first simultaneous and common volume observations of noctilucent clouds and polar mesosphere summer echoes by lidar and radar we present the results of first simultaneous and common volume observations of noctilucent clouds nlc and polar mesosphere summer echoes pmse by two ground based lidars and one vhf radar the measurements were performed at the alomar facility 69 n 16 e during the time period july 23 through august 18 1994 throughout this period nlc layers were observed by the lidars on four occasions during each of these four lidar observed nlc events pmse layers were also observed overhead by the radar these joint nlc pmse events divide into two distinct types 1 tightly coupled and 2 loosely coupled nlc and pmse layers in one of the events the pmse layer developed into a well defined double layer with only 0 8 km vertical separation while the lidar observed nlc layer matched closely in time and space the lower pmse sublayer within all four nlc pmse layers the wind speed increased sharply with increasing altitude with wind shears amounting to 0 03 s 1 and larger current theories can explain some of the observed layer features

first observations of polar mesosphere summer echoes in antarctica a 25 kw peak power 50 mhz radar was installed at the peruvian base on king george island antarctica 62 s in early 1993 a search for polar mesospheric summer echoes pmses was made during late january and early february of the first year of operation with negative results these results have been reported in the literature balsley et al 1993 1995 we report here results obtained during the austral summer of the second year 1994 of operation observations during the second year were begun earlier i e closer to the austral summer solstice pmses were observed during this period albeit the echoes were much weaker than what one would expect based on earlier poker flat radar results at a comparable latitude 65 n in the northern hemisphere a large and measurable asymmetry in pmse strength in the two hemispheres therefore exists we explain this asymmetry by postulating a difference in summer mesopause temperatures between the two hemispheres of 7 5 k this difference has been estimated using an empirical relationship between the variations of the poker flat pmse power as a function of temperature given by the mass spectrometer incoherent scatter extended msise 90 model

fluctuation of organic carbon isotopes of the lower cretaceous in coastal southeastern china terrestrial response to the oceanic anoxic events oae1b abstract whether there are terrestrial responses to the oceanic anoxic events oaes remain enigmatic in this paper we report a case study in the lower cretaceous continental and transitional sequences of coastal southeastern china it may represent the first late aptian to albian terrestrial carbon isotope record from china several organic rich black shale and grayish black mudstone horizons were found to develop widely in the coastal southeastern china during the period from 113 3 ma to 99 3 ma when the cretaceous oaes were recorded primarily in marine sequences organic carbon isotope 13 c org total organic carbon toc and total nitrogen tn were analyzed for the black shales from two sections i e the shipu transitional and chong an continental sections five negative 13 c org excursions can be recognized for both the sections termed as si sv and ci cv events for the shipu s and chong an c sections respectively correlations between 13 c org toc and n c ratio suggest that the si siii and ci ciii events might have been caused by global factors i e the oae1b event based on analogs to typical oae1b reported in the tethyan and pacific basins they archived the terrestrial carbon isotope response to the oae1b accompanied with a disturbance of carbon isotope in carbon reservoir of the global ocean atmosphere system under a warm and humid climate

the use of stable oxygen and carbon isotope stratigraphy as a dating tool abstract oxygen isotope stratigraphy in foraminifera from deep sea sediments provides a time series record of globally synchronous events with a resolution of a few thousand years for the quaternary despite deficiencies from problems of discerning local from global effects and from isotopic disequilibria and ecological effects oxygen isotope stratigraphy remains a highly powerful tool for dating and correlating deep sea sediments as well as for paleoclimatology in general oxygen isotope records per se do not provide absolute age control although carbon isotope records in some respects are more difficult to interpret than oxygen isotopes and are influenced by local factors such as biological productivity ocean ventilation rates and foraminiferal ecological factors carbon isotope records also reflect global phenomena they can therefore be utilized for correlation and dating purposes in a manner similar to oxygen isotope records and provide additional age control especially in areas where the oxygen isotope records may be influenced by temperature and low salinity overprints

upper mesosphere summer echoes detected with the antarctic syowa hf radar 1 peculiar hf radar echoes observed at syowa station antarctica 69 0 s 39 6 e are reported the echoes occurred in summer at slant ranges between 180 first range gate and 315 km under very quiet geomagnetic conditions they are characterized by a duration of less than 80 min quasi periodic oscillations of velocity and echo power with periods of 5 20 min velocities between 40 and 20 ms 1 and narrow spectral widths less than 40 ms 1 from data of june july december 1997 and january 1998 we identified such echoes on 4 days in december and january summer but not in june and july winter although range resolution of the hf radar 45 km is very poor we believe that our echoes are antarctic polar mesosphere summer echoes pmse relying on that the echo characteristics are very similar to the arctic pmse

