kunashir kuriles oak 400 year reconstruction of temperature and relation to the pacific decadal oscillation paleoclimatic records of northwest pacific variations are scarce but can be extended by proxy records from old aged trees around the north pacific rim in july of 2001 on kunashir island at the southern extent of the kuriles tree cores were extracted from century old oaks quercus crispula and developed into a 400 year tree ring width index series analyses showed the ringwidth indices to correlate strongly with summer june september temperatures as recorded at ugno kurilsky on the island the summer temperatures were reconstructed using the tree ring data and 52 of the variance was explained by the tree ring indices the recorded temperature data and the tree ring data show similar correlation patterns with sea surface temperatures ssts of the north pacific studies of north pacific variations as quantified by the pacific decadal oscillation pdo show the pdo to be an important index of large scale climate variation the tree ring series explains more than 33 of the variance of the july september pacific decadal oscillation and has similar spectral properties further supporting the concept of multidecadal variation or shifts in north pacific climate for four centuries d 2004 elsevier b v all rights reserved

role of indian ocean warming in the development of philippine sea anticyclone during enso 1 the anomalous low level anticyclone near the philippines and suppressed convection over the western pacific associated with the mature warm phase of el nino southern oscillation enso have been suggested as important elements in the interaction between enso and the east asian monsoon we examined the causes of these anomalies in the circulation and convection using a newly developed linear baroclinic model that includes interactive moist processes of the cumulus convection and surface heat fluxes a conventional version of the linear model forced by prescribed heating indicates that the diabatic cooling due to suppressed convection over the maritime continent generates the philippine sea anticyclone from a series of the moist linear model experiments we found that the modest warming of the indian ocean in addition to the strong warming in the central eastern pacific and weak cooling in the western pacific is significant to suppress the convection over the maritime continent observed data also show a coincidence of the development between the philippine sea anticyclone indian ocean warming and the ascending motion over the indian ocean supporting the model results the above results indicate that the atmosphere ocean system in the indian ocean may be one of important factors to improve predictability of the east asian climate during enso

the extreme drought event during winter spring of 2011 in east china combined influences of teleconnection in midhigh latitudes and thermal forcing in maritime continent region abstractthe middle and lower reaches of the yangtze river mlryr in china experienced an extremely severe and persistent drought event from january to may of 2011 using both the observational data and ncep ncar reanalysis features of the drought event and the related circulation anomalies were investigated it is found that the precipitation during the investigated period of 2011 was deficient mostly along the yangtze river the water vapor diverged from mlryr southward into the bay of bengal south china sea and the philippines there were two factors facilitating the drought event one was the quasi stationary rossby wave related teleconnection which propagated eastward at midhigh latitudes from the north atlantic to east asia reinforcing the siberian high and the east asian trough henceforth resulting in the divergence anomalies in mlryr in the lower troposphere this quasi stationary wave train though originating from the north atlantic region was not essentially related to the north atlantic

a new paradigm for the predominance of standing central pacific warming after the late 1990s canonical el nino has a warming center in the eastern pacific ep but in recent decades el nino warming center tends to occur more frequently in the central pacific cp the definitions and names of this new type of el nino however have been notoriously diverse which makes it difficult to understand why the warming center shifts here we show that the new type of el nino events is characterized by 1 the maximum warming standing and persisting in the cp and 2 the warming extending to the ep only briefly during its peak phase for this reason we refer to it as standing cp warming cpw global warming has been blamed for the westward shift of maximum warming as well as more frequent occurrence of cpw however we find that since the late 1990s the standing cpw becomes a dominant mode in the pacific meanwhile the epochal mean trade winds have strengthened and the equatorial thermocline slope has increased contrary to the global warming induced weakening trades and flattening thermocline we propose that the recent predominance of standing cpw arises from a dramatic decadal change characterized by a grand la nina like background pattern and strong divergence in the cp atmospheric boundary layer after the late 1990s the anomalous mean cp wind divergence tends to weaken the anomalous convection and shift it westward from the underlying sst warming due to the suppressed low level convergence feedback this leads to a westward shift of anomalous westerly response and thus a zonally in phase sst tendency preventing eastward propagation of the sst anomaly we anticipate more cpw events will occur in the coming decade provided the grand la nina like background state persists

late pleistocene glaciation of the mt giluwe volcano papua new guinea abstract the mt giluwe shield volcano was the largest area glaciated in papua new guinea during the pleistocene despite minimal cooling of the sea surface during the last glacial maximum glaciers reached elevations as low as 3200 m to investigate changes in the extent of ice through time we have re mapped evidence for glaciation on the southwest flank of mt giluwe we find that an ice cap has formed on the flanks of the mountain on at least three and probably four separate occasions to constrain the ages of these glaciations we present 39 new cosmogenic 36 cl exposure ages complemented by new radiocarbon dates direct dating of the moraines identifies that the maximum extent of glaciation on the mountain was not during the last glacial maximum as previously thought in conjunction with existing potassium argon and radiocarbon dating we recognise four distinct glacial periods between 293 306 ka gogon glaciation 136 158 ka mengane glaciation centred at 62 ka komia glaciation and from 20 3 11 5 ka tongo glaciation the temperature difference relative to the present during the tongo glaciation is likely to be of the order of at least 5 c which is a minimum difference for the previous glaciations during the tongo glaciation ice was briefly at its maximum for less than 1000 years but stayed near maximum levels for nearly 4000 years until about 15 4 ka over the next 4000 years there was more rapid retreat with ice free conditions by the early holocene

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

interactive feedback between enso and the indian ocean abstract a feedback process of the indian ocean sst on enso is investigated by using observed data and atmospheric gcm it is suggested that warming in the indian ocean produces an easterly wind stress anomaly over indonesia and the western edge of the pacific during the mature phase of el nino the anomalous easterly wind in the western pacific during el nino helps a rapid termination of el nino and a fast transition to la nina by generating upwelling kelvin waves thus warming in the indian ocean which is a part of the el nino signal operates as a negative feedback mechanism to enso this indian ocean feedback appears to operate mostly for relatively strong el ninos and results in a la nina one year after the mature phase of the el nino this 1 yr period of phase transition implies a possible role of indian ocean enso coupling in the biennial tendency of the enso atmospheric gcm experiments show that indian ocean sst forcing is mostly responsible for the easterly wind anomalies in the western pacific

