flooding history of lake nakaumi western japan inferred from sediment records spanning the past 700 years management of flood risk can benefit from a knowledge based approach to flooding history however the data on such events are often insufficient for an objective evaluation of flooding characteristics such as their intensity therefore we analyzed a 14c dated sediment core recovered from near the iinashi river mouth in lake nakaumi western japan and reconstructed flooding records over the past 700 years from rock magnetism grain size distribution and sediment geochemistry the sediment core contained three black layers characterized by high magnetic susceptibility low anhysteretic remanent magnetization to saturation isothermal remanent magnetization ratio high total organic carbon toc to total nitrogen ratio and coarse mean grain size which we identified as possible flooding event deposits moreover the chemical index of alteration was low and the toc to total sulfur ratio was high in these layers indicating intensified erosion associated with more freshwater inflow due to the flood events we tentatively correlated the three event deposits with historical floods along the iinashi river in ad 1596 1666 and 1826 the variations in rock magnetic and geochemical properties suggest that the flooding in ad 1666 may have been the least extreme of the events detected in the core

applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

coherence between solar activity and the east asian winter monsoon variability in the past 8000 years from yangtze river derived mud in the east china sea ams 14 c dating and grain size analysis for core pc 6 located in the middle of a mud area on the inner shelf of the east china sea ecs were used to rebuild the holocene history of the east asian winter monsoon eawm the 7 5 m core recorded the history of environmental changes during the postglacial transgression the core s mud section the upper 450 cm has been formed mainly by suspended sediment delivered from the yangtze river mouth by the ecs winter coastal current ecswcc since 7 6 kyr bp using a mathematical method called grain size vs standard deviatiow we can divide the core pc 6 s grain size distribution into two populations at about 28 mu m the fine population 28 mu m is considered to be transported by the ecswcc as suspended loads content of the fine population changes little and represents a stable sedimentary environment in accord with the present situation thus variation of mean grain size from the fine population would reflect the strength of ecswcc which is mainly controlled by the east asian winter monsoon abrupt increasing mean grain size in the mud section is inferred to be transported by sudden strengthened ecswcc which was caused by the strengthened eawm thus the high resolution mean grain size variation might serve as a proxy for reconstruction of the eawm a good correlation between sunspot change and the mean grain size of suspended fine population suggests that one of the primary controls on centennial to decadal scale changes of the eawm in the past 8 ka is the variations of sun irradiance i e the eawm will increase in intensity when the number of sunspots decreases spectral analyses of the mean grain size time series of core pc 6 show statistically significant periodicities centering on 2463 1368 128 106 100 88 91 7678 and 70 72 years the eawm and the east asian summer monsoon easm agree with each other well on these cycles and the east asian monsoon eam and the indian monsoon also share in concurrent cycles in holocene which are in accord with the changes of the sun irradiance c 2005 elsevier b v all rights reserved

seasonal and interannual variability in deep ocean particle fluxes at the oceanic flux program ofp bermuda atlantic time series bats site in the western sargasso sea near bermuda abstract since 1978 the oceanic flux program ofp time series sediment traps have measured particle fluxes in the deep sargasso sea near bermuda there is currently a 20 yr flux record at 3200 m depth a 12 yr flux at 1500 m depth and a 9 yr record at 500 m depth strong seasonality is observed in mass flux at all depths with a flux maximum in february march and a smaller maximum in december january there is also significant interannual variability in the flux especially with respect to the presence absence of the december january flux maximum and in the duration of the high flux period in the spring the flux records at the three depths are surprisingly coherent with no statistically significant temporal lag between 500 and 3200 m fluxes at our biweekly sample resolution bulk compositional data indicate an extremely rapid decrease in the flux of organic constituents with depth between 500 and 1500 m and a smaller decrease with depth between 1500 and 3200 m depth in contrast carbonate flux is uniform or increases slightly between 500 and 1500 m possibly reflecting deep secondary calcification by foraminifera the lithogenic flux increases by over 50 between 500 and 3200 m depth indicating strong deep water scavenging repackaging of suspended lithogenic material concurrent with the rapid changes in flux composition there is a marked reduction in the heterogeneity of the sinking particle pool with depth especially within the mesopelagic zone by 3200 m depth the bulk composition of the sinking particle pool is strikingly uniform both seasonally and over variations in mass flux of more than an order of magnitude these ofp results provide strong indirect evidence for the intensity of reprocessing of the particle pool by resident zooplankton within mesopelagic and bathypelagic waters the rapid loss of organic components the marked reduction in the heterogeneity of the bulk composition of the flux and the increase in terrigenous fluxes with depth are most consistent with a model of rapid particle turnover and material scavenging from the suspended pool during new particle formation we suggest that much of the deep mass flux is generated in situ by deep dwelling zooplankton and that mass flux as well as scavenging of suspended materials from the deep water column varies in proportion to changes in grazer activity labile very rapidly sinking aggregates e g salp fecal material arriving in the bathypelagic zone within days of their upper ocean production may act to stimulate zooplankton grazing rates and increase large particle production and deep mass flux days to weeks in advance of the arrival of bulk of surface produced material this process could reconcile mean particle sinking rate estimates with the phase coherence observed between upper and deep ocean mass fluxes

