energy flux of nonlinear internal waves in northern south china sea 1 we analyze three sets of adcp measurements taken on the dongsha plateau on the shallow continental shelf and on the steep continental slope in the northern south china sea scs the data show strong divergences of energy and energy flux of nonlinear internal waves nliw along and across waves prevailing westward propagation path the nliw energy flux is 8 5 kw m 1 on the plateau only 0 25 kw m 1 on the continental shelf 220 km westward along the propagation path and only 1 kw m 1 on the continental slope 120 km northward across the propagation path along the wave path on the plateau the average energy flux divergence of nliw is 0 04 w m 2 which corresponds to a dissipation rate of o 10 7 10 6 w kg 1 combining the present with previous observations and model results a scenario of nliw energy flux in the scs emerges nliws are generated east of the plateau propagate predominantly westward across the plateau along a beam of 100 km width that is centered at 21 n and dissipate nearly all their energy before reaching the continental shelf

global dinoflagellate event associated with the late paleocene thermal maximum the late paleocene thermal maximum or lptm ca 55 ma represents a geologically brief time interval 220 k y characterized by profound global warming and associated environmental change the lptm is marked by a prominent negative carbon isotope excursion cie interpreted to reflect a massive and abrupt input of 12 c enriched carbon to the ocean atmosphere reservoir possibly as a result of catastrophic gas hydrate release on time scales equivalent to present day rates of anthropogenic carbon input the lptm corresponds to important changes in the global distribution of biota including mass extinction of marine benthic organisms the dinoflagellate cyst record indicates that surface dwelling marine plankton in marginal seas also underwent significant perturbations during the lptm we report on the dramatic response of representatives of the genus apectodinium from two upper paleocene lower eocene sections in the southern new zealand and northern austria hemispheres where the dinoflagellate records are directly correlated with the cie benthic foraminifera extinction event and calcareous nannofossil zonation the results indicate that the inception of apectodinium dominated assemblages appears to be synchronous on a global scale and that the event is precisely coincident with the beginning of the lptm apectodinium markedly declined in abundance near the end of the lptm this apectodinium event may be associated with 1 exceptionally high global sea surface temperatures and or 2 a significant increase in marginal marine surface water productivity such a globally synchronous acme of dinoflagellate cysts is unprecedented within the dinoflagellate cyst fossil record

anti cyclonic eddies northwest of luzon in summer fall observed by satellite altimeters anti cyclonic eddies northwest of luzon of the philippines in summer fall are identified in the merged data products of satellite altimeters of topex poseidon jason 1 and european research satellites the generation and propagation of the anti cyclonic eddies which are confirmed by satellite ocean color data are found to be a seasonal phenomenon that is phase locked to the onset of the southwesterly monsoon and the relaxation of the cyclonic wind curl in the northeastern south china sea the eddies originate from northwest of luzon in summer move across the northeastern south china sea to reach the china continental slope in fall and propagate southwestward along the continental slope in fall winter inducing shelfbreak current variations in the western south china sea in fall winter the anti cyclonic eddy discovered by li et al 1998 in the northern south china sea is found to originate from northwest of luzon and carry primarily the south china sea waters it does not appear to be an eddy shed from the kuroshio in the luzon strait area as alluded by li et al 1998 and others

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

differential patterns of benthic foraminiferal extinctions near the paleocene eocene boundary in the north atlantic and the western tethys bathyal benthic foraminifera and stable isotopes from the caravaca and zumaya sections of spain indicate that the mass extinction near the paleocene eocene p e boundary upper planktic foraminiferal zone p6a was rapid coinciding with a negative 13c shift of 2 4 the onset of dark grey shale deposition and increased carbonate dissolution prior to the extinction event diverse benthic foraminiferal assemblages and high 13c values suggest the presence of a stable intermediate deep watermass rich in oxygen and saturated in calcium carbonate in both caravaca and zumaya sections after the extinction event small finely agglutinated haplophragmoides glomospira and thin walled epifaunal taxa nuttallides truempyi dominate in the north atlantic zumaya section this assemblage indicates sluggish circulation bottom waters undersaturated in calcium carbonate and dysaerobic conditions low oxygen conditions prevailed for the succeeding 400 kyr and are characterized by 1 2 fluctuations in benthic 13c in the western tethys caravaca section infaunal taxa buliminids dominate after the extinction event and prevailed through the succeeding 400 to 450 kyr of decreased 13c values indicating low oxygen conditions despite these common features benthic foraminiferal assemblages from these two sections exhibit significant differences during the extinction event at the zumaya section the extinction event occurred over less than 50 kyr and resulted in a sudden reduction in species richness after the 13c shift in contrast at the caravaca section species diversity declined gradually beginning prior to and in concert with the gradually declining 13c values this gradual change occurred over a period of 250 kyr and culminated in a 4 13c shift these differences in 13c values and benthic assemblages between caravaca and zumaya suggest that the p e oceanographic changes that triggered the benthic foraminiferal mass extinction exhibited its first manifestation in the tethys region

ostracode turnover and sea level changes associated with the paleocene eocene thermal maximum the ostracode response to oceanographic changes during the paleocene eocene thermal maximum petm ca 55 ma is largely unknown the gebel duwi section egypt provides a detailed ostracode record across the petm in a middle neritic setting quantitative analysis of this record reveals two significant results 1 the petm is marked by a sharp faunal turnover as indicated by abundance changes local extinctions and immigrations this turnover punctuated a gradual basin wide faunal transition 2 during the 60 k y period prior to the petm relative sea level fell rapidly by 15 m this sea level fall was followed by an 20 m sea level rise during the petm a possible eustatic control on these fluctuations suggests the presence of a cryosphere and variations in its size during this time of global warmth

observed wintertime tidal and subtidal currents over the continental shelf in the northern south china sea synthesis analyses were performed to examine characteristics of tidal and subtidal currents at eight mooring sites deployed over the northern south china sea nscs continental shelf in the 2006 2007 and 2009 2010 winters rotary spectra and harmonic analysis results showed that observed tidal currents in the nscs were dominated by baroclinic diurnal tides with phases varying both vertically and horizontally this feature was supported by the cc fvcom results which demonstrated that the diurnal tidal flow over this shelf was characterized by baroclinic kelvin waves with vertical phase differences varying in different flow zones the northeasterly wind induced southwestward flow prevailed over the nscs shelf during winter with episodic appearances of mesoscale eddies and a bottom intensified buoyancy driven slope water intrusion the moored current records captured a warm core anticyclonic eddy which originated from the southwestern coast of taiwan and propagated southwestward along the slope consistent with a combination of plane and topographic rossby waves the eddy was surface intensified with a swirl speed of 50 cm s and a vertical scale of 400 m in absence of eddies and onshore deep slope water intrusion the observed southwestward flow was highly coherent with the northeasterly wind stress observations did not support the existence of the permanent wintertime south china sea warm current scswc the definition of scswc which was based mainly on thermal wind calculations with assumed level of no motion at the bottom needs to be interpreted with caution since the observed circulation over the nscs shelf in winter included both barotropic and baroclinic components

