precision of seafloor gravity and pressure measurements for reservoir monitoring changeswithgravityovertimehaveproventobevaluable forinferringsubsurfacedensitychangesassociatedwithproduction from oil and natural gas reservoirs such inferences allowthemonitoringofmovingfluidfrontsinareservoirand provideanopportunitytooptimizeproductionoverthelifeof the reservoir our group began making time lapse seafloor gravityandpressuremeasurementsin1998 todate wehave surveyed sixfields offshore norway we have made three repeatsurveysatonefieldandonerepeatsurveyatanother we incorporated a land gravity sensor into a remotely operated seafloor housing three such relative gravity sensors mountedinasingleframearecarriedbyaremotelyoperatedvehicle rov to concrete benchmarks permanently placed on the seafloor reference benchmarks sited outside the reservoir boundaries are assumed to provide stable fiducial points typicalsurveyslastfromafewdaystoafewweeksandcover from8to80benchmarks withmultipleobservationsofeach in our earliest surveys we obtained an intrasurvey repeatability of approximately 20 gal but recently we have been achieving 3 gal repeatability in gravity and approximately 5 mminbenchmarkdepthdeducedfromsimultaneouslyrecorded ambient seawater pressure we attribute the improved precision to several operational factors including the use of multiple gravity sensors frequent benchmark reoccupation precise relocation and orientation of the sensors repeated calibrations on land and minimization of vibrational and thermal perturbations to the sensors we believe that high precision time lapse gravity monitoring can be used to trackchangesintheheightofagas watercontactinaflooded reservoir withaprecisionofafewmeters

japan sea oxygen isotope stratigraphy and global sea level changes for the last 50 000 years recorded in sediment cores from the oki ridge abstract we obtained twenty ams accelerator mass spectrometry radiocarbon dates 2 tephra layer chronologies and a planktonic foraminiferal 18 o stratigraphy for the last 50 000 years from japan sea cores from the oki ridge in this paper we report ams 14 c results that allow us to reconstruct a high resolution chronology of the cores and discuss millennial scale climate changes recorded in japan sea sediments the sedimentation rate for the site increased dramatically from the glacial stage to the holocene as a result of significant hydrological changes associated with deglaciation and global sea level rise a lighter 18 o anomaly for the planktonic foraminifers was found during the lgm last glacial maximum this shift corresponds to a freshening of the japan sea surface waters and is mainly due to a global sea level drop rather than anomalously warm ssts sea surface temperatures as previously reported our record combined with the global sea level data suggests that the lgm started about 30 kyr ago and that the salinity of the japan sea became fresher than at present the ssts during mis marine oxygen isotope stage 3 were relatively stable and global sea level was not lower than ca 80 m the surface water of the japan sea attained normal saline levels following the younger dryas cold event and reached the present day 18 o values 7 kyr ago

enso reconstructions over the past 60 ka using giant clams tridacna sp from papua new guinea we present 12 seasonally resolved delta o 18 profiles of giant clams tridacna sp from the huon peninsula papua new guinea spanning discrete periods of time 9 38 years over the past 60 ka the interannual anomaly time series of these shells are used to reconstruct interannual variability which can predominantly be attributed in the modern climate to the el nino southern oscillation enso in this region we have found a significant reduction in interannual delta o 18 variance during the early holocene whereas during marine isotope stage 3 there were at least some periods with variance not significantly different to the twentieth century we show that enso variability seen during the late twentieth century is rare but not unprecedented within glacial climates

sea surface temperature records in the northern south china sea from mid holocene coral sr ca ratios 1 three mid holocene sea surface temperature sst records spanning more than 30 years were reconstructed for the northern south china sea using sr ca ratios in porites corals the results indicate warmer than present climates between circa 6100 yr b p and circa 6500 yr b p with the mid holocene average minimum monthly winter ssts the average maximum monthly summer ssts and the average annual ssts being about 0 5 degrees 1 4 degrees c 0 degrees 2 0 degrees c and 0 2 degrees 1 5 degrees c higher respectively than they were during 1970 1994 summer ssts decrease from circa 6500 yr b p to circa 6100 yr b p with a minimum centered at circa 6300 yr b p the higher average summer ssts are consistent with a stronger summer monsoon during the mid holocene and the decreasing trend indicates a secular decrease of summer monsoon strength which reflects the change in summer insolation in the northern hemisphere el nino southern oscillation enso cycles were apparent in both the mid holocene coral and modern instrumental records however the enso variability in the mid holocene ssts was weaker than that in the modern record and the sst record with the highest summer temperatures from circa 6460 yr b p to 6496 yr b p shows no robust enso cycle this agrees with other studies that indicate that stronger summer monsoon circulation may have been associated with suppressed enso variability during the mid holocene

late holocene asian monsoon variations recorded in lake rara sediment western nepal the himalayas are a key location for understanding centennial to millennial scale variations in the asian monsoon yet few studies of the late holocene have been conducted in this sensitive area direct evidence for shifts in monsoonal wind strength is often limited to marine proxy records while terrestrial reconstructions e g lake levels and spleothems focus on precipitation here we present the first evidence of terrestrial summer monsoon wind strength changes from lake rara western nepal based on mn ti ratios a proxy for lake stratification these data indicate a link between the arabian sea and the himalayas suggesting that centennial to millennial scale changes in wind strength occurred synchronously distinct similarity is also observed between lake rara and the southern part of china which may support previous suggestions that the southern part of china is influenced by indian summer monsoon copyright 2012 john wiley sons ltd

