multi scale variability of the sea surface temperature in the tropical atlantic 1 tropical atlantic ta sea surface temperature sst variability is studied using the continuous wavelet transform cwt of the sst indices in the tropical north atlantic tna tropical south atlantic tsa and equatorial atlantic eqa cwt of the difference index tnsd between the tna and tsa indices and the cross wavelet spectrum for the tna and tsa indices are also examined the analyses focus the short interannual interannual and decadal scales the global wavelet power of the tna tsa and eqa indices confirm previous findings on the dominant scales of the sst variability in different ta sectors the decadal peaks are dominant for the tna and tsa indices while the interannual peaks are significant only for the eqa index the scale averaged series for all scales feature a number of abrupt reversals of 180 which depends on the scale with larger number for smaller scales the during the period between two subsequent abrupt reversals remains close to 180 or varies within sub intervals of the 180 to 180 range thus the dipole like cross equatorial sst anomaly gradient monopole and equatorial patterns are established as evolving modes for all scales the periods of abrupt reversals of 180 occur within the periods with change in the meridional propagation directions of the sst anomalies or with reduced sst anomalies this result strongly suggests that the establishment of the sst anomaly patterns in the ta depends crucially on the meridional propagation of the sst anomalies this is a new aspect not discussed before

correlation of changes in gravity elevation and strain in southern california measurements made once or twice a year from 1977 through 1982 show large correlated changes in gravity elevation and strain in several southern california networks precise gravity surveys indicate changes of as much as 25 microgals between surveys 6 months apart repeated surveys show that annual elevation changes as large as 100 millimeters occur along baselines 40 to 100 kilometers long laser ranging surveys reveal coherent changes in areal strain of 1 to 2 parts per million occurred over much of southern california during 1978 and 1979 although the precision of these measuring systems has been questioned the rather good agreement among them suggests that the observed changes reflect true crustal deformation

eight centuries of north atlantic ocean atmosphere variability climate in the tropical north atlantic is controlled largely by variations in the strength of the trade winds the position of the intertropical convergence zone and sea surface temperatures a high resolution study of caribbean sediments provides a subdecadally resolved record of tropical upwelling and trade wind variability spanning the past 825 years these results confirm the importance of a decadal 12 to 13 year mode of atlantic variability believed to be driven by coupled tropical ocean atmosphere dynamics although a well defined interdecadal mode of variability does not appear to be characteristic of the tropical atlantic there is evidence that century scale variability is substantial the tropical atlantic may also have been involved in a major shift in northern hemisphere climate variability that took place about 700 years ago

tropical atlantic variability modes 1979 2002 part ii time evolving atmospheric circulation related to sst forced tropical convection abstract the ways in which deep convection over the tropical atlantic affects the midlatitude climate variability through meridional circulation planetary wave teleconnection and wave mean flow interaction is examined for the 1979 2002 period by following the north atlantic anomalous rainfall evolution from summer to late winter in this way the first two covariability modes between anomalous summer tropical atlantic sea surface temperature sst and anomalous summer late winter precipitation over the north atlantic basin are analyzed using the same methodology of extended maximum covariance analysis developed for part i this work updates the results given by other authors whose studies are based on different datasets dating back to the 1950s to this end the climate prediction center cpc merged analysis of precipitation cmap dataset which includes measures over the ocean is used to give a complete picture of the interannual rainfall patterns for the last decades the first mode which accoun

relationship between the equatorial and meridional modes of climatic variability in the tropical atlantic the tropical atlantic ocean exhibits two primary modes of interannual climate variability an equatorial mode analogous to but weaker than the pacific el nino phenomenon and a meridional mode that does not have a pacific counterpart the equatorial mode is responsible for warm and cold sea surface temperature sst events mainly in the gulf of guinea and is identifiable by abnormal changes in the equatorial thermocline slope resulting from zonal wind anomalies in the western tropical atlantic the meridional mode is characterized by a north south interhemispheric gradient of sst anomalies here it is shown using observed surface and subsurface oceanic temperatures that the meridional mode is linked to the equatorial mode at both decadal and short interannual 1 2 years time scales both modes involve north south displacements of the itcz as in the annual response

the southern ocean as a source region for tropical atlantic variability abstract a coupled model of intermediate complexity is used to examine the effect of the southern ocean on tropical atlantic variability model experiments with positive surface temperature freshwater and wind forcings in the southern ocean show an increased advection of polar water into the atlantic basin resulting in anomalously cold freshwater in the eastern atlantic ocean at 25 s with time these anomalies spread northward and away from the coast into the tropical thermocline the magnitude of the response increases linearly with the strength of the forcing the results of these experiments show that southeastern atlantic ocean temperature and salinity are particularly sensitive to changes in the southern ocean these findings suggest that this link could be the oceanic branch of a mode of variability linking the southern and tropical atlantic oceans a possible mechanism for the as yet unexplained decadal mode of tropical atlantic variability

how ubiquitous is the dipole relationship in tropical atlantic sea surface temperatures several kinds of analysis are applied to sea surface temperature anomalies ssta 1856 1991 to determine the degree to which ssta of opposite sign in the tropical north and south atlantic occur antisymmetric dipole configurations of ssta on basin scales are not ubiquitous in the tropical atlantic unless the data are stratified by both season and frequency inherent dipole behavior cannot be demonstrated upon removing the global el nino southern oscillation signal in ssta which is symmetric between the north and south atlantic from the data the regions north or south of the intertropical convergence zone have qualitatively different temporal variabilities and are poorly correlated dipole configurations do occur infrequently 12 15 of the time but no more so than expected by chance for stochastically independent variables nondipole configurations that imply significant meridional ssta gradients occur much more frequently nearly half of the time cross spectral analysis of seasonally averaged ssta indices for the north and south atlantic show marginally significant coherence with antisymmetric phase in two period bands 8 12 years for the boreal winter spring and 2 3 years for the boreal summer fall antisymmetric coherence is optimal for a small subregion west of angola in the south atlantic with respect to ssta of basin scale in the tropical north atlantic dipole variability even where optimal explains only a small fraction of the total variance in tropical atlantic ssta 7

prediction of tropical atlantic sea surface temperatures using linear inverse modeling the predictability of tropical atlantic sea surface temperature on seasonal to interannual timescales by linear inverse modeling is quantified the authors find that predictability of caribbean sea and north tropical atlantic sea surface temperature anomalies sstas is enhanced when one uses global tropical sstas as predictors compared with using only tropical atlantic predictors this predictability advantage does not carry over into the equatorial and south tropical atlantic indeed persistence is a competitive predictor in those regions to help resolve the issue of whether or not the dipole structure found by applying empirical orthogonal function analysis to tropical atlantic ssts is an artifact of the technique or a physically real structure the authors combine empirically derived normal modes and their adjoints to form influence functions maps highlighting the geographical areas to which the north tropical atlantic and the south tropical atlantic ssts are most sensitive at specified lead times when the analysis is confined to the atlantic basin the 6 month influence functions in the north and south tropical atlantic tend to be of the opposite sign and evolve into clear dipoles within 6 months when the analysis is performed on global tropical ssts the 6 month influence functions are connected

