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

post fire induced soil water repellency modeling short and long term processes soil water repellency has direct implications to hydrological as well as geomorphological processes especially in fire prone ecosystems five predominant mechanisms have been described as generating water repellency in soils fungal and microbial activity growth of particular vegetation species organic matter heating of the soils by wildfires and soil characteristics herein we synthesize among these mechanisms and propose a general model describing the long term properties of water repellency in soils using non linear regression analysis methods we compare among different variants of the model in order to assess the relative role of vegetation on water repellency dynamics we suggest that following a wildfire event hydrophobic peak soil properties are dictated by vegetation properties but that the rapid decrease is not associated with the vegetation following wildfires the recovery of the ecosystem commences and water repellency is characterized by increased predominance of the biotic activity thus the general pattern of a rapid decrease and a long term increase in water repellency can be described by a mathematical model presented herein

geochemistry and skeletal structure of diploria strigosa implications for coral based climate reconstruction abstract geochemical tracers incorporated into the skeleton of reef building corals are ideal proxies for reconstructing environmental parameters of ambient seawater such as temperature and salinity at subseasonal resolution however validation concerns of these environmental proxies due to the complex skeleton of some tropical atlantic corals have hindered such coral based environmental reconstructions in this region compared to the tropical pacific in order to identify complications associated with the complex skeletal architecture of the massive brain coral diploria strigosa we performed microsampling experiments along and across individual skeletal elements we demonstrate that the mesoscale heterogeneity of sr ca 18o and 13c is a systematic feature of d strigosa and is linked to different vital effects between skeletal elements the thecal wall is significantly depleted in sr 18o and 13c compared to the adjacent septa and columella and differences between apparent temperature signatures of several degrees are greater for sr ca suggesting that this temperature proxy is more sensitive to skeletal mixing than 18o parallel subseasonal microsampling experiments performed along individual skeletal elements of a single corallite of a d strigosa coral which grew at a rate of 0 65 cm year allow for investigating potential biases associated with its complex skeletal mesoarchitecture highest correlation between sr ca and 18o from skeletal material retrieved from the centre of the thecal wall suggests that microdrilling the theca provides the best environmental signal compared to adjacent microsampling profiles moreover based on monthly mean climatology the temperature dependence of sr ca for this profile is comparable to previous calibrations published from faster growing d strigosa based on these results we conclude that accurate microsampling along the centre of the thecal wall of d strigosa is a prerequisite for generating robust climate reconstructions from its skeleton

improving sst reconstructions from coral sr ca records multiple corals from tahiti french polynesia we reconstruct sst from coral sr ca ratios measured at three coral cores taken from the lagoon of tahiti french polynesia two coral cores were drilled from the same coral colony one horizontally and one vertically and a third core was drilled vertically from another coral growing at a different site we evaluate several sr ca records as proxies for regional sst variations 1 the three single core records from tahiti 2 an average sr ca record computed from the two cores drilled from the same coral colony 3 an average sr ca record computed from all three tahiti cores and 4 an average sr ca record computed from the three tahiti cores and a fourth core taken from a different island rarotonga on a monthly scale the average sr ca record including the four coral cores from tahiti and rarotonga shows the best correlation with regional sst the variance of the sst reconstruction is very realistic and the residual sst is low this suggests that reconstructing sst from average proxy records gives a better representation of regional sst variations of the three tahiti cores the one that was drilled horizontally shows the best correlation with grid sst on an annual mean scale all three tahiti corals show much larger interannual sst variations than that indicated by grid sst

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

interdecadal decadal climate variability from multicoral oxygen isotope records in the south pacific convergence zone region since 1650 a d 1 in the south pacific interdecadal decadal oceanic and atmospheric variability referred to as the interdecadal pacific oscillation ipo is most pronounced in the south pacific convergence zone spcz salinity front region here we have used annual average oxygen isotope 18o time series from five coral cores collected from fiji and tonga in this region to construct a fiji tonga interdecadal decadal pacific oscillation f t idpo index of low frequency 9 and 55 years climate variability back to 1650 a d we first demonstrate the consistency between this f t idpo index and a mean sea level msl pressure based spcz position index spi 1891 2000 thus verifying the ability of coral 18o to record past interdecadal decadal climatic variations in this region back to 1891 the f t idpo index is then shown to be synchronous with the ipo index 1856 2000 suggesting that this coral based index effectively represents the interdecadal decadal scale climate variance back to 1650 the regularity of the f t idpo index indicates that interdecadal decadal variability in the spcz region has been relatively constant over the past 350 years with a mean frequency of 20 years variance peaks near 11 and 35 years there is a consistent antiphase correlation of the f t idpo index and the interdecadal decadal components in equatorial pacific coral 18o series from maiana and palmyra this observation indicates that the eastward expansion westward contraction of the eastern salinity front of the western pacific warm pool wpwp occurs simultaneously 1 year with the westward eastward shift of the spcz salinity front during positive ipo negative ipo phases this is the same relationship observed during the phases of the el nino southern oscillation

