asymmetry of atmospheric circulation anomalies over the western north pacific between el nino and la nina the asymmetry of the western north pacific wnp low level atmospheric circulation anomalies between the el nino and la nina mature winter is examined an anomalous wnp cyclone wnpc center during la nina tends to shift westward relative to an anomalous wnp anticyclone wnpac center during el nino two factors may contribute to this asymmetric response thefirst factor is the longitudinal shifting of el nino and la nina anomalous heating the composite negative precipitation anomaly center during la ninai s located farther to the west of the composite positive precipitation anomaly center during el nino the westward shift of the heating may further push the wnpc westward relative to the position of the wnpac the second factor is the amplitude asymmetry of sea surface temperature anomalies sstas in the wnp namely the amplitude of local cold ssta during el nino is greater than that of warm ssta during la nina the asymmetry of ssta is originated from the asymmetric ssta tendencies during the enso developing summer although both precipitation and surface wind anomalies are approximately symmetric the surface latent heat flux anomalies are highly asymmetric over the key wnp region where the climate mean zonal wind speed is small both the anomalous westerly during el nino and the anomalous easterly during la nina in the region lead to an enhanced surface evaporation strengthening weakening the enhancement of the cold warm ssta in situ during el nino la nina the asymmetry of the ssta in the wnp is further amplified due to anomalous wind differences between el nino and la nina in their mature winter atmo spheric general circulation model experiments demonstrate that both factors contribute to the asymmetry between the wnpac and wnpc the asymmetric circulation in the wnp contributes to the asymmetry of temporal evolutions between el nino and la nina

chaos on europa the characteristics of chaos regions on europa suggest they may be sites of melt through from below they are wide ranging in size location and age the largest are hundreds of kilometers across most are similar to conamara with a matrix reminiscent of frozen slush and often rafts of preexisting crust edges are of two types ramps perhaps the tapering of crustal thickness to zero or cliffs where rafts appear to have broken clear from the shore the small features called lenticulae generally appear to be small chaoses with textured matrix and occasional rafts and many domes may be small chaoses raised by isostatic compensation following refreezing of the crust the extent of chaoses often appears to be limited by ridge systems with the coastline parallel and set back by a distance comparable to the width of the ridge system preexisting ridges often survive as causeways or chains of rafts boundaries of chaoses are apparently not controlled by preexisting cracks consistent with formation by a thermal rather than mechanical process ridges may thicken the crust such that melt through is more likely but not always between ridge systems subsequent cracks and ridges form across preexisting chaoses ranging from fresh cases with few cracks or ridges across them with paths somewhat jagged as they meander among rafts to heavily dissected examples isolated tilted raft like blocks surrounded by densely ridged terrain may be relics of former chaotic terrain thus two fundamental resurfacing processes have alternated over europa s geological history melt through at various places and times forming chaos terrain and tectonic cracking and dilation building densely ridged and banded terrain mapping of chaos features based on morphology at 200 m shows that they correlate albeit imperfectly with dark regions in global 2 km resolution mosaics except dark regions due to ridge margins or craters extrapolating from our mapping of the 5 of europa covered by appropriate images at least 18 of the surface of europa is fresh appearing chaos an additional 4 is slightly modified chaos and much more older chaotic terrain has been overprinted by tectonic structures considerable area has been available globally to accommodate the expansion of crust that occurs along extensional ridges and bands chaos ubiquity suggests that europan geology has been dominated by the effects of having liquid water under a very thin ice shell with chaos regions being widespread indicators of occasional zero shell thickness

the heat flow of europa the heat flow from europa has profound implications for ice shell thickness and structure as well as for the existence of an internal ocean which is strongly suggested by magnetic data the brittle ductile transition depth and the effective elastic thickness of the lithosphere are here used to perform heat flow estimations for europa results give preferred heat flow values for a typical geological strain rate of 10 15 s 1 of 70 110 mwm 2 for a brittle ductile transition 2 km deep the usually accepted upper limit for the brittle ductile transition depth in the ice shell of europa 24 35mwm 2 for an effective elastic thickness of 2 9 km supporting a plateau near the cilix impact crater and 130 mwm 2 for effective elastic thicknesses of 0 4 km proposed for the lithosphere loaded by ridges and domes these values are clearly higher than those produced by radiogenic heating thus implying an important role for tidal heating the 19 25 km thick ice shell proposed from the analysis of size and depth of impact structures suggests a heat flow of 30 45 mwm 2 reaching the ice shell base which in turn would imply an important contribution to the heat flow from tidal heating within the ice shell tidally heated convection in the ice shell ould be capable to supply 100 mwm 2 for superplastic flow and at the cilix crater region 35 50 mwm 2 for dislocation creep which suggests local variations in the dominant flow mechanism for convection the very high heat flows maybe related to ridges and domes could be originated by preferential heating at special settings

role of indian ocean warming in the development of philippine sea anticyclone during enso 1 the anomalous low level anticyclone near the philippines and suppressed convection over the western pacific associated with the mature warm phase of el nino southern oscillation enso have been suggested as important elements in the interaction between enso and the east asian monsoon we examined the causes of these anomalies in the circulation and convection using a newly developed linear baroclinic model that includes interactive moist processes of the cumulus convection and surface heat fluxes a conventional version of the linear model forced by prescribed heating indicates that the diabatic cooling due to suppressed convection over the maritime continent generates the philippine sea anticyclone from a series of the moist linear model experiments we found that the modest warming of the indian ocean in addition to the strong warming in the central eastern pacific and weak cooling in the western pacific is significant to suppress the convection over the maritime continent observed data also show a coincidence of the development between the philippine sea anticyclone indian ocean warming and the ascending motion over the indian ocean supporting the model results the above results indicate that the atmosphere ocean system in the indian ocean may be one of important factors to improve predictability of the east asian climate during enso

liquid water and active resurfacing on europa voyager images of the jovian moon europa show a bright icy surface transected by a complex pattern of long linear fracture like markings with a slightly lower albedo1 very few impact craters are observed with sizes generally hi the range 10 20 km indicators of surface composition and texture include deep ir h2o absorption features2 uv absorption features characteristic of sulphur in a water matrix on the trailing hemisphere3 and a photometric function indicating much more homogeneous scattering than areas of equal albedo on ganymede and callisto4 europe s mean density is 3 03 g cm 3 indicating a primarily silicate composition however if the density of the silicates is the same as for io the h2o mass fraction would be 6 enough to form an outer layer of h2o 100 km thick if completely differentiated several models have been suggested for the evolution and present state of europa5 8 we present here arguments for recent resurfacing by h2o from a liquid layer based on new interpretations of recent spacecraft and earth based observations and revised theoretical calculations

