the origins of s forms form similarity process analogy and links to high energy subglacial meltwater flows abstract this paper first presents the history of ideas on s form formation with an emphasis on meltwater models the main approach is based on form similarity between modern erosional marks and subglacial s forms form similarity is then extended to process similarity which promotes understanding of s forms three classes of erosional marks are identified obstacle scours basin shaped erosional marks and landforms related to escarpment flow identification is based on form with recognition of elements though it mainly depends on recognition of the whole form in much the same way as we recognize family members or familiar flowers flow conditions related to the various flow features are determined by flow visualization and computational fluid dynamics some s forms are produced in flume models though most are natural features observed in the field examples from beneath past ice sheets are seen in the field and illustrated by air and ground photographs satellite images and dem digital elevation model the results of this work show remarkable similarity between modern erosional marks and ancient subglacial s forms consequently established processes are attributed to ancient forms in turn s forms may be used abductively to interpret subglacial hydrological conditions the lack of waning stage bedforms scoured into primary forms suggests that erosional marks form under abruptly terminating catastrophic flow

cenozoic magmatism of the valencia trough western mediterranean relationship between structural evolution and volcanism abstract the cenozoic magmatism of the valencia trough is characterized by the existence of two volcanic cycles the first cycle early miocene middle miocene comprises calc alkaline rocks which have been recognized in the central to eastern offshore areas and in mallorca the second cycle middle miocene to recent is represented mainly by poorly differentiated alkaline rocks which are predominantly distributed along the iberian margin of the valencia trough in accordance with the inferred structural evolution of the valencia trough petrological and geochemical data as well as volcanological evidence we suggest that two different geodynamic environments existed during these magmatic cycles the early to middle miocene calc alkaline volcanism developed under compressive tectonic conditions and seems to be associated with the northwestern dipping subduction of the african plate in contrast the middle miocene to recent alkaline volcanism is associated with extensional tectonics and can be explained within the framework of a low volcanicity rift model three zones catalan valencian and columbretes each located at different parts of the rift structure can be distinguished in the middle miocene to recent volcanism this intraplate volcanism results from partial melting due to extension driven decompression with the largest degrees of melting in the centre of the valencia trough columbretes volcanic zone in the catalan volcanic zone a progressive increase in the extension rate from the first to the last volcanic episode has occurred favouring the interaction of two mantle sources

large reemergence of anthropogenic carbon into the ocean s surface mixed layer sustained by the ocean s overturning circulation abstractwe evaluate the output from a widely used ocean carbon cycle model to identify the subduction and obduction reemergence rates of anthropogenic carbon cant for climatological conditions during the world ocean circulation experiment woce era in 1995 using a new set of lagrangian diagnostic tools the principal scientific value of the lagrangian diagnostics is in providing a new means to connect cant reemergence pathways to the relatively rapid renewal time scales of mode waters through the overturning circulation our main finding is that for this model with 2 04 pgc yr 1 of uptake of cant via gas exchange the subduction and obduction rates across the base of the mixed layer mlbase are 4 96 and 4 50 pgc yr 1 respectively which are twice as large as the gas exchange at the surface given that there is net accumulation of 0 17 pgc yr 1 in the mixed layer itself this implies the residual downward cant transport of 1 40 pgc yr 1 across the mlbase is associated with diffusion importantly th

variability of 14c reservoir age and air sea flux of co2 in the peru chile upwelling region during the past 12 000 years abstract the variability of radiocarbon marine reservoir age through time and space limits the accuracy of chronologies in marine paleo environmental archives we report here new radiocarbon reservoir ages r from the central coast of chile 32 s for the holocene period and compare these values to existing reservoir age reconstructions from southern peru and northern chile late holocene r values show little variability from central chile to peru prior to 6000 cal yr bp however r values were markedly increased in southern peru and northern chile while similar or slightly lower than modern r values were observed in central chile this extended dataset suggests that the early holocene was characterized by a substantial increase in the latitudinal gradient of marine reservoir age between central and northern chile this change in the marine reservoir ages indicates that the early holocene air sea flux of co2 could have been up to five times more intense than in the late holocene in the peruvian upwelling while slightly reduced in central chile our results show that oceanic circulation changes in the humboldt system during the holocene have substantially modified the air sea carbon flux in this region

