palaeoenvironments and cultural sequence of the florisbad middle stone age hominid site south africa abstract florisbad an open air spring site with 7 m of strata has yielded the type assemblage of middle stone age msa fauna the cranium of an archaic hominid in 1932 and an extensive sequence of msa artefacts in the 1980s the cultural assemblages include an early msa dated broadly to 279 000 47 000 years a highly retouched form of msa at 157 000 21 000 years and a minimally retouched expedient msa assemblage from a series of occupation horizons at 121 000 6000 years the latter represents multiple brief visits to a hunting and butchery site on the edge of an active spring pool where periodic sedimentation gently buried occupation debris in a near pristine context periods of lower spring discharge are represented by organic horizons as swampy vegetation encroached on the springs while periods of higher spring discharge created pools overall the spring sequence indicates low energy subaqueous environments similar to lakes ponds or backwater sites the sequence is characterized by fine sands silts and clays responsible for the good archaeological preservation

vegetation history and climate in the savanna biome south africa since 190 000 ka a comparison of pollen data from the tswaing crater the pretoria saltpan and wonderkrater abstract the long term quaternary vegetation and climate history in south africa s savanna biome since ca 190 000 yr bp is elucidated by the palynological record of lake sediments in the tswaing crater the pretoria saltpan and spring deposits from wonderkrater despite hiatuses in both sequences palaeotemperature trends from the two places are presented by means of principal components analysis pca of pollen data allowing a new regional palaeoenvironmental reconstruction correlation in the older sections of the sequences beyond radiocarbon dating is tentative suggesting that the wonderkrater sequence is roughly 4 times younger than the tswaing sequence combined temperature indications from the two sites suggest cooling at ca 14 000 yr bp and slight warming at ca 15 000 yr bp although no data are available between ca 15 000 and 21 000 and 25 000 and 31 000 yr bp generally cool conditions are suggested between ca 11 000 and 33 000 yr bp between ca 33 000 and an extrapolated age of ca 80 000 yr bp at least three warmer pulses of varying intensity occurred no data are available between ca 80 000 and 150 000 yr but between 150 000 and ca 190 000 yr bp two cool and two moderately warm phases are suggested

persistent millennial scale climatic variability over the past 25 000 years in southern africa abstract data from stalagmites in the makapansgat valley south africa document regional climatic change in southern africa in the late pleistocene and holocene a new tims u series dated stalagmite indicates speleothem growth from 24 4 to 12 7 ka and from 10 2 to 0 ka interrupted by a 2 5 ka hiatus high resolution oxygen and carbon stable isotope data suggest that postglacial warming was first initiated 17 ka was interrupted by cooling probably associated with the antarctic cold reversal and was followed by strong warming after 13 5 ka the early holocene experienced warm evaporative conditions with fewer c4 grasses cooling is evident from 6 to 2 5 ka followed by warming between 1 5 and 2 5 ka and briefly at ad 1200 maximum holocene cooling occurred at ad 1700 the new stalagmite largely confirms results from shorter holocene stalagmites reported earlier the strongest variability superimposed on more general trends has a quasi periodicity between 2 5 and 4 0 ka also present are weaker 1 0 ka and 100 year oscillations the latter probably solar induced given similarities to the antarctic records the proximate driving force producing millennial and centennial scale changes in the makapansgat record is postulated to be atmospheric circulation changes associated with change in the southern hemisphere circumpolar westerly wind vortex

near surface dynamical structure of the kuroshio extension 1 lagrangian data from 657 svp drifters cnes aviso archiving validation and interpretation of satellite oceanographic data time variable satellite altimeter sea level anomaly and levitus 98 hydrographic data are used to develop 0 25 spatial resolution maps of the mean and eddy circulations in the northwestern pacific during the 1990s drifter velocities at 15 m depth and 200 m temperature data clearly indicate in the kuroshio extension ke jet two prominent meanders that culminate in a 300 km northward deflection east of the shatsky rise at 160 e the interannual trends of aviso mesoscale variance are absent along the path of the meandering ke jet three anticyclonic recirculations can be identified south or southeast of the kuroshio the southernmost around daito island being a new discovery about 3 of the drifters with drogues attached crossed the kuroshio front the aviso currents are correlated at 0 8 with drifter geostrophic velocity the aviso geostrophic currents are adjusted in amplitude to the contemporaneous drifter observations and are further used to compute an unbiased mean geostrophic circulation and the quasi geostrophic reynolds stresses in the ke region the principal axes of the eddy reynolds stresses are oriented along the unbiased mean velocity vectors within the meandering ke jet the time mean horizontal momentum balance that includes both the mean and eddy momentum convergences is used to compute absolute sea level map and its uncertainty at 145 e the 2000 m depth absolute dynamic height referenced to the sea level reveals a heretofore unknown 70 dynamic cm drop from 25 to 42 n

south indian countercurrent and associated fronts a striking feature of the south indian ocean circulation is the presence of the eastward south indian countercurrent sicc that flows in a direction opposite to that predicted by the classical theories of wind driven circulation several authors suggest that the sicc resembles the subtropical countercurrents stccs observed in other oceans which are defined as narrow eastward jets on the equatorward side of subtropical gyres where the depth integrated flow is westward these jets are associated with subsurface thermal fronts at thermocline depths by the thermal wind relation however the subsurface thermal front associated with the sicc has not been described to date other studies conjecture an important role for salinity in controlling the sicc in the present work we analyze three argo based atlases and data from six hydrographic cruises to investigate whether the sicc is accompanied by permanent thermal and density fronts including salinity effects the seasonal cycle of these fronts in relation to the sicc strength is also investigated we find that the sicc is better described as composed of three distinct jets which we name the northern central and southern sicc we find that the southern sicc around 26 s has an associated thermal front at subsurface depths around 100 200 m with salinity being of secondary importance the southern branch strength is related to mode waters poleward of the front similar to a stcc like current however the sicc multiple jet structure seems to be better described as resulting from pv staircases

profiling float measurements of the recirculation gyre south of the kuroshio extension in may to november 2004 1 during may to november 2004 20 profiling floats were deployed in the recirculation gyre rg region south of the kuroshio extension ke with the ke and rg being in a stable state most of these floats remained within the rg resulting in a large number of satellite position fixes for estimating the velocities at the parking depth 1500 db and a large number of temperature salinity profiles for estimating the geostrophic velocities above the parking depth the flows of the rg at different depths in the upper 1500 db are found to be approximately parallel to each other with the speed at the surface 35 cm s 1 being about three and a half times larger than that at the parking depth 10 cm s 1 by analyzing the full depth conductivity temperature depth profiles in the rg in addition to the velocity estimates we found that the vertical structure of the rg velocity field was dominated by the barotropic and first baroclinic modes the two modes are combined in such a way that the resulting rg circulates anticyclonically in the same direction from the surface to the bottom and has an anticyclonic bottom velocity on the order of 5 cm s 1 from the barotropic component depth averaged of the rg velocity field the rg transport with one standard error is estimated at 101 8 106 m3 s 1

