measurements of gravity wave activity within and around the arctic stratospheric vortex lidar measurements of gravity wave activity have been conducted at eureka in the high arctic since 1993 the waves are detected by the fluctuations they induce in temperature it has been found that the amount of wave energy in the upper stratosphere is related to the position of the stratospheric polar vortex in each of the four winters reported here the wave activity was a maximum within the westerly jet at the edge of the vortex a minimum inside the vortex near its centre and intermediate outside the vortex the spectra of wave induced fluctuations show that it is at the longest resolved vertical wavelengths 8 to 15 km that wave energy is being influenced by the background meteorological conditions these findings are interpreted in terms of the doppler shifting and critical level filtering that is imposed by the background wind profile

small scale waves encountered during aase variability on scales of 200 km or less in the lower stratosphere is examined using potential temperature data collected during the aase campaign enhanced variability is found over regions containing topography presumably due to gravity waves the effect of gravity wave critical levels on topographically induced variability is examined a significant reduction in variability is found when a critical level is present

gravity wave and orographic wave activity observed around the antarctic and arctic stratospheric vortices by the cosmic gps ro satellite constellation 1 polar stratospheric gravity wave activity is studied using data from the constellation observing system for meteorology ionosphere and climate cosmic global positioning system radio occultation gps ro waves with vertical wavelengths of 2 to 15 km are considered the temperature variance 2 is used as a measure of wave activity and is studied on isentropic surfaces large intermittent orographic wave activity is identified during austral spring 2007 above the patagonian andes and the antarctic peninsula where 2 in the stratosphere increases by up to a factor of 5 for periods of 5 days to a few weeks the 2 are also investigated in equivalent latitudes to allow a direct comparison with the changing vortex structure the october 2007 2 inside the antarctic vortex boundary region at 400 600 k is one and a half times that outside the vortex this region of enhanced 2 descends in time and is not observed during the decay of the arctic vortex during the boreal winter of 2006 2007 orographic wave activity is observed above scandinavia and greenland an analysis of the 400 k and the 450 k levels in both hemispheres shows a strong relationship between enhanced 2 and the location of the vortex edge suggesting that the waves observed are propagating poleward and are guided to higher altitudes by the vortex the line of sight of the occultations shows a preference for north south alignment indicating that cosmic favors the detection of orographic waves above the north south oriented mountain ranges considered here

downward control of the mean meridional circulation and temperature distribution of the polar winter stratosphere abstract according to the downward control principle the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level in this paper a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean meridional circulation and temperature distribution at lower levels in the polar winter stratosphere the results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km the effect is most important when planetary wave driving is relatively weak that is during southern winter and in early northern winter in southern winter downwelling weakens by a factor of 2 near the stratopause and by 20 at 30 km when gravity wave drag is not included

a review of the mesosphere inversion layer phenomenon an active topic of current research in aeronomy is the study of the dynamics of the mesosphere and lower thermosphere mlt from 60 to 130 km especially in regard to the influences that govern variability the physical processes of this region are diverse and complex with strong coupling between the mlt and the adjacent atmospheric regions brought about largely by the propagation and dissipation of atmospheric gravity waves gws from sources above and below the measurements of mlt winds and temperatures required for such studies represent daunting technical challenges at low and midlatitudes the mesosphere inversion layer mil phenomenon a 10 km wide region of enhanced temperatures t 15 50k is observed with great regularity in both the upper mesosphere 60 70 km and the mesopause 90 100 km observations are largely based upon rayleigh and na temperature lidar systems but coherent radar observations have shown that the mil phenomenon is linked to layers of turbulence occurring in both the topside and the bottomside regions gw activity is believed to play an important role in the development of a linkage between the mil and the tidal structure through gw coupling that results in an amplification of the tidal thermal structure this linkage is readily evident for the upper mil but is seen only occasionally for the lower mil further study of mil properties should emphasize continual 24 hour temperature observations especially for the lower mil region to confirm the linkage of the development of the mil to the mlt tidal structure

evolving geographic patterns of cenozoic magmatism in the north american cordillera the temporal and spatial association of magmatism and metamorphic core complexes four maps are presented here that show the location and extent of magmatic fields between eastern alaska and northern mexico during the successive time intervals of 55 40 40 25 25 10 and 10 0 ma and four others show the distribution of metamorphic core complexes during the same cenozoic time intervals the maps are based on u s geological survey and canadian cordilleran data bases contining about 6000 isotopic dates and extensive literature review for nearly 60 ma the development of metamorphic core complexes has coincided with the locus of a really extensive and voluminous intermediate composition magmatic fields the association is suggestive of a close link between magmatism and core complex formation namely that magma directly and indirectly lowers the strength of the crust magmatism thus controls the location and timing of core complex formation the stresses responsible may be inherited from mesozoic crustal thickening locally created by uplift and magmatic thickening of the crust and imposed by the global pattern of plate motions and driving forces since the miocene rates of magmatism extension and core complex formation have declined the modern basin and range province is not a suitable model for the situation that existed during major magmatic culminations the singular event of early miocene time the merging of two large magmatic fields extinguishing the laramide magmatic gap explains several disconnected observations the hyperextension episode of the colorado river corridor rapid reorientation of stress patterns across much of western north america and subsequent rapid tectonic movements in california magma triggered breakup of western north america lithosphere coincided with development of the san andreas transform system thermal destruction of the laramide magmatic gap created a california microplate about 22 ma ago that moved rapidly away from north america thus two plate tectonic processes thermal destruction of the lithosphere bridge and northward growth of a transform system interacted to produce miocene and later tectonic patterns and events

megacryst bulk rock isotopic disequilibrium as an indicator of contamination processes the edgecumbe volcanic field se alaska sr and nd isotopic ratios are reported from mineral separates and bulk rock samples from the edgecumbe volcanic field in southeast alaska a suite of lavas that has developed by assimilation megacrysts in the basaltic unit and the rhyodacites are in isotopic equilibrium with their matrices because the rhyodacites developed as the result of assimilation the assimilate must have been completely dissolved in contrast megacrysts in the two andesitic units are in isotopic disequilibrium with their matrix these megacrysts must be a mixture of those inherited from the contaminant crystals in equilibrium with the groundmass and possibly crystals inherited from a mafic liquid

sedimentation of biogenic constituents during the last century in western bransfield and gerlache straits antarctica a relation to currents primary production and sea floor relief abstract as part of the fruela experiment 11 sediment cores were recovered from the bellingshausen sea the western bransfield and gerlache straits antarctic peninsula to determine the spatial distribution of organic carbon oc biogenic silica bsi and nitrogen n in the sediment under regions of known irregular primary production rates pprs oc bsi and n contents ranged from 0 3 to 1 2 from 5 7 to 20 4 and from 0 03 to 0 17 respectively apparent mean sediment accumulation rates sars varied between 0 25 and 3 11 mm year 1 220 and 1750 g m 2 year 1 central gerlache and western bransfield straits the orleans canyon had the highest biogenic constituents contents and sediment accumulation rates whereas the northern coast off snow island bellingshausen sea showed the lowest values central gerlache strait with the highest primary production rates in the study area was the only region where the oc and bsi contents in the sediment corresponded to the photosynthetic activity in the euphotic zone above it at the extremes of gerlache strait as in western bransfield strait sediment focusing by currents enhanced by depressions in the sea floor contributed to develop regions with high biogenic constituent concentrations whereas at the bellingshausen sea and western gerlache strait winnowing by currents may drift away the biogenic material exported from the euphotic zone apparently bottom relief and currents rather than solely depth determined the modern distribution and accumulation rates of biogenic particulate matter in the study area paleoceanographic interpretations of the sedimentary record from antarctic marginal seas such as gerlache and bransfield straits should consider that focusing due to lateral transport and sea floor morphology and the preferential degradation of oc relative to bsi may increase to an important degree the biogenic contents in the sediment especially the opal oc and bsi accumulation in antarctic marginal seas could be as important as the broad continental shelves despite large spatial differences

