interannual enso and interdecadal enso like variability in the southern hemisphere tropospheric circulation abstract recent work has identified variability in the pacific ocean sst with a structure qualitatively similar to enso but at lower frequencies than enso zhang et al have documented the atmospheric circulation anomalies in the tropics and northern hemisphere that are associated with decadal enso like variability and compared these anomalies to those associated with the interannual enso cycle here the authors extend the study of zhang et al to the southern hemisphere using the national centers for environmental prediction national center for atmospheric research reanalysis data for 1958 96 consistent with previous studies the southern hemisphere circulation anomalies associated with enso display a teleconnection pattern from the central tropical pacific into the far southeastern pacific ocean comparatively larger circulation anomalies are found in the southern hemisphere associated with the decadal enso like variability though aloft the structure of the anomalies emphasizes the polar vortex wit

quasi steady state a real behaviour discussion discussions 191 in discussing the quasi steady state behaviour of sand under undrained condition a distinction should be made on whether the tests are conducted under load controlled or deformation controlled loading conditions if it is loadcontrolled as used in the authors experiments instability in the form of a runaway deformation will occur once the deviator stress exceeds its peak value as shown in fig 4b of the discussed paper in fig 4b the axial strain increased from 2 to about 15 in less than 2 s this process is accompanied by a sudden increase in pore water pressure also shown in fig 4b by any engineering standard the soil has failed in a catastrophic way this instability behaviour is un likely to be affected by whether the end platen is lubricated or not as the axial strain at which instability occurs is nor mally small e g 2 in the test shown in fig 4b after the occurrence of instability the deviator stress tends to increase with further deformation as shown in figs 4a and 4c this behaviour is defined as quasi steady state the discusser wonders whether it is still meaningful to study this quasi steady behaviour as an element behaviour as severe non homogenous deformation in the forms of distortion bulging etc normally will occur after the axial strain has suddenly increased to a large strain in addition to fig 4b another example is shown in fig 5 of the discussed paper the axial strain has increased to 27 in less than 2 s in this test a more visualized example was given by peters 1991 in which the development of non homogeneous deformation during instability is shown by a series of photographs a similar pattern of non homogenous deformation was observed by castro 1969 chu 1991 and lee 1997 after instability had occurred considerable bulging was also observed by the authors for their tests on medium loose sand dr c 31 4 as shown in fig 11 of the discussed paper as considerable non homogenous deformation has occurred

eolian dune interdune sand sheet and siliciclastic sabkha sediments of an offshore prograding sand sea dhahran area saudi arabia an offshore prograding sand sea exists along portions of the arabian gulf coastline near dhahran saudi arabia in this region sediments of eolian dune interdune sand sheet and siliciclastic sabkha intercalate with marine deposits this depositional setting is characterized by strong offshore winds which supply abundant sand to the coastline and cause at present time the outbuilding of the dune system this quartz detrital dominant setting contrasts markedly with the carbonate dominant setting resulting from onshore winds in the trucial coast area to the south the broad intercalation of eolian and marine deposits which results creates ideal potential for subregional stratigraphic petroleum traps due to pinch out of porous and permeable dune sands into impermeable m rine mudstones within the eolian system itself are potential reservoir rocks dunes sources organic rich sabkha and interdune deposits and seals zones of early cementation in all deposits early cementation is very common in all facies of the eolian sand sea the early cementation occurs owing to 1 soil formation 2 deposition of pore filling gypsiferous cements from saturated solutions near water table and 3 addition of sand size windblown evaporitic material to sands downwind of sabkhas

tectono sedimentary characteristics of late miocene quaternary extensional basins of the northern apennines italy abstract extensional and compressional regimes exist at the same time in adjacent parts of the northern apennines italy and the former regime succeeded the latter at the same place as the thrust mountain front moved eastward since miocene times numerous extensional basins have developed west of the present mountain divide the westernmost ones formed over attenuated continental crust since late miocene and have been subjected to several subsidence and uplift events with rates of subsidence generally faster than rates of sedimentation they contain continental deposits overlain by gypsum bearing upper miocene marine sequences and siliciclastic marine pliocene deposits these basins were affected by shallow magmatism and are still experiencing high geothermal gradient and late to post magmatic activities such as in the renowned thermal region of larderello to the east closer to the present mountain divide the extensional basins formed later from pliocene to quaternary contain continental fluvial and lacustrine deposits and have not experienced near surface magmatic activities the sedimentary fill architecture of the apennine extensional basins is similar to that of other european american and african extensional or transtensional systems for instance a common characteristic is the prevalence of large alluvial fan deposits at the hanging wall shoulder of half grabens coarser smaller alluvial fans at the footwall shoulder and some fluvial deposits introduced longitudinally unlike the african rifts though the sedimentary facies distribution of extensional basins which developed in active orogenic zones such as in the apennines may be strongly affected by uplifting steep mountain slopes and can have large thick coarse alluvial fans also on the footwall side of the half grabens

observations of ekman currents in the southern ocean abstract largely zonal winds in the southern ocean drive an equatorward ekman transport that constitutes the shallowest limb of the meridional overturning circulation of the antarctic circumpolar current acc despite its importance there have been no direct observations of the open ocean ekman balance in the southern ocean until now using high resolution repeat observations of upper ocean velocity in drake passage a mean ekman spiral is resolved and ekman transport is computed the mean ekman currents decay in amplitude and rotate anticyclonically with depth penetrating to 100 m depth above the base of the annual mean mixed layer at 120 m the rotation depth scale exceeds the e folding scale of the speed by about a factor of 3 resulting in a current spiral that is compressed relative to predictions from ekman theory transport estimated from the observed currents is mostly equatorward and in good agreement with the ekman transport computed from four different gridded wind products the mean tempe

climatic and tectonic signature in the fluvial infill of a late pliocene valley siena basin northern apennines italy abstract incised valleys entirely filled with fluvial deposits are rarely described in the literature and even rarer are accounts of incised valleys whose filling is not driven by relative sea level changes valleys of this type have not been widely recognized in the stratigraphic record because they are likely to occur in areas undergoing intense erosion or to be encased within alluvial deposits with no strong lithologic contrast in this paper an upper pliocene fluvial valley fill encased within shallow marine middle pliocene deposits and pre neogene bedrock eastern siena basin northern apennines italy and accumulated in response to tectonics and climate changes is described the recognition of this fluvial body up to 40 m thick in an incised valley setting is based on its overall geometry lithofacies characteristics gravel composition and fossil content upvalley fill is represented by amalgamated gravels emplaced by heavily sediment laden flows whereas downvalley fill shows a more organized depositional style and consists of two fining upward successions notable is the presence at the top of the lower succession of decameter thick floodplain fines which extend from one valley wall to another and have no fine grained correlatives in the upvalley fill valley incision resulted from a drop in relative sea level arising from late middle pliocene regional uplift stratigraphic and paleontological data constrain valley filling to the late pliocene early pleistocene time span such a filling stemmed from an increase in sediment supply which resulted from the interplay between uplift of the chianti ridge and a climatic change toward humid conditions as recorded in the coeval strata of the adjacent valdarno basin beyond the regional significance an important implication of the case study is that the incision and filling factors need not be genetically related moreover the stratigraphic architecture of the studied fluvial fill is discussed in terms of the relations between sediment supply and sediment storage en route from the source area to the depositional site and their association with tectonic movements specifically the valley wide floodplain fines are thought to record the response of the fluvial system to a tectonic rejuvenation of catchments which modified the valley gradient and promoted upstream gravel storage whereas the overlying gravels manifest the reestablishment of a new equilibrium river profile

contributions of wind forcing waves and surface heating to sea surface height observations in the pacific ocean the dominant processes affecting sea surface height ssh variability observed by the topex poseidon altimeter vary regionally in the pacific baroclinic rossby waves equatorially trapped kelvin waves steric response to seasonal heating and the response to wind stress curl forcing are all important the steric response to surface heating dominates seasonal ssh variability in the subpolar gyre and the eastern subtropical gyre south of the kuroshio extension and south of 20 n in the eastern pacific the dominant contribution to ssh is from near annual period rossby waves to quantify the wave energy observed ssh was assimilated into a kinematic model of westward propagating waves these waves account for 70 of ssh variance between 10 s and 10 n but only 30 between 10 n and 30 n although wave energy in the eastern pacific is correlated with ssh anomalies at the equator the much larger wave energy in the western pacific is correlated with wind stress curl suggesting that the rossby waves there are locally forced in addition to these planetary waves the ocean response to wind forcing via ekman pumping is observed in several places specifically in the north equatorial current a quasi steady topographic sverdrup balance is detectable over most of the north pacific at latitudes as low as 10 15 n as well as in the south pacific where it is seen north of 50 s the decomposition of the ssh signal into propagating waves an ekman pumping response and sverdrup transport is consistent with the results from an isopycnal numerical model

zonally asymmetric response of the southern ocean mixed layer depth to the southern annular mode interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface the depth of this layer is determined by wind forcing and heating from the atmosphere variations in mixed layer depth affect the rate of exchange between the atmosphere and deeper ocean the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton however the response of the southern ocean mixed layer to changes in the atmosphere is not well known here we analyse temperature and salinity data from argo profiling floats to show that the southern annular mode sam the dominant mode of atmospheric variability in the southern hemisphere leads to large scale anomalies in mixed layer depth that are zonally asymmetric from a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the sam from zonal symmetry cause anomalies in heat flux that can in turn explain the observed changes of mixed layer depth and sea surface temperature our results suggest that changes in the sam including recent and projected trends attributed to human activity drive variations in southern ocean mixed layer depth with consequences for air sea exchange ocean sequestration of heat and carbon and biological productivity

