rossby waves in the tropical north pacific and their role in decadal thermocline variability abstract a band of enhanced thermocline variability at 10 15 n in the pacific found in nature also occurs in an ocean general circulation model forced with observed fluxes of momentum heat and freshwater over the period 1958 97 the variability in the model is primarily associated with long baroclinic rossby waves characterized by periods in the decadal range 7 10 yr the waves are forced by westward propagating ekman pumping anomalies east of the date line and propagate at a speed of 13 cm s 1 which is slower than the phase speed of the first mode unforced baroclinic waves 15 16 cm s 1 west of the date line the correlations between thermocline displacements and local ekman pumping are relatively small and the ocean signals have a phase speed of 20 cm s 1 very similar to the phase speed of the first baroclinic mode in the western half of the basin 18 20 cm s 1 the phase speeds of the ocean model signals have been estimated using cospectral analysis while the wkb approximation has been us

ocean dynamical processes associated with the tropical pacific cold tongue mode the cold tongue mode ctm is the second eof mode of sea surface temperature anomaly ssta variability over the tropical pacific and represents the out of phase relationship in ssta variability between the pacific cold tongue region and elsewhere in the tropical pacific a positive ctm is characterized by cold ssta in the pacific cold tongue region and warm ssta in the rest of the tropical pacific with conditions reversed for a negative ctm the ctm is a coupled air sea mode and its long term variability is most probably induced by ocean dynamical processes in response to global warming zhang et al 2010 this study focuses on the specific ocean dynamical processes associated with the ctm and its possible relationship with global warming a heat budget diagnosis of ocean temperature in the eastern equatorial pacific shows that the net heat flux plays a damping role and the four ocean advection terms 2u0 t x 2 v t0 y 2 w t0 z and 2w0 t z contribute to the temperature change associated with the ctm among them the vertical advection of the anomalous temperature by the mean upwelling 2 w t0 z makes a dominant contribution to the long term change in the ctm the long term change of the term 2 w t0 z is controlled mainly by the decreasing vertical gradient of the ocean temperature anomaly t0 z the other three advection terms make a minor contribution to the long term change in the ctm

regime change of the boreal summer hadley circulation and its connection with the tropical sst the year to year variability of the boreal summer june august jja hadley circulation hc is dominated by an asymmetric mode centered in the northern hemisphere amn and a quasi symmetric mode centered at 58n qsm the regime change of the jja hc is revealed by the phase reversal of the time series of the amn showing significant weakening of the northern part of the jja hc and a reversed seesaw relationship of the zonal mean updraft over 108 208n and around the equator this transition is accompanied by the southward retreat of the hc core and is well correlated with the weakening of tropical summer monsoons the strong warming trends of the sea surface temperature over the tropical atlantic and indo west pacific warm pool play an important role in the regime change of the jja hc the high frequency interannual variability of the jja hc however is mainly featured by the qsm and is highly correlated with

decadal precipitation variability over europe and its relation with surface atmospheric circulation and sea surface temperature the relationships between decadal 5 year period observed winter precipitation pp variability over europe and atmospheric circulation and sea surface temperature sst during the period 1950 1995 are investigated more than 48 of the decadal precipitation variability is described by two modes a meridional dipolar pattern high pp over northern europe and low over southern europe the mediterranean and most of central europe explaining about 32 of the variance and an alternating pattern in latitude over europe high in central europe and low in far north western europe and the mediterranean explaining about 16 of the variance the first mode is strongly related to the north atlantic oscillation a canonical correlation analysis between regional precipitation and sea level pressure fields shows that a pp pattern similar to the first decadal pp mode is associated with a north westerly circulation anomaly pattern while a pp pattern similar to the second decadal pp mode is associated with a monopolar circulation anomaly pattern over most parts of europe the correlation map between the time series of expansion coefficients of the first pp mode and sea surface temperature emphasizes a global pattern which resembles the linear trend coefficients pattern of sst for the analysed period the second pp mode is associated with an sst anomaly pattern similar to that of the sst anomalies characterizing decadal el ni o southern oscillation sst pattern composite maps of global 500 mb geopotential height based on the time series of expansion coefficients of pp modes emphasize global patterns compatible with sst patterns after removing the linear trend from the data the first pp pattern remains almost unchanged but it emphasizes mainly regional connections the second spatial pattern of the second pp mode and its connections are not affected significantly by removing the trend

origin of decadal el nino southern oscillation like variability in a coupled general circulation model 1 the origin of decadal el nino southern oscillation like variability hereinafter referred to as dev is analyzed in coupled general circulation model cgcm simulations the cgcm experiments test the null hypothesis for the existence of dev that is that dev is linear damped and stochastically forced by atmospheric internal dynamics in order to test this hypothesis we employ the interactive ensemble coupling strategy it is found that the spatially averaged variance of sea surface temperature anomaly ssta and heat content anomaly hca associated with the dev is linearly related to the amplitude of atmospheric internal dynamics this result suggests that the dev is primarily noise forced but that damped coupled feedbacks and or internal ocean dynamics enhance this variability the ssta variability associated with the dev appears to be of a basin type standing mode with a triangular shape however the decadal evolution of the hca associated with the dev shows a systematic westward propagation from the central north pacific and the eastern south pacific both a singular vector analysis and noise variance analysis based on the coupled simulation results support the argument that atmospheric noise in the subtropics leads to the excitation of the dev

a tropical ocean recharge mechanism for climate variability part ii a unified theory for decadal and enso modes abstract decadal to interdecadal timescale variability in the pacific region commonly referred to as the pacific decadal oscillation pdo is studied in this research using analytical and numerical models a coupled analytical model is formulated to analyze the physical mechanism of both the pdo and enso it has the equatorial plane dynamics of a reduced gravity model coupled with the wind stress of fixed spatial patterns the amplitude of the latter is proportional to the sea surface temperature sst anomaly in the eastern equatorial pacific the sst anomaly is governed by a simple thermal dynamic equation used for enso modeling it is found that when a warm sst is coupled with cyclonic wind stress patterns in the eastern subtropical pacific an oscillation with a timescale of around 10 15 yr could be generated in contrast when a warm sst is coupled with only a westerly wind stress in the central equatorial pacific an enso like oscillation could be generated with a timescale of around 3 5 yr thu

holocene tsunamis in the southwestern bering sea russian far east and their tectonic implications the bering sea coast of kamchatka overlies a boundary between the proposed okhotsk and bering blocks or micro plates of the north american plate in the russian far east a history of tsunamis along this coast for the past 4000 yr indicates that the zone north of the kuril kamchatka subduction zone produces tsunamigenic earthquakes every few centuries such a record is consistent with convergence of the proposed okhotsk and bering blocks along the bering sea coast of kamchatka a tsunami deposit from the 1969 m w 7 7 ozernoi earthquake helps us interpret older tsunami deposits newly studied tephra layers from shiveluch volcano as well as previously established marker tephra layers in northern kamchatka provide age control for historic and prehistoric tsunami deposits based on 50 measured sections along 14 shoreline profiles tsunami deposit frequencies in the southwestern bering sea are about five per thousand years for tsunamis generated north of the kuril kamchatka trench

temperature trend of the last 40 yr in the upper pacific ocean abstract the linear temperature trend of the last 40 yr 1955 94 in the upper pacific ocean above 400 m is studied using an objectively analyzed dataset and simulations of an ocean general circulation model both the data and simulations suggest a warming trend in the western tropical pacific 10 s 10 n near the surface and in the eastern tropical pacific above 400 m but a cooling trend in the thermocline of the western tropical pacific in the midlatitude north pacific 30 50 n the temperature trend is positive east of 150 w but negative to the west simulated heat budget indicates that the temperature trend in the tropical pacific may result from oceanic advection in the central and western pacific the surface warming is associated with the reduction of cold advection from the off equatorial divergent flow and the south equatorial current while the cooling in the thermocline is related to the reduction of equatorward warm advection in the eastern pacific the warming is associated with the redu

coral proxy record of decadal scale reduction in base flow from moloka i hawaii 1 groundwater is a major resource in hawaii and is the principal source of water for municipal agricultural and industrial use with a growing population a long term downward trend in rainfall and the need for proper groundwater management a better understanding of the hydroclimatological system is essential proxy records from corals can supplement long term observational networks offering an accessible source of hydrologic and climate information to develop a qualitative proxy for historic groundwater discharge to coastal waters a suite of rare earth elements and yttrium reys were analyzed from coral cores collected along the south shore of moloka i hawaii the coral rey to calcium ca ratios were evaluated against hydrological parameters yielding the strongest relationship to base flow dissolution of reys from labradorite and olivine in the basaltic rock aquifers is likely the primary source of coastal ocean reys there was a statistically significant downward trend 40 in subannually resolved rey ca ratios over the last century this is consistent with long term records of stream discharge from moloka i which imply a downward trend in base flow since 1913 a decrease in base flow is observed statewide consistent with the long term downward trend in annual rainfall over much of the state with greater demands on freshwater resources it is appropriate for withdrawal scenarios to consider long term trends and short term climate variability it is possible that coral paleohydrological records can be used to conduct model data comparisons in groundwater flow models used to simulate changes in groundwater level and coastal discharge