long term tidal cycle influences on a late holocene clay mineralogy record from the cariaco basin abstract recent analyses of coastal mudbank dynamics along northeastern south america indicate significant sediment remobilization associated with the 18 6 y lunar nodal tide over the last 20 y we present a near annually resolved record of quartz and illite illite smectite abundances spanning the last 800 y from the cariaco basin venezuela that suggests effects of the lunar nodal tide have played an important role in coastal processes over the last 8 centuries spectral analysis results of the clay and fine silt data include a statistically significant peak at 18 3 y in both the quartz and illite illite smectite records that is identified with the 18 6 y lunar nodal tide remobilization of shelf sediments by mean high water line variations driven by the lunar nodal tide is presented as the probable explanation of this signal in the cariaco basin mineral content since the period of this astronomically determined signal is constant with time it can be used to calibrate high resolution age models we modify our existing age model by tuning the 18 3 y component of the illite data to the 18 6 y period and explore its impact on the age depth relationship we suggest that the 18 6 y signal can be used to refine existing chronologies where detected

an intensification trend of south pacific mode water subduction rates over the 20th century 1 in this paper the trend of the south pacific mode water subduction rate is assessed based on recently developed ocean and atmosphere reanalysis products for the 20th century it is found that the subduction volume of the mode water is intensified in the 20th century the intensification of the mode water in the subtropical gyre of the south pacific is primarily due to the strengthening of the vertical pumping velocity dominated by the enhanced wind stress curl over the past century in contrast the intensification of the south pacific subantarctic mode water samw is mainly caused by a deepening of the mixed layer depths and a strengthening of the advection in warm climate as a result the total subduction volume of the mode water over the south pacific is increased in the 20th century

antarctic circumpolar waves an indication of ocean atmosphere coupling in the extratropics recent observational studies have detected coherent oceanic and atmospheric antarctic circumpolar waves acws which propagate eastward at speeds of 6 8 cm s 1 with a circumpolar wavenumber of 2 analysis of global wind data suggests that the acws are not remotely forced by tropical el nino activity through atmospheric teleconnection rather a coupled instability of the antarctic circumpolar current and its overlying atmospheric motion is proposed to be responsible for the generation of the acws the phase relationship among the observed oceanic and atmospheric variables supports the coupled instability theory this study provides one clear example that extratropical ocean atmosphere dynamical coupling is essential in generating climate variations on time scales of several years and longer

relative influences of the interdecadal pacific oscillation and enso on the south pacific convergence zone 1 the south pacific convergence zone spcz one of the most extensive features of the global atmospheric circulation is shown to vary its location according to both the polarity of the el nino southern oscillation enso and of the interdecadal pacific oscillation ipo we first demonstrate that the ipo can be regarded as the quasi symmetric pacific wide manifestation of the pacific decadal oscillation that has been described for the north pacific shifts in the position of the spcz related to enso on interannual time scales and to the ipo on decadal time scales appear to be of similar magnitude and are largely linearly independent a station pressure based index of variations in spcz latitude is shown to be significantly related to the polarity of the ipo when enso influences are accounted for movements of this sensitive section of the spcz have occurred in phase with those of the ipo since the 1890s

a comparison of the atlantic and pacific bjerknes feedbacks seasonality symmetry and stationarity the bjerknes feedback is the dominant positive feedback in the equatorial ocean basins to examine the seasonality symmetry and stationarity of the pacific and atlantic bjerknes feedbacks we decompose them into three feedback elements that relate thermocline depth sea surface temperature sst and western basin wind stress variability to each other we partition feedback elements into composites associated with positive or negative anomalies using robust regression we diagnose the strength of each composite for the recent period 1993 2012 composites of the pacific bjerknes feedback elements agree well with previous work positive composites are generally stronger than negative composites and all feedback elements are weakest in late boreal spring in the atlantic differences between positive and negative composites are less consistent across feedback elements specifically wind variability seems to play a less important role in shaping atmosphere ocean coupling in the atlantic when compared to the pacific however a clear seasonality emerges feedback elements are generally strong in boreal summer and for the negative composites again in boreal winter the atlantic bjerknes feedback is dominated by subsurface surface coupling applying our analysis to overlapping 25 year periods for 1958 2009 shows that the strengths of feedback elements in both ocean basins vary on decadal time scales while the overall asymmetry of the pacific bjerknes feedback is robust the strength and symmetry of atlantic feedback elements vary considerably between decades our results indicate that the atlantic bjerknes feedback is non stationary on decadal time scales

el nino like events observed in the tropical pacific abstract the data provided by ships of opportunity operated by surtropac group centre orstom de noumea are used to study surface temperature and salinity in 1979 and 1982 negative anomalies of salinity occurred in the equatorial western pacific these are usually induced by el nino events although no el nino was noticed in the eastern pacific during the beginning of the year however along the tahiti panama shipping route the warm season in 1979 and 1982 lasted longer than usual empirical orthogonal analysis applied to the surface temperature along shipping routes in the eastern and central pacific reveal other events with the same signature as the 1976 el nino a weak event occurred in 1979 and we can also see the beginning of the 1982 major event eastern central and western anomalies are significant correlated

coherent heat patterns revealed by unsupervised classification of argo temperature profiles in the north atlantic ocean abstract a quantitative understanding of the integrated ocean heat content depends on our ability to determine how heat is distributed in the ocean and identify the associated coherent patterns this study demonstrates how this can be achieved using unsupervised classification of argo temperature profiles the classification method used is a gaussian mixture model gmm that decomposes the probability density function of a dataset into a weighted sum of gaussian modes it is determined that the north atlantic argo dataset of temperature profiles contains 8 groups of vertically coherent heat patterns or classes each of the temperature profile classes reveals unique and physically coherent heat distributions along the vertical axis a key result of this study is that when mapped in space each of the 8 classes is found to define an oceanic region even if no spatial information was used in the model determination the classification result is independent of the location and time of the argo profiles two classes show cold anomalies throughout the water column with amplitude decreasing with depth they are found to be localized in the subpolar gyre and along the poleward flank of the gulf stream and north atlantic current nac one class has nearly zero anomalies and a large spread throughout the water column it is found mostly along the nac one class has warm anomalies near the surface 50 m and cold ones below 200 m it is found in the tropical equatorial region the remaining four classes have warm anomalies throughout the water column one without depth dependance in the southeastern part of the subtropical gyre the other three with clear maximums at different depths 100 m 400 m and 1000 m these are found along the southern flank of the north equatorial current the western part of the subtropical gyre and over the west european basin these results are robust to both the seasonal variability and to method parameters such as the size of the analyzed domain

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

the impact of refraction correction on leveling interpretations in southern california recent investigations show that the refraction corrections in leveling are large but can be adequately modeled the corrections are proportional to the temperature differences and the square of the sight lengths changes in sight length with time have resulted in apparent crustal movements when non refraction corrected data were used applying refraction corrections to leveling data in southern california significantly alters the size and configuration of the southern california uplift uplift at palmdale and gorman lebec relative to los angeles bm v32 during the 1953 1978 time period is no greater than 10 cm the bulk of the motion about 6 cm occurs as localized motion along the san gabriel fault during the 1953 1964 time period this motion along the san gabriel fault and uplift of 8 cm directly north of the san fernando fault between 1955 and 1968 may represent precursors to the 1971 san fernando earthquake

observations of warm water volume changes in the equatorial pacific and their relationship to el nino and la nina abstract this paper describes observed changes in surface winds sea surface temperature sst and the volume of water warmer than 20 c wwv in the equatorial pacific ocean for the period 1980 99 the purpose is to test recent hypotheses about the relationship between variations in wwv and the el nino southern oscillation enso cycle the results confirm inferences based on theory models and previous empirical analyses using proxy data namely sea level that enso involves a recharge and discharge of wwv along the equator and that the cyclic nature of enso results from a disequilibrium between zonal winds and zonal mean thermocline depth the authors also find that the magnitude of enso sst anomalies is directly related to the magnitude of zonal mean wwv anomalies furthermore for a given change in equatorial wwv the corresponding warm el nino sst anomalies are larger than the corresponding cold la nina anomalies this asymmetry between the warm and cold phases of the enso cycle implies differences