palaeoclimatic interpretation of clay minerals in marine deposits an outlook from the continental origin abstract as distribution of clay minerals in modern oceans seems to be controlled by contemporary climates marine clays in ancient deposits have been widely used to reconstruct palaeoclimates in this review we examine this question mainly from the continental origin of the clay minerals and show the difficulties of retrospective analysis of the influence of climate on common marine deposits we examine successively how soils develop and behave are reworked and palaeoweatherings are preserved focusing the review on kaolinitic soils indicative of tropical wet climates several stages intervene between the time of clay mineral development in soils and their final deposition in the basin 1 the persistence over geological times of huge amounts of kaolinitic palaeoweathering materials in the landscapes may seriously alter the palaeoclimatic signal of kaolinite in the sedimentary record although the kaolinite deposited in recent sediments of the world oceans is consistent with wet climatic zones this is mainly because the major kaolinitic and bauxitic palaeosurfaces coincide with the tropical areas where kaolinite is still developing at present 2 possible development of deep kaolinitic profiles at high latitudes and cold conditions under co 2 enriched palaeoatmospheres or even by unusual acidic weathering linked with dry climates is misleading palaeoenvironments for palaeoclimatic reconstruction 3 erosion and transport processes always cloud the signal to some extent because frequently erosion products from the bedrock and different soil horizons will be mixed and major drainage systems may include soils of different climatic zones 4 the arrival of the soil clay assemblages in the basin inevitably lags against their formation on the continent and may occur several million years after formation of the soils on the continent and climate may have considerably changed at that time it is pointed out that sedimentologists and palaeoclimatologists should consider the complexity of the relations between soil and sedimentary clay minerals soil formation rates are slow and therefore the resolution of the palaeoclimatic record in marine clay may not be closer than 1 or 2 ma at present the palaeoclimatic interpretations of marine clay assemblages are yielding at best nothing more than rather broad palaeoclimatic information this approach cannot achieve the same degree of resolution as other techniques such as isotope or microfossil studies clay mineral assemblages may provide integrated records of overall climatic impacts whereas other techniques are more likely to reveal local or temporary climates

influence of initial cmb temperature and other parameters on the thermal evolution of earth s core resulting from thermochemical spherical mantle convection 1 here we present a wide ranging parameter study of the effects of initial core mantle boundary cmb temperature concentration of radioactive potassium in the core and density difference between harzburgite and mid ocean ridge basalt morb in a coupled spherical model of thermochemical mantle convection and parameterized core heat balance the initial cmb temperature is expected to be much higher than the solidus temperature of silicates at the base of the mantle the results indicate that as with previous purely thermal convection models the final state of the system is only weakly dependent on initial cmb temperature unless the cmb becomes blanketed by a global layer of dense material fully 3 d spherical cases have a very similar core evolution to cases in a 2 d spherical annulus giving confidence in the applicability of 2 d spherical annulus geometry for modeling earth s evolution obtaining a successful thermal evolution in the sense of obtaining the correct present day inner core size and maintaining a geodynamo over geological time is helped by the accumulation of piles of dense material at the cmb subducted morb in the present calculations and a concentration of radiogenic k in the core in the range 400 800 ppm the present day cmb heat flow is predicted to be around 9 tw while this is lower than estimates based on calculating temperature gradients in regions where the postperovskite transition is seismically imaged these tend to be areas of higher than average heat flux and thus likely overestimate the global heat flow

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

seasonal characteristics of internal tides on the continental shelf in the northern south china sea three across shelf acoustic doppler current profiler adcp moorings were deployed on the continental shelf in the northern south china sea in 2006 and 2007 in order to obtain time series of ocean currents during each of the three observational periods in spring autumn and winter seasons the observation was sustained for at least 1 month conductivity temperature depth data were also collected in the vicinity of these adcp moorings the two diurnal baroclinic constituents o 1 and k 1 are found to be more prominent than the semidiurnal baroclinic ones m 2 and s 2 at each mooring site which are different from the barotropic tides the highest diurnal semidiurnal baroclinic kinetic energy density exceeded 10 2 7 kj m 2 during the observational periods in each observational period the vertical structures of baroclinic tidal ellipses indicate mode 1 characteristics for o 1 and k 1 whereas some of the semidiurnal internal tides show mode 2 characteristics in autumn propagation directions of the diurnal and semidiurnal internal tides are basically across shelf and their phase speeds estimated from phase changes and buoyancy frequencies indicate deceleration of internal tides when the internal tidal waves propagate from deeper shelf break to shallower shelf the increased stratification in autumn is favorable for maintaining internal tidal waveform and preserving internal tidal energy while the intensity of the internal tidal flow decreases significantly in winter

a modeling study of the episodic cross frontal water transport over the inner shelf of the south atlantic bight abstract physical processes that control the episodic cross frontal transport over the inner shelf of the south atlantic bight were examined using a 3d primitive turbulent closure equation model the model results showed that significant cross frontal water exchange occurred under upwelling favorable wind conditions through the detachment of isolated low salinity lenses at the outer edge of the front the formation of isolated lenses was a 3d feature associated with complex nonlinear processes it depended on 1 the amount of multiple river discharges 2 direction and magnitude of the wind and 3 tidal mixing as the total amount of river discharges increased stronger winds were required to form the isolated lenses when the river discharges were larger tidal mixing tended to delay the occurrence of isolated lenses through 1 increasing the cross shelf gradients of density and surface elevation and thus enhancing the along shelf current and reducing the along shelf variation of salinity and 2 streng

generation of diurnal k1 internal tide in the luzon strait and its influence on surface tide in the south china sea 1 the predominance of diurnal surface tides over semidiurnal surface tides in the south china sea scs has been attributed to the near resonance response of the former in the scs recent observations further revealed vigorous internal tides in the northern scs conceivably internal tides generated in the luzon strait could modify the surface tide in the scs we use a three dimensional tide model of the east asian seas to address this issue with a typical summertime stratification of the scs as the initial condition energy budget indicates that one third of the incident k1 surface tide energy is converted to the baroclinic energy over topographic ridges in the luzon strait in comparison with a global tidal model matsumoto et al 2000 our numerical experiments that annihilated or reduced the k1 internal tide in the luzon strait led to up to 50 amplification of the simulated k1 surface tide in the scs this suggests that the baroclinic energy conversion substantially reduces the amplitude of k1 surface tide in the scs the simulated phases in the scs differ little from those calculated from matsumoto s tide model suggesting that the modification is primarily on the amplitude two dimensional surface tidal models lack baroclinic energy conversion in the luzon strait the consequent overestimation of surface k1 tide can be reduced only through precise prescription of sea levels in the luzon strait or assimilation of sea level data

evolutionary consequences of the latest paleocene thermal maximum for tropical planktonic foraminifera study of planktonic foraminiferal assemblages preserved in the central equatorial pacific odp site 865 reveal that genera which inhabited the near surface mixed layer diversified during the latest paleocene thermal maximum lptm this transient diversification gave rise to a suite of short lived 50 to several 100 ka distinctive morphotypes morozovella allisonensis sp nov m africana and acarinina sibaiyaensis that are restricted to the lptm interval parallel morphometric and stable isotopic data have been recorded from individual shells of members of the m velascoensis m allisonensis and a soldadoensis a sibaiyaensis lineages the single specimen isotope data confirm that m allisonensis and a sibaiyaensis are indeed stratigraphically restricted to the lptm carbon isotope excursion all specimens recorded anomalously low 13c values a stratigraphic succession of single specimen isotope data from within the 13c excursion interval was used to reconstruct the complex population dynamics which mediated the rapid 10 ka evolution of the lptm taxa these data reveal that local populations of ancestral m velascoensis temporarily collapsed with the descendant m allisonensis suddenly originating from a peripherally isolated population this pattern is most consistent with peripatric speciation overall the evolutionary transition from acarinina soldadoensis to a sibaiyaensis is most consistent with sympatric speciation although certain elements of this transition are suggestive of a parapatric mechanism we postulate that the rapid evolution of the lptm taxa a sibaiyaensis and m allisonensis was fostered by a deepening of the nutrient depleted mixed layer alternatively the lptm morphotypes m allisonensis and a sibaiyaensis may have been extreme ecophenotypic variants arrayed along an intensified ecological gradient support for this latter interpretation is derived from the morphometric data which clearly show the morphological intergradation of the lptm taxa with their respective ancestors thus the morphologic diversification seen during the lptm may represent failed speciations both scenarios invoke a temporary steepening of clinal gradients in response to intensified oligotrophy the strong size dependencies displayed by the 18o and 13c signatures of m allisonensis and a sibaiyaensis suggest that photosymbiosis facilitated the evolutionary success of the morozovellids and acarininids during the lptm

