uplift of quaternary shorelines in eastern patagonia darwin revisited during his journey on the beagle darwin observed the uniformity in the elevation of coastal eastern patagonia along more than 2000 km more than one century later the sequences of quaternary shorelines of eastern patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics consequently we i mapped the repartition of the quaternary coastal sequences in argentinean patagonia ii secured accurate altitudes of shoreline angles associated with erosional morphologies i e marine terraces and notches iii took into account previous chrono stratigraphical interpretations in order to calculate mean uplift rates since 440 ka mis 11 and proposed age ranges for the higher and older features up to 180 m and iv focused on the last interglacial maximum terrace mis 5e as the best constrained marine terrace in terms of age and altitude in order to use it as a tectonic benchmark to quantify uplift rates along the entire passive margin of eastern south america our results show that the eastern patagonia uplift is constant through time and twice the uplift of the rest of the south american margin we suggest that the enhanced uplift along the eastern patagonian coast that interested darwin during his journey around south america on the beagle could originate from the subduction of the chile ridge and the associated dynamic uplift

middle to late holocene relative sea level changes at puerto deseado patagonia argentina stratigraphic morphologic and radiocarbon data from puerto deseado coastal area santa cruz province argentina indicate that the holocene coastline formed in response to the discontinuous aggradation of coarse gravely beaches since c 6300 cal yr bp related to a progressive falling of relative sea level beach ridge crests crudely approximate to the sea level showing at least three steps of aggradation and relative sea level lowering two inactive abrasive notches at c 7 9 and 3 4 m a s l have recorded this sea level trend suggesting two important phases when sea level was stationary this allows the estimation of a rate of relative sea level fall in the last c 3500 years of c 1 8 mm yr moreover notches and morphological data indicate that the crest of the beach ridges exceeded the sea level height by c 2 0 5 m this value provides a reasonable regional estimate to be applied to produce comparable relative sea level curve for atlantic patagonia coast

tegula atra lesson 1830 mollusca gastropoda in the marine quaternary of patagonia argentina sw atlantic biostratigraphical tool and palaeoclimate palaeoceanographical signal results of the systematic review and regional palaeobiogeographical context of tegula atra including morphometric multivariate and cladistic analyses show that it is a keystone species in the marine quaternary of argentina that can be used as pleistocene biostratigraphical tool and paleoclimate palaeoceanographical signal while it was absent in warmer than present high sea level episodes during the miocene entrerriense transgression ca 10 ma and pleistocene mis11 it exhibits an excellent and abundant fossil record within dominantly cool coastal settings exclusively during the late pleistocene mis9 7 and 5 between rio negro and southern santa cruz provinces patagonia it first appeared in the sep during the late pliocene cooling trend dispersed during the late pleistocene into the swa presumably by rafting on macroalgae along the cabo de hornos and malvinas falkland currents but became extinct in the mar argentino magellan malacological province during the holocene amelioration trend its absence at present represents a climate change driven range shift and independent evidence of palaeoceanographical changes after the lgm and at the pleistocene holocene transition changes in sst ca 2 c higher wind velocities less light less nutrient availability less extension and intensity of cold less and warm increased shallow water currents altering water masses and biogeographical boundaries altogether these changes and the holocene scenario were disadvantageous causing direct effects on its physiology and survival in turn preventing the occurrence of the associated macroalgae durvillaea antarctica and its successful dispersal in the swa or retraction to the cold humboldt system waters this study reinforces the importance of dispersalist models to explain the origin of key taxa adding for a better understanding of molluscan taxonomic differences along the swa and sep margins of south america with implications for future coastal scenarios the distribution of t atra across time is a new example of the strong linkage between earth history climatic cycles atmospheric and oceanic circulation and the late quaternary biotic responses showing a possible consequence of future climate change on nearshore communities

thermohaline circulation hysteresis a model intercomparison we present results from an intercomparison of 11 different climate models of intermediate complexity in which the north atlantic ocean was subjected to slowly varying changes in freshwater input all models show a characteristic hysteresis response of the thermohaline circulation to the freshwater forcing which can be explained by stommel s salt advection feedback the width of the hysteresis curves varies between 0 2 and 0 5 sv in the models major differences are found in the location of present day climate on the hysteresis diagram in seven of the models present day climate for standard parameter choices is found in the bi stable regime in four models this climate is in the mono stable regime the proximity of the present day climate to the stommel bifurcation point beyond which north atlantic deep water formation cannot be sustained varies from less than 0 1 sv to over 0 5 sv

tsunami potential of moderate earthquakes the july 1 2009 earthquake mw 6 45 and its associated local tsunami in the hellenic arc on july 1 2009 a mw 6 45 earthquake ruptured south of crete island greece along the hellenic arc triggering a local tsunami eyewitness reported the tsunami from myrtos and arvi south eastern crete and from the north of chrisi islet located to the southeast of crete the earthquake occurred offshore about 80 km south of crete where routine earthquake locations are poor the hypocentre is relocated using a 2 d velocity model and several local 1 d velocity models epicentral locations obtained by using the different velocity models show very minor variations instead relocated hypocentres can be grouped into two sets of solutions 1 those with a shallower depth depth 25 km either in the upper plate or along the plate interface models accounting for either homogeneous or heterogeneous slip on the causative fault are tested with the heterogeneous one better reproducing the observations in terms of number of tsunami waves reaching the shoreline and duration of the sea disturbance the short travel time about 10 min of the first tsunami arrival at the southern coast of crete represents a big challenge for tsunami early warning systems operating in the area

palaeoenvironmental conditions during the early peopling of southernmost south america late glacial early holocene 14 8 ka b p abstract environmental conditions in southernmost south america the patagonian andes and the extra andean plains during the early peopling of the region in late glacial early holocene times are herein described different glacial advances or stabilization phases in valley glaciers occurred several millennia after the last glacial maximum lgm as a consequence of regional cold climatic episodes according to clapperton 1993 two advances during the late glacial took place ca 15 14 14 c ka and 12 10 14 c ka b p a cold event during this last period probably correlative with the younger dryas episode in the northern hemisphere has been observed in the palynological record a tundra environment dominated until ca 13 10 14 c ka b p afterwards a gramineous steppe with forest refuges developed the transition steppe forest lasted to the middle holocene when the nothofagus forest took over the arrival of man in southernmost south america ca 13 14 c ka b p or even before probably took place while glaciers were still present in most andean valleys sea level was much lower than today and tundra environments dominated the extra andean plains moreover peopling in the isla grande de tierra del fuego would have occurred not later than 11 8 14 c ka b p when the present magellan straits valley was still occupied by a meltwater discharge braided stream fed by the receding magellan glacier

the atlantic pacific seesaw abstract a global oceanic teleconnection of salinity meridional overturning circulation moc and climate of the north atlantic and north pacific is proposed simulations with a global climate model show that an extraction of freshwater from the pacific results not only in an increase of salinity there but also in a decrease of salinity in the atlantic as a result a pacific moc develops while the atlantic moc collapses without freshwater perturbation in the atlantic similarly an input of freshwater to the atlantic leads not only to a decrease of salinity there but also to an increase of salinity in the pacific the atlantic moc collapses whereas the pacific moc develops without freshwater perturbation in the pacific the mechanism behind this antiphase atlantic pacific relationship is the positive feedback between ocean circulation and salinity contrasts originally proposed by stommel to operate between low and high latitudes here the authors show that the same mechanism operates on the atlan

drop size distributions and radar observations of convective and stratiform rain over the equatorial indian and west pacific oceans abstracttwo dimensional video disdrometer 2dvd data were analyzed from two equatorial indian gan and west pacific ocean manus islands where precipitation is primarily organized by the intertropical convergence zone and the madden julian oscillation mjo the 18 3 5 months of 2dvd data from manus gan island show that 1 the two sites have similar drop size distribution dsd spectra of liquid water content median diameter rain rate r radar reflectivity z normalized gamma number concentration nw and other integral rain parameters 2 there is a robust nw based separation between convective c and stratiform s dsds at both sites that produces consistent separation in other parameter spaces the 2dvd data indicate an equatorial maritime average c s rainfall accumulation fraction frequency of 81 19 41 59 at these locations it is hypothesized that convective fraction and frequency estimates are slightly higher than previous radar based studies because the ubiquitous weak shallow convec

comparison of uranium series radiocarbon and amino acid data from marine molluscs baffin island arctic canada uranium series and sup 14 c dates and the extent of amino acid racemization are reported for 24 marine shell samples from three areas of baffin island arctic canada when the radiometric dates are plotted against the ratio of d alloisoleucene l isoleucene in the shells five broad age groups are recognized the uranium series data indicate that sup 231 pa is incompletely retained in most fossil shells and that sup 230 th is lost from some of the samples therefore their apparent ages are minimum however a few dated samples in each group have yielded useful age results and the minimum ages of the five groups of samples are estimated as 7 000 to 11 000 greater than or equal to70 000 greater than or equal to136 000 greater than or equal to190 000 and 300 000 yr calculated integrated thermal histories based on the epimerization reaction in the mollusc hiatella arctica linne give paleotemperature estimates of around 5 sup o c compared to the present mean annual air temperature of about 11 sup o c

structure and evolution of the 22 february 1993 toga coare squall line aircraft observations of precipitation circulation and surface energy fluxes abstract this study documents the precipitation and kinematic structure of a mature eastward propagating oceanic squall line system observed by instrumented aircraft during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare doppler radar and low level in situ observations are used to show the evolution of the convection from an initially linear nnw sse oriented convective line to a highly bow shaped structure with an embedded low to midlevel counterclockwise rotating vortex on its northern flank in addition to previously documented features of squall lines such as highly upshear tilted convection on its leading edge a channel of strong front to rear flow that ascended with height over a rear inflow that descended toward the convective line and a pronounced low level cold pool apparently fed from convective and mesoscale downdrafts from the convective line rearward the observations of this system showed distinct multiple maxima in updraft strength with

late pleistocene recent marine malacological assemblages of the colorado river delta south of buenos aires province paleoecology and paleoclimatology abstract the most recent quaternary marine transgressions are well represented along the south atlantic coast in the colorado river delta 39 15 s 39 55 s south of buenos aires province these deposits are mostly littoral ridges and tidal plains with abundant fossil marine fauna seventeen localities were analyzed five pleistocene seven holocene and five modern ones representing the interglacials mis 9 mis 5e and mis 1 a total of 51 species were recorded 29 bivalves and 22 gastropods together with nine micromolluscs mis 1 and the modern coast 37 and 42 species respectively are the richest ones in species unlike mis 5e and mis 9 18 and 2 species respectively in mis 9 the most abundant species is pitar rostratus mis 5e and mis 1 have in common the presence and abundance of the gastropod heleobia australis and the bivalve tagelus plebeius as typical fauna of low energy environments being the bivalve glycymeris longior and the gastropods bostrycapulus odites and buccinanops globulosus common species in both kinds of marine deposits approximately 90 of bivalves and 75 71 of gastropods of the marine fauna are recorded from mis 5e to the present according to the different descriptive analyses bray curtis index and ac the molluscan fauna was grouped in two and five assemblages respectively defined by age type of deposit and presence and or abundance of species marine species represented in the area of the colorado river delta vary in abundance among the interglacials but not in faunal composition one of the possible causes would be the global climatic changes e g rise of sea surface temperature sst and the heterogeneity of habitats that would have conditioned the development of the different faunal assemblages during the quaternary

