quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

holocene climatic fluctuations in the gujarat alluvial plains based on a multiproxy study of the pariyaj lake archive western india abstract a sediment core from pariyaj lake from the vatrak river basin located at the desert margin in the gujarat alluvial plains of western india was investigated in a multidisciplinary aspect the goal was to reconstruct the palaeoclimate palaeoenvironment and tectonic history and to understand the role these factors played in the geomorphological evolution of the area during the holocene palaeoclimatic interpretations also shed light on the factors responsible for the rise and fall of the harappan civilisation the results obtained based on multiproxy studies show five climatic phases during the last 11 000 yr bp phase 1 11 000 cal yr bp represents a very humid climate and high precipitation discharge leading to high lake stand as attested by the high pollen concentration of semi evergreen tree taxa phytoliths belonging to cool and moist grasses and large proportion of algae marking the onset of holocene in phase 2 8000 to 9000 cal yr bp a significantly reduced yield of pollen phytoliths and aquatic algae indicates shrinkage of the lake phase 3 7630 cal yr bp shows moderate yield of pollen and phytolith pointing towards fluctuating precipitation conditions phase 4 5864 to 4680 cal yr bp shows very low pollen and phytolith counts indicating a very dry spell finally phase 5 4680 to 3500 cal yr bp shows a good density and diversity of flora the wet climate and high lake stand 11 000 cal yr bp 7630 cal yr bp and after 4680 cal yr bp are synchronous with the lacustrine marine and aeolian records of western india the contribution of winter precipitation at 7630 cal yr bp and after 4680 cal yr bp can be correlated with similar records from rajasthan lake decrease in the precipitation activity the low lake stand and the onset of dry climatic condition between 8000 and 9000 cal yr bp corresponds to a near global anomaly of this period another dry event between 5864 and 4680 cal yr bp documented in pariyaj lake record is synchronous with various proxy records of the mid late holocene afro asiatic monsoonal belt

pollen and charcoal based evidence for climatic and human impact on vegetation in the northern edge of wuyi mountains china during the last 8200 years pollen and charcoal records derived from the sediment core of lantianyan lty peat bog northern wuyi mountain chains eastern subtropical china provide valuable information of landscape evolutio

amino acids and stable carbon isotope distributions in taihu lake china over the last 15 000 years and their paleoecological implications amino acid organic nitrogen and stable carbon isotope 13c 12c profiles through a core from east taihu lake are interpreted in terms of paleoecology and paleoclimate over the last ca 15 000 yr lower amino acid contents and higher 13c values at the base of the core represent a cool and arid climate and coincide with low organic productivity a marked increase in total amino acids and organic nitrogen with a decrease in 13c values from 193 to 90 cm ca 6500 6000 yr b p indicates a warmer and moist climate and greater organic productivity amino acids then decrease in abundance while 13c values increase progressively beginning at 73 cm ca 6000 yr b p reflecting cooling and lower organic productivity the average 13c values from a core from west taihu lake are evidently higher than values from east taihu lake the latter may reflect a stream environment whereas the high 13c values from west taihu lake likely reflect autotrophic carbon sources and a lacustrine environment since 11 000 yr b p

mid holocene east asian summer climate as simulated by the pmip2 models abstract in the present study datasets derived from twelve coupled ocean atmosphere general circulation models oagcms in the paleoclimate modelling intercomparison project phase two were used to analyze the east asian summer climate during the mid holocene about 6000 calendar years ago on the whole the oagcms reproduced warmer and wetter summer climate conditions in east asia during the mid holocene the multi model ensemble showed that in east asia the regionally averaged summer surface air temperature sat increased by 0 89 c summer precipitation was 5 8 higher and an obviously strengthened southerly wind corresponded to a strong summer monsoon in the mid holocene when compared to preindustrial levels the data model comparison in china reveals a good agreement between the oagcms results and the reconstructed changes in the summer sat in east china during the mid holocene in north china the simulated sat anomalies are 0 5 c lower overall than reconstruction in contrast the oagcms fail to capture the strongest warming in the southern qinghai tibetan plateau on the other hand the simulated precipitation agrees well with proxy data except for in the central parts of china where the simulated summer precipitation disagrees in sign with reconstruction in addition there is a large spread among the simulations particularly over and around the qinghai tibetan plateau and inter model discrepancies are larger for precipitation than for sat as a whole

pollen and non pollen palynomorph analyses of upper holocene sediments from dianshan yangtze coastal lowlands china hydrology vegetation history and human activity abstract the coastal deltaic plain of the yangtze river between taihu lake tai and shanghai in eastern china has been the scene of human settlement and agriculture since the early neolithic becoming increasingly intensive in the upper holocene when delta accretion and the establishment of a stable hydrological regime of freshwater lakes and wetlands allowed the development of extensive agriculture and complex society in late prehistoric and dynastic times during this period the area was significantly affected by changes in sea level climate and vegetation resulting in a dynamic and complex environmental history however little research has concentrated on environmental change and human impacts during the last few millennia this study focuses on this late period presenting the results of integrated sedimentary microfossil and radiocarbon analyses from a core near the eastern margin of lake dianshan to the east of taihu after the withdrawal of intertidal conditions and the conversion to freshwater lake at the core site about 2600 cal yr bp pollen and algal spore data show that increased sedimentation gradually reduced freshwater depth until a surface peat formed ca 1500 cal yr bp this also dates the start of a switch in woodlands from sub tropical and warm temperate trees to a mainly cool temperate and coniferous tree flora under climatic cooling and human impact after this time water depths at the site increased greatly partly due to climate change and flooding but also because of the establishment of deepwater paddy agriculture microcharcoal and pollen data show that a major episode of human impact using fire with deforestation and rice cultivation occurred between ca 1500 and 1200 cal yr bp these dates suggest it is one of the latest examples of flooded field paddy cultivation before more intensive agricultural techniques were adopted in the area after ca 800 cal yr bp