seasonal and interannual variability of the mid holocene east asian monsoon in coral δ18o records from the south china sea understanding the full range of past monsoon variability with reference to specific monsoon seasons is essential to test coupled climate models and improve their predictive capabilities we present a 54 year long high resolution skeletal oxygen isotope 6180 record extracted from a well preserved massive porites sp coral at hainan island south china sea to investigate east asian monsoon variability during summer and winter similar to 4400 calendar yr ago analysis of modem coral 6180 confirms that porites from hainan island are well positioned to record winter monsoon forcing of sea surface temperature sst as well as the influence of summer monsoon rainfall on sea surface salinity sss the coral record for similar to 4400 yr ago shows similar to 9 amplification of the annual cycle of 6 delta o 18 in good agreement with coupled ocean atmosphere models showing higher summer rainfall lower coral 618 0 and cooler winter ssts higher coral delta o 18 in response to greater northern hemisphere insolation seasonality during the middle holocene mean ssts in the south china sea during the mid holocene were within 0 5 degrees c of modem values yet the mean 6 180 for the fossil coral is similar to 0 6 parts per thousand higher than that for the modem coral suggesting that the 6 180 of surface seawater was higher by at least similar to 0 5 parts per thousand relative to modem values the o 18 enrichment is likely to be driven by greater advection of moisture towards the asian landmass enhanced monsoon wind induced evaporation and vertical mixing and or invigorated advection of saltier o 18 enriched pacific water into the relatively fresh south china sea the o 18 enrichment of the northern south china sea similar to 4400 yr ago contributes to mounting evidence for recent freshening of the tropical western pacific today winter sst and summer sss variability in the south china sea reflect the interannual influence of enso and the biennial variability inherent to monsoon precipitation spectral analysis of winter ssts similar to 4400 yr ago reveals a strong enso cycle at 6 7 y which is significantly longer than the average 3 6 y cycle observed since 1970 the results suggest that the influence of enso on winter ssts in the south china sea was well established by similar to 4400 yr ago however spectral analysis of summer sss similar to 4400 yr ago shows no significant enso cycle suggesting that teleconnections between enso and summer monsoon rainfall were restricted taken together the results indicate marked differences in enso monsoon interactions during the winter and summer monsoon seasons in the past the fossil coral delta o 18 record also shows that the amplitude of interannual sst and sss variability was stronger similar to 4400 yr ago despite enso variability being significantly weaker in the pacific region thus it appears that the strengthened mid holocene monsoon was sensitive to forces other than enso that acted as alternative drivers of interannual monsoon variability if this is the case greater interannual climate variability could accompany the strengthening of the asian monsoon predicted to occur during the 21st century as transient greenhouse warming preferentially warms eurasia even if enso perturbations remain relatively stable c 2005 elsevier b v all rights reserved

a seafloor and sea surface gravity survey of axial volcano seafloor and sea surface gravity measurements are used to model the internal density structure of axial volcano seafloor measurements made at 53 sites within and adjacent to the axial volcano summit caldera provide constraints on the fine scale density structure shipboard gravity measurements made along 540 km of track line above axial volcano and adjacent portions of the juan de fuca ridge provide constraints on the density over a broader region and on the isostatic compensation the seafloor gravity anomalies give an average density of 2 7 g cm 3 for the uppermost portion of axial volcano the sea surface gravity anomalies yield a local compensation parameter of 23 significantly less than expected for a volcanic edifice built on zero age lithosphere three dimensional ideal body models of the seafloor gravity measurements suggest that low density material with a density contrast of at least 0 15 g cm 3 may be located underneath the summit caldera the data are consistent with low density material at shallow depths near the southern portion of the caldera dipping downward to the north the correlation of shallow low density material and surface expressions of recent volcanic activity fresh lavas and high temperature hydrothermal venting suggests a zone of highly porous crust seminorm minimization modeling of the surface gravity measurements also suggest a low density region under the central portion of axial volcano the presence of low density material beneath axial caldera suggests a partially molten magma chamber at depth

the controlling mechanism of mid to late holocene carbon isotopic variations of tridacnidae in the south china sea abstract the carbon isotopic fractionation process in biogenic carbonate is very complex and the mechanism for seasonal and long term variations in biogenic carbonate 13c remains a matter of debate in this study 5 tridacnidae samples were collected from the south china sea and analyzed in detail to study seasonal variations the high resolution 13c records exhibited cyclic variations likely related to seasonality in environmental parameters e g chl a concentration salinity sst rainfall 57 tridacnidae were collected and analyzed to study the millennium scale changes of tridacnidae 13c during the mid to late holocene and the controlling mechanism the tridacnidae 13c over the period 500 5500 bp is statistically significantly correlated with solar activity tsi and sunspot number likely attributed to the presence of symbiotic zooxanthellae within tridacnidae s mantle lobes solar activity could significantly affect the metabolic activity of zooxanthellae tridacnidae s microenvironment and thus tridacnidae s 13c composition the decoupling between the tridacnidae 13c and solar activity over the past 200 years is most likely due to increased amount of anthropogenic co2 and the oceanic 13c suess effect this study improves our understanding about the seasonal and long term variations of 13c in tridacnidae

long term seafloor tidal gravity and pressure observations in the north sea testing and validation of a theoretical tidal model seafloor gravity and pressure measurements for 4d reservoir monitoring require precise models of the time varying tidal signals current seafloor instrumentation can resolve 0 003 mgal in time lapse gravity differences and 0 05 kpa 5 mm in pressure to verify model accuracy a seafloor gravimeter and pressure gauge were operated continuously for 446 days next to the troll a gas platform in the north sea 60 64227 north 3 72417 east at a depth of 303 m the seafloor gravity and pressure time series were filtered and corrected with estimates from the tidal model which predicts the solid earth tide ocean loading and direct gravitational attraction of the varying water level the rms difference between the observed tidal gravity signal and the prediction is about 0 0013 mgal during periods when there are no surface storms a slight difference is observed for the direct attraction of the water overhead as computed from the tidal prediction versus that computed from direct seafloor pressure measuremen

