australian east coast cyclones part i synoptic overview and case study abstract the meteorological conditions for the development of australian east coast cyclones are described the main synoptic precursor is a trough or dip in the easterly wind regime over eastern australia the cyclones are a mesoscale development which occurs on the coast in this synoptic environment they form preferentially at night in the vicinity of a marked low level baroclinic zone and just equatorward of a region of enhanced convection resulting from flow over the coastal ranges three different types of east coast cyclone have been identified types 1 and 3 are very small systems which can have lifetimes as short as 16 hours during which hurricane force winds have been observed to develop the other type 2 system is a meso synoptic scale cyclone that can bring sustained strong winds and flood rainfall over several days because of their intensity rapid development and occasional tiny size these systems are a major forecast problem

soil formation in coastal continental antarctica wilkes land recent antarctic soil studies suggest that in terrestrial ecosystems of coastal regions soil formation and chemical weathering occur to a greater extent than predicted by former models this paper summarizes pedogenic findings from the casey area on the coast of east antarctica and presents a proposal of soil formation sequences on a large scale data base soil organic matter accumulation and podzolization are important soil forming processes in regions outside the antarctic cold desert of the ross sea section the results suggest some correlations between the soil development and vegetation patterns nutrient supply in soil is affected by the high contents and availability of nitrogen phosphorus potassium and magnesium due to an input by seabirds the us soil taxonomy 8th edn gelisol order and the recently adopted world reference base for soil resources wrb cryosol soil group suggest a different understanding of impact of permafrost on soil formation according to the wrb and the us soil taxonomy organic permafrost affected soils are not cryosols but gelisols lithic haplorthels as well as haploturbels and to some extent aquaturbels and organic gelisols are suggested to be representative of the casey area in addition podzols occur to a great extent however the recent keys to soil taxonomy do not reflect the podzolization process in an adequate way and a classification is not possible according to a former version these soils would be lithic or pergelic haplocryods whereas according to the newly adopted wrb system these soils are spodic haplic cryosols

sea ice monitoring by l band sar an assessment based on literature and comparisons of jers 1 and ers 1 imagery spaceborne single polarization c band synthetic aperture radar sar imagery is widely used to gather information about the state of the sea ice cover in the polar regions c band is regarded as a reasonable choice for all season monitoring capabilities for specific mapping tasks however other frequency bands can be more suitable in the first part of this paper the summary of a literature study dealing with the utilization of l band sar imagery for sea ice monitoring is presented investigations reveal that if deformation features such as ice ridges rubble fields and brash ice are to be mapped l band radar is superior in a number of cases the second part of this paper addresses the comparison of jers 1 and ers 1 sar images that were acquired over sea ice east of svalbard and along the east coast of greenland the effects of the different frequencies polarizations and incidence angles of the two sar systems are discussed it is demonstrated that the images of both sensors complement one another in the analysis of ice conditions resulting in a more detailed view of the sea ice cover state

