blade and bifacial technology in mid holocene occupations at deseado massif santa cruz province argentina abstract in the deseado massif there are many stratified archaeological sites located in caves and rockshelters the cultural sequences proposed in the past century include an occupational hiatus and cultural changes that were developed on the basis of large tools from archaeological sites without debitage analysis the aim of this paper is to review the current debate on lithic technology and human occupations of this area during the mid holocene integrating new data as well as the latest environmental interpretations the contribution of new information from blade and bifacial technologies is central to discussion of the models proposed by other authors the new baseline information generated in the last decade allow original interpretations the evidence of coexistence between blade and bifacial technologies during the mid holocene constitutes the main contribution of this paper

laboratory model of a planetary eastward jet the concentration of eastward planetary currents into strong wavy jets is a major feature of the atmospheric general circulation for example the jet stream and of oceanic currents for example the gulf stream east of cape hatteras these strongly nonlinear jets are however not well understood here we describe experiments in which we have produced similar jets in a rotating annulus with mechanical forcing the coriolis force acting on fluid pumped radially inward from a ring of sources to a ring of sinks results in a strong eastward jet for a wide range of parameters the jet has a robust wavy shape as shown in fig 1 the wave velocity and wavelength of these rossby waves are accounted for by simple scaling arguments experiments with dye injected into the fluid show that the jet acts as a barrier to tracer transport see fig 1e much as the southern polar night jet may act as a barrier to the transport of ozone from lower latitudes into the polar region1 our observations are insensitive to the details of the arrangement of the sinks and sources

stable isotope compositions of waters in the great basin united states 3 comparison of groundwaters with modern precipitation 1 groundwater samples from wells and springs scattered over most of the great basin province were collected and analyzed for their isotopic makeup they were augmented by previously published isotopic data on groundwaters from southeast california and by several hundred unpublished isotopic analyses the ratio of 2h deuterium d to 1h in water samples from valleys in parts of california idaho nevada oregon and utah are here compared with the winter summer and annual isotopic compositions of precipitation falling in or near the sampled areas the main goal of this study was to identify basins where the groundwaters have isotopic compositions that are lighter depleted in the heavier isotope d relative to modern winter precipitation where these basins do not adjoin substantially higher terrain we consider those light groundwaters to be of pleistocene age and thus more than 10 000 years old where the groundwater is 10 to 19 lighter than local winter precipitation we consider it to be possibly an indication of pleistocene water where the d makeup is 20 lighter we consider it to be probably pleistocene water more than 80 sites underlain by waters of possible or probable pleistocene age were identified

reply to interbasin groundwater flow in south central nevada a further comment on the discussion between davisson et al 1999a 1999b and thomas 1999

jupiter s great red spot as a shallow water system most current models of jupiter s great red spot grs are cast in terms of a two layer model where a thin upper weather layer which contains the vortex overlies a much deeper layer which is meant to represent the neutrally stratified deep atmosphere any motions in the deep layer are assumed to be zonal and steady this two layer model is dynamically equivalent to a one layer model with meridionally varying solid bottom topography called the reduced gravity model specifying the motions or lack thereof in the lower layer of the two layer model is equivalent to specifying the bottom topography and hence the far field potential vorticity in the reduced gravity model current models of the grs start by guessing the deep motions and then proceed to study vortices using the implied bottom topography here using the grs cloud top velocity data we derive the bottom topography up to a constant that depends on the unknown radius of deformation or equivalently the product of the reduced gravity and the mean thickness of the upper layer the bottom topography is inferred from three quantities derived from the velocity data bernoulli streamfunction kinetic energy per unit mass and absolute vorticity all of which are functions only of horizontal position in the reference frame of the vortex far from the vortex potential vorticity versus latitude is calculated from the observed cloud top zonal velocity and the derived bottom topography the results show that the deep atmosphere is in differential motion and that the far field potential vorticity gradient changes sign at several latitudes numerical shallow water experiments are performed using both the derived bottom topography and the bottom topographies prescribed by current models the results of three published studies are reproduced in our numerical experiments each of these models is successful in maintaining a long lived isolated vortex but only the present model yields absolute vorticity profiles along streamlines that agree with those observed for the grs by dowling and ingersoll in all the models large vortices form by merging with smaller vortices in the present observationally based model and in one other published model the smaller vortices arise spontaneously because the observed cloud top zonal velocity profile is unstable these two models require an additional momentum source to maintain the upper layer zonal velocity profile in the other two models the bottom topography stabilizes the zonal velocity profile if dissipation is present the latter two models require an additional source of smaller vortices to maintain the larger one a crucial unanswered question for the present model and for jupiter itself is how the cloud top zonal velocity profile is maintained in its present unstable state

