age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

effects of spatial discretization in ice sheet modelling using the shallow ice approximation this paper assesses a two dimensional vertically integrated ice model for its numerical properties in the calculation of ice sheet evolution on a sloping bed using the shallow ice approxi mation we discuss the influence of initial conditions and individual model parameters on the model s numerical behaviour with emphasis on varying spatial discretizations the modelling results suffer badly from numerical problems they show a strong dependence on gridcell size and we conclude that the widely used gridcell spacing of 20 km is too coarse the numerical errors are small in each single time step but increase non linearly over time and with volume change as a result of feedback of the mass balance with height we propose a new method for the calculation of the surface gradient near the margin which improves the results significantly furthermore we show that we may use dimension analysis as a tool to explain in which situations numerical problems are to be expected

paleoproductivity in the equatorial indian ocean for the last 260 000 yr a transfer function based on planktonic foraminifera a principal component analysis pca of planktonic foraminifera in surface sediment of the northern equatorial indian ocean defines two major assemblages the first one dominated by globigerinoides sacculifer g ruber globigerinella aequilateralis and globoquadrina conglomerata characterizes non upwelling areas the second dominated by globigerina bulloides g falconensis and globigerinita glutinata characterizes upwelling areas the distribution of planktonic foraminiferal species in the area is mainly related to primary production pp the pca applied to core md 900963 samples defines an alternation of the two assemblages through time a non upwelling one similar to that present in the core tops and an upwelling assemblage which contains in addition neogloboquadrina dutertrei globorotalia menardii and g crassaformis equatorial indian ocean core top samples are introduced as additional rows in the pca calculated on core md 900963 samples and a transfer function is constructed correlating factorial coordinates of core tops within the range of changes occurring in core md 900963 with estimated pp values applied to the last 260 000 yr the transfer function indicates that the precession is the major orbital forcing on equatorial productivity changes and that annual pp increases by about 85 from interglacial to glacial interstadials these results are in agreement with an independent productivity index based on coccoliths direct impact of insolation on equatorial productivity could be explained by the link between southern oscillation and intensity of zonal winds which seem to lead the productivity of surface waters at the location of core md 900963

modelling a paleo valley glacier network using a hybrid model an assessment with a stokes ice flow model modelling paleo glacier networks in mountain ranges on the millennial timescales requires ice flow approximations hybrid models calculating ice flow by combining vertical shearing shallow ice approximation and longitudinal stretching shallow shelf approximation have been applied to model paleo glacier networks on steep terrain yet their validity has not yet been assessed quantitatively moreover hybrid models consistently yield higher ice thicknesses than last glacial maximum geomorphological reconstructions in the european alps here we compare results based on the hybrid parallel ice sheet model pism and the stokes model elmer ice on the rhine glacier a catchment of the former european alpine icefield for pism we also test two magnitudes of flux limitation in a scheme that reduces shearing velocities we find that the flux limitation typically used in pism yields significantly reduced shearing speeds and increases ice thicknesses by up to 500 m partly explaining previous overestimations however reducing the ice flux limitation allows the hybrid model to minimize this mismatch and captures sliding speeds ice thicknesses ice extent and basal temperatures in close agreement with those obtained with the stokes model

tropical sea surface temperatures during the last glacial period a view based on alkenones in indian ocean sediments abstract the quantification of tropical temperatures during the last glacial cycle 0 150 kyr bp is a controversial issue since different proxies seem to provide conflicting informations to obtain a complementary point of view we use the alkenone method to estimate sea surface temperatures and focus our work on deep sea sediments recovered from the tropical indian ocean we present alkenone data obtained in two cores which cover in detail the last deglaciation and in about twenty cores distributed between 20 s and 20 n that were chosen to evaluate the temperature contrast of the last glacial interglacial transition our results indicate that indian ocean tropical temperatures remained an average within 1 5 2 5 c of their present values during the last glaciation at 10 n the last deglaciation is characterized by two warming steps which is similar to the classical deglacial chronology observed in the north atlantic area at 20 s the deglacial warming occurred at ca 15 cal kyr bp lagging significantly 5 4 kyr behind the antarctic warming but in phase with northern hemisphere time series

upwelling rebound ephemeral secondary pycnoclines and the creation of a near bottom wave guide over the monterey bay continental shelf several sequential upwelling events were observed in fall 2012 using measurements from the outer half of the continental shelf in monterey bay during which the infiltration of dense water onto the shelf created a secondary near bottom pycnocline this deep pycnocline existed in concert with the near surface pycnocline and enabled the propagation of near bottom cold semidiurnal internal tidal bores as well as energetic high frequency nonlinear internal waves of elevation iwoe the iwoe occurred within 20 m of the bottom had amplitudes of 8 24 m periods of 6 45 min and depth integrated energy fluxes up to 200 w m 1 iribarren numbers 0 03 indicate that these iwoe were nonbreaking in this region of the shelf these observations further demonstrate how regional upwelling dynamics and the resulting bulk cross margin hydrography is a first order control on the ability of internal waves at tidal and higher frequencies to propagate through continental shelf waters

nonlinear internal waves in the south china sea observation of the conversion of depression internal waves to elevation internal waves 1 the conversion of depression nonlinear internal solitons to elevation internal waves has been observed twice at the south china sea continental shelf break shipboard x band radar tow yo ctd adcp and high frequency acoustic flow visualization of the process are presented the data focuses on up slope propagation of depression internal solitons from a water depth of 264 m to a water depth of 110 m dissipation by large amplitude shear instabilities was observed the kinetic energy density was found to be a decreasing monotonic function of range with an energy dissipation rate coefficient of 0 063 km 1 the rate of energy dissipation over the 16 5 km soliton propagation path was 0 17 w m m simple numerical models of the waveform evolution are qualitatively compared to the observations the observations extracted scale parameters and dissipation rates should be useful for testing a variety of evolution equation representations of internal soliton propagation

planktonic foraminifera of the northern indian ocean distribution and preservation in surface sediments in the northern indian ocean planktonic foraminiferal tests accumulate in a wide variety of surface water environments and depositional settings this variability enables us to isolate the effects that surface water ecology and differential dissolution have on the distribution of planktonic foraminifera from 251 geographically widespread surface sediment samples foraminiferal abundance varies from 0 to 104 whole foraminifera in the greater than 150 m fraction per gram dry sediment values 10 characterize the three deep basins of the equatorial indian ocean and the western bay of bengal foraminiferal tests are most abundant on carbonate covered ninety east and carlsberg ridges absolute abundance patterns are mainly controlled by non ecological processes variations in dissolution resistant species rsp with water depth reveal that the foraminiferal lysocline fl varies regionally the fl is deepest 3 800 m in the equatorial region rises abruptly to 3 300 m in the arabian sea and varies from 2 600 m to near 2 000 m moving northward in the bay of bengal deep samples with anomalously low rsp 30 suggest redeposition systematic geographic and depth related variation is observed for the 17 most abundant foraminiferal species dissolution resistant species g menardii g tumida g dutertrei p obliquiloculata generally exhibit a rapid and continuous increase in relative abundance at and below the fl susceptible species g ruber g bulloides g glutinata for example exhibit a rapid and continuous decrease in relative abundance at and below the fl moderately susceptible species g conglobatus g aequilateralis g conglomerata for example rapidly increase in abundance at the fl and systematically decrease with depth below the fl principal components analysis pca of faunal data from minimally dissolved 30 rsp samples reveals important ecologically related species intercorrelations the major biogeographic gradient is the negative covarying relationship between ag bulloides g glutinata species pair and a grouping ofg sacculifer g conglobatus g aequilateralis andg ruber pca of all samples demonstrates how differential dissolution alters this and other species relationships species groupings that incorporateg ruber g menardii andg dutertrei are particularly affected by dissolution comparison of average faunal data from minimally dissolved samples in the northern indian ocean with similar samples from other tropical regions suggests varying environmental factors produce distinct faunas within the tropical ocean for example g bulloides g falconensis andg hexagona are significantly more abundant in northern indian ocean surface sediments while such species asg ruber g sacculifer g dutertrei andp obliquiloculata dominate in other tropical regions