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

paleoenvironmental evolution of the late pliocene early pleistocene fluvio deltaic sequence of the denizli basin sw turkey abstract the late pliocene early pleistocene tosunlar succession denizli basin southwestern turkey represents fluvial dominated delta environments at the margins of a brackish long lived lake two main facies associations are documented i a delta front facies association with a distal df1 and proximal df2 deposits and ii a delta plain facies association that contains distributary channel dp1 and interdistributary swamp dp2 deposits the stable isotopic analysis of the mollusc faunas exhibit a narrow range of values 4 68 18 o 13 c 18 o 13 c correlation r 0 16 may indicate hydrologically open lake and significant diagenetic alteration the mollusc faunas and their stable isotope ratios show a biogeographically isolated brackish lake system under semiarid climatic conditions under special environmental conditions the endemic faunal composition remained constant which is very unusual for a semi isolated long lived lake setting

sequential architecture and cyclicity in permian desert deposits brodick beds arran scotland this study of ancient desert deposits permian brodick beds tests the possibility that cyclicityin these interbedded aeolian fluvial and lacustrine deposits was orbitally controlled the 740 m thicksuccession of desert deposits forms one sequence which can be divided into three genetic units a majordeflation surface forms the basal sequence boundary and represents a drop in base level groundwatertable on top of the sequence boundary are rather uniform aeolian dune and sand sheet sediments unit1 formed in an erg during low base level with increasing rates of base level rise they are followed byinterbedded aeolian dune aeolian sand sheet and flood reworked aeolian sediments unit 2 representingerg margin deposits formed during increasing rates of base level rise the uppermost part of the sequenceis composed of gravel sheets unit 3 representing alluvial fan deposition during a high base level withdecreasing rates of base level rise the succession is cyclic and spectral analysis of sedimentary andgeochemical parameters reveal cycles with a thickness of 25 7 29 3 m 34 5 m and 64 5 m and fieldworkreveals cycles of 155 m and 675 m these sedimentary cycles are thought to reflect climatic oscillations the lack of detailed time control makes it diffcult to link these climatic fluctuations to orbital cycles although the detected cyclicity matches well with milankovitch theory

hoanib river flood deposits of namib desert interdunes asanalogues for thin permeability barrier mudstone layers inaeolianite reservoirs abstract the ephemeral braided hoanib river of nw namibia ows for a few days ayear and only high discharges enable the river to pass through interdunaldepressions within the northern namib desert dune eld to the atlantic thedune eld comprises mainly large transverse dunes resulting frompredominant ssw winds river ood deposits between aeolian dunes areanalogous to mudstone layers conformably interbedded with ancientaeolianite dune foresets deep oods pond laterally to considerable depths metres to 10 m in adjacent interdunes depositing mud layers 1 50 cm toconsiderable heights on avalanche and stoss faces of bounding dunes fairlypassive ooding only disturbs aeolian strati cation minimally floodwaterclay in ltrates and settles as an impermeable seal with a ood pond on top perched above regional groundwater flood ponds evaporate slowly for longperiods 3 years early emergence desiccates higher parts of a mud layer subsequent oods can re ll a predecessor pond bene ting from the existingimpervious seal potential preservation of such mud layers is lower on thestoss face but high on the avalanche face after burial by subsequent dunereactivation and migration the leeward right hoanib bank a dune stoss face is river and wind eroded to exhume fossil interdune pond mud layers of anearlier hoanib channel the highly inclined layers are interbedded with duneavalanche foresets and represent the edges of two successive fossil pondsexposed in plan ancient ood pond mudstones occur in the permian triassichydrocarbon reservoir the sherwood sandstone group of the cheshire basin kinnerton formation and irish sea basin and were previously usederroneously to argue against the aeolian origin of cross bed sets hoanibstudies show that primary river interaction with a dune eld might preserveonly localized erosional omission surfaces in ancient aeolianites with littlesandy barform preservation prone to aeolian reworking around the main uvial channel locus however ood pond mudstone layers should form apredictable halo within which uid permeability will decrease keywords aeolian dunes aeolianite reservoir ash ood interdune namibdesert namibia permeability introductionhigh discharge oods of the hoanib river occa sionally break through the skeleton coast dune eld which forms part of the extensive namibdesert that parallels the western margin of thesouthern african subcontinent this arid regionis 140 km wide and over 2000 km long fromsouth western angola to the northern capeprovince south africa the northern namib dune eld termed the skeleton coast dune eld bywilson 1973 lancaster 1982 and ward sedimentology 2002 49 719 736

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

climate and biomes in the west mediterranean area during the pliocene a new pollen derived method of climatic quantification based on the mutual climatic range of plant taxa has been applied to 17 pliocene pollen sequences in the west mediterranean area the latitudinal gradient observed in the pollen data was confirmed by the climatic reconstructions there is a gradient from north to south both for temperatures and precipitation at the beginning of the pliocene 5 32 5 ma the climate in the north mediterranean area was on average warmer and more humid than today respectively 1 4oc and 400 700 mm in the south mediterranean region the climate was both warmer and drier than today respectively equal to or 5oc higher and drier or equal humidity the pollen based climate estimates were then used to reconstruct biomes for the region the results show the occurrence of three biomes the broad leaved evergreen warm mixed forest the xerophytic woods scrub biome and the warm grass shrub biome these biomes are still represented today in the mediterranean region despite different thermic and water conditions

40ar 39ar dating of latest pleistocene 41 ka marine tephra in the mediterranean sea implications for global climate records abstract fifty one 40 ar 39 ar laser heating analyses of sanidine crystals in the c 13 tephra layer recovered out of a piston core raised from 3000 m depth in the tyrrhenian sea yielded apparent ages between 25 and 112 ka twenty four of these measurements define an age probability maximum and generate an isochron of 41 1 2 1 ka 2 with a 40 ar 36 ar intercept of 288 21 that is indistinguishable from the modern atmosphere however the entire population is skewed toward older apparent ages with smaller peaks at 48 ka 55 ka 67 ka and 110 ka the composition of glass shards in the c 13 tephra overlaps that of the sio 2 rich phase of the 150 km 3 campanian ignimbrite which erupted from the campi flegrei caldera 130 km northwest of the core site although the 41 1 2 1 ka isochron is 15 older than k ar and 14 c ages for the campanian ignimbrite it is indistinguishable from recent 40 ar 39 ar age determinations the campanian ignimbrite eruptions were also chemically similar to and correlated with the y 5 ash layer the most voluminous and widely dispersed late pleistocene tephra in the mediterranean region the age of the y 5 layer was constrained originally at 38 0 2 5 ka on the basis of astronomical dating of o isotope stages the 40 ar 39 ar ages astronomical dating plus chemical similarities permit correlation of the c 13 tephra layer with both the campanian ignimbrite and the y 5 tephra layer the older ages preserved in the c 13 tephra layer may reflect xenocrysts incorporated during the explosive eruption accompanying collapse of the campi flegrei caldera 41 ka the c 13 tephra layer is correlated with a 10 be peak in an adjacent marine core o isotope stage 3 12 and immediately preceded a cooling episode corresponding to heinrich event 4 thus the age of these features is constrained by radioisotope dating the 41 ka peak in 10 be deposition is a global phenomenon whose age matches that of the laschamp geomagnetic excursion thus our results provide a new tie point among several polar ice core and marine proxy records of paleoclimate during the past 50 kyr precise age information independent of radiocarbon dating can be recovered from latest pleistocene marine tephra using the 40 ar 39 ar laser heating method despite the presence of multiple components that may have been incorporated during or after its deposition

observed low frequency variability of the brazil current front 1 the brazil current is a weak western boundary current the southwest component of the south atlantic subtropical gyre which is the main conduit of upper ocean waters in the region the objective of this work is to report on observed low frequency variability of the brazil current front using satellite derived sea height anomaly and sea surface temperature observations during the 1993 2008 period the variability of the front is studied in terms of the separation of the brazil current front from the continental shelf break during the study period estimates of this parameter vary 6 degrees in latitude and the mean monthly estimates exhibit a shift to the south of approximately 1 5 degrees statistically significant changes are not observed in the geostrophic transport of the brazil and malvinas currents suggesting that the low frequency changes of the brazil current front are governed by different mechanisms than the seasonal variability of these surface currents surface drifter trajectories and simulations using synthetic drifters are consistent with the observed shift to the south of the brazil current front trends of eddy kinetic energy sea height anomaly sea surface temperature and wind stress curl are also in agreement with the variability reported here wavelet transform analysis revealed interesting changes in the periodicity of the latitude of separation of the brazil current front from the continental shelf break with periods ranging from semiannual to biannual longer records together with comprehensive numerical experiments will ultimately be needed to determine the origin of these changes

the santa rosa event 40ar 39ar and paleomagnetic results from the valles rhyolite near jaramillo creek jemez mountains new mexico the jaramillo event was originally defined by doell and dalrymple in 1966 on the basis of k ar ages from sanidine in the normally transitionally and reversely magnetized rhyolite domes named cerro del abrigo cerro santa rosa i and cerro santa rosa ii respectively that erupted following collapse of the archetypal valles caldera new mexico we have collected new paleomagnetic data from the three domes and new 40 ar 39 ar laser fusion and furnace incremental heating experiments on sanidine crystals from the cerro santa rosa i rhyolite step wise alternating field and thermal demagnetization techniques applied to 52 samples from seven sites indicate that the original paleomagnetic results of doell and dalrymple science 152 1966 1060 1061 are valid cerro del abrigo is normally magnetized whereas the santa rosa i dome is transitional with an inclination of 363 toward the east and the santa rosa ii dome is of reversed polarity twenty five laser fusion experiments on sanidine crystals from the the cerro santa rosa i dome together with the saddle shaped spectrum obtained by incrementally heating the sanidine in a furnace reveal that this rhyolite contained a small but significant component of excess argon prior to eruption our preferred age of 936 8 ka 2c for the santa rosa i rhyolite is based on the concordant laser fusion isochron and incremental heating plateau ages this age is significantly older than was inferred on the basis of earlier laser fusion 40 ar 39 ar results that suggested a trapped component characterized by a 40 ar 36 ar ratio lower than the atmospheric value of 295 5 our new age distinguishes the santa rosa i dome by 65 kyr from the termination of the jaramillo normal subchron 1001 10 ka and by 37 kyr from basaltic lavas at haleakala and tahiti which record the kamikatsura event 899 6 ka moreover this determination is a factor of three more precise than the best previous estimate for a proposed geomagnetic event in this time period the cerro santa rosa i rhyolite dome once intimately linked with the end of the jaramillo event and the acceptance of plate tectonic theory now defines a highly resolved feature the santa rosa event in a terrestrial geomagnetic reversal time scale that is consistent with the global record of magnetic field intensity from marine sediments fl 2002 elsevier science b v all rights reserved