a review of coastal palaeoclimate and relative sea level reconstructions using δ13c and c n ratios in organic material holocene reconstructions of relative sea level rsl and environmental change in the coastal zone have become progressively more numerous since the importance of assessing possible future sea level rises has become apparent traditionally this has been achieved using a combination of biological and physical indicators e g pollen diatoms foraminifera grain size etc in some circumstances microfossils can be rare or absent from holocene sediments and in these cases carbon isotope ratios 13c and organic carbon to total nitrogen ratios c n can be used because they have the potential to provide information as to the origin of organic material preserved in coastal environments the distinction in 13c and c n of the various sources of carbon to estuarine sediments has led to its wide use as a tracer of carbon pathways and storage in estuaries more recently these techniques have been applied to holocene sediments to decipher changes in palaeocoastal environments and thus position relative to sea level and or palaeoriver discharge which have direct relevance to palaeoclimate this paper reviews the studies that have utilised this technique and explores examples from a wide range of coastal environments saltmarshes estuaries lagoons isolation basins and fjords it also discusses the potential alteration of geochemical signatures as a result of decompositional processes organic matter decomposition has been shown to change sediment 13c and c n values and thus an understanding of the processes involved is necessary in order to have confidence in the palaeoenvironmental interpretation of holocene 13c and c n decompositional shifts in c n and particularly 13c can occur over a relatively short time period however it is the direction of change in 13c and c n rather than absolute values that is key for interpreting changes in relative sea level and thus such changes are commonly preserved

holocene hydrological and climatic change on the northern mongolian plateau based on multi proxy records from lake gun nuur abstract a multi proxy study including analyses of 13corg for the lake sediment core gn 02 and grain size toc caco3 content 13ccarb and 18ocarb of bulk carbonate and the mineralogy of the parallel core gn 04 from gun nuur was performed to reconstruct the holocene hydrology and climate on the northern mongolian plateau the chronology was established using 40 14c dates of bulk organic matter in addition to nine previously published radiocarbon dates for core gn 02 and further five 14c dates for the new core gn 04 a lake reservoir effect of 1060 14c years was determined as the intercept of the high resolution gn 02 age depth model at the modern sediment surface the size of the reservoir effect is supported by the age of the core top sample 1200 40 14c years and the determined difference between a wood derived radiocarbon age from the gn 02 core base and the age model inferred age for bulk organic matter at the same stratigraphic level 1000 14c years low lake level and prevailing aeolian sediment deposition at gun nuur under dry conditions were recorded during the earliest holocene 10 800 10 300 cal a bp gun nuur expanded under significantly wetter conditions between 10 300 and 7000 cal a bp unstable climate conditions existed in the mid holocene 7000 2500 cal a bp and three periods of low lake levels and significantly drier conditions were recorded between 7000 5700 4100 3600 and 3000 2500 cal a bp intermediate lake levels were inferred for the intervening periods around 2500 cal a bp the climate change and wetter conditions were established again as a consequence the lake level of gun nuur rose again due to higher effective moisture and the relatively wet present conditions were achieved ca 1600 cal a bp our results suggest that the initial holocene climate change on the northern mongolian plateau was not accompanied by a rapid increase in precipitation as on the tibetan plateau the establishment of wetter conditions in northern mongolia lagged behind the early holocene moisture increase on the tibetan plateau by ca 1000 years subsiding dry air in the north of the tibetan plateau resulted from the strengthened summer monsoon on the tibetan plateau during the period of maximum summer insolation and probably inhibited a significant precipitation increase in mongolia the significant moisture increase in the gun nuur region at ca 10 3 cal ka bp is probably not related to the northward shift of the present summer monsoon boundary or the moisture delivery from the northern atlantic through the westerlies instead water from melting snow ice and frozen ground and the generation of precipitation from the local recycling of moisture are discussed as possible moisture source for the early onset of wetter conditions on the mongolian plateau

