modern and glacial tropical snowlines controlled by sea surface temperature and atmospheric mixing during the last glacial maximum tropical glacier snowlines were lower than expected based on estimates of tropical sea surface temperatures sea surface temperature reconstructions suggest the indo pacific warm pool was cooler than previously thought these temperatures and convective mixing processes can explain snowline altitude in this region

penetration electric fields at the nightside dip equator associated with the main impulse of the storm sudden commencement of 8 july 1991 1 the geomagnetic storm sudden commencement ssc of 8 july 1991 was reported wilson et al 2001 to be characterized by a reduction enhancement of x component at midlatitudes in the noon midnight sector in the 1 hour period after its start at 1636 ut this distinctive feature is seen even after accounting for the effects of the chapman ferraro current by subtracting the step like increase of x h component at low latitude stations on the same magnetic meridian from the midlatitude data we present evidence to show that over the same 1 hour period after the start of the ssc on 8 july 1991 an eastward electric field disturbance peak value 1 2 mv m grew up and decayed at the premidnight dip equator the eastward electric field evidenced at the nightside dip equator is interpreted as the signature of the penetration of the dawn to dusk electric field associated with an enhancement of region 1 field aligned currents facs driven by the solar wind the negative disturbance in the h x component at midlatitudes in the noon sector is explained as the magnetic effect of facs that carry the large scale electric fields from the magnetosphere to the polar ionosphere as well as the disturbance of polar origin type 2 ionospheric currents excited by the large scale electric field

varied response of western pacific hydrology to climate forcings over the last glacial period atmospheric deep convection in the west pacific plays a key role in the global heat and moisture budgets yet its response to orbital and abrupt climate change events is poorly resolved here we present four absolutely dated overlapping stalagmite oxygen isotopic records from northern borneo that span most of the last glacial cycle the records suggest that northern borneo s hydroclimate shifted in phase with precessional forcing but was only weakly affected by glacial interglacial changes in global climate boundary conditions regional convection likely decreased during heinrich events but other northern hemisphere abrupt climate change events are notably absent the new records suggest that the deep tropical pacific hydroclimate variability may have played an important role in shaping the global response to the largest abrupt climate change events

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

tropical pacific response to continental ice sheet topography the last glacial maximum was marked by maximum land ice extent and lowest greenhouse gases concentration during the last ice age we explore the impact of glacial continental ice sheet topography on the large scale tropical ocean atmosphere climate in particular the tropical pacific in an intermediate complexity coupled model increasing the thickness of continental ice sheets causes a southward displaced pacific intertropical convergence zone itcz and a strengthening weakening of northern southern hemisphere winter hadley cell the equatorial zonal sea surface temperature gradient weakened with an increased continental ice sheets thickness the reduction being caused by cooling in the western equatorial pacific and warming in the eastern equatorial pacific the evolution of the tropical climate with changing ice thickness has distinct quasi linear and nonlinear parts while the linear part is a direct response to the ice topographic changes the nonlinear part was a result of the tropical thermocline adjustment our analysis of a fully coupled transient deglacial simulation strongly indicates the dominant role of ice sheet topography in determining the deglacial evolution of the simulated pacific climate the thickness of continental ice sheet separate from ice albedo effect has significant impact on the tropical ocean atmosphere climate in particular with the meridional displacement in the pacific itcz the altered circulation states seen in the model may aid understanding of the relationship between tropical and high latitude climate records in glacial interglacial cycles

orbitally paced paleoproductivity variations in the timor sea and indonesian throughflow variability during the last 460 kyr 1 a high resolution 1 2 kyr multiproxy record from the timor sea in the easternmost indian ocean international marine global change images program core md01 2378 latitude 13 04 95 s longitude 121 47 27 e 1783 m water depth closely tracks changes in intermediate water ventilation and paleoproductivity over the last 460 kyr within one of the main outflow passages of the indonesian throughflow spectral analysis of five different flux based productivity proxies indicates spectral power concentrated in the 100 kyr glacial interglacial and the 23 kyr and 19 kyr precessional periods paleoproductivity maxima lead ice volume benthic 18o maxima by 20 to 40 1300 to 2600 years at the precession band the spectral differences in tropical paleoproductivity records from the pacific and indian oceans suggest that local processes wind and circulation patterns driven by insolation are dominant in driving productivity rather than large scale tropical features in the timor sea productivity fluctuations over the last 460 kyr were strongly influenced by monsoonal wind patterns offshore nw australia 23 and 19 kyr and were also modulated by sea level related variations in the intensity of the indonesian throughflow 100 kyr