chronological control of coral records using luminescent lines and evidence for non stationary enso teleconnections in northeast australia eight multicentury porites coral cores were used to develop a 373 year chronology by cross dating techniques adapted from dendrochronology characteristic patterns of distinct luminescent lines within the coral skeletons were matched between coral cores from inshore and mid shelf reefs in the central great barrier reef australia skeleton plots of luminescent banding were produced for each core and combined into a master chronology back to ad 1615 in addition to improving dating control the luminescence master chronology provides a proxy for burdekin river runoff and queensland summer rainfall variations in the magnitude of the correlation between the luminescence master and the mann et al 2000 nino3 sea surface temperature reconstruction provides insights into the long term stability of el nino southern oscillation enso telecon nections burdekin river runoff was significantly inversely related to enso variability for much of the period from the ad 1650s to 1800 suggesting that enso related te

oxygen isotope systematics in diploastrea heliopora new coral archive of tropical paleoclimate diploastrea heliopora forms dense robust dome shaped coral colonies throughout the reef ecosystems of the tropical pacific and indian oceans this slow growing 2 to 6 mm yr coral has the potential to yield continuous paleoclimate records spanning up to 1000 yr for the warmest waters on earth the indo pacific warm pool and has a long fossil history as a single recognizable species despite the potential of diploastrea to be an important new paleoclimate archive little is known about the systematics of geochemical tracers incorporated into its skeleton to fill this knowledge gap we compared skeletal delta 18 o signatures in live diploastrea and porites colonies from southwest lagoon near amedee lighthouse new caledonia at the southern latitudinal limit for diploastrea and alor indonesia in the core area of the indo pacific warm pool we designed a new microsampling technique to minimize smoothing and distortion of the isotopic records due to the complex calyx architecture and slow growth of diploastrea high resolution isotope profiles from the septal portion of the diploastrea corallite are attenuated whereas those restricted to the central columella are similar in quality to those extracted from the well established porites coral archive the delta 18 o temperature relationship for the columellar portion of diploastrea 0 18parts per thousand degreesc is in good agreement with that derived for a nearby porites 0 19parts per thousand degreesc quinn et al 1996 on the basis of comparison with an in situ sea surface temperature record from amedee lighthouse there is a measurable difference of 0 3 0 1parts per thousand between the kinetic biological disequilibrium offsets from seawater delta 18 o composition for diploastrea and porites despite this offset in mean delta 18 o diploastrea accurately records the regional differences in mean temperature and salinity between new caledonia and the indo pacific warm pool additional tests show that diploastrea records el nino southern oscillation enso interannual variability in sea surface temperature and salinity across the southwestern pacific indicating that it should yield dependable paleo enso records based on these results we propose that d heliopora has the potential to provide an important new coral archive of tropical paleoclimate c copyright 2003 elsevier science ltd

a coral oxygen isotope record from the northern red sea documenting nao enso and north pacific teleconnections on middle east climate variability since the year 1750 a 245 year coral oxygen isotope record from the northern red sea ras umm sidd egypt 28 n in bimonthly resolution is presented the mean annual coral 18o signal apparently reflects varying proportions of both sea surface temperature and 18oseawater variability in conjunction with instrumental observations of climate the coral record suggests for interannual and longer timescales that colder periods are accompanied by more arid conditions in the northern red sea but increased rainfall in the southeastern mediterranean whereas warmer periods are accompanied by decreased rainfall in the latter and less arid conditions in the northern red sea a 70 year oscillation of probably north atlantic origin dominates the coral time series interannual to interdecadal variability is correlated with instrumental indices of the north atlantic oscillation nao the el nino southern oscillation enso and north pacific climate variability the results suggest that these modes contributed consistently to middle east climate variability since at least 1750 preferentially at a period of 5 7 years