holocene explosive activity of hudson volcano southern andes fallout deposits in the vicinity of the southern andean hudson volcano record at least 12 explosive holocene eruptions including that of august 1991 which produced 4 km3 of pyroclastic material medial isopachs of compacted fallout deposits for two of the prehistoric hudson eruptions dated at approximately 3600 and 6700 bp enclose areas at least twice that of equivalent isopachs for both the 1991 hudson and the 1932 quizapu eruptions the two largest in the andes this century however lack of information for either the proximal or distal tephra deposits from these two prehistoric eruptions of hudson precludes accurate volume estimates andesitic pyroclastic material produced by the 6700 bp event including a 1 10 cm thick layer of compacted tephra that constitutes a secondary thickness maximum over 900 km to the south in tierra del fuego was dispersed in a more southerly direction than that of the 1991 hudson eruption the products of the 6700 bp event consist of a large proportion of fine pumiceous ash and accretionary lapilli indicating a violent phreatomagmatic eruption this eruption which is considered to be the largest for hudson and possibly for any volcano in the southern andes during the holocene may have created hudson s 10 km diameter summit caldera but the age of the caldera has not been dated independently

mid holocene climatic variability reconstruction from pollen records 32 52 s argentina abstract this study reviews 42 published pollen records to gain a better understanding of holocene climate variability especially of the past displacement and location of the arid semiarid region asr between 32 and 52 s in argentina at present the asr is delimited approximately between the 500 mm isohyet in the pampa region and the 300 mm isohyet in the andean sector south of 37 s represented by arid and semiarid climate types where precipitation can be as low as 200 mm mid holocene climatic variability affected the regional vegetation patterns and the borders of the asr paleoenvironmental reconstruction is based on comparison of fossil pollen records from different depositional environments maps of distribution patterns of plant formations are reconstructed at 2000 500 year intervals from 8000 to 4000 14 c years bp vegetation changes are mainly explained by changes in the position and the seasonal amplitude of latitudinal shifts of the pacific and atlantic anticyclones and of the westerlies from 8000 to 4000 bp the eastern limit of the asr was displaced eastward the western limit reached the maximum eastward displacement in the southern extreme of patagonia at 6000 years bp at this time at the center of asr shrub steppes and the monte developed suggesting maximum dry conditions and the establishment of the arid diagonal north of 42 s while the present day espinal dry pampa ecotone became established at 4000 years bp paleodata suggest a transitional stage towards the present situation of the asr

mountain torques and atmospheric oscillations theoretical work and general circulation model gcm experiments suggest that the midlatitude jet stream s interaction with large scale topography can drive intrasea sonal oscillations in large scale atmospheric circulation pat terns in support of this theory we present new observa tional evidence that mountain induced torques play a key role in 15 30 day oscillations of the northern hemisphere circulation s dominant patterns the affected patterns in clude the arctic oscillation ao and the pacific north american pna pattern positive torques both accelerate and anticipate the midlatitude westerly winds at these peri odicities moreover torque anomalies anticipate the onsets of weather regimes over the pacific as well as the break ups of hemispheric scale regimes

light stable isotope systematics of large scale hydrologic regimes in california and nevada surface waters shallow groundwaters and precipitation samples were collected along three traverses which begin at the california coast and are oriented in an east west manner roughly parallel to the atmospheric flow path of meteoric water the hydrogen isotope compositions from short term precipitation records varied as much as 40 at one location and were not representative of the average annual isotopic composition of precipitation the hydrogen isotope ratios of surface waters and shallow groundwaters distinguish segments with isotopic variations that correlate with measured vertical fluxes of meteoric water one coastal segment appears to closely approximate an open system in which precipitation dominates over evapotranspiration most segments are described by rather regular variations in d 3 45 per 100 km which represent different degrees of closure of the hydrologic system caused by variable partitioning of precipitation between runoff and evapotranspiration all partially closed systems imply terrestrial recycling of water a simple model estimates this amount to be about 20 across northern and central california three segments representing the great basin show virtually no geographic variation and appear to represent isotopically closed systems

vegetational changes during the holocene in extra andean patagonia santa cruz province argentina abstract modern pollen vegetation relationship was used in the interpretation of stratigraphical sequences from two archeological sites la martita cave 48 24 s 69 15 w and alero cardenas 47 18 s 70 26 w located in extra andean patagonia in the santa cruz province the modern pollen assemblages are related to vegetation units that extend from the andes toward the atlantic coast reflecting the increase of aridity from west to east the more humid areas in the west are represented by grass steppe with festuca pallescens in those areas of intermediate humidity shrub steppe can be found with a conspicuous stratum of stipa s speciosa s humilis and s chrysophylla and shrubs nardophyllum obtusifolium berberis heterophylla senecio filaginoides mulinum spinosum and in the most arid areas scrub steppe expands with nassauvia glomerulosa and cushion plants such as azorella caespitosa accantholippia seriphiodes chuquiraga aurea brachyclados caespitosus a vegetational and paleoclimatic history is presented based on comparison with modern analogs and with other palynological records from southern patagonia prior to 8000 yr b p a grass steppe extended indicating relatively high precipitation under cold conditions between 8000 and 6000 yr b p an increase of shrub steppe taxa dominated by asteraceae tubuliflorae would relate to an increase in temperature while precipitation remained in the previous range of about 200 mm the mid holocene 5000 yr b p is reflected in the la martita sequence by a short term return of steppe taxa primarily grasses this steppe could indicate cold conditions similar to those of the early holocene or an increase in precipitation after 4500 yr b p the vegetation is represented by grass shrub steppe after 3500 yr b p the alero cardenas record shows a shrub steppe dominated by asteraceae tubuliflorae in records near the steppe forest ecotone at 47 and 50 s the more extensive late holocene forest suggests greater effective moisture probably related to cooler temperatures in alero cardenas grasses increase and shrubs are irregularly present in altiplanicie central steppe vegetation is analogous to the present vegetation in the present century taxa indicative of disturbance are present rumex acetosella and brassicaceae