images of diagenetic textures in porites corals from papua new guinea and indonesia diagenesis is now recognized as a potentially major source of error in paleoclimatic reconstructions from fossil and modern coral geochemical records key to avoiding spurious results caused by diagenesis is thorough screening of coral material prior to geochemical analysis in this data brief we present color images from thin sections of fossil and modern porites corals and demonstrate the effectiveness of thin sections in detecting low levels of diagenesis the images presented here cover a range of coral preservation levels from pristine aragonite to 100 calcite we particularly focus on samples containing around 1 diagenetic material a level known to create artifacts in key climate parameters such as sea surface temperature and close to the detection limits of other screening methods such as x ray diffraction xrd a qualitative scheme is also presented to rate the degree of diagenesis in a coral where xrd results are not available or where secondary aragonite is present overall this collection of images is designed as a starting point in combination with other techniques to assist in identifying and screening corals for diagenesis

a new sea floor gravimeter a new reservoir management application uses precise time lapse gravity measurements on the sea floor to detect seawater infiltration in offshore natural gas fields during production reservoir models for the north sea troll field predict gravity changes as large as 0 060 mgal within a 3 5 year period we have constructed and deployed a new instrument the rovdog remotely operated vehicle deployed deep ocean gravimeter system for this application because the measurements must be relocated accurately within 3 cm we required a gravimeter which could be handled by an rov and placed atop sea floor benchmarks we have built an instrument based upon the scintrex cg 3m land gravimeter motorized gimbals level the gravimeter sensor within a watertight pressure case precision quartz pressure gauges provide depth information a shipboard operator remotely controls the instrument and monitors the data the system error budget considers both instrumental and field measurement uncertainties the instrument prototy

holocene sea level change and hydro isostasy along the west coast of kyushu japan abstract mid to late holocene sea level variations have been obtained at sites along the west coast of kyushu japan sea level observations for this relatively stable area are very important for evaluating the crustal tilting associated with the hydro isostatic adjustment due to the last deglaciation and for examining the cause of underwater jomon sites submerged archeological sites during the jomon period of mid holocene typically observed in this region for these purposes we conducted systematic boring samplings at sites from goto island to tamana along the latitude of about 33 n then we performed diatom assemblage and pyrite sulfur analyses of these sediment samples and 14 c datings for intertidal shells in order to get the sea level variations for these sites observations at tsumizu faced to oomura bay with tidal range of 0 9 m show a sea level high stand of 1 m at about 5500 yr b p years before present followed by smoothly falling to the present level evidences for sea level oscillation of greater than 50 cm have not been found here relative sea levels at about 5000 yr b p are however 2 m at goto island 125 km west of tsumizu and 2 m at tamana 50 km east of tsumizu thus observations at sites along the traverse from goto island to tamana are indicative of crustal tilting of about 3 4 m for the distance of 175 km which seems to be consistent with the prediction caused by the hydro isostatic adjustment

global ocean response to orbital forcing in the holocene 1 global upper ocean evolution in the holocene is studied in two coupled ocean atmosphere models under orbital forcing conditions at 3 6 8 and 11 ka the annual mean sea surface temperature sst changes in the early to mid holocene are found to be forced mainly by the annual mean insolation forcing with an overall symmetric response of colder equator 1 c in the arctic this sst change is consistent with a synthesis of mid holocene paleo sst records in contrast the temperature response in the thermocline is dominated by an antisymmetric pattern with a cooling warming in the northern southern hemisphere midlatitudes the thermocline response is determined predominantly by surface water subduction and ultimately the insolation forcing in local late winter

testing ocean tide models in the nordic seas with tidal gravity observations summary tidal gravity observations at ny alesund on spitzbergen made with a lacoste romberg gravimeter with electrostatic feedback have been used to assess the accuracy of ocean tide models in the nordic seas eight ocean tide models have been used to compute the ocean tide loading at ny alesund the station is very close to the coast and therefore experiences a significant direct gravitational attraction of the nearby tidal water mass for the bay adjacent to the station the model values have been replaced by the tide gauge values and a special effort has been made to fit the models correctly to the coastline the ocean tide models for m2 and o1 have also been compared with observations made over 30 years ago at longyearbyen spitzbergen with askania gravimeters the comparisons of the tidal gravity observations with computed ocean tide loading show that for the harmonic m2 the phase lag of the ocean tide model of schwiderski and the local tide model of gjevik et al are wrong by 15 and 5 in the norwegian basin for the harmonic s2 the models fes94 1 got00 2 and schwiderski give a poor fit to the observed tidal loading at ny alesund because of phase lags that are too large in the norwegian basin by 10 fes94 1 and got00 2 also have s2 amplitudes that are 5 cm too large in the norwegian basin for n2 fes94 1 fes95 2 got00 2 and schwiderski have phase lags that are 10 too large in the norwegian basin and fes94 1 and 95 2 also have n2 amplitudes that are 2 4 cm too large in that region overall for these three harmonics the global model fes99 gives the best fit to the tidal gravity observations at ny alesund and this agreement is even closer than that obtained using regional arctic ocean tide models