reconciliation of hydroclimate sequences from the chinese loess plateau and low latitude east asian summer monsoon regions over the past 14 500years we discuss replicated stalagmite 18o records with interannual to multidecadal resolution from lianhua cave on the chinese loess plateau to illustrate the precipitation history of the east asian summer monsoon easm region over the last 14 5 thousand years ka bp before 1950 ce hereafter and to re evaluate the inconsistency in the proxy inferred palaeoclimate time series in northern china agreement between the stalagmite 18o from lianhua and other caves from central southern china indicates that regional climate changes after the last glacial were concurrent across mainland china indicating that insolation was the primary factor controlling the evolution of the asian summer monsoon asm the stalagmite 18o enrichment of 2 5 in the younger dryas and 1 7 during the 8 2 ka bp event in lianhua were larger than those in caves from central and southern china the evidence suggests that different meridional responses of weak precipitation conditions in the asm realm occurred during these two abrupt events driven by high latitude forcing in the northern hemisphere the heterogeneous hydroclimate sequences in northern china inferred from different natural archives are most likely attributable to the complexity of the formations and or some chronological uncertainty

reconstruction of holocene relative sea level change and residual uplift in the lake inba area japan abstract we collected and analyzed fossil diatoms and volcanic ash and determined 14 c ages in core samples from the lowlands around lake inba in the eastern kanto plain central japan an area where late quaternary sea level change fluvial erosion and tectonic uplift have affected a region of archeological interest we inferred holocene paleoenvironmental changes and relative sea levels on the basis of indicators such as high tide levels derived from fossil diatom assemblages as well as the stratigraphic positions of 14 c dated samples and the k ah tephra our results lead to estimates of the upper half tidal range during 6800 7000 cal yr bp of 1 7 m the holocene highstand took place at approximately 6400 6500 cal yr bp and mean sea level reached an elevation of 1 9 m however the timing of this sea level rise is earlier in the lake inba area than documented in previous studies and it is suggested that the timing of the holocene highstand may appear at least 1000 years earlier as a result of holocene residual uplift after this sea level fell abruptly around 4000 cal yr bp we also recognized a sea level fall corresponding to the yayoi regression at about 2600 cal yr bp during which the mean relative sea level may have been as low as 2 5 m after compensating for uplift subsidence or geomorphologic effects in this area

dominant modes of interannual variability in eurasian surface air temperature during boreal spring abstractthis study investigates interannual variations of surface air temperature sat over mid and high latitudes of eurasia during boreal spring and their association with snow atmospheric circulation and sea surface temperature sst changes the leading mode of spring sat variations is featured by same sign anomalies over most regions the second mode features a tripole anomaly pattern with anomalies over the central part opposite to those over the eastern and western parts of eurasia a diagnosis of surface heat flux anomalies suggests that snow change contributes partly to sat anomalies in several regions mainly by modulating surface shortwave radiation but cannot explain sat changes in other regions atmospheric circulation anomalies play an important role in spring sat variability via wind induced heat advection and cloud induced surface radiation changes positive sat anomalies are associated with anomalous westerly winds from the north atlantic ocean or with anomalous anticyclone and souther

generating multi proxy holocene palaeoenvironmental records from blanket peatlands abstract ombrotrophic peatlands have provided important archives for understanding holocene palaeoenvironmental change however records are predominantly from raised bogs due to potential issues regarding preservation of proxy indicators record length and low temporal resolution in other peat types including blanket bogs by carrying out peat depth and stratigraphy surveys we demonstrate how blanket peatlands can provide archives capable of providing records that are not reliant on single proxies as has been often the case in the past and can provide good resolution records a record containing humification testate amoebae and plant macrofossils was derived for the last 3000 years with accumulation rates as high as 8 yrs cm 1 providing favourable temporal resolution particularly over the last 1500 years major changes in proxy indicators reflecting potential changes in water table depth were often coherent with changes in climate human activity also had a major impact on the peatland throughout the record especially in the last 100 years where the influence of wildfire and managed burning together with an effect of atmospheric pollution fundamentally changed the state of the peatland

climatology and variability of historical soviet snow depth data some new perspectives in snow indian monsoon teleconnections this study presents the monthly climatology and variability of the historical soviet snow depth data this data set was developed under the bilateral data exchange agreement between united states of america and the former union of soviet socialist republics the original data is for 284 stations for periods varying from 1881 upto 1985 the seasonal cycle of the mean snow depth has been presented both as spatial maps and as averages over key locations the deepest snow 80 cms day areas are found over siberia in particular over 80 100 e 55 70 n during march over the course of the annual cycle average snow depth over this region changes dramatically from about 10 cms in october to about 80 cms in march the variability is presented in the form of spatial maps of standard deviation to investigate the interaction of snow depth with indian monsoon rainfall imr lag and lead correlation coefficients are computed results reveal that the winter time snow depth over western eurasia surrounding moscow eastern eurasia in central siberia shows significant negative positive relationship with subsequent imr following the monsoon the signs of relationship reverse over both the regions this correlation structure is indicative of a midlatitude longwave pattern with an anomalous ridge trough over asia during the winter prior to a strong weak monsoon as the time progresses from winter to spring the coherent areas of significant relationship show southeastward propagation empirical orthogonal function analysis of the snow depth reveal that the first mode describes a dipole type structure with one centre around moscow and the other over central siberia depicting similar pattern as the spatial correlation structure the decadal scale imr variations seem to be more associated with the northern hemisphere midlatitude snow depth variations rather than with the tropical enso el nino southern oscillation variability

