spatio temporal structure of the pentadecadal variability over the north pacific abstract using a multi taper frequency domain singular value decomposition mtm svd a pentadecadal oscillation was detected in the winter spring sea level pressure slp field over the north pacific and surface air temperature in north america which was significant at the 95 confidence level the mtm svd captured the different slp and air temperature distributions between the winter and spring seasons in a consistent manner the pentadecadal slp signature in the spring season is centered nearer the west coast of north america than in the winter season this zonal displacement is consistent with the prominent springtime pentadecadal air temperature variability in mid latitude western north america a wavelet analysis of the pacific decadal oscillation index pdoi showed that the regime shifts in the 1920s 1940s and 1970s involved simultaneous phase reversals of the bidecadal and pentadecadal variations the two interdecadal variations are synchronized with one another such that a half period of the pentadecadal oscillation one epoch of an individual regime corresponds to one and half periods of the bidecadal oscillation these results are consistent with the wavelet analysis of the north pacific index npi similar resonance between the bidecadal and pentadecadal variations is evident in air temperatures over alaska the bidecadal and pentadecadal signals have different seasonality in these time series suggesting that although the two interdecadal variations arise from two different physical mechanisms they interact with each other the most distinct seasonal difference was observed in mid latitude western north america where the bidecadal variation prevails only in the winter season and the pentadecadal variation only in the spring season alaska air temperatures in the winter and winter spring of 1999 were the coldest since 1977 as were springtime air temperatures in mid latitude western north america in contrast to the warm anomalies that prevailed in this region during 1977 98 the npi and pdoi also exhibited an opposite polarity in 1999 to the respective regime mean polarities these anomalous conditions in winter and spring seasons of 1999 may signify a major regime shift in 1998 1999 in order to verify whether or not a regime shift did occur in 1998 1999 a careful examination of additional data in coming ten or so years will be necessary

interannual enso and interdecadal enso like variability in the southern hemisphere tropospheric circulation abstract recent work has identified variability in the pacific ocean sst with a structure qualitatively similar to enso but at lower frequencies than enso zhang et al have documented the atmospheric circulation anomalies in the tropics and northern hemisphere that are associated with decadal enso like variability and compared these anomalies to those associated with the interannual enso cycle here the authors extend the study of zhang et al to the southern hemisphere using the national centers for environmental prediction national center for atmospheric research reanalysis data for 1958 96 consistent with previous studies the southern hemisphere circulation anomalies associated with enso display a teleconnection pattern from the central tropical pacific into the far southeastern pacific ocean comparatively larger circulation anomalies are found in the southern hemisphere associated with the decadal enso like variability though aloft the structure of the anomalies emphasizes the polar vortex wit

anatomy of north pacific decadal variability abstract a systematic analysis of north pacific decadal variability in a full physics coupled ocean atmosphere model is executed the model is an updated and improved version of the coupled model studied by latif and barnett evidence is sought for determining the details of the mechanism responsible for the enhanced variance of some variables at 20 30 yr timescales the possible mechanisms include a midlatitude gyre ocean atmosphere feedback loop stochastic forcing remote forcing or sampling error decadal variability in the model is expressed most prominently in anomalies of upper ocean streamfunction sea surface temperature sst and latent surface heat flux in the kuroshio oyashio extension koe region off japan the decadal signal off japan is initiated by changes in strength and position of the aleutian low the atmospheric perturbations excite sst anomalies in the central and eastern north pacific with opposing signs and canonical structure the atmospheric perturbations also change the ekm

global patterns of decadal scale variability observed in sea surface temperature and lower tropospheric circulation fields the global patterns associated with decadal scale variability dsv are examined by a lag correlation technique based on local anomaly indices using the fields of measured sea surface temperature sst and 850 hpa geopotential height for the last 50 years the three dominant patterns are identified and the variability is examined the first spreads over the entire pacific which is concurrent with the decadal scale modulation of the el nino southern oscillation des variability the second is confined to the local midlatitude north pacific lnp variability and the third extends over the north atlantic with the decadal north atlantic oscillation nao dna variability the global sst pattern of des variability exhibits large scale equatorial symmetry in the pacific which is similar to that of the pacific decadal oscillation but is distinguished by the signals in the subtropical frontal zones these sst anomalies are accompanied by anomalous subtropical highs that appear prior to the anomalous depression around australia the lnp variability which is related with the arctic oscillation is characterized by the sst anomalies along the north pacific subarctic frontal zone moving eastward accompanied by the anomalous aleutian low this variability develops decays without with coherent variability in the tropics it shows the 6 year quadrature phase relationship with the des variability indicative of an interdecadal variability with a period of 24 years the dna variability is featured by the atmospheric nao and by the sst anomalies in four zonal bands that spread in the north atlantic from the tropics to high latitudes this variability is independent of either the des or lnp variability

interannual and decadal modulations recently observed in the pacific storm track activity and east asian winter monsoon abstract interannual variability of the north pacific storm track observed over 17 recent winters is documented the local storm track activity is measured by a meridional flux of sensible heat associated with the lower tropospheric subweekly fluctuations the interannual variability in the heat flux over the northwestern nw pacific is found to be strongest in midwinter the first empirical orthogonal function of the interannual variability in midwinter captures the decadal tendency toward the enhanced storm track activity in midwinter over the nw pacific in association with the decadal weakening of the east asian winter monsoon siberian high and the aleutian low that occurred in the late 1980s the most marked signature of this enhancement is that the midwinter minimum in the storm track activity which had been apparent in the early to mid 1980s almost disappeared afterward as opposed to linear theory of baroclinic instability the enhanced activity occurred despite the weakening of the pacific j