statistical evidence for the natural variation of the central pacific el nino 1 extensive studies claimed that the central equatorial pacific cp el nino has occurred more frequently and strongly than the eastern equatorial pacific el nino in recent years to explain this phenomenon spatial patterns and principal component time series from several sea surface temperature sst data sets in the tropical pacific are analyzed for the period of 1951 2010 cyclostationary empirical orthogonal function analysis separates two modes of sst variability which explain about 50 and 10 of the total sst variability respectively their spatial and temporal patterns are similar among the different sst data sets the first mode captures the typical el nino pattern while the second mode is a dipole pattern in the tropical pacific the two modes are by definition uncorrelated over the analysis period but are in phase since the late 1990s superposition of the two modes results in a significant warming in the cp region which is a potential explanation for a more frequent occurrence of the cp el nino in the recent decades similar analysis is conducted based on the 500 year data from the geophysical fluid dynamics laboratory climate model version 2 1 under the preindustrial condition the result is generally consistent with the observations yielding occasional in phase relationship between the two modes thus it cannot be ruled out that a more frequent occurrence of the cp el nino in recent years is a natural feature of the equatorial climate system

effects of dispersed particulates on the rheology of water ice at planetary conditions we have investigated the effects of initial grain size and hard particulate impurities on the transient and steady state flow of water ice i at laboratory conditions selected to provide more quantitative constraints on the thermomechanical evolution of the giant icy moons of the outer solar system our samples were molded with particulate volume fractions of 0 001 to 0 56 and particle sizes of 1 to 150 m deformation experiments were conducted at constant shortening rates of 4 4 10 7 to 4 9 10 4 s 1 at pressures of 50 and 100 mpa and temperatures 77 to 223 k for the pure ice samples initial grain sizes were 0 2 0 6 mm 0 75 1 75 mm and 1 25 2 5 mm stress strain curves of pure ice i under these conditions display a strength maximum u at plastic strains e 0 01 after initial yield followed by strain softening and achievement of steady state levels of stress ss at e 0 1 to 0 2 finer starting grain size in pure ice generally raises the level of u petrography indicates that the initial transient flow behavior is associated with the nucleation and growth of recrystallized ice grains and the approach to ss evidently corresponds to the development of a steady state grain texture effects of particulate concentrations 0 1 are slight at these concentrations a small but significant reduction in u with respect to that for pure water ice occurs mixed phase ice with 0 1 is significantly stronger than pure ice the strength of samples with 0 56 approaches that of dry confined sand the magnitude of the strengthening effect is far greater than expected from homogeneous strain rate enhancement in the ice fraction or from pinning of dislocations orowan hardening this result suggests viscous drag occurs in the ice as it flows around the hard particulates mixed phase ice is also tougher than pure ice extending the range of bulk plastic deformation versus faulting to lower temperatures and higher strain rates the high pressure phase ice ii formed in 0 56 mixed phase ice during deformation at high stresses bulk planetary compositions of ice rock 0 4 0 5 are roughly 2 orders of magnitude more viscous than pure ice promoting the likelihood of thermal instability inside giant icy moons and possibly explaining the retention of crater topography on icy planetary surfaces

indian ocean capacitor effect on indo western pacific climate during the summer following el nino significant climate anomalies persist through the summer june august after el nino dissipates in spring over the equatorial pacific they include the tropical indian ocean tio sea surface temperature sst warming increased tropical tropospheric temperature an anomalous anticyclone over the subtropical northwest pacific and increased mei yu baiu rainfall over east asia the cause of these lingering el nino effects during summer is investigated using observations and an atmospheric general circulation model gcm the results herein indicate that the tio warming acts like a capacitor anchoring atmospheric anomalies over the indo western pacific oceans it causes tropospheric temperature to increase by a moist adiabatic adjustment in deep convection emanating a baroclinic kelvin wave into the pacific in the northwest pacific this equatorial kelvin wave induces northeasterly surface wind anomalies and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone the gcm results support this kelvin wave induced ekman divergence mechanism in response to a prescribed sst increase over the tio the model simulates the kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest pacific an additional experiment further indicates that the north indian ocean warming is most important for the kelvin wave and northwest pacific anticyclone a result corroborated by observations these results have important implications for the predictability of indo western pacific summer climate the spatial distribution and magnitude of the tio warming rather than simply whether there is an el nino in the preceding winter affect summer climate anomalies over the indo western pacific and east asia

large impact features on europa results of the galileo nominal mission the galileo orbiter examined several impact features on europa at considerably better resolution than was possible from voyager the new data allow us to describe the morphology and infer the geology of the largest impact features on europa which are probes into the crust we observe two basic types of large impact features 1 classic impact craters that grossly resemble well preserved lunar craters of similar size but are more topographically subdued e g pwyll and 2 very flat circular features that lack the basic topographic structures of impact craters such as raised rims a central depression or central peaks and which largely owe their identification as impact features to the field of secondary craters radially sprayed about them e g callanish our interpretation is that the classic craters all 30 km diameter formed entirely within a solid target at least 5 to 10 km thick that exhibited brittle behavior on time scales of the impact events some of the classic craters have a more subdued topography than fresh craters of similar size on other icy bodies such as ganymede and callisto probably due to the enhanced viscous relaxation produced by a steeper thermal gradient on europa pedestal ejecta facies on europa and ganymede may be produced by the relief flattening movement of plastically deforming but otherwise solid ice that was warm at the time of emplacement callanish and tyre do not appear to be larger and even more viscously relaxed versions of the classic craters rather they display totally different morphologies such as distinctive textures and a series of large concentric structural rings cutting impact feature related materials impact simulations suggest that the distinctive morphologies would not be produced by impact into a solid ice target but may be explained by impact into an ice layer 10 to 15 km thick overlying a low viscosity material such as water the very wide near antipodal separation of callanish and tyre imply that 10 15 km may have been the global average thickness of the rigid crust of europa when these impacts occurred the absence of detectable craters superposed on the interior deposits of callanish suggests that it is geologically young 108years hence it seems likely that our preliminary conclusions about the subsurface structure of europa apply to the current day

tidal heating in an internal ocean model of europa considerable evidence suggests that europe s internal structure might consist of a liquid water layer that decouples a thin 30 km overlying ice lithosphere from an underlying silicate core1 2 a lack of impact features extremely subdued topography and positive spectroscopic identification of h2o all imply recent resurfacing by water in addition curvilinear features resembling cracks are ubiquitous over the surface their orientations are broadly consistent with tidally controlled tectonic activity3 compositional models of europea indicate that the h2o layer could be over 100 km thick1 cassen et al 4 first showed how tidal heating if sufficiently intense might stabilize a thin 30 km ice lithosphere over the internal ocean and prevent the water from freezing other models of europa do not include an internal ocean and instead have an ice layer perhaps as thick as 100 km or as thin as a few kilometres resting directly on the silicate interior5 6 however based on studies of crater relaxation thomas and schubert7 have shown the version of this model with a thin ice layer to be unlikely the plausibility of the internal ocean model vis a vis the thick ice model depends critically on the level of tidal heating in europa here we present new calculations of tidal heating based on a more realistic three layer model of europa the tidal distortion of a decoupled ice lithosphere is only half that previously thought at the current value of orbital eccentricity tidal heating is only marginally able to prevent the internal ocean from freezing