deconvolving the δ18o seawater component from subseasonal coral δ18o and sr ca at rarotonga in the southwestern subtropical pacific for the period 1726 to 1997 to reconstruct oceanographic variations in the subtropical south pacific 271 year long subseasonal time series of sr ca and delta 18 o were generated from a coral growing at rarotonga 21 5degreess 159 5degreesw in this case coral sr ca appears to be an excellent proxy for sea surface temperature sst and coral delta 18 o is a function of both sst and seawater delta 18 o composition delta 18 o sw here we focus on extracting the delta 18 o sw signal from these proxy records a method is presented assuming that coral sr ca is solely a function of sst and that coral delta 18 o is a function of both sst and delta 18 o sw this method separates the effects of delta 18 o sw from sst by breaking the instantaneous changes of coral delta 18 o into separate contributions by instantaneous sst and delta 18 o sw changes respectively the results show that on average delta 18 o sw at rarotonga explains similar to39 of the variance in delta 18 o and that variations in sst explains the remaining similar to61 of delta 18 o variance reconstructed delta 18 o sw shows systematic increases in summer months december february consistent with the regional pattern of variations in precipitation and evaporation the delta 18 o sw also shows a positive linear correlation with satellite derived estimated salinity for the period 1980 to 1997 r 0 72 this linear correlation between reconstructed delta 18 o sw and salinity makes it possible to use the reconstructed delta 18 o sw to estimate the past interannual and decadal salinity changes in this region comparisons of coral delta 18 o and delta 18 o sw at rarotonga with the pacific decadal oscillation index suggest that the decadal and interdecadal salinity and sst variability at rarotonga appears to be related to basin scale decadal variability in the pacific copyright c 2002 elsevier science ltd

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

sst artifacts in coral proxy records produced by early marine diagenesis in a modern coral from rabaul papua new guinea 1 we investigated the effects of early marine diagenesis on the skeletal geochemistry of a porites coral collected live offshore of rabaul papua new guinea the lowermost 14 cm of the 1 9 m coral core contains physical evidence of alteration which is clearly visible in x radiograph sem and petrography images abrupt and significant increases in coral 18o and sr ca and decreases in coral mg ca occur at the transition from unaltered to altered skeleton all of which imply significant sst cooling if the altered nature of the coral skeleton went unrecognized screening for the effects of early marine diagenesis should become a standard procedure in coral climate studies

impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in porites corals restricted zones of recent dissolution and secondary aragonite infilling were identified in a coral core collected in 1986 from a living massive porites colony from the central great barrier reef australia secondary aragonite needles 20 m long cover skeletal surfaces deposited from 1972 to late 1974 and increase bulk density by 10 dissolution is observed above this zone whereas older skeleton is pristine we investigate the impact of both types of early marine diagenesis on skeletal geochemistry and coral paleoclimate reconstructions by comparison with similar records from eight contemporary porites colonies collected at nearby reefs secondary aragonite overgrowth causes anomalies in skeletal density mg ca sr ca u ca o and c the secondary aragonite is consistently associated with a cool temperature anomaly for each of the sea surface temperature sst proxies o sst 1 6 c sr ca sst 1 7 c mg ca sst 1 9 c u ca sst 2 8 c dissolution through incongruent leaching also causes cool sst artifacts but only for trace element ratios mg ca sst 1 2 c sr ca sst 1 2 c u ca sst 2 1 c the sequence of preference with respect to dissolution of coral skeleton in seawater is mg ca sr u rigorous screening of coral material for paleoclimate reconstructions is therefore necessary to detect both dissolution and the presence of secondary minerals the excellent agreement between apparent sst anomalies generated by different modes of diagenesis means that replication of tracers within a single coral cannot be used to validate climate proxy interpretations poor replication of records between different coral colonies however provides a strong indication of nonclimatic artifacts such as dissolution and secondary aragonite copyright 2007 by the american geophysical union