fertility tracers and monsoon forcing at an equatorial site of the somali basin northwest indian ocean abstract temporal changes in biological and isotopic tracers have successfully been used to monitor monsoon variability in the arabian sea convincing evidence that fertility indicators such as the relative abundance of the planktic foraminifer globigerina bulloides and sio 2 and ba fluxes can monitor monsoon changes has also been published time series of the 13 c content of the thermocline foraminifer neogloboquadrina dutertrei and of an upwelling radiolarian index uri have been used to reconstruct upwelling changes in the somali basin at 5 n for the last 160 kyr in order to establish a reference site for comparison with other upwelling and or fertility records from the same area a time series of 8 climatic and fertility proxies 13 c content of n dutertrei and globorotalia menardii percentages of g bulloides and of a thermocline foraminiferal group minimal 18 values of globigerinoides sacculifer n dutertrei and g menardii are investigated in the spectral domain for the last 360 kyr at a site located at the equator and outside the somali upwelling centers core md 85668 chronostratigraphies for these records are developed by correlation of oxygen isotope record of g sacculifer to the martinson standard stacked benthic oxygen isotope record the temporal resolution of the data is between 2 and 5 kyr cross spectral comparisons with etp eccentricity tilt precession composite signal were used to estimate coherences in conjunction with phase relationships and to quantify relationships between fertility and climatic indicators the timing of fertility indicator cycles at the equator shows little obliquity band or no other orbital bands coincidence with monsoon proxies of the arabian sea at the equator fertility responses are dissociated and present important leads or lags with etp signal at the three orbital bands with the exception of the thermocline foraminifera in phase with maximum eccentricity due to significant leads with etp in the timing of 13 c minima and uri cycles no relationships with the northern hemisphere radiation can be deduced at the obliquity and precessional frequency bands thermocline foraminifera cycles display significant lag with etp and ice volume minima which suggests that radiation is not the sole forcing mechanism global climatic and ice volume changes may be an important forcing mechanism for these fertility proxies the g bulloides record is more complicated with cycles in phase with arabian sea monsoon proxies at the obliquity band and 18 o minima at the precession frequency it appears that at the equator the southwest monsoon winds are not the main force driving radiolarian and foraminiferal productivity

the importance of the oxygen minimum zone and sediment geochemistry in the distribution of recent benthic foraminifera in the northwest indian ocean abstract the relationship between the distribution of benthic foraminifera and sediment type and depositional environment in the arabian sea is discussed the benthic foraminiferal fauna were sampled in nineteen recent surface sediment samples and geochemical variables of the sediment of the same samples were measured the water depths for the box core samples varies from 440 to 4040 m a total of 103 species and six species complexes were identified the geochemical properties were found to correspond well to the sediment type and depositional environment and six different sediment depositional environment types could be distinguished analysis of the benthic foraminiferal fauna reveals specific faunal assemblages that are closely related to these sediment depositional environment types

direct reconstruction of glacier bedrock from known free surface data using the one dimensional shallow ice approximation abstract glaciers are an important component of the climate system that respond sensitively to climate change small glaciers respond more quickly to changing weather patterns compared to large polar ice sheets and ice caps that make them ideal to study climate variability this study relates to the numerical reconstruction of the glacier bed in order to generate basal boundary data for ice flow models bedrock elevation is a paramount input parameter in glacier flow modeling to accurately capture its flow dynamics but is difficult to measure we present an easy to implement direct numerical and analytical methodology to infer the bedrock geometry under glacial ice from the knowledge of the free surface elevation or the free surface velocity in one space dimension the numerical and analytical methods are both based on the shallow ice approximation and require the time series of the surface mass balance distribution moreover the analytical method requires the knowledge of the glacier thickness at one arbitrary location numerical benchmark test cases are used to verify the suitability and applicability of the algorithms and a sensitivity analysis demonstrates the robustness of the method

sea surface temperature and productivity records for the past 240 kyr in the arabian sea abstract deep sea sediments of two cores from the western ty93 929 p and the southeastern md900963 arabian sea were used to study the variations of the indian monsoon during previous climatic cycles core ty93 929 p was located between the sw monsoon driven upwelling centres off somalia and oman which are characterized by large seasonal sea surface temperature sst and particle flux changes by contrast core md900963 was situated near the maldives platform an equatorial ocean site with a rather small sst seasonality less than 2 c for both cores we have reconstructed sst variations by means of the unsaturation ratio of c37 alkenones which is compared with the 18o records established on planktonic foraminifera in general the sst records follow the 18o variations with an sst maximum during oxygen isotope stage 5 5 the last interglacial at about 120 130 kyr and a broad sst minimum during isotope stage 4 and 3 3 approximately 40 50 kyr the sst difference between the holocene and the last glacial maximum lgm is of the order of 2 c in both cores the ssts during isotope stage 6 are distinctly higher by 1 2 c than the cold sst minima during the last glacial cycle lgm and stage 3 to reconstruct qualitatively the past productivity variations for the two cores we used the concentrations and fluxes of alkenones and organic carbon together with a productivity index based on coccolith species florisphaera profunda relative abundance within each core there is a general agreement between the different palaeoproductivity proxies in the southeastern arabian sea core md900963 glacial stages correspond to relatively high productivity whereas warm interstadials coincide with low productivity all time series of productivity proxies are dominated by a cyclicity of about 21 23 kyr which corresponds to the insolation precessional cycle a hypothesis could be that the ne monsoon winds were stronger during the glacial stages which induced deepening of the surface mixed layer and injection of nutrients to the euphotic zone by contrast the records are more complicated in the upwelling region of the western arabian sea core ty93 929 p this is partly due to large changes in the sedimentation rates which were higher during specific periods isotope stages 6 5 4 5 2 3 and 2 unlike core md900963 no simple relationship emerges from the comparison between the 18o stratigraphy and productivity records the greater complexity observed for core ty93 929 p could be the result of the superimposition of different patterns of productivity fluctuations for the two monsoon seasons the sw monsoon being enhanced during interglacial periods whereas the ne monsoon was increased during glacial intervals a similar line of reasoning also could help explain the sst records by the superimposition of variations of three components global atmospheric temperature and sw and ne monsoon dynamics

late pleistocene variability of arabian sea summer monsoon winds and continental aridity eolian records from the lithogenic component of deep sea sediments the modern indian ocean summer monsoon is driven by differential heating between the asian continent and the indian ocean to the south this differential heating produces a strong pressure gradient which drives southwest monsoon winds during june july and august satellite and meteorological observations aerosol measurements sediment trap studies and mineralogical studies indicate an atmospheric mode of transport for modern lithogenic sediments in the northwest arabian sea analyses of lithogenic grain size and mass accumulation rate mar records from the owen ridge indicate that eolian transport has been the primary mode of transport for the past 370 kyr visual inspection shows that the mar record is positively correlated with global ice volume as indicated by the marine 18o record in contrast the grain size record varies at a much higher frequency showing little correlation to either the mar or the 18o records spectral analyses confirm these relationships indicating that the lithogenic grain size and mar records are coherent only over the precession band whereby the grain size leads the mar by 124 8 kyr we conclude that an eolian transport mechanism is the only mechanism that allows for this phase difference and at the same time is supported by comparison of the grain size and mar with independent eolian records we use lithogenic grain size as a paleoclimatic indicator of summer monsoon wind strength and lithogenic mar as a paleoclimatic indicator of source area aridity these interpretations are supported by comparison of the lithogenic records to independent indicators of wind strength globigerina bulloides upwelling record and aridity a loess record from central china such comparisons indicate high coherence and zero phase relationships our work supports the findings of previous studies which have documented the link between monsoon strength and the earth s axial precession cycles both the lithogenic mar and the grain size records have high coherency with precessional insolation maximum lithogenic mar source area aridity is in phase with 18o global ice volume and leads maximum precessional insolation by 88 6 kyr we attribute this lead to the influence of glacial conditions on the aridity and therefore the deflation potential of the source areas maximum lithogenic grain size summer monsoon wind strength lags maximum precession by 148 9 kyr we attribute this lag both to the influence of global and or local ice volume and to the availability of latent heat from the southern hemisphere indian ocean the two of which combine to determine the strength of the indian ocean monsoon