role of the enso indian ocean coupling on enso variability in a coupled gcm warming are only confined to the io and it has little impact on the tropical pacific during the boreal winter when the el nino is in its mature phase the anomalous warming extends eastward to cover the entire tropical io and the anomalous easterlies extend into the western pacific wp the anom alous easterlies in the wp generate oceanic upwelling kelvin waves which propagate eastward and accelerate the decay of the warm sst in the eastern pacific as a result the el nino is rapidly terminated and a la nina develops within one year from the el nino mature phase they concluded that the interaction between enso and the io may generate a biennial tendency for enso 4 the samples used for the composite analysis by kk06 are rather limited due to the relatively short length of the observational data in this study we intended to analyze a longer 200 yr data set obtained from the simulation of a sintex f scale interaction experiment frcgc cou pled gcm in order to verify the enso io feedback hypoth esis itturnsoutthatthefeedbackprocessbetweenensoand the io is quite plausible not only from observations but also from the state of the art coupled gcm

a moist linear baroclinic model coupled dynamical convective response to el nino a newly developed linear baroclinic model lbm and its application to the tropical enso teleconnection is described the model based on primitive equations linearized about the observed zonally varying basic state in northern winter involves linear schemes for the cumulus convection and surface sensible and latent heat fluxes referred to as the moist lbm this enables us to solve a steady state response of the coupled dynamical convective system to a given sst anomaly which is fairly different from the conventional dry lbm linear representation of the convection is acceptable for a realistic range of sst anomalies reproducing well the rossby wave train computed in the conventional lbm forced by a tropical heating the moist lbm is used to examine the formation mechanisms of an anomalous low level anticyclone near

friction of ice the frictional strength of ice seems to be well below that for all other rocks triaxial testing of cylinders of pure water ice containing a 45 inclined sawcut at temperatures of 77 t 115 k and confining pressures 0 1 p 250 mpa reveals the frictional laws 0 20 n 8 3 mpa for p 10 mpa and 0 55 n 1 0 mpa for p 5 mpa where and n are the shear and normal stresses on the sawcut surface friction is independent of t and over the one order of magnitude tested of average sliding velocity the sliding behavior is invariably stick slip examination of sliding surfaces shows only minor gouge development a curious arrangement of densely packed short vertical fractures occurs primarily in samples with anomalously low strength these results apply to models of near surface tectonic activity on jupiter s three large icy moons europa callisto and ganymede they indicate for example that a global expansion on ganymede of 3 linear percent will cause extensional movement on preexisting faults at depths to 7 3 km

interactive feedback between enso and the indian ocean abstract a feedback process of the indian ocean sst on enso is investigated by using observed data and atmospheric gcm it is suggested that warming in the indian ocean produces an easterly wind stress anomaly over indonesia and the western edge of the pacific during the mature phase of el nino the anomalous easterly wind in the western pacific during el nino helps a rapid termination of el nino and a fast transition to la nina by generating upwelling kelvin waves thus warming in the indian ocean which is a part of the el nino signal operates as a negative feedback mechanism to enso this indian ocean feedback appears to operate mostly for relatively strong el ninos and results in a la nina one year after the mature phase of the el nino this 1 yr period of phase transition implies a possible role of indian ocean enso coupling in the biennial tendency of the enso atmospheric gcm experiments show that indian ocean sst forcing is mostly responsible for the easterly wind anomalies in the western pacific

factors determining the extratropical response to equatorial diabatic heating anomalies abstract the steady linear response of a spherical baroclinic atmosphere to an equatorial diabatic heat source having a simple horizontal and vertical structure is examined this source is imposed upon representative zonally symmetric as well as zonally varying flows during the boreal winter two climatologies are considered one is a 6 year average of global observations analyzed at the european centre for medium range weather forecasts ecmwf the other is a 30 year average taken from a general circulation model gcm run at the geophysical fluid dynamics laboratory in princeton the extratropical response is found to be very sensitive to the basic state around which the governing primitive equations are linearized and in the case of the ecmwf climatology to the longitudinal position of the source with respect to the climatological waves there is also some sensitivity to the vertical level of maximum heating although again this is more evident in the case of the ecmwf basic state these results ar

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

reactive surface area of skeletal carbonates during dissolution effect of grain size abstract major advances have recently been made in quantifying the chemical parameters which control carbonate mineral reaction kinetics in natural waters one of the primary factors influencing rates of reaction is the amount of surface area per unit mass available for reaction for relatively smooth nonporous carbonates the relationship between reactive and total surface area measured by gas adsorption has proven simple however the dominant carbonates in the marine environment are biogenic and exhibit complex microstructures we have performed experiments to determine dinghy what proportion of the total surface area of these biogenic carbonates is actually available for reaction during dissolution three biogenic carbonates having widely differing microstructures halimeda coral and echinoid were chosen for study and comparison with rhombic calcite the influence of grain size on the relation between total surface area determined from gas adsorption and reactive surface area determined relative to rhombic calcite during dissolution in constant composition solutions was of primary concern unlike rhombic calcites total surface area for texturally complex biogenic grains varied slightly or not at all with increasing grain size however both rhombic calcite and biogenic carbonate dissolution rates were inversely related to grain radius this implies that much of the total surface area of biogenic carbonates is unavailable for reaction with the aqueous solution dissolution rates were a function of both grain size and microstructure we have defined an empirical roughness factor which quantifies the difference in reactive surface area between rhombic calcite and a given biogenic grain of equivalent size the roughness factor increased with grain microstructural complexity but was independent of grain size over the grain size range 51 513 microns studied the maximum roughness factor value observed was 7 for halimeda relative to a value of 1 for rhombic calcite our findings indicate that both microstructure and grain size can play important roles in controlling reactivity of biogenic carbonates during diagenesis the relative significance of grain size versus microstructure for carbonate dissolution rates in natural systems is discus ed

heat flow lenticulae spacing and possibility of convection in the ice shell of europa abstract two opposing models to explain the geological features observed on europa s surface have been proposed the thin shell model states that the ice shell is only a few kilometers thick transfers heat by conduction only and can become locally thinner until it exposes an underlying ocean on the satellite s surface according to the thick shell model the ice shell may be several tens of kilometers thick and have a lower convective layer above which there is a cold stagnant lid that dissipates heat by conduction whichever the case from magnetic data there is strong support for the presence of a layer of salty liquid water under the ice the present study was performed to examine whether the possibility of convection is theoretically consistent with surface heat flows of 100 200 mw m 2 deduced from a thin brittle lithosphere and with the typical spacing of 15 23 km proposed for the features usually known as lenticulae it was obtained that under europa s ice shell conditions convection could occur and also account for high heat flows due to tidal heating of the convective nearly isothermal interior but only if the dominant water ice rheology is superplastic flow with activation energy of 49 kj mol 1 this is the rheology thought dominant in the warm interior of the ice shell in this case the ice shell would be 15 50 km thick furthermore in this scenario explaining the origin of the lenticulae related to convective processes requires ice grain size close to 1 mm and ice thickness around 15 20 km

