a penultimate glacial monsoon record from hulu cave and two phase glacial terminations oxygen isotope records of three stalagmites from hulu cave china extend the previous high resolution absolute dated hulu asian monsoon record from the last to the penultimate glacial and deglacial periods the penultimate glacial monsoon broadly follows orbitally induced insolation variations and is punctuated by at least 16 millennial scale events we confirm a weak monsoon interval between 135 5 1 0 and 129 0 1 0 ka prior to the abrupt increase in monsoon intensity at asian monsoon termination ii based on correlations with both marine ice rafted debris and atmospheric ch 4 records we demonstrate that most of marine termination ii the full rise in antarctic temperature and atmospheric co 2 and much of the rise in ch 4 occurred within the weak monsoon interval when the high northern latitudes were probably cold from these relationships and similar relationships observed for termination i we identify a two phase glacial termination process that was probably driven by orbital forcing in both hemispheres affecting the atmospheric hydrological cycle and combined with ice sheet dynamics

effects of rainfall intensity and slope gradient on the dynamics of interrill erosion during soil surface sealing abstract soil erosion during rainfall is strongly affected by runoff and slope steepness runoff production is drastically increased when a seal is formed at the soil surface during rainfall therefore a complex interaction exists between soil erosion and surface sealing in this study the dynamics of interrill erosion during seal formation is studied under different simulated rainfall and slope conditions a sandy soil was exposed to 70 mm of rainfall at two intensities 24 mm h 1 and 60 mm h 1 and five slope gradients from 5 to 25 infiltration runoff and soil loss rates were monitored during rainfall final infiltration rates increased with slope gradient at both rainfall intensities this effect being stronger for the higher intensity cumulative runoff at the end of the rainfall event was lower as slopes were steeper while an opposite trend was obtained for soil loss for the 5 and the 9 slopes the sediment concentration in runoff reached quickly a stable value during the whole rainfall event while it reached a peak value before declining for the higher slopes the peak value and its timing were rainfall intensity dependent soil erodibility during seal formation was evaluated using two empirical multiplication of factors type models it seems that slope and rainfall erosivity are accounted for only partly in these models for mild slope gradients below 9 the value of k i estimated by means of the two expressions becomes practically constant shortly after runoff apparition consequently the estimates resulting from this type of expressions remain valuable from the practical point of view

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

interaction between bed roughness and flow hydraulics in eroding rills govers 1992 showed that the flow velocity in rills eroding loose nonlayered materials could be predicted from knowledge of discharge only without significant slope or soil effect the objective of this paper is to investigate to what extent the observed slope independence of flow velocity in eroding rills can be explained by the interaction between rill bed roughness and flow hydraulics in a laboratory study two situations were compared 1 rills which can freely erode a uniform soil layer and 2 rills with a fixed bed geometry during the experiments rill discharge and flow velocity were recorded after each experiment a detailed topographic survey of the rill bed was carried out using a laser scanner from these data the main hydraulic variables mean values of flow depth wetted perimeter and hydraulic radius were estimated the experiments confirmed the slope independence of rill flow velocities on mobile beds when the bed is fixed the flow velocity in rills is clearly slope dependent the slope independence of flow velocity on mobile beds is due to a feedback between rill bed morphology and flow conditions the roughness amplitude which was assessed from the standard deviation of corrected height values and the frequency of macroroughness elements which was assessed by counting the number of peaks per unit length in a previously simplified longitudinal profiles both increase and tend to counteract the effect of the increase in slope gradient on rill flow velocity the final rill flow velocity appears to be characterized by a constant average froude number

