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

strontium contents of a porites coral from xisha island south china sea a proxy for sea surface temperature of the 20th century 1 a porites coral collected from xisha island south china sea represents a skeleton secreted in the period from 1906 to 1994 the sr contents of the coral vary linearly with the instrument measured sea surface temperature sst giving a sr thermometer sst 1 9658 x sr 193 26 the reconstructed sst data show that the late 20th century was warmer about 1 degreesc than the early 20th century and that two cooling 1915 1916 and 1947 1948 and three warming 1935 1936 1960 1961 and 1976 1977 shifts occurred in the century the temperature shifts are more pronounced for winters implying a close effect of the west pacific warm pool and asian monsoon and suggesting that the former is a primary force controlling the climatic system of the region results of this study and previously published data indicate a close link of temperature shifts between the boreal summer and the austral winter or the boreal winter and the austral summer the annual sst anomalies in the south china sea and the south pacific reveal the existence of harmonic but opposite sst variations between the two regions on the decadal scale the comparative annual sst anomalies for the south china sea and for the equatorial west pacific show a similarity in temperature variations implying that the south china sea climate is coherent with climatic regime of the tropical west pacific

an 15 000 year record of el nino driven alluviation in southwestern ecuador debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the pacific ocean in ecuador these storm induced events were dated by radiocarbon and the age of laminae that are less than 200 years old matches the historic record of el nino events from about 15 000 to about 7000 calendar years before the present the periodicity of clastic deposition is greater than or equal to 15 years thereafter there is a progressive increase in frequency to periodicities of 2 to 8 5 years this is the modern el nino periodicity which was established about 5000 calendar years before the present this may reflect the onset of a steeper zonal sea surface temperature gradient which was driven by enhanced trade winds

on the stability of ocean overflows author posting cambridge university press 2008 this article is posted here by permission of cambridge university press for personal use not for redistribution the definitive version was published in journal of fluid mechanics 602 2008 241 266 doi 10 1017 s0022112008000827

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

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

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

evidence for ocean acidification in the great barrier reef of australia geochemical records preserved in the long lived carbonate skeleton of corals provide one of the few means to reconstruct changes in seawater ph since the commencement of the industrial era this information is important in not only determining the response of the surface oceans to ocean acidification from enhanced uptake of co2 but also to better understand the effects of ocean acidification on carbonate secreting organisms such as corals whose ability to calcify is highly ph dependent here we report an 200 year d 11 b isotopic record extracted from a long lived porites coral from the central great barrier reef of australia this record covering the period from 1800 to 2004 was sampled at yearly increments from 1940 to the present and 5 year increments prior to 1940 the d 11 b isotopic compositions reflect variations in seawater ph and the d 13 c changes in the carbon composition of surface water due to fossil fuel burning over this period in addition complementary ba ca d 18 o and mg ca data was obtained providing proxies for terrestrial runoff salinity and temperature changes over the past 200 years in this region positive thermal ionization mass spectrometry ptims method was utilized in order to enable the highest precision and most accurate measurements of d 11 b values the internal precision and reproducibility for d 11 b of our measurements are better than 0 2 2r which translates to a precision of better than 0 02 ph units our results indicate that the long term pre industrial variation of seawater ph in this region is partially related to the decadal interdecadal variability of atmospheric and oceanic anomalies in the pacific in the periods around 1940 and 1998 there are also rapid oscillations in d 11 b compositions equivalent changes in ph of almost 0 5 u the 1998 oscillation is co incident with a major coral bleaching event indicating the sensitivity of skeletal d 11 b compositions to loss of zooxanthellate symbionts importantly from the 1940s to the present day there is a general overall trend of ocean acidification with ph decreasing by about 0 2 0 3 u the range being dependent on the value assumed for the fractionation factor a b3 b4 of the boric acid and borate species in seawater correlations of d 11 b with d 13 c during this interval indicate that the increasing trend towards ocean acidification over the past 60 years in this region is the result of enhanced dissolution of co2 in surface waters from the rapidly increasing levels of atmospheric co2 mainly from fossil fuel burning this suggests that the increased levels of anthropogenic co2 in atmosphere has already caused a significant trend towards acidification in the oceans during the past decades observations of surprisingly large decreases in ph across important carbonate producing regions such as the great barrier reef of australia raise serious concerns about the impact of greenhouse gas emissions on coral calcification 2009 elsevier ltd all rights reserved

elemental carbon record of paleofire history on the chinese loess plateau during the last 420 ka and its response to environmental and climate changes an elemental carbon ec record covering the last 420 ka was reconstructed using chemical oxidation method on a loess and paleosol sequence from the lingtai section on the chinese loess plateau the ec record reveals the paleofire history and its relationship with climate and vegetation changes on the chinese loess plateau our results show that the ec abundance is generally higher in the paleosols than in the loess layers showing a glacial interglacial pattern which is coincident with biomass changes this variation pattern indicates that paleofires were intensified when biomass accumulated and climate changed abruptly especially from wet to dry conditions the ec abundance increases sharply at similar to 130 kab p indicating a dramatic change in the vegetation and climate variation patterns the occurrence of a peak value with the highest average ec abundance in the holocene may reflect the occurrence of a major climate event at similar to 6 kab p and may also be partly due to more frequent anthropogenic fire usages c 2007 elsevier b v all rights reserved

coral δ18o based reconstruction of el nino southern oscillation from the northern south china sea since 1851 ad abstract el nino southern oscillation enso is the largest source of interannual climate variability over the globe knowledge of enso variability back to the pre instrumental period and earlier can help to enhance our understanding of its mechanisms and impacts here we use the coral record from the northern south china sea where the interannual climate variability is associated with enso activity to reconstruct enso variability over the past 150 years our record together with other enso chronologies indicated not only the weakened enso activity between 1930s and 1960s but also the larger variations of el nino activity relative to that of la nina based on the sliding window method the comparison between the scs and pacific enso band coral records revealed the relatively stronger climatic coupling between the scs and the equatorial central eastern pacific compared with that between scs and western pacific indicating the reliability of teleconnection relationship between the scs climate and enso our result indicated that the coral 18o record from the scs could contribute to the pan pacific enso reconstructions

decadal variations in trace metal concentrations on a coral reef evidence from a 159 year record of mn cu and v in a porites coral from the northern south china sea geochemical cycles of trace metals are important influences on the composition and function of the marine ecosystem although spatial distributions of most trace metals have now been determined in at least some parts of the oceans temporal variations have barely been studied on account of data limitations in this paper we report on a 159 year record of trace metal concentrations from a porites coral from the northern south china sea scs and discuss how oceanic and climatic processes control variations in mn cu and v concentrations in this region our results show that trace metal concentrations in the coral skeleton demonstrate decadal to interdecadal fluctuations and that their variations are controlled by different mechanisms the input of mn to reef water is partly controlled by the pacific decadal oscillation pdo which controls precipitation and river runoff surface water concentrations of the nutrient like element cu are controlled by summer upwelling to the east of hainan island the concentrations of v show complex interrelationships and are linked to riverine input prior to the 1990 and to upwelling after the 1990 our results imply that in the northern scs ocean atmosphere climate fluctuations such as the pdo and the east asian summer monsoon easm are important factors that influence long term variability of mn cu and v concentrations in seawater by controlling precipitation related river runoff and the strength of upwelling systems