a composite record of late pleistocene relative geomagnetic paleointensity from the wilkes land basin antarctica abstract we report high resolution paleomagnetic records obtained from six piston cores recovered on the continental rise of the wilkes land basin wlb east antarctica in the frame of the italian australian wilkes land glacial history wega project the studied cores with a length of ca 4 m each were collected from the gentle and steep sides of sedimentary ridges present in the lower part of the continental rise and consist of very fine grained sediments paleomagnetic measurements were carried out on u channel samples apart from a low coercivity magnetic overprint removed after the first steps of alternating field demagnetization each core is characterized by a well defined characteristic remanent magnetization paleomagnetic inclinations fluctuate around the expected value of ca 77 for such high latitude sites and always indicate normal magnetic polarity short period oscillations to anomalously shallow paleomagnetic inclinations up to 20 were identified at different levels of the sampled sequences positive reverse inclination values were however not observed specific rock magnetic measurements indicate a substantial homogeneity of the magnetic mineralogy in the sampled sequences for each core we reconstructed curves of relative paleointensity rpi as computed by nrm 20 mt and nrm 20 mt arm 20 mt variation of the geomagnetic field an original age model was established by tuning the individual rpi curves with the available global and regional reference rpi stacks paleomagnetic results supported by other limited bio and chronostratigraphic constraints establish that all the cores are late pleistocene in age two provide an expanded record of the last ca 30 ka pc18 and pc19 three span the last ca 100 200 and 300 ka respectively pc25 pc27 and pc26 and one reaches back to ca 780 ka pc20 approaching the brunhes matuyama transition thus the wega paleomagnetic record provides the first experimental data documenting the dynamics and amplitude of the geomagnetic field variations at high southern latitudes during the brunhes chron the individual normalized rpi records were merged in a wega rpi stacking curve spanning the last 300 kyr the comparison of the wega rpi individual and stacked curves with the global references rpi stacks shows that geomagnetic paleointensity variations with periods longer than a few to tens kyr depending on the sedimentation rate can be safely recognized in this sector of the peri antarctic margins furthermore the stacking of the individual chrm inclination records indicates that the recurrent swings to shallow paleomagnetic inclinations may be correlated to the main known geomagnetic excursions of the brunhes chron supporting the validity of the age models the reconstructed average sediment accumulation rates for the individual cores range from 0 6 to 19 cm ka and are compatible with their position within the wlb with the lowest rates found close to the ridge of the sedimentary drifts moreover the high resolution age models obtained in this study provide original constraints to assess chronology rates and amplitudes of the climatic and environmental processes affecting this key area of the peri antarctic margins during the late pleistocene

sediment distribution and sedimentary processes across the antarctic wilkes land margin during the quaternary the study of existing cores collected across the wilkes land margin provides us with a better understanding of the sediment distribution and processes across this margin during the holocene and during pleistocene glacial and interglacial cycles holocene depositional rates are high in deep 1000 m inner shelf basins where diatomaceous ooze is deposited at estimated minimum sedimentation rates ranging from 40 to 60 cm kyr in the shelf troughs holocene sediment has a patchy distribution or is totally absent this is also the case on the shelf banks due to differential deposition because of the irregular relief of the continental shelf and the erosion and redistribution by bottom currents pleistocene interglacial sedimentation is well represented in sediment from the continental rise and is dominated by hemipelagic deposition of massive mud with the highest biogenic content as indicated by opal and with a high abundance of clasts ird during the pleistocene glacial cycles diamictons were deposited in the continental shelf troughs and on the banks reworking e g by bottom currents and remobilization e g gravity flows of these diamictons is a common process along the shallow continental shelf banks on the continental slope and the continental rise gravity flows are one of the most important sedimentary processes sediment from continental slope cores with a texture that greatly resembles the diamictons on the shelf is interpreted to represent either part of a slump block or the start of a debris flow downslope crudely stratified to laminated intervals represent the transition between an end member of a debris flow and a turbidity flow some of the laminated intervals in cores from the continental rise represent sediment deposited from a turbidity flow ages obtained from cores further support that slumps and gravity flows are dominant processes in this margin because numerous hiatuses apparently are present in cores from the base of the slope one of these cores extends into the miocene elsewhere on the continental rise massive and laminated sediments in cores of similar length record near continuous pleistocene sedimentation r 2003 elsevier science ltd all rights reserved

orographic influence on basic flow and cyclone circulation and their impacts on track deflection of an idealized tropical cyclone abstracta series of idealized numerical experiments and vorticity budget analyses is performed to examine several mechanisms proposed in previous studies to help understand the orographic influence on track deflection over a mesoscale mountain range when an idealized tropical cyclone tc is embedded in a uniform easterly flow and passes over a mountain with a moderate froude number it is deflected to the south upstream moves over the mountain anticyclonically and then resumes its westward movement the vorticity budget analysis indicates that the tc movement can be predicted by the maximum vorticity tendency vt the orographic effects on the above tc track deflection are explained by the following 1 upstream of the mountain the easterly basic flow is decelerated as a result of orographic blocking that causes the flow to become subgeostrophic which advects the tc to the southwest analogous to the advection of a point vortex embedded in a flow the vt is primarily dominated by the horizontal vo