a benthic foraminiferal record of paleocene sea level and trophic redox conditions at gebel aweina egypt we quantitatively analyzed benthic foraminiferal assemblages in order to reveal biotic and paleoenvironmental trends in the paleocene section of gebel aweina egypt on the southern tethyan shelf the first correspondence axis ranks taxa along an empirically derived bathymetric gradient with neritic taxa e g discorbis duwi and haplophragmoides walteri opposed to bathyal taxa e g nuttallides truempyi and gavelinella beccari ormis the estimated paleodepth as reflected by the various assemblages was mostly 200 m but varied between 50 m p3a np4 and 300 m p4 n p8 the resultant four relative sea level cycles appear to be at least of regional extent and may in part be eustatically controlled the second correspondence axis reflects trends in trophic and redox development low food high oxygen conditions prevailed during biochrons plc p3b np4 np5 and late p4 np8 when assemblages were mostly dominated by cibicidoides spp most oligotrophic conditions coincided with maximum paleodepth intermediate trophic levels were established during middle p4 np6 and early p5 np9 from the level of the latest paleocene benthic extinction event bee middle p5 and np9 onwards until biochron p6a np10 assemblages dominated by buliminids marked increased trophic levels and reduced ventilation probably resulting from enhanced surface productivity enhanced surface productivity along the southern tethyan margin started during biochron p4 and at least on some shelves intensified after the bee increasing productivity during the latest paleocene contrasts with global trends this may be expected during climatic warming and an expanding trophic resource continuum leading to regionally intensified eutrophy and oligotrophy high productivity through upwelling along the southern tethyan provides support for gcm predictions of intense wind stress in this region during the warm late to latest paleocene 1998 elsevier science b v

barium sio2 excess and p2o5 as proxies of biological productivity in the middle east during the palaeocene and the latest palaeocene benthic extinction event the distribution of barium and other elements related to biological productivity has been studied in two palaeocene sections from the middle east in the bathyal ben gurion section israel ba ba al2o3 15 concentrations are low in the range 0 04 to 0 3 in the lower palaeocene and very high 1 to 2 throughout most of the upper palaeocene in the neritic gebel aweina section in egypt ba values are low 0 1 throughout the entire palaeocene the ba enrichments at ben gurion and their correlations with increases in p2o5 and opaline silica and local and global 13c maxima indicate that upwelling and high productivity were important in this region during the late palaeocene the absence of ba enrichments in the shallower gebel aweina section probably reflects the strong depth dependence of biobarium deposition in the uppermost palaeocene at the level where the global benthic extinction event is registered ba concentrations in the ben gurion section increase to anomalous 6 which suggests that upwelling and possibly wind strengths intensified during this event the results speak against deep water formation in this region since downwelling and not upwelling is required

observational and model studies of the circulation in the gulf of tonkin south china sea 1 moored current measurements were made at one mooring site in the northern gulf of tonkin for about 1 year during 1988 1989 analyses were performed to examine characteristics and variability of tidal and subtidal flows rotary spectra showed two peaks at diurnal and semidiurnal periods with higher diurnal energy complex demodulations of diurnal and semidiurnal tidal currents indicated that the tidal current magnitudes varied significantly with seasons more energetic in the stratified summer than in the vertically well mixed winter the observed subtidal currents were highly correlated with the surface wind in winter but not in summer challenging the conceptual summertime anticyclonic circulation pattern derived using wind driven homogenous circulation theory the computed currents from a global ocean model were in good agreement with the observed currents similar to the current observations the model computed flow patterns were consistent with the conceptual wind driven circulation pattern in winter but opposite in summer process oriented experiments suggest that the summertime cyclonic circulation in the northern gulf of tonkin forms as a result of the combination of stratified wind driven circulation and tidal rectified inflow from qiongzhou strait the interaction between the southwest monsoon and buoyancy driven flow from hong river can significantly intensify the cyclonic circulation near the surface but its contribution to the vertically averaged flow of the cyclonic circulation is limited

atmospheric circulation upwelling and organic rich rocks in the mesozoic and cenozoic eras abstract by using the basic principles of atmospheric circulation and analogies from present circulation patterns it is possible to construct qualitative atmospheric circulation models on paleogeographic maps the wind patterns predicted by these models then serve as the basis for predicting the locations of ancient upwelling zones atmospheric circulation and upwelling models for seven geologic stages in the mesozoic and cenozoic were constructed and the distribution of the upwelling zones compared with the distribution of organic rich rocks for all time periods together the correlation was statistically significant when the individual time periods were analyzed separately the following pattern emerged significant correspondence between upwelling zones and organic rich rocks in the triassic middle early cretaceous to late cretaceous and middle paleogene to neogene no significant correspondence was found for the intervening times upwelling does not account for all organic rich rocks so called anoxic oceanic events and transgressions play an important role in their deposition it is suggested that upwelling contributes significantly to the pattern of organic rich rock distribution and is important in determining organic facies

a numerical study of wind induced near inertial oscillations over the texas louisiana shelf the wind induced near inertial oscillations over the texas louisiana shelf were studied using a two dimensional primitive equation model forced by an impulse of the surface wind numerical experiments reproduced the cross shelf structure of observed near inertial oscillations for a given spatially uniform impulse of the wind the model predicted the large near inertial oscillations that were surface intensified and characterized by a first baroclinic mode in the vertical the oscillations reached a maximum kinetic energy near the shelf break and decayed gradually toward the coast but rapidly offshore the magnitude and cross shelf distribution of the wind induced near inertial energy changed with wind direction effects of nonlinear advection on near inertial oscillations were largest near the shelf break and decreased both onshore and offshore where the bottom topography was gentle or flat they were stronger during the wind event and weaker after the wind ceased nonlinear interaction of tides and wind was weak on the shelf however it tended to provide a positive net contribution to near inertial currents for both cases where tides were in and out of phase with winds a simple theory suggests that the cross shelf variation of near inertial oscillations was controlled by the cross shelf gradient of surface elevation and the vertical gradient of reynolds stress

remote sensing evidence for baroclinic tide origin of internal solitary waves in the northeastern south china sea 1 evidence for baroclinic tide origin of internal solitary waves isws in the northeastern south china sea is presented based on 116 internal wave packets observed in satellite images from 1995 to 2001 these wave packets can be divided into two types a single wave isw packet containing only one isw with without an oscillating tail and a multiple wave isw packet composed of a group of rank ordered isws all of the 22 single wave isw packets occur in the deep water zone it is suggested that the isws instead of being generated by the lee wave mechanism are developed by nonlinear steepening of the baroclinic tides which are produced by the strong tidal currents flowing over a ridge in luzon strait this suggestion is verified by an ers 2 sar image which records such an evolution process from a baroclinic tide to a single isw in its spatial domain

current separation and upwelling over the southeast shelf of vietnam in the south china sea 1 the high resolution unstructured grid finite volume community ocean model fvcom was used to examine the physical mechanisms that cause current separation and upwelling over the southeast shelf of vietnam in the south china sea scs process oriented experiments suggest that the southwesterly monsoon wind is a key physical mechanism for upwelling in that area but not a prerequisite to cause current separation with no wind forcing current separation in summer can occur as a result of the encounter of a southward along shelf coastal current from the north and northeastward buoyancy driven and stratified tidal rectified currents from the southwest the southward current can be traced upstream to the hong river in the gulf of tonkin this current is dominated by semigeostrophic dynamics and is mostly confined to the narrow shelf along the northern vietnamese coast the northeastward currents are generated by tidal rectification and are intensified by the mekong river discharge and southwesterly monsoon wind forcing the dynamics controlling this current are fully nonlinear with significant contributions from advection and vertical turbulent mixing upwelling in the current separation zone can be produced by a spatially uniform constant wind field and can be explained using simple wind induced ekman transport theory this finding differs from previous theory in which the regional dipole wind stress curl is claimed as a key mechanism for current separation and upwelling in this coastal region our scs fvcom driven by the wind stress river discharge and tides is capable of reproducing the location and tongue like offshore distribution of temperature as those seen in satellite derived sea surface temperature imagery

