modeling mass balance changes during a glaciation cycle identification of present day climate setting and alpine glacier balance gradients indicates that the balance gradient of alpine glaciers is primarily determined by climatic conditions determination of balance gradients for specific climatic settings on present day ice sheets provides an analog for determining the mass balance on pal eo and future ice sheets

can the mass balance of a glacier be estimated from its equilibrium line altitude the possibility of replacing or supplementing direct measurements of mass balance by estimates calculated from equilibrium line altitude ela measurements is investigated by statistical analyses of data from 31 glaciers a linear relationship between mass balance and ela in terms of two parameters the effective balance gradient and the balanced budget ela is tested it is concluded that existing mass balance series can be usefully extrapolated by using ela data for additional years however accurate mass balance cannot be calculated for glaciers where no such measurements have been made because of the difficulties in prescribing the two model parameters with sufficient accuracy for example the effective balance gradient is of the order of 5 mm water m so that errors of only a few decametres in the estimation of the balanced budget ela can have a great effect upon calculations of mass balance

evidence of nonlinear dynamics in the eastward shift of the nao 1 hilmer and jung 2000 have identified an eastward shift in the sea level pressure slp pattern associated with interannual variability of the north atlantic oscillation nao that took place around 1980 we investigate the nature of the eastward shift using a primitive equation dry atmospheric model driven by diabatic forcing diagnosed from observations the model results reveal the nonlinear dependence of the spatial pattern of the nao on the nao index the pattern being shifted to the east west for high low nao index general agreement is found between the model and observations we suggest that the eastward shift noted by hilmer and jung 2000 is a consequence of the trend towards higher nao index during the last several decades of the 20th century

thermocline dynamics in the northwestern tropical pacific over the past 700 kyr abstract variations in thermoclinal conditions play an important role in the evolution of the western pacific warm pool wpwp and in connecting the tropical and extratropical regions of the pacific ocean however secular thermoclinal changes in the northwestern part of the wpwp and their forcing mechanisms are not yet well understood particularly on orbital timescales in this study we report thermoclinal variation at site md06 3047 b in the western philippine sea over the last 700 kyr our data show that variations in thermocline temperature and salinity in the study area were correlated with changes in earth s obliquity with warmer and saltier colder and fresher thermocline waters corresponding to high low earth axial obliquity at high obliquity increases in thermocline temperature and salinity may have been linked to advection of warm north pacific tropical water in the study area a lower higher vertical temperature gradient in the upper water column suggests a deeper shallower thermocline during glacials interglacials the main factor leading to thermoclinal deepening during glacials was strengthening of the east asian winter monsoon eawm and more la nina like conditions may have contributed to concurrent subsurface warming and thus thermoclinal deepening in phase thermoclinal deepening in the northern and peri equatorial southern wpwp during glacial stages may have been triggered by changes in glacial boundary conditions such as increased ice sheet thickness through intensification of the eawm and strengthening of the tropical trade winds

comment on barckhausen et al 2014 evolution of the south china sea revised ages for breakup and seafloor spreading abstract we re examined the cessation of the south china sea seafloor spreading by using radioactive dating and fossil assemblage of the eto and the te derived age the youngest available age for the fragment of the south china sea is 15 ma and is more consistent with those suggested by previous studies moreover recent iodp expedition preliminary results suggested that the hemipelagic claystone layer stratigraphically bounded by igneous sequences of massive lava flow rock is early miocene in age therefore the previous interpretations are more inclusive than those provided by barckhasen et al 2014 and indicate that a slow spreading ridge was more plausible to have occurred during the seafloor spreading of the south china sea

mid ocean ridge or marginal basin origin of the east taiwan ophiolite chemical and isotopic evidence the east taiwan ophiolite eto occurs as allochthonous fragments embedded in the plio pleistocene lichi melange in the coastal range of eastern taiwan it is probably the youngest among the known ophiolitic complexes of the world the overall geochemical and isotopic characteristics of the representative rock types are very oceanic and strongly argue for a mid ocean or marginal basin origin of the eto the best criteria include 1 major element compositions 2 ree distribution patterns 3 nd isotopic ratios some have nd 12 4 pb isotopic ratios and 5 the presence and nature of the red shale this conclusion is supported by previous studies of metamorphic evolution of the eto

