constraints on the magnitude and patterns of ocean cooling at the last glacial maximum observation based reconstructions of sea surface temperature from relatively stable periods in the past such as the last glacial maximum represent an important means of constraining climate sensitivity and evaluating model simulations1 the first quantitative global reconstruction of sea surface temperatures during the last glacial maximum was developed by the climate long range investigation mapping and prediction climap project in the 1970s and 1980s refs 2 3 since that time several shortcomings of that earlier effort have become apparent4 here we present an updated synthesis of sea surface temperatures during the last glacial maximum rigorously defined as the period between 23 and 19 thousand years before present from the multiproxy approach for the reconstruction of the glacial ocean surface margo project5 we integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins in contrast to the simulations of the last glacial maximum climate available at present6 7

sediment provenance in the western pacific warm pool from the last glacial maximum to the early holocene implications for ocean circulation and climatic change abstract sedimentary records including clay minerals major elements rare earth elements ree and 14c ages were analyzed in one core from the western pacific warm pool wpwp in order to identify the sources of sediments in the warm pool region from the last glacial maximum lgm to the early holocene the results showed that the sedimentation rate at the studied core site has decreased continuously since the lgm both major elements and clay minerals experienced staged changes in the study area in the studied core most major elemental concentrations decreased prior to 22 kyr bp but increased gradually after 13 kyr bp sediment provenance based on clay minerals and rees further revealed that sediments were likely a mixture of dominant new guinea sediments and asian dust the south equatorial current was the main force transporting new guinea particles while the east asian winter monsoon and the correlated north equatorial countercurrent might have loaded the asian dust into the study area moreover heinrich events were well imprinted in the western pacific and another cold climatic event that occurred at approximately 21 kyr bp was also recorded in the study area these events were similarly documented in ice from greenland but were undistinguished in ice from the antarctic and stalagmites from the hulu cave china a frequency analysis of multi proxies confirmed that sun irradiance essentially controlled the variation in sedimentary records in the western pacific from the lgm to the early holocene

glacial interglacial changes in equatorial pacific surface water structure during the plio pleistocene intensification of northern hemisphere glaciation the late pliocene early pleistocene intensification of northern hemisphere glaciation inhg represents the most recent major tipping point in earth s climate history in the equatorial pacific the inhg has been suggested to mark the transition from a warm pliocene climate state in which the pacific warm pool was greatly expanded relative to today giving rise to a surface ocean temperature field akin to modern el nino conditions to a climate state with strong upwelling in the east of the basin and stronger zonal temperature gradients here we examine this transition by presenting new high resolution 800 yr planktic foraminiferal mg ca and 18 18o based sea surface temperature sst and salinity sss based on 18o 18o residuals 18oivc sw 18oivc sw records from eastern equatorial pacific eep ocean drilling program site 849 spanning 2 75 2 4 ma our study interval contains the first large amplitude 1 in benthic 18 18o early pleistocene glacial interglacial cycles marine isotope stages 100 96 representing the culmination of inhg in this study we investigate west to east equatorial pacific sst and sss gradients we find that the zonal sst gradient increased by 1 5 c from 2 75 to 2 4 ma through eep cooling no glacial interglacial pattern is seen in this gradient on the other hand we document obliquity paced oscillations in the 18oivc sw 18oivc sw sss gradient we hypothesize that these oscillations originated from a response to a glacial southward and interglacial northward migration of the intertropical convergence zone over the eep

a late quaternary record of monsoon variability in the northwest kimberley australia abstract understanding of the late quaternary environment of australia s vast kimberley region has to date been hindered by the region s lack of classic palaeoenvironmental archives such as deep lake sediments however mound spring peat deposits in the region have been found to be a potentially rich archive of palaeoenvironmental data here we present a high resolution record from black springs mound spring in the kimberley s northwest filling some of the current gaps in knowledge of the region s environmental history this builds on a 6000 year record developed from the same site and indicates that since the last glacial interglacial transition the australian summer monsoon has varied greatly in intensity with an increase in monsoonal precipitation from 14 000 yr bp and pronounced drying in the late holocene despite some chronological uncertainties thought to be due to the inclusion of younger microscopic root fragments changes in the record compare well with other records of climatic change from the kimberley and across tropical northern australia

