the stratospheric major warming of winter 1984 85 observations and dynamical inferences the evolution and dynamics of the major stratospheric warming of 1984 85 are described and discussed using synoptic maps of geopotential height and temperature fields of q vectors isentropic maps of ertel s potential vorticity and diagnostics based on zonal averaging and departures therefrom it is argued that the stratosphere cannot be regarded as being pre conditioned before the warming in the conventional sense of the term and that an important element of the warming was that the flow was highly asymmetric at the onset of the rapid breakdown of stratospheric westerlies nonlinear dynamics was involved as evidenced by an anticorrelation in time between the amplitudes of zonal waves 1 and 2 by the magnitude of a nonlinear term compared with those of linear terms in a governing equation and by the irreversible rearrangement of potential vorticity apparent loss of potential vorticity in the stratosphere is associated in part with differential advection of air in a vertically sheared flow salient features of the large scale flow in the troposphere during the stratospheric warming are noted

role of orbital forcing in east asian monsoon climates during the last 350 kyr evidence from terrestrial and marine climate proxies from core rc14 99 proxy records of northeast asian precipitation marine pollen and northwest pacific sea surface temperatures marine fauna contain concentrations of variance frequency peaks coincident with those of orbital variations eccentricity obliquity and precession time series of these monitors of various components of the east asian monsoon system are coherent with changing solar insolation and climate boundary conditions ice volume snow cover albedo at 41 and 23 kyr frequencies winter sea surface temperature wsst maxima are in phase with global ice volume minima at all three milankovitch frequencies 100 41 and 23 kyr periods wsst maxima are also linearly related to summer insolation at 30 n lagging radiation maxima by 55 3 5 kyr across the precessional frequency band 23 kyr period our east asian monsoon rainfall indicator cryptomeria reaches highest values immediately following summer insolation maxima during periods of low ice volume interglacials across the eccentricity frequency band 100 kyr period cryptomeria maxima are in phase with ice volume minima at the higher frequency of orbital precession monsoon rainfall lags both summer radiation maxima 125 8 kyr and ice volume minima 60 3 8 kyr whereas much of the variation in northwest pacific wsst can be attributed to summer radiation forcing and changes in global climate mechanisms driving east asian monsoon precipitation are more complex involving other possibly internal factors

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

monsoon fluctuations over the past 350 kyr high resolution evidence from northeast asia northwest pacific climate proxies marine pollen and radiolarians abstract high resolution analyses of pollen and radiolarians from northwest pacific cores v28 304 and rc14 99 provide continuous directly linked evidence of oceanic atmospheric climate processes through the past three pleistocene glacial interglacial cycles systematic fluctuations in marine pollen assemblages which reflect changes in the forest communities of japan are compatible with fluctuations in faunal assemblages and inferred oceanographic properties offshore each interglacial has distinguishable characteristics which imply that the sequence timing and magnitude of climatic change were not identical during the three most recent interglacial intervals most interglacials contain at least one 10 15 kyr period of exceptionally high percentages 20 of cryptomeria which we interpret as reflecting increased levels of precipitation in response to intensification of the summer monsoon with the exception of oxygen isotope substage 5e in rc14 99 interglacial summer sea surface temperatures were similar to or slightly warmer than today glacial environments in central japan and in the northern subtropical gyre were similar to those which now support cold temperate and boreal forests on northernmost japan and a dominant subpolar fauna and associated low sea surface temperatures offshore climatic change was apparently not as severe in southern japan where temperate vegetation largely replaced warm temperate flora or in the southern subtropical gyre where only winter ssts were cooler than present we attribute these changes in vegetation and surface water conditions to shifts in the atmospheric polar and oceanographic subarctic fronts in response to the seasonal variations in the siberian high maxima in cryptomeria systematically lag maxima in solar insolation at 30 n this correlation between our summer monsoon indicator and summer insolation substantiates the view that the strength of the asian monsoon is linked to variations in northern hemisphere solar radiation

identification of density stratified waters in the late pleistocene north atlantic a faunal derivation abstract an expanded study of the radiolarian cycladophora davisiana in late pleistocene north atlantic marine sediments shows that over the last several hundred thousand years this species exhibits large variations in relative abundance the c davisiana curves in the north atlantic cores are quite similar with easily recognizable features common to all records minor deviations from the general pattern of this species abundance apparently reflect the response of c davisiana to specific oceanographic conditions characteristic of a particular area within the north atlantic c davisiana occurs today in high abundance 20 only in the sea of okhotsk extensive winter and early spring sea ice cover coupled with low surface water salinities during summer and fall is responsible for maintaining near freezing subsurface temperatures in this northwest pacific marginal sea as well as relatively stable temperatures and salinities at depths below a shallow subsurface temperature minimum during periods in the late pleistocene high c davisiana abundances 20 in the north atlantic were probably associated with oceanographic properties similar to those that exist in the sea of okhotsk today because of the relationship between relatively stable subsurface temperatures and salinities and high abundance levels of c davisiana analysis of this species abundance pattern at several locations throughout the high latitude north atlantic should assist in identifying source areas of deep water formation and determining the duration of deep convective processes at these sites

elliptical diagnostics of stratospheric polar vortices diagnostics based on the spatial moments of isopleths of a long lived tracer or of potential vorticity are presented that enable the structure and evolution of stratospheric polar vortices to be concisely summarized and quantified the area centre aspect ratio and orientation of the equivalent ellipse of the vortex on an isentropic surface are defined using the second and lower order spatial moments of contours within the vortex edge region by examining the variations of these elliptical diagnostics with time and altitude the temporal evolution and vertical structure of the polar vortices can be quantified the usefulness of the diagnostics is assessed by examining nitrous oxide data from the geophysical fluid dynamics laboratory skyhi general circulation model the diagnostics show and quantify several differences between the arctic and antarctic vortices in the skyhi model the arctic vortex moves further off the pole is generally more elongated and has a more complicated vertical structure than the antarctic vortex with larger variations of both the vortex centre and elongation with height the elliptical diagnostics also identify the occurrence of large scale rossby wave breaking events both at the vortex edge and in the subtropics in the model

