the warm pool sr ca shows an unusually large response the best estimate for the slope of a temperature calibration is 0 23 0 03 mmol mol per c this strong slope is partly a result of the high resolution sampling but is also due to additional biological mediation of the sr ca ratios which appears to be associated with seasonal changes of calcification rate and limits the prediction skills of this proxy thermometer high density bands synchronous with high sr ca ratios suggest that calcification may be enhanced by beneficial small amounts of nutrients available during el nino transient ba enrichment synchronous with colder than average sst is also observed during el nino and attributed to the shoaling of the new ireland coastal undercurrent the high level of enrichment in particular during upwelling triggered by westerly wind bursts suggests an origin from both dissolved seawater and marine biological barium

three monthly coral sr ca records from the chagos archipelago covering the period of 1950 1995 a d reproducibility and implications for quantitative reconstructions of sea surface temperature variations in order to assess the fidelity of coral sr ca for quantitative reconstructions of sea surface temperature variations we have generated three monthly sr ca time series from porites corals from the lagoon of peros banhos 71 e 5 s chagos archipelago we find that all three coral sr ca time series are well correlated with instrumental records of sea surface temperature sst and air temperature however the intrinsic variance of the single core sr ca time series differs from core to core limiting their use for quantitative estimates of past temperature variations averaging the single core data improves the correlation with instrumental temperature r 0 7 and allows accurate estimates of interannual temperature variations 0 35 c or better all sr ca time series indicate a shift towards warmer temperatures in the mid 1970s which coincides with the most recent regime shift in the pacific ocean however the magnitude of the warming inferred from coral sr ca differs from core to core and ranges from 0 26 to 0 75 c the composite sr ca record from peros banhos clearly captures the major climatic signals in the indo pacific ocean i e the el nino southern oscillation and the pacific decadal oscillation moreover composite sr ca is highly correlated with tropical mean temperatures r 0 7 suggesting that coral sr ca time series from the tropical indian ocean will contribute to multi proxy reconstructions of tropical mean temperatures

a snapshot of climate variability at tahiti at 9 5 ka using a fossil coral from iodp expedition 310 1 the integrated ocean drilling program iodp expedition 310 recovered drill cores from the drowned reefs around the island of tahiti 17 40 s 149 30 w many of which contained samples of massive corals from the genus porites herein we report on one well preserved fossil coral sample a 13 6 cm long porites sp dated by uranium series techniques at 9523 33 years monthly 18o and sr ca determinations reveal nine clear and robust annual cycles coral 18o and sr ca determinations estimate a mean temperature of 24 3 c 3 2 c colder than modern for tahiti at 9 5 ka however this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved the interannual variability in coral 18o is similar between the 9 5 ka coral record and a modern record from nearby moorea the seasonal cycle in coral sr ca is approximately the same or greater in the 9 5 ka coral record than in modern coral records from tahiti paired analysis of coral 18o and sr ca indicates cold wet warm dry interannual anomalies opposite from those observed in the modern instrumental record

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

early mid holocene sst variability and surface ocean water balance in the southwest pacific 1 we present early mid holocene records of sr ca 18o and 18osw from marine archives collected in vanuatu two porites sp corals 6 7 6 5 ka bp and a tridacna maxima giant clam 6 2 6 0 ka bp sr ca 18o and 18osw were used as proxies for sea surface temperature sst and sea surface salinity sss the fossil geochemical records were compared to modern porites sp and t maxima records reconstructed mean ssts from the two fossil porites sp and from the modern coral are similar implying that the western pacific warm pool wpwp southern edge had reached its modern location by 6 7 6 5 ka bp the post glacial sst rise in the southwest pacific was thus completed by the early mid holocene the two early mid holocene corals and the giant clam recorded saltier conditions than modern related to 1 a decoupling between the precipitation regime and the spcz due to a northerly position of this climatic feature and 2 an increase of the moisture transport to the extra tropics driven by a strengthened or extended hadley cell the longest 18o coral profile displays an el nino southern oscillation enso signal reduced by 20 30 compared to the period 1928 1992 in concordance with the reduced enso variability observed in the pacific area during the first half of the holocene however the decoupling between the spcz and the precipitation regime may have also contributed to the weak enso signal recorded in the early mid holocene coral 18o profile