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

interannual and interdecadal variations of the east asian summer monsoon and tropical pacific ssts part i roles of the subtropical ridge the interannual relationship between the east asian summer monsoon and the tropical pacific ssts is studied using rainfall data in the yangtze river valley and the ncep reanalysis for 1951 96 the datasets are also partitioned into two periods 1951 77 and 1978 96 to study the interdecadal variations of this relationship a wet summer monsoon is preceded by a warm equatorial eastern pacific in the previous winter and followed by a cold equatorial eastern pacific in the following fall this relationship involves primarily the rainfall during the pre mei yu mei yu season may june but not the post mei yu season july august in a wet monsoon year the western north pacific subtropical ridge is stronger as a result of positive feedback that involves the anomalous hadley and walker circulations an atmospheric rossby wave response to the western pacific complementary cooling and the evaporation wind feedback this ridge extends farther to the west from the previous winter to the following fall resulting in an 850 hpa anomalous anticyclone near the southeast coast of china this anticyclone 1 blocks the pre mei yu and mei yu fronts from moving southward thereby extending the time that the fronts produce stationary rainfall 2 enhances the pressure gradient to its northwest resulting in a more intense front and 3 induces anomalous warming of the south china sea surface through increased downwelling which leads to a higher moisture supply to the rain area a positive feedback from the strong monsoon rainfall also appears to occur leading to an intensified anomalous anticyclone near the monsoon region this sst subtropical ridge monsoon rainfall relationship is observed in both the interannual timescale within each interdecadal period and in the interdecadal scale the sst anomalies sstas change sign in northern spring and resemble a tropospheric biennial oscillation tbo pattern during the first interdecadal period 1951 77 in the second interdecadal period 1978 96 the sign change occurs in northern fall and the tbo pattern in the equatorial eastern pacific sst is replaced by longer timescales this interdecadal variation of the monsoon sst relationship results from the interdecadal change of the background state of the coupled ocean atmosphere system this difference gives rise to the different degrees of importance of the feedback from the anomalous circulations near the monsoon region to the equatorial eastern pacific in a wet monsoon year the anomalous easterly winds south of the monsoon enhanced anomalous anticyclone start to propagate slowly eastward toward the eastern pacific in may and june apparently as a result of an atmosphere ocean coupled wave motion these anomalous easterlies carry with them a cooling effect on the ocean surface in 1951 77 this effect is insignificant as the equatorial eastern pacific sstas already change from warm to cold in northern spring probably as a result of negative feedback processes discussed in enso mechanisms in 1978 96 the equatorial eastern pacific has a warmer mean sst a stronger positive feedback between ssta and the walker circulation during a warm phase tends to keep the ssta warm until northern fall when the eastward propagating anomalous easterly winds reach the eastern pacific and reverse the ssta

two contributors to the glacial co 2 decline it is generally accepted that the glacial drawdown of atmospheric co2 content is the sole result of uptake by the ocean here we make a case that the reduction of planetary co2 outgassing made a significant contribution we propose that the ocean contribution to co2 reduction closely followed northern hemisphere summer insolation and was superimposed on a ramp like decline resulting from a reduction in the input of planetary co2 we base this scenario on new records of 13c and b to ca ratio in cores from the upper and lower portions of the deep atlantic they demonstrate that the waxing and waning of the stratification of atlantic deep water follows summer insolation our thoughts were driven by the observation that over the last 30 kyr the extent of mountain glaciation in both hemispheres appears to have tracked the atmosphere s co2 content suggesting that the connection between orbital cycles and land ice cover is via the ocean instead of a direct connection between ice extent and summer insolation the tie is a modulation of the heat and fresh water budgets of the northern atlantic changes in the boundary conditions lead to reorganizations of ocean circulation and as a consequence changes in co2 storage in the ocean

southern patagonian glacial chronology for the last glacial period and implications for southern ocean climate the magellan region of southern south america is in a unique setting at 50 s on the equatorial side of the antarctic frontal zone to record in detail terrestrial glacial to interglacial events a 10be chronology shows growth and millennial fluctuations of a patagonian ice sheet between 25 and 17 6 17 0 cal ka in the strait of magellan the maximum ice margin position is dated to 24 6 0 9 ka and other moraine ages are 18 5 1 8 and 17 6 0 2 ka mean 1 standard deviation in bahia inutil dated moraine ages are 20 4 1 2 and 17 3 0 8 ka the chronology of the local last glacial maximum lgm reveals a record of atmospheric cooling that was broadly in phase with changes in southern ocean conditions such as sea ice fluctuations and surface water characteristics published modeling results indicate that a decline in temperature of 6 c and slight drying over southernmost patagonia could simulate the growth and sustained presence of an ice sheet to the mapped lgm limit the terrestrial record in southern patagonia and marine records in adjacent oceans indicate mean northward movement of the antarctic frontal zone which caused the last southern south american ice age the antarctic frontal zone at present lies only 3 5 to the south some significant changes in the magellan region occurred in step with north atlantic region and the northern hemisphere for example the overall time span of the last glaciation and the timing of maximum ice extent were similar between the hemispheres despite maximum local summer insolation intensity in southern south america other characteristics of the southern patagonian glacial history differ from the north atlantic region specifically an out of phase relationship during deglaciation which is more similar to that of southern ocean and antarctic records

seawater carbonate ion δ13c systematics and application to glacial interglacial north atlantic ocean circulation seawater carbonate ion and 13c are affected by many processes including biology air sea exchange alkalinity change and mixing between different water masses study of modern ocean data shows that deep ocean carbonate ion and 13c of dissolved inorganic carbon can be used together as useful tracers for deep water mass reconstructions in the past we present records of deep water carbonate ion concentration co32 changes of the north atlantic ocean water column since the last glacial quantitatively reconstructed using benthic foraminiferal boron calcium b ca ratios records from six cores over 1 to 4 km reveal that the carbonate chemistry of the glacial north atlantic was more stratified than the modern ocean with higher co32 by 20 30 mol kg 1 at 1 2 km and lower co32 by 20 mol kg 1 at sites deeper than 3 5 km producing an 800 m glacial shoaling of calcite saturation horizon comparison with benthic foraminiferal 13c and var epsilonnd of fe mn oxide leachates shows that the deep glacial waters with low co32 are consistent with a southern ocean source while those with high co32 but distinct 13c chemistry were supplied by two endemic sources one being the norwegian greenland sea ngs our carbonate ion results suggest that the glacial boundary between north and south sourced deep waters is at 2 8 km significantly deeper than 2 3 km estimated from benthic foraminiferal 13c weakened surface compensation inflow to the ngs promoted cooling and continental ice growth at north high latitude and a deeper boundary may reduce atmospheric co2 sequestration in the deep atlantic implying a greater role of other parts of the ocean