instability and cross boundary layer transport by shoaling internal waves over realistic slopes internal solitary and solitary like waves isw play an important role in mixing and sediment resuspension in naturally occurring stratified fluids primarily through various instabilities and wave breaking mechanisms when shoaling into shallow waters waves of depression may either fission into a packet of waves of elevation over mild slopes or break over steep slopes the fissioning process is generally considered a less efficient transport and resuspension mechanism compared to wave breaking since very little turbulent mixing or energy dissipation occurs during this process in the present work however we found that this is not always the case at least in the particular context of isw boundary layer interaction using high resolution numerical simulations performed in a domain representing a tilted laboratory tank we found that boundary layer instability in the form of a separation bubble consistently occurs during the fissioning process the separation bubble is generated beneath the wave of elevation that emerges from the fissioning process and is vitally influenced by currents induced by the leading wave of depression as the waves shoal further the growth and breakdown of the separation bubble leads to significant cross boundary layer transport the results suggest that the fissioning process which occurs over a considerable geographical region in the ocean can be as efficient as wave breaking when it comes to cross boundary layer transport

future fluctuations of mer de glace french alps assessed using a parameterized model calibrated with past thickness changes simulations of glacier evolution are needed to assess future changes in the runoff regime of mountain catchments a simplified parameterized model is applied here to simulate future thickness changes and glacier retreat of mer de glace french alps a normalized thickness change function describing the spatial distribution of surface elevation changes as a function of elevation has been determined the model reveals that under present climatic conditions mer de glace will continue to shrink dramatically in the coming decades retreating by 1200 m between now and 2040 the method has certain limitations related to the uncertainties of the normalized function based on thickness change data an error of 10 in the normalized function leads to uncertainties of 46 30 and 18 in mer de glace front surface area and glacier wide mass balance changes respectively in 2040 because the difference of the normalized function largely exceeds 10 from one glacier to another even within a given glacier size class and elevation range it would be very risky to extrapolate the normalized function to unmeasured glaciers consequently the method is applicable only on glaciers where past surface elevation changes are well constrained

planktonic foraminiferal assemblages in surface sediments from the southwest african continental margin abstract the relative abundance and distribution of planktonic foraminifera species on the southwest african continental margin have been determined from 152 surface sediment samples of the 23 recorded taxa only 8 make a significant contribution to the foraminiferal assemblages individual species proportions are closely related to the surface water hydrography of the benguela system and the associated upwelling phenomena three foraminiferal assemblages can be distinguished by correlation analysis on the abundances of the major taxa species composition of these assemblages range from polar taxa in the upwelling area left coiling neogloboquadrina pachyderma and globigerina quinqueloba to transitional taxa in the offshore oligotrophic environment globorotalia inflata and globorotalia truncatulinoides globigerina bulloides and right coiling neogloboquadrina pachyderma are preferentially distributed in the highly productive intermediate zone of the benguela system where upwelled and oligotrophic offshore waters mix variability of the hydrological processes upwelling intensity strength of the frontal features may be inferred from frequency variations of individual species and diversity patterns

seasonal changes in the isotopic composition of planktonic foraminifera collected in panama basin sediment traps abstract isotopic analyses have been made on five species of planktonic foraminifera collected in two deployments of parflux mark ii time series sediment traps in the panama basin the automated sampling system on the traps provided 4 one month samples from 29 july to 16 november 1979 and 6 two month samples from december 1979 to november 1980 the 18o values of globigerinoides ruber and globigerinoides sacculifer in this region are primarily affected by a low salinity surface layer that forms during the early winter these species each show a 1 total range in 18o the 18o values of the colder water species globorotalia menardii neogloboquadrina dutertrei and globorotalia theyeri show smaller seasonal changes in 18o the 13c values of g ruber and g sacculifer exhibit small seasonal changes 0 35 and 0 4 respectively despite large seasonal changes in surface water productivity the colder water species exhibit only slightly larger changes in 13c up to 0 55 throughout the year all colder water species exhibit minimum or near minimum 13c values during february and march which is the period of maximum upwelling and primary productivity seasonal variations in the flux of foraminifera in the water column at this location will have only a small effect on the isotopic composition of the sediment assemblage extreme values of 18o and 13c do not occur during the periods which are associated with the high flux of foraminiferal tests

dynamic behaviour analysis of glacier de saint sorlin france from 40 years of observations 1957 97 mass balance and dynamic measurements carried out on glacier de saint sorlin since 1957 provide a good opportunity to study the dynamics of this glacier ice flow analysis shows that dynamic changes have been important over the last 40 years and that these changes are not consistent with the concepts usually used in glacier modelling present velocities are larger than the 1960 velocities although the thickness decreased everywhere 10 30 m in the ablation zone a simple numerical ice flow model which does not include longitudinal stress gradients has been used to investigate these phenomena this model allows us to infer the sliding velocity from observed surface and calculated deformation velocities we conclude that 1 the sliding velocity cannot be described by weertman analysis or empirical relations which link the sliding to the thickness and surface slope 2 the inferred sliding velocity is uniform over at least half of the glacier and 3 there is no clear link between the sliding process and the quantity of water coming from surface ablation furthermore it may not be reasonable to calibrate model flow parameters from geometry changes because the surface geometry is relatively insensitive to velocity changes over some decades

dynamics of the monsoon in the equatorial indian ocean over the last 260 000 years abstract the coccolithophorids are excellent indicators of the variations in ocean productivity as an example the relative abundance of florisphaera profunda a species which lives exclusively in the deepest part of the photic zone constitutes a reliable monitor of the depth of the nutricline as a function of climatic variability productivity in the indian ocean is closely linked with the monsoon its intensity affects the depth of the mixing zone which deepens as the wind stress increases during the monsoon season the nutricline is shallow resulting in a higher productivity the variations in composition of coccolith assemblages in well dated oceanic sediments allows to describe the dynamics of productivity and therefore the fluctuation of the monsoon intensity core md900963 was retrieved in the equatorial indian ocean east of the maldives at a water depth of 2400 m a precise chronology was established by fine tuning the high resolution 18o record with the specmap stack coccoliths were counted from samples taken at 10 cm intervals in the core providing a resolution of 2000 years for the last 260 000 years the productivity estimates made from coccolith counts show that productivity varied greatly in the maldives area during this time the variations of the coccolith productivity index match the variations of the organic carbon content in the sediment spectral analysis reveals strong precessional cycles and weak obliquity and eccentricity cycles this implies that the solar radiation has a dominant effect on the monsoon variability south of india the productivity maxima occur during even numbered 18o stages this may indicate that the productivity events are related to increase of the winter monsoon however the analysis of the phase between the palaeoproductivity and seasonal solar radiation curves calculated for the past 260 000 years suggest an alternative hypothesis the westerlies which blow in april in the maldives area there the onset of the monsoon is in advance on the arabian sea would have a major effect on productivity since the insolation curve of the end of march at 5 n is in perfect phase with the paleoproductivity record for the last 260 000 years

improvement of a 2 d sia ice flow model application to glacier de saint sorlin france a number of improvements have been made to an existing two dimensional ice flow model applied to an alpine glacier analysis of the results of the existing model revealed several shortcomings the first concerns the lack of mass conservation of the applied alternating direction implicit adi scheme a semi implicit si scheme is therefore proposed and the effects on mass conservation assessed by a comparison with the adi scheme the comparison is first carried out with a simple theoretical glacier for which the improvement is significant concerning the real case of glacier de saint sorlin france the initial deviation in mass conservation was much less pronounced such that the new scheme although improving mass conservation does not significantly change the modelled dynamics however other shortcomings that have a more profound impact on the modelling of glacier behaviour have been identified the ice thickness may become negative over some gridpoints leading to an inconsistency the problem is partly resolved by incorporating extra checks on critical gridpoints at the glacier border finally with the help of ice particle tracking unrealistic ice settlement above the bergschrund has been identified as the main reason for spurious dynamic effects and has been corrected