marine isotope stage 11 palaeoclimates palaeoenvironments and its role as an analogue for the current interglacial abstract interglacials of the quaternary period are currently the focus of a great deal of attention within the scientific community this is primarily because they play a vital role in distinguishing between natural and human climate change in the current interglacial and in understanding how the holocene would evolve in the absence of anthropogenic greenhouse warming in this respect marine isotope stage 11 mis 11 ca 410 000 yr bp is one of the key interglacial stages of the past 450 000 yr the pattern of insolation variability that occurs during mis 11 matches that which occurs in the holocene more closely than in any other warm stage of the past half a million years in addition there is now an extensive range of evidence for mis 11 palaeoclimates and palaeoenvironments from marine ice core lacustrine and terrestrial sequences the aim of this paper is to provide a comprehensive review of the current state of our understanding of mis 11 this is the first paper to provide a detailed review of mis 11 that incorporates the wide range of marine ice core long lacustrine and terrestrial records that have been generated over the last ten years since the last major overview crucially it is the first review of mis 11 that incorporates a detailed synthesis of the high resolution terrestrial sequences of western and central europe this paper therefore provides a holistic integration of a diverse range of proxies and archives to provide a detailed understanding of the expression of mis 11 in the earth system in particular the review focuses on 1 the climatic background of mis 11 2 the robustness of the identification of mis 11 in a diverse range of sequences 3 the climatic structure of mis 11 4 the magnitude of warmth that occurred in this warm stage 5 mis 11 sea level magnitude and variability 6 the duration of mis 11 7 evidence for abrupt climatic events within the interglacial of mis 11 and 8 precipitation patterns and trends during this interglacial the paper concludes by considering how useful mis 11 is as an analogue for holocene climates and compares it with other proposed analogues such as mis 19 with particular reference to the early anthropogenic hypothesis

epica dome c record of glacial and interglacial intensities abstract climate models show strong links between antarctic and global temperature both in future and in glacial climate simulations past antarctic temperatures can be estimated from measurements of water stable isotopes along the epica dome c ice core over the past 800 000 years here we focus on the reliability of the relative intensities of glacial and interglacial periods derived from the stable isotope profile the consistency between stable isotope derived temperature and other environmental and climatic proxies measured along the edc ice core is analysed at the orbital scale and compared with estimates of global ice volume mis 2 12 and 16 appear as the strongest glacial maxima while mis 5 5 and 11 appear as the warmest interglacial maxima the links between edc temperature global temperature local and global radiative forcings are analysed we show i a strong but changing link between edc temperature and greenhouse gas global radiative forcing in the first and second part of the record ii a large residual signature of obliquity in edc temperature with a 5 ky lag iii the exceptional character of temperature variations within interglacial periods focusing on mis 5 5 the warmest interglacial of edc record we show that orbitally forced coupled climate models only simulate a precession induced shift of the antarctic seasonal cycle of temperature while they do capture annually persistent greenland warmth models fail to capture the warming indicated by antarctic ice core d we suggest that the model data mismatch may result from the lack of feedbacks between ice sheets and climate including both local antarctic effects due to changes in ice sheet topography and global effects due to meltwater thermohaline circulation interplays an mis 5 5 sensitivity study conducted with interactive greenland melt indeed induces a slight antarctic warming we suggest that interglacial edc optima are caused by transient heat transport redistribution comparable with glacial north south seesaw abrupt climatic changes

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

interglacial hydroclimate in the tropical west pacific through the late pleistocene records of atmospheric carbon dioxide concentration pco 2 and antarctic temperature have revealed an intriguing change in the magnitude of interglacial warmth and pco 2 at around 430 000 years ago 430 ka but the global climate repercussions of this change remain elusive here we present a stalagmite based reconstruction of tropical west pacific hydroclimate from 570 to 210 ka the results suggest similar regional precipitation amounts across the four interglacials contained in the record implying that tropical hydroclimate was insensitive to interglacial differences in pco 2 and high latitude temperature in contrast during glacial terminations drying in the tropical west pacific accompanied cooling events in northern high latitudes therefore the tropical convective heat engine can either stabilize or amplify global climate change depending on the nature of the climate forcing

the role of rock fragmentation in the motion of large landslides abstract by considering the implications of the comminution generally associated with very large landslides we arrive at a simple explanation for the remarkably low frictional resistance to motion demonstrated by large intact blockslides e g waikaremoana new zealand volcanic debris avalanches e g socompa chile and large rock avalanches e g falling mountain n z which allows such mass movements to achieve unexpectedly high velocities and long runout distances during rapid grain flow under high direct stress the overall grain motion generates stresses in many force chains that strain individual grains to failure most of the elastic strain energy accumulated in these force chains before failure is returned at failure to the resulting grain fragments resulting in apparent instantaneous pressures of 3q on the surroundings where q is the ambient strength of the previously intact grains gpa these intense pressures support some of the direct force on the shear layer so that the effective intergranular stress in the shear layer is reduced because frictional resistance is proportional to effective stress this reduces the overall frictional resistance to shear the steady state effective stress is that which just allows fragmentation to continue the resistance to motion estimated from this relationship explains to much better than order of magnitude accuracy the reported motions of the large rapid mass movements we also deduce that grain fragmentation can be sustained for sufficiently long to explain the phenomena without reducing the mean grain size by volume in the granular layer to unrealistically small values the presence of pore fluid does not appear to influence the effect of fragmentation dynamics in a major way the proposed mechanism requires further laboratory and simulation studies to reduce its current dependence on limited field data but its success suggests that it is worthwhile investigating further as an explanation for large mass movements in the types of brittle rock in which fragmentation occurs