sea surface temperature and salinity reconstruction from coral geochemical tracers massive scleractinian corals secrete an aragonitic skeleton which incorporates a large array of chemical tracers corals present several advantages for palaeoclimate research they grow continuously and can live up to 1000 years they are easy to date and they can be sampled at high resolution weekly to monthly resolution both live and fossil corals can be collected in the field in the past two decades significant efforts have been made to identify robust tracers of sea surface temperature sst and salinity sss in corals to date sr ca and 18o are considered to be the most reliable sst tracers although changes in seawater 18o can significantly alter sst reconstructed from coralline 18o because these variations in seawater 18o can be linked to sss changes this initial problem can in fact be turned into an advantage and provide us with an sss tracer the sst component in the coral 18o signal can either be evaluated through sr ca measurements or in some case simply filtered out however there is still much uncertainty concerning the exact mode of incorporation of trace elements and stable isotopes into the coral skeleton the effects of growth rate light intensity feeding habits ph and water chemistry are still poorly documented a review of the strength and weaknesses of sr ca and 18o is presented together with some examples of sst and sss reconstructions other potential sst tracers are also reviewed it is expected that the ability to grow corals in aquarium under controlled conditions and that the development of sophisticated analytical techniques at the micrometric level should help us understand better the robustness of each tracers and the factors controlling their incorporation in coral aragonite

reef core insights into mid holocene water temperatures of the southern great barrier reef the tropical and subtropical oceans of the southern hemisphere are poorly represented in present day climate models necessitating an increased number of paleoclimate records from this key region to both understand the earth s climate system and help constrain model simulations here we present a site specific calibration of live collected massive porites sr ca records against concomitant in situ instrumental water temperature data from the fore reef slope of heron reef southern great barrier reef gbr the resultant calibration and a previously published acropora calibration from the same site was applied to subfossil coral material to investigate holocene water temperatures at heron reef u th dated samples of massive porites suggest cooler water temperatures with reduced seasonal amplitude at 5 2 ka 2 76 1 31i c cooler than present and 7 ka 1 26i c cooler than present at heron reef these results contrast the previous suggestion of a mid holocene thermal maximum in the central gbr around 5 35 ka and 4 48 ka yet may be explained by differences in temperature of the shallow ponded reef flat central gbr and the deeper reef slope waters this study and potential large reservoir correction errors associated with early radiocarbon dates combining coral based water temperature anomaly reconstructions from the tropical and subtropical western pacific indicates a coherent temperature response across the meridional gradient from indonesia and papua new guinea down to the southern gbr this similarity in reconstructed temperature anomalies suggests a high probability of an earlier expression of a mid holocene thermal maximum on the gbr between 6 8 and 6 0 ka