detrital sediment supply in the southern okinawa trough and its relation to sea level and kuroshio dynamics during the late quaternary abstract during leg 195 of the ocean drilling program site 1202 was drilled in the subtropical northwestern pacific ocean beneath the kuroshio black current between northern taiwan and the ryukyu island arc on the northern flank of the i lan ridge at 1274 m water depth the upper 110 m of the site 1202 section composed of dark grey calcareous silty clay provide an expanded record of environmental changes during the last 28 kyr the sediments were deposited at high sedimentation rates between 3 0 and 5 0 m kyr and peak values of 9 0 m kyr between 15 1 and 11 2 ka bp variations in the modes and sources of detrital sediment input as inferred from sediment granulometry mineralogy and elemental xrf scanner data reflect changes in environmental boundary conditions related to sea level changes kuroshio variability and the climate driven modes of fluvial runoff the provenance data point to increased sediment supply from northwestern taiwan between 28 and 19 5 ka bp and from east china sources between 19 5 and 11 2 ka bp the change in provenance at 19 5 ka bp reflects increased fluvial runoff from the yangtze river and strong sediment reworking from the east china sea shelf in the course of increased humidity and postglacial sea level rise particularly after 15 1 ka bp the holocene was dominated by sediments that originated from rivers in northeastern taiwan for the pre holocene period prior to 11 2 ka bp low portions of sortable silt 63 10 m show that the kuroshio did not enter the okinawa trough because of low sea level in turn high proportions of sortable silt and sediment provenance from northeastern taiwan point to strong ocean circulation under the direct and persistent influence of the kuroshio during the holocene the reentrance of the kuroshio to the okinawa trough was heralded by two pulses in relative current strengthening at 11 2 and 9 5 ka bp as documented by stepwise increases in sortable silt in the lower holocene section from a global perspective environmental changes in the southern okinawa trough show affinities to climate change in the western pacific warm pool with little influence of climate teleconnections from the north atlantic realm otherwise seen in many other marine and terrestrial palaeoclimate records from southeastern asia

pollen and radiolarian records from deep sea core rc14 103 climatic reconstructions of northeast japan and northwest pacific for the last 90 000 years using modern pollen and radiolarian distributions in sediments from the northwest pacific and seas adjacent to japan to interpret floral and faunal changes in core rc14 103 44 02 n 152 56 e we recognize two major responses of the biota of eastern hokkaido and the northwest pacific to climatic changes since the last interglaciation relatively stable glacial environments 80 000 20 000 yr b p were basically cold and wet 8 c and 1200 mm mean annual temperature and precipitation respectively supporting climax broadleaf deciduous forest with quercus and ulmus zelkova with surface waters in the northwest pacific characterized by warm 1 5 c winter and cold 10 4 14 3 c summer temperatures climatic evidence from rc14 103 shows a high degree of local and regional variation within the context of global climatic change correlative ocean and land records provide the detailed input necessary to assess local regional responses to variations in other key elements i e solar radiation monsoonal variations of the northeast asian climate system

geomorphology and ecosystems challenges and keys for success in bridging disciplines geomorphology plays a fundamental role in controlling many ecosystem processes and in turn ecosystems can have a profound influence on many geomorphic forms and processes over the past few decades a proliferation of research has developed at the interface of geomorphology and ecosystems ecology the 2005 binghamton symposium brought together some of the leading researchers from both communities to address these critical interfaces between the disciplines this paper reviews some of the aspects of the disciplines of geomorphology and ecosystems ecology and the papers presented at the symposium the papers in this volume illustrate the current status of the disciplines the difficulties in bridging the disciplines and the issues that are emerging as research priorities

astronomical forcing of the east asian monsoon mirrored by the composition of pliocene south china sea sediments abstract high precision major and minor element records of pliocene core intervals from ocean drilling program odp site 1145 located in the northern part of the south china sea were generated at a 5 cm approximately 2 kyr resolution from the geochemical data distinct proxies those indicating changes in detrital matter provenance as well as those indicating productivity variations could be derived both the terrigenous input to the northern south china sea k si and variations in productivity ba al show a response to insolation forced monsoon variability while the fluvial input k si responds to changes in the summer monsoon productivity increases as documented by ba enrichments seem to reflect variations in winter monsoon intensity a stronger winter monsoon may have increased nutrient availability via dust input and or upwelling phenomena according to our geochemical proxy records summer and winter monsoons are approximately 180 out of phase this may imply forcing of the winter monsoon through southern hemisphere summer insolation maxima the k si ratio shows a linear correlation with the la90 1 0 5 northern hemisphere summer insolation record and has therefore been used to create an astronomical timescale for the investigated sediments of odp site 1145 carbonate contents and corresponding color reflectances display 41 and 100 kyr cycles we propose that these do not reflect glacial cycles but are rather the result of an interference signal of dilution by fluvial and eolian terrigenous material and carbonate production burial flux a sudden onset of gradual changes in sediment composition occurs after 3 0 ma this is also documented by an increase in sedimentation rates and may be caused by enhanced fluvial input from the pearl river due to intensified weathering rates on the asian continent this may be linked to tectonic processes around the himalayan tibetan complex and its consequences regarding land sea heating and atmospheric circulation

late pleistocene variability of arabian sea summer monsoon winds and continental aridity eolian records from the lithogenic component of deep sea sediments the modern indian ocean summer monsoon is driven by differential heating between the asian continent and the indian ocean to the south this differential heating produces a strong pressure gradient which drives southwest monsoon winds during june july and august satellite and meteorological observations aerosol measurements sediment trap studies and mineralogical studies indicate an atmospheric mode of transport for modern lithogenic sediments in the northwest arabian sea analyses of lithogenic grain size and mass accumulation rate mar records from the owen ridge indicate that eolian transport has been the primary mode of transport for the past 370 kyr visual inspection shows that the mar record is positively correlated with global ice volume as indicated by the marine 18o record in contrast the grain size record varies at a much higher frequency showing little correlation to either the mar or the 18o records spectral analyses confirm these relationships indicating that the lithogenic grain size and mar records are coherent only over the precession band whereby the grain size leads the mar by 124 8 kyr we conclude that an eolian transport mechanism is the only mechanism that allows for this phase difference and at the same time is supported by comparison of the grain size and mar with independent eolian records we use lithogenic grain size as a paleoclimatic indicator of summer monsoon wind strength and lithogenic mar as a paleoclimatic indicator of source area aridity these interpretations are supported by comparison of the lithogenic records to independent indicators of wind strength globigerina bulloides upwelling record and aridity a loess record from central china such comparisons indicate high coherence and zero phase relationships our work supports the findings of previous studies which have documented the link between monsoon strength and the earth s axial precession cycles both the lithogenic mar and the grain size records have high coherency with precessional insolation maximum lithogenic mar source area aridity is in phase with 18o global ice volume and leads maximum precessional insolation by 88 6 kyr we attribute this lead to the influence of glacial conditions on the aridity and therefore the deflation potential of the source areas maximum lithogenic grain size summer monsoon wind strength lags maximum precession by 148 9 kyr we attribute this lag both to the influence of global and or local ice volume and to the availability of latent heat from the southern hemisphere indian ocean the two of which combine to determine the strength of the indian ocean monsoon