faunistic changes between the middle late pleistocene and the holocene on the atlantic coast of tierra del fuego molluscan evidence abstract the marine terraces located on the atlantic coast of tierra del fuego argentina were previously assigned to different sea level highstands from the middle pleistocene to the holocene this study is focused on the analysis of the mollusc assemblages recovered from those terraces when comparing middle late pleistocene mollusc assemblages with adjacent holocene modern ones ecological changes in the fauna were recognized the pleistocene assemblages are less diverse and are dominated by infaunal bivalves whereas holocene and modern assemblages are more diverse and are dominated by epifaunal taxa with a higher presence of gastropods however on a biogeographic scale the fact that pleistocene taxa with the probable exception of retrotapes sp are living today in the region is attributed to the location of the study sites at the centre of the magellan biogeographic unit with species far away from the edges of their ranges of distribution regional faunistic changes and the local disappearance of retrotapes in post glacial benthic communities in the area are therefore interpreted on the basis of regional and local causes most probably associated to substrate changes and not on a global trend related to large scale patterns

late pleistocene and holocene palaeoenvironments in golfo san jorge patagonia molluscan evidence palaeoenvironments suggested by molluscan assemblages preserved in late pleistocene and holocene raised marine terraces along the golfo san jorge central patagonia coastline argentina are reviewed in this work a better precision of the stratigraphical and geographical ranges of the molluscs through their systematic review shows that all taxa have living representatives mostly within the argentine and or magellanean zoogeographical provinces in general no significant taxonomic appearances or disappearances are evident along this coastal area since the last pleistocene highstand reinforcing that the modern palaeoceanographical pattern dominated by the cool malvinas falkland current has not been substantially modified and that the magellanean malacological province has lasted at least since the pleistocene although with varying boundaries the so called marine terrace v recently assigned to the last interglacial highstand oxygen isotope substage 5e showed in this area a molluscan assemblage characterised by very low diversity dominantly large shells of mulinia edulis and by cold water taxa in disagreement with higher sea surface temperatures within oxygen isotope substage 5e last interglacial maximum and suggesting softer substrates than in the modern adjacent littoral zone

mesoscale organization of springtime rainstorms in oklahoma abstract radar reflectivity and raingage data obtained during six springtimes indicate the types of mesoscale organization that occur in association with major rain events in oklahoma at least 25 mm of rain in 24 h over an area exceeding 12 500 km2 in these storms the primary rain area is found to be a contiguous region of precipitation 10s to 100s of km in scale that consists partly of deep convection and partly of stratiform rain the patterns of rain formed by the convective and stratiform areas comprise a continuous spectrum of mesoscale structures about two thirds of the cases examined exhibited variations on the type of organization in which convective cells arranged in a moving line are followed by a region of stratiform rain storm organization was graded according to the degree to which it matched an idealized model of this leading line trailing stratiform structure the precipitation pattern was further graded according to whether its structure was relatively symmetric with respect to an a

high latitude salinity effects and interhemispheric thermohaline circulations a general circulation model for the ocean is used to investigate the interaction between the global scale thermohaline circulation and the salinity distribution it is shown that an equatorially asymmetric circulation can be maintained even under equatorially symmetric basin geometry and surface forcing multiple equilibrium solutions are obtained for the same forcing by perturbing the high latitude salinity field in an otherwise equatorially symmetric initial condition the timescale of the transition from the symmetric circulation to an asymmetric circulation depends critically on the sign of the initial salinity perturbation

bioerosion structures in crepidula mollusca gastropoda as indicators of latitudinal palaeoenvironmental changes example from the marine quaternary of argentina abstract late quaternary marine skeletal concentrations from argentina are rich in molluscs exhibiting a great variety of bioerosion structures the shells of crepidula a characteristic gastropod occurring along more than 2000 km of coastline between the rio de la plata margin and southern patagonia show traces of dwelling predation and anchoring activities made by porifers bryozoans annelids other gastropods and brachiopods caulostrepsis entobia maeandropolydora iramena oichnus finichnus pennatichnus pinaceocladichnus podichnus and renichnus occur on the outer shell surface finichnus and oichnus are the only traces present along the entire area and the full time span considered the most characteristic structures are produced by bryozoans polychaetes and predatory gastropods traces produced by annelids and predatory gastropods occur preferentially in the central shell sector where predators gained access to the soft parts of the prey by contrast encrusting or branching bryozoan colonies are widely distributed as they can attach to any sector regardless of shell features available no strict correlation is evident between ichnodiversity and either time or latitude but ichnodiversity is linked to local oceanographical biotic controls for patagonia with a great majority of ichnotaxa made by bryozoans the general trend of higher bioerosion degree and ichnodiversity at higher latitudes is controlled by sea surface temperature productivity for the modern and the holocene several ichnodiversity peaks match with well constrained conditions substrate salinity thermal fronts by contrast this does not hold for the pleistocene dissimilar conditions probably prevailed especially during the last interglacial colder waters richer in nutrients

stratigraphy structure absolute age and paleontology of the upper pleistocene deposits at sankaty head nantucket island massachusetts the sankaty head cliff of nantucket island massachusetts exposes drift of at least two glaciations and interglacial marine deposits radiocarbon amino acid racemization and uranium thorium analyses were used to determine the absolute ages of the beds the results indicate that 1 the sankaty sand correlates with oxygen isotope stage 5 sangamonian 2 the underlying drift is older than stage 5 illinoian or older and 3 the overlying drift is wisconsinan in age ostracodes and molluscs within the sankaty sand indicate that the marine climate during deposition of the lower part was somewhat warmer than the present climate off sankaty head and that the marine climate during the deposition of the upper part was as cold as or somewhat colder than the present climate the paleoenvironmental data support a stage 5 sangamonian age for the marine deposits

the relationship between emex mesoscale precipitation feature properties and their environmental characteristics abstract characteristics of the prestorm environment of equatorial mesoscale experiment emex mesoscale precipitation features mpfs are related to properties of them systems using regression analysis although environmental thermodynamic parameters are poorly correlated with emex mpf properties mainly because environmental thermodynamic conditions varied little among mpfs kinematic parameters are well correlated to these properties lines whose environments have low level shear the shear between about 950 and 750 mb exceeding 5 m s 1 are oriented normal to the direction of this shear lines where the low level shear is under 5 m s 1 are oriented along the direction of the midlevel shear the shear between about 800 and 400 mb convective line speeds correlate well with the maximum speed of the rear to front flow in the troposphere below 300 mb direction of mpf motion is nearly coincident with the tropospheric mean wind direction convective line length is proportional to the magnitude of the men

late quaternary molluscs from the northern san matias gulf northern patagonia argentina southwestern atlantic faunistic changes and paleoenvironmental interpretation the late quaternary in the coastal area of south america is represented mostly by littoral ridges cliffs and tidal plains with associated remains of gastropods and bivalves currently used as paleoclimatic indicators the aim of this study is to characterize the assemblages of molluscs bivalves and gastropods both pleistocene mis 9 mis 7 mis 5e and holocene mis 1 from the northern san matias gulf northern patagonia argentina in the southwestern atlantic ocean in order to assess whether faunal change occurred together with late quaternary climatic change twenty localities were studied seven from different interglacial stages of the pleistocene six holocene and seven modern beaches in which 42 species were recorded 20 bivalves and 22 gastropods among bivalves euryhaline infaunal from sandy substrates and filter feeders prevail amiantis purpurata is the dominant species of the whole mollusc assemblage among gastropods although also euryhaline the epifaunal species of rocky and sandy substrates and carnivores prevail on the basis of descriptive statistical analyses bray curtis and ac methods the localities formed three groups according to ages modern vs pleistocene and holocene and or presence abundance of species 70 of the marine malacofauna of mis 7 remains during mis 5e decreasing to 60 during mis 1 and to 27 when compared to the modern beaches the most notable changes in the distribution of the species were tegula atra currently extinct in the argentine atlantic coast but recorded in pleistocene interglacials mis 7 and mis 5e anomalocardia brasiliana which only appeared in mis 5e and mesodesma mactroides in mis 1 mis 5e was likely the warmest stage within the period considered followed by mis 7 both with higher sst temperatures than the present ones and since mis 1 molluscs of temperate cold lineages of the magellan malacological province are recorded

u series and amino acid dates from jersey understanding of the raised beach and other interglacial sequences in the southern part of the british isles has been improved through use of the amino acid racemization technique this method has permitted correlation of these isolated and fragmentary marine deposits1 2 which except for the portland site are located around the shores of the bristol channel1 by applying this technique with the u series method we have obtained a geochronometric date from the 8 m raised beach of the belle hougue cave jersey channel islands our results suggest that the 8 m raised beach of the channel should be correlated with isotope stage 5 and that raised beaches above this altitude in the area may pre date this stage and thus also the ipswichian interglacial which forms part of it

continuity and discontinuity in the human use of the north coast of santa cruz patagonia argentina through its radiocarbon record in this paper the analysis of a radiocarbon database of the north coast of santa cruz central patagonia argentina is presented dated archaeological samples were obtained from 56 different types of archaeological sites open air residential sites and burials and also rock shelters the objective of this paper is assessing the continuities and discontinuities in the chronological signal of the area and identifying tendencies along the holocene the database currently contains 75 radiocarbon dates falling between ca 8000 and 300 bp the radiocarbon data base provides information on the chronological spatial and contextual variability of the archaeological record of north coast of santa cruz by means of different analysis of sum of probabilities we present three different chronological moments of human use of the coast and intermediate zone can be identified a first moment is represented by early evidence of settlement during middle holocene a second moment corresponds to a hiatus between ca 5800 and ca 3900 bp without archaeological evidence finally a third moment is where an increasing of chronological signal occurred related to greater artifactual variability and an increase in the intensity of human settlement in the patagonian region the causes that could have influenced in the discontinuity of the chronological signal of the study area and the characteristics of the different moments identified are discussed

book review biogeochemistry of amino acids edited by p e hare t c hoering and k king jr wiley 1980 538 pp 30 50