stable isotope stratigraphy and paleoclimatology of the paleogene bighorn basin wyoming usa abstract climatic warming from the late paleocene into the early eocene had profound effects on atmospheric and marine circulation marine thermal gradients and benthic biota in addition marine carbon isotope values decreased substantially in both surface and deep waters because carbon is rapidly exchanged between reservoirs at the earth s surface such as marine surface water the atmosphere land plants and materials that obtain carbon from plants e g soil minerals and herbivores carbon isotope fluctuations provide time lines linking the marine and continental records we analyzed the carbon isotope composition of paleosol carbonates and mammalian tooth enamel from stratigraphic sections in northwestern wyoming carbon isotope correlation demonstrates that a short interval of extreme high latitude warming coincided precisely with the first appearance of several important modern mammalian orders in addition oxygen isotope analyses of fossils and paleosol carbonates provide information about climatic conditions on land in the paleogene we reconstructed the oxygen isotope composition of local meteoric water using biogenic minerals paleocene eocene meteoric water was significantly 18 o depleted indicating substantial loss of water vapor during its transport to the region soil temperature was calculated as a proxy for mean annual temperature assuming oxygen isotope equilibrium between soil carbonate and meteoric water calculated temperatures were plausible 10 25 c but highly variable prohibiting high resolution analysis of local temperature variations in response to global climatic warming

near inertial oscillations over the texas louisiana shelf wind induced near inertial oscillations over the texas louisiana shelf in spring and summer 1992 are described using the current and wind observations taken during the first year of the texas louisiana shelf circulation and transport processes study latex a rotary spectral analysis shows clockwise rotating energy peaks at near inertial frequencies for records from all current meter moorings after the suppression of principal tidal signals the vertical structure of near inertial oscillations is characterized by a first baroclinic mode with a near 180 phase difference between the upper mixed layer and the lower stratified layer the oscillations are intermittent with a modulation timescale of about 5 10 days they are surface intensified and have maximum values near the shelf break decaying gradually toward the coast but rapidly offshore near inertial oscillations appear to accompany a sudden change of the wind stress during frontal passages diagnostic analysis suggests that the large near inertial oscillations over the latex shelf are mainly generated by high frequency near inertial variation of the wind stress accompanying the passage of atmospheric fronts when the downward transfer of the near inertial energy to the deep stratified layer is small a simple mixed layer model forced by the observed wind stress provides a reasonable prediction of the near inertial currents in the mixed layer

stratigraphic and climatic implications of clay mineral changes around the paleocene eocene boundary of the northeastern us margin abstract kaolinite usually is present in relatively small amounts in most upper paleocene and lower eocene neritic deposits of the northern us atlantic coastal plain however there is a short period less than 200 000 k y in the latest paleocene upper part of calcareous nannoplankton zone np 9 when kaolinite dominated clay mineral suites replaced the usual illite smectite dominated suites during this time of global biotic and lithologic changes kaolinite increased from less than 5 of the clay mineral suite to peak proportions of 50 60 of the suite and then returned to less than 5 in uppermost paleocene lowermost eocene strata this kaolinite pulse is present at numerous localities from southern virginia to new jersey these sites represent both inner and middle neritic depositional environments and reflect input from several river drainage systems thus it is inferred that kaolinite rich source areas were widespread in the northeastern us during the latest paleocene erosion of these source areas contributed the kaolinite that was transported and widely dispersed into shelf environments of the salisbury embayment the kaolinite increase which occurred during a time of relatively high sea level probably is the result of intensified weathering due to increased temperature and precipitation the southern extent of the kaolinite pulse is uncertain in that uppermost paleocene beds have not been identified in the southern atlantic coastal plain the late paleocene kaolinite pulse that consists of an increase to peak kaolinite levels followed by a decrease can be used for detailed correlation between more upbasin and more downbasin sections in the salisbury embayment correlations show that more upbasin paleocene eocene boundary sections are erosionally truncated they have varying portions of the kaolinite increase and if present at all discontinuous portions of the subsequent kaolinite decrease as these truncated sections are disconformably overlain by lower eocene strata rapid erosional removal of large parts of the most kaolinite rich p e boundary clay deposits occurred by early eocene time erosion of the kaolinite rich p e boundary beds was enhanced during times of sea level fall when kaolinite rich sediments were redeposited to produce kaolinite spikes in basal beds of lower and middle eocene sequences that have little or no kaolinite elsewhere in the sequence in contrast more downbasin sites document only the upper decreasing part of the kaolinite pulse the absence of strata documenting the earlier kaolinite increase is attributed to slow sedimentation condensed interval as a result of a significant sea level rise that ponded most sediments in shallower waters combined with the probable subsequent erosional removal of these thin downbasin deposits by oceanic currents

the paleocene eocene transition in the marginal northeastern tethys kazakhstan and uzbekistan we studied two sections that accumulated during the paleocene eocene transition in shelf waters in the northeastern tethys stable carbon isotopic compositions of marine and terrestrial biomarkers are consistent with a 13c depletion in the oceanic and atmospheric carbon dioxide pools during the late paleocene thermal maximum lptm subzone p5b the 2 3 negative 13c excursion in planktic foraminifera coincides with minimum 18o values an incursion of transient subtropical planktic foraminiferal fauna and the occurrence of an organic rich sapropelite unit in uzbekistan which accumulated at the onset of a transgressive event biomarker distributions and hydrogen indices indicate that marine algae and bacteria were the major organic matter sources during the late paleocene subzones p4 and p5a the marginal northeastern tethys experienced a temperate to warm climate with wet and arid seasons most likely warm and humid climate initiated during the lptm subzone p5b and subsequently extended during the eocene zone p6 onto adjacent land areas of the marginal northeastern tethys

kuroshio intrusion and the circulation in the south china sea 1 the princeton ocean model is used to study the circulation in the south china sea scs and its seasonal transition kuroshio enters leaves the scs through the southern northern portion of the luzon strait the annually averaged net volume flux through the luzon strait is 2 sv into the scs with seasonal reversals the inflow season is from may to january with the maximum intrusion of kuroshio water reaching the western scs during fall in compensation of summertime surface offshore transport associated with coastal upwelling from february to april the net transport reverses from the scs to the pacific the intruded kuroshio often forms an anticyclonic current loop west of the luzon strait the current loop separates near the dongsha islands with the northward branch continuously feeding the south china sea warm current scswc near the shelf break and the westward branch becoming the south china sea branch of kuroshio on the slope which is most apparent in the fall the scswc appears from december to february on the seaward side of the shelf break flowing eastward against the prevailing wind diagnosis shows that the onshore ekman transport due to northeasterly monsoon generates upwelling when moving upslope and the particular distributions of the density and sea level associated with the cross shelf motion supports the scswc

climatic evolution on the southeastern margin of the tethys negev israel from the palaeocene to the early eocene focus on the late palaeocene thermal maximum during the early palaeocene zones p1 to p2 the southeastern tethyan margin experienced a warm and humid climate with high rainfall as indicated by the abundance of kaolinite within marine sedimentary rocks subsequently in zone p2 arid climatic conditions evolved in the coastal basins of the southern tethys margin as indicated by the gradual disappearance of kaolinite and the increased abundance of palygorskite and sepiolite arid climatic conditions persisted during the selandian and thanetian late palaeocene and reached a maximum in the ypresian early eocene during the late palaeocene thermal maximum warm climatic conditions were associated with increased aridity and led to sea surface warming though not bottom water warming as suggested by the planktic 18 o excursion observed at the zomet telalim basin negev israel strongly reduced surface productivity accompanied by unusually light 13 c are associated with the late palaeocene thermal maximum in the negev as well as globally