aspects of dynamics of the middle atmosphere inferred by using data from a satellite and from a numerical model the data used in this study are from a stratospheric sounding unit ssu on a polar orbiting satellite and from a numerical model of the middle atmosphere based on the primitive equations they are used to discuss the dynamics of the major stratospheric warming of 1984 85 the warming is of note because the westerly circulation started to break down rapidly when the westerly vortex was larger than might be expected of a state pre conditioned for a major warming at the height of the warming there is a sudden loss of high values of ertel s potential vorticity on isentropic maps derived from the ssu ground based measurements and a simulation of the warming with the numerical model indicate that strong gradients of temperature arise in westward sloping fronts which the ssu is unable to resolve fully the simulated stratospheric fronts have features in common with observed fronts that form in the upper troposphere although there may turn out to be dynamical differences between the two cases

a note on orbital control of equator pole heat fluxes we note that orbital milankovitch variations in particular the precession of the equinoxes can lead to profound variations in the flux of heat from the tropics to higher latitudes the mechanism involves changing the intensity of the hadley circulation by varying the maximum displacement from the equator of the zonally averaged surface temperature maximum in summer the precession of the equinoxes causes this quantity to vary by more than a factor of 2 the intensity of the hadley circulation has a major influence on the heat fluxes in the winter hemisphere summer heat fluxes are generally small although the precession cycle is characterized by periods in the neighborhood of 20000 years the variations are modulated by the eccentricity whose variation is dominated by periods in the neighborhood of 100000 years and 400000 years we show how the fact that both small and large heat fluxes lead to low snowfall and hence small glacial accumulation causes the demodulation of the heat flux leading to dominant eccentricity periods in the resulting glaciation

the fate of soil organic carbon upon erosion transport and deposition in agricultural landscapes a review of different concepts abstract erosion and deposition redistribute large quantities of sediment and soil organic carbon soc in agricultural landscapes in the perspective of global carbon cycling the coupling between erosion processes and the fate of soc is of particular interest however different concepts have been proposed to assess the impact of erosion induced lateral and vertical carbon fluxes on landscape scale this resulted in contrasting conclusions if agricultural soils represent either a carbon sink or source the large global area of arable soil and generally high erosion rates make these insights important in this review we aim to give an overview of the different conceptual relations described governing c dynamics at sites of erosion along the transport pathway and at depositional sites and the current state of knowledge on the fate of soc upon erosion transport and deposition in agricultural landscapes the impact of erosion on soc dynamics differs for sites of erosion deposition and during transport with further influences by agricultural practices e g tillage and fertilisation controlling processes are the detachment of sediment and soc net primary production resulting in dynamic replacement and changes in mineralisation upon transport and deposition due to aggregate breakdown and deep burial respectively however the exact magnitude and dominance of these processes are debated resulting in a controversy whether arable land functions as a sink or source for atmospheric co2 global estimations range between a net sink strength of 0 06 1 versus a source of 0 27 1 14 gt c yr 1 for agricultural soils an eco geomorphologic approach which encompasses physical and biological driven factors e g spatio temporal variation in biological geomorphological and biological processes environmental conditions mineralisation and net primary production is of importance to balance the carbon budget and ascertain sink or source formation at landscape scale high spatio temporal variability on process scale imposes constrains to measure and model the fate of soc upon erosion with limited quantitative data available prospective research across the landscape eroding sites transport pathway and depositional sites should include all relevant processes at broad temporal and spatial scales definitive resolution of the sink source controversy lies in further eco geomorphologic research on the fate of soc focussing on long term and spatial extensive monitoring studies combined with advanced measuring modelling and extrapolation techniques to cover broad spatio temporal soc dynamics ascertainment of carbon dynamics in agricultural landscapes provides important insights to balance the carbon budget and finally holds the answer on sink source formation

modeling impacts of erosion and deposition on soil organic carbon in the big creek basin of southern illinois abstract land use land cover lulc plays an important role in influencing the spatial intensity of water erosion which is the primary governor of horizontal translocation of soil organic carbon soc the fate of redistributed soc through erosion remains debatable and the mineralization rate of exposed soc protected in soil aggregates is the major focus of this argument cohesive spatially explicit modeling of soc and erosion can potentially reduce some of the controversy to this end we simulated erosion deposition and photosynthetic in situ flux of soc in a small watershed of 28 42 ha located in the big creek basin of southern illinois the main objectives of this research were a to study erosion and deposition dynamics under different lulc b to examine the extent of carbon dislocation and deposition possible in the study area and c to determine the net soc accretion and reduction possible by accounting for gains through annual photosynthesis and deposition and losses from erosion under different lulc scenarios to fulfill our objectives we combined geowepp an erosion deposition process model with century 4 0 an ecosystem model used for simulating soc our results show that between 11 and 31 of the eroded soil gets deposited in the same basin depending on the lulc type leaving the remainder to be transported downstream additionally as expected soc flux due to erosion and deposition varies with the type of management practices in the case of conservation management practices the flux associated with erosion and deposition remains below 10 in comparison to in situ soc transformations due to annual photosynthesis however in the case of non conservation management practices this proportion rises above 50

simulations of dynamics and transport during the september 2002 antarctic major warming abstract a mechanistic model simulation initialized on 14 september 2002 forced by 100 hpa geopotential heights from met office analyses reproduced the dynamical features of the 2002 antarctic major warming the vortex split on 25 september recovery after the warming westward and equatorward tilting vortices and strong baroclinic zones in temperature associated with a dipole pattern of upward and downward vertical velocities were all captured in the simulation model results and analyses show a pattern of strong upward wave propagation throughout the warming with zonal wind deceleration throughout the stratosphere at high latitudes before the vortex split continuing in the middle and upper stratosphere and spreading to lower latitudes after the split three dimensional eliassen palm fluxes show the largest upward and poleward wave propagation in the 0 90 e sector prior to the vortex split coincident with the location of strongest cyclogenesis at the model s lower boundary with an additional re

