morphology faunas and genesis of ordovician hardgrounds from southern ontario canada abstract we have used associations of different microfacies to define facies or microfacies associations which form reasonably well defined sequences which we infer from analogies with recent and ancient carbonate environments to have been deposited in a shelf environment characterized by small scale topographic differentiation into shoal slope and basinal environments shoal environments are characterized by typically cross bedded well sorted bioclastic sands with intershoal areas consisting of interbedded bioclastic sands and heavily bioturbated finer grained carbonates slope and basinal environments are typically represented by proximal and distal cycles respectively these we compare with deposits of carbonate ramp bypass channels and with the more thoroughly studied deep water clastic submarine fans many of the strong variations in environmental energy in these proximal and distal cycles can be attributed to migration of channels on the fans and the effect of funnelling of storm surges down the channels although hardground morphology and faunas are mostly related to local effects such as intensity of scouring time of exposure topographic differentiation of the surface and other factors differing hardground types tend to be found in different environments smooth and rolling hardgrounds occur in the deeper distal environments where the beds were subject to only slight scour and often limited exposure before renewed sedimentation hummocky and undercut hardgrounds are characteristic of the middle parts of proximal cycles where they developed marginally to the main bypass channel and in intershoal areas both these areas are sites of intermittent sedimentation and moderate turbulence where cemented beds may be exposed for some time in environments optimal for attached benthos these hardgrounds usually contain the most diverse hardground biotas pebbly and reworked hardgrounds occur in coarse basal units of proximal cycles which are interpreted as the grain flow fillings of the central parts of bypass channels though isolated examples occur in intershoal areas and in the higher parts of proximal channels these hardgrounds contain low diversity faunas reflecting the stresses imposed by intermittent or constant abrasion though some contain more diverse faunal assemblages formed after redeposition

modality of semiannual to multidecadal oscillations in global sea surface temperature variability 1 repeating the history of study on el nino southern oscillation enso in the 1980s interdecadal oscillation ido in climate variability is currently an area of active research and debate following the recognition of its emerging significance in nature and science in this work a two dimensional propagating modal extraction technique is applied to a reconstructed global monthly sea surface temperature sst data set spanning 1854 through 2007 to examine the spatiotemporal structure of sst variability with an emphasis on the fine modal pattern of idos in the time domain it is revealed that a canonical modal spectrum of decadal to centennial sst variability constitutes four most distinct oscillations with periodicities at 9 0 13 0 21 2 and 62 2 years which are naturally defined as primary modes and are respectively termed as the subdecadal mode the quasidecadal mode the interdecadal mode and the multidecadal mode modes s q i and m they join the energeticannual mode mode a and two major enso modes at 3 7 and 5 8 years modes b and c as well as a dozen of secondary modes ranging from semiannual to multidecadal in determining the key pattern of sst related climate variability in the space domain seven modally dynamic areas analogous to the nino regions for enso are clearly identified and are named as ido zones contrary to enso dominant ido zones are most visible in the extratropical oceans especially in the north atlantic north pacific sectors while secondary signatures are observed in the tropical oceans the array of four primary modes with respect to seven major zones yields a sophisticated yet canonical pattern of idos leading to a basic conclusion that multimodality for a given region and multiregionality for a given mode are fundamental features of the ido system

source of low frequency modulation of enso amplitude in a cgcm we study the relationship between changes in equatorial stratification and low frequency el nino southern oscillation enso amplitude modulation in a coupled general circulation model cgcm that uses an anomaly coupling strategy to prevent climate drifts in the mean state the stratification is intensified at upper levels in the western and central equatorial pacific during periods of high enso amplitude furthermore changes in equatorial stratification are connected with subsurface temperature anomalies originating from the central south tropical pacific the correlation analysis of ocean temperature anomalies against an index for the enso modulation supports the hypothesis of the existence of an oceanic tunnel that connects the south tropical pacific to the equatorial wave guide further analysis of the wind stress projection coefficient onto the oceanic baroclinic modes suggests that the low frequency modulation of enso amplitude is associated with a significant contribution of higher order modes in the western and central equatorial pacific in the light of these results we suggest that in the cgcm change in the baroclinic mode energy distribution associated with low frequency enso amplitude modulation have its source in the central south tropical pacific

a transition phase teleconnection of the pacific quasi decadal oscillation the atmospheric circulation patterns associated with the pacific quasi decadal oscillation qdo are investigated using available observational data from 1948 to 2007 previous studies indicate that the pacific qdo is characterized by a distinct lifecycle in the form of sea surface temperature sst patterns in the warm and cool phases of the pacific qdo the sst patterns resemble those associated with the el nino southern oscillation enso during the warm cool and cool warm transitions of the pacific qdo recurrent sst patterns are also clearly visible the rotated empirical orthogonal function analysis on the 10 15 year filtered data shows that the evolutions of sst and atmospheric circulation are well coupled while the warm cool phase pacific qdo generates an enso like circulation pattern the transition phases form a distinct short wave train emanating from southeast asia towards north america this short wave train is particularly robust in the streamfunction of water vapor flux diagnostic analyses of the heat budget the stationary wave flux and a barotropic model indicate that this short wave train is thermodynamically maintained and is likely forced by diabatic heating near southeast asia additional modulations of forcing sources in the western and eastern tropical pacific on this short wave teleconnection are also discussed

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

decadal variations of pacific north equatorial current bifurcation from multiple ocean products in this study we examine the decadal variations of the pacific north equatorial current nec bifurcation latitude nbl averaged over upper 100 m and underlying dynamics over the past six decades using 11 ocean products including seven kinds of ocean reanalyzes based on ocean data assimilation systems two kinds of numerical simulations without assimilating observations and two kinds of objective analyzes based on in situ observations only during the period of 1954 2007 the multiproduct mean of decadal nbl anomalies shows maxima around 1965 1966 1980 1981 1995 1996 and 2003 2004 and minima around 1958 1971 1972 1986 1987 and 2000 2001 respectively the nbl decadal variations are related to the first empirical orthogonal function mode of decadal anomalies of sea surface height ssh in the northwestern tropical pacific ocean which shows spatially coherent variation over the whole region and explains most of the total variance further regression and composite analyzes indicate that northerly southerly nbl corresponds to negative positive ssh anomalies and cyclonic anticyclonic gyre anomalies in the northwestern tropical pacific ocean these decadal circulation variations and thus the decadal nbl variations are governed mostly by the first two vertical modes and attribute the most to the first baroclinic mode the nbl decadal variation is highly positively correlated with the tropical pacific decadal variability tpdv around the zero time lag with a lead of about half the decadal cycle the nbl displays closer but negative relationship to tpdv in four ocean products possibly manifesting the dynamical role of the circulation in the northwestern tropical pacific in the phase shifting of tpdv

early diagenesis in sediments from danish coastal waters microbial activity and mn fe s geochemistry abstract depth distributions of bacterial respiration of o2 no3 and so42 were compared with geochemical data for mn fe and s in coastal sediments from water depths between 26 and 520 m as water depth increased the zone of so42 respiration was found deeper in the sediment and was eventually separated from the surface located activity of o2 and no2 respiration at the deepest station additional so42 reduction activity was observed in small detrital aggregates on the sediment surface dissolved mn2 and fe2 appeared between the o2 plus no3 containing surface layer and the h2s plus fes containing sediment below this was a result of mn and fe reductions coupled to either the oxidation of sulfide or the mineralization of organic matter tracer experiments showed that both fes fes2 and s0 were important radiolabelled products of sulfate respiration in this intermediate zone in the same zone the overall degradation of organic matter seemed to be underestimated by the assay of so2 4 respiration and additional mineralization by mn and fe reductions was likely