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

on the dynamics of the south china sea warm current 1 the south china sea warm current scswc flows northeastward over the shelf and continental slope in the northern south china sea scs this current persists in its northeastward direction in all seasons despite the fact that the annually averaged wind stress is decisively southwestward against it two major mechanisms have been proposed in previous studies one attributing it directly to the wind stress forcing within the scs and the other to the kuroshio intrusion through the luzon strait in this study we use a simple model to demonstrate that neither of them is the leading forcing mechanism instead the scswc is a source and sink driven flow induced by the taiwan strait current tsc a year round northward flow through the taiwan strait the two previously suggested mechanisms are important but secondary the model simulations show that the local wind stress alone would force a current in the opposite direction to the scswc blocking the kuroshio intrusion through the luzon strait on the other hand only weakens the scswc the scswc vanishes when the taiwan strait is closed in the model

manifold methods for assimilating geophysical and meteorological data in earth system models and their components abstract a novel manifold method of reconstructing dynamically evolving spatial fields is presented for assimilating data from sensor networks in integrated land surface subsurface oceanic lake models the method was developed based on the assumption that data can be mapped onto an underlying differential manifold in this study the proposed method was used to reconstruct meteorological forcing over lake michigan the bathymetry of an inland lake gull lake and precipitation over the grand river watershed in michigan in the first case study hourly meteorological forcing data were reconstructed and used to run a three dimensional hydrodynamic model of lake michigan and to quantify the improvement that results from the use of the new method in the second example the bathymetry of gull lake was reconstructed from measured scatter point data using the manifold technique a hydrodynamic model of gull lake was developed and refined using the improved bathymetry in the last case study improved daily participation data for a six year period over the grand river watershed were used as input to an integrated distributed hydrologic model all three examples illustrate the superior performance of the manifold method over standard methods in terms of accuracy and computational efficiency our results also indicate that using the cross validation technique to evaluate the performance of data reconstruction methods can lead to misleading conclusions about their relative performance

evidence of surface water oligotrophy during the paleocene eocene thermal maximum nannofossil assemblage data from ocean drilling program site 690 maud rise weddell sea 1 nannoplankton assemblages at ocean drilling program site 690 maud rise weddell sea experienced an abrupt and dramatic transformation at the onset of the paleocene eocene thermal maximum petm at 55 m y the major assemblage shift suggests a change from colder more productive surface waters to warmer more oligotrophic conditions significant restructuring of assemblages during the later part of the petm indicates that nannoplankton communities were not stable and that surface water conditions changed although they remained warm and oligotrophic combined with benthic foraminiferal assemblage data nannoplankton assemblage results suggest increased sequestration of nutrients in shelf environments and starvation of the open ocean although the petm was a short lived event it appears to have had long term effects on nannoplankton leading to the extinction of fasciculithus a dominant paleocene genus

environmental impact of volcanic margin formation late rift stage uplift and subsequent massive transient volcanism during breakup of rifted volcanic continental margins constrain paleoenvironments by modifying basin geometry and the composition of the atmosphere hydrosphere and thus biosphere on regional and global scales the early tertiary north atlantic breakup history shows that lava emplacement was accompanied by regional ashfalls and that extrusive complexes influenced paleogene oceanic and continental margin circulation and sedimentation temporal correspondence with the terminal paleocene deep sea extinction event and the earliest eocene greenhouse suggests a global impact possibly by enhanced atmospheric co 2 levels leading to polar warming and thereby changing patterns of deep water formation in this context transient subaerial volcanism at continental margins should be considered with the much discussed continental flood basalt provinces and oceanic plateaus

a case for a comet impact trigger for the paleocene eocene thermal maximum and carbon isotope excursion abstract we hypothesize that the rapid onset of the carbon isotope excursion cie at the paleocene eocene boundary 55 ma may have resulted from the accretion of a significant amount of 12c enriched carbon from the impact of a 10 km comet an event that would also trigger greenhouse warming leading to the paleocene eocene thermal maximum and possibly thermal dissociation of seafloor methane hydrate indirect evidence of an impact is the unusual abundance of magnetic nanoparticles in kaolinite rich shelf sediments that closely coincide with the onset and nadir of the cie at three drill sites on the atlantic coastal plain after considering various alternative mechanisms that could have produced the magnetic nanoparticle assemblage and by analogy with the reported detection of iron rich nanophase material at the cretaceous tertiary boundary we suggest that the cie occurrence was derived from an impact plume condensate the sudden increase in kaolinite is thus thought to represent the redeposition on the marine shelf of a rapidly weathered impact ejecta dust blanket published reports of a small but significant iridium anomaly at or close to the paleocene eocene boundary provide supportive evidence for an impact

coccolith sr ca records of productivity during the paleocene eocene thermal maximum from the weddell sea 1 a major perturbation of the global carbon cycle 55 million years ago believed to result from release of 1000 2000 gt of c from methane hydrates correlates with an intense but transient greenhouse warming event known as the paleocene eocene thermal maximum petm the rapid 105 years recovery of global temperatures reflects important negative feedbacks in the climate system and carbon cycle enhanced marine productivity may be one important feedback but indicators for productivity changes have yielded conflicting results here we use a new independent indicator sr ca in coccolith carbonate which covaries with the productivity of coccolithophorid algae to investigate the biotic response in the most complete petm deep sea record which was recovered at odp site 690 in the weddell sea in the dominant coccolithophorid genus toweius a large 40 sr ca increase immediately after the gas hydrate release signals a dramatic productivity increase productivity levels remained high for 60 000 years but decreased to pre event levels by 120 000 years after the gas hydrate release productivity levels during the petm are higher than observed at any other time in our 400 000 year record other coccolithophorid genera chiasmolithus and discoaster show a brief modest 25 sr ca increase increase in productivity that lags behind the methane event by 50 000 years and is within the range of productivity variation elsewhere in the record the timing of the toweius productivity increase agrees well with os isotope records of globally increased weathering intensity which may have provided higher nutrient fluxes to stimulate algal productivity if this type of productivity response occurred globally it would also be consistent with the timing of c drawdown that may have returned temperatures to near pre event levels

planktonic and benthic foraminiferal extinction events during the last 100 m y abstract five major planktonic and benthic foraminiferal extinction events occurred during the past 100 m y at the cenomanian turonian c t boundary at the cretaceous tertiary k t boundary in the latest paleocene in the late eocene and in the early middle miocene to clarify the character of the five events i estimated 1 paleo waterdepths and paleoenvironments where foraminifera were affected 2 the duration of each extinction event and 3 evaluated possible causes for each extinction event on the basis of recent literature these extinction events can be classified into three fundamentally different types 1 the mass extinction event at the k t boundary was abrupt and concentrated among surface dwelling species 2 extinctions at the c t boundary and during the latest paleocene were abrupt and mainly affected intermediate and deep water taxa over short periods 3 the late eocene and early middle miocene events affected surface and deep water species and involved stepwise or gradual extinctions over a long period 4 m y i attributed the extinction events to 1 a bolide impact for the k t event 2 a decrease in dissolved oxygen in intermediate and deep waters due to climatic warming for the c t and latest paleocene events and 3 long term global cooling for the late eocene and early middle miocene events the following relationships exist between the causes and types of extinction events 1 large extraterrestrial impacts strongly affected surface dwelling organisms in short term extinction events 2 intermediate and deep water low oxygen conditions induced by climatic warming have severely affected intermediate and deep water organisms over medium and short terms