seasonal variation and instability nature of the north pacific subtropical countercurrent and the hawaiian lee countercurrent 1 the relation between baroclinic instability of the north pacific subtropical countercurrent stcc and the hawaiian lee countercurrent hlcc and seasonal evolution of mesoscale sea surface height ssh variability was investigated by using historical hydrographic data and altimeter derived ssh anomaly data during 1992 2000 the annual and monthly mean dynamic height climatologies show two robust eastward flowing countercurrents the stcc extends typically along 24 n from 130 e to 160 w and slightly shifts to the north as it flows toward the east and the hlcc is located typically along 20 n and extends from about 150 e to just west of the hawaiian islands seasonal variations of the stcc in the western north pacific and the hlcc west of the hawaiian island where the eddy variability is relatively larger than the background were quite different the stcc hlcc is strong in winter summer to summer winter and weak in fall spring in contrast seasonal evolution of mesoscale ssh variability has almost the same cycle in the two countercurrent regions the eddy kinetic energy eke is a maximum in spring and a minimum in fall the dominant zonal scales are shortest in late winter and become longer with time a linear quasigeostrophic stability analysis using a three layer model indicates that instability properties are very similar between the two countercurrent regions the stcc and the hlcc become baroclinically more unstable during winter and late fall to winter respectively due to strong vertical velocity shear and weak stratification between the stcc hlcc and underlying westward flow and the most unstable wave during this season has an e folding timescale of about 2 3 months and a zonal wavelength of about 300 400 km the same behavior of the seasonal evolution of the mesoscale variability in the two countercurrent regions is a manifestation of these similarities in terms of increasing nonlinearity of the unstable waves and an inverse cascade of the eddy energy we discussed generation processes of the mesoscale ssh disturbances

a new paradigm for the north pacific subthermocline low latitude western boundary current system abstractsubthermocline western boundary circulation along the low latitude north pacific ocean 2 25 n is investigated by using profiling float and historical ctd expendable ctd xctd data and by analyzing an eddy resolving global ogcm output in contrast to the existing paradigm depicting it as a reversed pattern of the wind driven circulation above the ventilated thermocline i e depth 26 8 the subthermocline western boundary circulation is found to comprise two components governed by distinct dynamical processes for meridional scales shorter than 400 km the boundary flows along the philippine coast exhibit convergent patterns near 7 10 13 and 18 n respectively these short scale boundary flows are driven by the subthermocline eastward zonal jets that exist coherently across the interior north pacific basin and are generated by the triad instability of wind forced annual baroclinic rossby waves for meridional scales longer than 400 km a time mean mindanao undercurrent muc is obs

topex poseidon derived space time variations of the kuroshio current applications of a gravimetric geoid and wavelet analysis summary using topex poseidon t p altimeter data and a gravimetric geoid we derived 7 year time series of kuroshio s volume transport axis velocity width and axis locations northeast and southeast of taiwan for northeastern and southeastern taiwan the mean volume transports are 19 and 26 sv the mean widths are 112 and 96 km and the mean axis velocities are 50 and 82 cm s 1 respectively the t p derived volume transports agree well with in situ result drifter d21160 almost passes through the t p derived axes of the kuroshio the time series show intraseasonal semi annual annual and interannual variations but the frequency characteristics at the two locations are different owing to monsoon bottom topography and other factors wavelet analyses show that the amplitudes and phases of the frequency components vary with time a biennial component is found in almost all time series and may be excited by the tropical quasi biennial oscillation of the atmosphere the volume transport northeast of taiwan has a positive correlation 0 6 with enso with a 1 month lag and both the volume transport and velocity southeast of taiwan have a negative correlation 0 6 with enso with a 9 10 months lead

double celled subtropical gyre in the south atlantic ocean means trends and interannual changes 1 we present here a study of the mean upper layer structure of the south atlantic subtropical gyre sasg and its modes of variability based on archiving validation and interpretation of satellite oceanographic data sea level anomaly data gravity recovery and climate experiment based mean dynamic topography mdt models reynolds sea surface temperatures and two tide gauge time series from permanent service for mean sea level analysis of the mdts shows that the sasg mean structure is represented by a double cell circulation the southern cell being a narrow quasi zonal strip centered around 33 s its southern limb is limited by the recently discovered saint helena current tristan da cunha current sthc tcc and the north subtropical front around 35 s this system is shown to be well separated from the south atlantic current south subtropical front around 42 45 s a method based on singular spectrum analysis was used to determine the principal modes of variability through the decomposition of the data into band passed data sets the altimeter sea level trend analysis suggests that the sasg pattern is slowly migrating southward and has been growing in amplitude between 1994 and 2006 with local growth rates of 5 10 mm yr occurring in the southern cell flow intensifications in this period 2 3 cm s in the south equatorial current and north brazil undercurrent 3 5 cm s in the benguela current and weakening by 4 5 cm s in the sthc tcc are recorded the altimeter derived sea level trend is coherent with the growing phase of a bidecadal oscillation found from both tide gauges

a late middle stone age artifact assemblage from sibudu kwazulu natal comparisons with the european middle paleolithic abstract it has been suggested that many behavioral innovations said to appear during the late middle stone age in sub saharan africa facilitated the expansion of anatomically modern humans from africa and the near east into europe at about 50 kyr the process eventually led to the replacement of neanderthals by modern humans and the emergence of the upper paleolithic however assemblages in this time range are little known in south africa in fact the transition from middle to the later stone age in southern africa is controversial the early appearance in south africa of many innovations such as sophisticated knapping techniques e g the use of soft hammer or indirect percussion in blade production of composite tools of microlithic and bladelet technologies remains to be established through technological analysis we present here the first results of a project designed to carry out detailed technological studies of several lithic assemblages in south africa and france dated to the transition period at this time we have completed the study of a post howiesons poort assemblage from the rock shelter site of sibudu the 2 m deep stratigraphic sequence of sibudu extends from howiesons poort at its base to final middle stone age directly under iron age layers we have analyzed in detail layer rsp ca 53 kyr 1 m above the howiesons poort levels which has provided a large assemblage of several thousand stone artifacts compared to published msa assemblages this industry is unusual for the very high proportions of retouched pieces 15 the technology is not very elaborate and there is no strong standardization of the end products there are no flakes of predetermined shapes retouch is used to modify irregular flakes to obtain desired edges knapping of flakes and blades is done by hard hammer soft hammer is used only for retouching tools interestingly the older howiesons poort blades were produced on the same raw materials by soft hammer raw material hornfels and dolerite was procured from distances of less than 20 km unifacial points are the dominant type and there is strong evidence of hafting and use as spear armatures detailed comparisons with middle paleolithic assemblages of western europe show that the late middle stone age technology in south africa is very similar to that of the middle paleolithic in fact we see no fundamental differences between the two entities as far as lithic technology is concerned implications for the out of africa hypothesis are discussed

