paleoaltimetry from stable isotope compositions of fossils stable isotope systematics of phosphatic vertebrate and carbonate invertebrate fossils are reviewed emphasizing external vs biological controls on isotope compositions and their variation external controls include elevation and isotopic lapse rates temperature atmospheric circulation patterns aridity and changes to precipitation seasonality e g development of monsoons biological controls include temperature regulation and temperature dependent biological activity water balance behavior and rates of hard part secretion and maturation some key factors include what sources of water an animal samples how those sources respond isotopically to elevation and the isotopic sensitivity of a biologic tissue to environmental changes general research design criteria are enumerated including numbers of fossils and analyses required as well as uncertainties in the interpretability of isotopic shifts isotope zoning from fossil teeth and shells from the indian foreland demonstrate comparable seasonal monsoon signals at 11 ma vs today implying a high and broad plateau at that time mean isotope compositions of fossil teeth from the lee of the cascade range central oregon show a pronounced decrease in 18 o initiating 7 ma signaling topographic rise associated with impingement of basin and range extension on the arc mean compositions and zoning in fossil shells from the northern rocky mountains indicate high elevations and topographic relief in the late cretaceous and early paleogene paleoaltimetry will principally benefit from better estimates of temperature because temperature lapse rates are less variable than isotopic lapse rates and because the combination of temperature and isotopic studies may help distinguish between local isotopic changes and distal ones caused by catchment or rain shadow effects

observed evidence of the anomalous south china sea western boundary current during the summers of 2010 and 2011 seven years of directly measured current data from a mooring in the xisha area of the south china sea scs together with shipboard adcp and satellite data have shown the western boundary current wbc anomaly and its vertical structure during the summers of 2010 and 2011 the observed wbc presented obvious year to year variability especially in the summer overall the summer mean velocity at the mooring site over 7 year 2007 2013 was northeastward the moored adcp showed that the northeastward velocity was particularly strong in the summer of 2010 but the increase was confined in the upper 120 m in contrast the northeastward current disappeared throughout the observed depth range from 50 to 450 m in the summer of 2011 even at the deepest observed position the monthly velocity anomalies reached 14 cm s 1 westward and 12 cm s 1 southward in the zonal and meridional directions respectively both the vietnam offshore current voc and double gyres in the western scs disappeared and the southern anticyclonic gyre expanded to strengthened the northward wbc in the summer of 2010 however in summer of 2011 the voc intensified and the northern cyclonic gyre enlarged with its northern edge reaching 18 degrees n slightly north of mooring site which weakened the northeastward wbc the observed scs circulation anomalies during 2010 and 2011 were mainly induced by the basin scale wind field anomalies associated with the 2009 2010 el nino and 2010 2011 la nina

a gulf stream model and an altimetry assimilation scheme a continuous data assimilation scheme and a multilayer primitive equation numerical model are described the model is an eddy resolving coastal ocean model that has been extended to include the gulf stream region it has complete thermohaline dynamics a bottom following sigma vertical coordinate system and a coastal following curvilinear orthogonal horizontal coordinate system calculated model fields are used to provide a model climatology and correlations between subsurface temperature and salinity anomalies and surface elevation anomalies an optimal interpolation method the surface to subsurface correlations and estimated model and data errors are the basis of the assimilation technique altimetry anomaly data extracted from the model calculations according to the geosat orbital schedule are used to test the assimilation scheme and to provide nowcasts and forecasts sensitivity studies are performed to test the effects of various parameters of the scheme it is found that the scheme is less efficient in the shallow continental shelf area than in the deeper regions of the model the results show significant nowcast skill with area averaged rms error for surface elevation and subsurface properties of about 40 50 of the corresponding error of the unassimilated case good forecast skill better than persistence is demonstrated for 10 20 days there is little skill after 30 40 days increasing the density of the satellite altimetry data especially by decreasing the separation distance between tracks should decrease the nowcast rms error to about 15 and improve the forecast

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

tectonic significance of paleobotanically estimated climate and altitude of the late eocene erosion surface colorado erosion beveled the laramide front range uplift in colorado to a surface of low relief by the end of the eocene this study uses j a wolfe s new multivariate climate analysis techniques to determine the paleoelevation of this regional surface by examining the overlying 35 ma florissant flora a multiple regression model explaining 93 3 of the variance in mean annual temperature was developed using wolfe s dataset of 31 leaf physiognomic character states for 86 modern vegetation sites these character states were scored on 29 species collected from one facies of the florissant lake beds the paleotemperature estimate of mean annual temperature 10 7 plus minus 1 5c derived from these data when combined with sea level temperature and terrestrial lapse rate implies a late eocene paleoelevation of 2 4 2 7 km pliocene uplift is thus not required to explain the present elevation of 2 5 km it is unclear when and why the southern rocky mountains achieved this elevation magmatic crustal thickening can explain the late eocene high elevation of the southern rockies but neither this mechanism nor compressive thickening explains why the great plains which are tied to the florissant elevation by the wall mountain tuff were also high this paleoelevation estimate indicates that regional surfacesmore of planation could be formed at high elevation in the eocene probably because of peculiarities of the eocene climate less

a direct method for assimilating sea surface height data into ocean models with adjustments to the deep circulation abstract there is as yet no consensus an the best method for inserting surface data into ocean models so that appropriate information is transmitted to the deeper layers in a rapid and efficient manner first we consider the correlation of sea surface pressure which is related to sea surface height as measured by altimeters and the surface and subsurface currents within the framework or a four layer quasi geostrophic model we begin by suggesting that the homogenization of potential vorticity q in the unforced layers discussed by rhines and young ensures that the potential vorticity anomalies in the deep ocean are weak it follows that instantaneous q information from thew deep layers may not need to be accurately known in order to reconstruct the deep eddy currents i e climatological q information may be sufficient taking the fields from the model we use the instantaneous surface streamfunction 1 data along with various approximate subsurface q climatologies and attempt to reconstruct the low

terrestrial cosmogenic nuclides as paleoaltimetric proxies the production rates of terrestrial in situ cosmogenic nuclides depend on the altitude and can therefore be used to constrain paleoaltitudes if the history of cosmogenic nuclide production in a region can be constrained this chapter discusses the theory behind cosmogenic nuclide paleoaltimetry sampling strategies and practical limitations of the technique three exposure scenarios may allow for the calculation of past altitudes 1 exposure for a finite time period at a single elevation and without erosion or burial followed by immediate shielding from further production of cosmogenic nuclides 2 steady uplift of a surface throughout nuclide production without erosion or burial and 3 exposure of a sample without erosion or burial for a sufficient duration that the concentration of a cosmogenic radionuclide has reached equilibrium to constrain paleoelevation all exposure scenarios require independent evidence of the depth history of a sample during exposure to cosmic rays because production rates attenuate rapidly in rock depth profiles and measuring multiple nuclides allow for better constraints of parameters in paleoaltitude calculations

stable isotope based paleoaltimetry abstractthe quantitative estimation of paleoaltitude has become an increasing focus of earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts as well as the influence of mountain belt growth on regional and global climate the general observation of decreasing 18o and 2h values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation these studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming in this review we provide a theory behind the application of stable isotope based approaches to paleoaltimetry we apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations examples of the application of paleoaltimetry techniques to himalaya tibet and the andes are discussed

