variability of the low level cross equatorial jet of the western indian ocean since 1660 as derived from coral proxies 1 using monthly seasonally resolved coral proxies from the indian ocean basin we statistically reconstruct the june july august jja low level jet in western indian ocean from 1660 1957 with skillful estimates for high and low frequencies the el nino southern oscillation enso signals are reasonably captured the strength of the jet significantly increases from the late 17th century to late 19th century the decreasing in reconstructed jet in 20th century disagrees with previous studies which indicated an enhancement of southern asian summer monsoon sasm in association with the rapid global warming the jet reconstructions are useful for understanding of sasm variability and the validation of historical monsoon simulation

tropical sea surface temperatures for the past four centuries reconstructed from coral archives most annually resolved climate reconstructions of the common era are based on terrestrial data making it a challenge to independently assess how recent climate changes have affected the oceans here as part of the past global changes ocean2k project we present four regionally calibrated and validated reconstructions of sea surface temperatures in the tropics based on 57 published and publicly archived marine paleoclimate data sets derived exclusively from tropical coral archives validation exercises suggest that our reconstructions are interpretable for much of the past 400 years depending on the availability of paleoclimate data within and the reconstruction validation statistics for each target region analysis of the trends in the data suggests that the indian western pacific and western atlantic ocean regions were cooling until modern warming began around the 1830s the early 1800s were an exceptionally cool period in the indo pacific region likely due to multiple large tropical volcanic eruptions occurring in the early nineteenth century decadal scale variability is a quasi persistent feature of all basins twentieth century warming associated with greenhouse gas emissions is apparent in the indian west pacific and western atlantic oceans but we find no evidence that either natural or anthropogenic forcings have altered el nino southern oscillation related variance in tropical sea surface temperatures our marine based regional paleoclimate reconstructions serve as benchmarks against which terrestrial reconstructions as well as climate model simulations can be compared and as a basis for studying the processes by which the tropical oceans mediate climate variability and change

importance of the indian ocean for simulating rainfall anomalies over eastern and southern africa the relative contributions of the indian ocean and pacific ocean sea surface temperatures ssts to the rainfall variability over eastern central and southern africa during the austral spring summer are examined the variability of african rainfall is statistically related to both oceans but the variability in the two oceans is also related to separate the effects of the indian and pacific oceans a suite of numerical model simulations is presented goga the atmosphere is forced by observed ssts globally ioga the atmosphere is forced by observed ssts only in the indian ocean basin and poga the atmosphere is forced by observed ssts only in the tropical pacific basin while the sst variability of the tropical pacific exerts some influence over the african region it is the atmospheric response to the indian ocean variability that is essential for simulating the correct rainfall response over eastern central and southern africa analyses of the dynamical response s seen in the numerical experiments and in the observations indicate that the pacific and indian oceans have a competing influence over the indian ocean african region this competition is related to the influence of the two oceans on the walker circulation and the consequences of that variability on low level fluxes of moisture over central and southern africa finally given the high correlation found between sst variability in the indian and pacific oceans with the pacific leading by 3 months we speculate on an approach to long lead dynamical climate prediction over central east and southern africa

the reconstructed indonesian warm pool sea surface temperatures from tree rings and corals linkages to asian monsoon drought and el nino southern oscillation 1 the west pacific warm pool is the heat engine for the globe s climate system its vast moisture and heat exchange profoundly impact conditions in the tropics and higher latitudes here september november sea surface temperature sst variability is reconstructed for the warm pool region 15 degrees s 5 degrees n 110 160 degrees e surrounding indonesia using annually resolved teak ring width and coral delta o 18 records the reconstruction dates from a d 1782 1992 and accounts for 52 of the sst variance over the most replicated period significant correlations are found with el nino southern oscillation enso and monsoon indices at interannual to decadal frequency bands negative reconstructed sst anomalies coincide with major volcanic eruptions while other noteworthy extremes are at times synchronous with indian and indonesian monsoon drought particularly during major warm enso episodes while the reconstruction adds to the sparse network of proxy reconstructions available for the tropical indo pacific additional proxies are needed to clarify how warm pool dynamics have interacted with global climate in past centuries to millennia