heat treatment in the south african middle stone age temperature induced transformations of silcrete and their technological implications abstract it was recently found that silcrete raw material was heat treated during the south african middle stone age msa for altering its flaking properties this finding led to hypotheses about the implications for the msa hunter gatherers such as the cost of thermal treatment in terms of investment and firewood to date these hypotheses lack a solid basis for data on the thermal transformations of south african silcrete and hence the necessary heating procedure and heating environment is missing in order to produce such data we conducted an experimental study within the framework of the diepkloof project this work is based on the petrographic mineralogical and structural analysis of south african silcrete from the west coast and its thermal transformations our results shed light on the nature of these transformations the ideal heating temperatures and the tolerated heating speed the processes occurring in silcrete are comparable to flint i e the loss of chemically bound water and the formation of new si o si bonds but their intensity is less pronounced effective heating temperatures are significantly higher than for flint and the heating speed tolerated by south african silcrete is relatively fast these findings imply that silcrete heat treatment cannot be directly compared with flint heat treatment unlike flint heating silcrete does not require the setup of a dedicated heating environment and may have been performed in the same time as other fire related activities this would represent only a minor supplementary investment in time and firewood these results have broad implications for the discussion about technological evolution and the acquisition of specialised knowledge in the msa

variation of sea surface height at periods of 65 220 days in the subtropical gyre of the north pacific variations of sea surface height ssh in the north pacific subtropical countercurrent stcc region have been investigated using altimeter derived ssh anomaly data during 1992 1999 it is shown by spectral analyses that the dominant temporal scale of ssh variations in the stcc region is 65 220 days the energy of the ssh variations in this period band is mostly confined to the subtropical gyre and enhanced in the stcc the kuroshio and the kuroshio extension east of the shatsky rise the broad energetic band in the stcc region can be divided into two regions one is located in the latitudinal range of 21 26 n and extending zonally from the philippine sea to 190 along 22 n and the other extends from around 145 to the west of the hawaiian islands along 19 5 n slightly tilting northward toward the east the axes of these two high variability tongues are in agreement with those of the stcc multiple bands estimated from climatological hydrographic data the 65 220 day variations in the stcc region are characterized by westward propagating mesoscale disturbances with wavelengths of 400 1800 km in terms of ratio of the advective speed to the phase speed the mesoscale variations can be classified into two types i e nonlinear eddies with wavelengths of 500 700 km and quasi linear wave motions with longer wavelengths of 1200 km

a late quaternary pollen record from the transvaal bushveld south africa pollen spectra from cores of organic spring deposits from the transvaal provide evidence for the climatic evolution of the province during the last 35 000 yr b p or more the past climatic phases are derived from palynological reconstructions of past vegetation types by comparison of fossil pollen data with modern surface pollen spectra from various localities evidence is provided for an early moist cool phase with relatively mesic bushveld and expanded montane forest in the central transvaal followed by a drier period with drier bushveld which probably lasted until approximately 25 000 yr b p during the next phase which at the latest ended about 11 000 yr b p the temperatures were probably 5 6 c cooler than at present at that time bushveld vegetation in the central transvaal was replaced by open grassland with macchia elements climatic amelioration came and semiarid savanna returned to the plains at first gradually and then developing into a warm kalahari thornveld type vegetation after 6000 yr b p it apparently became slightly wetter and a more broad leafed bushveld developed about 4000 yr b p it again became cooler and slightly wetter and the bushveld vegetation on the central and northern plains was comparable to present open upland types after 2000 yr b p conditions gradually became warner until about 1000 yr b p when the modern climate of the central transvaal bushveld originated

a late quaternary record of monsoon variability in the northwest kimberley australia abstract understanding of the late quaternary environment of australia s vast kimberley region has to date been hindered by the region s lack of classic palaeoenvironmental archives such as deep lake sediments however mound spring peat deposits in the region have been found to be a potentially rich archive of palaeoenvironmental data here we present a high resolution record from black springs mound spring in the kimberley s northwest filling some of the current gaps in knowledge of the region s environmental history this builds on a 6000 year record developed from the same site and indicates that since the last glacial interglacial transition the australian summer monsoon has varied greatly in intensity with an increase in monsoonal precipitation from 14 000 yr bp and pronounced drying in the late holocene despite some chronological uncertainties thought to be due to the inclusion of younger microscopic root fragments changes in the record compare well with other records of climatic change from the kimberley and across tropical northern australia

a complex earthquake sequence captured by the continuous gps network in sw iceland a complex sequence of earthquakes struck the western part of the south iceland seismic zone sisz on 29 may 2008 the sequence initiated with a m w 6 3 neic earthquake in the western part of the sisz aftershocks from the earthquake delineate two parallel n s trending structures 4 km apart in addition to activity along an e w zone further westward continuous gps measurements can best be explained by right lateral strike slip motion on two parallel n s trending faults with little slip occurring on other structures illuminated by earthquake activity we estimate a total moment release of m w 6 2 with m w 6 1 on the first rupture and m w 6 0 on the second rupture high rate 1 hz cgps data from a near field station suggest that the main asperity on the kross fault ruptured within 3 s of the initial mainshock on the ingolfsfjall fault citation hreinsdottir s t amadottir j decriem h geirsson a tryggvason r a bennett and p lafemina 2009 a complex earthquake sequence captured by the continuous gps network in sw iceland geophys res lett 36 l12309 doi 10 1029 2009gl038391

first excavation of intact middle stone age layers at ysterfontein western cape province south africa implications for middle stone age ecology abstract excavations into a coastal cliff at ysterfontein yft 1 south africa have revealed 2 5 3 m of stratified sands containing classic middle stone age msa stone artifacts abundant mussel and limpet shells numerous fragments of ostrich eggshell and somewhat rarer bones from mammals birds tortoises and snakes the sands apparently filled a crevice like calcrete shelter where the artifacts and animal remains accumulated partly in place and perhaps partly through slippage down the face of a dune that once stood between the site and the sea accelerator radiocarbon dating of ostrich eggshell places the sequence before 33 400 years ago artifact typology provisionally suggests that it formed after 70 000 years ago the fauna resembles faunas from the handful of other known coastal msa sites and contrasts with faunas from regional later stone age lsa sites in its low diversity of coastal marine species and in the large size of its limpets and tortoises the difference suggests that msa people exploited local resources less intensively probably because their populations were less dense

southeast african records reveal a coherent shift from high to low latitude forcing mechanisms along the east african margin across last glacial interglacial transition abstract late quaternary climate variability in the southern african subtropics is still only poorly resolved with significant complexity and apparent contradictions in the regional dataset to more effectively interpret and synthesize key regional records we reanalysed the data from 13 pollen sequences from the summer rainfall zone of south africa spanning the last 45 000 years obtaining directly comparable quantitative reconstructions of mean annual temperature and summer rainfall temperature reconstructions from across the region provide consistent results with all sites reflecting trends observed in southwest indian ocean sea surface temperatures in the adjacent mozambique channel precipitation reconstructions are more heterogeneous with two distinct subregions being identified in the northeast long term trends in precipitation are determined by sea surface and continental temperature trends revealing a positive relationship between temperature and rainfall this long term pattern appears to be primarily driven by high northern latitude mechanisms with direct local insolation being subordinate their relative impact reversed during terminal glacial period early holocene at which time direct insolation forcing became the main driver of rainfall variability further south in central south africa precipitation variability appears also to be influenced by the latitudinal position of the southern hemisphere westerlies which combine with tropical flow to create tropical temperate trough advecting moisture into the interior in this region periods of maximum precipitation coincide with periods of elevated ssts and equatorward expansions of the westerly storm track this study allows for a fully constrained understanding of climate dynamics along the eastern african margin for the last 45 000 years linking dynamics to drivers and describing how the climate systems evolved across the last glacial interglacial transition