late aptian palaeoclimatic turnovers and volcanism insights from a shallow marine and continental succession of the apennine carbonate platform southern italy abstract this study reports an integrated facies analysis carried out on a new section from the upper aptian of the se matese mts civitella licinio northern campania s italy which includes several decimeter to meter scale lacustrine intervals straddling a meter scale plant rich plattenkalk these intervals are assigned to the late gargasian early clansayesian by their stratigraphic relationship with the upper salpingoporella dinarica acme as well as lithologic and biostratigraphic supra regional key markers found in the apennine carbonate platform apcp including the orbitolina level we infer that the monogeneric parautochthonous plant remains frenelopsis sp were deposited in a supratidal to paralic coastal mudflat close to a restricted shallow marine lagoon at the verge of an arid semiarid climatic phase the plattenkalk was rapidly replaced by persistent lacustrine lithofacies at the onset of a major climatic turnover glacial trigger the overlying shallow marine deposits are capped by a deeply incised palaeokarstic surface and in turn by unconformable middle clansayesian transgressive shallow marine deposits interlayering of reliable lithologic indicators of palaeoclimate and high resolution event stratigraphic hires correlation of the civitella licinio succession with the astrochronologically tuned mt faito reference section of the apcp bring evidence of rapidly fluctuating hydroclimatic conditions wet and arid phases in the short 100 ky and long 400 ky eccentricity time band hires and astrochronological age assignment to crucial key markers and humid arid phases at civitella licinio permit to further refine the detailed stratigraphy of the mt faito reference section and to assign the upper s dinarica acme of the apcp to a numerical age of 118 55 118 50 my sem and eds analyses document common to abundant windblown volcanic particles glass shards and sanidine crystals throughout the frenelopsis rich plattenkalk 118 3 to 118 2 my and the encasing units especially in the overlying brackish lacustrine deposits palaeogeographic and palaeoclimatic reconstructions suggest that the pyroclastic material was probably transported by northeasterly trade winds from orogenic volcanic centers located within the dinaridic carpatho balkan arc trench system and have been supplied to the apcp for a time span of 3 my during the late aptian a preliminary tephrostratigraphic correlation of the upper aptian volcaniclastic levels of the apcp with the bentonite levels of the vocontian basin is proposed

southern hemisphere pmse where are they we report a surprising absence of pmse polar mesospheric summer echoes in vhf radar observations of the southern summer high latitude mesosphere our observations cover about twenty days during january february 1993 from king george island antarctica

vhf echoes from the high latitude mesosphere and lower thermosphere observations and interpretations abstract recently published data ecklund and balsley describing vhf radar echo characteristics from the arctic mesosphere and lower thermosphere show a remarkable seasonal dependence of both the echo height and echo intensity during the three month period around the summer solstice intense and nearly continuous echoes are returned from a narrow 2 km half power region centered at 86 km during the remainder of the year however the echoes are much weaker more sporadic and occur at a much lower altitude 70 km 9 km in this paper we present additional data that suggest that the summer echoes are primarily the result of shear instability of low frequency tidal motions in the region of high stratification above the arctic summer mesopause while the winter echoes arise from the nonlinear breakup of upward propagating gravity waves

evidence of gravity wave saturation and local turbulence production in the summer mesosphere and lower thermosphere during the state experiment this study utilizes the unique data set obtained during the structure and atmospheric turbulence environment state experiment conducted during june 1983 at poker flat alaska to examine the structure and characteristics of the wave field near the summer mesopause it is shown that the rocket and radar data together permit a much more detailed specification of wave parameters than would be possible using either data set alone the results of this analysis suggest that the wave field near the summer mesopause is composed in general of a superposition of wave motions which act collectively to produce regions in which the wave field is convectively or dynamically unstable these regions are found to correlate well with zones of enhanced turbulence and small scale wave activity suggesting the processes and effects of wave field saturation

the evolution of pleistocene climate a time series approach abstract in the later part of the pleistocene variations in global ice volume have been dominated by an approximate 100 000 year cycle analysis of 2 myr long oxygen isotope record from an equatorial pacific core indicates that this is true only for the last 900 000 years prior to this time the amplitude of the 100 000 year cycle is much reduced as is the variance of all oscillations with periods greater than 60 000 years based on results of time series analysis of this 2 myr long record the pleistocene glacial cycles can be divided into three sections 1 the late pleistocene 0 900 kyr b p where the variations in the isotope record are dominated by the 100 000 year cycle 2 the middle pleistocene 900 1450 kyr b p in which low frequency components are not as important as in the later period of the pleistocene and 3 the early pleistocene late pliocene 1450 2000 kyr b p where general reductions of importance at all frequencies is seen as compared to the later intervals recent modeling efforts which describe variations in global ice volume show that the dominant low frequency component observed in the late pleistocene can result from different time constants for the rate of glacial growth and decay in response to variations in the earth s orbital parameters it is hypothesized that during the early pleistocene the rate of growth and decay of glaciers were more similar and that continental erosion by successive glacial advances lowered the land surface in areas of ice cap formation to below sea level when the ice caps became marine based more rapid decay of the ice became possible

long term observations of the arctic mesosphere with the mst radar at poker flat alaska in this report we summarize the results of 22 months of observations of arctic mesosphere echoes with the 50 mhz radar at poker flat alaska operation with a partially complete system began in february 1979 and has continued on a nearly continuous basis to the present time the altitude range of the mesospheric echoes obtained during this period shows a pronounced seasonal variation during summer months the mesospheric echoes are relatively continuous in time and extend from about 80 to 100 km with an unexpectedly strong peak in signal to noise ratio at about 85 km in contrast in nonsummer months mesospheric echoes are less intense and occur at lower altitudes in the range from 55 to 80 km these lower altitude nonsummer echoes are observed primarily during daytime hours when energetic auroral particle precipitation as determined by the poker flat 30 mhz riometer is present