saugus palmdale california field test for refraction error in historical leveling surveys a field test designed to measure atmospheric refraction error in historical and modern leveling was conducted in may june 1981 on a 50 km long grade from saugus to palmdale california during 1955 1971 the length of sights made between the level instrument and rods systematically decreased from 60 m to 26 m the difference in height near palmdale measured by single run long sight 42 m and short sight 22 m leveling during the test was 6 times larger than expected random error correction for refraction by using either the observed or modeled vertical temperature gradient in kukkamaki s balanced sight equation reduced the height difference to the level of random error uncertainty the observed temperature gradient obeyed a power law relation t a bzc where z is the height and a b and c are constants that depended on atmospheric conditions and the ground surface beneath the line of sight the refraction corrected leveling satisfies the specifications and meets all standards of first order control surveys the six historical surveys of the saugus palmdale grade were corrected for refraction error using the results of the experiment and for rod scale errors and nontectonic subsidence considered in previous investigations the corrected uplift near palmdale reached 56 16 mm with respect to saugus during the period 1955 1965 this amount of uplift is about one third that obtained before removal of refraction error the corrected displacement profiles also reveal previously unrecognized deformation in the epicentral region of the 1971 san fernando ml 6 4 earthquake during the decade before the main shock

wes feedback and the atlantic meridional mode observations and cmip5 comparisons the atlantic meridional mode amm is the dominant mode of tropical sst wind coupled variability modeling studies have implicated wind evaporation sst wes feedback as the primary driver of the amm s evolution across the atlantic basin however a robust coupling of the sst and winds has not been shown in observations this study examines observed amm growth propagation and decay as a result of wes interactions investigation of an extended maximum covariance analysis shows that boreal wintertime atmospheric forcing generates positive sst anomalies ssta through a reduction of surface evaporative cooling when the amm peaks in magnitude during spring and summer upward latent heat flux anomalies occur over the warmest ssts and act to dampen the initial forcing in contrast on the southwestern edge of the ssta sst forced cross equatorial flow reduces the strength of the climatological trade winds and provides an anomalous latent heat flux into the ocean which causes southwestward propagation of the initial atmosphere forced ssta through wes dynamics additionally the lead lag relationship of the ocean and atmosphere indicates a transition from an atmosphere forcing ocean regime in the northern subtropics to a highly coupled regime in the northern tropics that is not observed in the southern hemisphere cmip5 models poorly simulate the latitudinal transition from a one way interaction to a two way feedback which may explain why they also struggle to reproduce spatially coherent interactions between tropical atlantic sst and winds this analysis provides valuable insight on how meridional modes act as links between extratropical and tropical variability and focuses future research aimed at improving climate model simulations

seasonality in the local and remote atmospheric response to sea surface temperature anomalies abstract two apparently contradictory situations are provided by observations of the atmospheric response to sea surface temperature anomalies these are i the extratropical regions of the winter hemisphere appear to possess strong teleconnections with equatorial forcing but weak or non existent connections with local extratropical heating anomalies ii the extratropical regions of the summer hemisphere are quite sensitive to local thermal forcing but apparently unaffected by the remote forcing from equatorial regions an attempt is made to provide a consistent physical picture which simultaneously embraces these two situations with the aid of a simple linear model it is shown that the summer hemisphere is more sensitive to local forcing than the winter hemisphere because it is closer to the diabatic limit of webster 1981 thus allowing an efficient energy generation the winter hemisphere is much closer to the adjective limit the sensitivity of the midlatitudes to remote equatorial forcing

benefits of cmip5 multimodel ensemble in reconstructing historical ocean subsurface temperature variations abstracta complete map of the ocean subsurface temperature is essential for monitoring aspects of climate change such as the ocean heat content ohc and sea level changes and for understanding the dynamics of the ocean climate variation however global observations have not been available in the past so a mapping strategy is required to fill the data gaps in this study an advanced mapping method is proposed to reconstruct the historical ocean subsurface 0 700 m temperature field from 1940 to 2014 by using ensemble optimal interpolation with a dynamic ensemble enoi de approach and a multimodel ensemble of phase 5 of the coupled model intercomparison project cmip5 historical and representative concentration pathway 4 5 simulations the reconstructed field is a combination of two parts a first guess provided by the ensemble mean of cmip5 models and an adjustment by minimizing the analysis error with the assistance of error covariance determined by the cmip5 models the uncertainty of the field ca

tropical pacific sea surface temperature anomalies el nino and equatorial westerly wind events abstract the authors examine global statistical relationships between westerly wind events wwes and sea surface temperature anomaly ssta variability using a compositing technique for the period 1986 98 the authors describe the extent to which equatorial wwes are associated with central and eastern equatorial pacific waveguide warming and with local ssta changes under the wwe their goal is to quantify the extent to which equatorial wwes are fundamental to the onset and maintenance of warm el nino southern oscillation conditions in order to understand the effect of wwes on ssta evolution they begin by examining how ssta changes in the absence of equatorial wwes they find that ssta tends toward mean climate values in the absence of equatorial wwes whether the eastern equatorial pacific has close to normal ssta or warmer than normal ssta the two equatorial wwe types whose main surface wind anomalies are west of the date line are associated with weak local surface cooling the equatorial wwe type t

the north equatorial countercurrent and heat storage in the western pacific ocean during 1982 83 a sequence of extreme climate anomalies known as an el nino southern oscillation episode was observed in the tropical pacific ocean during 1982 831 2 models suggest that oceanic circulation has an important role in the formation of such anomalies1 3 4 by altering the pattern of sea surface temperature through advection the baroclinic structure of the upper 500 m of the ocean has been monitored routinely in the western pacific since 1979 providing indirect current measurements by the geostrophic method these observations reported here show large changes in the near equatorial currents during 1982 83 which are consistent with currents observed in the central and eastern pacific5 6 in particular the north equatorial countercurrent necc flowed with 25 50 increased strength during the early phase then weakened almost to zero flow the west pacific heat pool cooled by more than 1 c observed changes in circulation were large enough to alter surface heat storage by advection although other potentially important processes may not be negligible

decadal variability of the tropical atlantic ocean surface temperature in shipboard measurements and in a global ocean atmosphere model abstract numerous analyses of relatively short 25 30 years in length time series of the observed surface temperature of the tropical atlantic ocean have indicated the possible existence of decadal timescale variability it was decided to search for such variability in 100 yr time series of sea surface temperature sst measured aboard ships and available in the recently published global ocean surface temperature atlas gosta fourier and singular spectrum analyses of the gosta sst time series averaged over 11 subregions each approximately 1 106 km2 in area show that pronounced quasi oscillatory decadal 8 20 yr and multidecadal 30 40 yr timescale variability exists in the gosta dataset over the tropical atlantic motivated by the above results sst variability was investigated in a 200 yr integration of a global model of the coupled oceanic and atmospheric general circulations developed at the geophysical fluid dynamics laboratory gfdl the second 100 yr of sst in the coupled model s tropical