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

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

exploring the temperature dependence of clumped isotopes in modern porites corals porites corals are valuable geological archives for reconstructing past sea surface temperature sst in tropical oceans their clumped isotope compositions indicated by values provide a potential proxy for sst the value in porites coral usually departs from thermodynamic equilibrium due to vital effects to explore the temperature dependence of values in corals we determined c o and values in two modern porites corals from the south china sea our results indicate no intercolony or intracolony biases in values on annual timescales however on seasonal timescales enrichment associated with c depletion is observed at an intracolony level this cannot be explained by incomplete hydration and or hydroxylation of metabolic co instead we interpret this new pattern of isotopic anomalies as a peculiar evidence of vital effects on and c fractionation although complicated by vital effects the signature in porites corals still preserved a robust sst dependence similar to those of recently published t calibrations the observed offset relative to inorganic carbonate due to the vital effects is consistent and relative variations in seasonal sst can be obtained this study refines the thermometer in porites corals and strengthens its capacity to be used to reconstruct past sst

variations in the pacific decadal oscillation since 1853 in a coral record from the northern south china sea 1 the pacific decadal oscillation pdo has been shown to have significant climatic and environmental impacts across the pan pacific basin however there are no records of pdo activity from the south china sea scs the largest marginal sea in the northwest pacific ocean this study suggests that a series of geochemical profiles obtained from a modern coral in the northern scs records annual pdo activity dating back to 1853 these geochemical data are significantly correlated with the pdo index and their patterns of variation closely match those of the pdo index over the last century the relationship between the pdo and coral geochemistry may be related to the influence of the pdo on rainfall on hainan island rainfall patterns influence the volume of terrestrial runoff which in turn is a primary determinant of 18o and 18o values in coral however coral 13c values are also influenced by the 13c suess effect the results indicate that sr ca ratios in coral are affected by a combination of sea surface temperature and terrestrial runoff

mg ca sr ca and u ca ratios of a porites coral from sanya bay hainan island south china sea and their relationships to sea surface temperature high resolution mg ca sr ca and u ca ratios are reported in the skeleton of porites sp collected from sanya bay on the south coast of the hainan island china using inductively coupled plasma mass spectrometry combined with isotope dilution technique icp ms id the coralline mg ca ratios covary with sea surface temperatures sst for the 10 year interval giving the relationship between mg ca and sst as t degrees c 14 13 0 31 8 846 0 068 x 10 3 mg ca with the mean square weighted deviation mswd of 9 7 using this equation we are able to reconstruct sst record with a precision better than 0 5 degrees c several sr ca and u ca ratios show poor linear relationships with the measured sst this study indicates that the growth rates of the coral do not significantly affect coralline mg ca sr ca and u ca ratios however the high meteoric precipitation in this area which may cause a heavy run off from the island may change seawater sr ca and u ca ratios and ruin the relationships between coralline sr ca or u ca ratios and sst this implies that in coastal areas like hainan coralline mg ca ratios are valid for reconstructing the sst records but sr ca and u ca ratios may be suspected c 2000 elsevier science b v all rights reserved

temporal and spatial variability of the oxygen isotopic composition of massive corals from the south china sea influence of the asian monsoon coral colonies of porites lutea and p lobata were collected from areas to the east and south offshore of hainan island south china sea oxygen isotope ratios o 18 o 16 were analyzed along the major axis of growth at a resolution of 25 28 samples within an annual band from three colonies giving data series lengths of 15 20 and 30 years coral delta o 18 correlates well with sea surface temperature sst throughout most years particularly when the asian winter monsoon prevails over the region due to the same seasonal phases of sst and sea surface salinity sss it is estimated that most of the seasonal features of coral delta o 18 are controlled by changes in sst with a significant contribution of sss this indicates the importance of temperature as determined by the asian winter monsoon as a control on seasonal coral delta o 18 variations in the south china sea given the fact that annual sss maxima show minor inter annual changes the inter annual change of annual coral delta o 18 maximum mainly reflects the sst induced by the winter monsoon while the coral delta o 18 is mainly controlled by sst deviations of the delta o 18 from sst correlate statistically with sea surface salinity particularly for summer extreme events when sst reaches its annual maximum with minor inter annual change therefore we suggest that the inter annual variation of the annual coral delta o 18 minima is mainly controlled by seawater composition seawater composition analysis indicates that its delta o 18 and salinity are simultaneously affected by freshwater inputs primarily from precipitation which is mainly supplied by the asian summer monsoon thus seasonal alternations of the winter and summer monsoon mainly control the coral delta o 18 thereby allowing reconstruction of these monsoonal variables the three coral records consistently reveal clear inter decadal trends in delta o 18 a gradual increase from 1968 to 1987 and a subsequent decrease from 1987 to 2003 these inter decadal trends are roughly consistent with salinity changes but not with temperature and precipitation suggesting that seawater composition controlled by freshwater inputs from distant source areas rather than from local precipitation is responsible for the trends in seawater composition and coral delta o 18 over the last 30 years comparison of the three coral records indicates that spatial variations in coral delta o 18 coincide with variations in seawater salinity and local precipitation but not with temperature this confirms the dominant role of seawater composition mainly controlled by monsoonal precipitation on the spatial variability of coral delta o 18 in the south china sea c 2006 elsevier b v all rights reserved

effects of the earth s rotation and bottom slope on a density current descending a sloping bottom 1 the dynamic and transport processes associated with the descent of dense water along a sloping bottom are investigated by numerical experiments the focus is on effects of the earth s rotation the coriolis parameter f and bottom slope inclination s before baroclinic instability grows to finite amplitude development stage downslope volume transport agrees roughly with an estimate based on the ekman layer theory the volume transport decreases with increasing f and it is larger in steep slope cases the offshore extension scale of the dense water region is mainly determined by internal radius of deformation which decreases with increasing f and increases with increasing s the growth rate of the baroclinic instability increases with increasing f and s the baroclinic instability is also affected by energy transfer due to reynolds stress especially in the low and mid latitude regions after the instability grows to finite amplitude mature stage the dense water is effectively transported offshore by the eddy flows the eddy transport decreases with increasing f and it is lower in steep slope cases than in gentle slope cases that is although the flow instability becomes stronger with increasing f and s in the development stage the offshore eddy transport of dense water becomes less efficient with increasing f and s in the mature stage the mechanisms of these effects are also examined in detail