stable isotope evidence for rapid uplift of the central apennines since the late pliocene abstract the central apennines an accretionary wedge overlying an area of slab detachment are characterized by prominent topography active normal faulting and high uplift rates however previous studies have failed to resolve the surface uplift history complicating efforts to link the topographic evolution with underlying geodynamic processes we aim to better quantify orographic changes by using stable oxygen isotope paleoaltimetry modern surface water 18 o are 5 lower at high elevation than at sea level reflecting orographic rainout over the apennines we present 262 new lacustrine and paleosol carbonate 18 o measurements collected from ten extensional intermontane basins spanning both high and low elevations and combine these with 1 166 published 18 o data permitting us to constrain changes in 18 o both spatially and temporally since the pliocene 18 o in present day high elevation basins has continuously decreased even as 18 o in lowland basins has remained constant over time we attribute this continuous 5 shift to increased orographic rainout as the central apennines were uplifted we estimate an increase in mean elevation of approximately 1 2 km since the late pliocene and these estimates match the suggested timing and expected amplitude of slab break off related uplift this supports the hypothesis that the opening of the adriatic slab window and associated mantle flow contributed significantly to building topography in the central apennines

major bounding surfaces in aeolian sandstones a climatic model large areas of fixed vegetated dunes occur in the sahel and southern margin of the sahara these dunes were active during late pleistocene times and have been stabilized as a result of a change to more humid less windy conditions in the holocene the stabilized surfaces which are in part of erosional origin are of regional extent within aeolian sand sequences such surfaces form the highest order bounding surfaces since regional bounding surfaces of this type occur in all the world s major deserts it is suggested that they should also be present in some ancient aeolian sandstone sequences

low frequency variability of southern ocean jets both observations and high resolution numerical models show that the southern ocean circumpolar flow is concentrated in a large number approximately 8 to 12 of narrow filamentary jets it is shown here that coherent jets exhibit a range of low frequency variability on timescales of months to years that can lead to displacement and to intermittent formation and dissipation of jets using output from an eddy resolving ocean general circulation model in local regions near topographic features the impact of energy exchange between eddy and mean flow components on jet persistence and variability is examined a novel approach that uses a time dependent definition of the mean flow provides a clearer picture of eddy mean flow interactions in regions with spatially and temporally varying flow structure the dynamics are largely consistent with those in idealized quasi geostrophic models including topographically organized and surface enhanced reynolds stress forcing of the mean flow jets form during periods of enhanced eddy activity but may persist long after the eddy activity has decayed similarly jets may evolve in a downstream sense with jet formation localized near topography and undergoing modification in response to changing bathymetry the evolution of both temperature and potential vorticity is used to show that the low frequency variability of the jets impacts water mass structure and tracer transport this study highlights various examples of southern ocean dynamics that will prove difficult to capture through parameterizations in coarser climate models

an altimetry based gravest empirical mode south of africa 1 development and validation 1 hydrographic transects of the antarctic circumpolar current acc south of africa are projected into baroclinic stream function space parameterized by pressure and dynamic height this produces a two dimensional gravest empirical mode gem that captures more than 97 of the total density and temperature variance in the acc domain weekly maps of absolute dynamic topography data derived from satellite altimetry are combined with the gem to obtain a 16 year time series of temperature and salinity fields the time series of thermohaline fields are compared with independent in situ observations the residuals decrease sharply below the thermocline and through the entire water column the mean root mean square rms error is 0 15c 0 02 and 0 02 kg m 3 for temperature salinity and density respectively the positions of acc fronts are followed in time using satellite altimetry data these locations correspond to both the observed and gem based positions the available temperature and salinity information allow one to calculate the baroclinic zonal velocity field between the surface and 2500 dbar this is compared with velocity measurements from repeat hydrographic transects at the goodhope line the net accumulated transports of the acc derived from these different methods are within 1 3 sv of each other similarly gem produced cross sectional velocities at 300 dbar compare closely to the observed data with the rms difference not exceeding 0 03 m s 1 the continuous time series of thermohaline fields described here are further exploited to understand the dynamic nature of the acc fronts in the region and which is given by swart and speich 2010

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

is there a continuous subtropical front south of africa a 14 3 year series of weekly absolute sea surface height ssh and associated geostrophic velocities is used for a study of the subtropical to subantarctic frontal system in the region south of africa detecting the fronts from surface velocity maxima confirms a two stepped transition in both the southeastern atlantic ocean the northern and southern subtropical fronts nstf sstf and southwestern indian ocean the agulhas front and sstf as proposed previously from hydrographic data an additional front associated with westward flow north of the nstf is indicative of a partial eastern closure of the south atlantic subtropical gyre between 11 e and 17 5 e the role of northwestward propagating agulhas rings in connecting the two fronts explains the varying location the sstf which marks the southern limit of subtropical waters is found continuous from the atlantic to the indian ocean in the time averaged ssh field in the weekly fields however the velocity maximum criterion defining the front is often met at the southern flanks of agulhas rings or agulhas eddies at 12 e 23 e indicating front disruptions such discontinuities suggest that no south atlantic central water is directly advected into the indian ocean instead the eastward limb of the indo atlantic super gyre encompassing the subtropical gyres of both oceans would rest at these longitudes on diffusive processes at the upper levels and possibly be enhanced at depth a schematic diagram of the fronts and their relations to agulhas rings and eddies is proposed

wave driven zonal flow vacillation in the southern hemisphere the variability of the zonal mean flow in the southern hemisphere during the period 1985 94 is studied using european centre for medium range forecasts analyses the dominant mode of variability has approximately equivalent barotropic variations of opposite signs centered at 40 8 and 608s this structure is dominant in all seasons and has similar variance in all seasons the temporal variance of the amplitude of this mode is well modeled as gaussian red noise with a correlation e folding time of about 10 days zonal wind anomalies are maintained against frictional drag by variations in the zonal flow accelerations driven by transient eddies and associated mean meridional circulations the eddy structures suggest that equatorward propagation is favored when the jet is displaced poleward and zonal propagation is favored when the jet is displaced equatorward

morphology and genesis of asymmetric adhesion warts a new adhesion surface structure abstract adhesion surface structures have been studied during their formation on a fluvial bar in east greenland two main types occurred adhesion ripples and asymmetric adhesion warts adhesion ripples formed on moist surfaces their crests lay transverse to the wind direction and they migrated by trapping dry wind blown sand on their steep fronts asymmetric adhesion warts new structure formed because of falling moisture content by preferred upwind migration of small protuberances on the adhesion ripples the protuberances were apparently inherited from an initial rain sculpturing of the bar surface the asymmetric adhesion warts here described for the first time were elongate parallel to the wind associated with steep upwind facing fronts and commonly displayed sand shadow tails tapering in a downwind direction a study of devonian flood basin deposits hornelen basin norway revealed the existence of adhesion surface structures very similar to their modern analogues the devonian examples were associated with rain sculptured surfaces which are believed to have controlled the morphology of the adhesion surface structures as in the modern example the orientation of the ancient adhesion surface structures is here used for determination of the palaeowind which blew from the ene

stratigraphic evolution and preservation of aeolian dune and damp wet interdune strata an example from the triassic helsby sandstone formation cheshire basin uk new and previously published models of wet aeolian system evolution form a spectrum of types that may be explained in terms of aeolian dune dynamics rate of water table rise and or periodicity of interdune flooding this is illustrated with an example from the mid triassic anisian helsby sandstone formation cheshire uk lenses of damp and wet interdune strata exhibit an intertonguing transitional relationship with the toe sets of overlying aeolian dune units this signifies dune migration that was contemporaneous with water table controlled accumulation in adjacent interdunes downwind changes in the geometry and facies of the interdune units indicate periodic expansion and contraction of the interdunes in response to changes in the elevation of the groundwater table and episodic flooding during which accumulation of dune strata continued relatively uninterrupted this contrasts with other models for accumulation in wet aeolian systems where interdune flooding is associated with a cessation in aeolian bedform climbing and the formation of a bypass or erosional supersurface architectural panels document the detailed stratigraphy in orientations both parallel and perpendicular to aeolian transport direction enabling a quantitative three dimensional reconstruction of genetically related aeolian dune and interdune elements sets of aeolian dune strata are composed of grainflow and translatent wind ripple strata and are divided by a hierarchy of bounding surfaces originating from oblique migration of superimposed dunes over slipfaceless sinuous crested parent bedforms together with lee slope reactivation under non equilibrium flow conditions silty mudstone and sandstone interdune units are characterized by wind ripple wavy and subaqueous wave ripple laminae desiccation cracks mud flakes raindrop imprints load casts flutes intraformational rip up clasts and vertebrate and invertebrate footprint impressions and trackways these units result from accumulation on a substrate that varied from dry through damp to wet surface conditions interdune ponds were flooded by either fluvial incursions or rises in groundwater table and were periodically subject to gradual desiccation and reflooding red silty mudstone beds of subaqueous origin pass laterally into horizontally laminated wind ripple beds indicating a progressive transition from wet through damp to dry surface conditions within a single interdune