climate an exceptionally long interglacial ahead today9s comparatively warm climate has been the exception more than the rule during the last 500 000 years or more if recent warm periods or interglacials are a guide then we may soon slip into another glacial period but berger and loutre argue in their perspective that with or without human perturbations the current warm climate may last another 50 000 years the reason is a minimum in the eccentricity of earth9s orbit around the sun

interglacials of the last 800 000 years interglacials including the present holocene period are warm low land ice extent high sea level end members of glacial cycles based on a sea level definition we identify eleven interglacials in the last 800 000 years a result that is robust to alternative definitions data compilations suggest that despite spatial heterogeneity marine isotope stages mis 5e last interglacial and 11c 400 ka ago were globally strong warm while mis 13a 500 ka ago was cool at many locations a step change in strength of interglacials at 450 ka is apparent only in atmospheric co2 and in antarctic and deep ocean temperature the onset of an interglacial glacial termination seems to require a reducing precession parameter increasing northern hemisphere summer insolation but this condition alone is insufficient terminations involve rapid nonlinear reactions of ice volume co2 and temperature to external astronomical forcing the precise timing of events may be modulated by millennial scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere a variety of temporal trends is observed such that maxima in the main records are observed either early or late in different interglacials the end of an interglacial glacial inception is a slower process involving a global sequence of changes interglacials have been typically 10 30 ka long the combination of minimal reduction in northern summer insolation over the next few orbital cycles owing to low eccentricity and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future

centennial scale vegetation dynamics and climate variability in se europe during marine isotope stage 11 based on a pollen record from lake ohrid abstract to better understand climate variability during marine isotope stage mis 11 we here present a new centennial scale resolution pollen record from lake ohrid balkan peninsula derived from sediment cores retrieved during an international continental scientific drilling program icdp campaign our palynological data augmented by quantitative pollen based climate reconstructions provide insight into the vegetation dynamics and thus also climate variability in se europe during one of the best orbital analogues for the holocene comparison of our palynological results with other proxy data from lake ohrid as well as with regional and global climate records shows that the vegetation in se europe responded sensitively both to long and short term climate change during mis 11 the chronology of our palynological record is based on orbital tuning and is further supported by the detection of a new tephra from the vico volcano central italy dated to 410 2 ka our study indicates that mis 11c 424 398 ka was the warmest interval of mis 11 the younger part of the interglacial i e mis 11b 11a 398 367 ka exhibits a gradual cooling trend passing over into mis 10 it is characterized by considerable millennial scale variability as inferred by six abrupt forest contraction events interestingly the first forest contraction occurred during full interglacial conditions of mis 11c this event lasted for 1 7 kyrs 406 2 404 5 ka and was characterized by substantial reductions in winter temperature and annual precipitation most notably it occurred 7 ka before the end of mis 11c and 15 ka before the first strong ice rafted debris event in the north atlantic our findings suggest that millennial scale climate variability during mis 11 was established in southern europe already during mis 11c which is earlier than in the north atlantic where it is registered only from mis 11b onwards

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

sea level rise due to polar ice sheet mass loss during past warm periods background although thermal expansion of seawater and melting of mountain glaciers have dominated global mean sea level gmsl rise over the last century mass loss from the greenland and antarctic ice sheets is expected to exceed other contributions to gmsl rise under future warming to better constrain polarice sheetresponse to warmer temperatures we draw on evidence from in terglacial periods in the geologic record that ex perienced warmer polar temperatures and higher gmsls than present coastal records of sea level from these previous warm periods dem onstrate geographic variability because of the influence of several geophysical processes that operate across a range of magnitudes and time scales inferring gmsl and ice volume changes from these reconstructions is nontrivial and generally requires the use of geophysical models advances interdisciplinary studies of geo logic archives have ushered in a new era of deciphering magnitudes rates and sources of sea level rise advances in our understanding of polar ice sheet response to warmer climates have been made through an increase in the number and geographic distribution of sea level reconstructions better ice sheet constraints and the recognition that several geophysical processes cause spatially complex patterns in sea level in particular accounting for glacial isostatic processes helps to decipher spatial variability in coastal sea level records and has reconciled a number of site specific sea level reconstructions for warm periods that have oc curred within the past several hundred thou sand years this enables us to infer that during recent interglacial periods small increases in