significance of clay mineral assemblages in the antarctic ocean abstract typical examples from different morphological and geological settings in the antarctic ocean are reviewed in order to discuss the value of clay mineral assemblages for reconstructing the glacial history of antarctica the paleoceanographic history of the antarctic ocean and the sedimentary processes at the antarctic continental margin the significance of clay minerals for paleoenvironmental reconstructions strongly varies with both the position of the sites under investigation and the age of the sediments in late mesozoic to paleogene sediments clay mineral assemblages are sensitive tools for reconstructing climatic conditions for example the shift from smectite dominated assemblages to illite and chlorite dominated assemblages in the earliest oligocene clearly documents the transition from chemical weathering conditions under a warm and humid climate to physical weathering under cooler conditions submarine elevations such as maud rise and kerguelen plateau give the best record for direct paleoclimatic and paleoceanographic studies at the proximal sites of the continental slope and shelf as well as in the deep sea the paleoclimatic information normally is masked by a variety of processes resulting in sediment redistribution at those sites in contrast the clay mineral assemblages bear a wealth of information on different sedimentary processes after the establishment of a continental east antarctic ice sheet physical weathering prevailed variations in the clay mineral records predominantly reflect the influence of different sediment sources resulting from different glacial hydrographic or gravitational transport processes because these sedimentation processes are generally linked to climatic variations the clay mineral assemblages in most of the neogene and quaternary sediments provide indirect paleoclimatic information the processes are best documented in the clay mineral composition in those areas where changes in source regions with distinct petrographic differences are expected and where distances from the source region are low

further investigation of the impact of idealized continents and sst distributions on the northern hemisphere storm tracks abstractbuilding on previous studies of the basic ingredients of the north atlantic storm track examining land sea contrast orography and sst this article investigates the impact of eurasian topography and pacific sst anomalies on north pacific and atlantic storm tracks through a hierarchy of atmospheric gcm simulations using idealized boundary conditions in the hadley centre hadgam1 atmospheric circulation model the himalaya tibet mountain complex is found to play a crucial role in shaping the north pacific storm track the northward deflection of the westerly flow around northern tibet generates an extensive pool of very cold air in the northeastern tip of the asian continent which strengthens the meridional temperature gradient and favors baroclinic growth in the western pacific the kuroshio sst front is also instrumental in strengthening the pacific storm track through its impact on near surface baroclinicity while the warm waters around indonesia tend to weaken it through the impact on barocl

mid late pleistocene glacimarine sedimentary processes of a high latitude deep sea sediment drift antarctic peninsula pacific margin the effects of glaciation on sediment drifts is recognised from marked sedimentary facies variation in deep sea cores taken from the continental rise of the antarctic peninsula pacific margin nineteen sediment cores were visually described logged for magnetic susceptibility and x radiographed about 1000 analyses were performed for grain size clay minerals and biostratigraphy foraminifera nannofossils and diatoms four sediment types associated with distinct sedimentary processes are recognised based on textural compositional analysis 1 hemipelagic mud forms the bulk of the interglacial sediment and accumulated from the pelagic settling of bioclasts and ice rafted wind transported detritus 2 terrigenous mud forms the bulk of the glacial sediment and accumulated from a combination of sedimentary processes including turbidity currents turbid plumes and bottom current reworking of nepheloid layers 3 silty deposits occurring as laminated layers and lenses represent the lateral spillout of low density turbidity currents 4 lastly glacial interglacial gravelly mud layers derive from settling of ice rafted detritus five depositional settings are interpreted within sediment drift 7 each characterised by the dominance interaction of one or several depositional processes the repetitive succession of typical sedimentary facies is inferred to reflect a sequence of four climatic stages glaciation glacial deglaciation and interglacial each one characterised by a distinctive clay mineral assemblage and bioclastic content variations in clay mineral assemblage within interglacial stage 5 core sed 06 suggest minor colder climatic fluctuations possibly correlatable with substages 5a to 5e