paleoenvironmental evolution of the pliocene villarroya lake northern spain a multidisciplinary approach abstract the pliocene villarroya basin fill consists of lacustrine and alluvial deposits over 100 m thick the lacustrine deposits up to 30 m thick comprise three sequences the two lower sequences consist of profundal laminated deposits formed by mostly terrigenous facies that are overlain by charophytic carbonates and varves the uppermost third sequence made up of massive bioturbated mudstones corresponds to a very shallow lacustrine palustrine environment bulk mineralogy comprises carbonates clay minerals quartz and feldspars the carbonates are exogenic biogenic calcite and biogenic aragonite biogenic calcite constitutes ostracod shells and charophyte stem encrustations whereas aragonite forms gastropod shells and in some varve intervals charophyte encrustations the clay minerals are illite kaolinite palygorskite chlorite and paragonite which are inherited from source rocks and smectite and interstratified clays which are probably formed in the soils of the source area variations in clay mineralogy reflect the interplay between the climate tectonic rejuvenation and the paleogeography of the basin the pollen assemblages indicate significant variations in climate a first phase of varying climate was followed by cool temperate and sub humid phases that culminated in a temperate and dry episode which is recorded in the lower part of the second lacustrine sequence this was succeeded by a marked warm and humid episode which may be correlated with the mid pliocene warmth about 3 0 ma and the subsequent cooling phase which is recorded in the upper third sequence in the two lower sequences profundal lacustrine deposits ostracods indicate oligosaline to mesosaline waters with salinity variations and some warm and na cl episodes molluscs are characterized by hydrobiids suggesting a salinity stress in the upper palustrine deposits the ostracods and aquatic mollusc assemblages indicate fresh cold waters faunal records indicate that changes in salinity do not correlate with climate suggesting phases of significant saline inputs to the lake which were recorded in the lower first sequence and in the upper part of the second sequence the lacustrine sequence of villarroya record pronounced variations in climate and in the lacustrine environment however there are no consistent relationships between the climate conditions inferred from the pollen data and the sedimentary record of the environmental changes showing that other factors especially tectonics have exerted an influence on the paleoenvironmental evolution and on the sedimentary record of the pliocene villarroya lake

large and small mammal distribution patterns and chronostratigraphic boundaries from the late pliocene to the middle pleistocene of the italian peninsula abstract over the last 50 years the studies on terrestrial mammals of the italian peninsula have provided a large volume of data and a more detailed knowledge of faunal events during the late pliocene and quaternary moreover geological sedimentological palynological and magnetostratigraphical investigations on the pliocene pleistocene continental sedimentary basins have yielded the possibility of a detailed calibration of the faunal successions thus palaeontologists have been able to reconstruct faunal sequences and to propose biochronological scales based on large and small mammals respectively in the present contribution an integration of the two biochronological scales is proposed and the successions of bioevents are carefully compared this integrated approach allows the constraint of the sequence of large and small mammal events in a more reliable way and therefore it results in a more detailed and consistent chronological use of mammalian assemblages particular attention is paid to the faunal changes that correspond to the middle late pliocene 2 6 ma pliocene pleistocene 1 8 ma and early middle pleistocene gauss matuyama transition chronostratigraphical boundaries

circumpolar structure and distribution of the antarctic circumpolar current fronts 2 variability and relationship to sea surface height 1 in part 1 of this study we showed that the antarctic circumpolar current acc consisted of multiple fronts each of which was consistently associated with a particular contour of sea surface height ssh or approximate streamline in part 2 we have used maps of ssh to examine the variability of the acc fronts between 1992 and 2007 the ssh label associated with each frontal branch is nearly constant around the circumpolar belt the front labels are also nearly constant in time the bands of enhanced ssh gradient i e fronts occur along the same streamlines throughout the 15 year period of observations both short and long period changes of the ssh frontal labels of the acc are small based on a tight relationship between dynamic height and cumulative baroclinic transport of the acc the baroclinic transport variability of the individual branches of the acc is also expected to be small the major change in the total acc baroclinic transport occurs in the drake passage the streamline associated with the northern branch of the saf saf n does not pass through drake passage and the waters carried by this branch are not observed there instead the transport of the saf n turns north in the pacific to supply the export of water to the indian ocean north and south of australia strong eddy activity in the southeast pacific acts to dissipate the hydrographic signature of the saf n there in the atlantic the saf n reappears as the same streamline is again associated with enhanced ssh gradients to the east of the brazil malvinas confluence zone while the large changes in ssh have occurred in the southern ocean between 1992 and 2007 there are strong regional differences because the acc fronts are robustly associated with particular ssh contours the changes in ssh reflect shifts in the position of the acc fronts in the circumpolar average each of the acc fronts has shifted to the south by about 60 km the changes in ssh in the southern ocean are largely due to changes in ocean circulation rather than warming and freshening by atmospheric fluxes much larger changes in ssh are observed in some locations of the southern ocean particularly where the fronts interact with large scale topography the northern branch of the pf pf n near the kerguelen plateau is an extreme example where the pf n followed a path around the northern end of kerguelen plateau between 1992 and 1997 passed through the fawn trough after 2003 and oscillated between the two paths between 1997 and 2003

an altimetry based gravest empirical mode south of africa 2 dynamic nature of the antarctic circumpolar current fronts 1 swart et al 2010 applied altimetry data to the gravest empirical mode south of africa to yield a 16 year time series of temperature and salinity sections in this study we use these thermohaline sections to derive weekly estimates of heat content hc and salt content sc at the goodhope meridional transect of the antarctic circumpolar current acc these estimates compare favorably to observed data the resulting 16 year time series of hc and sc estimates are used to explain the subsurface thermohaline variability at each acc front and frontal zone the variability at the subantarctic zone saz is principally driven by the presence of agulhas rings which occur in this region approximately 2 7 times per annum and are responsible for the longest and highest scales of observed variability the variability of the saz is responsible for over 50 and 60 of the total acc hc and sc variability respectively poleward of the saz the variability is largely determined by the influence of the local topography on the fronts of the region and can be explained by the conservation of potential vorticity wavelet analysis is conducted on the time series of meridionally integrated hc and sc in each acc front and frontal zone revealing a consistent seasonal mode that becomes more dominant toward the southern limit of the acc the lower frequency signals are compared with two dominant modes of variability in the southern ocean the southern annular mode correlates well with the hc and sc anomaly estimates at the antarctic polar front while the southern oscillation index appears to have connections to the variability found in the very southern domains of the acc

properties of the subantarctic front and polar front from the skewness of sea level anomaly author s shao ae gille st mecking s thompson l abstract 2015 american geophysical union all rights reserved the region of the southern ocean that encompasses the subantarctic front saf to the north and the polar front pf to the south contains most of the transport of the antarctic circumpolar current here skewness of sea level anomaly sla from 1992 to 2013 is coupled with a meandering gaussian jetw model to estimate the mean position meridional width and the percent variance that each front contributes to total sla variability the saf and pf have comparable widths 85 km in the circumpolar average but their widths differ significantly in the east pacific basin 85 and 60 km respectively interannual variability in the positions of the saf and pf are also estimated using annual subsets of the sla data from 1993 to 2012 the pf position has enhanced variability near strong topographic features such as the kerguelen plateau the campbell plateau east of new zealand and downstream of drake passage neither the saf nor the pf showed a robust meridional trend over the 20 year period the southern annular mode was significantly correlated with basin averaged saf and pf positions in the east pacific and with the pf south of australia a correlation between the pf and the basin scale wind stress curl anomaly was also found in the western extratropical pacific but not in other basins

wind forced variability of the antarctic circumpolar current south of africa between 1993 and 2010 the variability of the antarctic circumpolar current acc system is largely linked to the atmospheric forcing the objective of this work is to assess the link between local wind forcing mechanisms and the variability of the upper ocean temperature and the dynamics of the different fronts in the acc region south of south africa to accomplish this in situ and satellite derived observations are used between 1993 and 2010 the main finding of this work is that meridional changes in the westerlies linked with the southern annular mode sam drive temperature anomalies in the ekman layer and changes in the subantarctic front saf and antarctic polar front apf transports through ekman dynamics the development of easterly anomalies between 35 s and 45 s during positive sam is linked to reduced increased saf apf transports and a warmer mixed layer in the acc the link between the changes in the wind stress and the saf and apf transport variations occurs through the development of ekman pumping anomalies near the frontal boundaries driving an opposite response on the saf and apf transports the observed wind driven changes in the frontal transports suggest small changes to the net acc transport in addition observations indicate that the saf and apf locations in this region are not linked to the local wind forcing emphasizing the importance of other factors e g baroclinic instabilities generated by bottom topography to changes in the frontal location results obtained here highlight the importance of repeat xbt temperature sections and their combined analysis with other in situ and remote sensing observations

eolian permian deposits in west and northwest argentina abstract the sedimentary and stratigraphic characteristics of eolian permian deposits exposed in mendoza la rioja and san juan provinces west and northwest argentina are described in this paper the eolianites are fine and medium sandstones with large scale cross bedding multiple parallel truncation planes and some asymmetrical ripples three genetic types of deposits have been identified dune facies eolian sand sheet facies and mixed fluvial eolian facies fine and medium sandstones with large scale cross bedding and multiple parallel truncation planes are here interpreted as dune deposits mainly crescentic dunes and unstratified or flat bedded sandstones as eolian sand sheet deposits mixed fluvial and eolian sequences composed of sandstones mudstones and some matrix supported conglomerates represent a transitional facies between those formed in eolian and fluvial environments this considerable deposition of eolian sediments was probably brought about by the existence of an extensive medium to low latitude continent and the withdrawal of marine environments the environments with highest aridity occurred towards the south and west of the region the eolian circulation pattern was controlled by a long ensialic volcanic arc emerging towards the west of the basin