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

anomalously weak labrador sea convection and atlantic overturning during the past 150 years the atlantic meridional overturning circulation amoc is a system of ocean currents that has an essential role in earth s climate redistributing heat and influencing the carbon cycle1 2 the amoc has been shown to be weakening in recent years 1 this decline may reflect decadal scale variability in convection in the labrador sea but short observational datasets preclude a longer term perspective on the modern state and variability of labrador sea convection and the amoc1 3 5 here we provide several lines of palaeo oceanographic evidence that labrador sea deep convection and the amoc have been anomalously weak over the past 150 years or so since the end of the little ice age lia approximately ad 1850 compared with the preceding 1 500 years our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the lia or as a more gradual continued decline over the past 150 years this ambiguity probably arises from non amoc influences on the various proxies or from the different sensitivities of these proxies to individual components of the amoc we suggest that enhanced freshwater fluxes from the arctic and nordic seas towards the end of the lia sourced from melting glaciers and thickened sea ice that developed earlier in the lia weakened labrador sea convection and the amoc the lack of a subsequent recovery may have resulted from hysteresis or from twentieth century melting of the greenland ice sheet 6 our results suggest that recent decadal variability in labrador sea convection and the amoc has occurred during an atypical weak background state future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the amoc weakening described here

variability of surface water characteristics and heinrich like events in the pleistocene midlatitude north atlantic ocean biomarker and xrd records from iodp site u1313 mis 16 9 1 a reconstruction of milankovitch to millennial scale variability of sea surface temperature sst and sea surface productivity in the pleistocene midlatitude north atlantic ocean marine isotope stage mis 16 9 and its relationship to ice sheet instability was carried out on sediments from integrated ocean drilling program iodp site u1313 this reconstruction is based on alkenone and n alkane concentrations u37k index total organic carbon toc and carbonate contents x ray diffraction data magnetic susceptibility and accumulation rates increased input of ice rafted debris occurred during mis 16 12 and 10 characterized by high concentrations of dolomite quartz and feldspars and elevated accumulation rates of terrigenous matter minimum input values of terrigenous matter on the other hand were determined for mis 13 and 11 peak values of dolomite coinciding with quartz plagioclase and kalifeldspar peaks and maxima in long chain n alkanes indicative for land plants are interpreted as heinrich like events related to sudden instability of the laurentide ice sheet during early and late deglacial phases of the glacials the coincidence of increased toc values with elevated absolute concentrations of alkenones suggests increased glacial productivity probably due to a more southern position of the polar front alkenone based sst reached absolute maxima of about 19 c during mis 11 3 and absolute minima of 10 c during mis 12 and 10 within mis 11 prominent cooling events mis 11 22 and 11 24 occurred the absolute sst minima recorded directly before and after the glacial maxima mis 10 2 and 12 2 are related to heinrich like event meltwater pulses as supported by the coincidence of sst minima and maxima in c37 4 alkenones and dolomite these sudden meltwater pulses especially during terminations iv and v probably caused a collapse of phytoplankton productivity as indicated by the distinct drop in alkenone concentrations ice sheet disintegration and subsequent surges and outbursts of icebergs and meltwater discharge may have been triggered by increased insolation in the northern high latitudes

orbital forcing of continental climate during the pleistocene a complete astronomically tuned climatic record from lake baikal se siberia abstract a new composite bdp 96 biogenic silica record over the entire pleistocene was generated by splicing bdp 96 1 and bdp 96 2 drill cores from lake baikal crosschecked against a similar record from a nearby bdp 98 drill core a new astronomically tuned age model is proposed based on correlating peak biogenic silica responses with the timing of september perihelia this target is derived from analysis of regional climate proxy responses during the holocene the last interglacial and around paleomagnetic reversals by resolving virtually every precessional cycle during the pleistocene the new age model represents a major improvement compared with previously reported lake baikal timescales the astronomically tuned ages of the pleistocene paleomagnetic reversals are consistent with published dates the minimal tuning approach we used precession only has also aligned high signal power in a narrow obliquity band confirming the strong presence of orbital forcing there are also strong ca 100 ka scale cycles but these are not aligned with the orbital eccentricity despite the location of lake baikal in a continental interior that is highly sensitive to insolation forcing the tuned biogenic silica record reveals a consistent phase difference of 32 ca 4 ka relative to insolation in the obliquity band an inherent lag embedded in a continental proxy record not driven by global ice volume is an intriguing finding another new observation is that long term changes in sedimentation rates in lake baikal appear to be related to the amplitude of orbital forcing both amplitudes and sedimentation rates undergo significant changes during mis 24 mis 19 interval corresponding to the middle pleistocene transition with potential for linking continental and marine climato stratigraphies the new baikal record serves a new benchmark correlation target in continental eurasia as an alternative to june 65 n insolation and odp correlated timescales