midlatitude atmosphere ocean interaction during el nino part i the north pacific ocean abstract atmosphere ocean experiments are experiments are used to investigate the formation of sea surface temperature sst anomalies in the north pacific ocean during fall and winter of the el nino year experiments in which the ncar community climate model ccm surface fields am used to force a mixed layer ocean model in the north pacific no air sea feedback are compared to simulations in which the ccm and north pacific ocean model are coupled anomalies in the atmosphere and the north pacific ocean during el nino are obtained from the difference between simulations with and without prescribed warm sst anomalies in the tropical pacific in both the forced and coupled experiments the anomaly pattern resembles a composite of the actual sst anomaly field during el nino warm ssts develop along the cost of north america and cold ssts form in the central pacific in the coupled simulations air sea interaction results in a 25 to 50 reduction in the magnitude of the sst and mixed layer depth anomalies

silica diagenesis ii general mechanisms abstract amorphous silica phases opal a precipitate in nature due to the formation of dense colloids in supersaturated alkaline aqueous solutions with low relative concentrations of other ions opal a dissolves and yields solutions of still relatively high silica content in pore waters containing abundant cations open framework polymers form which flocculate to yield opal ct opal ct becomes increasingly ordered primarily due to preferential growth of cristobalite relative to tridymite and crystal size increase opal ct dissolves to yield pore waters of low silica concentration which allows slow growth of quartz crystals from monomeric solution the quartz crystals then slowly increase in size and crystallinity carbonates appear to enhance opal ct formation possibly due to the activity of positively charged hydroxyl complexes hence polymerization in relatively pure systems is involved in opal a formation and polymerization in impure systems is involved in opal ct formation and slow growth from monomeric low silica concentration solutions is involved in precipitation of quartz in sedimentary realms

unstable relationship between the pacific decadal oscillation and eastern china summer precipitation insights from the medieval climate anomaly and little ice age the eastern china summer precipitation is related to the pacific decadal oscillation pdo on interdecadal time scales in modern times but it remains unclear whether such a relationship holds prio

north pacific gyre oscillation modulates seasonal timing and ecosystem functioning in the california current upwelling system 1 on interannual and longer time scales dynamical and biogeochemical fluctuations in the north pacific are dominated by two modes of variability namely the pacific decadal oscillation and the north pacific gyre oscillation npgo in this study the regional expression of the npgo in the california current system ccs is detailed the statistical relationship between the npgo index and nearshore wind variability mostly upwelling favorable along the u s west coast is strongest in the wintertime december to march off central california most importantly npgo fluctuations are associated with a seasonal shift of 1 2 months in the onset of the upwelling season regional numerical simulations show that an early late onset of upwelling during the positive negative phase of the npgo leads to a more less productive planktonic ecosystem throughout spring and summer i e several months after the direct npgo effects on the system have ceased these results bring new light on the california ecosystem variability as observed in atypical years such as 2005 and 2007

the origin of hydrothermal chlorite and anhydrite rich sediments in the middle okinawa trough east china sea abstract during the integrated ocean drilling program iodp expedition 331 five sites were drilled into the iheya north knoll hydrothermal system in the okinawa trough ot a back arc basin characterized by thick terrigenous sediment following up on the previous study by shao et al 2015 we present new mineralogical geochemical and sr nd isotope data to investigate the origin of the hydrothermal sediments and characterize the hydrothermal system the substrate at the iheya north knoll is dominated by pumiceous sediment and other volcanoclastic materials interbedded with hemipelagic terrigenous and biogenous sediments impermeable layers separate the hydrothermal sediments into distinct units with depth that are characterized by various assemblages of alteration materials including polymetallic sulfides sulfates chlorite and kaolinite rich sediments the rare earth elements rees and nd isotope data suggest that the chlorite rich and kaolinite rich layers primarily resulted from the alteration of pumiceous materials in different chemical and physical conditions kaolinite rich sediment likely reflects low ph and low mg concentration fluids while chlorite rich sediment formed from fluids with high ph and increased mg contents likely at higher temperatures the sr isotopic compositions of subsurface anhydrite reflect high seawater hydrothermal fluid ratios in the mid ot hydrothermal area compared with chlorite rich sediments from other sediment covered or felsic hosted hydrothermal systems the chlorite rich sediments in the mid ot are characterized by lower concentrations of al and fe but much higher y zr hf th and rees indicative of the distinct nature of the precursor rocks in this region

kuroshio extension variability and forcing of the pacific decadal oscillations responses and potential feedback abstract a forcing mechanism is sought for the large scale circulation changes in the kuroshio extension region of the western north pacific ocean as inferred by topex poseidon sea surface height ssh data the low frequency signal of the kuroshio extension over the last decade was characterized by a modulation in its zonal mean flow intensity the mean kuroshio extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997 the ability to simulate the major trends in the observed ssh signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern north pacific ocean related to the pacific decadal oscillations pdos to be specific the weakening strengthening trend in 1993 96 1997 2001 was caused by westward expansions of negative positive ssh anomalies south of the kuroshio extension and positive negative ssh anomalies north of the kuroshio extension emerg

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

the victoria mode in the north pacific linking extratropical sea level pressure variations to enso the victoria mode vm represents the second dominant mode empirical orthogonal function eof2 of north pacific variability independent of the pacific decadal oscillation and is defined as the eof2 of sst anomalies in the north pacific poleward of 20 n the present study indicates that the vm is closely linked to the development of el nino southern oscillation enso the vm may effectively act as an ocean bridge or conduit through which the extratropical atmospheric variability in the north pacific influences enso the vm can trigger the onset of enso via the following two dominant processes 1 surface air sea coupling associated with the vm in the subtropical tropical pacific and 2 evolution of subsurface ocean temperature anomalies along the equator associated with the vm these two processes may force sufficient surface warming to occur in the central eastern equatorial pacific from spring to summer which in turn initiates an enso event the vm influence on enso relies on a basin scale air sea interaction dynamic as opposed to more local scale dynamics typically associated with the seasonal footprinting mechanism or pacific meridional mode the majority of vm events are followed by enso events these enso events triggered by vm include el nino modoki em as well as conventional el nino there is no evidence that the vm tends to be more conducive to the initialization of em than conventional el nino