the influence of air sea exchange on the isotopic composition of oceanic carbon observations and modeling although the carbon isotropic composition of ocean waters after they leave the surface ocean is determined by biological cycling air sea exchange affects the carbon isotopic composition of surface waters in two ways the equilibrium fractionation between oceanic and atmospheric carbon increases with decreasing temperature in southern ocean surface waters this isotopic equilibrium enriches delta sup 13 c relative to the delta sup 13 c expected from uptake and release of carbon by biological processes alone similarly surface waters in the subtropical gyres are depleted in delta sup 13 c due to extensive air sea exchange at warm temperatures countering the tendency toward isotopic equilibration with the atmosphere a relatively slow process are the effects of the equilibration of co sub 2 itself a much faster process in regions where there is a net transfer of isotopically light co sub 2 from the ocean to the atmosphere e g the equator surface waters become enriched in sup 13 c whereas in regions where isotopically light co sub 2 is entering the ocean e g the north atlantic surface waters become depleted in sup 13 c a compilation of high quality oceanic delta sup 13 c measurements along with experiments performed using a zonally averaged three basin dynamic ocean model are used to explore these processes 40 refs 14more figs 1 tab less

glacial to holocene redistribution of carbonate ion in the deep sea we have reconstructed the glacial age distribution of carbonate ion concentration in the deep waters of the equatorial ocean on the basis of differences in weight between glacial and holocene foraminifera shells picked from a series of cores spanning a range of water depth on the western atlantic s ceara rise and the western pacific s ontong java plateau the results suggest that unlike today s ocean sizable vertical gradients in the carbonate ion concentration existed in the glacial age deep ocean in the equatorial pacific the concentration increased with depth and in the atlantic it decreased with depth in addition the contrast between the carbonate ion concentration in deep waters produced in the northern atlantic and deep water in the pacific appears to have been larger than in today s ocean

an interdecadal change in the relationship between boreal spring arctic oscillation and the east asian summer monsoon around the early 1970s previous studies suggested that the boreal spring arctic oscillation ao exerts a pronounced influence on the following east asian summer monsoon easm variability this study reveals that the relationship of spring ao with the following easm experienced a significant interdecadal change in the early 1970s the influence of spring ao on the following easm is weak during the 1950s and 1960s but strong and significant during the mid 1970s through the mid 1990s the spring ao related sea surface temperature sst atmospheric circulation and heating anomalies are compared between 1949 71 and 1975 97 results show that the spring ao related cyclonic circulation anomaly over the tropical western north pacific is weaker and located more northward in the former epoch than in the latter epoch correspondingly sst atmospheric circulation and heating anomalies over the tropical north pacific are located more northeastward in the former than latter epoch from spring to summer in the following summer the spring ao related cyclonic circulation anomalies over the tropical north pacific are located farther away from east asia in the former epoch this interdecadal change in the ao easm connection may be attributed to a significant change in the intensity of spring north pacificsynoptic scaleeddyactivityaroundtheearly1970sfromaweakregimetoastrongregime whichinduces a stronger eddy feedback to the low frequency mean flow after the early 1970s this may explain a stronger spring ao related cyclonic circulation over the tropical western north pacific and thus a closer relationship between the spring ao and the following easm in the latter than former epoch

loss of carbon from the deep sea since the last glacial maximum deep ocean carbonate ion concentrations co32 and carbon isotopic ratios 13c place important constraints on past redistributions of carbon in the ocean land atmosphere system and hence provide clues to the causes of atmospheric co2 concentration changes however existing deep sea co32 reconstructions conflict with one another complicating paleoceanographic interpretations here we present deep sea co32 for five cores from the three major oceans quantified using benthic foraminiferal boron calcium ratios since the last glacial period combined benthic 13c and co32 results indicate that deep sea released co2 during the early deglacial period 17 5 to 14 5 thousand years ago was preferentially stored in the atmosphere whereas during the late deglacial period 14 to 10 thousand years ago besides contributing to the contemporary atmospheric co2 rise a substantial portion of co2 released from oceans was absorbed by the terrestrial biosphere

sequestration of carbon in the deep atlantic during the last glaciation atmospheric co2 concentrations declined markedly about 70 000 years ago when the earth s climate descended into the last glaciation much of the carbon removed from the atmosphere has been suspected to have entered the deep oceans but evidence for increased carbon storage remains elusive here we use the b ca ratios of benthic foraminifera from several sites across the atlantic ocean to reconstruct changes in the carbonate ion concentration and hence the carbon inventory of the deep atlantic across this transition we find that deep atlantic carbonate ion concentration declined by around 25 mol kg 1 between 80 000 and 65 000 years ago this drop implies that the deep atlantic carbon inventory increased by at least 50 gt around the same time as the amount of atmospheric carbon dropped by about 60 gt from a comparison with proxy records of deep circulation and climate model simulations we infer that the carbon sequestration coincided with a shoaling of the atlantic meridional overturning circulation we thus conclude that changes in the atlantic ocean circulation may have played an important role in reductions of atmospheric co2 concentrations during the last glaciation by increasing the carbon storage in the deep atlantic

the last glacial maximum at 44 s documented by a 10be moraine chronology at lake ohau southern alps of new zealand abstract determining whether glaciers registered the classic last glacial maximum lgm 26 500 19 000 yrs ago coevally between the hemispheres can help to discriminate among hypothesized drivers of ice age climate here we present a record of glacier behavior from the southern alps of new zealand during the local lgm llgm we used 10 be surface exposure dating methods and detailed glacial geomorphologic mapping to produce a robust chronology of well preserved terminal moraines deposited during the llgm near lake ohau on central south island we then used a glaciological model to estimate a llgm glacier snowline and atmospheric temperature from the ohau glacier record seventy three 10 be surface exposure ages place culminations of terminal moraine construction and hence completions of glacier advances to positions outboard of present day lake ohau at 138 600 10 600 yrs 32 520 970 yrs ago 27 400 1300 yrs ago 22 510 660 yrs ago and 18 220 500 yrs ago recessional moraines document glacier recession into the lake ohau trough by 17 690 350 yrs ago exposure of an ice molded bedrock bench located inboard of the innermost llgm moraines by 17 380 510 yrs ago indicates that the ice tongue had receded about 40 of its overall length by that time comparing our chronology with distances of retreat suggests that the ohau glacier terminus receded at a mean net rate of about 77 m yr 1 and its surface lowered by 200 m between 17 690 and 17 380 yrs ago a long term continuation of ice retreat in the ohau glacier catchment is implied by moraine records at the head of irishman stream valley a tributary of the ohau glacier valley the irishman stream cirque glacier advanced to produce a set of lateglacial moraines at 13 000 500 yrs ago implying that the cirque glacier was less extensive prior to that advance we employed a glaciological model fit to these mapped and dated llgm moraines to derive snowline elevations and temperature parameters from the ohau glacier record the modeling experiments indicate that a snowline lowering of 920 50 m and temperature depression of 6 25 0 5 c below modern values allows for the ohau glacier to grow to an equilibrium position within the lgm moraine belt taken together with a glaciological simulation reported from the irishman stream valley snowlines and temperatures increased by at least 520 m and 3 6 c respectively between 18 000 and 13 000 yrs ago climate parameters derived from the ohau glacier reconstruction are similar to those derived from glacier records from patagonia to air temperature indicators from antarctica as well as to sea surface temperature and stratification signatures of the southern ocean we think that the best explanation for the observed southern llgm is that southern winter duration modulated southern ocean sea ice which in turn influenced southern ocean stratification and made the surface ocean cooler orbitally induced cooling of the southern ocean provides an explanation for the llgm in the southern alps having been coincident with the northern lgm we argue further that the global effect of north atlantic stadials led to disturbance of southern ocean stratification southward shifts of the subtropical front and retreat of southern alps glaciers collapse of southern ocean stratification during heinrich stadial 1 along with attendant sea surface warming triggered the onset of the last glacial termination in the southern alps of new zealand