chronology of pleistocene glacial advances in the central rocky mountains the distribution and ages of moraines in the wyoming type localities for pre pinedale rocky mountain glacial deposits are not well known through morphostratigraphic mapping river terrace longitudinal profile analysis and tephrochronology we place the age of sacagawea ridge moraines in the dinwoody lakes type area at about 660 ka outwash and river terrace deposits in the bull lake type area previously considered to be sacagawea ridge are actually older by one or two glacial cycles in the bull lake type locality 15 individual moraines are divided into 4 groups on the basis of relative age criteria using 36cl 10be cosmogenic dating of boulders the two older groups must be 130 ka the younger groups are given age ranges of 130 to 100 ka and 120 to 95 ka a terrace along wind river can be morphostratigraphically traced to the youngest of these moraine groups 36cl dating of boulders on the terrace provides an age range of 125 to 100 ka the combined relative age and cosmogenic nuclide chronology is consistent with previously published evidence from yellowstone national park demonstrating that mountain glaciers advanced not only prior to and during the later portion of marine isotope stage 6 but also during marine isotope stage 5d in contrast with some other areas of the rocky mountains we found no evidence for advances during marine isotope stage 4 at bull lake pinedale moraines that have a 36cl 10be age range of 23 to 16 ka suggest that glacial advances were limited to the later part of marine isotope stage 2 a river terrace that can be traced to these moraines has an age range of 23 to 16 ka a possible glacial advance during early marine isotope stage 2 is indicated by a river terrace whose age range is estimated by incision rate modeling at 46 to 28 ka but no moraines were identified along wind river there are eight terrace levels capped with outwash that are older than sacagawea ridge although the terraces are the record of early to middle pleistocene climatic cycles there are no correlative moraines preserved at the land surface

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

bottom up control of geomagnetic secular variation by the earth s inner core temporal changes in the earth s magnetic field known as geomagnetic secular variation occur most prominently at low latitudes in the atlantic hemisphere that is from 90 degrees east to 90 degrees east whereas in the pacific hemisphere there is comparatively little activity this is a consequence of the geographical localization of intense westward drifting equatorial magnetic flux patches at the core surface despite successes in explaining the morphology of the geomagnetic field numerical models of the geodynamo have so far failed to account systematically for this striking pattern of geomagnetic secular variation here we show that it can be reproduced provided that two mechanisms relying on the inner core are jointly considered first gravitational coupling aligns the inner core with the mantle forcing the flow of liquid metal in the outer core into a giant westward drifting sheet like gyre the resulting shear concentrates azimuthal magnetic flux at low latitudes close to the core mantle boundary where it is expelled by core convection and subsequently transported westward second differential inner core growth fastest below indonesia causes an asymmetric buoyancy release in the outer core which in turn distorts the gyre forcing it to become eccentric in agreement with recent core flow inversions this bottom up heterogeneous driving of core convection dominates top down driving from mantle thermal heterogeneities and localizes magnetic variations in a longitudinal sector centred beneath the atlantic where the eccentric gyre reaches the core surface to match the observed pattern of geomagnetic secular variation the solid material forming the inner core must now be in a state of differential growth rather than one of growth and melting induced by convective translation

paleoelevation measurement on the basis of vesicular basalts the vesicles bubbles in basaltic lava flows can be used to determine paleoelevation at the time of eruption in the repertoire of paleoelevation proxies presently available to the research community it represents one of very few direct proxies of elevation the technique is based on the sizes of vesicles at the tops and bottoms of lava flows we assume that bubbles do not know a priori that they will reside in one part of the flow or another when they are erupted from a volcanic vent as such the mass of gas is evenly distributed throughout the flow the volume of the bubbles will therefore depend on pressure which at the top of the flow is just atmospheric pressure and at the bottom is atmospheric plus hydrostatic pressure from lava overburden since lava thickness can be measured in the field and bubble size distributions most notably the modal size can be measured in the lab a simple relation can be solved for atmospheric pressure and using the standard atmosphere elevation can be determined the key parameters that must be determined are lava flow thickness at the time of emplacement and cooling of the upper and lower parts of the flow and the sizes of the vesicles each of these requires some analysis measured flow thickness in the field is not necessarily the same as that during solidification of the upper and lower several cm of the flow as inflation and deflation of the flow could have occurred thus changing the thickness from that which provided lava overburden to determine vesicles sizes in the lower part of the flow lava flows must be examined in cross section in the field to ensure that the indications of inflation or deflation are absent either would alter the proper vesicularity profile as a function of stratigraphic position within the flow for a given flow thickness only flows displaying the correct vesicularity profile can be meaningfully sampled vesicle sizes can be measured in a number of ways but the most accurate is computed x ray tomography which provides 3d information regarding size shape distribution and connectivity of vesicles in a sample we have developed numerical routines for extracting quantitative size distributions from tomographic data the basalt paleoaltimeter can be applied to any tectonic region in which basalts are present we tested the method by measuring the elevation of mauna loa hawaii and then as a first application to a tectonic issue placed constraints on the timing of uplift of the colorado plateau while further testing of this tool for paleoelevation analysis would always be helpful the technique is sufficiently refined for general use by the geologic community provided appropriate samples are collected from lavas demonstrating simple emplacement history and vesicle sizes are measured with sufficient quantitative accuracy to resolve elevation to within a few hundred meters as for any proxy the best results can be obtained with multiple sampling and when possible multiple independent proxies for the most reliable determination of paleoelevation history

a cosmic trip 25 years of cosmogenic nuclides in geology terrestrial cosmogenic nuclides produced by secondary cosmic ray interactions in the atmosphere and in situ within minerals in the shallow lithosphere are widely used to date surface exposure of rocks and sediments to estimate erosion and weathering rates and to date sediment deposition or burial their use has transformed geomorphology and quaternary geology for the first time allowing landforms to be dated and denudation rates to be measured over soil forming time scales the application of cosmogenic nuclides to geology began soon after the invention of accelerator mass spectrometry ams in 1977 and increased dramatically with the measurement of in situ produced nuclides in mineral grains near earth s surface in the 1980s the past 25 yr have witnessed the development of cosmogenic nuclides from their initial detection to their prevalence today as a standard geochronological and geochemical tool this review covers the major developments of the past 25 yr by comparing the state of the field in 1988 with that of today and by identifying key advances in that period that moved the field forward we emphasize the most commonly used in situ produced nuclides measured by ams for geological applications but we also discuss other nuclides where their applications overlap our review covers ams instrumentation cosmogenic nuclide production rates the methods of surface exposure dating measurement of erosion and weathering and burial dating and meteoric 10 be in memoriam devendra lal 1929 2012 whose vision inspired the field

assimilation of altimeter data in a two layer primitive equation model of the gulf stream abstract a two layer finite depth primitive equation model of the gulf stream region is used to study the effect of updating the model with simulated altimeter data as observations in this study both a complete field of sea surface height ssh and ssh sampled along satellite tracks are used as observations a simulated 17 day repeat orbit corresponding to the geosat erm and a 10 day repeat period corresponding to topex poseidon are used satellite observations give only information about the sea surface height but previous studies have shown that it is important to transfer the surface information to the lower layer as fast as possible in order for the model to have a realistic evolution a statistical inference technique is therefore used to update the lower layer pressure field the velocity fields in both layers are updated using a geostrophic correction calculated from the change in the pressure fields it is shown that updating the velocities is important for the assimilation to be successful w

measurement of ancient cosmogenic 21ne in quartz from the 28 ma fish canyon tuff colorado abstract measurement of 21 ne in quartz from the 28 ma buried fish canyon tuff of colorado yielded a maximum of 2 75 0 57 10 6 21 ne atoms g sio 2 1 above nucleogenic and modern concentrations this quantity represents cosmogenic 21 ne produced on the fish canyon tuff surface prior to the deposition of the overlying carpenter ridge tuff ancient 21 ne was isolated through the analysis and identification of 1 background 21 ne produced from particle interactions or inherited and 2 cosmogenic 21 ne produced from modern radiation multiple samples of fish canyon tuff shielded during both exposure periods 28 ma ago and in modern time yielded the background that was then subtracted from all samples likewise samples of fish canyon exposed today but well below the fish canyon carpenter ridge contact and therefore shielded 28 ma ago yielded a modern component that was also removed from all sample concentrations the presence of an ancient cosmogenic isotope in a buried surface has several potential applications including the quantification of paleoelevation paleolatitude and pre quaternary erosion rates