response of deep ocean circulation to initiation of northern hemisphere glaciation 3 2 ma carbon isotopic records from benthic foraminifera are used to map patterns of deep ocean circulation between 3 and 2 million years ago the interval when significant northern hemisphere glaciation began the 18o and 13c data from four atlantic sites 552 607 610 and 704 and one pacific site 677 show that global cooling over this interval was associated with increased suppression of north atlantic deep water nadw formation however the relative strength of nadw production was always greater than is observed during late pleistocene glaciations when extreme decreases in nadw are observed in the deep north atlantic our data indicate that an increase in the equator to pole temperature gradient associated with the onset of northern hemisphere glaciation did not intensify deepwater production in the north atlantic but rather the opposite occurred this is not unexpected as it is the warm high salinity characteristic rather than the low temperature of thermocline waters that is critical to the deepwater formation process in this region today

relating eolian bounding surface geometries to the bed forms that generated them etjo formation cretaceous namibia the cretaceous etjo formation is a 200 m thick eolian and fluvial sandstone succession exposed in the huab basin of northwestern namibia eolian sedimentation was terminated abruptly by the emplacement of flood basalts of the etendeka igneous province across much of the basin at 132 1 ma the lavas drowned the dunes and in doing so preserved bed forms with heights and wavelengths of up to 100 m and 1 3 km respectively subsequent erosion has resulted in the exposure of these bed forms and provides a rare opportunity to accurately reconstruct the three dimensional geometry of an ancient eolian system and to relate bed form morphology to bounding surface geometries some bed forms lacked a single active slipface but instead were characterized by a dome form over which smaller transverse dunes migrated other bed forms were characterized by an active slipface and a stoss slope over which smaller superimposed bed forms migrated one bed form records a transitional evolution between these two end member types preserved bed sets exhibit a positive but stoss erosional angle of downwind bed form climb of 1 bed forms of the etjo formation provide an opportunity to directly relate bed set thickness to original bed form height via the angle of climb

meridional heat transport across the sub tropical convergence by a warm eddy the heat transport of the ocean atmosphere system is strongly dependent on the meridional transport of heat in the oceans and in particular that between the southern ocean and adjacent ocean basins this ocean process may possibly be dominated by the propagation of energetic mesoscale eddies at certain distinct sectors of the sub tropical convergence such as those bordering the western boundary currents where eddies could be preferentially spawned i report here for the first time the shedding of a warm ocean eddy from the agulhas current across the sub tropical convergence its internal structure as well as rotational frequency the subsequent drift of the eddy and its further interaction with the sub tropical convergence is documented by sequential satellite infrared measurements as well as the behaviour of a free drifting buoy placed in the feature based on simultaneous hydrographic measurements the total heat flux across the sub tropical convergence achieved by the eddy is estimated at 26 7 x 1017 j

episodic deposition and preservation of eolian sands a late paleozoic example from southeastern utah the upper pennsylvanian and lower permian stratigraphic sequence in canyonlands national park contains about 40 flat topped eolian sand bodies rhizoliths burrows and traces of former evaporites abound at the tops of these tabular genetic units upper surfaces of units were created by eolian deflation to the level of the groundwater table analysis of cross stratification reveals that sands accumulated via migration and climb of relatively small dunes brief episodes of sand accumulation were triggered by regression and were terminated when upwind sand supplies were depleted upper surfaces of genetic units are diastems and represent much more geologic time than the rocks themselves

aeolian sediments in lower to middle triassic rocks of central wyoming abstract the lower to middle triassic red peak and crow mountain formations of central wyoming have commonly been interpreted as being of shallow marine or shelf origin this paper presents conclusive evidence of an aeolian origin for parts of the two formations the interpretation is based on highly indicative sedimentary structures including wind ripple grainfall and grainflow strata lag deposits and granule ripples in the sediments of these formations facies in the upper red peak and lower crow mountain formations represent aeolian dune sandsheet wet interdune and sabkha environments emphasis is placed on the recognition and interpretation of correlative surfaces of regional extent which not only allow subdivision of the aeolian sediments into different genetic sequences but also aid in the reconstruction of the depositional history the recognition of an aeolian deposystem and of regional bounding surfaces adds valuable information to the efforts of reconstructing the triassic paleogeography of the western interior

multiple jets of the antarctic circumpolar current south of australia abstract maps of the gradient of sea surface height ssh and sea surface temperature sst reveal that the antarctic circumpolar current acc consists of multiple jets or frontal filaments the braided and patchy nature of the gradient fields seems at odds with the traditional view derived from hydrographic sections that the acc is made up of three continuous circumpolar fronts by applying a nonlinear fitting procedure to 638 weekly maps of ssh gradient ssh it is shown that the distribution of maxima in ssh i e fronts is strongly peaked at particular values of absolute ssh i e streamlines the association between the jets and particular streamlines persists despite strong topographic and eddy mean flow interactions which cause the jets to merge diverge and fluctuate in intensity along their path the ssh values corresponding to each frontal branch are nearly constant over the sector of the southern ocean between 100 e and 180 the front positions inferred from ssh agree closely with

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

desert stream sequences in the sinai peninsula abstract desert sedimentary sequences of late quaternary age mainly subrecent were studied in several stream segments of wadi el arish northern sinai egypt morphologically these stream systems can be divided into three types confined open and terminal floodplains the confined and open floodplain sequences consist of repeated flood originated sedimentation units each around 50 cm thick an idealized sequence begins with mud clasts or either sand or pebble bearing plane beds reflecting the upper flow regime during peak flow stage of the flood these are overlain by cross bedded sands and climbing ripples lower intensities of the flow result in sequences beginning with cross stratified sands cracked mud layers represent the final desiccation stage of the flood in comparison with th confined floodplain units the open up to thousands of meters wide floodplain units are thinner 20 50 cm the horizontal strata are less developed and the mud layers are thicker the terminal floodplain which in the modern examples is a flat a few kilometers wide is the area where the remaining flood energy dissipates and therefore the resultant sedimentation units axe very thin usually less than 20 cm and consist of either finely laminated massive mud or cross laminated fine sand the wadi systems studied are in close geographic relationship with eolian dune fields nevertheless the wadi sequences consist of waterlaid units only

simulated changes in the extratropical southern hemisphere winds and currents 1 the results from 12 global climate models show a remarkably consistent strengthening and poleward shifting of the zonal wind stress through the 20th and 21st centuries at extratropical southern hemisphere latitudes changes in the zonal circulation of the ocean in the region are broadly consistent with the changes in zonal wind stress in particular the climate models simulate a strengthening and a poleward shift of the antarctic circumpolar current the strengthening of the zonal wind stress also results in intensifying northward ekman transport across the antarctic circumpolar current which in the unblocked latitudes of drake passage implies increasing southward geostrophic transport in the ocean below about 2000 m zonal wind stress changes such as these may be expected to enhance the mesoscale eddy activity in the southern ocean

on the age and morphology of the reunion event data pertinent to the age of the normal polarity reunion event or subchron and whether it is a split feature are critically examined new 40 ar 39 ar age determinations on lavas from two sequences on reunion island along with available potassium argon k ar 40 ar 39 ar and astrochronological analyses indicate an age of 2 15 2 13 ma although the possibility cannot be completely ruled out at present there is no convincing evidence supporting the contention of a short duration of normal polarity some 70 90 kyr later

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

the role of eddies in the southern ocean temperature response to the southern annular mode the role of eddies in modulating the southern ocean response to the southern annular mode sam is examined usinganoceanmodelrunatmultipleresolutionsfromcoarsetoeddyresolving thehigh resolution versionsof the model showan increase in eddy kinetic energy that peaks 2 3 yr after a positive anomalyin the sam index previous work has shown that the instantaneous temperature response to the sam is characterized by predominant cooling south of 458s and warming to the north at all resolutions the model captures this temperatureresponse this responseis also evidentin the coarse resolution implementation of the model with no eddy mixing parameterization showing that eddiesdo not play an important role in the instantaneous response on the longer time scales an intensification of the mesoscale eddy field occurs which causes enhanced poleward heat flux and drives warming south of the oceanic polar front this warming is of greater magnitude and occurs for a longer period than the initial cooling response the results demonstrate that this warming is surface intensified and strongest in the mixed layer non eddy resolving models are unable to capturethedelayededdy driventemperatureresponsetothesam theauthorsthereforequestiontheability

stokes surfaces and the effects of near surface groundwater table on aeolian deposition abstract stokes surfaces in aeolian deposits are caused by wind scour of unconsolidated material to a roughly planar horizon controlled by near surface water tables stokes 1968 a water table forms a downward limit of scour through the cohesion of damp or wet sand near water table and through early cementation by evaporites precipitated in the sediments as water evaporates near the sand air interface study of modern analogues reveals that stokes surfaces exist in a variety of depositional settings including a coastal offshore prograding sand sea jafurah saudi arabia a coastal onshore prograding sand sea guerrero negro mexico and a continental sand sea white sands new mexico usa these modern analogues indicate that our concept of stokes surfaces must be broadened to include the following i modern analogues for stokes surfaces described here cover areas on the order of 25 km2 these may be as representative of similar surfaces in ancient rocks as hypothesized plains of deflation requiring removal of entire sand seas ii stokes surfaces occupy a continuum in scale from local to extensive and erosional surfaces of different magnitude may be stacked closely in the sediments iii stokes surfaces although erosional in nature are commonly associated with deposits both above and below the stokes bounding surface which plainly reveal the influence of a near surface groundwater control on wind sedimentation moreover the erosional relief of the bounding surface itself as well as other features reveals the influence of a groundwater table iv stokes surfaces may be diachronous representing the lateral shift of a zone of scour within a sand sea rather than simultaneous removal of all dunes from the area encompassed by the erosional surface v stokes surfaces and associated deposits are often laterally transitional to surfaces and deposits of adjacent depositional environments including interdunes tidal flats lagoons beaches lakes and non aeolian sabkhas finally modern examples from different depositional settings suggest that while most stokes surfaces have many features in common such as erosional ridges due to early cementation there are some features which may with further study be revealed to be distinctive of an individual depositional setting