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

radiocarbon as a thermocline proxy for the eastern equatorial pacific an ocean model is used to test the idea that sea surface delta 14 c behaves as a thermocline proxy in the eastern equatorial pacific the orca2 model which includes delta 14 c as a passive tracer has been forced with reanalysis fluxes over 1948 1999 and the output is compared with a previously reported galapagos delta 14 c record the model reproduces the abrupt increase in the seasonally minimum delta 14 c in 1976 77 found in the data this increase is associated with neither a shift of thermocline depth over the nino3 region nor a change in the relative proportion of northern southern source waters rather it is due to a decrease in the sub antarctic mode water samw component of the upwelling water thereby representing a decrease in entrainment of water from below the base of the directly ventilated thermocline

observations of warm water volume changes in the equatorial pacific and their relationship to el nino and la nina abstract this paper describes observed changes in surface winds sea surface temperature sst and the volume of water warmer than 20 c wwv in the equatorial pacific ocean for the period 1980 99 the purpose is to test recent hypotheses about the relationship between variations in wwv and the el nino southern oscillation enso cycle the results confirm inferences based on theory models and previous empirical analyses using proxy data namely sea level that enso involves a recharge and discharge of wwv along the equator and that the cyclic nature of enso results from a disequilibrium between zonal winds and zonal mean thermocline depth the authors also find that the magnitude of enso sst anomalies is directly related to the magnitude of zonal mean wwv anomalies furthermore for a given change in equatorial wwv the corresponding warm el nino sst anomalies are larger than the corresponding cold la nina anomalies this asymmetry between the warm and cold phases of the enso cycle implies differences

eruptive mechanisms of the puig de la garrinada volcano olot garrotxa volcanic field northeastern spain a methodological study based on proximal pyroclastic deposits abstract an ephemeral and proximal outcrop at the quaternary basaltic puig de la garrinada cinder volcano was studied in order to decipher eruptive mechanism variations in the course of a single eruption once the volcanostratigraphy was established and recorded by photographs a very detailed sampling of underlying lava flows bombs and a large number of fine sized lapilli and ash beds was carried out an ad hoc description card was elaborated for study under stereo microscope in order to identify the different types of materials that form the volcanic cone ten material types were recognised sedimentary accidental clasts massive lava accidental clasts bombs xenoliths xenocrysts and phenocrysts oxidised scoria scoria with oxidised film fluidal pyroclasts non fluidal pyroclasts and coatings subsequent studies under sem eds and basic chemical characterization of the samples whole rock xrf for major and trace elements and empa were conducted all these studies make possible the reconstruction of the eruptive history of the la garrinada volcano which shows a transition from initial strombolian activity to gradually incorporated phreatomagmatic activity this permits the calculation of magma eruption rates magma column oscillations and aquifer interactions with magma column since our general conclusions agree well with the discrimination of eruptive episodes obtained from the stereo microscope description card macroscopic volcanostratigraphy and chemical results it is proposed that a similar study protocol quick volcanostratigraphy logging photographic record detailed sampling description following this card might be useful in the reconstruction of eruptive activity of other cinder cones in the garrotxa region and elsewhere and therefore can provide a good and quick methodological tool especially when rapid field description and sampling is required ephemeral outcrops risky sampling during active eruptive episodes etc moreover the conducted sampling allows for subsequent studies on the same set of pyroclasts

late quaternary environmental changes in the upper las vegas valley nevada abstract five stratigraphic units and five soils of late pleistocene to holocene age crop out in dissected badlands on corn creek flat 30 km northwest of las vegas nevada and at tule springs nearer to las vegas the record is dominantly fluvial but contains evidence of several moister marsh forming periods the oldest unit b dates perhaps to the middle wisconsin and the more widespread unit d falls between 30 000 and 15 000 yr b p unit d therefore correlates with pluvial maximum lacustrine deposits elsewhere in the great basin standing water was not of sufficient depth or extent during either period to form lake strandlines between 14 000 and 7200 yr b p unit e standing surface water gradually decreased a trend also apparent in great basin pluvial lake chronologies during the same period groundwater carbonate cementation and burrowing by cicadas cicadae accompany the moist phase units after 7200 yr b p increased wind action decreased biotic activity and at least 25 m of water table lowering accompanied widespread erosion of older fine grained deposits based on pack rat midden and pollen evidence this coincides with major vegetation changes in the valley from sagebrush dominated steppe to lower mohave desertscrub