recent hiatus caused by decadal shift in indo pacific heating recent modeling studies have proposed different scenarios to explain the slowdown in surface temperature warming in the most recent decade some of these studies seem to support the idea of internal variability and or rearrangement of heat between the surface and the ocean interior others suggest that radiative forcing might also play a role our examination of observational data over the past two decades shows some significant differences when compared to model results from reanalyses and provides the most definitive explanation of how the heat was redistributed we find that cooling in the top 100 meter layer of the pacific ocean was mainly compensated for by warming in the 100 to 300 meter layer of the indian and pacific oceans in the past decade since 2003

atmosphere ocean coupled variability in the south atlantic abstract the climate variability of the south atlantic region is determined from 40 yr 1953 92 of comprehensive ocean atmosphere data set monthly sea surface temperature sst and sea level pressure slp data using the empirical orthogonal function eof and the singular value decomposition svd analysis methods the eof method is applied to each field separately whereas the svd method is applied to both fields simultaneously the significance of the atmosphere ocean interaction is revealed by a strong resemblance between individual eof and coupled svd modes of sst and slp the three leading modes of coupled variability on interannual and interdecadal timescales are discussed in some detail the first coupled mode which accounts for 63 of the total square covariance represents a 14 16 yr period oscillation in the strength of the subtropical anticyclone accompanied by fluctuations of a north south dipole structure in the sst the atmosphere ocean coupling is strongest during the southern summe

upper equatorial pacific ocean current and salinity variability during the 1996 1998 el nino la nina cycle the recent el nino la nina cycle exhibited striking patterns of current and salinity variability in the upper equatorial pacific ocean this evolution is described from mid 1996 through 1998 using a remarkable data set of 35 meridional conductivity temperature depth ctd acoustic doppler current profiler adcp sections along with buoy data the sections nominally from 8 s to 8 n between 165 e and 95 w were occupied over the course of 27 months a wide range of current variability was sampled with currents that appeared or disappeared some time during the cycle including an equatorially trapped eastward surface current the equatorial undercurrent the northern branch of the south equatorial current and the north equatorial countercurrent basin wide interannual changes in upper ocean and pycnocline zonal transports were as large as 64 32 106 m3 s 1 changes in the salinity structure included a deep and fresh mixed layer in the central equatorial pacific that built up during the el nino and was then disrupted by upwelled salty water with the onset of la nina a very fresh mixed layer observed in the eastern equatorial pacific late in the el nino and a reduction in the strength of the meridional equatorial salinity gradient within the pycnocline to one third of the usual value during the el nino finally the zonal transports above the thermocline from 5 s to 5 n were well correlated with the rate of change of warm water volume west of the individual ctd adcp sections

the california current system in relation to the northeast pacific ocean circulation abstract the california current system is described in its regional setting using two modern datasets argo provides a broadscale view of the entire eastern north pacific ocean for the period 2004 2010 and the high resolution xbt network includes transects from honolulu to san francisco 1991 2010 and to los angeles 2008 2010 together these datasets describe a california current of 500 800 km width extending along the coast from 43 n to 23 n the mean southward transport of the california current is about 5 sv off central and southern california with about 2 5 sv of northward flow on its inshore side interannual variations are 50 or more of the mean transports the salinity minimum in the core of the california current is supplied by the north pacific current and by freshwater from the northern continental shelf and modified by alongshore geostrophic and across shore ekman advection as well as eddy fluxes and air sea exchange the heat and freshwater content of the california current vary in response to the fluctuating strength of the alongshore geostrophic flow on its offshore side the california current is influenced by north pacific intermediate waters at its deepest levels and by eastern subtropical mode waters on shallower density surfaces in total the sources of the california current its alongshore advection and its strong interactions with the inshore upwelling region and the offshore gyre interior combine to make this a rich and diverse ecosystem the present work reviews previous contributions to the regional oceanography and uses the new datasets to paint a spatially and temporally more comprehensive description than was possible previously

earthquake prediction a critical review summary earthquake prediction research has been conducted for over 100 years with no obvious successes claims of breakthroughs have failed to withstand scrutiny extensive searches have failed to find reliable precursors theoretical work suggests that faulting is a non linear process which is highly sensitive to unmeasurably fine details of the state of the earth in a large volume not just in the immediate vicinity of the hypocentre any small earthquake thus has some probability of cascading into a large event reliable issuing of alarms of imminent large earthquakes appears to be effectively impossible key word earthquake prediction

recent advances in wavelet analyses part 2 amazon parana orinoco and congo discharges time scale variability this paper is devoted to illustrating new wavelet analysis methods in the field of hydrology new wavelet indicators are applied to long term hydrological and climatologic proxies they are first applied to four atlantic large river monthly discharges amazon parana orinoco and congo and then applied to two well known long term climatologic indexes the southern oscillation and the north atlantic oscillation this approach makes it possible to suggest physical explanations for time scale dependant relationships six month variability is present in all the rivers except in the parana in the congo river this signal is near stationary with strong entropy the strength of this scale coincides with higher discharge variability before 1920 and over the orinoco basin with higher discharge values between 1940 and 1955 an annual cycle is present in all the rivers but is much stronger along with the entropy in the rivers with a large tropical basin as in the amazon and the orinoco this annual signal is not permanent in the congo and much more intermittent in the parana where the annual recharge appears as very irregular a quasi biennial variability is apparent in all the equator ward rivers and a nearly permanent 2 year coherence is found between soi and the amazon discharge a 3 6 year oscillation typical of enso variability is observed in all the rivers it is intermittent observed before 1930 in all the rivers and after 1980 mostly in the amazon river these peaks of activity correspond to periods of major soi variability an 8 year variability is particularly strong in the parana river before 1940 and around 1970 and to a lesser extent in the orinoco river during the low nao index period between 1940 and 1970 the congo river exhibits that time scale around 1970 a 13 year variability common to soi nao and the south atlantic ocean circulation is observed in the parana and congo discharges in all the rivers the greatest entropy is observed at bi and multi decadal time scales with the greatest coherence with both nao and soi a near 20 year time scale is observed in most of the series around 1970 although it is strongest in amazon and parana discharges finally a 30 year time scale is observed between 1940 and 1970 it is to be noted that most of the time scale dominant activities in all the rivers may have been influenced by the interdecadal shifts that took place around 1940 and 1970 in the pacific and in the atlantic therefore in this contribution the application of new wavelet indicators combined continuous and multi resolution analysis wavelet entropy wavelet coherence wavelet cross correlation leads to several improvements in the analysis of these global hydrological signal fluctuations and of their mutual time varying relationships it is demonstrated that wavelets should be used more systematically in preference to the classical fourier analysis notably in hydrology

a comparison of decadal climate oscillations in the north atlantic detected in observations and a coupled gcm abstract decadal climate variations in the atlantic ocean found in observational fields and a coupled general circulation model cgcm are investigated in particular physical processes responsible for the phase reversal are compared observed and modeled decadal variations have dominant periodicities around 12 3 and 9 9 yr respectively both variations show similar spatial features sea surface temperature sst anomalies in the western subtropical atlantic sandwiched by those with opposite sign to the north and south and a dipole of sea level pressure anomalies which resemble the north atlantic oscillation their temporal evolutions are however different from each other suggestive of different dynamics of the oscillation in the observations sst and surface layer 0 100 m temperature anomalies move eastward from the subtropical western atlantic to the european coast along the gulf stream northward propagation of sst anomalies are also found along the western boundaries including the gulf of me