the evolution of deep ocean chemistry and respired carbon in the eastern equatorial pacific over the last deglaciation the authors acknowledge funding by the spanish ministry of economy industry and competitiveness through grants ctm2009 08849 acdc project and ctm2012 32017 manifest project by generalitat de catalunya through grant 2014sgr1029 marine biogeochemistry and global change research group and by nerc grant ne l006421 1 isabel cacho thanks the icrea academia program from the generalitat de catalunya

glacial water mass geometry and the distribution of δ13c of σco2 in the western atlantic ocean 1 oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa cibicidoides and planulina from 25 new piston cores gravity cores and multicores from the brazil margin the cores span water depths from about 400 to 3000 m and intersect the major water masses in this region these new data fill a critical gap in the south atlantic ocean and provide the motivation for updating the classic glacial western atlantic 13c transect of duplessy et al 1988 the distribution of 13c of co2 requires the presence of three distinct water masses in the glacial atlantic ocean a shallow 1000 m southern source water mass with an end member 13c value of about 0 3 0 5 vpdb a middepth 1500 m northern source water mass with an end member value of about 1 5 and a deep 2000 m southern source water with an end member value of less than 0 2 and perhaps as low as the 0 9 values observed in the south atlantic sector of the southern ocean ninnemann and charles 2002 the origins of the water masses are supported by the meridional gradients in benthic foraminiferal 18o a revised glacial section of deep water 13c documents the positions and gradients among these end member intermediate and deep water masses the large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation

mismatch of glacier extent and summer insolation in southern hemisphere mid latitudes here we address a long standing puzzle of ice age climate called the fly in the ointment of the milankovitch theory using geomorphic mapping and 10be surface exposure dating we show that five moraine belts were formed during maxima of the last ice age by the pukaki glacier in new zealand s southern alps they afford ages of 41 76 1 09 ka 35 50 1 26 ka 27 17 0 68 ka 20 27 0 60 ka and 18 29 0 49 ka these five maxima spanned an entire precessional cycle in summer insolation intensity at the latitude of the southern alps a similar mismatch between summer insolation and glacier extent also characterized the chilean lake district in the mid latitudes of south america thus in apparent contrast to northern ice sheets linked by milankovitch to summer insolation at 65 n latitude the behavior of southern mid latitude glaciers was not tied to local summer insolation intensity instead glacier extent between 41 76 ka and 18 29 ka as well as during the last termination was aligned with southern ocean surface temperature and with atmospheric carbon dioxide

deep water mass geometry in the glacial atlantic ocean a review of constraints from the paleonutrient proxy cd ca 1 paleonutrient proxies currently provide the strongest constraints on the past spatial distribution of deep water masses we review the state of knowledge derived from the trace metal proxy cd ca for the atlantic ocean during the last glacial maximum lgm we compile published benthic foraminiferal cd ca data supplemented with new data to reconstruct meridional cd sections through the holocene and lgm atlantic holocene cd ca reflects the modern water masses north atlantic deep water nadw antarctic bottom water aabw and antarctic intermediate water aaiw reasonably well except for anomalously high values in the intermediate to mid depth far north atlantic lgm cd ca clearly shows that nadw was replaced by the shallower glacial north atlantic intermediate water gnaiw with significant northward expansion of aabw the boundary level between gnaiw and aabw was very abrupt occurring between 2200 and 2500 m modern water depth combined cd ca and cibicidoides d 13 c data allow us to also calculate the air sea signature of d 13 c d 13 cas the lgm atlantic can be explained entirely by mixing between high d 13 cas gnaiwand low d 13 cas aabw negative d 13 cas values in glacial aabw were likely caused by poor ventilation during formation probably associated with extensive sea ice coverage overall our knowledge base would benefit from improved data coverage in the south atlantic and southern ocean and a better understanding of ancillary effects on the cd ca proxy itself

contribution of the phase transition of pacific decadal oscillation to the late 1990s shift in east china summer rainfall based on our previous study the interdecadal changes in summer rainfall over east china in the late 1990s are further explored here the increased local rising motion is implicated as the dominant factor of increased rainfall in the lower huang huai river valley lhr both the observation and numerical experiments using community atmosphere model version 4 suggest that the negative pacific decadal oscillation pdo mode can result in rising anomalies and thus more rainfall in the lhr the east asian westerly jet stream eawjs is suggested as a bridge to link the pacific sea surface temperature anomalies and east asian summer rainfall model results reveal that the negative pdo mode can lead to significant easterly anomalies over east asia as a result the eawjs is weakened and shifts poleward which coincides with observed changes in eawjs after the late 1990s in addition weakened and poleward shifted eawjs can result in an anomalous ascending motion to its south in the lhr by modulating the jet related secondary meridional vertical circulation consequently rainfall increased in the lhr after the late 1990s besides the positive atlantic meridional oscillation can only induce insignificant changes over east asia and partly counteract the negative pdo effect there

interannual variability of summer monsoon onset over the western north pacific and the underlying processes climatological summer monsoon onset over the south china sea scs and the western north pacific wnp defined as the region of 108 208n 1208 1608e displays three distinct stages around mid may monsoon rain commences in the scs and the philippines in early to mid june the monsoon rain extends to the southwestern philippine sea after mid july the rainy season starts in the northeastern part of the wnp the onset anomaly however displays an in phase interannual variation across the entire wnp domain the standard deviation of the onset date increases eastward from 3 pentads in the scs to 5 pentads in the northeastern part of the domain the large onset variability in the wnp is mainly attributed to large year to year changes of the seasonal cycle