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

hydrologic variability and the onset of modern el nino southern oscillation a 19 250 year record from lake elsinore southern california there are very few terrestrial palaeoclimate archives spanning the last glacial maximum through the holocene from coastal southern california yet knowledge of past climate dynamics is critical for assessing present and future constraints on the region s dwindling freshwater resources we present initial results from two drill cores extracted from the present day edge of lake elsinore southern california s largest natural lake using a multiproxy approach including lithologic description mass magnetic susceptibility loi 550 c total organic matter and loi 950 c total carbonate we infer first order long term climate change over the past 19 250 calendar years furthermore we suggest possible first order forcing mechanisms that drive this change which include presence absence of continental ice sheets insolation and complex ocean atmosphere interactions our results indicate four distinct millennial scale climate modes over the past 19 250 calendar years these modes include a wet last glacial maximum 19 250 17 120 cal yr bp a relatively dry late glacial holocene transition 17 120 9450 cal yr bp a wet early holocene 9450 7670 cal yr bp and a highly variable mid to late holocene climate i e alternating wet dry cycles 7670 cal yr bp present we attribute the mid to late holocene climate interval to the onset of el nino southern oscillation ca 7000 cal yr bp and a more vigorous hydrologic system these results are supported by a variety of regional terrestrial and marine palaeoclimate archives copyright 2005 john wiley sons ltd

the reconstructed indonesian warm pool sea surface temperatures from tree rings and corals linkages to asian monsoon drought and el nino southern oscillation 1 the west pacific warm pool is the heat engine for the globe s climate system its vast moisture and heat exchange profoundly impact conditions in the tropics and higher latitudes here september november sea surface temperature sst variability is reconstructed for the warm pool region 15 degrees s 5 degrees n 110 160 degrees e surrounding indonesia using annually resolved teak ring width and coral delta o 18 records the reconstruction dates from a d 1782 1992 and accounts for 52 of the sst variance over the most replicated period significant correlations are found with el nino southern oscillation enso and monsoon indices at interannual to decadal frequency bands negative reconstructed sst anomalies coincide with major volcanic eruptions while other noteworthy extremes are at times synchronous with indian and indonesian monsoon drought particularly during major warm enso episodes while the reconstruction adds to the sparse network of proxy reconstructions available for the tropical indo pacific additional proxies are needed to clarify how warm pool dynamics have interacted with global climate in past centuries to millennia

simulation of heat storages and associated heat budgets in the pacific ocean 2 interdecadal timescale we use a primitive equation isopycnal model of the pacific ocean to simulate and diagnose the anomalous heat balance on interdecadal timescales associated with heat storage changes observed from 1970 1988 in the expendable bathythermograph xbt data set given the smallness of the interdecadal signals compared to the el nino southern oscillation enso signal the agreement between model and observations is remarkably good the total anomalous heat balance is made up of two parts the diabatic part from the model temperature equation and the adiabatic part from the model mass conservation equation due to thermocline heave we therefore describe our analysis of both the total and diabatic anomalous heat balances in four areas of the tropical and subtropical north pacific ocean in the upper 400 m the interdecadal total diabatic plus adiabatic heat balance in the north pacific ocean is characterized by a complicated interplay of different physical processes especially revealed in basin scale averages of the heat budget components that have comparable amounts of variance in smaller subregions simpler balances hold for example in the western equatorial pacific area 1 the total heat content tendency term is nearly zero so that a simple balance exists between surface heat flux vertical heat transport and horizontal mixing in the western subtropical pacific the total heat content tendency balances the three dimensional divergence of the heat flux we speculate that this complexity is indicative of multiple physical mechanisms involved in the generation of north pacific interdecadal variability the diabatic heat balance north of 24 n a region of special interest to the world ocean circulation experiment woce can be simplified to a balance between the tendency term surface heat flux and meridional advection the last term dominated by anomalous advection of mean temperature gradients for the western equatorial region the diabatic heat content tendency is nearly zero and the steady balance involves simply horizontal advection and the surface heat flux which at these latitudes has a damping role in the model an important finding of this study is the identification of two interdecadal timescales roughly 10 and 20 years both similar to those reported by other investigators in recent years tourre et al 1998 latif and barnett 1994 robertson 1995 white et al 1997 gu and philander 1997 jacobs et al 1994 the 20 year timescale is only present in diabatic heat budget components while the 10 year timescale is present in both diabatic and adiabatic components the 10 year timescale can also be seen in the surface heat flux time series but it occurs in the ocean adiabatic components which demonstrates the importance of oceanic adjustment through rossby wave dynamics on decadal timescales

quasi decadal signals of sahel rainfall and west african monsoon since the mid twentieth century 1 sahel rainfall shows pronounced decadal variability and a negative trend between wet conditions in the 1950s 1960s and dry ones in the 1970s 1980s using continuous wavelet transform the quasi decadal variability qdv of rainfall reveals zonal contrasts the highest qdv is identified in the 1950s 1960s over western sahel and in the 1970s 1980s over eastern sahel the quasi decadal atmospheric anomalies have been reconstructed using fourier transform for the 1950s 1960s and the 1970s 1980s respectively and assessed by the composite analysis of the qdv phases for the periods before and after 1968 over western sahel the rainfall qdv in the 1950s 1960s is related to the north atlantic sea surface temperature sst variability as highlighted by the wavelet coherence a southward shift trend of the intertropical convergence zone itcz is identified through an enhancement of northeasterly fluxes and moisture convergence over the western part of west africa a decrease increase of southern northern subtropical sinking motions seems to be involved in the 1970s 1980s a strengthening of cross equatorial atlantic sst and pressure gradients is related to an increase of monsoon flow from lower troposphere up to the midtroposphere and to the northward shift of the itcz mainly over eastern sahel the pacific sst influence is also identified which involves changes in the global zonal circulation