subsurface and deeper ocean remote sensing from satellites an overview and new results satellite remote sensors cannot see far beneath the surface layers of the ocean yet many important ocean processes and features are located well below the surface and at considerable depths examples include mediterranean eddies meddies mixed layer depth internal waves and bottom topography deeper ocean remote sensing is becoming even more important because recent data seem to indicate that the deeper ocean is responding to climate variability and change many of these subsurface phenomena have surface manifestations which can be interpreted with the help of models to derive key parameters of deeper ocean processes the objective of this paper is to provide an overview of satellite remote sensing and modeling techniques which enable scientists to characterize subsurface and deeper ocean processes and features and to present some new results

seasonal variation of solitary wave properties in lake constance 1 the properties of internal solitary waves isws depend on the stratification of the water body in most climatic regions the stratification in lakes and oceans varies during the year and hence the properties of the isws can also be expected to change over the seasons on the basis of a long term temperature time series recorded over 6 years this paper investigates seasonal changes in the characteristic properties of isws in lake uberlingen a subbasin of lake constance a large number of isws with amplitudes ranging from 3 m to 30 m were identified more than 15 of the leading isws of a wave train were associated with density inversions often indicating shear instabilities or trapped cores for all waves the propagation depth and the value of a nonlinearity index nlp providing the degree of nonlinearity were determined propagation depth being the rest height of the isotherm undergoing maximum displacement and nlp the ratio between wave amplitude and propagation depth the index nlp was found to be a good parameter for predicting the occurrence of inversions the statistical analysis of the wave properties derived from the observations revealed that the degree of nonlinearity of the isws changes with season complementary to the statistical analysis the seasonally averaged isw properties were compared with wave prototypes obtained numerically from the dubreil jacotin long djl and the stratified korteweg devries kdv models the simulations indicate that the typical stratification and its seasonal variation are responsible for the degree and the seasonality of nonlinearity of the isws

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

evolution of a shoaling internal solitary wavetrain 1 field observations of an internal solitary wavetrain impacting a shoaling bottom are presented measurements of the spatio temporal characteristics of the shoaling waves are given as well as estimations of the mixing they may have caused upon impact the observations are discussed in the context of numerical simulations laboratory experiments and hypotheses recently raised on the origin and evolution of internal solitary waves in coastal environments

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

three dimensional hindcast simulation of internal soliton propagation in the asian seas international acoustics experiment area 1 internal solitary waves referred to as solitons are common occurrences in the south china sea the asian seas international acoustics experiment asiaex experiment was carried out in april may 2001 to perform measurements on these solitons which are often highly energetic having isopycnal displacements well over 100 m and phase speeds greater than 2 5 m s of particular interest is the interaction of a soliton with the sloping shelf bottom that occurs as the soliton shoals to water depths less than its wave height observations during the experiment show that at such shallow depths a soliton undergoes strong refraction and transformation in this article we present hindcast simulation of a particular soliton observed during the experiment using a fully nonlinear nonhydrostatic three dimensional model and the actual bathymetry from the asiaex area the computation begins with the soliton at a distance about 100 km from the shelf and obtains the propagation and evolution of the soliton over the shelf slope the three dimensional hindcast is able to reproduce the refraction of the soliton propagation observed during the experiment as well as the propagation speed and direction in the range observed the final nonlinear transformation of the soliton from symmetrical to skewed elongated waveform is also obtained in the model consistent with the observations the hindcast simulation reveals that the relative position of soliton s vorticity core to the local water depth is a crucial indicator of the onset of transformation and formation of elevation waves

glacial to interglacial contrasts in the northern indian ocean differences between the 18o 16o ratios of planktonic foraminifera deposited during the last glacial maximum about 18 000 yr ago and those deposited during the holocene show that in the indian ocean the south west monsoon was weaker than today but that the north east monsoon was stronger the upwelling observed in modern conditions along the southern coast of arabia had disappeared because of the low speed of the southwestern winds during glacial summers the reduction in rainfall and runoff over the continent caused a reduction of the salinity gradient in the bay of bengal and along the western coast of india increased precipitation fell on the sea south of 10 n while strong evaporation over the northernmost arabian sea produced an enhanced salinity gradient in that area

multimodal internal waves generated over a subcritical ridge impact of the upper ocean stratification abstractinteraction of barotropic tides with subsurface topography is vital to ocean mixing yet the behavior of large amplitude nonlinear internal solitary waves isws that can cause strong mixing remains poorly understood especially that of higher mode and multimodal internal waves therefore a 2 5 dimensional nonhydrostatic model with adjustable vertical resolution was developed to investigate effects of upper ocean stratification on tidally induced multimodal internal waves and to show how they are generated by the subcritical ridge where only upward propagating internal wave beams iwbs are present the effects of the stratification on properties and characteristics of the excited iwbs and on the energy partition of the radiated mode 1 and mode 2 internal waves were investigated based on the model results higher modes of internal waves can also be effectively generated in the iwbs by the subcritical topography and the contribution to iwbs from higher modes increases with the upper ocean stra

late pliocene and pleistocene climatic oscillations and monsoon upwelling recorded in sediments from the owen ridge northwestern arabian sea

estimating parameters of a two layer stratified ocean from polarity conversion of internal solitary waves observed in satellite sar images this paper presents a method for estimating parameters of a two layer stratified ocean using satellite sar images according to weak nonlinearity shallow water theory internal solitary waves isws in stratified oceans may be either depression or elevation waves depending on the sign of the quadratic nonlinearity coefficient in the kdv equation it has been confirmed that isws can convert their polarity when passing through a turning point where the quadratic nonlinearity coefficient changes sign for a two layer stratified ocean the turning point is located where the upper and lower layer depths are equal the authors suggest that depression elevation and broadening isws can be discerned according to their different signatures in sar images it is also found that a sar image can record a continuous evolution process from depression to elevation isws in its spatial domain under conditions of a spatially inhomogeneous ocean environment therefore the upper and lower layer depths can be calculated by determining the polarity conversion of isws observed in satellite sar images furthermore the density difference between the upper and lower layers can also be estimated when the wave speed is known we extract ocean stratification parameters including upper layer depth and density difference from polarity conversion of isws observed in a radarsat 1 sar image taken over the northeastern south china sea comparing the estimated results with field measurements we find that this method can estimate the upper layer depth with considerable success in estimating the density difference between the upper and lower layers it also gives a quite reasonable result

monitoring the variations of the socotra upwelling system during the last 250 kyr a biogenic and geochemical approach abstract a combination of changes in the species composition of the radiolarian populations and in the sediment chemical composition content and mass accumulation rates of carbonate organic carbon and selected major and trace elements with special attention paid to ba is used to reconstruct the variations in upwelling activity over the last 250 kyr in the socotra gyre area somali socotra upwelling system nw indian ocean in the socotra gyre core md 962073 at 10 n the variations in upwelling intensity are reconstructed by the upwelling radiolarian index uri while the thermocline surface radiolarian index tsri testifies to productivity variations during non upwelling intervals despite an origin related both to marine and terrigenous inputs the geochemical records of organic carbon silica and trace elements ba p cu and zn normalized to al are controlled by the variations in surface paleoproductivity the data indicate a continuous increase in upwelling intensity during the last 250 kyr with a maximum activity within the mis 3 while high productivity periods in between the upwelling seasons occurred both during glacial and interglacial intervals a comparison of our data with published observations from another gyre of the somalian upwelling area located at 5 n in the somali gyre area shows differences regarding periods of upwelling activity and their geochemical imprint three hypotheses are proposed to explain these differences 1 changes in the planktonic community resulting in more silica rich deposits in the socotra gyre and more carbonate rich deposits in the somali gyre that are controlled by differences in the source water of the upwelling 2 a more important terrigenous input in the southern gyre and 3 a different location of the sites relative to the geographic distribution of the upwelling gyres and hydrologic fronts