identification characterization and hydrological implications of water repellency in mountain soils southern british columbia the physicochemical properties of soils which determine how readily the soils wet were shown to vary significantly in mountain soils collected at six sites in southern british columbia even within individual profiles the results of water drop penetration time tests were used to classify samples using a very simple scheme which is based upon our current understanding of the possible physicochemical interactions between solid surfaces water and soil air in all cases where the samples were collected at sites in the subalpine alpine ecotone a layer which either wets reluctantly or is water repellent exists at or near the surface of the profile these layers occur only where there is evidence for accumulation of organic matter and are usually no more than a few centimetres thick at the one site which was below the alpine subalpine ecotone the soils wet readily throughout the profile these results suggest that the type of organic matter which accumulates in soils of the alpine subalpine ecotone of southern british columbia either limits the affinity of soils for water or renders the soil water repellent the relation between infiltration rate and ponding depth was explored experimentally for a set of soil samples from a site in which a repellent layer was developed to depths greater than thirty centimetres it was found that the infiltration rate which was less than 2 0 millimetres per day for all samples was insensitive to changes in the ponding depth to a maximum applied depth of 400 millimetres and that it remained approximately constant over time these results suggest that water was transported primarily as a vapour rather than as a liquid given that water repellent soils are not uncommon in the alpine subalpine ecotone of southern british columbia and that ponding depths on hillslopes would be several orders of magnitude less than those applied experimentally it is inferred that transfer of water as a vapour within may be an important mechanism in such environments in their interpretation of variable solute sources and hydrological pathways in a small subalpine basin in british columbia gallie slaymaker 1984 suggested that water repellency could account in part for the observed tendency of water to bypass the soil matrix they noted that water repellency seemed to be preferentially associated with three of the six soil vegetation complexes found in their field area in explaining the relatively low solute yields from these same soils gallie slaymaker 1985 inferred the importance of hydrophobicity in years when segregated soil ice did not form reasonable though these assumptions were they were based on inference from scattered observations and barrett s masters thesis 1981 no systematic analysis of the phenomenon of water repellency was undertaken water repellency appears to be associated with accumulation of certain types of organic compounds on mineral grains bozer brandt hemwall 1969 suggested that the molecules involved are probably amphophilic that is they have a polar end which is attracted to mineral surfaces and a nonpolar end which is directed outwards to form a hydrophobic surface fig 1 it has been documented that forest fires and slash burning may result in transformation volatilization and distribution of organic compounds to produce a repellent layer which may revert to a non repellent condition over a number of years debano mann hamilton 1970 savage osborne letey heaton 1972 reeder jurgenson 1979 and giovannini lucchesi 1983 fungi and algae have been implicated in the production of water repellent soil bond harris 1964 savage martin letey 1969 and miller wilkinson 1977 as have a variety of plant species especially those native to semiarid environments the vegetation implicated includes chaparral in california krammes debano 1965 juniper in utah scholl 1971 and mallet trees in australia mcghie posner 1980 as far as the authors are aware there has been no previous documentation of water repellency as characteristic of soils in the alpine subalpine ecotone of southern british columbia this paper begins with a discussion of the conceptual basis for characterization of the physicochemical properties of soils in general and of water repellent soils in particular the results of field studies of water repellent mountain soils at the site studied previously by gallie slaymaker 1984 1985 and at other sites in southern british columbia are presented the paper closes with a summary of the results and conclusions a subsequent paper will explore the implications of this phenomenon for overland flow and runoff generation barrett slaymaker in preparation

early marine diagenesis in corals and geochemical consequences for paleoceanographic reconstructions detecting the potential geochemical consequences of early marine diagenesis is essential for establishing the validity of past climate reconstructions from coral we present coral skeletal 18o and sr ca data for two long coral cores spanning 1839 1994 ad at ningaloo reef western australia one of which includes significant secondary precipitation of marine inorganic aragonite long term trends in reconstructed sea surface temperatures ssts for the well preserved coral correlate strongly with instrumental sst records spanning the 20th century in contrast the 18o and sr ca for the diagenetically altered coral give identical cool sst anomalies of 4 5 c as a consequence of the addition of secondary aragonite enriched in 18o and sr our results indicate that cross checking of paleoclimate reconstructions with two supposedly independent paleothermometers may not be valid and that coral records showing cooler ssts in the past need to be interpreted with caution furthermore modern coral records with long term trends in 18o indicating recent warming and freshening of the ocean can be potentially explained by early marine diagenesis

nloadf a program for computing ocean tide loading the loading of the earth by the ocean tides produces several kinds of signals which can be measured by geodetic technique in order to compute these most accurately a combination of global and local models of the ocean tides may be needed the program nloadf convolves the green functions for loading with ocean tide models using a station centered grid with fixed dimensions making it easy to combine different ocean models without overlap in the convolution the program computes all the quantities of interest gravity displacement tilt and strain and includes the case where measurements are made beneath the surface of the ocean

patterns of soil water repellency change with wetting and drying the influence of cracks roots and drainage conditions laboratory experiments were used to investigate the influence of simulated cracks and roots on soil water repellency swr dynamics with and without basal drainage impedance in wetting drying cycles observations and measurements were taken following water application equivalent to 9 2 mm rainfall and then periodically during 80 h of drying in total 180 experiments were carried out using 60 samples of three homogeneous reconstituted soils with different organic matter contents and textures but of similar initial severity of swr 18 molarity of an ethanol droplet med water flowing down the cracks and roots left the soil matrix largely dry and water repellent except for vertical zones adjacent to them and a shallow surface layer a hydrophilic shallow basal layer was produced in experiments where basal drainage was impeded during drying changes in swr were largely confined to the zones that had been wetted soil that had remained dry retained the initial severity of swr while wetted soil re established either the same or slightly lower severity of swr in organic rich soil the scale of recovery to pre wetting med levels was much higher perhaps associated with temporarily raised levels up to 36 med of swr recorded during drying of these soils with all three soils the re establishment of the original swr level was less widespread for surface than subsurface soil and with impeded than unimpeded basal drainage key findings are that as follows 1 with unimpeded basal drainage the soils remained at pre wetting repellency levels except for a wettable thin surface layer and zones close to roots and cracks 2 basal drainage impedance produced hydrophilic basal and surface layers 3 thorough wetting delayed a return to water repellent conditions on drying and 4 temporarily enhanced swr occurred in organic rich soils at intermediate moisture levels during drying hydrological implications are discussed and the roles of cracks and roots are placed into context with other influences on preferential flow and swr under field conditions copyright 2014 john wiley sons ltd