cannibalisation of holocene gravel beach ridge plains northern tierra del fuego argentina abstract gravel beach ridge plains form where there is sufficient availability of gravels and wave energy competent to transport the gravel even though beach ridge plains are formed on coasts where sea level has risen during the holocene they occur extensively on stable or emergent coasts unfortunately the holocene evolution of these plains is hard to decipher because of the lack of datable material and their reworked character minimum age the rollover of barriers is expected on submerging coasts on falling sea level coasts the beach ridge plains are in a punctuated process of progradation cannibalisation is common in both settings that is sediment is eroded to maintain longshore growth we present morphological and sedimentological data from three gravel beach ridge plains san sebastian rio chico and cabo penas of the northern coast of tierra del fuego these beach complexes occupy embayments that were infilled during the last 5000 yr under different environmental conditions depth flooded area local oceanographic processes and sediment availability in the evolution of bahia san sebastian a strong control was imposed by high waves originating within the bay due to the strong westerlies the rio chico beach ridge plain evolved during different stages of beach progradation cannibalisation spit growth and saltmarsh development the cabo penas beach ridge plain evolved in opposite directions due to wave refraction caused by rocky reefs and cannibalisation also took place

pleistocene and holocene interglacial molluscan assemblages from patagonian and bonaerensian littoral argentina sw atlantic palaeobiodiversity and palaeobiogeography abstract our analysis of palaeobiodiversity and palaeobiogeography of quaternary molluscan assemblages provide information on the last coastal scenarios in the sw atlantic we present patterns of species richness areas of endemism and between areas relationships based on records 721 taxa from argentina and northwards in south america surinam brazil uruguay including pleistocene holocene and modern sites 48 localities in argentina our data since the mid late pleistocene mis11 1 ca 400 ka b p to present suggest environmental changes linked to sea level and climatic fluctuations large enough to alter benthic associations compositional geographical variations including a few extinctions the southwards decreasing diversity trend for modern bivalves mostly infaunal taxa and gastropods mostly epifaunal taxa from surinam to tierra del fuego responds mainly to latitudinal sst salinity barriers hydrodynamic forces rivers and shallow currents minima peaks fit with local estuarine and marginal marine sites influenced by the rio de la plata plume highest peaks with fully marine warmer waters influenced by the brazilian current bonaerensian sector a similar trend applies for the holocene pleistocene maxima peaks in patagonia belong to mis11 and mis5 highstands warmer than today multivariate cluster analysis ca minimum spanning trees superimposed to principal coordinates analysis pco and cladistic parsimony analysis of endemicity pae methods showed congruent relationships between localities discriminating marginal from open marine environments but pco combined with pae was most advantageous for our area and dataset 382 gastropods 339 bivalves 29 pleistocene 28 holocene and 35 modern sites allowing objective quick comparisons shifts of areas of endemism during the holocene and pleistocene relate with sst and salinity changes a more homogeneous mid holocene ca 7 5 ka b p scenario of regionally increased salinity and higher ca 2 c sst defined the bonaerensian and northern patagonian sectors facilitating southwards shifts of bivalve and gastropod taxa for patagonia a colder pleistocene scenario south of sao is documented by tegula atra exclusive pleistocene cold water species extinct in the swa probably a signal of post lgm palaeoceanographical changes in the mar argentino

el nino east asian monsoon teleconnection and its diversity in cmip5 models in this study we assess the performance of state of the art coupled models in reproducing el nino diversity and its impacts on the east asian summer monsoon easm based on simulations taken from the coupled model intercomparison project phase 5 cmip5 all of the 17 models used in this study are identified to give reasonable eastern pacific ep el nino related sea surface temperature anomalies ssta and anomalous walker circulation compared with observations whereas one third of the models fail to reproduce the walker circulation anomalies for central pacific cp el nino in these models negative ssta over the eastern to central pacific are found to be too strong while positive ssta shift to the western pacific during cp el nino there is thus sinking rising motion over the central western part of the pacific basin implying westward displaced anomalous walker cells relative to the observed this results in simulated low level cyclonic flow and positive rainfall anomalies over the far western north pacific south china sea during and after the peak phase of cp el nino which are opposite to the observed anomalous climate state the other two thirds of models with realistic cp el nino related anomalous walker cell can better reproduce the corresponding wind circulation and rainfall anomalies over east asian ea region the contrasting cp el nino related teleconnection among models mainly arises from the different simulated cp el nino ssta which in turn determine the circulation anomalies through a gill type response further analyses reveal that in the mean state of models with erroneous teleconnection there exists a large cold sst bias over the eastern pacific the stronger walker circulation and possibly the stronger bjerknes feedback might be responsible for the overly negative ssta associated with cp el nino in the vicinity our results highlight the sensitivity of el nino ea climate linkage to the oceanic state in models especially for cp el nino events

paleoenvironments and paleoclimates in tierra del fuego and southernmost patagonia south america abstract a continuous paleoclimatic history for the past 14 000 years is presented based on palynological records from south of latitude 50 s in south america prior to 12 500 yr b p dry empetrum heathlands not mesic tundra dominated throughout the high southern latitudes indicating high winds annual precipitation of less than 300 mm and freezing temperatures year round after 12 500 yr b p steppe replaced the heathlands suggesting decrease in wind intensity increase in effective moisture and increase in temperatures when forests expanded at 9000 yr b p along the rainward side and at 8000 yr b p in the rainshadow side of the andes precipitation reached holocene levels judging from the greater openness of the early holocene forests including those in the rainward part of the region precipitation levels probably ranged between 500 and 800 mm comparable to those from today s forest steppe transition after a pronounced mid holocene dry event the late holocene forests appeared more closed than the early holocene forests suggesting greater effective moisture probably related to cooler temperatures the high latitude paleoclimatic history differs from that of lower latitudes as far as the actual amplitude of change and the climatic signal is concerned low moisture levels prior to 12 500 yr b p between latitudes 45 and 55 c suggest that the westerly stormtracks responsible for precipitation patterns in southern south america may have been located year round closer to the equator than today the precipitation increase at 12 500 yr b p that extended only as far south as 50 s indicates that the stormtracks had shifted poleward but did not reach tierra del fuego by 9000 yr b p the stormtracks had shifted to the high southern latitudes but the large seasonal latitudinal shift comparable to the modern situation equatorwards in winter and polewards in summer did not develop until after 4500 yr b p

evolution properties and spatial variability of mjo convection near and off the equator during dynamo abstractthis study investigates the evolution structure and spatial variability of madden julian oscillation mjo convection observed during the 2011 12 dynamics of the mjo dynamo field campaign generally the c band radars located in the near equatorial indian ocean shared mobile atmospheric research and teaching radar smart r on addu atoll gan and nasa toga on the r v roger revelle revelle observed similar trends in echo top heights stratiform rain fraction and precipitation feature size across the mjo life cycle these trends are closely related to changes in mid to upper tropospheric moisture sea surface temperature sst zonal wind and diagnosed vertical air motions however the evolution of convection moisture and vertical air motion at the r v mirai mirai located in the intertropical convergence zone itcz at 8 s exhibited a pattern nearly opposite to gan and revelle when the mjo was active over the equator convection was suppressed around mirai owing to induced subsiden

early holocene bone technology at the la olla 1 site atlantic coast of the argentine pampas abstract la olla 1 in the pampas of argentina is an open air site located on the atlantic coast in the monte hermoso district southern buenos aires province bones in lacustrine layers outcrop during very low tide exposed by longshore drift based on an initial analysis of the faunal assemblage two species of sea mammal guanaco pampean deer greater rhea and a fish were represented in the almost 300 bones recovered during the rescue excavation the lithic assemblage consisted of unifacially flaked tools rounded cobbles reduced by bipolar technique flakes and artifacts with flat abraded surfaces radiocarbon determinations of c 7300 and 6600 bp came from sea mammal femora an informal bone tool recovered from the site is made from the left proximal tibia of an adult otariid it is identified as a utilitarian bone tool on the basis of use wear characters that are restricted in distribution and as a fracture based bone tool on the basis of technological characters the element was dynamically impacted in the mid diaphysis region use wear characters are loss of edge angularity microflaking pitting striae and polish microflaking occurs along the posterior fracture surface and exterior adjacent cortical surface pitting of the fracture surface extends along the entire length of the worn edge but is most concentrated along the posterior fracture surface a multitude of very fine striae runs parallel to the fracture edge the area of striations is limited to this edge with a well demarcated boundary covering all of these characters is differential wear polish this high gloss polish is strongly reflective and occurs over very worn and rounded areas providing a very bright melted appearance based on these different use wear patterns the la olla 1 bone tool is interpreted as a dual purpose implement most likely used for carcass dismemberment and hide processing the la olla 1 tool is unusual in that it is made from pinniped bone biomechanical analysis of southern fur seal bone indicates however a strong suitability for impact related tasks and therefore an appropriate choice for use as butchering tools

multiple equilibria of the global thermohaline circulation abstract a general circulation model with a highly idealized geometry is used to investigate which fundamentally different equilibria of the global thermohaline circulation may exist the model comprises two identical basins representing the atlantic and pacific oceans which are connected by a circumpolar channel in the south the model circulation is driven in addition to wind forcing by restoring the sea surface temperature to prescribed values and specified freshwater fluxes in the surface salinity budget mixed boundary conditions the boundary conditions are symmetric with respect to the equator and identical for both oceans four fundamentally different stable steady states are found under the same set of boundary conditions two of the equilibria show both oceans in the same state with high altitude deep water formation occuring either in both northern or in both southern oceans respectively two additional equilibria exist in which the thermohaline circulations of the basins differ fundament

reconstruction of the late holocene paleoenvironment of the western beagle channel argentina based on a palynological analysis abstract palynological analysis was performed on sediment samples from arroyo baliza site 54 51 s 68 33 w western sector of the beagle channel tierra del fuego argentina in order to reconstruct the palaeoenvironmental history during the holocene marine transgressive regressive cycle in the beagle channel the palynological analysis reveals the presence of a closed canopy nothofagus forest development in the coastal areas under a cold wet and variable climate conditions during the late holocene the marine assemblage composition shows similarities to those modern assemblages recorded in the surface samples from the beagle channel characterised by the dominance of peridiniales taxa suggesting environmental conditions during the late holocene comparable to today the increasing salinity during middle holocene was accompanied by an increase in number and diversity of the microplanktonic assemblages suggesting the gradual installation of a marine environment as it exists today in the beagle channel

quaternary climates and sea levels of the u s atlantic coastal plain uranium series dating of corals from marine deposits of the u s atlantic coastal plain coupled with paleoclimatic reconstructions based on ostracode marine and pollen continent data document at least five relatively warm intervals during the last 500 000 years on the basis of multiple paleoenvironmental criteria we determined relative sea level positions during the warm intervals relative to present mean sea level were 7 5 meters at 188 000 years ago 7 5 1 5 meters at 120 000 years ago 6 5 3 5 meters at 94 000 years ago and 7 3 meters at 72 000 years ago the composite sea level chronology for the atlantic coastal plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200 000 years hydroisostatic adjustment from glacial interglacial sea level fluctuations lithospheric flexure and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies alternatively current eustatic sea level estimates for the middle and late quaternary may require revision

