a late glacial high resolution site and source temperature record derived from the epica dome c isotope records east antarctica the timing and synchronisation of greenland and antarctic climate events that occurred during the last glacial period are still under debate as is the magnitude of temperature change associated with these events here we present detailed records of local and moisture source temperature changes spanning the period 27 45 kyr bp from water stable isotope measurements deltad and delta 18 o in the recently drilled epica dome c ice core east antarctic plateau using a simple isotopic model site deltat site and source deltat source temperatures are extracted from the initial 50 yr high resolution isotopic records taking into account the changes in seawater isotopic composition the deuterium isotope variability is very similar to the less precise deltad record from the vostok ice core and the site temperature inversion leads to a temperature profile similar to the classical palaeothermometry method due to compensations between source and ocean water corrections the reconstructed deltat site and deltat source profiles show different trends during the glacial the former shows a decreasing trend from the warm al event 38 kyr bp toward the last glacial maximum while the latter shows increasing values from 41 to 28 kyr bp the low frequency deuterium excess fluctuations are strongly influenced by obliquity fluctuations controlling the low to high latitude temperature gradients and show a remarkable similarity with a high resolution southeast atlantic sea surface temperature record a comparison of the temperature profiles site and source and temperature gradient deltat source deltat site with the non sea salt calcium and sodium records suggests a secondary influence of atmospheric transport changes on aerosol variations

sr nd isotope composition and clay mineral assemblages in eolian dust from the central philippine sea over the last 600 kyr implications for the transport mechanism of asian dust dust transport to the tropical subtropical northwestern pacific over the past 600 kyr was investigated using radiogenic isotopes 87sr 86sr and end together with the clay mineral composition of eolian dust preserved in a sediment core obtained from the philippine sea 12 30 n 134 60 e these data revealed the influence of two prevailing dust sources namely the asian deserts and nearby volcanic arcs e g the luzon arc with average contributions of around 70 and 30 respectively from each the clay mineral composition of the core resembled dust from the central asian deserts cads e g the taklimakan desert as in the north central pacific but published aerosol data collected near the study site during winter spring have the mineralogical signature of dust originating from the east asian deserts eads these data indicate that the relative contribution of ead dust increases with the northeasterly surface winds associated with the east asian winter monsoon eawm during winter spring but the prevailing westerlies and trade winds that carry dust from the cads is the dominant transport agent in the overall dust budget of the study site the results of this study contradict the prevailing view that direct dust transport by the eawm winds in spring dominates the annual flux of eolian dust in the northwest pacific

bay of bengal exhibits warming trend during the younger dryas implications of amoc a sharp decline in temperature during the younger dryas yd preceding the current warmer holocene is well documented in climate archives from the northern hemisphere high latitudes although the magnitude of yd cooling varied spatially the response of yd cooling was well documented in the atlantic and pacific oceans but not in the indian ocean here we investigate whether the modern remote forcing of tropical indian ocean sea surface temperature sst by northern hemisphere climate changes holds true for events such as the yd our sst reconstruction from the western bay of bengal exhibits an overall warming of 1 8 c during the yd we further compared our data with other existing mg ca based sst records from the northern indian ocean and found no significant negative sst anomalies in both the arabian sea and the bay of bengal compared to pre and post yd suggesting that no apparent cooling occurred during the yd in the northern indian ocean in contrast most part of the yd exhibits positive sst anomalies in the northern indian ocean that coincide with the slowdown of the atlantic meridional overturning circulation during this period

holocene aridification of india 1 spanning a latitudinal range typical for deserts the indian peninsula is fertile instead and sustains over a billion people through monsoonal rains despite the strong link between climate and society our knowledge of the long term monsoon variability is incomplete over the indian subcontinent here we reconstruct the holocene paleoclimate in the core monsoon zone cmz of the indian peninsula using a sediment core recovered offshore from the mouth of godavari river carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the cmz and document a gradual increase in aridity adapted vegetation from 4 000 until 1 700 years ago followed by the persistence of aridity adapted plants after that the oxygen isotopic composition of planktonic foraminiferglobigerinoides ruberdetects unprecedented high salinity events in the bay of bengal over the last 3 000 years and especially after 1 700 years ago which suggest that the cmz aridification intensified in the late holocene through a series of sub millennial dry episodes cultural changes occurred across the indian subcontinent as the climate became more arid after 4 000 years sedentary agriculture took hold in the drying central and south india while the urban harappan civilization collapsed in the already arid indus basin the establishment of a more variable hydroclimate over the last ca 1 700 years may have led to the rapid proliferation of water conservation technology in south india