tholeiitic and calc alkaline magma series at adatara volcano northeast japan 1 geochemical constraints on their origin abstract low alkali island arc by jakes and gill 1970 or low k by gill 1978 tholeiitic rocks are closely associated with calc alkaline rocks in the outer volcanic zone called the nasu volcanic zone of northeast japan major element trace element ni cr co sc v zr nb zn rb cs ba sr ce and y and sr isotope compositions are presented for 9 low alkali tholeiitic and 16 calc alkaline samples of adatara volcano belonging to the nasu volcanic zone in the trace elements vs sio 2 diagram the tholeiitic series and calc alkaline series show different trends to each other for co sc v zr rb sc ba and sr as expected from k 2 o contents the calc alkaline samples are enriched in incompatible elements such as rb cs ba ce and zr compared with the tholeiitic samples on the other hand contents of nb in the calc alkaline samples are somewhat lower than those in the tholeiitic samples plots of ni and cr contents vs sio 2 for the tholeiitic samples come near smooth trend lines whereas those for the calc alkaline samples are scattered sr isotopic ratios in the tholeiitic series lie within the range between 0 7056 and 0 7058 and between 0 7048 and 0 7052 in the calc alkaline series smooth major and trace element compositional trends in the tholeiitic series are successfully modelled by simple fractional crystallization of plagioclase hypersthene augite titanomagnetite and minor olivine similarly crystal fractionation models can closely reproduce major and most of the trace element variations in the calc alkaline series but failed to account for irregular variations of ni and cr the scattering of ni and cr probably reflects simultaneous crystal fractionation and subordinate magma mixing in the subvolcanic chamber the inferred fractionated phases for the calc alkaline series are richer in augite and titanomagnetite and slightly poorer in plagioclase than those for the tholeiitic series the tholeiitic magma and calc alkaline magma are not derived from a common parental tholeiitic magma and the calc alkaline parental magma is richer in sio 2 and incompatible elements in particular rb and zr poorer in radiogenic sr and possibly more oxidized than the tholeiitic parental magma

satellite observations of atmospheric variances a possible indication of gravity waves the microwave limb sounder mls on the upper atmosphere research satellite has now produced the first global maps of small scale variances in the middle atmosphere initial analyses are presented here that suggest these variances are due to gravity waves and the technique used to extract gravity wave information from saturated radiance measurements is described observations at 30 80km altitudes show that the variances of horizontal scales less than 100km are strongly correlated with upper tropospheric convection surface topography and stratospheric jetstreams mls monthly averages during solstice periods suggest that the normalized variance amplitude grows exponentially with height in the stratosphere and saturates in the mesosphere as expected from wave breaking and dissipation at these altitudes

a statistical study of gravity waves in the polar regions based on operational radiosonde data gravity waves in the lower polar stratosphere are examined using operational radiosonde observations gathered from 33 stations over a period of 10 years both the potential and kinetic energies of the gravity waves vary annually and reach maxima in winter in the arctic and in spring in the antarctic in the antarctic spring a region of large gravity wave energy propagates downward following the movement of a zone of high static stability associated with southern hemispheric warming moreover the enhanced energy region and the high stability zone coincide in the horizontal plane and move gradually from 135 e 50 s to 45 w 70 s over the south pole the vertical and horizontal directions of wave propagation are examined using hodograph analysis in the vertical most gravity waves transfer energy upward in the arctic while the percentage of downward energy propagation is relatively high in winter and spring in the antarctic horizontally gravity waves propagate westward relative to the mean wind in the arctic while in the antarctic the dominant direction varies from station to station the correlation between gravity wave energy in the lower stratosphere and the mean wind is also examined in the arctic gravity wave energy is highly correlated with the surface wind though in the antarctic it correlates with the stratospheric wind these results suggest that gravity waves observed in the arctic are forced by topography whereas in antarctica some sources may exist in the stratosphere one such source candidate is likely to be the polar night jet

a gravity wave climatology for antarctica compiled from challenging minisatellite payload global positioning system champ gps radio occultations 1 the seasonal geographical and altitudinal dependence of gravity wave activity in the lower stratosphere over antarctica is presented gravity wave activity is estimated by calculating potential energy ep from radio occultation profiles obtained by the challenging minisatellite payload global positioning system champ gps experiment significant seasonal variation of wave activity is observed smaller wave activity in summer is attributed to waves with small phase velocities experiencing critical level filtering at other times of the year when wave activity is large less filtering occurs and the strong background wind is likely to cause doppler shifting of waves to longer vertical wavelengths which can reach larger amplitudes before saturating relationships between gravity wave activity and geographic location indicate that topography is a strong source for wave activity especially over the antarctic peninsula however wind rotation in this area was found to reduce the wave energy in summer at certain altitudes a strong enhancement of wave energy is observed at the edge of the polar vortex again reduced critical level filtering and doppler shifting in the area of the jet are likely to be major causes for this finding possible limitations to this study due to observational filtering are discussed

combination of lidar and model data for studying deep gravity wave propagation the paper presents a feasible method to complement ground based middle atmospheric rayleigh lidar temperature observations with numerical simulations in the lower stratosphere and troposphere to study gravity waves validated mesoscale numerical simulations are utilized to complement the temperature below 30 km altitude for this purpose high temporal resolution output of the numerical results was interpolated on the position of the lidar in the lee of the scandinavian mountain range two wintertime cases of orographically induced gravity waves are analyzed wave parameters are derived using a wavelet analysis of the combined dataset throughout the entire altitude range from the troposphere to the mesosphere although similar in the tropospheric forcings both cases differ in vertical propagation the combined dataset reveals stratospheric wave breaking for one case whereas the mountain waves in the other case could propagate up to about 40 km altitude the lidar observations reveal an interaction of the vertically propagating gravity waves with the stratopause leading to a stratopause descent in both cases

subglacial morphology and glacial evolution of the palmer deep outlet system antarctic peninsula abstract the palmer deep is an erosional inner shelf trough located at the convergence of ice flow from three distinct accumulation centers it served as a funnel for ice flow out across the continental shelf of the antarctic peninsula swath mapping of 1440 km 2 of seafloor in and adjacent to the palmer deep basin defines a large paleo ice stream that flowed 230 km across the antarctic peninsula continental shelf during the last glacial maximum mis 2 the unique perspective and detail of the palmer deep physiography allow us to recognize several phases of erosion and deposition in the outlet basin these events are uniquely constrained by two odp drill cores sites 1099 and 1098 that together recovered over 150 m of latest pleistocene and holocene sediment we divide this region of the continental shelf into three zones based upon mega to meso scale bathymetric features and emphasize that all three were part of one glacial outlet during the most recent period of glaciation these zones include from inner shelf to outer shelf the palmer deep basin the palmer deep outlet sill and the hugo island trough specific seafloor features associated with these zones include relict terraces sub glacial lake deltas channels and levees debris slopes spindle and out bed forms mega scale glacial lineations morainal banks and bank breach points the origin of many of these features can be linked to the development of a sub glacial lake basin within the palmer deep during or prior to mis 2 its subsequent drainage and recession of the palmer deep ice stream system this sub glacial lake system is reconstructed at the head of a major paleo ice stream

lidar observations of stratospheric gravity waves from 2011 to 2015 at mcmurdo 77 84 s 166 69 e antarctica 1 vertical wavelengths periods and frequency and vertical wave number spectra five years of atmospheric temperature data collected with an fe boltzmann lidar by the university of colorado group from 2011 to 2015 at arrival heights are used to characterize the vertical wavelengths periods vertical phase speeds frequency spectra and vertical wave number spectra of stratospheric gravity waves from 30 to 50 km altitudes over 1000 dominant gravity wave events are identified from the data the seasonal spectral distributions of vertical wavelengths periods and vertical phase speeds in summer winter and spring fall are found obeying a lognormal distribution both the downward and upward phase progression gravity waves are observed by the lidar and the fractions of gravity waves with downward phase progression increase from summer 59 to winter 70

seasonal variations in lower stratospheric gravity wave energy above the falkland islands 1 the gravity wavefield in the lower stratosphere between 15 km and 22 km altitude above mount pleasant airport 51 49 s 58 26 w on the falkland islands is studied using over 2100 high resolution radiosonde soundings from 2002 to 2010 the seasonal variation in vertical direction of propagation shows a small decrease in numbers of upward propagating waves that is related to critical level filtering however there is a very large increase in numbers of downward propagating waves between july and september this is attributed to the proximity of the edge of the polar vortex there is a seasonal variation in gravity wave energy density with a large peak during the austral autumn equinox this is markedly different to results in the literature both from rothera on the antarctic peninsula and stations on the main antarctic continent this seasonal pattern has been shown to be linked to variations in the sources of upward propagating gravity waves the seasonal variation in gravity wave characteristics above mount pleasant airport seen in our results suggests that the gravity wavefield in this region is determined by a combination of different gravity wave sources located above and below the lower stratosphere