a 350 ky radiolarian record off luderitz namibia evidence for changes in the upwelling regime abstract the study of radiolarian assemblages from core md 962086 provides new information on the variability in the upwelling intensity and origin of upwelled water masses over the past 350 ky in one of the major filamentous regions of the benguela upwelling system bus located off luderitz namibia the use of key radiolarian species to trace the source of upwelled waters and the use of a radiolarian based upwelling index uri to reconstruct the upwelling intensity represent the first use of radiolarians for paleoceanographic reconstructions in the bus these radiolarian based proxies indicate strongest upwelling during marine isotope stages mis 3 5 and 8 which compares well with other studies while during mis 3 and 8 the radiolarian based proxies indicate the influx of waters of southern ocean origin they also point to the increased influence of tropical waters during the lower portion of mis 5 during mis 2 4 and 6 the radiolarian assemblages indicate generally lower upwelling intensities although this signal is complicated by the increased occurrence of organic carbon in the sediments during these intervals during mis 2 there appears to be less of an input of southern ocean waters to the bus although during the also glacial mis 4 and 6 there is evidence for an increased influence of cold antarctic waters the comparison of the results from core md 962086 with other studies in the bus area indicates a non uniform pattern of upwelling intensity and advection of cold southern waters into this system during mis 2 weaker upwelling signaled by the radiolarian based proxy in mis 4 is in contrast to other studies that indicate higher productivity during this time period in general the data show that there is a strong spatiotemporal complexity in upwelling intensity in the bus and that the advection of water into it is not strongly tied to glacial interglacial variations in climate

observations of internal bores and waves of elevation on the new england inner continental shelf during summer 2001 1 during july august 2001 oceanographic variability on the new england inner continental shelf was investigated with an emphasis on temporal scales shorter than tidal periods mooring and ship survey data showed that subtidal variation of inner shelf stratification was in response to regional ekman upwelling and downwelling wind driven dynamics high frequency variability in the vertical structure of the water column at an offshore mooring site was linked to the baroclinic internal tide and the onshore propagation of nonlinear solitary waves of depression temperature salinity and velocity data measured at an inshore mooring detected a bottom bore that formed on the flood phase of the tide during the ebb tide a second bottom discontinuity and series of nonlinear internal waves of elevation iwoe formed when the water column became for a time under hydraulic control a surface manifestation of these internal wave crests was also observed in aircraft remote sensing imagery the coupling of iwoe formation to the offshore solitary waves packets was investigated through internal wave breaking criterion derived in earlier laboratory studies results suggested that the offshore solitons shoaled on the sloping shelf and transformed from waves of depression to waves of elevation the coupling of inshore bore formation to the offshore solitary waves and the possible impact of these periodic features on mixing on the inner shelf region are discussed

turbulent dissipation on the margins of the south china sea 1 measurements of turbulence along the continental slope shelfbreak and shelf of the northern south china sea are presented from a 10 day measurement program during april 2005 the shelfbreak region was characterized by a deep stratification that appears to be typical of the late winter monsoon this appears to shift the wave field at the shelfbreak from the soliton like depression anomalies observed in previous years to a more complex wave field supporting high frequency waves in both upper and lower depth intervals of the water column on average 30 of the depth integrated turbulent dissipation occurs within 10 m of the bottom where baroclinic energy is preferentially dissipated dissipation levels reaching 50 mw m2 are an order of magnitude larger than those attainable through frictional dissipation of the local barotropic tide and an order of magnitude larger than levels typical in the open ocean

marine seismic observation of internal solitary wave packets in the northeast south china sea recently the novel seismic oceanography method has been reported to be an effective way to study the energetic internal solitary waves isws in the northern south china sea an optimized seismic oceanographic cruise was carried out to observe such near surface isws on dongsha plateau in july 2014 several soliton trains rather than single solitons were captured using the seismic technique after seismic data processing one prototypical rank ordered isw packet on northeast side of dongsha island was clearly identified for further analysis this included waveforms propagation velocities and vertical velocities for individual solitons in this study an improved scheme was applied to derive the transient phase velocities from the seismic data which is verified from independent satellite and hydrographic data analytical predictions from korteweg de vries equation fit better than the extended korteweg de vries equation ignoring background currents our results show that the seismic method can be successfully used to image targets in shallow water below 40 m and that seismic oceanography is a promising technique for studying near surface phenomena with high spatial resolution

insolation cycles as a major control of equatorial indian ocean primary production analysis of a continuous sedimentary record taken in the maldives indicates that strong primary production fluctuations 70 to 390 grams of carbon per square meter per year have occurred in the equatorial indian ocean during the past 910 000 years the record of primary production is coherent and in phase with the february equatorial insolation whereas it shows diverse phase behavior with 18o depending on the orbital frequency eccentricity obliquity or precession examined these observations imply a direct control of productivity in the equatorial oceanic system by insolation in the equatorial indian ocean productivity is driven by the wind intensity of westerlies which is related to the southern oscillation therefore it is suggested that a precession forcing on the southern oscillation is responsible for the observed paleoproductivity dynamics

mode 2 waves on the continental shelf ephemeral components of the nonlinear internal wavefield 1 shoreward propagating mode 2 nonlinear waves appear sporadically in mooring records obtained off the coast of new jersey in the summer of 2006 individual mode 2 packets were tracked between two moorings separated by 1 km however packets could not be tracked between moorings separated by greater distances from one another 10 km the inability to track individual packets large distances through the mooring array combined with detailed observations from a ship suggest that these waves are short lived the evolution of the ship tracked wave group was recorded using acoustic backscatter acoustic doppler current profilers and turbulence profiling the leading mode 2 wave quickly changed form and developed a tail of short small amplitude mode 1 waves the wavelength of the mode 1 oscillations agreed with that expected for a copropagating tail on the basis of linear theory turbulent dissipation in the mixed layer and radiation of the short mode 1 waves contributed to rapid energy loss in the leading mode 2 wave consistent with the observed decay rate and short life span of only a few hours the energy in the leading mode 2 wave was 10 100 times smaller than the energy of mode 1 nonlinear internal waves observed during the experiment however the magnitudes of wave localized turbulent dissipation were similar

paleoproductivity changes in the upwelling system of socotra somali basin nw indian ocean during the last 72 000years evidence from biological signatures abstract high resolution analyses of foraminiferal and radiolarian assemblages were performed on core md 85682 10 53 5n 52 23 e 3092 m depth 7 23 m length located close to the socotra island beneath the 10 n gyre of the upwelling area of the somali basin nw indian ocean in order to reconstruct the paleoproductivity changes during the last 72 kyr correspondence and cluster analyses of combined planktonic foraminiferal and radiolarian quantitative data show that the distribution pattern of the microfauna is partly controlled by temperature and hydrographic structures and their interrelations on water mass fertility the continuous occurrence of high abundances of foraminiferal species well known in fertile areas such as globigerinita glutinata globigerina bulloides and globigerina falconensis as well as radiolarian species characteristic of upwelling systems testifies to a sustained activity of the upwelling during the last 72 kyr downcore evolution of these biological proxies suggests an increase in paleoproductivity during isotope stages 1 and 3 which reflects a stronger upwelling activity during these periods these observations are in agreement with the results previously obtained by geochemical markers such as biogenic barium phosphorus organic matter and also trace elements related to the organic matter and indicators of redox conditions vanadium samples from isotope stage 2 record a more complex biological and geochemical signature resulting from increased terrigenous input comparison between the biological signatures obtained both under the socotra 10 n and somali 5 n upwelling areas indicates higher productivity throughout the last 72 kyr record of the socotra upwelling system in both areas a similar evolution of biological proxies indicative of high fertility is observed during isotope stages 1 and 3 however minor differences in the biological and geochemical signatures are related to local conditions prevailing beneath the two gyres