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

cold outflow from the faroe bank channel abstract the exchange of water between the norwegian sea and the north atlantic around the faroe islands was investigated in 1987 and 1988 combining ctd data with shipborne acoustic doppler current profiler adcp measurements tests were devised to assess the accuracy of the adcp measurements and the results are described it is found that estimating a reference velocity for geostrophic measurements is limited by the presence of tides of order 10 cm s 1 in the outflow of cold water from the faroe bank channel which reaches speeds of nearly 1 m s 1 the error is acceptably small but strong time dependent components are revealed the discharge of cold water is traced 75 km beyond the sill of this channel and changes in potential temperature salinity and potential vorticity on an isopycnal surface are attributed to intense mixing an effective diffusivity near 100 cm2 s 1 is derived and k h instability demonstrated as a plausible source of the turbulent energy six current meter moorings were deployed from

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

mass spectrometric 230th 234u 238u dating of the devils hole calcite vein the devils hole calcite vein contains a long term climatic record but requires accurate chronologic control for its interpretation mass spectrometric u series ages for samples from core dh 11 yielded 230 th ages with precisions ranging from less than 1 000 years 2 for samples younger than 140 ka thousands of years ago to less than 50 000 years for the oldest samples 566 ka the 234 u 238 u ages could be determined to a precision of 20 000 years for all ages calcite accumulated continuously from 566 ka until 60 ka at an average rate of 0 7 millimeter per 10 3 years the precise agreement between replicte analyses and the concordance of the 230 th 238 u 234 u 238 u ages for the oldest samples indicate that the dh 11 samples were closed systems and validate the dating technique in general

reconstructing dust storm frequency in china since 1617 ce using coral based estimates of sea surface temperature abstract dust storms occur frequently in arid and semi arid regions of china and other parts of the world exerting a considerable influence on air quality in densely populated areas instrumental observations of dust storms are only available over the past 50 to 60 years limiting our ability to understand dust storm variability over longer timescales however tropical sea surface temperatures have been reconstructed over the past four centuries using geochemical records from corals here we show that tropical pacific sea surface temperatures as recorded by corals can be used to reconstruct dust storm frequency at one year resolution based on the coral reconstructed annual sea surface temperature anomaly data from two regions the western pacific 25 n 25 s 110 155 e and the eastern pacific 10 n 10 s 175 e 85 w published by tierney et al 2015 we reconstructed the frequency of dust storms in northern china dsfcn for the period from 1617 to 1953 ce the reconstructed dsfcn variation can be divided into several distinct periods 1 dsfcn increased from 1617 to 1650 then 2 decreased from 1650 to 1675 3 remained unchanged from 1675 to 1755 4 increased again from 1755 to 1860 5 remained unchanged from 1860 to 1925 and finally 6 decreased rapidly from 1925 to 1995 we propose the following causal chain to explain the observed relationship between dsfcn and sst as tropical pacific ocean sst increases the siberian high weakens and the eastern asian trough strengthens as the air pressure difference weakens the east asian winter monsoon weakens and strong wind frequency decreases causing dsfcn to decrease as well the statistical results support this interpretation of the causal chain

rapid analysis of high precision sr ca ratios in corals and other marine carbonates a method for rapid determination of high precision sr ca ratios in scleractinian corals is presented using an inductively coupled plasma atomic emission spectrophotometer samples are corrected for instrument drift using a reference solution similar to the approach used for analysis of stable isotopes using gas source mass spectrometry further correction for variation of the sr ca ratio with ca concentration is accomplished using internal standards the precision once all corrections have been made is better than 0 1 relative standard deviation 1 for samples of similar ca concentration and better than 0 2 for samples with variable ca concentrations this method increases the sample throughput by approximately a factor of 20 relative to thermal ionization mass spectrometry and significantly reduces instrument and per sample costs comparison of sr ca data for a coral from the galapagos islands with an instrumental temperature record shows excellent agreement and demonstrates the potential for application of this technique to samples of modern and fossil scleractinian corals and other marine carbonates including foraminifera

ra 226 and rn 222 in saline water compartments of the aral sea region abstract the aral sea has been shrinking since 1963 due to extensive irrigation and the corresponding decline in the river water inflow understanding of the current hydrological situation demands an improved understanding of the surface water groundwater dynamics in the region 222 rn and 226 ra measurements can be used to trace groundwater discharge into surface waters data of these radiometric parameters were not previously available for the study region we determined 222 rn activities after liquid phase extraction using liquid scintillation counting lsc with peak length discrimination and analyzed 226 ra concentrations in different water compartments of the amu darya delta surface waters unconfined groundwater artesian water and water profiles from the closed large aral sea western basin the water samples comprise a salinity range between 1 and 263 g l the seasonal dynamics of solid water interaction under an arid climate regime force the hydrochemical evolution of the unconfined groundwater in the amu darya delta to high salinity na mg cl so 4 water types the dissolved radium concentrations in the waters were mostly very low due to mineral over saturation extensive co precipitation of radium and adsorption of radium on coexisting solid substrates the analysis of very low 226 ra concentrations 226 ra after solid phase extraction of radium using 3m empore high performance extraction disks purkl 2002 for the analysis of the radionuclide using an icp sector field mass spectrometer the 226 ra concentration of 17 unconfined groundwater samples ranged between 0 2 and 5 ppq and that of 28 artesian waters between 222 rn ingrowth after purging and trapping on super cooled charcoal the 226 ra concentrations were positively correlated with the salinity and the dissolved nacl concentrations the occurrence of unusually high 226 ra activities is explained by radium release from adsorption sites with increasing salinity the inferred spatial variability of 222 rn in the aral sea and of 222 rn and 226 ra in the groundwater of the amu darya delta is discussed in the context of our own previous hydrochemical studies in the study sites relatively low 222 rn activities in the unconfined gw 1 9 5 bq l indicate the alluvial sediments hosting the gw to be a low 238 u 226 ra substrate positive correlations between u and 226 ra and u and 222 rn are likely related to locally deposited fe mn ooh precipitates the 222 rn activity of the gw however distinctly exceeds the 222 rn concentration in the aral sea 10 mbq l in principle making 222 rn a sensitive tracer for the inflow of gw the high water volume of the large aral sea and wind induced mixing of its water body however hamper the detection of local groundwater inflow