decadal changes in the north pacific oceanic frontal zones as revealed in ship and satellite observations 1 influence of decadal climate changes upon the north pacific subarctic and subtropical oceanic frontal zones np safz and np stfz respectively is documented both satellite and ship measured sea surface temperature sst data reveal the strong confinement of wintertime decadal sst anomalies to those frontal zones the satellite data indicate that the wintertime np safz tended to be narrow and shift northward under the weakened surface westerlies during a warm event in the early 1990s the opposite was the case under the enhanced westerlies during a cool event in the mid 1980s decadal scale modulations in the frontal intensity are also evident in the satellite data a diagnosis based on a simple linearized mixed layer model suggests that the observed anomalous frontal intensity was contributed by the sign reversal of anomalous wind stress curl through the ekman processes and by an anomaly dipole of the net heat flux around the safz these decadal scale modulations in the np safz and their relationships with decadal fluctuations in the local surface westerlies are confirmed in the ship measured data over the 4 recent decades it is found that the safz happens to be a region where the decadal variability in the surface westerlies are unlikely to be masked by the higher frequency fluctuations as it almost coincides with the ridge trough line of the remote atmospheric response to the el nino southern oscillation

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

the forced and intrinsic low frequency modes in the north pacific abstract conditional maximum covariance analysis is applied to investigate the coherent patterns between the tropical and north pacific sst and the north pacific 500 hpa geopotential height anomalies two leading modes are identified one is an intrinsic midlatitude mode the north pacific np mode for which sst anomalies are mainly confined to the extratropical north pacific the other is a tropical ocean atmosphere coupled mode the enso mode in which an enso like sst pattern dominates the tropics but extratropical sst anomalies are relatively weak the np and enso modes exhibit distinct spatial and temporal characteristics for the np mode atmospheric variation leads to changes in sst while for the enso mode the opposite is true the np mode displays a persistence barrier during august september whereas the enso mode has a march april persistence barrier the upper tropospheric jet stream associated with the np and enso mode intensifies respectively over the central north pacific and the subtrop

wind driven shifts in the latitude of the kuroshio oyashio extension and generation of sst anomalies on decadal timescales abstract the causes of decadal variations of north pacific sea surface temperatures ssts are examined using a hindcast performed with an ocean general circulation model thermodynamically coupled to an atmospheric mixed layer model ogcm aml model and forced by the time history of observed surface winds the shift in north pacific ocean climate that occurred around 1976 77 is focused on since this is the best observed example available after the 1976 77 shift the aleutian low deepened and moved to the southeast of its previous position this placed anomalous cyclonic flow over the north pacific the sst response as simulated by the ocean model consisted of two components a fast and local part and a delayed and remote part in the central pacific stronger westerlies cool the ocean by increased equatorward ekman drift here the dynamical cooling is sufficiently large that the surface fluxes damp the sst anomaly this ekman response is fast and local and cools the ssts beginning in 1977 and persistin

wind forcing of the atlantic thermocline along 32 n at low frequencies abstract the bermuda tide gauge record extends back to the early 1930s that sea level fluctuations there are highly coherent with dynamic height from hydrographic data has two interesting implications first it should contain information about the low frequency circulation of the atlantic furthermore because dynamic height contains information on heat storage it might on the limited timescales accessible in the record also contain clues about climate a simple model of wind forcing of the atlantic from the african coast to bermuda uses the levitus mean density data to estimate the long rossby wave speed as a function of longitude sea level and thermocline variability estimated this way are in remarkably good agreement with observations at periods of more than a few years duration the peak to peak sea level signal is 18 cm which is nearly 25 of the slope across the gulf stream at this latitude the model results suggest that the variability is largest somewhat to the east of bermuda fluctuatio

a physical mechanism of the precipitation dipole in the western united states based on pdo storm track relationship it is known that the western united states us precipitation displays a north south contrast i e the so called precipitation dipole during el nino and la nina winters furthermore the pacific decadal oscillation pdo has been known to modulate this precipitation dipole however the underlying physical mechanism regulating this modulation is not well understood this study revisits previous studies and suggests a physical mechanism of precipitation dipole modulation based on the pdo storm track relationship we found that both jet stream and storm track tend to move northward southward over the north pacific during negative positive pdo winters contributing to the increase of precipitation over the northwestern southwestern us respectively this relationship is robust regardless of el nino southern oscillation enso possibly facilitating modulation of the precipitation dipole moreover changes in oceanic baroclinicity associated with the pdo phase are suggested to be responsible for anchorage of storm tracks over the north pacific

modes of climate variability synthesis and review of proxy based reconstructions through the holocene abstract modes of climate variability affect global and regional climates on different spatio temporal scales and they have important impacts on human activities and ecosystems as these modes are a useful tool for simplifying the understanding of the climate system it is crucial that we gain improved knowledge of their long term past evolution and interactions over time to contextualise their present and future behaviour we review the literature focused on proxy based reconstructions of modes of climate variability during the holocene i e the last 11 7 thousand years with a special emphasis on i proxy based reconstruction methods ii available proxy based reconstructions of the main modes of variability i e el nino southern oscillation pacific decadal variability atlantic multidecadal variability the north atlantic oscillation the southern annular mode and the indian ocean dipole iii major interactions between these modes and iv external forcing mechanisms related to the evolution of these modes this review shows that modes of variability can be reconstructed using proxy based records from a wide range of natural archives but these reconstructions are scarce beyond the last millennium partly due to the lack of robust chronologies with reduced dating uncertainties technical issues related to proxy calibration and difficulty elucidating their stationary impact or not on regional climates over time while for each mode the available reconstructions tend to agree at mutidecadal timescales they show notable disagreement on shorter timescales beyond the instrumental period the reviewed evidence suggests that the intrinsic variability of modes can be modulated by external forcing such as orbital solar volcanic and anthropogenic forcing the review also highlights some modes experience higher variability over the instrumental period which is partly ascribed to anthropogenic forcing these features stress the paramount importance of further studying their past variations using long climate proxy records for the progress of climate science