evaluating the use of the massive coral diploastrea heliopora for paleoclimate reconstruction 1 to date coral based paleoclimate research in the pacific has primarily utilized core samples from the genus porites and has been most successful reconstructing past variability on interannual timescales particularly the el nino southern oscillation enso the indo pacific coral genus diploastrea however owing to its slower extension rate denser structure and longer lifespan can potentially preserve geochemical proxy records 2 3 times longer than porites cores of the same length before its potential can be realized diploastrea must first be calibrated and its climate signal assessed we present oxygen isotope 18o and sr ca results from two diploastrea cores collected in fiji 16 49 s 179 14 e that allow for simultaneous evaluation of this coral s paleoclimatic utility and the reproducibility of each tracer at this site comparison to a porites record from the same location allows for further evaluation of diploastrea as a paleoclimatic archive we demonstrate that diploastrea s septal and columellar material yield similar 18o sst relationships and that despite some sacrifice of the seasonal 18o amplitude bulk sampling of either region is satisfactory for resolving interannual and lower frequency modes of climatic variability therefore paleoclimate reconstructions employing either a septal or columellar sampling regime of this genus may be useful at filling in spatial and temporal sampling gaps which currently hinder the reconstruction of long term changes in major climate fields in the western pacific

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

the stable oxygen and carbon isotopic record from a coral growing in florida bay a 160 year record of climatic and anthropogenic influence abstract a 160 year record of skeletal 13 c and 18 o was examined in a specimen of the coral solenastrea bournoni growing in florida bay variations in the 18 o of the skeleton can be correlated to changes in salinity while changes in the 13 c reflect cycling of organic material within the bay based on the correlation between salinity and skeletal 18 o we have concluded that there has been no long term increase in salinity in this area of florida bay over the past 160 years using salinity correlations between the various basins obtained from instrumental data we have been able to extend our interpretations to other parts of florida bay reaching similar conclusions in contrast to current ideas which have focused on changes in florida bay water quality over the past 20 yr history of the bay as causative in its decline we have determined that changes in water quality in this basin were already set in motion between 1905 and 1912 by the construction of the florida east coast railway from miami to key west the construction of the railway resulted in the restriction of the exchange of water between the florida reef tract and the gulf of mexico causing florida bay to become more eutrophic evidence of this process is observed in the sudden shift to relatively lower 13 c values coincident with railway construction natural events also appear to have influenced the water in the bay between 1912 and 1948 frequent hurricanes had the effect of increasing exchange of water between the bay and reef tract and removing large quantities of organic rich sediments however since 1948 the number of hurricanes affecting the area has decreased and the products of the oxidation of organic material have been increasingly retained within the basin promoting the initiation of eutrophic conditions

lidar observations of mesospheric fe and sporadic fe layers at urbana illinois lidar measurements of mesospheric fe were conducted at urbana il 40 degree n 88 degree w during 4 nights in late october 1989 the average fe abundances layer centroid heights and rms widths varied between 1 0 2 0 times 10 sup 10 cm sup minus 2 89 0 90 5 km and 3 2 4 1 km respectively the peak densities of the layer near 90 km varied between 15 25 times 10 sup 3 cm sup minus 3 considerable gravity wave and tidal activity was observed in the fe profiles on 3 nights the formation and dissipation of 3 large sporadic fe fe sub s layers was observed these are the first observations of this phenomenon the 2 largest fe sub s layers formed at 102 4 km and 91 4 km over a period of about 20 min and their widths were approximately 2 3 km fwhm the peak densities of the fe sub s layers were as high as 31 times 10 sup 3 cm sup minus 3 and the abundances were as high as 5 8 times 10 sup 9 cm sup minus 2 the observations are compared with previous measurements of mesospheric fe and with recent observations of sporadic na na sub s layers

reproducibility of geochemical and climatic signals in the atlantic coral montastraea faveolata 1 monthly resolved 41 year long stable isotopic and elemental ratio time series were generated from two separate heads of montastraea faveolata from looe key florida to assess the fidelity of using geochemical variations in montastraea the dominant reef building coral of the atlantic to reconstruct sea surface environmental conditions at this site the stable isotope time series of the two corals replicate well mean values of 18o and 13c are indistinguishable between cores compare 0 70 versus 0 68 for 13c and 3 90 versus 3 94 for 18o mean values from the sr ca time series differ by 0 037 mmol mol which is outside of analytical error and indicates that nonenvironmental factors are influencing the coral sr ca records at looe key we have generated significant 18o sea surface temperature sst r 0 84 and sr ca sst r 0 86 calibration equations at looe key however these equations are different from previously published equations for montastraea variations in growth parameters or kinetic effects are not sufficient to explain either the observed differences in the mean offset between sr ca time series or the disagreement between previous calibrations and our calculated 18o sst and sr ca sst relationships calibration differences are most likely due to variations in seawater chemistry in the continentally influenced waters at looe key additional geochemical replication studies of montastraea are needed and should include multiple coral heads from open ocean localities complemented whenever possible by seawater chemistry determinations