topographic influences on wind driven stratified flow in a β plane channel an idealized model for the antarctic circumpolar current abstract topographic influences are examined in an eddy resolving model of oceanic channel flow forced by steady zonal winds with small explicit lateral friction transient eddies generated by the baroclinic instability of the mean flow transfer momentum downward to the bottom layer in the flat bottom case bottom friction is the only efficient sink of eastward momentum when bottom topography is present the topographic form stress can replace the bottom friction sink in the momentum budget and a large decrease of the zonal transport results large wale topography of the scale of the forcing provides the largest form stress topographic effects decay with height as suggested by the prandit scaling and therefore only topographic scales larger than the rossby radius can affect the whole water column in that case the interfaces are deformed by standing eddies on topographic length scales and standing eddies replace transient eddies in transferring momentum downward the bottom layer mean streamfunc

multiple flow regimes in the northern hemisphere winter part i methodology and hemispheric regimes abstract recurrent and persistent flow patterns are identified by examining multivariate probability density functions pdfs in the phase space of large scale atmospheric motions this idea is pursued systematically here in the hope of clarifying the extent to which intraseasonal variability can be described and understood in terms of multiple flow regimes bivariate pdfs of the northern hemisphere nh wintertime anomaly heights at 700 mb are examined in the present paper using a 37 year dataset the two dimensional phase plane is defined by the two leading empirical orthogonal functions eofs of the anomaly fields pdfs on this plane exhibit synoptically intriguing and statistically significant inhomogeneities on the periphery of the distribution it is shown that these inhomogeneities are due to the existence of persistent and recurrent anomaly patterns well known as dominant teleconnection patterns that is the pacific north american pna pattern its reverse and zonal and blocked phases of the

palaeoclimates in central and south america since 18 000 bp based on pollen and lake level records abstract the last 18 ka of palaeoclimates are discussed at 3 ka intervals based on palaeoenvironmental changes shown in pollen and lake level records from central and south america a total of 61 pollen records fulfill the requirements of continuity and chronology to be used in this synthesis 8 records from tropical and subtropical lowlands in central and south america 7 records from the central american highlands 26 records from the high andes north and south of the equator 2 records from the southern subtropics and 18 from the southern andes and subantarctic islands palaeoclimatic interpretation of the pollen records is semiquantitative based on bioclimatic parameters such as e g elevational temperature gradients or latitudinal precipitation gradients that can be related to vegetation zonation additional palaeoclimatic information is obtained from lake level records derived either from dated shorelines or from the limnological history of lake sediment sections large scale palaeoclimatic comparison of the proxy data records indicates that full and late glacial climates throughout central and south america were cooler than today by about 4 to 5 c but that moisture patterns showed regional differentiation thus in both the southern subtropics and high latitudes in southern chile conditions were substantially moister than today during full and late glacial times whereas everywhere else conditions were far drier than today in terms of palaeocirculation this scenario can be interpreted as a poleward shift of the subtropical as well as the westerly circulation a scenario that has been suggested by palaeoclimatic simulations from general circulation models gcm another major palaeoclimatic aspect predicted by the gcm simulations is the suppressed early holocene summer monsoon in the southern subtropics although proxy records are few from this zone their palaeoenvironmental history during that time shows a period of aridity that would support the model one of the most controversial aspects of south american palaeoclimates concerns the existence of a younger dryas equivalent a cold period between 11 and 10 ka bp based on the existing data from south america that show a great diversity of palaeoclimatic trends the concept of an interval that is characterized by the same climatic signal as documented for the north atlantic seems too simplistic moreover at this point only very few records have been analysed in sufficient detail to yield unambiguous climatic information for the interval in question the principal outcome of this palaeoenvironmental and palaeoclimatic synthesis is the better understanding of the type and quality of data available at present and the realization of regions and periods where much more and concerted effort is needed to address problems of intra and interhemispheric palaeoclimatic correlations only then can questions concerning the mechanism of climatic change be tackled successfully