estimating global ocean heat content changes in the upper 1800 m since 1950 and the influence of climatology choice abstractocean heat content anomalies are analyzed from 1950 to 2011 in five distinct depth layers 0 100 100 300 300 700 700 900 and 900 1800 m these layers correspond to historic increases in common maximum sampling depths of ocean temperature measurements with time as different instruments mechanical bathythermograph mbt shallow expendable bathythermograph xbt deep xbt early sometimes shallower argo profiling floats and recent argo floats capable of worldwide sampling to 2000 m have come into widespread use this vertical separation of maps allows computation of annual ocean heat content anomalies and their sampling uncertainties back to 1950 while taking account of in situ sampling advances and changing sampling patterns the 0 100 m layer is measured over 50 of the globe annually starting in 1956 the 100 300 m layer starting in 1967 the 300 700 m layer starting in 1983 and the deepest two layers considered here starting in 2003 and 2004 during the implementation of argo furthermor

recording of el nino in ice core δ18o records from nevado huascaran peru the 68 year monthly resolved time series of 18 o from ice cores retrieved from the glaciated col of nevado huascaran peru 9 s 77 w 6050 m reflects climate variability over amazonia and the western tropical atlantic over the 25 year period 1968 1993 of midtroposphere observations the interannual variations in huascaran 18 o relate closely with the zonal wind variations over tropical south america at the 500 hpa level additionally there is some evidence that the spatial distribution of temperature anomalies in the western tropical atlantic has influence on the 500 hpa circulation and hence the isotopic fractionation of moisture advected across amazonia during el nino warming the moisture convergence axis over the atlantic ocean is commonly diverted northward leading to unusual warm and dry conditions over northeast brazil and 18 o enriched snowfall at huascaran this enrichment phase is enhanced when the peak pacific warming occurs during the first half of the calendar year coincident with the wet season over amazonia approximately 12 months later the el nino demise is affiliated with a reprisal of strong trade wind circulation and the resultant cool pluvial environment over amazonia triggers a reversal to strongly depleted isotope anomalies

tropical atlantic sea surface temperature variability and its relation to el nino southern oscillation past analyses of tropical atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics across the intertropical convergence zone itcz by analyzing an improved 43 year 1950 1992 record of sst smith et al 1996 and other data derived from the comprehensive ocean atmosphere data set coads it is shown that the regions north and south of the itcz are statistically independent of each other at the seasonal to interannual timescales dominating the data confirming the conclusions of houghton and tourre 1992 some dipole behavior does develop weakly during the boreal spring season when there is a tendency for sst anomaly west of angola to be opposite of that in the tropical north atlantic it is further shown that tropical atlantic sst variability is corre lated with pacific e1 nifio southern oscillation enso variability in several regions the ma jor region affected is the north atlantic area of ne trades west of 40ow along 10on 20on and extending into the caribbean there about 50 80 of the anomalous sst variability is associ ated with the pacific enso with atlantic warmings occurring 4 5 months after the mature phases of pacific warm events an analysis of local surface flux fields derived from coads data shows that the enso related atlantic warmings occur as a result of reductions in the surface ne trade wind speeds which in turn reduce latent and sensible heat losses over the region in ques tion as well as cooling due to entrainment this enso connection is best developed during the boreal spring following the most frequent season of maximum enso anomalies in the pacific a region of secondary covariability with enso occurs along the northern edge of the mean itcz position and appears to be associated with northward migrations of the itcz when the north at lantic warmings occur although easterly winds are intensified in the western equatorial atlantic in response to pacific warm events they do not produce strong local changes in sst contrary to expectations from studies based on equatorial dynamics these teleconnected wind anomalies do not give rise to significant correlations of sst in the gulf of guinea with the pacific enso as the teleconnection sequence matures strong se trades at low southern latitudes follow the de velopment of the north atlantic sst anomaly and precede by several months the appearance of weak negative sst anomalies off angola and stronger positive anomalies extending eastward from southern brazil along 15o 30os

an assessment of the accuracy of the geodetic measurements that define the southern california uplift examination of the charge that the geodetic measurements which define the southern california uplift are seriously flawed by height dependent systematic errors indicates that this charge is unfounded our review of those factors designed to minimize the effects of rod error shows that systematic errors attributable to rod miscalibration are trivial and would tend to cancel during the particularly pertinent period 1955 1965 comparisons between the results of measurements in which the correlation between topography and signal is generally poor reveal large aseismic tilts in a number of places within and around the margins of the uplift especially significant in this context are the results of preuplift and postuplift levelings over routes characterized by diverse length topography and atmospheric conditions that produce closely matching temporally equivalent heights for a representative bench mark within the uplift statistical analyses of the short wavelength components of uplift signal and elevation along a frequently repeated survey line indicate variable correlations between the two however the spatial and temporal patterns of these correlations are inconsistent with their attribution to height dependent systematic errors statistically significant short wavelength correlations along this survey line are reasonably explained in part as due to real movement associated with differentially subsiding bench marks and there is a strong likelihood that this movement tends to dominate many of the correlations

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

the unusual summer of 1994 in east asia iod teleconnections 1 an extremely hot and dry summer of 1994 was reported in east asian countries using observational data we have demonstrated that the indian ocean dipole iod is at least one possible cause of the abnormal east asian summer climate an anomalous cyclonic circulation over the western pacific and the southern china weakened the monsoonal northward flow in the lower troposphere an anomalous anticyclonic circulation with the equivalent barotropic structure around japan korea and the northeastern part of china caused the hot and dry summer of 1994 this accumulation of the lower potential vorticity in the far east is related to the wave activity from the mediterranean sahara region the monsoon desert mechanism connects a rossby wave source with the iod induced diabatic heating around the bay of bengal another rossby wave train pattern was generated in the upper troposphere and propagates northeastward from the southern china both the rossby wave patterns influenced the circulation changes over east asia

unsupervised clustering of southern ocean argo float temperature profiles the southern ocean has complex spatial variability characterized by sharp fronts steeply tilted isopycnals and deep seasonal mixed layers methods of defining southern ocean spatial structures traditionally rely on somewhat ad hoc combinations of physical chemical and dynamic properties as a step towards an alternative approach for describing spatial variability in temperature here we apply an unsupervised classification technique that is gaussian mixture modelling or gmm to southern ocean argo float temperature profiles gmm without using any latitude or longitude information automatically identifies several spatially coherent circumpolar classes influenced by the antarctic circumpolar current in addition gmm identifies classes that bear the imprint of mode intermediate water formation and export large scale gyre circulation and the agulhas current among others because gmm is robust standardized and automated it can potentially be used to identify structures such as fronts in both observational and model datasets possibly making it a useful complement to existing classification techniques

annual to interannual temperature variability in the caribbean during the maunder sunspot minimum we reconstruct caribbean seawater temperatures from sclerosponge sr ca ratios using a specimen of ceratoporella nicholsoni that grew at 20 m below sea level in a reef cave at jamaica we sample the time interval from 1620 to 1745 a d with almost monthly resolution this interval includes the maunder sunspot minimum one of the coldest periods of the little ice age reconstructed annual temperature amplitudes are on the order of about 1 c the mean growth rate calculated from the annual sr ca variations corresponds perfectly with u th based growth rates we find that the interannual climate variability is determined by el nino southern oscillation and by a decadal signal most likely originating from the tropical north atlantic on a multidecadal timescale the maunder minimum is characterized by a 1 2 c cooling and reduced amplitudes of the interannual and decadal temperature variations