improving coral base paleoclimate reconstructions by replicating 350years of coral sr ca variations abstract coral based climate reconstructions are typically based on a single record and this lack of replication leads to questions in regards to chronology accuracy and reliability of the inclusive geochemical variations to record climate viability here we present two multi century coral sr ca records recovered from a porites lutea colony offshore of amedee island new caledonia 22 28 8 s 166 27 9 e the chronology was developed by cross dating the coral sr ca time series and verifying the chronology with high precision absolute 230th dating we identify chronological discrepancies of 2 3 and 3 7 years century 1 for reconstructions based on a single core with uncertainty increasing after 250 years we assess the impact of porites skeletal architecture on coral geochemistry by characterizing centimeter scale architectural structures with respect to sampling optimal sampling paths are those on the slab surface parallel to the growth direction of individual corallites along the central axis of an actively extending corallite fan coral sr ca time series extracted from optimal skeletal structures are highly reproducible with a mean absolute difference of 0 021 mmol mol 1 or 0 39 c for monthly determinations suboptimal skeletal architecture is characterized by corallites extending through the slab surface and the coral sr ca determinations derived from suboptimal paths tend to produce a warm bias that varies between 0 04 and 2 30 c disorganized skeletal architecture is characterized by small terminating or unclear corallite fans that produce a cold bias of 0 11 to 2 45 c in coral sr ca determinations these problematic architecture types also produce biases in coral 18o determinations but to a lesser extent we assess the impact of sampling a coral colony along paths that vary from vertical to horizontal in large and small porites colonies with extension rates 6 mm year 1 and we determine there is no significant difference in the coral sr ca records

decadal sea surface temperature variability in the subtropical south pacific from 1726 to 1997 a d we present a 271 year record of sr ca variability in a coral from rarotonga in the south pacific gyre calibration with monthly sea surface temperature sst from satellite and ship measurements made in a grid measuring 1 degrees by 1 degrees over the period from 1981 to 1997 indicates that this sr ca record is an excellent proxy for sst comparison with sst from ship measurements made since 1950 in a grid measuring 5 degrees by 5 degrees also shows that the sr ca data accurately record decadal changes in sst the entire sr ca record back to 1726 shows a distinct pattern of decadal variability with repeated decadal and interdecadal sst regime shifts greater than 0 75 degrees c comparison with decadal climate variability in the north pacific as represented by the pacific decadal oscillation index 1900 1997 indicates that several of the largest decadal scale sst variations at rarotonga are coherent with sst regime shifts in the north pacific this hemispheric symmetry suggests that tropical forcing may be an important factor in at least some of the decadal variability observed in the pacific ocean

evaluation of sampling resolution in coral stable isotope records a case study using records from new caledonia and tarawa we have generated a 40 year long monthly stable isotope record from a porites lutea coral collected offshore of amedee new caledonia 22 s 167 e to investigate the relation between sampling resolution in coral isotope studies and retrieval of sea surface environmental information we interpret the high correlation between our oxygen isotope record and a twenty year long sea surface temperature record at the monthly timescale r 0 88 to indicate that our coral isotope record is an accurate monitor of environmental conditions offshore of amedee the character of the signal and the percent variance explained in the record at the annual band at the quasi biennial oscillation band qbo 2 0 2 4 years and at the el nino southern oscillation band enso 3 8 years changes little in response to a reduction in sampling density from monthly to bimonthly to quarterly similar results have been obtained in a reanalysis of a coral isotope record from tarawa kiribati our results indicate that a significant amount of the information obtained from high density sampling can also be retrieved from lower density sampling in particular bimonthly sampling yields virtually no drop off in variance explained and quarterly sampling is satisfactory for resolving interannual and decadal scale trends in time series the proposed sampling approach may enable a more rapid filling in of numerous spatial holes in coral sampling sites needed for reconstruction of long term decadal scale variations in climate