quasi periodicity and global symmetries in interdecadal upper ocean temperature variability recent studies find interannual i e 3 to 7 year decadal i e 9 to 13 year and interdecadal i e 18 to 23 year periodicities and a trend dominating global sea surface temperature sst and sea level pressure slp variability over the past hundred years with the interdecadal signal dominating sub el nino southern oscillation enso frequencies we isolate interdecadal frequencies in sst and slp records by band passing with a window admitting 15 to 30 year periods from 1900 to 1989 the rms of interdecadal filtered sst and slp anomalies is largest in the extratropics and eastern boundaries first mode empirical orthogonal functions eofs explain about half the interdecadal variance in both variables with the tropical warm phase peaking near 1900 1920 1940 1960 and 1980 from 1955 to 1994 eof spatial patterns of interdecadal sst slp and 400m temperature t400 anomalies reveals global reflection symmetries about the equator and global translation symmetries between ocean basins with tropical and eastern ocean ssts warmer cooler than normal covarying with stronger weaker extratropical westerly winds cooler warmer ssts in western central subarctic and subantarctic frontal zones safzs stronger weaker subtropic and subarctic gyre circulations in north pacific and north atlantic oceans and warmer cooler basin and global average ssts of 0 1 c or so evolution of interdecadal variability from the tropical warm phase to the tropical cool phase is propagative also characterized by reflection and translation symmetries during the tropical warm phase cool sst anomalies along western central safzs are advected slowly eastward to the eastern boundaries and subsequently advected poleward and equatorward by the mean gyre circulation the latter conducting extratropical sst anomalies into the tropics a delayed action oscillation model is constructed that yields the quasiperiodicity of interdecadal variability in a manner consistent with these global symmetries in both pattern and evolution

paleoenvironments of the mid ordovician upper caradocian trenton limestones of southern ontario canada storm sedimentation on a shoal basin shelf model abstract the mid ordovician caradocian limestones of southern ontario were deposited on a shelf undergoing collision with a magmatic arc within the general deepening upwards sequence shoals and islands complicate the facies patterns around these shoals and islands carbonate sediments can be divided into nine lithotypes reflecting shallow agitated to deep quiet marine environments many of these lithotypes show good evidence of storm deposition the lithotypes can be grouped into natural associations which define shoal intershoal slope and basinal facies though the basins were probably less than 100 m deep the closest recent analogues of these ordovician environments occur on the arabian shelf of the persian gulf and on the sahul shelf of northern australia which is undergoing collision with the banda arc in both these environments local shoal basin shelf topography controls the detailed carbonate shelf sedimentation which on a large scale is controlled by storm and tsunami effects on a seaward sloping ramp such shoal basin and ramp models now seem more suitable in explaining carbonate facies in epeiric seas than the flat slope models previously proposed glacio eustatic sea level changes may have controlled the larger aspects of carbonate sedimentation on the ordovician shelf as they did and continue to do now on the recent shelves such changes may explain the localization of the variety of ordovician hardgrounds which we previously described

atmosphere sea ice low frequency variability with a simple model of the southern hemisphere summary a simple primitive equation general circulation model sgcm is used as a representation of an aquaplanet with no orography to model constant southern hemisphere winter conditions the statistical signie cance of the decadal and quasi biennial variability is erst assessed in a long time sgcm run by means of a frequencydomain statistical decomposition the modelled long wave atmospheric pattern is then associated with the observed southern hemisphere annular mode as suggested by previous studies using the same sgcm a simple linear relationship between the low level wind and the ice velocity is then introduced into the sgcm to investigate the feedbacks between the sea ice cover and the baroclinic waves the zonal mean state reached by the sea ice cover in a long coupled run a few hundred years exhibits characteristics similar to the observations investigation of the low frequency variability in the coupled simulation leads to the following results 1 statistically signie cant variability is observed on interdecadal decadal interannual and quasi biennial time scales 2 interdecadal decadal and quasi biennial signals are associated with the atmospheric annular mode that forces changes in the northward extent of the sea ice cover at all southern ocean longitudes 3 the interannual signal 3 6 year period exhibits spatio temporal patterns and propagation speed similar to the wellknown antarctic circumpolar wave

a global quasi biennial wave in surface temperature and pressure and its decadal modulation from 1900 to 1994 zonal wave number frequency spectra of surface temperature st and sea level pressure slp anomalies extending around the global tropical ocean at 10 n from 1950 to 1997 display significant peaks for 2 0 and 2 4 year periods dominated by eastward propagating zonal wave numbers of global scale applying complex principal component analysis to quasi biennial st slp and surface wind sw anomalies for 25 years from 1973 to 1997 separates this global quasi biennial wave gbw from corresponding global standing modes with patterns and evolution of the former similar to those observed in the global el nino southern oscillation wave white and cayan 2000 but centered on the equatorial waveguide and taking only 3 to 4 years instead of 4 to 6 years to transit the global tropical ocean at 0 30 to 0 40 m s 1 we find the gbw contributing to the quasi biennial signal in nino 3 st and slp indices with amplitude twice that of global standing mode in the gbw the ocean forces the atmosphere with sw anomalies directed toward warm sea surface temperature anomalies while the atmosphere forces the ocean with sw induced kelvin waves on the equator and sw induced sensible plus latent heat flux and or vertical mixing anomalies elsewhere both advancing st anomalies eastward examining the gbw from 1900 to 1994 finds its amplitude modulated by the decadal signal of 10 year periodicity robust weak when tropical temperature gradients and trade winds were stronger weaker than normal

seasonal evolution of the qbo induced wave forcing and circulation anomalies in the northern winter stratosphere diagnostics of wave mean flow and wave wave interactions in isentropic coordinates are analysed regarding the mechanisms that govern the holton tan effect hte whereby the tropical quasi biennial oscillation qbo modulates the northern winter stratospheric polar vortex we find a clear seasonal evolution of a qbo modulation of rossby waves and linear and nonlinear wave interactions along with multiple mechanisms at work in early winter when the lower stratospheric qbo is easterly there is enhanced upward stationary planetary wave activity in the subtropical to midlatitude lower stratosphere these upward propagating waves are first refracted towards the zero wind line approximately one month later poleward propagating wave anomalies appear at midlatitudes as a result of nonlinear wave interactions the enhanced upward wave propagation appears to be due to a combination of the qbo influence on the latitudinal location of the zero wind line and the increased midlatitude baroclinicity associated with the qbo induced meridional circulation this is further aided by a gradual poleward shift over the winter of the middle stratospheric waveguide refracting waves poleward the associated wave breaking weakens the polar vortex and drives a stronger meridional circulation throughout the lower to middle stratosphere contributing to the high latitude warming it is additionally found that in late winter the modified high latitude waveguide associated with the weaker polar vortex consequently reduces upward propagating transient planetary waves at high latitudes whilst simultaneously enhancing upward propagating synoptic waves at midlatitudes this highlights the need to view the hte and its mechanisms as an evolving phenomenon throughout the winter