glacial interglacial changes in central tropical pacific surface seawater property gradients much uncertainty exists about the state of the oceanic and atmospheric circulation in the tropical pacific over the last glacial cycle studies have been hampered by the fact that sediment cores suitable for study were concentrated in the western and eastern parts of the tropical pacific with little information from the central tropical pacific here we present information from a suite of sediment cores collected from the line islands ridge in the central tropical pacific which show sedimentation rates and stratigraphies suitable for paleoceanographic investigations based on the radiocarbon and oxygen isotope measurements on the planktonic foraminifera globigerinoides ruber we construct preliminary age models for selected cores and show that the gradient in the oxygen isotope ratio of g ruber between the equator and 8 n is enhanced during glacial stages relative to interglacial stages this stronger gradient could reflect enhanced equatorial cooling perhaps reflecting a stronger walker circulation or an enhanced salinity gradient perhaps reflecting increased rainfall in the central tropical pacific

orbital and sea level changes regulate the iron associated sediment supplies from papua new guinea to the equatorial pacific abstract iron fe supplied to the equatorial pacific are thought to play a critical role in marine biogeochemical cycle and the related air sea co2 flux previous studies have shown that papua new guinea png is a major fe contributor for the western equatorial pacific however key issues of this fe supply including the exact sources transport processes and distribution range remain unclear especially its long term variability associated with hydroclimatic and paleoceanographic changes using a set of cores collected offshore the northern png and from the ontong java plateau ojp shown to situate along the pathway of fe delivery by undercurrents here we compile high resolution records to explore how the fe associated sediment supplies varied and distributed on orbital time scale during the past 400 ka the chronologic frameworks of these cores are established by using 14c datings and stratigraphic correlations of foraminiferal 18o records and carbonate contents the sedimentary fe and clay mineral smectite in the offshore png sites show a prominent precession cycle in phase with the march insolation change at 5 s such precessional predominance suggests the control of local precipitation and river runoff on the offshore deposition of the fe associated sediment for the ojp sites the proxies derived from terrigenous detrital component give a spectral pattern however prevailed by 100 ka cycle with secondary precessional highs the significant 100 ka cycle can best be attributed to glacial interglacial changes in oceanic transports likely caused by sea level regulated variability in the strength and or route of the coastal undercurrents off png this variability may have influenced the long distance transport of fe rich particulates from the png to the ojp and further eastwards via the equatorial undercurrent

tropical pacific ocean thermocline depth reconstructions for the last glacial maximum we evaluate the relationship between ten surface ocean 0 300 m hydrographic parameters and the spatial distribution of factor analyzed core top planktonic foraminiferal abundances in the tropical pacific ocean 24 n 24 s for core tops 3800 m the spatial distribution of the first three faunal factor loadings 88 of the variance are most highly correlated to subsurface variability mixed layer depth thermocline depth and resistant species percent rsp however rsp is not related to dissolution but is related to thermocline depth factor i mixed layer species g glutinata g ruber and factor iii g ruber can be distinguished from each other by low abundances of g glutinata in factor iii both assemblages spatially comprise the deep mixed layer region of the western tropical and equatorial pacific ocean but are associated with distinct water mass properties a combination of factor i and iii loadings shows a higher correlation to thermocline depth r 0 70 factor ii loadings dominated by thermocline dwelling species n dutertrei are most significantly correlated with the thermocline depth r 0 73 most factors show only marginally significant correlation to sea surface temperatures ssts indicating that sst is not the primary forcing factor on the planktonic foraminiferal species distributions in the tropical pacific a new transfer function was calculated to predict tropical pacific thermocline depth from planktonic foraminifera abundances using the imbrie kipp method ikm standard deviation of residuals 22 m 1 an additional 5 m error is attributed to low species counts in the core top database the modern analog technique mat was also used to predict thermocline depth standard deviation of residuals 21 m while last glacial maximum lgm thermocline depth changes by ikm and mat were generally within error estimated changes were geographically uniform suggesting an oceanographic response to climate forcing we estimate that the thermocline depth of the lgm was shallower than present by 20 m south of 8 s possibly due to a shift in the south pacific anticyclone to the northeast both the ikm and mat estimate a steeper east west thermocline slope along the equator suggesting that zonal wind stress walker circulation was intensified during the lgm collectively the thermocline estimates for the lgm suggest an equatorward compression of the climate zones in both hemispheres