far reaching effects of the hawaiian islands on the pacific ocean atmosphere system using satellite data we detected a wind wake trailing westward behind the hawaiian islands for 3000 kilometers a length many times greater than observed anywhere else on earth this wind wake drives an eastward ocean current that draws warm water from the asian coast 8000 kilometers away leaving marked changes in surface and subsurface ocean temperature standing in the path of the steady trade winds hawaii triggers an air sea interaction that provides the feedback to sustain the influence of these small islands over a long stretch of the pacific ocean

coastal palaeoenvironments and hunter gatherer plant use at waterfall bluff rock shelter in mpondoland south africa from mis 3 to the early holocene abstract waterfall bluff in eastern mpondoland eastern cape province south africa is a recently excavated archaeological site with deposits spanning marine isotope stage mis 3 to the middle holocene here we present preliminary results of a multi proxy palaeoenvironmental study combining macro botanical remains charcoal phytoliths pollen and plant waxes derived from the same archaeological record we aim to understand the interactions between hunter gatherer plant foraging and climate and environmental change in coastal mpondoland from mis 3 to the early holocene at waterfall bluff the charcoal and pollen records at waterfall bluff show the gathering of a variety of woody taxa characterised by their combustion and medicinal properties e g millettia grandis and apodytes dimidiate the leaves identified in the macrobotanics and in the phytolith record might belong to some of these taxa and it is likely that they were used for medicinal purposes from a palaeoenvironmental perspective our results indicate low precipitation and low rainfall seasonality under cool conditions during mis 3 and the last glacial maximum lgm under these conditions open woodlands interspersed with dry and hygrophilous grasslands and bushveld vegetation with significant representation of fynbos elements occurred in the local landscapes probably along podocarpus afrocarpus forests the latter could have been 1 present along river valleys and scarps on the mpondoland exposed continental shelf towards the south and west of waterfall bluff supported by palaeo rivers and cool temperatures favouring low evapotranspiration or 2 present in the interior with pollen grains possibly transported to the site by intensified westerly winds these forests contracted as a result of the post glacial marine transgression or reduced westerlies following the lgm during the early holocene the palaeoenvironmental signal points to higher summer rainfall and higher summer seasonality than during mis 3 the lgm and the lgit these changes are coeval with an increase of coastal forests and c4 mesic grasslands with localized wetland vegetation around waterfall bluff these multi proxy archaeobotanical and biochemical data show that landscapes surrounding waterfall bluff changed in relation to marine transgressions regressions and changes in rainfall intensity and seasonality the people of waterfall bluff foraged the coasts during glacial periods to collect wood

vegetation and environmental changes at the middle stone age site of wonderkrater limpopo south africa wonderkrater a middle stone age site in the interior of south africa is a spring and peat mound featuring both paleoclimatic and archaeological records the site preserves three small msa lithic assemblages with age estimates of 30 ka 45 ka and 138 01 7 7 ka here we present results of the pollen analysis of a core retrieved from the middle of the peat mound which covers with hiatuses the timespan between ca 70 10 ka and 30 ka pollen percentages of terrestrial local aquatic and semi aquatic plants reveal changes in the regional climate and in the water table of the spring results identify regional wet conditions at ca 70 10 ka followed by a dry and a wet period between 60 ka and 30 ka superimposed on these three phases recurring changes in the size and depth of the water table are observed between 45 ka and 30 ka wet conditions at 70 ka and 30 ka are tentatively correlated here with marine isotope stage 4 and heinrich stadial 3 respectively a warm and dry savanna landscape was present during human occupation older than 45 ka and a wet phase was contemporaneous with the final occupation dated at 30 ka

ubiquity of anomalous fading in k feldspars and the measurement and correction for it in optical dating anomalous fading rates were measured in k feldspars separated from 49 sediment samples mainly from north america the intensity of the optically stimulated luminescence was found to decrease linea

late quaternary dynamics of southern africa s winter rainfall zone abstract variations in the nature and extent of southern africa s winter rainfall zone wrz have the potential to provide important information concerning the nature of long term climate change at both regional and hemispheric scales positioned at the interface between tropical and temperate systems southern africa s climate is influenced by shifts in the intertropical convergence zone the westerlies and the development and position of continental and oceanic anticyclones over the last glacial interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems central to this discussion has been the extent to which the region s glacial climates would have been affected by expansions of antarctic sea ice equatorward migrations of the westerlies more frequent intense winter storms and an expanded wrz this paper reviews the developing body of evidence pertaining to shifts in the wrz and the evolution of ideas that have been presented to explain the patterns observed dividing the region into three separate axes along the western and southern margins of the continent and across the interior into the karoo and the kalahari a range of evidence from both terrestrial sites and marine cores is considered and potential expansions of the wrz expansions are explored despite the limitations of many of the region s proxy records a coherent pattern has begun to develop of a significantly expanded wrz during phases of the last glacial period with the best documented being between 32 17 ka while more detailed inferences will require the recovery and analysis of longer and better dated records this synthesis provides a new baseline for further research in this key region

uncertainties in the mean ocean dynamic topography before the launch of the gravity field and steady state ocean circulation explorer goce 1 in anticipation of the future observations of the gravity mission gravity field and steady state ocean circulation explorer goce the present day accuracy of mean dynamic topography mdt is estimated from both observations and models a comparison of five observational estimates illustrates that rms differences in mdt vary from 4 2 to 10 5 cm after low pass filtering the fields with a hamming window with wavenumber n 120 corresponding to an effective resolution of 167 km rms differences in observational mdt reduce to 2 4 8 3 cm for n 15 1334 km differences in data sources geoid model in situ data are mostly visible in the small scale oceanic features while differences in processing filtering inverse modeling techniques are reflected at larger scales a comparison of seven different numerical ocean models demonstrates that model estimates differ mostly in western boundary currents and in the antarctic circumpolar current rms differences between modeled and observed mdt are at best 8 8 cm for n 120 and reduce to 6 4 cm for n 15 for models with data assimilation a minimal rms difference of 6 6 cm n 120 to 3 4 cm n 15 is obtained with respect to the observational mdts the reduction of differences between mdts with increasing filtering scales is smaller than expected while it is expected that goce will improve mdt estimates at small spatial scales improvement of mean sea surface estimates from satellite altimetry may be needed to improve mdt estimates at larger scales