glacial to holocene swings of the australian indonesian monsoon the australian indonesian monsoon is an important component of the climate system in the tropical indo pacific region 1 however its past variability relation with northern and southern high latitude climate and connection to the other asian monsoon systems are poorly understood here we present high resolution records of monsoon controlled austral winter upwelling during the past 22 000 years based on planktic foraminiferal oxygen isotopes and faunal composition in a sedimentary archive collected offshore southern java we show that glacial interglacial variations in the australian indonesian winter monsoon were in phase with the indian summer monsoon system consistent with their modern linkage through cross equatorial surface winds likewise millennial scale variability of upwelling shares similar sign and timing with upwelling variability in the arabian sea on the basis of element composition and grain size distribution as precipitation sensitive proxies in the same archive we infer that austral summer monsoon rainfall was highest during the bolling allerod period and the past 2 500 years our results indicate drier conditions during heinrich stadial 1 due to a southward shift of summer rainfall and a relatively weak hadley cell south of the equator we suggest that the australian indonesian summer and winter monsoon variability were closely linked to summer insolation and abrupt climate changes in the northern hemisphere the seasonality of the global monsoon is of central importance to the global hydrologic cycle and its environmental influence on human societies palaeoclimate reconstructions generally agree that the strengths of the east asian monsoon and the indian monsoon are tightly coupled to the northern hemisphere climate through zonal migrations of the monsoon convection centres also interpreted as intertropical convergence zone itcz migration 26 the mechanism of the australianindone

climatic evolution of the central equatorial pacific since the last glacial maximum this paper investigates paleoceanographic changes at a central equatorial pacific site 6 40 n 177 28 w since the last glacial maximum using planktic foraminifera assemblages together with the oxygen isotope 18o and mg ca compositions of three species globigerinoides sacculifer pulleniatina obliquiloculata and globorotalia tumida that dwell in the mixed layer upper thermocline and lower thermocline respectively while the mg ca derived temperatures of the mixed layer and lower thermocline varied within a narrow range from 18 ka onward the upper thermocline temperature increased by as much as 3 c during the last deglaciation 18 12 ka with a simultaneous decrease of 18o these changes are best explained by an enhanced mixing of the upper ocean and a reduced habitat depth separation between p obliquiloculata and g sacculifer during the 18 12 ka interval the planktic foraminifera assemblage during the same period resembles modern composition at subtropical central pacific sites that are strongly influenced by the northeasterly trades and north equatorial current nec we suggest that the study site presently under the control of the intertropical convergence zone itcz north equatorial countercurrent had been influenced by the northeasterly trades and nec during the 18 12 ka interval this interpretation is consistent with previous documentation of a more southerly location of the itcz during two northern hemisphere cooling events the heinrich stadial 1 and the younger dryas and implies that the mean annual position of the itcz was located south of the study site by at least 2 of latitude

rapid precipitation changes in the tropical west pacific linked to north atlantic climate forcing during the last deglaciation abstract the cause of rapid hydrological changes in the tropical west pacific during the last deglaciation remains controversial in order to test whether these changes were triggered by abrupt climate change events in the north atlantic ocean variations in precipitation during the last deglaciation 18 10 ka were extracted from proxy records of chemical weathering and terrigenous input in the western philippine sea wps the evolution of chemical weathering and terrigenous input since 27 ka was reconstructed using the chemical index of alteration cia elemental ratios k al toc tn and ti ca 13corg terrigenous fraction abundance and flux data from international marine global change study program images core md06 3054 collected on the upper continental slope of eastern luzon northern philippines sediment deposited during the last glacial maximum lgm shows weathering equal to or slightly greater than holocene sediment in the wps this unusual state of chemical weathering which is inconsistent with lower air temperatures and decreased precipitation in luzon during the lgm may be due to reworking of poorly consolidated sediments on the eastern luzon continental shelf during the lgm sea level lowstand rapid changes in chemical weathering characterized by higher intensity during the heinrich event 1 h1 and younger dryas yd and lower intensity during the bolling allerod b a were linked to rapid variations in precipitation in the wps during the last deglaciation the higher terrigenous inputs during the lgm relative to those of the holocene were controlled by sea level changes rather than precipitation the terrigenous inputs show a long term decline during the last deglaciation punctuated by brief spikes during the h1 and yd related to sea level rises and rapid precipitation changes in the wps respectively the proxy records of chemical weathering and terrigenous input from eastern luzon suggest high rainfall during the h1 and yd events consistent with inferred rainfall patterns based on fe ca records from offshore mindanao rapid precipitation changes in the wps did not coincide with migrations of the intertropical convergence zone itcz but rather were related to state shifts of the el nino southern oscillation enso during the last deglaciation based on proxy records and modeling results we argue that the atlantic meridional overturning circulation amoc controlled rapid precipitation changes in the tropical west pacific through zonal shifts of enso or meridional migration of the itcz during the last deglaciation our findings highlight the dominant role of the north atlantic ocean in the tropical hydrologic cycle during the last deglaciation