roles of enso and pdo in the link of the east asian winter monsoon to the following summer monsoon abstractthe present study investigates the roles of el nino southern oscillation enso and the pacific decadal oscillation pdo in the relationship between the east asian winter monsoon eawm and the following east asian summer monsoon easm the variability of the eawm is divided into an enso related part named eawmen and an enso unrelated part named eawmres corresponding to a weak eawmen an anomalous low level anticyclone forms over the western north pacific wnp and persists from winter to the following summer this anticyclone enhances southerlies over the coast of east asia in summer hence a weak eawmen tends to be followed by a strong easm and vice versa as such a link is established between the eawmen and the easm the persistence of this wnp anticyclone may be mainly attributed to the sea surface temperature anomalies associated with the enso related eawm part in the tropical indian ocean and the extratropical north pacific in contrast corresponding to a weak eawmres the anomalous wn

structure and dynamics of the summertime pacific japan teleconnection pattern convective activity over the tropical western pacific is known to influence the extratropical circulation over east asia in the boreal summer in the form of teleconnection called the pacific japan pj pattern but its structure and dynamics have not yet been studied in depth in this study a composite analysis is performed for 32 monthly events of enhanced convection observed to the east of the philippines the composited monthly mean vorticity anomalies associated with the pj pattern are elongated zonally with a distinct poleward tilt with height this structure differs fundamentally from a combination of the first baroclinic mode in the tropics and the barotropic structure in midlatitudes as has widely been accepted as a conceptual model of the pj pattern a wave activity flux points polewards only in the lower troposphere indicating that rossby wave teleconnection occurs primarily through a low level south westerly jet those tilted anomalies over the western pacific can effectively gain kinetic energy in the exits of the mean jet streams in the upper and lower troposphere and available potential energy ape in the presence of the vertically sheared jets the enhanced convection can generate ape effectively and the associated low level anomalous circulation acts to increase moisture supply into the convective region while enhancing evaporation from the pre warmed ocean surface it is thus hypothesized that the pj pattern may be regarded as a dynamical mode that can be effectively excited in the zonally asymmetric baroclinic mean flow associated with the asian summer monsoon with an efficient self sustaining mechanism through moist processes copyright 2006 royal meteorological society

an evaluation of benthic foraminiferal b ca and δ11b for deep ocean carbonate ion and ph reconstructions reliable reconstructions of deep ocean carbonate ion concentration co32 and ph are crucial to understand mechanisms responsible for the past atmospheric co2 variations observed in ice cores however it is challenging to reconstruct past deep water co32 and ph and literature results from different proxies conflict warranting careful investigations on possible reasons for the existing inconsistencies here we present the first down core b ca and 11b records measured in an epifaunal benthic foraminifer cibicidoides wuellerstorfi from the caribbean sea during the last 160 kyr the two proxies yield quantitatively comparable deep water co3 2 and ph results showing high values during glacials relative to inter glacials differences in co32 and ph are 35 mol kg and 0 15 respectively consistent with past ocean circulation changes in the caribbean sea our data provide convincing evidence that both proxies serve as faithful proxies to estimate deep ocean co32 and ph despite our incomplete understanding of boron incorporation into foraminiferal carbonates

near constancy of the pacific ocean surface to mid depth radiocarbon age difference over the last 20 kyr although 13c to 12c and cadmium to calcium ratios provide information regarding the distribution of deep water masses during late glacial time and during the period of deglaciation our knowledge of the rate at which these water masses were ventilated comes mainly from the difference in radiocarbon age between coexisting bottom and surface dwelling foraminifera paired benthic planktonic foraminiferal radiocarbon age differences covering last 20 kyr in a high deposition rate western equatorial pacific core md01 2386 from a water depth of 2 8 km show no significant climate related variations over this period this result is surprising for we would have expected a change in this age difference between the last glacial maximum lgm and the holocene and also during the mystery interval 17 5 14 5 kyr ago when the waters in a radiocarbon depleted abyssal reservoir were presumably being mixed back into the remainder of the ocean

ventilation of the glacial deep pacific ocean measurements of the age difference between coexisting benthic and planktic foraminifera from western equatorial pacific deep sea cores suggest that during peak glacial time the radiocarbon age of water at 2 kilometers depth was no greater than that of today these results make unlikely suggestions that a slowdown in deep ocean ventilation was responsible for a sizable fraction of the increase of the ratio of carbon 14 14c to carbon in the atmosphere and surface ocean during glacial time comparison of 14c ages for coexisting wood and planktic foraminifera from the same site suggests that the atmosphere to surface ocean 14c to c ratio difference was not substantially different from today s

relative timing of last glacial maximum and late glacial events in the central tropical andes whether or not tropical climate fluctuated in synchrony with global events during the late pleistocene is a key problem in climate research however the timing of past climate changes in the tropics remains controversial with a number of recent studies reporting that tropical ice age climate is out of phase with global events here we present geomorphic evidence and an in situ cosmogenic 3 he surface exposure chronology from nevado coropuna southern peru showing that glaciers underwent at least two significant advances during the late pleistocene prior to holocene warming comparison of our glacialgeomorphic map at nevado coropuna to mid latitude reconstructions yields a striking similarity between last glacial maximum lgm and late glacial sequences in tropical and temperate regions exposure ages constraining the maximum and end of the older advance at nevado coropuna range between 24 5 and 25 3 ka and between 16 7 and 21 1 ka respectively depending on the cosmogenic production rate scaling model used similarly the mean age of the younger event ranges from 10 to 13 ka this implies that 1 the lgm and the onset of deglaciation in southern peru occurred no earlier than at higher latitudes and 2 that a significant late glacial event occurred most likely prior to the holocene coherent with the glacial record from mid and high latitudes the time elapsed between the end of the lgm and the late glacial event at nevado coropuna is independent of scaling model and matches the period between the lgm termination and late glacial reversal in classic mid latitude records suggesting that these events in both tropical and temperate regions were in phase

radiocarbon age constraints on rates of advance and retreat of the puget lobe of the cordilleran ice sheet during the last glaciation abstract calibrated radiocarbon dates of organic matter below and above till of the last fraser glaciation provide limiting ages that constrain the chronology and duration of the last advance retreat cycle of the puget lobe in the central and southeastern puget lowland seven dates for wood near the top of a thick proglacial delta have a weighted mean age of 17 420 90 cal yr b p which is the closest limiting age for arrival of the glacier near the latitude of seattle a time distance curve constructed along a flowline extending south from southwestern british columbia to the central puget lowland implies an average glacier advance rate of ca 135 m yr the glacier terminus reached its southernmost limit ca 16 950 yr ago and likely remained there for ca 100 yr in the vicinity of seattle where the glacier reached a maximum thickness of 1000 m ice covered the landscape for ca 1020 yr postglacial dates constraining the timing of ice retreat in the central lowland are as old as 16 420 cal yr b p and show that the terminus had retreated to the northern limit of the lowland within three to four centuries after the glacial maximum the average rate of retreat was about twice the rate of advance and was enhanced by rapid calving recession along flowline sectors where the glacier front crossed deep proglacial lakes