gravel drift and wind effects on the macrotidal san sebastian bay tierra del fuego argentina abstract in northeastern tierra del fuego the holocene mean sea level msl fluctuation reworked much pre wisconsin glacial drift into sand gravel beaches and spits and sand mud tidal flats for the last 7000 years sea level has been falling a southwards wave induced longshore transport of sand and gravel has constructed the 17 km long el paramo spit which partly encloses the wide san sebastian bay semidiurnal tides with a range of up to 10 m enter the bay from the south causing a dominance of flood currents and wave action in the southern part of the bay ebb currents predominate in the north this segregation of flows conditioned sedimentation and is thus responsible for the south north transition of welded gravel ridges sand flats mixed flats and mud flats on the southern coast of the bay wave action constructed discrete sets of gravel ridges which diverted the san mar in river inlet northwards over the tidal flats north of this inlet where gravels are not yet available storms produce chenier systems discrete deposits of shells and sands the lengths of which progressively shortened as the inlet of the bay became narrower and the bay infilled because storms affect both the bay and the atlantic beach washover fans cut these cheniers and the gravel ridges on the narrower part of the spit the fossil gravel ridges in the northern and southern parts of san sebastian bay are not the only supratidal environments fossil and active marshes evolve conditioned by the strong and persistent wind action seasonal ponds are produced by intense deflation salicornia marsh occurs as circular structures 2 3 m diameter clustered over the supratidal flats on the intertidal mud flats wind causes deflation during neap tides and silting during spring tides north of the bay the eastward migration of straight tidal channels or rills is conditioned by winds the effects of strong and persistent winds from the pacific influence not only the tidal flats but also the gravel spit if ocean waves induce a southward drift of gravels within the bay the wind induced gravel drift is to the north during winter there are no aeolian effects over the iced tidal flats

multiple equilibria of an asymmetric two basin ocean model abstract an ocean general circulation model is used to examine the role of model geometry and surface buoyancy and wind stress forcing in the asymmetry of the global thermohaline circulation the model domain is a highly idealized atlantic and pacific linked by a circumpolar ocean in the south and the integrations are performed under mixed boundary conditions diagnosed from spinups under various temperature and salinity profiles constructed from the present day climatology the model exhibits a tendency to favor either a conveyor type circulation with sinking in the northern north atlantic and upwelling in the north pacific or a southern sinking state with deep sinking in the antarctic only this bias is not dictated solely by the hydrological cycle nor apparently by the greater northern extension of the atlantic basin but presumably by the overall asymmetry of the geometry equilibria with northern sinking in both basins can appear however when the winds in the southern ocean are reduced or th

holocene raised beaches along the northern coast of the beagle channel tierra del fuego argentina abstract raised beaches developed during holocene times along the northern beagle channel coast these deposits contain a rich marine fauna especially shelled organisms such as mollusks four holocene marine sites along the northern coast of the beagle channel have been analysed from west to east they are bahia ensenada playa larga bahia brown and cutalataca airfield they were studied in relation to relative altitude sediment type faunal composition and radiocarbon dates the area is characterized by several discontinuous terraces with elevations varying from about 1 5 to 10 m above sea level their possible origin 1 due to tectonic uplifting in comparison with raised beaches of the northern part of tierra del fuego and 2 resulting from glacio isostatic recovery taking into account the ice retreat is discussed seventeen species of mollusks eight bivalves nine gastropods were collected from the study sites all of them are living species from the beagle channel and have been interpreted as representative of holocene paleocommunities in this channel these species show no evidence of substantial climatic changes during the holocene although minor temperature fluctuations cannot be ruled out yet

lithospheric thickness antarctic deglaciation history and ocean basin discretization effects in a global model of postglacial sea level change a summary of some sources of nonuniqueness the global model of postglacial relative sea level variations that has been developed over the past decade is employed to investigate the constraints that it may be invoked to place on the timing of the deglaciation of west antarctica the analyses presented here confirm the suggestion of p wu and w r peltier 1983 geophysical journal of the royal astronomical society74 377 450 that the model of this event employed inj a clark and c s lingle 1979quaternary research11 279 298 may be simply modified to rectify the misfits between theory and observation that are otherwise obtained at southern hemisphere sites a large number of southern hemisphere relative sea level data are shown to require that the retreat of antarctic ice substantially lagged the retreat of northern hemisphere ice if the deglaciation of antarctica was abrupt the time of onset of antarctic deglaciation is thereby shown to coincide with the time of most rapid northern hemisphere deglaciation sensitivity tests are performed which demonstrate that this result is relatively insensitive to the discretization employed to represent the ocean basins the only exception to this general rule obtains at some coastal sites at which a trade off is revealed between the delay of west antarctic melting and the thickness of the lithosphere required to reconcile the observed local variations of relative sea level at such sites which are all in the far field of the ice sheets some attention must be paid to the accuracy of the local finite element representation of the oceans and to the details of the antarctic deglaciation history

shear parallel tropical convective systems importance of cold pools and wind shear the impact of cold pools on line orientated convective systems is assessed using idealized simulations of tropical oceanic convection under weak moderate and strong wind shear regimes cold pools are weakened by suppressing evaporation in the shallow subcloud layer analysis of objectively identified convective systems reveals that the convection with weaker cold pools is more often oriented parallel rather than perpendicular to the wind shear the cold pool induced orientation changes are most pronounced in the strong shear environment interactions between convective orientation and the tropical atmosphere are assessed simulations with shear parallel convection demonstrate more top of atmosphere upwelling longwave radiation and less reflected shortwave radiation due to changes in convective anvils faster propagating larger scale gravity waves narrower cross shear moisture distributions and differences in convective momentum fluxes the results highlight critical interactions across convective scales mesoscales and climate scales as well as avenues for parameterizing structural modes of mesoscale organized convection in global models

atmospheric control on the thermohaline circulation abstract in an attempt to elucidate the role of atmospheric and oceanic processes in setting a vigorous ocean overturning circulation in the north atlantic but not in the north pacific a comparison of the observed atmospheric circulation and net surface freshwater fluxes over the north atlantic and pacific basins is conducted it is proposed that the more erratic meridional displacements of the atmospheric jet stream over the north atlantic sector is instrumental in maintaining high surface salinities in its subpolar gyre in addition it is suggested that the spatial pattern of the net freshwater flux at the sea surface favors higher subpolar atlantic salinity because the geographical line separating net precipitation from net evaporation is found well south of the time mean gyre separation in the north pacific whereas the two lines tend to coincide in the north atlantic numerical experiments with an idealized two gyre system confirm that these differences impact the salinity budget of the subpolar g

kinematic characteristics of air flowing into and out of precipitating convection over the west pacific warm pool an airborne doppler radar survey air flowing into and out of 25 cloud systems over the west pacific warm pool was sampled by doppler radars on board two noaa wp 3d aircraft and the ncar electra aircraft during the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare in convective cells updraught inflows and downdraught outflows tended to be positioned adjacent to each other at sharp updraught downdraught interfaces sloping at various angles and directions the updraught inflows were sometimes shallow and sometimes deep often extending well above the boundary layer downdraught outflow magnitudes were usually stronger than updraught inflows and the horizontal directions of the inflow and outflow were frequently offset from each other at angles of 90 in stratiform precipitation regions the dominant airflow features were descending mid level inflows located at the bases of anvils and often extending into the interior of the precipitation system these stratiform inflows originated at levels between 5 and 10 km and descended to about 3 km a few extended down to the surface stratiform inflows were typically strong and sandwiched between weaker stratiform outflows at upper and lower altitudes the stratiform region inflow and outflow directions were frequently offset by 90 in the horizontal the mid level inflow currents entered the stratiform regions horizontally from a direction similar to that of the large scale ambient wind the mid level stratiform inflow tended to occur in the same vertical plane as the convective downdraught outflow although the mid level stratiform inflow appeared to be slowed by horizontal pressure gradients before connecting with the convective downdraught outflow in other respects the mesoscale systems differed from a simplified two dimensional model of airflow the systems moved primarily by discrete propagation and updraughts and downdraughts tended to have orthogonal horizontal relative airflow

quaternary of tierra del fuego southernmost south america an updated review abstract the quaternary of tierra del fuego is represented by glacial glaciofluvial glaciolacustrine marine and aeolian deposits six drift units have been described the oldest dating from the late pliocene these are starting from the oldest the rio grande sierra de los frailes cabo virgenes punta delgada primera angostura and segunda angostura drifts neoglacial and little ice age events are represented in cirques and higher mountain valleys marine deposits and raised beaches were formed during middle pleistocene late pleistocene and holocene interglacial stages after the definitive ice retreat 10 ka ago vegetation changed from tundra and cold steppe to subantarctic forest environments marine deposits reflect also colder conditions than the present ones aeolian processes prevailed in northern tierra del fuego where semiarid conditions and the frequent westerlies favoured the retransportation of finer materials coming from pre existing deposits before the opening of the magellan straits earliest human colonization occurred in northern tierra del fuego ca 11 ka bp in tundra like environmental conditions pedestrian hunters of camelids and foxes co existed with pleistocene fauna that became extinct during late glacial earliest holocene times the steppe area inland and atlantic coast was successively occupied since then until recent times on the other hand the beagle channel coasts were occupied since 6 ka bp by hunter gatherer groups adapted to maritime littoral conditions finally the easternmost area of the island was inhabited at least since 1 5 ka bp the human settlements in these latter areas occurred under environmental conditions similar to the present ones when the fuegian forest was definitively established

the flooding of the san matias gulf the northern patagonia sea level curve abstract northern patagonia is characterised by tectonic depressions below present sea level some of them are today flooded by the sea others remain emerged although they are at altitudes of 50 m bajo del gualicho 35 m salinas grandes and 7 m salina la piedra san matias gulf also was such an emerged depression below contemporary mean sea level during the late pleistocene it flooded between 11 500 and 11 000 years ago when the sea level surpassed the sill of the gulf today 50 m below mean sea level during postglacial sea level rise in those days shrublands extended on the slopes of the tectonic depression in situ pieces of woods dredged from the bottom of the gulf at depths of 70 m gave a conventional age of 11 310 150 years bp we used the wood together with dated shells from the continental shelf and shells and organic matter dated from the san blas negro and chubut coastal plains to construct a sea level curve sea level rise surpassed the present level somewhat before 6000 years bp reaching a maximum stand of 6 m it has since gently diminished towards present sea level