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

research on snow and ice this review unlike its predecessor martinelli et al 1979 is an intentionally selective survey of recent advances in selected areas of snow and ice research i have chosen to concentrate on studies relating to large scale aspects of the cryosphere and to consider their wider significance for other disciplines results obtained by new measurement techniques and the application of remote sensing methods are also stressed at the same time the broad lines of advance in glaciological research as represented in books conference themes and major field or laboratory programs are noted and a detailed bibliography is appended

diatom evidence for late holocene climatic events in granite harbor antarctica downcore diatom data from a deep basin in granite harbor antarctica provide new high resolution information concerning changes in oceanographic and depositional processes that have occurred during approximately the last 1250 years the influence of global scale climatic change during the time of the medieval warm period and possibly the little ice age is revealed by long term changes in floral assemblages as recorded by changes in the relative concentration of nitzschia cylindrus the diatom data suggest that granite harbor experienced less annual ice and pack ice cover during both these periods possibly because of higher temperatures during the medieval warm period and stronger offshore winds during the little ice age the sedimentary record reveals several distinct short lived events in which nearly monospecific blooms of corethron criophilum and chaetoceros spp occurred possibly the result of strong stabilization of the upper water column and were most likely a response to regional rather than global conditions although short lived these events may play a significant role in the delivery of organic carbon and biogenic silica to the seafloor

environmental magnetism principles and applications 1 in environmental magnetism rock and mineral magnetic techniques are used to investigate the formation transportation deposition and postdepositional alterations of magnetic minerals under the influences of a wide range of environmental processes all materials respond in some way to an applied magnetic field and iron bearing minerals are sensitive to a range of environmental processes which makes magnetic measurements extremely useful for detecting signals associated with environmental processes environmental magnetism has grown considerably since the mid 1970s and now contributes to research in the geosciences and in branches of physics chemistry and biology and environmental science including research on climate change pollution iron biomineralization and depositional and diagenetic processes in sediments to name a few applications magnetic parameters are used to routinely scan sediments but interpretation is often difficult and requires understanding of the underlying physics and chemistry thorough examination of magnetic properties and of the environmental processes that give rise to the measured magnetic signal is needed to avoid ambiguities complexities and limitations to interpretations in this review we evaluate environmental magnetic parameters based on theory and empirical results we describe how ambiguities can be resolved by use of combined techniques and demonstrate the power of environmental magnetism in enabling quantitative environmental interpretations we also review recent developments that demonstrate the mutual benefit of environmental magnetism from close collaborations with biology chemistry and physics finally we discuss directions in which environmental magnetism is likely to develop in the future

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

temporal variability of microparticle properties in polar ice sheets abstract four recent ice core studies reveal a consistently recurring temporal correlation between increased microparticle concentrations and lower global temperatures more negative 13 o 16 o ratios a continuous 900 year record of particle deposition from the 101 m south pole core was obtained by analyzing 6218 samples the concentration of insoluble particles with diameters 0 63 m increases substantially between a d 1450 and 1850 a period of slightly reduced global temperatures encompassing the latest neoglacial or little ice age there is evidence suggesting that some of the additional material may be volcanic although further substantiation is required the microparticle analyses of selected sections from three deep cores coupled with the respective 18 o measurements reveal that in all three cores the last glacial or late wisconsin ice contained great quantities of microparticles the ratio of the average microparticle concentration in wisconsin sections to that in holocene sections is 6 for the 905 m dome c antarctica core 3 for the 2164 m byrd station antarctica core and 12 for the 1387 m camp century greenland core microparticle increases of this magnitude can not be accounted for merely by a reduction in net accumulation these data suggest that the global atmosphere was heavily laden with suspended particulates near the end of the last major glaciation

centennial scale east asian summer monsoon intensity based on δ18o values in ostracode shells and its relationship to land ocean air temperature gradients over the past 1700 years centennial scale variations in the east asian summer monsoon easm remain ambiguous in the present study the 18o of shells from the ostracode bicornucythere bisanensis from lake nakaumi japan were examined to identify the bottom salinity changes caused by easm variations over the past 1700 yr four weak easm periods were identified in lake nakaumi at a d 600 1000 1350 and 1900 we detected discordance among the centennial scale easm variations in japan and the 18o of stalagmites 18ostalagmite in southern china furthermore both total solar irradiance and atmospheric 14c concentration which were previously considered to be linked with the centennial scale easm variations were asynchronous with the easm variations conversely we observed significant positive and negative correlations between the easm from japan and the 18ostalagmite in north central china and the relationship was associated with the asia pacific oscillation apo index centennial scale easm periods dominated during the high apo period these synchronous variations imply that the strength of the easm variations is tied to temperature gradients between east china and the north central pacific ocean