transport of suspended particulate matter in an antarctic fjord abstract vertical profiles of temperature salinity and light attenuation were used in conjunction with underwater photography and water samples to characterize the nature and dynamics of particle transport in an antarctic fjord most of the particles are sand sized 0 1 2 mm floccules comprised of individual grains in the 5 to 50 m size range the quartz silt grains are derived from basal debris laden meltwater originating from beneath the submerged valley glacier the meltwater buoyantly rises to form cold water interflows at mid water depths turbulent mixing near the seafloor also plays a role in the transport and break up of floccules together the midwater cold tongues and near bottom turbidity account for 87 of the total sediment load thus attesting to the importance of non surface transport mechanisms in polar fjords

the influence of crustal structure on compositions of subduction related magmas abstract a survey of sr isotopic ratios and other compositional features of subduction related magma suites reveals significant correlations between these averaged parameters and characteristics of the underlying crust i e thickness composition and age these observations lead to the conclusion that crust and or mantle rocks in the hanging walls of subduction zones are involved in modification of primary mafic magmas typically basalt or basaltic andesite it is proposed that mafic magmas will stagnate within the crust or uppermost mantle where they may differentiate and react with wall rocks the extent to which such processes manifest themselves will depend upon details of the local crustal structure in particular the composition and age of the crust will strongly influence such parameters as sr nd and pb isotopic compositions such data strongly indicate the involvement of crustal rocks in locales underlain by old sialic crust e g central andes depending upon the level of magma stagnation and evolution within the crust different trends in isotopic composition may result these isotopic trends may be enhanced by partial melting of the wall rocks to produce relatively silicic anatectic magmas and locally they may reflect subduction of continental sediments interpretation of the isotopic data may be more ambiguous in locales underlain by younger and more mafic continental crust cascades e eleutians and those underlain by oceanic crust owing to the similarity in isotopic composition of primary magmas and the latter crustal materials yet some degree of crustal involvement in magmatic evolution seems highly probable even in these more primitive terranes consequently most island arc magmas and especially those more evolved than basalt are probably not primary in the sense that they do not represent direct melts of the upper mantle studies of arc volcanic rocks may yield misleading conclusions concerning processes of magma generation related to subduction unless evolutionary processes are defined and their effects considered it appears that modern volcanic arcs provide a poor analog for models of early crustal development because the modern mantle derived magmatic components are more mafic in composition than average continental crust

ice shelf history from petrographic and foraminiferal evidence northeast antarctic peninsula a detailed record of late pleistocene deglaciation followed by mid holocene ice shelf breakup and late holocene re growth is contained in continental shelf sediments in the northern larsen area northeast antarctic peninsula the zero age of core tops is confirmed by new and published 210pb profiles and 70 accelerator mass spectrometer ams 14c dates on bulk organic carbon define sedimentation rates of 7 6 92 cm ka the varied geology in the local ice drainage basins facilitates the use of ice rafted debris ird provenance in determining the presence or absence of ice shelves all inshore cores contain an interval of non local ird in the post glacial section demonstrating widespread ice shelf breakup in the mid holocene both breakup and re growth may have taken centuries and there are no widespread debris layers associated with breakup cores beyond and up to 30 km inside the historical ice shelf limit exhibit a varied ird provenance throughout the holocene suggesting the maximum ice shelf limit may date only from the little ice age benthic foraminiferal assemblages are related to water masses and position on the continental shelf and have been modified by taphonomic processes nevertheless we discern a deglaciation signal in prince gustav channel of a calcareous spike in predominantly agglutinated assemblages and this is repeated at the time of mid holocene ice shelf breakup the inferred mid holocene warm period occurred later in the northern larsen area than on the west coast of the antarctic peninsula

mountain wave drag in the stratosphere and mesosphere inferred from observed winds and a simple mountain wave parameterization scheme abstract a daily analysis of mountain wave propagation through observed global wind and temperature fields in january and august is presented winds and temperatures are obtained from the daily 18 level nmc climate analysis center mountain wave properties are deduced from a simple gravity wave parameterization scheme in which the effects of topographic anisotropy ridge orientation are explicitly included planetary waves in the northern winter stratosphere are found to play an important role in modulating the magnitude and distribution of inferred mountain wave drag in the middle atmosphere the aleutian anticyclone is found to effectively block mountain waves generated over western north america from reaching the mesosphere by inducing local mountain wave critical levels in the stratosphere stratospheric sudden warmings have a similar effect at all longitudes so that during months with sudden warmings have a similar effect at all longitudes so that during months with sudden warmings the average in

lidar observations of gravity wave activity and arctic stratospheric vortex core warming measurements of stratospheric thermal structure and gravity wave activity have been obtained with a rayleigh lidar in the canadian high arctic at eureka 80 n 86 w during five recent winters the observations reveal that an annual late december warming of the upper stratosphere occurred in the polar vortex core and was sustained through the winter increased gravity wave activity was detected in the vortex jet during the warming that these two phenomena developed in parallel suggests they are related it is proposed that increased gravity wave momentum deposition above the jet maximum forced flow into the vortex core where it descended and warmed adiabatically

queen charlotte area cenozoic tectonics and volcanism and their association with relative plate motions along the northeastern pacific margin cenozoic relative plate interactions along the queen charlotte margin based on published models for the north america and northeast pacific plates are related to the tectonic and igneous history of the region plate motion models indicate convergence and subduction prior to the eocene since that time there has been transcurrent motion with varying small amounts of oblique extension or compression assuming that the pacific america farallon triple junction was to the south of the region a late miocene or early pliocene about 4 ma to present period of oblique convergence is well resolved the present queen charlotte fault zone along the west coast of the islands may have initiated more recently within the cenozoic transcurrent regime a period of oblique extension in the mid tertiary 36 20 ma in one model is supported by a variety of volcanic and tectonic evidence a small plate motion change at about 20 ma may have resulted in the transfer of the yakutat terrane from the north america plate to the pacific plate and the resulting motion of the terrane northwestward to its present position along the margin of alaska the onset of tertiary masset volcanism that is extensive on the queen charlotte islands corresponds within a few million years to the time of major plate reorganization at 43 ma that has tectonic expression around the entire pacific basin the period of most extensive masset volcanism and plutonism appears to correlate with the model oblique extension in the mid tertiary for one model the geochemistry and physical volcanology of the masset volcanic s are indicative of an extension regime the main syntectonic deposition in the queen charlotte basin skonun formation as inferred from seismic reflection and well data also appears temporally correlated with this time interval of oblique extension a variety of data including plate models dikes normal faults basin subsidence crustal thickness from seismic refraction and present and paleo heat flow indicate mid tertiary crustal extension of at least 20 in the queen charlotte region with up to 150 up to 2 5 in the main queen charlotte basin posttectonic basin subsidence and deposition may correlate with the model time interval of general transcurrent or oblique convergence motion from 20 to 4 ma more recent shortening deformation observed in outcrop and seismic sections of the northern parts of the basin may correlate with plate model oblique convergence from 4 ma to the present the latter convergence is associated with underthrusting that formed a trough or trench and an accretionary sedimentary prism off the west coast of the queen charlotte islands and with inferred uplift and erosion of the western part of the islands

mls observations of atmospheric gravity waves over antarctica 1 stratospheric gravity waves over antarctica are studied with the radiance variances observed by upper atmosphere research satellite microwave limb sounder uars mls strong wave activities are found during august and september in 1992 1994 over the drake passage region 290 315 longitude and 50 s 70 s latitude where the enhancement seems associated with the topography of both south america and antarctic peninsula tips during the same period significant gravity wave activities are also evident along the antarctic coastal region the vertical growth of the wave variance shows a scale height of 14 km at low altitudes for both drake passage and the coastal regions but reduces substantially at high altitudes the growth rate transition occurs at a lower altitude in the drake passage region where the variance is larger the gravity wave activities observed near the antarctic may contribute significantly to the formation of polar stratospheric clouds psc because of the overlapping with the vortex edge and with the psc activities as observed by claes cryogenic limb array etalon spectrometer

the nepheloid bottom layer and water masses at the shelf break of the western ross sea in the austral summers of 2000 2001 and 2002 2003 the italian clima project carried out two oceanographic cruises along the northwestern margin of the ross sea where the antarctic bottom water forms here there is an interaction between the water masses on the sea floor of the outer shelf and slope with a consequent evolution of benthic nepheloid layers and an increase in total particulate matter we observed three different situations a the presence of triads bottom structures characterized by a concomitant jump in turbidity temperature and salinity data and high re suspension phenomena related to the presence of the circumpolar deep water and its mixing with cold salty shelf waters associated with gravity currents b the absence of triads with high re suspension implying that when the gravity currents are no longer active the benthic nepheloid layer may persist until the suspended particles settle to the sea floor suggesting that the turbidity data can be used to study recent gravity current events and c the absence of turbidity and sediment re suspension phenomena supports the theory that a steady situation had been re established and the current interaction no longer occurred or had finished sometime before