coral δ18o records as an indicator of winter monsoon intensity in the south china sea we have used correlative analysis between mean december january february winter wind velocities measured at the xisha meteorological observatory 16degrees50 n 112degrees20 e in the middle of the south china sea and mean 518 0 data for the corresponding month from porites lutea coral collected in longwan waters 19degrees20 n 110degrees39 e to obtain a linear equation relating the two datasets this winter wind velocity for the south china sea wmiiscs can then be correlated to the coral delta 18 o by the equation wmiiscs 1 213 1 351 delta 18 o parts per thousand pdb r 0 60 n 40 p 0 01 from this the calculated wmiiscs delta18o series from 1944 to 1997 tends to decrease during the 1940s to the 1960s it increases slightly during the 1970s and then decreases again in the 1980s and 1990s the calculated decadal mean wmiiscs delta18o series had a obvious decrease from 5 92 to 4 63 m s during the period of 1944 1997 the calculated yearly mean wmiiscs delta18o value is 5 58 m s from 1944 to 1976 and this decreases to 4 85 m s from 1977 to 1998 that is the opposite trend to the observed yearly mean sst variation the yearly mean sst anomaly is 0 27degrees from 1943 to 1976 and this increases to 0 16degrees from 1977 to 1998 spectral analysis used on a 54 year long calculated wmiiscs delta18o series produces spectral peaks at 2 4 7 yr which can be closely correlated with the quasibiennial oscillation band qbo band 2 2 4 yr and the el nino southern oscillation band enso band 3 8 yr hence most of the variability of the winter monsoon intensity in the middle of the south china sea is mainly constrained by changes in the thermal difference between the land and the adjoining sea area perhaps due to global warming c 2003 elsevier science usa all rights reserved

sr ca profile of long lived tridacna gigas bivalves from south china sea a new high resolution sst proxy abstract high resolution 18o and sr ca ratio profiles of a modern live caught and a fossil dead collected giant bivalve shell tridacna gigas from northern south china sea were analyzed the high resolution 18o profiles as documented in most of previous studies showed pronounced seasonal cycles and recorded the combined influence of seawater 18o and sea surface temperature the sr ca ratio profiles derived from icp oes had well defined annual cycles and significant and negative correlation with sea surface temperature while the sr ca profiles derived from la icp ms did not reveal clear annual cycles this difference was likely caused by the organics contents in t gigas shells which had a chemical composition different than caco3 crystals and a heterogeneous distribution across the shell the sampling methods and the experimental errors two calibration equations between sr ca ratios determined by icp oes of modern t gigas shell and instrumental sst were calculated based on all monthly and extremum sst data and the equation from extremum data produced better sst predictions these results suggested that the high resolution icp oes derived sr ca ratios of t gigas in the south china sea had the potential of providing a good proxy of historical sst

delta o 18 sr ca and mg ca records of porites lutea corals from leizhou peninsula northern south china sea and their applicability as paleoclimatic indicators combined seasonal to monthly resolution coral skeletal delta 18 o sr ca and mg ca records are reported for one modem and two late holocene porites lutea corals from a fringing reef at leizhou peninsula the northern coast of the south china sea scs all the profiles for the period 1989 2000 reveal annual cycles well correlated with instrumental sea surface temperatures sst and display broad peaks in summer and narrow troughs in winter reflecting seasonal growth rate variations calibration against instrumental sst yields the following equations delta 18 o 0 174 0 010 xsst degrees c 1 02 0 27 mswd 5 8 sr ca mmol mol 0 0424 0 0031 xsst degrees c 9 836 0 082 mswd 8 6 and mg ca mmol mol 0 110 0 009 xsst degrees c 1 32 0 23 mswd 55 the scatter in the mg ca sst relationship is much larger than analytical uncertainties can account for suggesting the presence of sst unrelated components in the mg ca variation calculated sr ca sst values for two later holocene porites lutea samples u series ages similar to 541 bc and similar to 487 ad respectively from the same reef suggest that sst in the scs at similar to 541 bc was nearly as warm as in the 1990s the warmest decade of the last century but at similar to 487 ad it was significantly cooler this observation is consistent with climatic data reported in chinese historic documents confirming that the sr ca sst relationship is a reliable thermometer removing the sst component in the delta 18 o variation based on calculated sr ca sst values the residual delta 18 o reflects the deviation of the holocene seawater delta 18 o from the modem value which is also a measure of the holocene sea surface salinity sss or the summer monsoon moisture level in mainland china such residual delta 18 o was close to zero at similar to 541 bc and 0 3 parts per thousand at similar to 487 ad suggesting that it was as wet as in the 1990s at similar to 541 bc but significantly drier at similar to 487 ad in mainland china which are also consistent with independent historic records calculated mg ca sst values for the two late holocene corals are significantly lower than the sr ca sst values and are also in conflict with chinese historic records suggesting that coral mg ca is not reliable proxy for sst at comparable sr ca ranges fossil corals always display negative mg ca offsets if compared with the modem coral of the same site we interpret this observation as due to preferential loss of mg during meteoric dissolution of cryptic mg calcite bearing microbialites in the exposed fossil corals microbialites mgo up to 17 sr only 100 300 ppm are ubiquitous during reef building processes and their presence in only a trace amount will have a significant impact on coral mg ca ratios without detectable influence on coral sr ca ratios c 2004 elsevier b v all rights reserved

modeling climate shift of el nino variability in the holocene a coupled ocean atmosphere general circulation model is used to investigate climatic shift of el nino in the holocene the model simulates a reduced enso intensity in the early and mid holocene in agreement with paleoclimate record the enso reduction is proposed to be caused by both an intensified asian summer monsoon and a warm water subduction from the south pacific into the equatorial thermocline

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

high frequency winter cooling and reef coral mortality during the holocene climatic optimum a detailed ecological micro structural and skeletal sr ca study of a 3 42 m thick goniopora reef profile from an emerged holocene reef terrace at the northern south china sea reveals at least nine abrupt massive goniopora stress and mortality events occurred in winter during the 7 0 7 5 thousand calendar years before present cal ka bp within the holocene climatic optimum whilst calculated sr ca sst sea surface temperature maxima during this period are comparable to those in the 1990s sr ca sst minima are significantly lower probably due to stronger winter monsoons such generally cooler winters superimposed by further exceptional winter cooling on inter annual to decadal scales may have caused stress and mortality of the corals about every 50 years sea level rose by similar to 3 42 m during this period with present sea level reached at similar to 7 3 ka bp and a sea level highstand of at least similar to 1 8 m occurred at similar to 7 0 ka the results show that it took about 20 25 years for a killed goniopora coral reef to recover c 2004 elsevier b v all rights reserved

environmental controls on coral skeletal δ13c in the northern south china sea in this paper we investigate the relationship between seasonal climatic and environmental variables and the skeletal c 13 of modern and mid holocene porites lutea corals from the southern coast of hainan island in the northern south china sea no significant correlations were observed between c 13 in the modern coral and solar insolation or sea surface temperature however seasonal variability of c 13 in the modern coral covaries with rainfall on hainan island furthermore the seasonal variations of c 13 in both the modern and mid holocene coral are synchronous with those of the coral o 18 which is a proxy for seawater o 18 and in turn largely controlled by local rainfall these observations suggest that coral c 13 variations are closely associated with rainfall in this region given that river runoff contains dissolved inorganic carbon dic with a negative c 13 we suggest that periods of high rainfall on hainan island deliver increased amounts of c 13 depleted dic to coastal seawater resulting in an enhanced negative c 13 in the corals our findings together with previous studies appear to demonstrate that in coastal environments coral skeletal c 13 levels are controlled mainly by terrestrial carbon input and are significantly influenced by terrestrial river runoff consequently the geochemical interpretation of coral c 13 records may differ between coastal areas and offshore areas or the open ocean