palaeoenvironmental developments in the lake tondano area n sulawesi indonesia since 33 000 yr b p abstract geo morpho logical sedimentological and ecological developments in the lake tondano area since 33 000 yr b p and limnological changes in the moderately sized lake situated at 680 m asl in the northern part of sulawesi indonesia are discussed first the environmental setting of the lake is presented study of the regional distribution of lacustrine sediments and a detailed analysis of their sedimentary facies texture organic matter content suggest major changes in size and depth of the lake and in past sedimentation insight into the long term development of the lake sedimentation processes is highly relevant for sustainable use of the present lake analysis of diatom assemblages provides further detail of the changing aquatic settings of the lake lake levels rise quickly around 33 000 and 12 000 yr b p fall dramatically between 30 000 and 13 000 yr b p and are lowered gradually since approximately 6000 yr b p following early holocene high lake levels drainage of the lake is affected by both volcanic depositional events and regional climatic events palynological analysis is indicative of local palaeoecological settings in the lake area and regional climatic change a distinct late pleistocene phase with lower precipitation and lowered mean temperatures is inferred furthermore progressive deforestation of the tondano uplands is evident as well as diffuse anthropogenic volcanic vegetation disturbance from the early mid holocene onwards information from sedimentary facies diatom assemblages and local palaeoecology pollen are integrated to reconstruct palaeoenvironmental settings and processes in the lake area this record of environmental change as well as the pollen based record of regional vegetation and climate change corroborates other palaeoenvironmental data derived from the few terrestrial sites in the region the data attribute a greater magnitude of temperature and precipitation change in the region than is commonly deduced in studies based on marine faunal and sedimentary records the lake tondano sedimentary record is highly suitable for further analysis aimed at determining the exact timing and amplitudes of environmental change in the se asian equatorial region

anomalous occurrence features of the preliminary impulse of geomagnetic sudden commencement in the south atlantic anomaly region 1 occurrence features of the preliminary impulse pi of geomagnetic sudden commencement sc both in the pacific ocean and south atlantic anomaly saa regions were investigated using the long term magnetic field data obtained from the circum pan pacific magnetometer network cpmn and nict space weather monitoring nswm magnetometer networks the low latitude preliminary reverse impulse pri at okinawa oki dip latitude 37 97 in the pacific ocean region appeared in all the magnetic local time mlt sectors with the peak occurrence rate of 40 around noon on the other hand the pri occurrence rate at santa maria sma dip latitude 34 35 near the center of the saa region showed a significant enhancement in the daytime sector 0800 1600 h mlt with the peak value of 80 which resembles the occurrence feature of the equatorial pri moreover the pri amplitude around noon at sma was about 3 0 times larger than that at oki from the calculation of the ionospheric conductivity derived from the iri 2007 and nrlmsise 00 models it is shown that the height integrated conductivity was more enhanced in the saa region sma where the ambient magnetic field intensity is weak compared with that in the pacific ocean region oki therefore the anomalous increase of the pri occurrence and amplitude is caused by the significant enhancement of the ionospheric conductivity due to the weakness of the ambient magnetic field intensity in the saa region