a central tropical pacific coral demonstrates pacific indian and atlantic decadal climate connections while instrumental and proxy based climate records describe significant decadal scale climate variabil ity throughout the tropical pacific indian and atlantic oceans the processes responsible for these variations and their interactionsare not readily apparent from the obs er vations a new 112 yr coral based sea surface temperature sst reconstruction from palmyra island in the central tropical pacific ctp exhibitss trong decadal variability with an amplitude of roughly 0 3 c a 12 13yr period sig nal in thiscoral record ishighly coherent with long equa torial atlantic and indian ocean climate records implying a unified phenomenon the atlantic pattern suggests that it may fall under direct influence of anomaloussst in the ctp as it does over interannual timescales while the in dian ocean pattern exhibits maximum response during the switch between warm cold states in the tropical pacific the results demonstrate that the ctp has played a significant role in determining the expression of global decadal climate variability over the twentieth century

monsoon tropical ocean interaction in a network of coral records spanning the 20th century abstract the 20th century evolution of basin wide gradients in surface ocean properties provides one essential test for recent models of the interaction between the asian monsoon and the tropical ocean because various feedback mechanisms should result in characteristic regional patterns of variability although the instrumental record of climate variability in the tropics is essentially limited to the last few decades the stable isotopic composition of living corals provides an effective means for extending the instrumental observations here we present two coral isotopic records from the indonesian maritime continent and we use these records with other previously published records to describe i the relationship between western pacific and central pacific climate variability over the past century with special emphasis on the biennial band and ii the strength of the west east indian ocean dipole we find that the amplitude of the biennial cycle in the pacific did not vary inversely with the strength of enso el nino southern oscillation as might be expected from some models of monsoonal feedback on the central pacific instead the biennial variability was modulated on decadal timescales throughout much of the pacific we also show that the zonal oxygen isotopic gradient in the indian ocean coral records was significantly correlated with central pacific sea surface temperature on a variety of timescales thus it is likely that this coral dipole was a product of strong enso like teleconnections over the indian ocean as opposed to being the result of unique indian ocean or monsoonal dynamics

interaction between the enso and the asian monsoon in a coral record of tropical climate the oxygen isotopic composition of a banded coral from the western equatorial indian ocean provides a 150 year long history of the relation between the el nino southern oscillation enso phenomenon and the asian monsoon interannual cycles in the coral time series were found to correlate with pacific coral and instrumental climate records suggesting a consistent linkage across ocean basins despite the changing frequency and amplitude of the enso however decadal variability that is characteristic of the monsoon system also dominates the coral record which implies important interactions between tropical and midlatitude climate variability one prominent manifestation of this interaction is the strong amplitude modulation of the quasi biennial cycle

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

orbital controls on the el nino southern oscillation and the tropical climate the global synchroneity of glacial interglacial events is one of the major problems in understanding the link between milankovitch forcing and the climate of the late quaternary in this study we isolate a part of the climate system the tropical pacific and test its sensitivity to changes in solar forcing associated with changes in the earth s orbital parameters we use a simplified coupled ocean atmosphere model that is run for the past 150 000 years and forced with milankovitch changes in the solar insolation this system responds primarily to the precessional cycle in solar forcing and is capable of generating a mean response to the changes in the seasonal distribution of solar radiation even while the annual mean insolation is roughly constant the mean response to the precessional forcing is due to an interaction between an altered seasonal cycle and the el nifio southern oscillation enso changes in the enso behavior result in a mean tropical climate change the hypothesis is advanced that such a change in the tropical climate can generate a globally synchronous climate response to milankovitch forcing

identification and composition of secondary meniscus calcite in fossil coral and the effect on predicted sea surface temperature this study uses electron backscatter diffraction ebsd and atomic force microscopy afm to identify secondary calcite in coral skeletons secondary calcite appears to have nucleated on the original aragonite dissepiments producing horizontal structures that mimic the morphology of the original coral aragonite forming dissepiment like meniscus structures the sr ca and 18o of the pristine aragonite and secondary calcite were analysed by secondary ion mass spectrometry sims the effect of calcite inclusion on the mean geochemistry of the coral carbonate and subsequent sea surface temperature sst calculations were determined for both sr ca and 18o inclusion of as little as 1 secondary calcite within the primary coral aragonite elevates the sr ca derived sst by 1 2 c and could markedly offset estimates of past tropical climate conversely inclusion of 10 secondary calcite has little effect on the sst estimated from 18o 0 6 c indicating that this proxy is relatively robust to even large amounts of calcite the different extents to which the two proxies would be influenced by inadvertent inclusion of such meniscus calcite demonstrate the importance of a multi proxy approach