a review of paleotemperature lapse rate methods for estimating paleoelevation from fossil floras one widely applied method for estimating paleoelevation from fossil floras uses the relation between vegetation and temperature to estimate mean annual temperature from two isochronous fossil assemblages one at elevation and one at or near sea level and the difference between these temperatures is multiplied by the reciprocal of a temperature lapse rate to estimate paleoelevation three fundamentally different approaches have been developed and these vary both in the method by which paleotemperatures are estimated and in the way by which modern lapse rates can be measured paleotemperature methodologies include the use of plant physiognomy or the use of nearest living relatives lapse rate methodologies use either a global terrestrial lapse rate as the world mean a regional terrestrial lapse rate that represents a large portion of a continent or a local terrestrial lapse rate for areas narrowly confined by latitude and longitude other variables and or corrective factors that should be considered in these applications include the thermal effects of continentality and elevated land surfaces in the continental interior and standardization to compensate for fluctuations or variability in sea level global climate change and paleolatitude these different methodologies can be contrasted by their common application to the late eocene florissant flora of colorado with results ranging from 455 to 4133 meters

stable isotope based paleoaltimetry theory and validation paleoaltimetry is the quantitative estimate of the surface height above mean sea level of ancient landforms atmospheric thermodynamic modeling of the behavior of 18o relative to 16o during condensation from water vapor establish the systematic relationship that exists between 18o p and elevation where 18o p is the difference between a low altitude preferably sea level 18o p and a potentially high elevation sample comparison of model predictions with observations suggests that the model captures the first order behavior of 18o p during condensation and precipitation in orographic settings the actual relationship between 18o p and elevation depends sensitively on climate and specifically starting temperature and to a lesser degree relative humidity thermodynamic modeling allows the 18o p and elevation relationship to be explicitly calculated for any given starting climate state this makes the theoretical approach significantly more appropriate than empirically calibrated approaches based typically on quite limited samples presently available in most orographic settings today paleoaltimetry archives derive their isotopic compositions from surface and or ground water and hence it is important to understand the systematic differences between these reservoirs and precipitation surface waters and ground waters integrate not just the change in isotopic composition with altitude but also variations in hypsometry within the drainage basin and precipitation amount as functions of elevation thus these archives should reflect the precipitation amount weighted hypsometric mean elevation of the paleo drainage basin from which they derive their waters analysis of modern data from the himalayan region supports this expectation foreland basin rivers are such integrators and it is shown using an example from the siwaliks that the rivers draining the front of the himalayas in the past had isotopic compositions comparable with modern rivers draining the himalayan front suggesting little net change in himalayan hypsometry over the past 11 million years

on the latitude dependence of drift velocity of the geomagnetic main field and its secular variation abstract there is an apparent difference in the westward drift between the geomagnetic main field and its time derivative secular variation the drift velocity of the main field is about 0 2 year definitely lower than that of the secular variation 0 3 year the drift velocity of the main field appears to change with latitude being low at high latitudes and higher at low latitudes whereas the velocity of the secular variation is nearly constant irrespective of latitude this paper examines what causes this difference by adopting the drifting and standing field model that assumes the geomagnetic field consists of the field steadily drifting westwards and the field remaining at nearly the same location in this study we confirm that the existence of the non drifting standing field significantly affects the estimate of the drift velocity of the total field i e the main field and makes it slower than that of the secular variation the drifting field is intense in low latitudes with its maximum at the equator while the standing field dominates in higher latitudes as a consequence reduction of the apparent drifting velocity of the total field by the standing field is conspicuous in higher latitudes and less so in low latitudes this creates the observed latitudinal structure of the drift velocity of the main field on the other hand the drift velocity of the secular variation is less affected by existence of the standing field and mostly reflects the velocity of the drifting field that is almost constant with latitude the velocity of the secular variation thus becomes almost uniform independent of latitude the observed difference between the main field and the secular variation is naturally derived from the drifting and standing field model this implies that physical mechanisms to generate the drifting and standing fields can be considered independently

surface expression of eastern mediterranean slab dynamics neogene topographic and structural evolution of the southwest margin of the central anatolian plateau turkey 1 the southwest margin of the central anatolian plateau has experienced multiple phases of topographic growth including the formation of localized highs prior to the late miocene that were later affected by wholesale uplift of the plateau margin our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1 5 km elevation to 7 17 ma and regional lithostratigraphic correlations imply that the age is 6 7 ma single grain ca tims u pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10 6 ma indicating a maximum age that is consistent with the biostratigraphy our structural measurements within the uplifted region and fault inversion modeling agree with previous findings in surrounding regions with early contraction followed by strike slip and extensional deformation during uplift focal mechanisms from shallow earthquakes show that the extensional phase has continued to the present broad similarities in the change in the tectonic stress regime after 8 ma and the onset of surface uplift after 7 ma imply that deep seated process es caused post 7 ma uplift the geometry of lithospheric slabs beneath the plateau margin pliocene to recent alkaline volcanism and the uplift pattern with accompanying normal faulting point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post 7 ma uplift of the southwest margin considering previous work in the region there appears to be an important link between slab dynamics and surface uplift throughout the anatolian plateau s southern margin

interannual variability of the south china sea in a data assimilation model 1 sea surface height ssh variations in the south china sea are examined using results from a data assimilation model after the ssh data have had the annual cycle removed principal component analysis illustrates two distinct anomaly patterns the first mode strongest off vietnam would affect the basin wide gyre intensity the second mode consists of a meridional dipole feature with a nodal line around 12 n and is related to the development of the eastward jet and upwelling off vietnam both eof modes have significant interannual variations and are highly correlated to the enso events the leading phase of mode 2 coefficient provides preliminary evidence for the air sea interaction and the pacific east asian teleconnection an innovative mechanism is proposed to describe a weakened upwelling off luzon in winter 1998 an extra strong basin wide warming in summer 1998 persists into fall and winter preventing the formation of winter upwelling off luzon in that year

isopycnal eofs in the azores current region a statistical tool fordynamical analysis and data assimilation abstract an empirical orthogonal function analysis of the vertical space time variability of the thermohaline structure of the ocean in summer and fall 1993 in the azores current region has been performed the analysis used data from ctd casts of the semaphore intensive experiment referred to as a seasonally varying climatology the relative merits of depth coordinate and isopycnal coordinate representations have been examined in regard to the quality of identification of physical processes and to the effectiveness of the extrapolation from a sea level anomaly in an attempt to improve the treatment of the vertical dimension in oceanic assimilation problems the isopycnal eofs consistently proved more efficient in capturing the vertical structure of both dominant processes in the area of investigation the variability linked to the mediterranean water and the coherent physical system made up of the azores front and the azores current the isopycnal analysis also proved more robust when meddies mediterra

terrestrial cosmogenic argon cosmogenically enriched 38 ar 36 ar ratios are detectable in ca bearing terrestrial samples and are resolvable from a uniform background value of 0 18826 0 00018 for materials lacking nucleogenic or kinetic mass fractionation effects relationships between 38 ar 36 ar and cosmogenic 3he in apatite and fluorite are systematic but difficult to reconcile with current estimates of terrestrial production rates for 38 ar and 36 ar from ca suggesting that production from cl and or other targets is significant or that the estimates are inaccurate in either case the effects of time varying production of 36 ar from decay of cosmogenic 36 cl produced from ca k or cl on the 38 ar 36 ar ratio must be accounted for