evidence for ice clouds causing polar mesospheric summer echoes we compare 22 temperature height profiles derived from falling sphere experiments with simultaneous 50 mhz mesospheric radar echoes obtained during the middle atmosphere co operation summer in northern europe campaign in the summer of 1987 above andenes norway common features of these observations are as follows 1 more than 80 of the echoes occur at temperatures below 140 k and more than two thirds of the bottommost echo maxima appear at temperatures that deviate less than 5 from 140 k 2 we can find no significant correlation between the echo strength or the echo occurrence probability and the local temperature once it is below 140 k 3 the echoes are not symmetrically distributed around the mesospheric temperature minimum but there are clearly more echoes below than above the temperature minimum equivalently while the local temperature at the height of the bottommost echoes is about 140 k it is much lower at the height of the topmost echoes we compare the height range of the observed polar mesospheric summer echo returns with the height range that can be inferred for an ice cloud from the observed temperature profile by means of a simple stationary nucleation sedimentation model for reasonable values of the height integrated ice particle nucleation rate of about 3 107 m 2 s 1 and for a water molecule mixing ratio at the bottom of the ice cloud of 0 1 to 1 0 ppmv we find excellent agreement between the height range within which the ice particles may exist and the height range from which mesospheric echoes are seen for example in 17 out of the 22 individual observations reasonable values for the water vapor mixing ratio can be found such that the height of the strong bottommost echo corresponds to within the resolution of the radar to the bottom height of our model ice cloud if our height estimates are correct and the observations are representative our results yield a somewhat smaller water vapor mixing ratio in the summer mesosphere at high latitudes compared to what has been measured at midlatitudes

first polar mesosphere summer echoes observed at davis antarctica 68 6 s 1 we report the first observations of polar mesosphere summer echoes pmse above the high latitude southern hemisphere sh station davis antarctica 68 6 s 78 0 e geographic 74 6 s magnetic observations were obtained using a 55 mhz atmospheric radar the first stage of which was commissioned late in the austral summer of 2002 2003 the radar commenced mesosphere observations with approximately 20 kw of transmitted power in october 2003 pmse were recorded from 19 november to 3 december 2003 and after a break in radar operation from 27 january to 21 february 2004 we present the initial seasonal and diurnal occurrence morphology from 180 hours of davis pmse observations our initial findings reveal that sh pmse show similar backscatter echo characteristics and occurrence properties to those reported for the northern hemisphere nh

role of glacial arctic ocean ice sheets in pleistocene oxygen isotope and sea level records abstract a comparison of the oxygen isotope signal in deep sea benthic foraminifera with the record of glacio eustatic sea level for the last 160 000 years reveals that the amplitude of the benthic 18 o records predicts more continental ice volume than appears to be reflected in lowered sea level stands these differences between the benthic 18 o ice volume estimates and radiometrically dated records of eustatic sea level are consistent with the presence of a large floating arctic ocean ice mass during glacial intervals the presence of an arctic ocean ice sheet during glacial intervals may account for the two climatic modes observed in oxygen isotope records which span the entire pleistocene the early pleistocene 1 8 to 0 9 myr b p interval is characterized by low amplitude high frequency 18 o fluctuations between glacial and interglacial periods while the late pleistocene 0 9 myr b p to present is characterized by large amplitude low frequency 18 o changes these two climatic modes can be explained by the initiation of earth orbital conditions favoring the co occurrence of glacial period arctic ocean ice sheets and large continental ice sheets approximately 900 000 years before present

glacial terminations in the oxygen isotope record of deep sea cores hypothesis of massive antarctic ice shelf destruction abstract glacial terminations i and ii in the deep sea core foraminiferal oxygen isotope ratios though not similar in form are each characterized by a short interval of about 3 ka during which a large negative change occurred in the ratios after correcting for temperature effects we estimate that each change was equivalent to a glacial disintegration capable of causing a 50 60 m eustatic sea level rise in the termination i interval 16 13 ka b p the estimated equivalent sea level rise is much larger than that suggested by the best evidence of deglacial ice loss from the laurentide ice sheet which is thought to dominate pleistocene glacial ice volume changes moreover in termination ii about 125 ka b p the estimated equivalent sea level rise is much larger than that inferred from the stratigraphy of coral reefs and beaches on new guinea and other locations which suggests quite high sea levels for 10 ka prior to this termination to reconcile these severely conflicting lines of evidence we propose that the rapid negative isotope ratio changes were largely caused by the disintegration of massive floating antarctic ice shelves which masqueraded as land ice in the oceanic isotope ratios but which contributed no sea level change we propose that such shelves were formed when oceanic circulation changes in the north atlantic under glacial conditions greatly reduced the formation of relatively warmer north atlantic deep water and its injection into circumpolar antarctic regions and that the shelves disintegrated rapidly with the resumption of large scale formation of this deep water and its input into the antarctic we find that high sea levels in the 125 135 ka b p interval prior to termination ii which imply very little northern ice then are well supported by dated coral reef stratigraphy although these ages were not accepted by the climap study of the last interglacial ocean minimal northern ice volumes at that time imply that strong milankovitch summer insolation is not always required for northern deglaciation a promising additional deglacial mechanism is the prolonged viscous depression of the crust beneath the laurentide ice sheet combined with atmospheric oceanic circulation factors