assimilation of crustal material by basaltic magma strontium isotopic and trace element data from the edgecumbe volcanic field se alaska the edgecumbe volcanics which range from basalt through rhyodacite have sr contents between 125 and 370 p p m rb contents of 1 to 70 p p m ba ranging from 50 550 p p m and initial l7sr sr ratios between 0 70291 and 0 70404 no simple correlation exists between these components and silica the highest sr sr values occur in a group of intermediate lavas 55 60 wt per cent sio2 while the rhyodacites have initial ratios between 0 7035 and 0 7038 with increasing silica sr increases to a maximum in the andesites and then steadily decreases ba and rb increase over the same compositional range the highest l7sr 86sr lavas have major and trace element concentrations which depart from trends defined by most of the lavas the variation in strontium isotopic compositions suggests interaction between parental basaltic magma and crustal material attempts to model the assimilation process using fixed end member assimilation and assimilation fractional crystallization models have failed to produce the observed chemical trends because the parental basaltic liquid underwent little fractionation the variability in hybrid lavas is attributed to variation in contaminant composition initial melts were low in cao al2oj mgo and sr and enriched in sio2 k2o na2o rb and ba as melting progressed melts became enriched in the more refractory components because hybrid strontium isotopic composition is a function of sr concentration as well as isotopic compositions the sr content of the assimilant strongly influences resultant isotopic systematics the development of the assimilants suggests plagioclase was a residual phase during early melting this model of crustal assimilation represents one end member in the spectrum of processes responsible for the generation of continental volcanic suites

saber observations of gravity wave responses to the madden julian oscillation from the stratosphere to the lower thermosphere in tropics and extratropics

evidence for critical level filtering of atmospheric gravity waves radiosonde measurements were used to investigate gravity wave activity within the lower stratosphere above the canadian high arctic the sondes were launched from the weather station at eureka 80 n 86 w on ellesmere island gravity waves were detected by the fluctuations they induced in temperature and the associated perturbation potential energy density was used to gauge the amount of wave activity it was found that over a 15 month period there were isolated episodes of enhanced wave activity rather than any distinct seasonal cycle profiles of wind velocity were also measured and used here to show that periods of high wave activity occurred only when there would be no or very little critical level filtering of the stationary waves generated by flow over the rough terrain in the vicinity of eureka it was also found that the potential energy spectral density was enhanced at all resolvable scales during the periods of high wave activity

pyroclastic deposits of the mount edgecumbe volcanic field southeast alaska eruptions of a stratified magma chamber abstract the mount edgecumbe volcanic field in southeastern alaska consists of 5 6 km 3 dre of postglacial pyroclasts that overlie pleistocene lavas all eleven pyroclast vents align with the long axis of the field implying that the pyroclast magma conduits followed a crustal fissure most of these vents had previously erupted lavas that are compositionally similar to the pyroclasts so a persistent magma system chamber had likely evolved by the onset of the pyroclastic eruptions the pyroclastic sequence was deposited in about a millennium and is remarkable for a wide range of upward increasing silica contents 51 72 sio 2 which is consistent with rise of coexisting magmas at different rates governed by their viscosity basaltic and andesitic lava flows have erupted throughout the lifetime of the field rhyolite erupted late we infer that it formed early but was hindered from rising by its high viscosity most of the magmas and all siliceous ones erupted from vents on the central fissure basalt has not erupted from the center of the field during at least the latter part of its lifetime thus the field may illustrate basalt underplating heat and mass flux are concentrated at the center of a stratified magma chamber in which a cap of siliceous melt blocks the rise of basalt major element strontium isotope and mineral compositions of unaltered pyroclasts are broadly similar to those of older lavas of similar sio 2 content slightly fewer phenocrysts inherited grains and trace amphibole in pyroclastic magmas may be due simply to faster rise and less undercooling and degassing before eruption relative to the lavas dacite occurs only in the youngest deposits the magma formed by mixing of andesitic and rhyolitic magmas erupted shortly before by the dacitic vents

energy enhancements of gravity waves in the antarctic lower stratosphere associated with variations in the polar vortex and tropospheric disturbances 1 gravity waves in the antarctic lower stratosphere are examined using original operational radiosonde data obtained at syowa station 69 0 s 39 6 e with fine vertical resolution in the lower stratosphere the temporal variation in gravity wave energy depends on height in the height region of 13 15 km just above the tropopause the seasonal variation in gravity wave energy is not evident the wave energy is rather enhanced when the absolute value of potential vorticity in the upper troposphere becomes small over syowa station this fact implies that tropospheric disturbances affect the dynamical processes of gravity waves there however the gravity wave energy in the height region of 15 25 km shows clear seasonal variation having a maximum in spring the time variation in gravity wave energy is examined in detail in terms of the polar vortex by using the equivalent latitude coordinate energy enhancements occur when the edge of the polar vortex approaches syowa station and the enhancements are especially large when the polar vortex breaks down in spring these results suggest that height variation in the background atmosphere leads to the difference of wave characteristics between the two height regions the enhancements of wave energy are partly explained as modification of the wave structure by the background wind speed and the static stability but it is also likely that enhancements of wave activity contribute to the energy enhancement at the edge of the polar vortex in spring

marine sedimentation at a calving glacier margin a 2 month study at a subpolar tidewater glacier was conducted at anvers island antarctic peninsula lat 64 s to improve understanding of sedimentary processes and associated deposits in glacial marine settings data collected in the ice proximal environment were 1 brash ice size distribution and melt rates to assess sediment source and transport mechanisms 2 conductivity temperature turbidity depth cttd profiles water samples and sediment trap catches to study processes and patterns of sediment dispersal 3 bottom cores and grabs to document recent glacial marine sedimentation and 4 remotely operated vehicle video surveys of the ice terminus and sea bottom to obtain images of physical and biological processes the water column is stratified and a halocline occurs at 20 30 m water temperature ranged from 1 to 1 6 c salinity was 32 34 and suspended solids were 3 5 mg l well above the bottom ephemeral turbid horizons contain 8 15 mg l suspended solids rare surface plumes and a quasipermanent turbid layer produced by resuspension during calving events reach 25 35 mg l meltwater drains from the glacier surface but no subglacial meltwater was detected directly entering the sea the most important sources of sediment appear to be the direct melting of the submerged ice front and melting of calved glacial ice most fragments of floating ice melt within 1 km of the ice front some sediment may be contributed as low density 1 1 g cm 3 algae bound sediment pellets by meltwater streams draining the ablating ice surface sediment enters the stratified water column and is moved by tidal and wind driven circulation marine sedimentation rates are low 3 mm yr relative to depth of bioturbation resulting in unstratified sandy mud with dispersed clasts

timescale dependence of glacial erosion rates a case study of marinelli glacier cordillera darwin southern patagonia 1 erosion rates have been estimated for a number of glaciated basins around the world mostly based on modern observations last few decades of sediment fluxes to fjords we use time constrained sediment volumes delivered by marinelli glacier 55 s an outlet glacier of the cordillera darwin ice cap southern patagonian andes tierra del fuego to determine erosion rates across different timescales sediment volumes are derived using a dense grid of high and low frequency single channel seismic data and swath bathymetry data along with piston and kasten cores our results show dramatic differences in erosion rates over different timescales erosion rates at marinelli glacier diminish about 80 or by factor of 5 with each ten fold increase in the time span over which erosion rates are averaged 29 3 mm yr for the last 45 years 5 3 mm yr for the last 364 years and 0 5 mm yr for the last 12 500 years these results indicate that modern sediment yields and erosion rates from temperate tidewater glaciers can exceed long term values over the time of deglaciation after the last glacial maximum centennial and millennial timescales by up to 2 orders of magnitude in view of the low exhumation rates of cordillera darwin 0 07 mm yr average for the last 30 myr modern erosion rates could be up to 3 orders of magnitude higher than rates over geological time we conclude that the pattern of erosion rate variation with time reflects the sensitivity of glaciers to climate variability