holocene east asian monsoonal precipitation pattern revealed by grain size distribution of core sediments of daihai lake in inner mongolia of north central china abstract two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for grain size distribution grain size distributions of the lake sediments are inferred to be a proxy for past changes in east asian monsoon precipitation such that greater silt size percentage and higher median grain size reflect increased monsoonal precipitation rates the grain size record of daihai lake sediments spanning the last ca 10 000 yr indicates that the monsoonal precipitation in the lake region can be divided into three stages the early middle and late holocene during the early holocene before ca 7900 cal yr bp the median grain size md and the silt fraction content were relatively low and constant suggesting relatively low precipitation over the lake region the middle holocene between ca 7900 and 3100 cal yr bp was marked by intensified and highly variable monsoonal precipitation as indicated by high and variable md values and silt contents of the lake sediments during this period average precipitation rate gradually increased from ca 7900 to 6900 cal yr bp displayed intense oscillations between ca 6900 and 4400 cal yr bp and exhibited a decreasing trend while fluctuating from ca 4400 to 3100 cal yr bp although generally high during the middle holocene both the md and the silt content assumed distinctly low values at the short intervals of ca 6500 6400 6000 5900 5700 5600 4400 4200 cal yr bp implying that monsoonal precipitation might have been significantly reduced during these intervals during the late holocene since ca 3100 cal yr bp grain size values suggest that precipitation decreased however during the late holocene relatively higher md values and silt contents occurring between ca 1700 to 1000 cal yr bp may denote an intensification of hydrological cycles in the lake area changes in the east asian monsoonal precipitation were not only directly linked with the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but also may have been closely related to variations in the temperature and size of the western pacific warm pool in the intensity of the el nino southern oscillation and in the path and strength of the north equatorial current in the western pacific

heavy metals in sinking particles and bottom sediments from the eastern turkish coast of the black sea concentrations of cd cu cr co ni zn fe mn pb as and sb were determined in sediment trap and bottom sediment samples collected seasonally from a station on the eastern turkish coast of the black sea cd pb and mn concentrations were highest in the sediment trap samples except during the summer period whereas co ni zn and fe levels were much lower than corresponding levels found in the surface sediments cu cr as and sb levels showed no definite trend with sediment type in general with the exception of cr relatively lower metal concentrations in the sediment trap material were determined in the summer period the highest mass flux 56 5 g m 2 day 1 was measured during autumn the highest flux of heavy metals also occurred during autumn and was strongly dependent on particle mass flux based on these results we suggest that the downward vertical transport of particulate heavy metals in this region is related to the high degree of land erosion and the resultant particulate flux dynamics which occur here it was noteworthy that the highest concentrations of cd cu co zn fe and sb in particles were measured during winter a finding which suggests that enhanced fossil fuel combustion which occurs during this period in adjacent urban and industrial areas plays an important role in the metal composition of sinking particles in nearshore waters 2008 elsevier ltd all rights reserved

holocene sea level changes and paleogeogrpahy of the central part of the san in district japan k ah 20m 0 5 0 2m k ah 0 5 0 2m 5 000yrsbp 1m 4 000yrsbp 0m 1 500 0 4 0 1m k ah k ah 4 800yrsbp 3 700yrsbp

tephra layers in the byrd station ice core and the dome c ice core antarctica and their climatic importance abstract volcanic glass shards from tephra layers in the byrd station ice core were chemically analyzed by electron microprobe tephra in seven layers have similar peralkaline trachyte compositions the tephra are believed to originate from mt takahe on the basis of their chemical similarity to analyzed rocks from mt takahe and because dated rock samples from the volcano are younger than 250 000 years old glass shards from 726 m deep in the dome c ice core which is 2400 km from byrd station are composed of peralkaline trachyte and may have also been derived from mt takahe the tephra could have resulted from eruptions which were triggered by increased ice loading during the late wisconsin glaciation preliminary grain size data suggest the eruptions were only minor and they were unlikely to have instantaneously altered global climate as have explosive eruptions in the tropics nevertheless the effect of this localized volcanic activity upon the antarctic energy budget warrants further investigation