a 300 kyr record of upwelling off oman during the late quaternary evidence of the asian southwest monsoon in the northwest arabian sea upwelling occurs each summer driven by the strong sw monsoon winds upwelling results in high biological productivity and a distinctive assemblage of plankton species in the surface waters off oman that are preserved in the sediments along the oman continental margin creating a geologic record of monsoon driven upwelling sediments recovered from the oman continental margin during ocean drilling program leg 117 provide an opportunity to examine how upwelling has varied during the late quaternary spanning a longer interval than piston cores recovered prior to the odp cruise variations in foraminifer shell accumulation and in the relative abundance of globigerina bulloides indicate dominant cycles of variation at 1 100 kyr the dominant frequency of glacial interglacial variations and at 1 23 kyr the frequency of precessionally driven cycles in seasonal insolation the strongest monsoon winds indicated by increased upwelling occurred during interglacial times when perihelion was aligned with the summer solstice an orbital change that increased the insolation received during summer in the northern hemisphere during glacial times upwelling was reduced and although the precessional cycles were still present their amplitude was smaller at both frequencies the upwelling cycles are in phase with minimum ice volume evidence that glacial interglacial climate changes also include changes to the climate system that influence the low latitude monsoon we attribute the decrease in the monsoon winds observed during glacial times to changes in bare land albedo over asia and or to changes in the areal extent and seasonal cycle in asian snow cover that decrease the summer land sea temperature contrast other mechanisms may also be involved these new upwelling time series differ substantially from previous results however the previous work relied on cores located farther offshore where upwelling is less intense and other physical mechanisms become important our results support the observations derived from atmospheric general circulation models of the atmosphere that indicate that both glacial boundary conditions and the strength of summer insolation are important variables contributing to cycles in the monsoon winds during the late quaternary

interdecadal variability over the north pacific in a multi century climate simulation interdecadal variability in the north pacific region is investigated in a 500 y control integration of the hamburg echam lsg coupled ocean atmosphere general circulation model the spectrum is predominantly red but a significant peak with a period of about 18 y is detected in the spectrum of sea surface temperature sst this peak is shown to be associated with an irregular oscillation that involves both the model ocean and atmosphere the sst sea level pressure and geopotential height at 500 hpa all undergo a primarily standing oscillation with an extensive monopole structure centered near the date line the surface anticyclone is situated to the northeast of the warm sst anomaly and there is a small westward tilt with height temporal changes are approximately in phase the anomalous surface heat flux accompanying the warm phase of sst is primarily out of the ocean but is compensated by anomalous warm advection by surface currents allowing the sst anomaly to persist oceanic thermocline anomalies propagate northward in the western pacific and lag the atmosphere indicating a disequilibrium with the atmosphere sub surface thermal advection appears to play an important role a comparison is made between the model s 18 y oscillation and oscillatory components identified in an analysis of the gisst observational sst dataset which have periods of approximately 6 and roughly 30 y

the development of narrow baroclinic zones and other small scale structure in the stratosphere during simulated major warmings numerical simulations of stratospheric major warmings with a multi level primitive equation model of the stratosphere and mesosphere reveal several examples of processes giving rise to small scale structure in the simulated flow for a simulation of the warming of 1984 85 the following examples are cited 1 the maintenance of the aleutian high by injections of air with low values of potential vorticity 2 the erosion of the main cyclonic vortex as it is stripped of air with high values of potential vorticity 3 the merger of a pair of anticyclones at the height of the warming 4 differential advection of potential vorticity in a vertically sheared flow and 5 the generation in the stratosphere of narrow baroclinic zones with strong temperature gradients in the horizontal and in the vertical for a simulation of the warming of 1979 the example given is of the in situ generation in the stratosphere of inertio gravity waves near a developing baroclinic zone the dynamics involved in the formation of narrow baroclinic zones in the simulated stratosphere is studied in some detail it is shown that the ageostrophic flow mainly the vertical motion provides a positive feedback on the frontogenetic effect of the geostrophic large scale flow similarities and differences with frontogenesis at the ground and in the upper troposphere are enumerated

a major stratospheric sudden warming event in january 2009 abstract the major stratospheric sudden warming ssw event of january 2009 is analyzed using the japan meteorological agency jma climate data assimilation system jcdas this ssw event is characterized by the extraordinary predominance of the planetary scale wave of zonal wavenumber 2 wave 2 the total amount of the upward eliassen palm ep flux for wave 2 was the strongest since the winter of 1978 79 it is found that the remarkable development of the upper troposphere ridge over alaska played important roles in the ssw in january 2009 during the first development stage the ridge excited wave packets upward as well as eastward over around alaska the eastward propagating packets intensified a trough over eastern siberia which led to the development of the planetary wave over eastern siberia during the second development stage the results of this study indicate that the pronounced wave 2 pattern observed in the stratosphere was brought about by accumulative effects of rather localized propagati

impact of enso on east asian winter monsoon during interglacial periods effect of orbital forcing orbital forcing influences climate phenomena by changing incoming solar radiation in season and latitude here changes in the el nino southern oscillation enso s impact on the east asian winter monsoon eawm due to orbital forcing especially for three selected time periods in each of two interglacial periods the eemian 126 122 115 ka and holocene 9 6 0 ka are investigated there was a high negative correlation between enso and eawm when the obliquity was low the processional angle was large and especially when accompanied by large eccentricity which corresponds to a weaker monsoon period the correlation was also high when enso variability was high which interestingly corresponded to lower obliquity and higher degree precession periods therefore as both lower obliquity and higher degree precession such as during 115 ka and 0 ka cause the eawm to be weakened through higher winter insolation over northern hemisphere and the enso to be enhanced through an intensified zonal contrast of the equatorial sea surface temperature the relationship between the enso and eawm becomes tighter the opposite case i e during 126 and 9 ka is also true dynamically furthermore the sensitivity of boreal winter precipitation against sea surface temperature sst anomaly over the tropical pacific which depends on mean sst was positively correlated to the strength of the enso eawm correlation implying that the warmer mean ocean surface causes the strong response of atmosphere to change in the sst anomaly thereby enhancing the impact of enso on eawm warmer wintertime tropical sst is attributed to higher insolation over the tropics especially during 115 and 0 ka while cooler ssts occurred during 126 and 9 ka