synoptic scale study of the arctic polar vortex s influence on the middle atmosphere 1 observations 1 we present nightly rayleigh lidar temperature measurements of the high latitude middle atmosphere taken at three arctic sites over similar time periods in midwinter the four reported case studies depict changes in the thermal structure of the stratosphere and lower mesosphere over a period of days to weeks that can be attributed to movement and interaction of the polar vortex the aleutian high and planetary waves as evidenced from the national center for environmental prediction tropospheric and stratospheric analyses in cases where substantial i e large horizontal scale movement of the vortex is observed it is noted that regional middle atmospheric arctic temperatures can change by tens of degrees in other cases we show that even very subtle i e small horizontal scale movement of the vortex system over similar timescales can result in notable temperature changes in the regional middle atmosphere it appears that the observed events are dependant on the location strength and structure of the polar vortex and aleutian high all of these synoptic scale measurements indicate a change in the local dynamical structure of the middle atmosphere and are discussed in regards to this issue

global measurements of stratospheric mountain waves from space temperatures acquired by the cryogenic infrared spectrometers and telescopes for the atmosphere crista during shuttle mission sts 66 have provided measurements of stratospheric mountain waves from space large amplitude long wavelength mountain waves at heights of 15 to 30 kilometers above the southern andes mountains were observed and characterized with vigorous wave breaking inferred above 30 kilometers mountain waves also occurred throughout the stratosphere 15 to 45 kilometers over a broad mountainous region of central eurasia the global distribution of mountain wave activity accords well with predictions from a mountain wave model the findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models

the separated polar winter stratopause a gravity wave driven climatological feature abstract an examination of satellite derived temperatures reveals that the winter polar stratopause is usually elevated and warmer than the adjacent midlatitude stratopause this separated stratopause occurs in both hemispheres but is more pronounced and persistent in the southern winter it descends with time towards spring and exhibits week to week variability observational diagnostics and results from a two dimensional 2 d model suggest that gravity wave driving can account for this separated polar stratopause by driving a meridional circulation with downwelling over the winter pole in the model the solar heating pattern induces stronger winter westerlies than summer easterlies which leads to a stronger gravity wave driven circulation in the winter hemisphere spherical geometry and the high latitude location of the winter westerly jet combine to yield a concentrated region of downwelling model results suggest that descent of the temperature maximum with time is probably caused by wave mean f

petrological evolution of the crust and mantle in its simplest form crust mantle evolution can be thought of as a study of the processes by which material is lost from the mantle and forms new crust the overall goal is achievement of mass balance between the average composition of material known to have been added to the crust and the estimated average composition of the entire crust attainment of this goal for the earth has been elusive primarily because the materials available for study have generally been involved in several stages of evolution including fractionation within both the crust and mantle and recycling of material from crust to mantle thereby complicating the interpretation of available data although the overall composition of the continental crust generally has been modelled as andesitic taylor and mclennan 1981a the present upper continental crust is granodioritic and requires a more mafic lower crust it has been proposed taylor and mclennan 1981a that originally the archean crust had an andesitic composition throughout its volume and that partial melting in the lower crust developed more felsic melts that rose to enrich the upper crust leaving a more mafic residuum of lower crust this concept has been challenged by weaver and tarney 1981a who argue that the granulites of presumed lower crustal origin do not have the correct compositions for this model if one considers more recent additions to the crust from the mantle over the past several hundred million years it appears that these latest additions are basaltic with very little if any granitic additions in fact barker 1981 in his introduction to a special issue of jgr on granites and rhyolites states to date no one has demonstrated that such magmas may form in the mantle indeed much experimental and geochemical work indicates that such siliceous liquids cannot originate there therefore such magmas must be generated in the crust in island arc environments where the average composition of added material normally is thought to be andesitic a anderson 1982 has shown that the parent melt is basaltic not andesitic in addition kay 1980 has shown that the k content of the newly added material is less than the average k content of the previously existing crust in the oceanic crust the additions from the mantle are basaltic and according to o hara 1982 probably are derived from very mafic picritic melts as parents continental flood basalts which have also added material from mantle to crust also are clearly derived from basaltic parental melts basaltic volcanism study project 1981 thus the evidence for the nature of material subtracted from the mantle and added to the crust for the past several hundred million or perhaps a billion years points to very mafic melts this contrasts significantly with the overall andesitic composition of continental crust it implies furthermore that if the overall archean crustal composition was andesitic as estimated by taylor and mclennan 1981a then additions to the crust have become more mafic with time a concept in direct conflict with most models in which secular trends are from mafic to felsic with time veizer and jansen 1979 and mclennan et al 198o a question which is beginning to appear either explicitly or implicitly is whether crustal volcanic rocks or the crust as a whole really represents the parent melt that formed in the mantle a anderson 1982 o hara 1982 and nisbet and walker 1982

tholeiitic and calc alkaline magma series at adatara volcano northeast japan 2 mineralogy and phase relations abstract low alkali low k by gill 1978 or island arc by jakes and gill 1970 tholeiitic magma suites are closely associated with medium k by gill 1978 calc alkaline suites in the outer volcanic zone called nasu volcanic zone nvz of northeast japan chemistry and phase relations of phenocrysts are studied for representative 5 low alkali tholeiitic and 8 calc alkaline rock samples of adatara volcano in nvz in order to examine the mineralogical evolutionary mechanisms of the two series of magmas also clarified are differences in the magmatic temperature and oxygen fugacity between the two magma series the correlations between whole rock chemical compositions and mineralogy in the tholeiitic suite at this volcano are well documented supporting the argument that the members of this suite are related through fractional crystallization of observed phenycrystic phases part 1 fujinawa 1988 mineralogical observations in the calc alkaline suite are compatible with the views based on their whole rock chemical compositions although fractional crystallization process is dominant in the evolution of the calc alkaline magma intermittent mixing of small amounts of magnesian high temperature magmas operates concurrently temperature estimates with the two pyroxenes geothermometer range from 1080 c to 970 c in the tholeiitic suite whereas from 990 to 850 c in the calc alkaline suite temperature oxygen fugacity trends indicate that the low alkali tholeiitic magma evolves under conditions of higher temperature and lower oxygen fugacity than the calc alkaline magma in view of the fact that the hyperstene and augite phenocryst cores in the calc alkaline samples are compositionally distinguishable from the relevant phases in the tholeiitic samples it is unlikely that magma mixing played an essential role in the generation of the calc alkaline suite at adatara volcano

warm stratopause in the antarctic winter abstract the fact that the temperature near the stratopause in the polar night is remarkably higher in the antarctic than in the arctic is described the reason why the stratopause can exist in the polar night and be warmer in the antarctic is considered in terms of gravity waves and planetary waves

seismic facies changes along a nearly continuous 24 latitudinal transect the fjords of chile and the northern antarctic peninsula abstract high resolution seismic reflection profiles and piston cores from bays fjords and straits of the inland passage of chile and the northern antarctic peninsula region were used to examine changes in seismic facies along a nearly continuous 24 latitudinal transect that encompasses temperate subpolar and polar climatic regimes these climatic regimes are characterized by differences in seismic facies eight seismic facies are recognized on the basis of reflection character intensity of acoustic contrast at bounding surfaces and external shape of the unit the northern and central chilean fjord region is a temperate maritime setting characterized by thick ice proximal and ice distal glacial marine strata and a variety of morainal features the southern inland passage and the south shetland islands of antarctica represent transitional sub polar glacial marine settings these areas are characterized by relict ice proximal glacialmarine facies and relatively thin ice distal glacial marine facies morainal ridges occur in bays and fjords of chile the northern antarctic peninsula is a polar climatic setting the straits bays and fjords of the region have been virtually scraped clean of sediments a thin draping glacial marine unit occurs locally in these areas

relevance of mountain wave cooling for the formation of polar stratospheric clouds over scandinavia mesoscale dynamics and observations for january 1997 the effect of mesoscale mountain wave induced temperature anomalies on the formation potential of polar stratospheric clouds above northern scandinavia is analyzed with a one month mesoscale model integration the simulation results are contrasted with synoptic scale analyses and compared with remote sensing and in situ observations the mesoscale mass flux of air parcels with temperatures below the threshold for cloud formation through a control volume is compared with its synoptic scale counterpart a classification of the synoptic scale flow into periods of large and small mountain wave activity in the stratosphere is proposed the derived classification will be used for a climatology of stratospheric mountain wave activity above scandinavia