the breaking and scattering of the internal tide on a continental slope abstracta strong internal tide is generated in the luzon strait that radiates westward to impact the continental shelf of the south china sea mooring data in 1500 m depth on the continental slope show a fortnightly averaged incoming tidal flux of 12 kw m 1 and a mooring on a broad plateau on the slope finds a similar flux as an upper bound of this 5 5 kw m 1 is in the diurnal tide and 3 5 kw m 1 is in the semidiurnal tide with the remainder in higher frequency motions turbulence dissipation may be as high as 3 kw m 1 local generation is estimated from a linear model to be less than 1 kw m 1 the continental slope is supercritical with respect to the diurnal tide implying that there may be significant back reflection into the basin comparing the low mode energy of a horizontal standing wave at the mooring to the energy flux indicates that perhaps one third of the incoming diurnal tidal energy is reflected conversely the slope is subcritical with respect to the semidiurnal tide and the observed

the blast in the past the rapidity and amount of carbon being released through human agency have been thought to be unprecedented not so it emerges from the evidence of anomalies in the ratios of carbon isotopes in an ocean core it seems that around 55 million years ago there was an equivalently swift and massive blast of carbon into the ocean and atmosphere the source was probably methane hydrates that are usually locked up in huge deposits on continental shelves

energy of nonlinear internal waves in the south china sea 1 four sets of adcp measurements were taken in the south china sea scs these results were combined with previous satellite observations and internal tide numerical model results analysis suggests that strong internal tides are generated in luzon strait propagate as a narrow tidal beam into the scs are amplified by the shoaling continental slope near tungsha island become nonlinear and evolve into high frequency nonlinear internal waves niw internal waves in the scs have geographically distinct characteristics 1 west of luzon strait the total internal wave energy eiw is 10 that predicted by garrett munk spectra egm levine 2002 there is no sign of niw 2 near tungsha island eiw 13 egm strong nonlinear and high harmonic tides are present repetitive trains of large amplitude niw appear primarily at a semidiurnal periodicity with their amplitudes modulated at a fortnightly tidal cycle the rms vertical velocity of niw shows a clear spring neap tidal cycle and is linearly proportional to the barotropic tidal height in luzon strait with a 1 85 day time lag consistent with the travel time of internal tides from luzon strait to tungsha island 3 at the northern scs shelfbreak eiw 4 egm single depression waves are found but no multiple waves packets are evident 4 on the continental shelf eiw 2 egm both depression and elevation niw exist

heat transport deep waters and thermal gradients coupled simulation of an eocene greenhouse climate for the first time a coupled general circulation model with interactive and dynamical atmospheric oceanic and sea ice components is used to simulate an eocene 50 ma greenhouse climate we introduce efficient ocean spin up methods for coupled paleoclimate modeling sea surface temperatures ssts and salinities evolve unconstrained producing the first proxy data independent estimates for these eocene climate parameters tropical and extratropical model predicted ssts are warmer than modern values by 3 and 5 c respectively salinity driven deep water formation occurs in the north atlantic and tethys the zonal average overturning circulation is weaker than modern eocene ocean heat transport is 0 6 pw less than modern in the northern hemisphere and 0 4 pw greater in the southern hemisphere the model predicted near modern vertical and meridional eocene temperature gradients imply that the dominant theory for maintaining low gradients increased ocean heat transport is incorrect or incomplete and other mechanisms should be explored

the seasonal variation of the intrusion of the philippine sea water into the south china sea the seasonal variation of the intrusion of the philippine sea water into the south china sea was studied by analyzing the historical hydrographic station data in the northern south china sea and the philippine sea water masses at 150 200 and 250 m were classified by discriminant analysis according to their temperature salinity characteristics at each depth most water in the study region was classified into two groups representing the philippine sea water and the south china sea water respectively the geographic distribution of water masses in the south china sea shows that the philippine sea water was present along the continental margin south of china between october and january a westward current in the northern south china sea in winter was inferred from the distribution of the intrusion water

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago

stratigraphy of late palaeocene events in the middle east implications for low to middle latitude successions and correlations we have investigated the upper palaeocene stratigraphical record in four sections in egypt and one in israel the sections are arranged on a depth transect across the southern tethyan margin in all sections a 13 c excursion and benthic foraminiferal extinctions coincide at a level within planktic foraminiferal zone p5 in three sections a bed sapropelic in two of the deeper profiles contains extraordinarily transient benthic and planktic foraminifera assemblages these planktic assemblages are dominated by acarinina and contain rare to common morozovella allisonensis and globanomalina luxorensis but unusually few other morozovella the extremely restricted stratigraphical range of m allisonensis to the lower part of the 13 c excursion enables 1 a three fold subdivision of zone p5 2 accurate correlation to the best sections spanning the 13 c excursion in the atlantic and pacific and 3 assessment of stratigraphical completeness over the 13 c excursion in other sub tropical successions discontinuities and especially dissolution intervals in many low to middle latitude marine successions elsewhere as in two middle east sections preclude an accurate correlation within the lower part of the 13 c excursion m allisonensis zone p5b three studied sections can provide the best coverage of the sequence of events over the onset and early part of the 13 c excursion in the middle east but as in most known sections probably none constitutes a complete upper palaeocene lower eocene record

cenozoic deep sea benthic foraminifers tracers for changes in oceanic productivity from late middle eocene through earliest oligocene high latitude regions cooled and by the end of the period continental ice sheets existed in antarctica diversity of planktonic microorganisms declined and modern groups of terrestrial vertebrates originated coeval faunal changes in deep sea benthic foraminifers have been related to cooling of deep waters and increased oxygenation cooling however occurred globally whereas species richness declined at high latitudes and not in the tropics the late eocene and younger lower diversity high latitude faunas typically contain common epistominella exigua and alabaminella weddellensis opportunistic phytodetritus exploiting species that indicate a seasonally fluctuating input of organic matter to the sea floor we speculate that the species richness gradient and increase in abundance of phytodetritus exploiting species resulted largely from the onset of a more unpredictable and seasonally fluctuating food supply especially at high latitudes

environmental perturbation in the southern tethys across the paleocene eocene boundary dababiya egypt foraminiferal and clay mineral records foraminiferal and clay mineral records were studied in the upper paleocene to lower eocene dababiya section egypt this section hosts the gssp for the paleocene eocene boundary and as such provides an expanded and relatively continuous record across the paleocene eocene thermal maximum petm deposition of illite smectite clay minerals is interpreted as a result of warm and arid conditions in the southern tethys during the latest paleocene benthic foraminiferal assemblages are indicative of seasonal variation of oxygen and food levels at the seafloor a sea level fall occurred in the latest paleocene followed by a rise in the earliest eocene foraminiferal diversity and densities decreased strongly at the p e boundary coinciding with the level of global extinction of benthic foraminifera bee and start of the carbon isotope excursion cie and petm in the lower cie the seafloor of the stratified basin remained nearly permanently anoxic and azoic a sudden increase in mixed clay minerals kaolinite and others suggests that warm and perennial humid conditions prevailed on the continent high levels of toc and phosphathic concretions in the middle cie are evidence for increased organic fluxes to the sea floor related to upwelling and to augmented continental runoff low densities of opportunistic taxa appeared indicating occasional ephemeral oxygenation and repopulation of the benthic environment the planktic community diversified although conditions remained poor for deep dwelling taxa an increase in illite smectite dominated clay association is considered to mark the return of a seasonal signature on climatic conditions during the late cie environmental conditions changed to seasonally fluctuating mesotrophic conditions and diverse and rich benthic and planktic foraminiferal communities developed post cie planktic faunas consisted of both deep and shallow dwelling taxa and buliminid dominated benthic assemblages reflect fluctuating mesotrophic conditions the frequent environmental perturbations during the cie petm at dababiya provided a rather specialized group of foraminiferal taxa i e anomalinoides aegyptiacus the opportunity to repopulate survive and subsequently dominate by a hypothesized capacity to switch to an alternative life strategy population dynamics habitat shift or different metabolic pathway the faunal record of dababiya provides insight into the cause and development of the bee various severe global changes during the petm e g ocean circulation caco3 dissolution productivity and temperature changes disturbed a wide range of environments on a geologically brief timescale explaining together the geographically and temporally variable character of the bee this allowed a number of specific but different foraminiferal assemblages composed of stress tolerant and opportunistic taxa to be successful during and after the periods of environmental perturbations associated with the petm