expression of seasonal and enso forcing in climatic variability at lower than enso frequencies evidence from pleistocene marine varves off california abstract upper pleistocene marine sediments along the upper continental slope off northern and central california contain alternations of varved and bioturbated sediments and associated changes in biota and sediment composition these alternations can be related to conditions that accompany el nino and anti el nino enso circulation anti el nino conditions are characterized by increased upwelling and productivity and by low concentrations of dissolved oxygen in the oxygen minimum zone that resulted in varve preservation el nino conditions are characterized by little or no upwelling low productivity and higher concentrations of dissolved oxygen that resulted in zones of bioturbation alternations of varves and zones of bioturbation that range from decades to millennia occur through the upper pleistocene section the inferred long term alternations in el nino and anti el nino conditions appear to be a re expression of enso s primary 3 7 year cycle decadal to millennial cycles of productivity associated with el nino and anti el nino conditions may have served as a carbon pump and transferred atmospheric co 2 to the marine reservoir changes in sediment composition and organisms associated with el nino or anti el nino conditions can be related to both seasonal and enso phenomena expression of these changes at lower than enso frequencies may be partly explained by adding the effects of seasonal variability to effects produced by a self oscillating enso system however deterministic mechanisms including solar modulation of enso may also contribute to long term alternations of el nino and anti el nino conditions

a climatology of stratospheric polar vortices and anticyclones 1 united kingdom meteorological office global analyses from 1991 to 2001 are used to create a global climatology of stratospheric polar vortices and anticyclones new methodologies are developed that identify vortices in terms of evolving three dimensional 3 d air masses a case study illustrates the performance of the identification schemes during february and march of 1999 when a merger of anticyclones led to a stratospheric warming that split the arctic polar vortex the 3 d structure and temporal evolution of the arctic vortex and identified anticyclones demonstrates the algorithm s ability to capture complicated phenomena the mean geographical distribution of polar vortex and anticyclone frequency is shown for each season the frequency distributions illustrate the climatological location and persistence of polar vortices and anticyclones a counterpart to the aleutian high is documented in the southern hemisphere the australian high the temporal evolution of the area occupied by polar vortices and anticyclones in each hemisphere is shown as a function of potential temperature large polar vortex area leads to an increase in anticyclone area which in turn results in a decrease in the size of the polar vortex during northern winter and southern spring 9 years of daily anticyclone movement are shown on the 1200 k 36 km 4 hpa isentropic surface preferred locations of anticyclogenesis are related to cross equatorial flow and weak inertial stability regimes of traveling and stationary anticyclones are discussed index terms 3309 meteorology and atmospheric dynamics climatology 1620 3319 meteorology and atmospheric dynamics general circulation 3334 meteorology and atmospheric dynamics middle atmosphere dynamics 0341 0342 keywords polar vortex stratospheric anticyclones

new arabian sea records help decipher orbital timing of indo asian monsoon abstract a recent study suggested that indian monsoonal proxies commonly used in the arabian sea in general productivity proxies could be impacted by changes in the atlantic overturning rate amoc throughout a control on the nutrient delivery into the euphotic zone this oceanic mechanism could lead to a misunderstanding between the indian summer monsoon sm and orbital forcing and could confuse a direct comparison with other archives derived from other monsoonal sub systems such as east asian or african records here we analyze three independent proxies bromine foraminifera assemblages and grain size extracted from a marine sediment core md04 2861 covering the last 310 ka and retrieved in the northern arabian sea near the makran margin an area influenced by summer and winter indian monsoon the grain size proxy deals with the regional continental climate through fluvial and eolian processes it cannot be linked to changes in nutrient content of amoc and present the same phase relationship timing than the other sm proxies this demonstrates that the productivity signals bromine in the northern arabian sea are mainly controlled by sm dynamics and not amoc modulated nutrients at orbital scale changes we thus build a multi proxy record of sm variability i e sm stack using statistical tools principal component analysis further compiled on an age model constructed independently from orbital tuning we find that strong sm lag by 9 1 ka the nh summer insolation maximum minimum of precession june 21 perihelion and obliquity maximum in the precession band and by 6 1 3 ka in the obliquity band these results are consistent with previous studies based on marine and terrestrial records in both indian and asian regions except asian speleothems our study supports the hypothesis that internal climate forcing decreased ice volume together with the increase of latent heat export from the southern indian ocean set the timing of strong indo asian summer monsoons within both the precession and obliquity cycle the external forcing direct sensible heating initiate monsoonal circulation strong indian winter monsoon wm occurs between ice maxima and northern hemisphere sensible heat minima indicating that both act to strengthen wm circulation the summer and winter monsoons are in antiphase in the precession band suggesting that the two systems are dynamically linked

late quaternary east asian monsoon variability in the south china sea evidence from planktonic foraminifera faunal and hydrographic gradient records the surface hydrographic conditions of the south china sea scs are influenced strongly by fluctuations of the east asian monsoon eam long term fluctuations of the eam have been previously investigated through analysis of several proxy records obtained from scs sediment cores however in this marginal sea interpretation of these records is complicated by ice volume sea level effects here we have extracted east west hydrographic gradients from two images core records in the scs which are proposed to indicate monsoon variability this strategy minimizes the effect of ice volume sea level on the monsoon signal highresolution records of planktonic foraminifer faunal assemblages and sea surface temperature sst of the last 135 kyr have been generated for two cores taken off the vietnam margin md012394 in the western scs and near palawan island md972142 in the southeastern scs these core sites represent contrasting hydrographic conditions in modern monsoon climates where the winter eam drives cold and strong mixing conditions in the western scs but maintains warm and deep thermocline conditions in the southeastern scs a planktonic foraminifera hydrographic index pfhi is established based on the abundance ratios of warm thermocline and cold mixing species assemblages and sst estimates from a modern analogue technique mat the records of the east west gradients for pfhi pfhi and for sst sst between the two cores md012394 and md972142 show a dominance of 23 kyr precession cycles in the precession cycles the pfhi and sst increased at the december 21 perihelion which is associated with seasons of minimum northern hemisphere winter and maximum southern hemisphere summer insolation cross spectral analysis between pfhi sst and the precession cycles indicates coherent and in phase relationships considering that the december 21 perihelion of the cycle of precession accorded with the time of maximum summer insolation in the southern hemisphere we suggest that the scs variability of hydrographic gradients for the last 135 kyr has been dominated by winter monsoon dynamics in response to geographic forcing controlled by the strength of the australian summer monsoon