utilizing the geophysical and hydrogeological data for the assessment of the groundwater occurrences in gallaba plain western desert egypt the investigated region is located in the western desert fringes of the nile valley which requires studies of groundwater related to the many projects of land reclamation the key objective of this paper is to estimate the qualitative and geometrical features of the investigated aquifer using 60 vertical electrical sounding and time domain electromagnetic soundings allows us to suggest one possible model of the geometrical features of the local aquifer a hydrogeological monitoring has been undertaken to investigate the current groundwater situation at the gallaba plain such hydrological monitoring has not been undertaken before in detail the results show that the investigated region has high groundwater potentialities in two main aquifers which belong to pleistocene shallow fresh water and deep brackish water the lithological and structural elements contribute mainly to recharge and store the groundwater in the western part of the river nile in kom ombo graben the geochemical properties of the groundwater of the studied aquifers reflect meteoric water which is a fresh to slightly brackish water the small amount of groundwater salinity arises from silicate weathering and evaporation processes occurring in the aquifer matrix moreover most of the studied groundwater samples are unfit for human consumption such samples are very satisfactory for livestock and poultry purposes and they can be used for irrigation using modern and improved irrigation methods e g sprinkler and drip methods furthermore the hydrogeological monitoring of the concerned area indicates that it has high groundwater potentialities which will support its sustainable development

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

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

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

pathline calibrated groundwater flow models of nile valley aquifers esna upper egypt abstract strongly concentrated agriculture along the river nile in egypt combined with hydrologic changes related to the construction of the aswan high dam in the 1970 s has led to increasing salinization and waterlogging of agricultural areas successful control and remediation of these problems requires accurate understanding of the shallow quaternary aquifers within the nile valley while extensive conceptual models have been developed by the egyptian rigw published numerical models have yet to incorporate all features of the conceptual model in particular marine affinity of some shallow groundwaters within the valley cl as the predominant anion indicates significant leakage from deeper cretaceous aquifers into the shallow quaternary aquifers a feature that is not present in current models in this study groundwater profile modeling incorporating the bedrock leakage demonstrates that its shallow appearance requires hydraulic separation of surficial from deep recharged zones of the quaternary aquifer this separation occurs near the boundary between reclaimed and traditional agricultural lands which is also the primary site of waterlogging apparently excessive recharge presumed to occur beneath the reclaimed lands does not penetrate deeply and therefore might be easily remediated with shallow drains profound similarities exist between the nile valley salinization cases and the occurrence of shallow nuisance water in desert southwestern u s cities e g las vegas the u s experience with this problem may provide useful guidance in addressing nile valley salinization and waterlogging issues in the future in general irrigation related recharge from the reclaimed lands in the nile valley may have a much more localized impact on traditional lands than previously thought

global electrodynamics observed during the initial and main phases of the july 1991 magnetic storm data acquired by seven fortuitously positioned satellites in the interplanetary medium the magnetosphere and the topside ionosphere as well as from numerous ground magnetometers have allowed us to follow the evolution of global currents and electric fields during the geomagnetic storm on july 8 9 1991 an interplanetary disturbance collided with the magnetosphere at 1636 ut on july 8th compressing the magnetopause inside of geostationary orbit for about 3 hours as observed by magnetometers on two goes satellites the resulting storm developed in four segments with a 7 hour lull separating the initial and main phases the initial phase was characterized by 1 an extensive dp 2 current system that produced an ae perturbation of 3500 nt with reporting stations on the dayside 2 a twenty fold increase in auroral electron fluxes and 3 the immediate appearance of electric fields in the inner magnetosphere the main phase intensification and earthward movement of the ring current are associated with southward turnings of the interplanetary magnetic field imf and a polar cap potential increase above 200 kv a significant fraction of the ring current growth was observed prior to the first of several substorms that occurred during the main and recovery phases the beginning of recovery was characterized by a diminution of the southward imf component the cross polar cap potential and magnetospheric electric fields it was also marked by a substorm onset considering the timing of dst modulations relative to substorm occurrence we conclude that during this magnetic storm the electric fields responsible for ring current transport energization were mostly associated with the dp 2 current system finally in the evening sector penetration electric fields of the initial and main phases led to the formation of upward moving equatorial plasma bubbles that were detected by two dmsp satellites in the topside ionosphere