mid holocene relative sea level changes along atlantic patagonia new data from camarones chubut argentina this paper concerns the relative sea level changes associated with the atlantic patagonian coast derived from sea level index points whose elevation was determined by a differential global position system dgps bioencrustations from outcrops located near camarones chubut argentina consist of autochthonous deposits characterized by austromegabalanus psittacus molina 1782 encrusting acervulinid foraminifera coralline red algae and bryozoans the association of the different organisms is interpreted as being associated with an intertidal environment and they have been used as index points to establish the relative sea level position the main conclusion is that the relative sea level between c 7000 and 5300 cal yr bp was in the range of c 2 4 m a s l with a mean value of c 3 5 m a s l our data seem to support the existence of different rates of relative sea level fall in different sectors of atlantic patagonia during the holocene and highlight the importance of a more precise and accurate r

interbasin transport of the meridional overturning circulation abstractthe meridional overturning circulation moc is studied in an idealized domain with two basins connected by a circumpolar channel in the southernmost region flow is forced at the surface by longitude independent wind stress freshwater flux and fast temperature relaxation to prescribed profiles the only longitudinal asymmetry is that one basin is twice as wide as the other two states a preferred one with sinking in the narrow basin and an asymmetrically forced one with sinking in the wide basin are compared in both cases sinking is compensated by upwelling everywhere else including the passive basin despite the greater area of the wide basin the residual overturning transport is the same regardless of the location of sinking the two basins exchange flow at their southern edge by a geostrophic transport balanced by the difference in the depth of isopycnals at the eastern boundaries of each basin gnanadesikan s model for the upper branch of the moc is extended to include two basins conn

relative sea level fall since the last interglacial stage are coasts uplifting worldwide the growing interest in quantification of vertical ground motion stems from the need to understand in detail how the earth s crust behaves for both scientific and social reasons however only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies although there are many local studies of quaternary vertical motions of coastlines we know of no comprehensive worldwide synthesis here we provide a compilation of 890 records of paleoshoreline sequences with particular emphasis on the last interglacial stage marine isotopic stage mis 5e 122 ka the quality of dating mis 5e makes it a reliable marker to evaluate vertical ground motion rates during the late quaternary on a global scale the results show that most coastal segments have risen relative to sea level with a mean uplift rate higher than 0 2 mm yr i e more than four times faster than the estimated eustatic drop in sea level the results also reveal that the uplift rate is faster on average for active margins than for passive margins neither dynamic topography nor glacio hydro isostasy may explain sustained uplift of all continental margins as revealed by the wide distribution of uplifted sequences of paleoshorelines instead we suggest that only plate tectonic processes reconcile all observations of quaternary coastal uplift we propose that long term continental accretion has led to compression of continental plates and uplift of their margins therefore this study concludes that plate tectonics processes impact all margins and emphasizes the fact that the notion of a stable platform is unrealistic these results therefore seriously challenge the evaluation of past sea levels from the fossil shoreline record

kinematic and precipitation characteristics of convective systems observed by airborne doppler radar during the life cycle of a madden julian oscillation in the indian ocean abstractthis study presents characteristics of convective systems observed during the dynamics of the madden julian oscillation dynamo experiment by the instrumented noaa wp 3d aircraft nine separate missions with a focus on observing mesoscale convective systems mcss were executed to obtain data in the active and inactive phase of a madden julian oscillation mjo in the indian ocean doppler radar and in situ thermodynamic data are used to contrast the convective system characteristics during the evolution of the mjo isolated convection was prominent during the inactive phases of the mjo with deepening convection during the onset of the mjo during the mjo peak convection and stratiform precipitation became more widespread a larger population of deep convective elements led to a larger area of stratiform precipitation as the mjo decayed convective system top heights increased though the number of convective systems decreased eventually transitioning back to isolated convection a distinct

late quaternary marginal marine deposits and palaeoenvironments from northeastern buenos aires province argentina a review the late quaternary marginal marine deposits along eastern argentina southwestern atlantic are reviewed according to our present knowledge in the northeastern coastal area of buenos aires province they have been assigned to a series of transgressions and regressions ranging from the late pliocene to the late quaternary the most widely accepted model is frenguelli s 1957 classical chronostratigraphical scheme of belgranense late pleistocene marine sediments at 3 6 m above m s l and ca 26 000 35 000 14c years bp the querandinense pleistocene holocene estuarine sediments below or at present m s l and the most extensive platense mid holocene marine deposits at 4 5 2 m above m s l dated at ca 8000 1340 14c years bp the restricted belgranense deposits recorded in samborombon bay in magdalena at ca 32 000 bp near mar chiquita at ca 24 900 and 30 500 bp and southwards in bahia blanca at ca 26 000 35 500 bp may belong to an interstadial gonzalez et al 1986 the molluscan composition suggests a marine invasion of the area but not a typical interglacial cycle characterized by euhaline and warm water elements however the oxygen isotope record argues against an interstadial during the interval 34 27 ka and the chronological control for these deposits is very poor suggesting that they most probably have been elevated neotectonically the pleistocene holocene querandinense deposits extensively distributed along the bonaerensian coastal plain and continental shelf ca 11 000 14c years bp with very low faunal diversity abundance of freshwater ostracods and absence of the warm water molluscs characteristic of the holocene ridges indicate low salinity and cool water conditions further dating and isotope analysis of these deposits are required for a better understanding of the chronology of climatic events by the end of the pleistocene in this area and to establish whether or not they could correspond to the younger dryas event of the northern hemisphere platense littoral ridges formed between ca 7600 and 2500 bp extend in several subparallel rows from ca 34 s to ca 39 s they formed either as beaches or possibly as sublittoral bars in samborombon bay where they reach 120 km long 10 30 m wide and up to 5 m thick at 4 5 5 m above m s l or in the supratidal and intertidal zones in mar chiquita at 2 4 m above m s l molluscs and ostracods suggest a brackish marine to marine brackish environment of lower salinity than the modern atlantic littoral during the mid holocene the oceanic waters were mixing with large amounts of antarctic ice melting in the south atlantic isla 1990 probably reducing salinity along the bonaerensian littoral the oldest littoral ridges accumulated during the hypsithermal and in the punta indio area their different geometry and alignment greatest age highest diversity and warmer affinity of the molluscan fauna suggest a short interval of reversal of the atmospheric circulation pattern further research is necessary for a better understanding of the chronology of the marine late quaternary deposits coastal evolution and climatic changes in this area

archaeological littoral sites on the northern coast of santa cruz valuable evidence of sea level changes on the continental patagonian coasts argentina geological studies are fundamental to archaeologists as they provide essential data to understand certain processes involved in the present archaeological record when working on marine coastal archaeology the information provided by geomorphologic studies with regards to the evolution and dynamics of coastal marine lines is essential to assess the availability and accessibility of certain marine coastal areas and their resources to human populations of the past this is also the key to reach correct cultural interpretations however on certain occasions archaeological information can also offer valuable alternative data for geologists to reach geological interpretations for instance when working on the evolution and changes of coastal sea lines in this case spatial and temporal scales must be regarded this idea is supported on the experience gained through research done on the patagonian atlantic coast at the two archaeological localities introduced in this paper cabo blanco where we evaluate models of evolution of the coastline with a number of radiocarbon dates from excavated sites and punta medanosa where we discuss the temporal depth of the formation of the coastal ridges for the mid holocene transgression

correlation and dating of quaternary littoral zones along the patagonian coast argentina six areas of the patagonian coast argentina were investigated in order to determine the number characteristics geomorphology and development of quaternary littoral zones it became apparent that utilizing dl ratios of aspartic acid and leucine of various molluscan species would be the most useful in correlation relative age dating and estimating the ages of these zones the oldest littoral zone is found at elevations between 24 and 41 m above mean sea level and is judged to be older than oxygen isotope substage 5e in age based on relatively high amino acid ratios and extrapolated from non linear kinetic models an intermediate aged littoral zone may be present at some locations based upon beach ridges or platforms varying in elevation between 16 and 28 m above mean sea level dl ratios are generally lower than those for the oldest zone but show a greater variation this zone may represent the substage 5e sea level stand well defined young beach ridges 8 12 m above mean sea level are found in most locations and have been 14c dated and verified by amino acid ratios as being holocene the presence of quaternary aged emerged littoral zones at roughly the same elevation suggest that the glacio eustatic contribution is the primary cause of the high sea level stands whereas secondary variations are attributed to other factors

dynamics of former ice lobes of the southernmost patagonian ice sheet based on a glacial landsystems approach reconstructions of former ice masses from glacial geomorphology help to constrain the nature and timing of glaciation in relation to climatic forcing this paper presents a new reconstruction of the glacial history of five ice lobes in southernmost south america the bahia inutil san sebastian magellan otway skyring and rio gallegos ice lobes we use previous geomorphological mapping of glacial landforms to reconstruct former glacial limits and proglacial lakes demarcate flow sets from the distribution of glacial lineations and evaluate glacial landsystem signatures and their palaeoglaciological implications evidence suggests that the ice lobes predominantly reflect active temperate glacial landsystems which may have switched to polythermal systems when periods of cold based ice developed ephemerally this complex landsystem signature implies that the ice lobes were sensitive to regional climate variability with active re advances during overall retreat of the ice margins there is also evidence for periods of fast ice flow and possible surge like activity in the region followed by the rapid retreat or even collapse of some of the ice lobes in association with proglacial lakes constraining our new reconstruction with published chronological information suggests that at least some of the ice lobes advanced before the global last glacial maximum glgm ca 26 5 19 ka during the last glacial cycle our new reconstruction demonstrates a more complex picture of ice dynamics than has previously been portrayed and one in which the advance and retreat of the ice lobes was likely to have been primarily driven by changes in climate as such ice advances before the glgm in the southernmost part of the patagonian ice sheet are likely to indicate a wider climatic forcing at this time

cosmogenic nuclide measurements in southernmost south america and implications for landscape change we measured in situ 10be 26al and 36cl on glacial deposits as old as 1 1 myr in the southernmost part of patagonia and on northern tierra del fuego to understand boulder and moraine and by inference landscape changes nuclide concentrations indicate that surface boulders have been exposed for far less time than the ages of moraines they sit upon the moraine ages are themselves constrained by previously obtained 40ar 39ar ages on interbedded lava flows or u series and amino acid measurements on related non glacial marine deposits we suggest that a combination of boulder erosion and their exhumation from the moraine matrix could cause the erratics to have a large age variance and often short exposure histories despite the fact that some moraine landforms are demonstrably 1 myr old we hypothesize that fast or episodic rates of landscape change occurred during glacial times or near the sea during interglacials comparison with boulder erosion rates and exhumation histories derived for the middle latitudes of semi arid patagonia imply different geomorphic processes operating in southernmost south america we infer a faster rate of landscape degradation towards the higher latitudes where conditions have been colder and wetter