rapid switch in monsoon wind induced surface hydrographic conditions of the eastern arabian sea during the last deglaciation abstract surface water hydrography in the arabian sea is primarily governed by the asian monsoon wind system changes in the composition of fossil planktic foraminiferal assemblages and sea surface temperatures sst in sediment core sk17 retrieved from offshore of central india are used to decipher past changes in sea surface hydrographic conditions linked mainly to the winter monsoon winds the planktic foraminiferal assemblage and the sst records indicate a rapid switch in sea surface hydrographic conditions around 17 5 ka bp marking the end of last glacial period the data show that intensified winter winds during 17 5 23 5 ka bp resulted in nutrient injection into surface waters and eutrophic conditions mainly through deep vertical mixing and or moderate upwelling and reduction in winter wind intensity caused stratification characterized by the high tropical sst since 17 5 ka bp the timing of the rapid switch in seawater conditions caused by a drop in strength of winter monsoon winds is coeval with the cold climate excursion in the northern hemisphere heinrich event 1 suggesting that the two areas are climatically linked

paleohydrographic changes in the somali basin 5 n upwelling and equatorial areas during the last 160 kyr based on correspondence analysis of foraminiferal and radiolarian assemblages this study documents the biological signatures impressed upon the sedimentary record underlying both the 5 n upwelling system of the somali current and the equatorial area of the somali basin out of the upwelling influence the evolution of these two distinct hydrographic systems is compared for the last 160 kyr correspondence and cluster analyses are performed on combined radiolarian and planktonic foraminiferal quantitative data in order to study the changes of the planktonic assemblages through time and space the upwelling radiolarian index uri is used as a productivity proxy the water temperature and hydrographic structure of the upper water masses appear to be the major factors controlling the distribution patterns of the fauna the relative abundances of three groups of foraminifera cold water form dextral n pachyderma mixed layer dwellers g trilobus g ruber g sacculifer g conglobatus and g glutinata and thermocline dwellers g menardii g tumida n dutertrei g crassaformis and p obliquiloculata follow distinct evolutionary patterns at the two sites during the last 160 kyr at the equatorial site core md 85668 downcore fluctuations in the relative abundances of the three groups are closely related to the glacial interglacial cyclicity and provide some insights into the interpretation of hydrographic changes the dominance of the mixed layer foraminifera at the transition intervals between isotope stages 6 5 and 2 1 combined with weak uri values is thought to reflect the reorganization of the oceanographic circulation these short term events with a duration of 5000 year could be related to the rapid inflow of oxygen depleted water through the indonesian straits as a result of sea level rise during deglaciation underneath the 5 n gyre core md 85674 the response to global climatic changes is overprinted by the regional effect of the somalian upwelling which has been persistent over the last 160 kyr

internal solitary wave propagation observed by tandem satellites internal solitary waves isws are observed 2 times within 30 min in synthetic aperture radar sar image pairs from the envisat and ers 2 tandem satellites three pairs of sar images were acquired in the south china sea scs in april 2007 august 2008 and march 2009 and 13 isws were tracked between the image pair in an arcgis environment the phase speeds of these isws are calculated from their spatial displacement and time interval the resultant isw speeds agree well with the theoretical values estimated from the sturm louisville equation using local bathymetric and monthly climatology ocean stratification data this technique reveals the spatial variation in the isws speed in the water depth between 100 and 4000 m in the scs the study shows that isws speed is mainly affected by bottom topography and generally decreases from deep to shallow water from east to west and from south to north

a high resolution record of late quaternary upwelling along the oman margin arabian sea based on planktonic foraminifera planktonic foraminiferal abundances fluxes test sizes and coiling properties are influenced in various ways by the southwest monsoon winds and associated upwelling in the western arabian sea to determine the short term changes in the southwest monsoon we have carried out a high resolution time series analysis of three upwelling indices total flux of planktonic foraminiferal tests and flux and relative abundance of the planktonic foraminiferal species globigerina bulloides from ocean drilling program odp site 723a oman margin western arabian sea spanning the last 19 kyr in addition we have determined the relationships between upwelling intensity and the relative abundance fluxes and shell concentrations of various planktonic foraminiferal species upwelling indices suggest that from 19 to 16 ka 22 to 18 2 cal kyr b p the sw monsoon was relatively strong compared to the period 15 8 to 12 5 ka 17 8 to 13 8 cal kyr b p the intensification of the sw monsoon took place at 12 ka 13 1 cal kyr b p and reached a peak between 10 and 5 ka 10 6 and 4 8 cal kyr b p the high resolution data further demonstrate that the sw monsoon has started weakening from 5 ka 4 8 cal kyr b p and the weakest phase was in place at 3 5 ka 3 cal kyr b p which coincides with evidence of an arid climate in western tibet fluxes and shell concentrations of many of the planktonic foraminiferal species increased between 12 and 5 ka in response to the intensification of the sw monsoon winds after the last glacial period globigerina bulloides shows a fivefold to tenfold increase in flux during this period of intense upwelling the other species whose fluxes are influenced by this upwelling change are in order from strongest to weakest response globigerinita glutinata globigerinoides ruber neogloboquadrina dutertrei globigerinella aequilateralis globigerina falconensis and globigerinoides sacculifer the relative abundances of g bulloides and g ruber increased during intense upwelling whereas the relative abundances of g glutinata n dutertrei g falconensis and g sacculifer did not increase during this period which might be due to differences in the productivity of various species in relation to upwelling change therefore the fluxes and shell concentrations provide better and more reliable information about the changes in the monsoon system in the arabian sea than relative abundance data

phase lag between intertropical convergence zone migration and subtropical monsoon onset over the northwestern indian ocean during marine isotopic substage 6 5 mis 6 5 high resolution faunal and isotopic analyses of foraminifera were performed on core md96 2073 10 94 n 52 62 e 3142 m depth located close to socotra island in the upwelling area of the somali basin nw indian ocean this work focuses on marine isotopic stage 6 5 in order to reconstruct paleo upwelling changes and their links with the arabian sea summer monsoon and the migration of the intertropical convergence zone itcz correspondence and cluster analyses of planktonic foraminiferal abundances partly controlled by temperature and water mass productivity together with an upwelling intensification index show the occurrence of a strong upwelling between 176 and 165 ka this upwelling intensification responds to a northward migration of the itcz an isotopic depletion in the planktonic foraminifera 18o records occurring between 180 and 167 ka is interpreted as proof of a large salinity decrease in the surface waters probably linked to a strong input of fresh rainfall waters induced by an intense monsoon activity the lag between the onset of upwelling intensification and the strong monsoonal impact over the same area suggests a decoupling between both phenomena the migration of the itcz is influenced by obliquity and precessional forcing while the arabian sea summer monsoon precipitation depends only on precessional forcing

simulations of changes to glaciar zongo bolivia 16 s over the 21st century using a 3 d full stokes model and cmip5 climate projections bolivian glaciers are an essential source of fresh water for the altiplano and any changes they may undergo in the near future due to ongoing climate change are of particular concern glaciar zongo bolivia located near the administrative capital la paz has been extensively monitored by the glacioclim observatory in the last two decades here we model the glacier dynamics using the 3 d full stokes model elmer ice the model was calibrated and validated over a recent period 1997 2010 using four independent datasets available observations of surface velocities and surface mass balance were used for calibration and changes in surface elevation and retreat of the glacier front were used for validation over the validation period model outputs are in good agreement with observations differences less than a small percentage the future surface mass balance is assumed to depend on the equilibrium line altitude ela and temperature changes through the sensitivity of ela to temperature the model was then forced for the 21st century using temperature changes projected by nine coupled model intercomparison project phase 5 cmip5 models here we give results for three different representative concentration pathways rcps the intermediate scenario rcp6 0 led to 69 7 volume loss by 2100 while the two extreme scenarios rcp2 6 and rcp8 5 led to 40 7 and 89 4 loss of volume respectively