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

expanded glaciers during a dry and cold last glacial maximum in equatorial east africa glaciers on the world s highest tropical mountains are among the most sensitive components of the cryosphere yet the climatic controls that infl uence their fl uctuations are not fully under stood here we present the fi rst 10 be ages of glacial moraines in africa and use these to assess the climatic conditions that infl uenced past tropical glacial extents we applied 10 be surface exposure dating to determine the ages of quartz rich boulders atop moraines in the rwenzori mountains 1 n 30 e located on the border of uganda and the democratic republic of congo the 10 be ages document expanded glaciers ca 23 4 and 20 1 ka indicating that glaciers in equatorial east africa advanced during the global last glacial maximum ca 26 19 5 ka a comparison of these moraine ages with regional paleoclimate records indicates that rwen zori glaciers expanded contemporaneously with dry and cold conditions recession from the moraines occurred after ca 20 1 ka similar in timing to a rise in air temperature documented in east african lake records our results suggest that on millennial time scales past fl uctua tions of rwenzori glaciers were strongly infl uenced by air temperature

dynamic storage of glacial co2 in the atlantic ocean revealed by boron co32 and ph records abstract the origin and carbon content of the deep water mass that fills the north atlantic basin either antarctic bottom water aabw or north atlantic deep water nadw is suggested to influence the partitioning of co2 between the ocean and atmosphere on glacial interglacial timescales fluctuations in the strength of atlantic meridional overturning circulation amoc have also been shown to play a key role in global and regional climate change on timescales from annual to millennial the north atlantic is an important and well studied ocean basin but many proxy records tracing ocean circulation in this region over the last glacial cycle are challenging to interpret here we present new b ca co 3 2 and boron isotope ph data from sites spanning the north atlantic ocean from 2200 to 3900 m and covering the last 130 kyr from both sides of the mid atlantic ridge these data allow us to explore the potential of the boron based proxies as tracers of ocean water masses to ultimately identify the changing nature of atlantic circulation over the last 130 kyr this possibility arises because the b ca and boron isotope proxies are directly and quantitatively linked to the ocean carbonate system acting as semi conservative tracers in the modern ocean yet the utility of this approach has yet to be demonstrated on glacial interglacial timescales when various processes may alter the state of the deep ocean carbonate system we demonstrate that the deep 3400 m north atlantic ocean exhibits considerable variability in terms of its carbonate chemistry through the entirety of the last glacial cycle our new data confirm that the last interglacial marine isotope stage mis 5e has a similar deep water geometry to the holocene in terms of the carbonate system in combination with benthic foraminiferal 13c and a consideration of the co 3 2 of contemporaneous southern sourced water we infer that aabw influences the eastern abyssal north atlantic throughout the whole of the last glacial mis2 through 4 whereas only in the coldest stages mis2 and mis4 of the last glacial cycle was aabw an important contributor to our deep sites in both north atlantic basins taken together our carbonate system depth profiles reveal a pattern of changing stratification within the north atlantic that bears strong similarities to the atmospheric co2 record evidencing the important role played by ocean water mass geometry and the deep ocean carbonate system in driving changes in atmospheric co2 on these timescales

responses of the deep ocean carbonate system to carbon reorganization during the last glacial interglacial cycle we present new deep water carbonate ion concentration co 3 2 records reconstructed using cibicidoides wuellerstorfi b ca for one core from caribbean basin water depth 3623 m sill depth 1 8 km and three cores located at 2 3 4 3 km water depth from the equatorial pacific ocean during the last glacial interglacial cycle the pattern of deep water co 3 2 in the caribbean basin roughly mirrors that of atmospheric co 2 reflecting a dominant influence from preformed co 3 2 in the north atlantic ocean compared to the amplitude of 65 mol kg in the deep caribbean basin deep water co 3 2 in the equatorial pacific ocean has varied by no more than 15 mol kg due to effective buffering of caco 3 on deep sea ph in the pacific ocean our results suggest little change in the global mean deep ocean co 3 2 between the last glacial maximum lgm and the late holocene the three records from the pacific ocean show long term increases in co 3 2 by 7 mol kg from marine isotope stage mis 5c to mid mis 3 consistent with the response of the deep ocean carbonate system to a decline in neritic carbonate production associated with 60 m drop in sea level the coral reef hypothesis superimposed upon the long term trend deep water co 3 2 in the pacific ocean displays transient changes which decouple with 13 c in the same cores at the start and end of mis 4 these changes in co 3 2 and 13 c are consistent with what would be expected from vertical nutrient fractionation and carbonate compensation the observed 4 mol kg co 3 2 decline in the two pacific cores at 3 4 km water depth from mis 3 to the lgm indicate further strengthening of deep ocean stratification which contributed to the final step of atmospheric co 2 drawdown during the last glaciation the striking similarity between deep water co 3 2 and 230 th normalized caco 3 flux at two adjacent sites from the central equatorial pacific ocean provides convincing evidence that deep sea carbonate dissolution dominantly controlled caco 3 preservation at these sites in the past our results offer new and quantitative constraints from deep ocean carbonate chemistry to understand roles of various mechanisms in atmospheric co 2 changes over the last glacial interglacial cycle

interior hydrography and circulation of the glacial pacific ocean abstract the deep water of the pacific ocean is a key component of the global climate system on the time scale of late pleistocene glaciation and deglaciation despite its importance the deep pacific during the last glacial maximum has received relatively little attention compared to the deep atlantic in part because the pacific poorly preserves carbonate sediments on the sea floor here we review the current state of knowledge of the deep hydrography and circulation of the glacial pacific by examining available nutrient proxy data including some new 13 c and 18 o data measured on benthic foraminifera planulina wuellerstorfi from the vicinity of japan available benthic 13 c and 18 o and radiocarbon data from the pacific support the presence of a deep hydrographic boundary at around 2000 m during the last glacial maximum paleoceanography 3 1988 343 paleoceanography 7 1992 273 paleoceanography 13 4 1998 323 the deep hydrographic divide in the glacial pacific is similar to what is inferred in the atlantic quaternary research 18 1982 218 paleoceanography 3 1988 317 paleoceanography 3 1988 343 annual reviews of earth planetary sciences 20 1992 245 science 259 1993 1148 the indian nature 333 1988 651 paleoceanography 13 1998 20 and the southern ocean paleoceanography 11 1996 191 suggesting that this is a global phenomenon during the glacial time the upper water mass has a distinctly enriched 13 c compared to the deeper water mass whose possible origins are discussed