the influence of topography on midlatitude cyclones on australia s east coast the east coast of australia has a relatively high frequency of midlatitude cyclones locally known as east coast lows ecls which can cause severe weather including widespread flooding and coastal erosion the elevated topography close to the east coast has been hypothesized to play a role in both the genesis and impacts of cyclones in this region but existing studies have been limited to case studies of individual events in this paper we present the results from two 20 year wrf simulations over the australian region and assess the results from removing all topography in the region on both mean atmospheric circulation and ecl frequency removing topography results in an increase in sea level pressure to the south of australia and an increase in moisture flux convergence and rainfall near the east coast as well as a decrease in potential vorticity to the north of the ecl region this results in a change in the spatial distribution of cyclones with a 37 decrease in the frequency of cyclones that develop to the south of the ecl region but a 20 increase in cyclones near the east coast this results in little overall change in the frequency of ecls and suggests coarse topography is unlikely to be responsible for the difficulties in simulating coastal cyclones in global climate models

clay mineral fluctuations and surface textural analysis of quartz grains in pliocene quaternary marine sediments from wilkes land continental rise east antarctica paleoenvironmental significance abstract pliocene quaternary marine sediments from wilkes land continental rise were investigated using clay mineral analysis and quartz grain surface texture observations the studied piston cores were collected during a geophysical and geological survey in the framework of the italian and australian wega project the cores were collected along two transects crossing the channel mound system that characterizes the wilkes land continental rise massive and laminated facies were recognized in these sedimentary sequences the clay mineral assemblages are dominated by illite smectite and chlorite occur in intermediate amounts whereas kaolinite is scarce illite derives from the hinterland of the mertz and ninnis glaciers smectite and kaolinite derive from the ross sea area and they are transported by westward marine bottom currents chlorite is derived both from the adjacent continent and from the victoria land different concentrations of individual clay minerals in the massive and laminated facies are controlled by the interplay between different source areas and the main sedimentary processes glacial and eolian quartz grains prevail in the massive units indicating short transportation and rapid deposition from melting ices with no further significant transport action by marine currents in the laminated facies the high amount of quartz grains affected by high energy subaqueous transport features are related both to turbiditic processes and to bottom current transport

the basic ingredients of the north atlantic storm track part i land sea contrast and orography understanding and predicting changes in storm tracks over longer time scales is a challenging problem particularly in the north atlantic this is due in part to the complex range of forcings land sea contrast orography sea surface temperatures etc that combine to produce the structure of the storm track the impact of land sea contrast and midlatitude orography on the north atlantic storm track is investigated through a hierarchy of gcm simulations using idealized and semirealistic boundary conditions in a highresolution version of the hadley centre atmosphere model hadam3 this framework captures the largescale essence of features such as the north and south american continents eurasia and the rocky mountains enabling the results to be applied more directly to realistic modeling situations than was possible with previous idealized studies the physical processes by which the forcing mechanisms impact the large scale flow and the midlatitude storm tracks are discussed the characteristics of the north american continent are found to be very important in generating the structure of the north atlantic storm track in particular the southwest northeast tilt in the upper tropospheric jet produced by southward deflection of the westerly flow incident on the rocky mountains leads to enhanced storm development along an axis close to that of the continent s eastern coastline the approximately triangular shape of north america also enables a cold pool of air to develop in the northeast intensifying the surface temperature contrast across the eastern coastline consistent with further enhancements of baroclinicity and storm growth along the same axis

plio quaternary sedimentation on the wilkes land continental rise preliminary results abstract the wilkes land continental rise is characterised by mounds and channels with approximately a north south elongation perpendicular to the margin proximal mound relief is up to 1000 m decreasing to about 300 m in the central part during the geophysical and geological survey conducted on in february march 2000 by the joint italian and australian wega project onboard r v tangaroa 11 piston cores were collected along two transects crossing the channel mound system all cores were logged for physical magnetic susceptibility and density and acoustic properties p wave velocity split cores were x rayed and samples were analysed for clay mineral assemblages chemical and micropaleontological diatoms foraminifera and nannofossils content glacial and interglacial intervals have been recognised in the sediment cores the interglacial facies consists of massive mud distinguished by a bioturbated massive mud occasionally with fine grained ice rafted debris ird and b structureless massive mud with abundant fine to coarse grained ird containing well preserved open ocean diatoms the glacial facies is represented by laminated mud with planar and or cross laminations with occasional isolated dropstones and rare poorly preserved sea ice diatoms the sharp boundary characterizing the limit between massive to laminated facies is interpreted to indicate a fast glacial onset in contrast the smooth passage presents from laminated to massive sediments indicates a gradual glacial waning recent down slope gravity flows have been identified in a turbidite a normally graded coarse grained sand recovered in the thalweg of jussie canyon and probably also in the massive debris facies from the steep side of mound a the massive debris is characterised by structureless and unsorted gravel and pebbles within a muddy matrix clay mineral assemblages and grain lithologies indicate a hinterland wilkes basin and continental shelf provenance for the terrigenous fraction