assimilating altimetric data into a south china sea model sea surface heights from the topex poseidon altimeter are assimilated into a three dimensional primitive equation model to derive the circulation in the south china sea with data assimilation the model resolves not only the basin wide circulation but also a dipole off vietnam and a low high feature near the luzon strait mesoscale features are missing in the simulation without data assimilation because of poor resolution in the wind field and inadequate knowledge of the transport through the luzon strait compared to the case without data assimilation data assimilation reduces the root mean square error between the simulated and observed sea surface heights by a factor of 2 3 circulation derived from data assimilation under climatological conditions is contrasted with that during el nino in the normal winter of 1993 1994 flow at 50 m depth is strong and cyclonic flow at 900 m depth is cyclonic as well the deep cyclone persists into the following summer during the 1994 1995 el nino winter features in the flow field at 50 m depth either weaken or disappear and circulation at 900 m depth is anticyclonic in the summer of 1995 the dipole and the eastward jet off vietnam at 50 m depth are missing and the anticyclonic circulation at 900 m depth persists temperature at 65 m shows significant warming from fall 1994 to summer 1995 a weakened flow field and warming in the upper ocean are consistent with findings from earlier el nino events

continuous assimilation of geosat altimeter data into a three dimensional primitive equation gulf stream model abstract a three dimensional data assimilation scheme is described and tested using the geosat altimeter data and a high resolution primitive equation numerical ocean model of the gulf stream region the assimilation scheme is based on an optimal interpolation approach in which data along satellite tracks are continuously interpolated horizontally and vertically into the model grid and assimilated with the model prognostic fields preprocessed correlations between surface elevation anomalies and subsurface temperature and salinity anomalies are used to project surface information into the deep ocean model and data error estimates are used to optimize the assimilation analysis fields derived from the navy s optimum thermal interpolation system are used to initialize the model and to provide some estimate of errors to evaluate the effectiveness of the assimilation scheme the errors of model oceanic fields surface elevation gulf stream axis temperature with data assimilation are compared with erro

interannual variability of the surface summertime eastward jet in the south china sea the summertime eastward jet sej located around 12 n 110 e 113 e as the offshore extension of the vietnam coastal current is an important feature of the south china sea scs surface circulation in boreal summer analysis of satellite derived sea level and sea surface wind data during 1992 2012 reveals pronounced interannual variations in its surface strength ssej and latitudinal position ysej in most of these years the jas july august and september mean ssej fluctuates between 0 17 and 0 55 m s 1 while ysej shifts between 10 7 n and 14 3 n these variations of the sej are predominantly contributed from the geostrophic current component that is linked to a meridional dipole pattern of sea level variations this sea level dipole pattern is primarily induced by local wind changes within the scs associated with the el nino southern oscillation enso enhanced weakened southwest monsoon at the developing decaying stage of an el nino event causes a stronger weaker sej located south north of its mean position remote wind forcing from the tropical pacific can also affect the sea level in the scs via energy transmission through the philippine archipelago but its effect on the sej is small the impact of the oceanic internal variability such as eddy current interaction is assessed using an ocean general circulation model ogcm such impact can lead to considerable year to year changes of sea level and the sej equivalent to 20 of the observed variation this implies the complexity and prediction difficulty of the upper ocean circulation in this region

seasonal structures of upper layer circulation in the southern south china sea from in situ observations 1 conductivity temperature depth and acoustic doppler current profiler data from six cruises spanning 1989 to 1999 are used to investigate the seasonal structure of the upper layer circulation in the southern south china sea scs the surveys were made during winter late spring summer and late fall more detailed structures not presented in previous studies are found in summer the upper layer circulation of the southern scs is dominated by an anticyclonic gyre with a strong eastward flow on its northern border which originates off the southeast coast of vietnam the summer southeast vietnam offshore current in winter a stronger cyclonic gyre exists in the western portion of the southern scs and a weaker anticyclonic circulation in the eastern portion at the juncture of these two gyres there is a strong northward upwind flow called the winter natuna off shelf current in late spring the anticyclonic gyre begins to form in the northwest and a trace of the natuna off shelf current can still be observed especially subsurface in the southern part of the study area mesoscale eddies are active in this period in late fall the winter type pattern begins to appear the natuna off shelf current and the cyclonic gyre in the northwest part of the southern scs emerge and the summer anticyclonic gyre vanishes in the southeast the currents are basically toward the northeast with an anticyclonic trend revealing a multi eddy feature these upper ocean currents appear consistent with the wind forcing

interannual mode of sea level in the south china sea and the roles of el nino and el nino modoki 1 enso scale variation of the summer ocean circulation in the south china sea scs is investigated the interannual mode of ssh features a north south dipole pattern that modulates the cold jet off vietnam during the summers before and after the el nino the mode has opposite signs of extrema strengthened circulations couple with the cold sstas during the el nino developing summers weakened circulations accompany the warm sstas during the decaying summers heat advection by the basin circulation modulates the sst variation the impact of the 1997 el nino on the scs circulation contrasting that of 1994 and 2002 el nino modoki is assessed with moderate sst warming but further westward shift of the low level convergence of the atmosphere in the equatorial pacific the el nino modoki phenomenon enhanced the western north pacific summer monsoon inside the scs driving stronger circulations in both the summers of 1994 and 2002

drifting and standing fields in the geomagnetic field for the past 400 years abstract based on the field model by jackson et al 2000 we reanalyzed the data of historical times and decomposed the geomagnetic field into drifting and standing fields it has been confirmed that the results are consistent with the earlier analyses when the field is expressed in a spherical harmonic series the drifting field is characterized by two remarkable features one is that the drifting field is represented mostly by sectorial harmonics and the other is that the drift velocity does not differ significantly between the harmonics the standing field that remains after subtraction of the drifting field from the main geomagnetic field is stronger than the drifting field the predominance of sectorial terms in the drifting field means that the vertical component for instance of the drifting field is symmetric about the equator on the other hand the standing field is antisymmetric due to this difference the drifting field largely controls the geomagnetic secular variation in the low latitude region whereas the standing field dominates in the middle and higher latitudes

fossil cosmogenic 3 he record from k ar dated basaltic flows of mount etna volcano sicily 38 n evaluation of a new paleoaltimeter this study investigates the reliability of a paleoaltimeter based on the elevation dependency of the cosmogenic nuclides production rate the proposed method relies on fossil cosmogenic record indeed measuring the cosmogenic nuclide concentration in an exposed and then buried lava flow combined with an independent estimate by k ar or 40ar 39ar dating of the past exposure duration theoretically allows recording fossil cosmogenic production rates which can thus be converted in paleoelevations this approach was tested by measuring cosmogenic 3he 3hec in olivines and clinopyroxenes of quaternary k ar dated basaltic flows of mount etna volcano sicily 38 n the agreement within uncertainties 1 500 m between current and cosmogenic derived elevations demonstrates the paleoaltimeter reliability however dating imprecision earth s paleomagnetic fluctuations and erosion contemporary to the flow exposure are parameters that may affect the accuracy and the precision of the method on older geological scales their respective influences were thus carefully evaluated and discussed to conclude that the paleoaltimeter can potentially reach resolutions better than 1000 m even for cenozoic records

assimilation of altimeter data into an ocean circulation model space versus time resolution studies abstract one of the most important forthcoming synoptic datasets for ocean circulation studies will he the sea surface height data provided by the topex poseidon satellite the topex poseidon project is in the planning stage and must still decide upon the particular characteristics of the satellite track the repeat period will be between 10 and 20 days for a variety of technical and strategic reasons these choices win give a global coverage with spatial resolution east west or north south separation of crossover points in midlatitudes of roughly 2 8 of latitude and longitude for a 10 day repeat orbit and 1 4 of latitude and longitude for a 20 day repeat orbit thus the crucial question we address in the present study is what is the effect of changing space or time resolution or both upon the success of a numerical model in reconstructing a four dimensional picture a the ocean circulation through the assimilation of altimetric data to answer this question we carry out a series of numerical experi