evidence for tropical south pacific climate change during the younger dryas and the bolling allerod from geochemical records of fossil tahiti corals abstract we present monthly resolved records of strontium calcium sr ca and oxygen isotope 18o ratios from well preserved fossil corals drilled during the integrated ocean drilling program iodp expedition 310 tahiti sea level and reconstruct sea surface conditions in the central tropical south pacific ocean during two time windows of the last deglaciation the two tahiti corals examined here are uranium thorium u th dated at 12 4 and 14 2 ka which correspond to the younger dryas yd cold reversal and the bolling allerod b a warming of the northern hemisphere respectively the coral sr ca records indicate that annual average sea surface temperature sst was 2 6 3 1 c lower at 12 4 ka and 1 0 1 6 c lower at 14 2 ka relative to the present with no significant changes in the amplitude of the seasonal sst cycle these cooler conditions were accompanied by seawater 18o 18osw values higher by 0 8 and 0 6 relative to the present at 12 4 and 14 2 ka respectively implying more saline conditions in the surface waters along with previously published coral sr ca records from the island cohen and hart 2004 deglacial sea surface temperatures of the western tropical pacific a new look at old coral paleoceanography 19 pa4031 doi 10 1029 2004pa001084 our new tahiti coral records suggest that a shift toward lower sst by 1 5 c occurred from 13 1 to 12 4 ka which was probably associated with a shift toward higher 18osw by 0 2 along with a previously published coral sr ca record from vanuatu correge et al 2004 interdecadal variation in the extent of south pacific tropical waters during the younger dyras event nature 428 927 929 the tahiti coral records provide new evidence for a pronounced cooling of the western to central tropical south pacific during the northern hemisphere yd event

early holocene climate variability and the timing and extent of the holocene thermal maximum htm in northern iceland the magnitude and timing of holocene maximum warmth in the arctic and sub arctic has been the subject of considerable recent interest particularly in the context of future climate change although lying at a crucial location in the north atlantic close to significant atmospheric and oceanic boundaries terrestrial holocene climatic data from iceland are few and predominantly derive from glacial and palaeoecological evidence here we present new datasets from trollaskagi based on chironomid inferred temperatures ci t using sub fossil chironomids from the same lake sediments supplemented by pollen data july air temperatures have been derived using an icelandic training set and the data suggest optimal temperatures at sea level up to 1 5 c above current levels around 8 k cal yr bp a time when birch woodland was well developed in trollaskagi but when woodland had still not fully developed in the more isolated nw peninsula our data thus suggest that optimal summer warmth did not occur in iceland until 8 kcal yr bp at the earliest possibly lasting until 6 7 kcal yr bp the amount of warming for july was therefore at least 1 5 c but possibly up to 2 3 c higher than the 1961 1990 average on the basis of the tree line data comparison with data from elsewhere in adjacent arctic regions greenland and eastern arctic canada show peak warmth to be later in iceland and less pronounced it also appears that there were enhanced temperature gradients during the first half of the holocene between the two study areas trollaskagi and the nw peninsula and that they influenced patterns of vegetation colonisation with current spatial temperature patterns only developing as holocene climate deteriorated after around 6 kcal yr bp

high resolution windows into early holocene climate srca coral records from the huon peninsula high precision measurements of srca ratios are reported for porites corals from the uplifted holocene coral terraces at huon peninsula papua new guinea the early holocene porites have u th mass spectrometric ages of 8920 60 yr and 7370 50 yr and 234u t values of 145 2 similar to modern seawater the srca coral records provide 5 6 year high resolution near weekly time windows into early holocene sea surface temperatures seasonal temperature fluctuations are generally in the range of 1 c with occasional excursions of 2 c which may indicate the more frequent recurrence of very strong enso el nino southern oscillation events mean annual srca temperatures of 24 2 1 1 c and 22 9 0 8 c have been obtained which are 2 3 c cooler than that exhibited by a modern porites these results indicate that during the early holocene the equatorial western pacific ocean was at least several degrees cooler than present day temperatures this is consistent with late glacial coral records from the caribbean that indicate lower 6 c sea surface temperatures for the equatorial oceans the huon peninsula corals also indicate that ssts were several degrees cooler than those in the caribbean during the early holocene thus although the northern hemisphere summer radiation maximum occurred at 10 ka there appears to have been a significant lag in the response of the equatorial western pacific ocean to this warming cooler early holocene sea surface temperatures in the western pacific may have been due to changing patterns of ocean atmosphere circulation resulting from the exposure of large areas of continental shelf in the southeast asia region a consequence of lower glacial sea levels it is likely that ocean temperatures in the huon peninsula were influenced by the opening at 7 ka of the torres strait that now separates new guinea from the australian mainland