support for tropically driven pacific decadal variability based on paleoproxy evidence two independent proxy reconstructions of sea surface temperature reflect a common pattern of pacific decadal sea surface temperature variability over the past two centuries since the pattern extends to both the north ern and southern hemispheres this result supports the idea that pacific decadal variability is a basin wide phenomenon originating in thetropics the causes of pacific decadal climate variability here termed pdv are the subject of much debate most work describing pdv has focused on the north pacific where the leading eof of low pass filtered sea surface temperature

experimental simulation of clay precipitation within reservoir sandstones 1 techniques and examples experiments have been performed in which cores of clay free sand and clay forming mineral phases placed beneath the cores have been treated hydrothermally with various solutions using experimental conditions in the range 150 500 degrees c and 0 75 1 0 kbar 75 100 mpa illite illite smectite kaolinite 7 a chlorite and trioctahedral smectite have been precipitated in the sand pore space with morphologies similar to those of authigenic clay minerals in sandstone petroleum reservoirs this study demonstrates that the mechanism rate of clay precipitation and controls on clay morphology and mineral stability can all be determined by experimental studies these results have direct application to the interpretation of clay mineral paragenesis in reservoir sandstones the study demonstrates 1 authigenic clays in sandstones are direct precipitates from solution and do not require a preexisting clay coating 2 grain surface effects such as abrasion and detrital clay coatings do promote nucleation of clays and 3 clay morphology is controlled by precipitation mechanism specifically the formation of metastable clays which are subsequently modified the synthesis of authigenic type illite and illite smectite is by direct precipitation from solution following dissolution of mineral phases such as detrital illite or feldspar both platy and fibrous illite morphotypes are synthesized platy illites are more readily formed the compositions of synthetic illite and illite smectite clays are controlled by temperature and a sub k super a sub h super fluid composition ratio platy illites show subtle changes in morphology with compositional variation illite smectite and illite with low k content forms a crenulated boxwork texture while more k rich illites approaching muscovite composition form larger discrete plates no correlation between illite composition and fibrous formation is recognized kaolinite and chlorites were also precipitated in experiments vermiform kaolinite appears to be a direct precipitate kaolinite morphology however is controlled by precipitation mechanism isolated discrete kaolinite plates are associated with early formation of a mixed layered smectitic phase chlorite synthesis proceeds via the formation of metastable 7 a chlorite and expandable phases which have previously been recognized as possible precursors to 14 a chlorites in reservoir sandstones

reaction of plagioclase feldspars with co2 under hydrothermal conditions abstract geological storage of co 2 in plagioclase bearing sediments granitic rocks and fractured basalts is expected to have a variety of geochemical and geomechanical effects including mineral trapping and porosity permeability changes the amount of co 2 trapped by mineralisation and the extent of any changes in host rock transport or mechanical properties depend on rock composition to date studies of mineralisation have mainly been based on dissolution and precipitation experiments performed at ambient surface conditions or at slightly elevated temperature and pressure however the reactions that occur under in situ conditions are poorly constrained in an attempt to determine the secondary phases formed in the plagioclase co 2 water system under such conditions we performed a set of batch experiments at temperatures in the range 200 300 c using carbon dioxide pressures from 0 4 to 15 mpa we investigated reaction of anorthite and albite which are expected to precipitate calcite and kaolinite and dawsonite and quartz respectively however in most of our experiments reactions precipitating clays kaolinite and smectite or illite boehmite and a mg ni fe hydrotalcite like phase dominated the nickel being derived from the reaction vessel little or no carbonate and no dawsonite were detected additional feldspar free control experiments employing mg rich brine showed that carbonates would be preserved in our feldspar experiments if formed but that a carbonate substrate is needed to promote precipitation since the secondary phases formed in our plagioclase experiments are stable under a wide range of conditions we expect that they will also form under co 2 storage systems with suitable fluid rock composition from our results we conclude that clay precipitation can proceed or accompany carbonate precipitation depending on the availability of carbonate substrate though an artefact in our experiments in the context of subsurface alkaline waste injection hydrotalcite may play a positive role here by immobilising heavy metals while carbonates will mineralise the co 2

interannual to decadal predictability of tropical and north pacific sea surface temperatures abstract a multivariate empirical model is used to show that predictability of the dominant patterns of tropical and north pacific oceanic variability el nino southern oscillation enso and the pacific decadal oscillation pdo is mostly limited to little more than a year despite the presence of spectral peaks on decadal time scales the model used is a linear inverse model lim derived from the observed simultaneous and 1 yr lag correlation statistics of july june averaged sst from the hadley centre global sea ice and sea surface temperature hadisst dataset for the years 1900 2002 the model accurately reproduces the power spectra of the data including interannual and interdecadal spectral peaks that are significant relative to univariate red noise eigenanalysis of the linear dynamical operator yields propagating eigenmodes that correspond to these peaks but have very short decay times and thus limited predictability longer term predictability does exist however due to two stationary eigen

influence of the meridional shifts of the kuroshio and the oyashio extensions on the atmospheric circulation abstract the meridional shifts of the oyashio extension oe and of the kuroshio extension ke as derived from high resolution monthly sea surface temperature sst anomalies in 1982 2008 and historical temperature profiles in 1979 2007 respectively are shown based on lagged regression analysis to significantly influence the large scale atmospheric circulation the signals are independent from the enso teleconnections which were removed by seasonally varying asymmetric regression onto the first three principal components of the tropical pacific sst anomalies the response to the meridional shifts of the oe front is equivalent barotropic and broadly resembles the north pacific oscillation western pacific pattern in a positive phase for a northward frontal displacement the response may reach 35 m at 250 hpa for a typical oe shift a strong sensitivity since the associated sst anomaly is 0 5 k however the amplitude but not the pattern or statistical significance strongly depends on the lag and an