multi model changes in el nino teleconnections over north america in a future warmer climate previous studies with single models have suggested that el nino teleconnections over north america could be different in a future warmer climate due to factors involving changes of el nino event amplitude and or changes in the midlatitude base state circulation here we analyze a six member multi model ensemble three models with increasing future el nino amplitude and three models with decreasing future el nino amplitude to determine characteristics and possible changes to el nino teleconnections during northern winter over the north pacific and north america in a future warmer climate compared to observed el nino events all the models qualitatively produce general features of the observed teleconnection pattern over the north pacific and north america with an anomalously deepened aleutian low a ridge over western north america and anomalous low pressure over the southeastern united states however associated with systematic errors in the location of sea surface temperature and convective heating anomalies in the central and western equatorial pacific the models anomaly patterns are shifted to the west the anomalous low pressure center in the north pacific is weaker and shifted somewhat south compared to the observations for future el nino events two different stabilization experiments are analyzed one with co2 held constant at year 2100 concentrations in the sres a1b scenario roughly doubled present day co2 and another with co2 concentrations held constant at 4xco2 consistent with the earlier single model results the future el nino teleconnections are changed in the models with a weakened as well as an eastward and northward shifted anomalous low in the north pacific this is associated with weakened anomalous warming over northern north america strengthened cooling over southern north america and precipitation increases in the pacific northwest in future events compared to present day el nino event teleconnections these changes are consistent with the altered base state upper tropospheric circulation with a wave 5 pattern noted in previous studies that is shown here to be consistent across all the models whether there are projected future increases or decreases in el nino amplitude the future teleconnection changes are most consistent with this anomalous wave 5 pattern in the models with future increases of el nino amplitude but less so for the models with future decreases of el nino amplitude

decadal sea level variability in the south pacific in a global eddy resolving ocean model hindcast sea level variability and related oceanic changes in the south pacific from 1970 to 2003 are investigated using a hindcast simulation of an eddy resolving ocean general circulation model ogcm for the earth simulator ofes along with sea level data from tide gauges since 1970 and a satellite altimeter since 1992 the first empirical orthogonal function mode of sea level anomalies slas of ofes exhibits broad positive slas over the central and western south pacific the corresponding principal component indicates roughly stable high low and high slas separated by a rapid sea level fall in the late 1970s and sea level rise in the late 1990s consistent with tide gauge and satellite observations these decadal changes are accompanied by circulation changes of the subtropical gyre at 1000 m depth and changes of upper ocean zonal current and eddy activity around the tasman front in general agreement with previous related studies it is found that sea level variations in the tasman sea can be explained by propagation of long baroclinic rossby waves forced by wind stress curl anomalies if the impact of new zealand is taken into account the corresponding atmospheric variations are associated with decadal variability of el nino southern oscillation enso thus decadal sea level variability in the western and central south pacific in the past three and half decades and decadal enso variability are likely to be connected the sea level rise in the 1990s which attracted much attention in relation to the global warming is likely associated with the decadal cooling in the tropical pacific

the role of the western pacific in decadal variability 1 recent observational studies indicate that the mechanisms of pacific decadal variability importantly involve the tropical indian western pacific oceans and south pacific convergence zone evidence for this suggestion is sought from the results of a 1000 year integration with the cccma coupled ocean atmosphere model which reasonably successfully simulates the principal mode of pacific decadal interdecadal variability both the western north pacific where ocean dynamics act to generate heat content anomalies and the western south pacific where surface heat flux forcing acts to generate heat content anomalies play a role these heat content anomalies are advected to and eastward along the equator providing the negative feedback to allow the system to change phase

interannual and decadal variability of the subsurface thermal structure in the pacific ocean 1961 90 heat content anomalies are analyzed to understand subsurface variability on both aparticular focus on the evolving basinwide patterns and oceanic connections between the extratropics and tropics various analyses indicate two distinct modes one interannual and the other decadal that involve the tropics and the north pacific subtropical gyre respectively interannual variability is associated with el nino in the tropics with a prominent see saw pattern alternately on and off the equator and in the east and west respectively the interannual cycle features a coherent propagation of subsurface signals around the tropical pacific eastward along the equator but westward off the equator at 10 15 n decadal signals are dominant in the subtropics and midlatitudes but also have a tropical component that appears to be independent of interannual variations an oceanic connection can be seen between subsurface anomalies in the midlatitudes in the subtropics and tropics on decadal time scales subsurface thermal anomalies associated with midlatitude decadal variability can propagate through the subtropics into the tropics which may modulate the intensity of interannual variability in the tropics for example in the middle and late 1970s a significant warm temperature anomaly appeared to penetrate into the western and central tropics at depth warming the tropical upper ocean and depressing the thermocline during the development of el nino therefore an extratropically preconditioned subsurface state e g an enhanced positive heat content anomaly in the western and central tropical pacific would favor a warmer sea surface temperature anomaly in the eastern equatorial pacific potentially increasing the intensity of ocean atmosphere coupling these changes in the thermocline structure and possibly in the coupling strength can further alter the very character of tropical air sea interactions this may help to explain decadal variability of el nino evolution in the tropical pacific as observed in the 1980s our subsurface variability analysis presents observational evidence for the detailed space time structure of decadal oceanic links between the extratropics and the tropics

long term el nino southern oscillation enso like variation with special emphasis on the south pacific mechanisms for el nino southern oscillation enso like decadal 7 35 years variability are analyzed using observational data when a decadal positive temperature anomaly occurs in the eastern tropical pacific the atmospheric response excites negative wind stress curl in the western tropical south pacific which causes the thermocline to shoal and induce a negative temperature anomaly there the cold anomaly moves northwestward to the western and central equatorial region and then turns eastward along the equator to reverse the original temperature anomaly in the east the eastward propagation of the oceanic signal along the equatorial thermocline correlates with a zonal wind anomaly the cold anomaly in the east grows through tropical air sea interaction and induces a positive wind stress curl in the western tropical south pacific associated with the atmospheric teleconnection in the southern hemisphere subsequent evolution of the negative phase is similar to that of the positive phase the complete scenario for this enso like decadal variability due to the air sea interaction processes within the tropics has a period of 14 years we also discuss enso like variation on the interdecadal 35 years timescale with possible relationship to the 1976 1977 climate regime shift

decadal amplitude modulation of two types of enso and its relationship with the mean state in this study we classified two types of el nino southern oscillation enso events within the decadal enso amplitude modulation cycle using a long term coupled general circulation model simulation we defined two climate states strong and weak enso amplitude periods and separated the characteristics of enso that occurred in both periods there are two major features in the characteristics of enso the first is the asymmetric spatial structure between el nino and la nina events the second is that the el nino la nina asymmetry is reversed during strong and weak enso amplitude periods el nino events during strong weak enso amplitude periods resemble the eastern pacific central pacific el nino in terms of the spatial distribution of sea surface temperature anomalies ssta and physical characteristics based on heat budget analysis the spatial pattern of the thermocline depth anomaly for strong weak el nino is identical to that for weak strong la nina but for an opposite sign and slightly different amplitude the accumulated residuals of these asymmetric anomalies dominated by an east west contrast structure could feed into the tropical pacific mean state moreover the residual pattern associated with el nino la nina asymmetry resembles the first principal component analysis pca mode of tropical pacific decadal variability indicating that the accumulated residuals could generate the change in climate state thus the intensified enso amplitude yields the warm residuals due to strong el nino and weak la nina over the eastern tropical pacific this linear relationship between enso and the mean state is strong during the mature phases of decadal oscillation but it is weak during the transition phases furthermore the second pca mode of tropical pacific decadal variability plays an important role in changing the phase of the first mode consequently the feedback between enso and the mean state is positive feedback to amplify the first pca mode whereas the second pca mode is a negative feedback to lead the phase change of the first pca mode due to their lead lag relationship these features could be regarded as evidence that the decadal change in properties of enso could be generated by the nonlinear interaction between enso and the mean state on a decadal to interdecadal time scale

combined interplay of the atlantic multidecadal oscillation and the interdecadal pacific oscillation on rainfall and its extremes over indian subcontinent this study provides a pertinent ground for acquiring deeper insight about the low frequency variability of precipitation and its extremes over india and its homogeneous monsoon regions under the combined interplay of both the atlantic multidecadal oscillation amo and the interdecadal pacific oscillation ipo the percent of variance in the total heavy rainfall on decadal to multidecadal timescales that can be attributed to these oceanic indices is 88 3 76 7 for west central and 84 4 72 6 for northeast regions which implies that the recent changes in rainfall and it extremes over respective regions is mainly caused by internal natural variability the opposite phases of amo and ipo together modulates the total moderate rainfall over west central and northeast regions in an asymmetric manner whereas their warm phase stimulates the heavy rainfall over west central region while their opposite phases together influences the precipitation extremes over northeast region based on the projected conditions of these oceanic indices the outlook for west central northeast regions is fairly good bad and these regions will experience above below normal precipitation in the upcoming decade or two the rainfall over northwest region is mainly influenced by the ipo and this region will also likely to receive above normal precipitation in the upcoming decade or so due to the present cold phase of ipo wind circulation pattern divulges that during the warm phase of amo the southwesterlies over indian region are strengthened by the equatorial atlantic winds coming through the equatorial africa while in the cold phase of ipo it gets strengthen by the easterlies from the equatorial pacific

role of the atmospheric and oceanic circulation in the tropical pacific sst changes a coupled climate model is used to explore the response of the tropical sea surface temperature sst to positive sst anomalies in the global extratropics the main model results here are consistent with previous numerical studies in response to prescribed sst anomalies in the extratropics the tropical ssts rise rapidly and reach a quasi equilibrium state within several years and the tropical subsurface temperatures show a slow response the annual mean hadley cell as well as the surface trades are weakened the weakened trades reduce the poleward ekman transports in the tropical ocean and furthermore lead to anomalous positive convergences of heat transport which is the main mechanism for maintaining the tropical pacific sst warming the process of an extratropical influence on the tropics is related to both the atmospheric and oceanic circulations the intertropical convergence zone itcz moves southward and eastward in the pacific corresponding to a reduction of the hadley circulation and walker circulation at the same time convective precipitation anomalies are formed on the boundary of the climatological itcz while the climatological mean convections centered in the southeast asia region are suppressed the largely delayed response of the tropical subsurface temperature cannot be explained only by the strength change of the subtropical cells stcs but can be traced back to the slow changing of subsurface temperature in the extratropics in the extratropical oceans warming and freshening reduce the surface water density and the outcropping lines of certain isopycnal layers are moved poleward this poleward movement of outcropping lines can weaken the positive temperature anomalies or even lead to negative anomalies on given isopycnal layers displayed on time dependent isopycnal layers positive subsurface temperature anomalies are present only in the region after subduction and are subsequently replaced by negative temperature anomalies in the deep tropics regions the noticeable features of the density compensation of temperature and salinity indicate that diapycnal processes play an important role in the equatorward transport of the temperature and salinity anomalies from the midlatitude