a conjugate study of mean winds and planetary waves employing enhanced meteor radars at rio grande argentina 53 8 s and juliusruh germany 54 6 n 1 two meteor radars with enhanced power and sensitivity and located at closely conjugate latitudes 54 6 n and 53 8 s are employed for interhemispheric comparisons of mean winds and planetary wave structures at periods of 8 to 20 days our study uses data from june 2008 through may 2010 during which both radars provided nearly continuous wind measurements from 80 to 100 km monthly mean winds at 53 8 s exhibit a stronger westward zonal jet in spring and early summer at lower altitudes and no westward winds at higher altitudes in contrast westward mean winds of 5 10 ms 1 at 54 6 n extend to above 96 km during late winter and early spring each year equatorward mean winds extend approximately from spring to fall equinox at both latitudes with amplitudes of 5 10 ms 1 meridional mean winds are more variable at both latitudes during fall and winter with both poleward and equatorward monthly means indicating longer period variability planetary waves seen in the 2 day mean data are episodic and variable at both sites exhibit dominant periodicities of 8 10 and 16 20 days and are more confined to late fall and winter at 54 6 n at both latitudes planetary waves in the two period bands coincide closely in time and exhibit similar horizontal velocity covariances that are positive negative at 54 6 n 53 8 s during peak planetary wave responses

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

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

global sst slp waves during the 20th century 1 a discrete number of global signals in covarying sea surface temperature sst and sea level pressure slp dominated climate variability from 40 s to 60 n during the 20th century they are the quasi biennial 2 2 year period interannual 3 to 7 year period band quasi decadal 11 year period and interdecadal 17 year period signals a joint frequency domain analysis of sst and slp anomalies over the global ocean finds these signals composed of mixed global standing modes and traveling waves that are similar in pattern and evolution on each period scale the global traveling wave is composed of global zonal wavenumbers 1 and 2 directed eastward with a phase speed that takes 1 to 2 cycles to traverse the global ocean between 40 s and 20 n the existence of these global traveling waves may enhance the predictability of regional climate variability

lims limb infrared monitor of the stratosphere observation of traveling planetary waves and potential vorticity advection in the stratosphere and mesosphere eastward and westward traveling waves were observed by the nimbus 7 limb infrared monitor of the stratosphere lims during the northern winter 1978 1979 eastward waves were prevalent in early winter and were involved in a minor canadian warming in december 1978 a large westward traveling wave as described by previous authors was observed in january 1979 during a series of minor warmings by comparing these two events it is shown that in both cases the superposition of traveling and quasi stationary waves led to constructive interference that was responsible for the warmings however there was significant asymmetry between eastward and westward traveling components eastward disturbances were confined mostly within the polar vortex whereas quasi stationary and westward traveling components propagated to the vortex periphery and beyond into the tropics and mid latitude mesosphere this behavior is consistent with rossby wave propagation and indicates that the location and magnitude of planetary wave breaking is sensitive to the frequency spectrum entering the middle atmosphere however this asymmetry is also a signature of the nonlinear critical layer as it projects onto the frequency spectrum both interpretations are shown to be valid during wave events observed by lims a local eulerian analysis of potential vorticity pv transport indicates that adiabatic geostrophic advection by the resolvable scales of motion explains qualitatively but not quantitatively the observed potential vorticity tendencies in the lims northern hemisphere winter in particular calculated advection explains the eastward rotation of the main vortex intrusion of low pv air into the polar cap and formation of high pv filaments at the vortex periphery

low frequency pycnocline depth variability at ocean weather station p in the northeast pacific abstract low frequency variability of the depth of the main pycnocline at ocean weather station p and over the northeast pacific is examined in terms of the one dimensional response to local ekman pumping according to the hasselmann stochastic climate model the model is forced with monthly wind stress curl anomalies derived from the national centers for environmental prediction reanalysis for the period 1948 2000 an empirical orthogonal function analysis shows that the leading mode of the response bears the signature of the pacific inter decadal oscillation pdo and that the associated principal component captures the regime shift of 1976 77 the correlation is 0 77 between annually averaged pycnocline displacement anomalies hindcast from the model and anomalies in the depth of the main pycnocline at station p 50 n 215 e observed over a 43 yr period the comparison indicates that variability in the depth of the upper layer on interannual to interdecadal timescales at station p occurs largely as

mechanisms determining the atmospheric response to midlatitude sst anomalies abstract previous gcm experiments demonstrated that a model atmosphere produces two different responses to a midlatitude warm sst anomaly over the pacific under perpetual january and february conditions to elucidate the mechanisms responsible for the different gcm responses and their dependence on the background flow experiments with two idealized models are conducted experiments with a linear baroclinic model reveal that the gcm responses at equilibrium are primarily maintained by the anomalous eddy forcing the anomalous flow induced directly by an idealized initial heat source exhibits little sensitivity to the background flow eddy feedbacks on the heating induced anomalous flow are examined using a linear storm track model the anomalous eddy forcing produced by the storm track model is sensitive to the basic state the eddy forcing in january acts to shift the heating induced upper level ridge toward the northeast of the gulf of alaska while in february it acts to reinforce the ridge this sugge

pacific decadal variability paced by rossby basin modes abstracta systematic study is presented of decadal climate variability in the north pacific in particular the hypothesis is addressed that oceanic rossby basin modes are responsible for enhanced energy at decadal and bidecadal time scales to this end a series of statistical analyses are performed on a 500 yr control integration of the community climate system model version 3 ccsm3 in particular a principal oscillation pattern pop analysis is performed to identify modal behavior in the subsurface pressure field it is found that the dominant energy of sea surface temperature sst variability at 25 yr the model equivalent of the pacific decadal oscillation cannot be explained by the resonant excitation of an oceanic basin mode however significant energy in the subsurface pressure field at time scales of 17 and 10 yr appears to be related to internal ocean oscillations however these oscillations lack the characteristics of the classical basin modes and must either be deformed beyond recogni

interdecadal dynamics of the north pacific ocean abstract an isopycnal ocean model forced by ncep ncar reanalysis wind stresses and heat fluxes is used to study the interdecadal variability of the pacific ocean in the 1958 97 period a reasonable agreement is found between the model s modes of variability and those obtained by other researchers from both 100 years of observations and theoretical predictions in agreement with previous observational work decadal and interdecadal timescales have different descriptions and from this study it is suggested that they indeed have different dynamics this study focuses on the dynamics of the ocean s interdecadal variability that is of timescales of about 20 yr the decadal timescale that is 10 yr is briefly outlined and compared with previous studies it is found that atmospheric heat fluxes play a key role in establishing the interdecadal sst pattern in the midlatitudinal north pacific these fluxes would excite a high baroclinic mode igniting a series of events that move around the basin in midlatitu