oceanic mechanisms for amplification of the 23 000 year ice volume cycle situated adjacent to the largest northern hemispher ice sheets of the ice ages the mid latitude north atlantic ocean has an important role in the earth s climate history it provides a significant local source of moisture for the atmosphere and adjacent continents forms a corridor that guides moisture bearing storms northward from low latitudes and at times makes direct contact along its shorelines with continental ice masses evidence of major ice ocean air interactions involving the north atlantic during the last 250 000 years is summarized outflow of icebergs and meltwater initially driven by summer insolation over the ice sheets affects midlatitude ocean temperatures summer heat storage winter sea ice extent and global sea level these oceanic responses in turn influence the winter moisture flux back to the ice sheets as well as ablation of land ice by calving spectral data indicate that the oceanic moisture and sea level feedbacks in part controlled by glacial melt products amplify milankovitch insolation forcing of the volumetrically dominant mid latitude ice sheets at the 23 000 year precessional cycle

equus stenonis cocchi as a biostratigraphical marker in the neogene quaternary of the western mediterranean basin consequence on galerian villafranchian chronostratigraphy abstract we cite the different forms of equus stenonis cocchi which allowed us to establish a time scale from middle villafranchian to galerian the various e stenonis forms can characterize the successive faunistic units of montopoli middle villafranchian st vallier olivola tasso and farneta upper villafranchian while the galerian phase is characterized by the appearance of equus caballus the lower villafranchian is characterized by the last form of hipparion hipparion rocinantis hernandez pachelo its age is considered by us to be greater than 3 ma in contrast with the age of 2 6 2 4 ma cited in the french literature for the les etouaires deposit which is incompatible with other documented ages of lower and middle villafranchian deposits we consider the galerian phase to be equivalent to the entire middle pleistocene and we propose a chronostratigraphical subdivision

terrestrial carbon isotope records from coastal deposits algarve portugal a tool for chemostratigraphic correlation on an intrabasinal and global scale the carbon isotope signature of terrestrial organic matter om offers a valuable tool to develop stratigraphic correlations for near shore deposits a mid cretaceous coastal succession of the western algarve basin portugal displays a marked negative 13c excursion ranging from 21 2 to 27 8 in the early aptian followed by two shifts towards higher values up to 19 3 during the early and late aptian respectively the dominance of cuticle and leaf debris in the bulk om fraction is confirmed by optical studies rock eval pyrolysis and by comparison with the 13c signature of four different types of fossilized land plant particles correlation of two terrestrial 13cbulk om records from different study sites leads to a significant enhancement of the intrabasinal stratigraphic correlation within the algarve basin three prominent excursions in the portuguese records can be correlated with existing 13c curves from pelagic and terrestrial environments the general carbon isotope pattern is superimposed by small scale fluctuations which can be explained by compositional variations within the om

modelling the younger dryas abstract an energy balance climate model ebcm having land sea surface air and latitudinal resolution and which simulates the seasonal growth and decay of sea ice in terms of a number of explicit physical processes is used to test the following hypotheses for the cause of the younger dryas cold episode 1 a low salinity meltwater lens from ablation of continental ice sheets which would have increased the freezing point and stability of the oceanic mixed layer thereby allowing more extensive sea ice 2 a flood of icebergs into the north atlantic from collapse of continental ice sheets or of a hypothetical arctic ocean ice shelf 3 a reduction or cessation in the rate of formation of north atlantic deep water nadw which would have led to a reduction in the northward oceanic heat flux in the north atlantic ocean and 4 a reduction in atmospheric co 2 concentration a low salinity meltwater lens leads to zonally averaged atmospheric cooling over land of up to 2 5 c in winter but warming of up to 1 5 c in summer temperature effects outside the latitudes of hypothesized low salinity meltwater are negligible an iceberg flood covering 30 of the ocean between latitudes 45 and 70 n causes a winter atmospheric cooling over land of up to 8 c and a summer cooling of up to 4 c in the northern hemisphere but maximum winter cooling at high southern hemisphere latitudes of only 1 3 c if the icebergs are initially 100 m thick and allowed to ablate without replenishment then the icebergs completely disappear in only 20 50 years and negligible temperature response occurs in the southern hemisphere a reduction in the northward meridional oceanic heat flux by 0 6 10 15 w at 45 n leads to maximum winter and summer atmospheric coolings over land of 5 6 c and 1 2 c respectively at high latitudes in the northern hemisphere but a warming at low latitudes and in the southern hemisphere however a reduction in the rate of nadw formation would also lead to a reduction in the upward heat flux at the base of the mixed layer at high latitudes in the southern hemisphere this is a parameter of the model used here and reducing its value by 20 causes a mean annual temperature cooling of up to 3 3 c in the southern hemisphere a co 2 decrease from 300 ppmv to 250 ppmv causes a global mean cooling of about 0 7 c and maximum mean annual atmospheric temperature responses of about 1 c in both hemispheres with greater response in winter this study identifies a number of specific types of paleoclimatic data which can help in discriminating among different hypothesized causes of the younger dryas in particular a seasonal patterns of temperature change b differences between high and low latitude and between northern hemisphere and southern hemisphere temperature changes as well as regional patterns of climatic change c phase lags of temperature change between different regions and d a more precise determination of the duration of the younger dryas in various localities