aerobic respiration along isopycnals leads to overestimation of the isotope effect of denitrification in the ocean water column abstract the nitrogen n isotopes provide an integrative geochemical tool for constraining the fixed n budget of the ocean however n isotope budgeting requires a robust estimate for the organism scale nitrogen isotope effect of denitrification in particular as it occurs in water column denitrification zones ewcd ocean field data interpreted with the rayleigh model have typically yielded estimates for ewcd of between 20 and 30 however recent findings have raised questions about this value in particular culture experiments can produce a substantially lower isotope effect 13 under conditions mimicking those of ocean suboxic zones in an effort to better understand prior field estimates of ewcd we use a geochemical multi box model to investigate the combined effects of denitrification aerobic respiration and isopycnal exchange on the 15n of nitrate in the context of this admittedly simplistic model we consider three isopycnals extending from the southern ocean to the eastern tropical north pacific etnp we show that the data from the etnp suboxic zone can be reproduced with an ewcd of 13 given a rate of aerobic respiration consistent with the nutrient data on these isopycnals and a plausible range in the 15n of the sinking flux being remineralized we discuss the limitations of our analysis additional considerations as well as possible data based tests for the proposal of a lower ewcd than previously estimated all else held constant a lower ewcd would imply a lower global ocean rate of denitrification that is more similar to the estimated rate of n input to the global ocean providing a major impetus for further investigation

esr dating stratigraphically well constrained marine terraces along the patagonian atlantic coast argentina abstract esr dating of marine mollusc shells is an important tool in coastal geomorphology as well as in palaeosea level and other research some severe problems however remain as far as the accuracy of the dating results are concerned case studies of patagonian middle and younger quaternary marine terraces help to illustrate the potential of an improved esr dating technique it can be demonstrated that a discrimination of holocene last interglacial penultimate interglacial and older samples is possible a chronostratigraphic separation of the well known last interglacial substages 5a 5c and 5e is still missing partly due to the misleading accuracy of esr dating results consequently it cannot be decided yet whether the morphologically well conserved last and penultimate interglacial age substages result from a relative sea level fall glacioeustatic and or decreasing wind intensities during the one and the same interglacial highstand shortly after the 5e or 7 transgression maximum or whether they were deposited during the much younger sea level sub highstands e g 5c 5a or 7c or 7a

subantarctic macrotidal flats cheniers and beaches in san sebastian bay tierra del fuego argentina abstract san sebastian bay is a large semicircular coastal embayment situated on the atlantic coast of tierra del fuego argentina it is a high energy subantarctic environment with a tidal range of 10 4 m influenced by large waves of atlantic and local origin and swept by constant strong westerly winds a 17 km long gravel spit protects the northern part of the bay giving rise to a gradient in sedimentary processes from south to north are seven distinct sedimentary environments coastal sedimentation started at least 5200 years before present bp and a rapid progradation related to a relative sea level drop has infilled about 6 kilometres of the bay with a sedimentary sequence 10 11 m thick 14 c dating of unabraded shells in the chenier ridges of the relict part of the complex allows for a precise reconstruction of the stages of the progradation that has slowed from 2 35 m year at 5000 years bp to 0 6 m year at present the possible causes of the sea level drop are discussed

does net e p set a preference for north atlantic sinking abstractthe present day global meridional overturning circulation moc with formation of north atlantic deep water nadw and the absence of a deep water formation in the north pacific is often considered to be caused by the fact that the north pacific basin is a net precipitative while the north atlantic is a net evaporative basin in this paper the authors study the effect of asymmetries in continent geometry and freshwater fluxes on the moc both in an idealized two dimensional model and in a global ocean model this study approaches the problem from a multiple equilibria perspective where asymmetries in external factors constrain the existence of steady moc patterns both this multiple equilibria perspective and the fact that a realistic global geometry is used add new aspects to the problem in the global model it is shown that the atlantic forced by net precipitation can have a meridional overturning circulation with northern sinking and a sea surface salinity that resembles the present day sali

holocene sea level changes along the strait of magellan and beagle channel southernmost south america abstract radiocarbon dated marine sediments from five coastal sites along the strait of magellan and beagle channel in southernmost chile permit construction of a curve of relative sea level fluctuations during the holocene morphologic and stratigraphic data point to coastal submergence during the early holocene as the sea rose to a maximum level at least 3 5 m higher than present about 5000 yr ago progressive emergence then followed during the late holocene data from widely separated localities define a smooth curve the form of which is explainable in terms of isostatic and hydroisostatic deformation of the crust resulting from changing ice and water loads apparently anomalous data from one site located more than 100 km behind the outer limit of the last glaciation may reflect isostatic response to deglaciation the sea level curve resembles one derived by clark and bloom 1979 in proceedings of the 1978 international symposium on coastal evolution in the quaternary sao paulo brasil pp 41 60 sao paulo using a spherical earth model both in amplitude and in the timing of the maximum submergence

quaternary glacial and marine stratigraphy of the qivitu peninsula northern cumberland peninsula baffin island canada summary sediments exposed along the outer coast of the qivitu peninsula record the advances and retreats of glaciers in the fiords bordering the peninsula and accompanying sea level fluctuations during the quaternary seven main lithofacies and 21 subfacies are recognized based on texture color bed thickness and lateral extent internal structures and abundance of macrofossils in contrast to earlier work in the area the interpretation of lithofacies genesis using a model of fiord glaciomarine sedimentation suggests that all lithofacies are of marine or glaciomarine origin with no evidence of grounded ice extending seaward of the peninsula the abundance and diversity of benthic foraminifera in selected samples and in situ subarctic molluscs shows that relatively warm water was present along the east baffin island coast during several periods of extensive fiord glaciers analysis of upward facies transitions in 54 stratigraphic sections suggests that facies sequences are cyclical these sedimentation cycles are interpreted in terms of glacier sea level responses during glacial interglacial cycles detailed relative time control for the lithofacies sequence is provided by time dependent amino acid ratios on the common shell fragments in many stratigraphic units because the stratigraphic sequence is marked by significant unconformities due to relative sea level regressions near the end of each glacial sedimentation cycle amino acid ratios on molluscs contemporaneous with particular cycles are statistically similar and distinct from ratios for older and younger cycles thus although few stratigraphic units can be physically traced for more than 0 5 km aminozones based on groups of animo acid ratios allow chronocorrelation and relative dating of units in each sedimentation cycle the qivitu stratigraphic sequence is divided into two formations consisting of a total of seven members for which formal names are proposed sediments predating the two most recent interglacials are lithologically similar to later beds suggesting that events during these earlier periods were of the same character as those of later glacial interglacial cycles biostratigraphic evidence suggests that a relatively mild climate prevailed in this region during the clyde and ayr lake glaciations and intervening cape broughton aquatherm the quajon interstade is correlative with the marine sediments deposited near the end of the ayr lake glaciation rather than the cape broughton aquatherm soil horizons indicate regressions at the end of the cape broughton aquatherm and ayr lake glaciation and pollen assemblages suggest that the terrestrial climate may have been warmer than the present climate a reinterpretation of u series dates and amino acid ratios on shells suggests that the cape broughton aquatherm and earlier events predate marine oxygen isotope substage 5e the ayr lake glaciation may have occurred well before the major interglacial glacial transition in more temperate latitudes but evidence from ocean cores in the north atlantic and ice cores from greenland and devon island supports the interpretation of warm water incursions into baffin bay during this ice advance following substage 5e by inference relative sea level during the period following the ary lake glaciation was lower than present sea level and glacier extent was restricted no evidence of an exceptionally cold dry climate has been found however distal glaciomarine sediments in the upper coastal cliffs suggest a limited readvance of fiord glaciers prior to the holocene near the beginning of the holocene 10 000 yr b p warmer water extended into the area as relative sea level fell and subsequently rose again to 15 m about 8 200 yr b p pollen assemblages in peat horizons suggest that during the earliest holocene a climate milder than that of the present day existed local deposition of eolian and soliflucted sediment may indicat deteriorating climate in late holocene time

middle late holocene palynology and marine mollusks from archipielago cormoranes area beagle channel southern tierra del fuego argentina abstract the palynology and marine mollusks of a marine sequence from rio ovando 54 51 s 68 35 w archipielago cormoranes beagle channel has been studied in order to reconstruct paleoenvironmental conditions during the middle late holocene the dinoflagellate cyst assemblages from rio ovando sequence reflect fjord estuarine environments close to terrestrial ice field affected by glacier meltwater discharge and characterized by short term oscillations of sea surface water parameters the base of the section which is dated at about ca 4160 14 c yr b p 4736 cal yr b p palynological subzone ro 2c is characterized by a high species diversity of dinocyst and mollusks and it is immediately followed by an interval palynological subzone ro 2b characterized by the presence of the echinidinium islandinium complex and the monospecific mytilus mollusk assemblage this subzone registers an inverse correlation between nothofagus dombeyi type and echinidinium islandinium complex concentration values during ca 4160 14 c yr b p 4736 cal yr b p 4064 14 c yr b p 4540 cal yr b p suggesting a variable climatic condition probably related to neoglacial episodes occurred in the southern patagonia andes during this interval the pollen assemblages permit direct correlations with the onshore palynostratigraphy from southern of tierra del fuego the high percentages of nothofagus dombeyi type recorded throughout most of the profile strongly suggest the presence of a closed forest confirming the existence of a variable cool and wet climate for the archipielago cormoranes area during the middle late holocene

multiscale variability of deep convection in relation to large scale circulation in toga coare deep convection over the indo pacific oceanic warm pool in the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare occurred in cloud clusters which grouped together in regions favoring their occurrence these large groups of cloud clusters produced large scale regions of satellite observed cold cloud top temperature this paper investigates the manner in which the cloud clusters were organized on time and space scales ranging from the seasonal mean pattern over the whole warm pool region to the scale of individual cloud clusters and their relationship to the large scale circulation and sea surface temperature sst the dominant convective variability was associated with the intraseasonal oscillation iso a large eastward propagating ensemble of cloud clusters marked the iso s progress the meridional structure of the iso was strongly affected by the seasonal cycle with a southward shift from the northern hemisphere in october november to the southern hemisphere in january february the sst had an intraseasonal signal in lagged quadrature with the cold cloudiness and rainfall in coare the sst increased decreased during the convectively suppressed active phases of the iso enhanced low level westerly winds occurred toward the later stages of the enhanced convection periods of the iso though not always centered at the equator the strongest westerlies tended to be located between two synoptic scale cyclonic gyres which were often not symmetric about the equator in the low level wind field this asymmetry in the anomalous equatorial low level westerlies may have different implications for the oceanic response in the coupled atmosphere ocean system than those centered on the equator the cyclonic gyres contained highly concentrated deep convection and in four cases the gyres developed into tropical cyclones within the envelope marking the convectively active phase of the iso cloud clusters were frequently concentrated into westward propagating disturbances with a local periodicity of similar to 2 days these 2 day disturbances have been identified in earlier spectral studies and appear to be related to westward propagating inertio gravity waves in coare they typically contained numerous cloud clusters which underwent a distinct diurnal cycle most of the cloud clusters embedded in the 2 day disturbances moved westward though some were stationary and a few moved eastward a cloud duster tracking program identified groups of clusters lime dusters that exhibited continuity in time and space in the most convectively active period of the iso the tracking program identified almost the entire iso cloud ensemble as a long lasting trackable superconvective system this observation indicates the lack of a distinct scale separation between convection and large scale disturbances during the most intense convective periods in coare

processes governing the recovery of a perturbed thermohaline circulation in hadcm3 abstract in an experiment with the latest version of the hadley centre climate model the model response has been analyzed after the thermohaline circulation thc in the atlantic ocean has been suppressed the suppression is induced by a strong initial perturbation to the salinity distribution in the upper layer of the northern north atlantic the model is then allowed to adjust freely salinity gradually increases and deep water formation in the greenland and norwegian seas restarts later also in the labrador sea the meridional overturning recovers after about 120 yr in the first few decades when the overturning is very weak surface air temperature is dominated by cooling of much of the northern hemisphere and weak warming of the southern hemisphere leading to maximum global cooling of 0 9 c the disruption to the atmosphere s radiation balance results in a downward flux anomaly at the top of the atmosphere maximally 0 55 w m 2 in the first decade then decreasing with the thc recovery the processes