evaluation of hycom in the kuroshio extension region using new metrics 1 a high resolution 0 08 at equator hybrid coordinate ocean model hycom simulation is evaluated using observations for the period 1993 2003 for a western pacific region containing the kuroshio extension ke 25 45 n and 135 180 e comparisons are made for the ke path and strength and for the upper ocean heat budget the mean strength and path agree well with observations except near the ke separation point where the jet is as much as 2 of latitude too far south however the model path variations are considerably more energetic than observed and this likely obscures the observed tendency for weaker meandering when the ke is strong the model accurately reproduces seasonal variations of upper ocean heat content but the long period about 10 yr variations of heat content and ke strength clearly differ in the region upstream of 150 e the long period variations in model ssh do not show the same relationship to wind forcing that is seen in the observations and in a low resolution ocean model simulation the hycom upper ocean heat budget is similar to a diagnostic heat budget inferred from observations in that the dominant contribution is from lateral fluxes advection however advection fluctuations again primarily in the upstream region are much larger in the model this evaluation of hycom shows realistic mean quantities and realistic variations away from the separation region however an overly energetic jet upstream of 150 e can obscure the longer period variability and its contribution to the upper ocean heat budget

middle stone age bone tools from the howiesons poort layers sibudu cave south africa abstract recently discovered bone implements from middle stone age msa deposits at sibudu cave south africa confirm the existence of a bone tool industry for the howiesons poort hp technocomplex previously an isolated bone point from klasies river provided inconclusive evidence this paper describes three bone tools two points and the end of a polished spatula shaped piece from unequivocal hp layers at sibudu cave with ages greater than 61 ka comparative microscopic and morphometric analysis of the sibudu specimens together with bone tools from southern african middle and later stone age lsa deposits an iron age occupation nineteenth century bushman hunter gatherer toolkits and bone tools used experimentally in a variety of tasks reveals that the sibudu polished piece has use wear reminiscent of that on bones experimentally used to work animal hides a slender point is consistent with a pin or needle like implement while a larger point reminiscent of the single specimen from peers cave parallels large un poisoned bone arrow points from lsa iron age and historical bushman sites additional support for the sibudu point having served as an arrow tip comes from backed lithics in the hp compatible with this use and the recovery of older larger bone and lithic points from blombos cave interpreted as spear heads if the bone point from the hp layers at sibudu cave is substantiated by future discoveries this will push back the origin of bow and bone arrow technology by at least 20 000 years and corroborate arguments in favour of the hypothesis that crucial technological innovations took place during the msa in africa

microscopic charcoal in sediments quaternary fire history of the grassland and savanna regions in south africa the microscopic charcoal content of several quaternary pollen sequences is used to investigate fire history in south africa both during the holocene and the late pleistocene although fluctuations in charcoal composition are recorded it is difficult to link them directly to either human made or natural fires strong long term variations in microscopic charcoal of middle and upper pleistocene layers are independent of pollen indications of past temperature and moisture conditions holocene charcoal sequences from different areas show no correlation so no phases of regional burning are found some fluctuations in charcoal probably are the result of local burning in the various regions the arrival of iron age people some 2000 yr ago apparently did not coincide with widespread wild fires as these events do not consistently appear in regional microscopic charcoal records the only exception appears to be the wonderkrater spring deposit relatively open savanna environments which are implied by pollen analysis at some sites during this period and the generally low microscopic charcoal contents were either caused by climate change or controlled burning by iron age people copyright 2002 john wiley sons ltd

gsfc00 mean sea surface gravity anomaly and vertical gravity gradient from satellite altimeter data a mean sea surface gsfc00 and its derivatives the altimetry gravity anomaly and vertical gravity gradient fields were computed using sea surface heights of topex ers and geosat satellite altimeter missions provided by the nasa ocean altimeter pathfinder project koblinsky et al 1998 a new estimation method distinct from the gsfc98 mean sea surface computation wang 2000a was explored and used to reduce ocean variability in the mean sea surface heights the gravity anomaly and vertical gravity gradient fields were then computed from the mean sea surface height implied geoid undulations validation of the gsfc00 mean sea surface and gravity anomaly was also performed

a high resolution satellite only grace based mean dynamic topography of the south atlantic ocean 1 a new filtering method based on singular spectrum analysis has been devised to extract high resolution 0 25 0 25 grid satellite only mean dynamic ocean topography mdt constructed by differencing of the ggm02 grace gravity model from the gsfcmss00 mean sea surface this data adaptive interpolation type filter is adequate for the finite domain mdt processing since it minimizes smoothing and does not lose boundary points it is applied to the computation of two new mdts and mdt derived mean geostrophic circulation maps of the south atlantic region from 15 n to 50 s advantages of these new maps are clarified when contrasted with the rio 2005 chambers zlotnicki 2004 and adcp cruise transect data

early use of pressure flaking on lithic artifacts at blombos cave south africa pressure flaking has been considered to be an upper paleolithic innovation dating to 20 000 years ago 20 ka replication experiments show that pressure flaking best explains the morphology of lithic artifacts recovered from the 75 ka middle stone age levels at blombos cave south africa the technique was used during the final shaping of still bay bifacial points made on heat treated silcrete application of this innovative technique allowed for a high degree of control during the detachment of individual flakes resulting in thinner narrower and sharper tips on bifacial points this technology may have been first invented and used sporadically in africa before its later widespread adoption

variability of the kuroshio extension jet recirculation gyre and mesoscale eddies on decadal time scales abstract twelve years of sea surface height ssh data from multiple satellite altimeters are used to investigate the low frequency changes and the interconnections of the kuroshio extension ke jet its southern recirculation gyre and their mesoscale eddy field the dominant signal is characterized by the steady weakening of the ke jet recirculation gyre from 1993 to 1996 followed by a gradual strengthening after 1997 during the weakening period of 1993 96 the ke path migrated southward in general and this path migration reversed in direction during the strengthening period of the ke jet and recirculation gyre after 1997 by hindcasting the ssh signals using linear vorticity dynamics it was found that weakening strengthening in the ke jet and recirculation gyre is consistent with westward propagation of negative positive ssh anomalies generating in the eastern north pacific and strengthening during their westward propagation when the ke jet and recirculation gyre were in a weak mode during 19

south african palaeoenvironments during marine oxygen isotope stage 4 a context for the howiesons poort and still bay industries abstract spanning the period from 74 58 ka and being broadly coeval with marine oxygen isotope stage 4 mis 4 the still bay and howiesons poort industries represent important phases in the development of the material culture of early modern humans how and why these industries occurred when they did however remain matters for speculation a key element of this debate has been the question of what role environmental change during the early stages of the last glacial period may have had on influencing human activity unfortunately well dated palaeoenvironmental evidence from this period is limited and the debate has out of necessity been driven by the application of conceptual models of environmental change many of which associate colder and warmer global climates with increased aridity and humidity respectively in this paper the regional marine and terrestrial evidence is synthesised to create an evidence based palaeoenvironmental context based on the information available to date it appears that rather than being characterised by dry conditions mis 4 was a period of relatively cool moist climates the ubiquity of which transcends the modern regional climate boundaries it is suggested that orbital parameters at this time created greater interaction between tropical and temperate circulation systems bringing more moisture to the subcontinent these findings highlight the distinct nature of southern african climate systems and caution against the application extra regional conceptual models or inferring linear relationships with polar records