tropical and high latitude forcing of enhanced megadroughts in northern china during the last four terminations abstract understanding the origin and evolutionary history of drought events is of great significance providing critical insight into future hydrological conditions under the changing climate due to the scarcity of drought proxies from northern china the occurrence and underlying mechanisms of the drought events remains enigmatic on longer timescales here we utilize microbial lipid proxies to reconstruct significant drought events over the last four ice age terminations in the southernmost section weinan section of the chinese loess plateau the abundance of archaeal isoprenoid gdgts glycerol dialkyl glycerol tetraethers relative to bacterial branched gdgts measured by ri b and bit indices is diagnostic of enhanced drought conditions the ri b and bit indices are stable and low high throughout most of the loess section spanning the last 350 thousand years but they do exhibit sharp transient peaks valleys during the intervals associated with the four ice age terminations and especially terminations ii and iv these enhanced drought events are non intuitively associated with a significant decrease in the relative abundance of c4 plants inferred by a decrease in the carbon isotope composition of bulk organic matter although the microbial records show some consistency with the weinan grain size profiles indicative of eastern asian winter monsoon variability they also show some apparent difference in fact some features of the microbial records exhibit strong similarities with marine sediment planktonic foraminiferal 13c records from the western pacific warm pool which reflect enso like changes during glacial terminations therefore enhanced droughts immediately before the interglacial warming in northern china could be explained at least in part by teleconnections in tropical ocean atmosphere circulation via shifts in the intertropical convergence zone itcz and associated jet stream over the asian continent according to our microbial biomarker data these enhanced megadroughts are apparently different both in terms of severity and causal mechanism from the more commonly discussed dry conditions observed during glacial periods

precipitation variability within the west pacific warm pool over the past 120 ka evidence from the davao gulf southern philippines proxy records of hydrologic variability in the west pacific warm pool wpwp have revealed wide scale changes in past convective activity in response to orbital and suborbital climate forcings however attributing proxy responses to regional changes in wpwp hydrology versus local variations in precipitation requires independent records linking the terrestrial and marine realms we present high resolution stable isotope u 37 k sea surface temperature x ray fluorescence xrf core scanning and coccolithophore derived paleoproductivity records covering the past 120ka from international marine global change images program core md06 3075 6 degrees 29n 125 degrees 50e water depth 1878m situated in the davao gulf on the southern side of mindanao xrf derived log fe ca records provide a robust proxy for runoff driven sedimentary discharge from mindanao while past changes in local productivity are associated with variable freshwater runoff and stratification of the surface layer significant precessional scale variability in sedimentary discharge occurred during marine isotope stage mis 5 with peaks in discharge contemporaneous with northern hemisphere summer insolation minima we attribute these changes to the latitudinal migration of the intertropical convergence zone itcz over the wpwp together with variability in the strength of the walker circulation acting on precessional timescales between 60 and 15ka sedimentary discharge at mindanao was muted displaying little orbital or millennial scale variability likely in response to weakened precessional insolation forcing and lower sea level driving increased subsidence of air masses over the exposed sunda shelf these results highlight the high degree of local variability in the precipitation response to past climate changes in the wpwp

the response of the walker circulation to last glacial maximum forcing implications for detection in proxies 1 the response of the walker circulation to last glacial maximum lgm forcing is analyzed using an ensemble of six coordinated coupled climate model experiments the tropical atmospheric overturning circulation strengthens in all models in a manner that is dictated by the response of the hydrological cycle to tropical cooling this response arises from the same mechanism that has been found to explain the weakening of the tropical circulation in response to anthropogenic global warming but with opposite sign analysis of the model differences shows that the ascending branch of the walker circulation strengthens via this mechanism but vertical motion also weakens over areas of the maritime continent exposed due to lower sea level each model exhibits a different balance between these two mechanisms and the result is a pacific walker circulation response that is not robust further even those models that simulate a stronger walker circulation during the lgm do not simulate clear patterns of surface cooling such as la nina like cooling or enhanced equatorial cooling as proposed by previous studies in contrast the changes in the walker circulation have a robust and distinctive signature on the tilt of the equatorial thermocline as expected from zonal momentum balance the changes in the walker circulation also have a clear signature on the spatial pattern of the precipitation changes a reduction of the east west salinity contrast in the indian ocean is related to the precipitation changes resulting from a weakening of the indian walker circulation these results indicate that proxies of thermocline depth and sea surface salinity can be used to detect actual lgm changes in the pacific and indian walker circulations respectively and help to constrain the sensitivity of the walker circulation to tropical cooling