interactive feedback between enso and the indian ocean in an interactive ensemble coupled model an interactive feedback between enso and the indian ocean is investigated using a center for ocean land atmosphere studies cola interactive ensemble coupled model from a long term simulation of the coupled gcm it is shown that el nino events terminate relatively rapidly when the indian ocean sst is anomalously warm the anomalous indian ocean warming induces the anomalous easterlies over the western pacific by modulating the walker circulation in turn the anomalous easterlies generate oceanicupwelling kelvin waves over the western pacific which propagate eastward and accelerate the decay of the warm sst in the eastern pacific as a result el nino terminates relatively quickly and the phase transition from el nino to la nina progresses rapidly these interactive processes are consistent with those derived from the previous observational analyses

role of moist energy advection in formulating anomalous walker circulation associated with el nino 1 the role of meridional moist energy advection in formulating anomalous walker circulation during el nino events is investigated using observational data and linearized gcm during the el nino mature phase the warm pool is extended to the central pacific so that the magnitudes of equatorial sst become uniform over the western central pacific in contrast to the uniform sst distribution over the western central pacific the maximum of equatorial convective activities are zonally displaced from the western to the central pacific that is in line with the fact that the strong anomalous descending motions are located over the western pacific without local negative sst anomalies it is demonstrated here that suppressed convection over the western pacific is associated with cold dry moist energy advection due to low level equatorward winds the meridional cold dry moist energy advection leads the vertical warm wet moist energy advection and adiabatic warming processes descending motion to balance the moist energy budget it is shown that this meridional wind is a part of a cyclonic rossby wave in response to the anomalous convection induced by el nino sst this mechanism suggested here is validated by using a linearized gcm the model results show the downward branch of the anomalous walker circulation over the western pacific is significantly reduced when the moist energy advection is not allowed

fault geometries on uranus satellite miranda implications for internal structure and heat flow abstract miranda a 470 km diameter uranian icy satellite has a surface that exhibits evidence of a complex tectonic history tectonic structures are mostly localized in three regions termed coronae but also form a rift system inferred to be global in extent ridges within the boundary of arden corona and those that make up the 340 chasma part of the global rift system have been interpreted as normal fault blocks using voyager data we test the hypothesis that these arden corona faults as well as those at the northern edge of the 340 chasma are listric in geometry for this testing we use four geometric criteria for listric faults 1 progressive down dip decrease in fault scarp dip 2 progressive down dip increase in back tilted face slope 3 concavity of the exposed scarp surface and 4 presence of a rollover structure results of this analysis support the hypothesis that the faults within the arden corona boundary are listric in geometry but do not strongly support the hypothesis for the faults within the 340 chasma by analogy with terrestrial structures the listric character of faults within the arden corona boundary suggests the presence of a subsurface detachment this detachment likely occurred at miranda s brittle ductile transition zone at the time of faulting measurements of the arden corona fault system geometry are used to estimate depths to the proposed brittle ductile transition zone at the time of faulting resulting in values of 6 7 9 0 km those depths in turn are used to estimate a thermal gradient of 6 25 k km 1 and a surface heat flux of 31 112 mw m 2 the weaker evidence of a listric geometry for the faults of the 340 chasma suggests that those faults did not interact with a brittle ductile transition at the time of their formation our estimated thermal gradient of the arden corona region is consistent with a previous heating event on miranda that was as significant as europa s current resonance induced tidal heating this heating event may be associated with a hypothesized previous tidal resonance of miranda with umbriel and or ariel

causes characteristics and consequences of convective diapirism on europa 1 we investigate the hypothesis that the 10 km diameter dome shaped features seen on europa s surface are caused by strongly temperature dependent convection in which upwellings form isolated diapirs or thermals we use the observed lower limit on dome diameter of 4 km to deduce that the conductive stagnant lid thickness must be 5 km such a lid thickness implies a minimum surface heat flux of 90 mwm 2 compatible with recent estimates of tidal heating we also use the mean observed dome diameter to infer a lower thermal boundary layer thickness of 1 km we find that the ice is probably deforming in the diffusion creep regime with a grain size in the range 0 02 0 06 mm the fraction of internal heating is 0 5 the ice viscosity 10 12 10 13 pa s and the crustal solidification rate 5km ma index terms 6218 planetology solar system objects jovian satellites 5430 planetology solid surface planets interiors 8147 5418 planetology solid surface planets heat flow 5455 planetology solid surface planets origin and evolution citation nimmo f and m manga causes characteristics and consequences of convective diapirism on europa geophys res lett 29 23 2109 doi 10 1029 2002gl015754 2002

surface temperature patterns associated with the southern oscillation abstract the typical global and large scale regional temperature patterns associated with the low warm and high cold phases of the southern oscillation so are investigated a total of 12 separate regions were found to have consistent temperature patterns associated with low phase of the so while 11 areas were found to have temperature patterns associated with the high phase of these areas 9 have expected temperature patterns during both phases of the so in the tropics temperature anomalies are of the same sign as the so related sea surface temperature sst anomaly in all land regions except for one area in the west pacific three extratropical responses to the low phase of the so are found over north america and one is found in japan high so temperature patterns were found in the extratropies for japan western europe and northwestern north america the identified temperature responses are more consistent in tropical regions than in the extratropies the so can influence the estimation of

how well do climate models simulate atmospheric teleconnctions over the north pacific and east asia associated with enso during the el nino and la nina mature phase atmospheric teleconnections over the north pacific and east asia vary considerably on sub seasonal time scales and are strongly phase locked to the sub seasonal evolution in this study we investigate how well climate models that participated in the coupled model intercomparison project phase 5 cmip5 simulate the sub seasonal evolution of teleconnections over the north pacific and east asia associated with el nino southern oscillation enso in the observations there is a prominent anticyclone anomaly over the kuroshio extension region i e kuroshio anticyclone which significantly affects east asian climate in the early winter november december of el nino years however in january the kuroshio anticyclone suddenly disappears and a cyclonic flow dominates over the north pacific it is found here that the cmip5 models simulate the overall extratropical teleconnection patterns but they fail to reproduce some of these sub seasonally varying features in atmospheric circulation for example the models tend to simulate a weaker kuroshio anticyclone in the early winter during el nino phases and fail to capture the abrupt decay of the kuroshio anticyclone in the late winter we demonstrate here that these systematic errors in enso teleconnection can be explained by systematic errors in tropical precipitation associated with enso that is negative precipitation anomalies over the western north pacific wnp are too weak in the models compared to that in the observations and their amplitude tends to be strengthened from december to the following january while they are weakened in the observations in addition analyses on the inter model diversity strongly support that relative magnitudes of wnp and central pacific precipitation anomalies are critical for determining sub seasonal evolution of enso teleconnections over the north pacific and east asia

thermal evolution of kuiper belt objects with implications for cryovolcanism abstract we investigate the internal thermal evolution of kuiper belt objects kbos small radii 2500 kg m 3 bodies orbiting beyond neptune focusing on pluto s moon charon in particular our calculations are time dependent and account for differentiation we review evidence for ammonia hydrates in the ices of kbos and include their effects on the thermal evolution a key finding is that the production of the first melt at the melting point of ammonia dihydrate 176 k triggers differentiation of rock and ice the resulting structure comprises a rocky core surrounded by liquids and ice enclosed within a 100 km thick undifferentiated crust of rock and ice this structure is especially conducive to the retention of subsurface liquid and bodies the size of charon or larger radii 600 km are predicted to retain some subsurface liquid to the present day we discuss the possibility that this liquid can be brought to the surface rapidly via self propagating cracks we conclude that cryovolcanism is a viable process expected to affect the surfaces of large kbos including charon