holocene climate change in the western part of taihu lake region east china abstract the taihu lake basin is one of the most sensitive areas to climate change in the east asian summer monsoon easm influenced region there are significant differences regarding the interpretation of climate history for this area during the holocene due to a lack of high resolution paleoclimate records to better understand this scientific issue here we provide a new record of holocene climate change from the western part of taihu lake region east china a 4 m depth profile from gaochun has provided a 13 200 year record of climate change holocene climate change was reconstructed for the western part of taihu lake area based on various proxy records including pollen charcoal degree of humification doh and loss on ignition loi from the gaochun site the results indicate that climate during the late pleistocene 13 200 10 700 cal yr b p and early holocene 10 700 8000 cal yr b p was warm and humid alternated with several cold and dry intervals the late pleistocene and early holocene was a transitional period from cold dry to warm wet climates the middle holocene 8000 4400 cal yr b p was still warm and humid with a relatively stable climate the period between 8000 and 5300 cal yr b p was the holocene climate optimum hco during the late holocene 4400 0 cal yr b p the climate was cool but still humid in addition climate change at the western part of taihu lake during the late pleistocene and holocene was unstable containing several short term climate events such as younger dryas yd 8 2 ka and 4 2 ka events these abruptly occurred climate events were indicated by various paleoclimatic proxy indicators and can be compared with related records from other regions our findings suggest that the easm strength was strongest during the middle holocene between 8000 and 5300 cal yr b p which can be depicted as the period of hco

holocene climate change and human impacts implied from the pollen records in anyang central china age constrained and high resolution pollen records from 12 000 cal bp to the late holocene from wangjiadian a site close to the yinxu and huanbei archaeological sites are presented and compared with archaeological data to reconstruct climate change and human impact during the holocene in the anyang region central china the pollen data demonstrate that the younger dryas event occurred between 11 500 and 10 000 cal bp and that the time between 8200 and 3400 cal bp was a period of warm temperature and high precipitation the megathermal period the pollen records also reflect human impact in this region since 3400 cal bp a sharp decrease in pinus pollen percentages as well as sharp increases in pollen abundance of ulmus ruderal species including planted poaceae and selaginella sinensis suggest forest clearance and selective felling associated with agriculture human impacts are also associated with changes in sedimentation as the palaeo soil ground surface was covered by yellow brown sandy silt at this time this might reflect anthropogenic soil erosion in anyang

relation between eurasian snow cover snow depth and the indian summer monsoon an observational study abstract satellite derived snow cover data for 22 yr and snow depth data for 9 yr over eurasia have been analyzed to reexamine the possible relation of snow with the indian summer monsoon in contrast to the previous studies that use snow cover averaged over all of eurasia as a single number the frequency of occurrence of snow at each grid point over eurasia is correlated with the indian summer monsoon rainfall thus specific geographical regions over eurasia that are responsible for the well known inverse relationship between eurasian snow cover and indian monsoon rainfall are delineated it is found somewhat surprisingly that western eurasia is the only geographical region for which a significant inverse correlation exists between winter snow cover and subsequent summer monsoon rainfall however composites for high and low snow cover over eurasia show spatially homogeneous large scale patterns of snow cover and surface temperature anomalies winters of high and low snow cover for eurasia are found t

regional change in snow water equivalent surface air temperature relationship over eurasia during boreal spring present study investigates local relationship between surface air temperature and snow water equivalent swe change over mid and high latitudes of eurasia during boreal spring positive correlation is generally observed around the periphery of snow covered region indicative of an effect of snow on surface temperature change in contrast negative correlation is usually found over large snow amount area implying a response of snow change to wind induced surface temperature anomalies with the seasonal retreat of snow covered region region of positive correlation between swe and surface air temperature shifts northeastward from march to may a diagnosis of surface heat flux anomalies in april suggests that the snow impact on surface air temperature is dominant in east europe and west siberia through modulating surface shortwave radiation in contrast atmospheric effect on swe is important in siberia and russia far east through wind induced surface sensible heat flux change further analysis reveals that atmospheric circulation anomalies in association with snowmelt over east siberia may be partly attributed to sea surface temperature anomalies in the north atlantic and the atmospheric circulation anomaly pattern associated with snowmelt over russia far east has a close association with the arctic oscillation

vegetation succession and east asian summer monsoon changes since the last deglaciation inferred from high resolution pollen record in gonghai lake shanxi province china a cal 20 year resolution pollen record from gonghai lake presented the detailed process of mountain vegetation succession and east asian summer monsoon easm changes since the last deglaciation i

palaeogeography and evolution of the godavari delta east coast of india during the holocene an example of wave dominated and fan delta settings abstract we investigated the holocene evolution of the godavari delta along the east coast of india by analyses of landforms and 11 borehole cores collected from the delta plain during 2010 2013 with 113 14c dates the godavari delta covering an area of 5820 km2 is one of the world s largest wave dominated deltas fringed by a 30 km wide beach ridge plain our analysis of sediment facies and their ages indicated that the holocene marine sequence thickens seaward from 10 m to more than 50 m and that the local relative sea level rapidly rose from 43 5 m to 7 5 m below the present sea level during 10 9 8 0 cal ky bp followed by a slow rise up to its current level around 5 cal ky bp spatio temporal variations in sediment accumulation rates and palaeo shorelines for the last 6 ky revealed successive changes of the main depocentre delta lobe we recognised six stages of delta evolution with distinct cyclic shifts of delta lobes controlled by avulsions a linear beach ridge located 12 14 km inland from the present shoreline which separates the first three lobes from the last three represents the effect of coastal erosion of past cuspate delta lobes as does the current linear shoreline of the central part of the delta our study documents continuous net progradation during the holocene on millennial to centennial time scales however a considerable decrease of sediment discharge due to dam construction and water diversion since the 1970s has exacerbated coastal erosion resulting in shrinking of the godavari delta plain and tipping it into a persistent destruction phase