the climate response of the indo pacific warm pool to glacial sea level growing climate proxy evidence suggests that changes in sea level are important drivers of tropical climate change on glacial interglacial time scales these paleodata suggest that rainfall patterns over the indo pacific warm pool ipwp are highly sensitive to the landmass configuration of the maritime continent and that lowered sea level contributed to large scale drying during the last glacial maximum lgm ca 21 000 years before present using the community earth system model version 1 2 cesm1 we investigate in detail the mechanisms by which lowered sea level influenced the climate of the ipwp during the lgm the cesm1 simulations show that in agreement with previous hypotheses changes in atmospheric circulation are initiated by the exposure of the sunda and sahul shelves ocean dynamical processes amplify the changes in atmospheric circulation by increasing the east west sea surface temperature sst gradient along the equatorial indian ocean the coupled mechanism driving this response is akin to the bjerknes feedback and results in a large scale climatic reorganization over the indian ocean with impacts extending from east africa to the western tropical pacific exposure of sahul shelf and the associated changes in surface albedo play a key role because it is more effective at exciting the positive feedback than exposure of the sunda shelf this mechanism could explain the pattern of dry wet eastern western indian ocean identified in climate proxies and lgm simulations however this response also requires a strengthened sst gradient along the equatorial indian ocean and it is currently unclear whether this is detectable in marine paleoreconstructions strategies to resolve this issue are discussed

variation of the asian summer monsoon since the last glacial interglacial recorded in a stalagmite from southwest china abstract a number of studies proposed a close link between the climate changes in the asian summer monsoon asm the southern hemisphere sh and high latitudes of the northern hemisphere nh but the mechanisms is still an open question although speleothems 18o records have displayed excellent values in the reconstruction of paleoclimate change at centennial millennial to orbital timescales the significance of speleothems 18o and 13c is still debatable here a high precise 230th dated stalagmite from southwestern china was used to reconstruct the changes of asm and regional hydrological conditions since the last interglacial 3 6 118 1 ka bp by the coupled 18o and 13c we found 1 the easm and ism are synchronous changing on the orbital timescale responding to the change of north hemisphere summer insolation nhsi and high latitude climate change there is a teleconnection between antarctic temperature change and asm through the mascarene high and the somali jet 2 during mis 5d the stalagmite 18o in yangzi cave is nearly 1 5 higher than that in mis 2 the maximum of last glacial this should be attributed to the different isotopic compositions in moisture source of ism and easm and the dynamic changes of monsoon circulations 3 from mis 3 to mis 2 the asm showed a stepped pattern in weakening consistent with the decreasing nhsi and increasing global ice volume 4 the changes in stalagmite 13c indicated the changes of local hydrological conditions and closely correlated with climate changes revealed by stalagmite 18o the effective humidity which determined by temperature evaporation and precipitation dominated the regional hydrological conditions the change of effective humidity recorded in stalagmite 13c by influencing surface biomass and soil co2 production

hydrological and vegetation shifts in the wallacean region of central indonesia since the last glacial maximum abstract precipitation is the most important variable of indonesian climate yet there are substantial uncertainties about past and future hydroclimate dynamics over the region this study explores vegetation and rainfall and associated changes in atmospheric circulation during the past 26 000 years in wallacea a biogeographical area in central indonesia wedged between the sunda and sahul shelves and known for its exceptionally high rainforest biodiversity we use terrestrial plant biomarkers from sediment cores retrieved from mandar bay off west sulawesi to reconstruct changes in wallacean vegetation and climate since the last glacial maximum lgm enriched leaf wax carbon isotope 13cwax values recorded in mandar bay during the lgm together with other regional vegetation records document grassland expansion implying a regionally dry and possibly more seasonal glacial climate depleted leaf wax deuterium isotope dwax values in mandar bay during the lgm and low reconstructed precipitation isotope compositions from nearby sites reveal an intensified austral asian summer monsoon circulation and a southward shift of the mean position of the intertropical convergence zone likely due to strong southern hemisphere summer insolation and the presence of large northern hemisphere ice sheets mandar bay 13cwax was anti correlated with dwax during the lgm and the last deglaciation but was positively correlated during most of the holocene indicating time varying controls on the isotopic composition of rainfall in this region the inundation event of the sunda shelf and in particular the opening of the java sea and karimata strait between 9 4 and 11 1 thousand years ago might have provided new moisture sources for regional convection and or influenced moisture source trajectories providing the trigger for shifts in atmospheric circulation and the controls on precipitation isotope compositions from the lgm to the holocene