insolation driven 100 000 year glacial cycles and hysteresis of ice sheet volume comprehensive climate and ice sheet models show that insolation and internal feedbacks between the climate the ice sheets and the lithosphere asthenosphere system explain the 100 000 year period on which the northern hemisphere ice sheets grow and shrink for the past million years earth s climate has been dominated by a 100 000 year cycle of glaciation involving the advance and retreat of the northern hemisphere ice sheets variations in insolation the solar radiation reaching earth s surface caused by constant changes in earth s orbit and orientation to the sun are closely associated with glaciations but the physical mechanisms driving the cycle have remained unclear now ayako abe ouchi and colleagues demonstrate that insolation variations interact with the size of the ice sheets and the solid earth to control the 100 000 year cycles their model shows that internal feedbacks between insolation climate and the elevation of the land beneath the ice sheet allows ice sheets to grow gradually until a maximum size is reached at that point the lowered ice sheet elevation caused by the delayed rebound of the solid earth means that a small increase in insolation can destroy the ice sheet in just a few thousand years the growth and reduction of northern hemisphere ice sheets over the past million years is dominated by an approximately 100 000 year periodicity and a sawtooth pattern1 2 gradual growth and fast termination milankovitch theory proposes that summer insolation at high northern latitudes drives the glacial cycles3 and statistical tests have demonstrated that the glacial cycles are indeed linked to eccentricity obliquity and precession cycles4 5 yet insolation alone cannot explain the strong 100 000 year cycle suggesting that internal climatic feedbacks may also be at work4 5 6 7 earlier conceptual models for example showed that glacial terminations are associated with the build up of northern hemisphere excess ice 5 8 9 10 but the physical mechanisms underpinning the 100 000 year cycle remain unclear here we show using comprehensive climate and ice sheet models that insolation and internal feedbacks between the climate the ice sheets and the lithosphere asthenosphere system explain the 100 000 year periodicity the responses of equilibrium states of ice sheets to summer insolation show hysteresis11 12 13 with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles the hysteresis loop of the north american ice sheet is such that after inception of the ice sheet its mass balance remains mostly positive through several precession cycles whose amplitudes decrease towards an eccentricity minimum the larger the ice sheet grows and extends towards lower latitudes the smaller is the insolation required to make the mass balance negative therefore once a large ice sheet is established a moderate increase in insolation is sufficient to trigger a negative mass balance leading to an almost complete retreat of the ice sheet within several thousand years this fast retreat is governed mainly by rapid ablation due to the lowered surface elevation resulting from delayed isostatic rebound14 15 16 which is the lithosphere asthenosphere response carbon dioxide is involved but is not determinative in the evolution of the 100 000 year glacial cycles

the influence of air and sea exchange on the carbon isotope distribution in the sea we explore here the influence of the temperature dependence of isotope fractionation between atmospheric co2and ocean co2 on the distribution of carbon isotopes in the ocean this is accomplished by an analysis of departures from the expected redfield tie between po4 and 13c we find that for the surface ocean the temperature influence largely compensates for the biologic influence in the deep ocean the temperature influence imprinted at the sites of deepwater formation reduces somewhat the biologically induced difference between the carbon isotope ratios for deep waters produced in the northern atlantic and in the antarctic these same features are reproduced in the hamburg ocean model in order to assess the impact of changes in the ratio of ocean mixing rate to wind speed we have made a model run in which co2 exchange rates between air and sea were everywhere doubled as expected the influence of the thermodynamic effect on the oceanic carbon isotope distribution is magnified

late pleistocene snowline fluctuations at nevado coropuna 15 s southern peruvian andes deposits preserved on peaks in the southern peruvian andes are evidence for past glacial fluctuations and therefore serve as a record of both the timing and magnitude of past climate change moraines corresponding to the last major expansion of ice on nevado coropuna date to 20 25 ka during the last glacial maximum we reconstructed the snowline at coropuna for this period using a combined geomorphic numeric approach to provide a first order estimate of the magnitude of late pleistocene climate change our reconstructions show that snowline was approximately 550 770m lower during the last glacial maximum than during the late holocene maximum which ended in the 19 th century and 750m lower than today while these values are similar to data from nearby nevado solimana reconstructions from the neighbouring peak of nevado firura reveal a smaller snowline depression suggesting the glacial response to climate forcing in the tropics is strongly influenced by non climatic factors these data constitute some of the first directly dated palaeo snowline data from the arid tropics and suggest that the magnitude of the last glaciation in at least parts of the tropical andes was similar to late pleistocene events at higher latitudes copyright 2011 john wiley sons ltd

benthic foraminiferal b ca ratios reflect deep water carbonate saturation state boron calcium ratios were measured in four benthic foraminiferal species three calcitic cibicidoides wuellerstorfi cibicidoides mundulus and uvigerina spp and one aragonitic hoeglundina elegans from 108 core top samples located globally comparison of coexisting species shows b ca of c wuellerstorfi c mundulus h elegans uvigerina spp suggestive of strong vital effects on benthic foraminiferal b ca a dissolution effect on benthic b ca is not observed core top data show large intra species variations 50 130 mol mol in b ca within a single species benthic foraminiferal b ca show a simple linear correlation with deep water co32 providing a proxy for past deep water co32 reconstructions empirical sensitivities of co32 on b ca have been established to be 1 14 0 048 and 0 69 0 072 mol mol per mol kg for c wuellerstorfi and c mundulus respectively the uncertainties associated with reconstructing bottom water co32 using b ca in c wuellerstorfi and c mundulus are about 10 mol kg a preliminary application shows that the last glacial maximum lgm b ca ratios were increased by 12 at 1 2 km and decreased by 12 at 3 5 4 0 km relative to holocene values in the north atlantic ocean this implies that the lgm co32 was higher by not vert similar 25 30 mol kg at intermediate depths and lower by not vert similar 20 mol kg in deeper waters consistent with glacial water mass reorganization in the north atlantic ocean inferred from other paleochemical proxies