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

geoarchaeological evidence from peru for a 5000 years b p onset of el nino for the tropical west coast of south america where el nino southern oscillation enso is most pronounced archaeological and associated paleontological deposits in northern peru revealed a major climate change at about 5000 years before the present yr b p the data implied the presence of stable warm tropical water as far south as 10 s during the early mid holocene about 8000 to 5000 yr b p these data suggest that enso did not occur for some millennia preceding 5000 yr b p when global and regional climate was warmer than today

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

three dimensional simulations of overflows on continental slopes abstract three dimensional features and instabilities of dense overflows from marginal seas onto continental slopes are investigated using a three dimensional primitive equation numerical ocean model the numerical simulations reveal important instability and three dimensional features of the overflow plumes that have not been included in previous simulations with a one dimensional streamtube model and a two dimensional plume model it is shown that the large primary plume breaks into a number of smaller subplumes on the offshore side of the plume due to instabilities manifested as growing topographic rossby waves over the slope the observed high temporal and spatial variabilities in the denmark strait overflow could be caused by the inherent dynamic instabilities as revealed by the numerical simulations the simulations indicate that the initial overflow velocity and width the properties of the source water the planetary rotation and the slope steepness play major roles in determining the scales of

intense mixing of the faroe bank channel overflow 1 the continuous swift flow of cold water across the sill of the faroe bank channel the deepest passage from the nordic seas to the north atlantic ocean forms a bottom attached dense plume overflow the amount and distribution of entrainment and mixing that the overflow encounters during its descent influence the ventilation of the deep north atlantic however remain poorly known due to lack of direct measurements using the first direct turbulence measurements we describe the dynamic properties and mixing of the overflow plume as it descends toward the iceland basin the vigorously turbulent plume is associated with intense mixing and enhanced turbulent dissipation near the bottom and at the plume ambient interface but with a quiescent core our measurements show a pronounced transverse circulation consistent with rotating plume dynamics a strong lateral variability in entrainment velocity and a vertical structure composed of order 100 m thick stratified interface and comparably thick well mixed bottom boundary layer with significant transport and entrainment

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

a composite sea surface temperature record of the northern south china sea for the past 2500 years a unique look into seasonality and seasonal climate changes during warm and cold periods abstract high resolution late holocene climate records that can resolve seasonality are essential for confirming past climatic dynamics understanding the late 20th century global warming and predicting future climate here a new composite record of the sea surface temperature sst variation in the northern south china sea scs during the late holocene is constructed by combining seven seasonally resolved coral and tridacna gigas sr ca based sst time windows with the instrumental sst record from modern interval between 1990 and 2000 this composite multi proxy marine record together with the reconstructions from mainland china and tropical western pacific indicates that the late holocene warm periods the roman warm period rwp and medieval warm period mwp were prominently imprinted and documented in the climatic and environmental history of the east asia western pacific region meanwhile substantial and significant sst seasonality variations during the late holocene were observed in the composite record the observed increase in seasonality or amplitude of seasonal cycles during the cold periods around our study area was probably caused by the different amplitudes between winter versus summer sst variations in northern scs with much larger sst variation during winters than during summers for the late holocene in addition the distinctive warm cold and neutral climatic episodes identified in our northern scs composite sst record correspond well with other paleo reconstructions from mainland china and especially well with the northern hemisphere wide composites by moberg et al 2005 and ljungqvist 2010 the overall agreement however also calls for more information and insights on how seasonal temperatures and their ranges vary on decadal centennial timescales

an assessment of the sr ca ratio in shallow water hermatypic corals as a proxy for sea surface temperature the high precision measurement of the sr ca ratio in corals has the potential for measuring past sea surface temperatures at very high accuracy however the veracity of the technique has been questioned on the basis that there is both a spatial and temporal variation in the sr ca ratio of seawater and that kinetic effects such as the calcification rate can affect the sr ca ratio of corals and produce inaccuracies of the order of 2 4 c in the present study a number of cores of the massive hermatypic scleractinian coral porites from the central great barrier reef have been analyzed for sr ca at weekly to monthly resolution results from a 24 year record from myrmidon reef show an overall variation from 22 7 c to 30 4 c the record shows a warming cooling trend with maximum warming centred on the 1986 1987 summer while some bleaching was reported to have occurred at myrmidon reef in 1982 the sr ca record indicates that subsequent summer temperatures were much higher the 4 5 year record from stanley reef shows a maximum sst of 30 c during the 1997 1998 el nino event the calibrations from myrmidon and stanley reefs are in excellent agreement with previously published calibrations from nearby reefs while corals do not calcify in equilibrium with seawater due to physiological control on the uptake of sr and ca into the lattice of coralline aragonite it can be argued that provided only a single genus such as porites sp is used and that the coral is sampled along a major vertical growth axis then the sr ca ratio should vary uniformly with temperature similarly objections based on the spatial and temporal variability of the sr ca activity ratio of seawater can be countered on the basis that in most areas where coral reefs grow there is a uniformity in the sr ca activity ratio and there does not appear to be a change in this ratio over the growth period of the coral evidence from several corals in this study suggest that stress can be a major cause of the breakdown in the sr ca sst relationship thermal stress resulting from either extremely warm or cool temperatures can produce anomalously low sr ca derived ssts as a result of the breakdown of the biological control on sr ca fractionation it is considered that other stresses such as increased nutrients and changes in light intensity can also lead to a breakdown in the sr ca sst relationship two of the main issues affecting the reliability of the sr ca method are the calibration of the sr ca ratio with measured sst and the estimation of tropical last glacial maximum lgm palaeotemperatures instead of producing a constant calibration just about every one published so far is different from the others what is obvious is that for most calibrations while the slope of the calibration equation is similar the intercepts are not while the cause for this variation is still unknown it would appear that corals from different localities around the world are responding to their own particular environment or that certain types of environments exert a control on the corals physiology sr ca derived sst estimates for the lgm and deglaciation of 5 c 6 c cooler than present are at odds with estimates of 2 c 3 c cooling by other climate proxies the apparent lack of reef growth during the lgm suggests that ssts were too cold in many parts of the tropics for reefs to develop this would lend support to the idea that tropical ssts were much cooler than what the climap data suggests

detection of deep overflows with satellite altimetry in situ observations downstream of the sills in the faroe bank channel and denmark strait show large temperature and current variability of the overflows with time scales of a few days these fluctuations are associated with meso scale eddies and have an impact on sea surface height this is confirmed by observations from the topex poseidon and ers 1 2 satellites that show substantial enhancement of eddy kinetic energy and sea level variability immediately down stream of the sills

assessment of coral δ44 40ca as a paleoclimate proxy in the great barrier reef of australia abstract the ca isotopic composition 44 40ca in a porites spp coral from the great barrier reef was analyzed at monthly intervals for two consecutive years it was found that variations in skeletal 44 40ca values over the 2 year period are slightly greater than the analytical precision of the measurements although other coralline geochemical records i e 13c 18o 11b and sr ca ratios show remarkable variations to evaluate the potential of 44 40ca as a paleoclimate proxy in corals we compared 44 40ca with other well established indicators and found that 44 40ca values show little relationship to 18o sr ca 18o or 11b values thus suggesting that the influence of seawater temperature seawater ph and river inputs on skeletal 44 40ca is limited or overwhelmed by other factors however skeletal 44 40ca values are significantly related to 13c values r 0 46 p