mid holocene east asian summer monsoon strengthening insights from paleoclimate modeling intercomparison project pmip simulations abstract the east asian summer june july august monsoon easm is typically thought to have been stronger during interglacial periods based on spatially sparse proxy data on a large scale however whether this view is true and if so its underlying dynamic mechanisms remain unclear using all pertinent experiments within the paleoclimate modeling intercomparison project pmip here we present an analysis of the easm during the mid holocene 6000 years ago supporting the paleodata the mid holocene easm as measured by regionally averaged meridional wind at 850 hpa became stronger than the baseline period in 27 out of 28 pmip models with a demonstrable ability to simulate the modern easm climatology on average the easm strengthened by 32 across all the models and by a larger magnitude in 23 coupled models 35 than in five atmospheric models 20 it is proposed that an enhanced land sea thermal contrast and hence sea level pressure gradient between the east asian continent and adjacent oceans as a result of orbital forcing was responsible for the easm strengthening during the mid holocene

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

vegetation history climatic changes and indian summer monsoon evolution during the last glaciation 36 400 13 400 cal yr bp documented by sediments from xingyun lake yunnan china abstract we obtained a 9 74 m long sediment core xy08a from xingyun lake in central yunnan province southwest china and used ams radiocarbon dating of terrestrial plant macrofossils to provide a chronology here we present the results of pollen and grain size analyses of the interval 36 400 13 400 cal yr bp and discuss the vegetation history and record of climate change associated with the evolution of the indian summer monsoon ism three stages of regional vegetation change are documented i during the late marine isotope stage 3 36 400 29 200 cal yr bp the study region was occupied by mixed coniferous and evergreen broad leaved forest dominated by pinus and evergreen quercus with tsuga abies picea growing on the surrounding mountains ii during the last glacial maximum lgm 29 200 17 600 cal yr bp cold temperate coniferous forest dominated by species of abies picea expanded and reached a maximum extent and at the same time the extent of evergreen broadleaved forest increased iii from 17 600 to 13 400 cal yr bp the hemlock forest and abies picea forest began to decline until they disappeared completely in the early phase of the last deglaciation while pine forest and evergreen broadleaved forest dominated the surrounding areas the vegetation history indicates a generally drying climate from 36 400 to 13 400 cal yr bp suggesting a gradual weakening of the ism with the weakest ism influence occurring during the early part of the last deglaciation when the climate was the driest the regional temperature first decreased intermittently and then increased gradually being mild and wet during the late mis3 stage followed by the coldest but not the driest climate during the lgm when the temperature was at least 3 c lower than at present

response of the indian summer monsoon circulation and rainfall to seasonal snow depth anomaly over eurasia several observational and modeling studies indicate that the indian summer monsoon rainfall ismr is inversely related to the eurasian snow extent and depth the other two important surface boundary conditions which influence the ismr are the pacific sea surface temperature sst to a large extent and the indian ocean sst to some extent in the present study observed soviet snow depth data and indian rainfall data for the period 1951 1994 have been statistically analyzed and results show that 57 of heavy snow events and 24 of light snow events over west eurasia are followed by deficient and excess ismr respectively out of all the extreme monsoon years care has been taken to identify those when eurasian snow was the most dominant surface forcing to influence ismr during the years of high low eurasian snow amounts in spring winter followed by deficient excess ismr atmospheric fields such as temperature wind geopotential height velocity potential and stream function based on ncep ncar reanalyses have been examined in detail to study the influence of eurasian snow on the midlatitude circulation regime and hence on the monsoon circulation results show that because of the west eurasian snow anomalies the midlatitude circulations in winter through spring show significant changes in the upper and lower level wind geopotential height velocity potential and stream function fields such changes in the large scale circulation pattern may be interpreted as precursors to weak strong monsoon circulation and deficient excess ismr the upper level velocity potential difference fields between the high and low snow years indicate that with the advent of spring the winter anomalous convergence over the indian region gradually becomes weaker and gives way to anomalous divergence that persists through the summer monsoon season also the upper level anomalous divergence centre shifts from over the northern hemisphere and equator to the southern hemisphere over the indian ocean and australia

under ice noise resulting from thermally induced fracturing of the arctic ice pack theory and a test case application a theory is presented that relates thermally induced fracturing of pack ice to under ice noise level variations it begins with the governing equations for the thermomechanics of pack ice the thermomechanics relates thermally induced strain rates to the stresses within various vertical layers of the floe in addition paradigms are developed which specify the relative quantity of fracturing and stress relief in the floe as the tensile yield strength of the ice is exceeded the thermomechanics is complemented by an acoustic propagation model that relates the number of fracture events at a given time to the acoustic levels at arbitrary frequency and depth below the ice the acoustic theory assumes that each fracture acts as a simple monopole source the fractures are evenly distributed horizontally and the energy of each fracture propagates through the ice and the water column on the basis of the governing equations for elastic waves in a horizontally stratified medium the results indicate that noise episodes resulting from fracturing occurring over the top 40 cm of a 160 cm thick floe will propagate over distances of up to 100 km however noise episodes associated with fracturing occurring in the lower 100 cm of the floe will only propagate over a range of 10 km the thermomechanics and acoustic propagation theories were used to develop a numerical model for predicting under ice noise levels for a given thermal forcing of floes within the arctic ice pack the model was used to simulate stresses in a multiyear floe and under ice noise levels at 500 hz at 305 m below the floe model predicted ice stresses and under ice noise levels compare quite well to observed stresses and noise variations during the fall of 1988 in the eastern arctic ocean the model predicts that most of the thermally induced under ice noise at 500 hz was a result of fracturing occurring between 5 and 30 cm below the ice surface for a 1 6 m thick multiyear floe