lidar observations of gravity wave activity in the upper stratosphere over toronto the rayleigh lidar technique has been applied to observe temperature fluctuations induced by gravity waves within the upper stratosphere observations were carried out on a routine basis for 1 year 130 clear nights at the campus of york university near toronto 44 n 80 w the waves were on occasion observed to induce marginal convective instability while exhibiting no substantial vertical amplitude growth in general the vertical variation in the amplitude of fractional temperature perturbations and associated available potential energy density implied the waves were strongly dissipated dramatic changes in the distribution of spectral energy with respect to vertical wave number were observed over the course of a few hours the total resolved available potential energy in the gravity wave field varied considerably from day to day and seasonally with a winter maximum and summer minimum

nonorographic generation of arctic polar stratospheric clouds during december 1999 1 during december 1999 polar stratospheric clouds pscs were observed in the absence of conditions conducive to generation by topographic gravity waves the possibility is explored that pscs can be generated by inertia gravity waves igw radiating from breaking synoptic scale rossby waves on the polar front jet the aerosol features on 7 and 12 december are selected for comparison with theory and with simulations using the university of wisconsin nonhydrostatic modeling system uwnms consistent with rossby adjustment theory a common feature in the uwnms simulations is radiation of igw from the tropopause polar front jet especially from sectors which are evolving rapidly in the rossby wave breaking process packets of gravity wave energy radiate upward and poleward into the cold pool while individual wave crests propagate poleward and downward causing mesoscale variations in vertical motion and temperature on 12 december the eastbound dc 8 lidar observations exhibited a fairly uniform field of six waves in aerosol enhancement in the 14 20 km layer consistent with vertical displacement by a field of igw propagating antiparallel to the flow with characteristic horizontal and vertical wavelengths of 300 and 10 km uwnms simulations show emanation of a field of igw upward and southwestward from a northward incursion of the polar front jet the orientation and evolution of the aerosol features on 7 december are consistent with a single psc induced by an igw packet propagating from a breaking rossby wave over western russia toward the northeast into the coldest part of the base of the polar vortex with characteristic period 9 hours vertical wavelength 12 km and horizontal wavelength 1000 km linear theory shows that for both of these cases igw energy propagates upward at 1 km hour and horizontally at 100 km hour with characteristic trace speed 30 m s the spatial orientation of the psc along igw phase lines is contrasted with the nearly horizontal filamentary structures in the psc which are indicative of flow streamlines it is suggested that vertical displacement is a crucial factor in determining whether a psc will form and that most pscs are relatable to specific synoptic and mesoscale motions

mesosphere inversion layers and stratosphere temperature enhancements 1 it has been known for at least 30 years that vertically narrow thermal layers form within the middle atmosphere two types of temperature enhancements the low latitude to midlatitude mesosphere inversion layer mil and the high latitude winter stratosphere temperature enhancement ste have both received much attention within the atmospheric science community because of their unexplained formation mechanisms and potential impacts on the middle atmosphere global circulation numerous experimental numerical and theoretical studies have attempted to explain certain aspects of these respective thermal layers but no one theory consistently and satisfactorily describes all the features observed we present a review of the literature and explicitly propose a classification scheme based on the different formation mechanisms suspected to cause these events for the mil we demonstrate that there are two subtypes the first one is tidally driven and tends to occur above 85 km this mil originates from large amplitude tidal waves propagating into the mesosphere and their subsequent nonlinear interactions with gravity waves which can often create the appearance of a double mil separated by approximately one vertical tidal wavelength 25 km the other subtype of mil is formed by a climatological planetary wave dissipation mechanism that occurs at a zero wind line the dissipation of the planetary wave tends to generate a mesoscale 1000 km inversion layer in the range of 65 80 km these two formation mechanisms explain a host of observed characteristics including the reason behind the downward progression of some mils and not others the different climatological nature of the two forms of mil events and the relative scarcity of mil observations at high latitudes the ste is believed to be generated by an altogether different process namely the nonlinear interaction between the polar vortex and planetary waves aleutian high the induced temperatures typically peak around 40 km and often exceed 300 k generating what appears to be a low hot stratopause when vertical temperature profiles are combined with synoptic analyses one observes that the ste is the consequence of high latitude vortex interactions creating a baroclinic atmosphere i e a downward adiabatic compression induced by an ageostropic flow we summarize the details of the relationship between this feature and sudden stratospheric warmings as well as the potential for in situ gravity wave generation we close with a review of currently unexplained mil ste features and offer new directions for future middle atmosphere thermal layer research

the characteristics of the lower stratospheric gravity wavefield above halley 75 s 26 w antarctica from radiosonde observations daily radiosonde observations between 2003 and 2013 from halley research station antarctica 75 s 26 w are used to determine climatologies of gravity wave properties in the lower stratosphere between 15 km and 22 km altitude individual waves are extracted from the radiosonde profile using wavelet analysis and separated into upward and downward propagating waves an increase in the percentage of downward propagating waves 30 of the waves is seen during the winter months for the upward and downward propagating waves their horizontal and vertical wavelength intrinsic frequency energy density pseudo momentum flux and direction of propagation are determined the upward propagating wave field is found to be dominated by waves with short vertical wavelength 1 km and low intrinsic frequency f the downward propagating wave field is composed of a wider distribution of vertical wavelength waves and has a larger proportion of higher frequency waves present the upward propagating waves show an increase in total energy density in autumn and spring the larger increase occurs during spring up to 1 7 j kg 1 in september the downward propagating waves increase in total energy density occurs during wintertime up to 0 7 j kg 1 in june during winter the contributions of the upward and downward propagating waves to the total energy density and pseudo momentum flux are almost equal this paper details the first study of individual gravity wave properties combined into upward and downward propagating wave climatologies in the lower stratosphere above halley

biogenic sedimentation in mcmurdo sound antarctica surface sediments from eastern mcmurdo sound and fjord basins of the victoria land coast are enriched in organic carbon and opal at depths below 600 m opal contents commonly exceed 30 organic carbon contents average 1 5 and are as high as 3 5 opal and organic carbon are supplied by local production within and below sea ice and by advection from open water areas of the southwestern ross sea the distribution of organic carbon and opal at the sea floor is consistent with cyclonic clockwise water circulation in mcmurdo sound advective transport from the ross sea supplies biogenic sediment to eastern and northern mcmurdo sound the southwestern shelf is bathed by waters derived in part from beneath the ross ice shelf which transport very little allochthonous carbon the supply of biogenic debris in southwestern mcmurdo sound is further curtailed by sea ice conditions e g more prevalent multi year sea ice which reduces photosynthesis and the absence of summer basal melting and ice breakout which restricts the flux of sea ice and open water production to the sea floor consistent with this hypothesis organic carbon fluxes measured via sediment trapping beneath fast ice are one to two orders of magnitude higher in eastern versus western mcmurdo sound pronounced cross sound gradients in shallow water benthic biomass and species diversity have previously been attributed to east west variations in productivity our surface sediment data suggest that similar or even more dramatic contrasts in benthic community structure may exist in the deeper water areas of mcmurdo sound pervasive resuspension is documented by pronounced near bottom flux increases measured by sediment trapping resuspension events which may be more common during the austral winter act to winnow and transport biogenic debris and fine terrigenous sediment from shallow regions 400 m to protected shelf basins despite oxidative loss within the water column the accumulation rate of organic carbon in the deep basins of mcmurdo sound averages 45 mg c m 2 day 1 more than an order of magnitude higher than the world average organic carbon flux to continental margins and equivalent to accumulation rates observed in many anoxic settings preservation efficiency of opal during transport and deposition appears anomalously high and the most opal rich sediments of mcmurdo sound are depleted in organic carbon relative to mid and low latitude siliceous deposits despite this observation if similar patterns of biogenic sedimentation exist on many other parts of the shelf the antarctic continental margin is an important sink for sedimentary organic carbon as has been previously suggested for the silica system