spatial and temporal features of enso meridional scales 1 the spatial and temporal features of the el nino southern oscillation enso meridional scales are investigated using the hadley center global sea ice and sea surface temperature hadisst data for the period of 1950 2007 the results show that the meridional scales of the enso warm and cold events are asymmetric and exhibit interdecadal changes the meridional extent of the sea surface temperature anomalies ssta during la nina years is wider than that during el nino years this is because strengthened trades and thus strengthened upwelling and meridional currents during la nina events more effectively spread ssta away from the equator with the walker circulation weakening in recent decades which tends to reduce upwelling and meridional currents over the central and eastern equatorial pacific the meridional scales of both el nino and la nina events also decrease citation zhang w j li and f f jin 2009 spatial and temporal features of enso meridional scales geophys res lett 36 l15605

maximal wavelet filter and its application to bidecadal oscillation over the northern hemisphere through the twentieth century based on a wavelet transform a new method referred to as maximal wavelet filter mwf is proposed to extract temporal structure changes of a climatic oscillation which varies its pattern corresponding to the changes of the oscillation period the mwf is a bandpass filter having a narrow pass band the central frequency of which temporally varies according to the periods of maximal wavelet amplitudes for a specific region mwf is applied to wintertime sea level pressures slps in the northern hemisphere from 1899 to 2000 to extract slp changes associated with the bidecadal oscillation bdo which distributes globally but has the strongest amplitudes in the north pacific in the pacific sector the bdo center of action captured by the mwf was located over alaska in the first few decades of the record and then moved southward to the central north pacific from 1920 to 1950 with maximal bdo amplitudes in the middle of the century the southward migration was accompanied by the previously reported increase of the oscillation period from 15 to 20 years on the other hand atlantic slp variations coherent with the pacific bdo had large amplitudes in midlatitudes high latitudes in the early late part of the twentieth century in association with these spatial structure changes the pattern of the recent bdo resembles the pattern of the arctic oscillation the analysis of the sea surface temperatures ssts gridded from the comprehensive ocean atmosphere data set coads and the newly digitized kobe collections suggests that bdo pattern in the ssts also shifted toward the south between the first and last few decades of the twentieth century furthermore covariability between the land air temperatures and aleutian low strength is observed through the twentieth century for alaska but only after 1940 for the midlatitudes of western north america and hawaii indicating that the bdo influence was limited to the high latitudes in the first few decades of the twentieth century in these regions consistent with the spatial structure changes in the slp field over the north pacific

interannual variability in a tropical atmosphere ocean model influence of the basic state ocean geometry and nonlinearity abstract the behavior of a tropical coupled atmosphere ocean model is analyzed for a range of different background states and ocean geometries the model is essentially that of cane and zebiak for the tropical pacific except only temporally constant background states are considered here for realistic background states and ocean geometry the model solutions feature oscillations of period of 3 5 yr by comparing the full model solution with a linearized version of the model it is shown that the basic mechanism of the oscillation is contained within linear theory a simple linear analog model is derived that describes the nature of the interannual variability in the coupled tropical atmosphere ocean system the analog model highlights the properties that produce coupled atmosphere ocean instability in the eastern ocean basin and the equatorial wave dynamics in the western ocean basin that are responsible for a delayed negative feedback into this instability growth the growth rate of the local instabil

on the structure of the southern oscillation abstract a realistic oceanic general circulation model is forced with winds observed over the tropical pacific between1967 and 1979 the structure of the simulated southern oscillation is strikingly different in the western andeastern sides of the basin because the principal interannual zonal wind fluctuations are confined to the westand are in the form of an equatorial jet this causes thermocline displacements to have maxima offthe equatorin the west where the curl of the wind is large but on the equator in the east zonal phase propagation bothon and offthe equator is at different speeds in the west and east the phase pattern is complex and there is on interannual time scale no explicit evidence ofindividuai equatorial waves these results lead to a modificationof the delayed oscillator mechanism originally proposed by schopfand suarez to explain a continual southernoscillation the results also permit an evaluation of the various coupled ocean atmosphere models that simulatethe southern osci

enso like and enso induced tropical pacific decadal variability in cgcms abstractoutputs from coupled general circulation models cgcms are used in examining tropical pacific decadal variability tpdv and their relationships with el nino southern oscillation enso herein tpdv is classified as either enso induced tpdv eit or enso like tpdv elt based on their correlations with a decadal modulation index of enso amplitude and spatial pattern eit is identified by the leading eof mode of the low pass filtered equatorial subsurface temperature anomalies and is highly correlated with the decadal enso modulation index this mode is characterized by an east west dipole structure along the equator elt is usually defined by the first eof mode of subsurface temperature of which the spatial structure is similar to enso generally this mode is insignificantly correlated with the decadal modulation of enso eit closely interacts with the residuals induced by enso asymmetries both of which show similar spatial structures on the other hand elt is controlled by slowly varying oc

the intav intercomparison of electron beam microanalysis of glass by tephrochronology laboratories results and recommendations abstract the international focus group on tephrochronology and volcanism intav of the international union for quaternary research inqua has conducted an intercomparison of tephrochronology laboratories with electron beam microanalytical data on volcanic glasses submitted from 27 instruments at 24 institutions in 9 countries this assessment includes most active tephrochronology laboratories and represents the largest intercomparison exercise yet conducted by the tephrochronology community the intercomparison was motivated by the desire to assess the quality of data currently being produced and to stimulate improvements in analytical protocols and data reporting that will increase the efficacy of tephra fingerprinting and correlation participating laboratories were each supplied with a mount containing three samples for analysis 1 rhyolitic lipari obsidian id3506 2 phonolitic sheep track tephra from mt edziza british columbia canada and 3 basaltic laki 1783 a d tephra a fourth sample rhyolitic old crow tephra was also distributed most laboratories submitted extensive details of their analytical procedures in addition to their analytical results most used some combination of defocused or rastered beam and modest beam current to reduce alkali element migration approximately two thirds reported that they routinely analyze one or more secondary standards to evaluate data quality and instrument performance despite substantial variety in procedures and calibration standards most mean concentrations compare favorably between laboratories and with other data typically four or fewer data contributions had means for a given element on a given sample that differed by more than 2 standard deviations from the overall means obtaining accurate na 2 o concentrations for the phonolitic tephra proved to be a challenge for many laboratories only one half of the data sets had means within 1 standard deviation of the 8 2 wt na 2 o value obtained by other methods one mean is higher and 14 are lower three of the data set means fall below 7 wt na 2 o most submissions had relative precision better than 1 5 for the major elements for low abundance elements the precision varied substantially with relative standard deviations as small as 10 and as large as 110 because of the strong response to this project the tephrochronology community now has a large comparative data set derived from common reference materials that will facilitate improvements in accuracy and precision and which can enable improved use of published data produced by the participating laboratories finally recommendations are provided for improving accuracy precision and reporting of electron beam microanalytical data from glasses

mid wisconsin sediment record from baldwin lake reveals hemispheric climate dynamics southern ca usa abstract recently acquired cores from baldwin lake southern california document the first regional terrestrial based evidence for glacial period millennial to orbital scale climate variability eight ams 14c dates on a 14 m core from the lake s present day depocenter provide initial age control over the interval from 20 000 to 48 000 years before present bp a linear age model extends the record to a minimum age of 65 000 years bp a combination of lithologic description and one cm contiguous sedimentological analyses indicates significant changes in the dominant type of depositional environment over the length of the record at millennial to orbital time scales as a first order interpretation the dominant sedimentary environments alternate between permanent and ephemeral lake systems orbital scale forcing includes long term winter summer insolation variability and its modulation of winter storm tracks and the north american monsoon respectively millennial scale variability is attributed to extra tropical ocean atmosphere dynamics akin to historical interdecadal pacific climate variability in addition there is notable correspondence to the independently dated greenland ice core record gisp 2 at millennial to orbital time scales suggesting that baldwin lake contains in addition to its local regional record a hemispheric record of climate change similar to owens pyramid and summer lake of central and northwestern north america an initial comparison to gisp2 18o ice indicates that north atlantic interstadials correlate to permanent lake environments in coastal southwestern north america these results present a notable conflict with the proposed super enso phenomenon in the western tropical pacific these results also highlight the necessity for acquiring additional high resolution glacial period records for resolving questions of spatial temporal phasing of late quaternary climates