spatial and source level distributions of ice cracking in the arctic ocean this paper reports measurements of the spatial and source intensity level distributions of ice cracking events occurring in the rough arctic pack ice these distributions are computed from a total of 916 detected events covering approximately 2 h of data distributed over several days during april 1988 measurements were obtained over the frequency band 4 200 hz on a 22 element vertical array and a 7 element horizontal array deployed below the arctic pack ice in 420 m of water the observed spatial distribution of detected events is consistent with the case where ice cracking events are uniformly distributed source levels from 110 to 180 db pa at 1 m were measured the calculated source level distribution for all events approximates a linearly decreasing function on a log db scale of the number of events versus source level the median mean and maximum numbers of events occurring per square kilometer per minute over a 1 db band of source levels centered at 110 db pa at 1 m are approximately 4 8 an

reconstructing late holocene vegetation and fire histories in monsoonal region of southeastern china abstract eastern subtropical china is a key region for understanding the variability of the east asian summer monsoon easm multidisciplinary studies in southeastern china have shown that the summer monsoon intensity declined in the mid late holocene we present a high resolution pollen record of the last 4000 cal yr bp in jinggang mts of jiangxi province southeastern china the identified pollen taxa from the core can be statistically divided into three groups corresponding to evergreen deciduous and wetland communities the transitions between evergreen and deciduous coniferous pollen associations is likely caused by temperature fluctuations indicating that climate was relatively cool at 3800 3200 cal yr bp and 2200 1300 cal yr bp and warmer at 3200 2800 cal yr bp and 1300 800 cal yr bp the vegetation study suggests that an alnus dominant association represents a secondary forest that usually takes place and expand after repeated forest fires the charcoal concentration from the core depicts at least six major forest fire events since 4000 cal yr bp most of which were followed by the development of an alnus forest community this result suggests that the easm weakened toward the late holocene and that its related decrease in moisture led to large forest wildfires furthermore the rapid formation of a swamp and the subsequent development of the alnus wetland community at 550 cal yr bp suggest a gradual drying up of the lake which was likely related to the little ice age as a result of a substantial burning related to an intensification of the human cultivation practices alnus reached its highest values in the last 200 years along with abundant wetland herbs pioneer ferns mainly dicranopteris and high charcoal concentrations the present evidence of several sharp floristic and climate changes coincides with either the collapse or the beginning of some chinese dynasties which will need further research on the relationship between natural and human cultural changes

observed relationship of spring and summer east asian rainfall with winter and spring eurasian snow abstract this study investigates the relationship between spring and summer rainfall in east asia and the preceding winter and spring snow cover depth over eurasia using station rainfall observations satellite observed snow cover satellite derived snow water equivalent and station observations of the number of days of snow cover and snow depth correlation analysis shows that snow depth anomalies can persist from winter to spring whereas snow cover anomalies cannot in most regions of eurasia locally snow cover and snow depth anomalies in february are not related in most regions to the north of 50 n but those anomalies in april display consistent year to year variations the results suggest that the winter snow cover cannot properly represent all the effects of snow and it is necessary to separate the winter and spring snow cover in addressing the snow monsoon relationship spring snow cover in western siberia is positively correlated with spring rainfall in southern china the circulation anomalies

source bearing estimation in the arctic ocean using ice mounted geophones this paper investigates the use of geophones mounted on the surface of arctic sea ice for estimating the bearing to acoustic sources in the water column the approach is based on measuring ice seismic waves for which the direction of particle motion is oriented radially outward from the source however the analysis is complicated by the fact that sea ice supports several types of seismic waves producing complex particle motion that includes significant nonradial components to suppress seismic waves with transverse particle motion seismic polarization filters are applied in conjunction with a straightforward rotational analysis computation of particle motion power as a function of angle the polarization filters require three dimensional 3d measurements of particle motion and apply theoretical phase relationships between vertical and horizontal components for the various waves types in addition the 180 ambiguity inherent in the rotational analysis can be resolved with 3d measurements by conside

holocene environmental change and its impacts on human settlement in the shanghai area east china abstract archaeological excavations and environmental archaeological studies over many years in the shanghai area have provided a wealth of information for holocene environmental changes growth and decline of human settlements and man land interaction distribution of archaeological sites between 7000 and 3000 cal yr bp indicates a regression process and a southward advance of the coastline in the study area temporal and spatial analyses of 14 c dates for archaeological sites shell ridges buried trees and peat suggest that holocene environmental changes may well have been a major cause of the rise and fall of human settlements and their civilization a relative sea level curve of the shanghai area was derived from dated shell ridges and peat and correlates well with the reconstructed sea level curves of the yangtze delta and east china the development of human settlements was interrupted at least four times in the shanghai area matching four periods of high sea level peat accumulation and increase in shell ridges after which neolithic communities moved onto the plain and reclaimed their lowlands for rice cultivation the chenier ridges played an important role in sheltering the neolithic settlers the collapse of liangzhu culture about 4000 cal yr bp was followed by the less developed maqiao culture these studies suggest that extreme environmental and hydrological conditions such as terrestrial inundation caused by sea level rise and heavy rainfall contributed to the cessation of paddy exploitation and to the social stress that led to the liangzhu culture demise