the asian monsoon over the past 640 000 years and ice age terminations oxygen isotope records from chinese caves characterize changes in both the asian monsoon and global climate here using our new speleothem data we extend the chinese record to cover the full uranium thorium dating range that is the past 640 000 years the record s length and temporal precision allow us to test the idea that insolation changes caused by the earth s precession drove the terminations of each of the last seven ice ages as well as the millennia long intervals of reduced monsoon rainfall associated with each of the terminations on the basis of our record s timing the terminations are separated by four or five precession cycles supporting the idea that the 100 000 year ice age cycle is an average of discrete numbers of precession cycles furthermore the suborbital component of monsoon rainfall variability exhibits power in both the precession and obliquity bands and is nearly in anti phase with summer boreal insolation these observations indicate that insolation in part sets the pace of the occurrence of millennial scale events including those associated with terminations and unfinished terminations records of the asian monsoon have been extended to 640 000 years ago and confirm both that the 100 000 year ice age cycle results from integral numbers of precessional cycles and that insolation influences the pacing of major millennial scale climate events prior records of the asian monsoon have revealed cyclic variations over hundreds of thousands of years probably driven by variations in insolation caused by the precession of earth s orbit hai cheng and colleagues now provide a speleothem record from chinese cave samples that extends earlier records to 640 000 years ago close to the maximum age possible with uranium thorium dating this spectacular record confirms that the characteristic 100 000 year ice age cycle corresponds to an integral number four or five of precession cycles and that insolation influences millennial scale variations in monsoon strength

reconstructing the western boundary variability of the western pacific subtropical high over the past 200 years via chinese cave oxygen isotope records cave oxygen isotope 18o records have been important in characterizing asian monsoon variations on a wide range of timescales the climatic significance of the 18o proxy of the cave records and its main control factors however remain hotly debated especially with respect to annual to decadal timescales in particular while the spatial and intensity variations of the western pacific subtropical high wpsh affects the east asian monsoon remarkably on annual to decadal timescales cave records up to present do not show clear evidence of the wpsh signal here we report a new high resolution average of 1 5 months 18o record from dongshiya cave qinling mountain central china the region is highly sensitive to variations in the position of the wpsh western boundary which in turn regulates the alternation of dominant moisture sources between the proximal pacific ocean and the remote indian ocean together with another cave record near the wpsh western boundary we established a new index to reconstruct variations of the wpsh western boundary over the past 200 years our new data revealed two significant periodicities 12 and 2 7 years respectively that can be causally linked to solar and enso variances correspondingly

hydrological responses and soil erosion potential of abandoned cropland in the loess plateau china recent changes in hydrological processes and soil erosion in the loess plateau china are immediate responses to cropland abandonment for revegetation which lead to a long term decrease in runoff generation and soil erosion however detailed hydrological responses and soil erosion changes have not been clearly evaluated in this study two issues were focused on the plot scale the first issue relates to changes in vegetation cover and soil properties during the early stages of revegetation given the occurrence of soil compaction it was hypothesized that runoff increased during this period and the soil erosion did not significantly decline even though vegetation increased the second issue is the effect of scale on runoff and soil erosion three plot groups of three vegetation types and two restoration stages were established for comparative experiments the results from these experiments confirmed that the soil compaction occurred during revegetation in this region greater runoff was produced in plot group that experienced both a longer restoration time and with higher vegetation cover such as groups 2 and 3 in this study than that with a shorter restoration time and lower vegetation cover group 1 in addition the total soil loss rates of all plot groups were rather low and did not significantly differ from each other this indicates that a reduction in runoff generation and soil erosion as a result of revegetation was limited in the early stages of restoration following the cropland abandonment with increasing plot area the runoff coefficient decreased for the plot group with a longer revegetation time groups 2 and 3 but gently increased for the one with a shorter restoration time group 1 in groups 2 and 3 soil loss rate decreased when plot area enlarged in group 1 it decreased before a plot area threshold of 18 m 2 was exceeded however the increase occurred when plot area crossed the threshold value in conclusion the high vegetation cover alone did not lead to reduction in the runoff coefficient during the early stages of revegetation when evaluating hydrological and soil erosion responses to revegetation the soil compaction processes should be considered additionally the effect of scale on runoff and soil erosion was found to be dependent on restoration extent and thus on restoration time c 2011 elsevier by all rights reserved