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

model assessment of decadal variability and trends in the tropical pacific ocean abstract in this report global coupled ocean atmosphere models are used to explore possible mechanisms for observed decadal variability and trends in pacific ocean ssts over the past century the leading mode of internally generated decadal 7 yr variability in the model resembles the observed decadal variability in terms of pattern and amplitude in the model the pattern and time evolution of tropical winds and oceanic heat content are similar for the decadal and enso timescales suggesting that the decadal variability has a similar delayed oscillator mechanism to that on the enso timescale the westward phase propagation of the heat content anomalies however is slower and centered slightly farther from the equator 12 vs 9 n for the decadal variability cool sst anomalies in the midlatitude north pacific during the warm tropical phase of the decadal variability are induced in the model largely by oceanic advection anomalies an index of observed sst over a broad triangular region of the tropi

interdecadal thermocline variability in the north pacific for 1958 97 a gcm simulation an ocean general circulation model is forced with the ncep reanalysis wind stress for 1958 97 to understand mechanisms of ocean subsurface variability with relatively high horizontal 1 83 18 and vertical 41 levels resolutions the model produces mode waters on a range of density surfaces in the western central and eastern north pacific in qualitative agreement with observations these mode waters appear as a thermostad or a region of weak stratification in the upper thermocline as they flow southward from their formation regions in the kuroshio and its extension in the model subsurface temperature variability in the central subtropical gyre reaches a maximum within the thermostad in contrast to what might be expected from the linear baroclinic rossby wave theory this variance maximum is associated with the longitudinal shift in the path of mode waters in particular deepened mixed layer and accelerated eastward currents in the kuroshio extension by wind changes in the mid 1970s act cooperatively to move the central mode waters toward the east causing large subsurface temperature anomalies besides the local maximum in the central north pacific subtropical gyre two additional maxima of the subsurface anomaly are identified in the northwestern and southern parts of the gyre respectively among these subsurface anomaly centers the one in the northwestern north pacific has a strong effect on the model sea surface temperature suggesting that the kuroshio and its extension are a key region to decadal interdecadal ocean atmosphere interaction finally possible effects of atmospheric thermal forcing are discussed

south pacific origin of the decadal enso like variation as simulated by a coupled gcm 1 the hypothesis of the south pacific origin of the decadal 7 35 years enso like variation is investigated based on 200 year outputs of the echam4 opa oasis coupled gcm associated with the decadal warm cold sst anomalies in the tropical pacific an anomalous cyclonic anticyclonic circulation which is tilted in a southeast northwest direction appears in the south pacific this results in anomalous upward downward ekman pumping along the northeastern edge of the anomalous circulation and hence shallowing deepening the oceanic thermocline there such an external source of heat content tends to slowly discharge recharge the tropical ocean on the decadal timescale the above result is consistent with the observational study of luo and yamagata 2001 besides the model reproduces amazingly a high lagged correlation between the global land surface temperature and the decadal nino3 sst despite the model biases this suggests a potential prediction skill of the global warming based on the enso like decadal variation

generation mechanism of quasidecadal variability of upper ocean heat content in the equatorial pacific ocean 1 we investigate the relationship between oceanic and atmospheric anomaly fields in the tropical pacific on the quasidecadal qd 10 to 18 years scale is explored it is suggested that the anomalous wind stress curl in the tropical south pacific can generate the equatorial upper ocean heat content ohc anomalies on the qd scale via the sverdrup transport resembling that of the recharge discharge oscillator model for the dynamics of el nino southern oscillation enso the results also show that the wind stress curl anomalies in the tropical south pacific are accompanied by enso like qd scale anomaly patterns of the sea level pressure and sea surface temperature furthermore the results indicate that the equatorial qd scale ohc anomalies can also be generated by the enso like propagations of the ohc anomalies in the tropical north and south pacific this study presents a systematic linkage between the enso like qd scale ohc propagation in the tropical north and south pacific the sverdrup transport variation in the tropical south pacific and the enso like qd scale sst and slp anomalies in the tropical pacific

simulation of the response of the north pacific ocean to the anomalous atmospheric circulation associated with el nino during el nino events when positive sea surface temperature sst anomalies form in the equatorial pacific sst anomalies also tend to develop in the north pacific this study attempts to model and explain the large scale features of the observed sst anomaly field in the north pacific during the fall and winter of the el nino year the experiment design consists of a mixed layer ocean model of the north pacific which is forced by atmospheric surface fields from two sets of community climate model ccm integrations the el nino set with prescribed positive sst anomalies in the tropical pacific and the control set which is obtained from an extended ccm integration with prescribed climatological ssts the response of the midlatitude ocean to atmospheric surface fields associated with el nino is obtained by compositing each set of model integrations el nino and control and then taking the difference between the composites the ocean model is able to reproduce the general features of the observed midlatitude sst anomaly pattern warm water in the northeast pacific and an elliptically shaped cold pool in the central pacific in these regions a large fraction of the temperature anomalies are significant at the 95 level as indicated by a two tailed t test the ocean temperature anomalies simulated by the model are primarily caused by changes in the sensible and latent heat flux and to a lesser extent the longwave radiation flux entrainment of cold water from below the mixed layer also influences ocean temperatures however the entrainment anomaly pattern has a complex spatial structure which does not always coincide with the simulated mixed layer temperature anomalies

the spatiotemporal structure of twentieth century climate variations in observations and reanalyses part ii pacific pan decadal variability abstract the spatiotemporal structure of pacific pan decadal variability pdv is isolated in global long term surface temperature st datasets and reanalysis atmospheric parameter fields from which el nino southern oscillation enso effects have been removed empirical orthogonal function eof and combined eof analysis of the resulting time series identify pdv as one of two primary modes of long term variability the other being a global warming gw trend which is addressed in a companion paper part i in this study it is shown that one of several pdv interdecadal regime shifts occurred during the 1990s this significant change in the pacific basin is comparable but antiphase to the well known 1976 climate regime shift and is consistent with the observed changes in biosystems and ocean circulation a comprehensive picture of pdv as manifested in the troposphere and at the surface is described in general the pdv spatial patterns in different parameter fields share some similarities with the patt

the 2001 2004 dome forming eruption of shiveluch volcano kamchatka observation petrological investigation and numerical modelling there have been three episodes of lava dome growth at shiveluch volcano kamchatka since the plinian explosive eruption in 1964 the episodes in 1980 1981 1993 1995 and 2001 2004 have discharged at least 0 27km 3 of silicic andesite magma a time averaged mean extrusion rate of 0 2m 3 s is thus estimated for the last 40years here the 2001 2004 activity is described and compared with the earlier episodes the recent activity involved three pulses in extrusion rate and a transition to ongoing lava extrusion estimated magma temperatures are in the range 830 to 900 c with 850 c as the best estimate using the plagioclase amphibole phenocryst assemblage and fe ti oxides melt inclusions in amphibole and plagioclase have maximum water contents of 5 1wt implying a minimum pressure of 155mpa for water saturated conditions the magma chamber depth is estimated to be about 5 6km or more a result consistent with geophysical data the thicknesses of opx mt amph reaction rims on olivine xenocrysts are used to estimate the residence time of olivine crystals in the shallow chamber in the range 2 months to 4 years suggesting replenishment of deeper magma into the shallow chamber contemporaneous with eruption the absence of decompression driven breakdown rims around amphiboles indicates ascent times of less than 7days volcanological observations of the start of the 2001 2004 episode suggest approximately 16 days for the ascent time and a conduit equivalent to a cylinder of diameter approximately 53 71m application of a conduit flow model indicates that the magma chamber was replenished during the 2001 2004 eruption consistent with the results of olivine reaction rims and that the chamber has an estimated volume of order 7km 3

magma evolution and open system processes at shiveluch volcano insights from phenocryst zoning phenocryst zoning patterns are used to identify open system magmatic processes in the products of the 2001 eruption of shiveluch volcano kamchatka the lavas and pumices studied are hornblende plagioclase andesites with average pre eruptive temperatures of 840c and fo2 of 1 5 2 1 log units above nickel nickel oxide nno plagioclase zoning includes oscillatory and patchy zonation and sieve textures hornblendes are commonly unzoned but some show simple multiple or patchy zoning apatite microphenocrysts display normal and reverse zoning of sulphur the textural similarity of patchy hornblende and plagioclase together with ba sr systematics in patchy plagioclase indicate that the cores of these crystals were derived from cumulate material plagioclase liquid equilibria suggest that the patchy texture develops by resorption during h2o undersaturated decompression when h2o saturated crystallization recommences at lower pressure reduced ph2o results in lower xan in plagioclase causing more al rich hornblende to crystallize plagioclase cores with diffuse oscillatory zoning and unzoned hornblende crystals probably represent a population of crystals resident in the magma chamber for long periods of time in contrast oscillatory zoning in the rims of plagioclase phenocrysts may reflect eruption dynamics during decompression crystallization increasing fe al in oscillatory zoned rims suggests oxidation as a result of degassing of h2o during decompression a general lack of textural overlap between phenocryst types suggests that different phenocryst populations were spatially or temporally isolated during crystallization we present evidence that the host andesite has mixed with both more felsic and more mafic magmas olivine and orthopyroxene xenocrysts with reaction or overgrowth rims and strong normal zoning indicate mixing with basalt sieve textured plagioclase resulted from mixing of a more felsic magma with the host andesite the mineralogy and mineral compositions of a mafic andesite enclave are identical to those of the host magma which implies efficient thermal quenching and thus small volumes of intruding magma mixing of this magma with the host andesite results in phenocryst zoning because of differences in dissolved volatile contents we suggest that small magma pulses differentiated at depth and ascended intermittently into the growing magma chamber producing incremental variations in whole rock compositions

implications of seawater mg ca variability for plio pleistocene tropical climate reconstruction abstract recent reconstructions of mg and ca concentrations of seawater indicate that seawater mg ca changed significantly over the last 5 million years ma tropical sea surface temperature sst records for the last 5 ma based on foraminiferal mg ca paleothermometry assume constant seawater mg ca these sst records suggest that average equatorial pacific ssts remained thermally stable from 5 to 2 ma after which significant cooling occurred only in the eastern equatorial pacific this study examines the implications of adjusting available equatorial pacific sst records based on mg ca paleothermometry to account for the inferred past variations of seawater mg ca the results suggest that both the cold and the warm regions of the equatorial pacific were much warmer during the early pliocene 30 31 c and that both regions experienced a marked cooling from 4 ma to 1 ma this new interpretation of foraminiferal mg ca creates a discrepancy with alkenone unsaturation based sst records from the eastern equatorial pacific which might be due to either overestimation of changes in past seawater mg ca or to factors affecting the interpretation of the u k 37 index the adjusted sst records are consistent with the hypothesis that higher levels of greenhouse gases maintained the warmth of the early pliocene