decadal characterization of indo pacific ocean subsurface temperature modes in soda reanalysis abstractstudies of decadal to multidecadal ocean subsurface temperature variability are fundamental to improving the understanding of low frequency climate signals the present study uses the simple ocean data assimilation soda version 2 2 4 product for the period 1950 2007 to identify decadal modes of variability that characterize the upper indo pacific ocean temperature structure 5 466 m depth an empirical orthogonal function eof analysis of the 10 yr low pass filtered temperature field applied across four depths shows that the dominant mode is characterized by a long term temperature trend with warming at the surface and cooling at the thermocline depth connecting the tropical western pacific with the southern indian ocean via the indonesian seas eof analysis of the detrended 10 yr filtered temperature data and correlation analyses of the eof time series with established large scale climate indices identified the interdecadal pacific oscillation as eof1 the north pacific gyre oscillation as e

a new view of integrating stratigraphic and tectonic analysis in south china sea and north borneo basins abstract this review outlines how se asian tectonic and stratigraphic studies could be more closely linked many tectonic papers on the region include comments on stratigraphic evidence and stratigraphic papers often allude to tectonic events but this paper highlights the benefits of a more detailed integration of the two fields of study into a single geological model by using inductive sequence stratigraphic methods supported by geohistory plots the south china sea and north borneo region has been traditionally been divided into provinces each with its own distinct stratigraphy a handicap in merging all the provinces into one geological model has been the inconsistent application of basic biostratigraphy and some examples are given that illustrate that more careful documentation of a complex data set is required in future work the inductive stratigraphic method requires increased analytical work to calibrate seismic data but even on current data an episodic stratigraphic history is indicated and a single tectono stratigraphic framework for the whole region is emerging with a greatly simplified and consistent terminology this review examines the impact of these methods on one important period of transition around the oligo miocene boundary the summary given for the oligo miocene transition questions the viability of the commonly cited slab pull tectonic model as both the historical order of geological events and geographic spread of effects does not fit that model as currently understood

spatial variations in effective elastic thickness in the western pacific ocean and their implications for mesozoic volcanism abstract we have used free air gravity anomaly and bathymetric data together with a moving window admittance technique to determine the spatial variation in oceanic elastic thickness t e in the western pacific ocean synthetic tests using representative seamounts show that t e can be recovered to an accuracy of 5 km for plates up to 30 km thick with increased accuracy of 3 km for t e 20 km the western pacific has a t e range of 0 50 km with a mean of 9 4 km and a standard deviation of 6 8 km the t e structure of the region is dominated by relatively high t e over the hawaiian emperor seamount chain intermediate values over the marshall islands gilbert ridge and marcus wake guyots and low values over the line islands mid pacific mountains caroline islands shatsky rise hess rise and musician seamounts plots of t e at sites with radiometric ages suggest that t e is to first order controlled by the age of the lithosphere at the time of loading in areas that backtrack into the south pacific isotopic and thermal anomaly sopita t e may be as low as the depth to the 180 120 c isotherm at least locally in the northern part of the study area including the hawaiian emperor seamount chain t e correlates with the depth to 310 120 c these best fitting isotherms imply peak rates of volcanism during 100 120 ma early cretaceous and 140 150 ma late jurassic the corresponding addition of 8 10 6 km 3 and 4 10 6 km 3 of volcanic material to the surface of the oceanic crust would result in long term sea level rises of 20 m and 10 m respectively the late jurassic volcanic event like the later early cretaceous event appears to have influenced the tectonic evolution of the pacific plate convergent boundaries resulting in increased volcanism and orogenesis

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

linear correlations in bamboo coral δ 13 c and δ 18 o sampled by sims and micromill evaluating paleoceanographic potential and biomineralization mechanisms using δ 11 b and 47 composition abstract bamboo corals represent an intriguing paleoceanographic archive with the potential to reconstruct variations throughout the water column over multiple centuries realizing this potential partially depends on if and at what resolution timeseries of variability can be generated recent work demonstrates that bamboo coral growth temperature averaged over its entire lifespan can be derived from linear correlations in its carbon and oxygen isotope composition 13 c 18 o when the apparent equilibrium fractionations for a coral s growth rate and calcifying ph are used building on this method this study applies it to coeval coral skeleton to assess the possibility of extracting paleoceanographic timeseries from bamboo coral skeletons using boron isotope 11 b based ph estimates micromilled samples yield accurate paleotemperatures with uncertainties of 2 c this is attributed to the inability to measure 13 c and 18 o in exactly the same skeleton as is the case for micromilled samples a micromilled sampling strategy is therefore likely the most practical means of applying the method carbonate clumped isotopes 47 estimate temperatures slightly warmer than observed suggesting they may not accurately record the subtle variations of the latest holocene when interpreted in conjunction 18 o 11 b and 47 data suggest that ph up regulation plays a role in generating linear 13 c 18 o trends however oxygen isotope fractionation and 47 are lower than would be predicted by ph alone potential explanations for this discrepancy include biological processes that favor the incorporation of carbonate ion into coral skeleton uncertainties in the 11 b ph proxy the influence of magnesium on calcite fluid isotope fractionation or uncertainties in the fractionation factors used to calculate apparent equilibrium despite some remaining uncertainties the method can resolve many observed decadal scale thermocline temperature anomalies suggesting that appropriately located bamboo corals could help constrain the behavior of similar temporal variability prior to instrumental monitoring