an 8 century tropical atlantic sst record from the cariaco basin baseline variability twentieth century warming and atlantic hurricane frequency 1 we present the first direct comparison and calibration of a downcore foraminiferal mg ca record to historical instrumental sea surface temperature sst mg ca measured on the planktic foraminifer globigerina bulloides from a cariaco basin sediment core strongly correlate with spring march may instrumental ssts between a d 1870 and 1990 a mg ca sst equation is derived and a paleo sst record is presented spanning the last 8 centuries an interval that includes the end of the medieval warm period and the little ice age the long term record displays a surprising amount of variability the temperature swings are not necessarily related to local upwelling variability but instead represent wider conditions in the caribbean and western tropical atlantic the mg ca sst record also captures the decadal and multidecadal variability observed in records of global land and sea surface temperature anomalies and atlantic tropical storm and hurricane frequency over the late nineteenth and twentieth centuries a divergence between the sst proxy record and atlantic storm frequency around 1970 appears to reflect a fundamental change in atlantic hurricane behavior noted in historical data on average twentieth century temperatures are not the warmest in the entire record but they do show the largest increase in magnitude and fastest rate of sst change over the last 800 a

on the variability of the tropical pacific thermal structure during the 1979 96 period as deduced from xbt sections abstract the thermal structure variability of the tropical pacific is investigated using an objective analysis of about 250 000 temperature profiles mainly xbt collected during the 1979 96 time period mean conditions and seasonal variability are briefly described to set the context and temperature anomalies are constructed relative to a mean seasonal cycle to focus on the enso el nino southern oscillation timescale heat content anomalies 0 450 m built up in the western equatorial basin prior to the 1982 83 1986 87 and 1997 98 el nino events but not clearly prior to the 1991 92 1993 and 1994 95 events which are thus found atypical low frequency migration of temperature anomalies located at the mean thermocline depth is evidenced eastward in the equatorial band as well as westward along a narrow zonal band located slightly north of the mean position of the intertropical convergence zone say 10 20 n this indicates that enso related temperature anomalies in the subsurface ocean are pres

correlation analyses between sea surface temperature anomalies in the eastern equatorial pacific and the world ocean based on data from the comprehensive ocean atmosphere data set coads objective analyses of the monthly mean sea surface temperature sst were prepared at gfdl for each month of the 110 year period 1870 1979 time series of various indices characterizing the sst anomalies averaged over the eastern equatorial pacific eep the tropical oceans and the world ocean are presented for monthly yearly and decadal time averaging periods global correlations maps are given for each decade of the 1870 1979 period they show the spatial connections between the monthly sst anomalies in the eep and in other parts of the world ocean and how these connections vary for the different decades on the intermonthly time scale the sst anomalies in the eep and those in the tropical and world oceans are found to be highly correlated with maximum correlations values of 0 91 at zero lag for the tropical oceans during the 1950 1959 decade and 0 81 for the world ocean during the 1970 1979 decade positive correlation values of r 0 36 persist on average from about 4 months before to about 8 months after the eep anomalies occur there is a clear tendency for the tropical and world ocean anomalies to lag behind the eep anomalies comparing different oceans we find the tendency for the tropical sst anomalies in the indian and atlantic oceans to lag behind those in the eep region by about 1 and 3 months respectively on the interannual time scale the eep anomalies are also well correlated with those in the other regions having an average correlation of 0 84 for the tropical oceans and of about 0 7 for the world ocean

factors that affect the amplitude of el nino in global coupled climate models historically el nino like events simulated in global coupled climate models have had reduced amplitude compared to observations here el nino like phenomena are compared in ten sensitivity experiments using two recent global coupled models these models have various combinations of horizontal and vertical ocean resolution ocean physics and atmospheric model resolution it is demonstrated that the lower the value of the ocean background vertical diffusivity the greater the amplitude of el nino variability which is related primarily to a sharper equatorial thermocline among models with low background vertical diffusivity stronger equatorial zonal wind stress is associated with relatively higher amplitude el nino variability along with more realistic east west sea surface temperature sst gradient along the equator the sst seasonal cycle in the eastern tropical pacific has too much of a semiannual component with a double intertropical convergence zone itcz in all experiments and thus does not affect nor is it affected by the amplitude of el nino variability systematic errors affecting the spatial variability of el nino in the experiments are characterized by the eastern equatorial pacific cold tongue regime extending too far westward into the warm pool the time scales of interannual variability as represented by time series of nino3 ssts show significant power in the 3 4 year enso band and 2 2 5 year tropospheric biennial oscillation tbo band in the model experiments the tbo periods in the models agree well with the observations while the enso periods are near the short end of the range of 3 6 years observed during the period 1950 94 the close association between interannual variability of equatorial eastern pacific ssts and large scale sst patterns is represented by significant correlations between nino3 time series and the pc time series of the first eofs of near global ssts in the models and observations

as el nino builds pacific warm pool expands ocean gains more heat el nino southern oscillation enso effects substantial redistributions of ocean temperature both horizontal and vertical on interannual time scales especially in the pacific ocean analyses of monthly argo based ocean temperature maps illustrate large scale ocean heat content redistributions with enso they quantify a globally averaged sea surface temperature warming of 0 1 c with a 1 c increase of the nino3 4 index a moderate el nino a substantial perturbation to the 0 13 c decade 1 trend in sea surface temperature monthly satellite based estimates of earth s energy imbalance suggest that a 1 c increase of the nino3 4 index corresponds to an increase of 3 4 zj in earth s energy storage more gently modulating the longer term 114 zj decade 1 trend yearly global ocean heat content estimates based on ocean temperature data with their reduced uncertainties compared to monthly maps reveal interannual variations in earth s energy storage that correspond well with satellite based estimates

atlantic climate variability and its associated atmospheric circulation cells abstract phenomena important for atlantic climate variability include the atlantic zonal equatorial mode the tropical atlantic meridional gradient mode and the north atlantic oscillation nao these climate phenomena and their associated atmospheric circulation cells are described and discussed using the ncep ncar reanalysis field and the ncep sea surface temperature sst from january 1950 to december 1999 atmospheric divergent wind and vertical motion are used for the identification of atmospheric circulation cells during the peak phase of the atlantic equatorial mode the atlantic walker circulation weakens and extends eastward which results in surface westerly wind anomalies in the equatorial western atlantic these westerly wind anomalies are partly responsible for warming in the equatorial eastern atlantic that occurs in the second half of the year the atlantic equatorial mode involves a positive ocean atmosphere feedback associated with the atlantic walker circulation similar to the pacific

trends interdecadal and interannual oscillations in global sea surface temperatures this study aims at a global description of climatic phenomena that exhibit some regularity during the twentieth century multi channel singular spectrum analysis is used to extract long term trends and quasi regular oscillations of global sea surface temperature sst fields since 1901 regional analyses are also performed on the pacific northern and southern atlantic and indian ocean basins the strongest climatic signal is the irregular long term trend characterized by overall warming during 1910 1940 and since 1975 with cooling especially of the northern hemisphere between these two warming intervals substantial cooling prevailed in the north pacific between 1950 and 1980 and continues in the north atlantic today both cooling and warming are preceded by sst anomalies of the same sign in the subpolar north atlantic near decadal oscillations are present primarily over the north atlantic but also over the south atlantic and the indian ocean a 13 15 y oscillation exhibits a seesaw pattern between the gulf stream region and the north atlantic drift and affects also the tropical atlantic another 7 8 y oscillation involves the entire double gyre circulation of the north atlantic being mostly of one sign across the basin with a minor maximum of opposite sign in the subpolar gyre and the major maximum in the northwestern part of the subtropical gyre three distinct interannual signals are found with periods of about 60 65 45 and 24 30 months all three are strongest in the tropical eastern pacific the first two extend throughout the whole pacific and still exhibit some consistent albeit weak patterns in other ocean basins the latter is weaker overall and has no consistent signature outside the pacific the 60 month oscillation obtains primarily before the 1960s and the 45 month oscillation afterwards