late cenozoic sea level and the rise of modern rimmed atolls this paper is not subject to u s copyright the definitive version was published in palaeogeography palaeoclimatology palaeoecology 451 2016 73 83 doi 10 1016 j palaeo 2016 03 018

the late quaternary tectonic biogeochemical and environmental evolution of ferruginous lake towuti indonesia abstract there is a paucity of long and continuous continental records from south east asia suitable to inform on past changes and underlying causes of the region s climate and associated diverse ecosystem evolution during the late quaternary in 2015 the towuti drilling project tdp collected a series of sedimentary drill cores from the tectonic ferruginous and highly biodiverse lake towuti sulawesi one of indonesia s oldest lakes the drill cores contain 1 myr of uninterrupted lacustrine sedimentation to document long term environmental and climatic change in the tropical western pacific the impacts of geological and environmental changes on the biological evolution of aquatic taxa and the geomicrobiology and biogeochemistry of metal rich ultramafic hosted lake sediment here we use lithostratigraphic mineralogical geochemical and geochronological datasets to elucidate lake towuti s tectonic emergence and its biogeochemical responses to climatic and volcanic forcings since lake formation our data document that lake towuti emerged during a phase of accelerated tectonic subsidence from a landscape characterized by active river channels shallow lakes and swamps into a permanent lake at 1 ma the lacustrine sediments feature quasi rhythmic alternations of green organic rich and red sideritic clay beds reflecting changes in lake mixing and biogeochemistry as a response to temperature and hydrological changes driven by orbital scale changes in insolation and continental ice volume through the mid to late pleistocene clay deposition is interrupted by two beds of diatomaceous oozes composed primarily of planktonic diatoms that reflect phases of substantially increased primary productivity the occurrence of these diatomaceous oozes in close association with multiple tephra beds suggests a trophic state change driven by the addition of volcanically sourced p possibly in combination with a lake mixing state that supports recycling of p data on lake age and ontogeny are also in agreement with molecular clock estimates of 0 7 ma 0 18 1 37 ma for the divergence of lake towuti s telmatherinid fishes from a riverine ancestor our data therefore are compatible with an evolutionary model in which lake towuti s endemic fauna is a result of geographic speciation in the malili lakes a set of large lakes in southeast sulawesi driven by physical or chemical dispersal limits imposed by the regional rivers and lakes more detailed chronological constraints and refined climate and environmental proxy datasets are currently in preparation and will help to paint a more detailed history of the region s climate and environmental history in future studies

the 520 km discontinuity although some of the earliest suggestions of a seismic discontinuity near 520 km depth in the upper mantle came from seismic studies of the structure to the north of australia results from more recent deployments of portable arrays of short period instruments are equivocal of the several hundred earthquakes recorded during these experiments only a small fraction provide data that could help to constrain the properties of the discontinuity of the few earthquake recordings that can address the question of whether such a discontinuity exists most indicate that it does not exist as a sharp feature i e less than 50 km thick at depths of less than 540 km the data do not however constrain the existence of a discontinuity at depths greater than 540 km furthermore the velocity increase could be distributed over a significant depth range even a 50 km transition would not appear in the short period observations and still provide sufficient reflectivity at near vertical incidence to be compatible with long period observations for waves traveling steeply in the mantle

abrupt increase in east indonesian rainfall from flooding of the sunda shelf 9500 years ago we present a precisely dated multi proxy stalagmite record from liang luar cave flores southeast indonesia that reveals a rapid increase in indonesian monsoon rainfall at 9 5 ka a ramp fitting method for detecting statistically significant inflections in a time series was applied to the stalagmite 18o mg ca and sr ca profiles to quantify the precise timing and magnitude of an abrupt increase in monsoon strength over a period of 350 years previously published lake level records from the monsoon affected australian interior show a sudden intensification of the australian monsoon at 14 ka however our records indicate that monsoon intensification in flores occured 4 5 kyr later the timing of the monsoon shift in flores is synchronous with the rapid expansion of rainforest in northeast australia and regional freshening of the southern makassar strait which under present day conditions is sensitive to monsoon variability the freshening of southern makassar was coeval with an abrupt 1 5 c cooling in the upper thermocline of the timor sea 9 5 ka indicative of reduced surface heat transport by the indonesian throughflow itf when the java sea opened during postglacial sea level rise this suggests that the abrupt increase in monsoon rainfall on flores was not due to a change in the itf because a decrease in rainfall would be expected to accompany cooler local sea surface temperatures ssts but rather by the sudden increase in ocean surface area and or temperature in the monsoon source region as the sunda shelf flooded during deglaciation we propose that it was the abrupt intensification of the monsoon through the late deglaciation that maintained the subsequent structure of the itf following the flooding of the sunda shelf at 9 5 ka