what can we learn from global altimetry hydrography comparisons differences and complementarities between altimeter and hydrographic data are studied to describe the sea level and ocean circulation variations in terms of steric and non steric contributions altimeter sea level anomalies sla and hydrographic dynamic height anomalies dha agree remarkably well they also reveal however systematic large scale differences in several areas of the pacific and indian oceans that are related to a barotropic sverdrup like response of the ocean to wind forcing in addition the use of the two data sets provides a good estimation of the partition between barotropic and baroclinic modes needed for data synthesis or assimilation studies

preservation of aeolian genetic units by lava flows in the lower cretaceous of the parana basin southern brazil the lower cretaceous geological record of the intracratonic parana basin in southern brazil comprises a thick succession of aeolian sandstones and volcanic rocks the intercalation between aeolian sandstone and volcanic floods allowed the preservation of distinct aeolian genetic units each genetic unit represents an accumulation episode bounded by supersurfaces that coincides with the base of lava flood events the entire package can be subdivided into a lower genetic unit which corresponds to aeolian sandstones preserved below the initial lava flows botucatu formation and an upper set of genetic units which comprises interlayered aeolian deposits and lava floods serra geral formation the lower genetic unit is up to 100 m thick its base is composed of ephemeral stream and aeolian sand sheet deposits that are overlain by cross bedded sandstones whose origin is ascribed to simple locally composite crescentic and complex linear aeolian dunes aeolian accumulation of the lower unit was possible as a result of the existence of a wide topographic basin which caused wind deceleration and a large sand availability that promoted a positive net sediment flux the upper genetic units comprise isolated sand bodies that occur in two different styles 1 thin lenses 3 m thick formed by aeolian sand sheets and 2 thick sand lenses 3 15 m comprising cross bedded cosets generated by migration and climbing of simple to locally composite crescentic aeolian dunes accumulation of the aeolian strata was associated with wind deceleration within depressions on the irregular upper surface of the lava floods the interruption of sedimentation in the lower and upper genetic units and related development of supersurfaces occurred as a result of widespread effusions of basaltic lava preservation of both wind rippled topset deposits of the aeolian dunes and pahoehoe lava imprints indicates that lava floods covered active aeolian dunes and hence protected the aeolian deposits from erosion thus preserving the genetic units

aeolian system sediment state theory and mojave desert kelso dune field example the sediment state of aeolian dune fields and sand seas at a basinal scale is defined by the separate components of sediment supply sediment availability and the transport capacity of the wind the sediment supply for aeolian systems is the sediment that contemporaneously or at some later point serves as the source material for the aeolian system numerous factors impact the susceptibility of grains on a surface to transport but these are cumulatively manifested by the actual transport rate which serves as a proxy for sediment availability transport capacity is the potential sediment transport rate of the wind because the three aspects of sediment state can be given as a volumetric rate they are directly comparable plotted simultaneously against time the generated curves define nine possible classes of sediment state sediment supply that is stored occurs because it is transport or availability limited or generated at a rate greater than the potential or actual transport rates respectively contemporaneous or lagged influx to an aeolian system may be limited by sediment availability but cannot exceed the transport capacity of the wind for the kelso dune field in the mojave desert of california a variety of stratigraphic and geomorphic evidence is used to approximate the sediment state of the system the sediment supply was generated during the latest pleistocene and earliest holocene during humid periods of enhanced discharge by the mojave river to form the lake mojave fan delta or terminal fan and has been calculated over time from the sedimentation rate and the frequency of floods estimation of transport capacity over time was based upon modern wind data with an allowance for greater winds during the pleistocene based upon climatic models sediment availability was approximated by calculation of a modern dune mobility index with variation over time based upon climatic inferences while quantifying the kelso or any natural system is subject to numerous uncertainties the sediment state approach reflects the temporal and spatial disjointed nature of accumulations at kelso as well as illuminating questions for future research

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

long term trends and interannual variability of temperature in drake passage abstract temperature data collected over the last 36 years 1969 2004 in drake passage are used to examine interannual temperature variation and long term trends in the upper ocean to reduce the effect of variation from different sampling locations and temporal variability introduced by meridional shifts in the polar front pf the data were divided into two sub regions north 3800 temperature profiles and south 3400 of the pf temperature anomalies were formed by removing a temporal mean field for each profile in each sub region at 100 m depth intervals from the surface to 700 m north of the pf statistically significant warming trends of 0 02 c yr 1 were observed that were largely depth independent between 100 and 700 m a statistically significant cooling trend of 0 07 c yr 1 was observed at the surface south of the pf which was smaller 0 04 c yr 1 but still statistically significant when possible seasonal sampling biases were accounted for the observed cooling at the surface and warming at depth is largely consistent with a poleward shift of the pf due to enhancement of westerly winds in the southern ocean as recently suggested by models and observations the observed annual temperature anomalies in the upper 400 m north of the pf and in the upper 100 m south of the pf are highly correlated to variability in sea ice and also to climate indices of the antarctic oscillation and the el nino southern oscillation variability in sea ice and temperature anomalies lag el nino variability in the pacific with a phasing consistent with the observed cyclical patterns of sea ice and sea surface temperature associated with the antarctic circumpolar wave or antarctic dipole mode in the southern ocean in contrast the sea ice variability and temperature anomalies at all depths north of the pf and at 0 100 m depth south of the pf were primarily coincident with or led the antarctic oscillation index no significant correlations were found with the large scale climate variability indices in southern drake passage below 100 m depth which is occupied by upper circumpolar deep water ucdw this water mass is not formed locally is largely isolated from the surface and exhibits vertical and lateral homogeneity hence changes may be difficult to detect in the available measurements and climate variation in the source water regions of ucdw may take a long time to reach drake passage

late pliocene and pleistocene small mammal chronology in the italian peninsula the abundant documentation of small mammals in the italian peninsula collected over recent years furnishes a detailed biochronological sequence mainly from the late pliocene onwards an updated stratigraphic framework is here presented based on the european small mammal biozonation the early villanyian is characterized by mimomys hassiacus m stehlini and later poorly documented m polonicus the late villanyian localities are well characterized with m pliocaenicus m pitymyoides and m tigliensis the older part of the early biharian is documented by assemblages containing microtus allophaiomys ex gr pliocaenicus m pusillus m cf ostramosensis and m tornensis while the later part of the early biharian is characterized by advanced microtus allophaiomys species occurring together with m pusillus or m blanci in the late biharian m savini microtus hintoni gregaloides microtus iberomys ex gr huescarensis brecciensis and terricola arvalidens occur the early toringian with a mosbachensis allocricetus bursae pliomys episcopalis and small sized microtus brecciensis and the late toringian with a terrestris in diversified associations are quoted the most important faunal events are calibrated by independent chronological controls thanks to the record of small mammals from lacustrine deposits several figures illustrate the most significant rodent species occurring in the succession of selected italian localities

impact of short term climatic events on latest pliocene land settings and communities in central italy upper valdarno basin abstract the upper valdarno italy plio pleistocene continental deposits record the latest uniform subtropical humid conditions and the successive climatic signature of glacial interglacial cycling the palynological and sedimentological analyses on the poggio rosso alluvial plain sediments reveal two major climatic fluctuations correlated to a glacial interglacial cycle just before the plio pleistocene boundary the glacial phase indicated by the expansion of herbs as well as by ephemeral streams associated with calcareous palaeosols extends from the base of the succession and culminates close to an impressive mammalian bone accumulation dated at 1 87 ma the associated increasing aridity had severe consequences on the faunal communities inducing the migration of open plain dwellers and the trapping of other residents around a few residual shrinking water bodies a cooperative pachycrocuta brevirostris clan acted as regulator of game populations debilitated by drought previous research indicates that hyenas were also the major bone accumulators the following moister and warmer interglacial phase ca 1 83 ma is documented by arboreal taxa and hydromorphic palaeosols in a floodplain crossed by migrating perennial sinuous streams the climatic amplitude method calculated mean annual temperatures around 12 5 14 c and mean annual precipitation around 800 mm with a minimum of 400 mm during the glacial phase and 15 16 19 c and 750 1200 mm during the interglacial phase the reconstruction reveals higher mean annual temperatures and precipitation during the interglacial as compared to the present day climate during the glacial conditions were similar to today s in all but lower precipitation values were reached during the acme drought phase just above the fossiliferous bed poggio rosso documents the ecological consequences the buildup of the apennine chain had under the effects of the latest pliocene global climatic changes it therefore represents one of the first signals of the patchiness that since then gradually increased leading to the eventual habitat fragmentation typical of the late pleistocene landscapes

wind driven ocean dynamics impact on the contrasting sea ice trends around west antarctica since late 1978 antarctic sea ice extent in the east pacific has retreated persistently over the amundsen and bellingshausen seas in warm seasons but expanded over the ross and amundsen seas in cold seasons while almost opposite seasonal trends have occurred in the atlantic over the weddell sea by using a surface forced ocean and sea ice coupled model we show that regional wind driven ocean dynamics played a key role in driving these trends in the east pacific the strengthening southern hemisphere sh westerlies in the region enhanced the ekman upwelling of warm upper circumpolar deep water and increased the northward ekman transport of cold antarctic surface water the associated surface ocean warming south of 68 s and the cooling north of 68 s directly contributed to the retreat of sea ice in warm seasons and the expansion in cold seasons respectively in the atlantic the poleward shifting sh westerlies in the region strengthened the northern branch of the weddell gyre which in turn increased the meridional thermal gradient across it as constrained by the thermal wind balance ocean heat budget analysis further suggests that the strengthened northern branch of the weddell gyre acted as a barrier against the poleward ocean heat transport and thus produced anomalous heat divergence within the weddell gyre and anomalous heat convergence north of the gyre the associated cooling within the weddell gyre and the warming north of the gyre contributed to the expansion of sea ice in warm seasons and the retreat in cold seasons respectively