north south precipitation patterns in western north america on interannual to decadal timescales the overall amount of precipitation deposited along the west coast and western cordillera of north america from 258 to 558n varies from year to year and superimposed on this domain average variability are varying north south contrasts on timescales from at least interannual to interdecadal in order to better understand the north south precipitation contrasts their interannual and decadal variations are studied in terms of how much they affect overall precipitation amounts and how they are related to large scale climatic patterns spatial empirical orthogonal functions eofs and spatial moments domain average central latitude and latitudinal spread of zonally averaged precipitation anomalies along the westernmost parts of north america are analyzed and each is correlated with global sea level pressure slp and sea surface temperature series on interannual defined here as 3 7 yr and decadal 7 yr timescales the interannual band considered here corresponds to timescales that are particularly strong in tropical climate variations and thus is expected to contain much p

a simple model of the decadal response of the ocean to stochastic wind forcing abstract a simple linear model is used to estimate the decadal response of the extratropical ocean to wind stress forcing assuming a flat bottom a mean state at rest and no dissipation the barotropic fields are governed by a time dependent sverdrup balance the baroclinic ones by the long rossby wave equation the ocean is bounded by a coast in the east and a radiation condition is used in the west at each frequency the baroclinic response consists of a forced response plus a rossby wave generated at the eastern boundary for zonally independent forcing the response propagates westward at twice the rossby phase speed the wind stress is assumed to be stochastic with a white frequency spectrum so the model represents the continuous excitation of the ocean interior by the weather fluctuations the model predicts the shape and level of the frequency spectra of the oceanic pressure field and their variation with longitude and latitude the baroclinic response is spread over a continuum of frequencies

experimental study of the hydrothermal formation of kaolinite kaolinite was hydrothermally precipitated starting from amorphous aluminosilicates with si al ratio from 1 8 to 0 76 at temperatures of 150 175 200 225 and 250 c at time periods varying from 6 h to 60 days the solutions were analysed for ph si al and k and their saturation state was calculated by using the computer program solmineq 88 the solids were studied by surface area xrd and dta tg analyses kaolinite was the only crystalline phase found in the products of the runs and its formation and crystallinity depended on time temperature and si al ratio of the starting material the kaolinite yield increased as starting material was aged for longer times products synthesized at higher temperature contain more kaolinite which was more crystalline than in the experiments carried out at lower temperature the gel with si al 0 99 produced the most disordered kaolinite and better crystallinity was obtained from products richest in al or si the process of kaolinite formation was the result of two stages during the first one aggregates of domains having a kaolinite like structure were formed the second stage corresponded to the formation of hexagonally outlined platy crystals the formation rates indicated that the first stage was approximately one order of magnitude faster than the second stage with average activation energies of 82 5 kj mol 1 and 71 5 kj mol 1 respectively si al ratio of the starting material exerted only a slight influence on the activation energies the precipitation rates obtained for the second stage were consistent with literature data and may be considered precipitation rates of kaolinite in hydrothermal environments

the role of tropospheric rossby wave breaking in the pacific decadal oscillation abstract the leading pattern of extratropical pacific sea surface temperature variability the pacific decadal oscillation pdo is shown to depend on observed variability in the spatiotemporal distribution of tropospheric rossby wave breaking rwb where rwb is the irreversible overturning of potential vorticity on isentropic surfaces composite analyses based on hundreds of rwb cases show that anticyclonic cyclonic rwb is associated with a warm moist cool dry column that extends down to a surface anticyclonic cyclonic circulation and that the moisture and temperature advection associated with the surface circulation patterns force turbulent heat flux anomalies that project onto the spatial pattern of the pdo the rwb patterns that are relevant to the pdo are closely tied to el nino southern oscillation the pacific north american pattern and the northern annular mode these results explain the free troposphere to surface segment of the atmospheric bridge concept wherein el nino anomalies eme

connections between the pacific ocean tropics and midlatitudes on decadal timescales abstract connections between the tropical and midlatitude pacific on decadal timescales are examined using a 137 yr run of a fully coupled ocean atmosphere general circulation model it is shown that the model does a credible job of simulating both enso scale and decadal scale variability and that there are statistically significant correlations between the midlatitudes and tropics on decadal timescales three physical mechanisms linking the regions are examined 1 oceanic advection along isopycnal surfaces from the midlatitude subduction regions to the tropics 2 coastally trapped or kelvin wave propagation between the tropics and midlatitudes and 3 near simultaneous communication between the regions affected by changes in the atmosphere it is found that communication via the atmosphere explains the strongest correlations found in the model further evidence is presented that is consistent with the idea that midlatitude sea surface temperature anomalies drive changes in the trade wind system that a

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

occurrence of kaolinite and mixed layer kaolinite smectite in hydrothermal sediments of grimsey graben tjornes fracture zone north of iceland the sediments at a site situated among high temperature vents in the grimsey graben tjornes fracture zone north of iceland exhibit features of strong hydrothermal alteration 1 almost total dissolution of the volcaniclastic material composing the background sediment 2 sulfate and sulfide precipitation 3 kaolinitisation smectite precipitated in the shallowest sediment is gradually replaced downward by mixed layer kaolinite smectite and pure well crystallised kaolinite the kaolinite smectite is interstratified with up to 10 swelling smectitic layers according to the oxygen isotope composition kaolinite smectite mixed layer mineral most likely formed at temperatures near 160 degrees c the vertical sequence kaolinite kaolinite smectite smectite as well as the distinct zonation across the kaolinitic veins almost pure kaolinite in the central zone and kaolinite smectite along the rim suggest hydrothermal transformation of initially formed smectite kaolinite smectite kaolinite most probably this conversion occurred in an evolving from alkaline to slightly acidic hydrothermal environment c 2004 elsevier b v all rights reserved