the thermal oceanographic signal of el nino reconstructed from a kiritimati island coral central equatorial pacific sea surface temperature sst anomaly is a critical predictor of basin wide oceanographic and atmospheric effects of the el nino southern oscillation enso phenomenon we employ two geochemical thermometers measured on coralline aragonite to reconstruct an independent proxy based measure of central equatorial pacific sea surface temperature anomaly in addition we assess the observational error associated with extraction of large scale sst anomalies from 18o and sr ca measurements on the basis of paired data for the 1981 1987 period rms error for the estimation of sst from kiritimati coral 18o is about 0 4 c assuming no seawater 18o influence for sr ca the observational error is about 0 5 c singular spectrum analysis of the 18o time series suggests that 1 3 of the variance is explained by sst anomaly and that this variance may be separated from other signals in the frequency domain the interannual component of the 18o record shares 70 variance with the interannual component of local sst anomaly estimates 0 84 and correlates as highly with nino3 region 150 w 90 w 5 n 5 s sst anomaly estimates comparison of annual averages of the 18o data with analyzed sst for 55 years suggests that the error in deriving annually averaged sst anomalies at kiritimati is about 0 4 c a global sst correlation analysis suggests significant correlation with the rest of the pacific basin and the tropical indian and atlantic sectors the ocean wide level of correlation achieved using the coral data is indistinguishable from that achieved using the nino3 sst anomaly index and suggests that a few well located coral reconstructions with low observational error may be sufficient to reconstruct the global sst anomaly field associated with enso activity

an evaluation of quantitative reconstruction of past precipitation records using coral skeletal sr ca and δ18o data abstract coupled records of 18o and sr ca in porites coral have been used to derive hydrological conditions by removing the sr ca inferred temperature component from the 18o signal nanwan a semi enclosed bay in southern taiwan provides an opportunity to demonstrate the feasibility of quantitatively reconstructing past precipitation history recurrence of seawater 18o offsets between wet and dry seasons in the early 1990s is well correlated with the precipitation record even though the hydrological signal only accounts for 20 of the total annual coral 18o variation of ca 1 offsets can be found in the residual 18o of modern corals after removing the thermal effect which contributes to the other 80 the observed timing and amplitude of the seasonal seawater 18o offsets in nanwan and their correlation with precipitation are reproduced by hydrological models in the mid holocene the seasonal anomaly of residual 18o was twice that of the modern value based on the 9 yr sr ca 18o data recorded in a 6 73 ka porites coral hydrological models suggest an annual rainfall of 1800 3000 mm yr at the window during mid holocene 20 higher than that of the average of 30 yr modern instrumental records of 1500 2500 mm consistent with the qualitative pollen record from lake sediments the seasonal decrease of residual 18o in 5 of 9 yr was earlier than the increase of the coral sr ca inferred temperature which implies that these rainy seasons probably occurred from the early mid spring to mid summer earlier than that from late spring to late summer today the driving force may be related to the changes of solar insolation and the east asian monsoon it is cautioned that the variability of hydrographic conditions imposes restrictions on a precise calculation of the amount of paleo precipitation the dynamic nature of local tectonics monsoons and water circulation should be further addressed to precisely quantify precipitation over the past 10 000 yr from coral geochemical records

western indian ocean marine and terrestrial records of climate variability a review and new concepts on land ocean interactions since ad 1660 we examine the relationship between three tropical and two subtropical western indian ocean coral oxygen isotope time series to surface air temperatures sat and rainfall over india tropical east africa and southeast africa we review established relationships provide new concepts with regard to distinct rainfall seasons and mean annual temperatures tropical corals are coherent with sat over western india and east africa at interannual and multidecadal periodicities the subtropical corals correlate with southeast african sat at periodicities of 16 30 years the relationship between the coral records and land rainfall is more complex running correlations suggest varying strength of interannual teleconnections between the tropical coral oxygen isotope records and rainfall over equatorial east africa the relationship with rainfall over india changed in the 1970s the subtropical oxygen isotope records are coherent with south african rainfall at interdecadal periodicities paleoclimatological reconstructions of land rainfall and sat reveal that the inferred relationships generally hold during the last 350 years thus the indian ocean corals prove invaluable for investigating land ocean interactions during past centuries