glacier thickening and decay analysis from 50 years of glaciological observations performed on glacier d argentiere mont blanc area france numerous glaciological data have been obtained from measurements carried out on glacier d argentiere mont blanc area france since the beginning of the 20th century moreover data on annual mass balance ice flow velocity thickness variation and length fluctuation have been obtained from yearly measurements performed since 1975 this dataset provides an excellent opportunity to analyze the relationships between surface mass balance and dynamic response over time periods during which net mass balance changed from positive to negative following a positive specific net balance period between 1960 and 1981 the ablation zone experienced a large increase in thickness and ice flow velocities conversely the highly negative specific net balance period since 1982 has led to strong thinning deceleration and retreat of the tongue the response of these observed dynamics to surface mass balance is analyzed from ice flux calculations performed on three transverse cross sections our results reveal that the ice fluxes are largely accommodated by ice flow velocities velocity fluctuations are synchronous over the entire area studied in the largest part of the glacier no compressing extending flow change has been observed over the last 30 years and thickness changes are solely driven by surface mass balance changes however on the tongue of the glacier thickness changes do not depend on surface mass balance but are mainly driven by changes in the longitudinal strain rate

oceanographic conditions associated with high abundances of the radiolarian cycladophora davisiana abstract the cosmopolitan radiolarian cycladophora davisiana usually comprises less than 5 of the radiolarian fauna in holocene sediments in recent sediments from the sea of okhotsk however this species frequently represents more than 20 of the radiolarian assemblage at times during the late pleistocene abundances of this species in excess of 40 are recorded in marine sediments from high latitude oceans 40 of both hemispheres the sea of okhotsk apparently represents a modern analogue of climatic and oceanographic conditions that existed throughout large portions of high latitude oceans at times during the late pleistocene the near surface water structure of the sea of okhotsk is characterized by a low salinity surface layer with a strong temperature minimum near its base the low surface salinities are responsible for maintaining near freezing subsurface temperatures as well as establishing relatively stable temperatures and salinities at depths below the temperature minimum this water structure is produced at least in part by intense freezing of sea ice in winter with subsequent summer melting the physical characteristics of the upper water column affect the abundance and activity of shallow dwelling flora and fauna while providing a stable subsurface environment for deeper dwelling fauna

observations of small scale processes associated with the internal tide encountering an island current meter temperature and microstructure observations of the large amplitude internal tide shoaling on the continental shelf of the east coast of northern new zealand show the complexity of the internal kinematics and mixing the propagation speed of the main internal wave was around 0 3 m s 1 and nonstationary time series analysis was used to locate the trailing short wavelength internal waves in frequency periods of around 40 min and tidal phase space the average energy dissipation rate 5 10 8 m 2 s 3 was an order of magnitude smaller than that observed on the open shelf in other studies but peaks in dissipation rate were measured to be much greater the vertical diffusivity of heat was around 10 4 m 2 s 1 comparable to or greater than other studies examples of the scale and sporadic nature of larger mixing events were observed the behavior was complicated by the nearby steeply shoaling coast of the poor knight islands consistent reflected wave energy was not apparent

time step limits for stable solutions of the ice sheet equation various spatial discretizations for the ice sheet are compared for accuracy against analytical solutions in one and two dimensions the computational efficiency of various iterated and non iterated marching schemes is compared the stability properties of different marching schemes with and without iterations on the non linear equations are compared newton raphson techniques permit the largest time steps a new technique which is based on the fact that the dynamics of unstable iterated maps contain information about where the unstable root lies is shown to improve substantially the performance of picard iteration at a negligible computational cost

prototypical solitons in the south china sea 1 surface signatures associated with non linear internal waves are often seen in satellite images of the western south china sea scs slope and shelf observation in the deep sea to the east are rare here we report on the evolution of an energetic packet as it propagated through the deep central basin of the scs toward the western slope and shelf the waves have amplitudes estimated at 170 m half widths of 3 km and phase speeds of 2 9 0 1 m s faster than the mode 1 linear phase speed of 2 6 m s the shape and observed phase speed were consistent with the korteweg devries kdv model over the 65 km path that they were tracked the intrinsic velocity shear of the waves is small compared to pre existing shears and the waves exhibit weak turbulence the kdv fit and a satellite derived estimate of horizontal wave extent imply a westward energy flux of 4 5 gw for each crest

observationally constrained modeling of sound in curved ocean internal waves examination of deep ducting and surface ducting at short range a study of 400 hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented sound propagation roughly along the crests of the waves is simulated with a three dimensional parabolic equation computational code and the results are compared to measured propagation along fixed 3 and 6 km source receiver paths the measurements were made on the shelf of the south china sea northeast of tung sha island construction of the time varying three dimensional sound speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data computed three dimensional propagation results compare well with field observations the simulations allow identification of time dependent sound forward scattering and ducting processes within the curved internal gravity waves strong acoustic intensity enhancement was observed during passage of high amplitude nonlinear waves over the source receiver paths and is replicated in the model the waves were typical of the region 35 m vertical displacement two types of ducting are found in the model which occur asynchronously one type is three dimensional modal trapping in deep ducts within the wave crests shallow thermocline zones the second type is surface ducting within the wave troughs deep thermocline zones

a review of internal solitary wave dynamics in the northern south china sea abstract the current research into internal solitary waves isws and the related dynamic processes in the northern south china sea scs are reviewed in this paper this unique wave phenomenon did not draw much interest until about one decade ago and is now one of the hot topics in the field of wave dynamics three methods of investigation are summarized in the paper namely remote sensing images in situ measurements and numerical simulations previous works have primarily been based on one or two of these methods and have provided great insights into such wave phenomena the lifetime of an isw in the northern scs from its origin in the luzon strait ls through to its formation and evolution in the deep basin and its transformation near the shelf break up until its dissipation on the continental shelf is summarized with the illustration of different investigation approaches various factors that can affect the wave generation processes are summed up as well such factors as are barotropic tides in the ls kuroshio intrusion temporal and spatial variation of stratification and the modulation of the western ridge in the ls can significantly alter the wave fields and are extensively discussed

aplanktonic zones in the red sea abstract we use micropalaeontological and stable isotope results for a series of cores from north to south through the red sea to assess temporal and spatial patterns of change in planktonic foraminiferal faunas leading up to the remarkable full glacial red sea aplanktonic zones aplanktonic zones reflect salinities in the red sea in excess of the lethal 49 p s u limit caused by reduced exchange transport through the strait of bab el mandab due to glacial sea level lowering concerning the last glacial cycle aplanktonic conditions began at 39 ka bp in the north where salinities eventually reached 55 57 p s u paradoxically planktonic faunas are reported to have survived the last glacial maximum in the northern gulf of aqaba suggesting a poorly understood freshwater dilution at that time aplanktonic conditions s 49 p s u reached the south central red sea by 22 ka bp while planktonic foraminiferal faunas continued albeit in very low abundances and limited diversity s 45 p s u in the southernmost red sea during marine isotope stage mis 6 the 49 p s u isohaline appears to have resided in the central red sea between cores kl11 and md921017 we observe a systematic sequence of species disappearances before all glacial maxima of the last 500 kyr absence of a logical relationship with sea levels suggests that the disappearance sequences are not related to a general salinity increase instead we argue that the sequences were driven by complex reorganisations in hydrography stratification productivity food availability and subsurface oxygenation reproduction habitats the onset is marked by dramatic basin wide expansion of conditions that today are restricted to only the southern red sea suggesting an expansion of the dominance of ne monsoonal circulation over the entire red sea this expansion occurred 15 or more kyr before the aplanktonic zones of mis 12 6 and 2 and also before mis 10 and 8 which never reach the aplanktonic stage regarding the last glacial cycle this event occurred as early as 75 ka bp mis 4 5 boundary after this major climatic reorganisation we reconstruct progressive intensification of the new conditions especially marked by northward expansion and intensification of the subsurface oxygen minimum zone omz during the last glacial cycle a shallow and very distinct omz affected the central red sea as early as 68 ka bp and the north as late as 55 ka bp the omz expansion intensification appears to have been interrupted by episodes of increased ventilation