the hydrothermal transformation rate of kaolinite to muscovite illite batch reactor experiments were performed to measure the rate of the reaction 1 5 kaolinite k muscovite h 1 5 water at temperatures ranging from 250 to 307 c in these experiments the rate of kaolinite conversion to muscovite illite was monitored as the rate of production of h runs were performed in small volume 50 ml titanium hydrothermal reactors charged with well crystallized georgia kaolinite indian ruby muscovite and 25 ml of kcl solution 0 5 2 0 m both solids and solutions were monitored at specific intervals throughout each experiment the determined rate law is dmh dt dmk dt amm k mk k mh where mk and mh are the concentrations of potassium ion and hydrogen ion k and k are the forward and reverse rate constants in kg m 2 sec 1 am is the total surface area of the muscovite in m2 and m is the mass of the solution in kg the initial rate method was used to find k and k was found by fitting data to an integrated rate equation temperature functions for the rate constants are in k 12 90 1 87 104 t r2 0 98 and in k 6 03 1 21 104 t r2 0 95 the activation energies ea for the forward and reverse reaction are 155 15 kj mol 1 and 101 10 kj mol 1 respectively

the forcing of the pacific decadal oscillation the pacific decadal oscillation pdo defined as the leading empirical orthogonal function of north pacific sea surface temperature anomalies is a widely used index for decadal variability it is shown that the pdo can be recovered from a reconstruction of north pacific sea surface temperature anomalies based on a first order autoregressive model and forcing by variability of the aleutian low el nino southern oscillation enso and oceanic zonal advection anomalies in the kuroshio oyashio extension the latter results from oceanic rossby waves that are forced by north pacific ekman pumping the sst response patterns to these processes are not orthogonal and they determine the spatial characteristics of the pdo the importance of the different forcing processes is frequency dependent at interannual time scales forcing from enso and the aleutian low determines the response in equal parts at decadal time scales zonal advection in the kuroshio oyashio extension enso and anomalies of the aleutian low each account for similar amounts of the pdo variance these results support the hypothesis that the pdo is not a dynamical mode but arises from the superposition of sea surface temperature fluctuations with different dynamical origins

garnets within geode like serpentinite veins implications for element transport hydrogen production and life supporting environment formation geochemical micro environments within serpentinizing systems can abiotically synthesize hydrocarbons and provide the ingredients required to support life observations of organic matter in microgeode like hydrogarnets found in mid atlantic ridge serpentinites suggest these garnets possibly represent unique nests for the colonization of microbial ecosystems within the oceanic lithosphere however little is known about the mineralogical and geochemical processes that allow such unique environments to form here we present work on outcrop scale vein networks from an ultramafic massif in norway that contain massive amounts of spherulitic garnets andradite which help to constrain such processes vein andradite spherulites are associated with polyhedral serpentine brucite ni fe alloy awaruite and magnetite indicative of low temperature 200 c alteration under low fo2 and low asio2 aq geochemical conditions together with the outcrop and micro scale analysis geochemical reaction path modeling shows that there was limited mass transport and fluid flow over a large scale once opened the veins remained isolated closed system forming non equilibrium microenvironments that allowed upon a threshold supersaturation the rapid crystallization seconds to weeks of spherulitic andradite the presence of polyhedral serpentine spheres indicates that veins were initially filled with a gel like protoserpentine phase in addition massive fe oxidation associated with andradite formation could have generated as much as 600 mmol h2 aq per 100 cm3 vein although no carboneous matter was detected the vein networks fulfill the reported geochemical criteria required to generate abiogenic hydrocarbons and support microbial communities thus systems similar to those investigated here are of prime interest when searching for life supporting environments within the deep subsurface

evidence for a wind driven intensification of the kuroshio current extension from the 1970s to the 1980s the spatial and temporal characteristics of oceanic thermal variations in the mixed layer and main thermocline of the midlatitude north pacific are distinctive suggesting different physical origins within the main thermocline 400 m depth the variability is dominated by a westward intensified pattern of decadal scale indicative of enhanced eastward geostrophic flow along the southern flank of the kuroshio current extension during the 1980s relative to the 1970s the authors argue that the decadal scale change in the strength of the kuroshio extension was a result of the dynamical adjustment of the oceanic circulation to a decadal variation in wind stress curl according to sverdrup theory four times daily wind stress fields from the national center for atmospheric research national centers for environmental prediction reanalysis project are used to compute the decadal change in sverdrup transport associated with the 1976 77 climate transition it is shown that the decadal changes in sverdrup transport inferred from the wind stress curl field and in observed geostrophic flow inferred from the upper ocean thermal field are consistent both in terms of spatial pattern and magnitude the decadal change in depth averaged geostrophic transport along the kuroshio extension referenced to 1 km is 11 6 sv similar to the sverdrup transport change 11 5 13 9 sv the decadal scale thermocline variation along the western boundary between 308 and 408n exhibits a lag of approximately 4 5 yr relative to the decadal variation in the basin wide wind stress curl pattern this delay may be indicative of the transient adjustment of the gyre scale circulation to a change in wind stress curl via long baroclinic rossby waves

predicting western north pacific ocean climate abstract it is shown that wintertime sea surface temperature anomalies in the confluence region of the kuroshio oyashio currents in the western north pacific can be skillfully predicted at lead times of up to 3 yr the predictions are based on the history of the wind stress over the north pacific and oceanic rossby wave dynamics the predictions may be exploitable in fisheries research and other ecological applications