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

contrasting eurasian spring and summer climate anomalies associated with western and eastern eurasian spring snow cover changes spring snow cover variations over eurasia consist of a same sign component and a west east dipole component the same sign component is dominant during late 1970s through 1980s and the two components are equally important during 1990s and 2000s present study contrasted eurasian spring and summer climate anomalies associated with western and eastern eurasian spring snow cover variations and between 1975 1989 and 1993 2007 and found notable differences and obvious interdecadal changes in eurasian climate anomalies after 1990 spring surface temperature anomalies display an obvious west east contrast pattern consistent with a prominent atmospheric wave pattern over eurasia the temperature anomalies are larger corresponding to western than eastern eurasian snow cover change snow albedo effect plays a main role in temperature change during 1975 1989 whereas atmospheric processes also contribute largely to temperature change during 1993 2007 large soil moisture anomalies occur corresponding to western eurasian snow cover and during 1975 1989 the snow hydrological effect on summer precipitation is mainly detected over the west siberian plain where soil moisture anomalies persist over 3 months over most of other eurasian regions atmospheric circulation pattern plays a dominant role in summer surface temperature and precipitation variations the relationship of indian summer rainfall to western eurasian spring snow cover was weakened since the mid 1990s and the correlation of northeast china summer rainfall with local spring snow cover changed from positive to negative around 1990

change in the contribution of spring snow cover and remote oceans to summer air temperature anomaly over northeast china around 1990 sea surface temperature sst snow cover and soil moisture anomalies are factors for climate variability over land regions the present study found that the relationship between in situ spring snow cover and northeast china summer surface temperature variations is not steady it is significant during mid 1970s through late 1980s but weak during the 1990s and 2000s this interdecadal change in the spring snow cover summer temperature relationship is found to relate to the effects of sst anomalies in the tropical indian ocean and western pacific regions during the recent decades these sst anomalies induce a meridional circulation pattern along the east asian coast the remote sst forcing induced circulation and precipitation anomalies overcome local snow cover induced soil moisture anomalies and thus disrupt the spring snow cover summer temperature connection during the recent decades the present study indicated that both the north atlantic sst anomaly pattern and local spring snow cover anomalies contribute to northeast china summer temperature variations during mid 1970s through late 1980s during the 1990s and 2000s the influence of the north atlantic sst anomalies is weakened and the sst anomaly in the tropical indo western pacific region is a major player in northeast china summer temperature variations

impact of eurasian spring snow decrement on east asian summer precipitation abstractin this study the relationship between eurasian spring snow decrement ssd and east asian summer precipitation and related mechanisms were investigated using observational data and the community atmospheric model version 3 1 cam3 1 the results show that a west east dipole pattern in eurasian ssd anomalies with a negative center located in the region between eastern europe and the west siberia plain eewsp and a positive center located around baikal lake bl is significantly associated with east asian summer precipitation via triggering an anomalous midlatitude eurasian wave train reduced ssd over eewsp corresponds to anomalously dry local soil conditions from spring to the following summer thereby increasing surface heat flux and near surface temperatures similarly the increase in ssd over bl is accompanied by anomalously low near surface temperatures the near surface thermal anomalies cause an anomalous meridional temperature gradient which intensifies the lower level baroclinicit

time transgressive onset of the holocene optimum in the east asian monsoon region abstract the east asian summer monsoon affects precipitation and hence vegetation in the densely populated northwest pacific region yet a long standing controversy exists concerning the spatial and temporal dynamics of the holocene optimum ho in the east asian monsoon region here we use a detailed 14 000 year record reconstructing vegetation variations from a strategically selected crater lake from northeast china as well as a compilation of previous paleoclimatic studies to show that the ho began around 6 000 cal a bp in northeast china significantly later than generally recognized by comparing our paleoenvironmental data with holocene vegetation records from other regions of east asia we identified a marked northward shift for the onset of the ho from 10 260 cal a bp in south china to 6 000 cal a bp in northeast china the gradual northward transgression of the vegetation change could be caused by both the temperature and precipitation changes in different regions finally we fitted a regression model of the start of the ho period versus latitude which allowed us to make predictions for the beginning of the ho at different geographical locations this study reveals a strong relationship between latitude and the initiation of the ho and provides a window towards better understanding the forcing of vegetation changes in the east asian monsoon region

particle size evidence for source areas of charcoal accumulation in late holocene sediments of eastern north american lakes abstract two methods of analyzing charcoal in sediment reveal changes in charcoal accumulation across temperate eastern north america during the last several hundred years in one method the analyst counts mostly small particles that reflect regional emissions in the other the analyst counts only larger particles derived mostly from such local sources as catchment fires we used these methods to compare charcoal accumulation at 14 lakes from the prairie forest border in minnesota to eastern maine the two methods gave concordant accumulation rates for sediments of pre 1850 age at each of 4 lakes analyzed by both methods this concordance is consistent with the interpretation that pre 1850 emissions were controlled by broad scale factors such as climatically controlled regional differences in fuels and moisture since 1900 large particles decreased greatly and small particles decreased slightly in minnesota and wisconsin by contrast in the northeast the large particle accumulation has remained at the low values measured in pre 1900 sediments at most sites while small particles increased everywhere east of central new york and pennsylvania the observed patterns suggest that 1 large particles primarily reflect local fires that were common in the midwest before fire suppression became effective 2 large particles were rare in the northeast especially before extensive land clearance 3 small particles reflect regional combustion that increased in the northeast after extensive use of fire for land clearance and wood burning for industrial purposes of the 19th century and 4 small particles remain abundant in the midwest long after effective fire suppression probably because these well dispersed small particles have a large source area that extends beyond the local wildfires that account for large particles before european settlement