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

a new approach to stable isotope based paleoaltimetry implications for paleoaltimetry and paleohypsometry of the high himalaya since the late miocene the change in oxygen isotopic composition of precipitation is modeled using equilibrium fractionation during rayleigh distillation linked to the thermodynamics of atmospheric ascent and water vapor condensation the primary controllers of the vertical variation in isotopic composition with elevation are the low elevation temperature and relative humidity as these control the vertical distribution of condensation an empirical fit of precipitation versus model condensation based on alpine stations is derived this fit is represented in the model as the weighted mean composition of condensation within a 1000 m thick air parcel 1500 500 m above the ground surface and is used for all other regions comparison of model versus observed modern precipitation reveals a close fit particularly of more highly elevated sites comparison of modern waters in the himalayas and southern tibet with model predictions particularly as revealed by comparison of observed and predicted hypsometry provides additional support to the validity of the model finally application of this model to estimates of paleo waters in the himalayas and southern tibet reveals that this region had already achieved its present hypsometry by the late miocene about 10 ma ago fl 2001 published by elsevier science b v

slow cenozoic uplift of the western andean cordillera indicated by cosmogenic 3he in alluvial boulders from the pacific planation surface to determine the mechanisms responsible for mountain belt growth it is important to accurately establish the timing of surface uplift here we exploit the altitude control on the production rate of in situ cosmogenic nuclides to test the hypothesis that the andes was uplifted in the late miocene high concentrations of in situ cosmogenic 3he 3hecos have previously been measured in alluvial boulders on the western flank of the central andes northern chile evenstar et al 2009 these are consistent with deposition soon after formation of the surface 13 14 ma we have modeled the accumulation of cosmogenic 3he in several different surface uplift scenarios and compared them to the measured concentrations the measured 3hecos concentrations are too high to be produced by late miocene uplift and imply that the western flank of the andean cordillera attained a substantial part of its current elevation prior to 14 myr ago

generation and life cycle of the dipole in the south china sea summer circulation 1 the south china sea scs summer circulation often has a dipole structure associated with an eastward jet appearing off central vietnam the dipole has an anticyclonic eddy ae south of the jet and a cyclonic eddy ce north of it the life cycle of the dipole structure is analyzed using satellite altimetry data and a reduced gravity model on average the dipole structure begins in june peaks in strength in august or september and disappears in october the dipole evolution lags behind the basin scale wind by about 40 days and 40 days are exactly what it takes for baroclinic planetary waves to cross the southern scs our results show that the vorticity transports from the nonlinear effect of the western boundary currents are crucial for the generation of the dipole structure in addition the strength and direction of the offshore wind jet also play a significant role in determining the magnitudes and the core positions of the two concomitant eddies

predicting paleoelevation of tibet and the himalaya from δ18o vs altitude gradients in meteoric water across the nepal himalaya the 18o value of meteoric water varies with elevation providing a means to reconstruct paleoelevation if the 18o values of paleowater are known in this study we determined the 18o values of water 18omw from small tributaries along the seti river and kali gandaki in the nepal himalaya we found that 18omw values decrease with increasing altitude for both transects 18omw vs altitude along the kali gandaki in west central nepal fit a second order polynomial curve consistent with increasing depletion of 18o with increasing elevation as predicted by a rayleigh type fractionation process this modern 18omw vs altitude relationship can be used to constrain paleoelevation from the 18o values of miocene pliocene carbonate 18oc deposited in the thakkhola graben in the southern tibetan plateau paleoelevations of 3800 480 m to 5900 350 are predicted for the older tetang formation and 4500 430 m to 6300 330 m for the younger thakkhola formation these paleoelevation estimates suggest that by 11 ma the southern tibetan plateau was at a similar elevation to modern

using in situ produced cosmogenic isotopes to estimate rates of landscape evolution a review from the geomorphic perspective the application of in situ produced cosmogenic isotopes to problems in geomorphology has increased rapidly over the past decade at least 57 papers and numerous abstracts have been published since the mid 1980s when the first mass spectrometric measurements of terrestrially produced cosmogenic isotopes were made taken at face value these studies provide quantitative information about rates of landscape evolution and landform age however the significance of calculated erosion rates and exposure ages depends strongly on the models used to interpret isotopic data the validity of assumptions inherent to these models and the geologic surroundings in which the samples were collected this paper attempts to place cosmogenic isotope studies in a geomorphic context by reviewing fundamentals of the method and evaluating the validity of assumptions under which these data have been interpreted at present the establishment of high precision cosmogenically based glacial and alluvial chronologies is stymied by the evolution of geomorphic surfaces the erosion of rock from sampled boulders the potential for isotope inheritance from previous exposure and the uncertainty of isotopic measurements uncertainties in isotope production rates and the observed variability of exposure ages on individual geomorphic surfaces limit the confidence with which cosmogenic ages can be correlated reliably with those obtained by other techniques estimation of erosion rates at single points on the landscape gives useful small scale information extrapolation of these rates over longer time and larger spatial scales is less sure and most likely biased toward lower erosion rates by die inadvertent selection of resistant sample sites however because erosion rates are so poorly constrained at present even estimates to within a factor of 2 may be of significant value to geomorphologists and tectonicists

the changing influences of enso and the pacific meridional mode on mesoscale eddies in the south china sea abstractthis study finds that the correlation between el nino southern oscillation enso and the activity of mesoscale oceanic eddies in the south china sea scs changed around 2004 the mesoscal

small scale structure of the geodynamo inferred from oersted and magsat satellite data the geodynamo in the earth s liquid outer core produces a magnetic field that dominates the large and medium length scales of the magnetic field observed at the earth s surface1 2 here we use data from the currently operating danish oersted3 satellite and from the us magsat2 satellite that operated in 1979 80 to identify and interpret variations in the magnetic field over the past 20 years down to length scales previously inaccessible projected down to the surface of the earth s core we found these variations to be small below the pacific ocean and large at polar latitudes and in a region centred below southern africa the flow pattern at the surface of the core that we calculate to account for these changes is characterized by a westward flow concentrated in retrograde polar vortices and an asymmetric ring where prograde vortices are correlated with highs and retrograde vortices with lows in the historical 400 year average magnetic field4 5 this pattern is analogous to those seen in a large class of numerical dynamo simulations6 except for its longitudinal asymmetry if this asymmetric state was reached often in the past it might account for several persistent patterns observed in the palaeomagnetic field7 8 9 10 we postulate that it might also be a state in which the geodynamo operates before reversing

spatial and temporal variations of the kuroshio east of taiwan 1982 2005 a numerical study 1 a 1 8 east asian marginal seas model nested to a larger domain north pacific ocean model is implemented over a span of 24 years from 1982 to 2005 to investigate the spatial and temporal variations of the kuroshio east of taiwan between 22 and 25 n the mean state and variability of the kuroshio such as the two paths observed in the trajectories of surface drifters southeast of taiwan and the branching of the kuroshio northeast of taiwan are well reproduced by the model southeast of taiwan the kuroshio is mostly in the top 300 m in the inshore path but extends to 600 m in the offshore path northeast of taiwan the kuroshio follows the shelf edge in the east china sea but may branch along a path south of the ryukyu islands the latter path often meanders southward and a significant portion of the kuroshio transport may be diverted to this path the kuroshio extends from the coast to 123 123 5 e between 22 and 25 n with currents reaching a depth of 1000 m at some latitudes the kuroshio transports averaged over five sections east of taiwan are 28 4 5 0 sv and 32 7 4 4 sv with and without the contribution from the countercurrent respectively