observed and simulated intraseasonal variability of the wintertime planetary circulation abstract the persistence of the planetary scale simulation over the north pacific ocean is investigated during 18 northern hemisphere winters from 1965 66 to 1982 83 quasi stationary flow patterns dominate 20 periods during the 6 el nino winters in contrast 29 such periods are observed during the remaining 12 winters nearly all of the quasi stationary episodes during el nino winters exhibit negative 500 mb geopotential height anomalies in the gulf of alaska aleutian island region during the other 12 winters episodes characterized by positive height anomalies in that region occur as frequently as those exhibiting negative height anomalies the observed persistence of the planetary circulation is contrasted to that simulated by the ucla general circulation model ten winters of model output are analyzed during five winters sea surface temperatures ssts are prescribed to evolve through their climatological seasonal cycle while during the other five winters sst anomalies corresponding to idealized

tool production processes in lithic quarries from the central plateau of santa cruz argentina abstract lithic resources at the central plateau of santa cruz argentina are abundant ubiquitous and of very good quality for knapping they have been exploited by hunter gatherer societies since the latest pleistocene until the late holocene the study of their distribution availability and ways of exploitation at the quarries together with the information stemming from the archaeological sites enable the understanding of the first stages of tool production and consumption in this paper two quarries from la maria archaeological locality cantera de silex de cdm and cantera bosque petrificado are studied and compared their geomorphologic location is described the lithological characteristics of the outcrops the size of the stones and the variability of raw materials available at them are also addressed the accessibility and visibility of the quarries are analyzed the way raw materials were exploited at the sources is evaluated taking into consideration their relationship with the local and regional structure of lithic resources the information generated for the quarries is complemented and compared with the local trends identified for the habitation sites this enabled the formulation of a general model about the first stages of production although the quarries have different types of raw materials flint and silicified wood results show that similar technological strategies were implemented in them these are in agreement with the general trend at the local and regional levels both sources are easily accessible from the surrounding landscape they are visible from nearby areas probably they were exploited mainly from nearby sites at the quarries the first stages of tool production were performed core decortication and preparation and the production of blanks the acquisition of raw material involved the selection of good quality nodules and boulders and the production of polyhedral cores knapped in multiple directions these cores could be transported to the habitation sites or could be discarded in situ while still presenting active platforms on the other hand differences in some procurement practices might be related to decisions and variations linked to the particular characteristics of the resources in both outcrops

intraseasonal variability in a barotropic model with seasonal forcing abstract it has recently been suggested that oscillatory topographic instability could contribute to low frequency variability over the northern hemisphere midlatitudes a barotropic potential vorticity model with a hierarchy of forcing and topography configurations on the sphere is used to investigate the nature of low frequency oscillations induced by such instabilities steady state solutions of the model include multiple unstable equilibria that sustain oscillatory instabilities with periods of 10 15 days 35 50 days and 150 180 days for a realistic forcing pattern time dependent solutions exhibit chaotic behavior with episodic oscillations featuring both the intraseasonal 35 50 day and biweekly 10 15 day modes the former is dominated by standing spatial patterns the latter by traveling wave patterns the phases of the intraseasonal oscillation are robust for all cases exhibiting a clear oscillatory exchange of atmospheric angular momentum with the solid earth via mountain torque it is d

experimental and numerical studies of an eastward jet over topography motivated by the phenomena of blocked and zonal flows in earth s atmosphere we conducted laboratory experiments and numerical simulations to study the dynamics of an eastward jet flowing over wavenumber two topography the laboratory experiments studied the dynamical behaviour of the flow in a barotropic rotating annulus as a function of the experimental rossby and ekman numbers two distinct flow patterns resembling blocked and zonal flows in the atmosphere were observed to persist for long time intervals earlier model studies had suggested that the atmosphere s normally upstream propagating rossby waves can resonantly lock to the underlying topography and that this topographic resonance separates zonal from blocked flows in the annulus the zonal flows did indeed have super resonant mean zonal velocities while the blocked flows appear subresonant low frequency variability periodic or irregular was present in the measured time series of azimuthal velocity in the blocked regime with dominant periodicities in the range of 6 25 annulus rotations oscillations have also been detected in zonal states with smaller amplitude and similar frequency in addition over a large region of parameter space the two flow states exhibited spontaneous intermittent transitions from the one to the other we numerically simulated the laboratory flow geometry in a quasi geostrophic barotropic model over a similar range of parameters both flow regimes blocked and zonal were reproduced in the simulations with similar spatial and temporal characteristics including the low frequency oscillations associated with the blocked flow the blocked and zonal flow patterns are present over wide ranges of forcing topographic height and bottom friction for a significant portion of parameter space both model flows are stable depending on the initial state either the blocked or the zonal flow is obtained and persists indefinitely showing the existence of multiple equilibria

changes in lithic technology and environment in southern continental patagonia the chico and santa cruz river basins abstract changes in artifact technology and environment during the holocene are documented within an organization of technology framework for three different regions of patagonia possible relationships between environmental changes and changes in artifact technology are explored we examine past vegetation and geomorphic evidence of holocene climate conditions in the three regions studied and what technologies were used during particular wetter and drier intervals our results suggest that many of the observed changes in technology use occurred at times of rapid climate change particularly towards much drier conditions