dissolution of nontronite in chloride brines and implications for the aqueous history of mars increasing evidence suggests the presence of recent liquid water including brines on mars brines have therefore likely impacted clay minerals such as the fe rich mineral nontronite found in martian ancient terrains to interpret these interactions we conducted batch experiments to measure the apparent dissolution rate constant of nontronite at 25 0 c at activities of water ah 2o of 1 00 0 01 m cacl 2 or nacl 0 75 saturated nacl or 3 00 mol kg 1 cacl 2 and 0 50 5 00 mol kg 1 cacl 2 experiments at ah 2o 1 00 0 01 m cacl 2 were also conducted at 4 0 c 25 0 c and 45 0 c to measure an apparent activation energy for the dissolution of nontronite apparent dissolution rate constants at 25 0 c in cacl 2 containing solutions decrease with decreasing activity of water as follows 1 18 10 12 9 10 14 mol mineral m 2 s 1 ah 2o 1 00 2 36 10 13 3 1 10 14 mol mineral m 2 s 1 ah 2o 0 75 2 05 10 14 2 9 10 15 mol mineral m 2 s 1 ah 2o 0 50 similar results were observed at 25 0 c in nacl containing solutions 1 89 10 12 1 10 13 mol mineral m 2 s 1 ah 2o 1 00 1 98 10 13 2 3 10 14 mol mineral m 2 s 1 ah 2o 0 75 this decrease in apparent dissolution rate constants with decreasing activity of water follows a relationship of the form log k diss 3 70 0 20 ah 2o 15 49 where k diss is the apparent dissolution rate constant and ah 2o is the activity of water the slope of this relationship 3 70 0 20 is within uncertainty of that of other minerals where the relationship between dissolution rates and activity of water has been tested including forsteritic olivine log r 3 27 0 91 ah 2o 11 00 olsen et al 2015 and jarosite log r 3 85 0 43 ah 2o 12 84 dixon et al 2015 where r is the mineral dissolution rate this result allows prediction of mineral dissolution as a function of activity of water and suggests that with decreasing activity of water mineral dissolution will decrease due to the role of water as a ligand in the reaction apparent dissolution rate constants in the dilute nacl solution 1 89 10 12 1 10 13 mol mineral m 2 s 1 are slightly greater than those in the dilute cacl 2 solutions 1 18 10 12 9 10 14 mol mineral m 2 s 1 we attribute this effect to the exchange of na with ca in the nontronite interlayer an apparent activation energy of 54 6 1 0 kj mol was calculated from apparent dissolution rate constants in dilute cacl 2 containing solutions at temperatures of 4 0 c 25 0 c and 45 0 c 2 33 10 13 1 3 10 14 mol mineral m 2 s 1 4 0 c 1 18 10 12 9 10 14 mol mineral m 2 s 1 25 0 c and 4 98 10 12 3 8 10 13 mol mineral m 2 s 1 45 0 c the greatly decreased dissolution of nontronite in brines and at low temperatures suggests that any martian nontronite found to be perceptibly weathered may have experienced very long periods of water rock interaction with brines at the low temperatures prevalent on mars with important implications for the paleoclimate and long term potential habitability of mars

numerical experiments of the storm track sensitivity to oceanic frontal strength within the kuroshio oyashio extensions the sensitivity of the north pacific storm track to midlatitude oceanic frontal strength within the kuroshio oyashio extensions is investigated by applying artificially changed meridional sea surface temperature sst gradients in the weather research forecasting model version 3 4 the result of sensitivity experiments further confirms the close relationship between the storm track activity and meridional sst gradient i e the storm track activity can be intensified as a response to increases in the oceanic frontal strength in order to better understand the mechanism for the storm track intensification due to increased sst gradient velocity temperature correlation and local energetics are analyzed the result indicates that the enhancement of the meridional sst gradient leads to amplitude magnification of eddy meridional velocity and temperature and their phase consistency suggesting that synoptic scale eddies tend to approach the optimum structure for the baroclinic energy conversion which is mainly responsible for the sst front induced enhancement of storm track activity in order to estimate the impact of the oceanic front on the maintenance of the near surface baroclinicity further investigation is made by the composite analysis with the increase in oceanic frontal strength the near surface baroclinicity experiences a slow but strong restoration the increase in the meridional sst gradient results in the intensification in the cross frontal differential sensible heat flux which can more effectively offset the relaxing effect of the transient eddy poleward heat transport

clay mineral distributions in and around the mississippi river watershed and northern gulf of mexico sources and transport patterns abstract maps of the distributions of the four major clay minerals smectite illite kaolinite and chlorite in and around the mississippi river drainage basin and in the northern gulf of mexico have been produced using newly acquired data from erodible alluvial terrestrial sediments and marine surface sediments as well as from previously published data east of the rockies north america can be divided into four large clay mineral provinces 1 the north western mississippi river watershed smectite rich 2 the great lakes area and eastern mississippi river watershed illite and chlorite rich 3 the south eastern united states kaolinite rich and 4 the brazos river and south western mississippi river watersheds illite and kaolinite rich the clay mineral distributions in surface sediments of the present day gulf of mexico are strongly influenced by three main factors 1 by relative fluvial contributions the mississippi river delivers the bulk of the clay input to the northern gulf of mexico whereas the apalachicola mobile brazos and rio grande rivers inputs have more local influences 2 by differential settling of various clay mineral species which is identified for the first time in northern gulf of mexico sediments and 3 by oceanic current transport the gulf of mexico surface and subsurface circulation distributes the clay rich sediments from river mouth sources throughout the northern gulf of mexico

sea surface temperature variability in coastal areas of the northeastern pacific related to the el nino southern oscillation and the pacific decadal oscillation we examined monthly time series 1950 to 1999 of sea surface temperature sst anomalies in 47 quadrants 2 2 along the coast of north america and their relation to the el nino southern oscillation enso and the pacific decadal oscillation pdo we used the multivariate enso index mei and the pdo index pdoi and assumed a linear interaction of the mechanisms behind their interannual variations then we examined sst anomalies as functions of mei and pdoi using multiple linear regression mlr on average enso influence decreases poleward but is still dominant at 31 n northward the pdo signal dominates mlr was also applied to selected sea level height slh series enso effects on slh were clear up to 48 n while pdo showed a weak effect only in the gulf of alaska this suggests that poleward of southern california enso effects may be largely restricted to the inshore coastal environment