interdecadal sea surface temperature sea level pressure coupled variability in the south pacific ocean 1 the main coupled sea surface temperature sst sea level pressure slp variability at interdecadal timescale in the south pacific is studied by means of correlation and combined complex empirical orthogonal function cceof analyses the sst slp coupled variability presents a bidecadal cycle from mid 1950s to 1970s and a decadal cycle from 1980s to early 1990s reproducing the enso like interdecadal oscillation particularly the first sst slp cceof mode describes the bidecadal cycle characterized by westward progression of sst and slp anomalies along the tropical pacific while the second sst slp cceof mode shows the decadal cycle with eastward development during both bidecadal and decadal cycles the sst fluctuations in the eastern equatorial pacific and along the western coast of south america are primarily forced by equatorial zonal wind variability specially during the bidecadal cycle the alongshore sst variability south of 30 s is maintained and reinforced by meridional coastal wind fluctuations associated with a stationary slp pattern off southern chile this stationary slp pattern appears connected to sst fluctuations in the central tropical pacific

pacific decadal oscillation documented in a coral record of north pacific winter temperature since 1873 1 the pacific decadal oscillation pdo the leading mode of sea surface temperature sst anomalies in the extratropical north pacific ocean has widespread impacts on precipitation in the americas and marine fisheries in the north pacific however marine proxy records with a temporal resolution that resolves interannual to interdecadal sst variability in the extratropical north pacific are extremely rare here we demonstrate that the winter sr ca and u ca records of an annually banded reef coral from the ogasawara islands in the western subtropical north pacific are significantly correlated with the instrumental winter pdo index over the last century the reconstruction of the pdo is further improved by combining the coral data with an existing eastern mid latitude north pacific growth ring record of geoduck clams the spatial correlations of this combined index with global climate fields suggest that sst proxy records from these locations provide potential for pdo reconstructions further back in time

patterns of coherent climate signals in the indian ocean during the 20th century 1 qbo enso and bdo fluctuations are identified in the indian ocean from a joint frequency domain analysis of sea surface temperature sst and sea level pressure slp conducted over the 20th century within the enso band 3 to 7 year period local fractional variance lfv is maximum near 3 4 year period revealing spatially coherent sst and slp variability propagating eastward from the horn of africa and southwest indian ocean respectively toward the eastern tropical indian ocean within the qbo band 2 1 to 2 8 year period lfv is maximum near 2 2 year period revealing spatially coherent sst and slp variability propagating northward and eastward from southwestern ocean toward the south china sea the 3 4 year period enso signal diminished in intensity in the 1920s and 1950s whilst the 2 2 year period qbo signal diminished in the 1910s 1940s and 1950s as observed for the global qbo and enso signals white and tourre 2003

palaeoecology and evolution of marine hard substrate communities abstract marine organisms have occupied hard substrates since the archaean shells rocks wood and sedimentary hardgrounds offer relatively stable habitats compared to unconsolidated sediments but the plants and animals which inhabit them must develop means to gain and defend this premium attachment space hard substrate communities are formed by organisms with a variety of strategies for adhering to and or excavating the substrates they inhabit while mobile grazers organically attached and even soft bodied organisms may leave evidence of their former presence in ancient hard substrate communities a superior fossil record is left by sessile encrusters with mineralised skeletons and by borers which leave trace fossils furthermore encrusters and borers are preserved in situ retaining their spatial relationships to one another and to the substrate spatial competition ecological succession oriented growth and differential utilisation of exposed vs hidden substrate surfaces can all be observed or inferred hard substrate communities are thus excellent systems with which to study community evolution over hundreds of millions of years here we review the research on modern and ancient hard substrate communities and point to some changes that have affected them over geological time scales such changes include a general increase in bioerosion of hard substrates particularly carbonate surfaces through the phanerozoic this is at least in part analogous to the infaunalisation trends seen in soft substrate communities encrusting forms show an increase in skeletalisation from the palaeozoic into the mesozoic and cenozoic which may be a response to increasing levels of predation hard substrate communities considering borers and encrusters together show a rough increase in tiering through the phanerozoic which again parallels trends seen in soft substrate communities this extensive review of the literature on living and fossil hard substrate organisms shows that many opportunities remain for large scale studies of trends through time at the community and clade levels palaeontologists will especially benefit by closer integration of their work with that of neontologists particularly in aspects of ecology such as larval recruitment competition and succession

patterns of coherent decadal and interdecadal climate signals in the pacific basin during the 20th century two distinct low frequency fluctuations are suggested from a joint frequency domain analysis of the pacific ocean 30 s 60 n sea surface temperature sst and sea level pressure slp the lowest frequency signal reveals a spatially coherent interdecadal evolution in phase sst and slp anomalies are found along the subarctic frontal zone safz it is symmetric about the equator with tropical sst anomalies peaking near 15 latitudes in the eastern pacific the other low frequency signal reveals a spatially coherent decadal evolution it is primarily a low latitude phenomenon tropical sst anomalies peak in the central equatorial ocean with evidence of atmospheric teleconnections these interdecadal and decadal signals join the enso and quasi biennial signals in determining dominant patterns of pacific ocean natural climate variability relative phasing and location of the sst and slp anomalies for the decadal enso and the quasi biennial signals are similar to one another but significantly different from that of the interdecadal signal

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

tree ring reconstruction of the level of great salt lake usa utah s great salt lake gsl is a closed basin remnant of the larger pleistocene age lake bonneville the modern instrumental record of the gsl level i e elevation change is strongly modulated by pacific ocean coupled ocean atmospheric oscillations at low frequency and therefore reflects the decadalscale wet dry cycles that characterize the region a within basin network of seven tree ring chronologies was developed to reconstruct the gsl water year september august level based upon the instrumental record of gsl level from 1876 to 2005 the result was a 576 year reconstruction of the gsl level that extends from 1429 to 2005 all calibration verification tests commonly used in dendroclimatology were passed the reconstruction explains 48 of the variance in the instrumental gsl level and exhibits significant periodicity at sub decadal scales over the past six centuries meanwhile predominance of multi decadal periodicity in the early half of the record shifted to quasi decadal dominance in the latter half and this is consistent with that of proxy reconstructions of the pacific decadal oscillation the gsl level reconstruction is a crucial component to improving our insight into the possible controls of coupled ocean atmosphere interactions on precipitation delivery