east asian monsoon evolution and reconciliation of climate records from japan and greenland during the last deglaciation abstract east asian monsoon eam evolution during the last deglaciation has been shown repeatedly to be aligned with paleoclimatic changes in the north atlantic based on climate reconstructions comparing asian speleothem records with greenland ice cores in contrast to this finding paleoclimatic reconstructions based on lake suigetsu sediment cores suggest that past eam variability in japan was not always coherent with climatic variability recorded in greenland ice cores we resolve this discrepancy using an absolute dated stalagmite 18 o record that covers the period between 15 5 and 10 7 thousand years before present ka before ad 1950 this stalagmite record is from nearby maboroshi cave japan and shows climate changes that are synchronous with those of chinese caves and greenland ice cores our results support an effective teleconnection between low and high latitudinal climate systems during the transitions into the bolling allerod ba warming at 14 6 ka and the younger dryas cooling at 12 8 ka in the north atlantic however our results also indicate monsoonal intensification during the ba coincident with decreasing temperatures in greenland from 14 6 to 12 8 ka we explain this decoupling as a result of the interhemispheric bipolar seesaw climate system discrepancies between lake suigetsu radiocarbon age data sets and other radiocarbon calibration archives can also be removed when our maboroshi record is used to adjust the lake suigetsu age model as well as resolving temporal ambiguities in the lake suigetsu paleoclimate record

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

validation of coral temperature calibrations geochemical analyses of coral skeletons are increasingly used to estimate past sea surface temperatures ssts in this paper we suggest that the standard method of calibrating geochemical time series against a usually short local time series requires modification in order to draw large scale inferences about climate from coral proxy data it is also necessary to 1 calibrate against larger fields such as the local gridded data sets and 2 validate results against an independent data set e g early 20th century this approach has been applied in a pilot study to a coral record from new caledonia despite a high 18o correlation r 0 88 with the in situ and gridded sst data sets estimated early 20th century temperatures are more than 1 5 c colder than observed if the standard seasonal calibration is used regression against mean annual temperatures which has a different slope relation yields better estimates of early 20th century ssts however testing of a sr ca record from new caledonia yields better agreement with early 20th century ssts routine validation exercises for other coral sites are necessary to clarify the robustness of geochemical coral proxies as estimators of past environmental change

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

the temperature relationship in coralline aragonite influence of variability in and skeletal growth parameters this paper provides an evaluation of two of the most likely pitfalls of sr ca thermometry i e the effect of biogenic cycling of sr vs ca in the surface ocean and the effect of variable extension rate on sr incorporation in coralline aragonite the authors also report calibration of the sr ca temperature relationship for three coral species porites lobata pocillopora eydouxi and pavona clavus collected for the hawaiian and galapagos islands analyses of seawater samples show significant spatial and depth variability in the sr ca ratio the uncertainty introduced by this effect is estimated to be 0 2 degrees c for corals located in tropical oligotrophic waters and potentially larger for corals located in upwelling areas sr ca along two different growth axes of a galapagos pavona clavus with annual extension rates of approximately 6 and 12 mm y respectively indicate an offset of 1 2 degrees c with higher sr ca values associated with slower extension rates the offset observed between the two growth axes may be the result of variations in extension and or calcification rate these results are important in determining past sea surface temperatures for reconstruction of paleoclimates

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

huge erratic boulders in tonga deposited by a prehistoric tsunami along some coastlines there are erratic boulders apparently emplaced by tsunamis or cyclonic storms evaluating their origin and time of emplacement places constraints on the frequency severity and location of coastal hazards seven such large coral limestone boulders are present near fahefa village on tongatapu island southwest pacific apparently emplaced by a prehistoric tsunami these boulders are 10 20 m above sea level and above any possible source and all are 100 400 m from the present shoreline coral 230th ages indicate that the limestone formed during the last interglacial sea level highstand ca 120 130 ka the largest boulder is 20 times more massive than any reported boulders emplaced by historically documented storms and may be the largest known tsunami or storm erratic worldwide situated above its source we performed computer simulations to assess whether tsunamis produced by earthquakes undersea landslides or volcanoes could emplace the boulders the simulations indicate that either volcanic flank collapse along the tofua arc 30 40 km to the southwest or undersea landslides on the submarine slopes of tongatapu could be responsible either could explain why these boulders are not widespread on tongatapu and instead occur in a localized group along the western coast this study demonstrates that small 1 km3 submarine slope failures sometimes generate locally large tsunamis the fahefa boulders are in a well studied and well populated area yet were unknown to the scientific community until recently this suggests that systematic searches elsewhere for erratic boulders and other tsunami deposits might provide new information for assessing the size and extent of prehistoric tsunamis