climate variability and ice sheet dynamics during the last three glaciations a composite north atlantic record from dsdp site 609 and iodp site u1308 spans the past 300 000 years and shows that variability within the penultimate glaciation differed substantially from that of the surrounding two glaciations hematite stained grains exhibit similar repetitive down core variations within the marine isotope stage mis 8 and 4 2 intervals but little cyclic variability within the mis 6 section there is also no petrologic evidence in terms of detrital carbonate rich heinrich layers for surging of the laurentide ice sheet through the hudson strait during mis 6 rather very high background concentration of iceberg rafted debris ird indicates near continuous glacial meltwater input that likely increased thermohaline disruption sensitivity to relatively weak forcing events such as expanded sea ice over deepwater formation sites altered sub tropical precipitation patterns and antarctic warming during high orbital precession and low 65 n summer insolation appear related to high abundance of icelandic glass shards and southward sea ice expansion differing european and north american ice sheet configurations perhaps aided by larger variations in eccentricity leading to cooler summers may have contributed to the relative stability of the laurentide ice sheet in the hudson strait region during mis 6

holocene tropical western indian ocean sea surface temperatures in covariation with climatic changes in the indonesian region the sea surface temperature sst of the tropical indian ocean is a major component of global climate teleconnections while the holocene sst history is documented for regions affected by the indian and arabian monsoons data from the near equatorial western indian ocean are sparse reconstructing past zonal and meridional sst gradients requires additional information on past temperatures from the western boundary current region we present a unique record of holocene sst and thermocline depth variations in the tropical western indian ocean as documented in foraminiferal mg ca ratios and 18o from a sediment core off northern tanzania for mg ca and thermocline 18o most variance is concentrated in the centennial to bicentennial periodicity band on the millennial time scale an early to mid holocene 7 8 5 6 ka warm phase is followed by a temperature drop by up to 2 c leading to a mid holocene cool interval 5 6 4 2 ka the shift is accompanied by an initial reduction in the difference between surface and thermocline foraminiferal 18o consistent with the thickening of the mixed layer and suggestions of a strengthened walker circulation however we cannot confirm the expected enhanced zonal sst gradient as the cooling of similar magnitude had previously been found in ssts from the upwelling region off sumatra and in flores air temperatures the sst pattern probably reflects the tropical indian ocean expression of a large scale climate anomaly rather than a positive indian ocean dipole like mean state

stable isotope composition of cave guano from eastern borneo reveals tropical environments over the past 15 000 cal yr bp abstract insular southeast asia is a key driver for global atmospheric and oceanic circulation is a hotspot for biodiversity and conservation and is likely to have played a unique and important role in early human dispersals despite this partially due to its vast size and remote tropical location very few continuous palaeoenvironmental records exist especially in eastern borneo therefore we investigated 13 c and 15 n values and geochemistry of two cave guano deposits to reconstruct palaeoenvironments in eastern borneo firstly a profile was recovered from gomantong caves sabah reflecting a continuous deposit over 15 cal kyr bp secondly a profile was recovered from bau bau cave east kalimantan that ranged from 15 5 cal kyr bp the geochemical signature of each deposit confirmed the material to be ancient guano 13 c values revealed that a continuous dense rainforest persisted over at least the last 15 cal kyr bp around the gomantong site that was relatively insensitive to regional climate change by contrast 13 c values at bau bau indicate that although rainforest remained dominant in the record a significant drying occurred between 7 7 and 6 3 cal kyr bp with up to 25 grasses present although most regional models suggest that sea level rise and increased holocene insolation led to an increase in monsoonal moisture we find some evidence of more regional variability and that a reduction in monsoonal precipitation could have occurred however we cannot discount the implementation of an anthropogenic fire regime that opened the canopy allowing more grasses to occur

upwelling variability off southern indonesia over the past two millennia modern variability in upwelling off southern indonesia is strongly controlled by the australian indonesian monsoon and the el nino southern oscillation but multidecadal to centennial scale variations are less clear we present high resolution records of upper water column temperature thermal gradient and relative abundances of mixed layer and thermocline dwelling planktonic foraminiferal species off southern indonesia for the past two millennia that we use as proxies for upwelling variability we find that upwelling was generally strong during the little ice age lia and weak during the medieval warm period mwp and the roman warm period rwp upwelling is significantly anticorrelated to east asian summer monsoonal rainfall and the zonal equatorial pacific temperature gradient we suggest that changes in the background state of the tropical pacific may have substantially contributed to the centennial scale upwelling trends observed in our records our results implicate the prevalence of an el nino like mean state during the lia and a la nina like mean state during the mwp and the rwp