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

role of off equatorial sst in el nino teleconnection to east asia during el nino decaying spring observational evidences are presented to show significant differences in pacific east asian pea teleconnections during the el nino decaying period depending on the northern off equatorial sea surface temperature sst conditions on the basis of the northern off equatorial central pacific sst nocp index we separate el nino events into two groups distinctive differences are observed between the two groups not only in tropical features but also in mid latitude teleconnections in particular the nocp index is closely related to the strength of the local feedback between the sst anomalies and the anticyclonic flow over the western north pacific wnp during the ensuing spring of the el nino events because the wnp anticyclone tends to persist until boreal spring in the case of negative nocp diabatic cooling due to the reduced precipitation over the wnp induces anticyclonic flow over the kuroshio extension region via a rossby wave response which leads to warm and wet conditions over east asia however because the wnp anticyclone decays early in the case of positive nocp cyclonic circulation exists over the north pacific which leads to cold and dry conditions over east asia consequently the maintenance of the wnp anticyclone during the el nino decaying period may explain the discrepancy in the pea teleconnections in various types of el nino accordingly the nocp index could be a possible predictor for boreal spring climate conditions over east asia

in stream phosphate removal by suspended sediments transported from volcanic catchments summary to better understand in stream phosphorus delivery and transformation processes we conducted field measurements and laboratory experiments to study the natural function of phosphate removal by suspended sediments from tributary streamflows of the abukuma river watershed field measurements revealed that phosphate concentrations and fluxes decreased along the abukuma river mainstream due to inflows from a tributary catchment located in a volcanic mountain range in the laboratory experiments water samples collected from tributaries were mixed with those from the abukuma river mainstream to examine the cause and effect of phosphate removal in the mainstream suspended sediments in the tributary samples removed up to about 70 of phosphate in the mainstream sample depending on the amount of sediment added x ray fluorescence spectrometer detected a high ratio of aluminum oxide on the surface of suspended sediments and scanning electron microscopic images showed relatively uniform 0 2 0 5 m spherical particles these findings and the geological condition of the tributary catchments studied led us to conclude that halloysite minerals were likely to comprise the majority of suspended sediments and play a significant role in phosphate adsorption the experimental results were up scaled and verified using field measurements in conclusion natural phosphate removal in the abukuma river can be attributed primarily to high ratios of aluminum oxide minerals transported by volcanic tributaries suggesting a significant hydrological contribution of volcanic catchments to in stream phosphate transport

evolution of lineaments on europa clues from galileo multispectral imaging observations abstract four distinct classes of lineaments can be described on the basis of galileo s improved spectral and spatial coverage of europa 1 incipient cracks are narrow the morphologies spectral properties and orientations of the lineaments vary systematically with age suggesting that these four classes represent different stages of development in an evolutionary sequence lineament formation appears to be the dominant resurfacing mechanism on europa and every landscape that has escaped erasure by heating from below is imprinted with generation after generation of intersecting ridges at various scales and orientations relatively recent fractures expose coarse grained clean ice in the shallow subsurface possibly accounting for the distinctive color of the satellite in comparison to the other icy moons of jupiter the process of lineament formation may be continuing today the bright band agenor linea is among the leading candidates for current activity

pacific east asian teleconnection part ii how the philippine sea anomalous anticyclone is established during el nino development the anomalous philippine sea anticyclone psac conveys impacts of el nino to east asian climate during the mature and decay of an el nino from the winter to ensuing summer it is shown that the anomalous psac forms in fall about one season prior to the peak el nino its strength increases with the el nino intensity and its sign reverses during a la nina the psac formation concurs with abnormal deepening of the east asian trough and with increasing number of northward recurvature of tropical storms in the western pacific the psac establishment is abrupt coupling with a swing from a wet to dry phase of an intraseasonal oscillation iso and often concurrent with early retreat of the east asian summer monsoon the iso becomes inactive after psac establishment the development of the psac is attributed to combined effects of the remote el nino forcing tropical extratropical interaction and monsoon ocean interaction the developing el nino induces off equatorial as cending rossby wave responses and land surface cooling in northeast asia both deepen the east asian trough in fall and induces vigorous tropical extratropical exchange of air mass and heat which enhances the cold air outbreak and initiation of the psac through exciting descending rossby waves the el nino induced indonesian subsidence generates low level anticyclonic vorticity over south asia which is advected by mean monsoon westerly instigating the anomalous psac the iso interacting with the underlying ocean plays a critical role in the abrupt establishment of psac the wind evaporation entrainment feedback tends to amplify suppress iso before after winter northeasterly monsoon commences suggesting the roles of atmosphere ocean inter action and the seasonal march of background winds in changing the philippine sea iso intensity and maintaining psac

heat flows through the ice lithosphere of europa some of the geological features on the surface of europa s ice shell suggest the existence of a brittle lithosphere that in some regions is no more than 2 km thick the surface heat flow needed to put the brittle ductile transition in ice at a depth of 2 km is at least 100 mw m 2 much higher than predicted by tidal heating models for a purely conductive ice shell a possible explanation lies in the probable existence of a convective layer beneath the brittle lithosphere which owing to tidal dissipation in warm ice could contribute to higher heat flows if a convective subsurface layer and grain size dependent flow behavior of ice are admitted the grain size at brittle ductile transition depth cannot be 1 mm which is consistent with the required value for the onset of convection in an ice shell thinner than 20 km

convective instability in europa s floating ice shell models of the tidally heated floating ice shell proposed for the jovian satellite europa generally find shell thicknesses less than 30 km past parameterized convection models indicated that such shells are stable against convective overturn which otherwise ostensibly leads to freezing of the ocean underneath here i apply the temperature dependent viscosity convection scaling developed by solomatov and coworkers to the europan ice shell the temperature dependent properties of ice are linearized about 260 k as any convective interior should be close to this temperature with the colder ice forming an essentially passive stagnant lid ice shells 10 km thick are found to be unstable to convection at their base for melting point viscosities of 1013 pa s as linearized by tidal stresses if the ice deforms by superplastic creep but such low viscosities require small grain sizes 1 mm this requirement may be met if grain sizes observed in terrestrial polar glaciers can be strain rate scaled to europa regardless convection at the base of the ice shell if initiated may not freeze the ocean because of tidal heating a stagnant lid regime ice shell is much more dissipative than a conductive shell of the same thickness such a shell should thin not thicken and the potential exists for further thermal instabilities and runaways