cenozoic tectonic and stratigraphic development of the central vietnamese continental margin abstract the east vietnam boundary fault zone evbfz forms the seaward extension of the red river shear zone and interacted with the extensional rift systems in basins along the central vietnamese continental margin the structural outline of the central vietnamese margin and the timing of deformation are therefore fundamental to understanding the development of the south china sea and its relation to indochinese escape tectonism and the india eurasia collision this study investigates the structural and stratigraphic evolution of the central vietnamese margin in a regional tectonic perspective based on new 2 d seismic and well data the basin fill is divided into five major oligocene to recent sequences separated by unconformities deposition and the formation of unconformities were closely linked with transtension rifting the opening of the south china sea and late neogene uplift and denudation of the eastern flank of indochina the structural outline of the central vietnamese margin favors a hybrid tectonic model involving both escape and slab pull tectonics paleogene left lateral transtension over the nnw striking evbfz occurred within the song hong basin and the quang ngai graben and over the da nang shelf western phu khanh basin related to the escape of indochina east of the evbfz paleogene ne striking rifting prevailed in the outer phu khanh basin and the hoang sa graben fitting best with a prevailing stress derived from a coeval slab pull from a subducting proto south china sea beneath the southwest borneo palawan region major rifting terminated near the end of the oligocene however late stage rifting lasted to the early miocene when continental break up and seafloor spreading commenced along the edge of the outer phu khanh basin the resulting transgression promoted lower and middle miocene carbonate platform growth on the da nang shelf and the tri ton high whereas deeper marine conditions prevailed in the central part of the basins partial drowning and platform retreat occurred after the middle miocene due to increased siliciclastic input from the vietnamese mainland as a result siliciclastic marine deposition prevailed offshore central vietnam during the pliocene and pleistocene

enso to multi decadal time scale changes in east australian current transports and fort denison sea level oceanic rossby waves as the connecting mechanism the connection between east australian current eac transport variability and australia s east coast sea level has received little treatment in the literature this is due in part to the complex interacting physical processes operating in the coastal zone combined with the sparsity of observations available to improve our understanding of these possible connections this study demonstrates a statistically significant at the 490 level relationship between interannual to decadal time scale variations in observed estimates of the eac transport changes and east coast sea level measured at the high quality long record fort denison tide gauge in sydney harbour australia 3315101800s 15111303200e we further demonstrate using a linear reduced gravity ocean model that enso to decadal time scale variations and the ocean adjusted multi decadal trend approx 1 cm decade in observed sea level at fort denison are strongly connected to modulations of eac transports by incoming westward propagating oceanic rossby waves we show that eac transport and fort denison sea level vary in a manner expected from both tasman sea generated rossby waves which account for the interannual and multi annual variability and remotely forced from east of new zealand rossby wave connections through the mid latitudes accounting for the ocean adjusted multi decadal trend observed at the new south wales coast with the regional tasman sea forcing explaining the greatest overall proportion of eac transport and sea level variances

calcareous nannofossil changes in response to the spreading of the south china sea basin during eocene oligocene abstract numerous models have been proposed to constrain the process of the south china sea formation yet the paleogene paleoenvironmental researches are hindered by the paucity of long continuous well dated geological records in this work eocene to oligocene nannofossil biostratigraphy and assemblage changes in a sediment section from the northern south china sea were studied to shed light on these issues we established an age model to confine the studied section between 40 and 22 ma based on 17 calcareous nannofossil datum levels the age model enabled to date the most prominent seismic reflector t60 centered at 26 8 ma a regional tectonic event interpreted as corresponding to the ridge jump event in the early phase of south china sea spreading changes in nannofossil abundance and assemblage compositions imply continuous transgression and deepening of water depth from the late eocene to early miocene during the late eocene the studied area was a neritic sea with relatively eutrophic conditions supporting abundant r lockeri group and c pelagicus from 34 ma to 27 ma during the oligocene the earlier neritic environment was replaced by relative warm and oligotrophic conditions in a shallow sea as indicated by higher concentration of c floridanus sphenolithus spp and helicosphaera spp since 26 ma pelagic conditions prevailed small reticulofenestra