8000 years of vegetation dynamics and environmental changes of a unique inland peat ecosystem of the jambi province in central sumatra indonesia abstract despite their importance as global carbon sinks peatlands of southeast asia have been rarely studied and our current knowledge of the dynamics and ecology of these ecosystems remains incomplete paleoecological and palynological multi proxy analyses including analysis of pollen spores charcoal testate amoebae and sediments were carried out on a 733 cm long core taken from the air hitam peatland in the jambi province central sumatra indonesia the radiocarbon chronology reveals that peat formation started ca 7800 years ago the site was covered by dipterocarp swamp mixed rainforest during the first 2000 years after which freshwater swamp taxa became more important in particular durio trees this lasted until ca 4500 years ago when the swamp vegetation shifted to a pole forest with abundant pandanus thickets in response to a system change from minerotrophic to ombrotrophic conditions for this period macro charcoal analysis reveals that fire frequency increased possibly as a consequence of climate change linked to the onset of the modern el nino southern oscillation enso in the late holocene the ombrogenous pandanus pole forest phases were characterized by lower water table fluctuations and higher peat accumulation rates the area of air hitam has been for thousands of years a highly effective carbon sequestering peatland natural climate variability in the past did not affect the carbon storage function as suggested by the general increase in peat accumulation during relatively drier phases and increasing enso variability in the late holocene however the recent changes caused by selective logging drainage and conversion to oil palm plantations have caused a decline in the peat swamp forest communities changing the ecological functions of the peatland it is likely that the accumulated carbon will be released in the atmosphere due to exposure to aerobic conditions and its function will be lost unless a better management of the watershed is applied

mid holocene environmental and human dynamics in northeastern china reconstructed from pollen and archaeological data abstract a pollen record from the taishizhuang site 40 21 5 n 115 49 5 e located in the transitional forest steppe zone near the present day limit of the summer monsoon is used to reconstruct vegetation and climate quantitative biome reconstruction suggests that between ca 5700 and 4400 cal years b p temperate deciduous forest dominated the vegetation cover around the taishizhuang site after that time the landscape became more open and the scores of the steppe biome were always higher than those of the temperate deciduous forest except for two oscillations dated to ca 4000 cal years b p and ca 3500 cal years b p however ca 3400 2100 cal years b p the common vegetation became steppe and the landscape was more open in comparison with the previous time interval the results of the pollen based precipitation reconstruction suggest that annual precipitation was ca 550 750 mm ca 100 300 mm higher than present during the mid holocene forest phase and ca 450 650 mm during the following forest steppe phase from ca 3400 cal years b p during the steppe phase annual precipitation was similar to modern values ca 300 500 mm archaeological records from 100 sites prove the habitation of northeastern china during the prehistoric and early historic periods from ca 8200 cal years b p but do not provide evidence of the use of wood resources intensive enough to influence the regional vegetation development and to leave traces in the pollen assemblages both archaeological and palaeoenvironmental data support the conclusion that changes in pollen composition in northeastern china between 5700 and 2100 cal years b p reflect natural variations in precipitation and not major deforestation caused by humans

possible impact of north atlantic warming on the decadal change in the dominant modes of winter eurasian snow water equivalent during 1979 2015 an east west dipole mode of winter eurasian snow water equivalent swe is found during the period of 1979 2015 it accounts for about 23 4 of the total variance and displayed a significant decadal change in the early 2000s the basin warming footprint of the north atlantic likely exerted an influence on this decadal change and the observation based evidence is reproduced by numerical experiments using the community atmosphere model cam3 1 a basin wide warming of north atlantic sea surface temperature induced atmospheric anomalies by exciting a stationary rossby wave train which prorogates from the subtropical north atlantic to the mid to high latitudes of the eurasian continent along with the rossby wave train an enhanced upper level ridge occurs over the ural mountain and a deepened upper level trough appears over the eastern siberian plateau which promotes heavy snowfall over the eastern siberian plateau and light snowfall to its west thus it is plausible that the north atlantic warming plays a role in exciting the rossby wave train to modulate the decadal change in the east west dipole swe mode of the extratropical eurasian continent the possible moisture transport paths associated with the decadal change in the east west dipole swe mode are also discussed

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

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

concordant monsoon driven postglacial hydrological changes in peat and stalagmite records and their impacts on prehistoric cultures in central china asian monsoon records are widely documented but specific proxies of monsoonal rainfall are limited we present here two new independent proxy records from peatland and stalagmite archives that indicate a high degree of concordance between monsoon driven hydrological changes occurring since the last deglaciation in a broad region of central china the wet periods elevated the water table in the dajiuhu peatland as recorded by reduced mass accumulation rates of hopanoids biomarkers for aerobic microbes confirmed by molecular phylogenic analyses the hopanoid based reconstruction is supported by the first report of the environmental magnetism parameter arm sirm anhysteretic remanent magnetization saturation isothermal remanent magnetization ratio of fine magnetic particles to total ferrimagnetic particles in a stalagmite from heshang cave in central china heavy rainfall resulted in the enhanced transport of coarse particles to the cave and thus low arm sirm values in the stalagmite the hydrological conditions inferred from the two records reveal three relatively long wet periods in central china 13 11 5 k y ago 9 5 7 0 k y ago and 3 0 1 5 k y ago archaeological evidence for the hydrological impacts on regional populations comes from the observation that temporal shifts among six distinctive cultures of the neolithic period to the iron age in central china occurred during wet periods or flood episodes spatiotemporal distributions of 1600 prehistoric settlement sites correlate with the proxy inferred fluctuating hydrological conditions with enhanced flooding risk forcing major relocations of human settlements away from riparian zones

inverse phase oscillations between the east asian and indian ocean summer monsoons during the last 12 000 years and paleo el nino abstract the inverse phase variations between the east asian and indian ocean summer monsoons on the interannual timescale result from the el nino southern oscillation activity in the tropical pacific which potentially provides a new way for studying paleo enso here we reconstruct a 12 000 yr proxy record for the east asian summer monsoon from 13 c time series of the plant cellulose of the hani peat bog in the northeastern china the comparison of it with the peat proxy record of the indian ocean summer monsoon suggests that the el nino conditions are coincident with strong east asian summer monsoons weak indian summer monsoons and drift ice events in the north atlantic at both orbital and millennial time scales the orbital scale inverse phase relationships between the monsoons indicate the occurrence of a long term enso like pattern confirming the sensitivity of the monsoon systems associated with enso to insolation forcing the nine inverse phase variations on the millennial time scales may suggest the nine el nino like patterns superimposing the long term enso like pattern the inverse phase variations between the monsoons also show close correspondence to the drift ice events at high northern latitudes in every case when the abrupt ice rafted debris events occurred in the north atlantic the inverse phase relationship established and the el nino like pattern occurred in the tropical pacific correspondingly the discussions on the influence of ocean thermohaline circulation on these global linkages have been made