evaluating highly resolved paleoclimate records in the frequency domain for multidecadal scale climate variability 1 do the chronological methods used in the construction of paleoclimate records influence the results of the frequency analysis applied to them we explore this phenomenon using the dongge cave speleothem record u series chronology with variable time steps t and the el malpais tree ring index cross dating of ring width series interpolation of the dongge cave record to a constant t resulted in the suppression of periodicities 20 years altering the red noise model used for significance testing frequency analysis of temporal subsets of the el malpais tree ring index revealed that concentrations of variance varied with the number of ring width series frequency analyses of these records identified significant periodicities some common to both 25 and 69 years cross wavelet analysis which examines periodicities in the time domain revealed that coherency between these records occurs intermittently we found the chronology methods can influence the ability of frequency analysis to detect periodicities and tests for coherency

environmental control of the oxygen isotope composition of porites coral microatolls abstract understanding the influence of climatic and non climatic factors on geochemical signals in corals is critical for assessing coral derived records of tropical climate variability porites microatolls form large disk shaped colonies constrained in their upward growth by exposure at or close to mean spring low water level and occur on indo pacific reefs microatolls appear suitable for paleoclimate reconstruction however the systematics of the microatoll chemistry climate relationship are yet to be characterized in this study the 18o signal in porites microatolls from well flushed reef flats on kiritimati christmas island central pacific was investigated for intra coral growth aspect and extension rate effects and between coral effects and to explore the climate signal contained within their skeletons samples for 18o analysis were taken from six individual transects from different positions within porites microatoll xm22 the results show that 1 the average standard deviation for the mean 18o values of transects that represent the same time periods is 0 03 and is within measurement error for a single analysis 0 04 2 the average standard deviation for time equivalent near monthly samples along the transects within the same microatoll is 0 07 and 3 comparison of the average 18o values of records for different microatolls from across kiritimati island show only a small between coral differences of 0 04 and 0 11 for different time periods these differences in mean 18o are within the range for intra and inter colony differences in seasonal and interannual 18o reported for dome shaped porites based on these results a stacked microatoll 18o record was constructed for the period 1978 2007 for comparison with published coral 18o records for nearby dome shaped porites there is a systematic offset between the two types of records which is probably due to variations in 18o seawater across kiritimati island despite the offset all records show similar amplitudes for the seasonal cycle of 18o and there is a strong correlation r 0 71 between microatoll 18o and local sea surface temperature sst the 18o sst slope relationship for microatolls is 0 15 c very similar to that reported for fast growing domed corals 0 18 to 0 22 c statistical analysis of the stacked microatoll 18o record shows that it is correlated with both local and large scale climate variables primarily sst at semiannual annual and interannual timescales our results show that the signal reproducibility and fidelity of skeletal 18o in coral microatolls is comparable to that observed for more conventional coral growth forms longer lived and fossil porites microatolls where they have grown in suitably flushed environments are likely to contain 18o signals that can significantly extend instrumental records of tropical climate variability

the effect of skeletal mass accumulation in porites on coral sr ca and δ18o paleothermometry 1 paleotemperature estimates based on coral sr ca have not been widely accepted because the reconstructed glacial holocene shift in tropical sea surface temperature 4 6 c is larger than that indicated by foraminiferal mg ca 2 4 c we show that corals over estimate changes in sea surface temperature sst because their records are attenuated during skeletogenesis within the living tissue layer to quantify this process we microprofiled skeletal mass accumulation within the tissue layer of porites from australasian coral reefs and laboratory culturing experiments the results show that the sensitivity of the sr ca and 18o thermometers in porites will be suppressed variable and dependent on the relationship between skeletal growth rate and mass accumulation within the tissue layer our findings help explain why 18o sst sensitivities for porites range from 0 08 c to 0 22 c and are always less than the value of 0 23 c established for biogenic aragonite based on this observation we recalibrated the coral sr ca thermometer to determine a revised sensitivity of 0 084 mmol mol c after rescaling most of the published sr ca sst estimates for the indo pacific region for the last 14 000 years 7 c to 2 c relative to modern fall within the 95 confidence envelope of the foraminiferal mg ca sst records we conclude that two types of calibration scales are required for coral paleothermometry an attenuated porites specific thermometer sensitivity for studies of seasonal to interannual change in sst and importantly the rescaled 0 084 mmol mol c sr ca sensitivity for studies of 20th century trends and millennial scale changes in mean sst the calibration scaling concept will apply to the development of transfer functions for all geochemical tracers in corals

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