soil and soil organic carbon redistribution on the landscape patterns of soil organic carbon soc vary widely across the landscape leading to large uncertainties in the soc budget especially for agricultural landscapes where water tillage and wind erosion redistributes soil and soc across the landscape it is often assumed that soil erosion results in a loss of soc from the agricultural ecosystem but recent studies indicate that soil erosion and its subsequent redistribution within fields can stimulate carbon sequestration in agricultural ecosystems this study investigates the relationship between soc and soil redistribution patterns on agricultural landscapes soil redistribution erosion and deposition patterns were estimated in three tilled agricultural fields using the fallout 137cesium technique 137cs and soc concentrations of upland soils are significantly correlated in our study areas upland areas eroding have significantly less soc than soils in deposition areas soc decreased as gradient slope increases and soils on concave slopes had higher soc than soils on convex slopes these data suggest that soil redistribution patterns and topographic patterns may be used to help understand soc dynamics on the landscape different productivity and oxidation rates of soc of eroded versus deposited soils also contribute to soc spatial patterns however the strong significant relationships between soil redistribution and soc concentrations in the upland soil suggest that they are moving along similar physical pathways in these systems our study also indicates that geomorphic position is important for understanding soil movement and redistribution patterns within a field or watershed such information can help develop or implement management systems to increase soc in agricultural ecosystems

a 350 000 year summer monsoon multi proxy stack from the owen ridge northern arabian sea five summer monsoon proxies from the northern arabian sea are combined using stacking and principal components analysis pca to create two very similar multi proxy records of summer monsoon variability the five individual proxies all respond to monsoon variability but are largely independent in terms of the processes that complicate their interpretation as summer monsoon indicators e g preservation dissolution diagenesis sediment reworking as such stacking and pca average out non monsoon variance yielding a more pure monsoon signal these stacked and pca records hereafter summer monsoon stack and summer monsoon factor allow evaluation of relative monsoon strength through time as well as the relative concentration of variance within orbital bands these two parameters are less reliable when estimated from individual proxy records in fact the summer monsoon factor smf accounts for only 33 of the total variance in the five records suggesting that relative amplitude variations in each individual proxy time series are influenced by non monsoon processes the summer monsoon stack sms and smf are spectrally very similar dominated by variance in the 41 k y obliquity and 23 k y precession bands there is very little variance at the 100 k y eccentricity band associated with large scale changes in global ice volume indeed equally strong monsoons occur in both glacial and interglacial intervals within the 23 k y precession cycle monsoon maxima fall at 121 relative to precession minima june 21 perihelion maximum northern hemisphere nh summer insolation this phase falls midway between 18o minima 78 and december 21 perihelion 180 indicating that two mechanisms exert equal influence in determining the timing of strong summer monsoons within the precession band 1 sensible heating of the asian plateau which is maximized at times of ice volume minima 78 and 2 latent heat export from the southern subtropical indian ocean which is maximized at times of december 21 perihelion 180 the seasonal cycle at december 21 perihelion is characterized by warm southern hemisphere sh summers followed by cold sh winters a combination that preconditions the ocean to export latent heat during the boreal summer monsoon season summer monsoon winds transport this latent heat into asia where it is released during precipitation enhancing the asian monsoon low within the 41 k y obliquity cycle monsoon maxima are in phase with obliquity maxima this indicates that two mechanisms quite similar to those in the precession band influence the timing of strong summer monsoons in the obliquity band 1 sensible heating of the asian plateau but with no ice volume delay and 2 latent heat export from the southern subtropical indian ocean which is maximized at times of obliquity maxima again the seasonal cycle at obliquity maximum is characterized by warm sh summers followed by cold sh winters ideal for maximizing latent heat export during the boreal summer monsoon

nonstationary phase of the plio pleistocene asian monsoon paleoclimate records indicate that the strength of the asian summer monsoon is sensitive to orbital forcing at the obliquity and precession periods 41 000 and 23 000 years respectively and the extent of northern hemisphere glaciation over the past 2 6 million years the timing phase of strong monsoons has changed by 83 degrees in the precession and 124 degrees in the obliquity bands relative to the phase of maximum global ice volume inferred from the marine oxygen isotope record these results suggest that one or both of these systems is nonstationary relative to orbital forcing

alluvial and colluvial sediment storage in the geul river catchment the netherlands combining field and modelling data to construct a late holocene sediment budget abstract we used a combined approach of a two dimensional erosion and hillslope sediment delivery model watem sedem and detailed geomorphological reconstructions to quantify the different components in a sediment budget for the geul river catchment southern netherlands since the high middle ages hillslope erosion and colluvium deposition were calculated using the model while floodplain storage was estimated using field data our results show that more than 80 of the total sediment production in the catchment has been stored as colluvium mostly generated by hillslope erosion while almost 13 is stored in the floodplain since the high middle ages this situation resembles a capacity limited system model results for the period prior to the high middle ages with a nearly completely forested catchment show that far less sediment was generated and that most of the sediments were directly transported to the main river valleys or out of the catchment a supply limited system geomorphological analysis of a large alluvial fan shows the sensitivity of the study area to changes in the percentage of arable land our combined field data modeling study presents an elegant method to calculate a catchment sediment budget for a longer period and is able to identify and quantify the most important sediment storage elements furthermore it provides a valuable tool to calculate a sediment budget while only limited dated fluvial sediment sequences are available

organic carbon in icelandic andosols geographical variation and impact of erosion abstract the extensive soil erosion in iceland during the past millennium has led to an irregular distribution of soil organic carbon soc intact and fully vegetated areas typically have andosols with large amounts of organic carbon whereas eroded areas are barren deserts with little organic carbon we estimate the amount of organic carbon eroded during the past millennium is 120 500 106 t whereas the total organic carbon in icelandic soils is 2 1 109 t approximately half of the eroded organic carbon 60 250 106 t c has been oxidized and released to the atmosphere current ongoing losses of soc are estimated to be 50 100 103 t c yr 1 we also consider procedures for sequestering carbon to restore the carbon dynamics of denuded areas