two types of el nino events cold tongue el nino and warm pool el nino abstract in this study two types of el nino events are classified based on spatial patterns of the sea surface temperature sst anomaly one is the cold tongue ct el nino which can be regarded as the conventional el nino and the other the warm pool wp el nino the ct el nino is characterized by relatively large sst anomalies in the nino 3 region 5 s 5 n 150 90 w while the wp el nino is associated with sst anomalies mostly confined to the nino 4 region 5 s 5 n 160 e 150 w in addition spatial patterns of many atmospheric and oceanic variables are also distinctively different for the two types of el nino events furthermore the difference in the transition mechanism between the two types of el nino is clearly identified that is the discharge process of the equatorial heat content associated with the wp el nino is not efficient owing to the spatial structure of sst anomaly as a result it cannot trigger a cold event it is also demonstrated that zonal advective feedback i e zonal adve

creep of water ices at planetary conditions a compilation many constitutive laws for the flow of ice have been published since the advent of the voyager explorations of the outer solar system conflicting data have occasionally come from different laboratories and refinement of experimental techniques has led to the publication of laws that supersede earlier ones in addition there are unpublished data from ongoing research that also amend the constitutive laws here we compile the most current laboratory derived flow laws for water ice phases i ii iii v and vi and ice i mixtures with hard particulates the rheology of interest is mainly that of steady state and the conditions reviewed are the pressures and temperatures applicable to the surfaces and interiors of icy moons of the outer solar system advances in grain size dependent creep in ices i and ii as well as in phase transformations and metastability under differential stress are also included in this compilation at laboratory strain rates the several ice polymorphs are rheologically distinct in terms of their stress temperature and pressure dependencies but with the exception of ice iii have fairly similar strengths hard particulates strengthen ice i significantly only at high particulate volume fractions ice iii has the potential for significantly affecting mantle dynamics because it is much weaker than the other polymorphs and its region of stability which may extend metastably well into what is nominally the ice ii field is located near likely geotherms of large icy moons

paleo heat flows radioactive heat generation and the cooling and deformation history of mercury estimates of lithospheric strength for mercury based on the depth of thrust faults associated with large lobate scarps which were most probably formed previously to similar to 3 ga or on the effective elastic thickness of the lithosphere supporting a broad rise in the northern smooth plains whose formation is poorly constrained but posterior to 3 8 ga serve as a basis for the calculation of paleo heat flows referred to the time when these structures were formed the so obtained paleo heat flows can give information on the urey ratio ur the ratio between the total radioactive heat production and the total surface heat loss by imposing the condition ur 1 corresponding to a cooling mercury consistent with the observed widespread contraction we obtain an upper limit of 0 4 times the average surface value for the abundance of heat producing elements in the outer solid shell of mercury we also find that if the formation of the northern rise occurred in a time posterior to 3 ga then in that time the urey ratio was lower and the cooling more intense than when most of large lobate scarps were formed thus because largest lobate scarps deform older terrains suggesting more intense contraction early in the mercurian history we conclude that the northern rise was formed previously to similar to 3 ga if the age of other smooth plains large wavelength deformations is similar then tectonic activity in mercury would have been limited in the last 3 billion of years

europa stratigraphy and geological history of the anti jovian region from galileo e14 solid state imaging data a tidal bulge and associated deformation are predicted to occur in europa s anti jovian region voyager data showed polygonal low albedo bands in this region it was demonstrated that when the low albedo material comprising these bands was removed the margins could be reconstructed suggesting that fracturing and lateral separation has occurred higher resolution galileo images of a 300 000 km2 portion of the anti jovian region permit recognition and mapping of a variety of features and documentation of the geological history we identify background ridged plains several distinctive types of bands and ridges lenticulae and regions of chaotic terrain these images are at relatively low incidence angles thus albedo variations predominate over topography this presents a challenge to morphologically based mapping but does not preclude development of a regional stratigraphy stratigraphic relationships show that dark bands crosscut the bright ridged plains and are themselves disrupted by lenticulae and chaos suggesting a geological history beginning with background ridged plains followed by a period dominated by band formation with the most recent history predominantly characterized by formation of lenticulae and chaos the paucity of impact craters in this region indicates that the entire sequence of units is geologically recent

on the persistence of decadal sst anomalies in the north atlantic abstract historical wintertime sea surface temperature sst data show that a sandwich pattern dominates on the decadal timescales in the north atlantic at least after the 1970s the authors investigated how such decadal sst anomalies can survive against local thermal feedback which acts to dampen them rapidly at the surface winter sst anomalies have a negligible projection with the subsequent summer anomalies while they show a significant projection with the sst anomalies in the next winter on the other hand observed summer temperature anomalies below the mixed layer tend to have the same sign as the previous winter sst anomalies although the magnitude of the former is roughly one third of the latter this suggests that a reemergence mechanism of sst anomalies associated with the seasonal cycle of the mixed layer depth mld which has been verified by alexander and deser helps maintain the decadal sst anomalies in order to examine this scenario a mixed layer model driven by daily atmospheric d

winter precipitation variability over korean peninsula associated with enso in this study winter precipitation variability associated with the el nino southern oscillation enso over the korean peninsula was investigated using a 5 pentad running mean data because significant correlation pattern cannot be revealed using seasonal mean data it was found a considerably significant positive correlation between nino3 sea surface temperature and precipitation during early winter from mid november to early december when the correlation coefficient is close to 0 8 in early december the correlation is distinctively weakened during late winter it is demonstrated that such sudden intraseasonal change in relation to enso is associated with the presence of anticyclonic flow over the kuroshio extension region kuroshio anticyclone in early winter there is strong southerly wind over the korean peninsula which is induced by the philippine sea anticyclone and kuroshio anticyclone however in january although the philippine sea anticyclone develops further the kuroshio anticyclone suddenly disappears as a result the impact of enso is considerably weakened over the korean peninsula these results indicate that the kuroshio anticyclone during el nino peak phase plays a critical role by strongly affecting northeast asia climate including the korean peninsula in addition it is also found that there are distinctive interdecadal changes of the relationship between enso and precipitation over the korean peninsula in particular the strong correlation in early winter is clearer in the recent 30 years than that in the previous period of 1950 1979

influence of el nino modoki on spring rainfall over south china 1 using observed data sets from 1979 to 2006 the relationship between el nino modoki and spring rainfall over south china sc is investigated of particular interest is the difference in the influence on spring rainfall of typical el nino events and the recently recognized el nino modoki events which are characterized by distinct warm sea surface temperature anomalies ssta in the central pacific and weaker cold anomalies in the western and eastern parts of the basin associated with the ssta anomalous ascent occurs over the central pacific and downward flow is observed over the eastern and western pacific the anomalous flow is associated with anomalous convergence in the upper troposphere over the western pacific sc is influenced by an anomalous anticyclonic circulation with prevailing northeasterly anomalies the convective activity in sc becomes weaker resulting in reduced rainfall however the situation is different in the case of el nino in terms of the influence on rainfall over sc while el nino modoki events are accompanied by a significant reduction in rainfall over sc there is enhanced rainfall associated with el nino events moreover there exists a strong asymmetry in the relationship between sc spring rainfall typical el nino southern oscillation enso and enso modoki events it appears that these relationships are only statistically significant for positive events the asymmetric influence of positive and negative in two enso phenomena may explain the difference in their respective relationships with spring rainfall over sc