predominance of arid climates indicated by mammals in the pampas of argentina during the late pleistocene and holocene abstract south american climates during the pleistocene and holocene are poorly known especially in the lowlands east of the andean ranges however there is relatively good biostratigraphic and climatic information for the late lujanian and platan local ages latest pleistocene to holocene of the pampas region most of the climatic data from the pampean area are based on land mammal assemblages pollen records and geology contrasting with north american faunal associations there are many non analogue assemblages in the holocene of the pampean area the climate was arid and relatively cold during most of the early lujanian however several relatively wet and warm events are suggested by the presence of subtropical mammals and evidence of tchernozoid paleosoils the late lujanian is well represented by the fossiliferous sediments of the la chumbiada and guerrero members of the lujan formation ca 30 000 and 21 000 13 000 yr b p respectively cropping out in stream valleys in the buenos aires province mammal assemblages suggest a change from a temperate to a cool climate from the la chumbiada member to the guerrero member the latter representing the last glacial maximum the lower portion of the eolian la postrera formation has been dated at 11 000 8000 yr b p this section was deposited on basin divides under dry and cool conditions the mammal association was similar to that of the gueffero member and includes the last megaherbivore mammals in south america e g megatherium americanum mammals occurring in platan beds usually indicate dry but not cool conditions warm and probably wetter conditions were detected in continental beds deposited synchronously with a mid holocene marginal marine ingression ca 7000 6000 yr b p a holocene non analogue assemblage of subtropical mammals and dry cold indicators occurred at latitude 38 30 s at ca 2000 yr b p subtropical mammals that require wetter conditions have been migrating southwards in the pampean region since 1500 1000 yr b p eolian sediments in the la postrera formation dated ca 440 yr b p yielded an arid to semiarid mammal assemblage which could relate to the little ice age period remarkably most of the present day manual biocenoses and climatic conditions in the pampas seem to have been recently established paleogeographic maps for the last glacial maximum and the mid holocene are also provided

raw material exploitation around the middle paleolithic site of ein qashish abstract lithic reduction sequences reflect decisions made by ancient tool makers the first stages of a reduction sequence concern raw material procurement and include identifying sources on the landscape testing the quality of raw material knapping on the spot or moving material to other locations the distance from raw material source to a destination location is a significant factor that has implications for artifact life history ein qashish is located in the western yizra el valley the lithic assemblage from the late middle paleolithic site of ein qashish is made exclusively on flint this raw material occurs as several different visual types distinguished by their colors and textures several geological formations some of which are flint bearing are known at various distances from the site which is situated on a distal alluvial fan of a drainage that carried sediments and small flint nodules from mt carmel towards the qishon stream in the east in order to associate archaeological flint from the assemblage of ein qashish to potential geological sources we used visual observations color and texture geochemical icp ms icp aes analyses and statistical methods e g anova and principle component analysis our analysis shows that icp ms and icp aes can be used to differentiate between flints from various geological formations and to assign archaeological artifacts to geological origin areas the inhabitants of ein qashish obtained flints from various distances and integrated on site knapping of flint from relatively closer sources with transport of finished tools from more distant locations the relationship between the distance of potential raw material sources and the distribution of raw materials among technological products from different stages of reduction is addressed in order to discuss mobility patterns and raw material economy

hunter gatherer provisioning strategies in a landscape with abundant lithic resources la primavera santa cruz argentina abstract the aim of this paper is to generate new data on raw material sourcing of multiple activities sites at la primavera locality to describe some provisioning strategies adopted by mobile hunter gatherer societies and contribute to the study of the local settlement in the wider regional context the local structure of lithic resources is characterized the natural distribution of useful rocks is modeled and the raw materials of artifacts from multiple activities sites are sourced the classification and sourcing technique applied is not a determinant method but a preliminary approach adequate to deal with a very large lithic artifact sample the rock distribution across the landscape was analyzed using a geographical information systems gis for compiling the available data and estimating the distances from the sites to the sources for each raw material found in them based on the circulation distances and different considerations regarding the characteristic of the lithic sources three different provisioning strategies are delineated they suggest that settlement at the locality involved a certain permanence time that surpasses a logistic use while keeping trade and social networks with other localities in the regional context

middle paleolithic open air industrial areas in the galilee israel the challenging study of flint extraction and reduction complexes abstract during the last dozen years we discovered tested and studied several paleolithic flint extraction and reduction complexes in northern israel these paleolithic industrial areas are assigned based on lithic techno typology to the lower middle paleolithic of the levant however the most conspicuous component in all these complexes is the constant use of the levallois technology the immense scale of these sites and the immense lithic assemblages allowed only preliminary field investigations and analyses such paleolithic industrial areas demand a different research design than the one used at habitation sites or other task specific localities previous work demonstrated the potential of these complexes in understanding patterns of human behavior related to flint economy the organization of quarrying and knapping operations the scale of human exploitation of the natural resources caching behavior and more our investigations thus far are however only the tip of the iceberg of the research potential embedded within these unique archaeological complexes this paper raises questions on methodological and conceptual challenges we are confronted within studying these paleolithic extraction reduction complexes especially their formation processes it also brings up the question of how such sites can be incorporated in the future study of middle paleolithic mousterian in the levant