carbon and oxygen isotopic composition of a guam coral and their relationships to environmental variables in the western pacific we examine the high resolution 32 samples year carbon and oxygen isotopic composition 13ccoral and 18ocoral in a coral core porites lobata from double reef guam over the years 1980 2000 the 13ccoral shows clear seasonal variations with mean seasonal amplitude of 1 89 which roughly corresponds with seasonal variations in solar radiation the seasonal amplitude of 18ocoral variations are small 0 23 0 57 but they are significantly correlated with sea surface temperature sst and salinity sss the 18ocoral and sst are more strongly correlated during el nino southern oscillation enso warm phases r 0 81 p 28 c and lower values of 18osw at guam these differences in oceanic parameters result from movements of the western pacific warm pool wpwp during the different phases of enso anomalies in 18osw inferred from the 18ocoral and instrumental sst are consistent with sss anomalies for the years 1980 2000 these 18osw anomalies may reflect changes in sss and evaporation precipitation due to movements of the wpwp this detailed analysis of a coral from guam suggests that it may contain an excellent archive of past enso events

glacial to holocene surface hydrography of the tropical eastern indian ocean quantifying the spatial and temporal sea surface temperature sst and salinity changes of the indo pacific warm pool is essential to understand the role of this region in connection with abrupt climate changes particularly during the last deglaciation in this study we reconstruct sst and seawater delta o 18 of the tropical eastern indian ocean for the past 40 000 years from two sediment cores geob 10029 4 1 degrees 30 s 100 degrees 08 e and geob 10038 4 5 degrees 56 s 103 degrees 15 e retrieved offshore sumatra our results show that annual mean ssts increased about 2 3 degrees c at 19 000 years ago and exhibited southern hemisphere like timing and pattern during the last deglaciation our sst records together with other mg ca based sst reconstructions around indonesia do not track the monsoon variation since the last glacial period as recorded by terrestrial monsoon archives however the spatial sst heterogeneity might be a result of changing monsoon intensity that shifts either the annual mean ssts or the seasonality of g ruber towards the warmer or the cooler season at different locations seawater delta o 18 reconstructions north of the equator suggest fresher surface conditions during the last glacial and track the northern high latitude climate change during the last deglaciation in contrast seawater delta o 18 records south of the equator do not show a significant difference between the last glacial period and the holocene and lack bolling allerod and younger dryas periods suggestive of additional controls on annual mean surface hydrology in this part of the indo pacific warm pool c 2010 elsevier b v all rights reserved

estimating the topography before volcanic sector collapses using tsunami survey data and numerical simulations large sector collapses and landslides have the potential to cause significant disasters estimating the topography and conditions such as volume before the collapse is thus important for analyzing the behavior of moving collapsed material and hazard risks this study considers three historical volcanic sector collapses in japan that caused tsunamis the collapses of the komagatake volcano in 1640 oshima oshima island in 1741 and unzen mayuyama volcano in 1792 numerical simulations of the tsunamis generated by each event were first carried out based on assumed collapse scenarios the primary objective of this study is to present conditions related to the topography before the events based on inverse models of the topography from those results and tsunami survey data the oshima oshima tsunami which is the subject of many previous studies was first simulated to validate the model accuracy and evaluate how run up heights changed during the simulation as the topographic conditions changed the run up height was especially sensitive to the collapsed volume and frictional acceleration affecting the collapsed material however the observed run up heights could be reproduced with high accuracy using proper conditions of frictional acceleration for the scenarios even if they were not exact a minimum requirement for the collapsed volume to generate the observed run up height was introduced and quantitatively evaluated using the results of numerical tsunami simulations the minimum volumes of the collapses of the komagatake and unzen mayuyama volcanoes were estimated to be approximately 1 2 and 0 3 km3 respectively

enhanced multidecadal climate variability in the seventeenth century from coral isotope records in the western indian ocean 1 the slowly growing coral diploastreaheliopora affords a novel opportunity to obtain multicentury records of paleoclimate including details of the interannual rhythms associated with the el nino southern oscillation enso system we examine climate variability in an enso teleconnected region using new oxygen isotope records from d heliopora spanning most of the twentieth 1896 1998 and seventeenth 1622 1722 centuries from the mafia archipelago tanzania the modern record demonstrates coherency with relevant instrumental and proxy time series documents twentieth century warming and displays significant power at enso periodicities the seventeenth century record lacks any trend exhibits interannual variance comparable to the modern record and displays a pronounced interdecadal signal not evident in the twentieth century that correlates with other tropical and hemispheric climate records we find no clear evidence of solar irradiance influence on interannual variability in the western indian ocean during these intervals although the mean sea surface temperature appears to vary inversely with insolation