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

structure and variability of the denmark strait overflow model and observations we report on a combined modeling and observational effort to understand the denmark strait overflow dso four cruises over the course of 3 years mapped hydrographic properties and velocity fields with high spatial resolution the observations reveal the mean path of the dense water as well as the presence of strong barotropic flows energetic variability and strong bottom friction and entrainment a regional sigma coordinate numerical model of interbasin exchange using realistic bottom topography and an overflow forced only by an upstream reservoir of dense fluid is compared with the observations and used to further investigate these processes the model successfully reproduces the volume transport of dense water at the sill as well as the 1000 m descent of the dense water in the first 200 km from the sill and the intense eddies generated at 1 3 day intervals hydraulic control of the mean flow is indicated by a region supercritical to long gravity waves in the dense layer located approximately 100 km downstream of the sill in both model and observations in addition despite the differences in surface forcing both model and observations exhibit similar transitions from mostly barotropic flow at the sill to a bottom trapped baroclinic flow downstream indicating the dominant role of the overflow in determining the full water column dynamics

faroe bank channel overflow 1995 2005 abstract the faroe bank channel fbc is the deepest passage across the greenland scotland ridge and there is continuous overflow of dense water through the channel which provides a substantial contribution to the global thermohaline circulation since november 1995 acoustic doppler current profilers adcps have been moored at the sill of the channel continuously except for short annual servicing periods in addition to this ctd sections have regularly been occupied across the channel and instruments recording temperature and salinity have been moored for short periods these observations demonstrate that the channel due to its small width can be monitored fairly well with only one adcp mooring and they allow the generation of a time series of overflow volume flux for the 1995 2005 period the kinematic overflow flux defined solely from the velocity field was found to have an average value of 2 1 0 2 sv with a seasonal and with inter annual variations of approximately 10 amplitude but with no discernible trend for the whole period the average flux of water with potential density exceeding 27 8 kg m 3 was found to be 1 9 0 3 sv with average properties 0 25 c s 34 93 28 01 kg m 3 for this period no evidence was found for a weakening overflow flux but the salinity of the fbc overflow especially the warmer parts has increased substantially during the period which implies an increased average density on the order of 0 01 kg m 3 previous observations of a helical cross channel circulation are confirmed and may explain the thin pycnocline layer but shear instability induces intensive mixing that puts a lower limit on the layer thickness critical control at one point of the sill cross section rather than friction seems to govern the overflow dynamics and simple layered models can explain much of the observed features as well as the seasonal variation but potential vorticity as defined for a single overflow layer is not conserved a previously suggested 1950 2000 weakening of the fbc overflow which was partly based on a subset of the data presented here is not supported by the full dataset

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

seawater temperature seasonality in the south china sea during the late holocene derived from high resolution sr ca ratios of tridacna gigas temperature seasonality the difference between summer and winter temperature has significant influences on global terrestrial and marine ecosystems however most of proxy based climate records are of limited temporal resolution and thus insufficient to quantify the past temperature seasonality in this study high resolution sr ca ratios of modern live caught and fossil dead collected tridacna gigas shells from the south china sea scs were used to reconstruct the seawater temperature seasonality during the late holocene the averaged seawater temperature seasonality around 2165 75 bc 4 46 1 41 c derived from the data of 18 yr were similar to the seasonality of recent decade 4 41 0 82 c during ad 1994 2005 but the temperature seasonality around ad 50 40 3 69 1 37 c derived from the data of 48 yr and ad 990 40 3 64 0 87 c derived from the data of 11 yr was significantly lower than that during ad 1994 2005 the reduced seasonality around ad 990 40 was attributable to the unusually warm winter during the medieval times probably caused by the weakening of east asian winter monsoon our study highlighted the potential of t gigas shells in providing high resolution seasonality climate information during the late holocene

faroe bank channel overflow mesoscale variability abstractthe faroe bank channel is the deepest connection through the greenland scotland ridge where dense water formed north of the ridge flows southward over the sill crest contributing to the formation of north atlantic deep water the overflow region is characterized by high mesoscale variability and energetic oscillations accompanied by a high degree of sea surface level variability here 2 month long time series of velocity and temperature from 12 moorings deployed in may 2008 are analyzed to describe the oscillations and explore their generation and propagation the observed 2 5 5 day oscillations in velocity and temperature are highly coherent both horizontally and vertically and they are associated with 100 200 m thick boluses of cold plume water flowing along the slope a positive correlation between temperature and relative vorticity and the distribution of clockwise counterclockwise rotation across the slope suggest a train of alternating warm cyclonic and cold anticyclonic eddies where t

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

topographic influence on overflow dynamics idealized numerical simulations and the faroe bank channel overflow 1 properties of the north atlantic deep water nadw depend on mixing that occurs in the denmark strait ds and the faroe bank channel fbc overflow regions how the sill s topography in those regions may affect mixing processes and downstream variability is thus investigated using a high resolution terrain following ocean model model results agree with observations that show enhanced mixing and entrainment downstream from the sill however mixing seems to occur over a longer distance downstream from the fbc sill and more abruptly downstream from the ds sill sensitivity experiments with various fbc sill widths demonstrate that the narrow sill is responsible for the enhanced mixing the downstream flow variability eddy propagation and deep water properties are affected by sill width and background stratification similar to the laboratory overflow experiments of cenedese et al 2004 three distinct mixing regimes characterized by the froude number are identified in the fbc simulations a steady subcritical flow regime upstream from the sill a supercritical wave like flow regime downstream from the sill and an irregular eddy dominated regime farther away from the sill satellite altimeter data near the fbc show cyclonic anomalies propagating along the northern slope of the channel resembling the surface eddies associated with the overflow variability in the model a cross channel circulation over the fbc sill driven by frictional bottom boundary layers resulted in convergence divergence zones near the southern northern slopes and pinching spreading of isotherms across the channel similar to the observation based mechanism proposed by johnson and sanford 1992

mixing in the stratified interface of the faroe bank channel overflow the role of transverse circulation and internal waves mixing in the stratified interface of the faroe bank channel overflow the role of transverse circulationand internal waves

el nino like pattern in ice age tropical pacific sea surface temperature sea surface temperatures ssts in the cold tongue of the eastern equatorial pacific exert powerful controls on global atmospheric circulation patterns we examined climate variability in this region from the last glacial maximum lgm to the present using a sst record reconstructed from magnesium calcium ratios in foraminifera from sea floor sediments near the galapagos islands cold tongue sst varied coherently with precession induced changes in seasonality during the past 30 000 years observed lgm cooling of just 1 2 c implies a relaxation of tropical temperature gradients weakened hadley and walker circulation southward shift of the intertropical convergence zone and a persistent el nino like pattern in the tropical pacific this is contrasted with mid holocene cooling suggestive of a la nina like pattern with enhanced sst gradients and strengthened trade winds our results support a potent role for altered tropical pacific sst gradients in global climate variations