persistent anomalies blocking and variations in atmospheric predictability abstract we consider regimes of low frequency variability in large scale atmospheric dynamics the model used for the study of these regimes is the fully nonlinear equivalent barotropic vorticity equation on the sphere with simplified forcing dissipation and topography twenty five modes are retained in a spherical harmonics expansion of the streamfunction solutions are studied as a function of the nondimensional intensity of the forcing and dissipation multiple stationary solutions are obtained as a result of nonlinear interaction between waves mean flow and orography the number of modes retained in the analysis permits these multiple equilibria to appear for realistic values of the forcing the equilibria exhibit blocked and zonal flow patterns bearing a marked resemblance to synoptically defined zonal and blocked northern hemisphere midlatitude flows wave wave interactions influence strongly the stability properties of the equilibria and the time evolution of nonequilibrium solutions time depe

the effects of boundary topography on convection in earth s core summary we present the first investigation that explores the effects of an isolated topographic ridge on thermal convection in a planetary core like geometry and using core like fluid properties i e using a liquid metal like low prandtl number fluid the model s mean azimuthal flow resonates with the ridge and results in the excitation of a stationary topographic rossby wave this wave generates recirculating regions that remain fixed to the mantle reference frame associated with these regions is a strong longitudinally dependent heat flow along the inner core boundary this effect may control the location of melting and solidification on the inner core boundary theoretical considerations and the results of our simulations suggest that the wavenumber of the resonant wave lr scales as ro 1 2 where ro is the rossby number this scaling indicates that small scale flow structures wavenumber in the core can be excited by a topographic feature on the core mantle boundary the effects of strong magnetic diffusion in the core must then be invoked to generate a stationary magnetic signature that is comparable to the scale of observed geomagnetic structures

transitions between blocked and zonal flows in a rotating annulus with topography the mid latitude atmosphere is dominated by westerly nearly zonal flow occasionally this flow is deflected poleward by blocking anticyclones that persist for 10 days or longer experiments in a rotating annulus used radial pumping to generate a zonal jet under the action of the coriolis force in the presence of two symmetric ridges at the bottom of the annulus the resulting flows were nearly zonal at high forcing or blocked at low forcing intermittent switching between blocked and zonal patterns occurs because of the jet s interaction with the topography these results shed further light on previous atmospheric observations and numerical simulations

representing topographic stress for large scale ocean models abstract interaction of eddies with seafloor topography can exert enormous systematic forces on the ocean circulation this interaction has been considered previously under idealized circumstances theoretical results are here simplified and extended toward practical application in large scale ocean circulation models among the suggestions is that coarse resolution models can correct a depth independent part of the velocity field toward a velocity given by z flh where z is the vertical unit vector f is coriolis form l is a length scale o 10 km and h is the total depth absence of this tendency may be implicated in a number of systematic defects that appear in present ocean models

mountain torques and northern hemisphere low frequency variability part i hemispheric aspects the ncep ncar reanalysis dataset for 1958 97 is used to analyze intraseasonal variations in mountain torques and the large scale atmospheric circulation patterns associated with them spectral analysis of the atmospheric angular momentum aam budget shows that the dominant variations of mountain torque have periodicities near 30 days and shorter while the dominant aam variations occur in the 40 60 day band this difference is due to the 40 60 day aam variations being primarily related to equatorial processes while mountain torque variations are associated mostly with extratropical processes the northern hemisphere nh mountain torque has enhanced power and significant spectral peaks in the 20 30 day band the signal in this band accounts for 33 of the nh mountain torque variance once the seasonal cycle has been removed lag composites of the nh 700 hpa geopotential heights based on the 20 30 day mountain torque signal show the latter to be associated with coherent large scale patterns that resemble lowfrequency oscillations identified in this band by previous authors the composite patterns that are in phase quadrature with the 20 30 day nh mountain torque have a pronounced zonally symmetric component these patterns are associated with substantial aam variations arguably driven by the nh mountain torque in this band principal component pc analysis of the nh 700 hpa heights shows that in the 20 30 day band the mountain torque is also in phase quadrature with the two leading pcs the first corresponds to changes in the midlatitude jet intensity near the subtropics while the second corresponds to the arctic oscillation the relationships with aam of the latter essentially occurs through the mass term mountain torques are furthermore nearly in phase with dominant patterns of low frequency variability that exhibit substantial pressure gradients across the rockies and the tibetan plateau

the latitude height structure of 40 50 day variations in atmospheric angular momentum abstract quasi periodic variations in the relative angular momentum of the atmosphere on time scales of around 40 50 days have been observed by langley et al 1981 a description of the two dimensional latitude height structure of the winds responsible for these changes is constructed here from five years of nmc twice daily global analyses using cross spectral and amplitude phase eigenvector techniques we find these variations are associated with wavelike motions in the tropical upper troposphere that propagate and downward in phase within the tropics a coherently connected midlatitude northern hemisphere component is also present whose phase is essentially independent of height we believe the tropical component to be the zonally averaged part of the motions described by madden and julian 1971 1972 the northern hemisphere midlatitude component may be a direct response to the tropical motions or both motions may be the common response to an as yet unidentified tropical forcing