identifying the sedimentary imprint of high frequency holocene river floods in lake sediments development and application of a new method abstract in an effort to improve the understanding of floods and how they relate to climate we have developed a method that objectively identifies the sedimentary imprint of individual river floods in downstream lake basins the method is applied to a high resolution lake sediment core retrieved from southern norway resulting in a detailed record of holocene river flood activity covering the last 10 000 years including floods also recorded by instrumental and historical data the minimum number of individual floods recorded for this period is 100 on multidecadal to centennial timescales significant change in flood frequency is observed that arguably can be attributed to large scale climatic changes such as the varying amount of winter precipitation and summer rainstorms flood frequency was low during the early holocene 9770 7700 cal yr bp and even lower for the period that followed lasting until 5500 cal yr bp for the next 2500 years a modest increase in flood activity followed this trend was truncated 2500 cal yr bp by a sudden shift towards increased flooding frequency with the exception of a short interval around 1000 cal yr bp when the number of floods again was low this tendency of increased flood activity prevailed until present including stor ofsen a large flood that occurred in ad 1789 and also three other historically documented river floods

multiproxy record of monsoon variability from the ganga plain during 400 1200 a d abstract understanding on the indian summer monsoon ism variability is chiefly based upon the marine proxies and a few continental records the ganga plain one of the most densely populated regions of the world marked by intensive cultivation of monsoon dependent crops and a rich cultural history is not yet well understood in the context of monsoon variability we present here a 400 1200 a d ams radiocarbon dated record of ropan chhapra tal in the central ganga plain using sedimentology environmental magnetism and stable isotope of oxygen for ism variability the environmental magnetic parameters lf arm sirm lf s ratio b 0 cr and hirm inferred antiferromagnetic mineralogy hematite and or goethite independent of grain size variation during 400 900 a d depicting climate variability within warm humid to warm arid conditions favouring stronger ism seasonality prevalence of ferrimagnetic mineralogy under less oxygenated conditions intermittently demonstrates an altered catchment regime or possibly in response to stronger winter monsoon the higher 18 o values around 500 580 and 740 a d indicate warm and arid conditions under weak ism the lower 18 o values around 480 540 and 700 a d and from 900 to 1200 a d occur during warm and humid conditions indicating maximum intensity of the ism increased silt content from 800 a d onwards is due to increased surface runoff in response to enhanced precipitation and the higher clay percentage around 500 580 and 740 indicates low energy ponding conditions under weak ism the well sorted nature of sediment indicates consistency of the lacustrine environments under fairly uniform energy and constant bottom water conditions under varied monsoonal intensity combinations of sediment textures and stable isotope indicate intense ism at 480 and 540 a d with flooding around 700 a d and a weak monsoon at 580 and 740 a d with drought at 500 a d during 900 1200 a d the multiproxy record suggests strong summer monsoon synchronous with medieval warm period mwp whereas after 1200 a d the weak monsoon phase coincides with the onset of the little ice age lia

heavy metal geochemistry of surface sediments from the southern black sea shelf and upper slope abstract a wide variety of sediment types mud to sandy gravel was obtained at fourty seven stations on the southern black sea shelf and upper slope and analyzed for their heavy metal geochemistry distribution of grain size carbonates organic carbon and heavy metals show marked changes in the topography biological activity and land geology of the region studied sediments constitued up to 39 caco3 mainly of biogenic origin from the shell remains of benthic organisms organic carbon contents of the sediments 0 13 3 09 usually reflect the prevailing primary productivities in the black sea although significant terrigenous influences are also inferred the heavy metal concentrations largely indicate the influences from the geochemical weathering of terrigenous sources on land in comparison with the average sedimentary rocks and other modern sediments from the adjacent regions the concentrations of cr ni cu zn and pb are somehow higher in the surface sediments from the southern black sea in particular cr ni and cu are found in high abundances in the eastern parts of the study area this is thought to reflect not only the well mixed fine grained nature of the sediments but also the possible contribution from metal rich rocks mafic and ultramafic sources and associated economic mineral deposits in the catchment areas of rivers which drain this part of the coast the presence of significant positive correlations between the concentrations of cr and ni and zn and pb strongly suggest common sources and or similar enrichment mechanisms for these metals the relationships among the geochemical variables revealed that fe and mn oxides hydrates and sulfides and organic phases together with the clay and silt sized grain fractions are the important associations of the studied heavy metals

glacial interglacial indian summer monsoon dynamics the modern indian summer monsoon ism is characterized by exceptionally strong interhemispheric transport indicating the importance of both northern and southern hemisphere processes driving monsoon variability here we present a high resolution continental record from southwestern china that demonstrates the importance of interhemispheric forcing in driving ism variability at the glacial interglacial time scale as well interglacial ism maxima are dominated by an enhanced indian low associated with global ice volume minima in contrast the glacial ism reaches a minimum and actually begins to increase before global ice volume reaches a maximum we attribute this early strengthening to an increased cross equatorial pressure gradient derived from southern hemisphere high latitude cooling this mechanism explains much of the nonorbital scale variance in the pleistocene ism record