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

paleoelevation reconstruction using pedogenic carbonates paleoelevation reconstruction using stable isotopes although a relatively new science is making a significant contribution to our understanding of the recent growth of the world s major orogens in this review we examine the use of both light stable isotopes of oxygen and the new clumped isotope 47 carbonate thermometer in carbonates from soils globally the oxygen isotopic composition 18 o of rainfall decreases on average by about 2 8 km of elevation gain this effect of elevation will in turn be archived in the 18 o value of soil carbonates and paleoelevation can be reconstructed provided 1 temperature of formation can be estimated 2 the effects of evaporation are small 3 the effects of climate change can be accounted for and 4 the isotopic composition of the carbonate is not diagenetically altered we review data from modern soils to evaluate some of these issues and find that evaporation commonly elevates 18 o values of carbonates in deserts an effect that would lead to underestimates of paleoelevation some assessment of paleoaridity using qualitative indicators or carbon isotopes from soil carbonate is therefore useful in evaluating the oxygen isotope based estimates of paleoelevation sampling from deep 50 cm in paleosols helps reduce the uncertainties arising from seasonal temperature fluctuations and from evaporation the new clumped isotope 47 carbonate thermometer expressed as 47 offers an independent and potentially very powerful approach to paleoelevation reconstruction in contrast to the use of 18 o values nothing need be known about the isotopic composition of water from which carbonate grew in order to estimate of temperature of carbonate formation from 47 values using assumed temperature lapse rates with elevation paleoelevations can thereby be reconstructed case studies from the andes and tibet show how these methods can be used alone or in combination to estimate paleoelevation in both cases the potential for diagenetic alteration of primary carbonate values first has to be assessed clear examples of both preservation and alteration of primary isotopic values are available from deposits of varying ages and burial histories 47 values constitute a relatively straightforward test since any temperature in excess of reasonable surface temperatures points to diagenetic alteration for 18 o values preservation of isotopic heterogeneity between different carbonate phases offers a check on diagenesis results of these case studies show that one area of south central tibet attained elevations comparable to today by the late oligocene whereas 2 7 0 4 km of uplift occurred in the bolivian altiplano during the late miocene

multi phased uplift of the southern margin of the central anatolian plateau turkey a record of tectonic and upper mantle processes abstract uplifted neogene marine sediments and quaternary fluvial terraces in the mut basin southern turkey reveal a detailed history of surface uplift along the southern margin of the central anatolian plateau from the late miocene to the present new surface exposure ages 10be 26al and 21ne of gravels capping fluvial strath terraces located between 28 and 135 m above the goksu river in the mut basin yield ages ranging from ca 25 to 130 ka corresponding to an average incision rate of 0 52 to 0 67 mm yr published biostratigraphic data combined with new interpretations of the fossil assemblages from uplifted marine sediments reveal average uplift rates of 0 25 to 0 37 mm yr since late miocene time starting between 8 and 5 45 ma and 0 72 to 0 74 mm yr after 1 66 to 1 62 ma together with the terrace abandonment ages the data imply 0 6 to 0 7 mm yr uplift rates from 1 6 ma to the present the different post late miocene and post 1 6 ma uplift rates can imply increasing uplift rates through time or multi phased uplift with slow uplift or subsidence in between longitudinal profiles of rivers in the upper catchment of the mut and ermenek basins show no apparent lithologic or fault control on some knickpoints that occur at 1 2 to 1 5 km elevation implying a transient response to a change in uplift rates projections of graded upper relict channel segments to the modern outlet together with constraints from uplifted marine sediments show that a slower incision uplift rate of 0 1 to 0 2 mm yr preceded the 0 7 mm yr uplift rate the river morphology and profile projections therefore reflect multi phased uplift of the plateau margin rather than steadily increasing uplift rates multi phased uplift can be explained by lithospheric slab break off and possibly also the arrival of the eratosthenes seamount at the collision zone south of cyprus

eastward and westward drift of the earth s magnetic field for the last three millennia abstract we analyse the secular variation captured by the archaeomagnetic field model cals7k 2 in an effort to determine episodes of eastward and westward motions of earth s magnetic field at the core mantle boundary cmb over the past 3000 yr the direction amplitude and geographical distribution of these motions are described we find that the clearest azimuthal motions are observed at mid to high latitudes in the northern hemisphere where both eastward and westward motions occur these azimuthal motions correspond to displacements and distortions of the two main quasi stationary high latitude magnetic flux patches similar motions are not observed in the southern hemisphere although this may be a consequence of the poorer data coverage there the globally averaged drift for the past 1000 yr has been westward since 1400 ad but eastward between 1000 ad and 1400 ad in the broad region of the cmb under europe the times of transition in the direction of the mean azimuthal motion coincide with the times at which archaeomagnetic jerks have been reported our results suggest that these are caused by a relatively rapid

quantification of large uncertainties in fossil leaf paleoaltimetry 1 estimates of paleoelevation potentially constrain geodynamic models of continental deformation and inform interpretations of landscape and climate evolution one widely used paleobotanical approach reconstructs paleoelevation from the difference in estimated atmospheric enthalpy between a known sea level and a targeted coeval elevated fossil floral site enthalpy is estimated using climate leaf analysis multivariate program clamp on 31 leaf size and shape variables that have been calibrated in living forests errors related to clamp are significantly greater than often reported and there are many sources of large potential error related to this method that are either difficult to quantify or unquantifiable and are thus not documented here we quantify one significant bias toward underestimation of leaf area in the clamp data set 50 that affects all clamp climate estimates including enthalpy crucially errors in paleoelevation when the leaf size bias is included are in the range of 2 km or more at least 2 times the previous estimates and exceeding the plausible paleoelevations of many fossil sites previously published paleoelevations derived from this technique are unlikely to be accurate either in magnitude or in estimated error

the significance of paleotopography topographic change is one of the most informative measures of continental deformation yet precise records of past elevation are scarce to non existent in most orogenic belts recent advancement and new development of techniques to measure paleoelevation promise significant progress in understanding continental tectonic processes and how erosion acts on rising topography to shape the earth s surface outstanding issues in continental tectonics include understanding driving forces to deformation how strain is vertically partitioned in the lithosphere and how mass is redistributed or conserved in the lithosphere during deformation geodynamic and mechanical models that explore these topics make testable predictions of topographic evolution this review explores key examples of how paleotopography relates to outstanding issues in continental tectonics that motivate development of robust quantitative measures of paleoelevation

assimilation of sea surface height data into an isopycnic ocean model abstract two different methods for assimilating sea surface height data into an isopycnic primitive equation model were developed and tested for the idealized case of an analytical gaussian warm core anticyclonic eddy then implemented using remotely sensed data from the brazil malvinas confluence region the first method makes a geostrophic assumption about the flow to relate sea surface height field gradients to the model velocities the second method nudges the model sea surface height itself toward the observed values using a linear vertical influence function in the upper layers the relationship between the surface height observations and the layer interface displacements is derived from observations of eddies in different regions of the atlantic ocean both assimilation methods were successful in transferring the dynamical influence of the sea surface height measurements deep into the water column but a combination of both gave the best results the application of both methods reproduced the det