the origin of monsoons abstract the monsoon is interpreted as an intertropical convergence zone itcz substantially away more than 10 from the equator and the existence of the itcz does not have to rely on land sea contrast land sea contrast can provide a favorable longitudinal location for the itcz but this role can be replaced by sea surface temperature contrast in the longitudinal direction thus the interpretation of the monsoon presented herein differs from the long held fundamental belief that its basic cause is land sea thermal contrast on the continental scale in the sense that the existence of landmass is not considered a necessary condition for monsoons through general circulation model experiments support has been found for this interpretation the asian and australian summer monsoon circulations are largely intact in an experiment in which asia maritime continent and australia are replaced by ocean with sea surface temperature sst taken from that of the surrounding oceans thus in these areas land sea c

astronomical timescale and palaeoclimatic implication of stacked 3 6 myr monsoon records from the chinese loess plateau abstract magnetic susceptibility and grain size records from two continuous red clay and loess palaeosol sequences on the chinese loess plateau have been generated to investigate the evolution and variability of the east asian monsoon eam during the late pliocene and pleistocene tuning the grain size records to orbital obliquity and precession yields an improved astronomical timescale for the loess palaeosol sequence 0 2 6 ma and an extended age model for the upper red clay formation 2 6 3 6 ma this timescale indicates older ages for a number of the magnetic polarity boundaries consistent with lock in depth offsets in loess sequences good site to site correlation enables generation of stacked grain size and susceptibility records spanning the last 3 6 myr these records indicate that monsoon evolution since the late pliocene can be subdivided into three phases 0 1 25 1 25 2 72 and 2 72 3 4 ma each phase is characterized by unique amplitude and frequency characteristics for both summer monsoon magnetic susceptibility and winter monsoon grain size spectral analyses of the stacked monsoon proxies indicate that characteristics of both the summer and winter monsoons are dominated mainly by variance in the eccentricity 410 and 100 kyr obliquity 41 kyr and precession 23 and 19 kyr bands over the past 3 4 myr implying a non linear response of the long term eam evolution to orbital and glacial forcing

calibrated late quaternary age indices using clast rubification and soil development on alluvial surfaces in pilot knob valley mojave desert southeastern california the orange coating varnish that forms on the undersides ventral sides of clasts in desert pavements constitutes a potential relative age indicator using munsell color notation we semiquantified the color of the orange ventral varnish on the undersides of clasts from 15 different alluvial fan and terrace surfaces of various ages ranging from less than 500 to about 25 000 yr all of the surfaces studied are located along the central portion of the left lateral garlock fault in the mojave desert of southern california the amount of left lateral offset may be used to determine the relative ages of the surfaces the previously published slip rate of the fault may also be used to estimate the absolute age of each surface the color of the ventral varnish is strongly correlated with surface age and appears to be a more reliable age indicator than the percentage coverage of dorsal varnish soil development indices also were not as strongly correlated with age as were the colors of the ventral varnish in particular rubification appears to be more useful than soils for distinguishing relative ages among holocene surfaces humidity sensors indicated that the undersides of clasts condensed moisture nightly for a period of several days to over a week after each rain these frequent wet dry cycles may be responsible for the rapid development of clast rubification on holocene surfaces

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

continuous 150 k y monsoon record from lake eyre australia insolation forcing implications and unexpected holocene failure our reconstructed history of lake eyre provides the first continuous continental proxy record of australian monsoon intensity over the past 150 k y this continental record s broad correspondence to the marine isotope record demonstrates that this very large catchment with its hydrology dependent on a planetary scale climate element responds to milankovitch scale climate forcing abrupt transitions from dry phases to wet phases ca 125 and 12 ka coincide with northern hemisphere winter insolation minima rather than southern hemisphere summer insolation maxima indicating that northern hemi sphere insolation exerts a dominant control over the intensity of the australian monsoon stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but within the uncertainties are consistent with northern hemisphere forcing regardless of the hemispheric forcing the low intensity of the early holocene australian monsoon by comparison with the last interglacial and particularly the last high level lacustrine event at 65 60 ka when all forcing elements were modest is an enigma that can be explained by a change in boundary conditions within australia

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

mid holocene sea level and coral reef demise u th dating of subfossil corals in moreton bay australia it is increasingly apparent that sea level data e g microfossil transfer functions dated coral microatolls and direct observations from satellite and tidal gauges vary temporally and spatially at regional to local scales thus limiting our ability to model future sea level rise for many regions understanding sealevel response at far field locations at regional scales is fundamental for formulating more relevant sea level rise susceptibility models within these regions under future global change projections fossil corals and reefs in particular are valuable tools for reconstructing past sea levels and possible environmental phase shifts beyond the temporal constraints of instrumental records this study used abundant surface geochronological data based on in situ subfossil corals and precise elevation surveys to determine previous sea level in moreton bay eastern australia a far field site a total of 64 u th dates show that relative sea level was at least 1 1 m above modern lowest astronomical tide lat from at least 6600 cal yr bp furthermore a rapid synchronous demise in coral reef growth occurred in moreton bay 5800 cal yr bp coinciding with reported reef hiatus periods in other areas around the indo pacific region evaluating past reef growth patterns and phases allows for a better interpretation of anthropogenic forcing versus natural environmental climatic cycles that effect reef formation and demise at all scales and may allow better prediction of reef response to future global change