microtextures on quartz grains in tills from antarctica quartz grains of the sand 63 2000 m fractions from tills of oligocene to quaternary age in antarctica were analyzed by scanning electron microscope sem to test the hypothesis that relative ice thickness and distance of transport influence the type and range of microtextures observed on individual grains in this study replicated subsamples were analyzed from tills emplaced by thick glaciers with both short and long transport distances till samples with grains transported over long distances up to several hundred km under thick ice 1000 m were compared with quartz grains from relatively thinner e g 500 m thick outlet glaciers with shorter transport distances 100 km a range of microtextures including subparallel linear fractures conchoidal fractures arc shaped steps grain relief edge sharpness grain angularity and roundness straight and curved grooves crescentic gouges dissolution features precipitation features and presence of adhering particles was used to determine the environmental history of these grains microtextures on sand size clasts including microfractures abrasion etching and coatings can provide important information on paleoenvironmental history including glacier activity and severity of weathering inferred from etching and dissolution features

implications of late eocene to early miocene clay mineral assemblages in mcmurdo sound ross sea antarctica on paleoclimate and ice dynamics abstract the clay mineral assemblages of upper eocene to lower miocene sediments recovered at the ciros 1 and mssts 1 drill sites on the mcmurdo sound shelf antarctica were analyzed in order to reconstruct the cenozoic antarctic paleoclimate and ice dynamics the assemblages are dominated by smectite and illite with minor amounts of chlorite and kaolinite the highest smectite amounts and best smectite crystallinities occur in the upper eocene part of ciros 1 below 425 445 mbsf they indicate that during their deposition chemical weathering conditions prevailed on the nearby continent large parts of east antarctica were probably ice free at that time but some glaciers reached the sea and contributed to the glaciomarine sedimentation in contrast only minor total amounts of smectite are present in oligocene and younger sediments due to the shift to mainly physical weathering on an ice covered antarctic continent however relative smectite percentages rise to more than 60 during two late oligocene intervals ca 27 5 26 2 and 25 0 24 5 ma and during one early miocene interval starting at ca 23 3 ma these intervals are characterized by ice masses coming probably from the south where volcanic rocks acted as a source as also indicated by the composition of the sand and gravel fractions during the other intervals the ice came from the west where the physical erosion of basement rocks and sedimentary rocks of the beacon supergroup in the transantarctic mountains provided high illite concentrations because the two drill sites are only 4 km apart their clay mineral records can be correlated this led to a new interpretation of the oligocene paleomagnetic data of the mssts 1 site and to a more detailed lithostratigraphic correlation of the miocene parts of the cores

the influence of orographic rossby and gravity waves on rainfall author s cohen ny boos wr abstract 2016 royal meteorological society orography is known to influence winter precipitation in asia and the indo pacific ocean by mechanically forcing winds but the dynamics involved in the precipitation response are incompletely understood this study investigates how two types of orographically forced oscillatory motions alter time mean winds and precipitation the quasi geostrophic omega equation is used together with previous ideas of downward control to develop a simple theory of the spatial distribution and amplitude of the vertical motion response to orographically forced stationary rossby waves and gravity wave drag in a precipitating atmosphere this theory is then used to understand the response of the boreal winter atmosphere to realistic asian orography in a global numerical model that includes representations of moist processes and unresolved gravity wave drag we isolate the effects of the orographically forced stationary rossby wave and the gravity wave drag by incremental addition of wave sources in this model the peak precipitation response to the forced rossby wave is about a factor of three larger than that of the gravity wave drag but the wave drag response has a distinct spatial structure that dominates in some regions both the rossby wave and the gravity wave drag perturb precipitation in areas distant from orography producing shifts in the equatorial intertropical convergence zone an increase in precipitation over southern asia and drying in much of northern asia