mid holocene palaeoceanography of the northern south china sea using coupled fossil modern coral and atmosphere ocean gcm model 1 high resolution records of past environments of the south china sea scs could provide important information to better understand the mechanisms of el nino southern oscillation enso and east asian monsoon evolution since scs is located between pacific ocean and eurasian continent scs plays a key role as the moisture source area of monsoon precipitation that affects the terrestrial climate of asia fossil and modern corals were obtained from south china sea scs to study changes in oceanographic conditions when the northern hemisphere experienced perihelion during the early to mid holocene and thermal contrast between scs and the asian continent was larger the fossil coral is 6600 years old and xrd and sem investigations confirmed pristine nature of this sample oxygen isotope measurement of modern coral yielded an average value of ca 6 whereas the fossil coral showed ca 5 5 given that previously reported alkenone sst thermometry and foraminiferal sst reconstruction indicate little changes in sst 0 5 c throughout the holocene in scs we consider the possibility of changes in 18o of seawater to be due to local sea surface salinity sss coral data from the present study 6600 years old coral as well as previously published record 4400 years old showed higher sss during the mid holocene coral data were then compared with the coupled ocean atmosphere gcm miroc3 2 higher sss during the mid holocene time was also seen in aogcm experiments we observed northward shift of inter tropical convergent zone itcz in the experiments that produced increased precipitation on the asian continent the cause of increase in salinity was therefore due to less precipitation in scs and increased continental precipitation inland of asia

saltier sea surface water conditions recorded by multiple mid holocene corals in the northern south china sea the typical features of the mid holocene can be used to better understand present day climate conditions and the potential trends of future climate change the surface conditions including sea surface temperature sst and sea surface salinity sss of the south china sea scs are largely controlled by the east asian monsoon system surface water conditions reconstructed from coral proxies can be used to study the evolution of the east asian monsoon during the mid holocene however there are some discrepancies among existing coral based studies regarding whether the mid holocene sea surface water was much saltier than the present day surface waters based on paired sr ca and 18o of modern and three fossil corals this paper reconstructs the patterns of seasonal variation in sss during the mid holocene in the northern scs the 18o records a proxy for sss derived from the three fossil corals were all heavier than that from the modern coral which suggests the presence of more saline surface waters during the mid holocene in the northern scs these results are consistent with previous studies based on records reconstructed from coral and foraminifera as well as from numerical simulations reduced rainfall caused by the strengthened asian monsoon and or the northward shift of the intertropical convergence zone during the mid holocene would explain the increased salinity of the surface waters of the northern scs the findings presented here clarify the discrepancies among previous studies and confirm the existence of saltier surface waters in the northern scs during the mid holocene this article is protected by copyright all rights reserved

inconsistent sea surface temperature and salinity changing trend in the northern south china sea since 7 0 ka bp abstract the south china sea scs is an important moisture and heat source in the asian monsoon system and its environmental changes influence economic and social stability in southeast asia and east asian previous records on sea surface temperature sst and salinity sss were mostly from one sediment core and or only showed fragmentary information it is hard to provide insights into the mechanisms of the overall paleoceanographical environmental variability in the northern scs in this study paired 18o and mg ca records of planktonic foraminifer globigerinoides ruber from core s0204b nearby the luzon strait 21 13 818 n 118 3 077 water depth 1822 m and core ghe 27l 19 85 n 115 34 e water depth of 1533 m in the central northern scs were analyzed so as to better understand the physical process of the sst and sss changes in the northern scs and its relationship with the tropical pacific the results demonstrate that the sst is relatively stable and seawater 18o 18osw values a salinity proxy shows a decrease trend since 7 0 ka bp in core s0204b by contrast sst and 18osw in core ghe 27l exhibit an overall increasing trend at the same time indicating apparent regional discrepancy on the changing trend of the sst and sss in the northern scs we suggest that the thermal and hydrographic conditions in core s0204b were primarily influenced by the outer western pacific water however the thermal and hydrographic conditions in core ghe 27l may be predominantly controlled by the weakened asian monsoon during the mid late holocene which was induced by the southern migration of intertropical convergence zone itcz and stronger ei nino southern oscillation

preferential flow paths in a water repellent clay soil with grass cover grass covered heavy basin clay soils in the netherlands appeared to be water repellent water repellency in the top layers of these soils occurred mainly as a coating on the aggregates the variation in soil moisture content over short distances was studied by sampling the soil 10 times during the period august 31 1993 to december 22 1994 each time 35 samples 100 cm3 were taken in close order over a distance of 195 cm at depths of 0 5 10 15 20 25 and 30 35 cm differences between minimum and maximum soil moisture contents were high in all layers sampled occasionally as much as 28 vol when the clay soil is dry a major proportion of the water from precipitation or sprinkler irrigation may flow rapidly through shrinkage cracks to the subsoil bypassing the matrix of the clay peds however preferential flow is not limited to macropore flow irregular wetting patterns are also formed through the small pores of the matrix the relationship between dry bulk density and volumetric water content was found to be positive when the clay soil was relatively dry and negative when it was relatively wet

refining the eustatic sea level curve since the last glacial maximum using far and intermediate field sites the eustatic component of relative sea level change provides a measure of the amount of ice transferred between the continents and oceans during glacial cycles this has been quantified for the period since the last glacial maximum by correcting observed sea level change for the glacio hydro isostatic contributions using realistic ice distribution and earth models during the last glacial maximum lgm the eustatic sea level was 125 5 m lower than the present day equivalent to a land based ice volume of 4 6 4 9 107 km3 evidence for a non uniform rise in eustatic sea level from the lgm to the end of the deglaciation is examined the initial rate of rise from ca 21 to 17 ka was relatively slow with an average rate of ca 6 m ka 1 followed by an average rate of ca 10 m ka 1 for the next 10 ka significant departures from these average rates may have occurred at the time of the younger dryas and possibly also around 14 ka most of the decay of the large ice sheets was completed by 7 ka but 3 5 m of water has been added to the oceans since that time