pleistocene terrace deposition related to tectonically controlled surface uplift an example of the kyrenia range lineament in the northern part of cyprus abstract in this study we consider how surface uplift of a narrow mountain range has interacted with glacial related sea level cyclicity and climatic change to produce a series of marine and non marine terrace systems the terrace deposits of the kyrenia range record rapid surface uplift of a long lived tectonic lineament during the early pleistocene followed by continued surface uplift at a reduced rate during mid late pleistocene six terrace depositional systems are distinguished and correlated along the northern and southern flanks of the range termed k0 to k5 the oldest and highest k0 terrace system is present only within the central part of the range the k2 k5 terrace systems formed later at sequentially lower levels away from the range the earliest stage of surface uplift k0 terrace system comprises lacustrine carbonates interbedded with mass flow facies early pleistocene the subsequent terrace system k1 is made up of colluvial conglomerate and aeolian dune facies on both flanks of the range the later terrace systems k2 to k5 each begin with a basal marine deposit interpreted as a marine transgression deltaic conglomerates prograded during inferred global interglacial stages overlying aeolian dune facies represent marine regressions probably related to global glacial stages each terrace depositional system was uplifted and preserved followed by subsequent deposits at progressively lower topographic levels climatic variation during interglacial glacial cycles and autocyclic processes also exerted an influence on deposition particularly on short period fluvial and aeolian deposition

conditions favourable for the formation of warm climate aeolian sand sheets aeolian sand sheets are areas of aeolian sand where dunes with slipfaces are generally absent sand sheets are ubiquitous to modern warm climate sand seas generally occurring marginal to dune fields although they may exist within the interior of a sand sea or independent of a dune field sand sheet deposits are recognized in ancient aeolian sequences where they may account for significant accumulations of low angle aeolian stratification we suggest that the occurrence of sand sheets instead of dunes indicates that conditions are outside the range within which dunes form or that one or more factors interfere with dune development while also favouring the accumulation of sand sheets a study of six modern sand sheets in north america located at great sand dunes gran desierto dumont algodones padre island and colorado river delta indicates that the factors favourable for sand sheet development are 1 a high water table 2 surface cementation or binding 3 periodic flooding 4 a significant coarse grained sediment population and 5 vegetation these factors are reflected in the nature of stratification and the accessory features of sand sheet accumulations within the areas of modern sand sheets as well as in their ancient counterparts in the triassic dolores and pennsylvanian permian rico formations

glacial differences of southern ocean intermediate waters in the central south pacific abstract southern ocean intermediate waters soiws such as antarctic intermediate water and subantarctic mode water play a key role in modulating the global climate on glacial interglacial time scales they link the southern ocean and the tropics via mechanisms such as oceanic tunneling that transport climatic signals across latitudes despite their importance the past evolution of the soiws in the central south pacific is largely unknown here we compare paired mg ca temperature stable carbon 13c and oxygen 18o isotope records from surface dwelling and deep dwelling planktic foraminifera to infer changes in the water column structure for the last 260 ka in the central south pacific 54 s our study focuses on the subsurface oceanographic variability controlled by soiws which are subducted at the subantarctic front our data show that the subsurface ocean in the central south pacific was colder and fresher during glacial stages than during the holocene 0 10 ka bp suggesting a general glacial enhanced presence of antarctic intermediate water in agreement with previous studies from the eastern equatorial pacific and the southeast pacific however the subsurface ocean salinity differs for both glacial stages with fresher condition during the last glacial maximum lgm 26 5 19 ka bp and more saline condition during the penultimate glacial maximum pgm 155 140 ka bp the 13c data also show contrasting conditions for both glacial time windows in the upper water column with a large depletion of 0 37 in 13c from the lgm values suggests a larger contribution of old low 13c deep waters at intermediate depths at the study site during the pgm plausibly due to stronger upwelling in high southern latitudes the dissimilar scenarios between the lgm and the pgm may have been caused by processes that are analogous to the phase switch in modern day southern annular mode

circumpolar structure and distribution of the antarctic circumpolar current fronts 1 mean circumpolar paths 1 high resolution hydrographic sections and maps of the gradient of sea surface height ssh reveal that the antarctic circumpolar current acc consists of multiple jets or frontal filaments here we use a 15 year time series of ssh observations to determine the circumpolar structure and distribution of the acc fronts the jets are consistently aligned with particular streamlines along the entire circumpolar path confirming and extending the results of an earlier study restricted to the region south of australia the intensity of the fronts as measured by the cross front gradient of ssh varies along the fronts and the individual branches merge and diverge often in response to interactions with bathymetry maps of absolute velocity at 1000 m depth derived from argo trajectories confirm the existence of multiple current cores throughout the southern ocean high resolution hydrographic sections and profiles of temperature and salinity from argo floats are used to show that the front locations derived from fitting ssh contours to maps of ssh gradient are consistent with locations inferred from the traditional criteria based on water mass properties suitably modified to account for multiple frontal branches three regions are examined in detail the crozet plateau the kerguelen plateau and the scotia sea these examples show how recognition of the multiple jets of the acc can help resolve discrepancies between previous studies of acc fronts

response of the antarctic circumpolar current to atmospheric variability abstract historical hydrographic profiles combined with recent argo profiles are used to obtain an estimate of the mean geostrophic circulation in the southern ocean thirteen years of altimetric sea level anomaly data are then added to reconstruct the time variable sea level and this new dataset is analyzed to identify and monitor the position of the two main fronts of the antarctic circumpolar current acc during the period 1993 2005 the authors relate their movements to the two main atmospheric climate modes of the southern hemisphere the southern annular mode sam and the el nino southern oscillation enso the study finds that although the fronts are steered by the bathymetry which sets their mean pathway on first order in flat bottom areas the fronts are subject to large meandering because of mesoscale activity and atmospheric forcing while the dominant mode of atmospheric variability in the southern hemisphere sam is relatively symmetric the oceanic response of the fronts is not show

aeolian architecture bedform climbing and preservation space in the cretaceous etjo formation nw namibia sets of aeolian cross strata within the cretaceous etjo formation of nw namibia are bounded by a hierarchy of surfaces the origin of which are ascribed to one of four processes related to aeolian bedform and erg behaviour the base of the main aeolian succession is characterized by a basin wide erosional supersurface that formed in response to a period of aeolian deflation before the onset of the main phase of erg building interdune migration surfaces formed by draa migration are planar in sections parallel to the palaeowind and are inclined at up to 5 in an upwind direction sw perpendicular to the palaeowind interdune surfaces form 500 m wide troughs signifying crestline sinuosity within the original bedforms superimposition surfaces are inclined at 5 10 in a downwind direction and indicate the migration of crescentic oblique dunes over larger slipfaceless transverse draa reactivation surfaces associated with minor changes in dune slipface orientation are distinct from other bounding surface types because overlying cross strata lie parallel to them rather than downlap onto them analysis of the geometry of these bounding surfaces together with the orientation of the cross strata within the sets that they bound has enabled the detailed morphology of the original bedforms to be reconstructed the maximum preserved thickness of individual aeolian sets varies systematically across the basin from 52 m in the basin depocentre to only 8 m at the basin margin the set architecture indicates that this spatial variation is primarily the result of decreased angles of bedform climb at the basin margin rather than the presence of smaller bedforms similarly a temporal reduction in the angle of climb rather than a reduction in bedform size is considered to be responsible for an upward decrease in preserved set thickness reductions in bedform climb angle reflect progressive loss of accommodation space as the accumulating erg filled the basin

circumpolar response of southern ocean eddy activity to a change in the southern annular mode 1 analysis of satellite altimeter data reveals anomalously high eddy kinetic energy eke in the antarctic circumpolar current acc during the period 2000 2002 around 2 3 years earlier 1998 the circumpolar eastward wind stress as quantified by the southern annular mode sam showed a significant positive peak and we have shown previously that the acc peaked around 1998 in response an eddy resolving ocean model is used to investigate the delay between wind forcing and the eddy response and demonstrates that the lag is due to the time taken to influence the deep circulation of the acc winds over the southern ocean have shown a strong climatic increase over the past few decades if this increase in winds is also reflected as an increase in eddy activity as our analysis suggests it might then the increased poleward heat flux may have played a significant role in the observed warming of the southern ocean citation meredith m p and a m hogg 2006 circumpolar response of southern ocean eddy activity to a change in the southern annular mode geophys res lett 33 l16608 doi 10 1029 2006gl026499

location of the antarctic polar front from amsr e satellite sea surface temperature measurements abstract the location of the southern ocean polar front pf is mapped from the first 3 yr of remotely sensed advanced microwave scanning radiometer for the earth observing system amsr e sea surface temperature sst measurements in agreement with previous studies the mean path of the antarctic pf and its standard deviation are strongly influenced by bottom topography however the mean pf path diverges slightly from previous studies in several regions where there is high mesoscale variability although the sst and sst gradient at the pf show spatially coherent seasonal variations with the highest temperature and the lowest temperature gradient during summer the seasonal variations in the location of the pf are not spatially coherent the temporal mean sst at the pf corresponds well to the mean pf path the temperature is high in the atlantic and indian ocean sections and is low in the pacific ocean section where the pf has a more southerly position the relationship of the wind field with the antar

aeolian stratification and facies association in desert sediments arran basin permian scotland abstract permian aeolian sediments on the island of arran are divisible into dune including draa and interdune deposits both types display a distinctive and unusually wide variation in grain size the dominant features of the dune deposits are grainfall lamination sandflow lamination and inverse graded lamination associated with ripple form lamination and normal graded lamination the flat lying aeolian interdune deposits are characterised by granule and sand ripples horizontal lamination in coarse sand and granules plane bed lamination and inverse graded lamination associated structures include ripple form lamination and deflation lags three types of trace fossil associated with completely bioturbated horizons occur in some low angle dune and interdune deposits the aeolian facies interfinger with alluvial fan deposits giving rise to three recognizable facies belts marginal aeolian deposits are associated with fluvial conglomerates and are dominated by interdune deposits and occasionally very thin barchan deposits set height 3 37 cm intermediate aeolian deposits are characterized by interbedded crescentic dune small draa dune set height 5 cm 4 5 m and interdune deposits and rare fluvial and lake sediments basinal aeolian deposits are dominated by draa deposits dune set height 0 2 28 m associated with rare interdune sediments transverse dunes and draas were moved by north eastern palaeowinds towards the foot of the alluvial fans the aeolian sediments were deposited in a fault bounded desert basin