soil erosion by surface water flow on a stony semiarid hillslope soil erosion on hillslopes occurs by processes of soil splash from raindrop impacts and sediment entrainment by surface water flows this study investigates the process of soil erosion by surface water flow on a stony soil in a semiarid environment a field experimental method was developed whereby erosion by concentrated flow could be measured in predefined flow areas without disturbing the soil surface the method allowed for measurements in this study of flow erosion at a much wider range of slopes 2 6 to 30 1 per cent and unit discharge rates 0 0007 to 0 007 m2 s 1 than have been previously feasible flow velocities were correlated to discharge and hydraulic radius but not to slope the lack of correlation between velocity and slope might have been due to the greater rock cover on the steeper slopes which caused the surface to be hydraulically rougher and thus counteract the expected effect of slope on flow velocity the detachment data illustrated limitations in applying a linear hydraulic shear stress model over the entire range of the data collected flow detachment rates were better correlated to a power function of either shear stress r2 0 51 or stream power r2 0 59 published in 1999 by john wiley sons ltd

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

modelling sheet erosion on steep slopes in the loess region of china abstract the relationship of sheet erosion rate se slope gradient s and rainfall intensity i and hydraulic parameters such as flow velocity v shear stress stream power and unit stream power p was investigated to derive an accurate experimental model the experiment was conducted at slopes of 12 23 17 63 26 8 36 4 40 4 and 46 63 under i of 48 60 90 120 138 and 150 mm h 1 respectively using simulated rainfall results showed that sheet erosion rate increased as a power function with rainfall intensity and slope gradient with r 2 0 95 and nash sutcliffe model efficiency nse 0 87 sheet erosion rate was more sensitive to rainfall intensity than to slope gradient it increased as a power function with flow velocity which was satisfactory for predicting sheet erosion rate with r 2 0 95 and nse 0 81 shear stress and stream power could be used to predict sheet erosion rate accurately with a linear function equation stream power r 2 0 97 nse 0 97 was a better predictor of sheet erosion rather than shear stress r 2 0 90 nse 0 89 however a prediction based on unit stream power was poor the new equation i e se 7 5 10 12 s 1 43 i 3 04 and se 0 06 0 0003 and se 0 011 0 01 would improve water erosion estimation on loess hillslopes of china

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

east asian hydroclimate modulated by the position of the westerlies during termination i speleothem oxygen isotope records have revolutionized our understanding of the paleo east asian monsoon yet there is fundamental disagreement on what they represent in terms of the hydroclimate changes we report a multiproxy speleothem record of monsoon evolution during the last deglaciation from the middle yangtze region which indicates a wetter central eastern china during north atlantic cooling episodes despite the oxygen isotopic record suggesting a weaker monsoon we show that this apparent contradiction can be resolved if the changes are interpreted as a lengthening of the meiyu rains and shortened post meiyu stage in accordance with a recent hypothesis model simulations support this interpretation and further reveal the role of the westerlies in communicating the north atlantic influence to the east asian climate

applications of stalagmite laminae to paleoclimate reconstructions comparison with dendrochronology climatology abstract laminated stalagmites observed in either ultra violet or visible light or recognized via trace elements are now widely recognized as a common deposition form annually laminated stalagmites should be expected in caves which have an overlying climate that has a strong seasonality similar climate zones to where trees grow with distinct annual rings continuous laminated stalagmite chronologies up to several thousand years should be expected where some mixing of stored water occurs such stalagmites can be used to reconstruct climate particularly through variations in lamina width such climate records would be relatively damped by mixing of event water with stored groundwater constraining the amount of high frequency climate signals contained in the stalagmite but relatively long continuous lamina sequences permit the preservation of low frequency centennial scale climate signals this contrasts with numerous tree ring climate records which are frequently limited in preserving multi centennial trends due to the necessary removal of age related noise from relatively short tree segments laminated stalagmites and tree rings should therefore to some degree provide complementary climate information appropriate methods for compiling stalagmite layer chronologies and climatologies are presented