holocene vegetation and climate histories in the eastern tibetan plateau controls by insolation driven temperature or monsoon derived precipitation changes abstract the climates on the eastern tibetan plateau are strongly influenced by direct insolation heating as well as monsoon derived precipitation change however the moisture and temperature influences on regional vegetation and climate have not been well documented in paleoclimate studies here we present a well dated and high resolution loss on ignition peat property and fossil pollen record over the last 10 000 years from a sedge dominated fen peatland in the central zoige basin on the eastern tibetan plateau and discuss its ecological and climatic interpretations lithology results indicate that organic matter content is high at 60 80 between 10 and 3 ka 1 ka 1000 cal yr bp and shows large magnitude fluctuations in the last 3000 years ash free bulk density as a proxy of peat decomposition and peatland surface moisture conditions oscillates around a mean value of 0 1 g cm 3 with low values at 6 5 4 7 ka reflecting a wet interval and an increasing trend from 4 7 to 2 ka suggesting a drying trend the time averaged mean carbon accumulation rates are 30 6 gc m 2 yr for the last 10 000 years higher than that from many northern peatlands tree pollen mainly from picea mostly reflecting temperature change in this alpine meadow forest ecotonal region has variable values from 3 to 34 during the early holocene reaches the peak value during the mid holocene at 6 5 ka and then decreases until 2 ka the combined peat property and pollen data indicate that a warm and wet climate prevailed in the mid holocene 6 5 4 7 ka representing a monsoon maximum or optimum climate for the region the timing is consistent with recent paleo monsoon records from southern china and with the idea that the interplays of summer insolation and other extratropical large scale boundary conditions including sea surface temperature and sea level change control regional climate the cooling and drying trend since the mid holocene likely reflects the decrease in insolation heating and weakening of summer monsoons regional synthesis of five pollen records along a south north transect indicates that this climate pattern can be recognized all across the eastern tibetan plateau the peatland and vegetation changes in the late holocene suggest complex and dramatic responses of these lowland and upland ecosystems to changes in temperature and moisture conditions and human activities

two distinct patterns of spring eurasian snow cover anomaly and their impacts on the east asian summer monsoon 1 the eurasian snow cover anomaly in spring has been considered as one of the important factors affecting east asian summer monsoon easm the spring snow cover data for the period from 1972 to 2004 are used to extract dominant spatial patterns over the eurasian region and to examine their impacts on the easm through empirical orthogonal function eof analysis the first eof mode is generally characterized by a continent wide snow cover anomaly over the whole eurasian region while the second eof mode is dominated by an east west dipole structure over eurasia our study indicates that the variability of dipole pattern snow cover is more closely related to the easm rainfall than that of continent wide snow cover a strong dipole pattern with positive negative snow cover anomalies over western eurasia and negative positive snow cover anomalies over eastern eurasia signifies enhanced reduced summer rainfall over east asia and the eurasian wave train pattern is apparent an important implication of these results is that the spring snow cover anomaly over eurasia provides a complementary precursor for easm variability

palaeosol development in the chinese loess plateau as an indicator of the strength of the east asian summer monsoon evidence for a mid holocene maximum the interpretation of the stalagmite delta o 18 record from southern china as an indicator of east asian summer monsoon easm rainfall amount or intensity is strongly debated soil development in the chinese loess plateau clp situated in the modern summer monsoon domain has long been treated as a direct and reliable easm proxy in this study we compiled 81 loess and 229 palaeosol dates from 77 profiles across the clp and synthesized the data statistically in order to investigate the easm history during the holocene the resulting history of holocene loess deposition and palaeosol development demonstrates that 1 loess deposition decreased and palaeosol formation increased across the clp after 11 5 ka 1 ka 1000 cal yr bp revealing a gradually intensified easm during the early holocene 2 numerous palaeosols developed in the clp between 8 8 ka and 3 4 ka indicating a generally strong easm during the mid holocene 3 the number of palaeosol dates decreased rapidly at around 3 ka suggesting a sudden retreat of the easm in the late holocene these trends of easm evolution are broadly consistent with variations in aeolian sand activity in the four main sandlands the mu us otindag horqin and hulun buir sandlands along the modern monsoon fringe in northern china and are supported by a wide range of independent evidence in addition we also found that high loess deposition and stronger aeolian activity occurred at similar to 5 ka representing a weak easm event within the context of an overall strong mid holocene easm the strong mid holocene easm revealed by palaeosol development in the clp and aeolian sand activity in the sandlands in northern china contrasts with the early holocene easm maximum suggested by stalagmite delta o 18 data from southern china our results are compatible with the proposal that the stalagmite delta o 18 variations in china do not result from changes in easm rainfall amount or intensity but instead reflect changes in moisture source driven by variations in atmospheric oceanic circulation c 2014 elsevier ltd and inqua all rights reserved

matched field localization for multiple sources in an uncertain environment with application to arctic ambient noise this paper describes a general method to localize multiple broadband sources in a range and azimuth dependent environment when properties of the environment are not well known both the source locations and the unknown environmental parameters are included as variables in a simulated annealing inversion that searches for the best match between the measured and modeled fields the example used to illustrate the method involves localizing an unknown number of ice ridge building events in an arctic environment where the bathymetry is poorly known a number of aspects of this problem are examined in a synthetic study including the effect of errors in the bathymetry on localization the importance of simultaneous localization and determining the number of sources present the inversion accurately localizes multiple synthetic sources particularly in cases where the sources are spatially separated and the spectral shape is known the inversion is also applied to a set of ambient noise measurements recorded i