glacial evolution of the plio pleistocene role of continental and arctic ocean ice sheets abstract an empirical method is developed for assessing long term trends in the growth of both mid latitude northern hemisphere continental and high latitude arctic ocean ice sheets during the last 5 million years the growth of arctic ocean ice sheets is assumed to be modulated principally by caloric insolation variations related to obliquity while variations in the extent of northern hemisphere continental ice sheets are controlled by precession dominated caloric insolation variations in developing empirical equations for the tendency of arctic ocean ice sheet growth a and the tendency for continental ice sheet growth c we have also assumed that there would be strong feedback effects between the two ice masses contingent upon north atlantic surface water heat transport a clear correspondence between high a values and cold paleotemperatures recorded in north atlantic deep sea cores spanning the last 2 0 m y is taken as evidence of a long term linkage with the north atlantic alternatively strong similarities were found to exist between the predicted record of c and the classical terrestrial glacial interglacial record back to about 3 2 m y b p a marked coincidence was also found between the combined tendency of continental and arctic ocean ice sheet growth a c with the deep sea 18o record a dramatic increase in the amplitude and period of 18o variations beginning at about 1 0 m y b p is reflected by a sharp increase in the number of a c values greater than the long term mean phase relationships between the earth s orbital parameters and north atlantic sea surface temperatures have apparently played a major role in the terrestrial and marine glacioclimatic records for at least the last 3 2 million years

correlation of aptian albian carbon isotope excursions in continental strata of the cretaceous foreland basin eastern utah u s a abstract nodular carbonates calcretes in continental foreland basin strata of the early cretaceous cedar mountain formation cmf in eastern utah yield 13c and 18o records of changes in the exogenic carbon cycle related to oceanic anoxic events oaes and terrestrial paleoclimate chemostratigraphic profiles of both forebulge and foredeep sections show two prominent positive 13c excursions each with a peak value of 3 0 vpdb and having background 13c values of about 6 0 vpdb these excursions correlate with the global early aptian ap7 and late aptian early albian ap12 al1 carbon isotope excursions aptian albian positive 13c excursions in the cmf also correspond to 3 4 per mil increases in carbonate 18o these phenomena record local aridification events the chemostratigraphic profile on the thinner forebulge section of the cmf is calibrated for the first time by a radiogenic u pb date of 119 4 2 6 ma on a carbonate bed and by detrital zircon u pb dates on two bounding sandstone units maximum depositional ages of 146 ma and 112 ma petrographic observations and diagenetic analyses of micritic to microsparitic carbonates from nodules indicate palustrine origins and demonstrate that they crystallized in shallow early meteoric phreatic environments meteoric calcite lines derived from cmf carbonates have 18o values ranging between 8 1 to 7 5 0 vpdb supporting an estimate of zonal mean groundwater 18o of 6 0 vsmow for an aptian albian paleolatitude of 34 n furthermore our two chemostratigraphic profiles exhibit a generally proportionate thinning of correlative strata from the foredeep on to the forebulge suggesting that there were consistently lower rates of accumulation on the forebulge during the aptian albian identification of the global aptian albian 13c excursions in purely continental strata as demonstrated in this paper opens a new avenue of research by identifying specific stratigraphic intervals that record the terrestrial paleoclimatic impacts of perturbations of the global carbon cycle

out of our depth on the impossibility of fathoming eustasy from the stratigraphic record the evolution of a sedimentary basin s gross morphology depends upon 1 basement movement 2 sediment accumulation and compaction and 3 variations of eustasy with time thus if an accurate history of eustasy could be derived it would aid in our understanding of basin stratigraphy and help in the prediction of sediment geometry from described areas techniques which attempt to determine the magnitude of eustatic sea level excursions include the measurement of 1 the amount of sedimentary onlap onto the continental margins with and without the use of hypsometric curves 2 the thickness of marine sedimentary cycles and the elevation and distance between indicators of old strandlines 3 the perturbations on individual thermo tectonic subsidence curves and stacked crustal subsidence curves 4 the variations in deep ocean oxygen isotopes found in sediments and 5 the size of variables used in graphical and numerical simulations of basin fill in terms of tectonic behavior rates of sediment accumulation and eustasy which invert the problem to date a combination of the use of relative sea level charts derived from sediment onlap of the continental margin with dimensioning by oxygen isotopes responding to glacial events offers the best potential for relative tectono eustatic sea level curves but even this method can not produce a unique solution for absolute eustatic variations mathematical modelling shows that at best it is possible to obtain only the sum of tectonic basement subsidence and sea level variations from the above methods and at worst not even that simple a combination thus every proposed scheme to measure eustatic sea level excursions assumes some behavior for two of the three underlying processes tectonic movement of the basement sedimentary accumulation and eustatic sea level each scheme then determines the third process relative to the assumed model behavior of the other two it would seem that like king canute we cannot command the sea though we can still use undifferentiated relative tectono eustatic sea level curves to generate a family of solutions which are the product of a variety of absolute sea level curves and tectonic models each solution has then to be assessed in terms of geologic setting and the hypotheses it generates