phenomena of pulsation tectonics related to the breakup of the eastern north american continental margin abstract new data from the recent ipod drilling of dsdp site 534 in the blake bahama basin give a definite age for the spreading center shift involved in the breakup of the north american atlantic margin a basal callovian age 155 m y is determined for the blake spur magnetic anomaly marking this spreadingcenter shift that signals the birth of the modern north atlantic ocean this is some 20 m y younger than previously thought an implication of this younger age for the blake spur event is that very high spreading rates are now required for the jurassic outer magnetic quiet zone along the north american margin this association of a relatively high spreading rate with a magnetic quiet zone is similar to that for the mid cretaceous and implies a link between the processes controlling plate spreading which are in the upper mantle and the processes controlling the magnetic field which are in the outer core a theory of pulsation tectonics involving the cyclic eruption of plumes of hot mantle material from the lowermost mantle could explain the correlation plumes carry heat away from the core mantle boundary and later reach the asthenosphere and lithosphere to induce faster spreading the pulse of fast spreading in the jurassic apparently followed the breakup of continents bordering the north atlantic ocean other pulses of fast spreading appear to correlate with major ocean openings on various parts of the globe implying that this might be a prevalent process rifting of passive margins may be controlled by the more fundamental global processes described by the theory of pulsation tectonics

major unconformities termination of extension events and associated surfaces in the south china seas review and implications for tectonic development abstract the distribution of unconformities and end of cenozoic rifting events in the south china seas scs reflects both the modes of rift development and the effects of driving mechanisms continental rifting began in the eastern basins during the paleocene and propagated westwards to the vietnam basin margin in the late eocene continental breakup around 32 28 ma caused a regional reduction or cessation in extensional activity particularly affecting basins furthest from the spreading centre basins in the slope and deepwater area north of the spreading centre exhibit reduced fault activity until 21 20 ma propagation of oceanic crust westwards between 25 and 23 ma and termination of seafloor spreading sometime between 20 5 and 16 ma affected fault activity in the qiongdongnan and nam con song basins in the phu khanh basin and south in the dangerous grounds area extension continued until about 16 ma ending at the red unconformity the end of seafloor spreading around 20 5 ma reflects loss of extensional driving force as thinned continental crust entered the nw borneo subduction zone controversially a key component of the driving force maybe attributed to slab pull a transitional period of about 5 7 my between the onset of subduction of continental crust and final jamming of the subduction zone deep regional unconformity dru is inferred the last pulse of extension was focussed in the western scs and terminated around 10 5 ma detailed understanding of proto south china seas development remains uncertain and controversial

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

reply to chang et al 2014 evolution of the south china sea revised ages for breakup and seafloor spreading abstract chang et al introduce some new lines of evidence for an end of seafloor spreading in the south china sea not before 15 ma however we find strong indications that their interpretation is not conclusive the origin of the east taiwan ophiolite from the scs as assumed by chang et al is not in agreement with recent studies which find continental crust in the deep water domain of the northeastern south china sea the age dating of the east taiwan ophiolite is based on one single k ar age of questionable accuracy the calculation of te derived ages leaves a thermal rejuvenation of the oceanic crust in the south china sea by post spreading volcanism out of consideration biostratigraphically determined ages of sediments recovered directly above igneous crust of the south china sea during iodp 349 drilling expedition are inconclusive so far the final key to unlocking the spreading history of the scs will be the ar ar age dating of the basaltic rocks recovered during iodp expedition 349

climate changes control offshore crustal structure at south china sea continental margin a b s t r a c t rifted continental lithosphere subsides as a consequence of combined crustal thinning and mantle lithosphere cooling yet basins on some continental margins experience anomalous subsidence events that postdate active extension deep basins on the northern margin of the south china sea notably the baiyun sag show basement subsidence accelerating after 21 ma postdating extension by several million years we combine geophysical observations and numerical forward modeling to show that loading of the offshore basins by increased sediment flux caused by faster onshore erosion following early miocene monsoon intensification is a viable trigger for ductile flow after the cessation of active extension this illustrates that offshore basin dynamics at continental margins with weak crust can be controlled by onshore surface processes in a newly recognized form of climate tectonic coupling