compound specific carbon isotope records of vegetation and hydrologic change in central sulawesi indonesia since 53 000 yr bp lake matano 2 29 1 s 121 20 e in central sulawesi the deepest and one of the largest lakes in indonesia provides an excellent opportunity to reconstruct long term hydrological and vegetation changes at the heart of the maritime continent within the tropical western pacific warm pool we measured the carbon isotopic composition of terrestrial leaf waxes 13cwax in new sediment cores from lake matano to understand regional variations in vegetation and their interactions with local and high latitude climate forcings during the past 53 kyr variations in 13cwax record the expansion and contraction of c3 versus c4 vegetation as well as changes in plants carbon and water use efficiency and by inference regional hydroclimate during marine isotope stages 1 and 3 more negative 13cwax values indicate that closed canopy c3 rainforests predominated in sulawesi reflecting a wetter less seasonal climate in contrast more positive 13cwax values record a terrestrial ecosystem with more abundant open canopy vegetation and possible expansion of c4 grasses between 29 and 14 ka bp indicating that during marine isotope stage 2 including the last glacial maximum the climate was more arid likely with increased precipitation seasonality in central sulawesi comparison of our record with other paleovegetation and paleohydrological records from sulawesi and nearby islands suggests coherent long term hydrological changes in central indonesia that appear to be sensitive to high latitude climate across glacial interglacial boundaries however variations in the amplitude of the response of vegetation to these glacial interglacial forcings highlight the importance of regional topographic control on climate and vegetation and suggest an important role for higher elevations in maintaining rainforest refugia during regionally arid time intervals when c4 savannas and grasslands expanded at lower elevations

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

dynamics of the australian indonesian monsoon across termination ii implications of molecular biomarker reconstructions from the timor sea abstract molecular biomarker derived proxies in a marine sediment core from the eastern timor sea have been employed to track changes in the australian indonesian monsoon system over the time period from the penultimate glacial to the last interglacial the average chain length of n alkanes originating from terrestrial higher plants reveals an expansion of woody plants during both termination ii and the last interglacial with respect to the penultimate glacial this is consistent with previous reconstructions for the last glacial interglacial cycle indicating that water stress conditions during dry seasons of southern indonesia should have been relieved during interglacials and deglacials relative to glacials however in contrast to an only muted response during heinrich stadial 1 the vegetation composition showed a dramatic and prominent change during heinrich stadial 11 this was probably caused by a much more significant and longer duration iceberg discharge event to the northern north atlantic during heinrich stadial 11 relative to heinrich stadial 1 which exerted a significant influence on the tropical hydrological cycle and monsoon rainfall seasonality in addition marine algae derived biomarkers are used to reconstruct primary productivity variations which are in agreement with previous studies from the same area the precessional cyclicity of paleo productivity variations is possibly induced by changes in the australian indonesian winter monsoon intensity showing a correlation with boreal winter insolation however this phase relationship is in contrast to the inference based on other lines of evidence which suggests strong winter monsoon strength during boreal summer insolation maxima new winter monsoon proxies are therefore required to clarify this discrepancy

north atlantic forcing of millennial scale indo australian monsoon dynamics during the last glacial period recent studies of the last glacial period indo australian summer monsoon iasm have revealed links to both northern and southern hemisphere high latitude climate as well as to regional ocean conditions particular interest has been paid to the monsoon response to heinrich events with variability explained by meridional shifts in positioning of the intertropical convergence zone itcz but this model has not been adequately tested in addition the shorter lived dansgaard oeschger d o events have not been detected beyond d o 1 the bolling allerod in land based records from the indo pacific despite their prominent expression in stalagmites from southern asia raising questions about the sensitivity of the iasm to these events here we present a southern hemisphere stalagmite oxygen isotopic time series from ball gown cave bgc tropical northern australia located on the margins of the modern austral summer itcz that spans 40e31 and 27e8 ka elevated iasm rainfall coincides with heinrich stadials and the younger dryas while decreased rainfall characterizes d o interstadials a response that is antiphased with sites spanning the indo pacific warm pool and with chinese records of the east asian summer monsoon the bgc time series thus reveals a precipitation dipole consistent with a southward northward migration of the itcz during periods of high northern latitude cooling warming as the primary driver of millennial scale iasm variability during the last glacial period our record indicates a strengthening of the iasm after the younger dryas period likely as a result of rising sea level and sea surface temperatures breaking the link with the high latitudes