low latitude 2 day planetary wave impact on austral polar mesopause temperatures revealed by a january diminution in pmse above davis antarctica 1 a new characteristic of the austral summer polar mesopause as revealed by ground based radar and satellite temperature measurements is reported that is linked to inter annual variability of the low latitude easterly wind jet four consecutive seasons of polar mesosphere summer echoes pmse and mesosphere temperature observations above davis antarctica 68 6 s show a mid january diminution in pmse occurrence rate that coincides with a minor mesopause warming of several degrees spectral analyses of pmse aura microwave limb sounder mls temperatures and radar meridional winds show the presence of 4 5 day planetary waves pws throughout the austral summer in the polar upper mesosphere together with enhanced 2 day pw activity from mid january to mid february analysis of mls temperatures show that the 2 day pws have zonal wavenumbers s with both westward s 2 3 and eastward s 2 3 components although displaying some inter annual variation in the peak onset time the mid january mesopause warming coincides with a weakening of the equatorward meridional wind above davis and enhancement of low latitude 2 day pw activity

statistics of antarctic mesospheric echoes observed with the superdarn syowa radar 1 an oblique sounding coherent hf radar of the superdarn super dual auroral radar network at about 11 mhz sometimes receives peculiar backscatter returns which are suspected as polar mesosphere summer echoes pmse from ranges very close to the radar site to disclose their statistical features we looked for such echoes that were observed under quiet geomagnetic conditions during 46 months from 1997 until 2000 with the superdarn radar at syowa station antarctica 69 0 s 38 6 e with some strict criteria for echo selection we identified 22 events in summer months and 2 events in august and september their distinct seasonal variation evidences that these near range echoes in summer months are indeed the antarctic pmse origin of the two spring echoes is not clear at the moment the occurrence probability of the summer echoes seems to increase with year we however need more data accumulation to confirm this trend these results indicate that the superdarn radars can be used to routinely monitor the activity of pmse in a wide area of the polar mesosphere in both hemispheres

polar mesosphere summer echoes at wasa antarctica 73 s first observations and comparison with 68 n 1 polar mesosphere summer echoes pmse have been observed for the first time at wasa antarctica 73 s 13 w 61 geomagnetic a new 54 5 mhz radar mara operated first in kiruna 68 n during late summer 2006 and then at wasa between 18 january and 5 february 2007 operation in kiruna allowed accurate cross calibration with the permanent 52 mhz radar esrad pmse at 73 s are found to have very similar characteristics to pmse at 68 n when observations from the same part of the summer season are compared volume reflectivities show very similar distributions over different intensities over height and over local time pmse at 68 n 65 geomagnetic are stronger in the midnight sector likely due to the different geomagnetic latitudes above 85 km altitude weak pmse have a higher occurrence rate at 73 s the height of peak pmse occurrence is 1 km higher at 73 s compared to 68 n

extraction of polar mesosphere summer echoes from superdarn data 1 an algorithm for automated extraction of polar mesosphere summer echoes pmse from near range measurements of the super dual auroral radar network superdarn is applied to observations obtained by the syowa east 69 01 s 38 61 e and iceland east 63 77 n 20 54 w radars whose fields of view are magnetically conjugate the rate of pmse occurrence in the superdarn data is greatly enhanced in summer months reaching a maximum of 90 in iceland and 60 in syowa near the summer solstice the diurnal variation of pmse occurrence reaches a maximum near the noon meridian with a distinct minimum at 20lt these features are consistent with those derived from previous vhf radar observations suggesting that the superdarn data contain large numbers of pmse events the interhemispheric asymmetry of pmse occurrence is also estimated and it is shown that the pmse activity is 1 5 times higher in the northern hemisphere n h than in the southern hemisphere s h thus interhemispheric asymmetry in pmse occurrence appears to exist but is much weaker than that predicted previously based on vhf radar observations

polar mesosphere summer echoes pmse at halley 76 s 27 w antarctica 1 polar mesosphere summer echoes pmse are a pointer to summer mesospheric conditions and have fuelled the debate over temperature differences between the antarctic and arctic mesopause regions however few pmse observations have ever been made in antarctica we present initial pmse observations from halley 76 s 27 w taken during january and february 2004 these are the first observations at such high southern latitude the first using a dynasonde for detection and the first at 28 mhz pmse are frequently observed and exhibit a double maximum in diurnal occurrence in contrast to published observations at similar arctic latitudes the pmse season ends slightly earlier relative to summer solstice than in the arctic the strength of the pmse appear similar to pmse observed in the northern hemisphere this is consistent with published falling sphere measurements showing similar summer mesopause temperatures in january in the antarctic as in july in the arctic