tropical pacific climate at the mid holocene and the last glacial maximum simulated by a coupled ocean atmosphere general circulation model 1 simulations for the mid holocene 6000 years before present 6 ka and the last glacial maximum lgm 21 ka have been performed by a global ocean atmosphere coupled general circulation model gcm after the initial spin up periods both runs were integrated for about 200 years for 6 ka the model shows an enhanced seasonal variation in surface temperature and a northward shift of the african and the indian summer monsoon rain area overall circulation features in the tropics correspond to a strong walker circulation state with negative sea surface temperature sst and precipitation anomalies in the central pacific and positive precipitation anomalies over the indian and australian monsoon regions it is noted that there is about a 0 35 c cooling of the global mean sst in contrast to the 6 ka result the simulated tropical climate anomaly at 21 ka corresponds to a weak walker circulation state the simulated lgm sst decrease is about 2 c over the tropical western pacific it is larger about 5 c over the caribbean sea this sst anomaly is in broad agreement with the observed proxy data interestingly the model simulates a warmer than present sst over the subtropical pacific this may be related to a weaker subtropical anticyclone due to weakened monsoon circulation at the lgm

paleoprecipitation record from coral sr ca and δ18o during the mid holocene in the northern south china sea coupled high resolution sr ca and delta o 18 records of a modern and a mid holocene coral from sanya in the southern hainan island northern south china sea scs were reported and the residual delta o 18 delta delta o 18 were calculated to indicate precipitation change in this region unlike other paleoclimate studies this study focused on changes of precipitation time rather than precipitation amount as negative delta delta o 18 peaks in coral generally correspond to peak precipitations or rainy seasons in the surrounding region the time offsets between negative delta delta o 18 peaks and other seasonal indicators such as sea surface temperature sst can well indicate the time of rainy seasons and the precise time offsets can be estimated by the method of cross spectral analysis the results of the modern coral indicate that the variation of the coral delta delta o 18 lags that of the instrumental measured precipitation by about 2 months and about 3 months to the sst derived from coral sr ca ratios this agrees well with the modern observation that the salinity change in the southern coastal regions generally lags that of the precipitation in hianan island by about 2 months and the precipitation change lags about 1 month behind the sst in this region thus coral delta delta o 18 records can be a reliable proxy for the change of rainy seasons in this region the results of the mid holocene coral show about 2 5 months leading of the delta delta o 18 variation ahead of the sst by compensating the approximate 3 months lag of the delta delta o 18 variation behind the sst in modern time the occurrence of rainy seasons during the mid holocene may have advanced about 5 6 months in detail it may start around december and end around april to may with maximum occurring around february therefore rainy seasons mainly occur in winter through early spring during the mid holocene compared with that from may through october in modern times such precipitation patterns appear to agree with the mid holocene pollen records in this region variations of large scale circulation may possibly result in such a different precipitation pattern further studies in particular climate model studies collaborated with meteorologists are required for a better understanding of the mechanism

calibration of stable oxygen isotope signatures in galapagos corals a 2 year 1993 1994 study was conducted in the galapagos islands ecuador to determine the relationship between 18o in skeletal carbonate and sea surface temperature sst in three species of reef building corals pavona clavus pavona gigantea and porites lobata coral samples were grown at 3 10 and 3 m depth at bartolome island champion iisland and urvina bay isabela island respectively hourly measurements of sst and sea surface salinity sss were taken at each site immediately adjacent to colonies which were stained biannually to establish the chronology of growth in addition surface waters were sampled periodically bimonthly to monthly at each site to determine variation in 18o seawater results indicate the mean annual ssts were similar between sites varying from 22 9 c at champion to 23 8 c at urvina bay comparisons of monthly sst averages between instrumental and remote sensing satellite 1 1 grid data show a high correspondence r2 ranging from 0 84 to 0 94 indicating that remote sensing data are useful for interpreting the 18o record in corals when instrumental data are lacking here 18ocoral analyses of eight specimens show that coralline aragonite is a reliable indicator of sst in galapagos in general higher resolution coral sampling year resolved more of the monthly variation in sst up to 97 at a sampling resolution of 1 4 samples per millimeter of linear skeletal growth comparisions of the 18ocoral signal among and between species at the same site showed consistent seasonal patterns of variation closely tracking sst in addition comparisons between sites were highly concordant with some differences reflecting local variation in sst seasonal patterns however were essentially the same over the entire region thus we conclude that the 18ocoral signal from coral skeletons in galapagos can be used to interpret regional changes in sst variation

investigating the dynamical behavior of the intertropical convergence zone since the last glacial maximum based on terrestrial and marine sedimentary records abstract the intertropical convergence zone itcz is an integral component of the earth s climate system it plays important roles in monsoon precipitation transport of chemical tracers between the hemispheres enso variability etc the itcz is characterized by seasonal movement that stays several degrees north of the equator during the boreal summer and a few degrees south of the equator during the boreal winter the seasonal movement across the hemisphere is driven by seasonal changes in insolation apart from seasonal migration itcz also moves in longer timescales that is governed by the orbital motion of the earth as well as by the internal dynamics of the earth s ocean atmospheric variability proxy records indicate the mean position of the itcz of the indian ocean sector was somewhat different relative to its estimated position considering solar insolation variability in orbital time scale in this paper we investigate the movement of the itcz that occurred in millennium time scales and discuss its implications mainly on south asian monsoon variabilities the study relies on proxy data the isotopic analysis of foraminifera and speleothem one of the important implications of this study is that the indian summer monsoon rainfall which is undergoing a slow decreasing trend for the last several decades is expected to experience a reverse trend in a few decades