diurnal to interannual rainfall δ 18 o variations in northern borneo driven by regional hydrology the relationship between climate variability and rainfall oxygen isotopic 18o variability is poorly constrained especially in the tropics where many key paleoclimate records rely on past rainfall isotopes as proxies for hydroclimate here we present a daily resolved 5 yr long timeseries of rainfall 18o from gunung mulu national park located in northern borneo 4 n 114 e in the heart of the west pacific warm pool and compare it to local and regional climatic variables daily rainfall 18o values range from 0 7 to 18 5 and exhibit a weak but significant inverse relationship with daily local precipitation amount r 0 19 p 0 05 consistent with the tropical amount effect day to day 18o variability at mulu is best correlated to regional precipitation amount averaged over the preceding week r 0 64 p 0 01 the inverse relationship between mulu rainfall 18o and local regional precipitation amount increases with increased temporal averaging reaching r 0 56 r 0 72 on monthly timescales large negative multi day rainfall 18o anomalies of up to 16 occur every 30 90 days and are closely associated with wet phases of the intraseasonal madden julian oscillation a weak semi annual seasonal cycle in rainfall 18o of 2 3 bears little resemblance to seasonal precipitation variability pointing to a complex sequence of moisture sources and or trajectories over the course of the year interannual rainfall 18o variations of 6 8 are significantly correlated with indices of the el nino southern oscillation with increased rainfall 18o during relatively dry el nino conditions and vice versa during la nina events we find that mulu rainfall 18o outperforms mulu precipitation amount as a tracer of basin scale climate variability highlighting the time and space integrative nature of rainfall 18o taken together our results suggest that rainfall 18o variability at mulu is significantly influenced by the strength of regional convective activity as such our study provides further empirical support for the interpretation of 18o based paleo reconstructions from northern borneo stalagmites as robust indicators of regional scale hydroclimate variability where higher 18o reflects regional drying

late quaternary palaeoecology palynology and palaeolimnology of a tropical lowland swamp rawa danau west java indonesia abstract sedimentological limnological and palynological analyses of a sediment core from a lowland site in west java indonesia provide a detailed palaeoenvironmental record for the late glacial and the holocene the record suggests open vegetation under inferred drier climatic conditions for the late glacial however there is no unequivocal evidence for cooler conditions at this time the onset of the holocene coincides with a change to more humid climatic conditions with the development of a fern rich closed forest vegetation type dramatic changes in diatom community composition provide a striking record of habitat change associated with lake shallowing but this process appears to be a result of basin in filling rather than variations in precipitation evaporation balance associated with climatic fluctuations evidence for human impact on the vegetation development is restricted to the last few hundred years

environmental change in the late pleistocene and later holocene at wanda site soroako south sulawesi indonesia abstract this paper reports the pollen analysis of an 8 m core from a mire at 445 m altitude and 2 s latitude on ultramafic soils near the western shore of lake matano south sulawesi the area is almost undisturbed by humans and the record is believed to cover about 50 75 000 yr b p with some breaks in the record a section from 17 000 to around 5500 yr b p and the last 1000 years of the record may be missing or disturbed the results show that montane forest grew around the site continuously through the late pleistocene with a maximum increase in higher altitude taxa from 35 000 to after 17 000 yr b p the time of glacial maxima elsewhere also in this period increases in grass and casuarina indicate possible drier conditions the holocene sections record lower altitude forest with increased taxonomic diversity including secondary species the results show that vegetation in the region has been sensitive to climatic change the pleistocene ecology being consistent with a temperature change of about 2 5 3 5 c with a phase up to 50 drier than present the site climate was possibly affected by shelf exposure in the gulf of bone due to lower sea levels however the tropical forest demonstrates overall long term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity a distinctive record of fine charcoal occurs throughout the deposit this shows that the forest has never been continuously fire free for a very long time the cause of the fires may be natural as no evidence for human occupation was discerned

stable isotope proxy records in tropical terrestrial environments abstract the tropics refers to an area that is loosely equatorial characterized by relatively high temperatures at low altitude comparatively low seasonal contrast in temperatures and generally high or highly seasonal rainfall the stable isotopes of carbon oxygen and hydrogen are increasingly important tools of relevance to understanding trajectories and mechanisms of past environmental change in the tropics in the case of carbon this is because at the broadest level the carbon isotope composition of organic and carbon containing inorganic proxy materials formed in the tropics can be read as being derived from the balance between c3 tree and c4 grass photosynthesis hence providing a relative measure of vegetation type and indirectly climate likewise changes in the oxygen and hydrogen isotope composition of many proxy materials again at the broadest level can be read as indicative of changes in hydrological conditions and or altitude in the past this review provides an entry point into the literature relating to the use of stable isotopes as terrestrial environmental proxies for past environmental change with a focus on the measurement and interpretation of stable isotope data from the wide range of proxy materials preserved in tropical environments