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

timing and duration of growth hiatuses in mid holocene massive porites corals from the northern south china sea growth hiatuses in massive corals are usually indicative of past ecological or environmental stresses among 37 fossil porites colonies surveyed from the reef flat of dadonghai fringing reef at sanya hainan island northern south china sea seven of them were found to show clear evidence of past mortality representing a population of similar to 19 among these samples two of them syo 13 and syo 28 display clear growth hiatuses reflecting mortality followed by subsequent recruitment and five others exhibit a well preserved mortality surface and no subsequent recruitment the growth hiatuses were dated using high precision thermal ionisation mass spectrometry u series techniques the age results suggest all the dated corals formed and died in the mid holocene multiple dates below the growth hiatuses suggest that syo 13 and syo 28 died at 6298 11 and 6929 19 a bp i e years before ad 1950 respectively multiple dates above the growth hiatuses indicate that growth in syo 13 and syo 28 resumed at 6257 14 and 6898 20 a bp respectively the calculated durations of growth hiatuses are therefore 41 18 a for syo 13 and 31 28 a for syo 28 respectively implying growth resumed within decades after the mortality events u series dating of four other samples with dead heads suggests that they died at 6035 53 6059 23 6127 22 and 6474 24 a bp respectively in addition using solution inductively coupled plasma mass spectrometry icp ms monthly resolution sr ca and mg ca ratios were determined for the annual growth bands below and above the growth hiatuses for three of the dated samples the sr ca and mg ca profiles indicate that the three corals probably died in different seasons from spring to autumn and the mortality appears to be unrelated to anomalous sea surface temperature induced bleaching copyright c 2010 john wiley sons ltd

principal modes of rainfall sst variability of the asian summer monsoon a reassessment of the monsoon enso relationship abstract using global rainfall and sea surface temperature sst data for the past two decades 1979 98 the covariability of the asian summer monsoon asm and el nino southern oscillation enso was investigated the findings suggest three recurring rainfall sst coupled modes characterized by a pronounced biennial variability the first mode is associated with generally depressed rainfall over the western pacific and the maritime continent stemming from the eastward shift of the walker circulation during the growth phase of el nino the associated sst pattern consists of an east west sst seesaw across the pacific and another seesaw with opposite polarity over the indian ocean the second mode is associated with a growing la nina comprising mixed regional and basin scale rainfall and sst variability with abnormally warm water in the vicinity of the maritime continent and western pacific it possesses a pronounced low level west pacific anticyclone wpa near the philippines and exhibits large sub

suppression of el nino during the mid holocene by changes in the earth s orbit a number of recent reports have interpreted paleoproxy data to describe the state of the tropical pacific especially changes in the behavior of the el nino southern oscillation enso over the holocene these interpretations are often contradictory especially for the eastern tropical pacific and adjacent areas of south america here we suggest a picture of the mid holocene tropical pacific region which reconciles the data enso variability was present throughout the holocene but underwent a steady increase from the mid holocene to the present in the mid holocene extreme warm el nino events were smaller in amplitude and occurred less frequently about a mean climate state with a cold eastern equatorial pacific and largely arid coastal regions as in the present climate this picture emerges from an experiment in which a simple numerical model of the coupled ocean atmosphere system in the tropical pacific was driven by orbital forcing we suggest that the observed behavior of the tropical pacific climate over the mid to late holocene is largely the response to orbitally driven changes in the seasonal cycle of solar radiation in the tropics which dominates extratropical influences

holocene marine 14c reservoir age variability evidence from 230th dated corals in the south china sea the south china sea scs is well connected with the western pacific and influenced by the east asian monsoon we have examined temporal variations in radiocarbon marine reservoir ages r and regional marine reservoir corrections delta r of the scs during the holocene using paired measurements of ams c 14 and tims th 230 on 20 pristine corals the results show large fluctuations in both r and delta r values over the past 7500 years yrs with two distinct plateaus during 7 5 5 6 and 3 5 2 5 thousand calendar years before present cal ka bp the respective weighted mean delta r values of these plateaus are 151 85 and 89 59 yrs which are significantly higher than its modern value of 23 52 yrs this suggests that using a constant modern delta r value to calibrate c 14 dates of the scs marine samples will introduce additional errors to the calibrated ages our results provide the first database for the holocene r and delta r values of the scs for improved radiocarbon calibration of marine samples we interpret the two delta r plateaus as being related to two intervals with weakened el nino southern oscillation enso and intensified east asian summer monsoon easm this is because the c 14 content of the scs surface water is controlled by both the c 14 concentration of the pacific north equatorial current nec which is in turn influenced by enso induced upwelling along the pacific equator and vertical upwelling within the scs as a result of moisture transportation to midlatitude region to supply the easm rainfall

sr ca sea surface temperature calibration in the coral porites lutea from subtropical northern south china sea strontium to calcium sr ca ratios in annual bands of porites corals are commonly used as past sea surface temperature proxy in tropical oceans whereas studies that refer to sr ca sst calibration in high latitude corals are rather rare in general here we present a 50 year 1961 2010 near fortnightly sr ca record in two porites lutea corals living near the northern limit of reef building corals in the subtropical northern south china sea where winter temperatures are extreme for hermatypic corals the sr ca time series shows a clear annual cyclicity with marked sharp narrow winter peaks comparison with an instrumental sst record since 1961 indicates that this sr ca record is chiefly modulated by sst two different methods are discussed for calibrating sr ca with sst the correlation between interpolated sr ca and sst is significant but the coefficient is relatively low mainly attributed to extreme cold winter ssts similar to 16 degrees c which cause a significant decrease or even cessation of coral skeletal extension another modified method using only annual low sr ca values which could clearly be matched with the same features in the instrumental sst record is more reliable the modified regression equation does not encompass ssts below 24 degrees c the fidelity of the coral based sr ca sst calibration was assessed and the precision of the method is estimated to be 031 0 62 degrees c based on the calibration verification exercise the modified method is suggested in marginal coral areas with extreme intra annual sst variation e g from 13 to 30 degrees c c 2013 elsevier b v all rights reserved