hydroclimate reconstruction in central japan over the past four centuries from tree ring cellulose δ18o abstract the east asian summer monsoon is an important part of the earth s climate system that is characterized by variations in the strength and expansion of the summer rain band rainfall reconstructions in china have revealed changing patterns of rainfall during the little ice age lia but limited hydroclimate reconstruction around japan have hindered detailed understanding of physical processes associated with the atmospheric system in the western north pacific here we report relative humidity variations in the meiyu baiu season from 1600 1959 ce by using tree ring cellulose oxygen isotopes from central japan this is the first record of the lia from the easternmost regions of the east asian monsoon domain our data suggest that the wettest period occurred around 1780 1880 ce corresponding to the final stage of the lia this shift was concurrent with sea surface temperature negative positive anomalies around the philippines off eastern japan we suggest that meridional atmospheric circulation was weak during the last stage of the lia

mid holocene climate in new caledonia southwest pacific coral and pmip models monthly resolved results abstract the mid holocene climate is characterized by an insolation seasonality decrease in the southern hemisphere but measurements of its actual impact on monthly resolved sea surface temperature sst in the southwest pacific region are still insufficient a new caledonian 5 5 ka cal bp coral provides a 20 year long seasonally resolved record of ocean surface conditions as inferred from coral sr ca and ba ca results were compared to monthly series of paleoclimate modeling intercomparison project phase 2 pmip2 model simulations anomalous stable isotope and u ca values are observed in a restricted area of the skeleton related to dissolution features the mid holocene sst seasonal amplitude mean and variability are higher than presently in new caledonia the increased seasonal amplitude in the mid holocene being most probably due to the occurrence of colder winters other southwest pacific mid holocene coral data showed also such an increased seasonal amplitude this could mean that the south pacific convergence zone spcz was weaker or reached locations more northerly than at present which could fit with northward shifts of the inter tropical convergence zone itcz during south hemisphere winter inversely strong rainfalls during the summer deduced from the ba ca signal and reconstructed sea surface salinity sss were interpreted as reflecting pronounced southwestward shifts of the spcz in summer as those occurring today during la nina events none of the six pmip2 models used reproduce the proxy based mid holocene increase of sst seasonal amplitude model maps show a less intense spcz in winter that would be consistent with higher sst seasonal amplitude finally we stress the need for more seasonally resolved data to validate this enhanced mid holocene sst seasonal amplitude in the southwest pacific region and to better understand the underlying mechanisms

variations in the timing of the rainy season in the northern south china sea during the middle to late holocene the amount and timing of precipitation in east asia are important aspects of the east asian monsoon many paleoclimate records that act as proxies for wet or dry climatic conditions have been linked to changes in precipitation amounts and are thus used to indicate changes in the east asian monsoon system however few studies have examined changes in the timing of the rainy season here we consider the timing of the seasonal precipitation cycle during the middle to late holocene using records derived from coupled high resolution sr ca and o 18 records preserved in porites corals from the northern south china sea these records indicate that the timing of the rainy season in this region changed during the middle to late holocene the present day rainy season generally occurs over the summer and autumn june october which has also been recorded in porites coral whereas the rainy season at around 1500 and 6800years b p occurred through the autumn and winter august december and the rainy season at around 2540 and 5000years b p occurred in the winter and spring january april or december march during the period around 5900years b p the seasonal distribution of precipitation varied from year to year these shifts in the timing of the rainy season require changes in temperature and humidity patterns and appear to agree with changes in the magnetic susceptibility of lake sediments in this region which may reflect movements of the intertropical convergence zone location and changes in atmospheric circulation during the middle to late holocene key points timing of rainy season changed during the middle to late holocene over northern scs variation patterns of rainy season agreed with magnetic susceptibility records shift of rainy season may be associated with itcz and atmospheric circulation

crustal structure of the mid atlantic ridge south of the kane fracture zone from seafloor and sea surface gravity data seafloor and sea surface gravity data are inverted together to construct a model for the near axis crustal structure of a slow spreading ridge the seafloor data set offers two main advantages it allows us to recover shorter wavelengths signal and to constrain the value of a potential field at two different levels the model we propose here would not have been derived from sea surface data alone it is based on a dense sea surface gravity coverage and on 121 sea bottom gravity measurements collected in the mid atlantic ridge at kane mark area during the hydrosnake 1988 and gravinaute 1993 cruises the primary goal of the seafloor surveys was to test for the presence of a magma reservoir beneath the axial neovolcanic ridge first a forward two dimensional 2 d model of the crustal structure across the axis is fit to observed gravity anomalies using constraints from geological and structural observations bouguer anomalies computed from sea bottom measurements and downward continuation of sea surface measurements both constrain the forward modeling this forward model is the starting point of a 2 d monte carlo inversion of seafloor and sea surface data in addition to the crustal thickness variations along axis our data document the amplitude variations of the crustal thickness and or its density in the across axis direction the model resulting from our inversion exhibits several features of the crustal structure in the mark area 1 the presence of a low density ap 300 50 kg m 3 body beneath the neovolcanic ridge is suggested and could correspond to a magma chamber or more probably to a highly hydrothermally fissured zone 2 both long and short wavelength gravity signals exhibit a difference between the western and eastern sides of the axial domain the mean value and the amplitude of bouguer anomalies are higher on the western part this difference suggests that axial processes in this area are very asymmetric 3 abyssal hills are not associated with a single gravity signature for instance on the west side of the axis one of the explored hills has no bouguer anomaly and is interpreted as a neovolcanic ridge whereas the others are associated with a shifted bouguer anomaly high and are interpreted as having thinner magmatic crust 4 the last feature of the crustal fabric we document here is the asymmetric emplacement of some deep rocks outcrops in the mark area we find that pink hill a topographic high where serpentinized peridotites are outcropping is much more serpentinized on its east flank toward the axial valley than on its west flank alteration occurring mainly by fluid circulation through faulted zones the asymmetric serpentinization suggests that deep origin rocks have outcropped by means of a main fault zone and are not emplaced by diapirism