130 000 yr continuous pollen record from clear lake lake county california pollen analysis of a 115 m sediment core from clear lake lake county california provides a climatic record that is continuous for the past 130 000 yr the pollen record reflects migrations of the tree species of the california coast ranges in response to the climatic changes of the last glacial cycle during interglacials the clear lake pollen rain was dominated by quercus oak pollen during cooler periods oak pollen was replaced by pollen of coniferous species the curve for quercus pollen strongly resembles and is used to correlate with both deep sea oxygen isotope curves and the climatic record from certain european pollen studies

parameter sensitivity of primitive equation ocean general circulation models abstract experiments with a low resolution primitive equation ocean general circulation model with idealized basin geometry and surface forcing have been carried out in order to identify the processes controlling the climatically important aspects of the circulation emphasis was placed on the sensitivity of the model solutions to the magnitude of the vertical diffusivity scaling arguments suggest and the numerical experiments confirm that the solutions are most sensitive to the magnitudes of the wind stress curl and the vertical diffusivity for small vertical diffusivity wind forcing dominates the solution the vertical scale of the thermocline is set by the strength of the ekman pumping and there is a multiple gyre circulation in the upper layers for large vertical diffusivity diabatic surface forcing dominates the solution vertical diffusion controls the vertical scale of the thermocline and there is a single large anticyclonic gyre in the upper layers both the meridionally and zonally inte

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

multi proxy evidence of late quaternary environmental changes in the coastal area of puerto lobos northern patagonia argentina abstract a multidisciplinary approach involving geomorphology taxa composition of mollusks and taphonomy performed on bivalve shells linked to mineralogical and microstructural analyses provide evidence of late quaternary environmental changes in the coastal area of puerto lobos in northern patagonia digital elevation models dems showed a beach ridge system developed parallel to the coast indicating sea level variations during mis1 mis5e and earlier in the pleistocene these ridges can be correlated with other marine ridges along the patagonian coast showing a similar geomorphological pattern and similar temporal evolution in relation to faunal composition when comparing the pleistocene with the holocene the most relevant differences are the presence of tegula atra and mactra patagonica in the pleistocene sediments and a diversification of taxa in the holocene during the late holocene the coastal area of puerto lobos also recorded a faunal shift in which species belonging to the magellan province displaced the fauna of the argentinean province to the north probably in coincidence with the little ice age lia taphonomic analysis on glycymeris longior and venus antiqua shells two common taxa in these beach ridges indicate greater energy in the depositional environment correlated with the youngest holocene beach ridge these shells exhibited taphonomic differences between them in relation to fracturing explained on the basis of higher elasticity in the g longior shell than in v antiqua shell because of its crossed lamellar microstructure

a review of amino acid racemization studies in quaternary mollusks stratigraphic and chronologic applications in coastal and interglacial sites pacific and atlantic coasts united states united kingdom baffin island and tropical islands abstract amino acid racemization aar studies of quaternary mollusks mostly marine mollusks from coastal deposits are reviewed data obtained in regional studies from the u s atlantic and pacific coasts baffin island the united kingdom and tropical islands are discussed as they relate to method evaluation kinetic model development and aminostratigraphic applications u s pacific coast studies have been employed for estimating tectonic deformation rates study of molluscan zonation patterns in the late pleistocene and in kinetic model evaluation u s atlantic coast studies have identified multiple aminostratigraphic zones in areas with complex morphostratigraphic relationships and have also revealed some important conflicts between aminostratigraphic temperature concepts and radiometric data studies in the united kingdom involving coastal sites and non marine interglacial sites identify some stratigraphic and kinetic conflicts but provide a preliminary chronostratigraphic model for the classical interglacial terminology of the u k middle to late pleistocene baffin island studies involving aar data and u th dating of shells have resulted in some significant revisions of previous chronologic models the arctic environment has also stimulated some novel approaches in the collection and interpretation of aar results tropical island studies though few in number aid in calibration of observed racemization and also aid in correlation of coastal deposits with late pleistocene isotopic ice volume records

stratigraphy of late quaternary estuarine deposits and amino acid stereochemistry of oyster shells beneath san francisco bay california abstract the sequence of quaternary deposits beneath the floor of san francisco bay includes four to seven noncontemporaneous estuarine units intercalated with alluvium and dune sand units l 0 10 000 b p m 40 000 b p probably ca 80 000 140 000 b p and n older than unit m are distinctly superposed the dominant molluscan fossil in each of these three units is ostrea lurida carpenter the native oyster along much of the pacific coast of north america despite a lamellar structure that suggests vulnerability to contamination o lurida shells generally yield amino acid enantiomeric ratios that are analytically reproducible and stratigraphically consistent the kinetics of racemization in o lurida conceivably resembles that of protothaca and saxidomus other bivalves whose kinetics of racemization are relatively well understood assuming such a resemblance enantiomeric ratios in o lurida imply that 1 unit m is the same approximate age as estuarine terrace deposits bordering san pablo bay and carquinez strait providing that the terrace deposits have been at diagenetic temperatures 1 2 c warmer than unit m and 2 the age of unit n is about four times greater than that of unit m providing that both units have been at the same approximate diagenetic temperature

quaternary glaciations of the southern andes abstract the southern andes comprise the southernmost portion of the andean cordillera beginning at the edge of the puna altiplano lat 27 s and ending at isla de los estados lat 55 s the late cainozoic glacial record of these mountains spans the interval from the late miocene to the present and is one of the most complete to be found anywhere in the world this has arisen for several reasons i the conterminous mountain ice cap extended to the piedmont zone on both flanks of the range where the sedimentary and morphological record has been well preserved ii periodic volcanism mainly from monogenetic fissure eruptions of basalt east of the range and from central tephra producing cones along the mountain crest has provided opportunity for the preservation and radiometric dating of interbedded glacial deposits iii a tectonically induced interval of stream incision in the mid pleistocene and simultaneous uplift has preserved glacial sediments on interfluves iv in the chilean lakes region west of the mountains late quaternary glaciers terminated in a well vegetated landscape thus creating scope for radiocarbon dating of interbedded and incorporated organic materials consequently the last glaciation in the llanquihue area of chile is one of the best dated sequences in south america thus the llanquihue glaciation is proposed as the south american equivalent of the wisconsin and weichsel glaciations of north america and north west europe respectively

the role of environmental shear and thermodynamic conditions in determining the structure and evolution of mesoscale convective systems during toga coare abstract a collection of case studies is used to elucidate the influence of environmental soundings on the structure and evolution of the convection in the mesoscale convective systems sampled by the turboprop aircraft in the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare the soundings were constructed primarily from aircraft data below 5 6 km and primarily from radiosonde data at higher altitudes the well documented role of the vertical shear of the horizontal wind in determining the mesoscale structure of tropical convection is confirmed and extended as noted by earlier investigators nearly all convective bands occurring in environments with appreciable shear below a low level wind maximum are oriented nearly normal to the shear beneath the wind maximum and propagate in the direction of the low level shear at a speed close to the wind maximum when there is appreciable shear at middle levels 800 400 mb convective bands form parallel to the shear with

three dimensional kinematic and microphysical evolution of florida cumulonimbus part ii frequency distributions of vertical velocity reflectivity and differential reflectivity abstract high resolution radar data collected in florida during the convection and precipitation electrification experiment are used to elucidate the microphysical and kinematic processes occurring during the transition of a multicellular storm from convective to stratiform stages a statistical technique is employed to examine the evolving properties of the ensemble small scale variability of radar reflectivity vertical velocity and differential reflectivity over the entire storm differential radar reflectivity data indicate that the precipitation at upper levels was nearly glaciated early in the storm s lifetime dual doppler radar data show that throughout the storm s lifetime both updrafts and down drafts were present at all altitudes and that most of the volume of the radar echo contained vertical velocities incapable of supporting precipitation size particles thus the ensemble microphysical properties of the storm were increasingly dominated by particles falling in an environment of weak vertic

a provisional aminostratigraphical framework for late quaternary marine deposits in buenos aires province argentina abstract amino acid analysis was carried out on 5 bivalve taxa mactra isabelleana corbula patagonica tagelus plebeius macoma uruguayensis and noetia bisulcata data from the two most common mactra isabelleana and corbula patagonica are reported in detail samples were collected from holocene shorelines ca 2000 6890 14 c yr b p along ca 350 km of the buenos aires province argentina the aminostratigraphy is in general agreement with the palaeoecological evidence and radiocarbon ages the deposits of the area of punta indio punta piedras in the north which show the highest d l ratios have a different geometry and a molluscan fauna of warmer water affinity than the remaining beach ridges and must be older they could correspond with the climatic optimum hypsithermal the deposits of samborombon and mar chiquita probably started accumulating immediately after deposition of the punta indio punta piedras deposits deposition at mar chiquita appears to have continued longer than at samborombon older d l ratios from pre holocene marine deposits are difficult to interpret without geochronological calibration

impact of north atlantic freshwater forcing on the pacific meridional overturning circulation under glacial and interglacial conditions abstractthe pacific meridional overturning circulation pmoc is not well known compared to the atlantic meridional overturning circulation amoc due to its absence today however considering pm