when patagonia was colonized people mobility at high latitudes during pleistocene holocene transition abstract the pleistocene holocene transition was a critical time for the dispersal of human societies all over south america people looking for places to settle had to accept high environmental variability during the colonizing process the case studied for this paper is patagonia southern south america where the oldest dates ca 13 10 5 ka bp have been obtained for the peopling in the deseado river basin and magellan basin as well however two archaeological sites yielded similar dates on the western side of the andes monte verde and tagua tagua following archaeological and palaeoenvironmental data palynological faunal sedimentological and glaciological information as well as radiocarbon datings a hypothesis about the colonization of patagonia is presented analysing the ways and time of colonization for this region it is remarkable the coincidence of these ages in the centre of the steppe and close to the magellan strait even in the present tierra del fuego island though the eastern andean foothills seems to be occupied at least two millennia later it is proposed that independent peopling entries would have occurred both through the atlantic and pacific facades and that the andean foothills were colonized much later only when the available spaces allowed it

mid holocene paleoenvironments and the archeological record of southern mendoza argentina the environmental heterogeneity of southern mendoza led to different environmental responses during the mid holocene more arid conditions and perhaps higher temperatures were dominant in the lowlands while the high andes experienced increased snowfalls and neoglacial readvances from ca 6000 to 4000 years bp the opposing climate pattern of the region in comparison with the western pacific foothills of the andes is apparently related to the different influences exerted by the westerlies on both sides of the cordillera the archeological record of this time period is represented by very few sites with a low density of material both the temporal distribution of the radiocarbon dates and the occupation index suggest a significant decrease of human occupations manifested by a chronological hiatus which varies in timing and duration according to the areal scale of analysis the coincidence of the occupational hiatus and the low amount of archeological evidences would point to abandonment and or a change related to a low intensity pattern of land use across the region these human responses seem to parallel the general arid climatic conditions of the mid holocene although more detailed information and particularly numerical dates are needed to test the hypothesis site formation processes including site disturbance produced by later human occupations are alternative explanations also evaluated to give account of the archeological record

the statistical properties of general atmospheric circulation observational evidence and a minimal theory of bimodality in this paper we address the problem of constructing a minimal model of atmospheric circulation able to describe the bulk of the statistical properties of the general circulation in middle latitudes after a brief reexamination of the charney devore theory of multiple equilibria we compare the statistical properties that can be deduced from it with those resulting from analysis of observations of the northern hemisphere middle latitude circulation at 500 mb while the prediction concerning the amplitude of the waves seems to be confirmed by the presence of a clear bimodality of the statistical distribution we find no trace of bimodality in the zonal wind we show how the theory can be brought into agreement with observations by introducing nonlinearity into the wave equation in such a way that the charney devore resonance curve is bent producing different states corresponding to the same value of the zonal wind we finally address ourselves to the question of what physical processes determine the observed unimodal statistics of zonal wind a subject of future work

intraseasonal oscillations in the global atmosphere i northern hemisphere and tropics abstract we have examined systematically oscillatory modes in the northern hemisphere and in the tropics the 700 mb heights were used to analyze extratropical oscillations and the outgoing longwave radiation to study tropical oscillations in convection all datasets were band pass filtered to focus on the intraseasonal is band of 10 120 days leading spatial patterns of variability were obtained by applying eof analysis to these is data the leading principal components pcs were subjected to singular spectrum analysis ssa ssa is a statistical technique related to eof analysis but in the time domain rather than the spatial domain it helps identify nonlinear oscillations in short and noisy time series in the northern hemisphere there are two important modes of oscillation with periods near 48 and 23 days respectively the 48 day mode is the most important of the two it has both traveling and standing components and is dominated by a zonal wavenumber two the 23 day mode has the spatial stru

interbasin groundwater flow in south central nevada a further comment on the discussion between davisson et al 1999a 1999b and thomas 1999 in their response to the comments by thomas 1999 davisson et al 1999a dismiss a large set of potentiometric measurements pertinent to an understanding of the hydrogeology of yucca and frenchman flats in southcentral nevada this commentary is submitted to demonstrate first that their dismissal of this data set is unfounded and second that these potentiometric data call into question the central thesis of the original paper by davisson et al 1999b

combining remote sensing geophysics and lithic provenance and reduction to understand long term continuity in paleo inuit chert quarrying and seasonal inland travels on southern baffin island nu abstract in 2013 we identified a large chert quarry located in the intermediate zone between southern baffin island s coast and interior in 2015 we used a combination of remote sensing and geophysical technology to assess how intensively pre dorset and dorset populations collectively known as paleo inuit used the site this paper presents the results of those investigations and explains how they articulate with geochemical and lithic reduction data from two large inland paleo inuit habitation sites on southern baffin island our findings suggest that despite a dramatic shift in the arctic climate c 5000 2500 bp human populations in this region maintained seasonal patterns of intensive resource exploitation in the interior regions of baffin island this was likely a result of ongoing need for vital resources only available in the interior including chert toolstone