variability of internal tides and near inertial waves on the continental slope of the northwestern south china sea structure and variability of internal tides it and near inertial waves niw on the continental slope of the northwestern south china sea were investigated based on 9 month moored current observations from autumn to early summer in 2008 and 2009 the diurnal it kinetic energy dominant over that of semidiurnal tides is found to exhibit apparent seasonal variability strongest in summer and weakest in winter whereas the semidiurnal variance remained nearly uniform throughout the observation period moreover the diurnal it were more coherent i e phase locked to the astronomical forcing than the semidiurnal constituents coherent diurnal variance accounts for about 40 of diurnal motions but semidiurnal tides contain a much smaller fraction 10 of coherent motions further analysis demonstrates that the diurnal it are dominated by the first mode whereas the semidiurnal tides show a variable multimodal structure the second mode is dominant in summer and comparable to the first mode in spring and autumn but the first mode predominates in winter multimodal semidiurnal it are more influenced by varying stratification structures and background currents and thus exhibit highly incoherent and intermittent behavior which may wash out seasonal variability during their long propagation from the generation source the observed niw are seasonally independent and comparable to the semidiurnal motions during the passage of typhoon hagupit however the niw became the most energetic component of the inertia gravity waveband motions niw energy and shear were significantly enhanced and exceeded tidal counterparts by a factor of 2 to 3 in the upper layer

the impact of paleocene eocene boundary events on middle neritic benthic foraminiferal assemblages from egypt abstract a 25 m upper paleocene to lower eocene marly sequence exposed at gebel duwi quseir red sea coast of egypt provides a good opportunity for studying paleocene eocene p e boundary stratigraphy and events various bio eco and isotope stratigraphic correlations accurately delineate the position of the p e boundary i e the level of stable isotopic excursions and deep sea benthic extinctions in the middle part of this section within zones p5 and np9 in this paper the impact of p e boundary environmental perturbations on benthic foraminiferal communities of the shallow tethyan shelf is examined benthic foraminiferal assemblages from gebel duwi characterized by large frondicularia phosphatica and f nakkadyi in addition to a number of other neritic taxa but without any typical outer neritic bathyal taxa suggest middle neritic 75 100 m deposition throughout the studied interval and only minor relative sea level variations perhaps some 10 20 m across the boundary sea level appears to have been stable yet a distinct faunal turnover marks the p e boundary of this shallow site which in contrast to deep sea records is less abrupt being preceded by a gradual diversity decrease starting some four meters below the boundary moreover most exits are either local or just temporary and thus not true extinctions many lazarus taxa reappear at some point above the boundary while all but one of the disappearing taxa are known from other lower eocene neritic deposits in egypt in general benthic foraminiferal assemblages display low diversities and high dominance values notably anomalinoides aegyptiacus up to 74 suggesting high levels of environmental stress at the sea floor in combination with occasionally very high p b ratio s up to 98 p and generally laminated sediments the character of the benthic assemblage points to a strong influence of recurrent dysoxia and or anoxia we suggest that these resulted from surface eutrophication by intermittent coastal upwelling and reduced ventilation of the bottom environment although these conditions prevailed during most of the time interval studied they were most severe during the latest paleocene and early eocene when eutrophication intensified and the organic carbon flux to the sea floor increased enhanced atmospheric contrasts between the tethys seaway and the african continent resulting in intensified longshore tradewinds may have controlled these changes at the p e boundary the bottom environment became minimally ventilated perhaps due to reduced oxygen advection from deeper waters three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual decrease of environmental stress and a return to more normal conditions although the organic carbon flux to the sea floor remained high

tropical coupled rossby waves in the pacific ocean atmosphere system abstract gridded fields of topex poseidon sea level height slh and national centers for environmental prediction sea surface temperature sst and meridional surface wind msw anomalies are constructed monthly on a 2 grid over the pacific ocean for nearly 6 years from 1993 to 1998 time longitude diagrams of monthly slh sst and msw anomalies from 10 to 22 lat yield significant peak spectral energy density in zonal wavenumber frequency spectra for periods of 1 2 yr near the free rossby wave dispersion curve subsequently temporal and spatial filtering of these slh sst and msw anomalies finds them propagating westward over the interior tropical pacific ocean in fixed phase with one another significant squared coherence exists between filtered slh and sst sst and msw anomalies over the entire latitude band yielding significant phase differences ranging over 90 45 70 45 at 10 s and 14 lat and ranging over 90 45 0 45 at 18 and 22 lat over the entire latitude domain warm

mammalian community response to the latest paleocene thermal maximum an isotaphonomic study in the northern bighorn basin wyoming new stratigraphic and paleontological information from the mccullough peaks northern bighorn basin wyoming is incorporated into an isotaphonomic faunal database and used to investigate the impact of the latest paleocene thermal maximum and coincident earliest wasatchian immigration event on local mammalian community structure surface collections from willwood formation overbank deposits provide taphonomically consistent and stratigraphically resolved samples of the medium to large sized components of underlying mammalian communities rarefaction shows that the immigration event caused an abrupt and dramatic increase in species richness and evenness after this initial increase diversity tapered off to more typical wasatchian levels that were still higher than those in the preceding clarkforkian wasatchian immigrants were rapidly incorporated into the new community organization representing 20 of the taxa and 50 of the individuals immigrant taxa generally had larger body sizes and more herbivorous and frugivorous dietary habits compared to endemic taxa causing significant turnover in body size structure and trophic structure there was a significant short term body size decrease in many lineages that may have been prompted by the elevated temperatures and or decreased latitudinal thermal gradients during the latest paleocene thermal maximum rapid short term climatic change transient climates and associated biotic dispersal can have abrupt and long lasting effects on mammalian community evolution

the source and fate of massive carbon input during the latest paleocene thermal maximum lithologic faunal seismic and isotopic evidence from the blake nose subtropical western north atlantic links a massive release of biogenic methane 55 5 million years ago to a warming of deep ocean and high latitude surface waters a large perturbation in the combined ocean atmosphere carbon cycle the largest of the past 90 million years a mass extinction event in benthic faunas and a radiation of mammalian orders the deposition of a mud clast interval and seismic evidence for slope disturbance are associated with intermediate water warming massive carbon input to the global exogenic carbon cycle pelagic carbonate dissolution a decrease in dissolved oxygen and a benthic foraminiferal extinction event these events provide evidence to confirm the gas hydrate dissociation hypothesis and identify the blake nose as a site of methane release