causes of decadal subsurface cooling in the tropical indian ocean during 1961 2000 1 the vertical structure of temperature change in the indian ocean io during 1961 2000 indicates that a region of tropical thermocline cooling accompanies the upper level warming results from data analysis and ocean general circulation model experiments suggest that the cooling signals exceed the cross data and cross model differences spatial patterns of the temperature trend above 200 m resemble the negative io dipole structure with the strongest cooling occurring in the western central basin south of the equator the upper thermocline cooling is mainly caused by enhanced ekman pumping velocity which shoals the thermocline the enhanced upwelling is consistent with the strengthened southern subtropical cell enhanced equatorial westerly winds contribute to the negative dipole pattern remote forcing from the pacific may contribute to the cooling below 200 m and further south

crustal structure north of the taiping island itu aba island southern margin of the south china sea abstract based on the multi channel seismic mcs and gravity data offshore north of taiping island itu aba island in the spratly islands nansha islands we revisited the crustal structures in the northern part of the southern margin of the southwest sw sub basin of the south china sea scs the mcs data suggest that the basement structural highs in the southwest margin of the scs are dominated by both fault blocks and volcanic basement structures that probably formed along with the basement faults the gravity modeling results reveal that these volcanic basement structures were probably associated with the high velocity or density lower crust hvdlc suggesting that the southern margin of the sw sub basin serves as an intermediate margin based on the tectonic features in the scs margins including 1 the transition between the magma poor margins of the northwest nw sub basin and intermediate margins of the east and sw sub basins 2 the cessation of the seafloor spreading in the nw sub basin being succeeded by a major ridge jump event which was very likely to reflect an active mantle upwelling event 3 the extensive distribution of the hvdlc beneath in the well investigated northern margin of the east sub basin and as explored in the sw sub basin in this study and 4 basement faulting and volcanism shown in this study that may be related to the hvdlc and hyper extension we proposed a conceptual model to interpret the origin of the hvdlc in the southern margin of the sw sub basin the margin of the scs basin was magma poor at the time it occurred an active mantle upwelling event caused by small scale mantle convection possibly related to the influence of the nascent hainan mantle plume was formed subsequently resulting in a southward ridge jump and the hvdlc beneath the current margins of the east and sw sub basins the east and sw sub basins continued to spread latitudinally dividing their hvdlcs as the margins separated accordingly afterwards the hyper extension in the distal margins may also be responsible for a crust weakening zone wherein the subsequent volcanic events could occur

seismic sequence stratigraphic analysis of the carbonate platform north offshore taiping island dangerous grounds south china sea abstract taiping island also known as itu aba is the largest natural terrestrial landmass in the south china sea and is centrally located using bathymetry and marine multi channel seismic data we explored the seismic stratigraphic features of the offshore and isolated carbonate platform north of taiping island the western flank of the carbonate platform is characterized by an intercalation between high amplitude and low amplitude reflections showing the landward and seaward migration of the platform foreslope deposits in addition there are two offshore carbonate build ups that are underlain by normal faults six sequence boundaries and five depositional sequences caused by eustatic sea level cycles are identified and correlated with the eustatic sea level change chart although the evolution of the seismic sequences is partly controlled by local tectonics the overall stacking pattern of the sedimentary strata in our study area reveals five third order cycles and one second order cycle which is in accordance with the eustatic sea level chart additionally the formations of the western taiping seamount group and the zhenghe daoming trough are preliminarily analyzed based on seismic data

crustal structure and extension mode in the northwestern margin of the south china sea combining multi channel seismic reflection and gravity modeling this study has investigated the crustal structure of the northwestern south china sea margin these data constrain a hyper extended crustal area bounded by basin bounding faults corresponding to an aborted rift below the xisha trough with a subparallel fossil ridge in the adjacent northwest sub basin the thinnest crust is located in the xisha trough where it is remnant lower crust with a thickness of less than 3 km gravity modeling also revealed a hyper extended crust across the xisha trough the postrift magmatism is well developed and more active in the xisha trough and farther southeast than on the northwestern continental margin of the south china sea and the magmatic intrusion extrusion was relatively active during the rifting of xisha trough and the northwest sub basin a narrow continent ocean transition zone with a width of 65 km bounded seaward by a volcanic buried seamount is characterized by crustal thinning rift depression low gravity anomaly and the termination of the break up unconformity seismic reflection the aborted rift near the continental margin means that there may be no obvious detachment fault like that in the iberia newfoundland type margin the symmetric rift extreme hyper extended continental crust and hotter mantle materials indicate that continental crust underwent stretching phase pure shear deformation thinning phase and breakup followed by onset of seafloor spreading and the mantle lithosphere may break up before crustal necking in the northwestern south china sea margin