revisiting the thermocline depth in the equatorial pacific abstract the thermocline depth is defined as the depth of the maximum vertical temperature gradient in the equatorial pacific the depth of 20 c isotherm is widely used to represent the thermocline depth this work proposes that under the circumstance of a significant mean climate shift it is better to use the original definition of the thermocline depth in studying the long term changes in mean climate and tropical coupled climate variabilities for instance during the transient period of global warming the tropical thermocline is usually enhanced because the surface layer warms more and faster than the lower layers the depth of maximum vertical temperature gradient shoals which is consistent with the enhanced thermocline however the 20 c isotherm depth deepens which suggests a weakened thermocline this discrepancy exists in both the observations and the future climate simulations of coupled models

the global ocean imprint of enso 1 the enso related spatial patterns and global averages of ocean temperature salinity and steric height are estimated from over 7 years of argo data 2004 2011 substantial extratropical variability is seen in all variables in addition to familiar tropical enso signals surface layer 0 100 dbar and subsurface 100 500 dbar temperature variations are both important in determining steric height and sea surface height patterns for the two years prior to the 2009 el nino the upper 100 dbar of the ocean gained 3 3 1022 j yr 1 of heat while the 100 500 dbar layer lost a similar amount the enso related vertical redistribution of globally averaged heat content between surface and subsurface layers occurring throughout the record is due primarily to changes in the east west tilting of the equatorial pacific thermocline the large temperature changes in the individual layers mask the smaller vertically averaged temperature change in which the ocean loses heat when the surface layer is anomalously warm and gains heat when the surface layer is cool

reduced enso variability at the lgm revealed by an isotope enabled earth system model studying the el nino southern oscillation enso in the past can help us better understand its dynamics and improve its future projections however both paleoclimate reconstructions and model simulations of enso strength at the last glacial maximum lgm 21 ka bp have led to contradicting results here we perform model simulations using the recently developed water isotope enabled community earth system model icesm for the first time model simulated oxygen isotopes are directly compared with those from enso reconstructions using the individual foraminifera analysis ifa we find that the lgm enso is most likely weaker comparing with the preindustrial the icesm suggests that total variance of the ifa records may only reflect changes in the annual cycle instead of enso variability as previously assumed furthermore the interpretation of subsurface ifa records can be substantially complicated by the habitat depth of thermocline dwelling foraminifera and their vertical migration with a temporally varying thermocline

stable oxygen isotopic composition of corals from the gulf of guinea as indicators of periods of extreme precipitation conditions in the sub sahara stable oxygen isotopic analyses of scleractinian coral skeletons from the gulf of guinea in the eastern atlantic reveal that the corals from this region can be used to identify periods of severe drought and above average precipitation in sub sahara africa data presented in this paper show an inverse correlation between precipitation in the sahel and the 18 o values of a coral skeletons of the species siderastrea spp collected from the island of principe in the gulf of guinea this is opposite to the correlation expected as previous work has suggested that higher sea surface temperatures occur in the gulf of guinea during periods of low rainfall in the sahel such an association would lead to a positive correlation between sahel precipitation and skeletal 18 o the explanation for the observed inverse correlation is that the salinity of the gulf of guinea is strongly influenced by the outflow from the niger and congo rivers these periods of high freshwater input also correlate with periods of higher rainfall in the sub sahara and therefore affect the 18 o values of the coral skeleton the correlation between 18 o values of the coral skeleton and temperature in the northern subtropical atlantic ocean r 0 34 the magnitude of the dipole r 0 45 and the latitudinal position of the intertropical convergence zone r 0 37 illustrate that the 18 o values in the coral skeleton reflect climate dynamics of the region that affect the precipitation patterns in sub sahara africa

south atlantic variability arising from air sea coupling local mechanisms and tropical subtropical interactions abstract interannual variability in the southern and equatorial atlantic is investigated using an atmospheric general circulation model agcm coupled to a slab ocean model som in the atlantic in order to isolate features of air sea interactions particular to this basin simulated covariability between sea surface temperatures ssts and atmosphere is very similar to the observed non enso related covariations in both spatial structures and time scales the leading simulated empirical coupled mode resembles the zonal mode in the tropical atlantic despite the lack of ocean dynamics and is associated with baroclinic atmospheric anomalies in the tropics and a rossby wave train extending to the extratropics suggesting an atmospheric response to tropical sst forcing the second non enso mode is the subtropical dipole in the sst with a mainly equivalent barotropic atmospheric anomaly centered on the subtropical high and associated with a midlatitude wave train consistent with atmospheric forcing of the sub

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

a stability analysis of tropical ocean atmosphere interactions bridging measurements and theory for el nino abstract interactions between the tropical oceans and atmosphere permit a spectrum of natural modes of oscillation whose properties period intensity spatial structure and direction of propagation depend on the background climatic state i e the mean state this mean state can be described by parameters that include the following the time averaged intensity of the pacific trade winds the mean depth h of the thermocline and the temperature difference across the thermocline t a stability analysis by means of a simple coupled ocean atmosphere model indicates two distinct families of unstable modes one has long periods of several years involves sea surface temperature variations determined by vertical movements of the thermocline that are part of the adjustment of the ocean basin to the fluctuating winds requires a relatively deep thermocline and corresponds to the delayed oscillator the other family requires a shallow thermocline has short periods of a year or two has sea surface tempe

equatorial pacific thermostad response to el nino el ninos are characterized by a shift of warm surface water from the western to eastern equatorial pacific due to weakening of easterly trade winds this shift is associated with the pycnocline or thermocline the large vertical density gradient beneath the surface mixed layer shoaling in the west and deepening in the east inducing a redistribution of ocean heat with global impacts here the response of the pacific equatorial thermostad a layer of low vertical stratification below the pycnocline to el nino is investigated using a monthly argo float climatology and argo float deep velocity data a mean seasonal cycle trend and time lagged linear response to the nino3 4 index are fit by least squares to temperature and salinity at each gridpoint as well as to deep float velocities omitting the trend the results of these fits are used to characterize the response of physical properties in the thermostad including layer thickness and velocity to el nino by comparing the mean properties following neutral conditions nino3 4 0 c versus those following a moderate el nino nino3 4 1 c following an el nino a strengthening of the westward flowing equatorial intermediate current of about 2 7 106 m3 s 1 shifts about 97 1012 m3 of thermostad water from the east to the west allowing conservation of volume within the thermostad as the pycnocline above deepens in the east and shoals in the west this transport and volume change imply a 14 month time scale consistent with el nino this article is protected by copyright all rights reserved

orbitally forced sedimentary rhythms in the stratigraphic record is there room for tidal forcing the imprint of orbital cycles which result from the varying eccentricity of the earth s orbit and changes in the orientation of its axis have been recognised throughout the phanerozoic rock record variations in insolation and their effect on climate are generally considered to be the sole transfer mechanism between the orbital variables and cyclic sedimentary successions common oceanographic principles however show that the ocean tide also responds to variations in the orbital parameters the ocean tide has not yet been considered to be a valid additional transfer mechanism for the orbital variations in geological studies of milankovitch cycles in sedimentary successions the insolation paradigm offers satisfying explanations and the role of long term variations of the ocean tide has not yet been appreciated variations in the ocean tide related to changing eccentricity at present 0 0165 theoretical maximum 0 0728 affect a variety of oceanographic and sedimentary processes in addition to the widely accepted paradigm of orbitally forced insolation changes the tidal transfer of orbital signals may explain certain less well understood aspects of orbitally induced cycles in the stratigraphic record related to ocean mixing organic productivity and tidal processes in shallow seas and deep water variations of the ocean tide in relation to the 18 6 year lunar nodal cycle which has no insolation counterpart by which they may be obscured indeed show that these relatively small variations can produce significant effects in sedimentary environments that are sensitive to variations in the strength of the ocean tide in analogy with the 18 6 year lunar nodal cycle orbital variations of the tide on milankovitch time scales are likely to have affected sedimentary systems in the past