bottom currents sedimentation and ice sheet retreat facies successions on the mac robertson shelf east antarctica abstract measurements of water turbidity currents seafloor sediment samples and geophysical data document the sedimentary processes and the late quaternary sedimentary history of a continental shelf valley system on the east antarctic continental margin the valley is up to 1200 m in depth and strikes across the shelf it is interpreted as having formed by glacial erosion processes on the outer shelf sill of the valley northwestward offshore currents with speeds of up to 0 47 m s referenced to 100 cm above the seabed were recorded over a 10 month period such currents are competent to initiate bedload transport of medium sand and formation of small ripple sized bedforms which explains the occurrence of ripple cross bedding observed in some x radiographs of cores a nepheloid layer with concentrations of up to 3 5 mg l was noted at two stations and the available evidence suggests that density flows resulting from the sea ice brine rejection mechanism are competent to entrain shelf bottom sediments episodically sediment cores taken from this environment document the succession of facies resulting from retreat of glacial ice from the shelf during the holocene transgression under low sea level glacial conditions the ice sheet is interpreted to have been grounded on the outer shelf where it deposited a grounding line moraine rising sea level and global warming caused the ice shelf to retreat leaving a sub ice shelf glacial marine mud this is overlain by a laminated to massively bedded ice rafted debris rich facies interpreted as being deposited at the glacial calving front above this is a siliceous mud and ooze facies having a basal age of about 10 000 years bp characterising modern open marine conditions two types of iceberg keel marks on the outer part of the shelf valley are recognised from sidescan sonographs one relict arcuate type formed during the retreat of the ice shelf prior to 10 000 years bp and a second modern elongate type that is presently being formed near the shelf break by iceberg grounding processes this facies succession has been described from other antarctic shelf environments and is probably representative of facies deposited during holocene glacial retreat from the antarctic shelf

environmental assessment from the sedimentary record of high latitude fiords the sedimentary record of fiords at high latitude where global change may be occurring earliest and will be greatest has the potential for assessment of environmental change at both low resolution the scale of millennia and high resolution decadal to less than daily unlike the lacustrine record which has been used very successfully in these studies the sedimentary processes and thus the sedimentary deposits of fiords differ 1 in the role of salt water in inhibiting mixing and promoting flocculation and through the role of sea ice 2 in the exchange of mass and energy with the much larger ocean beyond and 3 in the role of benthic biota in the sedimentary environment the work reviewed in this paper shows that fiord sediments are being used to assess sedimentary and oceanic processes as well as glacial periglacial and geomorphic history and that they are important proxies for long term climate and hydrology recommendations for advancing this work include long term monitoring of conditions in fiords and their drainage basins so that the transfer relations can be more solidly constructed from the proxy of fiord sediment integration of results from fiords in opposite polar latitudes and among proxies especially from lacustrine and ice core records will produce valuable insights assessment of the range of conditions in fiords from the most polar to temperate regions is important to building models of their processes and understanding of the paleoenvironmental signals that can be interpreted from each type

sub ice shelf deposition during the late devensian glaciation in western ireland abstract glacigenic sediments preserved around the margins of clew bay western ireland record deposition in a tidally influenced sub ice shelf environment during the late devensian glaciation 21 13 14 c kyr thick massive to normally graded glacial diamictons tills are interbedded with laminated to massive silt and clay beds these sediments interbed with each other on scales ranging from millimetres to metres in a generally shallowing up sequence associated with a decrease in accommodation space isolated dropstones and a downward going clastic dike are also observed these structures and sediments reflect a waterlain environment with rhythmically varying levels of water energy and sediment supply tidally driven uplift and downdraw of a retreating ice shelf is a likely control on sedimentation patterns and glacial dynamics of this sensitive atlantic facing ice margin

seasonal variations of gravity wave activity in the lower stratosphere over an antarctic peninsula station an 8 year series of 965 high resolution radiosonde soundings over rothera 67 degrees s 68 degrees w on the antarctic peninsula are used to study gravity wave characteristics in the lower stratosphere the gravity wave energy is shown to have a seasonal variation with peaks at the equinoxes the largest peak is around the spring equinox during the winter months and extending into the spring there is both an enhancement in the downward propagating wave activity and a reduction in the amount of critical level filtering of upward propagating mountain waves the horizontal propagation directions of the gravity waves were determined using hodographs it was found that there is a predisposition toward northward and westward propagating waves above rothera this is in agreement with previous observations of gravity wave momentum flux in the wintertime mesosphere over rothera these results are consistent with a scenario whereby the stratospheric gravity wavefield above rothera is determined by a combination of wind flow over topography generating waves from below and sources such as the edge of the polar stratospheric vortex generating waves from above especially during winter and spring

on the na2o content of convergent zone high alumina basalts abstract high alumina basalts in the convergent zone are classified into high medium and low na type the high na high alumina basalts occur in arcs without low alkali tholeiites where younger and warmer oceanic lithospheres are subducting the low na high alumina basalts occur in arcs where on the contrary older and cooler plates are descending and occur also in arcs with extensional tectonics even though younger lithospheres are underthrusting a good correlation is observed between the na2o content of high alumina basalts and the age of the subducting lithosphere this suggests that generation of high alumina basalt magma is controlled by the nature of the descending plate

rayleigh lidar observations of thermal structure and gravity wave activity in the high arctic during a stratospheric warming abstract during february and march 1993 rayleigh lidar observations of temperature structure and gravity wave activity were carried out in the high canadian arctic at eureka northwest territories 80 n 86 w a sudden warming was observed first in the upper stratosphere during late february and then at lower levels in early march the warming appeared to be part of a disturbance of the entire middle atmosphere with temperature changes in the mesosphere and lower stratosphere being opposite in sign to those in the upper stratosphere shorter time and length scale temperature fluctuations observed in the upper stratosphere are interpreted as being a result of atmospheric gravity waves the wave amplitudes are shown to be capable of inducing convective instability the rms perturbation and available potential energy density show substantial vertical and day to day variability in regions of conservative and dissipative growth rates vertical growth of the potential energy spectral density is seen to ceas

the role of the cryosphere in source to sink systems abstract glacial erosion and sediment production are of interest to diverse scientific communities concerned with the interaction of climatic tectonic and surface processes that influence the evolution of orogens and with the climatic signals archived in glacigenic strata we review the current state of knowledge on the generation transfer and accumulation of glacigenic sediment from land to sea we draw from geomorphology marine geology geochronology numerical modeling of surface processes and landscape evolution and experimental and field observations of glacier erosion and deposition and the interaction of ice with its bed and the ocean boundary our primary goal is to examine glacial systems using a holistic source to sink approach with a focus on describing a how glacial motion produces sediment b how the sediments sink record the dynamic nature of glacial systems under different climatic thermal regimes c the challenges in using the sedimentary record to interpret these dynamics in space and time and d the approaches still needed to further our understanding of how ice and associated sediment fluxes respond to climatic and other perturbations the dynamic state of ice i e the ice flux and ice extent is defined differently between the source and sink communities reflecting the challenges of establishing a stratigraphic signal that volumetrically constrains glacigenic sediment production as a function of the ice response to climate advances in marine geophysics have greatly assisted our understanding of mass transfer pathways and of former ice extents as a measure of ice dynamics and have identified the primary depocenters and key lithofacies of glacial sinks sediment fluxes associated with the dynamic state of the ice are best constrained where sediment volumes derived from key lithofacies and seismic reflection isopachs can be temporally partitioned of which there are few examples rather than from discrete point measures of sediment flux that are subject to sediment transfer biases forward numerical modeling of sediment fluxes as a function of ice dynamics agree with observational data at the continental margin scale but finer time space scale ice dynamic models do not yet recreate observed ice extent or flowpaths future source to sink work in glaciated systems should focus on refining empirical relationships between ice velocity and sediment production and expand the application of existing methods to develop sediment volumes and fluxes in known depocenters of former and modern ice streams

evidence for inertia gravity waves forming polar stratospheric clouds over scandinavia 1 at three successive days at the end of january 2000 the deutsches zentrum fur luft und raumfahrt dlr airborne lidar ozone lidar experiment explored mountain wave induced polar stratospheric clouds above the scandinavian mountain ridge global analyses and mesoscale modeling are applied to explain their complex internal structure and their day to day variability depending on the synoptical scale meteorological conditions stratospheric temperature anomalies of different amplitude and horizontal extent are generated by the upward propagating mountain waves short term excitation of about 6 hours resulted in localized stratospheric temperature anomalies directly above the mountain ridge as for 25 january 2000 in this case the elevation of the observed clouds differed not much from the synoptic scale clouds upstream above the norwegian sea on the other hand long lasting flow past the scandinavian mountain ridge formed huge 400 km horizontally extending stratospheric ice clouds in altitudes as much as 5 km above the elevation of the upstream clouds just 1 day later inertia gravity waves with horizontal wavelengths of about 350 km are responsible for their formation for the first time a predicted temperature minimum far downstream of the mountains could be proofed by the observation of an isolated stratospheric ice cloud above finland the observed particles are classified in terms of their measured optical properties such as backscatter ratio and depolarization in all cases mountain waves generated ice clouds in contrast to the nitric acid trihydrate tail of the ice cloud on 25 january the same classification results in a tail of liquid supercooled ternary solutions droplets 1 day later the particle structure downstream of the mountains is very complex and needs detailed microphyical modeling and interpretation