a delayed action oscillator shared by biennial interannual and decadal signals in the pacific basin 1 biennial interannual and decadal signals in the pacific basin are observed to share patterns and evolution in covarying sea surface temperature sst 18 c isotherm depth z18 zonal surface wind zsw and wind stress curl wsc anomalies from 1955 to 1999 each signal has warm sst anomalies propagating slowly eastward along the equator generating westerly zsw anomalies in their wake these westerly zsw anomalies produce cyclonic wsc anomalies off the equator which pump baroclinic rossby waves in the western central tropical north pacific ocean these rossby waves propagate westward taking 6 12 and 36 months to reach the western boundary near 7 n 12 n and 18 n on biennial interannual and decadal period scales respectively there they reflect as equatorial coupled waves propagating slowly eastward in covarying sst z18 and zsw anomalies taking 6 12 and 24 months to reach the central eastern equatorial ocean these equatorial coupled waves produce a delayed negative feedback to the warm sst anomalies there the decrease in rossby wave phase speed with latitude the increase in meridional scale of equatorial sst anomalies with period scale and the associated increase in latitude of rossby wave forcing are consistent with the delayed action oscillator dao model used to explain el nino however this is not true of the western boundary reflection of rossby waves into slow equatorial coupled waves this requires modification of the extant dao model we construct a modified dao model demonstrating how the various mechanisms and the size and sources of their delays yield the resulting frequency of each signal

quasi decadal variability in paleoclimate records sunspot cycles or intrinsic oscillations 1 paleoclimatic proxies for interannual variability reveal power within the 7 15 year quasi decadal qd band in earth s history despite the fact that the best established sources of qd variability in modern climate are internal this qd variability in paleoclimatic records is commonly attributed to the 11 year sunspot cycle of solar variability intrinsic qd variability has received little attention in paleoclimatology we apply two different modeling frameworks to assess the degree to which qd variability might have occurred in the past and question whether existing paleoclimate records no matter how well resolved distinguish between internally driven and solar driven variability we show that even a simple atmospheric general circulation model gcm driven by constant solar radiation produces climate oscillations with a period of 11 years then motivated by numerous studies arguing for the presence of sunspot cycles in eocene 50 ma paleoclimate records we demonstrate that a fully coupled gcm simulation with constant solar forcing reproduces the full spectrum of reconstructed eocene variability in the examples we consider there is no compelling reason to invoke solar cycles as a cause of interpreted variability we stress the importance of identifying internal modes of variability from paleoclimate records to increase understanding of the climate system

coherence between the great salt lake level and the pacific quasi decadal oscillation the lake level elevation of the great salt lake gsl a large closed basin lake in the arid western united states is characterized by a pronounced quasi decadal oscillation qdo the variation of the gsl elevation is very coherent with the qdo of sea surface temperature anomalies in the tropical central pacific also known as the pacific qdo however such coherence denies any direct association between the precipitation in the gsl watershed and the pacific qdo because in a given frequency the precipitation variation always leads the gsl elevation variation therefore the precipitation variation is phase shifted from the pacific qdo this study investigates the physical mechanism forming the coherence between the gsl elevation and the pacific qdo pronounced and coherent quasi decadal signals in precipitation streamflow water vapor flux and drought conditions are found throughout the great basin recurrent atmospheric circulation patterns develop over the gulf of alaska during the warm to cool and cool to warm transition phases of the pacific qdo these circulation patterns modulate the water vapor flux associated with synoptic transient activities over the western united states and in turn lead to the qdo in the hydrological cycle of the great basin as the gsl integrates the hydrological responses in the great basin the hydrological qdo is then transferred to the gsl elevation because the gsl elevation consistently lags the precipitation by a quarter phase about 3 yr in the quasidecadal time scale these processes take an average of 6 yr for the gsl elevation to eventually respond to the pacific qdo this creates a half phase delay of the gsl elevation from the pacific qdo thereby forming the inverse yet coherent relationship between them tree ring reconstructed precipitation records confirm that the quasi decadal signal in precipitation is a prominent feature in this region

quasi 16 day oscillation in the mesosphere and lower thermosphere a quasi 16 day wave in the mesosphere and lower thermosphere is investigated through analyses of radar data during january february 1979 and through numerical simulations for various background wind conditions previous workers have examined about 19 days of tropospheric and stratospheric data during january 10 28 1979 and present conflicting evidence as to whether a large westward propagating wavenumber 1 oscillation observed during this period can be identified in terms of the second symmetric rossby normal mode of zonal wavenumber 1 commonly referred to as the 16 day wave in the present work we have applied spectral analysis techniques to meridional and zonal winds near 95 km altitude obtained from radar measurements over obninsk russia 54 n 38 e and saskatoon canada 52 n 107 w these data reveal oscillations of the order of 10 m s 1 with a period near 16 days as well as waves with periods near 5 and 10 days these periodicities all correspond to expected resonant frequencies of atmospheric disturbances associated with westward propagating free rossby modes of zonal wavenumber 1 numerical simulations are performed which demonstrate that the 95 km measurements of the 16 day wave are consistent with upward extension of the oscillation determined from the tropospheric and stratospheric data noteworthy features of the model in terms of its applicability in the mesosphere lower thermosphere regime are explicit inclusion of eddy and molecular diffusion of heat and momentum and realistic distributions of mean winds especially between 80 and 100 km the latter include a westerly wind regime above the summer easterly mesospheric jet thus providing a ducting channel enabling interhemispheric penetration of the winter planetary wave disturbance this serves to explain the appearance of a quasi 16 day wave recently reported in the high latitude summer mesopause williams and avery 1992 however the efficiency of this interhemispheric coupling may be reduced by gravity wave stress no significant penetration of the 16 day oscillation above about 100 km is predicted by the model reported signatures of a 16 day periodicity in ionospheric data therefore require modulation of tidal or gravity wave accessibility to the thermosphere or perhaps in situ excitation

palaeoecological evidence for early aragonite dissolution in ancient calcite seas it has been proposed that shallow carbonate seas of upper ordovician and jurassic ages precipitated calcite as the primary calcium carbonate phase1 3 unlike such settings today it is expected that such seas were undersaturated with respect to the more soluble aragonite so that aragonitic invertebrate skeletons would have tended to dissolve here we describe examples in which this seems to have been the case our evidence consists of submarine cemented horizons in which aragonite fossils have been dissolved out to leave open moulds the walls of the moulds are encrusted by contemporaneous organisms confirming the early timing of the aragonite dissolution