an experimental study of baroclinic flows with and without two wave bottom topography abstract a series of laboratory experiments was performed in a thermally driven rotating annulus of fluid with and without two wave bottom topography velocity measurements were made by illuminating a thin layer of fluid at mid depth and photographing successive positions of tracer particles suspended in the fluid streamfunctions were determined from the calculated vorticity comparison of the rotational velocity field with the measured velocity field revealed negligible differences indicating that the flow was horizontally quasi nondivergent a detailed analysis was made of one experiment with and one without topography at the same point in dimensionless parameter space the results indicate that the effect of topography is 1 to modulate the synoptic scale waves in both space and time 2 to suppress the odd modes and 3 to force a planetary scale mode which oscillates about a climatological mean position with high pressure centers located in this experiment approximately 22 upstream of the mounta

stable isotope imaging of a dynamic groundwater system in the southwestern sacramento valley california usa abstract a dynamic image of a shallow 45 160 m below the surface aquifer in a 25km2 area in the southwestern sacramento valley california has been obtained by 18 o 16 o and d h determinations of groundwater from municipal wells the regular summertime drawdown of the water table is strongly correlated with municipal wide increases in the 18o values particularly in wells with shallow perforation levels thus demonstrating that the high 18o water resides in the upper reaches of the aquifer and penetrates more deeply with increased discharge rates these 1 5 enrichments in the 18o values are primarily attributed to infiltration of irrigation water that has penetrated to depths of at least 80 m the increased 18o values correlate with increased deviation from the meteoric water line and with increased nitrate levels indicating that the high 18o groundwater component represents local meteoric water that has been enriched by soil evaporation processes in nitrogen fertilized flood irrigated cropland isotopic gradients provide a new method for qualitatively determining subsurface permeability zones of low isotopic gradients interpreted as high 18o plumes probably follow coarse textured deposits of ancient stream channels the 18o gradients are primarily controlled by subsurface permeability although additional influences may include 1 the heterogeneous distribution of the high 18o groundwater 2 isotopic contributions from deeper groundwater 3 variable perforation depths of the wells 4 local differences in the water table level deeper sodium bicarbonate groundwaters 300 650 m below the surface have lower 18o values to 9 4 than the more shallow magnesium bicarbonate groundwaters suggesting derivation from 18o depleted meteoric groundwaters of the sierra nevada minor mixing of the deeper groundwater into the municipal discharge occurs even though previous workers considered the deeper groundwater to be confined

hydrochemistry and isotope composition of springs in the tecopa basin southeastern california usa abstract springs and seeps in the tecopa basin were sampled and analyzed for their major ion chemistry and oxygen hydrogen and boron isotope compositions in order to assess the possible origins of the waters the tecopa basin is a groundwater discharge area along the amargosa river drainage basin south of the nevada test site and proposed high level nuclear waste repository at yucca mountain nv the spring waters are categorized into three end member hydrochemical facies 1 ph neutral na ca mg so4 hco3 water with moderate to high total dissolved solids 2 mildly alkaline na cl so4 hco3 water with high total dissolved solids and 3 alkaline na hco3 co3 water with high total dissolved solids the temperatures of most of the springs range from 17 c to 32 c however waters in the tecopa hot spring area range from 9 c to 47 c the oxygen and hydrogen isotope compositions normalized to smow of the waters are as follows the facies 1 springs have a mean 18o of 12 77 0 14 1 and d of 94 9 0 5 1 the facies 2 springs have a mean 18o of 12 73 0 19 1 and d of 97 7 0 9 1 the facies 3 spring has a mean 18o of 13 09 0 17 1 and d of 103 5 0 7 1 the mean boron concentrations and isotope compositions range from 2 4 mg l and 11b of 2 5 for facies 1 springs to 72 8 mg l and 11b of 3 8 for the facies 3 spring the facies 1 waters have chemical and isotope compositions consistent with meteoric recharge in the spring mountains nv groundwater flow through the regional carbonate aquifer and minor mixing with more concentrated water the thermal facies 2 waters are isotopically and chemically distinct from waters in the regional basin fill and carbonate aquifer systems these waters are interpreted to originate from fractured water bearing strata beneath the regional carbonate aquifer that discharge only in the southernmost part of the great basin the facies 3 spring is isotopically and chemically similar to basin fill aquifer waters in the amargosa desert but has higher sodium alkalinity and boron contents due to interaction with saline alkaline lake deposits of the plio pleistocene lake tecopa beds geologic geochemical and isotope data suggest that these three distinct water types flow through hydrogeologic compartments in the tecopa basin the compartments are interpreted to have been created by the impermeable lake tecopa beds and geologic structures within the basin