carbon isotope analysis of fossil wood and dispersed organic matter from the terrestrial wealden facies of hautrage mons basin belgium pedogenic nodules calcitic shells dispersed organic carbon and bulk rocks affected by low diagenesis are judged to be reliable tools for carbon isotope chemostratigraphy up to now no systematic study has been carried out to check the reliability of fossil wood material for carbon isotope chemostratigraphy in terrestrial settings the 235 m thick wealden facies sediments of the danube bouchon quarry at hautrage hautrage clays formation mons basin belgium encompass dark to grey clays and sands rich in organic matter and coalified charcoalified fragments of fossil wood deposited in an alluvial plain during middle barremian to earliest aptian we measured and compared the carbon isotope ratios of 110 levels of the stratigraphic succession for dispersed organic carbon delta c 13 doc and fossil wood delta c 13 wood collected in the same geological level in the whole succession the averages of delta c 13 doc and delta c 13 wood have a significant difference of about 0 9 the delta c 13 wood is usually heavier than the delta c 13 doc which is consistent with measurements on different constituents of modern trees branches versus leaves and tissues in one single stratigraphic level the variability of delta c 13 wood is much higher up to 7 3 parts per thousand than that of delta c 13 doc 0 4 parts per thousand four main causes may explain these results firstly the delta c 13 doc averages the isotopic signal of different compounds and tissues such as leaves seeds cuticles as they become mixed and dispersed the delta c 13 wood reflects the carbon isotope ratio of a small part only of one single tree which is a complex system with delta c 13 variations over a range of 4 parts per thousand secondly there is strong delta c 13 variability between different species of plants in hautrage several gymnosperm genera were collected including podocarpoxylon taxodioxylon brachyoxylon and thujoxylon and numerous fern taxa thirdly coalification and charcoalification can affect the delta c 13 of the doc and the various kinds of woods in a different way fourthly the wood fragments may be reworked several times from more ancient geological levels especially in the alluvial plain environment of hautrage where thick levels of fluviatile coarse sand deposits are observed however in the whole succession both delta c 13 wood and delta c 13 doc curves show similar trends this suggests that carbon isotope curves on fossil wood can be matched to carbon isotope curves on doc for the whole trend fossil wood is a relatively good chemostratigraphic tool when sufficient samples are measured in the succession whenever possible both control of the wood taxa and estimation of degree of char coalification are however recommended in one single level charcoal has more stable delta c 13 wood values than delta c 13 wood of coalified fragments the delta c 13 positive trend can be due to several causes including global pco 2 variations and or regional changes and or local environmental conditions in the alluvial plain if global the dating of the hautrage succession may be refined to the late early barremian early late barremian by matching palynological and carbon isotope chemostratigraphical data c 010 elsevier b v all rights reserved

long term mean aspect sensitivity of pmse determined from poker flat mst radar data results of a long term study of aspect sensitivity of polar mesosphere summer echoes pmse are presented using archived poker flat mst radar 65 08 n 147 27 w data we have used data from the pmse region 80 to 90 km during the months of june and july for the years 1981 84 when three antenna beams were available one beam pointing vertical and two beams pointing 15 off vertical comparisons of calibrated vertical and 15 off vertical monthly average echo power profiles for each of the summer months show that vhf scattering from pmse is strongly aspect sensitive at the lowest heights 80 km and exhibits a clear decrease of aspect sensitivity with increasing height comparison of monthly average aspect sensitivity profiles during the four year period shows a reasonable consistency throughout the years the composite four year average aspect sensitivity profile for the months of june and july data suggests a strong tendency to isotropy at the higher mesospheric heights

on the occurrence of polar mesosphere summer echoes polar mesospheric summer echoes pmse have become a well known characteristic of radar backscatter from the summer mesopause regions in polar regions the phenomenon has been observed at frequencies from 50 mhz to almost 1 ghz in this paper we attempt to identify a space time manifold for the occurrence of pmse the resulting manifold defined only by temperature agrees well with observations and furthermore indicates when and where we might expect to observe pmse in the future

vhf radar echoes observed in the summer and winter polar mesosphere over andoya norway the mobile sousy vhf 53 5 mhz radar has been operated on a campaign basis on the island of andoya in northern norway 69 17 n 16 01 e with the aim of investigating the backseattering structures and dynamics of the polar middle atmosphere since november 1983 during winter the occurrence of mesospheric echoes at altitudes from 50 to 90 km is strongly correlated with radio wave absorption events measured with a riometer on 32 5 mhz individual structures are observed for up to 8 hours and in general appear as thin layers separated by 3 5 km with typical maximum signal to noise ratios snrs of 5 25 db many of these are related to variations in the background wind produced by long period gravity waves and tidal period motions and in as much are similar to mesospheric layers at middle and low latitudes in summer the echo region is largely restricted to a height interval from 75 to 95 km with 80 of the echoes occurring in the 80 to 93 km height range and on average it has a distinct maximum in snr near 86 km in the 83 to 91 km height region echoes are detected almost continuously with a minimum occurrence rate of 85 there is a low correlation 0 26 between echo strength and absorption many of the weaker echoing regions those with snrs up to 30 db are related to the background wind shear spectral analysis of time series of both snr and zonal velocity for a period of 9 days reveals 54 24 12 and 8 hour components with the 12 hour component dominating strong bursts in backscattered power tend to occur in the late afternoon and early morning hours so they coincide with the time of maximum westward velocity of the semidiurnal tide this suggests that the bursts are due to an increase in the turbulent intensity produced by dynamical instability of this mode layers consistent with dynamically unstable upward propagating inertio gravity waves are also often observed to move down through the 93 to 80 km height range thus dynamical instability of the semidiurnal tide and long period gravity waves appears to play a major role in determining much of the structure observed in the backscatter region however the strongest summer polar mesopause echoes those with peak snrs greater than 30 db while showing modulation due to the background winds often show no clear relation to the background wind shear this supports the view that the production mechanism of the very strong snrs associated with this layer is different in character from that of winter echoes observed in the polar mesosphere by vhf radars and to those mesospheric layers observed at mid latitudes using the same technique