nature and regional significance of unconformities associated with the middle ordovician hagan k bentonite complex in the north american midcontinent stratal patterns of the middle ordovician hagan k bentonite complex and associated rocks show that the black river trenton unconformity in the north american midcontinent formed through the complex interplay of eustasy sediment accumulation rates siliciclastic influx bathymetry seawater chemistry and perhaps local tectonic uplift the unconformity is diachronous and is an amalgamated surface that resulted from local late turinian lowstand exposure followed by regional early chatfieldian transgressive drowning and sediment starvation the duration of the unconformity is greatest in southern wisconsin northern illinois and northern indiana where the deicke and millbrig k bentonite beds converge at the unconformity on the basis of published isotopic ages for the deicke and millbrig beds it is possible that in these regions erosion and nondeposition spanned a period of as much as 3 2 m y two broad coeval depositional settings are recognized within the north american midcontinent during early chatfieldian time 1 an inner shelf subtidal facies of fossiliferous shale spechts ferry shale member and ion shale member of the decorah formation and argillaceous lime mudstone and skeletal wackestone guttenberg and kings lake limestone members extended from the canadian shield and transcontinental arch southeastward through minnesota wisconsin iowa and missouri 2 a seaward relatively deep subtidal sediment starved middle shelf extended eastward from the mississippi valley region to the taconian foreland basins in the central and southern appalachians and southward through the pericratonic arkoma and black warrior basins in the inner shelf region the black river trenton unconformity is a composite of at least two prominent hardground omission surfaces one at the top of the castlewood and carimona limestone members and the other at the top of the guttenberg and kings lake limestone members both merging to a single surface in the middle shelf region the inner and middle shelves redeveloped later in approximately the same regions during devonian and mississippian time

off equatorial westward propagating rossby waves in the tropical pacific during the 1982 83 and 1986 87 enso events abstract analysis of anomalous vertically averaged temperatures tav in the tropical pacific ocean for the eight year period 1979 86 finds the development during the onset phase one to two years before the mature phase of the two enso events of the period having dynamically significant similarities both north and south of the equator during the onset phase of both enso events each beginning in the off equatorial western tropical pacific about 10 latitude positive anomalies of tav occurred during northern autumn winter one year prior to the mature phase of each enso event in both northern and southern hemispheres this corroborates model results of pazan et al and supports the hindcasting forecasting capability of enso events obtained by white et al though the latter considered only the northern hemisphere it is also demonstrated that the development of positive tav anomalies in northern autumn winter along the tropical maritime western boundary of both hemispheres was associated with wind

interannual to interdecadal sea surface temperature variability along the western coast of south america 1 interannual and interdecadal regional scale sea surface temperature sst variability along peru and chile are described based on 9 coastal stations and global sst in the period 1951 1999 enso related interannual variability dominates the low passed time series along the coast with maximum amplitudes in the tropics decreasing southward at tropical latitudes interdecadal variance is about one third of the interannual variance while they are of similar amplitude in the midlatitudes 36 s the correlation between the low frequency coastal modes and the pacific and atlantic sst suggests that the coastal sst variability comprises two main large scale climate processes the enso cycle at interannual timescale and a basin wide perhaps even a global scale interdecadal oscillation

large scale rossby normal modes during some recent northern hemisphere winters abstractlarge scale rossby normal modes are studied for the northern hemisphere winters of 2005 2006 2008 and 2009 using global observational meteorological analyses spanning the 0 92 km altitude range spectral analysis of geopotential height fields shows pronounced peaks at westward propagating zonal wavenumber 1 near the theoretical locations of the free rossby waves at 25 16 10 and 5 days that in some cases have amplitudes significantly larger than the estimated background spectrum evidence is also found for a wavenumber 2 free mode near 4 days a coherence analysis is used to extract the amplitude and phase of the waves and to isolate those regions of the latitude altitude plane where the signals are statistically significant although the spectral location temporal evolution and vertical structure of several of these waves are suggestive of the presence of rossby normal modes this study shows that in the real atmosphere the waves only occasionally have the global properties of classical

wave transience and wave mean flow interaction caused by the interference of stationary and traveling waves abstract madden and labitzke reported an exceptionally large 18 day traveling wave 1 in the troposphere and lower stratosphere during january 1979 observations from the lims instrument on nimbus 7 indicate that during this period the regular westward phase regression extended upward as far as the lower mesosphere alternate destructive and constructive interference between the transient wave and the time mean wave 1 resulted in large variations in wave amplitude with time analysis of the zonal wind deceleration during the minor sudden warming of that month indicates that this wave 1 transience was the primary cause of the warming prior to the large wave 1 amplitude growth immediately preceding the sudden warming 18 22 january there were two other pulses of exceptionally large wave 1 amplitude 2000 m peak amplitude separated by about ten days thew earlier pulses were not associated with the traveling wave which first appeared around 10 january the change in the zonal wind associated with these

hindcast forecast of enso events based upon the redistribution of observed and model heat content in the western tropical pacific 1964 86 anomalous sea level anomalous observed dynamic height 0 400 db and anomalous model dynamic height are examined at the locations of 13 island sea level stations in the tropical pacific for each bimonth of the four year period 1979 to 1982 starting in 1981 the anomalous dynamic height data show off equatorial rossby waves propagated toward the w boundary of the pacific basin at the w boundary the model rossby wave activity was found to have excited coastally trapped kelvin munk waves which transmitted the anomalous dynamic height equatorward at the equator coastally trapped wave activity excited eastward propagating equatorial kelvin waves yielding a pair of anomalous peaks in dynamic height variability in the e equatorial pacific associated with the 1982 1983 enso event the evolution of the peaks in dynamic height associated with the rossby and kelvin wave activity reflects the redistribution of observed upper ocean heat content in the w tropical pacific providing a qualitative hindcast for the 1982 1983 enso event

control of decadal and bidecadal climate variability in the tropical pacific by the off equatorial south pacific ocean abstractdelayed negative feedback processes determining intrinsic decadal and bidecadal time scales for the tropical variability in the pacific are investigated based on climate model experiments by comparing a control run driven by preindustrial forcing and partial blocking runs driven by the same forcing but with ocean temperature and salinity restored to climatology in selected regions subsurface oceanic signals of south pacific origin are shown to precede sst variability in the nino 3 4 region using a linear reduced gravity ocean model driven only by wind stress changes and an offline tracer model oceanic wave adjustment triggered by changes of wind stress curl in the south pacific extratropics is suggested to be essential for the decadal component of the equatorial sst while slower isopycnal advection of subsurface temperature anomalies from the formation region of south pacific eastern subtropical mode water controls the bidecadal component the intrinsic time scales of the tropical variability