tracking the extent of the south pacific convergence zone since the early 1600s 1 the south pacific convergence zone spcz is the largest and most persistent spur of the intertropical convergence zone at the southeastern edge of the spcz near 170 w and 15 20 s a surface ocean salinity frontal zone exists that separates fresher western pacific warm pool water from saltier and cooler waters in the east this salinity front is known to shift east and west with the phase of the el nino southern oscillation we have generated subannually resolved and replicated coral oxygen isotopic time series from fiji 17 s 179 e and rarotonga 21 5 s 160 w that have recorded interannual displacements of the salinity front over the last 380 years and also indicate that at lower frequencies the decadal mean position of the salinity front and eastern extent of the spcz has shifted east west through 10 to 20 of longitude three times during this interval the most recent and largest shift began in the mid 1800s as the salinity front progressively moved eastward and salinity decreased at both sites our results suggest that sea surface salinity at these sites is now at the lowest levels recorded and is evidence for an unprecedented expansion of the spcz since the mid 1800s the expansion of the spcz implies a gradual change in the south pacific to more la nina like long term mean conditions this observation is consistent with the ocean thermostat mechanism for the pacific coupled ocean atmosphere system whereby exogenous heating of the atmosphere would result in greater warming in the western pacific and a greater east west surface temperature gradient components 8034 words 7 figures 2 tables

interglacial climates and the atlantic meridional overturning circulation is there an arctic controversy arctic palaeorecords are important to understand the natural range of forcing and feedback mechanisms within the context of past and present climate change in this temperature sensitive region a wide array of methods and archives now provide a robust understanding of the holocene climate evolution by comparison rather little is still known about older interglacials and in particular on the effects of the northward propagation of heat transfer via the atlantic meridional ocean circulation amoc into the arctic terrestrial records from this area often indicate a warmer and moister climate during past interglacials than in the holocene implying a more vigorous amoc activity this is in conflict with marine data although recognized as very prominent interglacials in antarctic ice cores cross latitudinal surface ocean temperature reconstructions show that little of the surface ocean warmth still identified in the northeast atlantic during older interglacial peaks e g mis5e 9 11 was further conveyed into the polar latitudes and that each interglacial developed its own specific palaeoclimate features interactive processes between water mass overturning and the hydrological system of the arctic and how both developed together out of a glacial period with its particular ice sheet configuration and relative sea level history determined the efficiency of an evolving interglacial amoc because of that glacial terminations developed some very specific water mass characteristics which also affected the climate evolution of the ensuing interglacial periods moreover the observed contrasts in the arctic directed meridional ocean heat flux between past interglacials have implications for the palaeoclimatic evaluation of this polar region crucial environmental factors of the arctic climate system such as the highly dynamical interactions between deep water mass flow surface ocean temperature salinity sea ice and atmosphere exert strong feedbacks on interglacial climate regionality that goes well beyond the arctic a sound interpretation of such processes from palaeoarchives requires a good understanding of the applied proxies fossils in particular are often key to the reconstruction of past conditions but the tremendously flexible adaptation strategies of biota sometimes hampers further in depth interpretations especially when considering their palaeoenvironmental meaning in the context of rapid palaeoclimatic changes and long term pleistocene evolution

reconstruction of deglacial sea surface temperatures in the tropical pacific from selective analysis of a fossil coral the sr ca of coral skeletons demonstrates potential as an indicator of sea surface temperatures ssts however the glacial interglacial sst ranges predicted from sr ca of fossil corals are usually higher than from other marine proxies we observed infilling of secondary aragonite characterized by high sr ca ratios along intraskeletal pores of a fossil coral from papua new guinea that grew during the penultimate deglaciation 130 2 ka selective microanalysis of unaltered areas of the fossil coral indicates that ssts at approx 130 ka were le 1 c cooler than at present in contrast with bulk measurements combining infilled and unaltered areas which indicate a difference of 6 7 c the analysis of unaltered areas of fossil skeletons by microprobe techniques may offer a route to more accurate reconstruction of past ssts