frequency spectra and vertical profiles of wind fluctuations in the summer antarctic mesosphere revealed by mst radar observations continuous observations of polar mesosphere summer echoes at heights from 81 93 km were performed using the first mesosphere stratosphere troposphere incoherent scatter radar in the antarctic over the three summer periods of 2013 2014 2014 2015 and 2015 2016 power spectra of horizontal and vertical wind fluctuations and momentum flux spectra in a wide frequency range from 8 min 1 to 20 days 1 were first estimated for the antarctic summer mesosphere the horizontal vertical wind power spectra obey a power law with an exponent of approximately 2 1 at frequencies higher than the inertial frequency of 13 h 1 and have isolated peaks at about 1 day and a half day in addition an isolated peak of a quasi 2 day period is observed in the horizontal wind spectra but is absent from the vertical wind spectra which is consistent with the characteristics of a normal mode rossby gravity wave zonal meridional momentum flux spectra are mainly positive negative and large fluxes are observed in a relatively low frequency range from 1 day 1 to 1 h 1 a case study was performed to investigate vertical profiles of momentum fluxes associated with gravity waves and time mean winds on and around 3 january 2015 when a minor stratospheric warming occurred in the northern hemisphere a significant momentum flux convergence corresponding to an eastward acceleration of 200 m s 1 d 1 was observed before the warming and became stronger after the warming when mean zonal wind weakened the strong wave forcing roughly accorded with the coriolis force of mean meridional winds

on the lack of southern hemisphere polar mesosphere summer echoes we report vhf radar observations of the southern high latitude mesopause region using wind profilers that were installed recently on king george island antarctica and ushuaia argentina briefly our observations which were made during january and february 1993 show almost no evidence of so called polar mesosphere summer echoes or pmse since these echoes are a predominant feature of the northern high latitude mesosphere in summer their absence in the southern hemisphere is both surprising and intriguing in this paper we present evidence demonstrating the virtual absence of the echoes and demonstrate that our systems were capable of detecting them had they been present we also outline some of the consequences of this intriguing result which are supported by observed hemispheric differences in polar mesospheric clouds mesospheric temperatures upper atmospheric gravity wave activity and mean circulation patterns

the upper valanginian early cretaceous positive carbon isotope event recorded in terrestrial plants our understanding of the ancient ocean atmosphere system has focused on oceanic proxies however the study of terrestrial proxies is equally necessary to constrain our understanding of ancient climates and linkages between the terrestrial and oceanic carbon reservoirs we have analyzed carbon isotope ratios from fossil plant material through the valanginian and lower hauterivian from a shallow marine ammonite constrained succession in the crimean peninsula of the southern ukraine in order to determine if the upper valanginian positive carbon isotope excursion is expressed in the atmosphere d 13 cplant values fluctuate around 23x to 22x for the valanginian hauterivian except during the upper valanginian where d 13 cplant values record a positive excursion to 18x based upon ammonite biostratigraphy from crimea and in conjunction with a composite tethyan marine d 13 ccarb curve several conclusions can be drawn 1 the d 13 cplant record indicates that the atmospheric carbon reservoir was affected 2 the defined ammonite correlations between europe and crimea are synchronous and 3 a change in photosynthetic carbon isotope fractionation caused by a decrease in atmospheric pco2 occurred during the upper valanginian positive d 13 c excursion our new data combined with other paleoenvironmental and paleoclimatic information indicate that the upper valanginian was a cool period icehouse and highlights that the cretaceous period was interrupted by periods of cooling and was not an equable climate as previously thought d 2005 elsevier b v all rights reserved

evidence for a diachronous late permian marine crisis from the canadian arctic region a high resolution chemostratigraphic study of a 24 m thick section at west blind fiord on ellesmere island canadian arctic documents stepwise environmental deterioration in the marine sverdrup basin during the late changhsingian late late permian as a result of volcanic disturbances to surrounding landmasses a horizon within the upper lindstrom formation datum a is characterized by increased fe oxyhydroxide fl uxes and weathering intensity as well as modest shifts toward more reducing watermass conditions and higher marine productivity recording an initial disturbance that washed soils into the marine environment the contact between chert of the lindstrom formation and silty shale of the overlying blind fiord formation which is 1 6 m higher and 50 k y younger than datum a records a large increase in detrital sediment fl ux more strongly enhanced marine productivity and a regional extinction of siliceous sponges herein termed the arctic extinction event the horizon equivalent to the latest permian mass extinction of tethyan shallow marine sections is 5 6 m higher and 100 k y younger than the arctic extinction event demonstrating the diachronous nature of the marine biotic and environmental crisis at a global scale it is associated with intensifi ed anoxia and possible changes in phytoplankton community composition in the study section marine environmental deterioration in the sverdrup basin probably triggered by terrestrial ecosystem deterioration and elevated detrital sediment fl uxes was under way by the early part of the late changhsingian well before the onset of main stage siberian traps fl ood basalt volcanism the event sequence at west blind fiord may record the deleterious effects of early stage explosive silicic eruptions that affected the boreal region possibly through deposition of toxic gas and ash within a restricted latitudinal band while having little impact on marine ecosystems in the peri equatorial tethyan region