a long vegetation history from lowland irian jaya indonesia abstract this paper reports the pollen analysis of a 10 m core from a mire at 780 m altitude and 2 s latitude on ultrabasic soils on a northern coastal range of new guinea the area is almost undisturbed by humans and the record is believed to cover about 60 000 yr b p the results show that montane forest grew around the site continously through the late pleistocene with a distinct increases in higher altitude taxa from 25 000 to 10 500 yr b p the time of glacial maxima elsewhere the invasion of the site by lower altitude forest which commenced at 10 500 yr b p was reversed after a few hundred years and was not finally completed until about 7000 yr b p the results show that vegetation in the region has been sensitive to climatic change the pleistocene ecology being consistent with a temperature change of about 3 4 c times of change agree with other tropical areas even though the site climate was probably affected by changing sea levels however the tropical forest demonstrates overall long term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity a distinctive record of fine charcoal occurs after 10 900 yr b p but not at any level prior to that time this shows that the forest was continously fire free for a very long time the charcoal is probably an indication of anthropogenic disturbance which may correlate with the spread of agricultural innovation in lowland new guinea an increase in secondary species after 7000 yr b p may be a result of minor anthropogenic activity or the result of warmer conditions and shorter tree life in the lower altitude forests

the influence of indian ocean atmospheric circulation on warm pool hydroclimate during the holocene epoch existing paleoclimate data suggest a complex evolution of hydroclimate within theindo pacific warm pool ipwp during the holocene epoch here we introduce a new leafwax isotope record from sulawesi indonesia and compare proxy water isotope data withocean atmosphere general circulation model oagcm simulations to identifymechanisms influencing holocene ipwp hydroclimate modeling simulations suggestthat orbital forcing causes heterogenous changes in precipitation across the ipwpon a seasonal basis that may account for the differences in time evolution of the proxydata at respective sites both the proxies and simulations suggest that precipitationvariability during the september november son season is important for hydroclimatein borneo the preeminence of the son season suggests that a seasonally laggedrelationship between the indian monsoon and indian ocean walker circulation influencesipwp hydroclimatic variability during the holocene

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

preliminary impulse of the geomagnetic storm sudden commencement of november 18 1993 the characteristics of the geomagnetic sudden commencement sc that occurred at 1211 30 ut on november 18 1993 following an interval of prolonged geomagnetic quietness are studied using high time resolution data of several magnetometer networks we present the first results concerning the behavior of the preliminary reverse impulse pri of the h component of the sc near the dip equator from simultaneous observations in different longitude local time sectors it is found that the preliminary reverse impulse appeared only in the prenoon 0912 lt sector very close to the magnetic equator dip 0 6 at locations farther away dip 6 0 7 2 but on the same meridian the preliminary reverse impulse diminished in amplitude and led to a delayed onset of the main impulse mi of the sc the preliminary reverse impulse is not apparent at locations close to the magnetic equator dip 1 2 2 7 in either the afternoon 1300 lt or the near dusk 1740 lt sectors what is seen instead here is an unambiguous reduction in the rate of increase of h component coincident with the preliminary reverse impulse in the forenoon sector hf doppler radar measurements of f layer vertical plasma drift close to the magnetic equator dip 4 9 near the dusk sector showed the sc related disturbance to be a decrease in ambient upward drift with considerable temporal structure which indicates the imposition of a westward electric field the preliminary reverse impulse is seen in the subauroral to polar region mlat 56 8 76 on the afternoon side simultaneous with that near the prenoon dip equator and with a conspicuous increase in amplitude and duration with latitude over mlat range 66 76 theoretical calculations suggest that the global current system set up by a pair of field aligned currents at 80 latitude and shifted to morningside centers at 1300 and 0300 lt could in general account for the observed behavior of the preliminary reverse impulse except in the dip equatorial region near dusk