glaciomarine sedimentation and its paleoceanographic implications along the fjord margins in the south shetland islands antarctica during the last 6000 years abstract two 3 m long cores were collected from maxwell and admiralty bays on king george island one of the south shetland islands west antarctica these cores were examined for their benthic foraminifer globocassidulina biora 18o and 13c records diatom abundance counts and biogenic constituents carbon and silica these high resolution data were used to reconstruct the paleoceanography of the bays and to link the marine record with deglaciation of the south shetland islands ice cap in maxwell bay extremely low diatom abundance the depletion of total organic carbon toc and biogenic silica biosi and enriched 18o between 6200 and 4000 bp indicate that this period was characterized by cold conditions with deposition of waterlain till unit 1 just seaward of the grounding line low sedimentation limitation of primary production on surface water and lack of meltwater supply deglaciation along the maxwell bay margin was dated from about 4000 bp until at least 2700 bp with increasing toc biosi and diatom abundance and decreasing the c n ratio up core at this time subglacial meltwater streams began to emanate from the glacier front sediment laden meltwater plumes from these streams deposited interlaminated sand and mud unit 2 in the ice proximal zone deglaciation was followed by marked climatic warming at around 2700 bp with evidence of toc and biosi maxima depleted 18o and markedly increased diatom valves with further glacier recession diatomaceous pebbly mud unit 3 was deposited in open marine conditions a large influx of organic materials by enhanced production during this period caused both rapid depletion of caco3 in sediment and resulted in marked increase in sedimentation since 2700 bp at 200 m water depth along the maxwell bay margin core s 19 in contrast the shallower platform along the admiralty bay margin core s 2 was deglaciated later about 1900 bp that is 2000 years after the maxwell bay margin this is possible as core s 19 is situated 200 m water depth more distal to the fjord head glacier while core s 2 in admiralty bay lies on a shallower platform

seismo stratigraphic analysis of the wilkes land continental margin east antarctica influence of glacially driven processes on the cenozoic deposition abstract multichannel seismic reflection data were collected from the wilkes land continental margin and particularly focusing on the lower rise area by the international wilkes basin glacial history wega project existing lower resolution seismic data also are used to understand the relationship between the basement and the sedimentary cover and to correlate the evolution of the rise and the shelf on the basis of the acoustic character and the internal geometry we recognise nine different sequences named wl s1 wl s9 from the deepest to the shallowest within the sedimentary section sequence wl s1 represents syn rift sediments deposited within tilted blocks of sedimentary crystalline and volcanic basement sequences wl s2 wl s9 represent the post rift sediments that show quite a complex architecture sequence wl s2 is a well developed wedge downlapping onto the break up unconformity sequences wl s3 wl s7 are parts of a margin prograding aggrading sequence during which large sediment ridges were deposited on the slope and rise in particular sequences wl s5 wl s7 began with the deposition of a turbidite fan system sequence wl s5 that developed in a braided channel levee complex wl s6 wl s7 dominated by downslope flows indirect correlation of the sequences wl s4 wl s6 with dsdp 269 about 600 km north of the study area suggests an early late miocene age sequences wl s8 and wl s9 represent the smoothing and filling of the pre existing morphology in a generally low energy environment with reduced bottom current activity during this time most of the sediment is deposited on the shelf and slope while the rise is generally starved differences in downslope current energy and in sediment load are interpreted to reflect variation of the terrigenous input from the shelf to the rise through time we suggest that channel levee systems on the rise reflect an increase in sediment supply from the continental shelf during the early miocene marking the growth of wet based temperate ice sheet on the near continent the youngest sequences on the rise and shelf reflect decreased sediment supply to the rise that may be related to the transition from a temperate to a polar glacial system