10 be and delta 2 h in polar ice cores as a probe of the solar variability s influence on climate and discussion by using the technique of accelerator mass spectrometry it is now possible to measure detailed profiles of cosmogenic cosmic ray produced 10 be in polar ice cores recent work has demonstrated that these profiles contain information on solar activity via its influence on the intensity of galactic cosmic rays arriving in the earth s atmosphere it has been known for some time that as a result of temperature dependent fractionation effects the stable isotope profiles delta 2 o and delta 2 h in polar ice cores contain palaeoclimate information thus by comparing the 10 be and stable isotope profiles in the same ice core one can test the influence of solar variability on climate and this independent of possible uncertainties in the absolute chronology of the records we present here the results of such a comparison for two antarctic ice cores one from the south pole covering the past ca 1000 years and one from dome c covering the past ca 3000 years

equatorially dominated magnetic field change at the surface of earth s core slow temporal variations in earth s magnetic field originate in the liquid outer core we analyzed the evolution of nonaxisymmetric magnetic flux at the core surface over the past 400 years we found that the most robust feature is westward motion at 17 kilometers per year in a belt concentrated around the equator beneath the atlantic hemisphere surprisingly this motion is dominated by a single wavenumber and persists throughout the observation period this phenomenon could be produced by an equatorial jet of core fluid by hydromagnetic wave propagation or by a combination of both discrimination between these mechanisms would provide useful constraints on the dynamics of earth s core

basalt vesicularity as a measure of atmospheric pressure and palaeoelevation the pressure in and thus the size of a bubble in a lava flow is determined by the atmospheric pressure and the hydrostatic pressure of the overlying lava if atmospheric sea level pressure is known or assumed vesicle size distributions in basalt flows can thus be used as an indicator of the palaeoelevation of emplacement1 here we show by analysis of the vesicle size distribution of basalt samples collected from the summit and base of mauna loa volcano in hawaii that the technique provides estimates of ambient pressure that are accurate to within 0 1 bar and thus estimates of elevation with a resolution of about 1 400m this palaeoaltimetric technique should find useful application in palaeogeographical reconstruction2 for times when sea level pressure was similar to the present value conversely if the elevation of emplacement is known our technique should be able to provide a measure of sea level palaeopressure unlike palaeo botanical methods for estimating elevations3 6 this method does not have to assume a relationship between temperature and altitude on the other hand its use is restricted to lava flows that have had a simple emplacement history

longevity and progressive abandonment of the rocky flats surface front range colorado abstract the post orogenic evolution of the laramide landscape of the western u s has been characterized by late cenozoic channel incision of basins and their adjacent ranges one means of constraining the incision history of basins is dating the remnants of gravel capped surfaces above modern streams here we focus on an extensive remnant of the rocky flats surface between golden and boulder colorado and use in situ produced 10be and 26al concentrations in terrace alluvium to constrain the quaternary history of this surface coal and ralston creeks both tributaries of the south platte river abandoned the rocky flats surface and formed the verdos and slocum pediments which are cut into cretaceous bedrock between rocky flats and the modern stream elevations rocky flats alluvium ranges widely in age from 2 ma to 400 ka with oldest ages to the east and younger ages closer to the mountain front numerical modeling of isotope concentration depth profiles suggests that individual sites have experienced multiple resurfacing events preliminary results indicate that verdos and slocum alluvium along ralston creek which is slightly larger than coal creek is several hundred thousand years old fluvial incision into these surfaces appears therefore to progress headward in response to downcutting of the south platte river the complex ages of these surfaces call into question any correlation of such surfaces based solely on their elevation above the modern channel

mesoscale eddies in the south china sea mean properties spatiotemporal variability and impact on thermohaline structure we investigated mean properties and the spatiotemporal variability of eddies in the south china sea scs by analyzing more than 7000 eddies corresponding to 827 eddy tracks identified using the winding angle method and 17 years of satellite altimetry data eddies are mainly generated in a northeast southwest direction and southwest of luzon strait there is no significant difference between the numbers of two types of eddies anticyclonic and cyclonic in most regions the mean radius and lifetime of eddies are 132 km and 8 8 weeks respectively both depending on where the eddies are formed anticyclonic and cyclonic eddies tend to deform during their lifetimes in different ways furthermore eddy propagation and evolution characteristics are examined in the northern scs eddies mainly propagate southwestward along the continental slope with velocities of 5 0 9 0 cm s 1 while in the central scs eddies tend to move with slight divergence but still in a quasi westward direction with velocities of 2 0 6 4 cm s 1 eddy propagation in the western basin to the east of vietnam is quite random with no uniform propagate direction investigation of 38 long lived eddies shows that eddies have a swift growing phase during the first 12 weeks and then a slow decaying phase that affects the eddy radii and eddy energy densities nevertheless vorticity has less variability in addition the effect of eddies on the thermocline and halocline is analyzed using 763 argo temperature profile data cyclonic eddies drive the thermocline shallower and thinner and significantly strengthen the thermocline intensity whereas anticyclonic eddies cause the thermocline to deepen and thicken and weaken the thermocline intensity to a certain degree the halocline impacted by cyclonic eddies is also shallower and thinner than that impacted by anticyclonic eddies finally eddy temporal variations are examined at seasonal and interannual scales eddy activity is sensitive to the wind stress curl and in the northern scs it is also related with the strength of the background flows

on the geomagnetic secular variation in the pacific region abstract it is widely believed that in the pacific region the geomagnetic secular variation is low and that the non dipole field is weak this is also known as hemispherical asymmetry between the pacific and the atlantic hemispheres representing the low secular variation in the pacific hemisphere with this characteristic feature a question has been left unsolved whether it is a permanent feature or a transient one reexamination of the geomagnetic field for the past 400 years indicates that in the early 17th century the non dipole field was not weak nor the secular variation was low in the pacific region implying that the hemispherical asymmetry is not a permanent phenomenon this paper examines the secular variation for the past 400 years from viewpoint of drifting and standing field model it has been found that the low secular variation in the pacific region is mainly caused by the drift of the drifting field at the earth s surface the drifting field is dominated by spherical harmonics y 2 2 with two pairs of ridges and troughs with their axes aligned in the meridional direction the two pairs are not equal one pair is stronger than the other movements of the different magnitude of the pairs are considered to have caused the hemispherical asymmetry of the secular variation for recent years giving rise to the non weak field in the pacific region in the early 17th century

oligocene miocene age of aridity in the atacama desert revealed by exposure dating of erosion sensitive landforms the age of onset of hyperaridity in the atacama desert chile which is needed to validate geological and climatological concepts has been heretofore uncertain measurement of cosmogenic 21 ne in clasts from erosion sensitive sediment surfaces in northern chile shows that these surfaces have been barely affected by erosion since 25 ma surface exposure ages of sediment clasts give replicate values at 25 20 and 14 ma and individual values at 37 and 9 ma predominantly hyperarid conditions are required to preserve these oldest continuously exposed surfaces on earth our findings are compatible with the hypothesis that the onset of aridity in the atacama desert could be the reason for rather than the consequence of uplift of the high andes

scaling factors for production rates of in situ produced cosmogenic nuclides a critical reevaluation abstract new scaling factors are presented describing the altitude and latitudinal dependence of production rates for in situ produced cosmogenic nuclides the new factors incorporate the influence of the non dipole contributions to the geomagnetic field on the cosmic ray flux the currently used scaling factors of lal earth planet sci lett 104 1991 424 439 are based on the assumption of a dipole field the overall strategy used in deriving the new scaling factors is however very similar to that of lal and relies on the same and or similar nuclear data in this reevaluation data are only used if the effective geomagnetic parameters inclination horizontal field strength can be reconstructed for the time of measurement the absorption free pathlengths for cosmic rays selected for this study are based on observational data at altitudes relevant for exposure age dating sea level to 7000 m at sea level and latitudes between 20 and 40 the new factors are up to 18 lower and at high altitudes more than 30 higher than those of lal in addition to accounting for the influence of the effective geomagnetic field and providing more applicable estimates of the new factors also allow for correction for the significant deviations from the standard pressure altitude relationship that exist in the atmosphere 10