el nino southern oscillation extrema in the holocene and last glacial maximum 1 the el nino southern oscillation enso is the largest engine of interannual climate variability on the planet yet its past behavior and potential for future change are poorly understood and vigorously contested reconstructions of past enso are indispensable for testing climate models tasked with predicting future enso activity in a warming world but suitable geologic archives are scarce especially for the last glacial period here we reconstruct mean climate and enso variability in the holocene and last glacial maximum lgm from oxygen isotopic ratios 18o of individual foraminifera retrieved from deep sea sediments our results document coordinated adjustments of the tropical pacific enso system between two diametrically opposite states an amplified enso state in the lgm associated with a reduced zonal temperature gradient and a damped enso state in the mid holocene with enhanced gradient orbital precession provided the switch between these states and acted as the dominant external driver of the tropical pacific enso system in the past 25 000 years the linked response of the mean state and variability to orbital forcing provides an integrated framework for testing enso theory and models

steering of westerly storms over western north america at the last glacial maximum the last glacial maximum hydroclimate over western north america differed from the modern climate a proxy model comparison suggests that the glacial storm track was squeezed and steered by atmospheric high pressure systems

the effect of sea level on glacial indo pacific climate the indo pacific warm pool is the largest source of heat and moisture vapour to the atmosphere proxy reconstructions and model simulations suggest that during the last glacial maximum the exposure of the sunda shelf of southeast asia weakened deep convection over the warm pool

natural and anthropogenic induced changes in a tidal inlet morphological evolution of oregon inlet abstract natural processes driving the dynamics of tidal inlets have been studied in length however as human influence in the coastal environment persists there is a need to comprehend how both natural and human induced processes drive different aspects of tidal inlet morphological evolution an effort to understand the combined effects of natural and anthropogenic induced processes in a tidal inlet is pursued by studying oregon inlet considered one of the most dynamic inlets in the outer banks of north carolina usa the temporal and spatial scales of the anthropogenic processes driving the morphological evolution of this tidal inlet are studied by means of remotely sensed data and in situ observations gathered from 2005 until 2015 effects of natural process that cannot be gathered from observations are studied via a morphological model based on delft3d evolutional trends include the cyclical response of the main channel of the inlet to dredging a 13 northward rotation of the main channel and frequent sediment transport reversal in the southern shoulder simulations indicate a net sediment transport rate into the inlet of 205 000 m3 yr tidal currents are responsible for 55 of such transport while waves account for the remaining 45 after a 2 year non dredging modeling scenario sediments from the subaqueous spit form a detached shoal in the north side of the flood delta and the main channel remains open branching into two dominant channels observations and model results indicate that oregon inlet has been in a state of stable equilibrium in the past decade natural and human induced processes contribute to such equilibrium this study exemplifies the decadal behavior of a tidal inlet influenced by natural processes infrastructure and dredging

variations in sea surface hydrology in the southern makassar strait over the past 26 kyr we present centennial scale records of sea surface temperature and oxygen isotopes in a sediment core from mandar bay offshore sulawesi in the southern makassar strait which provide new insights into the variability of indonesian climate over the past 26 kyr the age model for the core is constrained by 17 ams radiocarbon ages with a surface ocean reservoir age correction based on paired wood and foraminiferal samples small holocene reservoir ages of 105 180 years point to intense surface ocean atmosphere interchange linked to increased monsoonal precipitation whereas last glacial maximum and deglacial reservoir ages are significantly higher mg ca derived sea surface temperature reconstructions based on globigerinoides ruber s s white exhibit an extended plateau during the antarctic cold reversal suggesting an atmospheric connection to high latitude southern hemisphere climate and a seasonal bias on g ruber this is in agreement with southern hemisphere sites along the track of the indonesian throughflow and in contrast to northern hemisphere records from the south china sea sulu sea and western pacific off mindanao which exhibit warming during the bolling allerod ice volume corrected delta o 18 seawater delta o 18 sw increased during heinrich stadial 1 and the younger dryas whereas the bolling allerod is characterized by low delta o 18 sw we attribute delta o 18 sw variability in the southern makassar strait during the last glacial maximum and glacial termination to changes in provenance and seasonality of precipitation rather than to variability in the amount of local precipitation and runoff c 2016 elsevier ltd all rights reserved