impacts of wind stress on the antarctic circumpolar current fronts and associated subduction 1 recent studies suggest that the overturning circulation in the antarctic circumpolar current acc region shows a weak sensitivity to overlying wind stress changes due to balancing of changes in the eddy induced and eulerian mean transports using an eddy permitting coupled climate model we analyze the response of the acc transport and associated water mass subduction rates in response to an idealized poleward shift and intensification of the westerlies as in previous studies we find a small increase in the net acc transport and a poleward shift in the mean position of the acc flow however the acc is restructured with the subantarctic front saf and polar front pf branches shifting poleward by between 0 9 and 2 5 of latitude resulting in a weaker acc flow in both the saf and pf zones the wind stress anomaly drives a stronger northward ekman transport of cool surface waters deepening the winter mixed layer and causing a 12 7 sv increase in the subduction of subantarctic mode water samw north of the saf zone and a 6 5 sv increase in the subduction of antarctic intermediate water aaiw within the saf and pf zones our results suggest that changes in the wind stress restructure the southern ocean large scale circulation including the flow of the acc in its primary jets and that this affects the formation rates of samw and aaiw in this complex region citation downes s m a s budnick j l sarmiento and r farneti 2011 impacts of wind stress on the antarctic circumpolar current fronts and associated subduction geophys res lett 38 l11605 doi 10 1029 2011gl047668

arid climate 2 5 ma in the plio pleistocene valdarno basin northern apennines italy abstract distinctive eolian dominated sandy deposits 35 m thick exposed along the sw margin of the plio pleistocene valdarno basin in the northern apennines italy reflect an unusually arid period in the region paleomagnetic investigation and 40 ar 39 ar dating of a tephra layer 10 m above the eolian sand suggest that the sand was deposited between about 2 7 and 2 4 ma this age is coeval with the global climatic deterioration that occurred at the middle upper pliocene transition eolian sediments are represented by cross bedded sand rippled sand and horizontal bedded sand the alluvial deposits associated with the eolian sediment consist of sheet like beds of coarse sand and erosively based pebbly sand bodies eolian sand together with fluvial sandy deposits was formed in the medial distal portion of an alluvial system and represents the rena bianca sand unit the eolian and alluvial deposits are arranged into sedimentary cycles 2 6 m thick displaying a wetting drying wetting upward trend recording second order climatic oscillations of ca 40 ka each cycle is enclosed between major bounding surfaces defined by iron mineral encrustations these bounding surfaces represent periods of reduced eolian sand accumulation caused by a rising water table during the 2 5 ma global cooling the valdarno basin experienced a period of arid conditions owing to the influence of cold and dry easterly and northeasterly winds in contrast during the pleistocene the uplift of the pratomagno ridge protected the valdarno basin from easterly and northeasterly winds giving rise to relatively warm and wet conditions and mitigating the regional and global climatic changes

new cnes cls09 global mean dynamic topography computed from the combination of grace data altimetry and in situ measurements 1 an accurate knowledge of the ocean mean dynamic topography mdt is mandatory for the optimal use of altimetric data including their assimilation into operational ocean forecasting systems a new global 1 4 resolution mdt was computed for the 1993 1999 time period with improved data and methodology compared to the previous rio05 mdt field first a large scale mdt is obtained from the cls01 altimetric mean sea surface and a recent geoid model computed from 4 5 years of grace gravity recovery and climate experiment data altimetric sea level anomalies and in situ measurements are then combined to compute synthetic estimates of the mdt and the corresponding mean currents while the rio05 mdt was based on 10 years of in situ dynamic heights and drifting buoy velocities the new field benefits from an enlarged data set of in situ measurements ranging from 1993 to 2008 and includes all hydrological profiles from the argo array moreover the processing of the in situ data has been updated a new ekman model was developed to extract the geostrophic velocity component from the drifting buoy measurements the handling of hydrologic measurements has also been revisited compared to the previous rio05 solution the new global mdt resolves much stronger gradients in western boundary currents with mean velocities being doubled in some places moreover in comparison to several other recent mdt estimates we find that the new cnes cls09 mdt is in better agreement with independent in situ observations

the structure and genesis of weichselian to early hologene aeolian sand sheets in western europe abstract weischselian to early holocene aeolian sands are widespread in the lowlands of western europe to a large extent these deposits occur in the form of sheet like coversands with slipfaced dunes being much rarer whereas the latter type of landform corresponds to a single facies with dune foreset cross bedding aeolian facies 1 two structurally different facies are distinguishable in the sand sheets this paper concentrates on the two sand sheet facies which are referred to as aeolian facies 2 and aeolian facies 3 data on these two types are based on 1 a survey of existing literature and 2 a detailed analysis of lacquer peels and larger scale exposures in england the netherlands and the federal republic of germany aeolian facies 2 is defined by the spatial position of its beds which may be either horizontal inclined or oppositely dipping in the case of structures formed by fluctuating winds horizontal bedding is by far the most common type inclined bedding is related either to small isolated dome dunes or to scoop shaped deflation surfaces the structures resulting from fluctuating winds are rare and do not represent an inherently large measure of directional variability of the wind regime the internal structure of the beds is dominated by aeolian planebed lamination with or without concordantly infilled wind scours degradation of this stratification type because of interference by coarse particles is discussed aeolian facies 3 is uniquely typified by the alternation of coarser and finer grained horizontal thin beds that are either wavy or even in shape depositional models of facies 3 are given at both the local and regional scales in both cases the coarser grained layers result from tractional deposition of saltating and creeping grains whilst the finer grained strata were laid down by settling from suspension periodic changes in surface wind speed the presence of a damp depositional surface and the availability of both sand and silt in the source area are necessary conditions for the working of the models the large scale model is associated with specific environmental conditions of the weichselian upper pleniglacial the local scale model accounts for the fact that facies 3 is also found in units of weichselian late glacial or early holocene age the regional scale model involves stepwise tractional transport over long distances so that grains of distant provenance were mixed with material from sources nearer to the receiving site this process was an important control on the mineralogical composition of the resultant deposits the prevalence of aeolian planebed lamination in both facies 2 and the coarser grained layers of facies 3 is attributed to the interaction of three factors viz the rarity of topographic barriers the sparseness of vegetation cover and a high ratio between wind energy and sand availability during the processes of transport and deposition in the lowlands of europe sand sheets are gradually replaced in an easterly direction by coeval wind dunes the possible causes of this phenomenon are considered

plio quaternary stepwise drying of asia evidence from a 3 ma pollen record from the chinese loess plateau abstract a 3 ma pollen record was obtained from a continuous red clay loess paleosol sequence at chaona in the central chinese loess plateau clp the record shows a permanent change of a domination of typical cupressaceae forest vegetation representative of an ecological environment with a relative warm and humid climate during 3 0 2 6 ma to largely steppe vegetation under dry climate conditions after 2 6 ma the later is further manifested itself as steppe to forest or forest steppe spruce forest mostly mesophilous herbs between 2 6 ma and 1 5 ma forest steppe pine grass between 1 5 ma and 0 95 ma open forest steppe mesophilous and xeromorphic herbs pine between 0 95 ma and 0 5 ma and steppe xeromorphic herbs after 0 5 ma suggesting a process of stepwise aridification in central asia at the late pliocene and the quaternary

the baroclinic transport of the antarctic circumpolar current south of africa five hydrographic transects at nominal longitudes 0 e and 30 e and fourteen expendable bathythermograph xbt sections near the former longitude are used to study the baroclinic transport of the antarctic circumpolar current acc between africa and antarctica the bottom referenced geostrophic transport between the subtropical front and the acc southern boundary is 147 10 sv estimating the transport from the xbts using a technique previously employed south of australia proves delicate because of an irregular bathymetry and water mass variations it nevertheless confirms acc transports around 150 sv gathering these and other estimates from the atlantic sector suggests that while north atlantic deep water is injected in the current west of 35 w a partially compensating loss of deep circumpolar water occurs east of this longitude another transport increase from 0 e to 30 e might reflect southward transfer across the subtropical front south of the agulhas retroflection

sedimentology and stratigraphy of cenozoic deposits in the kagizman tuzluca basin northeastern turkey the kagizman tuzluca basin is located in the northeastern anatolia to the east of the intersection point near karliova of the major north and east anatolian fault systems this intermontane basin displays a thick sequence over 2000 m of mostly terrestrial deposits represented by repetitive alternations of the lake and fluvial environments ranging from late eocene oligocene to middle late miocene a marine incursion only mappable in the southeastern margin of the basin deposited limestones and sandy limestones rich in marine mollusks and nummulites in particular n fichteli that constrain an early oligocene age for this marine unit kagan fm the terrestrial basin fill deposits show different thicknesses throughout the basin due to irregular bottom topography and tectonic configuration of the basin margins the thickest deposits were accumulated along the different margins of the basin which received high quantities of siliciclastics from meandering river alluvial and coastal fans fan delta gilbert type delta and wave worked fluvial delta climate changes have also driven the development of lake environments during distinct depositional periods siliciclastic dominated overfilled lakes halikislak and kizilkaya formations and chemical dominated underfilled lakes turabi and tuzluca formations were formed they have been also classified as newark type and fundy type lakes respectively fluvial systems evolved from high energy meandering rivers deposited under humid climate gungoren formation to low energy meandering rivers resulted from arid and semiarid climates cincavat formation the transitional intervals from ephemeral river dry mudflat cincavat formation to saline pan lake tuzluca formation indicate wadi sand flat playa fluvial systems the chronostratigraphic constrains of the entire sequence remain poor and so far solely based on vertebrate fossil assemblages the evaporitic tuzluca formation would be middle miocene in age due to its stratigraphic position over the cincavat formation