paleocene and eocene kaolinite distribution in the south atlantic and southern ocean antarctic climatic and paleoceanographic implications abstract clay mineral associations of paleocene and eocene age have been examined in six drilled sequences from the southern south atlantic and southern ocean these sites are located to provide three depth transects across intermediate water masses widespread abundance of pedogenic smectite at all locations suggests globally warm climates and alternating wet and dry seasons on the adjacent continental margins including antarctica as was the case during the late cretaceous remarkably kaolinite is observed only in paleocene eocene sediments at the highest latitudes of these sites and must have originated from antarctica the restriction of kaolinite to the antarctic region is inferred to have resulted from especially higher rainfall there during the paleocene eocene relative to the lower latitude areas examined this inferred high rainfall is considered to have resulted from globally warm temperatures that increased poleward latent heat transport compensating for a strong heat deficit in the antarctic region relative to the tropics kaolinite was not observed in the latest cretaceous maastrichtian sediments of maud rise antarctica kaolinite first appears in the clay mineralogical assemblages in the earliest paleocene 64 to 64 5 ma at a time of relatively cool intermediate waters and before a warming trend of surface waters currents at intermediate water depths transported fine terrigenous sediments from the antarctica during the latest paleocene and early eocene 59 to 52 ma at a time when the oxygen isotopic strongly in east antarctica during the latest paleocene and early eocene 59 to 59 ma at a time when the oxygen isotopic data indicate maximum warmth of surface and intermediate waters of the southern ocean these are interpreted to reflect a paleocene maximum of antarctic rainfall this development peaked at 57 3 m close to the paleocene eocene boundary a time of maximum warmth based on oxygen isotopic data increased illite content and associated chlorite and random mixed layer clays at the end of the middle eocene 41 ma suggest local development of poorly weathered soils on antarctica favored by a cooling of the southern ocean coeval extension of kaolinite into shallower water depths and similar clay mineral associations in shallower and deeper sites indicate the development of cooler conditions led to an increasing influence of antarctic environments upon intermediate water masses at high latitudes

diurnal and semidiurnal internal tide energy flux at a continental slope in the south china sea 1 barotropic surface and baroclinic internal tides were measured at four mooring sites during a field investigation of acoustic propagation characteristics and physical oceanography in the northern south china sea the mooring positions were in a line moving up the shallow portion of a continental slope at water depths between 350 and 85 m using time series of temperature and velocity at several depths 1 month series of semidiurnal and diurnal species internal tidal energy flux vectors were computed for three sites with a 14 day series computed for the fourth shallow site the internal tides had a temporal signature that was not in complete accord with the barotropic tides showing an enhancement of diurnal internal tides with respect to semidiurnal bathymetric slope barotropic tidal fluid particle trajectories and scale of generation site versus internal tide wavelength are investigated as possible causes of the differing response of the species

palaeoenvironmental turnover across the palaeocene eocene boundary at the stratotype section in dababiya egypt based on benthic foraminifera the global stratotype section and point for the palaeocene eocene p e boundary was defined at dababiya quarry egypt at the base of the carbon isotope excursion cie we present the first detailed analysis of palaeocene eocene benthic foraminifera from dababiya in order to infer the palaeoenvironmental turnover across the p e boundary at dababiya the cie coincides with a major turnover in foraminiferal assemblages the last occurrence of angulogavelinella avnimelechi at the base of the cie may be correlated to the main phase of extinction of deep sea benthic foraminifera benthic foraminifera indicate that stressful conditions such as oxygen deficiency carbonate dissolution and changes in food supply persisted at the sea floor over most of the cie interval the main phase of recovery of benthic foraminifera is recorded c 250 cm above the p e boundary and it may be linked to increased productivity and oxygenation at the sea floor

rapid diversification of planktonic foraminifera in the tropical pacific odp site 865 during the late paleocene thermal maximum the planktonic foraminiferal generamorozovellaandacarininarapidly in 10 k y diversified during the late paleocene thermal maximum lptm giving rise to such morphotypes asm allisonensis new species m africana anda sibaiyaensis single specimen isotopicanalysisconfirmsthatm allisonensisanda sibaiyaensisarerestrictedtothelptm carbon isotope excursion recorded at ocean drilling program site 865 equatorial pacific ocean the short lived 50 to several 100 k y excursion taxa attest to the ephemeral effectsofthelptmonthecalcareousplankton single specimenoxygenisotopedatashow that evolution of m allisonensis and a sibaiyaensis was accompanied by migration to deeper water depths ancestralm velascoensisanda soldadoensiswere extremely rare or absent during the early stages of the lptm but immigrated back into the study area to coexist with their descendants in later lptm horizons photosymbiosis may have facilitatedthemorozovellidandacarininiddiversificationsduringtheoligotrophicconditionsof the lptm

mesoscale eddies in the south china sea observed with altimeter data 1 a composite time series 1993 2000 of sea surface height anomaly from several satellites is used to identify eddies in the south china sea scs the eddy lifetime radius strength and straight line travel distance are estimated altogether 58 anticyclonic eddies and 28 cyclonic eddies are identified for this period they are grouped into four geographical zones according to known eddy generation mechanisms and their statistics are discussed accordingly our geographical classification is a useful first step in gaining an overview of their generation

bolide summer the paleocene eocene thermal maximum as a response to an extraterrestrial trigger the standard paradigm that the paleocene eocene thermal maximum petm represents a threshold event intrinsic to earth s climate and connected in some way with long term warming has influenced interpretations of the geochemical climate and biological perturbations that occurred at this event as recent high resolution data have demonstrated that the onset of the event was geologically instantaneous attempts to account for the event solely through endogenous mechanisms have become increasingly strained the rapid onset of the event indicates that it was triggered by a catastrophic event which we suggest was most likely a bolide impact we discuss features of the petm that require explanation and argue that mechanisms that have previously been proposed either cannot explain all of these features or would require some sort of high energy trigger a bolide impact could provide such a trigger and in the event of a comet impact could contribute directly to the shape of the carbon isotope curve we introduce a carbon cycle model that would explain the petm by global warming following a bolide impact leading to the oxidation of terrestrial organic carbon stores built up during the late paleocene our intention is to encourage other researchers to seriously consider an impact trigger for the petm especially in the absence of plausible alternative mechanisms

benthic foraminiferal successions across late quaternary mediterranean sapropels abstract benthic foraminiferal records across late quaternary mediterranean sapropels s6 s5 and s1 are reviewed and re considered in the light of recent advances in foraminiferal ecology it is suggested that the main factor controlling the foraminiferal successions that occur immediately before and after sapropel deposition is the amount of time involved in the onset of anoxic conditions and in the re oxygenation of the benthic environment faunas dominated by deep infaunal taxa such as globobulimina and chilostomella reflect a very gradual decrease or increase of bottom water oxygenation post sapropel faunas dominated by small biconvex trochospiral taxa which are inferred to have a much more opportunistic life strategy are typical of a very rapid re oxygenation of the benthic environment after sapropel deposition the time involved in re oxygenation depends upon the mechanism causing sapropel formation the faunal succession found above sapropel s5 suggests a basin with a strong density gradient in the upper part of the water column during sapropel deposition followed by a rapid turnover of the following column and quick re oxygenation of the benthic environment in contrast the faunal succession above sapropel s6 suggests a water column with a more gradual density gradient deeper in the basin a progressive deepening of the halocline and a very slow increase of bottom water oxygenation

benthic foraminifera as proxies of organic matter flux and bottom water oxygenation a case history from the northern arabian sea abstract benthic foraminifera have been quantified in two sediment cores from a topographic high murray ridge in the northern arabian sea one core is from a station within the present day oxygen minimum zone omz the other from a station below the omz changes in the intensity of the omz linked to monsoonal climate variability had a strong impact on benthic foraminiferal composition and accumulation rates at the shallower omz station 920 m an intensification of the omz resulted in lower diversities and high dominances of low oxygen tolerant species the deeper station 1470 m was far less affected though at least once during the last 225 000 years the benthic faunal composition and accumulation rates show evidence for a deepening of the base of the omz to a level close to or even below 1470 m we suggest that percentages of miliolids can be used for rapid reconstruction of periods of increased ventilation in the northern arabian sea and are a promising proxy for tracing changes in bottom and pore water oxygenation in general omz conditions are characterised by high abundances of deep infaunal species and increased burial efficiency of organic matter the proportion of deep infaunal species appears to be a measure for the anoxic burial efficiency of organic matter and not a direct measure for the arriving flux at the seabed results furthermore show that benthic foraminiferal accumulation rates cannot be used as a proxy for surface water productivity under the prevalence of severe dysoxia