circulation of the north atlantic ocean from altimetry and the gravity recovery and climate experiment geoid 1 we discuss the ocean circulation derived from the temporally averaged sea surface height which is referenced to the recently released geoid from the gravity recovery and climate experiment grace mission grace gravity model 02 ggm02 the creation of a precise independent geoid allows for the calculation of the reference gravitational potential undulation surface which is associated with the resting ocean surface height this reference height is then removed from the temporally averaged sea surface height leaving the dynamic ocean topography at its most basic level the dynamic ocean topography can be related to the ocean s surface circulation through geostrophy this has previously been impracticable because of large uncertainties in previous estimates of the earth s geoid prior geoids included the temporally averaged sea surface from altimeters as a proxy for the geoid and therefore were unsuitable for calculations of the ocean s circulation geoid undulations are calculated from the grace geoid and compared to those from the nasa goddard space flight center and national imagery and mapping agency joint earth geopotential model egm96 geoid error estimates are made to assess the accuracy of the new geoid the deep ocean pressure field is also estimated by combining the calculated dynamic ocean topography with hydrography finally the derived circulation is compared to independent observations of the circulation from sea surface drifters and subsurface floats it is shown that the ggm02 geoid is significantly more accurate for use in estimating the ocean s circulation

finding resolution for the howiesons poort through the microscope micro residue analysis of segments from sibudu cave south africa in this paper i present the results of a micro residue analysis of stone segments the type fossils of the howiesons poort technocomplex in south africa with an age of more than 60 ka at sibudu cave kwazulu natal fifty three segments were systematically analysed and 1826 organic micro residue occurrences were documented on the sample the distribution patterns of micro residues and other use traces are interpreted in terms of hafting and function it is shown that most of the tools were indeed hafted and most were probably used as inserts for hunting weapons there is evidence for differences and changes over time in haft materials and hafting configurations of the segments the study demonstrates how functional studies could improve our understanding of change and variability in human behaviour during the middle stone age a period that used to be portrayed as static or slow changing

estimating mean dynamic topography in the tropical pacific ocean from gravity and altimetry satellites began in an attempt to understand and predict the climatic enso el nino southern oscillation phenomenon the satellite solution was compared with climatology model simulations and synthetic solutions in terms of dynamic topography and geostrophic circulation its contribution to absolute sea level is quantified with independent in situ data such as those from the tropical atmosphere ocean tao triton mooring arrays and xbts

eddy mean flow interaction in the decadally modulating kuroshio extension system abstract satellite altimeter sea surface height ssh data of the past 16 years are used to investigate the decadal changes of the kuroshio extension ke system that oscillated between a stable and an unstable dynamic state during the stable state of 10 1992 06 1995 and 01 2002 12 2004 the ke jet was intense and had a northerly zonal mean path and a well defined southern recirculation gyre during the unstable state of 07 1995 12 2001 and 01 2005 present the ke jet had a reduced eastward transport and a more southerly flow path transitions between the two dynamic states are caused by the basin scale wind stress curl forcing in the eastern north pacific related to the pacific decadal oscillations pdos or the north pacific gyre oscillations npgos during the positive pdo or negative npgo phase the intensified aleutian low generates negative ssh anomalies in the eastern north pacific through ekman divergence as these wind induced negative ssh anomalies propagate to the west as baroclinic rossby waves they weaken the zonal ke jet and shift its path southward as its path is pushed southward 32 n the deep reaching ke jet has to ride over the shallow shatsky rise generating localized disturbances that lead to their subsequent development along the ke jet west of the shatsky rise the sequence opposite to that listed above occurs when the pdo npgo changes to its negative positive phase after the ke system transitions from a stable to unstable state the enhanced eddy interaction is found to strengthen both the southern recirculation gyre and quasi stationary meanders along the ke s upstream path this nonlinear eddy interaction is important in determining the amplitude of the observed decadal ke variability

quantification of climate change for the last 20 000 years from wonderkrater south africa implications for the long term dynamics of the intertropical convergence zone abstract in southeast africa a region for which few palaeoenvironmental records are available the fossil pollen record from the wonderkrater spring mound has contributed substantially to our understanding of past vegetation change since the last glacial maximum lgm 21 ka multivariate analysis of the pollen data by scott and thackeray 1987 provided environmental reconstructions suggesting relatively mesic lgm conditions with warm and dry conditions during the early holocene 11 6 cal kbp this conforms to predicted patterns of precipitation change in the southern african tropics in response to northern hemisphere cooling and orbital forcing subsequent data from the cold air cave speleothems and a sea surface temperature record from the mozambique channel however indicate that conditions during the early to mid holocene may have been wetter than present in the wonderkrater region to explore this question further we have created a series of botanical climatological transfer functions based on a combination of modern climate and plant distribution data from southern africa applying these to the wonderkrater fossil pollen sequence we have derived quantitative estimates for temperatures during the cold and warm quarters as well as precipitation during the wet and dry quarters in addition a species selection method based on bayesian statistics is outlined which provided a parsimonious choice of likely plant species from what are otherwise taxonomically broad pollen types we do not propose that our findings invalidate the previous principal component analyses but they do have the advantage of being based more clearly on the relationship between modern plant distributions and individual climatic variables results indicate that temperatures during both the warm and cold seasons were 6 2 c colder during the lgm and younger dryas and that rainy season precipitation during the last glacial maximum was 50 of that during the mid holocene our results also imply that changes in precipitation at wonderkrater generally track changes in mozambique channel sea surface temperatures with a steady increase following the younger dryas to a period of maximum water availability at wonderkrater 3 7 ka these findings argue against a dominant role of a shifting intertropical convergence zone in determining long term environmental trends and indicate that the northern and southern tropics experienced similar climatic trends during the last 20 kyr

geodetic and geophysical results from a taiwan airborne gravity survey data reduction and accuracy assessment 1 an airborne gravity survey was conducted over taiwan using a lacoste and romberg lcr system ii air sea gravimeter with gravity and global positioning system gps data sampled at 1 hz the aircraft trajectories were determined using a gps network kinematic adjustment relative to eight gps tracking stations long wavelength errors in position are reduced when doing numerical differentiations for velocity and acceleration a procedure for computing resolvable wavelength of error free airborne gravimetry is derived the accuracy requirements of position velocity and accelerations for a 1 mgal accuracy in gravity anomaly are derived gps will fulfill these requirements except for vertical acceleration an iterative gaussian filter is used to reduce errors in vertical acceleration a compromising filter width for noise reduction and gravity detail is 150 s the airborne gravity anomalies are compared with surface values and large differences are found over high mountains where the gravity field is rough and surface data density is low the root mean square rms crossover differences before and after a bias only adjustment are 4 92 and 2 88 mgal the latter corresponding to a 2 mgal standard error in gravity anomaly repeatability analyses at two survey lines suggest that gps is the dominating factor affecting the repeatability fourier transform and least squares collocation are used for downward continuation and the latter produces a better result two geoid models are computed one using airborne and surface gravity data and the other using surface data only and the former yields a better agreement with the gps derived geoidal heights bouguer anomalies derived from airborne gravity by a rigorous numerical integration reveal important tectonic features