the faroe bank channel deep water overflow in the late 1950s it was recognised that a considerable transport of water from the deeper reaches of the norwegian sea into the atlantic takes place through the faroe bank channel which thereby serves as an important source for the renewal of the north atlantic deep water consequently substantial efforts have over the past decades been dedicated towards quantifying the overflow as well as clarifying the underlying dynamics in the present review an attempt is made to summarise the main body of the observational results as well as some theoretical considerations regarding the dynamical mechanisms the most prominent characteristic of the faroe bank channel overflow is that it is a persistent phenomenon with a yearly average deep water viz t 5degreesc transport of around 2 sv using inviscid rotating hydraulics the flow through the controlling section at the sill furthermore can be reasonably well predicted on the basis of upstream conditions in the norwegian sea after passing the threshold the descending overflow plume is subject to intense mixing a process very much in the focus of ongoing research c 2004 elsevier ltd all rights reserved

a description and analysis of mesoscale variability in the faroe shetland channel 1 a large part of the surface inflow to the nordic seas coalesces into a narrow slope current in the faroe shetland channel and flows along the shetland shelf edge with mean speeds of order 0 4 m s observations reveal that the flow is unstable and forms large mesoscale meanders with current speeds of up to 0 9 m s in a front between two water masses that lies along the channel the meanders tend to form at two specific locations long term analyses of drifter and altimeter archive data show hot spots in eddy kinetic energy that are greater than 300 cm2 s and in surface elevation variance that are nearly 40 cm2 a baroclinic instability analysis suggests that the growth time of the meanders should be a few days with a separation distance of order 65 km and that their group velocity could be very close to zero depending on the strength of the southward outflow below 500 m thus unlike their counterparts in the norwegian coastal current for example the instabilities do not propagate decay of the anticyclonic meanders probably leads to the formation of cyclonic eddies that mix north atlantic water and modified north atlantic water mnaw and create the more homogeneous forms of atlantic water that are observed as the water moves northward through the channel and into the norwegian sea mesoscale driven entrainment may help to draw mnaw into the faroe shetland channel from around faroe

gulf stream generated topographic rossby waves abstract an inverse ray tracing model is applied to observations of 40 day topographic rossby waves on the continental slope off of cape hatteras north carolina to determine their origin the rays are traced seaward and extend into the deep gulf stream where the bottom slope remains strong enough that topographic dominates planetary this enable coupling to occur between eastward propagating gulf stream meanders and topographic waves with eastward phase speed and matching zonal wavelength previous satellite observations indicate that the most frequently occurring gulf stream meanders have a period of 40 days and the model reveals that as these meanders pass a topographic bend near 71 72 w they are able to couple to the observed topographic waves traced back from cape hatteras the 40 day gulf stream meanders occur in bursts which leads to associated bursts of the topographic waves

wet and cold climate conditions recorded by coral geochemical proxies during the beginning of the first millennium ce in the northern south china sea abstract the past two millennia include some distinct climate intervals such as the medieval warm period mwp and the little ice age lia which were caused by natural forcing factors as well as the current warm period cwp that has been linked to anthropogenic factors therefore this period has been of great interest to climate change researchers however most studies are based on terrestrial proxy records historical documentary data and simulation results and the ocean and the tropical record are very limited the eastern han three kingdoms and western jin periods 25 316 ce cover the beginning first millennium ce in china and were characterized by a cold climate and frequent wars and regime changes this study used paired sr ca and 18o series recovered from a fossil coral to reconstruct the sea surface water conditions during the late eastern han to western jin periods 167 309 ce at wenchang eastern hainan island in the northern south china sea scs to investigate climate change at this time the long term sea surface temperature sst during the study interval was 25 1 c which is about 1 5 c lower than that of the cwp 26 6 c compared with the average value of 0 40 during the cwp the long term average seawater 18o 0 06 was more negative these results indicate that the climate conditions during the study period were cold and wet and comparable with those of the lia this colder climate may have been associated with the weaker summer solar irradiance the wet conditions were caused by the reduced northward shift of the intertropical convergence zone monsoon rainbelt associated with the retreat of the east asian summer monsoon interannual and interdecadal climate variability may also have contributed to the variations in sst and seawater 18o recorded over the study period

episodic coral growth in china s subtropical coral communities linked to broad scale climatic change evidence from the fossil coral record has shown that coral assemblages were able to extend their geographical range to higher latitudes during past global warming events in the face of future global warming scenarios we investigate the potential for china s subtropical coral communities to act as a refuge for corals as ocean temperatures continue to warm using uranium thorium dating to chronologically constrain the age of dead corals we reveal two distinct periods of coral growth between 6 85 and 5 51 ka b p and 0 11 to 0 05 ka b p relative to a d 1950 the former coincides with the mid holocene warm period when temperatures in south china were similar to 1 2 degrees c warmer than present very few ages 13 were obtained for the similar to 5 6 k y that followed an increased frequency of corals with th 230 ages dated to the past century suggests an increase in abundance coinciding with rising global temperatures nevertheless modern monitoring programs have reported a recent dramatic decline in coral cover over the past 34 yr attributable to human influences our results suggest that although coral communities existed around the subtropical islands of daya bay southeast china in the past their continued presence in the region largely depends on appropriate management of the adjacent coastline and coupled ocean atmosphere conditions similar to those experienced in the mid holocene

baroclinic instability of density current along a sloping bottom and the associated transport process numerical experiments with a three dimensional nonhydrostatic ocean model have been carried out to investigate the dynamic processes of downslope density current and associated transport of dense water focusing on the effects of bottom slope for the range of slope inclination s from 0 to 0 04 bottom slope has two effects on baroclinic instability of the flow one is the stabilizing effect due to the topographic effect and to offshoreward increase in water depth the other is the destabilizing effect due to steepened inclination of isopycnal surface which increases available potential energy since the destabilizing effect over the upper slope overcomes the stabilizing one in the early stage unstable waves develop more rapidly with increasing s nonlinear energy conversion due to reynolds stresses also affects the flow stability and then the growth rate of instability increases linearly with s in this stage after the unstable waves have finite amplitudes in the mature stage the stabilizing effect of bottom slope becomes dominant especially over the lower slope thus vigorous unstable eddies are confined to the upper slope region in steep slope cases while they cover the whole slope region in gentle slope cases and this difference in the eddy field causes a drastic change in downslope transport of dense water in gentle slope cases efficiency of the transport becomes higher with increasing s since the destabilizing effect overcomes the stabilizing one as a whole on the contrary the efficiency becomes lower with increasing s in steep slope cases since the stabilizing effect surpasses the destabilizing one as a result the most effective transport is realized in the case with s 0 005 although the transport due to eddies in steep slope cases becomes weak over the lower slope it is still larger than that due to the bottom ekman current since the eddy transport occurs in the bottom layer with a thickness of 100 200 m which is 4 8 times the ekman layer thickness