southern hemisphere origins of the 1976 climate shift 1 observations from the tropical pacific ocean identify an abrupt climate shift in 1976 with surface temperatures changing from cooler than normal to warmer than normal in the span of about 1 year model results show that this climate shift originates with subsurface temperature anomalies in the south tropical pacific ocean which propagate first to the western boundary then northward to the equator and finally eastward along the equator to 140 w where they rise to the surface the results suggest that changes in the north pacific respond to changes in the tropical pacific

oceanic climate and circulation changes during the past four centuries from radiocarbon in corals we analyzed radiocarbon in annual coral bands from the galapagos islands in the tropical east pacific to understand natural variability of past ocean circulation associated with climate change variability was observed on el nino timescales 3 7 years as well as at decadal and multi decadal periods low radiocarbon levels persisted for ten years during the early 1600s and for sixteen years during the early 1800s both coincident with periods of high volcanic aerosol loading in the atmosphere from massive eruptions intensification of tropical circulation at this time may be linked to climatically controlled changes in the structure of the tropical thermocline that is responsible for delivering cool upwelled waters to the tropical east pacific

morphological and sedimentological characteristics of the neogene submarine coherent lavas and hyaloclastites in southwest hokkaido japan abstract the neogene formations in southwest hokkaido japan are mostly composed of submarine volcanic products such as submarine coherent lavas and hyaloclastites associated with feeder dikes this paper presents criteria for recognition of submarine effusion products through description of the morphological and sedimentological characteristics of coherent lavas such as pillow lobes sheet flow lava lobes and pseudo pillow lavas and hyaloclastites and feeder dikes and a small amount of associate pyroclastic rocks

stasis and change in holocene small mammal diversity during a period of aridification in southeastern utah biological conservation depends on understanding and disentangling the effects of decadal to centennial scale dynamics from the millennial scale dynamics documented in the fossil record the american southwest is expected to become increasingly arid over the next few decades and will continue to experience large scale human land use in various forms a primary question is whether the ecological fluctuations recorded over the past few decades fall outside the range of variation expected in the absence of recent land use and management i excavated and quantified mammal diversity change in two fossil bearing alcoves east canyon rims 2 and rone bailey alcove located in san juan county utah ams radiocarbon dates on 33 bone samples from these sites span 4 4 0 5 kyr and shed light on pre industrial faunal dynamics in the region over the course of environmental change localities with comparable small mammal diversity have not been reported from this region previously so these deposits provide novel insig

groundwater flow regime recharge and regional scale solute transport in the semi arid kalahari of botswana derived from isotope hydrology and hydrochemistry summary a synthesis of isotope hydrological 2 h 3 h 18 o 13 c 14 c 3 he 4 he and hydrogeochemical tools was used to analyze flow regimes and their time scales to determine recharge conditions and to describe the regional scale hydrogeochemical evolution of groundwater from the triassic ntane sandstone aquifer between serowe and orapa in the kalahari of botswana this location is taken as an example of a complex hydrodynamic setting relating to semi arid climatic conditions low recharge amounts thick unsaturated zones up to 100 m and long groundwater residence time scales capabilities and limits of the individual methods are discussed and relations to solute transport are demonstrated for nitrate chemical classification allows the distinction of six different groundwater types this characterization is reflected in the isotopic composition and in part can be attributed to different age ranges up to greater than 20 ka we show that the regional scale groundwater flow regime in the aquifer is only slow and that groundwater is recharged in serowe and orapa however in both investigated regions mixing between over and underlying aquifers is evident which limits a clear derivation of one regional flow regime the challenges imposed on the identification of the regional groundwater flow regime by resulting mixing processes and for groundwater dating are discussed and evaluated