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

timing and structure of the 8 2 kyr b p event inferred from δ18o records of stalagmites from china oman and brazil oxygen isotope records of stalagmites from china and oman reveal a weak summer monsoon event with a double plunging structure that started 8 21 0 02 kyr b p an identical but antiphased pattern is also evident in two stalagmite records from eastern brazil indicating that the south american summer monsoon was intensifi ed during the 8 2 kyr b p event these records demonstrate that the event was of global extent and synchronous within dating errors of 50 years in comparison with recent model simulations it is plausible that the 8 2 kyr b p event can be tied in changes of the atlantic meridional overturning circulation triggered by a glacial lake draining event this in turn affected north atlantic climate and latitudinal position of the intertropical convergence zone resulting in the observed low latitude monsoonal precipitation patterns

delayed build up of arctic ice sheets during 400 000 year minima in insolation variability an east asian winter monsoon proxy record using grain size variations in chinese loess over the past 900 000 years shows that for up to 20 000 years after the interglacials at 400 000 year intervals the weak monsoon winds maintain a mild non glacial climate at high northern latitudes qingzhen hao and colleagues present a record of grain size variations in the chinese loess plateau a proxy of variations in the strength of the east asian winter monsoon and show that relatively high insolation at 400 000 year intervals held off the inception of the subsequent ice age for about 20 000 years relative to other glacial inceptions mechanistically the extension of warm conditions was probably linked to a weak siberian high pressure system associated with a delayed build up of northern ice and snow the authors speculate that these observations imply that arctic climate may remain in non glacial mode for more than 40 000 years even in the absence of anthropogenic greenhouse gases knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial1 may help to inform our understanding of future climate change unfortunately long term continuous records of ice sheet variability in the northern hemisphere only are scarce because records of benthic 18o content represent an integrated signal of changes in ice volume in both polar regions2 however variations in northern hemisphere ice sheets influence the siberian high3 an atmospheric pressure system so variations in the east asian winter monsoon eawm as recorded in the aeolian dust deposits on the chinese loess plateau can serve as a useful proxy of arctic climate variability before the ice core record begins here we present an eawm proxy record using grain size variations in two parallel loess sections representative of sequences across the whole of the chinese loess plateau over the past 900 000 years the results show that during periods of low eccentricity and precessional variability at approximately 400 000 year intervals the grain size inferred intensity of the eawm remains weak for up to 20 000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis in contrast there is a rapid increase in the eawm after the end of most other interglacials we conclude that for both the 400 000 year interglacials the weak eawm winds maintain a mild non glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records during these times the less severe summer insolation minima at 65 n ref 4 would have suppressed ice and snow accumulation leading to a weak siberian high and consequently weak eawm winds

sixty year quasi period of the asian monsoon around the last interglacial derived from an annually resolved stalagmite δ18o record abstract the 60 year quasi periodic variability of the asian monsoon in the mid late holocene has been found to be widespread in instrumental and various terrestrial records however whether this period exists in the older interglacial periods remains to be further studied this paper is based on an 1840 mm long stalagmite with clear annual laminae with a growth rate of about 1 mm yr from yongxing cave china that allows for the reconstruction of the asian monsoon evolution sequence during the period 123 20 121 21 kyr bp the stalagmite record closely tracks the 65 n solar insolation changes as a whole indicating the dominant control of solar insolation on the asian summer monsoon after removing the solar insolation signal from the yx108 record the 18o residuals 18o show 28 multidecadal monsoon cycles the average amplitude of these fluctuations is larger than 0 8 with a duration typically ranging from 50 to 80 yr about 64 yr on average which is very similar to the mid late holocene asian monsoon variability further wavelet analysis displays a significant quasi periodicity of 60 years throughout the studied period providing further evidence for assessing whether the 60 year quasi periodic variability of the asian monsoon found in the holocene exists in older periods our study thus suggests that this quasi periodic variability not only occurred during the modern period but also existed in the last interglacial and their influence may even be an intrinsic characteristic of the asian monsoon system during glacial interglacial cycles we manifested that the interactions between solar activity and the atlantic multidecadal oscillation may be the main reason for the 60 year quasi period of the asian monsoon

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