a high resolution record of late quaternary upwelling along the oman margin arabian sea based on planktonic foraminifera planktonic foraminiferal abundances fluxes test sizes and coiling properties are influenced in various ways by the southwest monsoon winds and associated upwelling in the western arabian sea to determine the short term changes in the southwest monsoon we have carried out a high resolution time series analysis of three upwelling indices total flux of planktonic foraminiferal tests and flux and relative abundance of the planktonic foraminiferal species globigerina bulloides from ocean drilling program odp site 723a oman margin western arabian sea spanning the last 19 kyr in addition we have determined the relationships between upwelling intensity and the relative abundance fluxes and shell concentrations of various planktonic foraminiferal species upwelling indices suggest that from 19 to 16 ka 22 to 18 2 cal kyr b p the sw monsoon was relatively strong compared to the period 15 8 to 12 5 ka 17 8 to 13 8 cal kyr b p the intensification of the sw monsoon took place at 12 ka 13 1 cal kyr b p and reached a peak between 10 and 5 ka 10 6 and 4 8 cal kyr b p the high resolution data further demonstrate that the sw monsoon has started weakening from 5 ka 4 8 cal kyr b p and the weakest phase was in place at 3 5 ka 3 cal kyr b p which coincides with evidence of an arid climate in western tibet fluxes and shell concentrations of many of the planktonic foraminiferal species increased between 12 and 5 ka in response to the intensification of the sw monsoon winds after the last glacial period globigerina bulloides shows a fivefold to tenfold increase in flux during this period of intense upwelling the other species whose fluxes are influenced by this upwelling change are in order from strongest to weakest response globigerinita glutinata globigerinoides ruber neogloboquadrina dutertrei globigerinella aequilateralis globigerina falconensis and globigerinoides sacculifer the relative abundances of g bulloides and g ruber increased during intense upwelling whereas the relative abundances of g glutinata n dutertrei g falconensis and g sacculifer did not increase during this period which might be due to differences in the productivity of various species in relation to upwelling change therefore the fluxes and shell concentrations provide better and more reliable information about the changes in the monsoon system in the arabian sea than relative abundance data

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

palaeoenvironmental change in tropical australasia over the last 30 000 years a synthesis by the oz intimate group the tropics are the major source of heat and moisture for the australasian region determining the tropics response over time to changes in climate forcing mechanisms such as summer insolation and the effects of relative sea level on exposed continental shelves during the last glacial period is an ongoing process of re evaluation we present a synthesis of climate proxy data from tropical australasia spanning the last 30 000 years that incorporates deep sea core coral speleothem pollen charcoal and terrestrial sedimentary records today seasonal variability is governed largely by the annual migration of the inter tropical convergence zone itcz influencing this region most strongly during the austral summer however the position of the itcz has varied through time towards the end of marine isotope stage mis 3 conditions were far wetter throughout the region becoming drier first in the south universally cooler land and sea surface temperature sst were characteristic of the last glacial maximum with drier conditions than previously although episodic wet periods are noted in the fluvial records of northern australia the deglacial period saw warming first in the coral sea and then the indonesian seas with a pause in this trend around the time of the antarctic cold reversal c 14 5 ka coincident with the flooding of the sunda shelf wetter conditions occurred first in indonesia around 17 ka and northern australia after 14 ka the early holocene saw a peak in marine sst to the northwest and northeast of australia modern vegetation was first established on indonesia then progressively south and eastward to ne australia flores and the atherton tablelands show a dry period around 11 6 ka steadily becoming wetter through the early holocene the mid late holocene was punctuated by millennial scale variability associated with the el nino southern oscillation this is evident in the marine coral speleothem and pollen records of the region

millennial scale trends in west pacific warm pool hydrology since the last glacial maximum models and palaeoclimate data suggest that the tropical pacific climate system plays a key part in the mechanisms underlying orbital scale and abrupt climate change atmospheric convection over the western tropical pacific is a major source of heat and moisture to extratropical regions and may therefore influence the global climate response to a variety of forcing factors the response of tropical pacific convection to changes in global climate boundary conditions abrupt climate changes and radiative forcing remains uncertain however here we present three absolutely dated oxygen isotope records from stalagmites in northern borneo that reflect changes in west pacific warm pool hydrology over the past 27 000 years our results suggest that convection over the western tropical pacific weakened 18 000 20 000 years ago as tropical pacific and antarctic temperatures began to rise during the early stages of deglaciation convective activity as inferred from oxygen isotopes reached a minimum during heinrich event 1 ref 10 when the atlantic meridional overturning circulation was weak pointing to feedbacks between the strength of the overturning circulation and tropical pacific hydrology there is no evidence of the younger dryas event in the stalagmite records however suggesting that different mechanisms operated during these two abrupt deglacial climate events during the holocene epoch convective activity appears to track changes in spring and autumn insolation highlighting the sensitivity of tropical pacific convection to external radiative forcing together these findings demonstrate that the tropical pacific hydrological cycle is sensitive to high latitude climate processes in both hemispheres as well as to external radiative forcing and that it may have a central role in abrupt climate change events