the mescal cave fauna san bernardino county california and testing assumptions of habitat fidelity in the quaternary fossil record abstract the late pleistocene and holocene vertebrate fossil record for the northern mojave desert southwestern usa is known primarily from five sites until now only two of these have been radiometrically dated and temporal placement of the others has been based on stratigraphic or biostratigraphic correlation leading to circular interpretations of mammal extirpations in the mojave here i report a revised and complete faunal list for mescal cave along with 22 ams radiocarbon dates from 5 vertebrate taxa recovered from its deposits the results reported here demonstrate time averaging in mescal cave encompassing around 34 ka a maximum age 14 ka older and minimum age 10 ka younger than previously thought furthermore radiocarbon analyses suggest local extirpation of marmota flaviventris around 3 6 cal ka bp considerably younger than expected based on regional patterns of warming and aridification in the mojave conversely radiocarbon dates from another presumably boreal species neotoma cinerea are considerably older than expected suggesting either that climate change at this site did not directly mirror regional patterns that habitat requirements for these two species are not strictly boreal or cool mesic as has often been assumed or that local edaphic conditions and or competitive interactions overrode the regional climatic controls on theses species distribution

upwelling signals in radiocarbon from early 20th century peruvian bay scallop argopecten purpuratus shells abstract we quantified 14c 18o and 13c cycles along ontogeny within four bay scallop argopecten purpuratus shells collected from callao bay salaverry and sechura bay peru following the 1907 1908 non el nino years and the 1925 1926 el nino 14c and 13c generally covary 14c and 18o vary inversely simultaneous decreases in 14c and increases in 18o in non el nino shells are followed by constant 14c and gradually decreasing 18o which we interpret as evidence for discrete marine upwelling events followed by warming of the initially cold upwelled water upwelling changes from el nino events are detectable with difficulty in mollusk shell 14c

bomb rich basaltic pyroclastic flow deposit from nakadake aso volcano southwestern japan abstract a bomb rich basaltic pyroclastic flow deposit the izumikawa pyroclastic flow deposit occurs at the northeastern foot of nakadake volcano which is the only active central cone of aso caldera southwestern japan the pyroclastic flow deposit covers a fan shaped area of about 1 9 km2 and the bulk volume is estimated at 9 4 106 m3 the deposit is poorly sorted and consists of subangular faceted clasts and spherical cauliflower bombs set in a sandy non cohesive matrix the deposit forms two different facies a black reversely graded lower unit and a reddish gray reversely graded upper unit the cauliflower bombs which have slightly vesiculated crusts 1 0 1 5 cm thick and denser interiors are more abundant in the lower unit than in the upper unit the presence of cauliflower bombs suggests that the izumikawa pyroclastic flow was generated by an explosion at the source lava lake or conduit which was filled with mixture of solidified and molten lavas we propose the term bomb and ash flow deposit to describe this type of deposit the age of the izumikawa pyroclastic flow deposit was estimated at ca 19 cal ka based on a 14c age obtained from charred wood fragments in the deposit although all recent activity of nakadake has been ash eruptions strombolian eruptions and phreatomagmatic explosions the izumikawa pyroclastic flow deposit underscores the hazard of bomb rich pyroclastic flows that rush down the flanks of the volcano

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

abrupt shift in subsurface temperatures in the tropical pacific associated with changes in el nino radiocarbon 14c content of surface waters inferred from a coral record from the galapagos islands increased abruptly during the upwelling season july through september after the el nino event of 1976 sea surface temperatures ssts associated with the upwelling season also shifted after 1976 the synchroneity of the shift in both 14c and sst implies that the vertical thermal structure of the eastern tropical pacific changed in 1976 this change may be responsible for the increase in frequency and intensity of el nino events since 1976

radiocarbon in annual coral rings from the eastern tropical pacific ocean sixty radiocarbon measurements were performed on aragonite from annually banded corals collected from three sites in the galapagos islands preanthropogenic 14c values of coral that grew around a d 1930 averaged 70 this is substantially lower than average values previously reported 51 for corals from florida and belize in the western north atlantic ocean a decrease of 6 was noticed in coral that grew from 1930 to 1954 this decrease could be interpreted as a suess effect in surface ocean water the 100 increase in 14c for coral that grew from 1954 to 1973 is the result of bomb produced 14c that was introduced to the surface ocean waters the 14c levels in corals that grew during el nino years were considerably higher than those for normal years these higher values are attributed to the absence of up welling at the equator during el nino events