wind driven interdecadal variability in the eastern tropical and south pacific 1 simulated interface elevation anomalies with a reduced gravity model forced by observed wind stress are used to investigate the origin of thermocline depth fluctuations in the eastern tropical and south pacific at interdecadal timescales it is found that interdecadal thermocline depth fluctuations in the eastern equatorial pacific and along the western coast of the americas are fundamentally driven by zonal wind fluctuations in the western equatorial pacific thus positive negative interface elevation anomalies which correspond to shallower deeper thermocline depths in the eastern tropical pacific and along the west coast of central and south america are related to easterly westerly anomalies in the western sector of the equatorial pacific however off equatorial wind fluctuations maintain and reinforce the interdecadal variability observed along the eastern equatorial pacific and along the west coast of south america in the latter region equatorial off equatorial wind forcing is relatively more important equatorward poleward of 30 s in the eastern equatorial pacific interface elevation anomalies are negatively correlated with sea surface temperature sst at interdecadal timescales according to our results the sst interdecadal anomalies are in part 50 60 driven by wind fluctuations likely through the modulation of vertical advection of cold waters which depends primarily on the thermocline depth forced remotely or locally by winds this relationship was especially strong during the 1970s and 1980s a period characterized by the larger zonal wind stress interdecadal fluctuations observed in the western equatorial pacific

spatiotemporal variability of interdecadal sea level oscillations in the north pacific 1 the interdecadal variations in the north pacific sea level field were investigated on the basis of two historical tide gauge data sets long term sea level records spanning 100 years but spatially limited in the midlatitudes the cl data set and records from a wider area but with a data length of about 50 years the hcl data set a seesaw like sea level oscillation between the eastern and the western pacific was extracted as the first mode of empirical orthogonal functions eof from the cl data set this mode shows a 22 5 year period of variation that has continued throughout the 20th century a similar variation was found in the hcl data set as the first mode of complex eof ceof though its dominant period was 14 5 years this interdecadal sea level oscillation is the steric sea level change associated with the pacific inter decadal oscillation pdo in the upper ocean temperature field because the temporal evolution and spatial structure in the interdecadal oscillation resemble those of the dominant modal pattern in the temperature field however this mode shows a standing wave characteristic in the midlatitudes rather than propagating though the clockwise phase propagation around the subtropical gyre has been reported in the temperature field another interdecadal oscillation is found in the ceof second mode which was dominant in the 1960s when the first mode was relatively weak the second mode shows a 15 to 16 years period of variation and phase lags of 3 4 years at the subtropical stations relative to those in the midlatitudes

evolution of interdecadal variability in sea level pressure sea surface temperature and upper ocean temperature over the pacific ocean abstract interdecadal variability in sea level pressure slp and sea surface temperature sst anomalies in the pacific ocean was quasiperiodic from 1900 91 the coherent variability of this phenomenon is investigated using gridded observational data from the turn of the century sst and slp and of upper ocean heat content hs from the recent two and a half decades the nominal cycle in atmosphere ocean variables is roughly two decades long but growth and decay can happen on a shorter timescale e g half a cycle or so the authors divide the full cycle into four phases an onset phase during which a weak slp anomaly pattern off japan takes approximately 2 4 yr to expand eastward leads to large slp anomalies in the region of the aleutian low a quasi stationary growth phase with the midlatitude slp anomaly pattern in the eastern ocean intensifies over a 2 4 yr period the persistent slp anomalies evolve in concert with large sst and hs anomalies of the same polarity located to the south sout

quasi decadal and inter decadal climate fluctuations in the pacific ocean from a cgcm diagnostic analyses in the pacific have revealed distinct quasi decadal qd and inter decadal id climate fluctuations with coherent varying patterns of sea surface temperature sst and sea level pressure slp anomalies from a 200 year cgcm simulation distinct low frequency fluctuations are also obtained qd i e 8 12 years period band and id i e 18 25 years period band traced modeled qd evolution reveals equatorial sst anomalies resembling enso while tropical recharge discharge mechanisms seem to be operating the traced modeled id evolution reveals high latitudes spatially coherent patterns with maximum sst anomalies in the vicinity of the subarctic frontal zone safz and subtropical gyres through advection contrary to qd sst anomalies the modeled id sst anomalies peak away from the equator as observed qd fluctuations may then be viewed as low frequency enso phenomena while id fluctuations may set up thermal background modulating frequency and intensity of enso

a sedimentary facies model for glacial age sediments in baldwin lake southern california abstract a combined sedimentological and high resolution petrographic analysis was conducted on a glacial age 20 000 65 000 cal yr bp sediment core from baldwin lake southern california the results of this research represent the most complete glacial age terrestrial climate record from southern california to date these results are used to characterize the different sediment types and to investigate the difference in depositional processes and environments between the core s three predominant sediment types massive semi laminated and laminated sediments massive sediments are commonly associated with a blocky texture and or desiccation cracks are organic poor have high magnetic susceptibility values and are coarser grained thin sections from massive sediments reveal a homogenous sediment fabric sub centimeter scale laminated and centimeter scale semi laminated sediments are generally organic rich have low magnetic susceptibility values and are finer grained thin sections from laminated and semi laminated sediments reveal diffuse sub millimeter to millimeter scale laminae this combination of sedimentological and high resolution petrographic data enabled us to characterize four sediment facies each related to specific depositional processes and environments 1 a playa lake 2 a perennial shallow lake 3 an intermediate lake with variable lake level and 4 a perennial deep lake at centennial to millennial timescales lower lake levels are represented by deposition of massive to semi laminated sediments in a playa to a perennial shallow lake environment at similar timescales higher lake levels are recorded by semi laminated to laminated sediments deposited in an intermediate lake to a perennial deep lake environment these results provide an additional sedimentological study for comparison to similar arid environment basins and for comparison to existing regional paleoclimatic reconstructions

genesis modification and preservation of complex upper ordovician hardgrounds implications for sequence stratigraphy and the great ordovician biodiversification event abstract hardgrounds from the upper ordovician strata of eastern laurentia exhibit a wide range of morphologies though the development of their complex surface topographies remains poorly understood these early lithified seafloors which can be laterally very extensive may provide key information about basin dynamics and global ocean fluctuations based on spectacular exposures and newly excavated material we examined a suite of hardgrounds from the upper ordovician katian of southern ontario and the cincinnati arch region and documented the processes of genesis development and modification of simple complex and block hardgrounds in this study we used extensive field work petrology and cathodoluminescence to determine the evolution and shaping of hardgrounds as a result of intense submarine erosion and prolonged exposure of these surfaces and reveal a progression from simple to complex hardgrounds and ultimately to isolated cobble to boulder sized block hardgrounds we survey the distribution of hardgrounds in a sequence stratigraphic framework to determine allocyclic controls on hardground development highlight the important role that mixed siliciclastic carbonate environments play in promoting the development of heterogeneous hardground topographies and analyze the effects of high surface reliefs on local depositional and erosional regimes in addition we interpret the impact of increasingly abundant complex hardgrounds throughout the ordovician on hard substrate community diversification and their contribution to the great ordovician biodiversification event we also discuss time specific aspects of the late ordovician that made it a peak interval of hardground proliferation