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

mid holocene sea surface conditions and riverine influence on the inshore great barrier reef we present measurements of sr ca 18o and spectral luminescence ratios g b from a mid holocene porites sp microatoll recovered from the nearshore great barrier reef gbr these records were used as proxies to reconstruct sea surface temperature sst the 18o of surrounding seawater 18osw and riverine influence respectively and compared with records from a modern porites sp microatoll growing in the same environment strong riverine influence in the mid holocene record is indicated by 1 an increased annual 18osw range in the mid holocene record 2 negative peaks in 18o characteristic of flood events and 3 a higher g b luminescence ratio seasonal cycles in g b suggest that humic acid inputs were elevated for a longer portion of the year during the mid holocene the seasonal cycle of 18osw peaked earlier in the year in the mid holocene record relative to the modern while mean 18osw values from the mid holocene record were similar to modern values these records provide an insight into the oceanographic conditions the nearshore gbr experienced during mid holocene climatic shifts and are consistent with a strong australian indonesian summer monsoon aism system at 4700 cal yr bp

interglacial climates and the atlantic meridional overturning circulation is there an arctic controversy arctic palaeorecords are important to understand the natural range of forcing and feedback mechanisms within the context of past and present climate change in this temperature sensitive region a wide array of methods and archives now provide a robust understanding of the holocene climate evolution by comparison rather little is still known about older interglacials and in particular on the effects of the northward propagation of heat transfer via the atlantic meridional ocean circulation amoc into the arctic terrestrial records from this area often indicate a warmer and moister climate during past interglacials than in the holocene implying a more vigorous amoc activity this is in conflict with marine data although recognized as very prominent interglacials in antarctic ice cores cross latitudinal surface ocean temperature reconstructions show that little of the surface ocean warmth still identified in the northeast atlantic during older interglacial peaks e g mis5e 9 11 was further conveyed into the polar latitudes and that each interglacial developed its own specific palaeoclimate features interactive processes between water mass overturning and the hydrological system of the arctic and how both developed together out of a glacial period with its particular ice sheet configuration and relative sea level history determined the efficiency of an evolving interglacial amoc because of that glacial terminations developed some very specific water mass characteristics which also affected the climate evolution of the ensuing interglacial periods moreover the observed contrasts in the arctic directed meridional ocean heat flux between past interglacials have implications for the palaeoclimatic evaluation of this polar region crucial environmental factors of the arctic climate system such as the highly dynamical interactions between deep water mass flow surface ocean temperature salinity sea ice and atmosphere exert strong feedbacks on interglacial climate regionality that goes well beyond the arctic a sound interpretation of such processes from palaeoarchives requires a good understanding of the applied proxies fossils in particular are often key to the reconstruction of past conditions but the tremendously flexible adaptation strategies of biota sometimes hampers further in depth interpretations especially when considering their palaeoenvironmental meaning in the context of rapid palaeoclimatic changes and long term pleistocene evolution

the holocene environmental changes in southern indonesia reconstructed from highland caldera lake sediment in bali island diatom pollen geomagnetic and geochemical analyses were carried out on a 3 6 m long sediment core taken from lake buyan a highland caldera lake in central bali island to reconstruct the holocene climate changes in equatorial southern indonesia the core represents 8 thousand years sedimentation of organic diatomaceous lake mud constant inclusion of benthic diatom fossils as main components indicated that suspension and inflow of littoral materials were the main sedimentary process the core contained laminated sediments in two distinct intervals at 6 5 5 0 and 3 6 3 1 cal ky bp and multi proxy records showed generally drier climate in these sections especially at 3 6 3 1 cal ky bp lake bottom waters were more reducing condition in these laminated periods probably due to increased lake productivity by prolonged dry season and wind mixing laminae structures were made up of a layer composed of benthic diatoms and amorphous organic materials and a layer made by only planktonic diatom fossils each of which may represent rainy and dry period deposits although southern indonesia shows clear australian monsoon rainfall seasonality at present counting of layer numbers showed interannual cycles of laminae formation prolonged dry seasons could obscured the rainfall seasonality in these periods but precise depositional patterns were elusive unlaminated sections showed homogeneous sediment mixture of benthic planktonic diatoms and more volume of terrigenous materials indicating wetter climate and seasonality similar to the present time this was supported by the higher share of marsh environment pollens reflecting more stable lake level trends the dry climate from 6 5 cal ky bp was in line with the general perception of stronger enso dynamics from the mid holocene due to weaker than before boreal summer insolation but the sporadic appearances of dry periods imply the influence of regional climate forcings such as temporal migrations of inter tropical convergence zone itcz it was however possible that temporal shifts of large climate mode occurred in equatorial pacific and indian oceans wettest climate was inferred from 3 1 cal ky bp to the present and this might reflect increased importance of austral hemisphere atmospheric convection and subsequent southerly position of itcz in austral summer time