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

indices of el nino evolution abstract to characterize the nature of el nino southern oscillation enso sea surface temperature sst anomalies in different regions of the pacific have been used an optimal characterization of both the distinct character and the evolution of each el nino or la nina event is suggested that requires at least two indices i sst anomalies in the nino 3 4 region referred to as n3 4 and ii a new index termed here the trans nino index tni which is given by the difference in normalized anomalies of sst between nino 1 2 and nino 4 regions the first index can be thought of as the mean sst throughout the equatorial pacific east of the date line and the second index is the gradient in sst across the same region consequently they are approximately orthogonal tni leads n3 4 by 3 to 12 months prior to the climate shift in 1976 77 and also follows n3 4 but with opposite sign 3 to 12 months later however after 1976 77 the sign of the tni leads and lags are reversed

improved extended reconstruction of sst 1854 1997 abstract an improved sst reconstruction for the 1854 1997 period is developed compared to the version 1 analysis in the western tropical pacific the tropical atlantic and indian oceans more variance is resolved in the new analysis this improved analysis also uses sea ice concentrations to improve the high latitude sst analysis and a modified historical bias correction for the 1939 41 period in addition the new analysis includes an improved error estimate analysis uncertainty is largest in the nineteenth century and during the two world wars due to sparse sampling the near global average sst in the new analysis is consistent with the version 1 reconstruction the 95 confidence uncertainty for the near global average is 0 4 c or more in the nineteenth century near 0 2 c for the first half of the twentieth century and 0 1 c or less after 1950

distributions of total inorganic and organic phosphorus in surface and recent sediments of the sub tropical and semi pristine guaratuba bay estuary se brazil this study addresses the distribution of total phosphorus tp and its inorganic ip and organic op fractions grain size and organic matter of surface and recent sediments coupled to the behavior of total and dissolved inorganic phosphorus tp and dip of the water column of the semi pristine guaratuba bay estuary se brazil surface sediment samples were taken at 43 sites spread along the estuarine gradient and recent sediments from 3 short 35 cm long cores from the upper central and lower portions of the estuary respectively highest tp and ip concentrations of surface sediments were detected within the upper sector and the transition zone between the upper and central sectors all characterized by fine sediments low salinities and water depths in contrast the lower sector and its narrow and deep tidal channel subject to more intense tidal forcing exhibited a higher fraction of sandy sediments with lower tp ip and op contents in spite of the spatial variability in sediment grain size ip corresponded to the major fraction of tp in all estuarine sectors and both tp and ip correlated significantly with the fine sedimentary silt clay grain size fraction the fine surface sediments acted as a trap for ip at the fresh water low salinity interface which also corresponded to the region of a dip sink in surface waters in general the short sediment cores showed that tp and ip contents increased from 15 cm depths to the top layer published sedimentation rates from additional cores taken at the sites of the short cores of this study implied that depositional alterations of tp and ip increased during the early 1970s which corresponded to the onset of anthropogenic disturbances from crop plantations in the lowland plains of the river end member and urbanization at the estuary s mouth and along the adjacent coast

anomalous winter climate conditions in the pacific rim during recent el nino modoki and el nino events present work compares impacts of el nino modoki and el nino on anomalous climate in the pacific rim during boreal winters of 1979 2005 el nino modoki el nino is associated with tripole dipole patterns in anomalies of sea surface temperature precipitation and upper level divergent wind in the tropical pacific which are related to multiple boomerangs of ocean atmosphere conditions in the pacific zonal and meridional extents of those boomerangs reflect their independent influences which are seen from lower latitudes in the west to higher latitudes in the east in the central pacific more moisture is transported from the tropics to higher latitudes during el nino modoki owing to displacement of the wet boomerang arms more poleward toward east discontinuities at outer boomerang arms manifest intense interactions between tropical and subtropical extratropical systems the pacific north american pattern and related climate anomalies in north america found in earlier studies are modified in very different ways by the two phenomena the seesaw with the dry north and the wet south in the western usa is more likely to occur during el nino modoki while much of the western usa is wet during el nino the moisture to the southwestern usa is transported from the northward shifted itcz during el nino modoki while it is carried by the storms traveling along the southerly shifted polar front jet during el nino the east asian winter monsoon related anticyclone is over the south china sea during el nino modoki as compared to its position over the philippine sea during el nino causing opposite precipitation anomalies in the southern east asia between the two phenomena

does europa have a subsurface ocean evaluation of the geological evidence it has been proposed that jupiter s satellite europa currently possesses a global subsurface ocean of liquid water galileo gravity data verify that the satellite is differentiated into an outer h2o layer about 100 km thick but cannot determine the current physical state of this layer liquid or solid here we summarize the geological evidence regarding an extant subsurface ocean concentrating on galileo imaging data we describe and assess nine pertinent lines of geological evidence impact morphologies lenticulae cryovolcanic features pull apart bands chaos ridges surface frosts topography and global tectonics an internal ocean would be a simple and comprehensive explanation for a broad range of observations however we cannot rule out the possibility that all of the surface morphologies could be due to processes in warm soft ice with only localized or partial melting two different models of impact flux imply very different surface ages for europa the model favored here indicates an average age of 50 myr searches for evidence of current geological activity on europa such as plumes or surface changes have yielded negative results to date the current existence of a global subsurface ocean while attractive in explaining the observations remains inconclusive future geophysical measurements are essential to determine conclusively whether or not there is a liquid water ocean within europa today

el nino la nina and the nonlinearity of their teleconnections the paradigm of an atmospheric system varying linearly with respect to extreme phases of the el nino southern oscillation is questioned it is argued that the global response to tropical pacific sea surface temperature forcing will be inherently nonlinear a physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection climate statistics for warm and cold events of the tropical pacific are analyzed separately for the northern winter periods during 1950 96 composite analysis of 500 mb heights reveal planetary scale teleconnection patterns as noted in earlier studies a new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites and the two wave trains appear to have different tropical origins a large nonlinear component in north american surface climate anomalies is also found which is consistent with such a phase shift in teleconnections in the tropics rainfall anomalies also show evidence of nonlinear behavior the maximum rain anomalies along the equator are located east of the date line during warm events but west of the date line during cold events the interpretation of this behavior is complicated however by the fact that composite warm event sst anomalies are not the exact inverse of their cold event counterparts idealized atmospheric general circulation model agcm experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system the model is forced with a composite sst anomaly that undergoes a realistic seasonally varying enso life cycle as described by e rasmusson and t carpenter both positive and negative phases of the sst anomaly are used and a 40 member ensemble of warm and cold event model simulations is conducted a nonlinear climate response in the agcm is found that closely resembles the observed composites including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns

blocking over the south pacific and rossby wave propagation abstract atmospheric blocking events over the south pacific are investigated using a 39 yr record of 500 hpa height fields from the ncep ncar reanalysis dataset the analysis extends earlier work using a 16 yr record and confirms that the occurrence of blocking over the southeast pacific is strongly modulated by the enso cycle during austral spring and summer comparison of results at 500 hpa with the 300 hpa meridional wind component showed that blocking events are associated with large scale wave trains lying across the south pacific from the region of australia to southern south america similar wave trains are evident in both hemispheres in singular value decomposition analyses between 300 hpa meridional wind components and tropical pacific outgoing longwave radiation olr anomalies the hypothesis that the divergence associated with tropical olr anomalies forces an extratropical wave response that results in enhanced blocking over the southeast pacific was tested using a linearized barotropic vorti

dynamics of rifting and modes of extension on icy satellites 1 a simple numerical model of extension in icy satellite shells is developed thinning of the ice weakens the shell promoting further extension if lateral flow in the lower part of the shell is unimportant extension is opposed and wide rifts are generated if lateral flow is rapid localized extension is favored and narrow rifts are produced thick shells or high strain rates favor the development of narrow rifts low strain rates favor wide rifting it is proposed that bands extensional features on europa are narrow rifts while groove lanes on ganymede are wide rifts the existence of wide rifting on ganymede is consistent with previous estimates of a conductive shell thickness at the time of rifting of 4 8 km and a strain rate of 10 15 s 1 strain rates at the time of rifting whether this shell thickness applies to present day europa depends on the age of band formation which is poorly known the difference between rifting behavior on ganymede and europa is due to either higher strain rates or higher shell thicknesses on europa during rifting the mean stresses required to cause the observed rifting are 0 2 mpa for ganymede and 0 3 mpa for europa these values are comparable to estimates derived from flexural features index terms 5475 planetology solid surface planets tectonics 8149 6218 planetology solar system objects jovian satellites 8109 tectonophysics continental tectonics extensional 0905 8160 tectonophysics rheology general keywords europa ganymede extension faulting ice

estimates of ice thickness in the conamara chaos region of europa europa the second galilean moon outward from jupiter is similar in size to earth s moon but has an outer water ice layer on the order of 100 km thick images acquired by the galileo spacecraft reveal domical features and iceberg like blocks in some areas that suggest the ice was regionally thin at the time the features formed this paper applies buoyancy and flexural models to some of the features to estimate ice thickness assuming that the ice blocks were floating in a liquid sublayer the buoyancy model suggests an ice layer 0 2 3 0 km thick also the flexural models suggest that only the upper 0 1 0 5 km of that ice layer responded elastically to stresses acting as an elastic lithosphere

factors controlling phosphorus speciation in a mediterranean basin river guadalfeo spain summary there is a lot of interest nowadays in the role of riverbed sediments in phosphorus cycling and particularly in the processes that lead the exchange of phosphorus between the sediment and the water column this study presents results on phosphorus forms and other properties from surface riverbed sediments of the river guadalfeo and its main tributaries results show a wide range of spatial variability within the basin with differences of phosphorus concentration higher than an order of magnitude among different sites the most abundant form is the apatite inorganic phosphorus aip which accounts for 68 of total phosphorus followed by total organic phosphorus op that represents 29 the high oversaturation of calcite reached during the summer and early autumn in most studied rivers shows as calcite phosphorus co precipitation is the most important self cleansing mechanism that removes phosphorus from the water column controlling the phosphorus content in the sediment and the dominance of aip hydroxyapatite formation is only important in a few sampling points in spite of the vastly oversaturation obtained external factors such as the lithology of drainage area and sewage inputs are less important in the concentration of sediment phosphorus than physico chemical and biological processes that take place in the rivers taking into account the low biodegradable characteristics of dominant phosphorus forms it could be concluded that the surface sediment in the guadalfeo basin acts as a phosphorus sink

enso regimes reinterpreting the canonical and modoki el nino 1 we propose that the first two empirical orthogonal function eof modes of tropical pacific sea surface temperature sst anomalies do not describe different phenomena i e el nino southern oscillation enso and el nino modoki but rather the nonlinear evolution of enso we introduce two new uncorrelated indices e and c based on the leading eofs that respectively account for extreme warm events in the eastern and cold moderate warm events in the central equatorial pacific corresponding to regimes with different evolution recent trends in enso can be described as an increase in the central pacific c variability that is associated with stronger cold events as well as a reduction in the eastern pacific e variability within the cold moderate warm regime consistent with model projections however little can be said observationally with respect to the extreme warm regime

different evolutions of the philippine sea anticyclone between the eastern and central pacific el nino possible effects of indian ocean sst abstractthe authors examine different evolution features of the low level anticyclone over the tropical northwestern pacific between eastern pacific ep el nino events and central pacific cp el nino events during ep el nino the low level anticyclone shows an eastward movement from the northern indian ocean to the east of the philippines during cp el nino however the anticyclone is mostly confined to the west of the philippines it is weaker exhibits a shorter lifetime and lacks eastward movement compared to the philippine sea anticyclone psac during ep el nino investigation into the possible impact of indian ocean io sea surface temperature sst on the evolution of the low level anticyclone during ep and cp el nino indicates that both sst and low level atmospheric circulation over the io are related more strongly with ep el nino than with cp el nino the io sst tends to exert a more prominent influence on psac during ep el nino than during cp el nino during the developing summer and autum

temperatures on europa from galileo photopolarimeter radiometer nighttime thermal anomalies galileo observations of europa s thermal emission show low latitude diurnal brightness temperatures in the range of 86 to 132 kelvin nighttime temperatures form an unexpected pattern with high temperatures on the bright ejecta blanket of the crater pwyll and an equatorial minimum in temperatures after sunset uncorrelated with surface albedo or geology the nighttime anomalies may be due to regional thermal inertia variations of an unknown origin which are equivalent to a two to threefold variation in thermal conductivity or to endogenic heat fluxes locally reaching 1 watt per square meter endogenic heat flow at this high level although consistent with some geological evidence is theoretically unlikely

ancient heat flow crustal thickness and lithospheric mantle rheology in the amenthes region mars surface heat flow calculations for the amenthes region of mars can be independently performed using the depth to the brittle ductile transition and the effective elastic thickness of the lithosphere estimated for the late noachian early hesperian equivalent to an estimated absolute age of 3 6 3 8 ga this along with crustal heat production rates estimated from heat producing elements abundances permits us to put constraints for that particular place and time on both the thermal and mechanical properties of the lithosphere and the crustal thickness the depth to the brittle ductile transition deduced from modeling of the topography of amenthes rupes is 27 35 km and the associated surface heat flow is 26 37 mwm 2 on the other hand the effective elastic thickness in this region is between 19 and 35 km the surface heat flow deduced by considering crustal and lithospheric mantle contributions to the total lithospheric strength as well as wet or dry olivine for lithospheric mantle rheology is 31 49mwm 2 the relatively limited overlap among te andzbdt based heat flowvalues implies a surface heat flowof 31 36mwm 2 with a high fraction originated from crustal heat sources and awet mantle rheology the so obtained local crustal thickness is 43 74 km which suggests an average thickness of 40 75 km for the martian crust for the frequently used crustal density of 2900 kgm 3 our results suggest a crustal thickness of 50 63km for theamenthes region and an average crustal thickness of 45 65 km for mars