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

paleoceanographic and paleoclimatic evolution in the weddell sea antarctica during the middle eocene late oligocene from a coarse sediment fraction and clay mineral data odp site 689 abstract paleoceanographic and paleoclimatic variations from the middle eocene to the late oligocene in the antarctic area atlantic sector have been deduced from a coarse fraction and clay mineral analysis of odp site 689 leg 113 sediments in the middle eocene smectite rich sediments were a consequence of warm climate with alternating wet and dry seasons on the antarctic margins productivity in the maud rise area of the southern ocean was low no opal was deposited preservation of carbonate is very good carbonate preservation shows cyclic changes clinoptilolite is a common mineral at the middle late eocene boundary 40 8 ma productivity suddenly increased enough to allow preservation of opal skeletons clinoptilolite disappeared where opal appeared illite appearance points to cooling of antarctic climates the presence of detrital kaolinite indicates a change in oceanic circulation in the late eocene cyclic changes in productivity cycle length 0 42 ma were associated with clay mineral compositional variations sediments from colder highly productive periods generally contain more illite and less smectite than warmer ones the early oligocene was a period of very high productivity highest opal accumulation rates correspond to strongest carbonate dissolution cyclic changes in productivity with a mean cycle duration of 0 4 0 5 myr were associated with cyclic changes in clay mineral composition highest productivity intervals are generally those with highest smectite content because of strong erosion of sediments of the antarctic margins sediments from less productive warmer periods most of the time contain more illite in the late oligocene the intensity of physical weathering on antarctica was stronger as documented by increasing fluxes of illite muscovite amphiboles and talc ice expanded on the east antarctic continent lower productivity than in the early oligocene is indicated by lower accumulation rates of opal and weaker carbonate dissolution cyclic variations in productivity correlate to cyclic variations in illite and smectite contents as in the early oligocene

microtextures of quartz grains from modern terrestrial and subaqueous environments north slope of alaska abstract scanning electron microscopic sem analysis of surface features on detrital monocrystalline quartz sand grains is used in conjunction with existing information on hydrology climate and depositional environment in an attempt to unravel the history of surface deposits on the alaskan north slope and shelf samples from along the colville and sagavanirktok rivers ranging from the high relief headwaters to the subaerial deltas were analyzed together with a suite of continental shelf samples that form a transect from shallow submerged deltas across barrier islands shoals and out to the shelf break twenty to thirty grains from each sample were analyzed and assigned to one of eight grain types the classification was devised by the authors to represent increasing aquatic and eolian a rasion and resultant destruction of the original grain form and evolution towards a rounded and chemically altered form our study leads to the following conclusions 1 increasing abrasion occurs with increasing river transport distance but this pattern does not extend across the shelf where modern erosion of underlying shelf deposits is believed to mask the riverine influence 2 a considerable number of freshly fractured grains occur in samples from delta nearshore and shelf environments but are completely absent in the fluvial environment suggesting that the process of refracturing grains is associated with modern littoral or marine processes 3 the large number of refractured grains in the shoal environment suggests that intense impacting of grains through ice related sediment ry processes may provide a mechanism for fracturing the grains 4 samples from the barrier islands stamukhi shoal and the general shelf surface are so similar that the question of whether such shoals represent drowned barrier islands or modern constructional features cannot be answered 5 the similarity between all shelf samples with a preponderance of eolian grain types suggest that sands with similar abrasional histories cover the shelf and this blanket may have developed from deposits strongly influenced by eolian processes during times when the shelf was subaerially exposed 6 the extensive chemical features on the surface of many of the grains from the shelf environment suggest a relict or erosional source for the grains

on the circulation and water masses over the antarctic continental slope and rise between 80 and 150 e abstract the circulation and water masses in the region between 80 and 150 e and from the antarctic continental shelf to the southern boundary of the antarctic circumpolar current acc 62 s are described from hydrographic and surface drifter data taken as part of the multi disciplinary experiment baseline research oceanography krill and the environment broke two types of bottom water are identified adelie land bottom water formed locally between 140 and 150 e and ross sea bottom water ross sea bottom water is found only at 150 e whereas adelie land bottom water is found throughout the survey region the bottom water mass properties become progressively warmer and saltier to the west suggesting a westward flow all of the eight meridional ctd sections show an antarctic slope front of varying strength and position with respect to the shelf break in the water formation areas between 140 and 150 e and 104 e the antarctic slope front is more v shaped while elsewhere it is one sided the shape of the slope front and the presence or absence of water formation there are consistent with other meridional sections in the weddel sea and simple theories of bottom water formation gill 1973 deep sea research 20 111 140 whitworth et al 1998 in jacobs and weiss eds ocean ice and atmosphere interactions at the antartic continental margin antarctic research series american geophysical union washington pp 1 27 adcp surface velocities and buoy drift tracks show a strong westward flow over the shelf and slope regions in the region 90 100 e there is a strong eastward flow of the waters just south of the southern boundary of the acc suggesting a recirculation of the westward slope current and the presence of a weak cyclonic gyre using the adcp velocities as a reference for the ctd data the average westward transport in this region is 29 4 14 7 sv