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

sensitivity of the australian monsoon to insolation and vegetation implications for human impact on continental moisture balance general circulation model experiments test the geologically based correlation of high monsoon rainfall over interior australia with northern hemisphere insolation and evaluate the sensitivity of the australian monsoon to ecosystem change our results suggest that northern hemisphere insolation control on the intensity of the siberian high rather than summer insolation over the australian continent determines the strength of the australian monsoon on millennial time scales unlike a classic monsoon regime additional simulations show that the penetration of monsoon moisture into the interior is sensitive to biosphere atmosphere feedbacks linked to vegetation type and soil properties this sensitivity offers a resolution to the observed failure of the australian monsoon to penetrate the interior in the holocene postulated regular burning practiced by early humans may have converted a tree shrub grassland mosaic across the semiarid zone to the modern desert scrub thereby weakening biospheric feedbacks and resulting in long term desertification of the continent

possible evidence for wet heinrich phases in tropical ne australia the lynch s crater deposit unarguably one of the most significant paleoclimatological discoveries of the last two decades has been that of abrupt climate events dansgaard oeschger cycles and heinrich events most evidence for these events has originated from the high latitude northern hemisphere with few records documenting the response of the low latitude southern hemisphere here we present new data from lynch s crater a unique terrestrial record from ne australia that may show evidence for southward propagations of the intertropical convergence zone itcz during abrupt climate perturbations as a result of alteration of the low latitude air masses proxies for precipitation wetness indicate enhanced rainfall in the region during heinrich events h events 1 3 and the 8 2 ka northern hemisphere cold event a fully coupled atmosphere ocean climate model simulating a 1 sv freshwater influx to the north atlantic ocean produces a scenario which agrees with the climate changes shown by the lynch s crater record the model shows precipitation anomalies that include a southward migration of the itcz and a zonal shift in mid latitude storm tracks over the southern hemisphere equatorial region these data indicate large scale shifts of the austral summer itcz position that is known to control monsoonal precipitation in ne australia this terrestrial record from australia may demonstrate the involvement of the tropical western pacific ocean in itcz migrations during abrupt climate events of the last glacial period defining such past migrations offers insight into the importance and role of the equatorial region in global climate dynamics

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

orbital scale timing and mechanisms driving late pleistocene indo asian summer monsoons reinterpreting cave speleothem δ18o 1 southeast china cave 18o often interpreted as a pure east asian summer monsoon proxy lags maximum northern hemisphere summer insolation by 2 9 0 3 kyrs at the precession cycle the arabian sea summer monsoon stack lags by 8 1 kyr consistent with 13 other indian and east asian summer monsoon proxies from marine lake and terrestrial archives this 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology it requires reconciliation in the context of proxy interpretation both of these lags are incompatible with a direct response to northern hemisphere summer insolation implicating additional forcing mechanisms analysis of heterodynes in the cave 18o spectrum demonstrates that variance contained in the arabian sea summer monsoon proxies also resides in the cave 18o record this variance is subtracted from the cave 18o record yielding a residual that is highly coherent and in phase with precession minima reflecting the impact of winter temperature change on cave 18o meteorological precipitation under cold conditions thus we argue that the timing of light cave 18o peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone the 2 9 kyr precession band phase lag of cave 18o reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima this interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast china

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

subsurface fault geometries in southern california illuminated through full 3d seismic waveform tomography f3dt abstract more precise spatial descriptions of fault systems play an essential role in tectonic interpretations deformation modeling and seismic hazard assessments the recent developed full 3d waveform tomography techniques provide high resolution images and are able to image the material property differences across faults to assist the understanding of fault systems in the updated seismic velocity model for southern california cvm s4 26 many velocity gradients show consistency with surface geology and major faults defined in the community fault model cfm plesch et al 2007 which was constructed by using various geological and geophysical observations in addition to faults in cfm cvm s4 26 reveals a velocity reversal mainly beneath the san gabriel mountain and western mojave desert regions which is correlated with the detachment structure that has also been found in other independent studies the high resolution tomographic images of cvm s4 26 could assist the understanding of fault systems in southern california and therefore benefit the development of fault models as well as other applications such as seismic hazard analysis tectonic reconstructions and crustal deformation modeling