floodplain sedimentation in the upper mississippi valley natural versus human accelerated abstract understanding the time scales and pathways for response and recovery of rivers and floodplains to episodic changes in erosion and sedimentation has been a long standing issue in fluvial geomorphology floodplains are an important component of watershed systems because they affect downstream storage and delivery of overbank flood waters and they also serve as sources and temporary sinks for sediments and toxic substances delivered by river systems here 14c and 137cs isotopic dating methods are used along with ages of culturally related phenomena associated with mining and agriculture to determine rates of sedimentation and morphologic change for a reach of the upper mississippi river and adjacent tributaries in southwestern wisconsin and northwestern illinois the most important environmental change that influenced fluvial activity in this region during last 10 000 years involved the conversion of a late holocene mosaic of prairie and forest to a landscape dominated by cropland and pastureland associated with euro american settlement results presented herein for the upper mississippi valley umv show that the shift from pre agriculture natural land cover to landscape dominance by agricultural land use of the last 175 200 years typically increased rates and magnitudes of floodplain sedimentation by at least an order of magnitude accelerated overbank flooding led to increased bank heights on tributary streams and in turn contributed to more frequent deep flows of high energy these high energy flows subsequently promoted bank erosion and lateral channel migration and the formation of a historical meander belt whose alluvial surface constitutes a new historical floodplain inset against the earlier historical floodplain the new historical floodplain serves as a flume like channel that provides efficient downstream transport of water and sediment associated with moderate and large magnitude floods floodplains on lower tributaries however continue to experience rates of overbank sedimentation that are of anomalously high magnitude given improved land cover and land conservation since about 1950 this lower valley anomaly is explained by minimal development of historical agriculture period meander belts because of relatively low stream power in these channel and floodplain reaches of relatively low gradient in general long term pre agriculture rates of vertical accretion between about 10 000 and 200 years ago averaged about 0 2 mm yr 1 in tributary watersheds smaller than about 700 km2 and about 0 9 mm yr 1 on the floodplain of the upper mississippi river where the contributing watershed area increases to about 170 000 km2 on the other hand rates of historical vertical accretion during the period of agricultural dominance of the last 200 years average between 2 and 20 mm yr 1 with short episodes of even higher rates during times of particularly poor land conservation practices significant hydrologic effects of mining and agricultural started by the 1820s and became widespread in the study region by the mid 19th century the hydrologic and geomorphic influences of mining were relatively minor compared to those related to agriculture high resolution dating of floodplain vertical accretion deposits shows that large floods have frequently provided major increments of sedimentation on floodplains of tributaries and the main valley upper mississippi river the relative importance of large floods as contributors to floodplain vertical accretion is noteworthy because global atmospheric circulation models indicate that the main channel upper mississippi river should experience increased frequencies of extreme hydrologic events including large floods with anticipated continued global warming instrumental and stratigraphic records show that coincident with global warming a shift to more frequent large floods occurred since 1950 on the upper mississippi river and these floods generally contributed high magnitudes of floodplain sedimentation

the southwest indian monsoon over the last 18 000 years previously published results suggest that the strength of the sw indian monsoon can vary significantly on century to millenium time scales an observation that has important implications for assessments of future climate and hydrologic change over densely populated portions of asia we present new well dated multi proxy records of past monsoon variation from three separate arabian sea sediment cores that span the last glacial maximum to late holocene to a large extent these records confirm earlier published suggestions that the monsoon strengthened in a series of abrupt events over the last deglaciation however our data provide a somewhat refined picture of when these events took place and suggest the primacy of two abrupt increases in monsoon intensity one between 13 and 12 5 ka and the other between 10 and 9 5 ka this conclusion is supported by the comparisons between our new marine data and published paleoclimatic records throughout the african asian monsoon region the comparison of data sets further supports the assertion that maximum monsoon intensity lagged peak insolation forcing by about 3000 years and extended from about 9 5 to 5 5 ka the episodes of rapid monsoon intensification coincided with major shifts in north atlantic european surface temperatures and ice sheet extent this coincidence coupled with new climate model experiments suggests that the large land sea thermal gradient needed to drive strong monsoons developed only after glacial conditions upstream of and on the tibetan plateau receded cold north atlantic sea surface temperatures european ice sheets and extensive asian snow cover it is likely that abrupt changes in seasonal soil hydrology were as important to past monsoon forcing as were abrupt snow related changes in regional albedo our analysis suggests that the monsoon responded more linearly to insolation forcing after the disappearance of glacial boundary conditions decreasing gradually after about 6 ka our data also support the possibility that significant century scale decreases in monsoon intensity took place during the early to mid holocene period of enhanced monsoon strength further highlighting the need to understand paleomonsoon dynamics before accurate assessments of future monsoon strength can be made

terrestrial sedimentation and the carbon cycle coupling weathering and erosion to carbon burial this paper examines the linkages between the carbon cycle and sedimentary processes on land available data suggest that sedimentation on land can bury vast quantities of organic carbon roughly 1015 g c yr 1 to evaluate the relative roles of various classes of processes in the burial of carbon on land terrestrial sedimentation was modeled as a series of 864 scenarios each scenario represents a unique choice of intensities for seven classes of processes and two different global wetland distributions comparison was made with presumed preagricultural conditions the classes of processes were divided into two major component parts clastic sedimentation of soil derived carbon and organic sedimentation of autochthonous carbon for clastic sedimentation masses of sediment were considered for burial as reservoir sediment lake sediment and combined colluvium alluvium and aeolian deposits when the ensemble of models is examined the human induced burial of 0 6 1 5 1015 g yr 1 of carbon on land is entirely plausible this sink reaches its maximum strength between 30 and 50 n paddy lands stand out as a type of land use that warrants future study but the many faces of rice agriculture limit generalization in an extreme scenario paddy lands alone could be made to bury about 1 1015 g c yr 1 arguing that terrestrial sedimentation processes could be much of the sink for the so called missing carbon is reasonable such a hypothesis however requires major redesign of how the carbon cycle is modeled unlike ecosystem processes that are amenable to satellite monitoring and parallel modeling many aspects of terrestrial sedimentation are hidden from space

late pleistocene and holocene aeolian dust deposition in north china and the northwest pacific ocean abstract rates of dust deposition in the north pacific and the central loess plateau of china show a poor correlation during the last 30 000 yr although in both cases the dust was derived from deserts in northern china loess accumulation rates were high at the time of the last glacial maximum while dust flux to the north pacific was low at this time maximum dust flux to the north pacific is recorded in the mid holocene but holocene rates of loess accumulation have been low these differences are shown to reflect the different nature of the wind conditions responsible for dust transport to the loess plateau and the north pacific dust transport responsible for formation of the loess occurred mainly in the lower 1 5 km of the atmosphere and was accomplished by cold low level northwesterly winds associated with cold waves emanating from the mongolian anticyclone at present such conditions occur quite frequently in winter but during the coldest phases of the pleistocene they probably also occurred in the spring and summer long range dust transport from northern china to the north pacific requires that the dust is lifted to high levels above 3 km where it can be incorporated into the strong mid latitude westerlies strong vertical motions of the atmosphere occur most frequently in the spring when the mongolian anticyclone begins to weaken and frontal depressions move across the deserts of northern china such frontal depressions were probably more frequent during the climatic optimum of the mid holocene and during previous interglacials changes in continental aridity have probably played a minor role in controlling the magnitude of the dust flux to the north pacific