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

glacial aridity in central indonesia coeval with intensified monsoon circulation abstract the last glacial maximum was cool and dry over the indo pacific warm pool ipwp a key region driving global oceanic atmospheric circulation both low and high latitude teleconnections with insolation ice sheets and sea level have been suggested to explain the pervasive aridity observed in paleoecological and geomorphic data however proxies tracking the h and o isotopic composition of rainfall e g speleothems sedimentary biomarkers suggest muted aridity or even wetter conditions than the present complicating interpretations of glacial ipwp climate here we use multiproxy reconstructions from lake sediments and modern rainfall isotopic measurements from central indonesia to show that contrary to the classical amount effect intensified australian indonesian monsoon circulation drove lighter h and o isotopic composition of ipwp rainfall during the lgm while at the same time dry conditions prevailed precipitation isotopes are particularly sensitive to the apparent increase in monsoon circulation and perhaps also decreased moisture residence time implied by our data explaining contrasts among proxy records while illuminating glacial ipwp atmospheric circulation a key target for climate models

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

increasing australian indonesian monsoon rainfall linked to early holocene sea level rise the australian indonesian summer monsoon affects rainfall variability across the indo pacific region reconstructions of monsoon strength from stalagmites show that precipitation increased from 11 000 to 7 000 years ago as rising global sea level caused the flooding of the indonesian continental shelf the australian indonesian summer monsoon affects rainfall variability and hence terrestrial productivity in the densely populated tropical indo pacific region it has been proposed that the main control of summer monsoon precipitation on millennial timescales is local insolation1 2 3 but unravelling the mechanisms that have influenced monsoon variability and teleconnections has proven difficult owing to the lack of high resolution records of past monsoon behaviour here we present a precisely dated reconstruction of monsoon rainfall over the past 12 000 years based on oxygen isotope measurements from two stalagmites collected in southeast indonesia we show that the summer monsoon precipitation increased during the younger dryas cooling event when atlantic meridional overturning circulation was relatively weak4 monsoon precipitation intensified even more rapidly from 11 000 to 7 000 years ago when the indonesian continental shelf was flooded by global sea level rise5 6 7 we suggest that the intensification during the younger dryas cooling was caused by enhanced winter monsoon outflow from asia and a related southward migration of the intertropical convergence zone8 however the early holocene intensification of monsoon precipitation was driven by sea level rise which increased the supply of moisture to the indonesian archipelago

a comparison of pmip2 model simulations and the margo proxy reconstruction for tropical sea surface temperatures at last glacial maximum results from multiple model simulations are used to understand the tropical sea surface temperature sst response to the reduced greenhouse gas concentrations and large continental ice sheets of the last glacial maximum lgm we present lgm simulations from the paleoclimate modelling intercomparison project phase 2 pmip2 and compare these simulations to proxy data collated and harmonized within the multiproxy approach for the reconstruction of the glacial ocean surface project margo five atmosphere ocean coupled climate models aogcms and one coupled model of intermediate complexity have pmip2 ocean results available for lgm the models give a range of tropical defined for this paper as 15 s 15 n sst cooling of 1 0 2 4 c comparable to the margo estimate of annual cooling of 1 7 1 c the models simulate greater sst cooling in the tropical atlantic than tropical pacific but interbasin and intrabasin variations of cooling are much smaller than those found in the margo reconstruction the simulated tropical coolings are relatively insensitive to season a feature also present in the margo transferred based estimates calculated from planktonic foraminiferal assemblages for the indian and pacific oceans these assemblages indicate seasonality in cooling in the atlantic basin with greater cooling in northern summer than northern winter not captured by the model simulations biases in the simulations of the tropical upwelling and thermocline found in the preindustrial control simulations remain for the lgm simulations and are partly responsible for the more homogeneous spatial and temporal lgm tropical cooling simulated by the models the pmip2 lgm simulations give estimates for the climate sensitivity parameter of 0 67 0 83 c per wm 2 which translates to equilibrium climate sensitivity for doubling of atmospheric co2 of 2 6 3 1 c