the response of a stochastically forced enso model to observed off equatorial wind stress forcing abstract this study investigates the response of a stochastically forced coupled atmosphere ocean model of the equatorial pacific to off equatorial wind stress anomaly forcing the intermediate complexity coupled enso model comprises a linear first baroclinic mode ocean shallow water model with a steady state two pressure level 250 and 750 mb atmospheric component that has been linearized about a state of rest on the plane estimates of observed equatorial region stochastic forcing are calculated from ncep ncar reanalysis surface winds for the period 1950 2006 using singular value decomposition the stochastic forcing is applied to the model both with and without off equatorial region wind stress anomalies i e poleward of 12 5 latitude it is found that the multiyear changes in the equatorial pacific thermocline depth background state induced by off equatorial forcing can affect the amplitude of modeled sea surface temperature anomalies by up to 1 c moreover off equatorial wind stress anom

evolution of the south china sea revised ages for breakup and seafloor spreading abstract the continental breakup which gave way to the formation of the oceanic south china sea scs basin began in the latest cretaceous in the northeastern scs and propagated in southern and western direction over a long period of time possibly more than 40 m y the seafloor spreading history of the south china sea has been interpreted in different ways in the past and the debate over the correct timing of the major tectonic events continues we review the different models that have been published and present a revised interpretation of seafloor spreading anomalies based on three datasets with documented high quality which cover all of the scs but the northernmost and southernmost parts we can precisely date the onset of seafloor spreading in the central part of the scs at 32 ma after a ridge jump at 25 ma spreading also began in the southwestern sub basin and spreading ended at 20 5 ma in the entire basin followed by a phase of magmatic seamount formation mainly along the abandoned spreading ridge spreading rates vary from 56 mm yr in the early stages to 72 mm yr after the ridge jump to 80 mm yr in the southwestern sub basin we find indications for a stepwise propagation of the seafloor spreading from northeast to southwest in segments bounded by major fracture zones seafloor spreading ended abruptly probably because the subduction zone along the eastern and southern boundary of the scs of which today the manila trench remains was blocked by collision with a continental fragment possibly the northern part of palawan or a part of the dangerous grounds

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

interdecadal sea surface temperature variability in the equatorial pacific ocean part i the role of off equatorial wind stresses and oceanic rossby waves the australian bureau of meteorology research centre cgcm and a linear first baroclinic mode ocean shallow water model swm are used to investigate ocean dynamic forcing mechanisms of the equatorial pacific ocean interdecadal sea surface temperature sst variability an eof analysis of the 13 yr low pass butterworth filtered sst anomalies from a century time scale cgcm simulation reveals an sst anomaly spatial pattern and time variability consistent with the interdecadal pacific oscillation results from an swm simulation forced with wind stresses from the cgcm simulation are shown to compare well with the cgcm and as such the swm is then used to investigate the roles of uncoupled equatorial wind stress forcing off equatorial wind stress forcing offeqwf and rossby wave reflection at the western pacific ocean boundary on the decadal equatorial thermocline depth anomalies equatorial pacific wind stresses are shown to explain a large proportion of the overall variance in the equatorial thermocline depth anomalies however offeqwf beyond 12 5 latitude produces an interdecadal signature in the nino 4 nino 3 region that explains approximately 10 1 5 of the filtered control simulation variance rossby wave reflection at the western pacific boundary is shown to underpin the offeqwf contribution to these equatorial anomalies the implications of this result for the predictability of the decadal variations of thermocline depth are investigated with results showing that offeqwf generates an equatorial response in the nino 3 region up to 3 yr after the wind stress forcing is switched off further a statistically significant correlation is found between thermocline depth anomalies in the offequatorial zone and the nino 3 region with the nino 3 region lagging by approximately 2 yr the authors conclude that there is potential predictability of the offeqwf equatorial thermocline depth anomalies with lead times of up to 3 yr when taking into account the amplitudes and locations of off equatorial region rossby waves