a pan atlantic decadal climate oscillation sea surface temperature sst variabilities on time scales of 10 14 years have been documented in various parts of the atlantic ocean here we present observational evidence that these regional variabilities are part of a coherent pan atlantic decadal oscillation pado characterized by zonal bands of sst and wind anomalies stacked in the meridional direction with alternate polarities from the south atlantic all the way to greenland we propose that the interaction of wind evaporation and sst is key to establishing this interhemispherical pado based on results from a new ocean atmosphere coupling model forced by extratropical wind forcing the model successfully reproduces the observed decadal oscillation in both sst and wind velocity over the tropics this decadal extratropical forcing of the tropics is in sharp contrast to the well known tropics to extratropics teleconnection that operates on interannual time scales in association with el nino southern oscillation enso

global scale modes of surface temperature variability on interannual to century timescales using 100 years of global temperature anomaly data we have performed a singular value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio temporal modes of global climate variability statistical significance is determined from confidence limits obtained by monte carlo simulations secular variance is dominated by a globally coherent trend with nearly all grid points warming in phase at varying amplitude a smaller but significant share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude north atlantic with a roughly centennial timescale spatial patterns associated with significant peaks in variance within a broad period range from 2 8 to 5 7 years exhibit characteristic el nino southern oscillation enso patterns a recent transition to a regime of higher enso frequency is suggested by our analysis an interdecadal mode in the 15 to 18 years period range appears to represent long term enso variability this mode has a sizeable projection onto global average temperature and accounts for much of the anomalous global warmth of the 1980s a quasi biennial mode centered near 2 2 years period and a mode centered at 7 to 8 years period both exhibit predominantly a north atlantic oscillation nao temperature pattern a potentially significant decadal mode centered on 11 to 12 years period also exhibits an nao temperature pattern and may be modulated by the century scale north atlantic variability

variability of the tropical ocean surface temperatures at decadal multidecadal timescales part i the atlantic ocean abstract gridded time series from the global ocean surface temperature atlas were analyzed with a variety of techniques to identify spatial structures and oscillation periods of the tropical atlantic sea surface temperature sst variations at decadal timescales and to develop physical interpretations of statistical patterns of decadal sst variations each time series was 110 yr 1882 1991 long the tropical atlantic sst variations were compared with decadal variations in a 74 yr long 1912 85 north nordeste brazil rainfall time series and a 106 yr long 1886 1991 tropical atlantic cyclone activity index time series the tropical atlantic sst variations were also compared with decadal variations in the extratropical atlantic sst multiyear to multidecadal variations in the cross equatorial dipole pattern identified as a dominant empirical pattern of the tropical atlantic sst variations in earlier and present studies are shown to be variations in the approximately north south gradient of sst anomalies

monotonic decrease of the zonal sst gradient of the equatorial pacific as a function of co2 concentration in ccsm3 and ccsm4 the west east sea surface temperature sst gradient in the equatorial pacific ocean is a key feature of earth s climate how this gradient responds to varying climatic forcing is a challenge to both climate theory and climate modeling using the coupled atmosphere ocean general circulation models community climate system model version 3 ccsm3 and version 4 ccsm4 we show that the zonal sst gradient is an almost monotonically decreasing function of atmospheric co2 concentration pco2 across a wide range from 17 5 to 4576 ppmv as pco2 is increased the optical depth of clouds over the western and central pacific increases significantly reflecting more insolation back to space suppressing surface warming in this region and thereby reducing the zonal sst gradient ocean adjustment to a weakening of surface zonal winds is characterized by relaxations of the equatorial thermocline tilt zonal surface currents and ocean upwelling

the mean and the time variability of the shallow meridional overturning circulation in the tropical south pacific ocean the meridional transport in the pacific ocean subtropical cell is studied for the period from 2004 to 2011 using gridded argo temperature and salinity profiles and atmospheric reanalysis surface winds the poleward ekman and equatorward geostrophic branches of the subtropical cell exhibit an el ni no southern oscillation signature with strong meridional transport occurring during la ni and weak meridional transport during el ni no at 7 58s mean basinwide geostrophictransportabove 1000 dbar is 48 56 2 5 sv sv 10 6 m 3 s 21 of which 30 3 38 4 sv return to the subtropics in the surface ekman layer whereas 10 2 18 3 sv flow northward feeding the indonesian throughflow geostrophic transport within the subtropical cell is stronger in the ocean interiorandweakerinthewesternboundaryduringlani theinteriordominatingbasinwide transport using atmospheric reanalyses only half of the mean heat gain by the pacific north of 7 58 si s compensated by oceanicheat transport outof theregion thenationaloceanography centreat southampton air sea flux climatology is more consistent for closing the oceanic heat budget in summary the use of argo data for studying the pacific subtropical cell provides an improved estimate of basinwide mean geostrophic transport includes both interior and western boundary contributions quantifies el ni ni transport variability and illustrates how the meridional overturning cell dominates ocean heat transport at 7 58s

contemporary plate motion and crustal deformation the measurement of relative plate velocities during the past few years is a signal accomplishment in earth science leading to refinement of the precepts of steady motion of plate interiors and cyclic deformation along plate margins regrettably deformation premonitory to an earthquake has yet to be detected with confidence delineation of the spatial and temporal buildup of strain between earthquakes however has put limits on models of the earthquake cycle a diverse set of fault structures and crustal rheologic conditions can explain the pattern of surface strain accumulation and release along strike slip faults in contrast the geometry of thrusts and normal faults revealed by earthquake deformation has been found to differ markedly from expectations geodetic observations have proved vital to monitor the ascent of magma through the earth s crust and to predict volcanic eruptions at the earth s surface episodic vertical and horizontal deformation in southern california remains a subject of dispute if anything it is less certain than it once seemed

oscillations in land surface hydrological cycle abstract hydrological cycle is the perpetual movement of water throughout the various component of the global earth s system focusing on the land surface component of this cycle the determination of the succession of dry and humid periods is of high importance with respect to water resources management but also with respect to global geochemical cycles this knowledge requires a specified estimation of recent fluctuations of the land surface cycle at continental and global scales our approach leans towards a new estimation of freshwater discharge to oceans from 1875 to 1994 as recently proposed by labat et al labat d godderis y probst jl guyot jl 2004 evidence for global runoff increase related to climate warming advances in water resources 631 642 wavelet analyses of the annual freshwater discharge time series reveal an intermittent multiannual variability 4 to 8 y 14 to 16 y and 20 to 25 y fluctuations and a persistent multidecadal 30 to 40 y variability continent by continent reasonable relationships between land water cycle oscillations and climate forcing such as enso nao or sea surface temperature are proposed even though if such relationships or correlations remain very complex the high intermittency of interannual oscillations and the existence of persistent multidecadal fluctuations make prediction difficult for medium term variability of droughts and high flows but lead to a more optimistic diagnostic for long term fluctuations prediction