staged fine grained sediment supply from the himalayas to the bengal fan in response to climate change over the past 50 000 years abstract the bengal fan as the largest submarine fan in the world receives a large amount of sediments discharged from the himalayas through the ganges brahmaputra g b river system however previous studies of this system seldom focused on the role of channels which are widely developed in the bengal fan in sediment transportation over the last glacial cycle here we discuss the coupled sedimentary archive in two gravity cores along the active channel in the bengal fan our findings are based on grain size clay minerals and sr and nd isotope compositions of these two sediment cores end member modeling of grain size data reveals that the intermediate end member represents the flux of distal fluvial particles from the g b river system the fine end member denotes regional sediment supply of weathered volcanic materials especially from the eastern indian peninsula and the coarse end member probably reflects nearby terrigenous input aeolian input and or volcanic glass sediment provenance analysis based on clay minerals and sr and nd isotopes confirmed sediment supply from the g b river system which was characterized by high illite percentage high 87sr 86sr ratios and low end values especially during five stages 50 45 ka 42 37 ka 31 28 5 ka 24 20 ka and 14 9 ka during these stages heavy fine grained sediment supply from the g b river system was discharged into the study area under the influence of climate change rather than sea level fluctuation additionally emphasizing the importance of channels in the sediment transport process moreover we find a significant alteration of sediment sources at 26 ka which may be related to conversion of the deep water currents in the bay of bengal

climate in sundaland and asian monsoon variability during the last deglaciation abstract the lack of semi quantitative paleo data from mainland southeast asia especially from the emergent sundaland creates a marked difficulty in following the past asian monsoon variability the published pollen records from the adjacent sites to the sundaland were selected in this study and evaluated for the relationship between taxa and plant functional types pfts and subsequently between pfts and biome to eventually reconstruct the semi quantitative temporal temperature and precipitation profile in order to comprehend the asian monsoon modification between 18 5 and 11 ka bp the derived pollen based temperature and precipitation records were further analyzed together with other selected speleothem records from the asian monsoon region with reference to the greenland and antarctic ice cores the warmer temperature in the southern hemisphere caused a southward shift of the mean position of the intertropical convergent zone itcz and weakened the summer monsoon in the asian monsoon region between 18 5 and 15 ka bp the northern hemisphere temperature played an important role in the asian monsoon modification between 15 and 13 5 ka bp where the warmer northern hemisphere conditions strengthened the summer monsoon intensity in the asian monsoon region and moved the mean position of the itcz to the north however the opposing precipitation pattern between the east and the west indian ocean suggested the potential influence of the walker circulation on the sundaland climate from 13 5 to 11 ka bp

deglacial δ18o and hydrologic variability in the tropical pacific and indian oceans abstract evidence from geologic archives suggests that there were large changes in the tropical hydrologic cycle associated with the two prominent northern hemisphere deglacial cooling events heinrich stadial 1 hs1 19 to 15 kyr bp kyr bp 1000 yr before present and the younger dryas 12 9 to 11 7 kyr bp these hydrologic shifts have been alternatively attributed to high and low latitude origin here we present a new record of hydrologic variability based on planktic foraminifera derived 18o of seawater 18osw estimates from a sediment core from the tropical eastern indian ocean and using 12 additional 18osw records construct a single record of the dominant mode of tropical eastern equatorial pacific and indo pacific warm pool ipwp hydrologic variability we show that deglacial hydrologic shifts parallel variations in the reconstructed interhemispheric temperature gradient suggesting a strong response to variations in the atlantic meridional overturning circulation and the attendant heat redistribution a transient model simulation of the last deglaciation suggests that hydrologic changes including a southward shift in the intertropical convergence zone itcz which likely occurred during these northern hemisphere cold events coupled with oceanic advection and mixing resulted in increased salinity in the indonesian region of the ipwp and the eastern tropical pacific which is recorded by the 18osw proxy based on our observations and modeling results we suggest the interhemispheric temperature gradient directly controls the tropical hydrologic cycle on these time scales which in turn mediates poleward atmospheric heat transport