evidence for progressive holocene aridification in southern africa recorded in namibian hyrax middens implications for african monsoon dynamics and the african humid period abstract presented here are stable nitrogen isotope data from a rock hyrax procavia capensis middens from northwestern namibia that record a series of rapid aridification events beginning at ca 3800 cal yr bp and which mark a progressive decrease in regional humidity across the holocene strong correlations exist between this record and other terrestrial and marine archives from southern africa indicating that the observed pattern of climate change is regionally coherent combined these data indicate hemispheric synchrony in tropical african climate change during the holocene with similar trends characterising the termination of the african humid period ahp in both the northern and southern tropics these findings run counter to the widely accepted model of direct low latitude insolation forcing which requires an anti phase relationship to exist between the hemispheres the combined dataset highlights 1 the importance of forcing mechanisms influencing the high northern latitudes in effecting low latitude climate change in africa and 2 the potential importance of solar forcing and variations in the earth s geomagnetic shield in determining both long term and rapid centennial scale climate changes identifying a possible mechanism for the variations marking the ahp termination in both the southern and northern tropics

pleistocene sea level fluctuations and human evolution on the southern coastal plain of south africa abstract humans evolved in africa but where and how remain unclear here it is proposed that the southern coastal plain scp of south africa may have served as a geographical point of origin through periodic expansion and contraction isolation in response to glacial interglacial changes in sea level and climate during pleistocene interglacial highstands when sea level was above 75 m human populations were isolated for periods of 360 3400 25 yr generations on the scp by the rugged mountains of the cape fold belt climate and vegetation barriers the scp expands five fold as sea level falls from 75 to 120 m during glacial maxima to form a continuous unobstructed coastal plain accessible to the interior an expanded and wet glacial scp may have served as a refuge to humans and large migratory herds and resulted in the mixing of previously isolated groups the expansive glacial scp habitat abruptly contracts by as much as one third in 300 yr during the rapid rise in sea level associated with glacial terminations rapid flooding may have increased population density and competition on the scp to select for humans who expanded their diet to include marine resources or hunted large animals successful adaptations developed on an isolated scp are predicted to widely disperse during glacial terminations when the scp rapidly contracts or during the initial opening of the scp in the transition to glacial maxima the hypothesis that periodic expansion and contraction of the scp as well as the coastal plain of north africa contributed to the stepwise origin of our species over the last 800 thousand years kyr is evaluated by comparing the archeological dna and sea level records these records generally support the hypothesis but more complete and well dated records are required to resolve the extent to which sea level fluctuations influenced the complex history of human evolution

does the taiwan warm current exist in winter 1 it has been argued for many years whether the taiwan warm current twc exists in winter though there is no question about its existence in summer a regional ctd survey and anchored adcp measurements were conducted off the mouth of the changjiang on the western shelf of the east china sea from 24 february to 10 march 2001 both hydrographic and current data showed an evidence of the twc which flowed northeastward along the 50 m isobath and intruded into the submerged river valley off the changjiang this current is sub surface intensified with a maximum velocity of 30 cm s occurring at a depth of 30 m below the surface this finding was consistent with the satellite derived sst image received on 26 30 january 1986 and modis sst image received on 18 february 2001 it suggests that the twc is at least an episodic feature in the east china sea and its occurrence and duration might vary due to meandering of the kuroshio around the taiwan strait

annual and interannual variability in the kuroshio current system abstract individual seasonal 300 m temperature maps were constructed over the kuroshio current system from 130 e to 170 w for a 4 year period from summer 1976 through spring 1980 using transpac xbt data and jodc temperature depth data quasi stationary meanders in the kuroshic current system occurred at 137 c i e kuroshio meander at 144 e and 150 e i e lee wave meanders and near 160 e i e meander over the shatsky rise a composite of the paths of the kuroshio i e the 12 c isotherm from the individual seasonal maps and the total variance map finds nodes i e minima and anti nodes i e maxima of variability to have existed along the mean kuroshio path the anti nodes coincided with the location of the quasi stationary meanders the nodes in between zonal propagation of temperature anomalies accounted for 20 30 of the total interannual variance these temperature anomalies propagated eastward at 0 5 1 5 cm s 1 in the region 140 155 e and westward at 1 to 2 cm s 1 in the re

variability in the middle stone age lithic sequence 115 000 60 000 years ago at klasies river south africa abstract stratified samples of artefacts from the late pleistocene deposit at the klasies river main site covering some 60 000 years have been studied variability in the artefact sequence has been documented in the technologies of artefact production in addition to conventional typological analysis particular emphasis has been given to the recognition of the reduction sequences used in producing the pre formed blanks that are a feature of the middle stone age the results show that the variability is due to changes between the dominant blade and or point technological conventions traditions through time technological study supports and gives meaning to the recognition of distinct sub stages msa i klasies river msa ii mossel bay howiesons poort and a post howiesons poort at main site these sub stages are more than convenient site specific organizational entities they delineate separate technological conventions that may have relevance on a sub continental scale

mean mesoscale global ocean currents from geodetic pre goce mdts with a synthesis of the north pacific circulation 1 a new milestone in satellite geodesy is about to be completed with the expected availability of the high resolution data from the already in orbit global ocean circulation explorer goce satellite there are still some open questions related to capability of recovering mean mesoscale 50 km plus geostrophic circulation mgc patterns from observational gravity recovery and climate experiment grace based geodetic mean dynamic topography mdts which we examine here in detail a new set of global geodetic mdts with high grid resolutions was computed 0 1 and 0 25 based on the newest egm08 and grace ggm02 geoid models the high resolution coupled to good mesoscale feature discrimination was derived using efficient filtering procedure based on singular spectrum analysis the new solutions were contrasted with five important mdts including the hybrid and the geodetic mdts through empirical orthogonal functions analysis which permit the determination of the mutual correlation among the mdts and establishment of error bounds the methodology made viable a detailed and robust analysis of the north pacific ocean circulation based on these mgcs including comparisons with known results from other studies we prove the superiority of the geodetic egm08 as opposed to hybrid mdt models by obtaining less noisy and more intense and slender western boundary currents and their recirculations the bifurcations at the shatsky rise and the known mean eddies in the low latitude shear region nec necc

climatic patterns in equatorial and southern africa from 30 000 to 10 000 years ago reconstructed from terrestrial and near shore proxy data abstract as part of a wider study of last glacial and deglacial climates in the southern hemisphere continents we here review terrestrial and near shore marine records from equatorial and southern africa between 30 000 and 10 000 years ago 30 10 ka this time interval covers the lead up to the last glacial maximum lgm 21 2 ka the lgm proper and the ensuing deglacial records selected for review needed to meet three requirements continuity or near continuity over the period a well established chronology and at least one but preferably several unambiguous proxy ies we aim to show how regional climates of the sub continent have responded to orbital forcing as opposed to other global glacial interglacial boundary conditions and how they are related to high latitude climates sea and land surface conditions positions of the intertropical convergence zone itcz and of the westerly belt evidence of past climates derived from many independent proxies is given from west to southwest africa moisture from the atlantic ocean then from equatorial east africa to the southern subtropical summer rainfall domain moisture mainly from the indian ocean the lgm was cooler than today and generally drier in the tropics north of 8 9 s glacial to holocene increase in monsoonal precipitation primarily related to orbitally induced summer insolation in the northern hemisphere occurred by steps of increasing amplitude 17 16 14 5 11 5 ka major wet dry spells coincide with abrupt warm cold events in high northern latitudes and related itcz migrations in the southern tropics the main post glacial increase in tropical rainfall generally appears more gradual and in phase with antarctic warming data suggest a restricted northward migration of the itcz and concentration of tropical rainfall well south of the equator during the lgm and the younger dryas drier glacial conditions prevailed in southeastern africa while parts of southwestern africa point to enhanced humidity during the lgm suggesting that the winter westerly belt was either stronger than today or displaced further north possibly as a result of more extensive antarctic sea ice inferred african climatic fluctuations show the competing influences of tropical and high latitude climates of both hemispheres and suggest changes in both meridional and zonal circulation modes this review also reveals major geographical and methodological gaps and a number of unresolved issues providing pointers for future research