geochemistry of the 1989 1990 eruption of redoubt volcano part i whole rock major and trace element chemistry the 1989 1990 eruption of redoubt volcano produced medium k calc alkaline andesite and dacite of limited compositional range 58 2 63 4 sio2 and entrained quenched andesitic inclusions 55 sio2 which bear chemical similarities to the rest of the ejecta the earliest december 15 magmas are pumiceous often compositionally banded and the majority is relatively mafic 59 sio2 the most silicic magmas of the eruption are the late december to early january domes up to 63 4 sio2 subsequent magmas formed domes and rare pumices which converge on 60 sio2 chemical variations among ejecta comprise tight linear two component arrays for all elements for which the analytical uncertainty is much less than the compositional range the two component arrays are interpreted as mixing arrays between unrelated magmas because several of the arrays are at steep angles to the normal liquid line of descent additionally the felsic endmember cannot be easily related to the mafic endmember by normal high temperature igneous processes e g the silicic endmember has higher zr yet lower hf than the mafic endmember also relative enrichments of highly incompatible elements are dramatically different across the arrays the mixing event must have preceded eruption by a significant yet unspecified amount of time because groundmass glass compositions are homogeneous for all post december samples swanson et al 1994 this volume in spite of the whole rock chemical diversity this implies time for additional crystallization after the mixing event swanson et al 1994 this volume discuss evidence for a potentially different mixing event recorded only in december 15 magmas cognate cumulate xenoliths composed of pl cpx opx hb mt melt were recovered from january and april deposits these blocks differ from local batholithic country rock in their low concentrations of incompatible elements e g rb 60 wt they have mg cr ni sc and v contents higher than the andesites but lower than redoubt basalts and basaltic andesites thus they may be crystallization products of andesites but do not represent the cumulate residue of basalt fractionation the xenoliths were probably derived from a shallow or intermediate crustal chamber

the mt edgecumbe volcanic field alaska an example of tholeiitic and calc alkaline volcanism major element trace element and isotopic composition data for lava samples have been collected from a holocene stratovolcano in southeastern alaska results indicate that a wide variation in chemical compositions exist 48 71 sio 2 10 14 16 mgo and the suite may be divided into two series on the basis of chemical mineralogical and isotopic characteristics the tholeiitic series lavas consist of generally phenocryst poor olivine basalts whose chemical and isotopic compositions are transitional between normal morb and lree enriched lavas of atypical areas such as the azores platform cao is high mgo feo 1 fe 2 o 3 k 2 o rb and sr are low while mgo and ni are high data show that the basalts are lree depleted and sr 87 sr 86 70304 the basalts compose 65 of the volcanic field and crystal fractionation appears to have produced the compositions of the more silicic basalts the calc alkaline series lavas are composed of basaltic andesites andesites and dacites of

late glacial to holocene environmental changes and climate variability evidence from voldafjorden western norway sedimentological micropalaeontological benthic foraminifers and dinoflagellate cysts stable isotope data and ams 14c datings on cores and surface samples in addition to acoustic data have been obtained from voldafjorden western norway based on these data the late glacial and holocene sedimentological processes and variability in circulation and fjord environments are outlined glacial marine sedimentation prevailed in the voldafjorden between 11 0 kyr and 9 2 kyr bp radiocarbon years in the later part of the allerod period and for the rest of the holocene there was deposition of fine grained normal marine sediments in the fjord basin turbidite layers recorded in core material and on acoustic profiles dated to ca 2 1 6 9 7 6 ca 9 6 and ca 11 0 kyr bp interrupted the marine sedimentation the event dated to between 6 9 and 7 6 kyr bp probably corresponds to a tsunami resulting from large scale sliding on the continental margin off norway the storegga tsunami during the later part of the allerod period voldafjorden had a strongly stratified water column with cold bottom water and warm surface water reaching interglacial temperatures during the summer seasons during the younger dryas cold event there was a return to arctic sea surface summer temperatures possibly with year round sea ice cover the entire benthic fauna being composed of arctic species the first strong holocene warming observed simultaneously in bottom and sea surface temperature proxies occurred at ca 10 1 kyr bp bottom water proxies indicate two cold periods possibly with 2 c lowering of temperatures at ca 10 0 pbo 1 and at 9 8 kyr bp pbo 2 these events may both result from catastrophic outbursts of baltic glacial lake water the remainder of the holocene experienced variability in basin water temperature indicated by oxygen isotope measurements with an amplitude of ca 2 c with cooler periods at ca 8 4 9 0 5 6 5 2 4 6 4 2 3 5 2 2 1 2 and 0 4 0 8 kyr bp changes in the fjord hydrology through the past 11 3 kyr show a close correspondence both in amplitude and timing of events recorded in cores from the norwegian sea region and the north atlantic these data suggest a close relationship between fjord environments and variability in large scale oceanic circulation copyright 2001 john wiley sons ltd

mechanisms of holocene palaeoenvironmental change in the antarctic peninsula region the antarctic peninsula is one of the three fastest warming regions on earth here we review holocene proxy records of marine and terrestrial palaeoclimate in the region and discuss possible forcing mechanisms underlying past change with a specific focus on past warm periods our aim is to critically evaluate the mechanisms by which palaeoclimate changes might have occurred in order to provide a longer term context for assessing the drivers of recent warming two warm events are well recorded in the holocene palaeoclimate record namely the early holocene warm period and the mid holocene hypsithermal mhh whereas there are fewer proxy data for the mediaeval warm period mwp and the recent rapid regional rrr warming we show that the early holocene warm period and mhh might be explained by relatively abrupt shifts in position of the southern westerlies superimposed on slower solar insolation changes a key finding of our synthesis is that the marine and terrestrial records in the ap appear to show markedly different behaviour during the mhh this might be partly explained by contrasts in the seasonal insolation forcing between these records circumpolar deep water cdw has been implicated in several of the prominent changes through the holocene but there are still differences in interpretation of the proxy record that make its influence difficult to assess further work is required to investigate contrasts between marine and terrestrial proxy records east west contrasts in palaeoclimate the history of cdw to retrieve a long onshore high resolution record of the holocene and determine the role of sea ice in driving or modulating palaeoclimate change along with further efforts to study the proxy record of the rrr and the mwp

rayleigh lidar observations of gravity wave activity in the winter upper stratosphere and lower mesosphere above davis antarctica 69 s 78 e 1 gravity wave activity in the upper stratosphere and lower mesosphere uslm is investigated using temperature data retrieved from a rayleigh lidar at davis antarctica 69 s 78 e during the 2007 and 2008 winters the temporal and height variabilities of waves with ground based periods greater than 2 h and vertical wavelengths between 4 km and 20 km are analyzed stratospheric gravity wave potential energy per unit mass shows a weaker correlation with stratospheric winds at davis than that reported in the arctic gravity waves dissipate above 40 km during winter while there is no dissipation in the autumn mesosphere a separate analysis of gravity waves with ground based periods of 2 6 h revealed lower dissipation in the winter mesosphere the seasonal cycle of gravity wave activity is evident throughout the uslm with peak activity observed during winter the gravity wave potential energy and vertical wavenumber power spectral density at davis are similar to that recorded at other high latitude sites

gravity wave forcing in the stratosphere observational constraints from the upper atmosphere research satellite and implications for parameterization in global models 1 global models that include parameterized gravity wave effects have an excessively broad range of tuning parameters to choose from that allow a very broad range of gravity wave momentum forcing distributions we derive a set of constraints on gravity wave characteristics near the tropopause from databased estimates of gravity wave effects in the stratosphere we use 5 6 years of upper atmosphere research satellite data and uk met office analyzed wind and temperature fields to first derive estimates of the gravity wave mean flow forcing in the stratosphere we then compare these estimates to a suite of gravity wave model calculations to infer the constraints on the gravity wave characteristics near the tropopause these constraints apply to the portion of the gravity wave spectrum that dissipates in the stratosphere and does not include those that dissipate and drive the mesosphere we focus on equatorial and extratropical regions separately and find substantially different wave characteristics between the two we also find a seasonal variation in gravity wave characteristics in the extratropics near the equator gravity waves assist in driving the quasibiennial and semiannual oscillations and our constraints on gravity waves likely include a blend of characteristics of both ordinary gravity waves and some kelvin wave modes in the extratropics gravity wave forcing primarily assists in the annual winter to summer transition from westward to eastward winds