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

role of sea surface temperatures in forcing circulation anomalies driving u s great plains pluvial years abstractin the u s great plains gp diagnosing precipitation variability is key in developing an understanding of the present and future availability of water in the region building on previous

generation of low frequency spiciness variability in the thermocline abstract the generation of variance by anomalous advection of a passive tracer in the thermocline is investigated using the example of density compensated temperature and salinity anomalies or spiciness a coupled markov model is developed in which wind stress curl forces the large scale baroclinic ocean pressure that in turn controls the anomalous geostrophic advection of spiciness the double integration of white noise atmospheric forcing by this markov model results in a frequency spectrum of large scale spiciness proportional to 4 so that spiciness variability is concentrated at low frequencies an eddy permitting regional model hindcast of the northeast pacific 1950 2007 confirms that time series of large scale spiciness variability are exceptionally smooth with frequency spectra 4 for frequencies greater than 0 2 cpy at shorter spatial scales wavelengths less than 500 km the spiciness frequency spectrum is whitened by mesoscale eddies but this eddy forced variability can be fi

surface water hydrography of the kuroshio extension during the pliocene pleistocene climate transition abstract the pliocene pleistocene climate transition offers an opportunity to study the effect of glaciation on the ocean climate system we present a globigerinoides ruber 18 o record from ocean drilling program site 1208 kuroshio current extension kce this exclusively sub tropical foraminifer a summer fall mixed layer dweller at the kce affords the first long 3 0 ma to 1 8 ma orbital scale 2 5 kyr time step account of the sea surface in this area the section s temperature corrected benthic foraminiferal 18 o record constrains global changes in ice volume yielding a 18 o record that primarily reflects summer fall kce hydrography temperature and salinity a 0 3 decrease in 18 o values at 2 7 ma coincides with the onset of northern hemisphere glaciation indicating as much as 1 5 c warming during the summer fall to suggest that the subtropical north pacific sea surface provided heat and moisture for expanding ice sheets on the orbital scale the 41 kyr cycle that dominates high latitude climate is absent from the 18 o record indicating a stable surface water hydrographic regime on this time scale rather the 18 o record varies at and is coherent with the 19 kyr precessional component of the regional insolation curve supporting a direct response to subtropical insolation and insensitivity to extra regional forcing factors such as ice sheets

experimental simulation of clay precipitation within reservoir sandstones 2 mechanism of illite formation and controls on morphology illite and illite smectite with various morphologies have been formed on quartz grains by precipitation from solution following dissolution of amorphous al si gels at 150 350 degrees c and 0 75 1 0 kbar 75 100 mpa initial solutions include deionized water chloride and oxalate the experimental results have application to the formation of authigenic illite in sandstones from pore waters containing carboxylic acid anions a series of experiments monitored the effects of reaction temperature and time on the composition and morphology of illitic minerals precipitated following the dissolution of an amorphous gel of illite composition in deionized water a progressive increase of 70 to 100 in the illite content of illite smectite occurs between 150 and 350 degrees c but there is no change in illite smectite composition for reaction times of 24 hours to 37 days these results indicate that illite and illite rich illite smectite form by direct precipitation from solution and do not require a smectitic precursor the compositional variation in illite smectite and illite has little or no effect on clay morphology all experiments produced a platy boxwork morphology experiments performed at 250 degrees c and initially containing oxalate in both acidic and alkaline k bearing solutions strongly promote illite precipitation following the dissolution of an amorphous al si oxide starting material the very rapid precipitation that occurs under these conditions is associated with the formation of fibrous lath type illites rather than platy types which are characteristic of slower precipitation in the absence of oxalate precipitation of fibrous illite is related to the breakdown of oxalate which lowers illite solubility by either ph variation or by breakdown of an al oxalate complex oxalate is not a direct requirement for fibrous illite formation although it controls fluid composition which favors fibrous illite formation the association of illite precipitation with carboxylate anion breakdown suggests that the formation of fibrous illite cements in petroleum reservoirs is related to fluids released from source rocks which contain both aqueous organic acids and inorganic solutes

the tropical indian ocean decadal sea level response to the pacific decadal oscillation forcing the tropical indian ocean sea level displayed decadal variations in response to pacific decadal oscillation pdo contrasting patterns of decadal oscillation in sea level is found during the opposite phases of pdo especially in the thermocline ridge region of the indian ocean trio 50 e 80 e 15 s 5 s epochal mean sea level rise is observed over the trio region during the cold phase of pdo 1958 1977 whereas epochal mean sea level fall is observed during the warm phase of pdo 1978 2002 analysis reveals that the decadal variability in the sea level pattern in the trio region is in accordance with the pdo phase shifts and is primarily caused by changes in the surface forcing over the indian ocean as a response to pdo the changes in the large scale walker circulation over the tropical indian ocean region during the different phases of pdo support our hypothesis the winds and wind stress curl variations associated with these large scale circulation changes are primarily inducing the observed regional decadal sea level variability over trio the decadal forcing through indonesian through flow itf oceanic channel however did not show any significant impact on the trio sea level variability further ocean general circulation model ogcm sensitivity experiments are carried out to understand the mechanisms and the possible contribution of the pacific ocean through oceanic pathways in the decadal variability of the trio sea level it is noted that wave propagation from the pacific ocean to the indian ocean through itf region has contributed to the sea level variations in the eastern indian ocean but on the decadal time scale tropical indian ocean trio sea level is unaffected by decadal variability in the itf moreover the itf contribution to the decadal sea level variability in the indian ocean is found to be significant only in the region south of 20 s

origin of decadal scale eastward propagating heat content anomalies in the north pacific abstractupper ocean heat content ohc is at the heart of natural climate variability on interannual to decadal time scales providing climate memory and the source of decadal prediction skill in the midlatitude north pacific ocean ohc signals are often found to propagate eastward as opposed to the frequently observed westward propagation of sea surface height another variable that represents the ocean subsurface state this dichotomy is investigated using a 150 yr coupled gcm integration simulated ohc signals are distinguished in terms of two processes that can support eastward propagation higher baroclinic rossby wave rw modes that are associated with density perturbation and spiciness anomalies due to density compensated temperature and salinity anomalies the analysis herein suggests a unique role of the kuroshio oyashio extension koe region as an origin of the spiciness and higher mode rw signals wind forced westward propagating equivalent barotropic rws cause meridional shifts of the sub