toward understanding the response of the tropical atmosphere ocean system to increased co2 using equilibrium asynchronous coupling we investigate the response of the tropical pacific climate system to a tripling of co2 in a coupled atmosphere ocean model equilibrium asynchronous coupling eac is used to diagnose the climatic forcing mechanisms our results corroborate those from most other coupled gcms which generally simulate an el nino like mean climate state under increased co2 this pattern is characterized by enhanced warming of the ocean surface in the equatorial pacific in conjunction with a reduction in the zonal sst gradient stronger atmospheric convection and precipitation in the central equatorial pacific a stronger subtropical westerly jet and a deepened wintertime aleutian low in association with a pna like geopotential pattern aloft we show that these climate changes are triggered by a weakening of the tropical walker circulation which leads to weaker surface easterly winds along the equator and therefore less oceanic upwelling furthermore the main el nino like atmospheric anomalies do not depend critically on the existence of an east west equatorial gradient either in the simulated modern ssts or in the sst anomalies under increased co2 regardless of the details of the sst boundary conditions the atmosphere seems to respond similarly to a co2 warming perturbation and in a manner that favors the evolution of the climate system toward an el nino like state an enhanced meridional atmospheric circulation in the pacific is linked to increased convection along the itcz coinciding with subtropical anomalies of higher surface pressure and stronger subsidence aloft this anomalous surface pressure pattern is much more pronounced in the northern hemisphere presumably due to a pna like atmospheric teleconnection these surface pressure anomalies produce a stronger meridional outflow of wind toward the equator and weaker easterly winds along the equator the weaker equatorial easterlies reduce oceanic upwelling in the central and eastern equatorial pacific thereby promoting a reduced east west sst gradient and a maximum warming in the central equatorial pacific around 140 170 w

indo pacific variability on seasonal to multidecadal time scales part ii multiscale atmosphere ocean linkages abstractthe coupled atmosphere ocean variability of the indo pacific domain on seasonal to multidecadal time scales is investigated in ccsm4 and in observations through nonlinear laplacian spectral analysis nlsa it is found that enso modes and combination modes of enso with the annual cycle exhibit a seasonally synchronized southward shift of equatorial surface zonal winds and thermocline adjustment consistent with terminating el nino and la nina events the surface winds associated with these modes also generate teleconnections between the pacific and indian oceans leading to sst anomalies characteristic of the indian ocean dipole the family of nlsa enso modes is used to study el nino la nina asymmetries and it is found that a group of secondary enso modes with more rapidly decorrelating temporal patterns contributes significantly to positively skewed sst and zonal wind statistics besides enso fundamental and combination modes representing the tropospheric biennial oscillation tbo are found to

mechanisms of tropical pacific interannual to decadal variability in the arpege orca global coupled model spatial and temporal structures of interannual to decadal variability in the tropical pacific ocean are investigated using results from a global atmosphere ocean coupled general circulation model the model produces quite realistic mean state characteristics despite a sea surface temperature cold bias and a thermocline that is shallower than observations in the western pacific the periodicity and spatial patterns of the modelled el nino southern oscillations enso compare well with those observed over the last 100 years although the quasi biennial timescale is dominant lag regression analysis between the mean zonal wind stress and the 20 c isotherm depth suggests that the recently proposed recharge oscillator paradigm is operating in the model decadal thermocline variability is characterized by enhanced variance over the western tropical south pacific 7 s the associated subsurface temperature variability is primarily due to adiabatic displacements of the thermocline as a whole arising from ekman pumping anomalies located in the central pacific south of the equator related wind anomalies appear to be caused by sst anomalies in the eastern equatorial pacific this quasi decadal variability has a timescale between 8 years and 20 years the relationship between this decadal tropical mode and the low frequency modulation of enso variance is also discussed results question the commonly accepted hypothesis that the low frequency modulation of enso is due to decadal changes of the mean state characteristics

low frequency modes of tropical ocean dynamics abstract basinwide very low frequency vlf modes with zonal uniformly deepening and shoaling of the equatorial thermocline are found as solutions of linear shallow water equations with the meridional basin boundaries under an equatorial plane they can be understood as the free heat content recharge oscillations the interannual vlf modes had been recognized as the essential part of the coupled recharge oscillator theory for the el nino southern oscillation it is suggested that the decadal vlf modes may also be transformed into coupled modes relevant to the pacific decadal climate variability through the ocean atmosphere interaction in the tropics

the shiveluch volcanic eruption of 12 november 1964 explosive eruption provoked by failure of the edifice abstract restudy of deposits at shiveluch in comparison with other data has shown that the sequence of eruptive events at shiveluch volcano on 12 november 1964 was the following edifice failure involving 1 154 km3 of material at 07 07 a m phreatic explosion with ejection of resurgent ash with a volume of 0 01 km3 plinian activity between 07 20 and 07 47 a m during which andesitic juvenile tephra with a volume of 0 3 km3 erupted during the final stage of the eruption between 07 47 and 08 22 a m pyroclastic flows with a volume of 0 3 0 5 km3 were erupted in this sequence there was no catastrophic directed blast with generation of a destructive pyroclastic density current like those that took place at bezymianny volcano in 1956 and at mount st helens in 1980 the absence of a directed blast is attributed to the fact that the 1964 eruption occurred before magma had enough time to intrude into the edifice and build a cryptodome the failure of the edifice depressurized only a hydrothermal system that existed around the old domes this appears to have been insufficient for the generation of a catastrophic directed blast the case history of volcanic activity at shiveluch before 1964 suggests that if the edifice of the young shiveluch had been stronger and had not failed by landsliding the eruption of 1964 might have consisted of prolonged dome extrusion with relatively weak explosive activity

the influence of climate regime shift on enso observations indicated that for the el nino southern oscillation enso there have been eastward displacements of the zonal wind stress ws anomalies and surface heat flux short wave heat flux and latent heat flux anomalies during el nino episodes in the 1981 1995 regime relative to the earlier regime of 1961 1975 without corresponding displacements during la nina episodes our numerical experiments with the zebiak cane coupled model generally reproduced such displacements when the model climatological fields were replaced by the observed climatologies of sea surface temperature sst surface ws and surface wind atmospheric divergence and simulated climatologies of oceanic surface layer currents and associated upwelling for the 1981 1995 regime sensitivity tests indicated that the background atmospheric state played a much more important role than the background ocean state in producing the displacements which enhanced the asymmetry between el nino and la nina in the later regime the later regime climatology state resulted in the eastward shifts in the enso system ws and sst only during el nino through the eastward shift of the atmosphere convergence heating rate in the coupled model the enso period and enso predictability were also enhanced in the coupled model under the later regime climatology that the change in the mean state of the tropical pacific atmosphere and ocean after the mid 1970s could have produced the observed changes in enso properties is consistent with our findings

oceanic rossby wave dynamics and the enso period in a coupled model abstract tropical ocean wave dynamics associated with the el nino southern oscillation cycle in a coupled model are examined the ocean atmosphere model consists of statistical atmosphere coupled to a simple reduced gravity model of the tropical pacific ocean the statistical atmosphere is simple enough to allow for the structure and position of the wind stress anomalies to be externally specified in a control simulation where the structure of the wind stress anomaly is determined from observations the model produces a regular 5 yr oscillation this simulation is consistent with the so called delayed oscillator theory in that subsurface wave dynamics determine the slow timescale of the oscillation and surface layer processes are found to be of secondary importance kelvin and rossby wave propagation is detected along the equator with periods considerably shorter than the simulated oscillation period the way in which these relatively fast waves are related to the simulated 5 yr oscillation is discusse

on the relationship between tropical and north pacific sea surface temperature variations abstract empirical orthogonal function analysis of winter sea surface temperature sst anomalies over the pacific domain 60 n 20 s reveals an el nino southern oscillation enso mode that is linked to the eastern north pacific and a north pacific mode that is linearly independent of enso the north pacific mode exhibits maximum amplitude and variance explained along 40 n west of 170 w ssts in this region have decreased by 1 5 c from 1950 to 1987 the cooling in winter has been associated with a strengthening of the overlying westerly winds

upper ocean thermal variations in the north pacific during 1970 1991 abstract a newly available extensive compilation of upper ocean temperature profiles was used to study the vertical structure of thermal anomalies between the surface and 400 m depth in the north pacific during 1970 1991 a prominent decade long perturbation in climate occurred during this time period surface waters cooled by 1 c in the central and western north pacific and warmed by about the same amount along the west coast of north america from late 1976 to 1988 comparison with data from coads suggests that the relatively sparse sampling of the subsurface data is adequate for describing the climate anomaly the vertical structure of seasonal thermal anomalies in the central north pacific shows a series of cold pulses beginning in the fall of 1976 and continuing until late 1988 that appear to originate at the surface and descend with time into the main thermocline to at least 400 m depth individual cold events descend rapidly 100 m yr 1 superimposed upon a slower cooling 15 m yr 1 the inter

multi year predictability in a coupled general circulation model multi year to decadal variability in a 100 year integration of a bmrc coupled atmosphere ocean general circulation model cgcm is examined the fractional contribution made by the decadal component generally increases with depth and latitude away from surface waters in the equatorial indo pacific ocean the relative importance of decadal variability is enhanced in off equatorial wings in the subtropical eastern pacific the model and observations exhibit enso like decadal patterns analytic results are derived which show that the patterns can in theory occur in the absence of any predictability beyond enso time scales in practice however modification to this stochastic view is needed to account for robust differences between enso like decadal patterns and their interannual counterparts an analysis of variability in the cgcm a wind forced shallow water model and a simple mixed layer model together with existing and new theoretical results are used to improve upon this stochastic paradigm and to provide a new theory for the origin of decadal enso like patterns like the interdecadal pacific oscillation and pacific decadal oscillation in this theory enso driven wind stress variability forces internal equatorially trapped kelvin waves that propagate towards the eastern boundary kelvin waves can excite reflected internal westward propagating equatorially trapped rossby waves rws and coastally trapped waves ctws ctws have no impact on the off equatorial sub surface ocean outside the coastal wave guide whereas the rws do if the frequency of the incident wave is too high then only ctws are excited at lower frequencies both ctws and rws can be excited the lower the frequency the greater the fraction of energy transmitted to rws this lowers the characteristic frequency reddens the spectrum of variability off the equator relative to its equatorial counterpart at low frequencies dissipation acts as an additional low pass filter that becomes more effective as latitude increases at the same time enso driven off equatorial surface heating anomalies drive mixed layer temperature responses in both hemispheres both the eastern boundary interactions and the accumulation of surface heat fluxes by the surface mixed layer act to low pass filter the enso forcing the resulting off equatorial variability is therefore more coherent with low pass filtered decadal enso indices e g nino3 sea surface temperature sst than with unfiltered enso indices consequently large correlations between variability and nino3 extend further poleward on decadal time scales than they do on interannual time scales this explains why decadal enso like patterns have a broader meridional structure than their interannual counterparts this difference in appearance can occur even if enso indices do not have any predictability beyond interannual time scales the wings around 15 20 s and sub surface variability at many other locations are predictable on interannual and multi year time scales this includes westward propagating internal rws within about 25 of the equator the slowest of these take up to 4 years to reach the western boundary this sub surface predictability has significant oceanographic interest however it is linked to only low levels of sst variability consequently extrapolation of delayed action oscillator theory to decadal time scales might not be justified