late quaternary climatic variability in northern patagonia argentina based on δ18o of modern and fossil shells of amiantis purpurata bivalvia veneridae abstract amiantis purpurata is a common warm temperate water bivalve species distributed from southern brazil to northern patagonia argentina which has a rich and well preserved fossil record in the san matias gulf smg dating back to the late quaternary this study aims to establish a purpurata shells as a new palaeoarchive of past marine conditions in south america we compared the stable oxygen and carbon profiles 18oshell 13cshell of eleven specimens of a purpurata from different geological times modern late holocene and interglacial late pleistocene and additionally present in situ oxygen isotope values of seawater within smg 18owater using both sets of information we calculated and reconstructed palaeowater temperatures for the late holocene and compared them to modern water temperatures our findings indicate that a purpurata records past environmental parameters such as water temperatures on a seasonal scale and can therefore be considered a suitable candidate for future palaeoenvironmental reconstructions in northern patagonia this study is the first step towards further stable isotope analyses on fossil a purpurata shells which will show whether and if so to what extent important global climate events such as the neoglacial early holocene the hypsithermal middle holocene and the little ice age late holocene occurred in south america

time stratigraphic aspects of a formation interpretation of surficial pleistocene deposits by analogy with holocene paralic deposits southeastern delaware pleistocene shoreline deposits in close spatial and temporal proximity to holocene deposits permit detailed interpretation of the development of pleistocene coastal deposits when a modern ancient analog approach is used peak sea levels during the past 1 m y or more have allowed the preservation of transgressive shoreline systems here referred to as paralic units along the inner continental margin these pleistocene paralic units are similar to holocene coastal deposits now forming on delmarva peninsula the omar formation early to late pleistocene age incorporates at least four juxtaposed transgressive paralic units of different ages each containing deposits of lagoonal sands and muds tidal marsh barrier sands and gravels tidal delta sands and silty sands and tidal channel sands and gravels the successive paralic units become younger in the seaward direction thus although the omar formation in the study area is almost entirely made up of transgressive deposits produced during rising sea levels in a longer time frame it forms a progradational sequence only about 2 to 5 of the elapsed time during the deposition of the studied part of the omar formation is represented by sedimentary units the internal time stratigraphy of the omar formation is extremely complex this makes the time stratigraphic interpretation of any one outcrop or drill hole difficult any lithologic change may represent a wide variety of time gaps from minutes to tens of thousands of years the analog approach in which sedimentary lithosome mapping is used allows one to infer a time stratigraphic framework of the deposits these concepts can aid in the interpretation of depositional history of older paralic deposits and the nature of the development of certain types of clastic formations

amino acid age estimates quaternary atlantic coastal plain comparison with u series dates biostratigraphy and paleomagnetic control amino acid enantiomeric dl ratios in the mollusk mercenaria are compared with recently published biostratigraphic and or u series solitary coral data from 22 quaternary localities on the central and southern atlantic coastal plain in all cases local relative aminostratigraphic sequences are consistent with relative ages inferred from u series or biostratigraphic data although occasionally more depositional events are recognized by aminostratigraphic than biostratigraphic methods however if the u series data are used as age calibrations for the dl values latitudinal trends of isochronous dl values are highly variable and conflict with trends expected from the present temperature gradient which is smooth and nearly linear between 45 and 25 n age estimation can be performed independently of the u series data using a kinetic model that relies on the assumption that pleistocene temperature gradients have also been smooth functions of latitude although significantly steeper than the present temperature gradient within the uncertainties of this assumption kinetic model age estimates for localities in the coastal plain fall into the following groups 70 000 130 000 yr 200 250 000 yr 300 000 400 000 yr 500 000 600 000 yr 700 000 800 000 yr and 1 000 000 yr major conflicts between these model age estimates are observed for localities near charleston south carolina and in central virginia these conflicts could indicate that the basic temperature assumptions of aminostratigraphy are incorrect and that apparent local aminostratigraphic sequences clusters of different dl values could be due to factors other than age difference alternatively some of the u series dates may be only minimum ages for these localities

convection over the pacific warm pool in relation to the atmospheric kelvin rossby wave abstract deep convection over the western tropical pacific warm pool is analyzed in terms of its relation to the atmospheric kelvin rossby wave which dominates the large scale flow during the austral summer the study uses doppler radar data collected by aircraft and ship radars during different time periods in the tropical ocean global atmosphere coupled ocean atmosphere response experiment to characterize the mesoscale circulations of organized convective cloud systems occurring throughout the season the study focuses on convection in two contrasting phases of the wave the westerly onset region just west of the point within the wave where low level easterlies change to westerlies and the strong westerly region or westerly wind burst lying between the large scale counterrotating gyres of the kelvin rossby wave in the westerly onset region the zonal wind component had midlevel easterlies overlying low level westerlies in the strong westerly region a deep layer of westerlies extended from the

bermuda sea level during the last interglacial bermuda is a stable mid oceanic carbonate platform for which a particularly complete record of sea level fluctuation during the period 135 70 kyr has been reconstructed from 230th 234u dating of corals and speleothems amino acid racemization dating of molluscs and a reinterpretation of geological field relations during the past 5 yr bermuda has been the focus of an extensive geochronological programme which has included a detailed re examination of the geology to be reported elsewhere1 3 here we focus only on the latest interglacial sequence we use the stratigraphie nomenclature of land et al 4 but will present new age data and interpretations of geological relationships this information as it relates to the last interglacial period is given in tables 1 and 2 and summarized in fig 1 we show that during the last interglacial period sea level was only above its present level for a few thousand years at about 125 kyr when it stood at 4 to 6m at 105 and 85 kyr sea level rose to between 15 and 20 m as constrained by ages for submerged speleothems and eolianites at 95 kyr sea level in bermuda was at least 15 m below present level

paleotemperatures and the glacially induced changes in the oxygen isotope composition of sea water during late pleistocene and holocene time in tanner basin california oxygen isotope analyses of the benthic foraminiferal species uvigerina peregrina show that glacially induced changes in the isotopic composition of sea water reached a maximum of 1 5 in late pleistocene time in tanner basin southern california isotopic data derived from the planktonic species globigerina quinqueloba corrected for glacial and regional water mass effects indicates that an increase in mean surface water temperatures of about 5 c took place from near the end of the wisconsin glaciation to the holocene thermal maximum at about 7 500 yr b p the isotopic minimum recorded by u peregrina at about 40 000 yr b p is unusually low compared to that found in open ocean cores

robustness of multiple equilibria in the global ocean circulation 1 in an idealized atlantic pacific ocean model we study the steady state solutions versus freshwater input in the northern north atlantic we find that four different states the conveyor c the southern sinking ss the northern sinking ns and the inverse conveyor ic appear as two disconnected branches of solutions where the c is connected with the ss and the ns with the ic we argue that the latter has the intriguing consequence that the parameter volume for which multiple steady states exist is greatly increased

extensive mis 3 glaciation in southernmost patagonia revealed by cosmogenic nuclide dating of outwash sediments abstract the timing and extent of former glacial advances can demonstrate leads and lags during periods of climatic change and their forcing but this requires robust glacial chronologies in parts of southernmost patagonia dating pre global last glacial maximum glgm ice limits has proven difficult due to post deposition processes affecting the build up of cosmogenic nuclides in moraine boulders here we provide ages for the rio cullen and san sebastian glacial limits of the former bahia inutil san sebastian bi ssb ice lobe on tierra del fuego 53 54 s previously hypothesised to represent advances during marine isotope stages mis 12 and 10 respectively our approach uses cosmogenic 10be and 26al exposure dating but targets glacial outwash associated with these limits and uses depth profiles and surface cobble samples thereby accounting for surface deflation and inheritance the data reveal that the limits formed more recently than previously thought giving ages of 45 6 ka 139 9 14 3 for the rio cullen and 30 1 ka 45 6 23 1 for the san sebastian limits these dates indicate extensive glaciation in southern patagonia during mis 3 prior to the well constrained but much less extensive mis 2 glgm limit this suggests the pattern of ice advances in the region was different to northern patagonia with the terrestrial limits relating to the last glacial cycle rather than progressively less extensive glaciations over hundreds of thousands of years however the dates are consistent with mis 3 glaciation elsewhere in the southern mid latitudes and the combination of cooler summers and warmer winters with increased precipitation may have caused extensive glaciation prior to the glgm

microphysical characteristics of mjo convection over the indian ocean during dynamo the microphysical characteristics of precipitating convection occurring in various stages of the madden julian oscillation mjo over the indian ocean are determined from data obtained from the national center for atmospheric research dual polarimetric doppler s band radar s polka deployed as part of the dynamics of the mjo dynamo field experiment active mjo events with increased rainfall occurred in october november and december 2011 during each of these active mjo phases in addition to enhanced rainfall convection became deeper and ice phase microphysics played a greater role s polka consistently showed nonoriented small ice particles dominating the radar echoes at altitudes of 9 10 km dry aggregates concentrated between 7 and 9 km and wet aggregates and graupel near the melting level 5 km graupel occurred mainly in actively convective towers while the wet aggregates occurred almost exclusively in the stratiform regions of mesoscale convective systems mcss during each of the three multiweek mjo active phases the maximum rainfall occurred in short bursts lasting a few days each multiday rainy period began with deepening convective elements and a concurrent increase in occurrence of dry aggregates which maximized just prior to organization into mcss the peak rainfall occurrence coincided with the maximum coverage of the radar domain by mcss reflecting large stratiform regions that exhibited the most frequent occurrence of wet aggregates during the december active mjo phase however the mcss were shallower and had a slightly lower tendency for wet aggregates in the stratiform regions and therefore generally weaker brightbands

quaternary marine terraces sea level changes and uplift history of patagonia argentina comparisons with predictions of the ice 4g vm2 model of the global process of glacial isostatic adjustment abstract quaternary marine terraces have been investigated along a 1000 km stretch of the coast of argentinian patagonia fossil mollusc shells most in living position and collected from raised beaches were dated using the u series esr and 14 c methods our analyses show that holocene sea level in this region culminated 7000 to 8000 bp at 6 7 m amsl this beach slightly increases in altitude southward the last interglacial stage 5e was identified at 16 17 m amsl whereas the highest and morphologically most distinctive radiometrically dated terrace at 250 000 to 330 000 bp exists at an elevation of 33 35 m amsl we estimate a constant rate of tectonic uplift of 0 09 m 1000 yr since the middle pleistocene using this estimate of the local rate of tectonic uplift we correct relative sea level r s l observations for the holocene epoch in turn the inferred holocene sea level histories are compared with those predicted using the ice 4g vm2 model of the global process of glacial isostatic adjustment this model accurately predicts r s l history from all sites along the northern part of the east coast of the south american continent venezuela brazil however along the southern part of the coast of argentinian patagonia there is evidence of an influence that is not accurately represented in this version of the model of the global process of glacial isostatic adjustment we suggest that this influence could be connected to the presence of the broad continental shelf that is located offshore of this region but the influence of significant neotectonic uplift cannot be dismissed