dispersion properties of the flow in the southern stratosphere during winter and spring the strateole project organized by france s centre national de la recherche scientifique cnrs will release a large number of isopycnal balloons to drift in the lower stratosphere of the southern hemisphere in preparation for strateole this paper studies the structure and dispersion properties of the flow in the lower stratosphere at high southern latitudes during winter and spring the approach for investigation is based on computing trajectories of fluid parcels and isopycnal balloons using the velocity field obtained on line during simulations with a three dimensional primitive equation model of the stratosphere and mesosphere a scheme for computation of isopycnal balloon trajectories is devised and a method for estimating the location of the polar night vortex edge is developed it is found that trajectories of fluid parcels initiated well inside the vortex remain within the vortex for a period of months a small number of fluid parcels released near the vortex edge cross this edge with about an equal number of crossings from inside to outside the vortex as from outside to inside the isopycnal balloons show a stronger tendency to cross the vortex edge than do fluid parcels the relative dispersion properties of the flow in the lower stratosphere are analyzed in the light of theories on two dimensional turbulence it is determined that the flow inside the polar vortex can be considered as quasi two dimensional isotropic homogeneous and stationary for a period of about 6 days outside the vortex the differential advection by the strong westerly flow primarily determines the balloon dispersion the mean square separation between balloons released 2 hours apart within the vortex 70 s 50 mbar increases in time following approximately 1 the kraichnan lin exponential law for small timescales and space scales 1 5 4 days 90 150 km 2 the richardson obukhov t3 law for intermediate timescales and space scales 7 18 days 180 640 km and 3 the asymptotic linear behavior found by babiano et al 1990 for large timescales and space scales 20 40 days 700 1200 km

alluvial sedimentation rates from southeastern australia indicate post european settlement landscape recovery increased catchment sediment yields are common following the introduction of european style agriculture to relatively undisturbed landscapes catchment erosion rates generally increase immediately after disturbance and then decline over time consequently where a catchment currently sits along this disturbance recovery sequence will strongly influence future catchment sediment yields and river morphology in this study field stratigraphy optical dating and hydraulic modelling are used to investigate changes in catchment sediment yield and storage in the lake burragorang catchment in australia with emphasis placed upon changes occurring since european settlement in a d 1820 on the southern tablelands and the upper cox s river subcatchment a large volume of sediment was liberated by gully erosion early in the post settlement period much of which was deposited at break of slope positions below the catchment s headwaters or stored in alluvial benches adjacent to the channel but within the confines of older holocene alluvium a lack of substantial sediment deposition over the last 20 to 40 years is evidence that catchment sediment yields have strongly declined this is consistent with both reduced erosion rates and re aggradation of the incised gullies that in their erosive phase dominated the catchment s post settlement sediment flux collectively these characteristics indicate the catchment is undergoing a phase of landscape recovery

late quaternary atmospheric and oceanographic variations in the western pacific inferred from pollen and radiolarian analyses abstract pollen and radiolarian analyses of sediment from four piston cores located along a south north transect 28 44 n off the east coast of japan yield detailed records of variations in terrestrial and marine climate of this region for the last 140 ka the last interglacial climate of the southern half of japan was characterized by increased temperature and precipitation at least across central japan compared with today off southern japan surface were cooler during summer than at present off central japan both summer and winter sea surface temperatures were cooler than today early glacial 115 71 ka bp climate across central and southern japan alternated between wet and dry warm temperate with surface waters offshore warmer in summer and winter than during the penultimate interglacial temperatures and precipitation in japan reached low levels early during the full glacial phase and remained relatively low throughout much of the full glacial 71 14 ka bp cold sea surface temperatures at all our sites coincided with these cold conditions on land temperatures across much of japan began to increase steadily during the deglacial with surface waters offshore remaining at or near their glacial lows holocene vegetation patterns which continued to reflect an increase in temperature reached a maximum during early to mid holocene surface waters offshore however remained relatively cool during the early holocene with temperature maxima at most western pacific sites occurring in mid to late holocene we propose specific changes in the seasonal positions of atmospheric pressure cells to explain these climate variations that have occurred across the northeast asian northwest pacific region through the most recent interglacial glacial cycle results of this exercise show that there are no major discrepancies between climate reconstructions for mainland japan inferred from pollen and those for the western pacific derived from radiolarians

coherent response of arabian sea upwelling and pollen transport to late quaternary monsoonal winds the indian summer monsoon causes large seasonal changes in the environments of both eastern africa and the arabian sea here we compare time series 140 kyr long of selected pollen types and foraminiferal upwelling faunas preserved in marine sediments to identify the frequencies of their variability and the coherence and phase of the terrestrial and marine responses to monsoonal circulation during interglacial intervals the pollen and upwelling records of the western arabian sea indicate stronger monsoons and are both coherent and in phase at periodicities near the precession of the earth s rotational axis 23 kyr we conclude that the strength of the monsoonal southwesterlies accounts for this high coherence of marine and terrestrial records during interglacial intervals low correlation during glacial phases indicates weaker monsoons and some decoupling of these two records these data indicate that two distinct modes of monsoon variability may exist an interglacial mode with strong monsoons and effective coupling of terrestrial and marine records and a glacial mode with both weaker monsoons and decreased linkage between arabian sea pollen and upwelling records

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

potential vorticity in the stratosphere derived using data from satellites maps of ertel s potential vorticity q are computed on an isentropic surface in the middle of the stratosphere they are derived using data from stratospheric sounding units on board noaa satellites the reliability of the maps is demonstrated mainly by conservation of q that is shown in successive analyses and by the close agreement obtained using independent data from two satellites the maps are used to follow the movement of material during the course of strong disturbances which occurred in december 1981 they clearly show the breaking of planetary waves in the stratosphere an inherently nonlinear process the effect of wave breaking on the structure of the westerly vortex is considered any mixing of q on isentropic surfaces during wave breaking is shown to be far from complete in the examples studied the behaviour of diagnostics based on zonal averaging such as the eliassen palm flux is accounted for by local changes in the distribution of q the implications of our findings for the study of stratospheric dynamics are discussed