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

decadal scale variability of upper ocean heat content in the tropical pacific 1 decadal scale variability of upper ocean heat content ohc in the tropical pacific is investigated and is compared with that of enso scale the decadal scale ohc anomaly with a period of about 13 years shows anticlockwise propagations in the tropical north pacific like as that of enso scale it is also shown that the entire equatorial ohc anomaly leads nino 3 index anomaly by about a quarter about 3 years of the period of the decadal variability in the tropical pacific this time lag of a quarter of the period is consistent with the idea of the recharge oscillator model for enso dynamics further it is shown that the magnitude of leading ohc anomalies in the entire equatorial pacific is linearly related to the subsequent magnitudes of nino 3 and nino 3 4 indices this relationship is also similar with that of enso scale but there are several different points between them particularly in contrast with the enso scale the amplitude is larger in central equatorial pacific nino 3 4 region than in the eastern region nino 3 region

simulation of el nino southern oscillation like variability in a global aogcm and its response to co2 increase abstract a 75 year integration of a coupled atmosphere ocean model is examined for tropical interannual variability the atmospheric model has interactive cloud and a seasonal cycle the fluxes of heat and salinity into the ocean component of the model are flux corrected the model has tropical variability that is qualitatively similar to that of the observed el nino southern oscillation enso the maximum amplitude of the model nino3 signal is approximately half that observed and the modeled enso timescale is greater than that observed in the first 50 years of the integration the model has eight warm events each event is one of two types one characterized by a standing sst anomaly in the central and eastern pacific and the other by a westward propagating sea surface temperature anomaly the majority of the model warm events are of the first type the first type of event is triggered by the eastward propagation of kelvin waves across the pacific and the second by westward propagation of warm temperat

phase relations and liquid lines of descent in hydrous ferrobasalt implications for the skaergaard intrusion and columbia river flood basalts crystallization experiments using a hydrous ferrobasalt as starting material conducted at 200mpa 940 12008c at a wide range of water activities 0 1 1 and redox conditions qfm 3 to qfm 4 where qfm is the quartz fayalite magnetite oxygen buffer show that h2o influences significantly the differentiation history of ferrobasaltic magmas a combination of our data with published experiments on dry ferrobasalt at 1atm provides an extensive experimental database for modeling and quantifying crystallization and differentiation processes within a typical fe rich tholeiitic system under both dry and hydrous conditions the addition of h2o decreases liquidus temperatures and changes significantly the proportions temperature range and sequence of crystallizing mineral phases the dry liquidus is at about 11708c whereas the liquidus for h2o saturated melts is at 10608c the main phases crystallizing from h2o bearing ferrobasalt at the investigated conditions are olivine ol clinopyroxene cpx plagioclase pl magnetite mt hematite hm ilmenite ilm and amphibole am the phase assemblage is similar to that of the dry system except for the presence of hm at extremely oxidizing conditions and am at low temperatures 59508c and h2o saturated conditions the important observation made in this study is that the stability of fe ti oxides and in particular mt as well as the simultaneous coprecipitation of mtand ilm are almost independent of the activity of h2o ah2o in the system whereas the liquidus temperatures of the silicate minerals are dramatically depressed by increasing ah2o the stabilities of oxides are controlled mainly by the redox conditions prevailing in the system the most pronounced effect of ah2o on the liquidus temperatures of silicates is observed for pl which shows a considerable delay in crystallization with progressive magma differentiation early crystallization of fe ti oxides in h2o bearing ferrobasaltic compositions precludes any significant fe enrichment during differentiation as fe enrichment is a characteristic feature of the skaergaard intrusion it implies that the skaergaard parental magma did not contain considerable amounts of water on the other hand our experiments indicate that the differentiation of some ferrobasaltic series from the columbia river flood basalt province might have occurred in magmatic systems containing significant amounts of volatiles 0 5 3 wt h2o

representation of topography in spectral climate models and its effect on simulated precipitation abstract spectral climate models are distinguished by their representation of variables as finite sums of spherical harmonics with coefficients computed by an orthogonal projection of the variables onto the spherical harmonics representing the surface elevation in this manner results in its contamination by gibbs like truncation artifacts which appear as spurious valleys and mountain chains in the topography these gibbs ripples are present in the surface topographies of spectral climate models from a number of research institutions integrations of the geophysical fluid dynamics laboratory gfdl climate model over a range of horizontal resolutions indicate that the gibbs ripples lead to spurious small scale extrema in the spatial distribution of precipitation this cellular precipitation pathology becomes more pronounced with increasing horizontal resolution causing a deterioration in the fidelity of simulated precipitation in higher resolution models a method is described for reducing the gib

late pliocene equatorial pacific 1 late pliocene foraminiferal mg ca and 18o records from ocean drilling program hole 806b in the western equatorial pacific wep reveal warm pool climate evolution during the onset of northern hemisphere glaciation 3 1 2 3 myr b p mg ca data indicate an average late pliocene sea surface temperature sst of 27 8 c a small long term cooling of 0 3 c between 3 1 and 2 3 ma and a glacial interglacial g i sst range of 2 c throughout this time interval for comparison pleistocene ssts at this site over the last 0 9 myr average 27 7 c with a g i range of 3 c orbital scale variability in hole 806b ssts during the late pliocene occurs predominantly at 100 ka in contrast to foraminiferal 18o records which show a dominant 41 kyr period variability at a 41 kyr period out of phase with local annual insolation changes driven by obliquity is also observed in the new wep sst record the wep sst record suggests that an 3 c equatorial pacific sst zonal gradient prevailed during the late pliocene compatible with a weaker walker circulation adjustment of hole 806b ssts for past changes in seawater mg ca suggests that ssts higher than 30 c prevailed at 3 myr b p followed by a progressive cooling of the warm pool through the late pliocene the characteristics of late pliocene tropical climate evolution suggest that atmospheric greenhouse gas forcing played a major role in driving the observed g i sst changes

identification of the fugloyarbanki tephra in the ngrip ice core a key tie point for marine and ice core sequences during the last glacial period a visible tephra horizon in the ngrip ice core has been identified by geochemical analysis as the fugloyarbanki tephra a widespread marker horizon in marine cores from the faroe islands area and the northern north atlantic an age of 26 740 390 yr b2k 1 uncertainty is derived for this tephra according to the new greenland ice core chronology gicc05 based on multi parameter counting of annual layers detection of this tephra for the first time within the ngrip ice core provides a key tie point between marine and ice core records during the transition between mis 3 and 2 identification of this volcanic event within the greenland records demonstrates the future potential of using tephrochronology to precisely correlate palaeoarchives in widely separated localities that span the last glacial period as well as providing a potential method for examining the extent of the radiocarbon marine reservoir effect at this time copyright 2008 john wiley sons ltd

vertical structure variability in the equatorial pacific before and after the pacific climate shift of the 1970s 1 oceanic baroclinic modes in the equatorial pacific are estimated using results from the soda system our result suggests that the vertical stratification increases at the upper levels after the late 1970s due to changes in the vertical temperature structure after the late 1970s the variability of the higher order baroclinic mode contributions to current anomalies and surface pressure significantly increases in the central equatorial pacific this is associated with an increase of the dominant period of the enso variability simple coupled model experiments indicate that when atmospheric forcing projects more onto the higher baroclinic modes according to the results of the soda decomposition the amplitude and dominant period of enso increase similarly to what is observed at the pacific decadal shift our results support that the changes in the behavior of enso after the late 1970s are associated with oceanic vertical structural changes in temperature that tend to increase the contribution of higher order baroclinic modes

tephra from andesitic shiveluch volcano kamchatka nw pacific chronology of explosive eruptions and geochemical fingerprinting of volcanic glass the 16 ka long record of explosive eruptions from shiveluch volcano kamchatka nw pacific is refined using geochemical fingerprinting of tephra and radiocarbon ages volcanic glass from 77 prominent holocene tephras and four late glacial tephra packages was analyzed by electron microprobe eruption ages were estimated using 113 radiocarbon dates for proximal tephra sequence these radiocarbon dates were combined with 76 dates for regional kamchatka marker tephra layers into a single bayesian framework taking into account the stratigraphic ordering within and between the sites as a result we report 1 700 high quality glass analyses from late glacial holocene shiveluch eruptions of known ages these define the magmatic evolution of the volcano and provide a reference for correlations with distal fall deposits shiveluch tephras represent two major types of magmas which have been feeding the volcano during the late glacial holocene time baidarny basaltic andesites and young shiveluch andesites baidarny tephras erupted mostly during the late glacial time 16 12 8 ka bp but persisted into the holocene as subordinate admixture to the prevailing young shiveluch andesitic tephras 12 7 ka bp present baidarny basaltic andesite tephras have trachyandesite and trachydacite sio2 71 5 wt strongly calc alkaline medium k characteristics of shiveluch volcanic glasses along with moderate cl cao and low p2o5 contents permit reliable discrimination of shiveluch tephras from the majority of other large holocene tephras of kamchatka the young shiveluch glasses exhibit wave like variations in sio2 contents through time that may reflect alternating periods of high and low frequency volume of magma supply to deep magma reservoirs beneath the volcano the compositional variability of shiveluch glass allows geochemical fingerprinting of individual shiveluch tephra layers which along with age estimates facilitates their use as a dating tool in paleovolcanological paleoseismological paleoenvironmental and archeological studies electronic tables accompanying this work offer a tool for statistical correlation of unknown tephras with proximal shiveluch units taking into account sectors of actual tephra dispersal eruption size and expected age several examples illustrate the effectiveness of the new database the data are used to assign a few previously enigmatic wide spread tephras to particular shiveluch eruptions our finding of shiveluch tephras in sediment cores in the bering sea at a distance of 600 km from the source permits re assessment of the maximum dispersal distances for shiveluch tephras and provides links between terrestrial and marine paleoenvironmental records