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

geochronology and paleoclimatic implications of the last deglaciation of the mauna kea ice cap hawaii we present new 3he surface exposure ages on moraines and bedrock near the summit of mauna kea hawaii which refine the age of the mauna kea ice cap during the local last glacial maximum llgm and identify a subsequent fluctuation of the ice margin the 3he ages when combined with those reported previously indicate that the local ice cap margin began to retreat from its llgm extent at 20 5 2 5 ka in agreement with the age of deglaciation determined from llgm moraines elsewhere in the tropics the ice cap margin receded to a position at least 3 km upslope for 4 5 5 0 kyr before readvancing nearly to its llgm extent the timing of this readvance at 15 4 ka corresponds to a large reduction of the atlantic meridional overturning circulation amoc following heinrich event 1 subsequent ice margin retreat began at 14 6 1 9 ka corresponding to a rapid resumption of the amoc and onset of the bolling warm interval with the ice cap melting rapidly to complete deglaciation additional 3he ages obtained from a flood deposit date the catastrophic outburst of a moraine dammed lake roughly coeval with the younger dryas cold interval suggesting a more active hydrological cycle on mauna kea at this time a coupled mass balance and ice dynamics model is used to constrain the climate required to generate ice caps of llgm and readvance sizes the depression of the llgm equilibrium line altitude requires atmospheric cooling of 4 5 1 c whereas the mass balance modeling indicates an accompanying increase in precipitation of as much as three times that of present we hypothesize 1 that the llgm temperature depression was associated with global cooling 2 that the temperature depression that contributed to the readvance occurred in response to an atmospheric teleconnection to the north atlantic and 3 that the precipitation enhancement associated with both events occurred in response to a southward shift in the position of the inter tropical convergence zone itcz such a shift in the itcz would have allowed midlatitude cyclones to reach mauna kea more frequently which would have increased precipitation at high elevations and caused additional cooling

cadmium and delta13c paleochemical ocean distributions during the stage 2 glacial maximum changes in heat and salt transport by ocean currents have been implicated in ice age climate cycles weyl 1 968 newell 1 974 broecker et al 1 990b in addition to the direct physical effects of the ocean on climate the ocean carbon system controls atmospheric co2 and the co2 fluctuations documented in ice core bubbles barnola et a1 1 987 neftel et a1 1 988 are thought to be a significant factor in climate oscillations hansen et al 1 984 dramatic changes in oceanic circulation patterns and carbon system chemistry have occurred during the late quaternary glacial interglacial global climate cycles boyle keigwin 1 982 curry lohmann 1 983 shackleton pisias 1 984 boyle keigwin 1 987 duplessy et al 1 988 curry et al 1 988 broecker et al i 990a these changes in the ocean system may be significant driving forces in the progression of ice age co2 cycles toggweiler sarmiento 1 985 ennever mcelroy 1 985 wenk siegenthaler 1 985 boyle 1 988a b broecker peng 1 990 the oceanic distributions of c513c cd and other carbon system linked properties are controlled by the interaction between biological uptake and decomposition with the general circulation of the ocean because records of past oceanic cd and c5 1 3c are preserved in shells of planktonic and benthic foraminifera

persistent severe drought in southern china during winter spring 2011 large scale circulation patterns and possible impacting factors 1 severe drought persisted in southern china from january to may in 2011 in this study a statistical analysis is carried out to discuss the multiple possible impacting factors including la nina the north atlantic oscillation nao and the thermal condition of the tibetan plateau tp the la nina event in 2010 11 excited a lower tropospheric anomalous cyclone over the northwestern pacific weakening the northwestern pacific subtropical high and caused an eastward shift of the high as a result transportation of wet and warm moisture from tropical oceans to southern china decreased the la nina event also strengthened the upper tropospheric east asian jet stream and deepened the east asian trough favoring a southward intrusion of dry northerly flow from the siberia the la nina condition in the previous two seasons also seemed to provide precursory signals for the drought moreover in january may 2011 the nao was in a positive phase and it tended to excite stationary rossby waves that were distributed along the sub polar and subtropical waveguides respectively the sub polar one induced an anomalous anticyclone over the siberia favoring a southward intrusion of high latitude northerly flow to southern china the subtropical one associated possibly with the enhanced convection over the broad region from the mediterranean to sahara was favorable for an influence of upper tropospheric flow on southern china the tp might also exert an influence on the drought by weakening the westerly flow to the southern flank of tp and reducing water vapor transport from the bay of bengal to southern china

interdecadal changes in the major modes of asian australian monsoon variability strengthening relationship with enso since the late 1970s abstract the present paper develops an integral view of the year to year variability across the entire asian australian monsoon a am system which covers one third of the global tropics between 40 and 160 e using season reliant empirical orthogonal function s eof analysis the authors identified two major modes of variability for the period 1956 2004 the first exhibits a prominent biennial tendency and concurs with the turnabout of el nino southern oscillation enso providing a new perspective of the seasonally evolving spatiotemporal structure for tropospheric biennial oscillation the second mode leads enso by one year the remote el nino forcing the monsoon warm pool ocean interaction and the influence of the annual cycle are three fundamental factors for understanding the behavior of the first mode the monsoon ocean interaction is characterized by a positive feedback between the off equatorial convectively coupled rossby waves and the underlying sea surface temperature sst dipole anoma

decadal variation of summer precipitation over china and associated atmospheric circulation after the late 1990s abstractin this study the authors found that the summer precipitation over china experienced different decadal variation features from north to south after the late 1990s in northeastern and north china and the lower middle reaches of the yangtze river precipitation decreased after 1999 while precipitation experienced a significant reduction over south and southwestern china and a significant increase over the southern parts of hetao region and huaihe river valley after 2003 the authors next analyzed the associated decadal variation of the atmospheric circulation and attempted to identify the mechanisms causing the two decadal variations of precipitation the wind anomalies for the former exhibit a barotropic meridional dipole pattern with anticyclonic anomalies over mongolia to northern china and cyclonic anomalies over the southeastern chinese coast to the northwestern pacific for the latter there is a southeast northwest oriented dipole pattern in the middle and lower troposphere with cyclonic

the enso asian monsoon interaction in a coupled ocean atmosphere gcm abstract in this study the authors evaluate the el nino southern oscillation enso asian monsoon interaction in a version of the hadley centre coupled ocean atmosphere general circulation model cgcm known as hadcm3 the main focus is on two evolving anomalous anticyclones one located over the south indian ocean sio and the other over the western north pacific wnp these two anomalous anticyclones are closely related to the developing and decaying phases of the enso and play a crucial role in linking the asian monsoon to enso it is found that the hadcm3 can well simulate the main features of the evolution of both anomalous anticyclones and the related sst dipoles in association with the different phases of the enso cycle by using the simulated results the authors examine the relationship between the wnp sio anomalous anticyclones and the enso cycle in particular the biennial component of the relationship it is found that a strong el nino event tends to be followed by a more rapid decay and i