speleothem derived asian summer monsoon variations in central china 54 46 ka the oxygen isotope signature delta o 18 of stalagmite si3 collected from shizi cave in north east sichuan province provides an asian summer monsoon asm record in central china for the period 54 46 ka the si3 delta o 18 record clearly shows a negative delta o 18 excursion centred around 49 4 ka which was reported in hulu cave in east china but not identified in the speleothem records from south west china as a whole this record displays a higher coherence with the two hulu records from east china than with the speleothem delta o 18 records from south west china suggesting that at 54 46 ka central china was influenced more by the east asian summer monsoon than by the indian summer monsoon it also displays a significant negative delta o 18 excursion at 47 5 46 6 ka which is not clearly documented in two other speleothem delta o 18 records previously reported from south west china this suggests that details of the greenland interstadial 12 warrant further investigations in future in monsoonal china the si3 delta o 18 record displays more significant centennial scale variations than the other four speleothem delta o 18 records from east and south west china which may be due to the fact that the study site is closer to the north west boundary of the asm and more sensitive to variations of the asm than east and south west china copyright c 2011 john wiley sons ltd

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

coral barium calcium record of mid holocene upwelling activity in new caledonia south west pacific abstract a variety of inimical factors i e sea surface temperature nutrient input nature of substrates were invoked previously to explain the retardation in reef settlement in new caledonia during the holocene in order to clarify the respective role played by temperature and nutrient level in the growth of fringing reefs along the southwest coast of the island trace element ratios i e sr ca and ba ca were used respectively as a paleothermometer and as a tracer of nutrient load from modern and mid holocene about 6000 calendar years old massive porites coral colonies the results obtained from the modern coral record indicate that near the outer barrier reef upwelling activity is controlled by southeast winds blowing in summer by contrast along the southwest coastline the fringing reefs are subjected to barium input mainly derived from weathering of barite rich rocks cropping out in the adjacent mainland comparison between the fossil and modern coral sr ca and ba ca records shed light on three different aspects of the mid holocene climate and coral reef evolution in new caledonia 1 the variability of paleo sea surface temperature sst seems to have been similar to the modern one although the island probably experienced sst about 1 c higher than at present 2 upwelling activity appears to have been greater than at present barium being supplied from the open sea to coastal zones by strong wind generated upwelling currents in relation to cooling events 3 the onset of reef development in the southwest areas of new caledonia was delayed due to the stronger upwelling of nutrient enriched waters during the early middle holocene the flowing of upwelled waters over the southwest coastal areas began at 8200 calendar years bp and ceased at the time when the outer barrier reef crest reached present day sea level about 5500 to 5000 calendar years ago

the effect of colony topography on climate signals in coral skeleton the stable oxygen isotope composition of the aragonitic skeleton of hermatypic corals is a potential archive of paleotemperature and rainfall data biological processes also influence coral 18o although it has been difficult to determine which processes are involved and whether or not they dominate the stable isotope signal we show here that colony topography or surface bumpiness is associated with significant differences in 18o 13c and the timing of high density band formation between same age corallites in the central and fastest growing region of a coral colony these differences reflect changes experienced by individual corallites as they grow from the summit of a bump toward the bottom of a valley corallites on the bump record isotopic temperatures more than 1 c higher and accrete high density skeleton about 2 months earlier than their valley counterparts just 20 mm away we propose that these changes are not caused by corallite aging but rather by changes in the overall rate and timing of light enhanced calcification which is lower and occurs later in shaded valleys than it does on exposed bumps although we conclude that sea temperature is the dominant influence on 18o values in our coral our results show that significant isotopic variations may be expected over a small surface area in a single colony the production of accurate and reproducible coral based climate records thus requires an understanding of the complexities of coral growth processes and incorporation of this knowledge into sampling strategies and interpretation of data