analyses of a 426 day record of seafloor gravity and pressure time series in the north sea continuous gravity observations of ocean and solid tides are usually done with land based gravimeters in this study we analyze a 426 day record of time varying gravity acquired by an ocean bottom scintrex spring gravimeter between august 2005 and november 2006 at the troll a site located in the north sea at a depth of 303 m sea bottom pressure changes were also recorded in parallel with a paroscientific quartz pressure sensor from these data we show a comparison of the noise level of the seafloor gravimeter with respect to two standard land based relative gravimeters a scintrex cg5 and a gwr superconducting gravimeter that were recording at the j9 gravimetric observatory of strasbourg france we also compare the analyzed gravity records with the predicted solid and oceanic tides the oceanic tides recorded by the seafloor barometer are also analyzed and compared to the predicted ones using fes2014b ocean model observed diurnal and semi diurnal components are in good agreement with fes2014b predictions smallest constituents reflect some differences that may be attributed to non linearity occurring at the troll a site using the barotropic tugo m dynamic model of sea level response to ecmwf atmospheric pressure and winds forcing we show a good agreement with the detided ocean bottom pressure residuals about 4 hpa of standard deviation of remaining sea bottom pressure are however not explained by the tugo m dynamic model

seawater isotope constraints on tropical hydrology during the holocene 1 paleoceanographic data from the low latitude pacific ocean provides evidence of changes in the freshwater budget and redistribution of freshwater within the basin during the holocene reconstructed holocene seawater 18o changes compare favorably to differences predicted between climate simulations for the middle holocene mh and for the pre industrial late holocene lh the model simulations demonstrate that changes in the tropical hydrologic cycle affect the relationship between 18osw and surface salinity and allow for the first time quantitative estimates of western pacific salinity change during the holocene the simulations suggest that during the mh the mean salinity of the pacific was higher because less water vapor was transported from the atlantic ocean and more was transported to the indian ocean the salinity of the western pacific was enhanced further due both to the greater advection of salt to the region by ocean currents and to an increase in continental precipitation at the expense of maritime precipitation the latter a consequence of the stronger asian summer monsoon

growth rate influences on coral climate proxies tested by a multiple colony culture experiment abstract as application of coral based climate reconstruction has become more frequent at tropical sites increased attention is being paid to the potential ambiguities of coral thermometers that are intrinsic to the biomineralisation process including the so called vital effect the growth rate related kinetic effect and the co 3 2 effect here we studied how the growth rate influenced the skeletal oxygen and carbon isotope ratios 18 o and 13 c and the sr ca ratio in a common garden experiment involving the long term culture of porites australiensis clone colonies comparison of the seasonal minimum 18 o values during summer showed a negligible influence of the large intercolony variation in growth rate 2 10 mm yr 1 on 18 o variation but 18 o was relatively sensitive to temporary intracolony growth rate changes related to colony health in contrast the sr ca ratio was robust against both inter and intracolony growth rate variation we found a positive shift in 13 c in slower growing corals which we attributed to the kinetic behaviour of the calcification reaction the seasonal fluctuation in 13 c corresponded not to changes in light intensity nor to 13 c of dissolved inorganic carbon in seawater but to photosynthetic efficiency as measured by pulse amplitude photometry these findings support the inference that coral skeletal sr ca and 18 o in a long lived colony can function as a palaeoclimate archive by recording signals of clonal growth we also propose practical guidelines for the proper interpretation of coral records

plant wax hydrogen isotopic evidence for postglacial variations in delivery of precipitation in the monsoon domain of china the asian monsoon is a key component of the earth s climate system that directly affects the livelihood of 60 of the world population reliable reconstruction of changes in monsoon precipitation during the holocene is required to better understand the present climate conditions and to predict future climate processes in the asian monsoon domain reconstruction of changes in holocene monsoon precipitation has been done in various regions of this domain using a variety of paleoclimate proxies however different proxies have yielded different paleoclimate records of long term monsoon rainfall variability we apply compound specific stable hydrogen isotope compositions of the plant wax n alkanes isolated from the hongyuan peat sequence in eastern tibet to reevaluate the regional carbonate oxygen isotopic and lake level records the d h ratios of the n alkanes resolve the apparent discrepancy among the different paleoclimate proxies our result indicates that lake level fluctuation is a reliable recorder of changes in the amount of summer monsoonal precipitation while long term isotope records largely reflect large scale changes in the source of water vapor rather than a local precipitation signal combining lake level biomarker and carbonate isotopic records we conclude that the early holocene monsoon precipitation in southwest china has been greatly influenced by the indian monsoon

fossil otoliths from the gulf of kutch western india as a paleo archive for the mid to late holocene environment abstract abundantly available catfish otoliths excavated from the ruins of the indus civilization in the coastal regions of western india are expected to preserve a detailed paleoclimatological record of the mid to late holocene in this study we analyzed saltwater catfish otoliths recovered from the gulf of kutch western india stable isotopes oxygen and carbon and elemental ratios ba ca and sr ca were measured by isotope ratio mass spectrometry irms and high resolution laser ablation inductively coupled plasma mass spectrometry la icp ms respectively oxygen isotopes of a modern otolith 18o indicates the interval when the catfish would have dwelt in the sea and appear to record seasonal temperature variability with a precision of 1 c calculated temperatures from 18o of a fossil otolith dated to 4 3 cal ka bp indicates that the minimum temperature in winter was 2 5 c lower than that of the present although comparison to alkenone results from the northwestern arabian sea indicates potential temperature underestimation further measurements of modern and fossil samples would lead to more precise reconstruction of temperature history during mid to late holocene