paleoaltimetry incorporating atmospheric physics and botanical estimates of paleoclimate we present a method for deducing paleoaltitudes that incorporates basic physical principles of atmospheric science and inferences of paleoclimates from plant leaf physiognomy we exploit the average west to east flow of the atmosphere at mid latitudes and a thermodynamically conserved variable in the atmosphere moist static energy the combined internal latent heat and gravitational potential energy of moist air to develop a method that relies on a parameter that varies with height in the atmosphere in a predictable fashion because the surface distribution of moist static energy is constrained by atmospheric dynamics and thermodynamics the combined internal and latent heat energies also known as the moist enthalpy should only vary with altitude provided we know the distribution of moist static energy thus we avoid having to make assumptions about the mean annual temperature lapse rate which varies spatially and temporally owing to unpredictable variations in atmospheric water vapor to estimate a paleoaltitude therefore we require 1 a priori knowledge of the spatial distribution of moist static energy for the paleoclimate and 2 the ability to estimate paleoenthalpy for two isochronous locations one at sea level the other at some unknown elevation to achieve this we investigated the spatial distribution of moist static energy for the present day climate of north america to estimate the deviations in moist static energy from zonal invariance in parallel we quantified the relation between moist enthalpy and plant leaf physiognomy of modern forests assuming that such deviations from zonal invariance and such relationships between physiognomy and enthalpy apply to ancient climates and fossil leaves these investigations yield an uncertainty estimate of 910 m in the paleoaltitude difference between two isochronous fossil assemblage locations

geomagnetic secular variation we analyse over 175000 magnetic observations from an interval spanning 1695 1980 to produce a sequence of maps of the magnetic field at the core mantle boundary we find that even the earlier data enable us to determine reliable maps we produce these maps at approximately 60 year intervals through the eighteenth and nineteenth centuries and at 10 year intervals in the twentieth century this span of maps is long enough to render straightforward the distinction between static and drifting features in the field we observe that some features show no sign whatsoever of drift over the entire 285 year time interval although others drift westwards in particular we observe that the secular variation is very low beneath the pacific ocean but beneath southern africa and the south atlantic ocean we observe rapid secular variation we interpret the morphology of the static field in terms of a simple model of the dynamo and conjecture that interactions between the core and the mantle are an important element of the process as part of the static field we identify four main concentrations of flux two in each hemisphere at high latitudes these features largely account for the earth s axial dipole moment we find unequivocal evidence that magnetic flux has not remained frozen over the time span of our models much of the diffusive behaviour that we identify is associated with the formation of a pair of flux spots a core spot beneath southern africa early in this century nevertheless we are able to construct maps that satisfy a set of necessary conditions for frozen flux and use these maps to construct maps of the core surface fluid flow based on the steady flow hypothesis although we find no strong evidence against the steady flow hypothesis we do find some grounds on which to doubt the validity of the flow maps

dating fluvial terraces with and profiles application to the wind river wyoming abstract fluvial strath terraces provide a record of river incision and the timing of climatic perturbations to the fluvial system dating depositional surfaces like terraces that are older than the range of 14 c however is difficult we employ a cosmogenic radionuclide crn profile technique that addresses a major problem of crn dating on such surfaces nuclide inheritance by measuring 10 be and 26 al profiles we constrain the exposure age and the mean crn inheritance for the deposit the crn profile also yields a self check on the assumptions underlying the method we report our attempts to date terraces along the wind river wy like many sequences of western north american fluvial terraces these are inferred to reflect oscillation between glacial and interglacial conditions in the headwaters previous dating of some of these terraces and the associated terraces and glacial deposits makes this a unique location to compare dating methods dates from five sites along the bull lake glacial correlative terrace wr 3 are 118 125 ka which agrees with dates on bull lake age moraines and independent age estimates on the terrace and is consistent with the model of terrace glacial relationship crn inheritance is significant and highly variable requiring it be considered despite the additional sampling complexity assuming all inheritance in wr 3 deposits arises during exhumation in the headwaters we obtain minimum mean rates of exhumation of 13 130 m my for the source rocks alternatively assuming the crns are inherited during clast transport the time of fluvial transport from source to terrace is 10 ka it increases downstream and is lower for sand than cobbles the crn ages for older terraces wr 7 300 ka and wr 15 510 ka are lower by 50 than previous estimates based on tephrochronology the most plausible explanation is eolian deflation of a once thicker loess cover on the terrace surfaces mean thicknesses of loess of 0 5 1 5 m are required to reconcile these concentrations of crn with the previous estimates of age difficulty in dating the older terraces emphasizes that geologic caution independent estimates of age and multiple sample sites should still be part of dating depositional surfaces with crns even when employing the inheritance correction technique

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

constraints on age erosion and uplift of neogene glacial deposits in the transantarctic mountains determined from in situ cosmogenic 10be and 26al 10 be and 26 al data from sandstone boulders in three neogene glacial deposits in the mcmurdo sound dry valleys region of southern victoria land antarctica indicate minimum exposure ages of approx 3 ma and maximum long term erosion rates of approx 5 12 cm m y supporting the suggestion that polar desert conditions have persisted in the dry valleys since at least late pliocene time variation of cosmogenic nuclide production rate with altitude also allows constraints on past uplift rates model calculations employing 10 be data indicate little or no uplift in the dry valleys region in the past 3 m y precluding rapid 1 km m y late pliocene uplift previously suggested for some parts of the transantarctic mountains

the intrusion of water masses into the sea southwest of taiwan characteristics of water masses were analyzed to study the kuroshio intrusion into the sea southwest of taiwan hydrographic data were obtained from ctd conductivity temperature and depth casts during two cruises in may and august 1986 in may remnants of water intruding from the kuroshio were found on the continental slope south of the penghu channel by august these were replaced by water from the south china sea during this period water from the kuroshio also appeared near the southern tip of taiwan the intrusion current reached a depth of at least 500 m and was probably part of a cyclonic circulation in the northern south china sea the results support the hypothesis of a seasonal pattern of the intrusion process intrusion of water from the kuroshio begins in late summer intensifies in winter and ceases by late spring when south china sea waters again enter this region

an airborne expendable bathythermograph survey of the south china sea may 1995 an extensive airborne expendable bathythermograph survey of the south china sea scs conducted in may 1995 and historical data are used to analyze and infer the upper layer 300 m synoptic structure and general circulation the primary thermal feature observed was a central scs warm pool surrounded by several cool pools the size of the warm pool decreased with depth from approximately 200 000 km2 at 50 m depth to about 70 000 km2 at 300 m depth the maximum temperature of the warm pool was 30 c appearing near the surface at the depth of 50 m the temperature of the central scs warm pool was 29 c and the temperature of the five surrounding cool pools ranged from 26 c to 22 c a three dimensional estimate of the absolute velocity field was obtained from the observed temperature field and a climatological salinity field using the spiral method striking circulation features were the existence of dual anticyclonic eddies in the central scs warm pool and the existence of cyclonic eddies associated with the cool pools in the upper layer the tangential velocity of the dual central scs anticyclonic warm core eddies is around 30 40 cm s and that of the five cyclonic cool core eddies varies from 10 cm s to 40 cm s the tangential velocity of all the eddies decreased with depth at 300 m depth it became less than 5 cm s for all the eddies