interdecadal changes of surface temperature since the late nineteenth century we present global fields of decadal annual surface temperature anomalies referred to the period 1951 1980 for each decade from 1881 1890 to 1981 1990 and for 1984 1993 in addition we show decadal calendar seasonal anomaly fields for the warm decades 1936 1945 and 1981 1990 the fields are based on sea surface temperature sst and land surface air temperature data the ssts are corrected for the pre world war ii use of uninsulated sea temperature buckets and incorporate adjusted satellite based ssts from 1982 onward our results extend those published in the 1990 intergovernmental panel on climate change scientific assessment and its 1992 supplement we assess the impact of various sources of error in the fields despite poor data coverage initially and around the two world wars the generally cold end of the nineteenth century and start to the twentieth century are confirmed together with the substantial warming between about 1920 and 1940 slight cooling of the northern hemisphere took place between the 1950s and the mid 1970s although slight warming continued south of the equator recent warmth has been most marked over the northern continents in winter and spring but the 1980s were warm almost everywhere apart from greenland the northwestern atlantic and the midlatitude north pacific parts of the middle to high latitude southern ocean may also have been cool in the 1980s but in this area the 1951 1980 climatology is unreliable the impact of the satellite data is reduced because the record of blended satellite and in situ sst is still too short to yield a climatology from which to calculate representative anomalies reflecting climatic change in the southern ocean however we propose a method of using existing satellite data in a step toward this target the maps are condensed into global and hemispheric decadal surface temperature anomalies we show the sensitivity of these estimated anomalies to alternative methods of compositing the spatially incomplete fields running decadal zonal means and annual global and hemispheric time series are also shown finally we discuss some salient features in terms of observed atmospheric circulation changes and of the results of climate model integrations with increasing atmospheric greenhouse gases

trend in northern hemisphere winter atmospheric circulation during the last half of the twentieth century abstract during the last half century the trend in the northern hemisphere tropospheric circulation has been associated with a deepening of both the aleutian and icelandic lows a pattern akin to the cold ocean warm land cowl pattern a simplified dynamical model is used to show that the observed simultaneous deepening trend in both the aleutian and icelandic lows can be largely explained as a hemispheric planetary wave response to tropical diabatic forcing in the indo pacific region in the model the extratropical storm tracks play a role in modulating the wave train tending to enhance weaken the anomalous icelandic aleutian low in the north atlantic north pacific sector the model results also suggest two ways in which the circulation trend over the north atlantic sector could have been influenced by tropical forcing one a direct linear planetary wave response from the eastern tropical pacific and the other an indirect response of the north atlantic storm track to tropical forcing over th

interdecadal variability of the pacific ocean model response to observed heat flux and wind stress anomalies variability of the pacific ocean is examined in numerical simulations with an ocean general circulation model forced by observed anomalies of surface heat flux wind stress and turbulent kinetic energy tke over the period 1970 88 the model captures the 1976 77 winter time climate shift in sea surface temperature as well as its monthly seasonal and longer term variability as evidenced in regional time series and empirical orthogonal function analyses examination of the surface mixed layer heat budget reveals that the 1976 77 shift was caused by a unique concurrance of sustained heat flux input anomalies and very strong horizontal advection anomalies during a multi month period preceding the shift in both the central pacific region where cooling occurred and the california coastal region where warming occurred in the central pacific the warm conditions preceding and the cold conditions following the shift tend to be maintained by anomalous vertical mixing due to increases in the atmospheric momentum flux tke input into the mixed layer which deepens in the model after the shift from the early 1970s to the late 1970s and 1980s since the ocean model does not contain feedback to the atmosphere and it succeeds in capturing the major features of the 1976 77 shift it appears that the midlatitude part of the shift was driven by the atmosphere although effects of midlatitude ocean atmosphere feedback are still possible the surface mixed layer heat budget also reveals that in the central pacific the effects of heat flux input and vertical mixing anomalies are comparable in amplitude while horizontal advection anomalies are roughly half that size in the california coastal region in contrast where wind variability is much weaker than in the central pacific horizontal advection and vertical mixing effects on the mixed layer heat budget are only one quarter the size of typical heat flux input anomalies

pacific ocean circulation rebounds 1 recent observations indicate that the shallow meridional overturning circulation in the tropical pacific ocean has rebounded since 1998 following 25 years of significantly weaker flow convergence of cold interior ocean pycnocline water towards the equator increased to 24 1 1 8 106 m3 s 1 during 1998 2003 from a low of 13 4 1 6 106 m3 s 1 during 1992 98 intensified circulation led to the development of anomalously cool tropical pacific sea surface temperatures which may have affected pacific marine ecosystems and global climate the abruptness of the rebound also obscures presumed anthropogenic warming trends in the instrumental temperature record of the tropical pacific

principal modes of rainfall sst variability of the asian summer monsoon a reassessment of the monsoon enso relationship abstract using global rainfall and sea surface temperature sst data for the past two decades 1979 98 the covariability of the asian summer monsoon asm and el nino southern oscillation enso was investigated the findings suggest three recurring rainfall sst coupled modes characterized by a pronounced biennial variability the first mode is associated with generally depressed rainfall over the western pacific and the maritime continent stemming from the eastward shift of the walker circulation during the growth phase of el nino the associated sst pattern consists of an east west sst seesaw across the pacific and another seesaw with opposite polarity over the indian ocean the second mode is associated with a growing la nina comprising mixed regional and basin scale rainfall and sst variability with abnormally warm water in the vicinity of the maritime continent and western pacific it possesses a pronounced low level west pacific anticyclone wpa near the philippines and exhibits large sub

characterizing and comparing the control run variability of eight coupled aogcms and of observations part 2 precipitation we examine the spatial patterns of variability of annual mean temperature in the control runs of eight coupled atmosphere ocean general circulation models aogcms and of observations we characterize the patterns of variability using empirical orthogonal functions eofs and using a new technique based on what we call quasi eofs the quasi eofs are computed based on the spatial pattern of the correlation between the temperature variation at a given grid point and the temperature defined over a pre determined reference region with a different region used for each quasi eof for the first four quasi eofs the reference regions are the entire globe the nino3 region western europe and siberia since the latter three regions are the centers of strong anomalies associated with the el nino north atlantic and siberian oscillations respectively the spatial pattern of the covariance with temperature in these regions gives the structure of the model or observed el nino north atlantic and siberian components of variability when eof analysis is applied to the model control runs the patterns produced generally have no similarity to the eof patterns produced from observational data this is due in some cases to large nao like variability appearing as part of eof1 along with enso like variability rather than as separate eof modes this is a disadvantage of eof analysis the fraction of the model time space variation explained by these unrealistic modes of variability is generally greater than the fraction explained by the principal observed modes of variability when qeof analysis is applied to the model data all three natural modes of variability are seen to a much greater extent however the fraction of global time space variability that is accounted for by the model enso variability is in our analysis less than observed for all models except the hadcm2 model but within 20 for another three models the space time variation accounted for by the other modes is comparable to or somewhat larger than that observed in all models as another teleconnection indicator we examined both southern oscillation index soi and its relation to tropical pacific ocean temperature variations the qeof2 amplitude and the north atlantic oscillation index naoi and its relation to north atlantic region temperatures the qeof3 amplitude all models exhibit a relationship between these indices and the qeof amplitudes are comparable to those observed furthermore the models show realistic spatial patterns in the correlation between local temperature variations and these indices

integrating the intimate records using tephrochronology rising to the challenge little has challenged our understanding of climate change more so than the abruptness with which large scale shifts in temperature occurred during the late quaternary the causal mechanisms driving