late glacial and early holocene vegetation and climate change near owens lake eastern california abstract pollen and algae from owens lake in eastern california provide evidence for a series of climatic oscillations late in the last glaciation juniper woodland which dominated the owens valley from 16 200 to 15 500 cal yr b p suggests much wetter conditions than today although still wetter and cooler than today the area then became fairly warm and dry with woodland being replaced by shrubs mainly sagebrush from 15 500 to 13 100 cal yr b p next chenopodiaceae shadscale increased woody species declined and lake levels fell all evidence for a brief ca 100 200 yr drought about 13 000 cal yr b p the climate continued to oscillate between wet and dry from 13 000 to 11 000 cal yr b p after 11 000 cal yr b p low lake levels and the increased dominance of desert shrubs indicate the beginning of warm dry holocene conditions the region s climate was unstable during the younger dryas but uncertainities in dating prevent identification of the younger dryas interval in the owens lake record comparison of the owens lake record with studies in the sierra nevada and great basin suggest that the climate was generally wetter between 13 000 and 11 000 cal yr b p with warmer summers although no consistent pattern of climate change emerges

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

decadal change in the south tropical pacific in a global assimilation analysis using an ocean general circulation model that incorporates data assimilation we show that the northward flowing portion of the subtropical gyre in the south pacific undergoes a well defined decadal variation the maximum variability of ocean temperature is located at around 10 degrees s and is largest in the western side of the basin with a vertical extension of up to 1000 m the anomalous temperature shows a rapid warm to cold transition in the late 1970s with a peak to peak value of more than 1 degrees c coupled with this change is a strengthened circulation in the northern portion of the subtropical gyre further analysis indicates that the decadal change in the south tropical pacific is linked to increased ekman suction induced by enhanced cyclonic wind stress curl in the region

experimental constraints on degassing and permeability in volcanic conduit flow this study assesses the effect of decompression rate on two processes that directly influence the behavior of volcanic eruptions degassing and permeability in magmas we studied the degassing of magma with experiments on hydrated natural rhyolitic glass at high pressure and temperature from the data collected we defined and characterized one degassing regime in equilibrium and two regimes in disequilibrium equilibrium bubble growth occurs when the decompression rate is slower than 0 1 mpa s 1 while higher rates cause porosity to deviate rapidly from equilibrium defining the first disequilibrium regime of degassing if the deviation is large enough a critical threshold of super saturation is reached and bubble growth accelerates defining the second disequilibrium regime we studied permeability and bubble coalescence in magma with experiments using the same rhyolitic melt in open degassing conditions under these open conditions we observed that bubbles start to coalesce at 43 vol porosity regardless of decompression rate coalescence profoundly affects bubble texture and size distributions and induces the melt to become permeable we determined coalescence to occur on a time scale 180 s independent of decompression rate we parameterized and incorporated our experimental results into a 1d conduit flow model to explore the implications of our findings on eruptive behavior of rhyolitic melts with low crystal contents stored in the upper crust compared to previous models that assume equilibrium degassing of the melt during ascent the introduction of disequilibrium degassing reduces the deviation from lithostatic pressure by 25 the acceleration at high porosities 50 vol by a factor 5 and the associated decompression rate by an order of magnitude the integration of the time scale of coalescence to the model shows that the transition between explosive and effusive eruptive regimes is sensitive to small variations of the initial magma ascent speed and that flow conditions near fragmentation may significantly be affected by bubble coalescence and gas escape