fluctuations of vegetation and climate over the last 75 000 years in the savanna biome south africa tswaing crater and wonderkrater pollen sequences reviewed abstract quaternary palynological information from the savanna biome of south africa is limited due to the scarcity of suitable pollen traps and new extensive pollen records of palaeoenvironments in the region are unlikely to be obtained easily those that are available including the tswaing crater and the wonderkrater spring sequences can however be reassessed and their data optimised these two pollen records are relevant to palaeo environmental research in the area although they have chronologies beyond the radiocarbon dating range that complicate interpretations the tswaing sequence in this study focuses on the upper 34 m of pollen rich layers out of a total of 90 m of lake deposits a new chronology is experimented with for this upper part of the sequence it differs slightly from the previous one in that it does not rely on adjustments of the ages according to the precession cycle accordingly the age at 34 m is estimated to be c 75 ka based on interpolation of the radiocarbon sequence and a basal fission track date of c 200 ka at 90 m in the case of the second site wonderkrater recently published excavation and dating of the deposits and comparisons with the tswaing pollen sequence provide new clues for the age of the lowermost deposit of the original borehole sequence of peats sands and clay which is estimated at c 60 000 years the new results better situate the two pollen sequences in a wider regional and global palaeoenvironmental framework

small mammals from marine isotope stage 5 at klasies river south africa reconstructing the local palaeoenvironment abstract klasies river a significant middle stone age msa site preserves remains of anatomically modern humans and a 21 m sequence of human habitation that shows use of sophisticated lithic technology and systematic exploitation of marine and terrestrial resources in this paper micromammals recovered from the lower msa sequence msa i and msa ii at klasies river main site have been analysed to provide proxy data for palaeoenvironmental reconstruction small mammals recovered from 183 separate layers ensure a detailed record of local climate and vegetation during marine isotope stage mis 5 taphonomic analyses indicate that avian predators accumulated the micromammals analysis of post depositional processes has provided information on intra site variability and utilisation the palaeoenvironmental reconstruction shows changes in rainfall seasonality within mis 5 there was transient movement towards more aseasonal rainfall and significant alterations in the vegetation composition from mis 5e to mis 5a our study adds new insights to palaeoenvironmental conditions on the cape coast during mis 5

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

multiproxy record of late quaternary climate change and middle stone age human occupation at wonderkrater south africa here we provide a multiproxy record of climate change and human occupation at wonderkrater a spring and peat mound site situated in the interior of southern africa recently extracted sediment cores yielded a number of middle stone age msa artefacts prompting exploratory excavation of the sediments to understand better the geomorphology of the site age of the sediments cultural lithic sequence vegetation and faunal remains and to try to establish whether human use of the site was to some extent climatically driven excavations yielded late pleistocene mammal fauna and flora and three small msa lithic assemblages with age estimates of 30 ka 45 ka and 138 01 7 7 ka the upper layers comprise peat that preserves macrobotanical and faunal remains implying local fen conditions in acacia savanna woodland at 12 ka below the upper peat layers a 1 m thick layer of white sand yielded two msa lithic assemblages in association with faunal remains dated to between 30 8 0 7 ka and 45 ka clay underlying the sand has an osl age of 63 1 5 8 ka and sandy peat below it has an infrared stimulated luminescence irsl age of 70 10 ka faunal remains in the lower sand levels and dental stable carbon isotope analysis of herbivores indicate a substantial grassland component in the landscape during late mis 3 45 ka charcoal phytolith and pollen data show a change from moderately warm and dry grassy savanna woodland in the lower sand levels to cooler and wetter grassland with woody shrubs in the uppermost levels by 30 ka the conditions that resulted in the deposition of the sand also attracted people to the site but whether it served as an oasis in an arid landscape or was occupied during wet phases is unclear the composition of the lithic assemblages which include many tools suitable for cutting suggest that the peat mound may have been used as a place to harvest reeds process plant materials and butcher animals that were either deliberately or accidentally trapped in mud or peat

mean dynamic topography intercomparisons and errors knowledge of the height of the sea surface above the geoid would allow one to determine the associated geostrophic surface currents and help to quantify subsurface currents and heat transports that regulate the earth s climate such a determination is presently hampered by our inability to accurately measure the geoid especially over the open ocean in anticipation of a future mean dynamic topography mdt provided by combining altimetry and a goce geoid this paper compares the mdts of several ocean models in the important north atlantic and nordic seas region focus area of the eu gocina project each of the models used in this study assimilates hydrography which is an essential requirement for a model to accurately interpolate the data and provide a realistic mdt the available mdts differ in resolution and time period both these issues are addressed a composite mdt is formed from the individual mdts and we assess the uncertainty in the composite mdt and in the associated geostrophic surface currents we find a remarkable level of agreement between this suite of model mdts the uncertainty in the composite mdt is less than 4cm over most of the study region and the uncertainty in the associated geostrophic surface velocities is of the order 2cm s these uncertainties can be used as error estimates when comparing with satellite derived mdts to judge consistency

interactions between hurricane catarina 2004 and warm core rings in the south atlantic ocean 1 the unexpected evolution of the first recorded south atlantic hurricane catarina over waters with homogeneous sea surface temperatures sst of 24 c in march 2004 was a challenge to the weather forecast community this work concentrates on a thorough data driven comparative analysis to make reliable diagnostics of the role of the ocean in the genesis and evolution of catarina we used several high resolution multisatellite derived products including three microwave based sst data sets multisatellite collinear data of sea surface height ssh anomalies significant wave heights and wind speeds four quikscat ocean surface wind vector products including the 12 5 km resolution swath data daily fields of absolute objectively analyzed ssh and corresponding geostrophic currents and argo floats the synergic use of these data sets showed that catarina interacted strongly with four warm core rings wcrs forcing upwelling of isotherms and mixed layer waters these interactions minimized the known negative sst feedback as attested by the sst differences being less than 1 2 c although the sst in the region was around 24 c below the palmen threshold the surface air temperatures were 14 c which still furnished a large air sea temperature gradient capable of extracting large enthalpy fluxes from the wcrs influenced by ekman pumping it is shown here that catarina achieved category 1 over the ocean on 26 march with its maximum intensity of 34 m s seen in the 12 5 km swath winds