ascent driven crystallisation of dacite magmas at mount st helens 1980 1986 we introduce a novel scheme that enables natural silicic glasses to be projected into the synthetic system qz ab or h2o in order to relate variations in volcanic glass chemistry to changing pressure p and temperature t conditions in the sub volcanic magma system by this means an important distinction can be made between ascent driven and cooling driven crystallisation under water saturated or undersaturated conditions in samples containing feldspar and a silica phase quartz or tridymite quantitative p t estimates of the conditions of last equilibrium between crystals and melt can be made formation of highly silicic melts i e 77 wt sio2 is a simple consequence of the contraction of the silica phase volume with decreasing pressure such that high silica glasses can only form by crystallisation at low pressure resorption of quartz crystals appears to be a further diagnostic feature of decompression crystallisation groundmass and inclusion glasses in dacites from the 1980 1986 eruption of mount st helens volcano wa span a wide range in sio2 68 80 wt anhydrous the compositions of the least evolved sio2 poor inclusions in amphibole phenocrysts record entrapment of silicic liquids with 5 4 wt water corresponding to a water saturation pressure of 200 mpa at 900 c the compositions of more evolved higher sio2 plagioclase hosted inclusions and groundmass glasses are consistent with extensive ascent driven fractional crystallisation of plagioclase oxide and orthopyroxene phenocrysts and microlites to low pressures during this polybaric crystallisation plagioclase phenocrysts trapped melts with a wide range of dissolved water contents 3 5 5 7 wt magmas erupted during the plinian phase of the 18 may 1980 eruption were derived from a large reservoir at depths of 6 km subsequent magmas ascended to varying depths within the sub volcanic system prior to extraction from glass chemistry and groundmass texture two arrest levels have been identified at depths of 0 5 1 and 2 4 km a single dome sample from february 1983 contains groundmass plagioclase tridymite and quartz testifying to temperatures of at least 885 c at 11 mpa these shallow storage conditions are comparable to those in the cryptodome formed during spring 1980 the corresponding thermal gradient 0 2 c mpa 1 is consistent with near adiabatic magma ascent from 8 km we argue that the crystallisation history of mount st helens dacite magma was largely a consequence of decompression crystallisation of hot magma beyond the point of water saturation this challenges the conventional view that phenocryst crystallisation occurred by cooling in a large magma chamber prior to the 1980 1986 eruption because the crystallisation process is both polybaric and fractional it cannot be simulated directly using isobaric equilibrium crystallisation experiments however calculation of the phase proportions in water saturated 910 15 c experiments by rutherford et al 1985 over the pressure range 220 125 mpa reproduces the crystallisation sequence and phenocryst modes of mount st helens dacites from 18 may 1980 by allowing for the effects of fractional versus equilibrium crystallisation entrained residual source material and small temperature differences between nature and experiment phase compositions can also be matched to the natural samples we conclude that decompression of water saturated magma may be the dominant driving force for crystallisation at many other silicic volcanic centres

pacific decadal variability the tropical pacific mode and the north pacific mode pacific decadal variability is studied in a series of coupled global ocean atmosphere simulations aided by two modeling surgery strategies partial coupling pc and partial blocking pb the pc experiments retain full ocean atmosphere coupling in selected regions but constrain ocean atmosphere coupling elsewhere by prescribing the model climatological sst to force the atmospheric component of the coupled system in pb experiments sponge walls are inserted into the ocean component of the coupled model at specified latitudinal bands to block the extratropical tropical oceanic teleconnection both modeling and observational studies suggest that pacific decadal variability is composed of two distinct modes a decadal to bidecadal tropical pacific mode tpm and a multidecadal north pacific mode npm the pc and pb experiments showed that the tropical pacific mode originates predominantly from local coupled ocean atmosphere interaction within the tropical pacific extratropical tropical teleconnections although not a necessary precondition for the genesis of the tropical decadal variability can enhance sst variations in the tropics the decadal memory in the tropics seems to be associated with tropical higher baroclinic modes the north pacific mode originates from local atmospheric stochastic processes and coupled ocean atmosphere interaction atmospheric stochastic forcing can generate a weaker npm like pattern in both the atmosphere and ocean but with no preferred timescales in contrast coupled ocean atmosphere feedback can enhance the variability substantially and generate a basin scale multidecadal mode in the north pacific the multidecadal memory in the midlatitudes seems to be associated with the delayed response of the subtropical subpolar gyre to wind stress variation in the central north pacific and the slow growing decaying of sst anomalies that propagate eastward in the kuroshio extension region oceanic dynamics particularly the advection of the mean temperature by anomalous meridional surface ekman flow and western boundary currents plays an important role in generating the north pacific mode

the asian australian monsoon and el nino southern oscillation in the ncar climate system model features associated with the asian australian monsoon system and el nino southern oscillation enso are described in the national center for atmospheric research ncar global coupled climate system model csm simulation characteristics are compared with a version of the atmospheric component of the csm the ncar ccm3 run with time evolving ssts from 1950 to 1994 and with observations the csm is shown to represent most major features of the monsoon system in terms of mean climatology interannual variability and connections to the tropical pacific this includes a representation of the southern oscillation links between strong asian australian monsoons and associated negative sst anomalies in the eastern equatorial pacific the equatorial sst gradient across the pacific in the csm is shown to be similar to the observed with somewhat cooler mean ssts across the entire pacific by about 18 28c the seasonal cycle of ssts in the eastern equatorial pacific has the characteristic signature seen in the observations of relatively warmer ssts propagating westward in the first half of the year followed by the reestablishment of the cold tongue with relatively colder ssts propagating westward in the second half of the year like other global coupled models the propagation is similar to the observed but with the establishment of the relatively warmer water in the first half of the year occurring about 1 2 months later than observed the seasonal cycle of precipitation in the tropical eastern pacific is also similar to other global coupled models in that there is a tendency for a stronger than observed double itcz year round particularly in northern spring but with a well reproduced annual maximum of itcz strength north of the equator in the second half of the year time series of area averaged ssts for the nino3 region in the eastern equatorial pacific show that the csm is producing about 60 of the amplitude of the observed variability in that region consistent with most other global coupled models global correlations between nino3 time series global surface temperatures and sea level pressure slp show that the csm qualitatively reproduces the major spatial patterns associated with the southern oscillation lower slp in the central and eastern tropical pacific when nino3 ssts are relatively warmer and higher slp over the far western pacific and indian oceans with colder water in the northwest and southwest pacific indices of asian australian monsoon strength are negatively correlated with nino3 ssts as in the observations spectra of time series of indian monsoon australian monsoon and nino3 sst indices from the csm show amplitude peaks in the southern oscillation and tropospheric biennial oscillation frequencies 3 6 yr and about 2 3 yr respectively as observed lag correlations between the nino3 sst index and upper ocean heat content along the equator show eastward propagation of heat content anomalies with a phase speed of about 0 3 m s21 compared to observed values of roughly 0 2 m s21 composites of el nino la nina events in the csm show similar seasonal evolution to composites of observed events with warming cooling of greater than several tenths of a degree beginning early in northern spring of year 0 and diminishing around northern spring of year 11 but with a secondary resurgence in the csm events later in northern spring of year 11 the csm also shows the largest amplitude enso sst and low level wind anomalies in the western tropical pacific with enhanced interannual variability of ssts extending northeastward and southeastward toward the subtropics compared to largest interannual sst variability in the central and eastern tropical pacific in the observations

megadroughts in the indian monsoon region and southwest north america and a mechanism for associated multidecadal pacific sea surface temperature anomalies abstract a 1360 yr control run from a global coupled climate model the parallel climate model is analyzed it simulates megadroughts in the southwestern united states and indian monsoon regions the megadroughts represent extreme events of naturally occurring multidecadal precipitation variations linked to the dominant pattern of multidecadal sst variability in the indian and pacific oceans gaining insight into the occurrence of megadroughts thus requires an understanding of the mechanism that is producing this multidecadal sst variability analysis of the model variability shows that the mechanism involves atmosphere ocean and tropical midlatitude interactions with a crucial element being wind forced ocean rossby waves near 20 n and 25 s in the pacific whose transit times set the decadal time scale at the western boundary the rossby waves reflect into the equatorial pacific to affect thermocline depth the resulting feedbacks involving surface temperature winds and the strength of the subtropi

enso like interdecadal variability in the pacific ocean as simulated in a coupled general circulation model spatial and temporal structures of interdecadal variability in the pacific ocean are investigated using results from an atmosphere ocean coupled general circulation model aogcm the model shows a basin wide spatial pattern of the principal sea surface temperature sst variability similar to the observed one both interdecadal and interannual temporal structures of the sst variability agree well between the observation and the aogcm on the other hand a slab ocean model coupled to the same atmospheric model as the aogcm fails to simulate the observed temporal structure therefore the timescale of the coupled variability is associated with dynamical processes in the ocean a distinct interdecadal mode of the coupled atmosphere upper ocean temperature variability is found in the aogcm with a spatiotemporal structure coherent with the sst variability the mode accompanies an el nino southern oscillation enso like spatial pattern of sst and the surface wind and behaves like a delayed oscillator in enso a wedge shaped anomaly pattern of the upper thermocline temperature is formed in the eastern pacific and its northern subtropical signal propagates westward enhanced by a subtropical wind forcing at the central basin arrival of the subtropical signal at the western pacific around 20 n switches the anomaly of subsurface temperature in the equatorial region through anomalous oceanic heat transport along the western boundary the travel time of the trans pacific signal in the subtropics appears to be responsible for the timescale of this mode the aogcm successfully simulated the second mode of sst with a major variation in the midlatitude north pacific as in the observed sst in the upper ocean heat content we found another distinct mode which is characterized by a midlatitude subtropics dipole pattern migrating around the north pacific subtropical gyre however the associated sst variation of this mode shows a poor correspondence in the dominant interdecadal modes for the observed sst

tephrochronological investigation at dvuh yurtochnoe lake area kamchatka numerous landslides and lake tsunami and their environmental impacts distal volcanic tephras in soil sections and lake sediments in the dvuh yurtochnoe two yurts lake area central kamchatka were investigated in order to provide a chronological framework for the reconstruction of late quaternary landscape development mineralogical and geochemical data point to sources from 5 volcanoes ten tephra layers were identified and correlated to known eruptive events the ages were corroborated by radiocarbon dating of the soil sections around two yurts lake these findings allow the reconstruction of regional paleoenvironmental change recorded in the soil sections around two yurts lake during the last glacial maximum lgm time the area was affected by glacial advances that produced the glacial moraines at the eastern outlet of the lake a large landslide ca 15 000 18 000 14c bp dammed the valley and led to formation of two yurts lake several more landslide events can be recognized in the holocene and one affected two yurts lake ca 3000 14c bp this event produced a tsunami documented by poorly sorted deposits with rounded pebbles in the onshore sections around the lake in contrast to the soil sections tephras buried in the soupy lacustrine sediments of two yurts lake are not well preserved and show inconsistent age depth relationships compared to those suggested by radiocarbon dating due to sinking through the lake sediments nevertheless tephrochronological data revealed the strong impact of terrestrial landslides on lake sedimentation