kinematics of the pacific equatorial undercurrent an eulerian and lagrangian approach from gcm results abstract three dimensional monthly velocity fields from an ocean general circulation model are used to study the annual mean mass balance of the pacific equatorial undercurrent euc eulerian diagnostics are used to evaluate the various meridional vertical and zonal mass fluxes related to the euc there are several distinct regimes along the equator showing clear asymmetries between the western and eastern parts of the basin and between the northern and southern edges of the euc meridional fluxes are decomposed into pure ekman divergence and geostrophic convergence and it is shown that the asymmetries are mainly related to the spatial structure of the ekman divergence and thus to that of the trade winds lagrangian calculations are used to evaluate accurately the mass transfers between various sections of the euc and between the euc domain and the tropics the authors show that geostrophic convergence only ventilates the upper layers of the euc and that the euc really is a tongue of water flowing

large variations in the holocene marine radiocarbon reservoir effect reflect ocean circulation and climatic changes accurate radiocarbon dating of marine samples requires knowledge of the marine radiocarbon reservoir effect this effect for a particular site region is generally assumed constant through time when calibrating marine 14c ages however recent studies have shown large temporal variations of several hundred to a couple of thousand years in this effect for a number of regions during the late quaternary and holocene here we report marine radiocarbon reservoir correction r r for heron reef and moreton bay in southwestern sw pacific for the last 8 ka derived from 14c analysis of 230th dated corals most of our r r for the last 5 4 ka agree well with their modern value but large r r variability of 410 yr from trough to peak with possible decadal centennial fluctuations is evident for the period 5 4 8 ka the latter time interval also has significant variations with similar features in previously published r r values for other sites in the pacific including southern peru northern chile in southeastern se pacific the south china sea vanuatu and papua new guinea with the largest magnitude of 920 yr from se pacific the mechanisms for these large r r variations across the pacific during the mid holocene are complex processes involving 1 changes in the quantity and 14c content of upwelled waters in tropical east pacific tep frequency and intensity of ocean upwelling in the tep and contribution of subantarctic mode water to the upwelled waters which is influenced by the intensity and position of southern westerly winds and 2 variations in ocean circulation associated with climate change la nina el nino conditions intensity of easterly trade winds positions of the intertropical convergence zone and the south pacific convergence zone which control the spreading of the older upwelled surface waters in the tep to the western sites our results imply the need for employing temporal changes in r r values instead of constant modern values for age calibration of holocene marine samples not only for the sw pacific sites but also for other tropical and subtropical sites in the pacific

mechanistic drivers of reemergence of anthropogenic carbon in the equatorial pacific relatively rapid re emergence of anthropogenic carbon cant in the equatorial pacific is of potential importance for its impact on the carbonate buffering capacity of surface seawater and thereby impeding the ocean s ability to further absorb cant from the atmosphere we explore the mechanisms sustaining cant re emergence upwelling from the thermocline to surface layers by applying water mass transformation diagnostics to a global ocean sea ice biogeochemistry model we find that the upwelling rate of cant 0 4 pgc yr 1 from the thermocline to the surface layer is almost twice as large as air sea cant fluxes 0 203 pgc yr 1 the upwelling of cant from the thermocline to the surface layer can be understood as a two step process the first being due to diapycnal diffusive transformation fluxes and the second due to surface buoyancy fluxes we also find that this re emergence of cant decreases dramatically during the 1982 1983 and 1997 1998 el nino events

rheological evolution of a pseudotachylyte bearing deep crustal shear zone in the western canadian shield abstract crustal scale continental strike slip fault systems are typically thought to be thermally segregated into an upper seismogenic expression and a lower zone of ductile deformation likely extending into the lower crust the ability of the lower crust to sustain stress is fundamental to understanding the mechanical behavior of the lithosphere yet significant debate exists regarding the strength of the ductile crust the cora lake shear zone in the western churchill province of the canadian shield is a 4 7 km wide zone of granulite to upper amphibolite facies mylonite which hosts synkinematic pseudotachylyte suggesting a locally strong lower crust kilometer scale mapping suggests that the shear zone localized at a major lithological and terrane boundary with the pseudotachylyte network centered within the ca 1 km wide more intensely deformed finer grained ultramylonitic core in this contribution we use optical petrography and electron backscatter diffraction to describe microstructure across a transect of the cora lake shear zone by combining these observations with grain size piezometry experimental flow laws and regional pressure temperature paths we conclude that stress amplification from a relatively common type of km scale lithological heterogeneity and cooling history is the most reasonable explanation for the deep crustal pseudotachylyte