glacial interglacial changes in the equatorial part of the somali basin nw indian ocean during the last 355 kyr planktonic foraminiferal and radiolarian signatures are analyzed in the 355 kyr record of a core from the equatorial part of the somali basin in order to reconstruct the amplitude of oceanographic processes and to test the reproducibility of the biological response to the glacial interglacial changes over four climatic cycles the correspondence analysis applied to the faunal data set reveals that the dominance of mixed layer foraminifera observed during isotope transitions 10 9 6 5 and 2 1 does not occur during transition 8 7 but appears later within isotope stage 7 this specific signature interpreted as related to the overflow of water from the south china sea can be related to the magnitude of sea level rises in this part of the indian ocean these deep oceanic records of high sea level stands are correlated with occurrences of emerged coral reef terraces in shallow environments

the degeneration of internal waves in lakes with sloping topography in a laboratory study we quantified the temporal energy flux associated with the degeneration of basin scale internal waves in closed basins the system is two layer stratified and subjected to a single forcing event creating available potential energy at time zero a downscale energy transfer was observed from the wind forced basin scale motions to the turbulent motions where energy was lost due to high frequency internal wave breaking along sloping topography under moderate forcing conditions steepening of nonlinear basin scale wave components was found to produce a high frequency solitary wave packet that contained as much as 20 of the available potential energy introduced by the initial condition the characteristic lengthscale of a particular solitary wave was less than the characteristic slope length leading to wave breaking along the sloping boundary the ratio of the steepening timescale required for the evolution of the solitary waves to the travel time until the waves shoaled controlled their development and degeneration within the domain the energy loss along the slope the mixing efficiency and the breaker type were modeled using appropriate forms of an internal iribarren number defined as the ratio of the boundary slope to the wave slope amplitude wavelength this parameter allows generalization to the oceanographic context analysis of field data shows the portion of the internal wave spectrum for lakes between motions at the basin and buoyancy scales to be composed of progressive waves both weakly nonlinear waves sinusoidal profile with frequencies near 10 24 hz and strongly nonlinear waves hyperbolic secant squared profile with frequencies near 10 23 hz the results suggest that a periodically forced system may sustain a quasi steady flux of 20 of the potential energy introduced by the surface wind stress to the benthic boundary layer at the depth of the pycnocline

paleoproductivity changes during the holocene in the inner shelf of cabo frio southeastern brazilian continental margin benthic foraminifera and sedimentological proxies abstract sedimentological and benthic foraminifera analyses carried out on a core length 4 15 m collected at 22 56 31 s and 41 58 48 w at a water depth of 43 m sampled from the inner shelf of cabo frio southeastern brazilian continental margin allowed identification of different hydrodynamic and productivity regimes related to sea level fluctuations and or climatic changes during the last 9 4 ka cal bp prior to 7 0 ka cal bp a less intense hydrodynamic and lower productivity regime occurred at lower sea levels and under drier climatic conditions between 7 0 and 5 0 ka cal bp relatively stronger local oceanic circulation and relatively high productivity were observed in a scenario of rising sea levels and more humid conditions from 5 0 to 3 0 ka cal bp bottom currents weakened and input of nutrients increased with productivity levels similar to the previous phase at lower sea level and in a drier climate from 3 0 ka cal bp up to the present stronger hydrodynamic conditions and a higher productivity regime are linked to the establishment of the upwelling process in cabo frio from 2 5 ka cal bp to the present upwelling enhancement has been recognized resulting from the combined action of ne winds and the intensification of the meandering pattern of the brazil current bc

footprints of obliquely incident internal solitary waves and internal tides near the shelf break in the northern south china sea a mooring system and two sites of bottom currents were deployed over the slope and near the shelf break on the propagating paths of internal solitary waves isws west off dongsha atoll in the northern south china sea data indicated that energetic isws obliquely shoaled onto the shelf west off dongsha atoll in an approximately 290 degrees direction causing strong reversing currents some exceeding 80 cm s near the bottom two types of sandwaves and short scour channels are discernible on the seafloor near the shelf break which have reasonable correlations with the obliquely incident isws and internal tides type 1 sandwaves featured by isws at the depths of 130 150 m have flat crests interacting with the isobaths at an angle of nearly 45 degrees which slightly incline and migrate upslope type 2 sandwaves are associated with internal tides which have crests parallel to the isobaths and distinctly incline and migrate downslope short channels are parallel to the depth contours and truncate the strata which could be formed and maintained by along slope currents that are probably produced by the obliquely isws on a large gradient gamma 0 8 degrees the isws can move coarse grains or suspend fine grains but do not change the long term trend of sediment transport on the seabed with larger gradients gamma c 1 which is dominated by internal tides these features are likely widespread near the shelf break in the northern south china sea and other seas but are limited on mild slopes where isws do not break

imprints of high salinity water plumes originating from the red sea during termination ii abstract the investigation of a core collected in the socotran area western indian ocean provides new insights into water mass exchanges between the red sea and the gulf of aden through the strait of bab el mandeb during the penultimate deglaciation the benthic oxygen isotope record documents the occurrence of stillstands and possibly reversals within the general trend of sea level rise plumes of warm and salty waters are recorded at the surface of the arabian sea and as far as the socotran coast for each increase in sea level these plumes disappeared whenever global sea level stopped rising or showed a brief lowering according to their high salinities these plumes can only originate in the red sea the sill of bab el mandeb becoming deeper and wider during the deglaciation allowed greater exchange between both seas and stronger flow out of the red sea at each episode of sea level rise isotopic and faunal evidence suggest a strengthening of coastal upwelling in the arabian sea during these periods this increase in upwelling activity may explain how plumes of highly saline waters were maintained at the surface moreover the high salinity surface plumes may have facilitated upwelling activity through the destabilisation of density stratification in the upper water column the occurrence of at least high salinity salty water outflows during termination ii confirms the step wise non linear structure of the penultimate deglaciation providing a perfect example of the threshold concept in rapid climate changes

evolution of nonlinear internal waves in the east and south china seas synthetic aperture radar sar images from ers i have been used to study the characteristics of internal waves northeast and south of taiwan in the east china sea and east of hainan island in the south china sea rank ordered packets of internal solitons propagating shoreward from the edge of the continental shelf were observed in the sar images on the basis of the assumption of a semidiurnal tidal origin the wave speed can be estimated and is consistent with the internal wave theory by using the sar images and hydrographic data internal waves of elevation have been identified in shallow water by a thicker mixed layer as compared with the bottom layer on the continental shelf the generation mechanism includes the influences of the tide and the kuroshio intrusion across the continental shelf for the formations of elevation internal waves the effects of water depth on the evolution of solitons and wave packets are modeled by the nonlinear kortweg devries kdv type equation and linked to satellite image observations the numerical calculations of internal wave evolution on the continental shelf have been performed and compared with the sar observations for a case of depression waves in deep water the solitons first disintegrate into dispersive wave trains and then evolve to a packet of elevation waves in the shallow water area after they pass through a turning point of approximately equal layer depths that has been observed in the sar image and simulated by the numerical model the importance of the dissipation effect in the coastal area is also discussed and demonstrated

large amplitude internal solitary waves observed in the northern south china sea properties and energetics abstractfive large amplitude internal solitary waves isws propagating westward on the upper continental slope in the northern south china sea were observed in may june 2011 with nearly full depth measurements of velocity temperature salinity and density as they shoaled at least three waves reached the convective breaking limit along wave current velocity exceeded the wave propagation speed c vertical overturns of 100 m were observed within the wave cores estimated turbulent kinetic energy was up to 1 5 10 4 w kg 1 in the cores and at the pycnocline the gradient richardson number was mostly 0 25 the maximum isw vertical displacement was 173 m 38 of the water depth the normalized maximum vertical displacement was 0 4 for three convective breaking isws in agreement with laboratory results for shoaling isws observed isws had greater available potential energy ape than kinetic energy ke for one of the largest observed isws the total wave energy per unit meter along the wave crest e