isotopic evidence for twentieth century weakening of the pacific walker circulation abstract the strength of the pacific walker circulation wc over the historical period is uncertain and strongly debated largely due to the limited length of reliable instrumental records tropical pacific corals provide continuous highly resolved records that can be used to overcome the limitations of the instrumental records here we combine coral 18 o records from the western pacific warm pool wpwp and tropical central eastern pacific cep to develop a coral wc index back to 1886 our coral wc index is in good agreement with post 1950 instrumental records justifying both a direct comparison with earlier instrumental records and an evaluation of twentieth century wc trends our results show that pre 1950 instrumental records appear to underestimate wc variability the coral wc index reveals a significant weakening of the wc over the twentieth century in response to development of el nino like sst pattern in the tropical pacific and enhanced hydrological cycle over the cep under greenhouse warming our results provide new evidence for twentieth century wc variability and offer an observational constraint for improving models and their prediction of future wc behavior

interannual and decadal variability of the western pacific sea surface condition for the years 1787 2000 reconstruction based on stable isotope record from a guam coral 1 we present a monthly resolved 213 year stable isotope time series from a coral from guam 13 n 145 e which is located on the northern edge of the western pacific warm pool oxygen isotopic composition of the coral skeleton 18ocoral shows seasonal interannual and decadal variability which documents significant oceanographic changes related to thermal and hydrologic variations in this region the 18ocoral anomaly reflects sea surface temperature sst anomaly and sea surface salinity sss anomaly with significant r values of 0 69 and 0 49 respectively which are strongly linked to oceanographic changes that occur during el nino southern oscillation enso warm and cool phases we identified 46 enso warm el nino and 53 cool phases la nina in the coral record which are consistent with those phases reconstructed by nino 3 4 sst anomaly spectral analyses of the 18ocoral anomaly record for the years 1790 1999 identified significant peaks around 3 to 7 years these results indicate that the guam coral has recorded enso periodicity the 18ocoral anomaly shows decadal variability of 15 to 45 year periodicity with significant shifts 0 2 from warmer to cooler condition and vice versa an accumulative decrease in 18ocoral time series may imply 0 75 c warming of sst and 0 23 freshening of seawater 18o corresponding to a decrease of sss by 0 85 in the northwestern tropical pacific over the last 2 centuries

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

depositional history of diamictites from the late paleoproterozoic dalma formation e india abstract the paleoproterozoic dalma formation situated on the singhbhum craton in eastern india consists almost entirely of mafic to ultramafic rocks that were deposited by effusive volcanic activity and as pyroclastic deposits the main focus of the present study however is on diamictites consisting like both other rock types exclusively of chlorite and actinolitic hornblende that are intercalated with these volcanic rocks these diamictites are interpreted as mass flow deposits the textures and mineralogical composition of the diamictites suggests a volcanic origin of the material most probably they are reworked pyroclastic deposits with the same mineralogy as the dalma lavas on this basis it is concluded that the diamictites represent the deposits of one or more volcanic mudflows they must have formed of material that had already travelled over a considerable distance in the form of grain by grain transport as indicated by the presence of both rounded and distinctly broken clasts and by the relatively small size of the clasts both the grain by grain and the mass transport must have occurred following pathways that were covered all over with volcanic material of mafic composition this transport must have taken place under terrestrial conditions as no marine or lacustrine clasts or matrix is included the results of the study suggest that the diamictites within the dalma formation cannot be seen as a possible equivalent of paleoproterozoic glacigenic sediments such as known from australia and south africa

on the weakening relationship between the indian monsoon and enso analysis of the 140 year historical record suggests that the inverse relationship between the el nino southern oscillation enso and the indian summer monsoon weak monsoon arising from warm enso event has broken down in recent decades two possible reasons emerge from the analyses a southeastward shift in the walker circulation anomalies associated with enso events may lead to a reduced subsidence over the indian region thus favoring normal monsoon conditions additionally increased surface temperatures over eurasia in winter and spring which are a part of the midlatitude continental warming trend may favor the enhanced land ocean thermal gradient conducive to a strong monsoon these observations raise the possibility that the eurasian warming in recent decades helps to sustain the monsoon rainfall at a normal level despite strong enso events