a cyclone phase space derived from thermal wind and thermal asymmetry abstract an objectively defined three dimensional cyclone phase space is proposed and explored cyclone phase is described using the parameters of storm motion relative thickness asymmetry symmetric nonfrontal versus asymmetric frontal and vertical derivative of horizontal height gradient cold versus warm core structure via the thermal wind relationship a cyclone s life cycle can be analyzed within this phase space providing substantial insight into the cyclone structural evolution an objective classification of cyclone phase is possible unifying the basic structural description of tropical extratropical and hybrid cyclones into a continuum stereotypical symmetric warm core tropical cyclone and asymmetric cold core extratropical cyclone life cycles are illustrated using 1 navy operational global atmospheric prediction system nogaps operational analyses and 2 5 ncep ncar reanalyses the transitions between cyclone phases are clearly illustrated within the phase space including extratro

seismic facies and sedimentary processes on the continental rise off wilkes land east antarctica evidence of bottom current activity abstract the slope and rise areas off wilkes land east antarctica encompass three large scale composite sediment ridges dissected by two broad deep sea valleys jussieu canyon and wega channel large scale depositional architecture revealed from multi channel seismic profiles acquired during the wilkes basin glacial history wega cruise indicates a wide temporal and spatial variability in the dominant depositional processes delivering or redistributing sediments on the slope and rise all three sediment ridges are built on a flat seafloor and resulted from the growth of a thick sediment section at least 2 km with a depositional relief in the order of hundreds of meters on the adjacent deep sea valleys the sediment ridges show their maximum internal complexity in areas shallower than 3000 m where they are also substantially thicker as much as 1 1 5 s in two way travel time high amplitude sediment waves typically 20 30 m and up to 50 70 m have wavelengths ranging from 1500 to 3500 m and occur in the deepest sectors of the continental rise where the sediment ridges toe out in the lower rise the sediment waves display a consistent decrease in wavelength with increasing water depth on seismic profiles the relief of the sediment waves decreases from older to younger sequences possibly indicating a decrease in bottom current intensity throughout their formation sediment waves occur also at the seafloor which is dominated elsewhere by irregular topography and widespread evidence of erosion however no conclusion can be drawn on the possible modern activity of these large scale bedforms in shallower upper rise areas where the sediment ridges are thicker sediment waves are evident in the upper stratigraphic units while the remaining section is characterized by the development of channel levee complexes seen as small scale erosional channels bordered by depositional reliefs consisting of variable amplitude reflector packages wedging out away from the channels channel levee complexes are locally associated with poorly developed sediment waves the origin of these features is likely related to transport by turbidity flows from the edge of the antarctic shelf and implies the presence of a more temperate glacial regime than the one dominating since the late miocene the formation of the sediment waves both in this more proximal area and on the deep rise is indicative of the impact of bottom hugging currents during intervals of the cenozoic history of the margin no constrains are available at present on the nature of these currents nor on the timing of their activity down slope turbidity currents downwelling dense waters or slope parallel contour currents are possible mechanisms despite this substantial uncertainty the observed progressive upward attenuation of the wave amplitudes indicates that substantial variations of sediment delivery and dispersal occurred through time we suggest that the interval of more complex depositional geometry in the proximal areas reflects higher bottom current velocity and or increased sediment input perhaps during conditions of temperate wet based ice sheet on the continent these conditions were conducive to high rates of melt water production formation of dense plumes and enhanced sediment input