geophysical and hydrogeological evaluation of pliocene aquifer in east esna egypt the current study of east esna area was selected due to its prosperous conditions in this area the reclamation of agricultural land is increasing and the population is growing which necessitate an equivalent development of groundwater the main aim of the study was to estimate geometrical and qualitative characteristics of the study aquifer this will help to have a systematic view of the hydrogeological setting in the area of investigation categorize and evaluate the influential factors of existence quality and protection of the groundwater the geometrical characteristics of the local aquifer were revealed by using 45 ves and tem soundings the study area has two main aquifers both hosted in sandstone of issawia formation the brackish groundwater lies above the fresh groundwater which is shielded by esna shale at the bottom the source of feeding to these aquifers is direct leakage of runoff and rain on the east side with sporadic leaks from the waters of the river nile on the west side the analyzed groundwater samples are geochemically homogenous indicating that their genesis is rain water they also belong to na ca so4 cl type the groundwater in the study area is assessed for drinking household livestock and agricultural purposes the current study recommends some advises for groundwater development in the study area

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

tooth enamel stable isotopes of holocene and pleistocene fossil fauna reveal glacial and interglacial paleoenvironments of hominins in indonesia abstract the carbon 13 c and oxygen 18 o isotope compositions of fossilized animal tissues have become important proxies of paleodiet and paleoenvironment but such stable isotope studies have not yet been extensively applied to the fossil assemblages of sundaland the biogeographical region comprising most of the indonesian archipelago here we use the isotope composition of tooth enamel to investigate the diet and habitat of bovids cervids and suids from several holocene and pleistocene sites on java and sumatra our carbon isotope results indicate that individual sites are strongly dominated by either c 3 browsers or c 4 grazers herbivores from the padang highlands sumatra and hoekgrot java cave faunas were mainly c 3 browsers while herbivores from homo erectus bearing sites trinil and sangiran java utilized an almost exclusive c 4 diet the suids from all sites show a wide range of 13 c values corroborating their omnivorous diet for the dataset as a whole oxygen and carbon isotope values are positively correlated this suggests that isotopic enrichment of rainwater and vegetation 18 o values coincides with an increase of c 4 grasslands we interpret this pattern to mainly reflect the environmental contrast between glacial drier more c 4 and interglacial wetter more c 3 conditions intermediate herbivore 13 c values indicating mixed c 3 c 4 feeding is relatively rare which we believe to reflect the abruptness of the transition between glacial and interglacial precipitation regimes in sundaland for seven homo erectus bone samples we were not able distinguish between diagenetic overprint and original isotope values underlining the need to apply this isotopic approach to homo erectus tooth enamel instead of bone importantly our present results on herbivore and omnivore faunas provide the isotopic framework that will allow interpretation of such homo erectus enamel isotope data

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

bulk organic carbon isotopic record of lacustrine sediments in dahu swamp eastern nanling mountains in south china implication for catchment environmental and climatic changes in the last 16 000 years abstract a combination of lithology organic matter accumulation rate bulk dry density mass magnetic susceptibility median grain size carbon to nitrogen and trace element rb sr ratio was utilized to characterize bulk organic carbon isotopic ratio 13corg of a lacustrine sediment core recovered at dahu swamp in the eastern nanling mountains as an indicator of past environmental and climatic changes chronological sequence of this core was established by twelve conventional radiocarbon dates and the bottom age was determined at ca 16 000 cal year bp multiproxies demonstrate that terrestrial source organic matter may have played a more important role in contribution to accumulation of organic matter in dahu swamp than autochthonous source multiproxies support the interpretation that bulk 13corg record reflects carbon isotopic signal of allochthonous c3 plants on which atmospheric precipitation may exert a strong impact although changes in bulk 13corg of lacustrine sediments may be resulted from a mixing of materials with different 13c signature and with different fraction and the cause and mechanism leading to the observed organic carbon isotope responses are presently not fully understood however this study demonstrates that bulk 13corg record of dahu swamp sediments has the potential to reflect variation of environmental and climatic changes of the lake catchment since the last deglaciation the more negative the bulk 13corg values the stronger the summer monsoon precipitation and vice versa

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